| changes in paramecium caudatum (protozoa) near a switched-on gsm telephone. | the protozoan paramecium caudatum was examined under normal conditions versus aside a switched-on gsm telephone (900 mhz; 2 watts). exposed individuals moved more slowly and more sinuously than usual. their physiology was affected: they became broader, their cytopharynx appeared broader, their pulse vesicles had difficult in expelling their content outside the cell, their cilia less efficiently moved, and trichocysts became more visible. all these effects might result from some bad functioning o ... | 2011 | 21554102 |
| dynamic behaviour of stationary pronuclei during their positioning in paramecium caudatum. | during conjugation of paramecium caudatum, there are two well-known stages when nuclear migration occurs. what happens to the nuclei is closely related to their localisations in cells. the first of these stages is the entrance of one meiotic product into the paroral region. this nucleus survives, while the remaining three outside this area degenerate. the second stage is the antero-posterior localisation of eight synkaryon division products. four posterior nuclei are differentiated into macronuc ... | 2011 | 21497073 |
| cytotoxicity assessment of monocrotophos in paramecium caudatum and oxytricha fallax. | experiments were conducted to evaluate the toxic effects ofmonocrotophos in ciliate models paramecium caudatum and oxytricha fallax. in acute toxicity studies higherconcentrations of monocrotophos caused marked increase in mobility of cells exhibiting rocking movements within two mins of exposure but were decreased after 30 mins. lc50 value by mortality curve for 3 hr acute toxicity test of oxytricha fallax and paramecium caudatum was found 307.744 +/- 33.27 mg l(-1) and 332.284 +/- 57.52 mg l(- ... | 2010 | 21387909 |
| thermal performance curves of paramecium caudatum: a model selection approach. | the ongoing climate change has motivated numerous studies investigating the temperature response of various organisms, especially that of ectotherms. to correctly describe the thermal performance of these organisms, functions are needed which sufficiently fit to the complete optimum curve. surprisingly, model-comparisons for the temperature-dependence of population growth rates of an important ectothermic group, the protozoa, are still missing. in this study, temperature reaction norms of natura ... | 2011 | 21277756 |
| morphological apoptotic characteristics of the post-meiotic micronuclei in paramecium caudatum. | in a previous study, the apoptotic degeneration of meiotic products outside the paroral region of paramecium caudatum was indirectly demonstrated by means of "apofluor" staining. in this experiment, conjugating pairs and exconjugants of p. caudatum were stained with either "apofluor" or carbol fuchsin or both to find some direct evidence to demonstrate the apoptotic characteristics of this process. as a result, asynchronous meiotic nuclear degeneration was observed. furthermore, a number of addi ... | 2010 | 20494562 |
| extreme heterogeneous composition of the paramecium caudatum macronuclear genomic dna between hemoglobin and nucleosome assembly protein-1 genes. | the intergenic region between the hemoglobin (hb) and nucleosome assembly protein-1 (nap-1) genes in the paramecium caudatum macronuclear genome was previously found to be heterogeneously composed. cloning of this intergenic region from the macronuclear genomic dna identified four unique dna fragments of different sizes. sequencing of the cloned fragments revealed extreme heterogeneity and characteristics of both internal eliminated sequence (ies) and imprecise internal deletion sequences (iidss ... | 2010 | 20410661 |
| the presence of chimeric dna consisting of 5' regions of the hemoglobin and nucleosome assembly protein-1 genes in paramecium caudatum macronuclear genomic dna. | we detected an unexpected small-sized dna fragment during polymerase chain reaction (pcr) analysis of the heterogeneity of a macronuclear intergenic region of paramecium caudatum. southern blotting of total genomic dna with the pcr product as a probe indicated that the small-sized dna fragment constituted part of the macronuclear genome. sequencing revealed that the pcr product was a chimeric dna structure that may be generated by tail-to-tail fusion of the 5' region of the hemoglobin (hb) gene ... | 2009 | 19798919 |
| [evaluation of the toxicity of returned and natural waters by biotesting techniques]. | the background of the development of a new procedure for calculating the value of water toxicity, by using the test object--paramecium caudatum infusoria is successively set forth. a series of experiments analyzing the toxic effect of water on the infusoria have been carried out by nongraphic method using the probit analysis. the high coefficient of a correlation between the unified toxicity values obtained by an example of various test objects allows adequate comparison of these results, which ... | 2009 | 19642552 |
| studies of paramecium caudatum by means of scanning electron microscope and projection x-ray microscope. | samples of paramecium caudatum are observed by means of a scanning electron microscope (sem) and a projection x-ray microscope (xrm) with computer tomography (ct) function. the samples are fixed with two kinds of fixatives, glutaraldehyde and osmium-tetra oxide acid. after the fixation and replacement procedure with t-buthyl alcohol, the samples followed by a freeze drying, well retain their structures. surface structures, cilia and microfibrillar systems including infraciliary lattice structure ... | 2009 | 19581701 |
| novel features of computer-simulated clonal life of paramecium caudatum. | the clone of the ciliated protozoan paramecium caudatum has the immaturity period of about 60 fissions and the lifespan of about 600 fissions. these life cycle figures have been depicted through laboratory experiments that allow continuous cell divisions for hundreds, which never occur in nature. we here constructed the nature-mimicking model culture that alternated the log- and stationary phases to allow conjugation, and computer-simulated the age structure modifying parameters such as cell dis ... | 2009 | 19490859 |
| a long-term conservation tool for cell characteristics: cryopreservation of paramecium caudatum. | | 2009 | 19427813 |
| cellular communication through light. | information transfer is a fundamental of life. a few studies have reported that cells use photons (from an endogenous source) as information carriers. this study finds that cells can have an influence on other cells even when separated with a glass barrier, thereby disabling molecule diffusion through the cell-containing medium. as there is still very little known about the potential of photons for intercellular communication this study is designed to test for non-molecule-based triggering of tw ... | 2009 | 19340303 |
| [biological effects of electromagnetic radiation of extremely high frequencies combined with physiologically active compounds]. | the study of the action of the electromagnetic radiation (emr) of low intensity (10 microw/cm2) in the range of frequencies 120-170 ghz at the test-reaction of infusoria paramecium caudatum was carried out. the resonant character of the effects was established. the emr action at 156.6 and 161.3 ghz caused the increase of infusorians mobility, the action at frequencies 151.8, 155.7, 167.1 ghz caused the mobility reduction. isolated and combined with emr effects of nicotine (10(-4)-10(-15) mol/l) ... | 2016 | 18825995 |
| survival of paramecium caudatum at various ph values and under normoxic and hypoxic conditions. | the objective of this study was to determine the survival of paramecium caudatum, a protozoan ciliate, with different ph under normoxic and hypoxic conditions. p. caudatum was exposed to 18 treatments (in triplicate) of varying ph (4, 4.7, 5.7, 6.7, 7.7, 8.7, 9.7, 10.7 and 11.7) with two different conditions of normoxic and hypoxic. survival was examined every second day for three weeks. p. caudatum mortality was 100% immediately when exposed to ph 4, 10.7 and 11.7 either in normoxic or hypoxic ... | 2008 | 18817161 |
| finding gas migration pathways in proteins using implicit ligand sampling. | implicit ligand sampling is a practical, efficient, and accurate method for finding the gas migration pathways for small hydrophobic gas molecules, such as oxygen, inside proteins. the method infers the gas migration pathways by calculating the potential of mean force for the gas molecule everywhere inside the protein by means of a molecular dynamics simulation of the protein in the absence of the gas molecule. pathways can be constructed by connecting the areas of the protein that are favorable ... | 2008 | 18433641 |
| calcium regulates independently ciliary beat and cell contraction in paramecium cells. | intracellular ca(2+) concentration is a well-known signal regulator for various physiological activities. in many cases, ca(2+) simultaneously regulates individual functions in single cells. how can ca(2+) regulate these functions independently? in paramecium cells, the contractile cytoskeletal network and cilia are located close to each other near the cell surface. cell body contraction, ciliary reversal, and rises in ciliary beat frequency are regulated by intracellular ca(2+) concentration. h ... | 2008 | 18179819 |
| oxygen affinity controlled by dynamical distal conformations: the soybean leghemoglobin and the paramecium caudatum hemoglobin cases. | the binding of diatomic ligands, such as o(2), no, and co, to heme proteins is a process intimately related with their function. in this work, we analyzed by means of a combination of classical molecular dynamics (md) and hybrid quantum-classical (qm/mm) techniques the existence of multiple conformations in the distal site of heme proteins and their influence on oxygen affinity regulation. we considered two representative examples: soybean leghemoglobin (lba) and paramecium caudatum truncated he ... | 2007 | 17469189 |
| direct observation of histone h2b-yfp fusion proteins and transport of their mrna between conjugating paramecia. | cytoplasmic exchange between conjugating cells of paramecium caudatum has been implicated by mating experiments using wild-type and behavioral mutant cells. to observe macromolecular transport between mating cells, we cloned and expressed the p. caudatum histone h2b gene as a fusion protein attached to an enhanced yellow fluorescent protein (yfp) named pcvenus. significant fluorescent signals derived from histone h2b-pcvenus were detected throughout the macro- and micronuclei of transformant cel ... | 2007 | 17408886 |
| interaction of two swimming paramecia. | the interaction between two swimming paramecium caudatum was investigated experimentally. cell motion was restricted between flat plates, and avoiding and escape reactions were observed, as well as hydrodynamic interactions. the results showed that changes in direction between two swimming cells were induced mainly by hydrodynamic forces and that the biological reaction was a minor factor. numerical simulations were also performed using a boundary element method. p. caudatum was modelled as a ri ... | 2006 | 17079716 |
| swimming paramecium in magnetically simulated enhanced, reduced, and inverted gravity environments. | earth's gravity exerts relatively weak forces in the range of 10-100 pn directly on cells in biological systems. nevertheless, it biases the orientation of swimming unicellular organisms, alters bone cell differentiation, and modifies gene expression in renal cells. a number of methods of simulating different strength gravity environments, such as centrifugation, have been applied for researching the underlying mechanisms. here, we demonstrate a magnetic force-based technique that is unique in i ... | 2006 | 16916937 |
| alteration of developmental program in paramecium by treatment with trichostatin a: a possible involvement of histone modification. | in the ciliate paramecium caudatum, the somatic macronucleus for the next generation differentiates from a zygotic germinal micronucleus during conjugation. subsequently, progeny are programmed to enter a sexually "immature" period, during which cells do not mate. this programming occurs at a critical period during the fifth cell cycle after conjugation. here, we show that treatment with trichostatin a, a histone deacetylase inhibitor, leads to a partial recovery of mating reactivity in immature ... | 2006 | 16839811 |
| selection of the germinal micronucleus in paramecium caudatum: nuclear division and nuclear death. | each cell of paramecium caudatum has a germinal micronucleus. when a bi-micronucleate state was created artificially by micronuclear transplantation, both micronuclei divided for at least 2 cell cycles after nuclear transplantation. however, this bi-micronucleate state was unstable and reduced to a uni-micronucleate state after several fissions. although the number of micronuclei was usually 1 during the vegetative phase, 4 presumptive micronuclei differentiated after conjugation. at the first p ... | 2006 | 16677339 |
| aligning paramecium caudatum with static magnetic fields. | as they negotiate their environs, unicellular organisms adjust their swimming in response to various physical fields such as temperature, chemical gradients, and electric fields. because of the weak magnetic properties of most biological materials, however, they do not respond to the earth's magnetic field (5 x 10(-5) tesla) except in rare cases. here, we show that the trajectories of paramecium caudatum align with intense static magnetic fields >3 tesla. otherwise straight trajectories curve in ... | 2006 | 16461406 |
| effects of perfluorinated amphiphiles on backward swimming in paramecium caudatum. | pfos and pfoa are ubiquitous contaminants in the environment. we investigated the effects of fluorochemicals on calcium currents in paramecium caudatum using its behavioral changes. negatively charged amphiphiles prolonged backward swimming (bws) of paramecium. pfos significantly prolonged bws, while pfoa was less potent (ec(50): 29.8+/-4.1 and 424.1+/-124.0microm, respectively). the bws prolongation was blocked by cadmium, indicating that the cellular calcium conductance had been modified. the ... | 2006 | 16300727 |
| effects of static magnetic fields on growth of paramecium caudatum. | little is known about the influence of magnetic fields on growth of primitive eukaryotes such as the ciliate paramecium. the latter are known to exhibit interesting characteristics such as electrotaxis, gravitaxis, and membrane excitability not commonly encountered in higher organisms. this preliminary study reports the effects of static magnetic fields on growth of paramecium caudatum. the microorganisms were either permanently or 24 h on-and-off exposed to north and south polarity magnetic fie ... | 2006 | 16283650 |
| behavioral responses of the ciliated protozoan paramecium caudatum to 2,4-dichlorophenoxyacetic acid and its analogues. | we found that the ciliated protozoan paramecium caudatum on-1 was repelled by 2,4-dichlorophenoxyacetic acid (2,4-d). p. caudatum was also repelled by phenoxyacetic acid, while it was attracted to benzoic acid. no significant behavioral response was detected with 2,4-dichlorophenol (2,4-dp) and phenol. these results suggested that the substitution of-oh of phenol with -och2cooh, but not the chlorination of phenol, was important for eliciting the avoiding response to 2,4-d in p. caudatum. electro ... | 2002 | 16233224 |
| experimental and mathematical modeling of the consumer's influence on productivity of algae in a model aquatic ecosystem. | a "producer-consumer" (chlorella vulgaris-paramecium caudatum) closed aquatic system has been investigated experimentally and theoretically. it has been found that there is a direct relationship between the growth of the paramecia population and their release of ammonia nitrogen, which is the best form of nitrogen for chlorella growth. the theoretical study of a model of a "producer-consumer" aquatic biotic cycle with spatially separated compartments has confirmed the contribution of paramecia t ... | 2005 | 16175674 |
| [an experimental study and a mathematical model of interactions in mixed culture of invertebrates and algae in the "producer-consumer" aquatic biotic cycle]. | an experimental investigation was carried out, and a mathematical model of interaction between invertebrates (infusoria paramecium caudatum and rotifera brachionus plicatilis) and algae (chlorella vulgaris and scenedesmus quadricauda) in the "producer-consumer" aquatic biotic cycle with spatially divided links was constructed. the model describes the dynamics of a mixed culture of infusoria and rotifera in the "consumer" link, when they consume a mixed culture of algae coming from the "producer" ... | 2013 | 15612555 |
| membrane potential responses of paramecium caudatum to external na+. | the membrane potential responses of paramecium caudatum to na+ ions were examined to understand the mechanisms underlying the sensation of external inorganic ions in the ciliate by comparing the responses of the wild type and the behavioral mutant. wild-type cells exhibited initial continuous backward swimming followed by repeated transient backward swimming in the na+-containing test solution. a wild-type cell impaled by a microelectrode produced initial action potentials and a sustained depola ... | 2004 | 15572860 |
| [a computer method for the evaluation of paramecium motor activity using video records of their movement]. | a method for the evaluation of paramecium caudatum motility was proposed as a tool for the investigation of magnetobiological as well as other physical and chemical effects. the microscopically observed movement of paramecia is recorded and processed using a special software program. the protozoan motility is determined as a function of their mean velocity in a definite time. the main advantages of the method are that it is easily modified for determining various characteristics of the motor act ... | 2006 | 15458256 |
| centrin is essential for the activity of the ciliary reversal-coupled voltage-gated ca2+ channels. | voltage-gated ca(2+) channels play a critical role in controlling ca(2+) entry in various cells. ciliary reversal in paramecium depends on the ca(2+) influx through voltage-gated ca(2+) channels on the ciliary membrane. one of the voltage-gated ca(2+) channel mutants in paramecium caudatum, cnrc, neither produces ca(2+) action potentials nor responds to any depolarizing stimuli. here, we report that the cnrc(+) gene product is p. caudatum centrin (pccentrin1p), a member of the ca(2+)-binding ef- ... | 2004 | 15381084 |
| delayed degradation of parental macronuclear dna in programmed nuclear death of paramecium caudatum. | in the ciliated protozoan paramecium caudatum, a parental macronucleus that is fragmented into some 40-50 pieces during conjugation does not degenerate immediately, but persists until the eighth cell cycle after conjugation. here we demonstrate that the initiation of the parental macronuclear degeneration occurs at about the fifth cell cycle. the size of parental macronuclear fragments continued to increase between the first and fourth cell cycle, but gradually decreased thereafter. by contrast, ... | 2004 | 15354289 |
| k+-induced ca2+ conductance responsible for the prolonged backward swimming in k+-agitated mutant of paramecium caudatum. | the k+-agitated (kag) mutant of paramecium caudatum shows prolonged backward swimming in k+-rich solution. to understand the regulation mechanisms of the ciliary motility in p. caudatum, we examined the membrane electrical properties of the kag mutant. the duration of the backward swimming of the kag in k+-rich solution was about 10 times longer than that of the wild type. in response to an injection of the outward current, the wild type produced an initial action potential and a subsequent memb ... | 2003 | 14692448 |
| interactions between newly developed macronuclei and maternal macronuclei in sexually immature multinucleate exconjugants of paramecium caudatum. | the macronucleus of paramecium caudatum controls most cellular activities, including sexual immaturity after conjugation. exconjugant cells have two macronuclear forms: (1) fragments of the maternal macronucleus, and (2) the new macronuclei that develop from the division products of a fertilization micronucleus. the fragments are distributed into daughter cells without nuclear division and persist for at least eight cell cycles after conjugation. conjugation between heterokaryons revealed that t ... | 2003 | 12919103 |
| kinetic modulation in carbonmonoxy derivatives of truncated hemoglobins: the role of distal heme pocket residues and extended apolar tunnel. | truncated hemoglobins (trhbs), are a distinct and newly characterized class of small myoglobin-like proteins that are widely distributed in bacteria, unicellular eukaryotes, and higher plants. notable and distinctive features associated with trhbs include a hydrogen-bonding network within the distal heme pocket and a long apolar tunnel linking the external solvent to the distal heme pocket. the present work compares the geminate and solvent phase rebinding kinetics from two trhbs, one from the c ... | 2003 | 12736253 |
| spatiotemporal sites of dna replication in macro- and micronuclei of the ciliate paramecium caudatum. | spatiotemporal sites of dna replication in macro- and micronuclei of the ciliated protozoan paramecium caudatum were analyzed by confocal laser scanning microscopy following incorporation of the thymidine analogue brdu and indirect immunofluorescence. in the macronucleus, replication sites were localized to numerous small domains and scattered throughout the nucleoplasm. this pattern persisted during all periods of the s phase. a single constant pattern with discrete replication foci was also ob ... | 2003 | 12733642 |
| photolysis of caged calcium in cilia induces ciliary reversal in paramecium caudatum. | intracellular ca(2+) concentration controls both the pattern and frequency of ciliary and flagellar beating in eukaryotes. in paramecium, it is widely accepted that the reversal of the direction of ciliary beating (ciliary reversal) is induced by an increase in intra-ciliary ca(2+) levels. despite this, the ca(2+)-sensitive region of the cilium that initiates ciliary reversal has not been clearly identified. we injected caged calcium into living p. caudatum cells and applied ultraviolet (uv) lig ... | 2003 | 12604576 |
| protein phosphatase 2c is involved in the camp-dependent ciliary control in paramecium caudatum. | forward swimming of the triton-extracted model of paramecium is stimulated by camp. backward swimming of the model induced by ca(2+) is depressed by camp. cyclic amp and ca(2+) act antagonistically in setting the direction of the ciliary beat. some ciliary axonemal proteins from paramecium caudatum are phosphorylated in a camp-dependent manner. in the presence of camp, axonemal 29- and 65-kda polypeptides were phosphorylated by endogenous a-kinase in vitro. these phosphoproteins, however, were n ... | 2003 | 12529856 |
| identification of the ca2+ conductance responsible for k+-induced backward swimming in paramecium caudatum. | membrane potential responses of paramecium caudatum to an application of k+-rich solution were examined to understand the mechanisms underlying k+-induced backward swimming. a wild-type cell impaled by a microelectrode produced action potentials followed by a sustained depolarization in response to an application of a k+-rich test solution. after termination of the application, a prolongation of the depolarization (depolarizing after-potential) took place. behavioral mutants incapable of exhibit ... | 2002 | 12474080 |
| microtubules mediate germ-nuclear behavior after meiosis in conjugation of paramecium caudatum. | microtubule dynamics in paramecium caudatum were investigated with an anti-alpha-tubulin antibody and a microinjection technique to determine the function of microtubules on micronuclear behavior during conjugation. after meiosis, all four haploid micronuclei were connected by microtubular filaments to the paroral region and moved close to this region. this nuclear movement was micronucleus-specific, because some small macronuclear fragments transplanted from exconjugants never moved to the regi ... | 2006 | 11908901 |
| transformation of paramecium caudatum with a novel expression vector harboring codon-optimized gfp gene. | we have developed a novel expression vector, ptub-tel3, for transformation in paramecium caudatum. the vector was constructed by cloning p. caudatum alpha-tubulin 5' and 3' non-coding regions. to examine transformation with the ptub-tel3 construct, we chose the green fluorescent protein (gfp) as a selection marker. when a linearized ptub-tel3 vector containing a gfp open reading frame was injected into the macronucleus, the gfp transcript was expressed in many clones whereas protein expression w ... | 2002 | 11891064 |
| [a computer method for assessing the average rate of movement of paramecium caudatum by a cross-sectional light beam]. | the possibility of using the motility of paramecium caudatum for computer biotesting of toxic substances was studied. the method is based on measuring the number and duration of impulses that arise when protozoa chaotically moving in a layer 0.5 mm thick cross a red light beam (1 mm in diameter). it was found that, in the presence of cu2+ ions and menadione bisulfite, a compound having prooxidant properties, the number of impulses decreased with a concurrent increase in the duration of impulses. ... | 2006 | 11855298 |
| odd mating-type substances may work as precursor molecules of even mating-type substances in paramecium caudatum. | mating-type substances are key molecules in the sexual recognition of the odd (o) and even (e) complementary mating-type cells in paramecium caudatum. indirect evidence suggested that the substances were proteins and were located on ventral surface cilia. monoclonal antibodies inhibiting the mating reactivity of the o cells have been obtained. using these antibodies, we tried to detect antigen molecules as dot-blot signals. strong dot-blot signals of antigens were only detected from the mating r ... | 2006 | 11831778 |
| aversive and attractive properties of electrical stimulation for paramecium caudatum. | although there are data to show that mild electrical stimulation from a cathode source can serve as positive or attractive stimulus for paramecia, the properties of anode stimulation have not been clear. this research gives evidence to support the previously reported positive properties of cathode stimulation but showed that anode stimulation has opposite (negative or aversive) properties. | 2001 | 11783560 |
| organization and expression of the paramecium caudatum gene encoding nucleosome assembly protein 1. | the complete genomic and partial complementary dnas encoding the ciliate paramecium caudatum nucleosome assembly protein 1 (nap1) have been sequenced. the nap1 gene is situated 1.2 kbp from the hemoglobin (hb) gene, with the 3' end of both genes facing each other. the nap1 gene contains no introns, and encodes a protein of 369 amino acid residues with a calculated molecular weight of 42,627. the p. caudatum nap1 amino acid sequence shares only 23-27% identity with nap1 amino acid sequences from ... | 2001 | 11738823 |
| zooplankton in the artificial pond of the botanical garden of the jagiellonian university in kraków. | paramecium caudatum and the predominant zooplanton organisms were registered in the studied pond of the botanical garden of the jagiellonian university in kraków. the finding of stentor coeruleus indicates an improvement in the environmental conditions in kraków, connected with the partial liquidation of the huge steelworks. | 2001 | 11732172 |
| negative gravitactic behavior of euglena gracilis can not be described by the mechanism of buoyancy-oriented upward swimming. | gravitactic behavior of microorganisms has been known for more than a hundred years. euglena gracilis serves as a model system for gravity-triggered behavioral responses. two basic mechanisms are discussed for gravitaxis: one is based on a physical mechanism where an asymmetric mass distribution pulls the cell passively in the correct orientation and, in contrast, the involvement of an active sensory system. a recently developed high-resolution motion-tracking system allows the analysis of singl ... | 1999 | 11542631 |
| theoretical and experimental dissection of gravity-dependent mechanical orientation in gravitactic microorganisms. | mechanisms of gravitactic behaviors of aquatic microorganisms were investigated in terms of their mechanical basis of gravity-dependent orientation. two mechanical mechanisms have been considered as possible sources of the orientation torque generated on the inert body. one results from the differential density within an organism (the gravity-buoyancy model) and the other from the geometrical asymmetry of an organism (the drag-gravity model). we first introduced a simple theory that distinguishe ... | 2001 | 11526060 |
| expression of telomerase reverse transcriptase and telomere elongation during sexual maturation in paramecium caudatum. | paramecium caudatum has a sexually immature period that lasts for about 60 fissions. to examine the possibility that telomere length is one of the determining factors of the duration of immaturity, we cloned the telomerase reverse transcriptase (tert) gene from p. caudatum, and analyzed its expression levels at mrna, telomerase activity, and telomere length during the course of clonal division. paramecium tert (pc_tert) cdna encodes a basic protein of 107 kda that harbors conserved rt motifs, t ... | 2001 | 11250070 |
| atp-regenerating system in the cilia of paramecium caudatum. | the energy supply for eukaryotic ciliary and flagellar movement is thought to be maintained by atp-regenerating enzymes such as adenylate kinase, creatine kinase and arginine kinase. in this study, the energy-supplying system for the ciliary movement of paramecium caudatum was examined. arginine kinase and adenylate kinase activities were detected in the cilia. to demonstrate that phosphoarginine satisfactorily supplies high-energy phosphate compounds into the narrow ciliary space, we prepared a ... | 2001 | 11222125 |
| changes in succinate dehydrogenase (sdh) activity in paramecium caudatum cells in culture as function of age. | sdh activity and its frequency distributions were determined cytophotometrically to investigate the change in respiratory oxidative energy metabolism in paramecium caudatum (p. caudatum) cell populations during their growth in cell culture. cells from 3 separate cultures were examined on day 2, 5 and 11 post-inoculation as measures of logarithmic, early and late stationary phases, respectively. sdh activity per individual cell is expressed as the increase in total absorbance (ta) at 590 nm of ni ... | 2000 | 10824615 |
| control of ciliary orientation through camp-dependent phosphorylation of axonemal proteins in paramecium caudatum. | ciliary reorientations in response to camp do not take place after a brief digestion with trypsin in ciliated cortical sheets from triton-glycerol-extracted paramecium. in this study, we examined the effects of tryptic digestion on the camp-dependent phosphorylation of axonemal proteins to clarify the relationship between phosphorylation and ciliary reorientation. as reported for paramecium tetraurelia, camp stimulated phosphorylations of the 29 kda and 65 kda axonemal polypeptides also in param ... | 2000 | 10744859 |
| [determination of growth parameters of the paramecium caudatum test-system during standardization of studies of biological activity of chemicals]. | | 1999 | 10445151 |
| disturbance of the determination of germinal and somatic nuclei by heat shock in paramecium caudatum. | during conjugation of paramecium caudatum, nuclear determination occurs soon after the third postzygotic division: one of the four anterior nuclei becomes the micronucleus and the remaining three degenerate, while four posterior nuclei differentiate into macronuclear anlagen. macronuclear differentiation is supposed to be dependent on a cytoplasmic differentiation factor. in this study, postzygotic cells were subjected to heat shock for 30 min and nuclear changes were observed by staining with c ... | 2013 | 10188260 |
| phosphohydrolytic activity in paramecium caudatum at neutral ph. | phosphohydrolytic activity was cytochemically characterized in paramecium caudatum, a ciliated protozoa, at neutral ph. we stained cells in the presence of several mononucleotides as substrates, namely adenosine 5'-monophosphate (5'-amp), adenosine 2'-monophosphate, guanosine 5'-monophosphate (5'-gmp) and beta-glycerophosphate (beta-glp) using a lead capture method at 37 degrees c. cells were also incubated in the presence of 5'-amp with the inhibitor for alkaline phosphatase, tetramisole. in al ... | 1998 | 9842419 |
| an exocytotic mutant of paramecium caudatum: membrane fusion without secretory contents release. | this is a detailed characterization of a secretory mutant incapable of releasing secretory contents despite normal exocytotic membrane fusion performance. trichocyst non-discharge strain tnd1 of paramecium caudatum and its wildtype (wt) both show a transient cortical [ca2+]i increase and exocytotic membrane fusion in response to the polyamine secretagogue, aminoethyldextran (aed), or to caffeine. tnd1 cells frequently display spontaneous ca2+ signals parallelled by spontaneous exocytotic membran ... | 1998 | 9681197 |
| relaxation and activation of graviresponses in paramecium caudatum. | the kinetics of gravitaxis and gravikinesis in paramecium caudatum were investigated by employing (1) step transitions from normal gravity (1 g) to weightlessness (microgravity) and (2) turns of the experimental chambers from the horizontal to the vertical position at 1 g. the transition to microgravity left existing cell orientations unchanged. relaxation of negative gravitaxis under microgravity took longer than 10 s and may be described by the time constant of the decay of orientation coeffic ... | 1998 | 9639585 |
| succinate dehydrogenase (sdh) activity in single paramecium caudatum cells. | we measured in situ the activity of succinate dehydrogenase (sdh), one of the mitochondrial marker enzymes, in single paramecium cells. sdh activity was detected with nitroblue tetrazolium (nitro bt). images of cells were captured every 30 sec at 590 nm, nearly the isosbestic wavelength of two reduction products of nitro bt, by using a microphotometric system for image analysis. activity was estimated by the slope of linear regression lines representing the relationship between total absorbance ... | 1998 | 9542579 |
| thermoregulatory changes by hypoxia: lessons from the paramecium. | 1. in organisms ranging from paramecia to mammals, hypoxia elicits a regulated decrease in body temperature (tb). a decrease in tb is an important adaptation to hypoxia primarily because it lowers metabolic rate when oxygen supply is limited, thus facilitating survival. 2. although this beneficial response is extremely widespread among taxa, little is known of the cellular mechanisms that mediate hypoxia-induced decreases in tb. this is due, in large part, to the extreme complexity of vertebrate ... | 1998 | 9493509 |
| membrane potential responses of paramecium caudatum to bitter substances: existence of multiple pathways for bitter responses | the membrane potential responses of paramecium caudatum to the external application of bitter substances were examined by employing conventional electrophysiological techniques. mutant cells defective in voltage-gated ca2+ channels were used to record the potential responses in the absence of contamination by ca2+ action potentials. the cells produced a transient depolarization followed by a transient hyperpolarization in response to a rapid whole-cell application of chloroquine, strychnine nitr ... | 1998 | 9390932 |
| variable telomeric repeat synthesis in paramecium tetraurelia is consistent with misincorporation by telomerase. | telomeric dna at the ends of chromosomes consist of short, tandem repeat sequences. the telomeres of paramecium tetraurelia are made up of variable repeats, whereas paramecium caudatum telomeric repeats are largely invariant. to investigate variable repeat synthesis in p. tetraurelia, mutated telomerase rna genes were expressed in vivo. we demonstrate that the p. caudatum telomerase rna can participate in telomere synthesis when expressed in the p. tetraurelia macronucleus, despite 24% primary s ... | 1997 | 9214639 |
| locus-dependent profiles of the rescue of nonexcitable behavioral mutants during conjugation in paramecium caudatum. | non-excitable mutants of paramecium caudatum, cnr (caudatum non-reversal) are unable to show the avoiding reaction due to the malfunction of voltage dependent ca2+ channels. cnr mutants are divided into four complementation groups and are controlled by four genes at different loci: cnra, cnrb, cnrc, and cnrd. when cnr mutants are mated with the wild type, the mutant cell temporarily expresses the wild-type phenotype (called conjugation rescue). transfer of diffusible wild-type gene products to t ... | 1995 | 8825064 |
| elucidation of nucleus-cytoplasm interaction: change in ability of the nucleus to express sexuality according to clonal age in paramecium. | the expression of sexual activity in paramecium caudatum is repressed for about 50 fissions after conjugation. the ability of the macronucleus to affect the expression of sexual activity according to the age of clonal development was investigated using the macronuclear fusion-reorganization method. when a mature macronucleus was transplanted into an immature cell and fused with a macronucleus in the immature cell, the clones derived from the recipient showed sexual immaturity. in a reverse exper ... | 1995 | 8719873 |
| induction of the thigmotaxis in paramecium caudatum. | induction of thigmotaxis in paramecium caudatum was examined. we succeeded in the induction by changing the ionic concentration and the ja-value ([k+]/[ca2+]1/2) of the surrounding medium. p. caudatum showed thigmotaxis stably in the solution containing a relatively high ionic concentration but a lower ja-value. we found that the paramecium cell touched the object with the tip of its oral groove and the cilia touching the object scarcely beat when the organism showed thigmotaxis. | 1995 | 7704627 |
| hairpin and dimer structures of linear plasmid-like dnas in mitochondria of paramecium caudatum. | the molecular structure of plasmid-like dnas (designated type-ii) which were isolated from mitochondria in the ciliated protozoan paramecium caudatum was characterized. these type-ii dnas are always detected as a set of four kinds with sizes of 8.2, 4.1, 2.8 and 1.4 kb. the dnas of 8.2 and 2.8 kb exist as dimers consisting of 4.1- and 1.4-kb monomer molecules, respectively. electron microscopic observations indicated configurations of a hairpin structure that had a protruding end of single-stran ... | 1994 | 7750152 |
| interactions between cellular respiration and thermoregulation in the paramecium. | an important adaptation to hypoxia is a regulated reduction in body temperature because it lowers metabolic rate when oxygen supply is limited. although this beneficial response occurs in organisms ranging from protozoans to mammals, little is known of the cellular mechanisms responsible for the hypoxia-induced reduction in temperature. using the unicellular protozoan, paramecium caudatum, we showed that inhibition of oxidative phosphorylation with sodium azide (nan3) under normoxic conditions m ... | 1994 | 8048642 |
| comparison between thermoreceptor and mechanoreceptor currents in paramecium caudatum | 1. a voltage-clamped paramecium produced an inward membrane current upon thermal or mechanical stimulation of its anterior region, whereas it produced an outward membrane current upon similar stimulation of its posterior region. 2. anterior thermo- and mechanoreceptor currents decreased when the membrane potential was shifted in a positive direction, showing sign reversal at a positive membrane potential, whereas posterior thermo- and mechanoreceptor currents decreased when the membrane potentia ... | 1994 | 9317455 |
| immunological similarities among trichocyst secretory proteins of paramecium caudatum, paramecium tetraurelia and pseudomicrothorax dubius. | secretory vesicles called trichocysts structurally show a body and a tip in paramecium and a shaft and four arms in pseudomicrothorax. biochemical and immunological relationships between both trichocyst types were examined. three polyclonal antibodies were produced against 3 groups of protein bands of isolated pseudomicrothorax dubius trichocysts separated by one-dimensional gel electrophoresis: g 1 (30-31 kda), g 2 (26-27 kda) and g 3 (15-20 kda). by indirect immunofluorescent binding assay, th ... | 1993 | 23195742 |
| structure of the paramecium caudatum gene encoding the b-type of the major hemoglobin component. | we have found the gene (hb) encoding the b-type of the major hemoglobin (hb) component in the ciliated protist, paramecium caudatum, stock k33 of syngen 3. gene hb, which encodes a protein consisting of 116 amino acids (aa), had the same sequence as the a-type hb in this species, with the exception of 10 nucleotides (nt) reflecting 5 single-aa differences. the coding region was interrupted at the position between codons 62 and 63 by one short intron, which was comparable with the second intron o ... | 1993 | 8482540 |
| the soret magnetic circular dichroism of ferric high-spin myoglobins. a probe for the distal histidine residue. | to find a simple criterion for the presence of the distal (e7) histidine residue in myoglobins and hemoglobins, the soret magnetic-circular-dichroic spectra were examined for ferric metmyoglobins from various species. a distinct and symmetric dispersion-type curve was obtained for myoglobins containing the distal histidine, whereas a relatively weak and unsymmetric pattern was observed for myoglobins lacking this residue, such as those from three kinds of gastropodic sea molluscs, a shark and th ... | 1992 | 1446682 |
| the unique structure of the paramecium caudatum hemoglobin gene: the presence of one intron in the middle of the coding region. | the gene encoding hemoglobin (hb) in the ciliated protist, paramecium caudatum, has been cloned and sequenced. a single hb locus was detected on an isolated genomic fragment with a size of approx. 15 kbp. this gene contained 443 bp. the 5' transcriptional regulatory region contained tata box- and caat box-like sequences which resemble the structure of the promoter region in higher eukaryotic genes. the amino acid sequence deduced from the gene agreed precisely with that of the major hb component ... | 1992 | 1420365 |
| inter- and intrasyngenic variations of the hemoglobin components in paramecium caudatum. | the ciliated protozoan paramecium contains hemoglobin in heterogeneous monomeric forms. in particular, paramecium caudatum is characterized by the presence of a major component called hb10 and a basic component named bhb. we found that in p. caudatum both of these hemoglobin components show some variation according to stock. the types and distributions of these hemoglobin components were examined on 16 stocks in five different syngens and one stock in an unidentified syngen using high performanc ... | 2008 | 1522547 |
| dihydroxy-carotenoid liposomes inhibit phototoxicity in paramecium caudatum. | the phototoxic effects of hematoporphyrin derivative, using paramecium caudatum as a model system, are significantly reduced in the presence of carotenoid-containing liposomes. multilammelar large or small unilammelar vesicles, containing specific carotenoids, were effective in protecting the organism, whether administered exogenously in the bathing solution, or via incubation of paramecia in starved culture media containing carotenoid liposomes. the effectiveness of the carotenoids as inhibitor ... | 1992 | 1438577 |
| behavioral hypothermia and survival of hypoxic protozoans paramecium caudatum. | hypoxia has been shown to elicit behavioral hypothermia in a number of different metazoan species, all with nervous systems. the protozoan, paramecium caudatum, has no nervous system and was not expected to display behavioral hypothermia. however, this species was also found to select a lower temperature in a thermal gradient under hypoxic conditions. this response proved to be beneficial as survival of hypoxic paramecia was greatly increased at lower temperatures. this unicellular species may p ... | 1992 | 1542790 |
| behavior and dna synthesis of the nuclei produced after meiosis in paramecium caudatum. | haploid micronuclei produced by meiosis in paramecium caudatum are destined either to survive or to degenerate depending upon their position in the cytoplasm. the behavior of the four meiotic division products in living cells and their dna synthesis patterns were examined to determine whether there were differences between nuclei destined to survive and those destined for degeneration. some prospective degenerating nuclei divided, as did the surviving nuclei, but then became pycnotic immediately ... | 1992 | 23194980 |
| behavior of germinal micronuclei under control of the somatic macronucleus during conjugation in paramecium caudatum. | in conjugating pairs of paramecium caudatum, the micronuclear events occur synchronously in both members of the pair. to find out whether micronuclear behavior is controlled by the somatic macronucleus or by the germinal micronucleus, and whether or not synchronization of micronuclear behavior is due to intercellular communication between conjugating cells, the behavior of the micronucleus was examined after removal of the macronuclei from either or both cells of a mating pair at various stages ... | 1992 | 1730388 |
| stable and unstable transformation by microinjection of macronucleoplasm in paramecium. | transformation by microinjection of macronucleoplasm in paramecium caudatum was investigated. macronucleoplasm with three genetic markers (behavior, trichocyst, and mating type) was injected into the macronucleus. to facilitate microinjection, in most cases, paramecia were immobilized in a gelatin (7.5%) solution. the injected cells began to express a dominant gene (cnra+ or cnrb+) of the donor 9-24 hr after injection. expression did not require cell division suggesting injected macronucleoplasm ... | 1992 | 1499153 |
| developmental expression of macronuclear specific antigen in paramecium caudatum. | we obtained a monoclonal antibody (ma-1) specific for macronuclei of the ciliate paramecium caudatum and p. dubosqui. immunoblotting showed that the antigen was a polypeptide of 50 kilodalton (kda). during the process of nuclear differentiation in p. caudatum, the ma-1 antigens appeared in the macronuclear anlagen immediately after four out of eight post zygotic nuclei differentiated morphologically into the macronuclear anlagen. afterwards, the antigens could be detected in the macronucleus thr ... | 1992 | 1395142 |
| differential effects of quin-2 and quin 2-am on ciliary responses of paramecium caudatum at moderate calcium levels. | paramecium cells were suspended in a ph 7.1 buffered solution containing various levels of total cacl2 (3.9 to 250 μm), quin-2 or quin 2-am and in the absence or presence of various concentrations of kcl, nacl or bacl(2). at lower calcium levels especially, quin-2 behaved as a potent antagonist of kcl-induced continuous ciliary reversal (50% inhibition at 4 μm) and, at higher concentrations, reduced the duration of periodic ciliary reversal responses to nacl and bacl(2). the efficacy of quin-2 a ... | 1989 | 23195873 |
| cytotoxicity of certain organic solvents and organophosphorus insecticides to the ciliated protozoan paramecium caudatum. | responses of paramecium caudatum, a ciliated protozoan, to acute exposures of certain organic solvents and organophosphorus insecticides (opi) were studied by determining their lethal concentration (10 min-lc100) and median lethal concentration (4 h-lc50). the solvents and opi evoked a distinct sequence of responses. among the five solvents tested, acetone proved most toxic [lc-2.9% and lc50-0.68% (v/v)], while dimethyl sulphoxide (dmso) showed least toxicity [lc-11.0% and lc50-3.16% (v/v)]. the ... | 1989 | 2593868 |
| combined treatment of immune nephropathies with plasmapheresis and immunosuppressants. | the treatment of patients with immune nephropthies is discussed: rapidly progressive nephritis, lupus nephropathy, wegener granulomatosis, goodpasture syndrome, schonlein-henoch nephritis. a combined treatment of plasmapheresis and immunosuppressants is applied. a definite result, specially with the cases of wegener granulomatosis, is registered for certain number of the patients. together with the usual tests: cic, immunoglobulins, complement, etc. a method for controlling of the detoxic effici ... | 2006 | 3252939 |
| meiotic nondisjunction and aneuploids in intersyngenic hybrids of paramecium caudatum. | artificially induced intersyngenic crosses in paramecium caudatum can produce viable and fertile hybrids. when f(1) hybrids of double e mating type (mt(1)/mt(3) or mt(12)/mt(3)) were crossed with mating type o (mt/mt), aberrant segregants of double e and single o type were produced. this segregation was not explained by ordinary equal or unequal crossing over. breeding analyses of these segregants by using linkage between mt and cnra (a behavioral mutant) revealed that they were produced by meio ... | 1985 | 17246304 |
| intracellular positional control of survival or degeneration of nuclei during conjugation in paramecium caudatum. | the survival or degeneration of nuclei produced after meiosis in paramecium caudatum depends upon their position in the cytoplasm. the surviving nucleus lies in the paroral region, which is the region around the cytostome. in this study, this was confirmed by quantitative measurements of the location of surviving nuclei in both stained and living conjugating cells. observation of nuclear behaviour in living cells shows that there is an active mechanism for localizing one of the four meiotic prod ... | 1985 | 3914481 |
| a gamma ray-induced non-excitable membrane mutant in paramecium caudatum: a behavioral and genetic analysis. | | 1985 | 4065563 |
| slow inactivation of the calcium current of paramecium is dependent on voltage and not internal calcium. | the isolated ca2+ current from paramecium caudatum was examined under voltage clamp with long conditioning depolarizations lasting for up to 5 min. the isolated transient ca2+ current inactivates with tens of milliseconds due to ca2+ -dependent ca2+ -channel inactivation (brehm & eckert, 1978). when this fast inactivation was blocked by internally delivered egta, a much slower inactivation of the ca2+ current was discovered. this slow inactivation had time constants of tens of seconds, depending ... | 1985 | 2411920 |
| modulation of the digestive lysosomal system in paramecium caudatum. ii. physiological effects of cytochalasin b, colchicine and trifluoperazine. | the heterophagic pathway of the digestive lysosomal system in paramecium caudatum includes at least four steps: digestive vacuole (dv) formation, acidification-condensation, lysosomal fusion-digestion, and defecation. the second and the third require about 20 min, during which dvs are not egested. because these steps occur at predictable intervals, the mechanism for each can be explored by exposing labeled dvs to different drugs prior to each step. in this study the effects of cytochalasin b (cb ... | 1985 | 4029169 |
| destruction of immaturin activity in early mature mutants of paramecium caudatum. | cells of paramecium in the sexually immature period of the clonal life cycle contain a protein called immaturin, which represses mating activity when injected into sexually mature cells. the amount of immaturin at various stages of the immaturity period was examined by injecting cytoplasm from immature cells of one wild-type and two early mature mutant clones into mature cells of wild-type. the proportion of immature cells brought about by the injection increased until about 10-15 fissions after ... | 1984 | 6533147 |
| retrieval of lysosomal membrane and acid phosphatase from phagolysosomes of paramecium caudatum. | little is known about the fate of lysosomal membrane in phagocytic cells. because the age of the digestive vacuoles in paramecium caudatum can be easily determined, we have been able to study the dynamic membrane events in the older vacuoles. late in the phagolysosomal stage (dv-iii) the vacuole membrane undergoes a burst of tubule formation. the tubules expand into vesicles which have characteristics resembling lysosomes in both thin sections and freeze-fracture replicas. the tubules also conta ... | 1984 | 6501410 |
| resistance of germinal nucleus to aging in paramecium: evidence obtained by micronuclear transplantation. | a diversity of time when increase in mortality after conjugation occurs during the lifespan was found in subclones of three stocks of paramecium caudatum. a possible micronuclear contribution to the increase in sterility has been investigated by micronuclear transplantation. we found two classes of micronuclei in aged clones: those that can function normally if the cytoplasmic environment is young, and those that cannot, even in a young cytoplasmic environment. the results indicate that in the f ... | 1984 | 6748755 |
| modulation of the digestive-lysosomal system in paramecium caudatum. i. effects of temperature. | the heterophagic pathway of the digestive-lysosomal system in axenically grown paramecium caudatum is divisible into vacuole formation, vacuole acidification-condensation, lysosomal fusion-digestion and defecation. these four processes can be separated in time, thus permitting the study of the effects of temperature on each process. the optimal growth temperature for this cell was 27 degrees c. the rate of digestive vacuole (dv) formation at varying temperatures was represented by a skewed bell- ... | 1984 | 6479175 |
| an anticalmodulin drug, w-7, inhibits the voltage-dependent calcium current in paramecium caudatum. | the anticalmodulin drug, w-7 [n-(6 aminohexyl)-5-chloro-1-naphthalenesulphonamide] specifically inhibits the voltage-dependent ca-current of paramecium as well as the behavioural consequence of ca2+ influx, backward swimming. the dechlorinated analogue, w-5, is four to five times less effective. analysis of membrane currents under voltage clamp shows that w-7 not only reversibly inhibits the voltage-dependent ca-current but also shifts the voltage sensitivity of this ca-current towards less nega ... | 1984 | 6747535 |
| effects of dimethylsulfoxide (dmso) on the digestive-lysosomal system in paramecium caudatum. | the effects of dmso (dimethylsulfoxide) on cell growth and on the digestive-lysosomal system of axenically grown paramecium caudatum were studied. a general protocol of exposing cells to different concentrations of dmso at the beginning of each of the four processes in the digestive cycle enabled us to analyze the effect of dmso at each step. vacuole formation and the beginning of a digestive cycle were initiated by adding latex beads to the cells. maximum cell densities at stationary phase of g ... | 1983 | 6667696 |
| intra- and interspecific complementation of membrane-inexcitable mutants of paramecium. | membrane excitation was the basis for backward swimming of paramecium facing stimulus. according to standard genetic tests, inexcitable mutants fell into three complementation groups for both paramecium tetraurelia (pwa, pwb, and pwc) and paramecium caudatum (cnra, cnrb, and cnrc). cytoplasm from a wild type transferred to a mutant through microinjection restored the excitability. transfusions between genetically defined complementation groups of the same species effected curing, whereas transfu ... | 1983 | 6885903 |
| [comparative analysis of the structure of the vacuolar system of the bladder granular cells in the frog and of the contractile vacuole complex of protozoans]. | a comparative morphological study of the vacuolar system of the frog urinary bladder epithelial cells and of the contractile vacuole complex of paramecium caudatum enabled us to reveal some common structural elements in these: spongial channels and general vacuole reservoir. the structural similarity of these organoids seems to be the base of their analogous functions in the cell. detection of vacuoles of various forms in different areas of granular cells may point to a possible migration of the ... | 1983 | 6356532 |
| genes controlling mating-type specificity in paramecium caudatum: three loci revealed by intersyngenic crosses. | in mating interactions in paramecium caudatum, initial mating agglutination is strictly mating-type specific, but subsequent conjugating pair formation is not mating-type specific. using this nonspecificity of pair formation, intersyngenic (intersibling species) pairs were induced by mixing four mating types of two different syngens. to distinguish intersyngenic pairs from intrasyngenic ones, the behavioral marker cnr (takahashi 1979) was mainly used. clones of intersyngenic hybrids showed high ... | 1983 | 17246132 |
| calcium and microtubule sliding in ciliary axonemes isolated from paramecium caudatum. | microtubule sliding was induced in axonemes obtained from isolated cilia of paramecium caudatum when they were exposed to a reactivating solution containing atp after mild treatment with trypsin. over a very wide range of concentrations (1 nm-4 mm), ca2+ in the reactivating solution had no effect on the proportion of axonemes that disintegrated as the result of microtubule sliding. also, the velocity of sliding, determined by cinematography, and the polarity of the direction of sliding-force gen ... | 1983 | 6885936 |
| microspectrophotometric and autoradiographic study of the timing and duration of pre-meiotic dna synthesis in paramecium caudatum. | timing and duration of pre-meiotic g1, s and g2 phases in paramecium caudatum have been clarified by microspectrophotometry of dna content and autoradiography with [3h]thymidine ([3h]dthd) and [3h]deoxyuridinemonophosphate ([3h]dump). microspectrophotometric measurement of dna content showed that cells in stationary phase have a g1 micronucleus, and that pre-meiotic dna synthesis begins with the micronuclear swelling and ends immediately before the nucleus enters meiotic prophase. the results in ... | 1983 | 6874734 |
| effects of protease inhibitors on early events in the conjugation of paramecium caudatum. | the effects of 11 different protease inhibitors on mating reactivity and pair formation in the conjugation process of the ciliated protozoan paramecium caudatum were investigated. of the 11 inhibitors tested, six microbial and three synthetic inhibitors showed no effect on either pair formation or mating reactivity even at their highest concentrations. soybean trypsin inhibitor and ovomucoid also showed no effect on pair formation even though they temporarily repressed mating reactivity. these r ... | 1983 | 6842164 |
| phagosome fusion vesicles of paramecium. ii. freeze-fracture evidence for membrane replacement. | phagosome fusion vesicles (pfvs), a new population of relatively large granules in paramecium caudatum which fuse with the first stage of digestive vacuoles (dv-i) shortly after these vacuoles are released from the cytopharynx (their site of formation), have been studied by using the freeze-fracture technique. identification of pfvs is possible in the resulting replicas at all sites where they are commonly found in thin sections, at the cytopharynx, bound but not fused with nascent digestive vac ... | 1983 | 6832165 |
| attachment of paramecium to polystyrene surfaces: a model system for the analysis of sexual cell recognition and nuclear activation. | in the ciliate paramecium caudatum, only mating-reactive cells can attach to the polystyrene surface of petri dishes. the attachment of mating-reactive cells occurs exclusively at the tips of ventrally located cilia (mating-reactive cilia) and appears to involve a hydrophobic interaction. an increase in the hydrophilic nature of the polystyrene surface following treatment with sulphuric acid results in the loss of attachment of reactive cells. the presence or absence of ca ions and varying the i ... | 1982 | 7183684 |