Biomedical subjects
C Wong
Publications and source records attributed to C Wong.
Shedding and immunoregulatory activity of YAC-1 lymphoma cell gangliosides.
YAC-1 lymphoma cells, both when cultured in vitro and when passaged in ascites form in vivo, synthesize gangliosides (means of 22.1 and 14.7 nmol lipid-bound sialic acid isolated per 10(8) cells, respectively) with potent inhibitory effects on mitogen- and antigen-induced lymphoproliferation: 10 to 30 nmol highly purified YAC-1 gangliosides/ml caused greater than 90% inhibition of proliferative responses of murine lymphocytes to concanavalin A, lysozyme (a soluble specific antigen), and allogeneic cells (mixed-lymphocyte response). Measureable quantities of these gangliosides were shed by the tumor cells in vitro and also were recovered from the ascites fluid in vivo. Furthermore, the gangliosides isolated from ascites fluid (mean of 15.3 nmol/ml) had inhibitory activity of a magnitude similar to that of the gangliosides isolated from the tumor cells. Therefore, significant inhibition of normal lymphoproliferative responses by tumor-derived gangliosides occurred at ganglioside concentrations which are actually present in the fluid surrounding the tumor cells in vivo. These results support the hypothesis that shedding of gangliosides may serve to protect tumor cells from host immune destruction.
Popliteal cyst rupture in septic arthritis.
Explore the source record for details and available documents.
The relationship between smoking and total immunoglobulin E levels.
Results of skin testing to common allergens, total serum IgE levels, and the responses to a respiratory questionnaire were obtained for 1768 individuals participating in a survey of a rural population. The geometric mean total IgE levels in a group of subjects without skin-test reactions and with no histories of asthma or hay fever was 14.8 U/ml for men and 11.9 U/ml for women. When individuals were classified according to skin reactivity and smoking history there was a significant difference in IgE levels among nonsmokers, exsmokers, and smokers, with smokers having the highest levels. The percentage of subjects with elevated total IgE levels was higher in smokers than in nonsmokers regardless of skin reactivity to common allergens. Among smokers there was no relationship between intensity and duration of smoking and IgE levels. Among exsmokers IgE levels tended to be lower in those who had stopped smoking earlier.
The neuroleptic malignant syndrome.
The neuroleptic malignant syndrome is an uncommon, potentially fatal, adverse reaction to major tranquillisers. Prompt diagnosis, cessation of medication and supportive medical care are essential in management.
Myocardial ischaemia, radiotherapy, and vinblastine.
Explore the source record for details and available documents.
Mediator-induced macrophage activation, as shown by enhanced cytotoxicity for tumor, requires macrophage surface fucose and sialic acid.
Explore the source record for details and available documents.
Estimating paternity index from HLA-typing results.
A procedure is described for estimating the chance of paternity from HLA-typing results. Phenotypes consisting of HLA-A and HLA-B antigens are divided into four groups. For each group, formulas have been derived to calculate the chance of passing a specific haplotype; those for common phenotypes have been predetermined and compiled into concise tables. Consequently, the paternity index can be derived in four simple steps. In reporting, paternity index is best expressed in percentages as relative chance of paternity and nonpaternity. In this way, the positive and negative aspects of estimation are both spelled out.
Pulmonary phosphatidic acid phosphatase. A comparative study of the aqueously dispersed phosphatidate-dependent and membrane-bound phosphatidate-dependent phosphatidic acid phosphatase activities of rat lung.
1. The properties of the aqueously dispersed phosphatidate-dependent phosphatidic acid phosphatase (EC 3.1.3.4) activities of rat lung have been studied in microsomal and cytosol preparations and compared with the properties of the membrane-bound phosphatidate-dependent activities. 2. The microsomal phosphatidic acid phosphatase displayed a prominent pH optimum at 6.5 with a minor peak which varied between 7.5--8 in different experiments. With the cytosol, the major activity was at the higher pH (7.5--8.0) but a distinct optimum was also observed at pH 6.0--6.5. With the membrane-bound substrate, a single broad optimum was observed between pH 7.4 and 8.0 with the cytosol and 6.5--7.5 with the microsomal fraction. 3. Subcellular fractionation studies revealed that the microsomal fraction possessed the greatest proportion of the total phosphatidic acid phosphatase activity and the highest relative specific activity. However, studies with marker enzymes indicated that the aqueously dispersed phosphatidate-dependent activity could be present in plasma membrane, lysosomes and osmiophilic lamellar bodies as well as in the endoplasmic reticulum. 4. The aqueously dispersed phosphatidic acid-dependent activities present in the microsomal and supernatant fractions were inhibited by Ca2+, Mn2+, F- and by high concentrations of Mg2+. In contrast to the membrane-bound phosphatidate-dependent activities, there was little Mg2+ stimulation and only a very slight inhibitory effect was noted with EDTA. A small EDTA-dependent Mg2+ stimulation could be observed with the microsomal fraction but only at the lower pH optimum (6.5). 5. The presence of a number of phosphate esters tended to stimulate rather than inhibit the microsomal activity, indicating that the hydrolase is relatively specific for lipid substrates. Marked inhibitions were noted with lysophosphatidic acid and phosphatidylglycerol phosphate. Phosphatidylcholine produced a slight inhibition. 6. The results indicate that the bulk of the aqueously dispersed phosphatidate-dependent phosphatidic acid phosphatase activities of rat lung microsomes and cytosol is not related to the activities observed with membrane-bound phosphatidate. The Mg2+-dependent hydrolase activities may be synonymous. However, unequivocal conclusions will only be possible when the polypeptide or polypeptides responsible for these activities can be purified.
Intermolecular cross-linking of a protein crystal--acid protease from Endothia parasitica--in 2.7 M ammonium sulfate solution.
Explore the source record for details and available documents.
The structure of acid protease from Endothia parasitica in cross-linked form at 3.5 A resolution.
Explore the source record for details and available documents.
Hepatic parasympathetic neural effect on glucose balance in the intact liver.
Sympathetic nerves to the intact liver of the cat were selectively destroyed by injection of 6-hydroxydopamine into the portal vein 1 week prior to the experiment. Glucose output was calculated from the product of the arterial-venous glucose difference and hepatic blood flow. Hepatic blood flow was monitored by an electromagnetic flowmeter using a hepatic venous long-circuit. Stimulation of the parasympathetic nerves isolated from around the common hepatic artery produced a rapid reduction in hepatic glucose output to one-quarter of control levels by 2 min and to zero by 10 min of nerve stimulation. The data show that hepatic glucose balance is readily influenced by the hepatic parasympathetic nerves.
Hepatic glucose balance in response to direct stimulation of sympathetic nerves in the intact liver of cats.
Changes in hepatic glucose balance in response to direct stimulation of the hepatic nerves were measured in cats. Simultaneous measurements were made of glucose concentrations entering and leaving the intact liver; this, combined with measured blood flows, allows calculation of hepatic glucose balance. Stimulation of the hepatic sympathetic nerves (8 Hz, 15 V, 1 ms) produced a rapid increase in hepatic glucose output that was statistically significant after 1 min and reached a peak 3--5 min after onset of stimulation, after which time the output declined somewhat. The half time for deactivation of the response was 1.8--2 min. Variability in the responses was largely accounted for by the variable control base lines measured immediately prior to stimulation. Those animals showing the highest basal output showed the least increase in output in response to the nerves. The response to stimulation of the mixed nerve trunk in the presence and absence of atropine (1 mg/kg, intraportal) was similar. Simultaneous activation of hepatic sympathetic and parasympathetic nerves therefore produces a purely sympathetic type of effect on net glucose balance across the liver. It was also shown that changes in net splanchnic output or simply in arterial--hepatic venous glucose differences are an adequate reflection of liver glucose balance under the currently tested responses.
An intracaval cannulation for obtaining pure, mixed hepatic venous blood samples.
A method for obtaining pure, mixed hepatic venous blood is described and evaluated in anesthetized cats. Hepatic vascular congestion does not occur with this "intracaval cannulation", however small elevations in central venous blood pressure were noted. Although these changes persisted they did not result in systemic vascular congestion, judging from the normal arterial and portal pressures and from the lack of progressive decrease in arterial blood pressure. Blood samples obtained using the intracaval cannulation were shown to contain identical levels of oxygen as those obtained using a more complex surgical preparation. Reflux of blood from the vena cava does not occur during sampling. The responsiveness of this sampling method to rapid changes in venous content was evaluated by following the changes in glucose balance caused by direct stimulation of the hepatic nerves. The responses measured were similar to those measured in a separate set of experiments obtained using blood samples from a surgically isolated hepatic venous supply.
Cortisol induction of pulmonary maturation in the rabbit foetus. Its effects on enzymes related to phospholipid biosynthesis and on marker enzymes for subcellular organelles.
1. Cortisol treatment of rabbit foetuses in utero at 24 days gestation produced a significant decrease in the lung-weight to body-weight ratio compared with littermate controls by day 26. Histological examination revealed that the alveoli of the treated lungs were more open, the walls were thinner and the osmiophilic bodies were more numerous. 2. Cortisol treatment as described above produced significant increases (P<0.05) in the rates of incorporation of [(14)C]choline into phosphatidylcholine and of [(14)C]ethanolamine into phosphatidylethanolamine in vitro compared with littermate controls. This indicates that glucocorticoids produce an overall increase in phospholipid metabolism rather than a specific increase in phosphatidylcholine production. 3. The addition of 1,2-diacyl-sn-glycerols from egg phosphatidylcholine produced a 10-fold increase in the activity of choline phosphotransferase and a 3-fold increase in the activity of ethanolamine phosphotransferase in rabbit lung homogenates. The addition of 1,2-dipalmitoyl-sn-glycerol did not affect these activities. These results demonstrate that in the presence of exogenous 1,2-dipalmitoyl-sn-glycerol, the activities of these enzymes are dependent on the presence of endogenous 1,2-diacylglycerols. 4. Cortisol administration had no significant effect on the activity of choline phosphotransferase or ethanolamine phosphotransferase with endogenous or exogenously added diacylglycerols. The activities of other endoplasmic-reticulum enzymes (sn-glycerol 3-phosphate phosphatidyltransferase, sn-glycerol 3-phosphate acyltransferase and NADPH-cytochrome c reductase) were not significantly altered by the hormone administration. Oestrone sulphate sulphohydrolase activity was significantly decreased (P<0.05) by cortisol injection, but this effect varied with the foetuses from different does. 5. Cortisol administration had no effect on the activities of mitochondrial (monoamine oxidase, succinate dehydrogenase), plasma-membrane (5'-nucleotidase) or lysosomal (acid phosphatase, N-acetyl-beta-d-glucosaminidase) enzymes. The activity of membrane-associated phosphatidate phosphohydrolase, an enzyme associated with the osmiophilic granules of the type-II alveolar cells, was increased in the lungs of treated foetuses, but the difference was not significant (0.10>P>0.05).
Comparative study of the thiourea carrier in erythrocytes.
A densimeter technique was used to measure the rate of exit of thiourea from erythrocytes of various species of mammals. The cells were first equilibrated with a 200 mM thiourea solution in 1% NaCl. An aliquot of these cells was added to 1% NaCl containing 4.6-23.1 mM thiourea. Facilitated diffusion was demonstrated in each case. Using exit times or initial rates, calculations of half-saturation constants (phi) in mM and maximum transport rates (K) in isotones per min were made by three different methods. The following values were obtained: human-phi=60, 42, 35; K=1.2, 2.9, 0.9; rabbit-phi=46, 33, 32; K=0.8, 2.1, 0.8; mouse-phi=46, 40, 30; K=3.4, 8.5, 3.2; rat-phi=65, 42, 23; K=6.1, 15.3, 3.7; ox-phi=107, 63, 88; K=0.6, 1.4, 0.4; sheep-phi=56, 38, 56; K=0.9, 2.2, 0.6; and pig-phi=110, 64, 49; K=1.6, 3.6, 1.1.
Purification and characterization of initiation factor IF-E2 from rabbit reticulocytes.
Initiation factor IF-E2 was isolated from rabbit reticulocytes and purified 120-fold to near homogeneity by ammonium sulfate fractionation, column chromatography on DEAE-cellulose and phosphocellulose, and, when suitable, by sucrose density gradient centrifugation. The factor is a complex protein containing three nonidentical polypeptides of molecular weight 57,000, 52,000, and 36,000. It behaves as a complex throughout its purification and during polyacrylamide gel electrophoresis in nondenaturing buffer but its thress components are readily separated by electrophoresis in denaturing buffers. None of its components corresponds to any of the polypeptides of the other initiation factors or to any proteins of ribosomes washed in buffers containing a high salf concentration. A stoichiometric ratio of 1:1:1 was determined for the three polypeptides; based on the assumption of one copy each per complex, the calculated factor molecular weight is 145,000, a value in agreement with the measured value of 160,000. Initiation factor IF-E2 was radioactively labeled in vitro by reductive alkylation or by phosphorylation with a protein kinase also isolated from rabbit reticulocytes. Neither procedure causes a measurable change in the ability of the factor to form a ternary complex with GTP and the initiator methionyl-tRNA. 5'-Guanylyl-methylenediphosphonate may substitute for GTP, but only at relatively high concentrations. The binding of labeled initiation factor IF-E2 and methionyl-tRNA to the 40 S ribosomal subunit was studied by sucrose density gradient centrifugation. Appreciable binding of the factor is seen only when all three components of the ternary complex are included in the reaction mixture. The binding of either the factor or methionyl-tRNA was not stimulated by the addition of globin messenger RNA and initiation factor IF-E3. It was shown that all three polypeptide components of initiation factor IF-E2 are bound to these nascent initiation complexes.
The solubility characteristics of SV 40 tumor antigen.
Explore the source record for details and available documents.