Distribution of insertion element IS1 in natural isolates of Escherichia coli

Total DNAs from twelve natural isolates of Escherichia coli from animals and humans were examined by hybridization with a probe for IS1. Considerable variation in copy number was found. In the case of two strains isolated from the same individual, one strain contained no copies of IS1 and the other, much greater than 30. Evidence was also obtained for the existence of IS1-like elements (iso-IS1s) of greater than 15% sequence divergence relative to the IS1 from antibiotic resistance plasmid R100.     

Isolation and long-term serial cultivation of endothelial cells from the microvessels of the adult human dermis

A method to isolate and maintain microvascular endothelial cells from the cutaneous vessels of adult human skin in long-term culture has been developed. Endothelial cells lining the microvessels of the papillary dermis are released from surrounding tissue during a brief trypsin incubation (0.3% trypsin, 1% EDTA). Cells are plated onto a fibronectin substrate and maintained in Leibovitz (L15) culture medium containing pooled human serum (50%) and antibiotics. Proliferation is dependent upon the presence of several additional growth factors, cholera enterotoxin (1 X 10(-9) M), isobutyl methylxanthine (3.3 X 10(-5) M), and medium conditioned by explant culture of the mouse EHS sarcoma. Using this supplemented medium, cells proliferate readily and can be cultivated serially for more than 6 passages (3 months in vitro). These cells retain their characteristic endothelial cell morphology, stain positively for Factor VIII antigen, and contain Weibel-Palade bodies.     

Studies on the lipid composition of the rat liver endoplasmic reticulum after induction with phenobarbitone and 20-methylcholanthrene

1. The cholesterol content, proportions of different phospholipids and fatty acid components of phosphatidylcholine and phosphatidylethanolamine were studied in rat liver endoplasmic-reticulum membrane, after a single injection of 20-methylcholanthrene or injections of phenobarbitone for 5 days. 2. A marked decrease in the proportion of cholesterol occurred 5 days after injection of 20-methylcholanthrene or phenobarbitone. 3. The proportion of phosphatidylcholine was increased by injection of phenobarbitone and minor changes occurred in other phospholipids. 4. Phenobarbitone caused the proportion of linoleic acid in phosphatidylcholine and phosphatidylethanolamine to increase to 120-125% of the control and the proportion of oleic acid, arachidonic acid and docosahexaenoic acid to decrease. 5. 20-Methylcholanthrene caused an increase in the proportion of oleic acid in phosphatidylcholine and ethanolamine to 125-140% of the control, 1 day after injection. 6. The increased proportion of linoleic acid in phosphatidylcholine after phenobarbitone injection occurs simultaneously with the increase of cytochrome P-450 concentration, the rate of oxidative demethylation of aminopyrine and the rate of hydroxylation of biphenyl. It is therefore considered that distinct species of phosphatidylcholine or phosphatidylethanolamine containing linoleic acid in the beta position are essential in the endoplasmic-reticulum membrane for optimal activity of oxidative demethylation.     

Microreactor for methanolysis of triglycerides before gas-liquid chromatography

A rapid, accurate microtechnique has been developed for gas chromatographic determination of the fatty acid composition of small (2-3 micro l) samples of vegetable oils. This microtechnique combines transesterification and sample injection into a single operation. The fatty acid compositions of soybean, linseed, and safflower oils thus determined are compared with those obtained by the usual two-step procedure.     

Metabolism of cellular membrane sulpholipids in the rat brain

1. Metabolism of [(35)S]sulpholipid was studied in rats of different ages after the injection of [(35)S]sulphate. 2. The turnover of sulphatide in brain myelin and subcellular fractions was followed for long periods. 3. A small fraction of adult myelin underwent rapid metabolism, the rest being relatively metabolically stable. 4. Fast turnover of brain microsomal sulphatide during development was related to the process of myelination. 5. Turnover of mitochondrial sulphatide was at a lower rate than that calculated for liver mitochondria. 6. The relevance of the results to the metabolism of the whole membrane is discussed.     

Denitrification under various aeration conditions in Comamonas sp., strain SGLY2

Abstract A number of bacteria were isolated from different anoxic reactors. Those having denitrifying potential were tested for their ability to denitrify under aerobic conditions. The activity of their denitrifying enzymes varied from partial inactivation by oxygen (strains NO2B9 and TCET1) to oxygen-independent activity in a strain named SGLY2 which was tentatively identified as Comamonas sp. The effect of different aeration conditions on growth and on denitrification of SGLY2 was studied more extensively. This strain was able to consume oxygen and nitrate simultaneously with the production of nitrogen and without build-up of nitrite. The dissimilatory nitrate-reductase of nitrate-adapted cells was found to be more active in the presence of oxygen than in micro-aerobic or strictly anaerobic conditions.     

Haematological changes in an Antarctic teleost,Trematomus bernacchii,following stress

The effect of an acute increase in temperature, exhaustive exercise and hypoxia on the haematology of the benthic Antarctic teleost, Trematomus bernacchii was investigated. High temperature and hypoxia caused the biggest changes to the blood, with increases in haematocrit, haemoglobin concentrations and plasma chloride levels. The spleen decreased in mass. Exercise produced the smallest changes. Changes were substantially less than reported for the more active cryopelagic species Pagothenia borchgrevinki. The magnitude of the haematocrit increase is discussed in relation to life-style of fish living in the Antarctic.