[Laser Doppler vibrometric measurements on human temporal bones]. / Laser-Doppler-vibrometrische Messungen an humanen Felsenbeinen.

Laser Doppler vibrometric (LDV) measurements on human temporal bones represent the standard method for predicting the performance of active middle ear implants (AMEI) and are used as preclinical tests in the development, approval process, and indication expansion of AMEI. The quality of the coupling of the floating mass transducer to the mobile structures of the middle ear is decisive for the performance of the implant and patients' hearing perception. The cochlea can be stimulated via the oval window (forward stimulation) or the round window (reverse stimulation). For forward stimulation, the ASTM standard F2504-05 defines a method to ensure physiologically normal properties of the temporal bones used in the experiments. For reverse stimulation, which depends even more critically on the quality of the temporal bone, a comparable standard method is lacking. Appropriate preparation and storage of the human petrous bone as well as suitable LDV test setups with respect to calibration and reproducibility of measuring positions and angles provide results that allow a comparison of different types of coupling and also correlate well with clinical data.

Passage of uranium through human cerebral microvascular endothelial cells: influence of time exposure in mono- and co-culture in vitro models.

PURPOSE: Depleted uranium (DU) has several civilian and military applications. The effects of this emerging environmental pollutant on human health raise some concerns. Previous experimental studies have shown that uranium (U) exposure can disturb the central nervous system. A small quantity of U reaches the brain via the blood, but the effects on the blood-brain barrier (BBB) remain unclear. MATERIALS AND METHODS: In the present work, two cell culture models were exposed to DU for different times to study its cytotoxicity, paracellular permeability and extracellular concentration of U. The well-known immortalized human cerebral microvascular endothelial cells, hCMEC/D3, were cultured on the filter in the first model. In the second model, human primary cells of pericytes were cultured under the filter to understand the influence of cell environment after U exposure. RESULTS: The results show that U is not cytotoxic to hCMEC/D3 cells or pericytes until 500 µM (1.6 Bq.L-1). In addition, acute or chronic low-dose exposure of U did not disturb permeability and was conserved in both cell culture models. However, U is able to reach the brain compartment. During the first hours of exposure, the passage of U to the abluminal compartment was significantly reduced in the presence of pericytes. Electronic microscopy studies evidenced the formation of needlelike structures, like urchin-shaped precipitates, from 1 h of exposure. Analytical microscopy confirmed the U composition of these precipitates. Interestingly, precipitated U was detected only in endothelial cells and not in pericytes. U was localized in multilamellar or multivesicular bodies along the endo-lysosomal pathway, suggesting the involvement of these traffic vesicles in U sequestration and/or elimination. CONCLUSIONS: We show for the first time the in vitro passage of U across a human cerebral microvascular endothelial cells, and the intracellular localization of U precipitates without any cytotoxicity or modification of paracellular permeability. The difference between the results obtained with monolayers and co-culture models with pericytes illustrates the need to use complex in vitro models in order to mimic the neurovascular unit. Further in vivo studies should be performed to better understand the passage of U across the blood-brain barrier potentially involved in behavioral consequences.

Probing consciousness with event-related potentials in the vegetative state.

OBJECTIVE: Probing consciousness in noncommunicating patients is a major medical and neuroscientific challenge. While standardized and expert behavioral assessment of patients constitutes a mandatory step, this clinical evaluation stage is often difficult and doubtful, and calls for complementary measures which may overcome its inherent limitations. Several functional brain imaging methods are currently being developed within this perspective, including fMRI and cognitive event-related potentials (ERPs). We recently designed an original rule extraction ERP test that is positive only in subjects who are conscious of the long-term regularity of auditory stimuli. METHODS: In the present work, we report the results of this test in a population of 22 patients who met clinical criteria for vegetative state. RESULTS: We identified 2 patients showing this neural signature of consciousness. Interestingly, these 2 patients showed unequivocal clinical signs of consciousness within the 3 to 4 days following ERP recording. CONCLUSIONS: Taken together, these results strengthen the relevance of bedside neurophysiological tools to improve diagnosis of consciousness in noncommunicating patients.

Mild hyperhomocysteinemia: risk factor or just risk predictor for cardiovascular diseases?

Elevated plasma levels of homocysteine (hyperhomocysteinemia) are increasingly recognized as a potential risk for atherothrombotic vascular diseases by numerous epidemiological and clinical studies. There are increasing experimental data that indicate mechanisms by which homocysteine may alter the vasculature in a way that predisposes to atherosclerotic vascular disease. A key event in the vascular pathobiology of hyperhomocysteinemia seems to involve the induction of endothelial dysfunction due to a reduction of the endogenous antiatherothrombotic molecular nitric oxide. Elevated homocysteine levels can be efficiently and safely reduced in most of hyperhomocysteinemic patients by supplementation of folic acid and cobalamin. This reduction is associated with an improvement in endothelial function and other surrogate markers of atherothrombosis, like carotid plaque area and the rate of abnormal stress electrocardiograms. Whether or not this translates into clinical benefits, is still under investigation. The first clinical study on homocysteine-lowering vitamin supplementation in patients that had undergone coronary intervention showed a benefitial effect on the rate on restenosis and the need for revascularization which translated into a reduction of major coronary events. In contrast, in three larger scaled secondary intervention trials in patients with stable coronary disease or post non-disabling stroke, vitamin supplementation had no effect on future vascular events although baseline homocysteine levels were significantly associated with a worse prognosis. Until the results of more clinical trials are available, the clinical relevant question whether or not homocysteine is just a risk predictor or a modifiable risk factor can not definitely be answered.

Preventive effect of artemether in experimental animals infected with Schistosoma mansoni.

The effect of artemether, an antimalarial drug developed from the plant Artemisia annua, has been tested against the larval stages of Schistosoma mansoni covering the time from skin penetration to the early adult liver-stage. The results show that the experimental animals used (hamster and mice) do not develop schistosomiasis mansoni if treated with artemether during the first month after infection. The parasite was found to be especially susceptible between the 3rd and 4th week after infection, resulting in worm reductions of 75.3-82.0% compared to non-treated controls. This level was boosted to 97.2-100% when the animals were subjected to various schedules of repeated treatment. Almost complete protection was also reached in parallel experiments with repeated infections carried out to mirror more closely the real situation of trickle infection.

Influence of folic acid, pyridoxal phosphate and cobalamin on plasma homocyst(e)ine levels and the susceptibility of low-density lipoprotein to ex-vivo oxidation.

Mild hyperhomocyst(e)inaemia is a risk factor for atherosclerotic vascular disease. In-vitro studies have shown that autooxidation of homocyst(e)ine is accompanied by the generation of oxygen radicals. This may lead to oxidative modification of low-density lipoproteins (LDL) and promote atherosclerotic vascular lesions. In male patients with peripheral arterial occlusive disease we determined fasting and post methionine load homocyst(e)ine levels by high performance liquid chromatography and the susceptibility of their LDL particles to ex-vivo oxidation by continously measuring the conjugated diene production induced by incubation with copper ions. Oxidation resistance (expressed as lag time), maximal oxidation rate, and extent of oxidation (expressed of total diene production) of LDL from patients with normal or mildly elevated homocyst(e)ine levels did not differ significantly. Folic acid, pyridoxal phosphate and cobalamin supplementation significantly decreased plasma homocyst(e)ine levels in hyperhomocyst(e)inaemic patients. This went along with a significant decrease in the extent of LDL oxidation and additionally increased HDL-cholesterol levels. The clinical relevance of these findings for the long-term course of atherosclerotic vascular disorders has to be determined by intervention studies.

Health outcomes associated with antihypertensive therapies used as first-line agents. A systematic review and meta-analysis.

OBJECTIVE: To review the scientific evidence concerning the safety and efficacy of various antihypertensive therapies used as first-line agents and evaluated in terms of major disease end points. DATA SOURCES: MEDLINE searches and previous meta-analyses for 1980 to 1995. DATA SELECTION: We selected long-term studies that assessed major disease end points as an outcome. For the meta-analysis, we chose placebo-controlled randomized trials. For randomized trials using surrogate end points such as blood pressure, we selected the largest studies that evaluated multiple drugs. Where clinical trial evidence was lacking, we relied on information from observational studies. DATA SYNTHESIS: Diuretics and beta-blockers have been evaluated in 18 long-term randomized trials. Compared with placebo, beta-blocker therapy was effective in preventing stroke (relative risk [RR], 0.71; 95% confidence interval [CI], 0.59-0.86) and congestive heart failure (RR, 0.58; 95% CI, 0.40-0.84). The findings were similar for high-dose diuretic therapy (for stroke, RR, 0.49; 95% CI, 0.39-0.62; and for congestive heart failure, RR, 0.17; 95% CI, 0.07-0.41). Low-dose diuretic therapy prevented not only stroke (RR, 0.66; 95% CI, 0.55-0.78) and congestive heart failure (RR, 0.58; 95% CI, 0.44-0.76) but also coronary disease (RR, 0.72; 95% CI, 0.61-0.85) and total mortality (RR, 0.90; 95% CI, 0.81-0.99). Although calcium channel blockers and angiotensin-converting enzyme (ACE) inhibitors reduce blood pressure in hypertensive patients, the clinical trial evidence in terms of health outcomes is meager. For several short-acting dihydropyridine calcium channel blockers, the available evidence suggests the possibility of harm. Whether the long-acting formulations and the nondihydropyridine calcium channel blockers are safe and prevent major cardiovascular events in patients with hypertension remains untested and therefore unknown. CONCLUSION: Until the results of large long-term clinical trials evaluating the effects of calcium channel blockers and ACE inhibitors on cardiovascular disease incidence are completed, the available scientific evidence provides strong support for the current national guidelines, which recommend diuretics and beta-blockers as firstline agents and low-dose therapy for all antihypertensive agents.

A case-control study to evaluate efficacy of screening for faecal occult blood.

OBJECTIVES: Faecal occult blood testing is routinely used for early detection of colorectal cancer, but evidence of its efficacy in preventing death from colorectal cancer is limited. A case-control study was carried out to evaluate whether screening for faecal occult blood is associated with a reduced risk of fatal colorectal cancer. SETTING: A health maintenance organisation in western Washington State, which has offered its members faecal occult blood testing every two years since 1983. METHODS: Cases (n = 248) were members of the health maintenance organisation who died from colorectal cancer between 1986 and 1991. For each case, two control subjects, who did not die from colorectal cancer and who were similar to each case in age, gender, and year of enrollment at the health maintenance organisation, were randomly selected from the membership list of the year in which the case was diagnosed (n = 496). Information about episodes of faecal occult blood testing (including the location and reason for the test, and the evaluation of positive tests) and potential confounders was obtained from medical records. RESULTS: Cases were less likely than controls to have ever been screened (odds ratio (OR) = 0.7, 95% confidence interval (CI) 0.5 to 1.0), consistent with a beneficial impact of screening. There was little difference, however, for screening that had taken place within a three year period before diagnosis (OR = 0.9, 95% CI 0.6 to 1.2), the maximum interval during which most tumours ought to have been detectable by faecal occult blood testing. A reduction in risk was seen for home testing but not for office testing, and in individuals aged less than 75 but not in those aged 75 or older. Although most of the 21 controls with a positive faecal occult blood test underwent some additional testing, only five (24%) were evaluated with colonoscopy or air contrast barium enema. CONCLUSIONS: While there can be uncertainty as to whether specific faecal occult blood tests were performed as screening or diagnostic tests, those performed at home and in younger persons may be relatively less likely to be diagnostic tests that were misclassified as screening. Thus the modest reduced risk associated with faecal occult blood testing in these settings/persons may reflect genuine benefit. However, the presence of a reduced risk associated with a screening faecal occult blood test received in the past, well before a tumour or polyp might bleed enough to allow detection, is compatible with uncontrolled confounding. Interpretation is further complicated by the fact that a number of individuals in the study group who had positive test results underwent limited or no diagnostic testing. Thus our results should be interpreted with considerable caution.

Should we consider a subject's knowledge of the etiologic hypothesis in the analysis of case-control studies?

In the context of a case-control study of vitamin supplements and neural tube defects, Werler et al. (JAMA 1993;269:1257-61) have argued that respondents who are aware of the etiologic hypothesis might particularly be prone to misreport their exposure status. They suggest that excluding such participants could offer the best chance for obtaining a valid risk estimate. However, knowledge of an etiologic hypothesis can be the reason for a person's being exposed or nonexposed. In addition, exposed cases selectively may become aware of the etiologic hypothesis after being diagnosed. If one of these, and not recall bias, is the basis for an association between knowledge of the hypothesis and exposure status, then "knowledgeable" subjects should be retained in the analysis so as not to compromise the precision or validity of the results.

A case-control study of oral cancer and pre-diagnostic concentrations of selenium and zinc in nail tissue.

A case-control study of oral cancer was conducted in western Washington state between 1983 and 1987. Cases (n = 379) were identified through a population-based registry, and controls (n = 514) were selected by telephone using random digit dialing. Subjects participated in a personal interview, completed a food-frequency questionnaire, and submitted clippings from the nails of each great toe for the determination of selenium and zinc concentrations. The odds ratio (OR) for low selenium levels in nail tissue (lowest 25% of the distribution compared to the upper 75%) was 1.4 (95% confidence interval (CI) 1.0-2.2). Likewise, the odds ratio for low zinc levels in nails was 1.6 (95% CI 1.0-2.3), but for low dietary zinc was 1.0 (95% CI 0.7-1.7). Men with oral cancer had lower nail selenium levels than did the controls (OR = 1.9), but women with oral cancer did not (OR = 0.6). Individuals 20 to 39 years of age with oral cancer, in particular, were more likely to have lower selenium levels in nail tissue than controls (OR = 16.4). There was a significant interaction between selenium and ascorbic acid levels which could not be explained by cigarette use. Subjects at greatest risk had low levels of both nutrients (OR = 3.8 for smokers and OR = 5.7 for non-smokers). However, since the elements were deposited in the nail matrix close to the date of diagnosis, the differences in the element concentrations between cases and controls may have been a result of the disease. Further etiologic studies of selenium, vitamin intake and oral carcinoma are warranted.

Serum levels of selenium and retinol and the subsequent risk of cancer.

A nested case-control study was conducted to assess the relation between serum levels of selenium and retinol and the subsequent risk of cancer. During the years 1972-1984, in northwest Washington State, 156 cases of cancer were identified among members of two employee cohorts from whom specimens had been previously obtained and stored. Two hundred eighty-seven controls were selected from these cohorts and matched to cases on the basis of employer, age, sex, race, and date of blood draw. Selenium and retinol levels were measured by neutron activation and high pressure liquid chromatography, respectively. Information on known cancer risk factors was collected by telephone interviews of subjects and next of kin. Levels of selenium and retinol were unassociated with the incidence of cancer of all sites combined, both overall and within subgroups defined by age, sex, levels of the other micronutrient, time between blood draw and diagnosis, smoking status, and family history of cancer. These findings suggest that neither serum levels of selenium nor those of retinol have an appreciable effect on the risk of cancer.

Long-term mortality study of oil refinery workers: V. Comparison of workers hired before, during, and after World War II (1940-1945) with a discussion of the impact of study designs on cohort results.

The mortality experience of a large refinery cohort (1937-1978) was examined by dividing it into three subcohorts according to hire dates: those hired before 1940, those hired during the period 1940-1945, and those hired after 1945. These three periods are approximately equivalent to before, during, and after World War II and span a total hiring period of more than 75 years. The results showed that a substantial portion of the cohort (3,330 or 27%) had been recruited during 1940-1945, and they contributed 980 or 28% of the total deaths. However, their mortality experience was quite different from the rest. A series of significant increases were seen among the external causes for accidents, suicide, and homicide. In terms of overall mortality and in contrast to the rest of the cohort, no "healthy worker effect" was seen (SMR = 1.00). They also showed increases in several types of cancer including cancers of the pancreas and prostate and leukemia. These unusual experiences cannot be explained either on the basis of their war-related deaths or on their period of employment (one-half were terminated within 1 year from date of hire), and data is insufficient to separate the role of hiring practices or their socioeconomic status. However, their life-styles were probably quite different judged from the fact that alcoholism-related deaths were increased as much as fivefold. Almost two-thirds of the total deaths occurred among 4,080 workers in the before 1940 subcohort. Further, the 5,117 workers of the after-1945 subcohort contributed only 5% of the total deaths. Thus, the results of the original refinery cohort (1937-1978) primarily reflect the experience of those employees hired before 1940. Given the same cohort method (historical prospective), cohort results vary widely according to different study designs, and this has implications for "generalizable" risk assessment or risk projections. A prospective study of new hires with 30 years of follow-up is rather inefficient because it would yield only a small number of deaths, with a strong healthy worker effect. The same is true for studies based on active workers with a short period of follow-up. Studies based on time of hire, however, provide a means for controlling time-related occupational exposures.

Long-term mortality study of oil refinery workers. IV. Exposure to the lubricating-dewaxing process.

A retrospective cohort mortality study of 1,008 male oil refinery workers who ever worked on the lubricating-dewaxing process of the lube oil department and who have been followed for a period of 43 years is presented. These workers were exposed to a number of solvents, primarily methyl ethyl ketone [(MEK) CAS: 78-93-3] and toluene (CAS: 108-88-3), but at levels far below the current Occupational Safety and Health Administration's standard. The standardized mortality ratio (SMR) for all causes (0.70) and the SMR for cancer (0.86) are much lower than unity when they are compared to the mortality experience of the U.S. population. Also observed in this study were 8 prostate cancer deaths (4.4 expected) with an SMR of 1.82, which was not statistically significant (P = .16). Seven of these 8 prostate cancer deaths occurred among nonwhite males, who showed an SMR of 2.47 (P = 0.53). However, only 1 prostate cancer death was seen among workers specifically assigned to the MEK units. The remaining deaths occurred among maintenance workers who had lube oil department-wide assignments. This cancer risk increased with increasing duration of employment in the lube oil department. A latency of 20 years or more was also observed for these prostate cancer deaths. In this study the processing of lubricating oils was found to be at least as important as the MEK solvents, and department-wide maintenance workers were as much at risk as the MEK unit workers. In view of this finding and findings obtained by others, it seems prudent to continue to study lubricating-dewaxing process workers, including the medical monitoring of all such workers for prostate cancer.

Pyridoxine treatment of childhood bronchial asthma.

Urinary xanthurenic and kynurenic acid levels were measured in five patients while they were receiving 50 mg and 100 mg of pyridoxine. The levels of tryptophane metabolite decreased progressively as the dose was increased but remained above basal levels. There was marked clinical improvement in these patients while receiving the higher dose only. The double-blind study with 76 asthmatic children followed for five months indicated significant improvement in asthma following pyridoxine therapy (200 mg daily) and reduction in dosage of bronchodilators and cortisone. The data suggest that these children with severe bronchial asthma had a metabolic block in tryptophane metabolism, which was benefitted by long-term treatment with large doses of pyridoxine.