Ammonia production and kinetic properties of glutamate dehydrogenase in the sipinculid Phascolosoma arcuatum exposed to anoxia

The amounts of total NH ₄ ⁺ detected in the external media in which Phascolosoma arcuatum had been exposed to various periods of anoxia were significantly greater than those in which the worms were exposed to normoxia for a similar period. The increased NH ₄ ⁺ production by P. arcuatum during anoxic exposure was unlikely to be due to an increased catabolism of adenine nucleotides or urea. In contrast, there were significant decreases in the concentrations of several free amino acids in the coelomic plasma and body tissues of individuals during the 48 h of anoxic exposure. The amount of NH ₄ ⁺ produced by the anoxic P. arcuatum could be accounted for by the decreases in the concentrations of aspartate or glycine. Increases in the catabolism of free amino acids (FAA), leading to the increased production of NH ₄ ⁺ , in P. arcuatum during anoxia were supported by the detection of significant changes in the kinetic properties of glutamate dehydrogenase (GDH), in the deaminating direction, from worms exposed to anoxia for 48 h. The apparent increase in the affinity of GDH from the anoxic worm to glutamate would bring about a greater deaminating activity at physiological concentrations of ths substrate. P. arcuatum used in these experiments were collected from the mangrove swamp at Mandai, Singapore between 1990 and 1993.     

Photodegradation of TCDD in soil containing organic solvents

Studies were conducted to understand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) behaviour in the near surface zone in relation to the operating conditions: UV-intensity, temperature and exposure modes. Comparisons have been made between Oriel lamp exposure tests and sunlight exposure tests. Under Oriel lamp exposure, the convective transport of TCDD, which depends on operating temperature, was the limiting factor in the cleanup process. The product differences between Oriel exposure tests and sunlight exposure tests probably result from the difference of UV-intensities.     

OBSERVATIONS ON PHYTOPLANKTON PRODUCTIVITY IN RELATION TO HYDROGRAPHY IN THE NORTHERN ADRIATIC

This work, carried out within the framework of the PRISMA II project, aims at evaluating the effects of the Po River flow on primary productivity, measured by C with in situ sample incubations. A total of four cruises was carried out in late winter and early summer (1996-1998) along transects from the coast offshore. In both seasons, the highest primary productivity was found in the most oligohaline stations. The effects of the Po River inputs were therefore clearly evident in the westernmost area, both in high productivity values and in the shape of productivity profiles. In late winter, extensive blooms of Skeletonema costatum and Pseudo-nitzschia delicatissima resulted in productivity values that were sometimes higher than in early summer. In early summer 1996, greatly reduced river flow clearly influenced productivity which was much lower than in 1997.     

Trophoblast-like cells sorted from peripheral maternal blood using flow cytometry: A multiparametric study involving transmission electron microscopy and fetal dna amplification

Three monoclonal antibodies (MAbs) against trophoblast (GB17, GB21, and GB25) and flow cytometry were used to sort trophoblast-like cells (TLCs) from peripheral blood of pregnant women. Sorted TLCs were processed for electron microscopy and fetal DNA amplification of the Y-specific sequences from mothers carrying male fetuses. At the ultra-structural level, most of the nucleated cells had the morphology of leucocytes, suggesting maternal contaminants, and we did not find the characteristic features of the free inter-villous trophoblast cells. Nevertheless, polymerase chain reaction (PCR) analysis showed an amplification of Y-specific sequences in two out of three samples of sorted TLCs. These results suggest that besides the maternal leucocytes, sufficient trophoblast nucleated fetal cells can be obtained using cell enrichment by sorting. This sensitive method holds promise for non-invasive prenatal diagnosis of fetal sex and if sufficient Y(positive) nuclei are found, for the diagnosis of selected numerical chromosome abnormalities.     

Disposal of Mine Wastes Containing Pb and Zn Near the Ocean: An Assessment of Associated Environmental Implications in the Arctic

The past two decades have witnessed an increase in the exploration for, and development of, mineral resources at Arctic latitudes. Such effort has resulted in the commencement of production at a number of different localities in close proximity to the ocean. Since proximity to a source of transportation for the conveyance of concentrates to the market is a primary requirement governing the economic decisions for the mine to proceed, it is logical that ore deposits near a coastline are primary targets for development.

Closely tied to coastal mining developments is the need to dispose of tailings and waste rock in the most economical manner. Prior to the advent of heightened public awareness and environmental concern, and the enactment of pollution legislation, disposal practices were largely based upon convenience. Currently, however, proposed disposal and operating practices receive closer scrutiny, with a view to providing adequate protection for aquatic resources and habitat. This paper summarizes some of the features of three Arctic mines, wastes from which enter the marine environment, and compares the disposal practices used at each to measures of environmental change as indicated by metal concentrations in various media.     

Violating the psychological contract: Not the exception but the norm

The occurrence and impact of psychological contract violations were studied among graduate management alumni (N = 128) who were surveyed twice, once at graduation (immediately following recruitment) and then two years later. Psychological contracts, reciprocal obligations in employment developed during and after recruitment, were reported by a majority of respondents (54.8 per cent) as having been violated by their employers. The impact of violations are examined using both quantitative and qualitative data. Occurrence of violations correlated positively with turnover and negatively with trust, satisfaction and intentions to remain.     

Marsh Frog (Rana ridibunda Pall.) in Cooling Ponds in the Middle Urals

Environmental conditions in cooling ponds of thermal power plants are favorable for marsh frogs. Their populations inhabiting Verkhne-Tagil and Reftinskoe reservoirs differ in some traits, such as size and age composition, growth rate after metamorphosis, spawning type, fecundity, and characteristics of larval development. Differentiation in body size manifests itself at the early stages of terrestrial life and progresses at later stages. As a consequence, larger individuals may reach maturity and participate in reproduction at an earlier age.