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Biomedical subjects

R Larsson

Publications and source records attributed to R Larsson.

269 records · Page 15Linked to original sources
PubMed1976

Thromboresistance and stability of a heparinized polymer.

Untreated shunts and shunts heparinized according to a modification of the method of Eriksson et coll. were inserted between the femoral artery and vein in mongrels. Scanning electron microscopy of pieces excised at different time periods of exposure to blood was performed. The heparinized surface had excellent thromboresistant properties with no thrombus formation after 4 hours, while the untreated shunts were covered with platelets already within 20 min. The leakage of heparin in vitro was less than 3 per cent of the total wall-bonded heparin during 90 min.

Animals↗
PubMedDate not supplied

Adenosine 5'-diphosphate-induced platelet aggregation in uremia shows resistance to inhibition by the novel nitric oxide donor GEA 3175 but not by S-nitroso-N-acetylpenicillamine.

Both bleeding and thrombosis are complications of uremia in patients on regular hemodialysis. An excessive endogenous formation of the vasodilator and platelet inhibitor nitric oxide (NO) has been proposed to contribute to the bleeding defect. Since exposure to pharmacological donors of NO, nitrovasodilators, can cause tolerance to NO, we investigated whether platelets from uremic patients on regular hemodialysis are influenced differently by NO donors than platelets from healthy subjects. A frequently used S-nitrosothiol, S-nitroso-N-acetylpenicillamine (SNAP), was compared to a recently synthezised mesoionic oxatriazole derivate, GEA 3175, regarding its capacity to inhibit adenosine 5'-diphosphate (ADP)-induced platelet aggregation in vitro. The final products of NO production, nitrite + nitrate, were found to be significantly increased in uremic patients. The capacity to inhibit platelet aggregation by SNAP was only slightly different between the groups. However, GEA 3175 showed a significantly marked and reduced capacity to inhibit aggregation of uremic platelets compared to controls. Interactions of erythropoietin (EPO) with NO have earlier been reported. Addition of EPO to platelets from healthy donors in vitro did not significantly influence the NO donor capacity to inhibit platelet aggregation, but showed a tendency to enhance the effect of SNAP while the effect of GEA 3175 was inhibited. These results suggest compound-specific resistance to NO donors in uremic platelet activation.

Adenosine Diphosphate↗
PubMedDate not supplied

Steady-state kinetics and dosage requirements of cimetidine in renal failure.

25 patients with different degrees of chronic stable renal failure received oral treatment with cimetidine over 6 days and a final dose in the morning of day 7. The doses of cimetidine were reduced according to the degree of renal failure. Plasma concentrations of cimetidine were determined before the morning dose on days 2,3,6 and before the final morning dose and during the day on day 7. 24-hour excretions of cimetidine were measured during the study and on day 7, 6 to 9 hours after the final morning dose. There were significant linear relationships between the values of creatinine clearance and plasma elimination rate constant of cimetidine (p less than 0.0025) and between the values of creatinine clearance and renal clearance of cimetidine (p less than 0.05). On the basis of the morning plasma concentrations before and the plasma concentration curve after the final morning dose on day 7 the following dose recommendations according to pretrial values of creatinine clearance are recommended for cimetidine treatment in renal failure: 5 to 15ml/min 200mg 2 or 3 times daily, 15 to 30ml/min 200mg 3 times daily and 30 to 75ml/min 200mg 4 times daily.

Adult↗
PubMedDate not supplied

Cyanoguanidine CHS 828 induces programmed cell death with apoptotic features in human breast cancer cells in vitro.

The cyanoguanidine CHS 828 was recently shown to possess potent anti-tumour effects both in vitro and in vivo. The exact mechanism of action of CHS 828 is not known, but recent results have indicated that induction of programmed cell death may be one mechanism by which CHS 828 exerts its anti-tumour effects. To investigate this aspect in more detail, we studied the effect of CHS 828 and the reference compound Taxol beta on programmed cell death in human breast cancer cells in vitro. Both compounds were found to induce DNA fragmentation in the cells. However, microscopic examination of the cells demonstrated that CHS 828 and Taxol triggered different types of cell death. In the CHS 828-treated cultures most cells were found to be Annexin-V positive, indicating that these cells were early apoptotic cells, while no morphological characteristics of classical apoptosis were seen. In contrast, the cells in the Taxol-treated cultures displayed morphological features characteristic of classical apoptotic cells, but no Annexin-V positive cells could be observed. These findings together with the previously reported potent effects of CHS 828 on tumour cells, makes CHS 828 a promising new agent for the treatment of cancer patients.

Annexin A5↗
PubMedDate not supplied

DNA-dependent protein kinase in leukaemia cells and correlation with drug sensitivity.

We investigated whether the levels of the DNA-dependent protein kinase (DNA-PK) activity and content correlate with drug sensitivity in different tumour materials and if this can be utilised in predicting treatment outcome. DNA-PK activity and expression were investigated in tumour cells from 8 patients with chronic lymphocytic leukaemia (CLL) and 18 patients with acute myeloid leukaemia (AML), using Western blot and DNA-PK kinase activity assay. Tumour cells from the patients were investigated for their drug sensitivity to topoisomerase II inhibitors (doxorubicin and etoposide), DNA reactive agents (melphalan, 4-hydroxycyclophosphamide and cisplatinum), an antimetabolite (cytosine arabinoside) and an antimicrotubule agent (vincristine) by fluorometric microculture cytotoxicity assay (FMCA). Within each group of leukaemia there was a large variation in both DNA-PK activity and DNA-PKcs expression, while the Ku subunits were expressed more homogeneously. In CLL cells, sensitivity to topoisomerase II inhibitors correlated with DNA-PKcs protein expression (r=0.7174, p=0.0452). In AML samples, sensitivity to DNA cross-linking alkylating agents correlated with Ku86 (r=-0.7512, p=0.0031) and Ku70 (r=-0.6134, p=0.0258) expression. Unexpectedly, DNA-PK activity was found to correlate with sensitivity to vincristine in both CLL (r=0.8557, p=0.0067) and AML (r=0.5480, p=0.0228) cells. The results indicate that DNA-PK is not only involved in the recognition of DNA double-strand breaks (DSB), but also other DNA lesions.

Acute Disease↗
PubMedDate not supplied

Combination of cyclosporin A and buthionine sulfoximine (BSO) as a pharmacological strategy for circumvention of multidrug resistance in small cell lung cancer cell lines selected for resistance to doxorubicin.

The small cell lung cancer (SCLC) cell lines U-1285 and U-1690 were adapted to growth in continuous presence of doxorubicin (Dox). The resulting cell lines U-1285R and U-1690R were investigated with respect to sensitivity to the glutathione (GSH) depleting agent buthionine sulfoximine (BSO) and the immunosuppressant cyclosporin A (CsA) as well as the Dox resistance modifying ability of these agents. The parental U-1285 cells were more sensitive to BSO compared to parental U-1690 and the multidrug resistant (MDR) sublines, whereas no difference in sensitivity to CsA was observed between parental and MDR lines. BSO (10 microM) or CsA (1 microgram/ml) alone were able to partially reverse Dox resistance in the MDR cell lines, CsA being only marginally active in U-1285R cells. However, the combination of these two drugs at the same concentrations completely reversed Dox resistance in the MDR U-1690R cells whereas the combination was less effective in the U-1285R cells. The results demonstrate that a combination of low concentrations of BSO and CsA, only partially active by themselves in modifying Dox resistance, may be used as a pharmacological strategy to increase Dox sensitivity in some MDR SCLC cells.

Antimetabolites↗
PubMedDate not supplied

Early ionic events associated with phorbol ester induced differentiation and inhibition of cell growth in hematopoietic tumor cell lines.

The effects of 12-O-tetradecanoylphorbol-13 acetate (TPA) on DNA synthesis, phenotypic expression, cytoplasmic Ca2+ (Ca2+i), intracellular pH (pHi) and membrane potential were studied in the monoblastic U-937 and the erythroleukemic K-562 cells. In both cell lines DNA synthesis was inhibited and in the U-937 cells this was accompanied by the appearance of macrophage differentiation markers. The erythroid characteristics of K-562 cells, on the other hand, were markedly suppressed. Intracellular pH (pHi) was increased by TPA treatment; however, while the alkalinization of K-562 cells was dependent on the presence of extracellular Na+, the response of U-937 cells was unaffected by the removal of this cation. In each cell type the protein kinase C (PKC) inhibitor H-7 largely attenuated the TPA induced increase of pHi. Moreover, the alpha-stereoisomer of TPA, which does not activate PKC, had no effects. TPA caused a dose-dependent decrease in Ca2+i which was more pronounced in U-937 cells. Measurements of membrane potential revealed a marked TPA depolarization of the K-562 cells, but no such effects were observed in the U-937 cell line. The depolarizing response of K-562 cells could be abolished by substituting extracellular Na+ with choline+, indicating the presence of a TPA sensitive Na+ permeability. The results show that the phorbol ester TPA, which inhibits proliferation and causes phenotypic modulation, also induced a number of early, apparently PKC dependent and cell type specific, changes of intracellular ion activities. The possible role of intracellular ion fluxes in the regulation of cell growth and differentiation is discussed.

Calcium↗
PubMedDate not supplied

A rapid fluorometric method for semiautomated determination of cytotoxicity and cellular proliferation of human tumor cell lines in microculture.

A fluorometric method for the determination of cellular growth and cytotoxicity of human tumor cell lines in 96-well microculture plates is described. The assay is based on the combined use of the DNA-binding dye Hoechst 33342 and the fluorogenic substrate fluorescein diacetate (FDA). Hoechst 33342 undergoes a dramatic enhancement of fluorescence when specifically intercalated with cellular DNA, whereas the FDA fluorescence is dependent on cellular hydrolysis of the non-fluorescent substrate into its fluorescent product. Fluorescence from both dyes was linearly related to the density of freshly seeded cells (6 x 10(3)-1 x 10(5)/well) and correlated well with physical cell count of cells under normal culture conditions as well as in response to the vinca alkaloid vincristine. However, the amount of FDA fluorescence produces and retained by the cultures was clearly dependent on the fraction of intact and viable cells, whereas the fluorescence reported by Hoechst 33342 was not. The assay was found to be simple, reliable and many samples could be analysed in a short period of time with minimal waste of cells and biological reagents. Apart from giving an estimate of cell density, the protocol described also provides a separate index of viability which in certain situations may be of importance for distinguishing between cytocidal and cytostatic drug actions. The method may be well suited for several applications, including the large scale screening for antitumor activity of compounds with potential cytocidal or cytostatic actions.

Adenocarcinoma↗
PubMedDate not supplied

Characterization of four doxorubicin adapted human breast cancer cell lines with respect to chemotherapeutic drug sensitivity, drug resistance associated membrane proteins and glutathione transferases.

Four human breast cancer cell lines with or without estrogen and progesterone receptors were adapted to growth in the continuous presence of doxorubicin (Dox) at 10 (Zr-75-1), 15 (HTB-122), or 50 (MDA-MB-231 and Hs578T) ng/ml. The sublines of Zr-75-1, MDA-MB-231 and Hs578T showed 5-10-fold Dox resistance and also cross-resistance to vincristine (VCR) and etoposide (VP16). The sublines of Zr-75-1, MDA-MB-231 and Hs578T showed 5-10-fold Dox resistance and also cross-resistance to vincristine (VCR) and etoposide (VP16). The sublines maintained or slightly increased their cis-platinum (CDDP) sensitivity. The sublines of HTB-122 showed resistance only to VP16 combined with a paradoxical increased sensitivity to VCR. The phenotypic alteration in the sublines with respect to Dox sensitivity was maintained for at least two months in the absence of Dox. The glutathione depletor buthionine sulfoximine (BSO) and the calcium channel blocker verapamil (Ver) increased the Dox sensitivity slightly only in the MDA-MB-231 and Hs578T sublines, respectively. Ver also tended to protect some of the sublines from CDDP. The sublines of Zr-75-1 and Hs578T showed increased expression of the 170-kDa permeability glycoprotein (P-gp), whereas expression of a 85-kDa membrane protein determined by the MRK20 antibody was increased in the sublines of Zr-75-1, and HTB-122. Class pi glutathione transferase (GST) levels varied greatly between the cell lines but increased during Dox selection only in the subline of Zr-75-1. Class mu GST was detectable in the MDA-MB-231, Hs578T and HTB-122 cell lines, whereas class alpha GST was detectable in these sublines but undetectable in their parental cell lines. The Zr-75-1 subline showed a 5-fold increase in the class alpha concentration. Except for a correlation between increased P-gp expression and resistance to Dox, VCR and VP16, no obvious correlations between receptor status, increased P-gp expression, membrane proteins, GST levels and acquired drug resistance were found. Thus, except for a possible role for P-gp in multidrug-resistance, these findings indicate a pronounced mechanistic heterogeneity responsible for cytotoxic drug sensitivity also in cells with a common histologic origin and exposed to the same drug.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMedDate not supplied

P-glycoprotein expression and activity of resistance modifying agents in primary cultures of human renal and adrenocortical carcinoma cells.

Tumor cells from patients with renal or adrenocortical carcinomas were tested in vitro for sensitivity to doxorubicin (Dox) and vincristine (Vcr), as well as for the modulation of this sensitivity by resistance modifiers and the immunohistochemical expression of the multidrug resistance associated P-glycoprotein (Pgp). Normal adrenocortical cells from one patient and Pgp-expressing cells of Dox-resistant myeloma RPMI 8226 sublines were included for comparison. The normal adrenocortical cells and cells from one adrenocortical carcinoma showed high Pgp expression, comparable to the most Dox-resistant myeloma cell line, whereas the other tumor samples showed variable but lower expression. The normal adrenocortical as well as the adrenocortical and renal tumor cells were highly resistant to Dox and Vcr. Whereas the cytotoxic effect of Dox was considerably increased by verapamil, cyclosporin A and its non-immunosuppressive analogue SDZ PSC 833 in the Pgp-expressing Dox-resistant sublines, comparatively small effects on the Dox and Vcr sensitivity were observed in the patient samples, irrespective of their Pgp expression. The results indicate that the Dox and Vcr resistance in human adrenocortical and renal carcinomas is mediated by mechanisms other than Pgp and that resistance modulating agents targeting Pgp may be much less efficient in the clinic than in Pgp-expressing cell lines, at least for the tumor types described in the present study.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMedDate not supplied

PDGF-BB, but not PDGF-AA, stimulates calcium mobilization, activation of calcium channels and cell proliferation in cultured rat mesangial cells.

The effects of different isoforms of platelet-derived growth factor (PDGF) on cellular growth and on cytoplasmic Ca2+ levels in mesangial cells using a microfluorometric system and the calcium indicator FURA-2 were investigated. A rapid increase of cytoplasmic calcium in response to PDGF-BB was found and in the presence of 1.25 mM extracellular calcium, the resting level of cytoplasmic calcium following the initial peak was significantly increased compared with a calcium-free medium, but was completely attenuated with the calcium channel blocker verapamil (50 microM). PDGF-AA did not cause any increase in cytoplasmic calcium. In growth arrested MC PDGF-BB, but not PDGF-AA, also enhanced cell growth. It is concluded that cultured rat mesangial cells react to PDGF-BB but not to PDGF-AA with a rapid mobilization of intracellular calcium followed by subsequent activation of calcium channels and a stimulation of cell growth. A PDGF-BB driven mechanism for MC proliferation in inflammatory and metabolic glomerular diseases is suggested.

Animals↗
PubMedDate not supplied

Prediction of individual patient response to chemotherapy by the fluorometric microculture cytotoxicity assay (FMCA) using drug specific cut-off limits and a Bayesian model.

The semiautomated fluorometric microculture cytotoxicity assay (FMCA) based on the measurement of fluorescence generated from cellular hydrolysis of fluorescein diacetate (FDA) to fluorescein in microtiter plates, has been used for determination of cytotoxic drug resistance of tumor cells from patients with hematological and solid tumors. In the present study we describe a calibration procedure based on statistically derived cut-off limits and assay-predicted response probabilities using Bayes' theorem. Test results at a specified drug concentration were divided into three categories: low, intermediate or extreme drug resistance (LDR, IDR and EDR, respectively) using the median and median +1 standard deviation as the cut-off limits. When correlated with clinical outcome, LDR samples showed a higher response rate than expected, IDR a lower and EDR samples no response at all. The sensitivity and specificity of the test, using the median as cut-off limit, were 0.92 and 0.69 respectively. By fitting these test characteristics to a statistical model based on Bayes' theorem it is possible to calculate response probabilities for each individual patient taking into consideration not only the test characteristics and the particular assay result, but also the clinical and patient specific characteristics influencing the pre-test probability of response. EDR predicts clinical drug resistance with high specificity and is also observed in tumor types with high response rate.

Antineoplastic Agents↗
PubMedDate not supplied

Difluoromethylornithine and ethylglyoxal bis(guanylhydrazone) as inhibitors of human renal carcinoma cell proliferation and polyamine metabolism.

The significance of the polyamines putrescine, spermidine and spermine for the neoplastic proliferation of the human renal carcinoma cell line ACHN was investigated. For this purpose cells were cultured in vitro for 4 days with or without the addition of pathway inhibitors of polyamine biosynthetic enzymes. It was found that treatment of ACHN cells with the specific ornithine decarboxylase (ODC) inhibitor difluoromethylornithine (DFMO) resulted in profound decreases of ODC activity, polyamine content and cell proliferation rates along with a compensatory increase in S-adenosylmethionine decarboxylase (SAMDC) activity. Ethylglyoxal bis(guanylhydrazone) (EGBG), a SAMDC inhibitor, evoked a similar reduction of cell proliferation and contents of spermidine and spermine. EGBG also seemed to stabilize SAMDC, as evidenced by a highly enhanced SAMDC activity during enzyme assays in the absence of the inhibitor. Furthermore, EGBG treatment caused on activation of ODC and a subsequent build-up of putrescine. The impact on polyamine contents and proliferation rates were synergistic when the inhibitors were used in combination. None of the inhibitors alone exerted a cytocidal activity. It is concluded that polyamines may be implicated in the regulation of the neoplastic proliferation of cultured human renal carcinoma cells and that polyamine synthesis inhibitors may prove valuable in clinical treatment of this disease.

Cell Division↗
PubMedDate not supplied

Modulation of calcium signalling and proliferation in monoblastoid U-937 cells.

The effects of TPA (12-0-tetradecanoylphorbol-13-acetate) and G-protein modulators on the concentration of cytoplasmic Ca2+ ([Ca2+]i), cytoplasmic pH and cell growth were investigated in monoblastoid U-937 cells. The G-protein activator NaF causes a dose-dependent increase of [Ca2+]i, that is partially sensitive to inhibition by pertussis toxin. The [Ca2+]i rise appears to come mainly from extracellular sources, and the Ca2+ influx is mediated by channels insensitive to the Ca2+ blocker verapamil. The Ca2+ ionophore ionomycin causes a biphasic rise of [Ca2+]i, reaching steady state levels slightly higher than those attained with NaF. TPA per se has no effect on [Ca2+]i, but potently reverses the NaF or ionomycin induced [Ca2+]i rise. Also, TPA partially counteracted the acidification induced by NaF. Both NaF and ionomycin per se had no effect on cell growth but partially counteracted TPA induced growth inhibition. Interferon-gamma and tumor necrosis factor-alpha did not affect [Ca2+]i by themselves but lowered the [Ca2+]i of NaF stimulated cells. The cytokines had no effect on cytoplasmic pH. This study indicates that elevations of [Ca2+]i in themselves does not trigger proliferation, but alterations of [Ca2+]i modulates the regulation of U937-cell growth.

Calcium↗