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Bruno Günther

Publications and source records attributed to Bruno Günther.

10 recordsLinked to original sources
PubMed2005

[Homeostatic range of the oxidative metabolism: 60 years of integrative fisiometry].

The energetic metabolism and its relationship with body weight generated a vivid controversy, since the Rubner's surface law was introduced into biology. Recently, the multifactor theory (Darveau et al) has caused again a revival of this polemic topic. Moreover, the investigations concerning metabolism and body weight include all terrestrial mammals, from the shrew (3 grams) to the elephant (three tons). The corresponding allometric exponent for standard metabolic rate, both theoretical and empirical, fluctuates around an average value of 0.75, in contrast with the surface law, which postulated a value of 0.67. The "metabolic range" (rest vs maximal exercise) does vary from 1 to 10, due to the prevalent influence of the skeletal muscle activity. Recent investigations have emphasized the fact that the allometric exponent is not unique (0.75), but it should be subjected to statistical variability, both in standard and in maximal exercise.

Animals↗
PubMed2005

Two alternative models concerning the perialveolar microcirculation in mammalian lungs.

Despite the fact that the concept of sheet-flow in the pulmonary microcirculation of mammals was introduced more than three decades ago, the capillary circulatory model still prevails in the physiological literature. Since cardiac output is identical in the systemic and in pulmonary circulations, it is noteworthy that in the former, the resulting arterial pressure is five times higher than that of the latter, which means that the corresponding microcirculations must be radically different. The present study addresses this problem from both morphological and physiological perspectives.

Animals↗
PubMed2005

Allometric scaling of biological rhythms in mammals.

A wide spectrum of cyclic functions in terrestrial mammals of different size, from the 3-gram shrew to the 3-ton elephant, yields an allometric exponent around 0.25, which is correlated--as a kind of common denominator--with the specific metabolic rate. Furthermore, the applicability of these empirical findings could be extrapolated to chronological events in the sub-cellular realm. On the other hand, the succession of growth periods (T98%) until sexual maturity is reached also follows the 1/4 power rule. By means of Verhulst's logistic equation, it has been possible to simulate three different biological conditions, which means that by modifying the numerical value of only one parameter, revertible physiological and pathological states can be obtained, as for instance isostasis, homeostasis and heterostasis.

Animals↗
PubMed2004

Wavelet and Fourier analysis of ventricular and main arteries pulsations in anesthetized dogs.

The purpose of this study was to characterize time-frequency behavior using the Continuous Wavelet Transform (CWT) and Fast Fourier Transform (FFT) to analyze ventricular and arterial pressure signals from anesthetized mongrel dogs. Both ventricular and arterial pressure pulsations were recorded using catheter-tip manometers and the CWT was applied to these signals to obtain module coefficients, associated contours, and the 3-D representation of these modules. FFT was applied to obtain the Fourier spectrum. The mathematical analysis of the cardiovascular pressure pulsations permitted the identification of the evolution of the frequency components for the aortic and pulmonary valve functions as well as the intra-ventricular and respiratory influences on the cardiovascular dynamics. The CWT is a very sensitive and reliable procedure for determining the three-dimensional (time-frequency-amplitude) of the oscillatory phenomena during each cardiac cycle, providing more, although complementary, information than the spectral analysis obtained with the FFT. Thanks to the FFT, exact values in Hz could be found for the different events produced in each cycle, and thus the information provided by CWT could be related to the information provided by FFT. The combination of both mathematical methodologies permitted identification of each component of the analyzed signals. The 3D representation allowed an easy comparison of the relative importance of the complex magnitudes in frequency for the different components of the pulsatile waves.

Anesthesia↗
PubMed2004

Time in physics and biology.

In contrast with classical physics, particularly with Sir Isaac Newton, where time is a continuous function, generally valid, eternally and evenly flowing as an absolute time dimension, in the biological sciences, time is in essence of cyclical nature (physiological periodicities), where future passes to past through an infinitely thin boundary, the present. In addition, the duration of the present (DP) leads to the so-called 'granulation of time' in living beings, so that by the fusion of two successive pictures of the world, which are not entirely similar, they attain the perception of 'movement,' both in the real world as well as in the sham-movement in the mass media (TV).

Biology↗
PubMed2003

Homeostasis and heterostasis: from invariant to dimensionless numbers.

In the present paper we have examined the applicability of dimensionless and invariant numbers (DN & IN) to the analysis of the cardiovascular system of mammals, whose functions were measured at standard metabolic conditions. The calculated IN did not change when we compared these figures with those obtained in dogs while they were submitted to graded exercise on a treadmill. In both instances, rest and exercise, the constancy of the IN prevailed, in accordance with Cannon's principle of "homeostasis" (1929). On the contrary, when dogs were examined during a standardized hypovolemic shock, we observed a breakdown of the IN, and the resulting DN evolved as a reliable index of the condition of "heterostasis" as defined by H. Selye. The robustness of the homeostatic regulations is based on high-gain integral feedback mechanisms, while "heterostasis" could be associated with low-gain integral feedback processes, when organisms are submitted to unitary step disturbances or to changes of the set-point at the entrance of the feedback loop.

Animals↗
PubMed2003

Dimensional analysis revisited.

The applicability of dimensional analysis (DA) is discussed in relation to the metabolic scaling laws. The evolution of different theories of biological similarity has shown that the calculated reduced exponents (b) of Huxley's allometric equation are closely correlated with the numerical values obtained from the statistical analysis of empirical data. Body mass and body weight are not equivalent as biological reference systems, since in accordance to Newton's second law, the former has a dimension of a mass, while the latter should be dimensionally considered as a force (W = MLT-2). This distinction affects the coefficients of the mass exponent (alpha). This difference is of paramount importance in microgravity conditions (spaceflight) and of buoyancy during the fetal life in mammals. Furthermore, the coefficients (beta) of the length dimension, and (gamma) of the time dimension do not vary when mass or weight are utilized as reference systems. Consequently, the "specific metabolic time," that results from the ratio of basal oxygen consumption and body mass or body weight yields the "biological meaning" of the time dimension, which is of fractal nature.

Animals↗
PubMed2002

An invariant number of the respiratory system of mammals: newborn and adult.

From four empirical allometric equations concerning the dynamics of the respiratory functions of mammals, it has been possible to obtain an invariant and dimensionless number after applying Buckingham's pi-theorem. In the present study, this invariant number (IN(R)), whose origin was interspecies comparisons in mammals of different sizes, was assayed with the aim to compare in a quantitative manner the possible difference between newborn and adult mammals. The results were compared with the predicted values from two theories of biological similarity, one mass-dependent, valid for newborns, and the other, weight-dependent, valid for adult mammals. Finally, we utilized Stahl's residual mass exponents (RME) to test the validity of the empirical and theoretical approaches.

Age Factors↗