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Biomedical subjects

F Riva

Publications and source records attributed to F Riva.

At least 19 recordsLinked to original sources
PubMed1992

Adenosine deaminase from Saccharomyces cerevisiae: kinetics and interaction with transition and ground state inhibitors.

Several adenosine analogs, such as coformycin, 2'-deoxycoformycin and erythro-9-(3-nonyl-p-aminobenzyl)adenine (EHNA), which are strong inhibitors of mammalian adenosine deaminase, are much weaker inhibitors of the Saccharomyces cerevisiae enzyme. The specificity of the yeast enzyme is more restricted than that of mammalian adenosine deaminase, particularly towards the ribose moiety and around position 6 and 1 of the substrate. The sulphydryl group appears to be more masked in the yeast than in the mammalian enzyme. The kinetic effects of pH with adenosine substrate and with the inhibitor purine riboside are reported. The findings on specificity and pH kinetic effects can be interpreted in a model involving proton transfer from the -SH group of the enzyme to the N-1 atom of the substrate.

Adenine↗
PubMed1992

Effects of angiotensin converting enzyme inhibitors and calcium antagonists on atrial natriuretic peptide release and action and on albumin excretion rate in hypertensive insulin-dependent diabetic patients.

Abnormalities in sodium homeostasis and in atrial natriuretic peptide (ANP) behavior could play a role in determining and accelerating the development of glomerular hypertension, hypertension, and microalbuminuria in insulin-dependent diabetes. The aim of the present study was to investigate in 32 hypertensive insulin-dependent diabetic patients (HD) with an altered albumin excretion rate the natriuretic response and ANP release to saline load (2 mmol/kg 90 min, and the effects angiotensin converting enzyme inhibitor therapy 2.5 to 5.0 mg cilazapril, once daily), and calcium antagonists (sustained release verapamil: 120 to 240 mg Isoptin Press, once daily, and long acting nifedipine: 20 to 40 mg Adalat AR, twice daily) on sodium homeostasis and albumin excretion rate. Eight normal subjects matched for sex, age, and weight served as controls. The 32 HD patients showed a blunted response in ANP release and sodium excretion during saline infusion in comparison with controls. The cilazapril and verapamil treatments were tested in 16 of the 32 HD patients and were both effective in ameliorating natriuretic and ANP response to saline load and in decreasing albumin excretion rate. The combined cilazapril and verapamil treatment further improved both these parameters in these patients, although blood pressure levels were comparable. The other 16 HD patients underwent sequential verapamil and nifedipine treatment. Verapamil was more effective than nifedipine in improving natriuresis and ANP release to saline load and in lowering the albumin excretion rate. The results of the present study demonstrate that sodium homeostasis and ANP release are altered in hypertensive nephropathic patients, and both cilazapril and verapamil are more effective than nifedipine in ameliorating natriuresis, ANP release, and albumin excretion rate.

Adult↗
PubMed1992

Renal hemodynamics and albumin excretion rate in patients with diabetes secondary to acquired pancreatic disease.

OBJECTIVE--To assess kidney function and AER in patients with PD. RESEARCH DESIGN AND METHODS--Thirty-three patients with PD (age 52 +/- 7 yr, duration of disease 11 +/- 6 yr, BMI 24 +/- 3 kg/m2) and 33 patients with IDDM were matched for sex, BMI, and duration of disease. GFR and RPF were determined by single injection of [51Cr]EDTA and [125I]hippurate. AER was measured by radioimmunoassay in a single timed overnight urine collection. RESULTS--GFR and RPF were, respectively, 113 +/- 35 and 441 +/- 145 ml.min-1.73 m2 in patients with PD and 123 +/- 30 and 549 +/- 94 (P < 0.001) in IDDM. FF was significantly higher in patients with PD (0.26 +/- 0.05 vs. 0.22 +/- 0.03; P < 0.001). Prevalence of hyperfiltration (GFR > 135 ml.min-1.1.73 m2) was similar in both groups (30% in patients with PD vs. 28% in those with IDDM). Geometric mean of urinary AER was 10.4 micrograms/min (range 1-186) in patients with PD and 11.2 (1-198) in IDDM patients. Some 30.3% of patients with PD and 18% of those with IDDM were microalbuminuric (AER > 20 micrograms/min). By multiple regression analysis, AER was significantly related to systolic (P < 0.04) and diastolic blood pressure (P < 0.01) and to BMI (P < 0.03) in patients with PD. Retinopathy was more frequent in microalbuminuric patients with PD than in those without elevated AER. CONCLUSIONS--We suggest that early renal abnormalities occur similarly in patients with PD and IDDM.

Adult↗
PubMed1992

Adenosine deaminase from bovine brain: purification and partial characterization.

Bovine brain adenosine deaminase cytoplasmatic form was purified about 450 fold by salt fractionation, column chromatography on DEAE-cellulose, octyl-sepharose 4B and affinity chromatography on CH-sepharose 4B 9-(p-aminobenzyl)adenine. The purified enzyme was homogeneous on disc gel electrophoresis; the enzyme had a molecular mass of about 65 kDa with an isoelectric point at pH 4.87. The Km values for adenosine and 2'-deoxyadenosine were 4 x 10(-5) and 5.2 x 10(-5) M, respectively. The enzyme showed a great stability to temperature with a half life of 15 hours at 53 degrees C significantly different compared to that known for other mammalian forms of this enzyme. Aza and deaza analogs of adenosine and erythro-9-(2-hydroxy-3-nonyl) adenine were good inhibitors of the bovine brain enzyme with little difference with respect to those reported for the adenosine deaminases purified from other sources. Kinetic constants for the association and dissociation of coformycin and 2'-deoxycoformycin with the bovine brain adenosine deaminase are reported.

Adenosine↗
PubMed1991

A reverse-phase HPLC method for cAMP phosphodiesterase activity.

A simple and fast method based on reverse-phase HPLC has been developed for measuring the activity of cAMP phosphodiesterase. It allows quantitation of product and substrate in less than 10 min. The sensitivity (1*10(-11) mol AMP), the accurate evaluation of nucleotides, the unequivocal analysis of product, and the reproducibility of the system, make this method suitable for the evaluation of cAMP phosphodiesterase in biological material, at different levels of purification, and also in kinetic studies.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1989

[Dima: a solution for many implant problems].

The Authors point out the importance of a preliminary detailed examination on cases where an intrabone implanthology operation is necessary. The patient is examined from a neuromuscolar point of view, then a stereognatograph is used to check his chewing function. The subject is carefully examined under the profile of his individual characteristics by means of a print which reveals the drawing of the bone's profile under the area of the tooth and the perforation of the cutting edges exactly at the right point and in the direction desired by the dentist.

Adult↗
PubMed1988

Adenosine deaminase inhibitors. Synthesis and biological activity of deaza analogues of erythro-9-(2-hydroxy-3-nonyl)adenine.

Two new deaza analogues of erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA, 1), 7-deaza-EHNA (6) and 1,3-dideaza-EHNA (11), were synthesized and evaluated for adenosine deaminase (ADA) inhibitory activity and compared with EHNA, 1-deaza-EHNA (2), and 3-deaza-EHNA (3). Substitution of a methine group for a nitrogen atom in the 7-position of the purine moiety of EHNA produces a dramatic drop in the inhibitory activity (Ki = 4 X 10(-4) M) whereas compounds 2 and 3 are still good inhibitors (Ki = 1.2 X 10(-7) M and 6.3 X 10(-9) M respectively). EHNA and its deaza analogues so far synthesized were also tested in vitro for their antiviral and antitumor activity in a range of cellular systems. EHNA and 1-deaza-EHNA are equiactive as inhibitors of human respiratory syncytial virus (HRSV) replication (MIC = 6.25 micrograms/mL) while the other compounds are inactive. On the other hand, all the examined compounds displayed an antitumor activity comparable to that of the reference compound 1-beta-D-arabinofuranosyladenine (ara-A), 7-deaza-EHNA being the most active of all. The results obtained showed that there is no correlation between adenosine deaminase inhibition and antiviral or antitumor activity in this series of compounds. 3-Deaza-EHNA, the most active inhibitor of ADA among the EHNA deaza analogues, greatly potentiates the antitumor activity of ara-A in vitro. In vivo activity was observed only when the two compounds were used in combination.

Adenine↗
PubMed1987

Adenosine deaminase from Saccharomyces cerevisiae: purification and characterization.

Adenosine deaminase from Saccharomyces Cerevisiae was purified about 1600 fold by salt fractionation, ion exchange and affinity chromatography. Some physico-chemical properties have been determined: the molecular weight of the enzyme by gel filtration is 85,000 daltons; one -SH is readily titrated by paramercuribenzoate per 78,000 mol. weight; optimum pH is 7; Km for adenosine is 40.7 microM; 2'-deoxyadenosine is not a substrate. Deazaadenosine analogues are good inhibitors, while erythro-9-(2-hydroxy-3-nonyl) adenine binds with low affinity. These properties are compared with those of other adenosine deaminases.

Adenosine Deaminase↗
PubMed1985

Specific labeling of cytosolic and mitochondrial aspartate aminotransferases.

The apoisozymes of cytosolic and mitochondrial aspartate aminotransferase are both irreversibly inhibited by alpha-N-fluorodinitrophenyl-beta-N-phosphopyridoxyldiaminopropi onate, an affinity-labeling reagent analog of the coenzyme. Analysis of the modified peptides shows that the active-site Lys-258, which in the holoenzyme binds the coenzyme pyridoxal 5'-phosphate, is labeled in both isozymes. Comparison with the results obtained using the parent compound 4'-N-fluorodinitrophenylpyridoxamine 5'-phosphate, which labels only the cytosolic enzyme, provides information about differences in active-site reactivity and geometry. Labeling external to the active site occurs in both isozymes. In the cytosolic enzyme the very reactive Cys-45 is modified, in the mitochondrial enzyme the surface residue Lys-342 reveals a peculiar reactivity.

Affinity Labels↗
PubMed1985

Inhibition of adenosine deaminase from several sources by deaza derivatives of adenosine and EHNA.

Deaza analogues of adenosine and EHNA were tested as inhibitors of the enzyme adenosine deaminase (ADA) obtained from several sources including human erythrocytes, calf intestine, Saccaromices cerevisiae, Escherichia coli and Takadiastase. Ki values of the inhibitors suggest differences among the enzymes both at purine and erythro-nonyl binding site. Among the ribofuranosyl derivatives, 1-deazaadenosine is the best inhibitor, its Ki ranging between 3.5 x 10(-7) and 4 x 10(-5) M for ADA from erythrocytes and Takadiastase respectively. Only ADA from erythrocytes and calf intestine bind EHNA and some of deazaEHNA analogues; 3-deazaEHNA behaves very similarly to EHNA both in affinity and slow binding mechanism, whereas 1-deazaEHNA, though less potent, is a good inhibitor.

Adenine↗
PubMed1984

Fixed drug eruption to erythromycin.

A case of repeated eruption after administration of erythromycin is described. It is the first report of erythromycin as proven agent of such an allergic reaction.

Drug Eruptions↗
PubMed1983

Monoclonal antibody-defined peripheral blood T lymphocyte subpopulations in patients with mycosis fungoides.

A panel of monoclonal antibodies has been used to identify peripheral blood lymphocyte subpopulations in 13 patients with mycosis fungoides and in 13 normal subjects. An increase in the T6+ population and a decrease in the T8+ population were noticed in our patients. Their T4/T8 ratio was considerably augmented. In 4 patients reevaluated after treatment, marked changes in the relative proportions of T lymphocyte subsets had occurred. The possible pathogenetic significance of these immunological alterations is discussed.

Adolescent↗
PubMed1983

Effects of isotretinoin on the neutrophil chemotaxis in cystic acne.

The authors show that the use of Isotretinoin (Ro 4-3740) in cystic acne brings a reduction of chemotactic activity of the neutrophil granulocytes, like another retinoid, Etretinate, in pustular and vulgar psoriasis. This effect of retinoids, with a direct action on the polymorphonuclear leukocytes plays an important role in the recovery of the disease.

Acne Vulgaris↗