bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gonadal histology and plasma sex steroids during sex differentiation in grey mullet, Mugil cephalus
Authors: Chang Ching‐Fong , Lan Shih‐Chieh , Chou Hsin‐Yiu 
Published: June 2005

AbstractGonadal histology and plasma levels of sex steroids were investigated during the period of sex differentiation and the annual cycle of grey mullet, Mugil cephalus. Primordial germ cells were observed in the gonads of 3‐month‐old grey mullet and appeared to be undifferentiated in fish at 3 to 6 months of age. At 7 to 14 months of age 23.3% of the fish examined had differentiated into males and females whereas 70–90% of 15‐ to 17‐month‐old fish and more than 95% of 18‐ to 24‐month‐old fish had completed gonadal differentiation. Differentiation into females occurred earlier than males. In 15‐ to 17‐month‐old fish, spermatogonia and primary oocytes in the perinucleolus stage were observed in the testes and ovaries, respectively. Testes underwent intensive spermatogenesis at 18 to 24 months whereas ovaries during this period contained both primary and well developed vitellogenic oocytes. There was no sexual dimorphism in the annual cycle of plasma estradiol‐17β (E2), testosterone (T) and 17α‐hydroxyprogesterone (17α‐OH P) in 7‐to 24‐month‐old grey mullet. Plasma E2 levels significantly decreased in 9‐ to 12‐month‐old presumptively female and male grey mullet. On the contrary, peak levels of plasma T were observed in both female and male grey mullet at 10 to 11 months. Plasma 17α‐OH P levels did not show significant profiles in the annual cycle of grey mullet. The data conclude that few gonads at 7 to 14 months begin to differentiate, but sex differentiation mainly occurs at the age of 15 months. It is 9 to 12 months of age when the decreases of plasma E2 and increases of T levels significantly occur in both female and male grey mullet, M. cephalus. © 1995 Wiley‐Liss, Inc.
Effects of acclimation and assay temperature on outer‐ and inner‐ring thyroxine and 3,5,3′‐triiodo‐L‐thyronine deiodination by liver microsomes of rainbow trout, Oncorhynchus mykiss
Authors: Johnston C. E. , Eales J. G. 
Published: June 2005

AbstractWe studied effects of temperature on the deiodinating enzymatic pathways governing hepatic production of 3,5,3′‐triiodo‐L‐thyronine (T3) from L‐thyroxine (T4) in rainbow trout. Kinetics of outer‐ring deiodination (ORD) and inner‐ring deiodination (IRD) of T4 and T3 were measured in vitro at 4°, 12°, and 18°C using liver microsomes of trout that were acclimated for 21 days at 4°, 13°, and 18°C and fed on temperature‐compensated food rations. For all temperatures the Vmax (level of functional enzyme) and Vmax/Km (index of enzyme efficiency) values for the T3‐generating T4ORD pathway greatly exceeded values for the T3‐degrading T3IRD pathway; T4IRD and T3ORD pathways were negligible. The main effects of temperature occurred between 4°C and 12°/13°C; T4ORD Vmax/Km rose from 0.48 at 4°C to 1.62 at 12°/13°C and to 1.83 at 18°C. This response correlated with in vivo deiodination rates measured previously. T4ORD apparent Km did not change over the temperature acclimation range, suggesting an absence of temperature‐induced isozymes. However, Km was depressed at the assay temperature of 4°C, indicating a direct effect of temperature to enhance enzyme‐T4 substrate affinity. T4ORD Vmax was insensitive to assay temperature but was depressed in trout acclimated at 4°C. We conclude that from 4° to 18°C T4ORD is the main thyroid hormone deiodinating pathway in trout liver. T4ORD activity increases more than threefold from 4° to 13°C. This is due to a direct effect of temperature to decrease Km and to an acclimatory increase in Vmax. © 1995 Wiley‐Liss, Inc.
Seasonal fiber growth cycles of ferrets (Mustela putorius furo) and long‐term effects of melatonin treatment
Authors: Nixon A. J. , Ashby M. G. , Saywell D. P. , Pearson A. J. 
Published: June 2005

AbstractPelage cycles of ferrets are poorly documented, although it is clear that their timing is sensitive to daylength, mediated by pineal melatonin. Hair follicles were monitored histologically in ferrets from 3 to 19 months of age in order to describe naturally occurring changes in follicle growth status and follicle number over three successive cycles of fur growth. Melatonin was administered to some of these animals in late summer to determine the long‐term effects of perturbation of hormonal control. Circulating melatonin was elevated for approximately 50 days by 8‐mg continuous release implants. Treated animals grew both their first winter coat, and subsequent summer coats 18 days in advance of untreated controls, but this effect did not extend to the second winter coat. Reimplantation the following year induced an advancement of the autumn follicle growth as in the 1st year. Autumn fiber growth occurred at similar times in untreated males and females, and response to melatonin did not differ between sexes. Hair follicle regression and shedding during the natural spring molt was also contemporaneous in males and females, but fiber regrowth occurred 4–6 weeks later in males as compared with females, suggesting that reproduction‐related factors affect fiber growth initiation, and that fiber growth and shedding are physiologically distinct processes. Melatonin implants in autumn also affected reproduction in the spring, advancing oestrus by 3–4 weeks. These results show that interference with photoperiodic and hormonal control mechanisms in ferrets can affect pelage and reproductive cycles for up to 10 months. © 1995 Wiley‐Liss, Inc.
Vitelline coat lysins from molluscan sperm and their use in microinjection
Authors: Solano‐Estrada Lourdes Aidée , Plenge‐Tellechea Luis Fernando , Stephano José Luis , Gould Meredith C. 
Published: June 2005

AbstractMicroinjection through the tough vitelline coats of oocytes from three molluscan species (Haliotis rufescens, Norrisia norrisi, and Astrea undosa) was facilitated by the local application of sperm vitelline coat lysin with a micropipet. Extracts containing lysin were the 12,000g supernates of frozen‐thawed sperm. In H. rufescens and N. norrisi, lysin extracts dissolved a small hole through the vitelline coat, whereas in A. undosa, the lysin created a pathway for microinjection by softening the vitelline coat without dissolving it. Similar effects were observed when oocytes were suspended in lysin extracts: Vitelline coats dissolved completely in H. rufescens (previously reported by Lewis et al. [1982], Dev. Biol. 92:227–239) and N. norrisi, but only softened and swelled in A. undosa (although they could then be removed by mechanical agitation). The lysin extracts were highly species specific and had no visible effects on heterologous vitelline coats even at concentrations higher than those required to dissolve/soften homologous coats. Evidence that N. norrisi lysin acts by a non‐enzymatic mechanism was provided by the observation that mobilities of radioactive bands in sodium dodecyl sulfate polyacrylamide gels were unchanged following dissolution of 125I‐labeled vitelline coats. Electron micrographs of the previously undescribed sperm from N. norrisi and A. undosa are also presented. © 1995 Wiley‐Liss, Inc.
Kinematics of ducklings swimming in formation: Consequences of position
Authors: Fish Frank E. 
Published: June 2005

AbstractThe kinematics of the paddling stroke of ducklings swimming in formation were analyzed to detect differences in relation to swimming effort and position in the formation. Paddling motions of the feet were filmed as ducklings swam in a constant 0.3 m/s water current behind a decoy which could be in the water or suspended above the water. Ducklings were tested in clutches of one, two, and four ducklings at ages of 3, 7, and 14 days of age. Ducklings swam in organized formations with the lead duckling 0.25 body length posterior of the decoy and with an average inter‐duckling distance of 0.1 body length. Stroke frequency was constant within any age and decreased with age. Age, decoy position, and clutch size affected the length of the arc traversed by the foot through the power stroke for the most posterior duckling in the formation. Trailing ducklings had an arc length 16.9% less than leading ducklings, and ducklings swimming in formation had an arc length as much as 29.8% less than a solitary duckling. These results suggest that mechanical energy is conserved when formation swimming is employed. © 1995 Wiley‐Liss, Inc.
Effects of space flight on Xenopus laevis larval development
Authors: Snetkova E. , Chelnaya N. , Serova L. , Saveliev S. , Cherdanzova E. , Pronych S. , Wassersug R. 
Published: June 2005

AbstractFifty‐three fertilized Xenopus laevis embryos at early tail bud stage were launched into orbit aboard a Biocosmos satellite and remained in microgravity for 11.5 days. During this period, the embryos hatched and continued to develop as free‐living larvae. Forty‐eight individuals survived the mission. Upon recovery these tadpoles had smaller heads/bodies and proportionately longer tails than ground controls. Almost all the flight animals had caudal lordosis and consequently swam in backward somersaults. Compared to ground‐based controls, their notochords were significantly larger in cross‐sectional area and were deformed. Caudal muscle fibers were less dense and involuted in a fashion indicative of degeneration. In contrast, cranial muscles associated with buccal pumping did not differ between the flight and control animals.Upon landing, the flight larvae were found to be negatively buoyant and lay on the bottom when they were not swimming. They had significantly smaller lungs than controls, suggesting that they had failed to inflate their lungs in microgravity. Additionally, the branchial baskets, gill filters and thymuses all showed signs of retarded development or degeneration.The caudal deformity that we observed in the flight X. laevis has been independently observed in three other space flight experiments where embryos were launched then hatched in space. In contrast, Xenopus larvae from another orbital experiment that were raised from fertilization through hatching in space did not exhibit any caudal abnormalities. These divergent results suggest that either features of the launch itself (i.e., high acceleration and vibration) or an abrupt decrease in gravity during the tail bud stage detrimentally affects musculoskeletal development in anurans. © 1995 Wiley‐Liss, Inc.
Intratesticular retention of sperm and premature decline in fertility in the domestic rooster, Gallus domesticus
Authors: Muncher Yossi , Sod‐Moriah Uriel A. , Weil Simy , Rosenstrauch Avi , Friedländer Michael 
Published: June 2005

AbstractIn domestic roosters, which were originally seasonal breeders and that are now kept under unnatural and unchanging conditions throughout the year, fertility peaks at 32 weeks of age (96%) but it subsequently declines rapidly to only 5% at 110 weeks despite the fact that roosters can live for about 10 years. Roosters exhibiting this low‐fertility syndrome have reduced levels of spermatozoa in the ejaculate. Concomitantly, however, superabundant but apparently normal spermatozoa are found attached to Sertoli cells and, in addition, the seminiferous epithelium fails to show evidence of the regression or atrophy that characterizes both aging non‐seasonal breeders and true seasonal breeders during non‐reproductive periods. This syndrome of premature low fertility appears to stem from impaired spermiation with resultant retention of spermatozoa by Sertoli cells. To examine this problem, we compared intratesticular incorporation of 3H‐thymidine between high‐fertility (32‐week‐old) and low‐fertility (82‐week‐old) roosters. Radioactivity associated with spermatozoa, 33 days post‐injection, was almost 50% higher in the low‐fertility roosters than in the high‐fertility ones. By contrast, both groups showed similar characteristics with respect to a) intratesticular incorporation of 3H‐thymidine, b) dynamics of spermatogenesis, c) intratesticular level of radioactivity just before the initiation of spermiation, and d) the duration of both spermatogenesis and the time required for sperm to pass through the genital tract. Our results confirm that intratesticular retention of sperm occurs in roosters with premature low‐fertility syndrome and suggest new possibilities for the study of the complex relationship between Sertoli cells and spermatozoa and the effects of this relationship on fertility. © 1995 Wiley‐Liss, Inc.
Isolation and characterization of opioid peptides in the avian brain
Authors: Kotegawa Takeru , Takahashi Toshio , Tsutsui Kazuyoshi , Ikeda Tetsuya , Minakata Hiroyuki , Nomoto Kyosuke 
Published: June 2005

AbstractNeuropeptides are supposed to be implicated in the regulation of hormone as well as nonhormone dependent behavioral processes in birds. Previous immunohistochemical studies have suggested that in birds opioid pentapeptides, Met‐ and Leu‐enkephalins, may be present in the brain including the regions that regulate sex hormone dependent behaviors, such as reproductive behaviors. To determine biochemically the presence of opioid peptides in the avian brain, a study was conducted to isolate these peptides from Japanese quails and zebra finches. Acetic acid extracts of the quail and finch brains were respectively forced through disposable C‐18 reversed‐phase cartridges, and then the retained material was subjected to the cation‐exchange and reversed‐phase high performance liquid chromatographic (HPLC) purifications. All of the purified substances showed a single peak on the reversed‐phase HPLC and these substances enhanced spontaneous contractions of the avian rectum. The purified bioactive substances were further subjected to amino acid sequence analysis and were characterized as peptides with the following sequences: Tyr‐Gly‐Gly‐Phe‐Met, Tyr‐Gly‐Gly‐Phe‐Leu, and Tyr‐Gly‐Gly‐Phe‐Met‐Arg‐Phe. These three peptides were identical with opioid pentapeptides, Met‐ and Leu‐enkephalins, and a heptapeptide, Met‐enkephalin‐Arg6‐Phe7, which had been previously isolated from mammalian species. This is the first direct demonstration of the presence of opioid peptides in the avian brain and confirms previous immunohistochemical findings suggesting a functional role for the opioid peptide in neural mechanisms of avian reproductive behavior. © 1995 Wiley‐Liss, Inc.
Effects of opioid peptides on the electrical activity of preoptic and hypothalamic neurons in the quail brain
Authors: Furukawa Yasuo , Kotegawa Takeru , Tsutsui Kazuyoshi 
Published: June 2005

AbstractWe have recently isolated three opioid peptides, i.e., Met‐ and Leu‐enkephalins and Met‐enkephalin‐Arg6‐Phe7, from the avian brain. In the present study, therefore, effects of these endogenous opioid peptides on the electrical activity of preoptic and hypothalamic neurons of the adult male Japanese quail were examined using a brain slice preparation. All of the three opioid peptides inhibited the spontaneous firing activities of subsets of neurons in the preoptic area and the paraventricular nucleus in the hypothalamus. Threshold concentrations for the inhibitory action were between 10−7 and 10−6 M in Met‐ and Leu‐enkephalins and approximately 10−6 M in Met‐enkephalin‐Arg6 ‐Phe7, respectively. In a few cells in these brain areas, however, Leu‐enkephalin rather potentiated the spontaneous activities, resulting in an increase of firing rates or a decrease of interburst intervals. The inhibitory effect of Met‐enkephalin was completely blocked by naloxone, an opioid receptor antagonist, but not affected by bicuculline, a γ‐aminobutyric acid A (GABAA) receptor antagonist. These results suggest that there are functional opiate receptors in subsets of preoptic/hypothalamic neurons and that one of their main physiological functions in these areas is an inhibition of neuronal activities. Because these brain regions are considered to be involved with the regulation of a variety of male reproductive behaviors, opioid peptides may regulate some reproductive behavior through the mechanism that provokes such an inhibition. © 1995 Wiley‐Liss, Inc.
Evidence for intracellular stores of calcium ions involved in regulating nematocyst discharge
Authors: Russell Thomas J. , Watson Glen M. 
Published: June 2005

AbstractIn sea anemones, nematocyst discharge is regulated in part by chemical substances derived from prey. Adding N‐acetylated sugars or proline to seawater sensitizes cnidocytes to discharge nematocysts. Extracellular calcium ions are required since discharge is inhibited by reducing the Ca2+ concentration in artificial seawater. Known inhibitors of L‐type Ca2+ channels, nifedipine and verapamil, reduce discharge sensitized by N‐acetylated sugars but not by proline. Conversely, known inhibitors of certain Ca2+ channels at intracellular storage sites, ryanodine and procaine, reduce discharge sensitized by proline but not by N‐acetylated sugars. Thapsigargin, an agent that inhibits uptake of Ca2+ into vesicles, sensitizes discharge. Discharge is sensitized upon incubating specimens in a caged analog of inositol 1,4,5‐trisphosphate (InsP3) and subsequently photoactivating it. Furthermore, following preincubation of specimens in certain low concentrations of caged InsP3 and subsequent photoactivation, lower concentrations of proline are required to maximally sensitize discharge. W7, an inhibitor of Ca2+/calmodulin (CaM), and KT5926, an inhibitor of CaM‐kinase II, reduce discharge sensitized by both N‐acetylated sugars and proline. Apparently, sugar receptors activate dihydropyridine‐sensitive Ca2+ channels, whereas proline receptors stimulate the production of InsP3, resulting in InsP3‐initiated release of Ca2+ from intracellular stores. This process may trigger Ca2+‐induced Ca2+ release from InsP3‐insensitive channels, which can be blocked by ryanodine or procaine. With either receptor, elevated intracellular Ca2+ binds calmodulin to form an active complex. CaM activates CaM‐kinase II, which, presumably, phosphorylates unidentified substrates, leading to sensitization of discharge. © 1995 Wiley‐Liss, Inc.
Do static electric forces contribute to the stickiness of a spider's cribellar prey capture threads?
Authors: Opell Brent D. 
Published: June 2005

AbstractCribellar thread is the most primitive type of prey capture thread produced by spiders. Its dry surface is formed of thousands of fine fibrils that catch on the setose surfaces of insects and, by an unknown mechanism, also hold smooth surfaces. Static electric attraction has been suggested as the force by which these smooth surfaces are held. However, when the stickiness of cribellar threads produced by Hyptiotes cavatus and Uloborus glomosus (family Uloboridae) was measured with contact plates that had similar textures but very different dielectric values, no support was found for this hypothesis. Differences in stickiness values were small and showed no relationship to the dielectric indexes of the surfaces used to measure stickiness. © 1995 Wiley‐Liss, Inc.
Interneurons involved in the control of multiple motor centers in crayfish
Authors: Burdohan John A. , Larimer James L. 
Published: June 2005

AbstractA number of studies have suggested that abdominal positioning interneurons (APIs) in the crayfish Procambarus clarkii can influence activity in multiple motor centers. Previous work on this population of neurons has demonstrated that they control the activity of tonic abdominal motor neurons (MNs) which generate postural movements of the abdomen and, to some extent, the activity of swimmeret MNs. This investigation demonstrates that many identified APIs also affect the activity of two populations of MNs which open and close the uropods and, in some cases, that of the swimmeret MNs as well. The majority (64%) of APIs examined in this study have an excitatory effect on both populations of uropod MNs. A smaller number (23%) increase the level of activity in one population of uropod MNs, and suppress, or have no effect on, the activity of the other population of uropod MNs. Approximately 25% of the APIs which were examined influence the output of swimmeret MNs, in addition to affecting the activity of uropod MNs. There are also indications that previous estimates of the number of APIs may have been too low. This is based on the observation that many APIs possess what appear to be similar morphologies but generate different patterns of motor output. Taken together, these findings support the idea that APIs influence the output of multiple motor centers which play a role in the control of general body posture and balance in crayfish. © 1995 Wiley‐Liss, Inc.
Inhibition of Fundulus heteroclitus oocyte maturation in vitro by serotonin (5‐hydroxytryptamine)
Authors: Cerdá Joan , Petrino Teresa R. , Lin Yu‐Wai P. , Wallace Robin A. 
Published: June 2005

AbstractThe effects of serotonin (5‐hydroxytryptamine [5‐HT]) on oocyte maturation in vitro were tested on Fundulus heteroclitus full‐grown prematurational ovarian follicles. F.heteroclitus pituitary extract (FPE)‐ and steroid (17α,20β‐dihydroxy‐4‐pregnen‐3‐one [DHP])‐induced oocyte maturation were both inhibited by 5‐HT in a dose‐dependent and reversible manner. Maximum inhibition was observed at concentrations of 0.5 and 5 μM 5‐HT, respectively. The inhibitory action was also less effective when 5‐HT was combined with human chorionic gonadotropin than with FPE, which may indicate the presence of 5‐HT and/or other inhibitory substances in the pituitary extract. Inhibition by 5‐HT was independent of FPE‐induced steroid production by the follicle, since the levels of 17β‐estradiol and DHP released into the culture medium were not modified by the presence of 5‐HT. When follicles were preincubated with DHP for increasing times, subsequently washed, and transferred to steroid‐free, 5‐HT‐containing medium, inhibition by 5‐HT was also observed in follicles preincubated for up to 4 h; however, inhibition by 5‐HT was reduced or eliminated after 8 h or 16 h preincubation with DHP, respectively. These results suggest the presence of a putative 5‐HT receptor(s) that does not affect steroidogenic pathways in the ovarian follicle yet inhibits steroid‐induced oocyte maturation at some point downstream in the steroid transduction pathway of the oocyte. © 1995 Wiley‐Liss, Inc.
Characteristic features of preleptotene spermatocytes in Xenopus laevis: Increase in the nuclear volume and first appearance of flattened vesicles in these cells
Authors: Takamune Kazufumi , Teshima Kaori , Maeda Masayuki , Abé Shin‐Ichi 
Published: June 2005

AbstractIn Xenopus laevis, the spermatogenic cells derived from a primary spermatogonium divide synchronously and form a cyst surrounded by somatic Sertoli cells. To clarify how many times the spermatogonia divide mitotically before differentiating to primary spermatocytes, the number of spermatogenic cells in the cysts was counted. Each cyst which consisted of cells morphologically identical to secondary spermatogonia contained discrete numbers of cells such as 26, 27, or 28 cells. On the other hand, the number of the germ cells in a cyst of zygotene/pachytene primary spermatocytes was approximately 28. These results indicate that spermatogenic cells which had finished eight mitotic divisions and showed a similar morphology to secondary spermatogonia were preleptotene spermatocytes. The nuclei of the preleptotene spermatocytes increased in volume concomitantly with premeiotic DNA replication and differentiation into zygotene/pachytene primary spermatocytes. Therefore the cells morphologically indistinguishable from secondary spermatogonia but with larger nuclei than typical secondary spermatogonia were identified as preleptotene spermatocytes. Electron microscopic observations of the preleptotene spermatocytes identified as above showed that flattened vesicles, 0.1–0.5 μm in length, about 0.05 μm in width, and with more electron‐dense membrane than typical endoplasmic reticulum, first appeared in the cytoplasmic area of preleptotene spermatocytes. © 1995 Wiley‐Liss, Inc.