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S I Turner

Publications and source records attributed to S I Turner.

5 recordsLinked to original sources
PubMed1988

Lipid and glucose metabolism in human placental culture.

Placental culture models have been used to increase the understanding of endocrinology and pathophysiology in pregnancy. This article describes glucose and lipid metabolism in several of these models. Of special interest is the availability of arachidonic acid for the production of prostanoids. Ten placentas were collected at the time of cesarean section in term pregnancies without labor. Minced villous tissue was incubated for 48 hours in media with a glucose concentration of 100, 200, or 500 mg/dl. Tissue was dispersed in the media or was left as a single clump during the incubation. Glucose levels in the culture media were measured at 8, 20, 32, and 48 hours. Tissue lipid levels were measured before and after incubation in seven placentas. At 8 hours, glucose utilization ranged from 2.38 +/- 0.40 to 9.44 +/- 1.22 mumol/gm tissue/hr (mean +/- SEM). By 48 hours the cumulative glucose utilization ranged from 1.56 +/- 0.09 to 6.87 +/- 0.38 mumol/gm tissue/hr. Tissue lipid analysis showed most of the fatty acids to be in the phospholipids initially (4477 +/- 179 micrograms/gm tissue). Subsequent to incubation for 48 hours, phospholipid levels fell to a range of 2686 +/- 90 to 3466 +/- 157 micrograms/gm tissue in various culture conditions (p less than 0.005 compared with initial values). Whereas phospholipid levels decreased during incubation, levels of triglycerides and nonesterified fatty acids increased significantly in placental tissue. Arachidonic acid, the precursor of prostaglandins, thromboxane, and prostacyclin, makes up about one quarter of the fatty acid in the initial placental phospholipid. Arachidonic acid follows the pattern of total fatty acids during incubation; it is released from phospholipid and is converted to nonesterified fatty acid and triglyceride. We may conclude from this study that each placenta has a unique glucose utilization rate and a unique capacity to produce triglyceride. In tissue culture, arachidonic acid is released to its nonesterified state much more quickly than it can be converted to prostanoids by cyclooxygenase. The choice of initial glucose concentration, tissue preparation (dispersed in media or left as single clump), and time of incubation all may determine the rate of glucose metabolism, the rate of phospholipid breakdown, the rate of triglyceride production, and the quantity of nonesterified arachidonic acid in placental tissue culture.

Arachidonic Acids↗
PubMed1987

A developmental study of rat sperm and testis selenoproteins.

Essentially all of the selenium in the rat spermatozoon is bound to a polypeptide of Mr 15,000-17,000 confined to the capsule that surrounds the sperm mitochondria. Isoelectric focussing of isolated 75Se-labelled, carboxymethylated mitochondrial capsule protein (MCP) reveals the presence of at least four radioactive components, with a predominant charge isomer at pI4.6. The sperm selenoprotein appears to be identical with MCP, as judged by the exact coincidence of radioactivity and protein stain during two-dimensional electrophoresis. The temporal pattern of 75Se-labelling of rat caput epididymal spermatozoa after intratesticular 75Se injection suggests that maximum incorporation of 75Se into MCP occurs in step 7-step 12 spermatids and that 75Se uptake ceases during step 15 of spermiogenesis. The developmental appearance of sperm selenoprotein in rat testis therefore appears to lag several days behind that reported for MCP in mouse testis, suggesting the presence of selenium-free MCP in immature germ cells. SDS gel electrophoretic analysis of testis subcellular fractions 24 h after 75Se injection into rat testis at 21, 28 and 90 days of age indicates that sperm selenoprotein first appears in very low concentration during late meiosis and that its concentration increases sharply during early spermiogenesis. Additional 75Se-labelled polypeptides were detected on the gels, most of them of higher molecular weight than MCP. At least two of these (Mr 47,000 and 54,000) displayed a marked decrease in labelling between 5 and 24 h after injection into adult testis, coincident with a comparable increase in 75Se-labelled MCP, indicating that they may be precursors of MCP.

Animals↗
PubMed1986

Essential fatty acid patterns in preeclampsia.

Fatty acid patterns were determined for maternal and cord sera from normal and preeclamptic pregnancies using gas liquid chromatography. Ten normal and 11 preeclamptic maternal sera were used; 6 preeclamptic and 6 normal cord sera were measured. Fatty acid patterns were measured in the nonesterified fatty acids (NEFA), the triglycerides (TG), the cholesterol esters (CE), and the phospholipids (PL). Preeclampsia showed significant differences in the essential fatty acid patterns in the maternal and cord sera compared to normal pregnancy. Oleic acid, an early indicator of essential fatty acid deficiency, made up a significantly greater proportion of preeclamptic cord blood NEFA, TG, and PL than in normal cord blood. Abnormalities in essential fatty acid patterns may be associated with decreased prostacyclin production and dysmaturity which may be seen with preeclampsia.

Arachidonic Acid↗