The role of biological needs in the genesis of self stimulation]

It has been found in fifteen rats with monopolar electrodes implanted in the lateral hypothalamus that after stimulation of the brain with bursts of electrical pulses of fixed duration, with definite combinations of stimulation parameters, the histograms of the duration of pedal pressing have a polymodal appearance. As the combinations of stimulation parameters change, the number, position and magnitude of the modes undergo a corresponding change. With unchanged parameters of stimulation the form of pressing duration histogram does not change significantly. A conclusion has been drawn that the modal duration of pressing in the course of self-stimulation is apparently an effector manifestation of central integration of reinforcing excitation. In a state of hunger and thirst as well as under weak nembutal anaesthesia, the previously monomodal histograms of the pressing durations produce additional modes which diminish and disappear after satiation and discontinuation of the nembutal effect. It is assumed that at least some modes of the histograms of the pressing duration of self-stimulation may reflect an activation of the systems of biological needs.     

The biological role of superoxide dismutase

Recent data available in literature on mechanisms for regulation of the activity of superoxide dismutase (an antioxidant enzyme) and its interrelation to other enzymes and antioxidants are generalized. The role of superoxide dismutase in the ontogenesis and under different pathologies accompanied by the formation of free radicals is considered.     

The biological properties of Bifidobacterium]

The possibility of the formation of exoenzymes, such as DNAase, RNAase and hemolysin, by bifidobacteria was studied in comparison with their acid-forming and adhesive activity. Bifidobacterium reference strains, originally isolated from healthy adults and children, were studied. The study involved altogether 73 strains of bifidobacteria, including 24 B. bifidum strains, 13 B. adolescentis strains, 7 B. infantis strains, 10 B. breve strains and 19 B. longum strains. The bifidobacteria under study were shown to differ not only in the presence and activity of properties useful for macroorganisms, but also in the presence of enzymes having depolymerizing activity (DNAase, hemolysin). Thus, out of 73 strains under study 9 proved to be DNAase-positive and 6, hemolysin positive. At the same time a specific feature of bifidobacteria was their high acid-forming activity with the complete absence of RNAase activity and insignificant DNAase- and hemolysin-forming activity.     

The integrating role of biological motivation in the realization of feeding and drinking behaviors]

In chronic experiments on rabbits with preliminary alimentary or water deprivation electrical and mechanic activity was studied of the chewer muscle proper and of the esophagus in the process of animals food or water taking. It has been established that in patterns of electrical and mechanic activity of the chewer muscle proper and esophagus specific differences of alimentary and drinking behaviour of animals are reflected. Dominating motivation of different biological properties determines the specific integration of motoneurones of chewing and swallowing centers and peripheral contraction elements of digestive tract in the functional systems of alimentary and drinking behaviour.     

The metabolism of estriol in rabbits

Rabbits have been shown to excrete 6, 7-³H-estriol, its conjugates and metabolites preponderantly in the bile during the initial 4 hours following the I.V. injection of the labeled steroid. The amount of radioactivity excreted in the urine was $\text{1}\text{3}$ of that in the bile. Since in intact rabbits most of the injected radioactivity of ³H-estriol is excreted in the urine over a period of days (and very little in the feces), it appears that estriol and its conjugates and metabolites are involved in an efficient enterohepatic. circulation. In the bile, the preponderant metabolite of ³H-estriol was the 3-glucosiduronate. Even though the latter constituted a substantial part of the urinary metabolites, other conjugates and metabolites of estriol were present in considerable amounts. It is possible that the latter have resulted from gastro-intestinal and/or renal metabolism. Incubation of rabbit liver with estriol led to 75% conjugation with glucuronic acid in the 3-position.     

Carnosine: biological role and prospects for use in medicine]

The biological role of the histidine-containing dipeptide carnosine (beta-alanyl-L-histidine) has been reviewed. The properties and putative biological role of the dipeptide in vertebrate tissues are considered. The antioxidative activity of carnosine and related compounds is described. The author's conception of the membranoprotective effect of carnosine on cells, tissues, and whole organism has been formulated. The properties of carnosine as an antistressory radioprotective agent are discussed. The data presented suggest that carnosine is a perspective immunomodulating tool which has many applications in medicine.     

The role of infectious diseases in biological conservation

Recent increases in the magnitude and rate of environmental change, including habitat loss, climate change and overexploitation, have been directly linked to the global loss of biodiversity. Wildlife extinction rates are estimated to be 100–1000 times greater than the historical norm, and up to 50% of higher taxonomic groups are critically endangered. While many types of environmental changes threaten the survival of species all over the planet, infectious disease has rarely been cited as the primary cause of global species extinctions. There is substantial evidence, however, that diseases can greatly impact local species populations by causing temporary or permanent declines in abundance. More importantly, pathogens can interact with other driving factors, such as habitat loss, climate change, overexploitation, invasive species and environmental pollution to contribute to local and global extinctions. Regrettably, our current lack of knowledge about the diversity and abundance of pathogens in natural systems has made it difficult to establish the relative importance of disease as a significant driver of species extinction, and the context when this is most likely to occur. Here, we review the role of infectious diseases in biological conservation. We summarize existing knowledge of disease-induced extinction at global and local scales and review the ecological and evolutionary forces that may facilitate disease-mediated extinction risk. We suggest that while disease alone may currently threaten few species, pathogens may be a significant threat to already-endangered species, especially when disease interacts with other drivers. We identify control strategies that may help reduce the negative effects of disease on wildlife and discuss the most critical challenges and future directions for the study of infectious diseases in the conservation sciences.     

The nature and biological role of near-weekly rhythm

Main peculiarities and possible mechanisms of the rhythms of proliferative activity and other characteristics of the tissue with near-weekly period are discussed. It is suggested that these variations may be explained by means of a simplest model which involves only processes of cell division and death with a delay of division stimulus about 24 hours, which corresponds to the duration of the mitotic cycle. In such a model there are periodic variations of the cell number with the period 4-7 times greater than the delay time.     

The biological age of the respiratory system]

A model of the biological age of the respiratory system is described. The following biological age determinants are used: vital lung capacity, maximal breathing capacity, mid-expiratory flow rate, oxygen consumption. They commonly meet the requirements of the biological age measurement tests as well as reflect main symptoms of the respiratory system ageing. The proposed model has been used to study the peculiarities of the respiratory system ageing in the Abkhasian population and to assess the effect of smoking on this process.