DPPH radical scavenging activity and contents of H2O2, malondialdehyde and proline in determining salinity tolerance in chickpea seedlings.

The involvement of 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and contents of H2O2, malondialdehyde (MDA) and proline was investigated in determining salinity tolerance among seedlings of thirty chickpea (Cicer arietinum L.) genotypes having different pedigrees. Chickpea genotypes, including cultivars and advanced lines were grown for 7 days under control and salt stress (50 mM NaCl) conditions. The genotypes showed differential response to salt stress in terms of growth, DPPH radical scavenging activity and contents of H2O2, MDA and proline in seedlings. On the basis of seedling growth, the genotypes having better performance under stress conditions had reduced levels of H2O2 and MDA contents, but increased levels of proline and DPPH radical scavenging activity. Stress tolerance index for these parameters was also determined. Agglomerative hierarchal clustering by Pearson correlation coefficient grouped the genotypes into two major clusters — MC I and MC II. MC II and A1-1 sub-cluster of MC-I comprised mainly of genotypes that showed higher stress resistance levels for the respective parameters in comparison to genotypes in other sub-clusters. Thus, it is possible to identify salt-tolerant genotypes on the basis of above parameters without a field trial.

Effect of water deficit on carbohydrate status and enzymes of carbohydrate metabolism in seedlings of wheat cultivars.

The effect of water deficit on carbohydrate status and enzymes of carbohydrate metabolism (alpha and beta amylases, sucrose phosphate synthase, sucrose synthase, acid and alkaline invertases) in wheat (Triticum aestivum L.) was investigated in the seedlings of drought-sensitive (PBW 343) and drought-tolerant (C 306) cultivars. The water deficit was induced by adding 6% mannitol (water potential -0.815 Mpa) in the growth medium. The water deficit reduced starch content in the shoots of tolerant seedlings as compared to the sensitive ones, but increased sucrose content in the shoots and roots of tolerant seedlings, indicating their protective role during stress conditions. It also decreased the alpha-amylase activity in the endosperm of seedlings of both the cultivars, but increased alpha and beta amylase activities in the shoots of tolerant ones. Sucrose phosphate synthase (SPS) activity showed a significant increase at 6 days of seedling growth (DSG) in the shoots of stressed seedlings of tolerant cultivar. However, SPS activity in the roots of stressed seedlings of sensitive cultivar was very low at 4 DSG and appeared significantly only at day 6. Sucrose synthase (SS) activity was lower in the shoots and roots of stressed seedlings of tolerant cultivar than sensitive ones at early stage of seedling growth. Higher acid invertase activity in the shoots of seedlings of tolerant cultivar appeared to be a unique characteristic of this cultivar for stress tolerance. Alkaline invertase activity, although affected under water deficit conditions, but was too low as compared to acid invertase activity to cause any significant affect on sucrose hydrolysis. In conclusion, higher sucrose content with high SPS and low acid invertase and SS activities in the roots under water deficit conditions could be responsible for drought tolerance of C 306.

Hypolactasia as a molecular basis of lactose intolerance.

Lactase-phlorizin hydrolase (LPH), a membrane-bound glycoprotein present in the luminal surface of enterocytes in the intestine is responsible for lactose intolerance, a phenomenon prevalent in humans worldwide. In the rodent intestine, the post-natal development of the LPH follows a specific pattern, such that the enzyme levels are high in the peri-natal period, but declines considerably upon maturation. The observed maturational decline in the LPH activity is very similar to adult-type hypolactasia observed in humans. Majority of the studies have been carried out using animal models or cell lines and a number of hypotheses have been put forward to explain the maturational decline of lactase activity such as: (a) decreased amount of lactase protein, (b) defect in post-translational modification of precursor lactase to the mature enzyme, and (c) synthesis of an inactive, high molecular weight lactase with altered glycosylation, however, the precise underlying mechanism of adult-type hypolactasia remains undefined. The present review describes the recent developments in understanding the regulation of lactase expression and the possible mechanism of adult-type hypolactasia, as a cause of lactose intolerance.

Susceptibility of lactase to luminal proteases in developing rat intestine.

BACKGROUND: Postnatal development of rat intestine is associated with a decline in brush-border lactase activity. This phenomenon is similar to the adulthood hypolactasia in humans. However, the mechanism underlying this process is not understood. METHODS: The effect of luminal proteases from adult rat intestine on the intestinal lactase activity in animals aged 7, 14, 21 and 30 days was studied in in vitro experiments. Lactase levels were estimated using enzyme assays and Western blot analysis. RESULTS: Incubation of purified brush borders with increasing concentrations of luminal proteases reduced the lactase activity in intestine of 7-day-old rats, but not in that of adult animals. Western blot analysis revealed low signal of the 220-kDa lactase protein in 7-day-old animals, but not that of older weaned animals. CONCLUSIONS: Our findings suggest that luminal proteases may be responsible for the maturational decline in intestinal lactase activity.

In vitro translation of RNA to lactase during postnatal development of rat intestine.

mRNA levels encoding lactase were detected by Northern blot analysis using two different probes in developing rat intestine. Probe I and probe II corresponding to second half of prolactase gene showed a 6.8 kb mRNA transcript in 7, 14, 21 and 30 day old rat intestine. There was no change in quantity of lactase mRNA detected using probe II, but hybridization with probe I showed a progressive decrease in mRNA transcript encoding lactase with age. At day 7 and 14 of postnatal development, the lactase mRNA was quite high, but it reduced upon weaning. The in vitro translation products of RNA detected by Western blot analysis using brush border lactase antibodies showed several isoforms of lactase antigen with molecular weight ranging from 100-220 kDa. Analysed at days 7 and 30 of postnatal development, lactase isoforms of molecular weight 130 kDa and 220 kDa were similar to those found in purified brush border membranes. The translation of RNA to 220 kDa lactase protein was high in 7 and 14 day old pups, but it was markedly reduced in 30 day old animals. These findings support the contention that translation of mRNA to lactase is impaired in weaned animals, which may also be responsible for the maturational decline in lactase activity in adult rat intestine.

Postnatal development of alcohol dehydrogenase in liver and intestine of rats exposed to ethanol in utero.

BACKGROUND AND OBJECTIVES: Ethanol exposure during gestation induces marked aberrations in growth and development of offsprings collectively known as foetal alcohol syndrome (FAS);. However, its effects on the postnatal development of alcohol dehydrogenase (ADH) are not adequately investigated. Therefore, ADH activity in liver and intestine of rats exposed to ethanol during gestation was studied in relation to postnatal development. METHODS: Pregnant female rats beginning at day 1 of gestation were fed 1 ml of 30 per cent ethanol daily during the entire gestation period. ADH activity was determined in liver and intestine postnatally at day 4, 8, 14, 20 and 30. DNA and RNA contents and intestinal histology were also examined. RESULTS: During the first two weeks of postnatal life, there was no difference in ADH levels of rat liver and intestine in control and prenatally ethanol exposed pups but ADH levels were significantly reduced at 3-4 wk in ethanol fed group compared to control. A similar decrease in DNA and RNA contents of intestine and changes in tissue morphology were observed in ethanol exposed pups during postnatal development. INTERPRETATION AND CONCLUSION: The findings of our study suggested that prenatal ethanol exposure modified ADH activity in liver and intestine during postnatal development. This could affect ethanol metabolism under these conditions.