Sequence homologies in the region preceding the transcription initiation site of the liver estrogen-responsive vitellogenin and apo-VLDLII genes.

In the liver of oviparous vertebrates vitellogenin gene expression is controlled by estrogen. The nucleotide sequence of the 5' flanking region of the Xenopus laevis vitellogenin genes A1, A2, B1 and B2 has been determined. These sequences have been compared to each other and to the equivalent region of the chicken vitellogenin II and apo-VLDLII genes which are also expressed in the liver in response to estrogen. The homology between the 5' flanking region of the Xenopus genes B1 and B2 is higher than between the corresponding regions of the other closely related genes A1 and A2. Four short blocks of sequence homology which are present at equivalent positions in the vitellogenin genes of both Xenopus laevis and chicken are characterized. A short sequence with two-fold rotational symmetry (GGTCANNNTGACC) was found at similar positions upstream of the five vitellogenin genes and is also present in two copies close to the 5' end of the chicken apo-VLDLII gene. The possible functional significance of this sequence, common to liver estrogen-responsive genes, is discussed.

Cloning and functional expression of the human islet GLP-1 receptor. Demonstration that exendin-4 is an agonist and exendin-(9-39) an antagonist of the receptor.

A complementary DNA for a glucagon-like peptide-1 receptor was isolated from a human pancreatic islet cDNA library. The isolated clone encoded a protein with 90% identity to the rat receptor. In stably transfected fibroblasts, the receptor bound [125I]GLP-1 with high affinity (Kd = 0.5 nM) and was coupled to adenylate cyclase as detected by a GLP-1-dependent increase in cAMP production (EC50 = 93 pM). Two peptides from the venom of the lizard Heloderma suspectum, exendin-4 and exendin-(9-39), displayed similar ligand binding affinities to the human GLP-1 receptor. Whereas exendin-4 acted as an agonist of the receptor, inducing cAMP formation, exendin-(9-39) was an antagonist of the receptor, inhibiting GLP-1-induced cAMP production. Because GLP-1 has been proposed as a potential agent for treatment of NIDDM, our present data will contribute to the characterization of the receptor binding site and the development of new agonists of this receptor.

Thyroid hormones stimulate expression and modification of cytoskeletal protein during rat sciatic nerve regeneration.

Peripheral neurons can regenerate after axotomy; in this process, the role of cytoskeletal proteins is important because they contribute to formation and reorganization, growth, transport, stability and plasticity of axons. In the present study, we examined the effects of thyroid hormones (T3) on the expression of major cytoskeletal proteins during sciatic nerve regeneration. At various times after sciatic nerve transection and T3 local administration, segments of operated nerves from T3-treated rats and control rats were examined by Western blotting for the presence of neurofilament, tubulin and vimentin. Our results revealed that, during the first week after surgery, T3 treatment did not significantly alter the level of NF subunits and tubulin in the different segments of operated nerves compared to control nerves. Two or 4 weeks after operation, the concentration of NF-H and NF-M isoforms was clearly increased by T3 treatment. Moreover, under T3-treatment, NF proteins appeared more rapidly in the distal segment of operated nerves. Likewise, the levels of betaIII, and of acetylated and tyrosinated tubulin isotypes, were also up-regulated by T3-treatment during regeneration. However, only the tyrosinated tubulin form appeared earlier in the distal nerve segments. At this stage of regeneration, T3 had no effect on the level of vimentin expression. In conclusion, thyroid hormone improves and accelerates peripheral nerve regeneration and exerts a positive effect on cytoskeletal protein expression and transport involved in axonal regeneration. These results help us to understand partially the mechanism by which thyroid hormones enhance peripheral nerve regeneration. The stimulating effect of T3 on peripheral nerve regeneration may have considerable therapeutic potential.

An angiotensin II- and NF-kappaB-dependent mechanism increases connexin 43 in murine arteries targeted by renin-dependent hypertension.

AIMS: Connexins (Cxs) play a role in the contractility of the aorta wall. We investigated how connexins of the endothelial cells (ECs; Cx37, Cx40) and smooth muscle cells (SMCs; Cx43, Cx45) of the aorta change during renin-dependent and -independent hypertension. METHODS AND RESULTS: We subjected both wild-type (WT) mice and mice lacking Cx40 (Cx40(-/-)), to either a two-kidney, one-clip procedure or to N-nitro-l-arginine-methyl-ester treatment, which induce renin-dependent and -independent hypertension, respectively. All hypertensive mice featured a thickened aortic wall, increased levels of Cx37 and Cx45 in SMC, and of Cx40 in EC (except in Cx40(-/-) mice). Cx43 was up-regulated, with no effect on its S368 phosphorylation, only in the SMCs of renin-dependent models of hypertension. Blockade of the renin-angiotensin system of Cx40(-/-) mice normalized blood pressure and prevented both aortic thickening and Cx alterations. Ex vivo exposure of WT aortas, carotids, and mesenteric arteries to physiologically relevant levels of angiotensin II (AngII) increased the levels of Cx43, but not of other Cx. In the aortic SMC line of A7r5 cells, AngII activated kinase-dependent pathways and induced binding of the nuclear factor-kappa B (NF-kappaB) to the Cx43 gene promoter, increasing Cx43 expression. CONCLUSION: In both large and small arteries, hypertension differently regulates Cx expression in SMC and EC layers. Cx43 is selectively increased in renin-dependent hypertension via an AngII activation of the extracellular signal-regulated kinase and NF-kappaB pathways.

Decreased thermogenic response to an oral glucose load in older subjects.

The thermogenic response to a 100 g oral glucose load was studied by indirect calorimetry in 13 older persons (age range, 38-68 years) and compared with that of 16 young matched controls of similar body weight (age range, 19-30 years). The glucose-induced thermogenesis measured over 180 min and expressed as a per cent of the energy content of the glucose load was found to be reduced in the older subjects, i.e., 5.8 +/- 0.3 per cent vs 8.6 +/- 0.7 per cent, P less than 0.002). This was also accompanied by a significant decrease in the glucose oxidation rate when averaged over the same three-hour period following the glucose load, i.e., 153 mg/min vs 213 mg/min in the control subjects (P less than 0.001) despite a similar time course of glycemia. This study suggests that the thermogenic response to an oral glucose load is blunted in older people, and this may represent an additional factor that contributes to the decreased energy requirement with age and therefore to the increased propensity to obesity if energy intake is not adjusted.

Probing the interaction between feline immunodeficiency virus and CD134 by using the novel monoclonal antibody 7D6 and the CD134 (Ox40) ligand.

The feline immunodeficiency virus (FIV) targets activated CD4-positive helper T cells preferentially, inducing an AIDS-like immunodeficiency in its natural host species, the domestic cat. The primary receptor for FIV is CD134, a member of the tumor necrosis factor receptor superfamily, and all primary viral strains tested to date use CD134 for infection. We examined the expression of CD134 in the cat using a novel anti-feline CD134 monoclonal antibody (MAb), 7D6, and showed that as in rats and humans, CD134 expression is restricted tightly to CD4+, and not CD8+, T cells, consistent with the selective targeting of these cells by FIV. However, FIV is also macrophage tropic, and in chronic infection the viral tropism broadens to include B cells and CD8+ T cells. Using 7D6, we revealed CD134 expression on a B220-positive (B-cell) population and on cultured macrophages but not peripheral blood monocytes. Moreover, macrophage CD134 expression and FIV infection were enhanced by activation in response to bacterial lipopolysaccharide. Consistent with CD134 expression on human and murine T cells, feline CD134 was abundant on mitogen-stimulated CD4+ T cells, with weaker expression on CD8+ T cells, concordant with the expansion of FIV into CD8+ T cells with progression of the infection. The interaction between FIV and CD134 was probed using MAb 7D6 and soluble CD134 ligand (CD134L), revealing strain-specific differences in sensitivity to both 7D6 and CD134L. Infection with isolates such as PPR and B2542 was inhibited well by both 7D6 and CD134L, suggesting a lower affinity of interaction. In contrast, GL8, CPG, and NCSU were relatively refractory to inhibition by both 7D6 and CD134L and, accordingly, may have a higher-affinity interaction with CD134, permitting infection of cells where CD134 levels are limiting.