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1.
Eosinophils have been implicated in the pathogenesis of the seasonal equine allergic skin disease, sweet itch. Protein kinase C (PKC) is involved in regulating eosinophil function and antigen challenge has been reported to alter PKC isotype expression in blood eosinophils from allergic human subjects. Here we have compared the pattern of PKC isotype expression in eosinophils from sweet itch ponies with that in cells from normal ponies both during the active and inactive phases of the disease. A role for PKC in histamine-induced eosinophil activation was also investigated. Conventional PKCs alpha and beta, novel PKCs delta and epsilon and atypical PKCs iota and zeta were identified in eosinophils pooled from four allergic ponies during the inactive phase, when no clinical signs were evident. The PKC isotypes, like those in eosinophils from normal ponies, were located primarily in the particulate fraction of the cell. Isotype expression in cells from normal and allergic animals did not appear to be different. In contrast, during the active phase of the disease, when the sweet itch ponies had clinical signs, the expression of PKCs beta, epsilon and iota in eosinophils from these animals appeared to be increased relative to that in cells from normal ponies. When PKC expression in eosinophils from five individual normal and sweet itch ponies was compared, small, but statistically significant, increases in PKC epsilon and PKCdelta expression were evident in eosinophils from the sweet itch ponies during the active and inactive phases, respectively. The non-selective PKC inhibitors, staurosporine and Ro31-8220, significantly reduced histamine-induced superoxide production. Use of G?6976, an inhibitor of conventional PKCs, suggested that PKCalpha and/or beta were involved and that there was significantly greater inhibition of the response in eosinophils obtained from sweet itch ponies during the active phase. There was no significant difference in histamine-induced superoxide production by eosinophils from allergic and normal ponies and the functional significance of the increased PKC isotype expression in eosinophils from sweet itch ponies relative to that in cells from healthy animals remains to be established.  相似文献   

2.
Circulating lymphocyte numbers are elevated in horses with the allergic skin disease sweet itch and skin lesions are typified by an infiltrate of eosinophils and mononuclear cells, the latter of which have not been fully characterised. The aim of the present study was to characterise the lymphocyte subpopulations in the circulation and skin of ponies with sweet itch by flow cytometry and a newly developed modified alkaline phosphatase immunohistochemical technique. Sweet itch ponies were found to have significantly greater numbers of circulating CD5+ and CD4+ T-lymphocytes than normal animals. Increased numbers of CD3+ T-lymphocytes, most of which were CD4+, and eosinophils were present in the skin of these animals following intradermal injection of a Culicoides antigen extract (97 +/- 21 vs. 449 +/- 49 CD3+ T-lymphocytes/mm2 in deep dermis of vehicle vs. antigen injected sites; 83 +/- 8% CD4+ T-lymphocytes at antigen injected site). T-lymphocytes, which are thought to be important in the pathogenesis of human allergic skin disease, may therefore contribute to the development of sweet itch lesions via the release of cytokines which can cause eosinophil accumulation and activation. An understanding of the pathology of this disease may lead to a more rational approach to therapy.  相似文献   

3.
The chemokine eotaxin is involved in the recruitment of eosinophils and T helper 2 lymphocytes in human allergic diseases, and drugs that block its activity, including eotaxin receptor (CCR3) antagonists, are being developed. The authors have recently cloned the horse ortholog of eotaxin and shown that it can induce equine eosinophil migration and activation in vitro. Moreover, eotaxin mRNA expression was upregulated in cultured horse dermal fibroblasts exposed to equine interleukin-4, suggesting a possible source of this eosinophil chemoattractant in equine skin. The results of this study show that eotaxin and monocyte chemoattractant protein (MCP) 1, but not MCP-2 or MCP-4, mRNA expression is upregulated in skin biopsies of sweet itch lesions when eosinophils are present, when compared with clinically normal skin from the same ponies.  相似文献   

4.
A survey of allergic dermatitis (sweet itch) in Sweden contained information on 441 Icelandic horses. Results of a questionnaire indicated that approximately 15 per cent of the country's Icelandic horses suffered from the disease. The prevalence of allergic dermatitis was significantly higher among horses imported from Iceland (26.2 per cent) compared to that of Swedish-born animals (6.7 per cent). In addition, horses born in Iceland were significantly more severely affected than horses born in Sweden. The risk of allergic dermatitis in Sweden appeared to be more than six times higher for horses exported from Iceland to Sweden relative to that of horses originally born in Sweden. The prevalence of disease for horses of seven years or older was 30 per cent for Icelandic-born individuals as compared to 7.3 per cent for horses born in Sweden. Similarly, the risk of allergic dermatitis in Sweden for horses of seven years or older appeared to be nearly 10 times higher for horses imported from Iceland relative to that of horses born in Sweden. Allergic dermatitis usually appeared during the third grazing season for imported horses and during the fourth season for horses born in Sweden. Furthermore, the course of the disease tended to become worse with time. Analysis of the prevalence of allergic dermatitis relative to gender revealed no significant differences. Certain geographical variations in the prevalence of the disease was also found.  相似文献   

5.
The tachykinin, substance P (SP), affects eosinophil function by direct and indirect mechanisms and has been shown to cause equine eosinophils to adhere to vascular endothelium and to release cytokines that increase cell adherence. The aim of this study was to determine whether SP could act directly on equine eosinophils in vitro. Eosinophil activation was also compared in cells from normal ponies and those with insect hypersensitivity as SP may be released in the skin of hypersensitive animals. SP caused equine eosinophils to adhere, migrate and produce superoxide, although high concentrations were required to produce these effects [10 +/- 2% adherence, 45 +/- 20 cells/0.3 mm2 and 48 +/- 7 nmol (of reduced cytochrome C)/106 cells, respectively, at 3 x 10-4 m]. That the 7-11, but not the 1-7, amino acid fragment of SP caused superoxide production, suggested the effects of SP were receptor mediated. Eosinophils from hypersensitive ponies produced more superoxide in response to SP, but not phorbol myristate acetate or histamine, over the concentration range tested when compared with cells from normal ponies. The data obtained in this study suggest that although SP can directly activate equine eosinophils, in view of the high concentrations required, such actions may be of less relevance physiologically than other SP-mediated effects.  相似文献   

6.
Accumulation of equine eosinophils at sites of parasite infestation or allergic inflammation depends upon their adherence to vascular endothelial cells and subsequent migration through the endothelium and extracellular matrix. This study has examined whether cytokines, which cause endothelial cell-dependent eosinophil adherence in other species, and histamine and substance P, which increase adherence of equine eosinophils to protein coated plastic, induce equine eosinophil adherence to cultured equine digital vein endothelial cell (EDVEC) monolayers. The EDVEC monolayers were stimulated with recombinant human (rh) interleukin (IL)-1beta, rhTNFalpha, substance P or histamine for different times and with a range of concentrations of mediators and the adherence of blood eosinophils from normal horses examined. All four mediators caused time- and concentration-dependent increases in adherence. However, neither the response to substance P, nor that to histamine, reached a maximum at the highest concentration tested (10-3 M: 10.6 +/- 2.6% and 4.5 +/- 0.6% adherent cells vs. background adherence of 1.9 +/- 0.4% and 1.1 +/- 0.2%; values for substance P and histamine, respectively, expressed as a percentage of total cells added initially; n=4). These data suggest that, as in other species, cytokines induce endothelial cell-dependent eosinophil adherence and mediators released during allergic inflammation may play a role in eosinophil recruitment by this mechanism.  相似文献   

7.
A preliminary investigation has been undertaken of blood rheology in horses and ponies, its variation in navicular disease and the changes following treatment with warfarin. Erythrocyte flexibility, measured by a centrifuge packing technique, is higher in horses (30 per cent min-1) than in ponies (23.8 per cent min-1). There are corresponding differences in blood viscosity. The high erythrocyte flexibility in horses is caused by an unknown factor present in plasma. The erythrocyte flexibility in horses with navicular disease is even higher, at 38.5 per cent min-1. Treatment with warfarin reduces the flexibility to just below the normal value. A significant fall in plasma viscosity and erythrocyte flexibility was found after treatment of four ponies with 6 mg warfarin daily for one week.  相似文献   

8.
The effect of factors including the horses' farm environment, their sex and age and whether they suffered from summer seasonal recurrent dermatitis (sweet itch) on the concentrations of zinc in the plasma, whole blood and blood cells of 104 Icelandic horses was investigated. Its concentration in plasma varied significantly between farms (P<0.01), but its concentration in blood and blood cells was not influenced by any of the variables. The concentration of zinc in the blood cells was 10.5 times greater than in plasma, but its concentration in plasma was not correlated with its concentration in whole blood or blood cells owing to the variability in the proportion of whole blood zinc present in plasma (relative plasma zinc), which ranged between 9 and 24 per cent. This variability was significantly influenced by a three-way interaction between farm, sex and sweet itch (P<0.05). Relative plasma zinc was positively correlated with absolute plasma zinc (r=0.78, P<0.001) and negatively correlated with whole blood and blood cellular zinc (r=-0.58, r=-0.71, P<0.001).  相似文献   

9.
Medical records of 27 horses (including 13 ponies) treated with pergolide or cyproheptadine for pituitary pars intermedia dysfunction were reviewed to determine the effect of treatment on plasma ACTH, insulin, and glucose concentrations and clinical signs. Prior to treatment, the most common clinical signs were laminitis, hirsutism, and abnormal body fat distribution. The median pergolide dose was 3.0 microg/kg p.o. q24h (range, 1.7-5.5 microg/kg). All horses treated with cyproheptadine were given 0.25 mg/kg p.o. q24h. After pergolide treatment, ACTH concentrations (n = 20; median = 30.4 pg/ml; range, 4.2-173) were significantly lower (P < .01) than those in horses treated with cyproheptadine (n = 7; median = 141.0 pg/ml: range, 10-1,230). Among horses treated with pergolide, there was a correlation between ACTH concentration after treatment and the duration of treatment (P < .001) and pergolide dose (P = .04). Significantly (P = .02) more owners of horses treated with pergolide (85%, 17/20) reported an improvement in clinical signs compared to owners of horses treated with cyproheptadine (28%, 2/7).  相似文献   

10.
An analysis was made of the causes of death in horses and ponies over one year of age which died suddenly (Group 1) or were found dead but were considered normal when last seen (Group 2). There were 49 animals in Group 1. Thoroughbreds were overrepresented, but there were no ponies in this group. No cause of death was found in 30.6 per cent of cases and 16.3 per cent died from each of the following causes: haemorrhage in the respiratory system, central nervous system, and adverse drug reactions. Cardiovascular lesions were the cause of death in 14.4 per cent and the remaining 3.1 per cent had lesions of the gastrointestinal system. Racehorses mostly died suddenly from severe haemorrhage in various sites, particularly the thorax. In Group 2 there were 151 animals, and in 33.1 per cent no cause of death was determined. Gastrointestinal lesions were considered the cause of death in 39.2 per cent of cases and respiratory lesions killed 8.6 per cent. Lesions of both the central nervous system and cardiovascular system were considered the cause in 4.6 per cent of cases. The remaining 9.9 per cent of animals had miscellaneous lesions. Toxicological studies were performed in 46 of the total 200 cases, and only two had positive results; lead in one and nicotine in the other.  相似文献   

11.
Sarcocystis was detected in oesophageal samples from 245 (62 per cent) of 394 horses and ponies killed at a Cheshire abattoir between February and August 1981. Prevalence of infection was closely related to age, increasing from 28.6 per cent of animals up to two years old to 88.9 per cent of those over eight years old. There were no significant regional differences in prevalence between horses from north west England, Yorkshire or South Wales. Significantly more female horses were infected (69.7 per cent) compared with males (56.2 per cent). Gross examination methods detected fewer than 55 per cent of all infections compared with a tissue digest method. Sarcocysts ranged from 1 to 15 mm in length (mean 5.5 mm) and were up to 0.5 mm wide. Cyst wall morphology and bradyzoite dimensions suggest that the species involved is Sarcocystis bertrami (syn equicanis).  相似文献   

12.
The demonstration of a reagin-like antibody againstCulicoides pulicaris extract in the serum of horses and ponies affected with recurrent seasonal dermatitis (sweet itch) is reported. This antibody can confer Prauznitz-Küstner (P–K) sensitivity on homologous skin for up to 5 days and, like human IgE, is thermolabile and susceptible to 2-mercaptoethanol reduction. It is eluted on diethylaminoethyl dextran-52 anion exchange chromatography independently of IgG, IgG(T) and IgM, and its elution characteristics indicate similarity in net molecular charge to human IgE.The P–K response observed in horse skin is biphasic, and is morphologically similar to the late cutaneous anaphylactic response in man. Both phases of the P–K response are dependent upon the reagin-like antibody, although other serum factors appear involved in the delayed phase of the response.  相似文献   

13.
Six hundred and twenty culicoides of five species were collected from a bait horse at Kannot, Israel, between April and September 1986. Seventy-two per cent of the midges were collected from the belly and 27 per cent from the dorsal aspect of the body, ie, the sweet itch summer seasonal recurrent dermatitis (SSRD) zone. Midges were active mainly from half an hour prior to half an hour after sunset. Only Culicoides puncticollis, C imicola and C schultzei group were collected in considerable numbers. While C imicola was present continuously throughout the season, the appearance of the two other species was intermittent. Ninety-five per cent of C schultzei group and approximately 100 per cent of the C puncticollis prefer to land on and most probably bite the belly. Culicoides imicola showed a clear preference for the dorsal ridge which overlaps the (SSRD) itch zone, and 70 per cent of the midges were collected there, while 28 per cent were collected from the belly. A considerably high proportion of the midges of this species were parous, ie, part of the population lived long enough to bite more than once. Skin temperature measurements showed the belly to be the warmest part of the body. Wind speeds of two to three knots reduced the number of midges collected. The findings of this study, together with a previous one (Braverman et al 1983), incriminate C imicola as the likely principal agent of SSRD in Israel.  相似文献   

14.
The cytokine, interleukin (IL)-5 stimulates eosinophil differentiation, activation and survival and can prime these cells, increasing the response to other mediators. In view of its many effects on eosinophils, IL-5 has been implicated in the pathogenesis of allergic disease in man. Here we report the cloning of equine IL-5 and expression of the recombinant protein by transfection of Chinese hamster ovary (CHO) cells. The cloned cDNA sequence consisted of 405 nucleotides and encoded a protein of 135 amino acids. There is >85% identity with feline, bovine, ovine, canine, and human IL-5 sequences at the nucleotide and protein level. Supernatants containing equine IL-5 were also examined for biological activity. CHO supernatant containing equine recombinant (eqr) IL-5, like the human ortholog (hrIL-5), induced concentration dependent equine eosinophil adherence to autologous serum-coated plastic (9.7+/-1.5% with a 1:100 dilution of eqrIL-5 and 9.1+/-1.6% adherence with 1 nM hrIL-5; n = 4). The eqr protein also caused concentration dependent superoxide production (11.9+/-2.4 nmol (reduced cytochrome (cyt) C)/10(6) cells at a 1:50 dilution, n = 4). In contrast, hrIL-5 only caused significant superoxide production when diluted in conditioned CHO medium, an effect that was inhibited by the anti-human mAb, TRFK5 (4.4+/-0.3 versus 0.3+/-0.4 nmol/10(6) cells for 0.5 nM hrIL-5 in the presence of the isotype matched IgG1 control (10 microM) and TRFK5 (10 microM), respectively). TRFK5 also significantly inhibited hrIL-5 induced adherence at concentrations of 0.3 microg/ml and above but had no significant inhibitory effect on either superoxide or adherence caused by eqrIL-5. These results demonstrate that equine IL-5 expressed by CHO cells stimulates equine eosinophils, suggesting that this cytokine could play a role in eosinophil recruitment and activation in equine allergic disease. The anti-human and murine moAb TRFK5 does not appear to recognise the equine protein.  相似文献   

15.
Ponies with recurrent airway obstruction (principal ponies) and their controls were given aerosolized Micropolyspora faeni antigen via endotracheal tube during a period when the principal ponies were in disease remission. In both groups of ponies, we performed bronchoalveolar lavage (BAL) and measured pulmonary function at base line, and 5 hours after aerosol administration of 30 ml of 0.9% NaCl solution or 30 ml of 1% w/v particulate M faeni antigen in 0.9% NaCl solution. In both groups of ponies, aerosolized M faeni antigen increased WBC count, neutrophil numbers, and albumin concentration in BAL fluid, but macrophage numbers decreased. In the principal ponies, BAL mast cell numbers were decreased 5 hours after administration of M faeni antigen. The M faeni antigen had no effect on the mechanical properties of the lungs or on gas exchange in the control ponies, but did increase respiratory frequency minute ventilation and pulmonary resistance, and decreased arterial oxygen tension in the principal ponies. Changes in pulmonary function were apparent only in the principal ponies, which suggests that neutrophils, per se, do not cause pulmonary dysfunction and that M faeni may be one of the etiologic agents involved in chronic obstructive pulmonary disease.  相似文献   

16.
Activation of circulating neutrophils has been observed following challenge of horses with chronic obstructive pulmonary disease (COPD) and may facilitate the accumulation of these cells in the airways. In this study, no significant difference was observed between adherence to protein coated plastic of blood neutrophils from asymptomatic COPD-susceptible and normal horses stimulated by the mediators PAF, human recombinant (hr)IL-8 and hrC5a. Twenty-four hours after the start of a 7 h antigen challenge, adherence of unstimulated neutrophils from COPD-susceptible horses increased from 2.5 (0.5-4.1)% and 3.4 (0.6-6.6)% to 19.6 (16.9-20.3)% and 21.8 (10.6-23.1)% adherence for cells in medium containing 0.1% or 0.2% BSA, respectively; (median [range]; n = 4). Adherence of cells from normal horses remained unchanged. Addition of an anti-CD18 monoclonal antibody, H20A, inhibited the increase in adherence at 24 h by 96 (45-100)%, n = 3. The percentage of neutrophils in bronchoalveolar lavage fluid at 24 h increased from 1 (0-2) to 80 (65-94), (median (range), n = 4). These results suggest that antigen challenge results in exposure of circulating equine neutrophils to one or more factors that prime, or activate, these cells, which may enhance their recruitment to the lungs. Inhibition of circulating neutrophil activation may therefore represent a therapeutic target.  相似文献   

17.
A quantitative investigation of equine tear and aqueous humor immunoglobulins was done using normal horses and ponies as well as horses and ponies infected with Onchocerca cervicalis. The equine immunoglobulin isotypes IgGa, IgM, IgA and IgG(T) were quantitated by either single radial immunodiffusion (SRID) or radioimmunoassay (RIA). Tear immunoglobulin levels for IgGa (128 +/- 151 micrograms/ml), IgA (1,664 +/- 1,038 micrograms/ml) and IgM (106 +/- 74 micrograms/ml) were measured, while IgG(T) was not detectable. In horses with ocular inflammation the IgGa was 18-fold higher in the tears, 2,269 +/- 3,077 micrograms/ml. Aqueous humor obtained by paracentesis of the normal equine eye under anaesthesia, resulted in values for IgGa (45.2 +/- 20.0 micrograms/ml), IgG(T) (5.2 +/- 2.0 micrograms/ml), IgM (1.3 +/- 4.8 micrograms/ml) and IgA (0.8 +/- 1.0 micrograms/ml). A pooled sample of normal aqueous fluid obtained from over 100 horses at an equine abbatoir in Indiana gave values of 1,150 micrograms/ml for IgGa, 65 micrograms/ml for IgG(T), 2.5 micrograms/ml for IgA and 3.0 micrograms/ml for IgM. In animals infected with 0. cervicalis and treated with Diethylcarbamazine (DEC), there was a marked elevation of IgGa and IgG(T) in the tears and aqueous humor while IgA and IgG(T) were also elevated slightly in the aqueous. The findings of elevated immunoglobulin isotypes in the aqueous humor may not be related to the DEC treatment and 0. cervicalis infections but rather to repeated paracentesis and the development of acute inflammation of the equine eye as a result of the trauma of paracentesis. The elevations in equine immunoglobulin isotypes in the tears after DEC treatment are not subject to the same caveat. The preferential elevation in IgGa and IgG(T) in the tears precedes the development of corneal opacities observed in the same horses. The concentration of specific antimicrofilarial antibody in these tears remains to be determined but may well account for a major share of the total immunoglobulins detected.  相似文献   

18.
The pharmacokinetic behaviour of ivermectin was investigated in adult llamas (Lama glama) by using high performance liquid chromatography with a lower limit of quantification of 2 ng/ml to measure its concentration in serum. Llamas were treated with one of three commercial formulations (injectable, pour-on or oral paste) at dosages recommended by the manufacturer, or with an experimental injectable sustained-release formulation. In five llamas given 1 per cent ivermectin subcutaneously at 200 microg/kg, the median peak serum concentration (Cmax) was 3 ng/ml and the area under the serum concentration-time curve (AUC) was 13.5 ng x day/ml. In six llamas treated topically with 0.5 per cent ivermedin pour-on at 500 microg/kg, Cmax was 2.5 ng/ml or less and the AUC was 7.75 ng x day/ml or less. In seven llamas with measurable concentrations of ivermedin, the median times to peak serum concentration (tmax) were six days after subcutaneous injection and seven days after treatment with the pour-on formulation. In six llamas, the serum concentration of ivermectin remained less than 2 ng/ml for 124 hours after treatment with a 1.87 per cent oral paste at 200 microg/kg. In five llamas treated subcutaneously with 25 per cent ivermectin sustained-release microspheres at 1500 microg/kg, the median Cmax was 5 ng/ml and the median AUC was 224 ng x day/ml.  相似文献   

19.
Weight maintenance and blood chemistry parameters of geriatric (>20 yrs) horses and ponies housed at a farm for retired horses were compared between animals fed a 14% protein pelleted/extruded feed (ES) formulated specifically for geriatric horses versus those fed the textured sweet feed used at the facility. A total of 48 geriatric horses and 3 ponies were initially examined, 28 of which were assigned to be fed ES, the other 23 continued to be fed an 8.5% protein textured sweet feed mix (SF). Horses and ponies were fed the feeds in amounts estimated to be necessary for weight maintenance or gain according to initial body condition scores, with hay being offered free choice. The horses were weighed, assigned body condition scores and had blood drawn for complete blood counts and blood chemistry panels in December, 1992 before feed changes were initiated. The same measurements were taken on surviving horses and ponies three months after the feed changes had been made (March, 1993).For statistical analyses, data were grouped according to the animal's initial body condition score. Horses (n=17) and a pony with initial body condition scores of three or less (Group 1) which were fed ES had greater weight gain (ES: 32kg±4; SF: −9kg±7; p<.001); higher final condition scores (ES: 4.5±2; SF: 3.6±.3; p<.05) and plasma total protein (ES: 6.3 gm/dl±.2; SF: 5.2 gm/dl±.3; p<.005) in March than those fed SF (n=14). Group 1 horses fed SF experienced a decrease (p<.0001) in hematocrit (December: 41.4%±1.3; March: 34.4±1.2) and hemoglobin (December: 14.6±.4 gm/dl; March: 11.9±.3 gm/dl, p<.001), whereas those fed ES had a slight increase (p<.15) in hematocrit and no change (p>.2) in hemoglobin over the same period. Blood phosphorus was increased (December: 2.21±.08 mg/dl; March: 2.48±.07 mg/dl; p<.05) in Group 1 horses fed ES and tended (p<.15) to be higher than in Group 1 horses fed SF (March: 2.27±.12 mg/dl). In horses and the pony with initial condition scores greater than 3 (Group 2), condition scores, body weights and hematocrit did not differ (p>.2) between animals fed ES (n-9) versus SF (n=9) in December or March. However Group 1 animals fed ES experienced greater weight gains (p<.001) and increases in body condition score (p<.05) than Group 2 SF fed horses during this period. Blood phosphorus in Group 2 ES fed horses tended to increase (December: 2.3±.1 mg/dl; March: 2.6±.1 mg/dl; p<.10) and was higher (p<.01) in March than in Group 2 horses fed SF (March: 2.1±.1 mg/dl). In both groups, liver enzymes and creatinine did not differ (p>.2) between diets in March. Blood urea nitrogen (BUN) was higher in ES fed horses than the SF fed horses in March in both Group 1 (p<.02) and Group 2 (p<.07) but was within the normal range for adult horses.Horses which were fed the ES were subjectively assessed by the farm manager to have better hair coats and higher activity levels than when they had been fed textured sweet feed and relative to horses that were not fed ES. Geriatric horses, especially those unable to maintain adequate weight on standard rations in the absence of hepatic or renal disease, appear to benefit from the special formulation of ES.  相似文献   

20.
OBJECTIVE: To determine the minimal infusion rate of propofol in combination with medetomidine for long-term anesthesia in ponies and the effects of atipamezole on recovery. ANIMALS: 12 ponies. PROCEDURE: Ponies were sedated with medetomidine (7 microg/kg of body weight, IV). Ten minutes later, anesthesia was induced with propofol (2 mg/kg, IV). Anesthesia was maintained for 4 hours, using an infusion of medetomidine (3.5 microg/kg per hour, IV) and propofol at a rate sufficient to prevent ponies from moving after electrical stimulation. Arterial blood pressures and blood gas analysis, heart rates, and respiratory rates were monitored. For recovery, 6 ponies were given atipamezole (60 microg/kg, IV). Induction and recovery were scored. RESULTS: Minimal propofol infusion rates ranged from 0.06 to 0.1 mg/kg per min. Mean arterial blood pressure was stable (range, 74 to 86 mm Hg), and heart rate (34 to 51 beats/min) had minimal variations. Variable breathing patterns were observed. Mean PaO2 (range, 116 to 146 mm Hg) and mean PaCO2 (range, 48 to 51 mm Hg) did not change significantly with time, but hypoxemia was evident in some ponies (minimal PaO2, 47 mm Hg). Recovery was fast and uneventful with and without atipamezole (completed in 20.2 and 20.9 minutes, respectively). CONCLUSIONS AND CLINICAL RELEVANCE: Infusion of a combination of medetomidine and propofol was suitable for prolonged anesthesia in ponies. Recovery was rapid and uneventful. A combination of propofol and medetomidine may prove suitable for long-term anesthesia in horses. Monitoring of blood gases is essential because of potential hypoxemia.  相似文献   

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