Acute, subacute and chronic effects of central neuropeptide Y on energy balance in rats.

Central neuropeptide Y (NPY) injection has been reported to cause hyperphagia and in some cases also hypometabolism or hypothermia. Chronic central administration induced a moderate rise of short duration in body weight, without consistent metabolic/thermal changes. In the present studies the acute and subsequent subacute ingestive and metabolic/thermal changes were studied following intracerebroventricular (i.c.v.) injections of NPY in cold-adapted and non-adapted rats, or the corresponding chronic changes following i.c.v. NPY infusion. Besides confirming basic earlier data, we demonstrated novel findings: a temporal relationship for the orexigenic and metabolic/thermal effects, and differences of coordination in acute/subacute/chronic phases or states. The acute phase (30-60 min after injection) was anabolic: coordinated hyperphagia and hypometabolism/hypothermia. NPY evoked a hypothermia by suppressing any (hyper)metabolism in excess of basal metabolic rate, without enhancing heat loss. Thus, acute hypothermia was observed in sub-thermoneutral but not thermoneutral environments. The subsequent subacute catabolic phase exhibited opposite effects: slight increase in metabolic rate, rise in body temperature, reaching a plateau within 3-4 h after injection -- this was maintained for at least 24 h; meanwhile the food intake decreased and the normal daily weight gain stopped. This rebound is only indirectly related to NPY. Chronic (7-day long) i.c.v. NPY infusion induced an anabolic phase for 2-3 days, followed by a catabolic phase and fever, despite continued infusion. In cold-adaptation environment the primary metabolic effect of the infusion induced a moderate hypothermia with lower daytime nadirs and nocturnal peaks of the circadian temperature rhythm, while at near-thermoneutral environments in non-adapted rats the infusion attenuated only the nocturnal temperature rise by suppressing night-time hypermetabolism. Further finding is that in cold-adapted animals, the early feeding effect of NPY-infusion was enhanced, whereas the early hypothermic effect in cold was limited by interference with competing thermoregulatory mechanisms.

Daily body temperature rhythm and heat tolerance in TRPV1 knockout and capsaicin pretreated mice.

Daily body temperature (DBT) rhythm of mice lacking one of the transient receptor potential (TRP) family of proteins, the capsaicin receptor or TRPV1, was recorded by biotelemetry and found to have significantly higher amplitude than that of wild-type mice. Capsaicin-desensitized wild-mice exhibited an even higher DBT amplitude than did TRPV1 deficient mice. A standard heat load (radiant temperature of 36-37 degrees C) resulted in similar rises in body core temperature in wild-type mice and in TRPV1 deficient mice, while capsaicin-desensitized wild-type mice exhibited a robust heat-intolerance. The lack of TRPV1 slightly modifies amplitude of daily body temperature rhythm but does not seem to influence physiological heat defence in mice. In vivo evidence for a TRP protein functioning in the physiological heat-defence range is still lacking.

Dual nature of the intracellular cations. Conductance of adsorbed intracellular cations in the region of microwave frequencies.

The majority of intracellular ions was "invisible" by classical conductance measurements over the regions of audio and radio frequencies. In the microwave region all the cations become "visible" in muscles. A non-invasive method is found to determine the cationic content of biological tissues. The better the physical condition of the muscle the greater the new parameter, the invisible cationic conductivity. 15% of the total cation content is released by thermal treatment that was probably associated with negative phosphate or carboxylate groups of the lipoid surface of the membrane structure. This K+ fraction in the frog muscle has been already discovered by three quite different methods.

Contraction due to bimetallic, short-lived super-coiling in the helical, double stranded filaments of striated muscle.

The possibility of a super-coiling of the thin filament is studied. The bimetallic super-coiling might contribute to the power-stroke. The calculation of the axial shortening of the proposed super-coiling leads to a very surprising geometric fitting: the maximal axial shortening of the super-coiling, without any loop, of the thin filament segment (38.5 nm) is equal to the axial repeat of cross-bridges (14 nm). According to the present model, the sarcomere shortening is caused by the axial shortening of the super-coiled actin filament. The top-view of the super-coiled segment shows a dual half-circle form. There are experimental evidences for such a type of formation in electron micrographs. According to this model, the widely accepted sterically hidrance model on association of actin and myosin can be neglected. One of the main roles of calcium is to make the thin filament segment flexible enough for the association.

Saturable, sodium-induced release of potassium in the muscle exposed to glycerol.

Investigating the kinetics of K+ efflux, two K+ fractions were found in the muscle exposed to 5.8 M glycerol solution at -12 degrees C. The minor K+ fraction was exchangeable with Na+. The amount of released K+ ions being in the K+/Na+ ion exchange was saturable with increase in the concentration of Na+ ion in the medium. It was 11 mmol K+/kg wet wt., which corresponds to the magnitude of the "medium" K+ fraction found by A. S. Troshin in the muscle by means of isotope technique. The minor K+ fraction was temperature and ouabain dependent. K+ fraction with similar features was found by W. Negendank in human lymphocytes, however, its magnitude was 120 mmol K+/kg w.wt. The ratio of the two magnitudes is equal to the ratio of the total cell surface of the muscle and the lymphocyte of one kg. From this fact, it can be concluded that the 11 mmol K+/kg fraction exchangeable with Na+ is bound directly to the cell membrane or to an unidentified structure near to the membrane surface. The preference of K+ binding at higher temperature is interpreted by the assumption that both K+ and Na+ bind to the binding sites of the 11 mmol/kg fraction with their hydration shells.

The kinetics of swelling in muscle exposed to hypertonic glycerol solution.

In frog skeleton muscle treated with glycerol, the efflux of the slow potassium fraction is four times faster than the hydration of macromolecules being a little faster than the total swelling process. The slow K fraction is assumed to exist in special salt linkages called intra- and intermolecular K bridges for describing the correlation between the solubilization of proteins and K release. Conformational change involving helix-coil transition and cooperative effects in the K release could produce together the time-lag between the efflux of slow K fraction and swelling of the muscle.

Kinetic investigation of K+ efflux during glycerol treatment of muscle.

The kinetics of K+ efflux was investigated in the membranes of frog sartorius muscle after disintegration by glycerol treatment. Data of the K+ concentration in the muscle as a function of time of the glycerol treatment fitted well the sum of two exponential fractions (with the correlation coefficient of more than 0.98). The half-lives of the two fractions of the K+ efflux were 1 and 75 hours respectively. On the basis of the value of its half life the efflux of the faster fraction was suggested to correspond to the free diffusion. At low temperature the magnitude of the faster fraction increased in a Na+-containing milieu. This could be due to K+-Na+ ion exchange. From the rate of loss of the slower fraction of K+ one finds that movement of K+ in cells without membranes is significantly slower than free diffusion. Presumably, part of the bound potassium exists in intra- or intermolecular "ion-bridges" of muscle proteins.

The effect of different alkali metal ions on the release of muscle potassium during glycerol treatment.

Frog sartorius muscles were pretreated in 11.6 M (87%) ion-free glycerol. Then half of them were put in 5.8 M glycerol solutions containing 55 mM LiCl, NaCl, RbCl or CsCl and their pairs in ion-free 5.8 M glycerol solutions at 1:40 Vol. muscle:Vol. solution ratio. The release of potassium during exposure to the 5.8 M glycerol solution was significantly faster in the presence of Li or Na, but significantly slower in the presence of Rb than in the ion-free circumstance. The effect of Rb can be related to a cooperative phenomenon that implies existence of a structured phase of K-protein complexes. Some postulates of Ling's association-induction hypothesis are used for interpretation of two phases and their phase transitions in this type of bound-K structure in muscle. The phase transitions in this system could have an important role in the fast processes of excitation in muscle.

Transmitters and/or metal atoms in muscle mechanics.

Acetylcholine in concentrations of 10-5, 2 x 10-5, 5 x 10-5 and 10-4 in normal Ringer's solution causes contracture of different muscles of Rana esculenta. The similar effect brought about by KCl solution does not necessarily mean the same basic process leading to similar changes in muscle mechanics. Experiments made on many particular questions of muscle mechanics will possibly clarify the real role of single factors (e.g. transmitters, kations, anions, acids, alkalis. ATP, heat etc.) changing the mechanical state of muscular organs.

Bound potassium in muscle II.

Experiments were performed to decide between the alternatives a) the ionized K+ is in a dissolved state in the muscle water, or b) a part of the muscle potassium is in a "bound' state. Sartorius muscles of Rana esculenta were put into glicerol for about one hour at 0-2 degrees C. Most of muscle water came out, but most of muscle potassium remained in the muscles. In contrast to this: from muscle in heat rigor more potassium was released due to glicerol treating than from the intact ones. 1. Supposition a) is experimentally refuted. 2. Supposition b) corresponds to the experimental results.

Bound potassium in muscle.

Joining to the debate on "bound" or "freely diffusible" muscle potassium, which is still going on nowadays, direct current was perfused through couples of semimembranous and sartorius muscles of frog for 0.5 to 1 hour. It was done in normal, fresh condition on one muscle, and on the other after having it over-stimulated with ac of 110 V supposing that a part of K is immobilly bound in fresh muscles, but in the overtired muscles a part of K is released and becomes mobile. As mobile K+ migrates to the negative electrode, we could really find a difference between the behavior of the K+ content of fresh and over-stimulated muscles, in so far as there was much more K in the overstimulated muscle near the negative electrode than near the positive one, as compared with the K content of the corresponding parts of normal muscle.