Towards an operational definition of oral frailty: A e-Delphi study

OBJECTIVES

Building upon our recently developed conceptual definition of oral frailty (the age-related functional decline of orofacial structures), this e-Delphi study aims to develop an operational definition of oral frailty by identifying its components.

METHODS

We used a modified e-Delphi study to reach a consensus among international experts on the components of oral frailty. Twelve out of fifteen invited experts in the field of gerodontology participated. Experts responded to three rounds of an online 5-point scale questionnaire of components to be included or excluded from the operational definition of oral frailty. After each round, scores and rationales were shared with all experts, after which they could revise their position. A consensus was reached when at least 70% of the experts agreed on whether or not a component should be included in the operational definition of oral frailty.

RESULTS

The experts achieved a high level of agreement (80 - 100%) on including eight components of oral frailty and excluding nineteen. The operational definition of oral frailty should include the following components: 1) difficulty eating hard or tough foods, 2) inability to chew all types of foods, 3) decreased ability to swallow solid foods, 4) decreased ability to swallow liquids, 5) overall poor swallowing function, 6) impaired tongue movement, 7) speech or phonatory disorders, and 8) hyposalivation or xerostomia.

CONCLUSION

This e-Delphi study provided eight components that make up the operational definition of oral frailty. These components are the foundation for the next stage, which involves developing an oral frailty assessment tool.

Frailty as a determinant of dental attendance among community-dwelling older adults

OBJECTIVES

The aim of this study was to assess the association between different levels of frailty and dental attendance among home-dwelling older adults, in Belgium.

BACKGROUND

While many determinants of dental attendance among older adults have been identified, no study has focused on the role of frailty.

MATERIALS AND METHODS

This was a cross-sectional study on a random sample of home-dwelling adults aged 60 and over from two Belgian cities. Data were collected with a structured questionnaire through a participatory peer-research method. Time since the last dental attendance was the dependent variable. The independent variable was frailty, assessed with the Comprehensive Frailty Assessment Instrument, including physical, psychological, social, and environmental subdomains. Covariates were age, gender, having a partner, educational level, and household income, as well as self-perceived oral health. Data analysis included descriptive, bivariate (Chi-Square, ANOVA, and Kruskal-Wallis), and binomial logistic regression analyses.

RESULTS

The sample consisted of 1329 older adults with a mean age of 72.5 years (SD 8.9, range 60-103). In the low frailty group, 73% attended the dentist in the previous 12 months, while it was 62% and 54% in the medium and high frailty groups, respectively. In the fully adjusted model, the initial gradient in the relationship between overall frailty and dental attendance remained; those in the medium and the high frailty groups were respectively 1.46 (95% CI: 1.09, 1.95) and 1.67 (95% CI: 1.15, 2.43) times more likely to report no dental attendance in the previous year than the low frailty group. Similar associations could be seen in the physical and environmental frailty subdomains.

CONCLUSION

Frailty is consistently associated with less favourable dental attendance, independent from age, gender, socioeconomic factors, family composition, and self-perceived oral health. Once frailty has been detected, good interprofessional communication and care are needed to avoid the drop-out of older adults from the oral healthcare system.

Clinical and Subjective Oral Health Status of Care Home Residents in Europe: A Systematic Review

OBJECTIVE

Several studies demonstrated the poor oral health of care home residents in Europe but there is no systematic overview of the relevant literature. The objective of this study was to systematically review the evidence on the clinical and subjective oral health outcomes of care home residents in Europe.

DESIGN

The study design is a systematic review.

METHODS AND PARTICIPANTS

All included publications presented data on clinical and/or subjective oral health outcomes in care home residents in Europe with no restrictions for language or study design. MEDLINE, Embase, and CINAHL were searched, including publications from January 2010 onward. Data extraction and quality assessment (Qualsyst tool) was performed by 2 researchers independently. Findings were synthesized narratively, lack in data homogeneity restricted the relevance of a meta-analysis.

RESULTS

Eighty-three papers from 18 countries were included in the systematic review, with a sample size ranging from 39 to 92,827 participants. Their mean age was older than 80 years. The residents had few natural teeth, with fewer than a third a functional natural dentition. Removable dentures were present in half to 80% of residents. A high prevalence of dental caries was reported. Oral hygiene was insufficient, for both natural teeth and removable dentures. Few residents had a healthy periodontium. Clinical treatment needs were found in most residents. Perceived treatment needs were high with at least one-third of care home residents reporting a need for care due to poor oral health. A fifth to half of the residents reported negative impacts of their oral condition on their everyday lives.

CONCLUSION AND IMPLICATIONS

This systematic review clearly highlights the poor oral health and high burden of oral conditions among care home residents across Europe, irrespective of country or health care system. There is need for substantial policy actions to improve oral health in care homes.

Assessment of oral health in older adults by non-dental professional caregivers-development and validation of a photograph-supported oral health-related section for the interRAI suite of instruments

OBJECTIVES

An optimized oral health-related section and a video training were developed and validated for the interRAI suite of instruments. The latter is completed by professional non-dental caregivers and used in more than 40 countries to assess care needs of older adults.

METHODS

The optimized oral health-related section (ohr-interRAI) consists of nine items and a video training that were developed in consecutive phases. To evaluate psychometric properties, a study was conducted in 260 long-term care residents. Each resident was assessed by a dentist and by four caregivers (two who received the video training, two who did not).

RESULTS

Mean kappa values and percent agreement between caregivers and dentist ranged between κ = 0.60 (80.2%) for dry mouth and κ = 0.13 (54.0%) for oral hygiene. The highest inter-caregiver agreement was found for dry mouth with κ = 0.63 [95% CI: 0.56-0.70] (81.6%), while for the item palate/lips/cheeks only κ = 0.27 [95% CI: 0.18-0.36] (76.7%) was achieved. Intra-caregiver agreement ranged between κ = 0.93 [95% CI: 0.79-1.00] (96.4%) for dry mouth and κ = 0.45 [95% CI: 0.06-0.84] (82.8%) for gums. Logistic regression analysis showed only small differences between caregivers who watched the video training and those who did not.

CONCLUSIONS

Psychometric properties of the optimized ohr-interRAI section were improved compared to previous versions. Nevertheless, particularly the items based on inspection of the mouth require further refinement and caregiver training needs to be improved.

CLINICAL RELEVANCE

Valid assessment of oral health by professional caregivers is essential due to the impaired accessibility of regular dental care for care-dependent older adults.

Oral healthcare delivery in institutionalised older people: A health-economic evaluation

OBJECTIVES

This health-economic evaluation aimed to assess the cost-effectiveness of a number of alternatives for preventive and curative oral health care in institutionalised older people in Flanders.

METHODS

A six-state Markov model was used to compare expected costs and healthy oral years (HOYs) of four alternatives: (1) usual care; (2) on-site preventive care; (3) on-site preventive care + curative care in the community; and (4) on-site preventive care + on-site curative care. A healthcare payer perspective was adopted, and the time horizon was 10 years. Deterministic and probabilistic sensitivity analyses were performed.

RESULTS

Incremental cost-effectiveness ratios (ICERs) of alternatives 2, 3 and 4 (all compared to alternative 1) were as follows: (2) 7944 €/HOY gained; (3) 1576 €/HOY gained; and (4) 1132 €/HOY gained. Hence, alternatives 2 and 3 were not cost-effective compared to alternative 4. The probability that oral care interventions are more effective and cost-saving than usual care was <3% for all three interventions.

CONCLUSIONS

For institutionalised older people, on-site solutions for preventive and curative oral health care might be the most cost-effective alternative. It should be kept in mind that on-site solutions require large initial investment and that the advanced age of the population and the high costs of oral health care make it unlikely that these interventions would become cost-saving, even in the long term.

[Research agenda oral care for older people in the Netherlands and Flanders (Belgium)]

Oral care for older people is an underexposed topic in dentistry as well as in general healthcare, while oral care professionals are increasingly confronted with frail and multimorbid older people with complex care needs. The research agenda 'Oral care for the elderly' was developed to encourage the collaboration of researchers in the Netherlands and Flanders (Belgium) to do more research in this area and in this way, to achieve an expansion and implementation of knowledge. This will make possible the provision of a socially responsible and robust basis for sustainable oral care for frail older people. The focus of the agenda is on 3 themes, namely oral health and oral function for older people; multi/interdisciplinary collaboration within primary care and the costs, benefits and long-term effect(s) of oral care throughout the entire course of life. This article provides an overview of this research agenda and the way in which it has been established.

[Oral health in older adults, a challenge? Determinants of oral health in older adults.]

Current data show many older adults to have poor oral health, deteriorating even more when they become frail or care dependent. In order to achieve a structural and sustained improvement of this situation, it is necessary to have a clear view of the factors determining oral health in older adults, such as (endogenous (biological, lifestyle), environmental determinants and determinants associated with the organisation of healthcare. The various determinants show oral health in older adults is the result of thecombined effects of very diverse factors and for that reason, a solution will have to be based on a multidisciplinary approach, also involving people outside of clinical care. To promote good oral health over the full course of life, it is important to invest in a good start in life, that helps accumulate oral health gains, and at the same time it is essential to adapt the healthcare system and prevention strategies to the individual's needs in order to make oral care effective for the full course of life.

[Towards proactive and personalised care for the elderly]

The Netherlands, like other Western countries, shows an obvious demography of aging, which is associated with many challenges. People age differently, after all. Some remain vital until very old age, while others become frail and disabled much earlier in life. Because of the indicated demographic trend, morbidity is expected to increase and with it, the number of older people needing care. 'Aging in place' has become a central phenomenon in healthcare policies. This means that older people should be empowered to lead a meaningful life in their own living environment as long as possible, even when they are frail and care dependent. Therefore, in the future, most care for older people will actually occur at home. This article aims to present a meaningful care model for the older people. Starting from the 'definition discussion' about frailty and a revaluation of the concept of' resilience, a basis will be provided for a sustainable, proactive and personalised elderly care, close to the living environment of older people, in which dentists and other oral health professionals play an important role as well.

Micronutrients encapsulation in enhanced nanoliposomal carriers by a novel preparative technology

Micronutrients administration by fortification of staple and complementary foods is a followed strategy to fight malnutrition and micronutrient deficiencies and related pathologies. There is a great industrial interest in preparation of formulations for joint administration of vitamin D3 and vitamin K2 for providing bone support, promoting heart health and helping boost immunity. To respond to this topic, in this work, uncoated nanoliposomes loaded with vitamin D3 and K2 were successfully prepared, by using a novel, high-yield and semi continuous technique based on simil-microfluidic principles. By the same technique, to promote and to enhance mucoadhesiveness and stability of the produced liposomal structures, chitosan was tested as covering material. By this way polymer–lipid hybrid nanoparticles, encapsulating vitamin D3 and vitamin K2, with improved features in terms of stability, loading and mucoadhesiveness were produced for potential nutraceutical and pharmaceutical applications.

Micronutrients administration by liposomal vectors is a growing strategy in fortification processes of staple and complementary foods to fight malnutrition and micronutrient deficiencies and related pathologies.

The oral health condition and treatment needs assessment of nursing home residents in Flanders (Belgium)

OBJECTIVES

A study was conducted of nursing home residents with limited access to regular oral health care services to evaluate their oral health status, to perform an assessment of the need for oral treatment and to determine the possible predicting value of age, gender, care dependency and income level on their oral health status and treatment needs.

MATERIALS AND METHODS

Three experienced dentists collected clinical oral health data with a mobile dental unit in 23 nursing homes. Socio-demographic data were extracted from the residents' records in the nursing home. Besides the descriptive and bivariate analysis, a general linear mixed model analysis was also performed with the nursing home as random effect.

RESULTS

The study sample consisted of 1,226 residents with a mean age of 83.9 years, of which 41.9% were edentulous. The mean D₃MFt in the dentate group was 24.5 and 77% needed extractions or fillings. In the group of residents wearing removable dentures, 36.9% needed repair, rebasing or renewal of the denture. The mixed model analysis demonstrated that with each year a resident gets older, the oral health outcomes get worse and that men have worse oral health and higher treatment needs than women. However, the level of income and care dependency had a less extensive role in predicting the oral health outcomes.

CONCLUSIONS

The nursing home residents presented a poor overall oral health status and high dental and prosthetic treatment needs. Gender and age were important predicting variables for the oral health outcomes.

An oral health survey of vulnerable older people in Belgium

OBJECTIVES

The aim of this study was to gain insight in the oral health of persons aged 65 years or more.

MATERIALS AND METHODS

Data were obtained from 652 vulnerable older persons (≥65) by means of a clinical oral examination. Additional demographic data were gathered including age, gender, residence, and care dependency.

RESULTS

The mean age of the total study sample was 83 (7.7) years and 71 % was female. Nearly 33 % of the sample was living at home with support, and 67 % was residing in nursing homes. The number of occluding pairs was low and the proportion of edentulous people was highest among persons with the highest care dependency. The mean Decay-missing-filled teeth index (DMFT) was 20.3 (9.0). A prosthetic treatment need and inadequate oral hygiene levels were observed in 40 % and more than 60 % of the subjects, respectively. The highest treatment need was observed in the oldest age group and the highest mean dental plaque in older persons with the highest care dependency.

CONCLUSIONS

The oral health in frail older people in Belgium is poor. The restorative and prosthetic treatment need is high and oral hygiene levels are problematic. Age, residence, and care dependency seemed to have some influence on oral health parameters.

CLINICAL SIGNIFICANCE

In the long term, the most important future challenge of oral health care policies is to identify older adults before they begin to manifest such oral health deterioration. Regular dental visits should be strongly promoted by all (oral) health care workers during the lifespan of all persons including older adults.

Tetanus: a diagnostic challenge in the Western world

Tetanus is a very serious neuromuscular disease caused by a powerful exotoxin, tetanospasmin, from the Clostridium tetani bacillus. Its incidence in the developed world has diminished considerably since the introduction of primary vaccination. Tetanus is diagnosed clinically, through recognition of the characteristically inducible muscle spasms. Three clinical forms described in adults are generalised, localised and cephalic tetanus. Management of tetanus aims at removing the source of tetanospasmin, neutralising circulating toxin, and providing adequate supportive care for muscle spasms, respiration and autonomic instability. Tetanus is a forgotten disease in developed countries since many practicing primary care physicians have not seen a single case in their career. We present a case of tetanus and review briefly the pathogenesis, clinical features and therapy in order to educate the internist in recognising and adequately treating this disease.

Offering integrated care for HIV/AIDS, diabetes and hypertension within chronic disease clinics in Cambodia

PROBLEM

In Cambodia, care for people with HIV/AIDS (prevalence 1.9%) is expanding, but care for people with type II diabetes (prevalence 5-10%), arterial hypertension and other treatable chronic diseases remains very limited.

APPROACH

We describe the experience and outcomes of offering integrated care for HIV/AIDS, diabetes and hypertension within the setting of chronic disease clinics.

LOCAL SETTING

Chronic disease clinics were set up in the provincial referral hospitals of Siem Reap and Takeo, 2 provincial capitals in Cambodia.

RELEVANT CHANGES

At 24 months of care, 87.7% of all HIV/AIDS patients were alive and in active follow-up. For diabetes patients, this proportion was 71%. Of the HIV/AIDS patients, 9.3% had died and 3% were lost to follow-up, while for diabetes this included 3 (0.1%) deaths and 28.9% lost to follow-up. Of all diabetes patients who stayed more than 3 months in the cohort, 90% were still in follow-up at 24 months.

LESSONS LEARNED

Over the first three years, the chronic disease clinics have demonstrated the feasibility of integrating care for HIV/AIDS with non-communicable chronic diseases in Cambodia. Adherence support strategies proved to be complementary, resulting in good outcomes. Services were well accepted by patients, and this has had a positive effect on HIV/AIDS-related stigma. This experience shows how care for HIV/AIDS patients can act as an impetus to tackle other common chronic diseases.

A unique and specific interaction between alphaT-catenin and plakophilin-2 in the area composita, the mixed-type junctional structure of cardiac intercalated discs

Alpha-catenins play key functional roles in cadherin-catenin cell-cell adhesion complexes. We previously reported on alphaT-catenin, a novel member of the alpha-catenin protein family. alphaT-catenin is expressed predominantly in cardiomyocytes, where it colocalizes with alphaE-catenin at the intercalated discs. Whether alphaT- and alphaE-catenin have specific or synergistic functions remains unknown. In this study we used the yeast two-hybrid approach to identify specific functions of alphaT-catenin. An interaction between alphaT-catenin and plakophilins was observed and subsequently confirmed by co-immunoprecipitation and colocalization. Interaction with the amino-terminal part of plakophilins appeared to be specific for the central ;adhesion-modulation' domain of alphaT-catenin. In addition, we showed, by immuno-electron microscopy, that desmosomal proteins in the heart localize not only to the desmosomes in the intercalated discs but also at adhering junctions with hybrid composition. We found that in the latter junctions, endogenous plakophilin-2 colocalizes with alphaT-catenin. By providing an extra link between the cadherin-catenin complex and intermediate filaments, the binding of alphaT-catenin to plakophilin-2 is proposed to be a means of modulating and strengthening cell-cell adhesion between cardiac muscle cells. This could explain the devastating effect of plakophilin-2 mutations on cell junction stability in intercalated discs, which lead to cardiac muscle malfunction.

A randomized open study to assess the efficacy and tolerability of dihydroartemisinin-piperaquine for the treatment of uncomplicated falciparum malaria in Cambodia

OBJECTIVES

To compare the efficacy and tolerability of dihydroartemisinin-piperaquine (DHA-PQP) with that of a 3-day regimen of mefloquine and artesunate (MAS3) for the treatment of uncomplicated falciparum malaria in Cambodia.

METHOD

Randomized open-label non-inferiority study over 64 days.

RESULTS

Four hundred and sixty-four patients were included in the study. The polymerase chain reaction genotyping-adjusted cure rates on day 63 were 97.5% (95% confidence interval, CI, 93.8-99.3) for DHA-PQP and 97.5% (95% CI, 93.8-99.3) for MAS3, P = 1. There were no serious adverse events, but significantly more episodes of vomiting (P = 0.03), dizziness (P = 0.002), palpitations (P = 0.04), and sleep disorders (P = 0.03) reported in the MAS3 treatment group, consistent with the side-effect profile of mefloquine.

CONCLUSIONS

DHA-PQP was as efficacious as MAS3, but much better tolerated, making it more appropriate for use in a routine programme setting. This highly efficacious, safe and more affordable fixed-dose combination could become the treatment of choice for Plasmodium falciparum malaria in Cambodia.

Truncated isoform of mouse αT‐catenin is testis‐restricted in expression and function

AlphaT-catenin is a recently identified member of the alpha-catenin family of cell-cell adhesion molecules. For decades it was thought that alpha-catenins mediate solid cell-cell adhesion by linking the cadherin-mediated cell-cell adhesion complex with the actin cytoskeleton. However, the roles of alpha-catenins in this classical adhesion model have been questioned recently. AlphaT-catenin has a restricted expression pattern, in contrast to the ubiquitously expressed alphaE-catenin. High levels of alphaT-catenin were detected in heart and testis. Northern and Western blot experiments indicated that besides the standard full-length alphaT-catenin transcript, smaller alternative transcripts are expressed in testis. We report the cloning of two alternative transcripts of the mouse alphaT-catenin gene (transcript-B and -X), both of which are expressed in a testis-restricted manner from two putative alternative promoters. Alternative transcript-X encodes a smaller protein, isoform-X, which lacks the amino-terminal beta-catenin binding domain of the standard mouse alphaT-catenin protein, and is therefore unable to restore cell-cell adhesion in an alpha-catenin-negative colon carcinoma cell line. Immunohistochemical analysis showed specific localization of the alphaT-catenin isoform-X in the differentiating germ cells. In contrast to the standard full-length alphaT-catenin protein, this shortened isoform-X can bind to l-afadin, an important component of the nectin/afadin/ponsin adhesion complex that reportedly is essential for spermatogenesis.

Differential downregulation of αT-catenin expression in placenta: trophoblast cell type-dependent imprinting of the CTNNA3 gene

The alphaE-catenin is a well-known invasion suppressor. A recently described novel alpha-catenin, i.e. alphaT-catenin (CTNNA3), shows related functions being necessary for the formation of cell-cell adhesion complexes. We recently demonstrated that the 10q21.3 region containing the CTNNA3 gene shows a parent-of-origin effect and that transcription of the CTNNA3 gene is downregulated in placental tissues of complete androgenetic origin. As this suggests that the CTNNA3 gene is subject to imprinting, we performed allele-specific RT-PCR on early placenta tissues using informative heterozygous samples. This was supplemented by immunostaining for alphaT-catenin, p57KIP2 and low molecular weight cytokeratin in tissues of a partial hydatidiform mole. As shown here we demonstrate that the CTNNA3 gene is subject to imprinting with preferential expression of the maternal allele in first trimester placental tissues. Imprinting, however, is trophoblast cell type-dependent: expression in extravillus trophoblast is biallelic; expression in villus cytotrophoblast is from the maternal allele only. Expression of alphaT-catenin is lost in villus syncytiotrophoblast as well as in extravillus trophoblast following epithelial-mesenchymal transition. The trophoblast cell type-dependent imprinting of CTNNA3 is identical to p57KIP2 imprinting with respect to trophoblast cell type (villus) and parental origin of the expressed allele (maternal). This suggests that gene dosage compensation of CTNNA3 and p57KIP2 in the placenta shares a conserved regulatory mechanism that correlates with an early step in trophoblast determination, i.e. differentiation into villus or extravillus trophoblast.

Alpha-T-catenin is expressed in human brain and interacts with the Wnt signaling pathway but is not responsible for linkage to chromosome 10 in Alzheimer's disease

The gene encoding alpha-T-catenin, CTNNA3, is positioned within a region on chromosome 10, showing strong evidence of linkage to Alzheimer's disease (AD), and is therefore a good positional candidate gene for this disorder. We have demonstrated that alpha-T-catenin is expressed in human brain, and like other alpha-catenins, it inhibits Wnt signaling and is therefore also a functional candidate. We initially genotyped two single-nucleotide polymorphisms (SNPs) in the gene, in four independent samples comprising over 1200 cases and controls but failed to detect an association with either SNP. Similarly, we found no evidence for association between CTNNA3 and AD in a sample of subjects showing linkage to chromosome 10, nor were these SNPs associated with Abeta deposition in brain. To comprehensively screen the gene, we genotyped 30 additional SNPs in a subset of the cases and controls (n > 700). None of these SNPs was associated with disease. Although an excellent candidate, we conclude that CTNNA3 is unlikely to account for the AD susceptibility locus on chromosome 10.

Mediterranean views on epithelial polarity

Developmental and cell biologists viewed polarity through each other's eyes at the EMBO workshop on Epithelial Polarity in Development and Disease, March 27-31 2004, in Carry-le-Rouet, France, a small village west of Marseille on the rocky Mediterranean coast. The presentations highlighted our growing understanding, not only of the molecular mechanisms underlying polarity and the conservation of polarity complexes from worms to mammals, but also the diverse roles that epithelial polarity has during development.

Alpha-catenin is required for IGF-I-induced cellular migration but not invasion in human colonic cancer cells

The mechanisms by which growth factors cooperate with cell adhesion molecules to modulate epithelial cell motility remain poorly understood. Here, we investigated the role of the E-cadherin/catenin complex in insulin-like growth factor (IGF-I)-dependent cell migration and invasion. We used variants of the HCT-8 colon cancer family that differ in their expression of alphaE-catenin, an intracellular molecule that links the E-cadherin/catenin complex to the actin cytoskeleton. Migration was determined using a monolayer wound model and cell invasion by the penetration of the cells into type-I collagen gels. We showed that alpha-catenin-deficient cells were not able to migrate in cohort upon IGF-I stimulation. Transfection of these cells with alpha-catenin isoforms (alphaN- or alphaT-catenin) restored migratory response IGF-I. These results suggest that alpha-catenins are involved in the signal issued from the E-cadherin/catenin complex to regulate IGF-I-stimulated migration. In contrast, IGF-I promoted invasion of both alpha-catenin-deficient and alpha-catenin-expressing cells, indicating that alpha-catenin did not participate in the regulation of IGF-I-induced invasion. Inhibition of E-cadherin function by treatment with MB-2 monoclonal antibodies inhibited both IGF-I-dependent cell migration and invasion. Taken together, our results indicate that functional alpha-catenin is essential for migration but not for invasion, while E-cadherin is involved in both phenomena.

Assessment of the CTNNA3 gene encoding human alpha T-catenin regarding its involvement in dilated cardiomyopathy

Alpha T-catenin is a novel member of the alpha-catenin family, which shows most abundant expression in cardiomyocytes and in peritubular myoid cells of the testis, pointing to a specific function for alpha T-catenin in particular muscle tissues. Like other alpha-catenins, alpha T-catenin provides an indispensable link between the cadherin-based cell-cell adhesion complex and the cytoskeleton, to mediate cell-cell adhesion. By isolating genomic clones, combined with database sequence analysis, we have been able to determine the structure of the CTNNA3 and Ctnna3 genes, encoding human and mouse alpha T-catenin, respectively. The positions of the exon-exon boundaries are completely conserved in CTNNA3, Ctnna3, and the alpha N-catenin encoding CTNNA2 gene. They overlap largely with the boundaries of the CTNNA1 and CTNNAL1 genes encoding alpha E-catenin and alpha-catulin, respectively. This emphasizes that these alpha-catenin genes evolved from the same ancestor gene. Nevertheless, the introns of CTNNA3 and Ctnna3 are remarkably large (often more than 100 kb) compared with introns of other CTNNA genes. The CTNNA3 gene was mapped to chromosome band 10q21 by both fluorescence in situ hybridization and polymerase-chain-reaction-based hybrid mapping. This region encodes a gene for autosomal dominant familial dilated cardiomyopathy (DCM), a common cause of morbidity and mortality. As alpha T-catenin is highly expressed in healthy heart tissue, we have considered CTNNA3 as a candidate disease gene in a family showing DCM linkage to the 10q21-q23 locus. Mutation screening of all 18 exons of the CTNNA3 gene in this family has, however, not detected any DCM-linked CTNNA3 mutations.

αT-Catenin: a novel tissue-specific β-catenin-binding protein mediating strong cell-cell adhesion

Cadherins are major cell-cell adhesion proteins whose cytoplasmic domains bind to catenin proteins. Strong intercellular adhesion depends on linkage of the cadherin/catenin complex to the actin cytoskeleton via α-catenin. To date, it is not clear how different cell types achieve the variable strength of cell-cell adhesion clearly needed in a multicellular organism. Here, we report the cloning and molecular characterization of αT(testis)-catenin, a novel human cDNA encoding a protein with homology to both human αE(epithelial)-catenin and αN(neural)-catenin. Although originally discovered in testis, αT-catenin is expressed in other tissues, the highest levels being observed in heart. Immunohistochemical analysis showed human αT-catenin localization at intercalated discs of cardiomyocytes and in peritubular myoid cells of testis. In cells transfected with αT-catenin cDNA, interaction with β-catenin was demonstrated by co-immunoprecipitation. Transfection of α-catenin-deficient colon carcinoma cells recruited E-cadherin and β-catenin to cell-cell contacts and functional cadherin-mediated cell-cell adhesion was restored in this way. Moreover, compaction of these cells was at least as prominent as in the case of cells expressing endogenous αE-catenin. We propose that αT-catenin is necessary for the formation of stretch-resistant cell-cell adhesion complexes, in particular, muscle cells.

Exopolysaccharide (EPS) biosynthesis by Lactobacillus sakei 0-1: production kinetics, enzyme activities and EPS yields

AIMS

To determine optimal exopolysaccharide (EPS) production conditions of the mesophilic lactic acid bacterium strain Lactobacillus sakei 0-1 and to detect possible links between EPS yields and the activity of relevant enzymes.

METHODS AND RESULTS

Fermentation experiments at different temperatures using either glucose or lactose were carried out. EPS production took place during the exponential growth phase. Low temperatures, applying glucose as carbohydrate source, resulted in the best bacterial growth, the highest amounts of EPS and the highest specific EPS production. Activities of 10 important enzymes involved in the EPS biosynthesis and the energy formation of Lact. sakei 0-1 were measured. The obtained results revealed that there is a clear link for some enzymes with EPS biosynthesis. It was also demonstrated clearly that the presence of rhamnose in the EPS building blocks is due to high activities of the enzymes involved in the rhamnose synthetic branch.

CONCLUSION

EPS production in Lact. sakei 0-1 is growth-associated and displays primary metabolite kinetics. Glucose as carbohydrate source and low temperatures enhance the EPS production. The enzymes involved in the biosynthesis of the activated sugar nucleotides play a major role in determining the monomeric composition of the synthesized EPS.

SIGNIFICANCE AND IMPACT OF THE STUDY

The proposed results contribute to a better understanding of the physiological factors influencing EPS production and the key enzymes involved in EPS biosynthesis by Lact. sakei.

Human alpha-catulin, a novel alpha-catenin-like molecule with conserved genomic structure, but deviating alternative splicing

A new human cDNA was cloned and termed alpha-catulin, based on sequence similarity with both alpha-CATenins and vincULIN. The mRNA is present ubiquitously, although low expression levels are found in neural tissues. The genomic organization of the alpha-catulin gene CTNNAL1 is closely related to that of the alphaE-catenin gene CTNNA1, but not at all to that of the vinculin gene. Alternative splicing of the last exon generates a frameshift, resulting in a truncated protein with a new carboxy-terminus.

The origins of marine bioluminescence: turning oxygen defence mechanisms into deep-sea communication tools

Bioluminescence, the emission of ecologically functional light by living organisms, emerged independently on several occasions, yet the evolutionary origins of most bioluminescent systems remain obscure. We propose that the luminescent substrates of the luminous reactions (luciferins) are the evolutionary core of most systems, while luciferases, the enzymes catalysing the photogenic oxidation of the luciferin, serve to optimise the expression of the endogenous chemiluminescent properties of the luciferin. Coelenterazine, a luciferin occurring in many marine bioluminescent groups, has strong antioxidative properties as it is highly reactive with reactive oxygen species such as the superoxide anion or peroxides. We suggest that the primary function of coelenterazine was originally the detoxification of the deleterious oxygen derivatives. The functional shift from its antioxidative to its light-emitting function might have occurred when the strength of selection for antioxidative defence mechanisms decreased. This might have been made possible when marine organisms began colonising deeper layers of the oceans, where exposure to oxidative stress is considerably reduced because of reduced light irradiance and lower oxygen levels. A reduction in metabolic activity with increasing depth would also have decreased the endogenous production of reactive oxygen species. Therefore, in these organisms, mechanisms for harnessing the chemiluminescence of coelenterazine in specialised organs could have developed, while the beneficial antioxidative properties were maintained in other tissues. The full range of graded irradiance in the mesopelagic zone, where the majority of organisms are bioluminescent, would have provided a continuum for the selection and improvement of proto-bioluminescence. Although the requirement for oxygen or reactive oxygen species observed in bioluminescent systems reflects the high energy required to produce visible light, it may suggest that oxygen-detoxifying mechanisms provided excellent foundations for the emergence of many bioluminescent systems.