bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ectodermal control of the avascular zone of the peripheral mesoderm in the chick embryo
Authors: Feinberg Richard N. , Repo Mary A. , Saunders John W. 
Published: June 2005

AbstractProspective skin ectoderm is underlaid by a relatively thick (100 ± 20 μm) avascular zone of mesoderm in most regions of the early embryo. To determine whether or not the ectoderm exercises a role in the establishment and maintenance of the avascular zone, trypsin‐isolated pieces of backskin ectoderm from chick or quail embryos were implanted as a sheet into a slit cut deep into the capillary bed of the wing bud of host chick embryos of stages 19–23. In sham operations, slits were cut at various anteroposterior levels, and the wing was allowed to heal. At intervals of 3–48 hr after these operations, embryos were injected with India ink, fixed, and cleared. Implants formed flattened vesicles, usually in continuity with host ectoderm, but sometimes completely internalized. Periderm cells from each side of the vesicle faced each other, and the cells of the cuboidal layer faced an avascular mesodermal layer at least 100 μm thick at all points.The implantation of prospective skin ectoderm resulted in the formation of an avascular zone in normally vascularized mesoderm of the wing bud. In contrast, the vascular bed of the limb bud abutted directly on implants of Millipore filters or of Silastic silicone (Dow Corning). Likewise, the capillary bed came in direct contact with implants of retinal pigment epithelium, an ectodermal derivative normally in close contact with the vascular choroid coat of the eye. These results, taken in conjunction with earlier experiments that show the necessity of the apical ectodermal ridge for the formation of the marginal veins of the limb bud, suggest that epithelial‐mesenchymal interactions are involved in important aspects of vasculogenesis in early embryos.
Heavy metal chelators prolong motility and viability of sea urchin sperm by inhibiting spontaneous acrosome reactions
Authors: Johnson Carl Hirschie , Epel David 
Published: June 2005

AbstractA variety of heavy metal chelating agents is known to prolong the fertilizing capacity and motility of sea urchin sperm. We report here that these agents maintain fertilizing capacity by preventing acrosome reactions which occur spontaneously after dilution of sperm into seawater. These chelating agents also inhibit acrosome reactions induced by high pH or egg jelly. Since induction of the acrosome reaction leads to steps that abolish motility, specifically a massive Ca2 + uptake and concomitant acidification of the cytoplasm, motility is prolonged by these chelators. These observations also suggest that heavy metals play a role in controlling the acrosome reaction in sea urchin sperm.
Studies on the flagellar ATPase of bull spermatozoa: Extraction and characterization
Authors: Young Leona G. , Smithwick Eleanor B. 
Published: June 2005

AbstractAdenosine triphosphatase (ATPase) activity of flagella isolated from ejaculated bull sperm was solubilized by 5 min exposure to 0.6 M KC1 at 4°C. ATPase activity in the flagellar extract was characterized with respect to enzyme, substrate, activator ion, salt, and hydrogen ion concentration. Flagellar extract required the presence of a divalent cation for activity: Mg2 +, Ca2 +, or Mn2+ could function as activator, but Zn2+ or Cd2+ could not. Magnesium‐activated ATPase was maximal in the presence of Mg2+ and ATP in equilimolar concentrations and at alkaline pH. Calcium activated ATPase was maximal over a wide range of Ca2 +:ATP ratios and at pH 8.0. The presence of increasing concentrations of Na+ and/or K+ ions in the assay medium (0.5–300 mM) had no effect on the ATPase activity of flagellar extract.
Inhibition of the acrosome reaction of sea urchin spermatozoa by a calmodulin antagonist, N‐(6‐aminohexyl)‐5‐chloro‐1‐naphthalenesulfonamide (W‐7)
Authors: Sano Kiyoshi 
Published: June 2005

AbstractA calmodulin antagonist, W‐7 (N‐(6‐aminohexyl)‐5‐chloro‐l‐naphthalenesulfonamide), inhibited induction of the acrosome reaction of sea urchin spermatozoa by egg jelly at 20–50 μM, but W‐5 did not. The latter, a chlorine‐deficient derivative of W‐7, has a lower affinity for calmodulin than does W‐7. These results suggest that a Ca2+ ‐calmodulin‐dependent process plays an important role in the triggering process of the acrosome reaction of Sea urchin spermatozoa.
What makes Blepharida jump? A structural study of the metafemoral spring of a flea beetle
Authors: Furth David G. , Traub Wolfie , Harpaz Isaac 
Published: June 2005

AbstractBlepharida sacra (Weise) is one of many species of flea beetles that have remarkable jumping abilities. The energy for its prodigious leaps is evidently stored in a central scroll‐shaped organ inside the hind femur of this insect—the metafemoral spring. X‐ray diffraction, scanning electron microscope, and analytical studies have established that this structure consists primarily of well‐oriented fibers of the polysaccharide α‐chitin, together with protein. The composition and orientation of these fibers appear to explain the role of this organ in the flea beetle jumping mechanism.
A histochemical and enzymatic study of the muscle fiber types in the water monitor, Varanus salvator
Authors: Gleeson Todd T. 
Published: June 2005

AbstractHistochemical analysis of five muscles from the water monitor, Varanus salvator, identified three major classes of fibers based on histochemical activities of the enzymes myosin ATPase (mATPase), succinic dehydrogenase (SDH), and α‐glycerophosphate dehydrogenase αGPDH. Fast‐twitch, glycolytic (FG) fibers were the most abundant fiber type and exhibited the following reaction product intensities: mATPase, dark; SDH, light; αGPDH, moderate to dark. Fast‐twitch, oxidative, glycolytic (FOG) fibers were characteristically mATPase, dark; SDH, light; αGPDH, moderate to dark. The third class of fibers had the following histochemical characteristics: mATPase, light; SDH, moderate to dark; αGPDH, light. These fibers were considered to be either slow twitch, or tonic, and oxidative (S/O). Pyruvate kinase (PK), αGPDH, and citrate synthase (CS) activities were measured in homogenates of the same muscles studied histochemically. There was a positive relationship between both PK and αgpdh activities and the percentage of glycolytic fiber types within a muscle. Likewise, CS activities were greater in muscles high in FOG and S/O content. Based on CS activities, Varanus S/O fibers were eight‐fold more oxidative than FG fibers within the same muscle. PK/CS ratios suggested that FG fibers possess high anaerobic capacity, similar to the iguanid lizard Dipsosaurus. The fiber type composition of the gastrocnemius muscle, relative to that of other lizard species, suggests that varanid lizards may possess a greater proportion of FOG and S/O fibers than other lizards.
Cytokinesis: Effects of blocks between the mitotic apparatus and the surface on furrow establishment in flattened echinoderm eggs
Authors: Rappaport R. , Rappaport Barbara 
Published: June 2005

AbstractThe physical mechanism which accomplishes cytokinesis in animal cells develops as a consequence of interaction between the mitotic apparatus and the surface. The purpose of this investigation was to determine whether successful furrow establishment depends upon normal geometrical relations between the interactants in some areas but not in others. Blocks were positioned between different regions of the mitotic apparatus and the surface in flattened sea urchin (Tripneustes gratilla) and sand dollar (Echinarachnius parma) eggs. The blocking agents used were slit‐shaped perforations, needles, and oil drops. Results were consistent regardless of which block was used. Blocks located outside the equatorial plane did not affect furrowing. Perforations located in the equatorial plane resulted in furrow formation on the proximal surface of the perforation; no furrows formed distal to the perforation, either in the cell margin or the distal surface of the puncture. Oil drops and glass needles positioned in the equatorial plane affected furrowing. The magnitude of the effect was directly related to the size of the block. The results demonstrate that furrow establishment is not affected by drastic modifications of the geometrical relationship between the mitotic apparatus and the poles, but it is very susceptible to interference in the region between the mitotic apparatus and the equator.
Role of progesterone on oocyte maturation in the egg‐brooding hylid frog Gastrotheca riobambae (fowler)
Authors: de Albuja Carmen M. , Campos Margarita , del Pino Eugenia M. 
Published: June 2005

AbstractIn the egg‐brooding frog Gastrotheca riobambae (Fowler), oocyte maturation is comparable to the situation of other frog species. In isolated follicles, progesterone induces only germinal vesicle breakdown (GVBD), while human chorionic gonadotropin (hCG) induces GVBD and ovulation. In addition, defolliculated oocytes respond with GVBD to the treatment with progesterone, while hCG has no effect. As in other frogs, oocyte maturation in vitro depends on hormonal action and on the presence of divalent cations. In this frog, progesterone or a similar hormone conditions the brooding pouch for reproduction and induces pouch closure. Follicles from frogs with closed pouches showed GVBD after 15–17 hours of incubation with progesterone, while those from frogs with open pouches took 19–24 hours for GVBD. These findings suggest that follicles become stimulated for maturation when the pouch is closed and that this stimulated condition is maintained for several weeks in advance of the process of oocyte maturation. In G. riobambae, the external appearance of the pouch aperture indicates the reproductive condition of the ovary.
Fine structure of the chorion and site of sperm entry in the egg of Brachydanio
Authors: Hart Nathan H. , Donovan Michael 
Published: June 2005

AbstractThe fine structure of the chorion and the region of the unfertilized egg immediately beneath the micropylar apparatus of the zebra danio, Brachydanio rerio, were studied using Nomarski differential interference optics, and scanning and transmission electron microscopy. The chorion consisted of three distinct zones: an outer, electron‐dense zone containing pore canal plugs (zona radiata externa), a middle fibrillar zone (superficial zona radiata interna), and an inner zone of 16 horizontal electrondense lamellae alternating with 15 interlamellae of lower electron density (deep zona radiata interna). The zona radiata interna was pierced by open pore canals. The single micropylar apparatus was regionalized into a cone‐shaped vestibule and a tapered micropylar canal traversing the entire chorion. The outer diameter of the micropylar canal was 7.5–8.5 μn and the inner diameter about 2.3 μn. Since the diameter of the inner micropylar aperture was slightly larger than the size of the sperm head, the block to polyspermy in eggs of the zebra danio appears to be mechanical and guaranteed by the morphological design of the micropyle. The egg plasmalemma beneath the inner micropylar aperture was differentiated as a circular cluster of 15–20 microvilli‐like projections. The cluster of surface projections, approximately 2.1–2.5 μn in diameter under scanning, electron microscopy, was distinguishable from the microplicae covering the rest of the egg surface and identified as the sperm entry site. The cortical cytoplasm subjacent to the sperm entry site was organized as a compact, electron‐dense, and homogeneous band. The sperm entry site itself was circumscribed by an area of cytoplasm (approximately 100 μn in diameter) in which cortical granules were typically arranged as a single layer immediately beneath the plasmalemma. However, there was a complete absence of cortical granules in the cytoplasm directly below the sperm entry site. The single row arrangement contrasted with the multilayered rows of cortical granules found throughout the remainder of the egg cytoplasm. Based upon Nomarski and ultrastructural analyses, there was a significant polarity in the cortex created by the size distribution and volume density of the cortical granules layered just beneath the plasmalemma. The cortical granules in the vicinity of the sperm entry site were 2.7 to 2.8 μm in diameter and densely packed. From this region to the vegetal pole, the cortical granules appeared to progressively increase in size and become less densely packed. The polarity in granule distribution established a distinct gradient in the structural organization of the egg cortex from the site of sperm entry to the vegetal pole.
The rate of estrone production by mouse blastocysts increases with estradiol‐17β concentration in medium
Authors: Wu Jung‐Tsung , Lin Guey‐Meei 
Published: June 2005

AbstractFollowing the finding of 17β‐hydroxysteroid dehydrogenase activity in mouse blastocysts, the present study examined the relation of estrone (E1) production rate to estradiol‐17β (E2) concentration in the medium. When Day 5 blastocysts were cultured in 107–6,860 ng E2/ml medium, the amount of E1 formed during the first 5 hours (y) was found to increase linearly with the logarithm of E2 concentration (x), as represented by the equation y = 2,161x − 3,947. However, there was a sharp decline during the next 5 hours of culture except for the 107 ng E2 culture. The E1 production then remained steady for up to 46–58 hours. There was a tendency for further decline during the 46–70‐hour period. The results indicate that (1) E2 may be metabolized to E1 and, probably, another unknown steroid; (2) E1 production rate is E2 ‐dose dependent; and (3) the blastocyst possesses the enzymatic capability to change the steroid milieu to suit its own needs and/or to cause local effects in the uterus for its proper implantation.
Lipids and the permeability of epidermis from snakes
Authors: Roberts Johnna B. , Lillywhite Harvey B. 
Published: June 2005

AbstractEvaporative water loss was measured in vitro from shed epidermis of 11 species of snakes from widely ranging habitats. Permeability of epidermis was inversely related to habitat aridity and increased 1.9‐ to 31.3‐ fold when lipids were extracted prior to measurements. The quantity of lipids extracted from epidermis varied severalfold among species, and was significantly greater in xeric‐adapted, terrestrial species than in aquatic species. However, there was no significant correlation between lipid quantity and the increase of permeability produced by extraction of lipids. Both quantity and composition of lipids are likely involved in evolutionary or physiological adjustments to habitat. Lipids were demonstrated histochemically to be located primarily in the mesos layer of the epidermis, with some lipids also present in the alpha and beta keratin. Alteration of keratin without lipid extraction increased permeability only 20% if that produced by lipid extraction in the same species. The data corroborate other recent findings indicating that epidermal lipids play a major role in regulating the permeability of reptilian integument.
Effect of complete tail amputation on the rate of metamorphosis in anuran tadpoles
Authors: Kumar T. Rajendra , Krishanaprasadan T. N. , Kotak V. C. 
Published: June 2005

AbstractComplete tail amputation enhanced the rate of metamorphosis threefold in the late prometamorphic tadpoles of Microhyla ornata and Rana tigrina. By contrast, premetamorphic tadpoles after tail amputation showed no acceleration of metamorphosis; instead, they regenerated their tails. Both these events could be reflective of the strategies employed in the different stages to enhance survival value.
A new technique for dechorionation and observations on the development of the naked egg in Oryzias latipes
Authors: Iwamatsu Takashi 
Published: June 2005

AbstractA simple technique for removing the chorion (egg envelope) of Oryzias latipes eggs is described in which the chorion is mechanically cut off with microsurgical scissors before and immediately after insemination. When dechorionated eggs were inseminated, a high incidence of polyspermic fertilization was observed. Fusion was induced among dechorionated eggs that were in contact when they were inseminated with a high concentration of spermatozoa. However, monospermic eggs that were dechorionated immediately after completion of the cortical reaction induced by insemination changed shape periodically during cleavage and developed normally to fry.
Electron microscopic observations during monospermic fertilization process of the brittle‐star Amphipholis kochii Lütken
Authors: Yamashita Masakane 
Published: June 2005

AbstractThis paper describes the process of monospermic fertilization in the brittle‐star, Amphipholis kochii Lütken, as observed by scanning and transmission electron microscopy: The observations concern the penetration of spermatozoon, the male and female pronuclei formation, and the fusion of pronuclei. The acrosomal process of this species is short, about 5 μm long. The thickness of the jelly coat is correspondently thin, confirming the notion that the length of the acrosomal process of the non‐echinoids corresponds to the thickness of the jelly coat. Decondensation of the sperm nucleus, formation of the male pronuclear envelope, and the growth of the male pronucleus occur irrespective of meiosis and the female pronucleus formation. This observation suggests the presence of different substances responsible for the decondensation of paternal and maternal chromosomes and for the formation of the male and female pronuclei. In spite of the different maturation state of eggs at insemination, the fertilization process of the ophiuroid, including the pronucleus formation and the association of pronuclei, is generally similar to that of the echinoid, indicating that Wilson's hypothesis may not apply to ophiuroids.
Inherited sex reversal in mice: Identification of a new primary sex‐determining gene
Authors: Eicher Eva M. , Washburn Linda L. 
Published: June 2005

AbstractWe present evidence that the inbred mouse strain C57BL/6J (B6) differs from Mus domesticus (DOM) at a locus involved in gonad determination and development as well as at the testis‐determining locus on the Y chromosome (Tdy). This newly identified gene is named testis‐determining, autosomal‐1 (tda‐1). Although the inheritance of tda‐1 suggests it is located on an autosome, its location on the X and Y chromosome in their pairing‐recombination region is not excluded. When mice are homozygous for the C57BL/6J‐derived tda‐1 allele (tda‐1B6) and carry the Y chromosome from M. domesticus, they develop as true hermaphrodites or, more rarely, as females. In contrast, when they are homozygous Tda‐1DOM/Tda‐1DOM or heterozygous Tda‐1DOM/tda‐1B6 and carry a B6‐derived or M. domesticus‐derived Y chromosome they develop as normal males.A simple genetic model is presented that integrates proposed steps in gonad determination and the results from genetic experiments reported here. In addition, arguments are presented for the existence of an ovary‐determining gene.
An attempt to approach the molecular mechanisms of primary sex determination: W‐ and Y‐chromosomal conserved simple repetitive DNA sequences and their differential expression in mRNA
Authors: Epplen Jörg T. , Cellini Alessandra , Romero Sally , Ohno Susumu 
Published: June 2005

AbstractThe biological role of simple repetitive DNA consisting of short, tandemly arrayed sequences, is still enigmatic. Previously we have described how simple quadruplet repeats (sqr)isolated from a sex‐specific snake satellite (Elaphe radiata) are also “sex‐specifically” arranged in mouse and man (Epplen et al, '81, '82a). In the mouse, these sqr are interspersed on all chromosomes, but a substantial part is concentrated in the pericentromeric region of the Y‐chromosome (Epplen et al., '82b). In one of the subcloned snake satellite DNA component (pErs5), the sqr are adjacent to a single‐copy sequence that in turn identifies a male‐specific putative mRNA in the mouse (Epplen et al. '82b). The isolated stretch of sqr themselves cross‐hybridizes with at least two species of poly (A)+ RNA from mice occurring in both sexes (Epplen et al., '82b, '83). By examining one of the non‐sex‐specific transcripts, we demonstrate here substantial open reading frames in the corresponding 2.5‐kilobase (kb)‐long mouse cDNA clone, including some 130 copies of sqr. The results are discussed in the context of mechanisms of primary sex‐determination in vertebrates, in particular the gonadal induction mechanism in heterogametic sex determination.
Studies of foreign genes transmitted through the germ lines of transgenic mice
Authors: Gordon Jon W. 
Published: June 2005

AbstractA novel gene transfer system has recently been developed in which DNA sequences isolated by molecular cloning can be introduced and permanently integrated into the genomes of developing mice. The procedure entails the microinjection of such cloned sequences into the pronuclei of onecelled embryos followed by reimplantation into pseudopregnant females for continued development. Although data obtained from this system are still few, they indicate it will have broad applicability to problems of mammalian developmental genetics. In order that such experiments be fully exploited, it will be necessary to understand the behavior of foreign genes introduced into the mouse and the relationship of that behavior to endogenous gene structure, function, and regulation. As a step in this direction, we have examined a line of mice into which has been transferred a recombinant plasmid consisting of a human leukocyte interferon genomic fragment cloned into the BamHI site of pBR322. The donor material has been integrated as a large concatameric structure which is inherited as a single Mendelian trait to several generations of progeny. Crossing of heterozygotes has apparently resulted in the production of viable homozygotes. In one animal, the structure of the integrated fragment was altered in spleen DNA but not in germ cells. This finding may reflect a normal processing mechanism whereby the structure of genes is altered during cell differentiation, or it may mean that transferred DNA does not behave as endogenous genes do.
Major histocompatibility complex (MHC)‐linked genes affecting development
Authors: Gill Thomas J. , Siew Shirley , Kunz Heinz W. 
Published: June 2005

AbstractGenes affecting growth and development which are linked to the major histocompatibility complex have been found in the mouse (t‐complex) and in the rat (growth and reproduction complex, grc), and there is some evidence that they also exist in humans. The genes of the t‐complex have different effects depending upon the specific combinations involved: skeletal and fertility abnormalities, complete or partial embryonic mortality, high transmission ratios (segregation distortion) in males, high level of linkage disequilibrium with H‐2, and suppression of recombination over the adjacent portion of the chromosome. The grc in the homozygous state causes small body size, sterility in the male and reduced fertility in the female, partial embryonic mortality, and a high level of linkage disequilibrium with RT1. It also interacts epistatically with the heterozygous Tal (tail anomaly lethal) gene to cause complete embryonic death. Mice carrying t‐haplotypes and rats carrying the grc have an antigen in the male germ cells whch cross‐reacts very strongly (t‐antigen). Suggestive evidence for such genes in humans comes from (1) studies on the relationship between skeletal defects and HLA haplotypes; (2) the association of specific HLA and complement haplotypes with a high transmission ratio in males, linkage disequilibrium among certain HLA and complement specificities and suppression of recombination in some MHC haplotypes; and (3) the lack of homozygotes in an isolated inbreeding population of desert nomads (Kel Kummer Tuaregs). In addition, immunogenetic studies on couples having chronic spontaneous abortions suggest that there is an unusually high incidence of homozygosity for the HLA‐D/DR and HLA‐A loci in these couples, and this finding is consistent with the presence of linked loci which behave like t or grc.