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Biomedical subjects

E Neumann

Publications and source records attributed to E Neumann.

At least 145 records · Page 8Linked to original sources
PubMed1981

[Causal therapeutic management of aplastic anaemia (author's transl)].

Aplastic anaemia is characterized by hypoplasia of haemopoietic tissue. The aetiology of aplastic anaemia is multifactorial, the majority of cases being termed "idiopathic" because of lack of discernible noxious agents. Treatment can include stimulation of haemopoietic stem cells or replacement of stem cells by bone marrow transplantation. Some cases show autoimmune-mediated marrow failure and these patients may respond to immunosuppressive therapy. Pathophysiological subclassification of individual cases is necessary to ensure the correct choice of therapy offering the best chance of success, at minimum risk, from amongst a multitude of therapeutic procedures.

Adrenal Cortex Hormones↗
PubMed1981

[Prognosis of panmyelopathy: a retrospective study (author's transl)].

45 patients with pancytopenia were admitted and treated at the 1st Department of Medicine, University of Vienna, between 1972 and 1978. Retrospective analysis disclosed a significantly longer survival time in association with a hypercellular bone-marrow smear. These patients showed a higher incidence of remission with cortisone anabolic therapy, but more often developed acute leukaemia as well. The median survival time of patients with pancytopenia and a hypocellular or blank marrow was five months. This group of patients should, therefore, be considered for early bone-marrow transplantation.

Adolescent↗
PubMed1981

Spectrophotometric determination of reaction stoichiometry and equilibrium constants of metallochromic indicators. I. General calculational method.

A calculational method is developed for spectrophotometric determination of stoichiometrics and individual equilibrium constants in the complexing of metal ions with metallochromic indicators. Implicit expressions are developed for the calculation of all parameters necessary to describe mixtures of 1 : 1, 1 : 2 and 2 : 1 metal-indicator complexes. The analysis of titration curves entails a series of one-variable best-fit determinations based on mass action and conservation laws; this reduction in the number of degrees of freedom in the curve-fitting procedure yields greater resolution of the complexing parameters than is allowed by conventional methods. Since a common application of metallochromic indicators is to the determination of metal-binding properties of biological molecules, accurate description of metal-indicator complexing is vital for investigation of the regulatory roles of metal ions in biological events.

Journal Article↗
PubMed1981

Spectrophotometric determination of reaction stoichiometry and equilibrium constants of metallochromic indicators. II. The Ca2+-arsenazo III complexes.

The analytical method described in the preceding article was applied to spectrophotometric Ca2+-titrations of the metallochromic indicator arsenazo III (Ar). At various reactant concentrations it was determined that Ar forms 1:1,1:2 and 2 : 1 complexes with calcium. The equilibrium constants and extinction coefficients at 602 nm were determined. Corrected to zero ionic strength at 293 K and pH 7.0, the reactions Ca + Ar = CaAr, CaAr + Ar = CaAr2 and CaAr + Ca = Ca2Ar are associated with dissociation equilibrium constants k(11) = 1.6 x 10(-6)M, K12 = 3.2 x 10(-4)M and K21 = 5.8 x 10(-3)M. respectively. The extinction coefficient of unbound indicator is (602) = 9.6 (+/-0.3) x 10(3) cm(-1) M(-1). Arscnazo III complexes with monovalent ions like Na+ and K+ : at zero ionic strength, the dissociation constant of the Na+-Ar complex is about 0.1 M.

Journal Article↗
PubMed1981

Spectrophotometric determination of reaction stoichiometry and equilibrium constants of metallochromic indicators. III. Antipyrylazo III complexing with Ca2+ and acetylcholine receptor protein.

Stoichiometries, equilibrium constants and optical extinction coefficients of calcium-antipyrylazo III (An) complexing are determined with the analytical method described in article I of this series. Spectrophotometric Ca titrations of An at the wavelengths 595 and 710 nm indicate overall dissociation equilibrium constants for the complexes CaAn, CaAn2 and Ca2An to be 4.5 x 10(-4) M, 1.1 x 10(-8) M2 and 1.5 x 10(-6) M2, respectively, extrapolated to zero ionic strength. Ca titrations of solutions containing An plus acetylcholine receptor protein give clear evidence that An binds to the protein to a large extent in the presence of Ca2+; furthermore, addition of acetylcholine results in release of protein-bound Ca and An. This is the first reported indication that antipyrylazo III binds to biological material and questions the usefulness of this dye as a Ca indicator in biological systems.

Animals↗
PubMed1981

Single channel gating events in tracer flux experiments I. Theory.

Tracer ion flux measurements are a commonly used method for studying ion transport through membranes of cellular systems, where the rate of ion flow is determined by gating processes which control the opening and closing of transmembrane channels. Due to recent advances in the theoretical analysis of tracer flux from or into closed membrane structures (CMS), the mechanism of gating reactions can, in principle, be derived from flux data. A physically well founded analysis is presented for the dependence of the total tracer ion content of a collection of CMS on the gating processes. For functionally uncoupled gating units a mean single channel flux contribution [equation, see text] can be defined, where k is the intrinsic single channel flux coefficient, t the time over which flux is measured, and p(tau,t) is the probability that a given channel was open for a total period tau during t. This quantity reflects the mean time course of the tracer content due to flux through a single channel. Expressions for are derived that explicitly take into account a distribution in the lifetime of open channels. On the basis of the results, kinetic and thermodynamic parameters of multiphasic gating reactions can be determined from the time course of the overall tracer content in a colleciion of CMS.

Journal Article↗
PubMed1981

Properties of agarose-encapsulated adsorbents. II. Elimination of endogenous and exogenous phenolic compounds from human serum.

Phenolic compounds derived from the amino acid tyrosine are endogenous toxins, which are believed to be involved in the pathogenesis of hepatic coma. There are also xenobiotic phenolic substances, such as p-hydroxy-acetanilide (paracetamol or acetaminophen), which can lead to serious complications if taken in an overdose. In both cases, a drastic therapeutic measure such as haemoperfusion may be indicated to eliminate the toxin from the blood. In the present work, human serum has been dosed with the phenolic compounds of immediate relevance in exogenous and endogenous intoxication, and the effectiveness of various adsorbent materials for the elimination of the toxins from the serum has been investigated. Resins and charcoal in the native state have been compared with those encapsulated into large agarose beads, a process which improves the haemocompatibility and thus the practicability of the adsorbents. A certain degree of specificity has been observed. Whereas phenolic acids are adsorbed quite effectively onto the strongly basic ion exchange resins of the Dowex 1X type, particularly 1X8 or 2X8, phenol or paracetamol are less effectively eliminated. In contrast to many other classes of toxin, the Amberlite XAD-type resins are ineffective for all the phenolic substances investigated. Charcoal is the most effective adsorber in most cases, particularly when encapsulated in powder form into agarose beads.

Absorption↗
PubMed1981

Ion flow gating by the acetylcholine system: kinetics of isolated receptor and esterase and of receptor-mediated ion flux.

1. Basic features of the elementary bioelectric signals such as miniature-endplate-potentials are molecularly interpreted on the basis of relaxation kinetic data of isolated acetylcholine receptor and acetylcholinesterase. Electrophysiological and molecular data suggest an essentially sequential processing of acetylcholine by receptor and esterase. 2. Flux measurements with sealed biomembrane fragments containing acetylcholine receptor show that the ion-transporting conformation of the receptor-channel is a short-lived metastable state. In the presence of neuroactivators the receptors inactivate. The description of the flux-inactivation requires a cyclic reaction scheme similar to the desensitization scheme of KATZ and THESLEFF (1957). 3. The recently introduced concept of integrated flux rate coefficients permits us to derive gating mechanisms from flux data under well-defined experimental conditions: sealed biomembrane vesicles, activator concentration, type of transported ion. 4. With respect to activation and inactivation and the metastability of the ion-conducting conformation, there are fundamental similarities between the axonal Na+ ion channel and the acetylcholine receptor-channel.

Acetylcholine↗
PubMed1981

Age-related classification of pyramidal and stellate cells in the rat visual cortex: a Nissl study with the 'Morphoquant'.

(1) Using Nissl preparations and the automatic picture processing system 'MORPHOQUANT', VEB Carl Zeiss JENA, age-related classification of pyramidal and stellate cells of the layer IV in the rat's visual cortex was performed. (2) 12, 16, 20, 30, 90, and 420 days old animals were investigated. (3) Due to the high cell density and immature stage the neurons of an 8-day-old animal could not be measured. (4) A review is given about the automatic picture processing system 'MORPHOQUANT' and the applied computer program. (5) The analysis of one cell soma with the 'MORPHOQUANT' amounts to about 30 seconds. (6) The computer accepted 30 to 50% of the offered objects. The remaining ones could not be discriminated from the neighbourhood. (7) 14 standard features are registered and 7 statistically evaluated preferential taking into consideration area, form and texture of the objects. (8) 4 features are statistically relevant: soma area in picture points (KOFL) and whole extinction (EXTS) correspond to soma size; compactness (KOMP) and concentration of high grey values in the central part of the object (ZNTR) correspond to structural features of the soma, i.e. the structural density and the distribution patterns of strong coloured RNA and DNA particles. Form factors are not statistically relevant. (9) With increasing age the morphological features are clearer and the performance of the classificator is higher. (10) Soma size and structure of pyramidal and stellate cells develop similarly to an overshooting growth curve. The values reach the maximum approximately on postnatal day 16. (11) Age-related methodological and neurobiological problems are discussed.

Aging↗
PubMed1980

Effective charge on acetylcholinesterase active sites determined from the ionic strength dependence of association rate constants with cationic ligands.

The reaction of the specific fluorescent cationic ligand N-methylacridinium with the active site of 11S acetylcholinesterase from electric eel was monitored by temperature-jump relaxation kinetics at a variety of ionic strengths. The ionic strength dependence of the bimolecular association rate constant is analyzed with a Brønsted-Debye-Hückel expression and leads to estimates of the association rate constant at zero ionic strength of K120 = 1.1 X 10(10) M-1 S-1 at 25 degrees C and the net charge number of the enzyme active site of ZE = -6.3. The ionic strength dependence of the second-order hydrolysis rate constant kcat/Kapp for acetylthiocholine under steady-state conditions is also very pronounced and indicates a value of ZE = -9. Thus, a large effective negative charge on the enzyme active site appears to be a general characteristic of its interaction with cationic ligands. The ionic strength dependence of Kcat/Kapp is identical with that of sodium chloride, sodium phosphate, and sodium citrate, thus ruling out any possibility that the phenomena arise from a specific, partially competitive binding of Na+ to the enzyme active site. Substitution of the calculated electrostatic parameters into theoretical equations indicates that the most significant effect of these ZE values is a 2-3 order of magnitude reduction in the rate constant for dissociation of the initial ligand-enzyme encounter complex; this decrease renders the bimolecular reaction diffusion controlled. The high value of k120 and the space requirements of six to nine charged groups suggest that regions of the enzyme surface area larger than the catalytic sites themselves are effective in trapping cationic ligands.

Acetylcholinesterase↗
PubMed1980

[How dangerous is splenectomy in Hodgkin's disease? (author's transl)].

Serious complications aetiologically connected with the operation were found in 8 out of 51 patients (19 females, 32 males) who had undergone splenectomy for Hodgkin's disease. Weighing potential complications against the expected beneficial effects, clear indications for splenectomy are only found in stages I and IIa. In all more progressed clinical stages splenectomy should only be performed when 1) platelet deficiency existed prior to treatment, 2) additional irradiation of the splenic area is to be avoided, 3) oophoropexy is to be performed at the same time. When discussing the indication for splenectomy one should remember that a delay of treatment by approximately three weeks will result.

Adolescent↗
PubMed1980

[Demonstration of an erythropoiesis inhibiting factor with low molecular weight].

In saline incubation media of normal human erythrocytes after 20 hours at 37 degrees C a factor is demonstrable which inhibits 59iron incorporation into mouse erythrocytes, as well as 3H-thymidine incorporation into fetal mouse erythroblasts in vitro. Ultrafiltration of this erythropoiesis-inhibiting factor (EIF) showed a molecular weight of less than 10,000 dalton. After gel filtration (Sephadex G 50) the maximum activity of the EIF was found in the fractions which eluted closely before vitamin B 12 (1250 dalton), indicating a similar molecular weight. The EIF is heat stable (100 degrees, 10 min.) and seems to be a peptide. The inhibiting activity, measured by thymidine incorporation, is strong against mouse erythroblasts and lacking against lymphatic cells. A weak inhibition--possibly a toxic effect--on myelopoiesis cannot be excluded. The inhibition of mouse erythroblasts is reversible. In serum of normal subjects EIF was not demonstrable, whereas it was found in normal urine, indicating rapid renal elimination. This EIF, which is demonstrable under physiological circumstances, is suggested to be the erythrocytic chalone and furthermore could play a role in the production of anaemia in terminal renal failure.

Culture Media↗