Transport of a series of D-phenylalanine-glycine hexapeptides across rat alveolar epithelia in vitro.

The effect of lipophilicity on the absorption of peptides from the lungs was investigated. D-phenylalanine (F)-glycine (G) hexapeptides were synthesised to differ, predominantly, only in their lipophilicity. Rat alveolar type II cells were isolated and cultured on plastic, or polycarbonate filters; by day 6 they had de-differentiated to an alveolar type I-like epithelium.

Homocysteine mediated endothelial cell toxicity and its amelioration.

In response to homocysteine induced toxicity in human umbilical vein endothelial cells, minimal changes in the concentration of cellular protein thiols but substantial changes in the concentration of intracellular soluble thiols were observed. The latter correlated closely with changes in cellular glutathione levels. No correlation existed between cellular glutathione levels and cell viability, whereas a close correlation between NAD+ levels and cell viability was demonstrated.

Lipid peroxidation and homocysteine induced toxicity.

Homocysteine induced toxicity has been examined in cultures of human umbilical vein endothelial cells. The toxic effects of the amino acid alone and the amino acid plus Cu2+ could be prevented by catalase and decreased by desferal, when either was present in the culture medium. When desferal was allowed to accumulate intracellularly, no significant protection from homocysteine induced toxicity was observed.

Homocysteine uptake by human umbilical vein endothelial cells in culture.

The characteristics of the uptake of L-homocysteine by cultures of human umbilical vein endothelial cells have been examined. Uptake occurred by Na(+)-dependent and Na(+)-independent systems, but was essentially independent of the pH of the uptake medium. The Na(+)-independent system corresponded to system L, being totally inhibited by the presence of beta-2-aminobicyclo(2,2,1)heptane-2-carboxylic acid (BCH) a system L analogue.

Transport of L-cystine in human umbilical vein endothelial cells in culture.

The uptake of L-cystine into cultured human umbilical vein endothelial cells has been shown to occur by a Na+-independent system which is inhibited by L-glutamate and L-homocysteine, but not by other amino acids. It is likely that the system transporting L-cystine is shared by L-glutamate. Thiol groups associated with membrane bound components appear to be essential for L-cystine uptake but it is not yet evident whether these constitute an integral part of the transporter per se.

Localization of S-adenosylhomocysteine hydrolase and adenosine deaminase immunoreactivities in rat brain.

Antisera against rat-liver S-adenosylhomocysteine hydrolase (SAH-hydrolase) and calf intestinal mucosal adenosine deaminase (ADA) were raised in rabbits and subsequently used to determine the distribution of the corresponding enzymes in rat-brain using the peroxidase-antiperoxidase immunohistochemical procedure. SAH-hydrolase antigenicity was prominent in the neocortex, hippocampal formation, cerebellum and olfactory tubercle. In the cerebellum, only those cells associated with the Purkinje layer possessed pronounced reactivity with anti-SAH hydrolase.

Adenosine deaminase and histidine decarboxylase coexist in certain neurons of the rat brain.

The enzymes adenosine deaminase (ADA) and histidine decarboxylase (HDC) were immunocytochemically detected in rat brain. The gross distributions of ADA- and HDC-immunoreactive neurons in the basal hypothalamus were very similar. The superficial layers of the superior colliculus showed only ADA-containing neurons.

The effects of S-adenosylhomocysteine and S-adenosylmethionine on some purine- and pyrimidine-metabolizing systems.

The effects of S-adenosylhomocysteine and S-adenosylmethionine on some purine- and pyrimidine-metabolizing systems have been examined. Both compounds were capable of acting as relatively good inhibitors of adenosine deaminase, nucleoside phosphorylase, and adenylate deaminase activities but as relatively poor inhibitors of myokinase and nucleoside monophosphate kinase. The inhibitory effects were freely reversible.

Studies on the neurochemical properties of cystathionine.

Following the intracerebral administration of [35S]cystathionine, the synaptosome fraction of rat brain was labelled, the greatest uptake of amino acid being associated with hypothalamus. The uptake of [35S]cystathionine by synaptosome preparations isolated from different regions of brain, was typical of that exhibited by amino acids which are not neurotransmitters. Depolarization of the synaptic membrane had no effect on the efflux of [35S]cystathionine from preloaded synaptosomes.

The molecular defect in a case of (cystathionine beta-synthase)-deficient homocystinuria.

1. Cystathionine beta-synthase activity isolated from fibroblast cultures obtained from the skin of a normal and a homocystinuric individual were both cross-reactive with normal human liver cystathionine beta-synthase antibody. 2.

Studies on the use of skin fibroblasts for the measurement of cystathionine synthase activity with respect to homocystinuria.

The levels of cystathionine synthase have been examined in cultured skin fibroblasts obtained from a patient suffering from pyridoxine-non-responsive homocystinuria and compared with the normal and heterozygous states. Levels of synthase activity were found to vary with time in culture and composition of culture media. The physical properties of normal and abnormal synthase activities were markedly different.

Substrate specificity of the L-serine O-sulphate degrading activities of Pseudomonas FR.

1. Two enzyme systems obtained from Pseudomonas FR capable of catalysing the alphabeta-elimination of L-serine O-sulphate exhibit a wide range of substrate specificity. Greatest activity was exhibited towards beta-substituted serine and cysteine derivatives.

Effect of induced elevated plasma levels of homocystine and methionine in rats on collagen and elastin structures.

Young growing rats were intraperitoneally injected with mixtures of homocystine and methionine for several weeks. The growth of the animals was inhibited. After 3 weeks 25% of the rats died and isolation of tail tendon collagen and aorta elastin showed that these proteins were deficient in chemical cross-links.

The role of histidine residues in glutamate dehydrogenase.

1. Glutamate dehydrogenase was subject to rapid inactivation when irradiated in the presence of Rose Bengal or incubated in the presence of ethoxyformic anhydride. 2.