Conversion of a radiolabelled ecdysone precursor, 2,22,25-trideoxyecdysone, by embryonic and larval tissues of Locusta migratoria

A high specific activity tritiated ecdysone precursor, 2,22,25-trideoxyecdysone, was used to probe the capacity of various embryonic and larval tissues to perform the last 3 hydroxylation steps in ecdysone biosynthesis. Embryos at early stages of development, prior to the differentiation of their endocrine glands and embryonic heads, thoraces and abdomens of later stages, were found to have the capacity to hydroxylate the precursor to ecdysone. Larval epidermis and fat body are also able to transform 2,22,25-trideoxyecdysone into ecdysone; Malpighian tubules and midgut hydroxylate the precursor at C-2 but are apparently unable to hydroxylate both at C-22 and C-25. Larval prothoracic glands convert the precursor to ecdysone at a very efficient rate, which is 1-2 magnitudes higher than that of the other tissues investigated; several data argue for the existence of a privileged sequence of hydroxylations, C-25, C-22, C-2, in the larval prothoracic glands.     

A clinical interactive technique for MR-CT image registration for target delineation of intracranial tumors

Replacement of current CT-based, three-dimensional (3D) treatment planning systems by newer versions capable of automated multi-modality image registration may be economically prohibitive for most radiation oncology clinics. We present a low-cost technique for MR-CT image registration on a "first generation" CT-based, 3D treatment planning system for intracranial tumors. The technique begins with fabrication of a standard treatment mask. A second truncated mask, the "minimask," is then made, using the standard mask as a mold. Two orthogonal leveling vials glued onto the minimask detect angular deviations in pitch and roll. Preservation of yaw is verified by referencing a line marked according to the CT laser on the craniocaudal axis. The treatment mask immobilizes the patient's head for CT. The minimask reproduces this CT-based angular treatment position, which is then maintained by taping the appropriately positioned head to the MR head coil for MR scanning. All CT and MR images, in DICOM 3.0 format, are entered into the treatment planning system via a computer network. Interactive registration of MR to CT images is controlled by real-time visual feedback on the computer monitor. Translational misalignments at the target are eliminated or minimized by iterative use of qualitative visual inspection. In this study, rotational errors were measured in a retrospective series of 20 consecutive patients who had undergone CT-MR image registration using this technique. Anatomic structures defined the three CT orthogonal axes from which angular errors on MR image were measured. Translational errors at the target isocenter were within pixel size, as judged by visual inspection. Clinical setup using the minimask resulted in overall average angular deviation of 3 degrees +/-2 degrees (mean +/- SD) and translational deviation within the edges of the target volume of typically less than 2 mm. The accuracy of this registration technique for target delineation of intracranial tumors is compatible with practice guidelines. This method, then, provides a cost-effective means to register MR and CT images for target delineation of intracranial tumors.     

Social representations of HIV/AIDS in Central and Eastern Europe

Although a relatively recent epidemic, HIV is now increasing in Eastern Europe faster than anywhere else in the world. In the study reported in this paper, we interviewed 511 business people and health professionals in five Central and Eastern European nations: Estonia, Georgia, Hungary, Poland and Russia, deriving our questions primarily from a Social Representations perspective. Respondents also freely completed their associations with the stimulus word 'AIDS'. Our findings indicate that, although there is considerable agreement about the threat posed by the epidemic, there are also notable cultural differences in attributions about the origin and spread of the virus and the nature of those groups at risk of infection. These findings are interpreted in the light of the historical legacies of the Communist era, as well as the real economic and social challenges faced by the population of this region.     

Prediction of the shelf life of cellulose acetate hemodialyzers by Monte Carlo simulation

A previous investigation by our laboratory linked cellulose acetate degradation with adverse health effects in hemodialysis patients. To establish the accumulation of degradation products with time, a Monte Carlo model of degradation kinetics was developed. The model tracks changes in a population of molecules representative of the dialyzer membrane during the degradation process. The degradation calculation is a two step process: First, the model uses a random number to select an individual polymer molecule out of the population, and then a second random number is used to identify a site on the selected molecule for the degradation reaction to occur. After the reaction calculation, the resulting degraded molecules are redistributed into the population. The course of the reaction is determined by recalculating the molecular weight averages in the changing population as the calculations proceed. The model was validated using gel permeation chromatography molecular weight results and total acetyl content measurements on dialyzers stored up to 13.3 years after manufacture. It was found that the degradation reactions can be accurately modeled as random events and that the chain scissions and deacetylation events occur at constant rates. The shelf life of these devices was estimated using the model predictions and animal test results.     

Involvement of acetaldehyde for full protection against alcoholism by homozygosity of the variant allele of mitochondrial aldehyde dehydrogenase gene in Asians

There is a functional polymorphism of the mitochondrial aldehyde dehydrogenase (ALDH2) gene with the variant allele (ALDH2*2) encoding a protein subunit that confers low activity to the tetrameric enzyme. Genetic epidemiologic studies have strongly suggested that homozygosity for the allele ALDH2*2 is sufficient in completely inhibiting the development of alcoholism in Asians. To study the pathophysiology of this unique pharmacogenetic effect, we recruited a total of eighteen adult Han Chinese men, matched by age, body-mass index, nutritional state and homozygosity at the alcohol dehydrogenase gene loci from a population base of 273 men. Six individuals were chosen for each of the three ALDH2 allelotypes: homozygous ALDH2*2/*2, heterozygous ALDH2*1/*2, and homozygous ALDH2*1/*1. Following a low dose of ethanol (0.2 g/kg body weight), blood ethanol/acetaldehyde concentrations, cardiac and extracranial/intracranial arterial hemodynamic parameters, as well as self-rated subjective sensations, were measured for 130 min. Homozygous ALDH2*2 individuals were found to be strikingly responsive to the small amount of alcohol, as evidenced by the pronounced cardiovascular hemodynamic effects as well as subjective perception of general discomfort for as long as 2 h following ingestion. This low-dose alcohol hypersensitivity, accompanied by a prolonged and large accumulation of acetaldehyde in blood, provides an explanation for the strong protection against heavy drinking and alcoholism in individuals homozygous for the ALDH2*2 gene allele.     

RP—HPLC测定痢必灵片中苦参碱和氧化苦参碱的含量

目的建立测定痢必灵片中苦参碱和氧化苦参碱含量的高效液相色谱法。方法采用KromasilC18（250mm×4．6mm，5μm）的色谱柱；以0．05mol／L的磷酸二氢铵水溶液（H3PO4调pH2．5）-甲醇-乙腈-高氯酸钠（90：2：8：0．65）为流动相；流速：1ml／min；检测波长：220nm；柱温为30℃。结果苦参碱在0．126～1．26μg／ml范围内与峰面积分别呈良好的线性关系（r=0．9994，n=6），氧化苦参碱在2．9215～29．215μg/ml范围内与峰面积分别呈良好的线性关系（r=0．9997，n=6）。平均回收率分别是99．2％（RSD=2．2％）、99．4％（RSD=0．9％）。结论HPLC法测定痢必灵片中苦参碱和氧化苦参碱含量简便、准确、可靠，可用于痢必灵片的质量控制。