Biomedical subjects
J Boyer
Publications and source records attributed to J Boyer.
The effect of delayed internal fixation on healing of the osteotomized dog radius.
Delay in surgical intervention has been reported to enhance the process of fracture healing. Quantitative observations or experimental osteotomies were made to investigate the mechanical for such enhancement. Eight mongrel dogs with bilateral radial osteotomies were prepared with immediate plate fixation on the right side, and with delayed fixation two weeks later on the left side. The response to delayed fixation was measured radiographically, mechanically, and by measurement of new bone formation using a quantitative tetracycline incorporation method. A clearly discernible stimulation of new bone formation occurred early in the osteotomy healing process. Delayed fixation has a transient stimulatory effect on the healing process of bone.
Activation of hormone-sensitive lipase: disparity between evaluations in intact and disrupted fat cells.
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Does the neurotropic action of adrenocorticotrophic hormone involve a lipolytic step?
The stimulatory effect of adrenocorticotrophic hormone (ACTH)-related synthetic peptides on the hydrolysis of emulsified trioleoylglycerol by a rat brain lipase was studied. The ACTH effect was related to the net positive charge associated with the basic amino acid residues at position 15-18 in the ACTH sequence, as well as to the presence of the NH2-terminal amino acid residues at position 1-2. The ACTH effect on lipolysis was markedly reduced when lipids were partially removed from the enzyme preparation by extraction with chloroform/acetone. Full restoration of the stimulatory effect was obtained upon addition of phosphatidylcholine (2 mg/ml) to the lipolytic medium. Striking similarities between the structure-activity pattern for the stimulatory effect of ACTH on brain lipase and that described for the receptor-mediated actions of ACTH on adrenal and fat cells suggest that the ACTH effect might involve recognition of a binding site associated with the brain enzyme. Complete log concentration response curves obtained with four ACTH analogs may also be regarded as simulating hormone-receptor interaction. These findings are discussed in relation to the possibility that ACTH may have a neurohormonal role via lipase-catalyzed changes in the lipid matrix of membranes.
Effect of adrenocorticotrophic hormone on the activity of sterol ester hydrolase from rat brain.
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Enhanced activity of brain lipase in the presence of adrenocorticotrophic hormone. Comparison with a colipase effect.
The characteristics of the pH-dependent stimulatory influence of adrenocorticotrophic hormone (ACTH) on lipolysis (Arnaud, J., Nobili, O. and Boyer, J. (1980) Biochim, Biophys. Acta 617, 524-528) were investigated further. ACTH enhanced 7-30 times the rates of hydrolysis of emulsified trioleoylglycerol by a rat brain lipase, when added to the medium both before and after the enzyme. When lipase activity was inhibited by sodium taurocholate, ACTH fully reversed the inhibition at bile salt concentration up to 2 mM. The reactivation process followed a sharp S-shaped pattern, leveling off at about 10(-4) M ACTH. With and without bile salt, the stimulatory effect of ACTH culminated at pH 5.75, and was dependent on the presence of trace amount of a water-insoluble solvent in the substrate emulsion. Taken together, the results suggest that ACTH acts at the lipid-water interface in facilitating the enzyme-substrate interaction. The relevance of the hormonal influence to a colipase-like effect is discussed.
Human erythrocyte monoester lipase: characterization and radiochemical assay of the cell-bound enzyme in normal subjects.
A monoester lipase (MEL) activity (EC 3.1.1.3) is described in human red blood cells (RBC). The lipase acts as a cell-bound enzyme and is able to exert its catalytic activity in vitro toward an exogenously added emulsified substrate. The enzyme activity, which appears to be confined to the cell membrane, is inhibited by Triton X-100. The MEL activity of human RBC is assayed using intact RBC as the enzyme source, with an emulsion of ethyl [3H]oleate (2 mM) as the substrate. The optimum pH for the reaction is 7.8 at 37 C. Lipolytic rates are monitored by quantitation of the amount of [3H]oleic acid released during 20 min of incubation after extraction by means of a liquid-liquid partition system. Suspensions of purified RBC obtained from 161 healthy adult subjects had a MEL activity of 1022 +/- 134 microunits/10(12) RBC (mean +/- SD), with a normal range (+/- 2 SD) between 754-1290 microunits. The individual activity values varied from 733-1490 microunits. The median of the 161 subjects was 1010 microunits/10(12) RB. There was no significant difference between the mean activities of RBC samples from men and women. MEL activity in RBC from the cord blood of 16 normal infants was found to be 43% higher than that in adults, with an average activity of 1458 +/- 174 microunits (mean +/- SD).
[Evolution of plasmatic apolipoprotein B, cholesterol and triglyceride levels in fourty-five long-term combined oral contraceptive users (author's transl)].
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Characterization of triacylglycerol lipase activity in human amniotic fluid.
A radiochemical assay was used to measure the triacylglycerol lipase activity found in normal human amniotic fluid at term. Enzyme activity was characterized in a partially purified extract of amniotic fluid and was found to be optimal at pH 8.0 +/- 0.2 in the presence of 5mM sodium taurocholate, with the use of emulsified tri-[3H]oleoyl glycerol as the substrate. The assay described made it possible to determine the lipase activity in as little as 25 microliters of a 12,000 x g supernatent of whole amniotic fluid as the source of enzyme. The lipase appeared to be distinct from another triacylglycerol lipase measurable in fetal membranes. In turn, it was shown that the amniotic fluid enzyme exhibited several catalytic properties which resembled those of pancreatic lipase. i.e., its substrate specificity, the bimodal effect of bile salt, and the influence of authentic pancreatic colipase on the catalytic process. The results suggest that the assay of triacylglycerol lipase activity may be clinically useful in the detection of enzyme abnormalities in human amniotic fluid.
In vitro effect of adrenocorticotrophic hormone on the pH profile of tri- and diester lipase activities from rat brain.
The influence of adrenocorticotrophic hormone (ACTH) on the hydrolysis of tri- and dioleoylglycerol by a cerebral lipase was studied using a synaptosomal preparation from rat brain as source of enzyme. When ACTH was added to the lipolytic medium, it caused a marked shift of the optimum pH values of catalysis towards alkaline values. In the pH range 5.8-6.5, these shifts resulted in reaction rates 5- to 20-fold higher, depending on the experimental conditions, than those measured without hormone. The ACTH effect was dependent on the NH2-terminal sequence extending through the amino acid residues 15-18. The results suggest that the hormonal influence is specific and mediated through a colipase-like effect.
Evolution of plasma levels of apolipoprotein B, cholesterol and triglycerides in women during long-term oral contraception.
Apolipoprotein B (apo B) was measured by a sensitive and specific double antibody radioimmunoassay in plasma from 15 normal women and 47 women taking oral contraceptives. The plasma apo B concentration in normal women was 0.90 +/- 0.10 g/l (mean +/- S.D.) whereas the overall value for all women taking contraceptives was 0.69 +/- 0.19 g/l. The maximum decrease (p less than 0.001) occurred in women investigated within three months after the beginning of the steroid intake, whose mean apo B value was 0.60 +/- 0.12 g/l (n = 12); decreases found after 3--24 months of contraception were of lesser magnitude. Apo B decreases were associated with significant decreases (p less than 0.01) in total plasma cholesterol, although the latter regained normal values after one year of contraception. Apo B and cholesterol values were in the normal range in women investigated after two years of steroid intake. An inverse trend was observed for plasma triglycerides, which showed a mean increase of 29% (p less than 0.01) after three months of steroid intake, and then stayed elevated without significant change with time.
Influence of corticotrophin on plasma testosterone in normal women.
The concentrations of ACTH and testosterone (T) in the plasma from 12 normal women (aged 18-35 years) were simultaneously determined at various times after im injection of 1 mg corticotrophin. The increase in the plasma level of total immunoreactive ACTH was maximal 0.5 h after the injection (mean value 1123 as compared to 36 pg/ml in the basal state); at 48 h, the ACTH level was still 2.4-fold that measured in the basal state. The administration of corticotrophin induced a broad increase in the mean level of plasma T which was highly significant (P < 0.001) at 4, 6, 8, 16 and 24 h after the injection. The maximum T response was detected at 16 h (mean value 477 as compared to 338 pg/ml in the basal state). The results indicate that plasma T is susceptible to stimulation by a pharmacological dose of ACTH in normal women. This effect should be taken into account in evaluating the indication of ACTH as a therapeutic agent.
[Double-label scintigraphy in the diagnosis of hepatocarcinoma].
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[Use of liquid sodium for the chemical removal of the skin of mackeral in the processing of canned fish appetizers marinated in white wine].
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Characterization of a monoester lipase active as membrane-bound enzyme in rat erythrocytes.
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Differential properties of lipases active as membrane-bound enzymes in isolated fat cells.
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Effect of estrogen on heparin-releasable liver lipases.
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Disposable humidifiers in a recovery room--a microbiological evaluation.
Humidification, unlike nebulization, does not produce water droplets in the process of producing desiccated gases, and therefore is considered low risk in terms of potential infection sources. However, direct inoculation of bacteria into these units has been shown to produce contaminated effluents. Therefore, the present study was designed to determine if the airborne route of contamination was a potential source of bacterial inoculum for these units and to determine the maximum number of days units remained free of bacterial contamination. Disposable humidifiers were placed in both high and low volume patient areas of the recovery room. Units were used on multiple patients with only the cannula replaced between patients. Our results showed that these units do have the potential for becoming inoculated through the airborne route, but did not produce contaminated effluents greater than background air. Units remained sterile during the entire time in use in both high and low volume areas. In conclusion, our data suggests that each institution should evaluate the usage of disposable humidifiers based on patient parameters and environment rather than manufacturer's guidelines.