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Biomedical subjects

L Karlsson

Publications and source records attributed to L Karlsson.

At least 109 records · Page 6Linked to original sources
PubMed1990

Intracellular transport of class II MHC molecules directed by invariant chain.

Three structural motifs in the invariant chain (li) control the intracellular transport of class II major histocompatibility complex molecules. An endoplasmic reticulum retention signal in the full-length li suggests a role for li in the alpha-beta heterodimer assembly. Another signal motif directs a truncated li, alone or associated with individual class II chains, to a degradation compartment by a pathway circumventing the Golgi. When this truncated li binds alpha-beta dimers, a third signal dominates, directing the complex by way of the Golgi to vesicles in the cell periphery, which may represent a subcompartment of recycling endosomes.

Antibodies, Monoclonal↗
PubMed1989

Transgenic HLA-DR alpha faithfully reconstitutes IE-controlled immune functions and induces cross-tolerance to E alpha in E alpha 0 mutant mice.

We have constructed transgenic mice that express the human class II MHC molecule HLA-DR alpha on a genetic background in which the equivalent endogenous gene, H-2 IE alpha, is not expressed. In these mice, DR alpha complemented the E beta chain such that tissue-specific expression of an interspecies hybrid DR alpha-E beta heterodimer was obtained. Despite 25% amino acid differences between DR alpha and E alpha, immune responsiveness to IE-controlled antigens, clonal deletion of IE-reactive T cells, and alloantigenicity were quantitatively and qualitatively indistinguishable in IE-positive mice and in mice that had integrated at least four copies of the transgene. These results demonstrate a remarkable degree of structural, regulatory, and functional conservation. They also suggest that tolerance induction involves only discrete portions of MHC molecules.

Animals↗
PubMed1989

Total protein determined in human breast milk by use of coomassie brilliant blue and centrifugal analysis.

This simple method of centrifugal analysis for total protein in human breast milk is based on the change in the wavelength of the absorbance maximum of Coomassie Brilliant Blue G-250 when the dye is bound to protein. Within-run and between-day CVs were 3.8% and 4.8%, respectively. Compared with a micro-Kjeldahl method for determination of total nitrogen, the coefficient of correlation was 0.99.

Adult↗
PubMed1988

Collective doses to the Swedish population from panoramic radiography and lateral cephalography.

A questionnaire was sent to all dental offices in Sweden equipped with panoramic and cephalographic x-ray units. Data were obtained for estimating the energy imparted from panoramic radiography and lateral cephalography during 1984 to the Swedish population. There were two units with intraorally placed focus among the 121 panoramic units studied. Approximately half of the panoramic radiographs, totally 79,000, were exposed on individuals younger than 20 years of age. Ninety-three cephalographic units were used to expose 40,000 lateral cephalograms, of which 10 per cent were exposed on children less than 10 years old and 12 per cent on adults. The energy imparted was estimated using the collected data, relative depth dose values and conversion factors from the literature. Mean energy imparted per panoramic examination was 0.50 mJ, and per cephalogram 0.43 mJ. From the panoramic and cephalographic examinations the energy imparted to the Swedish population was 40 J and 17 J, respectively. The corresponding collective effective dose equivalent to the population would be 0.75 manSv and 0.43 manSv, respectively. As a comparison, the collective effective dose equivalent from the annual natural irradiation including radon irradiation from dwellings is about 6.8.10(4) manSv.

Absorption↗
PubMed1987

Direct injection of urine on a high-performance liquid chromatographic column-switching system for determination of delta 9-tetrahydrocannabinol-11-oic acid with both ultraviolet and electrochemical detection.

A method is presented for determination of delta 9-tetrahydrocannabinol-11-oic acid in urine by means of a fully automated liquid chromatographic system. Aliquots (200 microliter) of hydrolysed urine from prison inmates were directly injected onto a pre-column, followed by chromatography on two columns with different selectivity: CN and C8 columns. To obtain both greater selectivity and a low detection limit a twin-detector principle was used, consisting of both ultraviolet and electrochemical detection. Urine samples found to be positive with the EMIT cannabinoid were analysed, and the results were compared with those obtained from a well established gas chromatographic-mass spectrometric method. The precision of the method was 2.8% at a mean concentration of 85 ng/ml and 13.4% for 6 ng/ml of the acid. The detection limit was below 5 ng/ml.

Autoanalysis↗
PubMed1987

Is the concentration of gamma-aminobutyric acid in the nerve terminal regulated via product inhibition of glutamic acid decarboxylase?

Fractions of synaptosomes were used to study the regulation of gamma-aminobutyric acid (GABA) synthesis. The isolated synaptosomes were superfused in media of various compositions. [3H]GABA and GABA released into the medium or remaining in the synaptosomes were analyzed by liquid scintillation and HPLC techniques. Different conditions, designed to increase the GABA efflux rate were used: the rate of superfusion was varied and the concentrations of K+ and Ca2+ were altered. Stimulation of GABA efflux was paralleled with an increased synthesis of GABA, since, in spite of the increased GABA efflux, a relatively constant intraterminal level was found. The findings suggest that the intraterminal concentration of GABA and thus also its synthesis is regulated via product inhibition. In addition, [3H]GABA, exogenous, and GABA, endogenous, responded to external stimulae (Ca2+, veretradine, various GABA concentrations and the glutaminase inhibitor diazo-nor-leucine) in a way which was compatible with them being localized in and/or released from different compartments.

Animals↗
PubMed1987

Effective dose equivalent from intraoral radiography.

By means of available data of mean organ doses from intraoral radiography the effective dose equivalent from dental radiography was calculated. The dose values used correspond to 65 kVp, 0.2 m FSD and 20 exposures with film in speed group D. The effective dose equivalent was calculated for circular (55 mm diameter) as well as rectangular collimator (35 mm X 44 mm) and amounted to 0.23 and 0.14 mSv, respectively. In comparison with the annual natural radiation the corresponding time would be 6 and 3 weeks, respectively. Following the definition of the effective dose equivalent by ICRP (1977) it was found that the most radiosensitive organs contributed 20-25 per cent of the total effective dose equivalent. The organs with the highest weighting factors thus received very small or negligible dose equivalents. The calculation necessitates a detailed knowledge of the absorbed doses and the weighting factors, which made the application for dental radiography somewhat uncertain. The concept of energy imparted might be a more direct measure to compare the risk from different examinations in dental radiography.

Energy Transfer↗
PubMed1986

Energy imparted from intraoral radiography.

During the recent decade the equipment for dental radiography in Sweden has been standardized by the Swedish National Institute for Radiation Protection. The aim of this study was to experimentally determine the energy imparted to a phantom from a full survey with 20 intraoral films as well as from a single bitewing projection, using this standardized technique. Thermoluminescence dosimeters in predetermined volume elements of an anatomically formed tissue equivalent Alderson-phantom were irradiated (65 k Vp) using both a rectangular and a circular collimator of 0.2 m FSD. Exposure times fitted to film in speed group D were used. The energy imparted was determined from the integrated absorbed doses in the volume elements as well as calculated using published depth dose data. The energy imparted was found to be 9.6 mJ (circular collimator) and 5.9 mJ (rectangular collimator) for the full survey. For the single bitewing exposure the energy imparted was 0.42 mJ (circular collimator) and 0.29 mJ (rectangular collimator). With the rectangular collimator and film in speed group D the energy imparted from a full survey will correspond approximately to two weeks of environmental irradiation. With more sensitive film in speed group E the energy imparted would further be reduced by 40 per cent with retained diagnostic information.

Head↗
PubMed1985

Topography and enterocyte morphology of the small bowel mucosal surface in equine granulomatous enteritis.

The jejunal mucosa of 4 cases of equine granulomatous enteritis and 2 control horses was investigated by light microscopy and by scanning and transmission electron microscopy. Attention was focused upon changes in mucosal topography and enterocyte morphology in the inflamed mucosa. Structural changes ranged in severity from only a slight thickening and shortening of villi to the appearance of a virtually flat mucosa, upon which crypts opened directly or through shallow cavities encircled by collars of epithelial cells. Between these extremes, the mucosa showed a variety of patterns, all characterized by distinctly abnormal villus projections. These were often united by epithelial bridges and were commonly markedly short, broad and irregular. Enterocytes of mildly changed mucosae showed a normal histology and fine structure, whereas more severely changed specimens displayed a flattened surface epithelium with ultrastructural abnormalities, the most consistent being a pronounced shortening of microvilli. In particular, greatly flattened cells showed evidence of cellular injury, such as prominence of cytolysosomes and degenerative changes of the rough endoplasmic reticulum, while other cells were chiefly characterized by an abundance of non-membrane-bound ribosomes and other features signifying an immature state. Cell-membrane-tight junctions of the surface epithelium appeared to be intact. No intracellular micro-organisms were detected. It is suggested that several factors are involved in the creation of the abnormal mucosal topography in this disease, including excessive enterocyte loss, crypt cell destruction, inflammatory distension of villi and villus fusions.

Animals↗
PubMed1985

Adrenergic vasoconstriction in peripheral nerves of the rabbit.

The blood flow in the sciatic nerve of the rabbit was estimated from the wash out of intraneurally injected 133Xe. To avoid diffusion of the tracer into the surrounding muscular tissue, the nerve was covered by a gas-tight plastic film. Using this technique, the basal blood flow in the sciatic nerve was estimated to 35 ml X min-1 X 100 g-1. It was found that intraarterial norepinephrine and electrical stimulation of the lumbar sympathetic chain strongly reduced the wash out of 133Xe, which only can be explained by a pronounced reduction of the blood flow in the nerve itself. The blood flow again increased within 4 min of stopping the infusion of norepinephrine or the sympathetic stimulation. The prolonged effect and higher neurotoxicity of local anesthetics containing adrenaline may be explained by an alpha receptor-mediated vasoconstriction of the microvessels of peripheral nerves.

Animals↗
PubMed1984

Combination of liquid chromatography with ultraviolet detection and gas chromatography with electron-capture detection for the determination of delta 9-tetrahydrocannabinol-11-oic acid in urine.

A method is described for the determination of delta 9-tetrahydrocannabinol-11-oic acid (delta 9-THC-11-oic acid) in urine by using a combination of liquid chromatography and glass capillary gas chromatography with electron-capture detection. Prior to extraction, the glucuronide conjugate of delta 9-THC-11-oic acid was enzymatically converted to the free acid and delta 8-THC-11-oic acid added as an internal standard. An aliquot of the extract was separated by liquid chromatography and one eluate fraction containing delta 8-THC-11-oic and delta 9-THC-11-oic acids was collected. Before gas chromatographic analysis the acids were converted to their pentafluoropropyl-pentafluoropropionyl derivatives. Authentic urine samples, positive with the EMIT cannabinoid assay, were analysed and the results compared with those obtained from an earlier described gas chromatographic-mass spectrometric method. The detection limit for the overall method was approximately 20 ng/ml. The precision was 8% for a sample concentration of 90 ng/ml of delta 9-THC-11-oic acid in urine.

Chromatography, Gas↗