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Biomedical subjects

L Mikkelsen

Publications and source records attributed to L Mikkelsen.

At least 19 recordsLinked to original sources
PubMed2000

Abiotrophia species in early dental plaque.

The most characteristic traits that distinguish Abiotrophia strains from other streptococci are nutrient requirements, satellitism and pyrrolidonyl arylamidase activity. The presence of Abiotrophia strains was studied in early dental plaque formed on sucrose-containing and sucrose-free (glucose-containing) diets. The isolates were from 0- to 3-day dental plaque formed on the buccal surface of a lower premolar in six subjects. Identification of Abiotrophia strains was based on their pyrrolidonyl arylamidase activity. They were among the predominant cultivable microorganisms isolated from diluted suspensions of early dental plaque formed on both diets. Using biochemical tests without testing for pyrrolidonyl arylamidase activity, the Abiotrophia strains would be biochemically identified as Streptococcus mitis or unidentified streptococci, and many isolates first classified as unidentified streptococci were Abiotrophia strains. Generally, identifications using partial 16S rRNA sequences confirmed the identifications obtained biochemically. However, Abiotrophia elegans and Gemella strains were biochemically identified as Abiotrophia adiacens. Abiotrophia strains produce hydrogen sulfide, which may influence the metabolism and ecology of dental plaque and act as a virulence factor in periodontal disease. They are not able to grow on tryptic soy agar. In the present study, some S. mitis strains were not able to grow on mitis salivarius agar, and some Abiotrophia strains were able to grow on this medium. These observations indicate that the use of these media for estimation of total viable counts and number of streptococci introduces systematic error in studies of microorganisms in dental plaque.

Aminopeptidases↗
PubMed1999

[Severe male infertility. Genetic investigation and counseling prior to intracytoplasmic sperm injection].

Intracytoplasmatic sperm injection (ICSI) has improved the success rate in treating severe male infertility. The method may now be used with sperm from the epididymis and testis. This article summarizes our knowledge on genetic factors affecting male gamete formation or function. Infertile men with severe impairment of spermatogenesis showed a higher than normal incidence of chromosomal abnormalities and 10-20% had microdeletion, in the Y-chromosome. About 75% of males with congenital bilateral absence of vas deferens (CBAVD) have mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. In conclusion, we recommend genetic counselling to all couples with a diagnosis of male infertility prior to ICSI. Men with severe oligozoospermia or non-obstructive azoospermia should have karyotype analysis performed and with establishment of diagnostic tools to reveal Y-chromosome deletions, this should be offered to the same group of men. Men with obstructive azoospermia and congenital albilateral absence of vas deferens as well as their wives should be screened for cystic fibrosis mutations.

Chromosome Aberrations↗
PubMed1998

[Lifet-threatening hemorrhage from a mandibular hemangioma].

A case of a nine year-old girl with a life-threatening episode of profuse bleeding after extraction of a loose deciduous molar is reported. An angiography confirmed the presence of a haemangioma in the right side of the mandible. The lesion was superselectively embolized. Two days later exploration of the haemangioma and resection of the bone was performed, and the bleeding stopped. Special concern must be exercised in cases with hypermobility of the teeth, and when episodes of spontaneous haemorrhage are encountered.

Female↗
PubMed1997

An overview of the population in Europe and North America.

This article is based on information from Trends in Europe, the statistical yearbook of the Economic Commission for Europe. It highlights some of the key population and health statistics for member countries, using the most recent data available--generally for 1995--collected from a wide range of national and international sources.

Adolescent↗
PubMed1996

[Use of restraints before and after the new psychiatric law].

The purpose of this research project was to examine, in retrospect, the effect of certain factors on the incidence of the use of restrains before and after the introduction of the Danish law reform concerning compulsory treatment. Data concerning the use of restraints on four locked wards in the Psychiatric Department of Glostrup Hospital during a six-month period in 1988 were compared with equivalent data from a six-month period in 1991. It was found that the law reform had no statistically significant influence on the incidence of the use of restraints. Factors such as high bed occupancy rate and shortage of staff did not lead to a higher incidence of use of restraint.

Commitment of Persons with Psychiatric Disorders↗
PubMed1996

Effect of sucrose intake on numbers of bacteria in plaque expressing extracellular carbohydrate metabolizing enzymes.

The effect of sucrose intake versus a sucrose-free diet (substituting glucose for sucrose) on numbers of isolates from early dental plaque expressing extracellular carbohydrate metabolizing enzymes was studied. The bacteria were isolated from 0- to 3-day-old dental plaque formed on the buccal surface of a lower premolar in 6 subjects. A total of 7,987 isolates were tested for the following activities: synthesis of glucan from sucrose, glucanase, fructanase, synthesis of polymers from glucose, and amylase. Sucrose intake was associated with relatively low numbers of isolates expressing the enzyme activities studied at the start of plaque formation and relatively high numbers in 2- and 3-day plaque. The enzyme activities studied are important elements in the pathophysiology of dental caries and may even be addressed as virulence factors.

Amylases↗
PubMed1994

Cytoprotective effect of tocopherols in hepatocytes cultured with polyunsaturated fatty acids.

When highly unsaturated fatty acids are added to cell cultures, it can become important to include antioxidants in the culture medium to prevent cytotoxic peroxidation. To find an optimal antioxidant for this purpose, the effect of 50 microM alpha-tocopherol, gamma-tocopherol, alpha-tocopheryl acetate, alpha-tocopheryl acid succinate, or alpha-tocopheryl phosphate, or of 1 microM N,N'-diphenyl-1,4-phenylenediamine, was investigated with respect to the agent's ability to prevent lactate dehydrogenase leakage in long-term rat hepatocyte cultures supplemented with 0.5 mM highly unsaturated fatty acids. Formation of thiobarbituric acid reactive substances in the cultures was also measured. alpha-Tocopheryl acid succinate was found to be the most effective cytoprotective compound, followed by N,N'-diphenyl-1,4-phenylenediamine, alpha-tocopherol, gamma-tocopherol and alpha-tocopheryl acetate, and alpha-tocopheryl phosphate was without effect.

Animals↗
PubMed1993

Inhibition of fatty acid synthesis in rat hepatocytes by exogenous polyunsaturated fatty acids is caused by lipid peroxidation.

Rat hepatocyte long-term cultures were utilized to investigate the impact of different polyunsaturated fatty acids (PUFA) on the insulin-induced de novo fatty acid synthesis in vitro. The addition of 0.5 mM albumin-complexed oleic, linoleic, columbinic, arachidonic, eicosapentaenoic or docosahexaenoic acid resulted in a marked suppression of fatty acid synthesis. By evaluation of cell viability (determined as the leakage of lactate dehydrogenase (LDH) it turned out, that the antioxidant used (50 microM alpha-tocopherol phosphate) had a low antioxidant activity, resulting in cytotoxic effects by the peroxidized PUFA. Arachidonic acid and eicosapentaenoic acid showed a dose- and time-dependent cytotoxicity. Two other antioxidants: 50 microM alpha-tocopherol acid succinate and 1 microM N,N'-diphenyl-1,4-phenylenediamine, both proved more efficient than alpha-tocopherol phosphate. There was a significant correlation between LDH-leakage and inhibition of fatty acid synthesis. Lipid peroxidation, measured as thiobarbituric acid-reactive substances, also showed a significant correlation with the degree of inhibition of fatty acid synthesis. Furthermore, PUFA had no inhibitory effect on fatty acid synthesis when peroxidation was minimized by the use of proper antioxidants. These data indicate that PUFA in vitro inhibit the insulin-induced de novo fatty acid synthesis in hepatocytes from starved rats, due to cytotoxic effects caused by lipid peroxidation.

Animals↗
PubMed1991

Radiographic detection of occlusal caries in noncavitated teeth. A comparison of conventional film radiographs, digitized film radiographs, and RadioVisioGraphy.

The aim of this study was to compare the accuracy of conventional film radiographs, digitized radiographs, and RadioVisioGraphy (RVG) for the detection of dentinal caries in occlusal surfaces of noncavitated extracted teeth. Eighty-one fully erupted extracted third molars were assessed by four observers using five radiographic methods: conventional film radiographs, digitized radiographs with contrast enhancement and with a filtering procedure, and RVG with contrast enhancement and with x function. Scoring criteria were dichotomous. Histologic sections (500 to 600 microns thick) served as the validation criterion. The two digital methods with contrast enhancement tended to perform more accurately than, although not significantly different from, the other three methods (p greater than 0.05). Average likelihood ratios (true positive/false positive) were 4.3 (conventional film radiographs), 4.4 (RVG with contrast enhancement), 3.6 (RVG with x function), 4.9 (digitized radiographs with contrast enhancement), and 3.7 (digitized radiographs with filtering procedure). Observers 1 and 2 (oral radiologists) performed better than observers 3 and 4 with all five methods (p less than 0.005).

Adolescent↗
PubMed1984

Appendix. Structural predictions on alpha 2-macroglobulin from the amino acid sequence.

The composite result from three different methods predicts that alpha 2-macroglobulin has a predominant pattern of alternating beta-strands and turns. Only scattered pieces of alpha-helix are present throughout its sequence. Predicted beta-strands constitute 43.8% and helices 8.6%, in fair agreement with circular dichroism spectra. Circular dichroism spectra and sequence data suggest that the tertiary structure of complement component C3b is similar to that of the alpha 2 macroglobulin monomer. At present, the beta-barrel configuration of prealbumin seems to be a better model than those of soybean trypsin inhibitor, serine proteases, and immunoglobulins. A repetitive pattern of disulfide loops could indicate structural units of about 200 residues in size, but this is not supported by amino acid sequence homology. The hydropathic pattern of the sequence reveals numerous examples of predicted immunogenic peptides and detects an approximately 100-residue hydrophobic core region, which could constitute parts of the tentatively assigned consecutive activation cleavage and thiol ester domains. This core is an obvious candidate of rearrangement transfer between the highly exposed bait region and the partly shielded thiol ester site. The presumed intersubunit half-cystine is moderately buried and has two nearby patches of high charge density which could guide the dimeric assembling.

Amino Acid Sequence↗
PubMed1983

The oxygen binding site of cytochrome oxidase. Structural predictions on subunit I from amino acid sequences.

Analyses of heme-attached amino acid sequences in known hemoprotein superfamilies provide a basis for prediction of such sequences in hemoproteins of unknown three-dimensional structure. Among 11 histidine residues conserved in subunit I of 3 mammalian and 2 fungal cytochrome oxidases the sequence around His-233 (human) is the most conserved and shows remarkable similarity to the sequence of the oxygen binding site in globins. Furthermore, the gene coding for subunit I in Saccharomyces cerevisiae and the gene for leghemoglobin in soybean are both split by introns right after these similar histidine sequences. The predicted distal histidine sequence of subunit I provides for heme a3 and Cua3 binding and has an extraordinarily high content of aromatic residues. These aromatic groups may serve as a molecular electron capacitor. Transmembrane sequences and electron transfer sequences are proposed.

Amino Acid Sequence↗
PubMed1982

Prediction of antigenic determinants and secondary structures of the K88 and CFA1 fimbrial proteins from enteropathogenic Escherichia coli.

Recently the amino acid sequences of the K88ab and the CFA1 fimbrial proteins from enteropathogenic Escherichia coli have become available. To elucidate the immunological interrelationships among the K88 family of antigenic variants, and to estimate the nature and position of the antigenic determinants in the K88 and CFA1 proteins, the positions of these features in the amino acid sequences have been predicted. This has been done by computerized algorithms, incorporating such factors as hydrophilicity and secondary structural potential. Some of the predicted determinants of K88 show good correlation with the known sequence differences between the antigenic variants of this protein. The presented results point to a possible use of synthetic vaccines against fimbriated pathogenic E. coli strains.

Amino Acid Sequence↗
PubMed1982

Scheuermann's disease with low localization. A problem of under-diagnosis.

Sequelae after Scheuermann's disease below the level of Th10/Th11 occur commonly and are presumed to produce low back pain in almost all cases. Despite this, the condition is frequently over-looked by both clinicians and radiologists. Of 55 rehabilitees with "low Scheuermann" this had only been diagnosed and acknowledged as a cause of pain in 20 prior to admission to the rehabilitation clinic. In 12 it had been diagnosed radiologically but not acknowledged as a cause of pain, while it had been completely over-looked in 23.

Adult↗