Micromorphology of the Dental Pulp Is Highly Preserved in Cancer Patients Who Underwent Head and Neck Radiotherapy

Introduction

Teeth are often included in the radiation field during head and neck radiotherapy, and recent clinical evidence suggests that dental pulp is negatively affected by the direct effects of radiation, leading to impaired sensitivity of the dental pulp. Therefore, this study aimed to investigate the direct effects of radiation on the microvasculature, innervation, and extracellular matrix of the dental pulp of patients who have undergone head and neck radiotherapy.

Methods

Twenty-three samples of dental pulp from patients who finished head and neck radiotherapy were analyzed. Samples were histologically processed and stained with hematoxylin-eosin for morphologic evaluation of the microvasculature, innervation, and extracellular matrix. Subsequently, immunohistochemical analysis of proteins related to vascularization (CD34 and smooth muscle actin), innervation (S-100, NCAM/CD56, and neurofilament), and extracellular matrix (vimentin) of the dental pulp was performed.

Results

The morphologic study identified preservation of the microvasculature, nerve bundles, and components of the extracellular matrix in all studied samples. The immunohistochemical analysis confirmed the morphologic findings and showed a normal pattern of expression for the studied proteins in all samples.

Conclusions

Direct effects of radiotherapy are not able to generate morphologic changes in the microvasculature, innervation, and extracellular matrix components of the dental pulp in head and neck cancer patients.     

Submandibular myofibroma: a case report

Purpose

Myofibroma is a rare benign spindle cell neoplasm, and the aim of the present study was to carry out a literature review and present a clinical case of a patient with a myofibroma in the submandibular region and its management.

Conclusions

Diagnosis of myofibroma can be reached by a histopathologic and immunohistochemical analysis and surgical excision is the treatment of choice.     

A hypothesis concerning distinct schemes of olfactory activation evoked by perceived versus nonperceived input

Odors of similar intensity may be perceived or not by human subjects. Perceived odors correlate with brain magnetic fields, delayed some hundreds of milliseconds, that are not present for unperceived ones. How might this occur? The endopiriform nucleus is an excitable structure, considered part of the claustrum, that is interconnected with the primary olfactory (piriform) cortex. A procedure called kindling allows the endopiriform nucleus to generate epileptiform activities in vitro that are delayed ∼100 ms after a stimulus, suggesting a mechanism for delayed activity. Using a detailed computational model of the piriform cortex, consistent with an in vitro experiment, we show that the addition of neurons with endopiriform properties could allow similar stimuli to generate either brief responses or prolonged ones, depending on parameters such as a persistent Na⁺ conductance. Brief responses putatively correlate with lack of conscious perception, and prolonged responses correlate with the presence thereof.

Crick and Koch (1) suggested that the claustrum might play a role in consciousness, given its widespread reciprocal connectivity with multiple cortical regions. By way of caution, however, some data indicate that connectivity between claustral principal neurons may be limited (2), raising questions as to how consciousness might be sustained. Nevertheless, endopiriform principal neurons (multipolar cells) are reciprocally interconnected (3), and this nucleus is considered to be part of the claustrum, at least in primates (4). As well, the endopiriform nucleus is interconnected with the primary olfactory cortex or piriform cortex. These data led to a hypothesis that the endopiriform nucleus might play a role in initiating olfactory conscious perception.Two pieces of experimental evidence support the hypothesis: 1) the existence of delayed synchronized neuronal bursting in the endopiriform nucleus in vitro after a procedure called kindling (for example, bathing tissue in low external [Mg²⁺]) that renders the tissue prone to epileptiform bursting and 2) the existence of delayed MEG (magnetoencephalographic) signals in human subjects who consciously perceive an odor.With respect to piece 1 above, Hoffmann and Haberly (5–8), following on earlier in vivo observations of epileptic properties of the endopiriform nucleus (9), observed that a kindled piriform/endopiriform brain slice could generate a synchronized burst of activity following a localized stimulus, with delays of tens of milliseconds or more, and this would occur despite the presence of synaptic inhibition. [This latter phenomenon had been observed previously in other epilepsy models (10).]With respect to piece 2 above, in accord with the notion that a given sensory stimulus may be perceived or not [and perception perhaps involving an “ignition” process (11)], it has been noted that odor stimuli, of comparable intensity, evoke different MEG signals; the MEG distributions over the brain depend on whether the odor was perceived or not, with odor perception evoking more widespread and delayed activation over timescales in the hundreds of milliseconds (12).We, therefore, asked whether the above observations might be mechanistically linked in the following way; there is cellular machinery within the endopiriform nucleus—enhanced by the kindling process but present in a less intense form under normal conditions—that could generate, or not generate, sustained signals capable of widespread communication, the latter being presumed to lead to perception.     

Heterogeneity in form and function of the rat extensor digitorum longus motor unit

The motor unit comprises a variable number of muscle fibres that connect through myelinated nerve fibres to a motoneuron (MN), the central drivers of activity. At the simplest level of organisation there exist phenotypically distinct MNs that activate corresponding muscle fibre types, but within an individual motor pool there typically exists a mixed population of fast and slow firing MNs, innervating groups of Type II and Type I fibres, respectively. Characterising the heterogeneity across multiple levels of motor unit organisation is critical to understanding changes that occur in response to physiological and pathological perturbations. Through a comprehensive assessment of muscle histology and ex vivo function, mathematical modelling and neuronal tracing, we demonstrate regional heterogeneities at the level of the MN, muscle fibre type composition and oxygen delivery kinetics of the rat extensor digitorum longus (EDL) muscle. Specifically, the EDL contains two phenotypically distinct regions: a relatively oxidative medial and a more glycolytic lateral compartment. Smaller muscle fibres in the medial compartment, in combination with a greater local capillary density, preserve tissue O₂ partial pressure (PO₂) during modelled activity. Conversely, capillary supply to the lateral compartment is calculated to be insufficient to defend active muscle PO₂ but is likely optimised to facilitate metabolite removal. Simulation of in vivo muscle length change and phasic activation suggest that both compartments are able to generate similar net power. However, retrograde tracing demonstrates (counter to previous observations) that a negative relationship between soma size and C‐bouton density exists. Finally, we confirm a lack of specificity of SK3 expression to slow MNs. Together, these data provide a reference for heterogeneities across the rat EDL motor unit and re‐emphasise the importance of sampling technique.     

Facilitating social support among community psychologists

Over the past few years, a network of regional coordinators has promoted a variety of community psychology activities in the United States and other countries, creating a base of social support for community psychologists in academic and field settings. This paper describes key organizing principles for creating viable support networks such as this one and presents specific examples of their use by the regional coordinators. The grassroots efforts of regional coordinators in stimulating social support, educational opportunities, resource exchanges, and a variety of other activities represent one of the more crucial and important functions undertaken by community psychologists and their organizations.     

Phosphorylation of proteoglycans from human articular cartilage

Previous studies have shown that sulfated proteoglycans from human articular and epiphyseal cartilage were phosphorylated. These macromolecules contribute to the stiffness and resiliency of this tissue. We demonstrate here that the phosphate moieties are an integral part of proteoglycan subunits. Specifically, evidence is presented which indicates that proteoglycan monomers contain 3 to 4 phosphate moieties per core protein and that these appear to exist as phosphoserine residues. Furthermore, the data illustrate that human articular cartilage also contains more than 20 different phospho-proteins, some of which are closely associated with proteoglycan aggregates. Proteoglycan subunits were purified from extracts of articular cartilage or from media fractions which had been used to label tissue specimens with ³²P-orthophosphate. Chemical and radiographic analyses revealed that the phosphate concentration with respect to sulfate and uronic acid content remained constant when purified proteoglycan monomers were subjected to equilibrium ultracentrifugation and size-exclusion chromatography. That the phosphate moieties were bound to proteoglycan monomers via monoester linkages was indicated by the release of ³²P-orthophosphate from proteoglycan subunits incubated under mild alkaline conditions or reacted with acid or alkaline phosphatases. Identification of serine residues in the core protein as the sites of phosphorylation was made by autoradiography of thin layer plates on which hydrolyzed samples of purified ³²P-proteoglycan sub-units had been subjected to 2-dimensional electrophoresis/chromatography. Quantification of 3 to 4 phosphate moieties per core protein of 200,000 daltons was made by chemical analysis of inorganic phosphate released from proteoglycans by acid hydrolysis.