A practical approach to estimating the true effect of exposure despite imprecise exposure classification

Accurate information on actual exposure to some possibly toxic agent usually is not available in long-term occupational studies. Any strategy for assigning exposure levels or categories necessarily results in misclassification, where some individuals classified as exposed have no real exposure and some individuals classified as not exposed have some exposure to the agent. Both misclassification errors serve to reduce the estimate of risk associated with exposure. The question arises, “How much does the true risk depart from the observed estimate given an assumed level of misclassification?” This paper quantifies the effect of such misclassification on several forms of standardized risk ratios. Our results express the true risk as a function of the apparent risk based on imprecise exposure classification and parameters representing the proportion of each of the groups that are correctly classified. In any practical situation, the apparent risk can be computed based on whatever classification scheme is being used. On the other hand, the proportions of the imprecisely classified groups actually exposed cannot. However, the investigator may have information or may make assumptions for likely ranges of values for these proportions. Given the apparent risk, estimated true risks can be calculated and plotted or represented in tabular form as a function of the proportions of actual exposure. The resulting graph or table enables the investigator to read off the range of possible true risk values based on what he is prepared to believe or what other information indicates about the range of proportions of misclassified subjects. For instance, results for a typical value of apparent risk of 1.8 show that the true risk may be twice the apparent risk with only 23% misclassification in each exposure group. The value of the true risk that would be necessary to be consistent with a given apparent risk increases rapidly as the extent of misclassification increases. We also show that, if the extent of misclassification is large, the apparent relative risk is close to 1.0 regardless of the actual value of the true risk. Therefore, a small apparent risk does not necessarily indicate that there is no occupational hazard.     

四川省部分地区主粮中杂色曲霉菌及其毒素的污染调查

通过对四川省部分地区大米和小麦两种主粮中杂色曲霉菌（Ａ．ｖ）和杂色曲霉素（ＳＴ）污染调查，结果表明在大米和小麦中，Ａ．ｖ污染率分别为５．５％和１０．５％；ＳＴ污染率为５３．４％和６５．８％；ＳＴ平均含量为１５．５μｇ／ｋｇ和５８．６μｇ／ｋｇ。对不同地区和不同贮藏期粮食进行分析，Ａ．ｖ检出率越高，粮食中ＳＴ污染率和含量越高；贮藏期延长，Ａ．ｖ和ＳＴ检出率及ＳＴ含量增高。实验产毒表明所有Ａ．ｖ菌株均能产生ＳＴ，平均产毒量达７１９０．２μｇ／ｋｇ，证实Ａ．ｖ是ＳＴ形成的主要菌种     

糖耐量减低肥胖儿童胰岛素原和真胰岛素水平测定意义

目的　探讨血清胰岛素原 (PI)及真胰岛素 (TI)测定对肥胖并糖耐量异常患儿的临床意义。方法　选择肥胖并糖耐量减低 (IGT)患儿 2 1例 ,肥胖糖耐量正常 (NGT) 5 2例 ,正常对照组 4 0例。测定各组空腹血清PI、TI、血糖 (G)、胰岛素 (I)和C 肽 (C P) ,并计算PI/I、PI/C P、PI/TI及胰岛素抵抗指数。结果　 1.肥胖并IGT和并NGT两组患儿比较 ,G、PI、C P及胰岛素抵抗指数均明显增加 (P均 <0 .0 1)。 2 .IGT组糖尿病阳性家族史明显高于NGT组 (P =0 .0 2 4 )。结论　高PI、高C P和胰岛素抵抗是肥胖并IGT患儿的突出表现 ,可能是儿童2型糖尿病的预示指标。有糖尿病阳性家族史肥胖儿童更应警惕IGT发生     

True hermaphroditism with bilateral ovotestis: a case report

A true hermaphrodite with a 46 XX/47 XXY karyotype, gynaecomastia, hypospadia and scrotal gonads was investigated. Gonadectomy performed at 14 years of age revealed bilateral ovotestes. The ovarian portion contained follicles of all developmental stages. The testicular portion was immature consisting of seminiferous cords with Sertoli cells at various steps of differentiation and few germ cells within massive aggregates of collagenous connective tissue. Leydig cells as well as germ cells remained in an embryonic stage of development. Sections of a differentiated Wolffian duct (ductuli efferentes, epididymis, vas deferens) as well as of a Müllerian duct (hypoplastic fallopian tube) were found adjacent to both gonads. Postoperative treatment consisted of androgen substitution therapy leading to progression of puberty.     

Studies of aqueous humour dynamics in man. VI. Effect of age upon parameters of intraocular pressure in normal human eyes

Parameters of aqueous dynamics have been evaluated for both eyes of each member of a group of young normal volunteers and of a group of old normal volunteers. In the old volunteers, the observed lower total facility is comprised of a lower true facility of outflow and a lower pseudofacility. The reduced outflow facility is partly counterbalanced by a lower aqueous flow. Also, in the older eyes, ocular rigidity is higher. Mean episcleral venous pressure is the same for the two groups. The major effect of age seen in this study is alteration of the function of the outflow pathways of the eye, with simultaneous, partially counter-balancing, decrease of aqueous production associated with decreased pseudofacility.     

A Novel Vascular-Friendly Thoracic Stent Graft for Endovascular Repair of Acute Complicated Type B Aortic Dissection

Purpose: To evaluate the safety and efficacy of a novel vascular-friendly thoracic stent graft for patients with acute complicated type B aortic dissection (ac-TBAD).Methods: A multicenter retrospective study was undertaken in which we prospectively collected data in consecutive ac-TBAD patients treated by thoracic endovascular aortic repair (TEVAR) with the Ankura Thoracic Stent. Complications, true lumen rate (TLR), and mortality were recorded. Follow-up computed tomography angiography (CTA) was performed at 1, 6, and 12 months postoperatively and yearly thereafter.Results: Altogether, 63 patients with ac-TBAD in four medical centers were included. No deaths or serious complications occurred during the perioperative period. The mean follow-up time was 30.1 ± 18.9 months. All-cause mortality rate was 3.1% (n = 2). TEVAR-related mortality rate was 1.6% (n = 1) because of retrograde type A dissection (RTAD) at 6 months. The other death was caused by acute myocardial infarction (AMI) during the third postoperative month. A distal endoleak detected at 3 months in one patient (1.6%) was treated by reintervention. The use of this novel vascular-friendly thoracic stent graft in ac-TBAD postoperative patients significantly improved their TLR.Conclusion: The novel vascular-friendly thoracic stent graft showed satisfactory results, with favorable stability of the aortic diameter during follow-up.     

True bipolar and integrated bipolar sensing and detection by implantable defibrillators

Introduction: Sensing and detection can be performed in true bipolar or integrated bipolar configuration by implantable defibrillators. New Medtronic generators (Medtronic Inc., Minneapolis, MN, USA) can be configured so that the sensing function of the device can be either true bipolar or integrated bipolar. We compared the sinus rhythm R‐wave amplitude and detection time of induced ventricular fibrillation (VF) at implant (acute phase), and sinus rhythm R‐wave amplitude 3 months or more after the implant (chronic phase) in these two configurations. Methods: Twenty‐eight patients were studied in the acute phase, and a subgroup of 15 patients was tested in the chronic phase. The generators were Medtronic model numbers D224VRC, D224TRK, D224DRG, D284VRC, D284TRK, and D284DRG. The leads were Medtronic 6947 or 6935. Sensing was evaluated by recording the electrogram and measuring the R‐wave peak‐to‐peak amplitude in the two configurations. Detection was evaluated by measuring the detection time in the two configurations in two consecutive inductions. The detection time was measured on programmer paper from the marker of the T shock to the marker of VF. Results: The acute‐phase values were: R wave in true bipolar configuration 13.9 ± 7.1 mV, R wave in integrated bipolar configuration 13.6 ± 6.9 mV (p = 0.38),VF detection time in true bipolar configuration 3.12 ± 0.39 seconds, and VF detection time in integrated bipolar configuration 3.17 ± 0.39 seconds (p = 0.52). Conclusions: Sensing and detection at implant were not significantly different between the true bipolar and the integrated bipolar configurations for the tested leads and generators. (PACE 2011; 34:1561–1568)     

Electron microscopic investigation of anterior lens capsule in an individual with true exfoliation

AIM: To determine the changes which occur in the anterior capsule in true exfoliation which is a very rare condition.METHODS: The anterior capsule from a 93 year-old patient and 6 other patients with age-related cataract during capsulorhexis was examined via transmission electron microscopy (TEM).RESULTS: TEM revealed apoptosis of lens epithelial cells in both two groups. Moreover, we observed lamellar delamination, granular belts in the anterior capsular zone and loss of the subcapsular epithelium cells in the posterior capsular zone, as well as abnormal fibrils located in the central capsular layer only in the sample from the patient with true exfoliation.CONCLUSION:We suggest that loss of lens epithelial cells and appearance of abnormal fibrils is important in disease developing, and our study supported age-related degeneration is one of causative factors in true exfoliation.     

久病误诊误治

误诊误治易成久病,严重危害患者身心健康,甚则威胁生命。究其始末,主要原因包括:虚虚实实,检诊困难;病证不明,似是而非;见病医病,不中机宜;疏忽大意,不达情理。为减少久病形成,医者应严格掌握疾病相关知识:研习经典,做好临床;中西汇通,取长补短;诊辨统一,熟谙药性;仔细观察,注意检诊。熟练运用五诊十纲、审证求因,辨病辨证等诊疗手法,从根源上减少甚至杜绝误诊误治的发生,将久病扼杀在摇篮。     

Large-scale navigational map in a mammal

Navigation, the ability to reach desired goal locations, is critical for animals and humans. Animal navigation has been studied extensively in birds, insects, and some marine vertebrates and invertebrates, yet we are still far from elucidating the underlying mechanisms in other taxonomic groups, especially mammals. Here we report a systematic study of the mechanisms of long-range mammalian navigation. High-resolution global positioning system tracking of bats was conducted here, which revealed high, fast, and very straight commuting flights of Egyptian fruit bats (Rousettus aegyptiacus) from their cave to remote fruit trees. Bats returned to the same individual trees night after night. When displaced 44 km south, bats homed directly to one of two goal locations--familiar fruit tree or cave--ruling out beaconing, route-following, or path-integration mechanisms. Bats released 84 km south, within a deep natural crater, were initially disoriented (but eventually left the crater toward the home direction and homed successfully), whereas bats released at the crater-edge top homed directly, suggesting navigation guided primarily by distal visual landmarks. Taken together, these results provide evidence for a large-scale "cognitive map" that enables navigation of a mammal within its visually familiar area, and they also demonstrate the ability to home back when translocated outside the visually familiar area.