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Biomedical subjects

E Kovacs

Publications and source records attributed to E Kovacs.

At least 19 recordsLinked to original sources
PubMed2000

Serum levels of IL-12 and the production of IFN-gamma, IL-2 and IL-4 by peripheral blood mononuclear cells (PBMC) in cancer patients treated with Viscum album extract.

A dysregulation between cellular immunity (Th1 cells) and humoral immunity (Th2 cells) is a characteristic of cancerous diseases. Viscum album (VA) extract has an immunomodulatory effect and can be used in the treatment of cancer patients, either following or in combination with chemo- /radiotherapy. In this pilot study, we investigated the effect of VA extract on the serum levels and production of cytokines in a group of cancer patients undergoing treatment (N = 16) in comparison with healthy untreated controls (N = 11). The serum levels of interleukin-12 (IL-12) (p40 and p70), and the production of gamma interferon (IFN-gamma), interleukin 2 (IL-2), and interleukin-4 (IL-4) in peripheral blood mononuclear cells (PBMC) were measured in patients before treatment and on days 3, 5, 8, 15, and 21-29 during therapy, and in the control group at the same time intervals over a two-week period. Cytokine levels were determined by ELISA. In cancer patients, the serum levels of IL-12 (p40 and p70) before therapy were about 3-fold higher than in controls. They increased during therapy, with a borderline significance (Wilcoxon paired signed-rank test, P = 0.06). In PBMC the production of IFN-gamma and IL-2 (before therapy respectively 3-fold and 9-fold lower than in controls) increased significantly (Wilcoxon paired signed-rank test and Mann-Whitney U-test, P < 0.05) during treatment. In PBMC, IL-4 production was in the same range as in controls, and remained unaltered during therapy. In conclusion, the results of this study show that treatment with VA extract leads an increase in Th1 cytokine levels (IFN-gamma and IL-2), which suggests that cell-mediated immunity could be positively affected.

Cells, Cultured↗
PubMed1999

Caffeine improves cognitive performance after strenuous physical exercise.

The effects of three carbohydrate electrolyte solutions (CES) containing different amounts of caffeine on cognitive function and the combined effects of these drinks and exercise on cognitive functions were investigated in a double-blind, cross-over study. On five separate occasions, fifteen endurance trained male athletes (23.3 years) received water placebo, CES placebo (68.8 g/l), and three CES drinks containing low, medium and high dosages of caffeine (150, 225 and 320 mg/l). Each occasion, 8 ml/kg of the drink was consumed before -- and 6 ml/kg of the drink was consumed during an all-out 1 hour time trial on a bicycle ergometer. Cognitive (attentional, psychomotor, and memory) tests were carried out immediately before and immediately after exercise. Before exercise, long term memory was improved by CES plus low dose caffeine compared to both placebos. Immediately after exercise, all cognitive functions were improved by CES plus low- and medium-dose caffeine compared to placebo. These results comprise the first practical demonstration of the cognition improving effects of low amounts of caffeine in CES after strenuous physical exercise.

Adult↗
PubMed1999

Metabolic effects of a protein-supplemented carbohydrate drink in marathon runners.

A field study was performed to investigate the acute influence of a milk protein hydrolysate supplemented drink (CHO+PRO) on metabolism during and after a marathon run compared to the same drink without protein (CHO). Carbohydrate metabolites and hormones were not influenced by CHO+PRO. Levels of plasma free fatty acids were significantly lower and levels of urea and most amino acids were significantly higher with CHO+PRO. Sweat urea and ammonia nitrogen excretion during the run as well as urinary 3-methylhistidine excretion during the entire exercise day was similar in both treatments. Urinary total nitrogen was significantly increased and urinary pH decreased with CHO+PRO. It was concluded that the supplemented protein was absorbed and probably at least partially oxidized during the run and that no obvious negative metabolic effects occurred. CHO+PRO did not acutely affect myofibrillar protein breakdown as assessed by the 3-methylhistidine method; however, total body protein breakdown was not measured.

Adult↗
PubMed1999

Restoration of immunity with interleukin-2 therapy.

HIV replication can now be effectively suppressed using antiretroviral combination regimens. The search continues, however, for ways to restore the immune response and eliminate reservoirs of latent infection. Interleukin-2 (IL-2) may augment the immune response in HIV-infected persons. This article discusses the rationale for using IL-2 in those with HIV disease and reviews key trials of IL-2 treatment regimens.

Antiretroviral Therapy, Highly Active↗
PubMed1996

Pore formation by S. aureus alpha-toxin in liposomes and planar lipid bilayers: effects of nonelectrolytes.

Nonelectrolytes such as polyethylene glycols (PEG) and dextrans (i) promote the association of S. aureus alpha-toxin with liposomes (shown by Coomassie staining) and (ii) enhance the rate and extent of calcein leakage from calcein-loaded liposomes; such leakage is inhibited by H+, Zn2+ and Ca2+ to the same extent as that of nonPEG-treated liposomes. Incubation of liposomes treated with alpha-toxin in the presence of PEG with the hydrophobic photo-affinity probe 3-(trifluoromethyl)-3-m-[125I]iodophenyl) diazirine (125I-TID) labels monomeric and-predominantly-hexameric forms of liposome-associated alpha-toxin; in the absence of PEG little labeling is apparent. At high concentrations of H+ and Zn2+ but not of Ca(2+)-all of which inhibit calcein leakage-the distribution of label between hexamer and monomer is perturbed in favor of the latter. In alpha-toxin-treated planar lipid bilayers from which excess toxin has been washed away, PEGs and dextrans strongly promote the appearance of ion-conducting pores. The properties of such pores are similar in most regards to pores induced in the absence of nonelectrolytes; the differ only in being more sensitive to "closure" by voltage (as are pores induced in cells). In both systems, the stimulation by nonelectrolytes increase with concentration and with molecular mass up to a maximum around 2,000 Da. We conclude (i) that most of the alpha toxin that becomes associated with liposome or planar lipid bilayers does not form active pores and (ii) that the properties of alpha-toxin-induced pores in lipid bilayers can be modulated to resemble those in cells.

Animals↗
PubMed1996

Peripheral blood mononuclear phagocyte subpopulations as cellular markers in hypercholesterolemia.

Mononuclear phagocytes play a major role in the development of vascular lesions in atherogenesis. The goal of our study was to characterize circulating blood monocyte subpopulations as potential cellular markers of systemic immunological abnormalities in hypercholesterolemia. In normal subjects, three-parameter immunophenotyping of whole blood revealed that 61.3 +/- 6.0% of monocytes showed "bright" expression of the lipopolysaccharide receptor (LPSR: CD14) and Fc gamma receptor I (RI: CD64) without expression of Fc gamma-RIII (CD16). Other monocyte subsets (populations 2, 3, 4, and 5) were characterized by the simultaneous expression of both Fc gamma-R's (25.6 +/- 5.0%), isolated expression of Fc gamma-RIII (9.4 +/- 1.7%), or high expression of CD33 (3.7 +/- 1.1%) with only dim expression of CD14, respectively. The smallest subset of monocytes (population 5: 2.1 +/- 0.8%) differed from the predominant population of CD14brightCD64+CD16- monocytes by additional expression of neural cell adhesion molecule (N-CAM: CD56). In a group of hypercholesterolemic patients (n = 19), high density lipoprotein cholesterol levels were negatively correlated to the population size of CD64-CD16+ monocytes. In both healthy subjects (n = 55) and hypercholesterolemic patients, the rare apolipoprotein E3/E4 and E4/E4 phenotypes were associated with a tendency toward a larger population of CD64-CD16+ monocytes. Expression of the variant activation antigen CD45RA by peripheral blood mononuclear phagocytes showed a positive correlation to plasma levels of the atherogenic lipoproteins low density lipoprotein and lipoprotein(a). These data suggest that systemic abnormalities in mononuclear phagocyte subpopulations may play a role in the pathogenesis of atherosclerosis.

Adult↗
PubMed1995

Activation of cytokine production and adhesion molecule expression on THP-1 myelomonocytic cells by macrophage colony-stimulating factor in combination with interferon-gamma.

THP-1 myelomonocytic leukemia cells cultured with either macrophage colony-stimulating factor (M-CSF) or interferon-gamma (IFN-gamma) alone produce, at best, only low levels of interleukin-1 beta (IL-1 beta) and tumor necrosis factor alpha (TNF-alpha). However, combinations of the two factors resulted in at least 3- to 20-fold greater amounts of IL-1 beta and TNF-alpha than would have been predicted by additive mechanisms. This enhanced cytokine production was observed when M-CSF and IFN-gamma were added simultaneously or when M-CSF was added 24 h after addition of IFN-gamma to the cells. Similar results were obtained with fresh human peripheral blood cells treated with IFN-gamma + M-CSF. Cycloheximide treatment of the cultures containing M-CSF and IFN-gamma inhibited the production of IL-1 beta and TNF-alpha. Northern blotting studies revealed no effect of IFN-gamma alone on IL-1 beta or TNF-alpha mRNA production. IL-1 beta and TNF-alpha mRNA expression was observed at 2 and 6 h after treatment with M-CSF or IFN-gamma + M-CSF. Higher TNF-alpha mRNA expression was observed at 2 and 6 h after treatment with IFN-gamma + M-CSF, and higher IL-1 beta mRNA expression was observed at 2 h after treatment with IFN-gamma + M-CSF compared with mRNA levels observed for cells cultured only with M-CSF. These results suggest that the augmented cytokine production resulting from treatments with combinations of M-CSF and IFN-gamma occurs due to increased cytokine mRNA and increased cytokine protein synthesis. In addition to up-regulating cytokines, combinations of IFN-gamma and M-CSF resulted in augmented cell surface expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1. This was accompanied by morphological and functional changes that included plastic adherence, extensive homotypic aggregation, and a macrophage-like appearance. These phenotypic changes and enhancements in cytokine expression and cell surface molecule expression may be related to activation of monocytic cells to become cytotoxic effectors by M-CSF and IFN-gamma combinations. In vitro cytotoxicity against A-375 melanoma cells was greatest for cultures that contained M-CSF and IFN-gamma in combination.

Cycloheximide↗
PubMed1993

Structure of the gene coding for the human retinoic acid-inducible factor, MK.

The retinoic acid-inducible MK gene shows a distinct developmental pattern of expression, which implies that it has potential growth regulation and differentiation functions, particularly in the brain. We report here the cloning of the human MK gene from a phage library constructed from placental tissue. The structure of this gene has been determined using Southern hybridization and DNA sequence analysis. An isolated fragment was cloned and found to contain sequences identical to those of a previously isolated human MK cDNA clone, MKHC4. The gene contains three introns within the MK coding region as well as additional sequence, which indicates the presence of an intron prior to the putative protein start site. As judged by sequence analysis of cDNA clones, primer extension studies, and Northern analysis, the most abundant human MK message corresponds to the major mRNA of the previously described mouse gene. Primer extension studies and cDNA sequence data suggest that minor messages may be transcribed from the human gene, but no evidence of additional messages has been found by Northern analysis. This is in contrast to the mouse MK gene, from which three mRNAs are transcribed. Nevertheless, the similarity in the overall genomic structure of the human and mouse genes is striking.

Amino Acid Sequence↗
PubMed1993

Cloning and identification of a two-component signal-transducing regulatory system from Bacteroides fragilis.

A DNA fragment was cloned from Bacteroides fragilis that bestowed low-level tetracycline resistance to Escherichia coli strains harbouring the cloned fragment on a multicopy plasmid. The tetracycline resistance determinant was localized to a 4.3kb Bg/II-PstI subfragment of the original clone. DNA sequence analysis of this fragment revealed that it contained an operon encoding two proteins: one of 519 amino acids, RprX, and a second of 236 amino acids, RprY. Protein sequence analysis revealed that the two proteins shared sequence identity with a family of multicomponent signal-transducing regulatory proteins identified from many diverse bacterial genera. RprX shared identity with the first component of the regulatory system, the histidine protein kinase receptor (for example EnvZ, PhoR, CheA, and VirA). RprY shared identity with the second member of the regulatory protein pair, the regulatory response protein (for example OmpR, PhoB, CheY, and VirG). Expression of these proteins from a multicopy plasmid vector in E. coli resulted in a decrease in the level of the outer membrane porin protein OmpF and an increase in the level of the outer membrane porin protein OmpC. The decrease in OmpF levels correlates with, and may be the cause of, the increased tetracycline resistance. Regulation of the levels of OmpF and OmpC is normally controlled by a multicomponent signal-transducing regulatory pair of proteins, EnvZ and OmpR. The effect RprX and RprY have on OmpF expression is mediated at the level of transcription. Thus, RprX and RprY may be interfering with the normal regulation of OmpF by OmpR and EnvZ.

Amino Acid Sequence↗
PubMed1993

Fluorescence flow cytometry of human leukocytes in the detection of LDL receptor defects in the differential diagnosis of hypercholesterolemia.

A flow-cytometric method with fluorescence-labeled monoclonal antibodies (MABs) against the low density lipoprotein (LDL) receptor (C7A MAB) or 3,3'-dioctadecylindocarbocyanin-iodide (DiI) LDL has been developed that allows the quantification of LDL receptors on leukocytes and the identification of patients with familial hypercholesterolemia (FH) within 48 hours. Leukocytes were isolated from 10 mL anticoagulated blood by density gradient centrifugation. To induce maximal expression of LDL receptors, mononuclear cells were preincubated with either phytohemagglutinine (PHA) or lipoprotein-deficient serum (LPDS). LPDS-treated monocytes provided a more homogeneous cell population with regard to LDL receptor activity than did the PHA-treated lymphocytes; they also provided a greater discrimination between the fluorescence of the receptor probes and cellular autofluorescence. The C7A MAB was able to compete for DiI LDL binding by about 40%. In competition with unlabeled LDL, DiI LDL revealed linear binding, indicating an affinity similar to native LDL. The binding characteristics of DiI LDL were also similar to 125I-LDL binding. LDL isolated from familial defective apolipoprotein B-100 was not able to compete for DiI LDL binding on monocytes, whereas native LDL reduced it by about 80%. In monocytes from FH heterozygous patients, the cellular mean fluorescence using either C7A MAB or DiI LDL at 4 degrees C was 30% to 70%; in FH homozygotes, cellular mean fluorescence was less than 20% of that in monocytes from normal individuals. In patients with familial defective apolipoprotein B-100 antibody binding was normal, but one patient's own LDL failed to compete with normal DiI LDL for 4 degrees C binding on U937 test monocytes. Patient monocytes having internalization defects showed normal 4 degrees C DiI LDL binding, but at 20 degrees C cell-associated fluorescence was reduced by about 40%. In our study 384 hypercholesterolemic patients (preselected according to serum cholesterol levels, clinical symptoms, and family history) were analyzed for LDL receptor expression using the C7A MAB-based assay. In 71.8% of the patients with cholesterol levels higher than 300 mg/dL, an LDL receptor deficiency was observed. Apolipoprotein E isoforms and lipoprotein[a] were found to be independent from the LDL receptor status. In some patients with high cholesterol levels but normal LDL receptor expression with the C7A MAB assay, LDL receptor defects could be diagnosed when either reduced binding or internalization of DiI LDL or familial defective apolipoprotein B-100 was detected.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1993

Effects of purinergic agents on human mononuclear phagocytes are differentiation dependent. Implications for atherogenesis.

The differentiation-dependent expression of purinergic receptors for metabolically stable analogues of adenosine and ATP was studied in human mononuclear phagocytes (MNPs). Ligands of these receptors are able to modulate cellular cholesterol metabolism. In addition, the intracellular signal transduction pathways of the purinergic receptor system were examined. ATP gamma S, the metabolic stable analogue of ATP, was used as a P2 ligand, and 2-p-(2-carboxyethyl)phenylethylamino-5'-N-ethylcarboxamido adenosine (CGS 21680) and 5'-(N-ethylcarboxamido)adenosine (NECA) were used as P1 ligands in binding studies. Binding of [35S]ATP gamma S to MNPs at 4 degrees C revealed saturable low-affinity binding sites with a Kd of 868 +/- 52 nmol/L and Bmax of 7.3 +/- 0.4 pmol per 10(6) cells in 1-day cultured human MNPs and a Kd of 780 +/- 30 nmol/L and Bmax of 14.0 +/- 0.8 pmol per 10(6) cells in 7-day cultured human MNPs. The characterization of the P1 receptors on 1- and 7-day cultured human MNPs showed that they are expressed only on 7-day cultured human MNPs. The specific binding curve of the adenosine A2 receptor agonist [3H]CGS 21680 was biphasic, with a Kd1 of 33 +/- 15 nmol/L and a Kd2 of 90 +/- 10 nmol/L and with Bmax1 of 0.19 +/- 0.06 pmol per 10(6) cells and Bmax2 of 0.41 +/- 0.09 pmol per 10(6) cells, whereas NECA did not exhibit specific binding. The typical agonists for probing A1 receptor subtypes did not bind to 1- and 7-day cultured human MNPs, indicating that only A2 receptors are expressed on 7-day cultured human MNPs. ATP gamma S enhanced [Ca2+]i in 1- and 7-day cultured human MNPs in a concentration-dependent manner, whereas the P1 ligands, adenosine and CGS 21680, induced Ca2+ flux only in 7-day cultured MNPs. All three drugs increased intracellular cAMP levels in 7-day cultured human MNPs at a concentration of 10(-5) mol/L, whereas no effect was observed in 1-day cultured human MNPs. The uptake of fluorescently labeled acetylated low-density lipoprotein (LDL) in 7-day cultured human MNPs was inhibited by adenosine, CGS 21680, ATP, and ATP gamma S. No significant influence of these compounds was measured on the uptake of LDL, acetylated LDL, and high-density lipoprotein, in 1-day cultured MNPs. Our investigations indicate that the expression of P2y and A2 receptors is increased during differentiation of blood monocytes to macrophages.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Triphosphate↗
PubMed1992

Do chemo- and radiotherapy affect the DNA repair ability of lymphocytes?

The DNA repair ability of unstimulated lymphocytes damaged by ultraviolet irradiation was measured in a group of 15 breast cancer patients before surgery, and 3 to 5 years later a) after surgery alone (n = 6), or b) after surgery with additional chemo- and/or radiotherapy (n = 9). In group a) 3 out of 6 patients had reduced repair before and 2 out of 6 after surgery. In the group b) 4 out of 9 patients had reduced repair before surgery, and 9 out of 9 after surgery plus chemo/radiotherapy. These results confirm our previous finding that chemo/radiotherapy influences DNA repair negatively. Because of the known association between reduced DNA repair and cancer occurrence, this could increase the risk of a secondary tumour.

Breast Neoplasms↗
PubMed1992

Interleukin-2 receptor positive cells in human decidua during the first trimester of pregnancy and their association with macrophages.

Maternal immune rejection of the fetus could sometimes be the cause of unexplained recurrent spontaneous abortion. Components of the T cell-mediated immunity were investigated in the first trimester of pregnancy in women having spontaneous abortion and compared to those with normal pregnancy having a termination on social grounds. Interleukin 2 (IL-2) had no proliferative effect on the trophoblasts of chorionic villi and there were also no IL-2 receptors in these cells. However IL-2 receptor positive cells were found in the decidua in 7 out of 24 women with normal pregnancy and in 12 out of 18 with spontaneous abortion. A high density of macrophages showed an association with IL-2 receptors in both groups. There were no differences with respect to T-cytotoxic cells and T-helper cells in cases of normal pregnancy (with and without IL-2 receptor positive cells), whereas in women having spontaneous abortion we found lower densities of T-helper and T-cytotoxic cells in those without IL-2 receptors than in those with IL-2 receptors.

Abortion, Induced↗
PubMed1991

Identification and DNA sequence of a new Bacteroides fragilis insertion sequence-like element.

A new Bacteroides fragilis insertion sequence (IS)-like element has been identified, cloned, and sequenced. The element is 1598 base pairs in length. It is flanked by a 15-base pair imperfect inverted repeat and contains a large open reading frame which could encode a 430 amino acid protein. There is an 8-base pair duplication of genomic DNA sequences at the site of integration. One copy of the IS-like element is integrated within the 5' upstream sequence of the metallo-beta-lactamase gene ccrA, cloned from B. fragilis TAL3636. The IS-like element is integrated 19 bp upstream of the predicted initiation codon and, therefore, probably provides the transcriptional start signals for the CcrA gene.

Amino Acid Sequence↗
PubMed1991

Improvement of DNA repair in lymphocytes of breast cancer patients treated with Viscum album extract (Iscador).

We investigated alteration in DNA repair during therapy with an immunomodulator. 14 patients with advanced breast cancer were treated parenterally with Iscador, an extract of Viscum album (mistletoe). As a parameter for measurement of DNA repair the incorporation of (3H) thymidine into DNA of unstimulated lymphocytes after ultra violet light (UV) damage was taken. The DNA repair values in the patients were very low before treatment and on day 1: on average 16% of those in a healthy control population. Values started to increase on day 2 and on days 7-9 were on average 2.7 times higher than before treatment. 12/14 patients showed an improvement in repair. The values of spontaneous DNA synthesis were not altered during the treatment. We suggest that the increase of DNA repair could be due to a stimulation of repair enzymes by lymphokines or cytokines secreted by activated leukocytes or an alteration in the susceptibility to exogenic agents resulting in less damage.

Adult↗
PubMed1991

Differences in the kinetics of DNA repair in cancer patients and healthy controls.

The time course of DNA repair, using (3H)thymidine uptake as parameter, was measured during 8 h after a single exposure to 2, 8, and 16 UV-C J/m2 in lymphocytes of 8 cancer patients, 1 xeroderma pigmentosum patient and 10 controls. All patients had reduced repair, and all controls normal repair, as calculated 2 h after a single exposure. Six patients reached normal levels with a delay of 2-6 h, whereas 2 patients and the xeroderma pigmentosum patient did not. Although the kinetic curves in controls and patients had a similar form, those for 8 and 16 J/m2 in patients were shifted so that they corresponded to that of 2 J/m2 in controls. Additionally the ability to repair repeated damage (cells irradiated twice or three times at 2-hour intervals with doses of 2 or 8 J/m2) was investigated in 6 patients and in 7 controls. The incorporation values showed significant differences between patients and controls at each dose and time point. Cancer patients tend to repair repeated damage less efficiently than controls. Using these parameters subtle differences between the repair ability of individuals might be identified. Because of the known connection between reduced DNA repair and carcinogenesis, this might help to distinguish cancer-prone individuals.

Anemia, Aplastic↗