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Biomedical subjects

D J Bjorkman

Publications and source records attributed to D J Bjorkman.

At least 37 records · Page 2Linked to original sources
PubMed1993

Computer-assisted fluorescence identification of colon cancer in rats.

Hematoporphyrin derivative (HPD) fluorescence is highly sensitive in identifying colon cancers in the rat. Its specificity, however, is compromised by HPD accumulation in lymphoid follicles. We developed a computer-assisted method to distinguish lymphoid from malignant tissue using HPD fluorescence. Colon cancer was induced in rats by weekly injections of 1,2-dimethylhydrazine. Twenty-four hours after intravenous HPD injection, the animals were sacrificed and the colonic surface was illuminated with a blue light (340-410 nm). Computer images were examined for characteristic patterns of fluorescence at 632 nm. The ratio of fluorescence intensity between lesions and adjacent background areas was also determined. The fluorescent areas were then coded and examined histologically. Eighty-one lesions (21 cancers, 60 lymphoid follicles) were identified. Only two lesions (one cancer, one lymphoid follicle) were incorrectly identified using computer images (concordance rate = 98%). The lesion:background fluorescence ratio was higher in malignant tissue than lymphoid follicles, but significant overlap was seen. These results indicate that computer-enhanced images of HPD fluorescence can distinguish malignant from lymphoid tissue in the rat colon and may have a potential role in the diagnosis of colon cancer.

Animals↗
PubMed1993

Review article: endoscopy-related infections.

Endoscopic procedures generate bacteraemia to different degrees. Under certain conditions, most notably valvular heart disease, clinically significant infections may occur. A large body of literature has grown around recommendations for antibiotic prophylaxis to prevent procedure-related infections. Most of this literature is in the form of anecdotal reports. Few prospective randomized studies have been performed. In this paper, the literature on endoscopy-related infections is reviewed. Recommendations for antibiotics from different sources are compared and a rational approach to prophylactic antibiotic therapy is presented.

Anti-Bacterial Agents↗
PubMed1992

Endoscopic laser therapy of the watermelon stomach.

Endoscopic laser therapy has been used in the treatment of vascular lesions throughout the gastrointestinal tract. The "watermelon stomach" is a pattern of vascular ectasia in the gastric antrum that results in chronic gastrointestinal blood loss and iron deficiency anemia. We have treated 7 transfusion dependent patients with a watermelon stomach using endoscopic laser therapy. Four of these patients were treated with the argon laser and 3 with the Nd:YAG laser. Patient age and prior transfusion requirements were similar in both groups. The mean number of treatments to obliterate vascular lesions and eliminate the need for transfusions was 5.75 +/- 0.89 (SEM) for the argon laser and 2.33 +/- 0.27 for the Nd:YAG laser (P < 0.05). Lesions recurred and required retreatment in 1 patient treated with the Nd:YAG laser and 3 patients treated with the argon laser (mean follow-up of 35 months). We conclude that endoscopic laser therapy with either the argon or Nd:YAG laser is an effective treatment modality for antral vascular ectasia (watermelon stomach). The Nd:YAG laser requires fewer treatment sessions than the argon laser to obliterate the lesions without increased risk of complications.

Aged↗
PubMed1991

Fluorescence localization of early colonic cancer in the rat by hematoporphyrin derivative.

Laser excitation of hematoporphyrin derivatives (HPD) localizing in tumors of the tracheobronchial tree and bladder is useful in the identification and treatment of those tumors. A comparable utility for HPD in the endoscopic localization of colonic tumors may be possible. In this study the ability of HPD to identify 1,2 dimethylhydrazine (DMH) induced colon cancer in rats is evaluated. A total of 111 rats were studied with HPD. Sixty-nine rats received weekly injections of DMH (20 mg/kg) and 42 received injections of the vehicle alone. Twenty-four hours after the intravenous injection of 5 mg/kg of HPD, 18 DMH-induced tumors were identified by visual fluorescence using excitation by either a blue light (390-436 nm) or an argon laser (488 and 514 nm). This represented 100% of the visually or microscopically detected tumors. Seventy-five fluorescent areas were noted that did not contain evidence of cancer. The majority (63) of false positive areas contained lymphoid follicles. All but 2 false positive areas (73/75, 97%, p less than .001) were seen in DMH-treated animals, suggesting that they were an artifact of DMH treatment. HPD fluorescence did not identify microscopic dysplasia. We conclude that HPD fluorescence is an effective method of identifying early colonic cancer and may have a potential clinical role in patients at high risk for colorectal cancer.

1,2-Dimethylhydrazine↗
PubMed1991

Argon laser therapy for perianal Bowen's disease: a case report.

Bowen's disease (intraepithelial squamous cell carcinoma) may occasionally occur in anal canal or perianal region. Surgical excision in this area may result in significant complications and a recurrence rate of 9-19%. A case of successful treatment of anal and perianal Bowen's disease using argon laser therapy is presented. No acute or chronic complications resulted from laser therapy. Twenty-eight months after the initial diagnosis the patient is disease free. Laser therapy also provides the potential for repeated treatment of recurrent lesions without significant patient discomfort or inconvenience. Argon laser therapy should be considered as a therapeutic option in the treatment of Bowen's disease.

Anus Neoplasms↗
PubMed1991

Age does not influence acute aspirin-induced gastric mucosal damage.

Gastroduodenal ulceration and complications occur more commonly in elderly patients consuming aspirin and other nonsteroidal antiinflammatory drugs than in younger cohorts. To test the hypothesis that the gastroduodenal mucosa of the elderly is more sensitive to nonsteroidal antiinflammatory drug damage, acetylsalicylic acid in low (325 mg) and high (1300 mg) doses was administered on separate days to 10 elderly (median age, 67.5; range, 60-74 years) and 10 young (median age, 24.5; range, 19-30 years) healthy, male volunteer subjects. Gastroduodenal mucosal damage was assessed 2 hours after aspirin dosage by video-endoscopic techniques. At the conclusion of the study, the videotapes of all procedures were randomly evaluated by two endoscopists blinded to subject identification or study sequence. Endoscopically observed lesions were counted in the duodenum, gastric antrum, and gastric body. Aspirin damage was dose-related and more severe in the stomach than in the duodenum. There were no significant differences in total gastroduodenal lesion counts between age groups. In addition, no differences in median gastric pH or tissue 6-ketoprostaglandin F1 alpha content were observed between age groups. These data suggest that age is not a significant factor in determining the extent of acutely administered aspirin-induced damage.

6-Ketoprostaglandin F1 alpha↗
PubMed1991

Post-sclerotherapy bacterial peritonitis.

Endoscopic variceal sclerotherapy has been associated with a number of complications. Peritonitis after sclerotherapy has rarely been reported. In this retrospective review of 213 consecutive sclerotherapy procedures among 65 patients over a 3-yr period, we found that six cases of peritonitis occurred, for an incidence of approximately 3%. All patients developing post-sclerotherapy peritonitis had low ascitic fluid protein. However, this did not differ from patients who did not develop peritonitis. No patient on antibiotics at the time of sclerotherapy developed peritonitis. Peritonitis should be considered in the diagnosis of post-sclerotherapy fever. The role of prophylactic antibiotics to prevent this complication is uncertain.

Adult↗
PubMed1991

13C-bicarbonate breath test as a measure of gastric emptying.

Radionuclide studies are widely used to estimate the gastric emptying rate of solids and liquids. Unfortunately, these methods carry the risk of radiation exposure and require expensive and complex equipment. Carbon-13, a stable, nonradioactive isotope, has been used successfully as a marker in the gastrointestinal tract for other purposes. A preliminary study using ingested NaH13CO3 and measuring 13CO2 breath excretion suggested that this test might be a simple, noninvasive, and inexpensive method for determining gastric emptying. To determine the efficacy of NaH13CO3 as a noninvasive marker for gastric emptying, the resulting 13CO2 breath excretion was determined simultaneously with standard radiolabeled meal measurements of gastric emptying of liquids and solids in 15 patients. 13CO2 breath excretion did not correlate with the gastric emptying of either solids or liquids, as determined by radionuclide techniques. These results suggest that NaH13CO3 is not a reliable indicator of gastric emptying. Factors other than gastric emptying may affect the rate of 13CO2 absorption and exhalation, rendering it unreliable as a measure of gastric emptying.

Adult↗
PubMed1990

Differences in composition and fluidity of intestinal microvillus membrane vesicles prepared by different methods.

Multiple methods have been developed to isolate the intestinal microvillus membrane and facilitate the study of its composition and function. Variations in membrane composition and fluidity may result from different preparative techniques. This study shows that the use of MgCl2 and/or KSCN in vesicle preparation alters phospholipid and protein composition of the membrane compared to CaCl2 precipitation. The use of MgCl2 in membrane preparation increased phosphatidylethanolamine and decreased phosphatidylinositol content. The use of KSCN in membrane preparation decreased the protein content. The structural changes seen with the use MgCl2 alone are accompanied by an increase in both static and dynamic membrane fluidity. These results suggest that different methods of membrane vesicle preparation affect membrane phospholipid and protein content as well as membrane fluidity.

Animals↗
PubMed1990

Formation of biliary thrombi in protoporphyrin-induced cholestasis in perfused rat liver.

The effect of bile acids on the formation of biliary thrombi in protoporphyrin-induced cholestasis was determined by perfusing isolated rat livers with taurocholate, chenodeoxycholate and ursodeoxycholate with and without protoporphyrin. Protoporphyrin-induced reduction of bile flow was similar in the presence of each bile acid. The cholestasis was greater at high doses (2,000 to 10,885 nmol) than at low doses (1,500 nmol) of protoporphyrin, unrelated to the amount of lactate dehydrogenase released into the perfusate, and it was not altered by increasing bile acid infusions. Bile acid excretion was inhibited by high protoporphyrin doses. Periportal birefringent pigment deposits were seen in canaliculi and ductules when the biliary protoporphyrin concentration exceeded 161 nmol/ml, 345 nmol/ml and 1,036 nmol/ml for ursodeoxycholate, chenodeoxycholate and taurocholate, respectively; or, when the protoporphyrin (nanomole) to bile acid (micromole) ratio exceeded 3.23, 7.03 and 23.43, respectively. The maximal ratio of ductular deposits to portal tract deposits examined was 0.9. Electron microscopy showed these deposits were associated with canalicular thrombi. Thus, biliary thrombi were produced by infusion of bile acids and protoporphyrin. The occurrence of thrombi varied with bile acid structure. Explanations for this finding are speculative. The presence of periportal thrombi, however, did not influence the degree of functional cholestasis.

Animals↗
PubMed1989

Photofrin II localization in rat cecum.

Laser excitation of photodynamic agents localizing in colonic tumors may allow the early diagnosis and treatment of colon cancer. The efficacy of these agents requires a high ratio of tumor to background photosensitizer accumulation and fluorescence. To assess normal colonic background fluorescence and hematoporphyrin accumulation 31 rats were studied after an intravenous injection of Photofrin II (PF-II) at a dose of 5 mg/kg. An increase in mucosal fluorescence and porphyrin content was noted in the cecum 24 hours after injection. Cecal accumulation of PF-II may affect its efficacy in the localization and treatment of cecal tumors. Further investigation into the mechanism and clinical significance of this finding is needed.

Animals↗
PubMed1989

NSAID-induced gastropathy in the elderly: understanding and avoidance.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are a significant cause of gastric mucosal injury and bleeding, particularly in elderly patients. The mechanism of this injury appears to be, at least in part, a disruption of normal cytoprotective mechanisms by the inhibition of prostaglandin production. Acute injury results from the local effect of some drugs and may resolve with time. Chronic injury may occur with any NSAID and may often be asymptomatic until a complication occurs. Treatment of either lesion centers around NSAID withdrawal and standard ulcer therapy. Although routine prophylaxis of all patients is not indicated, those patients with a history of NSAID injury or other risk factors may need preventive measures if they are treated with NSAIDs. Oral prostaglandins, such as misoprostol, are effective in the prevention of NSAID-induced injury. The efficacy of sucralfate and H2-blockers in this setting appears promising but requires further study.

Age Factors↗
PubMed1989

Perforated duodenal ulcer after gastric bypass surgery.

Gastric bypass procedures have been used widely in the surgical therapy of morbid obesity. Evidence exists that the bypassed gastric segment retains its ability to secrete acid. Acid-related ulceration and obstruction of the proximal gastric pouch after surgery have been well documented, but duodenal ulceration after gastric bypass has yet to be reported. We present the first reported case of duodenal ulceration and perforation after gastric bypass surgery for morbid obesity. This case demonstrates that acid-related gastroduodenal disease may occur in the bypassed gastrointestinal tract. Consideration should be given to this area in evaluating upper gastrointestinal bleeding and abdominal pain after gastric bypass. Because barium contrast studies may not adequately evaluate bypassed segments, and standard gastroscopes are not long enough to reach these areas, the use of longer endoscopes may be necessary to confirm the presence of gastroduodenal disease after gastric bypass.

Adolescent↗
PubMed1988

Hepatic ultrastructure after methotrexate therapy for rheumatoid arthritis.

Twenty-six patients receiving long-term oral methotrexate (MTX) therapy for rheumatoid arthritis (24 patients) or psoriasis (2 patients) were prospectively evaluated for alterations in liver morphology by light microscopy, electron microscopy, and immunofluorescence microscopy. Although only 4 MTX-treated patients had light microscopic evidence of mild fibrosis, all had evidence of collagen deposition in the space of Disse near Ito cells and changes in hepatocyte lysosomes on electron microscopy. These findings were absent from control livers. Fibrinogen, fibronectin, and type IV collagen were identified by immunofluorescence in both MTX-treated patients and controls. We conclude that long-term MTX therapy for rheumatoid arthritis is associated with alterations in hepatic ultrastructure, including collagen deposition in the space of Disse and changes in hepatocyte lysosomes.

Adult↗
PubMed1988

AM and PM measurement of gastric potential difference and prostacyclin production in humans: effects of ranitidine.

It has been previously documented that aspirin induced gastric injury of healthy male volunteers was greater in the morning than in the evening. We have also reported that fasting gastric acid secretion rates and gastric retention times for solids were lower in the morning hours of the circadian cycle. We hypothesized, therefore, that defensive factors in the human stomach may exhibit circadian rhythmicity with greater vulnerability to noxious agents during the morning hours. It has also been hypothesized that an antisecretory agent, with reported protective effects, such as Ranitidine, would affect gastric defense mechanisms differently at different times in the circadian cycle. Transmural electrical potential difference (PD) and prostacyclin (PGI2) production by mucosal biopsy specimens were chosen as putative indicators of gastric defensive status. Accordingly, morning (1000) and evening (2200) studies were performed on 10 fasting healthy male subjects with and without oral Ranitidine (150 mg) given 3 hr before oro-gastric intubation for the measurement of PD and the removal of mucosal biopsy samples.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Structural features of absorptive cell and microvillus membrane preparations from rat small intestine.

Absorptive cells of the small intestine are highly polarized cells with distinct microvillus membrane (MVM) and basolateral plasma membrane domains. We compared membrane structure in the following preparations of rat small intestine commonly used for in vitro study of MVM function: epithelial sheets, isolated epithelial cells, and four different MVM vesicle preparations, using electron microscopy of thin sections and freeze fracture replicas. We also quantitated mean vesicle diameter of the four MVM preparations by quasielastic light scattering and determined their actin content. Epithelial sheets maintained their plasma membrane polarity as judged by intramembrane particle (IMP) distribution for at least 30 min after isolation. In contrast, the plasma membrane of isolated cells showed redistribution of IMPs, indicating considerable loss of polarity in the few minutes required for cell recovery. The P-face IMPs in MVM prepared by Ca++ precipitation were randomly distributed but became aggregated after exposure to potassium thiocyanate, which removed approximately 50% of core actin. The P-face IMPs in Mg++ precipitated MVM were aggregated whether or not core actin was depleted with potassium thiocyanate. The shape and size of MVM vesicles differed considerably with different preparative techniques. The extremely rapid loss of plasma membrane polarity of isolated intestinal epithelial cells and the striking structural heterogeneity of MVM vesicles prepared by commonly used techniques should be considered in the interpretation of functional studies with these preparations.

Animals↗
PubMed1984

Esophageal, gastric, and intestinal candidiasis.

Gastrointestinal Candida infection is more prevalent than previously recognized. It is most often seen in patients with underlying impairment of the immune system but may also occur in apparently normal individuals. Esophageal involvement is most common, presenting with odynophagia, dysphagia, or bleeding. Gastric Candida infection may cause diffuse mucosal involvement or focal invasion of benign gastric ulcers. Intestinal candidiasis is uncommon and poorly characterized. The diagnosis is usually established by visualizing the characteristic yeast or mycelial forms in endoscopic brushings and biopsies. Oral nystatin is effective therapy in many patients, but other antifungal agents may be needed in extensive or persistent disease, especially in immunocompromised patients.

Candidiasis↗