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Biomedical subjects

R S Levy

Publications and source records attributed to R S Levy.

At least 19 recordsLinked to original sources
PubMed1992

Purification, subunit structure and inhibitor profile of cathepsin A.

Cathepsin A (EC 3.4.16.1), a lysosomal carboxypeptidase, has been purified 1374-fold from pig kidney. Purification steps included concanavalin A-Sepharose and phenyl-Sepharose chromatography and chromatofocusing. The specific activity (16.9 U/mg) of the purified enzyme was significantly higher than previously reported values. The enzyme preparation appeared homogeneous when analyzed by non-denaturing polyacrylamide gel electrophoresis and was free of detectable protease contamination. The molecular mass (M(r) = 97,000), isoelectric point (5.0), and sensitivity to inhibitors were consistent with reported properties of cathepsin A. However, the previously reported three-peptide chain structure was not observed. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the presence or absence of 2-mercaptoethanol demonstrated that the enzyme is composed of two M(r) 47,000 subunits, each of which dissociate in the presence of 2-mercaptoethanol into two polypeptide chains of 19,000 and 31,000.

Amino Acid Sequence↗
PubMed1991

Angiotensin carboxypeptidase activity in urine from normal subjects and patients with kidney damage.

Angiotensin carboxypeptidase (ACP) activity has been detected in urine samples from normal subjects and patients with hypertension and diabetes by determining the enzyme's ability to convert angiotensin I to des-Leu angiotensin I. Gel filtration chromatography of a concentrated urine sample indicated that about equal amounts of the enzyme exist as 100 kDa and 500 kDa molecular weight forms, respectively. This ACP activity co-eluted with activity that cleaved histidine from des-Leu angiotensin I to form angiotensin II and activity that cleaved tyrosine from benzyloxycarbonyl-glutamyl-tyrosine (ZGT). These results suggest that the urinary ACP activity is due to cathepsin A as we have reported previously for the porcine kidney enzyme. Analysis of sequential urine samples from a single individual over a 6-day period revealed as much as a 6-fold fluctuation in creatinine-normalized ACP activity. Of five male healthy adult subjects, the creatinine-normalized urinary ACP activity ranged from 1.7 to 3.7 mU/mL with a mean of 2.8 mU/mL. However, five male patients with renovascular hypertension had elevated levels of ACP activity with a mean of 11.6 mU/mL. Of five male patients with diabetic nephropathy, all had elevated ACP activity levels with a mean of 21.0 mU/mL. It is concluded that ACP activity in the urine is due to cathepsin A probably derived from kidney tissue, and that the release is increased in patients with kidney damage. We suggest that urinary ACP activity should be evaluated further for a possible relationship to renal hypertension and as a potentially early marker for diabetic nephropathy.

Carboxypeptidases↗
PubMed1990

A group intervention model for individuals testing positive for HIV antibody.

The development of a structured psychoeducational support group model for blood donors who tested positive for human immunodeficiency virus Type I antibody is described. Salient group therapy techniques and educational content are discussed, issues of group structure are identified, and the need for support of clinicians is highlighted.

Adaptation, Psychological↗
PubMed1988

Conversion of angiotensin I to angiotensin II by cathepsin A isoenzymes of porcine kidney.

We have reported the existence of a carboxypeptidase in a human renal extract that converts Angiotensin I (AI) to Angiotensin II (AII) in two steps with des-leu-AI (dl-AI) being formed as an intermediate. Since this carboxypeptidase had properties similar to cathepsin A, the ability of cathepsin A to metabolize AI was studied. Cathepsin A was purified from hog kidney with enzyme activity being monitored using both benzyloxycarbonyl-glutamyl-tyrosine (ZGT) and AI as substrates. The procedure separated the expected large and small molecular weight forms of cathepsin A as well as two additional isoenzymes. All of the isoenzymes had carboxypeptidase activity with ZGT, AI, and dl-AI. No detectable cleavage of AII was observed. Cathepsin A,S (small) activity with ZGT or AI as substrate was inhibited to a similar extent by diisopropylfluorophosphate, mersalyl acid, and a decapeptide renin inhibitor. It is concluded that the renal angiotensin carboxypeptidase activity is catalyzed by cathepsin A. By its ability to convert AI to AII, cathepsin A may be a component of the intrarenal renin-angiotensin system.

Angiotensin I↗
PubMed1988

Des-Leu angiotensin I: biosynthesis and drinking response.

The crude rat and bovine synaptosomal lysate from brain can hydrolyze angiotensin I (AI) to des-Leu angiotensin I (AI-dL) and no further. This cytosolic enzyme has a specificity for angiotensin-related sequences, R-His-Pro-Phe-His-Leu and therefore named angiotensin-related carboxypeptidase (ARC). These studies led to the biosynthesis and purification of AI-dL in order to determine if it can provoke a drinking response. This nonapeptide is a potent dipsogen when injected into the cerebroventricles of rats. The drinking response probably requires a second hydrolysis to angiotensin II (AII) since both captopril and saralasin can inhibit this response.

Angiotensin I↗
PubMed1988

Subcellular localization in rat brain of angiotensin-related carboxypeptidase activity distinct from converting enzyme.

Whole brain synaptosomes contain both an isorenin activity and angiotensin-related carboxypeptidase activity. Further hydrolysis of des-Leu angiotensin I (AI-dL) occurs more slowly; hydrolysis of angiotensin II (AII) is negligible. Vasopressin and oxytocin but not vasotocin can inhibit angiotensin-related carboxypeptidase activity. Since AII has been shown to induce vasopressin secretion, this correlation suggests a feedback inhibition by vasopressin of this enzymatic cascade. Commercially available radioimmunoassays for AI and AII show a 3.4 and 6.0% crossreactivity, respectively. When the absolute concentration of AI-dL exceeded 500 ng/ml, both antibodies to AI and AII showed maximal displacement of radiolabel. This suggests that these antibodies may not distinguish between AI-dL from other peptides during immunocytochemistry.

Angiotensin I↗
PubMed1986

Angiotensin II generated by a human renal carboxypeptidase.

Angiotensin II, the potent hypertensive octapeptide, can be generated by a sequential cleavage of the carboxyl-terminal leucine and histidine from angiotensin I by a human renal extract. This extract does not hydrolyze further the resulting octapeptide. The more widely recognized biosynthetic pathway is by the extracellular dipeptide cleavage of angiotensin I by an enzyme which also degrades bradykinin, i.e., angiotensin converting enzyme. The presence of a carboxypeptidase activity capable of generating but not further hydrolyzing angiotensin II was observed in an ammonium sulfate fraction of a human renal extract. This novel enzymatic activity is distinct from angiotensin converting enzyme activity in that it is not dependent upon calcium and is not inhibited by known angiotensin converting enzyme inhibitors.

Amino Acid Sequence↗
PubMed1984

Rapid purification of radioiodinated peptides with Sep-Pak reversed phase cartridges and HPLC.

A simple, rapid method is described for the purification of radioiodinated peptides for use in radioimmuno- and in radioreceptor assays. Iodinated reaction mixtures are applied directly onto Sep-Pak disposable, reversed phase cartridges equilibrated with phosphate buffer. Unreacted 125-iodide and other non-peptide reaction components are eluted with buffer. The peptide fraction is then eluted with 70% buffer: 30% acetonitrile. The peptide fraction is further purified by reversed phase high pressure liquid chromatography to separate the native peptide and the mono- and diiodo-derivatives. In this study the method is used to prepare 125-iodide-labeled monoiodo-leucine enkephalin and monoiodo-angiotensin II, which are free of the parent peptides and diiodo-derivatives and are of maximum obtainable specific radioactivity. The usefulness of these labeled peptides in radioimmuno- and radioreceptor assays is demonstrated by their binding to specific antibodies and receptors, respectively.

Chromatography, High Pressure Liquid↗
PubMed1983

Penicillamine: review and cutaneous manifestations.

D-Penicillamine, a heavy metal chelator used in the treatment of Wilson's disease and other conditions, may be associated with both noncutaneous and cutaneous side effects. Some of the cutaneous lesions are due to a toxic-metabolic effect on connective tissue; some may be explained on the basis of autoimmunity; some are acute sensitivity reactions, and some are secondary to unknown mechanisms. The types of cutaneous manifestations may, in some instances, be correlated with the disease being treated and the dosage and duration of penicillamine therapy.

Autoimmune Diseases↗
PubMed1983

Evoked potential correlates of left hemisphere dominance in covert articulation.

Evoked Potentials (EPs) to a click stimulus were recorded at the temporal areas of both hemispheres of dextral subjects engaged in covert rehearsal of a verbal passage or in covert rehearsal of musical passages. A pattern of left hemisphere attenuation of the click EPs was observed in all subjects during speech rehearsal but not during music rehearsal. The implications of these findings for the issue of electroencephalographic localization of speech production mechanisms in the left hemisphere are discussed.

Adult↗
PubMed1983

Clindamycin compared with penicillin for the treatment of anaerobic lung abscess.

The clinical efficacy of clindamycin was compared with that of penicillin in a randomized study of the treatment of community-acquired putrid lung abscess. After starting therapy, patients treated with clindamycin had a shorter febrile period and fewer days of fetid sputum than patients treated with penicillin (mean 4.4 versus 7.6 days and 4.2 versus 8.0 days, respectively, p less than 0.05). Four of 20 patients treated with penicillin had clinically significant pulmonary or pleural extension of their infection within 10 days after starting therapy; this was not found in any of 19 patients treated with clindamycin (p less than 0.05). Penicillin treatment failed in two additional patients after 20 days of therapy. Within 1 month after treatment, 1 of 4 patients given penicillin for 3 weeks had relapse, but none of the 13 patients given clindamycin for 3 or 6 weeks, and none of the 5 patients given penicillin for 6 weeks had relapse. Overall, only 8 of 15 patients treated with penicillin who could be followed to the end of the study were cured, whereas all 13 patients treated with clindamycin who could be followed were cured (p less than 0.01). These results suggest that penicillin may not be optimal therapy for anaerobic lung abscess.

Adult↗