Acute liver failure (ALF) is known for extremely high mortality
rate, the result of widespread damage of hepatocytes. Orthotopic
liver transplantation is the only effective therapy but its
application is limited by the scarcity of donor organs. Given the
importance in the liver biology of Wnt/β-catenin signaling
pathway, we hypothesized that its stimulation could enhance
hepatocyte regeneration and attenuate the course of
thioacetamide (TAA)-induced ALF in Lewis rats. Chronic
treatment with Wnt agonist was started either immediately after
hepatotoxic insult (“early treatment”) or when signs of ALF had
developed (“late treatment”). Only 23 % of untreated Lewis rats
survived till the end of experiment. They showed marked
increases in plasma alanine aminotransferase (ALT) activity and
bilirubin and ammonia (NH3) levels; plasma albumin decreased
significantly. “Early” and “late” Wnt agonist treatment raised the
final survival rate to 69 % and 63 %, respectively, and
normalized ALT, NH3, bilirubin and albumin levels. In conclusion,
the results show that treatment with Wnt agonist attenuates the
course of TAA-induced ALF in Lewis rats, both with treatment
initiated immediately after hepatotoxic insult and in the phase
when ALF has already developed. Thus, the pharmacological
stimulation of Wnt/β-catenin signaling pathway can present
a new approach to ALF treatment.
Glucocorticoids (GCS) are known to modulate cardiovascular response during stress conditions. The present study was aimed to test the hypothesis that permissive and/or stimulating effect of GCs is essential for the maintenance of peripheral vascular resistance and for the adequate response of cardiovascular system to stressor exposure. The effects of acute pharmacological adrenalectomy (PhADX) on humoral and cardiovascular parameters were studied in adult Wistar rats under the basal conditions and during the acute restraint stress. Acute PhADX was performed by the administration of metyrapone and aminoglutethimide (100 mg/kg s.c. of each drug) resulting in a suppression of endogenous glucocorticoid synthesis. Blood pressure (BP), heart rate (HR) and core body temperature were measured using radiotelemetry. BP responses to administration of vasoactive agents were determined in pentobarbital-anesthetized animals. PhADX considerably attenuated stress-induced increase of BP, HR and core body temperature. PhADX did not abolish BP and HR lowering effects of ganglionic blocker pentolinium indicating preserved sympathetic function in PhADX rats. BP response to exogenous norepinephrine administration was attenuated in PhADX rats, suggesting reduced sensitivity of cardiovascular system. Suppression of corticosterone synthesis by PhADX increased basal plasma levels of ACTH, aldosterone and plasma renin activity in unstressed animals but there was no further increase of these hormones following stressor exposure. In conclusion, PhADX attenuated stress-induced rise of blood pressure, heart rate and core body temperature indicating an important permissive and/or stimulating role of glucocorticoids in the maintenance of the adequate response of cardiovascular system and thermoregulation to several stimuli including acute exposure to stressor.
A phase field model for anti-plane shear crack growth in two dimensional isotropic elastic material is proposed. We introduce a phase field to represent the shape of the crack with a regularization parameter ϵ>0 and we approximate the Francfort-Marigo type energy using the idea of Ambrosio and Tortorelli. The phase field model is derived as a gradient flow of this regularized energy. We show several numerical examples of the crack growth computed with an adaptive mesh finite element method.
In this paper, a bacterial foraging algorithm (BFA) has been used for null steering in the antenna radiation pattern by controlling only the element phases of a linear array. The BFA is an optimization algorithm based on the foraging behavior of Escherichia (E.) coli bacteria in human intestine. Numerical examples of Chebyshev pattern with the single, multiple and broad nulls imposed at the directions of interference are given to show the accuracy and flexibility of the BFA. The sensitivity of the nulling patterns due to small variations of the element phases is also investigated.
The second order linear difference equation (1) ∆(rk∆xk) + ckxk+1 = 0, where rk ≠ 0 and k ∈ ℤ , is considered as a special type of symplectic systems. The concept of the phase for symplectic systems is introduced as the discrete analogy of the Borůvka concept of the phase for second order linear differential equations. Oscillation and nonoscillation of (1) and of symplectic systems are investigated in connection with phases and trigonometric systems. Some applications to summation of number series are given, too.
The univoltine leaf miner Chromatomyia fuscula Zetterstedt is a Scandinavian cereal pest. We wanted to compare the phenology of C. fuscula in southern Norway with that of its most important natural enemies: 15 parasitoids of the families Eulophidae and Pteromalidae (Hymenoptera: Chalcidoidea). The use of two Malaise traps in an organically-grown spring barley field and its boundary through 6 seasons (1992-1997) also allowed us to compare these two habitats and to observe the effect of harvesting on the parasitoid activity without interference from pesticides. C. fuscula overwinters as an adult and oviposits in May/June. Few specimens of the next generation, emerging in the crop, were caught in the boundary traps, suggesting the fly hibernates elsewhere. In contrast, the F1 generation of the parasitoids was caught in considerable amounts both in the crop and boundary. The abundance of parasitoids was highest in July/August; in the crop it usually started decreasing well before harvesting; in the boundary it peaked two weeks or more after harvesting. The results suggest that many parasitoids (especially females) move from the crop to the boundary (or beyond) before harvesting. In both habitats parasitoid species richness usually increased until harvesting, and thereafter decreased. The pooled parasitoid female proportion was 0.36; in crop and boundary it was 0.30 and 0.66, respectively, and the majority of species had a higher proportion of females in the boundary than in the crop. The phenology of two of the most common parasitoids is presented: The pupal parasitoid Cyrtogaster vulgaris Walker (Pteromalidae) had a high activity in the boundary, also very early (females only) and late (both sexes) in the season. The larval parasitoid Diglyphus begini (Ashmead) (Eulophidae) was less active early and late in the season, and had a much smaller boundary activity than C. vulgaris. Both sexes were present throughout the season. The annual sex ratio of D. begini was density dependent, being highly male biased in the two years with highest catches. In C. vulgaris neither density nor habitat explained the sex ratio. D. begini probably overwinters inside the mine as a preadult, having one generation on C. fuscula in the crop and another one in an alternate host away from the habitats sampled here. C. vulgaris overwinters as fertilized females in the border habitat.