Roger B. Johnson

The bearable lightness of being: Bones, muscles, and spaceflight

Bones and muscles support and move the body. Tendons link the two tissues and serve as a mechanism for transfer of forces from muscle to bone. These three tissues interact and respond to periods of activity or inactivity with appropriate alterations in structure and strength. There is substantial evidence that an environment devoid of mechanical stress on the skeleton (such as reduced gravitational forces during spaceflight, a “microgravity envi ronment”) produces direct effects on bone structure and function. There is little agreement concerning the biologic mechanisms for these atrophic changes. Changes in fluid balance and distribution coincident to spaceflight also affect muscles and bones by an unknown mechanism. Tendon‐bone junctions are presumed to be spared from the effects of spaceflight. However, recent evidence from rodents suggests that spaceflight profoundly effects both the skeleton and the tendon‐bone junctions. These effects include cortical bone resorption, which undermines the Sharpeys fibers that anchor the tendon to the bone matrix. The challenge to biomedical scientists is to devise methods for protecting spaceflight crews from these atrophic changes; such protection would allow for longer and more extensive spaceflights. Anat. Rec. (New Anat.) 253:24–27, 1998.

Relationship between Oral Alveolar Bone Loss and Aging among African-American and Caucasian Individuals

Background: The periodontal attachment apparatus consists of the periodontal ligament, alveolar bone, cementum and supra-crestal connective tissue. They are interdependent and provide protection and support to the dentition. It is theorized that the integrity of the periodontal apparatus can be maintained throughout life by exercising comprehensive oral hygiene practices and routine dental care. Additionally, it appears to be unaffected by aging. As a consequence, the investigators performed a study to determine the effects of chronological aging on alveolar bone loss. Objective: The present study was conducted to determine the relationship between oral alveolar bone loss, oral hygiene, and aging among African-American and Caucasian populations. Methods: The population consisted of 229 individuals. There were 131 men and 98 women. With respect to race there were 89 African-Americans and 140 Caucasians. Oral examinations, oral hygiene and missing teeth determinations and bitewing radiographs were performed on all the individuals. Radiographs were digitized and measurements were made from the cementum/enamel junction to the alveolar bone crest. Measurements were made for both the maxillary and mandibular jaws. Results: The results of the study showed a significant multiple linear regression model relationship between oral bone loss and aging. Oral hygiene was a factor, but contributed only slightly to the overall model. Race, gender and the number of missing teeth were not significant variables in the overall model. Conclusion: The results of this study suggest age-related alveolar bone loss.

Comparative gender differences in local and systemic concentrations of pro-inflammatory cytokines in rats with experimental periodontitis.

BACKGROUND AND OBJECTIVE There have been few studies of gender differences in response to periodontitis. Thus, we compared gender-specific differences in systemic cytokine concentrations in rats with and without ligature-induced periodontitis. MATERIAL AND METHODS Experimental periodontal disease was initiated in Sprague-Dawley rats by placing a ligature around the crowns of the second right maxillary molar tooth. Sham-operated control groups were also created. Two weeks later, the right and left maxillary quadrants of teeth, liver and serum were collected from all the rats, and uterine horns were collected from the female rats. Liver and uterine samples were ground in phosphate-buffered saline (10 mg of tissue/mL of phosphate-buffered saline + protease inhibitor) containing a protease inhibitor, and cytokine concentrations were determined by enzyme-linked immunosorbent assay. Digital radiographs were made of maxillary quadrants, and the distance from cemento-enamel junction to alveolar crest was measured using image analysis software. Data were compared by factorial analysis of variance and a post-hoc Tukey test. RESULTS Female rats with ligatures had greater, but not significantly different, alveolar bone loss than males with ligatures. However, they had higher serum concentrations of interleukin-6, tumor necrosis factor-alpha and C-reactive protein, and liver C-reactive protein (p < 0.05). These females also had higher interleukin-6, tumor necrosis factor-alpha and vascular endothelial growth factor concentrations within the uterine horn, compared to female controls (p < 0.05). Male animals with ligatures had lower serum concentrations of C-reactive protein and higher interleukin-6 and tumor necrosis factor-alpha concentrations within serum, compared to male controls (p < 0.05). CONCLUSION Our study suggests that females with periodontal disease have a greater risk for inflammatory-based systemic diseases than males.

Use of saliva for assessment of stress and its effect on the immune system prior to gross anatomy practical examinations.

The objective of this study was to determine the longitudinal effects of a series of stressful gross anatomy tests on the immune system. Thirty‐six freshman occupational therapy students completed a written stress evaluation survey, and saliva samples were obtained at baseline and prior to each of three timed‐practical gross anatomy tests. Cortisol, secretory IgA (sIgA), and IL‐12 concentrations were measured within the salivary samples by enzyme‐linked immunosorbent assay. The total scores from the stress surveys were used as markers for environmental stress. Data were compiled for each student at baseline and prior to each examination and were compared by repeated‐measures MANOVA and Pearsons correlation test. Following normalization for protein concentration and flow rate, the concentrations of IL‐2, IL‐6, IL‐12, and sIgA progressively increased from baseline to the third test. Cortisol concentrations, following normalization for flow rate, were highest prior to the first test and became significantly reduced prior to second and third test. Prior to second and third test, salivary concentrations of IL‐6, IL‐2, IL‐12, and sIgA were significantly correlated (P < 0.05). In contrast, prior to third test, there was a negative correlation between salivary concentrations of cortisol and IL‐12 (P < 0.05). Progressive increases in salivary sIgA, IL‐6, IL‐2, and IL‐12 concentrations from the first to the third test coincident to decreased salivary cortisol suggest that the initial examination stressors precede significant effects on the immune system. These data suggest that there may be latent effects of examination stress on the immune system and that saliva can be used to predict these effects. Anat Sci Educ.

Association between maternal periapical lesions and brain inflammation in rat pups

OBJECTIVE The objective of this study was to determine whether the presence of maternal tooth periapical lesions was associated with foetal brain inflammation in a pregnant rat model. METHODS Sprague-Dawley rats were divided into two groups: pregnant rats with induced periapical abscesses (E, n=8) and sham-operated control pregnant rats (S, n=8). The pulps of the first and second maxillary right molars had been exposed and the tooth left open to the oral environment for two weeks prior to initiation of the pregnancy. Following delivery of the pups (E, n=99; S, n=101), each pup was decapitated and the brain was removed and immediately frozen in liquid nitrogen. The tissues were solubilized in PBS containing a protease inhibitor, and norepinephrine (NE), IL-6, IL-1-β, TNF-α, and myelin basic protein (MBP) were determined by ELISA. Group means were compared by factorial analysis of variance, a post hoc Tukey test, and Pearsons correlation test. p<0.05 was used to reject the null hypothesis. RESULTS E pups were significantly heavier than S pups. Brain tissue concentrations of IL-6, IL-1-β, and TNF-α were significantly higher and MBP and norepinephrine concentrations significantly lower in E pups than S pups. Concentrations of IL-6, TNF-α and IL-1-β were significantly correlated between E serum, pup birthweight, and E pup brain tissue. MBP, NE and IL-6 were significantly correlated within the brain tissues of E pups. CONCLUSION The data suggest that brain inflammation may be associated with maternal periapical inflammation. This association identifies a modifiable risk factor for adverse pregnancy outcomes.

Osteoclast distribution within the rat interdental septum coincident to experimental tooth movement using light forces

There is little quantitative information concerning the number and distribution of bone‐matrix resorbing osteoclasts (BMRO) within the adjacent alveolar bone coincident to tooth movement. We moved the right first maxillary molar tooth anteriorly in 40 female rats (E), the left side was untreated, serving as an internal control (IC). Forty female age and weight matched rats were untreated, serving as external controls (EC). BMRO were identified on periosteal and endosteal surfaces of the interdental septum from 1–5 days after initial force application using the MTB‐322 antibody. The number of BMRO at periosteal surfaces of E was greater in IC and EC from 2–5 days (P < 0.001). Similarly, the number of BMRO at endosteal surfaces was greater from 1–5 days (P < 0.001). The number of BMRO at periosteal and endosteal surfaces was greater within E than within EC from 1–5 days (P < 0.001). Outcome data from IC were often significantly different from EC. Our data suggest that relatively low forces increase the number of BMRO, which are not uniformly distributed onto both periosteal and endosteal surfaces. Thus, the interdental septum resorbs at the alveolar wall and within spaces between the trabeculae, which, taken together, results in net removal of bone from areas of compression. These data also suggest that experimental tooth movement produces significant differences in the number and distribution of BMRO within IC and EC. Thus, EC groups should be included in studies of tooth movement. Anat Rec, 290:74–82, 2007.

Sex Differences in Inflammatory and Apoptotic Signaling Molecules In Normal and Diseased Human Gingiva

BACKGROUND The purpose of this study is to determine whether sex dimorphism exists in the expression of inflammatory and apoptotic mediators in gingiva obtained from normal and diseased sites of periodontal disease. METHODS Gingival papillae were obtained from individuals (56 males and 62 females) who required extraction of adjacent teeth. Gingival samples were grouped by adjacent sulcus depth: 1 to 3 mm (normal), 3 mm with bleeding on probing (slight disease), 3 to 6 mm (moderate disease), and >6 mm (severe disease). The tissue concentrations of cysteine-requiring aspartate-directed protease 3 (caspase-3), interleukin-2, tumor necrosis factor-related apoptosis-inducing ligand, Fas ligand, p38α mitogen-activated protein kinase, extracellular signal-related kinase 1/2, and survivin were determined by enzyme-linked immunosorbent assay. These mediator concentrations, age of donor, sex of donor, and gingival sulcular depth were the outcome variables. Data were compared by factorial analysis of variance, post hoc Tukey, and Pearson correlation test. P <0.05 was used to indicate significant differences among the outcome variables. RESULTS The mean gingival sulcular depth was significantly greater in male than in female groups (P <0.05). The majority of the tested mediators were significantly correlated with both sex and sulcular depth and with caspase-3 (P <0.05). The concentration of caspase-3 in female gingiva at all diseased sites was significantly greater than in gingiva derived from male sites (P <0.05). CONCLUSIONS These data suggest sex dimorphism in the presence of gingival apoptosis at sites of periodontal disease, with females having the highest incidence of apoptosis. Because apoptosis clears inflammatory cells and promotes healing, this phenomenon could provide a mechanism for sex dimorphism for the incidence of periodontal disease.