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Six horses were evaluated for colic and anorexia, choke or suspected oesophageal rupture with and without tracheal laceration. Clinical findings were variable, but a painful ventral neck swelling was noted in all cases. Two of the horses had signs of dehydration and sepsis. Additional findings included evidence of previous trauma over the trachea and oesophagus, ventral neck abscessation, choke and aspiration pneumonia. A diagnosis of oesophageal perforation was made using endoscopy. Two horses were subjected to euthanasia without treatment. All horses where treatment was attempted received debridement of the oesophageal perforation and surrounding tissues with or without surgical closure of the oesophageal defect. Other therapies included broad spectrum antimicrobials, anti-inflammatory drugs, fluid and nutritional support as well as additional therapeutics for sepsis and individual complications. Complications included diverticulum formation, thrombophlebitis, diarrhoea, laryngeal hemiplegia, azotaemia, aspiration pneumonia, oesophageal obstruction, weight loss and laminitis. All 4 treated horses recovered from the oesophageal perforation and are able to eat a normal diet. Two of the 4 horses have had infrequent episodes of recurrent choke. Oesophageal rupture should be considered as a differential diagnosis for horses with a painful swelling of the ventral neck. With surgical debridement and adequate supportive care, oesophageal perforation cases can have a fair to good long-term survival, although chronic complications can occur, therapy is prolonged, and a significant economic commitment is required.

These results suggest that, despite low plasma concentrations, quinapril has sufficient oral absorption to produce inhibition of ACE in healthy horses. Controlled studies in clinically affected horses are indicated. Quinapril provides a potential treatment alternative for horses with cardiovascular and renal disease.

Experientia 37 (1981), Birkh/iuser Verlag, Basel (Schweiz) 1307 rate. The mean rate of discharge of the isolated AVN was 72_+ 11/rain. 10 CT preparations, when isolated from the musculi pectinati, continued discharging. These were subsequently cut transversely into 2-4 pieces: after variable times (up to 1 min) each discharged at a rate varying between the initial rate of the entire CT and its half value. In 3 of the preparations, 1 CT piece did not show automaticity. Action potentials with a Variable slope of diastolic depolarization were recorded from a limited area of the deep layer of any spontaneously discharging isolated CT-musculi pectinati preparation, as shown in figure ia. The amplitude of these action potentials was between 80 and 90 mV and their Vma x between 90 and 140 V/see. The location of the pacemaker area varied within the CT deep layer. Similar pacemaker potentials were recorded by Paes de Carvalho et alp from the sinoatrial ring bundle, but not from the superficial CT layer. An example typical of action potentials recorded from the deep layer outside the pacemaker region is shown in figure lb. These action potentials were homogeneous, had a mean amplitude of 114_+2.1 mV and a mean gmax of 374_ 14 V/sec. Vma x of action potentials were plotted against the take-off potentials of all records of the CT deep layer and a sigmoidal relationship was found ( fig.2). Experimental data are in good agreement with the sigmoidal curve drawn from the equation of Hodgkin and Huxley 9where, according to Weidmann l~ h is the fraction of the highest value observed for the rate of rise, V the take-off potential in mV, V h the potential at which h is half maximum and s the slope factor. Vh= 75.3 mV and s = 5.78 were determined according to Noma and Irisawa I1. The sigmoidal relationship found is similar to that reported by Weidmann 1~ in the ventricular Purkinje fibers but largely differs from that in sinoatrial pacemaker fiberslL Another resemblance to Purkinje fibers is the relatively steep rate of rise.The fine morphology and particularly the ultrastructural features of the mitochondria shown in figure 3, demonstrate the excellent in depth preservation of the CT, comparable to the state of preservation of the CT excised from hearts perfused by the Langendorff method 1. The present findings demonstrate that a) the CT deep layer fibers can act as pacemaker, discharging at a rate intermediate to the rates of the 2 nodes, b) Pacemaker activity, as a property of the deep layer cells, can be observed throughout the CT (all the pieces cut from it discharged spontaneously), c) The high discharge rate recorded from the isolated crista indicates that this area, being inherently faster than the AVN pacemaker, would probably be the faster pacemaker in the absence of SAN pacing, d) From the electrophysiological characteristics a resemblance of the CT deep layer pacemaker potentials and those of Purkinje fibers emerges.Summary. The mean metabolic rate during day and night of 17 different humming-bird species is considerably ...

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