dna-relaxing activity and endonuclease activity in xenopus laevis oocytes.complex simian virus 40 dna produced by a soluble cell-free extract derived from stage 6 oocytes of xenopus laevis consists of fully relaxed circles (i.e., with no superhelical turns). an endonuclease and a dna-relaxing protein, either or both of which could be responsible for the relaxation of the complex dna, have been purified from the extract. the endonuclease(s) produces nicked circles (having a single-strand scission) and linear full-size molecules. the dna-relaxing protein is in the nucle ...1976188045
the structure of the mitochondrial cloud of xenopus laevis oocytes.the ultrastructure of the mitochondrial cloud (balbiani body) of the pre-vitellogenic oocytes of xenopus laevis has been examined using transmission and stereoscan electron microscopy. examination of conventional thin sections confirm previous observations which suggest that the cloud consists essentially of many thousands mitochondria and numerous small vesicles; larger clouds, in oocytes greater than 200 mum in diameter, contain relatively more vesicles. using a standard electron microscope at ...1976188969
assembly of sv40 chromatin in a cell-free system from xenopus eggs.a cell-free system is described which assembles chromatin from purified dna in 1 hr under physiological incubation conditions. it consists of a 145,000 x g (maximum) supernatant fraction from eggs of xenopus laevis. it converts sv40 dna to a nucleoprotein which co-sediments with naturally occurring sv40 chromatin and which can be cleaved by micrococcal nuclease to a highly ordered pattern of dna fragments resembling those from digestion of liver chromatin. it inserts superhelical turns into rela ...1977189936
developmental immunohistology of melanotrophs in xenopus laevis tadpoles.the adenohypophysial primordium of xenopus laevis tadpoles at stages 33/34 to 46 (nieuwkoop and faber, 1956) were examined immunohistologically for alpha-msh, beta-msh and acth. beta-msh was demonstrated from stage 37/38 onwards, and alpha-msh from stage 39. no signs of acth production were detected. alpha-msh and beta-msh occurred in the same cells. no differences were found in the intensity of immunofluorescence between tadpoles which were kept on a black and a white background. the present st ...1977194700
kynureninase-type enzymes and the evolution of the aerobic tryptophan-to-nicotinamide adenine dinucleotide pathway.kynureninase-type (l-kynurenine hydrolase, ec activity has been found to be present in the livers of fish, amphibia, reptiles, and birds. in addition to past information concerning this enzyme activity in mammalian liver, it is now clear that all the major classes of vertebrates carry a highly specialized kynureninase-type enzyme, which we have termed a hydroxykynureninase. to compare the reactivities of these enzymes with l-kynurenine and l-3-hydroxykynurenine, ratios of tau values (km ...1977195620
frog oocytes synthesize and completely process the precursor polypeptide to virion structural proteins after microinjection of avian myeloblastosis virus rna.after microinjection of xenopus laevis oocytes with rna from avian myeloblastosis virus, viral structural proteins p27, p19, p15, and p12 are formed by a sequence of posttranslational cleavages of a high-molecular-weight precursor polypeptide. the 60-70s rna aggregate or its 30-40s rna subunits obtained by heat or formamide treatment possess the same ability to serve as template in x. laevis oocytes. the processing pattern of virus-specific precursor polypeptides is the same in x. laevis oocytes ...1977198776
coupled transcription-translation of dna injected into xenopus oocytes.a previous report from this laboratory showed that purified dnas are transcribed after injection into the nucleus of xenopus laevis oocytes (mertz and gurdon, 1977). here we demonstrate that at least some of the rna synthesized is translated within these injected cells to produce the correct protein products. injection of simian virus 40 dna into oocytes induces the synthesis of at least two proteins not normally synthesized in these cells. using two-dimensional polyacrylamide gel electrophoresi ...1977198138
the activity of poly(adenosine diphosphate ribose) polymerase during the embryonic development of the south african clawed toad xenopus laevis [proceedings]. 1977198268
formation of branched dna structures by xenopus laevis oocyte extract. 1977201869
the activity of some intracellular oxidative enzymes in the thyroid follicular epithelium of xenopus laevis daud. in experimental long-term hypokinesia.histoenzymological methods were applied to examine the activities of previously little studied intracellular oxidative enzymes in the cells of the thyroid follicular epithelium of xenopus laevis daud. specimens kept in aquarium. succinate, lactate, alpha-glycerophosphate, glucose-6-phosphate and reduced nad and nadp dehydrogenases and cytochrome oxidase were studied. in comparison with other chordate species a very strong activity was revealed particularly by lactate dehydrogenase. the data obta ...1977202546
embryopathies due to spermatozoal impairment in xenopus in vitro test system, involving gametes of xenopus laevis has been used to study the effect of antifertility agents upon spermatozoa as manifest in developing embryos. exposure to either the isomeric forms of dimethylmyleran, methyl methanesulphonate or gamma-radiation led to development of a range of embryopathies, whereas treatment with steroidal drugs or the rodent epididymal chemosterilants alpha-chlorohydrin and trimethylphosphate was compatible with production of apparently normal offsp ...1978209323
method for the preparation of active maturation promoting factor (mpf) from in vitro matured oocytes of xenopus laevis.a method for the large scale extraction of maturation promoting factor (mpf) from in vitro matured oocytes of xenopus laevis is described. mpf has been previously described only as a component(s) of hormone-matured cytoplasm within amphibian oocytes (or eggs) which is able to induce the reinitiation of the meiotic process from late diplotene stage until second metaphase arrest, when microinjected into diplotene arrested (fully grown) recipient oocytes. standard biochemical methods for the extrac ...1978207616
amphibian oocyte maturation and protein synthesis: related inhibition by cyclic amp, theophylline, and papaverine.two inhibitors of cyclic amp phosphodiesterase (3':5'-cyclic-amp 5'-nucleotidohydrolase, ec, theophylline and papaverine, inhibit the maturation of xenopus laevis oocytes induced by four different stimuli: human chorionic gonadotropin, progesterone, testosterone, and lanthanum ions. addition of 1 mm cyclic amp to the medium delays maturation by approximately 2 hr. papaverine, theophylline, and cyclic amp inhibit amino acid incorporation into oocyte proteins by 50% or more but do not in ...1978206889
control of msh synthesis and release in the aquatic toad, xenopus laevis. 1977207601
chromatin assembly and transcription in eggs and oocytes of xenopus laevis. 1978209936
a biochemical comparison of xenopus laevis and mammalian myelin from the central and peripheral nervous systems.myelin purified from the central nervous system of xenopus laevis contained the same major lipid and protein components as human myelin. however, some minor differences in the myelin proteins were noted. the xenopus basic protein had a higher apparent mol wt. on sodium dodecyl sulfate gels than the corresponding mammalian protein. the absolute specific activity of 2',3'-cyclic nucleotide 3'-phosphohydrolase in the xenopus myelin was considerably higher than in mammals. there were differences in ...1978211203
high affinity of carozolol for beta-adrenoceptors coupled to the adenylyl cyclase in ventricular myocardium of kitten and xenopus laevis.catecholamine-induced stimulation of adenylyl cyclase in ventricular membranes of kitten and xenopus laevis was antagonized competitively by carazolol. apparent equilibrium constants ranging between 100-170 pm were estimated for the beta-adrenoceptor-carazolol complex.1978210404
the effects of alpha and beta adrenergic agents on spleen cell antigen binding in four amphibian species.adults of two urodele amphibian species (triturus cristatus carnifex and cynops hongkongensis) and two anuran species (rana temporaria and xenopus laevis laevis) were immunized with a 25% suspension of sheep or horse erythrocytes. after eight or 14 days, splenic lymphocytes were removed, and their specific red cell-binding capacities tested by immunocytoadherence. antigen-binding cells were classified as high-dose nonsecretory (s-) or secretory (s+), according to whether they bound a single laye ...1978211039
cytochrome oxidase activity of mitochondria in xenopus laevis previtellogenic oocytes. 1978211159
cap analogues do not inhibit mrna translation in xenopus laevis oocytes. 1978212317
progesterone-induced meiosis in xenopus laevis oocytes: a role for camp at the "maturation-promoting factor" level.cholera toxin inhibition of progesterone-induced meiosis of xenopus laevis oocytes in vitro has been correlated with increased camp levels. inhibition of germinal vesicle breakdown (gvbd) and camp increase occurred after a lag period of 2 hr, when cholera toxin was injected, or 4--5 hr, when applied externally. the ability of the maturation-promoting factor (mpf) to provoke gvbd when injected into recipient oocytes was found to be dependent upon whether the oocytes had been exposed to cholera to ...1978215320
stimulation of poly(adenosine diphosphate ribose) synthase activity of xenopus germinal vesicle by progesterone.a practical procedure for the isolation of massive numbers of gv from oocytes of xenopus laevis at various stages of oogenesis was developed. the method is simple, rapid, and easy to perform. the isolated gv possess high activity of poly(adp-ribose) synthase. incubation of class-a oocytes (stages v and vi) with progesterone resulted in a stimulation of the poly(adp-ribose) synthase activity in the gv. the stimulation of enzymatic activity occurred prior to gvbd. this stimulatory effect of proges ...1977214004
discussion paper: induction by progesterone and a "maturation-promoting factor" of soluble proteins in xenopus laevis oocytes in vitro incubation of isolated x. laevis oocytes with progesterone induces the specific labeling of proteins during maturation. they are detected as several discrete peaks with a double-labeling technique that involves the injection of [3h] leucine into hormone-treated and [14c] leucine into control cells. the peaks are separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis. identical proteins are obtained with two other steroids that provoke maturation and with p-chloromercurib ...1977214005
translation of type c viral rnas in xenopus laevis oocytes: evidence that the 120,000-molecular-weight polyprotein expressed in abelson leukemia virus-transformed cells is virus coded.the genomic rna of abelson leukemia virus (ablv) has been purified and translated in xenopus laevis oocytes. the primary ablv-specific protein synthesized is a polyprotein corresponding in molecular weight and immunological properties to a previously described p15 and p12 containing 110,000- to 130,000-molecular-weight polyprotein expressed in ablv-transformed cells. in contrast, translation of woolly monkey sarcoma virus genomic rna resulted in symthesis of a 55,000-molecular-weight polyprotein ...1978214586
[properties of sex steroid-binding protein from xenopus laevis blood serum and detection of an estradiol-binding component in frog liver cytosol which differs from sex steroid-binding protein].binding and physico-chemical properties of sex steroid-binding protein (sbp) from blood serum and those of estrogen-binding components from liver cytosol of pubertal male and female species of clawed frog xenopus laevis were studied. it was shown that sbp from both sex species of x. laevis specifically binds estradiol (e2) (ka=5 . 10(6) m-1). concentration of sbp binding sites for e2 is 7 . 10(-12) mole per mg of protein. testosterone 5alpha-dihydrotestosterone and e2 effectively compete with [3 ...1978216428
dna supercoiling by xenopus laevis oocyte extracts: requirement for a nuclear factor.a purified system is described for the introduction of negative supercoils into simian virus 40 dna. the system consists of histones h2a, h2b, h3, and h4, dna-relaxing enzyme, and a purified factor from xenopus laevis stage 6 oocyte nuclei. the nuclei are prepared en masse by the technique of f. scalenghe, m. buscaglia, c. steinheil, and m. crippa [(1978) chromosoma 60, 299-308]. the supercoiled simian virus 40 dna prepared by this method is indistinguishable from simian virus 40 supercoiled dna ...1978217004
effects of fasting and cortisol administration on carbohydrate metabolism in xenopus laevis daudin. 1978217800
translation of avian sarcoma virus rna in xenopus laevis oocytes. 1979218572
biochemical data on subtotally hypophysectomized xenopus laevis (daudin) adult specimens treated or not with prolactin.xenopus laevis (daudin) adult specimens were submitted to hypophysectomy. although the operation resulted subtotal, it served the purpose of removing the prolactin-producing cells, whereby the involvement of endogenous prolactin in osmoregulation phenomena was excluded. in the operated animals treated with ovine prolactin the following metabolic parameters, which are closely dependent upon interrenal activity, were estimated: 1) intestine alkaline phosphomonoesterase activity (e.c.; 2) ...1976218525
the role of the carbohydrate in the stabilization, processing, and packaging of the glycosylated adrenocorticotropin-endorphin common precursor in toad pituitaries.the neurointermediate lobes of dark adapted toads, xenopus laevis, were incubated for 30 min in [3h]arginine, [3h]arginine plus [14c]glucosamine, or [3h]glucosamine and then chased for various time periods ranging from 1--3 h. the labeled polypeptides synthesized and secreted by the lobes were analyzed by acid-urea polyacrylamide gel electrophoresis. a glycosylated acth-endorphin precursor (32,000 mol wt) was synthesized during the pulse and identified by immunoprecipitation by acth-(11--24) ant ...1979222574
histone 1 phosphotransferase activities during the maturation of oocytes of xenopus laevis. 1979220911
follicle-stimulating-hormone receptors in the testis of the frog, xenopus laevis. 1979221307
mitochondrial dna polymerase from xenopus laevis oocytes. 1979223552
dual innervation of end-plate sites and its consequences for neuromuscular transmission in muscles of adult xenopus laevis.1. electrophysiological study of dually innervated end-plate sites was carried out in xenopus laevis pectoral muscle fibres. end-plate potentials (e.p.p.s) and miniature end-plate potentials (m.e.p.p.s) have been recorded in mg-blocked preparations. 2. the mean quantal content (m) of each e.p.p. at dually innervated end-plates was significantly smaller than the corresponding values obtained at singly innervated ones. at a given doubly innervated end-plate site the values of m tended to be invers ...1979222897
two cell-free systems constructed from xenopus laevis oocytes: generalized genetic recombination; dna supercoiling. 1979225119
morphological and physiological aspects of melanophores in primary culture from tadpoles of xenopus laevis.melanophores from tadpoles of xenopus laevis (daudin) were isolated by digestion of tail fins with acetyltrypsin and collagenase and maintained in primary culture for 6 weeks up to 3 months. within 36 to 72 h the melanophores develop one to eight dendritic processes per cell; secondary and tertiary branchings of the processes were frequently observed. the melanophores in primary culture disperse under the influence of alpha-msh or cyclic amp; upon rinsing out these substances the cells aggregate ...1979223762
eukaryotic dna replication: the first steps toward a multienzyme system from xenopus laevis. 1979225118
roles of cyclic amp and calcium in maturation of xenopus laevis oocytes. 1979226799
characterization of interferon messenger rna from human lymphoblastoid cells.after treatment with sendai virus, namalwa cells form large amounts of interferon. rna extracted from treated whole cells or from their polysomes was injected into xenopus laevis oocytes and the interferon formed was titrated. the results show that the amount of interferon mrna was maximal by 9 h after treatment of the cells with sendai virus and then declined. sucrose gradient centrifugation of the mrna gave substantial purification and showed that its size was 12 s.1979227993
onset of neural function in the lateral line.the development of the nervous system includes the formation of specific neuronal connections. some insight into the mechanisms by which these connections are made may be obtained by determining the order in which the elements of a developing system begin to function and examining any changes that may occur in the system shortly after it begins functioning. i have investigated the lateral line of the south african clawed frog, xenopus laevis and i have classified the afferent system into three e ...1979228196
[effects of cyclic amp treatment on the migration of primordial germ cells in the embryo of xenopus laevis].after a treatment of early embryos by ampc, only 40% of the primordial germ cells are found in the gonads; the others are found in the dorsal mesentery and especially in the intestinal wall.1978226281
biochemical characterization of lysosomes in unfertilized eggs of xenopus laevis.relations between lysosomes and yolk platelets of amphibian eggs have been suggested. this work demonstrates the presence of acid hydrolases in oocytes induced to ovulate in vitro. about 40% of the acid hydrolases are found in a sedimentable fraction, and, in accordance with the lysosomal concept, they display structural latency. biochemical data did not indicate any association between lysosomal enzymes and yolk platelets. the mechanism of yolk resorption is discussed and it is suggested that t ...1979228752
alkaline phosphatase isozymes of xenopus laevis embryos and tissues.alkaline phosphatase was obtained by treating embryos of xenopus laevis with n-butanol at different developmental stages from gastrula to tadpole; the enzyme was also obtained from adult kidney, liver, and intestinal mucosa. purification was carried out by gel filtration and polyacrylamide gel electrophoresis. the enzyme activity is chromatographically spearated into two peaks, with molecular weights of approximately 200,000 and 400,000. alternatively, two groups may be characterized on the basi ...1975237058
the time course of experience-dependent synaptic switching of visual connections in xenopus laevis. 1975237285
osmotic and ionic regulation in xenopus laevis daud. during adaptation to different osmotic environments--v. quantitative alterations of the acid glycosaminoglycans in the kidney. 1975237733
na+/k+-dependent adenosinetriphosphatase activity in the skin, kidney and muscle in xenopus laevis (daud.) adult specimens under different experimental conditions.xenopus laevis adult specimens were exposed to environmental changes simulating those undergone by these animals in their natural "habitat". after keeping groups of animals under dry conditions, some of them were returned to water. in both cases some parameters were compared with those of control animals kept in water. a lower activity in the na+/k+-dependent atpase of the epidermis and striated muscle was detected in "dry" animals with respect to the control ones or those rehydrated whereas the ...1978233463
steady state current rectification in potential clamped nodes of ranvier (xenopus laevis).the membrane potential in single nodes of ranvier was changed in rectangular pulse steps while the membrane currents, associated with the potential steps, were measured. changes were made in the ionic composition of the external and the internal medium. the latter changes were obtained by free diffusion through a cut internode. the steady state currents, described on the basis of potassium and leak permeability, were affected by the solution composition in a characteristic way. increased inside ...1975238247
template preferences of dna polymerase and nuclease activities appearing during early development of xenopus laevis. 1975238871
changes in the activity and isozymes of acetyl and butyrylcholinesterase during xenopus laevis development. 1975240618
xenopus laevis cement gland as an experimental model for embryonic differentiation. i. in vitro stimulation of differentiation by ammonium chloride.ectoblastic cells explanted from the animal pole of young xenopus laevis gastrulae have been cultured in vitro. when these cells were cultured for five days in standard salt solutions they formed atypical epidermis. when they were first submitted for 6 h to holtfreter solution containing ammonium chloride and then transferred for five days in standard barth's solution they underwent differentiation into typical cement gland tissue. the optimum concentration of ammonium chloride was 10 mm. below ...1975240903
turnover of rod photoreceptor outer segments. ii. membrane addition and loss in relationship to light.the rate of disk addition to rod outer segments (ros) varies widely in xenopus laevis tadpoles kept in cyclic light (12l:12d). when measured as radioactive band (3h-band) displacement during the 2nd day after injection of [3h]leucine, 75% of the daily increment of displacement occurred during the first 8 h of light. during the same interval, the number of open disks at the ros base increased more than threefold. during the last 8 h of darkness, 3h-band displacement was undetectable and the numbe ...1977264121
selective and accurate transcription of the xenopus laevis 5s rna genes in isolated chromatin by purified rna polymerase iii.chromatin isolated from immature oocytes was found to contain an endogenous rna polymerase activity (rna nucleotidyltransferase; nucleoside triphosphate:rna nucleotidyltransferase, ec that synthesizes predominately 5s rna. however, the levels of total rna synthesis and 5s rna synthesis in chromatin were each stimulated 10- to 50-fold by an exogenous rna polymerase iii purified from x. laevis oocytes. the 5s genes in chromatin were transcribed by the exogenous enzyme in a highly selectiv ...1977264693
studies on aminoacyl trna synthetases and transfer rna in living xenopus laevis oocytes.the microinjection of transfer rna into amphibian oocytes permits one to study under in vivo conditions the reactions that affect this important macromolecule. a comparative study has been carried out between the in vivo and in vitro specificity of the aminoacylation reacton. the results obtained show that modifications of the trna structure affect aminoacyl-trna synthetase recognition in the same fashion in both conditions. the in vivo aminoacylation was not affected by the presence of puromyci ...1979261727
identification of rauscher murine leukemia virus-specific mrnas for the synthesis of gag- and env-gene products.polyadenylylated mrna isolated from cells infected with rauscher murine leukemia virus was fractionated by centrifugation in in a denaturing sucrose gradient into different sizes. each rna fraction was injected into oocytes of xenopus laevis and the virus-specific products were analyzed by immunoprecipitation with polyvalent and monospecific antisera against polypeptides of rauscher murine leukemia virus, and then by gel electrophoresis and scintillation autoradiography. it was shown that a 35s ...1977266707
aminoacyl transfer from phenylalanyl-trna microinjected into xenopus laevis oocytes. 1977244308
regulation by estrogen of the vitellogenin gene.the vitellogenin gene is inactive in the liver of male xenopus laevis, unless exogenous estrogen is administered. we have previously shown that conventional doses of estradiol-17beta result in the appearance of new hepatic messenger rnas, some of which are encoded for vitellogenin. we now report that much higher doses of the hormone (2 mg/frog per day for 4 days) are required to elicit maximal responses. the relative levels of membrane-bound polysomes and vitellogenin mrna were determined as a f ...1977267932
prescence of tadpole and adult globin rna sequences in oocytes of xenopus laevis.complementary dna transcribed from adult xenopus laevis globin mrna was used to assay ovary rna from xenopus for the presence of globin sequences by rna.cdna hybridization. these sequences are present at approximately the same concentration as the majority of poly(a)-containing ovary sequences. the sequences are also found at approximately 200,000 copies per cell in poly(a)-containing rna extracted from mature oocytes. to rule out contamination of the oocytes with somatic cells, two additional e ...1977269434
gene activation in somatic nuclei after injection into amphibian oocytes.genes that are unexpressed in somatic cells have been activated by injecting cultured cell nuclei of the frog xenopus laevis into oocytes of the newt pleurodeles waltlii. the genes that were activated are normally expressed in oocytes but not in cultured cells. conversely, genes that are normally expressed in cultured cells but not in oocytes became inactive when cultured cell nuclei were injected into oocytes. these changes in gene activity were detected by two-dimensional gel electrophoresis o ...1977267940
synthesis of human interferon by xenopus laevis oocytes: two structural genes for interferons in human cells.human fibroblasts and leukocytes produce interferons which may be distinguished by their antigenic and species specificity as well as by their molecular weight distributions. to elucidate the basis for these differences, we isolated mrna from induced human fibroblasts and lymphoblastoid (namalva) cells and studied the products of translation in xenopus laevis oocytes. the mrna from the respective cells yielded translation products, in oocytes, that were characteristic of the cells from which the ...1977269391
interferon messenger rna content of human fibroblasts during induction, shutoff, and superinduction of interferon production.translation of injected mrna in oocytes of xenopus laevis has been used as a highly sensitive and quantitative assay for interferon mrna. injection into oocytes of polyadenylylated rna extracted from poly(i).poly(c)-induced human diploid fibroblasts (fs-4) leads to the synthesis of biologically active human fibroblast interferon over a period of 24-32 hr. there is a linear relationship between the amount of mrna injected and the interferon yield obtained over a range of 1-20 ng of injected rna. ...1977269400
induction and decay of human fibroblast interferon mrna.polyadenylylated interferon mrna, obtained from induced human fibroblasts, was quantitatively assayed by synthesis of biologically active human interferon in xenopus laevis oocytes. the assay for interferon mrna was used to distinguish between various hypotheses relating to interferon induction and biosynthesis. the data demonstrate that on induction with poly(i-poly(c) human fibroblasts accumulate interferon mrna for 1-1.5 hr, after which time the mrna is rapidly degraded with a half-life (t 1/ ...1977270686
sites of transcription initiation in vivo on xenopus laevis ribosomal dna.we report the results of a novel method for locating sites of transcription initiation using a complex of capping enzymes from vaccinia virions that catalyze the reaction pppg + s-adenosylmethionine + (p)ppxpypzp..... -->(7m)gpppxpypzp..... [ensinger, m. j., martin, s. a., paoletti, e. and moss, b. (1975) proc. natl. acad. sci. usa 72, 2525-2529]. this enzyme complex will cap di- or triphosphate termini but will not cap monophosphate or hydroxyl termini. xenopus laevis 40s precursor rrna from oo ...1977271962
displacement-loop replication initiation sequence in animal mitochondrial dna exists as a family of discrete lengths.the single-stranded mitochondrial dna (mtdna) displacement-loop initiation sequence (7s mtdna) is hydrogen-bonded at the origin of replication in animal cell mtdna. analysis of 7s mtdna from several cell sources indicates that this initiation sequence exists as a family of fragments of relatively discrete lengths. mtdna from both mouse l cells and mouse liver has four major sizes of 7s mtdna fragments, ranging from 500 to 580 nucleotides in length. the 5'-end region of each of these species is t ...1978273230
the nucleotide sequence of the repeating unit in the oocyte 5s ribosomal dna of xenopus laevis. 1978277309
cloned single repeating units of 5s dna direct accurate transcription of 5s rna when injected into xenopus oocytes.single and multiple repeating units of three types of xenopus 5s dna recombined with the plasmid pmb9 serve as templates for the accurate synthesis of 5s rna after their injection into xenopus laevis oocyte nuclei. all 15 cloned single repeating units of x. laevis oocyte 5s dna that were tested supported 5s rna synthesis. three cloned fragments of x. borealis oocyte 5s dna and one cloned single repeating unit of x. borealis somatic 5s dna were templates for 5s rna synthesis. we conclude that the ...1978275856
transcription of cloned trna gene fragments and subfragments injected into the oocyte nucleus of xenopus laevis.cloned 3.18 kilobase fragments of xenopus laevis dna containing genes for trnamet1 and for at least one other 4s rna species are transcribed rapidly after their injection into the nucleus of x. laevis oocytes. the newly synthesized rna can be resolved by gel electrophoresis into a few predominant 4s rna species and a series of slower migrating components. one of the 4s rna species appears to be identical, by fingerprint analysis, to the trnamet1 isolated by hybridization of somatic cell rna to t ...1978274710
induction of maturation in xenopus laevis oocytes by a steroid linked to a polymer.a progesterone analog has been covalently linked via an amide bond to polyethylene oxide (molecular weight, 20,000). this macromolecular steroid molecule displays the biological activity of progesterone in inducing meiotic maturation when incubated with xenopus laevis oocytes (stage vi) in vitro. its efficiency (half-maximum effective concentration, 30 mum) is approximately 10 times lower than that of its low molecular weight homolog (3 mum). control experiments with polyethylene oxide and an es ...1978276879
does 3'-terminal poly(a) stabilize human fibroblast interferon mrna in oocytes of xenopus laevis?polynucleotide phosphorylase (polyribonucleotide:orthophosphate nucleotidyltransferase, ec purified from escherichia coli was used enzymatically to deadenylate polyadenylated human fibroblast interferon mrna preparations obtained from human diploid fibroblasts (fs-4 strain) induced by poly(i)-poly(c) (20 microgram/ml) in the presence of cycloheximide (50 microgram/ml, 4 hr). both the polyadenylated and the deadenylated interferon mrna preparations were translated into biologically activ ...1978283411
transcription of cloned xenopus 5s rna genes by x. laevis rna polymerase iii in reconstituted systems.when incubated with a soluble extract from large oocytes of xenopus laevis, recombinant dna plasmids containing either x. laevis oocyte 5s dna or x. borealis oocyte 5s dna direct the synthesis of discrete 5s rnas, which by size and sequence analysis are similar or identical to the corresponding 5s rnas synthesized in vivo. synthesis of the 5s rnas is mediated by a soluble endogenous rna polymerase iii (nucleosidetriphosphate:rna nucleotidyltransferase, ec, which presumably recognizes sp ...1979284325
isolation of a 7s particle from xenopus laevis oocytes: a 5s rna-protein complex.previtellogenic oocytes of xenopus laevis contain a free 5s rna-protein complex sedimentating at 7 s. this particle consists of one molecule of 5s rna and one 45,000-dalton protein. the protein of the 7s particle and the protein that is released in association with 5s rna when the ribosome is treated with edta are unrelated. because the 5s rna accumulated by small oocytes in storage particles is incorporated into the ribosome later in oogenesis, we conclude that 5s rna is succesively associated ...1979284338
electrical currents through full-grown and maturing xenopus extracellular vibrating electrode was used to map the current pattern around xenopus laevis oocytes. current was found to enter the animal hemisphere and leave the vegetal hemisphere; in fully grown oocytes from which the follicle cells had been removed, the maximal current density was about 1 microamperemeter/cm2. this current decreased to nearly zero in response to progesterone and several other maturation-producing agents. in the case of progesterone, the decline began within a few minutes ...1979284407
delimitation of a promoter for rna polymerase iii by means of a functional test.a xenopus laevis dna segment containing the structural gene for trna1met and 22 base pairs at the 5' side of the gene is active in trna production. the dna segment was ligated to sea urchin histone dna and was also inserted into plasmid pcr1. both recombinant dnas were shown to produce mature trna1met at a high rate when injected into centrifuged xenopus oocytes.1979288049
mitotic factors from mammalian cells induce germinal vesicle breakdown and chromosome condensation in amphibian oocytes.cytoplasmic extracts of hela cells synchronized in various phases of the cell cycle were injected into fully grown xenopus laevis oocytes to monitor the presence of factors that can induce meiotic maturation: i.e., germinal vesicle breakdown and chromosome condensation. extracts from gi and s phase cells had no activity. the maturation-inducing activity, which was found to be low during early and mid g2 phases, increased rapidly during late g2 and reached a peak in mitosis. the results of this s ...1979288067
structures of gustatory organs of xenopus laevis during metamorphosis. 1979297731
electron microscopic study on the early histogenesis of thymus in the toad, xenopus laevis.sequential electron microscopic observations of thymic histogenesis in the toad, xenopus laevis, reveal that the thymus arises as epithelial buddings of the visceral pouches at nieuwkoop-faber stage 40, and acquires its basic histological features at stages 48-49. in the rudiments and the surrounding mesenchyme at stages 43-45, there are non-epithelial cells with pseudopodia, abundant ribosomes, and marginated heterochromatin. these cells, possible precursor cells of thymic lymphocytes, are freq ...1977300655
photoreceptor outer segments: accelerated membrane renewal in rods after exposure to light.the rate of rod outer segment renewal in rana pipiens tadpoles under constant light and under diurnal conditions of 12 or 2 hours light per day is significantly increased compared to that in animals in darkness. furthermore, during 24 hours in light after 6 days in darkness the rate of renewal is three to four times that in darkness. in xenopus laevis tadpoles the rate of renewal is more than five times greater during the first 8 hours of a normal diurnal cycle than during the following 16 hours ...1977300504
early steroid metabolism in xenopus laevis, rana temporaria and triturus vulgaris embryos.embryos of xenopus laevis, rana temporaria and triturus vulgaris exposed to radioactive pregnenolone have been found to convert it to progesterone. incubations with radioactive progesterone showed that it was actively metabolized by oocytes and embryos. in xenopus incubations progesterone was converted to 5alpha-pregnane-3,20-dione, 17alpha-hydroxy-4-pregnen-3-one, 4-androstene-3,17-dione and 17alpha-20alpha-dihydroxy-4-pregne-3-one, indicating 5alpha-reductase, 17alpha-hydroxylase, 19-20-desmol ...1977303192
the effects of exogenous melatonin upon the gut of larval xenopus laevis. 1978310409
amphibian cells in culture. ii. isolation of drug-resistant variants and an asparagine-independent variant.with l-15 as the base medium, drug-resistant variants were isolated from two amphibian tissue culture strains: the xenopus laevis a8 diploid cell line and the icr 2a cell line of rana pipiens. four different classes of variants were obtained: (1) a8 cells resistant to chloramphenicol, an inhibitor of mitochondrial protein synthesis; (2) a8 cells resistant to ouabain, an inhibitor of the na+/k+-activated atpase of the plasma membrane;(3) icr 2a cells resistant to low (20 microgram/ml) and high (3 ...1978307557
somitogenesis in amphibian embryos. i. experimental evidence for an interaction between two temporal factors in the specification of somite pattern.somitogenesis is described in two species of anuran amphibians, xenopus laevis and rana temporaria, in which the cellular mechanics of somite formation are distinctly different. heat shocks are employed to demonstrate a wave of cellular change which precedes somite formation down the body axis. this prior wave is shown to be kinematic. it is not a propagated wave. it is a consequence of the temporal activities of the cells laid out in space, but there is no evidence that these activities depend ...1979314486
lens regeneration from cornea of larval xenopus laevis in the presence of the xenopus laevis tadpoles, wounding of the outer cornea failed to initiate lens regeneration. if both the outer and inner corneas were wounded or if the lens was dislocated, lens regeneration was initiated but failed to continue beyond stage iii. however, lensectomy followed by re-implantation of the lens resulted in the regeneration of a fully differentiated lens in several cases, despite the presence of the re-implanted lens. although some of the regenerates in these eyes were also arrested a ...1978311375
fine structural distribution of the surface-connected canalicular system in frog thrombocytes.the existence of the surface-connected canalicular system (sccs) has been demonstrated in semithick sections of the frog thrombocytes by the use of a high voltage electron microscope. the sccs of the thrombocytes in rana catesbeiana and rana nigromaculata consists of numerous canaliculi and vesicles with a diameter of 250 nm, which join with one another to make a complex network throughout the cytoplasm. although the sccs of xenopus laevis fits well into the pattern described in rana catebeiana, ...1979315820
the effect of adult thymectomy upon helper function in xenopus laevis, the south african clawed toad.carrier-primed helper activity enhancing anti-hapten (tnp-) responses in young adult xenopus laevis reached peak levels 2-4 days after a low dose challenge (0.005% rbc) of unconjugated carrier. it fell quickly to negligible levels by 10 days. adult thymectomized (atx) animals were consistently unable to generate substantial levels of hapten-specific antigen-binding spleen cell (abc) activity. since atx does not severely reduce splenic abc responses to the high dose (10% rbc) of carrier used for ...1979315915
properties of a cytostatic factor from xenopus laevis eggs. 1979315899
histological changes in xenopus laevis daudin adult specimens kept under dry conditions, then moved back to their natural aquatic environment. ii. skin, kidney and interrenal tissue.some cytological and histochemical characteristics of skin, the kidney and interrenal tissue were studied in xenopus laevis adult specimens (1) kept in their natural aquatic environment; (2) gradually exposed to dry conditions under which they were kept one week; and (3) returned from the dry environment to water for 24 hr or a week. in the skin, the most relevant changes are those exhibited by epidermal "flask" cells. these cells are generally rather lean, tall and pas-positive in "dry" animals ...1978318018
novel screening procedure for recombinant plasmids.lysed bacterial colonies containing potential recombinant plasmids were mixed with molten agar and sealed into slots of an agarose gel. after electrophoresis overnight, the gel was stained with ethidium bromide, which clearly reveals recombinant plasmids. xenopus laevis ribosomal dna and histone dna of psammechinus miliaris were ligated into pcri plasmids and screened by this method.1977318763
ionic requirements for induction of maturation (meiosis) in full-grown and medium-sized xenopus laevis oocytes.there is already good evidence that calcium ions are involved in the induction of maturation in full-grown amphibian oocytes; we show here that other cations (k+, mg2+) also play a role in this process. full-grown (1.3 mm in diameter) and medium-sized (0.8-1.0 mm in diameter) oocytes were compared in the present study. it was found that, provided the medium is k+-free, valinomycin induces maturation in full-grown, but not in medium-sized, oocytes. increasing the cacl2 (20 mm) or the mgso4 (40 mm ...1977333439
stimulation of cell division in ectopic kidney grafts following unilateral removal of the lung.small fragments of kidney tissue were grafted into the right lung (xenopus laevis) and the left lung was subsequently removed. this stimulated compensatory hyperplasia (increased mitotic rate) in alveolar tissue of the right lung and in the kidney graft. this suggests that the stimulus to compensatory hyperplasia is location-specific rather than tissue- or organ-specific. after implantation into the lung the kidney grafts are revascularized by the surrounding pulmonary supply. damage or functio ...1977322542
free calcium in full grown xenopus laevis oocyte following treatment with ionophore a 23187 or intracellular ca2+ was monitored in isolated xenopus laevis oocyte during induced maturation using the ca2+ -sensitive luminescent protein, aequorin. internal free ca2+ was not precisely measured but data suggest it was quite low (in the micromolar range). no change in internal free ca2+ was detected during maturation induced either by progesterone or by p-chloromercuribenzoate. by contrast, the ionophore a 23187 gave an increase in the free ca2+ level when there was a raised external ca2+ ...1977328329
transplantation of nuclei from lymphocytes of adult frogs into enucleated eggs: special focus on technical parameters.the technique of transplantation of nuclei from adult lymphocytes into enucleated eggs from xenopus laevis (south african clawed toad) is described. the splenic lymphocytes from the one-nucleolus mutant were bound via their immunoglobulin receptors to nylon fibers, derivatized with the antigen used for immunization. a technique for coupling other cell types with woodward reagent is also described. the cells were broken by aspiration into a micropipette and injected into enucleated eggs. the egg ...1977340313
indirect immunofluorescent identification of 19s immunoglobulin-containing cells in the intestinal mucosa of xenopus laevis.the lymphoid structures in the gastrointestinal tract of immunized and non-immunized adult xenopus laevis were studied by light and fluorescent microscopy. serial sections stained with may-grunnwald giemsa showed that lymphoid aggregations and scattered lymphoid cells are present along the whole digestive tract. the aggregations are few and rather small in the oesophagus and stomach, they are particularly voluminous in the duodenum. an indirect immunofluorescent technique using antisera against ...1977328818
intracellular motility of mitochondria: role of the inner compartment in migration and shape changes of mitochondria in xth-cells.mitochondrial movements have been followed by phase-contrast microscopy in living xth-cells (xenopus laevis tadpole-heart cells) in tissue culture. the same organelles have been viewed subsequently in electron micrographs. locomotion of mitochondria proceeds at velocities up to 100 micrometer/min. formation of branches of mitochondria and other shape changes may occur with the same speed. mitochondrial motility can be classified into 4 types: (i) alternating extension and contraction at the two ...1978348713
stimulation of cell division in ectopic liver tissue following partial removal of the lung.autografts of liver were implanted into the left lung (xenopus laevis). subsequent removal of the right lung stimulated increased mitotic activity in the lung and in the liver graft.1977336386
injected amphibian oocytes: a living test tube for the study of eukaryotic gene transcription?somatic-cell nuclei injected in xenopus laevis oocytes remain transcriptionally active for up to 4 weeks. the rate of rna synthesis increases as the somatic-cell nuclei enlarge. the message activity of the rna synthesized by the injected nuclei can be demonstrated, as new proteins are made a few days after injection of hela-cell nuclei. several lines of evidence demonstrate that these proteins are coded for by the hela-cell genome and that they result from rna synthesized within the oocytes in t ...1977339919
recombinant plasmids containing xenopus laevis globin structural genes derived from complementary dna.details are presented of the in vitro synthesis of double-stranded dna complementary to purified xenopus globin messenger rna, using a combination of reverse transcriptase, fragment 'a' of e. coli dna polymerase 1 and s1 endonuclease. after selection of duplex dna molecules approaching the length of xenopus globin messenger rna by sedimentation of the dna through neutral sucrose gradients, the 3'-oh termini of the synthetic globin gene sequences were extended with short tracts of oligo dgmp usin ...1978347404
a method for isolating uncontaminated nuclei from all stages of developing xenopus laevis embryos.a method for isolating nuclei from xenopus laevis embryos has been developed. this procedure enables the isolation of nuclei, free from contamination with yolk and pigment granules, at all stages of embryoic development. using this method the nuclear yield is 60--70% of the estimated number of cells in the embryo. the dna, rna, histone and non-histone protein content of these nuclei during embryogenesis (from early cleavage to the swimming tadpole stage) has been measured.1978370328
in vivo studies on the incorporation of microinjected acidic proteins of the large ribosomal subunit from escherichia coli and artermia salina into oocyte ribosomes from xenopus laevis.tritium-labeled acidic proteins from the large ribosomal subunit of artermia salina or escherichia coli were microinjected into the cytoplasm of stage iv/v oocytes from xenopus laevis. el12 from the large ribosomal subunit of a. salina but not l7/l12 or l7/l12--l10 from e. coli is specifically incorporated into 60s ribosomal subunits of oocytes. this incorporation is not significantly inhibited by actinomycin d. incorporation of el12 into the 60s subunits occurs in enucleated oocytes, suggesting ...1979385044
cloning of nematode trna genes and their expression in the frog oocyte.transfer rna genes of the nematode caenorhabditis elegans have been cloned in e. coli using the plasmid col e1 as vector. the trnas coded by 3 hybrid plasmids were purified by hybridisation of labelled nematode trna with the plasmid dnas. each plasmid appears to code for a single distinct trna species. the expression of the cloned dnas was analysed in vivo by injection into nuclei of xenopus laevis oocytes. evidence is presented which suggests that these nematode trna genes are accurately transc ...1978370775
lymphocyte surface immunoglobulin in xenopus laevis. light and electron microscopic demonstration by immunoperoxidase method. 1978355005
structure of deletion derivatives of a recombinant plasmid containing the transposable element tn9 in the spacer sequence of xenopus laevis 5s dna. 1979385229
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