Chaotic activity during iron-induced "epileptiform" discharge in rat hippocampal slices.

Low-dimensional chaotic dynamics have been suggested in the rat hippocampal slice during iron-induced epileptiform activity. The dimensionality of this chaotic activity has been found to be similar in slices bathed in the same ionic extracellular medium. Some slices also displayed a drop in dimensionality prior to the onset of seizure-like activity. We suggest that techniques of nonlinear dynamical analysis are a useful reverse-engineering tool for studying the in vitro brain slice. We further conclude that neuronal circuits capable of displaying chaotic activity could exist at the level of the in vitro brain slice.

[Determination of glucose with glucoseoxidase-UV, using hexokinase as the reference method (author's transl)]. / Bestimmung von Glucose in Vollblut und Serum mit dem Glucoseoxidase-UV-Verfahren und Hexokinase als Referenzmethode

Results obtained with the commercial test-set "GOD-UV" (Dr. Haury, München) are reported. This method permits the determination of serum-glucose within 3 minutes. The procedure is satisfactory in normal and hyperglycaemic patients. In the hypoglycaemic state, however, there is a danger of misinterpretation. The glucose oxidase-UV is compared with the hexokinase reaction.

[Influence of the dilution of serum-specimen for the determination of cations (author's transl)]. / Einfluss der Verdünnung von Serumproben auf die Bestimmung von Kationen.

The influence of the dilution of serum-specimen for the analyses of calcium, potassium and sodium was investigated. It could be shown, that the dilution has a marked effect on accuracy and precision. Therefore it is not possible to dilute serum for the investigation of potassium and sodium in such specimen.

[Amylase in serum, amylase excretion and the amylase-creatinine-ratio. Individual variation and diagnostic specifity (author's transl)]. / Diagnostische Wertigkeit der individuellen Langzeitvariation der Amylaseaktivität im Serum und Urin.

The amylase activity in serum, the amylase excretion and the amylase-creatinine-ratio was investigated in 25 volunteers monthly for one year and daily for two weeks. The intraindividual variation of the amylase-activity in serum showed only small oscillations. The large refernce value of the group and the need to use individual reference values prefer the 24 hour amylase excretion as a diagnostic tool. The amylase-creatinine-ratio showed individual and seasonal large variations. Therefore the ratio is not suitable for diagnostic questions.

[Concept of reliable laboratory test procedures (author's transl)]. / Gesichtspunkte für die Erstellung eines verlässlichen klinisch-chemischen Befundes.

Considering the multitude of tests in clinical chemistry and hematology, their low diagnositc sensitivity and specifity, and the low incidence of the diseases in a non selected population it is not possible presently to recommend a general screening procedure based on the definition of the reference, the methodological reproducibility and the diagnostic information of a test procedure it is possible to calculate the number of requests necessary to get any desired number of pathological results. "Tell me how many pathological results you want and I'll tell you how many requests you need". In order to get an optimal diagnostic information for clinical chemistry and hematological tests, it is necessary to increase the prevalence by proper selection of the patients and then to order test procedures specific for the suspected disease.

[Determination of aryl esterase activity in the human serum using 4-nitrophenyl acetate]. / Zur Bestimmung der Arylesteraseaktivität im menschlichen Serum mit 4-Nitrophenylazetat

A new determination of esterases and arylesterases (E. C. 3.1.1.2.) with 4-nitrophenylacetate is described. The results are compared with those of the method described by Pilz using phenylacetate. 4-nitrophenylacetate instead of phenylacetate allows a kinetic reaction. The precision of the determination is good, the method easy to handle. Normal values: 1100--2600 U/1 (total esterases), 700--2100 U/1 (arylesterases) at +25 degrees C.

[Urea and creatinine levels and clearances: observations in 25 healthy subjects for one year (author's transl)]. / Harnstoff, Kreatinin, Harnstoff- und Kreatinin-Clearance: Untersuchungen an 25 gesunden Probanden über ein Jahr.

The seasonal, intra- und interindividual variation of the creatinine and urea concentrations in serum and urine and the clearances of these compounds were examined monthly for one year in 25 healthy volunteers. In contrast to the other parameters (serum urea, clearance and excretion of creatinine and urea), the variations in serum-creatinine concentration were small and statistically unsignificant. The variations of the urinary excretion and the clearance of creatinine and urea is due to seasonal variations in the output of the kidney.

Effects of Ca2+ antagonism on energy metabolism: Ca2+ and heart function after ischemia.

Isolated rat hearts reperfused after 25 min of ischemia have 23% of control mechanical function, 65% of control nucleotides, 52% of control ATP, and 75% of control creatine phosphate, whereas cellular calcium is increased 2.3-fold. Initiating reperfusion with verapamil or low Ca2+-containing buffer did not alter these tissue parameters or improve function over hearts reperfused with control buffer only. Also, when verapamil was present before and during ischemia, improvement in cardiac function resulted, and the adenine nucleotides, tissue ATP, and creatine phosphate concentrations were increased while cellular Ca2+ was reduced compared with the other reperfused ischemic hearts. Verapamil apparently improves recovery of function by decreasing energy demand during ischemia rather than by blocking Ca2+ influx during reprefusion. The respiration of isolated mitochondria and homogenates from reperfused ischemic hearts and homogenates of ischemic hearts was decreased by 20-30%, possibly due to sarcolemmal damage, although the respiration of isolated cells from ischemic hearts was normal. Cells isolated from ischemic hearts may represent a selected population lacking sarcolemmal damage.

Adenine nucleotide transport during cardiac ischemia.

The suggestion that long-chain acyl coenzyme A (CoA) derivatives may inhibit mitochondrial adenine nucleotide transport in heart cells during ischemia has been reevaluated. The effectiveness of media palmitoyl-CoA as an inhibitor is a function of mitochondrial protein and media adenine nucleotide concentrations. Extrapolation to the protein and adenine nucleotide levels of the cardiac cell suggest that physiological concentrations of cytosolic long-chain acyl-CoA would not inhibit adenosine 5'-triphosphate (ATP) transport. Palmitoyl-CoA was varied in the mitochondrial matrix by incubating the isolated mitochondria with and without palmitoyl carnitine. Intramitochondrial nucleotides were depleted by incubating the isolated mitochondria for various periods of time with arsenite and phosphate. Even at low substrate (matrix ATP) concentrations, no palmitoyl-CoA inhibition of ATP transport could be demonstrated. Further experiments showed that endogenous nucleotide levels are significantly depleted in mitochondria isolated from hearts made ischemic for 30-90 min. Since mitochondrial adenine nucleotide transport occurs by an exchange mechanism, this depletion of the internal pool of nucleotides from ischemic heart mitochondria may result in an irreversible diminution of ATP transport.

[The influence of heparin and dilution of the results of blood gas analyses (author's transl)]. / Einfluss bon Heparin und Verdünnung auf die Messwerte der Blutgasanalyse.

The results of blood gas analyses are affected by the type and length of storage of the sample and by differences in dilution and heparin concentration. Experiments established that keeping the specimen in iced water for one hour had no effect. Increasing the heparin concentration affected the results less than did dilution of the sample despite the acidity of the solution. If, on the other hand, heparin in powder form was employed (Monovette) the results were influenced by the absence of dilution of the sample and by the different type of heparin used. This particularly affected the acid-base balance and has to be taken into account when evaluating the results. The use of heparin Monovette simplifies the technique of taking blood samples as there is no need to fill the dead space and it provides reproducible results as the problem of differences in dilution does not arise.

[Influence of specimen withdrawal on the results of chemical analyses of blood, plasma and serum in patients with stable or centralized circulation (author's transl)]. / Einfluss der Materialgewinnung auf Klinisch-Chemische Parameter in Blut, Plasma und Serum bei Patienten mit stabilem und zentralisiertem Kreislauf.

The influence of circulatory conditions, point of blood withdrawal (arterial, central or peripheral venous) and the plasma-serum relation on 29 clinical chemical and hematological parameters were studied with 22 polytraumatized patients. The conditions studied significantly affect the results, and must be taken into consideration in evaluating the results and their comparison to reference values. This is especially important for the determination of the catalytic activities of creatine kinase, aspartate and alanine aminotransferases, and alkaline phosphatase in centralized-circulatory patients, for the total protein the electrophoretic fractions and analyses of blood gas as a function of the point of blood withdrawal, and for the total protein, gamma-globulins and potassium when plasma is analysed instead of serum.

Sites of action of glucagon and other Ca2+ mobilizing hormones on the malate aspartate cycle.

Data from a number of laboratories suggest that the exchange of glutamate for aspartate across the mitochondrial inner membrane is stimulated by glucagon and by Ca2+-mobilizing hormones. The purpose of this study was to determine the site of action of these hormones. Two possibilities were considered and tested. The first hypothesis is that the mitochondrial membrane electrical potential gradient (delta psi m) in the cells is increased by the hormones; and that the putative increase in delta psi m stimulates aspartate efflux. The second possibility is that Ca2+ mediates decreases in cellular levels of alpha-ketoglutarate, secondary to stimulation of alpha-ketoglutarate dehydrogenase, and that the decrease in alpha-ketoglutarate stimulates aspartate production by mitochondria. The effect of glucagon on delta psi m was estimated in intact hepatocytes using the lipophilic cation tetraphenyl phosphonium. No increase in delta psi m was observed due to hormone treatment. On the other hand, alpha-ketoglutarate was found to be an effective competitive inhibitor of aspartate formation via glutamate transamination by isolated liver mitochondria (Ki = 0.55 mM).

The effect of hormones on proton compartmentation in hepatocytes.

Liver mitochondria isolated from rats treated acutely with glucagon exhibit higher respiration-dependent H+ ion gradients across the mitochondrial inner membrane than mitochondria from control rats. It has been suggested that similar increases in mitochondrial delta pH in situ could stimulate gluconeogenesis, chiefly because the transport of pyruvate into mitochondria would increase in response to the increase in mitochondrial matrix pH. In order to determine whether the increased delta pH observed in vitro in isolated mitochondria also occurs in situ, the effect of glucagon on the pH in the cytosol and mitochondria matrix spaces of isolated hepatocytes was determined. For qualitative results, the spectral responses of intracellularly trapped 6-carboxyfluorescein was used to monitor cytosol pH, while fluorescein-loaded hepatocytes were used to monitor the mitochondrial pH. Hepatocytes were incubated with the diacetate ester derivatives of these dyes. The esters are permeable to the cell membranes, but are rapidly hydrolyzed in the cells. The free unesterified dyes are relatively impermeable to the cell membranes. After being trapped in the cell, 6-carboxyfluorescein remains localized in the cell cytosol, whereas fluorescein is taken up by the mitochondria as a function of the mitochondrial delta pH. In order to quantitate the actual pH in these compartments, the spectral responses (490-465 nm) of 6-carboxyfluorescein-loaded hepatocytes were used to determine the cytosolic pH. Calibration of these responses was obtained within the cell by determination of the dye's differential absorption coefficient (epsilon 490-465 nm) in various high K+ buffers after equilibration of the internal and external pH with valinomycin and the uncoupler 1799. All absorbance values were corrected for dye leakage. Equal hematocrits of unloaded cells were used to correct for absorbance contributions from cellular constituents. The mitochondrial pH was determined by a combination of the indicator dye and [14C]5,5'-demethyloxazolidine-2, 4-dione (DMO) distribution ratio methods. The weak acid DMO freely distributes across the plasma membrane and mitochondrial membrane in whole cells according to the pH gradient across each membrane. Knowledge of the cytoplasmic pH from the 6-carboxyfluorescein data allows the expected distribution of DMO across the plasma membrane to be calculated. The excess accumulation of DMO in intact hepatocytes over that predicted from the plasma membrane pH gradient alone was then used to calculate the pH gradient across the mitochondrial inner membrane. The effects of valinomycin, uncouplers, and hormones on the pH in cytosolic and mitochondrial compartm