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Biomedical subjects

K Henriksen

Publications and source records attributed to K Henriksen.

At least 37 records · Page 2Linked to original sources
PubMed1997

Oxidation and assimilation of atmospheric methane by soil methane oxidizers.

The metabolism of atmospheric methane in a forest soil was studied by radiotracer techniques. Maximum (sup14)CH(inf4) oxidation (163.5 pmol of C cm(sup-3) h(sup-1)) and (sup14)C assimilation (50.3 pmol of C cm(sup-3) h(sup-1)) occurred at the A(inf2) horizon located 15 to 18 cm below the soil surface. At this depth, 31 to 43% of the atmospheric methane oxidized was assimilated into microbial biomass; the remaining methane was recovered as (sup14)CO(inf2). Methane-derived carbon was incorporated into all major cell macromolecules by the soil microorganisms (50% as proteins, 19% as nucleic acids and polysaccharides, and 5% as lipids). The percentage of methane assimilated (carbon conversion efficiency) remained constant at temperatures between 5 and 20(deg)C, followed by a decrease at 30(deg)C. The carbon conversion efficiency did not increase at methane concentrations between 1.7 and 1,000 ppm. In contrast, the overall methane oxidation activity increased at elevated methane concentrations, with an apparent K(infm) of 21 ppm (31 nM CH(inf4)) and a V(infmax) of 188 pmol of CH(inf4) cm(sup-3) h(sup-1). Methane oxidizers from soil depths with maximum methanotrophic activity respired approximately 1 to 3% of the assimilated methane-derived carbon per day. This apparent endogenous respiration did not change significantly in the absence of methane. Similarly, the potential for oxidation of atmospheric methane was relatively insensitive to methane starvation. Soil samples from depths above and below the zone with maximum atmospheric methane oxidation activity showed a dramatic increase in the turnover of the methane assimilated (>20 times increase). Physical disturbance such as sieving or mixing of soil samples decreased methane oxidation and assimilation by 50 to 58% but did not alter the carbon conversion efficiency. Ammonia addition (0.1 or 1.0 (mu)mol g [fresh weight](sup-1)) decreased both methane oxidation and carbon conversion efficiency. This resulted in a dramatic decrease in methane assimilation (85 to 99%). In addition, ammonia-treated soil showed up to 10 times greater turnover of the assimilated methane-derived carbon (relative to untreated soil). The results suggest a potential for microbial growth on atmospheric methane. However, growth was regulated strongly by soil parameters other than the methane concentration. The pattern observed for metabolism of atmospheric methane in soils was not consistent with the physiology of known methanotrophic bacteria.

Journal Article↗
PubMed1996

Lipopolysaccharide induced apoptosis of rat pancreatic acinar cells.

BACKGROUND: Bacterial lipopolysaccharide (LPS) has been proposed to participate in the pathogenesis of pancreatic inflammatory disease. AIMS: This study investigated the role of endotoxaemia in the pathogenesis of pancreatic acinar cell injury. METHODS: Sixty eight male Spraque-Dawley rats were used in the study. Escherichia coli LPS (5 mg/kg) was injected into the peritoneal cavity of the rats. The concentration of pancreatic phospholipase A2 (PLA2) in plasma was measured and pancreatic tissue examined by histology, in situ detection of free DNA 3'-ends, and electrophoretic DNA analysis. RESULTS: The concentration of pancreatic PLA2 increased in plasma and the catalytic activity of PLA2 increased in pancreatic tissue after an LPS injection. Apoptosis in pancreatic acinar cells and fragmentation of DNA typical of apoptosis in pancreatic tissue was seen 24 hours after an LPS injection. Pancreatic acinar atrophy was seen 72 hours after the LPS injection. CONCLUSIONS: These data show that LPS causes release of pancreatic PLA2 into blood plasma, activation of PLA2 in pancreatic tissue, and apoptosis of acinar cells.

Animals↗
PubMed1991

Molecular basis of phenotypic heterogeneity in phenylketonuria.

BACKGROUND: Phenylketonuria is a metabolic disorder that results from a deficiency of the hepatic enzyme phenylalanine hydroxylase. Its clinical phenotype varies widely, and to date more than 10 mutations in the phenylalanine hydroxylase gene have been identified in persons with the disorder. We attempted to relate the clinical phenotype of patients to their genotype. METHODS: We studied 258 patients with phenylketonuria from Denmark and Germany for the presence of eight mutations previously found in patients from these countries. The in vitro activity of the enzymes associated with these mutations was determined by expression analysis in heterologous mammalian cells. The level of activity was then used to predict the in vivo level of phenylalanine hydroxylase activity in patients with various combinations of mutant phenylalanine hydroxylase alleles. RESULTS: The eight mutations involved 64 percent of all mutant phenylalanine hydroxylase alleles in the patients. Expression analysis showed that these mutant enzymes produced from 0 to 50 percent of normal enzyme activity. The predicted level of phenylalanine hydroxylase activity correlated strongly with the pretreatment serum level of phenylalanine (r = 0.91, P less than 0.001 in the Danish patients and r = 0.74, P less than 0.001 in the German patients), phenylalanine tolerance in the Danish patients (r = 0.84, P less than 0.001), and the serum phenylalanine level measured after standardized oral protein loading in the German patients (r = 0.84, P less than 0.001). CONCLUSIONS: Our results strongly support the hypothesis that there is a molecular basis for phenotypic heterogeneity in phenylketonuria. The establishment of genotype will therefore aid in the prediction of biochemical and clinical phenotypes in patients with this disease.

Alleles↗
PubMed1989

[Methods of disinfection of water systems in dental units by water chlorination].

The aim of the present study was to develop a simple disinfection method to reduce the content of bacteria in the water system of dental units to an acceptable level. The study was carried out at the Royal Dental College, Copenhagen on 250 dental units. Samples of the cooling water to the ultrasonic scalers and of the water to the water glasses were obtained from eight different units representing different parts of the school. Disinfection of the water system was carried out by addition of chlorine to the pipe water near the main water intake to the institution. The chlorination af the water was automatically regulated, and the installation was so flexible that the concentration of chlorine and the time and frequency of the chlorination could be varied. Different modes of dosage of chlorine were examined. Before chlorination the bacterial content in the water system of the units was about 10(4)-10(5) c.f.u./ml. It was found that an intermittent chlorination with 0.5-1 ppm chlorine for 10 min. every day could normally reduce the bacterial counts in the water system to about a few hundreds per ml.

Chlorine↗
PubMed1989

Ultraviolet radiation at high latitudes and the risk of skin cancer.

Solar irradiance in the spectral region 280 to 800 nm was measured with a double monochromator at 2 locations in Norway, Tromsø (69.7 degrees N) and Longyearbyen (78.2 degrees N). During the observational (midnight sun) period in Longyearbyen, the maximum UVB irradiance recorded was less than 0.3 W/m2, and no radiation was detected for wavelengths below 300 nm. Such low levels are believed to be a consequence of the low solar elevation angle and the high ozone content of the Arctic ozone layer, which absorbs the incident UV light. With levels between 280 and 350 DU over the period of study, Tromsø and Longyearbyen recorded only one-ninth of the calculated UVB radiation at the equator. There is therefore a considerably higher risk of radiation damage to the skin in equatorial regions (controlling for skin type), a finding that agrees with the statistical evidence for a 7-8 times higher rate of skin cancer in the white population of equatorial countries.

Absorption↗
PubMed1988

Methods of disinfection of the water system of dental units by water chlorination.

The aim of the present study was to develop a simple disinfection method for reducing the content of bacteria in the water system of dental units to an acceptable level. The study was carried out at the Royal Dental College, Copenhagen, on 250 dental units. Samples of the cooling water supplying the ultrasonic scalers and of the water supplying the water glasses were obtained from eight different units representing different parts of the school. Disinfection of the water system was carried out by addition of chlorine to the pipe water near the institution's main water intake. The chlorination of the water was automatically regulated, and the installation was so flexible that the concentration of chlorine and the time and frequency of the chlorination could be varied. Different modes of chlorine dosage were examined. Before chlorination, the bacterial content in the water system of the units was about 10(4)-10(5) cfu/mL. It was found that an intermittent chlorination with 0.5-1 ppm chlorine for 10 minutes every day could reduce the normal bacterial counts in the water system to about a few hundred per mL.

Chlorine↗
PubMed1978

Urinary excretion of basement membrane antigen in normal persons and patients with febrile proteinuria--quantitated by means of rocket immunoelectrophoresis.

The urinary excretion of a glomerular basement membrane-like antigen was quantitated in 19 adult normal subjects and in 15 patients with febrile proteinuria by means of rocket immunoelectrophoresis. In the normal persons the excretion averaged 59 (S.D.8.9) U/24 hours' creatinine clearance. An increased excretion was demonstrated in 80% of the patients. There was a significant relation between the urinary excretions of albumin and protein in the patients with febrile proteinuria. The basement membrane antigen was also demonstrated in normal human serum, liver and placenta. No unusual basement membrane antigen could be demonstrated in the urine from patients with febrile proteinuria.

Adolescent↗
PubMed1975

Immunological characterization of human glomerular basement membrane antigens.

Normal human glomerular basement membrane (H-GBM) was solubilized by collagenase and subjected to crossed immunoelectrophoresis with rabbit antibodies against H-GBM. Seven precipitates appeared with the mobility of alpha, beta, and gamma globulins. Only two of these precipitates might be specific for GBM, since the other precipitates disappeared after absorption of the antiserum with liver and placenta. In normal human urine one precipitate, cross-reacting with one of the H-GBM precipitates, was found; this precipitate could also be demonstrated in human placenta and liver.

Antibodies↗