The postsurgical period during which neurons remain without target connections (chronic axotomy) and distal nerve stumps and target muscles are denervated (chronic denervation) deleteriously affects functional recovery. An autologous nerve graft and cross-suture paradigm in Sprague Dawley rats was used to systematically and independently control time of motoneuron axotomy, denervation of distal nerve sheaths, and muscle denervation to determine relative contributions of each factor to recovery failure. Tibial (TIB) nerve was cross-sutured to common peroneal (CP) nerve via a contralateral 15 mm nerve autograft to reinnervate the tibialis anterior (TA) muscle immediately or after prolonging TIB axotomy, CP autograft denervation, or TA muscle denervation. Numbers of motoneurons that reinnervated TA muscle declined exponentially from 99 ± 15 to asymptotic mean (± SE) values of 35 ± 1, 41 ± 10, and 13 ± 5, respectively. Enlarged reinnervated motor units fully compensated for reduced motoneuron numbers after prolonged axotomy and autograft denervation, but the maximal threefold enlargement did not compensate for the severe loss of regenerating nerves through chronically denervated nerve stumps and for failure of reinnervated muscle fibers to recover from denervation atrophy. Muscle force, weight, and cross-sectional area declined. Our results demonstrate that chronic denervation of the distal stump plays a key role in reduced nerve regeneration, but the denervated muscle is also a contributing factor. That chronic Schwann cell denervation within the nerve autograft reduced regeneration less than after the denervation of both CP nerve stump and TA muscle, argues that chronic muscle denervation negatively impacts nerve regeneration.

Older Mexican Americans with reduced handgrip strength at baseline demonstrated a statistically significant decline in cognitive function over a 7-year period. By contrast, participants in the highest handgrip strength quartile maintained a higher level of cognitive function.

Objectives-We examined frailty, particularly how diabetes and obesity impact disability and morbidity in Mexican American older adults.Methods-We studied the trajectory of frailty over 10 years in 2,049 Mexican Americans participating in the Hispanic Established Populations Epidemiologic Studies of the Elderly. A frailty index based on weight loss, exhaustion, grip strength, walking speed, and physical activity was computed and data were collected on sociodemographic and health status, comorbidities and performance-based functional measures.Results-The sample was 58% female with a mean age of 74.43 (sd = 6.04) at baseline. Analyses at 10 year follow-up revealed 75% of the surviving sample (N = 777) were classified as pre-frail or frail compared to 55% at baseline. 84% of persons identified as frail at baseline died by the end of follow-up. Baseline age, diabetes, arthritis, smoking status, body mass index, cognition, negative affect, and number of comorbid conditions were predictors of frailty at follow-up (R 2 = 0.29, p <. 05).Conclusions-Research is needed to reduce the number of Mexican American older adults who become frail and transition to disability and loss of independence. MeSH keywordsFrail elderly; Mexican Americans; health status; activities of daily living CONTRIBUTORSKenneth Ottenbacher was responsible for conceptualization of the longitudinal frailty component of the study and development of hypotheses. He contributed to writing and reviewing all sections of the paper and interpretation of data. James Graham assisted in data analysis, interpretation and contributed to writing discussion. Soham Al Snih conducted data analyses and prepared drafts of the results section. Mukaila Raji contributed to identification of covariates, interpretation of analyses, and prepared the methods section. Rafael Samper-Ternent contributed to management and analysis of the 2006 data and coding of variables. He also participated in writing results section. Glenn Ostir contributed to interpretation of data from all behavioral and psychological measures and helped prepare the methods section. He reviewed all aspects of the paper. Kyriakos Markides was responsible for overall design of the larger EPESE study and identification of variables and analyses of 1995/96 data. He also contributed to introduction, discussion and interpretation of longitudinal trends. HUMAN PARTICIPANT PROTECTION

Hand grip strength is an independent predictor of ADL disability among older Mexican American men and women. The hand grip strength test is an easy, reliable, valid, inexpensive method of screening to identify older adults at risk of disability.

Objective-Examine the association between frailty status and change in cognitive function over time in older Mexican Americans. Design-Data used are from the Hispanic Established Population for the Epidemiological Study of the Elderly (H-EPESE)Setting-Five Southwestern states: Texas, New Mexico, Colorado, Arizona, and California.Participants-1,370 non-institutionalized Mexican American men and women aged 65 and older with a Mini Mental State Examination (MMSE) ≥ 21 at baseline (1995−1996). Measurements-Frailty Financial disclosure: NoneSponsor's role: Had no role in the design, methods, subject recruitment, data collections, analysis and preparation of paper. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript slow walking speed (lowest 20% 16ft walk-time in seconds), and 5) low physical activity level (lowest 20% Physical Activity Scale for the Elderly (PASE) score). Socio-demographic factors, MMSE, medical conditions (stroke, heart-attack, diabetes, arthritis, cancer and hypertension), depressive symptoms and visual-impairment were obtained.Results-Of the 1370 subjects, 684 (49.9%) were not-frail, 626 (45.7%) were pre-frail (1 − 2 components) and 60 (4.4%) were frail (≥3 components) in 1995/96. Using general linear mixed models, we found that frail subjects had greater cognitive decline over 10-years compared with nonfrail subjects (Estimate = −0.67, SE = 0.13; p< .0001). This association remained statistically significant after controlling for potential confounding factors. Conclusion-Frail status in older MexicanAmericans with MMSE ≥ 21 at baseline is an independent predictor of MMSE score decline over a 10-year period. Future research is needed to establish pathophysiological components that can clarify the relationship between frailty and cognitive decline.