摘要:

AbstractA quantitative analysis of the muscle activity patterns (motor patterns) used by tiger salamanders (Ambystoma tigrinum) during terrestrial feeding is presented to provide comparative data on motor output during prey transport in amphibians, compare prey transport motor patterns to those used during initial prey capture, and test the generality of previously proposed models of the feeding cycle in tetrapods.Simultaneous electromyographic and kinematic recordings during prey transport reveal four phases in the prey transport cycle. The Preparatory phase precedes prey transport with activity found mainly in muscles of the buccal floor (genioglossus, geniohyoideus, interhyoideus, and inter‐mandibularis), but with all muscles silent at the end of this phase. Prey transport occurs during the Fast Opening and Closing phases. The Fast Opening phase begins with near simultaneous onset of activity in all jaw and hyoid muscles, including anatomical antagonists such as the depressor mandibulae and adductor mandibulae. The subarcualis rectus one muscle is active during the Fast Opening and Closing phases of transport despite the lack of accompanying tongue projection and may function to stabilize the hyobranchial apparatus. The motor pattern of terrestrial prey transport differs considerably from that of initial prey capture, but appears to be similar to the motor pattern used during aquatic prey capture and hydraulic prey transport. We hypothesize that post‐metamorphic tiger salamanders accomplish terrestrial prey transport by retaining the larval motor pattern employed during suction feeding. The motor pattern and kinematics of prey transport inAmbystoma tigrinumdiffer in nearly all aspects from previous models of the generalized tetrapod feeding cy

ISSN:0022-104X    

DOI:10.1002/jez.1402600102

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

年代:1991

数据来源: WILEY

摘要:

AbstractPrevious studies have revealed that freshwater bivalves subjected to acid stress suffer from severe electrolyte imbalance. A typical initial reaction is a transitory increase in concentration of Ca in the hemolymph during the first few days of exposure to such stress. Although this calcium obviously originates from the CaCO3reserves in the clam, a possible ambient origin has never been ruled out. In the present study the uptake of Ca was studied under both circumneutral and acid conditions: two freshwater unionids,Anodonta anatinaandUnio tumidus, were exposed to a bathing medium that contained45Ca for a period of 24 hrs. In order to study the effect of the ambient Ca concentration on the efficiency of uptake of Ca, two media with different Ca concentrations (35 and 3.5 mg Ca/1; 4 × 106cpm45Ca/1 and 4 × 105cpm45Ca/1, respectively) were used. The role of the ingested food as a source of Ca was evaluated by feeding the clams with algae labeled with45Ca. After the clams had been exposed for 24 hrs to45Ca, the accumulation of45Ca in the soft parts, including hemolymph, calcium concretions and glochidial larvae, was measured. Low pH (4–4.5) significantly decreased the uptake of45Ca from the medium, whereas the addition of aluminum (900 μg/1) had only a minor effect on the uptake of45Ca. The sites of accumulation of45Ca under acidified conditions did not change: in all cases highest values for45Ca concentration were measured in the gills, where the calcium concretions sequestered a large part of the45Ca. A 90% decrease in the ambient Ca concentration caused a similar decrease in the uptake of45Ca. Clams were able to utilize both dietary and waterborn

ISSN:0022-104X    

DOI:10.1002/jez.1402600103

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

年代:1991

数据来源: WILEY

摘要:

AbstractWe studied the effect of noradrenaline on the methaemoglobin (metHb) concentration in rainbow trout red cells. The erythrocytes were incubated in physiological medium with or without noradrenaline and the percentage of metHb of total Hb content was measured. Noradrenaline lowered the metHb content significantly as compared to controls. To study if the effect of noradrenaline was caused by adrenergic intracellular alkalinization, cells were treated with noradrenaline + carbonic anhydrase or noradrenaline + acetazolamide. Carbonic anhydrase inhibits the adrenergic increase in intracellular pH, but did not reduce the effect of noradrenaline on the metHb concentration. Acetazolamide accentuates the increase in intracellular pH. However, there was no difference in the methaemoglobin content of noradrenaline‐incubated and noradrenaline + acetazolamide‐incubated cells. These results show that the effect of noradrenaline on the methaemoglobin content is independent from the adrenergic increase in intracellular pH. However, amil‐oride treatment inhibited the effect of noradrenaline on the methaemoglobin content, suggesting that the protein mediating sodium/proton exchange may also be involved in controlling cellular methaemoglobin l

ISSN:0022-104X    

DOI:10.1002/jez.1402600104

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe Berkner and Marshall hypothesis suggests that the atmosphere was virtually anoxic until the late Precambrian, and that the abrupt and coincidental appearance in the fossil record of the major animal phyla reflects the rise of PO2to a level that supported animal life. In a more recent version the rise of PO2is supposed to permit previously soft‐bodied animals, which had arisen during the anoxic period, to form fossilizable hard parts. The animal kingdom is conceived as fundamentally and primitively anaerobic and only secondarily aerobic. These ideas were incorporated into the Thiobiotic Theory, which supposes that a meiofauna endemic to the anoxic sulfide layer in marine sediments is a relict community of the pre‐normoxic Precambrian. This fauna consists of a number of simple metazoan phyla, including free‐living platyhelminths (but not cnidarians) which this theory regards as representatives of the ancestral Eumetazoa.The development of geological and ecological thinking about these hypotheses is summarized and the pertinent physiological evidence for and against them is briefly reviewed. I conclude that the available information does not support either the Berkner and Marshall Hypothesis or the Thiobiotic Theory, and is inconclusive on the identity of the ancestral animals. Moreover, several aspects of respiratory and metabolic biology are far more consistent with a fundamentally aerobic than anaerobic way of animal

ISSN:0022-104X    

DOI:10.1002/jez.1402600105

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe in vitro effects of sodium orthovanadate (Na3VO4), a G‐protein activator, on ovulation and prostaglandin (PG) synthesis were investigated in the brook trout (Salvelinus fontinalis) ovary. PGE and PGF levels in incubation medium of either extrafollicular (EF) tissue or follicles were measured by specific radioimmunoassays (RIA). PGE levels in follicle incubates were increased by Na3VO4at both pre‐germinal vesicle breakdown (preGVBD) and preovulatory (preOV) stages. However, an increase of PGF levels in follicle incubates was observed only in preGVBD follicles in the presence of Na3VO4. The preOV follicles spontaneously released more PGF than preGVBD follicles and the level was not affected by Na3VO4treatment. In contrast, in incubates of EF tissue, Na3VO4induced dosage‐dependent increases in PGE and PGF at either stage. The Na3VO4‐stimulated increase of PGE in preOV follicle incubates was significantly reduced by the translational inhibitor, cycloheximide (5 μM), but not by the transcriptional inhibitor, actinomycin (5 μM). PGF levels in preOV follicle incubates were also significantly reduced by cycloheximide and actinomycin in controls, but not in the presence of 0.1 mM Na3VO4. The results suggest that protein synthesis was required for Na3VO4to increase accumulation of PGE, and in maintaining control PGF levels in preOV follicles. In addition, since PGF levels in preOV follicles were not reduced by either inhibitor in the presence of Na3VO4, a Na3VO4‐stimulated increase of PGF levels was unmasked that apparently acts through a non‐translational pathway. In vitro ovulation was also significantly increased by 0.1 mM Na3VO4. However, the Na3VO4‐induced ovulation was not inhibited by either actinomycin or cycloheximide. The data imply that the mechanism(s) by which Na3VO4induces ovulation are distinct from that for stimulating PG accumulation. When preOV follicles were incubated with 10 μM forskolin, no stimulatory effect on ovulation, or on PGE and PGF levels was observed. The data strongly indicate that the effects of Na3VO4on ovulation and ovarian PG levels were not mediated by an

ISSN:0022-104X    

DOI:10.1002/jez.1402600106

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

年代:1991

数据来源: WILEY

摘要:

AbstractVitellogenin (VTG) synthesis has been described as an ideal system to study the hormonal regulation of gene expression. InXenopusthe molecular aspects of this control have been analyzed; however, in other non‐mammalian species such as reptiles, very few studies approaching this level have been undertaken. We report on the induction by estradiol‐17β of VTG‐like proteins in liver explants from adult males and immature male and female lizards (A. pulchellus). A concentration of 10−7M was optimum for adult males while a higher concentration (10−6M) is required for the immature animals. No differences were observed in the hormonal induction in male and female immature animals, suggesting that there are no sexual distinctions in the liver at this stage.The effect of the hormone in male liver appears to be primarily on mRNA synthesis, since increases in3H‐uridine incorporation in total RNA were prevented by addition of 1 μg/ml of the RNA polmerase II inhibitor α‐Amanitin; however, rRNA synthesis was also increased as observed by agarose gel analysis. A 48 hr lag period was required for the detection of the intracellular as well as the secreted VTG‐like protein. Electrophoretical analysis of the secretory products revealed the induction of a group of phosphoproteins immunologically related to yolk lipovitellin whose molecular weights range from

ISSN:0022-104X    

DOI:10.1002/jez.1402600107

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe relation between seasonal changes in plasma thyroxine (T4) and T4binding activity was studied in three species of turtle previously shown to differ in the nature of their binding proteins; additional direct measurements of a high affinity T4binding protein (TBP) were made in one species using RIA. In the painted turtle,Chrysemys picta(Family Emydidae), a species with large seasonal changes in plasma T4, the binding protein measured by activity and RIA showed significant seasonality. Binding activity correlated with direct estimates of TBP by RIA. TBP was minimal upon emergence from hibernation and maximal in late summer (July–August), about a month after the peak in plasma T4. In contrast, two other nonemydid species, the green turtle (Chelonia mydas) and Mexican tortoise (Gopherus flavomarginatus) showed relatively low plasma T4and binding activity with no significant seasonality in either. Electrophoretic studies (PAGE) confirmed that T4binding inC. pictais almost wholly associated with a high affinity, low capacity TBP; whereas, it is confined to high capacity sites (probably albumin) in the other species. The transport of T4is clearly handled differently in these three turtles. In the green turtle and tortoise, one would expect relatively constant free T4(fT4) throughout the year. Marked seasonal fluctuations (an order of magnitude) in the ratios of TBP to total T4inC. pictadue to the temporal lag between the two may cause profound changes in fT4with peaks in late sprin

ISSN:0022-104X    

DOI:10.1002/jez.1402600108

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

年代:1991

数据来源: WILEY

摘要:

AbstractRanaovarian follicles at different developmental stages were obtained from frogs collected at different seasons. Isolated follicles were sorted into five different classes (Class I–V) by size and cytoplasmic pigmentation. They were incubated for 6 hours in amphibian Ringer in the presence or absence of frog pituitary homogenate (FPH, 0.05 pituitary/ml) and changes in steroid production by follicles were assessed by measuring estradiol (E2), testosterone (T), and progesterone (P4) in media and follicles by radioimmunoassay. Small follicles (size range 0.22–0.7 mm) secreted very low or non‐detectable levels of the three steroids in the presence or absence of FPH. Medium‐sized vitellogenic follicles (0.70–1.11 mm) actively secreted all the three types of steroids tested (E2, P4, and T). Larger follicles (1.15–1.58 mm), isolated during September–February, secreted much more T than E2and P4. In contrast, fully grown follicles (>1.50 mm) collected late in the hibernation period secreted more P4and less T than the large follicles and very low levels of E2; however, follicles (Class V) collected in breeding season (May) secreted solely P4and negligible amounts of T and E2. All types of follicles produced very low levels of the steroids without FPH stimulation. Intrafollicular levels of steroids essentially reflected those which accumulated in the medium. Oocyte responsiveness to exogenous hormone, as evidenced by germinal vesicle breakdown (GVBD), increased as the breeding season approached. The data indicate that only the medium‐sized follicles produced considerable amounts of E2while larger follicles produced mainly T and full‐grown follicles collected during breeding season

ISSN:0022-104X    

DOI:10.1002/jez.1402600109

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe ability of mouse forelimb buds at stage 1 (Wanek et al., '89a) of development to regenerate after amputation was investigated. The findings were as follows: 1. Outgrowths in the form of hillocks were found at the sites of amputation in 116 (95%) out of 122 embryos examined 24 hours after amputation. Examination of the amputated region after various intervals of time revealed that the outgrowths were established from flank tissues at the anterior and posterior borders of the wound. 2. Ectodermal thickening was found on the distal margin of the outgrowths in 21 (66%) out of 32 specimens examined. These thickenings were histologically similar to the apical ectodermal ridge (AER) present on the control limb buds. 3. Alkaline phosphatase activity was detected on the ectodermal thickening in 11 (79%) out of 14 experimental limb buds examined. The pattern of expression of alkaline phosphatase activity was similar to that observed in control limb buds. 4. There was no correlation between the size of the outgrowths and the presence of the ectodermal thickening or the enzymatic activity. The outgrowths developed despite the absence of ectodermal thickening and enzymatic activity, suggesting that the thickening and the presence of alkaline phosphatase are not crucial for the initiation and formation of the outgrowths. 5. Explants of the outgrowths, when grafted beneath adult kidney capsules, differentiated extensively into various tissues, which included bones, epiphyseal plates, skeletal muscles, and skin derivatives. Control explants also gave rise to the same spectrum of tissues. Hence, the flank tissues surrounding the site of amputation in E10 mouse embryos can regenerate to form a structure that is morphologically and histochemically similar to a limb bud and the mesenchyme within the structure is histogenetically competent to produce the variety of tissues that is normally found in the adult limb.

ISSN:0022-104X    

DOI:10.1002/jez.1402600110

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

年代:1991

数据来源: WILEY

摘要:

AbstractA putative defensive function of trichocysts inParameciumhas been tested experimentally. Cells of trichocyst‐non‐discharge (tnd) mutant, artificially induced trichocyst‐deficient cells, and intact wild‐type cells were compared as prey for a carnivorous ciliate,Dileptus margaritifer. Cells of tnd mutants were eaten 9–45 times faster than wild‐type cells by the predator inP. caudatumandP. tetraurelia. Encounters between paramecia and dilepti occurred in nearly the same frequency in mutant and wild‐type cells. Paramecia with reduced numbers of trichocysts were obtained inP. caudatum, P. jenningsi, andP. tetraureliaby treating wild‐type cells with lysozyme, an inducer of trichocyst discharge. These cells were eaten faster than intact cells by the predator and the rate of predation was inversely correlated with the remained capacity of trichocyst discharge. It was concluded that the discharge of trichocysts defends these species ofParameciumagainstD. margaritifer. Therefore, the results of this work strongly support the hypothesis that trichocysts inParameciumfunction as defensive organelles against predators. The results also support the hypothesis that the offense‐defense interaction betweenDileptusandPrameciumis mediated by their extrusomes (toxicysts and trichocysts) and suggest that extrusomes in ciliates function as organelles for interspecific cell

ISSN:0022-104X    

DOI:10.1002/jez.1402600111

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

年代:1991

数据来源: WILEY