NMR studies of L-dopa melanin-manganese(II) complex in water solution

The study of water relaxation rates of solutions of melanins with paramagnetic metal ions provides a powerful tool for investigating the binding sites and for obtaining useful structural and dynamic information. The measure of 1H- and 2H-longitudinal and transverse relaxation rates at a single, high-magnetic field for H2O/D2O (80:20) solutions allows the determination of tau c, tau R, tau e, tau M, r, q, and Z (the outer sphere contribution to the overall relaxation rate) for Mn(II)-L-Dopa melanin system.     

Changes in the amino acid sequence of hemagglutinin during sequential adaptation of human influenza virus A to replication in mice

The primary structure of hemagglutinin (HA) gene of Influenza virus A/USSR/90/77 (H1N1) variants after 3 and 11 passages has been determined. In the HA1 coding region of mice-adapted virus (11 passages) there are two amino acid substitutions: Thr 89----Ala and Asn 127----Asp. At the first stage of adaptation (3-rd passage) only a single mutation was detected: Asn 127----Asp. The adaptation is accompanied by the loss of specific carbohydrate attachment sites adjacent to the receptor-binding site located at HA1 subunit with a concomitant variation in antigenicity.     

The Effect of Academic Load and Work Conditions on the Sympathoadrenal Function and the Indices of Heart Rhythm Regulation in 17- to 18-Year-Old Girls

The dynamics of the sympathoadrenal function and the specific features of heart rhythm regulation were studied in female students and clothing factory female workers during their adaptation to academic and work conditions. Periods of the strongest functional tension in test systems were found in first-year students: the beginning of an academic year, the end of the first semester, and a period after winter examinations, all characterized by an increase in the central-circuit and sympathetic effects on sinus rhythm, acceleration of the heart rate, activation of sympathoadrenal mechanisms, and a decrease in sympathoadrenal reserves. The comparative analysis allowed us to disclose general trends typical of females of this age group such as the relative maturity of the sympathoadrenal system (SAS) and optimum correlation between autonomic and centralized heart rhythm regulation and to reveal the differences in the character and dynamics of functional shifts caused by a specific effect of academic load and work conditions. The degree of correlation between the indices characteristic of hormonal and mediator SAS mechanisms and the statistical characteristics of heart rhythm was proposed as the criteria for estimating the functional tension of the human body.     

Spectrophotometric determination of inorganic phosphate in the presence of thiol compounds

A spectrophotometric method for inorganic phosphate determination in the presence of thiol compounds is described. Thiol compounds, which interfere with the measurement of inorganic phosphate by a modification of the method of Gomori, are removed by carboxymethylation by iodoacetate prior to the formation and reduction of phosphomolybdate complex. A linear standard curve is obtained by this method, and the method is suitable for the assay of a phosphate-releasing enzyme when the measurement must be performed in the presence of thiol compounds.     

Effects of some protein kinases, cyclic nucleotides and specific inhibitors of phosphorylation on the mitotic cycle of Physarum polycephalum

The true slime mould Physarum polycephalum was treated with various agents by spraying them upon the cell surface 4 hrs before the second synchronous mitosis. The onset of mitosis was considerably approximated after the plasmodium treatment with protein kinases from rat hepatoma or Ph. polycephalum at the late G2 phase. The catalytic and regulatory subunits of cAMP-dependent pig brain protein kinase caused retardation of mitosis, while the holoenzyme, casein kinase and alkaline phosphatase did not affect the timing of mitosis. The cyclic nucleotides and inhibitors of their metabolic enzymes were used to investigate the role of phosphorylation processes in the mitotic cycle.     

Hypophysiotrophic thyrotropin releasing hormone (TRH) synthesizing neurons. Ultrastructure, adrenergic innervation and putative transmitter action

The neuropeptide thyrotropin releasing hormone (TRH) is capable of influencing both neuronal mechanisms in the brain and the activity of the pituitary-thyroid endocrine axis. By the use of immunocytochemical techniques, first the ultrastructural features of TRH-immunoreactive (IR) perikarya and neuronal processes were studied, and then the relationship between TRH-IR neuronal elements and dopamine-beta-hydroxylase (DBH) or phenylethanolamine-N-methyltransferase (PNMT)-IR catecholaminergic axons was analyzed in the parvocellular subnuclei of the hypothalamic paraventricular nucleus (PVN). In control animals, only TRH-IR axons were detected and some of them seemed to follow the contour of immunonegative neurons. Colchicine treatment resulted in the appearance of TRH-IR material in parvocellular neurons of the PVN. At the ultrastructural level, immunolabel was associated with rough endoplasmic reticulum, free ribosomes and neurosecretory granules. Non-labelled axons formed synaptic specializations with both dendrites and perikarya of the TRH-synthesizing neurons. TRH-IR axons located in the parvocellular units of the PVN exhibited numerous intensely labelled dense-core and fewer small electron lucent vesicles. These axons were frequently observed to terminate on parvocellular neurons, forming both bouton- and en passant-type connections. The simultaneous light microscopic localization of DBH or PNMT-IR axons and TRH-synthesizing neurons demonstrated that catecholaminergic fibers established contacts with the dendrites and cell bodies of TRH-IR neurons. Ultrastructural analysis revealed the formation of asymmetric axo-somatic and axo-dendritic synaptic specializations between PNMT-immunopositive, adrenergic axons and TRH-IR neurons in the periventricular and medial parvocellular subnuclei of the PVN. These morphological data indicate that the hypophysiotrophic, thyrotropin releasing hormone synthesizing neurons of the PVN are directly influenced by the central epinephrine system and that TRH may act as a neurotransmitter or neuromodulator upon other paraventricular neurons.     

Mobilization of iron from ferritin by isolated mitochondria effects of species compatibility between ferritin and mitochondria and iron content of ferritin

Mitochondria mobilize iron from ferritin by a mechanism that depends on external FMN. With rat liver mitochondria, the rate of mobilization of iron is higher from rat liver ferritin than from horse spleen ferritin. With horse liver mitochondria, the rate of iron mobilization is higher from horse spleen ferritin than from rat liver ferritin. The results are explained by a higher affinity between mitochondria and ferritins of the same species. The mobilization of iron increases with the iron content of the ferritin and then levels off. A maximum is reached with ferritins containing about 1 200 iron atoms per molecule. The results represent further evidence that ferritin may function as a direct iron donor to the mitochondria.     

Estimation of population parameters and their application to the development of fishery management models in two African rivers

The dynamics of fish populations in two African rivers are being investigated with a view to developing fishery management models for tropical non-floodplain rivers. Preliminary work was carried out in the Rufiji River, East Africa, to establish growth and mortality rates along with L _∞ and K for six species in a river where fishing mortality is zero. These parameters, derived from scale-reading and length frequency analysis, also allowed the development of phased management plans for the fishery resulting from impoundment.
A subsequent investigation has begun on a West African river, the Taia in Sierra Leone, to pursue observations over four seasons, two of which are now complete. A systematic daily sampling programme is being carried out of the whole community, to accumulate similar but more extensive data to those obtained previously. In the Taia, however, fishing mortality must also be estimated from catch surveys, and analysis is carried out using the recently developed ELEFAN programs which can be compared with results obtained by other methods such as scale-reading.     

Inactivation of microbial glutamin-(asparagin-)ase by azaserine and 6-diazo-5-oxo-L-norleucine

The effect of substrate analogues on glutamin-(asparagin-)ase from Pseudomonas aurantiaca-548 has been studied. The enzyme was demonstrated to be highly sensitive to the the action of 6-diazo-5-oxo-L-norleucine and azaserine. L-isomers of glutamine, aspartate, glutamate and several other substrate analogues with free alpha-amino groups protected the enzyme against the inhibitory DON effect. Thus, thorough preliminary selection of appropriate inhibitors, their dosage and treatment duration is needed for the recommendation of combined enzyme-inhibitor application in anti-tumour chemotherapy.