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Biomedical subjects

B Günther

Publications and source records attributed to B Günther.

At least 19 recordsLinked to original sources
PubMed1998

Comparison of different anticalcification treatments for stentless bioprostheses.

BACKGROUND: New anticalcificant treatments have been developed because tissue calcification is a major contributing factor for bioprosthetic valve failure. METHODS: Aortic valve leaflet and aortic root tissue samples from stentless bioprostheses treated with No-React (Biocor, Belo Horizonte, Brazil), AOA (Medtronic freestyle, Minneapolis, MN), and BiLinx (St. Jude Medical, St. Paul, MN) were compared to a control group by subcutaneous implantation in 60 male weanling Sprague-Dawley rats. RESULTS: Calcium levels were in the range of 0.3 to 2.2 mg/g dry tissue at 3 and 12 weeks in all three treated aortic valve leaflet implants. The BiLinx treatment proved anticalcificant effectiveness on aortic root samples as well. There were statistically significant differences for valve leaflet tissue samples: No-React = AOA < BiLinx < < Control and for aortic root tissue samples: BiLinx < < AOA < Control = No-React. CONCLUSION: Calcification of aortic valve leaflets was significantly reduced by all new anticalcificant treatments. Inhibition of cellular calcification (BiLinx) resulted in additional reduction of aortic root calcification. Maximum anticalcificant properties upon both leaflet and aortic root is important as these are considered a functional unit in stentless bioprostheses.

Aluminum↗
PubMed1997

Continuous wavelet transform of aortic pressure oscillations in anesthetized dogs: effects of 45 degrees tilting.

The time-frequency analysis of signals by means of continuous wavelet transform (CWT) was applied to blood pressure oscillations recorded from the aorta of anesthetized dogs. This method yielded two and three-dimensional representations of either the module or phase in function of time, in contrast with the fast Fourier transform (FFT) which gives the spectrum in the frequency domain. From the CWT of arterial pressure oscillations we obtained visual information on aortic valves closure, heart rate, respiratory rate and smooth muscle contractions in arterial and arteriolar walls (very low frequency component). The objective of this study was to analyze the frequency-time behavior in two and three-dimensional cardiovascular changes during 45 degrees head-up and head-down tilts, compared with zero degree supine position. In eight pentobarbitone anesthetized dogs, the postural changes were repeated for more than ten times in each one. Heart rate variability was derived by applying a new mathematical procedure. We utilized the pronounced changes of heart rate during each respiratory cycle (inspiratory tachycardia and expiratory bradycardia) to establish a correlation with the arterial pressure fluctuations during normal and tilting conditions. Significant differences in heart rate were observed between the 45 degrees head-up and head-down tilts, compared with the supine position. The results show that anesthetized dogs might constitute an appropriate model where to study orthostatic hypotension and microgravity blood shifts.

Anesthesia↗
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

Detection and measurement of Staphylococcus epidermidis slime using an ELISA technique.

A polyclonal rabbit anti-serum against the strong slime-producing Staphylococcus epidermidis strain RP62A was absorbed with the slime-negative phase variant of this strain PV1 in order to remove not slime-specific antibodies. Using this antiserum we established an ELISA which enables detection of slime production in S. epidermidis extracts. The ELISA showed high absorbance when extracts from slime-positive strains (confirmed in the tissue culture tube test) were used as antigens. The high absorbance of slime-positive strains was greatly reduced by periodate oxidation of the extracts and was resistant to proteinase digestion suggesting that the detected antigen is composed of polysaccharides. In contrast to other rapid and simple laboratory detection methods for S. epidermidis slime, the slime-specific ELISA gave positive results in the presence of human serum.

Animals↗
PubMed1996

[Surface law and allometric analysis of functions].

Since Rubner established in 1883 the "surface law", the basal metabolic rate (kcal/24 h) is expressed per square meter of body surface. This so-called biological law has been extrapolated to the standardization of several other functions as, for instance, to variables of the cardiovascular, respiratory and renal systems, which may lead to erroneous conclusions. The present paper is an attempt to establish, by means of the dimensional analysis and one of the theories of biological similarity, an allometric indexation procedure, which yields mass-independent numbers (MIN) for all functions which can be defined by means of the MLT-system of physics (M = mass; L = length; and T = time).

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

In memoriam Professor Jaime Talesnik, MD.

In memoriam Jaime Talesnik. Born in Santiago, Chile, 18 May 1915; deceased Toronto, Canada, 7 April 1996. Medical studies at University of Chile, 1935-1940. MD, University of Chile, 1941. Assistant Professor of Physiology, Faculty of Biology and Medicine, University of Chile, 1940-45. Rockefeller Research Fellow, Banting-Best Institute, Department of Medical Research, University of Toronto, Canada, 1945-46. Associate Professor of Physiology, Faculty of Medicine, University of Chile, 1947-51. British Council Research Scholar in Pharmacology, National Institute for Medical Research, London, England, 1951-52. Associate Professor of Pathophysiology, Faculty of Medicine, University of Chile, 1952-63. Professor and Chairman, Department of Experimental Medicine, Faculty of Medicine, University of Chile, 1963-67. Visiting Professor, Department of Pharmacology, University of Toronto, Canada, 1967-69. Professor, Department of Pharmacology, University of Toronto, Canada, 1969-81. Professor Emeritus, University of Toronto, Canada, 1981. Member Emeritus, Medical Association of Chile, 1991. Honorary Member, Chilean Society of Physiological Sciences, 1995. Author of textbook of pathophysiology and many articles in scientific journals.

Canada↗
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↗
PubMed1995

[Postoperative infusion therapy: electrolyte solution in comparison with hypocaloric glucose and carbohydrate exchange-amino acid solutions].

OBJECTIVES: Comparison of early postoperative hypocaloric nutrition with glucose or xylitol/sorbitol- amino acid solutions versus saline alone. Influence on substrate, especially protein metabolism. DESIGN: Prospective randomized study. SETTING: Intensive care unit of an university hospital. PATIENTS: 44 patients in three groups after major surgery with necessity of intensive care. RESULTS: Hypocaloric infusions were well tolerated immediately after operation and positively influenced functional proteins and N-balance. During saline infusion protein parameters deteriorated significantly already after 24 to 36 hours. Glucose was not inferior to the xylitol/sorbitol solution and both resulted in a stable metabolic state during four days. CONCLUSIONS: After major trauma or surgery hypocaloric nutrition should be started within 24 hours and can be given already directly after the operation period without metabolic deterioration.

Abdomen↗
PubMed1995

[Incidental endoscopic finding--ileum carcinoid. Treatment strategy and prognostic factors].

The malignancy of gastro-intestinal carcinoids is dependent on localisation and size of the tumor. Tumors of the small bowel seem to have a tissue infiltration depth and extension independent of the primary tumor size. We give a case report of a patient with a carcinoid tumor in the terminal ileum with a diameter of 5 mm and a tissue infiltration depth to submucosa. Based on the immunohistochemical investigation of lymphnode metastases for little, accidentally found carcinoids in the ileum a hemicolectomy with wide mesenteric lymph resection is necessary.

Biomarkers, Tumor↗
PubMed1994

Alexander Lipschütz (1883-1980). A biographical synopsis.

Alexander Lipschütz was born in Riga, Latvia, in 1883. He obtained his M.D. from the University of Göttingen, Germany, in 1901. He conducted research at the Universities of Zürich, Bonn, Göttingen, Bern and Vienna. He was full Professor of Physiology at the Universities of Dorpart (1919-1926), in Tartu, Estonia, and Concepción (1927-1936), in Chile. Later, he became the first Director of the Institute of Experimental Medicine, of the Chilean National Health Service. He authored 22 books and a large number of scientific papers, mostly on Endocrinology and Oncology. He directed 16 medical theses at the University of Concepción and 81 at the University of Chile. He was awarded with the first Chilean National Prize in Science (1969). He died in Santiago, Chile, in 1980.

Chile↗
PubMed1993

Technegas: a study of particle structure, size and distribution.

Technegas (TcG) was produced using a commercially available TcG generator. The structure and size distribution of TcG particles were examined by means of the following methods: (a) transmission electron microscopy (TEM), range: 1 nm-100 microns; (b) time-of-flight mass spectroscopy (MS), range: < 3 nm; (c) photon correlation spectroscopy (PCS), range: 3 nm-3 microns. The TEM images showed graphite particles (size 7-23 nm) agglomerated into larger secondary aggregates. The size of these aggregates, determined from PCS and TEM measurements, showed a log-normal distribution and typically ranged from 60 to 160 nm. No isolated particles smaller than 3 nm could be detected by MS. We conclude that TcG particles consist of technetium-99m labelled agglomerated graphite particles and have an average size of 97 nm (geometrice standard deviation (GSD): 1.55).

Particle Size↗
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↗
PubMed1993

Wavelet analysis of arterial pressure and blood velocity pulsations in the aorta of anesthetized dogs.

The arterial pressure and blood velocity pulsations were recorded from the aorta of anesthetized dogs by means of micro-tip pressure and velocity transducers. Wavelet transforms (Wt) were obtained by converting the analog signals into digital samples at the rate of 42.7 per second, which were subsequently subjected to an algorithm of WT. An iterative rarefaction (2(0) to 2(-4) resolutions) of the number of samples was followed by a substraction of the high frequency components (wavelet coefficients) from the corresponding resolutions. Analyses of the arterial pulsations revealed that the second WT always yielded four types of systolic apexes, which were apparently devoid of physiological meaning, since they were inherent to the "triangulation phase" of the WT algorithm. In addition, the third WT occasionally revealed slow amplitude modulations, which could not be identified in the original recordings and whose significance deserves further investigation. This is also valid for the wavelet coefficients, whose biological meaning is still obscure. In summary, the WT operates as a low pass filter, which brings to light the lower frequency components of arterial pulsations and which finally yields the mean values of both arterial pressure and blood velocities.

Algorithms↗
PubMed1993

[Differentiated treatment strategy for peritonitis: single stage closure with drainage or open with programmed reintervention/lavage?].

307 Patients with intraabdominal infections were operated between 8/1988 to 8/1991. Simple clinical parameters (according to the Mannheimer Peritonitis-Index) were evaluated before treatment. The classical therapeutic concept of one-stage laparotomy with drainage of the abdomen was performed in 223 patients initially. Because of recurrent infection and other complications in 19% of them 1 - 2 relaparotomies had to be done, and in 8% change to open treatment was necessary. Open treatment with planned relaparotomy was necessary in alltogether 101 patients, 93 abdominal complications due to primary disease or sepsis were detected in 43 of them. Abdominal treatment was successful (eradication of source of infection, no recurrence of infection) in 98% of the patients after closed and in 84% after open treatment. Mortality was 6.8% vs. 32.7% and on the whole 15.3%.

Adult↗
PubMed1992

Cholinergic and adrenergic drugs affect delayed type hypersensitivity in C57BL/6 mice.

The present study examined the influence of systemic administration of neuroactive drugs on delayed-type hypersensitivity (DTH) in C57BL/6 mice. The cholinergic agonist nicotine and the acetylcholinesterase inhibitor physostigmine decreased DTH, whereas the alpha-adrenergic agonist clonidine stimulated DTH. In contrast isoprenaline, a specific beta-adrenergic agonist suppressed DTH. It is concluded from these observations that the autonomic nervous system modulates those processes governing DTH. It seems that the alpha-adrenergic subsystem stimulates, whereas the beta-adrenergic subsystem and the parasympathicus inhibit DTH.

Animals↗