bluuebunny/crossref_metadata_2025 huggingface dataset:
Compliance, negotiation, and self-assertion in Japanese adolescents' disagreements with parents
Authors: Sugimura Kazumi , Yamazaki Mizuki , Phinney Jean S. , Takeo Kazuko
Published: January 2009

This study examined the ways in which Japanese adolescents handle disagreements with parents, and the extent to which the cultural values of emotional bonds within the family predict adolescents' reported handling of disagreements. Adolescents ( N = 1029), aged 12 to 25 years, reported their projected actions in response to six hypothetical adolescent—parent disagreements, and completed a scale of values of emotional bonds in the family. As hypothesized, self-assertion was the most common action, followed by negotiation and compliance. Although generally self-assertion and negotiation were higher and compliance lower with increasing age, adolescents' actions also varied depending on the situation. The values of emotional bonds predicted adolescents' reported handling of disagreements, as examined using structural equation modeling. Implications of these findings for the adolescent—parent relationship and adolescent development in Japanese cultural contexts are discussed.
Peer group homogeneity in adolescents' school adjustment varies according to peer group type and gender
Authors: Kiuru Noona , Nurmi Jari-Erik , Aunola Kaisa , Salmela-Aro Katariina
Published: January 2009

This study investigated whether the members of adolescents' peer groups are similar in terms of their school adjustment and whether this homogeneity varies according to peer group type and gender. A total of 1262 peer group members who had recently moved to post-comprehensive education filled in questionnaires measuring their academic achievement, satisfaction with their educational track, school engagement, and school burnout. They also gave positive peer nominations on the basis of which 360 peer groups were identified and categorized as cliques, loose groups, and isolate dyads. The results showed that the members of adolescents' peer groups particularly resembled each other in terms of academic achievement. Moreover, the members of girls' cliques showed greater similarity to each other in terms of their satisfaction with educational track and school engagement than did the members of girls' loose groups. Girls' isolate dyads were, in particular, at risk for low adjustment at school.
Age identity: A cross-cultural global approach
Authors: Barak Benny
Published: January 2009

A combination of recent international surveys establishes surprising universality of the subjective and ideal age self-construal constructs appraised in years. Results showed that in 18 culturally disparate countries, age-of-birth was older than subjective/cognitive age self-construal; in 15 nations ideal/ desired ages were measured as well, and those were even younger. Implications of the construct's universality , as well as the reliability, validity, and equivalence of the different measurements of age identity in a cross-cultural research context, are discussed from a global perspective.
Risk discourse and politics: Restructuring welfare in Hong Kong
Authors: Chan Raymond K.H.
Published: January 2009

This paper uses the concept of risk to frame an analysis of welfare reforms and politics in Hong Kong following the financial crisis. Recently, the government and the public have been increasingly exposed to, and aware of, risk. The old welfare policies were considered ineffective in coping with new risks and were gradually replaced by new strategies, formulated in accordance with risk-led welfare discourse. The new risks and the risk management policies have reconfigured political alignments and power relationships among various stakeholders, who continue to debate risk definitions and appropriate responses. The perception and significance of risk, especially after the financial crisis, in reconfiguring risk politics, reconstituting power among the state and various groups, and constructing welfare discourse and policies will be examined. Even though actual risk has greatly diminished since 2004, risk has been entrenched in government policy.
Reconciling agency with structure: The contradictions and paradoxes of capacity building in Wales' 2000—2006 Objective 1 programme
Authors: Fudge Shane
Published: January 2009

This article looks at the concept of `capacity building' and explores its role in the 2000—2006 European Union (EU) Objective 1 programme in west Wales and the Valleys. An increasingly significant area of policy in regard to addressing rising levels of social inequality and high unemployment, the structural funds have become illustrative of the European Commission's aims to promote social as opposed to economic Europe . Exploring interviews with policy-makers and beneficiaries involved with the community development measures of the programme, the paper looks at whether there is a fit between policy-makers' conceptions of capacity building and `agency responses to social exclusion', as viewed by those who have been directly engaged with projects in regeneration targeted areas. The argument developed explores the idea that the capacity building measures in programmes such as Objective 1 often adopt a `fixed' viewpoint of agency whereby the `capacity to act' will be facilitated by the output oriented framework of the programme. In contrast to this perspective, the paper explores the idea that capacity building programmes must acknowledge the importance of structures in addressing regeneration areas.
Mixed income housing policy and public housing residents' `right to the city'
Authors: Duke Joanna
Published: January 2009

Economic integration through various mixed income housing strategies has become the dominant housing policy in many parts of the world. In the United States, this strategy involves a restructuring of space often with conflict. Henri Lefebvre's `right to the city' is used to conduct a socio-spatial analysis of mixed income housing programmes, including the degree that integration increases public housing residents' access to diverse neighbourhoods, the use value of a city, and participatory space. The paper concludes that mixed income housing has the potential to increase public housing residents' `right to the city' but that policy implementers need to be proactive in the face of barriers such as community opposition to subsidized housing that can hinder the right. Future research should focus on evaluating the benefits of mixed income housing policy for neediest residents and ways to increase their rights to social, economic and political space.
Dementia and dying: The need for a systematic policy approach
Authors: Kellehear Allan
Published: January 2009

In November 2006 a joint National Institute for Health and Clinical Excellence (NICE) and Social Care Institute for Excellence (SCIE) guideline to improve the care of people with dementia was released. This influential policy document reflects both a medicalized approach to care (emphasizing pharmacological management and health services) as well as one characterized by professional dominance (an emphasis on professional authority and control). Despite the involvement of social sciences in its development the policy reflects common biases in other areas of policy and practice in the care of older people. Furthermore, the idea that people with dementia have complex end of life care needs is addressed only with the most cursory and clinically oriented approaches to palliative care. A critical commentary about this policy approach is supplemented with a brief description of an alternative policy vision that connects older people's care with a wider public health approach to end of life care for older people.
The Dilemmas of Radical Nostalgia in British Psychogeography
Authors: Bonnett Alastair
Published: January 2009

This article argues that British psychogeography is an arena of conflict between two important and unresolved strands within radicalism: the use of the past to critique industrial modernity and the suppression of nostalgia. The article begins by outlining the emergence of nostalgia as a site of dilemma and creativity within political radicalism. It is shown that as nostalgia became marginalized within mainstream radicalism it became available as a provocative resource for `counter-cultural' interventions. The article then turns to how the dilemma of nostalgia is negotiated within two forms of contemporary British psychogeography, the travel narratives of Iain Sinclair and the activities of revolutionary psychogeographical groups. Within Sinclair's travel books the modern landscape becomes a site of creative purgatory, a necessary violence that simultaneously anchors the writer in modernism while establishing marginal histories and spaces as expressions of cultural and social loss. In revolutionary psychogeography nostalgia is also refused and deployed. However, this process is enacted in a different way and to different ends. The development of `magico-Marxism' encapsulates the novelty but also the folk-historical inclinations of this project.
Seeking in Modern Athens an Answer to the Ancient Jerusalem Question
Authors: Bauman Zygmunt
Published: January 2009

Carl Schmitt's Political Theology, recycled into The Concept of the Political, was meant to be to political theory what the Book of Job has been to Judaism, and through Judaism to Christianity. It was intended/designed/ hoped to answer one of the most notoriously haunting of the born-in-Jerusalem questions: a sort of question with which the most famous of the born-in-Jerusalem ideas, the idea of the one and only God, omnipresent and omnipotent creator, judge and saviour of the whole Earth and the whole humanity, could not but be pregnant. The question, however, had to be born once the Hebrew Prophet Jesus declared the omnipotent God to be in addition the God of Love, and when his disciple, St Paul, brought the good tidings to Athens — a place where questions, once asked, were expected to be answered, and answered in tune with the rules of logic. Taking absolute power, the God of monotheistic religion took absolute responsibility for the blessings and blows of fate. The Book of Job recasts the frightening randomness of Nature as the frightening arbitrariness of its ruler: God speaks and gives commands. But just like numb Nature, he is not bound by what humans think or do. He can make exceptions. Indeed, the rule of norm is by definition irreconcilable with a true sovereignty — with the absolute power to decide. To be absolute, power must include the right to neglect/suspend/ abolish the norm. Schmitt's idea of sovereignty would engrave the preformed vision of divine order onto the ground of legislative order. Power to exempt founds simultaneously God's absolute power and the human's continuing, incurable fear born of insecurity. This is exactly what happens, according to Schmitt, in case of the human sovereign no longer handcuffed by norms. Thanks to that power of exemption, humans are, as they were in the pre-Law times, vulnerable and uncertain.
Global Modernization, `Coloniality' and a Critical Sociology for Contemporary Latin America
Authors: Maurício Domingues José
Published: January 2009

This article analyses recent social, cultural and political developments in Latin America, with special reference to the `modernity/coloniality' project, as well as offering an alternative sociological interpretation of the contemporary subcontinent. It analyses in particular Walter Mignolo's work as the main expression of that `post/decolonial' project, a general interpretive effort that reflects actual social changes but offers misguided theoretical and political perspectives. The article then proposes a discussion of modernity as a global civilization which is now unfolding its third phase, characterized by greater complexity and pluralism. In addition it argues that modernity should be seen as a two-pronged phenomenon, featuring not only domination but also emancipation. Against the reification of modernity, the article suggests that we see it as woven by multiple and contingent modernizing moves.
In Vitro Angiogenesis of 3D Tissue Engineered Adipose Tissue
Authors: Rui Yao  , Renji Zhang  , Yongnian Yan  , Xiaohong Wang
Published: January 2009

Using a cell assembly device developed in this laboratory, we coextruded adipose derived stem cells (ADSC) and gelatin/alginate hydrogel to form cubic 3D constructions (10 × 10 × 10 mm3) with regular distributed go-through pores. The ADSC grew, proliferated, and differentiated within these constructions. With the addition of basic fibroblast growth factor (bFGF), cells located on the scaffold walls differentiated into endothelial like cells while cells embedded in the hydrogel differentiated into adipose like cells. The integrity of the constructions remained for more than 60 days. This new technology enables us to construct 3D adipose tissue with blood vessel-like structures in vitro which is a significant enhancement in adipose tissue engineering and provides a better biomimic 3D model for studying cell—cell interaction, stem cell differentiation conditions and cell organization mechanisms.
Rat Cartilage Repair Using Nanophase PLGA/HA Composite and Mesenchymal Stem Cells
Authors: Huade Li  , Qiang Zheng  , Yuxiang Xiao  , Jie Feng  , Zhongli Shi  , Zhijun Pan
Published: January 2009

Biodegradable polymer/bioceramic composite poly(lactide- coglycolide)/hydroxyapatite(PLGA/HA) was studied for bone tissue engineering. The PLGA/HA composite was evaluated as a scaffold with the ability for mesenchymal stem cells (MSC) to participate in cartilage repair. The PLGA/HA composite and the PLGA/HA composite cultured with MSC were transplanted into cartilage defects created in rats. The PLGA/HA-MSC and PLGA/HA had better tissue morphology, structure integrity, matrix staining, and much thicker newly formed cartilage than the control group. The histological score for PLGA/ HA-MSC better than that for PLGA/HA; it appears that the MSC plays an important role in tissue repair. Based on these results, using PLGA/HA as the tissue scaffold and the addition of MSC significantly enhances cartilage repair.
Transfer of Buprenorphine Into Breast Milk and Calculation of Infant Drug Dose
Authors: Lindemalm Synnove , Nydert Per , Svensson Jan-Olov , Stahle Lars , Sarman Ihsan
Published: January 2009

Little is known about the safety of buprenorphine (BUP) in breastfeeding. The aim of this work was to investigate the transfer of buprenorphine and its main active metabolite, norbuprenorphine (n-BUP), into human milk and to determine the drug dose and effects in exposed infants. Seven lactating women, who were maintained on BUP treatment because of previous opiate addiction, were studied in an open observational study. All mothers had a strong wish to breastfeed their newborn infants. Buprenorphine samples for analysis were collected from the urine of 6 infants together with breast milk, blood, and urine from their mothers during a 24-hour period in the week after birth. One mother-infant pair was studied at 9 months of age. Buprenorphine and n-BUP were analyzed by a liquid chromatography/mass spectrometry method suitable for handling different matrices. Buprenorphine and n-BUP were found in low levels in the infants' urine. Breastfed infants were exposed to a calculated BUP dose per kg bodyweight less than 1%, with an average milk/plasma area under the curve of 1.7 (range, 1.1-2.8) for BUP and 0.7 (range, 0.4-1.2) for n-BUP. These data support the use of BUP during breastfeeding. However, the authors recommend that infants be monitored closely. J Hum Lact. 25(2):199-205.
Sources and Acceptance of Infant-Feeding Advice Among Low-Income Women
Authors: Heinig M. Jane , Ishii Kara D. , Bañuelos Jennifer L. , Campbell Elizabeth , O'Loughlin Colleen , Vera Becerra Luz Elvia
Published: January 2009

The purpose of this study is to identify sources and acceptability of infant-feeding advice among participants in the US-based Special Supplemental Nutrition Program for Women, Infants, and Children (WIC). Focus groups are used to identify sources of infant-feeding advice and factors that contribute to acceptance of or resistance to that advice among 65 WICeligible mothers (34 English speaking and 31 Spanish speaking). The mothers primarily rely on experienced family and friends for advice and frequently use their own intuition to find solutions that work to solve real or perceived infant-feeding problems. Professional advice is perceived as credible when caregivers exhibit characteristics similar to those of experienced family and friends: confidence, empathy, respect, and calm. Using this information, it may be possible for WIC staff to make programmatic modifications to increase their ability to promote optimal infant-feeding behaviors in this population, thereby contributing to the reduction in the prevalence of childhood overweight. J Hum Lact. 25(2):163-172.
Breastfeeding Mothers Returning to Work: Possibilities for Information, Anticipatory Guidance and Support from US Health Care Professionals
Authors: Angeletti Michelle A.
Published: January 2009

Today, more mothers in the United States are in the labor force, and returning to the workforce presents numerous challenges for the breastfeeding mother. Although it as been demonstrated that maternal employment is associated with a decrease in the length of time a mother continues to breastfeed, health care providers are in a unique position to enhance a mother's breastfeeding success as she transitions back into the workplace. This article describes various commonly perceived obstacles to combining breastfeeding and working and provides examples of information, anticipatory guidance, and support that health care providers can use to assist a breastfeeding mother with a successful return to the workforce. J Hum Lact. 25(2):226-232.
Saliva and Dental Pellicle-A Review
Authors: Lendenmann U. , Grogan J. , Oppenheim F.G.
Published: January 2009

The acquired enamel pellicle is an organic film covering the surfaces of teeth. When this film was first discovered, it was thought to be of embryologic origin. Only in the middle of this century did it become clear that it was acquired after tooth eruption. Initially, the small amounts of material that could be obtained have virtually limited the investigation of pellicle proteins to amino acid analysis. Nevertheless, this technique revealed that the pellicle is mainly proteinaceous and is formed by selective adsorption of salivary proteins on tooth enamel. Later, immunologic techniques allowed for the identification of many salivary and fewer non-salivary proteins as constituents of pellicle. However, to this date, isolation and direct biochemical characterization of in vivo pellicle protein have not been possible, because only a few micrograms can be obtained from a single donor. Therefore, the composition and structure of the acquired enamel pellicle are still essentially unknown. Information on the functions of pellicle has been obtained mainly from in vitro experiments carried out with saliva-coated hydroxyapatite and enamel discs. It was found that pellicle protects enamel by reducing demineralization upon acid challenge. Improved pellicle harvesting procedures and analysis by state-of-the-art proteomics with mass spectroscopy approaches promise to make major inroads into the characterization of enamel pellicle.
Saliva and Dental Plaque
Authors: Rudney J.D.
Published: January 2009

Dental plaque is being redefined as oral biofilm. Diverse overlapping microbial consortia are present on all oral tissues. Biofilms are structured, displaying features like channels and projections. Constituent species switch back and forth between sessile and planktonic phases. Saliva is the medium for planktonic suspension. Several major functions can be defined for saliva in relation to oral biofilm. It serves as a medium for transporting planktonic bacteria within and between mouths. Bacteria in transit may be vulnerable to negative selection. Salivary agglutinins may prevent reattachment to surfaces. Killing by antimicrobial proteins may lead to attachment of dead cells. Salivary proteins form conditioning films on all oral surfaces. This contributes to positive selection for microbial adherence. Saliva carries chemical messengers which allow live adherent cells to sense a critical density of conspecifics. Growth begins, and thick biofilms may become resistant to antimicrobial substances. Salivary macromolecules may be catabolized, but salivary flow also may clear dietary substrates. Salivary proteins act in ways that benefit both host and microbe. All have multiple functions, and many do the same job. They form heterotypic complexes, which may exist in large micelle-like structures. These issues make it useful to compare subjects whose saliva functions differently. We have developed a simultaneous assay for aggregation, killing, live adherence, and dead adherence of oral species. Screening of 149 subjects has defined high killing/low adherence, low killing/high adherence, high killing/high adherence, and low killing/low adherence groups. These will be evaluated for differences in their flora.
Salivary Cellular Signaling and Gene Regulation
Authors: Wen X. , Lin H.H. , Ann D.K.
Published: January 2009

Protein tyrosine kinase and protein serine kinase activation has been implicated in the regulation of salivary cell proliferation and differentiation. Aberrant expression and alterations of certain tyrosine or serine kinases, such as Raf or erbB2, are known to trigger salivary tumor development (Li et al., 1997; Cho et al., 1999). It has been estimated that there are about 1000 to 2000 protein kinases in the mammalian genome, with 100 to 200 of them ( i.e., 10%) being tyrosine kinase (Hanks and Hunter, 1995). At present, there are approximately 85 different tyrosine kinases identified in the GenBank database. Based on the relatively slow rate of discovery in the past few years, 100 is a better approximation of the total number of tyrosine kinases encoded by each mammalian genome. It is reasonable to assume that there are about 30 to 50 tyrosine kinases expressed in a given cell at a given differentiation/proliferation stage. This number is large enough to provide a characteristic tissue-specific tyrosine kinase expression profile, but small enough to be identified in a simple screening. The hope for tyrosine kinases as differentiation or proliferation markers rests with the possibility for the identification and characterization of a differentiation/proliferation stage-specific expression pattern in salivary cells. Several ligands that transmit signal through receptor tyrosine kinases and/or Ras/Raf/ERK kinases have been extensively studied in salivary cells. This review focuses mainly on the signaling pathways activated bv Raf and Etk.
Early Genes Required for Salivary Gland Fate Determination and Morphogenesis in Drosophila melanogaster
Authors: Myat M.M. , Isaac D.D. , Andrew D.J.
Published: January 2009

Studies of Drosophila salivary gland formation have elucidated the regulatory pathway by which the salivary gland fate is determined and the morphogenetic processes by which the primordial cells are internalized to form the tubular glands. Both the position of the salivary primordia and the number of cells recruited to a salivary gland fate are established through a combination of the localized expression of the transcription factors SEX COMBS REDUCED (SCR), TEASHIRT (TSH) and ABDOMINAL-B (ABD-B), and localized DPP-signaling. Similarly, the distinction between the two major cell types, duct and secretory, is determined by spatially limited EGF-signaling. Salivary gland formation also requires the function of two transcription factors expressed in nearly all cells of the developing embryo, EXTRADENTICLE (EXD) and HOMOTHORAX (HTH). Once the salivary gland fate is determined, cells of the secretory primordia are internalized by an apical constriction mode of invagination. We have characterized three genes encoding transcription factors, trachealess (trh), hückebein (hkb), and fork head (fkh), that are downstream targets of the salivary gland regulators. Mutations in these transcription factors profoundly affect salivary gland morphogenesis. trh is required for the formation of the salivary duct tubes. hkb determines the order of secretory cell invagination, a regulated process critical for determining the final shape of the salivary gland. fkh has two early roles in salivary gland formation. fkh both promotes secretory cell survival and facilitates secretory cell internalization. trh, hkb, and fkh are involved in the formation of not only the salivary duct and secretory tubes, but also of other tubular structures, such as the trachea and the gut endoderm. We propose that trh, hkb, and fkh may serve as "morphogenetic cassettes" responsible for forming tubular structures in a variety of tissues.
Salivary Growth Factors in Health and Disease
Authors: Kagami H. , Hiramatsu Y. , Hishida S. , Okazaki Y. , Horie K. , Oda Y. , Ueda M.
Published: January 2009

The salivary gland is considered to be a reservoir of many growth factors in rodents. In humans, the epidermal growth factor, basic fibroblast growth factor, and insulin and insulin-like growth factor family have also been detected in this gland, but their physiological role remains unclear. In this study, we focused on bFGF, which is a well-known mitogen for various types of cells, and is present in the salivary gland as well as in saliva. The roles of bFGF in the salivary gland were investigated by three different procedures. First, the effects of bFGF on the salivary gland cells were investigated with a monolayer culture of normal submandibular gland cells. The effects of different concentrations of bFGF on the second passage of these cultured cells were examined. In both human and rat cultured submandibular gland cells, bFGF accelerated the cell proliferation at a concentraion of 100 ng/mL or higher. Next, an atrophic model of the rat submandibular gland was used to examine the ability of bFGF to accelerate tissue repair. Two weeks after ductal ligation, the ligature was removed, and various amounts of bFGF, isoproterenol, or saline were administered via a retrograde duct instillation. Both isoproterenol and bFGF increased acinar and ductal cell proliferation significantly. To determine the role of bFGF in saliva, we investigated its effect on the healing process of oral mucosal defects. Four-millimeter mucosal defects were made to the depth of the periosteum in the rat palate under anesthesia. bFGF or vehicle alone was applied once only at the time of surgery as a suspension. At days 3, 5, and 7 in the bFGF group, significant increases in the degree of re-epithelialization were found in treated groups. These results indicate that its action as a mitogen stimulus is the major effect of bFGF on salivary gland cells and mucosal epithelium.
The in vitro and in vivo Influence of 4-META/MMA-TBB Resin Components on Dental Pulp Tissues
Authors: Inoue T. , Miyakoshi S. , Shimono M.
Published: January 2009

The purpose of this study was to qualitate the penetration of the major components of 4-META/MMA-TBB adhesive resin (4-META resin) and to characterize their influence on the in vitro and in vivo wound healing of dental pulp tissues. Fresh 4-META resin was applied to rabbit mesentery; its components penetrated the mesentery to form three of layers, depending on the amounts of monomer components in the tissue. The superficial layer was a soft-tissue hybrid layer (STHL), the intermediate layer contained small particles of polymerized 4-META resin, while the deepest layer contained unpolymerized monomer components including MMA and butanol, which were detected by gas chromatography (GC). To characterize the in vivo effects of the deepest layer, we immersed the pulp tissue in MMA or in 5% 4-META/MMA and autotransplanted it to placement beneath a rabbit kidney capsule. The MMA-immersed pulp was positive for osteocalcin and presented osteodentin formation at 7 days, as did the untreated control pulp tissue. In contrast, the 5% 4-META/MMA-immersed pulp collapsed into the cell-deficient fibrous connective tissue, with slight calcification by 7 days and less osteodentin formation at 14 days. Analysis of these data suggests that MMA does not inhibit osteogenic activity of pulp tissue, while 5% 4-META/MMA does inhibit osteogenic activity to some extent.
Enamel Matrix Derivative Promotes Reparative Processes in the Dental Pulp
Authors: Nakamura Y. , Hammarström L. , Lundberg E. , Ekdahl H. , Matsumoto K. , Gestrelius S. , Lyngstadaas S.P.
Published: January 2009

During odontogenesis, amelogenins from the preameloblasts are translocated to differentiating odontoblasts in the dental papilla, suggesting that amelogenins may be associated with odontoblast changes during development. In the present study, we have explored the effects of enamel matrix derivative (EMD) on the healing of a pulpal wound. Coronal pulp tissue of permanent maxillary premolars of miniature swine were exposed through buccal class V cavities. The exposed pulp was capped with EMD. The contralateral teeth served as controls and were capped with a calcium hydroxide paste (Dycal®). The cavities were sealed with glass-ionomer cement. After 2 and 4 weeks, the histology of the teeth was analyzed. In the EMD-treated teeth, large amounts of newly formed dentin-like hard tissue with associated formative cells outlined the pulpal wound separating the cavity area from the remaining pulp tissue. Inflammatory cells were present in the wound area but not subjacent to the newly formed hard tissue. Morphometric analysis showed that the amount of hard tissue formed in EMD-treated teeth was more than twice that of the calcium-hydroxide-treated control teeth (p < 0.001), suggesting that EMD is capable of promoting reparative processes in the wounded pulp more strongly than is calcium hydroxide.
Utilization of M06-G3 Immortalized Odontoblast Cells in Studies Regarding Dentinogenesis
Authors: MacDougall Mary , Unterbrink Aaron , Carnes David , Rani Sheela , Xianhong Luan  , Shuo Chen
Published: January 2009

Tooth formation is the result of reciprocal instructive interactions between oral epithelium and cranial neural-crest-derived ectomesenchymal tissues. These interactions lead to the cytodifferentiation of highly specialized matrix-forming cell types, the ameloblast, odontoblast, and cementoblast, that produce the mineralized tissues enamel, dentin, and cementum, respectively. Our laboratory has been developing immortalized dental cell lines representative of these various cell types to facilitate studies on gene regulation, cell differentiation, matrix formation, and mineralization. Odontoblasts are solely responsible for the synthesis and secretion of the dentin extracellular matrix bilayer that consists of non-mineralized predentin and mineralized dentin. The mouse immortalized M06-G3 cell line expresses the major matrix proteins associated with the odontoblast phenotype, producing a matrix that is capable of mineralization. This cell line serves as a useful tool in studies designed to explore the various processes of dentinogenesis. In this paper, we present studies using the mouse odontoblast cell line M06-G3 as examples of the various research applications. Studies highlighted are: in vitro promoter studies investigating the tooth-specific gene regulation of the major noncollagenous dentin matrix protein, dentin sialophosphoprotein; regulation of tertiary dentin formation by cytokines, such as transforming growth factor-Beta 1; and the utilization of dentally relevant cells in dental material biocompatibility testing
FGFs-1 and -2, and TGFβ 1 as Inductive Signals Modulating in vitro Odontoblast Differentiation
Authors: Unda F.J. , Martín A. , Hernandez C. , Pérez-Nanclares G. , Hilario E. , Aréchaga J.
Published: January 2009

We have studied the expression of FGF1 and FGF2 during mouse odontogenesis by immunohistochemistry. FGF1 was detected in differentiated odontoblasts and at the secretory pole of ameloblasts. Localization of FGF2 was mainly observed within the basement membrane interposed between dental epithelium and dental mesenchyme. These findings indicate that FGF1 and FGF2 may participate in the control of odontoblast and ameloblast differentiation. Thereafter, we studied the ability of FGF1 and FGF2, alone or in combination with TGFβ1, to induce polarization and/or functional differentiation of pre-odontoblasts. Dental papillae (DP) obtained from first lower molars of 17-day-old mouse embryo were cultured in the presence or the absence of growth factors. DP cultured with FGFl+TGFβ1 showed gradients of odontoblast-like cell differentiation, which displayed alkaline phosphatase reactivity. DP treated with FGF2+TGFβ1 exhibited pre-odontoblast cell polarization, and the cell bodies displayed long cytoplasm processes. However, following this treatment we did not observe extracellular matrix secretion, and alkaline phosphatase activity was completely inhibited. In summary, our results show that exogenous addition of FGF1 to pre-odontoblasts induces their terminal differentiation, by synergistically acting with TGFβ1. In contrast, FGF2 may regulate the effect of TGFβ1, permitting cell polarization but restraining pre-odontoblast functions.
The Effect of TGF-β2 on Dentin Apposition and Hardness in Transgenic Mice
Authors: DenBesten P.K. , Machule Darren , Gallagher Richard , Marshall Grayson W. , Mathews Catherina , Filvaroff Ellen
Published: January 2009

Transforming growth factor β, TGF-β, is expressed during tooth formation and can induce pre-odontoblast differentiation and formation of functional odontoblast-like cells in vitro. In addition, exogenous TGF-β can increase reparative dentin formation, presumably by acting on odontoblasts. In this study, we examined the tooth phenotype of transgenic mice, in which TGF-β2 expression is directed by the osteocalcin promoter. Previous studies have shown that these mice have a bone phenotype that resembles that of human osteoporosis, including the existence of spontaneous fractures. Microhardness testing of the enamel and dentin showed no differences in the molars of these transgenic mice as compared with those of their wild-type littermates. Consistent with the increase in bone mineral apposition rate previously reported in these mice, the dentin apposition rate appeared to be increased in the TGF-β2-overexpressing mice. Thus, in teeth, as in bone, TGF-β2 appears to stimulate the synthesis and deposition of matrix. Further studies are needed to understand the effect of TGF-β2 on distinct mineralized tissues (bone, dentin, and cementum) and to determine whether exogenous TGF-β2 may be useful for tooth repair.
Neural Crest and Tooth Morphogenesis
Authors: Sharpe Paul T.
Published: January 2009

Mammalian teeth develop from two types of cells: stomodeal ectoderm, which forms ameloblasts, and cranial neural-crest-derived (ecto) mesenchyme cells, which form odontoblasts and cementoblasts. These two cell types, juxtaposed in the developing oral cavity, interact to control the entire process of tooth initiation, morphogenesis, and cytodifferentiation. Cell-cell signaling pathways and their target nuclear factors have been identified as key mediators of the progressively complex exchange of information between ectoderm and ectomesenchyme. The constantly changing direction of the reciprocal signaling and cell responses between ectoderm and ectomesenchyme enables cells to monitor their relative spatial positions and differentiated states continuously. The least understood of the early processes in tooth development are morphogenesis and patterning. From a seemingly uniform layer of oral ectoderm and underlying mass of ectomesenchyme, different types (shapes) of teeth develop in different positions. Tooth type is determined very early in development, before the overt onset of morphogenesis. Thus, the early ectoderm-ectomesenchyme cell interactions must in some way either create or respond to positional differences in the jaw primordia.
Molecular Regulation of Odontoblast Activity under Dentin Injury
Authors: Magloire H. , Romeas A. , Melin M. , Couble M.-L. , Bleicher F. , Farges J.-C.
Published: January 2009

Pulp tissue responds to dentin damage by laying down a tertiary dentin matrix (reactionary or reparative) beneath the site of injury. Reactionary dentin is secreted by surviving odontoblasts in response to environmental stimuli, leading to an increase in metabolic activities of the cells. The inductive molecules that determine the success of the pulp healing may be released from the damaged dentin as well as from the pulp tissue subjacent to the injury. This paper will schematically consider two major growth factors probably implicated in the control of odontoblast activity: TGFβ-1 released from demineralized dentin and NGF from pulp. To analyze their role with an in vitro system that mimics the in vivo situation, we have used thick-sliced teeth cultured as described previously. The supply of factors was accomplished by means of a small tube glued onto the dentin. The tube was filled with TGFβ-1 (20 ng/mL) or NGF (50 ng/mL), and slices were cultured for 4 or 7 days. Results showed that TGFβ-1 binding sites are strongly detected on odontoblasts in the factor-rich zone. A strong expression of α1(I) collagen transcripts was also detected. In the NGF-rich environment, p75NTR was re-expressed on odontoblasts and the transcription factor NF-KB activated. Modifications in the odontoblast morphology were observed with an atypical extension of the cell processes filled with actin filaments. These results suggest that odontoblasts respond to influences from both dentin and pulp tissue during pulp repair.
Trans-dentinal Stimulation of Tertiary Dentinogenesis
Authors: Smith A.J. , Murray P.E. , Sloan A.J. , Matthews J.B. , Zhao S.
Published: January 2009

Trans-dentinal stimulation of tertiary dentinogenesis has long been recognized, and has traditionally been ascribed to diffusion of irritant substances arising during injury and restorative treatment. Identification of bio-active components, especially growth factors including TGF-βs, sequestered within dentin matrix provides a new explanation for cellular signaling during tertiary dentinogenesis. Both isolated dentin matrix components and pure growth factors (TGF-βs) have been shown to signal cellular events leading to reactionary and reparative tertiary dentinogenesis. Release of these bio-active components from dentin matrix may arise during carious attack and other injury to the tissue, and also during subsequent surgical intervention and restoration of the tooth. Both cavity-conditioning agents and leaching from restorative materials may contribute to release of these components. Distance of diffusion, as determined by cavity residual dentin thickness, and other restorative parameters may influence the signaling process after release of these components. Careful consideration of the interplay between tissue injury and surgical and restorative material factors is required for optimum exploitation of the exquisite regenerative capacity of dentin-pulp for more biological approaches to clinical treatment of dental disease.
Human Odontoblast Culture Method: The Expression of Collagen and Matrix Metalloproteinases (MMPs)
Authors: Tjäderhane L. , Palosaari H. , Wahlgren J. , Larmas M. , Sorsa T. , Salo T.
Published: January 2009

Studies on mature human odontoblasts have suffered for the lack of in vitro models. We recently introduced a human odontoblast and pulp tissue organ culture method, in which the odontoblasts are cultured in the pulp chamber after removal of the pulp tissue, and the pulp tissue can be cultured separately (Tjaderhane et al., 1998a). With this method, we have studied the effects of growth factors on the expression of collagen and extracellular matrix (ECM)-degrading enzymes, matrix metalloproteinases (MMPs), in mature human odontoblasts. TGF-β1 was selected because of its ability to regulate the response of the dentin-pulp complex to external irritation. The effect of TGF-β1 (10 ng/mL) on proal(I) collagen mRNA was analyzed by quantitative PCR, and type I procollagen propeptide (PINP) was analyzed from conditioned culture media with RIA. Odontoblast media were also assayed for respective type III procollagen propeptide (PIIINP). TGF-β had a negligible effect on collagen mRNA expression or protein synthesis, indicating that TGF-β alone does not markedly induce dentin matrix formation per se in the human dentin-pulp complex (Palosaari et al., 2001). However, TGF-β1 seems to regulate MMP expression in mature human odontoblasts differentially. A strong down-regulation of MMP-8 (Palosaari et al., 2000), a modest down-regulation of MMP-20 (Tjaderhane et al., 2000), and considerable up-regulation of MMP-9, with no apparent effect on MMP-2 expression (Tjaderhane et al., 1998b), indicate that growth factors may affect the matrix synthesis by controlling the expression and activity of MMPs instead of collagen synthesis. The altered expression of MMPs may result in altered ECM formation, which in turn may contribute to the formation of atubular reparative dentin.
Odontoblast Function Seen as the Response of Dentinal Tissue to Dental Caries
Authors: Larmas Markku
Published: January 2009

Microbes are responsible for the initiation and maintaining of carious processes. They have an efficient machinery for dissolving crystalline hydroxyapatite. When initiating carious processes, microbial acid formation determines the rate of the process in enamel. When the process reaches dentin, the micro-environment changes. Dentinal fluid in dentin tubules is the liquid where dissolving products of apatites are destroyed. Inorganic composition of dentinal fluid, however, is not altered much during the carious process, indicating that a functional secretory domain is working to pump the dissolved calcium and phosphate ions out of the fluid. Activation of odontoblast alkaline phosphatase and dentin latent collagenases is the known cellular event during the carious process in dentin. Because the caries lesion is by definition undermining, this suggests that, in this degradation process, the extracellular compartment, crystalline hydroxyapatite is dissolved by microbial acids, and a mixture of proteinases degrades the organic matrix. The degradation products of collagen and other matrix components in dentinal fluid must be transported either through the caries lesion in the enamel to saliva or through the odontoblast to the pulp (active transport). This facilitates further processing of the degradation products intracellularly during the passage through the cell.
The Effects of High levels of Glucose and Insulin on Type I Collagen Synthesis in Mature Human Odontoblasts and Pulp Tissue in vitro
Authors: Valikangas L. , Pekkala E. , Larmas M. , Risteli J. , Salo T. , Tjäderhane L.
Published: January 2009

High levels of dietary sucrose affect the metabolism of the pulp-dentin complex and enhance the caries process in dentin. The high-sucrose diet reduces dentin formation in young rats (Tjaderhane et al., 1994; Hietala and Larmas, 1995; Tjaderhane, 1996) and in pups of rat dams fed high-sucrose diet during lactation (Pekkala et al., 2000a). However, the mechanisms behind the effects are unknown. A direct effect of elevated blood glucose or an indirect effect via insulin has been suggested. We investigated the effects of high glucose and insulin on type I collagen synthesis in human odontoblasts and pulp tissue in vitro, using an organ culture method for functional post-mitotic odontoblasts. Odontoblasts and pulp tissue were cultured separately for 10 days in DMEM with 15% FBS containing additional glucose (G) (4.45 g/L) or insulin (I) (0.6 μg/mL) or both together (GI). We evaluated type I collagen synthesis with RIA, measuring the level of N-terminal propeptide of type I collagen (PINP) secreted into the culture media. PINP secretion decreased in odontoblasts and pulp tissue in G and GI groups when compared with the control and insulin samples (p = 0.001 in both groups in the pulp samples). Insulin alone did not affect PINP secretion distinctly. The results indicate that high levels of glucose, but not insulin, directly down-regulate the type I collagen synthesis in young, differentiated human odontoblasts and pulp tissue. Insulin does not affect the inhibitory effect of high sucrose. These in vitro findings indicate that the high-sucrose diet mav alter odontoblast function independently of insulin.
Further Observations on Tertiary Dentin in Human Deciduous Teeth
Authors: Klinge Randi Furseth
Published: January 2009

The structure of reparative tertiary dentin in human deciduous teeth has been studied. Reparative dentin is secreted by a new generation of odontoblast-like cells which have been subject to strong stimuli, e.g., trauma or deep active caries lesions with associated pulp inflammation. Ground sections of 25 teeth were prepared, and contact microradiographs were produced. Another 30 teeth were demineralized, embedded in paraffin, sectioned, and stained with hematoxylin and eosin. Some demineralized sections from each tooth were also studied in the scanning electron microscope. Most of the teeth showed some type of tertiary dentin formation. Mineralized tissue with a varied morphology was observed. In teeth which had been subject to trauma, the entire pulp chamber was sometimes obliterated. Mineralization seemed to start in the incisal region, and the central part of the pulp was the last part to be obliterated. Radiolucent voids and canals were seen. The organic matrix was dense and fibrous. In the pulp chamber and especially in the root canals, resorption had often occurred, indicating that signals giving rise to odontoclasts were also present. Resorption was often followed by deposition of various amounts of cementum-like repair tissue. The cells responsible for the formation of reparative dentin are believed to be subodontoblasts or undifferentiated ectomesenchymal cells. The varied morphology of the reparative dentin, observed in the pulp of the teeth examined, indicates that different stimuli lead to induction of hard-tissue-forming cells which produce different types of hard tissue.
Presence or Absence of Tertiary Dentinogenesis in Relation to Caries Progression
Authors: Bjørndal L.
Published: January 2009

Studies have shown that dental caries may or may not be associated with tertiary dentin formation in the pulp. On the basis of histological examinations of 69 clinical well-defined caries lesions, a hypothesis is proposed on the dynamics of the hard-tissue responses of the pulp to caries. In active non-cavitated lesions, the formation of tertiary dentin seems to be initiated by primary odontoblast cells that subsequently result in atubular dentin/fibrodentinogenesis, whereas, in similarly aged but more rapidly progressing cavitated enamel lesions, no tertiary dentin is laid down by primary odontoblast cells. In all old-dentin exposed lesions, a so-called closed lesion environment was defined with subjacent atubular dentin formation. As these lesions progress, a shift from a closed to a more large and open lesion environment may develop in the very old lesions, and a new tubular dentinal matrix is noted on the top of the fibrodentin, also defined as reparative dentinogenesis. In very old slowly progressing lesions, a relatively small open lesion environment is also observed, with tubular tertiary dentin resembling the primary dentin being strictly tubular. It is suggested that the absence of tertiary dentinogenesis can be expected in very rapid caries lesions, whereas a variety of tertiary dentin is observed in older dentin cavitated lesions guided by a changing external lesion environment over time.