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At least 1,243 records · Page 69Linked to original sources
PubMed1975

Neurologic manifestations of diabetic comas: correlation with biochemical alterations in the brain.

Coma and other neurologic abnormalities are present in patients with either diabetic ketoacidosis (DKA) or nonketotic coma (NKC), and the cause of such phenomena are not known. Patients with NKC also manifest seizures and focal neurologic changes. Treatment of diabetic coma with insulin may induce cerebral edema by as yet undefined mechanism(s). In patients with DKA, cerebral oxygen utilization is impaired, and there is hyperviscosity of the blood. A substantial part of the brain's energy source is derived from ketones, which in themselves can depress sensorium. Extracellular hyperosomolality is present, which may also contribute to the genesis of coma. In addition, most ketoacidotic patients have associated medical conditions, which may further impair consciousness. Biochemical changes in the brains of animals with DKA include impairment of both phosphofructokinase activity and pyruvate oxidation, and accumulation of citrate. The net effect upon sensorium in ketoacidotic patients probably represents the interaction of most of the above factors and differs markedly among individuals. Patients with NKC manifest not only depression of sensorium, but also focal motor seizures, hemiparesis, and other neurologic changes, such as aphasia, hypereflexia, sensory defects, autonomic changes, and brainstem dysfunction. Most of the aforementioned changes revert to normal after correction of hyperosomolality. Gamma amino butyric acid, which has been shown to elevate the seizure threshold, is normal in brains of ketoacidotic animals, but may be low in nonketotic coma. Also, hyperosomolality per se may produce seizures. Cerebral edema may complicate the treatment of either DKA or NKC. The available experimental evidence suggests that many of the commonly held theories for the production of such brain swelling probably do not occur. There is no breakdown of the sodium pump, sorbitol or fructose do not accumulate in brain, and brain glucose is only about 25 percent of that in plasma; Cerebral edema is probably produced largely by a direct action of insulin on brain at a time when plasma glucose is approaching normal values. Cerebral edema can thus theoretically be avoided by stopping insulin when plasma glucose has been lowered to values approaching normal.

Animals↗
PubMed1991

The mild hypertension enigma.

This study examines the problem of the correlation between mild arterial hypertension and cardiovascular damage. The authors examine the results of the most important trials carried out and, on the basis of their evaluations, suggest the need to review the current clinical policy of considering mild arterial hypertension as an important risk factor directly related to cardiovascular disease. Since the therapeutic trials carried out on mild hypertension did not substantially reduce the total and cardiac mortality rate, it seems to be probable that arterial hypertension is a progression acceleration marker of atheromatous disease. According to this theory, a therapy which aims merely at returning the pressure values to normal limits will probably not change the natural course of the atheromatous process.

Cardiovascular Diseases↗
PubMed1976

Contrast, induction, facilitation, suppression, and conservation.

Ten rats received all of their water in daily 1-hr sessions. Following a baseline phase in which lever and water spout were freely available throughout each session, subjects were trained to press the lever for water on mixed schedules composed of two alternating components. Each component gave access to water for a fixed cumulation of drinking time every time the rat cumulated a fixed amount of lever-pressing time. Changes in one component produced contrast and induction effects, both positive and negative, with respect to both lever pressing and drinking in the unchanged component. All schedules facilitated lever pressing relative to baseline. All schedules suppressed drinking relative to baseline, even though contingency sessions allowed ample time to perform the baseline amount of drinking. The entire pattern of results was predicted in quantitative detail by assuming that the total amount of a dimension apportioned to lever pressing and drinking is conserved between baseline and contingency sessions. Conservation theory was shown to predict several effects produced by simple fixed-ratio schedules, and was compared favorably with probability-differential (Premack, 1971) and response-deprivation (Timberlake and Allison, 1974) theory.

Journal Article↗
PubMed2002

On integrating the techniques of direct methods and SIRAS: the probabilistic theory of doublets and its applications.

The mathematical formalism of direct methods is here applied to the SIRAS (single-isomorphous replacement combined with anomalous scattering) case. Specifically, the joint probability distribution of three structure factors, which plays the central role in the probabilistic theory of the two-phase structure invariants (doublets), is derived. This distribution leads directly to the conditional probability distribution of the two-phase structure invariants, given the values of selected sets of magnitudes. Furthermore, a probabilistic formula for estimating individual phases of the derivative structure is derived, provided that the heavy-atom substructure is assumed to be known. The formulas were tested for experimental SIRAS data and results are reported.

Acetylesterase↗
PubMedDate not supplied

Uncertainty/information as measure of various urographic parameters: an information theory model of diagnosis of renal masses.

A new decision model for differentiating renal masses by urographic criteria has been developed and tested to demonstrate the use of uncertainty/information as a measure. The conditional probabilities used in this model are the relative frequency of occurrence of 15 specific uroradiographic signs in the presence of cyst, tumor, and benign cortical nodule. The decision model was applied to data obtained at the time of initial interpretation of 80 cases of renal mass discovered on urography. The probability of diagnosis was calculated by computer and compared to the radiologist's subjective probability estimate made prospectively at the time of initial interpretation. Information theory was applied to optimize the sequence in which signs were evaluated. The signs likely to maximally reduce the uncertainty of a diagnosis were evaluated first. The utility of this model and the comparative significance of various urographic signs used diagnose renal cysts, tumors, and benign cortical nodules were assessed. This model of renal mass evaluation at urography demonstrates principles of information theory that can be applied to more difficult and complex diagnostic and management problems.

Decision Making↗
PubMed2004

On the composition of risk preference and belief.

Prospect theory assumes nonadditive decision weights for preferences over risky gambles. Such decision weights generalize additive probabilities. This article proposes a decomposition of decision weights into a component reflecting risk attitude and a new component depending on belief. The decomposition is based on an observable preference condition and does not use other empirical primitives such as statements of judged probabilities. The preference condition is confirmed by most of the experimental findings in the literature. The implied properties of the belief component suggest that, besides the often-studied ambiguity aversion (a motivational factor reflecting a general aversion to unknown probabilities), perceptual and cognitive limitations play a role: It is harder to distinguish among various levels of likelihood, and to process them differently, when probabilities are unknown than when they are known.

Choice Behavior↗
PubMed2004

[Algorithm for diagnosing stable coronary artery disease].

UNLABELLED: The aim of the study was to develop simple algorithm for non-invasive estimating probability of the presence of CAD to optimize indications for cardiac catheterization. A prospective collection of clinical, electrocardiography (ECG), exercise electrocardiography (EE), dobutamine stress echocardiography (SE) and catheterization data was performed. All patients (n = 551, 65% male) complaining of chest pain, without prior history of myocardial infarction undergone EE (regarded as positive on the basis of > or = 1 mm ST-depression) SE (ischemia was defined as new or worsening wall motion abnormalities using a 16-segment model) and coronary angiography (CA): CAD was defined as > or = 50% narrowing of at least one major vessel. Two algorithms were developed with the use of probability analysis by computer program which employs Bayes' theory. They incorporated pretest variables: (age, gender, chest pain classification according to Diamond), ECG and results of one or two non-invasive test: EE and (or) SE. The studied population was divided into 3 groups on the basis of pretest likelihood of CAD: 1. low (< 10%), 2. intermediate (10-70%, in man divided into intermediate--low.: 10-29% and intermediate--high: 30-70%) and 3. high (> 70%). RESULTS: The prevalence of CAD in studied population was 61%. The sensitivity of the algorithm is 96% and specificity was 44%. Sensitivity and specificity of EE and SE was respectively: 93%, 21% and 85%, 69%). CONCLUSIONS: 1. An algorithm derived in our study is simple and may be useful in decision making that relates to CA. 2. We showed that when the likelihood of CAD is high on the basis of initial evaluation, diagnostic non-invasive testing is not indicated before CA, when the probability is intermediate or low, implementation of first choice test should be different in women (SE) and men (EE).

Aged↗
PubMed1992

Effects of probability mode on preference reversal.

Six analysts estimated verbally and numerically the chances that specific events will occur. Sixty decision makers used each type of estimate to make binary-choice decisions and to bid for lotteries based on the events. The usual reversal of preference between choice and bidding procedures was found in the numerical condition, but the frequency of preference reversals was significantly reduced in the verbal condition. This reduction occurred because risk aversion was reduced in choice when verbal estimates were given, whereas bidding was unaffected by presentation mode. The pattern of results was predicted by and supports the hypothesis that the relative importance given to the dimensions of a prospect depends on the form in which the information is displayed.

Decision Theory↗
PubMed1995

Radical AGEing in Alzheimer's disease.

The pathological presentation of Alzheimer's disease, the leading cause of senile dementia, involves regionalized neuronal death and an accumulation of intracellular and extracellular filamentous protein aggregates that form lesions termed neurofibrillary tangles and senile plaques, respectively. Several independent parameters have been suggested as the primary factor that is responsible for this pathogenesis, including apolipoprotein epsilon genotype, hyperphosphorylation of cytoskeletal proteins, or metabolism of amyloid beta. However, at present, no one theory explains adequately the host of complex biochemical and pathological facets of the disease. Recent findings suggest that age-related increases in oxidative stress and protein glycation either individually, or more probably in a synergistic manner, could, exclusive of the other theories or in concert with them, account for all aspects of Alzheimer's disease.

Aging↗
PubMedDate not supplied

A multiray model for calculating electron pencil beam distribution.

Based on the Fermi-Eyges theory, a set of recursion relations was derived for calculating electron distributions in the layered geometry. The electron distribution at a specific depth was obtained by convolving the upstream electron distribution with a kernel determined by the scattering parameters of the layer. Modifications were made to overcome some inherent limitations of the Fermi-Eyges theory. For each point in the medium, the most probable, or mean, path traversed by the electrons in reaching the point was derived. The skewness of the mean paths and the related energy degradation were included in a multiray model for pencil beam calculations. The resultant electron planar fluence distributions are no longer Gaussian as predicted by the original theory. The effects of edges or localized inhomogeneities are also included. Comparisons between our calculations and Monte Carlo simulations show good agreement.

Biophysical Phenomena↗
PubMed2005

N2 laser excited autofluorescence spectroscopy of formalin-fixed human breast tissue.

The paper reports results of an in vitro study on autofluorescence spectroscopy of fresh and formalin-fixed human breast tissue samples to investigate the effect of formalin fixation on the measured autofluorescence spectra. It also explores the applicability of the approach in discriminating cancerous from the uninvolved sites of the formalin-fixed breast tissues based on their autofluorescence spectra. A probability-based diagnostic algorithm, making use of the theory of relevance vector machine (RVM), a powerful recent approach for statistical pattern recognition, was developed for that purpose. The algorithm provided sensitivity values of up to 97% and specificity values of up to 100% towards cancer for both the independent validation data set as well as for the training data set based on leave-one-out cross-validation. These results suggest that autofluorescence spectroscopy may prove to be a valuable additional in vitro diagnostic modality in clinical pathology setting for discriminating cancerous tissue sites from normal sites.

Algorithms↗
PubMed2004

Calculation of the transition matrix and of the occupation probabilities for the states of the Oslo sandpile model.

The Oslo sandpile model, or if one wants to be precise, ricepile model, is a cellular automaton designed to model experiments on granular piles displaying self-organized criticality. We present an analytic treatment that allows the calculation of the transition probabilities between the different configurations of the system; from here, using the theory of Markov chains, we can obtain the stationary occupation distribution, which tells us that the phase space is occupied with probabilities that vary in many orders of magnitude from one state to another. Our results show how the complexity of this simple model is built as the number of elements increases, and allow, for small system sizes, the exact calculation of the avalanche-size distribution and other properties related to the profile of the pile.

Journal Article↗
PubMedDate not supplied

An annotated bibliography of decision analytic applications to health care.

This paper describes 110 applications of decision analysis to health care. Each paper is characterized according to the particular problem it addresses and the methods employed in the application. These applications span 15 years of study and are reported in a widely dispersed literature. Nearly half of the published articles appear in journals with a medical audience and more than 25% of the studies remain unpublished. The major areas of application identified in this review have been the evaluation of alternatives in treatment and health policy planning. Studies discussing conceptual issues in the application of decision analysis represent a substantial portion of those identified. Almost equal numbers of applications involve the use of single and multiattribute utilities in scaling decision outcomes and relatively few apply to group utilities. General discussions of decision analysis methods and applications focused on probability assessments/analyses represent the other major categories of studies cited.

Decision Theory↗
PubMed2006

SSL: a theory of how people learn to select strategies.

The assumption that people possess a repertoire of strategies to solve the inference problems they face has been raised repeatedly. However, a computational model specifying how people select strategies from their repertoire is still lacking. The proposed strategy selection learning (SSL) theory predicts a strategy selection process on the basis of reinforcement learning. The theory assumes that individuals develop subjective expectations for the strategies they have and select strategies proportional to their expectations, which are then updated on the basis of subsequent experience. The learning assumption was supported in 4 experimental studies. Participants substantially improved their inferences through feedback. In all 4 studies, the best-performing strategy from the participants' repertoires most accurately predicted the inferences after sufficient learning opportunities. When testing SSL against 3 models representing extensions of SSL and against an exemplar model assuming a memory-based inference process, the authors found that SSL predicted the inferences most accurately.

Adult↗
PubMed1990

Malformations of the epididymis in undescended testis.

Epididymal abnormalities in undescended testes are probably more common than suggested in the literature but only sporadic reports are found on this subject. For many years discussions have centered around the ideal age to operate on patients with undescended testes and consequently increase chances for future fertility. We analyzed 66 patients (82 testes) treated for undescended testis in our department, with special distinction between ectopia and cryptorchidism. Abnormalities ranged from simple epididymal elongation to more complex forms, such as complete disruption between the testis and epididymis. Among 49 ectopic testes the epididymides of 19 (38.8%) displayed more severe abnormalities in addition to elongation, while 16 (32.6%) showed only an elongated epididymis and 14 (28.6%) were normal. Among the 33 cryptorchid testes 29 (87.9%) showed the more complex anomalies and elongation, 3 (9.1%) were normal and only 1 (3%) was elongated. Our results demonstrate a much higher incidence of complex epididymal abnormalities in cryptorchidism (p less than 0.001). Elongated epididymis may present problems for sperm maturation and transportation, although with no other associated abnormality most can be regarded as patent. In our theory cases of elongation plus other major abnormalities probably are associated with severe impairment in sperm maturation and hindered transportation, with the future intrascrotal or extrascrotal position of the testis or early surgical repair being of little importance in terms of fertility.

Adult↗
PubMed1981

Estimate of the sticking probability for cells in uniform shear flow with adhesion caused by specific bonds.

A theory is developed for the aggregation rate of cells in uniform shear flow when the cell-cell adhesion is mediated by bonds between specific molecules on the cell surfaces such as antigen and antibody or lectin and carbohydrate. The theory is based on estimates of the frequency and duration of cell-cell collisions and of the number of bonds formed and required to hold the cells together. For high shear rates, the sticking probability is a function of a single dimensionless parameter, A, that is proportional to G-2, with G the shear rate. For low shear rates, the sticking probability is a function of a second dimensionless parameter, A' proportional to G-1. In either case the rate of cell-cell sticking is a maximum when A (or A') congruent to 1.0. For small values of A (or A') the cells collide frequently, but do not stick, whereas for large values of A (or A') the cells collide infrequently, but stick with larger probability. Studies in Couette viscometer or other flow having approximately uniform shear can test these models.

Animals↗