PubMed Health⌕ Search

Biomedical subjects

F Spirito

Publications and source records attributed to F Spirito.

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

The exact values of the probability of fixation of underdominant chromosomal rearrangements.

A numerical analysis of the probability of fixation of a chromosomal mutation with partial sterility of the heterozygote in a single population is performed. Three different genetic models are considered: the first model entails constant selection against the heterozygote and is the model almost universally used in previous works; in the other two models selection against the heterozygote depends on its frequency. The exact values of the fixation probability are found by iterating transition matrices with genotype specification. Differences in results among models are small. The exact values found in the first model are compared to estimates obtained from approximations. Solutions based on diffusion models give good approximations when selection against the heterozygote is low, especially if the population is very small. For the higher values of the selection coefficient against the heterozygote, the estimates are rather imprecise, especially when the populations are not very small.

Animals↗
PubMed1988

Granular cell tumor of the esophagus.

Granular cell tumor (GCT) of the esophagus is a rarely-met-with neoplasm. It is almost invariably benign in character and is of still-disputed histogenesis. Small lesions are asymptomatic. Those over 1 cm in diameter may be accompanied by painful swallowing or retrosternal discomfort. Local resection is the treatment of choice for lesions that are accompanied by symptoms, or that are larger than 1 cm. A tumor incidentally encountered in an asymptomatic patient may be safely followed endoscopically. A successful endoscopic removal of such a lesion is described.

Adult↗
PubMed1987

Reduction of neutral gene flow due to the partial sterility of heterozygotes for a linked chromosome mutation.

The effect of linkage between a chromosome mutation producing partially sterile heterozygotes and a neutral locus in reducing the gene flow at the neutral locus is studied using a two-population deterministic model. Chromosome mutations are more efficient in reducing gene flow with low migration rates than with high ones. The interaction between high values of partial heterozygote sterility and low recombination rates can produce, in the low migration pattern, a drastic reduction of gene flow. Nevertheless, since only chromosome mutations with low values of partial heterozygote sterility are likely to be involved in chromosomal speciation, a significant reduction of gene flow will probably occur only for a very limited part of the genome. Therefore, a single chromosome mutation is unlikely to play a primary role in speciation.

Biological Evolution↗
PubMed1987

The reduction of gene exchange due to a prezygotic isolating mechanism with monogenic inheritance.

The efficiency of an incomplete prezygotic reproductive isolating mechanism in one- and two-population models is studied. The isolating mechanism studied has a monogenic hereditary basis, and depends on the fact that the various genotypes "choose" different periods or sites to perform their reproductive activity. In the one-population models, the "neutral" gene exchange between the two morphs characterized by the alternative forms of the isolating mechanism decreases drastically only when there is an extremely low frequency of individuals with different genotypes reproducing in the same sites and during the same periods. Furthermore, the reduction in gene exchange caused by the prezygotic isolation is smaller with tight linkage between the gene-determining partial reproductive isolation and the neutral gene. In the two-population models the prezygotic isolation causes a reduction in gene exchange which is smaller with low migration rates, and is negligible for very low rates.

Gene Frequency↗
PubMed1978

[Recording of the right atrial monophasic action potential in humans. I. Subjects not affected by arrhythmia].

Using a bipolar suction electrode technique, right atrial monophasic action potential (RA MAP) was recorded in 18 patients surely free from any kind of arrhythmia. Two morphologically different kinds of RA AMP were obtained: the former exhibiting an evident transition between phase 1-2 (plateau) and phase 3 of repolarization (FP), the latter without any appreciable palteau (FL). Electrophysiological properties of human myocardial atrial tissue have been investigated by microelectrode technique. The two types of MAP recorded by us resemble the former the action potential obtained from conducting specialized fiber, the latter the action potential of contractile fibers. A statistically significant difference in RA MAP duration measured at 90% level of repolarization (D 90%) was found between the two kinds of MAP: therefore we suggest to perform quantitative evaluations and pharmaco-ogical investigations only including MAPs of similar morphology. The intraindividual variation coefficient of D 90% may be considered an expression of the range of variability of repolarization duration in man; we suggest that only MAPs of similar configuration should be accepted for its calculation in order to avoid errors of evaluation.

Action Potentials↗
PubMed1976

Chromosome constitution of in vitro segregated haploid and diploid cells of the mouse.

The composition in segregated haploid sets of paternal and maternal chromosomes has been studied in order to verify whether their composition is uniparental of mixed, fixed or variable. Primary cultures where prepared using kidneys from hybrids of strains of Mus musculus in which the parental chromosomes are distinguishable; the maternal set consists of 20 teleocentric chromosomes, the paternal set of 9 metacentric chromosomes, derived by Robertsonian fusion and 2 telocentrics. Applying Seabright's banding technique, an analysis of segregated haploid and diploid cells, which have originated spontaneously through polyploidisation-segregation processes was carried out. It was concluded that the haploid sets have a variable composition of paternal and maternal chromosomes.

Animals↗
PubMedDate not supplied

Cutaneous gene transfer and therapy: the present and the future.

The easy accessibility of the skin as a therapeutic target provides an exciting potential for this organ for the development of gene therapy protocols for cutaneous diseases and a variety of metabolic disorders. Thus far, full phenotypic reversion of a diseased phenotype has been achieved in vivo for junctional epidermolysis bullosa and X-linked or lamellar ichthyosis and in vitro for xeroderma pigmentosum. These recessive skin diseases are characterized by skin blistering, abnormalities in epidermal differentiation and increased development of skin cancers, respectively. Corrective gene delivery at both molecular and functional levels was achieved by transduction of cultured skin cells using retroviral vectors carrying the specific curative cDNA. These positive results should prompt clinical trials based on transplantation of artificial epithelia reconstructed ex vivo using genetically modified keratinocytes. Promising results have also been obtained in phenotypic reversion of cells isolated from patients suffering from a number of metabolic diseases such as gyrate atrophy, familial hypercholesterolemia or phenylketonuria. In these diseases transplantation of autologous artificial epithelia expressing the transgenes of interest or direct transfer of the DNA to the skin represents a potential therapeutic approach for the systemic delivery of active molecules. Successful cutaneous gene therapy trials, however, require development of protocols for efficient gene transfer to epidermal stem cells, and information about the host immune response to the recombinant polypeptides produced by the implanted keratinocytes. The availability of spontaneous animal models for genodermatoses will validate the gene therapy approach in preclinical trials.

Animals↗
PubMedDate not supplied

Aneuploidy in metaphases II of spermatocytes of wild house mice from a hybrid zone between a Robertsonian population (CD: 2n = 22) and a population with the standard karyotype (2n = 40).

Meiotic metaphases II from archival slides were studied of male house mice caught in a hybrid zone between a population monomorphic for nine centric fusions (2n = 22) and a population with the standard karyotype (2n = 40), near Rome. The frequency of aneuploidy increases, up to 50%, with increasing number of heterozygous centric fusions (1-4).

Aneuploidy↗
PubMedDate not supplied

[Peptic ulcer in liver cirrhosis].

The frequency of peptic ulcer and the role of ulcerogenic risk factors in cirrhotic patients were evaluated in a retrospective study. Peptic disease was observed in 18.2% of the cirrhotic patients examined. When compared to the prevalence of ulcerative lesions in the general population, this finding suggests that cirrhotic patients have the same probability of being affected by peptic ulcer as non-cirrhotic subjects. The analysis of ulcerogenic risk factors highlighted the importance of alcohol and smoking. The etiology of cirrhosis and portal hypertension were not found to be important. In conclusion, peptic disease is not more frequent in cirrhotic patients than in the general population.

Adult↗