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Biomedical subjects

A J Solari

Publications and source records attributed to A J Solari.

At least 55 records · Page 3Linked to original sources
PubMed1988

Pairing of ZW gonosomes and the localized recombination nodule in two Z-autosome translocations in Gallus domesticus.

Electron microscopic observations of synaptonemal complexes of oocytes from chickens heterozygous for two Z-autosome translocations have been used to identify and study the pairing region of the Z and W chromosomes. The two translocations, MN t(Z;1) and t(OH 10), have breakpoints in opposite arms of the Z, and the arm having the breakpoint of MN t(Z;1) is marked by the terminal C+ band. In both translocations the short arm of the W was specifically paired with the euchromatic short arm of the Z. In MN t(Z;1) only open quadrivalents (74%) and trivalents plus W univalents (26%) were observed, whereas t(OH 10) exhibited, in addition to the prevalent quadrivalents (62%), III + I (19%) and II + II (19%) configurations. The extent of W pairing was slightly decreased in MN t(Z;1) (68.4% of the W chromosomes paired) and considerably decreased in t(OH 10) (25.3% of the W chromosomes paired). Nonhomologous synapsis occurred regularly at the quadrivalent crosspoint in MN t(Z;1) and also in bivalents from t(OH 10). The recombination nodule normally located in the terminus of the pairing region in normal ZW pairs is present in both translocations without any alteration of its frequency or its strict terminal position. Based on these data and previous observations (Rahn and Solari, 1986), it is proposed that an obligatory recombination event occurs at a locus between 0.7 microns and 0.15 microns of the paired ZW telomeres, establishing a recombinational region and a pseudoautosomal region which determine partial sex-linkage and no sex-linkage, respectively. Most of the pairing region of the ZW pair is nonhomologously paired.

Animals↗
PubMed1986

Recombination nodules in the oocytes of the chicken, Gallus domesticus.

Chicken oocytes at pachytene were processed with the microspreading technique (Moses, 1977), and their synaptonemal complex (SC) complements were analyzed by electron microscopy. Ellipsoidal nodules, 140 X 120 nm in diameter, were associated with the central space of synaptonemal complexes. The average number of nodules per pachytene oocyte was 57.5. The number of nodules per bivalent showed a clear linear relationship with SC length, except for the microchromosomes, which showed a single obligatory nodule. The distribution of nodules along the 10 longest SCs was nonrandom, with low frequencies in the vicinity of kinetochores and high frequencies near the telomeres. The microchromosomes showed a single nodule whose average location was 1.21 micron from the kinetochore. In the ZW pair there was a single nodule whose average location was 0.31 micron from the paired telomeres and not more than 0.65 micron from them. The total number of nodules per cell and the number of nodules in each of the five major bivalents showed good agreement with the total number of chiasmata and the number of chiasmata of the major bivalents of roosters. Thus, these nodules share the characteristics of recombination nodules described in other organisms. The single, obligatory, strictly localized recombination nodule found in the pairing end of the ZW pair strongly suggests that recombination between the Z and W chromosomes in the female chicken is a regular process that may be similar to the obligatory recombination between the pairing ends of the human X and Y chromosomes that was recently described in studies using DNA probes.

Animals↗
PubMed1985

Fine structure and cytochemistry of the mitotic plaques of Trypanosoma cruzi and Crithidia fasciculata.

The mitotic plaques are double, electron-dense structures which are located at the equator of the nucleus during the equatorial (metaphase) stage of mitosis in Trypanosoma cruzi, Crithidia fasciculata and other trypanosomatids. Each part of the equatorial plaques separates from the other and becomes an hemiplaque at the beginning of nuclear elongation. Variations of size of the plaques in different species of Trypanosomatidae are restricted to a limited range (less than 30% of the average thickness). At least two different components are found in the plaques with cytochemical methods: a) a basic protein with a high affinity for ethanolic-phosphotungstic acid, which is located in a narrow band towards the cleavage plane in each hemiplaque; and b) an osmiophilic component (possibly a protein) with a low affinity for uranyl acetate and which is located throughout the body of the plaque. The affinity for uranyl acetate can be abolished by methylation and acetylation, but remains after extraction with cold perchloric acid. No cytochemical evidence for the presence of DNA in the plaques is found. However, electron microscopy and cytochemical observations show that the PTA-affine band of the plaques is associated at its sides with chromatin fibers. Thus plaques, as the outer layer of kinetochores in higher eukaryots, have a component with high affinity for phosphotungstic acid, strengthening the hypothesis that these structures are phylogenetically related.

Acetylation↗
PubMed1984

Isolation of Streptococcus lactis Bacteriophages and Their Interaction with the Host Cell.

Phages may cause lysis of lactic acid bacteria used in cheese production. Three virulent bacteriophages specific for Streptococcus lactis subsp. lactis C2 were isolated and purified from cheese whey. They showed distinct plaque sizes, and although they had similar morphology by electron microscope examination, their dimensions were slightly different. The phage heads were elongated and hexagonal in shape, and the flexible tails appeared periodically cross-striated. They were DNA phages based on the acridine orange test. On infection, phage was adsorbed on the bacterial surface by the free end of the tail. After 80 min of incubation at 25 degrees C, the phage heads appeared empty, slightly collapsed, and possessed a visible hollow tube through which the genetic material had been injected.

Journal Article↗
PubMed1983

The ultrastructure of mitotic nuclei of Blastocrithidia triatomae.

The fine structure of mitotic nuclei of the flagellate Blastocrithidia triatomae has been studied by serial thin sections and three-dimensional reconstructions. The sequence of changes during the four stages of mitosis are described. A set of three dense plaques is constantly found in the equatorial stage of mitosis. The microtubular spindle is organized around these plaques. The plaques split into halves at the end of the equatorial stage, and the half-plaques migrate to the spindle ends. Elongation of the mitotic nucleus occurs after the division of the plaques. This elongation is associated with the formation of an interpolar bundle of microtubules. The equatorial spindle is formed by 26-28 microtubules and is 1.5 micrometers long. The nucleolus attaches itself to the nuclear envelope and persists up to the elongational stage; then it disintegrates and is reorganized in daughter nuclei. Mitotic events in B. triatomae are essentially similar to those in Trypanosoma cruzi epimastigotes. As in this hemoflagellate, the dense plaques behave as kinetochores. It is concluded that B. triatomae is probably a haploid organism that contains three chromosomes.

Animals↗
PubMed1982

Methanol-acetic anhydride: an efficient blocking agent for electron microscope cytochemistry. Its application to mouse testis and other tissues.

A mixture of absolute methanol and acetic anhydride (MA) (5:1, v/v; 24 h at 25 degrees C) which is known to methylate and acetylate--respectively--free carboxyl and amino groups in proteins, was tested for its effectiveness as a blocking agent in glutaraldehyde-fixed mouse testis and skeletal muscle. In young spermatids the staining of the acrosome with either uranyl acetate (UA) or ethanolic phosphotungstic acid (PTA) was completely prevented by prior treatment with MA. Esterification of carboxyl groups with 0.1 N HCl in methanol (24 h at 30 degrees C) eliminated the UA staining without affecting that due to PTA. It is concluded that--COOH groups are responsible for UA binding and that acetylation (of amino groups) prevented PTA binding. MA also abolishes the strong affinity of PTA to the lateral elements of the synaptonemal complex in meiotic chromosomes, the axoneme and fibrous sheath of the spermatid tail and the Z band in skeletal muscle. Reactivity was diminished in nucleoli and remained unaffected in chromatin, the outer coarse fibers of the flagellum and collagen fibrils. Different functional groups may participate in PTA staining. The ultrastructure was well preserved in all cases.

Acetates↗
PubMed1981

Fine structure and behaviour of a pericentric inversion in the sand rat, Psammomys obesus.

In pachytene spermatocytes of the sand rat, Psammomys obesus, a long autosomal bivalent was observed, which was asynaptic for a large interstitial segment of its length in early pachytene. This bivalent also exhibited unaligned kinetochores. In late pachytene spermatocytes all autosomal bivalents were fully synapsed, but one of the shortest bivalents now possessed unaligned kinetochores. Evidence is presented in support of the proposition that the asynaptic interstitial region observed in early pachytene is due to the bivalent being heterozygous for a pericentric inversion. Using the maximum extent of homologous pairing, the break points were mapped at 26% from one end and 20% from the other. The unaligned kinetochores support the proposal that the aberration is an inversion and measurements of their positions confirm the estimated break points. In one cell a bivalent with interstitial (but no terminal) synapsis also confirms the inversion hypothesis. It is proposed that the bivalent is so small that topological considerations prevent the formation of the expected inversion loop. Evidence is also presented that complete synapsis of the bivalent during late pachytene can be attributed so 'synaptic adjustment', characterized by non-homologous synapsis (heterosynapsis). The position of the aberrant bivalent in relation to the sex chromosomes also changes during pachytene. When the bivalent is incompletely synapsed it generally associates by its ends with the ends of the sex chromosomes, but when it is non-changes during pachytene. When the bivalent is incompletely synapsed it generally associates by its ends with the ends of the sex chromosomes, but when it is non-homologously synapsed it is not associated with them.

Animals↗
PubMed1980

Synaptosomal complexes and associated structures in microspread human spermatocytes.

Human spermatocytes processed with a modified microspreading technique which involves the use of sodium dodecyl-sulphate (SDS) have been used to construct synaptonemal complex (SC) karyotypes. Twenty two pachytene spermatocytes were selected for length quantitation. The mean values of relative lengths and centromeric indexes of each SC agree closely with values obtained by three-dimensional reconstructions (Holm and Rasmussen, 1977), except for SCs #4--5, 6--7 and 19--20. Absolute lengths are consistently longer in spreads (10.7% longer than in sections, on average). The mean total length of the SC complement is 258.7 micrometer. Six morphological types of XY pairs have been described. On the basis of the relationships between the XY pair, nucleolar development and autosome behavior, these six XY types are assumed to develop in succession. Type O XY pairs occur during late zygotene, types I and II XY pairs occur during early to mid-pachytene, and types III, IV and V occur during later pachytene substages. Alignment of the X and Y axes is observed at late zygotene, and formation of the SC occurs in relation with type I XY pairs. Progressive desynapsis occurs in types II and III. Splitting and fusion of the X and Y axes attain a maximum in types IV and V. The breakdown of the dense bodies associated with the X and Y axes occurs during stage V. --Bar-like structures, having a mean length of 2,100 A are associated with SCs in all the pachytene substages defined by the XY types. The average number of bars per nucleus is 46.2 (SD = 8.4, N = 20), and the average SC length per bar is 5.57 micrometer. The distribution along the SCs of 923 bars shows that near-termini locations are preferred (SC length per bar, 2.98 micrometer) and centromere regions are avoided (SC length per bar, 16.9 micrometer). --On the basis of these data, bars are similar to recombination nodules described in other organisms. The availability of a standard SC karyotype for microspreads and a temporal sequence given by the XY pair provide a basis for rapid screening of chromosome aberrations in human testicular biopsies.

Adult↗
PubMed1978

Multiple complexes in human spermatocytes.

Multiple complexes develop during metaphase I in normal human spermatocytes. Usually they form two separate bodies about 1 micron in diameter, composed of tripartite units and a denser matrix. The tripartite units are structurally identical to the components of the central space of synaptonemal complexes (SCs). Formation of the multiple complexes occurs by shedding of SC fragments from a few chromosomal regions at prometaphase I. The combined total length of central elements in each multiple complex is 1 to 3 micron. Multiple complexes remain as cytoplasmic, perinuclear bodies during telophase I and interphase of spermatocytes II, but they were not observed during or after the second meiotic division. Although multiple complexes are initially located in the spindle, they do not show microtubular attachments and seem to be passively moved towards the periphery.

Chromosomes, Human↗
PubMed1977

Synaptonemal complex karyotyping in Melanoplus differentialis.

The chromosomal axes of the spermatocytes of the grasshopper Melanoplus differentialis have been studied with a modification of the microspreading procedure used previously. The whole complement of synaptonemal complexes (SCs) and the axis of the X chromosome have been described and measured. The relative length of each SC is characteristic and constant and permits the construction of an idiogram. Relative lengths of SCs are almost equal to the relative lengths of mitotic chromosomes of spermatogonia (with the exception of the X chromosome), thus extending to an invertebrate the relationship between SCs and mitotic chromosomes that has been demonstrated in mammals. All the SCs except the 3 smallest (which are apparently telocentric) show a small short arm beyond the kinetochore. The progression of changes in the chromosomal axes during meiotic prophase has been staged by centriolar behaviour. During leptotene, axes are first formed near the nuclear envelope at a special (polar) region. SCs also begin to appear in the polar region and extend towards the nuclear interior. The beginning and completion of synapsis is not synchronous among bivalents. The X-axis is formed in midzygotene and shows a characteristic sequence of changes in shape during pachytene. Cells in post-synaptic stages show whole chromosome complements with characteristic chiasmatic configurations. Kinetochores are prominent and bipartite during diplotene-diakinesis.

Animals↗
PubMed1975

The synaptic behaviour of the X and Y chromosomes in the marsupial Monodelphis dimidiata.

The pairing behaviour of the X and Y chromosomes of Monodelphis dimidiata was studied with light and electron microscopy. Pairing of the sex chromosomes is delayed with respect to autosome synapsis. Both the X and the minute Y chromosome show an axis attached by its two ends to the nuclear envelope. Synapsis of the sex chromosomes occurs by the joining of the chromatin sheaths that surround the axes and by a small, three-layered structure close to the nuclear envelope. The X and Y chromosomes remain joined to each other during the diffuse stage and diplotene-diakinesis but they do not show a synaptonemal complex. During the diffuse stage a dense plate is formed at the boundary between the X-Y body and the nuclear envelope. During early metaphase a folded sheet is attached to the periphery of the X-Y body. This sheet is formed by a piece of the nuclear envelope carrying the dense plate and it shows transverse fibrils and a central element similar to synaptonemal-complex remains. No evidence of a non-chiasmate segregation mechanism was observed. Polarization of the axial ends of the sex chromosomes is observed after X-Y synapsis. These important departures from the X-Y pairing pattern of eutherian mammals are discussed and assumed to present a special mechanism for holding the minute Y joined to the X chromosome in this marsupial.

Animals↗