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G Morpurgo

Publications and source records attributed to G Morpurgo.

At least 19 recordsLinked to original sources
PubMed1997

6-N-hydroxylaminopurine (HAP)-induced accumulation of variability in haploid and diploid strains of Aspergillus nidulans.

Haploid and diploid strains of Aspergillus nidulans have been repeatedly treated with the strong mutagen 6-N-hydroxylaminopurine (HAP) which causes only base substitutions. An enormous amount of variability may be rapidly accumulated in haploid or diploid strains of A. nidulans. In particular, in the diploids the analysis of the results shows that after 12 cycles of treatment the conidia differ from each other for about ten recessive lethals and therefore probably for several hundreds of mutations. The viability of the heterozygous multiply mutant diploids is not appreciably different from that of untreated controls. In the diploid strains the accumulated variability was very high. The treatment of a haploid strain during vegetative growth also caused a strong accumulation of mutations, even though deleterious, because they can be maintained in the heterokaryotic condition.

Adenine↗
PubMed1997

The base analog 6-N-hydroxylaminopurine (HAP) mutagenesis is dependent on the integrity of the uvsE, uvsF and uvsB genes in Aspergillus nidulans.

Most of the available data in lower eukaryotes are consistent with the idea that base analogs-induced mutagenesis is due to the mis-pairing properties of these compounds, which, in turn, is due to a shift in the tautomeric equilibrium of the molecule. A tautomeric shift may in fact lead to mismatches which, at least in Escherichia coli, can be repaired by genes involved in the post-replicative mismatch repair whose activity is necessary to control spontaneous mutagenesis. In filamentous fungi, such as Aspergillus nidulans, nothing is known about the repair of base pairing mistakes after base analogs treatment. For this reason, we have decided to screen UV-sensitive Aspergillus nidulans mutants for their mutagenic response to 6-N-hydroxylaminopurine (HAP). We have shown that three mutations (uvsB, uvsC and uvsE), which enhance the UV-sensitivity of germinating conidia, cause a lower mutagenic response to HAP. On the other hand, the uvsH mutation, has no effect on HAP-induced mutagenesis.

Adenine↗
PubMed1994

The genetic activity of 6-N-hydroxylaminopurine in Aspergillus nidulans.

The activity of a base analog (6-N-hydroxylaminopurine, HAP) has been tested on Aspergillus nidulans. In germinating haploid conidia HAP is a strong mutagen, while it does not have any activity in resting conidia. Moreover, HAP does not increase the frequency of recombination in germinating conidia. The mutagenic activity of this base analog has also been tested in diploid conidia of A. nidulans; in fact, it has been shown (Pavlov et al., 1991) that the HAP-induced frequency of heteroallelic recessive mutations in diploid cells of the yeast S. cerevisiae is higher than expected. In A. nidulans, we did not observe any increase in the frequency of recessive homozygous fpaA/fpaA (p-fluorophenylalanine-resistant) mutants over the expected one, which has been calculated on the basis of the observed mutation frequency in the haploid strain.

Adenine↗
PubMed1991

Protection against malaria morbidity: near-fixation of the alpha-thalassemia gene in a Nepalese population.

We have previously reported that the Tharu people of the Terai region in southern Nepal have an incidence of malaria about sevenfold lower than that of synpatric non-Tharu people. In order to find out whether this marked resistance against malaria has a genetic basis, we have now determined in these populations the prevalence of candidate protective genes and have performed in-vitro cultures of Plasmodium falciparum in both Tharu and non-Tharu red cells. We have found significant but relatively low and variable frequencies of beta-thal, beta S, G6PD (-), and Duffy (a-b-) in different parts of the Terai region. The average in-vitro rate of invasion and of parasite multiplication did not differ significantly in red cells from Tharus versus those from non-Tharu controls. By contrast, the frequency of alpha-thalassemia is uniformly high in Tharus, with the majority of them having the homozygous alpha-/alpha-genotype and an overall alpha-thal gene (alpha-) frequency of .8. We suggest that holoendemic malaria has caused preferential survival of subjects with alpha-thal and that this genetic factor has enabled the Tharus as a population to survive for centuries in a malaria-holoendemic area. From our data we estimate that the alpha-thal homozygous state decreases morbidity from malaria by about 10-fold. This is an example of selection evolution toward fixation of an otherwise abnormal gene.

Animals↗
PubMed1990

p-fluoro-phenylalanine resistance in Aspergillus nidulans diploid cells: evidence that dominant, lethal mutations are involved.

An unexpectedly large number of p-fluoro-phenylalanine (FPA)-resistant mutants have been recovered after UV-irradiation of wild type diploid conidia of Aspergillus nidulans. At least five different classes of mutants, possibly corresponding to five different loci, have been identified. Two of them may be the dominant loci which have already been described but the others (a minimum of three loci) are completely different. Mutations in these loci confer high level FPA resistance in the heterozygous diploids, being lethal in the haploids; one mutation has been preliminarily mapped to chromosome I and another to chromosome III.

Aspergillus nidulans↗
PubMed1990

Frequency of spontaneous and induced recessive mutations in a diploid strain of Aspergillus nidulans.

The spontaneous and UV-induced frequencies of recessive mutations have been studied in a diploid strain of Aspergillus nidulans, by the p-fluoro-phenylalanine (FPA) and 8-azaguanine (8-AZA) resistance tests, on either resting or germinating conidia. Observed frequencies are in the order of magnitude of those expected, which have been calculated considering the observed mutation frequencies in the haploid strain as well as the mitotic recombination frequencies. We also review some papers which claim to have found higher rates of recessive mutations in mammalian cell lines; in some cases no really higher rates are evident and the authors' conclusions often rest on misinterpretation of their own data.

Aspergillus nidulans↗
PubMed1988

An uvsB mutant of Aspergillus nidulans with high variable spontaneous mutation and intergenic mitotic recombination frequencies.

An UV-sensitive mutant has been isolated with a new technique which allows isolation of UV-sensitive and UV-non-mutable mutants in Aspergillus nidulans. This mutant is an allele of the known uvsB gene but shows some features not previously described in the alleles so far isolated. Its more important characteristics are: (1) Frequency of mitotic intergenic recombination is strongly increased in uvs/uvs diploids and it is highly variable in different clones: it varies from a minimum of 40-fold to a maximum of about 1000-fold in comparison with uvs+/uvs+ strains. (2) The frequency of mitotic intergenic recombination is increased also in the heterozygous diploids. (3) The frequency of spontaneous mutation is higher and highly variable in different subclones: it may be increased up to 1000-fold.

Aspergillus nidulans↗
PubMed1988

Decreased malaria morbidity in the Tharu people compared to sympatric populations in Nepal.

The Terai region of Nepal has been known to be heavily malarious since remote times, and it has, therefore, been regarded as uninhabitable by most Nepalese people. The Tharu people, who have been living in the Terai for centuries, were reputed to have an innate resistance to malaria. Following successful control of malaria by the Nepal Malaria Eradication Organization (NMEO), a large and heterogeneous non-Tharu population now inhabits the Terai along with Tharus. By analysing NMEO records, we have found that the prevalence of cases of residual malaria is nearly seven times lower among Tharus compared to sympatric non-Tharus. This difference applies to Plasmodium vivax, which is now much more common, and to Plasmodium falciparum. We suggest that the basis for resistance to malaria in the Tharu people is a genetic factor yet to be identified.

Adolescent↗
PubMed1986

A comparative study on selected chemical carcinogens for chromosome malsegregation, mitotic crossing-over and forward mutation induction in Aspergillus nidulans.

10 "false negative" chemical carcinogens, i.e. ineffective in bacterial mutagenicity assays, were thoroughly investigated for their genotoxic activity in the mould Aspergillus nidulans. Forward mutations (methionine suppressors), mitotic crossing-over and chromosome malsegregation were the end-points scored. Positive results were obtained in tests for the induction of mitotic segregation with benzene, ethylenethiourea and urethane, which increased the frequency of abnormal presumptive aneuploid colonies with euploid sectors showing whole chromosome segregation (i.e. non-disjunctional diploids and haploids). The same compounds were ineffective in increasing the frequency of mitotic crossing-over or forward mutations. The other chemical carcinogens investigated, namely acetamide, amitrole, dieldrin, heptachlor epoxide, nitrilotriacetic acid, p,p'-DDT and thiourea were ineffective both as inducers of forward mutations and mitotic segregation.

Aspergillus nidulans↗
PubMed1986

Genetic studies on the Tharu population of Nepal: restriction endonuclease polymorphisms of mitochondrial DNA.

The mitochondrial DNAs (mtDNAs) of 91 Tharus from Nepal were screened for restriction fragment length polymorphisms (RFLPs) using six highly informative restriction endonucleases. One pattern (morph) was found for BamHI, two for HpaI and HincII, three for HaeII, four for AvaII, and six for MspI. Two of the AvaII and four of the MspI morphs were "new" (not previously described). Virtually all of the "old" morphs found in the Tharus were previously observed in Orientals. The Oriental HaeII morph (HaeII-5) previously observed at a frequency of 5% was present in 25% of the Tharus. Of the 13 Tharu mtDNA types (defined by the six restriction endonuclease morphs) observed, five had previously been described ("old" types), all in Orientals. Three of these were unique for Orientals. All of the remaining eight "new" Tharu mtDNAs were all closely related to Oriental mtDNAs. Two of the "old" Tharu mtDNA types included the HpaI/HincII morph 1, a morph possibly indicative of the earliest human mtDNA types. From these data we have concluded that the Tharu mtDNAs are closely related to those of other Oriental populations. Further, our data support the hypothesis that human mtDNAs radiated from Asia.

Asian People↗
PubMed1985

Deregulation of immunoglobulin expression: is this the main cause of Burkitt's lymphoma?

We here examine the role of c-myc in the aetiology of Burkitt's lymphomas. We suggest that c-myc causes cellular clones to become immortal while the deregulation of cell multiplication is the consequence of an altered production and/or structure of immunoglobulin chains caused by the 8-14, 8-2 or 8-22 translocations. Data relative to other immunoproliferative disorders are consistent with the hypothesis that the immunoglobulins play a key role in the regulation of the multiplication of lymphocytic cells.

Burkitt Lymphoma↗
PubMed1985

Malignant melanoma in Rome, Italy, 1970-9.

An epidemiological study was conducted in the city of Rome and the incidence of malignant melanoma was determined retrospectively for the years 1970-9. All patients had legal residence in Rome and a histological diagnosis of melanoma during that period; only cases of malignant melanoma of the skin (ICD 172, 8th revision) were considered. A total of 17 public and 82 private hospitals were involved in the study with 11 081 and 6127 hospital beds respectively. All the hospitals in the study had one of the following therapeutic and diagnostic facilities: internal medicine, dermatology, oncology, radiology, surgery, plastic surgery, histopathology. Analyses of incidence are based on 500 cases, 237 males and 263 females, collected in the period 1970-9. The data indicate a positive time trend in incidence; the average annual increase is 0.27 cases/year per 100 000. The data show that in a Mediterranean and Latin country such as Italy the incidence of melanoma presents the same ascending trend as that of other Caucasian countries, whether European or not, the slope of the curves is similar for both sexes. The distribution of the primary site for both sexes is closely parallel to that described for all Caucasian populations, the lower limbs being more affected in females and the trunk in males.

Adult↗
PubMed1980

Effect of azelaic acid on human malignant melanoma.

In 23 patients with malignant melanoma, including some with metastases and terminal patients, topical and oral (10--15 g daily) azelaic acid given for 1--12 weeks before surgical excision of the lesions was followed by arrest and subsequent regression of the advancing edge of lesions, reduction in size and flattening of nodular areas, and progressive lightening of pigmentation. Histological and ultrastructural effects included: degeneration and disappearance of malignant epidermal and dermal melanocytes with reduction of junctional activity; epidermal proliferation and return towards normal organisation; reappearance of papillary dermis, pilosebaceous units, and sweat glands; separation of dermal melanoma tumour masses into smaller collections of cells by regenerating connective tissue; and increase in number of dermal mast cells, macrophages, and round cells. These preliminary results indicate a direct cytotoxic effect of azelaic acid on melanocytes of human melanoma.

Administration, Oral↗