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Biomedical subjects

F Mazzei

Publications and source records attributed to F Mazzei.

At least 37 records · Page 2Linked to original sources
PubMed1992

Determination of glutamic acid decarboxylase activity and inhibition by an H2O2-sensing glutamic acid oxidase biosensor.

The catalytic activity of the enzyme L-glutamic acid decarboxylase (GAD) is determined by an amperometric method based on a recently developed glutamate-selective biosensor. The biosensor is composed of an amperometric H2O2 electrode and a biocatalytic membrane containing the enzyme glutamic acid oxidase (GAO). The biosensor allows the direct and continuous measurement of GA levels by monitoring the H2O2 produced at the electrode interface as a coproduct of the GAO-catalyzed GA oxidation to alpha-ketoglutaric acid. Since GA is transformed to gamma-aminobutyric acid and CO2 under the catalytic activity of GAD, the rate of GA consumption in solution, monitored by the GAO biosensor, represents a reliable measure of GAD catalytic activity. Additional experiments performed in the presence of different concentrations of the GAD inhibitor valproic acid have shown the suitability of the proposed approach for the study of GAD inhibitors also. Discussion of the main experimental characteristics of this new analytical method is given in terms of sensitivity, reproducibility, and reliability of the experimental results and ease, time, and cost of operation.

Amino Acid Oxidoreductases↗
PubMed1991

[Patient exposure during radiodiagnosis. The Nationwide Evaluation of X-ray Trends (NEXT) program in Italy].

The aim of this paper is the critical analysis of the results obtained with the quality control program in X-ray diagnosis called NEXT (Nationwide Evaluation of X-ray Trends). It is also aimed at comparing the above results with guidelines and trends of international radiology, for both technical features and patient protection from radiations. The main purpose of patient protection is the reduction of unnecessary exposure through the optimization of radiodiagnostic procedures. In order to identify the fields requiring the application of specific quality control programs, the Istituto Superiore di Sanità, together with ENEA/DISP have been running the NEXT program in Italy since 1977. The program, through data collection and measurements in more than 2,500 radiologic units, allowed both state of the art and progress in radiodiagnostic practice to be studied over a long period of time. Data computation provides, for a standard patient, the skin entrance exposure and the main organ doses for the examinations which are most frequently performed. In this paper, the fundamentals of the NEXT program are reported and the most significant results are discussed, and compared, when possible, with the values recommended by international scientific organizations. The analysis of the results demonstrates a decreasing trend in patient exposure over the last years.

Humans↗
PubMed1990

Determination of inorganic phosphate in drug formulations and biological fluids using a plant tissue electrode.

A suitable biosensor for the analysis of inorganic phosphate was developed by coupling the enzyme glucose oxidase to a slice of potato (Solanum tuberosum) containing the acid phosphatase, and using an amperometric Clark electrode as an indicating sensor. Phosphate concentration can be determined from its inhibition on the acid phosphatase activity. Measurements were carried out at steady-state conditions and the available concentration range of phosphate, repeatability and accuracy, on phosphate standard solutions, were experimentally determined. Finally the sensor was used in pharmaceutical and biological matrices. The results were compared with those ones obtained by Bartlett's spectrometric method.

Acid Phosphatase↗
PubMed1989

Histamine 2 antagonists in allergic rhinitis. Relationship of clinical response and serum concentrations of total and specific IgE antibody levels.

During a double-blind clinical trial of a histamine (H2) antagonist (ranitidine) in monitoring allergic rhinitis, the clinical response, total serum IgE levels, and Parietaria IgE antibody levels were measured. Ranitidine induces an improvement in scores of subjective and objective symptoms, a decrease in total serum IgE levels, and no significant variations in Parietaria IgE antibody levels. Since H2 antagonists seem to induce these improvements by acting on suppressor T cells bearing H2 receptor, as shown in our previous studies, it is hypothesized that the lymphocytic subset that regulates the total IgE synthesis is not the same as that governing specific IgE synthesis.

Adolescent↗
PubMed1988

Benzylpenicillin PVC membrane electrode for the determination of antibiotics in formulations.

A PVC (polyvinychloride) ion selective electrode, employing benzyldimethyl-cetylammoniumbenzylpenicillin as sensor, was prepared, characterized and applied to the analysis of commercially available formulations containing benzylpenicillin and other antibiotics of the penicillin or cephalosporin group. The results are compared with those obtained by using the corresponding liquid membrane electrode.

Journal Article↗
PubMed1988

Polymeric membrane electrodes for drug analysis.

Two new polymeric membrane electrodes selective to cholate and to benzylpenicillinate, based respectively on PVC membranes containing polybenzyl-propargilamine as conductor polymer and benzyldimethylcethylammonium-cholate, or -benzylpenicillinate as exchangers, have been prepared, and applied to the determination of cholic acids, anionic surfactants and antibiotics. Results are compared with those ones obtained by analogous PVC sensors and liquid membrane sensors, previously described.

Journal Article↗
PubMed1987

Lactate and pyruvate electrochemical biosensors for whole blood in extracorporeal experiments with an endocrine artificial pancreas.

Glucose, lactate, and pyruvate can be continuously measured in whole blood by using three extracorporeal electrochemical biosensors. We fixed two newly developed sensors, for lactate and pyruvate, in series with an endocrine artificial pancreas ("Betalike") without affecting its performance. These new sensors for use with whole blood should be able to clarify the fate of the intermediary metabolites of glucose in diabetic patients receiving infusions of drugs or insulin.

Blood Glucose↗
PubMed1983

Secondary structure features of ribosomal RNA species within intact ribosomal subunits and efficiency of RNA-protein interactions in thermoacidophilic (Caldariella acidophila, Bacillus acidocaldarius) and mesophilic (Escherichia coli) bacteria.

Ribosomal subunits of Caldariella acidophila (max.growth temp., 90 degrees C) have been compared to subunits of Bacillus acidocaldarius (max. growth temp., 70 degrees C) and Escherichia coli (max. growth temp., 47 degrees C) with respect to (a) bihelical content of rRNA; (b) G . C content of bihelical domains and (c) tightness of rRNA-protein interactions. The principal results are as follows. Subunits of C. acidophilia ribosomes (Tm = 90-93 degrees C) exhibit considerable thermal tolerance over their B. acidocaldarius (Tm = 77 degrees C) and E. coli counterparts (Tm = 72 degrees C). Based on the "melting' hyperchromicities of the intact ribosomal subunits a 51-55% fraction of the nucleotides appears to participate in hydrogen-bonded base pairing regardless of ribosome source, whereas a larger fraction, 67-70%, appears to be involved in hydrogen bonding in the naked rRNA species. The G . C content of bihelical domains of both free and ribosome-bound rRNA increases with increasing thermophily; based on hyperchromicity dispersion spectra of intact subunits and free rRNA, the bihelical parts of C. acidophila rRNA are estimated to contain 63-64% G . C, compared to 58.5% G . C for B. acidocaldarius and 55% G . C for E. coli. The increment of ribosome Tm values with increasing thermophily is greater than the increase in Tm for the free rRNA, indicating that within ribosomes bihelical domains of the thermophile rRNA species are stabilized more efficiently than their mesophile counterparts by proteins or/ and other component(s). The efficiency of the rRNA-protein interactions in the mesophile and thermophile ribosomes has been probed by comparing the releases, with LiCl-urea, of the rRNA species from the corresponding ribosomal subunits stuck to a Celite column through their protein moiety; it has been established that the release of C. acidophila rRNA from the Celite-bound ribosomes occurs at salt-urea concentrations about 4-fold higher than those required to release rRNA from Celite-bound E. coli ribosomes. Compared to E. coli the C. acidophila 50 and 30 S ribosomal subunits are considerably less susceptible to treatment designed to promote ribosome unfolding through depletion of magnesium ions.

Bacillus↗
PubMed1982

Size heterogeneity of ribosomal RNA in eukaryote evolution--1. rRNA molecular weights in species containing intact large ribosomal subunit RNA.

1. The molecular weights of the two major rRNA species (L-rRNA, large ribosomal subunit RNA, and S-rRNA, small ribosomal subunit RNA) of a variety of deuterostomia, green plants and fungi have been investigated by gel electrophoresis in 99% formamide, pH 9; the overall pattern obtained under these conditions differs to some extent from that deduced by electrophoresis in neutral-salt solutions. 2. The molecular weights of the deuterostomian S-rRNA species have been conserved at a value of 0.65 X 10(6), whereas those of the L-rRNA have been kept at 1.40 X 10(6) in the lower species but have increased to 1.55 X 10(6) in birds and to 1.65 X 10(6) in mammals. 3. The molecular weights of the L-rRNA and S-rRNA components of the green plants (Dycotyledons, Monocotyledons and Gymnosperms) have been generally conserved at 1.30 X 10(6) and 0.65 X 10(6). 4. The molecular weight of the L-rRNA of the fungi has been conserved at 1.36-1.38 X 10(6), being 0.1 X 10(6) daltons heavier than that of the plants; the S-rRNA exhibits a limited degree of variability, ranging between 0.65 X 10(6) and 0.72 X 10(6).

Animals↗
PubMed1982

Size heterogeneity of ribosomal RNA in eukaryote evolution--2. rRNA molecular weights in species containing discontinuous large ribosomal subunit RNA.

1. The molecular weights and the integrity of the principal rRNA species derived from the large and small ribosomal subunit (respectively, L-rRNA and S-rRNA) of several species of Protostomia and Protozoa have been investigated. 2. Using gel electrophoresis in formamide, the molecular weights of protostomian L-rRNA species have been found to range from 1.30 X 10(6) (Annelida) to 1.61 X 10(6) (Diptera); those of the S-rRNA's cover the range 0.65 X 10(6) (Annelida)-0.81 X 10(6) (Diptera). 3. Both rRNA components have incurred extensive changes among the Protozoa; the L-rRNA ranges in weight from 1.35 X 10(6) (T. pyriformis) to 1.57 X 10(6) (A. castellanii) and the S-rRNA from 0.70 X 10(6) of T. pyriformis to 0.85 X 10(6) of A. castellanii and E. gracilis. 4. The L-rRNA components of all the species investigated are discontinuous molecules endowed with a latent median break; depending on whether the nick is located at the centre of the L-rRNA chain, or lies off-centre, the molecular weight of the S-rRNA equals that of either both, or only one, of the two fragments composing the L-rRNA.

Animals↗
PubMed1980

Physicochemical characterization of the ribosomal RNA species of the Mollusca. Molecular weight, integrity and secondary-structure features of the RNA of the large and small ribosomal subunits.

1. The rRNA species of the Cephalopoda Octopus vulgaris and Loligo vulgaris were found to have unexpectedly high sedimentation coefficients and molecular weights. In 0.1 M-NaCl the L-rRNA (RNA from large ribosomal subunit) has the same s20 value as the L-rRNA of the mammals (30.7S), whereas the S-rRNA (RNA from small ribosomal subunit) sediments at a faster rate (20.1S) than the S-rRNA of both the mammals and the fungi (Neurospora crassa) (17.5S). The molecular weights of the L-rRNA were determined by gel electrophoresis in formamide and found to be 1.66 X 10(6) (Octupus) and 1.89 X 10(6) (Loligo); the mol.wt. of the S-rRNA of both species is 0.96 X 10(6), i.e. much larger than that of the mammals (0.65 X 10(6)) and almost coincident with that of the '23S' RNA of the prokaryotes. 2. By contrast, the less evolved Gastropoda and Lamellibranchiata (Murex trunculus and Macrocallista chione) have S-rRNA and L-rRNA species with mol.wts. of 0.65 X 10(6) and approx. 1.40 X 10(6).3. All the mature L-rRNA molecules of the cephalopoda are composed of two unequal fragments held together by regions of hydrogen-bonding having a similar, low, thermal stability in the two species; the molecular weights of the two fragments composing the L-rRNA are estimated to be 0.96 X 10(6) and 0.88 X 10(6) (Loligo) and 0.96 X 10(6) and 0.65 X 10(6) (Octupus). THe S-rRNA of both species is a continuous chain with exactly the same molecular weight (0.96 X 10(6)) as the heavier of the two fragments of the L-rRNA. 4. The secondary-structure features of the L-rRNA and S-rRNA species of the Caphalopoda were investigated by thermal 'melting' analysis in 4.0 M-guanidinium chloride; 60-70% of the residues are estimated to form short, independently 'melting' bihelical segments not more than 10 base-pairs in length. 5. Bases are unevenly distributed between non-helical and bihelical portions of the rRNA molecules, G and C residues being preferentially concentrated in bihelical comains. 6. The secondary-structure regions of the L-rRNA species of Octopus and Loligo are heterogenous, including two discrete fractions of independently 'melting' species that give rise to biphasic 'melting' profiles: a fraction consisting of shorter (G + C)-poorer segments (60-68% G + C, not more than 5 base-pairs in length) and a fraction consisting of longer (G + C)-richer segments (80-88% G + C, 5-10 base-pairs in length). No evidence for heterogeneity has been detected in the S-rRNa.

Animals↗
PubMed1980

[Phono-mechano-cardiographic assessment in hypertensive heart disease: value of the apex cardiographic parameters (author's transl)].

In 15 normal subjects and in 19 patients with essential hypertension (NYHA I-II) systolic time intervals (STI) and diastolic more expressive parameters of the left ventricular performance were studied by phono-meccano-cardiography. ICT, LVET, ICT/LVET, iso-volumic relaxation period (A2-0) and rapid filling time (O-F) were measured. On the apexcardiogram relative height of rapid filling (RF) and atrial (A) waves measured too. "Diastolic index", a ratio between this two phenomena (hRFw/hAw) was calculated. Results were evaluated in relation with ECG, arterial pressure and subjective sympthoms. There were no statistically significant differences in mean values of the STI among normotensive and hypertensive subjects. On the contrary the parameters which explore into diastolic period result in disagreement and significantly influenced by diastolic arterial pressure. Comparison showed that patients in the hypertensive group had longer mean isovolumic relaxation period (P < 0.01), longer mean O-F time (P:ns), lower mean RF wave (P < 0,01) and higher mean atrial wave (P < 0,01). Consequently hRFw/hAw mean ratio was lower (P < 0,01) and frequently reversed. The lengthening of iso-volumic relaxation period and reduction of diastolic index were more consistent in the symtomatic patients (P:ns). It is concluded that poligraphic research, in patient with hypertensive heart disease, must not be restricted to the STI but it has to include a poliparametric evaluation of all phases of cardiac circle. The diastolic index may prove a simple, readily available and noninvasive guide in the assessment of left ventricular function.

Adult↗