Characterization of the intraflagellar transport complex B core: direct interaction of the IFT81 and IFT74/72 subunits.

Required for the assembly and maintenance of eukaryotic cilia and flagella, intraflagellar transport (IFT) consists of the bidirectional movement of large protein particles between the base and the distal tip of the organelle. Anterograde movement of particles away from the cell body is mediated by kinesin-2, whereas retrograde movement away from the flagellar tip is powered by cytoplasmic dynein 1b/2. IFT particles contain multiple copies of two distinct protein complexes, A and B, which contain at least 6 and 11 protein subunits, respectively. In this study, we have used increased ionic strength to remove four peripheral subunits from the IFT complex B of Chlamydomonas reinhardtii, revealing a 500-kDa core that contains IFT88, IFT81, IFT74/72, IFT52, IFT46, and IFT27. This result demonstrates that the complex B subunits, IFT172, IFT80, IFT57, and IFT20 are not required for the core subunits to stay associated. Chemical cross-linking of the complex B core resulted in multiple IFT81-74/72 products. Yeast-based two-hybrid and three-hybrid analyses were then used to show that IFT81 and IFT74/72 directly interact to form a higher order oligomer consistent with a tetrameric complex. Similar analysis of the vertebrate IFT81 and IFT74/72 homologues revealed that this interaction has been evolutionarily conserved. We hypothesize that these proteins form a tetrameric complex, (IFT81)2(IFT74/72)2, which serves as a scaffold for the formation of the intact IFT complex B.

The effect of site of application on the transcutaneous absorption of 17-beta estradiol from a transdermal delivery system (Climara).

OBJECTIVE: The effect of site of application on 17-beta estradiol bioavailability was assessed in an open-label, randomized, crossover study of a once-weekly transdermal estradiol patch (Climara). DESIGN: After placement of a transdermal patch delivering 0.1 mg/day of estradiol on either the buttocks or abdomen, serial plasma samples were obtained over 7 days and for the immediate 24 h after patch removal. Plasma estradiol concentrations were used to estimate pharmacokinetic parameters for the rate and extent of absorption between the two sites. RESULTS: Plasma estradiol concentrations were sustained at premenopausal levels over the week in most subjects. After application on the buttock, mean peak plasma concentration (Cmax) was 125.1% and mean relative bioavailability (AUC(0-168)) was 117.2% of that from the abdomen site. CONCLUSIONS: In summary, the buttocks seem to be an acceptable site for the application for this once-weekly 17-beta estradiol transdermal delivery system. Because the extent of absorption was significantly more for buttock than for abdomen application, this application site may provide an advantage in women who experience menopausal symptoms at the end of the week.

Mental retardation and decision making: balancing autonomy and protection.

Balancing autonomy with protection in caring for patients with mental retardation remains a formidable task for many clinicians. Though historical debate has resulted in an attitude supporting increased autonomy for all patients generally, and in legislation for enhanced decision making for the developmentally disabled specifically, the operationalization of such attitudes and policies lacks sufficient attention in the literature. The authors discuss three important areas of decision making as these relate to the care of patients with mental retardation: competence, respect, and multiple stakeholders; and, offer recommendations in each area to provide clinicians with some guidance in balancing the goals of autonomy and protection in clinical care when treating people with mental retardation.

Implementing human factors training in technical operations and maintenance.

NASA: The author reports experience with design of human factors training for aircraft engineering operations and maintenance. The program was based on five principles: observable skills-based training; integration with policies, practices, and procedures; data-driven and performance focused material; training needs fit organizational and national cultures; and training must be useful and beneficial.^ieng

Bioavailability of two manufacturers' sustained-release quinidine gluconate tablets at steady state.

Steady-state bioavailability of sustained-release quinidine gluconate tablets manufactured by two companies was compared in a crossover study. The tablets were Quinaglute Dura-Tabs, manufactured by Berlex Laboratories, Inc., and generic quinidine gluconate tablets, manufactured by Bolar Pharmaceutical Company. Sixteen healthy male volunteers were given multiple doses of the two products in randomized sequence. Blood samples were obtained immediately before administration of the seventh dose (hour 72) and at 1, 2, 3, 4, 5, 6, 8, 10, and 12 hours after administration. Plasma samples were assayed for quinidine content by high-performance liquid chromatography. The tablets manufactured by Berlex provided statistically significantly higher plasma levels during the second half of the dosing interval (six to 12 hours postdose). A 29% difference in plasma levels was observed between the products at the end of the dosing interval. The Bolar quinidine gluconate tablets had a statistically significant lower area under the curve (AUC). The greatest difference in AUC occurred during the last six hours of the dosing period. The six- to 12-hour AUC for the Bolar tablets was 24% less than that for Berlex tablets. The generic tablets also achieved peak plasma level 31% sooner than did Quinaglute Dura-Tabs. The pharmacokinetic characteristics of the two products at steady state indicate that the Bolar quinidine gluconate tablet exhibited a more rapid onset of peak plasma levels and a more rapid decline to minimum plasma levels. In summary, the data from this multiple-dose study, performed using commercially available material, indicate that differences exist in pharmacokinetic performance of the products. However, the exact correlation between pharmacokinetic data and clinical effectiveness has not been established.

Steady-state bioavailability of two sustained-release quinidine preparations: quinidine gluconate versus quinidine sulfate.

Steady-state bioavailability of a sustained-release quinidine gluconate formulation was compared with that of a sustained-release quinidine sulfate preparation in a crossover study. Sixteen healthy men were given multiple doses (two tablets every 12 hours) of the two drugs in randomized sequence. Blood samples were obtained immediately before administration of the seventh dose (hour 70) and at 1, 2, 3, 4, 5, 6, 8, 10, and 12 hours after administration. Plasma samples were assayed for quinidine content by high-performance liquid chromatography, with the analyst unaware of the identity of the drug in the sample. On a tablet-for-tablet basis, the sustained-release quinidine gluconate tablets achieved significantly higher plasma levels between two and six hours, higher mean area under the curve, and higher mean maximum concentrations than did the sustained-release quinidine sulfate tablets. When the data were adjusted to correct for the 23% higher quinidine content in the quinidine sulfate tablets, plasma levels from the sustained-release quinidine gluconate were significantly higher than those from quinidine sulfate at all sampling points. Moreover, the sustained-release quinidine gluconate provided significantly greater bioavailability as determined by all pharmacokinetic parameters. Steady-state pharmacokinetics of sustained-release quinidine products cannot be predicted from single-dose studies. The present multiple-dose study demonstrated that, under steady-state conditions, sustained-release quinidine gluconate tablets are more available systemically than sustained-release quinidine sulfate tablets.