Perspectives of Patients and Professionals on Information and Education After Myocardial Infarction With Insight for Mixed Reality Implementation: Cross-Sectional Interview Study.

BACKGROUND: Patient education is crucial in the secondary prevention of cardiovascular disease. Novel technologies such as augmented reality or mixed reality expand the possibilities for providing visual support in this process. Mixed reality creates interactive digital three-dimensional (3D) projections overlaying virtual objects on the real-world environment. While augmented reality only overlays objects, mixed reality not just overlays but anchors virtual objects to the real world. However, research on this technology in the patient domain is scarce. OBJECTIVE: The aim of this study was to understand how patients perceive information provided after myocardial infarction and examine if mixed reality can be supportive in this process. METHODS: In total, 12 patients that experienced myocardial infarction and 6 health care professionals were enrolled in the study. Clinical, demographic, and qualitative data were obtained through semistructured interviews, with a main focus on patient experiences within the hospital and the knowledge they gained about their disease. These data were then used to map a susceptible timeframe to identify how mixed reality can contribute to patient information and education. RESULTS: Knowledge transfer after myocardial infarction was perceived by patients as too extensive, not personal, and inconsistent. Notably, knowledge on anatomy and medication was minimal and was not recognized as crucial by patients, whereas professionals stated the opposite. Patient journey analysis indicated the following four critical phases of knowledge transfer: at hospital discharge, at the first outpatient visit, during rehabilitation, and during all follow-up outpatient visits. Important patient goals were understanding the event in relation to daily life and its implications on resuming daily life. During follow-up, understanding physical limitations and coping with the condition and medication side effects in daily life emerged as the most important patient goals. The professionals' goals were to improve recovery, enhance medication adherence, and offer coping support. CONCLUSIONS: There is a remarkable difference between patients' and professionals' goals regarding information and education after myocardial infarction. Mixed reality may be a practical tool to unite perspectives of patients and professionals on the disease in a more even manner, and thus optimize knowledge transfer after myocardial infarction. Improving medication knowledge seems to be a feasible target for mixed reality. However, further research is needed to create durable methods for education on medication through mixed reality interventions.

Postpartum hypertensive disorders in the Emergency Department - A retrospective review of local practice in Calgary, Alberta.

Hypertensive disorders of pregnancy (HDP) commonly occur postpartum and are associated with preventable maternal morbidity and mortality. HDP is the most common reason for presentation to the Emergency Department (ED) after delivery. However, given the broad range of non-specific symptoms, recognition and management of postpartum HDP may be delayed leading to serious adverse clinical outcomes. OBJECTIVES: To describe: (1) the clinical presentation; (2) ED physician's diagnosis; and (3) current ED management of women with HDP in Calgary ED's. METHODS: A retrospective review of postpartum women (within 42 days of delivery) attending three Calgary EDs between 2011 and 2012 was performed. Administrative data was used to randomly select 119 women; 44 with diagnostic codes for any HDP (labeled "HDP") and 75 with diagnostic codes for related diagnoses (e.g., abdominal pain, headache) (labeled "non-HDP"). Charts were reviewed for: maternal demographics; obstetrical history; and ED clinical findings, investigations and management. RESULTS: Maternal characteristics were similar between groups. There was considerable overlap in clinical presentation between groups, with no significant difference for any presenting symptom. Only 52.3% (CI 40.0-64.3%) of women in the "HDP" group had HDP investigations (bloodwork and urinalysis) vs. 30.4% (CI 18.7-58.5%) of "non-HDP" (p = 0.072). HDP was diagnosed by the ED team in 42.9% (CI 31.1-55.5%) of the HDP group of whom only 40.3% (CI 28.7-53.1) received antihypertensive therapy. CONCLUSIONS: Postpartum HDP is commonly under-recognized and under-treated in the ED, highlighting opportunities for interventions to improve the recognition and management of postpartum HDP.

The impact of age of onset on amygdala intrinsic connectivity in major depression.

BACKGROUND: Early-onset major depressive disorder (EO-MDD), beginning during childhood and adolescence, is associated with more illness burden and a worse prognosis than adult-onset MDD (AO-MDD), but little is known about the neural features distinguishing these subgroup phenotypes. Functional abnormalities of the amygdala are central to major depressive disorder (MDD) neurobiology; therefore, we examined whether amygdala intrinsic connectivity (IC) can differentiate EO-MDD from AO-MDD in a cohort of adult MDD patients. SUBJECTS AND METHODS: Twenty-one EO-MDD (age of onset ≤18 years), 31 AO-MDD patients (age of onset ≥19 years), and 19 healthy controls (HCs) underwent resting-state functional magnetic resonance imaging (7 minutes). Amygdala seed-based resting-state functional connectivity was compared between groups. RESULTS: AO-MDD patients showed loss of inverse left amygdala-left dorsolateral prefrontal cortex IC and increased inverse left amygdala-left inferior parietal IC, compared to both HCs and EO-MDD. EO-MDD showed a switch from inverse to positive IC with right dorsomedial prefrontal cortex, compared to HCs and AO-MDD. This effect was removed when we controlled for illness burden. CONCLUSION: Alterations in amygdala IC with the default-mode network were specifically related to EO-MDD, whereas amygdala IC with executive cognitive control regions was preferentially disrupted in AO-MDD. Increased illness burden, an important clinical marker of EO-MDD, accounted for its specific effects on amygdala IC. Brain imaging has the potential for validation of clinical subtypes and can provide markers of prognostic value in MDD patients.

Amygdala responses to quetiapine XR and citalopram treatment in major depression: the role of 5-HTTLPR-S/Lg polymorphisms.

OBJECTIVES: Genotype and drug pharmacology may contribute to variations in brain response to antidepressants. We examined the impact of two antidepressants with differential actions on serotonin transporter and the 5-HHTLPR-S/Lg polymorphisms on amygdala responses in major depressive disorder (MDD). METHODS: Caucasians with MDD were given either citalopram or quetiapine extended release for 8 weeks. Patients were genotyped for 5-HTTLPR. Clinical efficacy was assessed using the Hamilton Depression Rating Scale. fMRI responses to negative emotional faces were acquired at baseline, week 1 and week 8. The outcome measure was change in amygdala responses at week 8. RESULTS: Citalopram had no effect on amygdala responses in MDD patients with S/Lg alleles at weeks 1 and 8 compared with baseline, whereas it induced changes in amygdala responses in LL homozygotes. By contrast, quetiapine decreased amygdala responses at both time points in S/Lg carriers, and changes in amygdala responses at week 8 correlated with a reduction in depression scores. The small number of LL homozygotes in quetiapine group was a limitation. Efficacy of both treatments was comparable. CONCLUSIONS: These preliminary data suggest that pharmacological mechanisms and genetics need to be considered in the development of neuroimaging markers for the evaluation of antidepressant treatments.

Scale structure in the Australian lungfish, Neoceratodus forsteri (Osteichthyes: Dipnoi).

Scales of the Australian lungfish, Neoceratodus forsteri, are secreted within the dermis by a capsule of scleroblasts, and enclosed in a pouch made of collagen fibers, in contact with the epidermis over the posterior third of the scale. Each scale grows from a focus, which represents the first formed part of the scale. On the internal surface of the scale is elasmodin, made of collagen fiber bundles arranged in layers. Elasmodin, unmineralized in N. forsteri, contains cells in the living animal, and the number of layers increases as the scales grow. Squamulin, on the thin external part of the scale, is also laid down in layers, and based on a matrix of fine collagen fibrils, mineralized with a poorly crystalline biogenic calcium hydroxylapatite. Squamulin is divided into separate sections called squamulae, and contains long tubules with cells applied to the wall of the tubule. The anterior and lateral surfaces of the squamulin are ornamented with pediculae, and the posterior surface has longitudinal ridges, from which collagen fibers extend to anchor the scale within the pouch. Elasmodin and squamulin are linked by unmineralized collagen fibrils. The layers, formed at irregular intervals, are connected around the margin of the scale, effectively converting the whole scale into a flat structure resembling a pearl, with the first formed tissues deeply embedded inside the scale, and the youngest on the outer surface. Incremental lines in the hard tissue, and the number of layers in the elasmodin, do not reflect the chronological age of the fish.

Modulation of hippocampus-prefrontal cortex synaptic transmission and disruption of executive cognitive functions by MK-801.

Noncompetitive N-methyl-d-aspartate receptor antagonists such as phencyclidine and MK-801 are known to impair cognitive function in rodents and humans, and serve as a useful tool to study the cellular basis for pathogenesis of schizophrenia cognitive symptoms. In the present study, we tested in rats the effect of MK-801 on ventral hippocampus (HPC)-medial prefrontal cortex (mPFC) synaptic transmission and the performance in 2 cognitive tasks. We found that single injection of MK-801 (0.1 mg/kg) induced gradual and long-lasting increases of the HPC-mPFC response, which shares the common expression mechanisms with long-term potentiation (LTP). But unlike LTP, its induction required no enhanced or synchronized synaptic inputs, suggesting aberrant characteristics. In parallel, rats injected with MK-801 showed impairments of mPFC-dependent cognitive flexibility and HPC-mPFC pathway-dependent spatial working memory. The effects of MK-801 on HPC-mPFC responses and spatial working memory decayed in parallel within 24 h. Moreover, the therapeutically important subtype 2/3 metabotropic glutamate receptor agonist LY379268, which blocked MK-801-induced potentiation, ameliorated the MK-801-induced impairment of spatial working memory. Our results show a novel form of use-independent long-lasting potentiation in HPC-mPFC pathway induced by MK-801, which is associated with impairment of HPC-mPFC projection-dependent cognitive function.

Corpus callosal morphology in youth with bipolar depression.

OBJECTIVES: Recent evidence has demonstrated that corpus callosum maturation follows a similar developmental timeline to cognitive processes. Bipolar disorder (BD) has been associated with disruptions in error processing, response inhibition, and motor functioning, which are mediated by underlying white matter structures, including the corpus callosum. Disruptions in white matter integrity have been demonstrated in BD. However, it is unknown whether alterations in the developmental trajectory of the corpus callosum may contribute to cognitive impairments in the disorder. METHODS: We assessed the area of the corpus callosum and its subregions (the genu, rostral body, anterior and posterior bodies, isthmus, and splenium) in 14 treatment-naïve adolescents with BD (<21 years of age and in the depressed phase) and 18 healthy adolescent controls. RESULTS: In comparison with healthy controls, participants with BD demonstrated a significantly reduced overall corpus callosum area. We also noted smaller areas in the anterior and posterior mid-body of the corpus callosum in adolescents with BD. CONCLUSIONS: Our results suggest that commissural fibers of the corpus callosum are disrupted in early-onset BD. Specific decreases in the anterior and posterior mid-body callosal aspects may contribute to motor organization and inhibition deficits seen in BD. These findings are consistent with the involvement of inter-hemispheric tracts in early-onset BD, which may reflect an early deviation in white matter development.

Age of onset and corpus callosal morphology in major depression.

BACKGROUND: The corpus callosum and related white matter projections have been implicated in major depressive disorder (MDD). Previously, we found a smaller genu in adolescents with MDD as compared to controls. To date, no study has examined the age of depression onset (adult vs. pediatric) as it relates to genu area in adults with MDD. METHODS: The area of the corpus callosum and its sub-regions were measured in 21 MDD subjects with pediatric age of onset (≤18 years) (29.48±7.62 years; 16 female, 5 male) and 31 MDD subjects with adult age of onset (≥19 years) (41.42±8.85; 17 female, 14 male) and 19 healthy controls (32.89± years 9.98; 11 female, 8 male) using magnetic resonance imaging (MRI). RESULTS: A difference in genu area was noted between groups (p=0.03), after co varying for age with post-hoc tests revealing that the difference was driven by the subjects with an MDD onset of pediatric age (p=0.035). No other sub-regions or total corpus callosum area demonstrated a significant difference. Genu area correlated with age in controls (p=0.02) but not in MDD patients (p=0.35). No significant correlation was found between the confound illness duration and genu area in MDD subjects with pediatric age of onset. LIMITATIONS: Confirmation and extension of our findings requires a larger sample size and usage of diffusion tensor imaging. CONCLUSIONS: Our findings provide additional evidence of abnormalities in the genu of the corpus callosum in early onset depression that persist into adulthood.

Cartilage, bone, and intermandibular connective tissue in the Australian lungfish, Neoceratodus forsteri (Osteichthyes: Dipnoi).

The connective tissue that links the bones of the mandible in the Australian lungfish, Neoceratodus forsteri, has been described as an intermandibular cartilage, and as such has been considered important for phylogenetic analyses among lower vertebrates. However, light and electron microscopy of developing lungfish jaws demonstrates that the intermandibular tissue, like the connective tissue that links the bones of the upper jaw, contains fibroblasts and numerous bundles of collagen fibrils, extending from the trabeculae of the bones supporting the tooth plates. It differs significantly in structure and in staining reactions from the cartilage and the bone found in this species. In common with the cladistian Polypterus and with actinopterygians and some amphibians, lungfish have no intermandibular cartilage. The connective tissue linking the mandibular bones has no phylogenetic significance for systematic grouping of lungfish, as it is present in a range of different groups among lower vertebrates.

Learning-facilitated long-term depression requires activation of the immediate early gene, c-fos, and is transcription dependent.

De novo gene transcription is a prerequisite for long-term information storage in the brain. Learning-facilitated synaptic plasticity describes the ability of hippocampal synapses to respond with long-lasting synaptic plasticity to the coupling of afferent stimulation with a spatial learning experience. Strikingly, long-term depression (LTD) is facilitated by context-dependent spatial learning experiences suggesting it may play a role in information storage to enable spatial memory. Here, we investigated if learning-facilitated LTD requires the transcription factor, c-Fos and is transcription-dependent. Novel spatial learning about object-place configurations coupled with weak low frequency afferent stimulation induced robust LTD in control animals that persisted for >24h and was associated with elevations in hippocampal expression of c-Fos. Intracerebral application of a c-fos antisense oligonucleotide prevented the facilitation of LTD by novel spatial learning, inhibited elevations of c-Fos triggered by LTD and impaired spatial learning. The expression of the transcription factor zif268 was unaffected by the c-fos antisense oligonucleotide. Learning-facilitated LTD was prevented by a transcription inhibitor. These data support that learning-facilitated LTD requires elevations in c-Fos and is transcription dependent. The observation that LTD shares key regulatory mechanisms with learning and memory processes argues strongly for a role for this form of synaptic plasticity in long-term information storage in the hippocampus.

Passive spatial perception facilitates the expression of persistent hippocampal long-term depression.

Learning-facilitated plasticity describes the ability of hippocampal synapses to respond with synaptic plasticity when weak afferent stimulation is coupled with a spatial learning event. Qualitative differences appear to influence whether long-term potentiation or long-term depression (LTD) are facilitated by spatial learning. At many hippocampal synapses, LTD is facilitated when rats actively explore a novel spatial context. We investigated whether learning-facilitated plasticity is expressed when an unconstrained but stationary rat observes a computer-generated spatial environment. Visual fields were separated. Novel object configurations were presented to one field; familiar constellations were presented to the other field. LTD was facilitated in the CA1 region of the hemisphere to which novel object constellations were presented. Familiar constellations had no effect. LTD facilitation was prevented by treatment with the protein translation inhibitor, anisomycin. LTD in the dentate gyrus was not facilitated by novel object constellations, suggesting that effects are not common to all hippocampal subfields. These data support a unique association of LTD in the CA1 region with learning about spatial context and indicate that rats can passively perceive space.

Formation and structure of scales in the Australian lungfish, Neoceratodus forsteri (Osteichthyes: Dipnoi).

The large elasmoid scales of the Australian lungfish, Neoceratodus forsteri, are formed within the dermis by unpigmented scleroblasts, growing within a collagenous dermal pocket below a thick glandular epidermis. The first row of scales, on the trunk of the juvenile lungfish, appears below the lateral line of the trunk, single in this species, at around stage 53. The scales, initially circular in outline, develop anteriorly and posteriorly from the point of initiation in the mid-trunk region, and rows are added alternately below the line, and above the line, until they reach the dorsal or ventral midline, or the margins of the fins. Scales develop later on the ventral surface of the head, from a separate centre of initiation. Scales consist of three layers, all produced by scleroblasts of dermal origin. The outermost layer of interlocking plates, or squamulae, consists of a mineralised matrix of fine collagen fibrils, covered by unmineralised collagen and a single layer of cells. Squamulae of the anterior and lateral surfaces are ornamented with short spines, and the mineralised tissue of the posterior surface is linked to the pouch by collagen fibrils. The innermost layer, known as elasmodin, consists of bundles of thick collagen fibrils and cells arranged in layers. An intermediate layer, made up of collagen fibrils, links the outer and inner layers. The elasmoid scales of N. forsteri can be compared with scale types among other osteichthyan groups, although the cellsand canaliculi in the mineralised squamulae bear little resemblance to typical bone.

Functional morphology of digestion in the stomachless, piscivorous needlefishes Tylosurus gavialoides and Strongylura leiura ferox (Teleostei: Beloniformes).

Belonidae are unusual in that they are carnivorous but lack a stomach and have a straight, short gut. To develop a functional morphological model for this unusual system the gut contents and alimentary tract morphology of Tylosurus gavialoides and Strongylura leiura ferox were investigated. The posterior orientation of the majority of the pharyngeal teeth supports the swallowing of whole large prey, but not their mastication. Mucogenic cells are abundant in the mucosa lining, particularly the esophagus, and their secretions are likely to protect the gut lining from damage while lubricating passage of the prey. Esophagus, anterior intestine, posterior intestine, and rectum all have highly reticulate mucosae. The anterior three gut sections are distensible to accommodate the passage of prey. However, following ingestion large prey are passed to the highly distensible posterior intestine where they rest head first against the ileorectal valve. Alimentary pH ranges from neutral to weakly acidic. Fish prey is digested head first with the head being largely digested while the remainder of the body is still intact. The nondistensibility of the rectum and the small aperture provided by the ileorectal valve suggest the products of intestinal digestion are either small particulates or fluids that pass into rectum where they are absorbed.

Ultrastructure and the importance of wear in the dentition of the halfbeak (Pisces: Hemiramphidae) pharyngeal mill.

To assess how tooth microstructure and composition might facilitate the pharyngeal mill mechanism of halfbeaks, apatite structure and iron content were determined by scanning electron microscopy and energy dispersive X-ray analysis for Hyporhamphus regularis ardelio, Arrhamphus sclerolepis krefftii, and Hemiramphus robustus. Iron was present in developing teeth and was concentrated along the shearing edge of spatulate incisiform teeth, which dominate the occlusive wear zone in all three species. A model based on tooth structure and wear rate is proposed to explain how halfbeaks maintain a fully functional occlusion zone throughout growth and consequent tooth addition and replacement. Replacement teeth erupt and wear rapidly so that a constant occlusion plane is always present. Iron within the tooth tissue reduces the wear rate of the cutting edge while simultaneously maintaining its sharpness and efficiency.

The hippocampal CA1 region and dentate gyrus differentiate between environmental and spatial feature encoding through long-term depression.

Novel spatial information is encoded in the hippocampus by plastic changes of synaptic properties. Novel space consists of several types of information that may evoke differential synaptic responses in individual hippocampal subregions. To examine this possibility, we recorded field potentials from the dentate gyrus (DG) and CA1 region in freely moving adult rats. Stimulation protocols that were marginally subthreshold for the induction of persistent long-term potentiation (LTP) or long-term depression (LTD) were implemented, concurrent with exposure to novel spatial information. We found that in both hippocampal subregions, exploration of a novel empty hole board facilitated LTP. However, LTD facilitation was subregion specific and dependent on the nature of the cues. In the CA1 region, partially concealed cues had a facilitatory effect on LTD. LTD in the DG was facilitated by large directional cues. Thus, although LTP was facilitated uniformly in both areas by the same novel environment, LTD was facilitated in a region-specific manner, based on the nature of the cue. This implies that spatial changes within an environment elicit local changes of synaptic weights dependent on the type of information and, hence, generate a complete cognitive map as a consequence of cooperation of synaptic plasticity in all participating subregions.

Beta-adrenoreceptors comprise a critical element in learning-facilitated long-term plasticity.

A novel spatial environment consists of several different types of information that may be encoded by cellular information storage mechanisms such as long-term potentiation (LTP) and long-term depression (LTD). Arousal, mediated, for example, by activation of the noradrenergic system, is a critical factor in information acquisition and may enhance the encoding of novel spatial information. Using electrophysiological recordings of hippocampal responses in freely moving rats during spatial learning, we investigated the role of the beta-adrenoreceptor in Schaeffer collateral-CA1 synaptic plasticity. We found that novel exploration of spatial context facilitates induction of LTD that is inhibited by intracerebroventricular application of the beta-adrenoreceptor antagonist, propranolol. Long-lasting homosynaptic LTD, that was electrically induced by low-frequency stimulation, was unaffected by the antagonist. Although application of a beta-adrenoreceptor agonist (isoproterenol) did not affect electrically induced LTD, agonist application facilitated short-term depression (STD) into LTD and mimicked the augmentation, through spatial exploration, of STD into LTD. Exploration of a novel empty environment facilitated LTP that was prevented by application of propranolol. These results suggest that beta-adrenoreceptors may facilitate encoding of spatial information through synaptic plasticity in the hippocampus and that noradrenaline is a key factor in effective information acquisition.

High resolution transmission electron microscopy of developing enamel in the Australian lungfish, Neoceratodus forsteri (Osteichthyes: Dipnoi).

The permanent tooth plates of the Australian lungfish, Neoceratodus forsteri, are covered by enamel that develops initially in a similar manner to that of other vertebrates. As the enamel layer matures, it acquires several unusual characteristics. It has radially oriented protoprismatic structures with the long axes of the protoprisms perpendicular to the enamel surface. Protoprisms can be defined as aggregations of hydroxyapatite crystals that lack the highly ordered arrangement of the rods of mammalian enamel but are not without a specific structure of their own. The protoprisms are arranged in layers of variable thickness that are deposited sequentially as the tooth plate grows. They may be confined to the separate layers, or may cross the boundary between each layer. Crystals within the protoprisms are long and thin with hydroxyapatite c-axis dimensions of between 30 and 350 nm, and with typical a-b axis dimensions of 5-10 nm. The hydroxyapatite crystals of lungfish enamel have no centre dark lines of octacalcium phosphate, an unusual character among vertebrates. As each crystal develops, arrays of atoms may change direction, and regions exist where dislocations and extra lattice planes are inserted into the long crystal. The resulting hydroxyapatite crystal is not straight, and has a rough surface. The crystals are arranged in tangled structures with their crystallographic c-axes closely aligned with the long axis of the protoprism. Lungfish enamel differs from the enamel of higher vertebrates in that the hydroxyapatite crystals are of different shape, and, in mature enamel, the protoprisms remain as protoprisms and do not develop into the conventional prismatic structures characteristic of mammalian enamel.

Hippocampal long-term depression: master or minion in declarative memory processes?

The neural mechanisms for the formation of declarative memory (memory for facts and events) are believed to be integrated from processes mediated by hippocampal long-term potentiation (LTP) and long-term depression (LTD). Traditionally, LTP has been designated as the main mediator of spatial memory storage in the hippocampus, whereas LTD has been assigned an auxiliary role in signal-to-noise regulation or in forgetting. It has recently become apparent, however, that LTD contributes directly to hippocampal information storage. In fact, LTD could dominate in the processing of precise spatial characteristics. Accumulating evidence supports the idea that LTP and LTD enable distinct and separate forms of information storage, which together facilitate the generation of a spatial cognitive map.

Effect of phosphate functional groups on the calcification capacity of acrylic hydrogels.

The incorporation of negatively charged groups into the structure of synthetic polymers is frequently advocated as a method for enhancing their calcification capacity required in orthopedic and dental applications. However, the results reported by various research groups are rather contentious, since inhibitory effects have also been observed in some studies. In the present study, phosphate groups were introduced in poly(2-hydroxyethyl methacrylate) (PHEMA) by copolymerization with 10% mol of either mono(2-acryloyloxyethyl) phosphate (MAEP) or mono(2-methacryloyloxyethyl) phosphate (MMEP). Incubation of these hydrogels for determined durations (1-9 weeks) in a simulated body fluid (SBF) solution induced deposition of calcium phosphate (CaP) deposits of whitlockite type. After 9 weeks, the amount of calcium deposited on the phosphate-containing polymers was four times lower than that found on PHEMA, as determined by X-ray photoelectron spectroscopy (XPS). Samples of copolymer HEMA-MAEP were implanted subcutaneously in rats and evaluated after 9 weeks. No CaP deposits could be detected on the copolymer by XPS or energy dispersive X-ray spectroscopy, while PHEMA samples were massively calcified. It was concluded that the presence of phosphate groups decreased the calcification capacity of the hydrogels, and that in the conditions of this study, the phosphate groups had an inhibitory effect on the deposition of CaP phases on HEMA-based hydrogels.

Inferring parrotfish (Teleostei: Scaridae) pharyngeal mill function from dental morphology, wear, and microstructure.

Morphology, occlusal surface topography, macrowear, and microwear features of parrotfish pharyngeal teeth were investigated to relate microstructural characteristics to the function of the pharyngeal mill using scanning electron microscopy of whole and sectioned pharyngeal jaws and teeth. Pharyngeal tooth migration is anterior in the lower jaw (fifth ceratobranchial) and posterior in the upper jaw (paired third pharyngobranchials), making the interaction of occlusal surfaces and wear-generating forces complex. The extent of wear can be used to define three regions through which teeth migrate: a region containing newly erupted teeth showing little or no wear; a midregion in which the apical enameloid is swiftly worn; and a region containing teeth with only basal enameloid remaining, which shows low to moderate wear. The shape of the occlusal surface alters as the teeth progress along the pharyngeal jaw, generating conditions that appear suited to the reduction of coral particles. It is likely that the interaction between these particles and algal cells during the process of the rendering of the former is responsible for the rupture of the latter, with the consequent liberation of cell contents from which parrotfish obtain their nutrients.