Biomedical subjects

C Tsoi

Publications and source records attributed to C Tsoi.

8 recordsLinked to original sources

PubMed2005

Sulfation in dog.

Sulfation has been thoroughly studied in several species including e.g. man and rat. However, one important species often used for pharmacological drug studies is the dog. Here we describe recent advances as well as older data in the field of dog sulfation. Species differences in sulfation have been reported. Stereoselectivity, inhibition by pentachlorophenol, bioactivation of DNA binding species, and gender differences have also been observed for canine sulfotransferases (SULTs). Several drugs are being sulfated in vivo in dog, e.g. xamoterol, 4'-hydroxypropanolol, paracetamol and salicylamide. However, studies have shown that also e.g. canine hepatocytes and liverslices will sulfate substrates e.g. paracetamol and 7-hydroxycoumarin in in vitro experiments. Recently, three different enzymes have been cloned and characterized from canine liver, cSULT1A1, cSULT1B1 and cSULT1D1. cSULT1A1 being very similar to the human ortholog in terms of substrate specificity and is also ubiquitously expressed in canine tissues. The cSULT1B1 enzyme is also very similar in both distribution pattern as well as substrate preference compared to the human ortholog. The third enzyme, cSULT1D1, sulfates dopamine with high efficiency and it has no counterpart in man since it is found as a pseudogene. The importance of amino acid residue 247 in cSULT1D1 will be discussed since it can alter the ratio of sulfation of dopamine versus para-nitrophenol. In addition, the phenomenon of the high expression of the canine enzymes in colon is discussed.

Animals↗

PubMed2004

Thiazolidinediones reduce the LDL binding affinity of non-human primate vascular cell proteoglycans.

AIMS/HYPOTHESIS: Retention of atherogenic lipoproteins in the artery wall by proteoglycans is a key step in the development of atherosclerosis. Thiazolidinediones have been shown to reduce atherosclerosis in mouse models. The aim of this study was to determine whether thiazolidinediones modify vascular proteoglycan synthesis in a way that decreases LDL binding. METHODS: Primate aortic smooth muscle cells were exposed to troglitazone or rosiglitazone, or no stimulus at all for a 24-hour steady-state labelling period. Sulphate incorporation, size and LDL binding affinity of proteoglycans were determined. Proteoglycans secreted by cells in the presence or absence of troglitazone were separated into large and small classes by size exclusion chromatography, and LDL binding affinity was determined. RESULTS: Proteoglycans synthesised by cells exposed to troglitazone or rosiglitazone were smaller, with decreased sulphate incorporation and decreased LDL binding affinity. However, troglitazone had a greater effect than rosiglitazone. Troglitazone reduced the LDL binding affinities of both the large and small proteoglycans compared with control. The binding differences persisted when glycosaminoglycan chains released from proteoglycans were incubated with LDL, indicating that troglitazone affects the glycosaminoglycan synthetic machinery of these cells. CONCLUSIONS/INTERPRETATION: Thiazolidinediones decrease the LDL binding affinity of the proteoglycans synthesised by primate aortic smooth muscle cells. This could, in part, account for the reduced atherosclerosis observed in animal models.

Animals↗

PubMed2001

Identification of a new subfamily of sulphotransferases: cloning and characterization of canine SULT1D1.

Sulphation is an important conjugation pathway in drug metabolism that has been studied in several species including humans. However, few studies have been performed using the dog as a subject. In this report we describe the cloning and characterization of a canine cytosolic sulphotransferase (SULT). The overall primary structure of this enzyme is very similar to that of a rat phenol-sulphating enzyme found in the EMBL Database and to a mouse SULT termed amine-N-sulphotransferase (81% identity). The expressed canine SULT conjugates small phenols and aromatic amines such as dopamine, minoxidil, p-nitrophenol and 5-hydroxytryptamine, but not dehydroepiandrosterone or beta-oestradiol. These results are in agreement with the results reported for the mouse SULT. In contrast with the mouse enzyme, the canine SULT does not conjugate eicosanoid compounds, i.e. prostaglandins, thromboxane B(2) or leukotriene E(4). The canine SULT is expressed at high levels in the colon of both genders; it is also expressed in the small intestine, kidney and liver. Furthermore, because the canine, mouse and rat SULT forms exhibit significant sequence identity (more than 80%), they seem to represent a distinct group in the SULT family tree. This suggestion is strengthened by the low identity with other SULTs. The subfamily that is most similar to this new group is SULT1A, with approx. 60% similarity. However, the mouse and canine enzymes are not characterized by the efficient sulphation of p-nitrophenol, dopamine, beta-oestradiol or oestrone. Thus these results seem to exclude them from the SULT1A subfamily. We therefore propose a new subfamily in the phenol SULT family, designated SULT1D, and consequently the canine enzyme is termed SULT1D1.

Amino Acid Sequence↗

PubMed2001

Molecular cloning, expression, and characterization of a canine sulfotransferase that is a human ST1B2 ortholog.

Sulfation is an important conjugation pathway in deactivating thyroid hormones, keeping the proper hormonal balance, and increasing the rate of thyroid hormone metabolism. We have identified, cloned, and characterized a sulfotransferase (SULT) that is capable of thyroid hormone conjugation in the dog. This enzyme, designated cSULT1B1, displays a strong identity (>84%) to the human ST1B2 enzyme. However, cSULT1B1 displays less identity, about 73%, to mouse and rat orthologs. In addition, the canine enzyme is three amino acids shorter than the rodent ones but has the same length as the human ortholog, 296 amino acids. The bacterial expressed and partial purified cSULT1B1 enzyme sulfates p-nitrophenol and 1-naphtol, but not dopamine. The thyroid hormones 3,3'-diiodothyronine and 3,5,3'-triiodothyronine are efficiently sulfated. 3,3',5'-Triiodothyronine is sulfated to lesser degree while sulfation of 3,5'-diiodothyronine and 3,3',5,5'-tetraiodothyronine cannot be detected. The cSULT1B1 is found in the colon (highest level), kidney and small intestine in dogs, but surprisingly not in the male dog liver although low levels of immunoreactivity were detected in the female dog liver. The male dog expresses more of SULT1B1 enzyme in the lower part of the small intestine while the female dog displays an opposite pattern of expression. These results describe the cloning and characterization of a canine thyroid hormone sulfating enzyme that is more closely related to the human ortholog than to the rodent thyroid sulfating enzymes.

Amino Acid Sequence↗

PubMed2000

Oxidized low density lipoproteins regulate synthesis of monkey aortic smooth muscle cell proteoglycans that have enhanced native low density lipoprotein binding properties.

Oxidized low density lipoproteins (Ox-LDL) affect several biological processes involved in atherogenesis. However, it is not known whether Ox-LDL can regulate proteoglycan expression and thus affect arterial wall lipoprotein retention. This study evaluated whether Ox-LDL, as compared with native LDL, regulates proteoglycan expression by monkey arterial smooth muscle cells in vitro and whether proteoglycans synthesized in the presence of Ox-LDL exhibit altered lipoprotein binding properties. Ox-LDL stimulated glycosaminoglycan synthesis, as measured by (35)SO(4) incorporation, by 30-50% over that of native LDL. The effect was maximal after 72 h of exposure to 5 microg/ml of Ox-LDL. The molecular sizes of versican, biglycan, and decorin increased in response to Ox-LDL, as indicated by size exclusion chromatography and SDS-polyacrylamide gel electrophoresis. These effects could be mimicked by the lipid extract of Ox-LDL. These size increases were largely due to chain elongation and not to alterations in the ratio of (35)SO(4) to [(3)H]glucosamine incorporation. Affinity chromatography indicated that Ox-LDL stimulated the synthesis of proteoglycans with high affinity for native LDL. Ox-LDL also specifically stimulated mRNA expression for biglycan (but not versican or decorin), which was correlated with increased expression of secreted biglycan. Thus, Ox-LDL may influence lipoprotein retention by regulating synthesis of biglycan and also by altering glycosaminoglycan synthesis of vascular proteoglycans so as to enhance lipoprotein binding properties.

Animals↗

PubMed1999

Recruitment of a heparan sulfate subunit to the interleukin-1 receptor complex. Regulation by fibronectin attachment.

In this study, we identified an adhesion-regulated subunit of the interleukin-1 (IL-1) receptor complex. Transfection of fibroblasts with an IL-1 receptor-EGFP construct showed that the fusion protein was located at focal adhesions in cells attaching to fibronectin. Fibronectin attachment caused enhancement in endogenous IL-1 type I receptor levels from on average 2500 to 4300 receptors/cell. In addition, matrix attachment resulted in a decrease in binding affinity (Ka) from 1.0 x 10(9) (M-1) to 5.6 x 10(8) (M-1), due to a 2-fold reduction in association rate constant. The adhesion-mediated effects were reversed by soluble heparin. Cross-linking experiments showed that in cells attached to fibronectin, 50-70% of the radiolabeled IL-1 was associated with a heparinase sensitive, high molecular mass component of about 300 kDa, with a core protein of 80-90 kDa. Formation of the complex was dependent on cell interaction with the heparin binding region in fibronectin and required IL-1/type I IL-1 receptor binding. This report demonstrates the recruitment of a heparan sulfate to the IL-1 receptor complex, following attachment to fibronectin, which correlates with alterations in receptor function. The data suggest that the heparan sulfate constitutes an attachment regulated component of the IL-1 receptor complex with the role of mediating matrix regulation of IL-1 responses.

Amino Acid Sequence↗

PubMed1998

Human monocyte-derived macrophages secrete two forms of proteoglycan-macrophage colony-stimulating factor that differ in their ability to bind low density lipoproteins.

This study evaluated whether human monocyte-derived macrophages synthesize specific types of proteoglycans with lipoprotein-binding capability that could contribute to lipid retention in the arterial wall. After labeling with either [35S]SO4 or [35S]methionine, macrophages secreted a high molecular mass proteoglycan, with glycosaminoglycan chains of approximately 18 kDa and core protein bands of approximately 100 and 55 kDa. Both core protein bands were recognized by an antibody to PG-100, an antibody that recognizes the proteoglycan form of macrophage colony-stimulating factor (PG-100/PG-MCSF). The interaction between PG-100/PG-MCSF and low density lipoproteins (LDL) was examined by gel mobility shift. In this system, PG-100/PG-MCSF was resolved further into two forms. The two forms had the same core proteins but differed in their overall size and glycosaminoglycan content. The larger form contained glycosaminoglycan chains that were entirely chondroitin ABC lyase-sensitive, whereas the smaller form contained chains that were sensitive to both chondroitin ABC lyase and heparinase. Both forms bound native LDL with high affinity, but the larger form bound LDL with higher affinity than the smaller form. The glycosaminoglycan chains of PG-100/PG-MCSF, but not the core proteins, were responsible for binding to native LDL. Mildly oxidized LDL and methyl-LDL, which have an electrophoretic charge similar to that of native LDL, also bound PG-100/PG-MCSF. In contrast, extensively oxidized LDL and acetyl-LDL, which are more electronegative than native LDL, did not bind to either form of PG-100/PG-MCSF. The demonstration of two forms of human monocyte-derived macrophage PG-100/PG-MCSF which bind LDL may represent an additional role for macrophages in the extracellular trapping of lipoproteins in atherosclerosis.

Cells, Cultured↗

PubMed1995

Freehand technique to harvest partial-thickness skin to repair superficial facial defects.

BACKGROUND: The freehand-scalpel technique to harvest skin for grafting is a forgotten surgical art. Modern facial surgeons prefer to use local skin flaps or Wolfe-type full grafts to repair facial defects. OBJECTIVE: To determine the relative merits and cosmetic results of freehand skin grafts to cover facial defects following Mohs surgery. METHODS: We used the freehand-scalpel technique to harvest skin from the periauricular region of the neck and cheek, and other sites. After a local anesthetic is injected the number 15 or 10 blade is used to harvest skin by sequential tangential incisions. The average dermal thickness was about 1.0 mm. To improve cosmetic appearance, the overall shape and thickness of the graft was contoured during harvesting to fit cosmetic unit or facial line. RESULTS: For more than 5 years we have used the freehand technique to repair superficial facial defects of the nose, ear, scalp, temple, forehead, and other nonhead sites. A total of 65 freehand procedures were performed to repair facial defects. The distribution of the anatomic sites and sizes are presented. The size ranged from less than 1 cm to greater than 5 cm in diameter. Three typical cases are presented to illustrate the gratifying results that can be obtained with this technique. CONCLUSIONS: In selected sites and patients, the freehand graft is a rapid and convenient method of harvesting skin. When harvested from the preauricular cheek and subauricular neck, the graft is a good match to cover sun-exposed defects of the nose and ear. The major advantages of the freehand technique are that: 1) it expands the number of potential donor sites from which to select the most compatible skin to cover facial defects; 2) it allows the surgeon to efficiently configure the graft to the desired shape and depth to conform to the cosmetic unit or defect that is being reconstructed; 3) it does not require a dermatome or other specialized instrument to perform; and 4) it achieves wound repair with good appearance and function. The freehand partial-thickness skin graft has become our preferred method of grafting superficial facial defects.

Ear↗