Advances in coffee tissue culture and its practical applications

Genetic improvement of coffee, an important commercial crop, through classical breeding is slow and cumbersome. Biotechnology offers alternative strategies for generating new and improved coffee varieties, including those resistances to environmental extremes, pests, and diseases, low in caffeine, and with uniform fruit maturation. Large improvements in somatic embryogenesis, development of haploids, and scale-up of micropropagation have been accomplished in the last 5 yr. The recent identification of expressed sequence tags (EST) that are differentially expressed during the infestation of coffee plants by coffee leaf miners and the isolation and cloning of the promoter for the N-methyltransferase gene associated with caffeine production open up the possibility of producing varieties of coffee with new traits. This review provides a summary of in vitro biological advances and directions as to how they could be applied to improve the production and quality of coffee.     

A theoretical study of pentacyclo-undecane cage peptides of the type [Ac-X-Y-NHMe].

The conformational preferences of peptides of the type, Ac-X-Y-NHMe, where X and Y = Ala, cage and Pro, were studied by means of computational techniques within the framework of a molecular mechanics approach. For each of the eight peptide analogues, extensive conformational searches were carried out using molecular dynamics (MD) and simulated annealing (SA) protocols in an iterative fashion. Both results are in good agreement and complement each other. The conformational search indicates that the cage residue restricts the conformational freedom of the dipeptide considerably in comparison with the other model residues used. This study revealed that proline exhibits a greater tendency in promoting reverse-turn characteristics in comparison to the cage peptides, which show promising beta-turn characteristics. It was also found that 300-500 K is not sufficient to overcome rotational barriers for cage peptides. In all cases, the low-energy conformers have a tendency to form bent structures.     

T-20 and T-1249 HIV fusion inhibitors' structure and conformation in solution: a molecular dynamics study.

Fusion of the HIV envelope with the target cell membrane is a critical step of the HIV entry into the target cell. Several peptides based on the C-region of HIV gp41 have been used in clinical trials as possible HIV fusion inhibitors. Among these are T-1249 and T-20 (also known as enfurvitide). Despite recent works, a detailed molecular picture of the inhibitory mechanism of these molecules is still lacking. These peptides are usually depicted as alpha-helices by analogy with the structure of the sequence of the gp41 protein with which they are homologous. However, structures like these would be highly unstable in solution and thus would not explain, by themselves, the ability that the two fusion inhibitors have to become solvated by water and also interact effectively with cell membranes. To this effect, extensive molecular dynamics simulations were carried out to investigate the structure and conformational behavior of T-1249 and T-20 in water, as well as shorter homologous peptides CTP and 3f5, which show no inhibitory action. We found that the studied inhibitors have no stable structure in solution in the time scale studied. Additionally, the solvent accessible area varies significantly during the simulation. Our findings suggest that these peptides may assume not only one, but several possible sets of structures in solution, some of which more adequate to interact with the solvent, whereas others might be better suited to interact with cell membranes. Interestingly, and in accordance with published experimental studies, we verified that T-1249 displays considerably larger alpha-helical structure than T-20. Taking into account a recent study with design peptides with increased helicity, it is possible that this feature may be related to the increased inhibiting efficiency of T-1249 relative to that of T-20.     

Maryland veterans' knowledge of risk factors for and signs of oral cancers and their use of dental services

Objectives : The purpose of this study was to evaluate outpatient veteran'í knowledge about risk factors for and signs of oral cancers, and their utilization of dental services. Design : Patients receiving primary health care services were surveyed during August 1997. Setting : Primary health care services at three medical centres within the VA Maryland Health Care System (VAMHCS). Subjects: A total of 135 outpatient veterans were interviewed. Intervention: Questionnaire administered by trained interviewers. Main outcome measures : Fifteen percent of the sample were eligible for dental care at the VA, while over 40% of those veterans participating in the study were unaware of their VA eligibility for dental services. Fifty six percent of the total sample received dental services from a private dentist, while 13% reported they had no provider of dental care. Of those not eligible for dental care at the VA (n=115), the majority (67%) received dental care from a private dentist. Current use of tobacco and alcohol was reported by 27% of the sample. Nonsmokers were more likely to visit the dentist in the previous year than smokers (OR=2.39, 95%C.I. 1.11,5.12). Although 84% correctly identified tobacco use as a risk factor, only 39% correctly identified regular alcohol use as a risk factor. Conclusions : Veterans at higher risk for oral cancers were less likely to have visited the dentist in the previous year, and, overall, were ill informed and misinformed about these cancers.     

Architecture of spatial circuits in the hippocampal region

The hippocampal region contains several principal neuron types, some of which show distinct spatial firing patterns. The region is also known for its diversity in neural circuits and many have attempted to causally relate network architecture within and between these unique circuits to functional outcome. Still, much is unknown about the mechanisms or network properties by which the functionally specific spatial firing profiles of neurons are generated, let alone how they are integrated into a coherently functioning meta-network. In this review, we explore the architecture of local networks and address how they may interact within the context of an overarching space circuit, aiming to provide directions for future successful explorations.