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Biomedical subjects

A Parente

Publications and source records attributed to A Parente.

At least 55 records · Page 3Linked to original sources
PubMed1982

The amino acid sequences of eleven tryptic peptides of papaya mosaic virus protein by electron ionization mass spectrometry.

Eleven of the fourteen tryptic peptides of papaya mosaic virus protein have been sequenced by electron ionization mass spectrometry using chemical and enzymic hydrolyses and mixture analysis as required. Mid-chain cleavages of N-C bonds produced secondary ion series which allowed up to 16 residues to be sequenced without further hydrolysis. Mixture analysis on hydrolysis products enabled a 24 residue tryptic peptide to be sequenced from the data recorded in a single mass spectrum.

Amino Acid Sequence↗
PubMed1982

Endocrinologic milieu and susceptibility of the rat mammary gland to carcinogenesis.

The incidence of DMBA-induced mammary carcinomas in Sprague-Dawley rats depends upon their previous reproductive histories. Young virgin rats (YV) are highly susceptible to the carcinogen, while old virgin rats (OV) are less susceptible, and parous rats (P) are resistant. The authors performed endocrinologic studies in these three groups of rats in order to determine whether the different susceptibility to carcinogenesis, according to the reproductive history, is or is not related to the hormonal milieu. The pituitary, the ovaries, the adrenals, and the mammary glands were processed for light microscopy. Pituitary prolactin (PRL), follicle-stimulating hormone, and luteinizing hormone cells were immunostained by peroxidase-antiperoxidase and quantitated with an image analyzer. Radioimmunoassays of serum and pituitary PRL and serum estradiol were also done. The results showed no differences in the hormonal milieu of YV, OV, and P rats at the time of carcinogen treatment. Several changes were observed after DMBA administration, the most conspicuous being 1) hyperplasia of pituitary PRL cells, 2) high serum PRL levels, 3) nodular hyperplasia of the adrenal cortex, 4) high serum estradiol levels, and 5) lack of adrenal necrosis in P rats and some OV rats. These modifications did not correlate with the degree of susceptibility of YV, OV, and P rats to carcinogenesis, supporting the concept of the importance of the mammary gland differentiation at the moment of carcinogen administration. (Am J Pathol 1982, 109:47-56).

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1981

[Diagnostic value of copper and magnesium in hemolymphopathies and solid tumors].

The value and development of the copper and magnesium have been examined in thirty-four patients whose eighteen were affected by malignant lymphomas (9 L.H. and 9 non-H.), fourteen by solid tumors and two by acute leukemias. Our results prove clearly a manifest increase of the copper in the lymphomas' patients, especially in the Hodgkin's disease, and in none patients a decrease. Analogous trend has been found in the 71% of the patients with solid tumors. Scarcely significant are the results obtained in the acute leukemias. Contrary to copper, the values of the magnesium are nothing at all expressive for a diagnostic "dépistage"; a light increase of the metal is observed only in the 55% of the lymphomas non-H., while in the cancers the values are very variable. Our results confirm what other Authors have already referred, i.e. the copper's value is of a large aiding for the determination and the valuation of the diseases' activity in the above related conditions.

Adolescent↗
PubMed1980

Effects of RNA inhibitors on the development of Drosophila embryos permeabilized by a new technique.

The molecular analysis of Drosophila embryogenesis has been hindered by the impermeable nature of the vitelline membrane, which has made it difficult to introduce exogenous substances into the developing embryo. We have developed a modification of the permeabilization technique of Limbourg and Zalokar ('73) in which octane is used to permeabilize the vitelline membrane and dimethylsulfoxide is used to facilitate the transport of exogenous substance across the cell membranes. The procedure is highly effective (ca. 95%) and is consistent with a high frequency of normal development. We have used this technique to analyze the effect in vivo of four inhibitors of RNA synthesis (alpha-amanitin, actinomycin-D, rifampin, and rifamycin SV) on the embryogenesis of Drosophila. We have found that there are characteristic stage-specific alterations in the sensitivity of the embryo to these inhibitors which is reflected both by changes in the ID50 dosages and by changes in the developmental abnormalities caused by the drugs. Embryos aged 2-12 hours old undergo a developmental arrest within 30 minutes after application of the inhibitors. Embryos older than 12 hours are able to develop for 140+ minutes after treatment before arresting. The effects of these drugs are consistent with the idea that there exists a definite sequential program of gene activity that is necessary to the normal embryonic development of Drosophila.

Age Factors↗
PubMed1980

Effect of DNA inhibitors upon DNA synthesis and development of Drosophila embryos.

Staged wildtype embryos of Drosophila melanogaster were permeabilized and then subjected to a short pulse of either methyl-3H-thymidine, one of four different inhibitors of DNA synthesis (mitomycin C, 5-fluorouracil, nalidixic acid, or 1-beta-D-arabino-furanosylcytosine-5'-monophosphate), or a combination of both. The incorporation of methyl-3H-thymidine into acid insoluble material was at a maximum during the first half-hour of embryogenesis, after which the incorporation dropped to half the initial value and remained constant throughout the remainder of development. There was no correlation between the rate of incorporation of methyl-3H-thymidine into DNA and the known periods of high mitotic activity. The time course of the estimated specific activity of the DNA newly synthesized in vivo closely paralleled the known changes in the DNA polymerase activity determined in vitro. The known periods of high mitotic activity in the embryo (0-3 hours, 5-12 hours) agree with the periods of maximal sensitivity of the embryo to the inhibitors of DNA synthesis. All four DNA inhibitors affected the incorporation of methyl-3H-thymidine into DNA, although they did not affect it in any simplistic manner. Inhibitor treatment during early cleavage stages resulted in arrested development, treatment during late cleavage and blastoderm stages resulted in abnormal development, and treatment during late blastoderm and early gastrula resulted in normal development. The major phenotypic abnormality caused by the inhibitors is an abnormal distribution of blastoderm cells. As judged by the ID50 values, the embryos remained very sensitive to the effects of the inhibitors until the stages of head and body segmentation, when they then very rapidly became insensitive.

Age Factors↗
PubMed1976

Proteolytic enzymes as structural probes for ribonuclease BS-1.

Trypsin, pepsin and subtilisin have been used as conformational probes for the structure of bovine seminal ribonuclease BS-1 by studying, under definite conditions, their effects on the seminal enzyme, a dimeric protein made up to two identical subunits; on bovine pancreatic monomeric ribonuclease A (EC 3.1.4.22) with a polypeptide chain homologous to that of the seminal ribonuclease subunit chain; and on a monomeric, active and stable derivative of seminal ribonuclease. The results show: (1) that the C-terminal regions of the pancreatic and the seminal proteins are very similar as they appear to fit in an identical way to the active site of pepsin; (2) that the resistance of the N-terminal region of ribonuclease BS-1 to subtilisin is not due to the dimeric structure of the protein, but to the conformation of this region, where an essential feature is the presence of a proline residue at position 19; (3) that the monomer of ribonuclease BS-1 is resistant to tryptic action only when bound to the partner monomer in the quaternary structure of the protein. This indicates that dissociation of the seminal ribonuclease makes some potentially susceptible susceptible bond or bonds available to trypsin either through a conformational change of the protein subunit, or by simply exposing the protein area hidden at the intersubunit interfaces.

Animals↗
PubMed1975

Degradation of double-stranded RNA by a monomeric derivative of ribonuclease BS-1.

Double-stranded RNA, resistant to the action of pancreatic monomeric RNAase A, is actively degraded by seminal dimeric RNAase BS-1. Evidence is presented that a monomeric derivative of seminal RNAase degrades double-stranded RNA as efficiently as the parent dimeric molecule. This finding is discussed in the light of the hypothesis previously advanced that two active sites simultaneously available on an enzyme molecule may be responsible for degradation of double-stranded polyribonucleotides.

Animals↗
PubMed1975

Dissociation of bovine seminal ribonuclease into catalytically active monomers by selective reduction and alkylation of the intersubunit disulfide bridges.

The hypothesis previously advanced that interchain disulfide bridges link the two identical subunits of bovine seminal ribonuclease BS-1 has been confirmed. The sedimentation rate and the electrophoretic mobility of the protein are not affected by denaturing agents unless thiol reagents are present in the denaturation mixtures. Reduction under controlled conditions results in the immediate cleavage of only 2 disulfide bonds out of 10 percent in the dimeric protein. Under these conditions, and the results do not change when partial reduction is followed by S-alkylation, 30% of the protein dissociates, while the remaining is found to consist of a dimeric species easily dissociable by denaturing agents without addition of thiol reagents. This indicates that the dimeric structure of seminal ribonuclease is maintained not only by disulfide bridges, but also by noncovalent forces. The protein derivative prepared by selective reduction and alkylation has been identified as monomeric bis-S-carboxymethylcysteine-31,32-ribonuclease BS-1. This is on the basis of the characterization of the 14C-labeled S-carboxymethylated peptides isolated from a thermolytic hydrolysate of the derivative prepared with iodo-2-[14C]acetic acid. Monomeric, selectively alkylated ribonuclease BS-1 is stable and catalytically active. The importance of such a derivative is discussed both in the light of the recent studies on the biological actions of seminal ribonuclease and as the fourth component of an experimental system of ribonucleases consisting of two homologous dimers (bovine seminal ribonuclease BS-1 and dimerized bovine pancreatic ribonuclease A) and two homologous monomers (ribonuclease A and the monomeric derivative of ribonuclease BS-1.

Alkylation↗
PubMedDate not supplied

Pharmacological approaches to the management of alcohol addiction.

Alcohol abuse and alcoholism represent a world-wide problem, both from a medical and a social point of view. In the past the therapy for patients affected by alcoholism was based mainly on the psychological approach. In recent years the use of pharmacotherapy together with psychosocial interventions have enhanced the percentage of success in maintaining alcoholic patients in remission. The present review discusses the main drugs experimented both in preclinical and clinical studies. Pharmacotherapy of alcohol dependence seems to be effective in both alcohol-related emergencies and prevention relapse. However, pharmacotherapy should not be considered as the only form of treatment but as an integrated part of a multimodal approach including psychological and social support.

Alcohol Deterrents↗