Intracerebroventricular Administration of AT1 Receptor Antisense Oligonucleotides Inhibits the Behavioral Actions of Angiotensin II

Abstract: Antisense Oligonucleotides were developed to study the expression and function of angiotensin type 1 (AT₁) receptors in cultured cells and brain. In both liver epithelial WB and neuro-blastoma N1E-115 cells AT₁ antisense oligomers substantially decreased AT₁ receptor density, whereas angiotensin type 2 (AT₂) receptors remained unchanged. Similarly, repeated intracerebroventricular injections of AT₁ antisense oligomers in rats decreased AT₁ receptor density in hypothalamic-thalamic-septal tissue, and AT₂ receptors were unaffected. Intracerebroventricular antisense oligomers also attenuated drinking elicited by intra-cerebroventricular angiotensin II but not the cholinomimetic carbachol. Collectively, these results demonstrate that antisense Oligonucleotides attenuate angiotensin receptor expression and function in behaving animals.     

Evolution of the ATP-binding-cassette transmembrane transporters of vertebrates

The ATP-binding-cassette transmembrane transporters (ABC transporters) known from vertebrates belong to four major subfamilies: (1) the P- glycoproteins (Pgp); (2) the cystic fibrosis transmembrane conductance regulators (CFTR); (3) the Tap proteins encoded with the major histocompatibility complex of mammals; and (4) the peroxisomal membrane proteins. Both Pgp and CFTR have a structure suggesting a past internal gene duplication; a phylogenetic analysis indicated that these duplications occurred independently, while an independent tandem gene duplication occurred in the case of the Tap family. Both the Pgp and Tap proteins show evidence of relationship to bacterial ABC transporters lacking internal duplication, and both are significantly more closely related to the HlyB and MsbA families of transporters from purple bacteria than they are to ABC transporters from nonpurple bacteria. The simplest hypothesis to explain this observation is that eukaryotic Pgp and Tap genes are descended from a mitochondrial gene or genes that were subsequently translocated to the nuclear genome. The Pgp genes of eukaryotes are characterized by a remarkable degree of convergent evolution between the ATP-binding cassettes of their N- terminal and C-terminal halves, whereas no such convergence is seen between the two halves of CFTR genes or between the duplicated Tap genes. Exon 13 of the CFTR gene, which encodes a putative regulatory domain not found in other ABC transporters apart from CFTR, showed high levels of both synonymous and nonsynonymous difference in comparisons among different mammalian species, suggesting that this region is a mutational hot spot.      

Evidence for the presence of β-lactamase inStreptomyces glaucescens and its inhibition by sodium clavulanate

Streptomyces glaucescens is shown to possess -lactamase activity which is inhibitable by clavulanate. This is important in regard to its use as a cloning host for enzymes of \-lactam biosynthesis.     

Emerging mechanisms of the behavioral effects of steroids

Within two models of steroid-modulated behavior, sodium appetite and sexual receptivity, novel mechanisms of steroid action have emerged. These include interactions between different types of steroid receptors, plasticity of synapses, activation of unliganded steroid receptors, and rapid effects of steroids. These mechanisms highlight the diversity of steroid action in the central nervous system.     

Arysulfatase A modulation with pH in multiple sulfatase deficiency disorder fibroblasts.

It has been observed that multiple sulfatase deficiency disorder (MSDD) fibroblasts contained from profoundly deficient to near normal amounts of arylsulfatase (ARS) A depending on the medium in which they were cultured. Our present findings show that the major factor determining the enzyme level is the pH of the medium during growth. In media which became acidic or was maintained at low pH (less than 7), the cells expressed the enzymopathy, while in high pH media (7.4), the cells produced enzyme. The high and low enzyme states were reversible. The ARS A deficiency in MSDD must, therefore, be a secondary manifestation of a mutation in another system.     

Bile salt activation of cerebroside sulphate sulphohydrolase.

The cholate and taurodeoxycholate activations of cerebroside sulphate sulphohydrolase (cerebroside-3-sulphate 3-sulphohydrolase, EC 3.1.6.8) activity of arylsulphatase A (aryl-sulphate sulphohydrolase, EC 3.1.6.1) were compared. Taurodeoxycholate caused a sharp peak of response at a concentration of 1.25 mg/ml (type-I activation). Cholate also showed type-I activation but, in addition, it evoked a second, higher, response plateau at concentrations between 5 and 10 mg/ml (type-II activation). At the pH of the reaction, cholate is converted largely to the sparingly soluble free aicd, so at the high concentrations associated with type-II activation, copious precipitates were formed. It was found that the precipitated material was essential for the type-II activation. Type-I activation appears to involve bile salt interaction with substrate, while type-II activation appears to involve enzyme interaction with solid-phase cholic acid. the putative mutant arylsulphatase A in an unusual form of metachromatic leukodystrophy hydolysed cerebroside sulphate only in the presence of high levels of cholate. The type-II activation may thus be simulating a physiological desulphation reaction.     

Solubilization and Partial Characterization of Angiotensin II Receptors from Rat Brain

Rat brain angiotensin II (Ang II) receptors were solubilized with a yield of 30-40% using the synthetic detergent 3[(3-cholamidopropyl)dimethylammonio)]-1-propanesulfonate. Kinetic analysis employing the high-affinity antagonist 125I-Sar1,Ile8-Ang II indicated that the solubilized receptors exhibited the same properties as receptors present within intact brain membranes. Furthermore, there was a positive correlation (r = 0.99) between the respective pIC50 values of a series of agonist and antagonists competing for 125I-Sar1,Ile8-Ang II labeled binding sites in either solubilized or intact membranes. Moreover, covalent labeling of 125I-Ang II to solubilized receptors with the homo-bifunctional cross-linker disuccinimidyl suberate, followed by gel filtration, revealed one major and one minor binding peak with apparent molecular weights of 64,000 and 115,000, respectively. Two binding proteins of comparable molecular weights (i.e., 112,000 and 60,000) were also identified by covalent cross-linking of 125I-Ang II to solubilized brain membranes followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. In contrast, only the smaller molecular mass binding protein was observed when solubilized membranes were labeled with the antagonist 125I-Sar1,Ile8-Ang II prior to gel filtration, and chromatofocusing of antagonist labeled sites revealed only one peak with an isoelectric point of 6.2. The successful solubilization of these binding sites should facilitate continued investigation of Ang II receptors in the brain.     

Cerebroside sulfatase activator deficiency induced metachromatic leukodystrophy

Two siblings of consanguineous parents had presented with a variety of findings indicative of juvenile metachromatic leukodystrophy (MLD). However, instead of the expected profound deficiency of arylsulfatase A (ARS A), their enzyme levels were about half-normal, and enzyme from fibroblasts had properties identical with the properties of enzyme from normal fibroblasts. Nevertheless, the hydrolysis of cerebroside sulfate by growing fibroblasts was markedly attenuated. Supplementation of the fibroblasts with cerebroside sulfatase activator normalized the response in the loading test. These results imply that the fibroblasts, and by extension the patients, are deficient in activator. Although the defective catabolism of cerebroside sulfate and the clinical manifestations in these patients mimic MLD, the molecular basis is distinct from the classical forms of the disorder.