AAV-mediated delivery of the caspase inhibitor XIAP protects against cisplatin ototoxicity.

HYPOTHESIS: Delivery of the gene encoding X-linked inhibitor of apoptosis (XIAP) using an adeno-associated viral (AAV) vector can protect against cisplatin-mediated ototoxicity. BACKGROUND: Cisplatin is a widely used chemotherapeutic agent with significant ototoxic side effects. One possible mechanism of toxicity is apoptotic death of many cochlear cell types. Acute treatment with inhibitors of caspases- enzymes critical for apoptosis- has been shown to prevent hearing loss in vivo, but is too short-acting for therapeutic use. Gene therapy provides a specific and chronic means of delivering potential therapeutic gents. Introducing an anti-apoptotic gene into the cochlea could provide long-term prophylaxis against the ototoxic effects of cisplatin. METHOD: Two groups of rats were treated with unilateral injection into the round window of AAV harboring a gene encoding either XIAP or green fluorescent protein (GFP). After at least two months of gene expression, auditory-brainstem-response (ABR) threshold shifts and outer-hair-cell (OHC) number were measured in these two groups of animals after 72-hour treatment with cisplatin. RESULTS: Consistent with previous reports, uninjected and AAV.GFP-injected ears displayed profound ABR threshold elevations and OHC loss after cisplatin treatment. Ears that had been injected with AAV encoding XIAP, however, were significantly protected from these effects: cisplatin-induced ABR-threshold shift and hair-cell loss were attenuated by as much as 78% and 45%, respectively, when compared with contralateral (untreated) ears. CONCLUSION: XIAP delivery to the cochlea can protect against the audiometric changes and hair-cell loss associated with cisplatin ototoxicity. The efficacy, specificity, and duration of the protective effects make this a potentially attractive therapeutic paradigm.     

Dermal, oral, and inhalation pharmacokinetics of methyl tertiary butyl ether (MTBE) in human volunteers.

Methyl tertiary butyl ether (MTBE), a gasoline additive used to increase octane and reduce carbon monoxide emissions and ozone precursors, has contaminated drinking water and can lead to exposure by oral, inhalation, and dermal routes. To determine its dermal, oral, and inhalation kinetics, 14 volunteers were exposed to 51.3 microg/ml MTBE dermally in tap water for 1 h, drank 2.8 mg MTBE in 250 ml Gatorade(R), and inhaled 3.1 ppm. MTBE for 1 h. Blood and exhaled breath samples were then obtained. Blood MTBE peaked between 15 and 30 min following oral exposure, at the end of inhalation exposure, and ~5 min after dermal exposure. Elimination by each route was described well by a three-compartment model (Rsq >0.9). The Akaike Information Criterion for the three-compartment model was smaller than the two-compartment model, supporting it over the two-compartment model. One metabolite, tertiary butyl alcohol (TBA), measured in blood slowly increased and plateaued, but it did not return to the pre-exposure baseline at the 24-h follow-up. TBA is very water-soluble and has a blood:air partition ratio of 462, reducing elimination by exhalation. Oral exposure resulted in a significantly greater MTBE metabolism into TBA than by other routes based on a greater blood TBA:MTBE AUC ratio, implying significant first-pass metabolism. The slower TBA elimination may make it a better biomarker of MTBE exposure, though one must consider the exposure route when estimating MTBE exposure from TBA because of first-pass metabolism. Most subjects had a baseline blood TBA of 1-3 ppb. Because TBA is found in consumer products and can be used as a fuel additive, it is not a definitive marker of MTBE exposure. These data provide the risk assessment process of pharmacokinetic information relevant to the media through which most exposures occur-air and drinking water.     

Single nucleotide polymorphisms in the human progesterone receptor gene and spontaneous preterm birth

Progesterone supplementation can prevent preterm birth in some high-risk women. Progesterone binds to progesterone receptor (PR) and modulates the expression of target genes. This study investigates the association between single nucleotide polymorphisms (SNPs) in the PR gene and spontaneous preterm birth. DNA was extracted from consecutive patients with preterm birth (n = 78) and term controls (n = 415), and genotyping was performed for 3 PR SNPs (+331[G>A], + 770[C>T], +660[G>T]) using Sequenom matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Data were analyzed by chi(2) test and logistic regression analysis. Multivariate analysis showed no association between maternal carriage of minor + 331T, +770T, and/or +660T alleles and preterm birth when controlled for maternal age, ethnicity, gravidity, parity, prior preterm birth, route of delivery, or neonatal outcome. Carriage of +770T and +660T (but not +331T) was associated with preterm birth in women with a body mass index <18.5 kg/m(2) (relative risk, 10.8; 95% confidence interval, 1.4-82.6; P = .02). Maternal carriage of minor alleles of +331(G>A), +770(C>T), and +660(G> T) SNPs in the PR gene is not associated with spontaneous preterm birth.     

Revisiting the sponge sources, stereostructure, and biological activity of cyclocinamide a

The dramatic biogeographical variations in the secondary metabolites from Psammocinia aff. bulbosa have complicated our efforts to reisolate the two most cytotoxic of its metabolites, (+)-psymberin and (+)-cyclocinamide A. Reported now are the results of a new study that demonstrates our ability to repeatedly isolate these two compounds through targeted collection efforts. Additional study of the new sample of (+)-cyclocinamide A has enabled finalizing its biological activity and absolute stereochemistry as 4S, 7S, 11S, 14S.     

THE GRADIENT OF VASCULAR PERMEABILITY : III. THE GRADIENT ALONG THE CAPILLARIES AND VENULES OF FROG SKIN

A steeply mounting gradient of permeability is demonstrable along the meshwork of capillaries which connects the arterioles and venules of the skin of the frog. The venules incorporated in the meshwork are even more permeable than the capillary meshes giving into them. The presence of the gradient under such differing conditions as exist along frog and mammalian capillaries enables one to rule out certain factors which might be invoked to explain it; and it is not explainable in terms of those influences generally recognized as conditioning exchange between the blood and tissues. Not improbably it results from a structural differentiation along the capillary.