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Biomedical subjects

M Halmann

Publications and source records attributed to M Halmann.

At least 19 recordsLinked to original sources
PubMed1987

Human cell lines secreting lymphokines. I. Establishment of T-T hybridomas.

Lymphokines (Lks) are conventionally produced by mitogen stimulation of T lymphocytes. However, this procedure results in a mixture of factors, some of which may have antagonistic effects. An alternative method of producing Lks is the construction of monoclonal T-T hybridomas which secrete distinct Lks. By adapting the hybridoma technology for T cells, one can select distinct T hybridomas which may serve as constant sources for the production of uniform and well defined Lks. Since the compatibility of a certain cell line to serve as a fusion partner is unpredictable, several lines were tried in the hybridization procedure. An obligatory requirement of such a mutant line is its sensitivity to a selective medium, in which only the hybrid cell would survive. For this purpose three 8-azaguanine (8AG) resistant mutant lines (Jurkat/12 CEM/14 and Molt-4/10) were established from the respective T leukemic cell lines. This was achieved by culturing the cells in the presence of 200 microM 8AG. The surviving resistant cells were sensitive to aminopterin and azaserine inhibitors. Depending on the cell line and the inhibitor, death of these mutants was complete in 7 to 14 days. Non-adherent peripheral blood lymphocytes (PBL) stimulated for 48 hours with 1 microgram/ml phytohemagglutinin (PHA), were fused with the CEM/14 line. Fifteen hybridomas secreted a substance with B cell growth factor (BCGF) activity, nineteen hybridomas secreted T cell growth factor (IL-2), and eight hybridomas secreted gamma-interferon (gamma-IFN). The six lines which exhibited BCGF activity only, were expanded and cloned. The BCGF activity in the supernatant of a positive clone, designated TH-5, was found to be 3-fold more potent than a preparation of BCGF obtained by stimulation of PBL with PHA.

Cells, Cultured↗
PubMed1987

Human cell lines secreting lymphokines. II. BCGF production by a T hybridoma and B cell lines.

B cell growth factor (BCGF) is a lymphokine (LK) primarily produced and secreted by activated T cells. This LK induces proliferation of B cells in culture and can maintain continuous growth of human B cells. One of the putative uses of this factor might be the establishment of monoclonal B cell lines which secrete specific antibodies. These antibodies could be used for passive immunization or in vivo immunodiagnostics. As conventional mitogen activation of T cells induces the secretion of many factors, some of them with opposite effects, the approach taken by us and others was to establish monoclonal hybridomas which produce constitutively a single factor. Such a human T-T cell hybridoma (TH-5), has been established and is growing and secreting constitutively BCGF for the tested 18 months. This BCGF induces proliferation of human B-cells without the requirement of B cell preactivation. No secretion of interleukin-2 or gamma-interferon by this hybridoma was detected. Furthermore, no influence of this factor was detected on T cells. Under optimal growth conditions, the generation time of this hybridoma is 16 hours and it reaches a maximum concentration of 3 X 10(6) cells/ml. The hybridoma cells could grow in serum-free-media and secrete BCGF for a limited time. The produced BCGF was found to be stable for the four tested months at -20 degrees C, at least one week at 4 degrees C and several hours at 37 degrees C. Its activity was destroyed at pH 2.(ABSTRACT TRUNCATED AT 250 WORDS)

B-Lymphocytes↗
PubMed1982

The molecular composition of the volutin granule of yeast.

The volutin granule was isolated from yeast by disruption of freeze-dried cells in an organic solvent and density-gradient-gradient centrifugation. The granule is composed of two types of macromolecule, a linear-chain polyphosphate and four basic proteins, of molecular weights ranging from 10 000 to 20 000. In the dissolved granule these macromolecules are in a complex that is uniform by hydrodynamic criteria (s20,w = 22.3 S). The polyphosphate separated from this complex gives a single 31P n.m.r. resonance and in the analytical ultracentrifuge behaves as a monodisperse solute of molecular weight 245 000 +/- 1000. In the 31P n.m.r. spectrum of yeast used for its isolation, this polyphosphate accounts for 14% of total cell polyphosphate.

Amino Acids↗
PubMed1977

Rapid identification and quantitation of small numbers of microorganisms by a chemiluminescent immunoreaction.

A method (patent pending) for rapidly identifying and quantitating small numbers of microorganisms was developed based on the specific immunoreaction of microorganisms with homologous antibodies linked by conjugation to peroxidase. The high sensitivity of the method is due to the use of a chemiluminescent reaction for the determination of the enzyme. The reaction was performed on Alcar supports with low nonspecific adsorption. The very low noise achieved permitted the detection of as few as 30 to 300 bacterial cells.

Bacteria↗
PubMed1975

Cyanogen induced phosphorylation of D-fructose.

Cyanogen-induced phosphorylation of D-fructose at pH 8.8 led to the formation of a phosphorylated sugar identified as alpha-D-furcto-pyranose 2-phosphate on the basis of its chromatographic and electrophoretic properties, its lability to hydrolysis by alkaline phosphatase, the rate of its acid-catalysed hydrolysis, the results of periodate oxidation and optical rotatory measurements.

Biological Evolution↗
PubMedDate not supplied

Models of prebiological phosphorylation.

The hypothesis that contemporary metabolic pathways envolved from analogous chemical reaction sequences on the primitive Earth leads to a reexamination of models of prebiological phosphorylation. Present-day phosphate uptake by algae and bacteria seems to involve two transport systems: (a) A n active transport process occurring at low external phosphate concentrations (as in umpolluted natural waters), with a transport constant Ks of 10(-7) to 10(-6) M Pi. (b) Another (probably diffusive) process at higher phosphate concentrations (greater than 10-6 M)(as in the interstitial water of reducing sediments). Laboratory model experiments are described for the reation of reducing sugars with orthophosphate in the presence of cyanogen, producing glycosyl phosphates. These reactions proceed with appreciable yields only at high phosphate concentrations (greater than 10-3 M), and may thus possibly serve as simulations of prebiological phosphorylation with diffusive transport, as it may have occurred in the intestial water of reducing sediments.

Bacteria↗
PubMedDate not supplied

Dynamic analysis of left-ventricular shape based on curvature function.

The local curvature function is defined as the change in curvature around the circumference of the LV silhouette. The local instantaneous curvature function is used here to quantify regional left-ventricular (LV) performance throughout the cardiac cycle. Left ventriculography images, taken in the right anterior oblique (RAO) view from nine patients with normal ventricular contraction, and eight patients with anterior hypokinesis (AHK) are used. The local curvature around the circumference of the LV is calculated for each heart throughout the ejection period. The dynamic increase in the curvature of the apex, defined as apical sharpening, is a typical feature of LV contraction. Apical sharpening from end-diastole to end-systole is closely related to the degree of hypokinesis. Normal hearts show larger apical sharpening (128 +/- 57%, SD) than do AHK hearts (46 +/- 13%, p = 0.002). The ratio between apical and anterior curvatures at ES has been found to be 7 +/- 3.5 for normal hearts and 2.3 +/- 0.6 for AHK hearts (p = 0.003). Linear regression between the ventricular volume and apical curvature yields a significant relationship for the normal hearts (r = 0.82 +/- 0.06, average p = 0.07), but not for the AHK hearts (r = 0.72 +/- 0.2, average p = 0.24). Thus, the information inherent in the local curvature of the LV and its dynamic change throughout the cardiac cycle may be used to distinguish between normal and anterior hypokinetic hearts.

Cardiomyopathies↗
PubMedDate not supplied

Digital subtraction myocardial contrast echocardiography: design and application of a new analysis program for myocardial perfusion imaging.

Myocardial contrast echocardiography may provide important physiologic information on myocardial perfusion. Most current analysis programs use manual frame grabbing and selecting of the area of interest. This is time-consuming and not highly reproducible. A system for automatic analysis of myocardial contrast echocardiographic studies was developed and evaluated. The program acquires an electrocardiographically gated sequence of end-diastolic images with a frame grabber in a personal computer. The baseline image is subtracted and the videodensity versus time contrast curve parameters are calculated on-line. Fast color-coded analysis is done automatically with a running square window that covers the entire image. A second mode of contrast analysis allows manual selection of multiple regions of interest. The program was evaluated with contrast echo data from open-chest dogs and two demonstrative patients. This myocardial contrast analytic package is an inexpensive, rapid, flexible, convenient, and reproducible on-line method that facilitates myocardial contrast echocardiographic analysis.

Albumins↗