摘要:

AbstractThe role of the proton motive force (PMF) and significance of the common intracellular monovalent cations (Na+and K+) in proline oxidation by oyster (Crassostrea virginica) gill mitochondria were examined. Proline was oxidized at moderate rates in the presence of ADP under isosmotic conditions. Oxidation of proline was inhibited by CCCP (carbonyl cyanide m‐chlorophenylhydrazone), an uncoupler of oxidative phosphorylation. Oxidation of pyruvate, but not succinate (each oxidized at moderate rates), was inhibited by CCCP, confirming that the PMF was at least partially dissipated. These data suggest that transport of proline is dependent on some component of the PMF, either the pH gradient or the membrane potential. Less inhibition of proline oxidation by CCCP was achieved at higher proline concentrations suggesting that diffusional penetration may become more important as proline concentrations increase. Oxidation of proline was not substantially affected by reducing concentrations of Na+or K+or both Na+and K+(Na+<9 mM; K+choline+). The high rate of oxidation achieved using Na+is unusual and is probably an adaptation related to the high intracellular Na+concentrations found in many bivalve mollusc

ISSN:0022-104X    

DOI:10.1002/jez.1402430102

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

年代:1987

数据来源: WILEY

摘要:

AbstractLevels of digestive enzymes were analyzed in water snakes following artificial feeding. A prominent increase of total proteolytic activity in the stomach was evident after feeding with a casein solution or after the snake was offered a fish (9‐ and 6‐fold that of the fasting level, respectively). The activity following feeding with starch was much lower. Increased levels of chymotrypsin(ogen) as well as of amylase were evident in the pancreas 1 day after feeding the snake with fish. A specific induction of increased level of chymotrypsin in the pancreas of adult snakes was achieved by feeding with casein (12‐fold that of the fasting level). In the group fed with starch, the chymotrypsin level dropped, while a 3‐fold increase of amylase was evident. In newborn snakes, fed for the first time, casein induced a dramatic increase in the level of chymotrypsin in the pancreas (58 times the fasting level); feeding with starch induced an approximate 2‐fold increase of chymotrypsin. Histological examination of the pancreas 1 day following casein feeding showed acinar cells loaded with zymogen granules. In starved animals and in snakes fed with starch, a much lower concentration of zymogen granules was observed. The pancreas of the snake may, thus, be most suitable for studying the specific induction of synthesis of digestiv

ISSN:0022-104X    

DOI:10.1002/jez.1402430103

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe transient accumulation of proline in the gills of the osmotically stressed ribbed mussel (Modiolus demissus), may be controlled by a transient regulation of the α‐ketoglutarate dehydrogenase (KGDH) activity. In this study, KGDH was partially purified from lysed mitochondria of gill tissue by differential centrifugation techniques. Various modulators of enzyme activity assayed at a saturating concentration (2.5 mM) of ketoglutarate (KG), showed inhibition by high concentrations of Cl−(10–100 mM) and a slight activation or inhibition by the other compounds (10 mM), when assayed in the absence of added Ca++. Addition of Ca++at pH 7.2 caused no change in Ks0.5for KG and a 1.5‐fold increase in Vmaxwhereas at pH 7.8, no change in Vmaxbut a 40–50% decrease in Ks0.5and slight positive cooperative effects (“napp” 1.4–1.7) were observed. At pH 7.8, addition of adenine nucleotides (AMP, ADP, ATP at 5mM) had no effect on the Vmax; however, ATP and ADP lowered the Ks0.5by 3.5–4‐fold. The CoA derivatives of short chain fatty acids were found to inhibit the enzyme by 30–60%. This inhibition was reversed by Ca++but only at higher KG concentrations (250 μM). The enzyme showed a major change in activity at nicotinamide adenine dinucleotide/reduced nicotinamide adenine dinucleotide ratio (NAD/NADH)>1, an effect that could not be modified by Ca++. It appears, therefore, that the mussel gill KGDH is mainly regulated by changes in mitochondrial pH and ketoglutarate or adenine nucleotide levels, rather than by changes in mitoc

ISSN:0022-104X    

DOI:10.1002/jez.1402430104

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

年代:1987

数据来源: WILEY

摘要:

AbstractTauropine dehydrogenase (pyruvate + taurine + NADH ⇋ tauropine + NAD+) was partially purified from the pedicles of the inarticulate brachiopod,Glottidea pyramidata. The molecular mass of this enzyme, as determined by high performance liquid chromatography (HPLC) using a TSK‐ 3000 SW column, was 39,500 daltons. This molecular mass value is consistent with a monomeric structure characteristic of all opine dehydrogenases. Kinetic studies revealed that taurine and pyruvate were the preferred substrates, although other amino acids and keto acids were used to some extent. This enzyme readily oxidized tauropine displaying an apparent Kmof 3.1 mM. Taurine was found to be the most abundant free amino acid in neutralized perchloric acid extracts of pedicles. Thus, it is likely that taurine is a physiological substrate. This enzyme shows striking similarities to tauropine dehydrogenases from archeogastrop

ISSN:0022-104X    

DOI:10.1002/jez.1402430105

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

年代:1987

数据来源: WILEY

摘要:

AbstractExperiments were carried out to investigate the role of the gut in the osmotic balance of the land slugAriolimax columbianus.Previous investigators have shown that absorption of nutrients, calcium, and some heavy metals occurs in the slug's digestive gland and intestine. The only function suggested for the rectum, beyond transfer of the fecal mass, has been its possible involvement in lipid absorption. We collected hemolymph and fluids contained in different regions of the gastrointestinal tract and compared these with respect to osmotic pressure as well as to concentrations of ions (sodium, potassium, calcium, and chloride), glucose, and amino acids. The osmotic pressure of rectal contents was found to average one‐quarter the values of other fluids. In in vitro experiments sacs of intestine and rectum exposed to 1:4 mucosa:serosa osmotic gradients for 1 h showed transfer of fluid across the sac wall into the surrounding fluid. This transfer was significantly enhanced in the case of the rectum but not of the intestine, after dehydration or loss of hemolymph, and during immersion of the sacs in media containing the gastropod neurotransmitters FMRFamide, norepinephrine, and 5‐hydroxytryptamine, as well as arginine vasotocin. The data indicate that the rectum of the slug serves as a small but ready source of water available for use under conditions of acute water deficie

ISSN:0022-104X    

DOI:10.1002/jez.1402430106

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

年代:1987

数据来源: WILEY

摘要:

AbstractPrevious work has suggested a common migratory strategy among fishes may involve changes in recruitment pattern of skeletal muscle types, allowing fast muscle to function continuously. In this study no evidence was found for changes in adenine nucleotide metabolism, thought to be important in fatigued muscle, with metamorphosis from the nonmigratory yellow to migratory silver eel in either slow or fast muscle tissue. Myofibrillar ATPase activity was found to be lower than reported values for other teleosts, around 0.075 and 0.17 μM inorganic phosphate mg−1min−1for slow and fast muscle, respectively. No change was found in the Ca+ +‐kinetics of the enzyme within either muscle type. Likewise, no change in the contractile performance of fast muscle was evident, arguing against changes in activity pattern. In contrast to mammalian endurance exercise training where major changes in aerobic capacity occur in fast muscle, migratory pre‐adaptation in eel appears to be restricted to changes in slow muscle performance. A displacement of the slow muscle force‐velocity curve to the right upon metamorphosis results in 30% increase in the tension developed at maximal power output from 2.4 to 3.2 N cm−2. The difference in migratory potential between yellow and silver eels was shown previously to involve an increased aerobic capacity. The change in contractile characteristics may further improve endurance by permitting a portion of the tissue to periodically replenish endogenous e

ISSN:0022-104X    

DOI:10.1002/jez.1402430107

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

年代:1987

数据来源: WILEY

摘要:

AbstractTwo new monoclonal antibodies (McAbs), ALD‐180 and ALD‐88, produced against the myosin of the slow anterior latissimus dorsi (ALD) muscle of the chicken are described. Their specificity for myosin heavy chain (MHC) was established by radioimmunoassay, immunoautoradiography, and immunofluorescence. They were used in conjunction with McAbs MF‐14 and MF‐30 (which have been characterized previously to be directed against MHC of the fast skeletal muscle) to examine the developmental changes of the chicken ALD muscle. At the 16‐day embryonic, early posthatch, and adult stages the ALD muscle fibers differed in their reaction pattern with the McAbs: at the embryonic stage all fibers reacted strongly with ALD‐180 and weakly with ALD‐88 and MF‐30; at the early posthatch stage there was a checkerboard pattern with many fibers not reacting with any of these three McAbs; and at the adult stage all fibers reacted strongly with ALD‐180 and ALD‐88 and weakly with MF‐30. The MF‐14 antibody did not react with ALD muscle at any developmental stage. The mature pattern of immunoreactivity of the ALD muscle fibers with the antibodies was established only after 9 weeks posthatch, and during this 9‐week period the immunofluorescence changes were nonsynchronous. Based on immunocytochemical evidence of changes in myosin isoform expression, this study clearly demonstrates a distinctive neonatal (early posthatch) stage in the development o

ISSN:0022-104X    

DOI:10.1002/jez.1402430108

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

年代:1987

数据来源: WILEY

摘要:

AbstractChick embryos were denervated early in development in order to disrupt the normal inductive interactions between the nervous system and developing populations of mononucleated myoblasts and their precursors in the leg. Neural tissue, either spinal cord or ciliary ganglion, was transplanted to one leg of the denervated embryos; the other leg remained aneural. Clonal analysis of cell populations in the transplant‐containing legs showed that ectopic nerve tissue can recapitulate some of the neuromuscular interactions that occur in normally developing embryos. Chief among these was the observation that transplantation induced the appearance of the CMR‐III myoblast class in the leg muscle. Since the process by which CMR‐III myoblasts are produced from a precursor is dependent on nerve both in vivo and in vitro (Bonner, P.H. and T.R. Adams, Dev. Biol.,90:175–184, 1982), it was concluded that transplanted nerve tissue can also induce myoblast differen

ISSN:0022-104X    

DOI:10.1002/jez.1402430109

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

年代:1987

数据来源: WILEY

摘要:

AbstractTyrosinase activities and dopachrome conversion activity were evaluated in extracts made from skins of 6‐day‐old mice that were mutant at the agouti and albino loci. Dopa oxidase (DO) activity of tyrosinase in fully pigmented (C/C) mice is reduced in extracts made from skins of yellow 6‐day‐old mice as compared to those of black mice. Dopachrome conversion (DC) activity is absent from skin extracts of normal yellow mice and is present in normal black mice. DC activity is a characteristic of a separate enzyme which has been called dopachrome conversion factor or dopachrome oxidoreductase. We measured the dopa oxidase activity and dopachrome conversion activity in skin extracts of yellow mice and black mice that were mutant at the albino (C) locus. Extracts made from extreme‐dilution (ce/ce) mice do not have DO activity. Those from yellow extreme‐dilution mice do not have DC activity, while those from black, extreme‐dilution mice do. The DO and DC activities that characterize skin extracts made from platinum (cp/cp) yellow mice are similar to those of platinum black mice. These observations suggest possible mechanisms by which the functions controlled by the agouti and albino loci interact to control

ISSN:0022-104X    

DOI:10.1002/jez.1402430110

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

年代:1987

数据来源: WILEY

摘要:

AbstractIt is not known if the male sterility caused by the pleiotropic mutationsp6H(pink‐eyed 6H) andqk(quaking) is intrinsic or extrinsic to spermatogenic cells. This question was addressed by juxtaposing mutant and normal cells in the testes of chimeric mice and determining whether the mutant germ cells could form functional sperm. Twenty‐one male chimeras consisting of normal cells andp6H/p6Horqk/qkcells were analyzed. For each, breeding productivity and testicular and sperm morphology were determined. Karyotypes and isozyme analyses were performed to identify the two cellular components of each chimera. All male chimeras that containedp6H/p6H, XY cells were sterile. Although some chimeras with aqk/qk, XY mutant component were fertile, none produced offspring from the homozygousqkcomponent. Spermatids of the sterile chimeras showed abnormalities characteristic of the mutations.We conclude from this study that the presence of normal XY germ and somatic cells in the testis did not rescue the male sterile phenotype of homozygousp6HorqkXY germ cells. Therefore, the action of these mutant genes in causing sperm abnormalities and sterility is autonomous to the germ ce

ISSN:0022-104X    

DOI:10.1002/jez.1402430111

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

年代:1987

数据来源: WILEY