Biomedical subjects
S Ekelund
Publications and source records attributed to S Ekelund.
The combination of the antitumoural pyridyl cyanoguanidine CHS 828 and etoposide in vitro--from cytotoxic synergy to complete inhibition of apoptosis.
1. The present study was aimed at elucidating the apoptosis inhibitory properties of the cyanoguanidine CHS 828. CHS 828 exhibits impressive cytotoxic activity in vitro and in vivo. Apoptosis is not its main mode of cytotoxic effect, and we have previously proposed a dual mechanism, where CHS 828 inhibits its own cell death pathways. 2. Etoposide on the other hand, is a well-established anticancer agent with documented effect in a number of malignancies, induces apoptosis through extensively studied caspase dependent pathways. 3. Here we studied the combined effect of the two drugs in the human lymphoma cell line U-937 GTB. Cytotoxicity was evaluated as total viability measured by the fluorometric microculture cytotoxicity assay (FMCA). Caspase activity was assessed by colorimetric detection of specific cleavage products for caspases 3, 8 and 9, respectively. Morphology was evaluated in May-Grünwald/Giemsa stained preparations. Interaction analysis based on FMCA results of simple combination exposure revealed impressive synergistic effect on cell kill. 4. Detailed investigations of the kinetics involved showed that short pre-exposure (0-12 h) to CHS 828 enhanced caspase activation by etoposide, while longer pre-exposure (18-48 h) inhibited both caspase activation and apoptotic morphology otherwise induced by etoposide. The present results support the theory that CHS 828 block specific cell death pathways. 5. The synergistic results are promising for future combination trials in animals, however, different dosing schedules should be considered, in order to investigate whether the above findings translate into the in vivo setting.
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.
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.
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.
Day-to-day, postprandial, and orthostatic variation of total plasma homocysteine.
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Microphysiometry: new technology for evaluation of anticancer drug activity in human tumor cells in vitro.
Microphysiometry is a non-invasive, physiological method where measurement of metabolic activity can be made on living human tumor cells. Indirect measurement of the extracellular acidification is measured over a pH-sensitive silicon membrane. In this study microphysiometry was employed for the study of cytotoxic agents used in therapy of cancer. Standard cytotoxic drugs with different postulated mechanisms of action were investigated using cell lines as well as primary cultures of patient tumor cells. Each investigated cytotoxic drug induced a characteristic pattern of metabolic activity. From these patterns, key features, like stimulation and inhibition of acidification, the time point when the response curves of the drugs fall below the control curve, and the maximum inhibition of acidification at 20 h, could be quantified. Most of the investigated drugs showed some initial stimulation of acidification rate during the experiments. For drugs producing a reduced metabolic rate at 20 h a concentration-response relationship was observed. The drug effects measured at 20 h were irreversible and correlated reasonably well with parallel measurements of membrane integrity using a standard cytotoxicity test. The results demonstrate the feasibility of 'on-line' measurements of metabolic activity using this approach and also revealed an unexpected variety of drug response profiles.
Homocysteine in Greenland Inuits.
Patients with homozygous homocystinuria are at greatly increased risk for development of atherosclerosis and thrombosis (1). Elevated plasma levels of homocysteine (HCY) are caused by reduced enzymatic catabolism or reduced enzymatic remethylation of HCY, due to either hereditary enzyme defects or to nutritional deficiencies of vitamins functioning as cofactors. However, several recent studies have suggested that persons with mildly elevated plasma levels of HCY also are at increased risk for coronary heart disease. (2-4). There are some indications that dietary n-3 polyunsaturated fatty acids (PUFAs) may offer protection against coronary heart disease (5-6). Several mechanisms may be involved, including beneficial effects of n-3 PUFAs on plasma lipids, platelet and leukocyte reactivity, blood pressure and vasoreactivity (7). Interestingly, Olszewski el al. recently found HCY-levels to be lowered 36% in 15 type IIa or IIb hyperlipemic men by n-3 PUFA supplementation. A possible beneficial effect of n-3 PUFA on the incidence of coronary heart disease was initially suggested from studies in Greenland Inuits by our group (8). We therefore investigated plasma levels of homocysteine in a group of traditionally living Greenland Inuits with a diet consisting mainly of marine food and with a very high content of n-3 PUFAs.
Determination of the exocrine pancreatic function with the NBT-PABA test using a novel dual isotope technique and gas chromatography-mass spectrometry.
We describe a tubeless test of exocrine pancreatic function based on a new dual isotope technique, using N-benzoyl-L-tyrosyl-p-aminobenzoic acid (NBT-PABA) as a substrate for intestinal chymotrypsin activity and the stable isotope, 13C-PABA as marker. Gas chromatography-mass spectrometry (GC-MS) was used for the quantification of PABA and 13C-PABA in blood. The method involves hydrolysis, extractions, separation by HPLC, and methyl ester formation of the test substances before GC-MS analysis. The test is precise and shows good separation of healthy volunteers from patients with pancreatic insufficiency. The PABA/13C-PABA ratios in serum after 1.5 h were 2.64 +/- 0.14 (mean +/- SEM) in 10 healthy volunteers and 1.26 +/- 0.22 in 10 patients with exocrine pancreatic insufficiency. We present a sensitive and specific assay, which is free of analytical interference and radiation hazards and, additionally, it illuminates extrapancreatic pharmacokinetic conditions. This test can eliminate the need for duodenal intubation, which makes it very acceptable to the patients.
Folate and homocysteine status and haemolysis in patients treated with sulphasalazine for arthritis.
In an attempt to estimate the frequency of folate deficiency and haemolysis in a group of 25 outpatients with arthritis treated with sulphasalazine (SASP), haematological measurements, including plasma total homocysteine (tHcy) which is a sensitive marker of folate deficiency, serum folate (S-folate), erythrocyte (RBC) folate, S-cobalamin and routine indices of haemolysis were performed. No patient had been taking folate-containing vitamins for at least 8 weeks prior to the study. Compared to a group of 72 healthy hospital staff, the median plasma tHcy was significantly higher in the patient group (8.8 mumol 1(-1) vs. 6.8 mumol 1(-1); p = 0.003). Five patients (20%) had plasma tHcy levels that exceeded the upper normal limit of plasma tHcy (median+2 SD of the reference group). Median S-folate was significantly lower in the patient group (6.0 nmol 1(-1) vs. 8.5 nmol 1(-1); p < 0.001), and 11 (44%) patients had depressed S-folate. Only three (12%) patients had RBC folate values below the reference interval. There was no difference in the levels of RBC folate between the two groups. A comparison of S-cobalamin levels in the two groups disclosed a significantly lower level in the patient group. However, no patient had cobalamin deficiency as assessed by S-cobalamin and S-methylmalonate measurements. Thus, it is unlikely that any patient had increased plasma tHcy due to cobalamin deficiency. Of 24 patients having a HbA1c measurement performed, 12 (50%) had decreased levels indicating chronic haemolysis. Only seven (28%) patients had reticulocytosis. HbA1c was positively correlated to haptoglobin levels (r = 0.77; p < 0.001) and negatively correlated to the percentage of reticulocytes (r = -0.50; p = 0.02). The percentage of reticulocytes was negatively correlated to haptoglobin levels (r = -0.42; p = 0.04). The chronic haemolysis of the patients' blood due to SASP might explain the similar RBC folate values in the two groups because of a relatively higher folate content of young erythrocytes. In conclusion, our results support previous findings of folate deficiency and haemolysis occurring in a considerable fraction of patients receiving treatment with SASP. Measurements of plasma tHcy suggest that a substantial number of patients may have folate deficiency at the tissue level.
[Hydrogen sulfide poisoning in a farmer].
A case of hydrogen sulfide intoxication in a farmer is described. He collapsed in a mobile tank, recently used for spreading manure and was comatose on arrival at the hospital. He survived, but still suffers from a toxic/anoxic psychosyndrome. On site measurements showed high concentrations of hydrogen sulfide. The treatment is controversial and is discussed.
Sensitive enzyme-linked immunosorbent assay for measurement of autoantibodies to human thyroid peroxidase.
The development of a sensitive assay for detection of autoantibodies against one of the major thyroid antigens, thyroid peroxidase (TPO), is described. TPO was purified from human thyroid tissue by: (1) isolation of thyroid microsomes using homogenization and differential centrifugation, (2) solubilization of membrane proteins by Zwittergent 3-14, and (3) anion exchange liquid chromatography on a FPLC Mono Q column. Autoantibodies against TPO (TPO-Ab) were measured using an enzyme-linked immunosorbent assay (ELISA) with serum samples diluted 1:100. Standards containing 70, 7, 0.7, 0.02 and 0 U ml-1 TPO-Ab were employed (reference standard code 66/387 NIBSC, London, UK). The detection limit was 0.02 U ml-1 corresponding to 2 U ml-1 in undiluted serum. The inter- and intra-assay coefficients of variation were 8.6% and 5.3%. In 109 healthy control subjects TPO-Ab was found in 9 (8.3%), while 43 (97.7%) out of 44 patients with newly diagnosed untreated Graves' disease had detectable TPO-Ab in serum. All of 16 patients with newly diagnosed spontaneously developing primary hypothyroidism had circulating TPO-Ab (range 16-7000 U ml-1). The new assay is a valuable tool for evaluation of thyroid autoimmunity in individual patients and for studying the epidemiology of thyroid autoimmunity.
High-performance liquid chromatographic determination of creatinine.
A high-performance liquid chromatography (HPLC) method for creatinine has been developed. The method is based on ion-pair chromatography. The method is precise and easy to perform. Recoveries from enriched sera were from 98-105% with a mean of 100.5%. At 28 mumol l-1, 52 mumol l-1 and 487 mumol l-1 within-series standard deviations of 2 mumol l-1, 2 mumol l-1 and 10 mumol l-1, respectively were obtained. At 102 mumol l-1 among-series standard deviation of 6 mumol l-1 was obtained. Comparisons between HPLC and autoanalyser (Jaffé reaction) methods showed that the autoanalyser plasma and serum results, which are known to be sensitive to 'pseudocreatinines', varied between 93-217% of the HPLC results. Comparisons between HPLC, autoanalyser and enzymatic methods showed that the methods agree well for urine samples. The method presented appears suitable as a secondary reference method.
Xanthine and hypoxanthine in amniotic fluid during pregnancy.
Xanthine and hypoxanthine are indicators of cellular hypoxia. The purpose of our study was to establish a reference range for the concentrations of xanthine and hypoxanthine in amniotic fluid. Of a total of 38 included in the investigation, 27 pregnant women were found to have low values for xanthine (less than 1.2 mumol/l) and hypoxanthine (less than 0.4 mumol/l). To our knowledge, this is the first attempt to define a reference range for xanthine and hypoxanthine concentration in amniotic fluid during pregnancy.
[A case of intermittent hypermethioninemia as the cause of disagreeable body odour].
A physically and mentally healthy man aged 22 years was referred for biochemical investigation in a department for clinical biochemistry on account of disagreeable body odour. Ion-exchange chromatographic amino acid analysis revealed intermittent hypermethioninaemia. Dietary treatment with a methionine-poor diet solved the problem both subjectively and objectively. Amino-acidopathy should be borne in mind in cases of individuals with abnormal body odours.
Cod liver oil inhibits neutrophil and monocyte chemotaxis in healthy males.
Epidemiological evidence suggests a reduced rate of chronic inflammatory diseases and ischaemic heart disease in populations with a high consumption of fish. This has been ascribed to the high content in sea food of polyunsaturated fatty acids (PUFAs), belonging to the n - 3 family. We have studied neutrophil and monocyte chemotaxis in 12 healthy males before and after 6 weeks supplementation with cod liver oil, corresponding to 5.3 g n - 3 PUFAs daily. Neutrophil and monocyte chemotaxis were investigated using the under agarose technique with N-formyl-methionyl-leucyl-phenylalanine (N-FMLP) and autologous serum as chemoattractants. Neutrophil chemotaxis towards both chemoattractants and monocyte chemotaxis towards N-FMLP were significantly reduced after supplementation with cod liver oil.
99mTc-sucralfate scintigraphy in inflammatory bowel disease.
Technetium-99m-labeled albumin-sucralfate was orally administered to 11 patients (Crohn's disease, 8; ulcerative colitis, 3) and 3 healthy volunteers. Serial scintigraphy was performed, and scintigraphic interpretations were compared with radiographic and endoscopic findings in an open study. We were not able in any patient to relate the scintigraphic findings to the localizations of inflammatory bowel disease, nor could we distinguish the scans in the patients from the scans of the healthy volunteers. We conclude that 99mTc-albumin-sucralfate scintigraphy is of no value in the detection of inflammatory bowel disease.
Effects of intravenous radiographic contrast media on the blood pressure and on factors of the contact activation system in the rat.
Blood pressure (BP), plasma prekallikrein (PK), and the extent of activation of factor XII (XII-ACT) were studied after the intravenous injection into rats of dextran (Macrodex), the ionic radiographic contrast substance iodipamide (Biligrafin), or the non-ionic contrast substance iohexol (Omnipaque). After acetone activation plasma kallikrein was assayed as plasminogen activator, BAEe esterase or S-2302 amidase, and factor XIIa was assayed as kaolin-activated prekallikrein activator. Dextran induced a strong and lasting hypotension, preceded by significant lowerings in PK and XII-ACT. Iodipamide induced a rapid and dose dependent BP fall, no change in plasma PK, but a slightly reduced XII-ACT. Iohexol induced no significant alterations, neither in BP, nor in plasma parameters. Pretreatments of the rats with iodipamide abolished the dextran-induced reductions in PK and XII-ACT, and almost blocked the fall in BP. We conclude that the ionic contrast substance iodipamide is capable of blocking dextran shock in the rat by preventing an activation of the contact activating system in plasma.