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Biomedical subjects

R Larsson

Publications and source records attributed to R Larsson.

At least 163 records · Page 9Linked to original sources
PubMed1990

Verapamil and cyclosporin A potentiate the effects of chemotherapeutic drugs in the human medullary thyroid carcinoma TT cell line not expressing the 170 kDa P-glycoprotein.

The TT-cell line, derived from a patient with metastatic medullary thyroid carcinoma (MTC), was found to exhibit intrinsic resistance to vincristine (VCR) despite the absence of immunohistochemically detectable 170 kDa P-glycoprotein (PGP 170) associated with multidrug resistance (MDR). Verapamil and cyclosporin A, two well known resistance modifiers of MDR, were found to significantly potentiate the action of VCR (60-fold) and to a lesser degree also of VP-16 and daunorubicin (dnr). The present results suggests that resistance of MTC to chemotherapy may be at least partly circumvented by the addition resistance modifiers to chemotherapeutic regimens.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1990

Pharmacological modification of multi-drug resistance (MDR) in vitro detected by a novel fluorometric microculture cytotoxicity assay. Reversal of resistance and selective cytotoxic actions of cyclosporin A and verapamil on MDR leukemia T-cells.

A novel fluorometric microculture cytotoxicity assay (FMCA), based on measurements of fluorescein diacetate (FDA) hydrolysis and DNA staining by Hoechst 33342, was used for drug sensitivity testing and detection of resistance reversal in acute lymphoblastic leukemia (ALL) cell lines. The 72-hr assay was found to be sensitive, reproducible and linearly related to the number of viable cells within a broad range of cell concentrations. At clinically achievable drug concentrations, the calcium channel blocker Verapamil (ver) and the immunosuppressant Cyclosporin A (csA) were found to partly reverse acquired Vincristine (vcr) resistance in multi-drug resistant (MDR) T-ALL L100 cells with little or no effect on the drug-sensitive parental L0 cell line. By combining the fluorometric indices, we found that low concentrations of csA were growth-inhibitory, whereas higher concentrations (greater than 10 micrograms/ml) were progressively cytotoxic for drug-sensitive L0 cells. In MDR L100 cells, on the other hand, csA produced significant cell kill even at low drug concentrations. Ver had no effects on sensitive L0 cells but showed considerable cytotoxic action towards MDR L100 cells. There was no apparent relationship between drug reversal of vcr resistance and the cytotoxic actions of the drug per se since the calcium channel blocker diltiazem (dil) significantly potentiated the actions of vcr on MDR L100 cells without being more toxic to these cells (compared to vcr-sensitive L0 cells).

Benzimidazoles↗
PubMed1990

Modulation of vincristine sensitivity of human kidney tumor cells by pharmacological agents interfering with intracellular signals. No apparent relationship to changes in cytoplasmic Ca2+ or pH.

The effect of substances proposed to modulate intracellular signal systems on growth and sensitivity to vincristine in the human kidney tumor cell line ACHN was investigated and related to changes in cytoplasmic free Ca2+ concentration ([Ca2+]i) and cytoplasmic pH (pHi). Presence during culture of the protein kinase C (PKC) activator 12-O-tetradecanoyl phorbol 13-acetate (TPA) had no effect on cell growth but significantly increased the EC50 concentration for vincristine inhibited cell growth. There was no indication for endogenous PKC activity being responsible for basal vincristine insensitivity since it was not affected by the PKC inhibitor H-7. The Ca2+ ionophore ionomycin tended to increase cell growth and induced vincristine resistance, whereas the calmodulin inhibitor W-7 had opposite effects. Presence during culture of the adenylate cyclase activator forskolin did not affect basal cell growth but dose-dependently made the cells more sensitive to vincristine. The modulators of vincristine sensitivity had no immediate effect on pHi, whereas after 3 days of incubation ionomycin and forskolin tended to increase pHi. Ionomycin and forskolin induced an immediate increase in [Ca2+]i which remained after 3 days only for ionomycin, whereas TPA decreased [Ca2+]i, a change which tended to remain after 3 days of incubation. It is concluded that perturbation of the intracellular signal system may affect both cell growth and cytotoxic drug sensitivity. However, there is no apparent relationship between immediate or late changes in [Ca2+]i and pHi and vincristine sensitivity.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1990

Acute and steady-state pharmacokinetics and antihypertensive effects of felodipine in patients with normal and impaired renal function.

Eighteen patients (14 men and 4 women, aged 36-74 years) treated with metoprolol for a month were included in the study. Twelve had impaired renal function (IRF) with a glomerular filtration rate (GFR) of 7.5-77.1 mL/min and six having normal renal function (NRF) with a GFR of 84.9-113.0 mL/min. Plasma and urine concentrations of felodipine and metabolites, heart rate, and blood pressure were recorded over 24 hours on day 1 after an oral dose of 10 mg felodipine and 0.04 mg 3H-felodipine IV and repeated on day 29 during continuous treatment with felodipine, 10 mg bid. The bioavailability of the oral dose on day 1 and day 29 was 13% and 12.5%, respectively. The terminal plasma half-life (t1/2) on day 29 was 22 hours and systemic clearance was 490 mL/min on day 1 and 434 mL/min on day 29 (NS). There were no differences in these parameters between NRF and IRF. The protein binding determined by equilibrium dialysis in the six patients with the lowest GFR was 99.74% on day 1 and 99.73% on day 29 and did not differ significantly from previously reported values in healthy subjects. The mean supine blood pressure before the acute dose of felodipine was 164/96 mm Hg in the IRF patients and 145/95 mm Hg in the NRF patients. A maximum decrease of 37/22 mm Hg and 32/19 mm Hg, respectively, was seen within 1.5 hours after dose and at 12 hours the reduction was 12/9 and 15/10 mm Hg, respectively, compared to baseline values. At steady state the morning blood pressure before dose was 152/87 mm Hg in the IRF patients and 129/86 mm Hg in the NRF patients. Similar maximum decreases and effects at 12 hours were seen after dose on day 29 as on day 1. Data on the effect on diastolic blood pressure and plasma felodipine concentrations were well fitted to the Emax model. The maximum reduction in diastolic blood pressure using this model was 27% and the plasma concentration leading to 50% of the maximum effect was 6.2 nmol/L. In conclusion, renal disease does not affect the pharmacokinetics of felodipine. The pharmacokinetic and pharmacodynamic effects of felodipine are not altered during steady state. The renal excretion of inactive metabolites is reduced in IRF. However, the accumulation of metabolites in the blood does not affect the protein binding or the clearance of felodipine. No dosage adjustment of felodipine seems to be necessary in patients with hypertension and renal impairment.

Adult↗
PubMed1990

Verapamil and cyclosporin A sensitize human kidney tumor cells to vincristine in absence of membrane P-glycoprotein and without apparent changes in the cytoplasmic free Ca2+ concentration.

Vincristine (Vcr) dose dependently inhibited growth of the kidney adenocarcinoma cell line ACHN during 4 days of culture. Verapamil (Ver) at 10 microM and cyclosporin A (CsA) at 1 microgram/ml had no effect on cell growth but significantly potentiated the action of Vcr, despite the absence of the multidrug resistance associated membrane P-glycoprotein (P-gp). Neither Ver nor CsA had any acute or long term effects on cytoplasmic free Ca2+ concentration (Ca2+i), except for a small Ver induced increase after 36 h of incubation. The results indicate that Ver and CsA may have a sensitizing effect on chemotherapeutic drug sensitivity also in absence of P-gp. However, these effects are probably not mediated by changes in Ca2+i.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1990

Felodipine in the treatment of patients with severe hypertension and impaired renal function.

Twenty-three patients with severe hypertension and impaired renal function were included in an open study of the efficacy and tolerance of felodipine treatment over 6 months. All patients were previously treated with a diuretic, a beta blocker, and a vasodilator, and eight of them also received an ACE inhibitor. At the start of felodipine treatment the previously used vasodilator was withdrawn. In nine patients the concomitant antihypertensive treatment was reduced during the study. The glomerular filtration rate (GFR), as 51Cr EDTA clearance, was determined before and at the end of the study. The blood pressure (BP) and heart rate (HR) were recorded at all clinical visits in the morning 12 hours after the evening dose of felodipine and 2 hours after the morning dose. Plasma concentrations of felodipine were measured at every visit before the morning dose and 2 hours after dose. The BP was reduced after felodipine was substituted for the previously used vasodilator. A significant additional anti-hypertensive effect was recorded 2 hours after the dose and amounted to -37 +/- 22/-15 +/- 12 mmHg (p = 0.0001/p = 0.0002) at 6 months. The effect measured 12 hours after the dose was less pronounced and was -11 +/- 28/-6 +/- 10 mmHg (p = 0.15/p = 0.03). Mean GFR was unchanged during the study, 38 +/- 19 versus 38 +/- 19 ml/min (n = 16). There was a sixfold interindividual variation in the trough plasma concentrations at steady state at the same drug dosage. Higher plasma concentrations seemed to be required to achieve the same antihypertensive effects as in patients with less severe hypertension and normal renal function.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Improved biocompatibility of intraocular lenses by heparin surface modification: a 12-month implantation study in monkeys.

To evaluate the long-term biocompatibility and potential side effects of heparin surface modification of a poly(methyl methacrylate) intraocular lens (IOL), a heparin surface modified IOL was implanted in the left posterior chamber of 24 cynomolgus monkeys and a reference IOL (without surface modification) was implanted in the right eye in 12 of these animals. Twelve eyes were not operated on. Eleven eyes in seven monkeys were lens extracted as a control of the surgical method. Slitlamp examinations and intraocular pressure recordings were made one day, one and two weeks, and 1, 2, 2 1/2, 3 1/2, 6, 8, 10, and 12 months after the operation. Eleven monkeys were sacrificed after 3 1/2 months and the remaining animals after 12 months for morphological examination of the eyes. Slitlamp and morphological examinations showed that cell deposits, pigmentation, and posterior synechias were significantly less in eyes with heparin surface modified IOLs than in eyes with reference IOLs throughout the 12-month observation period. The intraocular pressure was equally reduced in eyes with heparin surface modified IOLs and reference IOLs for about one month, after which it returned to normal. No side effects following the implantation of heparin surface modified IOLs were observed. We concluded that heparin surface modification of IOLs is efficient for long-term reduction of cell deposits and posterior synechias after implantation in monkey eyes and may also be effective in lowering the degree of side effects to IOL implantation in humans.

Animals↗
PubMed1990

Chemotherapeutic drug sensitivity testing of human leukemia cells in vitro using a semiautomated fluorometric assay.

A simple and reproducible semiautomated fluorometric method for drug sensitivity testing of leukemic cells in microculture is described. The assay is based on hydrolysis of nonfluorescent fluorescein diacetate (FDA) to a strongly fluorescent product (fluorescein) by cells with intact plasma membranes after 72 hr of culture and was in the present study applied to acute lymphocytic leukemia (ALL) cell lines and specimens from patients with lymphocytic and myelocytic leukemia. FDA fluorescence was linearly related to viable cell number within a wide range of cell densities (3-4 logs) as well as in the presence of different added proportions of dead cells. The assay reliably detects high and low grade resistance to vincristine (vcr) and daunorubicin, respectively, as well as the subsequent reversal of vcr resistance by cyclosporin A and the calcium channel blocker verapamil. Using ALL cell lines, drug sensitivity was in good correspondence with data obtained by the microculture tetrazolium assay. Furthermore, drug sensitivity data of fresh leukemia cells from patients with leukemia were readily obtained. The results indicate that the presently described method is applicable for simple and reliable chemosensitivity testing of leukemia cell lines as well as tumor specimens from patients with leukemia.

Cell Count↗
PubMed1989

Translocation and enhancement of phosphotransferase activity of protein kinase C following exposure in mouse epidermal cells to oxidants.

We have studied changes in intracellular localization and phosphorylating activity of protein kinase C (PKC) in mouse epidermal JB6 cells treated with oxidants. Exposure to hydrogen peroxide, reagent grade or generated enzymatically by glucose/glucose oxidase, at concentrations known to result in elevated intracellular free Ca2+ resulted in an increase in binding of [3H]phorbol dibutyrate to intact cells. Ca2+ chelation, either intracellularly by quin 2 or extracellularly by ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, abolished the increase in radioligand binding. In contrast to H2O2, superoxide generated extracellularly by xanthine/xanthine oxidase or intracellularly by menadione was inactive. Scatchard plot analysis revealed that the enhancement in binding resulted from both increased receptor affinity and increased maximal binding capacity. Treatment of cells with superoxide, generated extracellularly by xanthine/xanthine oxidase or intracellularly by menadione, diminished the [3H]phorbol dibutyrate-binding capacity of the cytosol fractions prepared at low Ca2+ concentration. This decrease was not accompanied by a compensatory increase in the binding to membrane components. In contrast to superoxide, reagent H2O2, H2O2 produced by glucose/glucose oxidase, and the Ca2+ ionophore A23187 had no significant effect on the [3H]phorbol dibutyrate-binding capacities of either cellular fraction. Exposure of cells to low concentrations of extra- or intracellular superoxide resulted in an increase in the Ca2+- and phospholipid-dependent phosphorylating activity of cytosolic extracts towards adenosine diphosphoribose transferase which has been reported to be a specific substrate for PKC. The increase in phosphorylation could be diminished by the extracellular addition of copper-zinc-containing superoxide dismutase but not catalase suggesting that superoxide rather than H2O2 represents the active oxygen species in this reaction. The observation that reagent H2O2 or glucose/glucose oxidase failed to increase the phosphorylating activity of cytosolic preparations supports this conclusion. Treatment of cells or cytosolic extracts with the sulfhydryl reagent diamide stimulated the Ca2+/phospholipid-dependent phosphorylating activity toward adenosine diphosphoribose transferase. In a reconstituted system containing purified PKC, diamide induced a 25-30% increase in phospholipid-dependent phosphorylation of H1 whereas no change in activity was observed with the reducing agent dithiothreitol. It is concluded that H2O2 but not superoxide induces an increase in the phorbol ester binding, presumably to PKC, of intact JB6 cells. On the other hand

Animals↗
PubMed1989

Pathophysiological mechanisms of active oxygen.

Besides being toxic, oxidants can induce pathophysiological effects in mammalian cells. For example they can stimulate rather than inhibit cell growth. Since oxidants are ubiquitous they may represent 'natural' tumour promoters. Our work with xanthine/xanthine-oxidase as an extracellular source of active oxygen (AO) and promotable (clone 41) and non-promotable (clone 30) mouse epidermal cells JB6 allows insights into the mechanism of action of oxidant promoters. We found that AO stimulated the growth only of promotable clone 41 after an initial period of moderate inhibition while it was strongly cytostatic for non-promotable clone 30. Active oxygen induced larger amounts of DNA-strand breaks and poly ADP-ribosylation of chromosomal proteins in non-promotable cells. In addition, AO was capable of inducing the growth- and differentiation-related proto-oncogenes c-fos and c-myc in promotable and non-promotable JB6 cells. We speculate that these genes can exert their functions only in the promotable clone 41 because the general cytostatic effects of AO are moderate. A possible explanation for the differences between these 2 clones was discovered when we compared the constitutive activities, protein concentrations and mRNA levels for the antioxidant enzymes catalase (CAT), Cu,Zn-superoxide dismutase (SOD) and glutathione-peroxidase (GPx). We found that CAT and SOD (but not GPx) levels were 2-3-fold higher in the promotable clone 41. We propose that promotable cells possess a superior antioxidant defence which protects them from excessive cytostatic effects of AO.

Animals↗
PubMed1989

Intraocular PMMA lenses modified with surface-immobilized heparin: evaluation of biocompatibility in vitro and in vivo.

Intraocular lenses (IOL) were surface modified with covalently linked heparin. The surface-bound heparin could not be removed by incubation in solutions known to be effective in breaking non-covalent bonds, nor by incubation in a solution of proteinase K and only to a limited extent by incubation with heparinase. In vitro studies demonstrated improved biocompatibility by the heparin surface-modified lens with respect to outgrowth of fibroblasts and macrophages, activation of granulocytes and adhesion of platelets. These results were subsequently verified in vivo in terms of less inflammatory cells on the lens surface and fewer incidences of synechiae after 3 and 6 wk IOL implantation in the rabbit eye.

Animals↗
PubMed1989

Interaction of monoclonal antiparathyroid antibody with Ca2+ agonistic actions of Mn2+ in normal human parathyroid cells.

Effects of the monoclonal antiparathyroid antibodies G11 and E11 on Mn2+ interaction with individual normal human parathyroid cells were studied. At 0.5mM Ca2+, 3mM Mn2+ induced a rapid transient increase in cytoplasmic Ca2+ [Ca2+i] followed by quenching of the fluorescence from the Ca2+ indicator fura-2 as Mn2+ entered into the cells. Whereas the antibody E11 had no effects, treatment with G11 abolished the Ca2+i transient and considerably delayed the entry of Mn2+. The results support the presence of a cation-sensitive receptor mechanism on parathyroid cells and indicate that the antibody G11 not only blocks the interaction between Ca2+ and this receptor mechanism but also that of Mn2+.

Antibodies, Monoclonal↗