bluuebunny/crossref_metadata_2025_split huggingface dataset:
Germ cell differentiation in mouse adrenal glands
Authors: Zamboni Luciano , Upadhyay Shakti 
Published: June 2005

AbstractThe differentiation of germ cells in the adrenal glands of 26 male and female Swiss albino mice was studied in sequential stages of development, from day 12½ of intrauterine life to postnatal day 21; the study was performed by means of high‐resolution light microscopy and electron microscopy. In 12½‐ and 13‐day‐old embryos, the ectopic cells had morphologic characteristics typical of primordial germ cells, whereas in 14‐ and 15‐day‐old fetuses they were identifiable as oogonia. In male and female fetuses from day 17 to term, all ectopic germinal elements entered meiotic prophase, reached diplotene, and differentiated into oocytes in perfect adherence to mouse ovarian timetables. In the postnatal animals, females as well as males, all oocytes progressed through the postmeiotic phase of growth just as they normally do in ovarian follicles, and, in the 2‐ and 3‐week‐old animals, they displayed features identical to those exhibited by oocytes in large antral follicles, including a zona pellucida. Germinal elements were no longer seen in the adrenals of animals older than 3 weeks. Our study shows that mammalian germ cells are capable of developing even outside the gonads, and that in ectopic sites they all differentiate as oocytes irrespective of their genetic sex.
Nuclear transplantation in mouse embryos
Authors: McGrath James , Solter Davor 
Published: June 2005

AbstractThe ability of foreign nuclei to support development in nuclear transplantation manipulations has proven an effective means to assess the consequences of nuclear differentiation. In addition, nuclear transplantation might serve to define the persistence and role of maternally inherited cytoplasmic constitutents during embryogenesis. We have extended the use of a technique that enables the efficient transfer of one‐cell‐stage pronuclei into the cytoplasm of enucleated mouse embryos, and have successfully transferred two‐, four‐, eight‐cell‐stage and inner cell mass (ICM) cell nuclei. We have also used this technique as a means to determining that the stage‐specific embryonic antigen, SSEA‐3, is a cytoplasmic contribution of the unfertilized ovum. The potential value of this technique in determining the developmental capacity of nuclei from various embryonic stages, and in determining nuclear/cytoplasmic origins of early embryonic gene products, is discussed.
Intra‐ and interspecific embryo transfer
Authors: Kraemer Duane C. 
Published: June 2005

AbstractThe procedures that are collectively referred to as embryo transfer (ET) have many uses. They were first used as research tools to study fetal‐maternal physiology. Since the first successful mammalian embryo transfer in 1890, ET has been utilized for enhancement of genetic selection; diagnosis and treatment of infertility; control of infectious disease transmission; screening for genetic defects; propagation of rare and endangered species; and the study of developmental biology. Most of the embryo transfers have been intraspecific. A listing of the species includes rabbit, rat, sheep, mouse, goat, cattle, pig, hamster, ferret, mink, horse, baboon, cat, dog, water buffalo. In two species, rhesus monkey and humans, the successful embryo transfers have been limited to within‐animal, homologous replacement of the embryos. There have been a few successful interspecific embryo transfers. The most common were between Bos taurus and B. indicus cattle. Other interspecific transfers involved Bos gaurus and B. taurus, cattle; Ovis musimon and O. aries, sheep; Equus asinus and E. caballus, horses. There are several examples of integeneric embryo transfers in which embryos implanted but did not develop to term: sheep and goat, mouse and rat. The factors that determine the degree of compatibility between embryos and uteri of various species and genera are not clearly understood. The ability to hybridize successfully is probably a dependable indication of compatibility for embryo transfer. The limits of tolerance for differences between the donor and recipient in such factors as placental structure and gestation length have not been defined, but the recently developed technique of inner cell mass transfer will be very useful in such studies.
Alternatives to lactic acid: Possible advantages
Authors: Fields Jeremy H. A. 
Published: June 2005

AbstractMany groups of invertebrates use metabolic strategies that do not lead to the accumulation of lactate during periods of hypoxia or anoxia. These animals may accumulate some combination of the following: alanine, octopine, alanopine, strombine, acetate, propionate, 2‐methylbutyrate, 2‐meth‐ylvalerate, and succinate. An organism may derive a benefit from production of an alternative end product when the yield of ATP per mole of glucose 6‐phosphate is greater than that found in lactate production. Formations of succinate, propionate, 2‐methylbutyrate, and 2‐methylvalerate have been shown to yield more ATP in a few species. This analysis can be extended to the formation of alanine, as this is accompanied by the conversion of aspartate to succinate.Formations of octopine, alanopine, or strombine apparently do not increase the yield of ATP per mole of glucose 6‐phosphate, because the enzymes forming these compounds are functionally analogous to lactate dehydrogenase. A potential advantage of producing these compounds might be maintenance of a constant intracellular osmotic pressure during periods of anoxia. The significance of this is uncertain, because if lactate were to accumulate, the expected change in osmotic pressure appears to be trivial. Another possible advantage of accumulating octopine, alanopine, or strombine, would be the ability to maintain a lower NADH/NAD+ ratio as compared with the accumulation of lactate. This might assist the organism in maintaining a high rate of glycolysis by reducing the inhibition of glyceraldehyde 3‐phosphate dehydrogenase by NADH. Other possibilities are smaller perturbations of the acid–base balance of the cell, or producing a compound that has less effect on the catalytic and regulatory properties of enzymes in the cell.
Properties of amino acid transport in preimplantation rabbit embryos
Authors: Miller J. G. O. , Schultz G. A. 
Published: June 2005

AbstractThe kinetics, specificity, time dependency, Na+ dependency, and exchange behavior of the uptake of methionine, as a model for the uptake of the neutral amino acids, was investigated in rabbit eggs, morulae, and 6‐day blastocysts. Uptake by the blastocyst was physically resolved into components representing uptake into the cellular and cavity compartments. The kinetic data for all material, except the cellular compartment of the blastocyst, could be described mathematically by the parallel activity of a saturable and a linear transport system. The Km decreased from 91 μM in the unfertilized egg to 38 μM in the fertilized egg to 13 μM in the 69‐hr morula. The Km of uptake into blastocysts was 131 μM. The Vmax of uptake into the whole blastocyst was calculated to be about 5000 times that of uptake into the egg. Competition of methionine uptake by other amino acids indicated that the egg had somewhat more “L‐like” transport specificity than subsequent developmental stages, while the system(s) in the blastocyst were reactive with most neutral amino acids. Uptake into the egg, 69‐hr morula, and the cellular compartment of the blastocyst reached a steady state with time, in contrast to uptake into the 76‐hr morula and the cavity compartment of the blastocyst. Compatible with this, was the observation that eggs and 69‐hr morula, but not blastocysts, exhibited considerable efflux into amino acid‐containing media. The cavity compartment of the blastocyst may, however, act as a reservoir of amino acids for the cellular compartment. The Na+ dependency of transport was unchanged throughout the developmental period studied in this investigation.
TMAO (trimethylamine oxide)‐independence of oxygen affinity and its urea and ATP sensitivities in an elasmobranch hemoglobin
Authors: Weber Roy E. 
Published: June 2005

AbstractUrea and trimethylamine oxide (TMAO), the major osmolytes in the body fluids of marine elasmobranch fishes, are known to exert counteracting effects on the functions of a variety of enzymes and other proteins of vertebrates (cf. Yancey et al., '82). Although urea raises the O2 affinity of the hemoglobin (Hb) of Squalus acanthias and reduces its sensitivity to the major allosteric cofactor, ATP, the oxygenation reactions of the Hb are insensitive to TMAO, reflecting the absence of urea‐TMAO counteraction in the absence or in the presence of the phosphate.
Fluorescent localization of calcium at sites of cell attachment and spreading
Authors: Moran Denis 
Published: June 2005

AbstractChlorotetracycline (CTC), a calcium‐chelating fluorescent probe identifies and localizes calcium when applied to cultured neural crest cells. The fluorescence occurs at specific membrane regions involved in cell attachment and spreading as well as with the formation of cytoskeletal stress fibers (actin microfilament bundles). The observed CTC reaction indicates that calcium sequestration and the development of these membrane‐cytoskeletal features share a temporal and spatial pattern. Thus, the selective availability of calcium may be an important determinant of cell morphogenesis.
Intracellular optical physiology of the eye of the pyralid moth Amyelois
Authors: Bernard Gary D. , Owens Elizabeth D. , Hurley Andrea Voss 
Published: June 2005

AbstractAs in most nocturnal moths, the eyes of pyralid moths contain crystalline tracts formed by long, thin, distal extensions of the photoreceptor cells. Eyes of pyralid moths are unusual, however, because these thin extensions of the photoreceptor cells contain both pigment granules and rhabdomeric microvilli. Published anatomical and optical studies show that granules of both the photoreceptor cells and the primary/secondary pigment cells migrate as pyralid eyes adapt to light.The purpose of this paper is to describe noninvasive optical methods that characterize quantitatively the migration of pigment granules of both photoreceptor cells and pigment cells within the eye of the adult pyralid moth Amyelois. We find that: 1) Short, dim, monochromatic flashes (5 sec; 350–600 nm; quantum flux Q = 1010−1012 photons/cm2/sec) delivered to the dark‐adapted eye cause migration of the granules within photoreceptor cells, but no migration of the granules within pigment cells. The shape of a response is simple for the dimmest flashes and is complex for the brighter flashes. 2) The 12 photoreceptor cells that contribute microvilli to the distal rhabdom in each ommatidium are of three spectral types, maximally sensitive at about 350, 430, and 530 nm, respectively. 3) Short, bright flashes (Q > 1013) or long flashes (duration > 1 min; Q > 4 × 1012) delivered to the dark‐adapted eye cause migration of granules within pigment cells as well as receptor cells. Action spectra (350–665 nm) for movements of pigment‐cell granules are dominated by green‐receptors, with minor input from UV‐receptors and negligible input from the blue‐receptors.
Notochord formation in the Mexican salamander (Ambystoma mexicanum) is different from notochord formation in Xenopus laevis
Authors: Brun Rudolf B. , Garson John A. 
Published: June 2005

AbstractThe cytoskeletons of cells from gastrula and neurula stages of the Mexican salamander (Ambystoma mexicanum) and the African clawed toad (Xenopus laevis) were analyzed. Bundles of intermediate filaments were found in the superficial layer of the epidermis in neurulae (but not in gastrulae) of both organisms. The bundles (tonofilaments) were observed in the forming notochord of the axolotl but not in the differentiating notochord in Xenopus. Serial semithin sections demonstrated that the notochord develops from invaginated deep cells in Xenopus, but from invaginated superficial layer in the axolotl. Scanning electron microscopy of neurula stages from the axolotl and from Xenopus laevis confirmed this difference in notochord formation. This dissimilarity in notochord formation seems to be a typical difference between anurans and urodeles as was clearly pointed out by Ruffini ('25). This has implications for the fate maps published by Vogt ('29). The considerable differences in early embryonic development suggest to us that the salamanders (urodeles) and frogs and toads (anurans) are not monophyletic in origin.
Electrophysiological effects of cholinergic agents on the CNS of a nicotine‐resistant insect, the tobacco hornworm (Manduca sexta)
Authors: Morris Catherine E. 
Published: June 2005

AbstractTo assess the relative sensitivity of Manduca sexta central nervous system (CNS) to nicotine and other cholinergic agonists, global electrophysiological recording techniques were used. Comparisons were made between the tobacco hornworm and Periplaneta americana. Cords were tested in intact and partially desheathed conditions using two different recording methods (differential recording of activity in interganglionic connectives and non‐electrolyte gap recording of potentials developed in the ganglion). Both recording methods indicate that the Manduca tissue is about 100‐fold less sensitive to nicotine than Periplaneta, suggesting that mechanisms local to the CNS contribute to Manduca's ability to subsist on a nicotine‐rich diet. The threshold for response of desheathed Manduca cords to nicotine (during 5‐min exposures) is 5 × 10−5 M nicotine. Desheathing increases the sensitivity of the Manduca CNS to nicotine but does not make the tissue equally as responsive as the Periplaneta CNS. The cholinergic agonists acetylcholine, muscarine, lobeline, and tetramethylammonium and the anticholinesterase, eserine, all induce neural activity in Manduca, indicating that the tissue is not intrinsically insensitive to cholinergic agents. The tertiary amide N'‐methylnicotinamide potentiates the toxicity of nicotine to the Manduca CNS.
Larval innervation of the lobster claw closer muscle
Authors: Hill R. H. , Govind C. K. 
Published: June 2005

AbstractThe excitatory innervation of the claw closer muscle in the three larval (1st, 2nd, 3rd stage) and first postlarval (4th stage) forms of the lobster Homarus americanus was determined principally by electrophysiology. In the 3rd and 4th stages only two excitatory axons were found. One of these had a larger spike with a shorter latency and elicited a larger muscle EJP and a twitch‐like closing of the dactyl compared to the other axon, which had a smaller spike with a longer latency and elicited smaller EJPs and a slow closing of the dactyl with repetitive stimulation. These two axons resemble, respectively, the fast and slow axons of the adult muscle. In the 2nd stage only two excitor axons were demonstrated, one of which resembled the fast axon in evoking large EJPs with regenerative responses. In the 1st stage, excitatory innervation is present, though the number and character of the axons remain unknown. Motor axons, therefore, innervate the claw closer muscle right from the time of hatching and are completely differentiated into fast and slow types by the end of the larval period of development.
Evidence suggesting the importance of fatty acids and the fatty acid moieties of sperm membrane phospholipids in the acrosome reaction of guinea pig spermatozoa
Authors: Fleming Alan D. , Yanagimachi Ryuzo 
Published: June 2005

AbstractWhen guinea pig spermatozoa were preincubated 1 hr in Ca2+‐free medium containing dilysocardiolipin (100–125 μg/ml) then exposed to Ca2+, the majority underwent an immediate acrosome reaction. Monolyso‐cardiolipin was much less effective and the native cardiolipin was totally ineffective. Some fatty acids added to the medium could also render the spermatozoa capable of undergoing their acrosome reactions, arachidonic acid in methyl ester form being most potent. It is known that sperm membrane contains phospholipase A which cleaves membrane phospholipids into lysophospholipids and fatty acids. Most lysophospholipids are known to be potent acrosome reaction–promoting agents. As some forms of fatty acids are also potent acrosome reaction–promoting agents, both products of membrane phospholipid hydrolysis by phospholipase A (i.e., both fatty acids and lysophospholipids) may work synergistically to effect the conversion of stable sperm membranes to a fusion competent state capable of engaging in the acrosome reaction.
Two healing patterns correlate with different adult neural connectivity patterns in regenerating embryonic Xenopus retina
Authors: Ide Charles F. , Reynolds Patrick , Tompkins Robert 
Published: June 2005

AbstractNasal and temporal one‐third‐sized eye fragments, formed by ablation at stage 32–33 of Xenopus laevis embryos, heal and, in about 50% of the cases, survive to make eyes in the postmetamorphic animal which have mappable visuotectal projections. The majority of nasal one‐third eyes have duplicate projections whereas the majority of temporal one‐third eyes have unduplicated projections. Most nasal one‐third eye fragments and a minority of temporal eye fragments heal by the extrusion of cells from the center of the cut edge into the region of the ablation, forming a tongue of cells between the distal cut edges. This healing pattern is correlated with duplicated visuotectal projections. Most temporal one‐third fragments and a minority of nasal one‐third fragments heal by rounding up; that is, the distal cut edges collapse to meet in the region of the ablation. This healing pattern is correlated with the formation of unduplicated visuotectal projections. During tongue formation, neurons and undifferentiated cells are transferred from the original fragment into the tongue in a disorderly array, but quickly re‐form normal retinal order. We propose that the tongue cells retain their original determination to connect to the same tectal positions as the fragment from which they originated, despite their new positions, and that this mosaicism, coupled with cell movement into the tongue, established duplicate visuotectal projections.
Sources of calcium for embryonic development in eggs of the snapping turtle Chelydra serpentina
Authors: Packard Mary J. , Short Terry M. , Packard Gary C. , Gorell Thomas A. 
Published: June 2005

AbstractFlexible‐shelled eggs of snapping turtles (Chelydra serpentina) were analyzed for calcium content at different times in incubation to determine sources of mineral for developing embryos and to characterize the pattern of its mobilization. Yolk and albumen of freshly laid eggs contained 11.70 and 0.16 mg of calcium, respectively. Almost all calcium was withdrawn from the yolk during incubation, but this calcium was not sufficient to satisfy requirements of embryos. Calcium contained within eggs increased to 27 mg between oviposition and hatching owing to mobilization of approximately 15 mg of calcium from the calcareous eggshell. Thus, embryonic snapping turtles obtain slightly more than half (56%) of the calcium required for development from the eggshell, with the remainder (44%) coming from stores present in the yolk at oviposition.
Acetylcholine promotes progesterone‐induced maturation of Xenopus oocytes
Authors: Dascal Nathan , Yekuel Rivkah , Oron Yoram 
Published: June 2005

AbstractProgesterone‐induced maturation of follicle‐enclosed and denuded Xenopus laevis oocytes was significantly shortened by a concomitant exposure to acetylcholine. The promotion of maturation by acetylcholine was blocked by the specific muscarinic antagonist atropine. The action of acetylcholine was dose dependent, and the neurotransmitter was effective at very low concentrations. Progesterone progressively reduced the electrophysiological responses of X. laevis oocytes to acetylcholine, which completely disappeared close to the time of germinal vesicle breakdown. Progesterone alone did not elicit any electrophysiological responses. The in vitro effect of acetylcholine on oocyte maturation might reflect a physiological influence of the cholinergic system on an in vivo maturation process.
Conspecific odor detection by the male broad‐headed skink, Eumeces laticeps: Effects of sex and site of odor source and of male reproductive condition
Authors: Cooper William E. , Vitt Laurie J. 
Published: June 2005

AbstractOlfactory stimuli are sufficient for detection and discrimination of sex of conspecific lizards by the male broad‐headed skink, Eumeces laticeps, a member of a large group of lizards with pronounced chemosensory abilities, the Autarchoglossa.The capacity of male broad‐headed skinks to detect conspecific odors was assessed by measuring tongue extrusion rates in response to odor stimuli presented on moist cotton applicators. Tongue‐flick rates of postreproductive males were siginificantly higher for clocal odors of postreproductive conspecif‐ics of both sexes than to distilled water and higher to female than male odors over the initial 20‐ and 60‐sec intervals. In a second experiment using testosterone‐treated males and estrogen‐injected females, testosterone‐treated males emitted significantly more tongue flicks to female cloacal odors than to the other stimuli, and two males bit applicators bearing male odors. Testosterone did not affect reaction to male cloacal odors, but markedly increased tongue flick rates in response to cloacal odors of estrogen‐treated females. Post reproductive males also responded to female, but not male, skin odors at a significantly higher rate than to water. Possible sources and presumed adaptive significance of conspecific odors are discussed.
Quail melanoblast migration in two breeds of fowl and in their hybrids: Evidence for a dominant genic control of the mesodermal pigment cell pattern through the tissue environment
Authors: Hallet Marie‐Martine , Ferrand Raymond 
Published: June 2005

AbstractIn the Silkie fowl large numbers of melanocytes invade most internal tissues and organs. The factors involved in this internal pigment cell pattern were studied by grafting quail neural tube segments into White Leghorn, White Silkie, and F1 hybrids (White Silkie male × White Leghorn female). Sections of quail neural tube five somites long, excised at the level of the last formed somites, were grafted isotopically and isochronically. Various tissues and organs (mesenteries, muscles, testis, ovary, mesonephros, metane‐phros, and adrenals) excised from the internal region corresponding to the peripheral transverse strip of quail melanocytes, were studied after staining by the Feulgen‐Rossenbeck technique.Despite some variations in pigment cell density, Silkie and hybrid grafted embryos exhibited an extensive quail internal pigmentation similar to the melanocyte distribution in the Silkie breed. In white Leghorn host embryos, the internal pigmentation remained limited. These results show the part played by tissular factors in the expression of the Silkie pigment phenotype and that this genetic tissular character is dominant.On the contrary, White Leghorn embryos, grafted with Silkie neural tube segments, never exhibited any internal pigmentation; the melanocytes deriving from the grafted Silkie neural tube were only localized at the dermoepidermal level. Thus, the migrating and/or differentiating capabilities of the Silkie premelanoblasts are different from those of quail premelanoblasts. The sex‐linked inhibitor of the White Leghorn tissue interferes at the level of the pigment cells of chickens but not of quails.