Increased function of pronociceptive TRPV1 at the level of the joint in a rat model of osteoarthritis pain

OBJECTIVES

Blockade of transient receptor potential vanilloid 1 (TRPV1) with systemic antagonists attenuates osteoarthritis (OA) pain behaviour in rat models, but on-target-mediated hyperthermia has halted clinical trials. The present study investigated the potential for targeting TRPV1 receptors within the OA joint in order to produce analgesia.

METHODS

The presence of TRPV1 receptors in human synovium was detected using western blotting and immunohistochemistry. In a rat model of OA, joint levels of an endogenous ligand for TRPV1, 12-hydroxy-eicosatetraenoic acid (12-HETE), were quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Effects of peripheral administration of the TRPV1 receptor antagonist JNJ-17203212 on afferent fibre activity, pain behaviour and core body temperature were investigated. Effects of a spinal administration of JNJ-17203212 on dorsal horn neuronal responses were studied.

RESULTS

We demonstrate increased TRPV1 immunoreactivity in human OA synovium, confirming the diseased joint as a potential therapeutic target for TRPV1-mediated analgesia. In a model of OA pain, we report increased joint levels of 12-HETE, and the sensitisation of joint afferent neurones to mechanical stimulation of the knee. Local administration of JNJ-17203212 reversed this sensitisation of joint afferents and inhibited pain behaviour (weight-bearing asymmetry), to a comparable extent as systemic JNJ-17203212, in this model of OA pain, but did not alter core body temperature. There was no evidence for increased TRPV1 function in the spinal cord in this model of OA pain.

CONCLUSIONS

Our data provide a clinical and mechanistic rationale for the future investigation of the therapeutic benefits of intra-articular administration of TRPV1 antagonists for the treatment of OA pain.

Localization of neurones expressing the gap junction protein Connexin45 within the adult spinal dorsal horn: a study using Cx45-eGFP reporter mice

Connexin (Cx) proteins localized to neuronal and glial syncytia provide the ultrastructural components for intercellular communication via gap junctions. In this study, a Cx45 reporter mouse model in which the Cx45 coding sequence is substituted for enhanced green fluorescent protein (eGFP) was used to characterize Cx45 expressing neurones within adult mouse spinal cord. eGFP-immunoreactive (eGFP-IR) cells were localized at all rostro-caudal levels to laminae I-III of the dorsal horn (DH), areas associated with nociception. The neuronal rather than glial phenotype of these cells in DH was confirmed by co-localisation of eGFP-IR with the neuronal marker NeuN. Further immunohistochemical studies revealed that eGFP-IR interneurones co-express the calcium-binding protein calbindin, and to a lesser extent calretinin. In contrast, eGFP-IR profiles did not co-localize with either parvalbumin or GAD-67, both of which are linked to inhibitory interneurones. Staining with the primary afferent markers isolectin-B4 (IB4) and calcitonin gene-related peptide revealed that eGFP-IR somata within laminae I-III receive close appositions from the former, presumed non-peptidergic nociceptive afferents of peripheral origin. The presence of 5-HT terminals in close apposition to eGFP-IR interneuronal somata suggests modulation via descending pathways. These data demonstrate a highly localized expression of Cx45 in a population of interneurones within the mouse superficial dorsal horn. The implications of these data in the context of the putative role of Cx45 and gap junctions in spinal somatosensory processing and pain are discussed.

Kv3.1b and Kv3.3 channel subunit expression in murine spinal dorsal horn GABAergic interneurones

GABAergic interneurones, including those within spinal dorsal horn, contain one of the two isoforms of the synthesizing enzyme glutamate decarboxylase (GAD), either GAD65 or GAD67. The physiological significance of these two GABAergic phenotypes is unknown but a more detailed anatomical and functional characterization may help resolve this issue. In this study, two transgenic Green Fluorescent Protein (GFP) knock-in murine lines, namely GAD65-GFP and GAD67-GFP (Δneo) mice, were used to profile expression of Shaw-related Kv3.1b and Kv3.3 K(+)-channel subunits in dorsal horn interneurones. Neuronal expression of these subunits confers specific biophysical characteristic referred to as 'fast-spiking'. Immuno-labelling for Kv3.1b or Kv3.3 revealed the presence of both of these subunits across the dorsal horn, most abundantly in laminae I-III. Co-localization studies in transgenic mice indicated that Kv3.1b but not Kv3.3 was associated with GAD65-GFP and GAD67-GFP immunopositive neurones. For comparison the distributions of Kv4.2 and Kv4.3 K(+)-channel subunits which are linked to an excitatory neuronal phenotype were characterized. No co-localization was found between GAD-GFP +ve neurones and Kv4.2 or Kv4.3. In functional studies to evaluate whether either GABAergic population is activated by noxious stimulation, hindpaw intradermal injection of capsaicin followed by c-fos quantification in dorsal horn revealed co-expression c-fos and GAD65-GFP (quantified as 20-30% of GFP +ve population). Co-expression was also detected for GAD67-GFP +ve neurones and capsaicin-induced c-fos but at a much reduced level of 4-5%. These data suggest that whilst both GAD65-GFP and GAD67-GFP +ve neurones express Kv3.1b and therefore may share certain biophysical traits, their responses to peripheral noxious stimulation are distinct.

Cognitive dysfunction in intensive care survivors

Cognitive dysfunction is increasingly recognized as a common, often prolonged and potentially disabling complication of critical illness. While demonstrable in patients who have survived a variety of both medical and surgical conditions, its causes remain unclear. Screening of patients in intensive care units and at follow up may help identify those who could benefit from cognitive rehabilitation.

Retrospective analysis of an implant system

The reliability of dental implants results from a combination of design, placement, and reconstructive techniques. Retrospective analysis is one vehicle for evaluating implant success. This article presents the reliability of these techniques in Bicon dental implants. The survivability of this implant was evaluated retrospectively using life table survival analysis over a 10-year period in 13 practices. The parameters used for success included no implant loss, no mobility, no continuing bone loss that did not stabilize after 1 year, no discomfort, and no purulence.

Replacing posterior teeth with freestanding implants: four-year prosthodontic results of a prospective study

This article presents prospective four-year prosthetic results of the placement of 432 posterior freestanding, conventionally cemented prosthetic tooth implants in posterior edentulous spaces using the Bicon Dental Implants system (Bicon Dental Implants). Over four years, 0.74 percent of the abutments loosened, 0.5 percent of the abutments fractured, and 2.47 percent of the crowns experienced porcelain fracture, (all porcelain fractures occurred at time of placement). This low rate of problems appears to make free-standing single-tooth implant restorations a reliable solution to treating posterior edentulism.

The locking taper attachment for implant abutments: use and reliability

The locking taper abutment attachment for implants is a one and one-half-degree tapered post that relies on friction rather than a screw for retention of the abutment to the implant. A retrospective analysis of 1,757 consecutively loaded implants was made to determine the reliability of the locking taper abutment. Five hundred and four implants restored over a 7-year period from one practice and a total of 1,253 implants restored over 4 years from 2 practices were reviewed. Nine abutment posts fractured for a failure rate of 0.05 percent. Thirty one (1.7 percent) of the abutments loosened but were reinserted without further problems. The technique for use of the locking taper implant abutment attachment is described.

Angulation assessment of anterior single tooth root form implants: technical note

A technique is presented to evaluate the angulation and position of an anterior single tooth root form implant by means of a surgical template, a pilot osteotomy, and an abutment guide. The space available for the restorative materials can be assessed and the angulation modified, if necessary, to improve the esthetic potential. If the angulation is satisfactory and sufficient room is available for the prosthesis, the surgeon can continue with implant placement at the initial site.

Relative production of IL-1 beta and TNF alpha by mononuclear cells after exposure to dental implants

Interleukin-1 (also known as osteoclast activating factor, OAF) is a cytokine produced primarily by monocytes and macrophages and is thought to mediate many of the immunologic, metabolic, and endocrine alterations seen with microbial infection, tissue injury, inflammatory disease, and bone loss. Stimuli for IL-1 production include microorganisms, endotoxins (LPS), antigen-antibody complexes, clotting components, and other cytokines. The purpose of this study was to determine whether dental implants stimulated peripheral blood mononuclear cells (PBMCs) to produce IL-1 beta (OAF) as well as tumor necrosis factor (TNF alpha). This production may lead to bone loss or failure of an implant. Three duplicates of five different implants were incubated with 2 x 10(6) PBMCs/ml in 20% autologous serum; the esterase positive PBMCs amounted to 14.5%. Measured by radioimmunoassay techniques and compared to controls, all of the implants except one caused significant in vitro generation of IL-1 beta and TNF alpha. The stimulation of IL-1 beta/TNF alpha production by these materials suggests that they are not physiologically inert and that the IL-1 beta (OAF) production may contribute to a less favorable osseoadaptation. OAF has a physiologic (homeostatic) role in maintenance and alteration of osseous structures, but the level at which physiologic becomes pathologic is unknown. Although there were statistical differences between the cellular response to these implants, the clinical significance of the differences remains to be determined.

Occlusal contact variation with changes in head position

Ten healthy young adults were examined for changes in occlusal contacts related to three head positions: supine, sitting, and head forward. The contacts were analyzed using T-Scan special research software, which measured the time moments of the first five occlusal contacts. Time moment is a descriptive term calculated from a formula that considers both spatial (where contacts are) and temporal (when contact occurs) aspects of tooth contact and provides a quantitative basis for comparing the dynamics of tooth contact. Paired head positions were analyzed for differences using Student's t test, and it appears that in healthy young adults, initial tooth contacts are substantially influenced by posture.

A comparison of mandibular denture base extension in conventional and implant-retained dentures

A border outline for mandibular implant-retained dentures is described. The lingual extension of the impression is greatly reduced compared with a conventional mandibular denture. Because of the implant attachment, the shortened border is more comfortable and does not compromise denture retention. Improper implant position is also discussed with respect to denture extension.

Non-surgical embryo transfer and live birth in a llama

The uteri of two donor female llamas were flushed non-surgically and one viable 7-day-old embryo was recovered. The embryo was transferred non-surgically within four hours into a recipient female llama whose estrous cycle was synchronized with the donor by injection of gonadotropin releasing hormone (GnRH). Pregnancy was confirmed 20 days after transfer, at which time the level of serum progesterone was determined and found to be consistent with that of gestation (>/=100 ng/100 ml). A normal and healthy male weighing 33 1bs was born on October 8, 1984, 326 days following transfer of the embryo to the recipient.

Excessive wear of natural tooth structure by opposing composite restorations

Extreme care must be taken to evaluate the probable effect of using certain restorative materials to oppose existing tooth structure, particularly when dentin is exposed. In addition, frequent recall examination, every one or two months, is necessary to catch any problems in their beginning stages and to solve them before greater damage can be caused. It is also suggested that evaluation of any occlusal habits be made before deciding on a plan to alter vertical dimension and to carefully consider the effects of the materials used in a restoration on the opposing arch.

The cooperative information project: Part 2: some initial clinical, quality assurance, and practice management studies

Many of the obstacles inherent in the conduct of primary care research have been overcome by an experimental program in northern New England, the Primary Care Cooperative Information Project. This project uses a medical information network in 44 rural medical practices to carry out both clinical and management research. This paper describes the developmental problems encountered and the results of some initial clinical, quality assurance, and practice management studies conducted by the network and presents observations on its future research directions.

The Cooperative Information Project: Part 1: A sentinel practice network for service and research in primary care

This is the first of two papers describing the Primary Care Cooperative Information Project (COOP Project), a program that integrates the interests of community physicians, medical school faculty, and health policymakers. This integration has been accomplished through the uniting of 44 rural medical practices in Maine, New Hampshire, and Vermont with faculty at Dartmouth Medical School in clinical research, quality assurance, practice management, and continuing medical education activities. This paper describes the structure, goals, and history of the COOP Project, together with the design, cost, and output of its computerized medical information system.

The form of the mandibular anterior lingual alveolar process in partially edentulous patients

One hundred adult patients needing a Class I mandibular removal partial denture were selected to determine the incidence and prevalence of the form of the mandibular anterior lingual alveolar process. The processes ranged between 2 and 22 mm in height and from 37 degrees to 125 degrees angulations in relation to the occlusal plane. Shapes were found to be sloped (45), vertical (38), and undercut (17). The large variety of sizes and shapes of the lingual alveolar process stresses the importance of a precise impression technique to accurately register the anterior lingual alveolar process. Instructions to the dental laboratory for the design of the proper major connector for each specific situation will improve the quality of the removable partial denture service to the patient.

The medication seminar and primary care education

This paper defines the need to provide postgraduate psychiatric education to primary care physicians, as well as the need to provide psychiatrists with teaching experiences in the primary care setting. Two psychiatrists in rural New England developed and administered, over an eight-month period, a Balint-type seminar on psychotropic medications, designed to emphasize experiential and two-way learning. The process of the seminar reflected the special problems encountered in post-graduate education of physicians in a rural area. The impact on the instructors and participants had implications for the design and development of future educational programs in both psychiatry and primary care.

Maximizing support for maxillary defects

The use of the medical-grade silicone obturator can aid the prosthodontist attempting prosthetic closure of maxillary defects. This type of obturator prosthesis allows the patient to resume near-normal oral function. It aids in the preservation of the oral structures because it uses the support available from the defect to reduce the force per unit area on the remaining "normal" oral structures.

Trans-chest ventricular defibrillation of heavy subjects using trapezoidal current waveforms

Effectiveness of four truncated exponential waveform defibrillators for transchest ventricular defibrillation was evaluated in 27 human-sized animals. With all waveforms, effectiveness was virtually 100% for small subjects, but decreased as body weight increased. These data confirm the electrical dose concept for ventricular defibrillation and demonstrate that the truncated exponential waveform is effective only when adequate current is delivered through the subject's chest.