低频率‘习服’噪声暴露减轻成年人较高强度噪声暴露引起的暂时性听阈位移的研究

日的探讨低频率低水平‘习服’噪声暴露对成年人高噪声暴露引起的暂时性听阈位移（TTS）的影响。方法以听力正常、无噪声接触史、平均年龄25岁的22名成年志愿者为研究对象，随机分为实验组和对照组。其中实验组先接受连续10天、每天6小时、中心频率为0．5kHz的一个倍频程（OBN）、95dB的噪声训练（‘习服’暴露），然后休息2天，待听力恢复后再接触3天、每天2．5小时同样频率105dB的较高水平噪声暴露；对照组则只接受后者暴露。每天暴露前、后进行听力测试（0．5kHz至8kHz），观察TTS的变化。结果实验组在接受‘习服’噪声暴露期间，TTS几乎在各测试频率均呈现持续下降趋势，经过10天的暴露后，在0．5kHz和1kHz处TTS分别下降了10．6和10．4dB。在随后接受高噪声暴露时，实验组在除8kHz以外的所有测试频段均产生了比对照组显著性低的TTS（P〈0．05）。3天暴露期间，TTS均值在0．5kHZ至4kHz分别相差7．7、9．5、7．7、5．0dB。结论成年人在预先接受某一低频率低水平的噪声暴露（训练）后，对随后接触高噪声暴露引起的听力损伤具有一定的保护性作用。     

噪声性暂时性听阈位移（TTS）及其影响因素分析

本文对某麻纺厂织袋、纺麻、梳麻车间从事噪声作业的工人,排除非噪声性致聋因素及生活噪声的影响,共检查212人424耳的纯音听力以及工作一个班次（6小时）后的暂时性所阈位移（TTS）,同时测定各车间噪声强度（A声级）,数据采用直线回归、逐步多元回归和协方差分析等统计学方法处理。结果表明：性别间和左右耳间的语频听阈及TTS均无显著性差异;车间噪声强度与语频听阈及TTS间存在着正相关;TTS与语频听阈、年龄、工龄之间存在着负相关。经多元逐步回归分析,语频听阈、噪声强度和工龄对TTS的影响具有统计学显著性意义。     

听觉系统噪声习服的实验观察

目的观察反复暴露于一定强度噪声对人听觉系统的影响.方法以11名男女青年作为观察对象,连续暴露于中心频率为0.5 kHz、声压级(SPL)为95 dB SPL的一个倍频程窄带噪声10 d(每天暴露6 h).结果在暴露于95 dB SPL噪声的过程中,观察对象在各测定频率的暂时性听阈位移(TTS)呈逐渐减小趋势,与噪声暴露第1天的TTS相比,从第4天开始在某些频率上TTS出现差异显著性(P<0.05),连续暴露10 d后,在0.5～8 kHz的各个频率上均可观察到TTS显著减小的现象.结论反复暴露于一定强度的噪声后,人听觉系统可以产生习服效应.     

噪声习服对人体听觉系统保护作用

目的 探讨噪声习服对人体听觉系统的保护作用及其抗脂质过氧化机制.方法 适应组每天4 h低强度噪声的习服性暴露,连续6 d,结束后,休息2 d,然后每天3 h高强度噪声暴露,连续6 d;对照组,每天3 h的高强度噪声暴露,连续6 d.测量2组高强度噪声暴露后的暂时性阈移(TTS),及血液中丙二醛(MDA)、超氧化物歧化酶(SOD)、谷胱甘肽(GSH)的含量.结果 适应组高强度噪声暴露后的TTS明显小于对照组(0.4～4 kHz,平均差异6.7 dB,P≤0.05);血清MDA 下降、SOD上升、全血GSH上升.结论 噪声习服可降低TTS,减轻脂质过氧化反应对听力的损伤,提示应用自由基清除剂和抗氧化剂可能预防或减轻噪声引起的听力损伤.     

噪声习服对豚鼠耳蜗抗氧化酶的影响

目的探讨噪声习服对耳蜗抗氧化酶的影响。方法40只雄性豚鼠随机分为无噪声对照组(A组),噪声习服组(B组),噪声习服 强噪声暴露组(C组),单纯强噪声暴露组(D组)。B组动物在声压级为90 dB SPL (声压级)、中心频率为0.5 kHz的一个倍频程噪声下连续暴露10 d,每天6 h;C组动物在经过与B组相同的噪声习服处理后,休息5d,再暴露于105 dB的白噪声4 h;D组动物直接暴露于105 dB的白噪声4 h。噪声暴露结束后即刻测定耳蜗中的脂质过氧化物酶(GSH-Px)活力。结果D组的丙二醛(MDA)水平明显高于其他3组,A、B、C、D组水平分别为144.19±4.59,147.12±4.51,163.76±4.83,187.11±6.14(P<0.05):噪声暴露后C、D组的超氧化物歧化酶(SOD)和GSH-Px活力均有所增强,C组明显高于D组分别为282.20±22.46 vs 243.95±16.53;32.72±2.24 vs 26.84±2.22(P<0.05);D组的过氧化氢酶(CAT)活力明显低于其他3组。而C组的CAT活力增强,A、B、C、D 4组CAT活力分别为63.18±4.59,65.93±4.41,82.34±4.66和45.60±4.88(P<0.05)。结论噪声习服可以提高耳蜗抗氧化酶的活力。     

噪声适应性暴露对人听力保护作用的初步探讨

目的：观察适应性噪声暴露对听力的保护作用。方法：将44名青年志愿者随机分为4组（每组11人,男6人,女5人）,其中2组为适应性暴露组,另2组为直接暴露组,适应性暴露1组和2组先暴露于中心频率为0．5kHz,声压级为95dB SPL的一个倍频程噪声,每天6h,连续暴露10d,休息2d后,再连续3d分别暴露于声压级为105dB的一个倍频程噪声（2．5h/d)和白噪声（0．5h/d),而直接暴露的两组预先不进行适应性暴露,直接暴露于105dB的一个倍频程噪声和白噪声,连续3d,每天2．5h,以暂时性听阈位移（TTS）作为观察指标。结果：在高噪声暴露过程中,适应性暴露组与直接暴露组相比,除8kHz外,TTS在各个频率上差异均有显著性,结论：经过一定强度噪声的适应性暴露后,能够减轻更高强度噪声所致听力损伤的程度。     

噪声习服性暴露对听力的保护作用

目的　探讨噪声习服性暴露对人听觉系统的保护作用。方法　试验组首先接受 1 0天 ,每天 6h低强度噪声的习服性暴露 ,结束后 ,休息 2天 ,然后再接受 3天 ,每天 2 5h高强度噪声暴露 ;对照组只接受 3天 ,每天 2 5h的高强度噪声暴露。测量两组高强度噪声暴露后的暂时性阈移 (TTS)。结果　试验组高强度噪声暴露后的TTS明显小于对照组 (0 5～ 2kHz平均差异 9 5dB ,P <0 0 5)。结论　噪声习服性暴露可降低高噪声引起的TTS ,并对听觉系统有一定保护作用。     

噪声适应性暴露对人体血清中抗氧化酶活性的影响

目的观察在适应性噪声暴露过程中血清抗氧化酶活性的变化.方法将新进厂工人随机分为适应组和对照组.适应组先在实验室内经适应性暴露后与对照组接触车间强噪声.测定外周血血清超氧化物歧化酶、过氧化氢酶和谷胱甘肽-过氧化物酶的含量.结果在预暴露于适应性噪声10d的过程中,适应组血清抗氧化酶活性表现出增高的趋势.在暴露于车间强噪声13周过程中,两组对象的酶活性均表现出先升高后降低的趋势,且适应组酶活性明显高于对照组.结论预先反复暴露于中等强度的噪声可以增强工人血清抗氧化酶的活性,从而减轻噪声对听力的损伤.     

噪声习服对听觉系统保护作用的研究进展

根据等能量假说 ,噪声引起的听力损失程度与接受的刺激声音强度和持续时间成正比。但是 ,近年来的研究结果却与此假说产生分歧 ,研究表明在特定暴露条件下的听力损失中 ,部分是由受试对象以前的噪声暴露史决定的 ,噪声的暴露史可能是决定噪声性听力损伤易感性的一个因素 ,它可以使机体逐渐适应 ,从而提高机体对噪声的耐受性。在一定强度的同一噪声中重复暴露 ,随着暴露的继续 ,每天的暂时性听阈位移 (ｔｅｍｐｏ ｒａｒｙｔｈｒｅｓｈｏｌｄｓｈｉｆｔ ,ＴＴＳ)逐渐减小 ,这种现象被称为“习服”(ｃｏｎｄｉ ｔｉｏｎｉｎｇ)。而且 ,观察组 …     

噪声与γ射线暴露顺序对豚鼠听阈的影响

本研究观察了γ射线与噪声复合暴露对听阈的影响。结果表明,噪声与γ射线同时暴露组的阈移约等于单独噪声与单独γ射线暴露组阈移总和,它们的复合效应是相加的;先噪声后γ射线暴露组的阈移有小于“总和”的倾向。与我们以前的研究结果相比,先噪声后γ射线暴露组的阈移显著低于γ射线暴露在前,噪声暴露在后的动物。提示,噪声和γ射线双重暴露对听阈的复合效应与它们的暴露顺序有关。     

Studies of combined effects of sinusoidal whole body vibrations and noise of varying bandwidths and intensities on TTS2 in men

Summary This study analyses the data from three laboratory experiments concerning the separate and combined effects on temporary threshold shifts in hearing (TTS2) of sinusoidal low-frequency (5 Hz — 2.12 m/s² and 10 Hz —2.65 m/s²), whole body vibration (along the Z-axis), and continuous (white) noise with eight different bandwidths and intensity levels of 85 dB(A), 90 dB(A) and 98 dB(A). Altogether 370 separate personal experiments were performed using a one-man exposure chamber system. A single experiment consisted of a 30-min pre-exposure period, three 16-min exposure periods, and a 15-min post-exposure period. The data suggested that the TTS₂ induced by noise was increased by vibration. Actually, vibration at a frequency of 5 Hz and noise with bandwidths of 1–4 kHz, 1–8 kHz or 0.2–16 kHz comprised the most significant exposure combinations. After such exposures, the increase in TTS₂ values was defined most clearly for 4 kHz and 6 kHz test frequencies. The increase of thresholds was most marked during the first 16-min exposure period, even though most TTS₂ values determined after the third consecutive exposure period were higher than after the first and second exposures. Figures obtained after the third exposure period proved that exposure to simultaneous vibration and broad band noise (i.e. noise with a bandwidth of 0.2–16 kHz) increased TTS₂ values 1.2–1.5 times more in the 4 kHz audio range than such a broad band noise alone. No single vibration condition induced the same amount of TTS₂.     

锰烟尘对男工血脂质过氧化和抗氧化酶的影响

目的研究长期高浓度锰烟尘暴露对男工体内脂质过氧化和抗氧化酶的影响。方法用分光光度法测定59名接触锰烟尘男工和59名对照男工的红细胞血红蛋白(Hb)、丙二醛(MDA)含量以及超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、谷胱甘肽过氧化物酶(GSH-Px)和血清谷胱甘肽S-转移酶(GSH-ST)活力。结果作业环境空气中MnO2平均浓度为0.75 mg/m3(0.19~1.60 mg/m3)时,接锰作业组红细胞MDA含量、SOD、CAT、GSH-Px活力与对照组比较,差异无显著性。分层分析显示,接触锰男工红细胞SOD、CAT、GSH-Px的酶活力随接触锰工龄的增加而升高,接触锰工龄>10 a组,SOD、CAT、GSH-Px酶活力均降至对照组水平。结论接触高浓度的锰<10 a,可使体内抗氧化酶活力应激性增强,而脂质过氧化物保持不变。但接触高浓度锰>10 a,可导致男工血脂质过氧化物增加及抗氧化酶活力降低,对机体产生损害作用。     

噪声作业工人听觉脑干诱发电位反应阈与纯音听阈的相关分析

测定２只耳听觉脑干诱发电位（ＡＢＲ）反应阈和纯音听阈,结果表明,二者之差在１０ｄＢ以内的约占５０％,通过二者相关分析,说明语频听阈和高频听阈与ＡＢＲ反应阈均有显著相关。     

Temporary threshold shift of vibratory sensation induced by a vibrating handle and its gripping force

•Objective This study examines the effect of the force with which a vibrating handle is gripped on the temporary threshold shift of vibratory sensation (TTS_v) induced by hand-arm vibration. •Methods Six healthy subjects gripped a handle vibrating with a 1/3 octaveband vibration, with a central frequency of 200 Hz and an intensity of 39.2 m/s². Exposure was for 1 min and 10 min, respectively. Gripping forces for the 1-min exposure were 5 N, 10 N, 40 N and 80 N, respectively, with 0 N push-pull force. Gripping forces for the 10-min exposure were the same as for the 1-min exposure, but omitting 80 N. The vibratory sensation threshold at 125 Hz was measured before and after exposure of an exposed fingertip to vibration. The differences measured determine TTS_v,t at timet. TTS_v,t determines TTS_v,0, that is, the temporary threshold shift of vibratory sensation immediately after exposure to vibration according to the estimate made on the basis of the preceding study. The same experimental conditions were repeated 3 times on different days in a soundproof and thermoregulated room. •Results Our findings show that TTS_v increases significantly with increasing gripping force. We also determined the quantitative relationships between TTS_v,0 and gripping force as described by the equation wherek _f andc _f are constants andF is gripping force. •Conclusion This study revealed the importance of ergonomic design in reducing the force with which a vibrating handle is gripped to prevent an adverse effect of local vibration. The equation devised may help in the quantitative assessment of the effect of reduced gripping force.     

Prevention of hexachlorocyclohexane-induced neuronal oxidative stress by natural antioxidants

Objective

Decalepis hamiltonii roots are traditionally consumed as general vitalizer and used in ayurvedic medicine preparations. We have isolated/characterized potent antioxidants from the aqueous extract of the root of this plant. In this study, we examined the antioxidant potential of the aqueous extract of the roots of D. hamiltonii (DHAE) against hexachlorocyclohexane (HCH)-induced oxidative stress in four major regions of the rat brain.

Methods

The antioxidant activity of the standardized DHAE with known antioxidant constituents was tested against HCH-induced oxidative stress in the major brain regions of 60-day-old adult male Wistar rats.

Results

Pretreatment of rats with multiple doses of DHAE, 50 and 100 mg/kg body weight (b.w.), for 7 consecutive days significantly prevented the HCH-induced (single dose ?500 mg/kg b.w.) increase in lipid peroxidation, reduction in glutathione, and altered antioxidant enzyme activities viz. superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glutathione-S-transferase in major rat brain regions viz. cortex, cerebellum, midbrain, and brain stem. DHAE, per se, elevated the antioxidant status of the rat brain.

Discussion

DHAE shows protective action against HCH-induced oxidative stress in rat brain regions. The protective effect of DHAE could be ascribed to the isolated/characterized antioxidant compounds which could be prospective novel nutraceuticals.     

Effects of Pb and Ni stress on oxidative stress parameters in three moss species

Antioxidative responses of the mosses Hypnum plumaeforme, Thuidium cymbifolium, and Brachythecium piligerum to short-term Pb and Ni stress were investigated. Both Pb and Ni treatment increased the formation of reactive oxygen species and lipid peroxidation, decreased superoxide dismutase (SOD), and catalase (CAT) activities in H. plumaeforme and T. cymbifolium. However, SOD activity in B. piligerum was increased under 10 mM Pb stress and Ni increased CAT activity in B. piligerum under 1 mM Ni stress. Peroxidase (POX) activity in the three mosses was increased by Pb and Ni exposure, indicating that POX plays an important role in preventing heavy metal-induced oxidative stress. The accumulation of O₂⁻ and H₂O₂ in mosses is related to the decline in SOD and CAT activities. B. piligerum is the most sensitive and T. cymbifolium is the most tolerant species to Pb and Ni stress among the three bryophytes.     

缺锌和补锌对大鼠脂质过氧化及抗氧化系统的影响

健康雄性Ｗｉｓｔａｒ大鼠４５只，先进行２５天锌缺乏实验，而后２１只大鼠再进行１５天补锌治疗实验。结果显示，缺锌可致大鼠红细胞超氧化物歧化酶（ＳＯＤ）活性、全血谷胱甘肽过氧化物酶（ＧＳＨＰｘ）活性及还原型谷胱甘肽（ＧＳＨ）含量明显下降．而血清过氧化脂质（ＬＰＯ）含量显著升高。补锌１２．３０或２５０ｐｐｍ均可使原缺锌大鼠的各项指标完全恢复，并且血清锌含量与上述各项指标均呈明显的相关关系。结果提示，缺锌可致大鼠抗氧化能力减弱．脂质过氧化反应增强．且补锌治疗时．一个ＲＤＡ（推荐的每日膳食营养素供给量）剂量即可使大鼠体内氧化与抗氧化之间的平衡完全恢复。     

12^C^6＋对小鼠肝组织中脂类过氧化和血清抗氧化活力的影响

目的研究12^C^6＋重离子全身照射对小鼠肝组织中脂类过氧化和血清抗氧化活力的影响。方法采用硫代巴比妥酸法测定重离子6Gy辐照后各组肝组织中脂质过氧化值;采用电子自旋共振自旋捕集技术检测辐照后各组血清对羟基的清除率。结果12^C^6＋重离子全身辐照后46、70、82h组肝组织中脂质过氧化值明显增加,与对照组相比差异有显著性（P〈0.01）,但未出现峰值;辐照后各组血清对羟基的清除率明显下降,其中82h组的清除率最低,辐照后各组与对照组相比差异有显著性（P〈0.01）。结论12^C^6＋重离子全身辐照能引起小鼠肝组织中脂类过氧化并能使血清抗氧化活力下降。     

12C6+对小鼠肝组织中脂类过氧化和血清抗氧化活力的影响

目的研究12C6 重离子全身照射对小鼠肝组织中脂类过氧化和血清抗氧化活力的影响。方法采用硫代巴比妥酸法测定重离子6Gy辐照后各组肝组织中脂质过氧化值;采用电子自旋共振自旋捕集技术检测辐照后各组血清对羟基的清除率。结果12C6 重离子全身辐照后46、70、82h组肝组织中脂质过氧化值明显增加,与对照组相比差异有显著性(P<0.01),但未出现峰值;辐照后各组血清对羟基的清除率明显下降,其中82h组的清除率最低,辐照后各组与对照组相比差异有显著性(P<0.01)。结论12C6 重离子全身辐照能引起小鼠肝组织中脂类过氧化并能使血清抗氧化活力下降。