Potentiation of anti-cancer drug activity at low intratumoral pH induced by the mitochondrial inhibitor m-iodobenzylguanidine (MIBG) and its analogue benzylguanidine (BG). (1/428)

Tumour-selective acidification is of potential interest for enhanced therapeutic gain of pH sensitive drugs. In this study, we investigated the feasibility of a tumour-selective reduction of the extracellular and intracellular pH and their effect on the tumour response of selected anti-cancer drugs. In an in vitro L1210 leukaemic cell model, we confirmed enhanced cytotoxicity of chlorambucil at low extracellular pH conditions. In contrast, the alkylating drugs melphalan and cisplatin, and bioreductive agents mitomycin C and its derivative EO9, required low intracellular pH conditions for enhanced activation. Furthermore, a strong and pH-independent synergism was observed between the pH-equilibrating drug nigericin and melphalan, of which the mechanism is unclear. In radiation-induced fibrosarcoma (RIF-1) tumour-bearing mice, the extracellular pH was reduced by the mitochondrial inhibitor m-iodobenzylguanidine (MIBG) or its analogue benzylguanidine (BG) plus glucose. To simultaneously reduce the intracellular pH, MIBG plus glucose were combined with the ionophore nigericin or the Na+/H+ exchanger inhibitor amiloride and the Na+-dependent HCO3-/Cl- exchanger inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS). Biochemical studies confirmed an effective reduction of the extracellular pH to approximately 6.2, and anti-tumour responses to the interventions indicated a simultaneous reduction of the intracellular pH below 6.6 for at least 3 h. Combined reduction of extra- and intracellular tumour pH with melphalan increased the tumour regrowth time to 200% of the pretreatment volume from 5.7 +/- 0.6 days for melphalan alone to 8.1 +/- 0.7 days with pH manipulation (P < 0.05). Mitomycin C related tumour growth delay was enhanced by the combined interventions from 3.8 +/- 0.5 to 5.2 +/- 0.5 days (P < 0.05), but only in tumours of relatively large sizes. The interventions were non-toxic alone or in combination with the anti-cancer drugs and did not affect melphalan biodistribution. In conclusion, we have developed non-toxic interventions for sustained and selective reduction of extra- and intracellular tumour pH which potentiated the tumour responses to selected anti-cancer drugs.  (+info)

Effect of obesity on red cell mass results. (2/428)

Measurement of red cell mass with isotope dilution remains an important diagnostic test in the evaluation of patients with suspected polycythemia vera (PCV). Results and reference ranges are typically expressed in units normalized for body weight (mL/kg). Obesity is common in polycythemic patients, and it is important to know how the various published normative ranges compare across a wide range of body weights. METHODS: We retrospectively reviewed 51 consecutive patients referred for red cell mass determination with 51Cr red blood cell dilution. Results were expressed in milliliters per kilogram (mL/kg) by using the actual patient weight and after adiposity adjustments using ideal body weight, body mass index (BMI) and combinations of height-weight, including body surface area. Results were classified as normal, elevated or PCV. RESULTS: There was a high prevalence of obesity in our population (28/51 [55%] with BMI > 27 kg/m2, BMI range 16.0-54.8 kg/m2). The method used to compensate for obesity had a dramatic effect on the derived red cell mass, the fraction of patients with elevated measurements and the fraction of patients meeting criteria for PCV. Concordance for categorization as normal, elevated or PCV by all methods was only 47.1%. CONCLUSION: Obesity is a common confounding factor in the interpretation of red cell mass measurements. Currently published reference ranges generate inconsistent results when extrapolated to obese patients. Further normative data on obese subjects are needed to determine which method (if any) is optimal.  (+info)

Role of antioxidant defenses against ethanol-induced damage in cultured rat gastric epithelial cells. (3/428)

Reactive oxygen species appears to be involved in the pathogenesis of ethanol-induced gastric mucosal injury in vivo. Because ingested ethanol diffuses into the gastric mucosa, targeting both epithelium and endothelium, in the present study we examined the possible protective effect of antioxidants on ethanol damage in gastric epithelial cells and endothelial cells in vitro. Cytotoxicity by ethanol was quantified by measuring 51Cr release. The effects of impairment of the glutathione redox cycle and of inhibition of cellular catalase were examined. The generation of superoxide was assessed by the reduction in cytochrome c. Ethanol caused a time- and dose-dependent increase in 51Cr release from epithelial cells. Incubation of cells with DL-buthionine-(S,R)-sulfoximine, while reducing glutathione production, dose dependently enhanced ethanol-induced injury. 1,3-Bis(chloroethyl)-nitrosourea, while inhibiting glutathione reductase activity, also sensitized cells to ethanol. In contrast, the inhibition of catalase with 3-amino-1,2, 4-triazole did not alter the susceptibility of epithelial cells to ethanol. Ethanol induced damage to endothelial cells in a similar fashion. In endothelial cells, however, neither impairment of the glutathione cycle nor inhibition of catalase influenced ethanol-induced damage. Epithelial cells, when exposed to ethanol, increased superoxide production as a function of ethanol concentration, whereas endothelial cells did not. The glutathione redox cycle, but not cellular catalase, plays a critical role in protecting epithelial cells against ethanol damage, whereas neither antioxidant seems to play a role in protection of endothelial cells. The distinct difference in antioxidant protection against ethanol appears to depend on the capability of each cell to produce cytotoxic oxygen species in response to ethanol exposure.  (+info)

High predictive value of red cell volume measurement using carboxy-haemoglobin in a rabbit model of haemorrhage. (4/428)

We have studied the accuracy of blood volume measurements using carbon monoxide (CO)-labelled haemoglobin (COHb) injection and dilution (CO method) by comparing changes in red cell volume (RCV) measured using the CO method and 51Cr-labelled erythrocyte dilution (51Cr method) in a haemorrhage and infusion model in rabbits. RCV was measured repeatedly using the CO method at four different blood volume stages (stages I-IV). At stages I and IV, RCV was measured simultaneously using the 51Cr method. In comparing the sum of the circulating RCV and extracted RCV (SUM RCV) using the CO method, the values were almost equal and there were no significant differences between the values at the four stages. In comparing circulating RCV measured using the CO method and the 51Cr method, mean difference between the two methods was 0.80 (SD 0.76) ml kg-1 or 4.7 (4.6)%, and a positive correlation was observed (r = 0.91). We conclude that the CO method can be used to measure blood volume during perioperative periods in infants because it avoids use of a radioactive tracer, is simple and repeated measurements are possible.  (+info)

Urokinase receptor (uPAR, CD87) is a platelet receptor important for kinetics and TNF-induced endothelial adhesion in mice. (5/428)

BACKGROUND: Urokinase plasminogen activator receptor (uPAR, CD87) is a widely distributed 55-kD, glycoprotein I-anchored surface receptor. On binding of its ligand uPA, it is known to increase leukocyte adhesion and traffic. Using genetically deficient mice, we explored the role of uPAR in platelet kinetics and TNF-induced platelet consumption. METHODS AND RESULTS: Anti-uPAR antibody stained platelets from normal (+/+) but not from uPAR-/- mice, as seen by fluorescence-activated cell sorter analysis. 51Cr-labeled platelets from uPAR-/- donors survived longer than those from +/+ donors when injected into a +/+ recipient. Intratracheal TNF injection induced thrombocytopenia and a platelet pulmonary localization, pronounced in +/+ but absent in uPAR-/- mice. Aprotinin, a plasmin inhibitor, decreased TNF-induced thrombocytopenia. TNF injection markedly reduced the survival and increased the pulmonary localization of 51Cr-labeled platelets from +/+ but not from uPAR-/- donors, indicating that it is the platelet uPAR that is critical for their response to TNF. As seen by electron microscopy, TNF injection increased the number of platelets and polymorphonuclear neutrophils (PMNs) in the alveolar capillaries of +/+ mice, whereas in uPAR-/- mice, platelet trapping was insignificant and PMN trapping was slightly reduced. Platelets within alveolar capillaries of TNF-injected mice were activated, as judged from their shape, and this was evident in +/+ but not in uPAR-/- mice. CONCLUSIONS: These results demonstrate for the first time the critical role of platelet uPAR for kinetics as well as for activation and endothelium adhesion associated with inflammation.  (+info)

Role of 5-lipoxygenase products in the local accumulation of neutrophils in dermal inflammation in the rabbit. (6/428)

Studies were undertaken to define the role of 5-lipoxygenase (5-LO) products and, in particular, of leukotriene (LT) B4 in the polymorphonuclear leukocyte (PMN) emigration process using a rabbit model of dermal inflammation. Our results show that i.v. administration to rabbits of MK-0591, a compound that inhibits LT biosynthesis in blood and tissues when administered in vivo, significantly reduced 51Cr-labeled PMN accumulation in response to intradermally injected chemotactic agonists, including IL-8, FMLP, C5a, and LTB4 itself. In addition, pretreatment of the labeled PMN with MK-0591 ex vivo before their injection in recipient animals was equally effective in reducing 51Cr-labeled PMN emigration to dermal inflammatory sites. These results support a role for de novo synthesis of 5-LO metabolites by PMN for their chemotactic response to inflammatory mediators. Other studies demonstrated that elevated intravascular concentration of LTB4 interferes with PMN extravasation inasmuch as a continuous i.v. infusion of LTB4, in the range of 5-300 ng/min/kg, dose-dependently inhibited extravascular PMN accumulation to acute inflammatory skin sites elicited by the chemoattractants LTB4, FMLP, C5a, and IL-8 and by TNF-alpha, IL-1beta, and LPS; such phenomena may constitute a natural protective mechanism from massive tissue invasion by activated PMN in specific pathologic conditions such as ischemia (and reperfusion). These studies demonstrate additional functions of 5-LO products in the regulation of PMN trafficking, distinct from the well-characterized chemotactic activity of LTB4 present in the extravascular compartment.  (+info)

Impaired autoregulation of the glomerular filtration rate in patients with nondiabetic nephropathies. (7/428)

BACKGROUND: The ability of the kidney to maintain constancy of the glomerular filtration rate (GFR) over a wide range of renal perfusion pressures is termed autoregulation. Defective autoregulation of GFR has been demonstrated in diabetic nephropathy. Whether this is also the case in patients with nondiabetic nephropathies is not known. METHODS: We investigated the effect of acute lowering of blood pressure (BP) on GFR in 16 (8 males and 8 females) albuminuric subjects suffering from different nondiabetic nephropathies and in 14 (7 males and 7 females) controls matched with respect to sex, age, BP, and baseline GFR. The subjects received in random order an intravenous injection of either clonidine (150 to 225 microg) or saline (0.154 mmol/liter) within two weeks. We measured GFR ([51Cr]-EDTA), albuminuria (enzyme-linked immunosorbent assay; ELISA), and BP (Takeda TM-2420). RESULTS: Clonidine induced similar reductions in mean arterial BP 17 (2) versus 19 (2) mm Hg [mean (SE)] in patients with nephropathy and in controls, respectively. GFR diminished in average from 89 (6) to 82 (5) ml/min/1.73 m2 (P < 0.05), and albuminuria declined from a geometric mean of 1218 (antilog SE 1.3) microg/min to 925 (1.3) in the patients with nondiabetic nephropathies (P < 0.05), whereas these variables remained unchanged in the control group. The mean difference between changes in GFR (95% confidence interval) between the nondiabetic macroalbuminuric and control subjects was 6.1 (-0.03 to 12.21) ml/min/1.73 m2 (P = 0.051). CONCLUSION: Our study suggests that albuminuric patients with nondiabetic nephropathies frequently suffer from impaired autoregulation of GFR.  (+info)

Injurious effect of Helicobacter pylori culture fluid to gastroduodenal mucosa, and its detoxification by sucralfate in the rat. (8/428)

BACKGROUND: Helicobacter pylori plays an important role in the pathogenesis of peptic ulcer. Although several cytotoxins related to H. pylori have been reported, their effects on gastroduodenal mucosa have not been well evaluated in vivo. AIM: To investigate the effects of the combination of acid and toxic substances derived from H. pylori on gastroduodenal mucosa, and to observe the effect of sucralfate on such factors in the rat. METHODS: Male Sprague-Dawley rats were fasted overnight and anaesthetized. The pylorus was ligated, and a double-lumen cannula was inserted into the forestomach for gastric luminal perfusion. In other animals, a cannula was inserted to perfuse the proximal duodenum. 51Cr-EDTA was administered intravenously and mucosal integrity was monitored by measuring the blood-to-lumen 51Cr-EDTA clearance. After 72 h of culture of H. pylori (NCTC11637 and Sydney strain 1), Brucella broth containing 3% FBS was filtered to remove the bacteria (supernate of H. pylori culture fluid; HPsup). HPsup was acidified (pH=2.0) with HCl, and tested for its injurious action on gastric or duodenal mucosa by luminal perfusion. HPsup was incubated with sucralfate for 30 min. The supernate was collected by centrifugation and the pH was readjusted to 2.0. This sucralfate-treated HPsup was used to test the effect of sucralfate against H. pylori-related mucosal injurious factors. RESULTS: Non-acidified and acidified HPsup did not cause any detectable injury to the gastric mucosa. Non-acidified HPsup did not cause injury in the duodenal mucosa. However, acidified HPsup induced a significantly greater increase in 51Cr-EDTA clearance and greater histological damage than in controls. Sucralfate completely reversed this. CONCLUSION: These results suggest that an H. pylori-related toxic substance may aggravate duodenal acid injury by acting on luminal surfaces, and that the detoxification of this substance by sucralfate may contribute to its anti-ulcer action.  (+info)

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