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11.
Summary DNA containing structures (cellular, chloroplast and mitochondrial nuclei) were stained with the fluorochrome DAPI. Fluorescence intensity, as a measure of DNA content, was estimated during the mitotic cycle in synchronized populations of the chlorococcal alga,Scenedesmus quadricauda. In cells yielding eight daughter cells, three consecutive steps in chloroplast DNA increase occurred over one mitotic cycle. The first step was performed shortly after releasing the daughter cells, the second and third steps occurred consecutively during the first half of the mitotic cycle. Commitment to chloroplast DNA replication was chronologically separated from commitment to division of chloroplast nuclei, revealing that these two chloroplast reproductive steps were under different control mechanisms. The replication of chloroplast DNA occurred at a different time to that of cell-nuclear DNA. The coordination of chloroplast reproductive processes and those in the nucleocytoplasmic compartment were governed by the mutual trophic and metabolic dependency of these compartments rather than by any direct or feedback control controlled by either of them.Abbreviations DAPI
46-diamidino-2-phenylindole
- ptDNA DNA
in chloroplast nuclei
- nucDNA DNA
in cell nuclei 相似文献
12.
Epidermal growth factor (EGF) or saline was administered intraperitonally to hypophysectomized adult male CD2F1 mice or intact controls at 0700 hr. Subgroups of mice were killed at 4, 8, or 12 hr after injection. EGF was shown to stimulate [3H]TdR incorporation into DNA into several organs as previously reported. The response to EGF was found to be enhanced in both hypophysectomized and fasted mice. Differences in [3H]TdR incorporation into DNA, corneal epithelium mitotic index, RNA in pancreas and kidney of hypophysectomized and intact mice are reported. EGF was shown to result in stomach enlargement due to increased luminal contents in both hypophysectomized and intact mice. 相似文献
13.
Soyfer V. N. Akifjev A. P. 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1977,50(2):63-72
Summary A new hypothesis on the appearance of exchange chromosomal aberrations has been suggested. According to this hypothesis, temporal duplex polynucleotide structure should arise during G1 and G2 phases during the correction of DNA. The size of the duplex, as a rule, should be restricted to the size of complementary nucleotide sequences in the regions of repetitions. Any polynucleotide break in a duplex zone would result in chromosome breakage and if complementary broken ends interact with each other, then exchange chromosome aberrations may be formed. This hypothesis would explain such previously obscure phenomena as extremely high frequencies of exchanges after mutagen treatment, the nature of mitotic crossing-over, negative interference, change of aberration types before replication, the low frequency of damaged structural genes during aberration formation, etc. 相似文献
14.
The objective was to determine the effect of ACTH 1-17, an adrenocorticotropin analogue, on the mitotic index in the corneal epithelium of mice standardized in 12 hr of light alternating with 12 hr darkness. A question asked was whether the time of administration along the 24-hr time scale influenced any response found. The findings showed that ACTH 1-17 could, depending upon when it was administered, bring about a statistically significant decrease, an increase or even no such change in the mitotic index. The greatest responses found were increases, especially when ACTH 1-17 was administered during the dark span. Also the time after injection when the responses occurred varied. The greatest response recorded was at 12 hr after injection when ACTH 1-17 was given at 2 hr into the dark with a 641% and a 718% increase with a low (0.02 IU/kg) and a higher (20 IU/kg) dose, respectively. A 3-way analysis of variance supported the conclusion that the kind-of-treatment, time-of-treatment and treatment-to-kill interval (sampling time) are important factors when determining any response to ACTH 1-17 on the mitotic index. 相似文献
15.
Summary Five new elements of the mitotic control in the fission yeast Schizosaccharomyces pombe were isolated from gene libraries as multicopy suppressors of the conditional lethal phenotype of win1-1 weel
ts
cdc25ts triple mutant strains. These genes were designated wisl
+
–wis5+for win suppressing, and do not correspond to winl
+
or any of the previously characterised mitotic control genes. None of the wis genes is capable of suppressing the cdc phenotype of cdc25
ts
strains, suggesting that their effect is not simply to reverse the effect of loss of cdc25 function. wisl
+
has been previously reported to encode a putative serine/threonine protein kinase that acts as a dosage-dependent inducer of mitosis. wis4
+ appears to be a specific suppressor of the winl-1 mutation. wis2
+ and wis3
+ are capable of suppressing a wide range of cdc phenotypes arising from the combination of various mutations with wee1
ts and cdc25
ts, suggesting that the wis2
+ and wis3
+ products may interact with elements central to the mitotic control. 相似文献
16.
Summary We describe the mitotic cleavage patterns during blastoderm stage of the house flyMusca domestica L. Nuclear divisions up to mitotic stage 11 are apparently synchronous. Beginning with stage 12, nuclear divisions in the posterior third of the embryo lag behind, resulting first in a parasynchronous and finally in an asynchronous cleavage pattern. Thus a stage exists where all nuclei in the anterior region have completed 14 nuclear division cycles, while those in the posterior region have completed only 13 cycles. The border region between these nuclei is well defined and lies at 35% EL (egg length), the expression border of a gap gene. This border region is about 4–5 nuclei wide and shows a specialized mitotic behaviour. 相似文献
17.
Summary Injection of posterior pituitary powder induces an intense mitotic stimulation in the zona glomerulosa of the adrenal gland of young rats. This effect is much more pronounced in females than in males. It is maximal at two days treatment. Longer periods result in a hypertrophied zona glomerulosa and lower mitotic activity. A search for the hormone responsible for the stimulation shows that vasopressin, and to a lesser extent oxytocin, are mitogenic. ACTH, -MSH, -MSH and the pineal hormones have no effect. Renin (but not angiotensin) induces a significant stimulation. It is concluded that vasopressin exerts a potent influence on the glomerulosa. This is in contrast with the prevalent view that the glomerulosa is little affected by the hypophysis. 相似文献
18.
19.
Dr. Koji Kobayashi 《Cell and tissue research》1976,175(3):319-324
Summary Mitotic activity adjacent to a wound inflicted at different sites in the mouse skin was measured 24 h after injury. A regional difference in the epidermal mitotic activity due to injury was noted. Mitotic activity was high in the anterior parts of the body including the head, lower in the middle to posterior regions of the body and lowest in the posterior-most parts of the body. Regional differences in epidermal mitotic activity due to injury were demonstrated in both female and male mice. The existence of a cranio-caudal gradient in epidermal response to injury is suggested. 相似文献
20.
Halil Erhan Eroğlu Ahmet Aksoy Ergin Hamzaoğlu Ümit Budak Sevil Albayrak 《Cytotechnology》2009,59(1):65-72
Helichrysum Mill. (Asteraceae) species have been used in folk medicine for thousands of years in the world. The in vitro cytogenetic
effects in human lymphocytes of nine Helichrysum taxa used in Turkey folk medicine were investigated. Blood samples were obtained from healthy donors, non-smoking volunteers,
which were incubated and exposed to increasing concentrations of methanol extracts of Helichrysum taxa (0.01, 0.05, 0.1, 0.5 and 1 mg/mL). The inhibitory effects of H. stoechas (L.) Moench subsp. barrelieri (Ten.) Nyman, H. armenium DC. subsp. armenium, H. armenium DC. subsp. araxinum (Kirp.) Takht., H. plicatum DC. subsp. plicatum, H. compactum Boiss. and H. artvinense P.H.Davis & Kupicha on the mitotic index and replication index indicate that these taxa can have genotoxic and mutagenic
effects. They should therefore not be used freely in alternative medicine although their antiproliferative activity may suggest
anticarcinogenic properties. Increase effects of H. stoechas subsp. barrelieri, H. armenium subsp. armenium, H. armenium subsp. araxinum, H. chasmolycicum P.H.Davis, H. plicatum subsp. plicatum, H. compactum and H. artvinense on the micronucleus rates showed that these taxa can have genotoxic and carcinogenic effects. 相似文献