Specificity of meal pattern analysis as an animal model of determining temporomandibular joint inflammation/pain.

Analyzing feeding behavior, and in particular meal duration, can be used as a biological marker for temporomandibular joint (TMJ) inflammation/pain. The present study determined the specificity of meal duration as a measure of TMJ inflammation/pain in a rodent model. The model was also used to test the efficacy of dexamethasone (DEX) as a treatment for TMJ inflammation/pain that was induced by TMJ injection of complete Freund's adjuvant (CFA). In the first study, anesthetized male Sprague-Dawley rats housed in computerized feeding modules received bilateral intra-articular knee injections of CFA or saline. The next day, CFA-injected rats had significant knee swelling and impaired mobility. Food intake in the CFA-injected group was reduced over the next two days and this was due to reduced meal number with no change in meal size. Notably, meal duration was normal in both the CFA and saline knee-injected groups. In the second study, male rats were assigned to one of four groups: Group 1, no CFA and no DEX treatment; Group 2, no CFA and treatment with DEX (0.4 mg/kg i.m. once daily); Group 3, bilateral TMJ CFA injection and no DEX treatment; and Group 4, bilateral TMJ CFA injection and treatment with DEX. CFA significantly increased TMJ swelling and stress-induced chromodacryorrhea in Group 3, but treatment with DEX attenuated these effects in Group 4. Compared to the controls, meal duration was significantly lengthened 24 and 48 h post-CFA injection in Group 3, whereas DEX treatment attenuated TMJ swelling, chromodacryorrhea and normalized meal duration. The data demonstrate that meal pattern analysis, and in particular meal duration, can be used as a non-invasive specific measure of TMJ inflammation/pain and can be used as a marker of DEX treatment efficacy.

Meal pattern changes associated with temporomandibular joint inflammation/pain in rats; analgesic effects.

Establishing a valid animal model to study temporomandibular joint (TMJ) pain has proven extremely difficult. Using complete Freund's adjuvant (CFA) to induce TMJ inflammation, we recently showed that meal pattern analysis could be used as a noninvasive biological marker to study TMJ pain in an animal model. The purpose of this study was to further validate our animal model by determining whether aspects of CFA-induced TMJ inflammation/pain are reversed with ibuprofen (IBU) treatment. In the first trial, 48 male rats were used and in the second trial, 32 female ovariectomized rats, given 17beta-estradiol replacement, were used. The rats were assigned to one of four groups: control (CON-CON); control+IBU (CON+IBU); CFA-CON; and CFA+IBU. In the male trial, CFA injection (P<.01) caused TMJ swelling and chromodacryorrhea (CFA-CON); IBU eliminated these changes in the CFA+IBU group. Meal pattern analysis showed the pertinent CFA-induced change and the IBU effect was that meal duration was increased in the CFA-CON group (P<.01), but normal in the CFA+IBU-treated group on the first, but not second, day postinjection. In the female trial, CFA increased TMJ swelling, but did not cause significant chromodacryorrhea (CFA-CON); IBU eliminated swelling in the CFA+IBU group. Meal duration was increased (P<.01) in the CFA-CON group, but was normal in the CFA+IBU-treated group on both the first and second days postinjection. In both trials, interleukin-1beta (IL-1beta) levels were increased similarly in CFA-CON and CFA+IBU groups (P<.01). This study shows that CFA-induced TMJ inflammation/pain can cause changes in meal patterns (i.e., meal duration), which may be used as a behavioral marker for TMJ inflammation/pain.

Tgf-beta1, Tgf-beta2, Tgf-beta3 and Msx2 expression is elevated during frontonasal suture morphogenesis and during active postnatal facial growth.

OBJECTIVES: It is hypothesized that regulation of facial suture morphogenesis is similar to that of cranial sutures, with expression of similar regulatory molecules, governing suture formation and patency. The present study was designed to characterize the morphology of the frontonasal (FN) suture of the rat at different developmental stages and to investigate the presence and temporal-spatial expression of transforming growth factor-beta 1 (Tgf-beta1), Tgf-beta2, Tgf-beta3 and Msx2 mRNA within these structures. SETTING AND SAMPLE POPULATION: The Department of Biomedical Sciences at Texas A&M University System Health Science Center, Baylor College of Dentistry, Dallas, TX USA. Histological sections and RNA isolated from FN suture tissues of Sprague-Dawley rats, aged embryonic day 16 through postnatal day 20. METHOD: Sections were examined after immunohistochemical staining. Gene expression was determined by densitometric analysis of RT-PCR products run on agarose gels. RESULTS: FN sutures develop slightly later than cranial sutures and show increased complexity over time when compared to cranial sutures. FN sutures were closely associated with the nasal capsular cartilage, with intervening layers of perichondrium and periosteum. The pattern of expression of Tgf-betas within the FN suture tissues was similar to that seen in the cranial sutures. However, mRNA and protein of the Tgf-betas were differentially expressed over time compared to cranial sutures. In FN sutures, Tgf-beta mRNA levels were elevated both during the period of suture morphogenesis and during active bone growth from the suture in the early postnatal period. Msx2 mRNA expression was elevated in both the prenatal and postnatal periods, similar to Tgf-beta mRNA expression. CONCLUSION: Tgf-beta and Msx2 are present in facial sutures similar to cranial sutures, but are differentially expressed over time, perhaps reflecting different bone growth rates from these sutures.

Maximum shortening velocity and myosin heavy-chain isoform expression in human masseter muscle fibers.

While human masseter muscle is known to have unusual co-expression of myosin heavy-chain proteins, cellular kinetics of individual fibers has not yet been tested. Here we examine if myosin heavy-chain protein content is closely correlated to fiber-shortening speed, as previously reported in other human muscles, or if these proteins do not correlate well to shortening speeds, as has been demonstrated previously in rat muscle. Slack-test recordings of single, skinned human masseter fibers at 15 degrees C revealed maximum shortening velocities generally slower and much more variable than those recorded in human limb muscle. The slowest fiber recorded had a maximum shortening velocity (V0) value of 0.027 muscle lengths x s(-1), several times slower than the slowest type I fibers previously measured in humans. By contrast, human limb muscle controls produced V0 measurements comparable with previously published results. Analysis by gel electrophoresis found 63% of masseter fibers to contain pure type I MyHC and the remainder to co-express mostly type I in various combinations with IIA and IIX isoforms. V0 in masseter fibers forms a continuum in which no clear relationship to MyHC isoform content is apparent.

Meal pattern analysis in response to temporomandibular joint inflammation in the rat.

Inflammation of the temporomandibular joint (TMJ) can alter behavioral responses such as food intake and mobilize stress hormones. The hypothesis of this study was that food intake and diurnal corticosterone analysis can be used as indicators of adjuvant-induced TMJ inflammation. Groups of rats received adjuvant or no injections at the beginning of the resting (AM) or activity (PM) phase. Forty-eight hours (early) or 6 weeks (late) after adjuvant injection, plasma corticosterone was assayed and food intake was recorded. Food intake was suppressed up to 4 days post-injection. As expected, the non-injected group showed low AM and high PM corticosterone. AM corticosterone was elevated, but PM corticosterone was attenuated in both early- and late-stage-injected rats. A computerized pair-fed experiment showed that adjuvant-induced hypophagia did not alter corticosterone levels. Meal pattern analysis revealed decreased food intake due to a decrease in the number of meals taken. Notably, meal size remained the same but meal duration increased. This model demonstrated that food intake and stress hormone analysis could be used as indicators for sequelae of adjuvant-induced TMJ inflammation.

Implications of temporomandibular disorders for facial growth and orthodontic treatment.

The purpose of this article is to review the literature concerning the possible associations between temporomandibular disorders (TMD), orthodontic therapy, mandibular growth, and facial form. Consideration of the association between TMD and orthodontic treatment leads to one conclusion: there is no evidence that orthodontic treatment generally increases or decreases the chances of developing TMD later in life. Still, our understanding of TMD is not final, and the expanding diagnostic knowledge continues to call for new longitudinal studies focusing on the developmental basis of temporomandibular disorders. Little is known about the potential effect of TMD on facial development. However, information relating to the normal development, growth, and adaptation of the temporomandibular joint all tend to emphasize the significant ontogenetic plasticity of the growth-related secondary cartilage associated with the TMJ, within the bounds of normal function and histophysiology. With the exception of such diseases as juvenile rheumatoid arthritis and osteoarthritis, little is known about the influence of TM pathology or myofascial disorders on facial growth. Also, little is known about the possible influence of disc interferences on facial growth. However, the condyle is known to play a prominent role in normal mandibular growth and, consequently, facial development. Thus, categories of TMD that involve dysplasia of the condylar cartilage could be associated with aberrant facial growth and form.

Histomorphologic analysis of the soft palate musculature in prenatal cleft and noncleft A/Jax mice.

The two specific aims of this study were as follows: to evaluate the appropriateness of the A/Jax mouse model in the investigation of the key cellular stages in prenatal soft palate morphogenesis and myogenesis; and to describe structural differences in the histomorphology of the soft palate anatomy from cleft and noncleft mice prior to, during, and after palatogenesis. Cleft-induced and control groups of A/Jax mouse embryos from timed pregnancies were harvested sequentially on gestational days 15 to 19. Embryos were weighed and staged for external body morphology. The heads were removed and fixed for light microscopy, sectioned serially in the frontal plane at 10 microns and stained with hematoxylin-eosin to characterize and compare the soft palate musculature. All observations were made at the head depth of the trigeminal ganglion in both age- and stage-matched embryos. The following findings were made: (1) the A/Jax mouse is a suitable animal model for the study of soft palate myogenesis; (2) there were no discernible morphologic differences between the soft palate muscles in cleft and noncleft A/Jax mice when viewed under light microscopy; (3) the soft palate and related muscles were identifiable as muscle fields, in both the cleft and noncleft fetuses, as early as gestational day 15 and as specific muscles at gestational day 18; (4) in both the cleft and noncleft A/Jax fetuses, the soft palate muscles appeared in a sequential anatomic fashion (the palatine aponeurosis appeared first, next the tensor palatini, and then the levator palatini muscles); and (5) in the cleft palate fetuses, both pterygoid plates were angulated and displaced laterally.

Condylar adaptation after alteration of vertical dimension in adult rhesus monkeys, Macaca mulatta.

Remodeling in the cartilage of the mandibular condyle was investigated in young adult monkeys after an increase in vertical dimension of the midface through the use of a tooth-borne intraoral appliance. Six young adult male rhesus monkeys had bite-splints of 5 mm, 10 mm or 15 mm cemented to their maxillary dentition for 48 weeks. Five age- and sex-matched monkeys were used as controls. The thickness of the articular tissue and of the prechondroblastic and chondroblastic layers of the condylar cartilage in the superior, posterosuperior and posterior regions was measured from parasagittal sections of the temporomandibular joint (TMJ). It was found that articular tissue thickness was reduced in the superior region; the prechondroblastic layer, absent in control animals, was very distinctive (30-75 microns) in experimental animals; and there was a 62% increase in the thickness of the chondroblastic layer in the experimental animals. These findings indicate that chronic alteration of mandibular posture via increase in vertical dimension stimulates progressive remodeling of the mandibular condyle in young adult monkeys.

Myosin expression in the jaw-closing muscles of the domestic cat and American opossum.

Sodium dodecylsulphate-polyacrylamide gel electrophoresis (SDS-PAGE), glycerol SDS-PAGE, two-dimensional electrophoresis, and protein immunoblotting techniques were used to identify myosin heavy chain (MHC) and light chain (MLC) isoforms in limb and masticatory muscles of the cat and American opossum. The fibre types in which these isoforms are expressed were identified by histochemistry and immunohistochemistry. Antibodies specific for the type IIM MHC isoform characteristic of cat jaw-closing muscles and the type I MHC isoform were produced and characterized. The IIM antibody stained the majority of fibres found in the jaw-closing muscles of both species. These IIM-containing fibres characteristically had a histochemical ATPase that remained active after both acid and alkali pre-incubations. A minority of type I fibres was also present in cat jaw-closing muscles, and these reacted positively with antibody specific for type I MHC. It was confirmed that the vast majority of fibres in the cat jaw-closing muscles contained only the characteristic masticatory MHC (IIM) and masticatory MLCs (LC1m and LC2m). These muscles did not contain either the type II fibre isoforms of limb muscles or the atrial cardiac (alpha-cardiac) MHC. The type IIM MHC could also be identified in jaw-closing muscles of the opossum. Two-dimensional gel electrophoresis was used to identify the MLC composition of single, histochemically defined, type I fibres in the cat soleus and deep masseter. The type I fibres of limb muscle contained the usual slow MLCs, but type I fibres from the jaw-closing muscles contained only the masticatory light chains.

Evaluation of the beta energy spectrum from a distributed uranium mill tailings source.

The beta energy spectra from uranium mill tailings, 90Sr with different absorber thicknesses, and a uranium metal slab were measured and compared to select an appropriate beta source for calibrating a personal dosimeter to measure shallow dose equivalent when exposed to uranium mill tailings. The measured beta energy spectrum from the 90Sr source, with a 111 mg cm-2 cover thickness, was selected as a possible calibration source for a personnel dosimeter. The dose equivalent rate to the skin at 1 cm from a distributed tailings source of infinite thickness, with a 226Ra activity of 56 Bq g-1 (1.5 x 10(3) pCi g-1), was measured to be 0.024 mSv h-1 (2.4 mrem h-1).

Effect of maxillomandibular fixation on condylar growth in juvenile Macaca mulatta: a cephalometric and histologic study.

The effect of maxillomandibular fixation on the growth of the mandibular condyle was studied in eight control and eight experimental male juvenile monkeys. All animals had metallic implants placed throughout the craniofacial complex in order to facilitate cephalometric analysis of growth-related changes in the maxillomandibular complex during jaw immobilization. Every 3, 6, 12, and 24 wk after insertion of the appliance two experimental animals were killed for histologic analysis. Cephalometric analysis indicated no major deviation from normal maxillary or mandibular growth in the experimental animals. The condylar growth in the experimental animals was comparable with that of the controls. Histologic analysis indicated that the articular connective tissue in experimental joints remained the same thickness as in the controls. On the postero-superior aspect of the condyle, the thickness of the prechondroblastic-chondroblastic cell layer was reduced by 70-80% in the experimental animals. On the posterior aspect this cell layer was not visible after 12 wk of fixation, but was replaced by a periosteum-like, cell-rich tissue which appeared to be active in appositional formation of cancellous bone. These results indicate that long-term maxillomandibular fixation does not cause major alterations in the growth of condyle or the entire mandible despite a profound decrease of the prechondroblastic-chondroblastic cell layer in the postero-superior and posterior regions of the condyle. The growth is probably due to a compensatory appositional bone formation along the surface of the condyle. It is also concluded that jaw mobility is not a prerequisite for normal maxillary or mandibular growth.

Autoradiographic study of the effects of pulsed electromagnetic fields on bone and cartilage growth in juvenile rats.

Application of pulsed electromagnetic fields (PEMF) has been used in growth and repair of non-union bone fractures. The similarities between the fibrocartilage callus in non-union bone fractures and the secondary cartilage in the mandibular condyle, both histologically and functionally, lead naturally to study the effects of PEMFs on growth in the condyle. The purposes of this study were: (1) to describe the effects of PEMFs on the growth of the condyle using autoradiography, [3H]-proline and [3H]-thymidine, and (2) to differentiate between the effects of the magnetic and electrical components of the field. Male pre-adolescent Sprague-Dawley rats (28 days old) were divided into three experimental groups of five animals each: (1) PEMF-magnetic (M), (2) PEMF-electrical (E) and (3) control, and were examined at three different times-3, 7 and 14 days of exposure. Each animal was exposed to the field for 8 h per day. Histological coronal sections were processed for quantitative autoradiography to determine the mitotic activity of the condylar cartilage and the amount of bone deposition. The PEMF (magnetic or electrical) had statistically significant effects only on the thickness of the articular zone, with the thickness in the PEMF-M group being the most reduced. Length of treatment was associated with predictable significant changes in the thickness of the condylar cartilage zones and the amount of bone deposition.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth of the mandible following replacement of the mandibular condyle with the sternal end of the clavicle: an experimental investigation in Macaca mulatta.

This study was designed to investigate the long-term effects of transplanted clavicles to the temporomandibular joint (TMJ) in juvenile monkeys. Sixteen juvenile female monkeys (Macaca mulatta) were used in this experiment. Eight animals were used as controls and were allowed to grow undisturbed for an 18-month period (group control). Eight animals were divided into two groups and underwent bilateral condylar excision via extraoral vertical ramus osteotomies. Four of these animals had their condylar segments removed and immediately replaced to serve as surgical controls (group condyle). The other four underwent condylar replacement with the sternal end of their clavicles (group SCJ). Standardized lateral cephalometric radiographs with the aid of tantalum bone markers were used to evaluate maxillary and mandibular growth. One-way analysis of variance (ANOVA) was used to determine the significance of differences between groups. All animals showed good mandibular function and a class I molar relationship following an 18-month evaluation period. Statistical analysis showed there was no significant difference in maxillary or mandibular growth between any of the three groups. The results of this investigation show that the sternal end of the clavicle may be a viable option in mandibular condylar transplant surgery.

Influence of asymmetric occlusal relationships and decreased maxillary width on the growth of the facial skeleton in the guinea pig.

The purpose of this study was to evaluate the effect of muscle function and occlusal form on mandibular growth in guinea pigs. We hypothesized that restriction of maxillary width and asymmetric function of the mandible would lead to mandibular asymmetry. The hard palate of 12 animals was exposed at the age of ten days, and cyanocrylate was used to close the midpalatal suture in order to restrict transverse maxillary growth. The right incisors and right molars were ground obliquely at the time of surgery and every two weeks thereafter until the animals were sacrificed 4, 8 and 12 weeks later (four animals in each time group). Six age-matched animals served as controls. Dorsoversal x-rays were taken at sacrifice, followed by the removal of small biopsies from six different sites of the maxillomandibular skeleton for biochemical studies, which will be reported separately. Relative to controls, the treated animals exhibited a narrow maxilla and asymmetry in the height of the ramus and in the length of the mandible from the mental foramen to the angular process. The maximum width between the angular processes of the mandible was extremely narrow, as was the condylar neck especially on the right side. It was concluded that abnormal masticatory muscle function caused by occlusal deviation led to a narrowing and a slight asymmetry of the mandible in the growing guinea pig.

Proteinase, phosphatase and glucuronidase activities in the growing mandible and temporomandibular joint of the guinea pig.

This study investigated the effect of muscle function and occlusal form on the activity levels of several enzymes present in the mandible or temporomandibular joint of the guinea pig. Restriction of maxillary width and asymmetric function of the mandible was caused in 12 animals at the age of 10 days, as described in the accompanying paper (Isotupa et al. 1992). Tissue samples from six anatomical sites were obtained from the animals sacrificed 4, 8, or 12 weeks after manipulation (4 animals in each group). Six age-matched animals acted as controls. Five samples were from the following sites of the mandible: the condylar cartilage, the lower and upper parts of processus angularis, and the anterior and posterior halves of the condyle neck. A sample was also obtained from fossa mandibularis of the temporal bone. Buffer extracts of powderized samples were studied for acid and alkaline phosphatase, glucuronidase and two types of proteolytic activity. Although the asymmetric manipulation of occlusion caused observable, localized asymmetric growth, the enzyme findings were not consistently asymmetric. Manipulation generally increased all enzyme activities regardless of whether apposition or resorption was involved. The activities of alkaline phosphatase more consistently showed this pattern, and changes in enzyme activities seemed to be sensitive, reflecting cellular or molecular level of growth. The enzyme activities may also reflect a certain type of after-effect of irritation, or a healing period. The inclusion of several types of enzyme determinations is recommended to complete macroscopic measurements. Subsequent chromatographic and electrophoretic studies are also useful.

Uranium in vitro bioassay action level used to screen workers for chronic inhalation intakes of uranium mill tailings.

A uranium in vitro bioassay (urinalysis) action level was derived for use at the Department of Energy's Uranium Mill Tailings Remedial Action Project sites to identify chronic inhalation intakes of uranium mill tailings causing 0.5 mSv (50 mrem) annual effective dose equivalent. All radionuclides in the 238U decay chain that contribute 1% or more to the annual effective dose equivalent from an inhalation intake of uranium mill tailings were included in the derivation of the urinalysis action level. Using a chronic inhalation intake model, the uranium urinalysis action level for a 24-h urine sample, collected on a quarterly schedule, was calculated to be 1.5 micrograms.

Making a challenge out of an NLN visit: any more questions?

Any educator, regardless of experience, feels apprehension as the final preparations are made for a National League for Nursing (NLN) review. Recognizing that 70% of our faculty had never experienced the review process, school administrators decided to take a novel approach to prepare faculty for the NLN visit. The authors discuss program development for a faculty workshop that modeled a popular television game show.