摘要:

AbstractMature and intact red blood cells were found in hepatocytes of frogs during natural underground hibernation. No signs of erythrophagocytosis, e.g., separating membranes between erythrocyte and hepatocyte cytoplasm, and lysosomes, were observed. Red blood cells probably penetrated into hepatocytes by ameboid‐like mechanisms, which can be deduced by cytoplasmic protrusions and invaginations. Most of the hepatocytes had large amounts of stored glycogen and few organells, often segregated in condensed areas. The narrowed bile canalicular lumens without lysosomes and exocytotic vacuoles around them and the reduction of the Disse spaces indicate a low metabolic activity of liver during natural hibernation. The dramatic accumulation of red cells in the hepatocytes of hibernating frogs could share similarities with the phenomenon of internalization of leucocytes into epithelial cells of some vertebrate's tissues via emperipolesis, the mechanisms of which are not well understoo

ISSN:0022-104X    

DOI:10.1002/jez.1402580202

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

年代:1991

数据来源: WILEY

摘要:

AbstractEggs of softshell turtles (Trionyx spiniferus) were incubated on wet (water potential = −150 kPa) and dry (water potential = −1,500 kPa) substrates at 29°C. The rigid, heavily calcified eggshells restricted exchanges of water between eggs and their environment, but eggs exposed to wet substrates nonetheless contained more water at the end of incubation than eggs in the drier environment. However, differences in the amount of water contained by eggs had no demonstrable effect on patterns of metabolism and growth by embryos. The embryos in both treatments obtained about 75% of their calcium from the eggshell, but acquired all of their magnesium and phosphorus from the yolk. Residual yolk removed from hatchlings contained minimal quantities of all three elements. Thus, all the calcium mobilized during development was deposited in the carcass, and yolk was depleted of almost its entire store of this element. This pattern of mobilization and deposition of calcium is similar to that observed in embryos of other chelonians and in those of oviparous lepidosaurinas. In contrast, embryonic crocodilians and birds store some of the calcium mobilized from the eggshell in the yolk, and residual yolk consequently contains a substantial reserve of calcium. Our results indicate that the pattern of mobilization and deposition of calcium documented for birds and crocodilians probably is an attribute of the archosaurian lineage and not a simple result of embryos developing in rigid, heavily calcified eggsh

ISSN:0022-104X    

DOI:10.1002/jez.1402580203

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

年代:1991

数据来源: WILEY

摘要:

AbstractOrnithine decarboxylase (ODC) activity and polyamine levels were measured during early development of the frog,Microhyla ornata. ODC activity was found to be high and it showed three major peaks during the first 60 hr of development. Putrescine and spermidine levels increased gradually during the above period with little change in spermine. Treatment of developing embryos with exogenous putrescine and spermidine prevented the normal increase in ODC activity. Spermine did not have any significant effect. Addition of ornithine also prevented the increase in ODC activity. Experiment using exogenous ornithine and α‐methylornithine revealed that formation of putrescine and/or spermidine from ornithine is necessary for the suppression of ODC to occur. Suppression of ODC takes place even if conversion of putrescine to spermidine is blocked, indicating that putrescine, independent of its conversion to spermidine, also plays a role in ODC regulati

ISSN:0022-104X    

DOI:10.1002/jez.1402580204

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe bats,Noctilio leporinusandPizonyx vivesi, display similar hind foot morphologies specialized for their fish‐catching habits. The hydrodynamic drag force of isolated hind feet from fishing and closely related non‐fishing bats was measured in a water channel at velocities up to 0.74 ms−1. Drag force increased curvilinearly with increasing water velocity. The highest values of drag force for a given velocity were measured for the fishing bats, which have hind feet 1.8–3.9 times larger than related non‐fishing bats. However at high Froude Numbers, the dimensionless drag coefficient (CD) was 23–39% lower for fishing bats compared to non‐fishing bats. Cross‐sections of the laterally compressed toes ofN. leporinusandP. vivesiconformed to hydrofoil designs with minimum drag capabilities, indicated by Fineness Ratio and shoulder position. Moveing at high Froude Numbers at the water surface results in the addition of spray drag to the other components of the total drag force (i.e., frictional, pressure, and wave). Spray drag is suppressed by a foil shape with a long pointed leading edge with a short rounded trailing edge. The configuration of the fishing bat toe with a sharp leading edge and relatively long forebody region compared to the maximum thickness provided a measurable drag reduction at the air‐water interface. It was concluded that hydrodynamic drag considerations at the water surface were important in the design of hind feed for f

ISSN:0022-104X    

DOI:10.1002/jez.1402580205

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe presence and characteristics of a membrane‐bound adenylate cyclase fromMytilus galloprovincialismantle tissue has been investigated. Enzymatic activity was measured using α32P‐ATP as the substrate with chromatographic isolation of the32P‐cAMP formed. The enzyme has a Km for ATP of 0.35 mM at 20°C and requires divalent cations (Mg2+/Mn2+) for its activity. Optimal GTP concentrations are between 10−6M and 10−4M. The non‐hydrolyzable GTP analogs, GTPpNHp and GTPγS, increase the activity of the enzyme two‐ to fourfold. NaF stimulates the enzymatic activity ten‐ to 20‐fold. An inhibition of basal activity by ad

ISSN:0022-104X    

DOI:10.1002/jez.1402580206

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe effects of exogenous adenosine and adenine phosphorylated derivatives were tested on the adrenergic luminescence of isolated luminous organs of the fishPorichthys. Adenosine triphosphate, at concentrations ranging from 10−5M to 10−2M, strongly inhibited the two peaks of the biphasic‐shaped light emission induced by adrenalin. Adenosine diphosphate mimicked the effects of ATP, whereas adenosine monophosphate (AMP) and cyclic‐AMP were ineffective. Adenosine had no inhibitory effect but potentiated the first peak of light whose intensity was five times increased. It is concluded that P2‐purinergic receptors might be present on photocytes and exert a negative control on the luminescent system. Adenosine‐induced potentiation might be related to an intracellular effect of th

ISSN:0022-104X    

DOI:10.1002/jez.1402580207

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

年代:1991

数据来源: WILEY

摘要:

AbstractDeveloping a method for isolating skate (Raja erinacea) basolateral liver plasma membranes, as well as characterizing the lipid composition and fluidity of these membranes, was the primary purpose of this study. Membranes were isolated using self‐generating Percoll gradients. Marker enzyme studies indicate that this preparation is highly enriched in the basolateral domain of the liver plasma membrane and largely free of contamination by intracellular organelles or canalicular membranes. Further, these membranes contain the agency responsible for Na+‐dependent alanine transport. This finding indicates that this membrane prepration will be useful for the study of skate liver plasma membrane transport processes.The lipid composition and fluidity (as assessed by the fluorescence anisotropy of 1,6‐diphenyl‐1,3,5‐hexatriene) of the skate basolateral liver plasma membrane shows little variation among preparations. Further, DPH anisotropy plotted as a function of temperature yields a straight line (r = 0.99) which indicates that there is no lipid phase change in these membranes from 4° to 37°C. The membrane preparation does contain substantial phospholipase A2activity. The function of this enzyme is, in part, to modify membrane lipid composition and fluidity in response to temperature variations; therefore, this finding suggests that in situ lipid metabolizing enzymes may play a central role in the adaptation of skate basolateral liver plasma membranes to changes in the ambient

ISSN:0022-104X    

DOI:10.1002/jez.1402580208

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

年代:1991

数据来源: WILEY

摘要:

AbstractLarvalAmbystoma tigrinumwere non‐occlusively cannulated in the truncus arteriosus for blood collection. One group was infused with a single dose of 1 ml of 200 mM NaHCO3to induce a metabolic alkalosis. This increased pH from 7.79 to 8.22 after 5 minutes. Bicarbonate ion concentration increased from 16.3 mM to 48.6 mM during this time. After 2 h [HCO3−] was still elevated but pH had returned to control as the PCO2became elevated. A series of infusions of 1 ml of 200 mM NaHCO3at 40 minute intervals into a second group of animals produced a prolonged alkalosis that persisted 8 hours. During this period C1−influx increased by 130%. There was a similar increase in C1−efflux resulting in no change in net C1−flux. There was no significant change in Na+influx, however, Na+efflux increased by almost 150%. Bicarbonate fluxes were measured directly in a third group of serially infused animals whose cloacae were cannulated to permit partitioning of renal and extra renal routes of HCO3−excretion. There was a significant increase in total HCO3−excretion during alkalosis and 95% of it was extrarenal. Although the kidneys can increase base excretion during metabolic alkalosis their capacity is limited with the great majority of base excretion occurring across the skin

ISSN:0022-104X    

DOI:10.1002/jez.1402580209

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe sex of loggerhead turtle embryos is determined by incubation temperature. We are interested in identifying temperature‐dependent events during the development of the urinogenital system to more clearly define the “window” where sex is determined. Consequently, we have closely monitored the stages of whole embryo development in conjunction with the development of the urinogenital system. While an increase in constant incubation temperature shortens the length of the incubation period forCaretta caretta, the wet weight of whole embryos (set at the male‐ (26°), pivotal‐ (28°C), and female‐ (32°C) determining temperatures) is very similar at each developmental stage. However, different growth patterns for the male and female urinogenital systems are found during the sex‐determining period (stages 22–27) of embryognesis. Thus, within this critical period, incubation temperature has a particular influence on the growth of u

ISSN:0022-104X    

DOI:10.1002/jez.1402580210

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

年代:1991

数据来源: WILEY

摘要:

AbstractUsing rT3 as substrate, an in vitro 5′D assay was validated for use with liver tissue from adult Japanese quail, by defining conditions under which activity is proportional to enzyme (protein) concentration and is linear with incubation time. Activity was measured as the release of125I from labeled rT3. Using validated assay conditions we found the following 5′D characteristics: maximal activity from 10 to 50 mM dithiothreitol (cofactor), an apparentKmof 0.52 μM rT3, pH optimum of 7.6‐8.5, complete inhibition by 1 mM propylthiouracil and by 1.0 mM iopanic acid, and substrate “preference” of rT3>T4>T3. Based on these characterizations the quail hepatic 5′D activity is like the Type I 5′D activity found in mammalian liver and kidney and embryonic chicken liver. To determine how previous unvalidated assays, that used high tissue and relatively low substrate (T4) concentrations, influenced 5′D studies we reevaluated 5′D development using an assay validated for each developmental stage with rT3 as substrate. We found extreme quantitative differences in the activities measured and in the proportional relationships between stages, and only limited qualitative similarity in the pattern of 5′D development when unvalidated T4 assay results were compared with validated rT3 assay results. Our data in this paper show good correspondence between whole liver 5′D activity per unit body weight and plasma T3/T4 ratios for the develo

ISSN:0022-104X    

DOI:10.1002/jez.1402580211

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

年代:1991

数据来源: WILEY