Mucoid strains of Pseudomonas aeruginosa are devoid of mannuronan C-5 epimerase

Mucoid strains of Azotobacter vinelandii, Pseudomonas aeruginosa and Pseudomonas syringae var glycinia synthesize alginate, an extracellular copolymer comprising D-mannuronosyl and L-guluronosyl moieties. Extracellular mannuronan C-5 epimerase, which converts polymannuronate to alginate, was demonstrated in supernatant fluid from cultures of A. vinelandii. However, the enzyme could not be demonstrated, using the same assay, in supernatant fluids of cultures of mucoid strains of P. aeruginosa or of P. syringae var glycinia, or in cell-free sonic extracts of P. aeruginosa. The results suggest that the pathways of alginate biosynthesis in A. vinelandii and Pseudomonas species may differ.     

Proteins present in bovine papillomavirus particles.

Analysis by two-dimensional gel electrophoresis and silver staining of heavy full, light full, and empty bovine papillomavirus particles has shown that the major capsid protein L1 is highly modified. Besides exhibiting at least 13 isoelectric point variants of approximately the same molecular mass (54 kilodaltons), it is suggested that an additional heavier protein chain (69 kilodaltons) is also derived from L1 by glycosylation. These modifications may stabilize the particle structure. Treatment with neuraminidase reduces the number of modification products detectable, with a concomitant increase in the more basic forms of L1. Although it was not possible to detect histones in any of the preparations, proteins of similar molecular mass were detected. Therefore, it is suggested that the basic tails of L1 bind to the DNA in a manner similar to that of histone. Calculation of the theoretical mobilities of the papillomavirus proteins shows good agreement with the actual position of L1 and its isoelectric point variants and suggests that two of the proteins with molecular masses similar to those of the histones may actually be coded by the bovine papillomavirus E7 and E5 open reading frames.     

Appearance of purine-catabolizing enzymes in fix and fix root nodules on soybean and effect of oxygen on the expression of the enzymes in callus tissue

The appearance of enzymes involved in the formation of ureides, allantoin, and allantoic acid, from inosine 5′-monophosphate was analyzed in developing root nodules of soybean (Glycine max). Concomitant with development of effective nodules, a substantial increase in specific activities of the enzymes 5′-nucleotidase (35-fold), purine nucleosidase (10-fold), xanthine dehydrogenase (25-fold), and uricase (200-fold), over root levels was observed. The specific activity of allantoinase remained constant during nodule development. With ineffective nodules the activities were generally lower than in effective nodules; however, the activities of 5′-nucleotidase and allantoinase were 2-fold higher in ineffective nodules unable to synthesize leghemoglobin than in effective nodules. Since the expression of uricase has been shown to be regulated by oxygen (K Larsen, BU Jochimsen 1986 EMBO J 5: 15-19), the expression of the remaining enzymes in the purine catabolic pathway were tested in response to variations in O₂ concentration in sterile soybean callus tissue. Purine nucleosidase responded to this treatment, exhibiting a 4-fold increase in activity around 2% O₂. 5′-Nucleotidase, xanthine dehydrogenase, and allantoinase remained unaffected by variations in the O₂ concentration. Hence, the expression of two enzymes involved in ureide formation, purine nucleosidase and uricase, has been demonstrated to be influenced by O₂ concentration.     

The isolation and characterisation of a cDNA clone for human lecithin:cholesterol acyl transferase and its use to analyse the genes in patients with LCAT deficiency and fish eye disease

We have isolated cDNA clones coding for human lecithin:cholesterol acyl transferase (LCAT) from a liver-specific cDNA library by the use of two oligonucleotide probes based on the protein sequence. The clones span the sequence coding for the entire secreted LCAT, the 3' untranslated sequence and 12 amino acids of the signal peptide. The peptide sequence contains the conserved active site of serine lipases within a hydrophobic domain, flanked by a possible amphipatic alpha-helix. Only one gene for LCAT could be detected in genomic blots. We have used the cDNA as a probe to analyse the LCAT gene in patients suffering from LCAT deficiency and fish eye disease. No rearrangements or abnormal gene fragments were detected in these patients.     

Methylamine does not inhibit rates of endogenous lipolysis in isolated myocardial cells from rat heart

Triacylglycerol lipase activity with a pH optimum of 5 was present in homogenates of myocardial cells from rat heart. Acid lipase activity was inhibited by serum, heparin, and increased ionic strength. Methylamine, a lysosomotropic agent, did not inhibit the basal or isoproterenol-stimulated rate of endogenous lipolysis as measured by glycerol output from control myocytes. Similarly, accelerated rates of glycerol output that are a consequence of an elevation in the intracellular stores of triacylglycerols in myocytes from diabetic rat hearts and from myocytes prepared with free fatty acids in the isolation solutions were not reduced by methylamine. Therefore, the acid lysosomal triacylglycerol lipase must not be involved in the mobilization of endogenous triacylglycerols in myocardial cells from rat heart.     

Connective tissue influences on the expression of epithelial cell-surface antigens

Summary Adult mice were found to show regional variation in the epithelial expression of some molecules of the blood-group antigen series. To investigate connective tissue influences on such differences, heterotypic recombinants of epithelia and connective tissues from various regions were prepared and examined using monoclonal antibodies directed against bloodgroup antigens H and Le^y. The results indicate that epithelia may maintain a preexisting regionally specific pattern following recombination but that, in some recombinant matches, the connective tissue is capable of signalling redirection of the pattern of expression towards that typical of the epithelium with which it is normally associated.This work was supported by NIH-NIDR RO1-DEO-5190     

A morphometric and ultrastructural study of lithium-induced changes in the medullary collecting ducts of the rat kidney

Summary Rats were given a lithium-containing diet (40 mmol/kg) to Study the effect of lithium on the structure of collecting ducts from the inner stripe of the outer medulla. The results show that there is a significant increase in the volume density of collecting ducts already after one week on this diet. The volume density of both intercalated and principal cells increases, whereas the volume density of mitochondria in the cytoplasm increases in the intercalated cells only. The increased volume of both principal and intercalated cells seems to be part of a general hyperplasia and hyperactivity of the collecting duct, which may in some way be related to the effects of lithium on vasopressinmediated water transport. The specific changes in the intercalated cells may be a consequence of the effects of lithium on distal nephron potassium and hydrogen ion transport in the distal nephron.