Rehabilitation in the Philippines

The international community has perspective and experience that will freshen our approaches to rehabilitation. Martin Grabois, MD^*, editor of this special section, has gathered articles written by experts from other countries. The intention is to stimulate thought, discussion, and action—and to broaden horizons.     

NH(4)-Excreting Azospirillum brasilense Mutants Enhance the Nitrogen Supply of a Wheat Host

Spontaneous ethylenediamine-resistant mutants of Azospirillum brasilense were selected on the basis of their excretion of NH(4). Two mutants exhibited no repression of their nitrogenase enzyme systems in the presence of high (20 mM) concentrations of NH(4). The nitrogenase activities of these mutants on nitrogen-free minimal medium were two to three times higher than the nitrogenase activity of the wild type. The mutants excreted substantial amounts of ammonia when they were grown either under oxygen-limiting conditions (1 kPa of O(2)) or aerobically on nitrate or glutamate. The mutants grew well on glutamate as a sole nitrogen source but only poorly on NH(4)Cl. Both mutants failed to incorporate [C]methylamine. We demonstrated that nitrite ammonification occurs in the mutants. Wild-type A. brasilense, as well as the mutants, became established in the rhizospheres of axenically grown wheat plants at levels of > 10 cells per g of root. The rhizosphere acetylene reduction activity was highest in the preparations containing the mutants. When plants were grown on a nitrogen-free nutritional medium, both mutants were responsible for significant increases in root and shoot dry matter compared with wild-type-treated plants or with noninoculated controls. Total plant nitrogen accumulation increased as well. When they were exposed to a N(2)-enriched atmosphere, both A. brasilense mutants incorporated significantly higher amounts of N inside root and shoot material than the wild type did. The results of our nitrogen balance and N enrichment studies indicated that NH(4)-excreting A. brasilense strains potentially support the nitrogen supply of the host plants.     

Anaerobic degradation of m-cresol in anoxic aquifer slurries: carboxylation reactions in a sulfate-reducing bacterial enrichment

The anaerobic biodegradation of m-cresol was observed in anoxic aquifer slurries kept under both sulfate-reducing and nitrate-reducing but not methanogenic conditions. More than 85% of the parent substrate (300 microM) was consumed in less than 6 days in slurries kept under the former two conditions. No appreciable loss of the compound from the corresponding autoclaved controls was measurable. A bacterial consortium was enriched from the slurries for its ability to metabolize m-cresol under sulfate-reducing conditions. Metabolism in this enrichment culture was inhibited in the presence of oxygen or molybdate (500 microM) and in the absence of sulfate but was unaffected by bromoethanesulfonic acid. The consortium consumed 3.63 mol of sulfate per mol of m-cresol degraded. This stoichiometry is about 87% of that theoretically expected and suggests that m-cresol was largely mineralized. Resting-cell experiments demonstrated that the degradation of m-cresol proceeded only in the presence of bicarbonate. 4-Hydroxy-2-methylbenzoic acid and acetate were detected as transient intermediates. Thus, the parent substrate was initially carboxylated as the primary degradative event. The sulfate-reducing consortium could also decarboxylate p- but not m-hydroxybenzoate to near stoichiometric amounts of phenol, but this reaction was not sulfate dependent. The presence of p-hydroxybenzoate in the medium temporarily inhibited m-cresol metabolism such that the former compound was metabolized prior to the latter and phenol was degraded in a sequential manner. These findings help clarify the fate of a common groundwater contaminant under sulfate-reducing conditions.     

Molecular forms of alpha-1-acid glycoprotein in human blood serum. Differences in levels of di-, tri-, and tetra-antennary N-linked carbohydrate chains]

alpha 1-Acid glycoprotein isolated from healthy individuals blood was separated on Con A-Sepharose into three fractions: non-bound (AGP-1, 84%, 43.5 kDa), Con A-bound (AGP-2, 14%, 41.3 kDa), and Con A-tightly bound (AGP-3, 2%, 39.6 kDa). Amino acid compositions of these fractions were similar but carbohydrate ones differed. HPLC analysis of 7-amino-4-methylcoumarin derivatives of the oligosaccharides in combination with their sequential exoglycosidase digestion showed that AGP-1, AGP-2, and AGP-3 have the same set of oligosaccharides and differ only by their proposition. A minor quantity of agalacto-oligosaccharides (with a terminal GlcNAc residue) was identified.     

Spatial structure of the basic chain of the neurotoxin I molecule from the venom of cobra Naja naja oxiana and its crystal packing

The structure of the alpha-carbon chain was solved by molecular replacement method at 2.7 A resolution. Neurotoxin I (NTX-I) is one of the main protein components purified from the venom of the central asian cobra Naja naja oxiana. NTX-I is known to bind specifically to acetylcholine receptors thus preventing the transmission of the neuroconductivity signal from synapses to muscles. NTX-I crystals were grown either by vapour diffusion or dialysis methods using specially prepared microdialysis cell. The intensities of reflections from native NTX-I crystals were measured in the range of 38.0-2.1 A-1 by omega-scan method with a Syntex P21 diffractometer operated in automatic regime. To determine the position and mode of packing of NTX-I molecule in unit cell program packages MERLOT and BLANC were applied running on a NORD-500 computer.     

Photosystem II of rye. Nucleotide sequence of psbD, psbI genes encoding reaction center proteins

Structures of the rye chloroplast DNA regions, containing psbD and psbI genes coding for the components of the reaction centre of photosystem II, D2 protein and I polypeptide, respectively, have been determined. The gene trnS for tRNA(Ser) (GCU) is located 111 bp downstream from the stop codon of the psbI gene on the opposite strand. The high homology between the rye BamHI-fragment comprising these genes and his counterpart from wheat are discussed.     

Optimal hunting group size: the need for lions to defend their kills against loss to spotted hyaenas

This paper presents preliminary evidence that kleptoparasitism by spotted hyaenas may influence optimal hunting group size of lions. In the absence of adult male lions, hyaenas can drive female and subadult lions off their kills provided they outnumber the lions by a factor of four. Hence the larger the group of lions on the kill, the greater their chance of defending their food against invading hyaenas. At Savuti, where there was a shortage of adult male lions, the groups of female and subadult lions lost almost 20% of their food to hyaenas. Losses were most frequent for those living in small groups. These lions were often satiated by the time the hyaenas acquired the kill, so the hyaenas did not cause immediate need, yet constituted a constant energy drain on lions by forcing them to hunt more frequently. The implications of these observations for modelling optimal hunting group size of lions are discussed.