Publications

cerebrospinal fluid-contacting neurons and other somatostatin-immunoreactive perikarya in brains of tadpoles of xenopus laevis.	in untreated tadpoles of xenopus laevis, stage 60 (nieuwkoop and faber 1956), somatostatin-immunoreactive perikarya and fiber networks are already discernible in the pallium and the septum, as well as in the anterior and posterior hypothalamus. in addition, somatostatin-immunoreactive cerebrospinal fluid (csf)-contacting neurons were found in the periventricular gray of the most caudal division of the ventral tuber cinereum. the results are discussed with respect to the inhibitory influence of t ...	1982	6126275
translation of mrna from phytohemagglutinin-stimulated human lymphocytes: characterization of interferon mrnas.	human lymphocytes obtained by cytapheresis were stimulated in spinner culture conditions by nonpurified pha in order to study the production of gamma interferon, and the characterization of ifn-gamma mrna. titers of interferon prepared in 0.6 to 4 1 batches, varied in 20 preparations from 8,000 to 32,000 units/ml. this interferon was unstable at ph 2: the residual antiviral activity after 20 h treatment was less than 3%. antibodies raised against gamma interferon from con a and sea-stimulated ly ...	1982	6126511
effect of calmodulin inhibitor, stelazine, on the endocytosis of vitellogenin and transglutaminase activity in xenopus laevis oöcytes.	the specific endocytosis of vitellogenin was measured in the presence of various concentrations of stelazine, a specific inhibitor of the calcium regulating protein, calmodulin. stelazine (200 microm) was found to inhibit the endocytosis of vitellogenin by 63% as determined by decreased uptake of vitellogenin into transitional yolk bodies and yolk platelets. the enzymatic activity of transglutaminase, a calcium-requiring enzyme implicated in receptor-mediated endocytosis, was not affected by the ...	1982	6126807
properties of acetylcholine receptors translated by cat muscle mrna in xenopus oocytes.	poly(a)+ mrna, extracted from denervated skeletal muscles of the cat, directs the synthesis of acetylcholine receptors in xenopus laevis oocytes. the receptors are inserted in the oocyte membrane where they form acetylcholine receptor-channel complexes which have properties like those of the native receptors in the muscle membrane.	1982	6144542
effects of cold acclimation on the standard metabolic rate and osmotic fragility of erythrocytes in an aquatic anura, xenopus laevis.		1982	6128127
the effect of temperature on the contractile response of cardiac muscle from two frog species, rana temporaria and xenopus laevis, at two different calcium concentrations-i. at ph 7.7.	1. mechanical parameters were recorded from paced ventricular cardiac muscle strips of two amphibian species. rana temporaria and xenopus laevis. 2. the strips contracted at ph 7.7 and with either 1.6 or 3.0 mm ca2+ while the temperature was changed from 5 to 30 degree c. 3. it is concluded that the cardiac muscles of the two frog species exhibited similar contractile responses upon temperature and ca2+ elevations at physiological ph, although x. laevis hearts displayed greater variation in tens ...	1982	6128130
the effect of temperature on the contractile response of cardiac muscle from two frog species, rana temporaria and xenopus laevis, at two different calcium concentrations-ii. at ph 7.0 and ph 6.6.	1. mechanical parameters were recorded from paced ventricular cardiac muscle strips of two amphibian species. rana temporaria and xenopus laevis. 2. the strips contracted at ph 6.6 and 7.0 with either 1.6 or 3.0 mm ca2+ while the temperature was changed from 5 to 30 degree c. 3. in the hearts of r. temporaria, but not in those of x. laevis, in increased ca2+ concentration at low ph could compensate for the effect of lowered ph. 4. it is concluded that during high co2 tension and/or low ph the m ...	1982	6128131
co-existence of thyrotrophin releasing hormone and 5-hydroxytryptamine in the skin of xenopus laevis.	1. the location, release and re-synthesis of thyrotrophin releasing hormone (trh) and 5-hydroxytryptamine (5-ht) in the skin of xenopus laevis (the south african clawed toad) have been determined using both morphological and analytical procedures. 2. high levels of trh and 5-ht are located specifically within the dermal granular glands of x. laevis and discharged from these glands following alpha-adrenergic stimulation. 4. the common occurrence and separate production of high levels of trh and 5 ...	1982	6128147
forskolin increases camp and inhibits progesterone induced meiosis reinitiation in xenopus laevis oocytes.	the diterpene, forskolin, is a potent and reversible inhibitor of progesterone-induced meiosis in xenopus laevis oocytes (ed50 of inhibition approximately 3 microm). forskolin alone increases camp concentration in oocytes, but, unlike with cholera toxin treatment, there is no lag phase, and reversibility is obtained by washing the cells. progesterone decreases the forskolin effect on camp accumulation, but camp concentration remains above the level observed in oocytes treated with progesterone a ...	1982	6180891
medusoid fibril bodies: a novel type of nuclear filament of diameter 8 to 12 nm with periodic ultrastructure demonstrated in oocytes of xenopus laevis.		1982	6180897
mouse interferon messenger rna: characterization of the xenopus laevis oocyte translation product.		1982	6181741
isolation and characterization of ifn-gamma mrna derived from mitogen-induced human splenocytes.	human splenocytes from large cultures (5 1) were stimulated with staphylococcus enterotoxin a (sea). after 2.5 d of conditioning, poly a+rna was isolated from these cultures and its in-vitro translational capacity was evaluated in a wheat germ extract. injection of the rna into xenopus laevis oocytes yielded a low but reproducible amount of ifn activity, which was neutralizable only by an antiserum to gamma interferon (ifn-gamma) and not by antisera to alpha interferon (ifn-alpha) and/or beta in ...	1982	6182256
a study of the motion of organelles which undergo retrograde and anterograde rapid axonal transport in xenopus.	1. axonally transported organelles were detected optically in myelinated axons from xenopus laevis at room temperature (21-23 degrees c). details of the motion of organelles which were transported in the retrograde and anterograde directions were studied using filmed records.2. a group of 133 organelles with a mean retrograde velocity of 0.91 mum/sec was compared with a group of thirty-nine organelles with a mean anterograde velocity of 0.93 mum/sec.3. averaged power spectra of the positional de ...	1982	6182282
translation in vitro of rna from the human malarial parasite plasmodium falciparum.	rna has been isolated from the human malarial parasite, plasmodium falciparum, and translated in vitro using two systems: rabbit-reticulocyte lysate and xenopus laevis oocytes. polypeptides are synthesized that are characteristic of the parasite isolate and the developmental stage from which the rna was purified. many of these polypeptides are precipitated by antibody from an immune monkey. analysis of the primary structure of these polypeptides should give the information necessary to produce a ...	1982	6182932
regulation of protein synthesis and accumulation during oogenesis in xenopus laevis.		1982	6183158
divergence of the two albumins of x. laevis. evidence for the glycosylation of the major 74k albumin.	the mrnas coding for the 68,000 and 74,000 dalton serum albumins of xenopus laevis were purified by hybridisation to their corresponding cloned cdna and translated using the reticulocyte lysate. the primary translational product of the 68,000 dalton albumin has a molecular weight of 70,000 daltons suggesting that it is synthesised with a signal peptide which is cleaved during secretion. in contrast, the primary translational product of the 74,000 dalton albumin has a molecular weight of 72,000 d ...	1982	6184256
nature of albumin exported from the frog oocyte following microinjection of mouse liver mrna.	microinjections of mouse liver mrna into xenopus laevis oocytes induced efficient export of a polypeptide with an apparent mr or 68,000 which was immunoprecipitable with anti-mouse albumin antibody. analysis of the anti-albumin precipitate of the exported protein by two-dimensional gel electrophoresis showed that the electrophoretic behavior precisely coincided with that of authentic mouse serum albumin. this result indicates that the xenopus oocyte may perform secretory processes similar or ide ...	1982	6176576
sequence organization of the poly(a) rna synthesized and accumulated in lampbrush chromosome stage xenopus laevis oocytes.		1982	6176716
molecular cloning of human immune interferon cdna and its expression in eukaryotic cells.	starting with mrna derived from staphylococcal enterotoxin a induced human splenocytes, dsdna was synthesized and inserted into unique bamhi site of the eukaryotic expression vector psv529 (1). a recombinant plasmid containing human immune interferon (ifn-gamma) cdna was identified by hybridization of plasmid inserted dna bound onto nitrocellulose filters with mrna derived from sea-induced splenocytes, translation of the eluted rna in xenopus laevis oocytes and assaying for ifn activity. plasmid ...	1982	6176945
secretory proteins induced in human fibroblasts under conditions used for the production of interferon beta.	human fibroblast cells treated with a combination of inhibitors of protein and rna synthesis [cycloheximide and actinomycin d as used to superinduce interferon beta (ifn-beta)] secrete two proteins with molecular masses of 22000 and 27000 kilodaltons (called 22-kdal and 27-kdal) that are precipitable with an antiserum raised against impure ifn-beta but are antigenically distinct from ifn-beta 1. translation in vitro of mrna extracted from human fibroblast cells induced for the production of ifn- ...	1982	6178110
persistence of nonribosome bound 5 s rna in full-grown oocytes of xenopus laevis.		1982	6178636
parallel changes in protein synthesis and messenger rna content in growing and resting epithelial cells of xenopus laevis.	the regulation of cell growth can be achieved at many levels but ultimately the regulatory factors must alter protein synthesis since growing cells always exhibit an increased rate of protein synthesis compared to resting cells. some studies using growing and nongrowing mammalian cells have shown that the rate of protein synthesis is directly dependent on mrna content. other studies have shown that growing the resting cells have similar amounts of mrna and that protein synthesis is regulated by ...	1982	6178747
development of the marginal zone in the rhombenecephalon of xenopus laevis.	the marginal zone is the most superficial component of the developing central nervous system. in this study we describe the pattern of formation of the marginal zone in xenopus laevis as seen with the light microscope and correlate its appearance with developing axon bundles seen with the electron microscope. the marginal zone was first identified at stage 26 on the ventrolateral aspects of the neural tube in restrictive foci throughout the medulla. by stage 28 this presumptive fiber area had ex ...	1982	6179577
the determination of the instantaneous velocity of axonally transported organelles from filmed records of their motion.	a computational procedure is described for obtaining reproducible, low noise estimates of the instantaneous velocity of axonally transported organelles. axonally transported organelles were detected in myelinated nerve fibers from xenopus laevis by dark-field microscopy. the motion of the organelles was recorded on motion picture film at 3 frames/s, and the position of organelles travelling in the retrograde direction was obtained as a pair of x (axial) and y (transverse) coordinates at each 0.3 ...	1982	6179589
transcription of a gene for human u1 small nuclear rna.	transcription of u1 small nuclear rna from a 592 bp fragment of human dna was analyzed in vivo and in vitro. when injected into xenopus laevis oocyte nuclei, the cloned dna is transcribed by rna polymerase ii to make human u1 snrna. thus the sequences of this fragment are sufficient for expression of the u1 snrna gene. moreover, injection of templates carrying deletions of flanking sequences demonstrates that the dna sequences required for in vivo transcription are located at least 100 nucleotid ...	1982	6179630
[effects of lindane, an organochlorine insecticide, on the thyroid gland of larvae of xenopus laevis daudin in premetamorphosis].	the effects of 0.5 ppm of lindane were studied on the morphogenesis and the initial functioning of the thyroid gland. some disturbances were observed: the formation of the first follicles were delayed and ultrastructural changes were noted: increase in the number of mitochondria, reduction of the endoplasmic reticulum. this demonstrates a noxious effect of lindane at the beginning of the functional maturation of the thyroid gland.	1982	6188517
developmentally regulated poly(a) containing rna sequences in xenopus laevis.		1982	6125943
a calcium-dependent transient outward current in xenopus laevis oocytes.	membrane currents were investigated in xenopus laevis oocytes under voltage clamp. depolarizing pulses, given from a holding potential of about-100 mv, elicited a transient outward current when the membrane potential was made more positive than about-20 mv. as the potential was made increasingly positive the transient outward current first increased and then decreased. the amplitude of the transient current increased when the external ca2+ concentration was raised; and the current was abolished ...	1982	6127718
polyadenylated mrnas from various developmental stages of xenopus laevis. role of 26 s mrna.	in xenopus laevis embryos, the 26 s polyadenylated mrna, coding for the myosin heavy chain, shows a maximum relative concentration as measured by the 3h-poly(u)-hybridization technique, at the neural-plate stage (st. 12.5 of nieuwkoop and faber, [nf]) only in the dorsal (ectodermal and mesodermal) region, i.e. shortly before the morphological appearance of the somites. on the contrary, myosin-heavy-chain mrna cannot be observed in the ventral region with the same technique. this 26 s mrna begins ...	1982	6128265
effects of d-alpha-aminoadipate on excitation of afferent fibers in the lateral line of xenopus laevis.	the effects of d-alpha-aminoadipate (d alpha aa) on excitation of afferent nerve fibers in the xenopus laevis lateral line were studied in vitro. d alpha aa reversibly suppressed spontaneous activity and excitation induced by water motion at concentrations as low as 0.25-0.5 mm. higher concentrations (up to 10 mm) caused a greater suppression that was rapidly and fully reversible. l-alpha-aminoadipate at 0.25-1.0 mm had no suppressive effects. responses elicited by nmda (1.0-2.0 mm) were the mos ...	1982	6129604
the central projections of lateral line and cutaneous sensory fibres (vii and x) in xenopus laevis.	the central terminal fields of anterior (vii) and posterior (x) lateral line nerves, as well as the somatosensory fibres of vii and x, have been studied in xenopus laevis by cocl2 backfilling of appropriate nerves followed by timms intensification of whole brains. lateral line fibres terminate in a dorsomedial region of the medulla that extends from the auricular lobe of the cerebellum to the obex. there is great overlap in the terminal fields of lateral line fibres from nerves innervating diffe ...	1982	6129631
synthesis of chick brain gaba receptors by frog oocytes.	poly(a)-mrna, extracted from the optic lobe of chick embryos, directs the synthesis of gamma-aminobutyric acid (gaba) receptors in xenopus laevis oocytes. the receptors are inserted into the oocyte membrane, where they form receptor--channel complexes. when activated by gaba, and related agonists, the chick brain receptors open membrane channels that are permeable to chloride ions. thus, xenopus oocytes provide a novel and useful approach to the study of brain receptors.	1982	6129641
localized protein synthesis during oogenesis of xenopus laevis: analysis by in situ translation.		1982	6130012
behavior of individual maternal pa+ rnas during embryogenesis of xenopus laevis.		1982	6130013
transient localizations of messenger rna in xenopus laevis oocytes.		1982	6172301
presence of ranatensin-like and bombesin-like peptides in amphibian brains.	antibodies specific for the carboxyl-terminal regions of bombesin and of ranatensin were used to study the tissue distribution of substances immunochemically similar to these two peptides in three amphibian species. brain extracts of rana catesbeiana, rana pipiens, and xenopus laevis all contained considerable quantities of both types of immunoreactivity, with measured concentrations as high as several hundred pmol per g tissue. the two antibodies used in this study had very low crossreactivity ...	1982	6172810
argyrophilic nuclear and nucleolar proteins of xenopus laevis oocytes identified by gel electrophoresis.		1982	6173244
embryotoxic and teratogenic effects of aqueous extracts of tar from a coal gasification electrostatic precipitator.	aqueous extracts of tar from a coal gasification electrostatic precipitator were tested for its toxic and teratogenic potential in vitro on embryos of the amphibian xenopus laevis. the 96-h lc50 and ec50 were determined to be 0.83% and 0.48%, respectively. the developmental stage of normal-appearing exposed embryos is not affected by increasing concentrations of the extract. embryo growth, however, is significantly reduced at concentrations as low as 0.25%. motility and pigmentation were effecti ...	1982	6122275
changes in energy metabolism during the early development of xenopus laevis.	xenopus embryos at various development stages were incubated in the presence of labelled substrates and the 14co2 production determined. from the rates of oxidation of glucose labelled in positions 1 and 6 and from that of radioactive acetate, pyruvate and glutamate, it was concluded that the embden-meyerhof pathway and the krebs cycle are functional during early embryogenesis, but that their relative participation in the metabolic processes is limited and increases from gastrulation onwards. ea ...	1982	6124469
cloning of xenopus laevis nuclear poly(a)-rich rna sequences. evidence for post-transcriptional control.	cdna/rna hybridization experiments of polysomal and nuclear poly(a)-rich rna from early tadpole stages of xenopus laevis revealed that part of the nuclear poly(a)-rich rna sequences are not present within the polysomal polyadenylated rna. for a more detailed analysis of these sequences we have cloned double-stranded cdna derived from tadpole nuclear poly(a)-rich rna in the psti cleavage site of pbr 322. by colony screening with 32p-labelled cdna from polysomal and nuclear poly(a)-rich rna of the ...	1982	6174330
effects of ototoxic antibiotics on sensory hair cell functioning.	the isolated lateral-line organ of xenopus laevis was used to study reversible effects of low concentrations of aminoglycoside antibiotics on sensory hair cell functioning. extracellular receptor potentials and single fibre afferent nerve activity were recorded during stimulation of the lateral-line organ with sinusoidal water movements. the results show that dihydrostreptomycin in concentrations between 2.5 and 17.5 micrograms/ml caused an increase in spontaneous afferent nerve activity, probab ...	1982	6174496
the spatial pattern of rna in fully grown oocytes of an amphibian, xenopus laevis.	the possibility that maternal rna may be localized in specific oocyte regions was examined in fully grown oocytes of xenopus laevis. these oocytes were subdivided into six regions perpendicular to their animal-vegetal axis. each region was analyzed to determine the amount of total cellular rna, poly(a)+rna, and newly synthesized ribosomal rna. as would be expected from current evidence, total cellular rna was found to exist in a gradient-like fashion, highest at the animal pole and lowest at the ...	1982	6174679
effects of n-methyl-n-nitrosourea on carrier-primed anti-hapten responses in xenopus laevis.	young adult xenopus laevis were treated with n-methyl-n-nitrosourea at doses which temporarily or permanently remove the thymic cortex and suppress allograft immune competence. their ability to mount a carrier-primed, helper t cell-mediated, hapten-specific response was tested in terms of numbers of antigen binding cells in the spleen. animals which had retained skin allografts for more than 300 days lacked helper activity, while those which had eventually rejected their allografts were able to ...	1982	6215271
[detection of collagen by immunofluorescence during development of xenopus (xenopus laevis daud.)].	appearance of the different collagen types was studied during the clawed toad development from hatching to metamorphosis, using indirect immunofluorescence techniques. type-like iv collagen of basement membranes was first seen in the notochord streath. type i, type ii were detected at the same time, followed by type iii. developmental sequence and distribution of the four collagen types indicate the different stages of organogenesis.	1982	6217869
calcium requirement for alpha-msh action on tail-fin melanophores of xenopus tadpoles.	the role of ca2+ in alpha-msh action on melanophores was studied, in vitro, with a bioassay on ventral tail-fin pieces from tadpoles of xenopus laevis. melanosome dispersion induced by alpha-msh required 1-2 mm extracellular ca2+. gradual lowering of the extracellular ca2+ levels produced a concentration-dependent inhibition of the alpha-msh response; complete inhibition was obtained in a ca2+-free medium containing 10-4 m egta. in mg2+-free medium, normal dispersion was observed. the ca2+ antag ...	1982	6281099
isolation and characterisation of the xenopus laevis albumin genes: loss of 74k albumin gene sequences by library amplification.	the blood of the frog x.laevis contains 2 albumins of 68,000 and 74,000 daltons which are encoded in the liver by two related mrnas. when an amplified x.laevis dna library was screened with cloned albumin cdna only 68,000 dalton albumin gene sequences were isolated. hybridisation of the albumin cdna to southern-blots of eco r1 digested x.laevis dna showed that the sequences present in the recombinants did not account for all the fragments which hybridised on the southern-blots. this indicated th ...	1982	6285309
molecular cloning and characterization of ribosomal rna genes from the brine shrimp.	a library of genomic dna from the brine shrimp, artemia, has been constructed with the charon 4a phage vector, utilizing ecori passenger fragments. screening this library with purified xenopus laevis cloned rdna genes has resulted in the identification and plaque purification of a recombinant containing a complete artemia (18 s + 26 s) rdna repeat unit. a physical map derived from the analysis of restriction endonuclease digests of the repeat unit, which measures 13.9 kilobase pairs, is similar ...	1982	6285976
microinjected progesterone reinitiates meiotic maturation of xenopus laevis oocytes.	microinjection of progesterone dissolved in paraffin oil induces the reinitiation of meiotic maturation in the xenopus oocyte; 50% maturation is obtained when 50 nl of a 50 microm solution is microinjected into the oocyte. the kinetics of the response to microinjected progesterone are similar to the kinetics of response to externally applied hormone. when an aqueous solution of progesterone is microinjected instead of an oil solution, maturation is never observed, a result which confirms previou ...	1982	6291050
initiation of replication at specific origins in dna molecules microinjected into unfertilized eggs of the frog xenopus laevis.	initiation of dna replication at specific origins was observed by electron microscopy after microinjection of pxlr11, pxlr14 or col e1 plasmid dna molecules into unfertilized eggs of the frog, xenopus laevis. these results are in apparent contradiction with published reports (harland and laskey, cell 21, 761-771, 1980; laskey and harland, cell 24, 283-284, 1981) that specific origin sites were not used in xenopus laevis eggs. we suggest that eucaryotic origins exist that both increase the probab ...	1982	6291769
interaction of steroids and growth factors with the plasma membrane in the induction of oocyte maturation in xenopus laevis.		1982	6292941
nad-glycohydrolase activity in xenopus laevis oocytes and early embryos.		1982	6293487
simple, efficient in vitro synthesis of capped rna useful for direct expression of cloned eukaryotic genes.	a simple and efficient method for direct in vitro synthesis of capped transcripts of cloned eukaryotic genes is described. as an example capped transcripts were made from a plasmid containing the human fibroblast interferon gene cloned under the control of a prokaryotic promoter. these transcripts were translated in vivo in xenopus laevis oocytes and in vitro in reticulocyte and in wheat germ cell-free protein synthesizing systems.	1982	6294601
vitellogenin genes a1 and b1 are linked in the xenopus laevis genome.	genomic clones containing the xenopus laevis vitellogenin gene b1 have been isolated from dna libraries and characterized by heteroduplex mapping in the electron microscope, restriction endonuclease analysis, and in vitro transcription in a hela whole-cell extract. sequences from the 3'-flanking region of the previously isolated a1 vitellogenin gene were found in the 5'-flanking region of this b1 gene. thus, the two genes are linked, with 15.5 kilobase pairs of dna between them. their length is ...	1982	6294657
isolation and structural analysis of ribosomal protein genes in xenopus laevis. homology between sequences present in the gene and in several different messenger rnas.		1982	6296397
characterization of histone genes isolated from xenopus laevis and xenopus tropicalis genomic libraries.	using a cdna clone for the histone h3 we have isolated, from two genomic libraries of xenopus laevis and xenopus tropicalis, clones containing four different histone gene clusters. the structural organization of x. laevis histone genes has been determined by restriction mapping, southern blot hybridization and translation of the mrnas which hybridize to the various restriction fragments. the arrangement of the histone genes in x. tropicalis has been determined by southern analysis using x. laevi ...	1982	6296782
organization and expression of cloned histone gene clusters from xenopus laevis and x. borealis.	we have isolated several clones containing xenopus histone genes from genomic libraries of x. laevis and x. borealis dna. each genomic clone has been mapped and the positions of 26 histone genes in seven laevis clones and 5 histone genes in one borealis clone have been determined. in laevis, the histone gene clusters show considerable variation in gene order within a single individual. when the cloned dnas were microinjected into the nucleus of xenopus oocytes, expression of cloned genes at the ...	1982	6296783
methylation of simian virus 40 hpa ii site affects late, but not early, viral gene expression.	dna methylation has been correlated with reduced gene expression in a number of studies, although evidence for a casual link between the two events has been lacking. because microinjection of simian virus 40 (sv40) dna into the nucleus of xenopus laevis oocytes results in the synthesis of both early and late viral gene products, it was possible to test whether a specific methylation event can affect gene expression. the single sv40 hpa ii site at 0.72 sv40 map units was specifically methylated w ...	1982	6291026
adenylate cyclase in xenopus laevis oocytes: characterization of the progesterone-sensitive, membrane-bound form.	progesterone-induced reinitiation of meiosis in xenopus laevis oocytes involves a decrease in camp level. in these cells, adenylate cyclase is compartmentalized, with 25-30% in the plasma membrane fraction p-10000 (sedimenting at 10000 x g) and greater than 50% in the cytosol. soluble adenylate cyclase appears not to be regulated via a gtp-binding regulatory protein (g/f) and is insensitive to progesterone. in contrast, membrane-bound adenylate cyclase seems to be linked to g/f, since it is stim ...	1982	6290296
a restriction map of xenopus laevis mitochondrial dna.	the mitochondrial dna from xenopus laevis is a 17.4 x 10(3)-base-pair circular dna molecule. the mapping of this dna, using 19 different restriction endonucleases is reported here. the sites are as follows: 1 for bamhi, psti, saci, sali, bali; 2 for bglii, sacii, ecori, clai, 3 for xhoi, 4 for avai, xbai, pvuii, 5 for hindiii, 6 for hhai, bcli, hpai, 10 for avaii and 11 for hincii. the same sites (except for one of the two clai sites) are observed in the molecule cloned in pbr322 dna. the fragme ...	1982	6290211
cloning in a cosmid vector of complete 37 kb and 25 kb ribosomal dna repeat units from the chicken.	dna fragments of up to 40 kb containing rrna-coding sequences have been isolated from a chicken liver dna library prepared in the cosmid phc79. characterization of the cloned dna by r-loop and restriction mapping has shown that there are two size classes of repeat unit, one of 37 kb and one of 25 kb, the larger of which is a family of units which vary slightly in size. these two classes were shown to be present in the dna of a single chicken. the size of the internal transcribed spacer in the ch ...	1982	6289899
immunohistochemical demonstration of tsh-, lh- and acth-cells in the hypophysis of tadpoles of xenopus laevis d.	by use of the immunofluorescence technique tsh-, lh- and acth-cells were localized in the hypophysis of tadpoles of xenopus laevis. the first signs of the activity of these cells were observed in early stages of the development, i.e., stage 39 for acth, and stage 42 for tsh and lh.	1982	6288250
chromosome-bound mitotic factors: release by endonucleases.	additional evidence is presented to support our recently reported conclusion that the mitotic factors of mammalian cells, which induce germinal vesicle breakdown and chromosome condensation when injected into fully grown xenopus laevis oocytes, are localized on metaphase chromosomes. chromosomes isolated from mitotic hela cells were further purified on sucrose gradients and digested for varying periods with either the micrococcal nuclease or dnase ii. at each time point of digestion the amount o ...	1982	6287433
mrna- and dna-directed synthesis of herpes simplex virus-coded exonuclease in xenopus laevis oocytes.	microinjection of herpes simplex virus (hsv)-infected cell mrna into xenopus laevis oocytes resulted in the production of a new exonuclease activity. this enzyme strongly resembled the hsv alkaline exonuclease in many biochemical properties, and hybrid-arrested translation studies showed that it was virus coded, mapping at 0.080 to 0.185 genome map units. exonuclease mrna had a size and genome location equivalent to the mrna encoding v185 in reticulocyte lysates, suggesting that v185 is the exon ...	1982	6287023
dnaase i sensitivity and methylation of active versus inactive rrna genes in xenopus species hybrids.	we studied the chromatin structure and methylation of ribosomal rna genes (rdna) in hybrids between xenopus laevis and xenopus borealis. s1-nuclease protection experiments showed that 97%-98% of the rrna precursor in hybrid tadpoles was of the x. laevis type. preferential expression of the laevis rdna was correlated with its hypersensitivity to dnaase i compared to borealis rdna. borealis and laevis rdnas gave equivalent methylation patterns, however. the results show that hypomethylated sites i ...	1982	6286140
comparative analysis of xenopus tropicalis and xenopus laevis vitellogenin gene sequences.	analysis of cdna clones synthesized from vitellogenin mrna of x. tropicalis revealed three different types of cdna clones, i.e. a, a* and b. a and a* clones have a sequence divergence of about 6% and are both related to x. laevis vitellogenin cdnas of subgroup a1 as well as a2 with a sequence divergence of 6-9%. b clones however, are related to x. laevis cdna clones of subgroup b1 and b2 with a sequence divergence of about 7%. while the a and b clones correspond to vitellogenin mrnas of similar ...	1982	6280148
the organization of the tadpole and adult alpha globin genes of xenopus laevis.	adult erythrocytes of x. laevis contain six electrophoretically resolvable globin polypeptides while tadpole erythrocytes contain four polypeptides, none of which comigrates with an adult protein. we show that three of the adult proteins are alpha globin polypeptides (alpha 1, alpha 2, alpha 3) and three are beta globin polypeptides (beta 1, beta 2, beta 3). we find that a tadpole alpha globin gene (alpha t1) is linked to the major adult locus in the sequence 5'-alpha t1-alpha 1-beta 1-3' with 5 ...	1982	6298702
an amber suppressor trna gene derived by site-specific mutagenesis: cloning and function in mammalian cells.	we describe the synthesis, cloning, expression, and in vivo function of a suppressor trna gene in mammalian cells. by using "primer-directed mutagenesis" on a xenopus laevis tyrosine trna gene cloned into the recombinant single-strand phage m13mp5, we have generated an amber suppressor trna gene that has a nucleotide change--gta leads to cta--in the anticodon sequence. the suppressor (su) trna gene was introduced into monkey kidney cells (cv-1) by using simian virus 40 (sv40) dna as vector (sv40 ...	1982	6310546
inheritance of dna methylation in microinjected eggs of xenopus laevis.	plasmid dna methylated at hpa ii sites was injected into eggs of xenopus laevis. the methylated dna replicates extrachromosomally, and the methylated state of the h pa ii sites is inherited through replication. unmethylated sites remain unmethylated in progeny molecules. to test whether replication is necessary for new methylation to occur, dna methylated on one strand only was injected and unreplicated dna was selected for analysis. methylation was copied onto a previously unmethylated strand i ...	1982	6285378
sodium channels induced by depolarization of the xenopus laevis oocyte.	an electrically gated na+ channel can be made to appear in the membrane of the xenopus laevis oocyte by simple depolarization. this membrane normally responds passively to imposed transmembrane currents with resting potentials around -60 mv, but when it is held depolarized to more than about +30 mv it becomes possible to obtain long-lasting regenerative depolarizations up to +80 mv; these depolarizations can last as long as 20 min. this potential is due to an "induction" of a na+-dependent chann ...	1982	6285341
the dnase i sensitivity of xenopus laevis genes transcribed by rna polymerase iii.	since the initial discovery that the dnase i sensitivity of the globin genes in different cell types correlates with globin gene expression, this relationship has been shown to hold true for a variety of genes, including the genes for ovalbumin, conalbumun, alpha- and beta-globin in chicken, several heat-shock proteins in drosophila, the r-chromatin of tetrahymena and the viral polyoma minichromosome. although genes transcribed by rna polymerases i and ii have been studied extensively, the genes ...	1982	6285200
lipid environments in the yolk lipoprotein system. a spin-labeling study of the lipovitellin/phosvitin complex from xenopus laevis.	lipid/protein and lipid/lipid interactions in the yolk lipoprotein complex from xenopus laevis were examined by introducing a series of lipid spin-labels into the complex and observing the electron spin resonance spectra as a function of the position of the label along the lipid chains, temperature, ph, and charge on the lipid polar head group. analyses of the spectra show that, in addition to the expected component arising from lipid associated with protein, a second component with increased se ...	1982	6284201
nucleotide sequence of an external transcribed spacer in xenopus laevis rdna: sequences flanking the 5' and 3' ends of 18s rrna are non-complementary.	we have sequenced the external transcribed spacer (ets) of a ribosomal transcription unit from xenopus laevis, together with sections of the preceding non-transcribed spacer. our analysis was carried out on the same cloned transcription unit as that from which the internal transcribed spacers (its) were previously sequenced. the ets is approximately 712 nucleotides long and, like the its regions, is generally very rich in c plus g. features of the sequence include an excess of oligo-c tracts ove ...	1982	6283480
benzo(a)pyrene-binding proteins of hamster embryo cell nuclei: comparison of nuclear isolation procedures.	hamster embryo cells metabolize benzo(a)pyrene to derivatives that covalently modify the nuclear macromolecules including proteins. not all proteins are modified to the same extent nor by the same metabolites. in particular, a protein of apparent molecular weight 32,000 is highly modified by derivatives of trans-9,10-dihydro-9,10-dihydroxy b(a)p. this protein is shown here to be preferentially lost from nuclei during purification by centrifugation through high molarity sucrose solutions followed ...	1982	6282910
na,k-atpase from xenopus laevis kidney and epidermis: ouabain interaction studies.	a satisfactory purification from xenopus laevis epidermis is presented. ki and kd values for the ouabain-enzyme interaction have been evaluated. both parameters appear very low, as compared with those demonstrated in other anurans. very low digitalis-like compound level was demonstrated in xenopus; on the contrary in bufo, in which these substances play a defensive role, it is very high. our results strengthen the hypothesis of a physiological action of such compounds in regulating enzyme-driven ...	1982	6299312
quantitation of estrogen effect on xenopus laevis albumin mrna levels by hybridization to cloned albumin cdna.	the isolation and characterization of a xenopus laevis albumin cdna clone, pun18, is described. this clone was identified as a x. laevis albumin cdna clone by hybridization-mrna selection-translation and by other techniques. the clone was used in hybridizations to determine the effect of estrogen on albumin synthesis in livers of male x. laevis. we find that albumin mrna levels remain relatively constant during the massive induction of vitellogenin mrna synthesis and vitellogenin secretion which ...	1982	6282883
temperature dependence of the sodium channel gating kinetics in the node of ranvier.	temperature dependence of the na+ channel gating kinetics was measured from the ionic and charge displacement currents in the node of ranvier of xenopus laevis, m3h kinetics was applied, assuming a delay, delta t, in the activation process. the rate constants for the m- and h-process showed arrhenius temperature-dependence with q10 of 2.34 and 2.9 respectively, while delta t exhibited non-arrhenius temperature-dependence. q10 for pna, measured as 1.6, was smaller than for the rate constants and ...	1982	6281846
characterization of the soluble cyclic nucleotide phosphodiesterases in xenopus laevis oocytes. evidence for a calmodulin-dependent enzyme.	cyclic nucleotide phosphodiesterase activities (3',5'-cyclic nucleotide 5'-nucleotidohydrolase, ec 3.1.4.17) were found in the 40,000 x g supernatant fraction of homogenates of xenopus laevis oocytes. in the supernatant, the ratio of the specific activity of cyclic amp phosphodiesterase to that of cyclic gmp phosphodiesterase was 1.1 at the 1 micro substrate level. two phosphodiesterase forms were isolated by centrifugation on sucrose gradient: a 3-4 s form hydrolyzing specificity cyclic amp and ...	1982	6280770
cyclic amp-mediated control of meiosis: effects of progesterone, cholera toxin, and membrane-active drugs in xenopus laevis oocytes.	progesterone depressed rapidly (50% at 1 min) and persistently cyclic amp (camp) concentration that had been elevated by cholera toxin in xenopus laevis oocytes. camp remained below 1 pmol per oocyte (mean basal level) for approximately 1 hr and thereafter rose to approximately 120% of control values, while germinal vesicle (nucleus) breakdown did not occur. in the absence of cholera toxin, progesterone treatment for 6 hr maintained camp concentration below the basal level (but not lower than 80 ...	1982	6278498
cellular commitment for post-gastrular increase in alkaline phosphatase activity in xenopus laevis development.	xenopus embryos were dissociated into cells and cultured in ca2+-free medium to study the relationship between the cell-to-cell interaction and macromolecular synthesis. under the conditions, cells did not aggregate at all, and remained isolated even while they were dividing actively. synthesis of dna and protein as studied by the incorporation of (3h) thymidine and (3h) leucin proceeded as in the aggregating cells. also, the activity to synthesize rrna, 5s rna, and heterogeneous rna as determin ...	1982	6175549
biosynthesis of pairs of peptides related to melanotropin, corticotropin and endorphin in the pars intermedia of the amphibian pituitary gland.	this study concerns the biosynthesis of a number of peptides in the neurointermediate lobe of the pituitary gland of the aquatic toad, xenopus laevis. using pulse-chase incubations in vitro and high-performance liquid chromatographic analysis, it could be shown that these peptides are synthesized through processing of a prohormone, pro-opiomelanocortin; all peptides were released into the incubation medium. on the basis of electrophoretic analysis, selective amino acid incorporation and immunopr ...	1982	6277629
the unmethylated state of the promoter/leader and 5'-regions of integrated adenovirus genes correlates with gene expression.	an inverse correlation has been established between the levels of dna methylation at 5'-ccgg-3' (mspi/hpaii) sites in specific genes of integrated viral dna in adenovirus type 12 (ad12)-transformed hamster cell lines and the extent to which these genes are expressed ( sutter and doerfler , 1979, 1980). in general, early genes are transcribed into mrna, while late genes are permanently switched off in these cell lines. adenovirus type 2 genes methylated in vitro at 5'-ccgg-3' sites are not transc ...	1982	6329677
a prokaryotic trnatyr gene, inactive in xenopus laevis oocytes, is activated by recombination with an eukaryotic trnapro gene.	eukaryotic tdna promoters are composed of two essential regions contained within the coding sequence (box a and box b). due to the highly conserved structure of prokaryotic and eukaryotic trna, most prokaryotic trna genes are expected to be active templates in eukaryotic transcriptional systems. in this paper we show that escherichia coli tdnatyr is not transcribed in the nucleus of xenopus laevis oocytes. by in vitro construction of hybrid molecules between inactive prokaryotic tdnatyr from e. ...	1982	6329706
18s coding sequences in amplified ribosomal dna from xenopus laevis oocytes are highly homogeneous, unmethylated, and lack major open reading frames.	we have used two approaches to search for sequence variants in the 18s coding region of amplified ribosomal dna (rdna) from xenopus laevis oocytes. first, using clones derived from amplified rdna, we compared the equivalent of a complete 18s coding region from two clones and short regions from two other clones with the 18s sequence previously determined from a "reference" clone. the respective sequences in all the clones were identical. secondly, we examined greater than 60% of the 18s sequence ...	1982	6329693
cloning and structure of the human immune interferon-gamma chromosomal gene.	two clones containing the human immune interferon-gamma (ifn-gamma) chromosomal gene were isolated from a human dna library present in lambda charon4a phage. dna from these clones specified biologically active interferon upon injection into the nuclei of xenopus laevis oocytes. analysis of the clones revealed that they were derived from the same chromosomal segment. restriction fragments that hybridized with 32p-labeled cdna probes were subcloned into plasmids and the complete sequence of the if ...	1982	6329718
the organization of ribosomal genes in vertebrates.	the organization of the repeat unit of the ribosomal genes has been determined in 15 different species of vertebrates. the ecori and bamhi restriction maps of the rdna from single individuals of different species of fishes, amphibians, and reptiles have been analysed. two rdna clones from xenopus laevis (representing one complete repeat unit) were used as probes in southern blots to detect restriction fragments containing ribosomal genes. the results obtained indicate that the transcribed region ...	1982	6329726
membrane addition to rod photoreceptor outer segments: light stimulates membrane assembly in the absence of increased membrane biosynthesis.	the effect of light on the biosynthesis and the assembly of rod photoreceptor outer segment membranes was analyzed in vitro using retinas from xenopus laevis. the number of open discs at the base of the outer segment was used as a morphologic index to evaluate relative differences in rates of membrane assembly. assembly was stimulated in vitro by light, as evidenced by a greater number of open discs that accumulated in light-exposed retinas than that in retinas maintained under the same conditio ...	1982	6460718
an in vivo study of the ontogeny of alloreactivity in the frog, xenopus laevis.	pre- and perimetamorphic larval and post-metamorphic juvenile frogs (xenopus laevis) from a single family were grafted with skin from either of their patents (who differed from the hosts by one major histocompatibility complex (mhc) haplotype and multiple minor h loci) or from an unrelated adult (to provide a greater immunogenetic disparity). the fate of such skin grafts transplanted to hosts of various developmental stages indicated that a net destructive alloimmunity in this amphibian species ...	1982	6459993
establishment of mammalian cell lines containing multiple nonsense mutations and functional suppressor trna genes.	we describe the generation of mammalian cell lines carrying amber suppressor genes. nonsense mutants in the herpes simplex virus thymidine kinase (hsv tk) gene, the escherichia coli xanthine-guanine phosphoribosyl transferase (eco-gpt) gene and the aminoglycoside 3' phosphotransferase gene of the tn5 transposon (npt-ii) were isolated and characterized. each gene was engineered with the appropriate control signals to allow expression in both e. coli and mammalian cells. expression in e. coli made ...	1982	6760983
an immunocytochemical method for the visualization of tubulin-containing structures in the egg of xenopus laevis.	tubulin can be isolated and purified from xenopus laevis eggs through modification of olmstedt's (1970) tubulin isolation method, viz. by repeating the vinblastin precipitation step after resuspension of the sediment in a detergent-containing stabilizing medium. by this we overcome the deleterious influence of the yolk granules in the isolation procedure. from 11 of xenopus laevis eggs 25 mg vb-paracrystals can be obtained. the apparent molecular weight of the purified tubulin is 52,800. antiser ...	1982	6762372
active polypeptide fragments common to prokaryotic, eukaryotic, and mitochondrial dna polymerases.	with a procedure that allows the renaturation of the dna polymerase catalytic activity in situ after sds-polyacrylamide gel electrophoresis, we have compared the active polypeptides present in extracts from organisms covering a wide evolutionary range from prokaryotes to eukaryotes, namely: escherichia coli, oryza sativa, daucus carota , neurospora crassa, dictyostelium discoideum, saccharomyces cerevisiae, ceratitis capitata, leucophaea maderae , xenopus laevis, rat tissues and human lymphoblas ...	1982	6765191
restoration of antibody responsiveness in early thymectomized xenopus by implantation of major histocompatibility complex-mismatched larval thymus.	the restorative potential of isogeneic and fully allogeneic thymic implants to restore in vivo antibody responsiveness to a thymus-dependent antigen has been examined in thymectomized clawed toads. isogeneic clones (xenopus laevis/gilli and x. laevis/muelleri hybrids) of known major histocompatability complex (mhc) haplotypes were thymectomized at 5-7 days, implanted with mhc-identical or -mismatched (normal or irradiated ) thymuses from 5-week-old larvae and 4 months later injected with dinitro ...	1982	6749529
synthesis and maturation of xenopus laevis methionine trna gene transcripts in homologous cell-free extracts.	a cloned initiator methionine trna gene from xenopus laevis has been transcribed in cell-free extracts (s-100) prepared from cultured x. laevis kidney cells. rna polymerase iii produces two primary transcripts of this gene which initiate with a pppg and a pppa located seven and four nucleotides, respectively, in front of the mature trnamet1 5' end. both terminate with a dt5 tract just beyond the nucleotides encoding the mature trna. the trna precursors are readily processed in vitro to mature le ...	1982	6802833
development of harderian gland during metamorphosis in anurans.	development of harderian gland of larvae of rana japonica, bufo bufo japonicus, and xenopus laevis was studied. in the adult animals, well-developed harderian glands were invariably present in the orbit. in rana and bufo, the gland first appeared at late prometamorphic stage and in xenopus it appeared around climax stage. in thyroidectomized tadpoles of bufo and rana, the harderian gland was induced by thyroxine. in hypophysectomized tadpoles of bufo the gland developed when they were treated wi ...	1982	6803615
changes in mitochondrial respiration during the development of xenopus laevis.	mitochondria isolated from xenopus laevis embryos at various developmental stages show a good oxidative capacity and an acceptable respiratory control provided that certain requirements are fulfilled. the rates of respiration with pyruvate and krebs' cycle intermediates, especially with citrate and isocitrate, are very low during cleavage stages and increase after gastrulation. glutamate in the presence of malate is the only substrate to be readily oxidized during early development and its rate ...	1982	6811140
thymocyte precursors in early-thymectomized xenopus: migration into and differentiation in allogenic thymus grafts.	in an anuran amphibian, xenopus laevis, thymectomy of 4-day-old larvae abrogates t-cell dependent immune responsiveness. when such early-thymectomized (tx) diploid frogs were implanted with histocompatible triploid thymuses and grafted 8 weeks later with skin from third-party donors, the grafts were rejected relatively normally in 20-27 days. microspectrophotometric determination of ploidy 3-5 months after thymus reconstitution revealed that most thymocytes were donor-derived. in contrast, when ...	1982	6751892
[development of the adenylate cyclase activity of the embryonic chorda-mesoderm and endoderm during the migration of primordial germ cells in xenopus laevis (anuran amphibian)].	in the embryo of xenopus laevis, adenylate cyclase activity is higher in the chorda-mesoderm than in the endoderm. the peak of activity in the chorda-mesoderm is observed at the beginning of the migration of the primordial germ cells (pgc). there could be a correlation between the adenylate cyclase activity of the chorda-mesoderm and the intraendodermic migration of the pgc.	1982	6816405
dissection of a replication origin of xenopus dna.	a previously cloned 503-base pair (bp) ecori segment of genomic dna from xenopus laevis selected for enhancement of replication of its vector plasmid was moved to the ecori site of pbr322. this plasmid designated pjcc31 and five other clones, which were made by cleaving the 503-bp segment in relation to a dispersed repeated sequence and subcloning, were compared with pbr322 for replication by microinjection into xenopus eggs. the replication measured by incorporation of a 32p-labeled nucleotide ...	1982	6752953
immunogenetic aspects of in vivo allotolerance induction during the ontogeny of xenopus laevis.	this study describes the ontogeny of allograft immunity in a partially inbred strain of frogs (xenopus laevis). at various times during the frogs' premetamorphic, perimetamorphic, and postmetamorphic life, major histocompatibility complex (mhc) homozygous strain jj xenopus (mhc haplotype j) were grafted with skin from adult donors of defined mhc homozygous (j,f) and heterozygous (j/f,f/h) haplotypes. this protocol reveals that destructive allograft reactivity to mhc alloantigens in xenopus matur ...	1982	6754587
biochemical studies of xenopus laevis lymphocytes surface immunoglobulins.	cell surface immunoglobulins of adult xenopus laevis splenic small lymphocytes were analysed utilizing direct immunofluorescent staining and lactoperoxidase-catalysed radioiodination followed by immunoprecipitation of ig molecules and characterization on sds-page. nearly 30% of splenic lymphocytes are surface ig positive. the hmw and lmw ig classes are present on the surface of 23% and less than 5% of the cells, respectively. the mu chains of membrane hmw ig have an apparent m.w. of 84,000 versu ...	1982	6819167
in vitro digestion of actomyosin by extracts from tails of metamorphosing xenopus laevis.	1. actomyosin purified from the tails of immature tadpoles of xenopus laevis was degraded by exposure to low salt, 16,000 g supernatant extracts of involuting tadpole tails, as assayed by sds polyacrylamide gel electrophoresis. 2. the proteolytic activity of the tail extracts was inhibited by atp and leupeptin. myosin (193,000 daltons) is initially cut to produce a 161,000 dalton fragment, then in a second step yielding 95,000 dalton fragments. 3. both atp and leupeptin inhibit the formation of ...	1982	6749404