High impact information on Estivation

• NOS activity was highest during courtship and lowest during the refractory and estivation periods [1].
• Cyclic GMP levels were highest during courtship and lowest during the refractory period and estivation [1].
• DEAE-Sephadex chromatography separated two peaks of activity and in vitro incubations stimulating protein kinases or phosphatases showed that peak I (low phosphate) G6PDH was higher in active snails (57% of activity) whereas peak II (high phosphate) G6PDH dominated during estivation (71% of total) [2].
• The regulation of the antioxidant system during hypometabolism may constitute a mechanism to minimize oxidative stress during cycles of estivation and awakening [3].
• After 15 min of awakening, the glutathione disulphide (GSSG)/GSH-eq ratio increased significantly by 55% in hepatopancreas, slowly returning to the levels observed during estivation [3].

Biological context of Estivation

• Hematocrit, O2 capacity and blood hemoglobin concentration increased by about 50% during estivation [4].
• Hibernation in the ground squirrel and estivation in the lungfish result in region-specific decreases in TRH concentrations [5].
• The roles of enzymatic antioxidant defenses in the natural tolerance of environmental stresses that impose changes in oxygen availability and oxygen consumption on animals is discussed with a particular focus on the biochemistry of estivation and metabolic depression in pulmonate land snails [6].

Anatomical context of Estivation

• Total PTK activity decreased by 27-52 % in liver, lung and skeletal muscle during estivation but rose by 66% in heart [7].
• Reduction of thyrotropin-releasing hormone concentrations in central nervous system of African lungfish during estivation [8].

Associations of Estivation with chemical compounds

• The striking increase in O2-Hb affinity during estivation is regarded as an adaptation to a reduced alveolar O2 availability associated with estivation [4].
• Male plasma T peaked in January, 2-3 months after males emerged from their annual period of estivation [9].
• The higher levels of products of free radical damage during estivation may have resulted from low levels of ROS formation associated with decreased rates of lipid hydroperoxide detoxification and oxidized protein turnover caused by metabolic depression [3].
• Compared with active snails, G6PDH Vmax increased by 50%, Km for glucose-6-phosphate decreased by 50%, Ka Mg x citrate decreased by 35%, and activation energy (from Arrhenius plots) decreased by 35% during estivation [2].
• In general, estivation includes a strong reduction in metabolic rate, a primary reliance on lipid oxidation to fuel metabolism, and methods of water retention, both physical (e.g. cocoons) and metabolic (e.g. urea accumulation) [10].

Gene context of Estivation

• In total, this information allowed identification of the Peaks I and II enzymes as the phosphorylated and dephosphorylated forms, respectively, and the effect of estivation was to increase the proportion of dephosphorylated PK and PFK in muscle [11].
• Maximal activities of glutathione-S-transferase, glutathione reductase, glutathione peroxidase, superoxide dismutase and catalase were measured in six organs from 2-month-estivated toads and compared with activities in animals awakened for 10 days after estivation [12].
• Each fraction showed three major peaks of PTK activity, two of which shifted in elution position during estivation [7].
• Despite reduced oxygen consumption and PO2 during estivation, which should also mean reduced production of oxyradicals, the activities of antioxidant enzymes, such as superoxide dismutase and catalase, increased in 30 day-estivating snails [6].
• 5. The unique characteristics of lungfish RBC may be related to their adaptation to the high concentrations of urea produced during estivation [13].

References