Search

Circadian rhythm of DNA synthesis, mitotic activity, and duration of mitosis in rat liver were studied on days 3, 7, and 12 of life. Age-associated differences in the rhythmic parameters of these characteristics were detected. Epidermal growth factor plays an important role in the formation of cell proliferation rhythm in the early postnatal ontogeny and in the formation of proliferative hepatocyte pool.

Circadian rhythms of DNA synthesis, mitotic activity, and duration of mitosis in rat liver were studied on postnatal days 3, 7, and 12. Some age-related peculiarities of these rhythms were revealed. Epidermal growth factor was found to play an important role in the formation of cell proliferation rhythm during the early postnatal ontogeny and in the regulation of the pool of proliferating hepatocytes.

The paper shows that any system acquires a qualitatively new state if the elements of this system change in number (increase or decrease relative to the standard reference point, i.e. normalcy, the prior status of the system, etc. by less than one third).

Long-standing cholestatic syndrome (LSCS) was diagnosed in 41 patients with hepatitis A and hepatitis A plus chronic persistent hepatitis B (HA + CPHB). Some patients had a cholestatic form of the disease. Morphological and morphometric liver parameters were measured at the height of icterus in 74 patients. It was found that cholestatic syndrome in patients with HA and HA = CPHB is related to reparative regeneration which always has a favourable outcome.

Clinical and morphological characteristics were studied for a course of acute viral hepatitis A and delta with long-term cholestatic syndrome in asymptomatic carriers of HBsAg. 149 patients with moderate disease were examined, 53 of them had long-standing cholestasis syndrome. 96 viral hepatitis patients free of cholestasis served control. It is believed that the emergence of long-term intrahepatic cholestasis may be due to the following mechanisms of sinusoid lumina as a result of a drastic enlargement of multinuclear hepatocytes, hyperplasia and hypertrophy of Kupffer's cells. impaired binding of bilirubin in zone III of hepatic acinus. In cholestatic form of hepatitis A there occurs more pronounced reduction of sinusoid volume compared to other variants of viral hepatitis run.

G1- and G2-chalone effects of pig's stomach mucosa extract were registered in mice stomach gland epithelium. The inhibitory activity of chalones on cell's proliferation reduced following increased level of thyroid hormones. Local (chalones) and organism (thyroid hormones) factors cooperate in control of gland epithelial cell proliferation.

The control effects of thyroid hormones were registered in mice stomach gland epithelium. The growth fraction, rhythm, activity of proliferation changed differently in fundal and pyloric epithelium following increased level of thyroid hormones.

By means of autoradiography and metaphase arrest technique 24-hour rhythms and intensity of proliferative processes in the epithelium of gastric glands were studied, as well as morphometric status of these structures after vagotomy and drug sympathectomy in the rat. In both cases the reaction of glandular epithelium appeared with the increase of mitotic activity and the decrease of cell synchronization before the entry into DNA--synthesis and mitosis. The number of epithelial cells in gastric glands became reduced, but after vagotomy, unlike sympathectomy, mainly because of the lack of chief cells. Thus, the trophic control upon the dynamic structure of gastric glands may have different mechanisms of realization for parasympathetic and sympathetic nervous system, probably, through the influence on cell proliferation or differentiation.

The omental milky sports of the rat have been examined with the light and electron microscope after intraperitoneal stimulation by particulate coal and zymosan. No positive correlation between cell level proliferation in milky spots and alteration of their size has been found. The increase in size of milky spots is due to the inflow of cells from the blood and bone marrow. The development in milky spots of a great number of macrophages "tubercles" and multinucleated giant cells in the experimental conditions may respond to inflammation. The administration of zymosan result in the influx of lymphocytes forming lymphatic follicle-like structure. Despite the absence of germinative centres, the appearance of a great number of lymphoblasts and plasma cells in the milky spots provides the evidence of the active antibody production aimed at immunological protection of abdominal cavity.

Numbers of mitoses and of colchicine mitoses, and the duration of mitosis in corneal and tongue epithelium as well as in hepatocytes of intact and adrenalectomized rats have been studied in dynamics within 24 hours. In the control animals, the 24 hours rhythm of mitotic activity and the duration of mitosis were established. The length of mitosis falls during the high rate mitotic activity to increase when the number of dividing cells is reduced. Adrenalectomy results in decreasing the amplitude of mitotic activity fluctuations and in diminishing the amount cells entering mitosis during the 24 hours period. The rate of physiological regeneration in tissues of adrenalectomized animals is reduced. Different sensibilities of investigated tissues to adrenal cortex hormones deficiency have been revealed.

The intensity of capillaries growth in the rabbit's cornea was investigated after chemical burn and exposure to colchicine. Proliferative activity was determined in endothelial cells along the course of newly formed capillaries. Growth intensity proved to be 2 times higher when burn and colchicine effects were combined, than in case of burn alone. The increase in the proliferative activity of endothelial cells and the peculiarities of their arrangement were found in both cases. The most active proliferation was observed in cells located in a zone where capillaries originated from intact vessels of the limb. The process of new vessel formation depends on endotheliocyte shift from this zone towards the site where growth-stimulating factors were applied.

Unilateral nephrectomy was performed in mice in the morning and in the evening. Mitotic activity in the proximal parts of the nephron tubules of the resting kidney and in the corneal epithelium was examined 48 and 60 hours after the operation. As compared with control, after the operation performed in the morning the mitotic index proved to increase 4.3 times and remained at a high level for 60 hours; after the operation performed in the evening mitotic index increased 9.3 times and decreased in 60 hours. It is concluded that the cells of the kidney epithelium entered into division more synchronously in the animals operated in the evening than in those operated in the morning. Nephrectomy had no influence on the level and rhythm of cell proliferation in the corneal epithelium.

The epithelium of mouse cornea and lymph nodes was examined for DNA-synthetic and mitotic activity at different times after thymectomy and administration of T-activin, an active factor of the thymus. Thymectomy entails retardation of the rate of corneal epithelium regeneration, diminution in both tissues under study of the amplitude of oscillations in cell proliferation throughout the day. Administration to the animals of the immunoactive thymic factor T-activin makes the circadian rhythm of cell proliferation return to normal. It is assumed that T-activin raises the capacity of lymphocytes to interact with epithelial cells, which manifests itself in the enhancement of their mitotic activity.

The paper is concerned with the action of chalones, tissue-specific inhibitors of cell proliferation, on DNA synthesis and mitotic activity of hepatocytes in the intact and denervated liver during regeneration. Experiments were made on Wistar rats. Liver denervation was performed by bilateral subdiaphragmal vagotomy. In control and vagotomized animals, two thirds of the liver was resected. The data obtained indicate that chalones noticeably reduce the number of DNA-synthesizing cells and mitoses in the regenerating liver of intact animals. During regeneration of the denervated liver, chalones do not produce any inhibitory action on the intensity of proliferation. Analysis of the data obtained allows a conclusion that preservation of adequate innervation of the organ is needed for realization of the action of hepatic chalones.

In corneal epithelium of CBA mice the index of colchicine mitoses diminished after splenectomy in the day period characterized by rising mitotic activity in control animals. The duration of active phase of cell division rhythm shortened while the maximum of mitotic activity delayed in comparison with control animals. The total amount of cells entering mitosis during 24 hours diminished by 27.7% and the rate of physiological regeneration of corneal epithelium decreased.

Mitotic fluctuations during 24 hours and duration of motoses were studied in the corneal epithelium and in the leukemic-La spleen cells of mice. The existence of correlative changes between the mitotic index and the duration of mitosis in the course of 24 hours was revealed. It is supposed that a more rapid course of mitosis in the intensively proliferating tissues and a slower one in the tissues with a low proliferative capacity served as a reflection of general regularity.

Circadian rhythms of mitoses were studied in the epithelium of the cornea and esophagus of rats given hydrocortisone. The hormone was injected daily during 7 days at 4-5 p.m., i.e. at the height of the blood glucocorticoid content within the circadian rhythm. The tissues of experimental rats, manifested biphasic rhythms of mitoses as compared with monophasic rhythms seen in intact animals. The amplitude and daily average magnitudes of the mitotic index were unchanged.

In experimental hypercorticism the average daily concentration of glucocorticoids in blood plasma is 4 times higher than in control one, the amplitude of the circadian rhythm increases almost 3 times, the time of maximum concentration does not change. The adrenocorticotrophic hormone (ACTH) average circadian concentration decreases twofold. The adrenalectomy results in abrupt smoothing down of the circadian rhythm of glucocorticoids concentration and in increasing (in 2,4 times) of the average circadian concentration of ACTH. The pattern of circadian rhythm remains, however the acrophase of hormone secretion is shifted. The circadian rhythm of cells devision in esophagus epithelium changes. The maximum of mitotic index is absent in adrenalectomized rats and the amplitude of its circadian variations decreases. In experimental hypercorticism the biphase rhythm of mitoses in induced.

The diurnal changes of mitosis and DNA-synthesizing cells count in the tongue epithelium of intact and adrenalectomized mice were studied. A partial desynchronization of mitotic division, as well as diminution of mitotic index variation amplitude and prolongation of high mitotic activity were observed in the operated animals in the course of 24 hours. The average 24-hour mitotic index in the basal layer of the tongue epithelium was the same in the intact and the operated animals. The rhythm of the DNA synthesis failed to differe from control. Thus, adrenalectomy in mice led to distrubances of the diurnal mitotic rhythm in the tongue epithelium, but had no effect on the rhythm of the DNA synthesis and the level of the proliferative activity.

The action of hepatic chalone on cell proliferation in inoculated hepatoma 22a of mice was studied in the presence of a changed level of glucocorticoid hormones in experimental animals. Chalone was obtained from the liver of intact rats by ethanol precipitation. The intensity of cell proliferation in hepatoma was evaluated by the colcemide and autoradiography methods. Six hours after chalone injection c-mitosis in the tumor decreased 2.7-fold, and the DNA index 6.8-fold. It may be concluded that the preparation used contains both G1- and G2-chalones. Single or repeated injections of hydrocortisone to mice inhibits cell proliferation to a less degree than administration of chalone alone. Combination of hydrocortisone and chalone produces the same effect as injection of chalone alone. Adrenalectomy diminishes susceptibility of hepatoma cells to exogenous chalone. The degree of tumor proliferative activity in the adrenalectomized animals was half as much after chalone injection, as compared to that in intact animals. Thus, a certain level of glucocorticoid hormones in hepatoma tissue is necessary to reveal the action of chalones.

Bilateral subdiaphragmatic vagotomy in rats 7 days after surgery results in increasing proliferative activity of the jejunum epithelium not changing circadian rhythm of the mitotic process. Vagotomy induces changes in the diurnal rhythm structure of DNA-synthesis in the jejunum epithelial cells, i.e. monoapical rhythm in the norm becomes biapical.