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Ballenger BK, Carter SL, Norman G, Brown SP, Fernhall B, Motl RW, Agiovlasitis S. Physical activity and arterial stiffness: is body fat a mediator? Eur J Appl Physiol 2024; 124:527-535. [PMID: 37578537 DOI: 10.1007/s00421-023-05296-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Accepted: 08/04/2023] [Indexed: 08/15/2023]
Abstract
PURPOSE Physical activity (PA) and body fat percentage (%BF) are independently associated with arterial stiffness, but it has not been explored if there is an associative pathway among these variables. This study examined whether %BF mediates the relationship between PA or sedentary behavior levels with arterial stiffness. METHODS Fifty adults (1:1 men:women; age 28 ± 11 year) had carotid-femoral pulse wave velocity (CF-PWV) measured by applanation tonometry, %BF by bioelectrical impedance, and PA levels by accelerometry. Accelerometer data determined minutes per day spent in sedentary, light, moderate-to-vigorous physical activity (MVPA), and Total PA. RESULTS Pearson correlation indicated statistically significant associations among age, %BF, CF-PWV, MVPA, and Total PA (r = 0.34-0.65, p < 0.05). Sedentary and light PA were not associated with CF-PWV. Mediation analysis indicated significant total effects of MVPA (β = - 0.34, p = 0.044) and age (β = 0.65, p < 0.001) on CF-PWV. %BF mediated the relationship between Total PA and CF-PWV due to indirect effect of Total PA on %BF (β = - 0.34, p = 0.02) and %BF on CF-PWV (β = 0.44, p = 0.002), and partially mediated the relationship between age and CF-PWV (β = 0.54, p < 0.001). Total PA retained its significant effect on %BF (β = - 0.28, p = 0.04) and the effect of %BF on CF-PWV remained significant (β = 0.26, p = 0.03), despite age having a significant effect on both %BF (β = 0.31, p = 0.023) and CF-PWV (β = 0.54, p < 0.001). CONCLUSIONS %BF mediated the relationship between Total PA and arterial stiffness, even after accounting for age. Engagement in more Total PA may help to reduce %BF, resulting in decreased arterial stiffness.
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Affiliation(s)
- Brantley K Ballenger
- Department of Kinesiology, Mississippi State University, Mississippi State, MS, USA.
| | - Sydni L Carter
- Department of Kinesiology, Mississippi State University, Mississippi State, MS, USA
| | - Grant Norman
- Department of Kinesiology, Mississippi State University, Mississippi State, MS, USA
| | - Stanley P Brown
- Department of Kinesiology, Mississippi State University, Mississippi State, MS, USA
| | - Bo Fernhall
- Department of Exercise and Health Science, University of Massachusetts Boston, Boston, MA, USA
| | - Robert W Motl
- Department of Kinesiology and Nutrition, Univeristy of Illinois Chicago, Chicago, IL, USA
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Ballenger BK, Haider M, Brown SP, Agiovlasitis S. Analysis of sedentary behaviour levels and patterns in adults with Down syndrome. J Appl Res Intellect Disabil 2024; 37:e13176. [PMID: 37947453 DOI: 10.1111/jar.13176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 10/28/2023] [Accepted: 11/02/2023] [Indexed: 11/12/2023]
Abstract
BACKGROUND Sedentary behaviour (SB) among adults with Down syndrome (DS) may differ based on personal or environmental factors. OBJECTIVE Investigate differences in SB levels and patterns of adults with DS based on sex, age, and residence-type across weekdays and weekends. METHODS Thirty-four adults with DS (15 men; 37 ± 12 years) underwent accelerometry-based measurements of sedentary time, bouts, and breaks for 7 days. We evaluated differences with 2 × 2 mixed-model (group-by-day) ANOVA. RESULTS Younger (19-36 years) individuals had less sedentary time (p = .042), and shorter (p = .048) and fewer (p = .012) bouts than older (37-60 years) individuals. Group home residents had more bouts on weekends than adults living with parent/guardians (p = .015). CONCLUSIONS Adults with DS spent half their waking hours in SB of short bouts. Age and residence may influence SB.
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Affiliation(s)
- Brantley K Ballenger
- Department of Kinesiology, Mississippi State University, Starkville, Mississippi, USA
| | - Maria Haider
- Department of Kinesiology, Mississippi State University, Starkville, Mississippi, USA
| | - Stanley P Brown
- Department of Kinesiology, Mississippi State University, Starkville, Mississippi, USA
| | - Stamatis Agiovlasitis
- Department of Kinesiology, Mississippi State University, Starkville, Mississippi, USA
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Price F, Smith JW, Brown SP. Educating with Captain America: metabolic and nutritional considerations. Adv Physiol Educ 2022; 46:362-364. [PMID: 35482993 DOI: 10.1152/advan.00103.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 03/15/2022] [Accepted: 04/22/2022] [Indexed: 06/14/2023]
Abstract
Captain America can bring more than entertainment value to the public. The pop icon can also be used effectively in the science classroom, encouraging students to more effectively learn the content. How Captain America uses nutrients and how often he eats are novel ways to communicate real science. The point is to make a connection using science to explain how the superhero can run faster, jump higher, or lift more than is humanly possible. In this way fun, teachable moments are available for the educator.
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Affiliation(s)
- Ffion Price
- Department of Kinesiology, Mississippi State University, Mississippi State, Mississippi
| | - JohnEric W Smith
- Department of Kinesiology, Mississippi State University, Mississippi State, Mississippi
| | - Stanley P Brown
- Department of Kinesiology, Mississippi State University, Mississippi State, Mississippi
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Nichol G, Brown SP. Reply to Je Hyeok Oh. Resuscitation 2021; 169:188. [PMID: 34619298 DOI: 10.1016/j.resuscitation.2021.09.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Accepted: 09/24/2021] [Indexed: 10/20/2022]
Affiliation(s)
- G Nichol
- University of Washington, Seattle, WA, United States.
| | - S P Brown
- University of Washington, Seattle, WA, United States
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Ghosh S, Choi P, Brown SP, Motl RW, Agiovlasitis S. Levels and patterns of sedentary behavior in men and women with intellectual disability. Disabil Health J 2020; 14:101059. [PMID: 33446442 DOI: 10.1016/j.dhjo.2020.101059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 12/16/2020] [Accepted: 12/22/2020] [Indexed: 10/22/2022]
Abstract
BACKGROUND There are limited data on the levels and patterns of sedentary behavior (SB) among U.S. adults with ID. OBJECTIVE To examine SB levels and patterns in U.S. adults with ID and how these differ between sexes, age-groups, and week vs. weekend days. METHODS Fifty-two adults with ID (25 men; age 45 ± 14 years) wore a hip accelerometer (wGT3X-BT; Actigraph) during the waking hours for 7 days. We determined total sedentary time, percent of wear time spent sedentary bouts ≥1, ≥10, ≥30, and ≥60 min, and breaks in sedentary time for bouts ≥10 min. We examined differences in SB variables as a function of sex, age-group by median split (≤48 vs. >48 years), and day of the week. RESULTS Total sedentary time was 514 ± 139 min · day-1 accumulated in bouts 1-30 min and did not differ between sexes or age-groups. Bouts ≥1 min across days were longer for men than women and longer during weekend days than weekdays (p < 0.05). The number of bouts ≥1 min was greater during weekdays than weekend days (p < 0.05). Bouts ≥60 min were longer for men than women (p < 0.05). The duration of sedentary breaks was longer during weekdays than weekend days (p < 0.001). There were no differences between age-groups. CONCLUSIONS Adults with ID spend a large portion of the day in SB primarily of short bouts. Despite small differences, SB levels and patterns were similar for men and women with ID and across age-groups throughout the week.
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Affiliation(s)
| | - Poram Choi
- Mississippi State University, United States
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Ghosh S, Choi P, Brown SP, Motl RW, Agiovlasitis S. Sedentary Behavior Levels And Patterns In Men And Women With Intellectual Disability. Med Sci Sports Exerc 2020. [DOI: 10.1249/01.mss.0000678288.24317.01] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Brown SP, Smith JW, McAllister M, Joe L. Superhero physiology: the case for Captain America. Adv Physiol Educ 2017; 41:16-24. [PMID: 28143818 DOI: 10.1152/advan.00106.2016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 12/02/2016] [Accepted: 12/20/2016] [Indexed: 06/06/2023]
Abstract
Using pop icons in the science classroom represents a creative way to engage often-distracted students in a relevant and, perhaps more importantly, fun way. When the pop icon is as universally known as Captain America, the pedagogical stage is set. However, when the movies can also be employed to link dramatic references to the science concepts at hand, we may have a very powerful tool by which linkages between fiction and science can be forged. In this regard, Captain America's performances in several movies to date can be used to explain actual science. Granted, script writers and movie directors may or may not be interested in whether the physical performances they depict can be explained, but that is irrelevant. The point is to make a connection using science to explain how the superhero can run faster, jump higher, or lift more than is humanly possible. If a teachable moment has occurred and an important concept has been communicated, the educator has accomplished his or her job well.
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Affiliation(s)
- Stanley P Brown
- Department of Kinesiology, Mississippi State University, Mississippi State, Mississippi
| | - JohnEric W Smith
- Department of Kinesiology, Mississippi State University, Mississippi State, Mississippi
| | - Matthew McAllister
- Department of Kinesiology, Mississippi State University, Mississippi State, Mississippi
| | - LeeAnn Joe
- Department of Kinesiology, Mississippi State University, Mississippi State, Mississippi
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Popat R, Cornforth DM, McNally L, Brown SP. Collective sensing and collective responses in quorum-sensing bacteria. J R Soc Interface 2015; 12:20140882. [PMID: 25505130 PMCID: PMC4305403 DOI: 10.1098/rsif.2014.0882] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Accepted: 11/12/2014] [Indexed: 11/21/2022] Open
Abstract
Bacteria often face fluctuating environments, and in response many species have evolved complex decision-making mechanisms to match their behaviour to the prevailing conditions. Some environmental cues provide direct and reliable information (such as nutrient concentrations) and can be responded to individually. Other environmental parameters are harder to infer and require a collective mechanism of sensing. In addition, some environmental challenges are best faced by a group of cells rather than an individual. In this review, we discuss how bacteria sense and overcome environmental challenges as a group using collective mechanisms of sensing, known as 'quorum sensing' (QS). QS is characterized by the release and detection of small molecules, potentially allowing individuals to infer environmental parameters such as density and mass transfer. While a great deal of the molecular mechanisms of QS have been described, there is still controversy over its functional role. We discuss what QS senses and how, what it controls and why, and how social dilemmas shape its evolution. Finally, there is a growing focus on the use of QS inhibitors as antibacterial chemotherapy. We discuss the claim that such a strategy could overcome the evolution of resistance. By linking existing theoretical approaches to data, we hope this review will spur greater collaboration between experimental and theoretical researchers.
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Affiliation(s)
- R Popat
- Centre for Immunity, Infection and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, UK
| | - D M Cornforth
- Centre for Immunity, Infection and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, UK Molecular Biosciences, University of Texas at Austin, 2500 Speedway NMS 3.254, Austin, TX 78712, USA
| | - L McNally
- Centre for Immunity, Infection and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, UK
| | - S P Brown
- Centre for Immunity, Infection and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, UK
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Lothamer K, Brown SP, Mattox JD, Jumpponen A. Comparison of root-associated communities of native and non-native ectomycorrhizal hosts in an urban landscape. Mycorrhiza 2014; 24:267-280. [PMID: 24221903 DOI: 10.1007/s00572-013-0539-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 10/28/2013] [Indexed: 06/02/2023]
Abstract
Non-native tree species are often used as ornamentals in urban landscapes. However, their root-associated fungal communities remain yet to be examined in detail. Here, we compared richness, diversity and community composition of ectomycorrhizosphere fungi in general and ectomycorrhizal (EcM) fungi in particular between a non-native Pinus nigra and a native Quercus macrocarpa across a growing season in urban parks using 454-pyrosequencing. Our data show that, while the ectomycorrhizosphere community richness and diversity did not differ between the two host, the EcM communities associated with the native host were often more species rich and included more exclusive members than those of the non-native hosts. In contrast, the ectomycorrhizosphere communities of the two hosts were compositionally clearly distinct in nonmetric multidimensional ordination analyses, whereas the EcM communities were only marginally so. Taken together, our data suggest EcM communities with broad host compatibilities and with a limited numbers of taxa with preference to the non-native host. Furthermore, many common fungi in the non-native Pinus were not EcM taxa, suggesting that the fungal communities of the non-native host may be enriched in non-mycorrhizal fungi at the cost of the EcM taxa. Finally, while our colonization estimates did not suggest a shortage in EcM inoculum for either host in urban parks, the differences in the fungi associated with the two hosts emphasize the importance of using native hosts in urban environments as a tool to conserve endemic fungal diversity and richness in man-made systems.
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Affiliation(s)
- K Lothamer
- Division of Biology, Kansas State University, Manhattan, KS, 66506, USA
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10
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Agiovlasitis S, Webster RO, Abadie BR, Pongetti JC, Brown SP. Are Accelerometry-determined Cut-points For Activity Intensity Stable Within People? Med Sci Sports Exerc 2014. [DOI: 10.1249/01.mss.0000495876.54448.25] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Wax B, Kavazis AN, Brown SP. Effects of Supplemental Carbohydrate Ingestion During Superimposed Electromyostimulation Exercise in Elite Weightlifters. J Strength Cond Res 2013; 27:3084-90. [DOI: 10.1519/jsc.0b013e31828c26ec] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Wax B, Kavazis AN, Brown SP, Hilton L. Effects of supplemental GAKIC ingestion on resistance training performance in trained men. Res Q Exerc Sport 2013; 84:245-251. [PMID: 23930551 DOI: 10.1080/02701367.2013.784845] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
PURPOSE Glycine-arginine-alpha-ketoisocaproic acid (GAKIC) is a relatively new supplement that athletes and fitness enthusiasts ingest to enhance performance during anaerobic exercise. Therefore, the purpose of this study was to investigate the potential ergogenic effects of GAKIC ingestion during multiple bouts of resistance exercise. METHOD Seven resistance-trained men participated in a randomized, counterbalanced, double-blind study. Participants were randomly assigned to placebo or GAKIC (10.2 g) and performed 5 sets of 75% of 1-repetition maximum leg press to failure. Total load volume was calculated by multiplying the 75% of 1-repetition maximum mass lifted by the sum of repetitions to failure. One week later, participants ingested the other supplement (placebo or GAKIC) and the same exercise protocol was performed (i.e., crossover). Blood lactate, glucose, and heart rate were determined preexercise and immediately postexercise. RESULTS GAKIC supplementation significantly increased leg-press total load volume (GAKIC = 31,564 +/- 9,132 kg; placebo = 25,763 +/- 6,595 kg, p < .05). Heart rate and blood lactate were significantly increased (p < .05) postexercise compared with preexercise but were not significantly different between GAKIC and placebo. No significant changes (p > .05) were detected for one-repetition maximum and blood glucose. CONCLUSIONS These novel findings suggest that GAKIC increases total work performed during repeated bouts of lower-body resistance exercise. Thus, our data suggest that GAKIC ingestion before weight training may increase the training volume of athletes and resistance-trained individuals.
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Affiliation(s)
- Benjamin Wax
- Department of Kinesiology, Mississippi State University, P. O. Box 6186, Mississippi State, MS 39762, USA.
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Affiliation(s)
- Stanley P. Brown
- a Physical Education , University of Arkansas at Monticello , Monticello , AR , 71655 , USA
| | - David E. Cundiff
- b Department of Physical Education , Campbellsville College , Campbellsville , KY , 42718 , USA
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Wax B, Brown SP, Webb HE, Kavazis AN. Effects of Carbohydrate Supplementation on Force Output and Time to Exhaustion During Static Leg Contractions Superimposed with Electromyostimulation. J Strength Cond Res 2012; 26:1717-23. [DOI: 10.1519/jsc.0b013e318234ec0e] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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15
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Wax B, Kavazis AN, Webb HE, Brown SP. Acute L-arginine alpha ketoglutarate supplementation fails to improve muscular performance in resistance trained and untrained men. J Int Soc Sports Nutr 2012; 9:17. [PMID: 22510253 PMCID: PMC3428651 DOI: 10.1186/1550-2783-9-17] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Accepted: 04/06/2012] [Indexed: 12/31/2022] Open
Abstract
Background Dietary supplements containing L-arginine are marketed to improve exercise performance, but the efficacy of such supplements is not clear. Therefore, this study examined the efficacy of acute ingestion of L-arginine alpha-ketoglutarate (AAKG) muscular strength and endurance in resistance trained and untrained men. Methods Eight resistance trained and eight untrained healthy males ingested either 3000mg of AAKG or a placebo 45 minutes prior to a resistance exercise protocol in a randomized, double-blind crossover design. One-repetition maximum (1RM) on the standard barbell bench press and leg press were obtained. Upon determination of 1RM, subjects completed repetitions to failure at 60% 1RM on both the standard barbell bench press and leg press. Heart rate was measured pre and post exercise. One week later, subjects ingested the other supplement and performed the identical resistance exercise protocol. Results Our data showed statistical significant differences (p<0.05) between resistance trained and untrained males for both 1RM and total load volume (TLV; multiply 60% of 1RM times the number of repetitions to failure) for the upper body. However, 1RM and TLV were not statistically different (p>0.05) between supplementation conditions for either resistance trained or untrained men in the bench press or leg press exercises. Heart rate was similar at the end of the upper and lower body bouts of resistance exercise with AAKG vs. placebo. Conclusion The results from our study indicate that acute AAKG supplementation provides no ergogenic benefit on 1RM or TLV as measured by the standard barbell bench press and leg press, regardless of the subjects training status.
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Affiliation(s)
- Benjamin Wax
- Kinesiology Department, Mississippi State University, P,O, Box 6186, Mississippi State, 39762, USA.
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Rankin DJ, Rocha EPC, Brown SP. What traits are carried on mobile genetic elements, and why? Heredity (Edinb) 2011; 106:1-10. [PMID: 20332804 PMCID: PMC3183850 DOI: 10.1038/hdy.2010.24] [Citation(s) in RCA: 201] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Revised: 01/28/2010] [Accepted: 02/02/2010] [Indexed: 01/22/2023] Open
Abstract
Although similar to any other organism, prokaryotes can transfer genes vertically from mother cell to daughter cell, they can also exchange certain genes horizontally. Genes can move within and between genomes at fast rates because of mobile genetic elements (MGEs). Although mobile elements are fundamentally self-interested entities, and thus replicate for their own gain, they frequently carry genes beneficial for their hosts and/or the neighbours of their hosts. Many genes that are carried by mobile elements code for traits that are expressed outside of the cell. Such traits are involved in bacterial sociality, such as the production of public goods, which benefit a cell's neighbours, or the production of bacteriocins, which harm a cell's neighbours. In this study we review the patterns that are emerging in the types of genes carried by mobile elements, and discuss the evolutionary and ecological conditions under which mobile elements evolve to carry their peculiar mix of parasitic, beneficial and cooperative genes.
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Affiliation(s)
- D J Rankin
- Department of Biochemistry, University of Zürich, Zürich, Switzerland.
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Wax B, Brown SP, Kinzey S, Webb HE. Effect of Resistance Exercise on Indices of Fatigue. Med Sci Sports Exerc 2010. [DOI: 10.1249/01.mss.0000386534.53362.2d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Hung I, Wong A, Howes AP, Anupõld T, Past J, Samoson A, Mo X, Wu G, Smith ME, Brown SP, Dupree R. Determination of NMR interaction parameters from double rotation NMR. J Magn Reson 2007; 188:246-59. [PMID: 17707665 DOI: 10.1016/j.jmr.2007.07.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2007] [Revised: 07/18/2007] [Accepted: 07/19/2007] [Indexed: 05/16/2023]
Abstract
It is shown that the anisotropic NMR parameters for half-integer quadrupolar nuclei can be determined using double rotation (DOR) NMR at a single magnetic field with comparable accuracy to multi-field static and MAS experiments. The (17)O nuclei in isotopically enriched l-alanine and OPPh(3) are used as illustrations. The anisotropic NMR parameters are obtained from spectral simulation of the DOR spinning sideband intensities using a computer program written with the GAMMA spin-simulation libraries. Contributions due to the quadrupolar interaction, chemical shift anisotropy, dipolar coupling and J coupling are included in the simulations. In l-alanine the oxygen chemical shift span is 455 +/- 20 ppm and 350 +/- 20 ppm for the O1 and O2 sites, respectively, and the Euler angles are determined to an accuracy of +/- 5-10 degrees . For cases where effects due to heteronuclear J and dipolar coupling are observed, it is possible to determine the angle between the internuclear vector and the principal axis of the electric field gradient (EFG). Thus, the orientation of the major components of both the EFG and chemical shift tensors (i.e., V(33) and delta(33)) in the molecular frame may be obtained from the relative intensity of the split DOR peaks. For OPPh(3) the principal axis of the (17)O EFG is found to be close to the O-P bond, and the (17)O-(31)P one-bond J coupling ((1)J(OP)=161 +/- 2 Hz) is determined to a much higher accuracy than previously.
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Affiliation(s)
- I Hung
- Physics Department, University of Warwick, Coventry, UK
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Biron DG, Ponton F, Marché L, Galeotti N, Renault L, Demey-Thomas E, Poncet J, Brown SP, Jouin P, Thomas F. 'Suicide' of crickets harbouring hairworms: a proteomics investigation. Insect Mol Biol 2006; 15:731-42. [PMID: 17201766 DOI: 10.1111/j.1365-2583.2006.00671.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Despite increasing evidence of host phenotypic manipulation by parasites, the underlying mechanisms causing infected hosts to act in ways that benefit the parasite remain enigmatic in most cases. Here, we used proteomics tools to identify the biochemical alterations that occur in the head of the cricket Nemobius sylvestris when it is driven to water by the hairworm Paragordius tricuspidatus. We characterized host and parasite proteomes during the expression of the water-seeking behaviour. We found that the parasite produces molecules from the Wnt family that may act directly on the development of the central nervous system (CNS). In the head of manipulated cricket, we found differential expression of proteins specifically linked to neurogenesis, circadian rhythm and neurotransmitter activities. We also detected proteins for which the function(s) are still unknown. This proteomics study on the biochemical pathways altered by hairworms has also allowed us to tackle questions of physiological and molecular convergence in the mechanism(s) causing the alteration of orthoptera behaviour. The two hairworm species produce effective molecules acting directly on the CNS of their orthoptera hosts.
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Affiliation(s)
- D G Biron
- GEMI, UMR CNRS/IRD 2724, IRD, 911 av. Agropolis BP 64501, Montpellier cedex 5, France.
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Laver M, Forgan EM, Brown SP, Charalambous D, Fort D, Bowell C, Ramos S, Lycett RJ, Christen DK, Kohlbrecher J, Dewhurst CD, Cubitt R. Spontaneous symmetry-breaking vortex lattice transitions in pure niobium. Phys Rev Lett 2006; 96:167002. [PMID: 16712261 DOI: 10.1103/physrevlett.96.167002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2005] [Indexed: 05/09/2023]
Abstract
We report an extensive investigation of magnetic vortex lattice (VL) structures in single crystals of pure niobium with the magnetic field applied parallel to a fourfold symmetry axis, so as to induce frustration between the cubic crystal symmetry and hexagonal VL coordination expected in an isotropic situation. We observe new VL structures and phase transitions; all the VL phases observed (including those with an exactly square unit cell) spontaneously break some crystal symmetry. One phase even has the lowest possible symmetry of a two-dimensional Bravais lattice. This is quite unlike the situation in high-Tc or borocarbide superconductors, where VL structures orient along particular directions of high crystal symmetry. The causes of this behavior are discussed.
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Affiliation(s)
- M Laver
- Institut Laue-Langevin, BP 156, F-38042 Grenoble, France
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Honea KP, Mayo JJ, Kinzey SJ, DeLashmit SJ, Brown SP. The Effect Of Game-Stimuli On Arrhythmia Response In NCAA, Division I- A Football Coaches. Med Sci Sports Exerc 2005. [DOI: 10.1249/00005768-200505001-00458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Gilardi R, Mesot J, Brown SP, Forgan EM, Drew A, Lee SL, Cubitt R, Dewhurst CD, Uefuji T, Yamada K. Square vortex lattice at anomalously low magnetic fields in electron-doped Nd1.85Ce0.15CuO4. Phys Rev Lett 2004; 93:217001. [PMID: 15601051 DOI: 10.1103/physrevlett.93.217001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2004] [Indexed: 05/24/2023]
Abstract
We report here on the first direct observations of the vortex lattice in the bulk of electron-doped Nd1.85Ce0.15CuO4 single crystals. Using small-angle neutron scattering, we have observed a square vortex lattice with the nearest neighbors oriented at 45 degrees from the Cu-O bond direction, which is consistent with theories based on the d-wave superconducting gap. However, the square symmetry persists down to unusually low magnetic fields. Moreover, the diffracted intensity from the vortex lattice is found to decrease rapidly with increasing magnetic field.
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Affiliation(s)
- R Gilardi
- Laboratory for Neutron Scattering, ETH Zurich and PSI Villigen, CH-5232 Villigen PSI, Switzerland
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Abstract
We explore from both theoretical and empirical perspectives the hypothesis that a significant part of the worldwide variability in human birthweight results from adaptive responses to local selective pressures. We first developed an agent-based model to simulate the process of evolutionary selection on life history strategy, and then we performed a comparative analysis across 89 countries worldwide. The model illustrates that optimal birthweight depends on which fitness-reducing risk locally predominates (somatic diseases, parasitic diseases or adverse environmental conditions). When fitness variations between individuals mainly result from somatic diseases (e.g. industrialized countries), or conversely from infectious and parasitic diseases (e.g. developing countries), selection is expected to favour individuals producing larger children. Conversely, when environmental risks increase in relative importance, selective pressures for producing children with high birthweight are reduced. The comparative analysis supports these theoretical expectations, in particular the finding that birthweight is higher than predicted in highly parasitized countries.
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Affiliation(s)
- F Thomas
- Centre d'Etude sur le Polymorphisme des Micro-Organismes CEPM/UMR CNRS-IRD 9926 Equipe: Evolution des Systèmes Symbiotiques, IRD, Montpellier Cedex, France.
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Brown SP, Charalambous D, Jones EC, Forgan EM, Kealey PG, Erb A, Kohlbrecher J. Triangular to square flux lattice phase transition in YBa2Cu3O7. Phys Rev Lett 2004; 92:067004. [PMID: 14995265 DOI: 10.1103/physrevlett.92.067004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2003] [Indexed: 05/24/2023]
Abstract
We have used the technique of small-angle neutron scattering to observe magnetic flux lines directly in a YBa2Cu3O7 single crystal at fields higher than previously reported. For field directions close to perpendicular to the CuO2 planes, we find that the flux lattice structure changes smoothly from a distorted triangular coordination to nearly perfectly square as the magnetic induction approaches 11 T. The orientation of the square flux lattice is as expected from recent d-wave theories but is 45 degrees from that recently observed in La(1.83)Sr(0.17)CuO(4+delta).
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Affiliation(s)
- S P Brown
- School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom.
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25
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Abstract
Although very common under natural conditions, the consequences of multiple enemies (parasites, predators, herbivores, or even 'chemical' enemies like insecticides) on investment in defence has scarcely been investigated. In this paper, we present a simple model of the joint evolution of two defences targeted against two enemies. We illustrate how the respective level of each defence can be influenced by the presence of the two enemies. Furthermore, we investigate the influences of direct interference and synergy between defences. We show that, depending on certain conditions (costs, interference or synergy between defences), an increase in selection pressure by one enemy can have dramatic effects on defence against another enemy. It is generally admitted that increasing the encounter rate with a second natural enemy can decrease investment in defence against a first enemy, but our results indicate that it may sometimes favour resistance against the first enemy. Moreover, we illustrate that the global defence against one enemy can be lower when only this enemy is present: this has important implications for experimental measures of resistance, and for organisms that invade an area with less enemies or whose community of enemies is reduced. We discuss possible implications of the existence of multiple enemies for conservation biology, biological control and chemical control.
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Affiliation(s)
- K Poitrineau
- Génétique et Environnement, ISEM, Université Montpellier II, Montpellier 5, France.
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Brown SP, De Lorgeril J, Joly C, Thomas F. FIELD EVIDENCE FOR DENSITY-DEPENDENT EFFECTS IN THE TREMATODE MICROPHALLUS PAPILLOROBUSTUS IN ITS MANIPULATED HOST, GAMMARUS INSENSIBILIS. J Parasitol 2003; 89:668-72. [PMID: 14533671 DOI: 10.1645/ge-3122] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Numerous studies have demonstrated that parasites with complex life cycles frequently manipulate the phenotype of their hosts to increase their transmission rate. Little is known, however, concerning density-dependent processes within infrapopulations of manipulative parasites--whether parasites cooperate to manipulate the host, whether competition counteracts with these potential cooperative benefits, or both. Here we explored these ideas, focusing on the association between the manipulative trematode Microphallus papillorobustus and its second intermediate host, the gammarid Gammarus insensibilis. From the data collected in the field, we found no evidence that co-occurring M. papillorobustus individuals benefit from the presence of conspecifics; instead, individuals in larger infrapopulations suffered reduced size and fecundity. Thus, the net effect of increasing density suggests that competition rather than cooperation is the dominant force in infrapopulations of M. papillorobustus.
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Affiliation(s)
- S P Brown
- Institut des Sciences de l'Evolution, Université Montpellier 2, Place Eugène Bataillon 34095, Montpellier Cedex 05, France
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Brown SP, Loot G, Teriokhin A, Brunel A, Brunel C, Guégan JF. Host manipulation by Ligula intestinalis: a cause or consequence of parasite aggregation? Int J Parasitol 2002; 32:817-24. [PMID: 12062552 DOI: 10.1016/s0020-7519(02)00013-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Previous investigations suggest that the infection of the cyprinid roach, Rutilus rutilus, with the larval plerocercoid forms of the cestode, Ligula intestinalis, creates behavioural and morphological changes in the fish host, potentially of adaptive significance to the parasite in promoting transmission to definitive avian hosts. Here we consider whether these behavioural changes are important in shaping the distribution of parasite individuals across the fish population. An examination of field data illustrates that fish infected with a single parasite were more scarce than expected under the negative binomial distribution, and in many months were more scarce than burdens of two, three or more, leading to a bimodal distribution of worm counts (peaks at 0 and >1). This scarcity of single-larval worm infections could be accounted for a priori by a predominance of multiple infection. However, experimental infections of roach gave no evidence for the establishment of multiple worms, even when the host was challenged with multiple intermediate crustacean hosts, each multiply infected. A second hypothesis assumes that host manipulation following an initial single infection leads to an increased probability of subsequent infection (thus creating a contagious distribution). If manipulated fish are more likely to encounter infected first-intermediate hosts (through microhabitat change, increased ingestion, or both), then host manipulation could act as a powerful cause of aggregation. A number of scenarios based on contagious distribution models of aggregation are explored, contrasted with alternative compound Poisson models, and compared with the empirical data on L. intestinalis aggregation in their roach intermediate hosts. Our results indicate that parasite-induced host manipulation in this system can function simultaneously as both a consequence and a cause of parasite aggregation. This mutual interaction between host manipulation and parasite aggregation points to a set of ecological interactions that are easily missed in most experimental studies of either phenomenon.
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Affiliation(s)
- S P Brown
- Department of Zoology, University of Cambridge, Downing Street, UK.
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Brown SP, Pérez-Torralba M, Sanz D, Claramunt RM, Emsley L. Determining hydrogen-bond strengths in the solid state by NMR: the quantitative measurement of homonuclear J couplings. Chem Commun (Camb) 2002:1852-3. [PMID: 12271641 DOI: 10.1039/b205324a] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hydrogen-bonding strengths in the solid state are quantitatively determined by the accurate measurement of 15N-15N J couplings using a straightforward 2D MAS NMR spinecho approach.
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Affiliation(s)
- S P Brown
- Laboratoire de Stéréochimie et des Interactions Moléculaires, UMR 5532 CNRS/ENS, Ecole Normale Supérieure de Lyon, 69364 Lyon, France
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Abstract
Concomitant immunity (CI) against macroparasites describes a state of effective anti-larval immunity coupled with persistent adult infection. Experimental studies indicate that immunologically concealed adult worms might promote anti-larval immunity via the release of cross-reactive antigens, thus creating a barrier against continual infection and restricting burden size within the host. CI offers an important potential benefit to established worms by preventing overcrowding within the host. Thus, CI may be interpreted as akin to vaccination; relatively long-lived adult worms 'vaccinate' their host with larval surface antigens and so benefit from reduced conspecific competition. The shared responsibility for host vaccination among adult worms leads to a problem of collective action. Here, we build on earlier analytical findings about the evolutionary forces that shape cooperation among parasites in order to produce a stochastic simulation model of macroparasite social evolution. First, we theoretically investigate a parasite adaptation hypothesis of CI and demonstrate its plausibility under defined conditions, despite the possibility of evolutionary 'cheats'. Then we derive a set of predictions for testing the hypothesis that CI is partly a host-manipulative parasite adaptation. Evidence in support of this model would present an unusual case of adaptive population regulation.
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Affiliation(s)
- S P Brown
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK.
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Brown SP, Spiess HW. Advanced solid-state NMR methods for the elucidation of structure and dynamics of molecular, macromolecular, and supramolecular systems. Chem Rev 2001; 101:4125-56. [PMID: 11740929 DOI: 10.1021/cr990132e] [Citation(s) in RCA: 320] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- S P Brown
- Max-Planck-Institut für Polymerforschung, Postfach 3148, D-55021 Mainz, Germany
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31
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Abstract
Numerous studies have demonstrated that parasites with complex life-cycles can cause phenotypic modifications in their hosts that lead to an increased rate of transmission, and suggest that these modifications are the result of parasitic adaptations to manipulate the host. Little attention is paid, however, to separating the possibility of adaptive host manipulation from incidental (if fortuitous) side-effects of infection. In this study we combine statistical and analytical tools to interpret the impact of the macroparasite Ligula intestinalis L. (Cestoda, Pseudophyllidea) on the behaviour of its intermediate fish host (the roach, Rutilus rutilus L.), using field data on a natural system. Two distinct sets of generalized linear models agree that both the presence and the intensity of infection contribute to a modified behavioural response in the host. This was illustrated by a preference for the lake-edge in infected fish during autumn. Furthermore, the effect of parasites upon their host is heterogeneous with respect to parasite size, with larger parasite individuals having a disproportionate impact. A series of game-theoretic models of adaptive host manipulation illustrate a potential rationale for a size-dependent manipulation strategy in parasites. These findings illustrate the potential complexity and functionality of the impact of L. intestinalis upon its fish host, which together reduce the parsimony of the alternative 'incidental effect' hypothesis.
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Affiliation(s)
- S P Brown
- Department of Zoology, University of Cambridge, UK.
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Abstract
The study of quorum-sensing bacteria has revealed a widespread mechanism of coordinating bacterial gene expression with cell density. By monitoring a constitutively produced signal molecule, individual bacteria can limit their expression of group-beneficial phenotypes to cell densities that guarantee an effective group outcome. In this paper, we attempt to move away from a commonly expressed view that these impressive feats of coordination are examples of multicellularity in prokaryotic populations. Here, we look more closely at the individual conflict underlying this cooperation, illustrating that, even under significant levels of genetic conflict, signalling and resultant cooperative behaviour can stably exist. A predictive two-trait model of signal strength and of the extent of cooperation is developed as a function of relatedness (reflecting multiplicity of infection) and basic population demographic parameters. The model predicts that the strength of quorum signalling will increase as conflict (multiplicity of infecting strains) increases, as individuals attempt to coax more cooperative contributions from their competitors, leading to a devaluation of the signal as an indicator of density. Conversely, as genetic conflict increases, the model predicts that the threshold density for cooperation will increase and the subsequent strength of group cooperation will be depressed.
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Affiliation(s)
- S P Brown
- Department of Zoology, University of Cambridge, UK.
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Abstract
The authors assessed previously unexplored processes by which information seeking and self-efficacy contribute to self-regulatory effectiveness in industrial selling. They assessed the synergistic interaction of inquiry and monitoring with respect to role clarity and tested whether this interaction was further moderated by self-efficacy. Results indicated that the role-clarifying effects of feedback inquiry and monitoring were contingent rather than independent. Role clarity increased as the combination of inquiry and monitoring increased. Furthermore, these joint effects were moderated by self-efficacy, such that high-self-efficacy employees were able to effectively use the combination of inquiry and monitoring to clarify role expectations, whereas low-self-efficacy employees were not. Implications for theory, practice, and future research are discussed.
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Affiliation(s)
- S P Brown
- Department of Marketing, Edwin L. Cox School of Business, Southern Methodist University, Dallas, Texas 75275-0333, USA.
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Abstract
In European freshwater, cyprinid fish may be heavily infected by plerocercoids of the pseudophyllidea cestode Ligula intestinalis (L.). During their development, these parasites grow rapidly to a large size in the fish's body cavity, characteristically distending the abdomen. In this study, the influence of this tapeworm on roach (Rutilus rutilus L.) morphology was analyzed. Forty-five infected and 45 uninfected roach were collected from the Lavernose-Lacasse gravel pit in Toulouse, south western France and examined for 40 morphological measurements to study phenotypic modification of the body and 14 bilateral characters for an analysis of asymmetry. Results indicate that the degree of bilateral asymmetry does not change between infected and uninfected roach, despite the strong host-morphological modifications such as deformation of the abdomen, fin displacements at the level of the tail, and sagging of the vertebral column. The intensity of abdominal distension and fish morphology changes depends on the total parasite biomass present. Differences were observed in morphology at different levels of infection, which relate to established effects of L. intestinalis on the physiology and behavior of intermediate hosts. These morphological changes induced by the parasite could increase trophic transmission to the definitive avian hosts.
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Affiliation(s)
- G Loot
- C.E.S.A.C., U.M.R. 5576 C.N.R.S, UPS, Université Paul Sabatier, Toulouse, France
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Brown SP, Hash D, Lyons B. Clinical Exercise Physiology: Current Perspectives on Exercise Prescription. Physical Therapy Reviews 2001. [DOI: 10.1179/ptr.2001.6.3.189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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Abstract
Many species of deciduous trees display striking colour changes in autumn. Here, we present a functional hypothesis: bright autumn coloration serves as an honest signal of defensive commitment against autumn colonizing insect pests. According to this hypothesis, individuals within a signalling species show variation in the expression of autumn coloration, with defensively committed trees producing a more intense display. Insects are expected to be averse to the brightest tree individuals and, hence, preferentially colonize the least defensive hosts. We predicted that tree species suffering greater insect damage would, on average, invest more in autumn-colour signalling than less troubled species. Here, we show that autumn coloration is stronger in species facing a high diversity of damaging specialist aphids. Aphids are likely to be an important group of signal receivers because they are choosy, damaging and use colour cues in host selection. In the light of further aspects of insect and tree biology, these results support the notion that bright autumn colours are expensive handicap signals revealing the defensive commitment of individual trees to autumn colonizing insect pests.
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Affiliation(s)
- W D Hamilton
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
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Brown SP, Zhu XX, Saalwächter K, Spiess HW. An investigation of the hydrogen-bonding structure in bilirubin by 1H double-quantum magic-angle spinning solid-state NMR spectroscopy. J Am Chem Soc 2001; 123:4275-85. [PMID: 11457194 DOI: 10.1021/ja004231h] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The complex hydrogen-bonding arrangement in the biologically important molecule bilirubin IXalpha is probed by using 1H double-quantum (DQ) magic-angle spinning (MAS) NMR spectroscopy. Employing fast MAS (30 kHz) and a high magnetic field (16.4 T), three low-field resonances corresponding to the different hydrogen-bonding protons are resolved in a 1H MAS NMR spectrum of bilirubin. These resonances are assigned on the basis of the proton-proton proximities identified from a two-dimensional rotor-synchronized 1H DQ MAS NMR spectrum. An analysis of 1H DQ MAS spinning-sideband patterns for the NH protons in bilirubin allows the quantitative determination of proton-proton distances and the geometry. The validity of this procedure is proven by simulated spectra for a model three-spin system, which show that the shortest distance can be determined to a very high degree of accuracy. The distance between the lactam and pyrrole NH protons in bilirubin is determined to be 0.186 +/- 0.002 nm (corresponding to a dominant dipolar coupling constant of 18.5 +/- 0.5 kHz). The analysis also yields a distance between the lactam NH and carboxylic acid OH protons of 0.230 +/- 0.008 nm (corresponding to a perturbing dipolar coupling constant of 9.9 +/- 1.0 kHz) and an H-H-H angle of 122 +/- 4 degrees. Finally, a comparison of 1H DQ MAS spinning-sideband patterns for bilirubin and its dimethyl ester reveals a significantly longer distance between the two NH protons in the latter case.
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Affiliation(s)
- S P Brown
- Max-Planck-Institut für Polymerforschung, Postfach 3148, D-55021 Mainz, Germany
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Ochsenfeld C, Brown SP, Schnell I, Gauss J, Spiess HW. Structure assignment in the solid state by the coupling of quantum chemical calculations with NMR experiments: a columnar hexabenzocoronene derivative. J Am Chem Soc 2001; 123:2597-606. [PMID: 11456929 DOI: 10.1021/ja0021823] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We present a quantum chemical ab initio study which demonstrates a new combined experimental and theoretical approach, whereby a comparison of calculated and experimental (1)H NMR chemical shifts allows the elucidation of structural arrangements in solid-state molecular ensembles, taking advantage of the marked sensitivity of the (1)H chemical shift to intermolecular interactions. Recently, Brown et al. have shown that, under fast magic-angle spinning (MAS) at 35 kHz, the resolution in a (1)H NMR spectrum of the solid phase of an alkyl-substituted hexabenzocoronene (HBC) derivative is sufficient to observe the hitherto unexpected resolution of three distinct aromatic resonances ( J. Am. Chem. Soc. 1999, 121, 6712). Exploiting the additional information about proton proximities provided by (1)H double-quantum (DQ) MAS NMR spectroscopy, it was shown that the results are qualitatively consistent with the aromatic cores packing in a manner similar to that in unsubstituted HBC. Using the HBC-C(12) molecule as an example, we show here that the new combined experimental and theoretical approach allows the observed (1)H chemical shifts to be related in a quantitative manner to the intermolecular structure. In the quantum chemical calculations, a series of model systems of stacked HBC oligomers are used. On account of the marked dependence of the (1)H chemical shift to ring currents arising from nearby aromatic rings, the calculated (1)H chemical shifts are found to be very sensitive to the stacking arrangement of the HBC molecules. Moreover, the ring current effect is found to be particularly long range, with a considerable influence of the second neighbor, at a distance of 700 pm, being observed.
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Affiliation(s)
- C Ochsenfeld
- Institut für Physikalische Chemie, Universität Mainz, D-55099 Mainz, Germany
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Abstract
Human visual perception and many visual system neurons adapt to the luminance and contrast of the stimulus. Here we describe a form of contrast adaptation that occurs in the retina. This adaptation had a local scale smaller than the dendritic or receptive fields of single ganglion cells and was insensitive to pharmacological manipulation of amacrine cell function. These results implicate the bipolar cell pathway as a site of contrast adaptation. The time required for contrast adaptation varied with stimulus size, ranging from approximately 100 ms for the smallest stimuli, to seconds for stimuli the size of the receptive field. The differing scales and time courses of these effects suggest that multiple types of contrast adaptation are used in viewing natural scenes.
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Affiliation(s)
- S P Brown
- Program in Neuroscience, Goldenson 228, Harvard Medical School, Boston, Massachusetts 02115, USA
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Abstract
This study replicates, integrates, and extends prior research on the dispositional, contextual, and cognitive antecedents of feedback-seeking behavior. Regression analysis was used to analyze data collected from a sample of salespeople (N = 310) from 2 Fortune 500 companies. The study hypotheses were supported with the following results. First, the individual disposition of learning goal orientation and the contextual factors of leader consideration and leader initiation of structure influenced cognitions about the perceived cost and value of feedback seeking. Second, the strength of the relationship of learning goal orientation with the cost and value perceptions was moderated by the leadership style of the supervisor.
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Affiliation(s)
- D VandeWalle
- Organizational Behavior and Business Policy Department, Cox School of Business, Southern Methodist University, P.O. Box 750333, Dallas, Texas 75275-0333, USA.
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Abstract
We studied the fine spatial structure of the receptive fields of retinal ganglion cells and its relationship to the dendritic geometry of these cells. Cells from which recordings had been made were microinjected with Lucifer yellow, so that responses generated at precise locations within the receptive field center could be directly compared with that cell's dendritic structure. While many cells with small receptive fields had domeshaped sensitivity profiles, the majority of large receptive fields were composed of multiple regions of high sensitivity. The density of dendritic branches at any one location did not predict the regions of high sensitivity. Instead, the interactions between a ganglion cell's dendritic tree and the local mosaic of bipolar cell axons seem to define the fine structure of the receptive field center.
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Affiliation(s)
- S P Brown
- Program in Neuroscience, Harvard Medical School, Boston, Massachusetts 02115, USA
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Baldwin PJ, Paisley AM, Brown SP. [Qualifications profile of specialty graduate education for surgical assistant physicians from the viewpoint of surgically active senior surgeons]. Chirurg 2000; 71:suppl 110-4. [PMID: 10875024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Affiliation(s)
- P J Baldwin
- University Department of Surgery, Royal Infirmary of Edinburgh, UK
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Groom K, Brown SP. Caesarean section controversy. The rate of caesarean sections is not the issue. BMJ 2000; 320:1072-3; author reply 1074. [PMID: 10764376 PMCID: PMC1117951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
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Abstract
BACKGROUND Laparoscopy and laparoscopic ultrasonography (lapUS) have been shown to improve the staging of patients with oesophagogastric cancer but there remains doubt as to whether most benefit follows laparoscopy alone and how much is contributed by the addition of lapUS. METHODS The role of lapUS in surgical decision making was evaluated prospectively in a consecutive series of patients with oesophagogastric cancer following conventional radiological assessment. The results of the lapUS findings over and above the laparoscopic findings were documented in order to identify the additional benefit of lapUS. RESULTS After initial conventional assessment 41 patients were considered unsuitable for surgery and treated by palliation, with a further 25 patients proceeding to surgery without laparoscopy. Of the 93 patients who underwent laparoscopy, 18 were shown to have irresectable disease and avoided further surgery; a further seven avoided inappropriate surgery by the addition of lapUS. The open-close laparotomy rate was reduced from five of 25 in patients who did not undergo laparoscopy to nine (12 per cent) of 75 by the introduction of laparoscopy and to two (3 per cent) of 68 with the addition of lapUS. CONCLUSION Laparoscopy alone prevented unnecessary surgery in 18 (19 per cent) of 93 patients with oesophagogastric cancer and the addition of lapUS identified a further seven patients (8 per cent) in whom unnecessary surgery was avoided.
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Affiliation(s)
- A Smith
- University Department of Surgery, Royal Infirmary, Edinburgh EH3 9YW, UK
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45
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Abstract
BACKGROUND Accurate and appropriate assessment of surgical trainees requires clear determination of the skills needed for surgical competence. This study was designed to identify those skills, rank them in order of importance and translate them into behavioural terms. METHODS A Delphi technique, using anonymous postal questionnaires, was used. All consultant surgeons in South-East Scotland were asked to identify the skills they expected of surgical trainees. Skills identified were then returned to all consultants for weighting. Differences among specialties in the importance of each item were identified using analysis of variance. RESULTS The qualities identified fell into five domains: technical skills, clinical skills, interaction with patients and relatives, teamwork, and application of knowledge. Consultants from all specialties gave high weightings to the generic domains of clinical skills, teamwork, and interaction with patients and relatives. CONCLUSION This study has identified the skills considered necessary by consultant surgeons in Scotland for a successful surgical career. Contrary to expectation, consultant surgeons value many generic skills more highly than technical skills, indicating that they value well rounded doctors, not just those with technical ability. The characteristics identified are being used to develop an assessment tool for use on basic surgical trainees.
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Affiliation(s)
- P J Baldwin
- University Department of Surgery, Royal Infirmary of Edinburgh, Lauriston Place, UK
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Brown SP, Masland RH. Costratification of a population of bipolar cells with the direction-selective circuitry of the rabbit retina. J Comp Neurol 1999; 408:97-106. [PMID: 10331582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
We have stained a new population of bipolar cells in rabbit retina by using antibodies against the carbohydrate epitope, CD15. The CD15-positive bipolar cells comprise 6-8% of the total cone bipolar cells in peripheral retina. Their axonal and dendritic arbors are similar in size and range from 15 to 50 pm in diameter. The axonal arbors are narrowly stratified in sublamina b of the inner plexiform layer. Double label experiments using an antibody against the calcium binding protein, calbindin, or an antibody against protein kinase C, demonstrate that the CD15-positive bipolar cells are a separate population from the previously identified calbindin-positive cone bipolar cells and the rod bipolar cells. Labeling the processes of starburst amacrine cells with antibodies against choline acetyltransferase showed that the CD15-positive bipolar cells stratify within and slightly more distally to the processes of the ON-starburst amacrine cells. Confocal images of retinal wholemounts showed that the axons of the CD15-positive bipolar cells follow the pattern of the ON-starburst cells' processes. Axonal varicosities of the CD15-positive bipolar cells penetrate the bundles formed by the processes of the ON-starburst cells. This finding suggests that the CD15-positive bipolar cell provides input to the ON-starburst amacrine cells and/or the ON-plexus of the ON-OFF direction-selective ganglion cells.
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Affiliation(s)
- S P Brown
- Program in Neuroscience, Harvard Medical School, Boston, Massachusetts 02115, USA.
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Mercuri E, Dubowitz L, Brown SP, Cowan F. Incidence of cranial ultrasound abnormalities in apparently well neonates on a postnatal ward: correlation with antenatal and perinatal factors and neurological status. Arch Dis Child Fetal Neonatal Ed 1998; 79:F185-9. [PMID: 10194988 PMCID: PMC1720851 DOI: 10.1136/fn.79.3.f185] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AIM To evaluate cranial ultrasonography and neurological examination in a cohort of infants regarded as normal; and to determine the prevalence of ultrasound abnormalities and any potential association with antenatal or perinatal factors or deviant neurological signs. METHODS Cranial ultrasound findings and neurological status were evaluated in 177 newborns (gestational age 36.3 to 42 weeks), admitted to a postnatal ward directly after birth and regarded as normal by obstetric and paediatric staff. The age of the infants at the time of examination ranged between 6 and 48 hours. Ultrasound abnormalities were present in 35 of the 177 infants studied (20%). Ischaemic lesions, such as periventricular and thalamic densities were the most common finding (8%), followed by haemorrhagic lesions (6%). The possible sequelae of antenatal haemorrhages, such as focal ventricular dilatation or choroid cysts, were present in 6%. Abnormal ultrasound findings were not significantly associated with signs of perinatal distress, such as cardiotocographic abnormalities or passage of meconium. Abnormal ultrasound findings tended to be associated with antenatal problems, although this did not reach significance. Ultrasound abnormalities were strongly associated with deviant patterns on the neurological examination. CONCLUSIONS These results suggest that ultrasound abnormalities are more common than has been reported up to now. Lesions that could be ischaemic, such as flare densities, are seen even in the absence of any antenatal or perinatal risk factor.
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Affiliation(s)
- E Mercuri
- Department of Paediatrics and Neonatal Medicine, Hammersmith Hospital, London
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Abstract
Left ventricular hypertrophy is recognized as an independent risk factor for cardiovascular morbid events. The primary mechanisms responsible for stimulating it are unknown. Epidemiological theories suggest that left ventricular hypertrophy is a continuous variable with no threshold, while morphological studies argue that it is the structure, or quality, and function of the myocardium (and therefore non-continuous), not the quantity of the myocardial mass, that poses the cardiovascular risk. Although left ventricular hypertrophy has been classically viewed as an adaptive response of the cardiovascular system to an imposed load, it has been demonstrated that haemodynamic overloading in selected hypertensive patients is not the sole determinant of left ventricular structure and function. Pathological and physiological states of left ventricular hypertrophy have been described primarily using criteria focusing on normal chamber performance and oxygen delivery as well as the reversibility of the hypertrophy once the overload is removed. Both states are also defined by the nature of the imposed load and the resulting myocardial adaptations. This review addresses the pathological and physiological states of left ventricular hypertrophy, the hypertrophy patterns, and the corresponding structural and functional characteristics, together with some of the biochemical factors thought to influence remodelling.
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Affiliation(s)
- P A Richey
- Department of Pediatrics and the Crippled Children's Foundation Research Center, University of Tennessee, Memphis 38103, USA
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Abstract
An extended-spectrum cephalosporin has been considered appropriate therapy for non-meningeal infections caused by drug-resistant Streptococcus pneumoniae. We report a toddler who had breakthrough bacteremia and meningitis develop because of drug-resistant pneumococcus while receiving treatment with cefotaxime and cefuroxime for pneumonia.
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Affiliation(s)
- S C Buckingham
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, USA
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