bluuebunny/crossref_metadata_2025_split huggingface dataset:
Feedback inhibition of erythropoiesis induced in anaemic Xenopus
Authors: Aleporou Vassiliki , Maclean Norman 
Published: April 2021

ABSTRACT
Serum from normal Xenopus, when injected into anaemic Xenopus, causes reduction in both DNA and protein synthesis in erythroid cells as indicated by in vitro culture of the blood cells. Experiments with erythrocyte-conditioned medium, reveal that this inhibitory substance can be recovered from mature erythrocytes. Sephadex G-25 fractionation of normal serum and haemolysate demonstrates that the inhibitory factor consists of molecules of low molecular weight, and experiments with cells of Xenopus kidney reveal that the feedback inhibition may be tissue specific to erythroid cells.
Measurement of metabolites in single preimplantation embryos; a new means to study metabolic control in early embryos
Authors: Barbehenn Elizabeth K. , Wales Raymond G. , Lowry Oliver H. 
Published: April 2021

ABSTRACT
The preimplantation mammalian embryo offers many unique research opportunities. Among these is the possibility of studying the progression of metabolic systems during the transition from the single, free-living, migratory germ cell to the multicellular blastocyst, ready for sessile existence and dependence on second-hand nutrition.
Teratological evaluation of 5-fluorouracil and 5-bromo-2-deoxyuridine on hamster fetuses
Authors: Shah Ravindra M. , MacKay Robert A. 
Published: April 2021

ABSTRACT
A single intraperitoneal injection of 5-bromo-2-deoxyuridine (BUDR) between days 9 and 11 and a single intramuscular injection of 5-fluorouracil (FU) between days 8 and 11 of gestation were teratogenic in hamster. The malformation frequencies were related to the dose and time of BUDR and FU treatment but the pattern and types of malformations and their frequencies were different. BUDR showed lower embryotoxic effect than FU. Both drugs impaired general fetal growth. It is suggested that the differences between FU and BUDR may be related to the chemical nature and metabolism of the drug and their eventual effect on the species-specific target tissue.
Regeneration and compartments inDrosophila
Authors: Szabad Janos , Simpson Pat , Nöthiger Rolf 
Published: April 2021

ABSTRACTA clonal analysis was performed in order to study the process of regeneration in wounded wing discs of Drosophila. Regeneration was induced either by cutting the disc in situ, or by shifting gynandromorphic larvae whose male tissue was hemizygous for a temperature-sensitive cell lethal to the restrictive temperature. Fast growing M+ clones, labelled with y and/or mwh, were produced by X-irradiation of the following genotypes: y; scJi(y+)M(3)i55/ mwh jv M+ (series I), and l(1)ts 504 sn3l(1)ts 5697/ In(1)wvC; M(3)i55/mwh M+ (series II). The clones were induced either before or after the experimental lesion. Clones initiated one day prior to the lesion were able to cross compartment boundaries whereas clones initiated one day after the lesion did not do so. It is concluded that cells involved in the process of regeneration lose their compartmental commitment, but that later on the growing population of cells again becomes subdivided into the same compartments.
Myotypic Respecification of Regenerated Nerve-fibres in Cichlid Fishes
Authors: Arora H. L. , Sperry R. W. 
Published: April 2021

ABSTRACT
The mandibular portion of cranial nerve V of the teleost fish, Astronotus ocellatus, was totally severed and allowed to regenerate into its distal nervestump in a series of ten cases. In a second series of fourteen cases, the two nerve branches supplying the elevator and depressor muscles of the mandible were sectioned separately and the nerve of the depressor muscles was crossed into the levator muscles and vice versa. In both series, return of function in the re-innervated muscles was first detected about 8 days after nerve-section, and full recovery was achieved by the 18th to 21st day save for two exceptions in Series II in which the surgical crossunion proved faulty. The recovered mandibular action was properly timed and co-ordinated from the beginning with the mandibular muscles of the opposite side. It is inferred (a) that the regenerating motor-fibres establish functional connexions with foreign mandibular muscles, (b) that the muscles induce a local muscle specificity in the regenerated motor axons, and (c) that this ‘myotypic’ specificity determines in some way not yet analysed the central timing of motoneuron discharge in the trigeminal motor nucleus.
The Morphogenetic Influence of Innervation on the Ontogenetic Development of Muscle-spindles
Authors: Zelená J. 
Published: April 2021

ABSTRACT
The development of muscle-spindles in the calf-muscles of the rat was followed under normal conditions and after section of n. ischiadicus. The first differentiation of muscle-spindles in the muscles of the hind limb of the rat was observed on the 19th day of intra-uterine development and their morphogenesis is complete by the 25th day after birth. After section of n. ischiadicus in rat foetuses on the 19th-20th day of intrauterine development, differentiation of muscle-spindles does not take place; neither intrafusal fibres nor the connective tissue capsule are formed. Since only proprioceptive fibres have innervated the normal muscle at this time, it is the loss of the morphogenetic influence of these nerve-fibres, that prevents differentiation. Similar results were obtained in rabbits denervated 7 days before birth. When section of n. ischiadicus is performed in new-born rats, disintegration of intrafusal fibres in which the equatorial segment was already differentiated at the time of denervation occurs within 10 days. Denervation in a 20-day-old rat, the muscle-spindles of which are already morphologically mature, leads after the same interval, to a slight atrophy in the equatorial zone of the intrafusal fibres. The mechanism of the morphogenetic influence of the nervous system and its changes during ontogenesis are discussed.
Contribution à l’étude de la maturation et de la segmentation de l’œuf d’Aplysie
Authors: Fautrez J. 
Published: April 2021

ABSTRACT
Study of the maturation and the beginning of segmentation of the egg of Aplysia punctata by vital staining with toluidine blue demonstrates the appearance of a ‘colourless plasm’ and its unequal distribution between the various blastomeres. It may be a component analogous to the pole plasms of other Spiralia, correlated with the inequality of the cleavage divisions and with morphogenesis.
The temporal stability of the Drosophila oocyte
Authors: Wyman Robert 
Published: April 2021

ABSTRACT
Individual female Drosophila melanogaster were maintained without yeast for up to 18 days. Some of the females did not lay any eggs during this holding period. The females produce mature oocytes (stage 14) by day 3 and from day 5 onward the females each held about 60 mature oocytes. The nulliparous females were mated and it was shown that the first egg produced by females held up to 18 days before mating could be viable and develop into a normal, fertile adult. On day 2 each female contained about 500 oocytes in post-oogonial stages of oogenesis. The first 500 fertilized eggs were collected from females that had been held nulliparous for 7−10 days before mating. No period of significantly reduced viability was found. It is concluded that the developmental program of Drosophila eggs can be interrupted between oogenesis and fertilization for at least 15 days without loss of the ability to produce normal, fertile adult progeny.
Waves propagated during vertebrate development: observations and comments
Authors: Robertson Anthony 
Published: April 2021

ABSTRACTThe status and possible roles of propagated waves occurring during vertebrate embryogenesis are discussed. Some preliminary data for waves observed in time-lapse films of early chick (Gallus domesticus) and Medaka (Oryzias latipes, a teleost) are given. The general similarities between these phenomena and wave propagation during cellular slime mold aggregation are pointed out and it is suggested that the control of development by propagated waves in regulative embryos is not only widespread but also depends on a common cellular mechanism.
Neurotrophic and X-ray blocks in the blastemal cell cycle
Authors: Maden M. 
Published: April 2021

ABSTRACT
Using microdensitometry techniques the points in the cycle where blastemal cells become blocked after X-irradiation or denervation of the regenerating amphibian limb have been identified. X-irradiation blocks the cells in both G1 and G2 and those cells that were in S at the time of irradiation presumably proceed to G2. After denervation, however, cells accumulate only in Gx and those that were in S or G2 continue through the cycle to the next Gx. The latter results are clearly contradictory to a recent theory proposing a G2 neurotrophic control of blastemal cells and a solution to the contradiction is presented in the light of recent results.
Ontogeny and localization of the crystallins during lens development in normal and Hy-1 (hyperplastic lens epithelium) chick embryos
Authors: McDevitt David S. , Clayton Ruth M. 
Published: April 2021

ABSTRACT
A strain of chickens selected for high growth rate has been found to exhibit an anomalous eye lens morphology indicating a failure of the normal process of growth regulation. Hyper-plasia of the lens epithelium and annular pad, often with fiber formation, has recently been described in day-old chicks of this strain, termed Hy-1 (Clayton, 1975). The earliest evidence of this condition in this study has been found in the 11-day embryonic Hy-1 lens. Before this time, no definitive lens abnormality could be detected histologically in the Hy-1 embryos. However, the indirect immunofluorescence technique had revealed early temporal and spatial differences with regard to the lens crystallins. Antibodies, specific for δ, cathodal β, anodal β and α crystallins, were applied to sections through the lens of , 3-, , 4-, 5-, 8- and 16-day embryonic and 1-day post-hatch normal and Hy-1 chicks. δ crystallin appears precociously in the external layer, and α crystallin in the prospective fiber region, of the lens rudiment of Hy-1 embryos. Both anodal and cathodal β crystallins are retarded, however, in their appearance in the external layer/epithelium of Hy-1 lenses. Localization of the crystallin classes within the lenses of the two strains continues to vary during lens differentiation until 1 day post-hatch, at which time and during late embryogenesis annular pad and epithelium abnormalities can be frequently be seen in the Hy-1 lens. This inability to control normal lens histogenesis thus manifests itself early as alterations in the appearance of an organ-specific gene product, the crystallins.
The specification of metameric order in the insect Callosobruchus maculatus Fabr. (Coleoptera) : I. Incomplete segment patterns can result from constrictioninduced cytological damage to the egg
Authors: Meer Jitse M. Van Der 
Published: April 2021

ABSTRACT
Eggs of the pea-beetle Callosobruchus were divided into two at different stages of development. Both fragments were allowed to develop into partial larvae. The segment patterns of normal and partial larvae are described using cuticular markers of cell differentiation. To study the contribution of cytological damage to the segment gap phenomenon three different types of constriction were performed : complete and incomplete permanent constriction and complete temporary constriction.
Changes in the structure of the egg can produce absence of segments resulting from two different effects. First, partial absence of segments results from a decreased egg circumference in the constriction region and involves the disturbance of a morphogenetic process (dorsal closure). Secondly, cytological damage can result in a gap between two arrays of segments. The loss of segments in the gap occurred in two different ways. In a spatial segment gap the two arrays of segments were physically discontinuous, whereas in a non-spatial gap the segments bordering the gap were juxtaposed in a physically continuous cuticle.
The extent to which the gap phenomenon can be attributed to cytological damage is discussed. We also discuss, on the basis of certain dorsal defects, a possible stepwise specification of the dorsal transverse cuticular pattern.
The ultrastructure of the dorsal yolk-free cytoplasm and the immediately surrounding cytoplasm in the symmetrized egg of Xenopus laevis
Authors: Herkovits Jorge , Ubbels Geertje A. 
Published: April 2021

ABSTRACT
Cytoplasmic segregation and subsequent dorsad displacement of the segregated cytoplasm lead to symmetrization of the egg of Xenopus laevis. At 60 min post-fertilization (p.f.) the ‘dorsal yolk-free cytoplasm’ (DYFC) is located in the dorso-animal part of the egg. Its ultrastructure and that of the immediately surrounding cytoplasm have been studied with transmission electron microscopy (TEM).
The endoplasmic reticulum (ER) within the DYFC consists of single or paired cisternae and many small vesicles, both with moderately dense contents. Numerous particles, presumably ribosomes and glycogen, are present together with many mitochondria and some Golgi structures. The fraction of total yolk-free area occupied by mitochondria in the DYFC is about three times that in the adjacent cytoplasm. The number of cytoplasmic vesicles per unit area of cytoplasm is far larger in the DYFC than in the surrounding area.
The morphological characteristics of the DYFC at 60 min p.f. suggest that it represents a region of high metabolic activity. Since it is located in the dorso-animal quadrant of the uncleaved egg, it may be partly responsible for a difference in metabolism between the dorsal and the ventral side of the egg, and hence may play an essential role in the determination of dorso-ventrality.
Somitogenesis in amphibian embryos: I. Experimental evidence for an interaction between two temporal factors in the specification of somite pattern
Authors: Pearson Murray , Elsdale Tom 
Published: April 2021

ABSTRACT
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 upon an interpretation of their position.
Heat shocks cause characteristic segmental abnormalities over a zone of somites which is formed several hours after the shock. Evidence from double heat shock experiments suggests that the pattern of abnormality is the result of (i) a disturbance of co-ordination between pre-somitic cells, and (ii) the time available to those cells for recovery before they are recruited into a segmental pre-pattern at the time of passage of the prior wave. It is a temporal coordination that is disturbed and subsequently recovered following a heat shock. This temporal co-ordination of pre-somitic cells does not depend upon position along the axis.
The evidence for two physiologically independent temporal patterns of cellular processes, which interact to specify the segmental pattern of somites (their size, shape and number), gives experimental support for the theoretical account of somitogenesis proposed by Cooke & Zeeman (1976).
Effects of colchicine on spermiogenesis in the mouse
Authors: Handel Mary Ann 
Published: April 2021

ABSTRACT
The effects of colchicine on spermiogenesis in the mouse were examined. Mice were injected intratesticularly with colchicine in concentrations of 10−4M to 10−6M for various periods of time. The ultrastructure of the testes was examined and abnormal sperm in the epididymis were scored. Colchicine degraded microtubules in the testis and the treatment caused abnormalities of the head and acrosome of testicular spermatids and also resulted in an increase on the number of epididymal sperm showing abnormal head structure by 5 days after treatment of the testes. These results suggest that structurally intact microtubules are essential for the normal morphogenetic processes of spermiogenesis.
Latent effects on in vitro development following cytochalasin B treatment of 8-cell mouse embryos
Authors: Granholm N. H. , Brenner G. M. , Rector J. T. 
Published: April 2021

ABSTRACT
Eight-cell mouse embryos when treated with 4·0μg/ml cytochalasin B (CB) in vitro undergo a reversible developmental arrest. Upon rinsing of embryos and subsequent culture in control medium, normal morphogenetic processes such as compaction of 8-cell embryos, cavitation, and post-blastocyst attachment and outgrowth are restored. However, the effects of CB on mouse embryos are not completely reversible; latent post-blastocyst defects become increasingly more prevalent as CB treatment duration increases.
The present study was conducted to quantitatively determine latent effects of CB on post-blastocyst embryos by comparing their ability to attach and to sustain the growth and differentiation of 1CM and trophoblast tissues. Groups of 8-cell embryos were cultured in Brinster’s BMOC-3 medium containing 4·0μg/ml cytochalasin B for 6, 12, 18, and 24 h. Following treatment, embryos were rinsed and cultured until 190 h post coitum (h.p.c.) in Eagle’s MEM/10% fetal calf serum modified to contain optimal levels of essential amino acids. Blastocysts generally attached to the surface of the plastic substratum by 120 h.p.c. At selected time periods after attachment (130, 160, and 190 h.p.c.), embryos were scored for outgrowth size, ICM size, extent of peripheral hyaloplasmic fan, and number of trophoblast nuclei per outgrowth. Analyses of variance (ANOVAs) were conducted for each of the four parameters listed above. Rates of attachment were analyzed by χ2 test.
Results show that the treatments affect (P &lt; 0·01) embryo attachment, number of trophoblast nuclei per outgrowth, hyaloplasmic fan production, and ICM growth in a durationdependent manner. Interestingly, since treatment effects on outgrowth areas are nonsignificant apparently CB does not significantly change total outgrowth area. But CB tieatment does cause abnormal fan production and decreased trophoblast nuclei numbers. However, trophoblast cells are apparently more resistant than ICM to CB as is evident by the high incidence of trophoblast outgrowths devoid of ICM.
CB (4·0μg/ml) treatments at 8-cell stages for relatively short durations (6 and 12 h) induce latent effects on post-blastocyst embryos. Finally, there exists a definite 4·0μg/ml CB duration response over the 68–190 h.p.c. observation interval.
Foetal haemopoiesis during the hepatic period; II. Topographic histology
Authors: Nessi Analía C. , Bozzini Carlos E. 
Published: April 2021

ABSTRACTSerial sections of mouse foetal liver, during the 9th and 16th days of gestation, were studied.The erythropoietic process starts in the central area of the growing hepatic lobes, and subsequently spreads towards the periphery. Each lobe passes successively through an undifferentiated, proliferating and differentiating period, but does not proliferate and differentiate in a homogeneously synchronized way, since the onset of both histogenesis and erythropoiesis is delayed at the periphery, when compared with the central area. As a consequence, in sections it is possible to find three different zones, namely: marginal, which is the most undifferentiated; intermediate (transitional); and a central area, which is the most mature, since it is the first site where erythropoiesis arises. These zones are distinguishable not only by their cell distribution, but also by the biological behaviour of their elements, specially in the transitional areas between undifferentiated and proliferating zones.The hepatic lobes do not start their organogenesis at the same time; but those of them in which histogenesis is delayed, repeat courses of development similar to those previously organized. The first interstitial erythropoiesis appears in the central area, after the development of an organized network of sinuses, and in close relation to vascular channels. Dynamic images of immature blood cells, between interstitial and vascular spaces, suggesting passage through the endothelium, are often seen. These steps are followed, in a concentric form and spreading towards the periphery, by each hepatic lobe.
Time-dependent effects of α-amanitin on blastocyst formation in the mouse
Authors: Braude P. R. 
Published: April 2021

ABSTRACT
Early compacting mouse morulae were placed in α-amanitin at various times after HCG and the effect of this transcriptional inhibitor during formation of the blastocyst was noted. No cavitation was observed in those embryos transferred into α-amanitin before 77 h after HCG but the percentage of cavitation increased dramatically in those embryos transferred after 80 h post HCG. The large increase in amino acid incorporation which normally occurs during formation of the blastocyst was blocked in those embryos placed in the inhibitor before 80 h post HCG. Two-dimensional polyacrylamide gel electrophoresis of radiolabelled embryos showed that the changes in synthesis of certain polypeptides normally associated with blastocyst formation did not occur in those embryos placed in α-amanitin before 80 h after HCG. Only one cleavage division appears to occur in the presence of α-amanitin. However, groups of embryos which had completed their fifth division before exposure to the drug subsequently were able to form blastocysts and showed the quantitative and qualitative changes associated with blastocyst formation despite the continued presence of the inhibitor. These results suggest that a critical transcriptional event concerned with blastocyst formation occurs around 80 h after HCG and may be associated with the fifth cleavage division.
Cytoplasmic and nuclear protein synthesis in preimplantation mouse embryos
Authors: Howe C. C. , Solter D. 
Published: April 2021

ABSTRACTCytoplasmic and nuclear proteins synthesized by mouse embryos at different stages of preimplantation development were analyzed by two-dimensional polyacrylamide gel electrophoresis. Several nuclear-specific proteins (i.e. proteins more abundant in the nucleus than in the cytoplasm) and numerous cytoplasmic-specific proteins were observed. The trends of changes in the nuclear and cytoplasmic protein synthesis are similar. Moderate changes occur between the unfertilized egg and the zygote. Striking changes characterized by the disappearance of numerous major oocyte-specific proteins and the appearance of a large number of new, stage-specific proteins occur between the zygote and the 4- to 8-cell stages. Tn contrast, between the 4- to 8-cell and early blastocyst periods, only a few new proteins appear, and a small number of oocyte-specific or other stage-specific proteins disappear. Minor differences in protein synthesis were observed between the trophoblast and inner cell mass.