Effect of beta-adrenoreceptor blockade on cell division processes in the corneal and tongue epithelium of white rats with chronic oxygen starvation

A study was made of the changes in the mitotic activity, DNA synthesis, and the number of pathological mitoses after administration of the beta-adrenoblocker propranolol in the corneal and tongue epithelium of white rats kept in pressure chamber for 7 days (4 h daily) at a "height" of 9000 meters. The mitotic and the label indices (inclusion of 3H-thymidine by the epithelium nuclei) were analysed for mitotic activity and DNA synthesis, respectively. The experiments showed that the mitotic activity, DNA synthesis, the number of pathological mitoses were stabilized due to the propranolol administration.     

Effect of bifolar and chlofiden on DNA synthesis of sarcoma 45 cells and on mitotic activity of rat small intestine epithelium

Results of the study on the influence of new antitumor preparations chlofiden and bifolar on sarcoma 45 DNA synthesis and on mitotic activity are given. It was shown that bifolar and chlofiden led to inhibition of label incorporation into DNA (3H-thymidine). Inhibition of mitotic activity after injection of both preparations in toxic doses (DL50) was revealed. During injection of the bifolar functional character of changes was established that is mitotic activity of the preparation during injection was restored.     

Quantification of DNA synthesis in multicellular organisms by a combined DAPI and BrdU technique

The development of a novel method to detect and quantify mitotic activity in multicellular organisms is reported. The method is based on the combinatorial use of 4',6-diamidino-2-phenylindole (DAPI) as a dye for the specific staining of DNA and the thymidine analog 5-bromo-2'-deoxyuridine (BrdU) as a marker for DNA synthesis. It is shown that on nitrocellulose filters, the amount of DNA can be determined by DAPI as a prerequisite for the subsequent quantification of mitotic activity by BrdU. As a model system to prove the applicability of this technique, the blood fluke Schistosoma mansoni has been used. It is demonstrated that the DNA synthesis rate is higher in adult female schistosomes than in adult males. Furthermore, dimethyl sulfoxide, a widely used solvent for many mitogens and inhibitors of mitosis, has no influence on mitotic activity in adult schistosomes.     

Effect of different doses of a chalone-containing alcohol precipitate of Ehrlich ascitic tumor on the mitotic activity and DNA synthesis in this tumor

Chalone-containing preparation has been obtained from ascitic Ehrlich's tumour by alcohol precipitation and the effect of various preparation doses on mitotic activity and DNA synthesis in the tumour has been studied. The preparation was shown to suppress tumour cell proliferation, acting on mitosis initiation and mitotic S phase as well as on DNA synthesis in the cells at S phase of mitotic cycle. The effect of the preparation on DNA synthesis in phase S cells was more pronounced than on cells entering DNA synthesis phase. The changes in all the parameters examined were dose-dependent. The preparation effect was tissue-specific.     

Effects of acyclic analogs of atrial natriuretic factor on proliferative processes of the epithelial tissue in white rats]

The effect of atrial natriuretic factor (ANF) synthetic linear truncated analogues AP-H-6-OH and AP-FOR-6-OH on corneal, skin, duodenum and colon epithelium proliferation has been studied on male rats. The epithelium mitotic activity and DNA synthesis were evaluated 4 and 24 h after intraperitoneal injection of 10 or 100 micrograms/kg peptides. In a dose of 10 micrograms/kg both ANF synthetic analogues inhibited proliferation processes in corneal epithelium, but activated the DNA synthesis in duodenum and colon epithelium. AP-FOR-6-OH (10 micrograms/kg) decreased the mitotic activity of skin epithelium and increased the silver grain density over the cell nuclei at the same time. 100 micrograms/kg ANF analogues stimulated cell mitogenesis in all organs studied. According to the data obtained ANF linear truncated analogues influence on epithelium proliferation is similar to effector of previously studied cyclic atriopeptin AP II.     

Myelokaryocyte mitotic activity during microwave irradiation (2375 MHz)

Changes in mitotic activity of myelocaryocytes exposed to super-high frequency field (2375 MHz) of 10, 50 and 500 microW/cm2 for a month show the influence of this factor on the DNA synthesis, premitotic processes and cell reproduction biorhythms depending on the radiation intensity.     

Effect of diaminobutene and diaminopropane on diet-stimulated polyamine synthesis and cell proliferation in rat liver.

The effect of two putrescine analogs were studied on hepatic polyamine synthesis and cell proliferation, both of which were stimulated by food intake. Trans-1, 4-diamino-2-butene (diaminobutene), which is a potent competitive inhibitor of ornithine decarboxylase [EC 4.1.1.17] (ODC), repressed the induction of ODC and effectively inhibited the accumulation of putrescine in rat liver which was induced by the feeding of dietary protein. Unexpectedly, diaminobutene did not suppress DNA synthesis and mitotic activity in rat liver, suggesting that it can mimic the role of putrescine in cell proliferation. 1,3-Diaminopropane effectively repressed the induction of ODC caused by food intake and also suppressed DNA synthesis and mitotic activity without affecting the accumulation of RNA or protein. The suppression of mitotic activity by 1,3-diaminopropane was reversed by a single injection of putrescine, spermidine, spermine, or diaminobutene. It was concluded that rapid accumulation of polyamines, especially putrescine, was a prerequisite for the later enhancement of DNA synthesis and cell proliferation in rat liver caused by food intake.     

Effects of atrial natriuretic peptide AP II on proliferation processes in the epithelial tissue of white rats]

The effect of atrial natriuretic peptides synthetic analog AP II on corneal, skin, tongue and duodenum epithelium proliferation have been studied on male rats. The epithelium mitotic activity and DNA synthesis were evaluated in 4 and 24 h after intraperitoneal injection of 10 or 100 micrograms/kg AP II. 10 micrograms/kg AP II was found to have different influence on organs epithelium: it decreased the mitotic activity of skin and corneal epithelium, but activated the proliferation processes in tongue and duodenum epithelium. 100 micrograms/kg AP II stimulated cell mitogenesis in all organs studied. According to data obtained atrial natriuretic peptides are able to participate in cell division regulation in vivo.     

The influence of environmental factors upon induced compensatory hyperplasia in the rat liver

This study has examined the influence of a controlled environment upon the nature of the compensatory hyperplasia which occurs in the rat liver after two-thirds partial hepatectomy. Rats were adapted to a reversed lighting schedule (lights off 09.30 to 21.30 h), and food was only available during the first 8 h of the dark period. Partial hepatectomies were performed at either 10.00, 16.00 or 20.00 h, and the response over the first 36 h monitored by 2-hourly measurements of the flash tritiated thymidine labelling index and the mitotic index. DNA synthesis was initiated within 16-18 h of operation, irrespective of when hepatectomies were performed, though the ensuing patterns of DNA synthesis were rather different. On the other hand, the initiation of mitotic activity was very much dependent upon the time of day that resections were carried out. Hepatectomy at 20.00 h resulted in a rise in mitotic activity some 22-24 h later, but hepatectomy at 10.00 h caused a further 6 h delay in this rise. The onset of mitotic activity appeared to be related to recent feeding, and it is proposed that in the absence of recent nutrition, DNA-synthesizing hepatocytes may have an extended tS and/or tG2.     

Comparative study of the influence of renal endogenic factors on the proliferation activity of epithelial cells

The proliferation activity of monolayer culture of Madin Darby Canine Kidney (MDSK) cells is suppressed by a thermostable protein factor of renal tissue of white rats and of humans. Under the influence of renal factors (RF), a decrease in cell number, and suppression of DNA synthesis and mitotic activity in MDCK cells occur. The inhibition of proliferative activity of cultured cells under the influence of RF was substantiated also by MTT assay. It was established that the inhibitory influence of RF is stipulated by suppression of RNA synthesis. It follows that RF may inhibit division of MDCK cells via suppression of gene expression in G1-phase. Similar factors were obtained from renal cells of different systematic groups of organisms (snail, frog, fish, pigeon, guinea pig, swine).     

Regenerative ability of hepatocytes is inhibited in early stages of liver fibrosis.

Female Wistar rats were given three doses of carbon tetrachloride, 10.4 mmol/kg of body weight. The doses were administered within 16 days and another 16 days were allowed to pass before partial (37%) hepatectomy was done. The liver showed very mild fibrosis at that time. DNA synthesis (measured by 3H-thymidine incorporation) was decreased by 53% and mitotic activity of hepatocytes was decreased by 56% when compared to olive oil-pretreated partially hepatectomized controls. The results show that the mitotic potential of hepatocytes in early stages of liver fibrosis is impaired which may influence the course of the disease.     

12-O-tetradecanoylphorbol-13-acetate induces an immediate, but transient increase in mitotic activity uncoupled from DNA synthesis in the monolayer cultures of rat keratinocyte

A single wave of mitotic activity was observed in a monolayer culture of rat keratinocytes immediately after exposure to 12-O-tetradecanoylphorbol-13-acetate. A peak for cells in prophase, observed at 10 min after the exposure, was followed by a peak for metaphase at 20 min, for anaphase at 25 min and telophase at 30 min after the exposure. Thereafter, the mitotic activity began to subside. This transient stimulation of mitotic activity resulted in an increase of population density in the monolayer culture. There was neither a stimulation of DNA synthesis during this period nor a change of the DNA content after the mitotic activity was completed. This single burst of synchronous mitotic activity which did not require a substantial stimulation of DNA synthesis suggests that the effect was on the initiation process of mitosis among a subpopulation of cells, presumably cells delayed in the G2 phase of the cell cycle.     

The induction of transient increases in mitotic rate in murine tissues following prolonged intravenous infusions of hydroxyurea.

Intravenous infusions of hydroxyurea were established in mice and maintained for periods up to 48 hr. The influence of different rates of hydroxyurea infusion on the number of viable cells gathered in S phase was studied in eight different mouse tissues. An infusion rate which was sufficiently slow not to block thymidine incorporation completely, resulted in gathering of cells in S phase while offering some protection against hydroxyurea-induced cell death. The duration of the period of DNA synthesis following release from hydroxyurea inhibition appeared to be shortened in some tissues. After the release of hydroxyurea blockades maintained for 12-24 hr, each of the tissues showed sharp increases in mitotic activity and peak mitotic index values were as much as twenty times greater than values found in tissues of control animals. An important finding was that the time of maximal mitotic activity for different tissues after release of blockade could differ by many hours.     

Degradation of Cdc25A phosphatase in HeLa cells under normal and stress conditions

Cdc25A phosphatase regulates cell cycle progression by removing the inhibitory phosphates from cyclin-dependent kinases. Activity of Cdc25A depends on its phosphorylation status. During normal cell cycle progression and after DNA damage phosphorylation by Chk1 (or Chk2) triggers Cdc25A degradation via ubiquitin-proteasome pathway. In this study we investigate the role of various phosphorylation sites (Ser123, Ser75, Ser17 and Ser115) in the regulation of Cdc25A stability. We have shown that only S75A mutation abrogates Cdc25A degradation both in normal and stress conditions. We also studied the influence of stable form of Cdc25A on checkpoint progression after DNA damage. We have found out that delay in DNA synthesis after UV and IR does not depend on Cdc25A activity. However, the presence of stable Cdc25A increases the number of mitotic cells after these stresses.     

Cytological study of inhibitory effects of IAA on the root growth in the Pinus silvestris

It has been found that IAA at the concentrations 0.1--10.0 ppm retards the pine root growth and decreases mitotic activity. All the applied concentrations of this hormone cause a decrease of the 3H-thymidine incorporation index and inhibit endomitotic polyploidization in suprameristematic segments. The mean time of the cell cycle prolongs and the heterogeneity of cellular populations increases in parallel with the increase of IAA concentration. The template activity of DNA decreases under the influence of the applied concentrations of IAA; this effect is being particularly strong in the meristematic root segment. IAA exerts also an inhibitory influence on protein synthesis, especially reducing the synthesis of histones.     

Dependence of timing of mitotic events on the rate of protein synthesis and DNA replication in sea urchin early cleavages

Abstract. To understand what processes affect the cell-cycle timing of mitotic events in early cleavage cycles of sea urchin embryos, a study was made on the effects of (a) reducing protein synthesis with emetine and (b) DNA replication with aphidi-colin, on the timing of nuclear envelope breakdown, anaphase onset and cytokinesis. When protein synthesis was slightly inhibited by administration of emetine, the delay in the mitotic events increased, with an increase in the delay in accumulation of proteins up to the levels to which cells must synthesize the proteins to execute the cleavage. This indicated that protein synthesis affects the timing of mitotic events. The delay in cleavage cycles caused by a slight inhibition of DNA replication with aphidicolin was in proportion to the concentration of aphidicolin administered, suggesting that DNA replication also affects the timing of mitotic events. Furthermore, it was confirmed that accumulation of the proteins to the levels required for execution of the first cleavage precedes completion of DNA replication as a requirement for execution of the first cleavage. These results imply the existence of process(es) affected by protein synthesis that are included in a feedback control system which prevents the initiation of mitosis until after the completion of DNA replication; it is the characteristic of a cell-cycle control system that has been predicted theoretically.     

THE INDUCTION OF TRANSIENT INCREASES IN MITOTIC RATE IN MURINE TISSUES FOLLOWING PROLONGED INTRAVENOUS INFUSIONS OF HYDROXYUREA

Intravenous infusions of hydroxyurea were established in mice and maintained for periods up to 48 hr. The influence of different rates of hydroxyurea infusion on the number of viable cells gathered in S phase was studied in eight different mouse tissues. An infusion rate which was sufficiently slow not to block thymidine incorporation completely, resulted in gathering of cells in S phase while offering some protection against hydroxyurea-induced cell death. The duration of the period of DNA synthesis following release from hydroxyurea inhibition appeared to be shortened in some tissues. After the release of hydroxyurea blockades maintained for 12–24 hr, each of the tissues showed sharp increases in mitotic activity and peak mitotic index values were as much as twenty times greater than values found in tissues of control animals. An important finding was that the time of maximal mitotic activity for different tissues after release of blockade could differ by many hours.     

Effect of the parenteral administration of amino acid solutions in different phases after partial hepatectomy on the initiation and development of liver regeneration in rats

Amino acid solutions enriched with branched-chain amino acids or pure branched-chain amino acid solutions were administered parenterally to female laboratory rats (pre-operative weight 230 +/- 30 g) which had been subjected to 65-70% partial hepatectomy (PH), and specific liver DNA activity, the hepatocyte mitotic index and other indicators of the initiation of liver regeneration were studied. Both solutions were infused in an hourly dose of 3.3 ml/kg body weight, during the following postoperative intervals: 1-6, 7-12, 1-12, 1-18 and 1-24 hours. The control rats continued to be fed on the standard laboratory diet after the operation. The results show that the infusion of an amino acid solution enriched with branched-chain amino acids had an inhibitory effect on the onset of DNA synthesis in the liver 18 hours after partial hepatectomy whatever the administration interval. The situation in the case of pure branched-chain amino acid solutions was the same. Twenty-four hours after PH, neither type of solution, irrespective of the infusion interval, was followed by an increase in DNA synthesis compared with the controls fed on the standard laboratory diet. Neither the hepatocyte mitotic index, nor the total liver DNA concentration, showed any changes indicative of stimulation of the initiation of liver regeneration. An infusion stress effect, evaluated from the decrease in the weight of the thymus, was found chiefly in the case of infusions lasting 12 h or longer.     

Effect of opioid receptor ligands on cell division processes in the corneal epithelium of the white rat

The effects of the application of synthetic leu-enkephalin analogue--dalargin and naloxone on DNA synthesis and cell division in corneal epithelium were studied with the drugs injected once or five times. The influence of one and five intraperitoneal injections of the drugs in question at a dose of 10 micrograms/kg body weight was also investigated. In both cases the opioid receptor ligands examined activated DNA synthesis with the following adequate increase in mitotic index.     

Studies on the nature of serum stimulation of proliferation in cell culture

Summary Secondary platings of chick embryo fibroblast cells were found to be capable of subsisting in the absence of serum supplements for periods exceeding 1 week. No significant mitotic activity was detected in these serumdeprived cultures. When serum was added, a coordinated mitotic burst occurred between 12 and 14 hr after the serum addition had been made. A complete mitotic burst could also be obtained with an abbreviated serum exposure of only 6 hr. Patterns of DNA and RNA synthesis were investigated following serum addition to serum-deprived cultures or serum removal from normal cultures. The results obtained are commensurate with mitotic-specific serum stimulations which fall within the G1 growth phase. This investigation was supported by USPHS research grants CA 04774 and CA 05619 from the National Cancer Institute.