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E Morgado

Publications and source records attributed to E Morgado.

16 recordsLinked to original sources
PubMed1997

Allometry of ECG waves in mammals.

The present allometric study deals with the duration of three electrocardiographic intervals (PQ, QRS, QT) and their relationships with the corresponding cardiac cycle length (R-R interval) in mammals across a wide body mass range. The numerical values of the different ECG intervals were obtained from Grauwiler's (1965) monograph on the subject. Because the corresponding body masses were not given by this author, Heusner's (1991) data on basal metabolic rate as function of body mass were used to establish the most likely body mass figure for each case, based on the taxonomic identity between the corresponding specimens. On the other hand, in a recent study we established the "duality" of physiological times (Günther & Morgado, 1996) and, therefore, we adopted this novel approach to investigate the ECG intervals and their relationships with the R-R interval (heart rate reciprocal). Considering that the anatomy and physiology of auricles and ventricles are different (spheroids versus quasi-cylinders), and that excitation (sino-atrial node and His-Purkinje's system) and contraction processes can be described either by Euclidean or fractal geometries, only a quantitative analysis of the different ECG waves could resolve the dilemma. From the present preliminary study we can conclude that fractal geometry is prevalent with regard to ECG intervals.

Animals↗
PubMed1996

Allometric algorithms.

The aim of the present study is to emphasize the applicability and versatility of the allometric equation in the biological sciences. This equation (Y = a x Mb) was introduced by Huxley (1932) for intra- and interspecific comparisons of morphological, physiological and ecological variables (Y), when they are expressed as functions of body mass (M). The regression analysis of the experimental data, plotted in a double logarithmic scale, yields a straight line, which is equivalent to the logarithmic form of the above mentioned allometric equation [log Y = log(a) + (b) x log(M)]. Only the exponent (b) can be calculated a priori for a given function, based firstly on the corresponding dimensional analysis in accordance with the MLT-system of physics, and secondly on one of the theories of biological similarity, while parameter (a) is of empirical nature. A relevant feature of the allometric equations is that they can be treated algebraically to obtain allometric ratios, mass independent numbers (MIN), and even dimensionless numbers (M0L0T0), which are valid for all organisms pertaining to the same taxonomic classification.

Algorithms↗
PubMed1996

Duality in physiological time: Euclidean and fractal.

The aim of the present study was to differentiate two modalities of intrinsic time scales: i- the geometric or Euclidean modality, which is based on the constant speed of mass transport or of wave transmission in cylindrical structures (arteries, veins, nerves), whose allometric exponent (TE = aMb) is b = 0.33, where M is body mass (kg) and a the mass coefficient; ii- the fractal time scale (TF), which is characteristic of organs with self-similar branching structures and with volume-specific flows, whose allometric exponent is b = 0.25. The proposed dichotomy could be confirmed by means of the statistical analysis of empirical allometric exponents (b). Our findings demonstrate the need to separate the chronology of bulk transport at long distances (inter-organic) which follows an Euclidean geometry (cylinders), from the fractal time scale, which operates at short distances (intra-organic) and is represented by a self-similar branching system which determines both the morphometric and physiometric characteristics within each organ.

Axons↗
PubMed1993

Low activity of the yeast cAMP-dependent protein kinase catalytic subunit Tpk3 is due to the poor expression of the TPK3 gene.

Three genes TPK1, TPK2 and TPK3 encode in Saccharomyces cerevisiae distinct catalytic subunits of cAMP-dependent protein kinase (cAPK). We have measured cAPK activity in vitro and, indirectly, in vivo in yeast strains carrying only one of the three TPK genes. The strain containing TPK3 as the only intact TPK gene showed nearly undetectable phosphorylating activity and no TPK3 mRNA could be detected, although the cells grow normally. Overexpression of TPK3 in a high copy vector or under the control of the inducible GAL1 promoter did not by itself result in a corresponding increase in activity but coexpression of BCY1, the gene coding for the regulatory subunit, was necessary in both cases to achieve high levels of phosphorylating activity. Moreover, BCY1 overexpression not only increased Tpk3 catalytic activity but also increased the amount of TPK3 mRNA detected in Northern blots.

Catalysis↗
PubMed1993

Oxidative metabolism and body weight: inactive, active, and mitochondrial volumes.

In homeotherms, the standardized (basal) metabolic rate should not be expressed per kilogram of body weight (specific metabolic rate), nor per unit of body surface (square meters of body-ambient interface), since both mitochondrial thermogenesis and heat-loss mechanisms (radiation, conduction, convection, evaporation) are not uniform processes. On the contrary, each organism is an heterogeneous bioreactor, which is composed at least of two compartments: 1) a metabolically active volume (aV), where oxidative phosphorylation takes place; and 2) a metabolically inactive volume (iV), where oxygen consumption is negligible. The ratio (aV/iV) is not invariant, since iV increases disproportionately with the scaling up of body size, and as shown by us, when the three main components of iV, i.e., skeleton, fat deposits, and blood volume, are added together, a similar disproportionality is found. The aV was determined by subtracting the iV from the total volume (V) of an organism, or by estimating the volume occupied by all mitochondria, or mitochondrial volume (mtV). For this purpose two procedures are discussed: 1) the stereological or morphometric method; and 2) the oxygen consumption per unit time or physiometric method. The latter procedure is based on the equivalence between an VO2 = 3 ml O2.min-1 and a mtV of 1 ml, whose oxidative phosphorylation yields an approximate power output of 1 watt. The correspondence between oxygen consumption, heat production, and electron flux at the respiratory chain of the mitochondrial cristae, is discussed. From a physical point of view, the metabolic rate is a "power" function (P = M L2T-3), where M = mass, L = length, and T = time. The dimensional analysis and the statistical treatment of the corresponding numerical values of more than 200 allometric equations yields the 3/4 power, law established by Kleiber (1961), for the relationship between basal metabolism and body weight. Instead of expressing the metabolic rate per unit body weight (kg-1) or per unit body surface (m-2) structural and functional criteria should be taken into account as, for instance, the distinction between iV and aV, and particularly by emphasizing the paramount importance of the mtV where oxidative phosphorylation takes place. An allometric equation relating mtV and body weight (W) could be tentatively established for interspecies comparisons.

Adenosine Triphosphate↗
PubMed1992

Comparison of the subcellular distribution of alveolar surfactant in two mammalian species of similar body weight: cat and rabbit.

1. We studied the total amount and subcellular distribution of alveolar surfactant, extracted through bronchoalveolar lavage of anesthetized cats and rabbits. This was correlated to several morphometric and ventilatory variables of these animals. 2. Lung weight was significantly larger in the cat while respiratory frequency and minute ventilation were significantly larger in the rabbit. No significant differences were observed in tidal volume, total lung capacity, P(a)O2, P(a)CO2 and pH(a). 3. While both species had similar protein contents in the bronchoalveolar lavage, rabbits had larger phospholipid contents, mostly distributed in the lighter, more active subfractions. 4. With regard to the estimated values obtained from allometric equations derived for mammals, the rabbit presented a lung weight of nearly one-third of the estimated one, an exceedingly larger minute ventilation (by nearly 60%) and a respiratory frequency twice the calculated one. 5. We suggest that the different distribution of alveolar surfactant in these species may be explained by disparities in their ventilatory demands, the rabbit having a higher respiratory frequency and a larger minute ventilation, performed by a mass of lung tissue lower than that corresponding to its body mass.

Animals↗
PubMed1992

Biological similarity theories: a comparison with the empirical allometric equations.

Twelve biological variables were submitted to dimensional analysis in accordance with the MLT-system of physics (M, mass; L, length; T, time). Each of these variables has a characteristic numerical value for the exponents alpha for mass, beta for length, and gamma for time. By means of Newton's reduction coefficient (chi), the three dimensions (MLT) can be expressed as power functions of body mass (Mb); the exponent (b) is the result of the combination of the three dimensional exponents (alpha, beta, gamma). By linear regression analysis of 203 allometric exponents (betaE) obtained from the literature, the following equation was found for the regression exponent (bR) (equation: see text). The estimated numerical coefficients (ki) for the three exponents (alpha, beta, gamma) of the basic dimensions (MLT) do not agree with those of the prevailing theories of biological similarity.

Animals↗
PubMed1990

Three-dimensional morphometry of mammalian cells. II. Areas, volumes, and area-volume ratios.

From three-dimensional diameter measurements of eleven kinds of cells pertaining to five different organs, which were excised from eleven adult mammals (nine species) whose body weight range was 40 g to 450 kg, we calculated the corresponding cell soma areas (A), volumes (V), and finally their area-volume ratios (A/V). The dissimilarities among these eleven cell types could be established quantitatively by means of a cluster analysis. The dendrograms for cell areas (A), volumes (V), and their corresponding area-volume ratios (A/V), yielded similar groupings when cell areas and volumes were compared, yet the grouping of the area-volume ratios (A/V) for the eleven types of cells was different. These results were corroborated by means of the principal components analysis, where five distinct cell groupings could be established. The relationship between cellular morphometry, oxidative metabolism, and body mass, was established by means of the fractal geometry of the transport systems (respiration and circulation), which provides the tools for the scale-dependent analysis of the surfaces across which the transport of metabolites is performed.

Animals↗
PubMed1990

On the hidden physical dimensions of the allometric equation.

The aim of the present study was to submit Huxley's allometric equation (Y = aMb) to a dimensional analysis; in this equation Y is any biological variable, a is the mass-coefficient, M represents body mass, and b the mass-exponent. The dimensions of each of its components is thoroughly analyzed by means of the MLT-system of physics, as is the dimensionality of the whole equation. The relationship between the dimensional analysis and the postulates of some theories of biological similarity is discussed. In conclusion, parameter a of the allometric equation is always dimensionless, while the physical dimensions of the dependent variable Y can be defined by means of the power function Mb.

Biometry↗
PubMed1989

Three-dimensional morphometry of mammalian cells. I. Diameters.

Three-dimensional measurements of eleven kinds of cells, obtained from serial sections of five different organs, excised from eleven adult mammals of different body sizes-from a 40 g mouse to a 450 kg cow-were made. In order to minimize technical errors all organs were submitted to standardized fixation and staining procedures. Twenty cell diameters (at the nuclear level) were measured in each of the 7 microns serial tissue section which were made in two planes, after a 90 degree rotation of the fixed and embedded organ specimens. The mean values of the cell diameter measurements were submitted to a cluster analysis by means of a computer program, to establish the cell type groups with similar morphometric characteristics. The dendrograms of the cell-type groupings were then compared with the results obtained by applying the traditional statistical analysis of the cell sizes (in micrometers) in the three dimensions of space, and also with the principal component analysis. With the three statistical methods we came to analogous conclusions. The empirical allometric exponents for the three cell diameters, when expressed independently as functions of body mass, are not significantly different from zero, and in consequence cell sizes are independent of body mass. The physiological meaning of the body-size-independence of the mean three cell diameters is discussed.

Animals↗
PubMed1986

Physical bases for a triad of biological similarity theories.

The dimensional analysis of physics, based on the MLT-system (M = mass, L = length, T = time), can be applied to the living world, from mycoplasmas (10(-13) g) to the blue whales (10(8) g). Body mass (M), or body weight (W), are utilized as convenient reference systems, since they represent the integrated masses of all elementary particles--at the atomic level--which conform an organism. A triad of biological similarities (mechanical, biological, transport) have been previously described. Each similarity was based on two postulates, of which the first was common to all three, i.e., the constancy of body density; whereas the second postulates were specific for each of the three theories. In this study a physical foundation for these second postulates, based on three universal constants of nature, is presented, these are: 1) the acceleration of gravity (g = LT-2); 2) the velocity of light (c = LT-1); and 3) the mass-specific quantum (h/m = L2T-1). The realm of each of these biological similarities is the following: 1) the gravitational or mechanical similarity (where g = constant), deals mainly with the relationship between a whole organism and its environment, particularly with locomotion. The acceleration of gravity (g) is also one of the determining factors of the "potential" energy (E = m.g.H), where m is the mass, and H is the height above the reference level; 2) the electrodynamic similarity (formerly biological similarity), (c = constant), is able to quantitatively define the internal organization of an organism from both a morphological and a physiological point of view.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological Transport↗
PubMed1985

Intrinsic times in biology.

The meaning of time in the physical sciences (absolute vs. relational) is compared with the "intrinsic" times in the biological sciences. Since all organisms can be considered as "mixed regimes", the corresponding intrinsic times will be different in a mechanical similarity (organism and environment), in a biological similarity (morphometry and physiometry inside the organism), and in a transport similarity (diffusion processes at the cellular level). These three similarity criteria are based on specific postulates, and it is possible -through dimensional analysis- to obtain quantitative predictions of the numerical value for the reduced exponents of the body weight ratio (w), which can then be compared with the empirically found allometric exponent (b) of Huxley's power equation, which is expressed as a function of body weight (W). The correlation between the theoretically predicted values and the empirical findings of numerous chronological functions pertaining to living beings is satisfactory.

Biology↗
PubMed1984

Transport similarity: dimensional analysis of diffusion at cellular level.

Scale dependent variables in animals of different sizes can be studied by means of dimensional analysis and biological similarity criteria. The aim of this report is to demonstrate a transport similarity at the cellular level, based on two postulates derived from Fick's law of diffusion; the constancy of the "concentration gradient" between two compartments separated by a membrane; and the invariance of the "diffusion coefficient" of a given substance in homologous cells. A general equation for a transport similarity was deduced from these two postulates and it was then possible to calculate the corresponding "reduced exponents" as functions of body weight, which, in turn, can be compared with the empirical allometric exponents of Huxley's power equation. The biological meaning of the theoretically predicted reduced exponents of the transport similarity are discussed and the predicted values are compared with the experimental findings.

Animals↗