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Biomedical subjects

P A van Hees

Publications and source records attributed to P A van Hees.

At least 19 recordsLinked to original sources
PubMed2001

Aluminium speciation in forest soil solution--modelling the contribution of low molecular weight organic acids.

The concentrations of Al bound to identified low molecular weight organic acids (LMWOAs), phosphate and humic compounds in soil solutions (O1, O2, E, B1 and B2 horizons) from Fennoscandinavian coniferous forest soils were calculated. Two models were evaluated: WHAM (Winderemere Humic Aqueous Model) and a model treating the natural organic acids as monoprotic. The WHAM model was calibrated to find an average charge balance of unity, and then used for Al speciation. This was achieved considering approximately 80% of the natural fulvic acid to be 'active'. For the monoprotic model, constants obtained from previous fitting of soil solution data were used and the model was calibrated using acid/base titrations. The modelling confirms that the low molecular weight acids are important complex formers, binding on average 11-42% (O), 19-20% (E), and 0-30% (B) of the total Al in solution depending on the model used. The monoprotic model yielded higher concentrations than WHAM. Both models predicted that the major part of Al in solution was organically complexed to humic substances and LMWOAs, which was consistent with analytical values of 'quickly reacting' Al (monomenc inorganic forms; 12-14% of Al(tot) on average in the E and B1 solutions). Both models could predict the magnitude of the analytical values (RMSD = 4-5 microM). On average the WHAM model showed a better fit for the E horizon solutions and the monoprotic model for the upper B horizon. The pH dependence of the low molecular weight fraction of Al was modelled in the pH range 3-5.5 for a 'typical' O1 and E solution assuming no other changes in soil solution composition. The extrapolation showed that the models had a different pH dependence. The concentration of Al bound to LMWOAs in WHAM decreased with higher pH while the opposite was seen for the monoprotic model. Also the influence of the concentration of total Al in solution was modelled. The models showed similar trends but for the 'typical' O1 horizon sample the monoprotic model yielded higher concentrations of Al bound to LMWOAs than WHAM.

Aluminum↗
PubMed2001

Occurrence of esophageal granular cell tumors in The Netherlands between 1988 and 1994.

Granular cell tumors (GCT) of the esophagus are rare. The tumor is generally beleived to be of neurogenic origin and shows a malignant course in 2-4% of cases. No unanimity has been reached regarding the management of this tumor. A national survey was conducted on the incidence of GCT of the esophagus, related symptoms, management, and follow-up. A national survey was performed on all newly registered esophageal GCTs in the PALGA system (Dutch register of all pathology diagnoses) for seven consecutive years (1988-1994). Fifty-two new cases (17 men, 35 women; median age 46 years, range 22-77 years) were registered. In 44 cases clinical data could be obtained (survey response 85%). The majority of the GCTs were solitary (42/44) and localized in the distal esophagus (33/44). At endoscopy the size of the tumor was estimated at <5 mm in 50%, 5-10 mm in 25%, and 10-30 mm in 18%. Most patients (40/44) presented with nonspecific gastrointestinal symptoms, only four had dysphagia (tumor size >1 cm). No malignancies were reported. Management of the tumor included excisional biopsy (1/44), endoscopic polypectomy (3/44), and surgical excision (1/44). Endoscopic follow up (1-60 months) in 16 out of 17 patients left untreated showed either a stable tumor size or regression of the tumor. In one case with multiple GCT's a slight tumor growth was seen after a follow-up period of 48 months. Esophageal GCTs in the Netherlands are rare, and mostly diagnosed incidentally. Most patients suffer from nonspecific symptoms; dysphagia occurs only with tumors >1 cm. The usual clinical course of esophageal GCTs is benign. Patients without dysphagia probably do not require routine endoscopic follow-up, provided they are instructed to contact their physician, once dysphagia develops.

Adult↗
PubMed1999

Strongyloides stercoralis infection: how to diagnose best?

Four patients are described with a Strongyloides stercoralis infection. Several techniques to diagnose this infection are discussed. The so-called Baermann method is emphasised. Especially in chronic infections the combination of serology and the Baermann method seems the best diagnostic approach. Treatment with albendazole or ivermectin are suggested treatments.

Adult↗
PubMed1996

Low-amplitude distal esophageal spasm as a cause of severe dysphagia for solid food.

This case report presents a patient with progressive dysphagia, accompanied by weight loss, in the absence of organic disease. Esophageal motility studies initially failed to reveal a diagnosis. At simultaneous manometry and fluoroscopy, with bread/barium boluses, the diagnosis of esophageal spasm in a relatively weak esophagus was made. All conservative treatment modalities failed. Thoracoscopic myotomy resulted in partial field of symptoms. Finally, an esophagectomy was performed because of sever dysphagia accompanied by persisting weight loss.

Chronic Disease↗
PubMed1995

Comparison of the efficacy and safety of 1.5 compared with 3.0 g oral slow-release mesalazine (Pentasa) in the maintenance treatment of ulcerative colitis. Dutch Pentasa Study Group.

OBJECTIVE: To investigate a possible dose-effect relationship with two dosages of oral slow-release mesalazine in patients with quiescent ulcerative colitis. METHOD: One hundred and sixty-nine patients with ulcerative colitis in remission were treated with either 1.5 or 3.0 g/day mesalazine for 1 year or until relapse into active colitis. RESULTS: Fewer of the 3.0 g dose group relapsed than of the 1.5 g dose group (33 compared with 46%). This difference failed to reach statistical significance (P = 0.057). A significant relationship between age and relapse rate was established. No dose-related adverse events were found. Three serious drug-related adverse events were, however, reported. All of the serious adverse reactions resolved after the medication was discontinued. CONCLUSION: There is a trend for high doses of oral mesalazine to be more effective in prevention of relapse of ulcerative colitis. These higher doses are not associated with a higher incidence of adverse reactions.

Administration, Oral↗
PubMed1992

Bacterial acetylation of 5-aminosalicylic acid in faecal suspensions cultured under aerobic and anaerobic conditions.

After oral administration of 5-aminosalicylic acid a substantial proportion of the acetylated form is excreted in the faeces. We have studied the role of the faecal microflora in acetylating 5-aminosalicylic acid. In faeces incubated under both aerobic and anaerobic conditions there was acetylation of 5-aminosalicylic acid. Of the anaerobic bacteria isolated from a 10(8) faecal dilution 44% were able to acetylate 5-aminosalicylic acid. We conclude that the normal faecal microflora contribute to the acetylation of 5-aminosalicylic acid.

Acetylation↗
PubMed1992

Sulphasalazine-induced eosinophilic pneumonia.

Eosinophilic pneumonia and skin rash developed in a 21-yr-old man while taking sulphasalazine. After discontinuation of the drug and treatment with steroids the pulmonary infiltrates and rash resolved completely. A short review of the literature concerning sulphasalazine-induced lung disease is presented.

Adult↗
PubMed1989

The endoscopic spectrum of colonic mucosal injury following aortic aneurysm resection.

Ischemic colitis is a serious complication of aortic aneurysm resection. A knowledge of the endoscopic appearance and the clinical course of various forms of colonic mucosal injury is important for the clinician who has to decide which patient should be carefully monitored after aneurysm resection. This article reports on 48 patients with colonic mucosal injury, subdivided into non-specific lesions and ischemic colitis. Details are given of the endoscopic picture and the clinical course. It is concluded that only the gangrenous form of ischemic colitis is of clinical significance, and is related to bowel perforation and late stricture formation.

Aged↗
PubMed1988

Double-blind comparison of 5-aminosalicylic acid and acetyl-5-aminosalicylic acid suppositories in patients with idiopathic proctitis.

Suppositories containing 300 mg 5-aminosalicylic acid (1.96 mmol) or 425 mg acetyl-5-aminosalicylic acid (1.96 mmol) were used in 40 patients with idiopathic proctitis to determine the efficacy of acetyl-5-aminosalicylic acid in treating this bowel inflammation. Each patient was treated with 5-aminosalicylic acid or acetyl-5-aminosalicylic acid suppositories twice daily for 4 weeks in a double-blind trial. Four patients were included twice in the trial. The second time they were treated with the alternative regimen. Six patients in the acetyl-5-aminosalicylic acid group did not complete the trial, four of them because of diarrhoea. Complete clinical remission with normal rectal mucosa on sigmoidoscopy was achieved in 10 out of 18 patients on 5-aminosalicylic acid and in only two out of 15 in the acetyl-5-aminosalicylic acid group (P = 0.03). A favourable histological improvement was demonstrated with 5-aminosalicylic acid suppositories, but the difference with acetyl-5-aminosalicylic acid was not significant (P = 0.059). Three of the four patients who received both drugs recovered with 5-aminosalicylic acid; in none of them was acetyl-5-aminosalicylic acid effective. The results from this study and from previous investigations show that acetyl-5-aminosalicylic acid is not superior to placebo.

Adult↗
PubMed1985

Disposition of disodium azodisalicylate in healthy subjects. A possible new drug for inflammatory bowel disease.

The disposition of disodium azodisalicylate and salicylazosulfapyridine was studied in 6 healthy volunteers. After a single oral dose (1.0 g disodium azodisalicylate; 2.3 g salicylazosulfapyridine) maximum serum concentrations of the intact compound ranged between 1.4 and 6.8 mumol/L and 32 and 114 mumol/L, respectively. Mean residence time and serum half-life of disodium azodisalicylate were considerably longer than those of salicylazosulfapyridine, probably because of a higher apparent volume of distribution. Both compounds were largely split by colonic bacteria and comparable amounts of the active moiety, (acetyl-)5-aminosalicylic acid, were recovered in feces. During long-term ingestion of disodium azodisalicylate (1.0 g/day) it took 6-19 days to reach a steady state. Serum concentrations of disodium azodisalicylate at steady state were low: 2.2-8.4 mumol/L. The serum half-life was 6-10 days. It is concluded that the disposition of disodium azodisalicylate is similar, in important respects, to that of salicylazosulfapyridine. Disodium azodisalicylate, therefore, deserves therapeutic trial.

Administration, Oral↗