bluuebunny/crossref_metadata_2025_split huggingface dataset:
Defective zonae pellucidae in Zp2-null mice disrupt folliculogenesis, fertility and development
Authors: Rankin Tracy L. , O’Brien Marilyn , Lee Eric , Wigglesworth Karen , Eppig John , Dean Jurrien 
Published: April 2021

ABSTRACT
All vertebrate eggs are surrounded by an extracellular matrix. This matrix is known as the zona pellucida in mammals and is critically important for the survival of growing oocytes, successful fertilization and the passage of early embryos through the oviduct. The mouse zona pellucida is composed of three glycoproteins (ZP1, ZP2 and ZP3), each encoded by a single copy gene. Using targeted mutagenesis in embryonic stem cells, Zp2-null mouse lines have been established. ZP1 and ZP3 proteins continue to be synthesized and form a thin zona matrix in early follicles that is not sustained in pre-ovulatory follicles. The abnormal zona matrix does not affect initial folliculogenesis, but there is a significant decrease in the number of antral stage follicles in ovaries isolated from mice lacking a zona pellucida. Few eggs are detected in the oviduct after stimulation with gonadotropins, and no two-cell embryos are recovered after mating Zp2-null females with normal male mice. The structural defect is more severe than that observed in Zp1-null mice, which have decreased fecundity, but not quite as severe as that observed in Zp3-null mice, which never form a visible zona pellucida and are sterile. Although zona-free oocytes matured and fertilized in vitro can progress to the blastocyst stage, the developmental potential of blastocysts derived from either Zp2- or Zp3-null eggs appears compromised and, after transfer to foster mothers, live births have not been observed. Thus, in addition to its role in fertilization and protection of early embryos, these data are consistent with the zona pellucida maintaining interactions between granulosa cells and oocytes during folliculogenesis that are critical to maximize developmental competence of oocytes.
mKlf7, a potential transcriptional regulator of TrkA nerve growth factor receptor expression in sensory and sympathetic neurons
Authors: Lei Lei , Ma Long , Nef Serge , Thai To , Parada Luis F. 
Published: April 2021

ABSTRACT
Development of the nervous system relies on stringent regulation of genes that are crucial to this process. TrkA, the receptor for nerve growth factor (NGF), is tightly regulated during embryonic development and is essential for the survival and differentiation of neural crest-derived sensory and sympathetic neurons. We have previously identified a mouse TrkA enhancer and have characterized several cis regulatory elements that are important for appropriate TrkA expression in vivo. We now report the cloning of a novel gene encoding a Kruppel-like factor from a mouse dorsal root ganglion expression library. This Kruppel-like factor, named mKlf7, binds specifically to an Ikaros core binding element that is crucial for in vivo TrkA enhancer function. Using in situ hybridization, we demonstrate that mKlf7 is coexpressed with TrkA in sensory and sympathetic neurons during embryogenesis and in adulthood. These data are consistent with the idea that mKlf7 may directly regulate TrkA gene expression in the peripheral nervous system.
Orc mutants arrest in metaphase with abnormally condensed chromosomes
Authors: Pflumm Michelle F. , Botchan Michael R. 
Published: April 2021

ABSTRACT
The origin recognition complex (ORC) is a six subunit complex required for eukaryotic DNA replication initiation and for silencing of the heterochromatic mating type loci in Saccharomyces cerevisiae. Our discovery of the Drosophila ORC complex concentrated in the centric heterochromatin of mitotic cells in the early embryo and its interactions with heterochromatin protein 1 (HP-1) lead us to speculate that ORC may play some general role in chromosomal folding. To explore the role of ORC in chromosomal condensation, we have identified a mutant of subunit 5 of the Drosophila melanogaster origin recognition complex (Orc5) and have characterized the phenotypes of both the Orc5 and the previously identified Orc2 mutant, k43. Both Orc mutants died at late larval stages and surprisingly, despite a reduced number of S-phase cells, an increased fraction of cells were also detected in mitosis. For this latter population of cells, Orc mutants arrest in a defective metaphase with shorter and thicker chromosomes that fail to align at the metaphase plate within a poorly assembled mitotic spindle. In addition, sister chromatid cohesion was frequently lost. PCNA and MCM4 mutants had similar phenotypes to Orc mutants. We propose that DNA replication defects trigger the mitotic arrest, due to the fact that frequent fragmentation was observed. Thus, cells have a mitotic checkpoint that senses chromosome integrity. These studies also suggest that the density of functional replication origins and completion of S phase are requirements for proper chromosomal condensation.
Cell turnover in the spinal ganglia ofXenopus laevistadpoles
Authors: Prestige M. C. 
Published: April 2021

ABSTRACTHUGHES (1961) has drawn up a balance-sheet of the lumbar ventral horn cells during the development of Xenopus, based both on counts of numbers of ventral horn cells throughout differentiation and of the number of degenerating cells among them at each stage. In this way, he showed that the total number of ventral horn cells is reduced from between 3000 and 4000 at differentiation to 1200 at the end of metamorphosis; that the most rapid period of decline in cell numbers is accompanied by a peak in the time graph of the number of degenerations; and concluded that for every neurone which finally differentiates, some eight or nine neuroblasts undergo degeneration. This is an example of histogenetic degeneration (Glücksmann, 1951), that is, cell death relating to the differentiation of functioning organs.
Studies on the growth of 5-day-old rabbit blastocysts in vitro
Authors: Daniel Joseph C. 
Published: April 2021

ABSTRACT
The optimal concentrations of a variety of components for promoting growth of 5-day-old rabbit blastocysts in vitro were determined. Growth, under different modifications of the basic medium (F10 plus 15 per cent, maternal rabbit serum) was expressed as the tangent of the growth curve plotted after 4 hr. and 24 hr. of incubation, where the average normal in vivo tangent is equal to 1. Improved growth was observed with limited increase in the concentrations of glycine, alanine, glutamic acid, threonine, serine and pyruvate, with the addition of lactate and a reduction in concentration of glucose. Addition of glycogen made a slight improvement in growth but linoleic acid suppressed growth. The effective concentrations of pyruvate and serine appear to be mutually interdependent. From the optima so revealed, the F10 medium was modified. This modified F10 medium alone supports good growth of 5-day-old blastocysts but when serum is added to 5 per cent., growth is within the range of that occurring in vivo.
A quantitative study of the development of the nerves in the hind-limb ofEleutherodactylus martinicensis
Authors: Hughes Arthur 
Published: April 2021

ABSTRACTThe numbers of fibres within the peripheral nerves to the hind-limb of Eleutherodactylus martinicensis have been studied during development. The results have been collated with observations on the development of movement in the living embryo. By the time that the first movements of the limb occur, most of its nerves are recognizable, though the muscles themselves are still in an early stage of differentiation. The numbers of fibres in these nerves is then not greatly different from those which are found at the end of development. As the limb movements increase in scope, the numbers of fibres within the larger nerves increase to a maximum. In the last 2 days of development, when the tail of the embryo is being resorbed, a drastic loss of fibres occurs in the larger nerves, both muscular and cutaneous. This is accompanied by an increase in diameter in some of the remaining fibres. The larger muscles of the thigh decrease in volume towards the end of development, at approximately the same time as the number of fibres in the nerves by which they are supplied is reduced. A hypothesis is suggested of the origin of specific relationships between nerve fibre and end organ by selection.
Development of kidney-specific antigens: an immunohistological study
Authors: Okada T. S. 
Published: April 2021

ABSTRACTHighly ‘kidney-specific’ antiserum-globulins prepared against a particular sub-fraction isolated from the microsomal fraction of adult chicken kidney were conjugated with fluorescein and used as a staining reagent to study the development of mesonephros in the chick embryos. Mesonephric cords from the midabdominal region at different developmental stages from stage 16 to stage 31 were studied in (a) paraffin sections, and (b) smeared preparations of the dissociated cells. In the differentiated mesonephros at stages 27−30 specific fluorescence of antibody staining appeared in the cells of proximal secretory tubules. First intense fluorescence in the development occurred, coinciding with the first histological organization of epithelium at stage 20−21. Weak specific fluorescence was also detected in the cells of the condensed nephrogenic mesenchyme. Throughout the development of the tubular epithelium fluorescence appeared in a particular locus of the cells, i.e. only the apical part. In the earlier stages perhaps prior to epithelial formation, a fluorescent dot was sometimes detected apparently inside the nucleus. Diffuse reaction over the cytoplasm has never been observed. The proportion of the fluorescent positive cells in the whole cell population of the mesonephric cords steeply increased from stage 21 (9 per cent.) to stage 27 (45 per cent.). By combining the antibody staining technique with autoradiography, it was revealed that the percentage of the cells incorporating 3H-thymidine in the fluorescent positive cells was about twice as high as that in the negative cells at stages 22 and 25. At the final stage of the development (stage 28) there was little difference in the percentage of the isotopically labelled cells between positive and negative cells. The present results indicate that the antibody staining technique can be a potent tool to study acquisition of tissue-specificity in nephrogenesis. It is suggested that the initial synthesis of the molecules with immunological kidney specificity occurs in the nuclei in the early stages of development; in the next step when the proliferation rate of the cells with such molecules becomes particularly high, the synthesis may occur only in the apical part of the cells.
The effects of D- and L-threo-chloramphenicol on the early development of the chick embryo
Authors: Billett F. S. , Collini Rosalba , Hamilton Louie 
Published: April 2021

ABSTRACT
In the presence of 200-300 μg./ml. of D-threo-chloramphenicol, chick embryos explanted at the full streak to head-fold stage develop abnormally. In the presence of the same and higher concentrations (600 μg./ml.) of the L-isomer, development is almost normal. The most obvious features of the response to D-threo-chloramphenicol are a failure of the neural tube to close and an inhibition of haemoglobin formation. In order to inhibit haemoglobin formation in the area vasculosa, it is necessary to treat the embryos several hours before the haemoglobin would appear. The abnormalities are accompanied by a reduction in the area of the blastoderm and of the area vasculosa. A high concentration of the L-threo compound, although it does not produce the embryonic abnormalities, does reduce the size of the blastoderm. The failure of the L-isomer to give rise to the abnormalities caused by the D-isomer suggests that the teratological response is due to an inhibition of protein synthesis caused primarily by an interference with the function of messenger RNA.
Morphological and functional development of the ovary of the mouse II. The development of the ovary in transplantation conditions in adult spayed hosts
Authors: Ben-Or Sarah 
Published: April 2021

ABSTRACTGrafts of ovarian tissue transplanted into adult spayed hosts ‘take’ well and remain functional for relatively long periods, even in homologous systems (Parkes, 1956; Harris & Eakin, 1949). Under the influence of the high endogenous gonadotrophic potential of the host, grafts of very young ovaries continue to develop and reach maturity even earlier than they would in their normal surroundings (Goodman, 1934; Dunham, Watts & Adair, 1941).
The utilization of yolk platelets by tissues ofXenopusembryos studied by a safranin staining method
Authors: Selman G. G. , Pawsey G. J. 
Published: April 2021

ABSTRACTThe amphibian yolk platelet is a particular kind of food-reserve granule which may be easily recognized by microscopy and which is abundant in the cytoplasm of amphibian eggs and embryos. Wallace & Karasaki (1963) developed a method by which intact yolk platelets were isolated from eggs of Rana pipiens and were shown by electron microscopy to be practically free from other materials. Chemical analysis of such yolk platelets by Wallace (1963a, b) showed that the crystalline main body is made up of two components, a phosphoprotein of similar amino-acid composition to avian phosvitin and a lipoprotein similar to avian a-lipovitellin, the molecular proportions being 2 to 1 respectively. Surrounding this crystalline main body of the yolk platelet there is a granular peripheral zone which has been reported to contain both protein resembling histone (Horn, 1962) and polysaccharide (Ohno, Karasaki & Takata, 1964). Histochemical work by Ohno, Karasaki & Takata (1964) showed there was no nucleic acid detectable in yolk platelets, and although nucleic acids have often been reported present in isolated yolk fractions subjected to biochemical analysis, it seems probable in view of the experience of Wallace (1963a) that such reports were due to contamination either by follicle cells or cytoplasm. The ultrastructure of the amphibian yolk platelet has been described by Karasaki (1962, 1963a), Ward (1962) and Lanzavecchia (1965). Wallace (1963Ô) proposed a molecular structure for the main body component of a yolk platelet which appears to fit all known data from previous biochemical, biophysical and electron-optical analyses.
The oocyte of the domestic chicken shortly after hatching, studied by electron microscopy
Authors: Greenfield M. L. 
Published: April 2021

ABSTRACTOocytes taken from chickens from 1 day to 11 weeks after hatching have been examined by electron microscopy. Early extra-follicular oocytes have chromosome filaments in the nucleus at the prophase of meiosis. The fine structure of these filaments is described and is found to vary according to the size and age of the oocyte. The Balbiani body present in oocytes of about 8-20 μ in diameter has been shown to consist of paired centrioles surrounded by Golgi vesicles and an outer border of mitochondria. Golgi vesicles and mitochondria were dispersed in larger oocytes, and in those larger than about 80 μ the mitochondria formed a cortical layer. In oocytes with a diameter greater than about 100 μ macrobodies (clusters of lining bodies) were mainly confined to the periphery of the oocyte, whereas in others they were present, together with lipid drops, mainly in the interior. Folding of the oocyte membrane was observed in many oocytes measuring about 100 μ in diameter, but was much more pronounced in oocytes above 250 μ. In these oocytes cortical vesicles in close proximity to the crypts of the folds appear to have been formed by pinocytosis. In the follicle cells of oocytes 250 in diameter and over, large masses of glycogen granules occur in the cytoplasm near the oocyte membrane.
Oogenesis in adult prosimians
Authors: Ioannou J. M. 
Published: April 2021

ABSTRACT
It has been claimed that new germ cells are formed after maturity in certain female prosimians. A histological study was made of the ovaries of adults of four of these species (Galago crassicaudatus, G. demidoffi, Perodicticus potto and Loris tardigradus lydekkerianus), and of juvenile specimens of Loris. In addition, two adult female G. demidoffi were injected with 3H-thymidine and their ovaries subjected to autoradiographic examination. Mitotically active oogonia and/or oocytes in the early stages of meiotic prophase were present in all the adult prosimians examined; in G. demidoffi some of these cells incorporated 3H-thymidine, suggesting that DNA synthesis was in progress. These observations indicate that active oogenesis was taking place. There is no reason to believe, however, that new germ cells are formed other than by division of pre-existing oogonia.
The morphology and development ofDrosophilaeye
Authors: Hanly E. W. , Fuller C. William , Stanley M. S. Millam 
Published: April 2021

ABSTRACTThe development of pigment in the eye of Drosophila melanogaster and other insects has been the subject of many studies and much controversy. It has been established that the red color of eyes of wild-type D. melanogaster is due to the presence of two classes of pigments, ommochromes and pteridines (Ziegler, 1961). The relationships among the various members of each class are still obscure; the biosynthetic pathways are yet to be elucidated. No specific enzyme involved in the synthesis of any member of either group has been isolated or characterized. It has been suggested, however (Hadorn, 1955), that these metabolic pathways may involve several organs, including the eye, but that the final deposition and conversion occur only in the eye. The recent development of a satisfactory technique for the culture of Drosophila organs (Schneider, 1964) has made possible the study of pigment development in the isolated eye and in eyes associated with selected organs. Thus it is possible to test the hypothesis that organs interact in the formation of eye pigments.
The neural crest and the acoustic ganglion
Authors: Deol M. S. 
Published: April 2021

ABSTRACTThere is no agreement about the origin of the acoustic ganglion. Some investigators maintain that it originates in the neural crest, and others that it arises from the otic placode. It was thought that mutant genes might help in resolving the doubt. The gene piebald-lethal (s1) affecting pigmentation in the mouse was selected for this purpose. There was strong evidence that the piebald locus influenced the development of the neural crest before its differentiation into melanoblasts and ganglionic primordia. Histological examination revealed striking abnormalities in the inner ear of all piebald-lethal mice. The neural epithelium was invariably affected. In view of the known action of the piebald locus on the neural crest and the intimate developmental relationship between the acoustic ganglion and the neural epithelium, the most plausible explanation of these abnormalities is that the neural crest contributes to the formation of the acoustic ganglion in the mouse. This conclusion is supported by studies on two other mutants (white and pallid) in which defects of pigmentation and the inner ear occur together. The presence of similar abnormalities, either observed or deduced from deafness, in the inner ear of white cats and piebald dogs suggests that the acoustic ganglion in these animals has a similar origin.
Strontium-90 and intrauterine development in the rat
Authors: Hopkins B. J. , Casarett G. W. , Tuttle L. W. , Baxter R. C. 
Published: April 2021

ABSTRACTSingle doses of strontium-90 (191 μc or 382 μc) were injected intravenously to pregnant rats on the 2nd or 10th day post-conception and the developing offspring were observed for deleterious effects on the 20th day post-conception. Injection of either dose on the 2nd day post-conception caused a significant increase in intrauterine mortality and fetal growth retardation (stunting), but a significant increase in morphological defects other than stunting was not observed. Injection on the 10th day post-conception caused little or no increase in mortality or growth retardation following a dose of 191 μc, and only slight increases after doses of 382 μc. However, gross morphological defects of various types were observed at both dose levels, but fewer varieties of defect at the lower dose. The most common defects were, in decreasing order of frequency, taillessness, retarded growth, reduced eye volume, skeletal defects, and interscapular depression. The radiation dose rate to both the uterus and the embryo was high soon after injection, then declined to low levels. A second peak in dose rate to the embryo occurred during late fetal life while that to the uterus remained low. The deleterious effects observed appeared to be dependent upon the total dose of 90Sr to the dam and the gestation age at time of injection.
Ultrastructure of adrenal medulla of the prenatal rat
Authors: Ratzenhofer Max , Müller Otfried 
Published: April 2021

ABSTRACTThe ultrastructure of the adrenal medulla in adult laboratory animals has been described in a number of reports (Lever, 1955; Sjôstrand & Wetzstein, 1956; Wetzstein, 1957; de Robertis & vaz Ferreira, 1957; Erânkô & Hânninen, 1960; Yates, 1963, 1964a, b, c;Coupland, 1965a, b; Elfvin, 1965a, b). Since the introduction of the glutaraldehyde fixation technique, it has been possible to distinguish clearly between cells storing adrenalin and those storing noradrenalin by the different densities of their granules (Coupland, Pyper & Hopwood, 1964; Coupland, 1965 a; Elfvin, 1965 a). In order to study the histophysiology of the secretory process of catecholamines, suprarenal glands have been investigated under normal conditions and under the influence of mechanical, physical and chemical-pharmacological agents (the above references and Graf, 1966). The purpose of the present investigation was to study the structure of adrenal medulla of the rat during the prenatal period and to relate the findings to the process of secretion in the medullary cells.
Regeneration and growth control inNereis
Authors: Golding D. W. 
Published: April 2021

ABSTRACTCaudal regeneration in Nereis diversicolor is that rapid proliferation of segments which occurs after loss of part of the posterior of the body and the reformation of the pygidium. The rate of segment proliferation is highest during the production of the first new segments. Thereafter, the rate declines rapidly with each passing week, though if the regenerated segments are amputated, rapid proliferation is again resumed (Golding, 1967). Two explanations of these results are possible. First, the declining rate of segment proliferation during regeneration may be the result of a declining concentration of hormone in the body fluids. There may be a feed-back from the regenerating tail to the ganglion. As segments are proliferated, the secretory activity of the ganglion is suppressed. Secondly, the level of hormone in the body fluids may remain constant, the proliferating region of the pygidium becoming progressively more insensitive as regeneration proceeds.