摘要:

AbstractWe quantified natural variation in maximum aerobic capacity (V̊02max) exhibited by a free‐living by a free‐living population of bullfrogs (Rana catesbeiana) and examined the degree to which such variation is associated with key parameters of the systemic oxygen transport apparatus and oxidative enzyme (citrate synthase) activity at the tissue level. Regression analysis of these data revealed that only ventricle mass and hemoglobin concentration accounted for significant fractions of the variation in V̊02max. Neither variation in maximum heart rate nor in citrate synthase activity were significantly correlated with individual variation in maximum aerobic capacity. These results support the contention that, in at least some taxa, maximum aerobic capacity is limited by the ability of the cardiovascular system to deliver oxygen to the ti

ISSN:0022-104X    

DOI:10.1002/jez.1402390102

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

年代:1986

数据来源: WILEY

摘要:

AbstractNine hemoglobins were purified from blood ofSalmo clarkiby ion‐exchange chromatography and preparative isoelectric focusing. The subunit structures of eight of the purified hemoglobins were studied by electrophoresis of globins in the presence of urea. Six are α2β2tetramers while two appear to be heterotetramers of the type αα′ β2and αα′ββ′.The effects of pH, nucleotides, and temperature on the oxygen equilibria of the purified hemoglobins were studied. Five hemoglobins with isoelectric points from 9.1 to 7.1 and one minor hemoglobin with an isoelectric point of 5.9 appear to have essentially identical oxygen binding properties. All have similar oxygen equilibria which are independent of pH and temperature and not affected by saturating amounts of ATP. Another minor hemoglobin with an isoelectric point below 5.9 has similar oxygen equilibria except for a possible pH dependence. Two hemoglobins, with isoelectric points of 6.5 and 6.4, have oxygen binding properties which are strongly pH and temperature dependent. Addition of ATP or GTP causes a large decrease in the oxygen affinity without affecting the cooperativity of oxygen binding. The effect of GTP is slightly greater than that of ATP. No significant differences were observed in the oxygen equilibria of these two hemoglobins.The red blood cells ofS. clarkiwere found to contain large amounts of both ATP and GTP, with an ATP:GTP ratio of 3:1. Both nucleotides may be important modulators of hemoglobin oxygen affinity inS. clarki, in contrast to the situation inS. gairdneri, in which red blood cell GTP concentrations are considerably lower.The presence of six or possibly seven hemoglobins with identical oxygen binding properties inS. clarkisuggests that, to a large extent, the physiological role of multiple hemoglobins in this species involves phenomena not directly related to the oxygen binding properties of

ISSN:0022-104X    

DOI:10.1002/jez.1402390103

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

年代:1986

数据来源: WILEY

摘要:

AbstractAmmonia theoretically can traverse the gill epithelium of aquatic animals in a variety of ways. Recent experiments utilizing both whole animals (fish and arthropods), and perfused heads of fishes indicate that diffusional movement of both NH3and NH4+takes place, as well as basolateral (serosal) Na+/NH4+exchange. Data supporting the presence of apical (mucosal) Na+/NH4+exchange are more equivocal, and there is no published evidence for transport via basolateral NH4Cl + NaCl co‐transport. The relative roles of various pathways may depend upon the species and its salinity of acclimatio

ISSN:0022-104X    

DOI:10.1002/jez.1402390104

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

年代:1986

数据来源: WILEY

摘要:

AbstractA “slow calcium channel” blocking agent, Verapamil (VPL), induces tegumental disruption in schistosomes. The response of worms to VPL was compared to that caused by a widely used antischistosomal drug, Praziquantel (PZQ), whose mode of action has been related to a rapid influx Ca++.Scanning microscopy of worms exposed to micromolar concentrations of either PZQ or VPL in vitro revealed a striking similarity of tegumental damage. At high dosage (10−5M × 1 h), both compounds cause extensive surface bleb formation, which can proceed to shredding and denudation of the tegument. Early VPL‐induced changes in maleSchistosoma mansoniappear to consist of small intertubercular lesions, as well as head and neck microblebs and bullae. After longer exposure, the bleb formations develop into large lesions, which after fixation for scanning microscopy, appear as flower‐like outgrowths on and around the tubercles. Females show much less surface disruption than males.Physiologically, PZQ typically causes quick contraction of worm pairs into a tight, agonal coil. While VPL also induces spasm and clonic jerking, worms soon lengthen into a gentle coil. Both drugs kill the parasites in vitro.The findings suggest that both PZQ and VPL have a surface target, whose disruption can be noted visually as lipoidal oozing and eventual tegumental blebbing. The inference drawn is that a direct affect on worm internal calcium metabolism, or on calcium channel activities, can lead to pathological changes which are grossly indistinguishable. These two drugs have markedly dissimilar structures, and thus probably different mechanisms of action. Yet, they result in similar final pathological events. These studies raise the possibility that various calcium‐perturbing agents might be useful candidates in a search for alternative or synergistic chemotherapeutic agents against trematodes

ISSN:0022-104X    

DOI:10.1002/jez.1402390105

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe effects of cytochalasin B (CB), a microfilament inhibitor, and demecolcine (DC), a microtubule inhibitor, on freeze‐thaw survival and culture survival of early cleavage stage mouse embryos, was evaluated. In the first experiment, eight‐cell mouse embryos were frozen in dimethylsulfoxide (DMSO) or DMSO + 0.1 μg/ml DC + 7.5 μg/ml CB. In the second experiment, eight‐cell embryos were dehydrated and cultured in the presence of either DMSO, DMSO + DC, DMSO + CB, or DMSO + DC + CB for 45 min prior to rehydration and culture to simulate the osmotic and chemical changes encountered during the dehydration and rehydration procedures, but without the consequences of freezing and thawing. In the third experiment, additional eight‐cell embryos were frozen in either DMSO, DMSO + DC, DMSO + CB, or DMSO + DC + CB. The survival of embryos frozen in DMSO (75%) was significantly higher (P<0.01) than that of embryos frozen in DMSO + DC + CB (55%). No differences (P = 0.55) were observed after a 48‐hr culture period in the development of embryos dehydrated, cultured, and rehydrated but not frozen. Embryos frozen in the presence of both DC and CB had a lower (P = 0.06) survival rate (55%) than that of embryos frozen in the presence of DMSO, DC, or CB (˜ 70%). These results suggest that both microfilaments and microtubules have a role in maintaining the structural integrity of the plasma membrane during the freeze–thaw process and that the loss of either loss does not seem to be detrimental to survival, but the loss of both results in

ISSN:0022-104X    

DOI:10.1002/jez.1402390106

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe elimination of portions of chromosomes (chromosome diminution) inAscarissp. is an early event associated with divisions of somatic blastomeres. Germ‐line blastomeres do not undergo diminution during cell division. It has been proposed that the occurrence of chromosome diminution is under the control of morphogenetic determinant(s) in the ooplasm, which are fixed into specific blastomeres by the cleavage process. The nature of the morphogenetic determinant(s) contained in the cytoplasm remains an enigma. Two problems with theAscarissp. system have been an impermeable extra embryonic (ascaroside) layer and the difficulty of scoring interphase nuclei as somatic (diminished) or germ‐line (non‐diminished). We have successfully permeabilized the ascaroside layer by puncture with micropipettes. We also report a Ba(OH)2C‐banding technique, which preferentially stains germ‐line limited chromatin in anaphase, telophase, and interphase nuclei. These two techniques have allowed us to (1) produce early embryos with multinucleated blastomeres (coenocytic embryos) ofAscaris suumand (2) assay for the effects on chromosome diminution brought about by these altered cytoplasmic environments. The patterns of diminution seen in one‐cell and two‐cell coenocytic embryos strongly suggest the presence of cytoplasmic determinats. Since chromosome diminution serves as a marker of blastomere commitment, these determinants may also play a role in the commitment of blastomeres to

ISSN:0022-104X    

DOI:10.1002/jez.1402390107

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

年代:1986

数据来源: WILEY

摘要:

AbstractTo examine the effects of retinoic acid and dimethyl sulfoxide on regenerative ability of anuran amphibians, the left forelimbs of 60 postmetamorphic froglets ofRana catesbeiana(bullfrogs) were amputated through the distal zeugopodium. Fifteen of the froglets had their left forelimb stumps immersed in dimethyl sulfoxide (DMSO) for 3 minutes, once immediately after amputation and once on each of 5 subsequent days. Another 15 frogs had their left forelimb stumps immersed in a 0.01 M solution of retinoic acid dissolved in DMSO for the same period of time. The remaining 30 control froglets received no treatment to their forelimb stumps. The untreated group of froglets did not regenerate structures distal to the amputation surface, while all limbs in both treated groups produced regenerates by 120 days postamputation. Regenerates of limbs treated with both DMSO alone and DMSO combined with retionic acid, although hypomorphic, were composed of multiple cartilage elements, which in many cases (46.7%) were organized as patterns partially resembling the skeletal arrangement of a normal forelimb. All of these regenerates exhibited bundles of striated muscle. In addition, nearly half (46.7%) of the regenerates in the DMSO + retinoic acid group possessed two separate regenerate outgrowths. The results demonstrate that young bullfrogs (Rana catesbeiana) possess a latent epimorphic regenerative capability, which can be stimulated by topical application to the wound surface of DMSO alone or DMSO combined with retionic acid.

ISSN:0022-104X    

DOI:10.1002/jez.1402390108

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

年代:1986

数据来源: WILEY

摘要:

AbstractTo investigate the possibility of a relation between the moment of deletion of macromeres and the morphogenetic potential of the resulting embryo, the 2D‐, the 3D‐, or the 3(A–D)‐macromeres were deleted at regular intervals during the fifth or the sixth cleavage cycle. Ectoblasts, ‐3(A–D), are capable of extensive cellular differentiation and the formation of several organs. The developmental capacity of the ectoblasts is independent of the stage of deletion.Deletions of the D‐macromere at successive stages result in a decreasing number of internal shells; a minimum is reached 40–60 min after the fifth cleavage (24‐cell stage). Simultaneously, the number of external shells increases.Deletions of the 3D‐macromere during the first 60 min of the sixth cleavage cycle (24‐cell stage) lead to highly teratomorphic larvae; rather normal‐shaped larvae, but without heart and intestine, develop following deletions after 60 min. The moment of deletion of the D‐macromere affects morphogenesis.These results lead to the following hypothesis: each quadrant may induce an internal shell, irrespective of factors derived from the polar lobe; an internal shell is a differentiated non‐evaginated shell gland. During the first hour of the sixth cleavage cycle the 3D‐macromere suppresses shell field formation in the A‐, B‐, and C‐quadrants, and induces evagination of the shell gland in the D‐quadrant resulting in the formation of an external shell. At the same time the morphogeneti

ISSN:0022-104X    

DOI:10.1002/jez.1402390109

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe DNA content of fat body nuclei was measured cytophotometrically as a function of position along an anterior–posterior (A–P) axis of the tissue throughtout larval development. There was a dramatic 55‐fold increase in the average amount of DNA per nucleus during the first 3 days of this period, but there was no further increase during the final day. However, the rate of increase had regional specificity. The amount of DNA per nucleus correlated significantly with its position along the A–P axis of the tissue: nuclei in a posterior direction contain gradually increasing amounts of DNA. There was up to a seven‐fold difference between the smallest anterior and largest posterior nucleus. In addition, for three of the ages studied there was a subgradient in the posterior region with a slope that was considerably steeper than that of the overall tissue gradient. The tissue has three characteristic morphological regions, anterior, medial, and posterior, which can be recognized early in development and which are maintained throughout the larval period. The distribution of nuclear DNA classes determined for cells in each region for the final 2 days of larval life became fixed before the final day of development. The significance of the DNA gradient in terms of a protein storage gradient is

ISSN:0022-104X    

DOI:10.1002/jez.1402390110

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

年代:1986

数据来源: WILEY

摘要:

AbstractA daily random light‐dark regime (RLD), in which the onset of the photophase occurred at a random time of the 24‐h day, significantly shortened the life span of adultDrosophila melanogasterin 8 out of 23 strains tested. For the eight sensitive strains, the mean percent decrement in LT50 ± SE was 11.2 ± 0.6 d; for ten resistant strains, the mean decrement was 5.1 ± 0.8 d; for the remaining 5 strains, which could not be unambiguously classified as sensitive to RLD, the mean decrement was 8.6 ± 1.1 d. Strains homozygous for whole chromosomes (either X or one of the two large autosomes) exhibited continuous variation for sensitivity to clock shifting. No chromosome accounted for a disproportionate share of the variation, suggesting a multigenic basis for this phenotype. The LT50 in a normal, constant light‐dark regime (CLD) ranged from 31.7 d to 65.3 d, with chromosome 2 contributing most heavily to this variation. The correlation between LT50 and percent decrement in LT50 was not significant (r = .23, df = 21, P>.20). In most sensitive strains, RLD and CLD groups did not begin to differ in percent surviving until after .5 of CLD LT50; after this critical point, RLD animals started dying at an increased rate. RLD may be stressful by disrupting temporal organization of physiological processes immediately following phase shifts, during the period marked by transients in observed phase

ISSN:0022-104X    

DOI:10.1002/jez.1402390111

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

年代:1986

数据来源: WILEY