Design and development of a simple laboratory model to detect (15)N enrichment in cyanobacterial biomass and extra cellular ammonia using (15)N gas.

A laboratory scale working model that could detect the (15)N enrichment in cyanobacterial biomass and extracellular ammonia, using (15)N gas under in vitro conditions was designed and fabricated. Using the model, (15)N enrichment of 0.48% atom excess was detected in the cyanobacterial biomass on the 30 d after inoculation. The (15)N enrichment increased linearly in the extracellular ammoniacal fraction from the 20 d onward. The model would prove to be a useful tool to quantify the extent of (15)N enrichment under in vitro conditions using (15)N gas.

A simple method for efficient extraction and purification of C-phycocyanin from Spirulina platensis Geitler.

Phycocyanin is a major light harvesting accessory pigment of red algae and cyanobacteria. In the light of its many commercial applications in food and pharmaceutical industry, purity of the pigment plays a major role. Pharmaceutical industry demands a highly pure phycocyanin with A620/280 ratio of 4 and food industry a ratio of 2. In the present study phycocyanin was extracted in sodium phosphate buffer (pH 7) after macerating in liquid nitrogen. The crude phycocyanin thus extracted was precipitated with 50% ammonium sulphate, purified by dialysis and finally by gel filtration chromatography. Pure phycocyanin was finally obtained with an A620/A280 value of 4.98.

The xylem of rice (Oryza sativa) is colonized by Azorhizobium caulinodans.

Following inoculation with Azorhizobium caulinodans ORS571 (pXLGD4), lateral root development of rice and colonization of lateral root cracks by bacteria were shown to be stimulated by the flavonoid naringenin. Rice seedlings growing aseptically in the presence of naringenin were inoculated with ORS571 (pXLGD4), carrying the lacZ reporter gene. By microscopic analysis of sections of inoculated rice roots, it has been demonstrated that the xylem of rice roots can be colonized by Azorhizobium caulinodans. We discuss whether this colonization of the xylem of rice roots by azorhizobia could provide a suitable niche for endophytic nitrogen fixation.

Fractionation of cystine aminopeptidases ('oxytocinase') from term human placenta and maternal serum.

Cystine aminopeptidase (EC 3.4.11.3) enzymes, present in term human placenta and maternal serum, were compared with respect to their behaviour on ion-exchange columns, Km and pH optima, chelator, metal ion and L-methionine effects, Sepharose 6B elution profiles and molecular weights. From placental extracts two activity peaks (CAS I and II) hydrolysing S-benzyl L-cysteine paranitroanilide were separated on DEAE Sephacel. Differences in properties between the two forms were evident. Maternal serum enzyme eluted from the DEAE Sephacel column in a position similar to that of placental CAS I. In addition, the maternal serum enzyme was similar in properties to placental CAS I. It is possible that of all the different cystyl aminopeptidase enzyme systems present in placental tissue, only one appears in maternal blood.

Pigment analysis and ammonia excretion in herbicide tolerant cyanobacteria.

Isolation of cyanobacteria was attempted from herbicide applied rice soils. The predominant genera were Westiellopsis followed by Anabaena, Nostoc and Oscillatoria. The herbicide tolerance was further tested by growing the cyanobacterial cultures in BG-11 medium supplemented with varying concentrations of the commonly used rice herbicide, viz butachlor under in vitro condition. The chlorophyll-a, phycobiliproteins and ammonia excretion were assessed at periodic intervals. Westiellopsis showed the maximum tolerance followed by Anabaena, Nostoc and Oscillatoria.

Cystyl aminopeptidase in maternal serum for the antenatal recognition of fetal growth retardation.

An appraisal has been made of the usefulness of cystyl aminopeptidase (CAS, E.C. 3.4.11.3) activity patterns in the in utero detection of fetal growth retardation; 196 pregnancies at risk from placental insufficiency, classified into 9 aetiologic groups were considered. Absolute levels and trend of enzyme activity were studied in all cases and compared with the reference range of CAS activity established in 267 healthy pregnant subjects. Excluding multiple pregnancies, overall predictive value of CAS in defining fetal outcome in 186 'at risk' pregnancies was 72%, overall sensitivity and specificity being 82% and 71% respectively; 48% of the 'at risk' population delivered growth retarded infants, whereas the prevalence of growth retardation as diagnosed by CAS was 54%. Out of the 89 patients who delivered growth retarded infants, 73 exhibited abnormal CAS activity patterns. In twin pregnancies, values of CAS in 73% of the total number of assays were above mean plus 2 standard deviations for the respective gestational period. CAS in maternal serum is advocated as a simple and reliable antepartum indicator of fetal growth retardation and is suitable for the detection of twin pregnancy as early as the second trimester.