Genotype-by-environment interactions and local adaptation shape selection in the US National Chip Processing Trial.

KEY MESSAGE: We find evidence of selection for local adaptation and extensive genotype-by-environment interaction in the potato National Chip Processing Trial (NCPT). We present a novel method for dissecting the interplay between selection, local adaptation and environmental response in plant breeding schemes. Balancing local adaptation and the desire for widely adapted cultivars is challenging for plant breeders and makes genotype-by-environment interactions (GxE) an important target of selection. Selecting for GxE requires plant breeders to evaluate plants across multiple environments. One way breeders have accomplished this is to test advanced materials across many locations. Public potato breeders test advanced breeding material in the National Chip Processing Trial (NCPT), a public-private partnership where breeders from ten institutions submit advanced chip lines to be evaluated in up to ten locations across the country. These clones are genotyped and phenotyped for important agronomic traits. We used these data to interrogate the NCPT for GxE. Further, because breeders submitting clones to the NCPT select in a relatively small geographic range for the first 3 years of selection, we examined these data for evidence of incidental selection for local adaptation, and the alleles underlying it, using an environmental genome-wide association study (envGWAS). We found genomic regions associated with continuous environmental variables and discrete breeding programs, as well as regions of the genome potentially underlying GxE for yield.

Grower decision-making factors in adoption of specialty cultivars: A case study of potatoes in the San Luis Valley.

Potatoes are the most consumed vegetable worldwide and play an important role in the U.S. economy. Growers make critical decisions each year in choosing which cultivar to grow, based on factors such as yield, resilience to the growing environment, and utility in the food industry. Current research supports the finding that less-common specialty cultivars (SCs) have benefits for human health. However, growers have been slow to adopt SCs into mainstream operations. Here, we identify major factors in the decision-making process that determine whether a population of growers in the San Luis Valley, Colorado, a major potato-growing region, adopt SC potatoes. We used a combination of ethnographic techniques and quantitative methods to examine drivers of adoption. The data demonstrate grower perceptions within potato farming and the complexity of interacting factors in decision-making. An integration of the Theory of Planned Behavior, Rational Expectation Hypothesis, and Diffusion of Innovation models identifies economic and social factors that influence grower decision-making. Growers that were more aware of specialty cultivar innovation and associated consumer demand were more open to SCs adoption. Other influencing factors include a grower's experience selling a SC in the previous year and access to diverse markets. Based on these data, we developed a new model to explain grower decision-making processes in adopting SCs. The model demonstrates that one current barrier to adoption is access to buyers, including warehouses, retailers, and households. Taken together, this research demonstrates how rational expectations stem from economic outcomes, knowledge, and experience in the potato industry. These results are important in helping to consider opportunities for growers to access new, higher value markets, while also improving consumer access to nutritious cultivars.

The Bioaccessibility of Phenolics, Flavonoids, Carotenoids, and Capsaicinoid Compounds: A Comparative Study of Cooked Potato Cultivars Mixed with Roasted Pepper Varieties.

An in vitro method was used to assess the bioaccessibility of phenolics, flavonoids, carotenoids, and capsaicinoid compounds in different cooked potatoes mixed with roasted peppers (Capsicum annuum), Joe Parker (JP, hot), and Sweet Delilah (SD, sweet). The present study identified differences in the bioaccessibility of bioactive compounds among the potato cultivars (Solanum tuberosum) Purple Majesty (PM; purple flesh), Yukon Gold (YG; yellow flesh), Rio Grande Russet (RG; white flesh) and a numbered selection (CO 97226-2R/R (R/R; red flesh)). The bioactive compounds and capsaicinoid compounds in potatoes and peppers were estimated before and after in vitro digestion. Before digestion, the total phenolic content of potato cultivars mixed with JP was in the following order: R/R > PM > YG > RG. The highest levels of carotenoids were 194.34 µg/g in YG and 42.92 µg/g in the RG cultivar when mixed with roasted JP. The results indicate that the amount of bioaccessible phenolics ranged from 485 to 252 µg/g in potato cultivars mixed with roasted JP. The bioaccessibility of flavonoids ranged from 185.1 to 59.25 µg/g. The results indicate that the YG cultivar mixed with JP and SD showed the highest phenolic and carotenoid bioaccessibility. In contrast, the PM mixed with JP and SD contained the lowest phenolic and carotenoid bioaccessibility. Our results indicate that the highest flavonoid bioaccessibility occurred in R/R mixed with roasted JP and SD. The lowest flavonoids bioaccessibility occurred in PM and the RG. The maximum bioaccessible amount of capsaicin was observed in YG mixed with JP, while the minimum bioaccessibility was observed with PM.

Genetic diversity and population structure of advanced clones selected over forty years by a potato breeding program in the USA.

Knowledge regarding genetic diversity and population structure of breeding materials is essential for crop improvement. The Texas A&M University Potato Breeding Program has a collection of advanced clones selected and maintained in-vitro over a 40-year period. Little is known about its genetic makeup and usefulness for the current breeding program. In this study, 214 potato clones were genotyped with the Infinium Illumina 22 K V3 Potato Array. After filtering, a total of 10,106 single nucleotide polymorphic (SNP) markers were used for analysis. Heterozygosity varied by SNP, with an overall average of 0.59. Three groups of tetraploid clones primarily based on potato market classes, were detected using STRUCTURE software and confirmed by discriminant analysis of principal components. The highest coefficient of differentiation observed between the groups was 0.14. Signatures of selection were uncovered in genes controlling potato flesh and skin color, length of plant cycle and tuberization, and carbohydrate metabolism. A core set of 43 clones was obtained using Core Hunter 3 to develop a sub-collection that retains similar genetic diversity as the whole population, minimize redundancies, and facilitates long-term conservation of genetic resources. The comprehensive molecular characterization of our breeding clone bank collection contributes to understanding the genetic diversity of existing potato resources. This analysis could be applied to other breeding programs and assist in the selection of parents, fingerprinting, protection, and management of the breeding collections.

Evaluation of genetic diversity among Russet potato clones and varieties from breeding programs across the United States.

DNA fingerprinting is a powerful tool for plant diversity studies, cultivar identification, and germplasm conservation and management. In breeding programs, fingerprinting and diversity analysis provide an insight into the extent of genetic variability available in the breeding material, which in turn helps breeders to maintain a pool of highly diverse genotypes by avoiding the selection of closely related parents. Oblong-long tubers with russeting skin characterize Russet potato, a primary potato market class in the United States, and especially in the western production regions. The aim of this study was to estimate the level of genetic diversity within this market class potato, utilizing clones and varieties from various breeding programs across the United States. A collection of 264 Russet and non-Russet breeding clones and varieties was fingerprinted using 23 highly polymorphic genome-wide simple sequence repeat (SSR) markers, resulting in 142 polymorphic alleles. The number of alleles produced per SSR varied from 2 to 10, with an average of 6.2 alleles per marker. The polymorphic information content and expected heterozygosity of SSRs ranged from 0.37 to 0.89 and 0.50 to 0.89 with an average of 0.77 and 0.81, respectively. Out of these 23 markers, we propose nine SSR markers best suited for fingerprinting Russet potatoes based on polymorphic information content, heterozygosity and ease of scoring. Diversity analysis of these clones suggest that there is significant diversity across the breeding material and the diversity has been evenly distributed among all the regional breeding programs.

Metabolomics and Ionomics of Potato Tuber Reveals an Influence of Cultivar and Market Class on Human Nutrients and Bioactive Compounds.

Potato (Solanum tuberosum L.) is an important global food crop that contains phytochemicals with demonstrated effects on human health. Understanding sources of chemical variation of potato tuber can inform breeding for improved health attributes of the cooked food. Here, a comprehensive metabolomics (UPLC- and GC-MS) and ionomics (ICP-MS) analysis of raw and cooked potato tuber was performed on 60 unique potato genotypes that span 5 market classes including russet, red, yellow, chip, and specialty potatoes. The analyses detected 2,656 compounds that included known bioactives (43 compounds), nutrients (42), lipids (76), and 23 metals. Most nutrients and bioactives were partially degraded during cooking (44 out of 85; 52%), however genotypes with high quantities of bioactives remained highest in the cooked tuber. Chemical variation was influenced by genotype and market class. Specifically, ~53% of all detected compounds from cooked potato varied among market class and 40% varied by genotype. The most notable metabolite profiles were observed in yellow-flesh potato which had higher levels of carotenoids and specialty potatoes which had the higher levels of chlorogenic acid as compared to the other market classes. Variation in several molecules with known association to health was observed among market classes and included vitamins (e.g., pyridoxal, ~2-fold variation), bioactives (e.g., chlorogenic acid, ~40-fold variation), medicinals (e.g., kukoamines, ~6-fold variation), and minerals (e.g., calcium, iron, molybdenum, ~2-fold variation). Furthermore, more metabolite variation was observed within market class than among market class (e.g., α-tocopherol, ~1-fold variation among market class vs. ~3-fold variation within market class). Taken together, the analysis characterized significant metabolite and mineral variation in raw and cooked potato tuber, and support the potential to breed new cultivars for improved health traits.

Genetic Variance Partitioning and Genome-Wide Prediction with Allele Dosage Information in Autotetraploid Potato.

As one of the world's most important food crops, the potato (Solanum tuberosum L.) has spurred innovation in autotetraploid genetics, including in the use of SNP arrays to determine allele dosage at thousands of markers. By combining genotype and pedigree information with phenotype data for economically important traits, the objectives of this study were to (1) partition the genetic variance into additive vs. nonadditive components, and (2) determine the accuracy of genome-wide prediction. Between 2012 and 2017, a training population of 571 clones was evaluated for total yield, specific gravity, and chip fry color. Genomic covariance matrices for additive (G), digenic dominant (D), and additive × additive epistatic (G#G) effects were calculated using 3895 markers, and the numerator relationship matrix (A) was calculated from a 13-generation pedigree. Based on model fit and prediction accuracy, mixed model analysis with G was superior to A for yield and fry color but not specific gravity. The amount of additive genetic variance captured by markers was 20% of the total genetic variance for specific gravity, compared to 45% for yield and fry color. Within the training population, including nonadditive effects improved accuracy and/or bias for all three traits when predicting total genotypic value. When six F1 populations were used for validation, prediction accuracy ranged from 0.06 to 0.63 and was consistently lower (0.13 on average) without allele dosage information. We conclude that genome-wide prediction is feasible in potato and that it will improve selection for breeding value given the substantial amount of nonadditive genetic variance in elite germplasm.

Inhibition of α-glucosidase, α-amylase, and aldose reductase by potato polyphenolic compounds.

Diabetes mellitus is a chronic disease that is becoming a serious global health problem. Diabetes has been considered to be one of the major risks of cataract and retinopathy. Synthetic and natural product inhibitors of carbohydrate degrading enzymes are able to reduce type 2 diabetes and its complications. For a long time, potatoes have been portrayed as unhealthy for diabetic patients by some nutritionist due to their high starch content. However, purple and red potato cultivars have received considerable attention from consumers because they have high levels of polyphenolic compounds that have potent antioxidant activities. In this study, we screened the total phenolics (TP) and total anthocyanins (TA) and analyzed the phenolic and anthocyanin compounds in selected potato cultivars and advanced selections with distinct flesh colors (purple, red, yellow and white). Purple and red potato cultivars had higher levels of TP and TA than tubers with other flesh colors. Chlorogenic acid is the predominant phenolic acid, and major anthocyanin is composed of the derivatives of petunidin, peonidin, malvidin and pelargonidin. We tested the potential inhibitory effect of potato extracts on the activities of α-amylase and α-glucosidase, which were targeted to develop antidiabetic therapeutic agents. We also measured inhibitory effect of potato extracts on aldose reductase (AR) which is a key enzyme that has been a major drug target for the development of therapies to treat diabetic complications. Purple flesh tubers extract showed the most effective inhibition of α-amylase, α-glucosidase, and aldose reductase with IC50 values 25, 42, and 32 µg/ml, respectively. Kinetic studies showed that anthocyanins are noncompetitive inhibitors of these enzymes, whereas phenolic acids behaved as mixed inhibitors for α-amylase and α-glucosidase and noncompetitive inhibitors for AR. This study supports the development of a positive and healthful image of potatoes, which is an important issue for consumers.

A comparison of the in vitro moisture vapour transmission rate and in vivo fluid-handling capacity of six adhesive foam dressings to a newly reformulated adhesive foam dressing.

This study compared moisture vapour transmission rate (MVTR) and wear time or fluid-handling capacities of six adhesive foam dressings to a reformulated control dressing. Standardised in vitro MVTR methodology and a previously published in vivo artificial wound model (AWM) were used. Mean inverted MVTR for the reformulated dressing was 12 750 g/m(2) /24 hours and was significantly higher than four of the six comparator dressings (P < 0·0001), which ranged from 830 to 11 360 g/m(2) /24 hours. Mean upright MVTR for the reformulated dressing was 980 g/m(2) /24 hours and was significantly different than all of the comparator dressings (P < 0·0001), which ranged from 80 to 1620 g/m(2) /24 hours (three higher/three lower). The reformulated dressing median wear time ranged from 6·1 to >7·0 days, compared with 1·0 to 3·5 days for the comparator dressings (P = 0·0012 to P < 0·0001). The median fluid volume handled ranged from 78·0 to >87 ml compared with 13·0 to 44·5 ml for the comparator dressings (P = 0·0007 to P < 0·001). Interestingly, inverted MVTR did not correspond well to the AWM. These results suggest that marked differences exist between the dressings in terms of both MVTR and wear time or fluid-handling capacity. Furthermore, high inverted MVTR does not necessarily predict longer wear time or fluid-handling capacities of absorbent dressings.

Effect of cold storage on total phenolics content, antioxidant activity and vitamin C level of selected potato clones.

BACKGROUND: Twelve Colorado-grown specialty potato clones were evaluated for total phenolic content, antioxidant activity and ascorbic acid content at harvest and after 2, 4, 6 and 7 months cold storage at 4 °C. Potato clones were categorized as pigmented ('CO97226-2R/R', 'CO99364-3R/R', 'CO97215-2P/P', 'CO97216-3P/P', 'CO97227-2P/P', 'CO97222-1R/R', 'Purple Majesty', 'Mountain Rose' and 'All Blue'), yellow ('Yukon Gold') and white fleshed ('Russet Nugget', 'Russet Burbank'). Folin-Ciocalteu reagent was used to estimate total phenolic content, and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS(•+) ) and 2,2-diphenyl-1-picrylhydrazyl (DPPH(•) ) radical scavenging assays were used to estimate antioxidant capacity. RESULTS: Pigmented potato genotypes had significantly higher total phenolic content and antioxidant activity at all data points than yellow- and white-fleshed cultivars. Vitamin C content was higher in 'Yukon Gold' than in the other clones. The highest level of vitamin C in all clones was at harvest and after 2 months in cold storage. Vitamin C content in all potato clones dropped rapidly with longer intervals of cold storage. Although total phenolic content and antioxidant activity fluctuated during cold storage, after 7 months of cold storage their levels were slightly higher than at harvest. Total phenolic content was better correlated with Trolox equivalent antioxidant capacity (TEAC)/ABTS(•+) than the TEAC/DPPH(•) radical scavenging assay. CONCLUSION: Pigmented potato clones had significantly higher total phenolic content and antioxidant activity, while the yellow-fleshed potato cultivar 'Yukon Gold' had significantly higher vitamin C content. Vitamin C content decreased in all potato clones during cold storage, while total phenolics increased in pigmented clones.

Combined effects of storage and processing on the bioactive compounds and pro-apoptotic properties of color-fleshed potatoes in human colon cancer cells.

Potatoes can be stored for up to 1 year before being processed and consumed. The objective of this study was to determine the extent to which fresh and stored color-fleshed potatoes retain their anticancer properties after baking and chipping compared with unprocessed potatoes. We utilized white-, yellow-, and purple-fleshed potato clones and tested their phenolic and anthocyanin content, antioxidant activity, metabolite profile, and antiproliferative and pro-apoptotic properties. When compared with unprocessed samples, baking or chipping led to significant losses in the phenolic and anthocyanin content and antioxidant activity of the potatoes. However, with storage, total phenolic and anthocyanin content and antioxidant activity increased in baked samples while in the chipped samples they remained constant. Ethanolic extracts of baked and chipped samples suppressed proliferation and elevated apoptosis (p < 0.05) in HCT-116 (p53 wild-type; ras mutated) and HT-29 (p53 mutated; ras wild-type) human colon cancer cell lines. Antiproliferative and pro-apoptotic properties of baked potatoes were similar to that of fresh potatoes, while chipping caused a significant suppression. Phenolic content and antioxidant activity of purple-fleshed potatoes, after baking, were comparable with those of anthocyanin-rich berries. Hence, purple-fleshed potatoes can be a healthier choice for consumers as they possess greater levels of bioactive compounds and anticancer properties even after processing as compared with their white- and yellow-fleshed counterparts.

Storage elevates phenolic content and antioxidant activity but suppresses antiproliferative and pro-apoptotic properties of colored-flesh potatoes against human colon cancer cell lines.

Colored-flesh potatoes are an excellent source of health-benefiting dietary polyphenols, but are stored for up to 3-6 months before consumption. This study investigated the effect of simulated commercial storage conditions on antioxidant activity (DPPH, ABTS), phenolic content (FCR) and composition (UPLC-MS), and anticancer properties (early, HCT-116 and advanced stage, HT-29 human colon cancer cell lines) of potato bioactive compounds. Extracts from seven potato clones of differing flesh colors (white, yellow, and purple) before and after 90 days of storage were used in this study. The antioxidant activity of all clones increased with storage; however, an increase in total phenolic content was observed only in purple-fleshed clones. Advanced purple-fleshed selection CO97227-2P/PW had greater levels of total phenolics, monomeric anthocyanins, antioxidant activity and a diverse anthocyanin composition as compared with Purple Majesty. Purple-fleshed potatoes were more potent in suppressing proliferation and elevating apoptosis of colon cancer cells compared with white- and yellow-fleshed potatoes. The extracts from both fresh and stored potatoes (10-30 µg/mL) suppressed cancer cell proliferation and elevated apoptosis compared with the solvent control, but these anticancer effects were more pronounced with the fresh potatoes. Storage duration had a strong positive correlation with antioxidant activity and percentage of viable cancer cells and a negative correlation with apoptosis induction. These results suggest that although the antioxidant activity and phenolic content of potatoes were increased with storage, the antiproliferative and pro-apoptotic activities were suppressed. Thus, in the assessment of the effects of farm to fork operations on the health-benefiting properties of plant foods, it is critical to use quantitative analytical techniques in conjunction with in vitro and/or in vivo biological assays.

Pyrosequencing reveals a highly diverse and cultivar-specific bacterial endophyte community in potato roots.

In this study, we examined the bacterial endophyte community of potato (Solanum tuberosum) cultivar/clones using two different molecular-based techniques (bacterial automated ribosomal intergenic spacer analysis (B-ARISA) and pyrosequencing). B-ARISA profiles revealed a significant difference in the endophytic community between cultivars (perMANOVA, p < 0.001), and canonical correspondence analysis showed a significant correlation between the community structure and plant biomass (p = 0.001). Pyrosequencing detected, on average, 477 +/- 71 bacterial operational taxonomic units (OTUs, 97% genetic similarity) residing within the roots of each cultivar, with a Chao estimated total OTU richness of 1,265 +/- 313. Across all cultivars, a total of 238 known genera from 15 phyla were identified. Interestingly, five of the ten most common genera (Rheinheimera, Dyadobacter, Devosia, Pedobacter, and Pseudoxanthomonas) have not, to our knowledge, been previously reported as endophytes of potato. Like the B-ARISA analysis, the endophytic communities differed between cultivar/clones (integral-libshuff, p < 0.001) and exhibited low similarities on both a presence/absence (0.145 +/- 0.019) and abundance (0.420 +/- 0.081) basis. Seventeen OTUs showed a strong positive (r > 0.600) or negative (r < -0.600) correlation with plant biomass, suggesting a possible link between plant production and endophyte abundance. This study represents one of the most comprehensive assessments of the bacterial endophytic communities to date, and similar analyses in other plant species, cultivars, or tissues could be utilized to further elucidate the potential contribution(s) of endophytic communities to plant physiology and production.

Noninvasive detection of temozolomide in brain tumor xenografts by magnetic resonance spectroscopy.

Poor drug delivery to brain tumors caused by aberrant tumor vasculature and a partly intact blood-brain barrier (BBB) and blood-brain tumor barrier (BTB) can significantly impair the efficacy of chemotherapy. Determining drug delivery to brain tumors is a challenging problem, and the noninvasive detection of drug directly in the tumor can be critically important for accessing, predicting, and eventually improving effectiveness of therapy. In this study, in vivo magnetic resonance spectroscopy (MRS) was used to detect an anticancer agent, temozolomide (TMZ), in vivo in murine xenotransplants of U87MG human brain cancer. Dynamic magnetic resonance imaging (MRI) with the low-molecular-weight contrast agent, gadolinium diethylenetriaminepentaacetic acid (GdDTPA), was used to evaluate tumor vascular parameters. Carbon-13-labeled TMZ ([(13)C]TMZ, 99%) was intraperitoneally administered at a dose of approximately 140 mg/kg (450 mg/m(2), well within the maximal clinical dose of 1000 mg/m(2) used in humans) during the course of in vivo MRS experiments. Heteronuclear multiple-quantum coherence (HMQC) MRS of brain tumors was performed before and after i.p. administration of [(13)C]TMZ. Dynamic MRI experiments demonstrated slower recovery of MRI signal following an intravenous bolus injection of GdDTPA, higher vascular flow and volume obtained by T*(2)-weighted MRI, as well as enhanced uptake of the contrast agent in the brain tumor compared with normal brain detected by T(1)-weighted MRI. These data demonstrate partial breakdown of the BBB/BTB and good vascularization in U87MG xenografts. A [(13)C]TMZ peak was detected at 3.9 ppm by HMQC from a selected volume of about 0.15 cm(3) within the brain tumor with HMQC pulse sequences. This study clearly demonstrates the noninvasive detection of [(13)C]TMZ in xenografted U87MG brain tumors with MRS. Noninvasive tracking of antineoplastic agents using MRS can have a significant impact on brain tumor chemotherapy.

Flavonoid profiling and transcriptome analysis reveals new gene-metabolite correlations in tubers of Solanum tuberosum L.

Anthocyanin content of potato tubers is a trait that is attracting increasing attention as the potential nutritional benefits of this class of compound become apparent. However, our understanding of potato tuber anthocyanin accumulation is not complete. The aim of this study was to use a potato microarray to investigate gene expression patterns associated with the accumulation of purple tuber anthocyanins. The advanced potato selections, CO97216-3P/PW and CO97227-2P/PW, developed by conventional breeding procedures, produced tubers with incomplete expression of tuber flesh pigmentation. This feature permits sampling pigmented and non-pigmented tissues from the same tubers, in essence, isolating the factors responsible for pigmentation from confounding genetic, environmental, and developmental effects. An examination of the transcriptome, coupled with metabolite data from purple pigmented sectors and from non-pigmented sectors of the same tuber, was undertaken to identify these genes whose expression correlated with elevated or altered polyphenol composition. Combined with a similar study using eight other conventional cultivars and advanced selections with different pigmentation, it was possible to produce a refined list of only 27 genes that were consistently differentially expressed in purple tuber tissues compared with white. Within this list are several new candidate genes that are likely to impact on tuber anthocyanin accumulation, including a gene encoding a novel single domain MYB transcription factor.

Relationship between the kinetics and kinematics of a unilateral horizontal drop jump to sprint performance.

The aim of this study was to investigate the relationship between the kinematics and kinetics of a single-leg horizontal drop jump (SLDJ) to sprint performance. Twenty regional-level male team-sport athletes gave informed consent to participate in this study. All subjects performed a series of 25-m sprints (measured by dual-beam infrared timing lights) and SLDJ (with both legs) in randomized block order during the same testing session. The SLDJ required the subjects to step downwards off a 20-cm box, land on the force plate (operating at 500 Hz) with the specified foot, and jump for maximal horizontal distance while minimizing ground-contact time. Jump distance, particularly when normalized to a subject's height, was the strongest correlate to sprinting time for all three (5, 10, and 25 m) distances (-0.44 < r < -0.65). Multiple linear regression analyses indicated that the SLDJ could account for a high level of variance in sprint time (0.49 < r2 < 0.68) and that these predictions had a relatively low standard error of estimate (0.02-0.10 seconds). These results further support the contention that jump (particularly horizontal) and sprint ability for short distances are highly related. Whereas practitioners should consider using more horizontal than vertical jumps in the training and testing of most team-sport athletes, additional research into the kinetic determinants of jumping and sprinting may allow a more specific and individualized exercise prescription for improving certain aspects of sprinting such as step length or step rate or the vertical vs. horizontal contributions to propulsion.

Effect of paramagnetic manganese cations on (1)H MRS of the brain.

Manganese cations (Mn(2+)) can be used as an intracellular contrast agent for structural, functional and neural pathway imaging applications. However, at high concentrations, Mn(2+) is neurotoxic and may influence the concentration of (1)H MR-detectable metabolites. Furthermore, the paramagnetic Mn(2+) cations may also influence the relaxation of the metabolites under investigation. Consequently, the purpose of this study was to investigate the effect of paramagnetic Mn(2+) cations on (1)H-MR spectra of the brain using in vivo and phantom models at 4.7 T. To investigate the direct paramagnetic effects of Mn(2+) cations on the relaxation of N-acetylaspartate (NAA), creatine and choline, T(1) relaxation times of metabolite solutions, with and without 5% albumin, and containing different Mn(2+) concentrations were determined. Relaxivity values with/without 5% albumin for NAA (4.8/28.1 s(-1) mM(-1)), creatine (2.8/2.8 s(-1) mM(-1)) and choline (1.8/1.1 s(-1) mM(-1)) showed NAA to be the most sensitive metabolite to the relaxation effects of the cations. Using an in vivo optic tract tracing imaging model, we obtained two adjacent regions of interest in the superior colliculi with different water T(1) values (Mn(2+)-enhanced = 1.01 s; unenhanced = 1.14 s) 24 h after intravitreal injection of 3 microL 50 mM MnCl(2). Using phantom and in vivo water relaxation time data, we estimated the in vivo Mn(2+) concentration to be 2-8 microM. The phantom data suggest that limited metabolite relaxation effects would be expected at this concentration. Consequently, this study indicates that, in this model, the presence of Mn(2+) cations does not significantly affect (1)H-MR spectra despite possible toxic and paramagnetic effects.

Impact of bacteremia on the pathogenesis of experimental pneumococcal meningitis.

BACKGROUND: Bacteremia plays a major role in the outcome of pneumococcal meningitis. This experimental study investigated how bacteremia influences the pathophysiologic profile of the brain. METHODS: Rats with Streptococcus pneumoniae meningitis were randomized to 1 of 3 groups of infected study rats: (1) rats with attenuated bacteremia resulting from intravenous injection of serotype-specific pneumococcal antibody, (2) rats with early-onset bacteremia resulting from concomitant intravenous infection, or (3) a meningitis control group. The blood-brain barrier (BBB) breakdown, ventricle size, brain water distribution, and brain pathologic findings were analyzed using magnetic resonance morphological and functional imaging. Laboratory data and clinical disease scores were obtained. RESULTS: Attenuation of the bacteremic component of pneumococcal meningitis improved clinical disease symptoms and significantly reduced ventricle expansion and BBB breakdown (P< .05). Early-onset bacteremia did not further increase ventricle size or BBB leakage. Significantly increased brain edema developed among rats with both attenuated and early-onset bacteremia (P< .05). Focal brain pathologic findings were unaffected by bacteremia and were found to be associated with cerebrospinal fluid inflammation. CONCLUSION: Although brain lesions appear to result from local meningeal infection, systemic infection significantly contributes to clinical disease presentation and the pathophysiology of BBB breakdown and ventricle expansion. The different end points affected by the systemic and local infectious processes should be addressed in future studies.

Reliability of kinematics and kinetics associated with horizontal single leg drop jump assessment. A brief report.

Determining the reliability of a unilateral horizontal drop jump for displacement provided the focus for this research. Eighteen male subjects were required to step off a 20cm box and land on a force plate with one leg and thereafter jump for maximal horizontal displacement on two different days. Dependent variables from the jump assessment included mean and peak vertical (V) and horizontal (H) ground reaction forces (GRF) and impulses, horizontal displacement and contact time. The between-trial variability of all kinematic and kinetic measures was less than 7%. The most consistent measure over both trials was the horizontal displacement jumped (1.2 to 1.4%) and the most variable were the contact time the first day (6.5%) and peak HGRF the second day (4.3%). In all cases there was less variation associated with the second rather than the first day. In terms of test-retest variability the percent changes in the means and coefficient of variations (CVs) were all under 10%. The smallest changes in the mean (0.43 %), least variation (< 2.26 %) and second highest intraclass correlation co-efficient (ICC = 0.95) were found for horizontal displacement jumped. The highest ICC (0.96) was found for horizontal impulse. Given the reliability of the single leg drop jump, it may offer better prognostic and diagnostic information than that obtained with bilateral vertical jumps. Key pointsThere is a need for greater understanding and utilisation of assessment techniques that assess both the horizontal and vertical components of force/power production.The single leg drop jump is an assessment that exhibits high face validity (a unilateral jump involving both vertical and horizontal propulsive forces that also involves pre-load) but reliability needed to be quantified.The reliability of the many kinematic and kinetic variables quantified in this study were similar to those published in research in this area and future research needs to determine the clinical and practical significance of this test.

Slice profile optimization in arterial spin labeling using presaturation and optimized RF pulses.

OBJECTIVE: An important source of error in arterial spin labeling (ASL) is incomplete static tissue subtraction due to imperfect slice profiles. This effect can be reduced by saturating the spins in the imaging area prior to labeling. In this study, the use of optimized presaturation is compared with the use of optimized RF pulses for minimizing this error. MATERIALS AND METHODS: Different methods for optimizing presaturation were simulated by numerical solution of the Bloch equation. Presaturation was optimized by changing the number of presaturation pulses, their position in the pulse sequence and the area of the crusher gradients following each saturation pulse. It was also investigated whether the use of optimized presaturation could reduce the tag gap needed to ensure complete static tissue subtraction. Simulation results were verified using phantom and in vivo studies at 3T. RESULTS: In proximal inversion with control for off-resonance effects, optimized presaturation could reduce the necessary tag gap to 15% of the imaging slab for experiments using standard RF pulses, while c-FOCI RF pulses could reduce it to 11%. In flow-sensitive alternating inversion recovery, a single presaturation pulse could reduce the inversion width to 122% of the imaging slab and neither multiple presaturation pulses nor optimized RF pulses could reduce it further. CONCLUSION: Optimized presaturation can reduce the necessary inversion width to the same level as if using optimized RF pulses and can, therefore, be used to optimize ASL sensitivity. Furthermore, optimized presaturation can reduce the B(1)-dependent sensitivity in static tissue subtraction.