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Biomedical subjects

S Helland

Publications and source records attributed to S Helland.

33 records · Page 2Linked to original sources
PubMed1983

Neurotoxicity of deoxycoformycin: effect of constant infusion on adenosine deaminase, adenosine, 2'-deoxyadenosine and monoamines in the mouse brain.

The tight-binding adenosine deaminase inhibitor, 2'-deoxycoformycin (dCF), was continuously infused into mice by intraperitoneal implantation of microosmotic pumps delivering the compound at a rate of 0.16 mg hr-1 kg-1 for up to 6 days. The activity of cerebral adenosine deaminase was nearly totally inhibited. The amount of adenosine and 2'-deoxyadenosine was determined in the brain frozen in liquid nitrogen through the intact skull bone. The concentration of adenosine was about 1 nmol/g, and was essentially not altered following treatment with deoxycoformycin. Deoxycoformycin induced a progressive increase in cerebral content of 2'-deoxyadenosine, which after 1 day of treatment equalled the amount of adenosine. The concentrations of serotonin, dopamine and noradrenaline in the brain were not altered.

Adenosine↗
PubMed1983

Contact dermatitis to Synthaderm.

Allergic contact dermatitis is described in 2 patients treated with Synthaderm, a polyurethane covering for leg ulcers. One of the patients was patch tested with 3 extractions made from Synthaderm as well as with 5 isocyanate compounds. Her patch tests were negative to both extractions and isocyanates, but positive to Synthaderm samples with different batch numbers and years of production.

Aged↗
PubMed1983

Hearing threshold level and middle ear pressure in children with phonetic/phonemic disability.

Middle ear disease and hearing loss of moderate degree is a factor which alone or in combination with others, have been suggested to create phonetic/phonemic disability. The aim of the present investigation was to throw light upon this question. Twentytwo children with phonetic/phonemic disability, 19 boys and 3 girls, age 4.5-6.5 years, were examined. Twentytwo normal speaking children served as a control group. Oto-rhinolaryngological examination, tympanometry and hearing threshold measurements were performed. Abnormal middle ear pressure (less than -50 mm H2O) in one or both ears, and statistical significant elevated hearing threshold levels for pure tones (p less than 0.05) were found in 15 of the 22 children with phonetic/phonemic disability. Upper respiratory tract diseases, which may cause middle ear dysfunction, were supposed to be the etiology in most cases. Consequently, in all children with phonetic/phonemic disability, careful examination including tympanometry and accurate measurements of hearing threshold levels should be performed.

Auditory Threshold↗
PubMed1983

Effect of 2'-deoxycoformycin infusion on S-adenosylhomocysteine hydrolase and the amount of S-adenosylhomocysteine and related compounds in tissues of mice.

Mice were given constant infusions of the adenosine deaminase inhibitor, 2'-deoxycoformycin, by i.p. implantation of microosmotic pumps, delivering the compound at a rate of 0.16 mg hr-1 kg-1. In accordance with published data, we observed that adenosine deaminase in most tissues was nearly completely inhibited. In addition, the S-adenosylhomocysteine hydrolase activity decreased slowly and showed a half-life in liver of about 4 hr. The rate and extent of the inactivation were highest in spleen. The amounts of adenosine, 2'-deoxyadenosine, S-adenosylhomocysteine, and S-adenosylmethionine were determined in treated animals and control animals. The tissue levels of adenosine and, to a lesser degree, S-adenosylhomocysteine and S-adenosylmethionine were critically dependent on the procedure used for processing the tissues. Lowest concentrations were observed when the organs were frozen in situ by liquid nitrogen. Treatment with 2'-deoxycoformycin induced no or a moderate increase in tissue content of adenosine and S-adenosylhomocysteine, whereas the amount of 2'-deoxyadenosine increased markedly, especially in spleen and thymus. 2'-Deoxycoformycin treatment caused an increase in adenosine and 2'-deoxyadenosine, but not S-adenosylhomocysteine, in serum of mice.

Adenosine↗
PubMed1983

S-adenosylhomocysteine and S-adenosylhomocysteine hydrolase in various tissues of mice given injections of 9-beta-D-arabinofuranosyladenine.

The S-adenosylhomocysteine (AdoHcy) hydrolase (EC 3.3.1.1) activity and the metabolism of AdoHcy were investigated in various tissues of mice given a single injection or repetitive injections of 9-beta-D-arabinofuranosyladenine (ara-A) with and without the adenosine deaminase inhibitor, 2'-deoxycoformycin (dCF). A single injection of ara-A (50 mg/kg) rapidly inactivated AdoHcy hydrolase in several organs (liver, kidney, spleen, lung, heart, skeletal muscle, and brain). Then, the enzyme activity in these tissues gradually recovered. This process, termed reactivation of AdoHcy hydrolase, was not sensitive to cycloheximide but was partly inhibited by dCF. In the absence of dCF, nearly no increase in AdoHcy content in the tissues was observed, whereas a single injection of ara-A plus dCF induced a small, transient increase in AdoHcy content of most tissues. Repetitive injections of ara-A (without dCF) caused a moderate increase in the AdoHcy level of tissues, whereas repetitive injections of the drug combination ara-A plus dCF resulted in a massive accumulation of AdoHcy in liver and kidney and, to a lesser degree, in other tissues. A moderate increase in S-adenosyl-L-methionine was observed in some tissues. These metabolic effects were associated with a rapid inactivation of AdoHcy hydrolase, but a fraction of the enzyme activity (about 8% in liver) was not or only slowly inactivated. AdoHcy accumulated in serum of mice receiving this treatment. Treatment of mice with dCF alone for up to 10 hr induced no increase in AdoHcy content of the tissues.

Adenosylhomocysteinase↗
PubMed1982

Reactivation of S-adenosylhomocysteine hydrolase activity in cells exposed to 9-beta-D-arabinofuranosyladenine.

9-beta-D-Arabinofuranosyladenine (ara-A) inactivates isolated S-adenosyl-L-homocysteine (AdoHcy) hydrolase (EC 3.3.1.1) as well as AdoHcy hydrolase in intact cells. Whereas the inactivation in cell-free systems is an irreversible process, the AdoHcy hydrolase activity in rat hepatocytes exposed to ara-A gradually recovered upon prolonged incubation of the cells in a medium devoid of ara-A. This process, tentatively termed reactivation of the enzyme, was nearly totally dependent on a high level of adenosine deaminase in the extracellular medium, which induced a decrease in intracellular content of adenosine as well as ara-A. Reactivation of intracellular enzyme was inhibited by adenosine deaminase inhibitors [2'-deoxycoformycin and erythro-9-(2-hydroxy-3-nonyl)adenine] and the synthetic substrate for AdoHcy hydrolase, 3-deazaadenosine. An inhibitor of protein synthesis (cycloheximide) was without effect. Homocysteine, which protected the intracellular AdoHcy hydrolase against inactivation by ara-A, induced no reactivation of the enzyme. The half-life of the intracellular ara-A-AdoHcy hydrolase complex was about 90 min and was not affected by adenosine deaminase, 3-deazaadenosine, or homocysteine added to the cell suspension. However, the rate of elimination of the complex in the hepatocytes exceeded the rate of reactivation of AdoHcy hydrolase. Thus, the elimination process accounted for the reactivation, but not correlation between these two processes was observed. Reactivation of intracellular AdoHcy hydrolase caused a pronounced fall in cellular content of AdoHcy. The possibility that reduced cellular level of AdoHcy induced the reactivation of AdoHcy hydrolase seemed unlikely. This statement was based on the observation that reactivation was observed also under conditions of high concentrations of AdoHcy (obtained by the addition of homocysteine to the cell suspension). Reactivation of AdoHcy hydrolase with a concomitant decrease in cellular level of AdoHcy could also be demonstrated with mouse plasmacytoma (MPC-11) cells and mouse fibroblasts (L-929) exposed to ara-A, but the reactivation process was far less pronounced than with hepatocytes.

Adenosine Deaminase↗
PubMed1982

Inactivation of S-adenosylhomocysteine hydrolase by 9-beta-D-arabinofuranosyladenine in intact cells.

The inactivation of S-adenosylhomocysteine (AdoHcy) hydrolase (EC 3.3.1.1) in isolated rat hepatocytes by 9-beta-D-arabinofuranosyladenine (ara-A) was associated with tight binding of ara-A to the enzyme and showed an initial phase obeying first-order kinetics characterized by Ki (concentration of half-maximal rate of inactivation) of 12 microM for ara-A and a maximal rate of inactivation of 0.7 min-1. Two to 3% of the enzyme in rat hepatocytes was not available for inactivation. Similar results were obtained with some cultured cells, including mouse plasmacytoma cells (MPC-11), mouse fibroblasts (L-929), and human chronic myelogenic leukemia cells (K-562). In a cellular medium devoid of adenosine deaminase, inhibitors of this enzyme did not affect the inactivation process in rat hepatocytes and only slightly enhanced this process in the cultured cells (at low concentrations of ara-A). Inactivation of AdoHcy hydrolase in rat hepatocytes was associated with a massive build-up of AdoHcy (from 75 to 5200 pmol/10(6) cells after 3 hr of incubation) and a moderate increase in cellular S-adenosylmethionine. The accumulation of AdoHcy in the cultured cells exposed to ara-A was less pronounced and no increase in cellular S-adenosylmethionine was observed. There was a quantitatively important export of AdoHcy from the rat hepatocytes and the cultured cells into the extracellular medium, whereas no leakage of S-adenosylmethionine was detected. The inactivation of AdoHcy hydrolase by ara-A in rat hepatocytes was inhibited in the presence of adenosine or homocysteine in the cellular medium. This effect of homocysteine correlated with increased cellular level of AdoHcy induced by this agent but was also associated with reduction in cellular uptake of ara-A.

Adenosylhomocysteinase↗
PubMed1981

Interaction of 9-beta-D-arabinofuranosyladenine, 9-beta-D-arabinofuranosyladenine 5'-monophosphate, and 9-beta-D-arabinofuranosyladenine 5'-triphosphate with S-adenosylhomocysteinase.

9-beta-D-Arabinofuranosyladenine (ara-A), 9-beta-D-arabinofuranosyladenine 5'-monophosphate, and 9-beta-D-arabinofuranosyladenine 5'-triphosphate competitively inhibit both the synthesis and hydrolysis of S-adenosylhomocysteine catalyzed by S-adenosylhomocysteinase [S-adenosylhomocysteine hydrolase (EC 3.3.1.1)] from mouse liver, and the inhibitor constants were 5.0 X 10(-6), 1.1 X 10(-4), and 1.0 X 10(-3) M, respectively. A time-dependent inactivation of the enzyme was observed when the enzyme was preincubation with ara-A, 9-beta-D-arabinofuranosyladenine 5'-monophosphate, or 9-beta-D-arabinofuranosyladenine 5'-triphosphate. ara-A was the most potent inactivator. The inactivation with ara-A was less pronounced in the presence of adenosine, S-adenosylhomocysteine, adenine, adenosine 5'-monophosphate, or adenosine 5'-diphosphate, showed first-order kinetics, saturability, and irreversibility. The rate of inactivation was half-maximal at 5 X 10(-6) M ara-A, and the rate constant of inactivation was 0.43 min-1 at saturating concentrations of ara-A. ara-A was tightly but not covalently bound to the enzyme. ara-A bound to the enzyme was not available for deamination to 9-beta-D-arabinofuranosylhypoxanthine catalyzed by the enzyme adenosine deaminase.

Adenosylhomocysteinase↗
PubMed1981

The relation between the functions of 9-beta-D-arabinofuranosyladenine as inactivator and substrate of S-adenosylhomocysteine hydrolase.

9-beta-D-Arabinofuranosyladenine (ara-A) was converted to adenine in the presence of S-adenosylhomocysteine hydrolase (EC 3.3.1.1.) and to adenine and S-[5'-(9-arabinofuranosyladenyl)]-L-homocysteine (ara-AHcy) when the incubation mixture contained L-homocysteine. The formation of adenine proceeded until 3.3 mol of adenine was formed per mol of enzyme, and at this point the enzyme was totally inactivated. In the presence of homocysteine, the rate of ara-AHcy formation was about half the rate of adenine formation. The association of the conversion of ara-A to adenine with the inactivation process was further demonstrated by the kinetics of these processes and by the observation that in the presence of homocysteine both inactivation of the enzyme and formation of adenine were reduced by 30%, i.e. by a factor corresponding to the synthesis of ara-AHcy. Inactivation of the enzyme was associated with reduction of enzyme bound NAD+. Adenine or the substance liberating adenine was tightly bound to the enzyme, whereas ara-AHcy was dissociable. These data suggest that inactivation, adenine formation and reduction of NAD+ result from an abortive catalytic cycle, whereas enzyme entering a complete catalytic cycle leading to formation of ara-AHcy is not inactivated. The fact that the inactivation and the enzyme catalysis occur simultaneously at about equal rates offers an opportunity to demonstrate the competing relationship between these two processes.

Adenine↗
PubMed1979

Functional studies in patients with the glucagonoma syndrome.

Four patients with glucagon-producing tumours of the pancreas were investigated. Fasting plasma glucagon concentrations ranged from 209--625 pmol/l. Plasma insulin concentrations were normal except in one patient, where the tumour also produced insulin (558 pmol/l). Intravenous glucose (25 g/m2) depressed the glucagon concentration in two patients, while no change was noted in the others. Intravenous arginine stimulated glucagon secretion in three patients, but not in the fourth. Intravenous somatostatin suppressed glucagon secretion in all three patients investigated. All patients had abnormally low plasma levels of individual amino acids; glucogenic and branched-chain amino acids were equally depressed. Surgical removal of the tumours led to complete recovery from dermatosis and the glucagon levels were normalized. Postoperative tests were performed in three patients. The alpha-cell responsiveness to iv glucose was restored. Glucose tolerance (Kg-value) was improved in one patient (0.73 to 1.65), persistently low in one patient (0.75 to 0.72) and impaired in the third patient (1.35 to 1.09). It is concluded that none of these functional tests will be of diagnostic value in cases suspected of glucagonomas. The results also show that glucose homeostasis is remarkably unaffected by the extreme hyperglucagonaemia of these patients and that hypoaminoacidaemia is an important consequence of chronic hyperglucagonaemia.

Aged↗
PubMedDate not supplied

Coping with exacerbation in psoriasis and eczema prior to admission in a dermatological ward.

Chronic dermatologic diseases, such as psoriasis and eczema, may cause significant psycho-social problems and stress. Our objectives were to characterize how hospitalised patients coped with psoriasis and eczema, and to investigate the relationship between coping and quality of life. Data are based on survey forms completed upon admission to the dermatology ward from 212 patients with chronic dermatological diseases, 146 with psoriasis and 66 with eczema. 108 were men, average age 48 years. The Norwegian versions of the standardized survey questionnaires, Jalowiec Coping Scale and Dermatological Life Quality Index, were used to evaluate coping and quality of life. We found that optimism, belief-in-oneself and confrontational coping strategies were most frequently used. Long duration of the disease was correlated to the belief-in-oneself strategy, while short duration was related to supportive strategies. More frequent use of confrontational and optimistic modes was significantly related to better quality of life. More frequent use of emotional and evasive modes was significantly related to poorer quality of life. There was no significant difference between the psoriasis and eczema groups in terms of use of coping strategies, with exception of emotional strategies. Knowledge of coping strategies and quality of life among patients with chronic dermatological diseases is important for improvement in health services for these patients.

Adaptation, Psychological↗