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Zhang Y, Zheng N, Han R, Zheng B, Yu Z, Li S, Zheng S, Wang J. Occurrence of tetracyclines, sulfonamides, sulfamethazine and quinolones in pasteurized milk and UHT milk in China's market. Food Control 2014. [DOI: 10.1016/j.foodcont.2013.08.012] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Huang LC, Zheng N, Zheng BQ, Wen F, Cheng JB, Han RW, Xu XM, Li SL, Wang JQ. Simultaneous determination of aflatoxin M1, ochratoxin A, zearalenone and α-zearalenol in milk by UHPLC-MS/MS. Food Chem 2013; 146:242-9. [PMID: 24176338 DOI: 10.1016/j.foodchem.2013.09.047] [Citation(s) in RCA: 124] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Revised: 08/24/2013] [Accepted: 09/08/2013] [Indexed: 10/26/2022]
Abstract
In this study, a sensitive and rapid method has been developed for the simultaneous determination of aflatoxin M1, ochratoxin A, zearalenone and α-zearalenol in milk by ultra high performance liquid chromatography combined with electrospray ionisation triple quadrupole tandem mass spectrometry (UHPLC-ESI-MS/MS). The milk samples were purified using Oasis HLB cartridge. The matrix effects were evaluated by determining the signal suppression-enhancement (SSE) and corrected by external matrix-matched calibration. The limits of quantity (LOQ) of the mycotoxins were in the range of 0.003-0.015μgkg(-1). The high correlation coefficients (R(2)⩾0.996) were obtained in the range of 0.01-1.00μgkg(-1) of the mycotoxins, along with good recovery (87.0-109%), repeatability (3.4-9.9%) and intra-laboratory reproducibility (4.0-9.9%) at the concentrations of 0.025, 0.1 and 0.5μgkg(-1). The detected rates of the mycotoxins were from 16.7% to 96.7% in raw milk, liquid milk and milk powder samples collected from the dairy farms and supermarkets in Beijing. The method proposed is suitable for the simultaneous determination of aflatoxin M1, ochratoxin A, zearalenone, and α-zearalenol, and could be performed for analysing the mycotoxins in milk.
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Chen F, Zheng N, Wang Y, Wen JL, Tu WF, Du YQ, Lin JM. Sequential intravenous/oral moxifloxacin monotherapy for complicated skin and skin structure infections: a meta-analysis of randomised controlled trials. Int J Clin Pract 2013; 67:834-42. [PMID: 23952463 DOI: 10.1111/ijcp.12174] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Accepted: 03/13/2013] [Indexed: 11/29/2022] Open
Abstract
OBJECTIVES The presumed superiority of moxifloxacin for the treatment of complicated skin and skin structure infections (cSSSIs) is based on laboratory data, but has not yet been established on clinical grounds. The aim of this meta-analysis was to evaluate the efficacy and safety of sequential intravenous (i.v.)/oral (p.o.) moxifloxacin monotherapy for the treatment of cSSSIs. METHODS Randomised controlled trials (RCTs) published prior to November 2012 were systematically retrieved from PubMed, MEDLINE, EMBASE, ScienceDirect, ClinicalTrials.gov and the Cochrane Central Register of Controlled Trials. Finally, a meta-analysis of all RCTs eligible for inclusion criteria was performed. RESULTS Three studies that enrolled 2255 patients were included in the meta-analysis. There were no statistically significant differences between patients given moxifloxacin and those given other antibiotics with regard to clinical success rate [1667 patients, odds ratio (OR) = 0.83, 95% confidence interval (CI) 0.63 to 1.09, p = 0.18], bacteriological success rate (bacteriological success rates: 1502 patients, OR = 0.90, 95% CI 0.68-1.18, p = 0.45) or mortality (2207 patients, OR = 1.96, 95% CI 0.79-4.88, p = 0.15). Significantly, more overall adverse events (AEs) were associated with the use of moxifloxacin than with other antibiotics (2207 patients, OR = 1.21, 95%CI 1.00-1.45, p = 0.04). However, there was no statistically significant difference in the occurrence of drug-related AEs, serious AEs or serious drug-related AEs between patients given moxifloxacin and those given other antibiotics. CONCLUSION Sequential i.v./p.o. moxifloxacin monotherapy is an effective and relatively safe option for the treatment of cSSSIs. Other benefits of moxifloxacin may make it a more viable option compared with the currently used regimens.
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Tong G, Savant I, Jariwala N, Burt D, Zheng N, Buzescu A, Bertz R, Keswani S, Marcus R. Phase I single and multiple dose study to evaluate the safety, tolerability, and pharmacokinetics of BMS-927711 in healthy subjects. J Headache Pain 2013. [PMCID: PMC3619991 DOI: 10.1186/1129-2377-14-s1-p118] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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55
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Tong G, Savant I, Jariwala N, Burt D, Zheng N, Buzescu A, Bertz R, Keswani S, Marcus R. Phase I single and multiple dose study to evaluate the safety, tolerability, and pharmacokinetics of BMS-927711 in healthy subjects. J Headache Pain 2013. [DOI: 10.1186/1129-2377-1-s1-p118] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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56
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Zheng N, Sun P, Wang J, Zhen Y, Han R, Xu X. Occurrence of aflatoxin M1 in UHT milk and pasteurized milk in China market. Food Control 2013. [DOI: 10.1016/j.foodcont.2012.06.020] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Abstract
Throwing arm injuries are common and often related to the shoulder external and internal rotation. Quantitative assessment may provide new insights to physical assessment and options for treatment. After having signed IRB approved consents and filled out injury questionnaires, 96 baseball pitchers were examined on both shoulders using a custom-made wireless device. The resistance onset angle (ROA), end-point angle (EPA), shoulder rotational flexibility (SRF) in both external and internal rotation, and rotational ranges of motion (ROM) of both shoulders were determined. About 34% of subjects had surgeries on their throwing arm. Another 15% of subjects had throwing arm injuries that did not require surgical treatments. The throwing arm had significantly lower internal ROA, EPA and SRF, but significantly higher external ROA, EPA and SRF than the non-throwing arm. There were significant differences in shoulder rotational properties among groups with different surgery locations. Subjects with shoulder surgeries had greater internal rotation flexibility of their throwing arm than those with surgeries on the elbow. Throwers with injury and surgery history had significantly different shoulder rotational properties. Abnormal shoulder rotational properties may be related to throwing arm injuries. A better understanding of their relationship may lead us to effective preventive measures of throwing arm injuries.
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Zheng N, Pan C, Liu W. New serum biomarkers for detection of endometriosis using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. J Int Med Res 2012; 39:1184-92. [PMID: 21986120 DOI: 10.1177/147323001103900406] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
This study used proteomic fingerprint technology, combining nano-sized magnetic beads with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), to screen for potential protein biomarkers for the diagnosis of endometriosis. Serum proteins from 126 patients with endometriosis and 120 healthy controls were profiled and compared. Biomarker pattern software identified 46 discriminating mass-to-charge m/z ratio peaks that were related to endometriosis. The model constructed by the software, based on three of these peaks (m/z 5988.7, 7185.3 and 8929.8), generated excellent separation between the endometriosis and control groups. The sensitivity was 91.4% and the specificity 95.0%. Blind testing on a second series of serum samples from patients with endometriosis and healthy controls indicated a sensitivity of 89.3% and a specificity of 90.0%. Biomarkers for endometriosis can be discovered in serum by MALDI-TOF-MS in combination with nano-sized magnetic beads. The pattern of combined markers provides a powerful and reliable diagnostic method for endometriosis, with high sensitivity and specificity.
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Zheng N, Wang CX, Zhang X, Du LT, Zhang J, Kan SF, Zhu CB, Dong ZG, Wang LL, Wang S, Li W. Up-regulation of HLA-G expression in cervical premalignant and malignant lesions. ACTA ACUST UNITED AC 2011; 77:218-24. [DOI: 10.1111/j.1399-0039.2010.01607.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Lan X, Wang J, Bu D, Shen J, Zheng N, Sun P. Effects of Heating Temperatures and Addition of Reconstituted Milk on the Heat Indicators in Milk. J Food Sci 2010; 75:C653-8. [DOI: 10.1111/j.1750-3841.2010.01802.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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61
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Zhang ZS, Sun XJ, Wang QC, Zheng DM, Zheng N, Lv XG. Recovery from Mercury Contamination in the Second Songhua River, China. WATER, AIR, AND SOIL POLLUTION 2010; 211:219-229. [PMID: 20835296 PMCID: PMC2923708 DOI: 10.1007/s11270-009-0294-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Accepted: 11/24/2009] [Indexed: 05/09/2023]
Abstract
Mercury pollution in the Second Songhua River (SSR) was serious in the last century due to effluent from a chemical corporation. Effects of riverine self-purification on mercury removal were studied by comparing monitoring data of mercury concentrations varieties in water, sediment, and fish in the past, about 30 years. The present work suggested that a river of such a size like the SSR possessed the potential ability to recover from mercury pollution under the condition that mercury sources were cut off, though it needs a very long time, which might be several decades or even a century of years. During the 30 years with no effluent containing mercury input, total mercury (T-Hg) of water and sediment in some typical segments, mostly near the past effluent outlet, had decreased radically but still higher than the background values, though the decrease amplitudes were over 90% compared with that in 1975. T-Hg had decreased by more than 90% in most fishes, but some were still not suitable for consumption. Methylmercury concentrations (MeHg) of water, sediment, and fish were higher or close to the background levels in 2004. In the coming decades, the purification processes in the SSR would be steady and slow for a long period.
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Zheng N, Johnson JP, Williams CC, Wang G. Electronic characterization of individual monolayer protected Au clusters by single electron tunneling force spectroscopy. NANOTECHNOLOGY 2010; 21:295708. [PMID: 20601769 DOI: 10.1088/0957-4484/21/29/295708] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Gold monolayer protected clusters (MPCs) exhibit strong quantum confinement effects and size dependent electronic, optical and chemical properties. Chemical tuning of these properties can be achieved by established synthesis methods, providing an excellent system for the study of the relationship between chemical and electronic structure. In this paper, the first electronic spectra of individual Au MPCs (Au(25)) acquired by single electron tunneling force spectroscopy on non-conducting silicon dioxide surfaces are reported. A HOMO-LUMO (highest occupied molecular orbital-lowest unoccupied molecular orbital) energy gap is observed in the Au(25) spectra. Hysteretic charging of the particles is also observed while obtaining the energy spectra. The new single electron tunneling measurement methodology is described. A model explaining the measurements supports the existence of mid-HOMO-LUMO gap defect states.
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Crawford DC, Zheng N, Speelmon EC, Stanaway I, Rieder MJ, Nickerson DA, McElrath MJ, Lingappa J. An excess of rare genetic variation in ABCE1 among Yorubans and African-American individuals with HIV-1. Genes Immun 2009; 10:715-21. [PMID: 19657357 DOI: 10.1038/gene.2009.57] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Signatures of natural selection occur throughout the human genome and can be detected at the sequence level. We have re-sequenced ABCE1, a host candidate gene essential for HIV-1 capsid assembly, in European- (n=23) and African-descent (Yoruban; n=24) reference populations for genetic variation discovery. We identified an excess of rare genetic variation in Yoruban samples, and the resulting Tajima's D was low (-2.27). The trend of excess rare variation persisted in flanking candidate genes ANAPC10 and OTUD4, suggesting that this pattern of positive selection can be detected across the 184.5 kb examined on chromosome 4. Owing to ABCE1's role in HIV-1 replication, we re-sequenced the candidate gene in three small cohorts of HIV-1-infected or resistant individuals. We were able to confirm the excess of rare genetic variation among HIV-1-positive African-American individuals (n=53; Tajima's D=-2.34). These results highlight the potential importance of ABCE1's role in infectious diseases such as HIV-1.
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Johnson JP, Zheng N, Williams CC. Atomic scale imaging and spectroscopy of individual electron trap states using force detected dynamic tunnelling. NANOTECHNOLOGY 2009; 20:055701. [PMID: 19417360 DOI: 10.1088/0957-4484/20/5/055701] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We report the first atomic scale imaging and spectroscopic measurements of electron trap states in completely non-conducting surfaces by dynamic tunnelling force microscopy/spectroscopy. Single electrons are dynamically shuttled to/from individual states in thick films of hafnium silicate and silicon dioxide. The new method opens up surfaces that are inaccessible to the scanning tunnelling microscope for imaging and spectroscopy on an atomic scale.
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Zheng DM, Wang QC, Zhang ZS, Zheng N, Zhang XW. Bioaccumulation of total and methyl mercury by arthropods. BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2008; 81:95-100. [PMID: 18365125 DOI: 10.1007/s00128-008-9393-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2007] [Accepted: 03/11/2008] [Indexed: 05/26/2023]
Abstract
Three arthropods, Locusta migratoria manilensis, Acrida chinensis, and Paraten-odera sinensis were selected to study the bioaccumulation of total and methyl mercury. Concentrations of total mercury in the tissues of Locusta migratoria manilensis and Acrida chinensis were 0.013-0.154 and 0.009-0.138 mg/kg, respectively, while those of methylmercury were 0.001-0.012 and 0.001-0.006 mg/kg, respectively. Concentrations of total mercury in Locusta migratoria manilensis and Acrida chinensis, which are the primary consumers, are lower than those in their food, while mercury is accumulated more by the secondary consumer, Paraten-odera sinensis. For total mercury, the concentrations in Locusta migratoria manilensis are inversely proportional to body length and those in Acrida chinensis increase first and then decrease with increased body length. For methyl mercury, concentration is proportional to body length for both of these arthropods. Total mercury concentrations vary in different parts of the arthropod body, and increase in the order of: abdomen > thorax > head.
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Zheng N, Barrentine S, Fleisig G, Andrews J. Swing Kinematics for Male and Female Pro Golfers. Int J Sports Med 2008; 29:965-70. [DOI: 10.1055/s-2008-1038732] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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68
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Zheng N, Barrentine S, Fleisig G, Andrews J. Kinematic Analysis of Swing in Pro and Amateur Golfers. Int J Sports Med 2008; 29:487-93. [DOI: 10.1055/s-2007-989229] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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69
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Zheng N, Wang QC, Zheng DM. [Transfer characteristics of mercury, lead, cadmium, zinc and cuprum from soil to vegetable around zinc smelting plant]. HUAN JING KE XUE= HUANJING KEXUE 2007; 28:1349-54. [PMID: 17674748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The transfer characteristics of Hg, Pb, Cd, Zn and Cu from soil to vegetables near zinc smelting plant in Huludao City, China were investigated, and the sources of heavy metals in the soil and vegetable were also analyzed. The results indicate that the Hg, Pb, Cd, Zn and Cu contents of vegetables are 0.013, 5.476, 2.852, 41.16 and 1.515 mg/kg (fresh weight), respectively, and the environment around Huludao Zinc Plant are contaminated seriously. The transfer factors (TF) of heavy metals decrease in the order of Cd > Zn > Cu > Pb > Hg. The transfer factors of heavy metals from soil to leaves are higher than from soil to other tissues. The heavy metals in soil derive from atmosphere, and the parts of Pb in the leaves of vegetable derive from atmosphere. Uptake of gaseous mercury is the predominant pathway by which mercury accumulates in the vegetable.
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Zheng N, Gao B, Moser M, Indelicato P. BILATERAL DIFFERENCES OF 3-D MOTION IN ACL-DIFICENT AND ACL-RECONSTRUCTED KNEES. J Biomech 2007. [DOI: 10.1016/s0021-9290(07)70097-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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71
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Gao B, Subramanian S, Zheng N. MRI MODEL-BASED KNEE JOINT SURFACE MOTION ANALYSIS. J Biomech 2007. [DOI: 10.1016/s0021-9290(07)70152-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Fleisig GS, Zheng N, Stodden DF, Andrews JR. Relationship between bat mass properties and bat velocity. SPORTS ENGINEERING 2002. [DOI: 10.1046/j.1460-2687.2002.00096.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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73
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Wang C, Li Y, Bu X, Zheng N, Zivkovic O, Yang CS, Feng P. Three-dimensional superlattices built from (M(4)In(16)S(33))(10-)(M = Mn, Co, Zn, Cd) supertetrahedral clusters. J Am Chem Soc 2001; 123:11506-7. [PMID: 11707140 DOI: 10.1021/ja011739r] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Andrews JR, Heggland EJ, Fleisig GS, Zheng N. Relationship of ulnar collateral ligament strain to amount of medial olecranon osteotomy. Am J Sports Med 2001; 29:716-21. [PMID: 11734483 DOI: 10.1177/03635465010290060801] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Athletes at risk for valgus extension overload are also at risk for tears of the anterior bundle of the ulnar collateral ligament. Some athletes develop ligament tears after procedures for valgus extension overload such as posteromedial olecranon osteotomy. The amount of posteromedial olecranon that can be resected before ulnar collateral ligament strain, and risk of injury, increases is unknown. We dissected and mounted five fresh-frozen human cadaveric elbows to allow strain gauge monitoring of the ulnar collateral ligament with varying valgus stress, elbow flexion angle, and medial osteotomy. The average strain to failure was 11.96%+/-6.51%, corresponding to a load of 347.71+/-46.42 N. The maximum tensile force recorded at failure was 416.24 N. Three-way repeated-measures analysis of variance revealed no significant change in strain with change in the amount of osteotomy for a given applied load and angle of flexion. On the basis of these data, we conclude that the effect of medial olecranon osteotomy on ulnar collateral ligament strain may be small. Small sample size, elderly specimens, and the variables inherent in the experimental setup and mathematical modeling make it difficult to extrapolate these results to in vivo behavior of the anterior ulnar collateral ligament. Further work is needed before definitive guidelines for olecranon osteotomy can be formulated.
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Escamilla RF, Fleisig GS, Zheng N, Barrentine SW, Andrews JR. Kinematic comparisons of 1996 Olympic baseball pitchers. J Sports Sci 2001; 19:665-76. [PMID: 11522142 DOI: 10.1080/02640410152475793] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
The aim of this study was to compare and evaluate the kinematics of baseball pitchers who participated in the 1996 XXVI Centennial Olympic Games. Two synchronized video cameras operating at 120 Hz were used to video 48 pitchers from Australia, Japan, the Netherlands, Cuba, Italy, Korea, Nicaragua and the USA. All pitchers were analysed while throwing the fastball pitch. Twenty-one kinematic parameters were measured at lead foot contact, during the arm cocking and arm acceleration phases, and at the instant of ball release. These parameters included stride length, foot angle and foot placement; shoulder abduction, shoulder horizontal adduction and shoulder external rotation; knee and elbow flexion; upper torso, shoulder internal rotation and elbow extension angular velocities; forward and lateral trunk tilt; and ball speed. A one-way analysis of variance (P < 0.01) was used to assess kinematic differences. Shoulder horizontal adduction and shoulder external rotation at lead foot contact and ball speed at the instant of ball release were significantly different among countries. The greater shoulder horizontal abduction observed in Cuban pitchers at lead foot contact is thought to be an important factor in the generation of force throughout the arm cocking and arm acceleration phases, and may in part explain why Cuban pitchers generated the greatest ball release speed. We conclude that pitching kinematics are similar among baseball pitchers from different countries.
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Escamilla RF, Fleisig GS, Zheng N, Lander JE, Barrentine SW, Andrews JR, Bergemann BW, Moorman CT. Effects of technique variations on knee biomechanics during the squat and leg press. Med Sci Sports Exerc 2001; 33:1552-66. [PMID: 11528346 DOI: 10.1097/00005768-200109000-00020] [Citation(s) in RCA: 177] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE The specific aim of this project was to quantify knee forces and muscle activity while performing squat and leg press exercises with technique variations. METHODS Ten experienced male lifters performed the squat, a high foot placement leg press (LPH), and a low foot placement leg press (LPL) employing a wide stance (WS), narrow stance (NS), and two foot angle positions (feet straight and feet turned out 30 degrees ). RESULTS No differences were found in muscle activity or knee forces between foot angle variations. The squat generated greater quadriceps and hamstrings activity than the LPH and LPL, the WS-LPH generated greater hamstrings activity than the NS-LPH, whereas the NS squat produced greater gastrocnemius activity than the WS squat. No ACL forces were produced for any exercise variation. Tibiofemoral (TF) compressive forces, PCL tensile forces, and patellofemoral (PF) compressive forces were generally greater in the squat than the LPH and LPL, and there were no differences in knee forces between the LPH and LPL. For all exercises, the WS generated greater PCL tensile forces than the NS, the NS produced greater TF and PF compressive forces than the WS during the LPH and LPL, whereas the WS generated greater TF and PF compressive forces than the NS during the squat. For all exercises, muscle activity and knee forces were generally greater in the knee extending phase than the knee flexing phase. CONCLUSIONS The greater muscle activity and knee forces in the squat compared with the LPL and LPH implies the squat may be more effective in muscle development but should be used cautiously in those with PCL and PF disorders, especially at greater knee flexion angles. Because all forces increased with knee flexion, training within the functional 0-50 degrees range may be efficacious for those whose goal is to minimize knee forces. The lack of ACL forces implies that all exercises may be effective during ACL rehabilitation.
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Lovett BD, Lo Nigro L, Rappaport EF, Blair IA, Osheroff N, Zheng N, Megonigal MD, Williams WR, Nowell PC, Felix CA. Near-precise interchromosomal recombination and functional DNA topoisomerase II cleavage sites at MLL and AF-4 genomic breakpoints in treatment-related acute lymphoblastic leukemia with t(4;11) translocation. Proc Natl Acad Sci U S A 2001; 98:9802-7. [PMID: 11493704 PMCID: PMC55533 DOI: 10.1073/pnas.171309898] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/19/2001] [Indexed: 11/18/2022] Open
Abstract
We analyzed the der(11) and der(4) genomic breakpoint junctions of a t(4;11) in the leukemia of a patient previously administered etoposide and dactinomycin by molecular and biochemical approaches to gain insights about the translocation mechanism and the relevant drug exposure. The genomic breakpoint junctions were amplified by PCR. Cleavage of DNA substrates containing the normal homologues of the MLL and AF-4 translocation breakpoints was examined in vitro upon incubation with human DNA topoisomerase IIalpha and etoposide, etoposide catechol, etoposide quinone, or dactinomycin. The der(11) and der(4) genomic breakpoint junctions both involved MLL intron 6 and AF-4 intron 3. Recombination was precise at the sequence level except for the overall gain of a single templated nucleotide. The translocation breakpoints in MLL and AF-4 were DNA topoisomerase II cleavage sites. Etoposide and its metabolites, but not dactinomycin, enhanced cleavage at these sites. Assuming that DNA topoisomerase II was the mediator of the breakage, processing of the staggered nicks induced by DNA topoisomerase II, including exonucleolytic deletion and template-directed polymerization, would have been required before ligation of the ends to generate the observed genomic breakpoint junctions. These data are inconsistent with a translocation mechanism involving interchromosomal recombination by simple exchange of DNA topoisomerase II subunits and DNA-strand transfer; however, consistent with reciprocal DNA topoisomerase II cleavage events in MLL and AF-4 in which both breaks became stable, the DNA ends were processed and underwent ligation. Etoposide and/or its metabolites, but not dactinomycin, likely were the relevant exposures in this patient.
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MESH Headings
- Antigens, Neoplasm
- Antineoplastic Combined Chemotherapy Protocols/adverse effects
- Antineoplastic Combined Chemotherapy Protocols/therapeutic use
- Catechols/pharmacology
- Child
- Chromosome Breakage
- Chromosomes, Human, Pair 11/genetics
- Chromosomes, Human, Pair 11/ultrastructure
- Chromosomes, Human, Pair 4/genetics
- Chromosomes, Human, Pair 4/ultrastructure
- Combined Modality Therapy
- Cyclophosphamide/administration & dosage
- DNA Topoisomerases, Type II/metabolism
- DNA, Neoplasm/drug effects
- DNA-Binding Proteins/genetics
- Dactinomycin/administration & dosage
- Dactinomycin/adverse effects
- Dactinomycin/pharmacology
- Etoposide/administration & dosage
- Etoposide/adverse effects
- Etoposide/pharmacology
- Female
- Histone-Lysine N-Methyltransferase
- Humans
- Ifosfamide/administration & dosage
- Isoenzymes/metabolism
- Models, Genetic
- Molecular Sequence Data
- Myeloid-Lymphoid Leukemia Protein
- Neoplasm Proteins/metabolism
- Neoplasms, Second Primary/chemically induced
- Neoplasms, Second Primary/genetics
- Nuclear Proteins/genetics
- Precursor Cell Lymphoblastic Leukemia-Lymphoma/chemically induced
- Precursor Cell Lymphoblastic Leukemia-Lymphoma/genetics
- Proto-Oncogenes
- Radiotherapy, Adjuvant
- Recombination, Genetic
- Rhabdomyosarcoma, Alveolar/drug therapy
- Rhabdomyosarcoma, Alveolar/radiotherapy
- Soft Tissue Neoplasms/drug therapy
- Soft Tissue Neoplasms/radiotherapy
- Transcription Factors
- Transcriptional Elongation Factors
- Translocation, Genetic/genetics
- Vincristine/administration & dosage
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79
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Pang S, Zheng N, Felix CA, Scavuzzo J, Boston R, Blair IA. Simultaneous determination of etoposide and its catechol metabolite in the plasma of pediatric patients by liquid chromatography/tandem mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2001; 36:771-781. [PMID: 11473400 DOI: 10.1002/jms.173] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The anticancer drug etoposide is associated with leukemias with MLL gene translocations and other translocations as a treatment complication. The genotype of cytochrome P450 3A4 (CYP3A4), which converts etoposide to its catechol metabolite, influences the risk. In order to perform pharmacokinetic studies aimed at further elucidation of the translocation mechanism, we have developed and validated a liquid chromatography/electrospray/tandem mass spectrometry assay for the simultaneous analysis of etoposide and its catechol metabolite in human plasma. The etoposide analog teniposide was used as the internal standard. Liquid chromatography was performed on a YMC ODS-AQ column. Simultaneous determination of etoposide and its catechol metabolite was achieved using a small volume of plasma, so that the method is suitable for pediatric patients. The limits of detection were 200 ng ml(-1) etoposide and 10 ng ml(-1) catechol metabolite in human plasma and 25 ng ml(-1) etoposide and 2.5 ng ml(-1) catechol metabolite in protein-free plasma, respectively. Acceptable precision and accuracy were obtained for concentrations in the calibration curve ranges 0.2--100 microg ml(-1) etoposide and 10--5000 ng ml(-1) catechol metabolite in human plasma. Acceptable precision and accuracy for protein-free human plasma in the range 25--15 000 ng ml(-1) etoposide and 2.5--1500 ng ml(-1) etoposide catechol were also achieved. This method was selective and sensitive enough for the simultaneous quantitation of etoposide and its catechol as a total and protein-free fraction in small plasma volumes from pediatric cancer patients receiving etoposide chemotherapy. A pharmacokinetic model has been developed for future studies in large populations.
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80
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Liu B, Ye S, He P, Zheng N, Zhao Y, Sun R, Tang Z. [Study of the cytotoxity against human hepatocellular carcinoma cells induced by the MAGE-1 gene modified dendritic cells]. ZHONGHUA GAN ZANG BING ZA ZHI = ZHONGHUA GANZANGBING ZAZHI = CHINESE JOURNAL OF HEPATOLOGY 2001; 9:151-3. [PMID: 11412389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
OBJECTIVE To genetically modify dendritic cells (DC) with a tumor associated antigen gene MAGE-1 and to observe in vitro the cytotoxic effect induced by this genetically modified DC against human hepatocellular carcinoma (HCC) cell line SMMC7721, thus giving a primary verification of the possibility of this genetically modified DC to induce specific antitumor immunity against HCC and serving as a new type of vaccine. METHODS The MAGE-1 gene was inserted into the retrovirus vector LXSN to construct the recombinant retrovirus LMSN. The monocyte-derived DCs were transfected by LMSN and control virus LXSN respectively as well as a third group was set up as non-transfected control. The MAGE-1 gene expression in LMSN transfected DC was identified by Western blot and the in vitro cytotoxities against SMMC7721 induced by three groups of DC were tested by MTT assay. RESULTS A recombinant retrovirus LMSN containing the tumor rejection antigen gene MAGE-1 was successfully constructed and the MAGE-1 gene expression in LMSN transfected human monocyte-derived DC was induced. The LMSN transfected DC could induce very high lytic activity against SMMC7721 in vitro with the lytic activity of 78.9%+/-3.6%. Nevertheless, the LXSN transfected DC and non-transfected DC only induced relatively lower lytic activity as 34.7%+/-4.3% and 3.9%+/-2.0%, respectively. The difference of the lytic activities between those three groups as statistically significant (P<0.01). CONCLUSIONS The MAGE-1 gene transfected DC can induce higher in vitro cytotoxicity against SMMC7721, suggesting the possibility of this genetically modified DC to induce specific antitumor activity and to serve as a new type of vaccine for HCC.
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81
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Cleverley RM, Zheng N, Gierasch LM. The cost of exposing a hydrophobic loop and implications for the functional role of 4.5 S RNA in the Escherichia coli signal recognition particle. J Biol Chem 2001; 276:19327-31. [PMID: 11278844 DOI: 10.1074/jbc.m011130200] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The signal recognition particle (SRP) is an RNA-protein complex that directs ribosomes to the rough endoplasmic reticulum membrane by binding to targeting signals found on the nascent chain of proteins destined for export to the endoplasmic reticulum. We found evidence from studies with fragments of the protein component of the Escherichia coli SRP that a long hydrophobic loop (the so-called "finger loop") is detrimental to the stability of its signal peptide-binding domain, the M domain. This hydrophobic loop is highly conserved and thus may have a critical role in the function of the SRP. Given our previously reported evidence that 4.5 S RNA stabilizes the tertiary fold of the M domain (Zheng, N., and Gierasch, L. M. (1997) Mol. Cell 1, 79-87), we now propose that the functional requirement for 4.5 S RNA resides in its ability to counteract the destabilizing influence of the finger loop.
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82
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Fu Q, Zheng N, Li YZ, Chang WB, Wang ZM. Molecularly imprinted polymers from nicotinamide and its positional isomers. J Mol Recognit 2001; 14:151-6. [PMID: 11391785 DOI: 10.1002/jmr.526] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Imprinted polymers were prepared for nicotinamide and its positional isomers. The influence of porogenic solvent and functional monomer on recognition properties of the polymer was compared. The results indicated that two functional groups, the heterocyclic nitrogen and the amide group, in the nicotinamide or isonicotinamide molecule have a synergistic effect in binding to the polymer. The polymers prepared with nicotinamide and isonicotinamide can be used as HPLC stationary phase for the separation of positional isomers of nicotinamide or isonicotinamide, while the polymer prepared with picolinamide showed no specificity toward the template. The mechanisms for the differences in recognition are discussed. In addition to the retention of polymers to their templates the polymers also displayed excellent retention to nicotinic acid and isonicotinic acid, compounds structurally similar to the template. This dual recognition property of the polymer may be useful in circumstances where the preparation of a polymer for a specific template may be problematic because of poor stability or solubility.
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83
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Zheng N, Wang P, Jeffrey PD, Pavletich NP. Structure of a c-Cbl-UbcH7 complex: RING domain function in ubiquitin-protein ligases. Cell 2000; 102:533-9. [PMID: 10966114 DOI: 10.1016/s0092-8674(00)00057-x] [Citation(s) in RCA: 679] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Ubiquitin-protein ligases (E3s) regulate diverse cellular processes by mediating protein ubiquitination. The c-Cbl proto-oncogene is a RING family E3 that recognizes activated receptor tyrosine kinases, promotes their ubiquitination by a ubiquitin-conjugating enzyme (E2) and terminates signaling. The crystal structure of c-Cbl bound to a cognate E2 and a kinase peptide shows how the RING domain recruits the E2. A comparison with a HECT family E3-E2 complex indicates that a common E2 motif is recognized by the two E3 families. The structure reveals a rigid coupling between the peptide binding and the E2 binding domains and a conserved surface channel leading from the peptide to the E2 active site, suggesting that RING E3s may function as scaffolds that position the substrate and the E2 optimally for ubiquitin transfer.
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84
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Zheng N, Ruan J, Zhang Y. [Pharmacokinetic study on absorption of stachyose]. ZHONGGUO ZHONG XI YI JIE HE ZA ZHI ZHONGGUO ZHONGXIYI JIEHE ZAZHI = CHINESE JOURNAL OF INTEGRATED TRADITIONAL AND WESTERN MEDICINE 2000; 20:444-6. [PMID: 11789231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
OBJECTIVE To study the intestinal absorption and absorption site of stachyose, one of the oligosaccharides extracted from Rehmannia, in mice and rats. METHODS Plasma concentration of stachyose was measured by high performance liquid chromatography (HPLC) with postcolumn fluorescence derivatization after administration of stachyose to mice by oral or intravenous injection. The absorption of stachyose in different sections of digestive tract was evaluated using the intestine loop in situ technique. The kanamycin treated mice were used to study the metabolism of stachyose in intestine. RESULTS Absorption of stachyose in intestine after oral administration was quick but low, the bioavailability being 3.82%. The absorption rate in stomach, duodenum, jejunum and ileum was 6.03%, 13.80%, 8.33% and 0.53% respectively, no absorption was tested in large intestine. The residual rate of stachyose in the intestine of normal mice and kanamycin treated mice was 8.6% and 93.4% respectively. CONCLUSION The intestinal absorption rate of stachyose is low, the main absorption site is the upper portion of small intestine. The unabsorbed stachyose is metabolized by the intestinal microflora.
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85
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Zheng N, Barrentine SW. Biomechanics and motion analysis applied to sports. Phys Med Rehabil Clin N Am 2000; 11:309-22. [PMID: 10810763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
The development of motion analysis and the application of biomechanical analysis techniques to sports has paralleled the exponential growth of computational and videographic technology. Technological developments have provided for advances in the investigation of the human body and the action of the human body during sports believed to be unobtainable a few years ago. Technological advancements have brought biomechanical applications into a wide range of fields from orthopedics to entertainment. An area that has made tremendous gains using biomechanics is sports science. Coaches, therapists, and physicians are using biomechanics to improve performance, rehabilitation, and the prevention of sports related injuries. Functional analyses of athletic movements that were impossible a few years ago are available and used today. With new advancements, the possibilities for investigating the way a human interacts and reacts to environmental conditions are ever expanding.
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86
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Zheng N, Monckton DG, Wilson G, Hagemeister F, Chakraborty R, Connor TH, Siciliano MJ, Meistrich ML. Frequency of minisatellite repeat number changes at the MS205 locus in human sperm before and after cancer chemotherapy. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2000; 36:134-145. [PMID: 11013412 DOI: 10.1002/1098-2280(2000)36:2<134::aid-em8>3.0.co;2-d] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
To determine whether the measurement of repeat number mutations at a minisatellite locus could detect human germline mutations induced by chemotherapy, we performed a longitudinal study of the mutation frequencies in sperm from 10 patients treated for Hodgkin's disease. Polymerase chain reaction on small pools of DNA equivalent to 100 sperm and Southern blotting were used to screen at least 7900 sperm in each sample to quantify the mutation frequency at the minisatellite MS205 locus. Pretreatment and posttreatment semen samples were obtained at least 2 months after completion of therapy from 4 patients treated with a regimen (Novantrone, Oncovin, vinblastine and prednisone [NOVP]) that lacks alkylating agents and from three patients treated with regimens (Cytoxan, vinblastine, procarbazine and prednisone/Adriamycin, bleomycin, dacarbazine, lomustine, and prednisone [CVPP/ABDIC] or mechlorethamine, Oncovin, procarbazine and prednisone [MOPP]) containing alkylating agents. There were no effects of NOVP or CVPP/ABDIC on the mutation frequencies. In the 1 patient treated with MOPP, the treatment with the highest dose of gonadotoxic alkylating agents, there was a statistically significant increase in mutation frequency from 0.79% pretreatment to 1.14% posttreatment, indicating induction of mutations in stem spermatogonia. During-treatment semen samples obtained from 2 patients treated with ABVD, which does not contain gonadotoxic alkylating agents, and 1 with NOVP also did not show any increases above the baseline mutation frequencies, indicating no increase in the minisatellite mutation frequency in spermatocytes. Thus, measurement of repeat number changes at minisatellite MS205 appears to be able to detect induced germline mutations in human sperm. However, most chemotherapy regimens do not significantly increase this class of mutations.
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87
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Fleisig GS, Barrentine SW, Zheng N, Escamilla RF, Andrews JR. Kinematic and kinetic comparison of baseball pitching among various levels of development. J Biomech 1999; 32:1371-5. [PMID: 10569718 DOI: 10.1016/s0021-9290(99)00127-x] [Citation(s) in RCA: 376] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Proper biomechanics help baseball pitchers minimize their risk of injury and maximize performance. However previous studies involved adult pitchers only. In this study, 23 youth, 33 high school, 115 college, and 60 professional baseball pitchers were analyzed. Sixteen kinematic (11 position and five velocity), eight kinetic, and six temporal parameters were calculated and compared among the four levels of competition. Only one of the 11 kinematic position parameters showed significant differences among the four levels, while all five velocity parameters showed significant differences. All eight kinetic parameters increased significantly with competition level. None of the six temporal parameters showed significant differences. Since 16 of the 17 position and temporal parameters showed no significant differences, this study supports the philosophy that a child should be taught 'proper' pitching mechanics for use throughout a career. Kinetic differences observed suggest greater injury risk at higher competition levels. Since adult pitchers did not demonstrate different position or temporal patterns than younger pitchers, increases in joint forces and torques were most likely due to increased strength and muscle mass in the higher level athlete. The greater shoulder and elbow angular velocities produced by high-level pitchers were most likely due to the greater torques they generated during the arm cocking and acceleration phases. The combination of more arm angular velocity and a longer arm resulted in greater linear ball velocity for the higher level pitcher. Thus, it appears that the natural progression for successful pitching is to learn proper mechanics as early as possible, and build strength as the body matures.
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88
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Vella C, Gregory J, Bristow R, Troop M, Easterbrook P, Zheng N, Daniels R. Isolation of HIV type 1 from long-term nonprogressors in Herpesvirus saimiri-immortalized T cells. AIDS Res Hum Retroviruses 1999; 15:1145-7. [PMID: 10461835 DOI: 10.1089/088922299310449] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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89
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Pan L, Zheng N, Wu Y, Wu S, Huang X. Poly[mercury(II)-μ-4,4'-bipyridine-di-μ-bromo]. Acta Crystallogr C 1999. [DOI: 10.1107/s0108270198006325] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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90
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Zheng N, Fraenkel E, Pabo CO, Pavletich NP. Structural basis of DNA recognition by the heterodimeric cell cycle transcription factor E2F-DP. Genes Dev 1999; 13:666-74. [PMID: 10090723 PMCID: PMC316551 DOI: 10.1101/gad.13.6.666] [Citation(s) in RCA: 213] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The E2F and DP protein families form heterodimeric transcription factors that play a central role in the expression of cell cycle-regulated genes. The crystal structure of an E2F4-DP2-DNA complex shows that the DNA-binding domains of the E2F and DP proteins both have a fold related to the winged-helix DNA-binding motif. Recognition of the central c/gGCGCg/c sequence of the consensus DNA-binding site is symmetric, and amino acids that contact these bases are conserved among all known E2F and DP proteins. The asymmetry in the extended binding site TTTc/gGCGCc/g is associated with an amino-terminal extension of E2F4, in which an arginine binds in the minor groove near the TTT stretch. This arginine is invariant among E2Fs but not present in DPs. E2F4 and DP2 interact through an extensive protein-protein interface, and structural features of this interface suggest it contributes to the preference for heterodimers over homodimers in DNA binding.
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91
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Pan L, Zheng N, Zhou X, Wu Y, Wu Q, Jin X. catena-Poly[[tetrakis(imidazole-N3)copper(II)]-μ-(dichromato-O:O')]. Acta Crystallogr C 1998. [DOI: 10.1107/s0108270198006660] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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92
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Zheng N, Fleisig GS, Escamilla RF, Barrentine SW. An analytical model of the knee for estimation of internal forces during exercise. J Biomech 1998; 31:963-7. [PMID: 9840764 DOI: 10.1016/s0021-9290(98)00056-6] [Citation(s) in RCA: 137] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
An analytical model of the knee joint was developed to estimate the forces at the knee during exercise. Muscle forces were estimated based upon electromyographic activities during exercise and during maximum voluntary isometric contraction (MVIC), physiological cross-sectional area (PCSA), muscle fiber length at contraction and the maximum force produced by an unit PCSA under MVIC. Tibiofemoral compressive force and cruciate ligaments' tension were determined by using resultant force and torque at the knee, muscle forces, and orientations and moment arms of the muscles and ligaments. An optimization program was used to minimize the errors caused by the estimation of the muscle forces. The model was used in a ten-subject study of open kinetic chain exercise (seated knee extension) and closed kinetic chain exercises (leg press and squat). Results calculated with this model were compared to those from a previous study which did not consider muscle length and optimization. Peak tibiofemoral compressive forces were 3134 +/- 1040 N during squat, 3155 +/- 755 N during leg press and 3285 +/- 1927 N during knee extension. Peak posterior cruciate ligament tensions were 1868 +/- 878 N during squat, 1866 +/- 383 N during leg press and 959 +/- 300 N for seated knee extension. No significant anterior cruciate ligament (ACL) tension was found during leg press and squat. Peak ACL tension was 142 +/- 257 N during seated knee extension. It is demonstrated that the current model provided better estimation of knee forces during exercises, by preventing significant overestimates of tibiofemoral compressive forces and cruciate ligament tensions.
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93
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Escamilla RF, Fleisig GS, Zheng N, Barrentine SW, Wilk KE, Andrews JR. Biomechanics of the knee during closed kinetic chain and open kinetic chain exercises. Med Sci Sports Exerc 1998; 30:556-69. [PMID: 9565938 DOI: 10.1097/00005768-199804000-00014] [Citation(s) in RCA: 320] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
PURPOSE Although closed (CKCE) and open (OKCE) kinetic chain exercises are used in athletic training and clinical environments, few studies have compared knee joint biomechanics while these exercises are performed dynamically. The purpose of this study was to quantify knee forces and muscle activity in CKCE (squat and leg press) and OKCE (knee extension). METHODS Ten male subjects performed three repetitions of each exercise at their 12-repetition maximum. Kinematic, kinetic, and electromyographic data were calculated using video cameras (60 Hz), force transducers (960 Hz), and EMG (960 Hz). Mathematical muscle modeling and optimization techniques were employed to estimate internal muscle forces. RESULTS Overall, the squat generated approximately twice as much hamstring activity as the leg press and knee extensions. Quadriceps muscle activity was greatest in CKCE when the knee was near full flexion and in OKCE when the knee was near full extension. OKCE produced more rectus femoris activity while CKCE produced more vasti muscle activity. Tibiofemoral compressive force was greatest in CKCE near full flexion and in OKCE near full extension. Peak tension in the posterior cruciate ligament was approximately twice as great in CKCE, and increased with knee flexion. Tension in the anterior cruciate ligament was present only in OKCE, and occurred near full extension. Patellofemoral compressive force was greatest in CKCE near full flexion and in the mid-range of the knee extending phase in OKCE. CONCLUSION An understanding of these results can help in choosing appropriate exercises for rehabilitation and training.
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94
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Zheng N, Gierasch LM. Domain interactions in E. coli SRP: stabilization of M domain by RNA is required for effective signal sequence modulation of NG domain. Mol Cell 1997; 1:79-87. [PMID: 9659905 DOI: 10.1016/s1097-2765(00)80009-x] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The E. coli protein, Fth, binds to 4.5S RNA through its M domain to form the signal recognition particle (SRP). The other domain of Fth (NG) is a GTPase, which binds and is coordinately regulated by its receptor, FtsY. We find that the helical M domain is inherently flexible. Binding of 4.5S RNA to Fth stabilizes the M domain yet has little apparent effect on the binding of signal peptides. However, in the absence of the RNA, signal peptide binding results in a global destabilization of Fth, which is prevented by binding of 4.5S RNA. Signal peptide binding to isolated NG domain also causes a pronounced destabilization, implicating the NG domain in direct recognition of signal peptide.
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95
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Zheng N, Watson LG, Yong-Hing K. Biomechanical modelling of the human sacroiliac joint. Med Biol Eng Comput 1997; 35:77-82. [PMID: 9136197 DOI: 10.1007/bf02534134] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
From a mechanical point of view, the human pelvis can be considered as a stable, complex three link structure. This three-link closed-chain system explains why there is so little motion in the sacroiliac joint. Based on the minimum total potential energy principle, a quasi-static model of the human pelvis with its three joints is developed. In the model, the articular cartilage linings of the joint surfaces are considered as thin layers with a geometric non-linear behaviour. They lie between two rigid curved surfaces that are represented by small three-node elements. Accessory ligaments and capsules are represented by a number of non-linear springs. A primary model is developed based on a female cadaver. According to the primary model, the translation of the sacroiliac joint in the direction of force is about 0.5 mm in the lateral direction, about 1.8 mm in the antero-posterior direction, and about 1.5 mm in the superior or inferior direction, when a load of 1000 N is applied to the sacrum. When a load of 50 N m-1 is applied to the sacrum, the rotation in the load direction is about 1.6 degrees in axial rotation, about 1.0 degree in flexion or extension and about 1.1 degrees in lateral bending.
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96
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