Methacholine challenge test by wheezing and oxygen saturation in preschool children with asthma

Methacholine challenge test (MCT) performed with spirometry is a commonly used test to evaluate bronchial hyperreactivity (BHR) in children. However, preschoolers do not usually collaborate. OBJECTIVES: To assess the usefulness of MCT through clinical evaluation (wheezing auscultation and decreased pulse arterial oxygen saturation [SpO2]) in recurrent wheezing preschoolers with asthma, in comparison to healthy controls. METHODS: We performed the MCT (modified Cockroft method) on healthy and on asthmatic preschoolers. The end point was determined by the presence of wheezing in the chest and/or tracheal auscultation (PCw) and/or a decrease in SpO2 of ≥5 from the baseline value (PCSpO2). Maximal methacholine concentration was 8 mg/ml. RESULTS: The study population comprised 65 children: 32 healthy and 33 asthmatic children. There were no differences in demographic characteristics between the groups. The median methacholine doses for PCw and for PCSpO2 were significantly lower among asthmatic than healthy children: 0.5 mg/ml (0.25-0.5 mg/ml) vs. 2 mg/ml (1-4 mg/ml), respectively, p < 0.001; and 0.25 mg/ml (0.25-0.5 mg/ml) and 2 mg/ml (0.5-4 mg/ml), respectively, p < 0.001. The best cut-off point of PCw was observed at a methacholine concentration of 0.5 mg/ml (AUC = 0.72 [95% CI = 0.66-0.77]), its sensitivity was 91%, specificity 43%, PPV 16% and NPV 98%. For PCSpO2 the best cut-off point was a methacholine concentration of 1 mg/ml (AUC = 0.85 [95% CI 0.81-0.89]), with sensitivity of 80%, specificity 74%, PPV 49%, and NPV 92%. There were no adverse reactions. CONCLUSION: MCT using clinical parameters such as wheezing auscultation and SpO2 measurement could be a useful and safe test to confirm BHR among preschoolers

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Methacholine challenge test by wheezing and oxygen saturation in preschool children with asthma.

UNLABELLED: Methacholine challenge test (MCT) performed with spirometry is a commonly used test to evaluate bronchial hyperreactivity (BHR) in children. However, preschoolers do not usually collaborate. OBJECTIVES: To assess the usefulness of MCT through clinical evaluation (wheezing auscultation and decreased pulse arterial oxygen saturation [SpO2]) in recurrent wheezing preschoolers with asthma, in comparison to healthy controls. METHODS: We performed the MCT (modified Cockroft method) on healthy and on asthmatic preschoolers. The end point was determined by the presence of wheezing in the chest and/or tracheal auscultation (PCw) and/or a decrease in SpO2 of ≥5 from the baseline value (PCSpO2). Maximal methacholine concentration was 8 mg/ml. RESULTS: The study population comprised 65 children: 32 healthy and 33 asthmatic children. There were no differences in demographic characteristics between the groups. The median methacholine doses for PCw and for PCSpO2 were significantly lower among asthmatic than healthy children: 0.5 mg/ml (0.25-0.5 mg/ml) vs. 2 mg/ml (1-4 mg/ml), respectively, p<0.001; and 0.25 mg/ml (0.25-0.5 mg/ml) and 2 mg/ml (0.5-4 mg/ml), respectively, p<0.001. The best cut-off point of PCw was observed at a methacholine concentration of 0.5 mg/ml (AUC=0.72 [95% CI=0.66-0.77]), its sensitivity was 91%, specificity 43%, PPV 16% and NPV 98%. For PCSpO2 the best cut-off point was a methacholine concentration of 1 mg/ml (AUC=0.85 [95% CI 0.81-0.89]), with sensitivity of 80%, specificity 74%, PPV 49%, and NPV 92%. There were no adverse reactions. CONCLUSION: MCT using clinical parameters such as wheezing auscultation and SpO2 measurement could be a useful and safe test to confirm BHR among preschoolers.

Urinary leukotriene excretion profile in children with exercise-induced asthma compared with controls: a preliminary study.

BACKGROUND: Leukotrienes are among the most important mediators associated with inflammatory responses in patients with exercise induced asthma (EIA). The aim of this study was to investigate the impact of exercise on the urinary leukotriene profile. Hence, we compared post exercise changes of urinary leukotriene E4 (LTE4) concentration between children with EIA and healthy controls. METHODS: Ten children with EIA and 15 controls were enrolled. Both groups underwent a standardised exercise challenge test (ECT). LTE4 concentration was measured in urine samples obtained pre and post ECT, using enzyme immunoassay and adjusted by urinary creatinine concentrations. RESULTS: Median (minimum-maximum) pre ECT concentration of LTE4 was 17.82 (7.58-90.23 pg/ml) in EIA and 17.24 (4.64-64.02 pg/ml) in controls, p=0.86. LTE4 concentration post ECT were 23.37 (4.02-93.00 pg/ml) in EIA and 11.74 (0.13-25.09 pg/ml) in controls, p=0.02. Changes of LTE4 concentration post ECT were 2.54 (-31.98 to 43.31 pg/ml) in cases and -13.53 (-46.00 to 11.02 pg/ml) in controls, p=0.03. There was no significant correlation between basal predicted FEV(1) [%] and changes in LTE4 concentration in cases (i.e., r(s)=0.14) nor controls (i.e., r(s)=0.12). There was a tendency towards more pronounced changes in LTE4 concentration post ECT in children with moderate/mild persistent asthma compared to those with mild but intermittent asthma. CONCLUSIONS: Children with EIA had significantly higher changes of urinary LTE4 concentrations post ECT compared to healthy controls. Urinary measurement of LTE4 may be an interesting and non-invasive option to assess control of EIA in children.

[Home ventilatory assistance in Chilean children: 12 years' experience]. / Asistencia ventilatoria domiciliaria en niños chilenos: 12 años de experiencia.

OBJECTIVE: Home ventilatory support systems are a treatment option for patients with severe chronic respiratory failure. The objective of the present study was to characterize the children admitted to a home ventilatory assistance program. PATIENTS AND METHOD: The home ventilation program was created by our hospital to coordinate professional and technological support for chronic ventilator-dependent children. We revised and updated information on patient characteristics, type of assisted ventilation, respiratory morbidity, and equipment failures between 1993 and 2004. RESULTS: Follow-up of 35 children (18 male) was carried out by our hospital staff. Median age upon admission to the program was 12 months (range, 5 months to 14 years). Median length of time in the program was 21 months and we were able to wean 40% of patients from ventilators. Six patients died. The main indications for assisted ventilation were neuromuscular disease (12 cases), airway abnormality (11 cases), cardiopulmonary disease (7 cases), and hypoventilation syndrome (5 cases). The types of assisted ventilation used were continuous positive airway pressure (in 17 cases), bilevel positive pressure (in 8 cases), and synchronized intermittent mandatory ventilation (in 10 cases). Invasive ventilation via a tracheostomy was used in 26 cases. The use of noninvasive ventilation increased in the last 4 years. Respiratory morbidity (pneumonia and bacterial tracheitis) was the most frequent cause of hospitalization and the annual rate of such episodes was 1.6 per child. The annual rate of hospitalization due to equipment failures was 0.1 per child. CONCLUSION: The program provides safe and necessary home ventilatory assistance for children with severe chronic respiratory failure. The professional support that home hospitalization offers had a positive effect on outcome in these children. It is important to take our experience into account in creating a Chilean national home ventilatory assistance program.

Asistencia ventilatoria domiciliaria en niños chilenos: 12 años de experiencia / Home ventilatory assistance in chilean children: 12 years' experience

Objetivo: Los sistemas de apoyo ventilatorio domiciliario son una alternativa para el tratamiento de los pacientes con insuficiencia respiratoria crónica grave. El objetivo del presente estudio ha sido caracterizar a los niños ingresados en el Servicio de Asistencia Ventilatoria en Domicilio (SAVED). Pacientes y método: El SAVED es un programa de nuestro hospital que coordina el apoyo profesional y tecnológico para niños con dependencia de asistencia ventilatoria (AV) crónica. Se revisaron y actualizaron datos demográficos, tipo de AV, morbilidad respiratoria y fallos de equipo entre 1993 y 2004. Resultados: Se realizó seguimiento en nuestro centro a 35 niños (varones: 18). La mediana de edad al entrar en el programa fue de 12 meses (rango: 5 meses a 14 años). El tiempo de permanencia fue de 21 meses y la retirada del soporte se logró en el 40% del total. Fallecieron 6 pacientes. Las principales indicaciones de AV fueron: enfermedad neuromuscular en 12 casos, alteración de la vía aérea en 11, enfermedad cardiopulmonar en 7 y síndrome de hipoventilación en 5. Los tipos de AV utilizados fueron presión positiva continua de la vía aérea en 17 casos, presión positiva en 2 niveles (BiPAP) en 8 y ventilación mecánica intermitente sincronizada en 10. Se administró ventilación invasiva a 26 pacientes a través de traqueotomía. En los últimos 4 años se produjo un aumento de la utilización de la ventilación no invasiva. La morbilidad respiratoria (neumonía y traqueítis bacteriana) fue la causa más frecuente de hospitalización y alcanzó 1,6 evento/niño/año. Los fallos de sistema fueron causa de hospitalización en 0,1 evento/niño/año. Conclusión: El SAVED es un programa seguro y necesario para niños con insuficiencia respiratoria crónica de carácter grave. El apoyo profesional que proporciona la hospitalización domiciliaria ha beneficiado la evolución de estos niños. Es importante considerar esta experiencia para la formación de un programa nacional de AV domiciliaria

Objective: Home ventilatory support systems are a treatment option for patients with severe chronic respiratory failure. The objective of the present study was to characterize the children admitted to a home ventilatory assistance program. Patients and method: The home ventilation program was created by our hospital to coordinate professional and technological support for chronic ventilator-dependent children. We revised and updated information on patient characteristics, type of assisted ventilation, respiratory morbidity, and equipment failures between 1993 and 2004. Results: Follow-up of 35 children (18 male) was carried out by our hospital staff. Median age upon admission to the program was 12 months (range, 5 months to 14 years). Median length of time in the program was 21 months and we were able to wean 40% of patients from ventilators. Six patients died. The main indications for assisted ventilation were neuromuscular disease (12 cases), airway abnormality (11 cases), cardiopulmonary disease (7 cases), and hypoventilation syndrome (5 cases). The types of assisted ventilation used were continuous positive airway pressure (in 17 cases), bilevel positive pressure (in 8 cases), and synchronized intermittent mandatory ventilation (in 10 cases). Invasive ventilation via a tracheostomy was used in 26 cases. The use of noninvasive ventilation increased in the last 4 years. Respiratory morbidity (pneumonia and bacterial tracheitis) was the most frequent cause of hospitalization and the annual rate of such episodes was 1.6 per child. The annual rate of hospitalization due to equipment failures was 0.1 per child. Conclusion: The program provides safe and necessary home ventilatory assistance for children with severe chronic respiratory failure. The professional support that home hospitalization offers had a positive effect on outcome in these children. It is important to take our experience into account in creating a Chilean national home ventilatory assistance program

The prevalences of Brachyspira spp. and Lawsonia intracellularis in Swedish piglet producing herds and wild boar population.

The aim of the present study was to survey the prevalences of the enteric pathogens Brachyspira hyodysenteriae, Brachyspira pilosicoli and Lawsonia intracellularis in Swedish growing pigs and in the Swedish wild boar population and to relate these findings to clinical signs. The study included 105 randomly selected herds, constituting approximately one third of Swedish herds with a herd size of >100 sows. The herds were located all over the country. In these herds, growth promoters were not used and pigs sampled were not subjected to any medication. From each herd, samples were taken from 10 growing pigs aged 8-12 weeks, corresponding to approximately 2.5% of all growing pigs present in the herd at the sampling occasion. If possible, the samples were taken from pigs with diarrhoea. Forty-eight faecal samples and 71 rectal swabs were also taken from free-living wild boars (31 piglets, 19 growers and 21 adult animals) at shooting. The samples were analysed by culture and biochemical tests for the presence of Brachyspira spp. and by nested PCR for the presence of L. intracellularis. Brachyspira hyodysenteriae was not demonstrated in any sample. Brachyspira intermedia was detected in 22 samples originating from 15 herds, Brachyspira innocens/Brachyspira murdochii was detected in 370 samples from 82 herds and B. pilosicoli was detected in 134 samples originating from 34 herds. In 21 herds and in 534 samples, no Brachyspira spp. were detected. Lawsonia intracellularis was demonstrated in 285 samples from 50 herds. Further, 418 samples from conventional herds were negative with respect to L. intracellularis and in 345 samples the PCR had been inhibited. All samples from the wild boars were negative for Brachyspira spp., 12 of 48 samples were negative for L. intracellularis, and in 36 wild boar samples, the PCR was inhibited.

[Utility of bronchoalveolar lavage in immunocompromised children: diagnostic yield and complications]. / Utilidad del lavado broncoalveolar en niños inmunodeprimidos: rendimiento y complicaciones.

OBJECTIVE: Immunocompromised children are at high risk for developing pneumonia due to opportunistic pathogens. The role of bronchoalveolar lavage (BAL) in the evaluation of such patients is still controversial. MATERIAL AND METHOD: We reviewed the hospital records of immunosuppressed patients with respiratory symptoms who had undergone BAL in the pediatric department of the Hospital Clinico de la Pontificia Universidad Católica of Chile. RESULTS: Sixty-eight BAL were performed on 54 children (mean age: 7.5 years) receiving wide-spectrum antibiotic treatment. The most frequent respiratory signs and symptoms were fever (90%) and cough and respiratory distress (81%); 18% had neutropenia and 43% thrombocytopenia. A specific pathogen was identified in BAL samples for 25 patients (37%). The pathogens isolated were bacteria in 21 cases, viruses in 6, Pneumocystis carinii in 5, fungi in 4, and Mycobacterium tuberculosis in one. Fourteen (19%) of the children who underwent BAL were on mechanical ventilation. Outcome was satisfactory in all cases. Twenty-one complications were recorded, 17 of which were minor (mild hypoxemia or fever) and 4 major, requiring tracheal intubation. No deaths were recorded. CONCLUSIONS: Evaluation by fiberoptic bronchoscopy together with BAL proved to be a safe procedure with an adequate diagnostic yield that made it possible to determine the etiology of the pulmonary infiltrates seen in chest x-rays. Both positive and negative results of BAL were useful for treating the patients.

[Role of flexible bronchoscopy in the re-expansion of persistent atelectasis in children]. / Broncoscopia flexible en la reexpansión de atelectasias persistentes en pediatría.

OBJECTIVE: To evaluate the efficacy of flexible bronchoscopy plus bronchoalveolar lavage for the reexpansion of persistent atelectasis (course longer than 3 weeks) in children. PATIENTS AND METHODS: Retrospective review of the records of 83 children who underwent flexible fiberoptic bronchoscopy plus bronchoalveolar lavage for persistent atelectasis. Three categories of evolution were established for radiologic assessment: a) full re-expansion (full improvement over the initial image); b) partial re-expansion (decreased atelectasis of between 50% and 100%); and c) no change (if the decrease was less than 50% of the initial image). RESULTS: Endoscopy revealed mucus plugs in 54 patients (65%); bronchial malformations in 16 (19%); bronchial stenosis in 5 (6%); normal airways in 5 (6%) and other findings in 3 (4%). Radiologic changes after bronchoscopy showed full expansion for 34 patients (41%), partial re-expansion for 28 (34%) and no changes for 21 (25%). CONCLUSION: Flexible bronchoscopy plus bronchoalveolar lavage for the re-expansion of persistent atelectasis is useful in a high percentage of children.

Cystic fibrosis in three children with bronchopulmonary dysplasia.

Cystic fibrosis (CF) and bronchopulmonary dysplasia (BPD) are two common causes of chronic lung disease in children. Patients with BPD or CF often have recurrent respiratory symptoms, failure to thrive, and/or metabolic alkalosis during infancy and childhood. Thus, recognizing the diagnosis of CF in an infant with BPD can be difficult. We present three infants with both BPD and CF. The infants shared a history of respiratory distress and prolonged oxygen requirements. All three also had difficulty gaining weight, even after pancreatic enzyme supplementation was instituted. Metabolic alkalosis was observed in two infants. Previous studies in children with CF suggest that early diagnosis may impact both lung health and nutritional status. A high index of suspicion is necessary for clinicians to identify these children early and intervene with appropriate therapy.

The influence of parenterally administered alpha-tocopheryl acetate to sows on the vitamin E status of the sows and suckling piglets and piglets after weaning.

The main aim of the study was to test if parenteral administration of alpha-tocopheryl acetate twice before farrowing and weaning could increase the vitamin E status of the newborn piglets and piglets after weaning. In Trial I eight sows were given 1.5 g alpha-tocopheryl acetate intramuscularly 7 and 2 days before farrowing. Eight sows were untreated controls. The experimental sows had a higher vitamin E concentration in colostrum than the controls. No significant difference between the groups existed in milk at weaning. The serum vitamin E concentration in the experimental piglets 2 and 5 days after farrowing was higher than in the controls. Fifteen days after farrowing the difference between the groups had nearly disappeared. The serum vitamin E concentration in the piglets in the control group was higher during the first days after farrowing than later, and was gradually reduced until at least 2 weeks after weaning. In Trial II, eight sows were given 1.5 g of alpha-tocopheryl acetate 7 and 2 days before weaning of their piglets. They had higher vitamin E concentrations in milk and serum than untreated control sows at weaning. The increase did not, however, influence the serum vitamin E concentration of the piglets. The lowest concentration of vitamin E in serum of the piglets was reached at 45 days after farrowing. The activity of the selenium-dependent enzyme glutathione peroxidase in the serum of piglets was very low during the first week of life in both groups despite the fact that the sows' feed had been supplemented with 0.35 mg selenium/kg. This indicates that the selenium status of newborn piglets might be more critical for their health than their vitamin E status.

[Bronchiolitis obliterans with organizing pneumonia secondary to chemotherapy in a child with primary pericardial sarcoma]. / Bronquiolitis obliterante con neumonía en organización secundaria a quimioterapia, en un niño con sarcoma pericárdico primario.

The uncommon bronchiolitis obliterans organizing pneumonia can be idiopathic or caused by infection or medications. We report a 5 year old boy with pericardial sarcoma that was treated with chemotherapy (vincristine, doxorubicin, etoposide, cyclophosphamide) and radiotherapy. During the third cycle of chemotherapy, he developed progressive cough and dyspnea, needing oxygen therapy. Chest X-ray examination showed bilateral infiltrates. After discarding infectious etiologies, an open lung biopsy was performed, and the pathological examination showed a bronchiolitis obliterans organizing pneumonia. He was treated with prednisolone for 7 days, followed by prednisone for additional 45 days. He continued with fluticasone propionate as maintenance and remains in good condition with a chest X-ray showing mild interstitial images, after seven months of follow up.

Optimal Bayesian foraging policies and prey population dynamics-some comments on Rodriguez-Girones and Vasquez.

In this paper we show the density-dependent harvest rates of optimal Bayesian foragers exploiting prey occurring with clumped spatial distribution. Rodríguez-Gironés and Vásquez (1997) recently treated the issue, but they used a patch-leaving rule (current value assessment rule) that is not optimal for the case described here. An optimal Bayesian forager exploiting prey whose distribution follows the negative binomial distribution should leave a patch when the potential (and not instantaneous) gain rate in that patch equals the best long-term gain rate in the environment (potential value assessment rule). It follows that the instantaneous gain rate at which the patches are abandoned is an increasing function of the time spent searching in the patch. It also follows that the proportion of prey harvested in a patch is an increasing sigmoidal function of the number of prey initially present. In this paper we vary several parameters of the model to evaluate the effects on the forager's intake rate, the proportion of prey harvested per patch, and the prey's average mortality rate in the environment. In each case, we study an intake rate maximizing forager's optimal response to the parameter changes. For the potential value assessment rule we find that at a higher average prey density in the environment, a lower proportion of the prey is taken in a patch with a given initial prey density. The proportion of prey taken in a patch of a given prey density also decreases when the variance of the prey density distribution is increased and if the travel time between patches is reduced. We also evaluate the effect of using predation minimization, rather than rate maximization, as the currency. Then a higher proportion of the prey is taken for each given initial prey density. This is related to the assumption that traveling between patches is the most risky activity. Compared to the optimal potential value assessment rule, the current value assessment rule performs worse, in terms of long-term intake rate achieved. The difference in performance is amplified when prey density is high or highly aggregated. These results pertain to the foraging patch spatial scale and may have consequences for the spatial distribution of prey in the environment.

A humanized monoclonal antibody against respiratory syncytial virus (palivizumab) inhibits RSV-induced neurogenic-mediated inflammation in rat airways.

Respiratory syncytial virus (RSV) is the most important respiratory pathogen in infancy and early childhood and may predispose to subsequent lower respiratory tract illness. Recent data indicate that RSV up-regulates the substance P receptor, making the airways abnormally susceptible to the proinflammatory effects of this peptide released from sensory nerves. The present study was designed to determine whether the administration of RSV antibodies prevents the potentiation of neurogenic inflammation in rat airways. Five days after inoculation, sensory nerve-mediated extravasation of Evans blue-labeled albumin was significantly greater in the airways of RSV-infected rats than in pathogen-free controls. Polyclonal immune globulin enriched for RSV-neutralizing antibodies (RSVIG) reduced neurogenic extravasation when injected 24 h before intranasal inoculation of the virus but not when injected before endotracheal inoculation. A humanized MAb against RSV fusion protein (palivizumab) was twice as potent as RSVIG when given before intranasal inoculation and also caused significant inhibition after endotracheal inoculation. Furthermore, palivizumab inhibited neurogenic inflammation in RSV-infected rats when given 72 h after virus inoculation. These data suggest that palivizumab protects the respiratory tract from RSV-induced inflammation when given before or in the early phase of the viral infection. The administration of palivizumab to high-risk infants may limit the severity of the acute airway inflammation and may protect against subsequent lower respiratory tract illness.

Infections with Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae in fattening pigs. Influence of piglet production systems and influence on production parameters.

Two hundred and sixty-four feeder pigs from an age-segregated herd (A-pigs) and 264 feeder pigs from a continuous production system (C-pigs) were transferred into identical but separate rooms in a fattening herd employing all-in all-out production. On arrival, none of the A-pigs and 39% of the C-pigs were seropositive to Mycoplasma hyopneumoniae (M. hyo). At slaughter 30% of the A-pigs and 99% of the C-pigs were seropositive to M. hyo. Pigs with acute swine enzootic pneumonia (SEP) at slaughter and pigs that seroconverted to M. hyo late in the rearing period showed a lower growth rate compared with pigs with chronic SEP or pigs that seroconverted to M. hyo early or not at all. No A-pigs and 12% of the C-pigs were seropositive to Actinobacillus pleuropneumoniae 2 (A. pp 2) at arrival to the fattening herd. At slaughter, 10% of the A-pigs and 13% of the C-pigs were seropositive to A. pp 2. On arrival, the prevalence of pigs seropositive to A. pp 3 was lower among A-pigs than C-pigs. During the fattening period the situation was reversed. The prevalence of pleuritis at slaughter was low (2.7-4.2%) and there were no associations between pleuritis at slaughter and developments of antibodies to A. pp 2 or 3. However, pigs with pleuritis developed antibodies to M. hyo to a greater extent than pigs without pleuritis. Pigs with pleuropneumonia at slaughter and pigs that seroconverted to A. pp 2 or 3 had, during certain periods of the rearing, higher growth rates compared with pigs without pleuropneumonia or pigs that did not seroconvert to A. pp 2 or 3.

Muscle histopathology and plasma aspartate aminotransferase, creatine kinase and myoglobin changes with exercise in horses with recurrent exertional rhabdomyolysis.

Six horses with a history of recurrent exertional rhabdomyolysis (RER) (Horses A-F) and 7 control horses performed a submaximal and later a near-maximal treadmill exercise test. Blood samples were obtained before, during and after exercise and muscle biopsies were taken before and after exercise. At rest, plasma aspartate aminotransferase (AST) activities in horses with RER were above 95% confidence intervals for control horses. During submaximal exercise, 3 horses with RER (A, B and C) had much greater increases in plasma AST, creatine kinase (CK) and myoglobin concentrations than did Horses D, E and F and control horses. Clinical signs of muscle stiffness and pain were only obvious in Horse A. During near-maximal exercise, only Horse C showed a substantial increase in CK activity and myoglobin concentrations without any associated clinical signs of rhabdomyolysis. Muscle biopsies from Horses A, B and C contained necrotic type II fibres which, on electron microscopic examination, contained disrupted myofibrils and swollen mitochondria. These results suggest that, in RER, subclinical episodes of muscle fibre necrosis and associated increases in plasma AST, CK and myoglobin occur with exercise more frequently than could be detected clinically. Furthermore, the pattern of increase in muscle enzymes and myoglobin concentrations in the 6 horses with RER suggested that the high plasma AST and CK activities commonly observed at rest in symptom-free Standardbred horses are probably a result of repeated subclinical episodes of rhabdomyolysis after exercise, rather than leakage due to abnormal sarcolemmal permeability.

Measurement of serum myoglobin concentrations in horses by immunodiffusion.

Quantitative immunodiffusion in one dimension was performed in 6-mm Duran tubes containing a 1% Nobel agar solution and various dilutions of antisera. A series of dilutions of pure myoglobin in equine sera as well as plasma from horses with rhabdomyolysis were tested. Standard curves were prepared of the migration distance of the formed precipitate from the meniscus of the gel after 3, 6, 12, and 24 hours. The clearest line of precipitate was formed with a 1:20 dilution of antisera in agar. Standard curves were nonlinear and plasma myoglobin could be detected at 2 micrograms of myoglobin/ml or greater. The test was optimal, with an error of 5.6%, when read at 24 hours at approximately 25 C. Tubes with agar could be stored for 6 months at 4 C without affecting the accuracy of the test. The specificity of myoglobin for skeletal or cardiac muscle, and its rapid clearance from serum after muscle necrosis, make it ideally suited for evaluating acute muscle damage and for testing the susceptibility of horses for rhabdomyolysis following an exercise test.

Effect of a melatonin implant on the circadian variation of plasma prolactin and rectal temperature in newborn sheep.

Plasma prolactin and rectal temperature show a circadian rhythm in newborn sheep raised under continuous light. Melatonin lowers the concentration of plasma prolactin but it is not known if it affects its circadian rhythm. To detect whether melatonin acts on the circadian system we studied the effect of a subcutaneous melatonin implant in the circadian rhythms of prolactin and rectal temperature in newborn lambs raised under continuous light. We placed catheters in the pedal artery and vein in 9 newborn lambs (2-5 days of age). A subcutaneous melatonin implant was placed in 4 of the lambs at 9-12 days of age. Blood samples and rectal temperature measurements were obtained hourly for a period of 24 h, 11-15 days after the implant, at 20-27 days of age. To avoid interferences of heparin in our melatonin assay, serum melatonin concentration was measured before and during the implant in three additional newborns. Prolactin and melatonin were measured by RIA. Melatonin concentrations were 52.8 +/- 45.9 pg/ml (day) and 315.5 +/- 77.0 pg/ml (night) before treatment (SEM, P less than 0.001), and increased to 594.1 +/- 54.5 pg/ml after placing the implant (there was no difference in melatonin concentration between day and night during the time that the implant was in place). Melatonin had no effect on rectal temperature or its rhythm, but decreased basal plasma prolactin concentration (control: 97.5 +/- 11.3 ng/ml; treated: 25.1 +/- 2.4 ng/ml, P less than 0.001) and abolished the prolactin circadian rhythm, (Cosinor analysis): control: log prolactin (ng/ml) = 1.8 + 0.26 cos 15 (t - 11.16), p = 0.05; treated: log prolactin (ng/ml) = 1.2 + 0.14 cos 15 (t - 9.43), P = 0.36.

A field trial evaluating the use of cefoperazone in the treatment of bovine clinical mastitis.

A field trial was designed to investigate the efficacy of a single intramammary infusion of cefoperazone in the treatment of clinical bovine mastitis. 110 cases of naturally occurring mastitis were treated and the clinical and bacteriological cure rates at day 14 after treatment were recorded.

Rol de la serotonina en la génesis del bostezo / Serotonin role in the production of yawning behavior

El bostezo inducido por inyección intraperitoneal de eserina (0,15 mg kg-1) en ratas de 7 a 8 días de edad es potenciado por quipacina (5 mg kg-1), agonista serotoninérgico, y por fluoxetina (5 a 20 mg kg-1) y pirandamina (2,5 a 5 mg kg-1), bloqueadores de la recaptura neuronal de la serotonina. Estas drogas, en ausencia de serina, no inducen bostezo. Por otra parte, la metergolina (5 a 10 mg kg-1), antagonista serotoninérgico, inhibe, tanto el bostezo inducido por eserina, como su facilitación por la quipacina. Se discuten estos resultados como nuevas evidencias experimentales en apoyo de la hipótesis que propone a la serotonina como un agente modulador positivo de los mecanismos neurohumorales responsables de la conducta del bostezo (AU)