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Biomedical subjects

E Capanna

Publications and source records attributed to E Capanna.

At least 19 recordsLinked to original sources
PubMed2000

Female gonad of moles, genus Talpa (Insectivora, mammalia): ovary or ovotestis?

The female gonads of moles (genus Talpa) are composed of a cortex, functioning as an ovary, and a medulla, which is structurally similar to that of the testis. In the female reproductive apparatus there are masculine glandular annexes, such as a bilobate prostate, two Cowper glands, and a penis-like clitoris. All these features have recently led to the hypothesis of the presence of hermaphroditism due to sex-reversal in Talpa. The purpose of this study is to understand the functional significance of the structural organization of the female gonads in order to verify this hypothesis. Histological, histochemical and ultrastructural analyses have been carried out on several gonads of both sexes of two species: T. europaea and T. romana, including three fetuses. In both species, the cortical region of the female gonad shows a regular oogenetic activity. While the medulla is composed of interstitial cells that are partly organized in cord-like structures, no spermatogenetic activity has been ever observed inside of them. A histochemical analysis shows that in both sexes the interstitial cells secrete steroids, presumably estrogens as well as androgens. The presence of androgens in the female gonads would therefore explain the persistence of male glandular annexes in the female reproductive apparatus and both the sexual and behavioral monomorphism typical of the genus Talpa. Nonetheless, the female gonad of moles is a real ovary and a well-defined gonochorism exists. Therefore, there is no reason to assert the presence of hermaphroditism due to sex reversal.

Androgens↗
PubMed1999

Lazzaro Spallanzani: At the roots of modern biology.

The scientific work of Lazzaro Spallanzani is outlined, with emphasis on the elements of originality in his introduction of the experimental method in biology. Particular stress is placed on Spallanzani's contribution to solving the Theoria Generationis, from the problems connected with the spontaneous generation of living creatures to those of natural fertilization and artificial insemination and, finally, those of regeneration. J. Exp. Zool. (Mol. Dev. Evol.) 285:178-196, 1999.

Biology↗
PubMed1999

Contact zones between chromosomal races of Mus musculus domesticus. 1. Temporal analysis of a hybrid zone between the CD chromosomal race (2n=22) and populations with the standard karyotype.

A temporal analysis of a hybrid zone between chromosomal races of Mus musculus domesticus was performed to evaluate its dynamics over a 20-year period. The transect chosen was one previously analysed by Spirito et al. (1980) across the hycbrid zone between the chromosomal race CD 2n=22 (central Italy) and the surrounding populations with standard karyotype (2n=40). The results show that 20 years of hybridization have not had any significant effect on the position of this hybrid zone, nor on the location of its extreme margin, except for one site for which passive transport of mice may have been important. The absence of a significant shift of the tension zone excludes a possible imbalance between the two cytotypes; a fitness superiority of one homozygote greater than 0.01 would have produced an appreciable shift of the zone. The internal chromosomal structure of the zone shows a constant gradual increase in metacentric chromosome frequency towards the localities nearest the area inhabited by the 22-CD homozygote population. This contrasts with the previously reported data which indicated an irregular trend, particularly evident for the Rb(3.8), Rb(5.17) and Rb(6.13) chromosomes. For each Rb metacentric, we observed greater values of FST in the past sample than in the present one. These differences reveal a tendency towards the homogenization of adjacent populations, perhaps because of greater migration between adjacent demes resulting from increased commercial traffic. The Mantel test was performed for both temporal samples. A positive correlation between the geographical and chromosomal differentiation was demonstrated.

Animals↗
PubMed1997

Genome composition in Venezuelan spiny-rats of the genus Proechimys(Rodentia, Echimyidae). I. Genome size, C-heterochromatin and repetitive DNAs in situ hybridization patterns.

The genome sizes of the Venezuelan spiny-rats Proechimys guairae guairae (2n = 48) and P. trinitatis (2n = 62) were evaluated and proved to be 12.5 +/- 0.5 pg and 12.6 +/- 0.3 pg respectively, the highest so far recorded among mammals; also the C-heterochromatin (32.7%, Coefficient of Variation [CV] 3.8 and 35.8%, CV 4.4) and GC (44.2%, CV 2.7 and 43.6%, CV 2.9) contents are very high. Highly repetitive (rep) DNAs were isolated from restriction enzyme digested genomic DNAs of both species. The intra- and inter-specific chromosomal allocations of these rep DNAs were analyzed by direct and cross-hybridizations. Results show that the two genomes harbour several rep DNA families which show both species-specificity and interspecific relatedness in their in situ hybridization patterns. The rep DNA families show an equilocal distribution at both the pericentromeric areas of all chromosomes and in the whole arms of two pairs of the uniarmed group, suggesting co-evolution of the rep DNAs. P. g. guairae BamHI digested DNA, when cloned and sequenced, proved to consist of a long "composite" unit (1,239 bp) containing two copies of each of 75-bp and 110-bp internal subrepeats. Karyotype restructuring between P. g. guairae and P. trinitatis, mainly due to Robertsonian changes, was accompanied by slight intra- and intergenomic movements of the putative satellite DNA families within stable genome sizes and C-heterochromatin contents. We discuss the findings obtained in Proechimys in the light of those regarding the kangaroo rat, the pocket gopher and the house mouse; they support the idea that karyotype restructuring could be the expression of molecular driven events of rep DNA amplification and homogenisation through non-homologous chromosomes.

Animals↗
PubMed1995

Robertsonian metacentrics of the house mouse lose telomeric sequences but retain some minor satellite DNA in the pericentromeric area.

A combination of cytogenetic and molecular biology techniques were used to study the molecular composition and organisation of the pericentromeric regions of house mouse metacentric chromosomes, the products of Robertsonian (Rb) translocations between telocentrics. Regardless of whether mitotic or meiotic preparations were used, in situ hybridisation failed to reveal pericentromeric telomeric sequences on any of the Rb chromosomes, while all metacentrics retained detectable, although reduced (average 50 kb), amounts of minor satellite DNA in the vicinity of their centromeres. These results were supported by slot blot hybridisation which indicated that mice with 2n=22 Rb chromosomes have 65% of telomeric sequences (which are allocated to the distal telomeres of both Rb and telocentric chromosomes and to the proximal telomeres of telocentrics) and 15% the amount of minor satellite, compared with mice with 2n=40 all-telocentric chromosomes. Pulsed field gel electrophoresis and Southern analysis of DNA from Rb mice showed that the size of the telomeric arrays is similar to that of mice with all-telocentric chromosomes and that the minor satellite sequences were hybridising to larger fragments incorporating major satellite DNA. Since the telomeric sequences are closer to the physical end of the chromosome than the minor satellite sequences, the absence of telomeric sequences and the reduced amount of minor satellite sequences at the pericentromeric region of the Rb metacentrics suggest that the breakpoints for the Rb translocation occur very close to the minor satellite-major satellite border. Moreover, it is likely that the minor satellite is required for centromeric function, 50-67 kb being enough DNA to organise one centromere with a functionally active kinetochore.

Animals↗
PubMed1995

Whole-arm reciprocal translocation (WART) between Robertsonian chromosomes: finding of a Robertsonian heterozygous mouse with karyotype derived through WARTs.

The karyotype of a mouse trapped in a hybrid zone between a Robertsonian (Rb) population (2n = 22) and a population with the standard karyotype (2n = 40-alltelocentrics) shows two Rb chromosomes with new arm compositions. We suggest that whole-arm reciprocal translocations between Rb chromosomes gave rise to the new chromosome constitution and that such events can greatly help in understanding house mouse karyotype diversification and chromosomal speciation.

Animals↗
PubMed1995

Chromosomal distribution of the major satellite DNA of South American rodents of the genus Ctenomys.

The chromosomal distribution of the major satellite DNA of South American rodents of the genus Ctenomys was analyzed in eight species by in situ hybridization, using a probe isolated from C. porteousi. The hybridization patterns showed different numbers of chromosomes with positive pericentromeric regions and/or complete short arms. In some species, a positive signal was scarce (or not detectable, as in C. opimus), and was usually located in the pericentromeric areas (C. occultus and C. latro). In those species where the satellite was highly amplified, its chromosomal localization tended to encompass the entire length of the short arms. These patterns were compared with C-band distribution patterns in the same species. We discuss the putative evolutionary trend of this satellite DNA in the genus Ctenomys and suggest that it evolved from a strictly pericentromeric localization to comprising the whole short arms of some chromosomes.

Animals↗
PubMed1993

Genome distribution, chromosomal allocation, and organization of the major and minor satellite DNAs in 11 species and subspecies of the genus Mus.

We compared the genome distribution, chromosomal allocation, and organization of the major and minor satellite DNAs (satDNAs) in 11 species and subspecies of the genus Mus. Southern blot analysis of the major and minor satDNAs showed similar fragment profiles in all 11 species, with the exception of M. cervicolor and M. cookii for the major satDNAs and M. caroli, M. cervicolor, and M. cookii for the minor satDNAs, where these sequences could not be detected by the probes used. In situ hybridization of the major and minor satDNA probes revealed chromosome-specific allocations of these sequences with quantitative species-specific patterns. Fluorometric analysis of the organization of the satellite sequences suggested that in the M. domesticus genome satDNA sequences are clustered in tandem repeats that are longer than those present in other Mus genomes. When compared with the other Mus genomes so far studied, the domesticus genome shows the highest quantity of satDNA sequences with a long-range organization of satDNA sequences.

Animals↗
PubMed1989

Inter- and intra-individual chromosome variability in Thamnomys (Grammomys) gazellae (Rodentia, Muridae) B-chromosomes and structural heteromorphisms.

The present paper reports intra- and inter-individual variability related to the occurrence of numerous B-chromosomes in Thamnomys (Grammomys) gazellae, a species of African Climber rat belonging to the 'dolichurus' group. The frequency of B-chromosomes in somatic and spermatogonial metaphases is investigated, together with their behaviour during meiosis. Moreover, G-banding makes it possible to identify a structural polymorphism resulting from a pericentric inversion in a large chromosome (no. 6). The distribution of the constitutive heterochromatin has been assessed by C-banding. The nucleolus organizer regions (NOR's) were located by means of silver staining in four chromosomal pairs (nos. 1, 2, 4, and 6). The karyotype of T. (G.) gazellae is compared with that of other taxa of the dolichurus group, particularly the Somaliland population which also exhibits the occurrence of B-chromosomes. The origin and significance of B-chromosomes is discussed.

Animals↗
PubMed1987

Size and structure of the bird genome. II. Repetitive DNA and sequence organization.

1. Highly repetitive, middle repetitive and single copy DNA were evaluated in 19 species of birds, belonging to nine orders, by means of a reassociation kinetics method. 2. A rather uniform pattern is present in all the species studied (single copy = 60-75%; middle repetitive = 13-20% and highly repetitive 10-20%). 3. Reassociation kinetics of fragments of different length confirms the presence of a long period interspersion pattern. 4. Among different orders, no significant differences are observed. 5. DNA sequence organization seems to be related to genome size, with an inverse correlation between DNA nuclear content and amount of interspersed repetitive sequences.

Animals↗
PubMed1986

Size and structure of the bird genome--I. DNA content of 48 species of Neognathae.

The nuclear DNA content was evaluated in 48 species of Neognathae birds belonging to 13 orders, namely Anseriformes, Charadriiformes, Columbiformes, Ciconiiformes, Falconiformes, Galliformes, Gruiformes, Passeriformes, Pelicaniformes, Phoenicopteriformes, Piciformes, Psittaciformes and Strigiformes. The DNA content, expressed in pg/nucleus, ranges from 2.81 to 4.97. The genome size variability within and among families is discussed on the basis of the Hinegardner's (1976) model of genome evolution.

Animals↗
PubMed1984

Ultrastructural features of epididymal spermatophagy in subfertile chromosomally derived mice.

A cytochemical analysis of aneuploid gametes in chromosomally derived subfertile mice has demonstrated a prezygotic selection against the aneuploid gametes during the epididymal transit. The present investigation deals with an electron microscopic analysis of the epididymis in subfertile hybrid mice heterozygous for eight Robertsonian metacentrics. The epididymal epithelium of these mice appears to be formed by four cell types with different morphological features. In the tail of the epididymis all these cell types are present. Moreover, several giant vacuolizations of principal cells containing mature and immature spermatozoa are often visible in this region. This observation, confirming previous data on the fate of aneuploid spermatozoa on hypofertile Robertsonian heterozygotes, suggests a phagocytic activity of the epididymal epithelium of these mice. The epididymal epithelium "filter function" in recognizing and eventually disposing of immature or anomalous germ cells is discussed.

Animals↗
PubMed1983

Evolution of the genome size in Akodon (Rodentia, Cricetidae).

Nuclear DNA contents were estimated by microdensitometry in five species of Akodon rodents: Arodon molinae, A. dolores, A. mollis, A. azarae, Bolomys obscurus) and in three chromosomal varieties of A. molinae (2n = 42; 2n = 43, 2n = 22). The data obtained showed that the species with the highest DNA content was B. obscurus, followed in order of decreasing genome size by A. molinae, A. mollis, A. dolores and A. azarae. In A. molinae the forms with 2n = 42 chromosomes had the lowest and the forms with 2n = 44 the highest amount of DNA, while the forms with 2n = 43 had intermediate DNA contents. The variation in DNA amount detected in A. molinae was interpreted as a phenomenon of amplification occurring in the chromosomal areas involved in the chromosomal rearrangement giving rise to the polymorphism exhibited by this species. The DNA contents of shared chromosomes (chromosomes with similar size, morphology and G banding pattern, which are found in two or more phylogenetically related species), were compared and correlated with values of total nuclear DNA. The information obtained indicates that: (a) shared chromosomes have variable amounts of DNA: (b) in a given species there is a correlation between the amount of nuclear and chromosomal DNA in most shared chromosomes (and perhaps in most of the chromosomal complement), e.g., the higher the amount of nuclear DNA, the higher the content of DNA in shared chromosomes; (c) some chromosomes may undergo processes of amplification or deletion restricted to certain regions and usually related with mechanisms of chromosomal rearrangements.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

The chromosomes of the Hadada ibis and comments on the karyotype evolution in Threskiornithidae (Aves, Ciconiiformes).

The karyotype of Hagedashia hagedash differs from that of the other ibises karyotyped and introduces further karyotypic variability within the family Threskiornithidae. This variability is in contrast with the generalized karyotypic uniformity of birds and the karyotypic identity displayed by the family Ciconidae, which is closely related to the ibises. A discussion is presented of parameters of ethological structure of the populations that can, in some cases, allow chromosomal rearrangement to be fixed, thereby enhancing ongoing speciation phenomena in the Aves class.

Animals↗
PubMed1982

Robertsonian karyotype variation in wild house mice from Rhaeto-Lombardia.

The European longtailed house mouse (M. m. brevirostris and domesticus) in the Rhaetian Alps and Lombardia presents a complex system of Robertsonian (Rb) variation and karyotype diversity, several adjoining populations homozygous for multiple Rb metacentric chromosomes, sites of coexistence of different Rb types, and zones of hybridization with non-Rb populations. The original "tobacco mouse" is just one of many local Rb variants, such as those from other Alpine areas (e.g., Orobian Alps) or from Central Lombardia, where a relatively large region within which the population is homogeneous for multi-Rb metacentrics is found. The present study is based strictly on material in which the chromosome arms were identified by G-banding, so that karyotypes within the areas under investigation could be compared. Altogether 111 mice were studied.

Animals↗