Cytochemical localization of calcium in renal sac nephrocytes of Helix aspersa

In renal sac nephrocytes of Helix aspersa, intracellular calcium has been localized using the oxalate-pyroantimonate (OPA) and phosphate-pyroantimonate (PPA) methods. Pyroantimonate precipitates are preferentially localized in the excretory spherule and in vesicles located in the basal and lateral regions of the nephrocyte. Such vesicles appear to release their content into the excretory vacuole. Calcium may interact with diverse types of molecules present in the excretory vacuole, thus favouring stabilization and packaging of the excretory spherule.     

A standardized x-ray examination of mandibular fractures

Proceeding from an x-ray examination of 143 patients with mandibular fractures, the most informative methods and projections as well as the order of their use with account of the site of a fracture, were determined. The most informative method in all fracture sites was orthopantomography; panoramic roentgenography was indicated only in fractures of the frontal part. If panoramic tomography cannot be done, roentgenography or electroroentgenography in the frontal-nasal projection is recommended. If panoramic roentgenography cannot be done, extraoral roentgenography is indicated in the diagnosis of fractures of the frontal part of the mandible.     

A decrease in the level of unscheduled DNA synthesis in preparations of irradiated rat hepatocyte nuclei under the effect of polyamines

The results obtained show the possibility of polyamine (spermine and spermidine) utilization to stabilize the nuclear chromatin and to protect it against nuclease degradation in the course of isolation of liver cell nuclei. Besides, the inhibition of the unscheduled DNA synthesis induced by nuclease incision and by gamma- or UV-radiation was demonstrated in the presence of polyamines.     

New lines of spontaneously transformed cells obtained from "precrisis" cultures of embryonic rat cells

A new approach to selection of lines of spontaneously transformed cells from the rat embryo "precrisis" cultures is described and their phenotypes at the initial and advanced stages during a long-term cultivation are characterized. The new selective system, referred to as 2T7, differs from the well known 3T3, 2T6 and 3T12 systems (Todaro, Green, 1963; Aaronson, Todaro, 1968). It is based on the maintenance of cultures under maximum cell densities. Such an approach facilitated and accelerated the start of the "crisis" stage (up to 3-8 passages) with the following gradual death of almost the whole normal senescent cell population, the colony formation resulting from the proliferation of single clonogenic cells. The frequency of clonogenic cells was about 6 x 10(-6). Six lines of spontaneously transformed cells from embryos of noninbred white rats (LRec-1--LRec-6) and one line from the Wistar embryos (LRec-7) were established. All the lines are characterized as diploid or near-tetraploid, with 1-4 different marker chromosomes formed from chromosome 7, as was reported elsewhere (Artsybasheva et al., 1988). The values of saturation densities and the time of population doubling for all the 7 lines differed from those for the rat embryo primary cultures cells. LRec-1--LRec-6 cells were unable to form the colonies in soft agar, while LRec-7 cells were able to grow in agar. The lines LRec became oncogenic for 1-2 day old rats after different periods of cultivation in vitro--from 3 to 7 months. The line LRec-7 Wistar appeared to be highly oncogenic from the very beginning after its selection. The histological analysis revealed that the LRec-1 tumors could be classified as polymorphocellular sarcoma. Up to 20 passages the LRec-1 line had numerous clonogenic cells (50-60%) in sparse cultures independently on the serum content in the media. By a 3-step selection of LRec-1 cells, on cultivation in media with lower serum contents (1-0.1-0%), a semisuspension of LRec-1sf subline (serum free) was established. This line was highly oncogenic for 1-2 day old rats, was easily cryopreserved and proliferated in the serum-free media for unlimited time, forming small colonies in agar. Thus, the new approach allows to establish with high effectiveness spontaneous lines of rat embryo cells with differently transformed phenotypes, i.e. preneoplastic and oncogenic ones.(ABSTRACT TRUNCATED AT 400 WORDS)     

The effect of picolinic acid and iron ions on the proliferation of SPEV cells

The effect of picolinic acid (PA) on SPEV cell proliferation is found to be different from that on normal and virus transformed NRC cells, and on spontaneously transformed CHO cells. It is shown that SPEV cells are arrested by PA at the end of G1-phase and at the beginning of S-phase and probably in G2-phase of the cell cycle. Ferrous ions remove the G1/S block induced by PA to permit the cell transfer through S-phase. On the one hand, PA chelates ferrous ions from the cells, and on the other one it inhibits the replicative DNA synthesis. It can be suggested that PA may arrest the SPEV cell growth affecting the iron-depend stable radical formation which is introduced into the active centre of ribonucleotiDE reduCTase. This results in the lower enzyme activity.     

Hypothermic effect on mice of a 1-10 kD fraction of the small intestine of the hibernating suslik Citellus undulatus during hypoxia and hypercapnia

Studies have been made on a possibility of inducing a prolonged hypothermia by injections to albino mice of a fraction with a molecular mass 1-10 KD isolated from the small intestine of hibernating ground squirrels. Specific conditions for the onset of hibernation (hypoxia, hypercapnia, temperature) were simulated. Exposure of mice to hypoxia and hypercapnia for 2 hours in combination with injection of the mentioned fraction extended hypothermic condition in animals up to 24-36 hours as compared to 2-3 hours after sole injection of the fraction. After the injection of 5-OT under the same conditions, the prolonged hypothermia was less stable.     

The invariance of subjective time scales

Organization of subjective time scales was studied by various methods of duration scaling (reproduction, fractionation, multiplication, evaluation, measuring and cross-model selection). Computation of linear correlation coefficients between physical time and its subjective expression for various methods of scaling in different coordinate systems allows to make a conclusion about a degree form of psychophysical dependence. The value of function degree index varies in the range of 0.80-0.88 for verbal evaluation and 0.93-1.07 for other methods. The concept is suggested about the "active" and "passive" time.     

Spread of fast thermowaves through the cerebral cortex produced by visual stimulation

Thermowaves spreading through the cerebral cortex were observed and investigated during acute experiments on white rats using a new technique — that of thermoencephaloscopy (TES) through the intact skull. These waves were induced by regular visual stimulation (at intervals of 1.5–3 min) or by initiating one of the flashes and spread through the cortex along trajectories of five basic types; amplitude of thermowaves: 0.005–0.1°C; length: 10–15 mm; duration 1.2–11.4 sec; velocity: 1–33 mm/sec; extent of pathway: 2–56 mm. They appeared with a high degree of probability (of 0.92) during the interval between 15 sec before and 26 sec after the flash. Numbers of moving waves declined by the point of stimulus application and rose by 7–8 sec after the flash. Waves arose in 50% of cases in the contralateral visual cortex (areas 17 and 18a), spreading to the midline and crossing to the ipsilateral hemisphere (areas 17, 18a, and 7). Local waves moving along a circular trajectory were also discovered in the contralateral visual cortex. Several types of wave, differing in trajectory, also arose in the ipsilateral visual cortex. Mechanisms and possible significance of this effect are examined.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 21, No. 4, pp. 467–475, July–August, 1989.     

A division inhibitor and a topological specificity factor coded for by the minicell locus determine proper placement of the division septum in E. coli

The E. coli minicell locus (minB) was shown to code for three gene products (MinC, MinD, and MinE) whose coordinate action is required for proper placement of the division spetum. Studies of the phenotypic effects of expression of the three genes, alone and in all possible combinations, indicated the following: cell poles contain potential division sites that will support additional septation events unless specifically inactivated; the minC and minD gene products act in concert to form a nonspecific inhibitor of septation that is capable of blocking cell division at all potential division sites; and the minE gene codes for a topological specificity factor that, in wild-type cells, prevents the division inhibitor from acting at internal division sites while permitting it to block septation at polar sites.