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Biomedical subjects

R L Jackson

Publications and source records attributed to R L Jackson.

At least 181 records · Page 10Linked to original sources
PubMed1979

Long-term analgesic effects of inescapable shock and learned helplessness.

Although exposure to inescapable shocks induced analgesia in rats, the analgesia was not manifest 24 hours later. A brief reexposure to shock, however, restored the analgesia. This reexposure to shock had an analgesic effect only if the rats had been shocked 24 hours previously. Further, long-term analgesic effects depended on the controllability of the original shocks and not on shock exposure per se. Implications of these results for learned helplessness and stress-induced analgesia are discussed.

Analgesia↗
PubMed1979

A review of the unique features of HDL apoproteins.

The human plasma high density lipoproteins (HDL) are a heterogeneous ensemble of five proteins associated with both neutral and polar lipids. The sequence of all five proteins are known. ApoA-I and apoA-II are the major protein components; apoC-I, apoC-II and apoC-III are the minor protein components. All these apoproteins spontaneously recombine with phospholipids to give stable lipid-protein complexes and freely exchange between the two major HDL subclasses, HDL2 and HDL3. In addition, ApoC-I, apoC-II, and apoC-III exchange between HDL and very low density lipoproteins. Furthermore, certain HDL apoproteins are activators for plasma enzymes that are important in lipid metabolism. ApoA-I and apoC-I activate lecithin/cholesterol acyltransferase; apoC-II is an activator of lipoprotein lipase. The regions of apoC-I and apoC-II that are involved in the activation of these enzymes have been localized with synthetic peptides. Studies of synthetic and native fragments of apoA-II, apoC-I, apoC-II, and apoC-III as well as model lipid-binding peptides have identified specific regions with structural features common to lipid-binding proteins. These special properties, which include helical potential, sequences with a critical amphipathic length, and high hydrophobicity of the nonpolar side of the amphipathic helix, are the determinants of HDL structure and metabolism.

Amino Acid Sequence↗
PubMed1978

Islet-cell-surface antibodies in juvenile diabetes mellitus.

Using an indirect immunofluorescence test on suspensions of viable, insulin-producing islet cells from rats, we found that 32 per cent (28/88) of insulin-treated patients with juvenile diabetes have islet-cell-surface antibodies in their circulation. These antibodies also occurred in four of nine children with glucose intolerance, in one of 24 healthy children and in nondiabetic children with thyroid disorders. In the diabetic children, the immunofluorescent reaction was inhibited by preadsorption of serum to islet cells but was little affected by preadsorption to rat hepatocytes or erythrocytes or to acetone powders of various rat tissues, including pancreas. These results show that organ-specific, nonspecies-specific antibodies reactive with the cell surface of the islet cells can be present in serum from diabetic children, and provide an approach to investigation of immunopathological aspects of diabetes mellitus.

Adolescent↗
PubMed1978

Sequence homology of the Ca2+-dependent regulator of cyclic nucleotide phosphodiesterase from rat testis with other Ca2+-binding proteins.

A Ca2+-dependent regulator protein of cyclic 3':5'-nucleotide phosphodiesterase (EC 3.1.4.17) has previously been isolated from rat testis and shown to be a heat-stable, Ca2+-binding protein with a molecular weight of approximately 17,000. The Ca2+-dependent regulator protein is also structurally similar to troponin-C, the Ca2+-binding component of muscle troponin and Ca2+ mediator of muscle contraction. The present report describes a partial amino acid sequence of the Ca2+-dependent regulator. The protein (148 amino acids) is 50% homologous with skeletal muscle troponin-C, but is 11 residues shorter than the muscle protein. The Ca2+-dependent regulator protein has an NH2-terminal sequence of acetyl-Ala-Asp-Glu, a COOH-terminal sequence of Thr-Ala-Lys and 1 residue of epsilon-trimethyllysine located at position 115. All of these properties are distinct from those of other homologous Ca2+-binding proteins. These properties may account for the biological specificities demonstrated by these proteins as compared to the Ca2+-dependent regulator protein. Based on the sequence and a comparison of the Ca2+-dependent regulator protein to other calcium-binding proteins, our data support the view that all of these moecules contain common sequences, especially at their proposed metal-binding sites.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1978

The interaction of human plasma glycosaminoglycans with plasma lipoproteins. II. Hemagglutination studies.

Formalinized, tannic acid-treated sheep erythrocytes coated with low density lipoproteins (LSL) or apoprotein B (apo-B) are are agglutinated by anti-apo-B immunserum. Those coated with high density lipoproteins (HDL) or apoprotein A-I(apo-A-I) are agglutinated by anti-apo-A-I immunserum. These coated formocells have been used to study the interactions of lipoproteins and apoproteins with plasma glycosaminoglycans (GAG). The sulfate-rich species of plasma GAG agglutinates cells coated with LDL, HDL, apo-B, and apo-A-I at ionic concentrations above 0.15 M. The less-sulfated species of plasma GAG does not agglutinate the coated cells but inhibits the agglutination caused by the sulfate-rich species. Treatment of the sulfate-rich GAG with papain causes a reduction in molecular weight by one-half and also causes a loss of its agglutinating activity. These results suggest that the sulfate-rich plasma GAG, consisting of two glycan chains linked to a peptide backbone, cause agglutination by binding to two or more formocells. In contrast, the less-sulfated plasma GAG, consisting of single, short glycan chains, are incapable of causing agglutination but may prevent it by covering specific binding sites present on the coated cells.

Apoproteins↗
PubMed1978

Control of 3-hydroxy-3-methylglutaryl-CoA reductase activity in cultured human fibroblasts by very low density lipoproteins of subjects with hypertriglyceridemia.

Very low density lipoproteins (VLDL) and low density lipoproteins (LDL) from human normolipemic plasma, and the VLDL, the intermediate density lipoprotein (IDL), and LDL from patients with Type III hyperlipoproteinemic plasma were tested for their abilities to suppress the activity of 3-hydroxy-3-methylglutaryl-Coenzyme A (HMG-CoA) reductase in cultured human fibroblasts from normal subjects and a Type III patient. Regulation of cholesterol synthesis in the fibroblasts of a patient with Type III hyperlipoproteinemia appears to be normal. VLDL from normal subjects, isolated by angle head ultracentrifugation (d < 1.006) or by gel filtration on BioGel A-5m, were about 5 times less effective than LDL in suppressing HMG-CoA reductase activity, based on protein content, in agreement with previous reports with normal fibroblasts. Zonal centrifugation of normal VLDL isolated by both methods showed that the VLDL contained IDL. Normal VLDL from the angle head rotor, refractionated by the zonal method, had little, if any, ability to suppress the HMG-CoA reductase activity in either normal or Type III fibroblasts. VLDL, IDL, and LDL fractionated by zonal ultracentrifugation from Type III plasma gave half-maximum inhibition at 0.2-0.5 mug of protein/ml, indistinguishable from the suppression caused by normal LDL. Type III VLDL did not suppress HMG-CoA reductase in mutant LDL receptor-negative fibroblasts. Zonally isolated VLDL obtained from one Type IV and one Type V patient gave half-maximal suppression at 5 and 0.5 mug of protein/ml, respectively. Molecular diameters and apoprotein compositions of the zonally isolated normal and Type III VLDL were similar; the major difference in composition was that Type III VLDL contained more cholesteryl esters and less triglyceride than did normal VLDL. The compositions and diameters of the Type IV and Type V VLDL were similar to normal VLDL. These findings show that the basic defect in Type III hyperlipoproteinemia is qualitatively different from the cellular defect found in familial hypercholesterolemia, since the regulation of HMG-CoA reductase activity is normal in Type III fibroblasts. The metabolic defect in hypertriglyceridemia is related to the triglyceriderich lipoproteins which, free of other lipoproteins, have an enhanced ability to interact with cultured fibroblasts to regulate HMG-CoA reductase activity. These studies suggest that, in hypertriglyceridemia, there is a mechanism for direct cellular catabolism of VLDL which is not functional for normal VLDL.

Adult↗