The B3 Subunit of the Cone Cyclic Nucleotide-gated Channel Regulates the Light Responses of Cones and Contributes to the Channel Structural Flexibility.

Cone photoreceptor cyclic nucleotide-gated (CNG) channels play a pivotal role in cone phototransduction, which is a process essential for daylight vision, color vision, and visual acuity. Mutations in the cone channel subunits CNGA3 and CNGB3 are associated with human cone diseases, including achromatopsia, cone dystrophies, and early onset macular degeneration. Mutations in CNGB3 alone account for 50% of reported cases of achromatopsia. This work investigated the role of CNGB3 in cone light response and cone channel structural stability. As cones comprise only 2-3% of the total photoreceptor population in the wild-type mouse retina, we used Cngb3(-/-)/Nrl(-/-) mice with CNGB3 deficiency on a cone-dominant background in our study. We found that, in the absence of CNGB3, CNGA3 was able to travel to the outer segments, co-localize with cone opsin, and form tetrameric complexes. Electroretinogram analyses revealed reduced cone light response amplitude/sensitivity and slower response recovery in Cngb3(-/-)/Nrl(-/-) mice compared with Nrl(-/-) mice. Absence of CNGB3 expression altered the adaptation capacity of cones and severely compromised function in bright light. Biochemical analysis demonstrated that CNGA3 channels lacking CNGB3 were more resilient to proteolysis than CNGA3/CNGB3 channels, suggesting a hindered structural flexibility. Thus, CNGB3 regulates cone light response kinetics and the channel structural flexibility. This work advances our understanding of the biochemical and functional role of CNGB3 in cone photoreceptors.

Acetylcholine receptors in the retinas of the α7 nicotinic acetylcholine receptor knockout mouse.

PURPOSE: The α7 nicotinic acetylcholine receptor (nAChR) is widely expressed in the nervous system, including in the inner retinal neurons in all species studied to date. Although reductions in the expression of α7 nAChRs are thought to contribute to the memory and visual deficits reported in Alzheimer's disease (AD) and schizophrenia , the α7 nAChR knockout (KO) mouse is viable and has only slight visual dysfunction. The absence of a major phenotypic abnormality may be attributable to developmental mechanisms that serve to compensate for α7 nAChR loss. We hypothesized that the upregulation of genes encoding other nAChR subunits or muscarinic acetylcholine receptor (mAChR) subtypes during development partially accounts for the absence of major deficiencies in the α7 nAChR KO mouse. The purpose of this study was to determine whether the deletion of the α7 nAChR subunit in a mouse model resulted in changes in the regulation of other cholinergic receptors or other ion channels in an α7 nAChR KO mouse when compared to a wild-type (WT) mouse. METHODS: To examine gene expression changes, we employed a quantitative real-time polymerase chain reaction (qPCR) using whole retina RNA extracts as well as RNA extracted from selected regions of the retina. These extracts were collected using laser capture microdissection (LCM). The presence of acetylcholine receptor (AChR) subunit and subtype proteins was determined via western blotting. To determine any differences in the number and distribution of choline acetyltransferase (ChAT) amacrine cells, we employed wholemount and vertical immunohistochemistry (IHC) and cell counting. Additionally, in both WT and α7 nAChR KO mouse retinas, the distribution of the nAChR subunit and mAChR subtype proteins were determined via IHC for those KO mice that experienced mRNA changes. RESULTS: In the whole retina, there was a statistically significant upregulation of α2, α9, α10, ß4, nAChR subunit, and m1 and m4 mAChR subtype transcripts in the α7 nAChR KO mice. However, the retinal layers showed complex patterns of transcript expression. In the ganglion cell layer (GCL), m2 and m4 mAChR subtype transcripts were significantly upregulated, while ß3 and ß4 nAChR subunit transcripts were significantly downregulated. In the inner portion of the inner nuclear layer (iINL), α2, α9, ß4, nAChR subunit, and m3 and m4 mAChR subtype transcripts were significantly downregulated. In the outer portion of the inner nuclear layer (oINL), ß2, ß4, and m4 AChR subunit transcripts were significantly upregulated. Western blot experiments confirmed the protein expression of α3-α5 and α9-containing nAChR subunits and m1-m2 mAChR subtypes in mouse retinas. IHC results supported many of the mRNA changes observed. Finally, this is the first report of α9 and α10 nAChR subunit expressions in the retina of any species. CONCLUSIONS: Rather than a simple upregulation of a single AChR subunit or subtype, the absence of the α7 nAChR in the KO mice was associated with complex layer-specific changes in the expression of AChR subunits and subtypes.

Older adults in cardiac rehabilitation: a new strategy for enhancing physical function.

PURPOSE: This study contrasted the effect of a group-mediated cognitive-behavioral intervention (GMCB) versus traditional cardiac rehabilitation (CRP) upon changes in objective and self-reported physical function of older adults [mean (SD) age of 64.7 (7.5) yr] after 3 months of exercise therapy. METHODS: This randomized clinical trial enrolled 147 participants who were eligible for inclusion into cardiac rehabilitation. Baseline to 3-month changes in self-reported and performance related measures of physical function were assessed using a physical functioning questionnaire, a 6-min walk test, and measured MET levels. RESULTS: Paired t-tests revealed that participants made improvements in all measures across the first 3 months of the study, irrespective of group treatment (P < 0.001). General linear models including effects for baseline levels of physical function, treatment, and gender revealed that lower functioning men in the GMCB treatment made greater improvements than any other subgroup on the two performance outcomes: 6-min walk and measured MET levels (P < 0.01). Gender did not moderate change in self-reported level of physical function (P > 0.05); however, the lower functioning participants in the GMCB intervention experienced greater improvements in self-reported physical function than those in CRP (P < 0.05). CONCLUSIONS: Exercise therapy is a valuable intervention for improving physical function of older adults with cardiovascular disease (CVD) and those at increased risk for CVD. Baseline level of physical function and gender are important variables to consider when studying the relationship between exercise therapy and improvements in physical function.

Eight-month follow-up of physical activity and central adiposity: results from an Internet-delivered randomized control trial intervention.

BACKGROUND: Less than half of U.S. adults engage in the recommended amount of physical activity (PA). Internet-delivered PA programs increase short-term PA but long-term adherence is largely equivocal. PURPOSE: To determine whether increased PA following the 16-week Internet-delivered Active Living Every Day (ALED-I) program is maintained 8 months later in sedentary and overweight rural adults. METHODS: In our previous randomized controlled trial (N = 32; 18 intent-to-treat controls, 14 ALED-I interventions), the ALED-I group increased PA (+1384 steps/day; E.S. = 0.95) and reduced central adiposity. Nine original intervention participants and ten delayed intent-to-treat control participants completed ALED-I and an 8-month followup. Pedometer-measured PA, anthropometric variables, and cardiometabolic disease risk factors were assessed at baseline, postintervention, and at 8 months. RESULTS: Control crossover participants increased PA (+1337 steps/ day; P = .04). Eight months following completion of ALED-I (N = 19), PA levels relapsed (-1340 steps/day) and were similar to levels before the intervention (6850 +/- 471 steps/day vs. 6755 +/- 543 steps/day; P = .89). Total cholesterol and triglycerides improved, -9.9% and -18.2%, respectively, and reductions in central adiposity were maintained (97.1 +/- 2.2 cm vs. 97.2 +/- 2.2 cm; P = .66). CONCLUSIONS: The ALED-I intervention was efficacious in the short-term but did not produce longer-term adherence to PA. Future theory-based internet-delivered interventions that produce habituation of increased PA are warranted.

Internet-delivered behavior change program increases physical activity and improves cardiometabolic disease risk factors in sedentary adults: results of a randomized controlled trial.

OBJECTIVES: To determine whether the Active Living Every Day (ALED-I) internet-delivered theory-based physical activity (PA) behavior change program increases PA and improves cardiometabolic disease risk factors (CDRF) in sedentary overweight adults. METHODS: The study was a randomized control trial that took place in southern Wyoming and northern Colorado from 2005-2007. Thirty-two men and women (21-65 years) were randomized to a 16-week ALED-I intervention (n=14; age=41.4+/-3.7 years; BMI=32.3+/-1.3 kg/m(2)) or a delayed intent-to-treat control condition (n=18; age=49.4+/-1.7 years; BMI=30.6+/-0.8 kg/m(2)). At baseline and post-intervention, PA by pedometer and CDRFs were measured. RESULTS: Both groups had similar baseline PA levels. ALED-I increased PA by an average of 1384 steps/day (p=0.03) compared to 816 steps/day (p=0.14) for the control group. Waist circumference (100.6+/-2.4 vs. 96.6+/-2.7 cm) and Coronary Risk Ratio (5.1+/-0.3 vs. 4.7+/-0.3) decreased in the ALED-I group and did not change in the control group (99.2+/-2.2 vs.99.8+/-2.1 cm) and (3.7+/-0.1 vs. 3.7+/-0.1), respectively. CONCLUSIONS: The internet-delivered ALED program increased PA and improved some CDRFs in sedentary overweight/obese adults. To our knowledge, this is the first efficacy trial of the internet-delivered ALED program. Further studies are warranted due to the reach and cost-effectiveness of internet-delivered PA programs.