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I F Zhimulev

Publications and source records attributed to I F Zhimulev.

At least 109 records · Page 6Linked to original sources
PubMed1980

Cytogenetic analysis of the 2B3-4--2B11 region of the X-chromosome of Drosophila melanogaster. I. Cytology of the region and mutant complementation groups.

There are, at least, 11 distinct single bands and one real doublet in the region 2B1-2--2C1-2 of the X-chromosome of Drosophila melanogaster. This figure coincides with that in Bridges' revised map with most of the "doublet" bands being artifacts. Three puffs appear in the region. The early ecdysone-specific puff 2B5-6, small at PS(puffing stage) 1, increases sharply at PS 2. The late ecdysone-specific puff 2C1-2 appears at PS 4--5. At PS 9--10, when 2B5-6 disappears completely and 2C1-2 decreases, a third puff at 2B11 appears. None of these puffs is active at PS 11. Morphological analysis of puff appearance and autoradiographic study of 3H-uridine incorporation into chromosomes carrying rearrangements within the 2B region suggest that the early ecdysone-specific puff derives from bands 2B5 and may be 2B6, while the neighbouring bands 2B1-4, and 2B7-10 do not show appreciable transcription at the investigated stages. There are 42 mutations affecting viability in the region where the 2B5-6 puff is located. The mutations belong to 6 complementation groups; two of the groups dor and swi, are independent while the rest are overlapped by several lethal mutations (overlapping complex.) Mutants of the different groups have series of similar characteristics: temperature sensitivity, dose sensitivity, larva-pupal lethality and similar morphological abnormalities. It can be assumed that there is a functionally linked cluster of genes within the region 2B. Complementation groups br, rbp, l(1)pp-1, l(1)pp-2 (overlapping complex) have been located by rearrangements in very narrow cytological limit 2B3-4--2B5 that is in the area of developing puff. Two other loci dor and swi are situated some to the right of 2B5.

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PubMed1980

Transcription of intercalary heterochromatin regions in Drosophila melanogaster cell culture.

Labelled RNA preparations (total newly synthesized RNA, as well as stable cytoplasmic RNA) isolated from a cell culture of D. melanogaster were hybridized in situ with polytene chromosomes. Apart from the nucleolus, in all cases the regions adjacent to the chromocentre in the polytene chromosomes and the intercalary heterochromatin regions in the X chromosome and the autosomes are the most intensively labelled. In the case of asynapsis of polytene chromosomes in heterozygotes the label is detected in a number of intercalary heterochromatin sites in one homologue only ("the asymmetrical label"). The same kind of radioactivity distribution in intercalary heterochromatin regions was observed after a hybridization of polytene chromosomes with cloned DNA fragments (Ananiev et al., 1978, 1979) coding for the abundant classes of messenger RNA (Ilyin et al., 1978) in a cultured D. melanogaster cells. In some regions of intercalary heterochromatin which do not contain these fragments the "'asymmetrical" type of label distribution is observed after hybridization with cell RNA. - These results lead one to regard the intercalary heterochromatin regions as "nests" comprising different types of actively transcribable genes, the composition of each nest varying in different stocks of D. melanogaster.

Animals↗
PubMed1980

[Transcription of portions of chromosomes corresponding to regions of intercalary heterochromatin in Drosophila melanogaster cell cultures].

Labelled RNA preparations (total newly synthesized RNA, as well as stable cytoplasmic RNA) isolated from a cell culture of Drosophila melanogaster were hybridized in situ with polytene chromosomes. Apart from the nucleolus, in all cases the regions adjacent to he chromocentre in the polytene chromosomes and the intercalary heterochromatin regions in the X chromosome and the autosomes are the most intensively labelled. In the case of asynapsis of polytene chromosomes in heterozygotes the label is detected in a number of intercalary heterochromatin sites in one homologous only ("the asymmetrical label"). The same kind of radioactivity distribution in intercalary heterochromatin regions was observed after a hybridization of polytene chromosomes with cloned DNA fragments (Ananiev et al.,, 1978, 1979) coding for the abundant classes of messenger RNA (Ilyin et al., 1978) in cultured D. melanogaster cells. In some regions of intercalary heterochromatin which do not contain these fragments the "asymmetrical" type of labelled distribution is observed after hybridization with cell RNA. These results lead one to regard the intercalary heterochromatin regions as "nests" comprising different types of actively transcribable genes, the composition of each nest varying in different stocks of D. melanogaster.

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PubMed1976

Comparative study of the function of polytene chromosomes in laboratory stocks of Drosophila melanogaster and the l(3)tl mutant (lethal tumorous larvae). II. Changes of banding pattern and transcriptional activity in the salivary chromosome of l(3)tl.

The salivary chromosomes of the l(3)tl mutant of D. melanogaster are considerably thicker and shorter than those of normal larvae. In most nuclei, chromosome shortening is associated with morphological changes of two types. a) The bands lose their distinctive pattern and become loose. The chromosome appears as a granular mass. In extreme cases pompon-like chromosomes arise. Most frequently male X-chromosomes undergo such changes and begin to shorten as early as in the middle of third larval instar. "Pompon" transformation is not associated with a change in the relative intensity of RNA synthesis: the ratio of silver grain number over the male X-chromosome to that over regions 61A-63F is the same in pompon-like l(3)tl chromosomes and in the male and female X-chromosomes of the normal lines. b) Shortened chromosomes occassionally retain distinct band organization and, in these cases, chromosome shortening is observed to be due to the condensation of the chromatin of many puffs and interbands resulting in the fusion of a large number of bands into "new" chromatin blocks. In regions of fused bands, transcriptional activity is decreased as compared with regions where this union does not occur. The chromosomes of l(3)tl larvae lack ecdysone-stimulated puffs and other prominent puffs. In 144-192 hour larvae, puffs can be induced by ecdysone and until 384 hours by temperature shock. The capacity of puff induction decreases with larval age.

Animals↗
PubMed1976

Comparison of in vivo and in vitro RNA synthesis on polytene chromosomes of Drosophila.

A comparative radioautographic study of the RNA precursors incorporation on polytene chromosomes of Drosophila in vivo in the cells of salivary glands, and in vitro during incubation of E.coli RNA polymerase on slides with fixed chromosomes was performed.--The pattern of in vivo 3H-uridine incorporation on different sections of the chromosomes drastically differed from the in vitro 3H-UTP incorporation which seems to be much more related to DNA content of the individual small sections. In both cases puffing of the loci resulted in the increase of RNA synthesis but in vitro only 2-3 fold and in vivo much more. Hence, RNA synthesis in vitro was unspecific and did not reflect the in vivo RNA synthesis.--On the other hand, E.coli RNA polymerase completely mimics in vitro the dosage compensation phenomenon making twice as much RNA on one X-chromosome of males (1X2A) as on each of X-chromosomes of diploid (2X2A) and triploid (3X3A) females and super-females (3X2A), and the intermediate amount of RNA on each of X-chromosomes of intersexes (2X3A). It is suggested that the differences in the in vitro template activity of X-chromosomes of cells with different X:A ratio are due to different extent of condensation of their deoxyribonucleoprotein (DNP). Yet, both male and each of female X-chromosomes bind the same amount of thymus histone FI labelled with fluorochrome which indicates that they contain the same amount of "open" regions with exposed chromosomal DNA accessible to external proteins.--On the basis of these observations a hypothesis is put forward which suggests that RNA transcription in animal chromosomes is regulated at two levels by different mechanisms; the first one controls the extent of condensation of DNP of genetic loci and determines their competence to the second mechanism which involves the action of gene-specific activator proteins. According to this hypothesis the phenomenon of dosage compensation of sex-linked genes is due to decondensation of DNP of male X-chromosome which renders its loci twice as responsive to activators as compared to the same loci in females.

Animals↗
PubMed1976

RNA synthesis in the Drosophila melanogaster puffs.

Autoradiographical analysis of [3H]-uridine incorporation into three large puffs of Drosophila melanogaster has revealed that after 1 min pulse with isotope the label is observed above the whole puff area. When puffs were induced by high temperature, RNA synthesis was sharply increased (or started) in many sites of the developing puff. No significant delay in the transport of newly-synthesized RNA in large puffs, in comparison with small ones, has been found. In regions without temperature-induced puffs RNA synthesis and its transport are apparently delayed under influence of heat shock.

Animals↗
PubMed1975

[Snythesis of mucoprotein secretion in the salivary glands of Drosophila melanogaster IIIrd instar larvae].

The process of mucoprotein (glue) accumulation is described. This substance is secreted by salivary glands of the III instar larvae of Drosophila melanogaster. Granules of the secretory substance appear in the glandular cells 90 hrs after egg laying. Its secretion takes place within 120 hrs. The template RNA of glue proteins appears to be synthesized within the range of 72-85 hrs since actinomycin treatment of larvae at this time suppresses the formation of secretory substance. The portion of secretory proteins amounts to 23-32% of the total gland protein. In a mutant, 13tl, deficient by the absence of pupation, no PAS-positive, staining of glands or secretory granules identified under the phase-contrast microscope was found. A possible participation of fat body in the formation of mucoprotein secretory substance is discussed.

Animals↗
PubMed1975

[Hormonal regulation of mucoprotein secretion by salivary gland cells of Drosophila melanogaster larvae during metamorphosis].

The secretion of mucoproteins by the Drosophila melanogaster salivary gland cells into the gland lumen is associated with the high ecdysone content. Mucoproteins are synthesized but not discharged by these cells in ecdysone-deficient homozygous 1(2)gl larvae, as well as in normal larvae devoid of ecdysone by ligatures and transplantation of salivary gland into the imago abdomen. Ecdysone injections stimulate the mucoprotein secretion into the gland lumen.

Animals↗
PubMed1975

[Method of selection of synchronously developing larvae of Drosophila melanogaster].

Methods of obtaining synchronously developing larvae were comparatively evaluated. Larvae were selected by distinct morphological features: time of hatching, second larval moult, pupation. Both virgin and non-virgin females were taken in the experiment. The degree of synchronism was estimated by the interval during which pupation took place in all larvae of the sample. When selecting larvae at the time of second moult, the pupation of all selected larvae was completed within 8 hrs. All other methods of obtaining synchronously developing larvae give a spread of pupation from 12 to 25 hrs. A simple modification of the method of larval selection during the second moult is proposed which allows to obtain a large amount of synchronously developing larvae of the 3rd instar.

Animals↗
PubMed1974

[A comparison of bacterial RNA-polymerase RNA synthesis on polytene Drosophila chromosomes with transcription in living cells].

The incorporation of 3H-uridine in different regions of polytene chromosomes in live cells of the Drosophila melanogaster salivary glands was compared with the incorporation of 3H-UTP in the same regions under the incubation of cytological preparations of these chromosomes with the E. coli RNA polymerase. The label distribution by regions was compared with the DNA content in them. Individual regions of chromosomes differ by 3H-uridine incorporation in live cells to a much greater extent than by 3H-UTP incorporation in vitro under the incubation with a non-homologous enzyme. RNA synthesis in an exogenous enzyme depends on the DNA content in different chromosome regions to a much greater extent than RNA synthesis in vivo. The correlation of label distribution after 3H-uridine incorporation in live cells and after RNA synthesis in vitro on the preparations by the bacterial RNA polymerase is, correspondingly, very low. This enzyme forms, however, RNA's on puffs 2-3 times more actively than on the same regions in non-puffing state but this difference is dozens of times greater in live cells. RNA synthesis in vitro is, thus, non-specific and does not correspond practically to the intensity of RNA synthesis on the same chromosome regions in live cells. At the same time, as in live cells, the E. coli enzyme synthesizes twice more RNA on the single X-chromosome of males (1X2A) than on each of X-chromosomes of diploid (2X2A) and triploid (3X3A) females or superfemales (3X2A), whereas in intersexes (2X3A) X-chromosomes display intermediate template activity. Thus, RNA synthesis by a heterologous enzyme in vitro does not differ by this index from the synthesis in live cells. It is suggested that differences in the template activity of X-chromosomes in vitro depending on the sex index (X : A) are due to different degree of DNP condensation in these chromosomes. In spite of differences in the degree of condensation, the male X-chromosome binds on the fixed preparation approximately the same amount of thymus histone F1 carrying fluorochrome as each of two female X-chromosomes. Hence, there is no sharp difference between the male and female X-chromosomes by the number and length of DNA regions accessible for interaction with exogenous proteins. On the basis of the data obtained, a hypothesis about two levels and, respectively, two mechanisms of control gene activity in animal chromosomes is considered. The first mechanism is, supposedly, based on decondensation of DNP appears to result in that the same proteins-regulators in the same amount activate corresponding genes in X-chromosome in males twice more strongly than in females.

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