We have used site-specific heavy-atom labelling and X-ray diffraction to localize single amino acid residues in the cytoplasmic domain of the integral membrane protein rhodopsin, the dim-light photoreceptor of retinal vertebrate rod cells. Two-dimensional orthorhombic crystals of the space group p22(1)2(1)(a=59.5(+/-1) A and b=82.7(+/-1.5) A) were produced from detergent-solubilized, partially delipidated rhodopsin. To obtain milligram amounts of two-dimensional crystals, which are required for X-ray diffraction, the yield of the crystalline material was significantly increased by reconstitution of rhodopsin in the presence of cholesterol (1:2 to 1:10 mol/mol) and by adding polar organic solvents to the dialysis buffer. The native cysteine residues C140 and C316 were then selectively labelled with mercury using the sulphydryl-specific reagent p-chloromercuribenzoate (1.6-2.1 mol Hg per mol rhodopsin). The labelling did not affect the unit cell dimensions. Optical absorption spectra of labelled and native two-dimensional rhodopsin crystals showed the characteristic 11-cis-retinal peak at 498 nm, which corresponds to the dark state of rhodopsin. The in-plane position of the mercury label was calculated at 9.5 A resolution from the intensity differences in the X-ray diffraction patterns of labelled and native crystals using Fourier difference methods and the phase information from electron crystallography. The label positions were in excellent agreement with the positions of C140 at the cytoplasmic end of helix 3 and of C316 in the cytoplasmic helix 8 recently obtained from three-dimensional rhodopsin crystals. Whereas these high-resolution diffraction studies were performed under cryogenic conditions (100 K), our results were obtained at room temperature with fully hydrated membranes and in the absence of loop-loop crystal contacts. To study the structural changes of the cytoplasmic loops involved in activation and signal transduction, our more physiological conditions offer important advantages. Furthermore, the localization of C316 is the first direct proof that the electron density on top of helix 1 observed by cryo-electron microscopy is a part of the C-terminal loop. Our approach is of particular interest for investigations of other membrane proteins, for which 3D crystals are not available. Structural constraints from heavy-atom labels at strategic sites enable the assignment of a position in the amino acid sequence to features visible in a low-resolution density map and the study of conformational changes associated with different functional states of the membrane protein.

Background: Dementia is a common syndrome in the geriatric population. Subsequent impairment of cognitive functioning impacts the patient's mobility, ADLs, and IADLs. It is suggested that older persons with lower levels of cognition are less likely to achieve independence in ADLs and ambulation (1-2). Frequently, nursing home residents are viewed as too frail or cognitively impaired to benefit from exercise rehabilitation. Often, persons with Mini Mental State Score (MMSE) score below 25 are excluded from physical rehabilitation programs. However, Diamond (3) and Goldstein (4) concluded that geriatric patients with mild to moderate cognitive impairment were just as likely as cognitively intact patients to improve in functional abilities as a result of participation in exercise rehabilitation programs. Purpose: The objective of this study is to compare, through a meta-analysis endurance and strength outcomes of Cognitively Impaired (MMSE < 23) and Cognitively Intact (MMSE superior 24) older adults who participate in similar exercise programs. Methods: Published articles were identified by using electronic and manual searches. Key search words included exercise, training, strength, endurance, rehabilitation, cognitive impairment, cognition, MMSE, older adult, aged, and geriatrics. Articles were included if the were from RCTs or well-designed control studies. Results: A total of 41 manuscripts met the inclusion criteria. We examined 21 exercise trials with cognitively impaired individuals (CI=1411) and 20 exercise trials with cognitively intact individuals (IN=1510). Degree of cognitive impairment is based on the reported MMSE score. Moderate to large effect sizes (ES = dwi, Hedges gi) were found for strength and endurance outcomes for the CI groups (dwi =.51, 95% CI=. 42-.60), and for the IN groups (dwi =. 49, 95% CI=. 40 -.58). No statistically significant difference in ES was found between the CI and IN studies on strength (t=1.675, DF= 8, P=.132), endurance (t=1.904, DF= 14, P=.078), and combined strength and endurance effects (t=1.434, DF= 56, P=. 263). Conclusions: These results suggest that cognitively impaired older adults who participate in exercise rehabilitation programs have similar strength and endurance training outcomes as age and gender matched cognitively intact older participants and therefore impaired individuals should not be excluded from exercise rehabilitation programs.

The transformation from a foraging way of life to a reliance on domesticated plants and animals often led to the expansion of agropastoralist populations at the expense of hunter-gatherers (HGs). In Africa, one of these expansions involved the Niger-Congo Bantu-speaking populations that started to spread southwards from Cameroon/Nigeria approximately 4,000 years ago, bringing agricultural technologies. Genetic studies have shown different degrees of gene flow (sometimes involving sex-biased migrations) between Bantu agriculturalists and HGs. Although these studies have covered many parts of sub-Saharan Africa, the central part (e.g. Zambia) was not yet studied, and the interactions between immigrating food-producers and local HGs are still unclear. Archeological evidence from the Luangwa Valley of Zambia suggests a long period of coexistence ( approximately 1,700 years) of early food-producers and HGs. To investigate if this apparent coexistence was accompanied by genetic admixture, we analyzed the mtDNA control region, Y chromosomal unique event polymorphisms, and 12 associated Y- short tandem repeats in two food-producing groups (Bisa and Kunda) that live today in the Luangwa Valley, and compared these data with available published data on African HGs. Our results suggest that both the Bisa and Kunda experienced at most low levels of admixture with HGs, and these levels do not differ between the maternal and paternal lineages. Coalescent simulations indicate that the genetic data best fit a demographic scenario with a long divergence (62,500 years) and little or no gene flow between the ancestors of the Bisa/Kunda and existing HGs. This scenario contrasts with the archaeological evidence for a long period of coexistence between the two different communities in the Luangwa Valley, and suggests a process of sociocultural boundary maintenance may have characterized their interaction. Am J Phys Anthropol 2010.(c) 2009 Wiley-Liss, Inc.

OBJECTIVE: To determine by meta-analysis whether physical exercises are beneficial for people with dementia and related cognitive impairments. DATA SOURCES: Published articles and nonpublished manuscripts from 1970 to 2003 were identified by using electronic and manual searches. Key search words included exercise, rehabilitation, activities of daily living, dementia, Alzheimer's disease, aged, and geriatrics. STUDY SELECTION: Reviewed studies were limited to randomized trials evaluating exercise in persons 65 years of age or older with cognitive impairment. Studies included quantitative results (means, standard deviations, t tests, F tests) for physical fitness, physical functioning, cognition, or behavior outcomes. DATA EXTRACTION: One reviewer extracted data on study characteristics and findings. Selected articles were evaluated for methodologic quality by 2 raters. DATA SYNTHESIS: A total of 2020 subjects participated in the 30 trials that met the inclusion criteria. Summary effects were computed using a fixed effects (Hedge's g(i)) model. Significant summary effect sizes (ES) were found for strength (ES=.75; 95% confidence interval [CI],.58-.92), physical fitness (ES=.69; 95% CI,.58-.80), functional performance (ES=.59; 95% CI,.43-.76), cognitive performance (ES=.57; 95% CI, 0.43-1.17), and behavior (ES=.54; 95% CI,.36-.72). The overall mean ES between exercise and nonexercise groups for all outcomes was .62 (95% CI,.55-.70). CONCLUSIONS: Exercise training increases fitness, physical function, cognitive function, and positive behavior in people with dementia and related cognitive impairments.

PURPOSE: We conducted a cross-sectional study examining potentially modifiable factors associated with cognitive impairments (mild or severe) in older whites, African Americans and Hispanics attending an outpatient eye clinic. METHODS: In-clinic interviews and physical examinations assessed social, demographic and health information from 100 consecutive Hispanic, African-American and white adults aged > or = 55. Our primary outcome was presence of any cognitive impairment (mild or severe) using the St. Louis University Mental Status Examination (SLUMS) scale. RESULTS: Of the 100 subjects, 65 screened positive for cognitive impairments on the SLUMS cognitive instrument: 46 with mild cognitive impairment and 19 with severe impairment (possible dementia). African-American and Hispanic adults (nonwhites) were significantly more likely to have cognitive impairment compared to white adults (OR 2.80: 95% CI = 1.05-7.44), independent of age, years of education and systolic blood pressure. Subjects with diabetes also had increased odds of cognitive impairments (OR 3.28, 95% CI = 1.21-8.90) even after adjusting for relevant confounders. There was a nonsignificant trend between visual acuity impairment and cognitive impairment (p = 0.059). CONCLUSIONS: Sixty-five percent of adults aged > or = 55 attending the eye clinic screened positive for cognitive impairments, with higher rates among nonwhites and adults living with diabetes.

Metastasis (the spread of cancer from a primary tumor to secondary organs) is responsible for most cancer deaths. The ability to follow the fate of a population of tumor cells over time in an experimental animal would provide a powerful new way to monitor the metastatic process. Here we describe a magnetic resonance imaging (MRI) technique that permits the tracking of breast cancer cells in a mouse model of brain metastasis at the single-cell level. Cancer cells that were injected into the left ventricle of the mouse heart and then delivered to the brain were detectable on MR images. This allowed the visualization of the initial delivery and distribution of cells, as well as the growth of tumors from a subset of these cells within the whole intact brain volume. The ability to follow the metastatic process from the single-cell stage through metastatic growth, and to quantify and monitor the presence of solitary undivided cells will facilitate progress in understanding the mechanisms of brain metastasis and tumor dormancy, and the development of therapeutics to treat this disease. Magn Reson Med, 2006. Published 2006 Wiley-Liss, Inc.