Adenosine 3'5'-monophosphate phosphodiesterase of buffalo spermatozoa.

The cyclic AMP-phosphodiesterase (EC 3.1.4.17) of buffalo spermatozoa is distributed in the head, mid-piece and tail fractions and has multiple forms, 70% of which is in the bound form. The bound enzyme was not solubilized by Triton X-100, lubrol or hyamine 2389. Kinetic measurements of the soluble enzyme showed two apparent Km values for low and high cAMP concentrations, i.e. 4.5 and 100 micro M with Vmax values of 0.25 and 2.0 nmol cAMP hydrolysed min-1 mg protein-1. The bound enzyme had an apparent Km of 66.6 microM with a Vmax of 0.75 nmol cAMP hydrolysed min-1 mg protein-1. The pH for optimum enzyme activity was 7.5 and Mg2+ was essential for the activity of the soluble and bound enzymes. Methylxanthines, ATP, ADP and ppi inhibited the soluble and bound enzymes, ATP being the most potent inhibitor.     

Mechanism of nitrogen effect on zinc nutrition of flooded rice

Summary Nitrogen application increased Zn contents of flooded rice on two calcareous soils. Urea and (NH₄)₂SO₄ being better N carriers than NH₄NO₃ resulted in higher increase. Nitrogen enhanced Zn contents partly through growth promotion but mainly by increasing soil Zn solubility and root efficiency for Zn absorption. Zinc solubility rose by an enigmatic mechanism and not from pH reduction or soluble Zn-HN₃ complex formation as occurs for upland plants. Nitrogen aggravated Zn retention in upland plant roots as immobile Zn-protein complex was not important for rice. Bicarbonate inhibition of Zn uptake by rice from CO(NH₂)₂ application or its stimulation by lower redox potential from NH₄NO₃ addition were not involved.No. V in the series Micronutrient availability to cereals from calcareous soils.     

Micronutrient availability to cereals from calcareous soils

Summary By contrast of strong phosphorus-zinc antagonism in upland crops, P strongly enhanced Zn uptake in flooded rice on a calcareous soil. Radioisotopic studies indicated increase to occur preferentially from applied Zn fertilizer. Phosphorus appeared to stimulate uptake predominantly by enhancing Zn concentration in soil solution and by increasing metabolic Zn absorption by plant roots. The ‘A’ value was not a reliable measure of labile soil Zn for rice as it markedly changed with levels of P and Zn fertilizers. No. VI in the series: Phosphorus-zinc interaction in rice. No. VI in the series: Phosphorus-zinc interaction in rice.     

Photonic Switching Techniques and Architecture for Next Generation Optical Networks

Currently, the growth in capacity demand is still increasing by the emergence of a large number of applications that dramatically increase bandwidth demand and generate a large number of resource requirements in the network. Since the emerging applications require increased bandwidth capacity, the vision of using optical technology in the communication channel, signal processing, and switching fabric is very promising. This article presents an overview of optical switching techniques currently under research investigations. It introduces enabling technologies that have been recently researched and then presents some newly proposed architectures. It describes the SKYLIGHT switch that has been recently developed by the author. The architecture design of the switch is based on a optical code division multiple access (OCDMA) technique. Performance evaluation of the switch fabric based on the analytical evaluation of the code and numerical simulations of the optical components used to implement the system is presented.     

Hydrolysis of carbaryl by a Pseudomonas sp. and construction of a microbial consortium that completely metabolizes carbaryl

Two Pseudomonas spp. (isolates 50552 and 50581) isolated from soil degraded 1-naphthol and carbaryl, an N-methylcarbamate pesticide, respectively. They utilized these compounds as a sole source of carbon. 1-Naphthol was completely metabolized to CO2 by the isolate 50552, while the carbaryl was first hydrolyzed to 1-naphthol and then converted into a brown-colored compound by the isolate 50581. The colored metabolite was not degraded, but 1-naphthol produced by the isolate 50581 during the exponential phase of growth was metabolized by the isolate 50552. The two isolates were used to construct a bacterial consortium which completely catabolized carbaryl to CO2. No metabolite was detected in the cell cultures of the consortium. The isolate 50581 harbored a 50-kb plasmid pCD1, while no plasmid was detected in the isolate 50552. The isolated bacteria individually or as a consortium may be used for detoxification of certain industrial and agricultural wastes.     

Effect of month and season of calving on the length of subsequent calving interval in Nili-Ravi buffaloes

Data pertaining to records of 1,274 calving intervals for 400 breeding buffaloes maintained at the Livestock Experiment Station, Qadirabad, District Sahiwal (Pakistan), were analyzed to investigate the magnitude of influence of month and season of calving on the length of subsequent calving interval. The longest average calving interval of 609.9 days was recorded for buffaloes calving in January, while the shortest average calving interval of 502.8 days was observed for those calving in June, the difference being highly significant (P < 0.01). When the data were split in accordance with season of calving, the calving intervals for buffaloes calving in winter, spring, summer and autumn averaged 569.1, 570.6, 506.6 and 515.7 days, respectively. The differences between intervals for winter and spring calvings and between intervals for summer and autumn calvings were non-significant. All other differences were highly significant (P < 0.01). Thus, in most of the buffaloes calving in winter or spring, the first post-partum oestrus and conception are delayed till the following autumn or winter, resulting in significantly longer calving intervals. In contrast, animals calving in summer or autumn exhibit post-partum heat and conception during autumn or winter, resulting in shorter calving intervals.     

Preliminary investigations on available and potentially available phosphorus using electro-ultrafiltration (EUF)

Summary Preliminary investigations were carried out on calcareous silty loam (clay content 25%, pH 8.0) at the Cotton Research Institute, Multan to determine the solubility and desorption rates of phosphorus at various soil depths throughout the cotton growing season using the EUF technique. The treatments included two applications of single superphosphate, equivalent to 0, 75, 150, 250 and 350 kg P₂O₅/ha. There was no significant difference in seed cotton yield between the five treatments. EUF-extracted phosphorus decreased with depth in all samples. There was an increase in phosphorus concentration during the growing season, but most of the increase was noted in the slowly available phosphorus fraction (10–30 minutes EUF aliquots). This was attributed to continuous transformation of phosphorus into less soluble calcium phosphate forms. The available phosphorus fraction (0–10 minute EUF aliquots) remained small throughout the growing season. It was concluded that this fraction was in equilibrium with the slowly available phosphorus fraction and was continually being replenished as crop uptake continued. A high level of effectively available phosphorus (0–30 minute EUF aliquots) was recovered in all five treatments and was above the sufficiency level of 12 ppm phosphorus reported by Nemeth and Makhdam⁷. There was therefore no difference between treatments in phosporus concentration nor in phosphorus uptake by plants. This work was carried out under UNDP/FAO Project-PAK 73/026