Controls on nitrification in a water-limited ecosystem: experimental inhibition of ammonia-oxidising bacteria in the Patagonian steppe

We studied controls on nitrification in an undisturbed water-limited ecosystem by inhibiting autotrophic nitrifying bacteria in soils with varying levels of vegetative cover. The activity of nitrifying bacteria was disrupted using nitrapyrin, 2-chloro-6-(trichloromethyl)-pyridine, under field conditions in three microenvironments (underneath shrubs, next to grasses and in bare soil). Ammonia-oxidising bacteria were detected by PCR analysis of DNA in soils. The inhibition of nitrification changed the concentrations of NO₃⁻ and NH₄⁺ in the soil, while the microenvironment was most important in determining the response of bacteria to the inhibitor. Nitrapyrin application resulted in a significant (p<0.05) reduction in soil NO₃⁻ concentration (39%) and a significant increase (p<0.001) in soil NH₄⁺ concentration (41%). Untreated bare-soil microenvironments had the lowest concentrations of NH₄⁺ (1.57 μg/g of dry soil) and NO₃⁻ (0.49 μg/g of dry soil) when compared to the other microenvironments, and showed the highest impacts of nitrification inhibition. For example, NH₄⁺ concentrations increased 288% and NO₃⁻ concentrations decreased 60% in inhibited bare-soil microenvironments. In contrast, untreated microenvironments underneath shrubs had the highest levels of NH₄⁺ (10.01 μg/g of dry soil) and NO₃⁻ (0.69 μg/g of dry soil), but showed no significant effects of inhibition of nitrification on soil nitrogen concentrations.     

Nutritive evaluation of the seed,germinated seed,and string bean of Erythrina americana and the detoxification of the material by boiling

The nutritive and toxicological values of the dry seeds, germinated seeds, and string beans of Erythrina americana were studied using raw and boiled samples. Raw germinated seeds had a higher protein content and lower fiber content than dry seeds. The whole string bean had lower protein content and higher fiber content. However, the seeds of the green pod showed the same protein concentration as the dry seeds (dry basis). Boiling and elimination of broth was beneficial in diminishing the alkaloid concentration in all the samples. The trypsin inhibitors, lectins, and tannins were also diminished as was expected. The raw string bean showed the lowest LD(50). Although the total essential amino acids content of the boiled germinated seeds was increased, the quality of protein, protein efficiency ratio (PER), was lower than in boiled dry seeds, and in these, the PER was similar to the control (casein). The present results suggest that for the protein quality and low alkaloid content, the boiled dry seeds and string beans could be used for animal feeding. It could be interesting to test the raw string beans in ruminants since in this stage E. americana showed the lowest toxicity.     

COLOR DOPPLER AND DOPPLER SPECTRAL ANALYSIS IN THE SPINAL CORD OF NORMAL DOGS

Doppler ultrasonography of the spinal cord was performed in 34 normal, anesthetized dogs following hemilaminectomy. This study was part of an investigation to evaluate the efficacy of a 21-aminosteroid compound and high dose methylprednisolone for the treatment of spinal cord trauma. Grey-scale images of the canine spinal cord were similar to those described for the spinal cord of people. Doppler waveforms of intraparenchymal spinal arteries exhibited high end diastolic blood flow velocities, indicating low resistance to flow. Doppler values (mean ± SD) for arteries immediately ventrolateral to the central canal were: Peak Systolic Velocity = 5.78 ± 2.5 cm/sec, Minimum Diastolic Velocity = 3.5 ± 1.62 cm/sec, Mean Velocity = 4.45 ± 1.96 cm/sec, Minimum Diastolic Velocity = 3.5 ± 1.62 cm/sec, Mean Velocity = 4.45 ± 1.96 cm/sec, Systolic/Diastolic ratio = 169 ± 0.19, Pulsatility Index = 0.53 ± 0.09, and Resistance Index = 0.4 ± 0.06.     

Effects of forest patch size on avian diversity

The effects of landscape patchiness on the diversity of birds of the Georgia Piedmont were investigated during 1993. Birds were sampled along line transects within relatively large (10–13.25 ha) and small (less than 3.25 ha) forest patches located within nonforest agricultural landscapes. Patterns of habitat use in these patches were compared to those in contiguous forest patches larger than 13.25 ha. Analysis of variance revealed significant differences in diversity between large and small woodlots and between contiguous and fragmented landscapes, especially in terms of the numbers of edge and interior species and winter-resident, summer-resident, and year-round birds observed.     

Residue levels and cholinesterase activities in sheep poisoned experimentally with diazinon

Sheep were dosed orally with diazinon at 450 and 600 mg/kg: residues of diazinon were determined in the blood, brain, liver, kidney cortex and medulla, muscle, fat and rumen contents at intervals after dosing, and cholinesterase activities in the erythrocytes and the brain were determined at the same intervals. The relations between residues, cholinesterase activity and clinical symptoms are discussed from the points of view of their diagnostic value and the possibility of undesirable residues occurring in poisoned animals. Rough estimates of the residues of two metabolites, hydroxydiazinon and dehydro-diazinon, in one sheep are also discussed. The oxygen analogue of diazinon was not detected although it was specifically sought.     

Gender related issues in international development assistance for agriculture and rural life

In this paper, the author points out that although by-passed by international development assistance in many parts of the world, women have been providing skill and labor for agricultural production, as well as subsistence of food, water and firewood for their families. Some of the assumptions which have contributed to the marginal attention to women as agriculturalists in international development assistance programs are reviewed. Factors contributing to these assumptions, examples of achievements in development projects and persistent problems are discussed. Some issues which continue to challenge national policy makers in developing countries as well as donors are identified. The author notes that while various donors and organizations address bits and pieces of the issues intermittently, a systematic, organized and universally shared approach to the issues, within a nation state or on a global basis is lacking. She concludes that just as agricultural production inputs and information need to be modified to fit the unique constraints of any ecological niche, similarly, modifications must be made in development assistance programs to fit the specific needs of women in their agricultural roles and cultural settings.     

The influence of preplanting dips and postplanting temperatures on root growth and development of nonprecooled tulips,daffodils and hyacinths

The effects of preplanting dips and postplanting temperatures were studied, using nonprecooled bulbs of Tulipa gesneriana L. ‘Paul Richter’, Narcissus pseudonarcissus L. ‘Explorer’ and Hyacinthus orientalis L. ‘Pink Pearl’, for 2 consecutive years. Preplanting treatments consisted of a non-dip control, and 30-min dips of either tap water or benomyl—ethazol. After planting, the tulips and daffodils received temperatures of 5, 9, 13, 17 or 21° C for a 5-week period. Hyacinths received temperatures of 9, 13, 17, 21, 25, 29 or 33° C for 5 weeks in the first year and for 25 days in the second year.It was determined that 17° C for 3 weeks and 17° C for 3–4 weeks were the optimal temperatures and periods of time for root development of tulips and daffodils, respectively. For hyacinths, a range of from 17 to 25° C for 10–14 days was optimal. Under these conditions, a minimum root length of 70 mm was obtained and all bulbs of each species had rooted.The benomyl-ethazol and water preplanting dips stimulated root growth for the first 2 weeks for tulips. This effect was not observed for daffodils and hyacinths.     

Cervical and Thoracic Vertebral Malformation ("Weak Neck") in Colombia Lambs

The purpose of this study is to describe a developmental defect of the caudal cervical and cranial thoracic vertebrae in 11 purebred Colombia lambs. The lambs were either affected at birth, or developed the condition within the first 18 days of age. Cervicothoracic kyphosis, with a compensatory cervical lordosis and ataxia were common; 8 lambs had abnormal head posture, characterized by inability to lift the head from the ground. One lamb had rigid head and neck, and had to move the entire body to look to the left or right. Neurological signs included ataxia, tetraparesis, diminished conscious proprioception, and increased patellar and triceps reflexes. One lamb had inspiratory stridor because of compression of the trachea in the area overlying the abnormal vertebrae (cervical vertebrae 6 [C6] and 7 [C7]). Radiographic and pathological abnormalities included malalignment and malarticulation of the caudal cervical and cranial thoracic spine, rounded cranioventral margins in the bodies of vertebrae C7 and T1, wedging of the intervertebral disc spaces between C6 and T1 vertebrae, and hypoplasia of the dens. Pathological changes in the soft tissues included hypoplasia of the cervical epaxial and hypaxial musculature, with associated focal areas of myodegeneration. Mild Wallerian axonal degeneration, compatible with a mild cord compression syndrome, was found in 3 lambs in the cervicothoracic spinal cord adjacent to the vertebral anomalies. The concentrations of copper and selenium in blood, plasma, or tissues were normal in 10 of 11 lambs. All but one of the lambs in which pedigree information was provided were genetically related. Siblings born as twins to 5 of the affected lambs were normal, but both lambs from one twin pregnancy were affected. Owners reported that breeding stock had been shared among the ranches. Because of the close familial relationships of the affected lambs, the condition is suspected to have a hereditary basis.