Identification of a peptidase which processes atrial natriuretic factor precursor to its active form with 28 amino acid residues in particulate fractions of rat atrial homogenate

With the objective of identifying specific peptidase responsible for the processing of atrial natriuretic factor precursor pro-ANF to the circulating active form ANF (99-126), a fluorometric assay method was devised using synthetic fluorogenic substrate Boc-Ala-Gly-Pro-Arg-MCA(methylcoumarinamide) which contains the amino acid sequence immediately adjacent to the arginyl peptide bond which is cleaved in the natural processing of pro-ANF. A protease which selectively cleaves this bond and produces the natural circulating peptide was identified in the particulate fraction of rat atrial homogenate and was solubilized by 1.6 M KCl. It was partially purified by affinity chromatography heparin-agarose column and was shown to be a serine protease. Its reaction product with natural pro-ANF was identified as ANF (99-126) containing 28 amino acid residues.     

Evidence for age-related change in plasma 19-hydroxyandrostenedione

The steroid, 19-hydroxyandrost-4-ene-3, 17-dione (19-hydroxyandrostene-dione, 19-OH-A-dione) has been known to enhance the mineralocorticoid action of aldosterone. To investigate the age-related change in the plasma 19-OH-A-dione concentration, plasma 19-OH-A-dione, androst-4-ene-3, 17-dione (A-dione), aldosterone and cortisol of 38 non-hypertensive healthy subjects (18 young men and 20 aged men) measured by specific radioimmunoassays. The basal plasma 19-OH-A-dione and A-dione concentration in aged men was significantly lower than in young men (P less than 0.01). Moreover, there was found to be a positive correlation between plasma 19-OH-A-dione and A-dione (P less than 0.01). On the other hand, plasma aldosterone and cortisol in aged men showed a tendency to decrease, but no statistical significance compared to young men was observed. This study demonstrated that there was an apparent age-related decrease not only in plasma A-dione, but also in plasma 19-OH-A-dione, an amplifier or aldosterone action.     

Binding of [3H]befunolol to beta-adrenoceptors in cardiac muscles of fetal and neonatal rat

Characterization of beta-adrenoceptors was studied in heart muscles of rat fetus and neonate. The results of binding assay with [3H]befunolol, a beta-adrenergic partial agonist, to membrane fractions from rat heart muscles indicate that beta-adrenoceptors contain two different affinity sites. In the presence of 5'-guanylylimidodiphosphate, the low affinity site was reduced, while the high affinity site was not affected. The dissociation constants for both sites did not change during pre- and post-natal development. But the maximum binding sites for both sites decreased slightly but significantly (p less than 0.05) during development. A 10-fold decrease in norepinephrine sensitivity and isoprenaline sensitivity during pre- and post-natal development was not explained by the slight decrease in the maximum binding sites.     

Nucleosomelike structures associated with chromosomes of the archaebacterium Halobacterium salinarium.

Chromosomes of the halophilic archaebacterium Halobacterium salinarium were examined by electron microscopy after being spread onto water. The major part of the chromosomal DNA was associated with protein particles with diameter of 9.4 nm, arranged tandemly along the DNA fibers. Thus, the primary structure of the chromosome resembles that of eucaryote chromosomes.     

Synthesis of aminosterols and their derivatives

Reactions of steroidal epoxides such as 5,6 alpha-epoxy-5 alpha-cholestane (I) and its 3 beta-chloro (II) and 3 beta-acetoxy (III) analogs with urea in dimethylformamide afforded 6 beta-amino-5 alpha-cholestan-5-ol (IV-VI), 6 beta-amino-N-formyl-5 alpha-cholestan-5-ol (VII-IX), and 6 beta-amino-N-amido-5 alpha-cholestan-5-ol (X-XII), along with the 5 alpha-cholestane-5,6 beta-diol (XIII-XV). In addition to these compounds, the 3 beta-acetoxy analog also afforded the N-carboxyl derivative (XVI).     

Porcine brain natriuretic peptide receptor in bovine adrenal cortex

The action of porcine brain natriuretic peptide (pBNP) on the steroidogenesis was investigated in cultured bovine adrenocortical cells. Porcine BNP induced a significant dose-dependent inhibition of both ACTH- and A II-stimulated aldosterone secretion. 10(-8) M and 10(-7) M pBNP also significantly inhibited ACTH-stimulated cortisol and dehydroepiandrosterone (DHEA) secretions. Binding studies of [125I]-pBNP to bovine adrenocortical membrane fractions showed that adrenal cortex had high-affinity and low-capacity pBNP binding sites, with a dissociation constant (Kd) of 1.70 x 10(-10) M and a maximal binding capacity (Bmax) of 19.9 fmol/mg protein. Finally, the 135 Kd radioactive band was specially visualized in the affinity labeling of bovine adrenal cortex with disuccinimidyl suberate (DSS). These results suggest that pBNP may have receptor-mediated suppressive actions on bovine adrenal steroidogenesis, similar to that in atrial natriuretic peptide (ANP).     

Molecular cloning, sequence analysis and expression of a cDNA encoding human type-1 angiotensin II receptor.

We isolated a cDNA encoding type-1 angiotensin II receptor from a human liver cDNA library. The cDNA had an open reading frame encoding a protein of 359 amino acid residues with a relative Mr of 41,060. The deduced amino acid sequence of the human angiotensin II (Ang II) receptor was 95.3% and 94.2% identical to those of bovine and rat type-1 Ang II receptors, respectively, and had a significant similarity with the G protein-coupled receptor. The rank order of the binding to the receptor expressed in COS-7 cells was Ang II greater than Ang III greater than Ang I. The expression of the Ang II receptor mRNA was detected in human liver, lung, adrenal and adrenocortical adenomas but not in adrenomedullary tumor, pheochromocytoma, by Northern blot analysis.     

Structure-receptor binding relationships of sarafotoxin and endothelin in porcine cardiovascular tissues

The specific binding of 125I-sarafotoxin S6b was observed in the microsomal fractions from porcine thoracic aorta, and two vasoconstrictive peptides with strikingly homologous structures, sarafotoxin (SRT) and endothelin (ET), interact with a common receptor of the vasculature. The order of the potency of an each endothelin or sarafotoxin analogue as a competitor against 125I-sarafotoxin S6b binding was ET-1 greater than ET-2 greater than SRT S6b greater than ET-3 much greater than SRT S6c. The hydrophobic carboxyl-terminal tail and intramolecular disulfide bridges are essential for the binding activity. In addition, Ser4, Ser5 and Lys9 seem to be important for the activity while the 6th residue does not affect the activity.     

DNA Damage Levels Determine Cyclobutyl Pyrimidine Dimer Repair Mechanisms in Alfalfa Seedlings

Ultraviolet radiation in sunlight damages DNA in plants, but little is understood about the types, lesion capacity, and coordination of repair pathways. We challenged intact alfalfa seedlings with UV doses that induced different initial levels of cyclobutyl pyrimidine dimers and measured repair by excision and photoreactivation. By using alkaline gel electrophoresis of nonradioactive DNAs treated with a cyclobutyl pyrimidine dimer-specific UV endonuclease, we quantitated ethidium-stained DNA by electronic imaging and calculated lesion frequencies from the number average molecular lengths. At low initial dimer frequencies (less than ~30 dimers per million bases), the seedlings used only photoreactivation to repair dimers; excision repair was not significant. At higher damage levels, both excision and photorepair contributed significantly. This strategy would allow plants with low damage levels to use error-free repair requiring only an external light energy source, whereas seedlings subjected to higher damage frequencies could call on additional repair processes requiring cellular energy. Characterization of repair in plants thus requires an investigation of a range of conditions, including the level of initial damage.