摘要:

AbstractExtraintestinal calcium influxes were measured in the killifish,Fundulus heteroclitus, in solutions with different calcium concentrations, from distilled water level (near 0) to seawater level (approximately 12 mM). The extraintestinal influx is modified by the concentration of calcium in the medium during the adaptive period. In freshwater‐adapted fish, calcium depletion resulted in an increase in calcium uptake. Such an adaptation was not observed in calcium‐depleted fish in artificial calcium‐deficient seawater. Calcium depletion in either medium seems to increase the calcium permeability. No correlation was found between Ca‐ATPase activity in the gill tissue and calcium

ISSN:0022-104X    

DOI:10.1002/jez.1402270302

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

年代:1983

数据来源: WILEY

摘要:

AbstractHeart output, arterial pressures, and buccal pressure were measured in conscious, unrestrained eels (Anguilla australis). The branchial ventilatory pattern comprised alternating periods of eupnea and apnea. The transition from eupnea to apnea was always associated with significant decreases in ventral aortic blood pressure (−20%), dorsal aortic blood pressure (−16%), ventral aortic blood flow (−39%) and heart rate (−27%), and a significant increase in systemic vascular resistance (+39%). Although there were, significant decreases in cardiac stroke volume in some animals, heart output was primarily determined by heart rate. The rapidity of the transition to apnea and the occasional occurrence of Mayer waves in the circulation ofA. australisis considered as evidence in favour of the neural regulation of systemic vascular res

ISSN:0022-104X    

DOI:10.1002/jez.1402270303

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe intracellular concentrations of sodium, potassium, and chloride ions, together with total phosphorous, in the cytoplasm of the chloride cells of the opercular epithelium ofFundulus heteroclitushave been estimated by X‐ray emission analysis of bulk frozen hydrated tissue. The estimated concentrations are Na, 171 ± 12; Cl, 155 ± 6; K, 62 ± 4 mE/kg water, together with 80 ± 6 mM P/kg water. It is shown that these high concentrations are consistent, with the Silva model of chloride secretion in which a sodium‐chloride linked carrier, driven by the inward diffusion of sodium ions, concentrates chloride in the cytoplasm. The intracellular concentration of chloride is such that if the potential across the apical membrane is greater than 34 mV, inside negative, there will be a net efflux of chloride ions out of the cell. If the linkage between sodium and chloride on the carrier is one to one, it is shown that energy dissipation is minimal when the product of the cytoplasmic concentrations of sodium and chloride approaches the product of those in the plasma and it would be energetically disadvantageous to maintain low intracellular concentrations of these ions. In practice, however, optimum concentrations are not attainable because of other intracellular solutes that contribute substantially to the osmotic p

ISSN:0022-104X    

DOI:10.1002/jez.1402270304

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe allozymes involved in a one‐locus, two‐allele polymorphism for phosphoglucose isomerase from populations of the sea anemoneMetridium senilefrom the northeast coast of North America exhibit different heat stabilities. The electrophoretically slow form is more stable than the fast, whether or not the enzyme is protected by added 6‐phosphogluconate. In addition, Kmof glucose‐6‐phosphate (G6P) values are significantly higher for the slow than for the fast allozyme, the reverse of the situation in the gluconeogenic direction. Kmof G6P values for the mixture of isozymes produced by heterozygotes fall intermediate between those for the two homozygotes. All genotypes produce enzymes that have slightly U‐shaped Kmvs. temperature curves; these patterns result in differences in thermal sensitivity of reaction rates at low substrate concentrations between high and low temperature ranges. The fast allozyme has higher Vmaxvalues than the slow at all environmentally realistic temperatures. These kinetic differences in the glycolytic direction result in higher Vmax/Kmratios for the fast than for the slow allozyme at all tested temperatures, with the greatest absolute difference falling at 25°C; again, the heterozygote is intermediate. These kinetic differences may yield increased adaptation to thermal aspects of the

ISSN:0022-104X    

DOI:10.1002/jez.1402270305

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

年代:1983

数据来源: WILEY

摘要:

AbstractIsolated gills of the eel (Anguilla australis) were perfused with various solutions and subsequently examined using light or scanning electron microscopy. Oxygen transfer was measured in some perfusions. Ringer perfusion impaired O2transfer and caused irreversible structural damage to the gills. Severe edema was consistently observed as a massive enlargement of the secondary lamellar subepithelial space. Addition of plasma protein substitutes (1–8% polyvinylpyrrolidone; 2–3% dextran) to Ringer perfusates failed to prevent edema, even when used in combination with 0.2% bovine serum albumin. Perfusion with fresh mammalian blood or plasma for up to 30 min did not cause edema, plasma perfusion significantly improving O2transfer.Unless autologous blood or plasma is available, mammalian plasma is the most suitable perfusate for exchange studies in fish gills.As yet unidentified proteins in plasma probably reduce the pore dimensions of the pillar cell flanges, thereby reducing colloid loss from the vascular sp

ISSN:0022-104X    

DOI:10.1002/jez.1402270306

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

年代:1983

数据来源: WILEY

摘要:

AbstractThis study incorporates contractile, structural (sarcomere length), histochemical (myofibrillar ATPase and NADH diaphorase), and physiological (fast and slow axon innervation) parameters to define fiber types in lobster muscle. Single fibers were examined in the closer muscle of adult cutter and crusher claws and of developing larval claws of the lobsterHomarus americanus. Fibers with short sarcomeres (6 μm) had rise times of 90–800 msec for reaching maximum tension, which either was subsequently held at this level or continued to increase. The contractile properties and sarcomere length of single fibers were correlated with their enzymatic properties such that fast‐contracting, short‐sarcomere fibers had high myofibrillar ATPase activity and low oxidative capacity compared to their slow‐contracting, long‐sarcomere counterparts. The slow fibers were also further differentiated into subcategories based on contractile and histochemical properties. Fibers with the fastest rise times tended to be innervated primarily by the fast axon, and those with the slowest rise times were supplied solely by the slow axon. The organization of the massive closer muscle into discrete bundles in which fibers have uniform contractile, structural, and physiological properties leads to functional subdivision within the muscle. The contractile properties of developing fibers were similar to the adult except that larval fibers did not possess very

ISSN:0022-104X    

DOI:10.1002/jez.1402270307

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

年代:1983

数据来源: WILEY

摘要:

AbstractEmbryos of the sea urchin,Strongylocentrotus droebachiensis, develop normally at temperatures ranging from 8°C to 0°C. An embyro cultured at 8°C cleaves symmetrically about its equator whereas one cultured at 0°C cleaves unilaterally. In embryos cultured at 8°C the mitotic apparatus (MA) occupies the entire cell volume at late anaphase whereas at 0°C the MA at the same stage is 20% smaller (Anstrom and Summers, '83). At 8°C the MA is centered within the zygote whereas at 0°C it is located eccentrically. The cleavage furrow always forms at the cell surface closest to the eccentric MA. We attribute the unilateral cleavage furrow in the 0°C embryo to the small size and eccentric placement of the mitotic apparatus within it. Both symmetrical and unilateral cleavage are apparently normal in this species, suggesting a common mechanism for both types of

ISSN:0022-104X    

DOI:10.1002/jez.1402270308

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

年代:1983

数据来源: WILEY

摘要:

AbstractWhen antiactin antibody produced against carp skeletal muscle actins was microinjected into monolayer‐cultured swordtail erythrophores, pigment displacement was almost completely blocked. Moreover, the injected antibody was equally effective at blocking the aggregation of dispersed pigment and the dispersion of aggregated pigment. If antibody saturated with carp actins was microinjected, no such blockade occurred.Microinjection of phalloidin or DNase I into these cells brought about an incomplete inhibition of their pigment displacement. These two drugs tended to inhibit pigment dispersion more than aggregation, suggesting that actins are differently involved in the two phases of pigment movement. The results all indicate that actins are functional elements in the pigment displacement of swordtail erythrophores, and that G‐F transformations of these molecules play little or no role in pigment aggregation, but are implicated in some way in dispers

ISSN:0022-104X    

DOI:10.1002/jez.1402270309

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

年代:1983

数据来源: WILEY

摘要:

AbstractThis investigation was undertaken to study the ontogeny of hepatic, renal, and intestinal peroxisomes and/or microperoxisomes during thyroxine‐induced anuran metamorphosis. Catalase activity was localized cytochemically after incubation in DAB medium, and studied biochemically by a spectrophotometric method. Our morphological and biochemical investigations suggest the formation of a new population of peroxisomes during the hormonal treatment. This is obvious especially for microperoxisomes of the intestinal epithelium since the larval tissue is completely replaced by a new layer during thyroxine‐induced metamorphosis. For the peroxisomes of hepatocytes and kidney proximal tubule cells, our assumption is based on the following observations: (1) The number of peroxisomes increases in liver and kidney during thyroxine treatment; (2) this proliferation is accompanied by an enlargement of renal peroxisomes; and (3) 16 days after the beginning of the hormonal treatment, 5.4‐ and 2.4‐fold increases are found for the specific activities of hepatic and renal catalase, respectively. A temporal coordination exists between the structure and the metabolism of peroxisomes and mitochondria during thyroxine‐induced meta

ISSN:0022-104X    

DOI:10.1002/jez.1402270310

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

年代:1983

数据来源: WILEY

摘要:

AbstractA full‐thickness cut 7 mm long was made on the middorsal skin of C57BL/10J mice using fine iridectomy scissors. Specimens from the wounded skins were fixed at various days after wounding and were subjected to the dopa reaction and to the combined dopa‐premelanin reaction. In the epidermis within 1 mm from the wound edge, the melanocyte population positive to the dopa reaction as well as the melanoblast‐melanocyte population positive to the combined dopa‐premelanin reaction increased dramatically until the third day, then gradually decreased. In contrast, both populations in the regenerating wound epidermis appeared on the third day and increased until the seventh day, then gradually decreased. However, the maximal population density in the regenerating epidermis did not exceed the initial density. The size of the melanocyte population in both the epidermis within 1 mm from the wound edge and the regenerating epidermis did not differ from that of the melanoblast‐melanocyte population in all stages of wound healing. Moreover, pigment‐producing melanocytes in mitosis were found immediately after wounding in the epidermis within 1 mm from the wound edge, but not in the regenerating epidermis and control epidemis. These results indicate that the epidermal melanocytes in neonatal mouse skin can be stimulated to undergo mitosis immediately adjacent to a skin wound and, thèreafter, to migrate into the regenerati

ISSN:0022-104X    

DOI:10.1002/jez.1402270311

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

年代:1983

数据来源: WILEY