bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mouse mammary gland DNA synthesis during pregnancy
Authors: Borst David W. , Mahoney William B. 
Published: June 2005

AbstractMammary explants from virgin and pregnant Balb/c mice were incubated with 3H‐thymidine, and its incorporation into TCA‐precipitable material was determined. In addition, the labeling index of alveolar and ductal epithelial cells was determined by autoradiography. Incorporation of precursor into mammary tissue from pregnant animals was elevated above that of virgin animals on each day of pregnancy. During pregnancy, there were three periods of peak incorporation (on days 3, 7, and 11‐15). The labeling index of epithelial cells also increased during this period. Ductal cells had a peak labeling index on day 3 (3%), which dropped thereafter to comparatively low levels (3‐6%) for the rest of pregnancy. With the exception of days 1 and 3, the labeling index of ductal cells showed no difference between midnight and noon. Alveolar structures were first observed in histological preparations on day 5 of pregnancy. The labeling index of alveolar cells was higher than that of ductal cells during the rest of pregnancy, and on most days showed a diurnal fluctuation, being greater at midnight than at noon. The labeling index of alveolar cells had peak values at midnight on days 7 (23%) and 11‐13 (20%). This daily fluctuation in DNA synthesis by alveolar cells is a circadian rhythm; pregnant animals continued to show this rhythm after 13 days in constant darkness, and animals maintained on a reversed light schedule had a reversed rhythm. Mammary tissue shows a complex pattern of DNA synthesis during pregnancy, reflecting the different characteristics of ductal and alveolar epithelial cells.
Structural and biosynthetic studies on the two molecular forms of the (Na+ + K+)‐activated adenosine triphosphatase large subunit in Artemia salina nauplii
Authors: Peterson Gary L. , Churchill Lynn , Fisher James A. , Hokin Lowell E. 
Published: June 2005

AbstractThe large subunit of (Na+ + K+)‐activated ATPase from brine shrimp, Artemia salina, migrates as two bands in sodium dodecyl sulfate‐polyacrylamide gels. The slower migrating band, as observed in neutral or alkaline gel systems, is designated α1 and the faster, α2. Structural and biosynthetic studies have been performed to determine if these two bands represent independent molecular forms or precursor products. Peptide mapping of partial proteolytic digests of α1 and α2 showed no distinguishable difference between them, whereas this technique produced very distinct differences in the large subunit derived from three different species. The two large subunit bands also behaved identically when cross linked with cupric phenanthroline either in the presence or absence of digitonin, whereas other proteins in these preparations were unaffected. The peptide mapping and cross‐linking experiments demonstrate that α1 and α2 have identical or nearly identical primary and probably higher order structure. Their different mobilities may be due to post‐translational modification leading, for example, to different oligosaccharide composition. During development of the brine shrimp nauplius, α1 increases in relative abundance while α2 decreases. NaH14CO3 incorporation and pulse‐chase experiments indicate that α1 and α2, as well as the small subunit of the brine shrimp (Na+ + K+)‐activated ATPase, are synthesized at the same time during development and that all changes in the rates of synthesis of these subunits occur at the same time. The apparent rates of degradation of the subunits are also similar. These results are inconsistent with a precursor‐product relationship between α1 and α2.
The developmental potential of mouse 16‐cell blastomeres
Authors: Ziomek C. A. , Johnson M. H. , Handyside A. H. 
Published: June 2005

AbstractBased on the criteria of relative size and cell surface polarization, subpopulations of outer (larger, polar) and inner (smaller, apolar) blastomeres have been isolated from mouse 16‐cell morulae and reaggregated in groups of 16 cells, and the developmental potential of the aggregates has been assessed both in vitro and in vivo. Aggregates of outer, inner, or mixed groups of cells all formed blastocysts which outgrew and contained both characteristic trophectoderm and alkaline phosphatase positive inner cell masses in vitro. However, significant differences were observed in the timing of blastocyst formation, depending on cell type. Aggregates of outer cells recompacted more slowly, commenced fluid accumulation earlier, and contained more cells at the blastocyst stage than did inner cell aggregates. Aggregates containing both outer and inner cells were intermediate. Postimplantation development of blastocysts derived from aggregates of outer or inner cells, after transfer to pseudopregnant recipients, was normal and comparable to zona‐intact control embryos. This relationship between the expression of different morphological and behavioural properties by the precursor cells of the trophectoderm and inner cell mass and the existence of totipotent cells in both outer and inner subpopulations is discussed.
Changes in mouse oocyte membrane potential and permeability during meiotic maturation
Authors: Douglas Powers R. 
Published: June 2005

AbstractMouse oocytes spontaneously undergo meiotic maturation when removed from the ovary and cultured in vitro. This paper describes the changes in cell surface membrane potential from the germinal vesicle (GV) stage (− 46 mV, inside negative), through germinal vesicle breakdown (GVBD) (− 31 mV), to the polar body (PB) stage (− 17 mV). Radioisotope tracer flux experiments established the total exchangeable internal K at the GV stage in 190 mM, the K efflux rate coefficient as 6.7 × 10−5 sec−1 and the K permeability as 46.7 × 10−8 cm sec−1. In comparison with previous results with PB stage oocytes, this suggests that the membrane potential depolarization is caused largely by a decrease in K permeability. When GVBD is blocked with 0.11 mM dibutyryl cyclic AMP, the membrane potential does not depolarize. This suggests a linkage between depolarization and GVBD. However, incubation in 80 mM K medium, which depolarizes the oocyte, does not trigger GVBD. It is concluded that membrane depolarization by itself is not sufficient to cause GVBD.
Hemocyanin‐oxygen affinity in hermit crab blood is temperature independent
Authors: Jokumsen Alfred , Weber Roy E. 
Published: June 2005

AbstractThe oxygen affinity of the blood of the hermit crab Pagurus bernhardus is temperature independent at constant physiological pH (7.8 to 8.0) reflecting zero overall heat of oxygenation under these conditions. Combined with the absence of an indirect temperature effect (via changed in vivo pH), this represents a unique situation compared with previously investigated hemocyanins, and reflects adaptations to stabilize hemocyanin O2 loading in the thermolabile natural environments.
Bovine serum albumin, sperm motility, and the “dilution effect”
Authors: Harrison R. A. P. , Dott H. M. , Foster G. C. 
Published: June 2005

AbstractEpididymal spermatozoa from rabbit and ram were washed either once or twice using an efficient washing procedure and were then diluted in various media to a final concentration of approximately 1.4 × 107 cells/ml and incubated at 30°C for up to 12 hours. Bovine serum albumin (BSA), either untreated or defatted, was found to be better than polyvinylpyrrolidone, ovalbumin, or α‐lactalbumin, both at stimulating and maintaining motility levels and at reducing the tendency of the washed spermatozoa to stick to glass. BSA was effective in all media tested, being independent of Ca2+, PO43−, HCO3−, and ionic strength.BSA has a reversible stimulatory effect on motility. If BSA was added to sperm suspensions 3½ hours after they had been washed and diluted in protein‐free medium, motility was stimulated to levels not significantly lower than those observed in samples that had been washed and diluted in the presence of BSA. However, samples washed into BSA and then washed free of it behaved essentially as though they had never been in contact with the protein.The motility, survival, and response to BSA of twice‐washed spermatozoa were the same as those of once‐washed spermatozoa, showing that epididymal plasma factors are not required for survival in vitro. It was concluded that dilution is not essentially detrimental to rabbit and ram spermatozoa. However, severe dilution of semen may result in levels of male reproductive tract fluids insufficient either to stimulate motility or to prevent sticking of motile cells to container surfaces. Few motile spermatozoa are recovered from samples of such diluted semen.
Infertility in bitches induced by active immunization with porcine zonae pellucidae
Authors: Mahi‐Brown Cherrie Ann , Huang Thomas T. F. , Yanagimachi Ryuzo 
Published: June 2005

AbstractIn a study designed to evaluate the contraceptive potential of anti‐egg zona pellucida immunization, bitches were injected with isolated and solubilized zonae pellucidae of either the pig or the dog in saline and Freund's adjuvant or with saline and adjuvant alone (controls). They were boosted monthly, and serum samples were collected before the first injection and 10 days after each injection. The titers of anti‐zona pellucida antibodies in each serum sample were measured by treating fresh canine oocytes with the serum, then evaluating antibody binding as indicated by indirect immunofluorescence, precipitation of the zona surface, and penetrability of the zonae by spermatozoa in vitro. The bitches were bred when they came into estrus.All three bitches immunized with porcine zonae developed high titers (1:10,000 or more by indirect immunofluorescence) of antibodies that cross‐reacted with canine zonae to cause precipitation of the zona surface both in vivo and in vitro and that completely inhibited penetration of the zonae by spermatozoa in vitro. The two bitches immunized with canine zonae developed only low titers, and their sera had little or no effect on treated zonae. The two control bitches did not develop anti‐zona antibody. None of the bitches immunized against porcine zonae became pregnant when bred, but one bitch immunized against canine zonae and one control did become pregnant. The bitches immunized with porcine zonae had somewhat abnormal cycles for unknown reasons. Thus, we could not establish with certainty whether the infertility resulted from specific interference with fertilization, as in vitro, or from alterations in ovarian function, or both.
Changes in temperature tolerance during the development of Xenopus laevis embryos
Authors: Nelson Lennart , Mild Kjell Hansson , Løvtrup Søren 
Published: June 2005

AbstractDeterminations of the temperature tolerance of embryos of Xenopus laevis during the course of development show that the lower limit of the tolerance range declines from 11 °C to 6 °C as the embryo undergoes gastrulation; subsequently no further changes occur. The mechanism involved is unknown; possibly an increase in the proportion of unsaturated fatty acids in the lipids of the cell membrances is responsible.
Cytochemical demonstration that acrosin is unavailable in intact ejaculated boar and bull spermatozoa
Authors: Berruti Giovanna , Martegani Enzo 
Published: June 2005

AbstractThe cytochemical localization of acrosin (EC 3.4.21.10) was investigated using a fluorescent technique, based on the use of fluorogenic substrates, derivatives of 4‐methoxy‐β‐naphthylamine, which liberate a fluorescent tag that, if coupled to 5‐nitrosalicylaldehyde, generates an insoluble, fluorescent product. From the data obtained from boar and bull spermatozoa that had been subjected to different treatments, we have found that the acrosomal, trypsinlike proteinase is practically inaccessible in intact, freshly ejaculated spermatozoa. Acrosin activity was detected after subjecting the spermatozoa to a treatment that simulates the process they undergo at the moment of fertilization, showing a particulate localization in the acrosome of some of the spermatozoa.
The role of androgens in follicular development in the ovary. I. A quantitative analysis of oocyte ovulation
Authors: Ware Vassie C. 
Published: June 2005

AbstractIn an attempt to understand more fully processes that control the selection or recruitment of follicles for ovulation, the superovulation paradigm in combination with the androgen, 5α‐dihydrotestosterone, or the antiandrogens, cyproterone or cyproterone acetate, was used in the immature mouse to alter the developmental potential of follicles destined to ovulate or to become atretic. Quantitative analysis of the numbers of eggs ovulated after one or more rounds of stimulation by pregnant mare's serum gonadotrophin followed by human chorionic gonadotrophin (PMSG‐hCG), revealed a dose‐dependent ovulation response to exogenous androgen and antiandrogen. Low dosages of androgen improved the ovulation response significantly. Large dosages of cyproterone and cyproterone acetate (100 mg/kg body weight) generally decreased the ovulation number in gonadotrophin‐injected mice, suggesting a role for androgen in preovulatory events that occur within the ripened follicle after the ovulatory stimulus (hCG) has been received. Low dosages of cyproterone, particularly 25 mg/kg, significantly enhanced the ovulatory response, a phenomenon not observed for cyproterone acetate at this dosage. Radioimmunoassays of serum LH suggested that the differential response of the ovary to the two antiandrogens was probably related to endogenous LH release. Experiments in which the time of administration of hCG± cyproterone was varied after PMSG priming suggested that cyproterone at a dosage of 25 mg/kg had a “rescuing” effect on follicles destined to become atretic for up to 96 hr after PMSG priming. Cyproterone at a dosage of 100 mg/kg had no such effect, and actually decreased the magnitude of the ovulatory response at all time points tested, suggesting that follicular atresia was accelerated by this treatment. Experiments in which the time of administration of cyproterone (100 mg/kg) was varied after hCG suggested that whatever the important androgen‐mediated events preceding ovulation, these events occur within 2 to 3 hr after the hCG signal. By quantitating the numbers of eggs over several superovulation cycles, it could be shown that hormonal treatment in one induced cycle could affect significantly the ovulation response in subsequent cycles, suggesting that androgens influence the development of classes of follicles other than preovulatory follicles. These studies suggest that the process through which follicles are selected for ovulation is extremely sensitive to the androgenic environment and that the developmental pathways leading to ovulation or preovulatory follicular atresia are closely linked.
Termination of seasonal breeding in the photoperiodic weaver bird
Authors: Chandola Asha , Chakravorty Krishna 
Published: June 2005

AbstractTermination of seasonal breeding in the photoperiodic weaver bird does not occur as a result of photorefractoriness, and yet, in nature birds become refractory. Earlier studies indicated a seasonal variation in photosensitivity of this bird during the reproductive cycle and it was suggested that setting of the photoperiodic response threshold at a higher level might explain gonadal regression. Such a possibility was now examined by keeping birds in constant 13L/11D (the near maximal day length at Varanasi, India) and 15L/9D simultaneously for over 8 mo. While breeding in birds in 15L/9D continued, gonads regressed in 13L/11D indicating that the day length which was stimulatory in spring is no more sufficient to permit gonadal activity. Cyclicity in 13L (and in artificial 12L as well as natural daylength) may be explained on the basis that these schedules exceed the basic photoperiodic response threshold—hence the initiation of gonadal development. Once the gonads are developed due to decline in photosensitivity (caused perhaps by sex hormones) gonadal regression occurs, thus resulting in reproductive periodicity.
Mouse embryos and uterine epithelia show adhesive interactions in culture
Authors: Morris John E. , Potter Sandra W. , Buckley Patricia M. 
Published: June 2005

AbstractTo investigate the cellular mechanisms in preimplantation adhesion of the mammalian blastocyst to uterine epithelium, it is essential to avoid the complexities of the maternal environment but at the same time prevent the introduction of competing artificial surfaces, to which embryos preferentially adhere. We demonstrate here that sealed vesicles of isolated uterine epithelium cultured together with blastocysts in hanging drops provide an optimum system for encouraging and observing the adhesive interactions. The responses of the embryonic and maternal cells were identical to those known in vivo. Microvilli were seen on both surfaces, and in places the membranes were drawn into close apposition with some desmosomelike junctions. After blastocyst adhesion occurred trophoblast cells invaded the epithelium and showed phagocytic activity, closely resembling the invasion that follows adhesion during normal pregnancy in mice.
The truth about saturation deficiency—an historical perspective
Authors: Edney E. B. 
Published: June 2005

AbstractStudies on the water relationships of arthropods originated from the needs of applied entomology early in this century. Saturation deficiency (S.D.) was hailed as a measure whereby the effects of temperature and humidity on transpiration, and thus on development and longevity, could be simply combined. Errors in curve fitting and lack of physiological knowledge led to early misconceptions, but S.D. helped to focus attention on the need for laboratory analysis of field data and played a part in the move toward a more scientific approach leading to a great expansion of the whole field. Application of the concept to arthropods has usually been controversial, and examples of this drawn from the literature on the bionomics of the plague fleas and on cuticular waterproofing are discussed. A controversy exists at present concerning S.D. and the physics of transpiration. The concept of S.D. has been most useful where it has stimulated research to find out how arthopods avoid its consequences.
Why don't tobacco hornworms (Manduca sexta) become dehydrated during larval‐pupal and pupal‐adult development
Authors: Jungreis Arthur M. , Ruhoy Michael , Cooper Paul D. 
Published: June 2005

AbstractStudies of water loss during metamorphosis of insects have usually been confined to the pupal stage where both cuticular and respiratory control of transpiration have been reported. In Manduca sexta and other lepidopterans, preparation for pupation actually begins several days before pupation when the animals stop feeding and begin searching for an appropriate pupation site, a burrow for M. sexta. This study examines some aspects of water balance maintenance from the initial period of searching to the final time of eclosion. Behavior is important for reducing water loss, as animals which fail to find an appropriate pupation site continue to lose water at twice the rate of animals which are burrowed (10 vs. 5 mg H2O/g·h). Part of this is explained by exposure to light as unburrowed animals in constant dark are intermediate in water loss. The epicuticle during the pupal stage reduces water loss rate eight to tenfold, removal causing animals to lose water at 4 mg (g·h)−1. M. sexta does appear to be capable of storing water in preparation for metamorphosis, since individually raised animals consistently have water contents higher than animals reared in large groups. A drop in water loss during the larva‐pupal development is correlated with increased hemolymph ecdysone titer, although how is unknown. Pupal water loss can be divided into cuticular and respiratory pathways, with cuticular loss accounting for two‐thirds of 0.7 mg H2O (g·h)−1 loss rate. Finally, an increase in hemolymph osmotic pressure just prior to ecdysis may aid in reclamation of molting fluid.
Control of ion reabsorption in locust rectum: Implications for fluid transport
Authors: Phillips J. E. , Meredith J. , Spring J. , Chamberlin M. 
Published: June 2005

AbstractHormonal control of fluid reabsorption in the rectum is a major mechanism of water balance homeostasis in terrestrial insects. We report that steady‐state fluid transport in the absence of, or against, an osmotic gradient can be driven by absorption of Na+, K+, or Cl− from the lumen. Therefore chloride transport stimulating hormone (CTSH), a newly discovered hormone which stimulates KCl reabsorption by elevating tissue cAMP, might enhance fluid absorption indirectly by its action on transport of the major solute. This prediction was not confirmed and explanations are discussed. Rectal tissue volume increases considerably during the first hour in vitro and this epithelia only switches from slow transport of primarily NaCl to rapid absorption to predominantly KCI (the in vivo situation) after stimulation. Metabolic support of KCl transport depends largely on proline absorption from Malpighian tuble fluid entering the rectum. Since these specific requirements and properties of in vitro rectal preparations were not known during earlier investigations, most reports of putative diuretic and antidiuretic factors acting on rectal fluid transport in vitro require reexamination and confirmation.
Prolactin induces increase in the specific gravity of salamander, Hynobius retardatus, that raises adaptability to water
Authors: Moriya Tsuneo 
Published: June 2005

AbstractThe migration of the salamander, Hynobius retardatus, from land to water, which normally occurs in the breeding season, was induced by the injection of prolactin. The migration was accompanied by certain morphological changes (wider tail or swollen body); the observed morphological changes resembled those of salamanders collected from ponds during the breeding season. The prolactin‐treated salamanders sank to the bottom of the water. In contrast, the control salamanders that did not receive prolactin floated near the water surface. The specific gravity of the whole body of the prolactin‐treated animals was greater than unity. Prolactin injection induced a remarkable enlargement of the tissue between the skin and muscle, in which a considerable amount of mucopolysaccharide‐rich substance accumulated. Because of the hydrophilic nature of the mucopolysaccharides, the increased mucopolysaccharide may absorb more water, which, in turn, may result in an increase of the osmotic pressure of the serum. This may eventually cause the animals to migrate from land to water to quench the “thirst.” The absorption of water may make the specific, gravity greater, and this allows the animals to sink in water.