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Biomedical subjects

J C Lawrence

Publications and source records attributed to J C Lawrence.

At least 19 recordsLinked to original sources
PubMed1992

GLUT4 facilitates insulin stimulation and cAMP-mediated inhibition of glucose transport.

The glucose transporter isoform GLUT4 is found only in cells that exhibit insulin-sensitive glucose transport. To investigate the function of this transporter, L6 myoblasts were stably transfected with GLUT4 cDNA. GLUT4 underwent insulin-dependent movement to the cell surface in myoblasts overexpressing the transporter. One cell line (243-6) expressed sufficient levels of the GLUT4 protein to study insulin-dependent glucose transport. Unlike wild-type L6 cells, 243-6 myoblasts exhibited two features that are characteristic of differentiated muscle fibers and adipocytes in vivo: a large insulin-stimulated component of glucose transport and inhibition of this stimulated component by cAMP. Relative to normal L6 cells, 243-6 cells responded to insulin or insulin-like growth factor 1 with a 5-fold larger increase in 2-deoxy[3H]glucose uptake. N6,O2'-Dibutyryladenosine 3',5'-cyclic monophosphate (Bt2cAMP) did not inhibit transport in normal L6 myoblasts, which express only GLUT1, but inhibited IGF-1/insulin-stimulated transport by 50% in 243-6 cells. The effect of cAMP was investigated further by using Chinese hamster ovary cells transiently expressing GLUT1 and GLUT4. Bt2cAMP inhibited glucose transport only in Chinese hamster ovary cells expressing GLUT4. These results indicate that cAMP-mediated inhibition of glucose transport is dependent on expression of the GLUT4 isozyme.

Animals↗
PubMed1992

Bilateral metastatic endophthalmitis as a complication of major burns.

Metastatic infection of the eye is a rare complication of burns. The following report describes a patient with endophthalmitis occurring as a complication of major burns. The diagnostic difficulties that arose are discussed and the recommended treatment outlined.

Accidents, Occupational↗
PubMed1991

Wound infection under occlusive dressings.

It is often supposed that occlusive dressings potentiate wound infection. However, even though heavy colonization by skin and wound flora is often seen under certain types of occlusion, clinical infection is not a frequent occurrence. Commensal wound flora consists of a variety of Gram-positive and Gram-negative organisms and fungi which do not appear to be detrimental to healing. Certain aspects of wound healing may in fact be promoted by bacterial colonization, although clinical infection can lead to wound breakdown and systemic infection. Wounds compromised by devitalized tissue, drains or sutures are more susceptible than clean wounds to clinical infection. Occlusive dressings may help prevent infection by presenting a barrier to potential pathogens, and hydrocolloid occlusive dressings have been shown to prevent dissemination of methicillin-resistant Staphylococcus aureus. The rate of clinical infection as deduced from published trials of dressings is lower under occlusion than when non-occlusive dressings are used, and this is likely to be a result of normal activity of the host defences under occlusive dressings.

Bacteria↗
PubMed1991

The use of GORE-TEX bags for hand burns.

Clinical and laboratory studies were made to compare the water vapour permeability, bacteriological properties and clinical performance of polythene and polytetrafluoroethylene fabric (GORE-TEX) bags in the treatment of hand burns. Polythene bags are virtually impermeable to saline, whereas GORE-TEX bags containing silver sulphadiazine cream show a water vapour permeability of 0.53 ml/cm2/day, resulting in a 30 per cent weight reduction of added water after 48 h. Clinically, hand maceration and accumulation of exudate are significantly reduced in hands treated in GORE-TEX bags. The mean daily volume of accumulated exudate for GORE-TEX bags was 37 ml compared to 83 ml for polythene (P less than 0.01). When adjusted for the percentage area of the hand surface burned, this reduction remained significant (P less than 0.005). A tendency for less pain and better hand movement was noted with GORE-TEX bags. There were no significant differences in rate of healing or bacterial colonization of the burned hand between the two type of bags. GORE-TEX bags prevent skin maceration and accumulation of exudate, allowing ease of burn assessment and improved hand function. They are also durable and non-slip, thus increasing patient independence.

Adult↗
PubMed1991

Treating burns.

Explore the source record for details and available documents.

Burns↗
PubMed1990

Stimulation of glucose transport and glucose transporter phosphorylation by okadaic acid in rat adipocytes.

Okadaic acid, an inhibitor of Type I and IIa protein phosphatases, was recently found to stimulate 2-deoxyglucose uptake in rat adipocytes (Haystead, T. A. J., Sim, A. T. R., Carling, D., Honnor, R. C., Tsukitani, Y., Cohen, P., and Hardie, D. G. (1989) Nature 337, 78-81). In the present experiments the effect of okadaic acid on the phosphorylation and subcellular distribution of the insulin-regulatable glucose transporter (IRGT) was investigated. At maximally effective concentrations, insulin and okadaic acid increased the amount of IRGT in the plasma membrane by 10- and 4-fold, respectively. Thus, the stimulation of glucose transport by okadaic acid was apparently due to an increase in the surface concentration of the IRGT. However, despite its stimulatory actions, okadaic acid partially inhibited the ability of insulin to enhance glucose transport and translocation of the transporter. When cells were incubated with okadaic acid alone or in combination with insulin, phosphorylation of the IRGT in the plasma membrane was increased by approximately 3-fold relative to the intracellular pool of transporters in control cells. Phosphorylation of the IRGT was confined to the presumed cytoplasmic domain at the COOH terminus of the protein. Glucose transporters were dephosphorylated in vitro by Type I or Type IIa protein phosphatases, indicating that inhibition of one or both of these phosphatases could account for the increased phosphorylation produced by okadaic acid. The observation that okadaic acid stimulated translocation of the IRGT implicated a serine/threonine phosphorylation event in triggering movement of the intracellular IRGT-containing vesicles (GTV) to the cell surface. Immunoadsorption of GTV from 32P-labeled adipocytes revealed that the IRGT was the major phosphoprotein in these vesicles. The phosphorylation of at least three other GTV proteins was increased by okadaic acid, and these species would appear to be candidates for regulators of GTV movement to the plasma membrane. It is unlikely that phosphorylation of the IRGT is the signal for translocation because insulin did not increase phosphorylation of the protein. Rather, the inhibitory effect of okadaic acid on insulin-stimulated translocation is consistent with the hypothesis that phosphorylation of the IRGT promotes its internalization.

Adipose Tissue↗
PubMed1990

Phosphorylation of the glucose transporter in rat adipocytes. Identification of the intracellular domain at the carboxyl terminus as a target for phosphorylation in intact-cells and in vitro.

Phosphorylation of the insulin-regulatable glucose transporter (IRGT) is increased by incubating rat adipocytes with isoproterenol or by incubating microsomal membranes with cAMP-dependent protein kinase. To attempt to locate the sites of phosphorylation, the IRGT (apparent Mr = 46,000) was immunoprecipitated from 32P-labeled adipocytes and cleaved with CNBr or trypsin. Essentially all of the 32P could be recovered in a single CNBr fragment, denoted CB-T (Mr = 8,000), which bound a polyclonal antibody (R820) against a peptide having the sequence of the last 12 amino acids in the COOH terminus of the IRGT. 32P-Labeling of the IRGT was also confined to CB-T when membranes were incubated with [gamma-32P]ATP and cAMP-dependent protein kinase. Isoproterenol increased phosphorylation of CB-T, but insulin was without effect. To resolve phosphorylation sites further, IRGT from 32P-labeled cells was subjected to exhaustive proteolysis with trypsin. Samples were applied to a C-18 column, and 32P-labeled fragments were resolved into three peak fractions by elution with an increasing gradient of acetonitrile. [32P]Phosphoserine was the only phosphoamino acid detected in any of the peaks. Peak III contained approximately 80% of the 32P and was increased by isoproterenol. Almost all of the 32P introduced by cAMP-dependent protein kinase in vitro eluted in Peak III. In all cases, the 32P-labeled species in Peak III were quantitatively immunoprecipitated by R820. Digesting the peptide(s) in Peak III with V8 protease generated a single peak of 32P which eluted at lower acetonitrile than Peak III and contained 32P-labeled species that did not interact with R820. Automated Edman degradation indicated that the serine residue in Peak III phosphorylated by cAMP-dependent protein kinase was the 3rd or 4th residue from the NH2 terminus of the peptide. These findings indicate that phosphorylation of the IRGT is restricted to the presumed intracellular domain at the COOH terminus and that Ser488 is a major site phosphorylated both by cAMP-dependent protein kinase in vitro and in response to isoproterenol in vivo.

Adipose Tissue↗
PubMed1990

Phosphorylase kinase isozymes and phosphorylase in denervated skeletal muscles.

The effects of motor denervation on levels of phosphorylase kinase isozymes and phosphorylase were investigated in rat epitrochlearis, hemidiaphragm, and soleus muscles. Amounts of the proteins were measured after quantitative immunoprecipitation and found to be decreased by as much as 70% 2 weeks after denervation. Unexpectedly, denervation had little, if any, effect on the relative proportions of the two phosphorylase kinase isozymes. Phosphorylase and phosphorylase kinase were decreased by essentially the same extent after denervation, and the effects of denervation were comparable in all three muscles. The decreases in these enzymes explain, at least in part, the marked alterations in glycogen metabolism that occur after motor denervation.

Animals↗
PubMed1989

Insulin stimulates dephosphorylation of phosphorylase in rat epitrochlearis muscles.

We have investigated the effects of insulin on the phosphorylation of glycogen phosphorylase in skeletal muscle. Rat epitrochlearis muscles were incubated in vitro with 32Pi to label cellular phosphoproteins, before being treated with hormones. Phosphorylase, phosphorylase kinase, and glycogen synthase were immunoprecipitated under conditions that prevented changes in their phosphorylation states. Based on measurements of the activity ratio (-AMP/+AMP) and the 32P content of phosphorylase, 4-8% of the phosphorylase in untreated muscles appeared to be phosphorylated. Epinephrine promoted increases of approximately 4-fold in the 32P content and activity ratio. Neither these effects nor the epinephrine-stimulated increases in phosphorylation of glycogen synthase and phosphorylase kinase were attenuated by insulin. However, insulin at physiological concentrations rapidly decreased the 32P content of phosphorylase in muscles incubated without epinephrine. Results from peptide mapping experiments indicate that phosphorylase was phosphorylated at a single site in both control and insulin on phosphorylase represented a decrease in 32P of approximately 50%. By comparison, the 32P content of glycogen synthase and the beta subunit of phosphorylase kinase were decreased by only 20 and 16%, respectively; the 32P content of the kinase alpha subunit was not affected by insulin. The results provide direct evidence that insulin decreases the amount of phosphate in phosphorylase and phosphorylase kinase. These findings have important implications with respect to both the regulation of glycogen metabolism in skeletal muscle and the mechanism of insulin action.

Animals↗
PubMed1989

Ca2+-dependent and cAMP-dependent control of nicotinic acetylcholine receptor phosphorylation in muscle cells.

Mouse BC3H1 myocytes were incubated with 32Pi before acetylcholine receptors were solubilized, immunoprecipitated, and subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis. More than 90% of the 32P found in the receptor was bound to the delta subunit. Two phosphorylation sites in this subunit were resolved by reverse phase high performance liquid chromatography after exhaustive proteolysis of the protein with trypsin. Sites 1 and 2 were phosphorylated to approximately the same level in control cells. The divalent cation ionophore, A23187, increased 32P in site 1 by 40%, but did not affect the 32P content of site 2. In contrast, isoproterenol increased 32P in site 2 by more than 60%, while increasing 32P in site 1 by only 20%. When dephosphorylated receptor was incubated with [gamma-32P]ATP and the catalytic subunit of cAMP-dependent protein kinase, the delta subunit was phosphorylated to a maximal level of 1.6 phosphates/subunit. Approximately half of the phosphate went into site 2, with the remainder going into a site not phosphorylated in cells. The alpha subunit was phosphorylated more slowly, but phosphorylation of both alpha and delta subunits was blocked by the heat-stable protein inhibitor of cAMP-dependent protein kinase. Phosphorylation of the receptor was also observed with preparations of phosphorylase kinase. In this case phosphorylation occurred in the beta subunit and site 1 of the delta subunit, neither of which were phosphorylated by cAMP-dependent protein kinase. The rate of receptor phosphorylation by phosphorylase kinase was slow relative to that catalyzed by cAMP-dependent protein kinase. Therefore, it can not yet be concluded that phosphorylase kinase phosphorylates the beta subunit and the delta subunit site 1 in cells. However, the results strongly support the hypothesis that phosphorylation by cAMP-dependent protein kinase accounts for phosphorylation of the alpha subunit and the delta subunit site 2 in response to elevations in cAMP.

Amino Acids↗
PubMed1989

Identification of an adipocyte protein that binds to calmodulin in the absence of Ca2+ and is phosphorylated in response to insulin and tumor-promoting phorbol esters.

The present experiments were performed to identify calmodulin-binding proteins phosphorylated in response to insulin. Homogenates were prepared from 32Pi-labeled rat adipocytes. After centrifugation, the supernatants (+/- Ca2+) were applied to calmodulin-Sepharose columns. The bound proteins were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and phosphoproteins were visualized by autoradiography. Several proteins bound to the affinity resin in the presence of Ca2+, two bound +/- Ca2+, but only one protein, Mr = 170,000 (denoted pp170), bound in the absence of Ca2+. Binding of pp170 was inhibited by adding calmodulin (micromolar) or Ca2+ (nanomolar) to extracts prior to affinity chromatography. Physiological concentrations of insulin rapidly and reversibly increased (by as much as 4-fold) 32P-labeled pp170. Phorbol 12-myristate 13-acetate (PMA) increased (up to 3-fold) phosphorylation of pp170; but 4 alpha-phorbol 12,13-didecanoate was without effect. Phosphorylation of pp170 in response to insulin and PMA occurred predominantly on serine residues; no phosphotyrosine was detected. Protein kinase C inhibitors attenuated PMA-stimulated phosphorylation of pp170, but had no effect on insulin-stimulated phosphorylation. Peptide mapping indicated that pp170 was phosphorylated on multiple sites and that insulin stimulated the phosphorylation of at least one site not phosphorylated in response to PMA. The results indicate that insulin and PMA stimulate the phosphorylation of pp170 via different pathways, the latter presumably via protein kinase C.

Adipose Tissue↗
PubMed1989

Chemical burns.

This study reports the incidence and nature of chemical burns admitted to a large regional burns unit between 1 January 1981 and 31 December 1987. Of the 3251 patients admitted, 100 had sustained chemical burns; although they only comprised 3.1 per cent of the workload they accounted for 16.5 per cent of all industrial burning accidents. The victims were mainly male adults of working age. Alkaline materials caused 37 per cent of the accidents, 26 per cent attributable to caustic soda; acids caused a further 27 per cent, hydrofluoric acid accounting for half of these. The nature of the chemical was unknown in 13 per cent of the cases; this, together with the fact that workers were often unaware that they were using hazardous substances gives cause for concern. The methods for managing a diverse range of chemical burns are described.

Accidents, Home↗
PubMed1989

Isoproterenol stimulates phosphorylation of the insulin-regulatable glucose transporter in rat adipocytes.

We have examined the acute effects of insulin and isoproterenol on the phosphorylation state of the insulin-regulatable glucose transporter (IRGT) in rat adipocytes. The IRGT was immunoprecipitated from either detergent-solubilized whole-cell homogenates or subcellular fractions of 32P-labeled fat cells and subjected to sodium dodecyl sulfate/polyacrylamide gel electrophoresis. The 32P-labeled IRGT was detected by autoradiography as a species of apparent Mr 46,000. Insulin stimulated translocation of the IRGT from low-density microsomes to the plasma membrane but did not affect phosphorylation of the transporter in either fraction. Isoproterenol inhibited insulin-stimulated glucose transport by 40% but was without effect on the subcellular distribution of the transporter in either the presence or absence of insulin. Isoproterenol stimulated phosphorylation of the IRGT 2-fold. Incubating cells with dibutyryl-cAMP and 8-bromo-cAMP also stimulated phosphorylation 2-fold, and the transporter was phosphorylated in vitro when IRGT-enriched vesicles were incubated with cAMP-dependent protein kinase and [gamma-32P]ATP. These results suggest that isoproterenol stimulates phosphorylation of the IRGT via a cAMP-dependent pathway and that phosphorylation of the transporter may modulate its ability to transport glucose.

8-Bromo Cyclic Adenosine Monophosphate↗