bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hyperactivated motility induced in mouse sperm by calcium ionophore A23187 is reversible
Authors: Suarez Susan S. , Vincenti Leila , Ceglia Matthew W. 
Published: June 2005

AbstractThe reversibility of hyperactivated motility was tested in caudal epididymal mouse sperm by treating them with 1 μM calcium ionophore A23187 in dimethyl sulfoxide (DMSO), followed 2 min later by the addition of medium containing high levels of bovine serum albumin (BSA) (final concetrations: 0.5 μM A23187, 22 mg/ml BSA). Controls received DMSO alone, followed by BSA. Immediately following treatment with A23187, motility was weak and vibratory. Two minutes after the addition of high levels of BSA, motility was hyperactivated, as determined by videotape analysis of linearity of trajectory and acuteness of flagellar bending. Ten minutes after the addition, the movement pattern returned to that of fresh, uncapacitated epididymal sperm. Control sperm retained the linear swimming pattern of fresh caudal epididymal sperm during the 10 min of observation. Ninety minutes later, however, both control and treated sperm became hyperactivated. The percentage of motile sperm was not affected by treatment or time. Thus, ionophoreinduced hyperactivation is reversible and does not interfere with the normal development of hyperactivation during incubation under capacitating conditions in vitro.
Intracellular voltage recordings in the opercular epithelium of Fundus heteroclitus
Authors: Zadunaisky J. A. , Curci S. , Schettino T. , Scheide J. I. 
Published: June 2005

AbstractOpercular epithelial cells of Fundus heteroclitus were investigated using conventional microelectrodes. The area of interest was the cells lining the inside of the opercular epithelium closest to the gill arches, an area with a high density of chloride cells. Only one cell type could be discerned from the values of 60 opercular cells measured with the opercular epithelium in open circuit conditions. A mean apical voltage of −18.0 ± 0.6 mV was observed with intracellular values ranging from −10 to −30 mV. The predicted intracellular chloride content was 59 mM/liter. Apical fractional resistance (f) was 0.78 ± 0.02. The intracellular potential measurements were typically difficult to maintain for extended periods (longer than 3 min). The opercular cells depolarize with serosal isoproterenol treatment (10−6 M) corresponding to the increase in opercular transepithelial potential. The opercular cell apical fR decreased with isoproterenol treatment. These data indicate the observed opercular cells were involved in opercular chloride transport.
Light‐induced release of Artemia dried embryos from diapause: Analysis of metabolic status
Authors: Van Der Linden A. , Blust R. , Van Laere A. J. , Decleir W. 
Published: June 2005

AbstractCommercially obtained Artemia cysts were hydrated and incubated for prolonged periods in aerobic conditions, but deprived from light. A part of these cysts refused to hatch and remained in diapause until they were activated by illumination. During a dark incubation period of 20 days, the light‐induced hatchability remained constant, while the respiration rate and the ATP concentrations slowly decreased to the very low values of 0.01 μl O2/hour mg WW and 0.3 nmol ATP/mg protein, respectively. The endogenous trehalose reserves did not measurably decrease and glycerol was not synthesized during this treatment.Furthermore, we have demonstrated that light, acting as a diapause breaker, induced, in an irreversible manner, an enhancement of respiration and a concomitant breakdown of trehalose. The fact that a very short period of illumination was sufficient to induce hatching and that the induction was irreversible demonstrated that we were definitely not dealing with an exogeneous dormancy, whereby the environment causes the arrest of development. Light acted as a transient signal suspending diapause and triggering development.
Thyroid hormones act at the level of the pituitary to regulate thyrotropin and growth hormone secretion in hatchling slider turtles (Pseudemys scripta elegans)
Authors: Denver Robert J. , Licht Paul 
Published: June 2005

AbstractPituitaries from hatchling turtles (Pseudemys scripta elegans) were incubated with different doses of L‐thyroxine (T4: 1–500 ng/ml) or 3,5,3′‐triiodothyronine (T3: 1–50 ng/ml) for various times (1–48 hr) to assess their effects on basal thyrotropin (TSH) and growth hormone (GH) secretion and responsiveness to thyrotropin‐releasing hormone (TRH: 10 ng/ml). Pretreatment with a pharmacological dose of T4 (500 ng/ml) for 1 hr inhibited the TSH response to TRH, and physiological doses were effective after slightly longer times. The TRH effect was reduced by exposure to 50 ng/ml T4 for 1 hr, and abolished after 4 hr. Pretreatment with 50 ng/ml T4 or T3 for 6 hr did not affect basal TSH secretion, but the attenuation of the TRH response persisted for at least 20 hr after removal of thyroid hormones. Longer exposure (16 hr) to 50 ng/ml T4 or T3 reduced both TSH basal secretion and the response to TRH. A low dose (1 ng/ml) of T4 or T3 for the same amount of time had no effect on basal TSH secretion and only slightly reduced the TRH response; T3 was more potent than T4. Basal secretion and TRH responses of glands pretreated with 5 ng/ml T4 were not different from controls after 4 and 6 hr, but were significantly reduced after 24 hr of exposure; 15 ng/ml T4 reduced the TRH response after 6 hr, but basal secretion was not affected until 24 hr. Treatment with 2 ng/ml T4 for 48 hr reduced the response to TRH but did not affect the baseline. Basal and TRH‐stimulated GH secretion was also inhibited by thyroid hormones, but the onset of these effects were delayed (16 to 24 hr after exposure) and required a relatively high dose (50 ng/ml).These data are consistent with an earlier report from this laboratory (Denver and Licht: J. Exp. Zool. [in press], '88) that in vivo treatment with thyroid hormone or a goitrogen alters in vitro pituitary hormone secretion in turtles and provide evidence for a direct action of thyroid hormones at the level of the pituitary.
Sperm nuclear enlargement in fertilized hamster eggs is related to meiotic maturation of the maternal chromatin
Authors: Wright Shirley J. , Longo Frank J. 
Published: June 2005

AbstractExperiments were conducted to test the hypothesis that sperm nuclear expansion in fertilized hamster eggs is correlated with meiotic processing of the maternal chromatin. In vitro fertilized hamster eggs were fixed at regular intervals following insemination, stained with the DNA specific fluorochrome, Hoechst 33342, and the extent of sperm nuclear expansion measured. Sperm nuclei enlarged in multiple, distinct phases (A–E) that were temporally correlated with meiotic processing of the maternal chromosomes: phase A, metaphase II; phase B, early anaphase II; phase C, late anaphase II, and phases D and E, female pronuclear development and expansion. During phase A, sperm nuclei were unchanged but enlarged at different rates during phases B (272 μm2/min), D (106 μm2/min) and E (29 μm2/min), and condensed during phase C (rate = −102 μm2/min). Area increases of both sperm nuclei and female pronuclei during phase D were significantly less in polyspermic and polygynic zygotes. If sperm nuclear enlargement and the status/activity of the maternal chromatin were correlated, it would be anticipated that alterations in the normal progression of meiotic maturation would be manifested in sperm nuclear expansion. The following agents affected both meiotic maturation and sperm nuclear enlargement: colchicine, antimycin A, and puromycin. These observations suggest that processes attending sperm nuclear transformations, the completion of maternal meiotic maturation, and development of the female pronucleus are coupled and may be linked by common regulatory agents.
Effect of sodium dodecyl sulfate on polar lobe formation and function in Ilyanassa obsoleta embryos
Authors: Render Joann 
Published: June 2005

AbstractPolar lobes, anucleate vegetal pole protrusions formed by Ilyanassa obsoleta embryos, serve as a mechanism for shunting morphogenetic determinants to one cell during the first two cleavages. Polar lobe material becomes segregated in the CD cell during first cleavage and in the D cell during second cleavage, resulting in a very unequal four‐cell stage. Larval structures including external shell, foot, operculum, statocysts, and eyes develop only when polar lobe material is present. Treatment with the anionic detergent sodium dodecyl sulfate (SDS) before and during the first cleavage inhibited polar lobe formation and equalized cleavage, as the lobe material was distributed to two cells. No polar lobes formed during second cleavage in SDS‐equalized embryos, and the four‐cell stage consisted of four equal cells with reduced cell contacts. SDS irreversibly inhibited polar lobe formation without affecting cytokinesis. Although 27% of the larvae from SDS‐equalized embryos had one or more lobe‐dependent structures duplicated, morphogenesis was impaired: more than 40% of such larvae failed to form shell and/or statocysts. When cells were separated after equalized first cleavage and raised as pairs, the pairs of resulting larvae duplicated lobe‐dependent structures with the same frequency as whole equalized embryos. Possible explanations for impaired morphogenesis in SDS‐treated embryos are discussed.
Effects of capture and temperature stresses on plasma steroid concentrations in male tuatara (Sphenodon punctatus)
Authors: Cree Alison , Guillette Louis J. , Cockrem John F. , Joss Jean M. P. 
Published: June 2005

AbstractThe effects of capture and temperature stresses on plasma concentrations of testosterone (T) and progesterone (P) were examined in wild male tuatara (Sphenodon punctatus), the only living sphenodontid reptile. Free‐roaming male tuatara on Stephens Island, New Zealand, had low levels (0.3–0.5 ng/ml) of plasma T in July (winter), and high levels (15–17 ng/ml) in January (summer). Levels in November appeared intermediate (5 ng/ml) but were measured with reference to standards prepared in human rather than tuatara plasma. These seasonal variations are consistent with available information on the annual cycle of spermatogenesis and reproductive behavior in male tuatara. In November, plasma T was unchanged in males bled at 0, 3, and 12 h after capture but had fallen significantly to 57% of the initial value by 24 h after capture (experiment 1). In January, males held in collecting bags for 3 h prior to blood sampling had levels of plasma T similar to those of free‐roaming males sampled at the same time (experiment 2). In July, an acute heat stress (12.8°C elevation in body temperature over 30 min) had no effect on plasma T (experiment 3). Significant changes in plasma P were seen prior to changes in plasma T in experiment 1: plasma P was elevated at 3, 12, and 24 h after capture. No difference in plasma P was observed between free‐roaming and captive males in experiment 2. In experiment 3, no change in plasma P occurred in response to heat stress. Free‐roaming males showed no evidence of a diurnal cycle in plasma T or plasma P in November. These data indicate that plasma T in male tuatara is unaffected by short‐term (3 h) capture; however, longer‐term (24 h) capture combined with repeated blood sampling causes a significant reduction in plasma T, as previously reported for other male reptiles. Changes in plasma P suggest that activity of the adrenal gland may be sensitive to captivity stress in this species. These data provide the first values for circulating steroid levels in free‐roaming wild male tuatara and help define conditions of captivity that influence plasma steroid concentrations, a prerequisite for further studies of steroid cycles in this species.
Germ cell deficiency causes testis cord differentiation in reconstituted mouse fetal ovaries
Authors: Hashimoto Naohiro , Kubokawa Reiko , Yamazaki Kimie , Noguchi Motoko , Kato Yoshihiro 
Published: June 2005

AbstractSex‐reversal in fetal ovaries was studied by using a dissociation‐reconstitution technique. Gonads of 12.5 gestation‐day male and female mouse fetuses were dissociated into single cells. To eliminate germ cells, the dissociated cells were cultured for 14 h, and then somatic cells attached to culture dishes were harvested and aggregated by gyratory culture for 24 h. The aggregates were then transplanted into ovarian bursa in ovary‐ectomized nude mice. The recovered explants were examined histologically. Male somatic cells developed into testes containing Sertoli cells, Leidig cells, and tunica albuginea. Female somatic cells formed testis cords and differentiated into Sertoli cells, but they did not differentiate into other testis components or ovarian tissues. However, aggregates consisting of both female and male somatic cells differentiated into well‐developed testes containing Leidig cells and tunica albuginea as well as Sertoli cells. Enzyme marker analysis showed significant contributions of female cells in these organized testes. In contrast, aggregates containing both female germ cells and somatic cells developed into ovaries and did not differentiate into any testicular tissues.The results indicate that female somatic cells in fetal gonads at 12.5 gestation day have the potency to form testis cords and differentiate into Sertoli cells. The subsequent steps in testis development require the contributions of male cells. The present study also suggests that testicular differentiation is independent of germ cells but ovarian development involves the interaction between germ cells and somatic cells.
Carbonic anhydrase in branchial tissues of osmoregulating shore crabs, Carcinus maenas
Authors: Böttcher K. , Siebers D. , Becker W. 
Published: June 2005

AbstractActivities of carbonic anhydrase (CA) were determined in various organs of shore crabs, Carcinus maenas, acclimated to salinities of 10, 20, 30, 40, and 50‰. In addition, some properties of the branchial enzyme (effects of detergents, storage conditions, and specific inhibitors) were tested. Subcellular distribution of gill CA was analyzed by means of centrifugation procedures. In hemolymph no CA activity could be detected. In all other organs except gills activities were low and insensitive to salinity change. High activities of CA were found in the gills. Activities in posterior gills were—in comparison with anterior gills—more than twofold increased. Acclimation of crabs to reduced ambient salinities resulted in significant increases in CA only in posterior gills. In the gill enzyme specific activities and stability during storage could be increased by means of the detergent Triton X‐100 used at 1% (v/v) in the homogenizing medium. Sulfonamide inhibitors reduced CA activities effectively. Inhibition constants Ki of the gill enzyme were 7.0 × 10−9 M for acetazolamide and 3.1 × 10−8 M for methazolamide. Measurements of CA activities in supernatants and pellets obtained by differential centrifugation and in fractions obtained by centrifugation of 7,500g supernatants in a sucrose density gradient indicated that the major portion of CA activity in the gill (ca. 75%) was bound to cellular particulates including plasma membranes and ca. 25% occurred in a soluble form in the cytoplasm. Both the bound and the soluble forms of CA were increased in crabs acclimated to low salinity, suggesting that CA in crab gills, besides its known role in CO2 excretion and acid‐base balance, functions in osmoregulatory processes.
Seawater inflow through the madreporite and internal body regions of a starfish (Leptasterias hexactis) as demonstrated with fluorescent microbeads
Authors: Ferguson John C. 
Published: June 2005

AbstractSince the tube feet of starfish can continue to function by osmotic inflation after being separated from the madreporite, doubt has been raised in recent years that this organ is significant for keeping fluid balance. To clarify this question, small specimens of Leptasterias hexactis were exposed to a suspension of fine fluorescent beads for 48 hr and then studied as cryostatic sections under UV light. Abundant beads were found in tube feet and ampullae, clearly showing that madreporite uptake does help sustain their activity under normal circumstances. Even larger accumulations of beads were located in Tiedemann's bodies, indicating that they filter high‐pressure water from the stone canal to generate perivisceral coelomic fluid. Since beads were found only in the upper axial sinus, near madreporitic pores and an opening to the stone canal, perihemal fluid is probably drawn up the axial sinus into the low‐pressure end of the stone canal where it is mixed with incoming seawater and recirculated. In addition to contributing to tube feet inflation, these flows probably form part of a previously unrecognized pattern of fluid replenishment, purification, and circulation in starfish involving the stone canal, Tiedemann's bodies, perivisceral coelom, and distal perihemal spaces and return via the axial sinus.
Nuclear transplantation in the pig embryo: Nuclear swelling
Authors: Prather R. S. , Sims M. M. , First N. L. 
Published: June 2005

AbstractThe transfer of nuclei from cleavage stage embryos to enucleated activated meiotic metaphase II oocytes results in a reprogramming of the transferred nucleus such that it behaves as a zygotic nucleus. One estimator of nuclear reprogramming is nuclear swelling after nuclear transfer. The diameter of nuclei after nuclear transfer was not found to be dependent upon the amount of cytoplasm transferred with the donor cell or the amount of cytoplasm in the recipient cell. Nuclei from 4‐, 8‐, and 16‐cell stage embryos swelled to a similar diameter after nuclear transfer (26.9, 27.3, and 27.2 μm, respectively) and this was significantly different from the diameter of contemporary donor embryos (18.3, 14.3, and 13.0 μm, respectively). This is a swelling of 47, 91, and 109%, respectively. Since the degree of nuclear swelling does not appear to be related to cytoplasmic volume it is concluded that the components mediating nuclear swelling are not in a limiting supply.
Steroid production by amphibian (Rana nigromaculata) ovarian follicles at different developmental stages
Authors: Kwon Hyuk B. , Choi Han H. , Ahn Ryun S. , Yoon Yong D. 
Published: June 2005

AbstractRana ovarian follicles at different developmental stages were obtained from frogs collected at different seasons. Isolated follicles were sorted into five different classes (Class I–V) by size and cytoplasmic pigmentation. They were incubated for 6 hours in amphibian Ringer in the presence or absence of frog pituitary homogenate (FPH, 0.05 pituitary/ml) and changes in steroid production by follicles were assessed by measuring estradiol (E2), testosterone (T), and progesterone (P4) in media and follicles by radioimmunoassay. Small follicles (size range 0.22–0.7 mm) secreted very low or non‐detectable levels of the three steroids in the presence or absence of FPH. Medium‐sized vitellogenic follicles (0.70–1.11 mm) actively secreted all the three types of steroids tested (E2, P4, and T). Larger follicles (1.15–1.58 mm), isolated during September–February, secreted much more T than E2 and P4. In contrast, fully grown follicles (> 1.50 mm) collected late in the hibernation period secreted more P4 and less T than the large follicles and very low levels of E2; however, follicles (Class V) collected in breeding season (May) secreted solely P4 and negligible amounts of T and E2. All types of follicles produced very low levels of the steroids without FPH stimulation. Intrafollicular levels of steroids essentially reflected those which accumulated in the medium. Oocyte responsiveness to exogenous hormone, as evidenced by germinal vesicle breakdown (GVBD), increased as the breeding season approached. The data indicate that only the medium‐sized follicles produced considerable amounts of E2 while larger follicles produced mainly T and full‐grown follicles collected during breeding season produced only P4.
Sex pheromones in a marine polychaete: Biologically active compounds from female Platynereis dumerilii
Authors: Zeeck E. , Hardege J. D. , Bartels‐Hardege H. , Willig A. , Wesselmann G. 
Published: June 2005

AbstractA sex pheromone from Platynereis dumerilii females was extracted from the coelomic fluid of ripe heteronereids by a closed loop stripping technique. It was identified by coupled gas chromatography and mass spectroscopy and synthesis as 3,5‐octadien‐2‐one. In an electrophysiological bioassay, the two isomers of this substance were found to be active on both sexes. In contrast, in behavioural bioassays no effect was found on males while female heteronereids were induced to release eggs.
A method for obtaining a pure population of t6/t6 mouse embryos prior to developmental arrest
Authors: Lu Rong , Palter Karen , Hillman Nina 
Published: June 2005

AbstractDevelopmental delay, as the result of ovariectomy, causes mouse blastocyst embryos obtained from +/t6 inter se matings to separate into two distinct populations when placed into outgrowth medium. One population remains as free floating embryos for a significantly longer period of time than the other population. Based upon their phenotypic expression following attachment and outgrowth, the former population was considered to be composed entirely of t6/t6 embryos and the latter, to be composed of +/+ and +/t6 embryos (Nadijcka et al., '81). In the present study, two‐dimensional gel electrophoresis identified the embryos which were delayed in attachment as t6/t6 embryos since they synthesize only p63/6.9a, a product of the Tcp‐1a locus which is unique to t‐haplotypes. The early attaching embryos, assumed to be +/+ and +/t6, synthesize both p63/6.9a and b. The p63/6.9b protein is coded for by Tcp‐1b on the wild‐type homologous chromosome. Control +/+ blastocyst embryos synthesize only p63/6.9b. The data show that t6/t6 embryos can be identified prior to their lethal period and, thus, subjected to comparative studies to determine the cause of their lethality. Developmental delay is the first method established to enable one to unambiguously identify t6/t6 embryos prior to developmental arrest.
Synergism between temperature and estradiol: A common pathway in turtle sex determination?
Authors: Wibbels Thane , Bull J. J. , Crews David 
Published: June 2005

AbstractIn many reptiles, the temperature at which the eggs are incubated determines the sex of the hatchlings. Administration of estradiol will counteract the masculinizing effects of a male‐producing temperature, resulting in female hatchlings. To address whether temperature and estrogen are biologically equivalent, two experiments were conducted with the red‐eared slider turtle, Trachemys scripta. In the first experiment, varying dosages of estrogen were administered at Stage 17 (the middle of the temperature‐sensitive window) to eggs maintained at two temperatures, 26°C (which normally produces all males) and 28.2°C (which produces mostly males but lies at the threshold of the transition from male‐ to female‐producing temperatures). Results indicate that estrogen and temperature exert a synergistic effect on sex determination. In the second experiment, estrogen was administered at different stages of embryonic development. The results indicate an estrogen‐sensitive period ranging from Stage 14 through Stage 21, a period similar to the temperature‐sensitive period for this species. The results of these experiments are consistent with the hypothesis that temperature and estradiol act in a common pathway in temperature‐dependent sex determination.