Seeds of Sesbania cannabina cultivar ND-1 were subjected to different doses of gamma irradiation (20, 40, 60 and 80 KR) and irradiation effects on seed germination, survival, and several morphological and cytological characters of adult plants were studied. The irradiated seeds were tested for lethal doses at which 50% of the seeds germinated (LD50) i.e. 40 KR dose. Plants grown from the gamma ray-treated seeds showed variation regarding their morphological and cytological characters. The plant height, stem girth, number of leaves per plant, and pod length decreased as the doses of irradiation increased. However, internode length increased with increasing doses of irradiation. Meiotic analysis revealed the presence of various types of chromosomal abnormalities at all phases. Meiotic aberrations increased according to the doses of irradiation. A reduction in pollen fertility was also noticed.
Seeds of Capsicum annuum L. cv. Pusa jwala and G4 were treated with varying concentrations of methyl methane sulphonate (MMS), and the effect of various concentrations of MMS on each stage of meiosis has been studied in M1 generation. Various types of meiotic abnormalities and reduction in chiasma frequency were observed in treated populations. However, MMS treatment were found to be more effective in inducing meiotic abnormalities and reduction in chiasma frequency in Pusa jwala as compared to G4. Moreover, a co-linear relationship between increasing concentrations of MMS and reduction in chiasma frequency was also observed. Taking the percentage of meiotic abnormalities and reduction in chiasma frequency as an index of sensitivity of genotype to MMS, Pusa jwala was found to be more sensitive than G4.
Cytological work on Vicia pallida Turcz. presents male meiotic studies in wild accessions gathered from the Kinnaur district of Himachal Pradesh. All 3 accessions uniformly shared the same meiotic chromosome number of n=12 in which 5 bivalents are relatively small sized as compared with the remaining 7 bivalents. This is the first report of tetraploid cytotype in the species against the earlier record of diploid cytotype (n=7) from the other region of Himalaya. Out of the 3 accessions scored presently, 1 accession showed a regular 12 bivalent formation, equal chromosome segregation during anaphases/telophases, normal tetrad formation and 99% pollen fertility with uniform sized pollen grains. The remaining 2 accessions depicted pollen mother cells (PMCs) with irregular meiotic behaviour which included the phenomenon of chromatin transfer among proximate meiocytes at different stages of meiosis, interbivalent connections and chromatin stickiness, out of plate bivalents at metaphase-I, lagging of chromosomes/laggards at anaphases, abnormal sporads (tetrads with micronuclei and polyads) and consequently some pollen sterility and pollen grains of variable sizes. The phenomenon of cytomixis which induces various meiotic abnormalities in the PMCs and consequently pollen sterility and pollen grains of heterogeneous sizes in V. pallida seems to be under direct genetic control.
Cytological studies were performed in 20 populations of 3 Silene species of the section Auriculatae L., Silene gynodiocia Ghazanfar, S. crispans Litw., S. indeprensa Schischk. The populations studied had 2n=2x=24, 2n=4x=48 and 2n=8x=96 chromosome number, showing 2 polyploidy levels for S. indeprensa and S. gynodiocia. The chromosomes were mostly metacentric and submetacentric but 1 pair of teloentric chromosome was observed in the octaploid Dargaz population of S. indeprensa. The ANOVA test showed no significant difference among populations of S. indeprensa and populations of S. gynodiocia for size of the chromosomes, mean chromosome length, A1 and A2 indices as well as TF value. This indicates that no significant chromatin loss or gain has occurred in the process of karyotype differentiation in these populations, and in the case of octaploid and tetraploid populations, still the mean value of chromosomes are maintained. However, the species differed significantly for CV value, indicating that during species diversification a change has occurred in the size of chromosomes within a karyotype due to structural changes of the chromosomes. Meiosis analysis showed that the chromosomes mainly form bivalents and univalents in the metaphase of meiosis I, although some amounts of quadrivalents were observed in all populations including diploids due to heterozygote translocations. T-test analysis showed significant difference in the relative values of total and terminal chiasmata as well as a number of ring bivalents between the populations having 2n=24 and 2n=48 chromosome number indicating that with an increase in polyploidy level, significant change has occurred in the number of genes controlling chiasma frequency. The occurrence of unreduced pollen grains indicates the role of this phenomenon in polyploidy incidence in the species studied.
At present, cytomorphological studies have been made on population basis in Filipendula vestita, a medicinally important species of the family Rosaceae from the geographically different areas of Kashmir and the districts Kangra and Sirmaur of Himachal Pradesh in the Western Himalayas. Morphologically, 3 distinct variants have been recognized, 2 of these reported for the first time. All the populations are found to be diploid with meiotic chromosome number as n=7. However, male meiosis shows variation in meiotic behaviour in the different populations. 8 populations exhibit normal meiosis whereas other 7 populations are marked with meiotic abnormalities in the form of cytomixis, chromosomal stickiness, formation of laggards and bridges resulting into abnormal microsporogenesis and reduced pollen fertility.
Polyploidization affects chromosomal behavior especially during meiosis. After the establishment of polyploid plants, autopolyploids featured with polysomic inheritance show numerous multivalents such as trivalents and quadrivalents, rather than unique bivalent formation, but allopolyploids usually exhibit diploid-like features that are characterized with disomic inheritance. In the present study, we aimed to analyze meiotic chromosomal behavior in 2 specific meiotic mutations (dmc1 and asy1), and attempted to seek cytological interpretation of polyploidy dominance in flowering plants. The results show tetraploids dmc1 and asy1 display reduced fertility but are rather fertile in comparison with diploid mutants (dmc1 and asy1). The cytological analyses demonstrate that tetraploid asy1 has a higher frequency of residual chiasmata and/or bivalent formation than those of diploids, although tetraploid dmc1 did not show improved meiotic progression after polyploidization. These results to some extent indicate that polyploidy can potentially alleviate lethal effects brought by some mutations via more aneuploidy propagated in plant reproductive life cycles.
Karyotype analysis was performed in 10 Salvia species (Lamiaceae) of Iran, S. spinosa, S. reuterana, S. sclarea, S. ceratophylla, S. xanthocheiala, S. limbata, S. hypoleuca, S. staminea, S. nemorosa and S. verticillata showing 2n＝14, 20, 22 and 32 chromosome numbers indicating the role played by polyploidy and aneuploidy in Salvia species diversification. Some of the species differed significantly in the size of chromosomes but occupied 1A and 1B classes of Stebbins system indicating them to have primitive karyotype.
Cytokinesis is a pivotal event in cell division in all living organisms. In mammals, cytokinesis progresses via constriction of the contractile ring, a bundle of actin filaments and myosin that is located on the equatorial plane. The eukaryotic elongation factor 1α (eEF-1α) is associated with the contractile ring in sea urchin eggs. Although eEF-1α is a ubiquitous protein translation factor and is highly conserved in eukaryotes, archaea, and prokaryotes, the archaebacterial EF-1α and the prokaryotic EF-1α ortholog EF-Tu do not function in cytokinesis, suggesting that the association between the contractile ring and EF-1α appeared at about the same time as the establishment of eukaryotic cells. However, the role of EF-1α in cytokinesis in primitive cells is unclear. In this study, we show that the primitive alga Cyanidioschyzon merolae elongation factor-lα (CmEF-1α) is localized in the contractile division plane, but not in the actomyosin contractile ring. The genome of C. merolae contains 2 unexpressed actin genes and lacks a myosin gene. Immunoblotting analyses revealed that the protein level of CmEF-1α remained constant during the G1 to M phase, and then peaked during cytokinesis. Immunofluorescent microscopy revealed 2 patterns of localization of CmEF-1α during the cell cycle: it was dispersed throughout the cytoplasm from G1 to early M phase, and then localized to the contractile region during cytokinesis. From the results of current study on cytokinesis in the primitive red algae C. merolae, our findings led us to hypothesize that when first established in the lower eukaryotes, cytokinesis fundamentally relied on eEF-1α, and the actomyosin system was acquired later during evolution.
The structural characteristics of chloride and pavement cells of the gills of snow trout, Schizothorax curvifrons, were investigated with the aid of the great depth and resolving power of a transmission electron microscope. Ultrastructural analysis showed that the chloride cells were distributed in the filament and interlamellar epithelia. They were circular to elongated in form having a central euchromatic nucleus, expanded tubular system and an abundance of mitochondria with parallel patterns of mitochondrial crests. On the other hand, the squamous to polygonal shaped pavement cells were endowed with irregular nucleus and electrodense cytoplasmic matrix embracing rough endoplasmic reticulum and lesser number of mitochondria, abundant filament bundles and dark vesicles of varying electrodensity. Some of the dark vesicles were bound to the apical plasma membrane of the primary lamellae bearing microridges covered with glycocalyx, however, the apical plasma membrane of the pavement cells of the secondary lamellae did not reveal any signs of the presence of microridges.
This research was the first cytogenetic study of the lesser bamboo rat (Cannomys badius) from Nongbualamphu, Nongkhai, Loei and Udonthani Provinces, Thailand. Blood samples were taken from 8 males and 6 females and then subjected to standard whole blood T-lymphocyte culture. The samples were harvested by colchicine-hypotonic-fixation-air-drying technique and followed by conventional, GTG-, CBG-, Ag-NOR banding and high-resolution techniques. The results showed that the diploid number was 2n=50 and the fundamental number (NF) was 94 in both males and females. The autosomes consist of 12 large acrocentric, 2 medium submetacentric, 10 medium acrocentric, 4 small metacentric, 6 small submetacentric, 8 small acrocentric and 6 small telocentric chromosomes. X chromosome was the largest submetacentric chromosome, while the Y chromosome was small acrocentric chromosome. From GTG-banding and high-resolution techniques, the numbers of bands and locations in the C. badius were 262 and 302, respectively, each chromosome pair could be clearly differentiated. CBG-banding shown C-positive (dark band) on the centromere of all autosomes. However, C-negative (light band) shown on Y chromosome. From Ag-NOR banding, there is no detection of nucleolar organizer regions. All of these results can advantage as the useful basic genetic information for C. badius cytogenetic study. The karyotype formula for C. badius could be deduced as: L12a+M2sm+M10a+S4m+S6sm+S8a+S6t+sex chromosomes.
In eukaryotic cells, the Aurora kinase family contributes to the successful progression of mitosis by regulating centrosome maturation, spindle formation, microtubule attachment to kinetochores, and cytokinesis. A primitive red alga, Cyanidioschyzon merolae, contains a single mitochondrion, which divides just before nuclear division. In this study, we identified a single orthologue of Aurora kinase in C. merolae, which was designated CmAUR. Analysis of the dynamics during mitosis of CmAUR fused with the green fluorescent protein showed CmAUR is localized to the mitotic spindle and polar microtubules along the mitochondrion. Interestingly, CmAUR signals were also detected in the mitochondrial division site. These results indicate Aurora kinase in C. merolae is related to mitochondrial division in addition to mitotic spindle formation.
As endangered species in Thailand, the wild animal species of the common palm civet (Paradoxurus hermaphrodites), masked palm civet (Paguma larvata), large Indian civet (Viverra zibetha), large-spotted civet (Viverra megaspila), and binturong (Arctictis binturong) were selected for karyological study. Blood samples were taken from 1 male and 1 female of each species. After the standard whole blood lymphocyte culture in the presence of colchicine, the prometaphase spreads were performed on microscopic slides and air-dried. High resolution GTG-banding technique was applied to stain the chromosomes. The results showed that 2n (diploid) of Par. hermaphrodites, Pag. larvata, V. zibetha, V. megaspila and A. binturong were 42, 44, 38, 38, and 42, respectively. The autosomes presence of metacentric, submetacentric, acrocentric and telocentric autosomes were 6-10-14-10, 6-8-12-16, 8-6-18-4, 4-12-16-4 and 6-12-4-18, respectively. The X chromosome were submetacentric, submetacentric, metacentric, submetacentric and metacentric, and the Y chromosome were submetacentric, acrocentric, telocentric, telocentric and acrocentric chromosome, respectively. The numbers of bands in one set of prometaphase haploid chromosomes from the high resolution GTG-banding technique were 233, 262, 198, 222, and 247 bands, respectively and each chromosome pair could be clearly differentiated.
In septic orthopaedic surgery, one of the most common used antiseptics is polyhexanide, in contrast to chlorhexidine. Our hypothesis was that the use of low concentrated chlorhexidine has the same toxic effects on human chondrocytes as does treatment with polyhexanide. Human chondrocytes were isolated and cultured and 0.04% polyhexanide, 2% chlorhexidine or 0.1% chlorhexidine were added to the cultures. Toxicity analyses were performed by visualization of cell structure and quantification of LDH activity. Determination of vital chondrocytes was investigated by Cell-Counter and by fluorescence microscopy. Light microscopic data revealed cell structure defects and change of cell morphology after antiseptic treatment. A significant increase of LDH enzyme activity was shown after treatments with 0.04% polyhexanide and 0.1% chlorhexidine if compared to control. The determination of vital chondrocytes showed a significant decrease. Both antiseptics induce significant cell death of chondrocytes. No significant differences of toxic potential after the treatments with 0.04% polyhexanide and 0.1% chlorhexidine were found.
The 2 morphological forms of Xanthium strumarium L., namely the purple form and the green form, available in Bangladesh were studied cytogenetically for critical analysis after staining with orcein, CMA and DAPI. Both of the forms were found to possess 2n=36 chromosomes. The centromeric formula was determined 27 m+9 sm in the purple form and 23 m+13 sm in the green form. The purple form showed more heterogenous karyotype than the green form. No satellite was found in these 2 forms after orcein staining. However, after CMA-staining a pair of conspicuous satellite was found in the purple form, which was absent in DAPI-staining. In this form (purple), 2 interstitial CMA-positive bands were found which showed deep DAPI-negative band. In the green form, 6 CMA-positive upper terminal bands were found. Out of 6 CMA-positive bands 2 showed deep and complete DAPI-negative bands whereas another 2 bands showed partial DAPI-negative bands. The reversible banding indicated the presence of fully GC-rich repeats of those portions. These chromosomes could be used as marker for respective forms. The fluorescent banding revealed the occurrence of inversion in pair II of the purple form. Thus the 2 forms have distinct and unique karyotypes. The comparative karyotype analysis would provide strong support for authentic taxonomic diversification of these 2 forms of Xanthium strumarium.