SWI by 7T MR Imaging for the Microscopic Imaging Diagnosis of Astrocytic and Oligodendroglial Tumors

BACKGROUND AND PURPOSE

Despite advances in molecular imaging, preoperative diagnosis of astrocytomas and oligodendrogliomas can be challenging. In the present study, we assessed whether 7T SWI can be used to distinguish astrocytomas and oligodendrogliomas and whether malignant grading of gliomas is possible.

MATERIALS AND METHODS

7T SWI was performed on 21 patients with gliomas before surgery with optimization for sharp visualization of the corticomedullary junction. Scoring for cortical thickening and displacement of medullary vessels, characteristic of oligodendroglial tumors, and cortical tapering, characteristic of astrocytic tumors, was performed. Additionally, characteristics of malignancy, including thickening of the medullary veins, the presence of microbleeds, and/or necrosis were scored.

RESULTS

Scoring for oligodendroglial (highest possible score, +3) and astrocytic (lowest score possible, -3) characteristics yielded a significant difference between astrocytomas and oligodendrogliomas (mean, -1.93 versus +1.71, P < .01). Scoring for malignancy was significantly different among the World Health Organization grade II (n = 10), grade III (n = 4), and grade IV (n = 7) tumors (mean, 0.20 versus 1.38 versus 2.79). Cortical thickening was observed significantly more frequently in oligodendrogliomas (P < .02), with a sensitivity of 71.4% and specificity of 85.7%; observation of tapering of the cortex was higher in astrocytomas (P < .01) with a sensitivity of 85.7% and specificity of 100%.

CONCLUSIONS

Visualization of the corticomedullary junction by 7T SWI was useful in distinguishing astrocytomas and oligodendrogliomas. Observation of tapering of the cortex was most sensitive and specific for diagnosing astrocytomas. Reliably predicting malignant grade was also possible by 7T SWI.

Long-term survivors of primary central nervous system lymphoma

Objective

In this study, we provide long-term outcome data of patients with primary central nervous system lymphoma.

Methods

The long-term outcomes of PCNSL patients diagnosed between 1982 and 2006 were reviewed. Neurological late neurotoxicity symptoms, neuroradiological brain atrophy and leukoencephalopathy were evaluated. Surviving patients completed the Quality of Life Questionnaire-30 and Brain Cancer Module-20. The differences in overall survival were assessed using the Kaplan-Meier method and log-rank test. The differences between groups in terms of each investigated parameter were analyzed using the Wilcoxon signed-rank test.

Results

Among 112 PCNSL patients, there were 33 (29.4%) long-term (> 5 years) survivors. The median survival of all long-term survivors was 105.7 months; of these, 8 (7.1%) were alive at the latest follow-up, with a mean survival time of 170.2 months (range, 121.8–286.4). Clinical assessment revealed severe neurotoxicity in 14 patients (42.4%), moderate neurotoxicity in 5 (15.1%), and normal status in 14 (42.4%). Correlations were seen between the neuroradiological imaging score changes and neurocognitive condition (P=0.0001), neurocognitive condition and the whole brain irradiation dose (P=0.0004), and atrophy and the whole brain irradiation dose (P=0.0035).

Conclusions

A more severe clinical condition was found to be associated with increasing age and whole brain irradiation dose in long-term survivors with PCNSL.

Free nucleosides and bases in the hyperkeratotic epidermis

The metabolism of both free nucleosides and bases in hyperkeratosis induced by topical application of n-hexadecane on the epidermis of guinea pig was discussed, based on the technique of high-pressure liquid chromatography. The level of nucleosides and bases decreased in the hyperkeratotic stage of epidermis, in spite of the high concentration of nucleotides. The concentration of purine bases in the epidermis was under the virtual control of the salvage enzyme pathway and uric acid formation. The significant increase of salvage enzyme activity with phosphoribosylation was responsible for the expansion of the purine nucleotide pool in the hyperkeratotic epidermis. It was noted that the increased nucleotide pool plays a role as a source of cellular energy and a precursor of nucleic acid for epidermal proliferation.

High-pressure liquid chromatography of free nucleotide patterns in normal and abnormal keratinocytes

A method for analyzing free nucleotides in the epidermis of the guinea pig is presented. Free nucleotides were extracted by using a methylalethanol mixture, and the analysis was carried out by high-pressure liquid chromatography on a column of Lichrosorb-NH2 with a single buffer of potassium phosphate. The concentration of total free nucleotides in the epidermis is about 4 times greater than that in the liver, kidney, spleen, or intestinal epithelium.l The free nucleotide level is markedly elevated in the hyperkeratotic epidermis induced by n-hexadecane. The alternation of free nucleotides in hyperkeratotic epidermis is discussed in relation to nucleic acid content, DNase, disc-electrophoretic properties of DNase, and salvage pathway enzymatic activity. Significant increases in the enzyme activity of the salvage pathway and in neutral DNase were observed in the hyperkeratotic stage. However, the DNA content and acid DNase activity were decreased. It is suggested that the pool size of free nucleotides in the epidermis is affected by the salvage enzyme system.

The relationship between bite force and oral sensation during biting in molars

BACKGROUND

In prosthodontic treatment, the occlusal form should be designed such that bite force is applied at the position that has higher load-bearing capacity and is comfortable for the patient. The purpose of this study was to clarify the differences in bite force and occlusal sensation with different loading positions on the occlusal surface.

METHODS

Twelve healthy subjects were recruited for this study. Bite force and occlusal sensation were measured at five loading points on the upper and lower left first molars. Occlusal sensation was evaluated using a Visual Analogue Scale (VAS).

RESULTS

Bite forces on the lingual side of the upper first molar and the buccal side of the lower first molar were significantly higher and VAS scores were significantly lower, i.e. the subjects felt less discomfort during biting on the buccal side of the upper first molar and the lingual side of the lower first molar compared to the other side of each molar.

CONCLUSIONS

Loading on the occlusal surfaces of the functional cusps of the upper and lower first molars produces more load-bearing capacity and is more comfortable than loading on the non-functional cusps.

Antifungal activity of DNA-lipid complexes and DNA-lipid films againstCandida species

In this study amphiphilic lipids, DNA-lipid complexes, and DNA-lipid films were prepared, and their antifungal activity against Candida species was examined. The amphiphilic lipids were synthesized from a reaction of glycine or L-alanine with n-alkyl alcohol in the presence of p-toluene sulfonic acid. DNA-lipid complexes, which were prepared by the simple mixing of DNA and amphiphilic lipids, were insoluble in water. Self-standing, water-insoluble DNA-lipid films were prepared by casting the DNA-lipid complexes from a chloroform/ethanol solution. The antifungal activities of the lipids and DNA-lipid complexes against the Candida species were evaluated by minimum inhibitory concentrations (MICs); those of DNA-lipid films were evaluated by the disk diffusion method. The seven kinds of lipids, DNA-lipid complexes, and DNA-lipid films showed antifungal activity, and no differences were seen in the antifungal activities between glycine and L-alanine derivatives. The lipids, DNA-lipid complexes, and DNA-lipid films, which have shorter alkyl chain length in lipids, showed antifungal activity against all Candida species. However, the effect of antifungal activity against Candida species decreased with increased alkyl chain length in lipids. In this study, it was found that lipids, DNA-lipid complexes, and films with a decyl or dodecyl group exhibit more favorable antifungal activity.

Genotoxicity studies on dietary diacylglycerol (DAG) oil

Dietary diacylglycerol (DAG) oil is an edible oil enriched in DAG (more than 80%). A recent investigation indicated that DAG oil or its components may have beneficial effects on the prevention and management of obesity. We evaluated the genotoxic potential of DAG oil using standard genotoxicity tests. Bacterial reverse mutation assay (Ames test), the chromosomal aberration assay in cultured Chinese hamster lung cells (CHL/IU), and a bone marrow micronucleus assay in ICR CD mice were employed in the present study. In addition we have tested the possibility that genotoxic substances may be formed during cooking, heated DAG oil (HDG) was prepared by batch frying potato slices in the oil at 180 degrees C for 8 h/day for three consecutive days. Therefore, genotoxicity tests were also performed on HDG. Results obtained did not show any genotoxic effect on either unheated DAG oil (UDG) or HDG. We conclude that there are no safety concerns on the genotoxicity of DAG oil under the conditions for normal use.

Relation between the TIMI frame count and the degree of microvascular injury after primary coronary angioplasty in patients with acute anterior myocardial infarction

OBJECTIVE

To investigate the relation between thrombolysis in myocardial infarction (TIMI) frame count (TFC) and coronary blood flow velocity (CBFV) parameters reflecting the degree of microvascular injury in patients with acute myocardial infarction.

RESULTS

TFC and CBFV were measured after primary coronary angioplasty in 103 consecutive patients with their first anterior wall acute myocardial infarction. TFC correlated inversely with the averaged peak velocity (r = -0.43, p < 0.0001). However, TFC did not correlate significantly with diastolic deceleration time and with the averaged systolic peak velocity (r = -0.16, p = 0.22, and r = -0.23, p = 0.16, respectively). The patients were divided into two groups according to presence (35 patients) or absence (68 patients) of systolic flow reversal. There was no significant difference in TFC between the two groups (29 (16) v 25 (13), p = 0.20).

CONCLUSIONS

These findings suggest that the TFC reflects epicardial CBFV. However, it is not accurate enough to assess the degree of microvascular injury after primary coronary angioplasty.

Cardiac rescue of an infant with fulminant myocarditis using extracorporeal membrane oxygenation

A 7-month-old boy presented with fulminant myocarditis. He was in cardiac shock and cardiac dysfunction progressed despite aggressive support. Extracorporeal membrane oxygenation (ECMO) was applied for 8 days and he recovered with mild dilated cardiomyopathy.

Properties of Ca(2+)-dependent K+ channels of human gingival fibroblasts

Cells in the oral cavity are normally exposed to different temperatures. Ion transport systems are influenced by temperature in other tissues: In particular, changes in intracellular K+ ion can affect cell growth and synthesis of macromolecules. The purpose of this investigation was to identify K+ channels in human gingival fibroblast cells and analyze the effect of temperature on their K+ conduction properties. Ca(2+)-dependent K+ channels with a large conductance (125 pS in symmetrical K(+)-rich solutions) were identified in human gingival fibroblasts and studied by the patch-clamp technique. The open probability of the channels varied with membrane potential between +40 and -100 mV. When the bath temperature was decreased from 40 to 4 degrees C, channel conductance was reduced, but the mean open time of the channels was increased. The activation energies for the conductance and the reciprocal of the mean open time were estimated to be 9.1 and 22.9 kJ/mol, respectively. These values are lower than those reported for these and other types of channels in cells from other tissues. The open probability of the channels was nearly constant in the temperature range studied. These results suggest that the properties of Ca(2+)-dependent K+ channels of gingival fibroblasts remain relatively unchanged when the cells are exposed to a wide range of temperatures.

Hydroxyl radical generation and membrane fluidity of erythrocytes treated with lipopolysaccharide

The effect of lipopolysaccharide (LPS) and/or bile acids on rat erythrocyte membranes was studied in vitro. Addition of LPS isolated from E. coli (J5 mutant) into the erythrocyte resulted in the decrease of membrane fluidity as determined by spin labelling using electron paramagnetic resonance (EPR). This was accompanied by membrane fragility. It was found that hydroxyl radicals were generated from erythrocytes treated with LPS by using DMPO spin trapping. However, pretreatment of erythrocytes with taurine-conjugated bile acids was found to modify the membrane response induced by LPS. Taurocholic acid (TCA) and tauroursodeoxycholic acid (TUDCA) prevented the decrease of membrane fluidity induced by LPS, and, as a result, the membrane integrity was maintained although no significant changes were observed in the amount of hydroxyl radicals produced by LPS addition. However, taurochenodeoxycholic acid (TCDCA) exhibited little beneficial effect on the dynamic properties and the function of the erythrocyte membranes, although the hydroxyl radical declined markedly in the erythrocytes. Therefore, it is suggested that TCA and TUDCA have a protective effect against LPS-induced membrane fragility by modulating membrane fluidity.

Effect of alpha-tocopherol on high energy phosphate metabolite levels in rat heart by 31P-NMR using a Langendorff perfusion technique

To examine the action of alpha-tocopherol on high energy phosphate compounds, a 31P-NMR technique was applied to perfused Langendorff rat hearts. Rats were treated with tocopherol acetate (25 mg/kg body wt i.p.) for 7 consecutive days. On the 7th day, the rat hearts were isolated for the Langendorff experiment. After 30 min of global ischemia the NMR signals of creatine phosphate and ATP in myocardium disappeared, and then recovered slightly in the reperfusion following ischemia. However, in the tocopherol-treated rat hearts, the restoration of high energy phosphate compounds occurred quickly after the beginning of reperfusion, although there was no significant difference in the destruction of high energy phosphate compounds during the ischemia. The alpha-tocopherol level in the myocardium was severely depleted by ischemia-reperfusion. In the alpha-tocopherol-treated animals, the alpha-tocopherol level in myocardium was still significantly higher than the control level at the end of 30 min of global ischemia. The heart mitochondrial respiratory function was simultaneously protected against ischemia-reperfusion injury. The role of alpha-tocopherol was discussed as a radical scavenger and membrane stabilizer against oxygen stress.

Fatal encephalitis/encephalopathy in primary human herpesvirus-6 infection

An encephalitic illness with a fatal outcome occurred in a 9 month old girl with virologically confirmed exanthem subitum. Human herpes-virus-6 (HHV-6) DNA was found in the cerebrospinal fluid at the acute stage of the disease by the polymerase chain reaction, but the virus antigen was not detected in her brain tissue. This suggests that HHV-6-induced encephalitis/encephalopathy may be due to a non-infectious process.

Effect of vitamin E on cytotoxicity, DNA single strand breaks, chromosomal aberrations, and mutation in Chinese hamster V-79 cells exposed to ultraviolet-B light

The effect of pretreatment with vitamin E on cytotoxicity, DNA single strand breaks, and chromosomal aberrations as well as on mutation induced by ultraviolet-B light (UV-B) was investigated in Chinese hamster V-79 cells. Cellular pretreatment with non-toxic levels of 25 microM alpha-tocopherol succinate (vitamin E) for 24 h prior to exposure resulted in a 10-fold increase in cellular levels of alpha-tocopherol. Using a colony-forming assay, this pretreatment decreased the cytotoxicity of UV-B light. However, alkaline elution assays demonstrated that pretreatment with vitamin E did not affect the number of DNA single strand breaks caused by UV-B light. In addition, UV-B exposure produced a dose-dependent induction of chromosomal aberrations and mutations at the HGPRT locus, and neither of these actions of UV-B was influenced by pretreatment with the vitamin. These results suggest that vitamin E protects cells from UV-B-induced cytotoxicity, possibly through its ability to scavenge free radicals. The results also suggest that the extent of genotoxicity induced by UV-B light may not correlate directly with the cytotoxic action of this wavelength region in sunlight.

Identification of free and esterified hydroxyoctadecadienoates (HODEs) and linoleate-hydroxylating pathway in the epidermis of hairless mice

Epidermal homogenates of hairless mice contained a large amount of lipid material showing a single peak on reverse phase (RP)-high pressure liquid chromatography (HPLC) with a maximum absorbance of 234 nm, which was different in retention time from arachidonate metabolites such as 12-HETE, 15-HETE and 5-HETE. The production of this material was dependent on exogenous linoleate concentration, protein concentration and buffer pH. This material was identified to be a mixture of 13-HODE and 9-HODE on the basis of UV absorbance spectra, retention times on RP-HPLC, straight phase (SP)-HPLC, gas chromatography-mass spectrometry (GC/MS) and mass spectra obtained. As assessed by SP-HPLC after saponification, these two HODEs were found to exist primarily in esterified forms in the skin. Neither substance was produced following heat denaturation of the homogenate. These results indicate that 13- and 9-HODEs are produced from linoleate enzymatically at physiologically relevant levels in the epidermis of hairless mice. Thus, it is possible that these two materials may play some important role in pathophysiology of the skin.

Hydroxyl radical generation from heart mitochondria damaged by ischemia

The hydroxyl radicals are known to be a biologically active oxygen species. A remarkable enhancement of hydroxyl radical generation was observed in the mitochondria obtained from ischemic myocardium. The hydroxyl radicals are the primary reactive species leading to cellular damages, such as membrane damages, DNA damages, enzyme inactivation, protein denaturation and so forth. The origin of the hydroxyl radicals appeared in mitochondria was discussed.

Mechanism of lipid radical formation following exposure of epidermal homogenate to ultraviolet light

It has been suggested that oxygen free radicals are important mediators of lipid peroxidation in the epidermis exposed to ultraviolet (UV) light. However, it is not clear whether it is the superoxide anion radical (O2-.) or the hydroxyl radical (.OH) that plays the major role in producing the lipid radicals (L.) following UV exposure. In this study, we used electron spin resonance (ESR) technique with the spin trap (5,5-dimethyl-1-pyrroline-N-oxide [DMPO]) to determine which active oxygen species is involved in the UV-induced lipid radical formation (DMPO-L.: aN = 15.5 G, aH = 22.7 G). In the presence of superoxide dismutase or the metal-chelating agent, the DMPO-spin adduct spectrum of lipid radicals was reduced remarkably. The lipid radicals were formed by the hydroxyl radical generation system, not the superoxide anion generation system. The hydroxyl radical was found to be the direct active oxygen species that can generate lipid radicals as a result of .OH-mediated hydrogen atom abstraction. Superoxide anion radical stimulated the generation of hydroxyl radical via the iron-catalyzed reaction.

Generation of leukotrienes and hydroxyeicosatetraenoic acids in peritoneal macrophages of tumor-bearing mice

To examine the potential role of lipoxygenase products in the pathophysiology observed after experimental tumor implantation, we examined the generation of leukotrienes (LTs) and hydroxyeicosatetraenoic acids (HETEs) in peritoneal macrophages. C57BL/6 mice were given subcutaneous inoculations of B16 melanoma cells, and peritoneal macrophages were isolated various days after the inoculation. Macrophages were incubated for 1 h at 37 degrees C in serum-free RPM11640 containing 10 microM calcium ionophore A23187, 10 microM exogenous arachidonic acid (AA), 5 mM cysteine hydrochloride and 1 mM reduced glutathione. LTs and HETEs were separately extracted, passed through Sep-Pak cartridges, then identified and quantitated with a HPLC system using UV absorbance. The B16 melanoma-cell-treated/untreated macrophages were found to produce substantial amounts of 15-HETE, 12-HETE and 5-HETE and LTC4 by enzymatic mechanisms. Thus, when determined under various conditions, the production of HETEs was dependent on substrate-concentration, incubation-time and cell-number. The production of LTC4 was dependent on incubation-time and cell number but not substrate-concentration, indicating utilization of endogenous AA stores. Of these products, 12-HETE and LTC4 showed a significant increase on the fourth day after the tumor cell inoculation and returned to the control level by the 11th day after the same treatment. These results suggest that in vivo tumor cell implantation may induce a transient increase of 12-HETE and LTC4 production in macrophages.

Riboflavin deficiency caused by treatment with adriamycin

The present study was undertaken to determine whether administration of adriamycin causes the depletion of riboflavin content. Rats received intraperitoneal injections of adriamycin (4 mg per kg body weight) for 6 consecutive days. Urinary riboflavin excretion began to increase after 2 days of treatment with adriamycin. Erythrocyte FAD levels decreased gradually and plasma lipid peroxide contents increased markedly at the 6th day. The activity coefficient of erythrocyte glutathione reductase showed a significant increase before the decrease of flavin content and the elevation of lipid peroxide level. Therefore, the value of this coefficient obtained from erythrocyte appears to be a reliable index of riboflavin deficiency, particularly during the early stage.

Prevention of 4-pentenoic acid-induced liver injury in rats by 16,16-dimethyl PGE2

16,16-Dimethyl PGE2 (dmPGE2) is known to protect against cellular damage in various tissues. Histological and biochemical approaches were used to examine the effect of this prostaglandin on hepatocellular damage in an experimental Reye's syndrome model produced in rats by 4-pentenoic acid. Chronic intraperitoneal administration of 4-pentenoic acid induced an accumulation of fatty droplets throughout the hepatic lobules along with mitochondrial abnormalities including swelling, disappearance of christae, and heterogeneity of matrix. These abnormalities were more intense in the marginal zone and successively decreased nearer to the central vein. Such hepatic abnormalities were markedly reduced by the combined administration of dmPGE2 with 4-pentenoic acid. Biochemical examination confirmed that dmPGE2 was able to inhibit the accumulation of hepatic triglyceride seen after the treatment with 4-pentenoic acid alone. These results indicated that dmPGE2 can prevent characteristic hepatocellular damage in this experimental Reye's syndrome model, suggesting that the involvement of prostaglandins should be taken into account in discussing the etiology and management of this syndrome.

Non-dimer DNA damage in Chinese hamster V-79 cells exposed to ultraviolet-B light

To understand and characterize non-dimer DNA damage and cytotoxicity induced by ultraviolet-B light (UV-B, 290-320 nm), an alkaline elution technique for analysis of DNA damage was used on Chinese hamster V-79 cells. Ultraviolet-B exposure produced a dose-dependent induction of DNA single strand breaks and DNA-protein crosslinks; however, there was an absence of DNA-DNA interstrand crosslinks. Neither of these types of DNA damage were repaired within a a 24 h incubation of the cells following a single UV-B exposure; rather the damage increased. Using a colony forming assay, we found that UV-B exposure resulted in an increase of cytotoxicity in a dose-dependent fashion. In addition, UV-B exposure inhibited DNA and RNA synthesis. The role of non-dimer DNA damage in the cytotoxicity induced by UV-B is discussed.

Reduction of chromium(VI) in Chinese hamster V-79 cells

The cellular reduction of chromate(VI) was studied by electron spin resonance spectrometry. Incubation of Chinese hamster V-79 cells with Na2CrO4 resulted in the formation of both chromium(V) and chromium(III) complex in a manner dependent on time (30 min-2 h) and concentration (50-500 microM). Following removal of extracellular chromate, the level of chromium(V) complex decreased quickly during the first hour but more slowly for the next hour, whereas the level of chromium(III) remained unchanged, indicating that chromium(III) is the ultimate ion of this metal in cells. Alkaline elution studies demonstrated that treatment of cells with Na2CrO4 induced DNA single-strand breaks that decreased quickly and DNA-protein crosslinks that persisted for 2 h after removal of this metal. These results suggest that the cellular levels of chromium(V) and chromium(III) may be associated with the formation of DNA damage induced by chromium (VI).

Electron spin resonance studies on the mechanism of adriamycin-induced heart mitochondrial damages

Rats were given i.p. injections of Adriamycin (4 mg/kg body weight) for 6 consecutive days. Electron spin resonance spectrometry with spin labeling and a trapping technique was applied to heart mitochondria obtained from treated and control animals, in order to examine the physical response of heart mitochondrial membrane affected by Adriamycin. The Adriamycin treatment resulted in a decrease of membrane fluidity (and an increase in order parameter S), with concomitant dysfunction of respiratory responses. The generation of hydroxyl radicals from mitochondria was enhanced in the Adriamycin-treated group. In addition, superoxide dismutase activity in the mitochondrial matrix was found to decrease. The heart mitochondria of Adriamycin-treated animals contained a large amount of lipid peroxide. These results suggest that the enhancement of hydroxyl radical formation in mitochondria affected by Adriamycin is one of the factors involved in Adriamycin-induced cardiotoxicity.

Involvement of active oxygen in lipid peroxide radical reaction of epidermal homogenate following ultraviolet light exposure

To elucidate the radical mechanism of lipid peroxidation induced by ultraviolet light (UV) irradiation, an electron spin resonance (ESR) study was made on epidermal homogenate prepared from albino rat skin. The exposure of the homogenate to UV light resulted in an increase in lipid peroxide content, which was proportional to the time of UV exposure. Using ESR spin trapping (dimethyl-1-pyrroline-N-oxide, DMPO), the DMPO spin adduct spectrum of lipid radicals (L.) was measured following UV exposure (DMPO-L.:aN = 15.5 G, aH = 22.7 G), as was the spectrum of DMPO-hydroxyl radical (DMPO-OH, aN = aH = 15.5 G). In the presence of superoxide dismutase, the DMPO spin adduct spectrum of lipid radicals was found to be reduced remarkably. Therefore, it was shown that the generation of the lipid radicals partially involves superoxide anion radicals, in addition to hydroxyl radicals. In the ESR free-radical experiment, an ESR signal appeared at g = 2.0064 when the ESR tube filled with homogenate was exposed to UV light at -150 degrees C. The temperature-dependent change in the ESR free radical signal of homogenate exposed to UV light was observed at temperatures varying from -150 degrees C to room temperature. By using degassed samples, it was confirmed that oxygen is involved in the formation of the lipid peroxide radicals (LOO.) from the lipid radicals (L.).

Effect of ascorbic acid on DNA damage, cytotoxicity, glutathione reductase, and formation of paramagnetic chromium in Chinese hamster V-79 cells treated with sodium chromate(VI)

The effect of pretreatment with ascorbic acid (vitamin C) on chromate-induced DNA damage, cytotoxicity, and enzyme inhibition as well as on the cellular reduction of chromium(VI) was investigated using Chinese hamster V-79 cells. Cellular pretreatment with nontoxic levels of 1 mM ascorbic acid for 24 h prior to exposure resulted in a significant increase (1.7-fold) in cellular levels of this vitamin. Alkaline elution assays demonstrated that this pretreatment decreased cellular levels of Na2CrO4-induced alkali-labile sites while the numbers of DNA-protein crosslinks produced by chromate increased. In colony-forming assays, pretreatment with ascorbic acid enhanced the cytotoxicity of chromate. However, the inhibition of glutathione reductase attributed to Na2CrO4 was attenuated by this pretreatment. Under the same experimental condition, the uptake of chromate in pretreated cells was found to increase. ESR studies revealed that cellular pretreatment with ascorbic acid reduced the level of chromium(V) intermediate and increased the level of chromium(III) complex, indicating that cellular reduction of chromium(VI) to chromium(III) was accelerated by this vitamin. These results suggest that ascorbic acid decreases chromate-induced alkali-labile sites and chromium inhibition of glutathione reductase, but it enhances DNA-protein cross-links and cytotoxicity caused by this metal through its ability to directly reduce chromium(VI).

Arachidonate metabolism in bovine gallbladder mucosa

Incubation of [1-14C] arachidonicacid (AA) with homogenates of bovine gallbladder mucosa in the presence or absence of reduced glutathione (GSH) generated large amounts of products that cochromatographed with PGE2 and 6-keto-PGF1 alpha and small amounts of products comigrating with PGF2 alpha, TxB2 and PGD2. In the presence of GSH PGE2-like material was predominantly produced while in the absence of GSH 6-keto-PGF1 alpha-like material was a major product. Identification of PGE2 was performed by its chemical conversion with NaBH4 or KOH treatments and by gas chromatography-mass spectrometry. Identification of 6-keto-PGF1 alpha was confirmed by gas chromatography-mass spectrometry. Gallbladder muscle produced predominantly 6-keto-PGF1 alpha in the presence or absence of GSH. The total amount of cyclooxygenase products was approximately 2 times higher in the mucosa than in the muscle. These results indicate that bovine gallbladder mucosa contains higher levels of fatty acid cyclooxygenase, and PGE2 isomerase and PGI2 synthetase in a proportion different from that in the muscle.

O2-. spin trapping on cardiac submitochondrial particles isolated from ischemic and non-ischemic myocardium

An electron spin resonance (ESR) spin trapping technique was applied to determine the generation of superoxide anions in submitochondrial particles prepared from the ischemic heart. Ischemia was produced in the dog heart by occlusion of the circumflex coronary artery for 60 min. Mitochondria were prepared from ischemic and non-ischemic regions of myocardial tissue. To avoid the influence of superoxide dismutase located in the mitochondrial matrix, submitochondrial particles were utilized instead of whole mitochondria. Using the spin trap 5,5'-dimethyl-1-pyrroline-N-oxide (DMPO), the kind of active oxygen species generated from the mitochondrial electron transport system was determined from ESR spectrum. The relative signal intensity of the DMPO-superoxide anion adduct was found to be high in submitochondrial particles prepared from subsarcolemmal mitochondria obtained from the ischemic region, as compared with those from the non-ischemic region.

Effects of diethyl maleate (DEM), a glutathione depletor, on prostaglandin synthesis in the isolated perfused spleen of rabbits

To investigate the role of glutathione (GSH) on prostaglandin (PG) synthesis, isolated rabbit spleens were perfused with Tyrode's solution with or without the addition of diethyl maleate (DEM) in concentrations up to 1 mM. In the absence of DEM, PG synthesis was stimulated by the Ca2+ ionophore A23187 (20 nmole) or arachidonate (0.4 mumole). Prostaglandin (PG) E2 was a major product, accounting for 60-70% of the total cyclooxygenase products. Small amounts of PGF2 alpha, 6-keto-PGF1 alpha, PGD2 and thromboxane (Tx) B2 were also produced. When DEM was added to the perfusion medium, GSH content decreased dose-dependently with increasing DEM concentration. Lactate dehydrogenase activity was not detected in the venous effluent, indicating that DEM depleted intrasplenic GSH without causing any lysis of cellular membranes. A23187-induced production of PGs and of Tx was decreased with increasing concentrations of DEM up to 0.5 mM, whereas at 1.0 mM DEM, these products showed a tendency to increase as compared with levels at 0.5 mM DEM. However, this increase was only significant for TxB2, which returned to levels obtained in the absence of DEM. DEM 1 mM did not cause cell lysis, but it appears to perturb the cell membrane to a degree similar to that which occurs with stimulation of phospholipase A2. The small but significant increase of TxB2 with 1.0 mM DEM could be a result of decreased PGE2 isomerase activity. Perfusion with arachidonate gave virtually identical results: 1.0 mM DEM attenuated the production of all prostanoids except for TxB2 as compared with untreated controls. These results suggest that GSH contributes to the regulation and/or maintenance of PGs synthesis.

Distribution of superoxide dismutase activity in the epidermis: measurement with electron spin resonance spin trapping

Superoxide dismutase (SOD) activity in cow snout epidermis was determined by the method of electron spin resonance (ESR) using the 5, 5 dimethyl-1-pyrroline-N-oxide (DMPO) spin trapping agent. The procedure was found to be a reliable measurement as compared with the ordinary method using xanthine oxidase NBT. SOD activity was distributed through the whole epidermis. This activity was higher in the lower layer than in the upper and middle layers.

Influence of vitamin B2 on formation of chromium(V), alkali-labile sites, and lethality of sodium chromate(VI) in Chinese hamster V-79 cells

The effect of vitamin B2 on the cellular reduction and cytotoxicity of chromate(VI) was studied using Chinese hamster V-79 cells. Electron spin resonance studies showed that incubation of cells with Na2CrO4 resulted in the formation of both chromium(V) and chromium(III) complex and that cellular pretreatment with riboflavin (Vitamin B2) for 24 h prior to exposure increased the level of chromium(V) complex, but the level of chromium(III) remained unchanged. Analysis of flavin derivatives revealed that pretreatment with vitamin B2 increased free riboflavin without altering flavin adenine dinucleotide and flavin mononucleotide. In addition, the level of the flavoenzyme glutathione reductase, which is capable of reducing chromate, was unaffected by pretreatment with vitamin B2. However, treatment of cells with vitamin B2 and Na2CrO4 augmented the inhibition of glutathione reductase attributable to Na2CrO4 alone. Using a colony-forming assay, pretreatment with vitamin B2 resulted in a decrease of cytotoxicity after exposure to the lethal concentration of chromate (15 microM) but did not affect the cytotoxicity at sublethal concentration of this metal (5-7.5 microM). Alkaline elution studies demonstrated that Na2CrO4 induced alkali-labile sites in the DNA of cells in a concentration-dependent manner (5-15 microM) and pretreatment with vitamin B2 resulted in an increase of these DNA lesions at all concentrations of Na2CrO4. The results, showing that vitamin B2 enhances chromate-induced alkali-labile lesions and chromium inhibition of glutathione reductase, might be due to an increase of chromium(V) species, possibly through its ability to directly reduce chromium(VI). The results also suggest that the extent of DNA lesions induced by chromate may not correlate directly with the cytotoxic effects of this metal.

Stimulation of prostaglandin synthesis by cholecystokinin in primary culture cells of bovine gallbladder muscle

Primary culture cells derived from bovine gallbladder muscles synthesize PGE2 as a major cyclooxygenase product with a trace amount of 6-keto-PGF1 alpha-like material. The synthesis of PGE2 and total cyclooxygenase products was enhanced in response to cholecystokinin (CCK). In the presence of indomethacin the synthesis of PG was inhibited and the release of arachidonic acid (AA) in response to CCK was enhanced. These data suggest that CCK may stimulate the release of AA, probably by activating phospholipase A2/C, from membrane phospholipids in the gallbladder muscle.

Changes of electron spin resonance membrane fluidity in hexadecane-induced hyperproliferative epidermis

To study some of the biochemical and physical states of membranes associated with hyperproliferation, the effect of topical hexadecane on membrane fluidity in guinea pig epidermis was investigated by electron spin resonance using a 5-doxylstearic acid spin labeling agent. Guinea pig epidermal cells were separated into three regions of keratinocytes by Percoll density gradient centrifugation. Membrane fluidity and Na+, K+-ATPase activity were higher in hyperproliferating epidermal cells than in control. The free cholesterol content and the molar ratio of free cholesterol to phospholipid were found to decrease significantly. Also elevated levels of palmitic acid, stearic acid and omega-3 unsaturated fatty acid derived from phospholipid were observed. Normal differentiation of epidermis was found to be accompanied by a decrease in membrane fluidity, whereas a relatively high membrane fluidity was maintained in the hexadecane-induced hyperproliferation.

Detection of mitochondrial membrane damages in myocardial ischemia with ESR spin labeling technique

The ultrastructure and membrane fluidity were examined in two fractions of myocardial mitochondria isolated from the ischemic region following occlusion of the circumflex coronary artery of the dog. Transmission electron microscopy revealed that 60 min of ischemia produced more structural change in the subsarcolemmal mitochondria than in the intermyofibrillar mitochondria. Changes in the dynamic properties of the mitochondrial membranes were examined using the spin labeling technique with electron spin resonance (ESR). From the ESR spectra, the membrane fluidity of the subsarcolemmal mitochondria was found to decrease significantly after ischemic injury, whereas no difference was observed in intermyofibrillar mitochondria. In addition, a negative correlation between the increase of order parameter S and dysfunction of respiratory responses of subsarcolemmal mitochondria was found. These results suggest that the two fractions of mitochondria in the myocardium showed different responses to acute ischemic injury. The damage to mitochondrial membranes occurred during the period of ischemia.

Effect of vitamin E on survival, glutathione reductase and formation of chromium (V) in Chinese hamster V-79 cells treated with sodium chromate (VI)

The effect of vitamin E on cytotoxicity induced by Na2CrO4 was evaluated by colony-forming assay using Chinese hamster V-79 cells. Pre-treatment with alpha-tocopherol succinate (vitamin E) for 24 h prior to exposure to Na2CrO4 resulted in a marked decrease in the cytotoxicity caused by this compound. The reduction of chromate-induced cytotoxicity was observed at all concentrations of Na2CrO4 (5-15 microM), and the protective effect increased with higher concentrations of vitamin E (5-25 microM). The level of glutathione reductase activity, which is capable of reducing chromate, was not affected by cellular pre-treatment with vitamin E. However, Na2CrO4 decreased glutathione reductase activity in a concentration-dependent fashion (5-15 microM) and pretreatment with vitamin E resulted in a significant recovery of enzyme activity suppressed by Na2CrO4, suggesting that this enzyme inhibition is linked to the cytotoxicity of this metal. Electron spin resonance studies showed that a paramagnetic chromium (V) complex was formed in cells treated with Na2CrO4, and that cellular pre-treatment with vitamin E reduced the formation of this chromium (V) intermediate. These results indicate that vitamin E protects cells from chromate-induced cytotoxicity as well as from enzyme inhibition, and also suggest that Na2CrO4-induced cytotoxicity is mediated by the generation of a reactive intermediate.

Vitamin B2-enhancement of sodium chromate (VI)--Induced DNA single strand breaks: ESR study of the action of vitamin B2

Incubation of Chinese hamster V-79 cells with Na2CrO4 plus vitamin B2 resulted in an increase of Na2CrO4-induced DNA single strand breaks. Electron spin resonance (ESR) studies showed that vitamin B2 enhanced the formation of both hydroxyl radical and tetraperoxochromate (V) during the reaction of Na2CrO4 with hydrogen peroxide. Furthermore, ESR studies demonstrated that a chromium (V) species with a g value of 1.977 was formed by the reaction of Na2CrO4 with vitamin B2. These results indicate that chromate reacts with vitamin B2 to form chromium (V) species and also suggest that the enhancement effect of vitamin B2 on chromate-induced DNA single strand breaks may result from an increase of chromium (V)-related hydroxyl radical formation.

Effect of UV-B irradiation on release of arachidonic acid from B-16 melanoma cells

B-16 melanoma cells in culture were prelabeled with (3H)-arachidonate, and exposed to UV radiation. Immediately after irradiation the cells released labeled materials. This UV-stimulated release was inhibited by mepacrine (20 microM) and calmodulin inhibitor W7 (0.5 microM). To determine the influence of extracellular Ca2+ on the UV-stimulated release, experiments were made with media containing various concentrations of Ca2+. The release decreased significantly at lower Ca2+ concentrations. These results suggest that Ca2+-calmodulin-dependent phospholipase A2 was involved in UV-stimulated release of radiolabeled materials, possibly arachidonic acid and its metabolites, from the cells.

Membrane responses of B-16 melanoma cells to single exposure to ultraviolet light

Electron spin resonance spectroscopy using the spin probe (5-, 12- and 16-deoxylstearic acid) was employed to analyze the changes in membrane fluidity in B-16 melanoma cells following UV-B exposure. The UV exposure resulted in the immediate accumulation of lipid peroxide, being accompanied by a change in membrane fluidity. The 12-DSA is the most sensitive to the changes in membrane organization caused by UV light. Na+,K+-ATPase activity was regulated by a change in membrane fluidity. Following UV exposure, the release of the prelabeled arachidonic acid from the cells was observed immediately. Ca2+-dependent calmodulin-dependent phospholipase A2-like activity was involved in the UV-stimulated arachidonic acid release from phospholipid.

Action of the antileukemic and anti-HTLV-III (anti-HIV) agent avarol on the levels of superoxide dismutases and glutathione peroxidase activities in L5178y mouse lymphoma cells

The antileukemic and anti-HTLV-III (anti-HIV) agent avarol, a sesquiterpenoid hydroquinone, was determined to be converted into its corresponding quinone derivative avarone via the semiquinone free radical. Its g-value was 2.0047; after hyperfine splitting the energy levels revealed 16 isotropic Hfs. The redox reaction products were identified at the pH values 4.0, 7.0 and 12.0 and the overall reaction pathways were formulated. In vivo experiments with L5178y mouse lymphoma cells in the ascites of mice revealed that the cytostatic potencies of avarol and avarone cannot be augmented by lowering the pH value. Incubation studies with L5178y cells in vitro showed that the intracellular levels of superoxide dismutases (SODases) and of glutathione (GSH) peroxidase activities significantly change after avarol administration. While both the Mn-SODase and the Cu/Zn-SODase activities dropped significantly, the GSH peroxidase activity increased inversely. From these experiments we assume that the anti-tumour and the antiviral effects of avarol/avarone may be due to an increase, induced by the drug, of the intracellular concentrations of superoxide radicals.

Stimulation of polyadenosine diphosphoribose synthesis by DNA lesions induced by sodium chromate in Chinese hamster V-79 cells

Polyadenosine diphosphoribose [poly(ADP-ribose)] synthesis was stimulated by DNA lesions induced with Na2CrO4 and methyl methanesulfonate (MMS) in Chinese hamster V-79 cells. Na2CrO4 and MMS induced DNA single-strand breaks in a concentration-dependent manner; however, the breaks induced by Na2CrO4 were "protein associated" while those induced by MMS were not. MMS stimulated in a dose-dependent fashion the synthesis of poly(ADP-ribose) up to 6-fold above the control. Na2CrO4 also induced poly(ADP-ribose) synthesis, but the level of synthesis was less than 3-fold. Control experiments demonstrated that Na2CrO4 treatment of cells did not affect their ability to synthesize poly(ADP-ribose) in response to DNA damage. Treatment of cells with Na2CrO4 and MMS induced more poly(ADP-ribose) synthesis than each agent alone; however, whenever Na2CrO4 was utilized, the breaks required proteinase K to be detected. Following removal of extracellular chromate, the DNA strand breaks induced by 0.2 mM Na2CrO4 were repaired quickly during the first hour but more slowly for the next 3 h. In the presence of 3-aminobenzamide, an inhibitor of poly(ADP-ribose) synthesis, the repair of DNA breaks was reduced. These results suggest that DNA protein-associated breaks produced by Na2CrO4 were recognized by poly(ADP-ribose) polymerase and that there are differences in poly(ADP-ribose) synthesis in response to Na2CrO4 and MMS. The results also suggest that the repair of breaks induced by Na2CrO4 are associated with poly(ADP-ribose) synthesis, but perhaps because most of these breaks are protein associated, there is less stimulation of poly(ADP-ribose) synthesis.

Increased platelet thromboxane synthesis in renal glomerular diseases

Washed platelets were prepared from healthy children and adults, and patients with renal glomerular diseases, and incubated with [1-14C] arachidonate to measure the generation capacities of thromboxane (Tx) A2 and 12-hydroxyeicosatetraenoate (12-HETE). Tx generation capacity of platelets was significantly higher in patients with chronic glomerulonephritis, purpura nephritis and lupus nephritis than in healthy control subjects. There was no significant increase in minimal change nephrotic syndrome. 12-HETE showed a decreasing tendency in the glomerular diseases, which was restored to normal level by in vitro addition of indomethacin. Such increased Tx generation capacity of platelets may cause abnormal enhancement of platelet functions and conceivably constitute an aggravating factor of glomerular and microvascular damage in the affected kidney.

Changes of membrane fluidity and Na+,K+-ATPase activity during cellular differentiation in the guinea pig epidermis

The dynamic properties of plasma membrane in epidermal cells were determined by means of electron spin resonance using two kinds of doxyl stearic acid spin labeling agents: 5-DSA and 12-DSA. 5-DSA and 12-DSA are stearic acid analogues with a nitroxide radical ring at the 5th and 12th carbon positions, and these motions reflect molecular motion of lipid bilayer surrounding the hydrophilic region and the hydrophobic region, respectively. Guinea pig epidermal cells were separated into three regions of keratinocytes by Percoll density gradient centrifugation; the upper, middle, and lower epidermal cells. The order parameter S values for 5-DSA and 12-DSA incorporated into the isolated keratinocytes increased, suggesting a decrease in the plasma membrane fluidity, as cells approached the upper epidermal cell layer. The Na+,K+-ATPase activity as a plasma membrane-bound enzyme was determined in each epidermal cell region, and was found to decrease gradually as the cells approached the upper layer. Accordingly, the differentiation of epidermal cells in the keratinization process was found to be associated with a decrease in plasma membrane fluidity and with a decline of Na+,K+-ATPase activity.