Developing students' clinical reasoning skills: correlates of perceived relevance of two teaching and learning approaches.

INTRODUCTION: 'Relevance' is a key concept in adult learning. Hence, this study sought to examine students' perceptions of relevance of the teaching and learning in relation to different instructional designs employed in a Comprehensive Patient Care (CPC) course that aims to develop integrated clinical reasoning skills. METHODS: Third to fifth year students (2009-2011) were asked to anonymously rate the relevance of the instructional design (RELID) they participated in by means of visual analogue scales at the School of Dentistry, University of Pretoria. They were also asked to rate their perceptions of the alignment between teaching and learning and outcomes (ATLO), assessments' contribution to learning (ACL), course organisation (CO) and teacher competence (TC). RELID served as the outcome measure in stepwise linear regression analyses. ATLO, ACL, CO, TC and the instructional design (case-based learning (CBL = 1) and the combination of discipline-based and lecture-based teaching in CPC (DB-LBT = 0)) served as the co-variables for each of the years of study. RESULTS: The analyses showed positive correlations between RELID and ATLO and between RELID and ACL for all the years of study. RELID was associated with TC in year three and four and CO was associated with RELID in year four and five. CBL outperformed DB-LBT in terms of perceived relevance of the teaching and learning. CONCLUSION: The results suggest that students' perceptions of the relevance of the instructional design may be enhanced when outcomes, teaching, learning and assessment are constructively aligned during the development of clinical reasoning skills.

Socio-demographic and academic correlates of clinical reasoning in a dental school in South Africa.

INTRODUCTION: There are no empirical studies that describe factors that may influence the development of integrated clinical reasoning skills in dental education. Hence, this study examines the association between outcomes of clinical reasoning in relation with differences in instructional design and student factors. MATERIALS AND METHODS: Progress test scores, including diagnostic and treatment planning scores, of fourth and fifth year dental students (2009-2011) at the University of Pretoria, South Africa served as the outcome measures in stepwise linear regression analyses. These scores were correlated with the instructional design (lecture-based teaching and learning (LBTL = 0) or case-based teaching and learning (CBTL = 1), students' grades in Oral Biology, indicators of socio-economic status (SES) and gender. RESULTS: CBTL showed an independent association with progress test scores. Oral Biology scores correlated with diagnostic component scores. Diagnostic component scores correlated with treatment planning scores in the fourth year of study but not in the fifth year of study. 'SES' correlated with progress test scores in year five only, while gender showed no correlation. CONCLUSION: The empirical evidence gathered in this study provides support for scaffolded inductive teaching and learning methods to develop clinical reasoning skills. Knowledge in Oral Biology and reading skills may be important attributes to develop to ensure that students are able to reason accurately in a clinical setting.

Students' perceptions of vertical and horizontal integration in a discipline-based dental school.

INTRODUCTION: Integration is a key concern in discipline-based undergraduate dental curricula. Therefore, this study compared feedback on integration from students who participated in different instructional designs in a Comprehensive Patient Care course. METHODS: The study was conducted at the University of Pretoria (2009-2011). Third-year cohorts (Cohorts A, B and C) participated in pre-clinical case-based learning, whilst fourth-year cohorts (Cohorts D and E) received didactic teaching in Comprehensive Patient Care. Cohorts A, D and E practised clinical Comprehensive Patient Care in a discipline-based clinic. Cohort B conducted their Comprehensive Patient Care patient examinations in a dedicated facility supervised by dedicated faculty responsible to teach integration. Students had to indicate on visual analogue scales whether the way they were taught at the school helped them to integrate knowledge from the same (horizontal integration) and preceding (vertical integration) year of study. The end-points of the scales were defined as 'definitely' and 'not at all'. Analysis of variance (ANOVA) was employed to measure the differences between cohorts according to the year of study. RESULTS: Third-year case-based learning cohorts rated the horizontal integration close to 80/100 and vertical integration ranging from 64 to 71/100. In year four, Cohort B rated vertical and horizontal integration 9-15% higher (ANOVA, P < 0.05) than Cohorts A and D. In year five, Cohort A rated vertical and horizontal integration 11-18% higher (ANOVA, P < 0.05) than Cohorts D and E. CONCLUSION: Pre-clinical case-based learning and Comprehensive Patient Care supervised by dedicated faculty were associated with more favourable perceptions about integration in the discipline-based undergraduate dental curriculum.

Developing integrated clinical reasoning competencies in dental students using scaffolded case-based learning - empirical evidence.

INTRODUCTION: This study provides empirical evidence of the development of integrated clinical reasoning in the discipline-based School of Dentistry, University of Pretoria, South Africa. Students were exposed to case-based learning in comprehensive patient care (CPC) in the preclinical year of study, scaffolded by means of the four-component instructional design model for complex learning. METHODS: Progress test scores of third- to fifth-year dental students, who received case-based teaching and learning in the third year (2009-2011), were compared to the scores of preceding fourth- and fifth-year cohorts. These fourth- and fifth-year cohorts received content-based teaching concurrently with their clinical training in CPC. The progress test consisted of a complex case study and 32 MCQs on tracer conditions. Students had to gather the necessary information and had to make diagnostic and treatment-planning decisions. RESULTS: Preclinical students who participated in the case-based teaching and learning achieved similar scores compared to final-year students who received lecture-based teaching and learning. Final-year students who participated in the case-based learning made three more correct clinical decisions per student, compared to those who received content-based teaching. Students struggled more with treatment-planning than with diagnostic decisions. CONCLUSION: The scaffolded case-based learning appears to contribute to accurate clinical decisions when compared to lecture-based teaching. It is suggested that the development of integrated reasoning competencies starts as early as possible in a dental curriculum, perhaps even in the preclinical year of study. Treatment-planning should receive particular attention.

Developing clinical reasoning in the classroom - analysis of the 4C/ID-model.

OBJECTIVES: The purpose of this study is to provide a theoretical rationale for the implementation of the four-component instructional design model for complex learning (4C/ID-model) at the University of Pretoria with the aim of systematically developing the clinical reasoning of undergraduate dental students in a classroom setting. METHODS: Recent literature provides a rationale for the use of the 4C/ID-model to teach clinical reasoning in terms of four strategic teaching and learning needs: (i) the need for authenticity in the learning process; (ii) the need to manage cognitive load during the learning process; (iii) the need for repeated practice; (iv) a need for valid assessment, feedback and reflection. RESULTS AND DISCUSSION: The literature review indicated that the 4C/ID-model makes provision for teaching and learning in an authentic context and proposes systematically structured methods that could be practically applied to manage cognitive load during repetitive exercises. The model also makes provision for cognitive feedback following assessment in order to eliminate misconceptions about content and to develop the cognitive strategies of the learner. CONCLUSIONS: On the basis of the literature review above, it is recommended that the 4C/ID-model be considered as a basis for classroom teaching and learning to develop competence in clinical reasoning in undergraduate dental students, even at pre-clinical level. The model may also have an application in medical education.

Familial dyserythropoietic anaemia and thrombocytopenia due to an inherited mutation in GATA1.

Haematopoietic development is regulated by nuclear protein complexes that coordinate lineage-specific patterns of gene expression. Targeted mutagenesis in embryonic stem cells and mice has revealed roles for the X-linked gene Gata1 in erythrocyte and megakaryocyte differentiation. GATA-1 is the founding member of a family of DNA-binding proteins that recognize the motif WGATAR through a conserved multifunctional domain consisting of two C4-type zinc fingers. Here we describe a family with X-linked dyserythropoietic anaemia and thrombocytopenia due to a substitution of methionine for valine at amino acid 205 of GATA-1. This highly conserved valine is necessary for interaction of the amino-terminal zinc finger of GATA-1 with its essential cofactor, FOG-1 (for friend of GATA-1; refs 9-12). We show that the V205M mutation abrogates the interaction between Gata-1 and Fog-1, inhibiting the ability of Gata-1 to rescue erythroid differentiation in an erythroid cell line deficient for Gata-1 (G1E). Our findings underscore the importance of FOG-1:Gata-1 associations in both megakaryocyte and erythroid development, and suggest that other X-linked anaemias or thrombocytopenias may be caused by defects in GATA1.

Successful rehabilitation and release of a powerful owl chick with suspected rodenticide poisoning.

The successful rehabilitation and release of raptor chicks can be challenging, especially when the chicks are still in the post-fledging dependency period. Here, we report on a recently fledged powerful owl chick that was held in care for 33 days before being successfully reunited with its parents. We document the steps undertaken during the entire process from collection from the wild to post-release monitoring and recommend clinical procedures for treatment of raptors entering veterinary facilities. Success of this rehabilitation was facilitated by early care and treatment for potential rodenticide poisoning, as well as the integration of citizen scientists monitoring the family unit in the field while the chick was in care and during the post-release period. Given the emerging evidence of widespread rodenticide poisoning in raptors both in Australia and globally, it is critical to suspect all raptors may have been exposed to anticoagulant rodenticides and commence treatment with vitamin K immediately. Routine treatment for rodenticides early increases the probability of successful recovery post-trauma as well as reducing the time in treatment as much as possible.

Novel mutations in the HPS1 gene among Puerto Rican patients.

Hermansky-Pudlak syndrome (HPS) is a disorder of oculocutaneous albinism (OCA) and platelet storage pool deficiency. Eight different disease-causing genes have been identified, whose gene products are thought to be involved in the biogenesis of lysosome-related organelles. HPS type 1 (HPS-1) is the most common HPS subtype in Puerto Rico, with a frequency of 1:1800 in the northwest of the island due to a founder mutation, i.e. a 16-bp duplication in exon 15 of the HPS1 gene (c.1472_1487dup16; p.H497QfsX90). We identified three Puerto Rican HPS-1 patients who carried compound heterozygous HPS1 mutations. One patient was heterozygous for c.937G>A, causing a missense mutation (p.G313S) at the 3 splice junction of exon 10. This mutation resulted in activation of a cryptic intronic splice site causing an aberrantly spliced HPS1 mRNA that included 144-bp of intronic sequence, producing 11 novel amino acids followed by a stop codon. The other two patients were heterozygous for the previously reported c.972delC in HPS1, resulting in a frameshift and a premature stop codon (p.M325WfsX6). These findings indicate that, among Puerto Ricans, other HPS1 mutations apart from the 16-bp duplication should be considered in the analysis of this population.

An analysis of complaints against oral health professionals charged with misconduct at the HPCSA: 2004-2009.

AIM: This study investigates the nature, frequency, and outcome of complaints relating to misconduct laid against oral healthcare professionals (OHPs), charged with misconduct in South Africa. METHODS: Records of the Health Professions Council of South Africa (2004-2009) were analysed and classified using the ethical rules as a reference. "Clinically-related complaints" and "fraud" were added as extra categories. The nature and outcome of the complaints and the penalties were quantified, and the detailed nature of the complaints was qualitatively reported. RESULTS: Two percent of the registered dentists and 5.5% of the registered dental therapists were charged with misconduct. Clinically related complaints (59%) and fraud (29%) were most prevalent amongst the accused dentists. Fraud (46%), clinically related complaints (19%), advertising (15%), infection control (8%), and creating expectations that could not be met (8%) were the most common complaints against dental therapists. CONCLUSIONS: Substandard dental treatment and fraud were the main reasons for patient dissatisfaction that led to OHPs being charged with misconduct. Both these undesirable practices may be financially motivated. OHPs should take cognisance of these statistics and should adjust their professional approach accordingly in order to reflect acceptable ethical behaviour.

Gels of normal and sickled hemoglobin: comparative study.

Electron microscopic studies of the sickling phenomenon have described at least three different structural arrangements of sickled hemoglobin, including empty hexagonal crystals, microtubules, and solid rods. It is unlikely that sickling results in several different polymers, and it is essential to determine the true structure of sickled hemoglobin in order to define the mechanism of molecular assembly. The present study has explored the fine structure of gels formed in cell-free solutions of normal and sickle reduced and oxyhemoglobin. Gels of reduced sickled hemoglobin consisted entirely of solid rods. The gels formed from sickle oxyhemoglobin, normal oxyhemoglobin, and normal reduced hemoglobin contained masses of hollow polymers essentially identical in appearance with microtubules. These findings indicate that solid rods are the characteristic polymers of sickled hemoglobin and tubular polymers represent aberrant structures which are not related to erythrocyte sickling.

Indirect visualization of Staphylococcus aureus protein A.

Specific but nonimmunologic reaction between staphylococcal protein A and the Fc portion of gamma globulin provided the basis for ultrastructural studies to determine the localization of protein A, using intact staphylococci and labeled myeloma gamma G-globulin. Protein A appeared to be part of the outermost layer of the staphylococcal cell wall. Strains with protein A demonstrated a coating of myeloma globulin over the entire bacterial surface. There was no coating of strains without protein A. Identification of protein A on the surface of the staphylococcal cell wall provides evidence that this may be the first material in contact with host environment. It probably accounts for apparent cross-reactions of staphylococci with antibodies to many antigens. More importantly, even in the nonimmune host protein A immunoglobulin reactivity may initiate complement activation and inflammatory reactions including chemotaxis and pus formation.

The secretory mechanisms in equine platelets are independent of cytoskeletal polymerization and occur through membrane fusion.

Studies in animal models are useful to understand the basic mechanisms involved in hemostasis and the functional differences among species. Ultrastructural observations led us to predict differences in the activation and secretion mechanisms between equine and human platelets. The potential mechanisms involved have been comparatively explored in the present study. Equine and human platelets were activated with thrombin (0.5 U/ml) and collagen (20 µg/ml), for 90 seconds, and samples processed to evaluate: i) ultrastructural changes, by electron microscopy, ii) actin polymerization and cytoskeletal assembly, by polyacrylamide gel electrophoresis, and iii) specific molecules involved in activation and secretion, by western blot. In activated human platelets, centralization of granules, cytoskeletal assembly and fusion of granules with the open canalicular system were observed. In activated equine platelets, granules fused together forming an organelle chain that fused with the surface membrane and released its content directly outside the platelets. Human platelets responded to activation with actin polymerization and the assembly of other contractile proteins to the cytoskeleton. These events were almost undetectable in equine platelets. When exploring the involvement of the synaptosomal-associated protein-23 (SNAP-23), a known regulator of secretory granule/plasma membrane fusion events, it was present in both human and equine platelets. SNAP-23 was shown to be more activated in equine platelets than human platelets in response to activation, especially with collagen. Thus, there are significant differences in the secretion mechanisms between human and equine platelets. While in human platelets, activation and secretion of granules depend on mechanisms of internal contraction and membrane fusion, in equine platelets the fusion mechanisms seem to be predominant.

Clinical and cellular characterisation of Hermansky-Pudlak syndrome type 6.

BACKGROUND: In the last decade, Hermansky-Pudlak syndrome (HPS) has arisen as an instructive disorder for cell biologists to study the biogenesis of lysosome related organelles (LROs). Of the eight human HPS subtypes, only subtypes 1 through 5 are well described. AIM: To characterise extensively the HPS-6 subtype, caused by defects in HPS6, a subunit of the biogenesis of lysosome related organelles complex-2 (BLOC-2). METHODS: Mutation analysis for the HPS6 gene was performed on DNA from our group of unclassified HPS patients. The clinical phenotype of patients with HPS6 mutations was then carefully ascertained, and their cultured dermal melanocytes were employed for cellular immunofluorescence studies. RESULTS: Molecular studies showed a variety of mutations in the single exon HPS6 gene, including frame shift, missense, and nonsense mutations as well as a approximately 20 kb deletion spanning the entire HPS6 genomic region. Cellular studies revealed that the melanogenic proteins tyrosinase and tyrosinase related protein 1 failed to be efficiently delivered to the melanosomes of HPS-6 patients, explaining their hypopigmentation. Clinical studies indicated that HPS-6 patients exhibit oculocutaneous albinism and a bleeding diathesis. Importantly, granulomatous colitis and pulmonary fibrosis, debilitating features present in HPS subtypes 1 and 4, were not detected in our HPS-6 patients. CONCLUSION: The HPS-6 subtype resembles other BLOC-2 defective subtypes (that is, HPS-3 and HPS-5) in its molecular, cellular and clinical findings. These findings are not only important for providing a prognosis to newly diagnosed HPS-6 patients, but also for further elucidation of HPS function in the biogenesis of LROs.

Strategy for teaching communication skills in dentistry.

AIM: To develop and evaluate a teaching strategy for teaching communication skills in dentistry. METHODOLOGY: Phase I: Development and implementation of a course in communication skills. Phase II: Implementation of a teaching strategy by means of an experiential learning strategy complemented by a didactic teaching strategy. SUBJECTS: Third year dental students (n = 67). The instruments included the following: (i) Study guide; (ii) Case study; (iii) Assessment rubric; (iv) Two questionnaires: "Patient's and "Dentist's feedback; (v) Standardised patient. RESULTS: The class as a whole scored significantly higher after training compared to before training (p < 0.0001). Both male and female students rated the value, appropriateness and effectiveness of the teaching strategy employed during the study, rather highly (4.18 and 4.26 on a five-point Likert scale, respectively). CONCLUSION: The teaching strategy employed for teaching third year dental students communication skills, proved to be effective and was perceived by the students as a valuable and appropriate strategy.

Cortical and cytoplasmic flow polarity in early embryonic cells of Caenorhabditis elegans.

We have examined the cortex of Caenorhabditis elegans eggs during pseudocleavage (PC), a period of the first cell cycle which is important for the generation of asymmetry at first cleavage (Strome, S. 1989. Int. Rev. Cytol. 114: 81-123). We have found that directed, actin dependent, cytoplasmic, and cortical flow occurs during this period coincident with a rearrangement of the cortical actin cytoskeleton (Strome, S. 1986. J. Cell Biol. 103: 2241-2252). The flow velocity (4-7 microns/min) is similar to previously determined particle movements driven by cortical actin flows in motile cells. We show that directed flows occur in one of the daughters of the first division that itself divides asymmetrically, but not in its sister that divides symmetrically. The cortical and cytoplasmic events of PC can be mimicked in other cells during cytokinesis by displacing the mitotic apparatus with the microtubule polymerization inhibitor nocodazole. In all cases, the polarity of the resulting cortical and cytoplasmic flows correlates with the position of the attenuated mitotic spindle formed. These cortical flows are also accompanied by a change in the distribution of the cortical actin network. The polarity of this redistribution is similarly correlated with the location of the attenuated spindle. These observations suggest a mechanism for generating polarized flows of cytoplasmic and cortical material during embryonic cleavages. We present a model for the events of PC and suggest how the poles of the mitotic spindle mediate the formation of the contractile ring during cytokinesis in C. elegans.

Determination of cell division axes in the early embryogenesis of Caenorhabditis elegans.

The establishment of cell division axes was examined in the early embryonic divisions of Caenorhabditis elegans. It has been shown previously that there are two different patterns of cleavage during early embryogenesis. In one set of cells, which undergo predominantly determinative divisions, the division axes are established successively in the same orientation, while division axes in the other set, which divide mainly proliferatively, have an orthogonal pattern of division. We have investigated the establishment of these axes by following the movement of the centrosomes. Centrosome separation follows a reproducible pattern in all cells, and this pattern by itself results in an orthogonal pattern of cleavage. In those cells that divide on the same axis, there is an additional directed rotation of pairs of centrosomes together with the nucleus through well-defined angles. Intact microtubules are required for rotation; rotation is prevented by inhibitors of polymerization and depolymerization of microtubules. We have examined the distribution of microtubules in fixed embryos during rotation. From these and other data we infer that microtubules running from the centrosome to the cortex have a central role in aligning the centrosome-nuclear complex.

An evaluation of confocal versus conventional imaging of biological structures by fluorescence light microscopy.

Scanning confocal microscopes offer improved rejection of out-of-focus noise and greater resolution than conventional imaging. In such a microscope, the imaging and condenser lenses are identical and confocal. These two lenses are replaced by a single lens when epi-illumination is used, making confocal imaging particularly applicable to incident light microscopy. We describe the results we have obtained with a confocal system in which scanning is performed by moving the light beam, rather than the stage. This system is considerably faster than the scanned stage microscope and is easy to use. We have found that confocal imaging gives greatly enhanced images of biological structures viewed with epifluorescence. The improvements are such that it is possible to optically section thick specimens with little degradation in the image quality of interior sections.

Ultrastructure of clots during isometric contraction.

We explored the retraction or contraction of platelet-fibrin clots under isometric conditions. In the presence of micromolar calcium clots of normal platelet-rich plasma developed tension at an initial rate of 0.1 to 0.2 g/min per cm2 (initial cross-sectional area). Electron microscopy of clots fixed after attaining a force of 1.6 g/cm2 revealed platelets with elongated bodies and pseudopods in close apposition to fibrin strands which were oriented in cablelike fashion in the direction of tension. The development of tension could not be explained simply on the basis of platelet-platelet association and interaction alone. First, factor XIII-dependent cross-linking of fibrin fibers was critical to normal isometric contraction. Second, tension decreased linearly, rather than exponentially, when the platelet count in the platelet-fibrin clot was decreased, suggesting that platelets must be interacting with another component (i.e. fibrin). Thrombasthenic platelets, deficient in fibrinogen receptors, failed to develop tension or to align fibrin strands or pseudopods in the clot. Platelet-fibrin clots treated with vincristine to disassemble microtubules or cytochalasin B to disrupt microfilaments failed to develop tension and relaxed if these agents were added after tension had developed. Relaxation under these conditions, however, was not associated with loss of orientation of fibrin strands. Our findings suggest that platelet-fibrin interaction in clots under isometric conditions leads to orientation of fibrin strands and platelets in the direction of force generation. Tension develops as platelets simultaneously attach to and spread along fibrin strands, and contract. The contraction draws some fibrin into platelet-fibrin clumps and aligns other strands in the long axis of tension. The achievement and maintenance of maximum tension appears to depend on the development of platelet-fibrin attachments and extension of platelet bodies and long pseudopods containing bundles of microfilaments and microtubules along the oriented fibrin fibers.

Recycling of platelet phosphorylation and cytoskeletal assembly.

The shape change and aggregation of washed platelets induced by 10 microM arachidonic acid (AA) can be reversed by 20 ng/ml prostacyclin (PGI2), but these platelets can be reactivated by treatment with 30 microM epinephrine and subsequent addition of 10 microM AA mixture. These events may be modulated by cAMP since 2 mM dibutyryl cAMP also reversed activation without reactivation by epinephrine and AA. We examined protein phosphorylation and formation of cytoskeletal cores resistant to 1% Triton X-100 extraction of these platelets and correlated these processes with aggregation, fibrinogen binding, and changes in ultrastructure. Unactivated platelet cores contained less than 15% of the total actin and no detectable myosin or actin-binding protein. AA-induced cytoskeletal cores, which contained 60-80% of the total actin, myosin, and actin-binding protein as the major components, were disassembled back to unactivated levels by PGI2 and then fully reassembled by epinephrine and AA. Phosphorylation of myosin light chain and a 40,000-dalton protein triggered by AA (two- to fivefold) was reversed to basal levels by PGI2 but was completely restored to peak levels upon addition of the epinephrine and AA mixture. The reversibility of actin-binding protein phosphorylation could not be established clearly because both PGI2 and dibutyryl cAMP caused its phosphorylation independent of activation. With this possible exception, cytoskeletal assembly with associated protein phosphorylation, aggregation, fibrinogen binding, and changes in ultrastructure triggered by activation are readily and concertedly recyclable.

Reconstitution of cytokeratin filaments in vitro: further evidence for the role of nonhelical peptides in filament assembly.

The in vitro renaturation and assembly of cytokeratin molecules to form intermediate filaments (IF) illustrates that these molecules contain all of the structural information necessary for IF information. These molecules contain nine structural domains: the amino- and carboxyterminal extra helical regions, and three conserved extra helical segments that separate four helical rod-like domains. Chymotrypsin treatment of these molecules removes the end-peptide domains and inhibits the self-assembly process. We have examined the renaturation and assembly of cytokeratin molecules using solution conditions that favor the presence of intermediate forms of IF organization. Dialysis against low salt buffers revealed the presence of bead-like chains of filaments in which the 6-8-nm beads are separated by a distance of 21 nm. These data suggest that a lateral stagger of protofilaments was among the primary events in IF assembly. Chymotrypsin-modified cytokeratin enriched for alpha-helix barely initiated a turbidity increase at conditions favoring self-assembly. Addition of small amounts of intact cytokeratin accelerated the rate and extent of this reaction. These results indicate that the nonhelical peptides on intact cytokeratin potentiate the assembly of IF by orientating the stagger of laterally associated protofilaments.