non-Swiss Albino Research Articles

The disassembly of the neuromuscular synapse in high-fat diet-induced obese male mice

ObjectiveA sustained high fat diet in mice mimics many features of human obesity. We used male and female Non-Swiss albino mice to investigate the impact of short and long-term high-fat diet-(HFD)-induced obesity on the peripheral neuromuscular junction (NMJ) and whether obesity-related synaptic structural alterations were reversible after switching obese mice from HFD to a standard fat diet (SD). MethodsHFD-induced obese and age-matched control mice fed SD were used. We carried out in vivo time lapse imaging to monitor changes of synapses over time, quantitative fluorescence imaging to study the regulation of acetylcholine receptor number and density at neuromuscular junctions, and high resolution confocal microscope to study structural alterations in both the pre- and postsynaptic apparatus. ResultsTime-lapse imaging in vivo over a 9 month period revealed that NMJs of HFD obese male mice display a variety of obesity-related structural alterations, including the disappearance of large synaptic areas, significant reduction in the density/number of nicotinic acetylcholine receptor (AChRs), abnormal distribution of AChRs, high turnover rate of AChRs, retraction of axons from lost postsynaptic sites, and partially denervated synapses. The severity of these synaptic alterations is associated with the duration of obesity. However, no substantial alterations were observed at NMJs of age-matched HFD obese female mice or male mice fed with a standard or low fat diet. Intriguingly, when obese male mice were switched from HFD to a standard diet, receptor density and the abnormal pattern of AChR distribution were completely reversed to normal, whereas lost synaptic structures were not restored. ConclusionsThese results show that the obese male mice are more vulnerable than female mice to the impacts of long-term HFD on the NMJ damage and provide evidence that diet restriction can partially reverse obesity-related synaptic changes.

Venom Ontogeny in the Mexican Lance-Headed Rattlesnake (Crotalus polystictus).

As trophic adaptations, rattlesnake venoms can vary in composition depending on several intrinsic and extrinsic factors. Ontogenetic changes in venom composition have been documented for numerous species, but little is known of the potential age-related changes in many rattlesnake species found in México. In the current study, venom samples collected from adult and neonate Crotalus polystictus from Estado de México were subjected to enzymatic and electrophoretic analyses, toxicity assays (LD50), and MALDI-TOF mass spectrometry, and a pooled sample of adult venom was analyzed by shotgun proteomics. Electrophoretic profiles of adult males and females were quite similar, and only minor sex-based variation was noted. However, distinct differences were observed between venoms from adult females and their neonate offspring. Several prominent bands, including P-I and P-III snake venom metalloproteinases (SVMPs) and disintegrins (confirmed by MS/MS) were present in adult venoms and absent/greatly reduced in neonate venoms. Age-dependent differences in SVMP, kallikrein-like, phospholipase A2 (PLA2), and L-amino acid oxidase (LAAO) activity levels were confirmed by enzymatic activity assays, and like many other rattlesnake species, venoms from adult snakes have higher SVMP activity than neonate venoms. Conversely, PLA2 activity was approximately 2.5 × greater in venoms from neonates, likely contributing to the increased toxicity (neonate venom LD50 = 4.5 μg/g) towards non-Swiss albino mice when compared to adult venoms (LD50 = 5.5 μg/g). Thrombin-like (TLE) and phosphodiesterase activities did not vary significantly with age. A significant effect of sex (between adult male and adult female venoms) was also observed for SVMP, TLE, and LAAO activities. Analysis of pooled adult venom by LC-MS/MS identified 14 toxin protein families, dominated by bradykinin-inhibitory peptides, SVMPs (P-I, P-II and P-III), disintegrins, PLA2s, C-type-lectins, CRiSPs, serine proteinases, and LAAOs (96% of total venom proteins). Neonate and adult C. polystictus in this population consume almost exclusively mammals, suggesting that age-based differences in composition are related to physical differences in prey (e.g., surface-to-volume ratio differences) rather than taxonomic differences between prey. Venoms from adult C. polystictus fit a Type I pattern (high SVMP activity, lower toxicity), which is characteristic of many larger-bodied rattlesnakes of North America.

Maternal Choline Supplementation Modulates Placental Nutrient Transport and Metabolism in Late Gestation of Mouse Pregnancy

BackgroundFetal growth is dependent on placental nutrient supply, which is influenced by placental perfusion and transporter abundance. Previous research indicates that adequate choline nutrition during pregnancy improves placental vascular development, supporting the hypothesis that choline may affect placental nutrient transport. ObjectiveThe present study sought to determine the impact of maternal choline supplementation (MCS) on placental nutrient transporter abundance and nutrient metabolism during late gestation. MethodsFemale non-Swiss albino mice were randomly assigned to the 1×, 2×, or 4× choline diet (1.4, 2.8, and 5.6 g choline chloride/kg diet, respectively) 5 d before mating (n = 16 dams/group). The placentas and fetuses were harvested on gestational day (E) 15.5 and E18.5. The placental abundance of macronutrient, choline, and acetylcholine transporters and glycogen metabolic enzymes, and the placental concentration of glycogen were quantified. Choline metabolites and docosahexaenoic acid (DHA) concentrations were measured in the placentas and/or fetal brains. Data were stratified by gestational day and fetal sex and were analyzed by using mixed linear models. ResultsAt E15.5, MCS downregulated the placental transcript and protein abundance of glucose transporter 1 (GLUT1) (−40% to −73%, P < 0.05) and the placental transcript abundance of glycogen-synthesizing enzymes (−24% to −50%, P ≤ 0.05). At E18.5, MCS upregulated GLUT3 protein abundance (+55%, P = 0.016) and the transcript abundance of glycogen-synthesizing enzymes only in the female placentas (+36% to +60%, P < 0.05), resulting in a doubling (P = 0.01) of the glycogen concentration. A higher placental transcript abundance of the transporters for DHA, choline, and acetylcholine was also detected in response to MCS, consequently altering their concentrations in the placentas or fetal brains (P ≤ 0.05). ConclusionsThese data suggest that MCS modulates placental nutrient transporter abundance and nutrient metabolism in late gestation of mouse pregnancy, with subsequent effects on nutrient supply for the developing fetus.

Carbon Nanotube and Asbestos Exposures Induce Overlapping but Distinct Profiles of Lung Pathology in Non-Swiss Albino CF-1 Mice.

Carbon nanotubes (CNTs) are emerging as important occupational and environmental toxicants owing to their increasing prevalence and potential to be inhaled as airborne particles. CNTs are a concern because of their similarities to asbestos, which include fibrous morphology, high aspect ratio, and biopersistence. Limitations in research models have made it difficult to experimentally ascertain the risk of CNT exposures to humans and whether these may lead to lung diseases classically associated with asbestos, such as mesothelioma and fibrosis. In this study, we sought to comprehensively compare profiles of lung pathology in mice following repeated exposures to multiwall CNTs or crocidolite asbestos (CA). We show that both exposures resulted in granulomatous inflammation and increased interstitial collagen; CA exposures caused predominantly bronchoalveolar hyperplasia, whereas CNT exposures caused alveolar hyperplasia of type II pneumocytes (T2Ps). T2Ps isolated from CNT-exposed lungs were found to have upregulated proinflammatory genes, including interleukin 1ß (IL-1ß), in contrast to those from CA exposed. Immunostaining in tissue showed that while both toxicants increased IL-1ß protein expression in lung cells, T2P-specific IL-1ß increases were greater following CNT exposure. These results suggest related but distinct mechanisms of action by CNTs versus asbestos which may lead to different outcomes in the 2 exposure types.

Protection from cyanide-induced brain injury by the Nrf2 transcriptional activator carnosic acid.

Cyanide is a life-threatening, bioterrorist agent, preventing cellular respiration by inhibiting cytochrome c oxidase, resulting in cardiopulmonary failure, hypoxic brain injury, and death within minutes. However, even after treatment with various antidotes to protect cytochrome oxidase, cyanide intoxication in humans can induce a delayed-onset neurological syndrome that includes symptoms of Parkinsonism. Additional mechanisms are thought to underlie cyanide-induced neuronal damage, including generation of reactive oxygen species. This may account for the fact that antioxidants prevent some aspects of cyanide-induced neuronal damage. Here, as a potential preemptive countermeasure against a bioterrorist attack with cyanide, we tested the CNS protective effect of carnosic acid (CA), a pro-electrophilic compound found in the herb rosemary. CA crosses the blood-brain barrier to up-regulate endogenous antioxidant enzymes via activation of the Nrf2 transcriptional pathway. We demonstrate that CA exerts neuroprotective effects on cyanide-induced brain damage in cultured rodent and human-induced pluripotent stem cell-derived neurons in vitro, and in vivo in various brain areas of a non-Swiss albino mouse model of cyanide poisoning that simulates damage observed in the human brain. Cyanide, a potential bioterrorist agent, can produce a chronic delayed-onset neurological syndrome that includes symptoms of Parkinsonism. Here, cyanide poisoning treated with the proelectrophillic compound carnosic acid, results in reduced neuronal cell death in both in vitro and in vivo models through activation of the Nrf2/ARE transcriptional pathway. Carnosic acid is therefore a potential treatment for the toxic central nervous system (CNS) effects of cyanide poisoning. ARE, antioxidant responsive element; Nrf2 (NFE2L2, Nuclear factor (erythroid-derived 2)-like 2).

Depletion by Styrene of Glutathione in Plasma and Bronchioalveolar Lavage Fluid of Non-Swiss Albino (NSA) Mice

Styrene is a widely used chemical, but it is known to produce lung and liver damage in mice. This may be related to oxidative stress associated with the decrease in the levels of reduced glutathione (GSH) in the target tissues. The purpose of this study was to investigate the effect of styrene and its primary metabolites R-styrene oxide (R-SO) and S-styrene oxide (S-SO) on GSH levels in the lung lumen, as determined by amounts of GSH in bronchioalveolar lavage fluid (BALF) and in plasma. When non-Swiss albino (NSA) mice were administered styrene (600 mg/kg, ip), there was a significant fall in GSH levels in both BALF and plasma within 3 h. These returned to control levels by 12 h. The active metabolite R-SO (300 mg/kg, ip) also produced significant decreases in GSH in both BALF and plasma, but S-SO was without marked effect. Since GSH is a principal antioxidant in the lung epithelial lining fluid, this fall due to styrene may exert a significant influence on the ability of the lung to buffer oxidative damage.

Activity of telavancin against heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) in vitro and in an in vivo mouse model of bacteraemia

Infections caused by heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) are associated with high rates of vancomycin treatment failure. Telavancin is a bactericidal lipoglycopeptide active in vitro against Gram-positive pathogens including hVISA and vancomycin-intermediate S. aureus (VISA). This study characterizes the microbiological activity of telavancin against vancomycin-susceptible S. aureus (VSSA), hVISA and VISA strains. Reference strains of VSSA, hVISA and VISA were assessed for potential telavancin heteroresistance by population analysis. In addition, the efficacies of telavancin (40 mg/kg subcutaneously every 12 h for 4 days) and vancomycin (110 mg/kg subcutaneously every 12 h for 8 days) were compared in a neutropenic murine model (immunocompromised female non-Swiss albino mice) of bacteraemia caused by hVISA strain Mu3. Blood and spleen bacterial titres were quantified from cohorts of mice euthanized pre-treatment and at 24 h intervals post-treatment for 8 days. Telavancin was active against all strains of S. aureus tested, with MIC values < or =0.5 mg/L. Population analyses revealed no evidence of subpopulations with reduced susceptibility to telavancin. In the murine bacteraemia model of hVISA infection, all animals were bacteraemic pre-treatment and mortality was 100% within 16-24 h post-infection in untreated animals. Treatment with telavancin was associated with lower spleen bacterial titres, lower rates of bacteraemia and lower overall mortality than treatment with vancomycin. These in vitro and pre-clinical in vivo studies demonstrate that telavancin has the potential to be efficacious in infections caused by hVISA.

Oxidative Stress Due to (R)-Styrene Oxide Exposure and The Role of Antioxidants in Non-Swiss Albino (NSA) Mice

Styrene produces lung and liver damage that may be related to oxidative stress. The purpose of this study was to investigate the toxicity of (R)-styrene oxide (R-SO), the more active enantiomeric metabolite of styrene, and the protective properties of the antioxidants glutathione (GSH), N-acetylcysteine (NAC), and 4-methoxy-L-tyrosinyl-γ-L-glutamyl-L-cysteinyl-glycine (UPF1) against R-SO-induced toxicity in non-Swiss Albino (NSA) mice. UPF1 is a synthetic GSH analog that was shown to have 60 times the ability to scavenge reactive oxygen species (ROS) in comparison to GSH. R-SO toxicity to the lung was measured by elevations in the activity of lactate dehydrogenase (LDH), protein concentration, and number of cells in bronchoalveolar lavage fluid (BALF). Toxicity to the liver was measured by increases in serum sorbitol dehydrogenase (SDH) activity. Antioxidants were not able to decrease the adverse effects of R-SO on lung. However, NAC (200 mg/kg) ip and GSH (600 mg/kg), administered orally prior to R-SO (300 mg/kg) ip, showed significant protection against liver toxicity as measured by SDH activity. Unexpectedly, a synthetic GSH analog, UPF1 (0.8 mg/kg), administered intravenously (iv) prior to R-SO, produced a synergistic effect with regard to liver and lung toxicity. Treatment with UPF1 (0.8 mg/kg) iv every other day for 1 wk for preconditioning prior to R-SO ip did not result in any protection against liver and lung toxicity, but rather enhanced the toxicity when administered prior R-SO. The results of the present study demonstrated protection against R-SO toxicity in liver but not lung by the administration of the antioxidants NAC and GSH.

Efficacy of telavancin against glycopeptide-intermediate Staphylococcus aureus in the neutropenic mouse bacteraemia model

The aim of the study was to compare the efficacies of telavancin and vancomycin against glycopeptide-intermediate Staphylococcus aureus (GISA) and heterogeneous vancomycin-intermediate S. aureus (hVISA) in a neutropenic murine bacteraemia model. Immunocompromised mice (female non-Swiss albino, 18-30 g) were inoculated intraperitoneally with 10(7) cfu/mL of GISA (strain HIP-5836 or Mu50) or hVISA (strain Mu3). Infected mice received a subcutaneous dose of telavancin (40 mg/kg) or vancomycin (110 mg/kg) at 4 and 16 h post-inoculation. Control animals received a subcutaneous dose of vehicle at 4 h post-inoculation only. Blood and spleen bacterial titres were quantified in drug-treated mice at 16, 28 and 52 h post-inoculation. Telavancin was 8-fold more potent than vancomycin against HIP-5836 (MIC 1 versus 8 mg/L), 16-fold more potent against Mu50 (MIC 0.5 versus 8 mg/L) and 8-fold more potent against Mu3 (MIC 0.25 versus 2 mg/L). Telavancin produced significant (P < 0.05) and sustained reductions in blood and spleen titres from pre-treatment levels in mice infected with HIP-5836, Mu50 or Mu3. Vancomycin lowered blood and spleen HIP-5836 counts transiently, but did not lower blood or spleen Mu50 or Mu3 counts significantly at any timepoint. Reductions in blood and spleen HIP-5836 and Mu3 titres and in spleen Mu50 titres at 52 h post-inoculation were significantly greater with telavancin than vancomycin (P < 0.05). Telavancin was more efficacious than vancomycin in clearing infections caused by GISA strains HIP-5836 and Mu50 and hVISA strain Mu3 in a neutropenic mouse bacteraemia model. Further evaluation of telavancin for GISA and hVISA bacteraemia is warranted.

In Vivo Regulation of Acetylcholinesterase Insertion at the Neuromuscular Junction

The efficiency of synaptic transmission between nerve and muscle depends on the number and density of acetylcholinesterase molecules (AChE) at the neuromuscular junction. However, little is known about the way this density is maintained and regulated in vivo. By using time lapse and quantitative fluorescence imaging assays in living mice, we demonstrated that insertion of new AChEs occurs within hours of saturating pre-existing AChEs with fasciculin2, a snake toxin that selectively labels AChE. In the absence of muscle postsynaptic activity or evoked nerve presynaptic neurotransmitter release, AChE insertion was decreased significantly, whereas direct stimulation of the muscle completely restored AChE insertion to control levels. This activity-dependent AChE insertion is mediated by intracellular calcium. In muscle stimulated in the presence of a Ca2+ channel blocker or calcium-permeable Ca2+ chelator, AChE insertion into synapses was significantly decreased, whereas ryanodine or ionophore A12387 treatment of blocked and unstimulated synapses significantly increased AChE insertion. These results demonstrated that synaptic activity is critical for AChE insertion and indicated that a rise in intracellular calcium either through voltage-gated calcium channels or from intracellular stores is critical for proper AChE insertion into the adult synapse.

Comparison of the susceptibility of wild-type and CYP2E1 knockout mice to the hepatotoxic and pneumotoxic effects of styrene and styrene oxide

Styrene causes both liver and lung damage in non-Swiss albino, CD-1, and other strains of mice. This is considered to be due to the bioactivation of styrene to styrene oxide by cytochromes P450, principally CYP2E1 and CYP2F2. If so, one would expect CYP2E1 knockout mice to be less susceptible to styrene-induced toxicity than wild-type mice. However, previous in vitro and in vivo studies demonstrated little difference in the metabolism of styrene to styrene oxide between wild-type and CYP2E1 knockout mice. These findings would suggest that there should be no difference in the toxic responses to styrene between these two strains. To determine which of these possibilities was correct, styrene (600 mg/kg) or styrene oxide (300 mg/kg) was administered i.p. 24 h prior to measurement of serum sorbitol dehydrogenase as a biomarker of hepatotoxicity or lactate dehydrogenase activity, protein, and cells in bronchoalveolar lavage fluid as biomarkers for pneumotoxicity. Styrene was more hepatotoxic in the wild-type mice than in the knockout mice suggesting CYP2E1 activity is important. Strain differences were not observed with styrene oxide indicating no difference in intrinsic susceptibility. For lung, the response was similar in both strains to both styrene and styrene oxide supporting the idea that CYP2F2 is important in the bioactivation of styrene in this tissue and that there is no strain difference in susceptibility to the active metabolite.

Differential effects of MK-801 on cerebrocortical neuronal injury in C57BL/6J, NSA, and ICR Mice

1. 1. Antagonists of the N-methyl-D-aspartate (NMDA) glutamate (Glu) receptor, including [(+)-5-methyl-10, 11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate], dizocilpine maleate (MK-801), injure pyramidal neurons in the posterior cingulate/retrosplenial (PC/RS) cortex when administered systemically to adult rats and mice. 2. 2. These results have, to our knowledge, only been reported previously in Harlan Sprague Dawley albino rats and International Cancer Research (ICR) mice, an outbred albino strain. 3. 3. Male Non-Swiss Albino (NSA) mice, an albino outbred strain, and male C57BL/6J (B6) mice, a pigmented inbred strain, were injected systemically with 1 mg/kg of MK-801 in the first experiment. This dose of MK-801 reliably produces cytoplasmic vacuoles in neurons in layers III and IV of the PC/RS cortex in 100% of ICR mice treated. 4. 4. There was a significant difference in the number of vacuolated neurons in B6 and NSA mice, as assessed by ANOVA. The NSA were not significantly different than previously examined ICR mice, but the B6 had fewer vacuolated neurons than either of the two outbred strains. 5. 5. In the second experiment, male NSA, ICR, and B6 mice were injected systemically with a high dose, 10 mg/kg, of MK-801. This dose has been demonstrated to result in necrosis in the same population of neurons injured by lower doses of MK-801. 6. 6. An ANOVA indicated that there was a significant difference among the three strains of mice, and a Fisher's protected t revealed that the B6 mice were significantly different from both the NSA and ICR, but that, with our test, those two strains were indistinguishable 7. 7. Male ICR, NSA, and B6 mice were tested in the holeboard food search task 5 hours after 1 mg/kg of MK-801. There were significant differences between the strains in performance both pre and posttreatment. The effect of the drug was not statistically significant. 8. 8. These results suggest that there may be a genetically mediated difference in the reaction to NMDA receptor antagonists, a finding which may be important given the NMDA receptor hypofunction hypothesis for the etiology of schizophrenic symptoms.

METABOLISM OF STYRENE OXIDE TO STYRENE GLYCOL BY MOUSE LIVER AND LUNG

Styrene is a widely used chemical that causes both liver and lung damage in mice. Strain and sex differences in susceptibility to styrene-induced toxicity have been reported. Understanding the relationship of the metabolism of styrene to its toxicity depends upon knowing the balance between the bioactivation of styrene to the epoxide by cytochromes P-450 and the detoxication of the oxide to the glycol by microsomal epoxide hydrolase. When hepatic and pulmonary microsomal preparations from non-Swiss albino (NSA) and Swiss (CD-1) mice were compared for their abilities to metabolize racemic, S - and R -styrene oxide to styrene glycol, enzymic activities were higher in liver than in lung. R -Styrene glycol formation was favored with racemic styrene oxide as the substrate. Only minor strain differences were found that could not account for the differences in reported susceptibility to styrene-induced toxicity. While the oxidation of styrene to styrene oxide was similar in male and female NSA mice, male hepatic microsomes were more active in the metabolism of the oxide to the glycol. Hepatic metabolism of styrene oxide to styrene glycol was inducible by butylated hydroxyanisole, whereas pulmonary metabolism was not. The data indicate that strain differences in susceptibility cannot be accounted for by this detoxication step, and there are sex differences in this reaction.

EFFECTS OF INDUCERS AND INHIBITORS ON THE MICROSOMAL METABOLISM OF STYRENE TO STYRENE OXIDE IN MICE

Styrene is both hepatotoxic and pneumotoxic in mice, with non-Swiss albino (NSA) mice being more sensitive than Swiss (CD-1) mice. The toxicity of styrene is potentiated by treatment with phenobarbital, β-naphthoflavone, or pyridine. Since the toxicity of styrene is generally associated with its metabolism to styrene oxide (SO), the formation of SO by hepatic and pulmonary microsomes of NSA and CD-I mice was measured to examine correlations with toxicity. Both enantiomers of SO were quantified since the R-SO enantiomer is more toxic than the S-SO enantiomer. No strain differences in rates of styrene metabolism or enantiomeric ratio were observed in control mice or mice treated with inducers. Pyridine, an inducer of CYP2E I, increased S-SO but not R-SO formation in liver. Phenobarbital, an inducer of CYP2B, increased the production of both enantiomers. β-Naphthoflavone, an inducer of CYP1A, had no effect. None of the inducers had any effect in lung. Addition of the CYP2E1 inhibitor diethyldithiocarbamate decreased the formation of both enantiomers in both tissues from control mice, whereas 5-phenyl-l-pen-tyne (an inhibitor of CYP2F2) inhibited metabolism primarily in lung. In both control and phenobarbital-treated mice, SKF525A inhibited both R-SO and S-SO in liver but only S-SO in lung. Thus there are tissue differences in metabolism and susceptibility to induction and inhibition but no strain differences in metabolism to explain differences in susceptibility to styrene-induced toxicity.

COMPARISON OF MOUSE STRAINS FOR SUSCEPTIBILITY TO STYRENE-INDUCED HEPATOTOXICITY AND PNEUMOTOXICITY

Styrene is known to cause both hepatotoxicity and pneumotoxicity in mice. Strain differ ences have been reported by other investigators suggesting that Swiss mice are less suscep tible than non-Swiss mice to styrene-induced liver damage. In this study, A/I and C57BL/6 mice were found to be similar to non-Swiss albino (NSA) mice in susceptibility whereas CD-1 (Swiss) mice were more resistant to hepatotoxicity as assessed by serum sorbitol de hydrogenase levels and pneumotoxicity as determined by gamma-glutamyltranspeptidase and lactate dehydrogenase measurements in bronchoalveolar lavage fluid. Styrene was hepatotoxic in CD-I mice treated with pyridine to induce CYP2E1. CYP2EI apoprotein levels and p-nitrophenol hydroxylase activities in control and pyridine-induced mice were similar in the two strains. Hepatic and pulmonary microsomal preparations from both strains metabolized styrene to styrene oxide at similar rates. CD-1 mice were as susceptible as the NSA mice to the effects of styrene oxide. The data suggest that there are no differ ences in the bioactivation of styrene to styrene oxide or innate susceptibility to the active metabolite that would account for the differences between the CD-1 and NSA mice.

Pulmonary Lesions in Mice Inoculated with Actinobacillus pleuropneumoniae Hemolysin and Lipopolysaccharide

Non-Swiss albino (CF1) male mice were used as a model to study the effects of specific toxic components of Actinobacillus pleuropneumoniae on the respiratory system. Mice were divided into five groups of ten each and were inoculated by the intranasal route with whole-cell Actinobacillus pleuropneumoniae serotype 1, cell-free culture supernatant fluid (CFCSF) containing hemolysin protein, purified lipopolysaccharide (LPS), heat-treated CFCSF, or phosphate-buffered saline solution. Pulmonary lesions were evaluated at 6 and 12 hours after inoculation. Mice inoculated with whole cells, CFCSF, and LPS developed severe purulent bronchiolitis and alveolitis. Focal pulmonary necrosis was also observed in these three groups but was most consistent in the CFCSF-inoculated mice. Ultrastructurally, lungs from mice inoculated with whole cells, LPS, and CFCSF were characterized by severe degenerative changes in type I and type II pneumocytes. Alveolar spaces contained cellular debris and fibrin. Endothelial cells were swollen, and selected pulmonary capillaries were occluded with platelets and fibrin. Infiltrating neutrophils were often swollen, vacuolated, and degranulated. Although inoculation with relatively large numbers of A. pleuropneumoniae are required to kill mice, the mouse lung appears quite sensitive to the toxic components produced by these bacteria. The elaboration of these two toxic components by A. pleuropneumoniae may be responsible for the characteristic pulmonary inflammatory and necrotic lesions observed in infected swine.

Lung Clearance of Inhaled Insoluble and Soluble Particles

Lung Clearance of Inhaled Insoluble and Soluble Particles