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Topic:In Vivo
In vivo studies involving horses refer to research conducted within living organisms to understand various biological processes, disease mechanisms, and therapeutic interventions in equine species. These studies provide insights into the physiological and pathological responses of horses under natural conditions. In vivo research encompasses a range of investigations, including pharmacokinetics, disease modeling, and the evaluation of treatment efficacy. It often involves the use of controlled environments to simulate real-life scenarios while observing the effects of specific variables on equine health. This page gathers peer-reviewed research articles and scholarly studies that explore the methodologies, findings, and implications of in vivo research in horses, contributing to the advancement of equine science and veterinary medicine.
A potential technique error in stapled side-to-side anastomosis of the small intestine of the horse. Anastomotic leakage was noted to occur at the junction of the staple lines used to create the stoma during small intestine side-to-side anastomosis. The anastomosis was performed in a clinical equine patient by joining the lateral surfaces of the intestinal segments using a gastrointestinal anastomosis stapling instrument (GIA). The cause of this problem was investigated by performing six anastomoses in the jejunum of a single anesthetized adult horse using the GIA; three anastomoses were created by joining the antimesenteric edges of the bowel segments and three anastomoses were created by jo...
Use of acupuncture for the treatment of chronic back pain in horses: stimulation of acupuncture points with saline solution injections. Fifteen horses that could not train or perform their sport at an acceptable level because of chronic back pain of 2 to 24 months' duration, and that did not obtain lasting improvement from other previous treatments, were treated with acupuncture. The treatments consisted of injection of 1 ml of sterile saline (0.9% NaCl) solution, with no preservatives, at 9 acupuncture points. The horses were treated once a week for a mean of 9 treatments. The mean number of treatments before obvious improvement was 4. After treatment, 13 of the 15 horses had apparent alleviation of their signs of pain and co...
Phagocytic function of equine neutrophils exposed to Mycoplasma felis in vitro and in vivo. Neutrophils were isolated from the peripheral blood of adult equids (group 1) and were purified on a density gradient of polyvinylpyrrolidone-coated silica gel. A bactericidal assay was developed, using an equine skin isolate of Staphylococcus epidermidis as target bacterium in medium containing pooled fresh equine serum for opsonization. Significant (P less than 0.05) killing was observed after 60 or 120 minutes' incubation. Reduction in bactericidal function of blood neutrophils was not found after incubation with a virulent strain of Mycoplasma felis for 30 or 60 minutes. Similarly, the fun...
Effects of multiple low doses of flunixin meglumine on repeated endotoxin challenge in the horse. Previous work has shown repeated low doses of flunixin meglumine (FM) inhibit thromboxane production in normal horses. Enhanced concentrations of thromboxane in serum occurred after the drug therapy was discontinued. Our study was performed to evaluate the effects of low doses of FM in horses repeatedly challenged with endotoxin. Group I horses received E. coli endotoxin (0.1 microgram/kg IV) at 0 and 90 h. Group II horses received endotoxin and were also treated with FM (0.25 mg/kg IV) at 2, 10, 18, 26, 34, and 42 h after the initial administration of endotoxin. Clinical signs of endotoxemia ...
Low dose flunixin meglumine: effects on eicosanoid production and clinical signs induced by experimental endotoxaemia in horses. The efficacy of low doses of flunixin meglumine in reducing eicosanoid generation and clinical signs in response to experimentally induced endotoxaemia was investigated. Thromboxane B2 and 6-keto-prostaglandin F1 alpha were measured in serum and plasma by radioimmunoassay. Plasma flunixin concentrations were determined by high performance liquid chromatography and pharmacokinetic parameters derived non-compartmentally. In horses administered flunixin meglumine before endotoxin challenge, a significant suppression in plasma thromboxane B2 and 6-keto-prostaglandin F1 alpha generation was observe...
Regulation of equine herpesvirus type 1 gene expression: characterization of immediate early, early, and late transcription. The regulation of equine herpesvirus type 1 (EHV-1) transcription was examined in infected rabbit kidney cells using metabolic inhibitors. In order to map EHV-1 immediate early, early, and late transcripts, viral RNA was 32P-labeled in vivo and hybridized to EHV-1 DNA restriction fragments immobilized on nitrocellulose filters. Immediate early viral RNA was mapped to one region of the viral genome within the inverted repeat DNA sequences (map units 0.78-0.83 and 0.95-1.0). Northern blot hybridization analysis using a 32P-labeled cloned DNA probe from this region identified a single immediate e...
Development of an enzyme-linked immunosorbent assay for the detection of phenothiazine tranquillisers in horses. An acepromazine (ACP) hapten was synthesised, coupled to bovine serum albumin and injected into a horse to produce antibodies to the drug. A competitive ELISA was developed whereby ACP attached to the solid phase via lysozyme competed with free ACP present in phosphate buffered saline, horse serum or horse urine for limiting amounts of antibody. The assay could detect the presence of ACP and, or, some of its metabolites in horse urine for at least 25 hours after intravenous injection of 0.1 mg kg-1 ACP maleate, but because of non-specific interference, horse serum could not be used. As little ...
Evidence that the recently discovered theta 1-globin gene is functional in higher primates. A new subfamily of the alpha-globin-like family has recently been identified in higher primates, rabbit, galago and possibly the horse. One member of this subfamily, theta 1, is downstream from the adult alpha 1-globin gene. In orang-utan, but not in rabbit or galago, the theta 1-gene appears to be structurally intact, suggesting that it may be functional in this species. The orang-utan theta 1-gene possesses initiation and termination codons, and the predicted polypeptide differs from the orang-utan alpha 1-globin by 55 amino acids. The upstream promoter boxes CCAAT and ATA are present, altho...
2-Hydroxypyridine-N-oxides: effective new chelators in iron mobilisation. The 2-hydroxypyridine-N-oxide derivatives, 2-hydroxypyridine-N-oxide, 2,4-dihydroxypyridine-N-oxide, 2-hydroxy-4-methoxypyridine-N-oxide and 2-hydroxy-4-(2'-methoxyethoxy)pyridine-N-oxide have been shown to remove iron from human transferrin and horse spleen ferritin at pH 7.4 at levels higher than those caused by desferrioxamine. Their reactions with transferrin were mainly biphasic and took 2-5 h to reach completion but iron mobilisation from ferritin was slower and their reactions continued after 40 h of incubation. The intraperitoneal and intragastric administration of 2,4-dihydroxypyridin...
Clinical pharmacology of the gastrointestinal tract. This article discusses the various drugs that affect the equine gastrointestinal tract. Drugs that alter intestinal motility, that protect the gastrointestinal tract, and that alter secretions, as well as analgesics, appetite stimulants, and orally administered antimicrobial agents are reviewed.
An equine rotavirus (FI-14 strain) which bears both subgroup I and subgroup II specificities on its VP6. An equinine rotavirus FI-14 strain, originally isolated from a diarrheic foal in New York state, was shown to belong to serotype 3 by neutralization assay. In addition, it was found to react with both subgroup I and subgroup II monoclonal antibodies by enzyme-linked immunosorbent assay (ELISA), thus representing the first rotavirus strain to exhibit both subgroup specificities. By using hybridoma technology, we successfully produced monoclonal antibodies directed against the major inner capsid protein VP6 (the sixth gene product) of FI-14 virus. Such monoclonal antibodies reacted specifically ...
Actions of BW540C in an equine model of acute inflammation: a preliminary study. An equine model of acute non-immune inflammation has been developed to facilitate studies of the inflammatory process and the actions of novel anti-inflammatory drugs. Five polyester sponge strips soaked in sterile 2% carrageenin solution were placed in subcutaneous pouches prepared under local anaesthesia in the necks of conscious ponies. Serial removal of the strips and harvesting of the exudate enabled studies to be made of the cellular, biochemical and mediator aspects of the localised, acute inflammation, and the heat generated by the lesion was monitored by infra-red thermometry. Maximal...
Opsonins of Streptococcus in uterine flushings of mares susceptible and resistant to endometritis: control of secretion and partial characterization. The release of opsonins into the uterine lumen of mares susceptible or resistant to endometritis was examined after intrauterine inoculation of a filtrate of Streptococcus culture fluid or vehicle. Uterine flushings were collected at 0.5 hour before and 2, 4, 6, 8, and 24 hours after inoculation on day 2 or 3 of estrus and on day 7 or 8 after ovulation. Amounts of opsonins in flushings were quantified as the H2O2 produced by leukocytes incubated with flushings-opsonized bacteria, compared with H2O2 produced by leukocytes incubated with nonopsonized bacteria. Opsonin values in flushings increas...
Micropolyspora faeni causes airway inflammation but not hyperresponsiveness in sensitized ponies. We assessed the effect of aerosol Micropolyspora faeni challenge in two groups of ponies by measuring lung function, airway reactivity to aerosol histamine, and bronchoalveolar lavage fluid cytology. One group of ponies was sensitized by subcutaneous injection of M. faeni in complete Freund's adjuvant, and the other group served as control. In both groups of ponies, measurements were made at base line and 5 h after aerosol administration of 30 ml of saline or 30 ml of 1% wt/vol particulate M. faeni antigen in saline. Saline challenge had no effect on any of the measured variables. M. faeni cha...
Beta-endorphin: peripheral opioid activity of homologues from six species. The peripheral opioid activity of six homologous beta-endorphins (beta-EPs) were assayed on the guinea pig ileum and the vas deferens of the mouse, the rat and the rabbit. In the guinea pig ileum assay, human beta-EP (beta h-EP) was less potent than camel, turkey, and ostrich beta-EPs, of the same potency as equine beta-EP and more active than des-acetyl salmon beta-EP. In the rat vas deferens, mammalian beta-EPs showed higher activity than those from the bird and the fish, whereas in the mouse vas deferens assay, beta h-EP is more active than those from other species. In the rabbit vas defere...
Effect of yohimbine on xylazine-induced hypoinsulinemia and hyperglycemia in mares. Serum insulin and plasma glucose concentrations were determined in 8 mares. Four IV treatments were studied: xylazine (1.1 mg/kg of body weight); yohimbine (0.125 mg/kg); yohimbine (0.125 mg/kg) followed 5 minutes later by xylazine (1.1 mg/kg); and 5 ml of isotonic saline solution as a control. Blood samples were collected before (time 0) and at 5, 15, 30, 60, 120, and 180 minutes after drug administration. Serum insulin concentration decreased and plasma glucose concentration increased in mares given xylazine. Plasma glucose concentration was unchanged in control mares and in mares given yohi...
Role of progesterone in mobility, fixation, orientation, and survival of the equine embryonic vesicle. Luteal progesterone was removed by an injection of prostaglandin F2alpha or bilateral ovariectomy on Day 12 of pregnancy in pony mares. The embryonic vesicle remained mobile in the uterus until loss occurred on Days 13, 13, 15, or 19 in four prostaglandin-treated mares and Days 15, 17, 19, or 26 in four ovariectomized mares. Exogenous progesterone given daily, starting on Day 12, maintained pregnancy until Day 40 in five of five prostaglandin-treated and three of four ovariectomized mares. During two-hour mobility trials on Day 14, embryonic vesicles in mares without luteal or exogenous proges...
A proton NMR study of the non-covalent complex of horse cytochrome c and yeast cytochrome-c peroxidase and its comparison with other interacting protein complexes. Cytochrome-c peroxidase (ferrocytochrome-c:hydrogen-peroxide oxidoreductase, EC 1.11.1.5) forms a noncovalent 1:1 complex with horse cytochrome c in low ionic strength solution that is detectable by proton NMR spectroscopy. When the entire proton hyperfine-shifted spectrum is considered only five hyperfine resonances exhibit unambiguously detectable shifts: the heme 8-CH3 and 3-CH3 resonances, single proton resonances near 19 ppm and -4 ppm and the methionine-80 methyl group. These shifts are very similar to those observed for the covalently crosslinked complex of cytochrome-c peroxidase and h...
Immediate split-thickness autogenous skin grafts in the horse. Case reports on the treatment of equine sarcoids in 3 horses. Three horses with equine sarcoids were treated with radical surgical excision and immediate split-thickness skin grafts. Graft take ranged from 50 to 100%, and the epithelial coverage attained resulted in an early functional repair. In no instance was there a recurrence of the sarcoid.
Experimental crush of the equine recurrent laryngeal nerve: a study of normal and aberrant reinnervation. Experimental reinnervation of the equine larynx in healthy ponies was studied after the recurrent laryngeal nerve was crushed, using endoscopic, electromyographic, and microscopic techniques. In 12 ponies, the recurrent laryngeal nerve was crushed unilaterally in the midcervical area. All showed postoperative paralysis of the larynx on the operated side. In 8 ponies, recovery of movement of the vocal folds occurred at different times (2.5 to 8 months) after surgical operation was done. These movements, which were often abnormal, included trembling and asynchronism. In 2 of these ponies, comple...
Comparison of various treatments for experimentally induced equine infectious arthritis. To evaluate the effects of 5 treatments on clinical responses, synovial fluid analysis, radiographic changes, bacteriologic culture results of the synovial fluid and synovial membrane, microscopic characteristics of the synovial membrane, and articular cartilage histochemistry, Staphylococcus aureus organisms (1.6 X 10(6) colony-forming units) were inoculated into the tarsocrural joints of 12 horses (n = 24 joints; 2 joints/horse). Each horse was given phenylbutazone (2 g) orally, every 24 hours, beginning 24 hours after inoculation. Two horses (ie, 4 joints) were not given other treatment (co...
Evaluation of creatine kinase and lactate dehydrogenase activities in clinically normal and abnormal equine joints. Creatine kinase (CK) and lactate dehydrogenase (LD) enzyme activities and isoenzymes were determined for synovial fluid, synovial membrane, and articular cartilage from 24 clinically normal equine tarsocrural (tibiotarsal) and femoropatellar joints. All 3 tissues contained LD isoenzymes LD1 to LD5, and CK isoenzymes BB and MM. The CK isoenzyme MB was not found. The similarities in isoenzyme composition of these 3 tissues made differentiation of the source of LD and CK impossible by isoenzyme pattern alone. Reference values for the total enzyme activities of specific joint tissues also had wide...
Specific serum protein changes associated with primary and secondary Strongylus vulgaris infections in pony yearlings. The concentrations of haptoglobin, immunoglobin (Ig)G(T) and IgG were measured in the serum of four previously parasite-free pony yearlings following a single dose of 700 (Group H) or 200 (Group L) stage three Strongylus vulgaris larvae (L3) and following a reinfection with the same doses 34 weeks later. The results are compared with an uninfected control pony. The haptoglobin concentration increased during Weeks 1 to 6 and 14 to 17 after infection in the serum of the ponies receiving 200 L3, but in only one pony dosed with 700 L3 (during Weeks 1 to 16). The serum haptoglobin also increased du...
Role of carotid chemoreceptors and pulmonary vagal afferents during helium-oxygen breathing in ponies. Our purpose was to assess compensatory breathing responses to airway resistance unloading in ponies. We hypothesized that the carotid bodies and hilar nerve afferents, respectively, sense chemical and mechanical changes caused by unloading, hence carotid body-denervated (CBD) and hilar nerve-denervated ponies (HND) might demonstrate greater ventilatory responses when decreasing resistance. At rest and during treadmill exercise, resistance was transiently reduced approximately 40% in five normal, seven CBD, and five HND ponies by breathing gas of 79% He-21% O2 (He-O2). In all groups at rest, He...
Pharmacokinetics and renal clearance of sulfamethazine, sulfamerazine, and sulfadiazine and their N4-acetyl and hydroxy metabolites in horses. Plasma disposition, protein binding, urinary recovery, and renal clearance of sulfamethazine (SMZ), sulfamerazine (SMR), and sulfadiazine (SDZ) and their N4-acetyl and hydroxy derivatives were studied in 4 horses in a crossover trial. The plasma concentration-time curves of the metabolites paralleled those of the parent drug in the elimination phase. Sulfamethazine and SMR were extensively metabolized. In plasma and urine, the main metabolite of the 3 sulfonamides tested was the 5-hydroxypyrimidine derivative, which was highly glucuronidated. Difference in elimination half-life of SMZ, SMR, an...
Radiolabeling of equine platelets in plasma with 111In-(2-mercaptopyridine-N-oxide) and their in vivo survival. A method is presented for the in vitro isolation and radiolabeling of equine platelets with the isotope indium 111 (111In: half-life = 2.8 days, gamma = 173 keV, 89%; 247 keV, 94%). The technique described involves complexing 111In with the lipid-soluble chelating agent, 2-mercaptopyridine-N-oxide (merc), in an aqueous medium. 111In-merc platelet-labeling efficiencies in autologous plasma pretreated with or without ferric citrate reagent were 82 +/- 7% and 24 +/- 12%, respectively. Mean intravascular survivals of 111In-merc-radiolabeled platelets in 8 healthy horses according to simple linear,...
Preliminary study of quantitative aspects and the effect of pulsed electromagnetic field treatment on the incorporation of equine cancellous bone grafts. The quantitative aspects of equine cancellous bone graft incorporation and the possibility of influencing graft incorporation by daily exposure to a pulsed electromagnetic field (PEMF) was studied in eight yearling ponies. In order to be able to quantify formative aspects of graft remodelling, a double and treble tetracycline intravital labelling technique was used. Intravital radiographs were obtained at regular intervals throughout the trial, but were found to be of little assistance in assessing any differences between stimulated and non-stimulated grafts. The ponies were humanely destroyed...
Single- and repeat-dose pharmacokinetic studies of chloramphenicol in horses: values and limitations of pharmacokinetic studies in predicting dosage regimens. A single-dose pharmacokinetic study of chloramphenicol in propylene glycol was done in 6 horses after 22 mg/kg was administered IV. Serum drug concentrations obtained at various predetermined intervals were determined by an electroncapture gas-chromatographic technique. The time-concentration data were described by a 2-compartment open model, and various pharmacokinetic variables were estimated. The median elimination rate constant was estimated to be -0.0185 minute-1 (-0.0225 to -0.0148 minute-1), and the median half-life was 37.36 minutes (30.74 to 46.90 minutes). The median apparent volume ...
