Age-related blood flow changes in the rat intrinsic laryngeal muscles.

CONCLUSIONS: These results indicate that a deceased laryngeal blood flow (BF) could be one contributing factor to age-related phonatory and airway dysfunction. OBJECTIVE: Studies of non-laryngeal muscles suggest that decreased BF may contribute to an age-related decline in muscle performance. We hypothesized that there is an age-related BF decrease to the intrinsic laryngeal muscles. MATERIALS AND METHODS: Intrinsic laryngeal muscle BF was measured in young (3-6 months old; n=11) and old (28-30 months old; n=21) male Fischer 344 rats during quiet respiration using the radiolabeled microsphere technique. RESULTS: BF to the posterior cricoarytenoid (PCA) was very high even during this submaximal recruitment, consistent with its specialization for oxidative metabolism and fatigue resistance. The results demonstrated significant (p<0.05) age-related BF decreases in the thyroarytenoid (young, 163; old, 64 ml/min/100 g), cricothyroid (young, 104; old, 52 ml/min/100 g), and PCA (young, 404; old, 235 ml/min/100 g).

Stereological estimates indicate that aging does not alter the capillary length density in the human posterior cricoarytenoid muscle.

Studies of some human skeletal muscles demonstrate an age-related capillarity decrease. An age-related decrease in blood flow to the posterior cricoarytenoid muscle (PCA) in rats has been reported, as well as a decreased ability to abduct the vocal folds. We, therefore, hypothesized that decreased muscle capillarity may contribute to PCA dysfunction in the elderly. Using immunological and stereological techniques, human PCAs (ages 18-98 yr; 28 men, 23 women) were examined for age-related changes in muscle fiber-type-specific and/or total capillary length density. While analysis shows no age-related changes in total muscle or fiber-type-specific capillary length densities (L(V cap)), there are significant age-related increases in L(V cap) within the interstitial tissue (P = 0.001) and in the ratio of the type I L(V cap) to type I surface (P = 0.002), with a strong trend for type II L(V cap) (P = 0.055). There is also an age-related decrease in the muscle fiber surface density for both type I and II fibers (P < 0.001 and 0.04, respectively). Data also show that women have a significantly higher type II L(V cap) (P = 0.039), regardless of age. In addition, with the exception of female type I L(V cap), all measured variables are significantly higher for type I fibers (P < 0.001), independent of age or sex. While data indicate there are age-related changes of capillary-muscle fiber relationships within the PCA, they do not support the hypothesis of an age-related loss of capillarity.

Defect repair in the rat mandible with bone morphogenic proteins and marrow cells.

OBJECTIVE: To investigate the ability of a bone growth factor mixture and bone marrow cells to repair a critical size defect of the rat mandibular body. DESIGN: Prospective, randomized controlled trial. SUBJECTS: Thirty-seven male Fischer rats. INTERVENTIONS: Critical size defects 4 mm in diameter were created in the left mandibular bodies of the rats. The defects were filled with a bone marrow cell suspension (group 1), a synthetic bone matrix consisting of bovine collagen and calcium hydroxyapatite cement (group 2), the matrix and marrow cells (group 3), the matrix with 100 micro g of bone growth factor mixture (group 4), or the matrix with bone growth factor mixture and marrow cells (group 5). Animals were killed after 8 weeks, and the nondemineralized specimens were processed histologically. Specimens from group 1 were not processed because there was no grossly appreciable bone regeneration. Stereologic techniques were used to determine and compare the volume fractions and volume estimates of mature bone, new bone, osteoid, marrow, remaining cement, and fibrous tissue in each defect. RESULTS: Volumes of mature bone, new bone, and remaining cement did not differ significantly among the groups (P =.30 for mature bone, P =.17 for new bone, and P =.34 for cement). However, group 4 and 5 specimens contained significantly more osteoid and larger marrow spaces than did the group 2 and 3 specimens (P<.001 for both). The specimens in groups 2 and 3 contained significantly more fibrous tissue ingrowth than did those in groups 4 and 5 (P<.001). CONCLUSION: The synthetic bone substitute containing bone growth factor mixture was effective in stimulating new bone and osteoid development in the rat mandibular model.