Effect of electrolytic lesion of the median raphe nucleus on behavioral and physiological measures of stress.

The effect of electrolytic lesion of the median raphe nucleus was measured on behavioral and physiological parameters related to stress 24 h after the lesion. In of the elevated plus-maze the lesion decreased the percentage of open arm entries and tended to shorten the time spent on the open arms indicating an increase in anxiety. In contrast, the lesion markedly increased the time spent in the bright (aversive) compartment of the light-dark box and decrease in attempts to cross from the dark toward the bright compartment, an anxiolyic effect. With the exception of plasma prolactin level, which was lowered by the lesion, the physiological measures used in the present study indicate that the lesioned animals are under stress. Thus, death rate and weight loss after the surgery were higher in lesioned than in control animals. In addition, lesioned animals showed higher plasma corticosterone levels, a high incidence of gastric ulcers in the fundus and a depressed immune response to the mitogen concavaline A. These results highlight the importance of the median raphe nucleus in the regulation of stress and anxiety. They also show that behavioral and physiological measures of stress may be dissociated.

The effect of changing the mode of ventilation on the arterial-to-end-tidal CO2 difference and physiological dead space in laterally and dorsally recumbent horses during halothane anesthesia

Objective - To evaluate the effect of changing the mode of ventilation from spontaneous to controlled on the arterial-to-end-tidal CO2 difference [P(a-ET)CO2] and physiological dead space (VD(phys)/VT) in laterally and dorsally recumbent halothane-anesthetized horses. Study Design - Prospective, experimental, nonrandomized trial. Animals - Seven mixed breed adult horses (1 male and 6 female) weighing 320 ± 11 kg. Methods - Horses were anesthetized in 2 positions - right lateral and dorsal recumbency - with a minimum interval of 1 month. Anesthesia was maintained with halothane in oxygen for 180 minutes. Spontaneous ventilation (SV) was used for 90 minutes followed by 90 minutes of controlled ventilation (CV). The same ventilator settings were used for both laterally and dorsally recumbent horses. Arterial blood gas analysis was performed every 30 minutes during anesthesia. End-tidal CO2 (PETCO2) was measured continuously. P(a-ET)CO2 and VD(phys)/VT were calculated. Statistical analysis included analysis of variance for repeated measures over time, followed by Student-Newman-Keuls test. Comparison between groups was performed using a paired t test; P < .05 was considered significant. Results - P(a-ET)CO2 and VD(phys)/VT increased during SV, whereas CV reduced these variables. The variables did not change significantly throughout mechanical ventilation in either group. Dorsally recumbent horses showed greater P(a-ET)CO2 and VD(phys)/VT values throughout. PaCO2 was greater during CV in dorsally positioned horses. Conclusions and Clinical Relevance - Changing the mode of ventilation from spontaneous to controlled was effective in reducing P(a-ET)CO2 and physiological dead space in both laterally and dorsally recumbent halothane-anesthetized horses. Dorsal recumbency resulted in greater impairment of effective ventilation. Capnometry has a limited value for accurate estimation of PaCO, in anesthetized horses, although it may be used to evaluate pulmonary function when paired with arterial blood gas analysis. © Copyright 2000 by The American College of Veterinary Surgeons.

Energetic and physiological correlates of prey handling and ingestion in lizards and snakes

In this review, we summarize the energetic and physiological correlates of prey handling and ingestion in lizards and snakes. There were marked differences in the magnitude of aerobic metabolism during prey handling and ingestion between these two groups, although they show a similar pattern of variation as a function of relative prey mass. For lizards, the magnitude of aerobic metabolism during prey handling and ingestion also varied as a function of morphological specializations for a particular habitat, prey type, and behavior. For snakes, interspecific differences in aerobic metabolism during prey handling seem to be correlated with adaptations for prey capture (venom injection vs. constriction). During ingestion by snakes, differences in aerobic metabolism might be due to differences in cranial morphology, although allometric effects might be a potentially confounded effect. Anaerobic metabolism is used for prey handling and ingestion, but its relative contribution to total ATP production seems to be more pronounced in snakes than in lizards. The energetic costs of prey handling and ingestion are trivial for both groups and cannot be used to predict patterns of prey-size selection. For lizards, it seems that morphological and ecological factors set the constraints on prey handling and ingestion. For snakes, besides these two factors, the capacity of the cardio-respiratory system may also be an important factor constraining the capacity for prey handling and ingestion. © 2001 Elsevier B.V.

Transient stability indices from a hybrid approach

This paper deals with hybrid method for transient stability analysis combining time domain simulation and a direct method. Nowadays, the step-by-step simulation is the best available tool for allowing the uses of detailed models and for providing reliable results. The main limitation of this approach involves the large time of computational simulations and the absence of stability margin. On the other hand, direct methods, that demand less CPU time, did not show ample reliability and applicability yet. The best way seems to be using hybrid solutions, in which a direct method is incorporated in a time domain simulation tool. This work has studied a direct method using the transient potential and kinetic energy of the critical machine only. In this paper the critical machine is identified by a fast and efficient method, and the proposal is new for using to get stability margins from hybrid approaches. Results from systems, like 16-machine, show stability indices to dynamic security assessment. © 2001 IEEE.

Influence of angiotensin II receptor subtypes of the paraventricular nucleus on the physiological responses induced by angiotensin II injection into the medial septal area

Objective - We determined the effects of losartan and PD 123319 (antagonists of the AT1 and AT2 angiotensin receptors, respectively), and [Sar1, Ala8] ANG II (a relatively peptide antagonist of angiotensin receptors) injected into the paraventricular nucleus (PVN) on water and 3% NaCl intake, and the diuretic, natriuretic, and pressor effects induced by administration of angiotensin II (ANG II) into the medial septal area (MSA) of conscious rats. Methods - Holtzman rats were used. Animals were anesthetized with tribromoethanol (20 mg) per 100 grams of body weight, ip. A stainless steel guide cannula was implanted into the MSA and PVN. All drugs were injected in 0.5-μl volumes for 10-15 seconds. Seven days after brain surgery, water and 3% NaCl intake, urine and sodium excretion, and arterial blood pressure were measured. Results - Losartan (40 nmol) and [Sar1, Ala8] ANG II (40 nmol) completely eliminated whereas PD 123319 (40 nmol) partially blocked the increase in water and sodium intake and the increase in arterial blood pressure induced by ANG II (10 nmol) injected into the MSA. The PVN administration of PD 123319 and [Sar1, Ala8] ANG II blocked whereas losartan attenuated the diuresis and natriuresis induced by MSA administration of ANG II. Conclusion - MSA involvement with PVN on water and sodium homeostasis and arterial pressure modulation utilizing ANGII receptors is suggested.

Morphological and physiological caste differences in Synoeca cyanea (Hymenoptera, Vespidae, Epiponini) according to the ontogenetic development of the colonies

Morphological caste differences in different stages of the biological cycle in Synoeca cyanea were not distinct. Females presented a gradual sequence in ovarian development from filamentous ovarioles to well developed ones with the presence of intermediates, with shorter ovaries than queens, which can be present or not according to the stage of colonial development. Such data suggest that access to the reproductive status would only be possible in some intervals of colonial development.

Performance and physiological parameters of broiler chickens subjected to fasting on the neonatal period

Broiler chicks aged 12 h after hatching were allotted according to a block design in a 7 x 2 factorial schedule of 14 treatments and four replications of 50 chicks each one. The main experimental factors were fasting for 0, 6, 12, 18, 24, 30, and 36 h after chick placement and sex. Independent of sex, fasting had a negative linear effect on weight and productivity of broilers at market age (42 d) without affecting feed conversion or mortality index. Groups subjected to 18 and 36 h of fasting after placement, corresponding to 30 and 48 h posthatching fasting, had lower biometrical values for small intestine (length, weight, and size; villus height; and crypt depth) than chicks fed immediately after placement. According to the Pearson test, BW of birds at 21 and 42 d were significantly correlated to BW at 7 d (r = 0.77) and 21 d (r = 0.45), respectively. Males performed better than females but had higher mortality rates. Fasting did not influence serum concentrations of corticosterone or sexual steroid hormones. Nevertheless, early signs of sexual dimorphism arose from the high estradiol (E2) concentration on female serum. Heterophil:lymphocyte ratio was not different among treatments, indicating that early fasting did not seem to be a stress factor 21 or 42 d after fasting. The results suggested a maximum fasting of 24 h after hatching in order to preserve broiler productivity at market age.

Influence of the colony cycle on physiological and morphological caste variation in the perennial neotropical swarm-founding social wasp, Protonectarina sylveirae (Hymenoptera, Vespidae, Epiponini)

This paper describes the influence of the colony cycle on caste differences in Protonectarina sylveirae. Despite invariably keeping the main aspects of the conspicuous dimorphism between the castes, it is shown that: 1- queen-worker differences varied according to the progress of the colony cycle, 2- queens in pre-emergence colonies were smaller than those in male-producing ones, 3- workers were larger in pre-emergence than in other colony stages, 4- at particular steps of the colony cycle, non-inseminated ovary-developed queens and workers were detected. The size of the spermatheca differed between inseminated and non-inseminated queens with the highest values appearing in those bearing the most developed kind of ovary development. Differences between inseminated and non-inseminated queens were found in tergites III and IV, ovarian development and amount of fatty tissues. Because tergite size relates to gaster size, this character may be an important stimulus for selection of larger queens in the course of the colony cycle.

Physiological responses associated with capture and crowding stress in matrinxã Brycon cephalus (Gunther, 1869)

The dynamics of plasma cortisol, blood glucose, plasma chloride and liver glycogen were investigated in matrinxã (Brycon cephalus) submitted to capture and various periods of crowding. A total of 400 fish (700 ± 22 g weight) were distributed in four ponds divided into four 50-m2 squares (25 fish/square, 350 gL-1), where they were acclimated for 30 days. On the sampling day, after 24 h without food, all fish from three squares were transferred to the fourth square. Six fish were sampled before the procedure (control group, zero time) and 1, 3, 6 and 24 h after the capture and crowding. Each sampling was performed in a different pond to prevent additional stress. Fish were anaesthetized and blood and liver collected for biochemical analysis. Water temperature, pH, dissolved oxygen, alkalinity, ammonia and nitrite levels were within acceptable levels for matrinxã rearing. Slight but not significant increases were verified in plasma cortisol and blood glucose levels, as were decreases in plasma chloride and liver glycogen levels. The results suggest that matrinxã is highly tolerant to the procedures of capture and short-term crowding.

Physiological responses of broiler chickens to heat stress and dietary electrolyte balance (sodium plus potassium minus chloride, milliequivalents per kilogram)

Individually caged male Cobb broilers (24), 44 d of age, were used to evaluate effects of heat stress (1 d of data collection) and dietary electrolyte balance (DEB; Na + K - Cl, mEq/kg from 1 d of age). During summer rearing, mortality was variable, but DEB 240 improved growth, feed conversion ratio, water intake, and waterrfeed ratio vs. DEB 0. The temperature sequence for heat stress was 24 to 32°C in 30 min, 32 to 36°C in 30 min, 36 to 37°C in 15 min, and 37 to 41°C in 45 min. Maximum temperature was held for 15, 60, 90, or 360 min for data collection (relative humidity averaged 42 ± 7%). Results from the same room before and after heat stress were analyzed by DEB (1-factor ANOVA) and before vs. after heat stress compared across DEB (2-sample t-test). Heat stress decreased blood Na, K, and pCO2, and lymphocytes but increased heterophils. Blood HCO3 rose, Cl declined, and hematocrit gave a concave pattern (lowest at DEB 120) as DEB increased. After heat stress, DEB O decreased blood Na and K, and DEB O and 120 levels decreased blood HCO3. After heat stress blood pCO2 and hemoglobin decreased with DEB 240, but it had highest pCO2, a key factor. The DEB 120 gave longest times to panting and prostration with DEB O and 240 results lower but similar statistically. In heat stress, DEB 360 was excessive, DEB 120 and 240 were favorable, and DEB 0 was intermediate based on hematology, panting, and prostration responses.

Neonatal rat exposure to pyrethroid and organophosphate insecticides: A physiological and biochemical trial of progeny

A manufactured product (Ectoplus®) composed by a cypermethrin (44.7%) and dichlorvos (4.2%) mixture was administered (10mg/kg/day, orally, by gavage) to pregnant rats, during the periods of gestation+lactation, gestation, and lactation. Control mothers received vehicle aqueous solution during the gestation+lactation period. With the progeny, in the 1-15 post-natal days (PNDI-15) there were observed alterations in the periods of occurrence of teeth, hair, unfolding of ears, and in the developmental period for following reflexes: postural, palmar grasp, negative geotaxis, and acoustic startle reflex. After weaning (PND21), there were observed the presence of cypermethrin and dichlorvos in the blood brain and liver; decrease in weight of liver, of cholinesterase activity in the plasma, liver, and brain, and hepatic metabolizing activity of drugs; alterations of levels of gamma glutamyl transferase enzymes, of creatinine, and of potassium in the serum of the animals. In conclusion, neonatal exposure to a formulated mixture of cypermethrin and dichlorvos is inductive to alterations in characteristics that indicate somatic and neuromuscular development of the progeny, and in certain biochemical parameters. The results suggest that enzymatic assessment associated with somatic and neuromotor assessment can be important markers of developmental characteristics in neonatal toxicity by pesticide formulations based on mixtures of insecticides.

Optimized allocation of sectionalizing switches and control and protection devices for reliability indices improvement in distribution systems

Reliability of power supply is related, among other factors, to the control and protection devices allocation in feeders of distribution systems. In this way, optimized allocation of sectionalizing switches and protection devices in strategic points of distribution circuits, improves the quality of power supply and the system reliability indices. In this work, it is presented a mixed integer non-linear programming (MINLP) model, with real and binary variables, for the sectionalizing switches and protection devices allocation problem, in strategic sectors, aimed at improving reliability indices, increasing the utilities billing and fulfilling exigencies of regulatory agencies for the power supply. Optimized allocation of protection devices and switches for restoration, allows that those faulted sectors of the system can be isolated and repaired, re-managing loads of the analyzed feeder into the set of neighbor feeders. Proposed solution technique is a Genetic Algorithm (GA) developed exploiting the physical characteristics of the problem. Results obtained through simulations for a real-life circuit, are presented. © 2004 IEEE.

A new method for real time computation of power quality indices based on instantaneous space phasors

One of the important issues about using renewable energy is the integration of dispersed generation in the distribution networks. Previous experience has shown that the integration of dispersed generation can improve voltage profile in the network, decrease loss etc. but can create safety and technical problems as well, This work report the application of the instantaneous space phasors and the instantaneous complex power in observing performances of the distribution networks with dispersed generators in steady state. New IEEE apparent power definition, the so called Buccholz-Goodhue apparent power, as well as new proposed power quality (oscillation) index in the three-phase distribution systems with unbalanced loads and dispersed generators, are applied. Results obtained from several case studies using IEEE 34 nodes test network are presented and discussed.

Physiological and cellular responses in two populations of the mussel Perna perna collected at different sites from the Coast of São Paulo, Brazil

The physiological conditions of mussels from Ubatuba and Santos and also of organisms transplanted from Ubatuba to Santos were studied by using different techniques. Assays for lysosomal stability were conducted on the haemolymph. Heart rate activity was monitored for 6h. The embryonic development of larvae obtained from the collected mussels was analysed. For all the compared groups of mussels, no significant differences were observed for the cardiac activity monitoring and the embryonic bioassays. The mean Neutral Red (NR) retention time was similar for the animals from Santos and Ubatuba, whereas the organisms transplanted to Santos showed a reduction in the retention time of the dye, indicating damage in the lysosomal membranes. These differences were possibly due to environmental factors, but further investigations are required to confirm this hypothesis.

Antimony glasses with large nonlinear refractive indices, small two-photon absorption coefficients and ultrafast response at telecom wavelengths

Nonlinear (NL) optical properties of antimony oxide based glasses (AG) were characterized for excitation wavelengths from 800 to 1600 m. The NL refractive indices, n2, and the two-photon absorption (TPA) coefficient, β, have been evaluated using the Z-scan technique. Values of n2≈ 10-15 - 10-14 cm2/W of electronic origin were measured and negligible TPA coefficients (β < 0.003 cm/GW) were determined. The response time of the nonlinearity is faster than 100 fs as determined using the Kerr shutter technique. The figure-of-merit usually considered for all-optical switching, T = 2βλ/n2 , indicates that AG are very good materials for ultrafast switches at telecom wavelengths. © 2007 IEEE.