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At least 1,099 records · Page 61Linked to original sources
PubMed1972

Subcellular fractionation by differential and zonal centrifugation of aerobically grown glucose-de-repressed Saccharomyces carlsbergensis.

1. Homogenates were prepared from sphaeroplasts of aerobically grown glucose-de-repressed Saccharomyces carlsbergensis and the distributions of marker enzymes were investigated after differential centrifugation. Cytochrome c oxidase and cytochrome c were sedimented almost completely at 10(5)g-min, and this fraction also contained 37% of the catalase, 27% of the acid p-nitrophenyl phosphatase, 53 and 54% respectively of the NADH- and NADPH-cytochrome c oxidoreductases. 2. Zonal centrifugation indicated complex density distributions of the sedimentable portions of these enzymes and of adenosine triphosphatases and suggested the presence of two mitochondrial populations, as well as a bimodal distribution of peroxisomes and heterogeneity of the acid p-nitrophenyl phosphatase-containing particles. 3. Several different adenosine triphosphatases were distinguished in a post-mitochondrial supernatant that contained no mitochondrial fragments; these enzymes varied in their sensitivities to oligomycin and ouabain and their distributions were different from those of pyrophosphatase, adenosine phosphatase and adenosine pyrophosphatase. 4. The distribution of NADPH-cytochrome c oxidoreductase demonstrated that it cannot be used in S. carlsbergensis as a specific marker enzyme for the microsomal fraction. Glucose 6-phosphatase, inosine pyrophosphatase, cytochrome P-450 and five other enzymes frequently assigned to microsomal fractions of mammalian origin were not detected in yeast under these growth conditions.

Adenosine Triphosphatases↗
PubMedDate not supplied

[Photodynamic damage of yeast subcellular fraction induced by elevated levels of endogenous protoporphyrin IX].

The 2,2'-dipyridyl-induced accumulation of protoporphyrin IX in Saccharomyces cerevisiae cells was shown to be accompanied by the photoinhibition of cell respiration and the enhancement of the photoinduced permeability of plasma membranes to the fluorescent dye primuline. The visible-light illumination (at 400-600 nm) of the mitochondria and plasma membranes isolated from yeast cells with a high level of endogenous protoporphyrin IX intensified lipid peroxidation in these subcellular organelles. Comparative studies showed that the rad 52 mutant cells, which are deficient in the postreplicative recombinational DNA repair system, are considerably more sensitive to the inactivating action of visible light than are the wild-type cells and the rad 3 mutant cells, which are deficient in the excision DNA repair system. The contribution of photodynamic damage to the yeast subcellular organelles to the lethal photodynamic effect is discussed.

2,2'-Dipyridyl↗
PubMed1976

The effect of trimepranol on the binding of [3H] norepinephrine in myocardial subcellular fractions of the dog.

The effect of Trimepranol on the binding of 3H norepinephrine to myocardial particles from dogs (to fractions 1,000 g and 78,000 g resp.) has been studied and compared with the effect of propranolol, isoprenaline, phentolamine and ephedrine. Displacement of 3H norepinephrine by propranolol and isoprenaline was found in both fractions. Trimepranol, in low concentrations, inhibited the binding of 3H norepinephrine; in higher concentrations the binding of 3H norepinephrine was stimulated. Phentolamine and ephedrine were without effect in both fractions. The problem of specificity of adrenergic binding sites is discussed.

Adrenergic alpha-Antagonists↗
PubMedDate not supplied

[Thyroxine induction of aminotransferases in subcellular fractions of rat heart].

Administration of thyroxine toxic doses to rats results in a considerable increase in the alanine aminotransferase and aspartate aminotransferase activity in nuclear, mitochondrial and supernatant fractions of the rat heart. The hormone action is more pronounced in the mitochondrial fraction. A simultaneous administration of thyroxine and actinomycin D decreases the hormone effect in case of nuclear and supernatant enzymes. The enzymes of mitochondrial fractions do not change after actinomycin D injection. It is possible to suggest that in mitochondria there occurs a synthesis of some enzymes.

Alanine Transaminase↗
PubMed1993

Specificity studies of particulate binding sites for steroid hormones in subcellular fractions of the porcine corpus luteum.

We have studied the binding of a number of radiolabelled steroids and lipophilic substances to porcine corpus luteum (CL) particulate fractions. Following preincubation of CL homogenates with radiolabelled progesterone or pregnenolone prior to fractionation on continuous sucrose density gradients, a broad peak of binding was observed associated with a particulate fraction of buoyant density 1.05-1.10 g/cm3. Progesterone content also peaked at a similar buoyant density (1.06-1.12 g/cm3). Pretreatment of luteal homogenates with digitonin perturbed the buoyant density of the progesterone-binding particulate fraction to 1.10-1.14 g/cm3 and sharpened the binding peak. Progesterone content was also perturbed to a similar extent by digitonin pretreatment, without release of the steroid. Oestrogens were also sequestered by this fraction, but steroid precursors (cholesterol, cholesterol ester), corticosteroids (cortisol, corticosterone), sterol conjugates (oestrone sulphate, pregnanediol glucuronide) and other lipophilic substances (arachidonic acid, phospholipid, prostaglandins E1, E2 and F2 alpha) were not bound. Androgens were bound weakly by fractions from control gradients but, in the presence of digitonin, significant binding could be demonstrated. Radiolabelled steroids were shown to interact directly with luteal membrane fractions, rather than interacting first with cytosolic steroid receptors which then bound to membranes. Furthermore, [3H]progesterone was not bound by porcine granulosa cell particulate fractions. These observations suggest that this fraction may be involved in sequestration or packaging of progesterone for secretion by the luteal cell.

Animals↗
PubMed1980

[Conversion of erucic acid in subcellular fractions from liver, kidneys and heart of rat, 8 min after intravenous injection (author's transl)].

Rats were intravenously injected with albumin-bound [14 14C] erucic acid, and after 8 min the 14C radioactivity (RA) of the fatty acids were studied in mitochondria, microsomes and other fractions of liver, kidneys and heart cells. 1. In liver, which contained 15% of the injected RA, oleic acid (18 : 1) was the main fatty acid (FA) formed (26% of the 14C recovered) whereas in kidneys (0,53% of the injected RA) the proportion of nervonic acid (24 : 1) was higher (20%) than that of 18 : 1 (14%). No appreciable transformation was encountered in heart, which contained 0,53% of the injected RA. 2. In liver, the microsomes showed the higher converted 14C RA (45%), mainly as 18 : 1 (33%), much higher than in mitochondria (11%), whereas the amount of total 14C FA was a little higher in the latter fraction. 3. In kidneys, the mitochondrial and microsomal fractions contained the same percentage of 14C oleic acid (15%), whereas nervonic acid was recovered in higher proportion, 29 and 20%, in microsomes and in mitochondria respectively. 4. Results show that the same kind of metabolic activity, i.e., shortening or elongation, was observed in the whole cell as that previously shown with isolated fractions. However, mitochondrial oxidation and exchanges of transformed fatty acids between organelles can modify the extent of the phenomenon.

Animals↗