bluuebunny/crossref_metadata_2025_split huggingface dataset:
Origin and organization of the zebrafish fate map
Authors: Kimmel Charles B. , Warga Rachel M. , Schilling Thomas F. 
Published: April 2021

Abstract
We have analyzed lineages of cells labeled by intracellular injection of tracer dye during early zebrafish development to learn when cells become allocated to particular fates during development, and how the fate map is organized. The earliest lineage restriction was described previously, and segregates the yolk cell from the blastoderm in the midblastula. After one or two more cell divisions, the lineages of epithelial enveloping layer (EVL) cells become restricted to generate exclusively periderm. Following an additional division in the late blastula, deep layer (DEL) cells generate clones that are restricted to single deep embryonic tissues. The appearance of both the EVL and DEL restrictions could be causally linked to blastoderm morphogenesis during epiboly. A fate map emerges as the DEL cell lineages become restricted in the late blastula. It is similar in organization to that of an amphibian embryo. DEL cells located near the animal pole of the early gastrula give rise to ectodermal fates (including the definitive epidermis). Cells located near the blastoderm margin give rise to mesodermal and endodermal fates. Dorsal cells in the gastrula form dorsal and anterior structures in the embryo, and ventral cells in the gastrula form dorsal, ventral and posterior structures. The exact locations of progenitors of single cell types and of local regions of the embryo cannot be mapped at the stages we examined, because of variable cell rearrangements during gastrulation.
Changes in the allelic methylation patterns of c-H-ras-1, insulin and retinoblastoma genes in human development
Authors: Ghazi H. , N.Magewu A. , Gonzales F. , Jones P.A. 
Published: April 2021

ABSTRACT
The methylation status of the c-H-ras-1, insulin and retinoblastoma genes was determined in human sperm, hydatidiform mole, fetal tissues, adult lymphocytes and adult kidney. Individual alleles of c-H-ras-1 and insulin were distinguishable due to presence of endogenous variable number of tandem repeat (VNTR) polymor-phisms. Both alleles of the latter two genes were extensively methylated in sperm compared to the other tissues. Several sites within these genes were less methylated in fetal tissues and the two alleles were differentially methylated in some cases. The retinoblas-to ma gene was highly methylated in all tissues examined, with the exception of a single site that was under-methylated in sperm only. The sperm-specific methyl-ation patterns in all three genes could represent imprinting of the parental chromosomes. Since 5-methylcytosine is inherently mutagenic, it is possible that methylation imprinting could alter the susceptibili-ties of human genes to point mutations.
Genomic imprinting and allelic exclusion
Authors: Holliday Robin 
Published: April 2021

ABSTRACT
In diploid cells, allelic exclusion reduces genes to functional haploidy, because only one of two alleles is active. It is best known in cells producing immunoglobulins, but other examples also exist. X-chromosome inactivation in female mammals is related to allelic exclusion, but in this case the dosage compensation mechanism extends to the whole chromosome. Functional hemizygosity in some mammalian cell lines is probably also due to allelic exclusion, where one autosomal allele is active and the other is methylated and inactive.
In early development, it may be important to have only one functional copy of specific regulatory genes. If one considers the possible mechanisms whereby genes are switched from an active to an inactive form, or vice versa, complications arise if the same type of switch operates in two homologous chromosomes segregating independently at mitosis. This complication is avoided if one of the genes is totally inactive. It is therefore suggested that important regulatory genes are subject to allelic exclusion and that this provides a basis for genomic imprinting. Male or female gametes complement in the zygote, because they may have different inactive genes, and the active allele in each case is then functionally haploid in the zygote and developing embryo. These haploid genes would be those involved in critical switches of gene activity during the developmental process. Allelic exclusion imposed by imprinting might be based on the heritable DNA methylation of the regulatory regions of silent genes.
Preferential X-chromosome inactivation, DNA methylation and imprinting
Authors: Monk Marilyn , Grant Mark 
Published: April 2021

ABSTRACT
Non-random X-chromosome inactivation in mammals was one of the first observed examples of differential expression dependent on the gamete of origin of the genetic material. The paternally-inherited X chromosome is preferentially inactive in all cells of female marsupials and in the extra-embryonic tissues of developing female rodents. Some form of parental imprinting during male and female gametogenesis must provide a recognition signal that determines the nonrandomness of X-inactivation but its nature is thus far unknown. In the mouse, the imprint distinguishing the X chromosomes in the extra-embryonic tissues must be erased early in development since X-inactivation is random in the embryonic cells. Random X-chromosome inactivation leads to cellular mosaicism in expression and differential methylation of active and inactive X-linked genes. Transgene imprinting shares many features with X-inactivation, including differential DNA methylation.
In this paper we consider when methylation differences in early development affecting X-chromosome activity and imprinting are established. There are processes of methylation and demethylation occurring in early development, as well as changes in the activity of the DNA methylase itself. Methylation of a specific CpG site associated with activity of the X-linked PGK-1 gene has been studied. This site is already methylated on the Inactive X chromosome by 6·5 days’ gestation, close to the time of X-inactivation. However, differential methylation of this site is not the primary imprint marking the paternal X chromosome for preferential inactivation in the extra-embryonic membranes.
A consideration of factors influencing both X-chromosome inactivation and imprinting suggests that a process of communication and comparison between nonidentical alleles might by the basis for the differential modification and expression patterns observed.
A transgene insertional mutation at an imprinted locus in the mouse genome
Authors: DeLoia Julie A. , Solter Davor 
Published: April 2021

ABSTRACT
Genetic imprinting in mice results in functional differences in the oocyte and spermatocyte genomes, as evidenced by both genetic and pronuclear transfer experiments. To gain insights into the molecular mechansims involved in the imprinting process, researchers have studied methylation phenotypes and expression of hemizygous transgenes associated with parental origin. In this report, we describe a transgenic mouse lineage in which expression of both the transgene and an endogenous gene at the insertion site are determined by the parent of origin. The mutation caused by transgene insertion shows variable expressivity and incomplete penetrance in addition to a modified dominant pattern of inheritance.
Disuse and passive stretch cause rapid alterations in expression of developmental and adult contractile protein genes in skeletal muscle
Authors: Loughna Paul T. , Izumd Seigo , Goldspink Geoffrey , Nadal-Ginard Bernado 
Published: April 2021

ABSTRACT
Contractile proteins exist as a number of isoforms that show a developmental and tissue-specific pattern of expression. Using gene-specific cDNA probes, the expression of the sarcomeric myosin heavy chain (MHC) multi-gene family and of cardiac (foetal) α -actin was analysed in three different rat hindlimb muscles immobilised for 5 days in either the shortened or lengthened positions. For each of the MHC genes normally expressed in adult muscle (slow, DA and IIB), the effect of disuse alone (immobilisation in the shortened position) upon expression was markedly different to that of passive stretch (immobilisation in the lengthened position) in each of the three muscles. However, the same adult sarcomeric myosin heavy chain gene can be affected in a different, or even opposite, manner by either disuse or passive stretch depending on the muscle in which it is being expressed. The fast IIB MHC gene, for example, exhibits a rapid induction in the slow postural soleus muscle, in response to disuse but no such induction occurs in the faster plantaris and gastrocnemius muscles. Furthermore, the induction of this gene in the soleus was prevented by passive stretch. The MHC gene, normally only expressed in embryonic skeletal muscle, showed a similar response in all three muscles and was reinduced in adult muscle in response to passive stretch but not by disuse alone. In contrast, the isoform of α -actin which is normally only present in significant quantities in embryonic skeletal muscle and which is reduced postnatally, is not reinduced by passive stretch but is reduced still further by immobilisation in the shortened position.
The effects of protease inhibitors on axon growth through astrocytes
Authors: Fawcett James W. , Housden Elizabeth 
Published: April 2021

ABSTRACT
We have shown in a previous paper (Devi Biol. 135, 449, 1989) that axons regenerating from postnatal neurons are unable to penetrate three-dimensional cultures of mature astrocytes, while axons from embryonic dorsal root ganglia (DRGs) and retina will grow through such cultures for considerable distances. We have now investigated the role of proteases in the penetration of three--dimensional astrocyte cultures by axons from embryonic DRGs. Embryonic DRGs were grown in association with three-dimensional astrocyte cultures, with astrocyte monolayers, and with-air dried collagen. The effects of inhibitors of the three families of proteases that have been shown to be involved in tumour cell invasion were investigated. The serine protease inhibitors EACA and Trasylol both reduced growth in three-dimensional astrocyte cultures to around 50% of control, but had little effect on growth on astrocyte monolayers or on collagen. TIMP, which inhibits collagenases, had no effect on growth on two- or three-dimensional cultures. Cbz-gly-phen-amide, an inhibitor of enteroproteases, reduced growth in all three types of culture.
Retinoid-binding protein distribution in the developing mammalian nervous system
Authors: Maden M. , Ong D. E. , Chytil F. 
Published: April 2021

ABSTRACT
We have analysed the distribution of cellular retinol-binding protein (CRBP) and cellular retinoic acidbinding protein (CRABP) in the day 8.5–day 12 mouse and rat embryo. CRBP is localised in the heart, gut epithelium, notochord, otic vesicle, sympathetic ganglia, lamina terminalis of the brain, and, most strikingly, in a ventral stripe across the developing neural tube in the future motor neuron region. This immunoreactivity remains in motor neurons and, at later stages, motor axons are labelled in contrast to unlabelled sensory axons. CRABP is localised to the neural crest cells, which are particularly noticeable streaming into the branchial arches. At later stages, neural crest derivatives such as Schwann cells, cells in the gut wall and sympathetic ganglia are immunoreactive. An additional area of CRABP-positive cells are neuroblasts in the mantle layer of the neural tube, which subsequently appear to be the axons and cell bodies of the commissural system. Since retinol and retinoic acid are the endogenous ligands for these binding proteins, we propose that retinoids may play a role in the development and differentiation of the mammalian nervous system and may interact with certain homoeobox genes whose transcripts have also been localised within the nervous system.
Mouse Hox-3.4: homeobox sequence and embryonic expression patterns compared with other members of the Hox gene network
Authors: Gaunt S. J. , Coletta P. L. , Pravtcheva D. , Sharpe P. T. 
Published: April 2021

ABSTRACT
A putative mouse homeobox gene (Hox-3.4) was previously identified 4 kb downstream of the Hox-3.3 (Hox-6.1)* gene (Sharpe et al. 1988). We have now sequenced the Hox-3.4 homeobox region. The predicted amino acid sequence shows highest degree of homology in the mouse with Hox-1.3 and -2.1. This, together with similarities in the genomic organisation around these three genes, suggests that they are comembers of a subfamily, derived from a common ancestor. Hox-3.4 appears to be a homologue of the Xenopus Xlhbox5 and human cpll genes (Fritz and De Robertis, 1988; Simeone et al. 1988). Using a panel of mouse-hamster somatic cell hybrids we have mapped the Hox-3.4 gene to chromosome 15.
From the results of in situ hybridization experiments, we describe the distribution of Hox-3.4 transcripts within the day mouse embryo, and we compare this with the distributions of transcripts shown by seven other members of the Hox gene network. We note three consistencies that underlie the patterns of expression shown by Hox-3.4. First, the anterior limits of Hox-3.4 transcripts in the embryo are related to the position of the Hox-3.4 gene within the Hox-3 locus. Second, the anterior limits of Hox-3.4 expression within the central nervous system are similar to those shown by subfamily homologues Hox-2.1 and Hox-1.3, although the tissuespecific patterns of expression for these three genes show many differences. Third, the patterns of Hox-3.4 expression within the spinal cord and the testis are very similar to those shown by a neighbouring Hox-3 gene (Hox-3.3), but they are quite different from those shown by Hox-1 genes (Hox-1.2, -1.3 and -1.4).
Developmental regulation of expression of the lactate dehydrogenase (LDH) multigene family during mouse spermatogenesis
Authors: Thomas Kelwyn , Mazo Jesus Del , Eversole Pam , Bellvé Anthony , Hiraoka Yukihiro , Li Steven S. L. , Simon Melvin 
Published: April 2021

ABSTRACT
Expression of the Lactate Dehydrogenase (LDH) genes during various stages of spermatogenesis was studied by using a combination of Northern blot analyses and in situ hybridization techniques. These studies have indicated that developmentally programmed expression of all three functional LDH genes occurs during differentiation of germ cells. The LDH/C (ldh-3) gene was expressed exclusively during meiosis and spérmiogenesis, beginning in leptotene/zygotene spermatocytes and continuing through to the elongated spermatids. LDH/C (ldh-3) gene expression was accompanied by transient expression of the LDH/A (ldh-1) gene in pachytene spermatocytes and round spermatids. The LDH/B (Idh-2) gene was expressed mainly in Sertoli and spermatogonia! cells. By using somatic cell hybrids, the LDH/C (ldh-3) gene has been mapped to mouse chromosome 7, establishing that it is syntenic with the LDH/A (ldh-1) gene locus. Experimental observations made in this study provide new insight into the order and sequence of events involved in the regulation of gene expression of the LDH gene family during spermatogenesis.
Electrical Potential Differences Across the Foetal Membranes of the Rabbit
Authors: Krespi V. , Davies J. 
Published: April 2021

ABSTRACT
The chemical composition of the foetal fluids in the rabbit was studied by Davies & Routh (1957). These investigators showed that the amniotic and exocoelomic fluids resembled extracellular fluid in their ionic composition whereas the allantoic fluid more closely resembled intracellular fluid. These findings were confirmed by Dickerson & McCance (1957).
The Effects of Vitamin A and Citral on Epithelial Differentiation in vitro 1. The Chick Tracheal Epithelium
Authors: Aydelotte Margaret B. 
Published: April 2021

ABSTRACT
Differentiation of the tracheal epithelium of embryonic chicks was studied in organ cultures in a normal medium and in media containing added vitamin A and citral. In normal medium, the tracheal epithelium differentiated well, but usually fewer mucous cells developed than in the intact chick. High concentrations of vitamin A alcohol inhibited the differentiation of mucous cells and favoured that of ciliated cells. Citral, in fairly low concentrations, had opposite effects: it stimulated mucus-secretion and inhibited the differentiation of ciliated cells. In higher concentrations it stimulated division of the basal cells, and the epithelium became stratified and sometimes keratinized. Vitamin A and citral added together to the culture medium produced a citral effect, which varied in intensity according to the proportions of the two compounds, but was always milder than that resulting from treatment with the same concentration of citral alone. These results suggest that citral inhibits both the natural vitamin A in the plasma and the added synthetic vitamin A, thus producing changes in the tracheal epithelium characteristic of vitamin A deficiency. The results indicate that secretion of mucus by the tracheal epithelium is maximal at a lower concentration of vitamin A than that to which it is normally exposed in the body. It is suggested that vitamin A may influence epithelial differentiation partly by affecting the mitotic rate.
The Effect of Chloroacetophenone on the Development of Planorbis (Indoplanorbis) exustus (Deshayes)
Authors: Mulherkar Leela , Sherbet Gajanan V. 
Published: April 2021

ABSTRACT
The effect of chloroacetophenone (CAP) on the developmental stages of Planorbis (Indoplanorbis) exustus (Deshayes) has been studied. Treatment with the substance caused (a) exogastrulation, (b) inhibition of cytoplasmic and nuclear division of the big endoderm cells, (c) arrest of development accompanied by enlargement of blastomeres or delay in development, (d) a reversal of the flattening which normally follows cleavage, and (e) a secondary fusion of the micro- and megameres. The phase of development from the second cleavage to the fourth cleavage seemed to be CAP-susceptible and the period between the third cleavage and the third cleavage-flattened stages seemed to be critical from the point of view of production of exogastrulae. The exogastrulae which had developed for 77 hours showed some differentiation. The effect of CAP on the vegetative hemisphere was striking. The CAP-susceptible phase in general coincides with the process of ooplasmic segregation taking place in the cleaving egg, and the critical phase, in particular, coincides with the establishment of the -SH rich ectoplasm. The other abnormalities caused by the substance are interrelated and are explained on the basis of a probable –SH and –SS– balance existing in the cortical region of the blastomeres. The results have been interpreted to indicate that integrity of –SH groups is important in the morphogenesis of the species studied.
A Study of the Developmental Relationship Between Enterochromaffin Cells and the Neural Crest
Authors: Andrew Ann 
Published: April 2021

ABSTRACTExplants were made of blastoderm of chick embryos from definitive primi-tive streak-to 22-somite stages. Definitive and potential neural crest and neural plate were excluded from experimental expiants, and included in controls. The expiants were cultured as chorio-allantoic grafts for a total of 17 to 18 days ; the grafts were, therefore, of 18 to 20 days’ total incubation age on their final retrieval. This period was more than adequate for the differentiation of enterochromaffin cells. The elimination of neural crest cells from experimental expiants, and their inclusion in control ones, was confirmed by the absence of known neural crest derivatives from the former, and their presence in the latter. Differentiation of intestine in grafts, adequate for the appearance of entero-chromaffin cells, was assessed according to criteria based on the histology of normal chick embryo gut at, and soon after, the first appearance of enterochromaffin cells. Enterochromaffin cells occurred in well-differentiated gut, whether in control or experimental grafts. They appeared to be present in numbers at least as great as in normal gut. It is concluded that enterochromaffin cells are not derived from the neural crest. Evidence purporting to support their origin from other sources is discussed and found to be inconclusive.
An Immunoembryological Study of the Chick Iris
Authors: Maisel Harry , Harmison Charles 
Published: April 2021

ABSTRACT
Using immunological techniques it has been shown that in all major vertebrate species the lens, iris and pigment retina of the eye share common antigens (Langman & Prescott, 1959; Maisel & Langman, 1961; Flickinger & Stone, 1960; Maisel, 1962). These data are of particular interest since in certain animals the iris has the ability to form a lens or lens cells in the absence of the original lens. Indeed, lens regeneration from the dorsal iris is well documented in the genus Triturus (Stone, 1952; Reyer, 1954). Although McKeehan (1961) and Woerdeman (1962) did not record lens regeneration in the chick embryo in vivo, other observers have reported on the formation of lens cells from embryonic chick pigment retina and iris explanted in vitro (Dorris, 1938; van Deth, 1940; Reinhold, 1958).
Homograft Implants of Young Testes, Ovaries and Ovotestes in the Intact Female Chick
Authors: Erickson Alan E. , Pincus Gregory 
Published: April 2021

ABSTRACT
Attempts to control differentiation of the reproductive system of vertebrates have been made by use of hormone treatment, grafting, and parabiosis of embryos, larvae and neonates (for reviews, see Domm, 1939; Burns, 1949; Willier, 1952; Witschi, 1961; Burns, 1961). True sex reversal by use of steroid compounds has been accomplished only in certain amphibians (Witschi & Chang, 1950; Chang & Witschi, 1955) and in more primitive forms. Among birds and mammals such manipulations have modified components of the reproductive system but have not resulted in ovulation and fertilization of ova from the cortex of feminized gonads of the male. Spermatogenesis in the hypertrophied right rudiment of a small percentage of hens ovariotomized prior to 30 days has been reported by Domm (1929) but in only rare instances has it occurred in birds similarly treated at an older age (Domm, 1927). No chicks have hatched from eggs of hens artificially inseminated with sperm derived from such experimentally modified birds.
The Induction of Deciduomata in the Rat
Authors: Finn C. A. , Keen P. M. 
Published: April 2021

ABSTRACT
One of the main steps in the elucidation of the mechanism of ovum implantation is to determine how the blastocyst stimulates the uterus to undergo a decidual reaction. The extent of this reaction varies between species but is particularly marked in rodents, and normal ovum implantation does not occur without it. It has been known for several years, however, that the uterus of a suitably primed rodent can be stimulated to produce decidual cells in the absence of a blastocyst simply by traumatization of the uterus. The so-called deciduoma which results is thought to be analogous to the decidual reaction of normal implantation because (a) it is histologically similar (Krehbiel, 1937), and (b) the hormonal requirements for its formation are similar to those for implantation. Thus the deciduoma is a useful model on which to investigate factors which may be important in the initiation of the decidual response. It is also of interest as an example of extremely rapid cellular proliferation (the uterus may increase its weight four-fold in 72 hours) and so may provide information about cellular growth in general. If the deciduoma is analogous to the decidual reaction it is a reasonable assumption that the mechanisms by which the two responses are initiated have at least a final stage in common.