Mathematical modeling of electron and protein transport, coupled with ATP synthesis in chloroplasts

A mathematical model of electron and proton transport in chloroplasts of higher plants was developed, which takes into account the lateral heterogeneity of the lamellar system. Based on the results of numerical experiments, lateral profiles of pH in the thylakoid lumen and in the narrow gap between grana thylakoids under different metabolic conditions (in the state of photosynthetic control and under photophosphorylation conditions) were simulated. Lateral profiles of pH in the thylakoid lumen and in the intrathylakoid gap were simulated for different values of the proton diffusion coefficient and stroma pH. The model demonstrated that there might be two mechanisms of regulation of electron and proton transport in chloroplasts: (1) the slowing down of noncyclic electron transport due to a decrease in the intrathylakoid pH, and (2) the retardation of plastoquinone reduction due to slow diffusion of protons inside the narrow gap between the thylakoids of grana.     

Neuronal interaction at the cell body level in the snail CNS. Neuroactive environment heterogeneity

In experiments on Lymnaea stagnalis, a single neuron isolated from the PeA cluster was used as moveable sensor for monitoring extracellular environment of the CNS surface. At the serotoninergic PeA area, two novel neuroactive factors were detected: inhibitory and excitatory ones. The former is transiently released whenever extracellular 5-HT increases. A distinctive feature of the latter is that it narrows the action potential of the sensor cell. The findings demonstrate that natural neuro-active factors occur in the soma vicinity in effective concentrations, thus suggesting that, in the snail brain, activity of central neurons is controlled by neurotransmitters operating at the cell body level.     

Types of the peptide modulation of the vagus nerve effect on the heart rhythm

In anaesthetised cats, effects of 24 regulatory peptides upon inhibitory tonic and synchronizing components of vagal chronotropic action, were studied. The findings allowed to divide the peptidergic vagotropic activity into three types: (1) a selective action upon inhibitory tonic vagal effect; (2) a selective modulation of synchronizing vagal effect; (3) opposite changes in the vagal chronotropic effect components. The peptides seem to be able to modulate both the vagal bradycardia and the functional structure of parasympathetic chronotropic effect.     

Tumor-associated changes in the buccal epithelium in human breast and thyroid pathology

The estimation of the malignancy-associated changes in oral mucosa of patients with benign and malignant processes in mammary and thyroid gland is carried out on the basis of textural and densitometric indices of the interphase nuclei of the epitheliocytes with the help of the methods of mathematical statistics.     

Atropine effect on physostigmine- and stress-induced secretion of catecholamines by adrenal gland: microdialysis study in awake rats

Physostigmine and an 1-hour immobilisation stress similarly affected functions of the sympatho-adrenal and cardiovascular systems activating the catecholamine secretion and increasing the blood pressure. Yohimbine potentiated the secretory effect but did not change the pressor effect. Intermediate administration of atropine completely eliminated both effects of physostigmine but, being administered prior to the immobilisation, it potentiated the secretory response without affecting the pressor response. The findings reveal a difference in central cholinergic mechanisms of neurohumoral and haemodynamic responses to physostigmine and stress.     

Endocytosis of EGF-receptor complexes at various cell cycle stages

Parameters of EGF-receptor complex endocytosis have been studied in the early and late G1 phase and in mitosis. As a model, mouse mammary epithelial cells HC11 were used, whose growth depends on EGF presence in the medium. The Scatchard analysis has demonstrated that the surface receptors are represented by two receptor populations: 4800 high affinity (KD = 10(-11) M) receptors, and 73,000 low affinity (KD = 4.10(-9) M) receptors. Incubation of cells with the growth factor (5 ng/ml) resulted in a decrease in 125I-EGF binding, with its level being low until entering the S-phase. Under these conditions, receptors disposed on the plasma membrane presented a homogeneous population (KD = 8.10(-11) M, 14,000 receptors per cell). No reliable difference was revealed between the EGF-receptor complexes, internalized in early and late G1 phases, in respect to the internalization rate, level of recycling, degradation, and dynamics of compartmentalization. However, endocytosis of EGF-receptor complexes was found to be completely blocked in mitosis at the stage of internalization.     

Magnesium ions prevent development of hyperkinesis produced by picrotoxin intrastriatal microinjections into the rat neostriatum

The effects of daily bilateral microinjections of GABA-A receptor antagonist picrotoxin (2 mcg) into rostral neostriatum of the rats in chronic experiments were investigated. The picrotoxin was injected in volume of 1 mcl of saline or in 1 mcl of 1.0 M or 1.5 M MgCl2 solution; 1 mcl of saline or 1.0 M MgCl2 solution were injected in control groups of animals. The impairment of the avoidance conditioning in shuttle box, changes in free locomotor activity and the stereotypic choreo-myoclonic limb jerks were registered in rats with picrotoxin with the saline microinjections. The motor deviation registered are similar with Huntington chorea hyperkinesis in humans. The addition of magnesium ions into injected solution prevented both the lyperkinesis and condition behaviour realization impairment. As the magnesium is a universal calcium channel blocker, the calcium homeostasis of striatal neurons impairment as one of principal elements of hyperkinesis pathogenesis is proposed.