Evolution of termination codons of proteins and the TAG-TGA paradox

In most eukaryotes and prokaryotes TGA is used at a significantly higher frequency than TAG as termination codon of protein-coding genes. Although this phenomenon has been recognized several years ago, there is no generally accepted explanation for the TAG-TGA paradox. Our analyses of human mutation data revealed that out of the eighteen sense codons that can give rise to a nonsense codon by single base substitution, the CGA codon is exceptional: it gives rise to the TGA stop codon at an order of magnitude higher rate than the other codons. Here we propose that the TAG-TGA paradox is due to methylation and hypermutabilty of CpG dinucleotides. In harmony with this explanation, we show that the coding genomes of organisms with strong CpG methylation have a significant bias for TGA whereas those from organisms that lack CpG methylation use TGA and TAG termination codons with similar probability.

Multivalent γ-PGA-Exendin-4 conjugates to target pancreatic β-cells

Targeting of glucagon‐like peptide 1 receptor (GLP‐1R), expressed on the surface of pancreatic β‐cells, is of great interest for the development of advanced therapies for diabetes and diagnostics for insulinoma. We report the conjugation of exendin‐4 (Ex‐4), an approved drug to treat type 2 diabetes, to poly‐γ‐glutamic acid (γ‐PGA) to obtain more stable and effective GLP‐1R ligands. Exendin‐4 modified at Lysine‐27 with PEG4‐maleimide was conjugated to γ‐PGA functionalized with furan, in different molar ratios, exploiting a chemoselective Diels‐Alder cycloaddition. The γ‐PGA presenting the highest number of conjugated Ex‐4 molecules (average 120 per polymeric chain) showed a double affinity towards GLP‐1R with respect to exendin per se, paving the way to improved therapeutic and diagnostic applications.

Use of signals of positive and negative selection to distinguish cancer genes and passenger genes

A major goal of cancer genomics is to identify all genes that play critical roles in carcinogenesis. Most approaches focused on genes positively selected for mutations that drive carcinogenesis and neglected the role of negative selection. Some studies have actually concluded that negative selection has no role in cancer evolution. We have re-examined the role of negative selection in tumor evolution through the analysis of the patterns of somatic mutations affecting the coding sequences of human genes. Our analyses have confirmed that tumor suppressor genes are positively selected for inactivating mutations, oncogenes, however, were found to display signals of both negative selection for inactivating mutations and positive selection for activating mutations. Significantly, we have identified numerous human genes that show signs of strong negative selection during tumor evolution, suggesting that their functional integrity is essential for the growth and survival of tumor cells.

Differences in the sensitivity of classically and alternatively activated macrophages to TAK1 inhibitor-induced necroptosis

Controlling the balance of pro-inflammatory M1 versus anti-inflammatory M2 macrophages may have paramount therapeutic benefit in cardiovascular diseases, infections, cancer and chronic inflammation. The targeted depletion of different macrophage populations provides a therapeutic option to regulate macrophage-mediated functions. Macrophages are highly sensitive to necroptosis, a newly described regulated cell death mediated by receptor-interacting serine/threonine-protein kinase 1 (RIPK1), RIPK3 and mixed lineage kinase domain like pseudokinase. Antagonists of inhibitors of apoptosis proteins (SMAC mimetics) block RIPK1 ubiquitination, while TGF-activated kinase 1 (TAK1) inhibitors prevent the phosphorylation of RIPK1, resulting in increased necroptosis. We compared the sensitivity of monocyte-derived human M1 and M2 cells to various apoptotic and necroptotic signals. The two cell types were equally sensitive to all investigated stimuli, but TAK1 inhibitor induced more intense necroptosis in M2 cells. Consequently, the treatment of co-cultured M1 and M2 cells with TAK1 inhibitor shifted the balance of the two populations toward M1 dominance. Blockage of either Aurora Kinase A or glycogen synthase kinase 3β, two newly described necroptosis inhibitors, increased the sensitivity of M1 cells to TAK1-inhibitor-induced cell death. Finally, we demonstrated that in vitro differentiated tumor-associated macrophages (TAM-like cells) were as highly sensitive to TAK1 inhibitor-induced necroptosis as M2 cells. Our results indicate that at least two different necroptotic pathways operate in macrophages and the targeted elimination of different macrophage populations by TAK1 inhibitor or SMAC mimetic may provide a therapeutic option to regulate the balance of inflammatory/anti-inflammatory macrophage functions.

Synthesis of 68Ga-Labeled Biopolymer-based Nanoparticle Imaging Agents for Positron-emission Tomography

AIM

The purpose of this study was to develop a folate receptor-targeted ⁶⁸Ga-labeled agent for the detection of cancer cells in mouse models of ovarian cancer by dual positron-emission tomography (PET) and magnetic resonance imaging (MRI). Moreover, we aimed to develop a controlled biopolymer-based chemistry that enables linking metal-binding (here Ga-68) chelators.

MATERIALS AND METHODS

The nanoparticle (NP) agent was created by self-assembling of folic acid-modified polyglutamic acid and chelator-modified chitosan followed by radiolabeling with ⁶⁸Ga (III) ions (⁶⁸Ga-NODAGA-FA). The structure of modified biopolymers was characterized by spectroscopy. Particle size and mobility were determined.

RESULTS

Significant selective binding of NPs was established in vitro using folate receptor-positive KB and - negative MDA-MB-231 cell lines. In vivo tumor uptake of folate-targeted ⁶⁸Ga³⁺-radiolabeled NPs was tested using subcutaneous tumor-bearing CB17 SCID mice models. PET/MR dual modalities showed high tumor uptake with 6.5 tumor-to-muscle ratio and NP localization.

CONCLUSION

In vivo results supporting the preliminary in vitro tests demonstrated considerably higher ⁶⁸Ga-NODAGA-FA nanoparticle accumulation in KB tumors than in MDA-MB-231 tumors, thereby confirming the folate receptor-mediated uptake of this novel potential PET imaging agent.

Structure, function and disease relevance of Wnt inhibitory factor 1, a secreted protein controlling the Wnt and hedgehog pathways

Wnts and Hedgehogs (Hh) are large, lipid-modified extracellular morphogens that play key roles in embryonic development and stem cell proliferation of Metazoa. Both morphogens signal through heptahelical Frizzled-type receptors of the G-Protein Coupled Receptor family and there are several other similarities that suggest a common evolutionary origin of the Hh and Wnt pathways. There is evidence that the secreted protein, Wnt inhibitory factor 1 (WIF1) modulates the activity of both Wnts and Hhs and may thus contribute to the intertwining of these pathways. In this article, we review the structure, evolution, molecular interactions and functions of WIF1 with major emphasis on its role in carcinogenesis.

Morphological Stasis and Proteome Innovation in Cephalochordates

Lancelets, extant representatives of basal chordates, are prototypic examples of evolutionary stasis; they preserved a morphology and body-plan most similar to the fossil chordates from the early Cambrian. Such a low level of morphological evolution is in harmony with a low rate of amino acid substitution; cephalochordate proteins were shown to evolve slower than those of the slowest evolving vertebrate, the elephant shark. Surprisingly, a study comparing the predicted proteomes of Chinese amphioxus, Branchiostoma belcheri and the Florida amphioxus, Branchiostoma floridae has led to the conclusion that the rate of creation of novel domain combinations is orders of magnitude greater in lancelets than in any other Metazoa, a finding that contradicts the notion that high rates of protein innovation are usually associated with major evolutionary innovations. Our earlier studies on a representative sample of proteins have provided evidence suggesting that the differences in the domain architectures of predicted proteins of these two lancelet species reflect annotation errors, rather than true innovations. In the present work, we have extended these studies to include a larger sample of genes and two additional lancelet species, Asymmetron lucayanum and Branchiostoma lanceolatum. These analyses have confirmed that the domain architecture differences of orthologous proteins of the four lancelet species are because of errors of gene prediction, the error rate in the given species being inversely related to the quality of the transcriptome dataset that was used to aid gene prediction.

Biopolymer based nanosystem for doxorubicin targeted delivery

This study describes formation of an actively and passively targeted, water-soluble drug delivery system (DDS) which contains doxorubicin (DOX). The system comprises two biocompatible and biodegradable polymers: poly-γ-glutamic acid (PGA) and chitosan (CH). Self-assembly of these biopolymers in aqueous medium results stable nanoparticles (NPs) with a hydrodynamic size of 80-150 nm and slightly negative surface charge. Folic acid (FA) was used as targeting agent bonded to the polyanion (PA) and also to the surface of the NPs. The NP's physical stability, active targeting effect, cellular toxicity, release profile and in vivo anti-tumor efficacy were investigated. It was found that the targeted, self-assembled nanoparticles are stable at 4°C for several months, cause better in vitro toxicity effect on folate receptor (FR) positive cell lines than the doxorubicin or the non-targeted nanosystem and based on its release profile it is expected, that the nanosystem will remain stable during the circulation in the body. Pharmacodynamic studies demonstrated that the DOX-loaded nanoparticles can deliver greater tumor growth inhibition than the free drug molecules and the liposomal compound, with less general toxicity. It was observed that the overall survival is the main benefit of the biopolymer based drug delivery system.

Targeting vascular endothelial growth factor receptor 2 and protein kinase D1 related pathways by a multiple kinase inhibitor in angiogenesis and inflammation related processes in vitro

Emerging evidence suggests that the vascular endothelial growth factor receptor 2 (VEGFR2) and protein kinase D1 (PKD1) signaling axis plays a critical role in normal and pathological angiogenesis and inflammation related processes. Despite all efforts, the currently available therapeutic interventions are limited. Prior studies have also proved that a multiple target inhibitor can be more efficient compared to a single target one. Therefore, development of novel inflammatory pathway-specific inhibitors would be of great value. To test this possibility, we screened our molecular library using recombinant kinase assays and identified the previously described compound VCC251801 with strong inhibitory effect on both VEGFR2 and PKD1. We further analyzed the effect of VCC251801 in the endothelium-derived EA.hy926 cell line and in different inflammatory cell types. In EA.hy926 cells, VCC251801 potently inhibited the intracellular activation and signaling of VEGFR2 and PKD1 which inhibition eventually resulted in diminished cell proliferation. In this model, our compound was also an efficient inhibitor of in vitro angiogenesis by interfering with endothelial cell migration and tube formation processes. Our results from functional assays in inflammatory cellular models such as neutrophils and mast cells suggested an anti-inflammatory effect of VCC251801. The neutrophil study showed that VCC251801 specifically blocked the immobilized immune-complex and the adhesion dependent TNF-α -fibrinogen stimulated neutrophil activation. Furthermore, similar results were found in mast cell degranulation assay where VCC251801 caused significant reduction of mast cell response. In summary, we described a novel function of a multiple kinase inhibitor which strongly inhibits the VEGFR2-PKD1 signaling and might be a novel inhibitor of pathological inflammatory pathways.

Characterization of a Wnt-binding site of the WIF-domain of Wnt inhibitory factor-1

A Wnt-binding site of the WIF-domain of Wnt inhibitory factor-1 was localized by structure-guided arginine-scanning mutagenesis in combination with surface plasmon resonance assays. Our observation that substitution of some residues of WIF resulted in an increased affinity for Wnt5a, but decreased affinity for Wnt3a, suggests that these residues may define the specificity spectrum of WIF for Wnts. These results hold promise for a more specific targeting of Wnt family members with WIF variants in various forms of cancer.

The beta subunit of the type I Fcepsilon receptor is a target for peptides inhibiting IgE-mediated secretory response of mast cells

Peptides originally derived from complement component C3a were earlier shown to inhibit the type I FcepsilonR (FcepsilonRI)-mediated degranulation of mucosal type mast cells. In the present study, we show that C3a7, a peptide with a natural sequence, and its modified derivative, C3a9, are powerful inhibitors of the above response of both serosal and mucosal type mastocytes. We demonstrate that these peptides inhibit FcepsilonRI-induced membrane proximal events, suppress phosphorylation of the FcepsilonRI beta subunit, the protein tyrosine kinase Lyn, as well as the transient rise in free cytosolic Ca2+ level. The late phase of cellular response was also inhibited, as demonstrated by the reduced TNF-alpha secretion. Experiments using two independent methods provided evidence that the interaction site of complement-derived peptides is the FcepsilonRI beta-chain. This was further supported by fluorescence confocal microscopic colocalization and resonance energy transfer measurements. Taken together, these results suggest the presence of distinct "activating" and "inhibitory" motifs in the C3a sequence. Response to both is in balance under physiologic conditions. Furthermore, present data predict that such inhibitory peptides may serve as potent agents for future therapeutic intervention.

Characterization of factor H-related cell membrane molecules expressed by human B lymphocytes and neutrophil granulocytes

The human factor H protein family comprises six plasma glycoproteins. Earlier we described a membranal factor H-related (mFHR) molecule that is expressed by human B lymphoblastoid cell lines and exerts cofactor activity. In our present study we screened human blood cells for the presence of mFHR proteins and further characterized these molecules. By cytofluorimetry it is shown that the factor H-specific rabbit antiserum reacts strongly with B cells and neutrophil granulocytes, but not with T cells and monocytes. On B lymphocytes mFHR is shown to be down-regulated upon activation of the cells via sIg. In experiments studying which short consensus repeat (SCR) domains are part of the cell membrane proteins we found that antibodies raised against SCRs 1-4, 19-20 and FHR-3 bound to neutrophils but not to B cells. While mFHRs derived both from B cells and granulocytes are shown to bind heparin, their size and structure are different as revealed by Western blotting. A further characteristic of the granulocyte-derived mFHR is its sensitivity to the PI-specific PLCgamma enzyme. These data demonstrate the existence of new members of the FHR protein family, as two distinct, membranal forms are identified. Based on the differences, the B cell derived molecule is termed mFHR-1 and the neutrophil derived protein mFHR-2.

Soluble gC1q-R/p33, a cell protein that binds to the globular "heads" of C1q, effectively inhibits the growth of HIV-1 strains in cell cultures

C1q and the outer envelope protein of HIV, gp120, have several structural and functional similarities. Therefore, it is plausible to assume that proteins that are able to interact with C1q may also interact with isolated gp120 as well as the whole HIV-1 virus. Based on this hypothesis, we studied the potential ability of the recombinant form of the 33-kDa protein, which binds to the globular "heads" of C1q (gC1q-R/p33), to inhibit the growth of different HIV-1 strains in cell cultures. gC1q-R/p33 was found to effectively and dose-dependently inhibit the production of one T-lymphotropic (X4) and one macrophage-tropic (R5) strain in human T cell lines (MT-4 and H9) and human monocyte-derived macrophage cultures, respectively. At a concentration range of 5-25 microg/ml, gC1q-R caused a marked and prolonged suppression of virus production. The extent of inhibition was enhanced when gC1q-R was first incubated with and then removed from the target cell cultures before virus infection, compared to that when the cells were infected with gC1q-R-HIV mixtures. The extent of inhibition was comparable to that of the Leu3a anti-CD4 antibody. Addition of gC1q-R to the cell cultures on day 1 or 2 after infection induced markedly less inhibition of HIV-1 growth than pretreatment of the cells just before or together with the infective HIV strains. In ELISA experiments, gC1q-R did not bind to a solid-phase recombinant gp120 while strong and dose-dependent binding of gC1q-R to solid-phase CD4 was observed. Our present findings indicate that gC1q-R is an effective inhibitor of HIV-1 infection, which prevents viral entry by blocking the interaction between CD4 and gp120. Since gC1q-R is a human protein, it is most probably not antigenic in humans. It would seem logical, therefore, to consider gC1q-R or its fragments involved in the CD4 binding as potential therapeutic agents.

Adjuvant effect of gamma-inulin is mediated by C3 fragments deposited on antigen-presenting cells

The adjuvant effect of gamma-inulin, a strong activator of the alternative complement pathway, is well-known, but its exact mechanism is not revealed yet. Here, we show that macrophages, isolated from the peritoneal cavity of gamma-inulin-injected mice and used as antigen-presenting cells, enhance the proliferation of antigen-specific T-cells up to 2.5-fold when compared with macrophages of non-treated animals. This effect is abrogated by the presence of anti-C3 F(ab')2 fragments and by prior decomplementation of the donor animals with CVF. It is demonstrated that treatment of mice with the adjuvant results in deposition of C3-fragments onto the surface of peritoneal macrophages, as does in vitro incubation of the cells with gamma-inulin in the presence of fresh autologous serum. Prior incubation of macrophages with gamma-inulin plus serum in vitro enhances subsequent C3 production. Because it has been shown earlier that CR1/2 expressed on activated T-cells and interacting with covalently bound C3-fragments plays an important role in the augmentation of the adaptive response, our present results reveal a mechanism that contributes to the adjuvant effect of gamma-inulin and point to a further link between innate and adaptive immunity.

H1 histamine receptor antagonist inhibits constitutive growth of Jurkat T cells and antigen-specific proliferation of ovalbumin-specific murine T cells

Histamine is produced from histidine by histidine decarboxylase (HDC) in many cells including normal and malignant lymphocytes. We examined the expression of HDC and the effect of histamine receptor antagonists on the proliferation of a human T cell line, Jurkat and on antigen-driven proliferation of lymphocytes from ovalbumin-immunized mice. Our results demonstrate that HDC is inducible in Jurkat cells by anti-CD3. The H1 receptor antagonist triprolidine dose dependently inhibits proliferation of both Jurkat cells and ovalbumin-stimulated murine lymphocytes, while the H2 antagonist ranitidine was ineffective. Alpha-fluoro-methyl-histidine blocking HDC activity did not inhibit the T cell proliferation, suggesting an existing pool of histamine in T cells.

A further link between innate and adaptive immunity: C3 deposition on antigen-presenting cells enhances the proliferation of antigen-specific T cells

Murine cells of the B lymphoblastoid line A20 and concanavalin A-elicited peritoneal macrophages are shown to activate and fix C3 fragments covalently when incubated in fresh, autologous serum under conditions allowing the initiation of the alternative complement pathway. For the detection of cell-bound C3, cytofluorimetry was performed using FITC-labeled F(ab')2 fragments of anti-mouse C3. Cell-bound C3 fragments are not internalized or shed by the cells under culture conditions for at least two hours. When the antigen-presenting capacity of serum-treated cells was tested using various antigens and experimental systems, augmentation of the proliferation of antigen-specific T cells was found. This enhancing effect was particularly pronounced at suboptimal antigen doses. The elevation of T cell proliferation induced by C3-opsonized antigen-presenting cells (APC) could be abrogated by F(ab')2 fragments of goat anti-mouse C3, suggesting the involvement of C3 receptors expressed by T cells in the process. Using the 7G6 mAb recognizing murine CR1/CR2, the presence of these complement receptors on activated T cells is demonstrated by cytofluorimetry and immunoprecipitation, as well. These results point to the role of C3 bound to acceptor sites on APC in the facilitation of antigen presentation, providing a further link between innate and adaptive immunity.

Two parallel routes of the complement-mediated antibody-dependent enhancement of HIV-1 infection

OBJECTIVE

To study the mechanism of the complement-mediated antibody-dependent enhancement (C'-ADE) of HIV infection which may play a significant role in the progression of HIV-disease.

METHODS

In vitro complement activating and complement-mediated HIV-infection enhancing abilities of three human anti-gp41 monoclonal antibodies (MAb) were tested. C'-ADE was estimated using HIV-1IIIB and CR2 (CD21)-carrying MT-4 target cells. Normal human serum (NHS), purified C1q, C1q-deficient (C1qD) and C2-deficient (C2D) human sera were applied as complement sources.

RESULTS

All MAb mediated increased C1q binding to solid-phase gp41. All MAb had a marked dose-dependent and strictly complement-mediated HIV-infection enhancing effect. Mixtures of the MAb with purified C1q also significantly increased HIV-1 infection. C1qD serum had a markedly lower enhancing effect than NHS, which could be raised to normal level by addition of purified C1q. Pretreatment of the target cells with anti-CR2 antibodies only partially inhibited the enhancing effect of the MAb plus normal human serum.

CONCLUSION

These novel findings indicate that besides the well-known facilitation of entry of HIV-1 by the interaction between virus-bound C3 fragments and CR2 present on the target cells, fixation of C1q to intact virions also results in an enhanced productive HIV-1 infection in the MT-4 cell cultures.

Role of C3a and C5a in the activation of mast cells

Mast cells and basophils are known to be triggered by allergens via cross-linking with their high-affinity IgE-binding receptors, Fc epsilon RI. The anaphylatoxic activity of the complement-derived peptides C3a and C5a has been known for a long time; however, it has also been reported that serosal- and mucosal-type mast cells respond differently to peptidergic stimuli. The mechanism of mast cell activation by cross-linking of Fc epsilon RI has been the subject of intensive studies in the past few years, while the action mode of the anaphylatoxic complement peptides has been revealed only recently. We report about a novel function of C3a: its inhibitory activity on IgE-mediated triggering of the mucosal RBL-2H3 cells. Surprisingly, the other anaphylatoxic peptide C5a, which has been shown to be significantly more effective in several biological assays, did not influence antigen-induced triggering of the RBL-2H3 cell line at all.

[Questions of habilitation-rehabilitation in diabetes mellitus]

As a result of the up to date treatment the life quality of diabetic patients is improved, their life span is prolonged. The authors recite the guidelines of vocational guidance and disability evaluation of diabetics. It is generally accepted that patients treated by diet alone may choose any profession, their lifestyle need not differ from that of healthy people. Well educated diabetic patients on oral antidiabetics or insulin, who have near normoglycemic blood sugar levels, can follow the lifestyle of a healthy individual; yet they should avoid occupations where their own or others lives might be put in danger. The authors recite effective departmental orders about the questions that influence the lives of diabetic patients-for example drivers licence, sports facilities for diabetics- and are the most frequently encountered by experts. Problems of rehabilitation that arise during the management of diabetics are also discussed.

Identification of a major T-cell epitope within VP3 amino acid residues 24 to 37 of Theiler's virus in demyelination-susceptible SJL/J mice

Intracerebral inoculation of susceptible strains of mice with Theiler's murine encephalomyelitis virus (TMEV) results in a chronic, immunologically mediated demyelinating disease that shares many features with human multiple sclerosis. CD4+ T lymphocytes play a critical role in the pathogenesis of virus-induced demyelinating disease. We have identified a region within amino acid residues 24 to 37 of the VP3 capsid protein of TMEV (VP3(24-37)) that is recognized by T lymphocytes from the demyelination-susceptible SJL/J strain of mice. The T-cell response to VP3(24-37) represents a predominant Th-cell response against the virus from either TMEV-immunized or TMEV-infected SJL/J mice, and viral epitopes VP1(233-250), VP2(74-86), and VP3(24-37) account for most of the Th-cell response to TMEV.

A novel, complement factor H-related regulatory protein expressed on the surface of human B cell lines

Complement regulatory proteins present on the surface of various mammalian cells play an important role in controlling homologous lysis, by interacting with C3 (and usually C4). These proteins have a similar structural motif ("short consensus repeat") (Reid, K.B.M., Bentley, R.D., Campbell, R.D., Chung, L.P., Sim, R.B., Kristensen, T. and Tack, B.F., Immunol. Today 1986. 7:230), and the genes encoding them are members of the family of regulators of complement activation. Here we describe a hitherto unknown member of this family, a molecule expressed by B lymphoblastoid cells. This protein is recognized by polyclonal antibodies to factor H and by MAH4, a monoclonal antibody reacting with the N-terminal portion of factor H. The cell surface protein is built up of two disulfide-linked chains of approximately 68 and 75 kDa. Biosynthetic labeling studies confirmed that it is synthesized by B cells only, but not by the investigated lines of other origin. When tested for its functional activity, this molecule was shown to act as cofactor for factor I-mediated cleavage of fluid-phase C3b to C3bi. The protein appears to be encoded by a 3.5-kb mRNA, hybridizing with a cDNA probe coding for the N-terminal portion of factor H. Due to its cross-reactivity with anti-H antibodies, cofactor activity for factor I and hybridization with factor H cDNA, despite its two-chain composition, it is considered a factor H-like protein.

Scanning electron microscopy of bacteria in the apical part of root canals in permanent teeth with periapical lesions

The most apical 2 mm of the root canals of periapically diseased roots were examined for microorganisms by scanning electron microscopy (SEM). Bacteria in this area were observed in 10 out of 12 (83.3%) cases. The two remaining cases exhibited bacteria more coronally, with tissue remnants between the bacterial front and the apical foramen. Rod-shaped bacteria dominated, but filaments, spirochetes and cocci were also seen. Cocci and rods sometimes formed micro-colonies. Occasionally, cocci were seen attached to filaments forming "corn-cob"-like structures. Deposits resembling bacterial plaque were also found inside the root canal. SEM is useful for studying microbial topography of the apical root canal.

Effects of extensive apical reaming and calcium hydroxide dressing on bacterial infection during treatment of apical periodontitis: a pilot study

An apical dentine sampling technique was applied in order to monitor the bacteriology of the pulp canal and radicular dentine before and during treatment of teeth with chronic apical periodontitis. Twenty-three teeth with a radiographic diagnosis of apical periodontitis were studied. They were subjected to a standardized two-appointment treatment regimen of extensive apical reaming in the absence of antimicrobial agents and 1-week dressing with calcium hydroxide. Bacteriological samples were taken from the root canal at the start, and apical dentine samples at the end, of each sitting. Provision was made to allow growth of anaerobic bacteria. All root canals but one showed growth at the start of treatment. Dentine samples were positive in 14 of the 23 teeth at the end of the first appointment. Eight of the 23 canals had detectable growth from the canal at the start of the second appointment, but in sufficient numbers for quantification in only one root canal. The subsequent dentine samples were otherwise negative at the second appointment. There was a tendency for teeth causing symptoms to harbour more bacteria than symptomless teeth.

Similarities in the microfloras of root canals and deep periodontal pockets

Although not universally accepted, retrospective histological, roentgenological and microbiological studies have indicated that cross-infection can occur between infected pulps and deep periodontal pockets. This review provides examples of similarities in the microfloras of these adjacent oral sites, supporting the idea that infection spreads from one site to the other. The organisms most often involved are probably bacteroides, fusobacteria, eubacteria, spirochetes, wolinellas, selenomonas, campylobacter, and peptostreptococci. Important qualities of cross-infecting organisms may be the ability to survive in highly reduced environments and motility. Precautions should be taken to prevent in vivo seeding of such micro-organisms, particularly in compromised teeth and hosts.

Image analysis of endodontic radiographs: digital subtraction and quantitative densitometry

In this study computerized image analysis procedures were applied to endodontic radiographs. Kontron IBAS 2000 is a commercially available image analysis system with processing routines applicable to radiograph digitizing and transformations. The system was evaluated for: its ability to harmonize blackening and contrast in endodontic radiographs; its ability to compensate for angulation distortion of sequential exposures of individual teeth; its potential for application of digital subtraction methods; and its use in automated gray-level analyses of diseased and healthy bone areas in endodontic radiographs. The Kontron IBAS 2000 system proved suitable for all applications. However, the specificity of the subtraction procedure was limited by some inherent problems in the harmonization of blackening and in the subtraction process itself. On the other hand, automated gray level measurements proved to be a robust method for unbiased and quantitative assessment of healing of apical periodontitis.

Diagnosis and treatment of pulp necrosis in permanent anterior teeth with root fracture

A follow-up study was made of 20 traumatized permanent incisors with pulp necrosis observed as a sequel to root fracture. The material included 19 patients aged 8-17 years (mean 11.6 years) at the time of injury. Negative response to electric stimulation was noted in 16 teeth from the first examination. In four teeth an initial positive response changed to negative within 2-9 months. The negative response was supported by additional signs and symptoms of necrosis in 19 teeth. Radiolucencies adjacent to the fracture line or coronal discolorations were the most important diagnostic factors. Discolorations occurred within 2 months, whereas radiographic changes in the fracture area took from 3 to 5 months to develop. Four teeth were extracted without attempting endodontic therapy. Endodontic treatment confined to the coronal fragment was performed in 16 teeth. In most cases the canal was filled temporarily with calcium hydroxide until a closure at the fracture site was observed. Two apical fragments showing radiographic changes were surgically removed in conjunction with the permanent filling of the coronal fragments. During the postoperative observation period one tooth was extracted due to communication between the fracture area and the oral cavity. The treatment of the remaining 15 teeth was judged as successful after a mean observation period of 4.2 years, ranging from 2 to 5 years.

Long-term prognosis of traumatized permanent anterior teeth showing calcifying processes in the pulp cavity

122 traumatized teeth with radiographic evidence of abnormal hard tissue formation in the pulp cavity were examined 10-23 years (mean 16 years) after the time of injury. Judged radiographically, partial obliteration (pulp chamber not discernible, root canal markedly narrowed but clearly visible) had occurred in 44 teeth (36%). Normal periradicular conditions were found in all teeth with partial obliteration. Seventy-eight teeth (64%) were recorded as totally obliterated. Pathologic periradicular changes indicating pulp necrosis as a sequel to the total obliteration was observed in 16 teeth (21%). The late development of pulp necrosis was significantly related to teeth classified as severely injured, and to teeth with complete root formation at the time of injury. Furthermore, a comparatively rapid progress of the calcifying process appeared to be correlated with periradicular radiolucency.