Cannula Site Research Articles

Long-term effects of early cortical epileptiform activity on development of visuocortical receptive fields in the rabbit

We studied the long-term effects of early epileptiform activity on the development of receptive fields in the visual cortex of the rabbit. Aqueous penicillin was injected twice daily into a cannula implanted over the monocular region of one visual cortex. Drug administration was initiated on postnatal day 8–9 and was discontinued on postnatal day 24–30. Coincidental with the penicillin injections a mixture of penicillin and penicillinase was similarly applied to the monocular visual region of the contralateral (control) cortex. Following each drug administration interictal epileptiform activity was observed only from the penicillin-treated (epileptic) cortex. Single-unit recordings were made in the visual cortex 5 or 11 months after the drug-treatment period. In both 5-month and 11-month postepileptic cortex, cell samples from areas adjacent to the cannula site showed abnormal percentages of receptive field types relative to control cortex percentages. After 5 months a low proportion of oriented type cells and a high proportion of no response and indefinite type cells were found. After 11 months a low proportion of oriented type cells was also found but the proportion of no response and indefinite type cells was normal; however, an unusually high proportion of non-oriented type cells was now evident. These results indicate that although previously epileptic visual cortex eventually develops a normal complement of cells with specific receptive fields, the quantitative distribution of those cells with regard to their various functional specificity remains abnormal.

Actions of a tremorgenic mycotoxin on amino acid transmitter release in vivo

The tremorgenic mycotoxin verruculogen was administered directly into the brain of freely moving rats by the use of cannula systems that superfused either the cortical surface or the lateral ventricular space. The tremor produced by these CNS routes was compared with that produced by i.p. administration of the toxin or the dried mycelium of the fungus that synthesizes the verruculogen. The nature and degree of tremor produced by the central vs peripheral routes suggest that the site of action of verruculogen is not immediately adjacent to the cannula sites in the brain. Measures of the amino acids in the superfusates collected during the verruculogen-induced tremor showed an increase in the excitatory neurotransmitters, glutamate and aspartate in superfusates from the lateral ventricle but not in superfusates from the cortical surface. This differential effect on transmitter release suggests that a subcortical action of verruculogen is responsible for its tremorgenic activity.

Intestinal cannulation of cattle and sheep with a T-shaped cannula designed for total digesta collection without externalizing digesta flow.

An intestinal cannula was prepared that was designed to have the advantages of a reentrant cannula without permanently exteriorizing digesta flow or adding significantly to the resistance of digesta flow. The cannula was fabricated in the shape of a T from a Teflon fluorocarbon polymer. Total passage of digesta through the lumen of the cannula was accomplished by suturing a support boot around the outside of the intestine at the cannulation site. The support boot prevented the intestine from stretching away from the cannula. Digesta leakage around the barrel of the cannula was eliminated by a special peritoneal ring attached to the cannula in a position that interrupted the continuity of the tubular scar tissue that formed from the intestine alongside the barrel to the skin. The cannula was supported by an outer ring held in place by a simple stainless steel retaining ring. The low external profile of the cannula minimized mechanical disturbance of the cannula and cannula site. Diet consumption and growth rates were normal, and no blockage was encountered in either the duodenal or the ileal cannula with a wide variety of diets, indicating that the cannula added no significant resistance to digesta flow. Total digesta collection or simultaneous collection and addition were easily accomplished with special collection gates. The cannula preparation has a long functional life; in one case, the cannula remained functional for more than 2 1/2 years.

Drinking in the rhesus monkey: peripheral factors.

Rhesus monkeys prepared with chronic cannulae implanted in the stomach and duodenum were water deprived for 22.5 hr. With both cannulae closed, a mean of 137 ml was drunk within a 60-min period. When ingested water drained freely from an open gastric cannula, continuous drinking far in excess (878 ml mean intake) of normal occurred. Sham drinking also exceeded (634 ml mean intake) normal when ingested water drained through an open duodenal cannula. This pattern of continuous sham drinking indicates that oropharyngeal stimulation is not sufficient alone, or together with the passage of water through the stomach and the initial part of the duodenum, to terminate drinking. Duodenal infusions of water (25-100 ml) slowed or stopped gastric sham drinking in a dose-dependent fashion, but equivalent infusions of isotonic saline were without effect. Thus, pre- or postabsorptive signals at or beyond the level of the intestine distal to the site of the duodenal cannula are probably important for the termination of drinking in the rhesus monkey.

Studies on digestion and absorption in the intestines of growing pigs

1. Digesta were collected from seventeen pigs initially of 30 kg live weight fitted with single re-entrant cannulas in either the duodenum, jejunum or ileum. A further twenty-four pigs were used in a conventional digestibility trial. 2. The pigs received three types of diet containing: barley, fine wheat offal, white fish meal, minerals and vitamins (diet BWF); starch, sucrose, maize, oil, cellulose, minerals and vitamins and either groundnut (diet SSG) or casein (diet SSC). 3. Amino acids were measured in samples representative of the digesta flow in 24 h periods and in the faeces collected in 5 d periods. 4. For each diet the total flow in 24 h periods in the duodenum for aspartic acid, threonine, serine and glycine exceeded or equalled intake, while the amounts of the other amino acids were usually rather less than intake. 5. For each diet in the jejunum, the amounts of glycine and cystine exceeded intake in 24 h periods, while methionine, arginine and tyrosine were the most rapidly absorbed amino acids anterior to the cannula site. On average 0.22, 0.25 and 0.31 of the dietary amino acids were absorbed anterior to the cannula site for diets BWF, SSG and SSC, respectively. 6. For each diet in the ileum, the least apparently absorbed dietary amino acids were glycine and cystine. On average 0.81, 0.83 and 0.95 of the dietary amino acids were absorbed anterior to the cannula site for diets BWF, SSG and SSC, respectively. 7. There was net disappearance of most amino acids in the large intestine, but some net accumulation occurred in this region. 8. The results are discussed in relation to the amino acid composition of endogenous secretions (particularly glycine in bile), protease and peptidase specificity, free amino acid absorption and the role of the microflora in the large intestine.

Dry matter and nitrogen in the duodenal contents of growing pigs: a discrepancy explained

1. Discrepancies between the results obtained from experiments on pigs with re-entrant duodenal cannulas have been investigated with reference to diet, cannula site and collection procedure. 2. The results obtained from a sealed automatic collection system were different from those obtained from an open manual method and it was concluded that the maintenance of gut intra-luminal pressure in the automatic system was the causative factor.

A SERVO CONTROLLED TRANSAPICAL LEFT VENTRICULAR TO AORTIC ASSIST DEVICE WITH IMPLANTABLE CANNULAE

A servo controlled transapical LV to aortic bypass system employing a roller pump was evaluated. The pump achieved complete LV decompression with reduction of LV pressure below systemic pressure. The servo control was responsive to LA pressure and allowed stable complete bypass during interventions designed to raise and lower LA pressure. A permanently implantable transapical LV cannula and aortic cannula without obturators was evaluated with and without anticoagulants. The teflon felt surface 'healed' rapidly and developed a multi-layered fibrous pseudointima. Anticoagulants appeared to avoid excessive thrombus formation at the cannula sites and embolization.

Tracheostomy in children.

Tracheostomies were performed on 47 children, using the flap technique. Thirteen patients (28%) died of their basic disease and two (4%) died of complications resulting from the tracheostomy. Decannulation was difficult in four patients, and there was one case each of bleeding, infection, and tracheocutaneous fistula. Thus, the primary complication rate was 19%, including the two deaths. Clinical reexamination with tracheography was made on 20 patients after a follow-up period varying from four to ten years (average, eight years). One small stenotic ring in the area of the distal end of the cannula site and two slight depressions in the tracheal forewall were found. According to these results, the flap technique, if properly performed, is safe also in children.

Chemical stimulation of discrete brain loci as a method of producing dyskinesia models in primates

The technique of chemical stimulation of the CNS was utilized in a study designed to develop models of dyskinesias in a primate. Four sites in the extrapyramidal motor system of squirrel monkeys were stimulated with carbachol, a cholinergic drug. This was achieved by intracranial injection of microgram amounts of the drug via chronically implanted cannulae. Injection of carbachol into the neostriatum, both caudate nucleus and putamen, produced a hyperkinetic choreiform syndrome. Tremor and chorea in the contralateral limbs and facial dyskinesia with sialorrhea were the most common results of this procedure. Carbachol stimulation of the medial globus pallidus produced an akinetic hyperextension syndrome characterized by an immobile extension of the contralateral limbs. The extended limbs had the appearance of being rigid. Brief bursts of tremor or chorea were rarely superimposed. Carbachol stimulation of the subthalamus produced a hyperactive state consisting of ceaseless ambulation, climbing, and circling. All of the above effects were reproducible and consistent for each cannula site, suggesting that specific dyskinesias can be elicited by cholinergic stimulation of discrete loci in the extrapyramidal system. Such information is critical to the understanding of the physiology of these structures.

Secondary septicaemia from intravenous cannulae.

Within a period of only seven months three patients in one hospital under treatment with antibiotics by intravenous infusion developed secondary bloodstream infection originating from the site of insertion of the cannula. Two of these infections were fatal. Precautions suggested include strict asepsis, the skin being sterilized with iodine in spirit solution; antibiotic spray; and changing the cannula site.

Histochemical fluorescence after application of neurochemicals to caudate nucleus and septal area in vivo.

The movement of carbachol, norepinephrine, and dopamine from cannula sites in caudate nucleus and septal area of freely moving rats was traced by means of biogenic amine fluorescence. Fluorescent patterns seen after application of carbachol and norepinephrine to brain tissue did not appear to differ from controls. Three types of movement from the cannula site after administration of dopamine were observed. There was a spherical distribution approximately 2 millimeters in diameter. Fluorescence also followed axonal pathways in the orthodromic direction, suggesting that dopamine may have been transported by " axonal streaming " or by some other unknown mechanism in periaxonal spaces. Because fluorescence was present in both the ependymal lining and the choroid plexus, it was inferred that the cerebral ventricles were also involved in the movement of chemical. Any attempt to ascribe anatomical localization to behavioral effects resulting from chemical stimulation of the brain should take into account the widespread movement of chemicals after their local application to brain tissue.