Biomedical subjects

R Larsson

Publications and source records attributed to R Larsson.

At least 19 recordsLinked to original sources

PubMed2002

Relative therapeutic index between inhaled formoterol and salbutamol in asthma patients.

A double-blind, randomized crossover study in 28 asthmatic patients assessed the relative therapeutic index for inhaled formoterol and salbutamol. Pre-drug administration FEV1 (mean 2.08 l) was 49-93% of predicted and reversibility 16-82% after inhalation of salbutamol. Patients inhaled single doses of formoterol (Oxis) (4.5,18 and 54 microg, delivered doses) via Turbuhaler, salbutamol (Ventolin) (200 and 1800 microg) via pressurized metered dose inhaler (pMDI) and placebo at intervals of 48 h or more. Individual maximum FEV1 and minimum S-K+ were calculated. Relative local (maximum FEV1) and systemic (minimum S-K+) dose potencies, and their ratio, the relative therapeutic index, were estimated using a non-linear mixed effect model. The drug effects were well tolerated and dose dependent. A log-linear approximation was used to describe the bronchodilatory effect, whereas a sigmoid approximation was more apt to describe the decrease in serum potassium concentration. A bivariate dose-response model based on these principles was fitted simultaneously to all data. The mean relative therapeutic index between formoterol 4.5-54 microg given via Turbuhaler and salbutamol 200-1800 microg given via pMDI was estimated to be 2.5 in favour of formoterol; this trend was not statistically significant.

Adult↗

PubMed2001

Guanidino-containing drugs in cancer chemotherapy: biochemical and clinical pharmacology.

The pharmacology and clinical application of three guanidino-containing compounds are reviewed in this commentary with special focus on a new member of this group of drugs, CHS 828 [N-(6-(4-chlorophenoxy)hexyl)-N'-cyano-N"-4-pyridylguanidine]. m-Iodobenzylguanidine (MIBG) and methylglyoxal bis(guanylhydrazone) (MGBG) have been extensively studied, preclinically as well as clinically, and have established use as anticancer agents. MIBG has structural similarities to the neurotransmitter, norepinephrine, and MGBG is a structural analog of the natural polyamine spermidine. CHS 828 is a pyridyl cyanoguanidine newly recognized as having cytotoxic effects when screening antihypertensive compounds. Apart from having the guanidino groups in common, there are many differences between these drugs in both structure and their mechanisms of action. However, they all inhibit mitochondrial function, a seemingly unique feature among chemotherapeutic drugs. In vitro in various cell lines and primary cultures of patient tumor cells and in vivo in various tumor models, CHS 828 has cytotoxic properties unlike any of the standard cytotoxic drugs with which it has been compared. Among these are non-cross-resistance to standard drugs and pronounced activity in tumor models acknowledged to be highly drug-resistant. Similar to MIBG, CHS 828 induces an early increase in extracellular acidification, due to stimulation of the glycolytic flux. Furthermore, ATP levels decrease, and the syntheses of DNA and protein are shut off after approximately 30 hr of exposure, indicating active cell death. CHS 828 is now in early clinical trials, the results of which are eagerly awaited.

3-Iodobenzylguanidine↗

PubMed2001

Cellular pharmacodynamics of the cytotoxic guanidino-containing drug CHS 828. Comparison with methylglyoxal-bis(guanylhydrazone).

N-(6-(4-chlorophenoxy)hexyl)-N'-cyano-N"-4-pyridylguanidine (CHS 828) is a new guanidino-containing compound with antitumoral activity both in vitro and in vivo. Its activity profile differs from those of standard cytotoxic drugs but the mechanism of action is not yet fully understood. CHS 828 is presently in early phase I and II clinical trials. In the present study, the pharmacodynamic effects at the cellular level of CHS 828 was compared to another compound containing two guanidino groups, methylglyoxal-bis(guanylhydrazone) (MGBG). MGBG is known to inhibit the synthesis of polyamines, which are important in, e.g., proliferation and macromolecular synthesis. The concentration-response relationship of CHS 828 closely resembled that of MGBG and the drugs were similar with respect to inhibition of DNA and protein synthesis. On the other hand, CHS 828 induced a significant increase in cellular metabolism while MGBG did not. The cytotoxic effect of MGBG was reversed by the addition of exogenous polyamines, while that of CHS 828 was unaffected. Unlike MGBG, there was also no effect of CHS 828 on the levels of decarboxylating enzymes in the polyamine biosynthesis. In conclusion, CHS 828 does not appear to share any major mechanisms of action with the polyamine synthesis inhibitor MGBG. Further studies will be required to define the exact mechanism of action of CHS 828.

Antineoplastic Agents↗

PubMed2001

Cell death with atypical features induced by the novel antitumoral drug CHS 828, in human U-937 GTB cells.

N-(6-(4-chlorophenoxy)hexyl)-N'-cyano-N"-4-pyridylguanidine (CHS 828), with promising antitumoral effects in vitro and in vivo, is currently in clinical Phase I and II studies. Its exact mechanism of action is unclear, but previous studies indicate that CHS 828 induces a controlled, delayed mode of cell death. The characteristics of the cell death process were investigated in vitro in the apoptosis-prone cell line U-937 GTB. Mitochondria showed hyperpolarization at 24 to 32 h and a subsequent late disruption of mitochondria membrane potential (Deltapsi(m)). Between 44 and 72 h of CHS 828 exposure, there was an increasing frequency of terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) positive cells indicative of apoptosis, but caspase-3 was only modestly increased and caspases-8 and -9 showed no activation upon CHS 828 exposure. Furthermore, the morphology of exposed cells did not conform to classical apoptosis, and viability and morphology were unaffected by inhibition of caspases. Thus, CHS 828 induces several unexpected features in this system, suggesting a potentially novel mechanism of action.

Antineoplastic Agents↗

PubMed2001

In vivo activity of CHS 828 on hollow-fibre cultures of primary human tumour cells from patients.

Fresh human tumour cells from patients with ovarian cancer and chronic lymphocytic leukaemia were cultured in semipermeable hollow fibres. The fibres were implanted on immunocompetent rats, which were treated with the cyanoguanidine N-(4-chlorophenoxyhexyl)-N'-cyano-N"-4-pyridylguanidine (CHS 828). CHS 828 showed high antitumour activity against all eight tumour samples; the fibres from control animals had a mean net growth of 73% while CHS 828 treatment induced a 37% mean reduction of cell density, without observable haematological toxicity. The results show a feasibility of using tumour cells directly from patients in the hollow-fibre rat model.

Aged↗

PubMed2001

Coagulation and complement activation.

UNLABELLED: The purpose of this investigation was to assess the effect of heparin coating of a new stent construction (Stent Graft, Jomed Implantate GmbH, Germany) on platelet and coagulation activity. METHODS: Stent grafts with an ePTFE membrane interfoliated between two stents were deployed in tubings to form Chandler loops. Fresh human blood with a low concentration of heparin was rotated for 1 h, then collected and used for measurements of platelet number, thrombin-antithrombin complex (TAT), CD11b, C3a and C5b-9. There were five study groups: Group 1, conventional unmodified stents (n = 8); Group 2, untreated stent grafts (n = 8); Group 3, heparin-coated stents and untreated membrane (n = 7); Group 4, heparin-coated stents and membrane (n = 8); Group 5, heparin-coated PVC tubings with no stents (n = 8). RESULTS: There was a significant drop in platelet count, increase in TAT-values and CD11b expression in Groups 1-3 but not in Group 4 compared to Group 5. Examination by scanning electron microscopy revealed extensive activation on non-modified stents but almost no deposition of thrombotic material on heparin-modified stent grafts. CONCLUSIONS: With unmodified stents and membrane there were signs of significant activation of platelets and coagulation. In contrast, the heparin-coated stent graft induced much less alterations, indicating improved blood compatibility.

Blood Coagulation↗

PubMed2001

Binding of a model regulator of complement activation (RCA) to a biomaterial surface: surface-bound factor H inhibits complement activation.

The complement system is an important inflammatory mediator during procedures such as cardiopulmonary bypass and hemodialysis when blood is exposed to large areas of biomaterial surface. This contact between blood and the biomaterials of implants and extracorporeal circuits leads to an inflammatory response mediated by the complement system. The aim of this study was to assess the ability of a complement regulator (factor H) immobilised on a biomaterial surface to inhibit complement cascade mediated inflammatory responses. The cross-linker N-succinimidyl 3-(2-pyridyldithio) propionate was used to immobilise factor H on a model biomaterial surface without affecting the biological activity of the inhibitor. Binding of factor H was then characterised using quartz crystal microbalance-dissipation (QCM-D) and enzyme immunoassays for products of complement activation: bound C3 fragments and soluble C3a, sC5b-9, and C1s-C1INA. Immobilised factor H reduced the amount C3 fragments deposited on the biomaterial surface after incubation with serum, plasma. or whole blood. In addition, lower levels of soluble C3a and sC5b-9 were generated after incubation with whole blood. In summary, we have demonstrated that complement activation on a highly activating model surface can be inhibited by immobilised factor H and have defined prerequisites for the preparation of future biomaterial surfaces with immobilised regulators of complement activation.

Biocompatible Materials↗

PubMed2001

Temporal effects of the novel antitumour pyridyl cyanoguanidine (CHS 828) on human lymphoma cells.

CHS 828, a novel pyridyl cyanoguanidine, has shown potent antitumour activity both in vitro and in vivo and is currently undergoing phase I evaluation in humans in collaboration with the European Organization for Research and Treatment of Cancer (EORTC). Here we study the temporal effects of CHS 828 on cytotoxicity, protein and DNA synthesis, cellular morphology and ultra structure using the lymphoma cell line U-937 GTB as the primary tumour model. In vitro analysis of tumour cell survival in response to CHS 828 revealed a cytotoxic effect progressively increased as a function of exposure time with maximum efficacy observed after 72 h. Activity of CHS 828 on U-937 GTB cells grown in vivo was also found. CHS 828 induced-cell death was dependent on intact protein synthesis and most cells appeared to lose their membrane integrity in the presence of a relatively well preserved nuclear structure. The results indicate that CHS 828 induced active and delayed cell death with a non-apoptotic morphology.

Antineoplastic Agents↗

PubMed2001

Outcome of surgery for cervical radiculopathy evaluated by determination of trapezius muscle microcirculation and electromyography.

Surgery for cervical radiculopathy was evaluated in 27 patients after anterior Cloward procedure (19 patients) or posterior decompression (eight patients). In addition, we examined 10 conservatively treated patients. Each patient was studied prospectively with regards to the effects on microcirculation in the local trapezius muscle during a fatiguing series of stepwise increased contractions. The right and left muscles were simultaneously examined pre-operatively and postoperatively after 9 months using laser-Doppler flowmetry and simultaneous surface electromyography (EMG). Preoperatively, a reduced microcirculation was found in the most painful side compared with the opposite side. This is in accordance with earlier reports on patients with chronic neurogenic neck pain, who also show reduced muscle tension on EMG. Postoperatively, the muscle blood flow became increased, but only in patients operated on via a posterior approach. A tendency at increased EMG-amplitude and reduced mean power frequency of the EMG was noted. These EMG signs of muscle fatigue suggest increased ability to exhaust the trapezius muscle postoperatively. The observed postoperative changes were consistently more frequent in the less painful side. We conclude from these objective measurements showing only a tendency at increased microcirculation and muscle tension postoperatively, that the effect on the trapezius muscle is limited.

Adult↗

PubMed2001

Contact between a polymer and whole blood: sequence of events leading to thrombin generation.

The mechanism by which thrombin is generated on a polymer surface in an extracorporeal circuit is not yet fully understood. To address this question we have developed an in vitro chamber model in which whole blood containing heparin (1 IU/mL) comes in contact with a commonly used biomaterial, polyvinyl chloride (PVC). Incubation of blood in the chamber for 60 minutes at 37 degrees C resulted in the binding of platelets to the material surface and the generation of thrombin-antithrombin complexes. Corn trypsin inhibitor, a specific inhibitor of factor XIIa, inhibited this thrombin-antithrombin complex generation in blood in contact with PVC, which is not considered an efficient activator of factor XII. The addition of the glycoprotein IIb/IIIa inhibitor Ro44-9883 abrogated platelet binding and aggregation and resulted in decreased generation of thrombin-antithrombin complexes. Thrombin-antithrombin generation was also negligible in platelet-rich plasma but could be partially restored in the presence of erythrocytes. Taken together, these data are compatible with a model in which thrombin generation is triggered by factor XII. The response to contact with PVC appears to begin with a low-grade generation of thrombin that involves both erythrocytes and leukocytes and that activates platelets, followed by the activation of a platelet-dependent amplification loop that produces most of the thrombin.

Acetates↗

PubMed2001

A hollow fiber model for in vitro studies of cytotoxic compounds: activity of the cyanoguanidine CHS 828.

The hollow fiber assay is currently used as an in vivo model for anticancer drug screening in nude mice, but it can also be used as an in vitro model. In the current study, an in vitro hollow fiber model was used to study the effect and mode of induced cell death of a new cyanoguanidine, CHS 828. Human leukemia, adenocarcinoma and lymphoma cell lines as well as primary cultures of human tumor cells from patients with chronic lymphocytic leukemia (CLL) and ovarian cancer (OC) and normal human lymphocytes were cultured in semipermeable hollow fibers. The fibers were incubated for 3 or 14 days prior to CHS 828 exposure for 72 h, followed by determination of living cell density by MTT staining. For cell morphology, using harvested cultures on cytospin slides had technical advantages compared to using paraffin sections of the formalin-fixed fibers. CHS 828 showed higher antitumor activity on CLL and normal human lymphocyte cultures compared to OC cultures, and cell lines cultured 3 days were more sensitive than those cultured 14 days. Morphological examination of CHS 828-treated cultures revealed a mixture of apoptosis and necrosis.

Antineoplastic Agents↗

PubMed2001

Cytotoxicity of digitoxin and related cardiac glycosides in human tumor cells.

The saponin digitonin, the aglycone digitoxigenin and five cardiac glycosides were evaluated for cytotoxicity using primary cultures of tumor cells from patients and a human cell line panel (representing different cytotoxic drug-resistance patterns). Of these seven compounds, proscillaridin A was the most potent (IC(50): 6.4--76 nM), followed by digitoxin, and then ouabain, digoxin, lanatoside C, digitoxigenin and digitonin. Correlation analysis of the log IC(50) values for the cell lines in the panel showed that compound cytotoxicity was only slightly influenced by resistance mechanisms that involved P-glycoprotein, topoisomerase II, multidrug resistance-associated protein and glutathione-mediated drug resistance. Digitoxin and digoxin expressed selective toxicity against solid tumor cells from patients, while proscillaridin A expressed no selective toxicity against either solid or hematological tumor cells. The results revealed marked differences in cytotoxicity between the cardiac glycosides, both in potency and selectivity, and modes of action for cytotoxicity that differ from that of commonly used anticancer drugs.

Antineoplastic Agents↗

PubMed2001

Characteristics of etoposide-induced apoptotic cell death in the U-937 human lymphoma cell line.

Cell death induced by etoposide in the human lymphoma cell line U-937 GTB was characterized. Activity of caspases -3, -8 and -9 was measured by spectrophotometric detection of specific cleavage products, DNA fragmentation by TdT-mediated dUTP nick end-labelling (TUNEL), and apoptotic morphology by conventional staining and microscopy, as well as by a novel method-the microculture kinetics (MiCK) assay. Synthesis of protein and DNA during exposure was monitored by incorporation of radioactive leucine and thymidine, respectively. The effects of caspase inhibitors on total viability, as well as early and late morphological changes were studied. Etoposide rapidly induced apoptosis, dependent on caspase-3 and -8, but inhibition of these caspases did not prevent major cell death, but promoted a switch in late morphology. The novel MiCK assay added valuable information on early morphological events during cell death. Hence, this study provides support for caspase-8-mediated apoptosis in U-937 GTB when exposed to etoposide. General caspase inhibition switches cell death to one with a different morphology.

Apoptosis↗

PubMed2001

Activity of CHS 828 in primary cultures of human hematological and solid tumors in vitro.

CHS 828 is a pyridyl cyanoguanidine that has shown promising preclinical anticancer activity against various experimental tumor models and is presently being tested in a phase II trial in man. In the present study the fluorometric microculture cytotoxicity assay was used for in vitro evaluation of CHS 828 activity in primary cell cultures from hematological and solid tumors. In total, 156 samples from various diagnoses were tested with 72-h continuous drug exposure. CHS 828 showed high relative in vitro activity against tumor cells from chronic lymphocytic leukemia as well as from acute leukemia and high-grade lymphoma. Activity was also observed in several solid tumor cell samples, although the group as a whole appeared less responsive. CHS 828 was significantly more active against hematological malignancies compared to normal lymphocytes. Correlation analysis with standard drugs revealed low to moderate correlation coefficients. The results show that CHS 828 has potent antitumor activity against primary cultures of human tumor cells from patients and might have a unique mechanism of action.

Adolescent↗

PubMed2001

A new in vitro model for the study of pig-to-human vascular hyperacute rejection.

Studies on vascular hyperacute xenograft rejection (HAR) are usually conducted in vitro on cultured endothelial cells (EC) exposed to human serum, in complex whole organ perfusion models using heparinized blood or in vivo models. Here we describe a new model allowing perfusion of pig vessels with human whole blood without anticoagulants. Segments of the porcine iliac artery were connected to circular polyvinyl chloride (PVC) tubing, whose inner surface was conjugated with immobilized heparin. The vessels were perfused with 7 to 8 ml of fresh, non-anticoagulated human blood by rocking of the tubing device for 5, 15 or 60 min in an incubator at 37 degrees C. Human iliac arteries (n = 4) were perfused with fresh human ABO-compatible blood as controls. Perfusion of human vessels resulted in changes in the blood and plasma parameters similar to those in the PVC control loop. Overall, perfusion of the porcine vessels generated high levels of C3a, sC5b-9 and thrombin-anti-thrombin (TAT). Platelet consumption was near total (97.2 +/- 1.2%; "high" responders) in six of 13 vessels perfused and only moderate (55.8 +/- 9.9%; "low" responders) in the remaining seven vessels. The "high" responder vessel group showed a significantly higher platelet reduction, neutrophil loss and monocyte consumption and higher C3a and TAT factor at 60 min compared with the human vessels. The "low" responder porcine vessel group also generated significantly higher TAT levels at 60 min compared with the human vessels, but lower levels compared with the "high" responder porcine vessel group. Immunohistochemical examination of perfused porcine vessels revealed binding of human IgM, IgG, IgA, C1q, C3, fibrin and platelets at 5 min. The binding of these proteins was even stronger at 15 and 60 min, and at 60 min C9 could also be detected. Addition of soluble complement receptor 1 (sCR1) to the blood resulted in a significant reduction in C3a and sC5b-9 (P = 0.046 and P = 0.046, respectively). However, sCR1 did not reduce C1q, C3c or C5 staining, but did abolish C9 binding to the endothelium. In conclusion, in vitro perfusion of porcine vessel segments with non-heparinized, fresh human blood triggered events characterizing HAR. The small quantity of blood and xenogenic tissue that is needed makes this model ideal for investigations of the mechanisms and treatments of rejections associated with xenogeneic pig-to-human xenotransplantation.

ABO Blood-Group System↗

PubMed2001

Model for time dependency of cytotoxic effect of CHS 828 in vitro suggests two different mechanisms of action.

CHS 828 is a novel drug belonging to the cyanoguanidines. It has shown promising anticancer activity in many preclinical systems and is currently in early clinical trials. Our aim in this study was to assess the growth inhibitory effect of CHS 828 in comparison with paclitaxel, etoposide, and topotecan as a function of concentration and time. U937 GTB, RPMI 8226/S, MDA 231, primary cells from chronic lymphocytic leukemia, and normal mononuclear cells were exposed to CHS 828 and U937 GTB cells were exposed to paclitaxel, etoposide, and topotecan in 18 concentrations for times ranging from 1 to 72 h. Cell survival was measured after 72-h incubation by using the fluorometric microculture cytotoxicity assay. Nonlinear mixed effect modeling was used to model the concentration-effect curves with a modified Hill equation. Patterns of change of drug potency (IC(50)), slope of the concentration-effect curves, and plateau with time were studied. The log IC(50) for CHS 828 decreased with log time in a sigmoid manner for all cell types tested. Although very steep at short and long incubation, the concentration-effect curves became shallow at intermediate times. The log IC(50) for etoposide and topotecan was decreased with log time in a sigmoid manner. The log IC(50) for paclitaxel decreased linearly with log time. The information obtained from modeling the cytotoxic effect of CHS 828 and changes of IC(50) and slope parameters with exposure time suggests a heterogeneous cell response to CHS 828. This could indicate two distinct mechanisms of induction of cell death.

Antineoplastic Agents↗

PubMed2000

Apoptosis induced by calcein acetoxymethyl ester in the human histiocytic lymphoma cell line U-937 GTB.

Effects of calcein acetoxymethyl ester (calcein/AM) on macromolecular synthesis, mitochondrial membrane potential, and mode of death were studied in U-937 GTB lymphoma cells. This was accomplished by measurements of (14)C-labeled thymidine and leucine incorporation, 5,5',6,6'-tetrachloro-1,1',3, 3'-tetraethylbenzimidazolyl carbocyanine iodide (JC-1) and caspase-3 activity measurements, TdT-mediated dUTP nick end labeling (TUNEL) staining, morphology, and a newly developed assay of apoptosis detection, the microculture kinetic assay (MiCK). This assay, based on absorbance measurements of cells, has been reported to reflect morphological changes in apoptosis. At 2.5 microg/mL, rapid inhibition of DNA and protein synthesis resembling that of the known inhibitors, aphidicholin and cycloheximide, was observed. Decreased mitochondrial membrane potential was evident after 1 hr of exposure and was followed by an increase in caspase-3 activity, while at 6 hr 30% of cells appeared positive with TUNEL staining. After 12 hr of exposure, viability was less than 5% as judged by morphological examination. In the MiCK assay, calcein (2.5 microg/mL) gave a rapid rise in absorbance after 3.5 hr of exposure with a peak at 5 hr, indicating maximum extent of apoptosis at that time. This was similar to the pattern generated for etoposide and doxorubicin. The results indicate that calcein, similar to cytotoxic drugs, induces a strong apoptotic response within hours of exposure.

Antineoplastic Agents↗

PubMed2000

Early stimulation of acidification rate by novel cytotoxic pyridyl cyanoguanidines in human tumor cells: comparison with m-iodobenzylguanidine.

CHS 828, a newly recognized pyridyl cyanoguanidine, has shown promising antitumor activity both in vitro and in vivo and is presently in early phase I clinical trial in collaboration with EORTC. In this study, the effects of CHS 828 and a series of analogues on extracellular acidification and cytotoxicity were compared with those of m-iodobenzylguanidine (MIBG) in human tumor cells. The extracellular acidification rate was measured using the Cytosensor microphysiometer, and determination of cytotoxicity and proliferation was [(14)C] performed by the fluorometric microculture cytotoxicity assay (FMCA) and measurement of [(14)C]thymidine and leucine uptake. CHS 828 significantly increased the acidification rate during the first 15-24 hr in a concentration-dependent manner. This effect was abolished by removal of glucose from the medium, substituted with 10 mM of pyruvate, indicating stimulated glycolysis as the source of the increased acidification rate. However, CHS 828 induced cytotoxicity at concentrations well below those that affected the rate of acidification; when a series of closely related pyridylguanidine analogues were tested and compared, no apparent relationship between cytotoxicity and acidification could be discerned. Furthermore, comparable increases in the acidification rate were evident in one subline with high-grade resistance to the cytotoxic actions of CHS 828. The results indicate that CHS 828 may share the inhibitory actions of MIBG on mitochondrial respiration with a subsequent increase in glycolysis and acidification rate. However, this mechanism of action appears neither necessary nor sufficient to fully explain the cytotoxic actions of CHS 828 in human tumor cells, actions which remain to be mechanistically clarified.

3-Iodobenzylguanidine↗