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Biomedical subjects

G Zimmermann

Publications and source records attributed to G Zimmermann.

At least 127 records · Page 7Linked to original sources
PubMed1977

Antagonism of morphine with naloxone in dogs: cardiovascular effects with special reference to the coronary circulation.

The cardiovascular effects of naloxone 15 microgram/kg following morphine 2.0 mg/kg were studied in closed-chest dogs during light nitrous oxide-halothane anaesthesia. The bolus injection of naloxone caused an increase in heart rate (73%), cardiac output (20%) and mean arterial pressure (20%). Total peripheral resistance was unaffected. LV dP/dt max and LV dP/dt max/IP increased by 25% and 14% respectively, but positive inotropic effects could not be shown when load data, heart rate and the decrease in left ventricular ejection fraction (22%) were taken into consideration. The cardiovascular stimulation resulted in an increase in myocardial oxygen demand (66%) which was met by an increase in coronary blood flow (59%). The data suggest that the antagonism of narcotics with high doses of naloxone may impair the myocardial oxygen supply in patients suffering from coronary insufficiency. It is concluded that naloxone should be titrated for each patient to ensure adequate reversal of respiratory depression and to avoid circulatory stress.

Animals↗
PubMed1977

[Effect of high dosages of morphine and meperidine on haemodynamics, coronary blood flow and myocardial oxygen consumption in comparison to fentanyl and piritramide (author's transl)].

Although morphine is one of the oldest drugs known to man, it has only recently been used in large doses as an anesthetic agent. The main advantage is the cardiovascular stability. The purpose of this investigation was to study the circulatory response to high equianalgesic doses of morphine and meperidine. In 10 closed chest dogs during normoventilation and light background-anaesthesia (0.5 Vol. % halthane; N2O:O2 = 2:1) 2.0 mg/kg morphine and 15.0 mg/kg meperidine were given at random. Morphine produced a decrease in mean arterial blood pressure by 28%, which was paralleled by an identical fall in total peripheral resistance. No negative inotropic effects were found. In contrast to this, the severe hypotension developing with meperidine (decrease in blood pressure by 54%) was the result of peripheral vasodilatation (46%) and of myocardial depression indicated by a sharp drop in dp/dtmax (59%), dp/dtmax/IP (14%) and in left ventricular ejection fraction (33%). Utilizing the thermodilution technique, the cardiac output remained largely unaffected with both narcotic analgesics, as the increase in heart rate (morphine 27%; meperidine 101%) compensated for the fall in stroke volume (morphine 19%; meperidine 55%). In spite of the altered haemodynamics there was no change in the myocardial energy demand, which was adequately met by the coronary blood flow measured with the pressure-difference technique. Both, morphine and meperidine, produced initially an increase in coronary blood flow and coronary venous oxygen saturation indicating coronary vasodilation. While the mechanism for the change in cardiovascular status with high doses of morphine is vasodilatation probably due to histamine release, the results of this study suggest a peripheral as well as a central (myocardial depression) site of action with meperidine. The results obtained from this study were compared with the data from a previous investigation on equianalgesic doses of fentanyl and piritramide and their clinical implications were discussed.

Animals↗
PubMed1977

[The cardiovascular effects of the inspiratory N2O-concentration during piritramide anaesthesia in the dog (author's transl)].

Administration of nitrous oxide following large doses of narcotics has been reported to impair myocardial performance. In this investigation the effect of the inspiratory N2O-concentration (F1N2O = 0.0; 0.2; 0.4; 0.6; 0.8) upon haemodynamics, inotropism of the heart, coronary blood flow and myocardial oxygen consumption was studied in 8 dogs, which were normoventilated and narcotized with piritramide infused continuously (2.5 mg/kg-h). While 40% N2O(F1N2O = 0.4) decreased cardiac index (18%) and mean arterial pressure (5%) and increased total peripheral resistance (11%) significantly, the remaining inspiratory N2O-concentrations did not affect these parameters considerably. Load data, heart rate and the continuous decrease of LVdp/dtmax from 3170 mm Hg/s (F1N2O - 0.0) to 2175 mm Hg/s (F1N2O = 0.8) indicated negative inotropic properties of high concentrations of nitrous oxide. The myocardial oxygen demand, which was adequately met by the coronary blood flow, decreased with increasing N2O-concentrations initially by 18% (F1N2O = 0.4) due to bradycardia, slight hypotension and reduction in inotropism. Inhalation of 80% N2O, however, returned the energy demand of the heart to control levels (F1N2O = 0.0) resulting from increased myocardial wall-tension (increase in left ventricular end-diastolic pressure by 30%). The efficiency of left ventricular external work decreased from 18.6% (F1N2O = 0.0) to 14.7% (F1N2O - 0.8) indicating that myocardial performance was uneconomically influenced by high inspiratory N2O-concentrations and large doses of narcotics. The clinical implications of the results were discussed.

Anesthesia, General↗
PubMed1976

Efficient purification and molecular properties of spinach chloroplast fructose 1,6-bisphosphatase.

A relatively straightforward procedure has been developed for the purification of chloroplast fructose bisphosphatase from spinach leaves to apparent homogeneity and with 80% yield. The molecular weight of the enzyme was about 160 000. Chloroplast fructosebisphosphatase consists of four possibly identical subunits and, at pH 8.8, EASILY DISSOCIATES INTO EQUAL HALVES WITH LOWered activity. Sigmoid saturation curves with Hill coefficients between 3.0 and 3.7 were obtained for fructose 1,6-bisphosphate and Mg2+. Incubation of the enzyme with 20 mM dithiothreitol slowly altered the response to pH from no activity measured at pH 7.5 and full activity at pH 8.8 to equal activity at each of these pH values; at the same time the number of freely available sulphydryl groups increased from four to twelve per molecule. These properties are considered in the context of the observed activation of this enzyme following illumination of chloroplasts.

Chloroplasts↗
PubMed1976

Self-association of human erythrocyte phosphofructokinase. Kinetic behaviour in dependence on enzyme concentration and mode of association.

The kinetic behaviour of human erythrocyte phosphofructokinase has been analyzed over a relative wide range of enzyme concentration (0.01 -- 1.7 mug/ml). The kinetic cooperativity which becomes apparent when the enzymic reaction rate is plotted versus the fructose 6-phosphate concentration decreases with increasing enzyme concentration. Simultaneously, a decrease of the half-saturation concentration for fructose 6-phosphate [S]0.5 is observed. Maximum velocity passes through a maximum at increasing enzyme concentrations. Sets of curves representing specific enzymic activity of phosphofructokinase versus enzyme concentration obtained at various fixed concentrations of fructose 6-phosphate and ATP are analyzed. The shapes of these curves are interpreted in terms of an association model of human erythrocyte phosphofructokinase, in which an inactive dimer (Mr 190000) and active multimers of the dimeric form are involved. The conclusion is drawn that the sigmoidal shape of the plots of the enzymic reaction rate versus fructose 6-phosphate concentration is partially caused by a displacement of the equilibrium between different states of association of phosphofructokinase to multimers by this substrate. On the other hand, the inhibition of the enzyme by high concentrations of ATP may be partially caused by a shift of this equilibrium to the state of the inactive dimer.

Adenosine Triphosphate↗
PubMed1976

Organic dyestuffs as catalysts for fuel cells.

Electrocatalysis in fuel cells requires as well substances capable of catalyzing the anodic oxidation of fuels as catalysts for the cathodic reduction of oxygen. Several dyestuffs that catalyze oxygen reduction are known, but up to now only one has been described as active in anodic reactions. All these dyestuffs are N4-chelates. Comparative studies have shown that chelates with other types of coordination, in particular N202-, 04-, N2S2- and S4-chelates, are able to catalyze the reduction of oxygen, though they are considerably less active than the N4-compounds. With a given type of coordination, the nature of the central atom has a decisive influence on the catalytic activity of the dyestuff, whereas substitution on the organic skeleton has only a slight effect. Thermal pretreatment of the N4-chelates can considerably increase their stability in electrolytes containing sulfuric acid. All the experimental results point to the conclusion that, with electrocatalysts, as with natural oxygen carriers, the interaction essential for catalysis takes place between the oxygen and the central metal ion. Various assumptions may be made as to the nature of the rate-determining step. The cathodic reduction of oxygen can be regarded as redox catalysis, or it can be considered from the standpoint of molecular orbital theory. The models hitherto suggested for the mechanism of oxygen reduction are tested against the experimental results and a modified model based on MO theory is put forward.

Catalase↗
PubMed1976

[Etiology of benign papillary stenoses].

In domestic pigs repeated applications of gastrointestinal hormones (pancreozymin, secretin) as well as cholecystectomy lead to histologic transformation of the epithelium in the area of the papilla of Vater and to inconstant pressure changes in the common duct.

Ampulla of Vater↗
PubMed1976

[Contributions to the study of properdin. 4. Report: in vitro model study on the effect of cattle properdin on Escherichia coli].

Light and electron microscopy were used in model experiments to study a high-titre "properdine-system" culture and its action in terms of altering E. coli bacteria. The reaction was altogether strongly predominated by the three following phases of lysis. 1. Onset of massive agglutination after few minutes; 2. Decomposition of bacterial structure by lysis after ten to twelve hours; 3. Terminal phase of lysis after two to three days (amorphous detritus).

Agglutination↗
PubMed1976

[Combined radiomanometric and histological studies in the surgery of Vater's ampulla].

In 34 patients a transduodenal sphincteroplasty was performed for benign stenosis of the papilla of Vater or stones in the area of the papilla. The combined intraoperative radiomanometric investigations as well as the histological examinations of intraoperative biopsis of the liver and the papilla of Vater suggest that in most cases with elevated pressure values of the common duct pathological changes of the liver with signs of cholostasis as well as of the papilla of Vater either with pathohistological alterations or with stones in this area can be detected. Constantly, histological changes of the papilla of Vater lead to pathologically elevated pressures in the common duct. In these cases transduodenal sphincteroplasty is recommended instead of only treating with a bougie or dilating the papilla. The indication for this procedure can be objectified by intraoperative radiomanometry.

Adolescent↗