Incidence Of Mitoses Research Articles

A MECHANICAL AND NUMERICAL APPROACH APPLIED TO EPITHELIUM TOPOLOGY AND DEVELOPMENT

A key decisive in the understanding of morphogenesis processes concerns the description of the development of regular topolgy epithelial tissue as usually observed. The cell pattern is characterized by the average number of the cell neighbours (frequency distribution). Nevertheless, the mechanisms of packing geometry formation, such as the follicular tissue surrounding the Ciona Intestinalis egg, are poorly understood. In order to study further this epithelium development, we made a numerical model based on the mechanics of divided media. Here we propose two scenarii: one governed by cell accretion and the other managed by cell division. With the first one, we explore the influence of the growth rate and with the second one the incidence of mitosis.

Salicylic acid triggers genotoxic adaptation to methyl mercuric chloride and ethyl methane sulfonate, but not to maleic hydrazide in root meristem cells of Allium cepa L.

Salicylic acid (SA), 0.01 mM, a signalling phytohormone, was tested for induction of adaptive response against genotoxicity of methyl mercuric chloride (MMCl), 0.013 mM; ethylmethane sulfonate (EMS), 2.5 mM, or maleic hydrazide (MH), 5 mM, in root meristem cells of Allium cepa. Induction of adaptive response to EMS by hydrogen peroxide (H 2O 2), 1 mM, and yet another secondary signal molecule was tested for comparison. Assessed by the incidence of mitoses with spindle and/or chromosome aberration and micronucleus, the findings provided evidence that SA-conditioning triggered adaptive response against the genotoxic-challenges of MMCl and EMS, but failed to do so against MH. H 2O 2, which is known to induce adaptive response to MMCl and MH, failed to induce the same against EMS in the present study. The findings pointed to the possible role of signal transduction in the SA-induced adaptive response to genotoxic stress that perhaps ruled out an involvement of H 2O 2.

Different roles of p53 between Epstein-Barr virus-positive and -negative gastric carcinomas of matched histology.

To clarify the role of p53 in the development of Epstein-Barr virus (EBV)-associated gastric carcinoma, we examined DNA-ploidy pattern, the immunoreactivity of p53, p21(WAF1) and Ki-67 and the incidence of mitosis and apoptosis in EBV-positive and -negative gastric carcinomas of similar histology: a lace pattern and/or gastric carcinoma with lymphoid stroma. There was no significant difference in DNA-ploidy pattern, Ki-67 index or frequencies of mitosis and apoptosis between the two groups. In deeply invasive tumours (involving the muscularis propria or deeper), p53-positive ones were rare in the EBV-encoded small RNA (EBER)-positive group and very common in the EBER-negative group, while in superficial tumours, around one-half of them were p53-positive in both groups. In p53-positive superficial tumours, p21(WAF1)-positive ones accounted for 80% in the EBER-positive group and were scarce in the EBER-negative group. It is thus possible that p53 immunoreactivity reflects the overexpression of wild-type p53 and the stabilization of mutant p53 in the EBER-positive and -negative groups, respectively. The role of p53 in tumour development seems to be smaller in EBER-positive than in -negative gastric carcinomas.

Experimental study of the effects on apoptosis of docetaxel alone and in combination with irradiation.

The effects of docetaxel alone and in combination with irradiation were experimentally investigated in terms of induction of apoptosis. A human ependymoblastoma was transplanted into nude mice, and they were intravenously injected with docetaxel, followed or preceded by irradiation with a single dose of 2 Gy. Apoptosis was less common in the docetaxel-alone group than in the irradiation-alone group. When administration of docetaxel was followed by irradiation, apoptosis was equal to or less common than in the irradiation-alone group. Apoptosis was most common in the irradiation-followed-by-docetaxel group. The incidence of mitosis was lower in the irradiation-alone group and the irradiation-followed-by-docetaxel group than in the docetaxel-alone group and the docetaxel-followed-by-irradiation group. The combined effect of irradiation and docetaxel appears to be useful in inducing apoptosis, but the sequence of irradiation and docetaxel is important.

Estrogen-depleted condition induces apoptosis of rat mammary cancer cells after entering the S-phase of the cell cycle.

To elucidate the relationship of estrogen-depleted condition to apoptosis and tumor regression, 7,12-dimethylbenz[a]anthracene-induced mammary cancers of Sprague-Dawley rats were ovariectomized or treated with the anti-estrogenic agent epitiostanol after which proliferative activity and the incidence of apoptosis were investigated using the nick end labeling method, agarose gel electrophoresis of DNA, electron microscopy, the BrdU-labeling method and mitotic count. Tumor regression was found after 7-day treatment, and apoptosis induced by the agent on the 3rd day was clearly shown in both agarose gel electrophoresis of DNA and electron microscopy, which are two major methods used to judge apoptosis. The incidence of apoptosis revealed by the nick end labeling method reached its maximum, about threefold the control level, on the 3rd day of epitiostanol treatment compared with control tumors (P < 0.01). The incidence of the cells incorporating BrdU reached its maximum of 9.7% on the 2nd day of the treatment, while the incidence in tumors without treatment was 7.5% (P < 0.05). Subsequently, the incidence of apoptosis was reduced after 7-day treatment, and the incidence of BrdU-positive cells was significantly reduced to about 3% after 5-day treatment. The incidence of mitosis did not change until the 3rd day of the treatment and was reduced after 5-day treatment. Similarly, chronological changes of the incidences of BrdU-labeled cells, apoptotic cells and mitosis were observed in the tumors after ovariectomy. BrdU-labeled apoptotic bodies were detected in the tumors on the 3rd day in epitiostanol-treated rats that received a 6-hr bolus of BrdU before sacrifice.(ABSTRACT TRUNCATED AT 250 WORDS)

Neoplastic transformation in the planarian: II. Ultrastructure of malignant reticuloma.

Cadmium and phorbol ester induced tumorigenesis in the planarian, Dugesia dorotocephala, develops as a cocarcinogenic process involving initiation and promotion in the progression of neoplastic disease. Treatment of intact planarians with sublethal concentrations of cadmium sulfate and 12-O-tetradecanoylphorbol-13-acetate (TPA) induced a type of infiltrating tumor that proved to be potentially lethal. Surgical transplantation of such tumorous tissues into otherwise healthy planarians resulted in the same histopathological progression to lethality, which confirmed the metastatic nature of the neoplasia. Electron microscopic studies revealed that both the chemically-induced and the transplantation-based tumors involved, exclusively, the proliferation and differentiation of abnormal reticular cells, referred to as reticuloma cells. Reticular cells normally are ameboid, phagocytic, and are thought to provide the planarian with a phylogenetic predecessor of an immune surveillance system. A considerable incidence of mitosis was observed within the tumor areas; and the sequence of differentiation, from transformed stem cells to mature but nonfunctional reticuloma cells, was elucidated. This profile of differentiation supports the concept of cellular derivation via stem cell dynamics as opposed to dedifferentiation. A variety of ultrastructural abnormalities were characterized: several of which tend to substantiate the anaplastic quality of the reticuloma, while others are more specifically diagnostic for malignancy. These findings further extend the potential usefulness of the planarian malignant reticuloma as a model system for the study of neoplastic stem cell diseases.

Effect of dibutyryl cyclic adenosine 3'5'-monophosphate on mitotic activity in the thyroid of hypophysectomized rats.

Effect of dibutyryl cyclic adenosine 3'5'-monophosphate (dbcAMP) on mitotic activity in the thyroid of hypophysectomized rats has been examined. It has been demonstrated that dbcAMP stimulates the incidence of mitoses in the thyroid follicular cells. It is therefore suggested that cAMP may be a mediator of the proliferogenic effect of TSH on the thyroid in vivo. Cyclic AMP could also release some unidentified growth-promoting factors for the thyroid. A direct stimulating effect of dbcAMP on the proliferation of the thyroid follicular cells is assumed to be possible as well.

Improvement of preparative conditions for cytogenetic studies by short-term liquid culture of haemopoietic cells

In patients with haemopoietic failure, the low incidence of cells in mitosis often prevents successful chromosome preparations. By performing liquid cultures of myeloid cells a high incidence of mitoses could be obtained even in those cases failing to provide mitoses when the direct preparation technique was used. The cytogenetic studies demonstrated that the mitoses achieved by culture techniques were aneuploid and, thus, there is evidence that they are of leukaemic origin. The combination of short-term liquid culture and chromosome analysis appears to be a diagnostic approach in selected cases of hemopoietic insufficiency.

Endocrine control of gland proliferation in the mouse uterus.

Glandular epithelial cells of the mouse uterus divide in response to estrogens, but the pattern of response is different from that in the luminal epithelium. During continuous treatment the luminal epithelium shows maximum mitosis by 24 h whereas the glands show little response until 72 h and require three daily injections for maximum response. The incidence of mitosis then drops for the duration of treatment but there is a second wave of mitosis in the glands 72 h after the cessation of estrogen administration. NI) such secondary wave occurs in the luminal epithelium. Progesterone inhibits both waves of glandular mitosis and the luminal mitosis. The uterine glands form a variable part of the endometrium. In some species; for example, the cat, rabbit, and primates, they are very conspicuous, especially during early pregnancy, while in others, including the mouse, they are less prominent. Developmentally they arise by downgrowths of the luminal epithelium, and in situations

The response of the sebaceous glands of hypophysectomized-castrated male rats to adrenocorticotrophic hormone and to testosterone.

SUMMARY Administration of 1 i.u./24h of adrenocorticotrophic hormone (Cortrophin ZN, ACTH) to hypophysectomized—castrated rats significantly increased sebum production to the level of that in castrated rats with intact pituitaries. The incidence of mitoses in the sebaceous glands was also significantly increased. Neither the preputial glands nor the seminal vesicles showed any response. No significant increase in sebum production in hypophysectomized—castrated rats could be detected 24 days after giving implants releasing 0·2 or 0·6 mg testosterone/24 h, although sebaceous mitoses were significantly increased in both instances. Concomitant administration of both ACTH and testosterone raised sebum production to the same extent as ACTH alone, and raised the incidence of sebaceous mitoses to a level equal to that produced by ACTH plus testosterone. It is concluded that the sebaceous glands respond—either directly or indirectly as the result of stimulation of the adrenal cortex—to ACTH and that this response is less dependent on the presence of the pituitary than is the action of testosterone. ACTH does not itself facilitate the response of the sebaceous glands to testosterone.

Effect of enzyme injections on mitosis in regenerating liver.

THE addition of deoxyribonuclease to tissue-culture media affected mitosis in tissue cultures1,2. In mice bearing Ehrlich ascites tumours, injections of the enzyme decreased the incidence of mitoses in the tumour cells and increased the survival-time of the animals3. Similarly, injections of xanthine oxidase and ribonuclease affected the rate of tumour growth and the survival time4–6.

Endocrine factors affecting cell replacement and cell loss in the epidermis and sebaceous glands of the female albino rat.

SUMMARY 1. Hypophysectomy and adrenalectomy in female albino rats aged 9 months were followed by an enlargement of the sebaceous glands and a thickening of the stratum germinativum plus stratum granulosum in the skin of the back. In similar rats aged 5 months hypophysectomy produced a very significant increase in epidermal thickness, but the increase in the mean volume of the sebaceous glands was not statistically significant. 2. In rats aged 5 months hypophysectomy appeared to increase the incidence of mitoses in both tissues, as measured 5 hr after the injection of colchicine. In rats aged 9 months these increases were less marked in the sebaceous glands and insignificant in the stratum germinativum. 3. Implantation of oestradiol/cholesterol for 3–4 weeks caused a marked reduction in size of the sebaceous glands in intact, in hypophysectomized, and in adrenalectomized rats. Epidermal thickness remained unaffected in intact adult rats, but was reduced in hypophysectomized or adrenalectomized rats. 4. The incidence of mitoses in the sebaceous glands and stratum germinativum was not affected 3–4 weeks after the implantation of oestradiol in intact, in hypophysectomized, and in adrenalectomized rats. 5. Spaying had no significant effect on sebaceous gland size, epidermal thickness, or incidence of mitoses. 6. The following main conclusions are suggested by the results: (a) The normal breakdown of sebaceous cells, epidermal keratinization and subsequent cell loss in the skin of the back of the rat are delayed by interference with the pituitary-adrenal system. (b) Oestradiol accelerates the breakdown processes even in the absence of the pituitary and adrenal glands. (c) In the adult female rat mitosis in the epidermis and sebaceous glands neither requires nor is greatly affected by the presence of oestradiol. (d) In the absence of the pituitary the incidence of mitoses in the epidermis and sebaceous glands may be increased; it is possible therefore that a pituitary or adrenal hormone may inhibit mitosis.

Changes in the sebaceous glands and epidermis during the oestrous cycle of the albino rat.

SUMMARY 1. In the dorsal skin of female albino rats, the sebaceous glands reached their maximum size, and the stratum germinativum its greatest thickness during prooestrus. At oestrus, and on the day following it, both these tissues were significantly reduced in size. 2. During the oestrous cycle, there appeared to be no significant changes in the incidence of mitoses in either tissue, as measured 5 hr after injection of colchicine. 3. An analysis of correlation showed that in neither tissue was size correlated with incidence of mitoses. Sebaceous gland size was very significantly correlated with epidermal thickness, and the two incidences of mitoses were themselves correlated. 4. In immature female rats, which had been implanted with oestradiol benzoate 3–4 weeks before death, both sebaceous gland size and epidermal thickness were greatly reduced, although the incidences of mitoses were significantly raised. 5. These results are interpreted as indicating that oestrogens affect both holocrine secretion of the sebaceous glands and epidermal keratinization, and that these actions are independent of any possible influence on the incidence of mitoses in these tissues.

THE USE OF COLCHICINE IN THE ASSAY OF ANDROGENS

THE EFFECT of androgens on mitotic activity in the seminal vesicle of the castrate rat or mouse was first used by Loewe and Voss1 for the assay of these substances.The test was considered positive if mitoses were found in the epithelium of the seminal vesicles of the castrate rodent 48 hours after injection of the substance: to be tested. This test has not been widely accepted as the finding of mitosis is not uniform. Even in rapidly growing organs the incidence of mitosis is not high. In an animal treated even with large doses of androgens mitoses may be found in some sec' tions of the seminal vesicles but not in others. Through the work of Dustin2 colchicine has become a valuable help in studying mitotic activity. This alkaloid arrests mitosis in metaphase. Mitotic figures in cells which divide during the period in which colchicine is active are accumulated.

CHANGES IN GROWTH AND FUNCTION OF THE THYROID AFTER THYROTROPIC STIMULATION

THE EXPERIMENTAL use of colchicine makes it possible to separate changes offunction from changes of growth in thyroid glands stimulated by thyrotropic extracts. Thyroid function is ordinarily estimated by metabolic, and to some extent histological, changes, while growth is determined by the incidence of mitosis. The latter may be made evident by colchicine, which arrests cell division in the metaphase, thus allowing all mitosesto be counted for a considerable period. This paper reports the use of these methods in a study of the correlation of function and growth of the thyroid at various times after the induction of experimental hyperthyroidism. Female, virgin guinea pigs, weighing about 250 gm. each, were injected daily for periods up to 4 weeks, with from 10 to 25 mg. of a flavianate (1) extract of beef anteriorpituitary glands. Simultaneously, with the final injection of this extract, colchicine (or the colchicine derivatives colchicein or oxycolchicine), 0.1 mg., was given in solutionsubcutaneously.