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Biomedical subjects

J C Chow

Publications and source records attributed to J C Chow.

68 records · Page 4Linked to original sources
PubMed1990

Gluconeogenic dependence on ketogenesis in isolated sheep hepatocytes.

Dependence of gluconeogenesis on beta-oxidation and ketogenesis from long-chain fatty acids was examined in isolated sheep hepatocytes. Hepatocytes were incubated with a combination of gluconeogenic precursors (2 mM pyruvate, 20 mM lactate, and 5 mM propionate) plus other fatty acids, in the presence and absence of tetradecylglycidic acid, an inhibitor of the carnitine palmitoyltransferase reaction. Palmitate oxidation to total acid-soluble metabolites or beta-hydroxybutyrate was markedly inhibited by the addition of tetradecylglycidic acid. In general, oxidation of palmitate to carbon dioxide was not altered by tetradecylglycidic acid. Glucose production was inhibited 28 to 50% in the presence of tetradecylglycidic acid. Addition of acetate and butyrate inhibited gluconeogenesis, but octanoate addition had a slight stimulatory effect. In the presence of tetradecylglycidic acid, butyrate, but not acetate, addition further reduced gluconeogenesis. In contrast, addition of octanoate in the presence of tetradecylglycidic acid restored gluconeogenic rates to control values. The results are consistent with observations in several nonruminant species and suggest that, as in those species, ruminant gluconeogenesis requires at least a basal rate of beta-oxidation and ketogenesis from long-chain fatty acids to support maximum gluconeogenic rates.

Acetates↗
PubMed1989

Endoscopic release of the carpal ligament: a new technique for carpal tunnel syndrome.

This is a preliminary report outlining an endoscopic technique to release the carpal ligament employing current arthroscopic methods. The technique has been used successfully on 62 hands in 46 patients with no known complications. In some cases, the follow-up period has been rather short. Based on our results, however, there has been rapid recovery with decreased scarring and postoperative pain and no loss of grip or pinch strength, which is sometimes seen with the conventional method of carpal ligament release.

Arthroscopy↗
PubMed1989

An assessment of the Arthritis Impact Measurement Scales in 3 ethnic groups.

The Arthritis Impact Measure Scales (AIMS) have established validity and reliability in general adult populations with medically diagnosed rheumatoid arthritis. Our analysis extends this work to a community based sample of elderly individuals with self reported joint systems in 3 ethnic groups: Hispanics (N = 100), whites of Eastern European origin (N = 112) and blacks (N = 105). With the exception of the Social Activity and ADL scales, acceptable reliability and validity of the AIMs scales are found for all 3 groups. The assumption of factor invariance across ethnic groups is also supported.

Aged↗
PubMed1983

Physical stability of insulin formulations.

Insulin aggregation remains a fundamental obstacle to the long-term application of many insulin infusion systems. We here report the effects of physiologic and nonphysiologic compounds on the aggregation behavior of crystalline zinc insulin (CZI) solutions. Under conditions chosen to simulate the most severe that would be encountered in delivery systems (presence of air, continuous motion, and elevated temperature), both highly purified and regular CZI at 5 U/ml formed turbid gels in 5 days. At concentrations of 100 and 500 U/ml stability was increased with turbid gels forming at 12 and 15 days, respectively. Under identical conditions, 5 U/ml CZI formulations containing the physiologic surfactant lysophosphatidylcholine (0.02%) or the synthetic surfactants SDS (1%), Brij 35 (0.1%), Tween (0.01%), or Triton X (0.01%) retained a transmittance at 540 nm of greater than 96% for 67-150 days. These nonionic and ionic surfactants containing the hydrophobic group, CH3(CH2)N, with N = 7-16, remarkably stabilized CZI formulations while those lacking such groups demonstrated little or no effect. The alcohols glycerol (30-50%) and isopropanol (10-50%) were moderately effective stabilizers. Silicone rubber drastically accelerated aggregation in all but one formulation (1% SDS). Emphasis in this study was placed on the properties of 5-U/ml formulations. Controls run at higher concentrations indicated a positive correlation between concentration and stability. It was concluded that the aggregation of insulin into high-molecular-weight polymers may be inhibited by reducing the effective polarity of the solvent. In this regard, anionic and nonionic surfactants containing appropriately long hydrophobic groups demonstrated the greatest degree of stabilization. Finally, of all the medical grade materials likely to be used in pumps, silicone rubber is the most active in promoting insulin aggregation.

Alcohols↗
PubMed1982

Prenatal diagnosis of hemoglobinopathies: evaluation of techniques for analysing globin-chain synthesis in blood samples obtained by fetoscopy.

Three techniques for analysing hemoglobin synthesis in blood samples obtained by fetoscopy were evaluated. Of the fetuses studied, 12 were not at risk of genetic disorders, 10 were at risk of beta-thalassemia, 2 were at risk of sickle cell anemia and 1 was at risk of both diseases. The conventional method of prenatal diagnosis of hemoglobinopathies, involving the separation of globin chains labelled with a radioactive isotope on carboxymethyl cellulose (CMC) columns, was compared with a method involving globin-chain separation by high-pressure liquid chromatography (HPLC) and with direct analysis of labelled hemoglobin tetramers obtained from cell lysates by chromatography on ion-exchange columns. The last method is technically the simplest and can be used for diagnosing beta-thalassemia and sickle cell anemia. However, it gives spuriously high levels of adult hemoglobin in samples containing nonlabelled adult hemoglobin. HPLC is the fastest method for prenatal diagnosis of beta-thalassemia and may prove as reliable as the CMC method. Of the 13 fetuses at risk for hemoglobinopathies, 1 was predicted to be affected, and the diagnosis was confirmed in the abortus. Of 12 predicted to be unaffected, 1 was aborted spontaneously and was unavailable for confirmatory studies, as were 3 of the infants; however, the diagnosis was confirmed in seven cases and is awaiting confirmation when the infant in 6 months old in one case. Couples at risk of bearing a child with a hemoglobinopathy should be referred for genetic counselling before pregnancy or, at the latest, by the 12th week of gestation so that prenatal diagnosis can be attempted by amniocentesis, safer procedure, with restriction endonuclease analysis of the amniotic fluid cells.

Amniocentesis↗
PubMed1975

Blood flow: theory, effective viscosity and effects of particle distribution.

A study is made of blood flow by assuming that the blood constitutes a suspension of cells in plasma instead of a simple homogeneous fluid. A macroscopic theory governing the motion of plasma in a plasma-cell system is derived from the local volume averaging method for a system without mass transfer between the phases, and its characteristic length is much larger than the size of the cells. The equations governing the motion of the local averaged fluid quantities include one additional term in the equation of motion and two additional terms in the energy equation. These terms represent, respectively, the force exerted upon the fluid by the particles, and the rate of heat transfer and work kone upon the fluid by the particles. The theory is applied to obtain the effective viscosity as the explicit function of the volume concentration of the cells by assuming that the cells behave like rigid spherical particles with slip-collision, and the plasma is an compressible Newtonian fluid. Comparison with existing experimental results shows a good agreement. The theory is also used to obtain the effects of cell distribution upon the overall effective viscosity in a circular tube. The quantitative result shows that there is a decrease in overall effective viscosity as the concentration of cells increases toward the center of the tube, and the overall effective viscosity is smaller than the flow with evenly distributed cells.

Blood Flow Velocity↗
PubMed1975

Spontaneous remodeling of the peripheral retinal vasculature in sickling disorders.

Periodic photographic and angiographic surveys of patients with the earliest stages of sickle retinopathy showed a number of fundus findings. In seven cases (sickle cell anemia, four; sickle cell hemoglobin C, three), these findings included: (1) a variety of vascular abnormalities in the equatorial and post-equatorial retina such as segmented dilations of the vessel walls, hairpin-shaped vascular loops, hypertrophic, tortuous A-V anastomoses, intraluminal plugs, closure and loss of capillary bed, and terminal budding of capillaries; and (2) a continuous, spontaneous remodeling of the peripheral retinal vasculature due to successive closures and reopenings of equatorial retinal vessels. A centripetal recession of the peripheral retinal vasculature usually resulted. No correlation between the ophthalmoscopic and the systemic condition of the patients could be made.

Adolescent↗
PubMedDate not supplied

Aerosol chemical and optical properties during the Mt. Zirkel Visibility Study.

Aerosol chemical and optical properties were measured near the Mt. Zirkel Wilderness Area in northwestern Colorado. Six-hour PM2.5 (particles with aerodynamic diameters less than 2.5 microm) mass concentrations and PM2.5 dry particle light scattering at 550 nm averaged 4.6 microg m(-3) and 8.6 Mm(-1), respectively. Sulfates, organic carbon, and geological material were the principle components of particle mass and light scattering. Hygroscopic growth was consistent with that expected for ammonium sulfate aerosols. Size distributions derived from three-wavelength (i.e., 450, 550, and 700 nm) nephelometer data were similar to those measured in other remote areas of the western USA. Quasi-dry chemical light scattering efficiencies derived using Mie theory were 3.6 m2 g(-1) for organic carbon, 2.5 m2 g(-1) for sulfates (ammonium sulfate and ammonium bisulfate), 2.6 m2 g(-1) for ammonium nitrate, and 1.76 m2 g(-1) for geological material. These values are lower than but consistent with previously reported results. Realistic efficiencies could not be derived using the multiple linear regression (MLR) approach.

Aerosols↗