Effect of high temperature and water stress on in vitro germination and growth in isolates of the entomopathogenic fungus Beauveria bassiana (Bals.) Vuillemin

In non-irrigated agricultural fields in tropical zones, high temperature and water stress prevail during the main cropping season. Natural epizootics of Beauveria bassiana on lepidopteran pests occur during winter. Application of B. bassiana during hot months when pest populations are at their climax may prove an effective management strategy. Therefore, 29 isolates of B. bassiana were tested for their ability to germinate and grow in temperature and water availability conditions prevailing during the pest season in these fields. The effect of temperature cycles with 8 h duration of high temperature fluctuating with 16 h duration of lower temperature (similar to field conditions); low water availability; and a combination of these two stress conditions was studied. Germination and growth assays were done at fluctuating temperature cycles of 32, 35, 38, and 42+/-1 degrees C (8 h)/25+/-1 degrees C (16 h) and in media with water stress created by 10, 20, 30, and 40% polyethylene glycol (PEG 6000). Assays set at a continuous temperature of 25+/-1 degrees C with no PEG in the medium served as controls. Stress was assessed as percentage germination or as growth relative to control. Isolates showing 90% growth relative to the control at temperature cycles including high temperatures of 35 and 38+/-1 degrees C were identified. One isolate (ARSEF 2860) had a thermal threshold above 43 degrees C. At 25 degrees C, all but one isolate of B. bassiana showed >90% growth relative to the control in 10% PEG (-0.45 MPa). Some isolates were found with >90% growth relative to control in medium having 30% PEG with water availability (1.33 MPa), nearly equivalent to that in soils which induce permanent wilting point of plants. When isolates that showed >90% growth relative to the control at both stress conditions, were stressed simultaneously, a decrease in growth was observed. Growth was reduced by approximately 20% at 35+/-1 degrees C (8 h)/25+/-1 degrees C (16 h) and 10% PEG and was affected to a greater degree in combinations of harsher stress conditions. The isolate ARSEF 2860 with a thermal threshold of >43 degrees C showed approximately 80% relative growth at a combined stress of 38+/-1 degrees C (8 h)/25+/-1 degrees C (16 h) and 10% PEG. These findings will aid the selection of isolates for use in field trials in hot or dry agricultural climates.     

Effect of propolis extract on acute carbon tetrachloride induced hepatotoxicity

Ethanolic extract of propolis was administered to rats intoxicated by carbon tetrachloride. Administration of bolus dose of CCl4 (1.5 ml/kg, ip) resulted in elevation of serum transaminases and serum alkaline phosphatase activities. Levels of hepatic lipid peroxidation were significantly increased. On the contrary, there was significant decrease in hepatic reduced glutathione level. The propolis extract (100 and 200 mg/kg, po) exhibited recoupment in both pre- and post-treatment (prophylactic and curative studies) of biochemical changes induced by CCl4. The post treatment of 200 mg/kg, po extract showed most significant hepatoprotective effect. Histopathological studies showed damage in hepatocytes and disturbed chord arrangement after toxicant administration. Propolis extract (200 mg/kg, po) was found to be more effective in restoring CCl4 induced histopathological alterations.     

Serotonin Turnover in Discrete Regions of Young Rat Brain After 24 h REM Sleep Deprivation

The present study has attempted to elucidate the alteration of serotonin turnover after 24 h REM sleep deprivation in different regions in brain of young rat. Sleep deprivation was induced by the inverted flowerpot technique. Results of this study show increased serotonin turnover after 24 h REM sleep deprivation in all the brain regions except in the hypothalamus. The decreased 5-HT ratio shows increased serotonin in the hypothalamus after 24 h sleep deprivation. This study indicates increased activity of serotonergic neurons in the hypothalamus after 24 h sleep deprivation. This also indicates that the hypothalamus plays a role in the immediate compensatory mechanism during 24 h REM sleep deprivation in young rats.     

Blood lipid profile and myocardial superoxide dismutase in swim-trained young and middle-aged rats: comparison between left and right ventricular adaptations to oxidative stress

Region-wise interactive effects of age, swim intensity, and duration on exercise performance in the myocardium and serum lipid profile in young (4 months) and middle-aged (12 months) rats were examined. Animals were allocated to the sedentary control (SE-C) or one of the nine trainee groups. Swim training was for 6 days/week and for 4 weeks at 3 durations (20, 40, and 60 min/day) and intensities (2%, low; 3%, medium; 5%, high). Swim velocity and external work showed an age-related decline with low-intensity of 20 min/day in the middle aged. Reduction in serum cholesterol, low-density lipoproteins (LDLs), and triglycerides were accompanied by elevated levels in high-density lipoprotein in the low-to-moderately trained ones for 20 and 40 min/day. Training at 2%, intensity for 20 min/day was sufficient to alter the blood lipid profile and improve swim performance, and endurance in terms of blood lactate. A concomitant increase in Mn-superoxide dismutase (Mn-SOD) activity and reduced malondialdehyde in the left ventricle (LV) and right ventricle (RV) were evident. Lipofuscin was higher in the LV compared to RV. Our results reflect the minimization of free radical generation through appropriate exercise protocols. Our findings on improved blood lipid profile could be related to lower free radicals, which would otherwise oxidize LDLs. Further, swim training when initiated in the young and middle age for as low as 20 min/day at 2% intensity improves the Mn-SOD in the LV and RV. However, the adaptive response of the LV was weaker when compared to the RV, more so in the middle aged.     

Siderophore Cross-Utilization Amongst Rhizospheric Bacteria and the Role of Their Differential Affinities for Fe3+ on Growth Stimulation Under Iron-Limited Conditions

The majority of bacteria isolated from rhizospheres of Arachis hypogea (Groundnut) and Vigna radiata (Mung bean) predominantly produced catechol-type siderophores except for a few fluorescent pseudomonads that produced hydroxamates in addition to catecholates. The rhizospheric isolates differed in their ability to cross-utilize siderophores produced by other rhizospheric isolates (heterologous); some were highly proficient at utilizing heterologous siderophores, while others were poor cross-utilizers. Isolate G9, which utilized hydroxamate as well as catecholate siderophores, was found to be an efficient siderophore cross-utilizer, while isolates G2 and G6 were poor-utilizers of catecholate and non-utilizers of hydroxamate siderophores. Growth stimulation of two isolates G9 and G6 was seen when grown in the presence of externally supplied heterologous siderophores, which they cross-utilized. The iron-regulated outer membrane protein (IROMP) profiles differed for the most cross-utilizer and the least cross-utilizer strains, but in both the cases no new outer membrane proteins (OMP) were induced in response to the exogenous siderophores supplied. The growth of the organisms in the presence of heterologous siderophores that they failed to cross-utilize led to growth inhibition in the case of isolate G9. This appears to be due to a lower affinity of the siderophore of G9 as compared to the exogenously supplied G6 siderophore. A simple method was devised to measure relative affinities of respective siderophores for iron based on CAS solution decolorization by the siderophore preparations. The effect on the growth of the differential affinities of the siderophores for iron and the interactions of the organisms through cross-utilization is also discussed.