Search PubMed⌕ Search

Biomedical subjects

M Gatti

Publications and source records attributed to M Gatti.

At least 127 records · Page 7Linked to original sources
PubMed1981

Cytological dissection of sex chromosome heterochromatin of Drosophila hydei.

Prophase chromosomes of Drosophila hydei were stained with 0.5 microgram/ml Hoechst 33258 and examined under a fluorescence microscope. While autosomal and X chromosome heterochromatin are homogeneously fluorescent, the entirely heterochromatic Y chromosome exhibits an extremely fine longitudinal differentiation, being subdivided into 18 different regions defined by the degree of fluorescence and the presence of constrictions. Thus high resolution Hoechst banding of prophase chromosomes provides a tool comparable to polytene chromosomes for the cytogenetic analysis of the Y chromosome of D. hydei. - D. hydei heterochromatin was further characterized by Hoechst staining of chromosomes exposed to 5-bromodeoxyuridine for one round of DNA replication. After this treatment the pericentromeric autosomal heterochromatin, the X heterochromatin and the Y chromosome exhibit numerous regions of lateral asymmetry. Moreover, while the heterochromatic short arms of the major autosomes show simple lateral asymmetry, the X and the Y heterochromatin exhibit complex patterns of contralateral asymmetry. These observations, coupled with the data on the molecular content of D. hydei heterochromatin, give some insight into the chromosomal organization of highly and moderately repetitive heterochromatic DNA.

Animals↗
PubMed1981

[Multicenter study on the distribution of Streptococcus pneumoniae strains in Italy].

Pneumococcal serotyping by quellung reaction has been performed in five Italian areas on 267 strains, isolated from throat swab, sputum, blood, liquor, etc. 37 serotypes have been identified. The most frequent types resulted 19, 6, 3, 20, 9, 4 (in 50% of total samples), with no difference from those detected in other European countries. The proportion of type 19 was the highest among all age group, in four out of five different areas and in bacteremic pneumonia and meningitis. 36 strains were isolated from infection sites among which type 19 resulted more frequent than in isolates from throat swab and sputum (27.7% versus 16.1%). Pneumococcal serotyping should be routinely done in the light of forthcoming use of polysaccharide vaccine.

Adult↗
PubMed1980

Effects of recombination-deficient and repair-deficient loci on meiotic and mitotic chromosome behavior in Drosophila melanogaster.

The results of recent genetic and cytological studies on recombination-defective and repair-defective mutants of Drosophila melanogaster are summarized. These studies show that there is substantial overlap between the functions used in various aspects of DNA metabolism in Drosophila. Most loci first identified by either recombination-defective or mutagen-sensitive mutants have been shown also to function in nonmutagenized mitotic cells where their action is necessary to maintain the integrity of the genome: mutants at particular loci produce elevated frequencies of chromosome breakage, mitotic exchange, mutation, and/or chromosome loss. Genetic studies of meiotic recombination show that many of the loci identified by recombination-defective mutants restrict where along the chromosome arms exchange may occur. Recent EM studies suggest that the products of at least some of these loci are components of recombination nodules. Region-specific control of DNA metabolism is also indicated by the finding of nonrandom patterns of chromosome breakage in some mutagen-sensitive mutants. Recombination-defective mutants at two loci have been studied for their effects on sister chromatid exchanges (SCEs) and x-ray induced aberrations. Mutants at both loci are defective in steps necessary for the production of symmetrical chromatid interchanges but have little effect on SCEs.

Animals↗
PubMed1980

Intraspecific polymorphism of sex chromosome heterochromatin in two species of the Anopheles gambiae complex.

The Hoechst 33258 banding pattern of the mitotic chromosomes of several laboratory and natural populations of the sibling species A. gambiae and A. arabiensis has been analyzed. A clear intraspecific polymorphism of sex chromosome heterochromatin has been observed. Nevertheless in each species heterochromatic variations fall within a characteristic species-specific pattern. Moreover, while laboratory polulations tend to be monomorphic for a given heterchromatic variant, natural populations exhibit a high degree of intrapopulation polymorphism. The possible role of sex chromosome heterochromatin in controlling fertility and mating behaviour of Anopheles mosquitoes is discussed.

Animals↗
PubMed1980

Relationships among chromatid interchanges, sister chromatid exchanges, and meiotic recombination in Drosophila melanogaster.

Repair- and recombination-defective mutations at two loci (mei-9 and mei-41) of Drosophila melanogaster have been examined for their effects on the induction of chromosome aberrations by x-rays and the formation of sister chromatid exchanges (SCEs). Irradiation of larval neuroblast cells during the S phase with x-rays showed that mutants at both of these loci are about 10 times more sensitive than wild type to the induction of chromosome aberrations. The pattern of induced aberrations was characteristic for each mutant locus: in cells bearing mei-9 mutations most breaks were chromatid deletions, whereas in the presence of mei-41 mutations similar frequencies of chromatid and isochromatid deletions were observed. Furthermore, chromatid interchanges could not be induced in cells carrying mei-9 alleles; therefore these mutations define a step necessary for chromatid rejoining. mei-41 alleles also define a function involved in the formation of chromatid interchanges; total exchanges were less frequent than expected from nonmutant controls; and the proportion of exchanges arising by symmetrical rejoining was markedly reduced. These data indicate that chromatid and isochromatid deletions have different molecular steps in their formation, and that different molecular mechanisms are also involved in the symmetrical and unsymmetrical rejoining in chromatid interchanges. Neuroblast cells of larvae bearing mei-9 and mei-41 alleles were also treated for 13 hr with 5-bromodeoxyuridine at 9 mug/ml in order to differentiate sister chromatids for the scoring of SCEs. Whereas mei-41 had a normal level of SCEs, mei-9 exhibited a frequency of SCEs that was about 70% that of the control. Because both mei-9 and mei-41 mutations result in defective meiotic recombination, these data suggest that they define steps shared by symmetrical interchange formation and meiotic recombination that do not participate in the formation of most SCEs.

Animals↗
PubMed1979

A renal abnormality as a possible cause of "essential" hypertension.

The renal abnormality which causes hypertension in the Milan hypertensive strain of rats disappears as hypertension develops. Because of the many analogies between the condition in these rats and "essential" hypertension in man, the same pattern of change may occur if a renal abnormality is the cause of essential hypertension in man. This hypothesis was tested in two groups of young normotensive subjects matched for age, sex, and body-surface area; in the first group both parents were hypertensive, and in the second group both parents were normotensive. Renal plasma-flow, glomerular filtration-rate, plasma-volume, plasma-renin activity, plasma-concentrations of Na+, K+, and catecholamines, 24 h urinary excretion of Na+, K+, and aldosterone, and the cardiac index were measured so that renal function and the role of factors affecting blood-pressure regulation could be assessed. Renal plasma-flow was significantly higher (p less than 0.01) in the first group, whereas results of tests for all the other factors were almost the same in both groups. The hypothesis that a primary kidney abnormality causes hypertension in a proportion of patients with essential hypertension is proposed.

Adult↗
PubMed1979

Genetic control of chromosome breakage and rejoining in Drosophila melanogaster: spontaneous chromosome aberrations in X-linked mutants defective in DNA metabolism.

Eight X-linked recombination-defective meiotic mutants (representing five loci) and 12 X-linked mutagen-sensitive mutants (representing seven loci) of Drosophila melanogaster have been examined cytologically in neuroblast metaphases for their effects on the frequencies and types of spontaneous chromosome aberrations. Twelve mutants, representing five loci, significantly increase the frequency of chromosomal aberrations. The mutants at these five loci, however, differ markedly both in the types of aberrations produced and the localization of their effects along the chromosome. According to these criteria, the mutants can be assigned to four groups: (i) mutants producing almost exclusively chromatid breaks in both euchromatin and heterochromatin; (ii) mutants producing chromatid and isochromatid breaks in both euchromatin and heterochromatin; (iii) mutants producing chromatid mutants producing chromatid and isochromatid breaks clustered in the heterochromatin.

Animals↗
PubMed1979

Lack of spontaneous sister chromatid exchanges in somatic cells of Drosophila melanogaster.

Neural ganglia of wild type third-instar larvae of Drosophila melanogaster were incubated for 13 hours at various concentrations of BUdR (1, 3, 9, 27 micrograms/ml). Metaphases were collected with colchicine, stained with Hoechst 33258, and scored under a fluorescence microscope. Metaphases in which the sister chromatids were clearly differentiated were scored for the presence of sister-chromatid exchanges (SCEs). At the lowest concentration of BUdR (1 microgram/ml), no SCEs were observed in either male or female neuroblasts. The SCEs were found at the higher concentrations of BUdR (3, 9, And 27 micrograms/ml) and with a greater frequency in females than in males. Therefore SCEs are not a spontaneous phenomenon in D. melanogaster, but are induced by BUdR incorporated in the DNA. A striking nonrandomness was found in the distribution of SCEs along the chromosomes. More than a third of the SCEs were clustered in the junctions between euchromatin and heterochromatin. The remaining SCEs were preferentially localized within the heterochromatic regions of the X chromosome and the autosomes and primarily on the entirely heterochromatic Y chromosome.--In order to find an alternative way of measuring the frequency of SCEs in the Drosophila neuroblasts, the occurrence of double dicentric rings was studied in two stocks carrying monocentric ring-X chromosomes. One ring chromosome, C(1)TR94--2, shows a rate of dicentric ring formation corresponding to the frequency of SCEs observed in the BUdR-labelled rod chromosomes. The other ring studied, R(1)2, exhibits a frequency of SCEs higher than that observed with both C(1) TR94--2 and rod chromosomes.

Animals↗
PubMed1978

3h-actinomycin-D binding to mitotic chromosomes of Drosophila melanogaster.

The binding of 3H-AMD to the metaphase chromosomes of Drosophila melanogaster has been analyzed after two different periods of exposure to photographic emulsion. The entirely heterochromatic Y chromosome was markedly less labelled than euchromatin and other heterochromatic regions. Moreover, the few grains present on the Y chromosome were clustered in two regions, one localized in the middle Ys and the other in the proximal third of YL. This labelling pattern is not affected by removing histones with a 2-hour treatment with 2N HCl. It is suggested that the specific underlabelling of the Y chromosome reflects a peculiar AT richness.

Animals↗
PubMed1977

Fluorescence banding techniques in the identification of sibling species of the anopheles gambiae complex.

The mitotic chromosomes of the sibling species A and B of the Anopheles gambiae complex were stained with Hoechst 33258 and examined by fluorescence microscopy. The autosomes fluoresce homogenously and similarly in both species while the sex chromosomes differ in the location and brightness of some heterochromatic blocks. These cytochemical differences allow the cytotaxonomic identification of these cryptic species.

Animals↗
PubMed1977

Mutagen specificity in the induction of chromosomal aberrations in somatic cells of Drosophila melanogaster.

The distribution of chromosomal aberrations between and within chromosomes of male D, melanogaster somatic cells after treatment with UV has been analyzed. -- Distribution of the breaks between chromosomes was largely nonrandom since we found a higher aberration frequency than that expected on the Y chromosome. Moreover, within the chromosomes the aberrations are clustered in the pericentromeric heterochromatic regions. The above distribution is compared with that of the breaks induced by X rays and methyl-methane-sulphonate (MMS) which were distributed in a different pattern.

Animals↗