The temperature-dependent catalytic activity of rat liver 3-hydroxy-3 -methylglutaryl coenzyme A reductase (HMG-CoA reductase) displays the nonlinear Arrhenius behavior characteristic of many membrane-bound enzymes. A two-conformer equilibrium model has been developed to characterize this behavior. In the model, HMG-CoA reductase undergoes a conformational change from a low specific activity to a high specific activity form. This conformation change is apparently driven by a temperature-dependent phase transition of the membrane lipids. It has been found that this model accurately describes the data from diets including rat chow, low-fat, high-carbohydrate, and diets supplemented with fat, cholesterol or cholestyramine. The effects characterized by the model are consistent with the regulation of HMG-CoA reductase by enzyme-lipid interactions.

Calcium/phospholipid-dependent protein kinase (PKC) was partially purified from P1798 lymphosarcoma. Phospholipid-dependence was specific for phosphatidylserine. PKC phosphorylated Histone 1, with an apparent K_m of 14.1 μM. Chlorpromazine, a lipid-binding drug, inhibited PKC activity by 100%. Further studies were undertaken to establish analytical conditions which could be applied to the study of PKC in intact cells. The conditions included (1) determining optimum cell concentration for measuring PKC activity, (2) recovering PKC into the soluble fraction of cell extracts, (3) evaluating calcium and phospholipid requirements of PKC in this fraction, and (4) inhibiting PKC in this fraction. Final studies involved treatment of intact cells with potential activators. Both phytohaemagglutinin and a phorbol ester increased PKC activation.

Huian plasma high-density lipoprotein (HDL) were isolated by a procedure employing polyanion precipitation and column chromatography. Lipid and protein composition of the HDL isolated by this method was found to be similar to another HDL preparation isolated by ultracentrifugation. However, minor differences were noted, including a higher phospholipid and apoproteinE content and lower triglyceride content of the HDL isolated by column chromatography. Four subfraction of HDL were obtained following chromatography on an anion exchange column. The subfraction four had the highest esterified to free cholesterol ratio, the second highest phospholipid to unesterified cholesterol, and the lowest molecular weight. In addition it was consistently coincided with lecithin: cholesterol acyltransferase (LCAT) activity and found to be the best substrate for the enzyme.

Recent studies have shown that the Sudden Infant Death Syndrome (SIDS) is related to abnormal control of respiration (Ischemic degeneration of the brainstem may play an important role in altered respiratory control leading to death). In our studies we have examined brainstem ganglioside compositions in samples derived from SIDS victims and appropriate controls. Gangliosides are acidic glycosphingolipids that contain sialic acid. The high concentration of gangliosides in the central nervous system (CNS) implies that these lipids play an important role in CNS function. Some studies have indicated that gangliosides may function as receptor site determinants or modifiers, and in neural transmission. In our studies we used the Tettamanti, et al methodology to extract gangliosides, and High Performance Thin Layer Chromatography (HPTLC) and laser densitometry techniques for ganglioside analysis. The results of these analyses are being employed to establish lipid profile patterns to determine if there are significant variations in these lipid patterns between SIDS and control groups.

The objectives of these investigations were (1) the purification of MG reductase from sheep liver and (2) studies of some of its characteristics. MG reductase was purified 40 fold and showed a single band on SDS-PAGE. Molecular weight estimations with SDS-PAGE showed a molecular weight of 44,000; although gel filtration with Sephadex G-150 gave a molecular weight of 87,000 indicating that the enzyme might be a dimer. The Km for MG is 1.42 mM and for NADH it is 0.04 mM. The pH optimum for the purified enzyme is pH 7.0. Isoelectric focusing experiments showed a pI of 9.3. In vivo experiments involving rats treated with 3,3',5-triiodothyronine (T_3) and 6-n-propyl-2-thiouracil (PTU) indicated that MG reductase was depressed by T_3 and elevated by PTU.

A method for purification and radiolabelling phosphoglucose isomerase was devised in order to develop a sensitive quantitative radioimmunoassay for the detection of the enzyme irrespective of its catalytic activity. For four genetic variants of PGI no difference in the molecular specific activity was observed. In one variant (PGI-Denton), liver and heart tissue extracts, and in mature erythrocytes (as compared to normal erythrocytes), a decreased molecular specific activity was observed which initially may imply that these samples contain cross-reactive material which is not catalytically active.

A Differentiation Factor (DF) was purified from rat lung conditioned medium by a four-steps procedure. The DF has a molecular weight of 27000, and an isoelectric point of 4.70. Although DF is stable up to 60°C, it is sensitive to digestion by trypsin, chymotrypsin and subtilisin. DF forms granulocyte colonies in soft agar. Studies using anti-NRK CSF antibody demonstrated that DF is distinct from GM-CSF.

In this study, the production of monoclonal antibodies directed against the activating enzyme for an S6 kinase is examined and described. Evidence is presented for the association of an Mr. 55,000 abd Mr. 95,000 protein with the s6 kinase. These proteins are phosphorylated in the presence of Activating Enzyme. A sequence of regulatory events for insulin-stimulated phosphorylation of ribosomal protein S6 in cells is postulated as follows: insulin activates the receptor tyrosine kinase, which phosphorylates the Mr 116,000 subunit of Activating Enzyme. The Activating Enzyme then activates the S6 kniase by phosphorylation, and phosphorylation of the ribosomal protein s6 is promoted.

Delivery of photoassimilate, mainly sucrose (Suc) from photoautotrophic source leaves provides the substrate for the growth and maintenance of sink tissues such as roots, storage tissues, flowers and fruits, juvenile organs, and seeds. Phloem loading is the energized process of accumulating solute in the sieve element/companion cell complex of source leaf phloem to generate the hydrostatic pressure that drives long-distance transport. In many plants this is catalyzed by Suc/Proton (H+) symporters (SUTs) which are energized by the proton motive force (PMF). Overexpression of SUTs was tested as means to enhance phloem transport and plant productivity. Phloem specific overexpression of AtSUC2 in wild type (WT) tobacco resulted in enhanced Suc loading and transport, but against the hypothesis, plants were stunted and accumulated carbohydrates in the leaves, possibly due to lack of sufficient energy to support enhanced phloem transport. The energy for SUT mediated phloem loading is provided from the PMF, which is ultimately supplied by the oxidation of a small proportion of the loaded photoassimilates. It was previously shown that inorganic pyrophosphate (PPi) is necessary for this oxidation and overexpressing a proton-pumping pyrophosphatase (AVP1) enhanced both shoot and root growth, and augmented several energized processes like nutrient acquisition and stress responses. …

Conditioned media prepared from umbilical cord (UC) segments or endothelial cells (EC) contain colony stimulating activity, Both UCCM and ECCM were partially purified by DEAE-Sepharose and ACA44 gel filtration chromatography. The molecular weights were estimated as 25,000 and 31,000 for UC-CSF and EC-CSF, respectively. UC-CSF was further fractionated by Con A Sepharose, IEF and HPLC on a hydrophobic phenyl column. The highly purified CSF stimulates human macrophage and granulocyte colony formation, indicating it is GM-CSF in nature. Characterization studies have revealed that both CSFs are heat stable at 60°C for 30 min. They are sensitive to digestion by protease and to periodate oxidation but are stable to treatment with sulfhydryl reagents. The synthesis of CSF in endothelial cells is inhibited by actinomycin D, cycloheximide and puromycin, indicating that protein and RNA synthesis are required for CSF production. Among the mitogens tested, only LPS exhibited stimulatory activity on the production of CSF. Metabolic modulators such as dibutyryl cAMP, isobutylmethylxanthine, PGE2 and lactoferrin inhibit CSF production, while PGF2 enhances CSF production.