Initial Plaque Research Articles

An evolving story of lipoprotein-associated phospholipase A2 in atherosclerosis and cardiovascular risk prediction

This editorial refers to ‘Association of lipoprotein-associated phospholipase A2 levels with coronary artery disease risk factors, angiographic coronary artery disease, and major adverse events at follow-up’† by E.S. Brilakis et al. , on page 137 Over the past 50 years, the age-adjusted mortality rate from cardiovascular disease has decreased substantially. Despite the improved mortality rate, there is evidence that actual cardiovascular event rates remain relatively unchanged (i.e. more people are surviving acute events), and heart disease and stroke continue to be leading causes of death in Western societies.1 Intensive research efforts are currently under way with the goal of further reducing the global burden of cardiovascular disease. An improved understanding of vascular biology and the pathogenesis of atherosclerosis—including the role of inflammatory processes—may prove helpful in achieving this goal. Atherosclerosis is a condition involving numerous complex processes within the vessel wall that can be characterized as an inflammatory response to injury. The ‘injury’ is most likely attributable to oxidized low-density lipoprotein (LDL) cholesterol, and the inflammatory response is mediated predominantly by monocyte-derived macrophages and T-lymphocytes.2 Together, these cells, along with endothelial cells and vascular smooth muscle cells, express or enhance the expression of inflammatory mediators—cytokines, chemokines, adhesion molecules, growth factors, and other bioactive substances—that play an important role in each stage of atherosclerosis, from initial plaque formation to plaque (in)stability/rupture. Improvements in the understanding of vascular biology have led investigators to evaluate whether certain components of the inflammatory processes may be helpful in identifying high-risk individuals with … *Corresponding author. Tel.: +1 610 270-7227; fax: +1 610 270-6206 E-mail address : colin.h.macphee{at}gsk.com

Genome–genome interactions: bacterial communities in initial dental plaque

The usual context for genome-genome interactions is DNA-DNA interactions, but the manifestation of the genome is the cell. Here we focus on cell-cell interactions and relate them to the process of building multi-species biofilm communities. We propose that dental plaque communities originate as a result of intimate interactions between cells (genomes) of different species and not through clonal growth of genetically identical cells. Although DNA exchange might occur between cells within these communities, we limit our opinions to discussions of the spatiotemporal and metabolic relationships that exist here. We believe the multi-species interactions occurring during the early stages of biofilm formation determine the species composition and nature of the mature biofilm. The human oral cavity provides easy access to natural biofilms on a retrievable enamel chip, which is an excellent model for the study of genome-genome interactions.

Suppression of herpes simplex virus 1 in MDBK cells via the interferon pathway.

Herpes simplex virus (HSV) normally undergoes productive infection in culture, causing cell destruction and plaque formation. Here we characterize an unusual pattern of HSV type 1 (HSV-1) infection in MDBK cells which surprisingly results in suppression of replication, cell recovery, and maintenance of virus. Compared to Vero cells, MDBK cells supported a normal productive infection at a high multiplicity with complete cell destruction. At low multiplicity, HSV also showed an identical initial specific infectivity in the two cell types. Thereafter, the progression of infection was radically different. In contrast to the rapid plaque expansion and eventual destruction in Vero monolayers, in MDBK cells, after initial plaque formation, plaque size actually decreased and, with time, monolayers recovered. Using a green fluorescent protein (GFP)-VP16-expressing virus, we monitored infection in live individual plaques. After early stages of intense GFP-VP16 expression, expression regressed to a thin boundary at the edge of the plaques and was completely suppressed by 10 days. Cells lacking expression then began to grow into the plaque boundaries. Furthermore, following media replacement, individual cells expressing GFP-VP16 could be observed reinitiating infection. The results indicated the production of a potent inhibitory component during infection in MDBK cells, and we show the continued and prolonged presence of interferon in the medium, at times when there was no longer evidence of ongoing productive infection. We exploited the ability of V protein of simian virus 5 to degrade Stat1 and prevent interferon signaling. We established MDBK cells constitutively expressing the V protein with the resultant loss of Stat1. In comparison to the parental cells, infection in these cells now progressed at a rapid rate with expanding plaque formation. We believe the conclusions have significant implications for the study of HSV-1 and interferon signaling both in culture and in animal models.

Spectrum of remodeling behavior observed with serial Long-Term (≥12 months) Follow-Up intravascular ultrasound studies in left main coronary arteries

Most intravascular ultrasound (IVUS) studies of arterial remodeling in native coronary arteries reported a remodeling index obtained at a single time point. We analyzed serial IVUS examinations, including the vessel cross-sectional area changes (remodeling behavior), of 60 hemodynamically nonstenotic left main lesions (baseline vs 18.4 ± 9.4 months follow-up). Lumen reduction resulted from vessel reduction (sometimes despite plaque + media decrease), plaque + media increase (with or without vessel increase), or both. The percent annual changes in lumen area correlated strongly with changes in vessel (r = 0.84), but not with changes in plaque + media area. Plaques were classified as group A lesions, reflecting positive remodeling behavior (vessel changes >0), or group B lesions, reflecting negative (or intermediate) remodeling behavior (vessel changes ≤0). Both groups did not differ significantly in demographics, laboratory data, and medications. Group A lesions (n = 40) more often showed plaque + media increase than group B lesions (32 of 40 [80%] vs 9 of 20 [45%]; p = 0.02). Group A lesions had, on average, mild annual lumen increase despite mild plaque + media increase, i.e, overcompensation of remodeling for plaque + media increase (vessel increase greater than plaque + media area increase, 19 of 40 [47%]). Conversely, group B lesions (n = 20) showed a significant lumen area reduction (−2.8 ± 2.6 mm 2/year) as a result of a decrease in vessel area only. Thus, serial long-term reduction of lumen size may result from vessel shrinkage (sometimes despite plaque decrease), plaque increase (with or without vessel increase), or both; overall, only the remodeling behavior has a significant relation to lumen changes. More than 30% of lesions show a negative remodeling behavior, which shows no relation to patient characteristics or initial plaque burden.

Coaggregation-mediated interactions of streptococci and actinomyces detected in initial human dental plaque.

Streptococci and actinomyces that initiate colonization of the tooth surface frequently coaggregate with each other as well as with other oral bacteria. These observations have led to the hypothesis that interbacterial adhesion influences spatiotemporal development of plaque. To assess the role of such interactions in oral biofilm formation in vivo, antibodies directed against bacterial surface components that mediate coaggregation interactions were used as direct immunofluorescent probes in conjunction with laser confocal microscopy to determine the distribution and spatial arrangement of bacteria within intact human plaque formed on retrievable enamel chips. In intrageneric coaggregation, streptococci such as Streptococcus gordonii DL1 recognize receptor polysaccharides (RPS) borne on other streptococci such as Streptococcus oralis 34. To define potentially interactive subsets of streptococci in the developing plaque, an antibody against RPS (anti-RPS) was used together with an antibody against S. gordonii DL1 (anti-DL1). These antibodies reacted primarily with single cells in 4-h-old plaque and with mixed-species microcolonies in 8-h-old plaque. Anti-RPS-reactive bacteria frequently formed microcolonies with anti-DL1-reactive bacteria and with other bacteria distinguished by general nucleic acid stains. In intergeneric coaggregation between streptococci and actinomyces, type 2 fimbriae of actinomyces recognize RPS on the streptococci. Cells reactive with antibody against type 2 fimbriae of Actinomyces naeslundii T14V (anti-type-2) were much less frequent than either subset of streptococci. However, bacteria reactive with anti-type-2 were seen in intimate association with anti-RPS-reactive cells. These results are the first direct demonstration of coaggregation-mediated interactions during initial plaque accumulation in vivo. Further, these results demonstrate the spatiotemporal development and prevalence of mixed-species communities in early dental plaque.

Calcium phosphate deposition in human dental plaque microcosm biofilms induced by a ureolytic pH-rise procedure

The objectives were to develop and characterize a procedure based on a ureolytic pH rise to deposit calcium phosphate into microcosm dental plaque biofilms and to test the importance of the plaque pH range. Plaque biofilms were cultured in a multiplaque culture system (‘artificial mouth’) with a continuous supply of a simulated oral fluid (basal medium mucin; BMM) with 146 mmol/l (5% w/v) sucrose periodically applied over 6 min every 8 h. After initial plaque growth, the biofilms were periodically exposed for up to 16 days to 6-min applications of calcium phosphate monofluorophosphate urea (CPMU) solution containing 20 mmol/l CaCl 2, 12 mmol/l NaH 2PO 4, 5 mmol/l monofluorophosphate and 500 mmol/l urea (pH 5.0). Three application regimes were examined, one included a sucrose-induced acidic pH fluctuation. Plaque hydrolysis of the urea in CPMU caused the pH to rise to between 8.2 and 8.8, depositing fluoridated and carbonated calcium phosphates, and possibly some calcium carbonate, into the plaque. Calcium, phosphate and fluoride deposition was rapid for about 4 days and then slowed. After 10 days’ treatment under standard conditions (BMM containing 1 mmol/l urea and 1 mmol/l arginine), plaque calcium and phosphate concentrations had increased up to 50-fold and 10-fold to approximately 2–4 and 1–2 mmol/g plaque protein, respectively. The calcium, phosphate and fluoride content increased steadily. Calcium phosphate deposition was proportional to the plaque resting pH, increasing over four-fold when the BMM urea concentration was increased from 0 to 20 mmol/l, which raised the resting pH from 6.4 to 7.2 and yielded a mean plaque calcium concentration of 14.3 mmol/g protein, one subsample reaching 20.8 mmol/g protein. Supplementation of BMM with 20% human serum inhibited deposition. These results support the hypothesis that an alkaline pH in plaque is critical in promoting plaque mineralization and that mineral deposition is modulated by serum. These factors are likely to be important in regulating calculus formation.

P16INK4a Is Selectively Silenced in the Tumoral Progression of Mycosis Fungoides

Knowledge about the molecular mechanisms involved in the pathogenesis of tumoral progression in mycosis fungoides (MF) is still scarce. Because the 9p21 locus seems to be a good target for a detailed study in MF, this prompted us to compare the mechanisms of inactivation of the p16INK4a, p15INK4b, and p14ARF genes in aggressive and stable forms of MF, performing microsatellite analysis, methylation-specific polymerase chain reaction, direct sequencing, and p16INK4a protein expression by immunohistochemistry. Additionally, the p53 gene was also sequenced in tumoral lesions. Thirty-nine patients with stable MF were studied. Alterations in p16INK4a and p15INK4b genes were detected in 18% and 5% of the cases, respectively. None of the cases analyzed showed alterations of the p14ARF gene. In contrast with these findings, in the 11 patients with aggressive MF, alterations of the p16INK4a, p15INK4b, or p14ARF genes were found in 8 (73%), 3 (27%), and 2 (18%) cases, respectively. A significant proportion (4/11) of these alterations were already present in the p16INK4a gene in the initial plaque lesions in these aggressive forms of MF. Alterations in the p16INK4a gene, either methylation or loss of heterozygosity, were clearly more frequent than those in the p15INK4b and p14ARF genes. These p16INK4A alterations were confirmed using immunohistochemistry. None of the nine tumoral lesions analyzed showed mutations in exons 1-2 of the p16INK4a gene or in exons 5-8 of the p53 gene. These results seem to suggest that 9p21 alterations, and selectively p16INK4a silencing, could be a characteristic phenomenon in MF progression.

Mutualism versus independence: strategies of mixed-species oral biofilms in vitro using saliva as the sole nutrient source.

During initial dental plaque formation, the ability of a species to grow when others cannot would be advantageous, and enhanced growth through interspecies and intergeneric cooperation could be critical. These characteristics were investigated in three coaggregating early colonizers of the tooth surface (Streptococcus gordonii DL1, Streptococcus oralis 34, and Actinomyces naeslundii T14V). Area coverage and cell cluster size measurements showed that attachment of A. naeslundii and of S. gordonii to glass flowcells was enhanced by a salivary conditioning film, whereas attachment of S. oralis was hindered. Growth experiments using saliva as the sole carbon and nitrogen source showed that A. naeslundii was unable to grow either in planktonic culture or as a biofilm, whereas S. gordonii grew under both conditions. S. oralis grew planktonically, but to a much lower maximum cell density than did S. gordonii; S. oralis did not grow reproducibly as a biofilm. Thus, only S. gordonii possessed all traits advantageous for growth as a solitary and independent resident of the tooth. Two-species biofilm experiments analyzed by laser confocal microscopy showed that neither S. oralis nor A. naeslundii grew when coaggregated pairwise with S. gordonii. However, both S. oralis and A. naeslundii showed luxuriant, interdigitated growth when paired together in coaggregated microcolonies. Thus, the S. oralis-A. naeslundii pair formed a mutualistic relationship, potentially contact dependent, that allows each to grow where neither could survive alone. S. gordonii, in contrast, neither was hindered by nor benefited from the presence of either of the other strains. The formation of mutually beneficial interactions within the developing biofilm may be essential for certain initial colonizers to be retained during early plaque development, whereas other initial colonizers may be unaffected by neighboring cells on the substratum.

Recurrent unstable angina after directional coronary atherectomy is related to the extent of initial coronary plaque inflammation

OBJECTIVESThis study was performed to evaluate the relationship between plaque inflammation of the initial culprit lesion and the incidence of recurrent angina for one year after directional coronary atherectomy (DCA).BACKGROUNDA positive correlation between coronary plaque inflammation and angiographic restenosis has been reported.METHODSA total of 110 patients underwent DCA. Cryostat sections were immunohistochemically stained with monoclonal antibodies CD68 (macrophages), CD-3 (T lymphocytes) and alpha-actin (smooth muscle cells [SMCs]). The SMC and macrophage contents were planimetrically quantified as a percentage of the total tissue area. T lymphocytes were counted as the number of cells/mm2. The patients were followed for one year to document recurrent unstable angina pectoris (UAP) or stable angina pectoris (SAP).RESULTSRecurrent UAP developed in 16 patients, whereas recurrent SAP developed in 17 patients. The percent macrophage areas were larger in patients with recurrent UAP (27 ± 12%) than in patients with recurrent SAP (8 ± 4%; p = 0.0001) and those without recurrent angina (18 ± 14%; p = 0.03). The number of T lymphocytes was also greater in patients with recurrent UAP (25 ± 14 cells/mm2) than in patients with recurrent SAP (14 ± 8 cells/mm2; p = 0.02) and those without recurrent angina (14 ± 12 cells/mm2; p = 0.002). Multiple stepwise logistic regression analysis identified macrophage areas and T lymphocytes as independent predictors for recurrent UAP.CONCLUSIONSThere is a positive association between the extent of initial coronary plaque inflammation and the recurrence of unstable angina during long-term follow-up after DCA. These results underline the role of ongoing smoldering plaque inflammation in the recurrence of unstable angina after coronary interventions.

Three-dimensional power-mode ultrasound for quantification of the progression of carotid artery atherosclerosis

Elucidation of the dynamic nature of plaque progression has important implications for clinicians. The present study sought to establish an in vivo method for visualizing structural changes in carotid plaques. Three-dimensional reconstruction of parallel two-dimensional gray-scale B-mode ultrasound combined with power-mode examination of 38 carotid artery plaques was performed in a prospective study of 32 patients (18 men, 14 women; mean age 67.5 +/- 7.6 years). Initial mean plaque volume was 391 microl. After a mean of 18.9 months carotid artery plaque progression had occurred in 15% of carotid artery plaques, with plaque volume increasing 59% in these cases. Plaque volume remained constant, within a range of +/- 20% in 85% of cases. Progressive plaques were predominantly hypoechoic (3/5 cases) or had an ulcerated surface in cases of a hyperechoic echogenicity (2/5 cases). Risk factors and drug therapy were unrelated to plaque progression. This study illustrates that the combination of three-dimensional ultrasound with power-mode imaging improves the separation of the intraluminal plaque surface from the vessel lumen. Three-dimensional reconstruction of atherosclerotic carotid artery plaques enables the reproducible quantification of plaque volume and is therefore an excellent technique for longitudinal trials assessing progression or regression of carotid artery disease.

The pH of dental plaque in its relation to early enamel caries and dental plaque flora in humans.

Dental caries appears to result from the action of multiple, interrelated factors. A companion study dealt with the plaque-flora/caries relationship (van Ruyven et al., 2000). The plaque-pH/caries relationship is the subject of this study. Since both studies involve the same subjects, plaques, and tooth surfaces, data on the examined factors have also been integrated. In vivo plaque pH determinations (microelectrode) were done on buccal sound (s) and "white-spot" (ws) caries surfaces in a selected dentition area in a low-caries (no ws) and higher-caries subject group. The pH response to sugar was evaluated before and after a sugar rinse, a local sugar application, or sucking on a sugary lozenge. pH profiles with sugar rinsing and normal or limited salivary flow conditions, showed progressively decreasing plaque pH values at various time points in the order of: low-caries subjects (s sites), higher-caries subjects (s sites), higher-caries subjects (s + ws sites), and higher-caries subjects (ws sites). The minimum pH values showed the same trend. Analyses of all data indicated only a statistical difference for minimum values for s sites in low-caries subjects vs. ws sites in higher-caries subjects, and for s and ws sites in the latter. Local sugar application and sucking on a sugary lozenge induced smaller pH drops than sugar rinsing; such suboptimal sugar exposure caused a disappearance of the difference between the minimum pH values for s and ws sites observed with sugar rinsing in the higher-caries subjects. Initial plaque pH values were similar regardless of subject or tooth caries status. The values were also not correlated with the plaque levels of strongly iodophilic polysaccharide-storing bacteria. Collectively, both studies indicate that increasing subject caries status is characterized by increasing plaque levels of highly-acid-tolerant, acidogenic bacteria and an increasing plaque-pH-lowering potential and support the dynamic relationship between these parameters.

Intraoperative echographic localization of iodine-125 episcleral plaque for brachytherapy of choroidal melanoma

PURPOSE: To report intraoperative echographic localization of iodine-125 episcleral plaque for brachytherapy of choroidal melanoma. METHODS: In a retrospective study, 117 eyes with medium-sized choroidal melanoma in 117 patients not participating in the Collaborative Ocular Melanoma Study underwent iodine-125 episcleral plaque radiotherapy with intraoperative echographic verification of plaque placement between January 1992 and December 1998 at the Bascom Palmer Eye Institute. RESULTS: After initial plaque placement using standard localization techniques, intraoperative echography demonstrated satisfactory tumor–plaque apposition in 76% of eyes (89 of 117). In the 28 eyes (28 of 117, 24%) that required repositioning of the plaque, the extent of misplacement was less than 1 mm in 10 eyes, 1.1 to 3.0 mm in six eyes, and greater than 3 mm in eight eyes. Two eyes had tilting of the plaque, and in two additional eyes, although the plaque covered all tumor margins, the centration was considered suboptimal. Repositioning was necessary in 1 eye with an anteriorly located tumor (1 of 13, 7.7%) and in 20 eyes with peripapillary or posterior pole tumors (20 of 67, 26.3%). Anteriorly located tumors required plaque repositioning significantly less frequently than did posteriorly located tumors ( P = .041). Misalignment involved one tumor margin in 23 eyes and two margins in five eyes. The most commonly misaligned margins were the lateral (35%) and posterior margins (26%). In no case was an anterior marginal misalignment documented. At a mean follow-up of 37 months, no tumor-related death or metastatic disease was noted. Two of the 117 patients (1.7%) had local tumor recurrence and underwent enucleation. CONCLUSIONS: Intraoperative echography is an effective adjunct for localization and confirmation of tumor–plaque relationship. This technique facilitates the identification and correction of suboptimal plaque placement at the time of surgery, potentially minimizing treatment failures.

Psychological stress and the progression of carotid artery disease.

We examined the relation between cardiovascular reactivity (the response of the cardiovascular system to psychological stress) and the severity and progression of carotid atherosclerosis. Using duplex ultrasonography, we measured the change in the area of all detectable plaques in the extracranial carotid arteries during 2 years. Cardiovascular reactivity was assessed by measuring changes in hemodynamics during a frustrating cognitive task (the Stroop Color Word Interference Task). Established risk factors for atherosclerosis were measured by interviewing patients, a physical examination, and blood assays for 351 subjects with a wide range of types of atherosclerotic disease. Atherosclerotic plaques were present in the carotid arteries of 273 (78%) subjects. In a forward stepwise multiple regression analysis, it was found that greater age (beta = 0.46), a history of hypertension (beta = 0.20), use of lipid level-lowering agents (beta = 0.18), a longer history of smoking (beta = 0.13), a larger cholesterol:high-density lipoprotein ratio (beta = 0.13), a smaller change in heart rate during the task (beta = -0.12), and a higher resting systolic blood pressure (SBP; beta = 0.11) were associated significantly with a greater plaque area (R2 = 0.35). In 136 untreated subjects who were followed up for 2 years, a greater change in SBP during the task (beta = 0.28), a higher total cholesterol: high-density lipoprotein ratio (beta = 0.23), a shorter resting preejection period (beta = -0.19), and a lower body mass index (beta = -0.17) were significant predictors of the change in atherosclerosis, after controlling for age and initial plaque area in a stepwise multiple regression analysis (R2 = 0.24). These results support the hypothesis that hemodynamic responses under conditions of mental stress may influence the progression of atherosclerosis.

Sucrose-dependent accumulation of oral streptococci and their adhesion-defective mutants on saliva-coated hydroxyapatite.

The adhesion and accumulation of oral streptococci on saliva-coated hydroxyapatite was examined in strains representing species that appear in initial plaque (Streptococcus sanguise FC1 and Streptococcus oralis C5) and in more mature plaque (Streptococcus gordonii G9B). Washed cells of strains FC1 and C5 did not attach better to saliva-coated hydroxyapatite than did strain G9B, suggesting that the degree of initial adhesiveness does not alone account for the temporal appearance of these bacteria in dental plaque. Growing cells of each strain were also examined for their ability to accumulate on saliva-coated hydroxyapatite. The addition of sucrose to the medium promoted the accumulation of strain G9B more than it promoted the accumulation of strains FC1 and C5. Sucrose also enhanced the accumulation of adhesion-defective mutants of each strain to levels similar to those of the respective parent strains. These results suggest that sucrose-dependent accumulation may facilitate the colonization of the tooth surface by these species of oral streptococci when adhesion is limited by reduced bacterial adhesiveness or limited pellicle-binding sites.

Prognosis of overdenture abutments in elderly patients with controlled oral hygiene. A 5 year study

The effect of controlled oral hygiene was studied in 31 elderly overdenture patients involving 72 abutments over a period of 5 years. Intensive instruction and motivation in oral hygiene care were carried out prior to prosthodontic treatment and two to four times yearly during the study period. The initial dental and periodontal conditions were very poor, with a mean loss of proximal bone adjacent to the abutments of 61%. During the study period, it was possible to maintain mean plaque index scores of 0.45-0.73 and mean gingival index scores of 0.89-0.95 adjacent to the abutments. There was no relationship between the patients' initial plaque index score and the oral and denture hygiene observed during the study. There was spontaneous regression of 4-5 mm periodontal pockets, whereas deeper pockets persisted. Seven abutments were extracted due to periodontal complications. Caries was a minor problem which could be controlled by hygienic measures, topical fluoride or fillings. The present study has shown that it was possible to maintain teeth as overdenture abutments to a large extent in elderly patients initially having a poor dental and periodontal status.

A descriptive epidemiological study on pleural plaque cases identified from the worker's periodical health examinations in Kitakyushu, Japan.

Thirty-six pleural plaque (PP) cases, were identified from the worker's periodical health examination and were described in terms of its association with occupational exposure to asbestos and radiographic findings. Based on thorough interviews about job histories, 23 (64%) of the cases were classified to have had "definite" and an additional 5 (14%) with "possible" asbestos-exposed job histories. Asbestos-exposed job histories were represented mostly by plumbing and pipe fitting, insulating, and boiler and pipe insulating. The latency period between initial age of asbestos exposure and age at time of initial plaque detection was 31.1 +/- 10.3 yr. Calcified plaques were most prevalent in the diaphragm and the most frequent combination of multi-site PPs was found in the diaphragm and lung fields. All cases were either current or ex-smokers. The findings suggest that subjects with a history of asbestos exposure can be identified through the detection of PPs in chest X-ray films obtained in the worker's periodical health examinations.

Accumulation of talin in nodes at the edge of the lamellipodium and separate incorporation into adhesion plaques at focal contacts in fibroblasts.

The focal contact forms beneath F-actin-rich ribs, or cytoplasmic precursors, present in the lamellipodia of fibroblasts. The basal part of the precursor is retained at the contact as the initial adhesion plaque. We have examined the distribution of talin in the lamellipodia and adhesion plaques of chicken embryo fibroblasts relative to the process of focal contact formation. Motility of single cells was recorded with differential interference contrast or interference reflection microscopy before fixation and fluorescent staining for talin, F-actin, and vinculin. Talin is present along the extreme edge of the lamellipodium, where it is further concentrated into a series of nodes. The nodes of talin are present at the tips of both larger and finer F-actin-rich ribs and at small structural nodes at the edge of the lamellipodium. We suggest that the talin in the nodes functions, via a cross-linking activity, in the convergence of actin filaments at the membrane during development of the ribs. Talin accumulates de novo in the adhesion plaque, independent of that at the tip of the precursor, in response to contact with the substrate. This second accumulation of talin at the focal contact starts before vinculin, consistent with a sequential binding of talin at the membrane and of vinculin to talin. The results imply that talin functions independently at two steps during formation of the focal contact: the development of the F-actin-rich precursor of the contact; and development of the contact-associated adhesion plaque, both involving organization of F-actin at the membrane.

Ecology of viridans streptococci in the oral cavity and pharynx

Recently published taxonomic studies of viridans streptococci have resulted in several changes in the nomenclature and definition of oral streptococcal species. With this background, the ecology of streptococci in the oropharyngeal cavities was reinvestigated. The results based on the examination of 1426 streptococcal isolates confirmed and extended earlier findings. Apart from mature supragingival plaque, which contained a mixture of all orally encountered streptococci, each site showed a characteristic streptococcal flora. Initial dental plaque formation is primarily associated with Streptococcus sanguis, Streptococcus mitis biovar 1 and Streptococcus oralis. Our investigation showed that S. sanguis and S. mitis biovar 1 were the most prominent streptococci, also on buccal mucosa. In contrast, S. oralis was almost exclusively found in initial dental plaque. Streptococcus gordonii, formerly part of S. sanguis, was found in small numbers on the oropharyngeal mucosa and in mature supragingival plaque. The dorsum of the tongue was dominated by S. mitis biovar 2 and Streptococcus salivarius, the latter of which was predominant also on the pharyngeal mucosa. Streptococcus anginosus was by far the most predominant streptococcus in subgingival plaque. Immunoglobulin A1 (IgA1) protease-producing streptococci were primarily isolated from initial dental plaque and from the buccal mucosa. This lends further support to the concept of IgA1 proteases being important for the ability of streptococci to evade the local immune defence during their initial colonization of certain oral surfaces.

Long-Term Results of Coronary Balloon Angioplasty

Long-term results after coronary balloon angioplasty are characterized by an eventful early period up to six months, with about a 30% recurrence rate per lesion, and by a stable situation thereafter. Myocardial infarction due to the dilated site is extremely rare during follow-up because the smooth, elastic, inner lining of a restenosis is much less prone to thrombosis than the initial plaque. A positive effect of coronary angioplasty on survival has not been documented, but there is clear functional improvement over the natural course of the untreated disorder. The improvement is comparable to that attained by bypass surgery if repeat angioplasty during the first months is considered as part of the procedure rather than as proof of failure.

Increased senile plaques without microglia in Alzheimer's disease

To clarify the association of microglia with senile plaques, the brains from 13 patients with Alzheimer's disease (AD) and 23 nondemented aged controls were investigated immunohistochemically by a double-labeling method using anti-beta-protein antiserum and anti-ferritin antibody, which is a recently reported microglia marker. In addition, a quantitative analysis was performed. The senile plaques which appeared initially in the nondemented aged controls consisted of a diffuse type without any amyloid cores and these were found in the group aged 50-59 years. The great majority of them were found to contain no ferritin-positive microglia. The number and proportion (percentage) of microglia-containing diffuse plaques increased with age. Classical and compact plaques began to appear in the brains of the group aged 70 years and over, and practically all of them contained microglia. These results suggest that microglia are not associated with initial plaque formation, but correlate with amyloid core formation. In AD, the most prominent feature was that the diffuse plaques, which contained either no or only a few ferritin-positive microglia, increased markedly.