Seroprevalence of Toxoplasma gondii and Neospora spp. Infections in Arab Horses, Southwest of Iran

Background: Because of the economic importance of the Arab race horses and also the role of Toxoplasma gondii and Neospora spp. in abortion and reproductive failure of these animals, we decided to perform this study. Objectives: We designed this study to investigate the seroprevalence of anti-Toxoplasma gondii and anti-Neospora spp. antibodies in Arab horses from 12 cities of Khuzestan province in southwest of Iran. Materials and Methods: From October 2009 to March 2011, a total of 235 blood samples were collected from jugular veins of Arab horses of different ages and genders from 12 cities of Khuzestan province. All the sera were tested for anti-Toxoplasma antibodies using the modified agglutination test (MAT) and the existence of anti-Neospora antibodies were tested using N-MAT for Neospora spp. Results: According to the MAT results, antibodies to T. gondii were found in 114 (48.5%) of 235 sera with titers of 1:20 in 84, 1:40 in 19, 1:80 in four, 1:160 in four, and 1:320 in three horses. According to the N-MAT results, antibodies to Neospora spp. were found in 47 (20%) of 235 sera with titers of 1:40 in 39, 1:80 in five, and 1:160 in three horses. We did not observe any statistically significant differences regarding age groups and genders between seropositive and seronegative horses for Neospora spp. using chi-square (chi(2)) test, but it seemed that anti-Toxoplasma antibodies were more prevalent in older horses ( >= 10 years old). Conclusions: The results indicated that Arab horses are exposed to these parasites in southwest of Iran. Further research is required to determine the genomic structures of these parasites in Arab horses in southwest of Iran

Age-Related Changes of Myelin Basic Protein in Mouse and Human Auditory Nerve

Age-related hearing loss (presbyacusis) is the most common type of hearing impairment. One of the most consistent pathological changes seen in presbyacusis is the loss of spiral ganglion neurons (SGNs). Defining the cellular and molecular basis of SGN degeneration in the human inner ear is critical to gaining a better understanding of the pathophysiology of presbyacusis. However, information on age-related cellular and molecular alterations in the human spiral ganglion remains scant, owing to the very limited availably of human specimens suitable for high resolution morphological and molecular analysis. This study aimed at defining age-related alterations in the auditory nerve in human temporal bones and determining if immunostaining for myelin basic protein (MBP) can be used as an alternative approach to electron microscopy for evaluating myelin degeneration. For comparative purposes, we evaluated ultrastructural alternations and changes in MBP immunostaining in aging CBA/CaJ mice. We then examined 13 temporal bones from 10 human donors, including 4 adults aged 38–46 years (middle-aged group) and 6 adults aged 63–91 years (older group). Similar to the mouse, intense immunostaining of MBP was present throughout the auditory nerve of the middle-aged human donors. Significant declines in MBP immunoreactivity and losses of MBP+ auditory nerve fibers were observed in the spiral ganglia of both the older human and aged mouse ears. This study demonstrates that immunostaining for MBP in combination with confocal microscopy provides a sensitive, reliable, and efficient method for assessing alterations of myelin sheaths in the auditory nerve. The results also suggest that myelin degeneration may play a critical role in the SGN loss and the subsequent decline of the auditory nerve function in presbyacusis

Increases in peripheral oxygen demand affect blood flow distribution in hemorrhaged dogs

Blood flow redistribution away from the gastrointestinal tract and kidney occurs during progressive hemorrhage and stress. However, the effects of remote increases in oxygen demand on a circulation with limited ability to respond have not been described. Thus, we observed the effect of remote increases in oxygen demand on splanchnic and renal blood flow in hemorrhaged dogs. Nine α-chloralose-anesthetized, splenectomized dogs were subjected to hemorrhage of 10 ml/kg followed by an additional 5 ml/kg. At each of these two stages, bilateral femoral nerve stimulation was used to increase lower extremity oxygen demand while lower extremity, splanchnic, renal blood flows and arteriovenous oxygen content differences were monitored. Hemorrhage was associated with redistribution of blood flow away from the lower extremities and kidneys and increasing the oxygen extraction ratio of the splanchnic bed. Lower extremity stimulation increased whole-body oxygen consumption (7.3 ± 2.7 to 11.4 ± 4.5 ml O2/min/kg, p 90% of baseline value, n = 9), visceral organ blood flow did not change. However, when blood pressure decreased (< 70% of baseline, n = 8), splanchnic (226.3 ± 143.5 to 140.9 ± 126.4 ml/min, p < 0.01) and renal (59.6 ± 30.2 to 28.5 ± 26.0 ml/min, p < 0.01) blood flow also decreased. Thus, in the anesthetized, hemorrhaged dog, increased peripheral oxygen demand results in further redistribution of blood flow away from the gastrointestinal tract and kidneys only when there is a concurrent decrease in blood pressure

Cardiopulmonary effects of positive pressure ventilation during acute lung injury

Study objectives: To assess the gas exchange and hemodynamic effects of pressure-limited ventilation (PLV) strategies in acute lung injury (ALI). We hypothesized that in ALI, the reduction of plateau airway pressure (Paw) would be associated with less alveolar overdistention and thus have better hemodynamic and gas exchange characteristics than larger tidal volume (VT) ventilation. Setting: Laboratory. Design: Prospective time-controlled sequential animal study. Measurements: Right atrial, pulmonary artery, left atrial, arterial, lateral pleural (Ppl), and pericardial (Ppc) pressures, Paw, ventricular stroke volume, mean expired CO2, and arterial and mixed venous oxygen contents. Airway resistance and static lung compliance were also measured. Interventions: Intermittent positive pressure ventilation (IPPV) given before (control) and after induction of ALl by oleic acid infusion (0.1 mL/kg). IPPV at FIO2 of 1, VT of 12 mL/kg, and frequency adjusted to maintain normocarbia. ALI PLV was given during ALI and defined as that VT which gave a similar plateau Paw to that of control IPPV. High- frequency jet ventilation (HFJV) and ALI HFJV were also given and defined as frequency within 10% of heart rate and mean Paw similar to that during control IPPV. Results: After ALI, static lung compliance, PaO2, and pH decreased, whereas airway resistance and PaCO2 increased. For a constant lung volume, Ppl and Ppc were not different between control and ALI. Both absolute dead space (VD) and intrapulmonary shunt fraction increased after ALI, but absolute VD was lower with ALI PLV and ALI HFJV when compared with ALI IPPV. Ventilation did not alter hemodynamics during ALI. Conclusions: Changes in lung volume determine Ppc and Ppl. PLV strategies do not alter hemodynamics but result in less of an increase in VD/VT than would be predicted from the obligatory decrease in VT

On-line estimation of stroke volume by means of echocardiographic automated border detection in the canine left ventricle

Echocardiographic automated border detection (ABD) is a new on-line technique that can determine the interface between blood and myocardial tissue and calculate left ventricular (LV) cavity area in real time. The objective of this study was to determine whether ABD measurements of the LV cavity area could be used to estimate LV stroke volume at basal conditions and during large changes in LV stroke volume induced by inferior vena caval occlusions in an open-chest canine model. Seven dogs had LV stroke volume measured by electromagnetic flow from the ascending aorta with epicardial recordings of ABD echocardiographic area at the midventricular short-axis level. Simultaneous beats of stroke volume were recorded along with ABD echo area during baseline apnea and during IVC occlusions. Neither ABD echo stroke area nor stroke volume varied significantly during apnea baseline. Changes in stroke area were closely correlated with changes in stroke volume for 540 matched beats from 24 IVC occlusions: R = 0.93, standard error of the estimate = 5%, y = 0.92x + 0.4 (p < 0.001). Echocardiographic ABD appears to be a promising new on-line method of determining rapid alterations in LV stroke volume; it also has potential applications to multiple investigational and clinical settings. © 1993

Effect of inhaled nitric oxide on pulmonary hemodynamics after acute lung injury in dogs

Increased pulmonary vascular resistance (PVR) and mismatch in ventilation- to-perfusion ratio characterize acute lung injury (ALI). Pulmonary arterial pressure (Ppa) decreases when nitric oxide (NO) is inhaled during hypoxic pulmonary vasoconstriction (HPV); thus NO inhalation may reduce PVR and improve gas exchange in ALI. We studied the hemodynamic and gas exchange effects of NO inhalation during HPV and then ALI in eight anesthetized open- chest mechanically ventilated dogs. Right atrial pressure, Ppa, and left ventricular and arterial pressures were measured, and cardiac output was estimated by an aortic flow probe. Shunt and dead space were also estimated. The effect of 5-min exposures to 0, 17, 28, 47, and 0 ppm inhaled NO was recorded during hyperoxia, hypoxia, and oleic acid-induced ALI. During ALI, partial β-adrenergic blockade (propranolol, 0.15 mg/kg iv) was induced and 74 ppm NO was inhaled. Nitrosylhemoglobin (NO-Hb) and methemoglobin (MetHb) levels were measured. During hyperoxia, NO inhalation had no measurable effects. Hypoxia increased Ppa (from 19.8 ± 6.1 to 28.3 ± 8.7 mmHg; P < 0.01) and calculated PVR (from 437 ± 139 to 720 ± 264 dyn · s · cm-5, P < 0.01), both of which decreased with 17 ppm NO. ALI decreased arterial PO2 and increased airway pressure, shunt, and dead space ventilation. Ppa (19.8 ± 6.1 vs. 23.4 ± 7.7 mmHg) and PVR (437 ± 139 vs. 695 ± 359 dyn · s · cm-5, P < 0.05) were greater during ALI than during hyperoxia. NO inhalation had no measurable effect during ALI before or after β-adrenergic blockade. MetHb remained low, and NO-Hb was unmeasurable. Bolus infusion of nitroglycerin (15 μg) induced an immediate decrease in Ppa and PVR during ALI. Short-term NO inhalation does not affect PVR or gas exchange in dogs with oleic acid-induced ALI, nor does it increase NO-Hb or MetHb. In contrast, NO can diminish hypoxia-induced elevations in pulmonary vascular tone. These data suggest that NO inhalation selectively dilates the pulmonary circulation and specifically reduces HPV but not oleic acid-induced increases in pulmonary vasomotor tone

Inhaled nitric oxide partially reverses hypoxic pulmonary vasoconstriction in the dog

Nitric oxide (NO) inhaled during a hypoxia-induced increase in pulmonary vasomotor tone decreases pulmonary arterial pressure (Ppa). We conducted this study to better characterize the hemodynamic effects induced by NO inhalation during hypoxic pulmonary vasoconstriction in 11 anesthetized ventilated dogs. Arterial and venous systemic and pulmonary pressures and aortic flow probe- derived cardiac output were recorded, and nitrosylhemoglobin (NO-Hb) and methemoglobin (MetHb) were measured. The effects of 5 min of NO inhalation at 0, 17, 28, 47, and 0 ppm during hyperoxia (inspiratory fraction of O2 = 0.5) and hypoxia (inspiratory fraction of O2 = 0.16) were observed. NO inhalation has no measurable effects during hyperoxia. Hypoxia induced an increase in Ppa that reached plateau levels after 5 min. Exposure to 28 and 47 ppm NO induced an immediate (<30 s) decrease in Ppa and calculated pulmonary vascular resistance (P < 0.05 each) but did not return either to baseline hyperoxic values. Increasing the concentration of NO to 74 and 145 ppm in two dogs during hypoxia did not induce any further decreases in Ppa. Reversing hypoxia while NO remained at 47 ppm further decreased Ppa and pulmonary vascular resistance to baseline values. NO inhalation did not induce decreases in systemic arterial pressure. MetHb remained low, and NO-Hb was unmeasurable. We concluded that NO inhalation only partially reversed hypoxia-induced increases in pulmonary vasomotor tone in this canine model. These effects are immediate and selective to the pulmonary circulation

Hemodynamic effects of synchronized high-frequency jet ventilation compared with low-frequency intermittent positive-pressure ventilation after myocardial revascularization

Background: The purpose of this prospective study was to examine the effect on cardiac performance of selective increases in airway pressure at specific points of the cardiac cycle using synchronized high-frequency jet ventilation (sync-HFJV) delivered concomitantly with each single heart beat compared with controlled mechanical ventilation in 20 hemodynamically stable, deeply sedated patients immediately after coronary artery bypass graft. Methods: Five 30-min sequential ventilation periods were used interspersing controlled mechanical ventilation with sync-HFJV twice to control for time and sequencing effects. Sync-HFJV was applied using a driving pressure, which generated a tidal volume resulting in gas exchanges close to those obtained on controlled mechanical ventilation and associated with the maximal mixed venous oxygen saturation. Hemodynamic variables including cardiac output, mixed venous oxygen saturation and vascular pressures were recorded at the end of each ventilation period. Results: The authors found that in 20 patients, hemodynamic changes induced by controlled mechanical ventilation and by sync-HFJV were similar. Cardiac index did not change (mean ± SD for controlled mechanical ventilation: 2.6 ± 0.7 1 · min-1 · m-2; for sync-HFJV: 2.7 ± 0.7 1 · min-1 · m-2; P value not significant). This observation persisted after stratification according to baseline left- ventricular contractility, as estimated by ejection fraction. Conclusions: The authors conclude that after coronary artery bypass graft, if gas-exchange values are maintained within normal range, sync-HFJV does not result in more favorable hemodynamic support than controlled mechanical ventilation. These findings contrast with the beneficial effects of sync-HFJV, resulting in marked hypocapnia, on cardiac performance observed in patients with terminal left-ventricular failure

Estimating left ventricular contractility using inspiratory-hold maneuvers

Objective: To compare estimates of left ventricular (LV) end-systolic elastance created by inferior vena caval (IVC) occlusion with those by apneic continuous positive airway pressure (CPAP). Design and setting: Prospective interventional study in a university large animal research laboratory. Subjects: Sixteen intact, pentobarbital-anesthetized mongrel male dogs. Interventions: Insertion of LV conductance and pressure catheters, then during apnea sequentially performed IVC occlusion and CPAP of 5, 10, and 15 mmHg for 10 s, each interspersed by positive-pressure breathing. In the final 11 dogs runs were repeated during both esmolol (2 mg min-1) and dobutamine (5 μg kg-1 min-1) infusions. Measurements: LV pressure-volume relationships during apneic baseline and then as LV end-diastolic volume decreased by each maneuver to calculate LV end-systolic elastance and preload-recruitable stroke work as measures of contractility. Results: End-systolic elastance estimated at 5 mmHg CPAP levels and IVC occlusions were similar while 10 and 15 mmHg CPAP gave different values. However, end-systolic elastance was lower during esmolol infusion and higher during dobutamine for all CPAP and IVC occlusion maneuvers. Preload-recruitable stroke work measures were similar across maneuvers. With increasing CPAP the LV filling and end-systolic elastance were progressively shifted upward and to the left, with volume on the x-axis, consistent with an unaccounted for increase in intrathoracic pressure. Conclusions: The use of 5 mmHg CPAP-induced preload-reduction allows estimation of LV end-systolic elastance and preload-recruitable stroke work in intact dogs. Increasing CPAP to more than 10 mmHg creates estimates of LV contractility that are different but covary with IVC occlusion-derived values. © 2006 Springer-Verlag