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J Stankova

Publications and source records attributed to J Stankova.

32 records · Page 2Linked to original sources
PubMed1994

Characteristics of virulence signs of enteroinvasive Escherichia coli (EIEC) isolated in CSFR and Bulgaria in 1988-1990.

During 1988-1990 a total of 345 virulent and avirulent strains of enteroinvasive E. coli (EIEC) were isolated from human faeces in microbiological laboratories in Prague and Sofia. This group of strains belonged to a total of 11 serotypes. The most frequently encountered serotypes in both laboratories were: 0124, 0164 and 028ac. From patients 205 strains were obtained and from healthy subjects 140 strains of EIEC. In all strains the following signs of virulence were investigated: biochemical properties, serotypes, Serény's test, test on HeLa cells, sensitivity to colicine JS and the plasmid profile. The presence of high molecular plasmid 140 MDa correlated closely with positive results of the above mentioned tests. Plasmid 140 MDa was more frequently present in E. coli strains isolated from faeces of patients (in 76.09%) than in strains from healthy subjects (in 23%). The strains circulating in the healthy population were in the majority avirulent.

Animals↗
PubMed1993

Transforming growth factor-beta up-regulates the gene expression of the human platelet-activating factor receptor in monocytic and B cell lines.

Platelet-activating factor is a potent phospholipid mediator which produces a wide range of biological responses by binding to a specific, high-affinity receptor on the target cell surface. Platelet-activating factor has been shown to have a very important pro-inflammatory role while the cytokine transforming growth factor-beta, also known for its diverse and potent effects, can act as both a pro- and anti-inflammatory agent. To ascertain whether transforming growth factor-beta could modulate the expression of the human platelet-activating factor receptor, different cell types were stimulated with this cytokine and the effect determined by Northern blot analysis and Ca2+ influx studies. The results demonstrate that transforming growth factor-beta induces the expression of the platelet-activating factor receptor in monocytic and B cell lines and indicate that transforming growth factor-beta could play a role in the modulation of the inflammatory response by up-regulating the expression of the platelet-activating factor receptor.

Azepines↗
PubMed1993

PAF activation of a voltage-gated R-type Ca2+ channel in human and canine aortic endothelial cells.

By the use of fura-2 and digital imaging techniques, [K]o depolarization or PAF (10(-9) M) were shown to induce a sustained increase of [Ca]i in human or canine single aortic vascular endothelial cells (VEC) that was insensitive to nifedipine but sensitive to (-)-PN200-110 or to lowering of [Ca]o. The PAF-induced effect on [Ca]i was blocked by the PAF receptor antagonist, WEB2170. Our results suggest that [K]o depolarization and PAF increase [Ca]i via the activation of R-type Ca2+ channels.

Azepines↗
PubMed1992

Differentiation-dependent modulation of TNF production by PAF in human HL-60 myeloid leukemia cells.

Platelet-activating factor (PAF) can augment tumor necrosis factor (TNF) production by human monocytes in a bimodal manner, with two peaks of activation at picomolar and micromolar concentrations. These peaks are partially associated with monocyte subsets presenting different characteristics in terms of size, density, phenotypic markers, and [Ca2+]i mobilization responses. In the present study, we used the human promyelocytic leukemia cell line HL-60, at various times during differentiation with 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] toward the monocyte lineage, in order to study the relation of cell differentiation to responsiveness to PAF in terms of cytokine production. TNF production was induced by pretreatment with interferon gamma for 24 h and treatment with muramyl dipeptide. Although detectable TNF was produced by 4 day-differentiated cells, no effect was seen with PAF (10(-16)-10(-6) M) at this or earlier stages. In contrast, 5 day-differentiated cells had a comparable baseline production of TNF but responded with a 2.5-fold increase to PAF with a single peak, maximal at 10(-8) M. Moreover, 6 day- or 7 day-differentiated HL-60 cells showed a further increase in TNF production in response to PAF, and the response was bimodal, similar to that of the less dense subset of monocytes, with peaks at 10(-14) and 10(-7) M PAF. In parallel, undifferentiated HL-60 failed to respond to PAF in terms of [Ca2+]i mobilization. The earliest responsiveness to PAF (10(-7) M) was observed by 4 days of treatment with 1,25(OH)2D3, and by day 7 the response to PAF became bimodal (10(-14) and 10(-7) M). These results indicate that myeloid cells acquire, during maturation toward the monocyte lineage, a progressive responsiveness to PAF in terms of [Ca2+]i mobilization and enhanced cytokine production, and they suggest that the heterogeneity in responses to PAF observed in normal monocytes may be related to their stage of differentiation or maturation.

Calcitriol↗
PubMed1991

Leukotriene B4 up-regulates IL-6 rather than IL-1 synthesis in human monocytes.

Leukotriene B4 (LTB4) preferentially induced IL-6 mRNA accumulation and IL-6 protein release as assessed by ELISA and the B9 cell bioassay. In contrast, minimal IL-1 mRNA or protein was induced by LTB4 either in the absence or presence of muramyl dipeptide. Supernatants of LTB4-treated monocytes consistently showed enhanced thymocyte costimulatory activity and this was abrogated by 75-80% by anti-IL-1 antibody. Baseline production of IL-1 appeared however to be sufficient for a synergistic stimulation of thymocytes in the presence of IL-6. Our results now help clarify that LTB4 stimulated preferentially IL-6 production and that the observed LTB4-induced augmentation in thymocyte responses to monocyte supernatants is due to augmented IL-6 contents in the presence of baseline minimal IL-1 production.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1989

A functional and phenotypic comparison of murine natural killer (NK) cells and lymphokine-activated killer (LAK) cells.

Lymphokine-activated killer (LAK) cells have been defined as interleukin 2 (IL-2)-activated cytolytic effector cells exhibiting non-MHC restricted killing against a wide range of NK-sensitive and NK-resistant tumor cells. There has been considerable debate as to whether LAK cells are derived from NK cells or from a unique precursor population. In the present study, we compare LAK cells derived from T-cell-depleted nylon-wool-non-adherent spleen cells with endogenous NK cells and NK cells activated with the interferon inducer polyl.C., in terms of their phenotype and functional characteristics. The predominant splenic LAK precursor in the mouse was found to be a nylon-wool-non-adherent, thy1-, MICG-, J11d.2-, asialo GM1+ cell. This phenotype is shared by endogenous NK cells. A significant number of activated NK cells express macromolecular insoluble cold globulin (MICG) in addition to asialo GM1. Neither endogenous nor activated NK cells express a heat-stable antigen found on bone-marrow cells, immature T cells, and most B cells and defined by monoclonal antibody (MAb)J11d.2. However, J11d.2 is expressed on some LAK precursor and effector cells. The asialo GM1 marker is common to all LAK effector cells, while many are also thy1+, and/or MICG+. LAK effector cells are therefore a heterogeneous population sharing some phenotypic characteristics in common with NK cells. In addition, there is a positive correlation between LAK and NK activity in "high NK" and "low NK" mouse strains, suggesting that NK cells and LAK cells share a common lineage. Monoclonal antibodies to the alpha and beta chains of LFA-I inhibit LAK and activated NK function, while endogenous NK and CTL killing is affected only by anti-alpha chain antibodies. LAK cells, like MHC-restricted and non-restricted CTL clones, express mRNA transcripts of the C11 serine protease gene. We conclude that LAK cells share several features in common with cells of the NK lineage and may therefore represent NK cells in a unique state of activation. LAK cells appear to employ cytolytic machinery common to other lytic cell types.

Animals↗
PubMed1989

Amelioration of experimental lung metastasis in mice by therapy with anti-CD3 monoclonal antibodies.

Binding of CD3-specific antibodies to the TcR-CD3 complex results in T cell activation without the need for occupation of the T cell receptor (TcR) by its ligand. Murine T cells activated in this manner will kill a broad range of tumor targets but not normal lymphoblasts. We report here that non-specific cytolytic activity can be induced in vivo by a single i.p. injection of nonlytic 145-2C11 anti-CD3 monoclonal antibody. At least three populations of effector cells are activated in these mice. These are non-MHC (major histocompatibility complex) restricted cytotoxic T lymphocytes, activated natural killer cells, and lymphokine-activated killer cells. Anti-CD3 treatment is effective in significantly reducing the number of lung tumor nodules which form in mice inoculated with oncogenic ras-transfected syngeneic 10T1/2 fibroblasts. Anti-CD3-activated killer cells may, therefore, find a future role in cancer immunotherapy.

Animals↗
PubMed1989

Decreased p21 levels in anti-sense ras transfectants augments NK sensitivity.

We have shown that the oncogenic EJ-ras gene, under the control of a metallothionein-I (Mt) promoter, can be induced to cause an increased susceptibility of transfected 10T1/2 fibroblasts to cytolysis mediated by natural killer (NK) cells. This effect may be specific to the ras gene family, since other oncogenes that we have tested here (src) and elsewhere (myc) do not show this effect. We have now examined the effect of modulating the level of p21 in both a positive or negative manner. The level of p21 ras was decreased by two independent mechanisms. First Zn2+ was removed from Mt-EJ-ras transformed cells. In the second approach we transfected 10T1/2 cells with a Mt-anti-sense c-H-ras construct which reduced p21 expression, slowed the growth rate and altered the morphology of 10T1/2 cells when induced with Zn. Surprisingly, the decrease in p21 ras levels by both approaches caused a marked increase in NK susceptibility (NKS) which was equivalent to that observed when the p21 ras levels were increased either by inducing EJ-ras or removing Zn2+ from Mt-anti-sense c-H-ras containing cells. The kinetics of induction of NK sensitivity due to decreasing normal p21 ras levels was identical to that observed for increasing mutated p21 ras levels. Peak enhancement of NKS was observed 24 hr after ras perturbation. These results suggest that either a positive or negative change in the steady-state level of p21 ras is sufficient to induce NK sensitivity, and NK sensitivity is not inextricably linked to cellular transformation by the ras gene.

Animals↗
PubMed1984

alpha-Fucose inhibits human mixed-lymphocyte culture reactions and subsequent suppressor cell generation.

Carbohydrate moieties serve as important sites of interaction for many lymphocyte activities. The potential role of saccharides in the cellular interactions involved in mitogen-, antigen-, and alloantigen-induced proliferation was investigated. Eight different monosaccharides were tested for their inhibitory potential when added to uni- and bidirectional mixed-lymphocyte culture (MLC) reaction as well as to mitogen (Con A, PHA, PWM)-stimulated cultures. Only alpha-L-fucose blocked the MLC reaction in a dose-dependent fashion while having no effect on mitogen stimulation, although antigen-specific stimulation was also blocked by fucose. Similarly alpha-L-fucose specifically inhibited the MLC-induced generation of suppressor cells. Pretreatment of the MLC responder cells with fucose dehydrogenase abolished the MLC reaction while stimulator cell pretreatment had no effect, suggesting that the recognition site of the former contained alpha-L-fucose. The generation and the effector phase of Con A-induced suppressor cells was not affected by fucose, indicating that different receptors are involved in the latter. Apparent competitive inhibition by exogenous fucose of the cell-cell interaction required for the MLC reaction suggested that this monosaccharide is an essential constituent of allogeneic recognition sites.

Antigens, Viral↗
PubMed1984

Suppressor cells in the human maternal-fetal relationship.

The mixed lymphocyte culture (MLC) of maternal and newborn (cord) cells is significantly weaker than that of father-newborn and control-newborn cultures. This hyporeactivity was found not to be due to an impaired function or tolerance of either the maternal or neonatal cells. We investigated the possibility that a specific, in vivo-induced suppressor cell was active in the diminished maternal-newborn reaction. Suppressor cells were found to be active in both the stimulating and responding populations in the unidirectional MLC. The removal of TG cells from the responding (maternal or newborn) population resulted in an increase of reactivity specific for the corresponding stimulating population (newborn or maternal). The suppressor activity within the stimulating population was carried out by a radiosensitive cell, which did not require proliferation to exert its effect. We suggest that the observed hyporeactivity of maternal-newborn mixed lymphocyte cultures is due to the modulation of the reaction by specific, in vivo-induced suppressor cells.

Adult↗
PubMed1979

Glucose tolerance and erythrocyte insulin receptors in Friedreich's ataxia.

Detailed in vivo and in vitro studies of glucose and insulin metabolism in Friedreich's ataxia patients and unaffected family members have further defined the extent of the abnormalities in carbohydrate metabolism. The high incidence of glucose intolerance and a hyperinsulinemic response to a glucose challenge in a high percentage of Friedreich's ataxia patients has been confirmed. An increased incidence of glucose intolerance among heterozygotes is suggested, while the siblings show a more normal distribution of diabetes and a nearly normal insulin response to the glucose tolerance test. Human growth hormone patterns are normal for all groups. Preliminary studies of insulin binding to erythrocytes suggest a difference in the binding characteristics among diabetic Friedreich's ataxia patients, while the binding in the non-diabetic Friedreich's ataxia group is similar to that of non-diabetic controls. Results from a small group of non-diabetic siblings suggest a normal insulin binding, while a tendency toward increased binding at low insulin concentrations among diabetic family members is noted.

Diabetes Complications↗
PubMedDate not supplied

The in vivo clearance of Ha-ras transformants by natural killer cells.

The experiments in this study were designed to test the hypothesis that natural killer (NK) cells play a role in host surveillance against early neoplastic changes in the malignant process. C3H 10T1/2 mouse fibroblasts were transfected with a pSV2-neo plasmid vector which contains EJ, the mutated c-Ha-ras, regulated by its own promoter. Control cells were transfected with pSV2-neo alone and did not contain the ras gene. Oncogene-transfected cells were compared with control cells for lung colony formation following tail vein injection into C3H mice. Intravenous injection of ras-transfected 10T1/2 cells induced marked lung colony formation in vivo, whereas C3H 10T1/2 parental lines or 10T1/2 cells transfected with pSV2-neo alone induced no lung colonies in C3H mice. The colonising potential of ras transfectants could be decreased by augmentation of NK activity by injection of polyinosinic cytidylic acid and increased by depletion of NK effectors with anti-asialo GM1. Experiments with beige mice demonstrated that the mortality of syngeneic, NK-deficient C3H-bg/bg mice injected with ras tranfectants was significantly greater than similarly treated NK-normal C3H(-)+/bg littermate controls. The results support the view that NK cells are capable in vivo of recognizing early defined stages in the neoplastic process initiated by oncogenes.

Animals↗
PubMedDate not supplied

Differential regulation of cytokine and cytokine receptor genes by PAF, LTB4 and PGE2.

Immune and inflammatory responses involve a whole array of cells and cell products which interact and mutually regulate each other. Many of these interactions are mediated by cytokines acting through specific receptors. Furthermore, lipid mediators such as PAF and the arachidonic acid metabolites LTB4 and PGE2 are known to affect several of the mechanisms involved in the regulation of the immune and inflammatory responses. In this paper, we review recent data from our laboratory illustrating the differential regulation of IL-6 and TNF alpha production and IL-2 receptor alpha and beta expression by these lipid mediators. We show that the regulation of these genes is both transcriptional and post-transcriptional, and that LT and PG can also be involved as second messengers in these regulatory processes.

Animals↗