Protecting the permeability pore and mitochondrial biogenesis.

Recent evidence links the pathogenesis of multiple organ dysfunction syndrome (MODS) in sepsis to mitochondrial damage. Our hypothesis is that cellular mechanisms maintaining mitochondrial function must be protected in order to prevent MODS. Recent animal experiments indicate that host defences which target and kill microbes, in part via reactive oxygen and nitrogen production, also injure mitochondria, thus activating mitochondrial cell death pathways. To limit such collateral damage, the cell up-regulates and imports into mitochondria several nuclear-encoded proteins for antioxidant defence and mitochondrial DNA (mtDNA) replication. Fully integrated responses lead to mitochondrial biogenesis, which may alter cellular phenotype to avoid mitochondrial permeability transition, apoptosis, or energy failure. Key to the cell's vulnerability to oxidant generation by the innate immune response is the mtDNA content. MtDNA depletion is opposed by oxidation reduction (redox) signals that communicate the extent of mitochondrial damage to the nucleus. Molecular studies suggest that redox mechanisms activate two biogenic transcription factors, nuclear respiratory factors 1 and 2, which forestall a deterioration of oxidative phosphorylation during infection. Biogenic failure or an intrinsic biogenic arrest could hasten degradation of mitochondrial function and drive the cell to apoptosis or necrosis. By implication, novel protective strategies for biogenesis hold promise for the prevention of MODS.

Metabolic capacity regulates iron homeostasis in endothelial cells.

The sensitivity of endothelial cells to oxidative stress and the high concentrations of iron in mitochondria led us to test the hypotheses that (1) changes in respiratory capacity alter iron homeostasis, and (2) lack of aerobic metabolism decreases labile iron stores and attenuates oxidative stress. Two respiration-deficient (rho(o)) endothelial cell lines with selective deletion of mitochondrial DNA (mtDNA) were created by exposing a parent endothelial cell line (EA) to ethidium bromide. Surviving cells were cloned and mtDNA-deficient cell lines were demonstrated to have diminished oxygen consumption. Total cellular and mitochondrial iron levels were measured, and iron uptake and compartmentalization were measured by inductively coupled plasma atomic emission spectroscopy. Iron transport and storage protein expression were analyzed by real-time polymerase chain reaction and Western blot or ELISA, and total and mitochondrial reactive oxygen species (ROS) generation was measured. Mitochondrial iron content was the same in all three cell lines, but both rho(o) lines had lower iron uptake and total cellular iron. Protein and mRNA expressions of major cytosolic iron transport constituents were down-regulated in rho(o) cells, including transferrin receptor, divalent metal transporter-1 (-IRE isoform), and ferritin. The mitochondrial iron-handling protein, frataxin, was also decreased in respiration-deficient cells. The rho(o) cell lines generated less mitochondrial ROS but released more extracellular H(2)O(2), and demonstrated significantly lower levels of lipid aldehyde formation than control cells. In summary, rho(o) cells with a minimal aerobic capacity had decreased iron uptake and storage. This work demonstrates that mitochondria regulate iron homeostasis in endothelial cells.

Oxygen-induced mitochondrial biogenesis in the rat hippocampus.

The hypothesis that damage to mitochondrial DNA by reactive oxygen species increases the activity of nuclear and mitochondrial transcription factors for mitochondrial DNA replication was tested in the in vivo rat brain. Mitochondrial reactive oxygen species generation was stimulated using pre-convulsive doses of hyperbaric oxygen and hippocampal mitochondrial DNA content and neuronal and mitochondrial morphology and cell proliferation were evaluated at 1, 5 and 10 days. Gene expression was subsequently evaluated to assess nuclear and mitochondrial-encoded respiratory genes, mitochondrial transcription factor A, and nuclear respiratory transcription factors-1 and -2. After 1 day, a mitochondrial DNA deletion emerged involving Complex I and IV subunit-encoding regions that was independent of overt neurological or cytological O(2) toxicity, and resolved before the onset of cell proliferation. This damage was attenuated by blockade of neuronal nitric oxide synthase. Compensatory responses were found in nuclear gene expression for manganese superoxide dismutase, mitochondrial transcription factor A, and nuclear respiratory transcription factor-2. Enhanced nuclear respiratory transcription factor-2 binding activity in hippocampus was accompanied by a nearly three-fold boost in mitochondrial DNA content over 5 days. The finding that O(2) activates regional mitochondrial DNA transcription, replication, and mitochondrial biogenesis in the hippocampus may have important implications for maintaining neuronal viability after brain injury.

Inhaled carbon monoxide and hyperoxic lung injury in rats.

Because carbon monoxide (CO) has been proposed to have anti-inflammatory properties, we sought protective effects of CO in pulmonary O(2) toxicity, which leads rapidly to lung inflammation and respiratory failure. Based on published studies, we hypothesized that CO protects the lung against O(2) by selectively increasing expression of antioxidant enzymes, thereby decreasing oxidative injury and inflammation. Rats exposed to O(2) with or without CO [50-500 parts/million (ppm)] for 60 h were compared for lung wet-to-dry weight ratio (W/D), pleural fluid volume, myeloperoxidase (MPO) activity, histology, expression of heme oxygenase-1 (HO-1), and manganese superoxide dismutase (Mn SOD) proteins. The brains were evaluated for histological evidence of damage from CO. In O(2)-exposed animals, lung W/D increased from 4.8 in normal rats to 6.3; however, only CO at 200 and 500 ppm decreased W/D significantly (to 5.9) during O(2) exposure. Large volumes of pleural fluid accumulated in all rats, with no significant CO treatment effect. Lung MPO values increased after O(2) and were not attenuated by CO treatment. CO did not enhance lung expression of oxidant-responsive proteins Mn SOD and HO-1. Animals receiving O(2) and CO at 200 or 500 ppm showed significant apoptotic cell death in the cortex and hippocampus by immunochemical staining. Thus significant protection by CO against O(2)-induced lung injury could not be confirmed in rats, even at CO concentrations associated with apoptosis in the brain.

Induction of urinary excretion of 3-nitrotyrosine, a marker of oxidative stress, following administration of pyridostigmine bromide, DEET (N,N-diethyl-m-toluamide) and permethrin, alone and in combination in rats.

In this study, we determined levels of 3-nitrotyrosine in rat urine following administration of a single oral dose of 13 mg/kg pyridostigmine bromide (PB) (3-dimethylaminocarbonyloxy-N-methylpyridinum bromide), a single dermal dose of 400 mg/kg N,N-diethyl-m-toluamide (DEET) and a single dermal dose of 1.3 mg/kg permethrin, alone and in combination. Urine samples were collected from five treated and five control rats at 4, 8, 16, 24, 48, and 72 h following dosing. Solid-phase extraction coupled with high-performance liquid chromatography with ultraviolet detection at 274 nm was used for the determination of tyrosine and 3-nitrotyrosine. A single oral dose of PB and a single dermal dose of DEET or their combination significantly (P<0.05) increased levels of 3-nitrotyrosine starting 24 h after dosing compared with control urine samples. The maximum increase of 3-nitroytyrosine was detected 48 h after combined administration of PB and DEET. The ratio of 3-nitrotyrosine to tyrosine in urine excreted 48 h after dosing was 0.19+/-0.04, 0.20+/-0.05, 0.28+/-0.03, 0.32+/-0.04, 0.19+/-0.05, 0.42+/-0.04, 0.27+/-0.03, 0.36+/-0.04, and 0.48+/-0.04 following administration of water, ethanol, PB, DEET, permethrin, PB+DEET, PB+permethrin, DEET+permethrin, and PB+DEET+permethrin, respectively. The results indicate that an oral dose of PB and a dermal administration of DEET, alone and in combination, could generate free radical species, and thus increase levels of 3-nitrotyrosine in rat urine. Induction of 3-nitrotyrosine, a marker of oxidative stress, following exposure to these compounds could be significant in understanding the proposed enhanced toxicity following combined exposure to these compounds.

Prevention of influenza-induced lung injury in mice overexpressing extracellular superoxide dismutase.

Reactive oxygen and nitrogen species such as superoxide and nitric oxide are released into the extracellular spaces by inflammatory and airway epithelial cells. These molecules may exacerbate lung injury after influenza virus pneumonia. We hypothesized that enhanced expression of extracellular superoxide dismutase (EC SOD) in mouse airways would attenuate the pathological effects of influenza pneumonia. We compared the pathogenic effects of a nonlethal primary infection with mouse-adapted Hong Kong influenza A/68 virus in transgenic (TG) EC SOD mice versus non-TG (wild-type) littermates. Compared with wild-type mice, EC SOD TG mice showed less lung injury and inflammation as measured by significant blunting of interferon-gamma induction, reduced cell count and total protein in bronchoalveolar lavage fluid, reduced levels of lung nitrite/nitrate nitrotyrosine, and markedly reduced lung pathology. These results demonstrate that enhancing EC SOD in the conducting and distal airways of the lung minimizes influenza-induced lung injury by both ameliorating inflammation and attenuating oxidative stress.

Differential localization of placental extracellular superoxide dismutase as pregnancy progresses.

OBJECTIVE: The aim of this study was to determine placental localization and activity of extracellular superoxide dismutase, a nitric oxide modulator, during early gestation and to correlate these characteristics with fetal vascular development. STUDY DESIGN: First-trimester (n = 10) and second-trimester (n = 10) villi were obtained at elective pregnancy termination. Extracellular superoxide dismutase was localized by means of an immunoperoxidase method. Activity was measured by determining the inhibition of cytochrome c reduction at pH 10 and messenger ribonucleic acid expression by in situ hybridization. RESULTS: Extracellular superoxide dismutase was intracellular within villous trophoblasts until 17 weeks' gestation, when it relocated to the villous extracellular matrix. Activities were similar between first- and second-trimester villi. In situ hybridization confirmed extracellular superoxide dismutase messenger ribonucleic acid within trophoblasts throughout gestation. CONCLUSION: Extracellular superoxide dismutase is produced by trophoblasts early in pregnancy, but it remains intracellular until 17 weeks' gestation, which may be related to fetal vascular development.

Extracellular superoxide dismutase in the airways of transgenic mice reduces inflammation and attenuates lung toxicity following hyperoxia.

Extracellular superoxide dismutase (EC-SOD, or SOD3) is the major extracellular antioxidant enzyme in the lung. To study the biologic role of EC-SOD in hyperoxic-induced pulmonary disease, we created transgenic (Tg) mice that specifically target overexpression of human EC-SOD (hEC-SOD) to alveolar type II and nonciliated bronchial epithelial cells. Mice heterozygous for the hEC-SOD transgene showed threefold higher EC-SOD levels in the lung compared with wild-type (Wt) littermate controls. A significant amount of hEC-SOD was present in the epithelial lining fluid layer. Both Tg and Wt mice were exposed to normobaric hyperoxia (>99% oxygen) for 48, 72, and 84 hours. Mice overexpressing hEC-SOD in the airways attenuated the hyperoxic lung injury response, showed decreased morphologic evidence of lung damage, had reduced numbers of recruited inflammatory cells, and had a reduced lung wet/dry ratio. To evaluate whether reduced numbers of neutrophil infiltration were directly responsible for the tolerance to oxygen toxicity observed in the Tg mice, we made Wt and Tg mice neutropenic using anti-neutrophil antibodies and subsequently exposed them to 72 hours of hyperoxia. Both Wt and Tg neutrophil-depleted (ND) mice have less severe lung injury compared with non-ND animals, thus providing direct evidence that neutrophils recruited to the lung during hyperoxia play a distinct role in the resultant acute lung injury. We conclude that oxidative and inflammatory processes in the extracellular lung compartment contribute to hyperoxic-induced lung damage and that overexpression of hEC-SOD mediates a protective response to hyperoxia, at least in part, by attenuating the neutrophil inflammatory response.

Analysis of erythropoietin and erythropoietin receptor genes expression in cattle during acute infection with Trypanosoma congolense.

Acute Trypanosoma congolense infection induced moderate, transient anemia in N'Dama cattle (trypanotolerant) and severe anemia in Boran cattle (trypanosusceptible). Erythropoietin receptor (EpoR) was cloned and sequenced from the two breeds of cattle. A single position mutation of Tyr in the Boran to His in the N'Dama predicted amino acid sequence was revealed. The mRNA transcription of erythropoietin (Epo) in kidneys and EpoR in the bone marrow of infected cattle was determined by competitive reverse transcription and the polymerase chain reaction (RT-PCR). Though Epo mRNA transcription increased in the kidneys during infection, the increase was not significantly different (p>0.05) between the two breeds of infected cattle. The level of EpoR transcripts in the bone marrow of infected N'Damas was significantly higher (p<0.05) than that detected in the marrows from infected Boran cattle. While infection seem to increase levels of transcription of IL-1alpha and beta, and TNFalpha in kidneys from both Boran and N'Dama cattle, no significant difference was detected in the level of mRNAs of these cytokines in the kidney from the two breed of cattle. The amount of IFNgamma mRNA transcripts were not changed with infection in N'Dama cattle, while on the contrary a significant higher levels of IFNgamma was found in kidneys from infected Boran cattle as compared to the other groups. A significant (p<0.05) increase in the levels of IL-1alpha and beta, and IFNgamma mRNA transcripts were detected in the marrows of infected Borans as compared to the infected N'Dama cattle. In this study the increase in the level of TNFalpha mRNA in the marrows of the two infected breeds was not different. This implies there is no negative effect of TNFalpha on hematopoiesis during acute infection. These findings suggest that the levels of Epo and EpoR in the infected Boran cattle were inadequate for their degree of anemia, which might be due in part to high expression of IFNgamma during acute infection with T. congolense.

Cloning of a cDNA encoding bovine erythropoietin and analysis of its transcription in selected tissues.

A bovine cDNA encoding erythropoietin (Epo) was isolated by polymerase chain reaction (PCR) amplification and screening of a bovine kidney cDNA library. The sequenced cDNA has a length of 1312 bp and an open reading frame that encodes a predicted 192-amino-acid (aa) protein, including a putative signal sequence of 25 aa. A mature protein of 167 aa (18.4 kDa) results upon cleavage of the putative signal peptide. The deduced bovine mature Epo peptide exhibits 96, 88, 83, 82 and 79% sequence identity to that of sheep, swine, human, monkey and rat, respectively. The expression of the bovine Epo gene in tissues from a severely anemic calf, bovine fetus and a healthy steer was analysed by a competitive RT-PCR method. In kidneys of the severely anemic calf, Epo mRNA levels increased 60-fold relative to that from the kidneys of the healthy steer. Epo mRNA levels were threefold higher in the liver of the bovine fetus than that in its kidneys. Low levels of Epo transcripts were detected in RNA from spleen of the severely anemic calf and the bovine fetus. No Epo transcripts were detectable in spleen from the healthy steer.

Prevalence of mastitis in imported Friesian cows in Sudan.

Three hundred twenty-two lactating Friesian cows were examined for mastitis by different diagnostic techniques. The predominant pathogens encountered were Staphylococci, Streptococci, Corynebacterium and Escherichia coli spp.

Zinc deficiency in sheep: field cases.

Zinc deficiency was diagnosed in a sheep farm in Khartoum Province; the young sheep and lambs were mostly affected. Skin lesions, depression, wool eating, flexed knees and a markedly stiff gait were observed. Histopathology of the skin revealed mainly hyperkeratosis accompanied sometimes by parakeratosis. The animals responded rapidly to oral administration of zinc oxide.

Acute mycotoxicosis in sheep: field cases.

Inappetence, apathy and neurological signs were seen in a flock of sheep at an out-station of Khartoum, that were fed on groundnut cake meal contaminated with aflatoxins (750 ppb). The gross and microscopic lesions were confined to the liver. The biochemical analysis of the serum was consistent with the presence of liver damage. The presence of aflatoxins in the feeds and tissues of the dead sheep supports that the condition was due to aflatoxin poisoning.

Normal serum activities of some diagnostic enzymes in dromedary camel in Sudan.

76 adult camel (30 males and 46 females) sera were surveyed for the normal activities of alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatine phospho-kinase (CPK), gamma-glutamyl transpeptidase (GGT) and lactate dehydrogenase (LDH). The values recorded for the above enzymes were compared to other data in the literature.

The pathological and biochemical effects of feeding fermented leaves of Cassia obtusifolia 'Kawal' to broiler chicks.

Fermented leaves of Cassia obtusifolia 'Kawal' were mixed in the food of broiler chicks at concentrations of 25, 50 and 100 g/Kg and then fed to chicks from 1 day to 8 weeks of age. Growth rate was depressed in relation to the concentration of Kawal. Lesions of an inflammatory-degenerative type were seen in the proventriculus, intestine, liver, heart, lungs and kidneys, their severity increasing with the amount of Kawal eaten. These were accompanied by similar increases in the activities of lactate dehydrogenase, alkaline phosphatase, glutamate oxaloacetate and glutamate pyruvate transaminases and in the concentrations of bilirubin, potassium, phosphorus, total lipids and carotenes in the blood and dose-related decreases in total protein, albumin, cholesterol, globulin, sodium, calcium and alkaline phosphatase in the blood. Birds fed on Kawal tended to become anaemic but white blood cell counts increased. It is concluded that Kawal even at an inclusion rate of 25 g/Kg is unacceptable as a protein supplement.

Toxic effect of the roasted and unroasted beans of Cassia occidentalis in goats.

The toxic effects of roasted and unroasted beans of the wild coffee, C occidentalis were compared. Both types of beans intoxicated goats in varying degrees, but roasting partially reduced the toxic effects of the beans. Histopathological, biochemical and enzyme histochemical studies showed that the toxin of C occidentalis damages the liver, vascular system, heart, and lungs.

Some effects of imidocarb in goats.

Clinically normal Nubian goats were given the antiprotozoal drug imidocarb at single intramuscular doses of 6, 12, 18 and 24 mg/kg, and the various clinical, biochemical and pathological manifestations were recorded. At a dose of 6 mg/kg the drug produced no change in any of the parameters studied. At higher doses, the drug produced dose dependent changes which included increased heart and respiratory rates, increased defaecation, urination, depression, incoordination of movement, weakness of the hindlegs, recumbency, and finally death. Just prior to death, there was a significant decrease in the number of erythrocytes, and in packed cell volume, and haemoglobin concentration. In plasma there was an increase in the activity of aspartate transaminase, urea and creatinine concentrations and inhibition of cholinesterase activity. The main histopathological changes were associated with hepatic and renal damage. Three goats were pre-treated with atropine sulphate (1 mg/animal) and after one hour given imidocarb intramuscularly at a dose of 12 mg/kg. The changes were similar but much less severe when compared with those in animals given imidocarb alone at the same dose.