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Biomedical subjects

R Zander

Publications and source records attributed to R Zander.

At least 109 records · Page 6Linked to original sources
PubMed1986

A new photometric method for oxygen consumption measurements in cell suspensions.

A new technique is described for measuring O2 consumption rates and O2 concentrations in suspensions of respiring cells. Aliquots of a cell suspension kept in a special thermostated precision syringe are injected into the measuring system in defined time intervals. The O2 content of these samples is determined photometrically, as reported previously. The O2 consumption per cellular wet weight and/or per single cell can be calculated from the cell volume fraction, the physical density, the cell concentration in the suspension, and the time-dependent decline of the O2 concentration in the precision syringe. The minimum detectable amount of O2 is 0.1 microliter O2, which corresponds to 0.001 (vol/vol) of O2 if a 100-microliters sample of suspended cells is analyzed. Reproducibility of the O2 consumption measurement is 9% of the measured value. The advantages offered by this method are the straightforward calibration in absolute terms, the short time required for one analysis (2-6 min), a high sensitivity, the simultaneous determination of overall O2 concentration and O2 consumption rates in cell suspensions, and the great variability in the application.

Animals↗
PubMed1985

[Utilization of 15N marked urea by the laying hen. 2. Incorporation and metabolism of 15N for the synthesis of egg protein].

In an N-metabolism experiment 3 colostomized laying hybrids received 2870 mg 15N-excess (15N') per animal in 6 days in the form of urea with their conventional feed rations. During the 8-day experiment the 21 eggs laid were separated into eggshell, white of egg and yolk. Weight, N-content and 15N' were determined of the individual fractions of the eggs. On an average of the 21 eggs 4.6% of the heavy nitrogen was in the egg-shells, 50% in the white of egg and 45.5% in the yolk. 2.8%, 4.5% and 5.5% (hens 1...3) of the 15N' consumed were detected in the eggs. The maximum 15N'-output in the white of egg was reached on the 6th day, whereas 15N'-output in the yolk showed a nearly linear increase in the time of the experiment. The results show that labelled nitrogen from urea is incorporated into the egg to a lower degree than after the feeding of 15N-labelled proteins and that the development of its incorporation into the white of egg and the yolk differ from that after the feeding of 15N-labelled native proteins.

Animals↗
PubMed1984

Alkaline haematin D-575, a new tool for the determination of haemoglobin as an alternative to the cyanhaemiglobin method. I. Description of the method.

A new method for the rapid and accurate measurement of haemoglobin has been developed as an alternative to the conventional cyanhaemiglobin method. This method is based on the conversion of all haeme, haemoglobin, and haemiglobin species into a stable end product by an alkaline solution of a non-ionic detergent ('AHD reagent'). The reaction product, designated as alkaline haematin D-575, is extremely stable and shows a characteristic absorption peak at 575 nm. As compared to the cyanhaemiglobin method, the determination of haemoglobin by alkaline haematin D-575 offers several advantages such as (1) extreme stability of the AHD reagent and the conversion product, (2) decreased conversion time of all haemoglobin species into the end product, (3) decreased amounts of plasma and cell errors, and errors caused by delayed conversion of carboxy- and fetal haemoglobins, and (4) standardisation by a primary standard (purified crystalline chlorohaemin).

Heme↗
PubMed1984

Alkaline haematin D-575, a new tool for the determination of haemoglobin as an alternative to the cyanhaemiglobin method. II. Standardisation of the method using pure chlorohaemin.

Chlorohaemin with high purity (greater than 99%), a stable and well-defined compound, can be used as a primary standard for the standardisation of a haemoglobin assay based on alkaline haematin D-575 [6]. Dissolved in a solution of 25 g Triton X-100 per litre of 0.1 mol/l NaOH ('AHD solution'), the millimolar absorbance coefficient of the end product (alkaline haematin D-575) is 6.960 +/- 0.046 [l X mmol-1 X cm-1] at 575 nm. Within the range of haemoglobin concentrations of 5 to 25 g/100 ml there is a strong linear relation between chlorohaemin concentration and absorbance with a deviation of less than or equal to 2% from the theoretical values. As compared to the conventional cyanhaemiglobin standard solutions, standardisation with pure chlorohaemin is the method of choice because of the simplicity of the preparation of standard solutions, which can be done in every laboratory, and the stability of both the solid compound chlorohaemin and its solutions in alkaline Triton X-100. For the first time a real standard for quality control in haemoglobinometry is recommended: a concentrated solution which behaves like blood, i.e. the simulation of all steps in haemoglobin determination (dilution and photometry) is possible.

Heme↗
PubMed1981

[Assessment of potential blood substitute solutions with oxygen-carrying properties and their possible uses].

Beside the necessary volume effect (isoosmotic and isooncotic solution) and the physiological bicarbonate concentration (prevention of dilution acidosis) a possible blood substitute with O2 carrier characteristics should enable an optimal O2 transport: Viscosity as low as possible and shear rate independent (Newtonian behavior), O2 concentration at the given O2 partial pressure at least 6 ml/dl, and mean capillary O2 partial pressure as high as possible. For the judgement of such a blood substitute, the so-called O2 supply index is recommended, i.e., O2 concentration times mean capillary O2 partial pressure divided by viscosity.

Acid-Base Equilibrium↗
PubMed1979

Enzymatic sulfation of glycochenodeoxycholic acid by tissue fractions from adult hamsters.

Using a radiometric assay with glycochenodeoxycholic acid as substrate, bile acid:3'-phosphoadenosine-5'-phosphosulfate sulfotransferase activity was found in 105,000 g supernatant fractions of liver, proximal intestine, and adrenal gland homogenates from adult hamsters. Optimum conditions for measurement of the hepatic enzyme were determined. In both male and female animals sulfation only occurred at the 7 alpha-position. Saturation analysis with glycohenodeoxycholic acid revealed that the higher activity observed in fractions from female compared to male hamsters was due to a 4-fold lower apparent Km (79 muM vs. 317 muM) for this bile acid in the females. The sulfation of glycohenodeoxycholic acid was competitively inhibited by glycolithocholic acid, chenodeoxycholic acid, and ursodeoxycholic acid. The data are consistent with the concept that sulfation of many, if not all, bile acids can occur in vivo.

Adrenal Glands↗
PubMed1978

[Oxygen transport by solutions for blood replacement in comparison with other infusion solutions (author's transl)].

To investigate the oxygen transport capacity of solutions for blood replacement the oxygen solubility coefficients (ml/ml atm) at 37 degrees C of 12 solutions for volume replacement were determined and compared with those of 12 solutions for parenteral nutrition, 4 electrolyte solutions and 5 solutions for osmotherapy. All solutions for volume replacement have lower values for oxygen solubility than human plasma which shows a very constant oxygen solubility value even under extreme conditions. For clinical use of volume replacement solutions it is recommended that the oxygen solubility of the substitute be considered when any of the following conditions presents: a) large amounts are infused (hemodilution), b) isobar of hyperbar oxygen therapy is employed (hyperoxia), c) the body temperature is lowered (hypothermia). This is valid especially in the case of any impairment of the microcirculation.

Biological Transport↗
PubMed1975

[Experimental Research on the O2 supply of the eye author's transl].

To investigate the O2 supply conditions of the corneal endothelium and the lens by the aqueous hymor, O2 solubility coefficients of aqueous humor as well as in the lens had to be determined. The current assumption that the vitreous body is a possible O2 pool had to be examined. The following conclusions are drawn from the measured values of Bunsel O2 solubility coefficients (ml O2ml atm) of bovine aqueous humor, lens homogenates, vitreous bodys as well as of solutions of hyaluronic acid at temperatures from 10 to 40 degrees C: 1. The physiological rate of oxygen transport by the aqueous suffices to supply the corneal endothelium and the lens with oxygen, the temperature gradients within the anterior chamber favour the O2 supply of the corneal endothelium compared to other ocular tissues. 2. The O2 content of the aqueous can maintain O2 consumption of corneal endothelium for about 20 min theoretically or for about 5 min the lens ones. 3. The vitreous body can act as a possibel O2 pool only with regard to the O2 supply of the lens. In this case the pool can maintain O2 consumption of the shole lens for about 20 min. 4. During physiological growth of the lens the central part expands, which is characterized by an O2 concentration near zero. Therefore, the O2 supply of the lens is maintained for only less than one minute by the content of the lens itself.

Animals↗