The Case for Accurate Labeling of Superchilled Fish

1970 ◽  
Vol 27 (11) ◽  
pp. 2101-2103
Author(s):  
Edith Gould
Keyword(s):  
Skeletal Muscle ◽  
Enzyme Activity ◽  
Malic Enzyme ◽  
Objective Test ◽  
Melanogrammus Aeglefinus ◽  
Tissue Fluid ◽  
Freezing And Thawing ◽  
Malic Enzyme Activity ◽  
Frozen Fish ◽  
Haddock Melanogrammus Aeglefinus

The skeletal muscle of haddock (Melanogrammus aeglefinus) contains a malic enzyme activity that can be solubilized by freezing and thawing the flesh but that is not present in the tissue fluid of unfrozen haddock. An objective test, previously used to detect the presence of this normally latent enzyme activity in the tissue fluid of frozen and thawed fish, has been used to discover whether the latent enzyme appears in the tissue fluid of superchilled fish. Enzymograms for superchilled fish are the same as for frozen fish, both showing the latent enzyme activity that is not present in unfrozen fish. The test underscores the need for precise labeling of superchilled fish.

Collaborative Study of a Test to Determine Whether Shucked Oysters Have Been Frozen and Thawed

1973 ◽  
Vol 56 (3) ◽  
pp. 541-543
Author(s):  
Edith Gould
Keyword(s):  
Enzyme Activity ◽  
Crassostrea Virginica ◽  
Malic Enzyme ◽  
Collaborative Study ◽  
Bacterial Activity ◽  
Tissue Fluid ◽  
Migration Rates ◽  
Electrophoretic Migration ◽  
Malic Enzyme Activity

Abstract Six laboratories have collaboratively tested a method to determine whether shucked oysters have been frozen and thawed at any time. The method utilizes the differing electrophoretic migration rates of various forms of malic enzyme activity, some of which are not present in the tissue fluid until after the tissue has been frozen and thawed. The technique is enzymography, which combines electrophoresis and a specific histochemical medium. Five laboratories tested Crassostrea virginica, obtaining markedly different patterns for the unfrozen oysters compared with the frozen and thawed oysters. The sixth laboratory tested C. gigas, and was similarly successful in distinguishing between the storage treatments. In shucked oysters stored up to 3 weeks at 4°C, neither autolysis nor bacterial activity altered the enzymographic patterns. The method has been adopted as official first action.

Malic Enzyme: Evidence for Two Molecular Forms in the Sarcoplasm of Fish Skeletal Muscle

1968 ◽  
Vol 25 (8) ◽  
pp. 1581-1589 ◽  
Author(s):  
Edith Gould
Keyword(s):  
Skeletal Muscle ◽  
Malic Enzyme ◽  
Molecular Forms ◽  
Free Form ◽  
Tissue Fluid ◽  
Migration Rates ◽  
Catalytically Active ◽  
A Subunit ◽  
Malic Enzyme Activity ◽  
Latent Activity

A latent form of malic enzyme activity (latent ME), which appears in the centrifuged tissue fluid of haddock skeletal muscle after the tissue has been frozen and thawed, appears also in the fluid of unfrozen haddock muscle after homogenization. It is more labile to refrigerated storage, ionizing radiation, and heat than is its normally soluble counterpart (free ME), and the two forms have demonstrably different electrophoretic migration rates. Although there is some evidence for catalytically active subunits for both forms, it has not yet been determined whether the latent activity is a true isoenzyme or a subunit of the free form.

Test to Determine Whether Shucked Oysters Have Been Frozen and Thawed

1970 ◽  
Vol 53 (6) ◽  
pp. 1237-1241 ◽  
Author(s):  
Edith Gould ◽  
Michael J Medler
Keyword(s):  
Enzyme Activity ◽  
Gel Electrophoresis ◽  
Malic Enzyme ◽  
Polyacrylamide Gel Electrophoresis ◽  
Histochemical Staining ◽  
Soluble Form ◽  
Buffer System ◽  
Freezing And Thawing ◽  
Bacterial Action ◽  
Malic Enzyme Activity

Abstract An objective test is described that will detect whether refrigerated, shucked whole oysters have been frozen and thawed at any time. Latent forms of malic enzyme activity are solubilized by freezing and thawing and can be differentiated from the normally soluble form by their differing rates of electrophoretic migration under the conditions described in this paper. SuperchiUed (23°F) oyster meats showed the same latent malic enzyme activity as the frozen. A sharply discontinuous buffer system during the polyacrylamide gel electrophoresis and a carefully timed incubation period for the histochemical staining are essential to the test. In oyster meats stored at 34°F for up to 3 weeks, neither autolysis nor bacterial action was great enough to produce the enzymogram peculiar to oysters that have been frozen or superchilled and thawed.

Morphological and biochemical analyses of changes in rat hepatocytes related to wine and ethanol consumption

1984 ◽  
Vol 42 ◽  
pp. 232-233
Author(s):  
S.M. Geyer ◽  
C.L. Mendenhall ◽  
J.T. Hung ◽  
E.L. Cardell ◽  
R.L. Drake ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Enzyme Activity ◽  
Malic Enzyme ◽  
Smooth Endoplasmic Reticulum ◽  
Rat Hepatocytes ◽  
Mature Male ◽  
Treatment Groups ◽  
Malic Enzyme Activity ◽  
Biochemical Analyses

Thirty-three mature male Holtzman rats were randomly placed in 3 treatment groups: Controls (C); Ethanolics (E); and Wine drinkers (W). The animals were fed synthetic diets (Lieber type) with ethanol or wine substituted isocalorically for carbohydrates in the diet of E and W groups, respectively. W received a volume of wine which provided the same gram quantity of alcohol consumed by E. The animals were sacrificed by decapitation after 6 weeks and the livers processed for quantitative triglycerides (T3), proteins, malic enzyme activity (MEA), light microscopy (LM) and electron microscopy (EM). Morphometric analysis of randomly selected LM and EM micrographs was performed to determine organellar changes in centrilobular (CV) and periportal (PV) regions of the liver. This analysis (Table 1) showed that hepatocytes from E were larger than those in C and W groups. Smooth endoplasmic reticulum decreased in E and increased in W compared to C values.

‘Malic Enzyme’ Activity in Blowfly Muscle

Nature ◽  
1956 ◽  
Vol 177 (4514) ◽  
pp. 842-843 ◽  
Author(s):  
S. E. LEWIS ◽  
G. M. PRICE
Keyword(s):  
Enzyme Activity ◽  
Malic Enzyme ◽  
Malic Enzyme Activity

An in situ cell marker for clonal analysis of development of the extraembryonic endoderm in the mouse*

Development ◽  
1984 ◽  
Vol 80 (1) ◽  
pp. 251-288
Author(s):  
R. L. Gardner
Keyword(s):  
Enzyme Activity ◽  
Malic Enzyme ◽  
Cell Mass ◽  
Differential Staining ◽  
Wild Type ◽  
Primitive Endoderm ◽  
Extraembryonic Endoderm ◽  
Blue Tetrazolium ◽  
Malic Enzyme Activity ◽  
Parietal Endoderm

Conditions were found for staining whole mid-gestation capsular parietal endoderms and visceral yolk sacs for malic enzyme activity that gave excellent discrimination between wildtype (Mod-1+/Mod-1+) cells and mutant (Mod-ln/Mod-1n) cells that lack the cytoplasmic form of the enzyme. Reciprocal blastocyst injection experiments were undertaken in which single primitive endoderm cells of one genotype were transplanted into embryos of the other genotype. In addition, Mod-1+/Mod-1+ early inner cell mass (ICM) cells were injected into Mod-1n/Mod-1n blastocysts, either in groups of two or three singletons or as daughter cell pairs. A substantial proportion of the resulting conceptuses showed mosaic histochemical staining in the parietal endoderm, visceral yolk sac, or in both these membranes. Stained cells were invariably intimately intermixed with unstained cells in the mosaic parietal endoderms. In contrast, one or both of two distinct patterns of staining could be discerned in mosaic visceral yolk sacs. The first, a conspicuously ‘coherent’ pattern, was found to be due to endodermal chimaerism; the second, a more diffuse pattern, was attributable to chimaerism in the mesodermal layer of this membrane. The overall distribution of cells with donor staining characteristics resulting from primitive endoderm versus early ICM cell injections was consistent with findings in earlier experiments in which allozymes of glucosephosphate isomerase were used as markers. The conspicuous lack of phenotypically intermediate cells in predominantly stained areas of mosaic membranes suggested that the histochemical difference between Mod-1+/Mod-1+ and Mod-1n/Mod-ln genotypes was cell-autonomous. This conclusion was strengthened by the results of staining mixed in vitro cultures of parietal endoderm in which presence or absence of phagocytosed melanin granules was used as an independent means of distinguishing wild type from null cells. By substituting tetranitro blue tetrazolium for nitro blue tetrazolium in the incubation medium, satisfactory differential staining was obtained for both the extraembryonic endoderm and other tissues of earlier postimplantation wild type versus null embryos. Finally, absence of cytoplasmic malic enzyme activity does not appear to have a significant effect on the viability or behaviour of mutant cells.

scholarly journals Identification and Characterization ofMAE1, the Saccharomyces cerevisiae Structural Gene Encoding Mitochondrial Malic Enzyme

1998 ◽  
Vol 180 (11) ◽  
pp. 2875-2882 ◽  
Author(s):  
Eckhard Boles ◽  
Patricia de Jong-Gubbels ◽  
Jack T. Pronk
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Enzyme Activity ◽  
Pyruvate Kinase ◽  
Malic Enzyme ◽  
Fold Increase ◽  
Growth Conditions ◽  
Anaerobic Growth ◽  
Oxidative Decarboxylation ◽  
Mrna Levels ◽  
Malic Enzyme Activity

ABSTRACT Pyruvate, a precursor for several amino acids, can be synthesized from phosphoenolpyruvate by pyruvate kinase. Nevertheless, pyk1 pyk2 mutants of Saccharomyces cerevisiae devoid of pyruvate kinase activity grew normally on ethanol in defined media, indicating the presence of an alternative route for pyruvate synthesis. A candidate for this role is malic enzyme, which catalyzes the oxidative decarboxylation of malate to pyruvate. Disruption of open reading frame YKL029c, which is homologous to malic enzyme genes from other organisms, abolished malic enzyme activity in extracts of glucose-grown cells. Conversely, overexpression ofYKL029c/MAE1 from the MET25 promoter resulted in an up to 33-fold increase of malic enzyme activity. Growth studies with mutants demonstrated that presence of either Pyk1p or Mae1p is required for growth on ethanol. Mutants lacking both enzymes could be rescued by addition of alanine or pyruvate to ethanol cultures. Disruption of MAE1 alone did not result in a clear phenotype. Regulation of MAE1 was studied by determining enzyme activities and MAE1 mRNA levels in wild-type cultures and by measuring β-galactosidase activities in a strain carrying a MAE1::lacZ fusion. Both in shake flask cultures and in carbon-limited chemostat cultures,MAE1 was constitutively expressed. A three- to fourfold induction was observed during anaerobic growth on glucose. Subcellular fractionation experiments indicated that malic enzyme in S. cerevisiae is a mitochondrial enzyme. Its regulation and localization suggest a role in the provision of intramitochondrial NADPH or pyruvate under anaerobic growth conditions. However, since null mutants could still grow anaerobically, this function is apparently not essential.

scholarly journals YtsJ Has the Major Physiological Role of the Four Paralogous Malic Enzyme Isoforms in Bacillus subtilis

2006 ◽  
Vol 188 (13) ◽  
pp. 4727-4736 ◽  
Author(s):  
Guillaume Lerondel ◽  
Thierry Doan ◽  
Nicola Zamboni ◽  
Uwe Sauer ◽  
Stéphane Aymerich
Keyword(s):  
Enzyme Activity ◽  
Bacillus Subtilis ◽  
Malic Enzyme ◽  
Metabolic Flux ◽  
Physiological Role ◽  
Extreme Case ◽  
Growth Defect ◽  
Flux Analysis ◽  
Malic Enzyme Activity

ABSTRACT The Bacillus subtilis genome contains several sets of paralogs. An extreme case is the four putative malic enzyme genes maeA, malS, ytsJ, and mleA. maeA was demonstrated to encode malic enzyme activity, to be inducible by malate, but also to be dispensable for growth on malate. We report systematic experiments to test whether these four genes ensure backup or cover different functions. Analysis of single- and multiple-mutant strains demonstrated that ytsJ has a major physiological role in malate utilization for which none of the other three genes could compensate. In contrast, maeA, malS, and mleA had distinct roles in malate utilization for which they could compensate one another. The four proteins exhibited malic enzyme activity; MalS, MleA, and MaeA exhibited 4- to 90-fold higher activities with NAD+ than with NADP+. YtsJ activity, in contrast, was 70-fold higher with NADP+ than with NAD+, with Km values of 0.055 and 2.8 mM, respectively. lacZ fusions revealed strong transcription of ytsJ, twofold higher in malate than in glucose medium, but weak transcription of malS and mleA. In contrast, mleA was strongly transcribed in complex medium. Metabolic flux analysis confirmed the major role of YtsJ in malate-to-pyruvate interconversion. While overexpression of the NADP-dependent Escherichia coli malic enzyme MaeB did not suppress the growth defect of a ytsJ mutant on malate, overexpression of the transhydrogenase UdhA from E. coli partially suppressed it. These results suggest an additional physiological role of YtsJ beyond that of malate-to-pyruvate conversion.

Metabolic alterations after dehydroepiandrosterone treatment in Zucker rats

1984 ◽  
Vol 246 (2) ◽  
pp. E123-E128 ◽  
Author(s):  
A. Shepherd ◽  
M. P. Cleary
Keyword(s):  
Enzyme Activity ◽  
Adipose Tissue ◽  
Fatty Acid ◽  
Malic Enzyme ◽  
Fatty Acid Synthetase ◽  
Metabolic Effects ◽  
Zucker Rats ◽  
Obese Rats ◽  
Malic Enzyme Activity ◽  
Dhea Treatment

Dehydroepiandrosterone (DHEA) is a known noncompetitive inhibitor of glucose-6-phosphate dehydrogenase (G6PD). In the present investigation, the effects of chronic DHEA treatment on G6PD and several other enzymes involved in lipid metabolism were examined in lean and obese Zucker rats. Significant decreases in body weight were found in DHEA-treated rats in comparison with nontreated rats. In lean rats, DHEA treatment did not decrease either liver or adipose tissue G6PD and fatty acid synthetase activity, but malic enzyme activity was increased. In obese rats, decreased liver and adipose tissue G6PD and fatty acid synthetase activities were found. Malic enzyme activity in liver of obese DHEA rats was increased but not in adipose tissue. Adipose tissue lipoprotein lipase activity was decreased in both lean and obese DHEA rats. Serum insulin in obese DHEA rats was also decreased compared with control obese rats. These results indicate that the inhibition of G6PD may not be the mechanism of action of the antiobesity effect of DHEA. However, the metabolic effects of DHEA seen in obese rats may contribute to its antiobesity action.

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