bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of season and photoperiod on the plasma and intratesticular testosterone levels in Indian weaver birds inhabiting the subtropical zone
Authors: Tsutsui Kazuyoshi , Saxena Tanushri , Saxena Rajendra N. 
Published: June 2005

AbstractPrevious studies showed marked changes in the plasma gonadotropin concentration in response to fluctuations in natural and artificial environmental conditions in Indian weaver birds. Therefore, we studied the effects of season and photoperiod on the plasma and intratesticular testosterone levels in this subtropical bird. Although the plasma testosterone concentration changed markedly during the annual breeding cycle, the level did not show a parallel change with testicular weight. The testicular weight was maximal in the breeding phase (June) and minimal in the nonbreeding phase (December), while the plasma testosterone concentration showed two large peaks, one in the breeding and the other in nonbreeding phases. No significant difference in the plasma testosterone level was detected between these two phases. A similar change in plasma testosterone levels was evident in female birds. The intratesticular testosterone content per unit weight was unexpectedly higher in the nonbreeding phase than in the breeding phase. Therefore, calculated total testosterone content per testis showed no statistically significant difference between the two phases despite the small testicular mass in the nonbreeding phase. On the other hand, exposure to short‐day (SD) photoperiods for 10 weeks during the breeding phase, which caused a marked decrease in the testicular weight, tended to decrease the plasma testosterone concentration. Similarly, exposure to long‐day (LD) photoperiods for 10 weeks during the nonbreeding phase tended to induce an increase in the circulating testosterone level in addition to a marked increase in the testicular weight. However, such an effect of artificial photoperiod on testosterone levels was statistically not significant due to a large variance. These results suggest that in Indian weaver birds testosterone actively circulates not only in the breeding phase but also in the nonbreeding phase. Not only photoperiod but also other environmental factors may be involved in the regulation of circulating testosterone in male birds. © Wiley‐Liss, Inc.
Oocyte nuclear maturation at the time of oocyte aspiration is independent of in vitro fertilization potential in the domestic cat
Authors: Byers A. P. , Donoghue A. M. , Roth T. L. , Wildt D. E. 
Published: June 2005

AbstractThis study determined (1)the temporal kinetics of nuclear maturation at and after follicular oocyte aspiration and (2) the significance of variations in nuclear maturation and sperm‐oocyte co‐incubation interval on in vitro fertilization (IVF) in the domestic cat. Female cats were treated with pregnant mares' serum gonadotropin followed 84 h later with human chorionic gonadotropin (hCG). Twenty‐five hours after hCG, ovarian follicular oocytes were aspirated laparoscopically and classified according to morphological criteria. Oocytes classified as mature were cultured for 0,2,4,6, or 8 h in Ham's F10 medium and then stained for nuclear maturation. The proportion of oocytes at metaphase II was similar (P > 0.05) at 0 (38.2%) and 2 (48.5%) h of culture, but was higher (P < 0.05) at 4 (76.5%), 6 (82.8%), and 8 (92.3%) h. Oocytes also were collected and cultured as described above and then co‐incubated for 2 or 18 h with 5 × 105 motile cat sperm cells/ml. The incidence of IVF (cleavage to 2‐cells by 30 h post‐insemination) was consistently 2‐fold higher (P > 0.05) for the 18 h compared to the 2 h gamete co‐incubation groups. However, despite differences in nuclear maturation at the time of oocyte recovery, IVF success was unaffected (P > 0.05) by pre‐insemination culture interval (0 h, 72.7%; 2 h, 73.3%; 4 h, 70.7%; 6 h, 57.8%; 8 h, 62.5%; 18 h group). Thus, the majority of oocytes recovered from cats treated with this gonadotropin regimen has not achieved metaphase II by follicular aspiration. These oocytes appear grossly mature, but nuclear maturation often is incomplete until 4–8 h in culture. Ability of these oocytes to fertilize in vitro is independent of stage of nuclear maturation at recovery, but IVF success is influenced by sperm‐oocyte co‐incubation interval. © Wiley‐Liss, Inc.
Midgut metabolism in different instars of the tobacco hornworm (Manduca sexta)
Authors: Gibellato C. M. , Chamberlin M. E. 
Published: June 2005

AbstractEnzyme activities and mitochondrial substrate oxidation were measured in the posterior midguts of tobacco hornworms at different larval stages. A comparison of third, fourth, and fifth instars demonstrated no differences in citrate synthase activity (per gram of midgut), indicating that maximal aerobic capacity is unchanged during larval growth. The midguts of fifth instars had the highest activity of 3‐hydroxyacyl‐CoA dehydrogenase and carnitine acetyltransferase. Furthermore, mitochondria isolated from the midguts of fifth instar larvae had higher rates of palmitoyl carnitine oxidation when compared to mitochondria isolated from the fourth instar larvae. These results indicate that there is an increased preference for fatty acid oxidation in the midguts of fifth instar larvae. The presence of succinyl‐CoA ketotransferase and acetoacetyl‐CoA thiolase as well as the mitochondrial oxidation of acetoacetate and β‐hydroxybutyrate indicate that ketone bodies can serve as substrates for the midgut. The activities of malic enzyme and glucose‐6‐phosphate dehydrogenase were significantly higher in fifth instars than in fourth instars, indicating an increased capacity for lipid synthesis. © Wiley‐Liss, Inc.
Characterization of partially purified betaine aldehyde dehydrogenase from horseshoe crab (Limulus polyphemus) cardiac mitochondria
Authors: Dragolovich Julia , Pierce Sidney K. 
Published: June 2005

AbstractGlycine betaine is an organic osmolyte which is often accumulated in response to hyperosmotic stress in euryhaline species. In mitochondria isolated from horseshoe crab (Limulus polyphemus) heart tissue, the synthetic pathway, which is a two step oxidation of choline (choline→betaine aldehyde→glycine betaine), appears to be associated with the matrix. The majority of the betaine aldehyde dehydrogenase (BADH) activity, the terminal synthetic enzyme, is found in this subcellular fraction. Partially purified Limulus BADH is highly specific for the substrate betaine aldehyde (Km of 133 μM). Two alternative substrates, glyceraldehyde and glycoaldehyde, do not stimulate NAD+ reduction in the presence of BADH. NAD+ is an essential co‐factor in the oxidation of betaine aldehyde to glycine betaine. Limulus BADH can utilize NADP+, although a higher Km indicates a much lower affinity than that for NAD+, 267 μM and 22 μM, respectively. The end‐product, glycine betaine, competitively inhibits BADH activity. Cations have a profound effect on Limulus BADH activity. At physiological concentrations, enzyme activity is stimulated by increases in both [K+] but decreased by elevated [Na+]. Although inorganic ions modulate this enzyme, it does not appear that BADH is the rate limiting step in osmotically stimulated glycine betaine synthesis. © Wiley‐Liss, Inc.
Elevated ornithine decarboxylase activity and polyamine levels during early development in the brine shrimp Artemia franciscana
Authors: Watts Stephen A. , Lee Kara J. , Cline George B. 
Published: June 2005

AbstractRehydrated Artemia cysts were assayed for ornithine decarboxylase (ODC) activity and levels of putrescine, spermidine, and spermine during pre‐emergent development, emergence and hatching. Low but detectable ODC activity levels increased significantly within 2 hr, suggesting de novo synthesis of ODC protein and representing one of the earliest enzymatic biochemical markers in post dormancy development. ODC activity increased 100‐fold during preemergent development (occurring in the absence of an increase in tissue polyamine content). This increase in enzyme activity occurs in the relative absence of DNA synthesis but may be related to an enhanced polyamine synthetic capacity necessary for other physiological processes such as early transcriptional and translational activity. A second, higher ODC activity peak (correlated with a significant increase in polyamines) prior to hatching may be related to DNA synthesis and other biochemical processes associated with hatching of stage 1 nauplii and is correlated with increasing ecdysteroid titres reported previously. Putrescine and spermidine levels were significantly higher than spermine levels (2.5, 2.65, and 0.13 μmoles/g dry weight) at the onset of rehydration. High endogenous polyamines levels in encysted embryos are most likely available for use in metabolic processes associated with early differentiation. Polyamine levels increased significantly just prior to emergence and continued increasing throughout hatching. Spermidine to spermine ratios (>18) should reflect high rates of overall biosynthetic processes throughout preemergence, emergence, and hatching. © Wiley‐Liss, Inc.
Heat and oxygen flux as a function of environmental po2 in juvenile Australian crayfish, Cherax quadricarinatus
Authors: Meade Mark E. , Doeller Jeannette E. , Kraus David W. , Watts Stephen A. 
Published: June 2005

AbstractOxygen and heat flux of the juvenile Australian red claw crayfish, Cherax quadricarinatus, were measured in parallel respirometry and calorimetry systems at 28°C at varying levels of environmental po2. Juvenile crayfish maintained an average oxygen flux of 5.0 ± 0.4 (SEM) pmol O2/(s*mg fresh weight) over the po2 range from 20.7 to 5 kPa. At approximately 4 kPa po2, oxygen flux decreased, conforming to decreasing oxygen tensions. Juvenile crayfish maintained an average heat flux of −2.2 ± 0.2 μW/mg fresh weight when exposed to 100 and 50% air saturated conditions (18.1 to 20.7 and 7.8 to 10.4kPa po2, respectively). The ratio of the amount of heat dissipated per oxygen consumed, called the calorimetric/respirometric (CR) ratio, at 100 and 50% air saturated conditions averaged −440 kJ/mol O2. When crayfish were exposed to 25% air saturated conditions (2.5 to 5.2 kPa po2), heat flux decreased initially to −1.1 ± 0.4 μW/mg fresh weight. Within 4 hr, however, heat flux returned to normoxic values. When crayfish were exposed to anoxic conditions, heat flux decreased to zero. Most juvenile crayfish did not survive short‐term (1–2 hr) anoxic stress. These data suggest that juvenile C. quadricarinatus are excellent oxygen regulators over a wide range of environmental po2. These data indicate also that juvenile C. quadricarinatus can compensate metabolically, possibly via aerobic and/or anaerobic adjustments, in order to maintain metabolic rate at critically low po2. Last, this crayfish appears limited in its ability to utilize anaerobic pathways to maintain metabolic rate in anoxic environments. © Wiley‐Liss, Inc.
Study of the regenerating newt retina by electrophysiology and immunohistochemistry (bipolar‐ and cone‐specific antigen localization)
Authors: Saito T. , Kaneko Y. , Maruo F. , Niino M. , Sakaki Y. 
Published: June 2005

AbstractImmunohistochemical and electrophysiological examinations were carried out to investigate the sequence of appearance of the retinal neurons during regeneration after a complete surgical removal of the original retina of the newt. We produced a monoclonal antibody, RB‐1, specific for cone photoreceptors and a subtype of bipolar cells in adult newt retina. This antibody was used as a major tool for this analysis. Appearance of spiking activity as a possible marker of ganglion cell differentiation was examined with whole‐cell patch‐clamp techniques. Spiking cells, which possessed voltage‐dependent Na+, K+, and Ca2+ channels similar to those of mature ganglion cells, appeared in the regenerating retina by 24 days before cone photoreceptors had been labeled by the RB‐1 antibody. Cones and ganglion cells differentiated before the retina had been segregated into distinct synaptic layers. The RB‐1‐labeled bipolar cells as well as PKC‐immunoreactive bipolar cells appeared in the regenerating retina after the segregation of the synaptic layers. Their appearance seemed to coincide with the appearance of immunoreactive amacrine cells described previously (Negishi et al. [1992] Dev. Brain Res. 68:255–264). During embryonic development of the newt retina, cone photoreceptors appeared prior to bipolar cells. Thus the process of reformation of a functional retina seems to follow the same steps as differentiation of retina during development. © Wiley‐Liss, Inc.
Calcium‐binding properties of fetuin in fetal bovine serum
Authors: Suzuki Michiko , Shimokawa Hitoyata , Takagi Yuzo , Sasaki Satoshi 
Published: June 2005

AbstractFetuin, an abundant protein in fetal bovine plasma, is the bovine homolog of human α2HS glycoprotein (α2HS). In spite of numerous studies, the biological functions of both proteins remain elusive. We now report the remarkable 45Ca‐binding activity of fetuin in fetal bovine serum that has been blotted on a membrane after electrophoresis. The Ca‐binding ability of the purified protein was analyzed by equilibrium dialysis, which revealed that bovine fetuin had multiple Ca‐binding sites, one of which had a Kd of 0.95 × 10−4 M. It was also shown that the Ca‐binding activity of fetuin was greater than that of albumin in serum of the bovine fetus at the late gestational stage. Since fetal bovine serum contains not only a high concentration of fetuin but also a high concentration of Ca, it is possible that fetuin functions to maintain high levels of Ca in fetal serum via normalization of the concentration of Ca2+ ions. © Wiley‐Liss, Inc.
Localization of proline receptors involved in regulating nematocyst discharge
Authors: Watson Glen M. , Roberts Julia 
Published: June 2005

AbstractAt least two distinct classes of chemoreceptor are known to regulate nematocyst discharge in sea anemones. One class of receptor binds N‐acetylated sugars and the other class binds certain amino compounds including the imino acid, proline. Previously, receptors for N‐acetylated sugars were localized using colloidal gold conjugates of bovine submaxillary mucin. The sugar receptors are known to cycle by receptor‐mediated endocytosis from the apical surface of supporting cells. In this study, colloidal gold conjugates of polyproline were used to determine the distribution of proline receptors. We find that polyproline‐gold, like mucin‐gold, localizes to the apical surface of supporting cells. Binding of polyproline‐gold to supporting cells is blocked by excess free polyproline or free proline. After appearing at the cell surface, polyproline‐gold enters endosomes, followed by multivesicular bodies. To test for possible artifact due to colloidal gold, trafficking of cationized ferritin (CF) was monitored in the presence of proline. CF appears at the cell surface, followed by endosomes, multivesicular bodies, and lysosomes. Some evidence is presented that proline receptors are sorted from N‐acetylated sugar receptors in endosomes. We propose that receptor‐mediated endocytosis functions in anemone tentacles to enhance the temporal resolution of chemosensing. © Wiley‐Liss, Inc.
Snake yolk sac as a site for in vivo organ incubation: A new method in the research of snake embryo development
Authors: Reshef Ram , Ovadia Michael , Wollberg Miriam , Kochva Elazar 
Published: June 2005

AbstractThe snake embryo yolk sac served as a culture medium for the development of isolated reptilian organs. Isolated upper jaws of Natrix tessellata and Vipera palaestinae embryos at the early stages of jaw organogenesis were implanted into the yolk, close to the yolk sac blood vessels of Natrix tessellata embryos in order to determine natural conditions for long‐term incubation of organ culture. Tissues were incubated in the yolk for approximately 1 month until 1 day before host embryo hatching. Histological inspection showed full morphological differentiation of all tissues including scales, bones, teeth, glands, and connective tissue. The biochemical marker phosphodiesterase showed the typical developmental pattern in the main oral gland, Duvernoy's gland, and was comparable to the same gland in the host embryo. Vipera implants developed almost normally, except for differentiation of the skin which remained in the stage of one to two cell undifferentiated layers. Natrix was chosen for these experiments owing to the special chemical composition of its yolk that allows the penetration of blood vessels. This characteristic is probably crucial for the success of angiogenesis, which in turn is an essential condition for tissue survival. The ability of the yolk to support normal differentiation of isolated organs provides a valuable tool for the long‐term incubation experiments that are indispensable in order to achieve maximal tissue differentiation. © Wiley‐Liss, Inc.
Fiber types and myosin heavy chain composition in muscles of common shrew (Sorex araneus)
Authors: Savolainen Jukka , Vornanen Matti 
Published: June 2005

AbstractRed‐toothed shrews of subfamily Soricinae are small mammals with very high mass‐specific metabolic rate. Owing to their high aerobic power they are interesting objects for studies concerning the limits and constraints of skeletal muscle adaptation. In order to clarify the correlation between metabolic rate and muscle properties, we have analyzed fiber types, fiber size, and myosin heavy chain composition of the common shrew(Sorex draneus)and compared them to those of rat (Rattus norvegicus).Three distinct differences between shrew and rat muscles were noted. 1) The fibers of shrew muscles are exceptionally small in comparison to rat myofibers. 2) Electrophoretic and histochemical analysis showed that shrew muscles are composed of only fast fibers (fiber types IIB and IID), the slow type I fibers being totally absent. 3) The shrew muscles are much more homogenous than rat muscles in regard to myosin heavy chain and fiber type composition. The shrew diaphragm consists exclusively myosin heavy chain type IId (MHCIId), while masseter and soleus are composed 95% and 87% of MHCIId, respectively. Other four studied muscles contain MHCIIb and MHCIId approximately in equal proportions.The present findings show that shrew muscles are composed of small, highly aerobic, fast type II fibers, which may be sufficiently fatigue‐resistant to function both as postural muscles and to power fast and high frequency movements of limbs and diaphragm. © 1995 Wiley‐Liss, Inc.
External and internal influences on indices of physiological stress. I. Seasonal and population variation in adrenocortical secretion of free‐living lizards, Sceloporus occidentalis
Authors: Dunlap Kent D. , Wingfield J. C. 
Published: June 2005

AbstractThe plasma levels of glucocorticoid hormones (e. g., corticosterone and cortisol) are often used as an index of physiological stress. However, under natural conditions, glucocorticoid secretion can respond to both environmental influences (e. g., extreme climatic conditions) and internal influences (populational differences and annual seasonal cycles). To distinguish between these kinds of influences, we examined seasonal variation in basal levels of corticosterone and the adrenocortical response to acute stress in six populations of western fence lizards Sceloporus occidentalis. Three populations (Mojave CA, Lone Pine CA, and Tulalip WA) were near the periphery of the species distribution, and three were in the central part of the range (Ojai CA, Hopland CA, and Bend OR). Basal corticosterone showed no consistent pattern of variation, but the adrenocortical response to acute stress was consistently highest 1) in populations living at the margin of the species range, 2) during the hottest and driest seasons, and 3) in individuals with the largest decrements in physiological condition (length‐adjusted mass). Thus, basal adrenal secretion and adrenal responsiveness to acute stress were dissociated, and the latter more likely reflected the physiological condition of an individual and the severity of its environment. However, further analysis showed that physiological condition only partially explains the variation in adrenocortical responsiveness and that intrinsic seasonal and population differences may be as important as the external influences of the physical environment. After factoring out seasonal changes in physiological condition, adrenocortical response of two populations under identical controlled laboratory conditions also showed that a peripheral population (Mojave, CA) maintained a higher response than a central population (Bend, OR) that was not attributable to population differences in physiological condition. © 1995 Wiley‐Liss, Inc.
Antarctic fish tissues preferentially catabolize monoenoic fatty acids
Authors: Sidell Bruce D. , Crockett Elizabeth L. , Driedzic William R. 
Published: June 2005

AbstractTissues of Antarctic marine fishes are very high in lipids, predominantly triacylglycerols (TAG). In addition to conferring static lift to these swimbladderless fishes, these rich lipid stores long have been considered as an important caloric resource to the animals. We have performed in vitro measurements of the rates of oxidation of 14C‐labeled carbohydrates and fatty acids by oxidative skeletal muscle and heart ventricle of an Antarctic teleost, Gobionotothen gibberifrons to assess the relative importance of these substrates to aerobic energy metabolism. Capacities for regeneration of ATP calculated from oxidation rates of these fuels clearly indicate that fatty acids are more effective substrates of energy metabolism than either glucose or lactate with both tissues. Substrate competition experiments conducted between the saturated fatty acid palmitate (16:0) and the monoenoic unsaturate oleate (18:1) comparing the oxidation rate of radiolabeled fatty acid in the presence and absence of unlabeled competitor demonstrate a clear preference of both tissue types for catabolism of the monounsaturated substrate. Measurements of maximal activity of the putative flux‐generating enzyme of mitochondrial β‐oxidation, carnitine palmitoyltransferase (CPT), with a variety of fatty acyl CoA esters also show significant preference for a monoenoic fatty acyl CoA, palmitoleoyl CoA (16:1). The general pattern of results suggests that monounsaturated fatty compounds are the most readily utilized substrates for energy metabolism by oxidation muscle tissues of this Antarctic species. © 1995 Wiley‐Liss, Inc.
Studies on the autolysis of m‐calpain from the skeletal muscle of the amphibian Rana ridibunda
Authors: Sargianos N. , Gaitanaki C. , Beis I. 
Published: June 2005

AbstractThe autolytic mechanisms responsible for the regulation of m‐calpain purified from the skeletal muscle of the amphibian Rana ridibunda were examined. Both subunits of the calpain molecule were found to undergo autolysis in the presence of Ca2+. Various divalent cations were examined for their ability to induce calpain autolysis. The concentrations of these cations required for the complete calpain autolysis were: 500 μM Ca2+, 2 mM Sr2+, 10 mM Ba2+, whereas Mg2+, even at 10 mM did not induce any autolysis. Calpain autolysis induced by the above divalent cations is a temperature dependent process. Presence of Mn2+or Sr2+reduces the Ca2+requirement of calpain for autolysis. The rate of autolysis depends on the protease concentration; protease inhibitors such as E‐64, leupeptin, antipain, and iodoacetic acid inhibit the autolysis of calpain; E‐64 inhibits irreversibly while leupeptin inhibits reversibly the autolysis; and irreversibly inactivated by E‐64 calpain is fully digested by native calpain. Autolysis of calpain in the presence of alkali denatured casein increase the Ca2+sensitivity of the protease for its half maximal and maximal caseinolytic activity. Limited autolysis of calpain is also induced in the presence of the endogenous substrate G‐actin, and the rate of autolysis is slower than that obtained in the absence of substrates. © 1995 Wiley‐Liss, Inc.