The hemidesmosomal plaque

To examine whether constituent proteins of hemidesmosomal structures can be used as markers for certain pathways of epithelial differentiation we have examined the occurrence of the major M- approximately 230,000 plaque protein, the "bullous pemphigoid" (BP) antigen. Several bovine, rat and human tissues and bovine cell culture lines were examined, using different human autoantibody preparations in immunocytochemistry and immunoblotting. We report that this protein, also unequivocally identified by cDNA cloning from expression libraries and DNA sequencing, occurs not only in different stratified epithelia but also, apparently always in hemidesmosomal structures, in urothelium of bladder and the complex epithelia of trachea, bronchus and several glands, notably myoepithelium-containing skin glands, the mammary gland and salivary glands. The protein is absent, however, in all single-layered epithelia and in several tissues reported to have subplasmalemmal densities structurally similar to hemidesmosomes, such as Purkinje fibers of heart, meninges and perineuria. A mammary-gland-derived epithelial cell line (BMGE + H) is particularly rich in hemidesmosomes. This has been used to study the endocytotic uptake of hemidesmosome-containing plasma membrane domains into cytoplasmic vesicles upon detachment of cell sheets during treatment with dispase, a proteolytic enzyme. We propose to use the Mr- approximately 230,000 plaque protein as a marker selective for certain subsets of epithelial cell types and epithelium-derived tumors in studies of fetal and tumor development, including differentiation diagnosis of carcinomas.     

The kinetics of hemolytic plaque formation. IV. IgM plaque inhibition.

An analysis of the inhibition of hemolytic plaques formed against IgM antibodies is presented. The starting point is the equations of DeLisi &; Bell (1974) which describe the kinetics of plaque growth, and DeLisi &; Goldstein (1975) which describe inhibition of IgG plaques. However, the physical chemical models which were used previously to describe IgG inhibition data are shown to be inadequate for describing the characteristics of IgM inhibition curves. Moreover, it is shown that the experimental results place severe restrictions on the possible choices of physical chemical models for IgM upon which to base the calculations. It is argued that in order to account even qualitatively for all the data, one must assume (1) a very restricted motion of IgMs about the Fab hinge region and (2) a very narrow secretion rate distribution of IgM by antibody secreting cells.     

The electrophoretic hemolytic plaque assay - theory

We use the mathematical theory of plaque growth to determine if there is merit in performing a hemolytic plaque assay in the presence of an external electric field. In particular, we study the effects of an electric field on the transport of anti-bodies secreted by a single lymphocyte and on the size and shape of the plaques they produce. Our results indicate that in the presence of an applied electric field: (1) The mobility of the antibodies produced by the antibody forming cell can be determined from the plaque shape. (In the electric field the plaques are no longer circular, but cigar shaped.) (2) By changing the magnitude or direction of the applied electric field more than one plaque can be generated by a single AFC. Thus changes in mobility or the rate of antibody secretion can be assayed. (3) Plaques will reach a steady state size; for good emitters (cells that secrete antibodies at a high rate or that secrete high affinity antibodies) this steady state will be achieved rapidly.Equations are given which describe both the temporal development and steady state plaque size and shape. From the equations, computer generated plots of plaques produced by typical antibody farming cells are presented. These plots are then used to show how pictures of plaques formed in an electric field can be analyzed to determine the antibody mobility.     

The association of pericardial fat with calcified coronary plaque

Background: Pericardial fat has a higher secretion of inflammatory cytokines than subcutaneous fat. Cytokines released from pericardial fat around coronary arteries may act locally on the adjacent cells. Objective: We examined the relationship between pericardial fat and calcified coronary plaque. Methods and Procedures: Participants in the community‐based Multi‐Ethnic Study of Atherosclerosis (MESA) underwent a computed tomography (CT) scan for the assessment of calcified coronary plaque in 2000/2002. We measured the volume of pericardial fat using these scans in 159 whites and blacks without symptomatic coronary heart disease from Forsyth County, NC, aged 55–74 years. Results: Calcified coronary plaque was observed in 91 participants (57%). After adjusting for height, a 1 s.d. increment in pericardial fat was associated with an increased odds of calcified coronary plaque (odds ratio (95% confidence interval): 1.92 (1.27, 2.90)). With further adjustment of other cardiovascular factors, pericardial fat was still significantly associated with calcified coronary plaque. This relationship did not differ by gender and ethnicity. On the other hand, BMI and height‐adjusted waist circumference were not associated with calcified coronary plaque. Discussion: Pericardial fat is independently associated with calcified coronary plaque.     

The complement of desmosomal plaque proteins in different cell types

Desmosomal plaque proteins have been identified in immunoblotting and immunolocalization experiments on a wide range of cell types from several species, using a panel of monoclonal murine antibodies to desmoplakins I and II and a guinea pig antiserum to desmosomal band 5 protein. Specifically, we have taken advantage of the fact that certain antibodies react with both desmoplakins I and II, whereas others react only with desmoplakin I, indicating that desmoplakin I contains unique regions not present on the closely related desmoplakin II. While some of these antibodies recognize epitopes conserved between chick and man, others display a narrow species specificity. The results show that proteins whose size, charge, and biochemical behavior are very similar to those of desmoplakin I and band 5 protein of cow snout epidermis are present in all desmosomes examined. These include examples of simple and pseudostratified epithelia and myocardial tissue, in addition to those of stratified epithelia. In contrast, in immunoblotting experiments, we have detected desmoplakin II only among cells of stratified and pseudostratified epithelial tissues. This suggests that the desmosomal plaque structure varies in its complement of polypeptides in a cell-type specific manner. We conclude that the obligatory desmosomal plaque proteins, desmoplakin I and band 5 protein, are expressed in a coordinate fashion but independently from other differentiation programs of expression such as those specific for either epithelial or cardiac cells.     

A novel workflow combining plaque imaging,plaque and plasma proteomics identifies biomarkers of human coronary atherosclerotic plaque disruption

Background

Atherosclerotic plaque rupture is the culprit event which underpins most acute vascular syndromes such as acute myocardial infarction. Novel biomarkers of plaque rupture could improve biological understanding and clinical management of patients presenting with possible acute vascular syndromes but such biomarker(s) remain elusive. Investigation of biomarkers in the context of de novo plaque rupture in humans is confounded by the inability to attribute the plaque rupture as the source of biomarker release, as plaque ruptures are typically associated with prompt down-stream events of myocardial necrosis and systemic inflammation.

Methods

We developed a novel approach to identify potential biomarkers of plaque rupture by integrating plaque imaging, using optical coherence tomography, with both plaque and plasma proteomic analysis in a human model of angioplasty-induced plaque disruption.

Results

We compared two pairs of coronary plaque debris, captured by a FilterWire Device, and their corresponding control samples and found matrix metalloproteinase 9 (MMP9) to be significantly enriched in plaque. Plaque contents, as defined by optical coherence tomography, affect the systemic changes of MMP9. Disruption of lipid-rich plaque led to prompt elevation of plasma MMP9, whereas disruption of non-lipid-rich plaque resulted in delayed elevation of plasma MMP9. Systemic MMP9 elevation is independent of the associated myocardial necrosis and systemic inflammation (measured by Troponin I and C-reactive protein, respectively). This information guided the selection of a subset of subjects of for further label free proteomics analysis by liquid chromatography tandem mass spectrometry (LC–MS/MS). We discovered five novel, plaque-enriched proteins (lipopolysaccharide binding protein, Annexin A5, eukaryotic translocation initiation factor, syntaxin 11, cytochrome B5 reductase 3) to be significantly elevated in systemic circulation at 5 min after plaque disruption.

Conclusion

This novel approach for biomarker discovery in human coronary artery plaque disruption can identify new biomarkers related to human coronary artery plaque composition and disruption.

     

Dental bacterial plaque

The literature on the subject of dental bacterial plaque is extensive. In spite of considerable research, the mode of its formation together with the variability in bacterial content requires further clarification. Mechanical methods of plaque control are effective but limited in a population sense. Of the numerous chemotherapeutic agents in plaque control, chlorhexidin appears the most effective.     

Dental plaque formation

Dental plaque is a complex biofilm that accumulates on the hard tissues (teeth) in the oral cavity. Although over 500 bacterial species comprise plaque, colonization follows a regimented pattern with adhesion of initial colonizers to the enamel salivary pellicle followed by secondary colonization through interbacterial adhesion. A variety of adhesins and molecular interactions underlie these adhesive interactions and contribute to plaque development and ultimately to diseases such as caries and periodontal disease.     

Atherosclerotic plaque development

Atherosclerosis is now recognized as an inflammatory/immunomodulatory reaction to the presence of oxidized low-density lipoproteins within the arterial wall, often times in the setting of such risk factors as family history, hypercholesterolemia, high blood pressure, diabetes mellitus and smoking. The progression to high-risk lesions such as thin-fibrous cap atheromas results in an increased risk of sudden death, acute myocardial infarction and ischemic stroke. The interplay of macrophages, T lymphocytes and mast cells play a central role in both the development but more importantly in the progression of coronary and carotid artery disease to high-risk phenotypes.     

The structure and formation of the byssus attachment plaque in Mytilus

The byssus attachment plaque and the tissues responsible for its formation were studied in M. califomianus by light microscopy and by transmission and scanning electron microscopy. It was shown that the plaque consists of at least three phases which ultrastructurally resemble three secretions considered to be collagen, mucoid material and polyphenol. The mucoid and polyphenol appear to mix as a colloidal suspension in which the latter is the continuous phase and forms the definitive bonding surface. Plaque collagen represents an extension of thread material into the cementing substance. Stimulated secretion within the ducts and distal depression of the mussel's foot shows a continuum of increasing heterogeneity from the inner toward the outer regions. This reflects the distribution of exocrine cell apices wherein exocytosis of polyphenol granules predominate deeply, mucous granules superficially and collagen granules in between. It is proposed that the morphology of the plaque conforms to theoretical physical-chemical requirements for adhesion under water.     

The hemolytic plaque assay: theory for finite layers.

We extend the mathematical theory of hemolytic plaque growth to include plaques produced by cells secreting antibodies in layers of finite thickness. Previous theories have assumed that the layer was either two-dimensional or of infinite thickness. By using the method of images we derive an equation for the plaque radius as a function of time for layers of any thickness. We show that at short times and at long times the equation reduces to the appropriate infinite three-dimensional and two-dimensional limiting forms, and obtain expressions for estimating the range of times for which these limiting results are valid. For the liquid monolayer technique we obtain a new limiting result. The equation for the plaque radius is a transcendental equation which we solve numerically for a number of cases of interest. These results illustrate a variety of different features of plaque growth associated with the finite thickness of the layer. Experimental studies are usually carried out in layers whose thicknesses are not standardized. In the assays commonly used the thickness h can vary more than six hundred fold, i.e. 1 × 10^?3 cm ?h? 6.5 × 10^?1 cm. Such variation in h will cause widely different kinetics of plaque growth. For typical plaque experiments of one hour duration the two-dimensional limit is valid when h ? 3 × 10^?3 cm while the infinite thickness limit is valid when h? 10^?1 cm. For thicknesses in between these values the finite layer results must be used.     

Molecular mechanisms of plaque instability

PURPOSE OF REVIEW: Coronary artery thrombosis superimposed on a disrupted atherosclerotic plaque initiates abrupt arterial occlusion and is the proximate event responsible for 60-80% cases of acute coronary syndromes. This article provides a concise update on the evolving concepts in the pathophysiology of plaque rupture and thrombosis. RECENT FINDINGS: Over the past several years, the critical role of plaque composition rather than plaque size or stenosis severity, in plaque rupture and thrombosis have been recognized. The necrotic lipid core and plaque inflammation appear to be key factors. Extracellular matrix loss in the fibrous cap, a prelude to rupture, is attributed to matrix degrading enzymes as well as to death of matrix synthesizing smooth muscle cells; inflammation appears to play a critical role in both these processes. Inflammatory cell derived tissue factor is a key contributor to plaque thrombogenicity. Inflammation has also been implicated in plaque neovascularity, intraplaque hemorrhage and plaque expansion. Recent observations have also highlighted the important modulatory role of immune system in atherosclerosis and plaque composition. SUMMARY: Improved understanding of mechanisms causing plaque instability should provide novel insights into prevention of athero-thrombotic cardiovascular events.     

The modulation of exoglycosidic enzymes in the supragingival plaque of macaque monkeys

Abstract Dental plaque was collected from the teeth of monkeys either fed a low-sucrose diet, fasted, or fasted and provided with drinking water supplemented with either 0.025 M N -acetylglucosamine or 0.025 M glucose. Each plaque sample was assayed for α- l -fucosidase, β-N-acetyl- d -galactosaminidase, β- N -acetyl- d -glucosaminidase and neuraminidase activity. Fasting significantly raised the levels of each of these enzymes, while N -acetylglucosamine in the drinking water of fasted monkeys reduced the enzyme levels to those found in the fed monkeys. With the exception of neuraminidase, the addition of glucose to the drinking water of fasted monkeys did not significantly alter the enzyme levels below those found in the fasted monkeys. These results suggest that N -acetylhexosamines, major constituents of salivary glycoproteins, may serve as a readily available source of both carbon and nitrogen for bacterial growth in vivo.     

Optimizing bacteriophage plaque fecundity

Bacteriophages (phages), the viruses of bacteria, form visible lesions within bacterial lawns (called plaques), which are employed ubiquitously in phage isolation and characterization. Plaques also can serve as models for phage population growth within environments that display significant spatial structure, e.g. soils, sediments, animal mucosal tissue, etc. Furthermore, phages growing within plaques, in experimental evolution studies, may become adapted to novel conditions, may be selected for faster expansion, or may evolve toward producing more virions per plaque. Here, we examine the evolution of the latter, greater plaque fecundity, considering especially tradeoffs between phage latent period and phage burst size. This evolution is interesting because genetically lengthening latent periods, as seen with phage lysis-timing mutants, should increase phage burst sizes, as more time is available for phage-progeny maturation during infection. Genetically shortening latent periods, however, is a means toward producing larger phage plaques since phage virions then can spend more time diffusing rather than infecting. With these larger plaques more bacteria become phage infected, resulting in more phage bursts. Given this conflict between latent period's impact on per-plaque burst number versus per-infection burst size, and based on analysis of existing models of plaque expansion, we provide two assertions. First, latent periods that optimize plaque fecundity are longer (e.g. at least two-fold longer) than latent periods that optimize plaque size (or that optimize phage population growth within broth). Second, if increases in burst size can contribute to plaque size (i.e. larger plaques with larger bursts), then latent-period optima that maximize plaque fecundity should be longer still. As a part of our analysis, we provide a means for predicting latent-period optima-for maximizing either plaque size or plaque fecundity-which is based on knowledge of only phage eclipse period and the relative contribution of phage burst size versus latent period toward plaque size.     

The mechanics of atherosclerotic plaque rupture by inclusion/matrix interfacial decohesion

Histological investigation along with finite element analysis of arterial wall/atherosclerotic plaque geometries indicates the paradoxical result that ruptures often occur at sites with predicted stresses of half the plaque cap strength. Recent experiments have revealed calcified cells within the cap suggesting that these inclusions, situated close to the cap/luminal blood surface, precipitate rupture at low nominal loads by concentrating stress. In this paper, we investigate the proposition that rupture at low nominal loads occurs by (possibly brittle) decohesion of the calcification/cap interface followed by tearing of cap tissue. A novel boundary value problem is analyzed consisting of a remotely loaded linear elastic layer (extracellular matrix cap) containing a rigid spherical inclusion (calcified cell) that interacts with it through a nonlinear structural interface which models the binding of the calcified cell to the extracellular matrix via integrin receptor proteins. Equilibrium solutions are obtained from equations derived from the Boussinesq potentials for spherical domains. Results indicate a brittle character to the rupture process with the size of the domains between the inclusion center and the matrix surfaces determining the concentration of stress. For an inclusion close to a surface the abrupt unloading of the interface during brittle decohesion produces a sharp spike in circumferential stress. We conjecture that when this dynamic stress exceeds the cap strength, tearing occurs followed by thrombus formation and possibly infarction.     

The cytoplasmic plaque of tight junctions: A scaffolding and signalling center

The region of cytoplasm underlying the tight junction (TJ) contains several multimolecular protein complexes, which are involved in scaffolding of membrane proteins, regulation of cytoskeletal organization, establishment of polarity, and signalling to and from the nucleus. In this review, we summarize some of the most recent advances in understanding the identity of these proteins, their domain organization, their protein interactions, and their functions in vertebrate organisms. Analysis of knockdown and knockout model systems shows that several TJ proteins are essential for the formation of epithelial tissues and early embryonic development, whereas others appear to have redundant functions.