Biomedical subjects

R Shapiro

Publications and source records attributed to R Shapiro.

At least 37 records · Page 2Linked to original sources

PubMed1991

Dual site model for the organogenic activity of angiogenin.

The residues that are indispensable for the ribonucleolytic activity of angiogenin are also known to be essential for its angiogenic activity. We now demonstrate that residues in another region of the protein, devoid of catalytic residues, are additionally required for angiogenesis. Endoproteinase Lys-C or a baby hamster kidney cell protease cleaves angiogenin at the peptide bond either between Lys-60 and Asn-61 or between Glu-67 and Asn-68, respectively. The two polypeptide fragments resulting from either cleavage remain linked by disulfide bonds. These two derivatives and des-(Asn61-Glu67)-angiogenin--in which both bonds are cleaved--retain their ribonucleolytic activities toward tRNA, 18S and 28S rRNA, and dinucleoside phosphates but are no longer angiogenic on the chicken embryo chorioallantoic membrane. Further, their capacity to elicit a second messenger response in endothelial cells is greatly decreased. Moreover, none of these three derivatives inhibit angiogenin-induced angiogenesis. This contrasts with two active site mutants of angiogenin. These results identify the residues from 60 to 68 as a region of angiogenin that is part of a cell-surface receptor binding site [see accompanying manuscript: Hu, G.-F., Chang, S.-I., Riordan, J.F. & Vallee, B.L. (1991) Proc. Natl. Acad. Sci. USA 88, 2227-2231] and serve as the basis for a dual site model of the organogenic activity of angiogenin.

Amino Acid Sequence↗

PubMed1991

Interaction of human placental ribonuclease with placental ribonuclease inhibitor.

The interactions of human placental ribonuclease inhibitor (PRI) with bovine pancreatic ribonuclease (RNase) A and human angiogenin, a plasma protein that induces blood vessel formation, have been characterized in detail in earlier studies. However, studies on the interaction of PRI with the RNase(s) indigenous to placenta have not been performed previously, nor have any placental RNases been identified. In the present work, the major human placental RNase (PR) was purified to homogeneity by a five-step procedure and was obtained in a yield of 110 micrograms/kg of tissue. The placental content of angiogenin was also examined and was found to be at least 10-fold lower than that of PR. On the basis of its amino acid composition, amino-terminal sequence, and catalytic properties, PR appears to be identical with an RNase previously isolated from eosinophils (eosinophil-derived neurotoxin), liver, and urine. The apparent second-order rate constant of association for the PR.PRI complex, measured by examining the competition between PR and angiogenin for PRI, is 1.9 X 10(8) M-1 s-1. The rate constant for dissociation of the complex, determined by HPLC measurement of the rate of release of PR from its complex with PRI in the presence of a scavenger for free PRI, is 1.8 X 10(-7) s-1. Thus the Ki value for the PR.PRI complex is 9 X 10(-16) M, similar to that obtained with angiogenin, and 40-fold lower than that measured with RNase A. Complex formation causes a small red shift in the protein fluorescence emission spectrum, with no significant change in overall intensity. The fluorescence quantum yield of PR and the Stern-Volmer constant for fluorescence quenching by acrylamide are both high, possibly due to the presence of an unusual posttranslationally modified tryptophan residue at position 7 in the primary sequence.

Amino Acids↗

PubMed1991

Effects of in utero and postnatal sodium saccharin exposure on the nutritional status of the young rat. I. Effects at 30 days post-birth.

The incidence of sodium saccharin (NaS)-associated bladder tumours in male rats increases when exposure to high doses begins in utero or at birth compared with treatment after weaning. The present experiment evaluated the effect of NaS exposure on selected physiological parameters in young second generation rats. 6-wk-old male and female Sprague-Dawley rats were placed on either a diet supplemented with 7.5% NaS or an untreated diet, and mated 4-6 wk later. Treatment was continued through lactation and the offspring were weaned on to the same diet. Body weights were significantly depressed in NaS-treated litters by 4 days after birth, and were 35% lower than controls by 30 days when the animals were killed. NaS treatment of the offspring was associated with an increase in faecal moisture content and caecal content weight, changes in several urinary analytes, a 50% increase in serum cholesterol a 10-fold increase in serum triglycerides and decreases in serum and hepatic vitamins. In addition, NaS-treated dams and pups were anaemic. Relatively few differences between males and females were noted, but significant inter-litter differences existed. The numerous physiological changes indicate that 7.5% dietary NaS exceeds the maximum tolerated dose for weanling rats.

Animals↗

PubMed1991

Effects of in utero and postnatal sodium saccharin exposure on the nutritional status of the young rat. II. Dose response and reversibility.

A previous study in our laboratory demonstrated that 30-day-old Sprague-Dawley rats exposed to 7.5% sodium saccharin (NaS) since conception differ from untreated rats in several physiological parameters. In the present study, to determine the dose response of the changes associated with NaS treatment, animals were evaluated at 30 days post-birth, after treatment with dietary levels of 0, 1, 3 or 7.5% NaS since conception. Most physiological consequences of NaS treatment in the weanling rat, including anaemia and reductions in serum folate and vitamin A concentrations, were dose dependent. Serum vitamin E, cholesterol and triglyceride concentrations were decreased at the two lower doses of NaS but were significantly increased with 7.5% NaS. The no-effect level (NOEL) was similar for physiological effects and for bladder tumour production in two-generation studies (1% NaS in the diet). The reversibility of the effects of 7.5% NaS was examined in 90-day-old rats. The increases in lipids and vitamin E were reversible. Although values for haematological parameters and serum vitamin A remained significantly reduced at 90 days, changes were less severe than at 30 days. Histological examinations revealed that the effects of 7.5% dietary NaS on the bladder were negligible, indicating that the physiological changes observed in the young rat are probably not directly related to the production of bladder tumours.

Animals↗

PubMed1991