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At least 991 records · Page 55Linked to original sources

PubMed1990

Longitudinal Gompertzian analysis of Parkinson's disease mortality in the U.S., 1955-1986: the dramatic increase in overall mortality since 1980 is the natural consequence of deterministic mortality dynamics.

Age-adjusted mortality rates for Parkinson's disease (PD) for men and women in the United States, from 1955 to 1986, were calculated and subjected to longitudinal Gompertzian analysis. Annual age-adjusted PD mortality rate distributions were determined by a common intersect point and a variable environmental factor. For men, the death rate at age 73.75 years was 19.15/100,000; for women, the death rate at age 78.99 years was 28.64/100,000 for each year from 1955 to 1986. The environmental factor declined (improved) 360.7-fold for men and 319.6-fold for women in 1986 compared to 1955. Despite this dramatic environmental improvement favoring survival in PD, there has been a 57.6% increase since 1980 in the annual crude PD mortality rate for men compared to the stable annual crude mortality rate from 1955 to 1979. A corresponding 37.9% increase in the annual crude PD mortality rate for women has also occurred since 1980. The increase in overall mortality is due entirely to rapidly increasing age-adjusted mortality rates at ages greater than the intersect points for men and women. The results suggest that overall mortality due to common 'degenerative' diseases may increase dramatically as has occurred in PD.

Age Factors↗

PubMed1991

Longitudinal Gompertzian analysis of ischemic heart disease mortality in the U.S., 1962-1986: a method of demonstrating the deterministic dynamics describing its decline.

Age-adjusted mortality rates for ischemic heart disease (IHD) in the United States from 1962 to 1986 were subjected to longitudinal Gompertzian analysis. Age-adjusted IHD mortality rate distributions between age 40 and 85 years were determined by a variable environmental factor and an extrapolated common intersect point. The environmental factor declined (improved) 3.73-fold for men and 2.07-fold for women in 1986 as compared to 1962. However, the environmental factor in 1986 remained 15.34 fold more conductive to IHD mortality among men than women. The age at the extrapolated common intersect point was 126.7 years for men and 267.4 years for women. Longitudinal Gompertzian analysis of IHD mortality data suggests that IHD will remain a significant cause of mortality for men despite advances in risk factor reduction and medical therapy.

Adult↗

PubMed1991

Longitudinal Gompertzian analysis of primary malignant brain tumor mortality in the U.S., 1962-1987: rising mortality in the elderly is the natural consequence of competitive deterministic dynamics.

Age-adjusted mortality rates for primary malignant brain tumors (PMBT) in the United States from 1962 to 1987 were subjected to longitudinal Gompertzian analysis. Age-adjusted PMBT mortality rate distributions between age 25 and 65 years were determined by a variable environmental factor and a common intersect point. The environmental factor declined (improved) 1.58-fold for men and 2.34-fold for women in 1987 as compared to 1962. The age at the common intersect point was 68.4 years for men and 64.1 years for women. Between 1962 and 1987, non-age-standardized annual crude PMBT mortality rates increased 14.5% for men and 37.8% for women. However, PMBT mortality rates at age 77.5 years rose 259% for men and 409% for women between 1962 and 1987. Longitudinal Gompertzian analysis of PMBT mortality data suggests that rapidly rising PMBT mortality rates in the elderly are the natural consequence of competitive deterministic mortality dynamics and should not be attributed to environmental factors, past or present, that are directly contributing to PMBT mortality. Furthermore, longitudinal Gompertzian analysis demonstrates that PMBT mortality should not be studied in isolation, but rather should be examined in relation to other causes of death. When viewed from this perspective, the basis for the dramatic rise in PMBT mortality in the elderly becomes quite evident.

Adult↗

PubMed1991

Longitudinal Gompertzian analysis of prostate cancer mortality in the U.S., 1962-1987: a method of demonstrating relative environmental, genetic and competitive influences upon mortality.

Age-specific mortality rates for prostate cancer (PC) in the United States from 1962 to 1987 were subjected to longitudinal Gompertzian analysis. Age-specific PC mortality rate distributions between age 55 and 85 years were determined by a variable competitive factor and a common intersect point. The intersect point for PC occurred at age 61.5 years and mortality rate 27.9 per 100,000 and reflects genetic and environmental influences upon mortality. Between 1962 and 1987, non-age-standardized annual crude PC mortality rates increased 41.6%. Longitudinal Gompertzian analysis suggests that rising PC mortality rates in the United States are the natural consequence of competitive deterministic mortality dynamics. Moreover, longitudinal Gompertzian analysis is a method that demonstrates the relative contribution of environmental, genetic and competitive influences upon disease specific mortality.

Age Factors↗

PubMed1991

Longitudinal Gompertzian analysis of lung cancer mortality in the U.S., 1968-1986. Rising lung cancer mortality is the natural consequence of competitive deterministic mortality dynamics.

Age-adjusted mortality rates for lung cancer (LC) in the United States from 1968 to 1986 were subjected to longitudinal Gompertzian analysis. Age-adjusted LC mortality rate distributions between age 20 and 50 years were determined by a variable environmental factor and a common intersect point. The environmental factor declined (improved) 1.89-fold for men and 3.11-fold for women in 1986 as compared to 1968. The age at the common intersect point was 47.2 years for men and 39.1 years for women. Between 1968 and 1986, the non-age-standardized annual crude LC mortality rate increased 44.8% for men and 217.6% for women. Longitudinal Gompertzian analysis of LC mortality data suggests that the rising LC mortality rates in the United States are the natural consequence of competitive deterministic mortality dynamics and not a reflection of an environment that is directly more conductive to LC mortality. That is, more people are dying of LC because they are not dying from other diseases such as ischemic heart disease and stroke. Longitudinal Gompertzian analysis demonstrates that single disease mortality should not be studied in isolation, but rather examined in relation to other causes of death. When viewed from this perspective, the basis for the more dramatic rise in LC mortality in women becomes immediately evident.

Adult↗

PubMed1986

Disorders of classificatory activity in aphasia.

Two nonverbal tasks of classificatory activity ("class inclusion" and "class intersection") were administered to 46 aphasics, 28 normal controls, 19 nonaphasic left-brain-damaged and 17 right-hemisphere-damaged patients in order to study if aphasic patients are more impaired than nonaphasic brain-damaged patients on these two tasks of elementary logic and if a relationship exists within the aphasic patients between inability to perform the tasks of classifiactory activity and impairment of the semantic-lexical level of integration of language. Results were for the most part in line with expectations because aphasics scored worse than normal controls and nonaphasic brain-damaged patients (even if the difference reached the level of statistical significance only on the test of "class intersection") and within the aphasic patients the worst results were obtained by subjects presenting clear signs of semantic-lexical disintegration.

Aphasia↗

PubMed1985

Haemodynamics of coronary artery-saphenous vein bypass.

The velocity distribution of a suspension of red blood cell ghosts in an idealized model of the coronary artery-saphenous vein bypass has been investigated with the aid of laser Doppler anemometry. Pulsatile flow simulated pressure variations in the ascending aorta and ghost cell velocities were determined by the Doppler shift of scattered laser light. Using four different model bypasses it was demonstrated that turbulent flow at the graft-coronary intersection can be delayed by decreasing the discontinuity in diameter between the bypass vein and coronary artery, and also by reducing the bypass vein and host coronary artery intersection angle.

Biomedical Engineering↗

PubMed1993

Optimization of release from magnetically controlled polymeric drug release devices.

Release rates from drug:polymer matrices embedded with small magnets increase in the presence of oscillating magnetic fields. Previous studies of these systems have defined those parameters that determine the extent of the increase in release, and implied that not only was the force generated within the matrix an important determinant of the extent of modulation but also that the greater the amount of matrix actually displaced, the greater the observed modulation. We investigated this possibility in the magnetic system and developed a model taking into account the intersection of the volume of a cylindrical polymer-drug magnet embedded matrix with an imaginary sphere representing the upper limit of matrix deformation by the magnet. The intersection correlated in a linear fashion with the increase in release (slope = 1.16 +/- 0.26, R = 0.864, P = 0.003, s.e.e. = 1.38). Magnet orientation alone was insufficient to explain the data. It appears that a modulated system is optimized when the modulating force overlaps precisely with the maximum amount of matrix drug that can be released. If the size of the matrix, position of the magnet, force generated on the matrix by the magnet, viscoelastic properties of the matrix, etc. are not matched then modulation is inefficient. These results should provide further insight into and a means of optimization for externally regulated controlled release systems.

Chemistry, Pharmaceutical↗

PubMed1990

Comparison of three related methods to select T cell-presented sequences of protein antigens.

A comparison of three methods to predict T cell-presented sequences within antigenic proteins led to the view that recurrent hydrophobic residues might nucleate excised peptides as alpha-helices against hydrophobic surfaces. Such helices could be protease-protected structures on their way to desetope binding. The compared methods were: the amphipathicity algorithm of DeLisi and Berzofsky [Proc. natn. Acad. Sci. U.S.A. 82, 7048-7052. (1985)] as modified by Margalit et al. [J. Immun. 138, 2213-2229. (1987)] the strip of-helix hydrophobicity algorithm (SOHHA) of Stille et al. [Molec. Immun. 24, 1021-1027. (1987)] and the motifs algorithm of Rothbard and Taylor [EMBO J. 7, 93-100. (1988)]. Correct prediction was defined at two levels of stringency: (1) the predicted sequence overlapped the experimentally reported sequence when the ratio of the intersection of both to the union of both greater than or equal to 0.5 or (2) the sequences touched when there was a non-empty intersection of both sequences. We determined the sensitivity (correct predictions/number of reported T cell-presented sequences) and efficiency (correct predictions/number of predictions) at each level of stringency. In terms of overlap, the SOHHA was more sensitive (0.43) than the amphipathicity (0.29) (not significant) and motifs (0.0, 0.0) (p less than 0.05) predictions and more efficient (0.35) than the amphipathicity (0.14) and motifs (0.0, 0.0) predictions. At the less stringent criterion touching, the amphipathicity method (0.71) was as sensitive as motif Rothbard-4 (0.79) and more sensitive than SOHHA (0.57) and motif Rothbard-5 (0.43). At that criterion, the SOHHA was more efficient (0.47) than the amphipathicity (0.36) and motifs (0.25, 0.40) methods. We hypothesize that the comparability of these approaches reflected the common, predominant influence of recurrent hydrophobicity in their predictions.

Algorithms↗

PubMed1993

Neurite promoting activity of insulin, insulin-like growth factor I and nerve growth factor on spinal motoneurons is astrocyte dependent.

Mouse motoneurons were isolated from dissociated E15 mouse spinal cord and grown on polyornithine-coated round coverslips in a growth medium (DMEM/F12) supplemented with progesterone, trans-ferrin, selenium, horse serum and muscle extract. Astrocytes from newborn mouse neopallium were grown on rectangular coverslips. The motoneuron neurite growth was determined at day 8 of culture by counting, using the light microscope, the intersections produced by neurites radiating from the perikaryon placed centrally in a graticule eyepiece of concentric circles. The mean intersections for cultures without addition of astrocytes, insulin, insulin-like growth factor I (IGF-I) or nerve growth factor (NGF) was 12.6 +/- 0.8. When astrocytes on a separate coverslip were introduced from day 1, there was a small increase in neurite growth (16.3 +/- 0.9). The neurite growth was further increased significantly with the addition of insulin (27.3 +/- 1.4), IGF-I (31.5 +/- 1.4) or NGF (21.8 +/- 1.1) to cultures with astrocytes. Insulin, IGF-I or NGF in the absence of astrocytes did not greatly increase the neurite growth. We conclude that insulin, IGF-I and NGF promote neurite growth through some interactions with astrocytes.

Animals↗

PubMed1995

Kinetic mechanism of pyrophosphate-dependent phosphofructokinase from Giardia lamblia.

The steady-state kinetics of the reaction catalyzed by inorganic-pyrophosphate-dependent D-fructose-6-phosphate 1-phosphotransferase from Giardia lamblia have been investigated. The reactants for the forward and reverse reactions were the Mg-chelated complexes of pyrophosphate (PPi) and Pi. Uncomplexed ligands were not substrates. In the direction of phosphorylation of fructose-6-phosphate (F6P), initial velocity double-reciprocal plots for both PPi and F6P were intersecting suggesting sequential addition of substrates. Similarly, intersecting patterns were observed in the reverse reaction with either Pi or fructose-1,6-bisphosphate (FBP) as the variable substrate. Although the catalytic constants for the forward and reverse reactions were found to be identical (83 s-1), the kcat/Km for PPi is about two orders of magnitude higher than the kcat/Km for Pi, indicating that PPi is utilized much more efficiently than Pi. Product inhibition of Pi is competitive vs. PPi and noncompetitive vs. F6P, when the fixed substrate is subsaturating. Product inhibition by FBP was found to be noncompetitive with either Pi or F6P as the variable substrate. These results are consistent with a sequential ordered Bi Bi mechanism with PPi adding first and Pi dissociating last. In the reverse reaction, however, PPi and F6P were found to be noncompetitive with either Pi or FBP. Dead-end inhibition analysis with fructose 2,6-bisphosphate, a competitive substrate analog of FBP, gave uncompetitive inhibition with respect to Pi, indicating that fructose 2,6-bisphosphate (and hence FBP) binds after Pi. This kinetic mechanism is different from that observed with the enzyme from Propionibacterium freudenreichii, Entamoeba histolytica or Mung bean, which were concluded to be rapid equilibrium random mechanism.

Animals↗

PubMed1993

Precision in reporting the dose given in a course of radiotherapy.

A knowledge of the precise dose given in a course of radiotherapy is vital to the interpretation of the result. Despite this, an acceptable level of reporting was found in only 72 (36%) of 200 papers published in the two leading journals of radiation oncology. Analysis of the treatment data of the cases with head and neck tumours in the pilot study of CHART showed that the mean of the minimum tumour doses given was 5.1% lower than the mean of those at the intersection points. Had the same total dose been prescribed to the intersection point instead of the minimum there would have been a similar lowering of dose. There is evidence from published clinical data and a suggestion from an analysis of the CHART pilot study data that a dose difference as small as 5% may lead to real impairment or enhancement of tumour response, as well as altering the risk of morbidity. Inadequate reporting may lead to a false interpretation of a study and to its wrongful application. It is strongly recommended that it should be editorial policy to publish only those papers where the radiation dose is fully described.

Absorption↗

PubMed1985

PCS System I: point counting stereology programs for cell biology.

PCS System I (PCS) is a set of four software modules designed to simplify the application of stereology to problems in cell biology. It is written in BASIC for the Tektronix 4052A microcomputer (Beaverton, OR). A Counting Module collects raw data counts in either a Density Mode (points, intersections, transections, profiles) or a Boundary Mode (intersections with complete nuclear profiles). This information is stored on tape or disk data files and can also be printed. Three analysis modules use data files created with the Counting Module. The Density Module uses Density Mode data files to calculate volume, surface, length, and numerical densities. The B Numerical Density Module uses both Boundary Mode and Density Mode data to calculate the means for the boundary, diameter, and surface area of a nuclear compartment. The mean nuclear surface area is then used with the nuclear surface density to estimate the nuclear numerical density, which, in turn, is used to calculate surface areas of membrane compartments in average cells and in 10(6) cells. The Format Module reformats raw data files for analysis with Tektronix statistical software.

Biometry↗

PubMed1990

A quantitative study of dendrite complexity in selected areas of the human cerebral cortex.

This study seeks relationships between the degree of dendrite complexity of four areas of the human cerebral cortex and the type of function subserved by those areas. Quantitative studies of basilar dendrite patterns in the trunk and hand-finger receptive zones of areas 3 and 1, superior gyrus of the prefrontal cortex (area 9), and supramarginal gyrus (area 39) of the parietal lobe, in the left hemisphere of 10 subjects are reported. Measurements of dendrite complexity were based on the Sholl method of counting dendrite intersections with a series of superimposed concentric rings centered on the middle of the neuron soma. The data were analyzed graphically to show (1) characteristic dendrite profiles generated by cells in each of these areas, (2) comparisons between dendrite systems of two paired areas, i.e., trunk vs. hand-finger, and hand-finger vs. supramarginal, and (3) cumulative dendrite-ring intersection patterns for all areas studied. The data provided only partial support for our working hypothesis suggesting a relationship between complexity of the dendrite arbor and the nature of the computational tasks performed by the area. However, complexity of dendrite systems in the trunk area was found to be generally less than that of any other. In addition, there were suggestive associations between the complexity of dendrite systems of the hand-finger zone of the primary sensory receptive area and the nature of the work with which the individual had been associated during his/her working life. It proved more difficult to discern relationships between structure and function in the cortical associative areas. The study underlines the large degree of interindividual variation in dendrite structure and the need for much more extensive information about the life history of individuals who serve as subjects for this type of study.

Aged↗

PubMed1989

An algorithm for design of beam compensators.

Beam compensators are optimally designed to give a uniform dose to any plane or midsurface that intersects a single beam, or to give a uniform dose to the volume defined by the intersection of two or more beams. The primary and scatter components are taken into account separately, as well as the patient's shape and internal heterogeneities. The design of the beam compensators is formulated as a linear programming problem and solved with a variation of the Simplex Method. Beam weighting factors are also obtained as part of the solution.

Algorithms↗

PubMed1993

The investigation and rectification of field placement errors in the delivery of complex head and neck fields.

PURPOSE: To evaluate a novel technique for resolving field placement errors into their components and to quantify the improvement in accuracy potentially achievable by translation and rotation of the radiation beam. METHODS AND MATERIALS: One hundred and eighty-five films (both simulator and portal) from seventeen patients receiving radiotherapy to the head and neck region were analyzed in pairs. The computer based comparisons of complex fields with curved edges employed the intersections of perpendiculars from two reference points with the field periphery to define field match points. Field placement errors were resolved into those due to patient motion within the immobilization shell and those due to incorrect beam position, orientation, or shape. RESULTS: The median and the 95 percentile of the distribution of differences between prescribed (simulator) fields and treated (portal) fields referenced to the patients anatomy were 4.4 mm and 8.9 mm, respectively. The analysis suggests that with appropriate translation and rotation of the beam with respect to the immobilization shell these figures could be reduced to 3.1 mm and 8.2 mm, respectively, confirming the large contribution of patient motion within the shell to field placement accuracy. Comparisons between treated fields indicated smaller variability during treatment than between simulation and treatment. CONCLUSION: The perpendicular intersection method described here was found appropriate for the identification of field match points. The distributions of field placement errors were similar to those in a published study of straight edged fields. Translation and rotation of the applied field with respect to the immobilization shell would generally result in only a small improvement in field placement accuracy.

Head and Neck Neoplasms↗

PubMed1994

Comparison of the E-test and conventional agar dilution methods for susceptibility testing of gram-negative anaerobic rods.

The E test was used to determine the susceptibility of 209 anaerobic Gram-negative rods to ampicillin, amoxicillin-clavulanate, ticarcillin, ticarcillin-clavulanate, piperacillin, piperacillin-tazobactam, clindamycin, chloramphenicol, and cefoxitin. Minimum inhibitory (MICs) were read where growth intersected the strips or where the upper indentation intersected the strips for beta-lactamase inhibitor-containing strips. Reference MICs were performed by the National Committee for Clinical Laboratory Standards agar dilution method. Organisms tested consisted of 117 Bacteroides fragilis group, 24 fusobacteria, and 68 other species (mainly Prevotella species). Agreement of MICs by both methods occurred in 33.4% of cases; 80.8% were within one, 99.0% were within two, and 99.95% were within three doubling dilutions apart. E-test results, expressed as MIC50/MIC90 values (microgram/ml), were as follows: ampicillin: 16/> 256; amoxicillin-clavulanate (2:1), 0.5/4; ticarcillin, 16/> 256; tircarcillin-clavulanate (2 micrograms/ml), 0.5/4; piperacillin, 16/> 256; piperacillin-tazobactam (4 micrograms/ml), 1/8; piperacillin-tazobactam (8:1), 2/8; cefoxitin, 8/64; clindamycin, 0.25/4; and chloramphenicol, 2/8. Conventional MIC methodology yielded MIC50s and MIC90s either identical to, or within one doubling dilution of, E-test results. Percentages of strains susceptible varied by < 3% between the two methods, except for cefoxitin (E test 5.2% lower). Based on these results, the E test is an accurate and practical method for use with the agents and organisms evaluated.

Agar↗

PubMed2005

Bayesian ranking of sites for engineering safety improvements: decision parameter, treatability concept, statistical criterion, and spatial dependence.

In recent years, there has been a renewed interest in applying statistical ranking criteria to identify sites on a road network, which potentially present high traffic crash risks or are over-represented in certain type of crashes, for further engineering evaluation and safety improvement. This requires that good estimates of ranks of crash risks be obtained at individual intersections or road segments, or some analysis zones. The nature of this site ranking problem in roadway safety is related to two well-established statistical problems known as the small area (or domain) estimation problem and the disease mapping problem. The former arises in the context of providing estimates using sample survey data for a small geographical area or a small socio-demographic group in a large area, while the latter stems from estimating rare disease incidences for typically small geographical areas. The statistical problem is such that direct estimates of certain parameters associated with a site (or a group of sites) with adequate precision cannot be produced, due to a small available sample size, the rareness of the event of interest, and/or a small exposed population or sub-population in question. Model based approaches have offered several advantages to these estimation problems, including increased precision by "borrowing strengths" across the various sites based on available auxiliary variables, including their relative locations in space. Within the model based approach, generalized linear mixed models (GLMM) have played key roles in addressing these problems for many years. The objective of the study, on which this paper is based, was to explore some of the issues raised in recent roadway safety studies regarding ranking methodologies in light of the recent statistical development in space-time GLMM. First, general ranking approaches are reviewed, which include naïve or raw crash-risk ranking, scan based ranking, and model based ranking. Through simulations, the limitation of using the naïve approach in ranking is illustrated. Second, following the model based approach, the choice of decision parameters and consideration of treatability are discussed. Third, several statistical ranking criteria that have been used in biomedical, health, and other scientific studies are presented from a Bayesian perspective. Their applications in roadway safety are then demonstrated using two data sets: one for individual urban intersections and one for rural two-lane roads at the county level. As part of the demonstration, it is shown how multivariate spatial GLMM can be used to model traffic crashes of several injury severity types simultaneously and how the model can be used within a Bayesian framework to rank sites by crash cost per vehicle-mile traveled (instead of by crash frequency rate). Finally, the significant impact of spatial effects on the overall model goodness-of-fit and site ranking performances are discussed for the two data sets examined. The paper is concluded with a discussion on possible directions in which the study can be extended.

Accidents, Traffic↗