摘要:

AbstractIn the red‐eared slider turtle,Trachemys scripta, sex is determined by the incubation temperature of the egg: warm temperatures produce females, cool ones produce males, and a narrow range of intermediate temperatures produce both sexes. We asked whether the influence of temperature is modified by the effects of carbon dioxide. Under one current hypothesis, sex is more closely linked to total incubation time and than to temperature. Higher levels of carbon dioxide should lengthen total incubation time and thus mimic the longer incubation times produced by low incubation temperatures. By this hypothesis longer incubation times should increase the tendency to produce males.Trachemys scriptaeggs were incubated in atmospheres containing various concentrations of carbon dioxide. While total incubation times were significantly lengthened with elevated carbon dioxide (as if mimicking cool temperatures), sex ratios were altered in favor of females (as if mimicking warm temperatures). This result is compatible with a hypothesis that pH changes affect sex in turtles with TSD. Turtles incubated at elevated levels of carbon dioxide absorbed less yolk, and had more residual yolk, and were somewhat smaller than turtles incubated at lower of carbon dioxide. In some cases, clutches were heterogeneous in their responses to the various levels of carbon dioxide. © 1992 Wiley‐Liss,

ISSN:0022-104X    

DOI:10.1002/jez.1402640102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe possible mechanisms of Cl−‐exit across the basolateral membrane of the enterocyte in sea water (SW) and freshwater (FW) eel intestine were investigated by observing the response of the short‐circuit current, Isc, equivalent to net Cl−‐absorption, and transepithelial voltage, Vt, to specific or relatively specific inhibitors of different Cl−‐transport pathways. Serosal NPPB [5‐nitro‐2(3 phenylpropylamino)‐benzoate] (10−4M), the potent blocker of Cl−‐channels in different epithelia, produced a negligible effect on Iscand Vteither in presence or in absence of HCO3−in the bathing solutions. In the presence of HCO3−serosal bumetanide, better than furosemide and torasemide, at a concentration of 10−4M inhibited Iscand Vtby ∼90% within 15–30 min without changing the transepithelial resistance, Rt. In HCO3−‐free solutions the drug completely collapsed Iscand Vt. The results were similar in both SW and FW eels. In SW fishes serosal SITS (2.5 × 10−4M) reduced Iscand Vtby ∼50% when HCO3−was present in the solutions. In absence of HCO3−SITS inhibited Iscand Vtby ∼35%, a finding consistent with the presence of a Cl−‐conductance in the basolateral membrane. Under these conditions SITS inhibition disappeared after bumetanide pretreatment. There is little evidence for the presence of a basolateral K+‐conductance since serosal Ba2+(1 mM) elicited variable effects on Iscand Vt.The results are interpreted as evidence for the presence of bumetanide‐ and SITS‐sensitive Cl−‐ conductance channels in the basolateral membrane of SW and FW eel intestine which would contribute at least 35% of the net Cl−‐absorption. An HCO3−‐dependent Cl−‐transport was also identified since Iscand Vtwere reduced by ∼

ISSN:0022-104X    

DOI:10.1002/jez.1402640103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractHypoosmotic 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 of3H2DIDS 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 of3H2DIDS 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

ISSN:0022-104X    

DOI:10.1002/jez.1402640104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe division mechanism of animal cells is positioned by the mitotic apparatus. The mitotic apparatus determines the position by a pattern of regional inequality of its effect on the surface and cortex. Because the effect of the asters decreases with distance, the location of the division plane can be manipulated geometrically. It follows that cytokinesis should be preventable by imposition of a cell shape that prevents the normal pattern of unequal aster effect. The shape that inhibits division reveals something of the normal pattern of aster effect as well as the nature of the immediate response of the surface to the aster.In 13 of 13 experiments, sand dollar (Echinarachnius parma) eggs fail to cleave when the polar and subpolar regions are extruded in the mitotic axis, although some surface contraction may develop in the extruded region. Extrusion was accomplished by sucking the appropriate regions into opposed pipets. A computer model of the relative aster effect in this circumstance indicates that the minimum is at the equator, and the maximum is in the extruded regions. These experiments indicate that furrows do not form where the aster effect is minimal. Previous experiments showed that cells divide when cells are artificially constricted in the equatorial plane where the aster effect is maximal. Together, the geometrical experiments strongly suggest that furrowing activity occurs in maximally affected areas. These results are consistent with the equatorial contraction theory of cell division, but inconsistent with the aster relaxation theory. © 1992 Wiley‐Liss, I

ISSN:0022-104X    

DOI:10.1002/jez.1402640105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe 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. ©

ISSN:0022-104X    

DOI:10.1002/jez.1402640106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractTwo experiments were performed to test putative puberty‐accelerating pheromones. In the first experiment, 37 weanling female house mice of the ICR strain were exposed to 1 of the following 3 treatments: an airborne mixture of 0.05 M isoamylamine and 0.05 M isobutylamine, fresh male mouse urine, or distilled water, as the control. Neither the amine mixture nor the male urine accelerated first estrus in the mice following airborne exposure to these compounds. In the second experiment, 37 weanling female mice of the same strain were exposed to the same chemicals as in the first experiment by direct contact to the oro‐nasal groove. The mixture of isoamylamine and isobutylamine did not accelerate puberty, but direct contact with the male urine accelerated puberty as evidenced by uterine weights. © 1992 Wiley‐Lis

ISSN:0022-104X    

DOI:10.1002/jez.1402640107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractProlactin (PRL) is thought to play a significant role in the freshwater (FW) adaptation of euryhaline teleost fishes, including the tilapia,Orechromis mossambicus. Two PRLs (tPRL188and tPRL177) have been characterized in the anteriormost portion of the tilapia pituitary, the rostral pars distalis (RPD; Specker et al., '85a,b; Yamaguchi et al., '88). Our studies were undertaken to determine whether the in vivo RPD content of tPRL188and tPRL177varied with environmental salinity. To this end, tilapia were reared from the period of yolk‐sac absortion for 7 months or acclimated for 21 and 35 days in FW or seawater (SW). In a parallel study, we also examined whether the release of the 2 tilapia PRLs from the RPD of FW or SW tilapia might be differentially sensitive to changes in medium osmotic pressure during 18–20 hr incubations. In agreement with earlier work, we found that the smaller tPRL177molecule was present in greater quantities in the RPD of FW tilapia compared to the content in RPD of SW fish. For the first time, we show here that the content of tPRL188, like that of tPRL177, is also significantly greater in the RPD of FW fish compared to the quantity in RPD of SW tilapia. Nevertheless, the relative content or ratio of the 2 PRLs in the pituitary was dependent on rearing salinity. Thus, the relative content or ratio of the larger tilapia PRL to smaller PRL (tPRL188/tPRL177) in the RPD of FW tilapia was significantly higher (1.5:1) than that seen in SW fish (0.75:1). This ratio was not altered after 18–20 hr in vitro incubations in hyposmotic or hyperosomtic medium, suggesting that the shift in ratios did not result from differential release by osmotic pressure. During 18–20 hr incubation in either hyposmotic or hyperosmotic medium, the RPD of FW tilapia released more of both forms of PRL than did the RPD of SW fish. Consistent with previous studies, reductions in medium osmotic pressure within the physiological range of the tilapia stimulated the release of botg tPRL188and tPRL177from RPD of FW fish over levels observed during exposure to hyperosmotic medium. We report here, for the first time, that the reduction of medium osmotic pressure also stimulates the release of both tPRL188and tPRL177from RPD of SW fish. Throughout the experiments we did not observe differences between the release of tPRL188and tPRL177under our incubation conditions. The transfer of FW‐reared fish to SW and vice versa for 49 days altered the ratio of the 2 PRLs (tPRL188/tPRL177) to that observed in the RPD of SW‐reared and FW‐reared fish, respectively. Overall, our studies indicate that the processing of the 2 PRLs may be differentially sensitive to environmental salinity. © 1992 W

ISSN:0022-104X    

DOI:10.1002/jez.1402640108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractChanges in ovarian morphology, brain gonadotropin‐releasing hormone (GnRH), plasma estradiol, and progesterone were examined during the 1988 and 1989 spawning migrations of the adult female sea lamprey,Petromyzon marinus. There were significant increases through time in brain GnRH (1989) and plasma estradiol (1988 and 1989), with progesterone levels fluctuating (1988 and 1989) during the freshwater phase of the spawning migrations. In 1989, brain GnRH and plasma estradiol levels gradually increased through time until just prior to spawning when levels decreased. During 1988, there were no significant changes in GnRH, which may reflect lower temperatures in that year. These data provide new information on brain GnRH during final maturational processes in the female sea lamprey. © 1992 Wiley‐Liss,

ISSN:0022-104X    

DOI:10.1002/jez.1402640109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractTraditional limb regeneration studies have been focused on events transpiring during or subsequent to the 24–48 hour wound healing stage. In this study, amputation‐induced changes in limb protein expression were identified during the first few hours following amputation of the limb. These changes included the elevated expression of several amputation‐induced proteins (AIPs). Exposure of newts to a temperature of 37°C also resulted in teh enhanced synthesis of several heat shock proteins (HSPs) in similar molecular weight ranges. However, the amputation and heat shock responses differed in terms of the relative levels of induction of the various protein size classes. Furthermore, amputation resulted in the induction of an array of proteins that differed from those induced by heat shock. Unlike HSPs, AIPs were found to be synthesized exclusively in the forelimb tissue and were not seen in brain, liver, hindlimb, or tail tissues of forelimb‐amputated animals. However, AIP synthesis was not localized to limb tissue adjacent to the amputation site but rather was found at similar levels throughout the entire forelimb area. Moreover, in unilaterally amputated animals AIPs were found in both the amputated limb and the unamputated, contralateral limb. In addition to induced proteins, amputation also resulted in the suppression of several protein species. The latter occurred rapidly following amputation and was localized within the forelimb tissue immediately adjacent to the amputation site but not in proximal limb tissue. © 1992 Wiley

ISSN:0022-104X    

DOI:10.1002/jez.1402640110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractForelimbs of the adult mud frogRana rugosa, when amputated midway through the zeugopodium, regenerate heteromorphically. The resulting regenerative outgrowths were mostly rod shaped and consisted of a cartlaginous core, in which the base was ossified, and muscle elongated distally along the cartilage, the whole being covered by connective tissue and skin. The tip of the regenerating muscle reached a point distally about one third of the length of the regenerative outgrowths. When the innervation of forelimb stumps was augmented by surgical diversion of the ipsilateral sciatic nerve, the amputated limbs regenerated mostly as spatula‐shaped outgrowths, which were longer those of normally innervated forelimbs. Such hyperinnervated regenerates exhibited less ossification of cartilage, or sometimes none at all. However, the regeneration of muscle was more extensive. That is, it reached more than half way along the regenerative outgrowth. Furthermore, denervation resulted in the absence of regeneration in all cases examined. Theses results clearly indicate that limb regeneration inRana rugosais dependent upon the degree of innervation, not only for the early stages of regeneration, but also for the growth and differentiation of the regenerative outgrowth. © 1992 Wiley‐Liss,

ISSN:0022-104X    

DOI:10.1002/jez.1402640111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY