A comparison between bipedal and quadrupedal rats: do bipedal rats actually assume an upright posture?

STUDY DESIGN: A basic science animal investigation. OBJECTIVES: To determine if bipedal rats differ in upright posture compared with quadrupedal rats. SUMMARY OF BACKGROUND DATA: It has been reported that surgically induced bipedalism in the rat leads to habitual upright posture. Based on this finding, bipedal rats have been used to study the changes erect posture induces in bone, ligament, muscle, and intervertebral discs. Previous studies have used direct observation as a means to describe posture. This study is the first to quantify postural differences between bipedal and quadrupedal rats. METHODS: Eleven bipedal rats were created by forelimb and tail amputation within 24 hours of birth. Eleven quadrupedal rats served as controls. Specialized cages were used with infrared sensors, and a computer program measured the total amount of time in the upright stance, the number of stands, and the amount of horizontal movement in the upright stance. Statistical comparisons were made between bipedal and quadrupedal rats hourly and over a 24-hour period of time. RESULTS: Quadrupedal rats assumed an upright posture for a significantly greater amount of time than bipedal rats when monitored over 24 hours (P = 0.016). Quadrupedal and bipedal rats did not differ in the number of stands (P = 0.63) or in the amount of horizontal movement in the upright stance (P = 0.34) over 24 hours. Similar results were obtained when comparing hourly intervals. CONCLUSION: This study quantifiably indicates that bipedal rats do not assume a more erect posture and spend no more time in an upright position compared with quadrupedal rats. The upright posture may not be the cause of some previously reported anatomic changes observed in the bipedal rat.

Further development and validation of the Scoliosis Research Society (SRS) outcomes instrument.

STUDY DESIGN: Outcome study to determine response distribution, internal consistency, and validity of a Modified SRS Outcomes Instrument (MSRSI). OBJECTIVES: Refinement and validation of the SRS Outcomes Instrument for idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Experience with the SRS Outcomes Instrument suggested several refinements and the need for validation. METHODS: Following experience-based modification, the Modified SRS Outcomes Instrument and Short Form 36 (SF-36) questionnaires were administered to 35 previously surveyed postoperative idiopathic scoliosis patients. RESULTS: Thirty (86%) patients with an average age of 25 years returned the questionnaires at an average of 10 years postoperative. Distribution of scores was acceptable. Internal consistency utilizing Cronbach's alpha was 0.80, 0.81, 0.77, 0.89, and 0.88 for pain, self-image/appearance, function/activity, mental health, and satisfaction with surgery, respectively. Validity, determined by Pearson correlation coefficients with comparable SF-36 domains, was 0.70 or greater for 13 of the 14 relevant domains between SF-36 and MSRSI (P < 0.001). CONCLUSION: The SRS Outcomes Instrument is simple and internally consistent. Based on experience, a number of modifications have been made that improve the instruments scope and internal consistency. Finally, the instrument is valid in comparison to SF-36.

Does delay in acquiring childhood infection increase risk of multiple sclerosis?

Multiple sclerosis (MS) appears to be more common in technically advanced countries than in underdeveloped regions, and migration from one area to another at a young age affects the risk of acquiring MS. One way of explaining both the peculiar frequency distribution and the effect of migration while young is to postulate that an infection early in life decreases the chance of central demyelination. However, no specific infection has been implicated consistently. Alternatively, an aberrant host response to infection in childhood might induce central demyelination. Thus, the aberrant host response could be age-dependent. In seeking associations between age of infection and risk of MS, we observed a direct relationship: where childhood diseases were acquired early in life, the frequency of MS in that population was low; where childhood diseases tended to occur nearer adolescence, MS frequency in that population was high. Since immune responsiveness to antigenic challenges matures through early adolescence, we reason that early infection might be protective and that delay in acquiring childhood infections might increase the risk of developing MS. Indeed, in experimental models, the chance of inducing chronic relapsing central demyelination is increased by using adolescent rather than newborn or mature animals. In this paper, epidemiologic evidence showing the strong association between age of infection and risk of MS is presented.

Does delay in acquiring childhood infection increase risk of multiple sclerosis?

Multiple sclerosis (MS) appears to be more common in technically advanced countries than in underdeveloped regions and migration from one area to another at a young age affects the risk of acquiring MS. One way of explaining both the peculiar frequency distribution and the effect of migration while young is to postulate that an infection early in life decreases the chance of central demyelination. However, no specific infection has been implicated consistently. Alternatively, an aberrant host response to infection in childhood might induce central demyelination. Thus, the aberrant host response could be age-dependent. In seeking associations between age of infection and risk of MS, we observed a direct relationship: where childhood diseases were acquired early in life, the frequency of MS in that population was low; where childhood diseases tended to occur nearer adolescence, MS frequency in that population was high. Since immune responsiveness to antigenic challenges matures through early adolescence, we reason that early infection might be protective and delay in acquiring childhood infections might increase the risk of developing MS. Indeed, in experimental models, the chance of inducing chronic relapsing central demyelination is increased by using adolescent rather than newborn or mature animals. In this paper, epidemiologic evidence showing the strong association between age of infection and risk of MS is presented.