Alfonso Lopez

Biochemical and cytologic alterations in the respiratory tract of rats exposed for 4 hours to hydrogen sulfide

Fischer-344 rats were killed by exsanguination 1, 20, and 44 hr after a single 4-hr exposure to an atmosphere of 0, 10, 200, and 400 ppm of hydrogen sulfide (H2S). Alterations in the activities of lactate dehydrogenase and alkaline phosphatase, and cytomorphology of epithelial cells in fluids obtained by nasal and bronchoalveolar lavage were used as indicators of cell injury. Changes in the number of leukocytes were used as indicators of inflammatory response, and changes in the concentration of protein were used as indicators of altered vascular permeability. Inhalation of H2S resulted in 139, 483, and 817% increased cellularity in the nasal cavity of rats exposed to 10, 200, and 400 ppm, respectively. This was due to marked exfoliation of degenerated epithelial cells and exudation of neutrophils. The high dose of H2S resulted in a moderate increase in lactate dehydrogenase and protein in nasal passages; values returned to baseline levels 20 hr later. Bronchoalveolar cell counts were decreased in rats exposed to 400 ppm and unchanged in those exposed to 10 and 200 ppm. Enzymatic activities in lung lavage fluid were moderately elevated (up to 90%), yet protein concentrations were increased by more than 3000% and remained significantly elevated up to 44 hr after exposure to 400 ppm. It was concluded that inhalation of H2S has a severe cytotoxic effect on the nasal epithelium and a severe edematogenic effect on lung parenchyma. These results are in agreement with autopsy findings of individuals killed by accidental exposure to H2S-containing sour gas.

Peracute Toxic Effects of Inhaled Hydrogen Sulfide and Injected Sodium Hydrosulfide on the Lungs of Rats

This study was designed to test whether intraperitoneally injected sodium hydrosulfide (NaHS) would mimic the pulmonary alterations induced by lethal peracute exposure to an atmosphere containing hydrogen sulfide. Groups of five Sprague-Dawley rats were exposed to an atmosphere of either 2317.6 +/- 547.3 mg m-3 H2S (H2S group) or no H2S (air group), or were injected intraperitoneally with a solution containing 30 mg kg-1 sodium hydrosulfide (NaHS group) or saline solution (vehicle control). Rats of the air and saline groups were killed by cervical dislocation. All rats exposed to H2S or injected with NaHS died within 3 min; however, only rats exposed to H2S showed severe respiratory distress in the agonic phase preceding death. In addition, rats in the H2S group had a notable discharge of serous fluid from the mouth and nostrils. At necropsy, all rats in the H2S group had gross and histologic evidence of pulmonary edema characterized by massive extravasation of eosinophilic fluid into the bronchoalveolar space. In contrast, the lungs of rats injected with NaHS or saline or exposed to air were unaffected. It was concluded that the edematogenic effect of H2S in the lungs cannot be reproduced by injection of NaHS. The severity of lung edema induced by a peracute exposure to H2S was extensive enough to account for death.

Histologic and Ultrastructural Alterations in Lungs of Rats Exposed to Sub-lethal Concentrations of Hydrogen Sulfide

Fischer-344 rats were killed 1, 18, and 42 hr after a single 4-hr exposure to an atmosphere of 0, 116, or 615 mg m-3 of hydrogen sulfide (H2S). Lungs, fixed by the intratracheal route, were examined by light and electron microscopy. Histologic changes were transient and mainly present in rats exposed to 615 mg m-3 H2S. Lesions included severe but transitory pulmonary edema and fibrinocellular alveolitis which was restricted to the proximal alveolar region of the lung. Electron microscopically, ciliated bronchiolar cells were the only cells that developed necrosis; they were rapidly replaced by mitosis. Alveolar endothelium had cytoplasmic blebs, but alveolar epithelium had minor changes. No mast cell degranulation was detected in lungs with edema. A 4-hr exposure to 615 mg m-3 is markedly edematogenic for the lung but only moderately cytotoxic for pulmonary cells.

Pulmonary Inflammation Associated with Aspirated Meconium and Epithelial Cells in Calves

“Meconium aspiration syndrome” is a condition resulting in respiratory distress and the occasional death of newborn human beings. A retrospective study was conducted on 52 calves that were submitted for postmortem examination to the Atlantic Veterinary College, Charlottetown, Prince Edward Island, Canada. These calves died of infectious and noninfectious diseases within the first 2 weeks of life due to a variety of causes. The most common cause of death was infectious enteric disease. Histologic examination of lungs revealed that 42.5% of calves had evidence of meconium, squamous cells, or keratin in the lung. There was considerable variation in the magnitude of histologic changes in lungs containing aspirated material. Typically, affected lungs had only a few inconspicuous pieces of meconium, keratin, and squamous cells within bronchoalveolar spaces. Sporadically, the entire lumen of airways was obliterated by aspirated material. Lungs with aspirated material had a mild but diffuse alveolitis characterized by exudation of a few neutrophils, macrophages, and occasional multinucleated giant cells. Obstruction of small airways and focal atelectasis were also observed. Similar lesions have been reported in human meconium aspiration syndrome. It is concluded that histologic changes similar to those of human meconium aspiration syndrome occur commonly in calves that die within 2 weeks of birth. Further studies involving healthy age-matched calves are required to evaluate the clinicopathologic significance of meconium aspiration in this species.

Capsaicin Pretreatment Modifies Hydrogen Sulphide-Induced Pulmonary Injury in Rats*

One of the major target organs of hydrogen sulphide gas is the lung. Exfoliation of upper respiratory epithelia and pulmonary edema are prominent effects. Various neuropeptides contained in afferent C-fibres are intimately associated with the epithelia of the conducting airways and are liberated upon exposure to noxious gases. We sought to determine their role in the pathogenesis of hydrogen-sulphide-induced pulmonary injury by pretreating rats with the neurotoxin, capsaicin, which is known to ablate a subpopulation of vagal afferent C-fibres. Groups of capsaicin and saline (control) pretreated Fischer 344 rats were exposed to an edemogenic concentration of hydrogen sulphide (525-559 mg/rn3) for 4 hr. Mortality was significantly greater (p < 0.01) in the capsaicin treated rats (12/12) compared to the control animals (2/12). Pulmonary injury was also more severe in the capsaicin pretreated animals as assessed by lung water content, histological grade of pulmonary edema and protein in the broncho-alveolar fluid. Animals depleted of substance P exhibited a significantly greater (p < 0.01) degree of bronchial epithelial cell exfoliation and ulceration following exposure to hydrogen sulphide. These experiments indicate that capsaicin sensitive sensory nerves may play a major role in pulmonary defense against the effects of inhaled toxic gases such as hydrogen sulphide.

Meconium inhibits phagocytosis and stimulates respiratory burst in alveolar macrophages.

The meconium aspiration syndrome is an important cause of respiratory distress in newborn infants. Alveolar macrophages (AMs) provide a first line of defense in the lower respiratory tract against inhaled pathogens and particles such as meconium. In this study, we examined the effect of meconium on two primary macrophage functions: phagocytosis and respiratory burst. Short-term exposure of rat NR8383 AMs to sterile meconium from human or equine neonates (1.2–24 mg/mL) produced a dose-dependent decrease in phagocytosis of fluorescent latex beads. This effect was not due to decreased cell viability or to an elevation of intracellular cAMP. The effect of short-term exposure to meconium on the respiratory burst response in AMs was quantified using flow cytometry to measure oxidation of dichlorofluorescin diacetate. A robust respiratory burst was triggered when AMs were exposed to 12 or 24 mg/mL meconium. This effect was attenuated but not eliminated by filtration of the meconium. However, subsequent to meconium exposure, AMs had a reduced respiratory burst in response to stimulation with phorbol myristate acetate. In addition, AMs that were exposed to meconium for an extended period (24 h) showed DNA fragmentation indicative of apoptosis. Meconium therefore may interfere with AM function by inducing oxidative stress and apoptosis. Tissue injury from release of reactive oxygen species by AMs may be important in the pathophysiology of the meconium aspiration syndrome.

Distribution of Crenosoma Vulpis and Eucoleus Aerophilus in the Lung of Free-Ranging Red Foxes (Vulpes Vulpes):

Crenosoma vulpis and Eucoleus aerophilus are nematode parasites that can cause verminous pneumonia in wild carnivores. There is a paucity of information regarding the distribution of parasites in the lungs and the relationship between histopathological and parasitological diagnoses in naturally infected foxes. The objectives of this study were: first, to study the lobar and airway distribution of C. vulpis and E. aerophilus in wild red foxes and second, to investigate the relationship between fecal and histopathological diagnoses. Samples from 6 sites of the lung and fecal contents were obtained from 51 wild foxes in Prince Edward Island. By fecal examination, 78.4% of wild foxes tested positive for C. vulpis and 68.6% for E. aerophilus. In contrast, 66.6% and 49% of foxes had histopathological evidence of C. vulpis and E. aerophilus in the lungs, respectively. Anatomically, C. vulpis was observed in the small bronchi and bronchioles of all pulmonary lobes whereas E. aerophilus was restricted to the large bronchi and the caudal lobes. Affected airways exhibited severe epithelial glandular hyperplasia and bronchiolar mucous metaplasia. It was concluded that C. vulpis is widely distributed in airways of all pulmonary lobes, whereas E. aerophilus is mainly restricted to the bronchi of caudal lobes. Also, this study showed that histological examination of lung underestimates the infection with E. aerophilus.

Berberine Improves Glucose Homeostasis in Streptozotocin-Induced Diabetic Rats in Association with Multiple Factors of Insulin Resistance

The present study was carried out to determine the effect of berberine on glucose homeostasis and several biomarkers associated with insulin sensitivity in male Wistar rats with intraperitoneal injection of streptozotocin (STZ)-induced diabetes. Rats with fasting blood glucose 16.7 mmol/L after 2 weeks of STZ injection were divided into two groups. One group was used as the diabetic control and another treated by gavage feeding with 100 mg/kg/d of berberine in water containing 0.5% carboxymethyl cellulose. A group of rats without receiving STZ was used as the normal control. After 7 weeks, berberine supplementation moderately but significantly lowered fasting blood glucose levels and improved oral glucose tolerance. Berberine lowered plasma free fatty acids and C-reactive protein levels without affecting plasma insulin levels. Diabetic rats treated with berberine showed significantly lower plasma triacylglycerol and cholesterol levels. Furthermore, berberine inhibited dipeptidyl peptidase-4 and protein tyrosine phosphatase-1B activities. In conclusion, berberine showed a dramatic effect of lowering blood cholesterol and triacylglycerols and improved moderately glucose homeostasis in STZ-induced diabetic rats in association with multiple factors related to insulin resistance.

Comparison of eight different procedures for harvesting avian reoviruses grown in Vero cells

14 avian reovirus isolates adapted to replicate in an African green monkey (Vero) cell line were studied for the nature of their replication. The growth curves of 5 viruses showed them to be highly cell-associated in Vero cells. Different procedures were examined for releasing the cell-associated virus following propagation in Vero cells, including several freeze-thaw cycles, treatment with sterile distilled deionized water (ddH2O), freon extraction, and trypsin treatment. Treatment of virus infected cultures with ddH2O was the most effective, and trypsin treatment was the least effective procedure for dissociation of virus from cells. Treatment of virus infected cultures with ddH2O is a simple and effective procedure which can be used where large amounts of virus are required for experimental purposes.

Pulmonary Sarcocystosis in a Puppy with Canine Distemper in Costa Rica

Canine distemper and pulmonary sarcocystosis were diagnosed in a 10-week-old Rottweiler with 4-day history of diarrhea, vomiting, and weakness. Microscopic examination of the lung revealed bronchointerstitial pneumonia typical of morbillivirus infection. Also, numerous apicomplexan parasites were scattered in the alveolar walls. This protozoan infection was first thought to be toxoplasmosis but immunoperoxidase staining revealed large numbers of Sarcocystis canis. This is the first case of canine sarcocystosis reported from Latin America that further emphasizes the importance of immunohistochemistry in the differential diagnoses of apicomplexan infections in dogs.