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R T Lee

Publications and source records attributed to R T Lee.

At least 37 records · Page 2Linked to original sources
PubMed2001

Receptor-based differences in human aortic smooth muscle cell membrane stiffness.

Cells respond to mechanical stimuli with diverse molecular responses. The nature of the sensory mechanism involved in mechanotransduction is not known, but integrins may play an important role. The integrins are linked to both the cytoskeleton and extracellular matrix, suggesting that probing cells via integrins should yield different mechanical properties than probing cells via non-cytoskeleton-associated receptors. To test the hypothesis that the mechanical properties of a cell are dependent on the receptor on which the stress is applied, human aortic smooth muscle cells were plated, and magnetic beads, targeted either to the integrins via fibronectin or to the transferrin receptor by use of an IgG antibody, were attached to the cell surface. The resistance of the cell to deformation ("stiffness") was estimated by oscillating the magnetic beads at 1 Hz by use of single-pole magnetic tweezers at 2 different magnitudes. The ratio of bead displacements at different magnitudes was used to explore the mechanical properties of the cells. Cells stressed via the integrins required approximately 10-fold more force to obtain the same bead displacements as the cells stressed via the transferrin receptors. Cells stressed via integrins showed stiffening behavior as the force was increased, whereas this stiffening was significantly less for cells stressed via the transferrin receptor (P<0.001). Mechanical characteristics of vascular smooth muscle cells depend on the receptor by which the stress is applied, with integrin-based linkages demonstrating cell-stiffening behavior.

Antibodies↗
PubMed2000

Overexpression of eotaxin and the CCR3 receptor in human atherosclerosis: using genomic technology to identify a potential novel pathway of vascular inflammation.

BACKGROUND: Unstable atherosclerotic lesions typically have an abundant inflammatory cell infiltrate, including activated T cells, macrophages, and mast cells, which may decrease plaque stability. The pathophysiology of inflammatory cell recruitment and activation in the human atheroma is incompletely described. METHODS AND RESULTS: We hypothesized that differential gene expression with DNA microarray technology would identify new genes that may participate in vascular inflammation. RNA isolated from cultured human aortic smooth muscle cells treated with tumor necrosis factor-alpha (TNF-alpha) was examined with a DNA microarray with 8600 genes. This experiment and subsequent Northern analyses demonstrated marked increases in steady-state eotaxin mRNA (>20 fold), a chemokine initially described as a chemotactic factor for eosinophils. Because eosinophils are rarely present in human atherosclerosis, we then studied tissue samples from 7 normal and 14 atherosclerotic arteries. Immunohistochemical analysis demonstrated overexpression of eotaxin protein and its receptor, CCR3, in the human atheroma, with negligible expression in normal vessels. Eotaxin was predominantly located in smooth muscle cells. The CCR3 receptor was localized primarily to macrophage-rich regions as defined by immunopositivity for CD 68; a minority of mast cells also demonstrated immunopositivity for the CCR3 receptor. CONCLUSIONS: Eotaxin and its receptor, CCR3, are overexpressed in human atherosclerosis, suggesting that eotaxin participates in vascular inflammation. These data demonstrate how genomic differential expression technology can identify novel genes that may participate in the stability of atherosclerotic lesions.

Actins↗
PubMed2000

Matrix matters.

Explore the source record for details and available documents.

Animals↗
PubMed2000

Plaque stabilization: the role of lipid lowering.

The unstable atheroma characteristically has a thin, eccentric fibrous cap and a large necrotic core of lipid and cellular debris. This plaque configuration is particularly unstable because large mechanical stresses develop in the thinnest portions of the fibrosis cap over the lipid pool. Numerous recent observations tell us that critical biological factors other than lesion morphology also contribute to the ultimate fracture of the fibrous cap. Matrix-degrading enzymes, particularly members of the metalloproteinase family, are overexpressed in atherosclerotic tissue. The regions with the greatest amounts of these enzymes are the critical high stress regions, which are usually also infiltrated with inflammatory cells. At the cellular level a number of factors regulate expression of these enzymes by vascular smooth muscle cells. These factors include mechanical stimuli and cytokines known to be overexpressed in atheroma by both smooth muscle cells and macrophages. Low density lipoprotein cholesterol in the lesion plays a significant role in most or all of these processes, and our current understanding of the unstable atheroma is consistent with the dramatic clinical successes of lipid-lowering therapy.

Animals↗
PubMed2000

Direct extracellular contact between integrin alpha(3)beta(1) and TM4SF protein CD151.

Previously we established that the alpha(3)beta(1) integrin shows stable, specific, and stoichiometric association with the TM4SF (tetraspannin) protein CD151. Here we used a membrane impermeable cross-linking agent to show a direct association between extracellular domains of alpha(3)beta(1) and CD151. The alpha(3)beta(1)-CD151 association site was then mapped using chimeric alpha(6)/alpha(3) integrins and CD151/NAG2 TM4SF proteins. Complex formation required an extracellular alpha(3) site (amino acids (aa) 570-705) not previously known to be involved in specific integrin contacts with other proteins and a region (aa 186-217) within the large extracellular loop of CD151. Notably, the anti-CD151 monoclonal antibody TS151r binding epitope, previously implicated in alpha(3) integrin association, was mapped to the same region of CD151 (aa 186-217). Finally, we demonstrated that both NH(2)- and COOH-terminal domains of CD151 are located on the inside of the plasma membrane, thus confirming a long suspected model of TM4SF protein topology.

Amino Acid Sequence↗
PubMed2000

Atherosclerotic lesion mechanics versus biology.

The world-wide importance of acute vascular syndromes is increasing. Acute events are usually triggered by fibrous cap disruption and subsequent thrombus formation. Histological studies have established specific structural features common among unstable plaques. The eccentric, lipid-laden plaque has to bear remarkably high mechanical stresses at the "shoulder regions". These internal stresses can reach thousands of millimeters of mercury. In addition, weakening of the extracellular matrix at these sites leads to fibrous cap rupture. Dynamic interactions between inflammatory mediators and matrix cause weakening of the plaque at these high stress locations, and it is likely that lowering cholesterol reduces both mechanical stresses and the inflammation that promotes fibrous cap weakening. Understanding the interplay of plaque architecture, mechanical properties, and matrix biology is critical in the future development of therapies to stabilize lesions.

Animals↗
PubMed2000

Biomechanical regulation of human monocyte/macrophage molecular function.

When the monocyte infiltrates a tissue, adhesion to the extracellular matrix provides structural anchors, and the cell may be deformed through these attachments. To test the hypothesis that human monocytes/macrophages are mechanically responsive, we studied the effects of small cyclic mechanical deformations on cultured human monocytes/macrophages. When monocytes/macrophages were subjected to 4% strain at 1 Hz for 24 hours, neither matrix metalloproteinase (MMP)-1 nor MMP-3 was induced; however, in the presence of phorbol myristate acetate, strain augmented MMP-1 expression by 5.1 +/- 0.7-fold (P < 0.05) and MMP-3 expression by 1. 6 +/- 0.1-fold (P < 0.05). In contrast, MMP-9 expression was not changed by mechanical strain in the presence or absence of phorbol myristate acetate. Deformation rapidly induced the immediate early response genes c-fos and c-jun. In addition, mechanical deformation induced the transcription factor PU.1, an ets family member that is essential in monocyte differentiation, as well as mRNA for the M-CSF receptor. These studies demonstrate that human monocytes/macrophages respond to mechanical deformation with selective augmentation of MMPs, induction of immediate early genes, and induction of the M-CSF receptor. In addition to enhancing the proteolytic activity of macrophages within repairing tissues, cellular deformation within tissues may play a role in monocyte differentiation.

Acetylcysteine↗
PubMed2000

Gemcitabine for relapsed or resistant lymphoma.

BACKGROUND: Gemcitabine therapy has not been widely assessed in the treatment of hematological malignancies. We have examined the efficacy and safety of gemcitabine in patients with relapsed or resistant lymphoma. PATIENTS AND METHODS: Gemcitabine (1 g/m2) was given weekly for 7 consecutive weeks, followed by a week off treatment. The drug was then given for 3 consecutive weeks, followed by a week off treatment; this regimen was continued until disease progression or drug intolerance. Fifteen patients have enrolled. Most have been extensively pre-treated for advanced diffuse large-cell or mantle-cell lymphoma. RESULTS: The drug was well tolerated; no patient suffered treatment-related sepsis, hemorrhage or death. Non-hematopoietic toxicity led to discontinuation of gemcitabine therapy in two patients. Dose reductions or delays were required for about two-thirds of treatments. Of 13 evaluable patients, one had a complete response, 3 a partial response, 3 stable disease, and 6 disease progression. After 6 infusions of gemcitabine, a patient with advanced Hodgkin's disease has had a complete remission lasting 21 months. CONCLUSIONS: Gemcitabine has substantial activity and acceptable toxicity in heavily pre-treated patients with advanced lymphoma. Further study is warranted.

Aged↗
PubMed2000

alpha3-galactosylated glycoproteins can bind to the hepatic asialoglycoprotein receptor.

In mammals, clearance of desialylated serum glycoproteins to the liver is mediated by a galactose-specific hepatic lectin, the 'asialoglycoprotein receptor'. In humans, serum glycoprotein glycans are usually capped with sialic acid, which protects these proteins against hepatic uptake. However, in most other species, an additional noncharged terminal element with the structure Galalpha1-->3Galbeta1-->4R is present on glycoprotein glycans. To investigate if alpha3-galactosylated glycoproteins, just like desialylated glycoproteins, could be cleared by the hepatic lectin, the affinities of alpha3-galactosylated compounds towards this lectin were determined using an in vitro inhibition assay, and were compared with those of the parent compounds terminating in Galbeta1-->4R. Diantennary, triantennary and tetraantennary oligosaccharides that form part of N-glycans were alpha3-galactosylated to completion by use of recombinant bovine alpha3-galactosyltransferase. Similarly, desialylated alpha1-acid glycoprotein (orosomucoid) was alpha3-galactosylated in vitro. The alpha3-galactosylation of a branched, Galbeta1-->4-terminated oligosaccharide lowered its affinity for the membrane-bound lectin on whole rat hepatocytes 50-250-fold, and for the detergent-solubilized hepatic lectin 7-50-fold. In contrast, alpha3-galactosylation of asialo-alpha1-acid glycoprotein caused only a minor decrease in affinity, increasing the IC50 from 5 to 15 nM. Fully alpha3-galactosylated alpha1-acid glycoprotein, intravenously injected into the mouse, was rapidly cleared from the circulation, with a clearance rate close to that of asialo-alpha1-acid glycoprotein (t1/2 of 0.42 min vs. 0.95 min). Its uptake was efficiently inhibited by pre-injection of an excess asialo-fetuin. Organ distribution analysis showed that the injected alpha1-acid glycoprotein accumulated predominantly in the liver. Taken together, these observations suggest that serum glycoproteins that are heavily alpha3-galactosylated will be rapidly cleared from the bloodstream via the hepatic lectin. It is suggested that glycosyltransferase expression in murine hepatocytes is tightly regulated in order to prevent undesired uptake of hepatocyte-derived, circulating glycoproteins.

Animals↗
PubMed2000

The Royal London Space Planning: an integration of space analysis and treatment planning: Part I: Assessing the space required to meet treatment objectives.

The Royal London Space Planning process has evolved since 1985 to ensure a disciplined approach to diagnosis and treatment planning and to provide a record to justify treatment decisions for professional accountability. The analysis takes into consideration most aspects of a given malocclusion and aims to quantify the space required in each dental arch to attain the treatment objectives. Space planning also helps determine whether the objectives are likely to be attainable and helps in the planning of treatment mechanics and the control of anchorage. The process of analysis is divided into 2 sections. The first part consists of assessing the original malocclusion according to various component parts, any of which may have an effect on space if altered during treatment. These components are crowding and spacing, occlusal curves, arch width, anteroposterior position of labial segments, mesiodistal angulation, and incisor inclination. The second part of the analysis, which will be published in a separate article, deals with the effect of treatment procedures, such as extractions, tooth-size modifications, distal or mesial molar movements, as well as natural growth, on the space required. Space planning should be regarded only as a useful guide, as many areas of orthodontics-including growth, biological response, and patient compliance-cannot be controlled with total accuracy.

Cephalometry↗
PubMed2000

The Royal London Space Planning: an integration of space analysis and treatment planning: Part II: The effect of other treatment procedures on space.

The Royal London Space Planning process is carried out in 2 stages. The first stage, assessing the space required to attain the treatment objectives, was described in Part I of this report, published earlier. In Part II, the process of integrating space analysis with treatment planning continues with consideration of the effects other treatment procedures have on space. These procedures include tooth enlargement or reduction, tooth extraction, the creation of space for prosthetic replacement, and mesial and distal molar movement. The effects of favorable and unfavorable growth are also considered. A brief case report is presented to demonstrate use of the Royal London Space Planning.

Cephalometry↗
PubMed2000

Photoaffinity glycoprobes-a new tool for the identification of lectins.

One of the proposed functions for the carbohydrate structures on glycoconjugates is the transfer of information through interaction with specific lectin receptors. However, the number of elucidated functional lectin-carbohydrate interactions is still relatively small, largely due to the lack of adequate methods to identify lectin activity in complex biological samples. Aiming to solve this problem, we have developed a method based on the novel group of compounds we named glycoprobes. The glycoprobe consists of three vital parts: (1) glycan, (2) digoxin tag, and (3) photoreactive crosslinker. When incubated in dark, oligosaccharide part of the glycoprobe forms a complex with lectin. After illumination, covalent link between the probe and the lectin is formed resulting in a digoxin-tagged lectin. Using antibodies against digoxin, this complex can easily be identified immuno/cytochemically, or by Western blots. To demonstrate the applicability of glycoprobes we have used Man(9)-glycoprobe (containing Man(9)oligosaccharide) and YEE(ahGalNAc)(3)-glycoprobe (containing a synthetic neoglycopeptide with three terminal N-acetyl-galactosamine residues; Lee and Lee, Glycoconjugate J., 1987,4, 317) to identify lectins in bovine serum and rat liver membranes. The simplicity of the method enables its application in routine monitoring of changes in lectin activity during various developmental or pathological processes. An example of GalNAc-binding analysis in human serum is shown.

Acetylgalactosamine↗
PubMed2000

How much space is created from expansion or premolar extraction?

The aim of this study was first to investigate the relationship between maxillary arch expansion and change in arch depth (overjet), and secondly to quantify the reduction in maxillary arch depth following extraction of 4\4 with complete space closure. A model of maxillary typodont teeth was constructed to allow expansion and premolar removal. Arch dimensions were recorded using a reflex microscope. A linear relationship was found between arch expansion and reduction of the arch depth. When the premolars were removed, there was a greater reduction in arch depth than the mesio-distal width of these teeth.

Bicuspid↗
PubMed2000

Molecular responses of rat tracheal epithelial cells to transmembrane pressure.

Smooth muscle constriction in asthma causes the airway to buckle into a rosette pattern, folding the epithelium into deep crevasses. The epithelial cells in these folds are pushed up against each other and thereby experience compressive stresses. To study the epithelial cell response to compressive stress, we subjected primary cultures of rat tracheal epithelial cells to constant elevated pressures on their apical surface (i.e., a transmembrane pressure) and examined changes in the expression of genes that are important for extracellular matrix production and maintenance of smooth muscle activation. Northern blot analysis of RNA extracted from cells subjected to transmembrane pressure showed induction of early growth response-1 (Egr-1), endothelin-1, and transforming growth factor-beta1 in a pressure-dependent and time-dependent manner. Increases in Egr-1 protein were detected by immunohistochemistry. Our results demonstrate that airway epithelial cells respond rapidly to compressive stresses. Potential transduction mechanisms of transmembrane pressure were also investigated.

Animals↗
PubMed2000

Targeted deletion of matrix metalloproteinase-9 attenuates left ventricular enlargement and collagen accumulation after experimental myocardial infarction.

Matrix metalloproteinase-9 (MMP-9) is prominently overexpressed after myocardial infarction (MI). We tested the hypothesis that mice with targeted deletion of MMP9 have less left ventricular (LV) dilation after experimental MI than do sibling wild-type (WT) mice. Animals that survived ligation of the left coronary artery underwent echocardiographic studies after MI; all analyses were performed without knowledge of mouse genotype. By day 8, MMP9 knockout (KO) mice had significantly smaller increases in end-diastolic and end-systolic ventricular dimensions at both midpapillary and apical levels, compared with infarcted WT mice; these differences persisted at 15 days after MI. MMP-9 KO mice had less collagen accumulation in the infarcted area than did WT mice, and they showed enhanced expression of MMP-2, MMP-13, and TIMP-1 and a reduced number of macrophages. We conclude that targeted deletion of the MMP9 gene attenuates LV dilation after experimental MI in mice. The decrease in collagen accumulation and the enhanced expression of other MMPs suggest that MMP-9 plays a prominent role in extracellular matrix remodeling after MI.

Animals↗
PubMed2000

How orthodontic functional appliances work.

Orthodontic functional appliances are an essential part of an orthodontist's armamentarium. The amount of their use varies greatly, some feeling they have limited use with minor effects, others claiming dramatic changes in facial growth and appearance, without significant genetic constraints. The evidence on clinical use is not equivocal, the general results however not showing an unlimited amount of skeletal change, but rather a balance of change in the growth of the facial bones and dentition with clinically significant changes in the facial soft tissues. This article examines the current evidence.

Adolescent↗
PubMed2000

Use of microarrays to identify targets in cardiovascular disease.

The year 2000 will long be remembered in biology for the completion of the basic sequence of the human genome. This remarkable achievement comes at a time when the technology for exploiting differential expression of genes in cells and tissues is rapidly progressing. Although many methods have been available over the past two decades for exploring differential expression of genes, DNA microarray technology has already proven revolutionary. The capability of monitoring expression of thousands of genes simultaneously has already yielded unique insight into many physiologic and pathophysiologic processes. For cardiovascular disease, microarray technology promises to provide new understanding of mechanisms of cardiac hypertrophy, heart failure and vascular disease. As the availability of this technology expands and the costs decrease, microarray technology will be an essential method for identifying novel therapeutic and diagnostic targets in cardiovascular disease. In addition to identifying new targets, microarrays have the potential to decrease the long research and development time required to bring a concept to the bedside. Although microarray technology will help fuel the imminent explosion of novel approaches to cardiovascular disease, the technology also requires cautious interpretation and well-considered validation strategies.

Journal Article↗