Body composition estimates using different measurement techniques in a sample of highland subsistence farmers in Guatemala

This study aims at assessing the accuracy of estimates of body composition provided by bioimpedance (BIA) equations developed for U.S. populations when applied to a sample of Guatemalan farmers. If these equations were shown to have low validity, the second objective was to develop more accurate estimates of fat-free mass (FFM). One hundred males and females 19 to 45 years of age were randomly selected from four rural communities in the Western Highlands of Guatemala. Bioimpedance equations explained 59 and 33% of the variation in FFM, with a RMSE of 2.7 and 2.8 kg in males and females, respectively. Body fat (BF) predictions had a lower R². Using the “all possible regressions” procedure, the best subset for prediction of FFM used anthropometric and BIA variables as predictors. The best model for men and women included only anthropometric variables: 75% of the variance in FFM for men and 70% of the variance in women was explained by this model. The RMSE was 2.1 and 1.9 kg for both groups, respectively. It is concluded that FFM can be estimated from anthropometric dimensions with a high degree of accuracy and use of BIA does not provide more valid estimates.     

Aging and the human vestibular nuclei: morphometric analysis

The data concerning the effects of age on the brainstem are scarce and few works are devoted to the human vestibular nuclear complex. The study of the effects of aging in the vestibular nuclei could have clinical interest due to the high prevalence of balance control and gait problems in the elderly. We have used in this work eight human brainstems of different ages sectioned and stained by the formaldehyde-thionin technique. The neuron's profiles were drawn with a camera lucida and Abercrombie's method was used to estimate the total number of neurons. The test of Kolmogorov-Smirnov with the correction of Lilliefors was used to evaluate the fit of our data to a normal distribution and a regression analysis was done to determine if the variation of our data with age was statistically significant. Aging does not affect the volume or length of the vestibular nuclear complex. Our results clearly show that neuronal loss occurs with aging in the descending (DVN), medial (MVN), and lateral (LVN) vestibular nuclei, but not in the superior (SVN). There are changes in the proportions of neurons of different sizes but they are not statistically significant. The neuronal loss could be related with the problems that elderly people have to compensate unilateral vestibular lesions and the alterations of the vestibulospinal reflexes. The preservation of SVN neurons can explain why vestibulo-ocular reflexes are compensated after unilateral vestibular injuries.     

Intrathoracic pressure fluctuations move blood during CPR: Comparison of hemodynamic data with predictions from a mathematical model

Whether blood flow during cardiopulmonary resuscitation (CPR) results from intrathoracic pressure fluctuations or direct cardiac compression remains controversial. We developed a mathematical model that predicts that blood flow due to intrathoracic pressure fluctuations should be insensitive to compression rate over a wide range but dependent on the applied force and compression duration. If direct compression of the heart plays a major role, however, the model predicts that flow should be dependent on compression rate and force, but above a threshold, insensitive to compression duration. These differences in hemodynamics produced by changes in rate and duration form a basis for determining whether blood flow during CPR results from intrathoracic pressure fluctuations or from direct cardiac compression. The model was validated for direct cardiac compression by studying the hemodynamics of cyclic cardiac deformation following thoracotomy in four anesthetized, 21–32-kg dogs. As predicted by the model, there was no change in myocardial or cerebral perfusion pressures when the duration of compression was increased from 15% to 45% of the cycle at a constant rate of 60/min. There was, however, a significant increase in perfusion pressures when rate was increased from 60 to 150/min at a constant duration of 45%. The model was validated for intrathoracic pressure changes by studying the hemodynamics produced by a thoracic vest (vest CPR) in eight dogs. The vest contained a bladder that was inflated and deflated. Vest CPR changed intrathoracic pressure without direct cardiac compression, since sternal displacement was <0.8 cm. As predicted by the model and opposite to direct cardiac compression, there was no change in perfusion pressures when the rate was increased from 60 to 150/min at a constant duration of 45% of the cycle. Manual CPR was then studied in eight dogs. There was no surgical manipulation of the chest. Myocardial and cerebral blood flows were determined with radioactive microspheres and behaved as predicted from the model of intrathoracic pressure, not direct cardiac compression. At nearly constant peak sternal force (378–426 N), flow was significantly increased when the duration of compression was increased from short (13%–19% of the cycle) to long (40%–47%), at a rate of 60/min. Flow was unchanged, however, for an increase in rate from 60 to 150/min at constant compression duration. In addition, myocardial and cerebral flow correlated with their respective perfusion pressures. Thus vital organ perfusion pressures and flow for manual external chest compression are dependent on the duration of compression, but not on rates of compression of 60 and 150/min. These data are of course similar to those produced by vest CPR, where intrathoracic pressure is manipulated without sternal displacement, and to those predicted for movement of blood by intrathoracic pressure changes. These data are, however, opposite to those produced by cardiac deformation and to those predicted for movement blood by direct cardiac compression. We conclude that intrathoracic pressure fluctuations generate blood flow during manual CPR.     

Development and application of a nonradioactive nucleic acid hybridization system for simultaneous detection of four potato pathogens

cDNA clones of potato virus X (PVXcp strain), potato virus Y (PVYo strain), potato leaf roll virus (PLRV) and potato spindle tuber viroid (PSTV) were used separately or combined for the detection of the corresponding RNAs in extracts of infected plants. A general method for the rapid preparation of RNA extracts without use of organic solvents (i.e. phenol) was developed for this purpose. Plant extracts from a range of field, artificially inoculated germplasm genotypes, micro-propagated and protoplast samples, as well as vector insect extracts, were dot-blotted onto nylon or nitrocellulose membranes, subjected to sandwich nucleic acid hybridization with non-labelled specific single-stranded DNA probes followed by a biotin-labelled second step hybridization probe. Each probe was virus-specific but not strain-specific. Healthy or non-related plant extracts developed very faint or no signals. Sensitivity was tested by slot-blot hybridization. Detection levels were between 1.5 to 6 pg of viral nucleic acids and between 20 to 50 times more sensitive than standard double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). The assay developed was tested with material that was prepared for processing in the field (combination of fresh sap with extraction solution) and tested under simple laboratory conditions for detection. It was also successfully employed for screening of germplasm for virus resistance, detection of pathogens in vector insects, plantlets grown in vitro and in more sophisticated quantitative determinations of viral replication in artificially inoculated plants and protoplasts.     

Pattern of spatial distribution inDrosophila melanogaster

The effect of temperature and sex on spatial distribution ofDrosophila melanogaster adults was studied in a specially designed apparatus. It was observed that individuals tend to aggregate in sections of the sphere independently of sex and temperature. Nevertheless, decrease in temperature increase aggregation. The mobility of both males and females indicates a megative geotactic tendency.     

Lymphoepithelioma-like carcinoma of the bladder: three cases with clinicopathological and p53 protein expression study

Lymphoepithelioma-like carcinoma of the bladder is an uncommon neoplasm, of which 49 cases have been described in the English literature, none of which has been studied for p53 protein expression. We studied three muscle-infiltrating cases of this tumor using immunohistochemical, in situ hybridization and polymerase chain reaction (PCR) methods. The three cases were positive for epithelial markers and negative for lymphoid antigens in the tumoral syncytial areas. The intensive infiltrate of small cells was negative for epithelial and positive for lymphoid markers. This population was mainly made up of cytotoxic T-lymphocytes, positive for TIA-1. p53 protein was intensely positive in more than 90% of the epithelial component nuclei, being negative in the lymphoid cells. PCR study did not show mutations on p53. Both lymphocytes and epithelium were negative for Epstein–Barr virus markers, such as the latent membrane protein and EBER (Epstein–Barr-encoded RNA). The prognosis was very good after radiotherapy and chemotherapy treatment, preserving the bladder despite the muscle infiltration. The presence of an intense cytotoxic T-lymphocyte population may be related to this good prognosis. Both aspects, p53 protein status and T-lymphoid population, had never been studied before in bladder lymphoepithelioma-like carcinoma.     

Global dendritic calcium spikes in mouse layer 5 low threshold spiking interneurones: implications for control of pyramidal cell bursting

Interneuronal networks in neocortex underlie feedforward and feedback inhibition and control the temporal organization of pyramidal cell activity. We previously found that lower layer neocortical interneurones can reach action potential threshold in response to the stimulation of a single presynaptic cell. To better understand this phenomenon and the circuit roles of lower layer neocortical interneurones, we combined two-photon calcium imaging with whole cell recordings and anatomical reconstructions of low threshold spiking (LTS) interneurones from mouse neocortex. In both visual and somatosensory cortex, LTS interneurones are somatostatin-positive, concentrated in layer 5 and possess dense axonal innervation to layer 1. Due to the LTS properties, these neurones operate in burst and tonic modes. In burst mode, dendritic T-type calcium channels boosted small synaptic inputs and triggered low threshold calcium spikes, while in tonic mode, sodium-based APs evoked smaller calcium influxes. In both modes, the entire dendritic tree of LTS interneurones behaved as a 'global' single spiking unit. This, together with the fact that synaptic inputs to layer 5 LTS cells are facilitating, and that their axons target the dendritic region of the pyramidal neurones where bursts are generated, make these neurones ideally suited to detect and control burst generation of individual lower layer pyramidal neurones.     

Molecular epidemiology of HIV-1 variants in the global AIDS pandemic: an update

The picture of HIV-1 genetic diversity in the global pandemic continues to evolve. Identification of new variants, including circulating and unique recombinant forms, recognition of new outbreaks and of changes in established epidemics, and characterization of growing numbers of full-length genomes provide a view of high dynamism and increasing complexity. The pervasive role of recombination as a major driving force in the generation of diversity in the HIV-1 pandemic is becoming evident, and is particularly visible in areas in which different genetic forms meet, referred to as "geographic recombination hotspots". The importance of superinfection and its impact on HIV-1 diversification and propagation is surfacing, although restrictions to superinfection are also apparent. Genetic diversity within subtypes is increasing over time and new geographically localized lineages deriving from point introductions are being recognized. Characterization of such variants may be of relevance to vaccine development and may allow the detection of intrasubtype recombination and superinfection. Recent studies supporting the correlation of HIV-1 clades to immune responses and to drug resistance-associated mutations lend increasing relevance to the role of molecular epidemiology as an essential tool in combating the AIDS pandemic. However, knowledge on the global HIV-1 genetic diversity and its implications is still far from adequate and a major scaling up of efforts is needed.     

Digoxin dosing in the aged: new pharmacokinetic system versus Jellife and Koup methods

To evaluate three methods for digoxin dose adjustment in aged patients, we determined the plasma digoxin levels that would be attained in 87 aged patients with doses adjusted to the kidney function by means of three separate procedures. Mean patient age was: 79.0 +/- 6.3 years; creatinine clearance (Clc): 0.70 +/- 0.23 mL/Kg of lean body weight and minute; digoxinemia/dose ratio (RCpD): 0.421 +/- 0.237 Kg/L. The dose that would attain a digoxinemia of 1.2 ng/mL, calculating the elimination constant (K) and the volume of distribution (V) as linear functions of the Clc, so that K ranges between 0.173 and 0.462 days-1 and V between 4 and 10 L/Kg of lean body weight when the Clc varies from 0 to 110 mL/minute, was 2947 ng/Kg of lean body weight, coefficient of variation (CV): 25.2%. The digoxinemia that patients would have with this D, taking into account the individual RCpD, was 1.1 ng/mL, CV: 38.0%; with figures between 0.8 y 2.0 ng/mL and above 2.0 ng/mL in the 81.6% and the 0.0% of the patients (95% confidence intervals (95% CI): 72.2% to 88.4 and 0.0% to 4.6%), respectively. The precision and the bias were 0.43 and -0.06 ng/mL (95% CI: 0.38 to 0.48 and -0.16 to 0.03 ng/mL), respectively, and with this method the digoxinemia was not associated with the Clc. We concluded that the described method would lead to good results if digoxin has not been prescribed in order to control the cardiac frequency in the setting of auricular fibrilation.     

Dystrophin and utrophin influence fiber type composition and post-synaptic membrane structure

The X-linked muscle wasting disease Duchenne muscular dystrophy is caused by the lack of dystrophin in muscle. Protein structure predictions, patient mutations, in vitro binding studies and transgenic and knockout mice suggest that dystrophin plays a mechanical role in skeletal muscle, linking the subsarcolemmal cytoskeleton with the extracellular matrix through its direct interaction with the dystrophin-associated protein complex (DAPC). Although a signaling role for dystrophin has been postulated, definitive data have been lacking. To identify potential non-mechanical roles of dystrophin, we tested the ability of various truncated dystrophin transgenes to prevent any of the skeletal muscle abnormalities associated with the double knockout mouse deficient for both dystrophin and the dystrophin-related protein utrophin. We show that restoration of the DAPC with Dp71 does not prevent the structural abnormalities of the post-synaptic membrane or the abnormal oxidative properties of utrophin/dystrophin-deficient muscle. In marked contrast, a dystrophin protein lacking the cysteine-rich domain, which is unable to prevent dystrophy in the mdx mouse, is able to ameliorate these abnormalities in utrophin/dystrophin-deficient mice. These experiments provide the first direct evidence that in addition to a mechanical role and relocalization of the DAPC, dystrophin and utrophin are able to alter both structural and biochemical properties of skeletal muscle. In addition, these mice provide unique insights into skeletal muscle fiber type composition.