Changes In Mitotic Activity Research Articles

Changes in mitotic activity in the corneal epithelium of rats of different ages after nociceptive stimulation

The effect of nociceptive stimulation on mitotic activity in the corneal epithelium was investigated in 21-day-old rat fetuses and in rats aged 3, 4, 5, 7, 10, 15, 20, and 25 days. Mitotic activity was not significantly changed 45 min after nociceptive stimulation of the animals (amputation of one-third of the tail) in the corneal of the fetuses and day-old rats. Between the 3rd and 10th days of postnatal development reactive inhibition of mitosis in response to nociceptive stimulation was gradually formed. After 10 days this response was intensified and reached a maximum by the 25th day. Reactive inhibition of mitotic activity is connected with delayed entry of the cells into mitosis.

Changes in mitotic activity of hepatocytes and resorption of necrotic areas during induction of cirrhosis of the liver

Cirrhosis of the liver was induced in rats weighing 120–140 g by administration of CCl4 for 2 months. Iodinated oil was injected through the spleen of the experimental and intact animals to produce embolism of the branches of the portal vein and foci of necrosis in the liver tissue. The volume of the necrotic foci and the mitotic activity of the hepatocytes were determined. In cirrhosis of the liver the necrotic foci were resorbed more rapidly. The increase in the mitotic index on the second day after injection of the iodinated oil was greater in the control rats. The results suggest the appearance of a new cell clone in the liver which is responsible for resorption of the necrotic tissue and the reduction in mitotic activity of the hepatocytes in animals during development of cirrhosis of the liver.

Transport of amino acids and related compounds from plasma to aqueous humour in man

Bilateral adrenalectomy alone had no specific effect on the mitotic activity of the adult rat lens. However, at 15.00 hr, left superior cervical ganglionectomy produced a change in mitotic activity of the lenses from both eyes that was eliminated by bilateral adrenalectomy. It is suggested that local trauma either affects the blood-aqueous barrier and allows blood constituents of adrenal origin to enter the eye, or causes the release of a substance that interacts with an adrenal constituent to produce the effects on lens mitosis.Left superior cervical ganglionectomy also had a specific action on the mitotic activity of the lens.Mitotic duration in the normal adult rat lens has been estimated as 104 min.

Age-dependent sensitivity of basal cells in mouse vaginal epithelium towards the diferentiating action of estrogen.

Following ovariectomy, the vaginal epithelium of the mouse is reduced to two layers of cells, the basal layer that constitutes the germinative compartment and surface layer. Under estrogenic influence, this tissue undergoes keratinization at the expense of asal cell only. The initially superficial cells are progressively sloughed, without taking part in the cornification process. We have shown previously that within the first 12 hours after estrogen administration (that is, before any change in mitotic activity is detected) an intermediate layer of cells is formed. Thurs, a migratory process is induced, which leads to a very rapid redistribution to basal cells into two layers...

CALCIUM AND THE CONTROL OF CIRCADIAN MITOTIC ACTIVITY IN RAT BONE MARROW AND THYMUS

SUMMARY Circadian changes in mitotic activity in rat bone marrow and thymus have been demonstrated to closely parallel variations in total and ionized calcium concentrations in plasma. These fluctuations in plasma calcium concentration and tissue mitosis were abolished by parathyroidectomy. Significant changes in plasma phosphate and magnesium concentrations were also observed over the 24 h period. The evidence suggests that hour-to-hour variations in the systems controlling calcium homeostasis determine the levels of mitosis in rat bone marrow and thymus.

Diurnal changes in mitotic activity and DNA synthesis in normal and tumor tissues of rats.

Diurnal changes in mitotic activity and DNA synthesis in normal and tumor tissues of rats.

Diurnal changes in mitotic activity in the epithelium and stroma of the thyroid and parathyroid glands of young rats

Diurnal changes in mitotic activity in the epithelium and stroma of the thyroid and parathyroid glands of young rats

Mechanism of compensatory renal hypertrophy.

1. Adult rats were unilaterally nephrectomized and the weight of the remaining kidney up to 42 days after the operation compared with that of rats of comparable weight which underwent a sham operation.2. After unilateral nephrectomy the rate of renal hypertrophy varied with the protein content of the diet: it was faster when animals were fed on a high protein diet (22% casein) and lowest in animals fed on a low protein diet (7% casein).3. In rats fed on a standard diet (18% casein), after unilateral nephrectomy there was a sharp increase in glomerular filtration rate (G.F.R.), as measured by inulin clearance estimations; this was accompanied by an enhanced oxygen uptake and by an increase of RNA/DNA ratios in the renal cortex. Changes in rate of oxygen uptake and of RNA/DNA ratios in the medulla were negligible.4. A marked increase in mitotic activity of cells of the cortex occurred only 48 hr after the operation. It lasted for about 2 days. No significant changes in mitotic activity of cells in the medulla were observed.5. After its initial marked rise glomerular filtration rate in the renoprival kidney settled down to about 30-40% above its pre-operative level, and remained at that level for the whole period of observation (6 weeks), while the increase of oxygen uptake returned to its control level in some 10-14 days. RNA/DNA ratios in the cortex remained high, but did not increase further.6. The increase of RNA/DNA ratios in the renal cortex was correlated with a steady increase in the dry weight of the renoprival kidney.7. Water and solutes excretion were restored to normal in about 3-5 days after the operation.8. Though the increase in glomerular filtration rate may be the prime mover in the mechanism of compensatory renal hypertrophy, it does not explain why there is an increase in the size of tubules.

The effect of superior cervical ganglionectomy and bilateral adrenalectomy on the mitotic activity of the adult rat lens

Bilateral adrenalectomy alone had no specific effect on the mitotic activity of the adult rat lens. However, at 15.00 hr, left superior cervical ganglionectomy produced a change in mitotic activity of the lenses from both eyes that was eliminated by bilateral adrenalectomy. It is suggested that local trauma either affects the blood-aqueous barrier and allows blood constituents of adrenal origin to enter the eye, or causes the release of a substance that interacts with an adrenal constituent to produce the effects on lens mitosis. Left superior cervical ganglionectomy also had a specific action on the mitotic activity of the lens. Mitotic duration in the normal adult rat lens has been estimated as 104 min.

Effect of follicle size on diurnal changes in mitotic activity in thyroid cells

Effect of follicle size on diurnal changes in mitotic activity in thyroid cells

Changes in mitotic activity during limb regeneration in Triturus.

Preliminary data on the relationship of mitosis to cell differentiation was obtained for tissues involved in the regeneration of the right forelimb of Triturus viridescens following

Action of Ypenyl [5-bis-(2-chloroethyl)-aminomethyluracil] on the chromosomes ofVicia faba

An investigation was carried out on ability of Ypenyl,i.e. 5-bis-(2-chloroethyl)-aminomethyluracil to induce structural disturbances of chromosomes and changes of mitotic activity of meristematic cells ofVicia faba. The cytostatic employed induced chromosomal aberrations mostly of the chromatide type, the greater part of which were localized in the group of small chromosomes. The frequency of aberrations was proportional to the concentration of the substance used as well as to the duration of treatment. After a 24 hour treatment with 0·01mm solution of Ypenyl the maximum incidence of aberrations was found after 8 hour recovery in water. Longer recovery periods resulted in a gradual decrease in the number of aberrant post-metaphases in the cell population studied. Increasing concentration of Ypenyl led to the decrease in mitotic activity. Short recovery periods caused a considerable decrease in the mitotic index, which was compensated as late as 16 hours after treatment with the cytostatic.

Changes in mitotic activity of the uterine epithelium in mice produced by small doses of dienestrol

Changes in mitotic activity of the uterine epithelium in mice produced by small doses of dienestrol

Diurnal changes in mitotic activity and glycogen content in rat liver during prolonged starvation

Diurnal changes in mitotic activity and glycogen content in rat liver during prolonged starvation

Protection of the gastric mucosa against the lesions caused by reserpine through degranulation of mucosal mast cells.

AbstractThe ulcerating effects of reserpinisation in the gastric mucosa of rats were studied by special observation of the function of the gastric mucosal mast cells and the changes in mitotic activity of the epithelial cells. The significance of degranulation of the mucosal mast cells for the ulcerating effect of reserpine was also studied after the pretreatment of rats with dexamethasone. Immediately after the dexamethasone treatment there was a pronounced decrease in mitotic count of the gastric mucosal epithelium which 2—3 days later when the mast cells of the gastric mocusa were almost completely degranulated was followed by a 2—3 fold increase in mitotic activity as compared with controls. 10 and 20 days later the mitotic count in the gastric mucosal epithelium decreased below the controls values, the mucosal mast cells being re‐granulated over the control values. The changes in mitotic count in the epithelium of duodenum. ileum and colon under the same conditions were scanty. The degranulation of the mast cells was markedly slighter in the intestinal than in the gastric mucosa. In the reserpinized rats the number of mitoses in the gastric epithelium decreased simultaneously with the degranulation of the mast cells. The degranulation of the mast cells in the duodenal mucosa was slighter and no changes in mitotic activity occurred in the duodenal epithelium. Lesions appeared during reserpinisation in the ventricular mucosa. Reserpinisation after the dexamethasone treatment did not cause ulcer formation in the gastric mucosa, nor did it in this phase cause inhibition in the mitotic activity, typical of which was an overshooting 2—3 days after dexamethasone treatment. The mechanism of gastric mucosal ulceration is discussed.

Changes in Mitotic Activity During Early Callus Development

Changes in Mitotic Activity During Early Callus Development

The 24-hour rhythm of mitotic activity during reparative regeneration of the salivary gland, liver and epidermis in white mice and rats

Comparison of the curves of the 24 hour mitotic rhythm in the submaxillary salivary gland, liver and skin epidermis during regeneration demonstrated that they were parallel and had a single peak. The maximum mitotic activity was observed at 8 A. M. and the minimum at 8–11 P.M. The same changes of the 24 hour mitotic rhythm in the mentioned organs were observed during physiological regeneration. Consequently during physiological and repair regeneration of various animal organs there are general regularities in the 24 hour changes of mitotic activity of the cells evidently caused by the close interrelationship of these processes.

Diurnal changes in mitotic activity and distribution of mitoses in the gastric mucosa of albino rats

A study was made of the daily changes of mitotic activity and of mitosis distribution in the mucosa of the pylorus and the fundus of the stomach of albino rats. In the pylorus 99.1% of mitoses occurred in the lower portion of the gland. The average daily mitotic coefficient in the glands of the pyloric portion was 7.8%. The curve of the daily rhythm is double-peaked in shape with maximal levels at 10 A.M. and 7 P.M. In the glands of the gastric fundus 88.5% of all the mitoses occurred in the surface-epithelial and mucous cells of the cervix, 7.4% in the peptic cells, 4.1% in the parietal cells. The average daily mitotic coefficient in the glands of the fundus is 2.04%..

A radioautographic study of the inhibitory influence of repeated injections of estrone on cell division of the uterine epithelium of mice

Spayed female mice received a daily injection of 2.3 γg of esterone. Intraperitoneal injection of 13 γCH3 thymidine was given to mice after a various number of estrone injections. The mice were killed 4 h later. The mitotic index of the uterine epithelium increased after two estrone injections, fell after six and rose again after the injections had been discontinued. The changes of mitotic activity were accompanied by similar changes in the number of labeled cells, whereas the percentage of labeled mitosis and the number of silver grains per labeled cell remained constant. These results indicate that depression of mitotic activity after prolonged estrone administration was due to inhibition of transition of the cells from the period G1 to the S-period. At the same time the rate of DNA synthesis and the capacity of the cells to pass through the G2 period to start mitosis remained unchanged.

The level and daily rhythm of mitotic activity in hypophysectomized rats

Subject to assessment was the mitotic activity in the epithelium of the cornea, tongue, esophagus, liver, outer orbital gland, renal convoluted tubules of adult hypophysectomized rats (170–210 gm). It was studied at 4, 7, and 10 AM and at 6 and 10 PM; mitoses were calculated as per 4–18 thousand cells. Mitotic activity proved to be the same in the corneal and lingual epithelium of experimental and control animals. Following hypophysectomy the curve of the daily mitotic activity changes exhibited but insignificant changes, i.e., its peak shifted to earlier hours. Mitotic activity level decreased by 45% in the esophageal epithelium; however, its daily rhythm here remained unchanged. Mitotic activity of the epithelium in the rest of the organs decreased 5–12 times, the curve of the daily changes ovtdently remaining unchanged. Thus, hypophysectomy did not eliminate mitosis, even had no decreasing effect on this activity in a number of organs.