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Biomedical subjects

L A Amaral

Publications and source records attributed to L A Amaral.

16 recordsLinked to original sources
PubMed2006

Potential microbiological contamination of effluents in poultry and swine abattoirs.

Health risks in the effluents of seven swine abattoirs and of seven poultry abattoirs were evaluated with regard to environment degradation and to dissemination of pathogenic microorganisms during the rainy and dry seasons. Supply-water samples from affluents and effluents of the treatment systems at different sites within the abattoir processing system were analysed. Similarly, water samples from the three recipient sites (emission point, 100 m upstream, 100 m downstream) were also analysed. Temperature, free residual chlorine (FRC), total coliform bacteria, Escherichia coli, enterococci, identification and serotyping of salmonellae were assessed. Scalding is the most significant stage in the slaughtering chain (P<0.05) when temperature is taken into account. Temperatures at effluents and at the sampled sites in the water bodies accorded to state and federal legislation standards. Supply waters did not meet the standards for FRC and microbial count standards according to the Ministry of Health and within limits imposed by the Industrial and Sanitary Inspection Regulations for Animal Products. Feather plucking and evisceration in poultry slaughter and the cleansing of carcasses and facilities in poultry and swine slaughtering had the highest contamination impact. The three loci at the water bodies were above the microbiological standards for classes II and III sites, in conformity with Law 8468 of the state of São Paulo, Brazil and Conama. Salmonella was found at several sites during slaughter, at both types of abattoirs, including in the effluent treatment system. This showed that these sites were the dissemination sources of the microorganism.

Abattoirs↗
PubMed2000

Classes of small-world networks.

We study the statistical properties of a variety of diverse real-world networks. We present evidence of the occurrence of three classes of small-world networks: (a) scale-free networks, characterized by a vertex connectivity distribution that decays as a power law; (b) broad-scale networks, characterized by a connectivity distribution that has a power law regime followed by a sharp cutoff; and (c) single-scale networks, characterized by a connectivity distribution with a fast decaying tail. Moreover, we note for the classes of broad-scale and single-scale networks that there are constraints limiting the addition of new links. Our results suggest that the nature of such constraints may be the controlling factor for the emergence of different classes of networks.

Interpersonal Relations↗
PubMed2000

PhysioBank, PhysioToolkit, and PhysioNet: components of a new research resource for complex physiologic signals.

The newly inaugurated Research Resource for Complex Physiologic Signals, which was created under the auspices of the National Center for Research Resources of the National Institutes of Health, is intended to stimulate current research and new investigations in the study of cardiovascular and other complex biomedical signals. The resource has 3 interdependent components. PhysioBank is a large and growing archive of well-characterized digital recordings of physiological signals and related data for use by the biomedical research community. It currently includes databases of multiparameter cardiopulmonary, neural, and other biomedical signals from healthy subjects and from patients with a variety of conditions with major public health implications, including life-threatening arrhythmias, congestive heart failure, sleep apnea, neurological disorders, and aging. PhysioToolkit is a library of open-source software for physiological signal processing and analysis, the detection of physiologically significant events using both classic techniques and novel methods based on statistical physics and nonlinear dynamics, the interactive display and characterization of signals, the creation of new databases, the simulation of physiological and other signals, the quantitative evaluation and comparison of analysis methods, and the analysis of nonstationary processes. PhysioNet is an on-line forum for the dissemination and exchange of recorded biomedical signals and open-source software for analyzing them. It provides facilities for the cooperative analysis of data and the evaluation of proposed new algorithms. In addition to providing free electronic access to PhysioBank data and PhysioToolkit software via the World Wide Web (http://www.physionet. org), PhysioNet offers services and training via on-line tutorials to assist users with varying levels of expertise.

Databases as Topic↗
PubMed1999

Application of statistical physics to heartbeat diagnosis.

We present several recent studies based on statistical physics concepts that can be used as diagnostic tools for heart failure. We describe the scaling exponent characterizing the long-range correlations in heartbeat time series as well as the multifractal features recently discovered in heartbeat rhythm. It is found that both features, the long-range correlations and the multifractility, are weaker in cases of heart failure.

Adult↗
PubMed1999

Sleep-wake differences in scaling behavior of the human heartbeat: analysis of terrestrial and long-term space flight data.

We compare scaling properties of the cardiac dynamics during sleep and wake periods for healthy individuals, cosmonauts during orbital flight, and subjects with severe heart disease. For all three groups, we find a greater degree of anticorrelation in the heartbeat fluctuations during sleep compared to wake periods. The sleep-wake difference in the scaling exponents for the three groups is comparable to the difference between healthy and diseased individuals. The observed scaling differences are not accounted for simply by different levels of activity, but appear related to intrinsic changes in the neuroautonomic control of the heartbeat.

Astronauts↗
PubMed1999

Statistical physics and physiology: monofractal and multifractal approaches.

Even under healthy, basal conditions, physiologic systems show erratic fluctuations resembling those found in dynamical systems driven away from a single equilibrium state. Do such "nonequilibrium" fluctuations simply reflect the fact that physiologic systems are being constantly perturbed by external and intrinsic noise? Or, do these fluctuations actually, contain useful, "hidden" information about the underlying nonequilibrium control mechanisms? We report some recent attempts to understand the dynamics of complex physiologic fluctuations by adapting and extending concepts and methods developed very recently in statistical physics. Specifically, we focus on interbeat interval variability as an important quantity to help elucidate possibly non-homeostatic physiologic variability because (i) the heart rate is under direct neuroautonomic control, (ii) interbeat interval variability is readily measured by noninvasive means, and (iii) analysis of these heart rate dynamics may provide important practical diagnostic and prognostic information not obtainable with current approaches. The analytic tools we discuss may be used on a wider range of physiologic signals. We first review recent progress using two analysis methods--detrended fluctuation analysis and wavelets--sufficient for quantifying monofractual structures. We then describe recent work that quantifies multifractal features of interbeat interval series, and the discovery that the multifractal structure of healthy subjects is different than that of diseased subjects.

Biophysical Phenomena↗
PubMed1999

Multifractality in human heartbeat dynamics.

There is evidence that physiological signals under healthy conditions may have a fractal temporal structure. Here we investigate the possibility that time series generated by certain physiological control systems may be members of a special class of complex processes, termed multifractal, which require a large number of exponents to characterize their scaling properties. We report on evidence for multifractality in a biological dynamical system, the healthy human heartbeat, and show that the multifractal character and nonlinear properties of the healthy heart rate are encoded in the Fourier phases. We uncover a loss of multifractality for a life-threatening condition, congestive heart failure.

Adult↗
PubMed1999

Modeling heart rate variability by stochastic feedback.

We consider the question of how the cardiac rhythm spontaneously self-regulates and propose a new mechanism as a possible answer. We model the neuroautonomic regulation of the heart rate as a stochastic feedback system and find that the model successfully accounts for key characteristics of cardiac variability, including the 1/f power spectrum, the functional form and scaling of the distribution of variations of the interbeat intervals, and the correlations in the Fourier phases which indicate nonlinear dynamics.

Heart↗
PubMed1993

Application of rRNA-based probes for observing marine nanoplanktonic protists.

The use of small-subunit rRNA-based oligonucleotides as probes for detecting marine nanoplanktonic protists was examined with a ciliate (an Uronema sp.), a flagellate (a Cafeteria sp.), and mixed assemblages of protists from enrichment cultures and natural seawater samples. Flow cytometry and epifluorescence microscopy analyses demonstrated that hybridizations employing fluorescein-labeled, eukaryote-specific probes intensely stained logarithmically growing protists, whereas these same protist strains in late stationary growth were barely detectable. The fluorescence intensity due to probe binding was significantly enhanced by the use of probes end labeled with biotin, which were detected by fluorescein-labeled avidin. The degree of signal amplification ranged from two- to fivefold for cultured protists in both logarithmic and stationary growth phases. Mixed assemblages of heterotrophic protists from enrichment cultures were also intensely labeled by rRNA-targeted oligonucleotide probes by the biotin-avidin detection system. Protists in late stationary growth phase and natural assemblages of protists that were otherwise undetectable when hybridized with fluorescein-labeled probes were easily visualized by this approach. In the latter samples, hybridization with multiple, biotin-labeled probes was necessary for detection of naturally occurring marine protists by epifluorescence microscopy. The signal amplification obtained with the biotin-avidin system should increase the utility of rRNA-targeted probes for identifying protists and facilitate characterization of the population structure and distribution of protists in aquatic environments.

Animals↗
PubMed1982

Effect of insulin on protein catabolism after injury in young animals.

Injury is followed by a negative nitrogen balance, muscle protein breakdown and loss of body mass. The intensity of these changes correlates with trauma severity. Reversion of the catabolic state has long been attempted. Recently, it has been shown that the use of insulin might inhibit protein catabolism after severe trauma. The present study was undertaken to assess the effect of insulin on post-injury catabolism in young rabbits submitted to parenteral nutrition. Concomitantly, changes in liver and skeletal muscle nitrogen contents were also studied to elucidate the mechanism of insulin's anabolic effect after trauma. We found that only in catabolic states did insulin produce a significant nitrogen-sparing effect, probably due to the capacity of the hormone to inhibit muscle proteolysis.

Animals↗
PubMed1981

[Sensitivity of different biological methods for differentiating the protein value of various foods].

The nutritive value of proteins from different sources was studied. The value for PER, weight of the animals, IEC, NPR, NDpCal%, digestibility (D), and biological value (BV) was determined with diets containing 7% of total protein. The best results were obtained for milk, opaque-2 corn, rice and soybeans. The association of rice + soybeans was optimum. The results suggest also that it is advantageous to supplement wheat with cassava. Comparison of the results obtained by the different biological methods, classified by sensitivity for different protein qualities, revealed that the best methods are weight gain, PER and IEC better than NPR and NDpCal%, which in turn were better than BV, food intake and D (P less than 0.01).

Animals↗
PubMedDate not supplied

Imbalanced protein and appetite.

Free amino acid concentration in the plasma of rats fed on different diets were compared. The diets contained 7 g protein/100 g furnished by: casein, or common corn, or opaque 2 corn, or eggalbumin, or gelatin. A protein free diet was also included. The results showed that imbalance of the protein diet influenced the appetite; whenever the NE/E aminoacid ratio increased, body development, appetite and plasma albumin decreased. An inverse correlation between the NE/E of free aminoacids of the plasma and voluntary intake was observed. The results also show that the plasma aminogram did not reflect the composition of the protein in the diet. The results obtained are discussed.

Animals↗