摘要:

AbstractThe pyruvate dehydrogenase complex has been demonstrated in high speed pellet preparations from sonicated ribbed mussel gill mitochondria. The activity of the complex is inhibited by low chloride (<100 mM) concentrations, EDTA (1 mM), succinate, ATP, and NAD/NADH ratios below 4. Inhibition by EDTA is relieved by addition of 10 mM MgCl2‐1 mM CaCl2. ATP inhibition was enhanced by NaF and reversed by high Mg+ +concentrations in the absence of NaF. Pyruvate and thiamine pyrophosphate inhibited the inactivation by ATP. The nonhydrolyzable ATP analog AMP‐PNP caused inhibition of the overall catalytic activity that was identical to ATP. Factors involved in the ATP inhibition and Mg+ +reversal are lost with freezing or cold storage. Preliminary results using γ‐32P‐ATP indicate that a protein kinase that phosphorylates the α subunit of E1(pyruvate dehydrogenase) from the mammalian PDC is associated with the gill PDC. The activity of the complex may be regulated by a phosphorylation/dephosphorylation mechanism and by the relative levels of substrates, products, and other metabolites in the mit

ISSN:0022-104X    

DOI:10.1002/jez.1402360302

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

年代:1985

数据来源: WILEY

摘要:

AbstractSince the male oyster toadfish (Opsanus tau) is more active in sound production than the female, we hypothesized that sonic muscles of the male are biochemically specialized to perform more work. In order to categorize the muscle biochemically and test for sexual differences, we measured the activity of two anaerobic enzymes, 3‐phosphoglyceraldehyde dehydrogenase (3PG) and lactic dehydrogenase (LDH), and two aerobic enzymes, malate dehydrogenase (MDH) and glutamic oxaloacetic transaminase (GOT). Males exhibited greater 3PG and GOT activity than females (p<0.05). Both MDH and LDH showed little activity in either sex. High 3PG and low LDH levels indicate a substained level of glycolysis, with pyruvate shuttled into aerobic metabolism, and high GOT activity indicates a high level of aerobic metabolism. From this and other data, we conclude that toadfish sonic muscle can be classified as fast‐twitch oxidative glycolytic or fast‐twitch fatigue resistant. The endocrine basis for these sexual differences was examined by implanting steroid pellets into ovariectomized females. Testosterone induced a doubling of 3PG activity (p<0.02), and dihydrotestosterone induced an eight‐fold increase (p<0.0005) in GOT concentration over controls. The steroids had no effect on LDH and MDH activities. Hormones, therefore, trigger one of the fundamental sexual differences underlying toadfish communication, namely a difference in metabolism, providing the male with the capacity for increased sound pro

ISSN:0022-104X    

DOI:10.1002/jez.1402360303

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

年代:1985

数据来源: WILEY

摘要:

AbstractWhen the rock crabCancer irroratusis exposed to hypoosmotic artificial seawater (ASW) its muscle cell volume is regulated, in part, by a reduction of the intracellular glycine concentration. Therefore, the effect of reduced ASW osmolarity on the unidirectional glycine influx and efflux of isolated rock crab muscle cells was assessed to determine whether changes in these fluxes might contribute to the decreased intracellular glycine concentration. The glycine influx (extracellular glycine concentration = 1mM) into muscle cells exposed to 60% ASW decreased from 810 nmol/g dry wt × 8 min (100% ASW) to 470 nmole/g dry wt × 8 min, whereas the glycine efflux increased from 3,410 nmole/g dry wt × 8 min (100% ASW) to 5,930 nmole/g dry wt × 8 min. The decrease in influx was due to the reduced osmolarity rather than the reduced Na+concentration of the 60% ASW. Further, even the total replacement of Na+(Li+and Tris substituted) reduced the glycine influx by only 34%. Thus Na+‐coupled glycine influx is not an important factor in adjusting the intracellular glycine concentration of muscle cells exposed to reduced ASW osmolarity. Since under isosmotic conditions glycine efflux exceeds influx by a factor of four, the hypoosmotically induced increase in glycine efflux is largely responsible for the decrease of the intracellular glycine concentration during the initial stages of hypoosmotic s

ISSN:0022-104X    

DOI:10.1002/jez.1402360304

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

年代:1985

数据来源: WILEY

摘要:

AbstractCation sensitivities (K+, Na+, and Ca2+) of luminal and basolateral membrane surfaces of secretory acinar cells were compared using a luminally perfused and externally superfused salivary gland from the aquatic snail,Helisoma trivolvis. Tight junctions delimiting the two membrane surfaces were observed near the acinar lumen suggesting that the total membrane area exposed to the superfusion solution exceeded that in contact with the luminal perfusion solution.The resting membrane potential of acinar cells was found to be dependent upon the K+concentration in both the external superfusion and the luminal perfusion solutions. Unilateral K+elevation at either membrane surface produced a rapid and sustained depolarization of the acinar cell. For a given K+concentration, the level of depolarization produced by K+elevation at the basolateral surface was significantly higher than at the luminal surface. The highest level of membrane depolarization was observed following simultaneous K+elevation at both membrane surfaces.The ability of acinar cells to generate overshooting action potentials in response to electrical field stimulation was dependent upon both Na+and Ca2+.Complete blockade invariably occurred following bilateral removal of either cation. The effects of unilateral removal of either Na+or Ca2+proved to be somewhat variable. In general, unilateral removal of Na+was more effective in reducing the regenerative response than Ca2+while removal of either cation from the basolateral surface was more effective in reducing the regenerative response than its removal from the luminal surface.Electrically evoked action potentials in acinar cells could also be blocked with unilateral application of the Ca2+antagonist, cadmium (Cd2+), at either membrane surface. However, higher Cd2+concentrations were required to achieve complete blockade when applied to the luminal than to the basolateral gland surface. This result fails to support a hypothesis of voltage‐sensitive Ca2+channels being spatially restricted to the luminal cell surface in this preparatio

ISSN:0022-104X    

DOI:10.1002/jez.1402360305

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe role of glutamate dehydrogenase (GDH) in amino acid catabolism of the mantle ofMya arenariawas examined using coupled mitochondria and in vitro enzyme activity measurements. The maximal activities of mitochondrial glutamate‐oxaloacetate transaminase (GOT) and glutamate‐pyruvate transaminase (GPT) are fourfold and twofold greater, respectively, than GDH (deaminating). Based on pH profiles, the relative activities of these enzymes in vivo may be highly dependent on mitochondrial pH. Addition of ADP resulted in a 15‐fold activation of GDH (deaminating) and a shift in the pH optimum from 8.1 to 8.6. The in vitro activity of GDH was sufficient to account for all NADH produced in intact mitochondria oxidizing glutamate. In intact mitochondria at pH 7.4 and 8.2, addition of the aminotransferase inhibitor aminooxyacetic acid (AOA) had no effect on the state 3 rate of glutamate oxidation. However, at pH 6.7 in situ GDH (deaminating) activity was insufficient to maintain the rate of glutamate oxidation in the absence of transaminase activity. Glutamate oxidation between pH 6.4 and 8.0 is limited by the electron transport system. At pH 8.3, transport of glutamate into the mitochondria may be rate limiting. Mitochondria oxidizing glutamate in state 4 in the presence of phosphate or in state 2 in the absence of phosphate demonstrated increased oxygen consumption in response to the uncoupler carbonyl m‐chlo‐rophenyl‐hydrazone (CCCP). These studies suggest that in spite of low activities compared to vertebrates, GDH activities could be physiologically significant in amino acid metabolism ofMya are

ISSN:0022-104X    

DOI:10.1002/jez.1402360306

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

年代:1985

数据来源: WILEY

摘要:

AbstractStructural proteins of scales with various morphologies were compared. Ventral reticulate scales have soluble proteins that differ from both dorsal reticulate scales and scutellate scales. Ventral reticulate scale proteins are more like those in reptilian scales, whereas both dorsal type scales have proteins of the ϕ‐keratin family found in beaks, claws, and feathers. The morphological similarity in avian reticulate scales is due to convergence as the result of functional requiremen

ISSN:0022-104X    

DOI:10.1002/jez.1402360307

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe transient embryonic diapause associated with delayed implantation in mice is characterized by decreases in the rates of synthesis of RNA and protein as well as a cessation of development. The present experiments were undertaken to examine the possibility that controls on protein synthesis at the level of translation of mRNA provide a regulatory mechanism in this situation. Rates of peptide chain elongation were determined in dormant embryos as well as in embryos that were reactivated either in vivo by estradiol‐17β or by incubation in vitro. In dormant embryos the rate of peptide elongation was found to be approximately half that in active embryos. Although this change in translational efficiency appears to be sufficient to account for previously observed differences in overall rates of protein synthesis in dormant and reactivated embryos, the possibility that some changes also occur at the level of transcription during reactivation is not ruled o

ISSN:0022-104X    

DOI:10.1002/jez.1402360308

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

年代:1985

数据来源: WILEY

摘要:

AbstractThis study was designed to test the ability of adult bullfrogs (Rana catesbeiana) to regenerate forelimbs, both with and without various experimental treatments. Distal humerus‐level forelimb amputations provided with additional deviated (sciatic) nerve and/or repeated soft‐tissue injury exhibited considerable outgrowth. However, control sham‐operated forelimbs also produced regenerates with comparable frequency, size, and morphological complexity. The lengths of the regenerates ranged from 0.4 to 2.6 cm, representing an outgrowth of 10–65% of the portion removed by the distal humerus amputation plane; some regenerates exhibited an external morphology indicative of digitlike structures. Some outgrowths were flexible but only one was capable of independent movement. Victoria Blue staining of whole regenerates revealed a variety of internal cartilage elements. Staining showed a single solid mass of cartilage in some regenerates while others had several individual and variably shaped cartilages projecting distally. Histological analysis also revealed the presence of connective tissue, striated muscle, and abundant nerve fibers in addition to the individual cartilage elements. We have tentatively termed these responses pattern‐deficient reg

ISSN:0022-104X    

DOI:10.1002/jez.1402360309

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

年代:1985

数据来源: WILEY

摘要:

AbstractMelanophores of adult fish ofOryzias latipesin culture exhibited light‐sensitivity. They responded with pigment aggregation to darkness, and with dispersion to light. These responses, which could be repeated more than several times by changing the light intensity, were not affected by α‐ or β‐adrenergic blockers. These facts suggest that melanophores of Oryzias directly respond to light with pigment displacement. The degree of melanosome translocation was changed depending on the intensity of illumination. The most effective wavelength for the induction of melanosome dispersion was near 415 nm, and light with wavelength around 550 nm was scarcely effective. Theophylline (2mM) and cyclic AMP (50 μM) inhibited dark‐induced melanosome aggregation. Such inhibition suggests that light may act as a trigger to induce changes in the intracellular levels of cyclic AMP. Seasonal variation was observed in the light‐sensitivity of melanophores in culture; dark‐induced melanosome aggregation was less significant in winter. These facts suggest that a photoreceptive substance may play a role in the light‐sensitivity of melanophores as a trigger to induce the aggregatio

ISSN:0022-104X    

DOI:10.1002/jez.1402360310

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe measurement of cellular DNA content by DNA microfluorometry revealed that medaka embryos that were fertilized with normal sperm and exposed to heat shock (41°C for 3 min) or hydrostatic pressure (700 kg/cm2for 10 min) at 85–95 min after insemination were tetraploid. Embryos fertilized with normal sperm and exposed to heat shock (41°C for 2 min at 2–3 min after insemination) were triploid. These results suggest that heat shock or hydrostatic pressure at 85–95 min after insemination arrests the first cleavage, while heat shock at 2–3 min after insemination arrests the second meiotic division.Medaka clones have been produced by the following method: Eggs from orange‐red or variegated variety were activated by UV‐irradiated, genetically impotent sperm of wild‐type fish (UV sperm). The haploid eggs obtained were diploidized by preventing the first cleavage with heat shock or hydrostatic pressure to produce homozygous females. Each of the two homozygous females was mated with vasectomized male in isotonic balanced salt solution to collect unfertilized eggs. The collected eggs were activated with UV sperm and converted from haploid to diploid by arrest of the second meiotic division with heat shock. Hatched fry of each homozygous diploid (all females) were fed with a methyltestosterone‐containing diet (40 μg/gm diet) to produce sex‐reversed males, which were mated with brood females, and thus two cloned

ISSN:0022-104X    

DOI:10.1002/jez.1402360311

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

年代:1985

数据来源: WILEY