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Biomedical subjects

B Bohn

Publications and source records attributed to B Bohn.

At least 37 records · Page 2Linked to original sources
PubMed1987

Flow-cytometric studies with eleutherococcus senticosus extract as an immunomodulatory agent.

A placebo-controlled study of the effect of an Eleutherococcus senticosus extract (Eleukokk) on the immune system was performed with 36 healthy volunteers utilising quantitative multi-parameter flow cytometry with monoclonal antibodies directed against specific surface markers of human lymphocyte subsets. Volunteers in the verum group received 10 ml of an ethanolic (vincamine free) eleutherococcus senticosus preparation, 3 times daily for 4 weeks. In the placebo, the eleutherococcus extract was substituted by additional wine, resulting in identical final concentrations of ethanol in both preparations. The purpose of the double-blind study was the demonstration of possible effects on the cellular immune status, as determined by quantitative flow cytometry. The most salient feature in the verum group was a drastic increase in the absolute number of immunocompetent cells, with an especially pronounced effect on T lymphocytes, predominantly of the helper/inducer type, but also on cytotoxic and natural killer cells. In addition, a general enhancement of the activation state of T lymphocytes was observed. No side effects were observed during the trial or afterwards (observation period 6 months).

Adjuvants, Immunologic↗
PubMed1987

Biochemical characterization and immunomodulatory action of thymic components as determined by flow cytometry on human lymphocytes.

A commercial preparation from calf thymus was separated into its components, then chemically characterized and tested for immunomodulatory efficiency. For the latter, a novel in vitro test system is described as a relatively simple screening procedure. It employs whole blood cultures and flow cytometry with fluorescent monoclonal antibodies defining human T-cell subsets. As a reference substance, thymosin fraction 5 was used. It could be shown that the effects of the entire thymic preparation as well as of one of its peptidic components resembled closely the ones obtained with thymosin fraction 5. In several cases, i.e. with donors relatively deficient in suppressor/cytotoxic T-lymphocytes, the effect of the former was even superior to that of thymosin fraction 5.

Antibodies, Monoclonal↗
PubMed1986

Isolation of human haemoglobin variants with altered Bohr effect. Application to haemoglobin Rainier.

Isoelectric focusing on polyacrylamide gel in the absence of haem ligands represents a useful, convenient and rapid procedure to isolate silent Hb variants in their native forms, provided that they exhibit an abnormal Bohr effect. The amount of material which is eluted is sufficient for both a limited functional study and a structural determination using microscale high-performance liquid chromatography. This is exemplified by the isolation and the study of Hb Rainier.

Chromatography, High Pressure Liquid↗
PubMed1985

A comparison of established human lymphoma lines by flow cytometry: quantitation of Ricinus communis agglutinin binding and the effect of specific glycosidases.

Two established cell lines of human B-cell lymphomas derived from Burkitt lymphomas and their Epstein-Barr virus-transformed counterparts were analyzed with respect to their ability to bind the beta-galactoside-specific lectin Ricinus communis agglutinin (RCA). Native and sialidase- as well as sialidase-beta-galactosidase-treated cells were compared. The method for the quantitative determination of average numbers of binding sites and of apparent affinity constants was flow cytometry with fluorescence-labeled lectin. Although with native cells there was no significant deviation of the values for virus-transformed cells from those for the parent cells, some differences could be detected after glycosidase treatment. The general procedure of the combined application of specific glycosidases and the quantitation of sugar-specific lectin binding is recommended as a general strategy for the differentiation of cells with known or putative differences in biological functions.

Binding Sites↗
PubMed1985

A new case of hemoglobin Providence (alpha 2 beta 2 82 (EF6) Lys----Asn or Asp) discovered in a French Caucasian family. Structural and functional studies.

A new case of Hb Providence was discovered in a French caucasian family presenting a mild polycythemia. Structural and functional studies of the two abnormal fractions (Hb Providence Asn and Asp) have been performed. These confirm the abnormal characteristics of Hb Providence described previously. Red cells containing Hb Providence were fractionated with a Percoll Albumin density gradient. The respective amounts of the two components were determined in the youngest and oldest cells. We observed a slight increase of Hb Providence Asp from 34 to 37% during the life span of the erythrocytes which confirms that the deamidation of Hb Providence Asn to Hb Providence Asp is a fast process, already present and close to its maximum, in the reticulocytes. Both abnormal components are stable in the presence of isopropanol.

Adolescent↗
PubMed1985

[Simple and rapid method for the fractionation of red blood cells in sickle cell anemia].

The density of normal red blood cells increases during their 3-month life span. This characteristic has been used for many years to separate younger from older cells by centrifugation, allowing biochemical and physiological studies on the ageing process in red cells to be performed. The methods which have been proposed to date using discontinuous density gradients made of high density chemical compounds required high speed centrifugation of long duration. These gradients with pre-established density layers are well designed to separate red cells when their density varies over a small range as in blood from healthy donors. Pathological red cells such as found in sickle cell anaemia, thalassaemia syndromes or haemolytic anaemia of various origins display a wide and unpredictable range of densities which precludes the use of a standard discontinuous gradient. Because the fractionation of such pathological blood specimens is of great clinical and biochemical interest we report the details of a new method which combines two steps: firstly and analytical method performed with phthalate esters which allows estimation of the distribution of particular red cells, secondly a preparative method using Percoll solutions to prepare the discontinuous density gradient according to the histogram given by the first step. Two examples are described illustrating this interesting method which may possibly be applied to other blood disorders.

Anemia, Sickle Cell↗
PubMed1979

Interaction of butene with human hemoglobin A.

The binding of various alkanes by proteins was recognized years ago. We have studied the effect of butene (C4H8), a short-chain aliphatic hydrocarbon, on the functional properties of human adult hemoglobin. Under 1 atm pressure (100 kPa) butene decreased the affinity of hemoglobin (Hb) for oxygen (p50) by 45% without altering the cooperativity of ligand binding. This effect was independent of pH (from 7.0 to 8.0) and of ionic strength. The changes in the affinity of hemoglobin for oxygen were dependent upon the partial pressure of butene and evoked a saturating mechanism of the binding site(s). Mathematical simulation of the curve relating p50 to the concentration of dissolved butene allowed us to calculate the apparent association constants for one single binding site KHb = 10.4 mmol-1 and KHbO2 = 1.53 mmol-1 to Hb and HbO2 respectively. The larger binding of butene by Hb was confirmed by a 25% decrease in K1, the first association constant of oxygen to the tetrameric hemoglobin. It is concluded that butene is an allosteric effector of human Hb which acts most likely through hydrophobic interactions. It is postulated that the oxygen-linked binding site may be located at the alpha 1 beta 2 interface.

Alkenes↗
PubMed1979

The binding of lactate and chloride ions to human adult hemoglobin.

The effects of sodium lactate (Lact) on the oxygen affinity and the Bohr effect of purified human adult hemoglobin solutions have been compared to the effects of sodium chloride (Cl). Changes in the affinity for oxygen have been estimated from the variations of log(O2)50 with pH and at various salt concentration from 0.005 up to 2.0 mol.l-1. (O2)50 was calculated as alpha.P0.5 where alpha is the solubility coefficient of oxygen in the solutions at various salt concentrations. Variations of log(O2)50 with pH at constant salt concentration and variations of log(O2)50 with anion concentration at constant pH have been studied according to the linked-functions theory (Wyman, 1968). Bohr curves and salt binding curves were calculated from standard iterative curve fitting procedures and various parameters relevant to the effects of salts on hemoglobin function were estimated. It is shown that Lact and Cl increase (O2)50 and the alkaline Bohr effect in a comparable way at low salt concentration. At high concentration the effect of Lact predominated over that of Cl. The amount of oxygen linked Lact was larger than that of Cl. Binding constants for both anions to deoxy and oxy Hb were estimated. Lact and Cl have comparable binding constants to deoxy hemoglobin. By contrast Lact binds to oxy hemoglobin to a lesser extent than Cl. This may account for the differences observed in the effects of Lact and Cl on the function of hemoglobin. The reason for the low affinity of oxy hemoglobin for Lact may be related to steric differences between the two anions.

Chemical Phenomena↗
PubMed1978

Oxygen transport in children on maintenance haemodialysis.

1. Adaptive mechanisms of oxygen transport by blood have been studied in severely anaemic young patients on maintenance haemodialysis, in conditions of hyperphosphataemia (Pi greater than or equal to 2.2 mmol/l) or normophosphataemia. 2. In hyperphosphataemia whole-blood affinity for oxygen was slightly decreased, as measured by an increase in P50 (the partial pressure of oxygen necessary to half saturate haemoglobin). 2,3-Diphosphoglycerate was increased by 10% (P less than 0.10) whereas Pi, total erythrocyte phosphate and ATP were increased by 100%, 47% and 36% respectively, compared with control values. 3. After correction of hyperphosphataemia a small but significant decrease in P50 and 2,3-diphosphoglycerate, to normal values, was observed whereas the other variables, although significantly lowered, remained above control values. 4. In these severely anaemic and hyperphosphataemic patients P50 and 2,3-diphosphoglycerate are only slightly increased. ATP synthesis appears to be favoured over that of 2,3-diphosphoglycerate. This is possibly due to alterations in the erythrocyte membrane elicited by bi-weekly extracorporeal circulation. Adequate oxygen transport can be achieved only through a drastic increase in blood flow. Correction of hyperphosphataemia adds further to the abnormality. It is concluded that this condition could induce a long-term myocardial fatigue, which might be prevented with occasional small blood transfusions.

Adaptation, Physiological↗
PubMed1976

Renal hemodynamics and renal O2 uptake during hypoxia in the anesthetized rabbit.

The effects of hypoxic hypoxia on renal hemodynamics and metabolism have been studied in anaesthetized mechanically ventilated rabbits. Acute hypoxa (FIO2 = 0.10, PaO2 = 35 torr) induces at constant mean arterial pressure a 45% decrease in RBF, GFR, TNa and RVO2 whereas free water clearance increases. These alterations were still apparent 50 min after resuming normal arterial oxygenation. In order to assess the role of the stimulation of catecholamine release in these observations, two other sets of experiments were performed: 1) the animals were ventilated with the same hypoxic gas mixture but after alpha adrenergic blockade (phentolamine: 0.2 mg - kg - min-1 i.v.), 2) hypoxia was induced by ventilating the animals with CO (FICO = 0.002) at constnat PaO2. Increase in renal vascular resistance and reduction of renal O2 uptake were still observed. This indicates that adrenergic stimulation cannot fully explain the renal vasoconstriction encountered in hypoxia. The role of a local vasoactive factor, especially that of the renin angiotensin system is discussed. The apparent O2 cost of Na reabsorption was not greatly modified by any type of hypoxia and the Na: O2 ratio remained close to the value observed in normoxic animals. This indicates that the kidney may adapt to hypoxia by reducing its O2 demand keeping unaltered its tubular function and basal O2 needs.

Animals↗