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Biomedical subjects

K A Conklin

Publications and source records attributed to K A Conklin.

At least 37 records · Page 2Linked to original sources
PubMed1980

Epidural anaesthesia with chloroprocaine. Delayed onset, extensive spread, and prolonged duration.

A case report of continuous lumbar epidural anaesthesia with chloroprocaine is described in which delayed onset, extensive and delayed spread, and prolonged duration were observed. Although placement of neither the needle nor the catheter was confirmed radiographically, the anaesthetic course may be consistent with extra-arachnoid subdural injection of the local anaesthetic solution. Other reported cases, with similar features and which may be explained in the same way, are also discussed.

Adult↗
PubMed1980

Midazolam and diazepam: maternal and fetal effects in the pregnant ewe.

Maternal and fetal hemodynamic effects and placental transfer of midazolam (RO 21-3981, Hoffman-LaRoche) and diazepam were studied in chronically instrumented pregnant ewes. Diazepam administration resulted in greater increases of maternal and fetal heart rates and maternal blood pressure, and greater alteration of total uterine blood flow than did administration of comparable doses of midazolam. Neither drug altered fetal mean arterial pressure or maternal and fetal respiratory gases. Although the absolute blood concentrations were higher, the fetal:maternal drug concentration ratios were consistently less for midazolam than for diazepam, suggesting less placental permeability of midazolam.

Animals↗
PubMed1979

Halothane does not inhibit synthesis of nucleic acids in Tetrahymena pyriformis.

The effect of halothane on precursor incorporation into nucleic acids was studied in Tetrahymena pyriformis, a ciliate protozoan. At concentrations that blocked cell division (1.2 and 2.4 per cent), halothane inhibited incorporation of 14C-thymidine and 14C-uridine into DNA and RNA, respectively, in intact cells. However, in nuclei isolated from T. pyriformis, the anesthetic did not inhibit DNA and RNA synthesis when these processes were assayed using the nucleoside triphosphates (3H-thymidine triphosphate and 3H-uridine triphosphate) as precursors. It is concluded that halothane does not directly inhibit nucleic acid synthesis (i.e., the nucleic acid polymerase reactions), and that the inhibition of precursor incorporation observed in intact cells is due to an effect at a locus other than the DNA and RNA polymerase reactions.

Animals↗
PubMed1976

Sucrase-isomaltase deficiency. Absence of an inactive enzyme variant.

Deficiency of sucrase-isomaltase, an intestinal enzyme complex that is essential for digestion of nutritionally important carbohydrates, appears to be inherited as an autosomal recessive in 0.2 per cent of North Americans. The molecular basis of the deficiency has not been elucidated. To characterize the enzyme defect quantitatively, papain-solubilized intestinal biopsies were analyzed for total enzyme protein by radioimmunoassay and for enzyme activity by hydrolytic assay. Normal intestine had a close correlation between immunologically reactive enzyme and enzymic activity. In contrast, seven patients with sucrase-isomaltase deficiency were found to have complete absence of the enzyme protein by radioimmunoassay even though up to 10 times more intestinal protein was present than with normal tissue. This absence of an inactive enzyme variant can be explained by a major (no-sense) mutation of the structural gene or by a complete repression of the regulatory mechanism that controls structural gene function.

Carbohydrate Metabolism, Inborn Errors↗
PubMed1976

Effects of hypolipidemic agents on lipid synthesis in subcellular fractions from Tetrahymena pyriformis.

Lipid synthesizing systems have been prepared from subcellular fractions of Tetrahymena pyriformis, GL. These fractions, the mitochondrial fraction, the microsomal fraction and the soluble cell fraction, have been characterized as to cofactors and cations required for optimal lipid synthesis. The effects of hypolipidemic agents on lipid synthesis by all fractions are presented.

Acetates↗
PubMed1975

Human intestinal sucrase-isomaltase. Identification of free sucrase and isomaltase and cleavage of the hybrid into active distinct subunits.

Sucrase-isomaltase complex and its functional subunits have been identified in homogenates of human small intestinal mucosa by use of Sephadex G-200 (superfine) chromatography aided by affinity of the isomaltase moiety for the dextran gel. The isomaltase subunit binds strongly to the gel at 4 degrees, and is eluted only after 2 column volumes; earlier recovery as a sharp peak can be achieved by raising column temperature to 37 degrees after elution of other proteins. Bio-Gel P-300 chromatography, density gradient, and equilibrium centrifugation demonstrated that the sucrase subunit (Stokes radius = 45 A, frictional ratio = 1.32, s20,w = 6.9, MW = 130,000) and the isomaltase subunit (Stokes radius = 45 A, frictional ratio = 1.30, s20,w = 6.6, MW = 120,000) are similar but unequal in size. The sucrase-isomaltase complex (Stokes radius = 70 A, frictional ratio = 1.61, s20,w = 9.8, MW = 280,000), appears to be an elongated hybrid molecule that is less symmetrical than either of itt subunits. Apparent Km and pH activity curves were indistinguishable for each enzyme whether present in the hybrid or in the free state. The sucrase-isomaltase complex, accounting for approximately 90 percent of native intestinal sucrase and isomaltase activities, was isolated and cleaved by 0.01 M beta-mercaptoethanol/6 M urea treatment into active sucrase and isomaltase subunits having biochemical characteristics identical with those of the free native moieties. Sodium dodecyl sulfate acrylamide gell electrophoresis of the complex also produced subunits having molecular weights very close to those for the active free sucrase and isomaltase moieties, indicating that each alpha-glucosidase appears to consist of a single polypeptide chain. Immunization of rabbits with pure sucrase-isomaltase complex yielded a monospecific precipitating antibody that reacted with the hybrid and the sucrase subunit, but had minimal affinity for the isomaltase subunit, providing further evidence that the sucrase-isomaltase molecule is a hybrid consisting of two distinct alpha-glucosidases.

Animals↗