Past studies of the healing of the medial collateral ligament (MCL) in animal models have been conducted over a variety of healing intervals, some as early as 1 week. One concern with testing at early healing intervals is the difficulty in identifying and isolating the tissues that carry load. The purpose of this study was to determine if isolation of the MCL and healing time are critical factors in the assessment of structural strength in this model. Furthermore, the effect of immobilization on these critical factors was investigated. Our approach was to calculate the load-sharing ratio between the MCL and the MCL plus capsule. A 4 mm gap was created in the midsubstance of both hindlimb MCLs of 52 female New Zealand White rabbits (n = 104). Of these, 29 rabbits had their right hindlimb pin immobilized (immobilized group), leaving the left hindlimb non-immobilized. Testing was performed at 3 (n = 12), 6 (n = 22), and 14 (n = 24) weeks. The remaining 23 rabbits, which had both limbs non-immobilized (non-immobilized group), were tested at 3 (n = lo), 6 (n = 12), 14 (n = 12), and 40 (n = 12) weeks. For both groups, half of the specimens at each healing interval were used to test the MCL alone and half to test the MCL plus capsule, except for 3 week immobilized joints where only the MCL plus capsule was tested. Additionally, MCL (n = 12), MCL plus capsule (n = 6), and capsule alone (n = 5) were tested from normal animals. The load-sharing ratio at MCL failure for the normal joint was 89%, suggesting an MCL-dominated response. For the nonimmobilized group, the load-sharing ratio was 24% at 3 weeks of healing, suggesting a capsule-dominated response. At and after 6 weeks of healing, an MCL-dominated response was observed, with the ratio being 68% or greater. Thus, at less than 6 weeks of healing, the structural strength capabilities of the joint may be better represented by the medial structures rather than the isolated MCL. Immobilization delayed the transition from a capsule-dominated response to an MCL-dominated response in this model.
ABSTRACT. The Coquerel's sifakas were chosen for this study on hand preference because little is known about handedness in Indriidae. Fifteen Coquerel's sifakas were observed at the Duke University Primate Center as they fed on chopped fruit, vegetables, and primate chow. Analysis of age, sex, and hand preference indicated that the adult males both individually and as a group tended toward left-handedness. Adult females as a group did not show a trend in the direction of handedness. However, individual adult females showed consistent right-or left-hand preference. Younger sifakas tended toward ambipreference, suggesting that lateralization of hand preference is gradual, becoming more stable in adulthood. These findings suggest that sex and age may be strong indicators for lateralization of hand preference in Coquerel's sifakas.
Patients with familial adenomatous polyposis (FAP) have a cumulative lifetime risk of over 90% for developing duodenal adenomas, which are the precursor lesions for duodenal adenocarcinoma. Consequently, these patients have a 5% to 10% lifetime risk of periampullary or duodenal adenocarcinoma, making this the leading cause of cancer death in FAP patients who have had prophylactic colectomies. The increased relative risk of duodenal carcinoma in FAP patients and the poor outcomes associated with the treatment of advanced duodenal cancer have led to the development of prevention strategies for this cancer in the setting of FAP. It is generally accepted that surveillance for duodenal adenomas and adenocarcinomas should be included in the management of patients with FAP, although there are few data from clinical trials that demonstrate the effectiveness of surveillance strategies or chemoprevention for the prevention of death from duodenal cancer. Prospective case series have shown that endoscopic surveillance with endoscopic or surgical treatment of high-risk lesions in the duodenal or periampullary region can be performed with successful removal of the at-risk lesion(s). Surveillance should begin at about 21 years of age and should be performed using both an end-viewing and a side-viewing upper endoscope. An interval of 3 to 5 years between examinations appears to be adequate if no polyposis is evident. Once polyposis develops, an interval of 1 to 3 years between screenings for mild polyposis is appropriate. Patients with denser polyposis or larger adenomas are recommended to undergo examination every 6 to 12 months because of their increased risk of developing duodenal adenocarcinoma. Nonsteroidal anti-inflammatory drug therapy with sulindac, a nonselective cyclooxygenase (COX) inhibitor, or celecoxib, a COX-2 selective inhibitor, may be of benefit after the development of duodenal polyposis by inducing the regression or stabilization of the polyposis, although there is limited evidence from randomized, controlled trials to support its routine use. Almost all cases of adenocarcinoma occur in patients with advanced polyposis (Spigelman stage IV disease), and approximately 33% of this group will go on to develop adenocarcinoma if left untreated. The most definitive procedure for reducing the risk of adenocarcinoma is surgical resection of the ampulla and/or duodenum. Pancreaticoduodenectomy or pancreas-sparing duodenectomy are appropriate surgical therapies that are believed to substantially reduce the risk of developing periampullary adenocarcinoma. However, these procedures are associated with significant morbidity and mortality, including the risk of inducing desmoid tumor formation in FAP patients.
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