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Biomedical subjects

A Klein

Publications and source records attributed to A Klein.

At least 289 records · Page 16Linked to original sources
PubMed1990

Construction of an integration vector for use in the archaebacterium Methanococcus voltae and expression of a eubacterial resistance gene.

An integration vector for use in Methanococcus voltae was constructed, based on the Escherichia coli vector pUC18. It carries the structural gene for puromycin transacetylase from Streptomyces alboniger, which is flanked by expression signals of M. voltae structural genes and hisA gene sequences of this bacterium. Transformed M. voltae cells are puromycin resistant. Several types of integration of the vector into the chromosome were found. Only one case was due to nonhomologous recombination. The integrated sequences were stable under selective pressure but were slowly lost in some cases in the absence of the selective drug. The vector could be excised from M. voltae chromosomal DNA, recircularized and transformed back into E. coli.

Blotting, Southern↗
PubMed1990

The effect of HIV-1 infection on the lipid fatty acid content in the membrane of cultured lymphocytes.

Elevations in the levels of unsaturated fatty acids (FAs) in membrane lipids lead to an increase in cell membrane fluidity and may also be involved in cell fusion and death through the loss of normal membrane function and integrity. Since the infection of susceptible cells with HIV leads to cell fusion and subsequent loss of viability, the present study was undertaken to see whether HIV infection can alter the relative content of unsaturated FAs in the host cell membrane and to determine whether this change correlates with cell death. Peripheral lymphocytes (PBLs) of a healthy donor and two CD4+ cell lines were chosen: MT-4, which is killed following HIV infection, with significant cell death being observed 5 days postinfection, and H9 which is not killed. Measurements of FA content of the two cell lines and PBLs, either before or at 6, 24, and 48 h after infection, showed a significant rise in the concentration of unsaturated FAs followed by a drop in the concentration of saturated FAs in the MT-4 cell line. With regard to the H9 cell line similar results were obtained at 6 h from infection. However, at 24 and 48 h the concentrations of saturated FAs returned to preinfection levels while the concentrations of unsaturated FAs dropped to levels even lower than those obtained at zero time. No significant changes in FA composition were found with PBLs.

CD4-Positive T-Lymphocytes↗
PubMed1990

NADP+ reduction by human lymphocytes.

The hexose monophosphate shunt (HMPS) is known to be responsible for the reduction of NADP+ by lymphocytes. We tried to find other enzymatic systems that might provide the lymphocytes with NADPH. By measuring the absorbance at 340 nm we noted that the addition of NADP+ to a preparation of disrupted lymphocytes resulted in the formation of NADPH at a rate of 4 nmol/10(6) cells per min. This phenomenon could not be changed by negative feedback inhibition of HMPS, and could not be attributed to the low concentration of glucose, glucose-6-phosphate (G-6-P) and isocitrate found in the cell preparation (NADP(+)-dependent isocitrate dehydrogenase in addition to HMPS NADP+ reducing enzymes was found to be present in lymphocytes). Because of the activity of a NADP(+)-dependent lactate dehydrogenase, pyruvate oxidized the NADPH as it was being formed. Here we demonstrate the presence of an unknown NADP+ reducer in lymphocytes which seems to play an additional role to HMPS in NADP+ reduction by lymphocytes. NADP(+)-dependent lactate dehydrogenase may play a role in regulating the NADP+/NADPH ratio.

Humans↗
PubMed1990

Cortisol catabolism by lymphocytes of patients with chronic lymphocytic leukemia.

A low rate of catabolism of cortisol by lymphocytes correlates with high sensitivity of the cells to the steroid and causes them to die at a greater rate than control samples. Since lymphocytes of patients with chronic lymphocytic leukemia respond to treatment with glucocorticosteroids and are cortisol sensitive, we attempted to see whether their capability to catabolize cortisol differs from that of normal lymphocytes. No difference was found between the two groups of cells with regard to the pattern of cortisol metabolites. However, the lymphocytes of the chronic lymphocytic leukemia groups showed a total cortisol catabolism per cell that was significantly lower than that of the control group. Patients with low lymphocyte count in peripheral blood showed a relatively higher cortisol metabolism by lymphocytes per cell than those with high counts.

B-Lymphocytes↗
PubMed1990

[Exclusion chromatography for the separation of cryoprotective agents from freeze-preserved blood cells].

A method for separating low molecular cryoprotectiva from freeze-conserved erythrocyte- and thrombocyte-concentrates by exclusion chromatography has been described. A new vesicular packing material has been used. Only 25 to 30 minutes are necessary in order to separate glycerol respectively dimethylsulphoxide (DMSO) completely from the cells. 86.5% of the erythrocytes and 75.4% of the thrombocytes were recovered after the separation process.

Blood Platelets↗
PubMed1990

Growth properties of RSV-transformed rat sarcoma (XC) cells.

RSV-transformed rat sarcoma (XC) cells were characterized as to their ability to anchorage-dependent and anchorage-independent growth in various culture conditions. The proliferation of XC cells was dependent on serum concentration and initial cell density. The relationship between seeding density and the growth rate of XC cells indicated that the investigated cells produce factors with growth stimulating and growth inhibiting activity. The anchorage-independent growth inhibiting activity was found in ultrafiltrate (500 Mr 10,000) of XC cells conditioned medium. The obtained results suggests that anchorage-independent growth of XC cells may be regulated by two types of autocrine factors, which are antagonistic in their biological affects.

Animals↗
PubMed1990

[Electrical impedance and time of death in the animal model].

To study passive electric parameters of the rat skeletal muscles in relation to the time of death, investigations were carried out using the impulse distortion method of Pliquett. This measuring method enables the evaluation of the electric rectangular impulse distorted by the biological tissues, which contains any essential information on the passive electric properties of the object to be measured. The passive electric parameters change in the studied time interval up to 79 h post mortem in a characteristic fashion. The linear correlation of the evaluated impulse parameters at the time of death is closest (r = 0.75) between 0.5-8.5 h post mortem, the scatter of single values in late postmortal periods is in part considerable. A further development of the measuring technique and standardization of the measuring method let the passive electric parameters appear to be appropriate magnitudes for estimating the time of death.

Animals↗
PubMed1990

Cortisol catabolism by lymphocytes of patients with systemic lupus erythematosus and rheumatoid arthritis.

We have shown that low cortisol catabolism by lymphocytes correlates with a high sensitivity of the cells to the steroid. In the present study, we aimed to assess whether high resistance to corticosteroid treatment correlates with a high rate of cortisol catabolism by lymphocytes. Since patients with systemic lupus erythematosus (SLE) usually require high doses of corticosteroids, while patients with rheumatoid arthritis (RA) respond to relatively low doses of steroids, we compared the capability of lymphocytes of patients with SLE and RA to catabolize cortisol. The rate of cortisol catabolism obtained with the RA group was not significantly different from that obtained with the control group. The catabolism of cortisol by lymphocytes of the SLE group was significantly higher than both the control group (p less than 0.05) and the RA group (p less than 0.01). A significant correlation was demonstrated between the SLE disease activity index and rates of cortisol catabolism attained by lymphocytes of SLE patients (p less than 0.001).

Adrenal Cortex Hormones↗
PubMed1989

Methyl-coenzyme-M reductase from Methanobacterium thermoautotrophicum (strain Marburg). Purity, activity and novel inhibitors.

Methyl-coenzyme-M reductase from Methanobacterium thermoautotrophicum (strain Marburg) was purified to a stage where, besides the alpha, beta and gamma subunits, no additional polypeptides were detectable in the preparation. Under appropriate conditions the enzyme was found to catalyze the reduction of methyl-CoM with 7-mercaptoheptanoylthreonine phosphate (H-S-HTP) to CH4 at a specific rate of 2.5 mumol.min-1.mg protein-1. This finding contradicts a recent report that methyl-CoM reductase is only active when some contaminating proteins are present. The two polypeptides encoded by the open reading frames ORF1 and ORF2 of the methyl-CoM reductase transcription unit did not co-purify with the alpha, beta and gamma subunits. They were neither required nor did they stimulate the activity under the assay conditions. 3-Bromopropanesulfonate (apparent Ki = 0.05 microM) and 2-azidoethanesulfonate (apparent Ki = 1 microM) were found to be two new competitive inhibitors of methyl-CoM reductase. Both inhibitors were considerably more effective than the "classical" 2-bromoethanesulfonate (apparent Ki = 4 microM).

Cloning, Molecular↗
PubMed1989

Anchorage-independent growth of RSV-transformed rat (GCA, W 12 and XC) cells.

Three RSV-transformed rat cell lines: GCA, W12 and XC were characterized as to their ability to anchorage-independent growth in comparison to normal rat kidney (NRK-49F) cells. Differences in the threshold density (TD) and colony forming efficiency (CFE) of the investigated cells are described. The ability of virally transformed cells to stimulation of soft agar colony formation of NRK cells in coculture assay was presented. The production of TGFs-like factors by GCA, W12 and XC cells was suggested.

Animals↗
PubMed1989

Experimental and clinical monitoring of free jejunal transfers using an implantable ultrasonic Doppler probe.

Postoperative assessment of the continued viability of a "buried" free jejunal transfer remains a difficult problem. The reliability of a 20 MHz pulsed ultrasonic Doppler probe to detect arterial or venous occlusion has been investigated experimentally in isolated vascularised jejunal segments in dogs. Clinically, the probe has been used intraoperatively to confirm normal flow in both the mesenteric artery and mesenteric vein of free jejunal transfers. Continuous recording of the acoustic signal from the probe during closure of the incisions has allowed immediate detection of any adverse effect due to pedicle kinking or excessive skin tension. Sixteen patients undergoing free jejunal transfer have been monitored continuously using the implantable 20 MHz pulsed ultrasonic Doppler probe positioned on the inflow mesenteric artery.

Animals↗
PubMed1989

The effect of fatty acids on the vulnerability of lymphocytes to cortisol.

We have shown previously that cortisol-sensitive lymphocytes (thymocytes) have a much lower capacity than cortisol-resistant cells to catabolize cortisol and that linoleic acid inhibits the catabolism of cortisol by lymphocytes and modulates the sensitivity of lymphocytes to cortisol. In the present study, we attempted to see whether other fatty acids are inhibitory and if inhibition of cortisol catabolism by lymphocytes indicates a change in resistance of the cells to cortisol. Measuring the effect of fatty acids on cortisol catabolism by lymphocytes indicated that the polyunsaturated fatty acids, linoleate, arachidonate, and eicosapentaenoic, inhibit cortisol catabolism by lymphocytes. Using prostaglandin PGE2 and indomethacin as a blocker of prostaglandin formation, we observed that the effect of the polyunsaturated fatty acids was not due to the formation of prostaglandins. Examining the effect of fatty acids on the vulnerability of lymphocytes to cortisol, we noted that saturated fatty acids had no significant effect, whereas the aforementioned polyunsaturated fatty acids make lymphocytes more sensitive to cortisol.

Arachidonic Acid↗