Genetic architecture of ovary size and asymmetry in European honeybee workers.

The molecular basis of complex traits is increasingly understood but a remaining challenge is to identify their co-regulation and inter-dependence. Pollen hoarding (pln) in honeybees is a complex trait associated with a well-characterized suite of linked behavioral and physiological traits. In European honeybee stocks bidirectionally selected for pln, worker (sterile helper) ovary size is pleiotropically affected by quantitative trait loci that were initially identified for their effect on foraging behavior. To gain a better understanding of the genetic architecture of worker ovary size in this model system, we analyzed a series of crosses between the selected strains. The crossing results were heterogeneous and suggested non-additive effects. Three significant and three suggestive quantitative trait loci of relatively large effect sizes were found in two reciprocal backcrosses. These loci are not located in genome regions of known effects on foraging behavior but contain several interesting candidate genes that may specifically affect worker-ovary size. Thus, the genetic architecture of this life history syndrome may be comprised of pleiotropic, central regulators that influence several linked traits and other genetic factors that may be downstream and trait specific.

Influence of carrying a backpack on pelvic tilt, rotation, and obliquity in female college students.

The purpose of this investigation was to examine the influence of different methods of backpack carriage on pelvic tilt, obliquity and rotation of college-age females. Thirty subjects (mean age 22.4 years) participated in three conditions: walking without a backpack, carrying a backpack unilaterally, and carrying a backpack over both shoulders. The backpack was loaded with material that comprised 15% of the subject's body weight. Gait was analyzed using the Oxford Metrics VICON Clinical Manager system while the subject walked with no backpack, with a backpack unilaterally and bilaterally. Repeated measures analysis of variance was used to determine differences in angular motion and range of motion in pelvic tilt, rotation, and obliquity in three complete trials during the three walking conditions. Angular pelvic tilt was greatest with bilateral backpack carriage compared to unilateral carriage or walking without a backpack. Angles of pelvic obliquity and rotation were not changed across the three walking conditions. Range of motion for pelvic obliquity and rotation was significantly decreased when walking with a backpack. These results suggest that backpack carriage could cause permanent posture deviations in young female college students. More study is required to evaluate compressive forces during various walking conditions.

Overuse injuries in youth sports: biomechanical considerations.

Many children today participate in highly organized sports programs that involve regimented year-round repetitive training. This type of training has led to an increased incidence of overuse musculoskeletal injuries. Sports physicians have dealt with sports injuries in children for many years and, on the basis of their clinical experience, have developed guidelines to treat and to try and prevent these injuries. The purpose of this article is to provide a biomechanical perspective of sports injuries in young athletes and blend ideas from this perspective with more traditional clinical perspectives that dominate the literature relative to this topic. Basic tissue and gross movement mechanics principles are used to identify growth, morphological, and movement factors that may predispose a child to an overuse injury. Several biomechanical analyses of simple movement tasks are presented to quantify the forces developed in various tissues and to illustrate the effects that growth can have on these forces. Guidelines are given for developing injury prediction models that may be used in the future to establish safe and effective training guidelines for children.

Skiing orthosis for recurrent shoulder dislocation.

A functional orthosis has been designed and implemented with the Alpine skier in mind. The unique features include a stabilizing pelvic band and dynamic abduction and external rotation check straps. A case report is presented.