Free Radical Intensity Research Articles

Sulfur-Promoted Degradation of Polyethylene/Polypropylene Detected by Electron Spin Resonance Spectroscopy

In situ electron spin resonance (ESR) spectroscopy is employed to investigate the thermal and catalytic degradation of a sample of commingled plastics (CP) containing about 95% polyethylene and 5% polypropylene. The materials tested include elemental sulfur (S), NiMo/Al2O3, and zeolite HZSM-5 for temperatures between ambient and 450 °C and pressures up to 500 psig of H2. The depolymerization temperature Td of CP, where an ESR signal is first observed, is about 360 °C thermally. With 1 wt % loading of CP with S, Td is reduced to about 250 °C. With 10 wt % S plus 10 wt % NiMo/Al2O3, Td is further reduced to about 230 °C and the free radical intensity N is reduced considerably compared to the CP + S case. HZSM-5 does not affect the Td of CP, but N is reduced considerably and with increase in temperature, N decreases, similar to the NiMo/Al2O3 case. These results, along with the observed increase in the ESR line width for the HZSM-5 and NiMo/Al2O3 cases, suggest capping of the free radicals by hydrogenation. ...

Effects of hydrogen pressure and temperature on free radicals produced in coal-tire coprocessing

In-situ ESR (Electron spin resonance) spectroscopy of free radicals is used to investigate the coprocessing of Blind Canyon coal with Michelin tire rubber for temperatures up to 480°C and under H 2 and argon pressures up to 1000 psig. Comparing the free radical intensities of the coal and the tire alone with those obtained for the 1:1 coal-tire mixtures, determined under 500 and 1000 psig of H 2 and under 1000 psig of inert argon, the following observations are made. First, a strong synergism between the coal and the tire polymer is indicated, as the intensity of the ESR-active free radicals in the coal-tire mixture under H 2 pressure are enhanced severalfold beginning at ≈ 200°C and peaking near 350°C. Second, increasing the H 2 pressure from 500 to 1000 psig reduces the free radical intensity, most likely because of enhanced hydrogenation. Third, the tire polymer gives a weak ESR-active signal whose characteristics change dramatically between 140°C and 200°C, indicating a phase change in the tire material. The synergistic effect observed here is consistent with the reported improved yields in direct liquefaction experiments using coal-tire mixtures.

Alkoxyl Radical Generation Following Nitric Oxide Synthase Inhibition 179

Background: Previous studies suggest that peroxynitrite is a mediator of lipid peroxidation. Hypothesis: Nitric oxide (NO) synthase inhibition by Nω-nitro-L-arginine (NNLA) will result in decreased peroxynitrite, leading to decreased alkoxyl radical, an index of lipid peroxidation during cerebral hypoxia. Subjects: 20 piglets Vn: vehicle, normoxia; Vh: vehicle, hypoxia; Nn: NNLA (40 mg/Kg), normoxia and Nh: NNLA, hypoxia. (n=5, each). Method: Tissue hypoxia was documented by measuring levels of ATP and phosphocreatine. Free radicals, trapped with PBN were measured by electron spin resonance spectroscopy (ESR). Signal characteristics were compared with chemically produced alkoxyl and hydroxyl radical. Results: Hyperfine splitting constant (Hfsc) of brain sample (αN=13.5-13.8 G, αH=2.1-2.3 G) were closely identical to reported Hfsc of alkoxyl and hydroxyl radical. The alkoxyl radical(αN=13.7 G, αH=2.2 G) was identical to those observed in hypoxic brain. Hypoxic brain tissue addition to the hydroxyl radical generating system decreased the signal by 63%, and increased signal 2500% for alkoxyl radical. Free radical intensity in Vn, Vh, Nn and Nh was 11.6 ± 4.4, 27.7± 18.8, 15.3 ± 6.5, and 11.6 ± 2.0, respectively. Free radical production was increased in Vh vs Vn and Nn (p<0.05). NNLA reduced predominantly alkoxyl radical in Nh vs Vh (p<0.05).Conclusion: Decreased generation of alkoxyl radical by NNLA suggests that peroxynitrite is a mediator of lipid peroxidation during hypoxia and NO is a limiting factor. (By NIH-HD-20337)

DOSE-DEPENDENT EFFECT OF ALLOPURINOL ON FREE RADICAL PRODUCTION DURING CEREBRAL HYPOXIA IN NEWBORN PIGLETS. ▴ 413

Previous studies have shown that allopurinol, a xanthine oxidase inhibitor and free radical scavenger, has a neuroprotective effect during hypoxia-ischemia. The present study tests the hypothesis that allopurinol has a dose-dependent effect on the hypoxia-induced generation of free radicals in the cerebral cortex of newborn piglets. Studies were performed on 15 piglets divided into 6 groups. Group 1 (control n=5) pretreated with saline and Groups 2-6 (n=2 each) pretreated with allopurinol at doses of 10, 20, 50, 100 and 200 mg/kg IV respectively. Hypoxia was induced by lowering the FiO2 to 5-7% for 1 hr to achieve a PaO2 of 18-20 mmHg. Cortical biopsies were obtained via cranial windows and tissue homogenized in 100 mMα-phenyl-N-tert-butyl-nitrone (PBN). PBN spin adducts were extracted in a 2:1 mixture of chloroform:methanol and electron spin resonance spectroscopy performed. Signal height (intensity) of spectrum divided by tissue weight was expressed as mm/g tissue. Brain tissue ATP and phosphocreatine (PCr) concentrations were used to determine cellular energy metabolism. Tissue levels of allopurinol were measured by HPLC and increased linearly with drug dose. Free radical intensity in Group 1 was 387±16 mm/g tissue(mean±S.E.). Groups 2-6 showed a linear decrease in free radical intensity with values approaching zero in the groups receiving 100 and 200 mg/kg of allopurinol (p<0.01). ATP concentrations (μmole/g tissue) increased linearly from 1.09±0.55 in Group 1 to 5.02±0.45 in the 200 mg/kg group (p<0.01). PCr concentrations (μmol/g brain) increased linearly from 0.19±0.03 in Group 1 to 1.10±0.29 in the 200 mg/kg group (p<0.01). The data show that administration of allopurinol decreases free radical production and preserves high energy phosphate compounds during hypoxia in a dose-dependent menner. We speculate that allopurinol reduces free radical production by inhibiting xanthine oxidase and scavenging free radicals and may play a direct neuromodulatory role in reducing excitotoxicity during hypoxia. (NIH-HD-20337, MOD-#6-FY94-0135).

NITRIC OXIDE SYNTHASE INHIBITION ON FREE RADICAL GENERATION DURING CEREBRAL HYPOXIA IN NEWBORN PIGLETS. ▴ 1389

Previous studies in vitro have shown that nitric oxide (NO) reacts with superoxide anion to form a strong oxidant, peroxinitrite, that can cause lipid peroxidation. The present study tests the hypothesis that inhibition of nitric oxide synthase by N-omega-nitro-L-arginine (NNLA) will result in decreased free radical generation and brain cell membrane lipid peroxidation during hypoxia in vivo. Twenty anesthetized, ventilated piglets were divided into 4 groups: Vn: vehicle (pH adjusted saline), normoxia; Vh: vehicle, hypoxia: Nn: NNLA, normoxia and Nh: NNLA, hypoxia. Vehicle and NNLA treated groups received 40 mg/Kg NNLA or its vehicle, respectively. Hypoxia induced with FiO2 0.07 for 60 min resulted in PaO2 18-20 mmHg, and documented biochemically by decreased ATP and phosphocreatine. Cerebral cortex was homogenized inα-phenyl-N-tert-butylnitrone (PBN). The PBN adducts were extracted in toluene and electron spin resonance spectroscopy (ESR) performed. Signal height (intensity) of spectrum divided by tissue weight is expressed in mm/g tissue. The character of the spin adduct signal was similar to that from the chemically produced alkoxyl radical. Free radical intensity in groups Vn. Vh. Nn and Nh was 11.6 ± 4.4, 27.7 ± 18.8, 15.3 ± 6.5, and 11.6 ± 2.0, respectively. Lipid peroxidation products (conjugated dienes) in groups Vn, Vh, Nn and Nh were 15 ± 34, 149 ± 46, 53± 55, and 99 ± 29 nmole/g brain, respectively. The results show that free radical production and lipid peroxidation products were increased in Vh compared with Vn and Nn (p<0.05). However, administration of NNLA significantly reduced the formation of predominantly alkoxyl radicals in the hypoxic brain (p<0.05) and reduced lipid peroxidation products. These data suggest that NO is a limiting factor in the reaction of peroxinitrite-mediated lipid peroxidation, presumably by the fact that NOS blockade directly inhibit peroxinitrite formation by reducing the one reactant, NO. (Funded by NIH20337, MOD #94-0135, UCPR-506-93)

EFFECT OF ALLOPURINOL ON FREE RADICAL FORMATION DURING CEREBRAL HYPOXIA IN NEWBORN PIGLETS. ▴ 247

Previous studies have shown that free radical production is increased during cerebral hypoxia in newborn piglets. The present study tests the hypothesis that the xanthine oxidase pathway is a significant source of free radical production during cerebral hypoxia in newborn piglets. Studies were performed in 15 anesthetized, ventilated piglets divided into 2 groups - 7 saline pretreated (Hx) and 8 pretreated with 20 mg/kg IV allopurinol, a xanthine oxidase inhibitor (All-Hx). Piglets were exposed to an FiO2 of 5-7% for 1 hr to achieve a PaO2 of 18-20 mmHg. Cortical biopsies were obtained via cranial windows and homogenized in 100 mMα-phenyl-N-tert-butyl-nitrone (PBN). PBN adducts were extracted in a 2:1 mixture of chloroform:methanol and electron spin resonance spectroscopy performed. Signal height (intensity) of spectrum divided by tissue weight was expressed as mm/g tissue. Brain tissue ATP and phosphocreatine (PCr) concentrations were determined to document cellular energy `metabolism. Conjugated dienes (CD) were determined as an index of lipid peroxidation. Free radical intensity (mm/g brain) was lower in the All-Hx (161±71, mean±S.E.) than the Hx group (387±16) p<0.05. ATP concentrations were higher in the All-Hx than the Hx group (2.2±0.6 vs. 1.1±0.3 μmol/g brain) p<0.05 as were PCr concentrations(0.55±0.14 vs. 0.19±0.03 μmol/g brain) p<0.05. There was no difference in CD levels between the two groups (0.19±0.09 All-Hx vs. 0.19±0.09 nmol/g brain Hx). Results demonstrate that administration of allopurinol prior to hypoxia significantly decreases free radical production and preserves high energy phosphates in the newborn piglet brain during hypoxia. We speculate that the xanthine oxidase pathway is a significant source of free radical generation in the newborn brain during hypoxia and that allopurinol may attenuate free radical production and neuronal injury.(NIH-HD20337, MOD 6-FY94-0135, UCPR 506-93).

ろ胞性歯嚢胞の病態（ＩＩ） 特に，小児ろ胞性歯嚢胞の成因について

The follicular dental cyst (FDC) was defined as “a cyst arising by separation of the follicle from around the crown of an unerupted tooth within the jaws”. But, what causes the development of follicular dental cysts around some unerupted teeth is unknown. A few works reported that it occurred most frequently in mandibular second premolars and mentioned the possibility of injury to the permanent tooth dental germ by endodontic treatment of deciduous teeth in childhood.To elucidate the pathogenesis of FDC, the authors investigated 11 cases of FDC in children with special regard to the clinical and radiographic findings and to the inflammatory changes of cyst fluids by biochemical analysis, including the studies on the generation of superoxide (O2-), SOD activity, free radicals and leukotorienes in cyst fluids.Clinical and radiographic findings revealed that the root apex of pulp-treated deciduous teeth contacted with cyst walls in 8 cases. Anaerobic bacteria were identified in 8 cases. Neutrophils separated from cyst fluid showed the same O2-production ability as those separated from peripheral blood of patients. SOD activity and free radical intensity of cyst fluid varied with the clinical findings of inflammation. Leukotorienes, migration mediator of leukocytes, were detected by HPLC in cyst fluid. Therefore, it was useful for improving inflammatory symptoms to treat FDC with the solvent of radical scavengers replacing the cyst fluid.These results suggested that the periapical lesion of a deciduous tooth mainly caused the pathogenesis and enlargement of the follicular dental cyst in children.

Free Radicals in Cellulose Fibers Treated with Low Temperature Plasma

Cellulose fibers such as cotton, linen, viscose rayon, and polynosic fibers were treated with low temperature plasmas of O2, N2, H2, Ar, CO, CH4, and CF4. For comparison wool, silk, nylon 6, and poly ( ethylene terephthalate ) (PET) were also subjected to the plasma treatments. The relative free-radical intensity of the plasma-treated fibers was measured by means of ESR spectroscopy. The free radicals in the fibers treated in the plasmas increased in the following order: cotton &gt; wool &gt; silk &gt; nylon 6 ≃ PET. cotton &gt; linen &gt; mercerized cotton &gt; polynosic fibers ≃ viscose rayon, and CF4 &gt; CO &gt; H2 &gt; Ar &gt; CH4 &gt; N2 ≃ O2. The natural fibers, in particular cotton and linen, showed larger free-radical intensity than the regenerated cellulose and the synthetic fibers. The free-radical intensity of the plasma-treated fibers depended considerably on the plasma characteristics and the fine structure of the fibers as well as their chemical constitution.

Treatment of jaw cysts with an irrigational method (II): The effect on the nature of cyst walls and surrounding bone

Cysts in jaws are generally excised by Partsch II when they are small. When they are large, they are excised by Partsch I to form a paranasal sinus in an oral cavity, or by an operation based on Caldwell-Luc's method to form it from nostrils, as Partsch II forms dead space after the operation and the cyst increases by the pressure of intracystic fluid. However, with Partsch I, the bone needs many days to regenerate, and since a surgical ciliated cyst of the maxilla is often formed after an operation of the maxillary sinus, Partsch I is not necessarily a good method. Therefore, in order to control cyst inflammation, the irrigation of cyst cavities was repeated, as it is held that prostaglandin-like (PG-like) substances are generated in the cyst walls when a cyst is inflamed by bacterial infection; prostaglandin E 2 (PGE 2) especially acts on the resorption of bone and enlarges the cyst. As a result of repeated irrigations, infection of the cyst cavities disappeared simultaneously with decreasing the pressure of intracystic cavities, the values of thiobarbituric acid, Prostaglandin E, Prostaglandin F 2α (TBA, PGE, PGF 2α), and the free radical intensity at g=2.003 decreased. The bone regenerated around the cyst walls, and finally the cyst diminished in size. In the case of the viscous cyst fluids, a solution containing hyaluronidase enabled complete disappearance. It would be better to apply Partsch II after the cyst has become smaller through irrigation. After the irrigational method, irregular formation and tendency toward malignancy could be found in none of the cyst wall cells.

The factor in the jaw cyst enlargement

It is said that cysts in jaws enlarge when the intracystic fluid pressure in the cyst cavities increases, and the jaw bone is absorbed. The author investigated that LPO and the prostaglandin-like substances generated in the cyst fluids, damaged the cyst walls, that the value of phospholipid in the cyst walls decreased, that the values of TBA, free radical intensity, PGE, PGF2αincreased, and that the calcification of the jaw bones around the cysts decreased. These facts indicate that PGE generated in the cyst wall when a cyst is infected, acts on the resorption of the jaw bone. It can be regarded that the factor in the jaw cyst enlargement is PGE2.