Biomedical subjects
Publications and source records attributed to M Sivak.
Caloric consumption in a society with readily available food is likely to be approximately proportional to the number of hours of being awake. Thus, replacing 1 h of inactive wakefulness (e.g. watching TV), with sleeping is likely to result in a substantial reduction in caloric intake. Calculations are presented to illustrate the possible benefits of such a switch on weight reduction.
Analysis of the primary structure of mBEII, with those of other branching and amylolytic enzymes as reference, identifies four highly conserved regions which may be involved in substrate binding and in catalysis. When one of the amino acid residues corresponding to the putative catalytic sites of mBEII, i.e., Asp-386, Glu-441, and Asp-509, was replaced, activity disappeared. These putative catalytic residues are located in three different regions (regions 2-4) of the four highly conserved regions (regions 1-4) which exist in the primary structure of most starch hydrolases and related enzymes, including branching enzymes. Region 3, which contains Glu-441 as one of the putative catalytic residues, was located downstream of the carboxyl-terminal position previously reported. The importance of the carboxyl amino acid residues was also demonstrated by chemical modification of the branching enzyme protein using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide.
BACKGROUND: Despite increased clinical use of endoscopic ultrasound (EUS), there are little data regarding complications of EUS or its impact on patient management. METHODS: A prospective multicenter study was completed to evaluate clinical outcomes of EUS. Before each EUS examination the endosonographer recorded further theoretical patient management plans as if EUS was unavailable. After the EUS, endosonographers recorded actual management plans based on EUS results. The actual management plan after EUS was compared to the theoretical management before EUS. Complications were assessed in short-term follow-up. RESULTS: Four hundred twenty-eight subjects were enrolled. Of subjects able to be evaluated, EUS changed the treatment plan in 74%. Management changes of major importance occurred in 120 patients (31% of subjects able to be evaluated) and included decisions regarding surgery (62 patients), decisions regarding nonsurgical invasive management (36 patients), and decisions regarding further follow-up (22 patients). When there was a change in management, the change was to less costly, risky, or invasive management in 55%, to more costly/risky/invasive in 37%, and to equally costly/risky/invasive in 8%. Short-term follow-up was completed in 81% of subjects, with six complications identified (1.7%). Three complications were mild, two were moderate, one severe, and none fatal. CONCLUSIONS: (1) Changes in management plan may occur in the majority of patients based on EUS results. (2) The management changes are often of major importance with regard to health care costs and safety, and are more often in the direction of less costly, risky, and invasive management. (3) EUS is safe in experienced hands.
The literature contains numerous claims that 90% of all the information used in driving is visual. This article presents a theoretical discussion, a citation search, and a review of evidence concerning such claims. The findings indicate that not only do we lack data from which to derive an accurate numerical estimate, but we lack a measurement system within which any numerical estimate would be meaningful. Consequently, although the information relevant to driving is likely to be predominantly visual, any claims about the precise percentage attributable to vision are premature. The proliferation of such claims in the absence of direct evidence is a reminder that researchers should be careful about assuring the validity of the claims they are passing on.
Elevated road fatality rates at night involve multiple variables, each of which contributes to an unknown degree. In order to determine the relative contributions of reduced visibility and drivers' consumption of alcohol, we performed two quasi-experiments analyzing data recorded by the U.S. Fatal Accident Reporting System from 1980 through 1990. The results confirmed that both variables play a major role in nighttime road fatalities and revealed new evidence that they contribute differentially to two classes of fatal collisions: Degraded visibility in low illumination is associated primarily with collisions involving pedestrians and pedalcyclists, whereas drivers' consumption of alcohol plays a larger role in other fatal collisions.
The structure of alpha-glucan, isolated from wild-type Escherichia coli B, a glycogen branching enzyme (BE)-deficient E. coli AC71 (glgB-), or from AC71 transformed with genes coding for maize BEI and BEII individually as well as with both genes, was analyzed by high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection. Transformation of the maize BE gene(s) in AC71 (glgB-) showed complementation in branching activity. Analysis by HPAEC revealed different structures between glycogen of E. coli B and alpha-glucan of AC71 transformed with a different maize BE gene(s). The individual chains of the alpha-glucan debranched with isoamylase were distributed between chain length (CL) 3 and > 30 and the chain with CL 6 was the most abundant. In comparison with the glycogen of E. coli B, the alpha-glucan of AC71 transformed with the maize BE gene(s) consisted of a lesser amount of chains with CL 7-9 and a larger amount of chains with CL > 14. It also showed a broad peak with chains of CL 9-12 as in maize amylopectin. This study provides in vivo evidence that glycogen BE and maize BE isozymes may have different specificities in the length of chain transferred. Furthermore, this study suggests that the specificity of glycogen synthase and starch synthase and their concerted action with BE play an important role in determining the structure of the polysaccharide synthesized.
Standard incandescent brake lamps have a relatively slow rise time. It takes approximately a quarter of a second for them to reach 90% of asymptotic light output, causing potential delays in responses by following drivers. The present study evaluated reaction times to brake signals from standard incandescent brake lamps and from three alternative brake lamps with substantially faster rise times: neon, LED, and fast incandescent. The study, performed in a laboratory, simulated a daytime driving condition. The subject's task was to respond as quickly as possible to the onset of either of two brake lamps in the visual periphery, while engaged in a central tracking task. Brake signals were presented at two levels of luminous intensity. The results showed that reaction times to the alternative brake lamps were faster than to the standard incandescent lamp, with the advantage averaging 166 ms for the LED and neon lamps, and 135 ms for the fast incandescent lamp. A reduction of the signals' luminous intensity from 42 cd to 5 cd increased the reaction time by 84 ms.
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We studied ocular motor function in 34 patients with motor neuron disease (MND) and in 18 age-matched controls. This included the latency, accuracy, and amplitude-velocity relationships of saccades. We also examined ocular pursuit, the slow phases of optokinetic nystagmus, and the ability to suppress the vestibulo-ocular reflex (VOR) with visual fixation of a head-mounted target. Five of the subjects with MND had pronounced parkinsonian features on neurologic examination. The nonparkinsonian MND subjects had normal ocular motor function for all measures. Most subjects suppressed the VOR completely. The parkinsonian-MND patients had impairment of both saccadic and pursuit eye movements, and one parkinsonian-MND patient with poor pursuit was unable to suppress the VOR. We conclude that ocular motor function is generally spared in MND. The occasional appearance of ocular motor dysfunction probably reflects the incidence of secondary abnormalities such as parkinsonism.
We have developed a method for defining diagnostic algorithms for pathologic conditions based on fluorescence spectroscopy. We apply this method to human colon tissue and show that fluorescence can be used to diagnose the presence or absence of colonic adenoma. This method uses fluorescence excitation-emission matrices (EEM) to identify optimal excitation regions for obtaining fluorescence emission spectra which can be used to differentiate normal and pathologic tissues. In the case of normal and adenomatous colon tissue, these were found to be: 330, 370, and 430 nm +/- 10 nm. At these excitation wavelengths, emission wavelengths for use in diagnostic algorithms are identified from average difference and ratio of the spectra from normal and pathologic tissues. In colon tissue, at 370 nm excitation, 404, 480, and 680 nm were found to be useful emission wavelengths for diagnosing the presence of adenoma in vitro. The basis of colon tissue autofluorescence was investigated using EEM of pure molecules and relevant excitation-emission maxima in the literature.
This study investigated differences in risk-perception among U.S., Spanish, West German, and Brazilian drivers. Subjects estimated the risk involved in slide-projected traffic scenes. The scenes, photographed in the United States and Spain, were rated for the amount of risk by using a seven-point scale. The subject groups in each country included younger, middle-aged, and older nonprofessional drivers, as well as middle-aged professional (bus, taxi, or truck) drivers. In the data analyses, the independent variables were subjects' country, age, professional driving experience, and sex, and 23 dichotomously coded characteristics of the traffic scenes. The following are the main findings: (1) Spanish drivers reported the highest risk, while U.S. drivers reported the lowest risk; (2) younger drivers tended to report lower risk than middle-aged and older drivers; (3) nineteen of the 23 analysed characteristics of traffic scenes contributed significantly to risk ratings, even after simultaneously controlling for the effects of all other scene characteristics; (4) ten scene characteristics had a differential effect on the risk ratings in the four tested countries; (5) two scene characteristics had a differential effect on the risk ratings in the four tested subject groups; (6) none of the variables affected differentially the risk ratings of professional vs. nonprofessional drivers and males vs. females. These findings provide information concerning the desirable country- and age-specific emphasis in driver education, driver licensing, and public information campaigns.
This study investigated differences in simulated driver risk-taking behavior among U.S., Spanish, and West German subjects. The task consisted of performing a simulated intersection crossing on a video display. Subjects were shown an intersection with moving traffic on a horizontal road, and they were asked to attempt (under time pressure) a fixed number of crossings with a car moving vertically. The subjects in all three countries included younger, middle-aged, and older persons of both sexes. The following are the main findings: (1) The performance of West German subjects tended to differ from those of U.S. and Spanish subjects. Specifically, West German subjects attempted fewer crossings, had a higher probability of success, and had greater safety margins. (2) Target risk-level of performance, measured by probability of successful crossings, was not affected by age or sex. (3) Probability of attempted crossings was greater for males and younger subjects than for females and older subjects. (4) Similarly, safety margins during attempted crossings were smaller for males and younger subjects than for females and older subjects. These results suggest that there are differences among countries in the target risk-level of performance. However, the present findings imply that within each country all subjects (regardless of age and sex) tended to have the same target risk-level. To attain this risk-level of performance, males and younger subjects (because of their presumed superior psychomotor skills and/or greater experience with video tasks) attempted to cross more gaps (and, consequently, smaller gaps), with resulting smaller safety margins.
This study investigated differences in driver self-assessment among U.S., Spanish, and West German drivers. Subjects responded to 14 questions that used five-point semantic scales dealing with driver performance and abilities. Pairs of questions, concerning the same driving-related aspects, differed by requesting a self-assessment on an absolute basis and in relation to the average driver. The subjects in all three countries included younger, middle-aged, and older drivers of both sexes. The following are the main findings: (1) a majority of drivers in each country rated themselves positively on all driving-related scales studied; (2) significant effects of country, age group, and sex of the subjects were present for several of the scales; (3) some of these effects remained significant even after controlling for the differential driving experience. For example, U.S. drivers assessed themselves as safer than did West German and Spanish subjects, younger subjects less wise than middle-aged and older subjects, and males more relaxed than females.
This study investigated the effects of prior headlighting experience on ratings of discomfort glare from headlamps in an actual driving situation. Specifically, discomfort glare ratings given by West Germans who had recently arrived in the United States and were, presumably, used to the relatively low levels of glare associated with headlamps in West Germany were compared with ratings given by U.S.-born subjects. The West German subjects reported significantly more discomfort than did the U.S. subjects. This finding is in agreement with the so-called range effect, in which subjective judgments are affected by the range of available stimuli. Consequently, the present findings support the hypothesis that discomfort glare ratings are affected by prior visual experience.
A survey concerning international harmonization of accident reporting was distributed to 80 experts in accident reporting and analysis. Completed surveys were received from 50 persons in 13 countries; 74% of the respondents had more than 10 years of experience in the field of traffic safety. The main findings of this survey are: (1) 86% of the respondents think that an international computer file of disaggregated fatal-accident data would contribute to understanding of traffic safety, and 84% would use such a file. (2) An international non-fatal-accident file was considered to be of value in research on human factors and accident causation (60%), and in determining black spots in the road network (57%). (3) Police was the most frequently mentioned source of data for both the fatal and non-fatal international data files. Nevertheless, fewer than one-quarter of respondents considered police as the suitable exclusive source of either data. (4) The majority view was that the data for both types of files should come from more than one agency. (5) In the case of the fatal-accident file, 78% of the respondents considered it important that the data be cross-checked with the public health records. (6) The 10 most useful variables for a fatal-accident file were traffic unit type (e.g. car), accident type (e.g. angle), road class, driver age, date/time of day, age of person killed, number of killed persons, number of injured persons, drinking or drug use, and restraint usage of person killed.(ABSTRACT TRUNCATED AT 250 WORDS)
This article presents a brief overview of the research performed at tge Human Factors Division of The University of Michigan Transportation Research Institute between 1977 and 1986. The focus of the research has been on human factors (ergonomics) aspects of road safety. Specifically, the research has dealt with the following issues: vehicle headlighting, vehicle rear lighting and signalling, vehicle displays and controls, vehicle components, conspicuity of vehicles, legibility of traffic signs and licence plates, driver reaction time, driver performance, stopping sight distance, driver seated position, individual differences (drivers with disabilities, older drivers), methods for measuring blood alcohol concentration, societal violence and traffic accidents, cross-cultural comparison of driver risk-perception, and theoretical issues.
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