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Biomedical subjects

P A Salmon

Publications and source records attributed to P A Salmon.

At least 19 recordsLinked to original sources
PubMed2000

Responses to light after retinal degeneration.

Transgenic rodless mice were given 1-h pulses of light of varying brightness at times of the night when they were normally active. The rodless mice showed decreases in locomotor activity during light pulses brighter than 2 lux; these decreases were significantly greater than those in wildtypes (ANOVA, P < 0.01). However, with very dim light, rodless mice showed no changes in activity, whereas wildtype mice actually increased their activity. It is suggested that irradiance detection could be enhanced by absence of image-forming vision. Enhanced inhibition of activity around twilight may be adaptive for mice in some circumstances and so help maintain genes for retinal degeneration in natural populations.

Animals↗
PubMed1999

Thresholds for masking responses to light in three strains of retinally degenerate mice.

Mutant mice with retinal degeneration (rd/rd) were given 1-h pulses of light of varying brightness at times of the night when they would normally be active. The mutant mice showed a significantly greater inhibition of locomotor activity to light (negative masking) than wildtype controls. Lack of impairment, or even enhancement of negative masking suggests that this response may depend on sparing in retinally degenerate mice of the same receptor type that mediates clock resetting, because synchronization of the circadian system is known to be unimpaired in these mutants. With very dim light pulses, mutants did not change their activity, but wildtypes actually became more active (positive masking). Positive and negative masking appear to depend on different sensory and central processes.

Animals↗
PubMed1998

Revolutionary science: an improved running wheel for hamsters.

Golden hamsters, Mesocricetus auratus, ran more in wheels with the floor covered by a plastic mesh than in wheels with the usual rods. This preference was evident both in tests with a single wheel and in tests when the animals were offered a choice between two wheels. Phase shifts following a 3h confinement to a novel wheel were greater if the novel wheel had the plastic cover.

Activity Cycles↗
PubMed1992

Nonphotic phase shifting in hamster clock mutants.

Golden hamsters with the tau mutation were kept in the dark and induced to become active through confinement to a novel running wheel for 3 hr. The response of the mutants to this nonphotic phase-shifting stimulus differed from that of wild-type hamsters. The mutants showed larger phase shifts, and their phase response curves differed in shape, with an advance portion at about circadian time 24, a phase at which wild types show delays. The results establish that the tau mutation, in addition to its already known effects, alters the response of the circadian system to nonphotic events.

Animals↗
PubMed1990

Triazolam and phase-shifting acceleration re-evaluated.

In two experiments, triazolam (2.5 and 1.5 mg/animal) failed to significantly enhance the rate of reentrainment of hamsters (Mesocricetus auratus) to an 8-hr advance of their light-dark cycle. Evidently the phase-shifting effects of triazolam are not robust. The animals did not run much in their wheels in response to the drug in these two experiments. In a third experiment, triazolam (0.5 and 2.5 mg/animal) produced phase advances of activity rhythms of hamsters in the dark. In this experiment, running in response to the drug was greater. Hamsters given triazolam but confined to their nest boxes over the next few hours did not show phase shifts. The phase-shifting effects of triazolam (when they do occur) appear to be mediated through activity increases. Triazolam-treated hamsters became ataxic in all three of these experiments. Suggestions that triazolam may be useful in ameliorating rhythm disturbances in people should be treated with a caution.

Animals↗
PubMed1989

Behavioural entrainment of circadian rhythms.

This paper reviews the discovery and characterization of a behavioural system for entrainment of circadian rhythms. This behavioural system depends on non-photic inputs but interacts with the light-entrainment system. Non-photic stimuli can be powerful quantitatively: behavioural events can shift rhythms by several hours. Non-photic entrainment offers scope for rephasing biological rhythms in circumstances where light input from the environment is inadequate.

Animals↗
PubMed1988

Gastroplasty with distal gastric bypass: a new and more successful weight loss operation for the morbidly obese.

Because of the unacceptable late failure rates associated with other surgical procedures for morbid obesity, the author has performed a new operation-vertical banded gastroplasty with distal gastric bypass-on 70 patients. In seven of these the gastroplasty stoma had to be debanded. The mean lowest loss of excess weight was 88% and the mean final loss of excess weight was 83% for the main group. The postoperative complication rate was acceptable and no late metabolic complications have been seen. This operation gives improved weight loss when compared with gastroplasty or gastric bypass alone and has none of the late complications associated with intestinal bypass.

Body Weight↗
PubMed1986

Failure of gastroplasty pouch and stoma size to correlate with postoperative weight loss.

At the University of Alberta hospitals patients who underwent gastroplasty--horizontal, vertical with multistranded nylon banding of the stomas and vertical banded with Teflon reinforced stomas--have been followed up for over 2 years. Pouch volume ranged from 25 to 30 mL. Pouch volume and stoma size were measured radiologically 2 years after operation and correlated with the percentage excess weight loss. Any patient failing to lose at least 40% of the excess weight was considered a failure. There was no consistent correlation between pouch or stoma size and percentage excess weight loss for any of the three procedures studied. The failure rate for patients included in the study group was 33.3% for horizontal, 32.4% for vertical and 32.8% for vertical banded gastroplasty. The probable reason for the lack of correlation is that some patients change their diets so as to subvert the restriction imposed by the gastroplasty.

Adult↗
PubMed1985

Technique for banding vertical gastroplasties.

The author describes a new technique for banding vertical gastroplasties, using polytetrafluoroethylene, in 177 patients. This material has several advantages over Marlex as a reinforcing material. It is inert, has no tendency to migrate and connective tissue invades its micropores holding it in place. Polytetrafluoroethylene 6 mm in diameter assumes an oval configuration and when placed around the stoma does not kink, collapse or impinge on the lumen. The leakage rate was only 1% and stomal narrowing occurred in only 1.7% of the patients. Follow-up films indicate that stomal size has remained stable in the patients followed up for 2 years. The technique has much to recommend it from the points of view of simplicity, economy and lack of complications associated with the grafting material.

Blood Vessel Prosthesis↗
PubMed1983

Incarceration of gastric fundus in a paraesophageal hernia after gastroplasty.

A tension hydropneumothorax developed suddenly in a 33-year-old woman, 5 days after gastroplasty. The cause was not immediately apparent. Radiologic investigation demonstrated incarceration of the fundus of the stomach together with the stapled pouch in a paraesophageal hernia. Abdominal exploration revealed a blow-out in the wall of the incarcerated fundus. After appropriate repair and management, the patient's course was uncomplicated. This case highlights the need for repairing paraesophageal hernias as soon as they are discovered, particularly during operations that require mobilization of the esophagus and cardia, as in gastroplasty.

Adult↗
PubMed1983

The digitus quintus, rigid stoma, 4-5 position gastroplasty.

In 55 patients a rigid stoma gastroplasty was performed. The operative technique is described. It includes the construction of a rigid stoma and a double line of staples across the stomach to give a pouch volume of 40 to 60 ml. The diameter of the stoma is established by a nasogastric tube and the digitus quintus of the assistant's hand at the level of the cuticle. A 1- to 2-year follow-up indicates that these stomas do not dilate but tend to decrease in diameter. Stomal stenosis occurred in 2 of the 55 patients studied. Weight loss was satisfactory, although incomplete in most patients. It is likely that the weight loss will not be as great as with intestinal bypass. There were no serious late postoperative complications. However, an appreciable number of patients had emesis early in the postoperative period, intolerance of red meat and constipation. It is apparent that a rigid stoma of constant diameter is at least as important as a small gastric pouch in achieving adequate and lasting weight loss. A longer follow-up is necessary to assess this procedure completely.

Adolescent↗
PubMed1981

Vascular access for hemodialysis using bovine heterografts and polytetrafluoroethylene conduits.

The University of Alberta's experience with the use of bovine and polytetrafluoroethylene (PTFE) grafts as renal dialysis conduits is reported. Over a 3 1/2-year period 100 patients had grafts placed. Most were placed in the forearm and a small number in the groin. Bovine grafts, while performing adequately as dialysis conduits, required multiple repairs to alleviate complications. The complications included thrombosis, stenoses at the graft-vein anastomosis and in the graft, aneurysm and infection. At the end of the study period 68% of the grafts were still functioning and 82% of the patients survived. The experience with PTFE grafts was less extensive. Analysis of the data indicates that there was a lower complication rate and that aneurysm formation and infection at puncture sites were rarely seen. Thrombosis secondary to stenosis at the graft-vein anastomosis was the most frequent complication. Graft and patient survival were nearly 90%. A comparison of bovine and PTFE grafts as replacement for failed bovine grafts showed that PTFE was much superior.

Adolescent↗
PubMed1975

Morbid obesity.

Explore the source record for details and available documents.

Adult↗
PubMed1975

Fatty metamorphosis in patients with jejunoileal bypass.

Two-thirds of all preoperative patients had some degree of fatty metamorphosis of the liver; at least 8 to 10 per cent had marked steatosis prior to performance of the jejunoileal shunt. In preoperative patients, marked fatty metamorphosis was seen most prevalently in the heaviest patients, while the incidence of moderate to minimal fatty infiltration was highest in those not as massively obese. Nevertheless, marked degrees of fatty metamorphosis were seen in patients just meeting the minimal weight criterion for operation, and minimal steatosis or normal livers were seen in more massive candidates. Subsequent to the bypass operation 95 per cent of patients had a moderate to severe degree of fatty metamorphosis apparent within the first 300 days. Subsequently, the incidence of fatty infiltration rapidly decreased so that by 1,500 to 2,000 days the incidence of severe steatosis had returned to that seen preoperatively. In fact, only those patients having associated problems late in the course showed a severe degree of fatty metamorphosis after 1,000 days. A screen of liver function studies was not found helpful in detecting minimal to moderate degrees of fatty metamorphosis and showed only inconsistent changes in those patients with severe steatosis. These tests were not helpful in detecting a quiescent cirrhosis of the liver. Cirrhosis of the liver was seen in two patients. In one, it occurred late in the course after the liver had completely cleared of fat. The cause was thought to be acute alcoholism, and steatosis cleared when drinking ceased. A second patient had a degree of cirrhosis at the time of the bypass operation. There has been slight progress in the ensuing seven or eight years that may be unrelated to the presence of the shortened intestine. Liver function studies do not indicate activity. Because the severe degrees of fatty infiltration seen in patients having previously normal or minimally infiltrated livers occurred during the time of rapid weight loss, it is presumed that the extensive mobilization of depot stores of fat to fulfill caloric requirements of the patient results in accumulation of triglyceride in the liver. Steatosis may be further aggravated by the fact that protein absorption is reduced and, therefore, the formation of low density lipoproteins by the liver is curtailed. In this series, no patients have died as a result of fatty infiltration and liver failure alone.

Alcoholism↗