Comparison of Two Shoot--Root Partitioning Models with Respect to Substrate Utilization and Functional Balance

A transport resistance model for shoot—root partitioningby Thornley and a more aggregated partitioning model by Reynoldsand Thornley are compared. Three functional forms of substrateutilization are applied, corresponding to different assumptionson the ability of carbon and nitrogen to compensate one anotherin promoting structural growth. On the basis of simulationsat balanced exponential growth, it is shown that the Reynoldsand Thornley model (in optimal form) is embedded in the Thornleymodel. Davidson's functional balance is studied as a functionof the degree of carbon-nitrogen compensation. The applicabilityof the models and the utilization functions is discussed. Model, shoot-root partitioning, substrate utilization, functional balance     

An antioxidant prevents and reverses calcium-induced uncoupling of rat liver mitochondria

Accumulation of Ca2+ by rat liver mitochondria in the presence of inorganic phosphate results in spontaneous activation of respiration accompanied by a progressive loss of the accumulated cation. The lipid peroxidation inhibitor, ionol, completely prevents and reverses the Ca2+/phosphate-induced loss of accumulated Ca2+ and restores the respiration to state 4 level without having any effect on the rate of Ca2+ accumulation and respiration in the presence of an uncoupler. No correlation between the ionol-dependent loss of Ca2+ and the formation of malonic dialdehyde in mitochondria was found. The measurements of delta psi across the inner mitochondrial membrane during a progressive loss of Ca2+ suggest that the Ca2+/phosphate-induced "uncoupling" is mainly due to the appearance of electrogenic fluxes (but not Ca2+ cycling) which is under control of some products of initial steps of lipid peroxidation.     

Role of protein kinase C in regulating smooth muscle electrical and contractile activity: the effect of phorbol ester

The effects of protein kinase C activation by 12-O-tetra-decanoyl-phorbol-13-acetate (TPA) on the functions of guinea-pig smooth muscle taenia coli have been studied, using double-sucrose-gap method. A 15-20-min treatment of the muscle with 2 X 10(-8) M TPA caused a progressing inhibition of spontaneous electrical activity and mechanical tension, suppression of post-hyperpolarizing electrical and contractile "off-responses", a decrease in the number of action potentials during superthreshold membrane depolarization, depression of electrical and mechanical responses induced by acetylcholine, histamine, bradykinin mediators. The treatment of pre-depolarized (140 mM kappa+) muscle with 2.10(-8) TPA has led to a considerable reduction in contractile responses induced by the above mediators. The results obtained indicate that protein kinase C is capable of regulating both voltage-sensitive and receptor-operated ionic channels in smooth muscle cells.     

Effect of dibunol and isoptin on the creatine kinase and myoglobin content of the blood serum in dogs undergoing postischemic coronary reperfusion

The effect of an antioxidant dibunol and calcium antagonist verapamil on postperfusion release of myoglobin (Mb) and MB-creatine kinase (MB-CK) has been assessed in 30 dogs with experimental coronary occlusive myocardial infarction. It has been shown that reperfusion after 3-hour ischemia does not only accelerate the release of intracellular proteins, but also leads to pronounced myoglobinemia and blood enzymes. In postischemic blood flow recovery with combined dibunol and verapamil preliminary injections, an almost threefold decrease in MB-CK and Mb blood content, as compared to "reperfusion" indexes, was observed by the 10th minute of reperfusion.     

Rescue of developmental lens abnormalities in chimaeras of noncataractous and congenital cataractous mice

In the study of the lens of a congenital cataractous mouse mutant (CAT), it has been shown that a loss of growth regulation at the cellular level causes gross lens abnormalities. The phenotypic characteristics of the cataractous mouse lens are similar to those seen in human congenital cataract and thus serves as a model system for medical research. In this present investigation, we have demonstrated that the abnormalities of the congenital cataractous lens can be rescued by forming chimaeras between DBA/2 (a noncataractous strain of mouse) and the CAT mutant. This report describes the histological, cellular and biochemical analysis of the resultant chimaeric eyes, and discusses possible mechanisms by which these results were achieved.     

Induction of specific-locus and dominant lethal mutations in male mice by chlormethine

Chlormethine (WHO), a nitrogen mustard (2,2'-dichloro-N-methyldiethylamine), induces dominant lethal and specific-locus mutations in spermatozoa and spermatids of mice.     

Histochemical reaction to biogenic amines of the nervous system of the larval and mature cestode Microsomacanthus microskrjabini

Histochemical reaction with glyoxylic acid has revealed a specific fluorescence caused by the presence of indolamine (apparently serotonin) in the nervous system of larva and mature cestode. Fluorescence manifests itself in neurons and nerve fibres of the central ganglion and its commissure, in nerve cells of the proboscis, in longitudinal trunks and transverse commissures, and in the nerve elements connected with genital system.     

Characteristics of the distribution of birds infected with hemosporidians (Sporozoa, Haemosporidia) during the fall migration in flight waves

Chaffinches, infected with hemoproteids (Haemoproteidae) and leucocytozoids (Leucocytozoidae), are uniformly distributed in the ranges of each nonequivalent from the point of view of bioenergetics migratory wave. Extensiveness of infection of birds with leucocytozoids in autumn increases reliably at the time of late migratory waves as compared to early ones. The last flight wave, which is observed in the Kurskaya Kosa in the second half of October, consists, in general, of chaffinches which have already gone through the leucocytozoonosis. Concentration of infected birds at the end of the species migration flow can be regarded as a peculiar parasitic filter delaying the birds, which have been seriously ill, from flying away to wintering places at the most favourable periods. The thesis on different influence of hemosporidians on energetic balance of birds during spring and autumn migrations is substantiated. Hypothesis has been advanced on the causal relationship between high bird mortality during spring migration and the most high extensiveness and intensity of their infection with hemosporidians.