Showing papers by "University at Buffalo published in 1971"
TL;DR: In this article, the existence of an absolutely continuous part having spectrum [λe, ∞], where λe is the lowest many body threshold of the system, and the point spectrum is discrete.
Abstract: Quantum mechanicalN-body systems with dilatation analytic interactions are investigated. Absence of continuous singular part for the Hamiltonians is proved together with the existence of an absolutely continuous part having spectrum [λe, ∞), where λe is the lowest many body threshold of the system. In the complement of the set of thresholds the point spectrum is discrete; corresponding bound state wave-functions are analytic with respect to the dilatation group.
1,206 citations
TL;DR: Congenic mice of the same H-2 type exhibited the same pattern of antibody response and thyroiditis, regardless of the strain's genetic background, thus showing a close relation between histocompatibility determinants and autoimmunity.
Abstract: Immunization of 33 inbred strains of mice with thyroid extract emulsified in complete Freund's adjuvant showed differences in both thyroid autoantibody response and autoimmune thyroid damage, related to the histocompatibility (H-2) type of the strain. Congenic mice of the same H-2 type exhibited the same pattern of antibody response and thyroiditis, regardless of the strain's genetic background, thus showing a close relation between histocompatibility determinants and autoimmunity.
387 citations
TL;DR: For example, the authors found that mice are capable of rejecting H-2-incompatible bone marrow grafts after a single lethal exposure to X-rays, and the onset of rejection begins 18-24 hours after transplantation and is completed by 96 hours.
Abstract: Mice are capable of rejecting H-2-incompatible bone marrow grafts after a single lethal exposure to X-rays. The onset of rejection begins 18-24 hr after transplantation and is completed by 96 hr. Maturation of this type of allograft reactivity does not occur until the 22nd day of life. In adult mice, the resistance to marrow allografts can be weakened by administration of cyclophosphamide or dead cultures of Corynebacterium parvum, but not heterologous anti-thymocyte serum. Sublethal exposures to X-rays 7 or 14 days before transplantation also weaken resistance. There is considerable interstrain variation in the ability of mice to resist allografts, even when H-2 differences between hosts and donor are kept identical. Although H-2 incompatibility is a necessary prerequisite for resistance, additional genetic factors influence the outcome of marrow allografts, presumably by controlling recognition. The regulator genes are determinant specific and the alleles for resistance or responder status appear to be dominant. The responder phenotype is expressed by hemopoietic cells and not by the environment. Accordingly, resistance is conferred to otherwise susceptible mice upon transfer of bone marrow cells but not of serum. The production and differentiation of effector cells for marrow graft rejection are thymus independent. In conclusion, bone marrow allografts elicit a particular transplantation reaction, previously unknown, in irradiated mice. Peculiar features of this reaction are the lack of proliferation of host lymphoid cells, tissue specificity, thymus independence, and regulation by genetic factors which apparently do not affect the fate of other grafts.
337 citations
TL;DR: The available evidence is not conclusive in excluding one of the two possibilities, but it favors the concept that allograft reactivity to hemopoietic cells is elicited by recessive tissue-specific antigens.
Abstract: F(1) hybrid mice are capable of rejecting inbred parental strain bone marrow grafts after a single lethal exposure to X-rays. The incompatibility is genetically controlled by the Hybrid-histocompatibility-1 (Hh-1) locus in or near the D end of the Histocompatibility-2 (H-2) region. The onset of parental graft rejection begins 9-12 hr after transplantation and is completed by 24 hr. Maturation of hybrid resistance does not occur until the 22nd day of life. In adults, the resistance to parental marrow grafts can be temporarily abrogated or weakened by administration of cyclophosphamide or dead cultures of Corynebacterium parvum, acute supralethal exposures to radiation, or by split-dose irradiation with 6-37-day intervals. Parental marrow grafts elicit a transplantation reaction in irradiated F(1) mice which is indistinguishable from that elicited in irradiated allogeneic (H-2-incompatible) hosts. Because of this immunogenetic similarity, the following question is raised: are the same or different alloantigens responsible for rejection of parental and allogeneic marrow grafts? In the first case, Hh-1 alleles would be recessive determinants of tissue-specific transplantation antigens, whereas in the second case they would be the determinants of parental- and tissue-specific antigens subject to genetic suppression in Hh-1 heterozygotes. Although the available evidence is not conclusive in excluding one of the two possibilities, it favors the concept that allograft reactivity to hemopoietic cells is elicited by recessive tissue-specific antigens.
337 citations
TL;DR: For semi-empirical molecular orbital methods, the gradient of the potential energy can be calculated with negligible additional computational expense as discussed by the authors, which allows powerful minimization methods to be used to calculate the geometries of large molecules.
315 citations
TL;DR: In this paper, the activation energy for crystal growth is 11.0 ± 1.0 kcal mole−1, and the rate is independent of the stirring rate, and photomicrographic evidence is presented in support of the suggestion that the initial surge in the growth curves results from additional nucleation at the surface of the added calcite crystals and in the bulk of the supersaturated solution.
307 citations
TL;DR: In this article, a rigorous formulation for the rate of capillary penetration by a liquid is presented, and the resultant differential equation is solved numerically, which explains an apparent anomaly posed by the Washburn equation.
298 citations
TL;DR: Plasma level data for propranolol in man have been used to indicate the utility of these equations, and the significance of these calculations to the design of clinical studies with new drugs intended for oral use is discussed.
286 citations
TL;DR: In this paper, the Fisher-Irwin treatment of a single 2 x 2 contingency table is extended to the case when the difference between the two populations on a logistic or probit scale is nearly constant for each table.
Abstract: SUMMARY Consider data arranged into k 2 x 2 contingency tables. The principal result is the derivation of a statistical test for making an inference on whether each of the k contingency tables has the same relative risk. The test is based on a conditional reference set and can be regarded as an extension of the Fisher-Irwin treatment of a single 2 x 2 contingency table. Both exact and asymptotic procedures are presented. The analysis of k 2 x 2 contingency tables is required in several contexts. The two principal ones are (i) the comparison of binary response random variables, i.e. random variables taking on the values zero or one, for two treatments, over a spectrum of different conditions or populations; and (ii) the comparison of the degree of association among two binary random variables over k different populations. Cochran (1954) has investigated this problem with respect to testing if the success probability for each of two treatments is the same for every contingency table. Cochran's recommendation is that the equality of the two success probabilities should be tested using the total number, summed over all tables, of successes for one of the treatments. Cochran considers the asymptotic distribution of the total number of successes, for one of the treatments, conditional on all marginals being fixed in every table. He recommends this technique whenever the difference between the two populations on a logistic or probit scale is nearly constant for each contingency table. The constant logistic difference is equivalent to the relative risk being equal for each table. Mantel & Haenlszel (1959), in an important paper discussing retrospective studies, have also proposed an asymptotic method for analysing several 2 x 2 contingency tables. Their worlk on this problem was evidently done independently of Cochran, for their method is exactly the same as Cochran's except for a modification dealing with the correction factor associated with a finite population. Birch (1964) and Cox (1966) clarified the problem by showing, that under the assumption of constant logistic differences for each table, same relative risk, the conditional distribution of the total number of successes, for one of the treatments, leads to a uniformly most powerful unbiased test. Birch and Cox also derived the exact probability distribution of this conditional random variable under the given model. In this paper, we investigate the more general situation where the difference between the logits in each table is not necessarily constant. Procedures are derived for making an inference with regard to the hypothesis of constant logistic differences. Both the exact and asymptotic distributions are derived for the null and nonnull cases. This problem has been discussed by several investigators. A constant logistic difference corresponds to no interaction between the treatments and the k populations. The case k = 2 corresponds to one in which Bartlett (1935) has derived both an exact and an asymptotic procedure. Norton (1945)
286 citations
TL;DR: Experiments show that retinol released by light from rhodopsin is probably not the toxic agent, and the normal diurnal cycle of light and dark seems to be the essential factor in controlling visual cell viability and susceptibility.
Abstract: Diffuse retinal irradiation by visible light produces in the rat the death of visual cells and pigment epithelium. Typically, cage illumination of 1500 lux from fluorescent light through a green filter leads to severe damage when continued for 40 hours. Vitamin A deficiency protects against this damage but experiments show that retinol released by light from rhodopsin is probably not the toxic agent. Protection against light damage depends on a long-range state of cell adaptation to light itself. The normal diurnal cycle of light and dark seems to be the essential factor in controlling visual cell viability and susceptibility.
265 citations
01 Jun 1971
TL;DR: In this paper, the kinetics of calcite at 25°C were examined by following the changes in calcium and hydrogen ion concentration when stable supersaturated solutions are inoculated with calcite seed crystals.
Abstract: The kinetics of crystallization of calcium carbonate (calcite) at 25°C has been examined by following the changes in calcium and hydrogen ion concentration when stable supersaturated solutions are inoculated with calcite seed crystals. The calcite growth follows a rate equation second order with respect to concentration suggesting a surface-controlled process. Calcium ion concentration changes were followed using 45Ca radiotracer and atomic absorption spectroscopy. Heterogeneous exchange of 45Ca between a calcium carbonate solution and calcite seed crystals has also been examined (by a liquid scintillation counting technique) in order to analyze the crystal growth data.
TL;DR: The subsequent effects of this increase in Na+ permeability evoked by batrachotoxin—such as membrane depolarization, enhanced spontaneous transmitter release, muscle contracture, and enhanced formation of cyclic AMP in brain slices—may be blocked reversibly by tetrodotoxin.
Abstract: Batrachotoxin has been shown to be a pyrrolecarboxylic ester of a novel steroidal base with unique and selective actions on a variety of electrogenic membranes. The effects of batrachotoxin in neuromuscular preparations both pre- and postsynaptically, in nerve axons, in superior cervical ganglion, in heart Purkinje fibers, and in brain slices appear to be due to the selective and irreversible increase in permeability of membranes to sodium ions. The subsequent effects of this increase in Na(+) permeability evoked by batrachotoxin-such as membrane depolarization, enhanced spontaneous transmitter release, muscle contracture, and enhanced formation of cyclic AMP in brain slices-may be blocked reversibly by tetrodotoxin.
TL;DR: The Standard Deviational Ellipse; An Updated Tool for Spatial Description as discussed by the authors is a tool for spatial description based on the Geografiska ANNALER (GANN).
Abstract: (1971). The Standard Deviational Ellipse; An Updated Tool for Spatial Description. Geografiska Annaler: Series B, Human Geography: Vol. 53, No. 1, pp. 28-39.
TL;DR: In this article, a structural model is presented for the non-catalytic reaction between a porous solid and a gas stream, which incoporates parameters such as solid grain size, porosity, effective pore diffusion coefficient and allows the quantitative assessment of the role played by these in determining the overall reaction rate.
TL;DR: Although this factor generated in an in vitro system, it has been shown to possess in vivo as well as in vitro activity, it is therefore possible that this factor may be of biological significance in situations where eosinophils are participants in inflammatory or immunologic reactions.
Abstract: When cultured in the presence of specific antigen, lymphocytes from delayed-hypersensitive guinea pigs release a number of biologically active substances into the culture medium. Such active supernatants can react with immune complexes in vitro to generate a factor which is chemotactic for eosinophils. The factor involved is unique, since previously described chemotactic factors for other cell types require for their generation either immune complexes or substances released into lymphocyte culture, but not both. In the case of the eosinophil chemotactic factor, the interaction between the substance elaborated by the lymphocytes and the immune complexes appears to be specific in that the immune complexes must contain the same antigen as that used to activate the lymphocyte cultures. Although this factor was generated in an in vitro system, it has been shown to possess in vivo as well as in vitro activity. It is therefore possible that this factor may be of biological significance in situations where eosinophils are participants in inflammatory or immunologic reactions.
TL;DR: Oral administration of 3 g of ascorbic acid 1.5 hr after an oral dose of 1 g of acetaminophen caused a rapid and pronounced decrease in the excretion rate ofacetaminophen sulfate in five healthy adult volunteers.
TL;DR: Three algorithms are described (all using Monte Carlo methods) which were designed to solve the problem of estimating gray levels of a digital picture at the individual points from the sums of the gray levels along straight lines (projections) at a few angles.
Abstract: There are situations in the natural sciences and medicine (e.g. in electron microscopy and X-ray photography) in which it is desirable to estimate the gray levels of a digital picture at the individual points from the sums of the gray levels along straight lines (projections) at a few angles. Usually, in such situations, the picture is far from determined and the problem is to find the “most representative” picture. Three algorithms are described (all using Monte Carlo methods) which were designed to solve this problem. The algorithms are applicable in a large and varied number of fields. The most important uses may be the reconstruction of possibly asymmetric particles from electron micrographs and three-dimensional X-ray analysis.
TL;DR: Evidence is provided that the processes of post-denervation changes occur in the following temporal sequence: a) partial depolarization of the postsynaptic muscle membrane; b) a decrease and subsequent cessation of the spontaneous transmitter release preceded in some fibres by a transient increase in m.e.p. frequency; c) appearance of extrajunctional ACh sensitivity; d) increase in the transverse resistance of a unit area of the muscle membrane.
Abstract: The first alteration noted after denervation of the extensor digitorum longus muscles of rats was a decrease in resting membrane potential (RMP) which occurred at about 2h. The exact time course of this membrane depolarization was dependent upon the intramuscular length of the degenerating nerve stump. The decrease in RMP occurred prior to any detectable alteration in adenosine triphosphate and phosphocreatine content of the muscle. Prior to failure of spontaneous transmitter release, which occurred 10 h after denervation, some muscle fibres showed an increase in frequency of the miniature end-plate potentials (m.e.p.p.) with no alterations in amplitude and shape of the single potentials. Appearance of areas sensitive to acetylcholine (ACh) on the extra-junctional membrane occurred at 24 h after crushing the motor nerve. At 48 h after denervation a high ACh-sensitivity appeared at the muscle-tendon region, but was not detected in the majority of the muscle fibres studied midway between end-plate region and muscle-tendon area. The transverse resistance of a unit area of the muscle membrane was increased 3 days after denervation. These results provide evidence that the processes of post-denervation changes occur in the following temporal sequence: a) partial depolarization of the postsynaptic muscle membrane; b) a decrease and subsequent cessation of the spontaneous transmitter release preceded in some fibres by a transient increase in m.e.p.p. frequency; c) appearance of extrajunctional ACh sensitivity; d) increase in the transverse resistance of a unit area of the muscle membrane. It is suggested that the motor nerve releases more than one neurotrophic substance.
TL;DR: In this article, a preprint of an article published in International Studies Quarterly, published by Oxford University Press, is presented, where the authors present a set of preprints of the article.
Abstract: This is a preprint of an article published in International Studies Quarterly, published by Oxford University Press.
TL;DR: Evaluation of IF studies, together with the clinical picture, histology, and response to sulfapyridine, points to the importance of immunopathology in the differentiation between dh and bp.
TL;DR: The effects of vitamin A deficiency in the rat eye, as measured by the electroretinogram and changes in rhodopsin content, are critically dependent upon the levels of illumination to which the animals are exposed daily.
Abstract: The effects of vitamin A deficiency in the rat eye, as measured by the electroretinogram and changes in rhodopsin content, are critically dependent upon the levels of illumination to which the animals are exposed daily. Depleted animals kept in darkness maintained virtually normal electroretinogram function and rhodopsin content for 5 to 6 months while those kept in weak cyclic light lost rhodopsin continuously. A fraction of the retinol released from rhodopsin during illumination disappears presumably from the pigment epithelium into the blood and becomes unavailable for rhodopsin regeneration. A sequence of three first-order reactions was assumed to estimate the rate constant of this disappearance (0.03 per hour). Computer simulation supporting the experimental data illustrates the dependence of the retinal abnormalities on light.
TL;DR: The data provide strong evidence that an α type chain, whose structure has been shown to be nearly identical in bovine pituitary thyrotropin and luteinizing hormones, is also utilized in the placenta for the formation of its gonadotropic hormone.
TL;DR: Blood pH and PCO2 values indicate that the North American ganoid fish relies strictly on ventilation of the gills for O2 and CO2 exchange at low temperatures, and as the temperature increases, the lung becomes the predominant organ for oxygen extraction, the bloodPCO2-increases, plasma bicarbonate does not rise and the plasma pH falls.
TL;DR: In this paper, a set of laboratory experiments were used to predict the subject's purchases recorded in seven months of diary data and the behavioral implications and predictive power of the models are interesting from both theoretical and applied points of view.
Abstract: Laboratory measures of brand preferences and survey measures of demographic, media exposure, attitudinal, activity and opinion characteristics of individual consumers have been combined to predict brand purchases in the market. Brands in the tooth paste, liquid household cleaner and cake mix product categories were employed in a set of laboratory experiments. Preference scales derived from the experiments are used in three separate models to predict the subject's purchases recorded in seven months of diary data. The behavioral implications and predictive power of the models are interesting from both theoretical and applied points of view.
TL;DR: With the present fast and convenient method, serum lipase appears to be a better test for pancreatitis than is serum amylase.
Abstract: Serum lipase is determined by following turbidity changes during two 1-min intervals after adding serum to an olive oil emulsion containing desoxycholate. The olive oil emulsion is simply prepared and is stable for a month under refrigeration. Our observations confirm the findings of other investigators that increases in serum lipase activity are more accentuated than increases in serum amylase activity during pancreatitis. With the present fast and convenient method, serum lipase appears to be a better test for pancreatitis than is serum amylase.
TL;DR: A laboratory technique for providing estimates of effects of repetitive exposures on consumers in particular advertising situations is suggested, and a study using this technique indicates the need for significantly different repetition functions for different kinds of products, brand positions, advertising formats, and advertising goals.
Abstract: Recent advertising media models demand estimates of effects of repetitive exposures on consumers in particular advertising situations. A laboratory technique for providing such estimates is suggest...
TL;DR: In this article, the dissolution of calcium sulfate dihydrate crystals into subsaturated solutions of the salt has been studied at various temperatures between 10° and 30°C using a calcium ion electrode.
TL;DR: Findings are confirmed that V max can be evaluated from pressure data alone; this finding in patients with mitral regurgitation as well as in those with normal outflow impedance.
Abstract: The maximal, no-load, velocity for the contractile element (V max ) was estimated in 45 patients. The patients included: 17 with normal left ventricular dynamics; eight with volume overload, compensated; 11 with volume overload, decompensated; three with pressure overload; and six with cardiomyopathy. Contractile element velocity (V CE ) during isovolumic contraction was estimated in two ways: (1) from left ventricular pressure data alone, where V CE =(1/28.8p) (dp/dt), and (2) pressure data combined with measurement of left ventricular geometry (right anterior oblique cine). V max obtained in these two ways agreed well for most patients (r = 0.82). In the normal patients, V max varied from 1.46 to 2.64 muscle lengths per sec; in contrast that of the patients with cardiomyopathy varied between 0.71 and 1.34 muscle lengths per sec. Other indices of contractility (ejection fraction, peak dp/dt, peak velocity of circumferential fiber [peak V CF ], peak V CE , and V CE at zero stress) were compared on the basis of statistical correlation and consistency of other clinical evidence (presence or absence of congestive failure). Good correlation was obtained between V max and peak V SE (r = 0.68). Ejection fraction and peak V CF were less sensitive. Neither the peak rate of pressure rise or V CE at peak stress show any significant correlation with V max or clinical state. Previous studies have shown that V max can be evaluated from pressure data alone; this study confirms this finding in patients with mitral regurgitation as well as in those with normal outflow impedance.