The role of kynurenines in the production of neuronal death, and the neuroprotective effect of purines.

The kynurenine metabolic pathway from tryptophan accounts for a large proportion of the metabolism of this amino acid in the brain. Although a major route for the generation of the essential co-factor nicotinamide adenine dinucleotide (NAD), two components of the pathway have marked effects on neurons. Quinolinic acid is an agonist at N-methyl-D-aspartate (NMDA)-sensitive glutamate receptors, while kynurenic acid is an antagonist and, thus, a potential neuroprotectant. The levels of quinolinic acid are known to increase substantially following cerebral insults or infection, and has been most clearly implicated in the AIDS-dementia complex. The actions of quinolinic acid and NMDA show subtle differences, however, which suggest other factors contributing to cell damage. In this article we review the evidence that free radicals may be involved in the neurotoxic effects of quinolinic acid and consider the possibility that quinolinic acid might be involved in Alzheimer's disease. Finally, adenosine receptor ligands can modulate neuronal damage, supporting the view that they may represent suitable targets for the development of novel neuroprotectant drugs for the treatment of Alzheimer's and other neurodegenerative disorders.

Nuclear fusion driven by coulomb explosions of large deuterium clusters

Recent experiments on the interaction of intense, ultrafast laser pulses with large van der Waals bonded clusters have shown that these clusters can explode with substantial kinetic energy. By driving explosions in deuterium clusters with a 35 fs laser pulse, we have accelerated ions to sufficient kinetic energy to produce DD nuclear fusion. By diagnosing the fusion yield through measurements of 2.45 MeV fusion neutrons, we have found that the fusion yield from these exploding clusters varies strongly with the cluster size, consistent with acceleration of deuterons via Coulomb explosion forces.

The dynamics of Rydberg electron wavepackets in NO

Rydberg electron wavepackets have been studied in molecular NO for a variety of rotational states of the ion core. Predominantly radial motion of the electron wavepacket is observed which is similar to that previously reported in atomic systems. Interference effects similar to those observed in unperturbed Rydberg series are evident and third and fourth order partial revivals are identified. Most interestingly, when the classical period of electronic motion is close to the classical period of rotation of the molecular ion, the molecular dynamics dominates the electronic dynamics.

Characterization of fusion burn time in exploding deuterium cluster plasmas

Exploiting the energetic interaction of intense femtosecond laser pulses with deuterium clusters, it is possible to create conditions in which nuclear fusion results from explosions of these clusters. We have conducted high-resolution neutron time-of-flight spectroscopy on these plasmas and show that they yield fast bursts of nearly monochromatic fusion neutrons with temporal duration as short as a few hundred picoseconds. Such a short, nearly pointlike source now opens up the unique possibility of using these bright neutron pulses, either as a pump or a probe, to conduct ultrafast studies with neutrons.

Effect of stream channel size on the delivery of nitrogen to the Gulf of Mexico

An increase in the flux of nitrogen from the Mississippi river during the latter half of the twentieth century has caused eutrophication and chronic seasonal hypoxia in the shallow waters of the Louisiana shelf in the northern Gulf of Mexico. This has led to reductions in species diversity, mortality of benthic communities and stress in fishery resources. There is evidence for a predominantly anthropogenic origin of the increased nitrogen flux, but the location of the most significant sources in the Mississippi basin responsible for the delivery of nitrogen to the Gulf of Mexico have not been clearly identified, because the parameters influencing nitrogen-loss rates in rivers are not well known. Here we present an analysis of data from 374 US monitor ing stations, including 123 along the six largest tributaries to the Mississippi, that shows a rapid decline in the average first-order rate of nitrogen loss with channel size--from 0.45 day (-1) in small streams to 0.005 day (-1) in the Mississippi river. Using stream depth as an explanatory variable, our estimates of nitrogen-loss rates agreed with values from earlier studies. We conclude that the proximity of sources to large streams and rivers is an important determinant of nitrogen delivery to the estuary in the Mississippi basin, and possibly also in other large river basins.

A Quantitative Method for Estimating Probable Public Costs of Hurricanes.

/ A method is presented for estimating probable public costs resulting from damage caused by hurricanes, measured as local government expenditures approved for reimbursement under the Stafford Act Section 406 Public Assistance Program. The method employs a multivariate model developed through multiple regression analysis of an array of independent variables that measure meteorological, socioeconomic, and physical conditions related to the landfall of hurricanes within a local government jurisdiction. From the regression analysis we chose a log-log (base 10) model that explains 74% of the variance in the expenditure data using population and wind speed as predictors. We illustrate application of the method for a local jurisdiction-Lee County, Florida, USA. The results show that potential public costs range from $4.7 million for a category 1 hurricane with winds of 137 kilometers per hour (85 miles per hour) to $130 million for a category 5 hurricane with winds of 265 kilometers per hour (165 miles per hour). Based on these figures, we estimate expected annual public costs of $2.3 million. These cost estimates: (1) provide useful guidance for anticipating the magnitude of the federal, state, and local expenditures that would be required for the array of possible hurricanes that could affect that jurisdiction; (2) allow policy makers to assess the implications of alternative federal and state policies for providing public assistance to jurisdictions that experience hurricane damage; and (3) provide information needed to develop a contingency fund or other financial mechanism for assuring that the community has sufficient funds available to meet its obligations. KEY WORDS: Hurricane; Public costs; Local government; Disaster recovery; Disaster response; Florida; Stafford Act

The oncogenic potential of Candida in the female genital tract.

The possible role of Candida species in carcinogenesis at the uterine cervix was investigated in 226 females attending a colposcopy clinic. Approximately 34% of the 226 subjects harbored Candida species in cervical/vaginal secretions, but there was no association with any particular histologic abnormality. Two independent analytical procedures were used for strain discrimination of the isolates of C. albicans, but again no relationship was found between individual strains and histologic diagnoses. Only three C. glabrata strains were isolated, but they were all in association with cervical intraepithelial neoplasia (CIN) II or III. A total of 18 strains of C. albicans, one C. glabrata and one C. parapsilosis all inhibited the formation of the nitrosamine nitrosodimethylamine (NDMA) from precursors. Furthermore, C. albicans strains did not convert NDMA to carcinogenic metabolites. The results of this study do not suggest that C. albicans has a role in cervical carcinogenesis.