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03-JCMA-060614.qxd
No full textBackground: Acute or chronic liver damage may lead to hepatic encephalopathy. Previous studies have indicated the hemodynamic and hormonal mimicry between portal hypertension and hyperthyroidism. Furthermore, medically or surgically induced hypothyroidism has been found to be beneficial in ameliorating hyperdynamic circulation in the portal hypertensive state and in alleviating acute or chronic liver injury in rats. However, the effect of chronic thyroid hormone inhibition on chronic hepatic encephalopathy in cirrhosis remains unknown. Methods: Liver cirrhosis was induced by bile-duct ligation (BDL) in male Sprague-Dawley rats. Three weeks after BDL, rats were randomized to receive either tap water (control) or 0.04% methimazole in drinking water for 3 weeks. At the end of 6 weeks after BDL, severity of encephalopathy was assessed by the Opto-Varimex animal activity meter and hemodynamic parameters were measured. Blood samples were collected for determination of thyroid stimulating hormone, ammonia and liver biochemistry. Results: The heart rate of the methimazole-treated group was significantly lower than that of the control group (p = 0.015), whereas there were no differences in the mean arterial pressure and portal pressure. The total amount of movements were significantly increased in the methimazole group (p = 0.029). Plasma levels of ammonia, aspartate aminotransferase and alkaline phosphatase were significantly lower (p = 0.01) and thyroid stimulating hormone significantly higher (p = 0.035) in the methimazole group. Conclusion: Chronic methimazole treatment alleviates hepatic encephalopathy and liver damage in rats with BDLinduced hepatic cirrhosis. [J Chin Med Assoc 2006;69(12):563-568
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No full textWe thank R. Neale for help with an initial draft, M. Feychting for comments, and M. Bittar for secretarial assistance. We also thank P. Vecchia for invaluable advice and P. Buffler for participation in planning of the work. This work was supported by the ICNIRP. The authors declare they have no competing financial interests. Received Distribution of Exposure in the Population Despite the rapid growth of new technologies using RFs, little is known about population exposure from these and other RF sources and even less about the relative importance of different sources. In a typical house, nonoccupational exposure could come from external sources, such as radio, television (TV), and mobile-phone base stations, as well as internal sources, such as a faulty microwave oven, in-house bases for cordless phones, or use of mobile phones. Radio and TV transmitters have a large coverage area and therefore operate at relatively high power levels up to about 1 MW Mobile-phone base stations are low-powered radio transmitters that communicate with users' handsets. In early 2000, there were about 20,000 base stations in the United Kingdom and about 82,000 in the United States. Base stations can transmit power levels of ≥ 100 W (Schüz and Mann 2000). It is expected that the number of base stations will roughly double to accommodate new technology and a larger percentage of sites will have to be shared between operators, complicating exposure assessment. The power density levels inside a building can be from 1 to 100 times lower than outside, depending on the type of building construction Mobile phones operate at a typical power of 0.25 W. Analog systems operated at higher power levels than the newer digital systems. Similarly, older cordless phones operated to the analog standard, whereas modern ones operate to the digital with a transmitted power of a base around 0.09 W in a home but higher in a business setting. The actual exposure of the user depends on a number of factors such as characteristics of the phone, particularly the type and location of the antenna; the way the phone is handled; and most important, the adaptive power control, which may reduce the emitted power by orders of magnitude (up to a factor of 1,000). Factors that influence adaptive power control include distance from the base station, the frequency of handovers, and RF traffic conditions. Thus, the emitted power is higher in rural than in urban areas and when the user is moving (e.g., in a car). In areas where there is a great deal of phone use, phones may operate more than half of the time at the highest power levels. To compensate for the shielding effect of materials, power levels of phones are, on average, higher when a phone is used indoors than outdoors. RF absorption is maximal on the side of the head to which the phone is held, greatest close to the antenna, and decreases to less than one-tenth on the opposite side of the head In an occupational setting, higher exposures occur, albeit infrequently; for example, radar exposed workers in the U.S. Navy had potential for exposures > 100 mW/cm 2 Epidemiologic Considerations in Exposure Assessment General. In the absence of information on what biologic mechanism is relevant, it is unclear what aspect of exposure needs to be captured in epidemiologic studies. Because heating is the only known effect of RFs, most research has assumed that the metric of choice must be a function of the specific absorption rate (SAR). Metrics used in epidemiologic studies of other agents, such as cumulative exposure, average exposure over specific time intervals, and peak exposure, need to be considered. Given the uncertainty about the relevant interaction mechanism, the dose needs to be assessed not just as external field intensity but also as SAR for specific anatomical sites. Integrating exposure over time is further complicated by the fact that sources vary markedly over very brief time periods relative to the time periods of interest. Epidemiologic studies thus far have relied on rather crude proxies for exposure, such as job title, proximity to a base station, or use of a mobile phone. Refinement of exposure assessment is critical to improved epidemiology. This requires a bridge between the rather disparate worlds of epidemiology and physics. Although it is of interest to know about sources of variation or uncertainty in general, the critical need in epidemiologic studies is to identify those variables that are most important in determining exposure levels and most amenable to capture within populations. A key element in linking the complexity of the exposure sources and patterns with the needs of epidemiology is a meter that is capable of monitoring individual exposure. Such meters have now been developed [National Radiation Protection Board (NRPB) 2003]. Ideally, the dose, time pattern, and frequencies (wavelengths) of exposure from all key sources should be estimated for each individual in the study. Dose-and durationresponse analyses are important to assessment of etiology but have often been absent in the existing literature (Swerdlow 1999). In addition, the possible lag period between exposure and disease manifestation needs to be considered. Handheld mobile phones were not used regularly until the 1990s. Thus, studies published to date have had little power to detect possible effects involving long induction periods or effects from long-term heavy exposure to mobile phones or base stations. Methodologically, it would be desirable to conduct studies to clarify the relative contributions of different spheres of life. Such knowledge would allow epidemiologists to design studies that incorporate all important sources of RF exposure, or at least determine how much it matters that the occupational studies to date have taken no account of residential or mobile phone exposures and vice versa. Occupational exposures. Most occupational epidemiologic studies have based their exposure assessments simply on job titles and have included no measurements (Tables 1-4). It is possible that some jobs (e.g., radar operator) are adequate indicators of RF exposure. However, many job titles that have been previously considered to indicate exposure may provide a poor proxy for RF exposure. In addition to improving exposure assessment in individual studies, there is the potential to develop job-exposure matrices, with the rows corresponding to relatively homogeneous groups with respect to RF exposure, defined by job title, perhaps specific work location, calendar time, and other recordable work history, and the columns corresponding to RF exposure metrics. Transmitter exposures. All published epidemiologic studies of transmitter exposures have based exposure assessment on distance from the transmitter. The relation between exposure and distance from the antenna is usually very complex, especially in urban areas. Close to the antenna, the field is very low because of the directional antenna characteristics. As one moves away, the field pattern can be complicated, with peaks and valleys in field Estimation of community exposure to RFs from transmitters may, however, be amenable to refinement. Geographic information systems allow for precise assignment of residence, topography, and some other likely determinants of exposure. Historical information on power output from the transmitters may well be available. This information combined with personal measurements may provide refined measures of exposure that can be applied retrospectively, with empirical validation. Mobile phones exposures. Studies on mobile phones have used the simple dichotomy of user versus nonuser, with some incorporating information on years of use, number of phone calls per day, and duration of calls. Some studies have separated analog and digital phone use. Few have included use of cordless phones, which also generate RFs but from which exposure pattern is different. Ongoing studies are attempting to incorporate information on intensity of use, place of use, position of the telephone, type of telephone, and calendar period of use. Each of these extensions need to be evaluated, however, to determine a) whether they are truly an important determinant of exposure and b) whether they are amenable to accurate historical reconstruction through recall or some type of written record. There is little benefit in knowing that the intensity of exposure varies by a parameter that cannot be captured, or gathering relatively precise information about, say, model of mobile phone, if no useful exposure variable can be derived from it. Mechanisms Heating of cells and tissues from RF exposure might have benign or adverse biologic effects. These effects, which reflect an imbalance in the amount of heat built up in the body and the effectiveness of mechanisms to remove it, can be due to either elevated temperatures or increased physiologic strain from attempts to remove the heat. Of particular concern for whole-body heating are effects in the elderly, people taking certain kinds of drugs, and the fetus and infant. Cardiovascular mortality, birth defects, and impaired ability to perform complex tasks are among the outcomes that have been associated with whole-body heating. The sensitivity of different tissues and cells to thermal damage from both localized and whole-body heating varies. The central nervous system, testis, and lens of the eye seem to be particularly sensitive, the last due to a limited capacity to dissipate heat rather than a greater sensitivity of its cells to heat-induced damage. Laboratory studies suggest that adverse biologic effects can be caused by temperature rises in tissue that exceed 1°C above their normal temperatures There has been concern about possible carcinogenic effects of RFs below levels that cause detectably harmful heating. RFs are not sufficiently energetic to destabilize electron configurations within DNA molecules. Thus, there is no direct link between RF exposure and genotoxic effects such as DNA mutations, DNA strand breaks, or other genetic lesions. Experimental evidence from animal and laboratory studies at the cellular level confirms the lack of genotoxic effect of RF
Power-managed smart lighting using a semantic interoperability architecture
Get PDFAbstract-This paper presents a power-managed smart lighting system that allows collaboration of lighting consumer electronics (CE) devices and corresponding system architectures provided by different CE suppliers. In the example scenario, the rooms of a building are categorized as low and high priority, each category utilizing a different system architecture. The rooms collaborate through a semantic interoperability platform. The overall smart lighting system conforms to a power quota regime and maintains a target power consumption level by automatically adjusting lights in the building
A Spatio-Temporal Study of Ischemia and the Time-Frequency Coupling Variations between the ST Amplitude, Heart Rate and Dominant Angle
Get PDFAbstract An analysis of the Long Term ST Database (LTSTDB) was conducted to quantify the spatio-temporal dynamics of ischemic and non-ischemic episodes. For all 86 recordings the ischemic episode length is decribed by a lognormal distribution and the non-ischemic episode length by a generalized extreme value distribution. For the 15 recordings that possess orthogonal (EASI) leads sets we derived the 12 standard leads and analyzed the spatial time course (from the j-point to j+120 ms) of each episode over time to identify dominant trends. Although the magnitude of the ischemic episodes did not reveal any inter-subject trend (except for generally exhibiting Brownian-like motion), there appeared to be strong correlations with the heart rate (HR). Wavelet cross-spectral coupling with significance testing was then applied to the ST-amplitude and HR evolution over the course of each episode. In all subjects significant cross-spectral correlations were found at very low frequencies (<0.04 Hz), as well as at respiration and baroreflex frequencies. This may indicate that the ischemic episodes are modulated by blood pressure and activity or HR-related phenomena and that all episodes in the LTSTDB may be of a 'mixed' type at some point in their duration. The dominant angle also showed significant correlation (p<0.01) with the ST amplitude and HR changes at similar frequencies to those described above. All three protocols used to define ischemia in the LTSTDB gave similar results. Introduction Modelling the short-and long-term spatial and temporal changes in the ECG during ischemia provides a mechanism for baseline testing of relevant signal processing algorithms. Our aim in this work was to provide a description of such changes in order to provide information to build an accurate simulation of the ECG during ischemia. Methods Data The data used in this study were taken from the LongTerm ST Database (LTSTDB) [1] available from PhysioNet which contains 21-24 hour multi-channel ECG recordings and annotated ischemic and non-ishemic ST changes. An ischemic episode was defined to start when the ST deviation exceeded a lower threshold, V lower = 50µV . Next, the deviation was required to reach or exceed an upper threshold, V upper , for at least a continuous interval of T min seconds. Finally, the episode ended when the deviation dropped to less than V lower = 50µV in the following T sep = 30 s. The values of (V upper , T min ) were (75 µV , 30 s), (100 µV , 30 s) and (100 µV , 60 s) defined as protocol STA, STB and STC respectively. All analysis was performed in the vectorcardiogram (VCG) space. The LTSTDB contains 15 recordings (s30691 through s30801) which used the EASI lead system Similarly they give the transformation from the EASI configuration to the vectorcardiogram (X, Y, Z) configuration, V , the matrix Temporal analysis of the episodes The lengths of each ischemic and non-ischemic episode for all 86 patients in the LTSTDB were calculated using all available leads. An episode was taken to start if any lead satisfied the criteria for the relevant protocol and was taken to end when all leads ceased to satisfy the same pro
Functional Characterization of YM928, a Novel Noncompetitive ␣-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA) Receptor Antagonist
Get PDFABSTRACT The ␣-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor is thought to play an important role in the pathogenesis of several neurological disorders as well as normal brain function. The search for AMPA receptor antagonists as potential therapeutics is ongoing. Here, we describe the functional characterization of a novel noncompetitive AMPA receptor antagonist, 2-[N-(4-chlorophenyl)-N-methylamino]-4H-pyrido[3,2-e]-1,3-thiazin-4-one (YM928). This compound inhibited AMPA receptor-mediated toxicity in primary rat hippocampal cultures with an IC 50 of 2 M. Its manner of inhibition was noncompetitive as the agonist concentration was increased. YM928 blocked AMPA-induced intracellular calcium influx with an IC 50 of 3 M and antagonized AMPA-induced inward currents with an IC 50 of 1 M in cultured cells. YM928 displaced neither [ 3 H]AMPA binding nor other existing glutamate receptor-related ligand binding in rat brain membranes. In terms of in vivo activity, YM928 had an anticonvulsant effect in sound-induced seizures in DBA/2 mice 45 min after oral administration at 3 mg/kg. Thus, YM928 has potential as an oral therapeutic drug for various types of neurological disorders
Through Thick and Thin: a Need to Reconcile Contradictory Results on Trajectories in Human Cortical Development
Get PDFAbstract Understanding how brain development normally proceeds is a premise of understanding neurodevelopmental disorders. This has sparked a wealth of magnetic resonance imaging (MRI) studies. Unfortunately, they are in marked disagreement on how the cerebral cortex matures. While cortical thickness increases for the first 8-9 years of life have repeatedly been reported, others find continuous cortical thinning from early childhood, at least from age 3 or 4 years. We review these inconsistencies, and discuss possible reasons, including the use of different scanners, recording parameters and analysis tools, and possible effects of variables such as head motion. When tested on the same subsample, 2 popular thickness estimation methods (CIVET and FreeSurfer) both yielded a continuous thickness decrease from 3 years. Importantly, MRI-derived measures of cortical development are merely our best current approximations, hence the term "apparent cortical thickness" may be preferable. We recommend strategies for reaching consensus in the field, including multimodal neuroimaging to measure phenomena using different techniques, for example, the use of T 1 /T 2 ratio, and data sharing to allow replication across analysis methods. As neurodevelopmental origins of early-and late-onset disease are increasingly recognized, resolving inconsistencies in brain maturation trajectories is important
Kinematic evaluation and forward kinematic problem for Stewart platform based manipulators
Get PDFAbstract -In this paper two methods are presented. The first is a kinematic evaluation method for two different hexapod structures: standard Stewart platform manipulator with extensible struts and second structure with fixed strut lengths but sliding guideways on fixed platform. The second method addresses the forward kinematic problem where different mathematical representations are combined with various optimization algorithms to find a suitable combination that may be utilized in real-time environment. Additionally, we note the existence of equivalent trajectories of the mobile platform and suggest an adaptation to the solving method that, having satisfied certain assumptions, is able to successfully solve the forward kinematic problem in real-time conditions with very high precision
Social Aspects Regarding the Single-Parent Families Vulnerability The Case Of Arad County
No full textAbstract Based on empiric investigations and the study of documents from specialized public institutions, the authors analyse in this article the extent, manifestations, causes and consequences of single-parent families in Arad County. As social entities with a high risk of social exclusion, the authors identify practical measures for intervention by public authorities in the sense of optimizing socialization, social work and balancing these families, especially their children, by taking into account both Romanian and European legislation in this field. Preventing the reproduction/increase in the number of single-parent families must rely on the complete knowledge of this social phenomenon, with the need to establish databases and map the dispersion of single-parent families within administrative-territorial units. The decrease in the number of families with a high social risk over time is the result of correlated and harmonized public policies, aimed at fighting poverty, discrimination, unemployment, lack of access to education, while ensuring the general background for economic development and prosperity. The study is determined by the fact that many times the parents and the children of single parent families find themselves in the situation of not being able to make ends meet, the lack of finances, education and proper housing making it impossible for them to live a decent life. By identifying, through specific scientific methods such as document analysis, interviews, case studies, the particular types of problems facing single parent families, we consider we will succeed in offering a strong basis to motivate decision makers to establish additional social protection measures that will contribute to the reduction of the causes that maintain this social category among vulnerable groups
