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Biomedical subjects

B J Day

Publications and source records attributed to B J Day.

At least 37 records · Page 2Linked to original sources
PubMed1997

Extracellular superoxide dismutase is upregulated with inducible nitric oxide synthase after NF-kappa B activation.

Inflammatory cytokines have been shown to upregulate secretion of the antioxidant enzyme extracellular superoxide dismutase (EC-SOD) in dermal fibroblasts and, in other cells, to stimulate production of nitric oxide (.NO). Because superoxide rapidly scavenges .NO, forming the injurious peroxynitrite anion (OONO-), we hypothesize that stimulated cells upregulate EC-SOD expression concurrently with .NO release. To test for coregulation of EC-SOD and .NO within the same cell, the timing of inducible nitric oxide synthase (iNOS) and EC-SOD transcription was measured after exposure of a rate type II pneumocyte analog, the L2 cell line, to a combination of interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha). Upregulation of iNOS and EC-SOD transcription occurred after 6 h of exposure, and transcription of both genes was linked by activation of the transcription factor nuclear factor-kappa B. Both EC-SOD and iNOS were elevated in rat lung homogenates 24 h after intratracheal instillation with IFN-gamma and TNF-alpha. The observation that EC-SOD and iNOS are temporally coregulated after cytokine exposure suggests the possibility of a critical mechanism by which cells might protect .NO and avoid the formation of OONO- during inflammation.

Animals↗
PubMed1996

Evaluation of the relative contribution of nitric oxide and peroxynitrite to the suppression of mitochondrial respiration in immunostimulated macrophages using a manganese mesoporphyrin superoxide dismutase mimetic and peroxynitrite scavenger.

Here we report that the cell-permeable superoxide dismutase mimetic Mn(III)tetrakis (4-benzoic acid) porphyrin (MnTBAP) inhibits the oxidation of dihydrorhodamine-123 by peroxynitrite, but does not scavenge nitric oxide (NO). MnTBAP protects against the suppression of mitochondrial respiration in J774 cells exposed to peroxynitrite or to NO donors. MnTBAP and N(G)-methyl-L-arginine provide additive protective effect against the suppression of respiration in immunostimulated cells. Our data suggest separate contributions of NO and peroxynitrite to the suppression of mitochondrial respiration and support the role of oxidative stress in the expression of the inducible isoform of NO synthase.

Animals↗
PubMed1996

A metalloporphyrin superoxide dismutase mimetic protects against paraquat-induced lung injury in vivo.

We employed a low-molecular-weight metalloporphyrin superoxide dismutase mimetic, MnTBAP, to protect mice against a known pulmonary toxicant, paraquat. Paraquat creates toxicity by elevating intracellular levels of superoxide through redox cycling with cellular diaphorases and oxygen. In vitro, paraquat-induced cell injury can be attenuated by MnTBAP. We assessed whether inhaled MnTBAP would protect whole animals from a single i.p. dose of paraquat. Mice were given either saline (10 ml/ kg, i.p.) or paraquat (45 mg/kg, i.p.) and 30 min later exposed to aerosolized saline or MnTBAP (5 mM) for 30 min twice daily. Mice were killed 48 hr after paraquat treatment. Lung injury was assessed by measuring lactate dehydrogenase (LDH), protein, and percentage polymorphonuclear leukocytes (PMN) in bronchoalveolar lavage (BAL) fluid and by histopathology. Paraquat treatment increased levels of BAL fluid LDH, protein, and number of PMNs and produced extensive blebbing of the type I epithelium. MnTBAP reduced lung injury as indicated by lower LDH levels, protein levels, and PMN influx in BAL fluid. This correlated with the reduction of type I epithelial damage in the group of mice that received paraquat. These data suggest that metalloporphyrins may be effective therapeutic agents against pathologies that involve overproduction of reactive oxygen species.

Animals↗
PubMed1996

Extracellular superoxide dismutase in vessels and airways of humans and baboons.

Extracellular superoxide dismutase (EC SOD) is generally the least abundant SOD isozyme in tissues, while the intracellular Cu,Zn SOD is usually the most abundant isozyme. The biological significance of EC SOD is unknown. Immunolocalization studies show that EC SOD is in the connective tissue surrounding smooth muscle in vessels and airways within the lung. Endothelium derived relaxing factor, thought to be a nitric oxide (NO) species, is a primary mediator of vascular relaxation. During NO.'s diffusion between the endothelium and smooth muscle, extracellular superoxide would be the most efficient scavenger of NO(.). High levels of extracellular superoxide dismutase in vessels could, therefore, be essential to enable NO. to modulate vascular tone. To evaluate the hypothesis that vessel walls are functionally rich in extracellular superoxide scavenging capacity, this study quantitates the EC SOD levels in pulmonary and systemic vessels and in airways. Both pulmonary and systemic arteries in humans and baboons were found to contain high activities of EC SOD. The level of EC SOD in all human and baboon arteries examined is greater than or equal to the level of intracellular Cu,Zn SOD, and EC SOD accounted for over 70% of the total SOD activity in some vessels examined. Immunolocalization of EC SOD in human and baboon vessels show similar distributions of this enzyme in pulmonary and systemic vessels. EC SOD is located beneath the endothelium, surrounding smooth muscle cells, and throughout the adventitia of vessels. The high level of EC SOD in vessels, and its localization between endothelial and smooth muscle cells, suggest that regulation of superoxide may be particularly important in this region, possibly in regulating vascular tone.

Aged↗
PubMed1996

Requirement for superoxide in excitotoxic cell death.

We tested the pathogenic role of O2-) radicals in excitotoxic injury. Inactivation of the TCA cycle enzyme, aconitase, was used as a marker of intracellular O2- levels, and a porphyrin SOD mimetic was used to scavenge O2-. The selective, reversible, and SOD-sensitive inactivation of aconitase by known O2- generators was used to validate aconitase activity as a marker of O2- generation. Treatment of rat cortical cultures with NMDA, KA, or the intracellular O2- generator PQ2+ produced a selective and reversible inactivation of aconitase, which closely correlated with subsequent cell death produced by these agents. The SOD mimetic, but not its less active congener, attenuated both aconitase inactivation and cell death produced by NMDA, KA, and PQ2+. These results provide direct evidence implicating O2(-) generation in the pathway to excitotoxic injury.

Aconitate Hydratase↗
PubMed1996

Lung epithelial cell-released nitric oxide protects against PMN-mediated cell injury.

A calcium-independent type II nitric oxide (NO) synthase has been localized in lung epithelial cells; however, the function of NO. released by epithelial cells is unclear. We hypothesized that epithelial-derived NO may affect the interactions between polymorphonuclear neutrophils (PMN) and the alveolar epithelium and studied PMN adhesion and cytotoxicity to lung epithelial cells. A dose- and time-dependent production of NO. by L2 cells can be induced by a mixture of inflammatory mediators (cytomix) containing lipopolysaccharide, tumor necrosis factor-alpha, and interferon-gamma. Increased NO. production by L2 cells was associated with decreased 51Cr release by the epithelial cells after they were incubated with activated PMN. Addition of NG-monomethyl-L-arginine or oxyhemoglobin reversed the protective effects of cytomix, suggesting that increased NO. production by L2 cells was responsible for the decreased 51Cr release. However, PMN adhesion and intercellular adhesion molecule-1, a major adhesion molecule involved in PMN adhesion to epithelium, were increased by cytomix. We conclude that NO. released by lung epithelial cells was involved in protecting epithelial cells from PMN-mediated cytotoxicity. NO.-mediated protection of lung epithelial cells occurred in spite of PMN adhesion being increased, suggesting that reduced adhesion is not required for NO.-mediated inhibition of PMN cytotoxicity.

Animals↗
PubMed1995

An easy and economical method to prepare cells for cytologic analyses.

A crucial step in any cytology application begins with the placement of cells on slides in a manner that provides good preservation of cell morphology. Commercial cytocentrifuges are the most commonly used devices for this purpose. However, there are instances when these devices are either not available or not applicable. We devised an easy and economical alternative method to prepare cells for cytologic analysis. The device (cytograv) was easily assembled from common laboratory and office supplies, and produced cell preparations of similar quality as those produced with a cytocentrifuge (cytospin-3). Cellular analyses of biological fluids is one of the most common applications for these kinds of devices. The cytograv device was successfully employed in the identification and verification of a PMN isolation procedure from whole blood. The cytograv device was also successfully used to quantitative increases in the number of PMNs in bronchoalveolar lavage fluid recovered from mice treated with increasing doses of paraquat. These two examples illustrate some of the many possible uses of the cytograv device to provide high-quality preparations for cytologic analyses.

Animals↗
PubMed1995

A metalloporphyrin superoxide dismutase mimetic protects against paraquat-induced endothelial cell injury, in vitro.

There is an increased interest in development of therapeutic agents to treat disease states that involve reactive oxygen species in their pathophysiology. The metalloporphyrins, MnTBAP and ZnTBAP, were found to be active in a superoxide dismutase (SOD) assay. The efficacy of these compounds were tested against a well established model of intracellular superoxide-mediated cell injury. Paraquat generates superoxide by redox cycling with intracellular diaphorases and molecular oxygen. SOD mimetics were employed in a cell culture model with calf pulmonary artery endothelial cells (CPA-47) grown to near confluence in 24-well plates. Cell injury was assessed by measuring the release of cytosolic lactate dehydrogenase into the cell medium and by the number of adherent cells remaining after treatment. Exposure to various concentrations of paraquat for 4 h produced a dose-dependent injury response that was attenuated by 50 microM SOD mimetic, MnTBAP. MnTBAP also protected endothelial cells in a dose-dependent manner (EC50 approximately 40 microM) against paraquat (2 mM), whereas its less active analog (ZnTBAP) did not protect them. The protective effect of MnTBAP appears to be due to its intracellular superoxide-scavenging activity because neither the zinc form or exogenous CuZnSOD protected the cells against paraquat-induced injury. These studies suggest that metalloporphyrin-based SOD mimetics may be useful agents in preventing injury and disease states associated with the generation of intracellular reactive oxygen species.

Animals↗
PubMed1994

Immunocytochemical localization of extracellular superoxide dismutase in human lung.

BACKGROUND: Extracellular superoxide dismutase (EC-SOD) is a principal enzymatic scavenger of the superoxide anion in extracellular spaces. It is thought to be important as a defense against superoxide-mediated damage to both cell surfaces and extracellular matrix proteins. EC-SOD may also be important in regulating intercellular signalling by extracellular superoxide. EC-SOD is believed to be mainly located in the extracellular matrix of tissues. However, the specific localization of EC-SOD is unknown. Knowledge of the distribution of EC-SOD is an essential step in defining its functions. EXPERIMENTAL DESIGN: Using light microscopic immunohistochemistry, electron microscopic immunocytochemistry and an EC-SOD affinity-purified polyclonal rabbit antibody to human recombinant EC-SOD, we evaluated the distribution of EC-SOD in human lungs. RESULTS: These studies revealed that in the lung EC-SOD is primarily located in the extracellular matrix. Specifically, EC-SOD is found in areas containing high amounts of type I collagen and other unidentified matrix elements, but was not seen in areas rich in elastin or cartilage. In the lung, EC-SOD is predominantly located around larger vessels and airways, and, to a lesser degree, in the extracellular matrix around alveolar and capillary regions. Some EC-SOD was found in bronchiolar epithelial cell junctions and around the surface of vascular and airway smooth muscle cells. No labeling was seen on endothelial cell surfaces of capillaries, small muscular, or large elastic vessels in the lung. Labeling for EC-SOD was limited to the extracellular spaces, consistent with it being a secreted protein, with the exception of a small amount of intracellular labeling seen in bronchial epithelial cells and type II cells. CONCLUSIONS: The labeling distribution of EC-SOD in human lungs was defined using immunohistochemistry and immunocytochemical techniques. The findings suggest that EC-SOD is not diffusely located throughout the lung, but has a specific distribution in the extracellular matrix. These findings on the distribution of EC-SOD suggest that specific roles for EC-SOD may include the protection of matrix elements such as collagen from oxidative stress and that it may also function in the regulation of intercellular signals that are modulated by reactive oxygen species.

Adult↗
PubMed1993

Cortical and spinal motor excitability during the transcranial magnetic stimulation silent period in humans.

We investigated the electromyographic silent period in abductor pollicis brevis (APB) and flexor carpi radialis muscles following transcranial magnetic stimulation of human motor cortex. In APB, we measured cortical stimulation silent period (CSSP) duration as a function of stimulus intensity, motor-evoked potential (MEP) amplitude and muscle twitch force. We used peri-stimulus-time histograms to study the effect of cortical stimulation on single-motor unit firing patterns. We compared F-waves, H-reflexes and magnetic MEPs elicited during the CSSP to control responses elicited at rest and during voluntary contraction. CSSP duration depended on the intensity of cortical stimulation. However, we found no relationship between CSSP duration and MEP amplitude or muscle twitch force, thus the CSSP is not dependent solely on Renshaw cell inhibition or on changes in Ia and Ib afferent activity following the cortically induced muscle twitch. At low intensities of stimulation, the interval to resumption of motor unit firing following the peak in the peri-stimulus-time histogram corresponding to MEP latency sometimes exceeded that which could be accounted for by the motor unit's firing rate prior to the stimulus, suggesting that synchronization of motor unit firing by cortical stimulation cannot account for the CSSP. We found brief inhibition of F-waves during the CSSP in some subjects, reflecting activation of inhibitory corticospinal projections or segmental effects. In contrast, we observed longer inhibition of H-reflexes during the CSSP in all subjects, perhaps resulting from presynaptic inhibition of Ia afferents. Magnetic MEPs also were inhibited during the CSSP, suggesting inhibition of cortical elements by transcranial magnetic stimulation.

Adult↗
PubMed1993

HTLV-I associated myelopathy in a Seychellois immigrant.

OBJECTIVE: To describe the clinical and laboratory features of human T-lymphotropic virus type I (HTLV-I) associated myelopathy in an immigrant from the Seychelles. CLINICAL FEATURES: A slowly progressive myelopathy has been recently diagnosed in a 64-year-old woman who emigrated to Australia from the Seychelles in 1957. Sphincter disturbance and back pain were the first manifestations, followed by gait disturbance. Neurophysiological investigation supported the clinical diagnosis of a myelopathy and radiological investigations revealed no structural cause. Serum antibodies to HTLV-I were detected by enzyme-linked particle agglutination and the presence of antibodies to individual HTLV-I gene products in the serum was confirmed by western blot. The virus was detected in a culture of the patient's peripheral blood mononuclear cells by antigen capture assay and by sequencing a polymerase chain reaction product amplified from the env gene. INTERVENTION AND OUTCOME: The patient was advised of the nature and prognosis of her illness. Oral corticosteroids were tried without benefit. CONCLUSIONS: The prevalence of HTLV-I infection is low in Australia although it may be endemic in some Aboriginal communities. Most infections are asymptomatic but the chronic neurological disease associated with HTLV-I infection has now been shown to exist in this country. HTLV-I infection should be considered in the aetiology of myelopathy without another obvious cause.

Australia↗
PubMed1993

Potentiation of carbon tetrachloride-induced hepatotoxicity and pneumotoxicity by pyridine.

Induction of P450IIE1 by pyridine was compared with that by ethanol, and the resulting potentiation of the pneumotoxicity and hepatotoxicity following carbon tetrachloride inhalation by pyridine was examined. Rats were treated with ethanol as either a 10% solution in the drinking water or as a daily bolus (3 ml/kg, ip) dose for 7 days or one bolus dose of pyridine (200 mg/kg, ip) and compared for P450IIE1 apoprotein content by immunoblot analysis. Ethanol in the drinking water and pyridine elevated both hepatic and pulmonary P450IIE1 apoprotein content, but bolus dose ethanol did not. The induction was greatest in the pyridine group. In the interaction study, rats were treated with pyridine (200 mg/kg, ip) and 12 hours later were exposed to CCl4 (8000 ppm for 3 hours). Pulmonary injury and hepatic damage were assessed 24 hours later by bronchoalveolar lavage fluid (BALF) analysis [gamma-glutamyl transpeptidase (GGT), lactate dehydrogenase (LDH), and total protein] and serum sorbitol dehydrogenase (SDH) activity, respectively. Pyridine alone had no effect on BALF or SDH but enhanced GGT and LDH release into the BALF and SDH release into the serum when compared with CCl4 exposure alone. Evaluation of the liver at the light microscopic level revealed characteristic CCl4-induced centrilobular necrosis which was potentiated by pyridine. No changes were observed in the lung by light microscopic evaluation. Pyridine induced pulmonary and hepatic microsomal apoprotein levels of cytochrome P450IIE1 two- and 2- to sixfold, respectively. Exposure to CCl4 decreased hepatic but not pulmonary P450IIE1 levels. Induction of cytochrome P450IIE1 by pyridine increases the bioactivation of CCl4 in both the liver and lung, leading to enhanced toxicity.

Administration, Inhalation↗
PubMed1992

Motor inhibition and excitation are independent effects of magnetic cortical stimulation.

We administered magnetic cortical stimulation (MCS) during voluntary contraction of intrinsic hand muscles to 8 patients with motor neuron disease (MND), 5 patients with pure lower motor neuron syndromes (LMN), a patient with severe subacute sensory neuropathy (SSN), and 10 healthy volunteers. Patients with MND had clinical evidence of upper MND and elevated thresholds for (3 patients) or absence of (5 patients) motor evoked potentials (MEPs). MCS during sustained contraction inhibited electromyographic activity in 6 of 8 patients with MND, without preceding MEPs. MCS had no effect on the electromyogram (EMG) of the other 2 patients with MND. In normal subjects and patients with LMN, inhibition of EMG was never seen without a preceding MEP, regardless of stimulus intensity. In the patient with SSN, MCS elicited normal MEPs and inhibited the EMG in a pattern similar to normal subjects, whereas supramaximal electrical stimulation of median and ulnar nerves failed to inhibit the EMG despite normal M and F responses. Our findings indicate that the inhibitory effects of MCS on EMG are not dependent solely on changes in afferent feedback caused by the muscle twitch produced by the MEP, or on Renshaw cell inhibition. We suggest that some of the inhibitory and excitatory effects of MCS on the motor system are mediated by distinct cortical elements, which may have different susceptibilities to pathophysiological processes in MND.

Adult↗
PubMed1992

Effect of p-xylene inhalation on the bioactivation of bromobenzene in rat lung and liver.

It is unclear whether the pneumotoxicity observed with bromobenzene (BB) in phenobarbital-induced rats is related to BB bioactivation in lung, liver or both. To help differentiate pulmonary from hepatic bioactivation, BB was administered alone and in combination with p-xylene, which inhibits pulmonary but induces hepatic cytochromes P450. Exposure to p-xylene alone (3400 ppm for 4 hr) produced no changes in bronchoalveolar lavage fluid (BALF) measurements (gamma-glutamyl transpeptidase, lactate dehydrogenase, protein, white blood cell count) or serum sorbitol dehydrogenase. p-Xylene increased hepatic microsomal benzyloxy- (BROD), pentoxy- (PROD), and ethoxy- (EROD) resorfuin O-dealkylase activities but decreased pulmonary microsomal BROD and PROD. Immunoblot analysis revealed an induction of hepatic but not pulmonary microsomal P450IIB apoprotein. When rats were exposed to p-xylene (2800 ppm) or room air for 4 hr, treated 12 hr later with BB (0.5 ml/kg, ip) or corn oil, and killed after 12 hr, p-xylene increased hepatic P450IIB (27-fold) concomittant with a similar increase in BROD activity. p-Xylene also increased hepatic P450IA apoprotein (3.4-fold) with a complimentary increase in EROD activity. p-Xylene potentiated BB-induced hepatotoxicity. In pulmonary microsomes p-xylene and BB each produced similar decreases in both EROD and BROD activities. The combination of p-xylene and BB had an additive effect on pulmonary P450IA1 reduction. BALF analysis and histopathology revealed no pneumotoxicity with any treatment. p-Xylene potentiation of BB-induced hepatotoxicity without pneumotoxicity suggests that the liver does not produce metabolites of BB which are directly involved in pulmonary damage.

Administration, Inhalation↗
PubMed1992

Induction by pyridine of cytochrome P450IIE1 and xenobiotic metabolism in rat lung and liver.

Pyridine has been shown to induce hepatic microsomal cytochrome P450IIE1 and dependent activities. In the present study a single dose of pyridine (200 mg/kg body weight i.p.) induced cytochrome P450IIE1 in both the liver and lung. Increases were observed in p-nitrophenol hydroxylation, ethoxyresorufin deethylation and N-nitrosodimethylamine metabolism in both tissues. Pyridine appears to be an excellent inducer of this isozyme in the lung and may be useful in studying xenobiotic metabolizing activities in this organ which are dependent upon this isozyme.

Animals↗