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Biomedical subjects

R Benveniste

Publications and source records attributed to R Benveniste.

At least 55 records · Page 3Linked to original sources
PubMed1977

Possible evidence for the existence of a growth hormone fragment in porcine pituitary.

In an attempt to search for growth hormone fragments in the pituitary, a radioimmunoassay was developed for a 55 residue S-amino-ethylated CNBr fragment (fragment B) of porcine growth hormone corresponding to residues 126-180 of human growth hormone. The assay was sensitive to 50 pg of fragment B whereas displacement of 125I-labelled fragment B by procine growth hormone required a 10(3) M excess and was non-parallel. In a homogolous porcine growth hormone radioimmunoassay, fragment B was non-reactive. Gel filtration of an extract of porcine pituitary on Sephadex G-75 revealed three peaks of fragment B immunoreactivity: peak I (29% of total immunoreactivity) eluted in the void volume, peak II (49%) eluted in the position of growth hormone, and peak III (12%) was more retarded than fragment B. Nearly all of the growth hormone immunoreactivity eluted as a single peak in the position of 125I-labelled porcine growth hormone. The dilution curve of peak III but not of peaks I or II was parallel to that of fragment B. The results indicate the existence within porcine pituitary of material cross-reactive with a portion of the growth hormone molecule, possible representing a growth hormone fragment.

Animals↗
PubMed1975

Alpha subunit of glycoprotein hormone: presence in peripheral serum after LHRH.

A method is described for the selective measurement of human luteinizing hormone (hLH) and alpha subunit. The assays employ highly purified tracers of hLH and of subunit of human chorionic gonadotropin (hCGalpha) and a "mixed population" of antibody: Population I (directed against determinants on beta subunit of hCG) and Population II (directed against determinants on alpha subunit of hCG). The former is present in greater concentration than the latter. When the mixed antibody is used at higher dilution (1:1.2x10(6)), Population II is effectively diluted out, and using 125I-labelled hLH as tracer, the assay recognize hLH, hCG and their beta subunits 20-50 times more sensitively than hCGalpha. When the mixed antibody is used at fivefold higher concentration, Population I is present in relative excess and acts as a "sink" for hCG, hLH and their beta subunits. Under these conditions, using 125I-hCGalpha as tracer, the assay recognize the alpha subunit 20 to 50-fold more sensitively than hLH and hCG. These assays have been employed in the study of sera which have been filtered over Sephadex G-100. Alpha subunit was detected in serum within minutes after intravenous injection of luteinizing hormone releasing hormone (LHRH) in four subjects tested.

Adolescent↗
PubMed1975

Heterogeneity of purified human pituitary luteinizing hormone: effect on hormone measurement by radioimmunoassay.

Purified preparations of human luteinizing hormone (hLH), Hartree IRC-2, and NIH LER-960, have been examined after gel filtration of unlabelled and iodinated hormone. Several peaks of radioactivity were observed corresponding to dimeric (peak I), monomeric (peak II), and sub-unit (peak III) lLH forms. The immunologic and receptor activities of each fraction have been evaluated, Receptor activity was found in peaks I and II but not in peak III. Within peak II all fractions were not equally active in the receptor assay, and maximum activity appeared to correspond to molecules with elution characteristics similar to the unlabelled molecule. All fractions of peak II were immunologically active when tested against rabbit anti-hCG in excess. Two immunoassay systems with improved specificity for hLH and hLH-alpha, respectively, have been employed to show the presence of alpha subunit in one of the hLH preparations. These data have relevance with respect to testing of immuno and receptor potencies of hLH preparations.

Animals↗
PubMed1975

Isolated deficiency of follicle-stimulating hormone: Further studies.

We record further studies over the past 2 yr on a unique female subject with isolated follicle-stimulating hormone (hFSH) deficiency, who developed human anti-gFSH antibodies after treatment with exogenous urinary gonadotropins. Administration of LRH resulted in a significant rise in serum hLH, but hFSH levels remained undetectable, "alpha Subunit" (the common alpha chain of the glycoprotein hormones) was detectable in basal samples obtained from our patient, and rose sharply after LRH. This is concordant with the hypothesis that the defect in our subject may be in the synthesis of the beta chain of hFSH, but it does not exclude other possibilities. The concentration of hFSH antibodies in the patient's serum has been monitored and her response to a further course of exogenous gonadotropins is recorded. The anti serum exhibits specificity for the hFSH molecule; the alpha and the beta chains of hFSH are virtually inert in competing with tracer 125-I-hFSH for binding to the antibody.

Adult↗
PubMed1975

Big growth hormone (GH): conversion to small GH without peptide bond cleavage.

Mercaptoethanol treatment of big growth hormone (GH) obtained from human pituitary resulted in a 60% conversion to small GH. Further dissociation was obtained by combined treatment with the reducing agent plus urea. The results indicate that the existence of big GH is dependent upon the formation of inter-polypeptide chain disulfide bonds.

Binding Sites↗
PubMed1973

Aminoglycoside antibiotic-inactivating enzymes in actinomycetes similar to those present in clinical isolates of antibiotic-resistant bacteria.

Various species of Streptomyces possess aminoglycoside-modifying enzymes. Streptomyces kanamyceticus contains an enzyme that acetylates the 6'-amino group of kanamycin A and B, gentamicin C(1a), and neomycin. Streptomyces spectabilis produces an enzyme that acetylates the 2'-amino group of the hexose ring of gentamicin C(1a). These enzymes catalyze reactions identical to those catalyzed by enzymes found in gram-negative bacteria containing R(antibiotic resistance)-factors. The discovery of these enzymes suggests the possibility of an evolutionary relationship between the aminoglycosideinactivating enzymes (produced by resistance determinants) in bacteria containing R-factors and similar enzymes found in the actinomycetes.

Acetyltransferases↗
PubMed1973

Structure-activity relationships among the aminoglycoside antibiotics: role of hydroxyl and amino groups.

The close structural similarity of several of the deoxystreptamine-containing aminoglycoside antibiotics (gentamicins, neomycins, kanamycins, tobramycin) and the recent isolation of enzymatically N-acetylated aminoglycosides have permitted a systematic comparison of the structure-activity relationships in this group of antibiotics. The number and location of amino groups on the hexoses and the site of attachment of the other rings to deoxystreptamine have been shown to exert a profound effect on the ability of these compounds to inhibit or to cause misreading of polypeptide synthesis in vitro. The conclusions allow certain predictions to be made concerning the interaction of these compounds with the bacterial ribosome.

Aminoglycosides↗