Biomedical subjects

T J Layden

Publications and source records attributed to T J Layden.

76 records · Page 5Linked to original sources

PubMed1976

Plasma trace metals during total parenteral alimentation.

The plasma concentrations of the trace metals zinc and copper were studied prospectively in 13 patients with gastrointestinal diseases treated with parenteral alimentation (TPA) for periods of from 8 days to 7 1/2 weeks. Plasma copper levels fell rapidly and consistently in all patients, with an overall rate of - 11 mug per 100 ml per week. Zinc concentrations declined in 10 of 13 patients at a more gradual rate. Analysis of the standard parenteral alimentation fluids revealed zinc content equivalent to 50% of the daily requirement and a negligible content of copper. From combined analysis of plasma zinc, hair zinc, and taste acuity, there is evidence that increased utilization or redistribution within the body may effect plasma concentrations in some patients. Neither an increase in urinary excretion nor a primary decrease in plasma binding proteins appeared to be a major factor in lowering plasma trace metal concentrations. These findings indicate that a marked decrease in plasma copper is regular and a decline in plasma zinc is common during TPA using fluids unsupplemented with trace metals. Supplementation of parenteral alimentation fluids with the trace metals zinc and copper is recommended.

Adolescent↗

PubMed1975

Scanning electron microscopy of the rat liver. Studies of the effect of taurolithocholate and other models of cholestasis.

The normal surface anatomy of rat hepatocytes, sinusoids, and bile canaliculi was examined by scanning electron microscopy following finger fracture of tissues that were perfused via the portal vein and fixed with 2.5% glutaraldehyde. These normal findings were contrasted with several models of cholestasis, including infusion of sodium taurolithocholate (TLC), bile duct ligation, and ethynyl estradiol treatment, in order to examine the effects of cholestasis on morphology of the bile canaliculus. TLC-induced cholestasis was associated with specific dilation and disruption of canalicular membranes, which corresponded to evaginations of pericanalicular ectoplasm observed by transmission electron microscopy, and suggested a direct toxic effect of the bile salt on membrane structure. Infusions of lithocholate sulfate or simultaneous infusions of TLC and sodium taurocholate prevented these severe abnormalities from occurring. Bile duct ligation produced progressive canalicular dilation (from 1 to 96 hr) and loss of microvilli, but did not result in the type of membrane changes produced by TLC. No significant changes in canalicular morphology were observed following ethynyl estradiol treatment. These studies demonstrate that scanning electron microscopy is a useful technique for the evaluation of both normal and abnormal hepatic surface morphology, and indicate that TLC produces a distinctive abnormality in the structure of the canalicular membrane, which was not seen in other models of cholestasis.

Animals↗

PubMedDate not supplied

Depletion of liver and esophageal epithelium vitamin A after chronic moderate ethanol consumption in rats: inverse relation to zinc nutriture.

This study was designed to determine whether chronic moderate ethanol ingestion alters the levels of vitamin A of liver and esophageal epithelium and if this is dependent on zinc nutriture. Forty male Sprague-Dawley 4-week-old rats were divided into five groups: zinc-deficient (0.9 ppm), ethanol-fed; zinc-deficient; zinc-adequate (25 ppm); zinc-adequate (25 ppm), ethanol-fed; and zinc-supplemented (50 ppm), ethanol-fed. All rats received liquid Lieber-DeCarli diet containing 4,000 IU per liter of vitamin A for 5 weeks. Zinc-deficient, ethanol-fed rats and zinc-adequate, ethanol-fed rats and zinc-supplemented, ethanol-fed rats received 15.5% of the caloric intake as ethanol while zinc-deficient and zinc-adequate rats received isocaloric amounts of maltose dextrin. All groups were pair-fed to zinc-deficient, ethanol-fed rats. In addition, a group of eight rats designated as weight-restricted controls were fed a diet similar to the one given to zinc-adequate rats but in the amount to obtain a final weight as in the zinc-deficient group. After 35 days, the liver histology was normal in all rats, and no fat accumulation was noted. Hepatic vitamin A concentration was significantly decreased in zinc-adequate, ethanol-fed rats (41 +/- 10 micrograms per gm) and further in zinc-supplemented, ethanol-fed rats (12 +/- 5 micrograms per gm) as compared to controls (137 +/- 49). A highly significant negative correlation between serum zinc and liver vitamin A was found in ethanol-fed animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

The paracellular pathway and bile formation.

Choleretic infusions of taurocholate (40 μ moles for one hour) result in a significant increase in the number of lateral cell surface invaginations observed by scanning electron microscopy adjacent to the junctional complex of bile canaliculi in rat liver. Transmission electron microscopy indicates that these invaginations resemble "blisters" induced by osmotic gradients across epithelial tissues, a morphologic change which correlates with increases in ionic and hydraulic conductivity of the paracellular "shunt" pathway in such tissue. Since taurocholate infusions result in localization of ionic lanthanum chloride within hepatocyte junctional complexes, bile acids may also stimulate the movement of fluid and electrolytes across paracellular pathways during the process of bile formation.

Animals↗