摘要:

AbstractEnzymatic and immunological properties of alkaline phosphatase (ALPase) in several tissues of bullfrog (Rana catesbiana) were investigated. Inhibition and thermal inactivation studies showed that bullfrog ALPases in kidney, liver, and intestine had similar enzymatic properties. In addition, mouse antiserum against bullfrog liver ALPase cross‐reacted with kidney and intestine enzymes as well as with liver enzyme. These results suggest that a single phenotype of ALPase exists in all tissues of bullfrog in contrast to two or three isoenzymes in mammal

ISSN:0022-104X    

DOI:10.1002/jez.1402540102

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe activity of glucose‐6‐phosphate dehydrogenase (G6PD) was measured in bone marrow, spleen, lung, liver, kidney, adipose tissue, brain, heart, muscle, and in the erythroid cell line of rabbit. In tissues, the activity ranged from 6.87 to 0.09 U/g wet tissue, found in bone marrow and muscles, respectively, whereas in the erythroid cell line it ranged from 14.3 to 2.4 U/g cells for erythroblasts and erythrocytes, respectively. The electrophoretic patterns of the tissue crude extracts shoed an identical set of three activity bands, and the immunotitration curves obtained with rat antirabbit erythrocyte G6PD antibodies shared the same equivalence point. The enzyme, purified to homogeneity from different tissues, showed no significant differences among the Km values for NADP and G6P. The results give a picture of the variability of the G6PD activity in rabbit tissues and suggest the presence of the same enzyme molecule in each tis

ISSN:0022-104X    

DOI:10.1002/jez.1402540103

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

年代:1990

数据来源: WILEY

摘要:

AbstractBath application of the excitatory amino acids L‐aspartate and/or L‐glutamate or their agonists N‐methyl‐D,L‐aspartate and/or kainate elicited swimming movements in spinal tadpoles. Swimming cycles induced by the amino acids were in the frequency range of natural movements, and could be evoked after sectioning all dorsal roots in the exposed spinal segments. Locomotion was only elicited by L‐aspartate or L‐glutamate at low concentrations when the bath medium was rapidly circulated over the exposed surface of the spinal cord, and was of much shorter duration than the agonist‐induced movements. These results indicate some differences between the actions of L‐aspartate and L‐glutamate and their agonists on the

ISSN:0022-104X    

DOI:10.1002/jez.1402540104

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe hemoglobin (Hb) concentration in a single parthenogenetic egg from Hb‐richDaphnia magnawas about three times that in an egg from a Hb‐poor animal. Hemoglobin‐rich animals first produced Hb‐rich eggs in air‐saturated water. The Hb concentration of the eggs gradually decreased, leading to a decrease in the Hb concentration in hemolymph in adult animals. The P50 values (equilibrium oxygen pressure at half saturation) of solutions of purified Hb were 2.9 and 7.2 torr at 20°C for Hb‐rich and Hb‐poor eggs, respectively. Hemoglobin from the eggs was separated into at least eight Hb components by isoelectric focusing. The pI values (isoelectric point) of the major Hb components of the eggs exceeded those of adult Hb. The relative amounts of Hb components with high pI values in Hb‐rich eggs were higher than those of Hb‐poor eggs. On sodium dodecyl sulfate‐polyacrylamide gel electrophoresis technique (SDS‐PAGE), the Hb from eggs was composed of 37,000 mol

ISSN:0022-104X    

DOI:10.1002/jez.1402540105

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

年代:1990

数据来源: WILEY

摘要:

AbstractIn contrast to previously described transformations of insect epidermal cells, morphological changes in the larval epidermis ofManduca sextainvolve large changes in cell volume: a threefold increase at the beginning and a twofold decrease at the end of the last feeding phase. The volume changes are determined, in part, or entirely, by changes in cell height (cell elongation and cell shortening). Initial cell elongation occurs in a region‐specific manner, whereas subsequent cell shortening affects all of the epidermis equally. As shown by ligation experiments and hormone treatments in tissue culture, larval changes in cell height, unlike cell elongation and differentiation in prepupae, are not regulated by developmental hormones (juvenile hormones, ecdysteroids). Instead, the maintenance of a normal columnar epithelium in fifth instars depends on continuous growth. Lack of food, especially protein, results in reversible cell shortening at any time during the feeding phase. Intake of water does not mitigate this cellular response; cell shortening is also insensitive to ouabain but inhibited by cold treatments. We propose that during larval growth epidermal cell height is under specific homeostatic control, independent of mechanisms regulating cell width, ploidy levels, or mitotic activit

ISSN:0022-104X    

DOI:10.1002/jez.1402540106

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe occasional occurrence of high frequencies of limb abnormalities, including extra limbs, in natural populations of amphibians has long been a puzzle. In this paper we report the discovery of a population in which such limb abnormalities appear to be caused by a parasitic flatworm (trematode) that uses amphibians as intermediate hosts. The cercarial larval stage of the trematode attacks amphibians, penetrating the skin to form cysts (metacercariae). The cysts are preferentially localized in the cloacal region, including the developing hind limb regions in larvae of both frogs (Hyla regilla) and salamanders (Ambystoma macrodactylum). A wide range of limb abnormalities are seen, including duplicated limb structures ranging from extra digits to several extra whole limbs. We hypothesize that these limb abnormalities result from localized regulatory responses of developing and regenerating limb tissues to mechanical disruption caused by the trematode cysts. We have tested this idea by implanting inert resin beads into developing limb buds of frogs and salamanders. Since this treatment can cause supernumerary limb structures, our hypothesis is sufficient to explain the naturally occurring extra limbs.

ISSN:0022-104X    

DOI:10.1002/jez.1402540107

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

年代:1990

数据来源: WILEY

摘要:

AbstractWe have re‐examined some of the factors affecting the induction of heart‐forming mesodern in the axolotl. The formation of functional, rhythmically contracting myocardial tissue was used as an assay. We have found that heart‐forming mesoderm is fully induced and capable of completing its developmental repertoire by the end of neurulation. As has been previously reported, pharyngeal endoderm appears to be the major inductor of heart mesoderm. Unlike previous workers, we have found that the inducing activity appears to be highly localized in the mid‐ventral pharyngeal endoderm. The endoderm retains its inductive properties, and the mesoderm retains at least some capacity to respond, long after the heart‐forming mesoderm is apparently fully induced.We have also found that RNA extracts from pharyngeal endoderm, which are capable of causing cardiac‐lethal (c/c) mutant axolotl hearts to begin beating, are not capable of inducing early wild‐type heart‐forming mesoderm. Based on these results, we speculate that induction of heart‐forming mesoderm is a two‐step process. The first signal, occurring during neurulation, directs the mesoderm to begin differentiating into cardiomyocytes, and the second, beginning in mid‐ to late neurulation and continuing until just prior to the onset of heartbeat, causes myofibrillogenesis and the initiation of rhythmic contractions. The latter signal, which is lacking inc/cmutant embryos, appears to be necessary to override an inhibition present in

ISSN:0022-104X    

DOI:10.1002/jez.1402540108

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe effects of scombroid insulin (10−7M) and bovine glucagon (10−7M) on key regulatory enzymes of glycolysis and gluconeogenesis are examined in freshly isolated hepatocytes of the sea raven,Hemitripterus americanus, following a 45 and 180 min incubation. Glucagon increased the Voptof PEPCK, PK, GPT, and LDH, but decreased the substrate activity ratios of both PK and PFK‐1 (the latter only at inhibitory ATP concentrations) at 180 min. Glucagon also decreased Fru‐2,6‐P2levels at both 45 and 180 min. Insulin decreased the Voptfor LDH at 180 min and decreased the F6P activity ratio for PFK‐1 at both 0.5 mM and 1.5 mM ATP at 45 and 180 min, with larger decreases occurring at the later time period (to 13% of the control value). Insulin also decreased Fru‐2,6‐P2concentrations at 180 min and increased alanine uptake. PEPCK and PK were not affected by insulin. These data indicate that glucagon alters the characteristics of a variety of enzymes in the glycolytic/gluconeogenic sequence, while the major impact of insulin is at the level of PFK‐1 a

ISSN:0022-104X    

DOI:10.1002/jez.1402540109

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe effects of several variables were tested on the in vitro binding affinity (Ka) and maximum binding capacity (MBC) of saturable 3,5,3′‐triiodo‐L‐thyronine (T3)‐binding sites (putative thyroid hormone receptors) extracted from hepatic nuclei of immature rainbow trout held on a 12L:12D photocycle at 12°C. Neither Kanor MBC varied during the daily photocycle, nor were they influenced by the growth rate, food ration, or a 13‐fold chronic elevation in plasma T3. However, MBC was inversely correlated with fish size and was depressed significantly by two injections of 17β‐estradiol (E2) or starvation for 3 or 12 days. The Kawas uninfluenced in either case. Since both E2and starvation also depress T3levels in the blood, the decrease in MBC could be secondary to this change. The drug ipodate, which depresses plasma T3, also lowered the MBC. However, MBC remained low in ipodate‐treated trout given exogenous T3, thus suggesting that the effect of ipodate was not due to T3deprivation. It remains to be shown, therefore, that plasma T3depression itself can modify MBC. It is concluded that increasing body size and catabolic states, both of which are associated with a decrease in specific growth rate, tend to decrease the abundance of he

ISSN:0022-104X    

DOI:10.1002/jez.1402540110

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe pituitary of the coho salmon (Oncorhynchus kisutch) was studied during the parr‐smolt transformation. Changes in pituitary prolactin (PRL) synthetic rate and influences of osmotic pressure (OP) and cortisol on PRL cell activity were investigated in vitro. After 20‐hr incubations in the presence of35S‐methionine, tissue and medium were separated and subjected to SDS‐polyacrylamide gel electrophoresis; bands stained with Coomassie Blue R‐250 (= total PRL) and bands on X‐ray film resulting from autoradiography of the gels (= newly synthesized PRL) were quantified by soft laser densitometry. Physiological changes in medium OP exerted no detectable effect on the % release of total or newly synthesized PRL (35S‐PRL), whereas some differences, mostly in the % release of35S‐PRL, were detected when extraphysiological medium OPs were used. Since OP effects on GH release are similar, these results suggest that OP has no specific direct effect on PRL release under physiological conditions. PRL synthetic rate during the parr‐smolt transformation increased beginning in mid‐February and peaked in mid‐March, but fell to undetectable levels in mid‐April; a second peak in PRL synthesis was observed in mid‐May. These data are in accord with reports on plasma levels of PRL, which further indicate that cortisol levels increase during the April decline in PRL levels. Our in vitro studies demonstrate that cortisol inhibits pituitary PRL synthesis and content in a dose‐related manner and also inhibits the % release of total and35S‐PRL, suggesting that cortisol may be an important regulator of PRL cell activity during

ISSN:0022-104X    

DOI:10.1002/jez.1402540111

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

年代:1990

数据来源: WILEY