Comparison of Tube, Gel, and Immunochromatographic Strip Methods for Evaluation of Blood Transfusion Compatibility in Horses.

BACKGROUND: Assessment of blood compatibility, typically by tube agglutination (TUBE) and hemolysis crossmatch or, less commonly, by blood typing and alloantibody screening, often is performed before blood transfusion in horses. In contrast, gel column (GEL) and immunochromatographic strip (STRIP) techniques are preferred for compatibility testing in dogs and cats. OBJECTIVE: To determine the accuracy of novel and standard crossmatch and typing methods. ANIMALS: Thirty-eight healthy horses, previously blood typed and alloantibody screened. METHODS: TUBE and GEL crossmatches were performed on 146 different recipient-donor pairs with 56 incompatible TUBE crossmatches. Crossmatches were compared by nonparametric area under the curve of receiver operating characteristic (AUC-ROC) analyses. Horses also were blood typed by the novel immunochromatographic Ca typing STRIP. RESULTS: Compared to TUBE crossmatch, GEL had excellent accuracy for agglutination (AUC-ROC = 0.903), but marginal accuracy for hemolysis (AUC-ROC = 0.639). Compared to macroscopic TUBE, microscopic TUBE had excellent accuracy for agglutination (AUC-ROC = 0.912). The predicted crossmatch compatibility based on blood type and alloantibody assay showed excellent accuracy compared to TUBE and GEL (AUC-ROC = 0.843 and 0.897, respectively). However, there were more recipient-donor pairs identified as incompatible by both TUBE and GEL than predicted by blood type and antibody screen, suggesting the presence of unidentified alloantibodies. A Ca typing STRIP exhibited 100% sensitivity and specificity for the 35 Ca+ and 3 Ca- horses tested. CONCLUSIONS AND CLINICAL RELEVANCE: Gel column crossmatch and Ca typing immunochromatographic strip are simple and accurate methods to evaluate clinical blood compatibility.

Clinical and Pathological Features of Pheochromocytoma in the Horse: A Multi-Center Retrospective Study of 37 Cases (2007-2014).

BACKGROUND: Pheochromocytoma is the most common adrenal medullary neoplasm of domestic animals, but it is rare in horses. Antemortem diagnosis in horses is difficult, with clinical signs often being vague or non-specific. OBJECTIVE: The objective of this study was to describe the clinical, laboratory, and pathologic findings of pheochromocytoma in horses. ANIMALS: Thirty-seven horses diagnosed with pheochromocytoma based on postmortem examination from 2007 to 2014. METHODS: Retrospective case series. RESULTS: Pheochromocytoma was identified in 37/4094 horses during postmortem examination. Clinical signs consistent with pheochromocytoma had been observed antemortem in only 7 cases, with the remainder being incidental findings. Colic was the most common presenting complaint (13 of 37 cases) and tachycardia was noted in 95% of cases (median heart rate of 86 bpm in clinical cases). Hyperlactatemia (median, 4.9 mmol/L) and hyperglycemia (median, 184 mg/dL) were the most common clinicopathologic abnormalities. Hemoperitoneum caused by rupture of pheochromocytoma was noted in 4/7 clinical cases. Concurrent endocrine abnormalities (eg, thyroid adenoma, adrenal hyperplasia, pituitary pars intermedia hyperplasia or adenoma, parathyroid C-cell carcinoma) were found in 27/37 horses, with 8/37 horses having lesions consistent with multiple endocrine neoplasia syndrome as described in humans. CONCLUSIONS: Pheochromocytoma was diagnosed in 0.95% of horses presented for necropsy. The majority of these were incidental findings, but pheochromocytoma was thought to contribute to clinical findings in 19% of cases, and multiple endocrine neoplasms were commonly seen. Usually an incidental finding at necropsy, pheochromocytoma may cause acute death from intraperitoneal exsanguination and should be considered in horses presenting with colic, tachycardia, and hemoperitoneum.

Efficacy of major anthelmintics for reduction of fecal shedding of strongyle-type eggs in horses in the Mid-Atlantic region of the United States.

In the last decade there have been numerous reports of anthelmintic resistant cyathostomins in many parts of the world. The objective of the present study was to evaluate the efficacy of the commercially available anthelmintics against cyathostomin egg shedding in the Mid-Atlantic region of the United States. A total of 989 horses from 67 different farms located in southeastern Pennsylvania, northern Delaware, and northeastern Maryland were treated with fenbendazole, oxibendazole, pyrantel pamoate, ivermectin, or moxidectin at their recommended dosages. Fecal egg count reduction testing was used to determine the efficacy of each anthelmintic on those horses with fecal egg counts of ≥ 200 eggs per gram on the day of treatment (272 horses). Decreased efficacy (reduction of strongyle-type fecal egg counts by less than 90%) was found for fenbendazole, oxibendazole, and pyrantel pamoate, with only 6%, 21% and 43% of horses showing reductions of greater than 90%, respectively. The macrocyclic lactones showed high efficacy in all horses sampled in this study. The decreased anthelmintic efficacy detected in this study adds further evidence for the existence of resistant cyathostomins throughout much of the eastern United States. Findings from this study can be used to create a more sustainable approach for parasite control programs.

Plasma Peak and Trough Gentamicin Concentrations in Hospitalized Horses Receiving Intravenously Administered Gentamicin.

BACKGROUND: Gentamicin is an aminoglycoside antimicrobial commonly used in horses at 6.6 mg/kg IV once daily. Therapeutic drug monitoring (TDM) can confirm desired peak concentration is reached for common bacterial isolates, and detect toxicosis associated with high trough values. OBJECTIVES: Determine the relationship between gentamicin dose and plasma concentration in hospitalized horses, and identify a starting dose range to achieve peaks > 32 µg/mL. ANIMALS: Sixty-five horses (2002-2010) receiving once-daily gentamicin with TDM performed (N = 99 sets). METHODS: Retrospective study. Data from hospitalized horses including weight, dose, plasma peak, and trough gentamicin concentration, creatinine concentrations and presence of focal or systemic disease were collected from medical records. Peak concentrations measured 25-35 minutes after administration were included (N = 77). Data were divided into low (<7.7 mg/kg), medium (7.7-9.7 mg/kg) and high (>9.7 mg/kg) dose groups, and were grouped by the horse having focal or systemic disease. RESULTS: Peak concentrations resulting from doses ≥7.7 mg/kg were 5.74 µg/mL (SE 2.1 µg/mL) greater than peaks from doses <7.7 mg/kg (P = .007). Peak concentrations was 3.6 times more likely to be >32 µg/mL if dose was ≥7.7 mg/kg (P = .04). There were no significant effects of dose on trough or creatinine concentration. At a given dose, horses with focal disease had higher peaks than those with systemic disease (P = .039). CONCLUSIONS AND CLINICAL IMPORTANCE: These data suggest gentamicin dosage should be individually determined in horses using TDM, but support an initial once-daily dose of 7.7-9.7 mg/kg IV to achieve peaks >32 µg/mL and trough concentrations <2 µg/mL. Further studies evaluating the safety of doses >6.6 mg/kg are required.

Survival Time of Cross-Match Incompatible Red Blood Cells in Adult Horses.

BACKGROUND: There is a markedly reduced half-life of transfused RBCs when donor and recipient cats or humans are cross-match incompatible. Only 10-20% of horses have naturally occurring alloantibodies. Therefore, cross-match testing before blood transfusion is not always performed. HYPOTHESIS: Cross-match incompatibility predicts shortened RBC survival time as compared to that of compatible or autologous blood. ANIMALS: Twenty healthy adult horses. METHODS: Prospective trial. Blood type, anti-RBC antibody screen (before and 1 month after transfusion) and major and minor cross-match determined 10 donor-recipient pairs. Two pairs were cross-match compatible, the remainder incompatible. Donor blood (4 L) was collected into citrate phosphate dextrose adenine-1, labeled with NHS-biotin, and transfused into recipients. Samples were collected at 1 hour and 1, 2, 3, 5, 7, 14, 21, 28, and 35 days after transfusion, and biotinylated RBCs were detected by flow cytometry. Horses were monitored for transfusion reaction during transfusion and daily for 5 days. RESULTS: Cross-match incompatibility was significantly associated with decreased RBC survival time (P < .001). The half-life of transfused incompatible (cross-match >1+) allogenic equine RBCs was 4.7 (95% CI, 3.2-6.2) days versus 33.5 (24-43) days for compatible pairings. Cross-match incompatibility was associated with acute febrile transfusion reaction (P = .0083). At day 30, only 1 horse had developed novel anti-RBC antibodies. CONCLUSIONS AND CLINICAL IMPORTANCE: Cross-match incompatibility was predictive of febrile transfusion reaction and shortened transfused RBC survival, but did not result in production of anti-RBC antibodies at 30 days. Cross-match testing before transfusion is recommended.

Effect of clenbuterol on tracheal mucociliary transport in horses undergoing simulated long-distance transportation.

BACKGROUND: Pneumonia is observed in horses after long-distance transportation in association with confinement of head position leading to reduction in tracheal mucociliary clearance rate (TMCR). HYPOTHESIS/OBJECTIVES: Clenbuterol, a beta-2 agonist shown to increase TMCR in the horse, will ameliorate the effects of a fixed elevated head position on large airway contamination and inflammation in a model of long-distance transportation model. ANIMALS: Six adult horses. METHODS: A cross-over designed prospective study. Horses were maintained with a fixed elevated head position for 48 hours to simulate long-distance transport, and treated with clenbuterol (0.8 µg/kg PO q12h) or a placebo starting 12 hours before simulated transportation. TMCR was measured using a charcoal clearance technique. Data were collected at baseline and 48 hours, and included TMCR, tracheal wash cytology and quantitative culture, rectal temperature, CBC, fibrinogen, and serum TNFα, IL-10, and IL-2 levels. There was a 18-21 day washout between study arms, and data were analyzed using regression analysis and Wilcoxon rank-sum tests. RESULTS: Tracheal mucociliary clearance rate was significantly decreased after transportation in both treatment (P = .002) and placebo (P = .03) groups. There was a significant effect of treatment on TMCR, with the treatment group showing half the reduction in TMCR compared with the placebo group (P = .002). Other significant differences between before- and after-transportation samples occurred for serum fibrinogen, peripheral eosinophil count, quantitative culture, tracheal bacteria, and degenerate neutrophils, though no treatment effect was found. CONCLUSIONS AND CLINICAL IMPORTANCE: Treatment with clenbuterol modestly attenuates the deleterious effects of this long-distance transportation model on tracheal mucociliary clearance.

Treatment of idiopathic headshaking in horses with pulsed high-dose dexamethasone.

BACKGROUND: Treatment of idiopathic headshaking in horses is complicated by an incomplete understanding of underlying pathophysiology and partially effective treatments. If an inflammatory etiology exists, corticosteroids could be beneficial. HYPOTHESIS: An anti-inflammatory dose of dexamethasone reduces the signs of idiopathic headshaking in a field setting. ANIMALS: Convenience sample of 20 adult horses with idiopathic headshaking syndrome. Cases were recruited from the general population and diagnosed by attending veterinarians. METHODS: Prospective, blinded clinical trial. Pulsed dosing was with oral dexamethasone (60 mg PO Q24h × 4 days, q3 weeks for 4 months) or placebo (inert paste). Owners were blinded and asked to score the headshaking from 0 to 4 (4 = most severe) 3 days per week. The change in headshaking scores (HS) over each treatment pulse was compared between groups by ordinal logistic regression. RESULTS: Twelve horses completed the trial. There was no significant difference between treated or placebo horses (P = .987). Sun (P ≤ .001), wind (P = .028), and exercise (P ≤ .045) significantly increased HS. CONCLUSIONS AND CLINICAL IMPORTANCE: No benefit of dexamethasone treatment was detected for idiopathic headshaking. The results confirmed previous reports of common triggers for headshaking behavior

Effect of sample storage on blood crossmatching in horses.

BACKGROUND: Blood samples banked for up to 1 month are typically used to perform pretransfusion testing in humans and small animals, but this has not been validated using blood from horses. HYPOTHESIS: Compatibility of equine blood samples is repeatable using fresh samples, and reproducible using donor blood samples stored for up to 4 weeks. ANIMALS: Six healthy adult horses. METHODS: Randomized, blinded experimental study. Immunologic compatibility of the blood of all horses was assessed using a major and minor saline agglutination and hemolysin crossmatch using blood samples refrigerated for 0-4 weeks and fresh blood from the same horses. Crossmatch results were scored and then compared to identify changes of compatibility in each of the 4 tests. In addition, repeatability of the crossmatch technique itself was assessed by performing 6 iterations of this procedure in immediate succession with fresh blood from 3 horses. RESULTS: No significant difference in crossmatch results was found using fresh blood (P = .39-1.00). Reproducibility was poor using blood stored for 1-4 weeks, especially in tests using stored erythrocytes (major antigen crossmatches), with significant differences from baseline at all weeks (P < .05); 13 of these differences were positive, indicating poorer compatibility. CONCLUSIONS AND CLINICAL IMPORTANCE: Equine blood crossmatching is repeatable using fresh blood, although decreased apparent compatibility after storage makes exclusion of compatible donors more likely than mistaken administration of incompatible blood. These data suggest that fresh samples should be collected from potential donors before crossmatching equine blood.

A multicenter retrospective study of 151 renal biopsies in horses.

BACKGROUND: Renal biopsies are uncommonly performed in horses and little is known about their diagnostic utility and associated complication rate. OBJECTIVE: To describe the techniques, the complication rate, risk factors, and histopathology results; as well as evaluate the safety and diagnostic utility of renal biopsy in the horse. ANIMALS: One hundred and forty-six horses from which 151 renal biopsies were obtained. Animals ranged in age from 48 hours to 30 years. METHODS: Multicenter retrospective study, with participation of 14 institutions (1983-2009). RESULTS: Renal biopsy in horses was associated with a similar rate of complications (11.3%) to that occurring in humans and companion animals. Complications were generally associated with hemorrhage or signs of colic, and required treatment in 3% of cases. Fatality rate was low (1/151; 0.7%). Biopsy specimens yielded sufficient tissue for a histopathologic diagnosis in most cases (94%) but diagnoses had only fair (72%) agreement with postmortem findings. Risk factors for complications included biopsy specimens of the left kidney (P = .030), a diagnosis of neoplasia (P = .004), and low urine specific gravity (P = .030). No association with complications was found for age, sex, breed, institution, presenting complaint, other initial clinicopathologic data, biopsy instrument, needle size, or use of ultrasonographic guidance. CONCLUSIONS AND CLINICAL IMPORTANCE: Renal biopsy in horses has low morbidity and results in a morphological histopathologic diagnosis in 94% of cases. However, this procedure might result in serious complications and should only be used when information obtained would be likely to impact decisions regarding patient management and prognosis.

Repeatability, reproducibility, and effect of head position on central venous pressure measurement in standing adult horses.

BACKGROUND: Central venous pressure (CVP) is a used as an estimation of intravascular volume status in various species. Techniques for measuring CVP in horses have been described, but the repeatability of these readings at a single time point or over time has not been established. HYPOTHESIS: That CVP measurements in healthy adult horses would be repeatable at each time point, that these readings would be reproducible over time, and that alteration in head position relative to the heart would alter CVP. ANIMALS: Ten healthy adult research horses. METHODS: In an experimental study, horses were instrumented with a central venous catheter. Readings were taken in triplicate q6h for 2 days by water manometry, and twice daily with the head in neutral, elevated, and lowered positions by electronic manometry. RESULTS: Variation in the "neutral" measurements obtained at each time point was <0.1 ± 1.0 cmH(2)O (P = .718). There was a significant decrease in CVP over time (P = .015), which was eliminated when results were controlled for acute decrease in body weight of -1.35% (presumed hypohydration because of lack of acclimatization and decreased water intake). Head height had a significant and directional effect on CVP in that the elevated head position decreased CVP -2.0 ± 6.5 cmH(2)O (P < .001) while the lowered head position increased CVP by 3.7 ± 5.5 cmH(2)O (P < .001). CONCLUSIONS AND CLINICAL IMPORTANCE: CVP values obtained by water manometry were repeatable in adult horses, but were reproducible only when controlled for changes in hydration. Care should be taken to maintain consistency in head position to prevent erroneous readings.

Comparison of water manometry to 2 commercial electronic pressure monitors for central venous pressure measurement in horses.

BACKGROUND: Central venous pressure (CVP) customarily has been measured in veterinary patients with water manometry. However, many institutions are now using stallside electronic monitors in both anesthesia and intensive care units for many aspects of patient monitoring. HYPOTHESIS: Electronic stall side monitoring devices will agree with water manometry for measurement of CVP in horses. ANIMALS: Ten healthy adult horses from the university research herd. METHODS: Central venous catheters were placed routinely, and measurements were obtained in triplicate with each of the 3 methods every 12 hours for 3 days. Data were analyzed by a Lin concordance correlation coefficient and modified Bland-Altman limits of agreement, with all devices compared pairwise. RESULTS: Compared with water manometry, agreement (bias) of the Passport was -1.94 cmH2O (95% limits of agreement, -8.54 to 4.66 cmH2O) and of the Medtronic was -1.83 cmH2O (95% limits of agreement, -8.60 to 4.94 cmH2O). When compared with the Passport, agreement of the data obtained with the Medtronic was 0.27 cmH2O (95% limits of agreement, -4.39 to 4.93 cmH2O). CONCLUSIONS AND CLINICAL IMPORTANCE: These data show that both electronic monitors systematically provide measurements that are approximately 2 cmH2O lower than water manometry, but differences between the 2 electronic devices are small enough (< 0.5 cmH2O) to be considered clinically unimportant. This discrepancy should be taken into account when interpreting data obtained with these monitoring devices.

Myocardial gene delivery using molecular cardiac surgery with recombinant adeno-associated virus vectors in vivo.

We use a novel technique that allows for closed recirculation of vector genomes in the cardiac circulation using cardiopulmonary bypass, referred to here as molecular cardiac surgery with recirculating delivery (MCARD). We demonstrate that this platform technology is highly efficient in isolating the heart from the systemic circulation in vivo. Using MCARD, we compare the relative efficacy of single-stranded (ss) adeno-associated virus (AAV)6, ssAAV9 and self-complimentary (sc)AAV6-encoding enhanced green fluorescent protein, driven by the constitutive cytomegalovirus promoter to transduce the ovine myocardium in situ. MCARD allows for the unprecedented delivery of up to 48 green fluorescent protein genome copies per cell globally in the sheep left ventricular (LV) myocardium. We demonstrate that scAAV6-mediated MCARD delivery results in global, cardiac-specific LV gene expression in the ovine heart and provides for considerably more robust and cardiac-specific gene delivery than other available delivery techniques such as intramuscular injection or intracoronary injection; thus, representing a potential, clinically translatable platform for heart failure gene therapy.

Echocardiographic changes in heart size in hypohydrated horses.

BACKGROUND: Hypohydration causes transient echocardiographic changes in pigs, dogs, humans, and cats. These changes mask the diagnosis of some cardiac diseases (valvular regurgitation, dilated cardiomyopathy) and promote the diagnosis of others (hypertropic cardiomyopathy and infiltrative disease), thus inhibiting accurate echocardiographic evaluation. OBJECTIVES: To describe the echocardiographic changes associated with hypohydration in normal horses. ANIMALS: Ten adult horses without detectable cardiac disease. METHODS: Experimental study. Echocardiographic examinations were performed on horses in the euhydrated and hypohydrated states. Horses were hypohydrated by combined water deprivation and furosemide administration until a 4-7% reduction in bodyweight was achieved. Statistical analyses were performed by paired t-tests. RESULTS: Hypohydration decreased left ventricular internal diameter in systole (0.8 ± 0.6 cm) and diastole (1.7 ± 0.9 cm), left atrial diameter (1.5 ± 0.4 cm) and left ventricular volume (490 ± 251 mL) (P-values < .01), and increased septal wall thickness in diastole (0.6 ± 0.3 cm), free wall thickness in diastole (0.5 ± 0.3 cm), mean wall thickness (0.5 ± 0.2 cm) and relative wall thickness (0.2 ± 0.1 cm) (P-values < .01). CONCLUSIONS AND CLINICAL IMPORTANCE: Hypohydration produces changes in left ventricular and atrial size that could mask or promote the severity of cardiac disease. The thickened, "pseudohypertrophied" appearance of the left ventricle in hypohydrated horses could affect interpretation of echocardiographic variables that are applied to the prediction of athletic performance. Echocardiography may prove a noninvasive method of monitoring volume status and response to fluid therapy in hypovolemic horses.

The effects of hypohydration on central venous pressure and splenic volume in adult horses.

BACKGROUND: Central venous pressure (CVP) is used in many species to monitor right-sided intravascular volume status, especially in critical care medicine. HYPOTHESIS: That hypohydration in adult horses is associated with a proportional reduction in CVP. ANIMALS: Ten healthy adult horses from the university teaching herd. METHODS: In this experimental study, horses underwent central venous catheter placement and CVP readings were obtained by water manometry. The horses were then deprived of water and administered furosemide (1 mg/kg IV q6h) for up to 36 hours. Weight, CVP, vital signs, PCV, total protein (TP), and serum lactate were monitored at baseline and every 6 hours until a target of 5% decrease in body weight loss was achieved. The spleen volume was estimated sonographically at baseline and peak volume depletion. Linear regression analysis was used to assess the association of CVP and other clinical parameters with degree of body weight loss over time. RESULTS: There was a significant association between CVP and decline in body weight (P < .001), with a decrease in CVP of 2.2 cmH(2)O for every percentage point decrease in body weight. Other significant associations between volume depletion and parameters measured included increased TP (P = .007), increased serum lactate concentration (P = .048), and decreased splenic volume (P = .046). There was no significant association between CVP and vital signs or PCV. CONCLUSIONS AND CLINICAL IMPORTANCE: These findings suggest that CVP monitoring might be a useful addition to the clinical evaluation of hydration status in adult horses.

Comparison of hematologic and biochemical results on blood obtained by jugular venipuncture as compared with intravenous catheter in adult horses.

BACKGROUND: During hospitalization, horses typically undergo frequent blood sampling for diagnostic testing and monitoring. The need for numerous samples in hospitalized horses makes acquisition from an intravenous catheter (IVC) both convenient and less stressful to the patient. HYPOTHESIS: We hypothesized that there would be no significant difference in the plasma chemistry and CBC variables from blood samples obtained from a jugular catheter as compared with direct jugular venipuncture. ANIMALS: Fifty adult hospitalized horses; 25 receiving constant rate crystalloid therapy, and 25 receiving low volume IV medication. METHODS: This study was conducted using a prospective, blinded, cross-over design. Samples were obtained sequentially by direct venipuncture of the jugular vein and aspiration from an IVC in the contralateral vein after an appropriate presample of blood was obtained and discarded. Samples were submitted for blinded analysis including CBC, plasma chemistry analysis, stall side plasma glucose concentration, PCV, and total protein concentration. Data obtained were analyzed using a Student's t-test with compensation for unequal variances between the 2 groups. Analyses were Bonferroni corrected for a 5% 2-tailed hypothesis test. RESULTS: There were no statistically significant or clinically relevant differences associated with sampling method (venipuncture versus catheter) regardless of fluid administration status in any of the 24 analytes measured. CONCLUSIONS AND CLINICAL IMPORTANCE: Blood samples obtained by IVC have clinically equivalent values to those taken by direct venipuncture in commonly performed analyses. Additional investigation is warranted to establish if this technique is associated with increased complications such as phlebitis or bacteremia.

Matrix modulation of compensatory lung regrowth and progenitor cell proliferation in mice.

Mechanical stress is an important modulator of lung morphogenesis, postnatal lung development, and compensatory lung regrowth. The effect of mechanical stress on stem or progenitor cells is unclear. We examined whether proliferative responses of epithelial progenitor cells, including dually immunoreactive (CCSP and proSP-C) progenitor cells (CCSP+/SP-C+) and type II alveolar epithelial cells (ATII), are affected by physical factors found in the lung of emphysematics, including loss of elastic recoil, reduced elastin content, and alveolar destruction. Mice underwent single lung pneumonectomy (PNY) to modulate transpulmonary pressure (mechanical stress) and to stimulate lung regeneration. Control mice underwent sham thoracotomy. Plombage of different levels was employed to partially or completely abolish this mechanical stress. Responses to graded changes in transpulmonary pressure were assessed in elastin-insufficient mice (elastin +/-, ELN+/-) and elastase-treated mice with elastase-induced emphysema. Physiological regrowth, morphometry (linear mean intercept; Lmi), and the proliferative responses of CCSP+/SP-C+, Clara cells, and ATII were evaluated. Plombage following PNY significantly reduced transpulmonary pressure, regrowth, and CCSP+/SP-C+, Clara cell, and ATII proliferation following PNY. In the ELN+/- group, CCSP+/SP-C+ and ATII proliferation responses were completely abolished, although compensatory lung regrowth was not significantly altered. In contrast, in elastase-injured mice, compensatory lung regrowth was significantly reduced, and ATII but not CCSP+/SP-C+ proliferation responses were impaired. Elastase injury also reduced the baseline abundance of CCSP+/SP-C+, and CCSP+/SP-C+ were found to be displaced from the bronchioalveolar duct junction. These data suggest that qualities of the extracellular matrix including elastin content, mechanical stress, and alveolar integrity strongly influence the regenerative capacity of the lung, and the patterns of cell proliferation in the lungs of adult mice.

Reproducibility of airway responsiveness in horses using flowmetric plethysmography and histamine bronchoprovocation.

BACKGROUND: Inflammatory airway disease has a high prevalence in horses, but is often a diagnostic challenge. Flowmetric plethysmography and histamine bronchoprovocation (FP/HBP) is a simple and effective tool for diagnosis, but reproducibility of these measurements made over time has not been established. HYPOTHESIS: We hypothesize that the measurement of airway responsiveness in horses using FP/HBP is consistent over both short and long periods of time. ANIMALS: Twenty-nine healthy adult horses from 2 university herds. METHODS: In this prospective experimental study, airway responsiveness was determined in each horse at day 0 (baseline [BL]) with FP/ HBP, using PC35 (provocative concentration of histamine needed to increase Delta(flow) by 35%) as a measure of airway responsiveness. Each horse was re-tested 1-4 weeks after BL (short-term [ST]) and again at 3-12 months after BL (long-term [LT]). RESULTS: In the ST period, 23/27 (85%) of the horses had a PC35 that was within 1 doubling concentration of histamine of their BL value, with a mean change of 0.52 doubling concentrations (95% CI 0.26-0.79, range 0-2.06). For the LT data, 19/26 (73%) of horses were within 1 doubling concentration of their BL value, with a mean change of 0.81 doubling concentrations (95% CI 0.45-1.17, range 0.14-3.10). There was no significant difference in reproducibility between the 2 groups of subjects. CONCLUSIONS AND CLINICAL IMPORTANCE: Repeated measurements of airway responsiveness obtained with FP/HBP show acceptable reproducibility over time periods up to a year. However, caution must be used when testing horses when ambient air temperature is low.

Branchial remnant cysts of mature and juvenile horses.

This clinical report describes 8 cases of branchial remnant cysts (BRC) in the horse. The horses presented with bimodal age distribution, with 5 cases in mature horses (age 8-21 years) and 3 in foals (age 1, 6 and 10 months). Mature cases presented for dysphagia or intermittent oesophageal obstruction (2/5), and retropharyngeal swelling (3/5), whereas respiratory stridor and visible mass were presenting complaints in the foals. Presence of a right-sided (5/8) or dorsally located (2/8) palpable retropharyngeal mass of 3-35 cm diameter was noted clinically; one left-sided mass was identified as an incidental finding at necropsy. Ultrasonography typically revealed a thick-walled cyst containing hypoechoic fluid with dependent hyperechoic masses consistent with blood clots. Radiographs and upper airway endoscopy were also consistent with a retropharyngeal mass. Fluid cytology revealed chronic haemorrhage in 6/8 cases, and squamous epithelial cells in one case. Histopathology in all cases demonstrated an epithelium-lined cyst with no smooth muscle or thyroid tissue. Two cases was subjected to euthanasia; one due to concurrent laryngeal anomalies and one due to financial constraints. The remaining 5 cases were treated via surgical excision. Post operatively, right laryngeal hemiplegia was observed in 4/5 cases. All previous reports of BRC in the horse have described juvenile individuals. Brachial remnant cyst should be considered a differential diagnosis for mature horses with masses of the throatlatch area and can be definitively diagnosed by the presence of squamous epithelium in aspirated fluid or by histopathology of the excised mass. Right recurrent laryngeal nerve damage is a common complication of surgery.