A study of the weights of some intrinsic laryngeal and palatine muscles in the thoroughbred horse

The weights of some intrinsic laryngeal and palatine muscles from 46 thoroughbred horses of varying ages are presented. Thesehorses had no clinical history of wind affliction. The muscles studied were the dorsal cricoarytenoid, the lateral cricoarytenoid, the cricothyroid, the palatine levator and the palatine tensor.

The muscles supplied by the left recurrent laryngeal nerve tended to be lighter in older horses than the muscles supplied by the right recurrent laryngeal nerve. However there was no significant difference in weight between the left and right side for all muscles studied except the lateral cricoarytenoid. In this muscle the left side was significantly lighter than the right (P<0.001).     

Type,diameter and distribution of fibres in some respiratory and abdominal muscles of the goat

This study was designed to determine the histochemical properties, size and composition of fibres in the diaphragm, intercostal and abdominal muscles of goats to clarify whether reported similarities in respiratory muscle physiology between goats and humans have a structural basis. Serial sections (10 µm) of muscular tissue from adult female goats were stained for myosin adenosine triphosphatase and reduced nicotinamide adenine dinucleotide dehydrogenase-tetrazolium reductase activities; the fibres were classified into types I, IIA and IIB; and their mean diameter and composition were determined. Abdominal and intercostal muscles contained types I, IIA and IIB fibres in the ratio 1:1:1, and the mean diameter of the fibres ranged from 49.2 to 62.2 µm. In contrast, the diaphragm contained 58.9% type I and 41.1% type II fibres, and the latter could not be differentiated into types IIA and IIB. Diaphragmatic fibres were also smaller (36.9 – 40.9 µm). These findings contrast with those in humans, where the diaphragm, intercostal and abdominal muscles contain >50% type I fibres and have fibres of identical diameter. The differences in fibre characteristics between the diaphragm, intercostal and abdominal muscles of goats and the differences between goats and humans need to be taken into consideration in interpreting the results from studies in respiratory muscle physiology.Abbreviations mATPase myosin adenosine triphosphatase - NADH-TR nicotinamide adenine dinucleotide dehydrogenase-tetrazolium reductase     

Viral respiratory disease of the horse.

The diagnosis of any viral respiratory disease relies on laboratory procedures to isolate the virus and demonstrate a significant rise in serum antibody titers. To isolate viruses from the upper respiratory tract, it is imperative that nasopharyngeal swabs are obtained from animals in the early acute stage of illness, i.e., during the pyrexic phase when the virus is replicating. Nasopharyngeal swabs must be placed in a virus transport medium and forwarded immediately to the laboratory at refrigerated temperature. Equine influenza, rhinopneumonitis, and equine viral arteritis are the three viral infections causing outbreaks of respiratory disease in North America. African horse sickness, although foreign to North America, could be introduced despite stringent horse importation regulations. Specific antiviral therapy is not available to treat viral respiratory disease in the horse. A variety of inactivated and modified live vaccines, however, are available to prevent clinical disease and the spread of infection caused by the common viral respiratory pathogens. A considerable amount of research is underway to enhance the potency and duration of immunity of the present vaccines against influenza and rhinopneumonitis. This research is directed at defining and characterizing the importance of specific glycoprotein antigens on the surface of the virus, which trigger the various host immune responses, and determining whether they are stimulatory or suppressive.     

Quantification of immunoglobulins in respiratory tract secretions of the horse

Lavage techniques were used to obtain secretions from the nasal cavity, trachea and bronchi of conscious horses. The techniques, which utilised fibreoptic endoscopy for recovery of tracheal and bronchial secretions, were well tolerated by the horses. The recovery rates of the lavaged fluids were acceptable, but were lowest for bronchial secretions, and there was minimal contamination by blood. The fluids were analysed for IgG and IgM by single radial immunodiffusion, and for IgA and albumin by rocket immunoelectrophoresis. Relative to albumin there was significantly more IgA and IgM, and significantly less IgG, in the nasal cavity than the trachea. IgA and IgM levels were greatest in the nasal cavity and decreased progressively to the bronchi, whereas IgG levels showed the reverse trend. The immunoglobulin: albumin ratios of secretions taken from many levels of the tract were significantly higher than those of serum, suggesting local production of immunoglobulin in the respiratory tract.     

The pharmacokinetics of some aminoglycoside antibiotics in the horse

The disposition kinetics and bioavailability of streptomycin, kanamycin and neomycin were determined following their administration as parenteral preparations to horses. Single doses (10 mg/kg) of each aminoglycoside were given by the intravenous (i.v.) and intramuscular (i.m.) routes and, at a later time, seven intramuscular doses were injected at 12-h intervals. The pharmacokinetic behaviour of the three aminoglycosides was similar, in that a rapid distribution phase was followed by a relatively short half-life. The half-life (mean ± SD, n= 6) of kanamycin (1.80 ± 0.17 h) was significantly (P<0.01; t test, 10 d.f.) shorter than that of streptomycin (3.40 ± 0.42 h), while neomycin half-life (2.10 ± 0.97 h) was of an intermediate length. The apparent volume of distribution of neither kanamycin nor neomycin varied significantly (P > 0.05) from that of streptomycin and numerically (V¹ d = 230 ml/kg) was the same as the extracellular fluid volume. The body clearance of kanamycin (88.5 ± 11.3 ml/kg.h) was significantly (P < 0.01) larger than that of streptomycin (47.5 ± 7.9 ml/kg.h), while a significant difference in this parameter did not exist (P > 0.05) between neomycin and streptomycin. Following intramuscular injection, each aminoglycoside was rapidly and completely absorbed from the injection site, although neomycin showed wide individual variation in the fraction absorbed. The administration of multiple doses did not change either the bioavailability or the apparent half-life from the values obtained after a single dose. The only pharmacokinetic difference between these aminoglycosides that is of clinical importance lies in the rate of their elimination. A dosage interval of 8 h would be appropriate for kanamycin compared with a 12-h interval for streptomycin. The dosage interval for neomycin based on half-life should be 8 h but, due to the relatively greater toxicity of this aminoglycoside, an interval of 12 h might be recommended. The height of the peak serum concentration is determined by the size of the dose.     

Some unusual cases of abnormal respiratory noises in the horse

Extract

Any condition which leads to a diminution in the size or alteration of the shape of the lumen of the respiratory tract in the horse may result in the production of abnormal respiratory noises at exercise.     

Daily pattern of some fatty acids in the athletic horse

In the sport field, non‐esterified fatty acids (NEFA) are important for the physical performance during the aerobic exercise of short intensity and long duration. In man, rat, goat and in the sedentary horse studies on the chronometabolism showed the presence of a circadian rhythm of the plasmatic concentration of NEFA while data for the athletic horse are lacking. To define a chronogram helpful for a specific planning and the differentiation of the training programmme in the athletic horse, the circadian pattern of some fatty acids (NEFA, palmitic, stearic, oleic, linoleic and linolenic acids) was studied in five Sella Italiana horses. These horses trained following a daily model of activity consisting of walk, trot, gallop and jump of obstacles of different heights. Blood samples were collected from the jugular vein every 4 h, starting at 08:00 hours, for 2 days to assess the concentrations of total NEFA (by spectrophotometry), palmitic, stearic, oleic, linoleic and linolenic acids (by gas chromatography). anova for repeated measures showed a statistical significant effect of the time of the day in NEFA, oleic and linolenic acids. The application of the periodic model showed the periodic pattern of NEFA, oleic, linoleic and linolenic acids. Acrophases were in the afternoon for all parameters. The results obtained showed a different trend of the circadian pattern of the studied parameters in the athletic horse than in the sedentary one because the physical activity and the post‐prandial metabolism acted as zeitgebers.     

Quantitative motor unit action potential analysis of skeletal muscles in the Warmblood horse

Motor unit action potential (MUP) analysis in human medicine is a valuable and important diagnostic technique enabling discrimination between myogenic and neurogenic problems. This study establishes normative data in subclavian, triceps and lateral vastus muscles for clinical application of MUP analysis in the Warmblood horse, and examines whether muscle differences are present. Electromyographic (EMG) needle examination and MUP analysis were performed of the triceps, lateral vastus and subclavian muscles in 7 awake, nonsedated, Warmblood horses age 4-10 years. The amplitude, duration, number of phases and turns were calculated from the recorded superimposed MUPs together with intramuscular and rectal temperatures. No significant differences were found in duration of insertional activity between the 3 muscles. The mean +/- s.d. duration of the insertional activity was 526 +/- 1483 ms. The MUP amplitude of all 3 muscles differed significantly, with the highest amplitude (427 +/- 3.20 microV) in the triceps and the lowest (220 +/- 2.08 microV) in the subclavian muscle. The number of turns of the lateral vastus (3.0 +/- 1.22) was significantly higher than that of the triceps muscle (2.7 +/- 1.51). No differences were found in MUP duration (5.9-6.4 ms).     

Diagnosis of upper respiratory tract diseases in the performance horse.

Wastage of performance horses because of respiratory dysfunction is common. Appropriate identification of the disease is paramount for treatment recommendations. Diagnostic modalities for upper respiratory tract dysfunction include a thorough physical examination, radiographic evaluation when appropriate, and upper respiratory tract endoscopy. Anatomical deviations or structural are easily identified during resting evaluation, while exercise testing is often necessary to assess thedynamic properties of the upper airway. Utilizing the many diagnostic tools available allows the clinician to make an accurate diagnosis and recommend appropriate treatment.     

Cell-specific activation of aflatoxin B1 correlates with presence of some cytochrome P450 enzymes in olfactory and respiratory tissues in horse

Horses may be exposed to aflatoxin B(1) (AFB(1)) via inhalation of mouldy dust, leading to high exposure of olfactory and respiratory tissues. In the present study the metabolic activation of AFB(1) was examined in olfactory and respiratory tissues in horse. The results showed covalent binding of AFB(1)-metabolites in sustentacular cells and cells of Bowman's glands in the olfactory mucosa, in some cells of the surface epithelium of nasal respiratory, tracheal, bronchial and bronchiolar mucosa and in some glands in these areas. Immunohistochemistry revealed that cells expressing proteins reacting with CYP 3A4- and CYP 2A6/2B6-antibodies had a similar distribution as those having capacity to activate AFB(1). Our data indicate that the cell-specific activation of AFB(1) correlates with presence of some CYP-enzymes in olfactory and respiratory tissues in horse.