Characterization of normal tidal breathing flow-volume loops for Thoroughbred horses

The purpose of this study was to characterize the normal equine tidal breathing flow-volume loop (TBFVL). The study was performed using 18 healthy Thoroughbred horses. TBFVLs constructed from data collected from resting horses had a typical biphasic inspiratory and expiratory phase. The interindividual variability of the indices used to describe TBFVLs was in the range 16–32%, which is comparable to the variability of other measures of equine pulmonary mechanics. The large variability of these data probably limits the value of resting TBFVL indices for detecting subclinical respiratory conditions in individual horses. Factor analysis of these data revealed that in excess of 90% of the variance of the initial response variables could be explained in terms of three common factors. Varimax rotation of these three common factors provided three subsequent factors that were readily identifiable as (1) a factor describing the time-volume relationships of TBFVLs, responsible for 81% of the total variance, (2) a factor explaining the expiratory portion of the TBFVL, explaining 12% of the variance, and (3) a factor describing the inspiratory portion of the loops, responsible for the remaining 7% of the variance. The analysis also provided standardized factor scoring coefficients for use in subsequent studies using similar experimental techniques.Abbreviations EF₂₅ expiratory flow at expiratory volume plus 25%V _E - EF₅₀ midtidal expiratory flow - f respiratory rate - IF₂₅ inspiratory flow at 25% of inspiratory volume - IF₅₀ midtidal inspiratory flow - MSA measure of sampling adequacy - PEF peak expiratory flow - PIF peak inspiratory flow - TBFVL tidal breathing flow-volume loop - T _E expiratory time - T _I inspiratory time - USPTM ultrasonic pneumotachometer - V _E expiratory volume - V _I inspiratory volume     

Pattern of breathing in brachycephalic dogs

The pattern of breathing was assessed in 19 brachycephalic dogs, using tidal breathing flow-volume loop (TBFVL) analysis. Fifteen dogs had TBFVL consistent with a fixed-type upper airway obstruction, whereas 4 dogs had a TBFVL indicative of a nonfixed upper airway obstruction. The dogs did not have a TBFVL shape the same as that considered normal for healthy nonbrachycephalic dogs. Tidal breathing flow-volume loops from brachycephalic dogs that were considered to have a normal respiratory tract (n = 11) were similar to those of dogs with clinical signs of upper airway obstruction (n = 8). Respiration was monitored continuously for short periods (20 to 50 minutes) in 3 brachycephalic dogs resting in a cage in a quiet, darkened laboratory; 2 of these dogs had periodic breathing patterns characterized by multiple episodes of alternating hypopnea and arousal. Brachycephalic dogs may be at risk for the development of disordered breathing during sleep.     

Tidal breathing flow-volume loop analysis for clinical assessment of airway obstruction in conscious dogs

Using a mask, pneumotachograph, and X-Y recorder, tidal breathing flow-volume loops (TBFVL) were evaluated in 33 healthy dogs and in 18 dogs with acquired obstructive respiratory tract disease. The loops were evaluated for qualitative shape, tidal volume (VT), respiratory rate, peak and midtidal inspiratory flow (PIF and IF50, respectively), peak and midtidal expiratory flow (PEF and EF50, respectively), inspiratory and expiratory flow at end expiratory volume plus 25% VT (IF25 and EF25, respectively), inspiratory time, and expiratory time. Indices of loop shape were developed by division of flow measurements (eg, PEF/PIF and IF50/IF25). Twenty healthy dogs had the same TBFVL (type 1). Typically, PEF occurred at the beginning of expiration, and PIF occurred toward the end of inspiration. Three other TBFVL types were identified in the remaining dogs. Mean coefficients of variation for TBFVL indices ranged from 7% to 18%. Dogs with a fixed-type upper airway obstruction (pharyngeal or laryngeal mass, n = 7) had TBFVL abnormalities, indicating inspiratory and expiratory phase flattening. Concavity or late expiratory phase flattening was detected in TBFVL from dogs with chronic bronchitis/tracheal collapse (n = 11). The TBFVL were easily evaluated in conscious dogs and were useful in the functional assessment of airway obstruction.     

Evaluation of partial arytenoidectomy as a treatment for equine laryngeal hemiplegia

The efficacy of partial arytenoidectomy was assessed in 6 Standardbred horses, with surgically induced laryngeal hemiplegia, at rest (Period A) and during exercise at speeds corresponding to maximum heart rate (Period C) and 75% of maximum heart rate (Period B). Peak expiratory and inspiratory airflow rate (PEF and PIF), and expiratory and inspiratory transupper airway pressure (P_UE and P_UI) were measured and expiratory and inspiratory impedance (Z_E and Z_I) were calculated. Simultaneously, tidal breathing flow-volume loops (TBFVL) were acquired using a respiratory function computer. Indices derived from TBFVL included airflow rates at 50 and 25% of tidal volume (EF₅₀, IF₅₀, EF₂₅. and IF₂₅) and the ratios of expiratory to inspiratory flows. Measurements were made before left recurrent laryngeal neurectomy (baseline), 2 weeks after left recurrent laryngeal neurectomy (LRLN) and 16 weeks after left partial arytenoidectomy coupled with bilateral ventriculectomy (ARYT). After LRLN, during exercise Periods B and C, Z₁ and the ratio of EF₅₀/IF₅₀ significantly increased and PIF, IF₅₀ and IF₂₅ significantly decreased from baseline values. At 16 weeks after ARYT, Z₁ returned to baseline values during Periods B and C. Although PIF, IF₅₀, IF₂₅, PEF/PIF, and EF₅₀/IF₅₀ returned to baseline values during Period B, these indices remained significantly different from baseline measurements during Period C. After ARYT, TBFVL shapes from horses during Period C approached that seen at the baseline evaluation. Partial arytenoidectomy improved upper airway function in exercising horses with surgically induced left laryngeal hemiplegia, although qualitative and quantitative evaluation of TBFVLs suggested that some flow limitation remains at near maximal airflow rates. These results indicate that, although the procedure does not completely restore the upper airway to normal, partial arytenoidectomy is a viable treatment option for failed laryngoplasty and arytenoid chondropathy in the horse.     

The effect of common bovine respiratory diseases on tidal breathing flow-volume loops

In order to better understand the bovine breathing pattern, tidal breathing flow-volume loops (TBFVL) were analyzed in 24 healthy cattle of different body weights (range: 37–660 kg) (Group A) and in 28 cattle suffering from the common respiratory diseases: verminous bronchitis (Group B); shipping fever (Group C); acute respiratory distress syndrome (Group D); respiratory syncytial virus pneumonia (Group E); organophosphate poisoning (Group F); and necrotic laryngitis (Group G).Respiratory airflow and tidal volume were measured with a breathing mask-Fleisch pneumotachograph assembly. TBFVL were traced from these values using a computerized method. All the loop indices proposed by Amis and Kurpershoek (1986a) were calculated from 5 representative breathing cycles for each of the 52 animals.The TBFVL shapes and indices were relatively constant in most healthy cattle and were not correlated with the body size. When compared to normal values, animals with moderate respiratory syndromes (Groups B and C) had a more flattened shape to their TBFVL. On the other hand, in most cattle with severe respiratory pathologies (Groups D, F and G) expiration tended to be biphasic with the peak expiratory flow (PEF) occurring significantly later than in healthy animals. Both PEF and peak inspiratory flow were increased in all the pathological conditions. The TBFVL indices were more frequently and more severely changed during expiration than during inspiration.     

Upper airway obstruction in canine laryngeal paralysis

The type and the severity of airway obstruction in 30 dogs with bilateral laryngeal paralysis was assessed, using tidal breathing flow-volume loop (TBFVL) analysis. The dogs had clinical evidence of mild-to-severe upper airway obstruction (ie, respiratory distress, exercise intolerance, stridor). Seventeen dogs had TBFVL consistent with a nonfixed (inspiratory) obstruction, 10 had TBFVL indicative of a fixed (inspiratory/expiratory) obstruction, and 3 had normal TBFVL. Analysis of TBFVL confirmed that dogs with laryngeal paralysis have upper airway obstruction that differs in type and severity. Use of TBFVL provided a quantitative evaluation of airway obstruction and demonstrated the effects of bilateral laryngeal paralysis on the breathing patterns of dogs.     

Tidal Breathing Flow-Volume Loops in Healthy and Bronchitic Cats

Tidal breathing flow-volume loops (TBFVL) were obtained from 19 healthy cats and 7 cats with chronic bronchial disease. Peak inspiratory flow (PIF) occurred late in the inspiratory cycle and was preceded by a gradual but more linear increase in the flow rate. Peak expiratory flow (PEF) occurred early during expiration and was followed by a curvilinear decrease in flow to a point near the end of expiration where flow ceased. The loops obtained were generally reproducible. The mean coefficient of variation (CV) for TBFVL indices of healthy cats ranged from 5.6% to 21.9%. Loop indices from cats with chronic bronchial disease had a mean CV between 6.6% and 28.4%. Significant differences were noted in the bronchitic cats' TBFVLs, including an increased ratio of expiratory time to inspiratory time, lower expiratory flow rates, decreased area under total and peak expiratory flow curves, and decreased tidal breathing expiratory volumes (TBEV) at 0.1 and 0.5 seconds. Selected TBFVL indices were also significantly reduced. TBFVL evaluation in the cat is easy to perform, is reproducible, and has allowed for the detection of changes during tidal breathing in cats with histories and physical findings of chronic lower airway disease. (Journal of Veterinary Internal Medicine 1993; 7:388–393. Copyright © 1993 by the American College of Veterinary Internal Medicine.)     

Temporal effects of inhaled histamine and methacholine aerosols on the pulmonary mechanics of Thoroughbred horses

This paper presents a method for on-line determination of pulmonary mechanics in standing, non-sedated horses during and following inhalation of aerosolized drug solutions. This method was used to evaluate the temporal effects of inhaled histamine and methacholine aerosols on pulmonary mechanics in 18 Thoroughbred horses. The following were concluded from this study. The extremely large between-breath variation, for all variables used to evaluate pulmonary mechanics in the horse, limits the usefulness of these variables for modeling the non-specific pulmonary responses to inhaled stimulants on a breath-by-breath basis. Following the implementation of averaging techniques to control the variation of these response variables, respiratory rate appears to be affected most predictably by inhalation of non-specific bronchoconstrictors. In the 18 subjects studied, the response of respiratory rate to inhaled histamine and methacholine aerosols was well described by a complex function consisting of exponential treatment and post-treatment phases in 10 and six of the subjects, respectively. Large intra-individual variation of the non-specific response to these stimulants in repeated studies of some subjects, suggests that differences in responses on a particular day may be due to inter-day variations in minute ventilation or baseline airway caliber.     

Measurement of tidal breathing flow-volume loop indices in horses used for different sporting purposes with and without recurrent airway obstruction

Tidal breathing flow-volume loop (TBFVL) indices in healthy horses and in horses suffering from mild and moderate to severe recurrent airway obstruction (RAO) were measured. In addition, the ability of these indices to differentiate healthy controls from horses with mild RAO by separating the horses according to their usage was investigated. The horses were assigned to three sporting categories: 1 Leisure horses; 2 Horses competing at events with a duration of more than five minutes (eventing, coaching and endurance); and 3 Horses competing at events with a duration of less than five minutes (dressage and show jumping). Flow-volume curves were recorded with an ultrasonic spirometer and TBFVL indices were calculated with specially dedicated software. The sporting usage of the horses had a significant effect on the differentiating ability of TBFVL indices in diagnosing different degrees of RAO. The index TIF50 differentiated control horses from horses with minor RAO in all sporting categories.     

Reactivity of Equine Airways—A Study on Precision-cut Lung Slices

A study was performed to evaluate the use of precision-cut lung slices (PCLS) for studies on the contraction of equine airways. Lungs of 10 horses were taken to prepare PCLS of ˜250 μm from equine lung tissue using a special microtome. The lung slices were cultured and the enclosed small airways were monitored using a microscope with coupled digital camera, which was used to determine the airway luminal area and diameter from digital images. As indicated by the beating of the ciliated epithelium and reactivity of airways on methacholine challenge, the tissue slices were found to be viable for at least 24 h. The airways were not precontracted, as indicated by a missing dilatory effect of 1 mmol/L clenbuterol. Bronchoconstriction induced by both methacholine and histamine was found to be dose dependent. EC₅₀ values based on luminal area were 1.12 μmol/L · /÷ 3.82 for methacholine and 0.68 μmol/L · /÷ 6.99 for histamine. In conclusion, the PCLS technique is promising for studies on small airways in the equine lung. In the present study the basic principles of in vitro (ex vivo) examinations with equine PCLS on airway reactivity were developed.     

Histamine relaxes constricted trachea and bronchi of horse

Horse trachea and bronchi contracted to slow-reacting substance of anaphylaxis, carbachol, 5-hydroxytryptamine, histamine, 2-methyl-histamine, bradykinin and prostaglandin F₂. Prostaglandins E₁ and E₂, isoprenaline and 4-methylhistamine caused relaxation of carbachol-contracted bronchi. Mepyramine (H₁-blocker) specifically inhibited histamine bronchoconstriction. In the presence of mepyramine, histamine caused relaxation of carbachol-contracted bronchi. Metiamide (H₂-blocker) inhibited histamine bronchorelaxation but not relaxation of the trachea. This suggests (1) the presence of both H₁- and H₂-receptors mediating bronchoconstriction and relaxation respectively (2) the existence of an atypical histamine receptor in the trachea. The study suggests that in equine respiratory hypersensitivity under therapy with classical (H₁) antihistaminics, further release of histamine may exert a beneficial broncholytic effect on airways contracted by other chemical mediators of immediate-type inflammation.     

Preliminary findings of altered follicular activity in Holstein cows with coagulation factor XI deficiency

Factor XI (F XI) deficiency is an autosomal recessive coagulopathy found in Holstein cattle. Affected animals have a 50% greater prevalence of repeat breeding. Therefore, several parameters describing ovarian function were studied. Daily blood sampling revealed that progesterone concentrations were slower to decline from a peak at day 16 (p<0.01) to values less than 3 nmol/L in F XI-deficient cows (5.14±0.69 days (mean ± SD) versus 4.05±0.63 days in control animals), resulting in an oestrous cycle length of 24.7±2.1 days compared to 22.9±3.0 days, respectively. This was not due to an alteration in the availability of prostaglandin F₂ (PGF₂) or oxytocin (OT) involved in luteolysis. No significant differences (p>0.05) were seen between normal (n=7) and F XI-deficient (n=7) cows in the peak values or the area under the curve for the pulse in 13,14-dihydro-15-keto PGF₂ in response to OT challenge or in the parameters describing the pulse of ovarian OT secretion after PGF₂ injection (n=7 for each) between days 12 and 14. Ovulatory follicular development was assessed by ultrasound monitoring and plasma 17-oestradiol values at 8-h intervals after a luteolytic injection of cloprostenol (n=6 for each). Follicular diameter was smaller (p<0.05) and accompanied by lower peak oestradiol values near the time of ovulation in F XI-deficient cows. The results suggest that the oestrous cycle in F XI-deficient cows is characterized by a slower process of luteolysis that may be associated with smaller follicular development.Abbreviations F XI factor XI - OT oxytocin - PGF₂ prostaglandin F₂ - PGFM 13,14-dihydro-15-keto-prostaglandin F₂ - i.m. intramuscularly     

The influence of ageing on muscarinic receptors, β-adrenoceptors and adenylate cyclase activity in the bovine lung

Muscarinic and -adrenoceptors were identified in airway epithelium, smooth muscle and lung parenchyma from Holstein-Friesian calves and cows and were characterized with [³H]quinuclidinyl benzilate and [³H]dihydroalprenolol, respectively. The muscarinic receptor density in the smooth muscle of cows (B _max=4803±245 fmol/mg protein) was 33% greater (p<0.01) than in calves. Low receptor numbers were detected in the epithelium and parenchyma. In both calves and cows, the density of epithelial -adrenoceptors was twice as high as in smooth muscle and parenchyma. The quantity of -adrenoceptors in the tracheal epithelium (B _max=994±83 fmol/mg protein) and smooth muscle (B _max=492±41 fmol/mg protein) in cows was respectively 37% (p<0.001) and 35% (p<0.01) lower than in calves. Adenylate cyclase (AC) assays indicated that the basal and the (–)-isopropylnoradrenaline- (ISO-) stimulated cAMP production were not significantly different between the calves and cows. After stimulation with NaF, significantly higher cAMP production was found in all tissues from cows. Significant correlations were found between absolute AC responses to NaF and -adrenoceptor density in epithelium (r=–0.75,p<0.001) and smooth muscle (r=–0.63,p<0.01). It seems that, in older animals, the production of cAMP is independent of the number of receptors, indicating the presence of fully active compensatory mechanisms.Abbreviations AC adenylate cyclase - cAMP intra-cellular adenosine monophosphate - G-protein GTP binding protein - GTP guanosine 5-triphosphate - ISO isopropylnoradrenaline - M muscarine - QNB quinuclidinyl benzilate     

Identification of Functional α-Adrenoceptor Subtypes in the Bovine Female Genital Tract During Different Phases of the Oestrous Cycle

The concentration and functionality of the -adrenoceptor (-AR) subtypes in the genital tract of cyclic heifers were investigated. In each tissue sample, a single class of ₁-ARs was observed, whereas two distinct classes of ₂-ARs were discriminated: low-affinity (LA) and high-affinity (HA) ₂-ARs. Statistical analysis showed the presence of significantly (p < 0.05) higher concentrations of all -AR subtypes in the follicle than in the corpus luteum. No significant differences were found in the ovary or myometrium between the luteal and follicular phases. In the ovary, the density of ₁-ARs was significantly (p < 0.05) higher than that of ₂-ARs. By contrast, there were significantly (p < 0.05) more ₂-ARs than ₁-ARs in the myometrium. As far as ₂-ARs are concerned, LA ₂-ARs were significantly (p < 0.05) higher than HA ₂-ARs in all tested tissues. Competition studies suggested that the rank order of potency of antagonists for ₁-ARs was prazosin > phentolamine > yohimbine, whereas for ₂-ARs the order of potency was yohimbine phentolamine > prazosin. Functional assays performed on myometrium showed that noradrenaline, phenylephrine and clonidine elicited concentration-dependent contractions only in dioestrus and pro-oestrus preparations and that clonidine was more effective than phenylephrine as a contractile agent. It appeared that there were no significant modifications in -AR affinity or concentration during the different stages of bovine oestrous cycle, whereas the uterine spontaneous activity and the responsiveness to -adrenergic stimulation was strongly influenced by hormonal levels. The modifications of uterine contractility observed during the oestrous cycle may be related to modifications induced in the transductional mechanisms of -ARs.     

Tidal Breathing Flow‐Volume Loop Analysis for the Diagnosis and Staging of Tracheal Collapse in Dogs

Background: Tracheoscopy is generally used for the diagnosis of tracheal collapse (TC) in dogs; yet, it is costly, requires anesthesia, and can irritate the airway. The tidal breathing flow‐volume loop (TBFVL) is a safe, quick, and noninvasive pulmonary function test currently used in humans. Hypothesis: TBFVL will differentiate dogs with TC from healthy controls and contribute to disease grading. Animals: Twenty‐eight dogs with naturally occurring TC and 10 healthy controls. Methods: Cross‐sectional, prospective clinical study: The 38 dogs were assigned to one of 4 groups based on tracheoscopy results: group A (n = 10, healthy controls), group B (n = 10, grade I TC), group C (n = 10, grade II TC), and group D (n = 8, grade III TC). The TBFVL measurement was performed on all dogs and loops were assessed for their shape. Forty‐four TBFVL parameters were calculated. Results: Two types of TBFVL shapes were identified: Type I, representative of the 10 healthy controls, and Type II, representative of the 28 dogs with TC. Statistical analysis showed the dogs could be differentiated into healthy or affected by TC by 3 indices, TE/TI (expiratory time divided by inspiratory time), TI/TTOT (inspiratory time divided by total respiratory time), and EF75/IF75 (expiratory flow at end tidal volume plus 75% end tidal volume divided by inspiratory flow at end tidal volume plus 75% end tidal volume). The TC could also be graded as mild‐moderate (grades I and II) or severe (grade III), showing a diagnostic value of 97.4%. Conclusion and Clinical Importance: TBFVL is accurate, quick, noninvasive, and safe and can contribute to the diagnosis of TC in dogs.     

Vasomotor effects of histamine on bovine and equine basilar arteriesin vitro

The vasomotor effects of histamine on isolated bovine and equine basilar arteries were examined. Histamine induced contractions in both these preparations. The maximal response to and pEC₅₀ value for histamine of the equine artery were larger than those of bovine tissue. Similar results were obtained with endothelium-denuded basilar arteries. Diphenhydramine (H₁-receptor antagonist) inhibited histamine-induced contractions of the basilar arteries from both species in a concentration-dependent manner and its pA ₂ values (with 95% confidence limits) were 7.61 (7.39–7.83) and 8.15 (8.01–8.29) for the bovine and equine preparations, respectively. Cimetidine (H₂-receptor antagonist) slightly potentiated histamine-induced contractions of bovine, but not equine, basilar arteries. 2-Thiazolylethylamine (H₁-receptor agonist) induced contractions in both preparations, whereas impromidine (H₂-receptor agonist) induced weak relaxation of the bovine, but not the equine, tissue. These findings indicate that bovine basilar arterial smooth muscle cells possess H₁- and H₂-receptors. Stimulation of the former results in contraction, whereas stimulation of the latter results in weak relaxation. Equine basilar arterial smooth muscle cells possess H₁-receptors, stimulation of which results in contraction.Abbreviations CR concentration ratio - EC₅₀ concentration producing 50% maximal response - pA ₂ negative logarithm of the molar concentration of antagonist that produces a twofold rightward shift of a concentration-response curve - pEC₅₀ negative logarithm of EC₅₀ - PGF₂ prostaglandin F₂ - PGI₂ prostaglandin I₂     

Pharmacokinetics of benzydamine in dairy cows following intravenous or intramuscular administration

Five lactating cows were given benzydamine hydrochloride by rapid intravenous (0.45 mg/kg) and by intramuscular (0.45 and 1.2 mg/kg) injection in a crossover design. The bioavailability, pharmacokinetic parameters and excretion in milk of benzydamine were evaluated. After intravenous administration, the disposition kinetics of benzydamine was best described using a two-compartment open model. Drug disposition and elimination were fast (t _1/2: 11.13±3.76 min;t _1/2: 71.98±24.75 min; MRT 70.69±11.97 min). Benzydamine was widely distributed in the body fluids and tissues (V _d(area): 3.549±1.301 L/kg) and characterized by a high value for body clearance (33.00±5.54 ml/kg per min). After intramuscular administration the serum concentration-time curves fitted a one-compartment open model. Following a dose of 0.45 mg/kg, theC _max value was 38.13±4.2 ng/ml at at _max of 67.13±4.00 min; MAT and MRT were 207.33±22.64 min and 278.01±12.22 min, respectively. Benzydamine bioavailability was very high (92.07%±7.08%). An increased intramuscular dose (1.2 mg/kg) resulted in longer serum persistence (MRT 420.34±86.39 min) of the drug, which was also detectable in milk samples collected from both the first and second milking after treatment.Abbreviations HPLC high-pressure liquid chromatography - IC50 concentration to inhibit the activity of an organism by 50% - IM intramuscular(ly) - IV intravenous(ly) - NSAID non-steroidal antiinflammatory drugs - pK _a negative logarithm of the ionization constant (K _a) of a drug; other abbreviations are listed in footnotes to tables     

Actions of histamine and other substances on the airway smooth muscle of swine (in vitro)

Isolated swine tracheal and bronchial smooth muscle strips contracted to carbachol and histamine. 5-HT, PGF₂ and bradykinin were inactive. Isoprenaline (a -adrenoceptor agonist), PGE₁, PGE₂, bradykinin and 4-methylhistamine (4-MeH: a specific H₂-receptor agonist) produced relaxation of carbachol contracted trachea and bronchi. Mepyramine (a specific H₁-antagonist) blocked histamine-induced contractions. After H₁-blockade, histamine induced relaxation of carbachol contracted trachea and bronchi. Metiamide (an H₂-receptor antagonist) antagonizes relaxation to 4-MeH and histamine, but not to isoprenaline. The results of this investigation showed the presence of both H₁- and H₂-histamine receptors mediating constriction and relaxation respectively in the airways of swine.     

The use of cultured hepatocytes from goats and cattle to investigate xenobiotic oxidative metabolism

The oxidative metabolism of aldicarb (ALD), a carbamate pesticide, and fenbendazole (FBZ), an anthelmintic, was studied using cultured hepatocytes obtained from 4 goats and a bullock and incubated with ALD (50 mol/L) and FBZ (10 mol/L). The parent compounds and the metabolites were measured by HPLC. Both compounds are metabolized at the sulphur atom via two sequential oxidations, first to the sulphoxide (aldicarb sulphoxide and oxfendazole, respectively) and then to the sulphone. Oxfendazole and fenbendazole sulphone from FBZ, and aldicarb sulphoxide from ALD were found in both species. Aldicarb sulphone was not produced by the hepatocyte preparations from the bullock. The good correlation obtained comparing the in vitro results of FBZ metabolism with published in vivo dat obtained on FBZ kinetics in the same species confirmed the usefulness of in vitro models for predictive analysis of in vivo xenobiotic biotransformations.Abbreviations ALD aldicarb - ALDSON aldicarb sulphone - ALDSOX aldicarb sulphoxide - BSA bovine serum albumin - ID internal diameter - EGTA ethylene glycol bis(-aminoethyl ether) N,N,N,N-tetraacetic acid - FBZ fenbendazole - FBZSON fenbendazole sulphone - HBSS Hanks' balanced saline solution - HPLC high-pressure liquid chromatography - LDH lactate dehydrogenase - MFO mixed function oxidase - NCS newborn calf serum - OXF oxfendazole - WME Williams' Medium E     

Acute ruminal indigestion,alkalosis and death of cattle grazing kikuyu

Abstract

Extract

The increased vascular permeability that follows the intrapleural injection of turpentine in the sheep is due to the local re-ease of histamine and is continued by the activation of other mechanisms (Lancaster and Vegad, 1967 Lancaster, M. C. and Vegad, J. L. 1967. Suppression of the early inflammatory response in the sheep by strophanthin G. Nature, Lond., 213: 840–841.  [Google Scholar]). In further studies of the inflammatory response, an attempt was made to deplete the skin locally of its histamine content. It was found that the intra-dermal injection of a total of 80 mg/kg of compound 48/80, a histamine liberator, into a 20 kg lamb, caused acute respiratory distress and death. Death was presumed to be due to the release of lethal amounts of histamine by this compound. To investigate the sensitivity of the sheep to histamine, the toxicity of compound 48/80 and of histamine was tested.