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Biomedical subjects

M Christensen

Publications and source records attributed to M Christensen.

At least 55 records · Page 3Linked to original sources
PubMed1999

ATP dependence of the ICl,swell channel varies with rate of cell swelling. Evidence for two modes of channel activation.

Swelling-induced activation of the outwardly rectifying anion current, ICl, swell, is modulated by intracellular ATP. The mechanisms by which ATP controls channel activation, however, are unknown. Whole cell patch clamp was employed to begin addressing this issue. Endogenous ATP production was inhibited by dialyzing N1E115 neuroblastoma cells for 4-5 min with solutions containing (microM): 40 oligomycin, 5 iodoacetate, and 20 rotenone. The effect of ATP on current activation was observed in the absence of intracellular Mg2+, in cells exposed to extracellular metabolic inhibitors for 25-35 min followed by intracellular dialysis with oligomycin, iodoacetate, and rotenone, after substitution of ATP with the nonhydrolyzable analogue AMP-PNP, and in the presence of AMP-PNP and alkaline phosphatase to dephosphorylate intracellular proteins. These results demonstrate that the ATP dependence of the channel requires ATP binding rather than hydrolysis and/or phosphorylation reactions. When cells were swollen at 15-55%/min in the absence of intracellular ATP, current activation was slow (0.3-0.8 pA/pF per min). ATP concentration increased the rate of current activation up to maximal values of 4-6 pA/pF per min, but had no effect on the sensitivity of the channel to cell swelling. Rate of current activation was a saturable, hyperbolic function of ATP concentration. The EC50 for ATP varied inversely with the rate of cell swelling. Activation of current was rapid (4-6 pA/pF per min) in the absence of ATP when cells were swollen at rates >/=65%/min. Intracellular ATP concentration had no effect on current activation induced by high rates of swelling. Current activation was transient when endogenous ATP was dialyzed out of the cytoplasm of cells swollen at 15%/min. Rundown of the current was reversed by increasing the rate of swelling to 65%/min. These results indicate that the channel and/or associated regulatory proteins are capable of sensing the rate of cell volume increase. We suggest that channel activation occurs via ATP-dependent and -independent mechanisms. Increasing the rate of cell swelling appears to increase the proportion of channels activating via the ATP-independent pathway. These findings have important physiological implications for understanding ICl, swell regulation, the mechanisms by which cells sense volume changes, and volume homeostasis under conditions where cell metabolism is compromised.

Adenosine Triphosphate↗
PubMed1998

[Information to young people about HIV/AIDS and drug abuse. A study of the knowledge and use of the information material in the youth center in Copenhagen].

A mailed questionnaire was carried out in the city of Copenhagen in which the leaders of 106 youth centres expressed their opinion on different publications concerning drug abuse and HIV/AIDS. The knowledge of the publications among the leaders was less than expected. The last known publication was recognized by 7% of the leaders, the most well known by 55%. A considerable part of the leaders stated that they had never received the publications. In centres where the leaders knew of the publications they were widely used, most often in centres for older members. A group of leaders stated, that the publications were irrelevant for members aged 9-14 years. The study points out specific problems in the health educations process: The publication should aim more specifically at the group and at subpopulations in the group. The distribution should be secured and the knowledge of the supply of health education material among the leaders of the youth centres should be raised.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Pronounced microsatellite instability in transitional cell carcinomas from young patients with bladder cancer.

Microsatellites may show loss of heterozygosity as well as instability of the repeats. We examined 22 different microsatellites in 14 bladder tumours (7 grade II non-invasive, 7 grade III/IV invasive) and found altered CA repeat length compared with leukocytes, indicating instability, in several microsatellites in all tumours. Instability was significantly more frequent in low stage tumours compared with high stage tumours. The number of new bands occuring was also significantly higher in low stage tumours (median 7.2) compared with high stage tumours (median 3.3). Furthermore, patients with a disease course > or = 1 year had significantly more unstable microsatellites (10.83) than those with a disease course < 1 year (mean 8.88). Examination of biopsies from normal bladder mucosa showed no instability. In 2 cases in which selected site biopsies were taken, alterations differed from the tumours, pointing at a different clonal development. LOH was most frequent in 9p markers in low stage tumours. In a group of markers located at 2p, 17p (p53), 9q, 5q and 10p, LOH was significantly more frequent in high stage tumours. Microsatellites placed at MSH2 and MLH1 loci showed LOH in several cases, indicating that the profound microsatellite instability could partly be an effect of damage to these genes.

Adult↗
PubMed1998

Hex1: a new human Rad2 nuclease family member with homology to yeast exonuclease 1.

Nucleolytic processing of chromosomal DNA is required in operations such as DNA repair, recombination and replication. We have identified a human gene, named HEX1 forhumanexonuclease 1, by searching the EST database for cDNAs that encode a homolog to the Saccharomyces cerevisiae EXO1 gene product. Based on its homology to this and other DNA repair proteins of the Rad2 family, most notably Schizosaccharomyces pombe exonuclease 1 (Exo1), Hex1 presumably functions as a nuclease in aspects of recombination or mismatch repair. Similar to the yeast proteins, recombinant Hex1 exhibits a 5'-->3' exonuclease activity. Northern blot analysis revealed that HEX1 expression is highest in fetal liver and adult bone marrow, suggesting that the encoded protein may operate prominently in processes specific to hemopoietic stem cell development. HEX1 gene equivalents were found in all vertebrates examined. The human gene includes 14 exons and 13 introns that span approximately 42 kb of genomic DNA and maps to the chromosomal position 1q42-43, a region lost in some cases of acute leukemia and in several solid tumors.

Amino Acid Sequence↗
PubMed1998

[Carcinoid tumors of the colon and rectum].

The article gives a review of the literature concerning carcinoid tumours of the colon and rectum. Carcinoid tumours of the rectum are more common than of the colon, although these tumours are rarities. The carcinoid tumour grows slowly and the patients can survive for years with the disease. Treatment of the rectal carcinoid depends on the size and invasiveness of the primary tumour, as a non-invasive tumour less than 2 cm in diameter can be locally excised. For carcinoids of the colon, the treatment of tumours of less than 2 cm and without invasion will be local excision. For larger and/or invasive tumours in both colon and rectum the treatment is resection. The prognosis for colonic carcinoids is worse than for rectal carcinoids. Adjuvant treatment forms are briefly described. Follow-up programmes for these patients are generally long (over five years) and include recto-/colonoscopy, and search for metastatic spread.

Carcinoid Tumor↗
PubMed1998

[Influenza vaccination of the elderly in the municipality of Copenhagen].

In October/November 1996 all people living in the city of Copenhagen aged 70 and above were invited to receive an influenza vaccination. Of a total of 62,600 people, 35,423 were vaccinated which is a participation rate of 56%. The participation rate increased with increasing age and in the older age groups the participation rate was 80%. The vaccinations were performed by nurses and most of the participants were vaccinated in special clinics (74.9%). Immobile participants were vaccinated either in their own homes (14.3%), in nursing homes (9.2%), or in hospitals (1.6%). One single case of hospitalisation of a chronically ill patient was registered, because of a weak influenza. No other side effects were registered. The total cost of all vaccinations was 4 million dkr. which is 115 dkr. (approximately 10 Pounds sterling) for each vaccination.

Aged↗
PubMed1998

The role of taurine in infant nutrition.

The importance of taurine in the diet of pre-term and term infants has not always been clearly understood and is a topic of interest to students of infant nutrition. Recent evidence indicates that it should be considered one of the "conditionally essential" amino acids in infant nutrition. Plasma values for taurine will fall if infants are fed a taurine-free formula or do not have taurine provided in the TPN solution. Urine taurine values also fall, which is indicative of an attempt by the kidney to conserve taurine. The very-low-birth-weight infant, for a variety of reasons involving the maturation of tubular transport function, cannot maximally conserve taurine by enhancing renal reabsorption and, hence, is potentially at greater risk for taurine depletion than larger pre-term or term infants, and certainly more than older children who have taurine in their diet. Taurine has an important role in fat absorption in pre-term and possibly term infants and in children with cystic fibrosis. Because taurine-conjugated bile acids are better emulsifiers of fat than glycine-conjugated bile acids, the dietary (or TPN) intake has a direct influence on absorption of lipids. Taurine supplementation of formulas or TPN solutions could potentially serve to minimize the brain phospholipid fatty acid composition differences between formula-fed and human milk-fed infants. Taurine appears to have a role in infants, children, and even adults receiving most (> 75%) of their calories from TPN solutions in the prevention of granulation of the retina and electroencephalographic changes. Taurine has also been reported to improve maturation of auditory-evoked responses in pre-term infants, although this point is not fully established. Clearly, taurine is an important osmolyte in the brain and the renal medulla. At these locations, it is a primary factor in the cell volume regulatory process, in which brain or renal cells swell or shrink in response to osmolar changes, but return to their previous volume according to the uptake or release of taurine. While there is a dearth of clinical studies in man concerning this volume regulatory response, studies in cats, rats, and dog kidney cells indicate the protective role of taurine in hyperosmolar stress. The infant depleted of taurine may not be able to respond to hyper- or hyponatremic stress without massive changes in neuronal volume, which has obvious clinical significance. The fact that the brain content of taurine is very high at birth and falls with maturation may be a protective feature, or compensation for renal immaturity Defining an amino acid as "conditionally essential" requires that deficiency result in a clinical consequence or consequences which can be reversed by supplementation. In pre-term and term infants, taurine insufficiency results in impaired fat absorption, bile acid secretion, retinal function, and hepatic function, all of which can be reversed by taurine supplementation. Therefore, this small beta-amino acid, taurine, is indeed conditionally essential.

Animals↗
PubMed1998

Salivary gland carcinomas: prognostic significance of simple mucin-type carbohydrate antigens.

The prognosis of salivary gland carcinomas is difficult to assess. Simple mucin-type carbohydrates (T and sialosyl-T antigens, Tn and sialosyl-Tn antigens) have been shown to be of value in predicting prognosis for carcinomas in other locations. We studied the prognostic significance of the expression of these structures in a retrospective study of 133 patients with salivary gland carcinomas, using immunohistochemistry and a panel of well-defined monoclonal antibodies (MAbs) on formalin-fixed paraffin-embedded tissues. Sialosyl-Tn, T and sialosyl-T antigens were not correlated with prognosis. Univariate analyses showed no overall difference in survival or locoregional control between patients with Tn-positive and patients with Tn-negative tumours, but indicated that expression of the Tn antigen was associated with early locoregional recurrences and deaths. Tn was, however, not an independent prognostic factor by multivariate regression analysis.

Adult↗
PubMed1998

Hypoxaemia and myocardial ischaemia during colonoscopy.

BACKGROUND: Myocardial ischaemia (defined as ST-segment deviation on electrocardiogram (ECG)) may occur during colonoscopy, but the pathogenic mechanisms are unknown. We have evaluated the occurrence of arterial hypoxaemia, tachycardia, and myocardial ischaemia during routine colonoscopy. METHODS: Eighteen patients underwent colonoscopy under conscious sedation and without supplementary oxygen. Arterial oxygen saturation was measured by continuous pulse oximetry, and ECG was monitored continuously with a Holter tape recorder during the procedure. RESULTS: Arterial oxygen desaturation and tachycardia were common during colonoscopy and occurred in 45% and 35% of patients, respectively. Two patients developed signs of myocardial ischaemia during the colonoscopy: one case of ST depression (1.7 mV) and one case of ST elevation (4.3 mV). In both patients the ST deviation disappeared when the colonoscope was retracted. Myocardial ischaemia occurred in both patients simultaneously with tachycardia, and in one of these arterial hypoxaemia was also present. CONCLUSIONS: Myocardial ischaemia occurs during routine colonoscopy, but with a lower incidence than previously reported during upper endoscopy. Myocardial ischaemia during colonoscopy may be associated with tachycardia and/or hypoxaemia. Further studies should clarify the relative role of tachycardia, hypoxaemia, and viscerocardiac reflexes in the pathogenesis of myocardial ischaemia during colonoscopy.

Adult↗
PubMed1998

Salivary gland carcinomas--prognostic factors.

A retrospective study of factors of prognostic significance for clinical course and survival was performed using uni- and multivariate analyses in 251 patients with primary salivary gland carcinoma admitted during the period 1958-1992. Univariate analyses indicated that site of primary tumour, histology, clinical stage, presence of node metastases at primary diagnosis, and status of surgical margins were important prognostic factors for cause-specific survival, locoregional control and distant metastases. Multivariate analyses confirmed that histology was important for both locoregional control and cause-specific survival, whereas primary site was only of importance for locoregional control. Presence of node metastases at diagnosis was more important for locoregional control than clinical stage, whereas clinical stage was the most important factor for cause-specific survival. Status of surgical margins was of major importance for both cause-specific survival and locoregional control. Radiotherapy in addition to surgery improved locoregional control only, whereas survival was not affected.

Adolescent↗
PubMed1998

Assessment of adherence with multiple informants in pre-adolescents with spina bifida: initial development of a multidimensional, multitask parent-report questionnaire.

Adherence to medical regimens was assessed in 67 pre-adolescents with spina bifida (8- and 9-year-olds; 37 boys, 30 girls), with mother, father, teacher, and health professional report. The Parent-Report of Medical Adherence in Spina Bifida Scale (PROMASB) was developed and includes multidimensional scales for the following tasks: catheterization, bowel care, skin care, medication, and ambulation. With few exceptions, the PROMASB has adequate psychometric properties. However, findings revealed modest to low correlations between respondents. Mothers and fathers reported significantly more noncompliance than teachers and health professionals. For the most part, all informants reported that most children were compliant across all tasks. Additional analyses based on qualitative data suggest that parents attribute compliance difficulties to motivational as well as attentional-memory factors.

Attention↗
PubMed1998

Characterisation of a novel AGE-compound derived from lysine and 3-deoxyglucosone.

Dicarbonyl compounds are supposed to be reactive intermediates in the non-enzymatic glycation of proteins. A process that eventually could lead to the development of late diabetic complications. Glyoxal lysine dimer (GOLD) and methylglyoxal lysine dimer (MOLD) have previously been described as such reactive dicarbonyls. Here a new compound 3-deoxyglucosone lysine dimer (DOLD), a cross-link resulting from the reaction between hippuryl-lysine and 3-deoxyglucosone, has been isolated by HPLC and the structure determined by mass spectrometry and NMR.

Chromatography, High Pressure Liquid↗
PubMed1997

Identification of a novel human RAD51 homolog, RAD51B.

The highly conserved Saccharomyces cerevisiae RAD51 protein functions in both mitotic and meiotic homologous recombination and in double-strand break repair. Screening of the public cDNA sequence database for RAD51-like genes led to the identification of a partial sequence from a breast tissue library present in the I.M.A.G.E. (Integrated Molecular Analysis of Genes and their Expression) collection. An extended 1764-bp cDNA clone encoding an open reading frame of 350 amino acids was isolated. This clone showed significant amino acid identity with other human RAD51 homologs. The new homolog, named RAD51B, was mapped to human chromosome 14q23-q24.2 using a panel of human-hamster somatic cell hybrids and fluorescence in situ hybridization. Northern blot analysis demonstrated that RAD51B mRNA is widely expressed and most abundant in tissues active in recombination. Functions associated with known RAD51 homologs suggest a role for RAD51B in meiotic recombination and/or recombinational repair.

Amino Acid Sequence↗