Binding of polonium-210 to liver metallothionein

The interactions of 210Po at the molecular level in biological systems have received little study even though this alpha-emitting radionuclide occurs widely in nature. Polonium-210 was given subcutaneously to rats and found to be incorporated into liver metallothionein as judged by a number of criteria including heat stability, acetone precipitation, and chromatography. In vitro studies confirmed this binding. The binding of 210Po to metallothionein has implications that may help explain some of the radiation damage 210Po causes intracellularly.     

Isoprenylation of proteins: what is its role?]

The role of mevalonate in the control of DNA synthesis during the cell cycle has been studied and has lead to the detection of isoprenylated proteins. These proteins are modified by a polyisoprenoid (farnesyl or geranylgeranyl) moiety via a thioether linkage. This modification is required for the following steps of the post-translational maturation of these proteins: proteolysis of the last three C-terminal amino-acids and carboxymethylation of the Cysteine-COOH. The isoprenylation could play a role in the membrane localisation of these proteins. Farnesylated proteins present a C-terminal CAAX domain. Moreover, the farnesylation is required for their biological activity independently of the membrane localization (Prelamine A, p21ras(Val 12)). Among geranylgeranyl proteins, two types of C-terminal sequences have been found: one with the motif CAAX, the other with the motif CC or CXC. In the last type, both Cysteines are geranylgeranylated. The hydrophobicity of the geranylgeranyl moiety leads to the membrane attachment, without any specificity. Moreover, geranylgeranylation as well as farnesylation seem important for protein-protein interactions. Among the identified isoprenylated proteins, the lamins, gamma-subunits of G proteins and the numerous (if not all) members of the Ras superfamily were characterized. The exact role of isoprenylation is still uncertain but it seems to affect the membrane localization and the protein-protein interactions.     

Fetal dexamethasone exposure impairs cellular development in neonatal rat heart and kidney: effects on DNA and protein in whole tissues

Fetal glucocorticoid exposure causes postnatal growth retardation. To examine the mechanisms underlying effects on specific organ systems, we administered 0.2 or 0.8 mg/kg of dexamethasone to pregnant rats on gestational days 17, 18, and 19 and assessed three biochemical markers of cell development in heart and kidney of the offspring: DNA content per organ as an index of total cell numbers, DNA per g tissue as an index of cell packing density, and protein/DNA ratio as an index of relative cell size. In both tissues, DNA content became markedly subnormal during the first postnatal week, the ontogenetic period of rapid cell division. Partial recovery occurred by the end of the first postnatal month. In the heart, cell packing density was subnormal initially and the cells were significantly enlarged. In contrast, packing density was slightly elevated in the kidney; protein/DNA was increased by the low dose of dexamethasone, but markedly decreased by the high dose. These results suggest that tissue growth impairment caused by prenatal dexamethasone treatment reflects primary deficits in cell proliferation that extend to a variety of different cell types; however, consequent effects on cell packing density and cell size are dose-specific, possibly reflecting actions of glucocorticoids selective for certain cell types or phases of cell development.     

The dopamine system in rat brain areas in the early period following irradiation with superhigh doses]

In studying the main indices that characterize the neurochemical system of biosynthesis and degradation of a dopamine neuromediator, tyrosine hydroxylase-dopamine-monoamine oxidase, in different brain regions 5-6 min, 1 and 18 h after whole-body irradiation with high energy electrons (100 Gy) the authors have revealed a 25-40% inhibition of tyrosine hydroxylase and monoamine oxidase activity, and a 40% increase in the dopamine content of basal ganglia of the brain that control behavioural reactions of the organism. The neurochemical disturbances revealed are involved in the mechanisms of early transient incapacity after irradiation with superhigh doses.     

Diagnosis of coronary artery restenosis after radiologic endovascular dilatation]

Altogether 40 patients with stable angina of effort were investigated in a long-term period after roentgenovascular dilatation of one or two coronary arteries. Control coronarography was performed in 22 patients with lowered exercise tolerance. A reliable feature in the development of hemodynamically significant restenosis and/or "new" coronary stenosis in 11 patients was a combination of average and low exercise tolerance with its negative dynamics. For patients with I functional class, a sign of restenosis and/or "new" stenosis was the appearance of the ischemic shift of the CT-segment on ECG during bicycle testing. An efficient selection of patients resulted in increased sensitivity and specificity of noninvasive tests.     

Echotomography in the diagnosis of pleural effusion]

USI of the pleural cavities was performed in 119 patients (65 men and 54 women) aged 30 to 90 with different abnormalities. Pleural fluid in 106 patients was the leading symptom of the main pathological process, in 13 patients it was a sign of pleural disease. USI was combined with routine x-ray methods. Minimum amounts of pleural fluid could be clearly visualized by ultrasound scanning. Echo-tomographic symptoms of free and encapsulated fluid as well as ultrasound signs permitted differentiation of pleural thickening and exudate accumulation. A program of diagnostic algorithm was worked out for pleural fluid.     

The effect of cycloheximide on the entry into the S period of the nuclei in heterodikaryons]

Serum-deprived (0.2%) resting NIH 3T3 mouse fibroblasts were fused with serum-stimulated (10%) proliferating cells to elucidate mechanisms of entering into S-period operating in the nuclei of the heterokaryons under the effect of cycloheximide--an inhibitor of protein synthesis. Using radioautography DNA synthesis was investigated in mono-, homo- and heterodikaryons. After short (0.5-3.0 h) depressing of protein synthesis, the nuclei of stimulated cells in heterokaryons were found to enter into S-period. Under these conditions no induction of DNA synthesis was found in the nuclei of resting cells in heterodikaryons. In other experiments, resting cells were under the effect of cycloheximide during 2-4 h before the fusion, that led to a great induction of DNA synthesis in the nuclei of these cells in heterodikaryons. The data obtained are consistent with the idea of fibroblast transition to the rest under the action of labile proteins-repressors.     

The recovery of the reactivity of the auditory system in the dolphin Tursiops truncatus to paired acoustic stimuli with different spectra]

Recovery cycles of the auditory brainstem responses were studied in the bottle-nosed dolphin, Tursiops truncatus, using paired acoustic clicks. The recovery time was longer if both clicks had identical spectra (50% recovery at 0.9 ms), as compared with that of different spectra (50% recovery at 0.35 ms). These results can explain a different recovery time of evoked responses after an artificial sound and after own locating one.     

Osmotic and ionic homeostasis in insects and vertebrates under extreme influences on water-salt metabolism]

Dehydration which is accompanied by the decrease in the body mass of frogs and pigeons approximately by 10%, results in the corresponding increase in osmolality of the blood serum, as well as in the increase of sodium content of the latter. Under the same conditions, the increase in osmolality and sodium level in rats does not exceed 2% which is associated with the effective renal function. In caterpillars of the insect Vanessa urticae whose haemolymph is rich in organic osmotically active substances and potassium ions, in spite of dehydration and loss of the body mass, osmolality of the haemolymph slightly decreases, while cation concentration in the latter remains essentially constant. Experiments with injections of hyperosmotic solutions to rats and caterpillars, showed that these animals, belonging to different phylogenetic branches, exhibit highly effective physiological mechanisms of ionic and osmotic homeostasis.     

Variation of glycine-activated conductivity of the membranes of spinal cord neurons in the chick embryo in culture

The method of leading off whole-cell currents is used to study the neuron responses elicited by applications of glycine at different stages of culturing of the chick embryo dissociated spinal cord. For two types of cells described earlier [4] differently directed shifts of the concentration dependence curves of the transmitter effect are shown to be characteristic. "Mature" cells, surviving several days in culture and represented by motoneurons, typically show a lowered sensitivity to glycine. The sensitivity of little-differentiated neurons increases more than tenfold by the end of the second week of culturing. The desensitization kinetics of the glycine-activated current also slows down with age. Blocking of the spontaneous electrical activity during development prevented these changes, and the presence of agonist in the culture medium did not affect them. Analogous patterns of formation of transmitter sensitivity are assumed to be exhibited by differentiating neurons of the intact nervous system.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 5, pp. 580–587, September–October, 1991.