Physiological responses of mules on prolonged exposure to high altitude (3 650 m)

Eight healthy male animals were inducted and kept for 2 1/2 years at 3 650 m altitude and subjected to normal work schedules. Physiological measurements viz. heart rate, blood pressure, minute ventilation, oxygen consumption, respiration rate, hemoglobin, packed cell haematocrit volume and eosinophil count were made on these animals at periodic intervals. On acute induction to an altitude of 3 650 m these animals demonstrated a sudden increase in tidal volume, a decrease in Rf and no change in V_E, suggesting a decreased dead space/tidal volume ratio at altitude.However, all these changes stabilised within 3 weeks but on prolongation of stay, the physical state of these animals was adversely affected. The respiratory adjustments occurring on return to sea level appear to be a response to thermal stress. The initial increase in heart rate and blood pressure stabilised by the 2nd week.     

Physiological and biochemical changes associated with cotton fibre development. II. Auxin oxidising system

Changes in IAA oxidase, and in cytoplasmic and ionically wall-bound peroxidase activities were studied in the developing fibres of three cotton cultivars ( Gossypium hirsutum L. cv. Gujarat-67, cv. Khandwa-2 and G. herbaceum L. cv. Digvijay), designated as long, medium and short staple cultivars, respectively. In all the three cultivars IAA oxidase activity was low during the fibre elongation phase, while the activity increased significantly during the secondary thickening phase. The increase in IAA oxidase activity in the three cultivars showed close correspondence with their respective total period of elongation. No relationship between cytoplasmic peroxidase activity and fibre development was discernible. The ionically bound wall peroxidase activity, however, recorded low levels during the elongation phase and higher levels during the secondary thickening phase. The role of wall peroxidase in cessation of elongation growth is discussed.     

A general multistate model for the analysis of hydrogen-exchange kinetics

In proton nmr, the chemical exchange rates of slowly exchanging labile hydrogens (with lifetimes in the range ～ 10 msec – ～ 1 sec) of peptides, proteins, and nucleic acids can be measured in H₂O by a combination of two separate experiments: (1) the transfer of solvent saturation and (2) saturation-recovery experiments. When these molecules exist in a dynamic equilibrium among different conformations, the experiments cannot be analyzed in a straightforward manner to derive the intrinsic exchange rates. In the present study we have derived analytical expressions for the above two experiments on a biomolecule under certain limiting conditions: (1) the extreme low-motility limit, where each of the conformational transitions is much slower than the corresponding hydrogen exchange rate with the solvent; (2) the high-motility limit (EX₂ mechanism), which is the opposite extreme of the previous limit; and (3) the low-motility limit (EX₁ mechanism), which is a mixture of limits (1) and (2), i.e., for some of the conformations, the exchange rate with the solvent is much faster than their conformational transition rates, while for the remaining conformations the reverse situation is realized. The results may be considered as a generalization to an arbitrary number of states of the two-state model treated by Hvidt. Equations have also been derived that are applicable to the iostope exchange method of measuring very slow exchange rates (with life-times of the order of minutes and longer) in biomolecules. The saturation recovery experiments performed in H₂O on the active pentapeptide fragment of thymopoietin serve to illustrate the high-motility limit. The theoretical formulation presented in this study can be easily adapted to other double-resonance techniques and also to situations where the kinetics of an arbitrary system existing in a multistate equilibrium are of interest.     

Structure and seasonal dynamics of humid tropical grasslands in Meghalaya,India

Abstract. Four humid grassland communities at three different locations in Meghalaya, India were analysed during 1988 and 1989 for species and life-form composition, diversity and dominance in relation to altitude, soil and prevailing disturbances. Due to the adverse interactive influences of exceptionally high annual rainfall (> 10 000 mm), topography and human interference on soil fertility, the grassland at Cherrapunji, at 1300 m altitude, had a low species diversity (H'= 1.74) and was dominated by three perennial grass species. Similar grasslands, at both higher and lower altitudes on fertile soil and with lower rainfall (ca. 2000 mm), showed higher diversity values (H'= 2.28 at Burnihat and 2.31 at Upper Shillong). The proportion of perennial species and chamaephytes increased with elevation. At the high altitude site a grassland under short-term protection from fires and grazing had a higher species richness, density and basal cover than an unprotected grassland. All grasslands show a clear seasonality, albeit with different patterns, with a maximum in density and basal cover in August. The differences in structure and seasonality are discussed in terms of different levels of stress.     

Ca(2+)-activated K+ currents underlying the afterhyperpolarization in guinea pig vagal neurons: a role for Ca(2+)-activated Ca2+ release.

We examined the possibility that Ca2+ released from intracellular stores could activate K+ currents underlying the afterhyperpolarization (AHP) in neurons. In neurons of the dorsal motor nucleus of the vagus, the current underlying the AHP had two components: a rapidly decaying component that was maximal following the action potential (GkCa,1) and a slower component that had a distinct rising phase (GkCa,2). Both components required influx of extracellular Ca2+ for their activation, and neither was blocked by extracellular TEA (10 mM). GkCa,1 was selectively blocked by apamin, whereas GkCa,2 was selectively reduced by noradrenaline. The time course of GkCa,2 was markedly temperature sensitive. GkCa,2 was selectively blocked by application of ryanodine or sodium dantrolene, or by loading cells with ruthenium red. These results suggest that influx of Ca2+ directly gates one class of K+ channels and leads to release of Ca2+ from intracellular stores, which activates a different class of K+ channel.     

X-Ray radiography for studying diffusion characteristics of sucrose in plaster of paris matrix containing yeast cells

Summary X-Ray radiography was employed to monitor the diffusion of sucrose into plaster of Paris matrix containing 20% yeast cells. It was observed that the depth of penetration of tracer P_b detected by radiography matched with the substrate penetration detected by chemical test. However electron probe microanalysis (EPMA) did not yield any conclusive evidence regarding the movements of tracer P_b and substrate to the same extent.     

Proton NMR study of iron(II)-bleomycin: Assignment of resonances by saturation transfer experiments

The assignment of the paramagnetically shifted resonances of the Fe(II)-bleomycin complex in D₂O has been accomplished using the transfer of saturation method. A number of additional resonances arising from labile N$\text{H}$ protons which are shifted by the metal ion are observed in the ¹H spectrum of the complex in H₂O. The temperature dependence of the chemical shifts is consistent with the formation of an isolated 1:1 complex, but does not obey either the Curie Law or the Curie-Weiss Law. The magnitude of the shifts suggests that the valeric acid hydroxyl (or carbonyl) group, the α-amino group, the imidazole N^π, the carbamoyl oxygen, the pyrimidine N₁ and/or the secondary amino group may be coordinated to the iron(II).     

Genic Heterogeneity within Electrophoretic "Alleles" and the Pattern of Variation among Loci in DROSOPHILA PSEUDOOBSCURA

An investigation, similar to our previously reported xanthine dehydrogenase study, was undertaken to examine the extent of hidden genic variation at nine loci (five larval proteins, three esterases and one aldehyde oxidase) by sequential application of various electrophoretic criteria employing pH, gel concentration and buffer variation. Polymorphic loci appear to fall into two distinct groups: weakly polymorphic, including larval protein 6, 7, 8, 10 and 13 and esterase-1 and -6; and highly polymorphic, including esterase-5, Xdh and possibly Ao. Monomorphic loci may belong to a third group different from all polymorphic loci. Bogota, a geographical isolate that is reproductively isolated from the mainland population, was found to be genetically distinct at four of the ten loci examined in detail so far, including Xdh, whereas previously it was found to be genetically distinct at none. These results are discussed in the light of balancing selection, neutral and mutation-selection hypotheses of genic variation in natural populations.     

Relative efficiency of rock phosphate and superphosphate for cowpea (Vigna sinensis Savi) fodder

Summary Cowpea responded well to phosphorus and P application increased green-fodder production and P uptake. With respect to green-fodder production, the rock phosphate was found to be 50–55% as effective as superphosphate. Phosphorus when applied at 50 kg P₂O₅/ha as superphosphate or rock phosphate almost doubled the P uptake by the summer-season crop of cowpea as compared to no phosphorus control. The residual effect did not differ significantly on succeeding rainy-season crop of cowpea. Application of starter N increased the total green-fodder yield of two crops by 38 q/ha. re]19750710