bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ca2+ and Mg2+ transport in gills and gut of tilapia, Oreochromis mossambicus: A review
Authors: Flik Gert , Van Der Velden Joan A. , Dechering Koen J. , Verbost Pieter M. , Schoenmakers Theo J. M. , Kolar Zvonimir I. , Bonga Sjoerd E. Wendelaar 
Published: June 2005

AbstractThe euryhaline tilapia Oreochromis mossambicus kept in fresh water takes up calcium mainly from the water via the gills, like other freshwater fish. In the gills specialized mitochondria‐rich cells, the chloride cells, are thought to mediate a transcellular Ca2+ transport. Second messenger operated calcium channels (SMOCs) in the apical membrane, regulated by the hormone stanniocalcin, allow minute‐to‐minute control over the entry of Ca2+. In the basolateral plasma membranes of these cells, an ATP‐consuming Ca2 + transporting enzyme provides the major driving force for extrusion of Ca2+ into the blood; in addition, an Na+ /Ca2+ exchanger is present in these membranes. The kinetics of the exchanger in vitro indicate that this extrusion mechanism dominates when intracellular calcium levels reach micromolar levels. In the gills, the transport of calcium appears primarily ATPase mediated and therefore largely independent of the Na+ status of the transporting cell. In enterocytes, similar mechanisms for transcellular transport of Ca2+ exist. However, in the intestinal epithelium the extrusion of Ca2+ is primarily via the Na+/Ca2+ exchanger and to a very limited extent mediated via the Ca2+‐ATPase. Indeed, calcium transport over the intestinal epithelium is dependent on the Na+ ‐status and the Na+/K+‐ATPase activity of the epithelium. Prolactin and cortisol are endocrine factors determining the relative densities of calcium pumps in basolateral plasma membranes.At least 80% of the magnesium required for growth and homeostasis is absorbed from the food via the intestine. Magnesium is transported transcellularly and actively via enterocytes. The movement of Mg2+ over the apical membrane is passive, down an electrochemical gradient. The cytosolic Mg2+ concentration is kept well below its equilibrium concentration. The extrusion over the basolateral plasma membrane is mediated by an ATP‐consuming enzyme. The gills contribute less than 20% to magnesium uptake, but up to 50% in tilapia fed a magnesium deficient diet. Evidence is accruing that prolactin is involved in the adaptation to low magnesium diets. © 1993 Wiley‐Liss, Inc.
Ion transport systems in membrane vesicles isolated from crustacean tissues
Authors: Towle David W. 
Published: June 2005

AbstractStudies with membrane vesicles isolated from crustacean gill have offered evidence for three major transport systems believed to play central roles in ion transport across the gill epithelium. First, ATP‐dependent sodium/potassium and sodium/ammonium exchanges have been demonstrated in Na+ + K+ ‐ATPase‐rich membrane preparations, supporting the concept that ammonium ion can serve as an effective counterion for sodium transport from cytosol to blood. Second, an amiloride‐sensitive Na+ /H+ antiporter, demonstrated using a pH‐sensitive fluorescent dye, has been shown to be electrogenic, apparently exchanging 2 sodium ions for 1 hydrogen ion. These two transport systems, the first in the basolateral membrane and the second likely in the apical membrane, can achieve net transport of sodium ions from water to blood. Third, a Cl−/HCO3− exchanger has been demonstrated in membrane vesicles from crab gill, most likely playing a central role in the sodium‐independent transfer of chloride across the epithelium. Finally, although no direct studies of calcium transport in crab gill have been reported, indirect evidence from other tissues suggests that part of the calcium flux across the gill may be mediated by Ca2+ /H+ exchange. © 1993 Wiley‐Liss, Inc.
What forces are responsible for the stickiness of spider cribellar threads?
Authors: Opell Brent D. 
Published: June 2005

AbstractThe surface of spider cribellar prey capture thread is formed of thousands of fine silk fibrils. The stickiness of this thread is often attributed to the ability of these fibrils to catch on irregular surfaces. However, 14‐month‐old cribellar threads of Hyptiotes cavatus (Uloboridae) were significantly less sticky than freshly spun threads. Slight changes in cribellar thread dimensions failed to fully explain this reduced stickiness, demonstrating that an auxiliary force contributes to the stickiness of cribellar threads. Because this force does not appear to rely on the snagging of fibrils, it may enhance the ability of cribellar threads to hold prey with smooth surfaces. © 1993 Wiley‐Liss, Inc.
Basal, diurnal, and stress‐induced levels of glucose and glucocorticoids in captive bats
Authors: Widmaier Eric P. , Kunz Thomas H. 
Published: June 2005

AbstractPlasma levels of glucocorticoids and glucose were measured in three species of fruit bats (Chiroptera) sampled from captive populations. Three species of Old World bats (Pteropus vampyrus, P. Hypomelanus, and Rousettus aegyptiacus) had plasma levels of glucose that were within the normal mammalian range (80–100 mg/dl), with no difference between males and females. All animals had detectable levels of one or both of the major glucocorticoids (cortisol and corticosterone) found in mammals. Steroid levels were highest in P. hypomelanus (cortisol: 1,269 ± 207 ng/ml; corticosterone; 590 ± 154 ng/ml) and lowest in R. aegyptiacus (corticosterone: 36 ± 4 ng/ml; cortisol not determined). Diurnal changes in these steroids and the effects of handling and restraint stress were further investigated in P. hypomelanus. Experimental animals were captured in their roost quarters, bled once by venupuncture within 3 min, placed singly into a small holding chamber for 50–60 min, and bled again. This procedure was performed at four different times over the course of 24 h with different groups of animals. Glucose was at a minimum just before and a maximum just after the period of food presentation. Cortisol levels remained relatively constant throughout the day‐roosting period and significantly declined to their lowest level in the period following food presentation. As expected, the effects of handling and isolation caused a significant increase in both plasma cortisol and glucose levels. When individual P. hypomelanus were subjected to 3 h restraint stress in small plastic wire‐mesh restraining devices, cortisol levels rose approximately 800% by 2 h, with the first significant increase at 20 min. Thus, effects of sampling time (time of day) on plasma levels of cortisol and glucose should be considered when designing field and laboratory studies in which hormones and other blood borne parameters are being measured. Handling and bleeding times that exceeded 3 min were associated with elevated plasma levels of cortisol and glucose above resting (unstressed) levels, suggesting that field and laboratory protocols should be designed to reduce or eliminate this problem. Finally, the exceptionally high levels of plasma corticoids in P. hypomelanus, and to a lesser extent in P. vampyrus, place these bats among the highest known circulating adrenal steroid levels of all mammals. © 1993 Wiley‐Liss, Inc.
Spawning in the zebra mussel (Dreissena polymorpha): Activation by internal or external application of serotonin
Authors: Ram Jeffrey L. , Crawford Gary W. , Walker James U. , Mojares Jon J. , Patel Nilesh , Fong Peter P. , Kyozuka Keiichiro 
Published: June 2005

AbstractThe zebra mussel, Dreissena polymorpha, was recently introduced accidentally into the Great Lakes and, due in part to its prodigious reproductive capacity, is spreading rapidly in temperate fresh waters of North America. The present studies examine some of the mechanisms that regulate spawning in this animal.In August and September 1990 and in May 1991 injection of serotonin (5‐hydroxytryptamine, 5‐HT) induced ripe male, but not female, zebra mussels to spawn. During mid‐summer 1991, 5‐HT induced spawning in both males and females, and 5‐HT could produce spawning responses by either injection or external application. External pH over a broad range (6.0 to 9.1) had no effect on spawning, neither inhibiting induction of spawning by 5‐HT nor significantly eliciting spawning itself. With external application, 10–3 M and 10–4 M 5‐HT caused spawning, but 10–5 M and 10−6 M did not. Cyproheptadine, a 5‐HT receptor antagonist, reduced the response of both males and females by more than half. Spawning in response to 5‐HT was blocked at 4°C, but not at 12°C, 20°C, or 27°C. For male zebra mussels morphological criteria for judging gonadal maturity were well‐correlated with probability of spawning in response to 5‐HT. For females, the likelihood of spawning in response to 5‐HT was not tightly coupled to morphological maturity of the gonad, with many morphologically ripe females failing to spawn and some apparently immature animals releasing oocytes. Prior spawning reduced subsequent responsiveness and intensity of spawning of animals to 5‐HT. These experiments support a role for 5‐HT in regulating reproduction in zebra mussels and help define conditions by which zebra mussel spawning may be stimulated or inhibited. © 1993 Wiley‐Liss, Inc.
Predator‐induced morphological changes in Euplotes (Ciliata): Isolation of the inducing substance released from Stenostomum sphagnetorum (turbellaria)
Authors: Kusch Jürgen 
Published: June 2005

AbstractThe turbellarian Stenostomum sphagnetorum releases a morphogenetically active substance (S‐factor) into the surrounding medium. Ciliates of the genus Euplotes, which are potential prey of Stenostomum, are able to recognize the S‐factor. In response to this factor, each Euplotes cell becomes transformed into an enlarged circular morph with extended lateral wings that make its engulfment by the predator more difficult. The S‐factor was purified to chromatographic and electrophoretic homogeneity. From the observation that its biological activity can be eliminated by treatments with proteases and from the absorption spectrum of the purified S‐factor, it appears that the S‐factor is a protein. Upon heating at 95°C for 10 min, the S‐factor lost 50% of its biological activity, and after 30 min at 95°C the activity had disappeared completely. Electrophoretic analysis revealed that the S‐factor has a molecular mass of 17.5 kDa. It is active at concentrations as low as 10–11 M. The factor from Stenostomum is not identical to the Lembadion factor, which is released from the predatory ciliate Lembadion bullinum and has a morphogenetic effect on Euplotes. © 1993 Wiley‐Liss, Inc.
Carnitine palmitoyltransferase activity is present and high in the muscle and liver of lampreys (Agnatha)
Authors: Power Glen W. , Cake Max H. , Potter Ian C. 
Published: June 2005

AbstractThe current study demonstrates for the first time that carnitine palmitoyltransferase (CPT), the rate‐limiting enzyme of fatty acid oxidation in gnathostomatous (jawed) vertebrates, is present in the myotomal musculature and liver of the adult migratory Southern Hemisphere lamprey Geotria australis, a representative of the agnathan (jawless) stage in vertebrate evolution. During the spawning run, the mean CPT capacity at 20°C remained relatively constant in the muscle at 115 to 153 nmol/min.g, whereas in the liver it increased from a minimum of 162 nmol/min.g after four months of migration to 705 nmol/min.g at sexual maturity. The maintenance of a substantial capacity for CPT activity in the muscle, when the animal is relatively inactive during the middle phase of the run, would enable the animal to respond at such times to any environmental exigencies. It is proposed that the very high CPT capacity in the liver at sexual maturity is associated with an increased demand for ATP generation to facilitate the synthesis of glycogen that occurs in lampreys at this time. The trends shown by the activity of cytochrome c oxidase in the liver and muscle parallel those of CPT, presumably reflecting the corresponding metabolic changes that are required by the animal. The results of the present and other studies indicate that the ability to store large amounts of lipid as triacylglycerol, to bind and transport nonesterified fatty acids in the blood and to utilise a CPT‐dependent oxidative capacity in both the muscle and liver was present early in vertebrate evolution. © 1993 Wiley‐Liss, Inc.
Rate of establishment of a fertilising population of spermatozoa in the sheep cervix after a single mating at the onset of oestrus
Authors: Hunter R. H. F. , Nichol R. 
Published: June 2005

AbstractIn order to study how soon a population of spermatozoa capable of fertilisation could progress into the cervical canal, the vaginal contents were flushed with a detergent solution at different intervals after mating at the onset of oestrus. Eggs recovered 1 or 2 days later from the oviducts were stained and examined by phase‐contrast microscopy. Flushing at 3 minutes after mating did not prevent fertilisation in 44% of instances, whereas similar flushes performed at 6 or 9 minutes completely prevented fertilisation in a total of 26 animals. In the groups flushed at 12 and 15 minutes, the proportion of eggs fertilised was 21% and 24%, respectively, and this increased to 37% after flushing at 18 minutes. An explanation is offered for the paradoxical finding at 3 minutes, and it is concluded that at least 30–60 minutes would be required for adequate colonisation of the cervix with a fertilising population of spermatozoa under the conditions employed in the experiment. However, multiple matings or mating closer to the time of ovulation might act to reduce this interval. © 1993 Wiley‐Liss, Inc.
Effects of an antiandrogen treatment on the antler cycle of male fallow deer (Dama dama L.)
Authors: Kierdorf Uwe , Schultz Michael , Fischer Klaus 
Published: June 2005

AbstractWeekly application of the antiandrogen cyproteron acetate (CA) to 3 adult (group 1, treatment starting 3 weeks prior to the rut) and 4 subadult (group 2, treatment starting after the rut) fallow bucks led to premature antler casting after about 9 weeks (group 1) or 16 to 17 days (group 2). Variation in time span between onset of CA administration and induced casting (in late November/early December) is attributed to age‐ and season‐dependent differences in androgen levels before and during the treatment period. Casting surfaces of the antlers were flat. In all bucks, casting was followed by a complete though shortened antler cycle, occurring under short day conditions. In February/March velvet was shed from the antlers, indicating a rise in plasma androgen levels at that time. At time of fraying, antlers exhibited signs of immaturity and were shorter than normal. In the most pronounced case of immaturity, the antlers consisted mainly of cancellous woven bone, revealing that bone remodeling and antler mineralization had not occurred to a larger extent. These observations prove that onset of fraying behaviour does not depend on prior maturation of antler bone or necrosis of velvet. Occurrence of the additional antler cycle in late autumn and winter had no negative effect on subsequent antler formation starting in the following spring. © 1993 Wiley‐Liss, Inc.
Gestation and placentation in two new world opossums: Didelphis virginiana and Monodelphis domestica
Authors: Harder John D. , Stonerook Michael J. , Pondy Jacqueline 
Published: June 2005

AbstractEstrus, gestation, and placentation were studied in the Virginia opossum (Didelphis virginiana) and the gray short‐tailed oppossum (Monodelphis domestica), representatives of the prototypic, New World marsupial family Didelphidae. Didelphis is a large (3,000 g), pouched opossum that exhibits a 28‐day estrous cycle, spontaneous estrus and ovulation, and a high ovulation rate (60 ova per cycle). Monodelphis is a small (100 g), pouchless opossum with male‐induced estrus and ovulation and a moderate ovulation rate (12 ova per cycle). Implantation occurs on day 10 of the 13‐day gestation period in Didelphis and on day 12 of the 15‐day gestation in Monodelphis. Gestation and placentation, including the ultrastructural features of trophoblastic apposition to the uterine mucosa, are very similar in Didelphis and Monodelphis. Differences, such as a larger increase in uterine volume and a more highly folded endometrium following implantation in Monodelphis are minor. They appear to be related to the smaller maternal body size and the relatively larger uterine load of embryos in Monodelphis. Because body size is one of the major variables among New World marsupials, the descriptions of gestation and placentation presented here for Didelphis and Monodelphis, provide a basis for comparison in future studies of didelphid marsupials. © 1993 Wiley‐Liss, Inc.
Giant and binucleate trophoblast cells of mammals
Authors: Hoffman Loren H. , Wooding F. B. P. 
Published: June 2005

AbstractThe cellular origin, structure, and function of trophoblastic giant cells (GC) and binucleate cells (BNC) are reviewed. Mammals in which these cells have received the greatest attention include rodents, rabbits, and humans (GCs), and ruminants and equids (BNCs). In almost all cases these cells arise from the cytotrophoblast. All are large cells and contain either two diploid nuclei (BNCs), multiple nuclei (human placental bed GCs), or single nuclei with amplified DNA content (rodent and rabbit GCs). Giant and binucleate cells typically exhibit the capacity for migration or invasion, although the degree of migratory activity varies between species. While most end up within, or at the interface with, endometrial tissue, in some instances the GCs or BNCs contribute directly to the interhemal membrane of the placenta. Hormone production is a property which most GC‐BNC populations have in common. Lactogen or gonadotropin has been documented in almost all cells of this type examined to date, and in some animals they are also steroidogenic (e.g., rats and sheep). In spite of some common features, both structural and functional differences remain and it is suggested that use of terms such as mononuclear giant cells, multinucleate giant cells, and binucleate cells be continued rather than assuming that these cells are all members of a single trophoblastic subtype. © 1993 Wiley‐Liss, Inc.
Structural interactions of trophoblast and uterus during hemochorial placenta formation
Authors: Enders Allen C. , Welsh Alerick O. 
Published: June 2005

AbstractIt is argued that the successful placental arrangements are those that decrease the exposure of the trophoblast to the efferent side of the cellular immune response. Examples are taken from three different groups with hemochorial placentation, to show that their placental morphology places most of the trophoblast in contact with maternal blood, not maternal connective tissue. In addition, maternal cells of the junctional area are modified either before contact with trophoblast (rat) or just after trophoblast invasion (primate), or the region of contact is limited as in the armadillo, in which maternal blood sinuses are expanded to form intervillous spaces. © 1993 Wiley‐Liss, Inc.
Carbohydrate metabolism in the brain of the adult lamprey
Authors: Foster Glen D. , Youson John H. , Moon T. W. 
Published: June 2005

AbstractCarbohydrate metabolism was examined in brain pieces isolated from spawning (anadromous, New Brunswick, N.B.) and prespawning upstream migrant (landlocked, Toronto) lampreys (Petromyzon marinus). Brain glycogen concentration in the N.B. lampreys was 2.61 μmol mg−1 protein or 286 μmol g−1 tissue wet wt., significantly above that in the Toronto group (0.34 μmol mg−1 protein; 37 μmol g−1 tissue wet wt.). When glucose was added to an incubate of brain pieces, there was no change in glucose concentration, except in the presence of 10−7 M insulin, which resulted in net glucose uptake by the tissue. Glucose was metabolized by the brain pieces to both glycogen and CO2, with 12% (N.B.) and 32% (Toronto) of the glucose converted to glycogen. Insulin significantly increased glucose flux to glycogen, and epinephrine increased glucose flux to both CO2 and glycogen. Total lactate utilization by the brain pieces was greater than glucose utilization. Although only 2% of the utilized lactate was converted to glycogen, glycogen synthesis from lactate was 25–30% of glycogen synthesis from glucose. PEPCK activities were found in the brain, indicating the potential for a traditional gluconeogenic pathway. This study supports the hypothesis that gluconeogenesis from C3 substrates can contribute to brain glycogen synthesis in adult lamprey. © 1993 Wiley‐Liss, Inc.
Scotopic spectral sensitivity of the optomotor response in the green treefrog Hyla cinerea
Authors: King Richard B. , Douglass John K. , Phillips John B. , Baube Charles L. 
Published: June 2005

AbstractAmphibians are unusual among vertebrates in having two spectral classes of rod photoreceptors, unique amphibian “green” rods and typical vertebrate “red” rods. Although amphibians have been the subject of extensive research on visual function, it is not known whether possession of two classes of rods is a general feature of Amphibia, nor is it clear to what behaviors each class of rods contributes. The Hylidae comprise one of the largest families within Amphibia but have been little studied with respect to visual function. Here, we demonstrate the presence of green and red rods in Hyla cinerea by microspectrophotometry and provide evidence for the contribution of green rods to one visually based behavior, the optomotor response. In addition, we discuss the role of green and red rods in visually based behavior in light of apparently conflicting demands resulting from the need to maximize absolute sensitivity, visual acuity, and color sensitivity. © 1993 Wiley‐Liss, Inc.
Fiber growth initiation in hair follicles of goats treated with melatonin
Authors: Nixon Allan J. , Choy Vernon J. , Parry Althea L. , Pearson Allan J. 
Published: June 2005

AbstractThe sequence of structural changes in goat hair follicles was investigated using melatonin implants to advance and synchronize spring hair growth. Ten pasture fed cashmere wethers each received a controlled release formulation of 70 mg of melatonin on September 1 1989, and showed plasma melatonin elevated above physiological levels over 14 days post‐treatment (914 ± 154 pg/ml [mean ± SEM] on day 14). In ten untreated animals, daytime plasma melatonin was 19.9 ± 4.7 pg/ml. Histological examination of skin biopsies taken over the 14 days from the start of the experiment showed that primary hair follicles of goats with manipulated hormone levels had initiated fiber growth (entered proanagen), whereas primary follicles of untreated goats largely remained in the quiescent phase (telogen). A standardized terminology was used to describe the sequence of events during induced proanagen. Structural reorganization of follicles began in treated animals between days 6 and 12 post‐treatment, and emergent fibers grew by day 24. Advancement of spring fiber growth was associated with a suppression of the normal rise in plasma prolactin concentration. Prolactin levels in untreated goats increased from 7.4 ± 1.8 ng/ml on day 1 to 12.8 ± 1.6ng/ml on day 14, but declined in treated goats from 6.3 ± 2.3 ng/ml to 2.2 ± 0.8 ng/ml over the same period. © 1993 Wiley‐Liss, Inc.