Micro-Computed Tomography Analysis of Peri-Implant Bone Defects Exposed to a Peri-Implantitis Microcosm, with and without Bone Substitute, in a Rabbit Model: A Pilot Study

Peri-implantitis is an inflammatory condition characterized by inflammation in the peri-implant connective tissue and a progressive loss of supporting bone; it is commonly associated with the presence of biofilms on the surface of the implant, which is an important factor in the development and progression of the disease. The objective of this study was to evaluate, using micro-CT, the bone regeneration of surgically created peri-implant defects exposed to a microcosm of peri-implantitis. Twenty-three adult New Zealand white rabbits were included in the study. Bone defects of 7 mm diameter were created in both tibiae, and a cap-shaped titanium device was placed in the center, counter-implanted with a peri-implantitis microcosm. The bone defects received a bone substitute and/or a resorbable synthetic PLGA membrane, according to random distribution. Euthanasia was performed 15 and 30 days postoperatively. Micro-CT was performed on all samples to quantify bone regeneration parameters. Bone regeneration of critical defects occurred in all experimental groups, with a significantly greater increase in cases that received bone graft treatment (p < 0.0001), in all measured parameters, at 15 and 30 days. No significant differences were observed in the different bone neoformation parameters between the groups that did not receive bone grafts (p > 0.05). In this experimental model, the presence of peri-implantitis microcosms was not a determining factor in the bone volume parameter, both in the groups that received regenerative treatment and in those that did not.

Dissection of white matter association fasciculi in bovine (Bos taurus), pig (Sus scrofa domesticus) and rabbit (Oryctolagus cuniculus) brains

The cerebral fasciculi (association, commissural and projection) pass through the cerebral white matter in organized groups connecting regions, hemispheres, gyri, areas and brain lobes to each other. The study can be done in vivo through diffusion tensor imaging (DTI) but presenting some technical problems. The post-mortem study by dissection allows to have a clearer view of its location, path and connections. In this work, we dissect, identify and compare the fasciculi of association of the white matter of the dorsolateral face of bovine hemispheres (Bos taurus), pig hemispheres (Sus scrofa domesticus) and rabbit hemispheres (Oryctolagus cuniculus), applying the Klingler´s technique. In 30 cerebral hemispheres (10 of each species, five right and five left), we applied the Klingler technique to identify and isolate the occipitofrontal fasciculus, uncinate fasciculus, inferior longitudinal fasciculus and superior longitudinal fasciculus; we established its location by fixing landmarks, and determined the difference in its length and width between the right and left hemispheres as well as between species using the statistical tests of t-student and one-way ANOVA. We identify the gyri, sulci and fasciculi of the dorsolateral surface of the cerebral hemispheres of the three species. We found statistically significant differences in several fasciculi between species principally in the occipitofrontal fasciculus. The preparation of the brains through the modified Klingler technique allowed a successful identification of the fascicules of association of the dorsolateral face of the cerebral hemispheres and the empowerment of these animal models for future research work in this field.

Temporomandibular joint arthrocentesis in a rabbit model: technique and recommendations in the study of temporomandibular disorders

INTRODUCTION

Arthrocentesis has been used in the temporomandibular joint (TMJ) to analyze components of the synovial fluid or as a therapeutic procedure associated or not with the administration of a drug. The rabbit is one of the most commonly used animal species as a model for pathologies that affect the TMJ. The aim of this study was to propose a specific technique to perform arthrocentesis on the rabbit TMJ, emphasizing descriptions of reference points and measurements for a successful puncture without complications.

MATERIALS AND METHODS

Fourteen adult rabbits (Oryctolagus cuniculus) were used. The project was approved by the Scientific Ethics Committee of the Universidad de La Frontera (File Nº083/2016).

RESULTS

The description of the technique was divided into three steps: 1) Location of the rabbit TMJ, 2) Positioning of the needles in the TMJ, and 3) Passage of fluid through the TMJ.

CONCLUSIONS

This arthrocentesis technique could help to simplify the procedure and give the investigator a guide for joint washing and extraction of synovial fluid in the rabbit TMJ.

Development of an ultrathin sheet plastination technique in rat humeral joints with osteoarthritis induced by monosodium iodoacetate for neovascularization study

Injection with monosodium iodoacetate (MIA) is widely used to produce osteoarthritis (OA). Ultrathin sheet plastination has been used to study the morphology of structures, with strong application in anatomical education and research. Our aim was to carry out, for the first time, ultrathin sheet plastination of rat humeral joints to observe the neovascularization provoked by OA. We injected 0.1 mL of MIA into the left humeral joints of ten Sprague-Dawley rats. The right shoulders of the same rats were used as control. Sixteen weeks after the injection, the animals were euthanized and were given an immediate red epoxy resin injection through the thoracic aorta. The samples were fixed in 10% formalin, prior to the plastination process, without decalcification. Samples were dehydrated with acetone (100%) at - 25 °C, for 10 days. Later, for degreasing, samples were immersed in methylene chloride at room temperature during 1 week. Forced impregnation was performed inside a stove within a vacuum chamber. The plastinated blocks obtained were cut with a slow velocity diamond blade saw. Slices were placed in curing chambers to achieve curing and final tissue transparentation. 230 μm thickness slices were obtained. The slices were analyzed under magnifying glass and microscope, achieving visualization of OA neovascularization. The cartilage affected by OA loses its ability to remain avascular, and blood vessels invade it from the subchondral bone to the calcified and uncalcified cartilage. Ultra-thin sheet plastination is useful to observe articular cartilage neovascularization, caused by OA induced with MIA in humeral rat joint.

Injection in temporomandibular joint of rats. Description of technical protocol

The development of animal models for research has been very diffused. Osteoarthritis is a joint degenerative pathology that induces cartilage erosion, chondrocyte proliferation and osteophyte formation. The aim of this paper is to present a technical procedure to perform the injection of monosodium iodine acetate in the temporomandibular joints of rats to generate osteoarthritis and to contribute to future research analysis related to pathology progression and proper treatment performance. The use of rat models may be a complex process because of their size, but they can be compared to the human temporomandibular joint due to the similar characteristics and the possibility of performing diagnosis and treatment protocols in order to detect this pathology.

Novel resistance to imipenem associated with an altered PBP-4 in a Pseudomonas aeruginosa clinical isolate

A Pseudomonas aeruginosa (isolate 416) from a patient with pneumonia, was initially susceptible to imipenem (MIC: 2 mg/l) but became resistant to this antibiotic (isolate 470, MIC: 32 mg/l) during imipenem therapy. Treatment failed. No parallel increases in MIC were observed for other antimicrobials tested. Isolates 416 and 470 shared the same pyocin type and serotype, produced small amounts of an inducible beta-lactamase, and had similar lipopolysaccharide compositions. On electrophoresis of outer membrane proteins, the porin F, identified by the monoclonal antibody MA4-4, was expressed similarly by the two isolates but the production of one band (apparent molecular weight: 47,000) was diminished in isolate 470. [14C]-Imipenem labelling of intact cells proceeded more slowly in 470 than in 416, especially when bacterial cells were treated by antibody MA4-4 to block the porin F channel. [14C]-Imipenem labelling of penicillin binding proteins (PBP) showed that the band identified as PBP-4 bound markedly less radioactivity in isolate 470 than in 416. After isolate 470 was passaged several times in antibiotic-free broth, the imipenem MIC was decreased from 32 to 8 mg/l, and the [14C]-imipenem PBP pattern recovered the initial profile as exhibited by isolate 416. Two resistance mechanisms, affecting imipenem electively, could have combined their effect in the post-therapy isolate, altered target protein and reduced permeability.