Nutrient cycling in an excessively rainfed subtropical grassland at Cherrapunji.

Cycling of six mineral elements (N, P, K, Na, Ca and Mg) was studied in a humid subtropical grassland at Cherrapunji, north-eastern India during 1988-1989. Elemental concentrations in the shoot of four dominant grass species, viz., Arundinella khaseana, Chrysopogon gryllus, Eragrostiella leioptera and Eulalia trispicata were very low, and none of the species appears suitable for fodder use. Among different vegetation compartments, live root was the largest reservoir of all the nutrients (except Ca) followed by live shoot, dead shoot, litter and dead root. For Ca, live shoot was the major storage compartment. The total annual uptake (kg ha-1) was 137·3, 10·4, 51·1, 5·5, 8·7 and 18·2 for N, P, K, Na, Ca and Mg, respectively. In an annual cycle 98% N, 77% P, 49% K, 109% Na, 87% Ca and 65% Mg returned to the soil through litter and belowground detritus. A major portion of Ν, Ρ and Na was recycled through the belowground system, whereas nearly half of K, Ca and Mg was recycled through the shoot system. Precipitation acts as the source of Ν and Ρ input, but at the same time causes loss of cations.

Urinary aspartate transaminase (AST) activity and detection of its inhibitors in normal urine.

Urinary aspartate-transaminase activity in the whole urine was found to be mean +/- S.D. = 8.46 +/- 0.69 l.U/l when measured immediately after urine collection. About 50% loss in enzyme activity was observed after 18 hours dialysis. An overall 176% increase in enzyme activity followed by Sephadex G-25 (fine) whole urine fractionation and a highly significant (P less than .001) partial inhibition by earlier Sephadex fractions and maximum inhibition by earlier Sephadex fractions and maximum inhibition of enzyme by fraction 7 have suggested the presence of both high and low molecular weight urinary inhibitors of aspartate-transaminase. Urea and ammonia presence and inhibitor activity in fraction 6 to 8 bear a close parallelism; both the substances produced 31% inhibition of partially purified goat liver GOT at concentrations approximating normal human urine. Therefore, low enzyme activity and its substantial loss in the whole urine and during dialysis may be due to the concomitant inhibitory effects of urea, ammonia and unidentified nature of high molecular weight substance(s). The present method may be effective in separating inhibitors and overcoming the disadvantages of dialysis in determining true urinary aspartate-transaminase activity.