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Biomedical subjects

L Karlsson

Publications and source records attributed to L Karlsson.

At least 91 records · Page 5Linked to original sources
PubMed1992

The alpha chain gene of H-2O has an unexpected location in the major histocompatibility complex.

A previously unknown major histocompatibility complex class II molecule consisting of the beta chain encoded by the H-2Ob gene and an unknown alpha chain was recently described. We now report that the alpha chain occurs in two allelic forms distinguished by charge difference. Using inbred recombinant mouse strains we were able to map the H-2Oa gene to a location between the A.TL and B10.MBR recombination points. Cosmids covering this region were used to isolate the gene. Sequence analysis revealed that the H-2Oa gene is the murine equivalent of the human HLA-DNA gene. These results indicate that the human HLA-DNA gene, the existence of which has long been known, is indeed coding for DO alpha, the alpha chain pairing with DO beta.

Amino Acid Sequence↗
PubMed1992

Two subsets of epithelial cells in the thymic medulla.

Information was sought on the features of epithelial cells in the murine thymic medulla. The expression of major histocompatibility complex (MHC) molecules on medullary epithelium was defined by light microscopy with the aid of bone marrow chimeras and MHC-transgenic mice. A proportion of medullary epithelial cells was found to show conspicuously high expression of conventional MHC (H-2) class I (K, D, L) and class II (I-A, I-E) molecules. These cells express a high density of the Y-Ae epitope, a complex of an E alpha peptide and I-Ab molecules found on typical bone marrow-derived cells. MHC+ medullary epithelial cells show limited expression of I-O molecules, a class of atypical nonpolymorphic MHC-encoded class II molecules present on B cells. Other medullary epithelial cells express a high density of I-O molecules but show little or no expression of typical MHC class I or II molecules. MHC and I-O expression thus appear to subdivide medullary epithelial cells into two phenotypically distinct subsets. This applies in adults. In the embryonic thymus most medullary epithelial cells express both types of molecules.

Animals↗
PubMed1992

Expression of a functional chimeric Ig-MHC class II protein.

We have generated a chimeric protein molecule composed of the alpha- and beta-chains of the MHC class II I-E molecule fused to antibody V regions derived from anti-human CD4 mAb MT310. Expression vectors were constructed containing the functional, rearranged gene segments coding for the V region domains of the antibody H and L chains in place of the first domains of the complete structural genes of the I-E alpha- and beta-chains, respectively. Cells transfected with both hybrid genes expressed a stable protein product on the cell surface. The chimeric molecule exhibited the idiotype of the antibody MT310 as shown by binding to the anti-idiotypic mAb 20-46. A protein of the anticipated molecular mass was immunoprecipitated with anti-mouse IgG antiserum. Furthermore, human soluble CD4 did bind to the transfected cell line, demonstrating that the chimeric protein possessed the binding capacity of the original mAb. Thus, the hybrid molecule retained: 1) the properties of a MHC class II protein with regard to correct chain assembly and transport to the cell surface; as well as 2) the Ag binding capacity of the antibody genes used. The generation of hybrid MHC class II molecules with highly specific, non-MHC-restricted binding capacities will be useful for studying MHC class II-mediated effector functions such as selection of the T cell repertoire in thymus of transgenic mice.

Animals↗
PubMed1992

An unusual class II molecule.

H-2O is a recently described non-polymorphic mouse MHC class II molecule. Here, Lars Karlsson and colleagues describe the discovery of the H-2Ob and H-2Oa loci and the pattern of expression of H-2O, and speculate on the possible function of this unusual molecule.

Animals↗
PubMed1992

Treatment of nummular psoriasis with a clobetasol propionate stick.

Twenty-two consecutive patients with nummular psoriasis were treated with a 0.05% clobetasol propionate stick on the right side of the body and with 0.05% clobetasol propionate ointment (Dermovate, Glaxo) on the left according to an intermittent application schedule. The trial was open and lasted for 3 weeks. The patients were assessed at the beginning and at the end of the trial. The variables studied included: an overall clinical assessment, assessment of the lesion area, scaling, erythema and thickness and the amount of clobetasol propionate used during the trial, and a questionnaire on patients' opinions about hygienic and cosmetic qualities of the stick. No significant difference was found between the stick and corresponding ointment. From a hygienic and cosmetic point of view, the patients preferred the stick formulation.

Adolescent↗
PubMed1991

A novel class II MHC molecule with unusual tissue distribution.

The repertoire of mature class II-restricted T cells is generated through a complex process of selection whereby early T cells confront class II molecules in the thymus, especially on epithelial cells. Expression of class II molecules on such cells is prominent both in the cortex and in the medulla. We have identified a novel class II molecule, H-20, which is expressed only in epithelial cells of the thymic medulla and in B cells. The unusual tissue distribution and the nonpolymorphic nature of H-20 suggest that its function is different from that of classical class II molecules.

Amino Acid Sequence↗
PubMed1991

Digital amputation, replantation, and cold intolerance.

In a controlled, retrospective, clinical study, the relationships between traumatic digital amputation, digital replantation, and cold intolerance were investigated. The results of the investigation indicate that cold intolerance is a major reason for disability after digital amputation. They also indicate that the cold intolerance experienced after digital replantation is due to the original injury, and that it is not aggravated by the reconstructive surgery. Cold intolerance, in and of itself, is not a contraindication to digital replantation, regardless of whether the patient lives or works in high- or low-temperature environments.

Adolescent↗
PubMed1991

On the inhibition of glutamic acid decarboxylase and gamma-aminobutyric acid transaminase by sodium cyanide.

The effects of sodium cyanide (NaCN) on the gamma-aminobutyric acid metabolizing enzymes glutamic acid decarboxylase (GAD) and gamma-aminobutyric acid transaminase (GABA-T) were studied in vitro. With no pyridoxal-5-phosphate added, GAD was non-competitively inhibited by NaCN, with an IC50 of 280 microM. GAD was also inhibited when exposed to an equimolar amount of NaCN and pyridoxal-5-phosphate. NaCN inhibited GABA-T. The inhibition kinetics suggests that NaCN may react with more than one of the substrates and products present during the reaction, i.e. pyridoxal-5-phosphate, alpha-ketoglutarate and/or succinic semialdehyde. The presence of pyridoxal-5-phosphate in the reaction mixture completely protected GABA-T from inhibition by NaCN. The gamma-aminobutyric acid synthesizing enzyme, GAD may thus be inhibited in vivo by NaCN or by a reaction product of NaCN and pyridoxal-5-phosphate. The gamma-aminobutyric acid catabolizing enzyme, GABA-T is not as vulnerable to inhibition by NaCN, since the cyanide-pyridoxal-5-phosphate complex is ineffective as inhibitor.

4-Aminobutyrate Transaminase↗
PubMed1991

Importance of creatinine analyses of urine when screening for abused drugs.

We report here a simple method involving urine creatine measurements for testing authenticity and reducing false-negative results in urine testing for drugs of abuse. Urinary creatinine in consecutive patient samples (n = 176) ranged between 0.1 and 31.9 mmol/L (mean 9.8 +/- SD 6.2) and the osmolality in these urines ranged between 49 and 1183 mOsm/kg (mean 595 +/- SD 276). With other consecutive samples in which creatinine was (arbitrarily chosen) less than 4.3 mmol/L (n = 85), the correlation with osmolality was lower. In 10 randomly selected urine samples from different patients, all "clean" for all drugs of abuse in initial immunological drug testing with approved methodology (in which creatinine was less than 4.3 mmol/L and osmolality was less than 200 mOsm/kg), five patients turned out to be drug positive after a simple concentration by volume. In a formerly heavy smoker of cannabis, the excretion of cannabinoids and creatinine was monitored for 93 days. The substances showed very good correlation throughout this period (r = 0.93, P less than 0.001), whereas simple measurements of cannabinoid concentrations would have falsely indicated several relapses of cannabis abuse. Urine samples used in drug-abuse testing should be tested for creatinine; if creatinine is less than 4.0 mmol/L, negative results for drugs may not be valid.

Cannabinoids↗