Radiolabeling of Methylphosphonate and Phosphorothioate Oligonucleotides and Evaluation of Their Transport in Everted Rat Jejunum Sacs

Purpose. The therapeutic use of antisense oligonucleotides will likely involve their administration over protracted periods of time. The oral route of drug dosing offers many advantages over other possible routes when chronic drug administration is necessary. However, little is known about the potential for oligonucleotide uptake from the gastrointestinal tract. This issue is addressed in the current work. Methods. We have developed a simple procedure for radiolabeling oligonucleotides by reductive alkylation with ¹⁴C-formaldehyde. We have utilized this approach, as well as 5 addition of fluorophores, to prepare labeled methylphosphonate and phosphorothioate oligonucleotides for use in intestinal transport studies. An everted rat gut sac model was employed to compare the transport of oligonucleotides to that of model compounds whose permeation properties are better understood. Results. We demonstrate that both methylphosphonate and phosphorothioate oligonucleotides are passively transported across the intestinal epithelium, probably by a paracellular route. The rates of transport for both types of oligonucleotides were similar, and were significantly greater than that of the very high MW polymer blue dextran, but were lower than the transport rate of valproic acid, a low MW compound known to have high oral availability. Conclusions. A significant degree of permeation of oligonucleotides across the gastrointestinal epithelium does occur, but it is still unclear whether this is sufficient to permit effective oral administration of oligonucleotides as drugs.     

Screening methods for thyroid hormone disruptors

The U.S. Congress has passed legislation requiring the EPA to implement screening tests for identifying endocrine-disrupting chemicals. A series of workshops was sponsored by the EPA, the Chemical Manufacturers Association, and the World Wildlife Fund; one workshop focused on screens for chemicals that alter thyroid hormone function and homeostasis. Participants at this meeting identified and examined methods to detect alterations in thyroid hormone synthesis, transport, and catabolism. In addition, some methods to detect chemicals that bind to the thyroid hormone receptors acting as either agonists or antagonists were also identified. Screening methods used in mammals as well as other vertebrate classes were examined. There was a general consensus that all known chemicals which interfere with thyroid hormone function and homeostasis act by either inhibiting synthesis, altering serum transport proteins, or by increasing catabolism of thyroid hormones. There are no direct data to support the assertion that certain environmental chemicals bind and activate the thyroid hormone receptors; further research is indicated. In light of this, screening methods should reflect known mechanisms of action. Most methods examined, albeit useful for mechanistic studies, were thought to be too specific and therefore would not be applicable for broad-based screening. Determination of serum thyroid hormone concentrations following chemical exposure in rodents was thought to be a reasonable initial screen. Concurrent histologic evaluation of the thyroid would strengthen this screen. Similar methods in teleosts may be useful as screens, but would require indicators of tissue production of thyroid hormones. The use of tadpole metamorphosis as a screen may also be useful; however, this method requires validation and standardization prior to use as a broad-based screen.     

Application of the Electrotopological State Index to QSAR Analysis of Flavone Derivatives as HIV-1 Integrase Inhibitors

Purpose. A QSAR study based on electrotopological state (E-state) indices was conducted for a series of flavone HIV-1 integrase inhibitors to guide drug design. Methods. E-state indices formulated to encode electronic and topological information for each skeletal atom in a molecule (Kier and Hall Pharm. Res. 7:801–807 (1990)) were calculated using the Molconn-X program, and partial least squares (PLS) multivariate regression was used to derive QSAR models. Results. Predictive models with correlation coefficients (r²) of 0.98 (3 PLS components) and 0.99 (5 PLS components) and corresponding cross-validated correlation coefficients (c.v. r²) of 0.51 and 0.73, were obtained for inhibition of cleavage and integration, respectively, with one molecule omitted from the analysis. Conclusions. E-state indices at C6, C3, C5, C5, and O4 were found to be more important for prediction of activity than those for any of the other 12 flavone skeletal atoms that are common to the molecules in the data set.     

A brief history of trying: man, NASA, and medicine.

The development of the V2 rocket during World War II raised the possibility of manned spaceflight to the level of "serious consideration." Concepts of aviation medicine led to the specialty of space medicine. Projects Mercury, Gemini, Apollo, Skylab, and Apollo-Soyuz, and the Space Transportation System have helped us gain important biomedical information, including but not limited to, microgravity and its effects on red cell mass, orthostatic tolerance, exercise capacity, bone density, and muscle nitrogen levels. Problems of "space motion sickness" and micro-organisms in space have become major concerns. This analytic review covers these topics and relevant others.     

Chronic fluphenazine treatment modifies circadian rhythms of neurotransmitter receptor binding in rat brain

Summary Binding to rat brain- and-adrenergic, muscarinic cholinergic, dopamine and opiate receptors was measured at 4-hour intervals throughout a 24-hour period in animals, chronically treated with fluphenazine, and in controls. Drug treatment significantly changed characteristics of the circadian rhythms in all 5 receptors. In the presence of the drug the 24-hour mean binding to the dopamine receptor was decreased; to the other 4 receptors it was increased. Moreover, there were changes in the timing of the maximal receptor binding (phase-position) and in the amplitude of the rhythms. These results extend previous studies, showing that chronic neuroleptic treatment not only affects the dopamine receptors, but also other neurotransmitter receptors, profoundly modifying their temporal organisation.     

An assessment of pharmaceutical inspection reports from nursing and residential homes for the elderly in Northern Ireland

Objectives To highlight issues currently being inspected in nursing, residential and dual‐registered homes (care homes) for the elderly in Northern Ireland as part of a pharmaceutical inspection. Methods A cross‐sectional survey and analysis of reports from pharmaceutical inspections in Northern Ireland care homes between January 1999 and December 2000 was undertaken, using reports provided by the four Registration and Inspection Units (R & I Units 1–4) within the region. Reports were reviewed and all recommendations made by inspectors were classified into 11 main categories. Binary logistic regression was used to examine possible relationships between the type of home (nursing, residential or dual‐registered) or the R & I unit and the recommendations made by the inspectors, with corresponding odds ratios and 95% confidence intervals. Key findings Reports from 415 homes (one report per home) formed the final sample for analysis. Each R & I unit used different documentation to conduct a pharmaceutical inspection. Homes received the majority of recommendations from inspectors in the categories ‘Records’ (66.7% of all homes), ‘Policies and protocols’ (39.3%) and ‘Medication’ (31.8%). More recommendations in a number of categories emanated from R & I unit 4 compared with R & I unit 1 (referent). Dual‐registered homes (those registered as a nursing and residential facility) were more likely to receive a recommendation in the categories ‘Storage of medicine’, ‘Order and receipt of medication’ and ‘Equipment’ than nursing or residential homes. Conclusion Inspections of care homes should be standardised in terms of documentation used and facilities should be given guidance on issues that are likely to result in recommendations from inspectors. In the longer‐term, pharmaceutical inspections should move from a focus on structure/process measures to those that emphasise quality in prescribing.     

The relationship between dietary fat intake and risk of colorectal cancer: evidence from the combined analysis of 13 case-control studies

The objective of this study was to examine the effects of the intakeof dietary fat upon colorectal cancer risk in a combined analysis of datafrom 13 case-control studies previously conducted in populations withdiffering colorectal cancer rates and dietary practices. Original datarecords for 5,287 cases of colorectal cancer and 10,470 controls werecombined. Logistic regression analysis was used to estimate odds ratios (OR)for intakes of total energy, total fat and its components, and cholesterol.Positive associations with energy intake were observed for 11 of the 13studies. However, there was little, if any, evidence of anyenergy-independent effect of either total fat with ORs of 1.00, 0.95, 1.01,1.02, and 0.92 for quintiles of residuals of total fat intake (P trend =0.67) or for saturated fat with ORs of 1.00, 1.08, 1.06, 1.21, and 1.06 (Ptrend = 0.39). The analysis suggests that, among these case-control studies,there is no energy-independent association between dietary fat intake andrisk of colorectal cancer. It also suggests that simple substitution of fatby other sources of calories is unlikely to reduce meaningfully the risk ofcolorectal cancer.