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Biomedical subjects

K Lundquist

Publications and source records attributed to K Lundquist.

10 recordsLinked to original sources
PubMed1999

Intraepidermal cytokeratin 7 expression is not restricted to Paget cells but is also seen in Toker cells and Merkel cells.

Histologically, extramammary Paget's disease and mammary Paget's disease (MPD) are characterized by large atypical cells distributed throughout the epidermis. Although classic examples of these disorders are easily diagnosed on morphologic grounds, some cases may cause differential diagnostic problems. Immunohistology with a wide variety of antibodies has been used as an aid for the identification of Paget cells, for their distinction from other entities, and for investigation of the origin or nature of the disorder. Recently, cytokeratin 7 has been proposed as a specific and 100% sensitive marker for Paget's disease. We studied 22 cases of mammary Paget's disease and 22 cases of extramammary Paget's disease with and without an underlying malignancy for their reactivity with monoclonal antibodies to cytokeratin 7 (CK7) and cytokeratin 20 (CK20). Our studies show that anti-CK7 is an effective but not 100% sensitive marker for Paget cells, staining 21 of 22 cases of mammary Paget's disease and 19 of 22 cases of extramammary Paget's disease, whereas CK20 stained 0 of 17 cases of mammary Paget's disease and 6 of 19 cases of extramammary Paget's disease. We also demonstrate that CK7, but not CK20, highlights intraepidermal clear cells with bland nuclear features (Toker cells) that have been reported in 11% of normal nipples. By using CK7 as a marker, however, we were able to identify Toker cells in most of the nipples we studied: 8 of 15 nipples from mastectomy patients without Paget's disease, and 15 of 18 autopsy cases (both male and female) with normal breasts and nipples. It also permitted us to perform more extensive phenotyping on them, showing that Toker cells share similar antigens with Paget cells and with cells lining the underlying normal lactiferous ducts. In 7 of 15 cases containing CK20-positive Merkel cells, CK7 was also seen to stain Merkel cells. In infrequent cases, Toker cells or Merkel cells may be so numerous focally that a CK7 stain may raise the possibility of involvement of the nipple by Paget's disease. An awareness of the CK7 reactivity of Toker cells and Merkel cells as well as attention to the cytologic features of the case should avoid this problem.

Aged↗
PubMed1994

Plantar pressures during level walking compared with other ambulatory activities.

This study was designed to determine the magnitude of plantar pressures during level walking in comparison to other activities. These activities included climbing up stairs, going down stairs, a simple pivot while walking, and a crossover pivot while walking in normal individuals. Twelve volunteers, six men and six women, mean age 28 years, served as subjects. Data were collected on the dominant foot with an EMED-SF pressure sensor platform as each subject walked barefoot and did each of the five activities. Maximum plantar pressure (MPP) and pressure-time integral (PTI) was found in the metatarsal and heel regions. The results of repeated-measures analysis of variance tests showed that the five experimental conditions were statistically different for both MPP and PTI in the metatarsal and heel regions. Post hoc analysis indicated that MPP and PTI were decreased during the going down stairs condition in the heel and increased during the crossover pivot while walking and pivot while walking conditions for the metatarsal region.

Adult↗
PubMed1993

Rapid development of lymphoma following liver transplantation in a recipient with hepatitis B and primary hemochromatosis.

We report a case of a posttransplant lymphoproliferative disorder (PTLD) which presented in a liver allograft shortly after transplantation. The patient, who had been transplanted because of cirrhosis due to primary hemochromatosis and chronic hepatitis B infection (HBV), developed early recurrent HBV in the graft, and 2 months after transplantation, liver biopsies showed a malignant large-cell lymphoma. The neoplastic cells demonstrated Epstein-Barr virus DNA by in situ hybridization. The patient died 3.5 months posttransplant due to liver failure. At autopsy, the liver showed nodules of malignant lymphoma, massive hepatic necrosis, and iron overload, but no evidence of rejection. This report suggests that the grafted liver can be the site of PTLD in recurrent HBV and hemochromatosis.

Adult↗
PubMed1990

Stereospecificity in enzymic and non-enzymic oxidation of beta-O-4 lignin model compounds.

The degradation of the erythro and threo isomers of the non-phenolic lignin model compound 2-(2,6-dimethoxyphenoxy)-1-(3,4-dimethoxyphenyl)-1,3-propanediol was examined. Enzymic and non-enzymic oxidation of the diastereomers was performed with Trametes versicolor lignin peroxidase and cerium(IV) ammonium nitrate, respectively. Mixtures of approximately equal amounts of the diastereomers were partially degraded and subsequently analyzed with TLC and 1H-NMR. Analysis of reaction mixtures from enzymic as well as non-enzymic oxidation, revealed a preferential degradation of the threo form. Preliminary analyses of enzymic reaction mixtures of either the erythro or threo isomer suggest they yield in part different products. The observations made would have implications for the understanding of how enzymes attack lignins. They should also be taken into consideration in experiments where model compounds are being used to mimic native lignin.

Isoenzymes↗
PubMed1989

Trametes versicolor ligninase: isozyme sequence homology and substrate specificity.

The substrate specificity of three ligninase isozymes from the white-rot fungus Trametes versicolor has been investigated using stereochemically defined synthetic dimeric models for lignin. The isozymes have been found to attack non-phenolic beta-O-4 as well as beta-1 lignin model compounds. This finding confirms the classification of the isozymes from T. versicolor as ligninases. The amino-terminal residues of the three isozymes from T. versicolor have been determined using Edman degradation. Minor differences found between the sequences suggest the existence of several structural genes for ligninase in T versicolor. Comparisons have been made with the sequences of three previously reported ligninases from Phanerocompaete chrysosporium, another lignin-degrading fungus. One of the sequences from P. chrysosporium is distinctly more similar to the T. versicolor isozymes than to the other two sequences from P. chrysosporium.

Amino Acid Sequence↗
PubMed1985

Exhaustive laccase-catalysed oxidation of a lignin model compound (vanillyl glycol) produces methanol and polymeric quinoid products.

Laccase-catalysed oxidation of the lignin-related phenol vanillyl glycol results in the initial formation of dimers and subsequent polymerization. The polymerization is accompanied by a liberation of methanol corresponding to 15-20% demethylation. Visible spectra together with reduction experiments suggest the simultaneous formation of o-quinones. The participation of quinone formation in the polymerization process and the possible role of such intermediates in lignin biodegradation is discussed.

Laccase↗