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S Garagna

Publications and source records attributed to S Garagna.

49 records · Page 3Linked to original sources
PubMed1986

Descriptive kinetics of spermatogenesis in four chromosomal species of the Spalax ehrenbergi superspecies in Israel.

The descriptive kinetics of the spermatogenic process has been studied in the four chromosomal species of Spalax ehrenbergi between November and March, the active period of reproduction. Spermatid development can be subdivided into 16 steps in which the acrosome formation is clearly distinguishable and the Golgi, cap and acrosomic phases are identifiable. The first 12 steps of spermiogenesis can be utilized for the definition of characteristic time-dependent relationships among different germ cell associations (stages): twelve stages, I-XII, are clearly identifiable. In this regard no differences exist among the four chromosomal species. In general, the spermatogenic process in this species has the same pattern as that of Mus domesticus. Two relevant points distinguish Spalax spermatogenesis from Mus spermatogenesis: 1) the presence, throughout the stages I-XII of the seminiferous epithelium cycle of a larger size, oval shaped spermatogonium type containing heterochromatic granulations; 2) the Sertoli cells show only one heterochromatic clump closely attached to the nucleolus; moreover, the Sertoli cell cytoplasm is more PAS-positive than that of Mus.

Animals↗
PubMed1986

Pericentromeric heterochromatin and A-T contents during Robertsonian fusion in the house mouse.

The pericentromeric heterochromatin of meiotic trivalents formed by the Robertsonian (Rb) chromosomes and the two homologous acrocentrics in the house mouse was evaluated by static cytophotometry after selective staining. To reveal pericentromeric heterochromatin specifically, C-banding Giemsa and Hoechst 33258 stains were utilized. Five different Rb chromosomes were investigated and none of them possessed less pericentromeric heterochromatin than the sum of the two homologous acrocentrics. Moreover the total A-T (DAPI) and DNA (PI) content was quantitatively evaluated, by flow cytometry, in G0/G1 nuclei belonging to four different Rb mouse populations, karyotypically characterized by the presence of up to nine Rb chromosomes. Again there were no significant difference, of DAPI and PI content, in the Rb populations nor between any of them and the NMRI/HAN strain with forty acrocentric chromosomes. We conclude that the main consequence of Robertsonian processes (i.e. the rapid variation of the karyotype structure) does not imply detectable quantitative variation in the genome portion involved in the Rb process. We also discuss the possibility that the high rate of Rb exchange in the house mouse could be favoured by the simultaneous effects of undetectable losses of chromosomal material, high repetitiveness of the DNA involved, the presence of the same major type of satellite DNA over each chromosome and the all acrocentric constitution of the karyotype.

Adenine↗
PubMed1986

Sperm-chromatin maturation in the mouse. A cytochemical approach.

Cytochemical techniques were used to study chromatin during spermiogenesis and sperm maturation in the mouse, starting from the stages at which the substitution of somatic histones by testis-specific proteins occurs. It was possible to distinguish and analyze the different temporal incidence of two processes involved in sperm maturation, i.e. chromatin condensation (a tridimensional highly compacted arrangement) and chromatin stabilization (a tough structure, which protects the genome DNA). The first process, involving a reduction in the nuclear size and a decrease in the amount of sperm DNA accessible to specific cytochemical reactions and stainings, was found to reach its maximum in caput-epididymidis spermatozoa, in which electron microscopy revealed that the sheared chromatin was mainly organized into 120-A-thick knobby fibers. No further changes were found in sperm up to their appearance in the fallopian tubes. On the contrary, chromatin stabilization, the onset of which occurs in the testis (at the late spermatid stage) via the formation of -S-S- cross-links, is completed in the vas deferens, where chromatin has a superstructure consisting of thicker fibers, with diameters of 210 and 350 A. The reductive cleavage of disulfides in vas-deferens spermatozoa does not completely destroy the superstructure of sperm chromatin, which could indicate 'coiling' of the basic knobby fiber. In fact, when the ion concentration was increased, the chromatin of vas-deferens spermatozoa appeared to be organized into fibers with diameters similar to those of the caput epididymidis. This unique organization of mature sperm chromatin should have an essential role in the fast swelling of spermatozoa during fertilization.

Animals↗
PubMed1986

Cytochemical evaluation of sperm and lymphocyte DNA content after treatment with 5 N HCl.

In situ as well as extra situm cytochemical methods were used to investigate why the observed Feulgen-DNA value of sperm versus lymphocyte cells is lower than expected. After treatment with 5 N HCl, in situ experiments involving the GCA reaction and the UV cytophotometry showed the loss of DNA in sperm nuclei to be 12% more than that in lymphocyte nuclei. Extra situm study of sperm and lymphocytes treated with 5 N HCl showed the phosphate and DABA contents of sperm to be 35% and 23%, respectively, less than those of lymphocytes. The data suggest that sperm chromatin is much more sensitive than somatic chromatin to HCl depolymerization during the Feulgen reaction, and this can tentatively be attributed to the protein complement of sperm chromatin.

Animals↗
PubMed1985

The effects of some Robertsonian chromosome combinations on the seminiferous epithelium of the mouse.

In Mammals, structural rearrangements of the karyotype cause considerable trouble to the spermatogenic process. Making use of an experimental animal model of Robertsonian chromosomal variation in the house mouse (Gropp, Winking & Redi, 1982a) the effects of these chromosome structural rearrangements on the spermatogenic process were studied in fertile and chromosomally derived subfertile and sterile mice. Each karyotype condition was related to the cytological composition of the twelve stages of the seminiferous epithelium, studied in PAS-haematoxylin-stained testicular sections, with the following results: in subfertile males there is a depletion of spermatogonia in the regenerating compartment but their differentiation is not affected. In the sterile males there is degeneration of primary and secondary spermatocytes and massive spermatid degeneration. Spermatocyte development is retarded in nearly 50% of the spermatocyte population in subfertile males. Moreover the ratio between primary spermatocytes and spermatids is reduced to about 1:2 in subfertile males, while the few spermatids produced in sterile males had degenerated during stages I to VIII. The number of Sertoli cells/100 micron throughout the cycle of spermatogenesis is the same in the three conditions studied. These data indicate that the spermatogenic process is affected by structural changes not only at the meiotic level (primary spermatocyte failure to follow the normal pattern of differentiation and occurrence of defective spermatids) but also at the premeiotic stage, when undifferentiated spermatogonia are regenerating.

Animals↗
PubMed1984

Influence of the C-banding procedure on DNA and proteins of mouse chromosomes: I. A microdensitometric study.

Cytochemical quantitative methods were used to investigate DNA protein contents of mouse metaphase plates during an alkaline C-banding procedure ( Sumner et al., 1971). Cytochemical stains and reactions for DNA and for total protein content were used to quantitatively assess the sequential involvement (losses) of DNA and protein during the appearance of the classic C-banding pattern which was monitored with Giemsa staining. The data point the preferential loss of DNA from euchromatic regions of chromosomes as the main cause of the C-banding pattern appearance. The effect of chromosomal protein is more likely indirect and perhaps tied to some specific interaction with centromeric DNA that contributes to DNA retention in C-bands. Following the C-banding procedure it was possible to differentially stain the centromeric area with Feulgen and GCA and even with non-fully specific stain for DNA such as methylene blue.

Animals↗
PubMed1983

Nuclear DNA content distribution in five parotid gland tumors. A preliminary report.

Quantitative cytophotometric evaluations of nuclear DNA content were made on epithelial cells obtained from five cases of parotid gland tumors. The measurements were performed on sections stained with Feulgen reaction and, as control of diploid value, adventitious small lymphocytes as well as normal epithelial cells were considered. A fairly good correlation between the type of histogram of DNA values and a progressive degree of atypia was found since particularly high levels of hyperdiploidy were found in more severe tumors.

Adult↗
PubMed1982

Cytochemical assessment of chromatin characteristics during sperm cytodifferentiation in mouse.

Cytochemical quantitative reactions either for DNA or proteins were performed on spermatozoa in the last stages of the sperm cytodifferentiative process. The analysis of the discrepancy between the expected (1C amount) and the evaluated reaction intensities sheds light on the chromatin condensation phenomenon. The high inactivation and protection of the paternal genome in a particularly packed chromatin has generally been regarded as the cause of non-stoichiometric responses by DNA specific reactions. We suggest that this interpretation fits well for specific DNA reactions based on intercalation between base pairs or DNA phosphate groups binding, but for the Feulgen reaction the cause is more complex and pertains to the particular susceptibility of the sperm chromatin to depolymerization by hydrolysis in the Feulgen reaction.

Animals↗
PubMedDate not supplied

Human-dominated ecosystems and restoration ecology: Seveso today.

Seveso is a town (40,000 inhabitants) 16 km north of Milan, which from 10 July 1976 became synonymous with the chemically induced ecological catastrophe because of the large number of people affected by dioxin exposure and of the large area involved. The most polluted area (about 43 ha) was artificially reconstructed and transformed into a wood composed mainly of oaks with some scattered green fields and some bushy areas, the Bosco delle Querce urban park. A four-year survey monitoring the present ecological and biological risk parameters of the artificially reconstructed ecosystem shows its full ecological recovery as an urban park. Plant and animal coenoses are well composed and the park has been colonized by annelids, insects, amphibians, reptiles, birds and mammals. All these animals are useful biological reagents for risk-assessment because of their potential long-term exposure to TCDD. When some of the endpoints of the xenoestrogen-like molecules' action were studied (i.e., gametogenesis and the gross morphology of genital organs in rabbits and house mice), no signs of TCDD effects were detected. Mutagenicity tests and the house mouse sperm DNA COMET assay do not reveal the presence of any biological risk. The study of the carabidocoenosis and the housefly cytogenetics corroborates this last indication, thus guaranteeing the successful ecological recovery of the formerly most polluted Seveso area.

Amphibians↗
PubMedDate not supplied

Chromosome variability and germ cell development in the house mouse.

Structural heterozygosities of the karyotype have detrimental effects on the meiotic process, resulting very often in impairment of fertility in the carriers. Both male and female germ cell development are affected by chromosomal variability although spermatogenesis seems particularly prone to be affected, probably because of the intrinsic characteristics of the male germ cell cytodifferentiation process (i.e. the histological architecture of the seminiferous epithelium). However, euploid and aneuploid sperm do not seem to differ in the molecular organization of the genome they carry, thus explaining the almost regular capacity to accomplish the first zygotic developmental stages by the aneuploid sperm (aneuploid both for gametogenic genes and for entire chromosomal arms). A survey of the molecular and morphological data available on germ cell development in conditions of chromosomal rearrangement leads to the conclusion that the current hypotheses accounting for this phenomenon can only partly explain it. A working hypothesis is proposed which considers the three-dimensional changes (produced by structural heterozygosity) in the spatial order of chromosomes within the nucleus as the primary cause potentially able to trigger distorted functioning of the germ cells.

Aneuploidy↗