ISSN:0022-104X    

DOI:10.1002/jez.1402330102

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

年代:1985

数据来源: WILEY

摘要:

AbstractSecretion from Duvernoy's gland of the colubrid snakesMalpolon, Spalerosophis, andThamnophiswas obtained by pilocarpine stimulation and tested for lethality and selected enzymatic activities. Pools of secretion fromMalpolonandSpalerosophiswere fractionated by gel filtration, and several major active fractions were examined. The secretion fromMalpolonhad an LD50of 6.5 μg/gm in mice; two lethal fractions with LD50's of 2.75 μg/gm and 4.5 μg/gm were isolated. One of these fractions appears to be a basic phospholipase A with a molecular weight of about 17,000.Spalerosophishad a secretion with an LD50of 2.75 μg/gm in mice; one main lethal fraction with an LD50of 2.5 μg/gm was isolated. Secretion fromThamnophishad an LD50of 33.3 μg/gm; it was not fractionated owing to a paucity of material.At least two of the snake species examined have toxic secretions that may be important during feeding by killing or weakening and helping to subdue the struggling

ISSN:0022-104X    

DOI:10.1002/jez.1402330103

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

年代:1985

数据来源: WILEY

摘要:

AbstractWe have reported previously that angiotensin II increases urine flow and Na and K excretion rates in the aglomerular goosefishLophius americanus. The present experiments were undertaken to determine if antagonism of endogenous angiotensin has the opposite renal effects. Arterial blood pressure, urine flow, and plasma and urine electrolytes were measured during two consecutive clearance periods in two groups of goosefish. The control group (n = 7) received saline intravenously during both periods; the experimental group (n = 8) received saline during the first period and a competitive antagonist of angiotensin II (saralasin, or [Sar1, Val5, Ala8] angiotension II) dissolved in saline during the second period. The control group exhibited no significant change over time in any of the measured variables: arterial blood pressure; plasma [Na], [K], [Mg], [Ca]; osmolality; urine flow; and excretion rates of Na, K, Ca, and Mg. Arterial blood pressure and plasma electrolytes and osmolality were stable over time in the experimental group also. However, during saralasin infusion there were significant decreases in urine flow and in excretion rates of K, Mg, and Ca. Taken together with our previous results, these observations suggest that endogenous levels of angiotensin in goosefish are sufficient to have direct renal effects. The mechanisms of action of angiotensin are not clear, but involve neither changes in systemic blood pressure nor filtration but might involve inhibitory effects of angiotensin on tubular reabsorptive processes.

ISSN:0022-104X    

DOI:10.1002/jez.1402330104

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

年代:1985

数据来源: WILEY

摘要:

AbstractParamecium tetraurelia, stock 51s, will not survive if shifted from normal medium to medium with 80–100 mM NaCl. But, if first kept in medium with 50 mM NaCl for at least 45–60 min, cells survive in medium with 80–100 mM NaCl. After shifting to medium with 50 mM NaCl, cells increase internal levels of ninhydrin‐positive substances (NPS) for the first 30 min, then decrease them again over the next 90 min. Total internal osmolarity probably remains constant over this 90 min since contractile vacuole output is constant. Treatment with the protein synthesis inhibitor G418 (geneticin) prevents acclimation in cells in 50 mM NaCl, but does not prevent the changes in NPS levels. Thus NPS are not sufficient to account for acclimation, nor is there evidence that they are r

ISSN:0022-104X    

DOI:10.1002/jez.1402330105

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

年代:1985

数据来源: WILEY

摘要:

AbstractDaily injections of dihydroxyphenylalanine (DOPA), a dopamine precursor, stimulate large increases in reproductive and body fat indices in gulf killifish,Fundulus grandis, when given 20 hours after daily injections of 5‐hydroxytryptophan (5‐HTP), a serotonin precursor. However, DOPA injections are inhibitory when given 8 hours after 5‐HTP. The drug effects persist for at least 3 weeks following drug treatment indicating a possible resetting of an endogenous mechanism involved in season

ISSN:0022-104X    

DOI:10.1002/jez.1402330106

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe sizes of the unifunctional dorsal longitudinal (DLM) and bifunctional subalar (Sa) metathoracic flight muscles of the cricketTeleogryllus oceanicusincrease by more than an order of magnitude between the second instar before the terminal molt and the tenth day of adult life. During the same developmental period isometric twitch duration (onset to 50% relaxation, 25°C) varies little, while muscle mitochondrial content increased by a factor of ten as measured by stereological analysis of electron micrographs and citrate synthase activity (μmoles citrate·min−1· gm protein−1, 25°C). The wing muscles of adults have abundant sarcoplasmic reticulum (SR), narrow myofibrils, and a high volume density of mitochondria. At two molts from adulthood muscles that will later be used in flight behavior also have narrow myofibrils and abundant SR, but unlike muscles at later stages, nymphal muscles have a low volume density of mitochondria. At the terminal molt muscles have at least as much SR as is seen in muscles at the tenth day of adult life, and the myofibrils are also more narrow at the earlier stage. Since there is significant variation in muscle structure and little change in twitch duration during late development, the efficacy of the SR in releasing and resequestering CA2+is seemingly lower in muscles at the terminal molt, a time of rapid muscl

ISSN:0022-104X    

DOI:10.1002/jez.1402330107

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

年代:1985

数据来源: WILEY

摘要:

AbstractHydrolysis of exogenous one‐acyl,2[3H]‐oleoyl phosphatidyl choline by intracellular phospholipase A2to yield free [3H]‐oleate and lysophosphatidylcholine was measured in isolated liver microsomes from warm (20°)‐ and cold (5°C)‐acclimated rainbow trout,Salmo gairdneri. Unlike mammalian phospholipase A2, which is not typically microsomal, over 18% of the total phospholipase A2activity from trout liver occurred in the microsomes. Specific activity in microsomal preparations (4.07 nmole · hr−1· mg−1) represented a 1.4‐fold purification of clarified liver homogenates (2.93 nmole· hr−1mg−1). The accumulation of free fatty acid was a function of both the duration and the protein concentration of the assay. Activity was enhanced fourfold in the presence of 0.1% Triton X‐100. Free Ca++stimulated activity up to 100 μM, but was not an absolute requirement of the enzyme. Maximal activity occurred at pH 8.0–8.5 at 20°C assay temperature and pH 9.0 at 5°C. Acclimation history did not influence the pH optima of the enzyme. Thermal acclimation did, however, result in perfect compensation of enzymatic rate; phospholipase A2activity from cold‐acclimated trout was not significantly different from that of warm‐acclimated trout when measurements were made at their respective acclimation temperatures. This perfect compensation for temperature as well as the unique intracellular localization of trout liver phospholipase A2implicate the enzyme in a deacylation‐reacylation cycle that could be partially responsible for the thermally modulated restructuring previously observed in

ISSN:0022-104X    

DOI:10.1002/jez.1402330108

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe amplitude of caffeine contractures, tissue redox‐state potential, and electrical activity were simultaneously measured in the sartorius muscle of the frog,Rana esculentafollowing oxidant (methylene blue) and reductant (ascorbate, hydroquinone) treatments.Pretreatment with oxidant, in parallel with the increment of redox‐state potential, increased, while pretreatment with reductant, in parallel with the decrement of redox‐state potential, decreased significantly the amplitudes of caffeine contractures. The electrical activity, registered simultaneously, was not changed significantly.The mechanism of action of caffeine contractures is related to the increase of cytoplasmic Ca2+, and the results indicate that the actual redox‐state potential level, as one of the determinants of the internal milieu, is also a regulatory factor in relation to the excitation‐contraction

ISSN:0022-104X    

DOI:10.1002/jez.1402330109

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

年代:1985

数据来源: WILEY

摘要:

AbstractA 60–140‐atm change in the hydrostatic pressure causes fresh water gammarid amphipods from Lake Baikal to lose Na+to the medium. This effect occurs whether the change is an increase in pressure for shallow species or a decrease in pressure for deep species. The pressure effect is predominantly upon unidirectional influx. A pressure‐induced change in the dynamic fluidity of the membrane is suggested as a possible mode of a

ISSN:0022-104X    

DOI:10.1002/jez.1402330110

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe regenerative ability of limb stumps bearing partial circumferences of flank skin was tested in the newt,Notophthalmus viridescens. Skin dorsal to the lateral line of the flank was removed and used to replace 1/4, 1/2, or 3/4 of the skin of the upper forelimb. Grafts were placed at anterior, posterior, dorsal, or ventral positions relative to the axes of the limb. After 30 days of graft healing the limbs were amputated through the grafts and were permitted to regenerate for 60 days. Limb stumps bearing 1/4 circumference of flank skin regenerated complete limbs in 85% of the experimental cases. After 1/2 circumference of limb skin was replaced, 57% regenerated complete limbs. When 3/4 of the limb skin was replaced by flank skin, 29% regenerated complete limbs. Only 2% of experimental limbs bearing a full circumference of flank skin regenerated complete limbs in an earlier study [Tank, P.W. (1984) J. Exp. Zool., 229:143–153]. The greatest effect on pattern formation was observed when flank skin grafts were placed at the ventral position of the limb stump regardless of graft size. These results are discussed in light of the idea that short‐range cellular interactions between limb cells are essential for pattern formation during limb regenerat

ISSN:0022-104X    

DOI:10.1002/jez.1402330111

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

年代:1985

数据来源: WILEY