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Biomedical subjects

C A Redi

Publications and source records attributed to C A Redi.

At least 37 records · Page 2Linked to original sources
PubMed1995

Descriptive kinetics of the seminiferous epithelium cycle and genome size in the mole Talpa occidentalis (Insectivora).

The male germ cell cytodifferentiative process of the mole Talpa occidentalis is described. Cytochemical procedures were used 1) to follow acrosome formation and spermatid differentiation, dividing the seminiferous epithelium cycle into ten stages, each characterized by typical germ cell-to-cell associations, and recognizing 13 steps in spermatid differentiation; 2) to monitor, in situ, histones replacement by protamines at step 11 of the spermiogenic process. The seminiferous epithelium cycle of the mole has the basic histological features present in all mammals and appears rather similar to that of the common shrew (Sorex araneus), the only one so far known among Insectivora. The metabolism of the DNA-associated proteins reveals that protamines replace histones during the late steps (11-13) of spermiogenesis, mRNA for protamines having been synthesized at an earlier step (assuming that in the mole this occurs at the first spermiogenic steps, as in the house mouse). In addition the genome size (5.0 pg) and the AT/GC ratio (1.3) were evaluated.

Acrosome↗
PubMed1995

Chromatin organization during mouse oocyte growth.

We investigated the changes in the organization of oocyte nuclear chromatin and nucleolar-associated chromatin throughout folliculogenesis. Zona-free oocytes were isolated from ovaries, grouped into seven classes according to size and chromatin organization, and analyzed after staining with Hoechst 33342. We show that oocyte differentiation from the dictyate stage to the conclusion of maturation is associated with either of two chromatin configurations. Initially, all oocytes are in the NSN configuration (nonsurrounded nucleolus oocytes; characterized by a Hoechst positive-chromatin pattern of small clumps forming a network on the nuclear surface, with a nucleolus nonsurrounded by chromatin). While growing some of these NSN oocytes continue their development in the NSN configuration, whereas others shift (from class IV on) into the SN configuration (surrounded nucleolus oocytes; characterized by a threadlike chromatin organization that may partially surround the nucleolus or project towards the nuclear periphery). The percentage of SN oocytes increases both with increasing size of the oocyte (class I-III, 10-40 microns in diameter: 100% NSN vs. 0% SN; class VII 70-80 microns in diameter: 47.3% NSN vs. 52.3 SN, in 4-6-week-old females), and with aging (class VII: 94.1% NSN vs. 5.9% SN in 2-week-old females; 11.8% NSN vs. 8.2% SN in 56-week-old females). Further, we suggest as a working hypothesis that those oocytes that switch to the SN chromatin organization early in maturation may not be ovulated, even though this particular chromatin structure normally occurs just prior to ovulation.

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↗
PubMed1995

Study of genome organization by DNA cytochemistry and fluorescence imaging: a review.

DNA analysis by quantitative cytochemistry has been a widely exploited approach to investigate chromatin superstructural changes in relation to cell function and cell cycle progress. To this aim, a number of dyes (especially fluorochromes) for nucleic acids have been used, exhibiting different peculiarities, in terms of both binding mechanism and base specificity. Less attention has been paid to the application of different DNA staining techniques for studying possible differences in genome organization among different taxa. The purpose of this paper is to review and discuss the present reports in the literature, concerning the cytochemical analysis of genome organization, in a comparative perspective. Special attention is given to the integration of quantitative studies based on cytofluorometric and imaging techniques.

Animals↗
PubMed1994

Development and loss of the ability of mouse oolemma to fuse with spermatozoa.

To further our knowledge on the mechanisms and molecules involved in mouse sperm-oocyte plasma membrane interaction, experiments were carried out to determine the stage during oogenesis at which an oocyte acquires the capacity to fuse with acrosome-reacted sperm. Zona-free oocytes 10 microns in diameter do not fuse with sperm. Oolemma fusibility is first acquired when the oocyte reaches about 20 microns in diameter. Fusibility is maintained even after fertilisation has occurred and is lost completely by the 4-cell stage.

Acrosome↗
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↗
PubMed1993

Further examination of the kinetics of gonadal development in XY female mice.

Y-chromosomes derived from house mouse populations of Mus domesticus are able to lead to the formation of XY females (i.e. hermaphrodite individuals with both ovarian and testicular tissues) when inserted, by appropriate crosses, into the C57BL/6J genome, which usually carries the Mus musculus Y chromosome. An abnormal interaction between the testis-determining gene on the Y (of domesticus origin) and an autosomal recessive allele (of musculus origin) needed for testicular formation is the likely explanation of this phenomenon. In the present paper we analyse the histological kinetics of gonadal development in hermaphrodites obtained by introducing the Y chromosomes from wild living house mice [from Zagreb, (Croatia) and Hohenentringen (Southern Germany)] into the C57BL/6J genome. Among 88 individuals, 9 XY hermaphrodites were detected, 6 before birth and 3 afterwards. The percentage of the ovarian-type tissues in the ovotestes fell drastically between day 18 of fetal life and day 20 after birth. These findings corroborate and extend those already published for other Y domesticus chromosomes and stress the possible role of Y chromosome differentiation in speciation processes.

Aging↗
PubMed1990

Protamine amount and cross linking in mouse teratospermatozoa and aneuploid spermatozoa.

The level of SH-group oxidation in spermatozoa from the cauda epididymis was measured by a cytofluorometric method in chromosomally normal mice and two chromosome mutants. The first one, a tertiary trisomic karyotype (Ts(1(13]7OH), is characterized by severe oligospermia and high levels (approximately 75%) of malformed spermatozoa. The second, a hybrid between two European feral mouse stocks, is heterozygous for multiple Robertsonian translocations and produces exclusively aneuploid spermatozoa. Neither the severe teratospermiogenesis nor the severe aneuploidy was reflected in total SH-group fluorescence values nor in free SH-group fluorescence. It is concluded that both the production of protamines and protamine cross linking by S-S bridge formation are rather autonomous processes during spermatogenesis because 1) the increased DNA variance of the aneuploid spermatozoa is not reflected in an increased variance of the total and free SH-groups, 2) aneuploidy for the protamine gene carrying chromosome 16 is not reflected by the SH-group values for individual spermatozoa, and 3) protamine production and cross linking are independent of the mild to severe terataspermiogenesis in the tertiary trisomic karyotype.

Aneuploidy↗
PubMed1990

Differences in the organization and chromosomal allocation of satellite DNA between the European long tailed house mice Mus domesticus and Mus musculus.

We compared the organization of satellite DNA (stDNA) and its chromosomal allocation in Mus domesticus and in Mus musculus. The two stDNAs show similar restriction fragment profiles after digestion (probed with M. domesticus stDNA) with some endonucleases of which restriction sequences are present in the 230-240 bp repetitive unit of the M. domesticus stDNA. In contrast, EcoRI digestion reveals that M. musculus stDNA lacks most of the GAATTC restriction sites, particularly at the level of the half-monomer. The chromosome distribution of stDNA (revealed by an M. domesticus stDNA probe) shows different patterns in the M. domesticus and M. musculus karyotypes, with about 60% of M. domesticus stDNA retained in the M. musculus genome. It is particularly noteworthy that the pericentromeric regions of M. musculus chromosomes 1 and X are totally devoid of M. domesticus stDNA sequences. In both groups, the differences in energy transfer between the stDNA-bound fluorochromes Hoechst 33258 and propidium iodide suggest that AT-rich repeated sequences have a much more clustered array in the M. domesticus stDNA, as if they are organized in tandem repeats longer than those of M. musculus. Considering the data as a whole, it seems likely that the evolutionary paths of the two stDNAs diverged after the generation of the ancestral 230-240 bp stDNA repetitive unit through the amplification, in the M. domesticus genome, of a family repeat which included the EcoRI GAATTC restriction sequence.

Animals↗
PubMed1990

Kinetics of oogenesis in mice heterozygous for Robertsonian translocation.

The total number of oocytes at different postmating time intervals (18-40 days) was determined in mice homozygous and heterozygous for different Robertsonian (Rb) translocations, of both laboratory and feral origin. The number of oocytes was lower in heterozygous than in homozygous mice throughout the period studied. Independently of the genetic background (i.e. laboratory or feral), structural heterozygosity had a progressive detrimental effect on oocyte numbers: open, or chain diakinetic configurations had a greater detrimental effect than close, or ring, configurations. The genetic background, however, affected the ovarian constitution in terms of the total number of germ cells, which are more numerous in laboratory than in feral mice. The kinetics of oogenesis seems to be faster in feral than in laboratory mice. At the light of the data here presented, and of those already available from the literature on male and female gametogenesis in conditions of structural heterozygosity, it appears that factors other than unsaturation of pairing sites or interference with pachytene X-chromosome inactivation have to be considered. In the wild, the reduced oocyte numbers in Rb heterozygous female can contribute to the retention of isolated populations in contact zones.

Animals↗
PubMed1989

Spermatogenesis in heterozygotes for Robertsonian chromosomal rearrangements from natural populations of the common shrew, Sorex araneus.

Twenty-two adult male common shrews were collected from 5 sites in the vicinity of Oxford (UK) close to the zone of hybridization between two karyotypic races. The shrews were subdivided into 3 karyotypic categories: homozygotes, simple Robertsonian heterozygotes (which form one or more trivalents at prophase I of meiosis) and complex Robertsonian heterozygotes (which form a quadrivalent). The ratio of primary spermatocytes to round spermatids was determined from transverse sections of seminiferous tubules, to provide an indication of germ cell death. In no individual was there severe germ cells loss. Homozygotes had the highest mean spermatocyte: spermatid ratio and complex heterozygotes the lowest, but there was substantial individual variation and the differences were not significant. Complex heterozygotes also had a higher proportion of defective seminiferous tubules and lower testis weights than did other categories and it is reasonable to propose that, as a population, complex heterozygotes had reduced fitness relative to other categories on the basis of spermatogenic performance. However, there is no evidence from studies of spermatogenesis that simple Robertsonian heterozygotes are less fit than homozygotes.

Animals↗
PubMed1988

Chromatin topology during the transformation of the mouse sperm nucleus into pronucleus in vivo.

Time relationships of sperm chromatin dispersion and sperm nucleoprotein replacement have been studied in vivo, by an in situ cytochemical approach. We used the Feulgen reaction to reveal DNA, which allow us to record both processes simultaneously, on the basis of the return after fertilization to haploid Feulgen values after sperm nucleoprotein replacement with somatic histones. We have shown that sperm nucleoprotein replacement occurs at around anaphase II, whereas sperm chromatin dispersion is massive between the anaphase and telophase II oocyte phases. The morphological pattern of sperm chromatin dispersion supports the idea that the process involves the whole sperm chromatin mass simultaneously, with the region located between the implantation fossa and the postacrosomial region the last to swell.

Anaphase↗
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↗