Daily variation in melatonin level, antioxidant activity and general immune response of peripheral blood mononuclear cells and lymphoid tissues of Indian goat Capra hircus during summer and winter.

Daily variation in circulatory melatonin level, during different seasons, has been reported to influence immune system and free-radical scavenging capacity in mammals, including human beings. Similar studies have not been carried out on small ruminant viz. goats that are susceptible to opportunistic infections, increased oxidative load and sickness during free-grazing activity and frequent exposure to agro-chemicals. Therefore, daily variation in immune status, antioxidant enzyme activity and its possible correlation with circulatory melatonin level during two different seasons, summer (long day) and winter (short day) were studied in the Indian goat, Capra hircus. The clinically important immune parameters, such as total leukocyte count, % lymphocyte count and % stimulation ratio of T-lymphocytes presented a day/night rhythm prominently in the winter. The oxidative load in terms of malonedialdehyde was always low during night while antioxidant enzymes superoxide dismutase, catalase and total antioxidant status were high during nighttime (1800 to 0600 hrs). Interestingly, the studied parameters were significantly higher during the winter in both the sexes. Rhythmometric analyses showed prominent rhythmicity in above parameters. The data presented strong positive correlation between high levels of nighttime melatonin levels and immune parameters during winter. It suggests that melatonin possesses immunoenhacing as well as antioxidative property during winter. This might be a necessity for maintenance of physiological harmony in goats to protect them from winter stress.

Slow and fast orthodromic and antidromic variants in acute 9-h jet-lagged pygmy field mice.

Biological clocks help organism to adapt temporally to a variety of rhythmic environmental cues. Acute changes in the rhythmicity of entraining cues causes short- to long-term physiological distress in individuals, for example, those occurring during jet-lag after long-haul transmeridial flights, or shift work. Variations in the rate of re-entrainment to a 9 h advanced schedule (simulation of acute Jet-lag/shift work) in the Indian pygmy field mouse, Mus terricolor are reported. Wheel- and lab-acclimated adult male mice were entrained to a 12:12 h light:dark (LD) cycles, followed by a 9 h advance in the LD cycle. In response, these mice either advanced or delayed their activity onsets, with individual variation in the rate and direction. Rapid orthodromic (advancing) re-entrainers exhibited a coincidence of activity onsets with the new dark onset in <=3 days, while gradually advancing re-entrainers took ~9 days or more. Delayers (antidromic) also either re-entrained very rapidly (<=2 days), or gradually (~9 days). Acrophase measurement confirmed the direction of the transients, which did not depend on the free-running period. Such different patterns might determine the differential survival of individuals under the pressure of re-entrainment schedules seen in jet-lag and shift work.