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Biomedical subjects

G Mazzola

Publications and source records attributed to G Mazzola.

At least 73 records · Page 4Linked to original sources
PubMed1987

Chemical modification of 3 alpha,20 beta-hydroxysteroid dehydrogenase with diethyl pyrocarbonate. Evidence for an essential, highly reactive, lysyl residue.

Diethyl pyrocarbonate inactivated the tetrameric 3 alpha,20 beta-hydroxysteroid dehydrogenase with second-order rate constants of 1.63 M-1 s-1 at pH 6 and 25 degrees C or 190 M-1 s-1 at pH 9.4 and 25 degrees C. The activity was slowly and partially restored by incubation with hydroxylamine (81% reactivation after 28 h with 0.1 M hydroxylamine, pH 9, 25 degrees C). NADH protected the enzyme against inactivation with a Kd (10 microM) very close to the Km (7 microM) for the coenzyme. The ultraviolet difference spectrum of inactivated vs. native enzyme indicated that a single histidyl residue per enzyme subunit was modified by diethyl pyrocarbonate, with a second-order rate constant of 1.8 M-1 s-1 at pH 6 and 25 degrees C. The histidyl residue, however, was not essential for activity because in the presence of NADH it was modified without enzyme inactivation and modification of inactivated enzyme was rapidly reversed by hydroxylamine without concomitant reactivation. Progesterone, in the presence of NAD+, protected the histidyl residue against modification, and this suggests that the residue is located in or near the steroid binding site of the enzyme. Diethyl pyrocarbonate also modified, with unusually high reaction rate, one lysyl residue per enzyme subunit, as demonstrated by dinitrophenylation experiments carried out on the treated enzyme. The correlation between inactivation and modification of lysyl residues at different pHs and the protection by NADH against both inactivation and modification of lysyl residues indicate that this residue is essential for activity and is located in or near the NADH binding site of the enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗
PubMed1986

Musical consonances and dissonances: are they distinguished independently by the right and left hippocampi?

Our study sought to determine whether, where and how the consonance or dissonance of musical intervals might be reflected in the electrical activity (depth EEG) of the human brain. Presenting an adequate musical test program to a patient with depth electrodes implanted within the planum temporale (near Heschl's gyrus) and the hippocampal formations of both sides, we found that the reactions shown by the depth EEG of the limbic system correspond in precise and distinctly differing patterns to the consonances and dissonances presented. The main findings are: the EEG of the left hippocampus reflects the consonance-dissonance dichotomy; the activity of the left hippocampus but not the right is affected by a previous sequence of dissonances in responding to a single consonance; the EEG activity of the right Heschl's gyrus (the left Heschl's gyrus was not analyzed), but neither the left nor the right hippocampus, responded differently to a given succession of intervals and its pitch inversion. These results may help to understand the different emotional responses which usually arise in response to consonant or dissonant musical intervals.

Adult↗
PubMed1985

High-performance liquid chromatography of glucagon and related compounds.

Glycerolpropylsilane bonded phases have been found to adsorb peptides and proteins via ionic interactions. In this paper high-performance liquid chromatography separation of glucagon and related compounds, using a Diol-silica matrix, is described. Crystalline, commercial preparations of glucagon, when analyzed on LiChrosorb Diol columns eluted with low-ionic-strength acidic buffers, contained up to four contaminant peaks, in different numbers and ratios. Three of these contaminants, called A, C, and D, were recovered and characterized. Contaminant A, representing a few percent of the total, was a mixture of mono- and didesamidoglucagon, as shown by treatment with bis(I,I-trifluoroacetoxy)iodobenzene, with which it is possible to differentiate between carboxamide and carboxylic acid residues. Contaminant C, ranging from 0 to about 30% of the total, was N-terminal degraded glucagon. Contaminant D, ranging from a few percent to about 25% of the total, was (Met27 sulfoxide) glucagon.

Amino Acids↗
PubMed1984

Separation of choline- and ethanolamine-labeled metabolites by ion-exchange high-pressure liquid chromatography.

Two methods utilizing ion-exchange high-performance liquid chromatography have been developed for the separation of choline- and ethanolamine-containing metabolic precursors for phosphatidylcholine and phosphatidylethanolamine. Both methods employ an analytical anion-exchange column supplemented with a cation-exchange column; the latter is required only to separate betaine from choline. Complete separation of choline- and ethanolamine-labeled metabolites from extracts of Chinese hamster ovary cells can be achieved in 20 min.

Animals↗
PubMed1981

L-glutaminase and L-asparaginase by extracorporeal route in acute lymphoblastic leukemia therapy.

Use of L-asparaginase by the extracorporeal route in the therapy of acute lymphoblastic leukemia (ALL) has been proposed. Results, however, are not so satisfactory as i.v. administration of this enzyme, because the levels of L-asparagine do not fall for a sufficient length of time due to the antagonistic action of the L-asparagine-synthetase. To avoid the L-asparagine rebound we have utilized, by extracorporeal route, L-glutaminase together with L-asparaginase, in order to reduce L-asparagine and L-glutamine levels. We have therefore performed a series of experiments in vitro and in vivo either using L-asparaginase alone or together with L-glutaminase. Results show that, contrary to what happens when L-asparaginase is used alone, L-asparagine levels decrease and remain low even after 24 hours from the treatment, when L-glutaminase is added to the system. Thus a lowering of L-glutamine levels, which seems to play an important role in the therapy of ALL, is obtained.

Animals↗
PubMed1980

Immobilization and characterization of L-asparaginase on hollow fibers.

L-Asparaginase was immobilized with various methods: cyanogen bromide, cyanuric chloride and cross-linking with glutaraldehyde. A dialysis device was transformed in a bioreactor with the enzyme immobilized on the outer surface of hollow fibers. Results on kinetic behavior, stability in storage and lyophilization are reported.

Asparaginase↗
PubMed1979

Immobilized hydroxysteroid dehydrogenases for the transformation of steroids in water--organic solvent systems.

The hydroxysteroid dehydrogenases: beta-HSDH, 20 beta-HSDH, and 3 alpha-HSDH, were immobilized on CNBr-activated Sepharose. The effect of various immobilization conditions on the activity recovery and stability were examined. The presence of cofactor during the immobilization reaction increased the activity recovery (40--60% of the total) and also led to materials highly stable in the presence of organic solvents. For example, beta-HSDH maintained 60% of its original activity two months after continuous use in the water--ethyl-acetate system. Kinetic experiments showed that the increase of the apparent Km values is poor and demonstrated that the organic solvent behaves as a weak inhibitor (ki greater than 0.2M) for the substrate. The immobilized enzymes lyophilized in the presence of sucrose had full activity restored even after several months storage at room temperature. Immobilized hydroxysteroid dehydrogenases were shown to be suitable for preparative transformation of steroids in water--organic solvent systems.

Cortisone↗
PubMed1976

Chemical and physical properties of the human urinary glycoprotein with gastric antisecretory activity.

The chemical and physical properties of the high-molecular-weight glycoprotein (SO20, w = 8S; Ve=Vo on Sephadex G-200) with gastric antisecretory activity extracted from the urine of pregnant women were studied. Gel filtration in the presence of sodium dodecyl sulphate and sodium dodecyl sulphate/polyacrylamide-disc-gel electrophoresis indicated subunit mol.wts. of 16 000 +/- 1500 and 13 000 +/- 1000 respectively. Reaggregation of the subunits and partial recovery of the biological activity were observed on removal of the detergent. The partial C-terminal sequence was found to be Phe-Tyr-Leu-Val-OH, whereas glycine appears to be the N-terminal amino acid. The carbohydrate composition was examined; all galactosamine was found to be O-glycosidically linked to the polypeptide chain.

Amino Acid Sequence↗
PubMed1976

The community hospital as a focus for health planning.

A community hospital focus for health planning has been developed by a Department of Community Medicine in a "non-teaching" voluntary hospital. Results of three years of planning experience have included: descriptions of service area populations and utilizer populations; implementation of neighborhood based health centers with transportation and outreach programs; integration of emergency services with other ambulatory care resources; and proposals for geriatric day-care, ambulatory surgery, and patient education. Working relationships have been developed between the hospital Department and local planning bodies, among them the Comprehensive Health Planning agency, the County Health Services Department, consumer groups, voluntary agencies and a University Health Services Center.

Aged↗