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Biomedical subjects

M A Wells

Publications and source records attributed to M A Wells.

At least 109 records · Page 6Linked to original sources
PubMed1983

Recovery from a viral respiratory tract infection. IV. Specificity of protection by cytotoxic T lymphocytes.

Immune spleen cells enhanced for influenza-specific cytotoxic activity after exposure to virus-infected stimulator cells in vitro effect recovery when transferred to nude and immunocompetent mice with influenza pneumonia (5). This protective effect correlated with the virus-specific cytotoxic activity of the transferred lymphocytes and is removed by treatment with anti-0 serum and complement. The experiments presented here indicate that spleen cells taken directly from mice undergoing a primary or secondary infection are less protective than immune spleen cells that are restimulated in vitro before transfer. This decreased ability to clear pulmonary virus and effect survival correlated with their relatively lower levels of influenza-specific cytotoxicity. Protection did not correlate with the level of natural killer cell activity of transferred cells. The results also indicate the immune spleen cells that are protective are influenza A subtype cross-reactive and are H-2-restricted; H-2d immune spleen cells effected recovery of H-2d but not H-2k challenged mice.

Animals↗
PubMed1983

Studies on fat digestion, absorption, and transport in the suckling rat. IV. In vivo rates of triacylglycerol secretion by intestine and liver.

The rate of triacylglycerol entry into plasma in 14- to 15-day-old suckling rats was measured using the Triton WR1339 method. When the pups were left with the mother and allowed to nurse continually, the rate was 31.8 +/- 2.3 mumol/hr per rat. If the pups were removed from the mother with full stomachs and kept in a warm box at 30-32 degrees C, the rate was 12.5 +/- 1.5 mumol/hr per rat. The rate of triacylglycerol output from the intestine measured in lymph duct-cannulated animals (kept in a warm box at 30-32 degrees C) was 14.9 +/- 2.7 mumol/hr per rat. Triton treatment of lymph duct-cannulated animals caused only a small increase in plasma triacylglycerol concentration (less than 2 mumol/hr per rat). These data suggest that nearly 100% of plasma triacylglycerol arises from intestinal input in the suckling rat.

Animal Population Groups↗
PubMed1983

Lipoprotein metabolism in the suckling rat: characterization of plasma and lymphatic lipoproteins.

Suckling rat plasma contains (in mg/dl): chylomicrons (85 +/- 12); VLDL (50 +/- 6); LDL (200 +/- 23); HDL1 (125 +/- 20); and HDL2 (220 +/- 10), while lymph contains (in mg/dl): chylomicrons (9650 +/- 850) and VLDL (4570 +/- 435) and smaller amounts of LDL and HDL. The lipid composition of plasma and lymph lipoproteins are similar to those reported for adults, except that LDL and HDL1 have a somewhat higher lipid content. The apoprotein compositions of plasma lipoproteins are similar to those of adult lipoproteins except for the LDL fraction, which contains appreciable quantities of apoproteins other than apoB. Although the LDL fraction was homogeneous by analytical ultracentrifugation and electrophoresis, the apoprotein composition suggests the presence of another class of lipoproteins, perhaps a lipid-rich HDL1. The lipoproteins of lymph showed low levels of apoproteins E and C. The triacylglycerols in chylomicrons and VLDL of both lymph and plasma are rich in medium-chain-length fatty acids, whereas those in LDL and HDL have little or none. Phospholipids in all lipoproteins lack medium-chain-length fatty acids. The cholesteryl esters of the high density lipoproteins are enriched in arachidonic acid, whereas those in chylomicrons, VLDL, and LDL are enriched in linoleic acid, suggesting little or no exchange of cholesteryl esters between these classes of lipoproteins. The fatty acid composition of phosphatidylcholine, sphingomyelin, and lysophosphatidylcholine were relatively constant in all lipoprotein fractions, suggesting ready exchange of these phospholipids. However, the fatty acid composition of phosphatidylethanolamine in plasma chylomicrons and VLDL differed from that in plasma LDL, HDL1, and HDL2. LDL, HDL1, and HDL2 were characterized by analytical ultracentrifugation and shown to have properties similar to that reported for adult lipoproteins. The much higher concentration of triacylglycerol-rich lipoproteins in lymph, compared to plasma, suggests rapid clearance of these lipoproteins from the circulation.

Animals↗
PubMed1982

Studies on fat digestion, absorption, and transport in the suckling rat. III. Composition of bile and evidence for enterohepatic circulation of bile salts.

Biliary secretions from suckling rats (10-15 days old) were characterized: bile flow rate was 197.3 microliters/hr per 100 g; bile salt pool size was 19.0 mumol/100 g; secretion rate was 14.5 mumol/hr per 100 g; synthesis rate was 12.0 mumol/day; and the daily turnover frequency was 18.3. Phospholipid and cholesterol secretion rates were 2.3 mumol/hr per 100 g and 0.17 mumol/hr per 100 g, respectively. The bile salt concentration in portal plasma was 0.17 mumol/ml. The fatty acid composition of biliary phosphatidylcholine and ethanolamine, as well as the stereospecific distribution of fatty acids in the former, were similar to that found in phospholipids from adult rat bile. Compositional analysis of bile acids showed greater than 98% taurine conjugates consisting of approximately 54% cholic acid, 40% beta-muricholic acid, 2% chenodeoxycholic acid, and 1% each of deoxycholic and hyodeoxycholic acids. Through the use of intestinal and liver perfusion experiments, we have obtained evidence for enterohepatic circulation of taurocholate in neonatal rats. The level of bile salts found in intestinal contents (49.5 mumol/g), and the biliary phospholipid concentration (11.8 mM) both exceed adult values (6-10 mumol/g and 6.3 mM, respectively) and may be important for the utilization of the large amount of milk triacylglycerols ingested during the suckling period.

Animals↗
PubMed1981

Thermodynamics of dihexanoylphosphatidylcholine aggregation.

Heats of dilution of aqueous solutions of dihexanoylphosphatidylcholine were determined by use of a flow microcalorimeter to monitor an exponential dilution gradient. Three different models of micelle formation were tested: monomer in equilibrium with micelles of fixed size, with micelles of varied size, or with small aggregates and micelles. The heat of dilution data for low solute concentration could be fit only by assuming the existence of premicellar aggregates. The critical micelle concentration determined calorimetrically is 0.016 +/- 0.002 M and is independent of the model. The enthalpy change for transfer of monomer into the micelle is 1.6 +/- 0.2 kcal/mol; about one-third of this heat effect is produced in formation of the premicellar aggregation. Comparison of the calorimetric measurements with results obtained by using other methods indicates the complexity of the micellization process.

Chemical Phenomena↗
PubMed1981

A further examination of the active form of Crotalus adamanteus phospholipase A2.

The phospholipase A2 from Crotalus adamanteus venom has been shown to be active as the dimer or 30 000 molecular weight species, at concentrations used for enzyme assay (0.1--10 microgram/ml). Gel filtration of the enzyme in the presence of Ca2+ and monomeric concentrations of the substrate dihexanoylphosphatidylcholine showed that all the protein migrated as a 30 000 molecular weight species. Active enzyme sedimentation velocity experiments using the same conditions gave s020,W=2.85 +/- 0.05 S, which compares favorably with the value obtained at mg/ml concentrations (3.11 S). These results confirm the results of Shen et al. (Shen, B.W., Tsao, F.H.C, Law, J.H. and Kézdy, F.J. (1975) J. Am. Chem. Soc. 97, 1205--1208).

Animals↗
PubMed1981

Recovery from a viral respiratory infection. I. Influenza pneumonia in normal and T-deficient mice.

Experiments were performed to serve as a basis for analyzing the immune responses of the host to a viral respiratory tract infection. In a comparative study, inbred BALB/c and nude (athymic mice bred on a BALB/c background) mice were infected intranasally with mouse adapted A/Port Chalmers/1/73 influenza virus. Survival was prolonged in the nude mice (16 days vs 10 days for BALB/c mice, t = 3.5, p less than 0.01), but significantly fewer of the nude mice survived 21 days (16% vs 42% of BALB/c mice). In addition, virus persisted longer in the lungs of nude mice (5.8 log10 of infectious virus on day 21 vs no detectable virus in BALB/c mice) and lung pathology progressed more slowly but lasted longer in nude mice, as measured by immunofluorescent and histologic examination of pulmonary tissue. Antibody production was significantly lower and there was no cytotoxic T cell response detected in lymphoid cells prepared from the spleens, peripheral blood, or the lung after the infection of nude mice. A significant increase in the number of lymphocytes isolated from the lung was observed by day 7 (t = 5.8, p less than 0.001) in the BALB/c mice but not until day 14 (t = 4.9, p less than 0.001) in the nude mice. Lymphocytes from nude mice did not respond to influenza virus antigens or Concanavalin A (Con A) but did respond to lipopolysaccharide (LPS), whereas lymphocytes from BALB/c mice responded to all 3 preparations.

Animals↗
PubMed1981

Studies on fat digestion, absorption, and transport in the suckling rat. I. Fatty acid composition and concentrations of major lipid components.

The lipids of rat milk, the contents of 9-- 10-day-old rat stomach and intestine, lymph, plasma, and liver were quantitated and their fatty acids were analyzed. Rat milk consists of 97% triacylglycerols, of which 35% of the fatty acids are of medium chain length (C8-C12). However, stomach triacylglycerols show a 25% reduction in medium chain fatty acids, which indicates preferential hydrolysis of medium chain fatty acids in the stomach. The intestinal lumen free fatty acid composition shows decreased medium chain fatty acids compared to long chain fatty acids, indicating preferential absorption of the former. Lymph was shown to contain a significant amount (approximately 22%) of medium chain fatty acids. The decreased content of medium chain fatty acids in vena cava blood compared to portal blood, and also the lower concentration of medium chain fatty acids in liver compared to blood, indicates preferential use of these fatty acids by the liver.

Animal Population Groups↗
PubMed1981

Studies on fat digestion, absorption, and transport in the suckling rat. II. Triacylglycerols: molecular species, stereospecific analysis, and specificity of hydrolysis by lingual lipase.

Triacylglycerols (TG) of rat milk supply about two-thirds of the energy consumed by suckling rat pups. The present studies were undertaken to determine stereospecific fatty acid composition and molecular species distribution of milk TG and TG produced during digestion, transported in lymph and blood, and present in the liver of 9-- 10-day-old pups. Results support non-random stereochemical fatty acid and molecular species distribution for all TG's analyzed. Stereospecific compositional results show loss of medium chain fatty acids (MCFA) during digestion, producing a shift to a larger average molecular weight TG than present in milk. These MCFA are esterified primarily at the sn-3 position of milk TG and appear to be hydrolyzed by the action of lingual lipase in the stomach. In vitro incubation of milk with tongue homogenate yields free fatty acids and glyceride products that resemble those found in suckling stomach contents. Further TG metabolism appears to involve redistribution of the long chain fatty acids that remain esterified in TG following gastric lipolysis and release of MCFA.

Animal Population Groups↗
PubMed1981

Facile acylation of glycerophosphocholine catalyzed by trifluoroacetic anhydride.

A simplified procedure for the synthesis of short acyl chain phosphatidylcholines is described. A mixed fatty acid-trifluoroacetic anhydride is used to acylate sn-glycero-3-phosphocholine (GPC) which has been dissolved in trifluoroacetic acid. Yields exceeding 70% are achieved in 30-min reaction time using 1.5 to 2.0 equivalents of mixed anhydride per, GPC hydroxyl. This allows a more economical use of labeled short chain acids.

Acetic Anhydrides↗
PubMed1981

Synthesis of sn-glycero-1-phosphocholine.

The preparation of sn-glycero-1-phosphocholine is described. 2,3-O-Isopropylidene-sn-glycerol is condensed first with the 1,2-dimethylethenylene phosphorochloridate in the presence of triethylamine to yield the cyclic phosphotriester derivative. Choline p-toluenesulfonate, as the second alcohol, is condensed with this intermediate to yield the phosphotriester bearing the 1-methyl-acetonyl blocking group. This is removed under basic conditions to afford the 2,3-O-isopropylidene-sn-glycerol-1-phosphocholine in 57% yield following silicic acid column chromatography. The acetone blocking group is then removed with aqueous HCl (pH 2.3) to give pure sn-glycero-1-phosphocholine.

Dioxolanes↗
PubMed1980

Cytotoxic lymphocytes and antibody-dependent complement-mediated cytotoxicity induced by administration of influenza vaccine.

Recently defined aspects of cellular and humoral antiviral immunity were evaluated in 10 young adults given influenza vaccines containing A/USSR/77 (H1N1) antigens. Cytotoxic lymphocytes were measured by using cryopreserved lymphocytes as effector cells and syngeneic, virus-infected lymphocytes as target cells. An assay previously developed in this laboratory was adapted for the measurement of antibody-dependent, complement-mediated cytotoxicity. Antiviral cytotoxic lymphocyte responses were detected in 5 of 10 volunteers between 3 and 10 days after the initial vaccination. These responses were found both in individuals who were previously primed and in individuals who were not primed to influenza A/USSR/77 antigens. The complement-mediated lysis assay was found to be more sensitive than the hemagglutination inhibition test and probably detected antibodies to both subtype-specific and cross-reactive antigenic determinants. These responses to influenza antigens are similar to those obtained in studies of murine influenza which indicate that cytotoxic lymphocytes and antibody-dependent, complement-mediated cytotoxicity have a role in the early response to acute infection.

Adult↗
PubMed1980

A simplified procedure for the preparation of 2,3-O-isopropylidene-sn-glycerol from L-arabinose.

A new procedure for the preparation of 2,3-O-isopropylidene-sn-glycerol is described. L-arabinose is converted to its 4,5-monoisopropylidene diethyl mercaptal derivative. This compound is then subjected to periodate oxidation and borohydride reduction. Following neutralization, the aceton-glycerol is extracted from the aqueous solution into chloroform. Evaporation of the chloroform and subsequent distillation yielded pure 2,3-O-isopropylidene-sn-glycerol ([alpha]D22 = -14.5 degrees (in substance)) in an overall yield of 15-25%.

Arabinose↗
PubMed1979

Phospholipase D from savoy cabbage: purification and preliminary kinetic characterization.

Phospholipase D has been purified 680-fold from an acetone powder of savoy cabbage in an overall yield of 30%. The purification involves solubilization of the acetone powder in a Ca2+-containing buffer and subsequent ammonium sulfate fractionation. Gel filtration on Sephadex G-200 and hydrophobic affinity chromatography using a gamma-aminopropane-agarose gel complete the purification. The two chromatographic steps were conducted in buffers containing 50% ethylene glycol, which was necessary in order to maintain stability of the enzyme. Purity was established on the basis of gel electrophoresis and ultracentrifugation. A preliminary kinetic characterization of the enzyme was carried out by using lecithins with short-chain fatty acids below the critical micelle concentration. A complex series of results were obtained which demonstrated the following. (1) The enzyme is quite sensitive to ionic strength, being inhibited at high ionic strength. (2) The pH optimum depends on the concentration of Ca2+ used in the assay. At 0.5 mM Ca2+ the pH optimum is 7.25, but it is 6.0 at 50 mM Ca2+. (3) The effect of substrate concentration at a given pH and ionic strength did not show simple hyperbolic kinetics but rather regions of parabolic and hyperbolic kinetics.

Kinetics↗