Issues in the evaluation of AIDS education programs. The case of California

Health education is currently considered the most important factor in the prevention of HIV infection. Many AIDS education programs have started within the past several years, but few have undergone rigorous evaluation. This article presents findings from an outcome evaluation of the state of California AIDS Education and Prevention Program, the largest AIDS public education program in the country. The data suggest that the specific educational intervention programs suffered from many design defects which made it impossible to determine accurately the effectiveness of the programs. The programs did not use standard pre/post design, for example, or use standardized testing procedures. Moreover, only cognitive knowledge about AIDS transmission and prevention was stressed in the educational interventions and measures of effectiveness. The Education and Prevention Program must now move to promoting and measuring attitude and behavior change in addition to cognitive knowledge. The article concludes that AIDS education and prevention programs must place greater emphasis on conducting thorough evaluations, if the goals of attitude and behavior change are to be achieved.

Optimized kinetics of reverse-triiodothyronine distribution and metabolism in the rat: dominance of large, slowly exchanging tissue pools for iodothyronines

We have estimated numerous physiological parameters of production, interpool transport, distribution, and metabolism of rT3 in the major rT3 pools of the unanesthetized male Sprague-Dawley rat. These results also have been combined with similar results for T3 and T4, generating a composite model for all three iodothyronines. Three different approaches were used to analyze the rT3 data, determined from five optimally timed blood samples collected in new tracer kinetic studies and processed by Sephadex chromatography and RIA. A model-structure independent approach generated a plasma clearance rate of 2.82 (ml/min)/100 g BW, a plasma turnover rate of 1.05 min-1, a plasma-to-total tissue flux of 0.107 (ng/min)/100 g BW and a plasma appearance rate (PAR) of 0.061 (ng/min)/100 g BW, the latter being the product of the plasma clearance rate and the endogenous rT3 plasma concentration. Multicompartmental analysis resulted in additional parameters of physiological interest, many only as ranges or minimum and maximum possible values, owing to complex factors intrinsic in rT3 kinetics. Whole body rT3 production can be as low as 0.061 (=PAR), and as high as 0.377 (ng/min)/100 g BW, i.e. possibly as much as 5 times greater than the PAR, the conventional estimate of production rate. Plasma contains only 3-12% of total body rT3 (Qtot); slow tissue pools, that exchange rT3 slowly with plasma, possibly muscle, skin, and brain, contain 63-95% of Qtot, and produce more than 42% of total body rT3 from T4 locally; and fast tissues like liver and kidney contain 2-26% of Qtot, and produce more than 12% of total body rT3 from T4 locally. The plasma equivalent distribution volume (VD) of rT3 is 38-146 ml/100 g BW, and its whole body mean residence time is only 14-52 min, both of which are an order of magnitude smaller than corresponding T3 values; but VD for rT3 and T4 are roughly the same. Noncompartmental analysis underestimated VD and mean residence time by somewhere between a factor of 1.2 and 4.6. Overall, these results indicate that tissue pools that exchange rT3 slowly with the plasma pool contain the majority of rT3, T3, and T4 in steady state; and these tissues also are implicated as major sites of T4 monodeiodination, to both rT3 and T3.

Some quantitative changes in iodothyronine distribution and metabolism in mild obesity and aging

Effects of high fat diet (HFD)-induced obesity and moderate aging on iodothyronine kinetics were studied in young adult (3 month old) chow-fed male rats and two groups of older 9- to 11-month-old) male rats, one on chow and the other on HFD. Labeled T4, T3, and rT3 were each injected via an intraatrial double lumen catheter in unanesthetized rats. Serial blood samples were collected according to optimally designed schedules, and labeled iodothyronines in serum were quantified with three different Sephadex gel chromatographic systems. Comprehensive kinetic analyses indicated the following. Several T4 metabolic indices were markedly different between the two older groups (chow vs. HFD), most notable, increased plasma T4 clearance rate (0.098 vs. 0.15 ml/min), decreased plasma T4 concentration (23 vs. 15 ng/ml), and a plasma T4 fractional turnover rate 2 times greater (0.10 vs. 0.19/min), all in the HFD group. There was also a high negative correlation between T4 concentration and body weight (r = 0.77), but not with age. However, the three groups manifested no significant differences in T4 secretion rates (2.0 vs. 2.2 vs. 2.3 ng/min) or whole body pool sizes (2.1 vs. 2.3 vs. 2.4 micrograms). Accounting for metabolic body size, there still were no differences in T4 secretion rate or pool sizes. For T3, we found an almost 3-fold increase in T3 whole body production rates, and a greater than 2-fold increase (from about 25% to 60%) in the percentage of T4 converted to T3 in both older groups relative to that in the young rats. There were almost no significant differences in T3 kinetics between older HFD and older chow-fed groups, and differences in rT3 kinetics among the three groups revealed no clear pattern. Our results suggest that age-related correlations in T4 concentration are a consequence of body weight differences, not age as such. However, the metabolic fate of T4 changes with age, with more than twice as much converted to T3 in older animals. Constancy of T4 production rate and total pool size in young and older animals, independent of body weight, together with the apparent increase in T4 conversion to T3 suggest that the metabolic needs of the animal are being met by regulation of T3 production from T4 conversion, not by regulation of T4 production as such.

Comprehensive kinetics of thyroxine distribution and metabolism in blood and tissue pools of the rat from only six blood samples: dominance of large, slowly exchanging tissue pools

We have estimated 24 physiological parameters of production, interpool transport, distribution, and metabolism of T4 in the major T4 pools of the unanesthetized male Sprague-Dawley rat from six optimally timed blood samples (at 1, 5, 23, 115, 465, 1440 min) and a comprehensive model and analysis. Despite 10-fold lower concentrations of T4 reported in tissues that exchange T4 with plasma at a slow rate (e.g. skeletal muscle) compared with rapidly exchanging tissues like liver and kidney, the composite of slow tissue pools contains 57% of total body T4, with only 17% in fast pools and 26% in plasma. At least 14% of the 0.53 ng/min/100 g BW of T4 secreted is converted to T3 in slow tissue pools, and 24% is an upper bound on whole body T4 to T3 conversion. The T4 fractional turnover rates in fast and slow tissue pools (0.154 and 0.007 min-1), corresponding tissue to plasma T4 fractional transport rates (0.152 and 0.006 min-1), and relative fluxes of T4 from plasma to fast vs. slow tissues (88% vs. 12%) were all found to be approximately the same as those we have reported for T3. As a consequence, the ratio of the fractional (or clearance) rate of entry of T3 into tissue to that of T4 was found to be equal to the ratio of the plasma equivalent distribution volume of T3 to that of T4 in the tissue, which also is the ratio of relative pool sizes of T3 and T4 in the tissue to those in plasma. This ratio (approximately 11) is approximately the same for all tissues, slow and fast, and it is also the same as the ratio of the net binding of T3 and T4 to plasma proteins. Finally, despite a 10 times slower early disappearance rate for a bolus of T4 than for T3 and reported single half-lives for T4 3-6 times greater, T4 actually spends only a third longer time (17.5 h) in the whole system, mostly in slow pools, before ultimate irreversible disposal.

Comprehensive kinetics of triiodothyronine production, distribution, and metabolism in blood and tissue pools of the rat using optimized blood-sampling protocols

We have determined estimates for 24 physiological parameters of production, interpool transport, distribution, and metabolism of T3 in the major T3 pools of the unanesthetized male Sprague-Dawley rat, from blood-borne data and a comprehensive model and analysis of this system. Most of these indices have previously been unavailable. Whereas only 3% (2 ng/100 g BW) of the total body T3 pool (74 ng/100 g BW) is in plasma, the composite of slowly equilibrating (slow) tissue pools (e.g. muscle, skin, and brain) appears to contain most of the T3, 76% (57 ng/100 g BW) of the total. The composite of rapidly equilibrating (fast) tissue pools (e.g. liver and kidney) contains the remaining 19% (16 ng/100 g BW). The total body T3 production rate is 0.12 ng/100 g BW . min, and we estimate that about half of this emanates directly from T4 in the slow pools, whereas the remainder is derived from both thyroidal secretion and T4 to T3 conversion in the fast pools. Our results also indicate that T3 molecules spend an average of only 0.5 min in transit each time through plasma, whereas the single pass mean transit times in fast and slow tissue pools (the times available for hormone action) are 10 times and 200 times greater. In contrast, the mean residence time for T3 in the entire system is greater than 12 h despite the extremely rapid early disappearance of injected T3 from plasma. To obtain the required accuracy, we used a novel optimization approach for choosing blood-sampling schedules (1, 4, 44, 202, and 600 min), a remarkably small number of sample times, and each was adjustable by about +/- 20% without effect on optimized parameter accuracies.