Clinical science and molecular medicine最新文献

1. Enterocytes, isolated from the proximal jejinum and distal ileum of the rat, were homogenized and their organelles separated by isopycnic centrifugation on continuous sucrose density gradients. The distributions of marker enzymes for the principal organelles, RNA and protein were determined in the sucrose gradients and related to the activities per entercocyte. 2. In the jejunum the modal equilibrium densities of the various organelles were: brush borders (1.20), lysosomes (1.20), peroxisomes (1.19), mitochondria (1.17) and basal-lateral membranes (1.13). The values were not significantly different in the ileum. The activities of brush-border enzymes, soluble and mitochondrial malate dehydrogenase, soluble and membrane-associated lactate dehydrogenase and particulate protein content, however, were greater in the jejunal than the ileal enterocytes. 3. Detergent exposed latent alkaline phosphatase activity in jejunal enterocytes and indicated that this enzyme is present not only in the brush border but also in the basal-lateral membrane and soluble fractions of the cell. 4. Isolated jejunal brush-border preprations showed latent activities of both alkaline phosphatase and gamma-glutamyltransferase whereas the activities of alpha-glucosidase and leucyl-beta-naphylamidase were not affected by detergent. Mechanical disruption of these preparations suggested the presence of two forms of alkaline phosphatase in the brush border and provides a technique to assess membrane fragility.

1. The effects of varying PCO2 on lactate uptake and intracellular pH (pHi) were studied in the isolated rat liver perfused with differing concentration of lactate. 2. In general, pHi and lactate uptake are inversely related to PCO2, and pHi and lactate uptake are directly related to each other, but the quantitative aspects and significance of these relationships vary with the availability of lactate. A model of hepatic lactate metabolism is proposed which may account for the quantitative variation. 3. The metabolism of lactate within the hepatocyte exerts a destabilizing effect on hepatocyte cell pH, in contrast to the buffering effect seen in predominantly glycolytic tissues. 4. An attempt is made to relate the findings to the disturbances of lactate metabolism in clinical respiratory failure.

1. A method for assessing cholecalciferol absorption in man is described. 2. The intestinal absorption of [3H]cholecalciferol was studied in 20 female geriatric patients, most of whom were vitamin D-depleted. 3. The plasma [3H]cholecalciferol response after oral ingestion was significantly lower than that of a group of younger female subjects. 4. The plasma response of labelled polar metabolites of cholecalciferol was also lower in the geriatric than in the younger group, suggesting that increased removal of label by conversion into more polar metabolites could not account for the reduced plasma [3H]cholecalciferol response. 5. There was no evidence that alteration in gastrointestinal motility could account for the different rate of appearance of the labelled vitamin in the plasma in the two groups. 6. It is suggested that there is a defect in intestinal absorption of cholecalciferol in the elderly.

1. Nine-months-old male rats were divided into a normal control group and one experimental group which received eight daily intraperitoneal injections 15 pmol of 1,25-dihydroxycholecalciferol/100 g body weight. After 5 days, 20 muCi of 109CdCl2 or 20muCi of 45CaCl2 was administered by stomach tube. The intestinal absorption and tissue retention of the radioisotopes were analysed during the next 3 days, the animals being kept in metabolic cages. 2. The administration of 1,25-dihydroxycholecalciferol caused significantly increased net absorption of intestinal calcium, hypercalcaemia and increased incorporation of calcium into bone. In comparison, there was no significant effect on the intestinal absorption of trace doses of cadmium or upon the accumulation of cadmium in the liver and kidneys.

A study has been made of urinary peptide output in rats before and after production of a Fanconi syndrome induced by a single injection of sodium maleate. There was an unequivocal increase of urinary peptides on the first and second days after the injection, without any detectable change in the concentration of plasma peptides. 2. Similar results were obtained in osteolathyritic rats in which skeletal lesions had been produced by ingestion of beta-aminopropionitrile. 3. The fractional amino acid content of urinary peptides after maleate and beta-aminopropionitrile is shown to be significantly different from that in control animals. 4. Evidence is presented that the increased output of peptides is mainly due to increased renal clearance similar to that previously described for amino acids, glucose and several electrolytes in this type of experimental Fanconi syndrome.

1. Evidence for the existence of 'natriuretic hormone' resides, in part, in the demonstration that blood volume expansion in the dog is followed by a transient fall in short-circuit current (SCC) across a frog skin incorporated within its circulation. 2. We have attempted to confirm this effect in the rat, with a toad skin (Xenopus laevis) incorporated within the circulation. The skins, bathed in whole rat blood, displayed low SCC; skins bathed in 'mammalian' Ringer solution displayed equally low SCC, but responded normally to pitressin or amiloride. 3. When volume expansion was induced in ten rats by infusion of equilibrated whole blood (28 ml/kg body weight) there was a brisk rise in systemic blood pressure, diuresis, natriuresis and kaliuresis. 4. This blood-volume expansion was without detectable effect on the SCC across the skins incorporated within the rats' circulations.

1. A human cancer cell line (COLO 16) derived originally from an epidermal squamous cell carcinoma was found to possess adenylate cyclase responsiveness to beta-adrenergic agonists. 2. The adenylate cyclase response was characterized with respect to activation constants (KA) for various beta-adrenergic agonists and inhibition constants (Ki) for antagonists. 3. Intact cells responded with dose-dependent increases in production of cyclic adenosine 3':5'-monophosphate. 4. Properties of the beta-adrenergic receptor were evaluated by using the specific binding of [3H]propranolol to cell membranes. Specific binding was saturable, with KD 5.79 nmol/l and binding sites 0.68 pmol/mg of protein. 5. Competition for binding to cell membranes was shown by beta-adrenergic agonists and antagonists and was stereospecific. There was close agreement between the affinity of these various agents on adenylate cyclase and receptor binding. 6. It is likely that the beta-adrenergic receptor-linked adenylate cyclase in COLO 16 cells represents persistence in a cancer cell line of a receptor present normally in epidermal cells.

1. Maximal acid output after pentagastrin stimulation, and fasting and postprandial serum gastrin concentrations were determined in 25 normal subjects, 30 patients with corpus gastric ulcers, 10 patients with prepyloric ulcers and 30 patients with both duodenal and gastric ulcers. 2. Corpus ulcers and prepyloric ulcers formed one distinct group. Maximal acid output was abnormally low in the corpus ulcer patients and no different from normal in prepyloric ulcer patients, whereas fasting serum gastrin and postprandial integrated gastrin response was abnormally high in the former and no different from the normal in the latter. Furthermore, as in the normal subjects, a significant negative correlation between maximal acid output expressed in mmol h(-1) kg(-1) body weight and postprandial integrated gastrin response was observed in the corpus and prepyloric ulcer patients taken as a group. 3. In complete contrast patients with both duodenal and gastric ulcers, in whom postprandial integrated gastrin response was statistically highest amongst the three types of gastric ulcers, had a significantly positive correlation between maximal acid output and the integrated gastrin response. 4. These findings suggest the operation of different pathophysiological mechanisms in gastric ulcers with and without associated duodenal ulcers.