In this study, the effects of lead acetate on the third instar larvae salivary gland polytene chromosomes of D. melanogaster have been investigated. In this research, the effects of a heavy metal compounds, lead acetate, were examined on the polytene chromosomes in D. melanogaster. The various clastogenic effects such as weak points (breaks, semibreaks, constrictions, etc.), hairpin and asynapsis were observed but not chromosomal aberrations in control groups (in the larvae untreated with lead acetate). Our findings suggest that lead acetate exerts a weak clastogenicity on salivary gland polytene chromosomes of D. melanogaster.
1. Cytogenetic analysis using lymphocytes of 50 patients with Rb in Indian population has been made. A late mean age at diagnosis, 3 (6%) sporadic patients with constitutional chromosomal deletion of 13q14 and midface dysmorphism in a few patients has been recorded and analyzed. 2. All the three patients showed a mosaic karyotype of 46XY/46XY del (13q14.1->q14.3) of whom two with bilateral and one with unilateral Rb. The Rb patients with deletion didn't differ significantly and is within the range (5%-10%) compared with other cytogenetic surveys done in the other parts of the world. None of the family members showed any chromosomal abnormality. 3. The need for genetic counseling and cytogenetic analysis in patients with Rb is stressed.
Cytological investigations were designed to check the somatic chromosome number and meiotic chromosome behaviour including the ploidy levels of an indigenous population of Setaria pallide-fusca of District Rawalakot, Azad Kashmir-Pakistan. This species was found to be octoploid having a chromosome number of 2n=72, which is not uncommon in most of the Setaria species. The meiotic results indicated that the course of meiosis was quite normal in all the plants under observation with 36 bivalents. A segmental allopolyploid origin to this race, under observation has been suggested.
The toxicity of lead acetate in the male germ cells of Swiss mice has been studied. A single intraperitoneal dose of lead acetate (50 mg/kg body weight) not only caused testicular atrophy but also affected the normal sperm count to decline significantly with the production of a significantly increased amount of morphologically abnormal sperm in the treated animals. Further, a marked decrease both in the body and testes weight in the lead injected animals associated with a significant decrease in the ascorbic acid content in the testicular tissue have been observed.
C-banding pattern of holokinetic chromosomes in Aphalara calthae is reported. The large C-positive regions are shown to be localized on the telomeres of the meiotic metaphase chromosomes. Two pairs of autosomes and the X-chromosome bearing blocks of C-heterochromatin on both telomeres. Nine pairs of autosomes have a block on one telomere while one chromosome pair shows no C-bands.
Four species of Curimatidae, collected in lakes situated in the floodplain of the Miranda river (Pantanal-MS), were analyzed cytogenetically. Karyotypes of Curimatella dorsalis, sectrogaster curviventris and Steindachnerina brevipinna were characterized by 2n = 54 metacentric and submetacentric chromosomes, one pair of chromosomes bearing NORs in terminal position (46 M/8 SM and 13th, 42 M/12 SM and 20th, 48 M/6 SM and 17th, respectively). The first two species showed constitutive heterochromatin on the centromeric region of some chromosomes and in the other species heterochromatic blocks were observed on the centromeric and telomeric regions of a few chromosomes. The karyotype of Curimatopsis myersi showed 2n = 46 (42 M/4 SM), one pair bearing terminal NORs, representing the lowest diploid number for the family.
Somatic chromosome numbers of 63 regenerated plants in the cultivar 'Okichidori' of Iris ensata were counted and tetraploid plants were recognized in 11.1 % of the regenerants examined. This indicated that polyploidization for these plants was induced during the subcultures of its multiple shoots. Variation in NORs of 30 diploid regenerants was further examined by the silver-staining method. Half of these regenerants had 4 NOR-bearing chromosomes which were recognized in 'Okichidori'. On the contrary, the other half showed variation in NORs. Among these regenerants, 14 plants had 5 NOR-bearing chromosomes. The increase of one NOR-bearing chromosome compared with 'Okichidori' could be explained by the translocation of a NOR to a non NOR-bearing chromosome during the subcultures of its multiple shoots. In addition, one regenerant (R91) had 3 NOR-bearing chromosomes with 1 Ag-NOR band and 1 NOR-bearing chromosome with 2 Ag-NOR ones. The appearance of the latter chromosome provided conclusive proof that the translocation of a NOR to a NOR-bearing chromosome was induced during the subcultures of multiple shoots in 'Okichidori'. Thus, it was proved that there were somaclonal variations in somatic chromosome numbers and NORs in the regenerated plants obtained from the subcultures of its multiple shoots.
Meiotic studies of PMCs and 4C DNA content from root tip cells of 8 species of Mammillaria of the family Cactaceae revealed significant interspecific variation in the genome. The haploid chromosome number n= 11 was recorded in M. bocasana, M. boolii, M. grandiflora, M. hahniana, M. occidentalis, M. plumosa, M. rhodantha and M. zeilmanniana. The chiasma frequency significantly varied from 19.42 to 28.80 per nucleus and 1.76 to 2.61 per bivalent. The formation of univalent in some of the cells, spindle anomalies i.e. early or late separation leads to the formation of pentads, sexads or octads instead of tetrads formation in the meiotic telophase II through differential pollen sterility from 9.12 to 32.83% in M. zeilmanniana and M. occidentalis respectively. The 4C DNA amount of root tip cells varied significantly from 18.42 to 27.78 pg in M. bocasana and M. rhodantha, respectively. Significant variation in DNA amount with gross or minor alteration of chiasma frequency leads to differential heritability with genetic drift at species level.
The effect of Temik on both mitosis and meiosis was studied. The insecticide decreased the mitotic activity of Vicia faba root tip cells and produced different kinds of abnormalities. These kinds of abnormalities were nearly identical in both mitosis and meiosis. Stickiness was the most common type of these abnormalities resulted after all treatments. Disturbance mitotic phases which is a mitotic poisons effect were also present with considerable percentage. Such phenomena indicate the toxicity of Temik and its low mutagenic potential.
Cells die either accidental or physiologically programmed deaths. Our results based onultrastructural changes observed in fly photoreceptors 15 and 30 min, 3, 6 and 24 hr postmortem, demonstrate that death by necrosis is not as uniform a process as had generally beenassumed, but depends on the nature and specific causes of the accidental cell demise, whichappears to begin peripherally and then moves inward. Consequently, as with programmed celldeaths, death by necrosis also requires the recognition of different sub-categories.
An alloplasmic line of maize (MDE) was produced by using the Multiple Dominant line (MDZ) as a recurrent male parent during 20 generations of backcrosses onto teosinte (Zea mays ssp. mexicana). The meiotic behaviour of both lines was carefully compared. The MDZ line has a transposon which can be activated by the cytoplasm of teosinte (Mazoti 1978). The analyses showed that all the individuals of MDZ had a regular meiosis, whereas the individuals of alloplasmic line presented several meiotic abnormalities in different parts of the panicle; the flowers showing cytomixis, fusion of nuclei, pseudomultivalents, asinapsis or persistent nucleolus at metaphase. The abnormal meiotic behaviour in alloplasmic line could be attributed to the action of the transposon carried by the MDZ line, which becomes activated in the cytoplasm of teosinte, such as it has been found by Mazoti (l.c.) for several morphological and cytological characteristics.
Gibasis schiedeana from the ERPSA-Mexico, showed an autotetraploid cytotype with 2n = 16, x = 4 and had a karyotype 12M + 4A, four acrocentrics had satellites. In the cytotype from the ERPSA-Mexico, heterozygous chromosome interchange was observed, evidenced in M-I by multivalent : HI (0.91%), IV (37.90%), V (1.18%) and VI (0.82%), some of them heteromorphic. In addition, the analysis in A-I showed cells with bridge and fragment (U-type chromatid exchange) and cells with bridge without fragment (sub-chromatid aberrations, SAB) in frequencies of 4.62% and 4.10% respectively. Heterozygous chromosome interchange and chromatid exchange were also evidenced in 8 heteromorphic chromosomes. Lagging chromosomes were also recorded in A-I (7.35%). The chromatid exchange and lagging chromosomes have not been reported in other cytotypes of G. schiedeana.
An unexpected growth-stimulating effect of 5-aminouracil (5-AU) 50, 100 and 150 μM concentration on long-term callus tissue culture of Cereus peruvianus was found during investigations of callus tissue growth and expression of Mdh genes in the presence of this inhibitor of DNA replication. Three-year-old callus tissues were cut and subcultured in culture medium containing the different 5-AU concentrations. The callus tissues were then collected at 15-day intervals up to 45 days to determine individual callus weight. At 45 days, the callus tissues were collected and submitted to starch gel electrophoresis for analysis of MDH isozymes. The in vivo effect of the various 5-AU concentrations on onion root-tip cell growth was also investigated, and a similar growth response pattern was observed. Unchanged MDH isozyme patterns in callus tissues indicated that Mdh gene expression was not directly related to increased growth of the callus tissues. The interference of 5-AU with DNA replication for cell proliferation and tissue did not change the expression of Mdh genes at the transcriptional level but seems to affect important genes that modulate enzyme-specific activity or degradation of MDH isozymes.
The cytological abnormalities produced by muriate of potash were evaluated using Allium cepa root meristem assay. Studies using different concentrations of the fertilizer showed that concentrations ranging from 200 ppm to 2000 ppm produced significant increase in chromosomal aberrations and other abnormalities over the control. This study indicates that the fertilizer is capable of upsetting normal cell divisions if excessive amounts are present in the soil.
Differentiation of leucoplast-like plastids to amyloplasts occurred when BY-2 cultured tobacco (Nicotiana tabacum L.) cells were grown for 2 days in auxin-depleted culture medium containing cytokinin (benzyladenine, 1 mg/l). Development of the amyloplasts was inhibited by addition of various inhibitors, such as actinomycin D, cycloheximide, and chloramphenicol, indicating that amyloplast formation in BY-2 cells requires de novo synthesis of RNA and proteins in nucleo-cytoplasm and in organelles (i.e., plastids and mitochondria). Actinomycin D and cycloheximide inhibited accumulation of starch effectively and promptly irrespective of the timing of addition, while the inhibitory effect of chloramphenicol decreased as the time until addition grew longer. This indicates that continuous expression of cell-nuclear genes is necessary for amyloplast formation in BY-2 cells, whereas organelle gene expression becomes less necessary in the late phase of amyloplast development.
We investigated the best fixation methods for the immunogold electron microscopy. Rapidfreeze substitution is better than conventional chemical fixation for preservation of structural integrity of cell nucleus, mitochondrion and plastid. When samples were embedded in LR White resin, fixation in absolute acetone gave a 2.6-fold increase in immuno-labelling of DNA compared to fixation with 1% glutaraldehyde in acetone. In contrast, no gold particles were identified when cells were fixed by 1% OsO4 and embedded in Spurr's resin. These results indicate that the rapidfreeze substitution in absolute acetone and embedding in LR White resin is the optimal approach for immunogold labelling.
MtDNA of Physarum polycephalum has duplicated specific regions that bind tightly to the mitochondrial membrane. In this study, we visualized the localization of the membrane-binding regions (MBRs) of mtDNA in the mitochondrial nucleus (mt-nucleus) by fluorescence in situ hybridization with a DNA probe specific for the MBR. The mt-nucleus of P. polycephalum contains 18-32 mtDNA molecules. In spite of the high copy number of mtDNA, the sites of MBRs were detected as a few globular fluorescence that were distributed along the mt-nucleus. This indicates that MBRs were clustered at a few discrete sites along the mt-nucleus. Furthermore, the number of MBR cluster in a mt-nucleus was proportional to the number of copies of mtDNA; one MBR cluster consisted of the MBRs of about 10 mtDNA molecules.
The G-, R-and C-banded karyotypes of the two hamster species, the greater long-tailed hamster (Cricetulus triton or Tscherskia triton) and the Chinese hamster (Cricetulus griseus), were analyzed. The diploid chromosome number of Chinese hamster is 22, and that of the greater longtailed hamster 28. These are morphological differences between two hamster species : the number of metacentric and submetacentric autosomes was only 4 in the greater long-tailed hamster, in contrast to 14 in the Chinese hamster, while the number of acrocentric and subtelocentric chromosome was 22 in the greater long-tailed hamster and 6 in the Chinese hamster. The analysis of banding patterns in the two hamster species revealed that each chromosome of the greater long-tailed hamster corresponded to one arm or one whole chromosome of the Chinese hamster. However, the large C-bands (or lightly stained with R-bands) such as those found around the centromeric region of the greaterlong-tailed hamster chromosomes did not exhist in the centromeric region, or any other segments, of any chromosome in the Chinese hamster. These findings may be related to the karyotypical evolution of the two hamster species, but it is difficult to say which these hamster species are belonged to the same genus Cricetulus or not.