Large cation-selective pores from rat liver peroxisomal membranes incorporated to planar lipid bilayers

Summary Fusion of a highly purified fraction of rat liver peroxisomal membranes to planar lipid bilayers incorporates large, cation-selective voltage-dependent pores. TheP _K/P _Cl ratio of these pores, estimated in KCl gradients, is close to 4. The pores display several conductance states and spend most of the time open at voltages near 0 mV, closing at more positive and negative voltages. At voltages near 0 mV the most frequent open state has a conductance of 2.4 nS in 0.3m KCl. At voltages more positive and more negative than 10 mV the most frequent open state displays a conductance of 1.2 nS in 0.3m KCl. With these results pore diameters of 3 and 1.5 nm, respectively, can be estimated. We suggest that these pores might account for the unusually high permeability of peroxisomes to low molecular weight solutes. Fusion also incorporates a perfectly anion-selective, two-open states channel with conductances of 50 and 100 pS in 0.1m KCl.     

Immunomicroscopical localization of human preformed natural antibodies against pig tissues in xenogeneic transplantation

Summary The targets of preformed natural antibodies need to be identified whenever the use of pig organs is considered for human transplantation. In this study we used extracorporeal perfusion of pig organs with human blood, immunocytological techniques and immuno-electron microscopy to identify the targets and the nature of human preformed natural antibodies against pig antigens. The antibodies were found to be mainly of the IgG and IgM type and directed not only against endothelial cells, but also against mesenchymal and epithelial structures. To reproduce an in vivo situation, a Bio-pump was used to xenoperfuse pig kidneys and livers with human fresh oxygenated blood at 37°C, drawn from polycythaemic patients. Biopsies showed a deposition of human IgG and IgM on tubuli and glomeruli of pig kidneys and on endothelial cells of pig livers. Preperfusion of pig liver with human blood for 45 minutes before perfusion of kidneys significantly reduced the deposition of the natural antibodies.     

Biogeneration of 2-phenylethanol and 2-phenylethylacetate important aroma components

Summary 2-Phenylethanol and 2-phenylethylacetate important aroma components are obtained in substantial amounts whenHansenula anomala CBS 110 andKloeckera saturnus CBS 5761 are grown with L-phenylalanine as sole nitrogen source. Up to 2 g/L of mixtures of alcohol and ester are obtained. While in the first microorganism the alcohol predominates, in the second the acetate is formed almost exclusively. Experiments with 1-¹³C-d-Glucose show complete incorporation of the label into the methyl group of the acetate.     

Cytoarchitecture of the periaqueductal gray matter in the cat: a quantitative Nissl study

We studied the periaqueductal gray matter (PAG) in cresyl-violet-stained serial sections from 5 cats applying quantitative determinations. No significant variations were observed in the cytological aspects in the various sites examined (lateral, ventral and dorsal regions, and external and internal portions). The neuronal density was constant in the different regions, but showed a gradual and significant increase in the most external regions of the PAG. Our findings do not, therefore, confirm the existence in the PAG of subnuclei with a specific cytoarchitecture; this does not, however, rule out the possibility that there are specific regions for connections, histochemical properties or functions.     

Primary tissue culture of human adrenocortical Conn's adenomata

Summary Angiotensin II-induced the hypertrophy of the cytoplasmic compartment and significantly increased (5-³H)uridine incorporation into RNA species by Conn's human adult adenomatous cells in primary tissue culture. On its own, bromocriptine, while enlarging only the nucleolar compartment, also intensely stimulated the incorporation of (5-³H)uridine into RNA species by the cultured adrenocortical adenomatous cells. However, an equimolar mixture of angiotensin II and bromocriptine was totally ineffective, eliciting no change in cellular morphometry or isotope incorporation with respect to the control specimens run in parallel.The present findings support the view that bromocriptine can influence the metabolism of Conn's cells directly at the cellular level by acting as an agonist-antagonist of angiotensin.     

Effects of ACTH and 3′,5′-cyclic purine nucleotides on the morphology and metabolism of normal adult human adrenocortical cells in primary tissue culture

Summary Stereological studies showed that treatment of normal adult human adrenocortical cells in primary culture with ACTH or cyclic-AMP for 2 days results in similar increases in the volume of cells, of the mitochondrial and membrane space compartments and of the surface area of the smooth endoplasmic reticulum and mitochondrial cristae, and decrease in the lipid content of the cells. These changes were more marked after 8 days of treatment. Treatment for 2 days with cyclic-GMP had no striking effects on cell ultrastructure, whereas an 8-day treatment led to ultrastructural changes similar to those obtained after 2 days of ACTH-or cyclic-AMP-treatment. A discrete population of untreated cortical cells maintained a slow proliferation that was not effected by exposure to cyclic-GMP, but was significantly increased in cultures treated with ACTH or cyclic-AMP. Radioimmunological studies showed that untreated cortical cells kept secreting progesterone and cortisol and that ACTH, but neither cyclic nucleotide, increased the secretion rate per cell of both hormones. These results assign a major role to cyclic-AMP and a minor one to cyclic-GMP in the mediation of the differentiation-promoting and trophic effects, but not in the steroidogenic effects of ACTH on the human adrenal cortex.The authors wish to thank Miss A. Coi and Mr. G. Gottardo for their technical assistance. These investigations were partly supported by a contract with CNR-Italy (CT 74.00226/115.3439)     

Neonatal rat hepatocytes in primary tissue culture free from density-dependent regulation of growth

Summary Studies employing [³H]thymidine and radioautography as well as colchicine and Feulgen staining of DNA showed that up to 19-fold increases in the degree of cell crowding in vitro, i.e. from 1.45 to 27.55×10⁴ cells per specimen, did not change the rates of entry into DNA synthesis and mitosis of cultivated primary neonatal rat hepatocytes.     

L-lysine production at 65°C by auxotrophic-regulatory mutants ofBacillus stearothermophilus

Summary The amino acid L-lysine was produced from auxotrophic-regulatory mutants ofBacillus stearothermophilus at a temperature of 60–65°C. One of the mutants (AEC 12 A5, S-(2-aminoethyl)-cysteine^r, homoserine^–), produced L-lysine at the concentration of 7.5 g/l in shaken flasks in minimal medium containing 5% glucose. Culture conditions for optimizing L-lysine production were not investigated. The aspartokinase activity of the wild strainB. stearothermophilus Zu 183 was inhibited by lysine alone and by threonine plus lysine. AEC resistant mutants showed an aspartokinase activity genetically desensitized to the feedback inhibition. Optimal temperature and pH of aspartokinase were 45°C and 9.5, respectively. The data provide significant evidence that mutants of the speciesB. stearothermophilus have a potential value for amino acid production.