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Biomedical subjects

L Rask

Publications and source records attributed to L Rask.

At least 181 records · Page 10Linked to original sources
PubMed1979

Chemical, physical-chemical, and immunological properties of papain-solubilized human transplatation antigens.

Papain-solubilized HLA-A, -B, and -C antigens have been isolated from cadaveric spleens. The isolated material was homogeneous and comprised subunits with the apparent molecular weights 33,000 and 12,000. Amino acid analyses of a mixture of HLA antigen heavy chains obtained from a great number of spleens with different HLA antigen phenotypes revealed a composition that is very similar to that of individual HLA-A and -B antigens. Likewise, the NH2-terminal 30 residues of the HLA-antigen heavy chain mixture were virtually identical with that recorded for individual specificities. The circular dichroism spectra for the isolated HLA antigens and for free beta2-microglobulin revealed similarities with spectra recorded for immunoglobulin chains and domains. The HLA-antigen heavy chain may contain an appreciable amount of beta structure. Antibodies raised against free beta2-microglobulin react better with beta2-microglobulin in free form than when bound to the HLA-A, -B, and -C antigen heavy chains. This is due to the fact that free beta2-microglobulin can bind a maximum of four Fab fragments simultaneously, whereas the HLA-antigen-associated beta2-microglobulin can bind only two Fab fragments without dissociating from the heavy HLA-antigen subunit.

Amino Acid Sequence↗
PubMed1979

Fragmentation of the human transplantation antigen heavy chain by limited proteolysis, acid cleavage, and cyanogen bromide treatment.

Highly purified, papain-solubilized HLA-A, -B, and -C antigens comprising a mixture of a great number of allelic forms from at least three loci have been fragmented by limited proteolysis, acid cleavage, and cyanogen bromide treatment. Limited proteolysis of 125I-labeled HLA-A, -B, and -C antigens with trypsin, chymotrypsin, thermolysin, and pepsin resulted in the production of two large fragments. One fragment was associated with beta 2-microglobulin and contained all of the carbohydrate. The other fragment, which had a molecular weight of about 13,000, is most probably derived from the COOH-terminal part of the heavy chain. Acid cleavage of the HLA antigen heavy chain gave rise to two main fragments with molecular weights of 22,000 and 11,000. Both fragments contained disulfide bonds. Two minor components, representing further cleavage products of the 22,000-dalton fragment, were also observed. Cleavage of the HLA antigen heavy chain at methionyl residues gave rise to one carbohydrate-containing, cysteine-free 14,000-dalton fragment and one 20,000-dalton fragment that contained all cysteines but no carbohydrate. NH2-terminal amino acid sequence analyses demonstrated that the 22,000-dalton acid cleavage fragment and the 14,000-dalton cyanogen bromide fragment were derived from the NH2-terminal part of the HLA antigen heavy chain.

Amino Acid Sequence↗
PubMed1979

Amino acid sequence of an immunoglobulin-like HLA antigen heavy chain domain.

The classical human transplantation antigens, derived from the HLA-A, -B, and -C loci, are cell-surface-expressed glycoproteins. On the exterior of the cell the transplantation antigen heavy chain exposes two disulfide-containing domains and a glycosylated NH2-terminal extension. The disulfide-containing domain closest to the membrane has been isolated and its amino acid sequence has been determined. The HLA antigens used for the sequence analysis were derived from two and possibly three loci and comprised several allelic forms. The primary structure was remarkably invariant, and amino acid variations were observed only at three positions. Whether this suggests that the allelic variation of the HLA antigens is preferentially confined to other regions of the molecule or is a result of fortuitous selection of peptides remains to be established. The sequenced portion of the HLA antigen heavy chain is as homologous to beta 2-microglobulin and immunoglobulin light and heavy chains as are the latter to one another. This observation strengthens the notion that the transplantation antigens and the immunoglobulins are evolutionarily related.

Amino Acid Sequence↗
PubMed1979

Primary structure of pooled, papain-solubilized HLA-A, -B, and -C antigens.

The tentative amino acid sequence of pooled, papain-solubilized HLA antigen heavy chains has been determined. The amino acid sequence comprises 273 residues. As the structural analyses were performed on HLA antigen heavy chains comprising a mixture of several allelic forms derived from the A, B, and possibly C loci, multiple residues were encountered in several positions. However, a quantitatively dominating residue could always be easily identified. The present data suggest that the amino acid variability of the HLA-A, -B, and -C antigens is found in restricted regions of the molecule. The COOH-terminal third of the HLA antigen heavy chain appears to be less variable than other regions of the molecule. Previous work has shown that the HLA antigen heavy chain contains two immunoglobulin-like disulphide loops. The COOH-terminal third of the heavy chain was shown to be similar in primary structure to beta 2-microglobulin and the immunoglobulin G constant domains.

Amino Acid Sequence↗
PubMed1979

Isolation and properties of detergent-solubilized HLA antigens obtained from platelets.

Deoxycholate-solubilized HLA antigens have been isolated from platelets and comprised a mixture of 43,000- and 39,000-dalton polypeptide chains associated with beta2-microglobulin. Limited proteolysis experiments suggested that the 39,000-dalton chain is a fragment of the intact 43,000-dalton chain. Further proteolysis of the 39,000-dalton fragment yields a 33,000-dalton component. The 39,000-dalton molecule is more acidic than both the 43,000- and the 33,000-dalton chains. Differences in the amino acid compositions of the 43,000- and 39,000-dalton species demonstrate that the peptide(s) released on generation of the 39,000-dalton component are charged. The proteolytic split most probably occurs in the COOH-terminal end, which, owing to its content of charged amino acids, most probably is not integrated into the hydrocarbon matrix of the membrane. The 39,000- and 43,000-dalton components bind detergent in micellar form and can be incorporated into liposomes. The 33,000-dalton fragment has lost the ability to bind detergent micelles and is not incorporated into liposomes.

Amino Acids↗
PubMed1979

Zinc status and serum levels of retinol-binding protein, tocopherol and lower density lipoproteins in male and female rats fed on semi-purified diets containing rapeseed protein or casein.

Experiments were carried out in order to evaluate the effect of various levels of dietary zinc supplementation on the zinc status, growth and contents of retinol-binding protein (RBP), tocopherol and lower density lipoproteins (VLDL + LDL) in serum of rats fed on diets containing rapeseed protein concentrate (RPC) or casein as the sole source of protein. In male rats fed on RPC diet at a 10% protein 5% fat level, a highly significant correlation was found between dietary zinc content and the total tibia zinc content (r = 0.946) in the dietary zinc range of 35-137 microgram/mg. In contrast, the casein rats attained almost maximal bone zinc contents even at the lower level of dietary zinc. No correlation was found between zinc status and the protein efficiency ratio obtained for the rapeseed protein. In female rats fed on a zinc-supplemented RPC diet at a 20% protein and 10% fat level, the serum levels of tocopherol and VLDL + LDL were reduced in comparison to the levels observed in female rats fed on a corresponding casein diet. No diet-related changes in serum levels of RBP were found. However, male rats showed significantly higher RBP values than the female rats.

Animals↗
PubMed1979

Expression of Ia antigen-like molecules on cells in the corneal epithelium.

Ia antigens, known to be expressed preferentially on cells of the immune system, have been shown to be present on cells in the cornea. By immunofluorescence studies, it was shown that a specific rabbit anti-Ia antigen serum stained cells in the corneal epithelium. The stained cells were well integrated into the corneal epithelial architecture and displayed short dendritic processes. Their location in the cornea and corneal limbus and their morphological appearance make it reasonable to suggest that the Ia antigen-expressing cells of the cornea are equivalents of the Ia antigen-bearing Langerhans' cells of the epidermis.

Animals↗
PubMed1978

Amino acid sequence homology between HLA-A,B,C antigens, beta2-microglobulin and immunoglobulins.

Papain-solubilized HLA-A,B,C antigen heavy chains have been cleaved by combined acid and CNBr treatment to yield three large fragments. A 14,000-dalton peptide comprises the NH2-terminal portion of the molecule, less a five-membered peptide. The 14,000-dalton fragment is followed in the linear sequence by a 9000-dalton peptide connected through an aspartyl-prolyl bond to the COOH-terminal 11,000-dalton fragment. The 9000- and 11,000-dalton fragments contain disulphide bridges that are immunoglobulin-like inasmuch as they encompass some fifty-five to sixty amino acid residues. The NH2-terminal portion of the HLA antigen heavy chain is devoid of cysteine. NH2-terminal amino acid sequence analyses do not reveal homologies between the 14,000- and 9000-dalton fragments, beta2-microglobulin, and the constant immunoglobulin domains. However, the NH2-terminal sequence of the 11,000-dalton fragment is as homologous to beta2-microglobulin and the constant immunoglobulin domains as they are to one another.

Amino Acid Sequence↗