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Biomedical subjects

E Haber

Publications and source records attributed to E Haber.

At least 289 records · Page 16Linked to original sources
PubMed1975

Competitive inhibitors of renin. Inhibitors effective at physiological pH.

Previously we reported the development of competitive inhibitors of renin effective at pH 5.5 (Poulsen, K., Burton, J., and Haber, E. (1973), Biochemistry 12, 3877). At physiologic pH (7.5), the inhibitory constants (Ki) increased and solubility decreased to the point that inhibition could not be demonstrated with these peptides. Modification of the octapeptide sequence, His-Pro-Phe-His-Leu-Leu-Val-Tyr, either by addition of serinol to the carboxyl terminus or by replacement of valine-7 with an isosteric threonyl residue failed to yield peptides active at pH 7.5. Attachment of polyproline sequences to the amino terminus increased solubility from threefold to tenfold and decreased Ki so that competitive inhibition was demonstrable at physiologic pH. In addition, if leucine-6 was replaced in these peptides with a phenylalanyl or tyrosyl residue, Ki decreased (3-12 muM) to give effective competitive inhibitors at physiologic pH in both buffer and in plasma.

Binding Sites↗
PubMed1975

Purification of hog renin by affinity chromatography using the synthetic competitive inhibitor (D-Leu6)octapeptide.

The renin substrate analog His-Pro-Phe-His-Leu-D-Leu-Val-Tyr ([D-Leu6]-octapeptide) acts as a potent inhibitor of renin because of the D-amino acid substitution at the cleavage site. This inhibitor was coupled to CNBr-activated Sepharose 4B to yield a support for affinity chromatography. Hog renin with a specific activity of 1.2 Goldblatt units/mg was in one step purified 195-fold to a final specific activity of 234 Goldblatt units/mg. Application of a pH gradient from 5.0 to 7.5 to the support was found to be the most successful elution program, probably because the [D-Leu6]-octapeptide is not an inhibitor for renin at neutral pH.

Animals↗
PubMed1975

The application of 0.1 M quadrol to the microsequence of proteins and the sequence of tryptic peptides.

In an effort to extend automated Edman degradation to nanomole quantities of protein, the method of sequenator analysis described by Edman and Begg (Edman, P., and Begg, G. (1967), Eur. J. Biochem. 1, 80) was modified to permit long degradations in the absence of carrier proteins. By using an aqueous 0.1 M Quadrol program with limited, combined benezene-ethyl acetate solvent extractions, as well as a change in the delivery system for heptafluorobutyric acid, it was possible to recover and identify the first 30 amino acid residues from a sequenator run on 7 nmol of myoglobin. For 3 nmol of myoglobin, 20 steps could be identified. PTH-amino acids were identified by gas-liquid chromatography and thin-layer chromatography on polyamide sheets. Without using a carrier protein the cup to prevent mechanical losses (Niall, H. D., Jacobs, J. W., Van Rietshoten, J., and Tregear, G. W. (1974), FEBS Lett. 41, 62), the repetitive yield using this program was 93-96%. The same program has been applied successfully to peptides of 14 or more residues with or without modification by Braunitzer's reagent and to a number of larger peptides and proteins including a 216 residue segment of rabbit antibody heavy chain in which a sequence of 35 steps was accomplished on 25 nmol.

Amino Acid Sequence↗
PubMed1975

Diversity of light chain variable region sequences among rabbit antibodies elicited by the same antigens.

We report the complete variable region sequences of three homogeneous rabbit antibody light chains and the partial sequences of five others. Wehn these are compared to other published rabbit light chain sequences, two regions of markedly increased variability are revealed, which are homologous in position to the first and third hypervariable regions of murine and human myeloma light chains. In addition, there is increased variability among the first three residues at the aminoterminal end. A hypervariable region homologous to that identified at positions 50 to 56 in myeloma light chains is not present in these rabbit antibody light chains. The available three-dimensional models of Fab fragments based on x-ray crystallography indicate that neither the amino-terminal portion of the light chain nor the region homologous to positions 50 to 56 forms a part of the combining site. Comparison of the hypervariable regions among six light chains from antibodies to Type III pneumococcal polysaccharide and among four from antibodies to Type VIII pneumococcal polysaccharide suggests that a large number of different sequences may be found in antibodies specific for these relatively simple antigens. Certain residues outside of the hypervariable regions are invariant in the rabbit light chains and correspond to residues that are required for proper chain folding in human and murine myeloma light chains, indicating that the general conformation of myeloma light chains is the same as that of light chains of elicited antibodies.

Amino Acid Sequence↗
PubMed1975

Inhibition of angiotensin conversion and prevention of renal hypertension.

Renal artery constriction in the unilaterally nephrectomized, trained dog, with maintained renal arterial hypotension, produces a prompt increase in systemic renin activity and blood pressure. The hypertension normally induced by renal artery stenosis is prevented by prior treatment with the nonapeptide Pyr-Trp-Pro-Arg-Pro-Gln-Ile-Pro-Pro (SQ 20, 881), which blocks conversion of angiotensin I to angiotensin II. Constant intravenous infusion of the inhibitor over several days of renal artery constriction prevents the development of chronic renovascular hypertension. Furthermore, a single injection of the nonapeptide restores blood pressure to normal in the early phase of renovascular hypertension, but becomes progressively less effective as salt and water retention occurs in the chronic stage when plasma renin activity returns to control levels. These data provide strong evidence that the renin-angiotensin system is responsible for the initiation of renovascular hypertension in the one-kidney Goldblatt dog, but that other factors become increasingly important in chronic renovascular hypertension.

Angiotensin II↗
PubMed1975

Suppression of plasma renin and plasma aldosterone during water immersion in normal man.

Previous studies from this laboratory have demonstrated that the redistribution of blood volume and concomitant relative central hypervolemia induced by water immersion to the neck (NI) results in a significant natriuresis which is quantitative identical to that induced by the acute administration of 2 liters of saline. Since the central hypervolemia induced by NI occurs without concomitant alterations in serum sodium and potassium concentration, the NI model was utilized to assess the role of volume in the regulation of both plasma renin (PRA) and plasma aldosterone (PA) in man. Nine normal subjects were studied on two occasions while in balance on a 10 meq Na, 100 meq K diet; Control and NI. The conditions of seated posture and time of day were identical. Blood for PRA and PA was obtained at 30-min intervals for 6 h. NI produced a profound suppression of PRA as early as 30 min with maximal suppression (62%) by 180 min (P less than 0.001). Recovery from NI was associated with a prompt return to pre-study levels. The changes in PA paralleled those of PRA with regard to both the rapidity and magnitude of the suppression (r = 0.993: P less than 0.001). These data emphasize the importance of central volume per se as a primary determinant of PRA and PA regulation in normal man. Furthermore, the current studies confirm the importance of the renin-angiotensin axis in the control of volume-related changes in PA in normal man. The ability of NI to induce a prompt and parallel suppression of PRA and PA without concomitant alterations in plasma composition, suggests that NI may be a preferred investigative tool for assessing the effects of volume expansion on renin-aldosterone.

Adult↗
PubMed1975

The role of the renin--angiotensin--aldosterone system in cardiovascular homeostasis in normal man.

1. To examine the role of angiotensin II in the maintenance of blood pressure and control of aldosterone secretion, eight normal human subjects were studied on a tilt table in sodium-replete and sodium-depleted states, before and after the administration of an angiotensin converting-enzyme inhibitor (CEI). 2. Administration of CEI was followed by a marked fall in blood pressure on tilting in sodium-depleted, but not in sodium-replete, subjects. CEI administration also resulted in a rise in plasma renin activity in the supine position, in the absence of haemodynamic change. The rise in plasma aldosterone observed both in response to tilting and sodium depletion did not occur after CEI, even though plasma renin activities were higher. 3. These results indicate that: (a) angiotensin II is essential for blood pressure control in the sodium-depleted individual; (b) angiotensin II exerts direct feedback control on renin secretion; (c) angiotensin II is the primary stimulus to aldosterone secretion in response to both sodium depletion and posture.

Adult↗
PubMed1975

The interdomain disulfide bond of a homogeneous rabbit pneumococcal antibody light chain.

Rabbit light chain 3315, prepared from a homogeneous antipneumococcal antibody, was subjected to hydrolysis by pepsin without prior reduction and alkylation of the intrachain disulfide bonds. Gel filtration of the hydrolysate on Sephadex G-10, G-15, and G-25 and ion exchange chromatography on SP-Sephadex yielded several disulfide bridge peptides. These were fully reduced and alkulated and sequenced by Edman degradation. The peptides were located in the light chain sequence determined in independent studies from our laboratory. The half-cystine residues in this KB rabbit chain are located at positions 23, 80, 88, 134, 171, 194, and 214. The extra disulfide bridge extends between residues 80 and 171, thus joining the variable and constant domains. This is consistent with x-ray diffraction crystallographic studies showing that the corresponding residues in human light chains are separated by a distance compatible with disulfide bond formation.

Amino Acid Sequence↗
PubMed1974

Transformation by simian virus 40 of spleen cells from a hyperimmune rabbit: evidence for synthesis of immunoglobulin by the transformed cells.

Spleen cells derived from a rabbit hyperimmunized with a Type III pneumococcal vaccine were exposed to simian virus 40 in vitro. After 114 days, transformed cells growing on the surface of one culture dish were observed and a cell line was established. The transformed cells had a morphology characteristic of cells transformed by simian virus 40, contained the simian virus 40-specific T antigen, and yielded infectious simian virus 40 upon cultivation with indicator cells in the presence of Sendai fusion factor. Transformed cells incorporated labeled amino acid into protein with the antigenic properties of rabbit immunoglobulin G.

Animals↗
PubMed1974

Transformation by simian virus 40 of spleen cells from a hyperimmune rabbit: demonstration of production of specific antibody to the immunizing antigen.

Extracts of spleen cells obtained from a rabbit hyperimmunized with Type III pneumococcal vaccine and transformed with simian virus 40, were subjected to agarose gel electrophoresis in the presence of an [(125)I]S3 polysaccharide-protein conjugate. Binding of radioactivity in the gamma globulin region was observed. Extracts and media obtained from labeled cell cultures contained a protein that bound to an S3, but not to an S8 or inactivated S3 immunoadsorbent. After elution, the bound protein showed a single band on isoelectric focusing which corresponded in isoelectric point to one of the serum anti-S3 antibodies of the donor rabbit. These observations strongly suggest that a normal committed lymphoid cell may be brought into continuous culture by virus transformation and yet retain its ability to synthesize specific antibody.

Animals↗