Circadian rhythm of the mitotic activity of pulmonary interalveolar septum cells in rats of different ages]

The daily rhythm of mitotic activity in the lungs of the 20-day-dd embryo coincides with the rhythm of the adult organism. The mitotic activity of the 1-, 3- and 10-day-old animals was the maximum in the evening and the minimum-in the morning hours. A definitive rhythm of cells division (with the maximal mitotic activity in the morning and the minimal-in the evening) is established beginning from the 17th day of the postnatal development. The average mitotic activity is very high in the embryos, but it falls immediately after birth. It rises on the 3rd day, and begins to decrease again from the 7th day after birth.     

The synchronizing effect of cyclic 3',5'-adenosine monophosphate on the mitotic cycle of Ehrlich ascitic carcinoma cells]

A study was made of the number of mitoses and of the DNA-synthesizing cells in the ascitic Ehrlich carcinoma in the course of 24 hours after the injection of cyclic 3',5'-adenosinmonophosphate to mice. It was found that as the result of the preprrophase inhibition and, possibly, of stimulation of the cell entry into the S-phase, 8 hours after the action a great number of cells began to divide almost simultaneously. The effect of mitosis synchronization was assessed in the tumour cell population.     

Regenerative growth of asvitic hepatoma 22A]

A study was made of the recurrent growth of ascite hepatoma 22A, occurring at transplantation of 11-12-day old tumours to new hosts. The mitotic activity of the hepatoma was found to increase by 3 to 4 times (12-15 hours after inoculation). This increased cell proliferation is due mainly to a sharp shortening of all the periods of mitotic cycle. During the recurrent growth, the resting R1 cells resume their mitotic cycle. No resumption of the mitotic cycle by the resting R2 cells was observed     

Effect of colchamine on Ehrlich ascitic carcinoma cells showing synchronized cell division]

The author studied the 24-hour changes in the number of normal and colchamine mitoses in the cells of Ehrlich's ascites carcinoma in mice after the injection of colchamine argainst the background of partial synchronization of cell division, obtained as a result of preliminary injection of dibutyryl cyclic 3',5'-AMP, and also in mice after the injection of colchamine alone or dibutyryl cyclic 3',5'-AMP. As shown, synchronization of cell division in the tumour led to the 2,6-fold increase in the number of tumour cells blocked by colchamine and also to the accelerated arrest of colchamine mitoses.     

The effect of ultraviolet radiation of different wave lengths on the concentration of DNA--fuchsin in the cells of Zajdel's ascitic hepatoma]

The cytophotometrical analysis of the relationships between the content of DNA--fuchsin and the duration of acid hydrolysis of the intranuclear DNA (the Feulgen reaction) in the Zaidela hepatoma cells allows to see the degree of the DNA--protein binding. The UV irradiation of different wave-lengths (254, 325 and 365 nm, resp.) irrespective of the degree of absorption by nucleic acids, causes changes in chromatin condensation, thus suggesting the labilization of DNA--protein bounds.     

Effect of isoprenaline on cells in different phases of the mitotic cycle

The effects of isoprenaline on parotid acinar cells in different phases of the mitotic cycle have been investigated. Cells in mitosis at the time of drug administration are not depleted of secretory granules whilst those in other phases are. The drug causes temporary blocks both in metaphase and in the G2 phase. The blocks are prolonged by repeated injections of the drug. Cells continue to undergo DNA synthesis during the period of secretion following the drug. The mitotic delay appears to be specific for the parotid and submaxillary glands.     

Distribution of alpha-fetoprotein and albumin in paraffin sections of cells of Zaidel's ascitic hepatoma]

The alpha-fetoprotein (AFP) and albumin localization were studied in the cells of rat Zaidel's ascitic hepatoma. It was shown in the paraffine sections of the hepatoma cells fixed by mixture of 96 degrees ethanol with 1% glacial acetic acid that 9.3% of hepatoma cells contained AFP and 0.6% of the cells--serum albumin. Small quantities of the tumour cells had both of these proteins simultaneously. There was no definite regularity in the distribution of the AFP and albumin-containing cells in the tumour islands.     

Splitting of phase G1 of the mitotic cycle of guinea pig large intestine crypt cells]

Changes in shape of the second wave of the labeled mitoses curve previously observed by Rowinski and Sawicki (1972) for three crypt zones of three different parts of guinea-pig ascending colon are explained by the complicated branching structure of the G1-phase. This structure is assumed to be the same for different crypt zones and for different sections of the intestine. Changes in shape of the second wave of the labeled mitoses curve are explained by the changes in distribution of proliferating cell stream between the alternative directions at the points of branching of the G1-phase, depending on the crypt zone, the intestine section, the cell state, and on the state of intestine.     

MCPH1 regulates the neuroprogenitor division mode by coupling the centrosomal cycle with mitotic entry through the Chk1-Cdc25 pathway

Primary microcephaly 1 is a neurodevelopmental disorder caused by mutations in the MCPH1 gene, whose product MCPH1 (also known as microcephalin and BRIT1) regulates DNA-damage response. Here we show that Mcph1 disruption in mice results in primary microcephaly, mimicking human MCPH1 symptoms, owing to a premature switching of neuroprogenitors from symmetric to asymmetric division. MCPH1-deficiency abrogates the localization of Chk1 to centrosomes, causing premature Cdk1 activation and early mitotic entry, which uncouples mitosis and the centrosome cycle. This misorients the mitotic spindle alignment and shifts the division plane of neuroprogenitors, to bias neurogenic cell fate. Silencing Cdc25b, a centrosome substrate of Chk1, corrects MCPH1-deficiency-induced spindle misalignment and rescues the premature neurogenic production in Mcph1-knockout neocortex. Thus, MCPH1, through its function in the Chk1-Cdc25-Cdk1 pathway to couple the centrosome cycle with mitosis, is required for precise mitotic spindle orientation and thereby regulates the progenitor division mode to maintain brain size.     

Effect of hydrocortisone on the mitotic cycle of epithelial cells in the mouse pylorus]

It was shown with the aid of thymidine-H3 that the mitotic cycle of mucous-forming cells (superficial epithelial mucosal cells of the neck) of the stomach pyloric glands of mice lasted 13.5 hrs (G1+1/2M = 7.6 hrs, S = 5.3 hrs; G2+1/2M = 0.6 hrs). With the administration of a physiological dose of hydrocortisone (0.1 mg) the duration of the mitotic cycle of mucous-forming cells of the stomach pyloric glands increased by 6.7 hrs (G1+1/2M = 11.6 hrs, S = 7.8 hrs; G2+1/2M = 0.8 hrs). A high dose of the hormone had a similar effect and increased the presynthetic period to 12.9 hours and the postsynthetic one--to 2.3 hours.     

Analysis of substances issuing from Zajdela ascitic hepatoma cells following exposure to UV radiation of different wavelength. II. Proton release]

The release of protein from the Zaidela ascitic hepatoma cells following irradiation with physiological doses of short-wave (254 nm) and long-wave (300--380 nm) UV light (far and near UV radiation) has been investigated. The amount of protein increases with dose making, upon the maximal radiation damage, 180 and 2 per cent of the protein against, resp., the protein amount releasing from non-treated cells and the total protein of the intact cell. The far UV light is by one order more efficient than the near UV light. Irradiation of cells with the former and the latter results in the release of high and low molecular proteins, resp. The near UV irradiation brings about heavier releasing of proteins than does the far UV light.     

Fractional composition of cytoplasmic RNP-particles in the cells of Zajdela ascitic hepatoma and the liver of a tumor-bearing animal]

The relative content of poly(A)-RNA in the cytoplasm was greater in the cells of Zajdela hepatoma and the liver of tumour-bearing rats than in the normal hepatocytes of rats. Besides, the tumour cells (and to a lesser extent the hepatocytes of the tumour-bearing animal) were characterized by the changes in the ratio of the polyribosomes and monoribosomes usual for normal hepatocytes (and correspondingly between the m-RNP-particles and the informosomes) in favour of the latter, this pointing to definite changes in their protein-synthesizing apparatus. As judged by some of the parameters, the cells of the tumour-bearing by some of the parameters, the cells of the tumour-bearing animal occupied an intermediate position between the normal and tumour cells.     

Interaction of laminin with the plasma membrane components of ascitic Zajdela hepatoma cells

The laminin affinity chromatography was used for isolating laminin-binding proteins from the plasma membrane of Zajdela hepatoma cells synthesizing laminin. These were components with mol. weights about 80, 67, 60, 55, 52, 48 and 43 kDa. The isolation of laminin integrin receptors from plasma membranes of Zajdela hepatoma cells in the presence of MnCl2 detected only a protein with mol. weight about 80 kDa in EDTA-elution conditions. This protein was identified by mass spectrometry method as the 78 kDa glucose-regulated protein precursor (GRP78). It belongs to the family of 70 kDa heat shock proteins, recently GRP78 was reported to be localized on the surface of different cell types, including hepatocytes.