Preparedness and competency of New Zealand graduates for general dental practice - perceptions from the workforce

BACKGROUND

Dental graduates need to demonstrate clinical competency. This mixed-methods study explored the perceptions of clinicians who employ or work with new graduates from the University of Otago, New Zealand, and identified themes reflecting graduates' preparedness for independent practice.

METHODS

An online survey using a semantic differential scale and open-ended questions collected opinions and experiences from the workforce. Quantitative data were analysed using SPSS software, and qualitative data were analysed thematically.

RESULTS

A representative sample of the workforce was obtained with a response rate of 35% (N = 83). Most clinicians engage new graduates to support the profession and/or rural communities. They perceived that graduates were well prepared in most areas, could translate theory to clinical practice and demonstrate professionalism. Graduates were reportedly stronger in basic dentistry, communication, ethics, and record keeping however were less strong in complex treatment planning, molar endodontics, fixed prosthodontics and exodontia. Clinical exposure during dental training was perceived as more limited, and mentoring and guidance in the transition to practice were deemed to be important.

CONCLUSIONS

New Zealand dental graduates appear prepared for independent practice; however, maximising clinical opportunities during training, mentoring and early professional development in advanced areas of practice is essential to enhance competency and confidence.

Storage-related stability and antimicrobial efficacy of bottled, neutral-pH Electrolysed Oxidising Water

OBJECTIVES

Denture stomatitis is prevalent in older people and poses serious health risks. Ready-to-use (RTU) neutral-pH Electrolysed Oxidizing Water (EOW) is an effective environmental disinfectant used in residential care settings and geriatric wards. However, the influence of storage on stability and effectiveness for denture disinfection has not been established. This research investigated the storage-related stability and antimicrobial activity of RTU EOW, and its efficacy against Candida albicans biofilms formed on denture resin.

METHODS

The pH, oxidation/reduction potential (mV), available chlorine content (mg/L) and [HOCl] (mM) of RTU EOW (Envirolyte, New Zealand) solutions (n = 22) were measured from bottle opening to 28 days following storage at 4 °C, room temperature (RT) or 37 °C. Staphylococcus aureus and C. albicans cells were incubated in 80% EOW for contact times (CTs) up to 15 min and colony-forming units (cfu) determined. Minimum inhibitory concentrations (MIC90 EOW-HOCl) after CTs up to five minutes were determined for S. aureus and C. albicans reference strains and clinical isolates. C. albicans-denture resin disc biofilms were assessed after a five-minute CT with undiluted EOW by XTT-metabolic activity assay.

RESULTS

[HOCl] remained stable when RTU EOW was stored at 4 °C or RT for five months after manufacture. One-minute CT resulted in log10 cfu reductions of >6 for S. aureus and >5 for C. albicans. Mean MIC90 for five-minute CT was 37 µM (S. aureus) and 54 µM (C. albicans). Undiluted EOW reduced C. albicans biofilm metabolic activity by 86%.

CONCLUSIONS

RTU neutral-pH EOW is stable over five-months storage and is an effective denture disinfectant.

CLINICAL SIGNIFICANCE

The efficacy of the RTU neutral EOW against C. albicans isolates and biofilms formed on denture resin surfaces supports its use as a denture disinfectant and can inform future research to assess its potential for preventing denture-related oral Candida infections in the older population, especially in resource-limited communities.

Cognitive and Metacognitive Processes Demonstrated by Pharmacy Students When Making Therapeutic Decisions

Objective. To characterize the types of cognitive and metacognitive processes demonstrated by third-year pharmacy students during a therapeutic reasoning activity.Methods. A qualitative, descriptive study following a think-aloud protocol was used to analyze the cognitive (analytical) and metacognitive processes observed by third-year pharmacy students as they completed a 25-minute therapeutic reasoning activity. Using a deductive codebook developed from literature about reasoning, two independent coders characterized processes from students' audio-recorded, transcribed think-aloud episodes while making therapeutic decisions about simulated clinical cases.Results. A total of 40 think-aloud episodes were transcribed among the cohort. Categorization of the think-aloud transcriptions revealed a series of cognitive analytical and metacognitive processes demonstrated by students during the therapeutic decision-making activity. A total of 1792 codes were categorized as analytical processes, falling into six major themes: 69% gathering information (1232/1792), 13% processing information (227/1792), 7% making assessments (133/1792), 1% synthesizing information (19/1792), 7% articulating evidence (117/1792), and 4% making a recommendation (64/1792). In comparison to gathering information, a much lower frequency of processing and assessment was observed for students, particularly for those that were unable to resolve the case. Students' movement between major analytical processes co-occurred commonly with metacognitive processes. Of the 918 codes categorized as metacognitive processes, two major themes arose: 28% monitoring for knowledge or emotions (257/918) and 72% controlling the planning of next steps or verification of correct information (661/918). Sequencing the codes and co-occurrences of processes allowed us to propose an integrated cognitive/metacognitive model of therapeutic reasoning for students.Conclusion. This study categorizes the cognitive (analytical) and metacognitive processes engaged during pharmacy students' therapeutic reasoning process. The findings can inform current instructional practices and further research into educational activities that can strengthen pharmacy students' therapeutic reasoning skills.

Preceptor Perceptions of Pharmacy Student Performance Before and After a Curriculum Transformation

Objective. To explore preceptors' perceptions about the performance of undergraduate pharmacy students during experiential placements in Australia, before and after curricular transformation.Methods. Using a semi-structured approach, we interviewed 26 preceptors who had recently supervised students who took part in the transformed curriculum and students from the previous curriculum. A directed content analysis approach was used to analyze the transcripts.Results. Preceptors described students from the transformed curriculum as having improved professional skills, behaviors, and attitudes and as having an increased ability to perform clinical activities compared to students of the previous curriculum. Preceptors also perceived that students in the transformed curriculum had improved clinical knowledge and knowledge application. They less frequently expressed that students in the transformed curriculum had lower-than-expected knowledge levels.Conclusion. The results of this study suggest that curricular transformation with a focus on skill-based and active learning can improve the performance of pharmacy students in terms of their professional behaviors and attitudes, skills, knowledge, and clinical abilities, as perceived by preceptors.

The clinical educator's guide to fostering learner motivation: AMEE Guide No. 137

Motivation theory and research remain underused by health professions educators. Some educators say it can seem too abstract. To address this, we applied health care language to learner motivation theories. Using a familiar metaphor, we examined the indications, mechanism of action, administration, and monitoring of learner motivation interventions. Similar to the treatment monographs in medicine compendia, we summarized each motivation intervention in the form of a monograph. The purpose of this guide is for health professions educators to develop an understanding of when (i.e. indication) and how (i.e. mechanism of action) learner motivation interventions work. With this information, they can then access ready-to-implement strategies (i.e. administration) to increase their learner interest and assess the effects of these interventions (i.e. monitoring).

Examining the relationship between measures of autistic traits and neural synchrony during movies in children with and without autism

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Neural synchrony during movie watching was measured in children with and without ASD.

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The ASD group had significantly less neural synchrony across the whole brain.

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The ASD group also had significantly less synchrony in the theory of mind network.

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Autistic traits did not predict neural synchrony in non-ASD children.

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These results suggest children with ASD process movies in a unique way.

Children who have been diagnosed with autism spectrum disorder (ASD) often show a marked deficit in measures of social cognition. In autistic adults, measures of social cognition have been shown to relate to differences in brain synchronization (as measured by fMRI) when individuals are processing naturalistic stimuli, such as movies. However, whether children who differ in their degree of autistic traits, with or without a diagnosis of ASD, differ in their neural responses to movies has not yet been investigated. In the current study, neural synchrony, measured using fMRI, was examined in three groups of children aged 7 to 12, who differed with respect to scores on a measure of autistic traits associated with social impairment and whether or not they had been diagnosed with ASD. While watching the movie ‘Despicable Me’, those diagnosed with ASD had significantly less neural synchrony in areas that have been previously shown to be associated with social cognition (e.g. areas related to ‘theory of mind’), and plot following (e.g. the lateral prefrontal cortex), than those who did not have an ASD diagnosis. In contrast, two groups who differed in their degree of autistic traits, but did not have a diagnosis of ASD, showed no significant differences in neural synchrony across the whole brain. These results shed some light on how autistic traits may contribute to an individual’s conscious experience of the world, and how, for children with ASD, that experience may differ markedly from that of those without ASD.

Predictors of Pharmacy Student Performance on Written and Clinical Examinations in a Flipped Classroom Curriculum

Objective. To examine the effects of student demographics, prior academic performance, course engagement, and time management on pharmacy students' performance on course examinations and objective structured clinical examinations (OSCEs).Methods. Study participants were one cohort of pharmacy students enrolled in a five-year combined Bachelor and Master of Pharmacy degree program at one institution. Variables included student demographics, baseline factors (language assessment and situational judgement test scores), prior academic performance (high school admission rank), course engagement, and student time management of pre-class online activities. Data were collected from course, learning management system, and institutional databases. Data were analyzed for univariate, bivariate, and multivariate associations (four linear regression models) between explanatory factors and outcome variables.Results. Three years of data on 159 pharmacy students were obtained and entered in the dataset. Significant positive predictors of OSCE communication performance included domestic (ie, Australian) student designation, higher baseline written English proficiency, and pre-class online activity completion. Positive predictors of OSCE problem-solving included workshop attendance and low empathy as measured by a baseline situational judgment test (SJT). Positive predictors of performance on year 2 end-of-course examinations included the Australian Tertiary Academic Rank, completing pre-class online activities prior to lectures, and high integrity as measured by an SJT.Conclusion. Several explanatory factors predicted pharmacy students' examination and OSCE performance in the regression models. Future research should continue to study additional contexts, explanatory factors, and outcome variables.

Sustainable Pharmacy Education in the Time of COVID-19

Pharmacy schools and colleges worldwide are facing unprecedented challenges to ensuring sustainable education during the novel coronavirus (COVID-19) pandemic. The experiences of pharmacy educators in the Asia-Pacific region in delivering emergency remote teaching, ensuring purposeful experiential placements, supporting displaced or isolated students, and communicating with faculty members, staff members, and students are discussed. The role of this pandemic in accelerating opportunities for new models of pharmacy education across the world is also discussed.

Antimicrobial Activity of a Colloidal AgNP Suspension Demonstrated In Vitro against Monoculture Biofilms: Toward a Novel Tooth Disinfectant for Treating Dental Caries

A novel silver nanoparticle (AgNP) formulation was developed as a targeted application for the disinfection of carious dentine. Silver nitrate (AgNO₃) was chemically reduced using sodium borohydrate (NaBH₄) in the presence of sodium dodecyl sulfate (SDS) to form micelle aggregate structures containing monodisperse 6.7- to 9.2-nm stabilized AgNPs. AgNPs were characterized by measurement of electrical conductivity and dynamic light scattering, scanning electron microscopy, transmission electron microscopy, and inductively coupled plasma mass spectrometry. Antimicrobial activity of AgNPs was tested against planktonic cultures of representative gram-positive and gram-negative oral bacteria using well diffusion assays on tryptic soy broth media and monoculture biofilms grown with brain heart infusion ± sucrose anaerobically at 37°C on microtiter plates. Biofilm mass was measured by crystal violet assay. Effects were compared to silver diamine fluoride and chlorhexidine (negative controls) and 70% isopropanol (positive control) exposed cultures. In the presence of AgNPs, triplicate testing against Streptococcus gordonii DL1, C219, G102, and ATCC10558 strains; Streptococcus mutans UA159; Streptococcus mitis I18; and Enterococcus faecalis JH22 for planktonic bacteria, the minimum inhibitory concentrations were as low as 7.6 µg mL^-1 and the minimum bacteriocidal concentrations as low as 19.2 µg mL^-1 silver concentration. Microplate readings detecting crystal violet light absorption at 590 nm showed statistically significant differences between AgNP-exposed biofilms and where no antimicrobial agents were used. The presence of sucrose did not influence the sensitivity of any of the bacteria. By preventing in vitro biofilm formation for several Streptococcus spp. and E. faecalis, this AgNP formulation demonstrates potential for clinical application inhibiting biofilms.

Low-intensity pulsed ultrasound (LIPUS) treatment of cultured chondrocytes stimulates production of CCN family protein 2 (CCN2), a protein involved in the regeneration of articular cartilage: mechanism underlying this stimulation

OBJECTIVE

CCN family protein 2/connective tissue growth factor (CCN2/CTGF) promotes cartilage regeneration in experimental osteoarthritis (OA) models. However, CCN2 production is very low in articular cartilage. The aim of this study was to investigate whether or not CCN2 was promoted by cultured chondrocytes treated with low-intensity pulsed ultrasound (LIPUS) and to clarify its mechanism.

METHODS

Human chondrocytic cell line (HCS)-2/8, rat primary epiphyseal and articular cartilage cells, and Ccn2-deficient chondrocytes that impaired chondrocyte differentiation, were treated with LIPUS for 20 min at 3.0 MHz frequency and 60 mW/cm² power. Expressions of chondrocyte differentiation marker mRNAs were examined by real-time PCR (RT-PCR) analysis from HCS-2/8 cells and Ccn2-deficient chondrocytes at 30 min and 1 h after LIPUS treatment, respectively. CCN2 production was examined by Western blotting after 5 h of LIPUS treatment. Moreover, Ca²⁺ influx was measured by using a Fluo-4 probe.

RESULTS

The gene expression of chondrocyte differentiation markers and CCN2 production were increased in cultured chondrocytes treated with LIPUS. In addition, Ca²⁺ influx and phosphorylation of p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK)1/2 were increased by LIPUS treatment, and the stability of TRPV4 and BK_ca channel mRNAs was decreased by siRNA against CCN2. Consistent with those findings, the LIPUS-induced the gene expressions of type II collagen (COL2a1) and Aggrecan (ACAN) observed in wild-type cells were not observed in the Ccn2-deficient chondrocytes.

CONCLUSION

These data indicate that chondrocyte differentiation represented by CCN2 production was mediated via MAPK pathways activated by LIPUS-stimulated Ca²⁺ influx, which in turn was supported by the induced CCN2 molecules in articular chondrocytes.

Connective tissue growth factor (CTGF/CCN2) in haemophilic arthropathy and arthrofibrosis: a histological analysis

INTRODUCTION

Joint haemorrhage is the principal clinical manifestation of haemophilia frequently leading to advanced arthropathy and arthrofibrosis, resulting in severe disability. The degree and prevalence of arthrofibrosis in hemophilic arthropathy is more severe than in other forms of arthropathy. Expression of connective tissue growth factor (CTGF) has been linked to many fibrotic diseases, but has not been studied in the context of haemophilic arthropathy.

AIM

We aim to compare synovial tissues histologically from haemophilia and osteoarthritis patients with advanced arthropathy in order to compare expression of proteins that are possibly aetiologic in the development of arthrofibrosis.

METHODS

Human synovial tissues were obtained from 10 haemophilia and 10 osteoarthritis patients undergoing joint surgery and processed for histology and immunohistochemistry.

RESULTS

All samples from haemophilia patients had synovitis with hypertrophy and hyperplasia of synovial villi. Histologically, synovial tissues contained hyperplastic villi with increased cellularity and abundant haemosiderin- and ferritin-pigmented macrophage-like cells (HMCs), with a perivascular localization in the sub-surface layer. CTGF staining was observed in the surface layer and sub-surface layer in all haemophilia patients, exclusively co-localizing with HMCs. Quantification showed that the extent of CTGF-positive areas was correlated with the degree of detection of HMCs. CTGF was not observed in any of the samples from osteoarthritis patients.

CONCLUSION

Using histological analysis, we showed that CTGF expression is elevated in haemophilia patients with arthrofibrosis and absent in patients with osteoarthritis. Additionally, we found that CTGF is always associated with haemosiderin-pigmented macrophage-like cells, which suggests that CTGF is produced by synovial A cells following the uptake of blood breakdown products.

Intraoral pH and temperature during sleep with and without mouth breathing

To measure and compare the intraoral pH and temperature of individuals during sleep with and without mouth breathing. Ten healthy participants [mean age = 25·8 (± 4·3)] wore a custom-made appliance fitted with a pH probe and thermocouple for two sets of 48 h. Continuous pH and temperature measurements were taken from the palatal aspect of the upper central incisors. To simulate mouth breathing during sleep, participants wore a nose clip for two nights of the four, with the first group (n = 5) wearing the nose clip during the first night and the rest (n = 5) wearing the nose clip during the second night of sleep to balance any potential bias from the wearing sequence. Both qualitative and quantitative analyses were conducted. The mean intraoral pH during daytime was 7·3 (± 0·4) and during sleep was 7·0 (± 0·5). The mean intraoral pH during sleep with mouth breathing was 6·6 (± 0·5), which was statistically significant compared with the normal sleep condition (P < 0·01). The intraoral pH decreased slowly over the hours of sleep in all participants. When sleeping with forced mouth breathing, intraoral pH showed a greater fall over a longer period of time. The mean intraoral temperature was 33·1 °C (± 5·2) during daytime and 33·3 °C (± 6·1) during sleep, with no statistical significance between sleep with and without mouth breathing (P > 0·05). The results suggest that mouth breathing during sleep is related to a decrease in intraoral pH compared with normal breathing during sleep, and this has been proposed as a causal factor for dental erosion and caries.

Abutment load transfer by removable partial denture obturator frameworks in different acquired maxillary defects

STATEMENT OF PROBLEM

Excessive stress on abutment teeth adjacent to a maxillary resection defect during loading of partial denture obturator frameworks may shorten the life of the teeth.

PURPOSE

The aim of this study was to photoelastically compare the forces exerted on the supporting structures of abutment teeth in 3 differently sized surgical resections with removable partial denture designs used to restore such maxillectomy defects.

MATERIAL AND METHODS

Composite photoelastic models were constructed of a human maxilla that had undergone each of 3 maxillectomies: partial, radical, and radical involving the contralateral premaxilla. The abutment teeth included all remaining anterior teeth, the first premolar, and second molar, except the radical maxillectomy, which included the contralateral premaxilla where all remaining teeth were used as abutment teeth. All abutment teeth were restored with complete metal crowns, and removable partial denture frameworks were fabricated. Loading zones were selected according to the resection, and a 10-lb load was applied at each load point. The resulting stresses were observed and recorded photographically in a circular polariscope. The 2 teeth adjacent to the resection were then splinted, and the loading regimens were repeated.

RESULTS

Without splinting, loads closer to the defect produced lingual tipping of the teeth adjacent to the resection and a mesial tipping tendency of the second molar. The tipping effects were greatest in the model with the largest resection. Splinting reduced tipping of the teeth adjacent to the resection and produced more uniform stress around these 2 abutment tooth roots for all of the models.

CONCLUSION

The results of this in vitro study suggest that splinting the 2 teeth adjacent to a resection defect improves stress distribution around the roots during loading. This could increase the clinical life of the abutment teeth.

An in-vitro investigation of the antibacterial effect of nisin in root canals and canal wall radicular dentine

AIM

To determine whether nisin, a bacteriocin, would be effective at killing Enterococcus faecalis and Streptococcus gordonii cells in solution and within the root canal system.

METHODOLOGY

Bacterial isolates of E. faecalis and S. gordonii were grown from glycerol stocks in closed tubes containing BHY broth at 37 degrees C. The minimum bactericidal concentration (MBC) of nisin for both bacterial species was determined by a microdilution method. Extracted human teeth were decoronated to produce roots of equal length with a single canal and divided into six groups of 10 roots. The canals were prepared to a master apical size 30 file using 0.04 taper Ni-Ti rotary instruments. Bacterial samples of each species were inoculated into three groups of prepared roots and incubated in closed tubes at 37 degrees C for 21 days. The root canals in each group were then medicated with water (control), calcium hydroxide powder mixed with sterile water [Ca(OH)2], or nisin and incubated for a further 7 days. Rotary Ni-Ti files were used to take radicular dentine samples from the walls of each canal which were then incubated in BHY broth for 24 h. Optical density (OD600) readings were taken as a measure of bacterial growth.

RESULTS

The MBC of nisin for E. faecalis and S. gordonii was 70 and 20 mg mL(-1) respectively. Calcium hydroxide and nisin medication eradicated infection within the root canal while cells remained viable in the control group. Mean optical density (OD600) readings from canal wall dentine shavings infected with E. faecalis were 1.32 +/- 0.98, 0.73 +/- 0.27 and 0.69 +/- 0.38 for the control, Ca(OH)2 and nisin samples respectively. Corresponding mean readings for S. gordonii were 1.19 +/- 0.18, 0.73 +/- 0.15 and 0.60 +/- 0.29. The Ca(OH)2 and nisin group readings were significantly (P < 0.01) lower than the control for each species as tested by Student's t-test and Mann-Whitney U statistical analysis. Values for Ca(OH)2 and nisin were not significantly (P > 0.01) different.

CONCLUSION

Nisin was effective at eradicating E. faecalis and S. gordonii cells in pure culture and was comparable with Ca(OH)2 in the elimination of these species from within the root canal system.

Autoimmune inner ear disease: steroid and cytotoxic drug therapy

The goal of this study was to assess the effects of immunosuppressive therapy on hearing in patients with presumed autoimmune sensorineural hearing loss (AISNHL) and a Western blot assay positive for a 68 kD inner ear antigen. To achieve this objective, we conducted a retrospective review of 39 such patients who were treated with either a steroid alone or with a steroid followed by a cytotoxic agent. Pure-tone average (PTA) at 500 Hz, 1 kHz, 2 kHz, and 3 kHz, and speech discrimination scores (SDS) were used as objective measures of outcome. At the completion of treatment, 23 of the 39 patients (59.0%) exhibited a positive response to therapy. The steroid-only responders (n = 6) tended to demonstrate a greater improvement in PTA (14.8 vs 4.5 dB), while the cytotoxic-agent responders (n = 17) had a significantly greater improvement in SDS (26.2 vs 6.9%; p < 0.01). We conclude that most patients with AISNHL benefit from immunosuppressive therapy and that cytotoxic medications appear to improve SDS, even in some patients who have not responded to corticosteroid therapy.

Vocal fold mucosal tears: maintaining a high clinical index of suspicion

Vocal fold mucosal tears have been discussed in the literature rarely, although they are not uncommon clinically. Disruptions in the epithelium usually follow trauma that may result from voice abuse and/or misuse, coughing, and other causes. A high index of suspicion is necessary to avoid missing vocal fold mucosal tears, and strobovideolaryngoscopy is indispensable in making the diagnosis. A brief period of complete voice rest is the standard of care and appears to be helpful in avoiding adverse sequelae and advancing the healing process, but there are no scientific studies to confirm its efficacy. Mucosal tears may heal completely or may be followed by the development of vocal fold masses, scar, and permanent dysphonia.

Müllerian inhibiting substance signaling uses a bone morphogenetic protein (BMP)-like pathway mediated by ALK2 and induces SMAD6 expression

Signal reception of Müllerian inhibiting substance (MIS) in the mesenchyme around the embryonic Müllerian duct in the male is essential for regression of the duct. Deficiency of MIS or of the MIS type II receptor, MISRII, results in abnormal reproductive development in the male due to the maintenance of the duct. MIS is a member of the transforming growth factor-beta (TGFbeta) superfamily of secreted protein hormones that signal through receptor complexes of type I and type II serine/threonine kinase receptors. To investigate candidate MIS type I receptors, we examined reporter construct activation by MIS. The bone morphogenetic protein (BMP)-responsive Tlx2 and Xvent2 promoter-driven reporter constructs were stimulated by MIS but the TGFbeta/activin-induced p3TP-lux or CAGA-luc reporter constructs were not. The induction of Tlx2-luc was dependent upon the kinase activity of MISRII and was blocked by a dominant negative truncated ALK2 (tALK2) receptor but not by truncated forms of the other BMP type I receptors ALK1, ALK3, or ALK6. MIS induced activation of a Gal4DBD-Smad1 but not a Gal4DBD-Smad2 fusion protein. This activation could also be blocked by tALK2. The BMP-induced inhibitory Smad, Smad6, was up-regulated by MIS endogenously in Leydig cell-derived lines and is expressed in male but not female Müllerian duct mesenchyme. ALK6 has been shown to function as an MIS type I receptor. Investigation of the pattern of ALK2, MISRII, and ALK6 in the developing urogenital system demonstrated overlapping expression of ALK2 and MISRII in the mesenchyme surrounding the duct while ALK6 was observed only in the epithelium. Examination of ALK6 -/- male animals revealed no defect in duct regression. The reporter construct analysis, pattern of expression of the receptors, and analysis of ALK6-deficient animals suggest that ALK2 is the MIS type I receptor involved in Müllerian duct regression.

The type I BMP receptor BmprIB is essential for female reproductive function

Maintenance of female reproductive competence depends on the actions of several hormones and signaling factors. Recent reports suggest roles for bone morphogenetic proteins (BMPs) in early stages of folliculogenesis. A role for the type I BMP receptor BmprIB as a regulator of ovulation rates in sheep has been described recently, but little is known about the roles of BMP signaling pathways in other aspects of reproductive function. We report here that BMPRIB is essential for multiple aspects of female fertility. Mice deficient in BmprIB exhibit irregular estrous cycles and an impaired pseudopregnancy response. BmprIB mutants produce oocytes that can be fertilized in vitro, but defects in cumulus expansion prevent fertilization in vivo. This defect is associated with decreased levels of aromatase production in granulosa cells. Unexpectedly, levels of mRNA for cyclooxygenase 2, an enzyme required for cumulus expansion, are increased. BmprIB mutants also exhibit a failure in endometrial gland formation. The expression of BmprIB in uterine linings suggests that these defects are a direct consequence of loss of BMP signaling in this tissue. In summary, these studies demonstrate the importance of BMP signaling pathways for estrus cyclicity, estradiol biosynthesis, and cumulus cell expansion in vivo and reveal sites of action for BMP signaling pathways in reproductive tissues.

BMP3: to be or not to be a BMP

BACKGROUND

Bone morphogenetic proteins (BMPs) are osteogenic but also have diverse functions during development. BMP3 is a major component of osteogenin, which has osteogenic activity. However, recombinant BMP3 (rhBMP3) has no apparent osteogenic function, raising the possibility that BMP3 has no bone-inducing activity or that the recombinant material is not properly processed. To resolve this apparent discrepancy, we utilized a retroviral system to study the effects of BMP3 in vitro. In addition, we generated Bmp3-deficient mice to elucidate the function of BMP3 in vivo.

METHODS

Retroviral as well as mammalian expression constructs were utilized to express BMP3 and to create BMP3 conditioned medium. Alkaline phosphatase (ALP) activity and transcriptional response assays were used to monitor the ability of BMP3 to elicit either a BMP-like or a transforming growth factor beta (TGF-beta)/activin-like response in osteoblastic cell lines. Finally, mice deficient in BMP3 were generated to investigate BMP3 function in vivo.

RESULTS

BMP3 was unable to induce an osteogenic response in W-20-17, MC3T3-E1, or C3H10T1/2 cells, although all three cell lines were responsive to BMP2. However, BMP3 inhibited responsiveness to BMP2 in these assays, suggesting that BMP3 antagonizes BMP2 signaling. This inhibition did not occur through inhibition of binding of BMP2 to its receptors. BMP3 activated the TGF-beta/activin-pathway in these cells, suggesting that BMP3 exerts its inhibiting effects by activating a signaling pathway that antagonizes the BMP pathway. To examine the potential functional consequences of BMP3 action, Bmp3-/- mice, which lack BMP3, were generated. On an outbred genetic background, Bmp3-/- mice are viable and show no obvious skeletal phenotype as embryos or neonates. However, adult mice exhibit twice as much trabecular bone as do their wild-type littermates. This observation is consistent with our in vitro observations suggesting that BMP3 is an inhibitor of osteogenesis in vitro and of bone formation in vivo.

CONCLUSIONS

BMP3 is an inhibitor of osteogenic BMPs and can signal through a TGF-beta/activin pathway. The ability of BMP3 to antagonize BMP2 activity may thus be a consequence of competition for signaling components common to TGF-beta/activin and BMP pathways. BMP3, the most abundant BMP in demineralized bone, may therefore play an essential role as a modulator of the activity of osteogenic BMPs in vivo.

CLINICAL RELEVANCE

Therapies to accelerate bone healing usually utilize administration of exogenous BMP either in recombinant form or by gene therapy approaches. It is conceivable that the potency of osteogenic BMPs would be increased by inhibiting the activation of antagonistic signaling pathways or by increasing levels of rate-limiting signaling components shared by both BMP and TGF-beta/activin pathways.

The molecular control of upper extremity development: implications for congenital hand anomalies

As the molecular aspects of limb development are being unraveled, more of the congenital anomalies seen by hand surgeons in the clinical setting will have an identifiable molecular basis. The majority of the data available regarding the molecular development of the upper extremity have come from experimental animal studies, specifically the mouse and chicken. These findings are being discovered by either direct surgical and molecular manipulation of the developing limb or by production of mice deficient in specific genes. Relatively few specific human mutations that cause limb abnormalities have been identified. Hand surgeons should be aware of the basic molecular pathways controlling limb development because they are in a unique position to be able to identify patients with such deformities. In turn, detailed clinical descriptions of congenital anomalies affecting the upper extremity will advance the understanding of the cellular events controlled by the molecular pathways of limb development. This review describes the general molecular basis of limb development and correlates it with disease processes affecting the upper extremity.

Bone morphogenetic protein-3 is a negative regulator of bone density

Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-beta (TGF-beta) superfamily. Many BMPs are produced in bone and show osteogenic activity, suggesting that they may be determinants of bone mass. BMP3 was originally purified from bone as osteogenin, which induces osteogenic differentiation. Recombinant BMP3 (rhBMP3) has no biological activity, however, leaving its role in skeletal growth unclear. Here we show that BMP3 is an antagonist of osteogenic BMPs: BMP3 dorsalizes Xenopus laevis embryos, inhibits BMP2-mediated induction of Msx2 and blocks BMP2-mediated differentiation of osteoprogenitor cells into osteoblasts. These effects appear to be mediated through activin receptors. Finally, Bmp3(-/-) mice have twice as much trabecular bone as wild-type littermates, indicating that BMP3, the most abundant BMP in adult bone, is a negative determinant of bone density.

Mice lacking Bmp6 function

Bmp6, a member of the 60A subgroup of bone morphogenetic proteins (BMPs), is expressed in diverse sites in the developing mouse embryo from preimplantation stages onwards. To evaluate roles for Bmp6 signaling in vivo, gene targeting was used to generate a null mutation at the Bmp6 locus. The resulting Bmp6 mutant mice are viable and fertile, and show no overt defects in tissues known to express Bmp6 mRNA. The skeletal elements of newborn and adult mutants are indistinguishable from wild-type. However, careful examination of skeletogenesis in late gestation embryos reveals a consistent delay in ossification strictly confined to the developing sternum. In situ hybridization studies in the developing long bones and sternum show that other BMP family members are expressed in overlapping domains. In particular we find that Bmp2 and Bmp6 are coexpressed in hypertrophic cartilage, suggesting that Bmp2 may functionally compensate in Bmp6 null mice. The defects in sternum development in Bmp6 null mice are likely to be associated with a transient early expression of Bmp6 in the sternal bands, prior to ossification. These sternal defects are slightly exacerbated in Bmp5/6 double mutant animals.

The type I BMP receptor BMPRIB is required for chondrogenesis in the mouse limb

Mice carrying a targeted disruption of BmprIB were generated by homologous recombination in embryonic stem cells. BmprIB(−/−) mice are viable and, in spite of the widespread expression of BMPRIB throughout the developing skeleton, exhibit defects that are largely restricted to the appendicular skeleton. Using molecular markers, we show that the initial formation of the digital rays occurs normally in null mutants, but proliferation of prechondrogenic cells and chondrocyte differentiation in the phalangeal region are markedly reduced. Our results suggest that BMPRIB-mediated signaling is required for cell proliferation after commitment to the chondrogenic lineage. Analyses of BmprIB and Gdf5 single mutants, as well as BmprIB; Gdf5 double mutants suggests that GDF5 is a ligand for BMPRIB in vivo. BmprIB; Bmp7 double mutants were constructed in order to examine whether BMPRIB has overlapping functions with other type I BMP receptors. BmprIB; Bmp7 double mutants exhibit severe appendicular skeletal defects, suggesting that BMPRIB and BMP7 act in distinct, but overlapping pathways. These results also demonstrate that in the absence of BMPRIB, BMP7 plays an essential role in appendicular skeletal development. Therefore, rather than having a unique role, BMPRIB has broadly overlapping functions with other BMP receptors during skeletal development.

Transient production of bone morphogenetic protein 2 by allogeneic transplanted transduced cells induces bone formation

The aim of this study was to evaluate the use of transplantation of genetically modified allogeneic cells as a method to induce bone formation. In this study, we infected a murine osteoprogenitor cell line with a retroviral vector containing the human bone morphogenic protein 2 (BMP2) gene. Transduced cells exhibited more alkaline phosphatase activity than cells treated with any of the tested doses of recombinant human BMP2 protein (rhBMP2). The transduced cells were suspended in a collagen solution and injected into the quadriceps muscle in immunocompetent outbred mice. Radiographic and histological examinations demonstrate abundant ectopic bone formation in 85% of the transplanted animals (n = 13). PCR and Southern blot analysis for the puromycin resistance gene revealed that the transplanted cells were detectable for up to 1 week, but not at later time points. None of the animals developed tumors. Our results suggest that allogeneic BMP2-expressing transduced cells may have therapeutic potential for enhancing new bone formation. This model also provides a simple, inexpensive, and sensitive assay for evaluating in vivo the osteoinductive potentials of secreted proteins without the requirement of protein purification or the use of immunodeficient animals.

Mouse model of Sanfilippo syndrome type B produced by targeted disruption of the gene encoding alpha-N-acetylglucosaminidase

The Sanfilippo syndrome type B is an autosomal recessive disorder caused by mutation in the gene (NAGLU) encoding alpha-N-acetylglucosaminidase, a lysosomal enzyme required for the stepwise degradation of heparan sulfate. The most serious manifestations are profound mental retardation, intractable behavior problems, and death in the second decade. To generate a model for studies of pathophysiology and of potential therapy, we disrupted exon 6 of Naglu, the homologous mouse gene. Naglu-/- mice were healthy and fertile while young and could survive for 8-12 mo. They were totally deficient in alpha-N-acetylglucosaminidase and had massive accumulation of heparan sulfate in liver and kidney as well as secondary changes in activity of several other lysosomal enzymes in liver and brain and elevation of gangliosides G(M2) and G(M3) in brain. Vacuolation was seen in many cells, including macrophages, epithelial cells, and neurons, and became more prominent with age. Although most vacuoles contained finely granular material characteristic of glycosaminoglycan accumulation, large pleiomorphic inclusions were seen in some neurons and pericytes in the brain. Abnormal hypoactive behavior was manifested by 4.5-mo-old Naglu-/- mice in an open field test; the hyperactivity that is characteristic of affected children was not observed even in younger mice. In a Pavlovian fear conditioning test, the 4.5-mo-old mutant mice showed normal response to context, indicating intact hippocampal-dependent learning, but reduced response to a conditioning tone, perhaps attributable to hearing impairment. The phenotype of the alpha-N-acetylglucosaminidase-deficient mice is sufficiently similar to that of patients with the Sanfilippo syndrome type B to make these mice a good model for study of pathophysiology and for development of therapy.

Notch signaling imposes two distinct blocks in the differentiation of C2C12 myoblasts

Notch signal transduction regulates expression of downstream genes through the activation of the DNA-binding protein Su(H)/CBF1. In Drosophila most of Notch signaling requires Su(H); however, some Notch-dependent processes occur in the absence of Su(H) suggesting that Notch signaling does not always involve activation of this factor. Using constitutively active forms of Notch lacking CBF1-interacting sequences we identified a Notch signaling pathway that inhibits myogenic differentiation of C2C12 myoblasts in the absence of CBF1 activation. Here we show that ligand-induced Notch signaling suppresses myogenesis in C2C12 myoblasts that express a dominant negative form of CBF1, providing additional evidence for CBF1-independent Notch signal transduction. Surprisingly mutant forms of Notch deficient in CBF1 activation are unable to antagonize MyoD activity, despite the fact that they inhibit myogenesis. Moreover, Notch-induced antagonism of MyoD requires CBF1 suggesting that the CBF1-dependent pathway mediates a cell-type-specific block in the myogenic program. However, Notch signaling in the absence of CBF1 activation blocks both myogenesis and osteogenesis, indicative of a general block in cellular differentiation. Taken together our data provide evidence for two distinct Notch signaling pathways that function to block differentiation at separate steps during the process of myogenesis in C2C12 myoblasts.

Barodontalgia: a review, and the influence of simulated diving on microleakage and on the retention of full cast crowns

This paper reviews the causes of barodontalgia and reports on a study that indicates a possible cause of barodontalgia in the diver. In the study, extracted teeth had full cast crowns cemented with either a zinc phosphate, a glass ionomer, or a resin cement, and simulated diving to 30 m (3.0 atmospheres) was performed. During simulated diving, the teeth were pressure cycled 15 times to 3 atmospheres and microleakage was monitored. The force required to dislodge the crown was then tested; a significant difference was found between the zinc phosphate and the glass ionomer cement groups (p < 0.01). No difference was found between the resin cement groups. Microleakage was also detected in the zinc phosphate and glass ionomer cement groups and was found to occur sooner, and to a greater extent with zinc phosphate. No microleakage was detected in the resin cement experimental group. This study showed that the retention of full cast crowns to extracted teeth is reduced after pressure cycling and that microleakage does occur if the crowns are cemented with either zinc phosphate cement or glass ionomer cement.

The bone morphogenetic protein 15 gene is X-linked and expressed in oocytes

We have taken advantage of the sequence relationships among the bone morphogenetic proteins (BMPs) to identify the mouse Bmp15 and human BMP15 genes. The 392-amino acid prepropeptides encoded by these BMP genes exhibit significant homology to each other, although the 70% identity observed between the 125-amino acid mature peptides is considerably lower than that seen in comparisons of other mouse and human orthologs. Both genes share a common structural organization and encode mature peptides that lack the cysteine residue normally involved in the formation of a covalent dimer. In addition, mouse Bmp15 and human BMP15 map to conserved syntenic regions on the X chromosome. We demonstrate, through a combination of Northern blot and in situ hybridization analyses, that mouse Bmp15 is expressed specifically in the oocyte beginning at the one-layer primary follicle stage and continuing through ovulation. Interestingly, BMP-15 is most closely related to and shares a coincident expression pattern with the mouse growth/differentiation factor 9 (GDF-9) gene that is essential for female fertility. Our findings will be important for defining the role of BMP-15 in follicular development.

The effect of environmental pressure changes during diving on the retentive strength of different luting agents for full cast crowns

STATEMENT OF PROBLEM

The effect of pressure cycling on the bond strength of cement luting agents is largely unknown.

PURPOSE

This study investigated the effect of pressure cycling on the retention of full cast crowns to extracted teeth.

MATERIAL AND METHODS

Sixty extracted single-rooted premolar teeth had full cast crowns cemented, 20 with a zinc phosphate cement, 20 with a glass ionomer, and 20 with a resin cement. After 7 days of storage, each of the teeth in the experimental groups was pressure cycled 15 times from 0 to 3 atmospheres (304 KPa), after which the force required to dislodge the crowns was tested in an Instron testing machine.

RESULTS

A significant difference was found (Students t test; p > 0.01) between the force required to remove the crowns in the zinc phosphate control (142.10 +/- 36.42 N) and experimental (15.93 +/- 11.13 N) groups and the glass ionomer cemented control (186.33 +/- 24.33 N) and experimental (91.50 +/- 33.07 N) groups; no difference was found between the resin cemented control (291.15 +/- 78.48 N) and experimental (281.32 +/- 85.43 N) groups.

CONCLUSION

This study showed that the retention of full cast crowns to extracted teeth is reduced after pressure cycling if the crowns are cemented with either zinc phosphate cement or glass ionomer cement. Dentists should consider using a resin cement when cementing crowns and fixed partial dentures for patients, such as divers, who are likely to be exposed to pressure cycling.

Use of a pressure chamber to compare microleakage of three luting agents

A pressure chamber was used to compare microleakage associated with complete metal crowns cemented to extracted teeth using three different luting agents. Complete crowns were cemented on 60 extracted premolar teeth: 20 were cemented using a zinc phosphate cement, 20 using a glass-ionomer cement, and 20 using a resin cement. Following 7 days of storage in normal saline, each of the teeth in the experimental groups was pressure cycled 15 times, during which time the occurrence of microleakage was monitored. Microleakage was found to occur in crowns cemented with the zinc phosphate and glass-ionomer cements; no microleakage was detected with the resin-cemented crowns. Microleakage was also found to occur sooner and to a greater extent with zinc phosphate than with glass-ionomer cement.

Bone morphogenetic protein-2: biology and applications

Bone morphogenetic protein-2 is a low molecular weight glycoprotein, classified as a morphogen. The sine qua non of bone morphogenetic protein is consistently reproducible induction of bone development in heterotopic sites. Bone morphogenetic proteins belong to the expanding transforming growth factor-beta superfamily. Bone morphogenetic protein-2 has pleiotropic functions that range from extraskeletal and skeletal organogenesis to bone generation and regeneration. Bone morphogenetic protein induced bone formation in postfetal life recapitulates the process of embryonic and endochondral ossification. Through recombinant gene technology, human bone morphogenetic protein-2 is available in almost unlimited amounts for basic research and clinical trials. Human bone morphogenetic protein-2 induces structurally sound orthotopic bone in a variety of experimental systems, including femoral defects in rats, tibial and ulnar defects in rabbits, femoral defects in sheep, mandibular defects in dogs, spinal fusion in dogs, and porous ingrowth in rats. Human bone morphogenetic protein-2 research extends to the fields of developmental biology, genetics, and evolution. Bone morphogenetic protein has been used successfully at the authors' institution to heal clinical nonunions and to achieve spinal fusion. This report reviews the current understanding of bone morphogenetic proteins in general and BMP-2 in particular and summarizes their potential applications.

A requirement for bone morphogenetic protein-7 during development of the mammalian kidney and eye

BMP-7/OP-1, a member of the transforming growth factor-beta (TGF-beta) family of secreted growth factors, is expressed during mouse embryogenesis in a pattern suggesting potential roles in a variety of inductive tissue interactions. The present study demonstrates that mice lacking BMP-7 display severe defects confined to the developing kidney and eye. Surprisingly, the early inductive tissue interactions responsible for establishing both organs appear largely unaffected. However, the absence of BMP-7 disrupts the subsequent cellular interactions required for their continued growth and development. Consequently, homozygous mutant animals exhibit renal dysplasia and anophthalmia at birth. Overall, these findings identify BMP-7 as an essential signaling molecule during mammalian kidney and eye development.

Colocalization of BMP 7 and BMP 2 RNAs suggests that these factors cooperatively mediate tissue interactions during murine development

Members of the bone morphogenetic protein (BMP) class of transforming growth factor beta (TGF beta)-related molecules have been implicated in a variety of inductive processes throughout vertebrate development. The 60A subclass of BMPs contains at least four vertebrate members, BMPs 5-8. We have shown by library screening and in situ hybridization that of these four genes, BMP 7 is expressed earliest, in gastrulating embryos. Furthermore, BMP 7 transcripts are present at diverse sites throughout development, in a pattern consistent with a role in a variety of inductive interactions. Recent studies have shown that BMP 2/7 heterodimers have unique activities compared to the corresponding homodimers. For this reason, we compared the patterns of expression of BMP 2 and BMP 7 using in situ hybridization. Our results demonstrate that these BMPs are coexpressed in a number of tissues that are known to be the source of inductive signals, including the zone of polarizing activity and apical ectodermal ridge of the developing limb and the notochord, raising the possibility that BMP 2/7 heterodimers may mediate aspects of these tissue interactions. We also show that BMP 2 transcripts are restricted within the developing gut to dorsal endoderm, whereas sonic hedgehog has been localized to ventral and medial regions of the developing gut endoderm. These markers provide the first molecular evidence for dorsal/ventral polarity in the developing gut.

A mammalian serine/threonine kinase receptor specifically binds BMP-2 and BMP-4

Bone morphogenetic proteins (BMPs) are a class of related growth and differentiation factors within the TGF-beta superfamily of proteins which are known to induce cartilage and bone formation in adult animals and to be involved in many inductive events throughout embryonic development. Here we describe the molecular cloning and characterization of a mammalian receptor, CFK-43a, which specifically binds BMP-2 and BMP-4. This molecule is a member of the serine/threonine kinase receptor family which includes receptors for other TGF-beta superfamily members. CFK-43a binds other BMP family members with lower affinity, but does not bind TGF-beta. During embryogenesis, in situ hybridization analysis indicates that CFK-43a mRNA is localized in developing skeletal tissues in a complementary fashion to the transcripts for its ligands.

A primary requirement for nodal in the formation and maintenance of the primitive streak in the mouse

The 413.d insertional mutation arrests mouse development shortly after gastrulation. nodal, a novel TGF beta-related gene, is closely associated with the locus. The present study provides direct evidence that the proviral insertion causes a loss of function mutation. nodal RNA is initially detected at day 5.5 in the primitive ectoderm. Concomitant with gastrulation, expression becomes restricted to the proximal posterior regions of the embryonic ectoderm. nodal RNA is also expressed in the primitive endoderm overlying the primitive streak. A few hours later, expression is strictly confined to the periphery of the mature node. Interestingly 413.d mutant embryos show no morphological evidence for the formation of a primitive streak. Nonetheless, about 25% of mutant embryos do form randomly positioned patches of cells of a posterior mesodermal character. Data presented in this report demonstrate the involvement of a TGF beta-related molecule in axis formation in mammals.

The structure and evolution of the human salivary proline-rich protein gene family

We present the nucleotide sequences of four members of the six-member human salivary proline-rich protein (PRP) gene family. The four genes are PRB1 and PRB2, which encode basic PRPs, and PRB3 and PRB4, which encode glycosylated PRPs. Each PRB gene is approximately 4.0 kb in length and contains four exons, the third of which is entirely composed of 63-bp tandem repeats and encodes the proline-rich portion of the protein products. Exon 3 contains different numbers of tandem repeats in the different PRB genes. Variation in the numbers of these repeats is also responsible for length variations in different alleles of the PRB genes. We have determined a probable evolutionary history of the human PRP gene family by comparing the nucleotide sequences of the six PRP genes. The present-day six PRP loci probably evolved from a single ancestral gene by four sequential gene duplications, leading to six genes that fall into three subsets, each consisting of two genes. During this evolutionary process, multiple rearrangements and gene conversion occurred mainly in the region from the 3' end of IVS2 and the 3' end of exon 3.

DVR-4 (bone morphogenetic protein-4) as a posterior-ventralizing factor in Xenopus mesoderm induction

Establishment of mesodermal tissues in the amphibian body involves a series of inductive interactions probably elicited by a variety of peptide growth factors. Results reported here suggest that mesodermal patterning involves an array of signalling molecules including DVR-4, a TGF-beta-like molecule. We show that ectopic expression of DVR-4 causes embryos to develop with an overall posterior and/or ventral character, and that DVR-4 induces ventral types of mesoderm in animal cap explants. Moreover, DVR-4 overrides the dorsalizing effects of activin. DVR-4 is therefore the first molecule reported both to induce posteroventral mesoderm and to counteract dorsalizing signals such as activin. Possible interactions between these molecules resulting in establishment of the embryonic body plan are discussed.

The DVR gene family in embryonic development

The DVR gene family consists of at least 15 members, including decapentaplegic from Drosophila, Xenopus Vg1 and the mammalian bone morphogenetic protein genes, encoding secreted proteins closely related to transforming growth factor beta Genetic and biochemical evidence supports the idea that DVR proteins form part of a cascade of extracellular signalling molecules mediating inductive tissue interactions during development.

Technique for three-dimensional measurements of the time development of turbulent flames

A three-dimensional imaging technique has been developed that permits the investigation of the time development of a scalar in turbulent reacting flows. An aerosol-seeded premixed flame was illuminated by four closely spaced parallel laser sheets of different wavelength. Lorenz-Mie scattering from the four illumination sheets was imaged onto an intensified two-dimensional charge-coupled-device array. Bandpass filters and a multi-image optical component in the collection optics allowed individual sheets to be imaged onto different areas of the charge-coupled-device array. A double-pulsed Nd:YAG laser was used in conjunction with a rotating mirror in the collection optics to enable instantaneous three-dimensional images to be obtained at two times separated by 100 micros.