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R C Harrison

Publications and source records attributed to R C Harrison.

At least 19 recordsLinked to original sources
PubMed1988

The retention mechanism of technetium-99m-HM-PAO: intracellular reaction with glutathione.

Preparations of d,l- and meso-hexamethylpropyleneamine oxime (HM-PAO) labeled with technetium-99m were added to rat brain homogenates diluted with phosphate buffer (1:10). The conversion of d,l-HM-PAO to hydrophilic forms took place with an initial rate constant of 0.12 min-1. Incubation of the brain homogenate with 2% diethyl maleate for 5 h decreased the homogenate's measured glutathione (GSH) concentration from 160 to 16 microM and decreased the conversion rate to 0.012 min-1. Buffered aqueous solutions of glutathione rapidly converted the HM-PAO tracers to hydrophilic forms having the same chromatographic characteristics as found in the brain homogenates. The rate constant for the conversion reaction of d,l-HM-PAO in GSH aqueous solution was 208 and 317 L/mol/min in two different assay systems and for meso-HM-PAO the values were 14.7 and 23.2 L/mol/min, respectively. Rat brain has a GSH concentration of about 2.3 mM and the conversion of the d,l-HM-PAO due to GSH alone should proceed with a rate constant of 0.48 to 0.73 min-1 and be correspondingly 14-fold slower for meso-HM-PAO. In human brain, the in vivo data of Lassen et al. show a conversion rate constant of 0.80 min-1. This correspondence of values supports the notion that GSH may be important for the in vivo conversion of 99mTc-labeled HM-PAO to hydrophilic forms and may be the mechanism of trapping in brain and other cells. A kinetic model for the trapping of d,l- and meso-HM-PAO in tissue is developed that is based on data of GSH concentration in various organs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

In vitro binding and in vivo localization in colorectal cancer of a high affinity monoclonal antibody to carcinoembryonic antigen.

A monoclonal antibody to carcinoembryonic antigen (CEA) (C46) was tested for its binding properties to colorectal cancer cells in vitro and for its localization in patients with primary colorectal cancer. Strong binding was found to disaggregated primary colorectal cancer cells, with a median of 66 per cent of the cells in the tumour gate binding the antibody. There was a median binding ratio of 8.6:1 compared with normal immunoglobulin. The pattern of immunohistological staining was typical of that for an antibody to CEA. All seven patients with primary colorectal cancer imaged pre-operatively using 111In-labelled C46 gave positive images. The median tumour:non-tumour antibody uptake ratio from resected specimens (n = 8) was 5.8:1. (1.7-7.6:1). Eight of 11 sites of secondary colorectal cancer gave positive images. The high affinity and good tumour localization of C46 have improved clinical imaging and increase the possibilities for targetting of antitumour agents.

Aged↗
PubMed1985

Cerebral uptake and retention of 99Tcm-hexamethylpropyleneamine oxime (99Tcm-HM-PAO).

A new radiopharmaceutical, 99Tcm-hexamethylpropyleneamine oxime (99Tcm-HM-PAO) is described. This agent displays considerable promise for imaging cerebral blood flow. In studies in rats and one human volunteer, 99Tcm-HM-PAO demonstrates good brain uptake, prolonged retention of activity in the brain, and slow regional redistribution. These properties suggest that this new radiopharmaceutical is ideal for single photon emission tomographic (SPECT) imaging of cerebral blood flow.

Animals↗
PubMed1985

Development of a 99Tcm-labelled radiopharmaceutical for cerebral blood flow imaging.

A new radiopharmaceutical, 99Tcm-hexamethylpropyleneamine oxime (99Tcm-HM-PAO) has shown considerable promise for single photon emission tomographic (SPECT) imaging of the brain. In animal biodistribution studies this complex demonstrates good brain uptake with prolonged retention of activity in brain. Further improvement of these properties, resulting in higher brain uptake with very slow washout and fixed regional distribution has been achieved following the isolation of the d,1-diastereoisomer of HM-PAO.

Animals↗
PubMed1984

Experimental evaluation of the resistance of the skin grafted rectum to ileal contents.

There are three general approaches to prevent the development of cancer in patients with premalignant colorectal diseases. One method requires total colectomy and excision of the rectal mucous membrane. For 35 years, patients have had their rectal muscle tube covered by a variety of full-thickness ileal pullthrough operations. For 30 years, various types of pelvic ileal pouches have been tried in attempts to improve bowel function. This report attempts to evaluate another approach in experimental animals. The rectal submucosa was skin grafted and subsequently anastomosed to the ileum to assess its ability to stand up to that milieu. The results were promising with a maximum follow-up of 1 year. This may prove to be another option to ileoanastomy with or without a pouch.

Anal Canal↗
PubMed1982

Effect of a biologic glue on the leakage rate of experimental rectal anastomoses.

Because bowel and omental adhesions offer some protection when an anastomosis leaks, the effect of a fibrin glue on the leak rate was determined in a prospective animal study. EEA stapled anastomoses of the rectum were evaluated in dogs with respect to mortality, postmortem leak rate, adhesions, and the accuracy of barium enema done just before the animals were killed 7 days postoperatively. There was a reduction in fatal, free, and confined leaks which did not reach statistical significance. Adhesions were reduced. There were no false-positive barium enemas but a 7 percent incidence of false-negative results. The clinical management of a suspected anastomotic leak is discussed.

Animals↗
PubMed1982

Management of duodenal diverticula.

Duodenal diverticula are not uncommon. Uncomplicated diverticula require no treatment. In the period 1970 to 1980, 104 patients with symptoms presented at the Vancouver General Hospital and the Swedish Hospital in Seattle. Of these, 26% presented with pain and 24% with anemia. Malabsorption and benign tumours were noted infrequently. Fifteen patients were treated surgically for pain, perforation, hemorrhage, tumour, blind loop syndrome and obstruction of the duodenum, biliary tract or pancreatic duct. Two patients died. The second part of the duodenum was involved in 82% and the third part in 10%. Anatomical variations are common in the area of the ampulla; these should be anticipated before operation. Surgical procedures in the area may be technically demanding and associated with high mortality and morbidity. The choice of procedure depends on the urgency and nature of the complication of the diverticulum. Endoscopic retrograde cholangiopancreatography can play a role in evaluating the possible significance of the diverticulum and the anatomy of the area. In some cases endoscopic sphincterotomy may be possible. In some situations diverticulectomy is contraindicated.

Adult↗
PubMed1980

Canadian contributions towards the comprehension of hyperinsulinism: the first successful excision of an insulinoma.

The authors review briefly the contributions to the "insulin story" made by Canadian doctors. A.G. Nichols from the department of pathology, McGill University, first described an adenoma arising from the islets of Langerhans. The authors also review the background to the first successful excision of a functioning tumour of the pancreas by R.R. Graham in 1929; in the preceding 2 years W. J. Mayo had found a malignant islet cell tumour with hepatic metastases and J.M.T. Finney had operated on a patient suffering from functional hypoglycemia. Graham found and successfully excised what was probably a solitary benign islet cell adenoma. The authors believe the patient was cured.

Adenoma, Islet Cell↗
PubMed1979

Mammography.

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Breast Neoplasms↗