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The commonly held cause for using the closed lock technique is the prevention of disc sliding by using the non-reducible disc. The purpose of this study was to re-evaluate the pathogenesis of sudden and persistent severely limited mouth opening associated with a total lack of disc sliding in view of the fact that it is promptly released by lavage of the upper compartment of the temporomandibular joint (TMJ). The proposed pathogenesis is based upon earlier clinical and laboratory findings of the first author coupled with pertinent informtaion culled from the literature. It is suggested that sliding of the disc in the TMJ is enabled due to the presence of phospholipids protected by hyaluronic acid (HA) that constitute an efficient lubrication system. Joint overloading may be associated with uncontrolled production of reactive oxygen species (ROS) that causes degradation of the HA, followed by the exposure of the phospholipids to lysis by phospholipase A₂ (PLA₂). The denuded, smooth and elastic articular surfaces that possess high surface energy become strongly adherent when placed in direct physical contact with each other. The presence of an extremely thin film of fluid (sub-boundary lubrication) between the mating surfaces may cause even higher adhesion. These adhesive forces are probably responsible for the flexible disc anchorage to the fossa and/or eminence. They also explain the immediate release of the disc and rehabilitation of its sliding following arthrocentesis. Since it is uncommon for two opposing surfaces to be stripped bare and to become adherent, the likelihood of anchored disc phenomenon (ADP) occurring and recurring is very low. Copyright 2002 International Association of Oral and Maxillofacial Surgeons

Background. This in vitro study aimed to elucidate the extent and kind of involvement of hyaluronic acid (HA) in the currently accepted view of synovial joint lubrication, in which surface-active phospholipids (SAPL) constitute the main boundary lubricant. The integrity of SAPL is apparently threatened by the lysing activity of phospholipase A<inf>2</inf> (PLA<inf>2</inf>).
Methods. The effects of increasing concentrations of HA degraded by free radicals and non-degraded HA on the lysing activity of PLA<inf>2</inf> were examined in vitro. Liposomes (lipid model membrane) containing phosphatidylcholine (PC) were used as the substrate, on the assumption that they are appropriate representatives of SAPL.
Results. HA adhered to the phospholipid membrane (liposomes), inhibiting their lysis by PLA<inf>2</inf>. However, in its degraded form, HA not only failed to inhibit PLA<inf>2</inf>-lysing activity, but accelerated it.
Conclusions. It is reasonable to assume that HA plays an important indirect role in the steady state of the boundary lubrication process of joints by protecting SAPL from being lysed by PLA<inf>2</inf>. However, as excessive loading generates free radicals within the joint (among other effects), the HA that is degraded in this way is incapable of protecting SAPL from lysis by PLA<inf>2</inf>. When the rate of degradation exceeds that of synthesis, there will be insufficient replacement of HA and/or SAPL, resulting in denudation of the articular surfaces. These are then exposed to increasing friction, and hence increased danger of degenerative joint changes.

Primary extranodal lymphoma of the salivary gland is an extremely rare disease. In this report we describe twelve cases of primary lymphoma of the parotid gland seen at a single centre, and review the relevant literature.The 12 cases were treated in different departments and did not receive a uniform therapeutic approach. All three patients with Hodgkin's disease are still alive and two are in complete remission after initial radiotherapy. One of these cases developed stage 4 disease and had to receive combination chemotherapy subsequently. Of the 9 non-Hodgkin's lymphoma (NHL) patients, four had low grade NHL and 5 intermediate or high grade NHL. Of these, 2 died with disseminated disease. However, 6 are still alive and well from 1 to 5 years after therapy. These cases were treated with surgery alone, radiotherapy alone or combination chemotherapy with an anthracycline-bearing regimen. Consequently, we are unable to draw any conclusions relating the success of therapy in these cases, nor can we suggest therapeutic guidelines on the basis of this study alone.The treatment of parotid lymphoma is discussed briefly in the light of the available literature. In most cases, symptoms related to an enlarging mass in the parotid region, were evident. In the light of the above data, we suggest that, despite its rarity, lymphoma of the salivary gland should always be considered in the differential diagnosis of a parotid mass. No correlation between lymphoma and Sjogren's syndrome was noted in the present study.

A square-loop magnetic core model,\dot{\phi} = \dot{\phi}_{elastic}(F,\dot{F}) + \dot{\phi}_{inelastic} (F,\phi), has been incorporated into the automated circuit-analysis computer-program TRAC. The modified program, named MTRAC, includes supplementary provisions for successive modes of operation, nonlinear resistor and inductor models, normal and circuit-failure run termination, monitor printout for debugging, etc. Based on linearization of nonlinear circuit elements and Kirchoff's current law, the computation involves an iterative solution ofV] = T]/[H], whereV] is the nodal-voltage matrix andT] and [H] are known current and conductance matrices of the circuit. Expressions are derived for the contributions to the [H] andT] matrices of various linear and nonlinear circuit elements, including magnetic cores. The input core parameters are based on either\phi(F)orB(H)data. The organization of MTRAC and that of a circuit-element subroutine are outlined. Time variables (voltages, currents, MMFs, fluxes, etc.) of complex magnetic-core circuits (up to 60 nodes) are computed and plotted automatically. All that the user has to supply is the general run-control specifications, the circuit topology, and the values of the circuit-element parameters. An example is given for a core-diode shift register.

A case of a sublingual epidermoid cyst is presented. The advantages of contrast medium radiography in diagnosis, localization and surgical treatment planning are exemplified.

Experimental anaerobic infections in mice are reviewed with a description of a model of pure Bacteroides fragilis infection. In this experimental situation, B. fragilis produces large subcutaneous abscesses in the groins of mice that can be diagnosed without autopsy. This infection was treated effectively with clindamycin in doses that produced levels of drug in blood similar to those attainable in humans.