bluuebunny/crossref_metadata_2025_split huggingface dataset:
Abnormal meiotic spindles cause a cascade of defects during spermatogenesis in asp males of Drosophila
Authors: Casal Jose , Gonzalez Cayetano , Wandosell Francisco , Avila Jesus , Ripoll Pedro 
Published: April 2021

Abstract
Since spermatogenesis in Drosophila is a series of interconnected and interdependent steps and most of the spermatogenic events take place in the absence of transcription, failures in a given stage can give rise to a cascade of defects later on. The asp locus of Drosophila melanogaster codes for a non-tubulin component implicated in proper spindle structure and/or function (Ripoll et al. 1985). Homozygous asp males exhibit abnormal meiotic spindles giving rise to altered segregation of chromosomes and mitochondria and failures in cytokinesis. Postmeiotic spermatogenic stages of asp males show a series of alterations that we interpret as due to the previously occurring defective meiosis because meiotic spindles are the only microtubular structure altered in mutant testes. The most conspicuous alterations are: (i) variable size of nuclei and nebenkerns of early spermatids, which are also multinucleate instead of having single and uniformly sized nuclei; (ii) elongating spermatids in which abnormal-sized mitochondrial derivatives elongate alongside more than one axoneme; (iii) failures in the individualization process, where abnormal spermatids remain syncytial, and seem to be eliminated during the coiling stage.
The three most downstream genes of the Hox-3 cluster are expressed in human extraembryonic tissues including trophoblast of androgenetic origin
Authors: Oudejans Cees B. M. , Pannese Maria , Simeone Antonio , Meijer Chris J. L. M. , Bonc1Nelli Edoardo 
Published: April 2021

Abstract
Human first trimester extraembryonic tissues of normal and androgenetic origin (molar pregnancies) were investigated for the expression of 6 homeobox genes from the chromosome 12-encoded Hox-3 cluster by non-autoradiographic in situ hybridization with biotinylated RNA probes. By comparative in situ hybridization involving the use of exon- or region-specific RNA probes, analysis included the cellular distribution of alternative Hox-3 transcripts in chorionic villous tissues. A bias in extraembryonic distribution was seen between transcripts of the three most upstream Hox-3 genes (Hox-3.7, -3.6, and -3.1) versus transcripts of the 3 most downstream genes (Hox-3.3, 3.4, and 3.5). Only genes from the latter group are transcribed in human extra-embryonic tissues including extraembryonic tissues of androgenetic origin. Moreover, comparative in situ hybridization showed that distinct alternative transcripts of Hox-3.3, Hox 3.4 and Hox-3.5 are exclusively found in trophoblast cells while others are present in chorionic villous stromal cells as well. These data demonstrate the existence of tissue- and cell-specific use of transcriptional (alternative gene promoters) or post-transcriptional (alternative splicing) regulation of homeobox genes in extraembryonic tissues.
Developmental expression of the creatine kinase isozyme system of Xenopus: maternally derived CK-IV isoform persists far beyond the degradation of its maternal mRNA and into the zygotic expression period
Authors: Robert Jacques , Wolff Jacques , Juakli Hassan , Graf Jean-Daniel , Karch François , Kobel Hans Rudolf 
Published: April 2021

Abstract
The differential expression of the multilocus CK isozyme system throughout development of the two Xenopus species X. laevis and X. borealis was investigated. A cDNA containing the nearly complete coding sequence of the CK-IV subunit of X. laevis was isolated and sequenced. Early development of X. laevis proceeds with a stock of maternally derived CK-IV/IV isozyme. While the mRNA declines rapidly after fertilization and disappears before neurulation, maternal CK-IV/IV isozyme is active far beyond the onset of zygotic expression and is still detectable when tadpoles start feeding. Zygotic expression of CK-IV begins after neurulation, at stage 22/24, and seems to start simultaneously with that of another gene, CK-IIL Modulation in the expression of these two genes and the appearance of two other isoforms, the CK-I and CK-II/III isozymes, take place during development in a tissue-specific manner. During metamorphosis, the CK phenotypes of eyes and skeletal musculature undergo additional changes. The final adult pattern only appears several weeks after metamorphosis. The presumed orthologous CK isozymes of X. borealis show a developmental profile similar to that of X. laevis, except that CK-Il/n is equally present in oocytes and during early development, in addition to CK-IV/IV isozyme. These results show that the expression of each of the four CK genes of Xenopus is under differential developmental control.
Transcription of a mutant collagen I gene is a cell type and stage-specific marker for odontoblast and osteoblast differentiation
Authors: Schwarz Michaela , Harbers Klaus , Kratochwil Klaus 
Published: April 2021

Abstract
The Movl3 allele of the mouse al(I) collagen gene carries a retroviral insert in its first intron and had been reported to be transcriptionally silent. We have recently shown, however, that this mutant gene is expressed in odontoblasts of transplanted teeth derived from homozygous and heterozygous carrier embryos. The expression of the Movl3 allele has now been followed throughout in vivo development of mandibular teeth and bone in heterozygous animals, by in situ hybridization with a probe that specifically recognizes transcripts of the mutant gene. We show that the onset of its transcription precisely coincides with the final differentiation of odontoblasts and the onset of dentinogenesis, i.e. on day E16 for the incisor and at birth for the first molar. The mutant allele is also transcribed in osteoblasts of mandibular bone, again starting precisely with the onset of osteogenesis (day E13/14). No other cells were seen to transcribe the mutant gene. By these criteria, transcription of the Movl3 allele constitutes a true differentiation marker for odontoblasts and osteoblasts. Expression of the mutant allele in these two specialized cell types, in contrast to its transcriptional block in all other mesodermal cells (‘fibroblasts’), suggests tissue-specific differences in the regulation of the al(I) collagen gene.
The parthenogenetic development of rabbit oocytes after repetitive pulsatile electrical stimulation
Authors: Ozil Jean Pierre 
Published: April 2021

ABSTRACT
Freshly ovulated rabbit oocytes were activated parthenogenetically by periodically repeated calcium stimuli generated by electric field pulses applied onto the plasma membrane. Electric field pulses of 1.8 kV cm-1 were delivered every 4 min for 1h 30 min (22 double pulses) in a specially designed chamber. Before each pulse, the culture medium was replaced by an isotonic glucose solution containing 10 μM Ca2+.
The effects of modulating the ionic stimuli (by changing the duration of EF pulse) on a postactivation reaction, and/or on the pre- and postimplantation development, were studied.
The rate of activation increased progressively as the pulse duration lengthened. For 22 pulses of 200 μs, 13 % of oocytes were activated versus 100 % for 1200 μs. The uniformity of the parthenogenetic response was obtained when oocytes were exposed to a series of pulses within which the reduction of pulse duration followed a negative exponential law. The influence of such activating treatment on the preimplantation development was tested using two treatments of 22 pulses with a total pulse duration equal to 14868 and 11228 μs, respectively. For the weaker treatment, a lower proportion of embryos underwent compaction and those that compacted were irregular. In contrast, the majority of embryos resulting from the stronger treatment compacted and developed into blastocysts. The most significant result that emerges from this study is that the level of stimulation affects in vitro developmental potency after the third cleavage division.
The postimplantation viability of parthenogenetic eggs was tested and the results showed that parthenogenetic rabbit embryos died at a similar stage of development to the parthenogenetic mouse embryos. But, in the present series, high implantation rates and embryonic development (66 %) till day 10−11 of pregnancy were obtained after the appropriate pulsatile EF treatment of oocytes. The parthenogenetic fetuses were of smaller size than the controls, but the developement of the trophoblast tissue was proportional to the development of the fetuses. Anomalies of fetuses were also observed. This study reveals that activation is not a time-limited event and that the type of activating treatment has a marked effect on the ability of the resulting parthenogenetic embryos to develop to the early postimplantation stages. The sustained alteration of the cytoplasmic activity provides a useful tool to study the function of embryonic or somatic nuclei introduced during the earliest stages of activation.
Detrimental effects of two active X chromosomes on early mouse development
Authors: Takagi Nobuo , Abe Kenji 
Published: April 2021

ABSTRACT
Matings between female mice carrying Searle’s translocation, T(X;16)16H, and normal males give rise to chromosomally unbalanced zygotes with two complete sets of autosomes, one normal X chromosome and one X16 translocation chromosome (XnX16 embryos). Since X chromosome inactivation does not occur in these embryos, probably due to the lack of the inactivation center on X16, XnX16 embryos are functionally disomie for the proximal 63 % of the X chromosome and trisomic for the distal segment of chromosome 16. Developmental abnormalities found in XnX16 embryos include: (1) growth retardation detected as early as stage 9, (2) continual loss of embryonic ectoderm cells either by death or by expulsion into the proamniotic cavity, (3) underdevelopment of the ectoplacental cone throughout the course of development, (4) very limited, if any, mesoderm formation, (5) failure In early organogenesis including the embryo, amnion, chorion and yolk sac. Death occurred at 10 days p.c. Since the combination of XO and trisomy 16 does not severely affect early mouse development, it is likely that regulatory mechanisms essential for early embryogenesis do not function correctly in XnX16 embryos due to activity of the extra X chromosome segment of X16.
The mechanical basis of cell rearrangement I. Epithelial morphogenesis during Fundulus epiboly
Authors: Weliky Michael , Oster George 
Published: April 2021

ABSTRACT
Many morphogenetic processes are accomplished by coordinated cell rearrangements. These rearrangements are accompanied by substantial shifts in the neighbor relationships between cells. Here we propose a model for studying morphogenesis in epithelial sheets by directed cell neighbor change. Our model describes cell rearrangements by accounting for the balance of forces between neighboring cells within an epithelium. Cell rearrangement and cell shape changes occur when these forces are not in mechanical equilibrium. We will show that cell rearrangement within the epidermal enveloping layer (EVL) of the teleost fish Fundulus during epiboly can be explained solely in terms of the balance of forces generated among constituent epithelial cells.
Within a cell, we account for circumferential elastic forces and the force generated by hydrostatic and osmotic pressure. The model treats epithelial cells as two-dimensional polygons where the mechanical forces are applied to the polygonal nodes. A cell node protrudes or contracts when the nodal forces are not in mechanical equilibrium. In an epithelial sheet, adjacent cells share common boundary nodes; in this way, mechanical force is transmitted from cell to cell, mimicking junctional coupling. These junctional nodes can slide, and nodes may appear or disappear, so that the number of polygonal sides is variable.
Computer graphics allows us to compare numerical simulations of the model with time-lapse cinemicroscopy of cell rearrangements in the living embryo, and data obtained from fixed and silver stained embryos. By manipulating the mechanical properties of the model cells we can study the conditions necessary to reproduce normal cell behavior during Fundulus epiboly. We find that simple stress relaxation is sufficient to account for cell rearrangements among interior cells of the EVL when they are isotropically contractile. Experimental observations show that the number of EVL marginal cells continuously decreases throughout epiboly. In order for the simulation to reproduce this behavior, cells at the EVL boundary must generate protrusive forces rather than contractile tension forces. Therefore, the simulation results suggest that the mechanical properties of EVL marginal cells at their leading edge must be quite different from EVL interior cells.
Multiple functions for NGF receptor in developing, aging and injured rat teeth are suggested by epithelial, mesenchymal and neural immunoreactivity
Authors: Byers M. R. , Schatteman G. C. , Bothwell M. 
Published: April 2021

ABSTRACT
We have used immunocytochemistry to analyse expression of nerve growth factor receptor (NGFR) in developing, aging and injured molar teeth of rats. The patterns of NGFR immunoreactivity (IR) in developing epithelia and mesenchyme matched the location of NGFR mRNA assayed by in situ hybridization with a complementary S35-labeled RNA probe. The following categories of NGFR expression were found. (1) There was NGFR-IR in the dental lamina epithelium and in adjacent mesenchyme during early stages of third molar formation. (2) NGFR-IR nerve fibers were posterior and close to the bud epithelium. (3) During crown morphogenesis NGFR expression was prominent in internal enamel epithelium and preodontoblasts; it faded as preameloblasts elongated and as odontoblasts began to make predentin matrix; and it was weak or absent from outer enamel epithelium, the cervical loop, and differentiated ameloblasts and odontoblasts. (4) When NGFR-IR nerve fibers entered the molars late in the bell stage, they innervated the most mature peripheral pulp and dentin in an asymmetric pattern which correlated more with asymmetric enamel synthesis than with mesenchymal NGFR-IR distribution. (5) The mesenchymal pulp cells continued to have intense NGFR expression in adult teeth, especially near coronal tubular dentin. (6) The pulpal NGFR-IR decreased in very old rats or subjacent to reparative dentin (naturally occurring or experimentally induced). (7) During root formation, the preodontoblasts had NGFR-IR but most root mesenchymal cells and Hertwig’s epithelial root sheath did not. This work suggests that there are important epithelial and mesenchymal targets of NGF regulation during molar morphogenesis that differ for crown and root development and that do not correlate with neural development. The continuing expression of NGFR-IR by pulpal mesenchymal cells in adult rats was most intense near coronal odontoblasts making tubular dentin; and it was lost during aging, or subjacent to sites of dentin injury that caused a phenotypic change in the odontoblast layer.
Myelinization of the Optic Nerve and its Dependence on Visual Function— A Quantitative Investigation in Mice
Authors: Gyllensten Lars , Malmfors Torbjörn 
Published: April 2021

ABSTRACT
Quantitative studies have been made of the number, myelinization and diameter of the fibres of the optic nerve during post-natal development in black mice, using phase-contrast and electron microscopy. The influence of complete darkness was investigated. In mice reared in the light no myelinated fibres are present up to 5 days of age, whereas a few hundred are demonstrable at 10 days. Between 15 and 20 days of age, myelinization is intense, the mean number of such fibres per nerve being about 22,000 at 20 days. After this time there is only a slight increase, i.e., to about 25,000 at 30 days. Up to 30 days, only a few per cent of the fibres are more than 1 μ. in diameter (measured in fixed and embedded specimens). In adult mice, three maxima in fibre diameter are observed; the largest group comprises those with a diameter less than 1 μ. (0·6–0·8 μ.), and the two smaller ones fibres more than 1 μ. in diameter (1·1–1·3 and about 2·0 μ.). The fibres are found to be more closely packed in the central part of the optic nerve than in its peripheral parts, but the coarser fibres are more numerous peripherally. No appreciable number of unmyelinated fibres is visible in mature animals. In mice reared in complete darkness for 20 and 30 days, delay in myelinization of the optic nerve fibres causes a reduction in the number of those myelinized by some 12–13 per cent. The coarser fibres are affected to a greater extent than the thin ones; thus at 30 days the number of those more than 1 p in diameter is reduced by almost 60 per cent. In mice reared in darkness, a retardation is observed in growth of the nuclei of the retinal ganglion cells, as well as in their shape maturation (decrease in eccentricity).
Observations of Dependent Histogenesis in Salamander Limb Development
Authors: Finnegan Cyril V. 
Published: April 2021

ABSTRACT
The prospective limb portion of the limb disc of Ambystoma punctatum and Taricha torosa tail-bud stages was transplanted homoplastically and heteroplastically to the ventral hypomere region of similar-aged host animals. The transplants were observed for growth (elongation) and for histogenesis of limb elements and in all cases less limb development was seen, both macroscopically and histologically, than was to be expected from the developmental age of the donors. In a parallel series of experiments a small amount of epibrachial somite tissue was transplanted with the limb cell mass to the ventral hypomere region. The limb histogenesis and growth were enhanced to a considerable degree. It was seen that chondrogenesis (of a girdle) occurred in the somite tissue and the limb cell mass seemed to demonstrate histogenesis (proximally) and elongation (distally) in relation to that development. The limb cell mass was transplanted to various superficial sites on the nonlimb trunk somites and it was observed that more advanced growth and histogenesis were obtained when the transplant was associated with the ventral somite region. Pronephric tissue was developed in all cases where limb cell mass was transplanted to the ventral hypomere region of Taricha torosa hosts. When the amount of dorsal tissue was increased, by adding dorsal ectoderm and/or epibrachial somite to the limb cell mass, no pronephric tissue developed in the graft area. No nephric differentiation was seen with similar transplants to Ambystoma punctatum hosts. The results are considered as indicative of a somite-dependent histogenesis in the development of the proximal portion of the transplanted limb.
The Development of the Inner Ear in Mice Homozygous for Shaker-with-Syndactylism
Authors: Deol M. S. 
Published: April 2021

ABSTRACT
A reinvestigation of the effects of the gene sy on the inner ear showed that the first abnormalities appear several days earlier than had hitherto been believed, and that they concern the periotic labyrinth and not the otic labyrinth. An excessive amount of mesenchymal tissue is laid down round certain, if not all, parts of the otic labyrinth in 13-day embryos, and as the periotic labyrinth is derived from this tissue it is abnormal. The abnormalities of the otic labyrinth appear at least 4 days later, and consist in a dedifferentiation of the epithelium and its penetration by the periotic mesenchymal tissue. As the otic labyrinth is surrounded by the periotic labyrinth, it is believed that the abnormalities of the former are consequent upon those of the latter, although the underlying mechanism is not understood. A possible connection has been suggested between the three major effects of the gene sy, namely, abnormalities of the inner ear, syndactylism, and defects of ossification involving the whole skeleton.
Constitutive Enzymes of the Chick Embryo. II. Cysteine Desulphydrase
Authors: Solomon J. B. 
Published: April 2021

ABSTRACT
Optimum substrate and co-factor concentrations and pH are given for the assay of cysteine desulphydrase in chick tissues. Endogenous desulphydrase activity (no added co-factor) was very low in the yolk from 4 — 12 days and in the whole chick embryo from 3 — 8 days of incubation, there was little in the chorio-allantoic membrane or in the brain and heart of older embryos. Specific desulphydrase activity in the area opaca of blastoderm increased rapidly with development of the yolk sac and was maximal at 7 — 11 days of incubation. Activity had fallen to half the value by 16 days of incubation. There was twice as much activity in White Leghorn yolk sac homogenates than those of Brown Leghorns. There was no deficiency of co-factor in such homogenates. The desulphydrase of Brown Leghorn livers increased from 7 — 16 days of incubation (per mg. protein) but remained constant during the embryonic development of White Leghorn livers. Livers showed a deficiency of co-factor. Just before hatching the liver desulphydrase of both breeds begins to decrease and in White Leghorns had decreased to adult level by 1 week after hatching; whereas in Brown Leghorns the rate of decrease was slower. Liver desulphydrase was increased when adult cockerels were fed on a hard-boiled egg diet. Attempts at enzyme induction by injection of cysteine were generally unsuccessful. When cysteine (16 mg.) was injected at 7 and 10 days of incubation liver desulphydrase had risen by 60 and 100 per cent, respectively 1 day later. Multiple injection of cysteine into young chickens produced only a 40 per cent, increase in liver desulphydrase. The paucity of evidence in favour of substrate-induced enzyme inductions in embryos is discussed.
Expression of TGF-β isoforms during first trimester human embryogenesis
Authors: Gatherer Derek , Duke Peter Ten , Baird David T. , Akhurst Rosemary J. 
Published: April 2021

Abstract
We have studied the expression of the genes encoding transforming growth factors (TGFs) β1, β2 and β3 in human embryos ranging from 32 to 57 days post-coitum, using in situ hybridization. The spatial and temporal pattern of expression of each gene is distinct, though each occasionally overlaps. TGF-β1 is expressed in haematopoietic, endothelial and osteogenic tissues. TGF-β1 and TGF-β3 are expressed in a wide variety of mesenchymal tissues including areas of chondrogenic activity. TGF-β2 is also found in several epithelia and in the ventral nervous system. The differential transcript distributions are broadly similar to those seen in mouse embryos suggesting that there is conservation of TGF-β3 gene regulatory sequences and developmental function across this species boundary.