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Biomedical subjects

J F Richards

Publications and source records attributed to J F Richards.

At least 19 recordsLinked to original sources
PubMed1993

Function and origin of multiple ionic forms of hormone-induced ornithine decarboxylase.

Ornithine decarboxylase (ODC) occurs in liver and kidney of control and hormone-treated rats as two ionic forms, A and B in order of elution, separable by ion-exchange chromatography of cell-free extracts. These studies were designed to investigate the origin of the multiple forms and their role in the hormonal stimulation of ODC activity. The percentage of activity present in A and B was determined in liver (73/27) and kidney (50/50) of control animals. The proportion of activity present as form B had increased by approximately 15% at 5 h after treatment with dexamethasone, prolactin, or growth hormone. In tissues of control rats, the half-life of both A and B was short, in the range of 7-11 min. The half-life of form A was unchanged after hormone treatment, but the half-life of B increased 2- to 3-fold in liver and 5- to 15-fold in kidney. When hormone-treated rats received LiCl 0.5-1 h before sacrifice, ODC activity was less than that after hormone treatment alone, the proportion of activity in A and B reverted to that present in control animal tissues, and the half-life of B reverted to the range of 7-10 min. Thus the production or maintenance of the enhanced stability of B is disrupted by lithium. A post-translational modification of A could be responsible for producing the more acidic and more stable B in the hormone-treated rats. A 3- to 5-fold increase in ODC mRNA occurred in kidney of rats treated with dexamethasone or prolactin, and was largely reversed by LiCl. Stimulation of ODC in kidney by growth hormone did not involve a major change in ODC mRNA, nor was the amount affected by LiCl.

Animals↗
PubMed1992

Tetanus. A threat to elderly patients.

Tetanus rarely occurs in young persons now that childhood immunization programs are widespread. Many older patients, however, are not completely immunized, and mortality in this group is high. Since many of the wounds from which tetanus arises are minor, patients may not bring them to medical attention. Thus, physicians should include assessment of immunization status during routine office visits in all age-groups and provide immunization against tetanus and against diphtheria if indicated.

Age Factors↗
PubMed1990

Inhibition of hormone-stimulated ornithine decarboxylase activity by lithium chloride.

Effects of Li+ on hormone-stimulated ornithine decarboxylase (ODC) activity were determined in kidney and liver of rats treated with dexamethasone or prolactin (PRL) and also in cultured, PRL-stimulated Nb2 lymphoma cells. In both systems, LiCl led to rapid and marked decreases in ODC activity. The inhibitory effect of Li+ in exponentially growing Nb2 lymphoma cell cultures, measured at 45 min, was dose-dependent, ranging from 10% at 0.1 mM LiCl to 95% at 10 mM LiCl. Surprisingly, on continued incubation with 10 mM LiCl, the lymphoma cells partially overcame the inhibition, showing ODC activities which reached a maximal value of ca 50% of the control at 4.5 h. The inhibition by Li+ could not be reduced by adding myo-inositol to the culture medium. LiCl did not inhibit ODC activity when added to cell-free extracts of rat tissues and Nb2 lymphoma cells indicating it did not act directly on the enzyme; however, there is evidence that, in intact cells, Li+ enhances the rate of inactivation of the enzyme.

Animals↗
PubMed1989

Changes in antizyme-ornithine decarboxylase complexes in tissues of hormone-treated rats.

The presence of antizyme-ornithine decarboxylase complex in thymus and kidney of rats was demonstrated using the method of Y Murakami et al. [(1985) Biochem. J. 225, 689-697]. A very small amount of complex was found in kidney of control rats, accounting for only 1-3% of total enzyme in the tissue, while in thymus, approximately one-third of the total ornithine decarboxylase in thymus occurred as an antizyme-enzyme complex. After treatment with dexamethasone, both free ornithine decarboxylase and antizyme-ornithine decarboxylase decreased in thymus, the free enzyme activity decreasing more rapidly. In kidney, the concentration of the antizyme-ornithine decarboxylase complex increased after dexamethasone treatment, but only after the induction of free enzyme activity had reached its peak and begun to decrease. The pattern of the changes in amount of antizyme-ornithine decarboxylase complex after prolactin treatment differed from those observed in the dexamethasone-treated animals. In both kidney and thymus, the concentration of antizyme-ornithine decarboxylase complex increased concurrently with the induction of free enzyme activity. Both free and complexed ornithine decarboxylase had increased at 2.5 h after prolactin treatment and continued to increase to maximum specific activities at similar rates. In thymus, the amount of ornithine decarboxylase present as a complex reached 70% of the total in the tissue. In both thymus and kidney, the concentration of antizyme-ornithine decarboxylase complex decreased more slowly than did free enzyme activity. Free antizyme was observed only in thymus of dexamethasone-treated animals. The amount of measurable inhibitor was decreased if cycloheximide was given with dexamethasone.

Animals↗
PubMed1988

Multiple ionic forms of ornithine decarboxylase differ in degree of phosphorylation.

Two major ionic forms of ornithine decarboxylase were separated by column chromatography of extracts of kidneys from androgen-treated male CD-1 mice on DEAE-Sepharose CL-6B, and purified individually to apparent homogeneity. On SDS-PAGE, a single major protein band of Mr 50000 was present in each. When incubated with casein kinase II, purified from rat liver cytosol, only one form of the enzyme, which represented 20% of the total ornithine decarboxylase in the tissue, became phosphorylated. The major form, which was eluted later from the column, could be phosphorylated only after treatment with alkaline phosphatase, indicating that the phosphatase removed enzyme-bound phosphate already attached at the casein kinase II phosphorylation site. Evidence for the occurrence of a phosphorylated form of the enzyme in kidneys of dexamethasone-treated rats is also presented.

Alkaline Phosphatase↗
PubMed1986

An inhibitor of ornithine decarboxylase in lactogen-deprived Nb2 node rat lymphoma cells.

A previous study has shown that the activity of ornithine decarboxylase in cultured Nb2 node rat lymphoma cells falls to undetectable levels when cells become quiescent following incubation in lactogen (prolactin)-deficient medium. In the present study, it was found that addition of extracts of the lactogen-deprived, quiescent cells to extracts of log-phase cells markedly reduced the ornithine decarboxylase activity of the latter, the inhibitory activity being proportional to the amount of quiescent cell extract added. Evidence is presented that the ornithine decarboxylase-inhibitory activity in the quiescent cell extracts is due to an antizyme-like, polypeptide factor with an Mr of approx. 28,000. The activity of the inhibitor appears to be directed rather specifically against ornithine decarboxylase, since the activities of S-adenosylmethionine decarboxylase, thymidine kinase and uridine kinase were not affected. The Nb2 cell ornithine decarboxylase inhibitor may have an important role in modulating the cellular levels of ornithine decarboxylase as they change in response to the withdrawal and restoration of extracellular mitogenic lactogens.

Animals↗
PubMed1985

An inhibitor of ornithine decarboxylase in the thymus and spleen of dexamethasone-treated rats.

A marked decrease in activity of ornithine decarboxylase in thymus and spleen occurs soon after treatment of rats with a glucocorticoid. In the present study, evidence was obtained that extracts of these tissues prepared 5 h after administration of dexamethasone, when the enzyme activity is very low, contain an inhibitor of ornithine decarboxylase. The inhibitor is also present at 12 h after treatment and, in lesser amount, at 2.5 h, but was not evident at 24 h. The inhibitory activity was destroyed by treatment with heat or with trypsin, and was not lost on dialysis of the extract. Preliminary experiments indicate that the Mr of the inhibitor is greater than 50 000, which differentiates it from antizyme, an inhibitor of ornithine decarboxylase found in several other cell types. The inhibitor seems to act by a non-catalytic and non-competitive mechanism. The inhibition is dependent on the amount of inhibitor and does not change with time. Since inhibition is not changed by dialysis of the inhibitory extract, its activity apparently does not require small-Mr substances. This differentiates it from inhibitors which inactivate ornithine decarboxylase by covalent modification, such as the polyamine-dependent protein kinase or transglutaminase. The formation of this inhibitor is an early event in lymphoid tissues in response to dexamethasone and may be important in causing the inhibition of cell division which precedes the destruction of lymphocytes.

Animals↗
PubMed1982

Biochemical response of lymphoma cells to mitogenic stimulation by prolactin.

A previous study showed that cultured Nb 2 node rat lymphoma cells stopped replicating when transferred to medium supplemented with horse serum instead of fetal calf serum; resumption of growth could be induced by the addition of prolactin or other lactogens. The present study shows that in the absence of prolactin cells accumulated early in the G1 phase from which, on stimulation by the hormone, they proceeded through the cell cycle in a synchronized fashion. Ornithine decarboxylase and S-adenosyl methionine decarboxylase activities were closely related to the proliferative status of the cells. In stationary cultures the enzyme activity was barely detectable; following the addition of prolactin, the levels increased over 100-fold and displayed well-defined changes as the cells proceeded through the cell cycle. The results suggest the lymphoma cells are very useful for studying biochemical events resulting from the interaction of a mitogenic polypeptide hormone and its target cell.

Adenosylmethionine Decarboxylase↗
PubMed1980

The effects of dietary selenium and vitamin E on avian white muscle disease as measured by both chemical and physical parameters.

Commercial chicken broilers were fed a semipurified diet deficient in vitamin E and selenium from day 1 to day 13 ex ova and subsequently fed varying levels of dietary selenium and vitamin E. All birds were sacrificed on the 28th day, stored for 36 hr at 2 C to allow the onset and resolution of rigor, and frozen at -32 C until needed. Total cathepsin content of the Pectoralis major depended upon dietary vitamin E for birds receiving 0 to 12 IU/kg, whereas selenium administered at .05 to .16 ppm in the diet showed no statistically significant effect. Similarly, total protein content of P. major increased with increasing level of dietary vitamin E, but the level of dietary selenium had no effect. Muscle break strength was significantly affected by dietary selenium and vitamin E (P = .0092) interacting together. Catheptic activity and muscle protein explained 6.36% and 3.58% of the viriability in muscle break strength. Birds with more advanced avian white muscle disease showed higher break strength values. Ultrastructural deterioration of the myipathic muscle included disintegration of blood vessel walls, transverse tubules, and mitochondrial membranes as well as the obvious disruption of the myofibrillar components. Myelin figures were present in diseased, but not in normal, muscle. Accumulation of adipocytes both extracellularly and intracellularly occurred in selenium and vitamin E-deficient birds.

Animals↗
PubMed1980

The effect of vitamin A deficiency on some postmortem parameters of avian muscle.

The effect of the dietary status of vitamin A on carbohydrate metabolism, postmortem isometric tension development, and shear resistance of Pectoralis major muscle was studied. Depletion studies conducted over a 5-week period indicated a definite influence of vitamin A deficiency on muscle carbohydrate metabolism. Mild hypovitaminosis A induced an increase in glycogen deposition, whereas severe deficiency led to a reduction of these elevated stores. Vitamin A deficiency did not affect the ability of P. major strips to develop isometric tension postmortem. The P. major strips sampled from deficient cockerels generally required longer to reach maximum tension than those of controls. The extended times to maximum tension reflected an increased muscle glycogen content. A significant increase in shear value similarly corresponded to the increased myofibrillar contraction noted in the later deficiency stages. Cockerels which had previously received for five weeks a ration completely deficient in vitamin A were utilized for a two-week repletion study. Although there was a distinct delay in response to the feeding of a vitamin A adequate ration, the muscle glycogen content, isometric tension parameters, and shear values of repleted birds were similar to those of controls within the two-week period.

Adenosine Triphosphate↗
PubMed1979

Characterization of prolactin binding by membrane preparations from rat liver.

Binding sites for prolactin were identified in a plasma-membrane-enriched fraction isolated from livers of mature female rats. 125I-labelled sheep prolactin prepared by the lactoperoxidase procedure retained the same molecular integrity and binding affinity as the native hormone at physiological pH. The receptors bound prolactin from different species, whereas non-lactogenic hormones were not bound. The binding of 125I-labelled sheep prolactin was activated equally by bivalent and univalent cations, bivalent cations exerting their maximal effect at much lower concentrations. The association of 125I-labelled sheep prolactin with the receptor was a time- and temperature-dependent process. Partial dissociation was detected. The binding of 125I-labelled sheep prolactin was strongly influenced by pH, with an optimum observed at pH 6.5. Receptor activity was destroyed by Pronase and phospholipase C, whereas neuraminidase increased binding. Treatment of the membranes by ribonuclease and deoxyribonuclease did not affect the binding. Binding of 125I-labelled sheep prolactin was inhibited by p-chloromercuribenzoic acid, dithiothreitol and by brief exposure to high temperatures. Scatchard analysis of the binding of 125I-labelled sheep prolactin to receptors indicated that prolactin has a high affinity for its receptor. Binding of prolactin to liver membranes showed some properties different from those observed with mammary cells. Binding by these tissues differed in pH optimum, in effects of ions, and in response to neuraminidase.

Animals↗
PubMed1979

Acute toxic delirium. Neurotoxicity of intrathecal administration of amphotericin B.

A patient with coccidioidal meningitis was treated with intrathecally administered amphotericin B, and an acute toxic delirium with EEG abnormalities developed. Clinical recovery followed discontinuation of therapy and paralleled EEG resolution. This complication was dose related and argues for caution when initiating intrathecal therapy with amphotericin B at doses greater than 0.025 mg.

Acute Disease↗