Enzymic synthesis,chemical characterisation and Sda activity of GalNAcß1-4[NeuAcα2-3]Galß1-4GlcNAc and GalNAcß1-4[NeuAcα2-3]Galß1-4Glc

The tetrasaccharides GalNAcß1-4[NeuAc2-3]Galß1-4Glc and GalNAcß1-4[NeuAc2-3]Galß1-4GlcNAc were synthesised by enzymic transfer of GalNAc from UDP-GalNAc to 3-sialyllactose (NeuAc2-3Galß1-4Glc) and 3-sialyl-N-acetyllactosamine (NeuAc2-3Galß1-4GlcNAc). The structures of the products were established by methylation and¹H-500 MHz NMR spectroscopy. In Sd^a serological tests the product formed with 3-sialyl-N-acetyllactosamine was highly active whereas that formed with 3-sialyllactose had only weak activity.     

Nutritional status and age at secondary sterility in rural Bangladesh

In a prospective study of 2324 women in Matlab, Bangladesh, the occurrence of primary and 2ndary sterility by age groups was examined. The results were related to the nutritional status of the women, as assessed by measurements of height, weight, arm circumference and ponderal index. Approximately 98% of the women who were in the age group 15-19 were found to be fertile. This proportion decreases gradually up to the age group 30-34 years and thereafter declines sharply, reaching only 31% in the age group 45-49. The height data suggest no significant difference in the age pattern of sterility among the 3 groups of women, although there is a slight tendency that women who were less tall reached menopause earlier than the other 2 groups. Variations in weight are more conspicuous than in height. There is the suggestion that thinner women may experience an earlier menopause. Women having an arm circumference less than 21 cm, between 21-22 cm, and 23 cm and above, and currently aged 17 years, have an expected fertile life estimated at 25.0, 25.8, and 26.6 years respectively. The median ages at sterility were 42.8, 44.0, and 44.3 years respectively with a difference of about 1 year between the 1st 2 groups. This suggests that sterility occurs earlier among the thinner women. Since detailed investigation of nutritional status was not possible, it was assessed by anthropometry. There was strong evidence that nutritional status is an important factor in the estimated age at sterility, with thinner women experiencing an earlier menopause. Although it is impossible to measure the onset of sterility, one can obtain a minimum estimate of it from the age-specific distribution of the proportion of women who have not produced a child for 5 years of being at risk.     

The synthesis of some fluoro derivatives of sucrose

2,3,1',3'4',6'-Hexa-O-benzylsucrose was obtained by mild acid-catalysed hydrolysis of the 4,6-O-isopropylidene derivative and then converted into its 4,6-di-O-mesyl derivative. Selective displacement of this disulphonate with fluoride anion (from tetrabutylammonium fluoride) then afforded the 6-fluoro-4-mesylate. Removal of the protecting groups yielded 6-deoxy-6-fluorosucrose, which was characterised as its crystalline hepta-acetate. A derivative of 6-deoxy-6-fluoro-galacto-sucrose was formed when the above 6-fluoro-4-mesylate was subjected to nucleophilic displacement with benzoate anion.     

Approaches to breeding for salinity tolerance - a case study on Porteresia coarctata

Cereals are the world's major source of food for human nutrition. Among these, rice (Oryza sativa) is the most prominent and represents the staple diet for more than two-fifths (2.4 billion) of the world's population, making it the most important food crop of the developing world (Anon., 2000a). Rice production in vast stretches of coastal areas is hampered due to high soil salinity. This is because rice is a glycophyte and it does not grow well under saline conditions. In order to increase rice production in these areas there is a need to develop rice varieties suited to saline environments. Research has shown that Porteresia coarctata, a highly salt tolerant wild relative of rice growing in estuarine soils, is an important material for transferring salt tolerant characteristics to rice. It is quite possible that Porteresia may be used as a parent for evolving better and truly salt resistant varieties. The inadequate results and the difficulties associated with conventional breeding techniques necessitate the use of the tools of crop biotechnology in unravelling some of the characteristics of Porteresia that have been highlighted in this report. In view of the limited resources available for increasing salinity tolerance to the breeders to wild rice germplasm, Porteresia is undoubtedly one of the key source species for elevating salinity tolerance in cultivated rice.     

Phytoplankton primary production in a mesotrophic pond in sub-tropical Bangladesh

Annual gross primary productivity in mesotrophic Shahidullah Hall pond (Dhaka, Bangladesh) was 1383.35 g C m⁻² y⁻¹ (arithmetic mean). Daily primary productivity (between 1.6 and 6.8 g C m⁻² d⁻¹ was correlated with chlorophylla, day length and dissolved silica. Chlorophylla related significantly withk, incident light, SRP, alkalinity and conductivity. A negative correlation existed between biomass and rainfall. Productivity, biomass, conductivity, alkalinity, and SRP increased after mid-winter.k, I _k andZ _eu varied according seasonally.P _max related directly with temperature. Seasonal variation of ∝ ^B was 0.0049–0.0258 mg C (mg chla mmol PAR)⁻¹ m⁻². Q₁₀ was 2.12, community respiration 1334.99 g C m⁻² y⁻¹, and the underwater light climate 186.43μE m⁻² s⁻¹.     

Immunochemical analysis of the membrane proteins of rat liver and Zajdela hepatoma mitochondria

The contents of mitochondrial inner membrane protein complexes were compared in normal liver and in Zajdela hepatoma mitochondria by the immunotransfer technique. Antibodies against core proteins 1 and 2, cytochrome c1, the iron-sulfur protein of Complex III, subunits I and II of cytochrome oxidase, and the alpha and beta subunits of the F1-ATPase were used. In addition, antibodies against a primary dehydrogenase, beta-hydroxybutyrate dehydrogenase, as well as the outer membrane pore protein were used. The results indicate that the components of the cytochrome chain and porin are greatly enriched in hepatoma mitochondria compared to normal rat liver mitochondria. This enrichment was also reflected in the rates of respiration in tumor mitochondria using a variety of substrates. Enrichment of porin may partially account for increased hexokinase binding to tumor mitochondria. In contrast to the respiratory chain components, the F1-ATPase and F0 (measured by DCCD binding) were not increased in tumor mitochondria. Thus, Zajdela hepatoma mitochondria components are nonstoichiometric, being enriched in oxidative capacity but relatively deficient in ATP synthesizing capacity. Finally, beta-hydroxybutyrate dehydrogenase, which is often decreased in hepatoma mitochondria, was shown here by immunological methods to be decreased by only 40%, whereas enzyme activity was less than 5% of that in normal rat liver.     

Altered metabolic states do not change the intracellular distribution of hexokinase in Zajdela hepatoma ascites cells.

The distribution of hexokinase between bound and soluble forms was studied by digitonin fractionation of Zajdela hepatoma ascites cells maintained under various metabolic conditions. Addition of glucose to Zajdela cells respiring on endogenous substrates induces an immediate inhibition of respiration by 50-60% ( Crabtree effect), and a production of acid due to glycolysis. Acid production decreases abruptly after 60s to 50% of the initial rate. The ATP/ADP ratio is not altered by the addition of glucose or by different rates of glycolysis. The uncoupling agent carbonyl cyanide m-chlorophenylhydrazone decreases the ATP/ADP ratio by 10-fold in cells respiring on endogenous substrate, but has little effect on cells oxidizing glucose. Rapid fractionation of the cells under these various metabolic conditions revealed no change in the distribution of hexokinase. Approx. 75% of hexokinase is bound in all cases, in contrast with lactate dehydrogenase, 95% of which was in the soluble form. Longer-term incubations (to 20 min) revealed only slight (10-15%) increases in soluble hexokinase in cells incubated with glucose. Various metabolic inhibitors had little additional affect on the subcellular distribution of hexokinase. Thus a rapid release of hexokinase from mitochondrial membrane is not a mechanism by which glycolysis is regulated in rapidly growing Zajdela hepatoma.