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Biomedical subjects

D Emond

Publications and source records attributed to D Emond.

6 recordsLinked to original sources
PubMed1993

Arterial partial pressure of oxygen required to achieve 90% saturation of hemoglobin in very low birth weight newborns.

Since very low birth weight preterm newborns are prone to oxygen toxicity and have red blood cells that have a high oxygen affinity, the knowledge of the P90 (the PaO2 required for 90% saturation of hemoglobin) could result in a more optimal oxygenation. This information could diminish the incidence of bronchopulmonary dysplasia and retrolental fibroplasia. To determine P90 and P50 (the PaO2 required for 50% saturation of hemoglobin), cord blood was obtained from 10 preterm newborns who were of less than 30 weeks' gestation (26.4 +/- 1.4 [SD] weeks) weighing less than 1000 g (816 +/- 119 g). The P50 and P90 were determined by gas mixing tonometry and expressed in millimeters of mercury at a temperature of 37 degrees C, a pH of 7.40, and PCO2 of 40 mm Hg. The tonometer permitted an equilibration and sampling of successive aliquots of blood at different oxygen tensions. Measurement of oxygen saturation, pH, and PaO2 provided the information for plotting the oxygen dissociation curve, the P50 and P90. There were at least six experimental points for each oxygen dissociation curve. The results showed that the mean P50 was 18.3 +/- 1.9 mm Hg (2.5 +/- 0.3 kPa) and the P90 was 40.8 +/- 3.6 mm Hg (5.4 +/- 0.5 kPa). This study demonstrates the fetal nature of the oxygen dissociation curve of very low birth weight newborns; but most importantly it also shows that when treating very low birth weight newborns with oxygen, a PaO2 of 41 mm Hg (5.5 kPa) is enough to saturate 90% of the hemoglobin at a physiological pH. This information could be of clinical importance to minimize oxygen toxicity.

Arteries↗
PubMed1981

High density lipoprotein subfractions isolated by heparin-Sepharose affinity chromatography and their role in cholesteryl ester transfer to very low density lipoproteins.

Normal human plasma HDL was applied to a column of heparin-Sepharose in the presence of MnCl(2) and three fractions were obtained by stepwise elution with increasing NaCl concentrations: a non-retained fraction (NR, 78% of protein) and two retained fractions (R(1) and R(2), 18 and 2.5% of protein, respectively). Both unesterified and esterified cholesterol increased from NR to R(1) to R(2) but the increment was more pronounced for unesterified cholesterol. ApoA-II to apoA-I ratio was-lower in R(1) compared to NR but R(1) contained more apoC than NR. ApoE increased from NR to R(1) to R(2) (0.07, 0.4, and 14% of protein in each fraction, respectively) while apoB was found only in R(2). Agarose gel electrophoresis and immunoadsorbers for apoB and apoE showed that R(2) consisted of two major lipoprotein populations, one containing apoB and some apoE and the other containing apoE and no apoB. Cholesteryl ester transfer between each HDL subfraction and VLDL in the presence of partially purified cholesterol ester transfer protein was studied. NR and R(1) gave the highest initial rates of transfer for labeled cholesteryl ester which were corroborated by significant mass transfer of cholesteryl esters. From these results, we concluded that there is no connection between cholesteryl ester transfer and apoE. On the other hand, transfer from R(2) to VLDL followed different kinetics with a high zero hour transfer but with subsequently lower rates when compared to NR and R(1). The cholesteryl ester transfer activity in R(2) was mainly due to the presence of apoE-containing lipoproteins whereas those containing apoB had minimal transfer activity. However, because this transfer of label was not translated into significant mass transfer of cholesteryl ester to VLDL, the apoE-containing lipoproteins appear involved mainly in the equilibration of cholesteryl esters.-Marcel, Y. L., C. Vézina, D. Emond, R. B. Verdery, and R. W. Milne. High density lipoprotein subfractions isolated by heparin-Sepharose affinity chromatography and their role in cholesteryl ester transfer to very low density lipoproteins.

Cholesterol Esters↗
PubMed1980

Heterogeneity of human high density lipoprotein: presence of lipoproteins with and without apoE and their roles as substrates for lecithin:cholesterol acyltransferase reaction.

By affinity chromatography on heparin-Sepharose, two classes of lipoproteins were separated from high density lipoproteins (HDL) isolated from patients with primary or secondary lecithin:cholesterol acyltransferase (LCATase; EC 2.3.1.43) deficiency and from normal subjects. The unretained fraction, HDL(A), was characterized by having apoA-I as a major apoprotein; it also contained apoA-II, -C-II, and -C-III but it contained only traces of immunodetectable apoE and no apoB. The retained fraction, HDL(E), had apoE as the major apoprotein; it also contained apoA-I, -A-II, -B, -C-II, and -C-III. The relative concentration of apoA-I increased with increasing density in the HDL(E) subclass. Compared to HDL(A), HDL(E) had a significantly higher cholesterol content and a lower protein concentration. HDL(E) was mainly (90%) contained within the HDL(2) subfraction. Contamination of HDL(E) by low density lipoproteins (LDL) or Lp(a) was minimal on the basis of pre-beta-electrophoretic mobility and absence of albumin, respectively. Contamination by LDL or Lp(a) could be resolved in part by application of HDL(E) to concanavalin A-Sepharose or to heparin-Sepharose with a shallow gradient. When evaluated as substrates for a highly purified LCATase preparation, the initial reaction rates and V(max) obtained with HDL(A) were always higher than those obtained with HDL(E) in any given plasma. However, both HDL subclasses from LCATase-deficient subjects were better substrates than the corresponding HDL subclasses from normal plasma. Also, both HDL(3A) and HDL(3E) isolated from normal HDL(3) were better substrates than the corresponding subclasses isolated from normal HDL(2). The recognition of this compositional and functional heterogeneity within HDL will allow a better understanding of the metabolism of this lipoprotein class.

Apolipoproteins↗
PubMed1979

Distinctive properties of glutamine synthetase from the cyanobacterium Anacystis nidulans.

The intracellular levels of glutamine synthetase (GS) in Anacystis nidulans grown under different conditions were determined using a whole-cell assay. Nitrate-grown cells have 64% more GS than cells grown in ammonium sulfate. Nitrogen starvation does not affect GS levels appreciably. Incubation of nitrate-grown cells with ammonium sulfate does not change the ratio of gamma-glutamyl transferase activities stimulated by Mg2+ and Mn2+ ions. An in vitro test of adenylylation indicates that algae do not have an endogenous adenylyl transferase (ATase) and that algal GS is not adenylylatable by the Klebsiella aerogenes ATase. Some characteristics of the GS-membrane complex were determined by centrifugation of the complex under varying conditions of pH and ionic strength. In this way, it was shown that acid pH (4.5) stabilizes the complex and high ionic strength tends to solubilize the enzyme. A simple partial purification of GS (89-fold) was developed based on the sedimentation properties of GS.

Cell Membrane↗