Benzimidazole-resistant gastrointestinal nematodes in indigenous Chiapas and Pelibuey sheep breeds from Chiapas, Mexico.

Because of the natural adaptation of Mexican sheep, the aim of the present study was to identify the presence or absence of gastrointestinal parasitic nematodes (GIN) resistant to benzimidazole (BZ) in both Chiapas and Pelibuey sheep breeds on local farms. Both male and female GIN-infected grazing sheep of the two breeds were selected. Sheep faecal samples were collected to obtain infective larvae (L3). This evolving stage of the parasite was used for taxonomic identification of the genus, based on its morphological characteristics. BZ anthelmintic resistance was evaluated using a nematode-compound in vitro interaction bioassay and the allele-specific polymerase chain reaction technique to detect mutations of residues 198 and 200 on isotype 1 of the ß-tubulin gene. Three BZ-based compounds (febendazole (FBZ), tiabendazole (TBZ) and albendazole (ABZ)) at concentrations of 1, 0.5, 0.25, 0.125, 0.062 and 0.03 mg/ml were used to estimate the anthelmintic efficacy and lethal dose (LD50, LD90 and LD99) of the drugs. Two parasitic nematodes, Haemonchus and Teladorsagia, were identified in both isolates. Also, the proportions of anthelmintic resistance identified in GIN of the two sheep breeds were 68% in isolates from the Chiapas breed and 71.8% in the Pelibuey breed. The specific lethal activity obtained with FBZ was higher than 90%. However, TBZ and ABZ showed a lethal activity lower than 50%. High variability in the discriminating dose values was found among the BZ drugs. For example, FBZ LD ranged from 0.01 to 1.20 mg/ml; on the other hand, TBZ and ABZ required a dose ranging from 0.178 to 759 mg/ml. In addition, amino acid changes of Phe (TTC) to Tyr (TAC) at codon 200 of the ß-tubulin gene, showing resistance to BZ, and no changes at codon 198 Glu (GAA) to Ala (GCA) were observed for both isolates. These results confirmed the presence of a genetic mutation associated with BZ in both Chiapas and Pelibuey nematode isolates.

Accuracy of pulmonary function tests in predicting exercise tolerance in chronic obstructive pulmonary disease.

The ability of pulmonary function tests (PFTs) to predict exercise capacity was investigated by using linear regression analysis to quantify the relationships between: (1) maximum oxygen consumption during treadmill exercise and PFT parameters; and (2) total external work performed during treadmill exercise and PFT parameters. In a group containing 11 healthy subjects, nine with mild/moderate chronic obstructive pulmonary disease (COPD) and ten with severe COPD, both maximum oxygen consumption (measured directly) and total external work (calculated indirectly from the sum of its horizontal and vertical components) correlated most strongly with indices of expiratory airflow (FEV1, FEF25-75%), less strongly with indices of ventilatory output (MVV) and resting levels of oxygen (PO2, SaO2), and weakly with indices of hyperinflation (FRC) and carbon dioxide retention (PCO2). Thus, FEV1, accounting for 56 percent and 60 percent of the observed variation in oxygen consumption and external work, respectively, can predict exercise tolerance from PFT measurements with some accuracy. If a more accurate evaluation is required, exercise testing should be prescribed.

Pentoxifylline improves pulmonary gas exchange.

Pentoxifylline is a xanthine derivative with hemorrheologic and vascular properties that may improve gas exchange in patients with chronic obstructive pulmonary disease (COPD). We tested this hypothesis in 12 patients with COPD (mean FEV1 = 40 percent predicted; mean DCO, 8.6 ml/min/mm Hg) randomly divided into a treatment and control group and six healthy volunteers. Following establishment of baseline DCO and maximum expiratory flow volume (MEFV) curve values, each subject in the treatment and healthy groups took 400 mg of pentoxifylline three times a day for 12 weeks. Weekly DCO and MEFV curves were measured before treadmill exercise in both COPD groups and before and after exercise in the healthy group. The MEFV curve parameters from the final three weeks of therapy did not differ significantly from baseline values. During this time, however, the treatment COPD group's resting DCO rose by 8.2 +/- 2.4 percent over baseline level (p less than 0.01). Treadmill walk time increased from 17.7 +/- 2.9 minutes to 23.2 +/- 2.9 minutes (p less than 0.02). This was accompanied by improved exercise oxygen saturation measured by oximetry (SoxiO2). Premedication SoxiO2 fell from 92.8 +/- 1.2 percent to 88.6 +/- 2.5 percent during exercise, and from 94.4 +/- 1.1 percent to only 91.8 +/- 1.0 percent after 12 weeks of medication (p less than 0.05). No such improvement was noted in the control COPD group. Although the healthy group's resting SoxiO2 and DCO did not change during treatment, their exercise DCO increased significantly from 36.3 +/- 3.1 ml/min/mm Hg to 41.8 +/- 3.5 ml/min/mm Hg (p less than 0.001). These data demonstrate that pentoxifylline improves gas exchange, possibly by increasing cardiac output, and/or by raising mixed venous PO2, and/or by improving blood flow to underperfused alveoli.

Effect of aerobic training on forced expiratory airflow in exercising asthmatic humans.

Pulmonary function after exercise was evaluated in 22 asthmatic subjects before and after a 36-session training sequence of aerobic exercise. Training did not change pulmonary function values, except for a small increase in maximal voluntary ventilation (P less than 0.02), which was attributed to respiratory muscle training. After aerobic training, both external work at a given heart rate and peak O2 consumption increased by 30 and 15%, respectively. At the same minute ventilation (VE), immediate postexercise forced expiratory airflow was higher after training (P less than 0.02), and reduction in forced expiratory airflow during the first 9 min postexercise was less after training (P less than 0.01). The posttraining airflow response to the pretraining work load was, as expected, less than the pretraining response (P less than 0.02). Although the difference in maximal-to-minimal airflow at the same VE was similar before and after training, the airflow increase accounted for 50% of the response after training compared with 16% of the pretraining response. Furthermore the strong negative correlation (P less than 0.01) between maximal and minimal airflow both pre- and posttraining indicates that exercise-induced bronchospasm (EIB) severity is, in part, determined by the degree of exercise-induced bronchodilation. We conclude that aerobic training significantly increases exercise-induced bronchodilation and diminishes EIB.

Effects of physical fitness on expiratory airflow in exercising asthmatic people.

Maximal expiratory flow-volume maneuvers were performed by self-trained (FIT) and sedentary (UNFIT) asthmatic subjects. Both groups had similar pre-exercise pulmonary function limitations and attained the same exercising heart rate. The FIT group, however, exercised significantly longer than the UNFIT group. Although expiratory airflow increased in both groups during exercise, the FIT group had significantly larger airflow increases than the UNFIT group and maintained them throughout the exercise. In contrast, the UNFIT group's airflow decreased prior to the end of exercise. Tidal volume (VT) expiratory curves surpassed pre-exercise maximum expiratory flow-volume (MEFV) envelopes in subjects whose tidal volume was greater than 55% of vital capacity, the majority of whom were FIT subjects. In no case, however, did the VT curve exceed the enhanced exercise MEFV curve. The increase in airflow reserve during exercise helps to explain why asthmatic athletes, despite their significantly impaired pulmonary function, can compete successfully in sports making high aerobic demands.

Treadmill exercise training in chronic obstructive pulmonary disease.

Eight men and six women with severe chronic obstructive pulmonary disease (COPD) performed a pulmonary function test and a treadmill exercise stress test before and after an individualized training program, which nominally consisted of three 20-minute sessions of treadmill exercise per week for five consecutive weeks. Training sessions were terminated before 20 minutes if there were subjective complaints, or if the subject's heart rate reached 80% of the maximum heart rate observed during the pretraining stress test. This program failed to improve any of the pulmonary function test parameters (lung volumes, airflows, maximum voluntary ventilation, and resting levels of blood gases) and failed to improve most exercise stress test parameters (maximum oxygen consumption and carbon dioxide production, respiratory exchange ratio, and heart rate at termination of exercise). This program, however, did increase the group's average stress test time from 9.0-13.7 minutes (p less than 0.001) and increased the total external work (calculated from the sum of its vertical and horizontal components) from 3.5-6.8kcal (p less than 0.01). Eight of the 11 subjects who initially received 2L/min of 100% oxygen, via a nasal cannula, to alleviate dyspnea and to promote endurance were completely weaned from supplemental oxygen by the end of the training program. These findings demonstrate that a treadmill exercise program based on stress test data can increase the efficiency (external work per unit of oxygen consumed) and thus, the exercise tolerance, of persons with severe COPD.

Diaphragmatic function following cervical cord injury: neurally mediated improvement.

Vital capacity measurements from 36 people rendered quadriplegic by traumatic cervical cord injuries generally increased during the first ten months after injury, indicating spontaneous improvement in respiratory muscle function. Reasoning that a renewal of neural supply to the diaphragm would probably be accompanied by a parallel renewal of neural supply to other muscles having adjacent motor pathways, the present study compared vital capacity measurements with concomitant muscle function evaluations from 20 of these people. Qualitatively, increases in vital capacity were invariably accompanied by increases in the function of a group of muscles (primarily of the shoulder and upper arm) having some segmental innervation in common with the diaphragm (C3-C5) but were only sometimes accompanied by increases in the function of a group of muscles (primarily of the forearm and wrist) having segmental innervation below that of the diaphragm (C6-C8). These findings suggest that the spontaneous improvement in vital capacity observed in quadriplegic people is mediated in part by corresponding improvement in the neural supply to the diaphragm. Quantitatively, however, linear regression analysis indicated that neither the rate nor the absolute amount of improvement in vital capacity could be predicted with any reliability from pulmonary function tests, neurologic examinations, or muscle function evaluations performed in the early stage of recovery.

Cardiopulmonary rehabilitation in a patient with Noonan syndrome.

Noonan syndrome, an autosomal dominant disease occurring with an incidence of 1 in 1,000 to 1 in 2,500 live births, is characterized by its particular cardiovascular abnormalities, including pulmonic valve stenosis, pulmonary artery stenosis, and, more rarely, septal defects and coarctation of the aorta. The case of a 20-year-old man admitted for inpatient cardiopulmonary rehabilitation after pulmonic valve repair, left pulmonary artery angioplasty, and pectus excavatum repair is presented. His endurance was markedly decreased, thus limiting his ability to perform activities of daily living and reducing his exercise tolerance. With participation in a comprehensive cardiopulmonary rehabilitation program, he experienced marked improvement with independence in his activities of daily living and an increase in his metabolic equivalent levels from to 2.8 to 5.4. After inpatient rehabilitation, he underwent left pulmonary stent placement before being discharged home. Subsequent outpatient cardiopulmonary rehabilitation has continued to improve significantly his overall exercise tolerance. Given that Noonan syndrome is viewed as the most common syndrome associated with congenital heart disease after Down syndrome, physiatrists must be familiar with its presentation, its associated abnormalities, and the treatment approach to optimize the patient's cardiopulmonary, musculoskeletal, and psychological status.

Timing of first feeding and life-history strategies in salmon: genetic data.

To investigate the relationship between genetic composition and some physiological traits of interest (age at smoltification, precocious maturation in male parr) in early and late first feeding Atlantic salmon, genetic variation at 6 isozyme and 8 microsatellite loci was examined. Early and late first feeding salmon showed different allelic and genotypic distributions at both isozyme and microsatellite loci. A positive relation between enzymatic loci heterozygosity and precocious active alimentation and earlier smoltification (S1 cf. S2) were also found.

Changes in serum K+ in healthy and in asthmatic subjects during exercise.

Adrenergic mechanisms modulate exercise-induced changes in blood serum K+ concentration ([K+]). Impairment of these same mechanisms may be associated with bronchial hyper-reactivity. If this is accurate, asthmatic subjects should show disturbed K+ regulation during exercise. We measured [K+] and FEV1 in 13 healthy control and in 13 asthmatic subjects pre-exercise, at peak exercise (within 1 min of stopping exercise), and 10 min postexercise. This was done on 2 separate days, one with and one without bronchodilator (BD) pretreatment. Both groups were equally fit, exercising to the same O2 consumption and heart rate. Resting [K+] was normal for both groups (two-day averages were 4.00 +/- 0.07 and 4.09 +/- 0.07 mmol/L, mean +/- SEM, in control and asthmatic subjects, respectively). Without BD pretreatment, at peak exercise, [K+] in control subjects rose by 0.56 +/- 0.08 compared with 0.96 +/- 0.09 in asthmatics (p less than 0.01). After exercise, [K+] returned to baseline (4.12 +/- 0.08) in control subjects but remained elevated in asthmatics (4.60 +/- 0.12, p less than 0.01). Although FEV1 was unchanged in control subjects, in asthmatics it fell after exercise (p less than 0.01). With BD pretreatment: peak exercise [K+] increased by 0.55 +/- 0.09 in control subjects, and by 0.49 +/- 0.01 in asthmatics (p less than 0.01). By 10 min postexercise, it returned to baseline in both groups (4.15 +/- 0.11 for control subjects and 4.32 +/- 0.07 for asthmatics). The asthma group's fall in FEV1 was also abolished. These data indicate that postexercise K+ remains elevated in asthmatics, supporting the suggestion that their adrenergic function is impaired.

Temporal pulmonary function changes in cervical cord injury.

Temporal changes in pulmonary function (PF) in subjects with complete cervical cord transection occur in two stages. The first, extending from the acute to post-acute periods, is characterized by relatively rapid increases in the following: vital, inspiratory, and total lung capacities (VC, IC, and TLC, respectively), and inspiratory and expiratory airflows coupled with decreases in functional residual capacity (FRC). Second stage changes--from the post-acute period on--are more gradual, with both VC increase and FRC decrease continuing while TLC and ventilatory indices remain unchanged. The initial stage appears to be caused in part by functional respiratory muscle return coincident with resolution of inflammation and edema above the injury level. Altered respiratory mechanics also contribute to these early changes and the continuing later changes. Mechanical changes in the lung are probably both decreased compliance (which decreases FRC) and increased airway resistance (which diminishes airflow). Chest wall changes, resulting from returning spinal cord reflexes, affect PF via: (1) increased rib cage stability, leading to a more effective transduction of diaphragmatic displacement into lung volume, and (2) abdominal and expiratory intercostal spasticity, which could limit maximum inspiration. The net effect of these changes, however, may eventually lead to chronic hypoventilation.

Venous plethysmography values in patients with spinal cord injury.

To determine whether venous hemodynamics differ fundamentally between patients with spinal cord injury (SCI) and the abled-bodied population, quantitation of lower extremity venous plethysmography values was performed in 14 SCI patients and ten able-bodied subjects. The control group had an average maximum venous outflow (MVO) of 59.3 +/- 2.75 mL/min/100mL of tissue, mean +/- SE, and an average venous capacitance (VC) of 3.2 +/- 0.13mL/100mL. In contrast, the SCI patients had an average MVO of 32.5 +/- 2.57mL/min/100mL and an average VC of 2.3 +/- 0.17mL/100mL. The differences between the two groups were statistically significant, suggesting that the standard venous function index of plethysmography values used in the general population may not be applicable to the SCI population and that, therefore, a new standard for SCI patients derived from a larger data base should be sought.

Correlations between fitness and heterozygosity at allozyme and microsatellite loci in the Atlantic salmon, Salmo salar L.

The relationship between heterozygosity at genetic markers (six allozyme and eight microsatellite loci), and fluctuating asymmetry (FA), length and weight was investigated in two samples of Atlantic salmon (Salmo salar L.) with different timings of first active feeding (early (EA) and late (LA) salmon). This trait had previously been related to fitness. EA fish show smaller values of FA, are longer, heavier and are more heterozygous at allozyme loci than are conspecific LA fish. Also within both samples, heterozygosity at allozyme loci was inversely related to FA and was positively related to weight and length. However, no significant differences in microsatellite diversity (heterozygosity and mean d2 measurements) were observed between samples (EA vs LA). Furthermore, no association was observed between the variability at microsatellite loci and FA, weight or length within each sample. These results suggest that allozyme loci, in themselves, influence fitness components, rather than associations arising from associative overdominance.