Effects of topoclimatic complexity on the composition of woody plant communities.

Topography can create substantial environmental variation at fine spatial scales. Shaped by slope, aspect, hill-position and elevation, topoclimate heterogeneity may increase ecological diversity, and act as a spatial buffer for vegetation responding to climate change. Strong links have been observed between climate heterogeneity and species diversity at broader scales, but the importance of topoclimate for woody vegetation across small spatial extents merits closer examination. We established woody vegetation monitoring plots in mixed evergreen-deciduous woodlands that spanned topoclimate gradients of a topographically heterogeneous landscape in northern California. We investigated the association between the structure of adult and regenerating size classes of woody vegetation and multidimensional topoclimate at a fine scale. We found a significant effect of topoclimate on both single-species distributions and community composition. Effects of topoclimate were evident in the regenerating size class for all dominant species (four Quercus spp., Umbellularia californica and Pseudotsuga menziesii) but only in two dominant species (Quercus agrifolia and Quercus garryana) for the adult size class. Adult abundance was correlated with water balance parameters (e.g. climatic water deficit) and recruit abundance was correlated with an interaction between the topoclimate parameters and conspecific adult abundance (likely reflecting local seed dispersal). However, in all cases, the topoclimate signal was weak. The magnitude of environmental variation across our study site may be small relative to the tolerance of long-lived woody species. Dispersal limitations, management practices and patchy disturbance regimes also may interact with topoclimate, weakening its influence on woody vegetation distributions. Our study supports the biological relevance of multidimensional topoclimate for mixed woodland communities, but highlights that this relationship might be mediated by interacting factors at local scales.

Mechanism-Based Inhibitors: Development of a High Throughput Coupled Enzyme Assay to Screen for Novel Antimalarials.

Identifying potent enzyme inhibitors through a robust HTS assay is currently thought to be the most efficient way of searching for lead molecules. We have developed a HTS assay that mimics a crucial step in an essential metabolic pathway, the purine salvage pathway of the malarial parasite Plasmodium falciparum. In this assay we have used purified recombinant enzymes: hypoxanthine guanine phosphoribosyl transferase (HGPRT) and inosine monophosphate dehydrogenase (IMPDH) from the malarial parasite and the human host, respectively. These two enzymes, which work in tandem, are used to set up a coupled assay that is robust enough to meet the stringent criteria of an HTS assay. In the first phase of our screen we seem to have identified novel inhibitors that kill the parasite by inhibiting the salvage pathway of the parasite.

Correlative study of exfoliative cytology and histopathology of oral carcinomas.

Cytology smears from 325 oral carcinomas were studied; the false-negative rate was 37%. Cancers of the floor of mouth exfoliated most malignant cells and those of the gingiva exofoliated the least. There was no correlation between the histologic grading, location, sex of the patient, and the result of the cytology smear. Oral exfoliative cytology should only be used as an adjunctive measure and is not a substitute for biopsy.

Evaluation of oral, pharyngeal, laryngeal and esophageal cancer risk in reverse smokers of chuttas.

Reverse smoking of chuttas seems to have no significance for the development of cancer of the hypopharynx, esophagus, larynx and nasopharynx. The conventional chutta smoker runs a slight risk of developing hypopharyngeal cancer. Other smoking and chewing habits do not seem to play any role in our area as these habits are very uncommon.