Role of Endothelium and Nitric Oxide in the Response of Equine Colonic Arterial Rings to Vasoconstrictor Agents

Objective- To determine the in vitro contractile responses of equine colonic arteries to angiotensin II, histamine, serotonin, norepinephrine, prostaglandin F_2α, vasopressin, and a thromboxane-B₂-analogue. Study Design- The tension generated in colonic arterial rings placed in organ baths with oxygenated Tyrode's solution at 37°C after exposure to the previously mentioned chemical agents was measured using force-transducers interfaced with a polygraph. Sample Population- Large colon arterial rings collected from eight horses. Methods- The rings were allowed to equilibrate for 45 minutes after applying 2 g tension. Bath solution was replaced and tension reapplied at 15-minute intervals. Cumulative-concentration-responses were determined for concentrations ranging from 10^-8M to 10^-4M on three vessel groups namely endothelium intact, endothelium denuded, and L-NAME treated. The maximal response for each vessel was considered as 100%; responses to lower concentrations were calculated as a percentage of the maximum. The EC₅₀ value was determined for each concentration-response relationship of each agent. Results- Vessels with denuded endothelium or those incubated with L-NAME had greater contractile responses. Angiotensin, histamine, serotonin, and norepinephrine produced greater maximal responses than the other agents. Endothelium denuded rings had lower EC₅₀ values. Responses to norepinephrine and serotonin were affected less by denudation. Conclusion- Endothelium plays an important role in modulating responses of colonic arterial rings to contractile agents. Endothelium-derived vasodilators, other than nitric oxide, may modulate contractile responses of equine colonic arteries. Clinical Relevance- Endothelial damage associated with colonic vovulus may be a major factor for sustained reduced perfusion after surgical correction.     

Effects of Left Recurrent Laryngeal Neurectomy, Prosthetic Laryngoplasty, and Subtotal Arytenoidectomy on Upper Airway Pressure during Maximal Exertion

Upper airway pressure was measured with a nasotracheal catheter system and a portable pressure transducer in 10 normal horses during maximal exercise before and after left recurrent laryngeal neurectomy. Measurements were repeated 16 weeks after prosthetic laryngoplasty (5 horses) or subtotal arytenoidectomy (5 horses). During maximal exertion, prosthetic laryngoplasty was more effective than subtotal arytenoidectomy in reversing the increases in upper airway pressure that followed left recurrent laryngeal neurectomy.     

Vaccination of stallions with a modified live equine viralarteritis virus

Sixteen stallions were vaccinated with modified live virus- EVA vaccine. Paired stallions were assigned a group of four susceptible mares to breedtwice by natural service between 10 and 25 days postvaccination. No significant adverse changes in hematologic parameters or temperatures that could be related to vaccination were observed. Vaccinated stallions showed no overt signsof illness and attempts to isolate the virus from buffy coat cells and semen were unsuccessful. Susceptible mares bred to these stallions between 10 and 25 days postvaccination failed to seroconvert     

Hepatic Lobectomy in the Dog A Comparison of Stapling and Ligation Techniques

The left lateral hepatic lobe was removed in six dogs with a stapling instrument and in six dogs by blunt dissection and ligation. Both techniques were safe and effective. Lobectomy by dissection and ligation was slower and less complete than by stapling. Major intraoperative or postoperative hemorrhage did not occur with either method. Serum chemistry values were elevated after surgery in all dogs but did not differ significantly between treatment groups. Microscopic hemorrhage, necrosis, and inflammation of the lobectomy site were more pronounced after dissection and ligation than stapling.     

Percutaneous Nephrolithotomy in the Dog An Experimental Study

Percutaneous nephrostomies (PN) were created with teflon fascial dilators under fluoroscopic guidance, to implant stones bilaterally into the renal pelves of five dogs weighing 7 to 35 kg. Between one and seven stones of 0.25 to 1.00 cm diameter were implanted into each renal pelvis. Two to 4 weeks later, PN tracts were recreated, and the implanted renal stones were successfully removed under fluoroscopic and endoscopic visualization. Results of gross and histopathologic evaluation of the kidneys 2, 7, 14, 30, and 90 days after stone removal showed minimal, localized renal parenchymal trauma. Complications, although infrequent, included proximal ureteral tears and hemorrhage. Difficulty was encountered in maneuvering equipment around large or numerous stones. Canine percutaneous nephrolithotomy was successful despite great variation in kidney size, as well as variations in the number, size, and shape of stones in the upper urinary tract.     

Anaerobic Bacteria Isolated from Osteomyelitis in Dogs and Cats

Anaerobic bacteria were isolated from 18 of 28 animals (64%) with osteomyelitis. The bones most commonly infected with anaerobic bacteria were radius and ulna, mandible, and tympanic bulla. Fights or abscesses commonly preceded the osteomyelitis. Seven anaerobic genera were isolated. Mixed infections of anaerobic and aerobic organisms occurred in 16 animals. Staphylococci were isolated in only one such mixed infection, but they were isolated commonly when there were aerobic bacteria only. Staphylococcal infections were often single.     

En Bloc Resection of Primary Rib Tumors in 40 Dogs

Single or multiple rib resection was performed in 40 dogs for the treatment of primary osteosarcoma or chondrosarcoma. The resulting thoracic wall defect was closed with polypropylene (12 dogs), primary muscle flap (16 dogs), diaphragmatic advancement (10 dogs), or a combination (2 dogs). Few immediate (less than 2 weeks) postoperative complications were observed. Twenty dogs with osteosarcoma had a median survival time of 3.3 months (range, 0.5 to 23 months), with a 20% 6-month survival time. Metastases occurred in all the dogs. Fourteen dogs with chondrosarcoma followed up longer than 2 weeks had a median survival time of 10.7 months (range, 0.5 to 36 months) with a 64% 6-month survival time. Eight dogs developed metastases, five died from concurrent disease, and one dog is alive. Dogs with chondrosarcoma survived significantly longer than dogs with osteosarcoma. Survival time was not related to tumor size or number of ribs resected.     

Excision of Oral Squamous Cell Carcinoma in a Horse

A large oral squamous cell carcinoma in a 27-year-old Arabian stallion was removed by partial excision of the incisive bone. There was no gross evidence of recurrence or metastasis 5 months later.     

Occlusion of the External Carotid and Maxillary Arteries in the Horse to Prevent Hemorrhage from Guttural Pouch Mycosis

Balloon-tipped catheters were used to occlude the external carotid artery and its branches in nine horses with hemorrhage caused by guttural pouch mycosis. The internal carotid artery on the affected side was occluded simultaneously in four horses and had been occluded previously in two others. In three horses, a single balloon-tipped catheter was inserted in the external carotid artery beneath the floor of the guttural pouch and its tip was advanced blindly into distal branches. In one horse, the superficial temporal artery was occluded briefly during surgery by a balloon-tipped catheter so a catheter inserted into the external carotid artery could be diverted into the maxillary artery. In the other five horses, the external carotid artery was occluded proximally and the maxillary artery was occluded immediately caudal to the alar canal by a balloon-tipped catheter inserted into the major palatine artery. Serious postoperative hemorrhage did not occur in eight horses, but one horse that had a single balloon-tipped catheter inserted into the external carotid artery had profuse hemorrhage 11 days after surgery and was euthanatized. One horse was euthanatized because of persistent dysphagia. The only complication related to use of balloon catheters was a mild incisional infection in one horse. It was concluded that the external carotid and maxillary arteries must be occluded on both sides of the eroded segment to prevent hemorrhage from normograde and retrograde flow.