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Biomedical subjects

B M Waite

Publications and source records attributed to B M Waite.

29 records · Page 2Linked to original sources
PubMed1975

Phospholipase A activities in rat placentas of 14 days' gestation.

1. Homogenates and subcellular fractions of placentas obtained from rats on the 14th day of gestation were assayed for enzymes characteristic of various subcellular organelles. Based on these assays it seemed the placental lysosomes (acid phosphatase activity) were distributed equally among the subcellular particulate fractions and that the cytosol was not contaminated by mitochondria or microsomes. 2. The placental preparations were assayed for phospholipase A activity using 2-[14-C] phosphatidylethanolamine. We found phospholipases A with pH optima of 4.0, 7.0, and 8.5. These enzymes had Ca-2+ requirements and subcellular localizations similar to those reported for adult rat liver (Waite, M., Scherphof, G.L., Boshouivers, F.M.G. and van Deenen, L.L.M. (1969) J. Lipid Res. 10, 411.) 3. The majority of the placental phospholipase A activity was found in the cytosol. We think this activity represents enzyme(s) solubilized from the plasma membranes of placental cells and speculate that this enzyme may be active in a placental transport mechanism.

Animals↗
PubMed1975

Incorporation of a phospholipid precursor into the hemochorionic and yolk sac placentas associated rat embryos.

Pregnant Long-Evans rats were subjected to a teratogenic regimen, i.e., were fed a synthetic diet lacking folic acid and containing 9-methylpteroylglutamic acid on the 11th to 14th days of gestation. Experimental and control pregnant rats injected with 10 muCi of [2-14C] ethanolamine on the 14th day were killed 1 or 2 days later. The total radioactivity and radioactivities of phosphatidylethanolamine (PE), phosphatidylcholine (PC), and lysophosphatidylethanolamine (LPE) were determined in chloroform extracts of homogenates and subcellular fractions prepared from hemochorionic and yolk sac placentas and maternal liver. The distribution of radioisotope into PC and PE of control and experimental yolk sac placentas was similar, and paralleled the distribution in maternal liver. However, the distribution of radioisotope into PC and PE of the hemochorionic placentas did not parallel that of the maternal liver, and radiolabeled PC accumulated faster in experimental placentas than in controls. We suggest that the ability of the hemochorionic placenta to synthesize PC from PE was impaired by the teratogenic regimen, and that the organ took up relatively more PC from the maternal plasma. We propose that this teratogen-induced shift from placental lecithin synthesis to selective lecithin uptake underlies the previous finding of an increased accumulation of radio-labeled PC in embryos from pregnant females subjected to this teratogenic regimen (Chepenik and Waite, '73).

Animals↗
PubMed1975

Phospholipase A and acid lipase activity during release of lysosomal hydrolases.

Hydrolysis of cardiac and hepatic lysosomal phospholipids by endogenous phospholipase A occurs during incubation at 37 degrees C at pH 5.0. Lysophospholipids and free fatty acids accumulate in association with release of hydrolases from the lysosomes into the supernatant. Acid-active neutral lipid lipases contribute to the release of free fatty acids. Albumin inhibits the production of these surface-active lipids as well as the release of hydrolases. The soluble phospholipase A is inhibited by albumin, soluble protein (cytoplasmic), heparin, and protamine sulfate. Thus, hydrolysis of lysosomal lipids, catalyzed by endogenous phospholipases, as well as acid-active neutral lipid lipases, may contribute significantly to the increased permeability, swelling, and subsequent lysis of lysosomes. Stabilization of the lysosomal membrane is associated with integrity of the structural lipids of the membrane.

Animals↗