Truncal vagotomy as a possible potentiator of gastric atony.

To stimulate ulcer patients undergoing operation for gastric outlet stenosis, pyloric obstruction was created in dogs and repaired with pyloroplasty to which was added truncal vagotomy, proximal gastric vagotomy, or no vagotomy. Gastric antral contractile activity after feeding a solid meal was studied before and after repair (2 week period of study). This activity was correlated with the initial lag and regulated phases of solid meal emptying. Five quantified indices of contractile activity measured during the first postprandial hour indicated variable and inconclusive results in the antrum during the lag phase (first 20 minutes). Consistent percentage changes in these indices after obstruction repair were seen during the subsequent regulated phase. Gastric work was reduced 28 to 35 percent, but not work capability (mean area), by pyloric obstruction in the no vagotomy dogs. Reductions seen in proximal gastric vagotomy dogs were not different from those in the no vagotomy dogs. Higher percentages of reduction in amplitude (70 percent) and mean area of contractions (53 percent) occurred after truncal vagotomy compared with what occurred in the no vagotomy dogs. Mean area was also reduced more compared with what occurred in the proximal gastric vagotomy dogs. These data indicate that the reduced gastric work after feeding and impaired work capability caused by truncal vagotomy when superimposed on that produced by pyloric obstruction may exaggerate gastric atony and contribute to the delayed recovery of gastric emptying seen in the clinical setting.

Canine cyclic motor activity of stomach and small bowel: the vagus is not the governor.

The influence of the vagus nerve on gastric cyclic motor activity and small bowel migrating motor complexes is controversial. Diaphragmatic vagesection does not alter their occurrence or periodicity, but cervical vagal cooling inhibits both gastric cyclic motor activity and duodenal phase II activity. We have clarified this contradictory data by reversible vagal cooling at the diaphragm level in 5 dogs implanted with strain gages and bipolar electrodes to record gastric and small intestinal cyclic activities. Circulation of coolant through an implanted convectional jacket surrounding the vagal trunks lowered jacket temperature to 2 degrees-8 degrees C and maintained this temperature for 3-5 h in each experiment. Vagal denervation during cooling was proven at the end of each trial by abolition of intravenous insulin-stimulated gastric contractions, which promptly appeared with warming. More than 90% of gastric motor cycles persisted during vagal cooling. The mean duration of gastric phase III activity was reduced during cooling but the mean period of gastric motor cycles was unchanged. Duodenal phase II and III activities were unchanged and migrated normally through the small bowel. We conclude that the vagus nerve may modulate the duration of gastric phase III activity but does not govern the initiation of gastric cyclic motor activity or the duration, period, and migration of small intestinal migrating myoelectric complexes. These findings concur with those after truncal vagectomy but are different from observations made with cervical vagal cooling.

Reversible truncal vagotomy in conscious dogs.

Prior attempts at in vivo reversible vagal denervation of the gastrointestinal tract have been limited to cervical cooling techniques that also denervate both sympathetic and vagal pulmonary and cardiac branches. Denervation of vagal efferent fibers at this level has produced results that are inconsistent with those obtained after surgical truncal vagotomy. We have, therefore, developed a technique to provide reversible vagal denervation below the pulmonary and cardiac branches for the study of gastric motility. Five dogs, previously equipped with gastric strain gages and electrodes, underwent implantation of a tubular cooling jacket around a distal thoracic vagal trunk with contralateral vagotomy (4 dogs), or around both vagal trunks (1 dog). The jacket was made of stainless steel tubing in a "J" design. Its inside channel was lined with a sterling silver sheet, and a thermistor was attached to record temperature change. Silicone tubing coursed externally to a pump and flask to which 95% ethanol at -70 degrees C was circulated at variable speeds. Thoracic vagal cooling, extending up to 5 h, reversibly blocked gastric contractions induced by insulin hypoglycemia. Contractile waves were terminated at device temperatures of 2 degrees-6 degrees C but promptly returned with warming. Dogs were tranquil during denervation, and enclosed nerves remained functional for greater than 40 days.

The use of cellulose products to reduce agar concentration in microbiological media.

The use of agar in media for culturing microorganisms is fundamental to microbiological investigations. Shortages of agar have caused increased costs and difficulty in obtaining media. Evidence is presented for the use of carboxymethylcellulose (CMC), an inert compound, in conjunction with agar to reduce the concentration of agar necessary to achieve a solid plating surface. A variety of bacteria, blue-green bacteria, fungi, and a yeast were tested for growth on CMC agar media. T-2 bacteriophage and three cyanophages were tested for plaque-forming efficiency on CMC agar plates. Selective and differential media were also formulated with a CMC agar supplement. Growth of all microorganisms was comparable on CMC and agar control. Use of cellulose products provides a means of decreasing agar consumption without affecting successful cultivation of microorganisms.