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J R Zhang

Publications and source records attributed to J R Zhang.

At least 37 records · Page 2Linked to original sources
PubMed1996

Direct measurement of lipid hydroperoxides in iron-dependent spinal neuronal injury.

The relationship between iron-dependent fetal mouse spinal cord neuron injury and the generation of endogenous lipid hydroperoxides (LOOHs) has been investigated. Cultured spinal cord neurons were incubated with ferrous iron (3-200 microM). Cell viability was measured in terms of the uptake of alpha-[methyl-3H]aminoisobutyric acid ([3H]AIB). Both endogenously and iron-generated LOOH, i.e., free fatty acid hydroperoxide (FFAOOH), phosphatidylethanolamine hydroperoxide (PEOOH), and phosphatidylcholine hydroperoxide (PCOOH), were measured directly by an HPLC-chemiluminescence (HPLC-CL) assay. The FFAOOH, PEOOH, and PCOOH levels in neurons incubated with 200 microM Fe2+ for 40 min were, respectively, 22-, 158-, and sevenfold higher than those in non-iron-exposed cultures, demonstrating that phosphatidylethanolamine (PE) was most sensitive to peroxidation. The dose-response and time course of Fe(2+)-induced generation of these LOOHs were also established. In both experiments, the LOOH levels were correlated directly with loss of neuronal viability, suggesting strongly a direct relationship between lipid peroxidation and cell injury. On examination of the time course of the LOOH generation, an immediate increase in PEOOH and PCOOH levels with only 30 s of Fe2+ incubation was observed. In contrast, a lag phase in the increase in FFAOOH level (2 min after Fe2+ addition) suggested a delay in the activation of phospholipase A2 (PLA2) required for the hydrolysis and generation of FFAOOH. This culture system provides an excellent model for screening antioxidant neuroprotective compounds with regard to their ability to protect against iron-dependent peroxidative injury and the relationship of the neuroprotection to inhibition of lipid peroxidation and/or PLA2.

Animals↗
PubMed1995

HPLC-chemiluminescence and thermospray LC/MS study of hydroperoxides generated from phosphatidylcholine.

Lipid hydroperoxides generated from phosphatidylcholine (PC) by two commonly employed phosphatidylcholine hydroperoxide (PCOOH) generation methods were examined by HPLC-chemiluminescence (CL) and thermospray LC/MS assay. This HPLC-CL assay is specific for hydroperoxides. In the HPLC-CL chromatograms, a major peak eluted at 4.7 min for the samples generated by the photooxidation of PC in the presence of methylene blue. The direct LC/MS analysis of the hydroperoxides contained in this peak determined that the hydroperoxides are mono- and di-PCOOH. Quantitation showed that over 90% of the hydroperoxides generated by photooxidation are PCOOH. In contrast, a different major peak appeared at 3.7 min for the hydroperoxides generated by the incubation of PC with the azo compound AMVN. We determined by LC/MS analysis that the hydroperoxides contained in this peak were not equivalent to either mono- or di-PCOOH. Indeed, 70%-95% of the hydroperoxides generated by AMVN incubation were not PCOOH, but rather a large portion were AMVN-derived hydroperoxides. The hydroperoxides contained in the 4.7-min peak (i.e., PCOOH) were preferentially responsive to cytochrome c-luminol CL cocktail (about 100-fold more responsive than the hydroperoxides in the 3.7-min peak), whereas the hydroperoxides in the 3.7-min peak (including AMVN-derived hydroperoxide) were preferentially responsive to microperoxidase-isoluminol CL cocktail (about 20-fold more responsive than the PCOOH), suggesting a substrate specificity for the CL cocktail.

Chromatography, High Pressure Liquid↗
PubMed1995

[Role of the lateroventral periolivary nucleus in the central chemoreception of respiration in rats].

Using the methods of microinjection, microiontophoresis, electrolytic destruction and electric stimulation, the present work was undertaken to investigate whether the lateroventral periolivary nucleus (LVPO) might play a role in the central mechanism of chemoreception on respiration. Experiments were performed on 38 chloralose-urethane anesthetized Sprague-Dawley rats. The results were as follows: (1) Bilateral microinjection of acidified mock CSF into the LVPO region, evoked an enhancement in respiratory activities. (2) Microiontophoretic application of H+ caused mainly excitatory effects on the spontaneously discharging units in LVPO region, and some of the excitatory units were also responsible to microinjection of acidified mock CSF to the ventrolateral medullary surface. (3) After the electrolytic destruction of bilateral LVPO region in carotid body denervated rats, respiratory response to inhaled CO2 was attenuated significantly. (4) Electric stimulation of LVPO region caused an increase in discharging frequency of some units in the NTS and NRA regions. The above results indicate that LVPO plays a significant role in the central mechanism of chemoreception.

Animals↗
PubMed1995

[Neural structural relations between the chemosensitive areas of the ventrolateral medulllary surface and the medullary nuclei in rats].

Experiments were done on 30 chloralose-urethane anesthetized Sprague-Dawley strain rats. The ventrolateral medullary surface was exposed and a small millipore filter paper soaked with horseradish peroxidase (HRP) was applied locally to different parts of the underlying chemosensitive areas separately, trying to identify location of the HRP-stained cells. (1) After HRP application to the rostral area (n = 10), quite a number of labelled cells were distributed at the ventrolateral part of the nucleus of trapezoid body (Tz), the lateroventral periolivary nucleus (LVPO) and the retrotrapezoid nucleus (NRT). (2) After HRP application to the caudal area (n = 10), HRP labelled cells were mainly located at the lateral reticular nucleus (LRt) and the ventral part of at the lateral paragigantocellular nucleus LPGi. (3) After HRP application to the intermediate area (n = 6), only 8 HRP labelled cells were observed at the (LPGi) in 6 rats. (4) After HRP application to the control area (n = 4), only 6 HRP labelled cells were found at the rostral ventrolateral reticular nucleus (RVL). The above findings demonstrated the existence of the neural structural relations between the chemosensitive areas of the ventrolateral medullary surface and Tz, LVPO, NRT, LPGi, LRt, which supports that all these nuclei might participate in the central chemoreception of respiration.

Animals↗
PubMed1994

Age-related phospholipid hydroperoxide levels in gerbil brain measured by HPLC-chemiluminescence and their relation to hydroxyl radical stress.

Phosphatidylcholine hydroperoxide (PCOOH) was directly quantified in the hippocampus, cortex and striatum from young (3 months), middle-aged (15 months) and old (20 to 24 months) gerbils by an HPLC-chemiluminescence assay. PCOOH levels in hippocampus and cortex were found between 8.05 to 8.58 pmol/mg tissue and no statistically significant difference was found across the age groups. In striatum, however, PCOOH levels were significantly higher in middle-aged and old gerbils compared to those in young animals. The regional comparison showed that PCOOH levels were significantly higher in striatum than in cortex or hippocampus for all the age groups. Moreover, this regional difference increased with aging, from approximately 20% in young animals to 30% and 40% in middle-aged and old gerbil striatum. PCOOH to phospholipid ratio is approximately the same for all age groups at the level of 1.5/10,000, although it is slightly lower in the cortex. The hydroxyl radical levels in the brain were also measured by the formation of its salicylate trapped product 2,3-DHBA and used as a measure of oxidative stress. The PCOOH levels was used as a measure of oxygen radical-induced lipid peroxidative damage. PCOOH as a function of hydroxyl radical stress was calculated and expressed as PCOOH/2,3-DHBA, representing the oxidative damage as a function of the level of oxidative stress. It also implies the tissue susceptibility to oxidative stress and the efficiency of the antioxidant systems. In hippocampus and cortex, the ratios are high in young gerbils, decrease at middle-age and significantly increase in the old.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1994

Direct measurement of hydroxyl radicals, lipid peroxidation, and blood-brain barrier disruption following unilateral cortical impact head injury in the rat.

We present data correlating the time courses of hydroxyl radical (.OH) production, lipid peroxidation, and blood-brain barrier (BBB) damage following unilateral head injury in the rat. Using a controlled cortical impact device to inflict head injury, we have directly measured brain .OH levels via the salicylate trapping method, and phosphatidylcholine hydroperoxide (PCOOH) levels via the HPLC-chemiluminescence technique, at 5, 30, and 60 min postinjury. These results were then correlated with the time course of BBB disruption, as measured by the extravasation of Evans blue dye (EB) into the injured cortex, over the same time period. In the present study, .OH levels were 62% higher than sham at 5 min postinjury, 25% higher at 15 min (both p < or = 0.05), and no different from sham at 60 min. PCOOH, on the other hand, increased linearly between 5 and 60 min postinjury. Whereas PCOOH levels were 25% greater than sham at 5 min, they were 35% and 52% higher than sham at 30 and 60 min, respectively (both p < or = 0.05 vs sham). Blood-brain barrier disruption followed a similar time course to PCOOH generation, except that the magnitude of the effect was much greater. Whereas EB extravasation was only slightly elevated in the injured cortex at 5 min postinjury, there was nearly an 8-fold increase at 30 min and an 11-fold increase at 60 min (all p < or = 0.05 vs sham). An additional experiment demonstrated that BBB damage can be attenuated by treatment with the 21-aminosteroid lipid peroxidation inhibitor, tirilazad mesylate (U-74006F). Rats were given a single i.v. injection of 3 or 10 mg/kg of U-74006F 5 min postinjury and killed 30 min postinjury. The 10 mg/kg dose of U-74006F reduced EB extravasation 52% (p < 0.025) in comparison to vehicle-treated controls. This is the first study to correlate the time courses of .OH formation, lipid peroxidation, and BBB disruption in injured brain. The results suggest that there is an immediate, posttraumatic burst in .OH formation, followed by a progressive increase in lipid peroxidation and a similar, although slightly delayed, time-related opening of the BBB. The attenuation of BBB damage by U-74006F suggests that this chain of events can be interrupted by administration of an antioxidant/lipid peroxidation inhibitor.

Animals↗
PubMed1994

Effects of alloxan on electric activity of mouse pancreatic B cells in vitro.

Microelectrode method for recording membrane potentials was used. It was observed that alloxan possessed stimulative and toxic dual effects on the electric activity of pancreatic B cells. A 10-min exposure to alloxan 14 mmol.L-1 in the perfusion medium without glucose caused a significant depolarization of B cells from -44 +/- 13 mV to -36 +/- 12 mV (n = 7, P < 0.05) and evoked spikes in B cells. But the spikes disappeared at 24 +/- 12 min (n = 8). In the presence of glucose 5.5 mmol.L-1 or 11.0 mmol.L-1, the dual effects became weaker or not obvious. After 10-min exposure to diazoxide (an ATP sensitive K+ channel opener) 0.8 mmol.L-1 in the perfusion medium with alloxan 14 mmol.L-1 but devoid of glucose, the amplitude of membrane potential went up from -31 +/- 11 mV to -48 +/- 21 mV and the mean value of spikes dropped from 31 +/- 24 spikes.min-1 to 5 +/- 5 spikes.min-1. It was suggested that the stimulative effect of alloxan was due to blocking of ATP sensitive K+ channel and a higher concentration of glucose could prevent B cells from alloxan injury.

Alloxan↗
PubMed1994

[Analysis of the acetylcholine action on the electrical activities of pancreatic islet B-cells in mice].

Intracellular potential recording and extracellular microiontophoretic techniques were used to study the acetylcholine (ACh) action on the electrical activities of pancreatic islet B-cells in mice. The B cell membrane potential was decreased (5-10 mV) and the spikes were increased (11-17/30 s) by the ACh microinotophoresis. These effects were dependent on glucose and completely blocked by atropine. However, pirenzepine could attenuate the electrical activity by approximately 70%. The ACh-induced membrane depolarization was Ca(2+)-independent and blocked by TTX. But the effect of ACh on spikes was Ca(2+)-dependent and not blocked by verapamil. The results showed that ACh action in the enhancement of glucose-dependent electrical activities of B-cell were mediated by muscarinic receptor, mainly by subtype M1. Then TTX-sensitive Na channel and verapamil-insensitive Ca channel were activated by M1 receptors. Na+ influx resulted in membrane depolarization and Ca2+ influx enhanced spike discharges.

Acetylcholine↗
PubMed1993

The genotoxic effects of arachidonic acid in V79 cells are mediated by peroxidation products.

Chinese hamster lung fibroblasts (V79 cells) were exposed to 2, 20, 160, and 200 microM arachidonic acid (AA). At 20 microM, a stimulatory effect on cell growth was observed, while at 200 microM, an inhibitory effect was found. AA at 160 and 200 microM induced a 10- to 12-fold increase of 6-thioguanine-resistant mutants in V79 cells, whereas increased alkaline labile sites on DNA were consistently produced only with 200 microM treatment doses. The induction of alkaline labile lesions was partially inhibited in the presence of an antioxidant NDGA. [3H]AA metabolism in cells was examined by HPLC analysis following reductive transmethylation of the cell lipid extracts. Two fractions corresponding to [3H]AA-derived peroxidation products were identified by HPLC-radiochromatography and analyzed by mass spectrometry. Quantitative evaluation of the radioactivity associated with these peaks revealed an increase in [3H]AA peroxidation products when cells were exposed to increasing amounts of AA. The AA-dependent stimulation of lipid peroxidation product formation was partially inhibited when cells were treated in the presence of NDGA. The results provide evidence that substantially enlarged AA pools in cells may induce genotoxic effects mediated through increased endogenous lipid peroxidation products.

Animals↗
PubMed1993

Age-related regional changes in hydroxyl radical stress and antioxidants in gerbil brain.

The levels of hydroxyl radicals and oxidized GSH have been examined as indices of oxidative stress in young (3 months), middle-aged (15 months), and old (20-24 months) gerbil brain hippocampus, cortex, and striatum. The hydroxyl radical stress was estimated by measuring the salicylate hydroxyl radical trapping products 2,5- and 2,3-dihydroxybenzoic acid. The stress was significantly higher in all three brain regions in middle-aged and old gerbils versus young animals (< or = 66.0%). Regional comparisons showed that the stress was significantly higher in cortex than in either the hippocampus or striatum of the middle-aged and old gerbils (< or = 32.0%). The ratio of oxidized to total GSH also increased progressively in middle-aged and old animals in all three brain regions (p < 0.05, < or = 41.1%), further indicating a general age-related increase in oxidative stress. Parallel to this age-related increase in oxidative stress, a significant, albeit slight (8%), decrease in neuronal number in hippocampal CA1 region was observed in both the middle-aged and old animals. Possible differences in antioxidant levels were also examined. Total GSH levels were similar across age groups (variance < 12%). However, the regional comparison showed that it was highest in striatum in all age groups. The levels of alpha-tocopherol (vitamin E) were significantly higher in the middle-aged and old animals in all three regions (< or = 70.4%). Vitamin E was highest in the hippocampus and the differences between the hippocampus and the cortex and striatum increased with age.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1993

[Inhibitory effect of diazepam or flurazepam on pressor response induced by the stimulation of midbrain in the rabbit].

Experiments were performed on 32 rabbits anaesthetized with alpha-chloralose and urethane, paralyzed with flaxidil and artificially ventilated. The pressor response was elicited by stimulation of dorsal part of midbrain periaqueductal gray (dPAG). Intravenous injection of diazepam (2 mg/kg) or intracerebroventricular application of flurazepam (2 mg/50 microliters) resulted in attenuation of the pressor response induced by the stimulation of midbrain. Bilateral microinjection of flurazepam (100 micrograms in 0.25 microliter) into rostral ventrolateral medulla (rVLM) depressed the pressor response to midbrain stimulation. Microinjection of flurazepam of the same dosage into caudal ventrolateral medulla (cVLM), however, had no depressant effect. Pretreatment with bicuculline in rVLM prevented the inhibitory effect of flurazepam on the pressor response. These results mentioned above suggest that diazepam or flurazepam inhibits the pressor response evoked by midbrain stimulation, and the effect may be mediated by the activation of the GABAA receptor in rVLM.

Animals↗
PubMed1991

Effect of vitamin E on arachidonic acid peroxidation and its binding to Chinese hamster V79 cell DNA.

Following 24 h incubation in standard culture medium (containing 2 microM of arachidonic acid, AA), and 10 and 20 microM supplemented AA, approx. 55, 40 and 33%, respectively, of the fatty acid was incorporated into Chinese hamster V79 cell lipids. The AA content of cells increased 5 to 7-fold with the 10 and 20 microM supplementations of AA and, there was a correspondingly marked decrease in the proportion of AA incorporated into phospholipids (94 vs. 50 and 32%), whereas an increased percentage of AA was recovered in triacylglycerols (1 vs. 30 and 50%) and free fatty acids (1 vs. 3 and 8%). AA at 12 and 22 microM induced a 50 and 80% increase, respectively, in cellular content of thiobarbituric acid reactive substances (TBARS), an indication of increased peroxidation of cell lipids. This formation of TBARS was inhibited by vitamin E but not by indomethacin or SKF-525. Binding of [3H]AA-derived counts to DNA increased in parallel to the levels of cellular lipid peroxidation. Vitamin E added to the culture medium at 10(-4) M was readily taken up by the cells within 48 h and significantly reduced both lipid peroxidation and binding of AA-derived counts to DNA, without affecting AA uptake. Cell vitamin E content was significantly reduced following 24 h incubation in the presence of 10 and 20 microM supplemented AA. This study indicates that products of lipid peroxidation can bind to DNA in cultured cells, and points to a potential cyto- and geno-toxic risk posed by increased cellular AA content relative to anti-oxidant defenses.

Animals↗
PubMed1991

Effects of substance P on electric activity of mouse pancreatic islet cells in vitro.

The effects of substance P (SP), [D-Pro2, D-Trp7,9]SP and verapamil on the electric activity of B cells of Langerhans islets of mice were investigated. Addition of SP 100 nmol.L-1 to the perfusion medium stimulated spontaneous electric activity induced by glucose 5.5 mmol.L-1 with an increase in frequency and amplitude of the spikes. [D-Pro2, D-Trp7,9]SP 50 nmol.L-1 reversed the stimulative effect of SP. There was no evidence for an enhancing interaction between SP and acetylcholine 1 mumol.L-1. Verapamil 60 mumol.L-1 blocked the stimulative effect of SP. These results suggest that the stimulative effect of SP on the electric activity of B cells may be due to the increase in Ca2+ influx through the voltage-dependent Ca2+ channels.

Acetylcholine↗
PubMed1991

Purification and partial characterization of a new group of gastric cancer associated antigens.

The corresponding antigens of MG series monoclonal antibodies (MG5, MG9, MGd1 and MGe1) against gastric cancer were purified and partially characterized. Each of these monoclonal antibodies was purified by passing through a DEAE-52 cellulose columns and covalently coupled with CNBr-activated sepharose 4B successively. By means of concanavalin A and antibody affinity chromatography, the corresponding antigens of MG series McAb were extracted from gastric cancer tissue respectively. Immunological and biochemical studies confirmed that the corresponding antigens of MG series McAb were a new group of gastric cancer associated neutral glycolipid and glycoprotein antigens.

Antibodies, Monoclonal↗
PubMed1991

Diagnostic significance of gastric cancer associated antigens (MG-AGS) in serum, ascitic fluid and gastric juice.

A group of monoclonal antibodies against gastric cancer, pooled in equal proportions, was used to investigate their corresponding antigens (MG-Ags) in serum and body fluid of patients with gastrointestinal cancer and benign diseases using microsphere-ELISA method. The mean serum level (plus 3 standard deviations) in 59 normal subjects was arbitrarily set as the positive threshold value. The positive rate was found to be 68.8% (135/196) in sera of patients with gastric cancer, 70% (14/20) in colonic cancer, 72.2% (24/33) in rectal cancer, 43.8% (7/16) in esophageal cancer, 45.5% (5/11) in cholecystic cancer and 34.9% (15/43) in lung cancer, which, however, was not found in primary liver cancer, pancreatic cancer and ovarian cancer. In 214 patients with benign diseases, a false positive rate was 7.48%. In gastric juice and ascitic fluid of patients with gastric cancer, the positive rates were found to be 61.7% (27/44) and 83.3% (20/24) respectively. These antigens were also determined repeatedly in sera of patients with gastric cancer who had undergone gastrectomy. It was found that the level of MG-Ags in sera began to decrease at 8-10 days after operation. These results suggest that the determination of MG-Ags is useful in the diagnosis of gastrointestinal cancer and evaluation of the treatments.

Antigens, Tumor-Associated, Carbohydrate↗