Surekha Bhat

Seasonal Variations in Markers of Stress and Oxidative Stress in Rats

High ambient temperature has been reported to increase oxidative stress by increasing lipid peroxidation and decreasing antioxidant defence in transition dairy cows. It is also known to cause an increase in plasma cortisol levels in goats, European hedgehog and human volunteers. High levels of glucocorticoids have been reported to decrease blood glutathione and erythrocyte superoxide dismutase activity in rats. Although institutional animal houses in research laboratories of developed countries maintain animals in air-conditioned rooms at constant temperature, the same is not true of animal houses in the developing countries especially those belonging to smaller institutions and this could affect the results of the experiments being conducted on these animals. The present research study was done to assess the effects of seasonal variations on the status of erythrocyte oxidative damage, antioxidant defence and plasma cortisol levels in adult female Wistar rats. Rats were kept in their home cages and were left in non-air-conditioned procedure rooms in two different seasons, Hot season (March-May) and Cool season (June to September). Erythrocyte Thiobarbituric acid reactive substances and plasma cortisol levels were significantly increased in rats exposed to high ambient temperature and humidity of the hot season as compared to the rats of the cool season. Erythrocyte reduced glutathione levels, erythrocyte glutathione peroxidase and superoxide dismutase activities were significantly decreased in the hot season group of rats. The results of our experiments showed that exposure of adult female Wistar rats to high ambient temperature and humidity of the hot season increases neuroendocrine stress, oxidative stress and decreases antioxidant defence in them.

Inverse Independence Number of a Graph

The concept of inverse domination was introduced by Kulli V.R. and Sigarakanti S.C. [9] . Let D be a  - set of G. A dominating set D1  V- D is called an inverse dominating set of G with respect to D. The inverse domination number   (G) is the order of a smallest inverse dominating set. Motivated by this definition we define another parameter as follows. Let D be a maximum independent set in G. An independent set S  V- D is called an inverse independent set with respect to D. The inverse independence Number β0-1(G) = max { S : S is an inverse independent set of G}.We find few bounds on inverse domination number and also initiate the study of the inverse independence number giving few bounds on inverse independence number of a graph.

Effect of varying durations of pyramid exposure — an indication towards a possibility of overexposure

Miniature replicas modeled after the Great Pyramid of Giza are believed to concentrate geoelectromagnetic energy within their cavities and hence act as antistressors in humans and animals. Although there are not many reports of adverse effects of ‘overexposure’ in the pyramid, subjects have claimed to feel uneasy after certain duration of staying in the pyramid. The present study was aimed to analyze the effects of prolonged pyramid exposure on plasma cortisol level, markers of oxidative damage and antioxidant defense in erythrocytes of adult female Wistar rats. Rats were divided into three groups, normal controls (NC, n=6) that were maintained under standard laboratory conditions in their home cages, pyramid exposed group-2 (PE-2, n=6) & pyramid exposed group-4 (PE-4, n=6) where the rats were housed under the pyramid for 6 hours/day for 2 weeks and 4 weeks respectively. Plasma cortisol and erythrocyte TBARS levels were significantly lower in both PE-2 and PE-4 rats and erythrocyte GSH levels and GSH-Px activity were significantly higher in them as compared to the NC rats. There was no significant difference in the results for these parameters between the PE-2 and PE-4 rats except for erythrocyte GSH-Px activity which was significantly more in the PE-2 rats than in the PE-4 rats. Although these results don’t confirm any adverse effects of prolonged exposure in pyramids, they indicate a possibility of such adverse effects.

RELATIONSHIP BETWEEN BLOCK DOMINATION PARAMETERS OF A GRAPH

Two vertices u, w ∈ V, vv-dominate each other if they are incident on the same block. A set S ⊆ V is a vv-dominating set (VVD-set) if every vertex in V – S is vv-dominated by a vertex in S. The vv-domination number γvv = γvv(G) is the cardinality of a minimum VVD-set of G. Two blocks b1, b2 ∈ B(G) the set of all blocks of G, bb-dominate each other if there is a common cutpoint. A set L ⊆ B(G) is said to be a bb-dominating set (BBD set) if every block in B(G) – L is bb-dominated by some block in L. The bb-domination number γbb = γbb(G) is the cardinality of a minimum BBD-set of G. A vertex v and a block b are said to b-dominate each other if v is incident on the block b. Then vb-domination number γvb = γvb(G) (bv-domination number γbv = γbv(G)) is the minimum number of vertices (blocks) needed to b-dominate all the blocks (vertices) of G. In this paper we study the properties of these block domination parameters and establish a relation between these parameters giving an inequality chain consisting of nine parameters.