bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hypoxia: A succinate‐fumarate electron shuttle between peripheral cells and lung
Authors: Cascarano Joseph , Ades Ibrahim Z. , O'Connor John D. 
Published: September 2005

AbstractThe objective of this investigation was to determine if the succinate that accumulates in anoxic or hypoxic tissues of mammals is (a) increased in concentration in the blood, (b) excreted in the urine or (c) recycled in some manner. Rats were subjected to 0.4 atm and the plasma analyzed for succinate and fumarate at 2 hours, 24 hours and 28 days. Significant increases of succinate or succinate plus fumarate were obtained at 2 hours and at 28 days at 0.4 atm. Analysis of 24‐hour samples of urine obtained from controls and animals at 0.4 atm for 28 days demonstrated that no substantial increase in succinate excretion occurred with acclimation. Lung slices were incubated in Krebs‐Ringer bicarbonate and succinate and gassed with O2:CO2 (95:5). Such oxygenated lung slices not only utilized succinate but produced a comparable quantity of fumarate plus malate. It is concluded that succinate produced from fumarate and α‐ketoglutarate in peripheral hypoxic tissue is transported by the blood to the oxygenated lungs. There it is oxidized to fumarate and recycled as fumarate and malate to the periphery. In this way metabolites can act as electron shuttles between peripheral cells and lung.
Breakdown of the germinal vesicle in pig oocytes in vivo and in vitro
Authors: Motlík Jan , Fulka Josef 
Published: September 2005

AbstractThe breakdown of the pig germinal vesicle (GV) was studied in follicular oocytes matured in vivo and in vitro. For better characterization, the whole process was divided into four well‐defined stages, based on the chromatin changes, and on nucleolus and nuclear membrane disappearance. In the intact germinal vesicle (GV I) nuclear membrane and nucleolus are clearly visible and chromatin forms a ring or horseshoe around the nucleolus. In the GV II a few orceinpositive structures (chromocenters) on the nuclear membrane can be detected. For the GV III slightly stained chromatin clumps, localized especially around the nucleolus, and the beginning of strand formation are typical. In the last stage ‐ GV IV ‐ the nuclear membrane is less distinct and the nucleolus disappears completely. Chromatin is seen as an irregular network or as individual bivalents. According to these criteria GV breakdown in vivo was completed in most oocytes between 20 to 24 hours after HCG injection. In culture a similar stage of development was reached between 16 to 20 hours. This difference in the progress of nuclear changes appeared at the beginning of nuclear maturation and remained unchanged throughout the whole period studied.
Morphology and kinetics of the hamster sperm acrosome reaction
Authors: Talbot Prudence , Franklin L. E. 
Published: September 2005

AbstractThe morphology and kinetics of the normal acrosome reaction were examined in vitro using hamster sperm incubated in detoxified sera. The reaction involved either swelling and elevation or crenulation and fragmentation of the acrosomal cap. Swelling and elevation occurred during both normal and degenerative reactions, as reported by others. Crenulation with subsequent fragmentation of the cap was observed during normal reactions. Early crenulation of the acrosome could be induced by cold shock (5°C, 25 minutes), but this did not decrease the incubation time required (at 37°C) for completion of the normal reaction. In appropriate sera, the occurrence of normal and degenerative acrosome reactions in motile sperm was significantly separated in time to study the reactions independently. The duration of the normal reaction, i.e., the time between the first morphological change in the acrosome (initiation) until the actual detachment of the cap (termination) was estimated to be 20 minutes. Saline dilution of these sera delayed initiation of the reaction and increased the duration of the reaction once it had started. Data from cold‐shock and serum dilution experiments indicate that the mechanisms which govern the initiation and termination of the normal reaction are independently variable, and further suggest that initiation involves a change in membrane permeability and that termination includes membrane vesiculation.
The development of the oxygen permeability of the avian egg shell and its membranes during incubation
Authors: Lomholt Jens Peter 
Published: September 2005

AbstractThe O2‐permeability of the avian egg shell and shell membranes is initially low (≅0.1·10−6 ml O2 STP‐sec−1·cm−2mmHg−1) during incubation but increases about 10‐fold after the first week. This increase correlates with a decline in water content of the membranes. A major increase in colloid osmotic pressure (up to 50 cm Hg) occurs and is the suggested cause for the onset of rapid removal of water from the membranes. A high membrane water content correlates with low O2‐permeability and vice versa. The final degree of membrane hydration reached during incubation is independent of ambient humidity; that is, the O2‐permeability of the shell and its membranes is controlled by conditions inside the egg. An hypothesis is presented to explain the profound increase in O2‐permeability while the rate of water loss from the egg remains stable during incubation. The removal of water from the shell membranes by the increased colloid osmotic pressure will increase the number of gas filled channels in the membranes which in turn will increase the O2‐permeability. In spite of the change in water content, the water vapor pressure in the shell membranes will always be very close to that of a free water surface and water loss will hence be determined by the ambient humidity and the porosity of the mineral shell.
Epithelial stratification in the developing chick cornea
Authors: Nuttall Robert P. 
Published: September 2005

AbstractThe process of epithelial stratification was studied in the embryonic chick corneal epithelium between 10 and 21 days of incubation. Information was collected on the DNA synthetic activity occurring in individual cell layers, on cell density changes in the basal layer, and on mitotic spindle orientation in each cell layer before, during, and upon the completion of layer formation.Prior to the initiation of stratification, mitotic spindles are oriented parallel to the basement membrane interface. This orientation changes to predominantly vertically directed spindles as layer formation proceeds. Later, the majority of the spindles are horizontally aligned once more. This pattern was observed as each successive cell layer formed. The possible relationship between the spindle data and that obtained on DNA synthetic activity and cell density changes is discussed in terms of the role these factors might play in layer formation in the cornea, as well as in other stratified epithelia.
Evidence for the presence of nasal salt glands in the roadrunner and the Coturnix quail
Authors: Dunson William A. , Dunson Margaret K. , Ohmart Robert D. 
Published: September 2005

AbstractThe purpose of this investigation was to determine whether or not the nasal glands of the roadrunner and the Coturnix quail show cytological specializations for salt secretion. In addition, the Na‐K ATPase content of the quail gland was determined before and after drinking of saline solutions, in an effort to evaluate the functional status of the gland. The ability to maintain weight while drinking salt water was also measured as a general index of tolerance to saline conditions. The ultrastructure of the nasal glands of the roadrunner injected with salt and of quail drinking 200 mM NaCl was similar to that of salt glands in reptiles and the fresh‐water acclimated duck. Numerous lateral cell evaginations and abundant mitochondria were present in the principal cell types. There was a significant increase in quail nasal gland Na‐K ATPase when young birds were offered only saline solutions to drink. The ability of Coturnix quail to maintain weight while drinking saline solutions improves with age and at adulthood is comparable to that of some North American desert quail. Roadrunners were previously known to possess functional salt glands whereas quail were not. However the characteristic fine structure and the high Na‐K ATPase content of the quail nasal gland suggest that it is a salt gland.
Cytophotometric study of nuclear proteins during embryogenesis in two nematode species, Ascaris lumbricoides and Panagrellus silusiae
Authors: Pasternak J. , Barrell R. 
Published: September 2005

AbstractPatterns of nuclear protein changes during embryogenesis in two nematode systems: Ascaris lumbricoides and Panagrellus silusiae were examined microspectrophotometrically. In both species, development is accompanied by an extensive loss of basic nuclear protein as noted by the diminished intranuclear binding of both the Sakaguchi reagent and fluorodinitrobenzene chromophore. The alkaline fast green (pH 8.1) procedure stained both nuclear and cytoplasmic regions of interphase cells to a similar extent throughout embryogenesis. In cells at metaphase the chromosomes bound the fast green dye intensely while the cytoplasm continued to give a positive reaction. Relative Feulgen stainability of nuclei during embryonic development varied between species. In Ascaris, the one‐celled stage nucleus was Feulgen‐negative and the LI juvenile somatic nuclei yielded a mean Feulgen‐DNA value which was considerably less than a postdiminution diploid DNA equivalent. In Panagrellus, the nuclei of one‐celled stage embryos contain DNA in excess of a 4C quantity which subsequently is reduced during embryonic divisions. As in Ascaris the nuclei of Panagrellus, LI juveniles give hypodiploid Feulgen‐DNA values. The significance of these changes remains to be determined.
Cytophotometric analysis of basic nuclear proteins during gametogenesis in the free‐living nematode Panagrellus silusiae
Authors: Pasternak J. , Barrell R. 
Published: September 2005

AbstractThe cytochemical staining characteristics of basic nuclear proteins during gametogenesis in both sexes of the free‐living nematode Panagrellus silusiae were monitored by absorption microspectrophotometry. During spermatogenesis, the levels of both of the nuclear‐bound Sakaguchi and 1‐fluoro‐2, 4‐dinitrobenzene (FDNB) reagents per Feulgen‐DNA content increase prior to meiosis and subsequently drop off during spermiogenesis. During oogenesis, the amount of Sakaguchi‐protein to DNA ratio rises slightly whereas the FDNB‐protein to DNA ratio undergoes a meagre decline. Since the oocyte of Panagrellus accumulates DNA in excess of a 4C DNA equivalent, the relative constancy of the ratio of basic nuclear protein content to DNA amount during oogenesis signifies that these proteins are being continuously produced during oocyte maturation. After treatment with alkaline fast green (pH 8.1) the cytoplasmic and nuclear regions of the gonocytes of both sexes yield such an intense reaction that microspectrophotometric measurements could not be taken. The basis of the cytoplasmic staining reaction to the fast green (pH 8.1) dye was not determined. The rapid, highly deterministic programme of embryogenesis in Panagrellus may require a substantial stockpiling of basic nuclear proteins duing oogenesis.
Testis specific phosphoglycerate kinase B in mouse
Authors: Vandeberg J. L. , Cooper D. W. , Close P. J. 
Published: September 2005

AbstractMammals possess two genetically distinct forms of phosphoglycerate kinase (PGK). Only the X‐linked PGK‐A isozyme is detectable by electrophoresis of somatic and ovarian tissues of the mouse and of most other eutherian mammals studied to date. The PGK‐B isozyme is highly active in testes and epididymides which contain spermatozoa, as well as in semen. PGK‐B activity is first detectable in testes of 22‐day‐old mice and shows rapid increase concomitant with germ cell proliferation until day 40, after which activity increases only slightly. Two allelic isozymes (F and S) in mice express equal enzyme activity and are inherited in an autosomal codominant manner. One is equally as heat stable as PGK‐A; the other is heat labile. Two of the 33 strains tested express neither F nor S, but do express a faintly staining PGK band which is of slightly faster mobility than F and which is absent from the other stains. This may represent a third allelic isozyme of PGK‐B with reduced enzyme activity.
X‐ray induced inhibition of DNA synthesis and mitosis in internal tissues during the initiation of limb regeneration in the adult newt
Authors: Wertz Richard L. , Donaldson Donald J. , Mason James M. 
Published: September 2005

AbstractLeft front limbs of adult male newts were given 2000r of X‐irradiation at least four weeks prior to amputation of both forelimbs. Internal stump tissues were evaluated for the ability to incorporate 3H‐thymidine and accumulate colchicine‐blocked mitotic figures. In otherwise uninjured limbs, irradiation stimulated low levels of DNA synthesis which did not increase significantly after amputation. Thus, as soon as DNA synthesis increased significantly in normal limbs as a result of amputation, it was demonstrably higher than in X‐rayed limbs. In general, mitotic activity in both groups reflected the DNA synthetic rates. Since others have shown that denervation at the time of amputation blocks subsequent mitosis in internal stump tissues yet allows normal levels of DNA synthesis for eight days, we conclude that X‐irradiation and denervation prevent cell division in potential blastema cells by different mechanisms.
The role of extracellular material in chick neurulation. I. Effects of concanavalin A
Authors: Lee Hsin‐Yi , Sheffield Joel B. , Nagele Robert G. , Kalmus Gerhard W. 
Published: September 2005

AbstractThe distribution of extracellular material (ECM) in developing neuroepithelium of stage 8+ chick embryos was investigated using lanthanum nitrate. The temporal changes in the distribution of ECM was correlated with the ongoing morphogenetic movements. The most striking finding was that as the folds were about to meet, thick dense ECM appeared between leading edges. Concanavalin A inhibited neural tube closure by binding to cell surfaces and disrupting the usual distribution of ECM in developing neuroepithelium.
Hydration measurements on individual Artemia cysts
Authors: Clegg James S. 
Published: September 2005

AbstractThe water contents of individual cysts of the brine shrimp, Artemia salina, equilibrated at different relative vapor pressures of water, have been measured using tritiated water. These measured hydration levels compared favorably with those calculated from measurements on large populations of cysts using gravimetric methods. Therefore, studies of cyst hydration using large populations can be interpreted in terms of the behavior of individual cysts.
Amiloride inhibition of angiogenesis in vitro
Authors: Alliegro Mark C. , Alliegro Mary Anne , Cragoe Edward J. , Glaser Bert M. 
Published: September 2005

AbstractAngiogenesis is important to such processes as normal embryonic development and tissue growth, and is also a central feature of diseases such as diabetic retinopathy and the growth of solid tumors. Understanding the basic events governing angiogenesis has therefore attracted great interest. The ion channel blocking agent, amiloride, has been shown to inhibit angiogenesis in an in vivo model (Lansing et al., '91). This suggested a vital role for Na+ ‐coupled transport processes in angiogenesis. A large number of structural analogues of amiloride have been synthesized (Kleyman and Cragoe, '88), and many of these are well characterized with respect to biological activity. These analogues present an opportunity to dissect the process of angiogenesis and identify potentially important physiological events. In this report we describe the effects of amiloride on an in vitro model for angiogenesis employing vascularized tissue explants. Amiloride inhibits capillary morphogenesis completely and reversibly at concentrations as low as 134 μM. It appears to act by blocking endothelial cell proliferation, but not migration. Inhibition is heightened by the introduction of hydrophobic groups on the terminal guanidino nitrogen atom, or on the 5‐amino position. An analogue substituted at both of these positions is 30‐fold more potent than the parent compound. Of amiloride's known biological activities, these results most closely correlate with the inhibition of Ca2+ transport processes, and thereby suggest an important role for Ca2+ transport in capillary morphogenesis. © 1993 Wiley‐Liss, Inc.
Infection with the avian polyomavirus, bfdv, selectively affects myofibril structure in embryonic chick ventricle cardiomyocytes
Authors: Conrad Abigail H. , Consigli Richard A. , Conrad Gary W. 
Published: September 2005

AbstractEmbryonic cardiomyocytes can both beat and divide. They assemble cardiac musclespecific proteins into sarcomeric myofibrils and contract. In addition, they periodically synthesize DNA, complete mitosis, disassemble sarcomeric myofibrils in the area of the mitotic spindle, assemble cytoplasmic isoform‐specific proteins into a cleavage furrow contractile ring, undergo cytokinesis, and then reform sarcomeric myofibrils in daughter cells. Little is known about how embryonic cardiomyocytes disassemble their myofibrils as they traverse the cell cycle and divide. In the present study, beating embryonic avian ventricular cardiomyocytes in primary culture were stimulated to initiate DNA synthesis without subsequent mitosis or cytokinesis by infection with the lytic avian polyomavirus, Budgerigar Fledgling Disease Virus (BFDV). Within 48 hours, infected, adherent cardiomyocytes disassemble most of their sarcomeric myofibrils, retaining cardiac myosin only in thin myofibrils with disrupted sarcomeric periodicity and in amorphous nonfibrillar pools. By 72 hours, infected cardiomyocytes contain no myofibrils and no longer react with antibodies to cardiac myosin. In contrast, infected cardiomyocytes continue to display cytoplasmic myosin localized in stress‐fiber‐like‐structures in adherent cells, or in disrupted fibers and dispersed pools in detaching cells. Infected cardiomyocytes also continue to display interphase‐like arrays of polymerized microtubules, even when rounded‐up just prior to lysis. These results suggest that polyomavirus infection may provide a useful model system for further study of the regulation of myofibrils disassembly in embryonic cardiomyocytes. © 1993 Wiley‐Liss, Inc.
Steroidogenic shift by cultured ovarian follicles of Rana dybowskii at breeding season
Authors: Ahn Ryun S. , Ko Sun K. , Bai Dong G. , Yoon Yong D. , Kwon Hyuk B. 
Published: September 2005

AbstractThe steroid secretory activity of cultured ovarian follicles of Rana dybowskii and the activities of relevant steroidogenic enzymes were examined during the natural hibernation period (October‐February). Enzyme activities were measured indirectly by monitoring the conversion of exogenous substrates to products by isolated follicles. Follicles were incubated for 6 h in amphibian Ringer in the presence or absence of frog pituitary homogenate (FPH, 0.1 pituitary/2 ml) and/or various steroid precursors. Progesterone (P4), 17α‐hydroxyprogesterone (17α‐OHP) or testosterone (T) secreted by the follicles into the medium were measured by RIA. In the presence of FPH, high levels of P4 were produced by follicles at the early and mid‐hibernation period (695 and 898 pg/follicle, respectively) whereas markedly elevated levels of P4 were produced during late hibernation (1,393 pg/follicle) (just prior to or breeding season, February). In contrast, high levels of T were produced by the follicles early in hibernation (1,206 pg/follicle) while negligible levels were produced in late hibernation (69 pg/follicle). Higher levels of 17α‐OHP were produced by follicles at early and mid hibernation (594 and 705 pg/follicle, respectively) than in later hibernation (221 pg/follicle). Addition of exogenous pregnenolone markedly increased P4 levels in a dose‐dependent manner when added to follicles at early and late stages of hibernation: FPH addition further enhanced conversion of pregnenolone. Similarly, addition of androstenedione (AD) increased T levels in a dose‐dependent manner by these follicles. However, following addition of exogenous P4, less 17α‐OHP was produced by follicles collected in late hibernation as compared to those collected earlier. Likewise, addition of 17α‐OHP to follicles during late hibernation produced a small increase in T accumulation while a marked increase occurred when follicles were obtained in early hibernation. Taken together, the data indicate that steroidogenesis shifts from T to P4 late in hibernation and this is probably due to decreases in 17α‐hydroxylase and C17, 20 ‐lyase activities. © 1993 Wiley‐Liss, Inc.
Serum corticosterone concentrations in immature captive whitetip reef sharks, Triaenodon obesus
Authors: Rasmussen L. E. L. , Crow Gerald L. 
Published: September 2005

AbstractSerum concentrations of the steroid hormone corticosterone were monitored over a four‐year period in two male and two female immature captive whitetip reef sharks, Triaenodon obesus. Corticosterone concentrations in the serum ranged from 69–999 pg/ml (319.8 ± 31.9; n = 36) for males and 3–246 pg/ml (116.0 ± 15.1; n = 32) for females. Males had significantly higher values than females (P < 0.001). No significant difference was detected between females; however, a significant difference was observed between the two males. No seasonality was observed in corticosterone levels. Corticosterone levels in elasmobranchs are only 10% the levels of the principal glucocorticoid, 1α‐hydroxycorticosterone, but the assay is inexpensive and readily available, and, once individual ranges are established, the corticosterone concentrations have utility. Our data suggest that, after these baseline levels are established for individual sharks, long‐term monitoring of serum corticosterone in captive populations may be utilized to monitor health or, conversely, stress. © 1993 Wiley‐Liss, Inc.
A series of normal stages for development of Scyliorhinus canicula, the lesser spotted dogfish (Chondrichthyes: Scyliorhinidae)
Authors: Ballard William W. , Mellinger Jean , Lechenault Henri 
Published: September 2005

AbstractBy observing numerous living eggs from the lesser spotted dogfish Scyliorhinus canicula (L.) caught near Roscoff (France) and reared at recorded temperatures as they developed from first cleavage to hatching, the first reasonably complete developmental table was worked out for this classical material in vertebrate embryology. The successive stages, described and numbered from 1 to 34, correct and replace the incomplete stages A–Q proposed by Balfour (J.Anat. Physiol., 10:555–576,1876) and other even less complete series later published, and is unique in the inclusion of a timetable at 16°C. The stages can be identified, usually through the cleared eggshell wall, with naked eye or low magnification. This table of normal stages of Scyliorhinus can be adapted with slight modification to other chondrichthyan fishes. © 1993 Wiley‐Liss, Inc.