Normal Adult Horses Research Articles

Endotoxin-induced production of interleukin 6 by equine peritoneal macrophages in vitro

Summary A study was performed to determine whether equine peritoneal macrophages produce interleukin 6 (il-6) in vitro in response to endotoxin. Peritoneal fluid was collected from 14 clinically normal adult horses and was used as the source of peritoneal macrophages. Macrophages from each horse were isolated and cultured separately in vitro in the absence or presence of various concentrations (0.5, 5, or 500 ng/ml) of endotoxin (lipopolysaccharide from Escherichia coli 055:B5). Culture medium supernatants were collected after 3, 6, 12, and 24 hours’ incubation and were frozen at −70 C until assayed for il-6 activity. Supernatant il-6 activity was determined by use of a modified colorimetric assay and the murine hybridoma cell line B 13.29 clone B.9, which is dependent on il-6 for survival. Results indicated that equine peritoneal macrophages produce il-6 in vitro and that supernatant medium il-6 activity was significantly (P < 0.05) increased by exposure to endotoxin. Significant (P < 0.05) time and treatment effects on macrophage il-6 production were apparent. The il-6 activity peaked at 6 or 12 hours’ incubation, then remained high through 24 hours’ incubation, regardless of endotoxin exposure. Medium il-6 activity during 3 and 6 hours’ incubation was significantly (P < 0.05) greater in macrophages exposed to 5 or 500 ng of endotoxin/ml than in those exposed to 0.5 ng of endotoxin/ml; however peak il-6 activity was similar among all endotoxin concentrations. Endotoxin concentration did not have an effect on medium il-6 activity from macrophages exposed to endotoxin for 12 or 24 hours.

Serum Levels of Type III Procollagen Peptide in Equidae before and after Intestinal Ischemia

Serum levels of type III procollagen peptide (P-III-P) were measured by radioimmunoassay in clinically normal adult ponies (n = 15) and horses (n = 10). The mean serum levels of P-III-P from the ponies, 10.4 +/- 2.9 (SD) ng/mL, and the horses, 12.2 +/- 2.6 (SD) ng/mL, were not significantly different. Segments of jejunum were made ischemic to induce fibrous peritoneal adhesions in two ponies, and serum P-III-P levels were measured on days 4, 5, 7, 14, and 21. An exploratory celiotomy on day 21 revealed that the ischemic injury had induced fibrosis of the mesentery and bowel, but no adhesions had formed. The fibrotic mesentery contained type III collagen. The highest mean serum level of P-III-P, 23.0 +/- 3.5 (SD) ng/mL on day 7, was more than 4 SD above the mean from the normal ponies. There was a significant difference in the serum P-III-P levels in the ponies on days 0 (7.1 +/- 1.6 ng/mL) and 7 (23.0 +/- 3.5 ng/mL). Serum levels of P-III-P may be useful to study fibrosis associated with intestinal ischemia.

Clinical relevance of monocyte procoagulant activity in horses with colic

Summary Endotoxin-activated monocytes express a thromboplastin-like procoagulant activity on the cell surface that may serve as a focal point for formation of microvascular thrombi. Because coagulopathy is a common sequela to endotoxemia in the equine species, we investigated the ability of monocytes, isolated from horses with colic, to express procoagulant activity. On the day of admission, and on the third and fifth day of hospitalization, monocytes were isolated from 30 adult horses with colic. A coagulation profile, including prothrombin time, activated partial thromboplastin time, thrombin time, and plasma fibrinogen and serum fibrin degradation products concentrations, was determined at each sample collection. The concentration of endotoxin in the plasma was quantitated at the time of admission. Ten clinically normal adult horses served as controls. The procoagulant activity of monocytes isolated from horses with colic was significantly (P < 0.05) greater than that of the monocytes isolated from clinically normal horses. On the first and third day of hospitalization, the mean prothrombin time was significantly (P < 0.05) longer in horses with colic, compared with clinically normal horses, and was the most common abnormality in the coagulation profile on the day of admission (25/30; 83%). Mean fibrin degradation products concentration was significantly (P < 0.05) greater in horses with colic on the day of admission and was the second most common abnormality in the coagulation profile on day 1 (23/30; 77%). In horses with colic, the mean prothrombin and activated partial thromboplastin times were significantly (P < 0.05) longer in horses that did not survive, compared with horses that survived. Of the 30 horses with colic, 9 had detectable endotoxin in the plasma at the time of admission. The presence of endotoxin in the plasma was useful in predicting survival in horses with colic; all horses with plasma endotoxin concentration ≥ 10 pg/ml (6/6) did not survive.

Synovial fluid pH, cytologic characteristics, and gentamicin concentration after intra-articular administration of the drug in an experimental model of infectious arthritis in horses

SUMMARY Chemical and cytologic effects and bactericidal activity of gentamicin in septic synovial fluid were evaluated in an experimental model of infectious arthritis in horses. Septic arthritis was induced by inoculation of approximately 7.5 × 106 colony-forming units of Escherichia coli into 1 antebrachiocarpal joint in each of 16 clinically normal adult horses. Clinical signs of septic arthritis were evident 24 hours after inoculation. Horses were allotted to 3 groups: group-1 horses (n = 5) each were given 150 mg of gentamicin (50 mg/ml; 3 ml) intra-articularly (ia); group-2 horses (n = 5) each were given 2.2 mg of gentamicin/kg of body weight, iv, every 6 hours; and group-3 horses (n = 6) each were given buffered gentamicin, consisting of 3 mEq of sodium bicarbonate (1 mEq/ml; 3 ml) and 150 mg of gentamicin (50 mg/ml; 3 ml), ia. Synovial fluid specimens were obtained at posttreatment hour (pth) 0, 0.25, 1, 4, 8, 12, and 24 via an indwelling intra-articular catheter. Synovial fluid pH was evaluated at pth 0, 0.25, and 24. Microbiologic culture and cytologic examination were performed on synovial fluid specimens obtained at pth 0 and 24, and gentamicin concentration was measured in all synovial fluid specimens. At pth 0, E coli was isolated from synovial fluid specimens obtained from all horses. Synovial fluid pH was lower (range, 7.08 to 7.16) and wbc count was higher (range, 88,000 to 227,200 cells/μl) and predominantly neutrophilic (95 to 99%) at pth 0 than before inoculation. Synovial fluid pH was lowered further (mean, pH 6.63) after ia administration of gentamicin in group-1 horses; mean pH remained unchanged (7.07) after buffered-gentamicin administration in group-3 horses. At pth 0.25, mean peak synovial fluid gentamicin concentration in horses of groups 1 and 3 (4,745 and 6,190 μg/ml, respectively) was 1,000 times greater than that in group-2 horses (5.1 μg/ml) at the same time. Synovial fluid gentamicin concentration in group-1 and group-3 horses was always greater than that in group-2 horses and remained greater than a minimal inhibitory concentration of gentamicin (2 μg/ml) against many common equine bacterial pathogens for at least 24 hours after injection. Further, the calculated apparent half-life and clearance of gentamicin in synovial fluid calculated after ia administration were similar in horses of groups 1 and 3. By pth 24, E coli could not be isolated from synovial fluid specimens obtained from group-1 horses. However, moderate to heavy growth of E coli was isolated from synovial fluid specimens obtained at pth 24 from horses in groups 2 and 3 (80 and 66%, respectively). In selected cases, ia administration of unbuffered gentamicin may be a useful supplement to drainage, lavage, and systemic antibacterial and anti-inflammatory treatment in horses with naturally acquired infectious arthritis.

Indices of renal function: values in eight normal foals from birth to 56 days

A series of blood and urine samples was collected from each of eight normal foals between birth and eight weeks. Blood chemistry relating to renal function was evaluated as well as physical and chemical characteristics of urine. During the first 4d of life it was impractical to suggest meaningful normal values due to wide variation among foals and with time. Serum urea and plasma creatinine fell markedly to levels less than those previously reported for normal adult horses, while urine, mildly hypersthenuric at birth, rapidly became hyposthenuric. There was also a marked proteinuria during the first 48h. After 4d clinicopathological values stabilised. Urea and creatinine remained at subadult levels and hyposthenuria was maintained. While there was some variation with time, generally the urinary activity of gamma-glutamyl transpeptidase (GGT) and alkaline phosphatase (AP) was greater in foals than in adults; plasma potassium, the creatinine clearance ratio of potassium (% Cr K), serum inorganic phosphate and the creatinine clearance ratio of phosphate (% Cr PO4) were greater than in adults while plasma chloride and the creatinine clearance ratio of chloride (% Cr Cl) were lower in foals than in adults. Urinary pH was acidic and epithelial cells and calcium oxalate crystals more prevalent in the urine of foals than in that of adults. The information presented here will be useful in the diagnosis and management of renal disease and azotaemia in foals.

Comparative immune response in four equine groups to common core antigens of gram-negative bacteria

The brood mare farm represents a situation where breeding, transportation and stresses associated with performance create the potential for repetitive challenge by both specific contagious and opportunistic microorganisms. Bacterial endotoxins are believed to play a significant role in the pathogenesis of many Gram-negative bacterial infections in the equine. Core antigens common to Gram-negative bacterial species, genera and group contain the lipopolysaccharide structure responsible for this endotoxic moiety. This report describes the results of an epidemiologic survey of equine serum IgG and IgM antibody activity recognizing common Gram-negative core antigens (GNCA) as determined by an enzyme-linked immunosorbent assay (ELISA). The study array consisted of a multiple source group of clinically normal adult horses and equine subjects categorized as foals, yearlings and adults from a San Joaquin Valley brood mare farm. The yearlings and adults from the brood mare farm possessed higher antigen-specific ELISA titers (IgM and IgG) when compared to the multiple source group of clinically normal adults. The foals exhibited the lowest ELISA titers of the groups examined from the brood mare farm. The lower titers observed in the foals are consistent with the anticipated decay of passively acquired colostral immunoglobulin. The data presented indicate the equine immune system has ascribed a degree of importance to recognition of shared core antigens of Gram-negative bacteria. Reports in other species have documented a significant level of protection associated with a similar immune response. Further investigations must be completed to determine if there is any degree of protection associated with this increased immune response in the equine.

The nephrotoxic potential of neomycin in the horse

Neomycin was administered intramuscularly to four normal adult horses at a dose rate of 10 mg/kg bodyweight every 12 h for 10 days (21 doses). The pharmacokinetic behaviour of neomycin with multiple dosing was characterised and a range of blood chemical and urinary parameters examined for evidence of nephrotoxicity. There was evidence of physical renal tubular injury (enzymuria and cylindriuria) within four days of neomycin administration but this subsided following cessation of treatment. No significant functional nephrotoxicity was detected. More severe nephrotoxicity might be expected in ill horses and it is recommended that several clinicopathological results be monitored serially in those horses receiving parenteral neomycin.

Indices of renal function: reference values in normal horses.

Urine and blood samples were taken at the same time from normal adult horses presented for routine investigations to establish reference values for a variety of parameters reported to be useful in the clinical evaluation of renal function. Blood biochemical values were consistent with previous studies and had well-defined normal ranges. Parameters representing urine concentration and electrolyte excretion however, varied widely reflecting the ability of the healthy kidney to change the composition of urine in response to differences in environment and management. Percent creatinine clearance ratios for potassium in particular were lower than those reported in normal horses in previous studies. Rational interpretation of these latter measurements should accept a wide range of normal values and management conditions must be considered in this interpretation.

Evaluation of Two Techniques for Large Intestinal Resection and Anastomosis in the Horse

Six normal adult horses had large colon resections at the sternal and diaphragmatic flexures. Stainless steel staples were used to close the stumps of the dorsal and ventral colons in all six. Intestinal continuity was restored with a side-to-side anastomosis of the dorsal and ventral colons. Three of these anastomoses were performed with staples, and three with a double inverting suture pattern. After one month, the horses were surgically reevaluated, and the anastomotic sites were examined. There was no significant difference between the stoma sizes in the two groups. No complications were observed with either of the methods. However, the stapling procedure was faster to perform and resulted in less contamination of the surgical field. For these reasons, the authors preferred the stapling technique. No adverse effects from large colon resection were observed. Although the results described are quite good, resection of more extensive portions of the large colon can be more demanding and more problematic.

Pharmacokinetics of ticarcillin and clavulanic acid given in combination to adult horses by intravenous and intramuscular routes.

The pharmacokinetics of ticarcillin and clavulanic acid following administration by the intravenous (i.v.) and intramuscular (i.m.) routes were investigated in six normal adult horses. Following i.v. administration, the ticarcillin disposition data conformed to a two-compartment model with an elimination half-life of 1.0 h. The disposition of clavulanic acid was described by a one-compartment model with an elimination half-life of 0.40 h. Following i.m. administration, the half-lives of both drugs were prolonged (ticarcillin 1.8 h, clavulanic acid 1.2 h). The bioavailability of ticarcillin was 84.4% and clavulanic acid 94.3%.

STANDING MYELOGRAPHY IN SIX ADULT HORSES

Standing myelography was conducted in six neurologically normal adult horses. Myelograms were performed without general anesthesia or tranquilization. Four horses were premedicated orally with 2.2 milligrams/kilogram (mg/kg) of phenobarbital 16 hours and 4 hours prior to myelography to raise their seizure threshold. One‐hundred milliters (ml) of cerebral spinal fluid (CSF) was withdrawn from the lumbosacral space prior to injection. Approximately 100 ml of technical grade metrizamide* was injected into the subarachnoid space via a lumbosacral tap. After injection the horse's head was lowered for approximately 10 minutes to facilitate cranial movement of the metrizamide. Lateral cervical radiographs were taken in a standing position. Filling of the subarachnoid space in the cranial cervical region was good to excellent in five horses. In one horse there was poor definition of the cranial cervical region. There was good to excellent filling of the subaranoid space in the caudal cervical region in all six horses. Reactions to metrizamide injection varied. The most severe reaction was generalized seizure.

ULTRASONIC ANATOMY OF THE TENDONS AND LIGAMENTS IN THE DISTAL METACARPAL‐METATARSAL REGION OF THE EQUINE LIMB

In a two‐phase study, ultrasound was used to delineate the normal sonographic anatomy of soft tissues of the equine distal limb. The study was limited to the soft tissues of the palmar surface of the limb just proximal to the fetlock joint. In the first phase, cadavers were evaluated with a B‐mode ultrasound machine, † Then the limbs were radiographed and dissected to compare their gross, radiographic, and ultrasonographic appearances. In the second phase, nine normal adult horses were ultrasonographically scanned. The sonographic appearance of the normal animals was compared with that of the cadavers. Front and rear limbs of all horses had similar ultrasonographic appearances. Flexor tendons and the suspensory ligament were easily identified as having linear, uniformly intense ecogenicity. The borders of the digital sheath and of the proximal palmar pouch of the fetlock joint had a less organized and less intense ecogenic appearance than the flexor tendons and suspensory ligament, and they were poorly delineated unless distended with fluid. Ultrasonography was used in three lame horses and aided the diagnoses of synovial proliferation in the fetlock joint, tendosynovitis, and bowed tendon. Diagnostic ultrasonography was effective in identifying and characterizing soft‐tissue structures of the distal equine limb. It is a valuable, noninvasive diagnostic aid.

ヒト用ラジオイムノアッセイによる各種動物の血清中α-フェトプロテイン値の測定

Serum a-fetoprotein (AFP) levels in several species of animals were measured by the polyethylene glycol method of radioimmunoassay for human AFP. The serum AFP level was less than 15 ng/ml in normal adult dogs, cats, cows, goats, horses, mice, rats, guinea pigs, rabbits, chickens and human beings.In newborn puppies, kittens, and calves it was high at birth and decreased rapidly within 24 hours and then gradually with an advance in age. In newborn rats and chicks it was low at birth and decreased gradually with an advance in age.No significant changes occurred in the maternal serum AFP level of normal pregnant dogs and cows in any stage of pregnancy. Radioimmunoassay seemed to be available for investigation of changes of AFP level in animals in which AFPs were strongly cross-reactive with the anti-human AFP.

Quantitative studies on immunoglobulins and transferrin in equine serum.

Normal adult horse serum was analyzed by electrophoretic and immunoelectrophoretic methods. Seven different protein bands were found by cellulose acetate electrophoresis, 20 fractions by polyacrylamide gel electrophoresis, and a total of 20 antigenic components by immunoelectrophoresis developed with antiserum to normal adult horse whole serum. Changes in the serum proteins, especially the immunoglobulins, IgG, IgG(T), and IgM, and fransferrin, with the advance in age were determined by electrophoretic analyses and a quantitative immunodiffusion method. Precolostral foal serum was almost entirely deficient of immunoglobulins. Very soon after the first ingestion of colostrum, the levels of IgG(T) and IgM of the foal reached a maximal level, which was lower than the mean adult level, while the IgG level of the foal generally exceeded the adult level. Transferrin level was within the adult range in the precolostral serum. It showed no significant changes with the advance in age. On the other hand, all the three immunoglobulin classes and transferrin were high in level in the colostrum collected immediately after parturition, but decreased in level rapidly with the lapse of time after parturition.

Chromatography of proteins. III. Human, horse and dog hemoglobins on cation-exchange cellulose

Normal adult human and horse carbon monoxide hemoglobins were distinctly heterogeneous when chromatographed on cation-exchange cellulose. Under similar chromatographic conditions, normal adult dog carbon monoxide hemoglobin was essentially homogeneous. Chromatography of human or horse hemoglobin at room temperature resulted in elution at lower pH values than at 5 °. Also, increased chromatographic heterogeneity of the latter was observed. As determined by both chromatographic and sedimentation techniques, human and dog hemoglobins are relatively resistant to dissociation by 4 M urea, whereas horse hemoglobin is extensively dissociated under the same conditions.

Detection by tissue culture of an organism resembling Histoplasma capsulatum in an apparently healthy horse.

SummaryIntracellular organisms resembling Histoplasma capsulatum have been observed in apparently normal amnio-allantoic membrane and adult horse spleen maintained in tissue culture.The significance of this finding and comparison with another fungus Cryptococcus jarciminosus is discussed.