Tyrosine and methionine metabolism in various states of melaninogenesis

Excretion with urine of tyrosine and methionine metabolites as well as the activities of enzymes involved in their metabolism are correlated with the state and type of melanin synthesized in the skin. The response of tyrosine aminotransferase to melaninogenesis induction was more pronounced in animals with predominant pheomelaninogenesis, especially after tyrosine load, while that to dopachrome oxidoreductase--in animals with predominant eumelaninogenesis and after methionine load. Glutathione reductase and cystathionine-beta-synthase responded more vigorously to methionine injections, which was especially well pronounced in animals with prominent pheomelaninogenesis and in albino animals. The metabolic "block" in melanine synthesis in albino animals seems to be observed after the 5-S-cysteinyl-DOPA synthesis, whereas the initial steps of melaninogenesis in these animals are identical to pheomelanine synthesis reactions.     

Participation of the thalamic reticular nucleus in the shaping of the interrelations of the mesencephalic reticular formation and the lateral geniculate body

On the awake rabbits and cats under nembutal anesthesia it has been shown that the reticular nucleus of the thalamus takes considerable part in the formation of reticulogeniculate response of the lateral geniculate body (LGB) to electrostimulation of the mesencephalic reticular formation. It is assumed that the reticular nucleus of the thalamus takes basic part in a realization of "rapid" physical influences of the reticular formation on the LGB.     

Changes in the osteoinductive activity of the bone matrix in ontogeny

Correlation between the animal's age, degree of mineralization of its bone tissue and the osteoinductive activity of the bone organic matrix was established in experiments with rats of the same litter at an age of 2, 4, 8, 16 weeks. The osteoinductive activity was estimated by the capacity of matrix to induce ectopic osteogenesis using biochemical methods. Bone mineralization increased and the capacity for osteoinduction decreased roughly 1,5-fold with the age of donor animals. It is suggested that the reduction of osteoinductive potencies is based on the decrease in lability of the bond between the protein osteoinducer and the collagen matrix, as shown by unequal sensitivity of bone matrix of rats of different age to the doubling of the shortest possible time of bone demineralization.     

Fleas of the eastern Kyzyl Kum and their epizootic significance]

The fauna of fleas in the East Kisil-Kum includes 24 species. Different physicogeographic regions of sands are characterized by different spectra and number of species of fleas. The greatest share in collections is composed by Xenopsylla gerbilli caspica--the parasite of Rhombomys opimus. In autumn the other parasite of this rodent, Coptopsylla lamellifer, is a mass species. All the most significant and long changes in the number of these species are associated with changes in the density of their hosts' population. The most significant in epizootic respect is the flea X. gerbilli caspica from which about 50% of plague agent cultures were isolated.     

Effect of intracellular administration of L-tyrosine and L-phenylalanine upon voltage-dependent calcium current in PC 12 pheochromocytoma cells

Using the voltage clamp technique under conditions of intracellular perfusion, we investigated changes in high-threshold voltage-dependent calcium current (I_Ca) in the surface membrane of PC 12 cells caused by intracellular administration of the aromatic amino acids L-tyrosine and L-phenylalanine. Administration of L-tyrosine (20 mmole/1) prevented decrease in I_Ca caused by perfusion of the cell with an artificial saline solution and had a transient restorative effect upon the cell. Administration of L-phenylalanine (20 mM) quickened the decrease in amplitude of I_Ca observed in the control. These effect of aromatic amino acids are maintained when ATP (2 mM) in the intracellular solution is replaced by an equivalent quantity of ADP. The tyrosine hydroxylase blocker -methyl D,L-tyrosine (20 MM) had an effect upon I_Ca analogous to that of L-tyrosine.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 1, pp. 105–111, January–February, 1991.     

Microbial colonization and succession in the large intestine of newborn infants during their stay with mothers at the maternity hospital]

Formation of microflora in the large intestine of 5-day old infants was studied in one of the Moscow maternity homes. The up-to-date procedures for isolation and identification of aerobic and anaerobic organisms were used in the study and the findings were processed on a computer. In the newborns of the maternity home of the "mother-infant" type there was observed colonization of the large intestine with aerobic and anaerobic organisms. A wave-like dynamics in the formation of the symbiotic microflora was revealed. It reflected the phenomenon of the microbial succession in the infants. The attempts to detect microbial interference between the species colonizing the large intestine showed that it was extremely rare in the 5-day old infants. This was likely the reason of the low intestine resistance to the colonization in the newborns which in its turn defined the frequent colonization of the intestine mucosa with S. aureus and the organisms of the Klebsiella, Enterobacter and Citrobacter group.     

Microbial colonization and succession on the faucial mucosa in newborn infants rooming in with their mothers in a maternity hospital]

The formation of microflora on the laryngeal mucosa in newborn infants during the first 5 days of their life was studied in one of the maternity hospitals of Moscow. In this work modern methods of the isolation and identification of aerobic and anaerobic microorganisms were used, and the results thus obtained were computer-processed. In the maternity hospital of the "mother-child" type the microbial colonization of the laryngeal mucosa by normal and opportunistic microorganisms was noted in newborn infants. A wave-like course of the formation of laryngeal microflora, indicative of microbial succession occurring in the child, was revealed. The attempt to establish the cases of microbial interference between the species colonizing the laryngeal mucosa revealed that it was very rarely observed in 5-day-old newborns. This feature was seemingly the cause of low resistance of the larynx to colonization in newborn infants, which determined frequent colonization of their laryngeal mucosa with Staphylococcus aureus and Klebsiella.     

Increased number of nucleoli in the salivary gland cells of Drosophila melanogaster under conditions of rDNA dose compensation

A considerable increase in the number of nucleoli non-associted with the nucleolar organizer (NO) was shown in the salivary gland cells of Drosophila melanogaster mutants, heterozygous for a deficiency of NO. The frequency of formation of additional nucleoli increased with the raising of the chromosome polyteny level. By means of in situ hybridization we showed that in the mutant and the wildtype polytene cells the ribosomal DNA (rDNA) of these unlawful nucleoli included ribosomal gene repeats (18S+28S) with two types of insertions: ivs-I and ivs-II Such additional nucleoli can be attached to varying sites of the polytene chromosomes containing type I insertion sequences.     

The causes of hydration changes during DNA protonation

Changes of DNA hydration provoked by protonation in the way of Na+- and H+-ions exchange, and in the way of HCl addition to Na+-DNA, were analysed by IR-spectroscopy. Water is shown not to contribute essentially to the formation and stabilization of conformations arising when DNA is protonated. The differences between hydratation of DNA protonated by different ways are in the main accounted for by alteration of the quantities of Na+ and Cl- ions forming the aqueous-salt envelope of polynucleotide.     

Stereochemistry and kinetics of interaction with DNA of the antineoplastic antibiotic olivomycin

The kinetics of interaction of antitumor glycoside antibiotic olivomycin with DNA has been investigated. The existence of two relaxation times in the experimental kinetics curves indicates that two types of antibiotic--DNA complex are formed. We have measured the rate constants of association and dissociation processes and determined their temperature dependences. It is suggested, that one of the complex form results from nonspecific interaction between glycoside residues of the antibiotic molecule and sugar-phosphate backbone of DNA whereas the other type of complex exhibits a pronounced specificity for GC-rich regions on DNA. The binding specificity probably results from formation of a H-bond between the antibiotic chromophore ring and guanine 2-amino group. A stereochemical model for olivomycin-DNA complex is proposed. According to this model the antibiotic chromophore and glycoside residues are located in the narrow groove of DNA.