Influence of a short-term increase in intraluminal pressure, with and without recovery, on ACh-induced dilation in senescent skeletal muscle feed arteries.

Influence of a short-term increase in intraluminal pressure, with and without recovery, on ACh-induced dilation in senescent skeletal muscle feed arteries. John W. Seawright1 and Christopher R. Woodman1,2 1. Vascular Biology Laboratory, Dept. of Health and Kinesiology, Texas A&M University, College Station, TX 77843 2. Dept of Veterinary Physiology and Pharmacology, Texas A&M University, College Station, TX 77843 We tested the hypothesis that a short-term increase in intraluminal pressure, to mimic a 1 h bout of exercise, would attenuate or reverse age-induced impairments in acetylcholine (ACh)-induced dilation in soleus muscle feed arteries (SFA). In addition, we hypothesized that improved endothelial function would persist following a 2 h recovery period at normal pressure. SFA were isolated from young (4 mo) and old (24 mo) Fischer 344 rats. SFA were cannulated and pressurized at 90 (p90) or 130 (p130) cm H2O for 1 h. At the end of the 1-h treatment period, p130 SFA were lowered to 90 cm H2O and ACh-induced vasodilation was assessed. In a separate group of SFA, pressure was raised to 130 cm H2O for 1 h and subsequently lowered to 90 cm H2O for a 2 h recovery period. ACh-induced vasodilator responses were significantly blunted in old p90 SFA relative to young p90 SFA. Pre-treatment with increased pressure (p130) for 1 h improved ACh-induced dilation in old (not young) SFA. The beneficial effect of pressure in old SFA was not apparent after a 2 h recovery period. To determine the importance of nitric oxide in endothelium-dependent dilation in pressure treated vessels, old SFA were pressurized at 130 cm H2O for 1 h, reset to p90, and ACh-induced vasodilator responses were assessed in the absence or presence of a NOS Inhibitor (L-NNA). Results indicate that the beneficial effect of pressure treatment on ACh-induced dilation was eliminated in the presence of L-NNA. Collectively, these results indicate that a short-term (1 h) increase in intraluminal pressure improves endothelium-dependent dilation in old SFA due to enhanced nitric oxide bioavailability. Contrary to our hypothesis, the beneficial effect of pressure did not persist following a 2 h recovery period. Research supported by AHA grant 0765043Y (CRW), AHA grant 4150031 (CRW), and a Sydney and J.L. Huffines Institute of Sports Medicine Graduate Student Research Grant (JWS). First author classification: Doctoral Studen

SNP-induced Dilation Following a Short-term Intraluminal Pressure Increase in Aged Skeletal Muscle Feed Arteries

A decline in peripheral vascular function occurs with age and is associated with an increased risk for cardiovascular disease. Moderate, aerobic exercise has been documented to improve or reverse the age-related decline in vascular function. The signal(s) associated with exercise responsible for the improvement in vascular function is not known; however, increased intraluminal pressure that occurs during a bout of exercise has been proposed to play an integral role. Previously, we reported that exposure to a short-term increase in intraluminal pressure improves endothelium-dependent vasodilator responses in aged arteries. The purpose of this study was to determine whether pressure treatment enhances endothelium-independent vasodilator responses. We hypothesized that a short-term (1 h) increase in intraluminal pressure, to mimic the intraluminal pressure believed to be present during a 1 h bout of exercise, would not improve endothelium-independent vasodilator responses. Soleus muscle feed arteries from young (4 month) and old (24 month) Fischer 344 rats were isolated, cannulated, and pressurized at 90 (P90) or 130 (P130) cmH20 for 1 h. Following the 1 h pressure treatment, intraluminal pressure was lowered to 90 cmH20 for all vessels and SNP-induced vasodilation was assessed immediately or following a 2 h recovery period. SNP-induced dilation was significantly blunted in old P90 SFA when compared to young P90 SFA. Pre-treatment with increased intraluminal pressure for 1 h improved SNP-induced vasodilator responses and abolished the age group difference between the old and young SFA. Maximal dilation to SNP was greater in the young P130 compared to the young P90 SFA. The effects of the 1 h increased intraluminal pressure treatment were no longer present following a 2 h recovery period. Collectively, these results indicate that treatment of aged arteries with a short-term increase in intraluminal pressure to mimic pressure during a bout of exercise improves endothelium-independent dilation in aged arteries. In addition, these results suggest that a short-term increase in intraluminal pressure, associated with a single bout of exercise, is one signal contributing to the beneficial effect of exercise on vasodilator responses in aged arteries

Association of Restriction Fragment Length Polymorphisms among Maize Inbreds with Agronomic Performance of Their Crosses

Restriction fragment length polymorphisms (RFLPs) have been suggested as molecular markers to facilitate improvement of agronomic traits in maize (Zea mays L.). The objective of this study was to evaluate the utility of RFLP data in elucidating heterotic patterns among maize lines. Eight maize inbred lines and their 28 singlecross hybrids werevaluated for grain yield at two Iowa locations in each of 2 yr in a randomized-complete block design. The diallel mating design permitted estimation of general and specific combining ability effects. Restriction fragment length polymorphism analysis of inbred lines included five restriction enzymes and five eDNA and 28 genomic clones distributed over the maize genome. Restriction fragment length polymorphism patterns of crosses were predicted from analysis of the inbred parents. Genetic distances between inbred lines were estimated as modified Rogers\u27 distance (MRD). Grain yield and specific combining ability were significantly correlated with MRD for six of the 10 chromosomes. Dispersion of inbred lines and hybrids for RFLP allele frequencies was generally consistent with expectations based on known pedigrees. Results from this study suggest RFLP analysis as a potential alternative to field testing when attempting to assign maize inbred lines to heterotic groups

Hardy-Weinberg and linkage equilibrium estimates in the BSSS and BSCB1 random mated populations

Because maize (Zea mays) is an annual species those working with it must frequently make crosses to preserve and periodically maintain populations. Random mating is performed either using hand-pollination techniques or in wind-pollinated isolated blocks. Eighty-two restriction fragment length polymorphism (RFLP) markers were used to examine samples of random mated, hand-pollinated BSSS(R) and BSCB1(R) maize populations to find out whether their genotypic proportions conformed to predicted outcomes of random mating. The majority of loci conformed to expectations for Hardy-Weinberg equilibrium (HWE). Excess homozygosity was observed at 87% of the loci where the null hypothesis of HWE was rejected. For pairs of polymorphic loci, linkage equilibrium was observed in the BSSS(R) and BSCB1(R) progenitor populations (fewer than 5% of all tests rejected the null hypothesis of equilibrium at the P≤0.05 significance level). The BSSS(R)CO, BSCB1(R)CO and BSCB1(R)C12 populations showed slight increases in the proportion of pairs of loci in linkage disequilibrium compared to the progenitors (approximately 8.4% of all pairs of loci rejected the null hypothesis at the P≤0.05 significance level). BSSS(R)C12 was an extreme outlier with 25.0% of all pairs of polymorphic loci displaying significant (P≤0.05) linkage disequilibrium. This result was likely caused by the artificial grouping of three BSSS(R)CO plants with 97 BSSS(R)C12 plants during sampling. Results from principal components analysis of all individuals based on RFLP alleles supported this interpretation. Overall, most of the observed deviations from equilibrium were likely to have been caused by positive assortative mating in the case of HWE, and natural selection for epistatic effects between unlinked loci in the case of linkage disequilibrium

Genetic Diversity for Restriction Fragment Length Polymorphisms: Relation to Estimated Genetic Effects in Maize Inbreds

Restriction fragment length polymorphisms (RFLPs) have been proposed for investigating relationships among inbred lines and predicting heterosis and performance of single-cross hybrids in maize (Zea mays L.). Such use was evaluated in 20 maize inbreds classified as first-cycle, second-cycle, good, and poor lines, and in diallel crosses within types. Eight generations (parents, F1, F2, F3, backcrosses, and backcrosses selfed) from 67 crosses were evaluated for grain yield in five Iowa environments. Genetic effects were estimated from generation means by ordinary diallel analyses and the Eberhart-Gardner genetic model. Poor inbreds showed significantly greater average heterosis than did good lines. Estimates of additive ✕ additive epistatic effects were negative and highly significant in all except first-cycle lines. Using two restriction enzymes and 82 genomic) DNA probes distributed throughout the maize genome, all but one probe revealed polymorphisms with at least one enzyme (~4.5 variants per RFLP locus). Genetic distances between lines within types were estimated as Rogers\u27 distances (RD). Within diallel sets, RD values were partitioned into general (GRD)and specific (SRD). All four types of lines showed similar means and substantial variation for RD; GRD explained ~40% of the variation among RD values. Cluster analyses revealed associations among lines generally consistent with expectations based on known pedigrees. Correlations of RD and SRD with F1 yield heterosis, specific heterosis, and specific combining ability were positive but small (r = ≤ 0.50) when combined for all crosses. Results indicated that RFLPs can be used to investigate pedigree relationships among maize inbreds, but also suggest that RFLP-based genetic distance measures are of limited use in predicting heterotic performance of single crosses between unrelated lines

Population Genetics of Increased Hybrid Performance between Two Maize Populations under Reciprocal Recurrent Selection

Heterosis, the superiority in one or more characteristics of crossbred organisms relative to their inbred parents, is the basis of the modern cultivars utilized in maize (Zed mays L.). Heterosis is of interest in nondomesticated species due to its relevance to the question how much polymorphism is maintained in natural populations due to selection? (Berger, 1976). For maize and certain other domesticated species that employ inbred lines to produce commercial hybrids, knowledge of the mechanisms of gene action producing heterosis could contribute to advances in breeding techniques

Diversity and Relationships among U.S. Maize Inbreds Revealed by Restriction Fragment Length Polymorphisms

Restriction fragment length polymorphisms (RFLPs) have been proposed as molecular markers for characterizing the genetic diversity in maize (Zea mays L.). The objectives of this study were to evaluate the usefulness of RFLP data for (i) elucidating heterotic patterns among maize inbreds and (ii) assessing genetic similarity among related and unrelated lines. Thirty-two maize inbreds from the U.S. Corn Belt were analyzed for RFLPs with two restriction enzymes and 83 DNA probes distributed over the maize genome. Eighty-two probes detected polymorphisms with at least one enzyme. On average, 4.3 variants were found per probe-enzyme combination across all 32 inbreds. Genetic distances among lines, estimated from RFLP data as Rogers\u27 distance (RD), revealed considerable diversity among lines from Iowa Stiff Stalk Synthetic (BSSS), Reid Yellow Dent (RYD), and Lancaster Sure Crop (LSC). Lines from different heterotic groups had a slightly greater RD mean than unrelated lines from the same heterotic group, yet differences were small when compared with the wide range of RDs for individual lines combinations within each group. RDs between related lines agreed well with expectations based on coancestry coefficients determined from pedigree data with few exceptions. Principal component analyses of RFLP data resulted in a separate grouping of lines from BSSS/RYD and LSC. Dispersion of lines of miscellaneous origins was generally consistent with expectations based on known breeding behavior and pedigrees. Results from this study suggest that RFLP data can be used for assigning inbreds into heterotic groups and quantifying genetic similarity between related lines, but it seems that a large number of probe-enzyme combinations are required to obtain reliable estimates of genetic distance

Vegetable and fruit intake and fracture-related hospitalisations: A prospective study of olderwomen

The importance of vegetable and fruit intakes for the prevention of fracture in older women is not well understood. Few studies have explored vegetable and fruit intakes separately, or the associations of specific types of vegetables and fruits with fracture hospitalisations. The objective of this study was to examine the associations of vegetable and fruit intakes, separately, and specific types of vegetables and fruits with fracture-related hospitalisations in a prospective cohort of women aged =70 years. Vegetable and fruit intakes were assessed at baseline (1998) in 1468 women using a food frequency questionnaire. The incidence of fracture-related hospitalisations over 14.5 years of follow-up was determined using the Hospital Morbidity Data Collection, linked via theWestern Australian Data Linkage System. Fractures were identified in 415 (28.3%) women, of which 158 (10.8%) were hip fractures. Higher intakes of vegetables, but not fruits, were associated with lower fracture incidence. In multivariable-adjusted models for vegetable types, cruciferous and allium vegetables were inversely associated with all fractures, with a hazard ratio (HR) (95% confidence interval) of 0.72 (0.54, 0.95) and 0.66 (0.49, 0.88), respectively, for the highest vs. lowest quartiles. Increasing vegetable intake, with an emphasis on cruciferous and allium vegetables, may prevent fractures in older postmenopausal women

Genetic diversity among progenitors and elite lines from the Iowa Stiff Stalk Synthetic (BSSS) maize population: comparison of allozyme and RFLP data

Data for restriction fragment length polymorphisms (RFLPs) of 144 clone-enzyme combinations and for 22 allozyme loci from 21 U.S. Corn Belt maize (Zea mays L.) inbreds were analyzed. The genetic materials included 14 progenitors of the Iowa Stiff Stalk Synthetic (BSSS) maize population, both parents of one missing BSSS progenitor, four elite inbreds derived from BSSS, and inbred Mo17. Objectives were to characterize the genetic variation among these 21 inbreds for both allozymes and RFLPs, to compare the results from both types of molecular markers, and to estimate the proportion of unique alleles in the BSSS progenitors. Genetic diversity among the 21 inbreds was substantially greater for RFLPs than for allozymes, but the percentages of unique RFLP variants (27%) and unique allozyme alleles (25%) in the BSSS progenitors were similar. Genetic distances between inbreds, estimated as Rogers\u27 distance (RD), were, on average, twice as large for RFLP (0.51) as for allozyme data (0.24). RDs obtained from allozyme and RFLP data for individual line combinations were only poorly correlated (r = 0.23); possible reasons for discrepancies are discussed. Principal component analysis of RFLP data, in contrast to allozyme data, resulted in separate groupings of the ten BSSS progenitors derived from the ‘Reid Yellow Dent’ population, the four BSSS elite lines, and Mo17. The remaining six BSSS progenitors were genetically rather diverse and contributed a large number of rare alleles to BSSS. The results of this study corroborate the fact that RFLPs are superior to allozymes for characterizing the genetic diversity of maize breeding materials, because of (1) the almost unlimited number of markers available and (2) the greater amount of polymorphisms found. In particular, RFLPs allow related lines and inbreds with common genetic background to be identified, but a large number of probe-enzyme combinations is needed to estimate genetic distances with the precision required

Measurements of the dynamics and coupling of the equatorial thermosphere and the F-region ionosphere in Peru

Simultaneous Fabry-Perot Interferometer (FPI) and Incoherent Scatter Radar (ISR) observations from Arequipa and Jicamarca, Peru, respectively, were obtained on 24 and 25 September 1986, during which there was substantial geomagnetic activity. Comparison of the neutral thermosphere's zonal velocity (measured by the FPI during twilight and night-time) and the F-region plasma's zonal drift (measured by the ISR throughout the day and night) indicate that at certain times, such as evening twilight, the two motions are not correlated, but that in the late night they are. The change from uncorrelated to correlated motion occurs as the ionospheric electron density decays, leading to a decreasing Pedersen conductivity which diminishes E-region shorting of the F-region dynamo, allowing the local thermospheric winds to control the F-region ionospheric drift.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27131/1/0000124.pd