Influx of γ-Aminobutyric Acid and α-Aminoisobutyric Acid into Mouse Cerebrum Slices Incubated in a Pyruvate Medium with or without Added Glucose or Glucose Analogues Compared with Influx from a Glucose Medium

Concentrative influx of γ-aminobutyric acid (GABA) and α-aminoisobutyric acid (AIB) into incubated mouse cerebrum slices is decreased when pyruvate is substituted for glucose. Influx of GABA from pyruvate medium is not increased by presence of glucose, 2-deoxy-d -glucose (2-DOG), or 3-O-methyl-d -glucose (3-O-MeG). Influx of AIB is restored to the rate from glucose medium if 2-DOG is present initially, but is not restored if 2-DOG is added with AIB. Influx is not restored if 3-O-MeG is present initially, but is restored if 3-O-MeG is added with AIB. Influx is restored if glucose is present initially or is added with AIB.     

Somatostatin inhibits adrenergic and cholinergic neurotransmission in smooth muscle.

Somatostatin reduced the response to field stimulation in the guinea pig ileum and reduced the spontaneous contractions in the rabbit jejunum, an effect that was blocked by tetrodotoxin. Somatostatin also inhibited field stimulated alpha adrenergic contractions in the rat vas deferens and rabbit ear artery. However, the responses to direct application of either acetylcholine in the ileum or to norepinephrine in the ear artery or vas deferens were not affected by somatostatin. These results strongly suggest that somatostatin inhibits neuronal release of cholinergic and adrenergic transmitter substances in smooth muscle.     

An endopeptidase associated with bovine neurohypophysis secretory granules cleaves pro-ocytocin/neurophysin peptide at paired basic residues

The octacosapeptide sequence [Tyr18] pro-ocytocin/neurophysin (1-18)NH2 [pro-OT/Np(1-18)NH2] was synthesized and used as substrate to detect endoprotease(s) possibly involved in the processing of this precursor in bovine hypothalamo-neurohypophyseal tract. An endopeptidase (58 Kda) was detected in Lysates made from highly purified neurosecretory granules. This protease which cleaves the peptide bond on the carboxyl side of the Lys-Arg doublet, and no single basic residue, generates both OT-Gly10-Lys11-Arg12+Ala13-Val-Leu-Asp-Leu-Tyr18 (NH2) from the octacosapeptide substrate. In addition, a carboxypeptidase B-like activity converting OT-Gly10-Lys11-Arg12 into OT-Gly10 was detected in the same granule Lysates. It is hypothesized that a combination of these endoprotease and carboxypeptidase B-like activities together with the amidating enzyme of secretory granules might participate in the cleavage and processing of pro-OT/Np in vivo.     

Caveolin-1 null mice develop cardiac hypertrophy with hyperactivation of p42/44 MAP kinase in cardiac fibroblasts

Recently, development ofa caveolin-1-deficient (Cav-1 null) mouse model has allowed thedetailed analysis of caveolin-1's function in the context of awhole animal. Interestingly, we now report that the hearts ofCav-1 null mice are markedly abnormal, despite the fact that caveolin-1is not expressed in cardiac myocytes. However, caveolin-1 is abundantlyexpressed in the nonmyocytic cells of the heart, i.e., cardiacfibroblasts and endothelia. Quantitative imaging studies of Cav-1 nullhearts demonstrate a significantly enlarged right ventricular cavityand a thickened left ventricular wall with decreased systolic function.Histological analysis reveals myocyte hypertrophy withinterstitial/perivascular fibrosis. Because caveolin-1 is thought toact as a negative regulator of the p42/44 MAP kinase cascade, weperformed Western blot analysis with phospho-specific antibodies thatonly recognize activated ERK1/2. As predicted, the p42/44 MAP kinasecascade is hyperactivated in Cav-1 null heart tissue (i.e.,interstitial fibrotic lesions) and isolated cardiac fibroblasts. Inaddition, endothelial and inducible nitric oxide synthase levels aredramatically upregulated. Thus loss of caveolin-1 expression drivesp42/44 MAP kinase activation and cardiac hypertrophy.

     

Immunoglobulin G galactosylation and sialylation are associated with pregnancy-induced improvement of rheumatoid arthritis and the postpartum flare: results from a large prospective cohort study

Introduction  

Improvement of rheumatoid arthritis (RA) during pregnancy has been causatively associated with increased galactosylation of immunoglobulin G (IgG) N-glycans. Since previous studies were small, did not include the postpartum flare and did not study sialylation, these issues were addressed in the present study.     

Fractionation of primary amyloid fibrils. Characterization and chemical interaction of the subunits.

Amyloid fibrils of kappa origin from a patient with primary amyloidosis are dissociated in various denaturants and fractionated into their subunit components on Sepharose 6B. Solubilization of the fibrils in 4 M guanidine-HCl followed by reduction and alkylation produced 22 000 and 17 000 dalton fractions. Without prior reduction and alkylation, these fractions exist as a high molecular weight protein which can be separated on Sepharose 6B. A high molecular weight protein can be directly dissociated from the amyloid fibril with 1% sodium dodecyl sulfate or 1 M NaCl. Reduction and alkylation of this material produces the two lower molecular weight fractions, i.e., 22 000 and 17 000. These have in the first 20 residues identical N-terminal amino acid sequences; they share immunologic identity and have similar tryptic peptide map profiles. Amino acid analysis of the 22 000 dalton fraction is identical with the intact immunoglobulin light chain isolated from the patient's serum. These data suggest that the insoluble amyloid fibril is the result of aggregation by disulfide linkages between the 22 000 and 17 000 dalton fractions.     

Cell type-specific association between two types of spectrin and two types of intermediate filaments

We have demonstrated a differential association between two types of spectrin, from erythrocytes and brain, with two types of intermediate filaments, vimentin filaments and neurofilaments. Electron microscopy showed that erythrocyte spectrin promoted the binding of vimentin filaments to red cell inside-out vesicles via lateral associations with the filaments. In vitro binding studies showed that the association of spectrin with vimentin filaments was apparently saturable, increased with temperature, and could be prevented by heat denaturation of the spectrin. Comparisons were made between erythrocyte and brain spectrin binding to both vimentin filaments and neurofilaments. We found that vimentin filaments bound more erythrocyte spectrin than brain spectrin, while neurofilaments bound more brain spectrin than erythrocyte spectrin. Our results show that both erythroid and nonerythroid spectrins are capable of binding to intermediate filaments and that such associations may be characterized by differential affinities of the various types of spectrin with the several classes of intermediate filaments present in cells. Our results also suggest a role for both erythroid and nonerythroid spectrins in mediating the association of intermediate filaments with plasma membranes or other cytoskeletal elements.