Infection with a gram-negative organism stimulates gingival collagenase production in nondiabetic and diabetic germfree rats

Experimental diabetes in the rat rapidly produces a shift in the gingival crevicular microflora which is followed, within weeks, by increased production of collagenase by the gingival tissues. To assess the contribution of endogenous (hormonal or metabolic) and exogenous (altered crevicular microflora) factors on this diabetes-induced abnormality in collagenase production, the following series of experiments was undertaken: In each experiment, the germfree rats were housed in two isolators. Half of the animals in both isolators were rendered diabetic (D) with streptozotocin while the remainder were left untreated (non-diabetic (ND) controls). All of the germfree ND and D rats in one isolator of the pair were then infected with either a Gram-positive (S. mitis or A. odontolyticus) or a Gram-negative (Capnocytophaga, A. aclmomycetemcomitans or B. gingivalis) organism. In the other isolator, the ND and D rats were maintained in their germfree state. After 3 wk, the germfree and monoinfected rats were killed and the gingiva (and in one experiment, skin) were dissected. Collagenase activity produced by gingiva in culture (or extracted from gingiva or from skin) was measured using ¹⁴C-collagen fibrils (or [³Hmethyl] collagen molecules) as the substrate. Diabetes increased the collagenolytic activity in the gingiva and skin of the germfree rats. Infecting the germfree rats with a Gram-positive organism had no effect on collagenase activity generated by the gingival explants in the tissue culture system. In contrast, infection with any of the Gram-negative organisms dramatically increased the collagenase activity in the gingival tissues of the ND rats in culture, an effect not seen in the D group of rats using this system. However, monoinfection with B. gingivalis did increase collagenase activity in the extracts of gingiva (but not in skin) from both ND and D rats, with the latter group showing the highest level of enzyme activity. We suggest (i) that experimental diabetes stimulates collagenase production in gingiva by both endogenous (hormonal) and exogenous (bacterial) mechanisms, and (ii) that crevicular Gram-negative organisms stimulate collagenolysis in the adjacent gingival tissues by releasing bacterial products (e.g. endotoxins) which penetrate into the connective tissue and enhance host cell collagenase production.     

Diabetes increases collagenase activity in extracts of rat gingiva and skin

The connective tissues of diabetic humans and experimental animals exhibit abnormalities in collagen metabolism including an increased production of collagenolytic enzymes by gingival explants in tissue culture. In the current study, gingival tissue and skin were obtained from control and diabetic rats, the latter on the 5th, 10th, 15th, and 22nd day after inducing the disease with streptozotocin. Extracts of the tissues were assessed for collagenase activity using either ¹⁴C-labeled collagen fibrils or Peptide-P as substrate and by detecting collagenase digestion products by SDS-polyacrylamide gel electrophoresis. Elastase was measured using the specific substrate, succinyl-(L-Alanyl)₃-p-nitroanilide. Diabetes increased the activity of collagenase in extracts of gingiva and skin; elastase, however, was increased dramatically only in the latter tissue. These findings (1) indicate that diabetes-induced enhanced gingival collagenase activity occurs in vivo as well as in vitro and (2) explain, at least in part, the greater loss of collagen in skin than in gingiva of the diabetic rat and other complications such as unusually severe periodontal breakdown.     

Percutaneous Management of Accidentally Retained Foreign Bodies During Image-Guided Non-vascular Procedures: Novel Technique Using a Large-Bore Biopsy System

Objective

To describe a novel percutaneous image-guided technique using a large-bore biopsy system to retrieve foreign bodies (FBs) accidentally retained during non-vascular interventional procedures.

Materials and Methods

Between May 2013 and October 2015, five patients underwent percutaneous retrieval of five iatrogenic FBs, including a biopsy needle tip in the femoral head following osteoblastoma biopsy and radiofrequency ablation (RFA); a co-axial needle shaft within a giant desmoid tumour following cryoablation; and three post-vertebroplasty cement tails within paraspinal muscles. All FBs were retrieved immediately following original procedures under local or general anaesthesia, using combined computed tomography (CT) and fluoroscopic guidance. The basic technique involved positioning a 6G trocar sleeve around the FB long axis and co-axially advancing an 8G biopsy needle to retrieve the FB within the biopsy core. Retrospective chart review facilitated analysis of procedures, FBs, technical success, and complications.

Results

Mean FB size was 23 mm (range 8–74 mm). Four FBs were located within 10 mm of non-vascular significant anatomic structures. The basic technique was successful in 3 cases; 2 cases required technical modifications including using a stiff guide-wire to facilitate retrieval in the case of the post-cryoablation FB; and using the central mandrin of the 6G trocar to push a cement tract back into an augmented vertebra when initial retrieval failed. Overall technical success (FB retrieval or removal to non-hazardous location) was 100 %, with no complications.

Conclusion

Percutaneous image-guided retrieval of iatrogenic FBs using a large-bore biopsy system is a feasible, safe, effective, and versatile technique, with potential advantages over existing methods.

     

Recurrent Brown’s Syndrome after Superior Oblique Tendon Recession Treated by Silicone Spacer

Introduction: Undercorrections have been reported after a number of surgical procedures for Brown’s syndrome. The reason for late undercorrections is not clear but may be related to the heterogeneous etiology of Brown’s syndrome.

Purpose: We report a patient with late undercorrection after superior oblique tendon recession for Brown’s syndrome that was partially relieved by a silicone spacer placed nasally.

Results: We noted on surgical exploration that the superior oblique tendon had attached to the sclera under the nasal border of the superior rectus. Further weakening of the tendon was achieved by a No. 240 band expander that resulted in improvement of adduction in elevation.

Conclusion: Undercorrections following surgery for Brown’s syndrome can be relieved by further weakening the superior oblique muscle. However, as late undercorrections have been reported, the optimal timing of surgery is not certain.     

Rotary Nickel-Titanium GT and ProTaper Files for Root Canal Shaping by Novice Operators: A Radiographic and Micro–Computed Tomography Evaluation

IntroductionThe purpose of this study was to assess canal preparation outcomes in vitro by novice clinicians after standardized teaching sessions.MethodsAll students received a training session. In experiment 1, twenty canals of mandibular molars were prepared with GT and ProTaper rotaries by 10 students. Standardized radiographs were exposed before and after canal preparation, and canal curvature was measured; canals were assessed for patency and preparation time. In experiment 2, mandibular molars (20 canals) were submitted to microcomputed tomography before and after canal preparation with ProTaper and GT rotaries by 2 dental students. Canals were metrically assessed for changes (volume, surface, cross-sectional shape, transportation) during canal preparation by using software.ResultsIn experiment 1, canal curvature decreased by 7.6° and 7.8° for GT and ProTaper preparations; there were no broken instruments, and 2 canals lost patency. The time for GT preparation was longer than for ProTaper (29.7 ± 6.8 vs 19.4 ± 8.1 minutes, P <.05). In experiment 2, canal volumes and surface areas increased (P < .001), and prepared canals were rounder in cross-section and more tapered. Mean canal transportation ranged between 0.14 ± 0.05 mm and 0.23 ± 0.09 mm for apical and coronal canal thirds. There were no significant differences between the instruments or the operators regarding center of mass shifts; qualitative and quantitative data for canal transportation were similar to earlier studies with experienced operators.ConclusionsBoth rotary instruments performed adequately with inexperienced operators who received a brief structured training session.     

Fast track method for the identification of multi–drug resistant tuberculosis on direct clinical specimen using combined drug media

ObjectiveTo combine isoniazid (INH) and rifampicin (RIF) in a single media to detect and evaluate multi-drug resistant Mycobacterium tuberculosis (MDR-TB) strains using clinical specimens by direct and indirect drug susceptibility testing (DST).MethodsDrug susceptibility testing for INH and RIF using individual and combined drug media was performed by minimum inhibitory concentration (MIC) method on direct clinical specimens.ResultsThe combined drug media showed complete concordance with individual drug media in the detection of MDR-TB by direct DST method and 89% efficiency with indirect DST method. Susceptibility results were available by 3 weeks after the receipt of clinical specimen using direct DST on combined drug media.ConclusionsCombined drug media can be used as a fast track method in large scale studies warranting detection of MDR-TB.     

The temporal impulse response function in infantile nystagmus

Despite rapid to-and-fro motion of the retinal image that results from their incessant involuntary eye movements, persons with infantile nystagmus (IN) rarely report the perception of motion smear. We performed two experiments to determine if the reduction of perceived motion smear in persons with IN is associated with an increase in the speed of the temporal impulse response. In Experiment 1, increment thresholds were determined for pairs of successively presented flashes of a long horizontal line, presented on a 65-cd/m2 background field. The stimulus-onset asynchrony (SOA) between the first and second flash varied from 5.9 to 234 ms. In experiment 2, temporal contrast sensitivity functions were determined for a 3-cpd horizontal square-wave grating that underwent counterphase flicker at temporal frequencies between 1 and 40 Hz. Data were obtained for 2 subjects with predominantly pendular IN and 8 normal observers in Experiment 1 and for 3 subjects with IN and 4 normal observers in Experiment 2. Temporal impulse response functions (TIRFs) were estimated as the impulse response of a linear second-order system that provided the best fit to the increment threshold data in Experiment 1 and to the temporal contrast sensitivity functions in Experiment 2. Estimated TIRFs of the subjects with pendular IN have natural temporal frequencies that are significantly faster than those of normal observers (ca. 13 vs. 9 Hz), indicating an accelerated temporal response to visual stimuli. This increase in response speed is too small to account by itself for the virtual absence of perceived motion smear in subjects with IN, and additional neural mechanisms are considered.