Using opportunistic screening with abdominal CT to identify osteoporosis and osteopenia in patients with diabetes.

Opportunistic osteoporosis screening involves measuring the attenuation of L1 vertebrae on abdominal computed tomography (CT), which correlates with DXA T-score. We found that this approach is useful for detecting low bone mass in patients with diabetes and propose L1 attenuation ≤ 135 Hounsfield units (HU) as a threshold for which DXA should be strongly considered. INTRODUCTION: Attenuation of the L1 vertebrae on computer tomography (CT) images done for other reasons ("Opportunistic Osteoporosis Screening") has been found to correlate well with DXA-derived T-score. However, the method and the thresholds have never been tested specifically in those with diabetes mellitus (DM), in whom the fracture risk is greater than explained by BMD. METHODS: In a retrospective study of subjects with DM who had both abdominal CT and DXA within 6 months of each other, we compared L1 attenuation and DXA T-score to define the sensitivity and specificity of thresholds previously established in the general population. RESULTS: There were 313 subjects among whom 18 (5.8%) had prior major osteoporotic fracture (MOF). Subjects with MOF had lower T-scores (- 2.3 ± 1.4 vs. - 0.9 ± 1.4, p < 0.001) and L1 attenuation (104 HU ± 46 vs. 149 HU ± 47, p < 0.001) than non-fracture subjects. L1 attenuation ≤ 160 HU was 91% sensitive for osteoporosis, while ≤ 110 HU was 80% specific. For a higher T-score of ≤ - 1.5, L1 attenuation ≤ 135 HU showed balanced sensitivity and specificity (65% and 69%, respectively). CONCLUSION: Opportunistic osteoporosis screening with abdominal CT is useful in determining the need for DXA screening in subjects with diabetes. We propose L1 attenuation ≤ 135 HU as a reasonable threshold for detecting the T-score of ≤ - 1.5, which is likely associated with increased fragility in DM.

Accelerated sea-level rise from West Antarctica.

Recent aircraft and satellite laser altimeter surveys of the Amundsen Sea sector of West Antarctica show that local glaciers are discharging about 250 cubic kilometers of ice per year to the ocean, almost 60% more than is accumulated within their catchment basins. This discharge is sufficient to raise sea level by more than 0.2 millimeters per year. Glacier thinning rates near the coast during 2002-2003 are much larger than those observed during the 1990s. Most of these glaciers flow into floating ice shelves over bedrock up to hundreds of meters deeper than previous estimates, providing exit routes for ice from further inland if ice-sheet collapse is under way.

High geothermal heat flow, Basal melt, and the origin of rapid ice flow in central Greenland.

Age-depth relations from internal layering reveal a large region of rapid basal melting in Greenland. Melt is localized at the onset of rapid ice flow in the large ice stream that drains north off the summit dome and other areas in the northeast quadrant of the ice sheet. Locally, high melt rates indicate geothermal fluxes 15 to 30 times continental background. The southern limit of melt coincides with magnetic anomalies and topography that suggest a volcanic origin.

Mass Balance of the Greenland Ice Sheet at High Elevations.

Comparison of ice discharge from higher elevation areas of the entire Greenland Ice Sheet with total snow accumulation gives estimates of ice thickening rates over the past few decades. On average, the region has been in balance, but with thickening of 21 centimeters per year in the southwest and thinning of 30 centimeters per year in the southeast. The north of the ice sheet shows less variability, with average thickening of 2 centimeters per year in the northeast and thinning of about 5 centimeters per year in the northwest. These results agree well with those from repeated altimeter surveys, except in the extreme south, where we find substantially higher rates of both thickening and thinning.

In vitro release and diffusion studies of promethazine hydrochloride from polymeric dermatological bases using cellulose membrane and hairless mouse skin.

The study was designed to investigate the feasibility of developing a transdermal drug dosage form of promethazine hydrochloride (PMH). The in vitro release and diffusion characteristics of PMH from various dermatological polymeric bases were studied using cellulose membrane and hairless mouse skin as the diffusion barriers. These included polyethylene glycol (PEG), hydroxypropyl methylcellulose (HPMC), cross-linked microcrystalline cellulose, and carboxyl methyl cellulose sodium (Avicel CL-611), and a modified hydrophilic ointment USP. In addition, the effects of several additive ingredients known to enhance the drug release from topical formulations were evaluated. The general rank order for the drug release from these formulations using cellulose membrane was observed to be PEG > HMPC > Avicel CL-611 > hydrophilic ointment base. The inclusion of the additives had little or no effect on the drug diffusion from these bases, except for the hydrophilic ointment formulation containing 15% ethanol, which provided a significant increase in the drug release. However, when these formulations were studied for drug diffusion through the hairless mouse skin, the Avicel CL-611 base containing 15% ethanol exhibited the optimum drug release. The data also revealed that this formulation gave the highest steady-state flux, diffusion, and permeability coefficient values and correlated well with the amount of drug release.

Gas chromatographic determination of residual levels of tert.-butanol from lyophilized liposomal formulations.

The use of liposomal formulations is rapidly gaining popularity in pharmaceutical research and development. Their preparation often involves the use of organic solvents such as tert.-butanol to dissolve lipophilic lipids. To improve the physicochemical stability of the liposomes, lyophilizing the product is one of the best available means. A gas chromatographic method for the determination of tert.-butanol residual levels in lyophilized liposomes, employing sec.-butanol as internal standard, using a flame ionization detector (FID) detector and a cross-linked dimethylpolysiloxane capillary column, was developed. The method described is simple, sensitive, rugged, reliable and reproducible and requires less time than other reported methods for the quantitation of tert.-butanol; it also has pharmaceutical applications.