CYTOLOGIA
Online ISSN : 1348-7019
Print ISSN : 0011-4545
Volume 56 , Issue 4
Showing 1-29 articles out of 29 articles from the selected issue
  • Bandla S. Giri, Y. B. K. Chowdary
    1991 Volume 56 Issue 4 Pages 491-494
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    Four freshwater centric diatom taxa, Cyclotella glomerata, C. striata, C. meneghiniana f. unipunctata and C. catenata were investigated karyologically and their important karyological features have been described and discussed. First two taxa contained same chromosome number 2n=12 while C. meneghiniana f. unipunctata and C. catenata revealed 2n=18 and 24 chromosomes, respectively. Chromosomes did not show structural organization and appear like either small or large dots ranging from 0.25 to 1.8μm in size. Chromosomes organize into either a ring or plate at metaphase in the equatorial region.
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  • V. A. Arefjev, A. I. Nikolaev
    1991 Volume 56 Issue 4 Pages 495-502
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    Hybrids between the great sturgeon and the Russian sturgeon in reciprocal crosses are found to exhibit non-intermediete chromosome number, 2n=167-169, on average. The hybrids are also characterized by sharp increase in variability of the quantitative karyotypic parameters such as diploid chromosome number, bi-armed chromosome number, number of uni-armed and microchromosomes, and chromosome arm number. Measurements of erythrocytes and their nuclei confirmed the di-tetraploid relationship of the parental species and non-intermediate pattern of the hybrid genome. Sharp disbalancing of karyotype of both reciprocal hybrids is indicative of high probability of their complete sterility.
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  • Ahmed E. Yaseen, Abdel-Baset M. Ebaid, I. S. Kawashti
    1991 Volume 56 Issue 4 Pages 503-509
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    Chromosomes were counted in the preparations of gonad tissues from the two species Bellamya unicolor and Lanistes bolteni collected from different localities around Qena City in Upper Egypt. A basic diploid chromosome number of 18 and 26 were presented in Bellamya unicolor and Lanistes bolteni, respectively. The karyotype of Bellamya unicolor consists of: five metacentric pairs, two submetacentric pairs and two subtelocentric pairs, while the karyotype of Lanistes bolteni consists of: eight metacentric pairs two subtelocentric pairs and three telocentric pairs. Shell measurements for these two species are also described in details in this paper. These results are reported for the first time in Egypt.
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  • M. A. Mannan, G. Kabir, N. N. Shaheen, F. N. Akhter
    1991 Volume 56 Issue 4 Pages 511-515
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    Seven pulse crops were studied meiotically. Meiosis was found to be normal except some irregularities such as lagging chromosomes, fragments etc. with a low frequency. Cytokinesis was found to take place at the end of second telophase and the arrangement of microspores was tetrahedral. Data on chromosome association and chiasma frequency were recorded from diakinesis as well as from first metaphase. A remarkable similarity was observed between the genome of L. culinaris and L. sativus and of V. mungo and V. radiata.
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  • M. A. Khadeer, S. Y. Anwar
    1991 Volume 56 Issue 4 Pages 517-522
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
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  • S. K. Dey
    1991 Volume 56 Issue 4 Pages 523-526
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    Chromosomes of five species of Cercopidae, viz., Cosmoscarta dimidiata, C. septempunctata, C. decisa, C. egens and C. fulviceps have been studied. Each species showed diploid count of 28 chromosomes. Except C. egens, all other species exhibited XY sex chromosome system in male. Neo-XY mechanism has been encountered in C. egens. Though the behaviour of the chromosome is found to be normal during meiosis, a laggard was observed in C. dimidiata.
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  • H. O. Misra, J. R. Sharma, R. K. Lal
    1991 Volume 56 Issue 4 Pages 527-531
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    Five distinct mutants differing for their phenotypic appearance and floral characters were identified in M2 generation of gamma ray irradiated (20 kR (200 Sv), 40 kR (400 Sv)) seed progeny of Hyoscyamus muticus (2n=28). They were subjected to meiotic analysis to understand their genotypic sensitivity to induced cytological changes. Genotype P7 was observed to be more susceptible to undergo chromsome mutations compared to genotype P9. The induced variation drastically affected the plant vigour and caused variation in the incision of corolla and number of petals. This was coupled with disturbance in meiotic behaviour, which included chromosome stickiness, desynapsis, anaphase nondisjunction, multiplolarity, simple and multiple interchanges. Pollen and seed fertility was moderately affected by spindle related disturbance but severely affected by chromosome interchanges.
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  • Ajay K. Jain, N. Sethi
    1991 Volume 56 Issue 4 Pages 533-538
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    Crude extracts of black and green tea (BT and GT) (Camellia sp.) were assayed for chromosomal aberration and sister chromatid exchanges (SCE's) inducing effects in cultured human lymphocyte cells. The concentrations used were 0.01, 0.1, 1.0 and 10.0μg/ml. Two types of treatments were performed:
    (1) Type ‘A’-Cells were grown in presence of different concentrations of tea extracts.
    (2) Type ‘B’-Precultured (for 24 hr) cells were treated for 3 hr in plain medium (without serum, PHA and BrdU) with different concentrations of tea extracts. After two washings, cells were resuspended in complete medium (containing serum, PHA and BrdU) and incubated for desired incubation period i. e. 48 and 72 hr for chromosomal aberration and SCE analysis, respectively.
    The percentage values of aberrant metaphases ranged from 3.33% to 6.0% and 0.0% to 5.0% due to respective treatments ‘A’ and “B” of BT and 2.0% to 7.0% and 1.0% to 4.0% after treatments ‘A’ and ‘B’ of GT respectively. Effects did not appear to be dose dependent. Chromatid gaps and breaks were commonly observed. Terminal deletions and chromosome gaps were observed only occasionally. Treatment ‘A’ and ‘B’ of BT enhanced the SCE frequency. Treatment ‘A’ of GT enhanced the SCE's but treatment ‘B’ decreased the SCE's which might be due to the induction of DNA repair process (es). Mutagenic and antimutagenic effects of tea have been discussed. From the present study it can be suggested that while tea may protect the human genome against certain environmental agents, the possibility can not be ruled out that alone or in combination of other co-factors it may pose genetic threat.
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  • Induced by Epigallocatechingallate
    Ajay K. Jain, N. Sethi
    1991 Volume 56 Issue 4 Pages 539-542
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    Epigallocatechingallate (EGCG) is a kind of catechin naturally present in black and green tea. The present study was undertaken to evaluate its cytogenetic effects in cultured human lymphocyte system. Used concentrations were 0.01, 0.1, 1.0 and 10.0μg/ml. Aberrant metaphases ranged from 0.0 to 5.47% and from 1.0 to 2.0% after treatment ‘A’ and ‘B’ respectively. Chromatid gap was most common abnormality. Chromatid breaks were observed rarely. Treatment ‘A’ enhanced the SCE frequency in dose dependent manner while treatment ‘B’ decreased the SCE's. This suggested that EGCG certainly has some interaction with DNA. Brief treatment may induce DNA repair while longer treatment may have lethal effects. However, from the present study it is difficult to conclude about its real genetic threat to human populations because it is consumed in a mixture or complex form.
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  • Induced by Ascorbic Acid (Vitamin-C)
    Ajay K. Jain, N. Sethi
    1991 Volume 56 Issue 4 Pages 543-547
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    Ascorbic acid (A. A.) (vitamin C) is one of the most widely used (singly or in combinations) vitamins. Because of its broad pharmacological significances and presence in natural food products, the present study was carried out to evaluate its cytogenetic effects in in vitro human lymphocytes. Concentrations screened were 0.1, 1.0, 10.0 and 100.0μg/ml. Aberrant meta-phases did not show significant variation after both types of treatments. 3 hr treatment in G2/early S phase did not affect the SCE frequency, while continuous treatment (100.0μg/ml) significantly reduced the same. This suggested that constant presence of A. A. might have potentiality to induce DNA repair. Mutagenic and antimutagenic effects of A. A. have been discussed in detail. From the present study it seems that A. A. itself is not mutagenic but may have mutagenic action in presence of metal ions (e. g. Fe+2).
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  • Ajay K. Jain, N. Sethi
    1991 Volume 56 Issue 4 Pages 549-554
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    It has been widely recognized that food factors play a significant role in carcinogenesis. This has led us to investigate chromosomal aberrations (CA) and SCE's inducing potentiality of black tea (BT), green tea (GT), epigallocatechingallate (EGCG) and ascorbic acid (AA) (See part I, II and III). On the basis of quantitative ratio of EGCG in BT and GT it seems that SCE enhancing effect of BT and GT after treatment ‘A’ is not entirely due to the presence of EGCG. They may contain some other factor (s) which diminish the DNA damaging potentiality of EGCG. BT and GT seems to contain different active factor (s) which may have different mode of actions because treatment ‘B’ of GT decreased the SCE frequency like EGCG, while treatment ‘B’ of BT significantly enhanced the SCE's and aberrant metaphases.
    An effort was made to know correlation between CA and SCE's. Various studies have been discussed. The results of present study support our earlier view that positive correlation between these biological end points seems specific and may depend upon the type of mutagens and their mode of action. The present study further suggests that the cell cycle's stage in which cells are treated or exposed to a mutagen also play a significant role in sharing common DNA lesions for the manifestation of CA and SCE's.
    On the basis of significant correlation coefficient ‘r’ value between aberrant metaphases (including chromatid gap) and mean SCE/cell and negative ‘r’ value between them (after deleting chromatid gap) after treatment ‘A’ of EGCG, it has been suggested that chromatid gap should not be excluded in scoring chromosomal aberrations.
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  • Saju Abraham. M, Susan Abraham
    1991 Volume 56 Issue 4 Pages 555-558
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    The present work was carried out as part of a comprehensive project initiated to evaluate the genotoxic potential of pollutants from the Titanium factory on plants. Detailed investigations on growth and cell divisions were conducted in C. laburnifolia found growing in these areas. For comparison, studies on control plants growing under the same environmental conditions, but in a different habitat were conducted. Toxic effects of pollutants in the environment were manifested in the plants growing near the factory by the presence of growth retardation, inhibition of cell divisions, chromosome clumping and a variety of chromosomal abberrations. Such abnormalities were lacking in the control plants.
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  • Hari Chand, Rajendra K. Grover, P. K. Sareen
    1991 Volume 56 Issue 4 Pages 559-566
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    Sunflower and pearl-millet grown from seeds treated with carbendazim showed a variety of chromosomal aberrations in somatic (root tips) and reproductive (pollen mother) cells. In pearl-millet, somatic and reproductive cells showed relatively more chromosomal aberrations than in sunflower. In somatic cells of pearl-millet aberrations were observed at late prophase leading to fragments and stickiness and production of laggards at meta- and ana-phases, while no aberrations were seen at telophase. In sunflower somatic cells, abnormal bridges were frequent at anaphase and laggards at metaphase. The reproductive cells of pearl-millet showed abnormalities at the diakinesis and metaphase whereas in sunflower laggards at metaphase were common.
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  • Wolfgang Staiber, Irmgard Wech
    1991 Volume 56 Issue 4 Pages 567-575
    Published: December 25, 1991
    Released: March 19, 2009
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    Oenocytes explanted and collected from prepupae of Acricotopus lucidus (Diptera, Chironomidae) were enzymatically dissociated into single cells by treatment with elastase. The isolated cells were kept viable for days over HeLa cells as feeder culture. Viability of the isolated cells was tested with flourescein diacetate and Trypan Blue. Carmine-orcein staining demonstrated that the oenocyte nuclei contain polytene chromosomes with distinct banding patterns. The DNA-content and polytenic level of prepupal oenocyte nuclei were measured using flow cytometry at 128 C. The morphology of oenocytes was investigated in differential interference contrast and with transmission electron microscopy.
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  • G. Kabir, R. M. Singh
    1991 Volume 56 Issue 4 Pages 577-585
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    Two species of Cicer and their hybrids were studied meiotically to draw a valid conclusion on their relationship. Meiosis was found to be normal except some irregularities such as lagging chromosomes, fragments, bridges etc. with a low frequency. However, the frequency of irregularities in the hybrids were somewhat high than that of their respective parents. Cytokinesis was found to take place at the end of second telophase and the arrangements of microspores were tetrahaedral. Data on chromosome association and chiasma frequency were recorded from diakinesis as well as from prometaphase. Both the parents and hybrids indicated a preponderence of rod bivalents. Univalents and quadrivalents were observed only in the hybrids. A remarkable similarity was observed between the genomes of the hybrids and their respective parents, and it indicated C. reticulatum rather in the range of C. arietinum primary gene pool and free gene exchange between them. This study also reflected C. arietinum as wild progenitor of cultivated C. arietinum.
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  • Genes disrupting pre- and post-meiosis
    C. Nirmala, M. L. H. Kaul
    1991 Volume 56 Issue 4 Pages 587-595
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    Following EMS, DES and gamma ray treatment in Arkel and Bonneville pea varieties, three male sterile mutants were induced in Pisum sativum. Sterility in each of these is conditioned by single recessive genes, the three genes being non-allelic. Whereas in one mutant, the ms gene acts during pre-meiosis, in the other two the genes act during post-meiosis. In the premeiotic mutant, the PMCs either degenerate before attaining genetic autonomy or after separating out from one another. Their chromatin either compacts or fragments to degenerate completely. Thus, no meiosis occurs in this mutant.
    In both the post-meiotic mutants, male meiosis is normal. In one, the microspores are released from the PMCs either in free or in adhered state. They develop thick walls, their chromatin condenses centrally and finally they degenerate. In the other mutant, monads are released from the PMCs. In 93% microspoes, the nuclear degeneration is faster than cytoplasmic degeneration, in 7% the reverse occurs. In both the post-meiotic mutants, microspores degenerate fully. Male sterility in all the three mutants is complete while female fertility is normal.
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  • S. K. Gupta, I. A. Hamal, A. K. Koul
    1991 Volume 56 Issue 4 Pages 597-602
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    Cytological studies on 5 Himalayan species of the genus Torilis revealed diversity in number as well as morphology of the somatic chromosomes. T. arvensis and T. leptophylla carry n=6; T. japonica, n=8; T. nodosa, n=12 and T. stocksiana n=18. Morphology of the chromosomes has indicated that while T. arvensis is a primitive diploid, T. leptophylla complement is a derived one. T. japonica represents a dysploid derivative. T. nodosa and T. stocksiana are polyploids with x=6. The former is an allotetraploid and the latter autoallohexaploid. Karyotypic data also supports the hybrid origin of polyploids.
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  • J. L. Karihaloo
    1991 Volume 56 Issue 4 Pages 603-611
    Published: December 25, 1991
    Released: March 19, 2009
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    Microsporogenesis was normal during summer in S. melongena and S. violaceum and during monsoon in S. torvum. The same plants showed desynapsis during other seasons of flowering; winter in the first 2 species and summer in the last one. Normal meiosis was characterized by the chromosomes pairing into 12 bivalents, regular segregation and high pollen fertility (86.5%-94.6%). Average per cell chromosome association at metaphase I during desynaptic meiosis was 5.72II+12.56I in S. torvum, 7.63II+8.73I in S. melongena and 9.26II+5.47I in S. violaceum. Microspore mother cells in a few flower buds of S. violaceum showed complete lack of pairing which may represent a case of asynapsis. Anaphase I showed irregular segregation, univalent laggards and precociously separating chromatids. In S. torvum, flower development stopped after microsporogenesis so that no pollen grains were formed. Pollen stainability in the other 2 species was low (2.6% in S. violaceum and 14.7% in S. melongena). Both per cell and per bivalent chiasma frequency were reduced during desynaptic meiosis. Desynapsis and the other observed abnormalities are ascribed to temperature stress.
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  • G. K. Manna, A. Sadhukhan, S. Datta
    1991 Volume 56 Issue 4 Pages 613-619
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    The mutagenic potential of the human intestinal amoeba, Entamoeba histolytica, NIH: 200 strain in TYI-S-33 culture medium added with sterile bovine serum, vitamins and antibiotics was intraperitoneally injected to individual mouse, Mus muculus a dose of 2ml containing 15×105 amoebae after 72 hr incubation and parallely another set of mice weighing about 20g were intraperitoneally injected to serve as control, was assessed at 30 min, 24 hr, 48 hr and on 7 th day after injection. The net increase over control in the E. histolytica treated mice in the combined data of all intervals was 9.94% for bone marrow chromosome aberration, 0.33% for micronucleated erythrocytes, 15.0% for first spermatocyte metaphase chromosome aberrations and 1.55 % for sperm with abnormal head frequency. The difference was statistically significant in each test.
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  • Neeru Seth, M. R. Vijayaraghavan
    1991 Volume 56 Issue 4 Pages 621-626
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    The mechanism of anther dehiscence in Sesbania speciosa was followed using light and scanning electron microscopic techniques. The following sequence of events occur (i) Epidermis and endothecium expand, (ii) Branched wall thickenings occur only in the endothecium cells, (iii) Septum cells dissociate, (iv) Tapeta of two adjacent locules lyse due to pressure exerted by pollen grains.(v) Stomium ruptures due to the pressure exerted by the desiccating endothecium.
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  • Anath Bandhu Das
    1991 Volume 56 Issue 4 Pages 627-632
    Published: December 25, 1991
    Released: March 19, 2009
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    A detailed karyotypic analysis and cytophotometric estimation of 4C DNA amount was carried out in six species of the subtribe Carinae of Umbelliferae. Intergeneric and interspecific chromosome number viz., 2n=14, 18, 20, 22 were varied in the subtribe level. Critical analysis of chromosome morphology revealed the structural alteration of chromosomes along with their changed DNA amount. Significant variation of DNA amount having numerical, gross or minor chromosomal alteration leads to the genetic drift in between the species of the subtribe suggesting the compromise between the structural and biochemical changes of the genome during macro- and micro-evolution.
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  • M. I. S. Saggoo, S. Kumari, Bindu
    1991 Volume 56 Issue 4 Pages 633-637
    Published: December 25, 1991
    Released: March 19, 2009
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    In the present investigation the cytological effects of leaf homogenate of T. indica on Allium cepa root meristem were studied. The lower concentration of leaf homogenate caused mitoactivation while higher ones were mitodepressive. The leaf homogenate induced both physiological (stickiness of chromosomes, lagging chromosomes, hyperploid cells, etc) and clastogenic (chromosome breaks, ring chromosome and chromatin bridges) type of aberrations. Recovery of roots with 24 hr over water after treatment with leaf homogenate was not enough for normalisation of pattern of cell division.
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  • N. A. Zeerak
    1991 Volume 56 Issue 4 Pages 639-643
    Published: December 25, 1991
    Released: March 19, 2009
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    Relative effects of differential and combined treatments of gamma rays, and ethyl methanesulphonate on the meiosis and on pollen and seed fertility in M1 generation of a local brinjal cultivar of Kashmir valley (Solanum melongena var. Local Long) were studied. Radiations and combined treatments were more efficient in inducing meiotic abnormalities than EMS treatments: However, combined treatments and EMS treatments induced greater pollen and seed sterility than radiations. Radiation induced sterility might be the result of chromosomal aberrations which in turn were dose dependent while sterility induced by EMS might be attributed to cryptic deletions and specific gene mutations. A dose dependent increase in chiasma frequency was observed with all single and combination treatments.
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  • S. S. Bir, Paramjeet Cheema, M. Sidhu
    1991 Volume 56 Issue 4 Pages 645-651
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    Population studies on five species of Scirpus namely, S. kyllingioides, S. litoralis, S. mucronatus, S. roylei and S. triqueter show fixed chromosome numbers in S. mucronatus (n=22) and S. triqueter (n=21) while S. kyllingioides and S. litoralis show high incidence of aneuploidy. Both diploid (n=11) and octaploid (n=44) cytotypes are recorded for S. roylei. On the basis of recorded base numbers (X=5, 7, 8) in Scirpus, it is very difficult to guess correctly the ploidy level for S. kyllingioides and S. litoralis cytotypes.
    Sedges show a high incidence of euploid and aneuploid numbers which is due to vegetative propagation so common in the group because this mechanism of race perpetuation helps in conservation of all the evolved cytotypes which is normally not the case with other groups of flowering plants not exhibiting vegetative propagation.
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  • A. P. Krishnaja, N. K. Sharma
    1991 Volume 56 Issue 4 Pages 653-658
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    A cytogenetic monitoring programme on human new borns carried out from 1983-1987 to find out the incidence of constitutional chromosome anomalies also included studies to obtain baseline data on spontaneous chromosomal aberrations (CA), sister chromatid exchanges (SCEs) and micronuclei (MN) from cord blood samples in limited number of human neonates. The results are compared with data obtained in our laboratory on these cytogenetic end points from adult peripheral blood lymphocytes. The micronuclei data was obtained from adult lymphocytes by the cytokinesis blocked lymphocyte assay, by Cytochalasin B. 120 cord blood samples analysed gave a mean frequency of 0.0052 chromatid breaks/metaphase and 0.0059 chromatid gaps/metaphase. Only one dicentric chromosome was noticed in the 12, 000 cells analysed. No statistically significant difference was noticed between male and female new borns in the spontaneous CA frequency. 20 adult blood samples analysed after 48 hr culture and 10 adult blood samples analysed after 72 hr culture gave mean frequency of 0.0085, 0.013 chromatid breaks/metaphase and 0.01414, 0.019 chromatid gaps/metaphase respectively. A large statistically significant elevation in SCE/cell was found when adult blood samples were compared to cord blood samples (the difference 1.94 SCE/cell, P<0.001 by simple ‘t’ test) the mean frequency of SCEs observed in cord blood samples and adult samples being 5.56±0.21 and 7.496±0.21 SCE/cell respectively. The frequency of micronuclei in cord blood lymphocytes was found to be 0-1.5/1000 cells, 1-3/1000 cells, 2-5/1000 cells in 48, 72 and 96 hr cultures respectively. Adult blood lymphocytes exhibited a micronuclei frequency of 0.0123±0.001 MN/CB cell. The low incidence reported here of all three cytogenetic end points may possibly reflect the influence of high folate levels in cord bloods on spontaneous chromosomal damage.
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  • Y. Sun, George H. Liang
    1991 Volume 56 Issue 4 Pages 659-664
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    Pollen surface sculpture provides very useful information about taxonomy and evolution of plants. Pollen exine sculpture of five Sorghum species and those of wheat (Triticum aestivum L.), rice (Oryza sativa L.), and maize (Zea mays L.) were compared using a scanning electron microscope (SEM). Differences in pollen surface structure occurred at the genus level and at the species level among Sorghum species at various ploidy levels. S. bicolor (2n=20), S. halepense (2n=40), and S. purpureo-sericeum (2n=10) had similar pollen exine sculptures, whereas S. versicolor (2n=10) and S. nitidum (2n=10) had distinctly different pollen surface sculptures from that of S. bicolor. Sizes of seeds and pollen grains were correlated to some extent. Maize had the largest seed and pollen, and S. nitidum had the smallest seed and pollen. For those species in which sizes did not differ greatly, variations of pollen sizes also were negligible. Ploidy level in Sorghum genus did not seem to have a great impact on pollen sizes.
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  • Y. S. Bedi
    1991 Volume 56 Issue 4 Pages 665-672
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    Numerical variability in hardwood timbers is observed from the great variation in chromosome numbers (2n=10 to 2n=196) as well as basic numbers (x=5-21, 23, 31 and 43). The most commonly represented chromosome number is 2n=24. Treating x=7 as the original base number for angiosperms, the possible role of polyploidy and/or aneuploidy in the origin of existing heterogeneity in the present day base numbers of Indian commercial timbers is discussed. Incidence of polyloidy is 33.3%. Amongst polyploids the tetraploids are the most common. Intraspecific polyploidy exists in 36 species. The highest level of ploidy 28x is in Bischofia javanica. The average somatic chromosome number in the present sample of timbers is quite high (38.15), this duly compensates the low recombination index resulting due to small sized chromosomes, a characteristic of majority of the hardwood timbers. Other phenomena of cytological interest are the existence of B-chromosomes (9 species) and cytomixis (8 species). There appears to be no consistent relationship between chromosome number and economic usefulness of tropical hardwood timbers.
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  • Xiuhai Ren, Jianxun Cui, Qixing Yu
    1991 Volume 56 Issue 4 Pages 673-677
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
    Chromomycin A3 and DAPI, together with silver nitrate, were used for staining the chromosomes of 4 species of cyprinid fishes, which led to the detection of CMA-positive heterochromatins, DAPI-positive heterochromatins, and CMA-negative NORs. Present work suggested three types of heterochromatins and three types of NORs in the genomes of Cyprinidae.
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  • Takayuki Nagashima, Nao Niwa, Shûji Okajima, Toshifumi Nonaka
    1991 Volume 56 Issue 4 Pages 679-684
    Published: December 25, 1991
    Released: March 19, 2009
    JOURNAL FREE ACCESS
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