Polyribosome disaggregation and cell-free protein synthesis in preparations from cerebral cortex of hyperphenylalaninemic rats

Abstract— Seven-day-old rats were injected intraperitoneally with l -phenylalanine (1 g/kg) and the time course of brain polyribosome disaggregation and changes in brain levels of phenylalanine, tryptophan and tyrosine were determined. Disaggregation of brain polyribosomes preceded the increase in levels of phenylalanine in brain, and followed the same time course as depletion of tryptophan from brain. The effects of several metabolites of phenylalanine (which are formed in phenylketonuria) on protein synthesis in vitro was determined for brain and liver systems. None of the compounds tested was inhibitory at concentrations below 10 mM and in all cases hepatic protein synthesis was more sensitive to inhibition than was the corresponding system from brain. Ribosomal dimers, formed in brain after injection of phenylalanine, were incapable of supporting high levels of protein synthesis in vitro, a finding that suggested that the inhibition of protein synthesis in vitro in cell-free systems of brain tissue after injection of phenylalanine into young rats was mediated by disaggregation of brain polyribosomes associated with tryptophan deficiency in brain.     

Immunocytochemical detection of estrogen receptors in a hormone-unresponsive mammary tumor

Summary A combination of two monoclonal antibodies and high resolution immunocytochemical technique was applied to label estrogen receptors in spontaneous mouse mammary tumors. Protein A-colloidal gold complex was used as an electron opaque marker. With this procedure estrogen receptors were labelled in the nuclei of cancer cells, predominantly over heterochromatin. In the cytoplasm a slight tagging of the rough endoplasmic reticulum was detected, apparently related with the sites of receptor biosynthesis. Other organelles and the mammary tumor viruses (MuMTV) were not stained immunocytochemically.The immunocytochemical procedure applied in this investigation allowed the detection of low levels of estrogen receptors in an estrogen-unresponsive mammary carcinoma. The presence of estrogen receptors with a specific distribution in estrogen-independent tumors suggests the need of a reevaluation of their capacity as indicators of hormone-dependence in mammary carcinomas.     

Acute effects of unsaturated fatty acids in splanchnic artery occlusion shock

Diets enriched with omega-3 unsaturated fatty acids are associated with decreased hypercholesterolemia and decreased risk of ischemic and atherosclerotic diseases. We studied the acute intravascular effects of some of these unsaturated fatty acids (i.e., eicosapentaenoic acid, EPA; docosahexaenoic acid, DHA) along with omega-6 unsaturated fatty acids, (i.e., linoleic and linolenic acid) in splanchnic artery occlusion (SAO) shock in rats. Anesthetized rats subjected to total occlusion of the celiac and superior mesenteric arteries for 40 minutes followed by reperfusion usually resulted in a fatal outcome 90-120 minutes after releasing the clamps. SAO shock rats treated with the omega-3 unsaturated fatty acid, EPA, exhibited an improved survival time and rate (p less than 0.05 from vehicle) compared to those receiving only vehicle (i.e., 50% ethanol). EPA and DHA treated SAO rats also exhibited lower plasma activities of the lysosomal protease, cathepsin D, free amino-nitrogen compounds, and the cardiotoxic peptide, myocardial depressant factor. These results indicate that omega-3 unsaturated fatty acids, especially EPA, have some acute beneficial effects in SAO shock in rats.     

Praziquantel-induced secretion of proteolytic enzyme from Schistosoma mansoni cercariae

The effect of praziquantel (PZQ) on secretion of proteolytic enzyme by Schistosoma mansoni cercariae was examined using an azocoll assay. The cercariae secreted proteolytic enzyme in various concentrations of PZQ (0.1, 1, and 10 micrograms/ml), but secretion of enzyme was highest at the lowest concentration. PZQ-induced secretion of proteolytic enzyme was partially inhibited by treatment with verapamil and ethylene glycol-bis(beta-aminoethyl ether)N,N,N',N'-tetra-acetic acid but not by calmodulin antagonist W-7 and protein kinase C inhibitor H-7.     

Factors contributing to cerebral hypomyelination in the growth hormone-deficientlittle mouse

We attempted to delineate the events leading to hypomyelination in the brain of thelittle mouse, a promising murine model of isolated growth hormone deficiency. At 20 days of age, the mutant mouse brain weighed less than its normal counterpart, and this difference in brain weight persisted. Increase in CNPase activity was found to be suppressed in the cerebrum throughout the developmental stage, but not in the other parts of the brain. Differences in cerebral DNA content between thelittle and normal mice first became apparent on the 10th day of age. Thereafter, the rate of increase in thelittle brain consistently lagged behind the normal. [³H]Thymidine incorporation into the DNA fraction in vivo on the 7th day of age, when glial cell proliferation in the normal cerebrum is most active, was approximately half that of the controls in all parts of thelittle brain. These findings indicate that the hypomyelination of the mutant cerebrum might result from reduced oligodendroglial proliferation due to growth hormone deficiency.     

Mechanism of Methane Transport from the Rhizosphere to the Atmosphere through Rice Plants

To clarify the mechanisms of methane transport from the rhizosphere into the atmosphere through rice plants (Oryza sativa L.), the methane emission rate was measured from a shoot whose roots had been kept in a culture solution with a high methane concentration or exposed to methane gas in the gas phase by using a cylindrical chamber. No clear correlation was observed between change in the transpiration rate and that in the methane emission rate. Methane was mostly released from the culm, which is an aggregation of leaf sheaths, but not from the leaf blade. Micropores which are different from stomata were newly found at the abaxial epidermis of the leaf sheath by scanning electron microscopy. The measured methane emission rate was much higher than the calculated methane emission rate that would result from transpiration and the methane concentration in the culture solution. Rice roots could absorb methane gas in the gas phase without water uptake. These results suggest that methane dissolved in the soil water surrounding the roots diffuses into the cell-wall water of the root cells, gasifies in the root cortex, and then is mostly released through the micropores in the leaf sheaths.     

Sulfonamide Resistance Gene in a Transferable R Plasmid of Pasteurella piscicida

The sulfonamide resistance (SA^r) determinant was cloned from a transferable R plasmid of Pasteurella piscicida, pSP9351, and the sequence was determined. The resistance gene (pp-sul) was localized to an approximately 1-kb region that includes the PstI-EcoRI site in the restriction map. An open reading frame coding a sul II-type gene composed of 810 nucleotides was identified. A direct repeat sequence was shown in the 5′ flanking region of pp-sul, and a plasmid recombinational event may have occurred during the construction of pSP9351. In the 3′ flanking region of the gene, a sequence homologous to the 5′ noncoding sequence of the trimethoprim resistance gene, dhfr IX was found.