J.H.P. Wilson

Adenosine triphosphate. Established and potential clinical applications

Adenosine 5′-triphosphate (ATP) is a purine nucleotide found in every cell of the human body. In addition to its well established role in cellular metabolism, extracellular ATP and its breakdown product adenosine, exert pronounced effects in a variety of biological processes including neurotransmission, muscle contraction, cardiac function, platelet function, vasodilatation and liver glycogen metabolism. These effects are mediated by both P1 and P2 receptors. A cascade of ectonucleotidases plays a role in the effective regulation of these processes and may also have a protective function by keeping extracellular ATP and adenosine levels within physiological limits. In recent years several clinical applications of ATP and adenosine have been reported. In anaesthesia, low dose adenosine reduced neuropathic pain, hyperalgesia and ischaemic pain to a similar degree as morphine or ketamine. Postoperative opioid use was reduced. During surgery, ATP and adenosine have been used to induce hypotension. In patients with haemorrhagic shock, increased survival was observed after ATP treatment. In cardiology, ATP has been shown to be a well tolerated and effective pulmonary vasodilator in patients with pulmonary hypertension. Bolus injections of ATP and adenosine are useful in the diagnosis and treatment of paroxysmal supraventricular tachycardias. Adenosine also allowed highly accurate diagnosis of coronary artery disease. In pulmonology, nucleotides in combination with a sodium channel blocker improved mucociliary clearance from the airways to near normal in patients with cystic fibrosis. In oncology, there are indications that ATP may inhibit weight loss and tumour growth in patients with advanced lung cancer. There are also indications of potentiating effects of cytostatics and protective effects against radiation tissue damage. Further controlled clinical trials are warranted to determine the full beneficial potential of ATP, adenosine and uridine 5′-triphosphate.

Nicotine inhibits the in vitro production of interleukin 2 and tumour necrosis factor-α by human mononuclear cells

Smoking protects against ulcerative colitis (UC), and treatment with nicotine patches has a beneficial symptomatic effect in patients with UC. To find an explanation for this response to nicotine in UC, we assessed the effects of nicotine on cytokine production by mononuclear cells (MNC). MNC were isolated from peripheral blood from healthy volunteers. Non-adherent MNC were preincubated with varying concentrations of nicotine or prednisolone for 24 h followed by addition of phytohemagglutinin (10 micrograms/ml). The concentrations of interleukin 2 (IL-2) and tumour necrosis factor-alpha (TNF alpha) in the supernatants were determined by ELISA. Nicotine as well as prednisolone caused a significant inhibition of IL-2 and TNF alpha production. The maximum inhibition caused by nicotine was about 50% of that caused by prednisolone and was reached at concentrations equivalent to nicotine levels measured in plasma of smokers. These results indicate that nicotine exerts its immunoregulatory role through modulation of the cytokine production by non-adherent mononuclear cells.

Body Composition in Patients With Acquired Immunodeficiency Syndrome: A Validation Study of Bioelectric Impedance Analysis

The objective of this validation study was to explore bioelectric impedance analysis (BIA) as a way to assess nutritional status and body composition. The study was done in the outpatient department of the AIDS unit at University Hospital Dijkzigt, Rotterdam, The Netherlands. Eleven clinically stable patients with AIDS were studied. Total body water, body fat, lean body mass, and body cell mass were measured and calculated with multiple dilution techniques and BIA. With linear regression analysis, a strong correlation was found between total body water and lean body mass derived from BIA and multiple dilution techniques (r2 = .96 and .98, respectively), and slightly weaker correlation was found for body cell mass and body fat (r2 = .88 and .76, respectively). These results suggest that BIA is a suitable method for the assessment of body cell mass in HIV-infected patients without opportunistic infections. The technique is safe, noninvasive, fast, and inexpensive.

Adjuvant intraoperative photodynamic therapy diminishes the rate of local recurrence in a rat mammary tumour model

The use of photodynamic therapy (PDT) as an adjunct to curative tumour resection was investigated in a tumour recurrence model, using rat mammary adenocarcinoma BN472. Tumours were inoculated subcutaneously in 60 animals and resected after 21 days of growth. Immediately after removal, the operation site was exposed to 320-450 nm light of 0.1 W cm-2 and 60 J cm-2 after photosensitisation with either Photofrin (5 mg kg-1 i.v. 48 h before illumination) or 5-aminolaevulinic acid (ALA) (2 mg ml-1 in drinking water for 9 days). Porphyrin concentrations were measured in tissue samples. After 28 days, animals treated with adjunctive PDT had a significantly longer tumour-free interval than controls (P < 0.01); median 25 days (Photofrin), 18 days (ALA), 14 days (controls). Moreover, in the PDT groups significantly fewer rats had lymph node metastasis. A prophyrin concentration ratio between tumour and mammary tissue of 2:1 was found after Photofrin and 4:1 after ALA. The results indicate that adjuvant intraoperative PDT may be a safe and effective method of destroying residual tumour, thereby preventing locoregional tumour recurrence.

Preparation of porphyrin methyl esters for high pressure liquid chromatography

Abstract High pressure liquid chromatography has distinct advantages over thin-layer chromatography for the rapid separation and quantitative determination of porphyrin methyl esters [1–3]. Our initial experience with the talc method of. extracting porphyrins from urine [3] was disappointing, poor recoveries being the rule rather than the exception. We therefore have developed new techniques for extracting and methylating porphyrins from biological samples, prior to HPLC.

Small bowel wall function in patients with advanced liver cirrhosis and portal hypertension studies on permeability and luminal bacterial overgrowth

Objective: Changes in small bowel function could contribute to the complications of cirrhosis including malnutrition, infection and encephalopathy. To evaluate small bowel function, we studied intestinal permeability and luminal bacterial overgrowth in patients with cirrhosis of the liver and portal hypertension. Design: The 14C-glycocholic acid breath test was used to evaluate the presence of bacterial overgrowth and urine excretion of orally ingested 51Cr-EDTA was used to measure intestinal permeability. Intestinal clearance of α-1-antitrypsin and faecal blood loss were also measured. Setting: Gastroenterology and hepatology unit of a university hospital. Patients: A total of 18 patients were studied. Results: No evidence of small intestinal bacterial overgrowth or increased permeability of the small bowel was found. However, 28% of the patients had increased faecal blood loss. Conclusions: Although the number of patients investigated was small, our data suggest that small bowel function is maintained to a large extent in patients with advanced liver cirrhosis and portal hypertension.

Serum procollagen III N-terminal peptide and laminin P1 fragment concentrations in alcoholic liver disease and primary biliary cirrhosis

Procollagen type III N-peptide (PIII NP) and laminin P1 fragment (LP1) have both been proposed as markers of liver fibrosis. In this study we evaluated the diagnostic application of both peptides in alcoholic liver disease and primary biliary cirrhosis. Serum concentrations of the peptides were measured by radioimmunoassay. PIII NP and LP1 levels appeared to be significantly raised in patients with alcoholic and primary biliary cirrhosis. Patients with alcohol abuse without cirrhosis had normal or slightly elevated PIII NP levels, but significantly raised LP1 levels. There was a strong correlation between PIII NP and LP1 concentrations.

Solid phase radioimmunoassay for determination of conjugated cholic acid in serum

A modified radioimmunoassay for conjugated cholates is presented. In this modification the antibody is chemically bound to Sepharose which enablproducibility (the coefficient of variation between samples is 4%). The whole procedure is carried out at room temperature and with a short incubation time (45 min). Serum can by analysed directly (no extractions or modifications needed). The assay is a suitable tool for liver function testing. A rough indication of total bile acid concentration in serum or bile can also be obtained with this assay.

Photodynamic Therapy for Gastrointestinal Tumors

Photodynamic therapy is based on the administration of a compound that is preferentially accumulated by a tumor and which causes tumor destruction after exposure to light of a specific wavelength. The photosensitizers most commonly used in treating tumors of the gastrointestinal tract are porphyrins--hematoporphyrin derivative and dihematoporphyrin ether. These compounds have been used with success to produce reduction in tumor size of esophageal, gastric, and colorectal cancers. In some instances long-lasting complete remission have been observed after photodynamic therapy. New developments include photosensitizers that react to light of a longer wavelength, which is able to penetrate tissue to a greater depth, the use of 5-aminolevulinic acid, which is preferentially converted to porphyrin in malignant cells, and combination of photodynamic therapy with thermic laser, radiotherapy, or chemotherapy.

Development of hexachlorobenzene porphyria in rats: Time sequence and relationship with lipid peroxidation

The relationship between the development of porphyria and free-radical formation induced by hexachlorobenzene was studied in iron-overloaded rats. The first sign of porphyria, an increase in porphyrins in the liver, was detected at day 22. Liver malondialdehyde was also increased at day 22. During the following weeks, liver porphyrins and malondialdehyde increased simultaneously, accompanied by a decrease in uroporphyrinogen decarboxylase activity and glucose-6-phosphate activity in liver, and a high excretion of porphyrins in the urine. In the rats given hexachlorobenzene, changes were detected in the pattern of lipids in the liver microsomes. In comparison with the controls, there were decreases in C20:4 and C22:5 fatty acids, whereas the fatty acid C20:3w6 was increased. In this study of hexachlorobenzene-induced liver damage there was no difference in the time course of the development of porphyria and that of lipid peroxidation.