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Biomedical subjects

H Kammermeier

Publications and source records attributed to H Kammermeier.

At least 55 records · Page 3Linked to original sources
PubMed1988

A one-vial method for routine extraction and quantification of free fatty acids in blood and tissue by HPLC.

A one-vial procedure has been developed to quantify free fatty acids in human blood serum and rat heart tissue. To allow routine analysis the system has been constructed to allow simultaneous processing of nine samples (Praechromat). The free fatty acids are extracted with Freon 11 and then derivatized to coumarin esters prior to HPLC. The Freon 11 extraction of the free fatty acids is rapid and complete. Neither hydrolytic degradation of natural fatty acid esters nor oxidative damage of unsaturated fatty acids was observed. Fifteen free fatty acids (FFA) were routinely quantified by isocratic elution with high reproducibility (SD less than 4%) and good recovery (0.1 mM FFA: 98-100%, 0.02 mM: 91-105%). The free fatty acids could be determined in the range from 20 pmol to 20 nmol.

Albumins↗
PubMed1988

Myocardial performance and free energy of ATP-hydrolysis in isolated rat hearts during graded hypoxia, reoxygenation and high Ke+-perfusion.

The effects of graded hypoxia, graded reoxygenation after anoxic perfusion and of different extracellular K+-concentrations on cardiac energy metabolism and performance were studied in isolated, perfused, electrically paced rat hearts. Graded hypoxia was induced by different oxygen partial pressure (PO2: 736 to 43 mmHg, nine intermediate steps; O2 supply: (AVD*CF): 300 to 21 microliters/g*min) in perfusate for 3 min, thus leading to different levels of relative mechanical steady state. Evaluated free energy change of ATP-hydrolysis (dG/d zeta) decreased largely in parallel with peak systolic pressure (Psyst) and systolic dP/dtmax, whereas diastolic dP/dtmin declined already to lowest values with moderate hypoxia. For regular beats and beats potentiated by paired stimulation the same relationships were found. Complete reoxygenation of hearts perfused anoxically beforehand (10 or 30 min, PO2 less than 6 mmHg), restored Psyst and dG/d zeta completely. Graded reoxygenation from different levels of hypoxia resulted in restitution of dG/d zeta and Psyst to the same levels as in graded hypoxia. The inotropic effect of paired stimulation was moderately reduced. Cytosolic Pi-levels remained increased during partial reoxygenation and exhibited no distinct relationship with mechanical performance. High extracellular K+ (13.5 mM) resulted in increased Psyst and elevated dG/d zeta-levels. Cardiac failure during graded hypoxia and high K+ occurred at comparatively high dG/d zeta levels. Reoxygenation with high K+, led to recovery of dG/d zeta levels but not of Psyst values. According to the results obtained in early hypoxic failure free energy dependence of Na+/K+-ATPase is of minor relevance whereas free energy dependence of sarcoplasmic Ca2+ regulating processes appears to be important.

Adenosine Triphosphate↗
PubMed1988

Intra- and extracellular markers in interstitial transudate of perfused rat hearts.

The interstitial transudate was investigated in isolated perfused rat hearts. Capillary permeability and the kinetics of interstitial uptake and release were characterized using four different marker molecules (mol wt 522 to 2 X 10(6)). The half-time (t1/2) values (less than 30 to 170 s) and the interstitial concentration after 30 min (100-44% of arterial concentration) reflected the order and inverse order of their molecular weights, respectively. Creatine kinase (CK) and glutathione (GSH) were measured during control state, hypoxia, and anoxia, followed by reoxygenation. Interstitial concentrations of CK and GSH were higher by a factor of 100 and 8, respectively, compared with the venous effluent. During hypoxia (PO2 = 110 mmHg, i.e., O2 supply = 30% of demand) and reoxygenation there was a significant increase only in the interstitial (not venous) release of CK and GSH, which was further increased during anoxia. Ischemia (75 min) and reperfusion cause no interstitial release of lysosomal (acid phosphatase) and mitochondrial (glutamate dehydrogenase) enzymes despite a massive loss of cytosolic enzymes. Examination of the interstitial transudate allows characterization of capillary transfer and provides a very sensitive measure of sarcolemmal release phenomena.

Aerobiosis↗
PubMed1988

Interstitial transudate concentration of adenosine and inosine in rat and guinea pig hearts.

Interstitial transudate (IT) was sampled from the surface of isolated constant pressure-perfused guinea pig and rat hearts. With endogenous adenosine (AR) formation, IT concentrations (Crr) of AR and inosine (IR) were 4- to 6.5-fold higher than those in the venous effluent. The AR-to-IR ratio varied between 0.5 and 0.1. During normoxic perfusion, CIT-AR reached a basal level of 0.18 microM. During maintained hypoxia, CIT-AR was elevated only initially up to 0.63 microM. Subsequently, it decreased to basal values, whereas coronary flow remained elevated. With repetitive hypoxia, CIT-AR decreased to basal values, with little alteration in the coronary flow response. Addition of 1,000 U/l adenosine deaminase reduced CIT-AR below 0.2 microM, with no change in coronary flow response to hypoxia. High concentrations of coformycin (Streptomyces antibioticus), an adenosine deaminase inhibitor (greater than 1 microM), were necessary to increase the AR-to-IR ratio to unity, indicating an intracellular site of action. During administration of 0.1 microM dipyridamole, no close correlation between CIT-AR and coronary flow was found. Administration of 1 microM AR did not induce a detectable change in Crr-AR despite a distinct coronary flow response. We conclude that at least in our heart preparation, interstitial adenosine seems to play no primary role in coronary flow regulation.

Adenosine↗
PubMed1987

High energy phosphate of the myocardium: concentration versus free energy change.

About 80% of the energy derived from the oxidation of substrates is stored in the form of ATP in sufficiently oxygenated hearts. This is reflected by a free energy and chemical potential respectively, of ATP of about 60 kJ/mol. This energy level does not need to be correlated with tissue ATP content and can also be reached with markedly lower amount of tissue ATP. With graded hypoxia, this energy level drops to 50 to 40 kJ/mol without a corresponding reduction in tissue ATP, but with a concomitant fall in peak systolic pressure. Various energy-dependent processes may be responsible for this impairment of cardiac performance. According to experiments with reduced energy demand of the sarcolemmal ion pumping processes and inotropic interventions, the reduced chemical potential of ATP still seems to be sufficiently above that required for the sarcolemmal ion pumping and for the chemo-mechanical energy transformation of the actomyosin system. In contrast, the reduced chemical potential of ATP seems to be no longer sufficient to meet the high level required for normal Ca++ accumulation in the sarcoplasmic reticulum.

Adenosine Diphosphate↗
PubMed1987

Interstitial fluid of isolated perfused rat hearts: glucose and lactate concentration.

Interstitial fluid (IF) emerging at the ventricular surface of isolated perfused rat hearts was collected and assayed for rate of production, protein content, glucose and lactate concentration. The influence of four perfusion media was investigated during an experimental period of 150 min: Krebs-Henseleit solution (KH) containing glucose (5.5 mM); KH containing glucose and pyruvate (2 mM); Hypoxic KH (20% O2), substrates as 2; KH containing isoprenaline (8 X 10(-9) M), substrates as 2. Interstitial fluid was produced at a rate of 20 to 100 microliters/min/gww and contained proteins (0.5 to 3 g/l). Interstitial glucose concentration was lower than venous concentration by up to 50%. Interstitial lactate concentration was higher by up to 600%. Permeability X surface area products of glucose calculated from transcapillary concentration differences and transfer rates were different depending on experimental conditions, but were within the rather large range of P X S values for molecules of similar size obtained by other authors. Those of lactate were higher by a factor of 3 to 9 and can be interpreted to be influenced by the metabolic activity of the endothelium. The results demonstrate that interstitial substrate concentration can differ very markedly from intravascular concentration and cannot be estimated reliably without assay of the interstitial fluid. Capillary permeability seems to be variable under the experimental conditions of this study.

Animals↗
PubMed1987

Interrelationship between the free energy change of ATP-hydrolysis, cytosolic inorganic phosphate and cardiac performance during hypoxia and reoxygenation.

Energy (ATP) dependent processes of the cell can in principle be divided into near equilibrium (high efficiency) processes, which depend on free energy (change) from ATP-hydrolysis and those not dependent on the free energy levels i.e. non-equilibrium processes. Due to the high efficiencies of the contractile process and the ion transport processes involved in excitation contracting coupling free energy dependence of these processes can be inferred. Though an apparent relationship between the free energy levels and performance can be observed in the early hypoxic failure and graded reoxygenation of isolated isometrically working rat hearts, EC-coupling alteration seem to preceed critical drop of free energy levels. These alterations appear not to be brought about by increasing cytosolic Pi. A pronounced negative staircase phenomenon in hypoxia accompanied by maintained free energy levels are interpreted in terms of a protective mechanism, which prevents critical drop of free energy levels of the cells at costs of their contractile performance.

Adenosine Triphosphate↗
PubMed1987

Electrically stimulated cardiomyocytes: evaluation of shortening, oxygen consumption and tracer uptake.

Progress in the utilisation of the model "isolated cardiac myocytes" was achieved by designing a special stimulation chamber. This chamber allows eliciting of contraction of suspended myocytes by electrical stimulation. Oxygen consumption was thereby linearly enhanced dependent on the rate of stimulation. Different extent of shortening was observed indicating different inotropic state. Considering the myocytes to behave as a spring (with small delta L) a correlate to work performed was obtained which allowed evaluation of changes in ATP/O-ratios. Uptake of 3-O-methyl-D-glucose was dependent on the mechanical and therefore metabolic activity of the cells. The results show that transfer of glucose across the myocardial sarcolemma is adapted to the metabolic demand by affinity variation and not by recruitment of the transporters.

3-O-Methylglucose↗
PubMed1986

Contraction and metabolic activity of electrically stimulated cardiac myocytes from adult rats.

An experimental setup has been developed, which allows electrical stimulation of cardiac myocytes and simultaneous measurement of oxygen consumption, lactate production, extent of shortening and of substrate uptake. In resting cells and in cells stimulated with 120 to 480/min the oxygen consumption ranged from 25 to 100 microliter/min X gww, with a linear relationship between rate of stimulation and oxygen consumption (VO2). When using 5 mM glucose plus 2 mM pyruvate or 10 mM lactate as substrates, isoproterenol (8 X 10(-8) M) augmented contraction and VO2 at all rates of stimulation. Assuming Hook's law for passive elastic behavior for the contracting myocytes over the length change observed, a good correlation exists between the degree of cell shortening calculated from VO2 per beat and the degree of contraction measured. This correlation can be used as a measure of the economy of O2 utilization.

Animals↗
PubMed1985

Characteristics of lactate transfer in isolated cardiac myocytes.

L-lactate uptake of isolated cardiac myocytes was investigated, since due to different lactate concentrations in the interstitial fluid and vascular space, lactate uptake cannot be studied satisfactorily in whole hearts. Lactate uptake exhibits sigmoidal saturation kinetics. Pyruvate (2.3 mM) inhibits L-lactate uptake at lower lactate concentrations (less than 15 mM) and enhances L-lactate uptake at higher (greater than 25 mM) lactate concentration. L-lactate uptake is increased at lowered pH (7.1) to an extent not explainable by non-ionic diffusion. The results are discussed in terms of a complex L-lactate carrier system which might involve cooperative mechanisms and H+-co- or OH- -countertransport.

Animals↗
PubMed1985

Essential contribution of thrombocytes to the occurrence of catecholamine-induced cardiac necroses.

The role of thrombocytes in the production of isoproterenol-induced cardiac necrosis was investigated in rats rendered thrombocytopenic (A) as well as in rats treated with a prostacyclin analogue (B). According to quantitative morphometric evaluation the area of necrotic tissue amounted to about 1% 9 h following administration of isoproterenol (40 mg/kg). In both groups of treated animals the number and area of necroses were strongly reduced (to 23% group A, to 34% group B, P less than or equal to 0.1 for both groups). In contrast, the reduction of myocardial adenine nucleotide levels induced by isoproterenol was the same (5.06 to 3.57 and 3.60 microM/g wet wt, respectively) in thrombocytopenic and non-thrombocytopenic rats. Quantitative comparison of the fraction of necrotic tissue and of the fraction of lost nucleotides suggests that non-necrotic rather than necrotic tissue predominantly contributes to the reduction of nucleotides. The dependence of cardiac necrosis production on the presence or normal aggregability of platelets points out at platelet-dependent microvascular alterations as a main cause of isoproterenol-induced cardiac necroses.

Animals↗
PubMed1985

Barriers in cardiac substrate supply.

The capillary wall, due to its diffusional resistance, causes concentration differences between the vascular space and the interstitial space for substances which are released or taken up by the heart. Estimation of capillary transfer and interstitial concentration in isolated hearts, however, indicates a variable diffusional resistance, which in the case of glucose results from an insulin dependent transfer mechanism and in the case of lactate from a dependence of lactate transfer on lactate concentration or direction of transfer. Due to the unpredictable interstitial concentration investigation of sarcolemmal transfer appears to be possible at present only with isolated cardiac myocytes. Sarcolemmal transfer was studied for glucose and lactate. Recent investigations of lactate transfer revealed saturation kinetics, dependence on pyruvate (inhibition at low lactate concentration and enhancement at high lactate concentration) and dependence on pH (linear increase with lowered pH [8.0 to 6.7]).

Animals↗
PubMed1982

Effects of Ca2+ deficiency, collagenase, and mechanical dispersion on the ultrastructure of cardiac myocytes of adult rats.

A new perfusion medium for isolating cardiac myocytes from adult rats was developed, thereby yielding numerous viable cells with few morphological changes. The main factors in the isolation procedure are Ca2+ deficiency, collagenase, and mechanical dispersion. Their effects on the ultrastructure of cardiac myocytes were separately tested. In isolated hearts, perfusion with a medium containing a physiological Ca2+ concentration (2.5 mM, controls) preserved the cellular fine structure well, whereas perfusion with a medium containing 2.5 mM Ca2+ plus 0.05% collagenase caused swelling and disruption of most cells. Perfusion with a Ca2+-deficient medium followed by a medium with a low Ca2+ concentration (25 microM) either containing or lacking collagenase resulted in widening of the T-tubules, reduced electron density of the external lamina and occasional separation, or even dissolution of this layer. Some cells were damaged and hypercontracted. These appeared more numerous in suspensions, that means after mechanical dispersion of the myocardium. However, most of the isolated cells were regularly shaped (up to 30-60 min as shown in another study) and their ultrastructure was only slightly altered. This corresponds to an adequate preservation of the cell membranes proven in earlier membrane transfer studies.

Animals↗