Cytological investigations on two taxa of Chara Linn. (C. vulgaris var. gymnophylla f. grovesii and C. zeylanica var. sejuncta f. formosa) and a taxon of Nitella Ag. Leonh. (N. heterodactyla) were carried out. Nuclear events conformed to the standard pattern of mitosis described. The chromosome numbers determined are n=35 for C. vulgaris var. gymnophylla f. grovesii, n=42 for C. zeylanica var. sejuncta f. formosa and n=18 for N. heterodactyla. All the three taxa were investigated for the first time and are new reports.
The aim of this study was to assess the degree of variability in the main morphological characteristics of individual B-genome chromosomes and the quantity and distribution of their heterochromatin blocks in nine T. aestivum cultivars, differing in origin, biological and economic characters. The summed up lengths of B-genome chromosomes in the various cultivars were assessed, as well as the degree of variability in individual chromosome sizes and arms, arm ratios, ranking of chromosomes in the genome for these characters and type of heterochromatin region distribution following staining after N-banding technique. Important regularities were revealed in range of chromosome size and arms in respect to summed up chromosome lengths of the genome in the various cultivars. They were of considerable importance for the construction of chromosome arrangement models in the genome. On the basis of these characteristics chromosomes with extreme values occupied most stable positions in chromosome arms with smal-lest or greatest lengths. Such were 5B chromosome in respect to both its arms, 4B and partially 6B chromosome in respect to their long arms, 3B and 4B chromosomes. Despite the stable behaviour of 5B chromosome in the various cultivars, within the framework of a given cultivar it changes most in respect to the long arm. Cultivar variations were found in type of chromosome heterochromatin regions. Chromosomes 5B, 6B and 4B were distinguished by most insignificant changes in the big heterochromatin regions near the centromere. Chromosome 1B was distinguished by its highest variability in type of staining. A hypothetical model has been proposed for ranking the chromosomes in the genome on the basis of the frequency with which a given chromosome occupied a definite position in the genome and its relative values in respect to the summed up lengths of all chromosomes.
Various species of the bacteria including Pseudomonas aeruginosa have been recognized as pathogens of fish. The mutagenic potential of P. aeruginosa log culture (17×107 cells/ml) has been assessed after intraperitoneal injection @ 1 ml per 100 g b. w. to cichlid mouth brooding fresh water tilapia, O. mossambicus by chromosome aberrations in gill epithelia and first spermatocyte metaphase, micronucleus test (MNT) in peripheral blood, gill epithelia and kidney cells, and lethal test for unfertilized eggs and dead embryos during development after mating treated male parents with normal virgin females. Moreover, dose dependent effect of 1/2 ml, 1 ml and 2 ml doses for chromosome aberrations in gill epithelia and MNT in cells of blood, gill and kidney were found to be highly positive against respective sterile peptone medium injected controls. The sperm head abnormality test yielded no positive result. Further, the intraperitoneal injection of log culture of P. aeruginosa of 1 ml dose to Indian climbing perch, A. testudineus yielded positive results in chromosome aberrations studied from kidney and gill epithelia and MNT in cells of blood, gill and kidney. The three species of Indian major carps, L. rohita, C. catla and C. mrigala also yielded positive genotoxic potential of P. aeruginosa by MNT. There was intraspecific tissue sensitivity among blood, gill and kidney cells found in MNT of O. mossambicus and interspecific sensitivity shown by MNT of blood of three species of Indian major carps. The mutagenic potential of P. aeruginosa evaluated by a battery of tests in directly treated and in F1 and F2 generations of experimental mouse recorded before revealed that P. aeruginosa can act as a potential mutagen to fish in aquatic media and to mice in terrestrial one. Thus ‘Microbes as living Mutagens’ advocated by Manna (1980, 1989) has been supported from the present result on fish.
Detailed karyotype analyses of 6 cultivars of tea vegetative clones are done. On the basis of centromere position, chromosomes are classified into 6 types. Number of different types varied within the varieties. Both ‘E’ and ‘F’ type are absent in TS 491. Total genomic length and volume are also considered as the parameters. Singnificant variation is observed at the varietal level. TV21, a quality clone, is found quite indifferent in karyotype, total length and volume of the chromosomes. The other characteristic features of this variety is also different from the rest of varieties. The overall study reveals a clear varietal demarcation.
Karyotypes and chromosomal nucleolus organizer region or NOR phenotypes of 19 described and two undescribed species of western North American cyprinids are documented. All 21 species examined possessed 2N=50 chromosomes and at least two pair of NOR-bearing chromosomes. The high incidence of multiple NOR chromosomes among western cyprinids is unusual. One pair of A NOR chromosomes was found in all 21 species, and 17 species possessed a second pair of A NOR chromosomes. An AA NOR state was hypothesized to represent a chromosomal synapomorphy uniting western cyprinids (including the genus Richardsonius) into a monophyletic assemblage. Within this clade, a transition from an A NOR to a D NOR was hypothesized to represent a chromosomal synapomorphy uniting three speices of the subgenus Gila, and an addition of an F NOR was hypothesized to represent a chromosomal synapomorphy uniting two species of the genus Rhinichthys. Chromosomal NORs in western cyprinids appear conserved relative to eastern cyprinids and may be the result of (i) a process of karyotypic canalization, and/or (ii) character state reversal in, or introgressive hybridization among, western cyprinid genera.
Genotoxic effect of sodium metabisulphite in mice in vivo test system was investigated with the help of three bioassays: Chromosomal aberration, micronucleus and sperm-shape abnormality. The genotoxicity was tested employing three doses (200, 300 and 400mg/kg b. w.), three routes of administration (ip, po, and sc), three hours of exposure acutely (6, 24 and 48) as well as chronic (80mg/kg/day) for chromosomal aberration. All three doses were also tested for MN (30 hr) and sperm-shape abnormality (35 days). Significant effects were observed in all assays. Chronic exposure to fractionated doses induced less effect than the equivalent acute dose. Chemical treated orally could not produce significant effect. The results in general indicated the genotoxic property of the chemical in mouse in vivo test system.
The fate of chloroplast nuclei (cp-nuclei) was followed in young zygotes after mating of male and female gametes in Chlamydomonas reinhardtii using two methods; i.e., observation of a single field by both epifluorescent and electron microscope, and observation by immunogold electron microscopy. Before mating, gametes contain several cp-nuclei in the cup-shaped chloroplast. In the DAPI-stained thin sections of Technovit 7100 resin, a few cp-nuclei of a gamete are clearly observed in the chloroplast and large cp-nuclei are often associated with starches around the pyrenoid in a male gamete. One hour after mating, before the fusion of cell unclei, the preferential disappearance of all male-derived cp-nuclei occurs. Two hours after mating, after fusion of cell nuclei, the preferential disappearance of cp-nuclei in all zygotes is complete. By electron microscopy, the female-derived cp-nuclei in young zygotes, which emit strong fluorescence due to 4'-6-diamidino-2-phenylindole (DAPI) under fluorescence microscope, appear to be composed of a network of fine DNA-like fibrils. By contrast, a similar network of fibrils is never observed in the male-derived chloroplast in young zygotes when the cell nuclei begin to fuse together. Gold-conjugated secondary antibodies to the primary anti-DNA antibodies have been detected on the regions around the pyrenoids in the chloroplasts in young zygotes of both male and female origin immediately after mating of the gametes. In zygotes 2 hr after mating, the gold particles appear on the regions around the female-derived pyrenoid and not on the chloroplast from the male parent. The results suggest that the preferential disappearance of cp-nuclei is caused by the digestion of the cp-DNA molecules and therefore lend support to the hypothesis that maternal inheritance of cp-genome is due to the preferential digestion of male-derived cp-DNA in young zygotes.
Ribosomal RNA (rRNA) genes were visualized in chromosomes of Vicia faba by high resolution in situ hybridization. The interphase nucleus showed two large and two small signals of rRNA genes associating nucleoli. At prophase and metaphase the signals with differences in sizes appeared at both adjacent sides of the secondary constriction of the large metacentric chromosomes. Two large signals were located at the proximal region of the satellite. The metaphase chromosome with the connecting thread at the secondary constriction was hybridized with rDNA. Chromomycin A3-bands appeared on the chromosomes which showed the signals of the hybridized rDNA. By silver nitrate staining, the nucleoli at interphase and the secondary constriction of the chromosome at mitotic prophase and metaphase were darkly stained. As Ag-NOR stained actively transcripting NOR, the large portion of rRNA genes condensed and located both chromosomal sides of the secondary constrictions was inactive during the cell cycle in the meristematic tissue of the root.
Administration of dietary dose of Vitamin B-complex, either concurrently or as pre- and post-treatment to the pesticide exposure, was very much helpful in appreciably nullifying the mitoinhibition and clastogeny induced by two Organophosphorus pesticides, Malathion and Rogor. The concurrent treatment of Vitamin was more effective than the two other modes of its supplementation.
Chromosome counts (2n=36) and karyotypes of Sabal yapa, S. mexicana and S. gretheriae are reported. The karyotypes of S. yapa and S. mexicana were closely similar. They presented metacentrics and submetacentrics as well as four pairs of chromosomes with satellites. S. gretheriae showed nine pairs of chromosomes with such satellites and pair of a heteromorphic chromosomes. They were almost 3 times bigger than the average of the other chromosomes in its complement. The high number of satellites as well as the presence of a heteromorphic pair could be related to the speciation process of S. gretheriae.
The primary trisomics in durum wheat, Triticum durum var. hordeiforme (2n=4x=28) were obtained from the hybrid progeny of the hexaploid (2n=6x=42) which was derived from the cross between the artifically induced octoploid (2n=8x=56) and tetraploid plant. In order to analyze the extra chromosome in each trisomic plants, Wright C-banding technique was applied, and then 13 primary trisomics out of the theoretically possible 14 trisomic types were cytologically identified. Thirteen trisomics consist of 7 types including extra chromosomes of A genome; 1A, 2A, 3A, 4A, 5A, 6A, 7A and 6 types of B genome; 1B, 2B, 4B, 5B, 6B, 7B. Thirteen primary trisomic types were different from normal plant and others in their external morphological traits. However, it was somewhat difficult to recognize morphologically the trisomic types containing A genome chromosome derived from the type with homoeologous chromosome in B genome.
Spores of the fungi, Helminthosporium orzyae and Aspergillus njger were isolated from the PDA culture medium in sterile distilled water separately and each sample containing 8×106 spores per ml of distilled water was intraperitoneally injected @ 1ml per 100g body weight to 5 individual normal pregnant mice separately in each set at their 4th, 8th and 12th day of gestation against parallelly injected pregnant mice at the same dose and time with sterile solid slant of PDA medium washed distilled water as controls. The embryotoxic effects leading to lethality of developing embryos were assessed by exposing the uteri of the individual treated and control sets of females at their 15th day of gestation. The data revealed significantly high frequency of lethality to developing embryos in each set of pregnant mice treated separately at their 4th, 8th and 12th day of gestation and in the combined data with spores of H. oryzue and A. njger than that of control indicating the embryotoxic potential of spores of each species of fungi. The embryotoxic potential of two species of fungi did not show any significant difference between themselves.
The localization of NORs in the somatic chromosomes of Aphis spiraecola Patch and A. craccivora Koch collected from the hosplants Solanum melongena and Dolichos lablab, respectively, was studied by the silver-staining method. In the interphase nuclei, frequently one or two, and rarely three silver-positive nucleoli appeared and continued to appear upto the early prophase. At metaphase, most of the plates revealed clearly the localization of NORs as tiny, round and deeply-stained dots at one terminal end of one pair of long chromosomes (pair no. 2) in the diploid complements (2n=8) of both the species. However, in a few slightly advanced metaphase plates in both the species, split NORs appearing as bifid structures were observed. The initiation of chromatid separation seemed to occur first from the NOR-bearing end in both the aphid species claimed to have holokinetic chromosomes.
Chromosome cytology of Setaria digitata, a bovine filarial nematode has been studied by means of acetocarmine squash technique in the spermatocytes, oocytes and embryos at early cleavage. The spermatocytes showed 5 bivalents and one univalent (n=6) at metaphase-I. Six bivalents were observed in the oocytes at diakinesis of first maturation division. Diploid chromosome number of 2n=12 as well as 2n=11 was observed in embryos at early cleavage. The cytological studies indicate that the diploid chromsome number is 5A-XX in female and 5A-XO in males. Existence of XX-XO mechanism of sex determination, with male as hetergametic sex, is thus suggested in S. digitata.
Cell-nuclear migration during the amoebo-flagellate transformation of Physarum polycephalum is mediated by the centrosome. The centrosome is expected to be strongly connected to the cell nucleus. An electron micrograph of a thin section of intact amoeba cell suggested that one of the structures consisting centrosome complex, mtoc, was directly attached to the outer membrane the of cell nucleus without any intervening microtubules. To analyze the fine details of the centrosome perimeter, and especially the space between the cell nucleus and mtoc, we used 0.1% Triton X-100 and different concentrations of NaCl to remove obstructive cytoplasm around the centrosome and the cell nucleus. The centrosome complex was shown to be composed of 2 centrioles, mtoc, link, ppks, extension, crown and lattice. With 100mM NaCl, the connection between the centrosome complex and the cell nucleus remained intact and was visible as a cell-nuclear appendage even by light microscope. This linkage was maintained even when 2mM Ca2+ ion was added to the samples to depolymerize and eliminate the effects of microtubules. This shows that the structure which connects the centrosome complex to the cell nucleus is mtoc, not microtubules. Electron micrography using whole mounts and thin sections of the treated amoeba cells demonstrated that the cell nucleus retained traces of its outer and inner membranes, and that the mtoc of the centrosome complex was directly connected to the outer membrane of the cell nucleus.