bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reduced calcium and inhibition of protein kinase C mimic the enhancement of ornithine decarboxylase activity by prolactin in Ambystoma tigrinum tissues
Authors: Ibrahim Ragaa H. , Platt James E. 
Published: June 2005

AbstractWe previously reported that prolactin (PRL) could increase the activity of ornithine decarboxylase (ODC) in liver slices taken from larval tiger salamanders (Ambystoma tigrinum). This action of the hormone was inhibited by oxytocin (OT), the calcium ionophore A23187, and diacyglycerol (DG) and was duplicated by 10 μM verapamil (VML), a calcium channel blocker. Here, we expand these results to show that 1) a higher dose of VML (50 μM) produces an additive effect with PRL; 2) addition of small amounts of calcium (0.1 mM) to the liver culture medium blocks PRL action; 3) neither nifedipine (NIF), a different type of calcium channel blocker, nor EDTA alter PRL action; and 4) gossypol, a reported inhibitor of protein kinase C, mimics PRL action. Additionally, we show that PRL increases ODC activity in tiger salamander tail skin in vitro, a tissue previously demonstrated to be a PRL target tissue in this species. The same set of treatments which we have shown to modify PRL effects on ODC in liver slices affects PRL action in the tail skin in a parallel manner. Thus, the mechanism whereby PRL enhances ODC activity appears to be the same in both these tissues. These results are discussed in conjunction with the findings from similar studies using mammalian tissues in an attempt to assess the current picture of the mechanism of PRL action and the possible role of inositol phospholipid turnover, calcium, and protein kinase C in the action of this hormone.
Initiation of placental lactogen‐I production by blastocysts growing on a two‐dimensional surface and in hanging drops
Authors: Nieder Gary L. , Nagy Frank 
Published: June 2005

AbstractThe mouse blastocyst undergoes a program of protein secretion during the periimplantation period including the initial production of placental lactogen‐I (mPL‐I) on day 6 of pregnancy. Although blastocysts collected on day 5 also produce mPL‐I when cultured to form outgrowths on plastic dishes, it was not known if embryos have an intrinsic ability to produce mPL‐I during culture in vitro, or if a specific uterine influence is necessary. Earlier experiments also suggested that attachment of the trophoblast to a stable surface may be a prerequisite for synthesis of mPL‐I. Both questions were addressed by examining mPL‐I production by day 3 and day 4 embryos cultured either on a two‐dimensional tissue culture dish surface or in hanging drops. The presence of intracellular mPL‐I was assayed by immunohistochemistry, while the secreted hormone was detected by its known position in two‐dimensional electrophoresis gels. These experiments demonstrated that these earlier stage embryos do have an intrinsic program for mPL‐I production which proceeds in vitro under various culture conditions. Synthesis of mPL‐I occurred in embryos suspended in hanging drops as well as in those spreading on a solid two‐dimensional surface, thus showing that adhesion to a surface is not required for production of this hormone. Although some mPL‐I synthesis was seen in embryos cultured in medium containing BSA as the sole macromolecule, the inclusion of fibronectin either in dishes, where it supports attachment, or in the hanging drop system stimulated mPL‐I secretion. Serum supplementation in both culture systems further increased growth and differentiation of the embryo, as well as mPL‐I secretion, compared to fibronectin supplementation.
Variations in urinary output of the lobster
Authors: Cheng Jin‐Hua , Chang Ernest S. 
Published: June 2005

AbstractUrinary rates were studied in cannulated juvenile lobsters. If animals were in intermolt and unfed, urinary rates were constant at daily rates of 2% and 20% of body weight in 100% and 75% seawater (SW), respectively. More than 4% of the body weight could be rapidly excreted as urine upon either feeding, forced drinking, or low salinity acclimation. These results indicate that the urinary bladders are usually filled with urine and that they are part of the body volume‐regulating system.At ecdysis, however, urinary flow ceased when drinking rate increased, suggesting that the intermolt mechanism regulating body volume may have been altered. In 100% SW, drinking was necessary for lobsters to gain sufficient water to withdraw their claws at ecdysis. While in 75% SW, osmotic entry of water across the body surface alone was sufficient to permit a successful molt. These results indicate that water influx across the body surface may contribute to much of the water intake at ecdysis if the osmotic gradient is substantial and that the cessation of urinary flow contributes to the overall water balance at ecdysis.
At least half of capacitated, motile mouse sperm can fertilize zona‐free mouse oocytes
Authors: Ivani K. A. , Seidel G. E. 
Published: June 2005

AbstractThe percentage of individual sperm capable of fertilizing zona pellucida‐free mouse oocytes was investigated by placing motile sperm near zona‐free oocytes with a micromanipulator. Incubation with one or two capacitated sperm per oocyte resulted in 50% and 70% fertilization, respectively, compared to 88% for cumulus intact (105 sperm/ml) and 87% for zona‐free (2 × 103 sperm/ml) control oocytes. When sperm were treated with .1 μM calcium ionophore A23187 to facilitate the acrosome reaction, fertilization rates for single motile sperm were markedly lower than for capacitated, nontreated single sperm (4% and 35%, respectively). Similar fertilization rates resulted when one sperm was incubated per two ova (4% and 48% per sperm for A23187‐treated and controls, respectively). When a lower dose of A23187 (.001 μM) was used to treat sperm, 7% of oocytes incubated with single sperm were fertilized. These experiments demonstrate that at least half of motile, capacitated mouse sperm are capable of fertilizing zona‐free mouse oocytes in vitro, and that motile, A23187‐treated mouse sperm resulted in poor fertilization rates.
Cyanide detoxification in the mudskipper, Boleophthalmus boddaerti
Authors: Chew S. F. , Ip Y. K. 
Published: June 2005

AbstractThe tolerance of the mudskipper, Boleophthalmus boddaerti, to cyanide is higher than those of other fishes reported elsewhere. The 24 h, 48 h, and 96 h LC50 for B. boddaerti were 0.37 mg HCN/liter, 0.34 mg HCN/liter, and 0.29 mg HCN/liter, respectively. The tolerance of B. boddaerti to cyanide does not involve a reduction of metabolic rate or an enhanced anaerobic metabolism, or a cyanide‐insensitive respiratory pathway. Instead, it is a result of the presence of a surplus of cytochrome oxidase and inducible cyanide‐detoxifying mechanisms in this mudskipper. Although cytochrome oxidase activities in the various tissues of the fish exposed to 0.23 mg HCN/liter were inhibited by more than 50%, no reduction in the O2 consumption rate was observed. B. boddaerti could detoxify cyanide to thiocyanate. The activity of rhodanese in the liver extract of fish exposed to cyanide increased significantly compared to that of the control. The activities of cysteine amino‐transferase (CAT) and 3‐mercaptopyruvate sulfurtransferase (MPST) in the extracts from the liver and the muscle of B. boddaerti exposed to cyanide also increased significantly compared to those of the control fish. Glutamate formed in the reaction catalyzed by CAT could undergo transamination leading to the accumulation of aspartate in the muscle of the fish exposed to cyanide.
Effects of gonadotropin‐releasing hormone variants on plasma and testicular androgen levels in intact and hypophysectomized male frogs, Rana esculenta
Authors: D'Antonio Mauro , Fasano Silvia , de Leeuw Renato , Pierantoni Riccardo 
Published: June 2005

AbstractThe effects of vertebrate gonadotropin‐releasing hormone (GnRH) variants on plasma and testicular androgen level in intact and hypophysectomized (PDX) male frogs, Rana esculenta, have been investigated. In intact animals, mammalian (m)‐GnRH, m‐GnRH analog (buserelin), salmon (s)‐GnRH, chicken (c) I‐GnRH, cII‐GnRH, D‐Arg6‐cII‐GnRH (cII‐GnRHA), and lamprey (l)‐GnRH (1.5μg and 6μg, total dose given on alternate days for 5 days) were able to enhance androgen production showing that specificity of pituitary responsiveness to GnRH variants appears to be low. Chicken II‐GnRH was more effective than s‐GnRH in eliciting testicular and circulatory androgen level increase. Moreover, in animals treated with 6μg of cII‐GnRH and s‐GnRH in combination, androgens decreased as compared with animal treated with cII‐GnRH only, suggesting that GnRH receptors bind preferentially the s‐GnRH form. In PDX animals, buserelin (1.5 and 6μg), cII‐GnRH, and its analog (6μg) were able to increase plasma androgen levels whereas testis androgen concentrations were increased by cII‐GnRH (1.5 and 6μg), D‐Arg6‐cII‐GnRHA, and buserelin (6μg). Since androgen production in PDX animals is influenced especially by peptides sharing cII‐GnRH structure, it is suggested that a testicular cII‐GnRH‐like material play a role as local modulator of the gonadal activity in Rana esculenta.
Evolutionary modification of regenerative capability in vertebrates: A comparative study on teleost pectoral fin regeneration
Authors: Wagner G. P. , Misof B. Y. 
Published: June 2005

AbstractThe regenerative ability of the pectoral fins of 14 species from 6 euteleostean families was tested. Blastema formation and distal outgrowth was observed in all species, indicating the initiation of regeneration in all species tested. Interspecific variation exists with respect to the frequency of malformations and the patterns produced by heteromorphic regeneration. Taking into account published reports on pectoral fin regeneration, the systematic distribution of homo‐ and heteromorphic regeneration leads to the following conclusions: 1) regenerative ability of pectoral fins is a property inherited from the common ancestor of euteleosteans. Whether it is also the ancestral condition for the whole teleostean group cannot be determined, because reports on more primitive teleosteans like the herring and the osteoglossimorphs are missing. 2) A propensity to produce high frequencies of heteromorphic regenerates originated independently at least three times in Cypriniformes, Scorpaeniformes, and Perciformes. 3) Impaired regeneration is most commonly found in bottom fishes, although not all ground fish groups show heteromorphic regeneration. This suggests that impaired regeneration is not directly related to bottom dwelling, but most probably originated as a side effect of other adaptive changes. Hence, neither the presence nor the loss of faithful regeneration can be associated with particular adaptive scenarios in this group, since regeneration seems to be ancestral to all major euteleost groups and its loss has no clear adaptive significance. Whether there are adaptive reasons to maintain regenerative capability or whether there are cases of reestablishment of regeneration after it was lost cannot be decided on the basis of recent evidence. More observations on phylogenetically closely related species with variable regenerative capability are necessary to assess adaptive explanations of regeneration.
Developmental changes in the incidence of chromosome anomalies of bovine embryos fertilized in vitro
Authors: Iwasaki S. , Hamano S. , Kuwayama M. , Yamashita M. , Ushijima H. , Nagaoka S. , Nakahara T. 
Published: June 2005

AbstractIn total, 196 two‐ to 32‐cell bovine embryo and 104 blastocysts were obtained by the in vitro fertilization of follicular oocytes matured in vitro, and 15 blastocysts fertilized in vivo were used. Chromosomal anomalies in these embryos and the inner cell mass (ICM) separated immunologically were investigated. Chromosomal anomalies were observed in 12.1% (5/41) of 2‐cell embryos, 20.0–36.4% of 4‐ to 16‐cell embryos, 7.1% (1/14) of 17‐ to 32‐cell embryos, 44.2% (15/34) of blastocysts, and 18.6% (13/70) of ICM cells derived from in vitro fertilization. These anomalies were mainly 3N and 4N at 2‐cell stage, 1N and 1N/2N at 4‐ to 32‐cell stages, and 2N/4N in blastocysts and in their ICM cells. Chromosomal anomalies of blastocysts from in vivo fertilization and their ICM were observed in 20.0% (1/5) of blastocysts and 33.3% (3/9) of ICM cells and these compositions were mainly 2N/4N. These results indicate that the abnormalities at early and blastocyst stages of embryos derived from in vitro fertilization were caused by abnormal fertilization in vitro and abnormal cleavage, respectively. Furthermore, a definite location of the chromosomal anomalies was observed in the trophectoderm of blastocysts derived from in vitro fertilization.
Chordate testis: The extracellular matrix hypothesis
Authors: Grier Harry J. 
Published: June 2005

AbstractTestis structure in the chordates has been evaluated based upon relationships between primary spermatogonia, Sertoli cells, and the changes in the chronological secretion of the extracellular basement membrane. Prespermatocystic, polyspermatocystic, lobular, and tubular testicular types are described. In all chordates, germinal and interstitial compartments are separated by a basement membrane. The timing of the formation of this separation varies with the chordate class. Although primary spermatogonia are not initially separated from the interstitial tissue in agnathans and elasmobranchs, a basement membrane forms around secondary spermatogonia and associated Sertoli cells before meiosis. The spermatocyst so formed is a unit of testicular evolution. In fishes and amphibians, Sertoli cells, primary spermatogonia, and the subsequent stages of germ cell development reside in spermatocysts. They are always sequestered from interstitial tissues by a basement membrane. Sertoli cells rest upon the basement membrane and their processes form the borders of spermatocysts. I propose the Extracellular Matrix Hypothesis to explain how changes in the chronological formation of basement membranes resulted in the evolution of lobular and tubular testes from spermatocystic testes.
Plasticity of gonadal development and protandry in fishes
Authors: Shapiro Douglas Y. 
Published: June 2005

AbstractSexual differentiation in eutherian mammals follows a simple governing paradigm: development proceeds in a female direction unless a masculinizing mechanism intervenes. Sexual development in fishes is much more plastic than in mammals. It permits the intervention of environmental factors and follows several different types of sequences that produce successive hermaphrodites and alternative pathways for the development of the same final sex. In spite of this plasticity, the primacy of female development is suggested by the initial ovarian phase in the development of gonads of both sexes in some gonochoristic fishes and by protogynous sex change. One barrier to the application of this principle to fishes generally is the existence of protandric hermaphrodites. Recent evidence suggests a reinterpretation of gonadal differentiation in a protandric anemonefish and a protandric sparid. In both cases, testicular development is both preceded and followed by ovarian development. These patterns are interpreted to mean that female development is primary and that male development is a temporary phase initiated by a masculinizing mechanism and terminated by its cessation.
Male reproductive system as sex pheromone producer in teleost fish
Authors: van den Hurk R. , Resink J. W. 
Published: June 2005

AbstractMale zebrafish, Brachydanio rerio, have paired testes and no additional reproduction glands. Incubation experiments with 3H‐labeled steroid precursors showed the capacity of testes to synthesize seven steroid glucuronides. Enzyme histochemical studies demonstrated interstitial (Leydig) cells as steroid and steroid glucuronide producing sites. Male holding water, testis homogenates, and testis fractions containing steroid glucuronides were able to induce ovulation in female zebrafish. Deglucuronidation of these fractions led to a loss of ovulation inducing potency, indicating steroid glucuronides as ovulation inducers. The chemical substances are perceived by the recipients by means of olfaction, as anosmic females do not have an ovulatory response after administration of male holding water. In African catfish, Clarias gariepinus, the male reproductive organ system consists of two paired structures, the testis and the seminal vesicle. Histochemical enzyme investigations pointed to interstitial cells as sites of steroid and steroid glucuronide production both in testis and seminal vesicle. Glucuronidation of steroids may also take place in the epithelium lining and seminal vesicle tubules. Biochemical studies showed the seminal vesicle as the main source of steroid glucuronides. Eight conjugated steroids were identified. Electrophysiological studies demonstrated that these compounds, especially 5β‐pregnane‐3α, 17α‐diol‐20‐one‐glucuronide are olfactory stimulants in female conspecifics. Males with enlarged seminal vesicles, caused by compensatory growth after castration, were more attractive to ovulated female catfish in a two‐choice test, using a U‐shaped tank. Males lacking seminal vesicles were less attractive. The steroid glucuronide fraction of seminal vesicle fluid appeared to be responsible for the attraction effect. A synthetic mixture of steroid glucuronides resulted in a dose dependent attraction effect. The data are indicative of a pheromonal function for steroid glucuronides that are produced by the reproductive organ system of male zebrafish and African catfish.
Drosophila single‐minded gene and the molecular genetics of CNS midline development
Authors: Crews Stephen , Franks Robert , Hu Song , Matthews Beverley , Nambu John 
Published: June 2005

AbstractOur goal is to understand the molecular mechanisms that govern the formation of the central nervous system. In particular, we have focused on the development of a small group of neurons and glia that lie along the midline of the Drosophila CNS. These midline cells possess a number of unique attributes which make them particularly amenable to molecular, cellular, and genetic examinations of nervous system formation and function. In addition, the midline cells exhibit distinctive ontogeny, morphology, anatomical position, and patterns of gene expression which suggest that they may provide unique functions to the developing CNS. The single‐minded gene encodes a nuclear protein which is specifically expressed in the midline cells and has been shown to play a crucial role in midline cell development and CNS formation. Genetic experiments reveal that sim is required for the expression of many CNS midline genes which are thought to be involved in the proper differentiation of these cells.In order to identify additional genes which are expressed in some or all of the midline cells at different developmental stages, a technique known as enhancer trap screening was employed. This screen led to the identification of a large number of potential genes which exhibit various midline expression patterns and may be involved in discrete aspects of midline cell development. Further molecular, genetic, and biochemical analyses of sim and several of the enhancer trap lines are being pursued. This should permit elucidation of the genetic hierarchy which acts in the specification, differentiation, and function of these CNS midline cells.
Specificity of VIIIthnerve regeneration in lower vertebrates
Authors: Davis Robin L. 
Published: June 2005

AbstractFrom the initial studies of Sperry (Am. J. Physiol, 144:735–741, 1945) to more recent investigations, the regenerative capacity of the VIIIthcranial nerve in nonmammalian vertebrates has been noted for its robust and accurate recovery of functional connections after transection. The VIIIthcranial nerve contains nerve fibers that link functionally distinct sensory epithelial to various areas within the central nervous system (CNS), yet after transection these multiple components of the nerve navigate back to their original central target areas, without innervating inappropriate nuclei. A number of factors may be required to establish and direct VIIIthnerve regeneration. Cellular interactions appear to be necessary for the initiation of outgrowth and the maintenance of neural connections. The release of chemotropic substances from target cells has been postulated as the most likely mechanism guiding the reinnervation of central targets. Furthermore, the growth characteristics of these neurons in tissue culture, without target cells present, indicates that intrinsically regulated growth features may also contribute to the process of VIIIthnerve regeneration.
Functional regeneration and recovery of locomotor activity in spinally transected lamprey
Authors: McClellan Andrew D. 
Published: June 2005

AbstractSpinally transected lamprey recovery locomotor function within 3–6 weeks, and recovery is due, in part, to functional regeneration of neural pathways in the central nervous system (CNS). Our data demonstrate for the first time in the lamprey that descending axons arising from brainstem command neurons can functionally regenerate and restore locomotor initiation below a healed spinal transection site. Immediately after behavioral recovery (3–6 weeks) the locomotor pattern was incomplete but returned to normal during the remainder of the recovery period (6–40 weeks). Initially, the extent of regeneration of descending axons was limited but increased to at least 30–50 mm at recovery times of 24–40 weeks. Regenerated giant Muller axons do not contribute significantly to recovery of locomotor function; rather, regenerated axons of smaller reticulospinal neurons appear to restore locomotor initiation. The restoration of locomotor coordination across a spinal lesion is dependent on two mechanisms: regeneration of spinal coordinating neurons and mechanosensory inputs. Comparisons are made to spinal cord regeneration in other lower vertebrates and to the relative lack of CNS regeneration and behavioral recovery in higher vertebrates.
Secondary sex characteristics and related physiological values in male fallow deer (Dama dama L.) and their relationships to changes in the annual cycle of daylengths: Frequency alterations to 4‐ and 3‐month photoperiodic cycles, and subsequent re‐synchronisation under natural conditions
Authors: Schnare H. 
Published: June 2005

AbstractFive adult male fallow deer were maintained in a barn with artificial light control. In a previous experiment, three 6‐month photoperiodic cycles entrained morphogenetic and associated physiological values that revealed typical relationships to the antler cycle.Presented here, the light cycle was accelerated to three 4‐ and one 3‐month photoperiods in the same group. Each artificial photoperiod generally resulted not only in an almost complete antler cycle but also in an entire cycle of seasonal fluctuations in neck girth. Increases in plasma levels of alkaline phosphatase (AP), total‐, LDL‐ and HDL‐cholesterol, were generally entrained and the maxima revealed positive correlations with antler formation, but the relationships slightly diverged. In neck girth and creatinine, positive correlations to the hard antler period as well as to each other prevailed but diverged. In the 3‐month photoperiodic cycle, these relationships were out of synchrony. In the second 4‐month cycle, two bucks “missed” shedding and subsequent casting, but commenced antler growth in the following cycle with an in‐time shedding. The possibility of desynchronisation of physiological conditions and the question of an endogenous circannual mechanism interacting with daylight are discussed.At the end of the 3‐month cycle, experimental indoor and natural outdoor casting was coincident so the group was transferred to outside conditions for re‐synchronisation. After spending altogether 36 months in frequency altered photoperiods, the represented values were neither synchronized nor revealed their typical relationships to the antler cycle, except of AP and neck volume. In the second cycle of re‐synchronisation, all parameters, except of creatinine, appeared to be resynchronized.