Effect of copper intrauterine contraceptive device on carbohydrate metabolism in rat endometrium

Activities of Phosphorylase, glyceraldehyde-3 -phosphate dehydrogenase, lactate dehydrogenase, malate dehydrogenase and succinate dehydrogenase in the rat endometrial tissue are significantly inhibited by an intrauterine copper device, while it stimulated glucose-6-phosphate dehydrogenase activity. The copper device decreased the lactate/pyruvate ratio in the tissue; pyruvate utilizationin vitro by the rat endometrium is also blocked by copper. These findings suggested that the normal carbohydrate metabolism of the tissue may be affected in presence of copper, thus resulting in a change of the endometrial function, which may be one of the factors responsible for the contraceptive and pharmacological action of an intrauterine copper device.     

Quantitative topography of organelles in the liver

Summary After seven days of feeding fructose the liver of Wistar rats showed enormous accumulations of glycogen, which completely altered the original pattern of distribution of organelles. A quantitative morphological method was used to analyze these changes.The cytoplasm was mapped into arbitrary distance classes corresponding to concentric rings beginning at the outer nuclear membrane. This allowed the density of organelles in a given zone to be estimated.In cells filled with glycogen as a result of the fructose feeding, the following rearrangements were found: in the intermediate zone of both cellular poles (i.e., bile canalicular pole and sinusoidal pole) the mitochondria disappeared, being replaced by glycogen.The endoplasmic reticulum was accumulated in the perinuclear zone of both cellular poles, as in control animals, but was reduced throughout the rest of cytoplasm. It showed a peripheral density maximum at the biliary canalicular pole, in contrast to the cells of control animals.These changes in the distribution of the organelles and cellular compartments correspond to histochemical findings and demonstrate an adaptive reaction in the liver parenchyma to fructose ingestion, the organelles arranging themselves in cytoplasmic regions which still show a metabolic activity.Supported by a grant from the Deutsche Forschungsgemeinschaft Az Ri 271/6-5     

Morphological aspects of the hypothalamic-hypophyseal system

Summary The ultrastructure of the tanycyte ependyma in male 160–180 g Wistar albino rats was studied under normal conditions and in experiments involving long-term suppression of ACTH secretion and its long-term stimulation. The former was accomplished by daily (for 8 days) intraperitoneal administration of dexamethasone phosphate at low (5 g/100 g) and high (100 g/100 g) concentrations. The effectiveness of suppression of the hypothalamic-hypophyseal-adrenal system in the experimental animals was judged by their reaction to two-minute ether stress (determination of plasma corticosterone) and by the results of measurement of the adrenal weights. Stimulation of ACTH secretion was achieved by bilateral adrenalectomy; the animals were examined on days 8, 10, 14, and 22 following the operation. The results obtained were in agreement with the previously established fact that there is a negative correlation between tanycyte activity and hypophyseal adrenocorticotrophic function (Akmayev and Fidelina, 1974). They also testified to the predominant involvement of the median eminence tanycyte ependyma (beta-tanycytes according to the authors' nomenclature) in these relationships.It is supposed that these correlations are regulated by a feedback mechanism and attest to the involvement of beta-tanycytes in the inhibiting control of hypophyseal adrenocorticotrophic function. The mechanism of this control may be explained alternatively: either the tanycytes transport ACTH-suppressing substances (catecholamines, corticosteroids, ACTH) from the CSF to the hypophyseal portal system or they themselves secrete substances possessing ACTH-suppressive activity. The authors distinguish several types of vesicles in the beta-tanycytes, the number of which changed with experimentally induced shifts in hypophyseal adrenocorticotrophic function. These vesicles are discussed in connection with the transport and secretory activity of the tanycytes and are considered to be a possible substrate of the hypothalamic inhibiting effect on ACTH secretion.     

Ribosomal RNA homologies and the evolution of the filamentous blue-green bacteria

Summary Ribosomal RNA (rRNA) sequence homology (as determined by comparisons of T1 oligonucleotide catalogs of³²P-labeled 16S rRNAs) has been used to assess phylogenetic relationships within the filamentous and unicellular blue-green bacteria, and to identify regions of evolutionary conservatism within blue-green bacterial 16S rRNAs.Nostoc andFischerella, representatives of two morphologically distinct and highly differentiated orders, are shown to be as closely related (on the basis of RNA sequence homology) as typical members of the non-blue-green bacterial genusBacillus. They are further shown to be (on the same basis) indistinguishable from typical unicellular members of a subgroup of the unicellular blue-green bacterial order Chroococcales. These results have general implications for studies of the origin of differentiated prokaryotes and of evolutionary change in prokaryotic macromolecules. In particular, they provide indirect evidence that the divergences of contemporary major prokaryotic groups are truly ancient ones.     

Cinnamic acid 4-hydroxylase from gherkin tissues

Homogenates from 4-day-old gherkin cotyledons and hypocotyls fractionated by sucrose density gradient centrifugation contain cinnamic acid 4-hydroxylase activity, the activity being highest in the endoplasmic reticulum fractions. These fractions also contain very low concentrations of cytochrome P₄₅₀. Hydroxylase activity is dependent on NADPH and on molecular oxygen, is optimal at pH 7.5 and is inhibited by carbon monoxide. The enzyme is very sensitive to inhibition by 2-mercaptoethanol, but it is not inhibited by the product, p-coumaric acid. Further, its responses to various potential inhibitors are fairly typical of mixed function oxidases from other sources.     

The nature of the changes in liver mitochondrial function induced by glucagon treatment of rats. The effects of intramitochondrial volume,aging and benzyl alcohol

(1) The effects of changes in the intramitochondrial volume, benzyl alcohol treatment and calcium-induced mitochondrial aging on the behaviour of liver mitochondria from control and glucagon-treated rats are reported. (2) The stimulatory effects of glucagon on mitochondrial respiration, pyruvate metabolism and citrulline synthesis could be mimicked by hypo-osmotic treatment of control mitochondria and reversed by calcium-induced aging of mitochondria or by treatment with 20 mM benzyl alcohol. Hypo-osmotic treatment increased the matrix volume whilst aging but not benzyl alcohol decreased this parameter. (3) Liver mitochondria from glucagon and adrenaline-treated rats were shown to be less susceptible to damage by exposure to calcium than control mitochondria and frequently showed slightly (15%) elevated intramitochondrial volumes. (4) Aging, benzyl alcohol and hypo-osmotic media increased the susceptibility of mitochondria to damage caused by exposure to calcium. (5) Glucagon-treated mitochondria were less leaky to adenine nucleotides than control mitochondria. (6) These results suggest that glucagon may exert its action on a wide variety of mitochondrial parameters through a change in the disposition of the inner mitochondrial membrane, possibly by stabilisation against endogenous phospholipase A₂ activity. This effect may be mimicked by an increase in the matrix volume or reversed by calcium-dependent mitochondrial aging.     

Further studies on bilitranslocase,a plasma membrane protein involved in hepatic organic anion uptake

Bilitranslocase, a plasma membrane protein involved in bilirubin and other organic anion uptake by the liver, exhibits a high molecular weight (170 000) when isolated in the presence of deoxycholate. This value is decreased to approx. 100 000 if deoxycholate is not included in the isolation medium. Both preparations can be resolved into two kinds of subunit, α and β, of 37 000 and 35 500, respectively, by reduction with 2-mercaptoethanol and addition of sodium dodecyl sulfate. Under these conditions the two subunits are still capable of high-affinity sulfobromophthalein binding and, despite the presence of the detergent, may be isolated by preparative polyacrylamide gel electrophoresis still associated with the dye. It may be suggested that the physiological subunit composition of bilitranslocase is α₂-β.     

Effect of N-ethylmaleimide on leucine transport in chang liver cells. I. Stimulatory effect on Na+-independent transport at low concentrations of leucine

Pretreatment of Chang liver cells with $\text{N-}\text{ethylmaleimide}$ (0.5 or 1 mM) stimulated Na⁺-independent uptake of leucine at low concentrations (?1 mM). The stimulatory effect of $\text{N-}\text{ethylmaleimide}$ on the uptake of leucine measured in Na⁺-replete medium was completely blocked by the addition of $\text{b-2-}\text{aminobicyclo}\text{[2,2,1]}\text{heptane}\text{-2-}\text{carboxylate}$ (5 mM), which shows that the L system participates in the stimulation. The Na⁺-dependent uptake of glycine was depressed by $\text{N-}\text{ethylmaleimide}$ pretreatment. The stimulation of the Na⁺-independent component of leucine uptake continued for at least 30 min after $\text{N-}\text{ethylmaleimide}$ treatment, while the inhibition of glycine uptake was progressive with time and the Na⁺-dependent uptake of leucine became depressed later, after the treatment. It has been demonstrated that treatment of cells with $\text{N-}\text{ethylmaleimide}$ is capable of increasing the Na⁺-independent influx of leucine and at the same time slightly decreasing the efflux of it. These results suggest that $\text{N-}\text{ethylmaleimide}$ attacks the Na⁺-independent system of amino acid transport at the reactive SH groups(s) of relevant protein(s) in favor of specific activation of that system in this cell.