Characteristics of the maintenance of the upright posture in subjects touching an external object while standing on a moving or immobile platform

Postural sway was compared for humans touching an external object while standing on an immobile or slowly moving posturographic platform. When the platform moves, the central nervous system may interpret the movement of the point of the contact with the external object as the movement of the body relative to the support or as the movement of the support itself. Thus, the information concerning the body position that is provided by the touch becomes ambiguous. It was demonstrated that contact with an external object during standing on an unstable support leads to a decrease in support sway. When a subject stands on a moving platform, this decrease is smaller than in the case of an immobile platform. Contact with an external object causes a decrease in postural responses to shank muscle vibrations on an immobile platform. On a moving platform, this decrease is nonsignificant. The change in postural sway depending on the unambiguity of afferent information is discussed in terms of the interaction between afferent signals of different modalities on the basis of the body scheme in subjects maintaining balance.Translated from Fiziologiya Cheloveka, Vol. 31, No. 1, 2005, pp. 59–65.Original Russian Text Copyright © 2005 by Kazennikov, Shlykov, Levik.     

Topography of the C terminus of cytochrome b5 tightly bound to dimyristoylphosphatidylcholine vesicles

Cytochrome b5 holoenzyme was bound asymmetrically in the tightly bound form to small unilamellar dimyristoylphosphatidylcholine vesicles. [3H]Taurine, a membrane-impermeant nucleophile, was added to the external medium and was then cross-linked to cytochrome carboxyl residues by the addition of a water-soluble carbodiimide. Nonpolar peptide was isolated after trypsin digestion of taurine-labeled apocytochrome b5 and contained 1.7-1.9 residues of taurine. The C-terminal tetrapeptide containing residues Thr130-Asn133 was generated by chymotryptic hydrolysis of radiolabeled nonpolar peptide and was purified by gel filtration and ion exchange chromatography. Amino acid analysis of the C-terminal tetrapeptide showed that about 1.6 mol of taurine was cross-linked per mol of peptide. When the experiment was performed with taurine trapped inside the vesicles, no cross-linking was observed. The results suggest that when cytochrome b5 holoenzyme is bound to vesicles in the tight binding form, the C terminus is located on the external surface of the vesicles.     

Comparative tissue ascorbic acid studies in fishes

Comparative tissue ascorbic acid levels in four species of major carp viz., Labeo rohila, L. calbasu, Cirrhina tnrigala and Catla catla , were investigated. The ascorbic acid level was found to be the highest in the spleen in the four species studied (range 430–380 μg/g) followed by the anterior (adrenal) kidney, gonads, liver, renal kidney, brain and/or eye. Heart and blood had the lowest levels (range 26–18 μg/ml) amongst the tissues studied. Overall tissue ascorbic acid levels were the highest in L. rohita and the lowest in C. mrigala . Investigation on seasonal variations in blood and kidney ascorbic acid levels of Notopterus notopterus revealed peak levels in spring (February-April) and the lowest levels in the postspawning period (August-September).     

Parathyroid hormone stimulates adenylate cyclase in rat cerebral microvessels

We have studied the effect of parathyroid hormone (PTH) on adenylate cyclase of microvessels isolated from rat cerebral cortex. Native bovine (b) PTH-(1–84), the synthetic amino-terminal fragment bPTH-(1–34) and the synthetic analog [Nle⁸, Nle¹⁸, Tyr³⁴]-bPTH- (1–34) amide stimulated adenylate cyclase in a dose-dependent manner with apparent ED₅₀ values of 16 nM, 6.3 nM and 15 nM respectively. The stimulation by bPTH was greatly enhanced by guanosine triphosphate. The PTH antagonist, [Nle⁸, Nle¹⁸, Tyr³⁴]-bPTH-(3–34) amide inhibited the action of bPTH-(1–84) and bPTH-(1–34). In summary, PTH stimulated adenylate cyclase in rat cerebral microvessels in a very similar manner to its stimulation in the renal cortex.     

Phenotype modulation in primary cultures of arterial smooth-muscle cells. Dual effect of prostaglandin E1

The effects of prostaglandin E1 (PGE1) on the phenotypic state of enzymatically isolated arterial smooth-muscle cells in primary culture were studied by transmission electron microscopy, thymidine autoradiography, and cell counting. Early in culture (day 0-2), PGE1 stimulated conversion of the cells from contractile (less euchromatic nucleus and cytoplasm dominated by myofilament bundles) to synthetic state (more euchromatic nucleus and cytoplasm dominated by cisternae of rough endoplasmic reticulum and a large Golgi complex). The rate of entrance of the cells into DNA synthesis and mitosis was also increased at this time. Later on (day 3-6), when the majority of the cells had entered synthetic state, PGE1 inhibited DNA synthesis and cellular proliferation. These observations indicate that the effect of prostaglandins on arterial smooth muscle is dual in nature and dependent on the state of differentiation of the cells.