Relationships between muscle lactate accumulation and surface EMG activities during isokinetic contractions in man

Summary In order to investigate the relationship between metabolic state and myoelectrical activity in working muscle during short term intense exercise, eleven healthy males performed isokinetic knee extensions at an angular velocity of 180 deg · sec^–1 for 30 and 60 s. The median frequency (MF) of the surface electromyogram (EMG) recorded from vastus lateralis was decreased while the time lag of torque production after the onset of electrical activity (EMD) was increased during exercise. These changes (MF and EMD) corresponded well to muscle lactate accumulation in the same muscle. Over the exercise period, the integrated EMG/knee extension peak torque ratio (E/T ratio) was increased, which indicated a decrease in the efficiency of electrical activity. It was concluded that the changes in the frequency components of the EMG and in the contractile property of the muscle during short term intense exercise correlated with lactate accumulation in the identical muscle, and that the decrease in efficiency of the electrical activity in the muscle suggested peripheral fatigue.     

Effects of data limitations on heartbeat detection in the method of constant stimuli

In the method of constant stimuli applied to measuring heartbeat detection, subjects judge the simultaneity of heartbeats and exteroceptive comparison stimuli presented at various intervals after the R-wave (0, 100, 200, 300, 400, and 500 ms). Using versions of this procedure, investigators have found that between 20% (Yates, Jones, Marie, & Hogben, 1985) and 54% (Brener, Liu, & Ring, 1993) of subjects can detect heartbeat sensations. Whereas Yates et al. used a single comparison stimulus on each trial and Brener et al. used 10, the present study examined whether this disparity in heartbeat detection performance could be attributed to the number of comparison stimuli presented on each trial. In each of 360 trials, 30 subjects judged the simultaneity of heartbeat sensations and tones following 1, 5, or 10 comparison stimulus presentations. Significantly fewer subjects met the criterion for heartbeat detection with I tone presentation (13%) than with either 5 (43%) or 10 (47%) tone presentations. It is concluded that a single stimulus presentation imposes data limitations that result in underestimation of the accuracy of heartbeat detection. The presentation of at least 5 stimuli in each trial alleviates this limitation.     

Periodic breathing and genetics

The episodic waxing and waning of ventilation is a fundamental event in sleep apnea syndromes. Post-hypoxic frequency decline (PHFD) and periodic breathing (PB) are evoked by brief hypoxic exposures in unanaesthetized and unrestrained inbred C57BL/6J mice, but not in A/J mice; and expression of PHFD differs not only among these mice strains but in among rat strains as well. These observations along with the current literature on genetic factors that operate on ventilatory behavior at rest and with chemosensory drive lead to the hypothesis that genetic factors infer some proportion of risk for the ventilatory instability observed in human sleep apnea syndromes.     

西北地区汉族人群HLA-A、-B、-DRB1基因座单倍型分析

目的 分析西北地区汉族群体HLA-A、-B和-DRB1基因座等位基因频率和HIA-A-B、B-DRB1和A-B-DRB1单倍型，获得单倍型频率数据。方法 采用序列特异性寡核苷酸探针反向斑点杂交技术对西北地区62个家系和101个无关个体HLA-A、-B和-DRB1基因座进行基因分型，分析HLA单倍型。结果 在西北地区汉族人群中检出15个HLA-A等位基因，28个HLA-B等位基因，13个HLA-DRB1等位基因，A02、A11、A24、B13、B15、1340、DRB1＊04、DRB1＊07、DRB1＊09和DRB1＊15基因频率较高（〉10％），A02（0．3244）、B13（0．1200）和DRB1＊15（0．1400）等位基因频率最高。分析得出HLA-A-B、B-DRB1、A-B-DRB1单倍型分别有122、147和278种，83种A-B-DRB1单倍型有至少两条以上相同的单倍型，占总单倍型数的18．44％（83／450）。A30-B13-DRB1＊07、A02-B46-DRB1＊09、A01-B37-DRB1＊10、A24-B15-DRB＊15、A02-B46-DRB1＊08、A33-B58-DRB1＊03是最常见的单倍型。结论 西北地区汉族群体HLA单倍型多态性较为丰富，等位基因频率和单倍型频率数据可用于骨髓移植供者的选择、法医学亲权鉴定以及人类学研究。     

Separate detectors for simple and complex grating patterns?

Grating having two sinusoidal components show a periodic variation in contrast which is visible as a "beat" pattern. The spatial frequency of the beat is the difference between the frequencies of the two components. Thresholds for a number of detection and discrimination tasks were measured using beat patterns of 1 c/deg (with components of 9 and 10 c/deg), and gratings of 1 and 10 c/deg. Temporal modulation at 6 Hz lowered detection thresholds for 1 c/deg gratings, but not for beats or 10 c/deg gratings. The effect of contrast on the range of temporal frequencies over which direction of movement can be discriminated differs for the three types of pattern: beats resemble neither low nor high spatial frequency gratings. Low and (for 2 of 3 observers) high spatial frequency gratings, but not beat patterns, are susceptible to a movement after effect induced by a low spatial-frequency grating. Beat patterns induce little or no movement after effect. We conclude that beat patterns are not detected by the same mechanisms that detect simple gratings.     

Pharmacodynamic modeling of the EEG effects of ketamine and its enantiomers in man

The pharmacodynamics of a racemic mixture of ketamine R,S (±)-ketamine and of each enantiomer, S(+)-ketamine and R(–)-ketamine, were studied in five volunteers. The median frequency of the electroencephalogram (EEG) power spectrum, a continuous noninvasive measure of the degree of central nervous system (CNS) depression (pharmacodynamics), was related to measured serum concentrations of drug (pharmacokinetics). The concentration-effect relationship was described by an inhibitory sigmoid E_max pharmacodynamic model, yielding estimates of both maximal effect (E_max) and sensitivity (IC₅₀) to the racemic and enantiomeric forms of ketamine. R(–)-ketamine was not as effective as R,S(±)-ketamine or S(+)-ketamine in causing EEG slowing. The maximal decrease (mean±SD) of the median frequency (E_max)for R(–)-ketamine was 4.4±0.5 Hz and was significantly different fromR,S (±)-ketamine (7.6 ±1.7 Hz) and S(+)-ketamine (8.3±1.9Hz). The ketamine serum concentration that caused one-half of the maximal median frequency decrease (IC₅₀) was 1.8±0.5g/mL for R(–)-ketamine; 2.0±0.5 g/mL for R,S(±)-ketamine; and 0.8±0.4 g/mL for S(+)-ketamine. Because the maximal effect (E_max) of the R(–)-ketamine was different from that of S(+)-ketamine and R,S(±)-ketamine, it was not possible to directly compare the potency (i.e., IC₅₀) of these compounds. Accordingly, a classical agonist/partial-agonist interaction model was examined, using the separate enantiomer results to predict racemate results. Although the model did not predict racemate results well, its failure was not so great as to provide clear evidence of synergism (or excess antagonism) of the enantiomers.This work was supported in part by a Starter Grant from the American Society of Anesthesiologists, the Biomedical Research Support Grant NIH 2S07RR5353-20, 1981, (P.F.W.); and NIH and NIA Research Grants NS-17956 and AG03104 (D.R.S., A.J.T., L.B.S). The research fellowship of Dr. Schüttler was made possible by a NATO Foundation Grant (300-402-511-3), awarded by the German Academic Exchange Service. This study is part of Dr. Schüttler's Habilitation Thesis for the Faculty of Medicine at the University of Bonn, West Germany. Dr. Verotta is a fellow of the program of advanced training established by EEC and Regione Lombardia on leave of absence from Mario Negri Institute of Pharmacological Research, Milan, Italy.     

重点部门常见典型操作时的高频接触表面

目的 明确不同部门的高频接触表面,为清洁消毒工作提供依据与指导。方法 采用直接观察法对西安市某三级甲等综合医院的消化内镜室、口腔科、血透室、手术室、检验科5个医院感染管理重点部门环境表面的接触频次进行调查,计算累积接触频次与频率。结果 5个重点部门高频接触表面均为5~9个。消化胃镜室高频接触表面频次（3.57~13.29次/操作）明显多于其他部门;血透室高频接触频次范围为0.56~3.44次/操作,为5个部门中最低者。接触频次最高的表面：消化内镜室为诊疗床（13.29次/操作）,口腔科为综合治疗台操作面板（3.64次/操作）,血透室为透析机触屏（3.44次/操作）,手术室为麻醉用电脑键盘及鼠标（8.25次/操作）,检验科为电脑键盘及鼠标（4.80次/操作）。治疗车为消化内镜室、手术室及血透室的高频接触表面。结论 因医疗诊疗操作的不同,各部门高频接触表面也不尽相同。电脑鼠标和键盘、治疗车、诊疗床、诊疗专用仪器以及操作台面在调查的各重点部门均为高频接触表面。     

无创高频振荡通气在极低出生体重早产儿呼吸窘迫综合征初始呼吸支持治疗中的应用

目的探讨经鼻无创高频振荡通气(NHFOV),在呼吸窘迫综合征(RDS)极低出生体重早产儿初始呼吸支持治疗的临床疗效。 方法选择2018年2月至2020年4月,于徐州市中心医院新生儿重症监护病房(NICU)治疗的92例RDS极低出生体重早产儿为研究对象。采用随机数字表法,将其分为NHFOV组(n＝48,采取NHFOV治疗)及经鼻持续气道正压通气(NCPAP)组(n＝44,采取NCPAP治疗)。对2组RDS极低出生体重早产儿一般临床资料,无创通气治疗前、后动脉血气分析指标,疗效,呼吸支持治疗相关并发症发生率及患儿死亡率,采用成组t检验、χ²检验及Mann-Whitney U检验进行统计学比较。本研究经徐州市中心医院医学伦理委员会审核批准(审批文号：XZXY-LJ-20170328-006),并且与患儿监护人均签署临床研究知情同意书。 结果①一般临床资料比较：2组RDS极低出生体重早产儿的性别、出生胎龄与体重及生后1、5 min Apgar评分,入院日龄及分娩前24 h母亲糖皮质激素使用率等一般临床资料比较,差异均无统计学意义(P>0.05)。② 2组RDS极低出生体重早产儿动脉血气分析指标组间比较：NHFOV组RDS极低出生体重早产儿无创通气治疗后1 h、24 h动脉血二氧化碳分压(PaCO₂)分别为(45.8±6.5) mmHg(1 mmHg＝0.133 kPa)及(40.8±4.7) mmHg,均显著低于NCPAP组的(49.3±5.7) mmHg及(44.2±5.2) mmHg;治疗后1 h、24 h动脉血氧分压(PaO₂)与吸入氧浓度分数(FiO₂)比值(P/F)分别为(198.8±30.5) mmHg及(215.1±32.1) mmHg,均显著高于NCPAP组的(176.4±28.1) mmHg及(190.0±29.7) mmHg,并且上述差异均有统计学意义(t＝2.809、3.301、3.663、3.881,P＝0.003、<0.001、<0.001、<0.001)。③2组动脉血气分析指标分别进行组内比较均为：无创通气治疗后24 h的pH值及治疗后1、24 h的PaCO₂水平,均较治疗前改善,而且治疗后24 h的P/F值高于治疗后1 h,并且差异均有统计学意义(P<0.05)。④无创通气疗效比较：NHFOV组RDS极低出生体重早产儿无创通气治疗后,肺表面活性剂(PS)使用率及有创机械通气率(22.9%、6.3%),均显著低于NCPAP组(45.5%、20.5%),并且差异均有统计学意义(χ²＝5.219、4.084,P＝0.022、0.043)。2组RDS极低出生体重早产儿无创通气时间、柠檬酸咖啡因使用率、频繁呼吸暂停发生率及总用氧时间比较,差异均无统计学意义(P>0.05)。⑤2组RDS极低出生体重早产儿鼻损伤、肺气漏、新生儿坏死性小肠结肠炎(NEC)、Ⅲ~Ⅳ级脑室内出血(IVH)、早产儿视网膜病(ROP)(≥Ⅱ期)及支气管肺发育不良(BPD)发生率,以及患儿死亡率比较,差异均无统计学意义(P>0.05)。 结论与NCPAP比较,NHFOV用于RDS极低出生体重早产儿初始呼吸支持治疗,能改善氧合、减少二氧化碳(CO₂)潴留、减少有创机械通气及PS使用,同时不增加呼吸支持治疗相关并发症发生。     

上海市青浦区噪声作业人员听力状况分析

目的 了解近3年青浦区噪声作业人员的听力变化趋势,为预防职业性噪声聋提供依据。方法 收集2018-2020年青浦区噪声作业人员在岗期间的听力数据,并运用SPSS软件进行统计分析。结果 噪声作业人员的双耳高频平均听阈升高率2018-2020年分别为6.09%、5.16%、3.06%,呈逐年降低趋势(P<0.01);男性升高率高于女性(P<0.01);随着年龄、工龄的增加,升高率呈现增高趋势(P<0.01)。双耳高频平均听阈升高率位于前三的行业分别为建筑业(28.57%)、租赁和商务服务业(18.72%)以及批发零售业(13.89%)。结论 噪声作业人员的职业病防控工作仍不可放松,应及时对噪声作业重点人员进行有针对性的干预。