Balance-dendrogram. A new routine of CoDaPack

A statistical analysis of compositional data based on the Aitchison geometry of the simplex requires an appropriate basis for representing the data. A simple and intuitive way of building such a basis employs a sequential binary partition of the compositional vector. The partition, together with some statistical summaries of the coordinates, or balances, can be represented in a dendrogram-type graph. In this paper we introduce an implementation of this methodology inside CoDaPack, which is freeware. An example with real data illustrates the use of the Balance-Dendrogram routine.     

Cross sections of proton induced nuclear reactions on enriched 111Cd and 112Cd for the production of 111In for use in nuclear medicine

Proton induced nuclear reactions on enriched 111Cd and 112Cd have been studied up to 30 MeV in the context of routine production of the medically used isotope 111In with low and medium energy cyclotrons. The excitation functions of 111Cd(p,n)111m,gIn and 112Cd(p,2n)111m,gIn as production reactions and 111Cd(p,2n)110mIn, 111Cd(p,2n)110In, 111Cd(p,3n)109ml,m2,In, 112Cd(p,3n)110mIn, 112Cd(p,3n)110gIn as competing processes have been measured using the activation method involving the stacked-foil technique. The deduced thick target yields are compared with those obtained experimentally.     

Degradation of the light-stress protein is mediated by an ATP-independent, serine-type protease under low-light conditions

Green plants respond to light stress by induction of the light-stress proteins (ELIPs). These proteins are stable as long as the light stress persists but are very rapidly degraded during subsequent low light conditions. Here we report that the degradation of ELIPs is mediated by an extrinsic, thylakoid-associated protease which is already present in the membranes during light stress conditions. Partial purification of the protease by perfusion chromatography indicates that this proteolytic activity may be represented by a protein with an apparent molecular mass of 65 kDa. The ELIP-directed protease is localized in the stroma lamellae of the thylakoid membranes and does not require ATP or additional stromal factors for proteolysis. The protease has an optimum activity at pH 7.5-9.5 and requires Mg2+ for its activity. The ELIP-degrading protease show an unusual temperature sensitivity and becomes reversibly inactivated at temperatures below 20 degree C and above 30 degree C. Studies with protease inhibitors indicate that this enzyme belongs to the serine class of proteases. The enhanced degradation of ELIP in isolated thylakoid membranes after addition of the ionophore nigericin suggests that a trans-thylakoid delta pH or changes in ionic strength may be involved in the mechanism of protease activation.     

Biochemical changes in cerebrospinal fluid associated with the neurotoxic action of HIV-1]

Different intravascular ultrasound (IVUS) systems vary in their image presentation. The purpose of this study was to compare four IVUS systems in vitro to determine the accuracy of tissue characterization of atherosclerotic plaque compared with histology. Ninety-eight plaque segments from 23 formalin-fixed human iliac arteries were imaged in saline at room temperature with four different IVUS systems. To assess the accuracy of IVUS in describing plaque, three types of analysis were performed: (1) the ability to identify the presence and extent of lumen or plaque boundary; (2) sensitivity, specificity, and interobserver variability of IVUS in qualitatively identifying plaque components compared with histology; and (3) quantification of calcification. The synthetic aperture device had a lower sensitivity in identifying lumen and plaque boundaries (87%, 38% respectively) compared with other machines (96%-100%, 95%-100%). All three mechanically rotating systems had fair to good sensitivities for identifying calcification (57%-73%) or lipid filled areas (50%-83%). The sensitivity of discriminating fibrous tissue from fatty areas was low (39%-52%). The synthetic aperture system had a significantly lower sensitivity for identifying all three tissue types (4%-21%). There was significant interobserver variability (kappa value = 0.47-0.68) as well as machine to machine variability (kappa value = 0.52) for tissue characterization. Calcified areas were underestimated by System 1 (p < .05) and System 4 (p < .01) because of weaker echo reflections or poor image quality. There are significant differences in image representation among these four IVUS systems in the diagnosis of tissue components of complex atherosclerotic plaque. These variabilities should be considered when interpreting studies performed with different machines.     

Stoffwechselwirkungen von ω-3-Fettsäuren

Metabolic Effects of ω-3 Fatty Acids Biological effects of ω-3 fatty acids are related to their properties as structural components of cell membranes, their role as precursors of eicosanoids and their effects on lipoprotein metabolism. This is the basis for a great variety of metabolic effects, many of which of increasing medical interest. Particularly in the cardiovascular field, ω-3 fatty acids have been shown to have a wide spectrum of potentially antiatherogenic effects. Among these are the inhibition of platelet aggregation, reduction of blood viscosity, lowering of blood pressure and suppression of inflammatory reactions in the arteriosclerotic plaque. The principal actions in lipid metabolism are a reduction in triglycerides and a small increase in HDL₂. The effect on LDL-cholesterol is complex and an adverse LDL-increase may occur in particular hyperlipoproteinemias.     

Chili pepper consumption and gastric cancer in Mexico: a case-control study

Laboratory studies indicate that capsaicin, the hot-tasting component of chili peppers, may be carcinogenic. A population-based case-control study was conducted in Mexico City during 1989-1990 to evaluate the relation between chili pepper consumption and gastric cancer risk. The study included 220 incident cases and 752 controls randomly selected from the general population. Information was collected by interview. Chili pepper consumers were at high risk for gastric cancer compared with nonconsumers (age- and sex-adjusted odds ratio = 5.49, 95% confidence interval (CI) 2.72-11.06). Among consumers, there was a highly significant trend of increasing risk with increasing self-rated level of consumption (low, medium, and high) (p = 2 x 10(-7). The odds ratio for high-level consumers compared with nonconsumers was 17.11 (95% CI 7.78-37.59). However, when consumption was measured as frequency per day, a significant trend among consumers was not observed. Multivariable adjustment increased the magnitude of the chili pepper-gastric cancer association, but a significant trend among consumers (measured as frequency per day) was still not observed. Chili pepper consumption may be a strong risk factor for gastric cancer, but further studies are needed to test this hypothesis.