Publications

the embryotoxic and osteolathyrogenic effects of semicarbazide.	the osteolathyrogenic agent semicarbazide was assayed for its toxicity and teratogenicity using early embryos of the frog xenopus laevis. the 96-h lc50 is 1504.20 mg/l while the 96-h ec50 is 76.28 mg/l. embryo length is altered prior to the onset of other effects indicated by a reduction in stage of development. the major malformation is associated with the notochord where the notochordal sheath is reduced owing to the disruption in the maturation and/or deposition of the connective tissue fiber ...	1985	4049430
(at)n is an interspersed repeat in the xenopus genome.	we have observed (at)34 and (at)23 tracts close to the coding sequences of the xenopus laevis tadpole alpha t1 and adult beta 1 globin genes, respectively. we show that (at)n sequences are found as interspersed repeats within the xenopus globin and histone gene loci. using (at)n co-polymer in filter hybridisation experiments we estimate that there are 10(4) (at)n tracts per haploid xenopus genome. hybridisation to genomic blots of dna from yeast, slime mold, trypanosome, fruit fly, salmon, chick ...	1985	4054102
gene-centromere mapping in xenopus laevis.	gynogenesis was used to map eight loci to their centromeres in xenopus laevis. several loci remote from their centromeres were identified. this information may be useful in distinguishing gynogenetic diploid progeny produced by suppression of second polar bodies from gynogenetic diploid progeny homozygous at all loci produced by suppression of first cleavage of gynogenetic haploids.	1985	4056365
association of maternal and newly synthesized ribosomes with membranous noncytoskeletal structures in xenopus laevis embryonic cells.	in xenopus laevis embryos a high concentration of both kcl and 0.5% doc (sodium deoxycholate) is needed for maximal extraction of ribosomes and polysomes. we studied the nature of the structures that keep ribosomes and polysomes immobilized within the cytoplasm of embryonic cells at cleavage through tailbud stages, using various combinations of a low-salt buffer (20 mm kcl), a high-salt buffer (500 mm kcl), 0.5% doc, and 0.5% triton x-100. with a low-salt buffer and 0.5% doc, but not triton x-10 ...	1985	4056690
purification and characterization of an n-acetyl-beta-d-glucosaminidase from cortical granules of xenopus laevis eggs.	the enzyme n-acetyl-beta-d-glucosaminidase was purified from the cortical granules of xenopus laevis eggs using affinity chromatography, gel filtration, and density gradient centrifugation. the enzyme had a molecular weight of 37,000-40,000 as determined by polyacrylamide gel electrophoresis and density gradient centrifugation, had a km for p-nitrophenyl-beta-d-n-acetyl-glucosaminide of 0.66 mm and a ki for glucosamine of 4.3 mm. the kinetic properties of the cortical granule enzyme were similar ...	1985	4056694
origin and voltage dependence of asparagine-induced depolarization in intestinal cells of xenopus embryo.	the kinetics and voltage dependence of asparagine (asn)-induced depolarization in endoderm cells from xenopus laevis embryos were analysed using current-clamp techniques. the depolarization is assumed to reflect the activation of an amino acid membrane carrier; it is accompanied by a slight increase in membrane resistance and cannot be explained by only the electrogenic character of the asn carrier. it is proposed that the asn depolarization arises, at least in part, from the decrease of the per ...	1985	4057089
multisensory interaction in the torus semicircularis of the clawed toad xenopus laevis.	interactions between the lateral-line, general somatosensory and auditory system were studied using field potential analysis and single unit recordings in the torus semicircularis of the clawed toad xenopus laevis. as a response to paired stimuli (electric shocks applied to the peripheral nerves or acoustic clicks), in all systems a reduction of the second evoked potential occurred for intervals of up to 5 s. following consecutive stimulation of two different systems, the amplitude of the second ...	1985	4058802
the development of the dendritic organization of primary and secondary motoneurons in the spinal cord of xenopus laevis. an hrp study.	during embryonic and larval development of the clawed toad, xenopus laevis, two different populations of motoneurons appear in the spinal cord. in this study the development of primary motoneurons which innervate the axial musculature (used during embryonic locomotion) and of secondary motoneurons which innervate the extremity musculature (used for locomotion during metamorphosis and thereafter) was analyzed with horseradish peroxidase (hrp) as a neuronal marker. after application of hrp to the ...	1985	4061871
interaction of the transplanted olfactory placode with the optic stalk and the diencephalon in xenopus laevis embryos.	the effect of olfactory placode transplantation on the differentiation of the optic vesicle and stalk has been studied in xenopus laevis embryos. host embryos (stages 23-24) received the transplant of two olfactory placodes from same-stage donors in place of a partially or totally removed optic vesicle. all tadpoles were sacrificed at stages 47-50. the host tadpoles were subdivided in three groups according to the amount of optic vesicle removed. in the first group all of the optic vesicle was r ...	1985	4069358
dna replication of single-stranded dna of phage fd microinjected into xenopus laevis eggs.	single-stranded circular dna of phage fd was microinjected into xenopus laevis eggs and dna synthesis was analyzed after incubation. an efficient dna synthesis occurred in the eggs: 2.7 ng of dna was newly formed in an egg whose volume is approximately 900 nl during a 5-h incubation at 20 degrees c. the dna synthesis was sensitive to aphidicolin, suggesting that dna polymerase alpha participates in the synthesis. agarose gel electrophoresis showed that full size of fd dna is synthesized and that ...	1985	4074353
differences of proteins in isolated egg surface after fertilization of xenopus laevis.	egg surface proteins of xenopus laevis were compared between unfertilized and fertilized egg surfaces before the first cleavage. the egg surfaces were isolated in acetone. the macromolecular compositions of egg surfaces were analyzed by two-dimensional gel electrophoresis and were shown to contain at least 30 proteins with molecular weights ranging from 27,000 to 200,000. at 50 min after fertilization, one spot with a molecular weight of 160,000 disappeared and two bands with molecular weights o ...	1985	4075414
timing of the initiation of rrna gene expression and nucleolar formation in cleavage embryos arrested by cytochalasin b and podophyllotoxin and in cytoplasm-extracted embryos of xenopus laevis.	the timing mechanism of rrna gene expression was studied in xenopus laevis embryos whose cleavage was arrested by treatment with cytochalasin b or podophyllotoxin, and in fertilized eggs from which about 40% of the cytoplasm was extracted by micromanipulation. rrna synthesis was activated in the cleavage-arrested embryos and also in cytoplasm-extracted embryos at the time when the control embryos commenced synthesizing rrna at the late blastula stage. formation of the nucleolar structure occurre ...	1985	4075851
experimental control of the site of embryonic axis formation in xenopus laevis eggs centrifuged before first cleavage.	in xenopus laevis, the dorsal structures normally develop from regions of the egg opposite the side of sperm entry. gravity is known to affect this topographic relationship in eggs inclined obliquely from their normal vertical orientation in the period before first cleavage. this effect has been explored in detail, making use of low-speed centrifugation (10-50 g) for short durations (4 min). eggs were immobilized in gelatin and oriented with their animal-vegetal axes 90 degrees to the force vect ...	1985	4076537
estrogen-dependent dna synthesis and parenchymal cell proliferation in the liver of adult male xenopus frogs.	estradiol-17 beta treatment of adult male xenopus laevis induces liver parenchymal cells to synthesize dna and proliferate. dna synthesis begins 3 to 4 days after estrogen treatment and continues for approximately 10 days. over this 2-week period, the total number of liver parenchymal cells increases fourfold, the wet weight of the liver remains constant, and there is a 50% reduction in cell volume. the elevated number of cells persists for several months and then returns to the control value. t ...	1985	4076538
characterization of the fourth component of complement in the serum of the clawed frog xenopus laevis.	the 202,000 mw protein xc, which is distinct from c3 but is essential for antibody-dependent haemolytic activity against srbc, was obtained from xenopus plasma following polyethylene glycol precipitation, ion-exchange chromatography and gel-filtration. the protein required other components of the xenopus serum in order to lyse sensitized srbc, but did not lyse unsensitized rrbc through the alternative pathway. the protein, contained at 0.17 mg/ml in the original plasma, comprised three distinct ...	1985	4077103
dynamics of the control of body pattern in the development of xenopus laevis. ii. timing and pattern in the development of single blastomeres (presumptive lateral halves) isolated at the 2-cell stage.	xenopus embryos have been selected in which the first cleavage plane is tending strongly to correspond with that of bilateral symmetry for the future larval pattern. the two blastomeres produced by this cleavage have been separated and allowed to develop as reciprocal pairs of presumptive lateral-half isolates. the early development and the time course of the gastrulation movements, and the qualitative and quantitative aspects of larval mesodermal patterns, have been studied in relation to synch ...	1985	4078526
dynamics of the control of body pattern in the development of xenopus laevis. iii. timing and pattern after u.v. irradiation of the egg and after excision of presumptive head endo-mesoderm.	a series of xenopus egg batches has been exposed to doses of u.v. (2537a) light on the vegetal hemisphere at precleavage stages, calculated to result in a range of minimal axial deficiency syndromes in the developing larvae. at the time of onset of gastrulation in synchronously fertilized but non-irradiated batch members, each experimental group was regularly scanned so that small subsamples of embryos could be set aside as showing particular, progressive degrees of delay in onset of the visible ...	1985	4078527
development of the lateral line system in xenopus laevis. iii. development of the supraorbital system in triploid embryos and larvae.	during normal development of the supraorbital lateral line system of xenopus, an elongated streak of primordial cells becomes subdivided into a linear series of cell groups containing only about eight cells each, thus forming a row of primary lateral line organs (winklbauer & hausen, 1983a,b). in triploid xenopus embryos, cell size is 1.5 x normal. when the formation of lateral line organs occurs in triploid primordia, the nascent organs contain only about five or six cells each, i.e. about two ...	1985	4078528
development of the lateral line system in xenopus laevis. iv. pattern formation in the supraorbital system.	the periodic pattern of the supraorbital lateral line organs forms in the epidermis of xenopus by the subdivision of a streak-like primordium into a linear series of small cell groups. in normal development, each such organ initially contains about 8 cells (winklbauer & hausen, 1983a,b). to see whether this initial organ size depends on the size of the streak-like primordium at the time of organ segregation, primordium size was reduced experimentally before the onset of pattern formation. in suc ...	1985	4078529
dynamics of the control of body pattern in the development of xenopus laevis. i. timing and pattern in the development of dorsoanterior and posterior blastomere pairs, isolated at the 4-cell stage.	xenopus embryos have been selected in which the second cleavage is occurring in a frontal plane, i.e. one tending to lie at right angles to the prospective plane of bilateral symmetry for the body pattern. some of these have been used to deduce a map of the disposition of materials for the normal mesodermal pattern (the normal 'fate map') by injecting blastomeres to found fluorescently marked clones from 4- to 32-cell stages. other such 4-cell embryos have been separated into two isolates across ...	1985	4078542
xenopus ribosomal gene enhancers function when inserted inside the gene they enhance.	the ribosomal dna of xenopus laevis contains repeated sequence elements in the intergenic spacer region that enhance transcription from the adjacent gene promoter (1,2). previous work has shown that these rna polymerase i enhancers influence the target promoter when they are in either orientation, at a distance of several kilobases, and only when they are in cis (3-5). in this work, we further show that enhancer activity is unaffected by inserting the enhancers within the transcription unit whos ...	1985	4080555
[regenerative capability in the hindlimb of xenopus laevis during ontogenetic development].	the regenerative capacity of hindlimb of xenopus laevis was investigated by amputating the limbs at four levels in various developmental stages including younger postmetamorphosed froglets. amputations of limbs were performed at the base of limb in stages 50, 51, 52, 53, 54, 55, 58, and 60 (nieuwkoop and faber's table), at the middle of limb bud in stages 50, 51, 52 and 54, and at mid-thigh and mid-shank in stages 58 and 60, and the froglets in 2 and 3 cm in snout-vent length. in the present exp ...	1985	4085572
structure of the lung of the clawed toad (xenopus laevis daudin).		1985	4085945
development and ciliation of the palate in two frogs, bombina and xenopus; a comparative study.	the morphological changes that occur during metamorphosis in the palates of two types of anuran larvae (a discoglossid, bombina orientalis, and a pipid, xenopus laevis) are compared. in b. orientalis the structural changes are accompanied by the ciliation of the palate epithelium. ciliation begins in the anterior region of the palate and continues in a posterior direction throughout metamorphosis. by contrast, the palate of x. laevis never becomes ciliated during its development. instead, two ci ...	1985	4089862
human 18 s ribosomal rna sequence inferred from dna sequence. variations in 18 s sequences and secondary modification patterns between vertebrates.	we have determined the dna sequences encoding 18 s ribosomal rna in man and in the frog, xenopus borealis. we have also corrected the xenopus laevis 18 s sequence: an a residue follows g-684 in the sequence. these and other available data provide a number of representative examples of variation in primary structure and secondary modification of 18 s ribosomal rna between different groups of vertebrates. first, xenopus laevis and xenopus borealis 18 s ribosomal genes differ from each other by onl ...	1985	4091818
effect of diadenosine tetraphosphate microinjection on heat shock protein synthesis in xenopus laevis oocytes.	bisnucleosides polyphosphates are thought to be chemical messengers signalling to the cell the onset of various stresses. diadenosine tri- and tetraphosphates (respectively, ap3a and ap4a) accumulate in prokaryotic and eukaryotic cells under heat shock conditions, suggesting they could trigger the synthesis of heat shock proteins (hsps). in this study, ap4a, ap3a and, as a control, ap4 (adenosine tetraphosphate) were injected into xenopus oocytes. whereas none of these compounds is able to trigg ...	1985	4092696
different conformations of ribosomal dna in active and inactive chromatin in xenopus laevis.	the chromatin structure of the ribosomal dna in xenopus laevis was studied by micrococcal nuclease digestions of blood, liver and embryonic cell nuclei. we have found that bgli-restricted dna from micrococcal nuclease-digested blood cell nuclei has an increased electrophoretic mobility compared to the undigested control. micrococcal nuclease digestion of liver cell nuclei causes a very slight shift in mobility, only in the region of the spacer containing the "bam islands". in contrast, the mobil ...	1985	4093984
information transfer during embryonic induction in amphibians.	neural induction and differentiation has been studied using concanavalin a, cyclic amp, tunicamycin and calcium ionophore a 23187. competent ectoderm of xenopus laevis treated with concanavalin a differentiates into neural (archencephalic) structures. binding studies with gold-labelled cona indicate that the superficial ectodermal layer contains fewer cona-sensitive sites (alpha-d-mannoside and alpha-d-glucoside residues of glycoproteins) than the inner ectodermal layer. the small number of cona ...	1985	3007651
structural effects of external media on isolated myelinated axons.	myelinated axons were isolated from the sciatic nerve of xenopus laevis by desheathing and teasing, and were mounted for short-term light microscope observation in different media. fibres mounted in a conventional physiological saline showed a tendency to gross structural changes, including collapse of axons and separation of the axon from the myelin sheath. with isotonic media based on 120mm potassium aspartate, or 120mm potassium glutamate, structural stability and axoplasmic function (assesse ...	1985	2858303
[nle4, d-phe7]-alpha-msh: a superpotent melanotropin with prolonged action on vertebrate chromatophores.	the in vitro and in vivo responses of integumental chromatophores to alpha-msh and a related analogue, [nle4, d-phe7] -alpha-msh, were studied in a number of vertebrate species: the teleost, lebistes reticulatus; the amphibians, rana pipiens, r. catesbeiana, xenopus laevis, bufo alvarius, and b. cognatus; the lizard, anolis carolinensis; the rattlesnake, crotalus atrox. the alpha-melanotropin analogue was a superpotent agonist in the in vitro frog (r. pipiens, r. catesbeiana) and lizard (a. caro ...	1985	2859941
comparative actions of gaba and acetylcholine on the xenopus laevis lateral line.	the effects of gaba, acetylcholine and carbachol on the spontaneous activity of afferent nerve fibers in the lateral line of xenopus laevis are characterized. atropine and bicuculline were also tested on drug- and water motion-evoked activity. gaba (0.019-1.25 mm) suppressed and both acetylcholine (1.25-80 microm) and carbachol (1.25-40 microm) increased spontaneous activity. these actions were blocked by bicuculline (100 microm) and atropine (4 microm) respectively. atropine (20 microm) and bic ...	1985	2861015
polyadenylation of the xenopus beta 1 globin mrna at a downstream minor site in the absence of the major site and utilization of an aauaca polyadenylation signal.	we show that adult reticulocytes of xenopus laevis produce two forms of the beta 1 globin mrna that differ in their site of polyadenylation. the minor site of polyadenylation is located 46 nucleotides downstream of the major site and is used in approximately 1% of mrna molecules. a fusion gene was constructed containing the promoter from the thymidine kinase gene of herpes simplex virus fused to the protein coding, 3'-noncoding and 3'-flanking sequences of the x. laevis beta 1 globin gene. when ...	1985	2862026
isolation, partial characterization and translation of mrnas for chymosin and pepsin, the two main aspartyl proteinases of bovine stomach.	poly(a) rna from the mucosa of the fundal region of the fourth stomach of suckling calf and adult cattle was isolated by the phenol or guanidine thiocyanate procedure. the mrnas for chymosin and pepsin were present in the 15s fraction of poly(a) rna. they were active both in cell-free translation systems and in oocytes of xenopus laevis and directed the synthesis of either chymosin or pepsin precursor, depending upon the age of the donor animal. in the reticulocyte and wheat germ system only pre ...	1985	2862064
calcium paradox from cyclostome to man: a comparative study.	in seven poikilotherm species, i.e. cyclostome, myxine glutinosa; teleosts, gadus morrhua; platichtys flesus; amphibia, r. pipiens; r. temporaria; xenopus laevis; reptiles, vipera berus. ca paradox could not be obtained in ventricular strips at 8-12 degrees c. in similar preparations from human atria at 30 degrees c and 37 degrees, ca paradox was obtained similarly as in other homoiotherms. in homoiotherms, lowered temperature (below 30 degrees c) has a protective effect. viper myocardium did no ...	1985	2863069
accurate and efficient transcription of human c-myc genes injected into xenopus laevis oocytes.	we investigated the expression of the cloned human c-myc gene in xenopus laevis oocytes microinjected with different recombinants. we found that microinjected plasmid dna carrying an intact human c-myc gene directs efficient and faithful transcription from its own two promoters in x. laevis oocytes. this active transcription was unaffected by the presence of previously identified enhancing elements such as simian virus 72-base pair repeats or mouse immunoglobulin heavy-chain gene enhancer sequen ...	1985	2863748
messenger rna from bovine retina induces kainate and glycine receptors in xenopus oocytes.	the retina contains several types of nerve cells that communicate through chemical synapses. the transmitter and receptor molecules that mediate signal transmission across these synapses need further characterization. for this purpose, poly (a)+ mrna was isolated from bovine retinas and injected into xenopus laevis oocytes. translation of the foreign mrna induced the oocyte membrane to acquire functional receptors to kainate and, to a lesser extent, also receptors to glycine, gamma-aminobutryic ...	1985	2863826
a comparative study of the membrane potential from before fertilization through early cleavage in two frogs, rana pipiens and xenopus laevis.	the membrane potential of rana pipiens eggs (-55.0 mv +/- 11.2(16)) was more likely to recover from impalement and was always more negative than that of eggs of xenopus laevis (-19.3 mv +/- 4.2(68)). it was also much more negative than previously reported. essentially similar membrane resistance changes were measured in the two frog species through fertilization and cleavage. small transient depolarizations only associated with the onset of the fertilization potential in xenopus could be prevent ...	1985	2864209
stimulation of photoreceptor disc shedding and pigment epithelial phagocytosis by glutamate, aspartate, and other amino acids.	it has been reported that aspartate and glutamate selectively impair the structure (olney, '82) and function (e.g., furakawa and hanawa, '55) of second- and third-order retinal neurons while leaving the photoreceptor unaffected. either amino acid may mimic the endogenous photoreceptor neurotransmitter (ehinger, '82). we report here that excitatory amino acids also induce massive rod photoreceptor disc shedding in eyecups of xenopus laevis maintained in vitro. disc shedding is the process whereby ...	1985	2864363
identification of microtubule-associated proteins (maps) in xenopus oocyte.	microtubules were isolated from prophase-blocked oocytes of xenopus laevis with the use of the anti-tumor drug taxol. in addition to tubulin, 5 microtubule-associated proteins (maps) were characterized. among them, 2 high molecular mass proteins (200-300 kda) are phosphorylated in ovo. the oocyte map extract promotes the assembly of rat brain 6 s purified tubulin.	1985	2865168
t-lymphocyte regulation of humoral immunity in xenopus laevis, the south african clawed toad.		1985	2867941
microtubules in immature oocytes of xenopus laevis.	previous work indicated that immature oocytes of xenopus were incapable of assembling microtubules but that competence was achieved during maturation. we report here that small numbers of microtubules do exist in immature oocytes. consistent with this finding, ultrastructural observations indicate that brain microtubules injected into immature oocytes persist in large numbers for at least 30 min. we report that the tubulin dimers of mature and immature oocytes are equally capable of assembling w ...	1985	2868018
gene expression in xenopus embryogenesis.	this article considers some aspects of the storage of macromolecules in the oocyte of xenopus laevis and the activation of previously unexpressed genes during early embryogenesis. the large quantity and complex nature of poly(a)+ rna accumulated in the egg provides the cleavage embryo with a supply of mrna sufficient to sustain protein synthesis for several hours of development. onset of gene activity at the midblastula transition (mbt) leads to the synthesis and accumulation of molecules of var ...	1985	2420914
altered morphogenesis and its effects on gene activity in xenopus laevis embryos.		1985	2420514
specific changes in axonally transported proteins during regeneration of the frog (xenopus laevis) optic nerve.	labeled proteins in intact and regenerating optic nerves of juvenile xenopus clawed frogs were examined at three different time points (2 to 4 hr, 18 hr, and 5 to 9 days) following [35s]methionine injection into the eye. the distal axon tips of optic nerves were transected at the margin of the tectal lobe and regeneration of the nerve was followed by three methods: autoradiography, tissue section counting following [3h]proline injection into the eye, and electrophysiological mapping of the visua ...	1985	2578186
2'-fluoro-2'-deoxycytidine triphosphate as a substrate for rna- and dna-dependent dna polymerases.	the ability of the analog 2'-fluoro-2'-deoxycytidine triphosphate (dcfltp) to be used as a substrate in the reactions catalyzed by xenopus laevis oocytes dna polymerase alpha and amv reverse transcriptase has been studied. the apparent km values for dctp and dcfltp, using activated dna as templates, were 0.6 microm and 7 mm with dna polymerase alpha and 0.14 microm and 7 microm with amv reverse transcriptase, respectively. as observed with dctp, aphidicolin was a noncompetitive inhibitor in the ...	1985	2578819
2'-fluoro-2'-deoxypolynucleotides as templates and inhibitors for rna- and dna-dependent dna polymerases.	poly(2'-fluoro-2'-deoxyadenylic acid) (poly(dafl)) and poly(2'-deoxycytidylic acid) (poly(dcfl)) were tested as templates in dna synthesis reactions catalyzed by xenopus laevis oocytes dna polymerase alpha, mouse cell dna polymerase gamma and avian myeloblastis virus (amv) reverse transcriptase. poly(dafl).(dt)12 can fully substitute for poly(ra).(dt)12 as template with dna polymerase gamma, to 50% with reverse transcriptase, but was poorly recognized by dna polymerase alpha. dna synthesis by re ...	1985	2578820
beta-adrenergic induced k+ current in xenopus oocytes: role of camp, inhibition by muscarinic agents.	the k+ current induced by isoprenaline acting on beta-adrenergic receptors in xenopus laevis has been studied in oocytes still surrounded by their follicular cells and inner ovarian epithelium. forskolin, an adenylate cyclase activator, induced a similar k+ current and when used at subliminal concentration it potentiated the current induced by isoprenaline. inhibition of phosphodiesterase by methylisobutylxanthine also enhanced the response to isoprenaline. 8-br-camp, a permeant analogue of camp ...	1985	2579401
in vitro activation of human sperm induced by amphibian egg extract.	in this paper we characterize a system for the activation of human sperm using cell-free extracts from xenopus laevis eggs. we characterize the kinetics of sperm activation in terms of morphological and dna synthetic parameters. we have optimized some of the components which are necessary for chromatin decondensation and present data to demonstrate that the in vitro process is efficient over a wide range of salt concentrations and amounts of supplementary reducing agents.	1985	2579835
gating kinetics of nonjunctional acetylcholine receptor channels in developing xenopus muscle.	the development of nonjunctional acetylcholine (ach) receptor gating kinetics was studied in myotomal muscle of xenopus laevis by spectral analysis of ach-induced noise. the results are consistent with the idea that there is a developmental shift in relative numbers of receptors with fast and slow gating kinetics. for about the first 20 hr following the onset of ach sensitivity, the majority of channel openings contributing to the ach noise were slow, having an apparent mean open time of about 3 ...	1985	2580068
three functions of sodium channels in the toad node of ranvier are altered by trimethyloxonium ions.	voltage-clamped nodes of ranvier of the toad xenopus laevis were treated with trimethyloxonium ions (tmo) which are known to methylate carboxyl groups. tmo did not affect potassium channels but the sodium system was modified in three ways: a) the current was reduced, b) channels were rendered insensitive to tetrodotoxin (ttx) and c) the inactivation of all channels, ttx-resistant or not, was slowed in a potential range between 50 and 110 mv. steady-state inactivation, however, was not changed. p ...	1985	2580267
light and temperature modulated staining of the rod outer segment distal tips with lucifer yellow.	external application of the dye lucifer yellow to isolated retinas of xenopus laevis causes a specific staining of the distal tips of the rod outer segment (ros). staining occurs most frequently in the distal 4 micron of the ros and does not diffuse throughout the ros cytosol. in contrast, damaged ros fill with the dye and exhibit a diffuse fluorescence. retinas from constant light-treated animals show a greater frequency of labeling when isolated in the light than when isolated in the dark afte ...	1985	2581915
rna directed synthesis of catalytically active drosophila sn-glycerol-3-phosphate dehydrogenase in xenopus oocytes.	xenopus laevis oocytes injected with poly(a)+ rna isolated from drosophila melanogaster direct the synthesis of catalytically active glycerol-3-phosphate dehydrogenase (nad+) (ec 1.1.1.8). the de novo synthesized enzyme reflects the electrophoretic properties appropriate to the stock of flies from which the injected rna was isolated and is electrophoretically distinct from endogenous xenopus activity. immunoprecipitation of 35s-labeled translation products has demonstrated two immunologically re ...	1985	2581943
vesicular transport of newly synthesized opsin from the golgi apparatus toward the rod outer segment. ultrastructural immunocytochemical and autoradiographic evidence in xenopus retinas.	each day, rod photoreceptors of the vertebrate retina synthesize rhodopsin and insert it into new membranes of the rod outer segment (ros). the authors determined which components of the rod cell transport opsin from the golgi to the ros by a combined em autoradiographic and immunocytochemical study using radiolabeled amino acid precursors and antiopsin antibodies. radiolabeled proteins in the ellipsoid region of xenopus laevis retinal rods were localized by comparison of the distribution of sil ...	1985	2931395
location of influenza virus m, np and ns1 proteins in microinjected cells.	when microinjected as cloned dna, the nucleoprotein (np) of influenza virus a/nt/60/68 (h3n2) accumulated in the nuclei of xenopus laevis oocytes, and cultured cells of rodent and primate origin. this accumulation appeared to be specific and a property of the np itself (or conceivably np in association with unknown cellular constituents) since no other influenza virus components were present in dna-injected cells. in the oocyte nucleus, clonally derived np achieved an eightfold concentration ove ...	1985	2932535
specific binding sites for ovine prolactin in three amphibian cell lines.	established cell lines (tb-6c and tb-m) obtained by continuous culture of epithelial cells from toad bufo marinus urinary bladder, which, in culture, maintained a high degree of functional differentiation, exhibited a significant number of high-affinity (ka = 1-2 x 10(10) m-1) binding sites detected both with radioiodinated (125i) ovine prolactin (oprl) and human growth hormone (hgh). binding capacity was higher in the case of tb-6c cells (7,573 +/- 581 sites/cell) than with the tb-m cells (1,16 ...	1985	2981477
co-existence of two different types of soluble histone complexes in nuclei of xenopus laevis oocytes.	the nuclear pool of soluble histones in xenopus laevis oocytes is organized into two major types of acidic histone complexes separable by sucrose density gradient centrifugation. one type of complex sediments at 5 s (mr approximately 120,000), is isoelectric at ph 4.6, and contains histones h3 and/or h4 tightly bound to one polypeptide of a pair of very acidic polypeptides, designated n1 and n2 (kleinschmidt, j. a., and franke, w. w. (1982) cell 29, 799-809). this complex can be selectively immu ...	1985	2981836
cyclic amp levels during the maturation of xenopus oocytes.	while several studies have suggested that the induction of oocyte maturation results from a transient decrease in camp levels, attempts to demonstrate such a change have led to inconsistent results with respect to whether or not a decrease occurs as well as timing of the decrease. in this report the results of experiments designed to demonstrate small changes in camp content in xenopus laevis oocytes are presented and a statistically significant 20% decrease in camp content from between 2 and 50 ...	1985	2982679
progesterone-inhibited phosphorylation of an unique mr 48,000 protein in the plasma membrane of xenopus laevis oocytes.	the meiotic maturation of xenopus laevis oocytes is induced in vitro by progesterone which interacts at the cell surface level. a cell-free membrane preparation (p-10,000) incorporated 32p from [gamma-32p]atp, mostly into two proteins, mr approximately 56,000 and approximately 48,000 (as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis). progesterone, added in vitro, specifically inhibited the phosphorylation of the mr approximately 48,000 protein (named p48). half-maximal ...	1985	2982868
development of the ipsilateral retinothalamic projection in the frog xenopus laevis. i. retinal distribution of ipsilaterally projecting cells in normal and experimentally manipulated frogs.	the distribution of ipsilaterally and contralaterally projecting cells within the retina in xenopus laevis was studied by injection of horseradish peroxidase into the thalamus on one side of the brain and subsequent determination of the locations of retrogradely labeled cells in both retinas. in normal animals, contralaterally projecting cells were found throughout the retina. ipsilaterally projecting cells, in contrast, were most frequent in temporoventral retina and largely absent from dorsona ...	1985	2984358
development of the ipsilateral retinothalamic projection in the frog xenopus laevis. ii. ingrowth of optic nerve fibers and production of ipsilaterally projecting retinal ganglion cells.	we have studied the development of the ipsilateral retinothalamic projection in the frog xenopus laevis by analyzing patterns of histochemical reaction product resulting from anterograde transport of horseradish peroxidase (hrp) applied to cut optic nerves in animals of various ages. we have also determined the stages during which ipsilaterally projecting ganglion cells are born using a combination of [3h] thymidine autoradiography and retrograde marking of ganglion cells following injection of ...	1985	2984359
development of the ipsilateral retinothalamic projection in the frog xenopus laevis. iii. the role of thyroxine.	the ipsilateral retinothalamic projection in xenopus laevis normally first appears at about stage 54, at a time when a number of other changes known to be dependent on a rise in circulating levels of thyroxine begin to occur. we have investigated the role of thyroxine in the development of the ipsilateral retinothalamic projection by studying retinal projections and patterns of retinal histogenesis in tadpoles whose ability to produce thyroxine was blocked by treatment with propylthiouracil (ptu ...	1985	2984360
two divergent cellular src genes are expressed in xenopus laevis.	genomic and cdna clones of the x. laevis src gene have been isolated and characterized by hybridization and dna sequence analyses. the haploid genome of x. laevis contains two src genes, which can be distinguished from one another by virtue of sequence divergence in the 3' untranslated regions. both of the genes are functional as indicated by the fact that oocytes contain rnas transcribed from each of the genes. the two genes each encode an rna which is 3.3 kb in length, or twice the length requ ...	1985	2987836
torsional stress induces an s1 nuclease-hypersensitive site within the promoter of the xenopus laevis oocyte-type 5s rna gene.	the internal promoter of the xenopus laevis oocyte-type 5s rna gene is preferentially cleaved by s1 and bal-31 nucleases in plasmid dna. s1 nuclease sensitivity is largely dependent on supercoiling; however, bal-31 cleaves within the 5s rna gene in linear as well as in supercoiled dna. the s1 nuclease-hypersensitive site is centered at position +48-52 of the gene at the 5' boundary of the promoter. a dnaase i-hypersensitive site is induced at this position upon binding of the transcription facto ...	1985	2987960
queuosine modification of the wobble base in trnahis influences 'in vivo' decoding properties.	the 'in vivo' decoding properties of four trnahis isoacceptors, two from drosophila melanogaster and two from brewer's yeast, were studied after their microinjection, along with turnip yellow mosaic virus (tymv) coat protein mrna, into xenopus laevis oocytes. the two drosophila isoacceptors are identical besides containing either a guanosine (g) or the hypermodified nucleoside queuosine (q) in the wobble position. the brewer's yeast isoacceptors differ by four bases in the anticodon stem, and by ...	1985	2988936
parthenogenetic activation decreases the polyphosphoinositide content of frog eggs.	polyphosphoinositides were quantified in metaphase ii-arrested eggs of the amphibian xenopus laevis and 8-10 min later in eggs activated by pricking. the content of phosphatidylinositol 4,5-biphosphate (pip2) was remarkably high in metaphase ii-arrested eggs with respect to that of phosphatidylinositol 4-phosphate (pip). it was found to drop dramatically at activation. in contrast pip content did not change significantly.	1985	2991011
constancy of dna organization of polymorphic and nonpolymorphic genes during development in xenopus.	a study was undertaken to test for the occurrence of dna rearrangements or amplifications during embryonic development in xenopus laevis. dna isolated from testes and liver was digested with four restriction enzymes, separated on agarose gels, transferred to nitrocellulose, and hybridized with over 50 cloned cdna probes generated from embryonic poly (a)+ rna. no qualitative or quantitative differences were detectable in the dna hybridization patterns of testes and liver dna, suggesting that, at ...	1985	2991055
identification by immunofluorescence of acth-producing cells in the pituitary gland of the tree frog hyla arborea.	the indirect immunofluorescence procedure was used to localize acth-producing cells in the pituitary distal lobe from hyla arborea adult specimens; the antiserum employed was rabbit anti-synthetic acth (1-24) conjugated with bsa. immunohistochemical staining was suppressed by solid-phase absorption of the anti-acth with the specific antigen. in the distal lobe one cell population is immunoreactive; these cells are predominantly localized in the anterior half, both ventrally and dorsally; they ex ...	1985	2991078
regulation of pro-opiomelanocortin synthesis by dopamine and camp in the amphibian pituitary intermediate lobe.	the modulation of pro-opiomelanocortin (pomc) synthesis in xenopus laevis pituitary intermediate lobe (il) during background adaptation and the role of dopamine and camp in mediating this effect were examined. neurointermediate lobes (nils) were pulselabeled in vitro with [3h]arginine and analyzed for pomc synthesis by acid-urea gel electrophoresis. after black background adaptation of the animal (7 days), pomc synthesis increased 5-6-fold, while after white background adaptation (7 days), pomc ...	1985	2991229
adenosine-induced k+ current in xenopus oocyte and the role of adenosine 3',5'-monophosphate.	voltage clamp technique was used in xenopus laevis oocytes in order to study and compare membrane currents evoked by extracellularly applied adenosine (0.1-10 microm) and intracellularly injected cyclic amp (0.15-10 microm). the adenosine response is a late long-lasting outward k+ current ("h" current), mediated by the ra purine receptor subtype. the h current amplitude is directly proportional to (occupancy)3; the kd for adenosine is 3.34 microm. the h current is inhibited by the intracellular ...	1985	2991737
a protein inhibitor of calmodulin-regulated cyclic nucleotide phosphodiesterase in amphibian ovaries.	the cytosol fraction of an extract of xenopus laevis ovaries contains a protein inhibitor that can specifically block the activation of calmodulin-sensitive cyclic nucleotide phosphodiesterase (pde i) found in that tissue. this inhibitor was purified by deae-cellulose chromatography, gel filtration on sephacryl s-200, and affinity chromatography on calmodulin-sepharose. it has a molecular weight of approximately 90,000, and is heat-labile and susceptible to inactivation by chymotrypsin. the inhi ...	1985	2992390
high level human interleukin 1 production by a hepatoma cell line.	the human hepatic adenocarcinoma cell line, sk-hep-1, was found to constitutively produce interleukin 1. addition of the ionophore a23187 and lipopolysaccharide resulted in a 30-fold enhancement in the release of biological activity. serum supplementation did not affect the level of production. interleukin 1 from these cells had a molecular weight of 10-20,000 daltons on gel exclusion chromatography. polyadenylated rna, when fractionated on sucrose density gradients and injected into xenopus lae ...	1985	2992486
point mutational analysis of the xenopus laevis 5s gene promoter.	we have introduced c to t transitions into gc and cg base pairs of the xenopus laevis somatic 5s gene coding region and its 5' flank in order to analyse their effects on transcription activity and regulation. these studies allow us to differentiate between the two promoter elements and their spacer, within the internal control region. mutations within the 5' element which dissent from the corresponding trna consensus sequence reduce transcription activity substantially without significantly affe ...	1985	2992947
homologous desensitization of the beta-adrenergic receptor. functional integrity of the desensitized receptor from mammalian lung.	previous work has demonstrated that injection of rats with isoproterenol is rapidly (10 min) followed by the development of a homologous form of desensitization of the beta-agonist-coupled adenylate cyclase in lung membranes. half the receptor pool becomes sequestered in a light membrane fraction while the other half remains in the plasma membranes but becomes functionally uncoupled. in the present work we sought to assess whether "local sequestration" of the functionally intact receptor away fr ...	1985	2993846
the pattern of expression of the xenopus laevis tadpole alpha-globin genes and the amino acid sequence of the three major tadpole alpha-globin polypeptides.	we have isolated cdna clones derived from three tadpole alpha-globin mrnas of xenopus laevis. the entire nucleotide sequence of the three mrnas has been determined from the cdna clones and is presented together with the deduced amino acid sequence of the encoded polypeptides. two of the three polypeptide sequences are 96% homologous whilst the third sequence is highly diverged, with only a 72% homology. the three tadpole alpha-globin genes are all similarly diverged from the two x. laevis adult ...	1985	2993998
acetylcholine and phorbol esters inhibit potassium currents evoked by adenosine and camp in xenopus oocytes.	in xenopus laevis oocytes, adenosine and other purinergic agonists induce a k+-conductance increase that is fully mimicked by intracellular application of camp. acetylcholine suppresses the k+-conductance increase caused by adenosine, by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine, or by intracellular injection of camp. this effect of acetylcholine is not mimicked by intracellular injection of ca2+ or of the ca-mobilizing agent inositol 1,4,5-trisphosphate. however, adenosine and ...	1985	2994058
adenosine stimulates sodium transport in kidney a6 epithelia in culture.	the effects of adenosine receptor agonists and antagonists were examined in epithelia formed in culture by a6 cells, a continuous cell line derived from xenopus laevis kidney. a6 epithelia have a high electrical resistance and a short-circuit current that is equal to net sodium flux from mucosal to serosal surface. adenosine, 2-chloroadenosine, 5'-(n-ethyl)carboxamidoadenosine, and n6-(l-2-phenylisopropyl) adenosine produced concentration-dependent increases in short-circuit current. stimulation ...	1985	2994488
circadian regulation of retinomotor movements. i. interaction of melatonin and dopamine in the control of cone length.	in lower vertebrates, cone retinomotor movements occur in response to changes in lighting conditions and to an endogenous circadian clock. in the light, cone myoids contract, while in the dark, they elongate. in order to test the hypothesis that melatonin and dopamine may be involved in the regulation of cone movement, we have used an in vitro eyecup preparation from xenopus laevis that sustains light- and dark-adaptive cone retinomotor movement. melatonin mimics darkness by causing cone elongat ...	1985	2999294
comparative nucleotide sequence analysis of two types of larval beta-globin mrnas of xenopus laevis.	the complete nucleotide sequence of the cdna insert of the clone pxgl25 derived from the larval beta ii-globin mrna of xenopus laevis has been determined. the sequence of 593 nucleotides represents part of the 5'nontranslated region, the coding region for 146 amino acids and the entire 3'nontranslated region. it diverges from the related larval beta i-sequence by 24.9% in the coding region. alignment of the 5' and 3'nontranslated regions of the two related larval beta-sequences to maximum matchi ...	1985	2999708
functional activity and chromatin configuration of sv40 enhancer injected in xenopus laevis oocytes.	the sv40 enhancer microinjected into the nuclei of x. laevis oocytes is able to activate transcription about 100-fold when cloned upstream of the sv40 early promoter region or about 10-fold regardless of its orientation when located at a long distance from a test gene (bacterial chloramphenicol acetyl transferase). this effect is qualitatively and quantitatively similar to that observed when analogous constructions were transfected into mammalian cells. making use of a direct labelling technique ...	1985	2999713
visualization of rna polymerase ii ternary transcription complexes formed in vitro on a xenopus laevis vitellogenin gene.	stable ternary transcription complexes assembled in vitro, using a hela whole-cell extract, have been isolated and visualized by electron microscopy. the formation of these stable complexes on the dna fragment used as template, the 5' end region of the xenopus laevis vitellogenin gene b2, depends on factors present in the whole-cell extract, rna polymerase ii and at least two nucleotides. interestingly, bending in the dna fragment was frequently observed at the binding site of rna polymerase ii. ...	1985	3000768
simian virus 40-mediated cis induction of the xenopus beta-globin dnase i hypersensitive site.	regions in chromatin which are hypersensitive to the action of dnase i appear to be associated with sites of genetic activity; the association between dnase i hypersensitivity and transcriptional activation is well known. in the case of the chicken beta-globin gene the establishment of a dnase i hypersensitive site is dependent on tissue-specific trans-acting factors. such factors have also been implicated in the action of viral and cellular enhancers, which are themselves hypersensitive to dnas ...	1985	3001531
functional domains of the xenopus laevis 5s gene promoter.	to study the fine structure of the xenopus laevis somatic 5s gene internal control region, we have created 15 different transversions using mutagenic oligonucleotide primers. the effects of these mutations on 5s dna transcription in vitro as well as on stable complex formation with transcription factor tf iii a and tf iii c in crude nuclear extracts were analyzed. mutations in the common class iii 5' promoter element (nucleotides 50-61 in the 5s gene) interfere with transcription activity and st ...	1985	3004969
the vi element. a transposon-like repeated dna sequence interspersed in the vitellogenin locus of xenopus laevis.	a repeated dna element in xenopus laevis is described that is present in about 7500 copies dispersed throughout the genome. it was first identified in the 5' flanking region of one vitellogenin gene and was therefore named the vi element. seven copies are present within the vitellogenin gene region, three of them within introns of the genes a1, a2 and b2, and the other four copies in the gene flanking regions. four of these copies have been sequenced. the vi element is bounded by a well-conserve ...	1985	3005589
localized maternal mrnas in xenopus laevis eggs.		1985	3006987
comparison of structural requirements of alpha-msh and acth for inducing excessive grooming and pigment dispersion.	alpha-msh and acth-like peptides are known to play an important role in the adaptation of many vertebrates to a new environment. these peptides induce pigment dispersion in amphibian melanophores through a receptor-mediated mechanism. in this study we compared the structural requirements of these peptides for melanotropic activity on xenopus laevis melanophores with those for inducing excessive grooming in the rat. with the exception of acth1-24 there is a close resemblance in structure-activity ...	1985	3010259
regulation of simian virus 40 gene expression in xenopus laevis oocytes.	expression of the simian virus 40 (sv40) early and late regions was examined in xenopus laevis oocytes microinjected with viral dna. in contrast to the situation in monkey cells, both late-strand-specific (l-strand) rna and early-strand-specific (e-strand) rna could be detected as early as 2 h after injection. at all time points tested thereafter, l-strand rna was synthesized in excess over e-strand rna. significantly greater quantities of l-strand, relative to e-strand, rna were detected over a ...	1985	3018545
membrane morphogenesis in retinal rod outer segments: inhibition by tunicamycin.	isolated xenopus laevis retinas were incubated with 3h-labeled mannose or leucine in the presence or absence of tunicamycin (tm), a selective inhibitor of dolichyl phosphate-dependent protein glycosylation. at a tm concentration of 20 micrograms/ml, the incorporation of [3h]mannose and [3h]leucine into retinal macromolecules was inhibited by approximately 66 and 12-16%, respectively, relative to controls. cellular uptake of the radiolabeled substrates was not inhibited at this tm concentration. ...	1985	3155750
suppression in xenopus laevis: thymus inducer, spleen effector cells.	studies were carried out on suppressor function in the amphibian xenopus laevis, the south african clawed toad. suppression by the thymus of haemagglutinin (ha) production by spleen is antigen-dependent, partially specific and not mhc-restricted in this species (ruben, buenafe & seivert, 1983). three questions were considered in this study. does the thymus effect suppression by stimulating peripheralized spleen effector cells, or do effector cells reside within the thymus? do macrophages partici ...	1985	3156089
xenopus mhc class ii molecules. i. identification and structural characterization.	class ii antigens from the xenopus laevis mhc (f haplotype) were identified by using a rabbit antihuman class ii beta-chain serum (anti-p29boost). this xenoantiserum inhibits bidirectional xenopus mlr (but not pha-stimulation), recognizes the same molecules as certain mhc-linked xenopus alloantisera, and immunoprecipitates class ii molecules from xenopus cells consistent with the tissue distribution of mammalian class ii molecules. the xenopus class ii molecules are composed of two different cha ...	1985	3156930
membrane assembly in retinal photoreceptors. ii. immunocytochemical analysis of freeze-fractured rod photoreceptor membranes using anti-opsin antibodies.	we have used a cytochemical technique for labeling freeze-fractured tissues (pinto da silva, p., c. parkison, and n. dwyer (1981) proc. natl. acad. sci. u.s.a. 78: 343-347) to examine the distribution of immunoreactive opsin in rod photoreceptor membranes. aldehyde-fixed retinas of african clawed frogs (xenopus laevis) embedded in a cross-linked protein matrix were frozen and fractured at -196 degrees c, then thawed and labeled with biotinylated sheep anti-cow opsin igg followed by avidin-ferrit ...	1985	3156972
isolation and characterization of the human tissue-type plasminogen activator structural gene including its 5' flanking region.	mrna specific for tissue type plasminogen activator (t-pa) is induced in hela cells by the tumor promoter phorbol myristate acetate (waller, e.k., and schleuning, w.d. (1985) j. biol. chem. 260, 6354-6360). to study the underlying mechanism, a cdna library was constructed from phorbol myristate acetate stimulated hela cell mrna and screened with two t-pa mrna specific oligonucleotides (edlund, t., ny, t., rånby, m., heden, l.-o., palm, g., holmgren, e., and josephson, s. (1983) proc. natl. acad. ...	1985	3161893
the recovery of organelle transport and microtubule integrity in myelinated axons that are frozen and thawed.	myelinated axons of xenopus laevis were rapidly frozen in liquid nitrogen and thawed in a potassium glutamate based medium. organelles within isolated, thawed axons were visualized by light microscopy. after thawing, organelles were stationary for about 5 min. following this quiescent period, organelles exhibited a low frequency oscillation in the longitudinal direction of the axon; some of the organelles then began to move in either the anterograde or retrograde directions. electron microscopic ...	1985	2408718
characterization of the rna binding properties of transcription factor iiia of xenopus laevis oocytes.	a nitrocellulose filter binding assay has been developed to study the interaction of xenopus transcription factor iiia with 5s rna. the protein binds xenopus oocyte 5s rna with an association constant of 1.4 x 10(9) m-1 at 0.1 m salt, ph 7.5 at 20 degrees c. tf iiia binds wheat germ 5s rna with a two-fold higher affinity, e. coli 5s rna with a four-fold weaker affinity, and has a barely detectable interaction with yeast trnaphe. the preference for binding eukaryotic 5s rna is enhanced in competi ...	1985	2410862
epidermal keratin gene expressed in embryos of xenopus laevis.	dg81 is a cdna clone derived from a subtracted library containing those rna molecules that are present in gastrulae but absent from eggs of the frog xenopus laevis. dg rnas (where dg indicates differentially expressed in gastrula) represent the products of new transcription activated in the embryo at the midblastula transition or shortly thereafter. dg81 rna is first detected in middle to late gastrulae, peaks in abundance in early tadpoles, and declines to background levels by the end of metamo ...	1985	2410923
the two embryonic u1 rna genes of xenopus laevis have both common and gene-specific transcription signals.	we have cloned and sequenced the 1842-bp repeat dna encoding the two xenopus laevis embryonic u1 rnas, xu1a and xu1b. although these two u1 rnas are almost identical in sequence and are coordinately expressed during early embryogenesis, the flanking sequences of their genes show very little homology. both genes contain two short conserved sequences, centered around positions -55 and +19, that probably are essential for 5' and 3' end formation of u1 rnas, respectively. efficient transcription of ...	1985	2411540
transcription signals in embryonic xenopus laevis u1 rna genes.	a genomic clone of the most abundant u1 rna genes from xenopus laevis was isolated from erythrocyte dna and sequenced. two different u1 rna genes, u1a and u1b, are encoded in an hindiii 1.5-kb fragment and both are expressed after microinjection in xenopus oocytes. deletions and site-directed mutagenesis of the clones revealed two promoter elements in the u1b gene; one, located 250-220 nucleotides upstream from the 5' terminus of mature u1 rna, functions as an activator, yielding a 10-fold promo ...	1985	2411541
a cell surface marker of thymus-dependent lymphocytes in xenopus laevis is identifiable by mouse monoclonal antibody.	a mouse monoclonal antibody (mab), named xt-1 (igg2b,lambda), was prepared against j strain xenopus laevis thymocytes. the determinant recognized by this mab (xt-1 determinant) was expressed by 92-98% thymocytes and 22-37% splenic lymphocytes from intact j strain frogs and larvae, as analyzed by flow cytofluorometry. the xt-1 determinant was also expressed by 20-30% peripheral blood lymphocytes and 5-11% bone marrow lymphocytes from adult, and 11-17% liver lymphocytes from larval j strain xenopu ...	1985	2411573
genes and pseudogenes for rat u3a and u3b small nuclear rna.	we report here the isolation and primary structure of two genes encoding rat u3 small nuclear rna. one of the genes encodes u3b rna; the other encodes an rna which is almost identical to u3a rna. both genes are expressed after microinjection into the nuclei of xenopus laevis oocytes and can direct the accumulation of mature u3 rna as well as longer transcripts which may be the u3 precursors. we have also isolated and sequenced four other regions of the rat genome homologous to u3 rna. one of the ...	1985	2411940
transcription, processing and nuclear transport of a b1 alu rna species complementary to an intron of the murine alpha-fetoprotein gene.	the alu sequence family comprises the major dispersed repeat sequences of rodent and primate genomes, numbering greater than 300,000 copies in the human haploid genome. the function of these elements is unknown. the sequences can be transcribed by rna polymerase iii and represent a substantial fraction of total heterogeneous nuclear rna. alu sequences can be found both in the flanking regions and within the transcription units of several well-characterized genes. here we show that some members o ...	1985	2412135
developmental changes in the pattern of larval beta-globin gene expression in xenopus laevis. identification of two early larval beta-globin mrna sequences.	we have analysed beta-globin mrna sequences in total rna extracted from embryos and tadpoles of xenopus laevis at different stages of development and we have identified the most abundantly transcribed beta-globin mrna (beta t1). the entire nucleotide sequence of a cdna clone corresponding to this mrna is known. we have now identified the gene corresponding to this mrna and we have determined the nucleotide sequences of its immediate 5'-flanking region. using a dna fragment from within the coding ...	1985	2413218