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Biomedical subjects

J C Chow

Publications and source records attributed to J C Chow.

At least 55 records · Page 3Linked to original sources
PubMed1996

Chronic growth hormone treatment in normal rats reduces post-prandial skeletal muscle plasma membrane GLUT1 content, but not glucose transport or GLUT4 expression and localization.

Whether skeletal muscle glucose transport system is impaired in the basal, post-prandial state during chronic growth hormone treatment is unknown. The current study was designed to determine whether 4 weeks of human growth hormone (hGH) treatment (3.5 mg/kg per day) would impair glucose transport and/or the number of glucose transporters in plasma membrane vesicles isolated from hindlimb skeletal muscle of Sprague-Dawley rats under basal, post-prandial conditions. hGH treatment was shown to have no effect on glucose influx (Vmax or K(m)) determined under equilibrium exchange conditions in isolated plasma membrane vesicles. Plasma membrane glucose transporter number (Ro) measured by cytochalasin B binding was also unchanged by hGH treatment. Consequently, glucose transporter turnover number (Vmax/Ro), a measure of average glucose transporter intrinsic activity, was similar in hGH-treated and control rats. hGH did not change GLUT4 protein content in whole muscle or in the plasma membrane, and muscle content of GLUT4 mRNA also was unchanged. In contrast, GLUT1 protein content in the plasma membrane fraction was significantly reduced by hGH treatment. This was associated with a modest, although not significant, decrease in muscle content of GLUT1 mRNA. In conclusion, high-dose hGH treatment for 4 weeks did not alter post-prandial skeletal muscle glucose transport activity. Neither the muscle level nor the intracellular localization of GLUT4 was changed by the hormone treatment. On the contrary, the basal post-prandial level of GLUT1 in the plasma membrane was reduced by hGH. The mRNA data suggest that this reduction might result from a decrease in the synthesis of GLUT1.

Animals↗
PubMed1996

Determinants of plasma concentrations of insulin-like growth factor-I and albumin and their hepatic mRNAs: the role of dietary protein content and tumor necrosis factor in malnourished rats.

Protein restriction decreases plasma concentrations of albumin and insulin-like growth factor-I (IGF-I) by reducing their hepatic mRNA levels, whereas protein restriction increases IGF-I binding protein-2 (IGFBP-2) gene expression in the liver. Tumor necrosis factor (TNF), as an inducer of the injury response, decreases plasma albumin concentration and albumin mRNA in the liver. The present study was designed to evaluate the effects of protein repletion and TNF on plasma albumin and IGF-I and their mRNAs and IGFBP-2 mRNA in the liver of protein-restricted rats. After 2 weeks of feeding a 2% casein diet, rats were assigned to four groups according to either being refed with a 2% or 20% casein diet or receiving saline or TNF by intraperitoneal injection (50 microg/kg x d) for 4 days. Plasma IGF-I and albumin were assayed. Hepatic mRNAs of IGF-I, albumin, and IGFBP-2 were determined. Protein repletion increased plasma concentrations of IGF-I and albumin and their mRNA content in the liver, but decreased IGFBP-2 mRNA. TNF did not alter plasma IGF-I concentration but did increase hepatic IGF-I mRNA in protein-repleted animals, and plasma albumin concentration was significantly decreased with unaltered hepatic albumin mRNA. Thus, protein repletion of malnourished rats increased plasma IGF-I and albumin concentrations in association with increased expression of their mRNAs in the liver. However, plasma albumin but not IGF-I decreased following TNF in protein-restricted rats, whereas TNF increased hepatic IGF-I mRNA in protein-repleted rats. Thus, only plasma albumin concentration responds to both principal determinants, diet and injury, in the development of malnutrition.

Animals↗
PubMed1996

Gut adaptation and the insulin-like growth factor system: regulation by glutamine and IGF-I administration.

Intestinal adaptation after extensive small bowel resection in rats is augmented by the provision of diets supplemented with the amino acid glutamine (Gln) or by administration of insulin-like growth factor-I (IGF-I). The goal of this study was to investigate potential synergistic effects of Gln and IGF-I on postresection ileal hyperplasia. Rats underwent 80% small bowel resection (SBR) and then were fed low-Gln or L-Gln-enriched diets and subcutaneously given recombinant human IGF-I or vehicle for 7 days. Gln and IGF-I each significantly enhanced adaptive ileal hyperplasia (DNA content) compared with rats receiving vehicle and low-Gln diet. Ileal DNA content was highest when IGF-I was administered together with Gln supplementation. Combined IGF-I plus Gln synergistically increased ileal weight and protein content. This was associated with higher plasma concentrations of IGF-I and Gln than observed when IGF-I or Gln was given individually. Ileal IGF-I mRNA expression rose nearly twofold during gut adaptation after SBR; this response was augmented with IGF-I administration but was unaltered by Gln feeding. In contrast, dietary Gln, but not IGF-I therapy, prevented a decrease in hepatic IGF-I mRNA induced by SBR. We conclude that parenteral IGF-I and enteral Gln have both individual and synergistic effects on ileal adaptation after massive small intestinal resection. These findings support the concept that specific gut-trophic nutrients and growth factors may be combined to enhance intestinal adaptation and possibly reduce the severity of short bowel syndrome after intestinal resection.

Animals↗
PubMed1996

Growth hormone stimulates tyrosine phosphorylation of JAK2 and STAT5, but not insulin receptor substrate-1 or SHC proteins in liver and skeletal muscle of normal rats in vivo.

GH has been shown to stimulate tyrosine phosphorylation of JAK2, several STAT proteins, insulin receptor substrate-1 (IRS-1), and SHC proteins in cultured cells. The goal of this study was to determine GH effects on protein tyrosine phosphorylation in liver and skeletal muscle of normal rats in vivo. Nonfasted male Sprague-Dawley rats (225-250 g) were injected with GH iv, and tissues were obtained after 5, 15, 30, or 60 min. At a maximally effective GH dose (1.5 mg/kg body weight), phosphotyrosine antibody immunoblots demonstrated marked stimulation of the tyrosine phosphorylation of JAK2 (maximal at 5 min) and a 95,000 Mr protein (maximal at 15 min) in both liver and skeletal muscle. The 95,000 Mr protein was recognized and immunodepleted by STAT5 antibody, but not by other STAT protein antibodies. Although basal tyrosine phosphorylation of IRS-1 and SHC was evident, GH did not stimulate tyrosine phosphorylation of either of these proteins in liver or skeletal muscle. In conclusion, GH stimulates the tyrosine phosphorylation of JAK2 and STAT5, but not IRS-1, SHC, or other STAT proteins in liver and skeletal muscle of normal rats. These results differ from findings in cultured cells and support the concept that selectivity for tyrosine kinase substrates is an important determinant of postreceptor signaling specificity in vivo.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Endoscopic carpal tunnel release.

The aspects of various techniques for endoscopic carpal tunnel release, including the Chow technique, the Japanese technique, and the Agee technique, are reviewed. Anesthesia, portal placement, and ligament cutting techniques are considered. Clinical results, complications, and long-term outcomes of the Chow technique are summarized.

Carpal Tunnel Syndrome↗
PubMed1995

Measurement methods to determine compliance with ambient air quality standards for suspended particles.

One of the most important parts of formulating a National Ambient Air Quality Standard is specifying the measurement methods for determining and attaining compliance. The samples taken for compliance are often pushed beyond their original purpose to identify sources, to evaluate the effectiveness of controls, and to determine relationships between pollution levels and public health. A full understanding of available sampling and analysis methods is needed, as well as an analysis of their costs, before acceptable monitoring approached can be specified. This review identifies issues related to measurement methods used to determine compliance with standards, describes current and future measurement methods and their limitations, and determines the extent to which existing technology can meet short-term and long-term needs for measuring compliance.

Air↗
PubMed1995

Resection-induced colonic adaptation is augmented by IGF-I and associated with upregulation of colonic IGF-I mRNA.

The effects of exogenous insulin-like growth factor-I (IGF-I) on colonic adaptation were examined in male Sprague-Dawley rats (n = 60, 225-275 mg) after either a 60% small bowel and cecal resection (RX) or mid-small bowel transection with reanastomosis (TX). Animals received a 7-day treatment with either IGF-I (2.4 mg.kg-1.day-1) or vehicle (V; 0.1 mol/l acetic acid). Body weight decreased significantly after resection (-25.6 +/- 4.0 g; P < 0.05 vs. TX/V). IGF-I treatment significantly reduced weight loss after resection (-12.4 +/- 3.8 g; P < 0.01 vs. RX/V) and induced significant weight gain after transection (15.6 +/- 4.0 g; P < 0.05 vs. TX/V). Plasma IGF-I decreased with resection (526 +/- 41 TX/V vs. 344 +/- 17 ng/ml RX/V; P < 0.01). IGF-I treatment significantly increased plasma IGF-I levels (805 +/- 100 ng/ml TX/IGF, 677 +/- 56 ng/ml RX/IGF). After resection, IGF-I treatment significantly increased colonic mucosal weight, DNA, protein content, and crypt depth when compared with resection alone (P < 0.05). Colonic water absorption, measured by an in vivo [3H]polyethylene glycol assay, was significantly increased by IGF-I treatment in resected animals (399 +/- 23 RX/IGF vs. 306 +/- 32 microliter.cm-1.h-1 RX/V; P < 0.05). Resection resulted in increased steady-state colonic IGF-I mRNA (182% of TX/V; P < 0.01) without significantly affecting IGF-I receptor mRNA expression. Regulation of IGF binding protein (BP)-3 and -4 was discoordinate, with IGFBP-3 mRNA tending to decrease with resection (67% of TX/V; P is not significant) and IGFBP-4 increasing significantly (191% of TX/V; P < 0.05). An important role for IGF-I in colonic adaptation after massive intestinal resection is indicated by 1) significantly enhanced colonic mucosal growth and water absorption with IGF-I treatment and 2) postresection upregulation of colonic IGF-I mRNA and alteration of IGFBP-3 and IGFBP-4 mRNA expression.

Adaptation, Physiological↗
PubMed1994

Differing patterns of carbohydrate metabolism in liver and muscle.

The effect of a period of starvation followed by refeeding on skeletal muscle glycogen was investigated by the use of double-labelled radioactive glucose precursors in rats. Skeletal muscle glycogen, which is not depleted to anything like the extent of liver glycogen, shows a remarkable stability with respect to its overall molecular size distribution during starvation and subsequent refeeding. The experiments also indicate that there is a control mechanism in muscle tissue enabling the synthesis of lysosomal glycogen to be switched off during the initial part of the refeeding process. The results emphasise the inadequacy of the Cori cycle and a modified version is proposed.

Animals↗
PubMed1994

Regulation of insulin-like growth factor-I and binding protein-3 expression in oMtla-oGH transgenic mice.

Growth hormone (GH)-transgenic mice provide a model for studying hormonal regulation of gene products responsible for efficient lean growth. Insulin-like growth factor-I (IGF-I) and IGF binding protein-3 (BP-3) are two products involved in mediating the growth promoting actions of GH. Mice carrying the ovine metallothionein la-ovine growth hormone (oMtla-oGH) transgene were used to study GH regulation of IGF-I and BP-3 expression because these mice do not exhibit elevated basal oGH levels without transgene stimulation by exogenous zinc. C57B1/6XCBA mice with (transgenic = TG) and without control = C) the oMtla-oGH transgene were activated (+ Zn) or inactivated (-Zn) by the addition or removal of 25 mM zinc sulfate in the drinking water. Plasma IGF-I and BP-3 levels were determined by radioimmunoassay and western ligand blotting, respectively. Hepatic IGF-I and BP-3 mRNA levels were determined by slot-blot analysis. TG+Zn mice had higher plasma IGF-I (p < 0.05) and hepatic IGF-I mRNA (p < 0.05) levels as compared to TG-Zn, C+Zn and C-Zn mice. Plasma IGF-I and hepatic IGF-I mRNA levels in TG-Zn mice were not different from C+Zn and C-Zn mice. Removal of Zn decreased hepatic IGF-I mRNA levels to C levels in TG mice. Plasma BP-3 and hepatic BP-3 mRNA levels in TG+Zn mice were increased (p < 0.05) as compared to TG-Zn, C-Zn and C+Zn. Plasma BP-3 and hepatic BP-3 mRNA levels did not differ between TG-Zn, C-Zn and C+Zn mice. Expression of the transgene also increased the level of plasma BP-3 during pregnancy as compared to that observed for pregnant C mice. We conclude that oGH regulates IGF-I and BP-3 expression in the oMtla-oGH transgenic mouse model system.

Animals↗
PubMed1994

Endoscopic carpal tunnel release. Two-portal technique.

The historical perspective, indications and contraindications, operating room setup and operative technique, and the ligament cutting technique for the two portal endoscopic carpal ligament release is outline in this article, as well as the potential complications and how to avoid them. The clinical results of 815 patients (1154 wrists) are described.

Arthroscopy↗
PubMed1993

Transligamentous motor branch of the median nerve discovered during endoscopically assisted carpal tunnel release.

The endoscopically assisted carpal tunnel release is an alternative to open procedures. A case is presented in which a transligamentous motor branch of the median nerve exits from the main trunk in a proximal and ulnar location. It is discovered from within the carpal canal during an endoscopically assisted procedure. The authors suggest adherence to strict principles to minimize potential complications in the rare event of an anatomic anomaly.

Aged↗
PubMed1993

The Chow technique of endoscopic release of the carpal ligament for carpal tunnel syndrome: four years of clinical results.

This article represents a review of the clinical results of 650 consecutive cases of carpal tunnel decompression in 456 patients from the first 4 years of endoscopic carpal tunnel release: 38% returned to normal activities within 1 week, 59% within 2 weeks, 73% within 3 weeks, and 84% within 4 weeks. A total of 98% returned to their normal activities. Also included is an analysis of the workmen's compensation and pinch-and-grip studies. The results of these studies appear to indicate that endoscopic release of the carpal ligament accomplishes results similar to the standard procedure with a more rapid recovery.

Adolescent↗
PubMed1993

Endoscopic extra-articular lateral release.

This article describes a new technique using the currently available endoscopic instrumentation to perform a lateral release of the knee joint. An extra-articular release is performed in an attempt to decrease complications and to produce a less painful postoperative period for the patient.

Arthroplasty↗
PubMed1993

Neutralizing monoclonal antibodies that distinguish three antigenic sites on human cytomegalovirus glycoprotein H have conformationally distinct binding sites.

Seven neutralizing murine monoclonal antibodies specific for the glycoprotein H of human cytomegalovirus were produced and used to construct a topological map of two nonoverlapping antigenic sites that are bridged by a third antigenic site. Neutralization assays with 15 laboratory or clinical human cytomegalovirus strains indicated that the monoclonal antibodies recognize three antigenically variable and three conserved epitopes within the three antigenic sites. The variable-domain genes encoding monoclonal antibodies representing each of the three antigenic sites were cloned and sequenced, and molecular models of their binding sites were generated. Conformational differences in the antibody-binding sites suggested a structural basis for experimentally observed differences in gH epitope recognition.

Amino Acid Sequence↗
PubMed1992

Interactions between gluconeogenesis and fatty acid oxidation in isolated sheep hepatocytes.

The interaction of gluconeogenesis and fatty acid oxidation in isolated sheep hepatocytes was studied. Addition of tetradecylglycidic acid, an inhibitor of carnitine palmitoyltransferase I (EC 2.3.1.21), to isolated hepatocytes inhibited gluconeogenesis from a mixture of pyruvate plus lactate and from propionate alone. Inhibition constants for tetradecylglycidic acid on gluconeogenesis were 4.77 +/- 1.00 microM and 7.25 +/- 1.52 microM, respectively, for pyruvate plus lactate and for propionate as gluconeogenic substrates. The inhibition constants were not different. At the highest substrate concentrations examined, gluconeogenesis from pyruvate plus lactate and from propionate in the presence of 10 microM tetradecylglycidic acid was 47.3 and 41.4% of their respective controls. Similar to previous observations with butyrate, caproate addition inhibited gluconeogenesis from propionate by isolated hepatocytes and was unable to prevent inhibition of gluconeogenesis induced by tetradecylglycidic acid. Carnitine palmitoyltransferase I activity was lower in mitochondria isolated from hepatocytes preincubated with insulin than in control hepatocytes. The data suggest 1) that maximum rates of gluconeogenesis in isolated sheep hepatocytes from either pyruvate plus lactate or from propionate as gluconeogenic substrates require beta-oxidation, 2) that intermediates common to the metabolism of butyrate and caproate may be involved in the inhibition of propionate conversion to glucose by isolated sheep hepatocytes, and 3) that carnitine palmitoyltransferase I activity in isolated sheep hepatocytes can be modulated by insulin treatment.

Animals↗
PubMed1990

Endoscopic release of the carpal ligament for carpal tunnel syndrome: 22-month clinical result.

This article represents a review of 149 carpal tunnel decompressions on 109 carpal tunnel syndrome patients, and a 22-month clinical result on endoscopic carpal ligament release. The symptoms were relieved and no permanent nerve damage, vascular complications, hematomas, infections, or recurrences were reported. Postoperatively, one patient had a temporary loss of the interosseous muscle but recovered spontaneously in 4 weeks. In this 22-month survey, 28.9% of the patients were able to return to normal activities and work within 1 week, 58.5% returned within 2 weeks, 75.4% returned within 3 weeks, and 85.9% returned within 4 weeks. A pinch-and-grip study was performed; 32% regained normal pinch-and-grip strength within 1 week, 74% regained it in 2 weeks, 93% regained it in 3 weeks, and 100% regained it in 4 weeks. Based on our results, there has been rapid recovery, less scarring, decreased postoperative pain, and no loss of pinch-and-grip strength.

Arthroscopy↗
PubMed1990

Detection of urinary TGF-alpha by HPLC and western blot in patients with melanoma.

Transforming growth factor-alpha (TGF-alpha) secretion in the urine may reflect autonomous production by neoplasms. Previous measurements of TGF-alpha in the urine were limited by the large volumes of urine required for detection. Sensitive assays are required to detect TGF-alpha in small urine samples from individual patients with melanoma. An assay which detects ng quantities of immunoreactive TGF-alpha in 10 ml of urine using dialysis, reverse-phase high-performance liquid chromatography (HPLC), and Western blot of the HPLC fractions was used to study the urine from 6 melanoma patients and 6 normal human volunteers. No TGF-alpha was detectable in the first voided urine specimens from the normal volunteers. In contrast, TGF-alpha was detected in the urine specimens of two of three patients with primary melanomas and two of three patients with metastatic melanoma. The sensitivity and reliability of the assay were most affected by methods of urine collection, sample preparation, and storage. TGF-alpha was less often found in randomly voided urine samples from melanoma patients (1 of 3 detectable) as compared to first voided morning urine samples (3 of 3 detectable). This data indicates urinary TGF-alpha assay may be useful in the diagnosis and management of patients with melanoma.

Blotting, Western↗