bluuebunny/crossref_metadata_2025 huggingface dataset:
Continuous cell movements rearrange anatomical structures in intact sponges
Authors: Bond Calhoun
Published: June 2005

Time‐lapse cinemicrography was used to record the active movements of cells in living intact sponges. Each of the three main cell types (pinacocytes, mesohyl cells, and choanocytes) continuously moved and rearranged themselves so that the internal anatomy of the sponge was continuously remodeled. The shape and appearance of the sponges' anatomical structures often changed substantially within a few hours.

The most motile were the mesohyl cells, with many moving as fast as one cell‐length per minute (15 μm/min). Mesohyl cell locomotion was often accompanied by displacements of spicules, canals, and choanocyte chambers; the patterns of these displacements suggested that the mesohyl cells were providing the motive forces for these rearrangements. The locomotion of the pinacocytes varied according to position: those along the outer sponge margins were most active, whereas those in other parts of the surface moved relatively little. Choanocytes were never observed to undergo independent locomotion but were always found grouped together in choanocyte chambers. These choanocyte chambers interacted with pinacocytes and mesohyl cells to form excurrent canals, which continuously moved, fused with, and branched from one another.

These observations suggest that the experimental phenomenon of sponge cell‐reaggregation and reconstitution, discovered by H. V. Wilson, represents an extreme version of morphogenetic processes that normally go on continuously within intact sponges. The results from the present study also suggest that these cellular rearrangements are controlled by active cell movements and behavioral responses that include but are not limited to selective cell adhesion. © 1992 Wiley‐Liss, Inc.
Effects of diapause on lethal Yellow (Ay/Ay) mouse embryos
Authors: Papaioannou Virginia E. , Gardner Richard L.
Published: June 2005

One of the problems in studying early acting recessive lethal genes is recognizing the homozygotes prior to their demise. Molecular probes can assist in this task, but their use generally requires removal of cells and consequent damage to the embryo, which may compromise its subsequent development. The present study was undertaken in an attempt to distinguish intact, living, lethal yellow (Ay/Ay) embryos from Ay/ae and ae/ae littermates before implantation by placing them in implantation delay or diapause. After 2 days in the reproductive tract of prepubertal females, the great majority of presumptive lethal Ay/Ay embryos had failed to hatch from the zona pellucida and they exhibited a marked deficiency of cells relative to controls, particularly in the inner cell mass. This argues against a stage‐specific role for the gene in implantation. © 1992 Wiley‐Liss, Inc.
Mitochondrial respiration in locust flight muscles
Authors: Suarez Raul K. , Moyes Christopher D.
Published: June 2005

Highly coupled mitochondria isolated from locust flight muscles display substrate preferences consistent with the use of carbohydrate and lipid as the major metabolic fuels during flight. Maximal rates of coupled respiration expressed per milligram mitochondrial protein exceed by severalfold published values obtained using vertebrate muscle mitochondria. These differences in maximal rates of coupled respiration in vitro are apparent even when rates are expressed per unit mitochondrial marker enzyme (citrate synthase) activity or per unit mitochondrial volume (exchangeable water space). Locusts in flight achieve a greater fraction of the flux measured in vitro through cytochrome oxidase than mammals exercising at maximum aerobic capacity. These data suggest that besides possessing “better” mitochondria, locusts may possess higher capacities for O2 (and/or substrate) delivery, allowing the achievement of higher rates of respiration in vivo than in mammals. © 1992 Wiley‐Liss, Inc.
Dopamine catabolism in goldfish (Carassius auratus) brain and pituitary: Lack of influence of catecholestrogens on dopamine catabolism and gonadotropin secretion
Authors: Sloley B. Duff , Trudeau Vance L. , Peter Richard E.
Published: June 2005

The catabolic pathways for dopamine degradation in the goldfish brain and pituitary were investigated. The major dopamine catabolite formed in vivo after L‐dihydroxyphenylalanine or dopamine injection was dihydroxyphenylacetic acid. Homovanillic acid and 3‐methoxytyramine are also formed but to a much lesser extent. In vitro studies also indicate that the major dopamine catabolite produced by pituitary tissue is dihydroxyphenylacetic acid. Pargyline at a dose which, in mammals, inhibits both monoamine oxidase A and B, and clorgyline at a dose which inhibits monoamine oxidase A, elevates dopamine concentrations in goldfish pituitary. Deprenyl at a dose which inhibits mammalian monoamine oxidase B or dinitrocatechol (OR‐468) which inhibits catechol‐O‐methyltransferase had no effects on pituitary dopamine concentrations in goldfish. Basal serum gonadotropin concentrations are reduced by injection of monoamine oxidase inhibitors but not by injection of the catechol‐O‐methyltransferase inhibitor. The neurotoxin 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP), which appears to require monoamine oxidase for its activity, selectively depletes noradrenaline and dopamine in the goldfish brain and pituitary. Intraperitoneal injection of large amounts of the catecholestrogens 2‐hydroxyestradiol or 4‐hydroxyestradiol (1 μg/g each hour for 5 hours) has no effect on brain or pituitary dopamine concentrations or serum gonadotropin levels. Catecholestrogens are normally not detectable in goldfish brain and pituitary; however, following intraperitoneal injection substantial amounts are measurable in the brain and pituitary. © 1992 Wiley‐Liss, Inc.
Taurine efflux, band 3, and erythrocyte volume of the hagfish (Myxine glutinosa) and lamprey (Petromyzon marinus)
Authors: Brill Susan R. , Musch Mark W. , Goldstein Leon
Published: June 2005

Hypoosmotic stress in skate RBC causes cell swelling followed by the release of solutes (osmolytes) to bring about a regulatory volume decrease (RVD). The β‐amino acid, taurine, is a primary osmolyte in RVD of skate RBC. Taurine efflux is inhibited by stilbene disulfonates and other inhibitors of the anion exchanger, band 3, suggesting that band 3 is involved in the release of taurine during RVD in skate RBC. Since RBC of the cyclostomes, hagfish and lamprey, are reported to be deficient in band 3, we examined taurine efflux, quantity of band 3, and volume response in these RBC. There was no significant increase in taurine efflux when hagfish RBC were exposed to hypoosmotic medium, and the rate of taurine efflux in these RBC was markedly lower than that in skate RBC. Hagfish RBC plasma membranes show only 11% of the level of 3H2DIDS bound to skate RBC membranes. In addition, DIDS‐sensitive sulfate exchange is much lower in hagfish compared with skate RBC. Similarly, lamprey RBC showed little taurine efflux compared with skate, and the amount of 3H2DIDS binding to these RBC membranes was 24% that of skate. Finally, although both hagfish and lamprey RBC swell in hypoosmotic medium, the lamprey cells show an RVD while the hagfish cells do not. Thus, in the RBC of the two cyclostomes, one showing an RVD and the other not, low band 3 is associated with low volume‐activated taurine efflux. These results support the hypothesis that band 3 is involved in volume‐activated taurine efflux. © 1992 Wiley‐Liss, Inc.
Influence of hypothalamic‐pituitary‐adrenocortical hormones on reproductive hormones in gray wolves (Canis lupus)
Authors: Kreeger Terry J. , Seal Ulysses S. , Plotka Edward D.
Published: June 2005

The release of hypothalamic‐pituitary‐adrenocortical hormones was studied in intact and neutered gray wolves (Canis lupus) to determine how these hormones interact and affect reproductive hormones. Experiments were performed on adult wolves anesthetized with 400 mg ketamine and 50 mg promazine. Intravenous (i.v.) injections with 50 μg ovine corticotropin releasing factor (oCRF) significantly increased adrenocorticotropin (ACTH; P ≤ 0.01), cortisol (CORT; P ≤ 0.004), and progesterone (P ≤ 0.036), but not β‐endorphin (P ≥ 0.52). Since neutered wolves demonstrated dose‐dependent elevations in response to ACTH, it was concluded that the progesterone was secreted from the adrenal gland. Basal luteinizing hormone (LH) concentrations in neutered wolves were similar before and 60 min after i.v. injection of 1, 5, or 25 IU ACTH (P ≥ 0.36) or 2.2 mg/kg cortisol (P = 0.42). Neither 25 IU ACTH (P = 0.55) nor 0.22 mg/kg dexamethasone (P = 0.49) altered the LH response to injection of LH releasing hromone in neutered wolves. Chronic administration of 0.22 mg/kg/day dexamethasone for 3 d did not alter baseline LH concentration (P = 0.75). Injection of 1.0 mg/kg naloxone (NAL), however, increased LH concentrations relative to baseline values in both intact (P = 0.032) and neutered (P = 0.0005) female wolves, but no in intact (P = 0.19) or neutered males (P = 0.07). These results indicated that in gray wolves (1) oCRF stimulated the release of pituitary and adrenal hormones in a fashion similar to that of other mammals; (2) the adrenal cortex was capable of secreting progesterone into the systemic circulation; (3) exogenous glucocorticoids did not alter LH concentrations; and (4) endogenous opioids may modulate LH secretion in female wolves. © 1992 Wiley‐Liss, Inc.
The possible role of vena cava peptides in regulation of the branchial hearts of Sepia officinalis L. (cephalopoda)
Authors: Fiedler Armin
Published: June 2005

An analysis was made of the effects of 5 neuropeptides on the isolated branchial heart of Sepia officinalis. There is evidence to suggest that these 5 neuropeptides occur in the neurosecretory system of the vena cava (NSV system) of cephalopods. YGGFMRFamide and oxytocin caused concentration‐dependent increases in pressure amplitude in the perfused preparations, with their effects on heart rate being negligible. The molluscan neuropeptide FMRFamide hardly had any effect on the branchial heart beat when applied alone, but it counteracted the positive inotropic actions of noradrenaline. FLRFamide and α‐melanotropin had no effect in our system. None of the peptides tested in bioassays on branchial hearts was as efficient as a perfusate obtained from the cephalic vein of Sepia (including the NSV area) that had been stimulated by electrical irritation of the attached visceral nerves. These findings suggest that there may be further neurohormones in the NSV system that are released into the vessel lumen. It is suggested that the branchial hearts of Sepia in vivo are influenced by humoral peptides from the NSV system and that these peptides may act directly on target myocytes or may alter (i.e., potentiate or oppose) the effects of other cardioactive compounds. © 1992 Wiley‐Liss, Inc.
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

In 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

Common 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

In 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

Genes 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

The 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

In 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

The 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

Freshwater 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

The 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

Previous 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

The 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

The 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

The 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

The 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

The 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.
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

The 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

Studies 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

The 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

Plasma 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

The 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

The 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

The 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

In 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.