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Biomedical subjects

Z Kolar

Publications and source records attributed to Z Kolar.

At least 19 recordsLinked to original sources
PubMed2005

Peroxisome proliferator-activated receptors (PPAR) agonists affect cell viability, apoptosis and expression of cell cycle related proteins in cell lines of glial brain tumors.

The nuclear receptors PPARs (peroxisome proliferator-activated receptors) are transcription factors activated by specific ligands. PPARs play an important role in carcinogenesis, inflammation, atherosclerosis, lipid metabolism and diabetes. There is evidence that activation of PPARs by specific ligands is able to suppress the growth of different types of human cancer by mechanisms including the growth arrest, apoptosis and induction of differentiation, although the detailed signalling pathways have not been completely elucidated to date. The aim of our study was to determine whether synthetic ligands of PPARalpha and PPARgamma could affect the viability, proliferation, differentiation, apoptosis and expression of some cell cycle related proteins in glial tumor cell lines. The study was performed on human glioblastoma cell lines U-87 MG, T98G, A172 and U-118 MG. Cell lines were treated by ligands of PPARalpha (bezafibrate, gemfibrozil) and PPARgamma (ciglitazone). MTT, flow cytometry, TUNEL assay and immunoblotting were used for detection of changes in cell viability, proliferation, differentiation and apoptosis. Bezafibrate, ciglitazone and gemfibrozil inhibited viability of glioblastoma cell lines. The synthetic ligands significantly reduced or induced the expression of cyclins, p27Kip1, p21Waf1/Cip1, MDM-2, Bcl-2, Bax, PARP, Caspase 3, androgen receptors, etc. and did not affect the expression of the differentiation marker GFAP. Flow cytometry confirmed arrest of the cell cycle although the detection of apoptosis was controversial. Apart from hypolipidemic and hypoglycaemic effects, PPAR ligands may also have significant cytostatic effects of potential use in anticancer treatment.

Apoptosis↗
PubMed2005

Mammary gland development and cancer.

The mammary gland is a complex organ that begins development early in gestation and constantly changes in size, shape and function from the time of puberty to menopause. The earliest stages of embryogenesis appear to be independent of steroid hormones, whereas after the 15th week breast structure is largely influenced by a variety of hormones. In most females, further breast development begins at puberty under the influence of cyclical estrogen and progesterone secretion. This process may continue into the 20s and it is enhanced by pregnancy. Growth and transcription factors contribute to the reciprocal stromal-epithelial interactions in growth, development and tumorogenesis of the mammary gland. From the embryological point of view the morphology of both mammary ductal and lobular cells results from the same developmental process. Numerous data suggest the existence of self-renewing, pluripotent mammary stem cells but their molecular characteristics and differentiation pathways are unknown. The extensive research currently being done in molecular biology and pathology, cancer genomics and proteomics will hopefully contribute to further elucidation of all the genetic and environmental factors involved in the development, differentiation, and involution of the mammary gland and this may give insight into the etiopathogenesis, early detection, treatment, and potential prevention of breast cancer.

Animals↗
PubMed2002

Reactivity and isotype profiling of monoclonal antibodies using multiple antigenic peptides.

The characterisation of monoclonal antibodies (MAbs) is essential for the development of assay systems particularly where antigens have been developed using synthetic peptides. Indeed some peptide-carrier conjugates fail to induce immune responses and may not generate antibodies that bind to native protein. As an alternative to peptide-carrier conjugates, multiple antigenic peptides (MAPs) have been used for immunization strategies, but with little regard to the characteristics of the MAbs produced. In this study, we used 3 MAPs of Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) to immunise BALB/c mice. Overall, the polyclonal antibody responses from tail bleeds showed that MAPs evoked B-cell responses. However, on screening 144 hybridomas, 24 MAb supernatants exhibited weak to moderate reactivity in enzyme-linked immunosorbant assay (ELISA) and against cell cytospin preparations (B95.8 and AG876 LCL), respectively. Isotype profiling of hybridoma supernatants also showed that 11 out of 24 were IgM. Further characterization of 6 MAbs in Western blotting showed reactivity to recombinant LMP1 and only one MAb (B28D) showed weak reactivity to the malignant cells (Hodgkin/Reed-Sternberg; HRS cells) of an EBV+ Hodgkin's lymphoma using paraffin-embedded tissue. It is probable that these MAPs failed to augment T-cell help and contributed to the production of low affinity (IgM) antibodies. These observations may be of importance to future immunization strategies, where MAPs are used in the production of monoclonal reagents.

Animals↗
PubMed2000

Apoptosis of malignant cells in Hodgkin's disease is related to expression of the cdk inhibitor p27KIP1.

Previous results from B-cell chronic lymphocytic leukaemia suggest that expression of p27KIP1 might be important in protection from apoptosis. Given the relevance of apoptosis to the pathogenesis of Hodgkin's disease (HD), it was decided to examine the expression of p27KIP1 in relation to apoptosis in these lesions. Paraffin-wax sections from a total of 65 histologically confirmed HD tumours were used to derive apoptotic index (AI) and DNA fragmentation index (DFI) scores, which were compared with the expression of various cell-cycle-regulating proteins, including p27KIP1 (p27), p21WAF1/CIP1 (p21) and cyclin D1, and with Epstein-Barr virus (EBV) status. The DFI was measured by TdT-mediated dUTP-FITC nick end-labelling (TUNEL), and the AI by conventional morphology. Cells showing the typical morphology of apoptosis, together with those resembling so-called 'mummified' Hodgkin/Reed-Sternberg (HRS) cells, were included in AI measurements. Increasing numbers of p27-positive HRS cells were associated with lower levels of apoptosis in these cells, as indicated by significantly lower AI and DFI scores. There was a trend towards poorer survival in those patients with the highest numbers of p27-positive HRS cells and with lower AI and DFI scores, but these differences were not statistically significant. p21-positive HRS cells were significantly more frequent in those cases with lower AI scores. A similar trend was observed for p21 and DFI, although this relationship was not statistically significant. There was also a trend towards higher levels of cyclin D1 protein in HD cases with high AI and DFI values. A tendency for increasing numbers of p27-positive and p21-positive HRS cells in EBV-positive cases was noted, but this relationship was not statistically significant. EBV status did not correlate with either AI or DFI scores. The results of this study suggest that p27, and possibly also p21, may be involved in protection from apoptosis in HD.

Apoptosis↗
PubMed2000

Expression of the matrix metalloproteinase 9 in Hodgkin's disease is independent of EBV status.

BACKGROUND: In vitro the Epstein-Barr virus (EBV) encoded latent membrane protein 1 (LMP-1) has been shown to upregulate expression of matrix metalloproteinase 9 (MMP-9), a member of a family of zinc dependent endopeptidases that is believed to facilitate tumour invasion and metastasis by degradation of the extracellular matrix. AIM: To test whether the expression of MMP-9 in Hodgkin's disease correlates with EBV status and survival and to investigate whether LMP-1 expression affects MMP-9 concentrations in the Hodgkin's disease cell line, L428. METHODS: MMP-9 expression was measured by means of immunohistochemistry in a series of Hodgkin's disease tumours and this expression was correlated with EBV status and survival. The influence of LMP-1 on MMP-9 expression was also investigated in the Hodgkin's disease cell line, L428. RESULTS: MMP-9 expression was demonstrated in the malignant Hodgkin and Reed-Sternberg cells of all (n = 86) formalin fixed, paraffin wax embedded Hodgkin's disease tumours examined. Although the intensity of MMP-9 immunostaining varied between cases, there was no correlation between MMP-9 expression and EBV status or survival. MMP-9 expression was also detected in a variety of non-malignant cells, including fibroblasts. MMP-9 was detected by zymography in the L428 and KMH2 Hodgkin's disease cell lines, whereas low or undetectable amounts of MMP-9 were found in the L591 Hodgkin's disease cell line. Induction of LMP-1 expression in the Hodgkin's disease cell line L428 did not result in a detectable increase in the values of MMP-9 as measured by zymography. CONCLUSIONS: These results demonstrate that MMP-9 is consistently expressed by the Hodgkin and Reed-Sternberg cells of Hodgkin's disease tumours and by the Hodgkin's disease cell lines, L428 and KMH2. However, this expression does not appear to be related either to LMP-1 values or to survival.

Biomarkers, Tumor↗
PubMed1997

Mg2+ transport in plasma membrane vesicles of renal epithelium of the Mozambique tilapia (Oreochromis mossambicus)

To elucidate the mechanisms involved in Mg2+ transport at the apical and basolateral poles of the renal tubular epithelium, apical and basolateral plasma membrane vesicle preparations were derived from kidney tissue of freshwater- and seawater-adapted Mozambique tilapia Oreochromis mossambicus. Brush-border preparations were enriched 15.8-fold in alkaline phosphatase activity and consisted almost exclusively of right-side-out membrane vesicles. Basolateral membrane preparations were enriched 7.5-fold in Na+/K+-ATPase activity and contained resealed vesicles and leaky membrane fragments. Mg2+ association with brush-border and basolateral plasma membranes, traced using radioactive 27Mg, occurred in an osmotically active space. In all instances, Mg2+ binding to the vesicular membrane was low compared with the vesicular uptake. Mg2+ equilibration across the vesicular membrane of brush-border preparations was rapid and sensitive to the presence of extravesicular Ca2+, suggesting that the apical membrane of the renal epithelium contains a transport pathway for divalent cations. Application of various ionic gradients did not affect vesicular Mg2+ transport in apical and basolateral membrane preparations, suggesting the presence of an ion-coupled transport mechanism. ATP or ATP--S did not stimulate Mg2+ fluxes, indicating that Mg2+ transport does not proceed via an ATP-driven or activated transporter. In these aspects, vesicular Mg2+ transport was similar in seawater and freshwater preparations. These results suggest that the apical membrane of renal epithelial cells lacks an active secretory Mg2+ transport mechanism. We propose that the Mg2+ conductivity of the apical membrane reflects a route for downhill Mg2+ entry and is involved in renal Mg2+ reabsorption.

Journal Article↗
PubMed1995

Calcium pump activities in the kidneys of Oreochromis mossambicus

The mechanism that underlies transcellular Ca2+ reabsorption in the kidney of the euryhaline teleost Oreochromis mossambicus was studied. Preparations of membrane vesicles made from the kidneys of freshwater- and seawater-adapted fish were more than sevenfold enriched in the basolateral plasma membrane marker Na+/K+-ATPase. Significant recovery of NADH­ cytochrome c reductase enzyme activity and of oxalate-stimulated Ca2+ pump activities in the membrane preparations indicated that the membrane fraction was of endoplasmic reticular origin. Indeed, thapsigargin specifically inhibited Ca2+ pump activity that could be attributed to oxalate-permeable endoplasmic reticular fragments. Kinetic analysis of thapsigargin-insensitive Ca2+ pump activity indicated the existence of a homogeneous, high-affinity, ATP-driven Ca2+ pump. No Na+-driven Ca2+ transport mechanism could be demonstrated. Plasma membrane Ca2+ pump activity was 56 % lower in preparations from seawater-adapted fish than in preparations from freshwater-adapted fish, suggesting a physiological role for this Ca2+ pump activity in renal Ca2+ handling by euryhaline species, with an involvement in the regulation of Ca2+ reabsorption.

Journal Article↗
PubMed1990

Prolactin cell activity and sodium balance in the acid-tolerant mudminnow Umbra pygmaea in acid and neutral water.

In East-American mudminnows, obtained from lakes and bogs of different water pH levels, prolactin cell size and ultrastructure reflect higher secretory activity in neutral water than in water of pH 3.5-6.5. This contrasts with observations on other species in which prolactin cell activity is higher at low water pH. Laboratory experiments involving acute exposure of mudminnows from pH 5.5 for 48 hr to different pH levels showed that prolactin secretion increased in water below pH 3 and above pH 6.5, which could be correlated with losses of blood electrolytes. No osmoregulatory stress was noticeable in the pH range of 3.5 to 5.5. Acclimation of fish for 5 to 6 months to either pH 4.5 or 7.2 confirmed that prolactin cell activity, as estimated with ultrastructural morphometry, was significantly higher in water of neutral pH than of pH 4.5. The growth rate was significantly higher at the lower pH. Determination of whole body sodium fluxes, with 24Na as a tracer, showed that both groups had a positive sodium balance. However, total body Na+ influx as well as efflux values were slightly but significantly reduced at pH 7.0 when compared to pH 4.5. The reduction of Na+ efflux at pH 7.0 is in line with increased secretion of prolactin since this hormone is known to limit the branchial permeability to water and ions, including Na+. The results show that the mudminnow is extremely acid tolerant, having an optimum water pH range of about 3.5 to 6.0, which is consistent with ecological observations. Prolactin secretion is at a minimum in this range. Exposure to neutral water represents osmoregulatory stress for the mudminnow, in contrast to all other teleost species examined so far.

Animals↗
PubMed1989

Prolactin cell activity and sodium fluxes in tilapia (Oreochromis mossambicus) after long-term acclimation to acid water.

In tilapia exposed for 3 months to water of pH 4.5, prolactin cell activity, as estimated by ultrastructural morphometry and determination of prolactin synthesis in vitro, was significantly higher than in controls from neutral water. Sodium influx from the water was 50% lower than in the controls, indicating impaired branchial sodium uptake mechanisms. In contrast to predictions based on the results of short-term exposure to acid water--which is known to induce an increase of sodium efflux--the sodium efflux rate was reduced to 70% of the control value. It is concluded that tilapia are able to acclimate to acid water by successful control--probably via prolactin--of diffusional sodium losses across the integument, in particular the gill surface. This compensates for the impaired sodium uptake, and enables the fish to reestablish a positive sodium balance in acid water.

Acclimatization↗
PubMed1989

Lectin histochemistry of colonic adenomas.

34 adenomas of the colon and adjacent flat mucosa were reexamined by morphological, histochemical and immunohistochemical means. Adenomas were grouped according to the degree of epithelial cell atypia: group 1 (dysplastic adenomas) showing mild and moderate dysplasia and group 2 (cancerous adenoma) with severe dysplasia and carcinoma. Morphological and secretive changes (hyperplasia with hypersialomucin secretion), considered typical of 'transitional mucosa', were constantly found in the adjacent and stalk mucosa. A panel of six lectins were tested using PAP and ABC system methods to compare amount and cytoplasmic localization of labelling sites with the morphological changes such as hyperplasia, dysplasia and carcinoma. All the tested lectins were reactive in up to 90% of adenomas as well as in adjacent mucosa. Positivity was unrelated to the severity of dysplasia and no preferential localization of labelled sites was shown in the adenoma groups. However, cytoplasmic distribution of reactivity was quite different in hyperplastic epithelium compared to dysplastic ones.

Colonic Polyps↗
PubMed1986

Effects of ovine prolactin on calcium uptake and distribution in Oreochromis mossambicus.

Ovine prolactin stimulated the net uptake rate of Ca2+ from the water by 96%, produced frank hypercalcemia, and increased total bone calcium content in fed rapidly growing freshwater male tilapia, Oreochromis mossambicus. It did not, however, alter the size of the readily exchangeable bone calcium pool. The increase in calcium accumulation resulted from an increase in whole-body Ca2+ influx and a decrease in Ca2+ efflux. It is concluded that prolactin exerts an important control over Ca2+ exchange between the fish and its environment and that through its hypercalcemic action prolactin indirectly facilitates bone mineralization.

Animals↗
PubMed1985

Whole-body calcium flux rates in cichlid teleost fish Oreochromis mossambicus adapted to freshwater.

Radiotracer techniques were used to measure influx and efflux rates of Ca2+ in freshwater-adapted Oreochromis mossambicus. The influx rate of Ca2+ is related to body weight (W) as Fin = 50W0.805 nmol Ca2+/h. For a 20-g fish the calculated influx rate was 558 nmol Ca2+/h, and this was attributed largely to extraintestinal uptake since the drinking rate was estimated to be only 28 microliter water/h, which corresponds to an intake of 22.4 nmol Ca2+/h. The Ca2+ efflux rate was calculated using the initial rate of appearance of radiotracer in the ambient water and the specific activity of plasma Ca2+. Tracer efflux rates were constant over 6-8 h, which indicated that there was no substantial loss of tracer in either the urine or the feces because this would have resulted in random bursts of tracer loss. Efflux rates then primarily represent integumentary and presumably branchial efflux rates. The efflux rate of Ca2+ is related to body weight as Fout = 30W0.563 nmol Ca2+/h, which means an efflux rate of 162 nmol Ca2+/h for a 20-g fish. The net whole-body Ca2+ influx, calculated as Fnet = Fin - Fout, was 396 nmol/h for a 20-g fish, which proves that the ambient water is an important source of Ca2+.

Adaptation, Physiological↗
PubMed1983

Grafting of a synthetic heparinoid polyelectrolyte onto silicone rubber.

Using a [3H]-labelled polyelectrolyte as a tracer, the 60Co grafting of a synthetic heparinoid polyelectrolyte onto silicone rubber was studied. The polyelectrolyte was labelled by the coupling of a radioactive amine to carboxylate groups of the polyelectrolyte. The amount of grafted polyelectrolyte was found to be dependent on the radiation dose.

Adsorption↗
PubMed1978

Diffusion of fluoride ions in dental enamel at pH 7.

The penetration and uptake of both radioactive (18F) and stable fluoride (19F) in bovine enamel were investigated. Buffered pH 7 NaF solutions were employed. Penetration profiles of both 18F and 19F in enamel were determined by using a sectioning technique. 18F and 19F concentrations decreased exponentially with increasing penetration distance. The uptake of 18F in enamel can be described by a power function of the immersion time, with an average power of 0.76. The results agree reasonably with our previously published theoretical model for the diffusion in enamel, based on simultaneous diffusion in enamel pores and in the hydroxyapatite crystallites. The diffusion coefficients of fluoride ions in enamel obtained from the application of the model to the results presented here, were: D = 0.9 x 10(-17) cm2/s in the crystallites and D' = 3.3 x 10(-10) cm2/s in the enamel pores. An average penetration depth of fluoride ions at pH 7.0 of 8 micron in 4 hours has been calculated.

Animals↗