New insights into body composition assessment in obese women.

During treatment of patients with non-insulin-dependent diabetes mellitus, there may be marked body weight loss. Therefore, body composition should be monitored to check for a decrease in fat mass alone, without an excessive decrease of both fat-free mass and total body water. Accordingly, it is useful to monitor the hydration of these patients. One method that allows us to check the status of body hydration is the multifrequency bioelectric impedance analysis (MFBIA). It makes use of formulas that estimate total body water on the basis of the concept that the human body may be approximated to a cylinder of length equal to body height. In normal subjects body water estimates are sufficiently accurate, but in obese subjects the true hydration status may be overestimated. In this report, we describe the accuracy of mathematical models previously described in the literature, and correct for the overestimation of total body water in obese subjects by means of a new equation based on a new model. The coefficients for each model have been recalculated by the weighing of our sample in order to test the accuracy of estimates obtained with the equations. This new model includes both body volume and two impedances at appropriate frequencies useful for identifying two terms strictly related to extra- and intra-cellular water. The new formulas do not include body weight, but they include the body volume, a parameter more closely related to the biophysical reference model. Fifty-five overweight females, body mass index ranging from 26.8 to 50.2 kg/m2, were enrolled in the study. The proposed equations, taking advantage of two impedance values at appropriate frequencies, better predict total body water in obese women. This was particularly evident when the results obtained with the multifrequency bioelectric impedance analysis and deuterium isotopic oxide dilution method were compared. Although this last method is considered the "gold standard," it is not suitable for use in routine clinical practice. In conclusion, evaluation of total body composition by means of bioelectric impedance analysis might be included in programs for the prevention of non-insulin-dependent diabetes and for monitoring weight loss during overt pathology.     

Virus-induced CD8+ T cell clonal expansion is associated with telomerase up-regulation and telomere length preservation: a mechanism for rescue from replicative senescence

In acute infectious mononucleosis (AIM), very large clones of Ag-specific CD8+ effector T cells are generated. Many clones persist as memory cells, although the clone size is greatly reduced. It would be expected that the large number of cell divisions occurring during clonal expansion would lead to shortening of telomeres, predisposing to replicative senescence. Instead, we show that clonally expanded CD8+ T cells in AIM have paradoxical preservation of telomere length in association with marked up-regulation of telomerase. We postulate that this allows a proportion of responding T cells to enter the memory pool with a preserved capacity to continue dividing so that long-term immunological memory can be maintained.     

Anopheles albitarsis eggs: ultrastructural analysis of chorion layers after permeabilization

Construction of transgenic Anopheles mosquitoes refractory to Plasmodium requires knowledge of mosquito developmental biology. In order to study Anopheles embryology the removal or, alternatively, the permeabilization of the melanized and sclerotized egg chorion were attempted. The protocol classically used for chorion removal of Drosophila eggs was applied, with partial efficacy, to Anopheles albitarsis, a neotropical malaria vector. Each step was monitored by scanning electron microscopy and the results suggest differences in chorion composition between the two taxa. As an alternative to chorion removal, mosquito eggs were permeabilized with benserazide, an inhibitor of Dopa Decarboxylase, one of the enzymes needed for mosquito eggshell sclerotization. Embryo morphology and viability were not affected by this treatment. Permeabilization of the egg chorion allowed the ultrastructural observation of an internal homogeneous endochorion and an external compound exochorion, the latter consisting of a basal lamellar layer and protruding tubercles.     

Evaluation of insecticide resistance and biochemical mechanisms in a population of Culex quinquefasciatus (Diptera: Culicidae) from São Paulo, Brazil

To establish an insecticidal resistance surveillance program, Culex quinquefasciatus mosquitoes from S?o Paulo, Brazil, were colonized (PIN95 strain) and analyzed for levels of resistance. The PIN95 strain showed low levels of resistance to organophosphates [malathion (3.3-fold), fenitrothion (11.2-fold)] and a carbamate [propoxur (3.0-fold)]. We also observed an increase of 7.4 and 9.9 in alpha and beta esterase activities, respectively, when compared with the reference IAL strain. An alteration in the sensitivity of acetylcholinesterase to insecticide inhibition was also found in the PIN95 mosquitoes. The resistant allele (Ace.1R), however, was found at low frequencies (0.12) and does not play an important role in the described insecticide resistance. One year later, Cx. quinquefasciatus mosquitoes were collected (PIN96 strain) at the same site and compared to the PIN95 strain. The esterase activity patterns observed for the PIN96 strain were similar to those of the PIN95 mosquitoes. However the occurrence of the Ace.1R allele was statistically higher in the PIN96 strain. The results show that esterase-based insecticide resistance was established in the PIN95 Cx. quinquefasciatus population and that an acethylcholinesterase based resistant mechanism has been selected for. A continuous monitoring of this phenomenon is fundamental for rational mosquito control and insecticide application programs.     

Characterization of Rhodnius neglectus from two regions of Brazil using isoenzymes, genitalia morphology and morphometry

Among the triatomines considered as secondary in the epidemiology of Chagas disease, Rhodnius neglectus is frequently captured in artificial ecotopes, especially peridomiciliary ones, rarely producing colonies indoors. Nevertheless, the presence of breeding colonies in houses was unquestionably demonstrated in some areas of the State of Goiás, Brazil. Previous isoenzyme comparisons of this species with morphologically close triatomines, such as R. prolixus, R. robustus or R. nasutus, did not produce definitive conclusions because of doubt about the geographical origin of the R. neglectus. We present here, for the first time, the isoenzyme profile of topotypes of R. neglectus. In addition, wild caught specimens from the type locality, Uberaba (Minas Gerais, Brazil), were compared to wild caught specimens from Jaraguá (Goiás, Brazil), where R. neglectus is more frequently reported invading houses. We used isoenzyme, morphology and morphometry analysis. Neither morphological nor enzymatic differences were found between areas, but metric, size-related divergence was evidenced between them.     

Evidence for the notch signaling pathway on the role of estrogen in angiogenesis

We have investigated the molecular mechanisms involved in 17 beta-estradiol-induced angiogenic pathway. We show here that 17 beta-estradiol promoted a 6-fold increase in Jagged1 expression and an 8-fold increase in Notch1 expression by cDNA arrays in breast cancer MCF7 cells. Interestingly, Jagged1 was abrogated by incubation with the estrogen antagonist, ICI182,780. A similar up-regulation of both Notch1 receptor and Jagged1 ligand was found in endothelial cells. Additionally, imperfect estrogen-responsive elements were found in the 5' untranslated region of Notch1 and Jagged1 genes. Treatment with 17 beta-estradiol also led to an activation of Notch signaling in MCF7 cells expressing Notch1 reporter gene or by promoting Jagged1-induced Notch signaling in coculture assays. Inoculation of MCF7 cells in 17 beta-estradiol-treated nude mice resulted in up-regulation of Notch1 expression as well as increased number of tumor microvessels in comparison to placebo-treated mice. Notch1-expressing endothelial cell cultures formed cord-like structures on Matrigel in contrast to cells expressing a dominant-negative form of Notch1, emphasizing the relevance of Notch1 pathway in vessel assembly. Finally, Notch1-expressing MCF7 cells up-regulated hypoxia-inducible factor 1 alpha gene, a well-known angiogenic factor that clustered with Notch1 gene. This study implicates Notch signaling in the cross talk between 17 beta-estradiol and angiogenesis.     

The endothelin/sarafotoxin-induced increase of the proliferation of undifferentiated and DMSO-differentiated GEM-81 goldfish erythrophoroma cells is mediated by ETB receptors

Endothelins (ETs) and sarafotoxins (SRTXs) have been reported to exert ET(B)-mediated effects on vertebrate pigment cells. GEM-81 cell line, a red pigment cell-derived cutaneous tumor of the teleost Carassius auratus, expresses ET(B) receptors and can be differentiated with 1.5% DMSO treatment, thus constituting an useful model to investigate ET and SRTX effects on cultured fish pigment cells. Our aim was to characterize the pharmacology and biological effects mediated by ET receptors in DMSO-differentiated and undifferentiated cells. ET subtype receptors and their respective Ki values in both cell types were determined by competitive binding assays using (125)I ET-1 and BQ-485 (an ET(A) antagonist) or BQ-788 (an ET(B) antagonist). BQ-788, but not BQ-485, significantly reduced (125)I-ET-1 binding in both cell types, with similar low (Ki > nM) affinities. To determine the proliferation effects of ETs/SRTXs, cells were treated for 72 h with the hormones, and counted in a hemocytometer. The proliferation assays were repeated for SRTX S6c in the presence or absence of BQ-788. The results demonstrated that, with the exception of ET-1 (biphasic effect) and ET-3 (no significant effect) in undifferentiated GEM-81 cells, all the tested hormones induced increases in the proliferation of both types of cells. The hormones were equipotent in DMSO-differentiated cells, which exhibited increased sensitivity to ETs, but not to SRTXs, as compared with undifferentiated cells. The BQ-788 antagonistic effect was also exerted on the proliferation responses to SRTX S6c. These results corroborate the long and important evolutionary history of the ET/SRTX receptor system in vertebrate pigment cells.     

Validation of the GROMOS force-field parameter set 45A3 against nuclear magnetic resonance data of hen egg lysozyme

The quality of molecular dynamics (MD) simulations of proteins depends critically on the biomolecular force field that is used. Such force fields are defined by force-field parameter sets, which are generally determined and improved through calibration of properties of small molecules against experimental or theoretical data. By application to large molecules such as proteins, a new force-field parameter set can be validated. We report two 3.5 ns molecular dynamics simulations of hen egg white lysozyme in water applying the widely used GROMOS force-field parameter set 43A1 and a new set 45A3. The two MD ensembles are evaluated against NMR spectroscopic data NOE atom–atom distance bounds, ³J_NH and ³J coupling constants, and ¹5N relaxation data. It is shown that the two sets reproduce structural properties about equally well. The 45A3 ensemble fulfills the atom–atom distance bounds derived from NMR spectroscopy slightly less well than the 43A1 ensemble, with most of the NOE distance violations in both ensembles involving residues located in loops or flexible regions of the protein. Convergence patterns are very similar in both simulations atom-positional root-mean-square differences (RMSD) with respect to the X-ray and NMR model structures and NOE inter-proton distances converge within 1.0–1.5 ns while backbone ³J_HN-coupling constants and ¹H– ¹5N order parameters take slightly longer, 1.0–2.0 ns. As expected, side-chain ³J-coupling constants and ¹H– ¹5N order parameters do not reach full convergence for all residues in the time period simulated. This is particularly noticeable for side chains which display rare structural transitions. When comparing each simulation trajectory with an older and a newer set of experimental NOE data on lysozyme, it is found that the newer, larger, set of experimental data agrees as well with each of the simulations. In other words, the experimental data converged towards the theoretical result.     

Cell cycle time and rate of entry of cells into mitosis in the small intestine of young rats

Cell cycle time (T(C)) and the rate of entry of cells into mitosis (r(M)) in the jejunum and duodenum of young rats were investigated using the stathmokinetic method. The cell cycle times in the jejunum were 24.3 and 28.3 h in light and dark periods, respectively. Cell cycle times in the duodenum were 17.1 and 21.5 h in light and dark periods, respectively. Rates of entry of cells into mitosis in the jejunum were 1.2 and 1.1 cells/cell/h in light and dark periods and rates of entry of cells into mitosis in the duodenum were 1.4 and 1.8 cells/cell/h in light and dark periods, respectively. Although these changes to cell cycle time values are not statistically significant, the variation between the two periods should be considered in relation to its possible biological effects.