bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sex differences in adrenal function in the lizard Cnemidophorus sexlineatus: I. Seasonal variation in the field
Authors: Grassman Mark , Hess David L. 
Published: June 2005

AbstractIn order to document sex differences in adrenal function and how this relates to gonadal function during the period of seasonal activity, blood samples from male and female six‐lined racerunners, Cnemidophorus sexlineatus, were taken immediately after capture in the field for determination of plasma corticosterone and gonadal steroid concentrations. Plasma testosterone and dihydrotestosterone levels for males, and 17β‐estradiol and progesterone levels for females, were measured. Trends in the concentration of plasma corticosterone differed significantly between males and females. In males the highest concentrations of corticosterone were measured in late spring and the lowest concentrations were measured in late summer. Whereas half of the variation in corticosterone levels among males could be explained as seasonal change, less than 1% of the variation among females could be explained as seasonal change. In males plasma corticosterone and androgens exhibited similar seasonal decreases. Corticosterone levels for females were not correlated with progesterone or 17β‐estradiol levels. Sex differences in seasonal variation in plasma corticosterone concentrations suggest that corticosterone may be involved in the different reproductive strategies and energy requirements of males and females during the seasonal period of activity. © 1992 Wiley‐Liss, Inc.
Physiological effects of low‐magnesium feeding in the common carp, Cyprinus carpio
Authors: van der Velden J. A. , Flik G. , Spanings F. A. T. , Verburg T. G. , Kolar Z. I. , Bonga S. E. Wendelaar 
Published: June 2005

AbstractCommon carp (Cyprinus carpio) initially weighing about 100 g were fed a low‐magnesium diet for 17 weeks. The fish survived this treatment and had a healthy appearance. However, the fish became hypomagnesemic and their growth rate decreased. The bone sodium concentration increased and the magnesium concentration decreased. It thus appears that in carp, under dietary magnesium deficiency, magnesium is mobilized from internal stores and that magnesium in the bone mineral is replaced by sodium. Low‐magnesium fed carp further showed a decreased branchial Na+/K+ ‐ATPase specific as well as total activity. Unexpectedly, the opercular chloride cell density increased. We tentatively conclude that more and new chloride cells with a lower Na+/K+‐ATPase content develop during this treatment. We further conclude that adult carp require dietary magnesium for the maintenance of their magnesium balance as well as for the proper functioning of branchial ionoregulatory mechanisms. Low‐magnesium fed carp do not acclimate but appear to tolerate a dietary magnesium deficiency. © 1992 Wiley‐Liss, Inc.
Formation of the peripheral nervous system during tail regeneration in urodele amphibians: Ultrastructural and immunohistochemical studies of the origin of the cells
Authors: Arsanto Jean‐Pierre , Komorowski Thomas E. , Dupin Frédérique , Caubit Xavier , Diano Monique , Géraudie Jacqueline , Carlson Bruce M. , Thouveny Yves 
Published: June 2005

AbstractIn the regenerating newt tail, epimorphic regeneration—which recapitulates morphologically normal embryonic development—proceeds along a rostrocaudal differentiation gradient. Innervation of the new myomeres results from the spinal roots of segments rostral to the amputation plane and from ventral roots emerging from the lateroventral region of the regenerating spinal cord, in which motor neurons are differentiating. Electron microscopy and an indirect immunofluorescence study with anti‐glial fibrillary acid protein (GFAP) confirm that the ventrolateral part of the regenerated ependymal tube gives rise to cells of the ventral root sheath and the spinal ganglia. Anti‐GFAP and anti‐neurofilament antibodies showed that ependymoglial cells and Schwann cells may play a role in neuronal pathfinding by helping guide and stabilize pioneering axons as they extend toward the myomeres. The carbohydrate epitope NC‐1 is expressed in the spinal cord, in sheath cells of the spinal ganglia and in the non‐myelin‐forming Schwann cells of the peripheral nervous system. L1, a Ca+ + independent neural cell adhesion molecule, was detected in the axonal compartments of the regenerating spinal cord, on immature and/or non‐myelin‐forming Schwann cells within the peripheral nervous system (PNS), and on nerve fibers within the regenerate. These immunohistochemical observations collectively support the hypothesis that Schwann cells already present in the blastema could be involved in organizing neural pathways. © 1992 Wiley‐Liss, Inc.
Dominant mutation of the murine Hox‐2.2 gene results in developmental abnormalities
Authors: Kaur Satbir , Singh Gurparkash , Stock Jeffrey L. , Schreiner Claire M. , Kier Ann B. , Yager Karen L. , Mucenski Michael L. , Scott William J. , Potter S. Steven 
Published: June 2005

AbstractGenes carrying the homeobox were originally identified in Drosophila, in which they are now known to play key roles in establishing segmentation patterns and in determining segment identities. A number of genes with striking homology to the Drosophila homeobox genes have now been found in the mouse genome, and mutational analysis is beginning to shed light on their function in mammalian development. To understand better the developmental significance of the murine Hox‐2.2 gene, we have generated gain of function mutants by using the chicken β‐actin promoter to drive ubiquitous expression in transgenic mice. The resulting Hox‐2.2 misexpression produces early postnatal lethality as well as craniofacial and axial skeletal perturbations that include open eyes at birth, cleft palate, micrognathia, microtia, skull bone deficiencies, and structural and positional alterations in the vertebral column. We repeatedly observe complete or partial absence of the supraoccipital bone and malformations of the exoccipital and the basioccipital bones. These results suggests a role for the Hox‐2.2 gene in specifying positional identity along the anterior‐posterior axis. © 1992 Wiley‐Liss, Inc.
Pregnancy‐associated murine protein‐1 (PAMP‐1) in wild rodents
Authors: Krog Nina Lindahl , Hau J. 
Published: June 2005

AbstractThe presence of pregnancy‐associated murine protein‐1 (PAMP‐1) in a number of wild rodent species was examined using tandem crossed immunoelectrophoresis and anti PAMP‐1 antisera raised in rabbits. PAMP‐1 is a protein present in female laboratory mice and rats; analogues were readily detected in the following species: Musculus domesticus, M. musculus, Apodemus sylvaticus, A. agrarius, A. flavicollis, and Microtus arvalus. Immunologically, cross‐reacting proteins could not be detected in the laboratory hamster and laboratory guinea pig. Maternal PAMP‐1 serum levels were recorded throughout pregnancy in the two species of house mouse: M. domesticus and M. musculus. Both proteins exhibited maximum concentration at day 11 of gestation. During early pregnancy, M. domesticus females had significantly higher serum levels than those of M. musculus females. © 1992 Wiley‐Liss, Inc.
The bimodal auditory–vibratory system of the thoracic ventral nerve cord in Locusta migratoria (Acrididae, Locustinae, Oedipodini)
Authors: Bickmeyer Ulf , Kalmring Klaus , Halex Heribert , Mücke Alfred 
Published: June 2005

AbstractIn locusts the auditory receptors of the tympanal organs and many of the vibratory receptors of all 6 legs converge at the level of the thoracic ventral nerve cord, forming a combined auditory–vibratory sensory system; it is represented by the VS‐, S‐, and V‐neurons ascending to the supraesophageal ganglion. The connections between vibratory receptors of the different legs and the dendritic inputs of the bimodal ascending neurons are investigated in this report. As an example, the dendritic branches of the G‐ and V3‐neurons for auditory and vibratory input could be localized by simultaneous recording at 2 different positions of the axon. The vibratory input from the receptors of the different legs was determined. Segmental and/or intersegmental thoracic interneurons are intercalated between the receptors and the ascending auditory–vibratory neurons (G‐ and V3‐neurons). The morphology and function of 2 intersegmental vibratory interneurons (VI1‐ and VI2‐neurons) are described. They probably connect the vibratory receptors of 1 (or 2) leg(s) of 1 thoracic segment with the different bimodal auditory–vibratory neurons. The importance of the anterior Ring Tract for synaptic connection between receptor cells, first order interneurons, and bimodal auditory–vibratory neurons is discussed on the basis of morphological and physiological data. © 1992 Wiley‐Liss, Inc.
Effects of temperature acclimation on Ca2+‐ATPase of the carp sarcoplasmic reticulum
Authors: Ushio Hideki , Watabe Shugo 
Published: June 2005

AbstractThe sarcoplasmic reticulum (SR) was prepared from the ordinary white muscle of carp Cyprinus carpio acclimated to either 10 or 30°C over 5 weeks, and its Ca2+ ‐ATPase and Ca2+ uptake activities measured.The SR Ca2+ ‐ATPase activities of the 10 and 30°C‐acclimated carp were 0.2 and 0.1 μmol Pi/min.mg at a reaction temperature of 10°C, respectively, and 1.1 and 0.6 μmol Pi/min.mg at 30°C, respectively. The corresponding Ca2+ uptake activities in the presence of sodium oxalate were 1.1 and 0.4 μmol Ca/min.mg at 10°C, and 2.1 and 1.5 μmol Ca/min·mg at 30°C, respectively. The break point in the Arrhenius plot of Ca2+ ‐ATPase activity was 9.2°C for the 10°C‐acclimated SR and 15.9°C for the 30°C‐acclimated SR. The activation energy of Ca2+ ‐ATPase for the 10°C‐acclimated SR between 10 and 40°C was 75 kJ/mol and similar to that for the 30°C‐acclimated SR between 16 and 40°C, 81 kJ/mol. The membrane fluidity of SR, which was determined with a fluorescence probe, Py(3)Py, was higher for the 10°C‐ than 30°C‐acclimated carp at any reaction temperature from 0 to 30°C. The peptide map in SDS‐gels of Ca2+ ‐ATPase with α‐chymotrypsin gave different patterns in the 40–70 kDa region between the two acclimated groups: the peptide of about 63k Da was specific to the 10°C‐acclimated SR, while the peptide of about 50 kDa to the 30°C‐acclimated SR. Tryptic peptide mapping also resulted in different fragmentation patterns in SDS‐gels for the two Ca2+ ‐ATPases. These results suggest that carp would modify the fluidity of SR membrane and the molecular structure of Ca2+ ‐ATPase to compensate for fluctuating ambient temperatures. © 1993 Wiley‐Liss, Inc.
Effects of calcitonin administration on serum calcium and inorganic phosphate levels of the fish, Heteropneustes fossilis, maintained either in artificial freshwater, calcium‐rich freshwater, or calcium‐deficient freshwater
Authors: Singh Sarita , Srivastav Ajai K. 
Published: June 2005

AbstractFreshwater catfish, Heteropneustes fossilis, were injected daily intraperitoneally either with vehicle (0.1 ml of 0.6% NaCl/100 g body wt) or calcitonin (0.5 MRC U/100 g body wt) and maintained either in artificial freshwater, calcium‐rich freshwater, or calcium‐deficient freshwater for 10 days. The blood samples were collected on days 1, 3, 5, and 10 after initiation of the experiment, and serum calcium and inorganic phosphate levels were analysed.(i) Artificial freshwater: There is no change in the serum calcium and inorganic phosphate levels of calcitonin‐injected fish.(ii) Calcium‐rich freshwater: In vehicle‐injected fish there is a progressive hypercalcemia from day 1 to day 5. On day 10 the value decreases but it is still hypercalcemic. No change has been noticed in the serum calcium level of calcitonin‐treated fish. In vehicle‐treated fish the serum inorganic phosphate level indicates a decrease on day 10. The serum inorganic phosphate level of calcitonin‐treated specimens exhibits no change.(iii) Calcium‐deficient freshwater: There is a progressive decrease from day 1 to day 3 in serum calcium level of vehicle‐injected fish. Thereafter, from day 5 the level increases thus resulting in hypercalcemia on day 10. Calcitonin treatment to the fish evokes a decrease in the serum calcium level from day 1 to day 3. Thereafter a significant hypercalcemia is recorded on day 5 and day 10. In vehicle‐injected fish the serum inorganic phosphate levels decrease from day 3 to day 5. However, the value increases on day 10. Serum inorganic phosphate level of calcitonin‐treated fish exhibits a decrease on day 1. Thereafter, it rises progressively from day 3 to day 10. © 1993 Wiley‐Liss, Inc.
Defining a role for calcium in the resumption and progression of meiosis in the pig oocyte
Authors: Kaufman Milissa L. , Homa Sheryl T. 
Published: June 2005

AbstractThe role of calcium (Ca+ +) during spontaneous meiotic maturation of pig oocytes was examined. The hypothesis that elevations of endogenously derived intracellular Ca+ + are prerequisite for germinal vesicle breakdown (GVBD) and progression through meiosis was tested. In addition, investigations were carried out to determine whether GVBD and meiotic progression were dependent upon extracellular Ca+ + influx. Elevation of endogenously derived Ca+ + was inhibited directly by loading cells with BAPTA, a specific Ca+ + chelator, or indirectly with neomycin. Extracellular Ca+ + influx was prevented by culturing oocytes in Ca+ +‐deficient medium, with EGTA, or in the presence of the Ca+ + channel blocker verapamil. Pretreatment with BAPTA/AM and subsequent culture in the absence of added exogenous Ca+ + resulted in a similar inhibition of GVBD (1 μM BAPTA/AM vs. untreated, P < 0.01). After 4 h following follicular release, oocytes were no longer sensitive to BAPTA/AM treatment. Neomycin also significantly inhibited GVBD (0.5 mM neomycin vs. untreated, P < 0.05) as well as meiotic progression past metaphase I (0.25 mM neomycin vs. untreated, P < 0.05). The incidence of GVBD was not significantly affected when oocytes were simply cultured in Ca+ + deficient medium or when cultured in the presence of EGTA or verapamil. However, progression of meiosis past GVBD to metaphase II was suppressed by reducing levels of Ca+ + in the culture medium (0.68 mM Ca+ + vs. 1.7 mM Ca+ +, P < 0.05) and by treatment with verapamil (0.25 mM verapamil vs. untreated, P < 0.05). Meiotic progression was completely blocked at metaphase I in the presence of 0.85 mM EGTA. These results implicate a central role for the mobilisation of intracellular Ca+ + for the initiation of GVBD, and suggest that external Ca+ + influx is not a direct requirement for GVBD, although it may be required for development past metaphase I in pig oocytes. © 1993 Wiley‐Liss, Inc.
C‐type natriuretic peptides are potent dilators of shark vascular smooth muscle
Authors: Evans David H. , Toop Tes , Donald John , Forrest John N. 
Published: June 2005

AbstractPrevious studies of the effects of C‐type natriuretic peptides (CNP) in intact mammals have demonstrated limited hypotensive responses, in contrast to other natriuretic peptides. Our previous studies, on isolated vascular smooth muscle (VSM) from various fish species, utilizing either mammalian or non‐homologous fish atrial natriuretic peptides (ANP), have demonstrated vasodilation with a relatively high sensitivity (EC50 ∼ 5 nM). The recent sequencing of a C‐type natriuretic peptide from the heart of the dogfish shark, Squalus acanthias, has enabled us to compare the efficacy of this peptide on aortic VSM from that species with two other CNPs (from killifish and pig), as well as rat ANP. The EC50 of dilation for sCNP, as well as kCNP and pCNP, was 0.5 nM, over 15 times lower than the EC50 of the response to rANP. These data suggest that CNP is released from the dogfish shark heart and is a circulating hormone with potent vasodilatory effects, in sharp contrast to the apparent role of CNP predominantly as a brain neuropeptide in mammals. © 1993 Wiley‐Liss, Inc.
A diel rhythm of the short‐circuit current expressed by the opercular epithelium of the killifish, Fundulus heteroclitus
Authors: Scheide John I. 
Published: June 2005

AbstractThe inner opercular epithelium of the killifish, Fundulus heteroclitus, may be separated as a single epithelial sheet and mounted in an Ussing‐style chamber with the short‐circuit current (Isc) approximating chloride secretion. Steady state opercular Isc values in seawater‐adapted killifish were higher in tissues removed from fish in the afternoon than those observed in the morning. Opercular conductance was also higher in the afternoon than the morning. The opercular steady state Isc from killifish on a 13:11 light:dark cycle exhibited a diel variation with the peak in the middle of the light cycle and a nadir near the end of the dark phase. Temperature and salinity remained constant during the experimental period. Daily variation cued by the photoperiod should be considered when using this preparation as an experimental model for ion transport in the gill of a seawater‐adapted fish. © 1993 Wiley‐Liss, Inc.
Progestins inhibit murine oocyte meiotic maturation in vitro
Authors: Barrett C. Brent , Powers R. Douglas 
Published: June 2005

AbstractThe in vitro culture of fully grown mammalian oocytes results in spontaneous meiotic maturation from prophase arrest to metaphase II. This maturation can be inhibited by steroid hormones in both murine and porcine oocytes. Using selected steroids, we have examined the structure‐activity relationships of steroids and oocyte inhibition. Experiments with androgens, estrogens, glucocorticoids, and progesterone revealed that at least one steroid from each class was inhibitory. Progesterone, however, was two to three times more effective than steroids from other classes. Examination of a variety of progestins showed that most substitutions decreased or abolished the inhibitory activity. Hydroxy group substitutions at different carbon atoms and substitutions at the 4‐ene group lessened the inhibitory effectiveness, with the exception of 5β‐dihydroprogesterone, which was as effective as progesterone. However, several steroids with substitutions at the C17 acetyl group were more active than progesterone, including 20β‐dihydroprogesterone which was the most inhibitory steroid tested (ID50 = 5 μM). The progesterone agonist R5020 was also very active (ID50 = 8 μM). This is the first report of a detailed examination of the steroid‐induced inhibition of murine oocytes. A comparison between the results reported here and previous reports of steroid‐induced inhibition in porcine oocytes reveals differences in the response of oocytes from the two families. The structure‐activity relationships of the inhibitory steroids examined here suggest that the steroids are acting via a receptor‐mediated system. © 1993 Wiley‐Liss, Inc.
Primitive sex chromosomes in poeciliid fishes harbor simple repetitive DNA sequences
Authors: Nanda Indrajit , Schartl Manfred , Epplen Jörg T. , Feichtinger Wolfgang , Schmid Michael 
Published: June 2005

AbstractThe demonstration of the chromosomal mode of sex determination via genetic experiments as well as the absence of heteromorphic sex chromosomes affirm poeciliid fishes as a unique group among vertebrates that are endowed with the most primitive form of sex chromosomes. In many different taxa the evolutionary process involved in the differentiation of advanced sex chromosomes is outlined through sex specifically organized repetitive sequences. In this investigation hydridization of synthetic probes specific to genomic simple repeat motifs uncovers a sex‐specific hybridization pattern in certain viviparous fishes of the family Poeciliidae. The hybridization pattern together with specific staining of the constitutive heterochromatin by C‐banding reveals heterogamety in males (Poecilia reticulata) as well as in females (P. sphenops). In P. velifera, however, C‐banding alone fails to unravel the heterogametic status. The female specific W‐chromosome can be detected by simple repetitive sequence probes. Therefore, the principal significance of heterochromatization as a means of generating differentiated sex chromosomes is evident. © 1993 Wiley‐Liss, Inc.
Maternal RNA content in oocytes of several mammalian and avian species
Authors: Olszańska Bożenna , Borgul Arletta 
Published: June 2005

AbstractThe amount of maternal RNA in the oocytes of several mammalian (mouse, rabbit, cow, pig, sheep) and avian (hen, Japanese quail, guinea hen, turkey) species was determined. For mammals these were in the range of 0.47 ng/oocyte (mouse) to 0.98 ng/oocyte (cow), with the exception of the rabbit, where it was up to 15 ng/oocyte. Birds' oocytes contain much higher levels of RNA, from 1.0 μg (Japanese quail) up to 2.1 μg/oocyte (hen). The RNA levels were determined by direct measurement of EtBr‐induced fluorescence of the oocyte homogenates without prior extraction and purification, and correlate well with standard spectrophotometric OD260 measurements. This method is useful when there are limited amounts of a sample, and it permits nucleic acid determination in the presence of proteins. © 1993 Wiley‐Liss, Inc.
Cumulus oophorus as a sperm sequestering device, in vivo
Authors: Bedford J. M. , Kim H. H. 
Published: June 2005

AbstractThe cumulus oophorus, unique to the egg of eutherian mammals, has been suggested to function either in egg transport to the oviduct ampulla, in avoidance of polyspermy, in enhancement of sperm fertilizing ability, or in sperm guidance to the egg. To examine its role further, the content of the oviduct ampulla was collected at 0700–0730 h, 1130–1200h, or 1600–1700 h on the day of ovulation from rats mated once or more than once, and analysed with an emphasis on sperm distribution in the ampullary fluid, in the cumulus, and in the eggs. The distribution of spermatozoa between cumulus and ampullary fluid was highly skewed (ca. 9:1) at all times in favor of the cumulus. In 14.1% of the ampullae collected by 0730 h the only spermatozoa present were those already within eggs; and in many other ampullae then there were no more than one or so additional spermatozoa outside fertilized eggs—a testament to the efficiency of the mechanisms that ensure an early meeting of gametes in the oviduct. There was a gradual increase in the total number of spermatozoa in the ampulla throughout the day of ovulation, and the time of eventual cumulus dispersal later in the day generally reflected the number of spermatozoa within it, rather than the occurrence of fertilization per se.These observations suggest that the cumulus oophorus sequesters and brings to the immediate vicinity of the eggs the few spermatozoa which gain the ampulla at or soon after ovulation, so favoring early fertilization. The sperm/cumulus relationship, sperm/egg communication, and the situation in viviparous vertebrates whose eggs are cumulus‐free are discussed briefly. © 1993 Wiley‐Liss, Inc.