Neuronal adaptation of corticospinal mechanisms of muscle contraction regulation in athletes

Physiological mechanisms of neuronal adaptation of the human corticospinal pathways in response to long-term intense motor activity have been studied insufficiently. In this work, we investigated adaptational changes in corticospinal mechanisms of muscular contraction control in athletes. We measured parameters of motor evoked potentials of lower limb skeletal muscles under voluntary static loads of various intensity and duration, using the transcranial magnetic stimulation method. Elite athletes, as compared to the reference group, in the course of increased intensity and duration of isometric muscular contractions demonstrated more expressed increase in the maximum amplitude of the motor evoked potentials of lower limb skeletal muscles, smaller decrease in the time of central motor conduction of nervous pulses and the peripheral period in electromyograms, and less expressed increase in the cortical and segmental silent periods. Mechanisms of adaptation of corticospinal regulation of human muscular contraction to specific conditions of extreme motor activities are discussed.     

Penetration of the peptide lactaptin into human cancer cells

Lactaptin, a human milk protein with a molecular weight of 8.6 kDa, is a fragment of human ?casein, which has cytotoxic activity toward mammalian cancer cells in vitro. RL2 is a recombinant analogue of lactaptin, which induces the apoptosis of human cancer cells in culture and suppresses the tumor growth in vivo. It has been shown earlier that RL2 penetrates into both human cancer and nonmalignized cells and binds to cytoskeletal structures. In this process, it induces the apoptosis of cancer cells and does not diminish the viability of normal cells. The mechanism of the penetration of RL2 into human cancer cells has been studied by flow cytometry and fluorescence microscopy using the inhibitors of different endocytosis pathways. It has been shown that RL2 penetrates into cells partly through lipid raft-mediated dynamin-independent pinocytosis and partly through direct penetration across the plasma cell membrane. An analysis of the primary structure of RL2 and the mechanism of its penetration into the cell suggests that it can be assigned to the class of cell-penetrating peptides.     

Effect of oxytocin on the calcium pump in myometrium sarcolemma

Oxytocin (10(-7) M) administered inside the myometrium sarcolemma vesicles closed outward by the cytoplasmic side is shown to inhibit Mg2+, ATP-dependent Ca2+ accumulation in these structures having no effect on the passive release of cation out of them. According to these results and to the data available in literature on the inhibitory action of the peptide hormone on Mg2+, Ca2+-ATPase of myometrium sarcolemma a conclusion is drawn that oxytocin inhibits the Ca pump activity in plasma membranes of the myometrium cells.     

Topography and parameters of the intertrabecular spaces of the heart ventricles in man and laboratory animals

The heart of the man, dog, cat and rabbit have been investigated using biometry and corrosive methods. In the horizontal sections the volume of the intertrabecular spaces (IS) of the ventricles has been estimated and the "coefficient of the myocardial sponginess" has been calculated as the ratio of the cavities volume to the myocardial volume. In the corrosive casts of the ventricular cavities the deviation angles of the IS casts from the axial line along the afferent and deferent tracts have been measured. Differences in manifestation of the IS in the hearts of the mammals studied have been revealed. The IS are best pronounced in the human heart, less in the dog heart and still less in the cat and rabbit hearts. For all the hearts studied predominance of the volume of the IS in the right ventricle is specific. The deviation angle of the IS casts from the axial line along the afferent tract increases from the cardiac basis towards its apex, while the deviation angle of the IS along the deferent tract decreases from the apex towards the basis. The functional predisposition of the IS is supposed to consist in providing systolic reserves of the cardiac ventricular cavities. The results of the mathematical analysis of the changes in the cast deviation angles of the IS along the afferent and deferent tracts demonstrate their role in twisting and acceleration of the blood stream in the systolic phase and slowing down of the blood stream in the diastolic phase.     

The effect of the oligomerization of pBR322 on the level of transformation in Escherichia coli

The ability of the known Escherichia coli strain JC3881 recB recC recF sbc15 to produce oligomeric and multimeric forms of pBR322 underlies the study presented. The individual oligomeric forms of pBR322 were isolated from the agarose gel. The plasmid forms were used for electron microscopic control and also introduced into the system of E. coli competent cells. The E. coli transformation level of different forms of plasmid DNA rose from monomers to pentamers. CCC forms of the plasmid possessed high efficiency of the E. coli cell transformation. The systems of the host recombination are to be significant in the process of plasmid oligomerization.     

Prevalence of Toxocara infection in schoolchildren from the Butantã region,São Paulo,Brazil

Visceral larva migrans syndrome by Toxocara affects mainly children between 2 and 5 years of age, it is generally asymptomatic, and the seroprevalence varies from 3 to 86% in different countries. A total of 399 schoolchildren from 14 public schools of the Butant? region, S?o Paulo city, Brazil, were evaluated by Toxocara serology (enzyme-linked immunosorbent assay). Epidemiological data to the Toxocara infection obtained from a protocol were submitted to multiple logistic regression analysis for a risk profile definition. Blood was collected on filter paper by finger puncture, with all samples tested in duplicate. Considering titers > or = 1/160 as positive, the seroprevalence obtained was 38.8%. Among infected children, the mean age was 9.4 years, with a similar distribution between genders. A significant association was observed with the presence of onychophagia, residence with a dirty backyard, living in a slum, previous wheezing episodes, school attended, and family income (p < 0.05). All data, except "living in a slum", were considered to be determinant of a risk profile for the acquisition of Toxocara infection. A monthly income > or = 5 minimum salaries represented a protective factor, although of low relevance. Toxocara eggs were found in at least one of the soil samples obtained from five schools, with high prevalence of Toxocara infections, indicating the frequent soil contamination by this agent.     

Presynaptic inhibition of spinal α motoneurons in humans adapted to different types of motor activity

Changes in the presynaptic inhibition of spinal α motoneurons were studied in athletes during motor activities of different types. In the state where muscles were at relative rest, the presynaptic inhibition of spinal α motoneurons of the m. soleus was stronger in samboists (athletes specializing in the martial art of sambo) and sprinters than in long-distance runners. In samboists performing repeated static efforts, the presynaptic inhibition of spinal α motoneurons became stronger from one trial to the next. Both technique training and strength training enhanced the presynaptic inhibition of spinal α motoneurons, this enhancement being greater after strength training.     

Evaluation of axillary lymph nodes from the results of radioisotopic study

The purpose of the investigation was to study the pattern of 99mTc (MIBI) technitrile uptake in the metastatically involved lymph nodes in breast cancer, by applying the plain scintigraphic technique. The scintigraphic study of the breast and regional metastatic areas by means of the radionuclide 99mTc (MIBI) technitrile was made on a Millennium GE tomographic gamma chamber. The radiotracer 550 (MBq) dissolved in 10-20 ml of saline solution was intravenously injected into the arm cubital vein contralaterally to the lesion. Following 20 minutes of injection of the agent, plain scintigraphy was carried out in three standard projections: frontal and two oblique ones. The scintigraphy was performed using a high-resolution collimator recording a 128 x 128 matrix image. The detector was maximally approximated to the organ being examined. A plain scintigraphic scan was recorded on each side for 10 minutes. By the degree of axillary lymph nodal involvement, the patients were divided into 3 groups in accordance with the international TNM classification: N0 (n = 55), N1 (n = 13), N2 (n = 4). Among 72 patients, axillary lymph nodes could be detected in 6, in 2 of them changes were not diagnosed by X-ray and ultrasound studies. The final pathomorphological study of intraoperative materials revealed axillary lymph nodal metastatic involvement in 17 patients. A micrometastasis in one lymph node was found in 1 patient. None of the radionuclide studies showed tumor spread in 5 cases. The sensitivity, specificity, and precision of the technique were 35.3, 100, and 84.7%, respectively. Thus, a combination of the high cost of the procedure, its radiation load on a patient, and its low sensitivity make the use of plain scintigraphy of axillary regions inexpedient in the complex of studies of the extent of breast cancer in the present development of technology.     

Lactaptin Induces p53-Independent Cell Death Associated with Features of Apoptosis and Autophagy and Delays Growth of Breast Cancer Cells in Mouse Xenografts

Lactaptin, the proteolytic fragment of human milk kappa-casein, induces the death of various cultured cancer cells. The mechanisms leading to cell death after lactaptin treatment have not been well characterized. In this study the in vivo and in vitro effects of a recombinant analogue of lactaptin (RL2) were examined. Following treatment with the recombinant analogue of lactaptin strong caspase -3, -7 activation was detected. As a consequence of caspase activation we observed the appearance of a sub-G1 population of cells with subdiploid DNA content. Dynamic changes in the mRNA and protein levels of apoptosis-related genes were estimated. No statistically reliable differences in p53 mRNA level or protein level were found between control and RL2-treated cells. We observed that RL2 constitutively suppressed bcl-2 mRNA expression and down regulated Bcl-2 protein expression in MDA-MB-231 cells. We demonstrated that RL2 penetrates cancer and non-transformed cells. Identification of the cellular targets of the lactaptin analogue revealed that α/β-tubulin and α-actinin-1 were RL2-bound proteins. As the alteration in cellular viability in response to protein stimulus can be realized not only by way of apoptosis but also by autophagy, we examined the implications of autophagy in RL2-dependent cell death. We also found that RL2 treatment induces LC3-processing, which is a hallmark of autophagy. The autophagy inhibitor chloroquine enhanced RL2 cytotoxicity to MDA-MB-231 cells, indicating the pro-survival effect of RL2-dependent autophagy. The antitumour potential of RL2 was investigated in vivo in mouse xenografts bearing MDA-MB-231 cells. We demonstrated that the recombinant analogue of lactaptin significantly suppressed the growth of solid tumours. Our results indicate that lactaptin could be a new molecule for the development of anticancer drugs.