Showing papers by "University of Colorado Boulder published in 1974"
TL;DR: This chapter reviews the morphological information on intercellular junctions derived from thin-sectioning, negative staining and freeze-cleave techniques, as well as from x-ray diffraction and biochemical investigations, and correlates the structural parameters with known or proposed physiological functions.
Abstract: Publisher Summary Intercellular junctions are specialized regions of contact between the apposed plasma membranes of adjacent cells, and recent evidence suggests that they are essential for the development of multicellular organisms. They provide the structural means for groups of cells to interact in certain defined ways, and thereby enable them to create structures of higher order. This chapter reviews the morphological information on intercellular junctions derived from thin-sectioning, negative staining and freeze-cleave techniques, as well as from x-ray diffraction and biochemical investigations, and correlates the structural parameters with known or proposed physiological functions. The membrane structure of intercellular junctions is described. Membrane proteins can be divided into two groups: peripheral and integral. Peripheral membrane proteins are believed to be associated with the membrane surface, based on the observation that they are held to the membrane by rather weak noncovalent interactions, and are not strongly associated with membrane lipids. Only mild treatments, such as an increase in ionic strength of the medium or the addition of a chelating agent, are needed to dissociate them molecularly intact from the membrane. Furthermore, in the dissociated state they are relatively soluble in neutral aqueous buffers. In contrast, integral membrane proteins appear much more strongly bound to the lipid matrix, since they can be dissociated from the latter only by drastic treatments with chemicals such as detergents, protein denaturants, and organic solvents. The diversity in structure and function of intercellular junctions offers an exciting field for future research in which morphologists, physiologists, and biochemists should be able to make significant contributions to the knowledge of how individual cells interact to form structures of higher order.
1,292 citations
TL;DR: In this article, the experimental studies of displacive phase transitions in solids are summarized, focusing on inelastic light scattering and neutron scattering; related infrared reflectivity measurements, as well as x-ray and EPR analyses are also summarized.
Abstract: This paper reviews the experimental studies of displacive phase transitions in solids. Primary emphasis is upon inelastic light scattering and neutron scattering; related infrared reflectivity measurements, as well as x-ray and EPR analyses are also summarized. Several prototype structures are considered in detail: (1) the rocksalt IV-VI semiconductors PbTe, SnTe, and GeTe; (2) the ferroelectric perovskites exemplified by PbTi${\mathrm{O}}_{3}$ and BaTi${\mathrm{O}}_{3}$; (3) perovskites which exhibit cell-doubling transitions, such as LaAl${\mathrm{O}}_{3}$, SrTi${\mathrm{O}}_{3}$, and KMn${\mathrm{F}}_{3}$; (4) crystals having the $\ensuremath{\alpha}$-quartz structure, including Ge${\mathrm{O}}_{2}$, Si${\mathrm{O}}_{2}$, and AlP${\mathrm{O}}_{4}$; (5) the "improper ferroelectrics" ${\mathrm{Gd}}_{2}$${(\mathrm{M}\mathrm{o}{\mathrm{O}}_{4})}_{3}$ and ${\mathrm{Tb}}_{2}$${(\mathrm{M}\mathrm{o}{\mathrm{O}}_{4})}_{3}$; (6) the V-VI-VII semiconductors typified by SbSI; (7) the hydrogen-bonded ferroelectrics of the K${\mathrm{H}}_{2}$P${\mathrm{O}}_{4}$ family; (8) Jahn-Teller systems such as DyV${\mathrm{O}}_{4}$ and RbCo${\mathrm{F}}_{3}$, in which structural distortions occur as secondary effects; (9) order-disorder systems such as NaN${\mathrm{O}}_{2}$ and the ammonium halides (N${\mathrm{H}}_{4}$Cl, N${\mathrm{H}}_{4}$Br), in which no "soft mode" occurs in the spectral region ($\ensuremath{\omega}g{10}^{11}$ Hz) probed by ir, Raman, and neutron spectroscopy; (10) $\ensuremath{\beta}$-tungsten ($A\ensuremath{-}15$) structures such as ${\mathrm{V}}_{3}$Si and ${\mathrm{Nb}}_{3}$Sn, which exhibit high-temperature superconductivity. These crystal categories are used to illustrate several phenomena of current physical interest: Specifically, we discuss harmonic and anharmonic mode coupling; "critical exponents" $\ensuremath{\beta}$ differing from one-half in the temperature dependences of the order parameter $\ensuremath{\phi}(T)={\ensuremath{\phi}}_{0}{(T\ensuremath{-}{T}_{0})}^{\ensuremath{\beta}}$ and of the soft-mode frequency $\ensuremath{\omega}(T)={\ensuremath{\omega}}_{0}{(T\ensuremath{-}{T}_{0})}^{\ensuremath{\beta}}$; and the recently discovered "central" modes centered at zero frequency, which grow in intensity as the transition temperature ${T}_{0}$ is approached from above or below. The review covers the period 1940-1972. A few 1973 works are mentioned for which the author had preprints in 1972 or very early 1973. This review is in no sense a comprehensive survey of ferroelectricity. Readers are referred to the following earlier reviews on that subject: Silverman (1966, 1969), Cochran and Cowley (1967), Blinc (1968), Murzin et al. (1968), Nettleton (1970), and Blinc and Zaks (1972).
639 citations
TL;DR: Rules are given that permit 0-1 polynomial programming problems to be converted to0-1 linear programming problems in a manner that replaces cross-product terms by continuous rather than integer variables, so that the continuous variables automatically receive integer values.
Abstract: Rules are given that permit 0-1 polynomial programming problems to be converted to 0-1 linear programming problems in a manner that replaces cross-product terms by continuous rather than integer variables. Since the difficulty of mixed integer programming problems often depends more strongly on the number of integer variables than on the number of continuous variables, such rules are expected to have advantages in practical applications. In addition, the continuous variables automatically receive integer values, and hence our formulation can also be exploited by methods designed to take advantage of a pure integer structure.
387 citations
TL;DR: Monolayer cultures of a mouse teratocarcinoma were established in vitro that contained embryonal carcinoma, the malignant stem cell, and its differentiated progeny: parietal yolk sac, neuroepithelial, and mesenchymal cells.
Abstract: Monolayer cultures of a mouse teratocarcinoma were established in vitro. These cultures contained embryonal carcinoma, the malignant stem cell, and its differentiated progeny: parietal yolk sac, neuroepithelial, and mesenchymal cells. Tissues such as squamous epithelium, cartilage, striated muscle, neuroepithelium, and glands were produced from embryonal carcinoma that was maintained under conditions of long term culture. Frequent subcultivation with pancreatin allowed the establishment of cell lines of embryonal carcinoma which have been maintained for more than 18 months in vitro and continue to produce differentiated cells under specific culture conditions. Chromosomally these lines of embryonal carcinoma have a stem line of 39 chromosomes. Two lines of parietal yolk sac cells have been established which produce basement membrane, are not tumorigenic, and chromosomally are hypotetraploid. This system may yield information concerning neoplastic differentiation and its possible use in therapy for cancer.
337 citations
TL;DR: The results show that macaque monkeys and normal human observers show a rod-cone break at the same flicker frequency, and are very similar in both relative and absolute scotopic and photopic sensitivity.
261 citations
TL;DR: The lower, more conventional doses of the ephedrine-theophylline combination were ineffective in significantly altering the course of the disease and the bronchodilator efficacy was examined in a randomized double-blind study.
259 citations
TL;DR: This article found that recall cues were more effective when the properties were relevant, rather than irrelevant, to the events described by corresponding acquisition sentences, which raised considerations pertinent to theories of semantic encoding, to semantic theories in linguistics, and to the role of normative data in psycholinguistic theories of comprehension.
247 citations
TL;DR: Bacteria rotate at the angular velocity at which the torque generated by the flagellar motor2 is balanced by the torque due to the viscous drag, and in general, M = bηΩ, where M is the torque, η is the viscosity, Ω is theangular velocity, and b is a coefficient which depends on the size and the shape of the cell, the position of the axis of rotation, and the distance between the cell and the wall
Abstract: TETHERED bacteria1 rotate at the angular velocity at which the torque generated by the flagellar motor2 is balanced by the torque due to the viscous drag In general, M = bηΩ, where M is the torque, η is the viscosity, Ω is the angular velocity, and b is a coefficient which depends on the size and the shape of the cell, the position of the axis of rotation, and the distance between the cell and the wall For a sphere of radius a (not too close to the wall) M = 8πη a3Ω (ref 3) Viscous forces are so large in comparison with inertial forces4 that Ω will change with M virtually instantaneously; any discontinuities in the one will be evident in the other Consider a cell of radius a and uniform density ρ rotating at an angular velocity Ω0; if its motor is suddenly disengaged, Ω will decay exponentially to 0 with a time constant ρ a2/15η, and the cell will stop in Ωρ a2/15η radians For Escherichia coli this is less than a millionth of a revolution The cell also is subject to rotational diffusion, but this will be evident only if the coupling between the flagellum and the body of the cell is fluid The root-mean-square deviation in the angular position is (2Dt)½, where D is the rotational diffusion constant and t is the time For a cell which can rotate freely, D = kT/bη, where k is Boltzmann's constant and T is the absolute temperature
225 citations
TL;DR: In 265 studies of alcoholism treatment, drinking criteria were used far more than other measures and were positively related to many non-drinking dimensions as discussed by the authors, and about two-thirds of patients improved their health.
Abstract: In 265 studies of alcoholism treatment, drinking criteria were used far more than other measures and were positively related to many nondrinking dimensions. About two-thirds of patients improved wi...
224 citations
TL;DR: In this article, a variant of Ho's algorithm that generates approximate realizations of specified dimension from approximate data is discussed. But it is not shown how to apply it to the problem of finite-dimensional linear systems.
Abstract: Ho's Algorithm generates exact realizations of finite-dimensional linear systems, given exact data. We discuss here a variant of the algorithm that generates approximate realizations of specified dimension from approximate data.
214 citations
TL;DR: Evidence is assembled which indicates that these large transmembrane macromolecules may represent the morphological correlate for functional acetylcholine receptor activity in mammalian motor endplates.
Abstract: The neuromuscular junctions and nonjunctional sarcolemmas of mammalian skeletal muscle fibers were studied by conventional thin-section electron microscopy and freeze-fracture techniques. A modified acetylcholinesterase staining procedure that is compatible with light microscopy, conventional thin-section electron microscopy, and freeze-fracture techniques is described. Freeze-fracture replicas were utilized to visualize the internal macromolecular architecture of the nerve terminal membrane, the chemically excitable neuromuscular junction postsynaptic folds, and the electrically excitable nonjunctional sarcolemma. The nerve terminal membrane is characterized by two parallel rows of 100–110-A particles which may be associated with synpatic vesicle fusion and release. On the postsynpatic folds, irregular rows of densely packed 110–140-A particles were observed and evidence is assembled which indicates that these large transmembrane macromolecules may represent the morphological correlate for functional acetylcholine receptor activity in mammalian motor endplates. Differences in the size and distribution of particles in mammalian as compared with amphibian and fish postsynaptic junctional membranes are correlated with current biochemical and electron micrograph autoradiographic data. Orthogonal arrays of 60-A particles were observed in the split postsynaptic sarcolemmas of many diaphragm myofibers. On the basis of differences in the number and distribution of these "square" arrays within the sarcolemmas, two classes of fibers were identified in the diaphragm. Subsequent confirmation of the fiber types as fast- and slow-twitch fibers (Ellisman et al. 1974. J. Cell Biol. 63[2, Pt. 2]:93 a. [Abstr.]) may indicate a possible role for the square arrays in the electrogenic mechanism. Experiments in progress involving specific labeling techniques are expected to permit positive identification of many of these intriguing transmembrane macromolecules.
TL;DR: Increasing cell density, and therefore number of cell contacts in untreated cultures, causes the morphology to change in the direction to be expected if the cellular concentration of cyclic AMP is increased.
TL;DR: In this article, the combined effects of radiator-perturber collisions and radiator translational motion in the context of foreign gas broadening of optical transitions in neutral radiators are investigated.
Abstract: An investigation is conducted of the combined effects of radiator-perturber collisions and radiator translational motion in the context of foreign gas broadening of optical transitions in neutral radiators. Questions concerning the speed-dependent collision frequency are considered and aspects of general theory are explored, taking into account the correlation function, the ensemble average, and the kinetic equation formalism. An elementary solution is discussed along with a one-perturber approximation, inverse power law model calculations, and a comparison with the Voigt profile.
TL;DR: There are more than ten times as many reactive amino groups in protein on the inner surface than on the outer surface of the membrane, which implies that the isolation of the human erythrocyte does not load to major structural rearrangements.
TL;DR: In this article, the authors investigated the use of the nonlinear device known as the Clegg integrator in the design of a nonlinear feedback system, which minimizes the effect of white sensor noise on the input to the plant.
Abstract: The problem considered is the design of a feedback system containing a linear, time invariant, minimum phase plant, whose parameters are known only within given bounds, such that the time response of the system remains within specified limits. A quasi-optimal design, for given design constraints, is one which minimizes the effect of white sensor noise on the input to the plant. An investigation was conducted on the use of the non linear device known as the Clegg integrator in the design of such a system. The describing function of the Clegg integrator has the same magnitude characteristic, apart from a scale factor, as the linear integrator, but has 52 deg less phase-lag, at all frequencies, than the linear integrator; thus, when used in a feedback system, it provides a larger stability margin than the linear integrator. This property allows the nonlinear feedback system to be designed so that the sensor noise is attenuated more than in the linear design.
TL;DR: The kinetics of entry of [3H]adenosine into ATP, cellular RNA, and nuclear RNA of mouse L cells were determined and analyzed and a molar accumulation curve for RNA was estimated from the specific radioactivities of RNA and ATP; this curve was resolved graphically into stable and unstable components.
TL;DR: The results suggest that the two lines of mice selectively bred for differences in “sleep-time” to ethanol differ in their central nervous system sensitivity to ethanol.
TL;DR: The primary cell walls of six suspension-cultured monocots and of a single suspended gymnosperm have been investigated and the compositions are remarkably similar, despite the fact that the cell cultures were derived from diverse tissues.
Abstract: The primary cell walls of six suspension-cultured monocots and of a single suspension-cultured gymnosperm have been investigated with the following results: (a) the compositions of all six monocot cell walls are remarkably similar, despite the fact that the cell cultures were derived from diverse tissues; (b) the cell walls of suspension-cultured monocots differ substantially from those of suspension-cultured dicots and from the suspension-cultured gymnosperm; (c) an arabinoxylan is a major component (40% or more by weight) of monocot primary cell walls; (d) mixed beta-1,3; beta-1,4-glucans were found only in the cell wall preparations of rye grass endosperm cells, and not in the cell walls of any of the other five monocot cell cultures nor in the walls of suspension-cultured Douglas fir cells; (e) the monocot primary cell walls studied contain from 9 to 14% cellulose, 7 to 18% uronic acids, and 7 to 17% protein; (f) hydroxyproline accounts for less than 0.2% of the cell walls of monocots. Similar data on the soluble extracellular polysaccharides secreted by these cells are included.
TL;DR: The study discloses the advantages, in both computation time and memory requirements, of the primal approach over the out-of-kilter method.
Abstract: : The paper presents extensive computational experience with a special purpose primal simplex algorithm. The performance is compared to that of several 'state of the art' out-of-kilter computer codes. The computational characteristics of several different primal feasible start procedures and pivot selection strategies are also examined. The study discloses the advantages, in both computation time and memory requirements, of the primal approach over the out-of-kilter method. The test environment has the following distinguishing properties: (1) all of the codes are tested on the same machine and the same problems, (2) the test set includes capacitated and uncapacitated transhipment networks, transportation problems, and assignment problems, and (3) problem sizes ranging from 100 to 8,000 nodes with up to 35,000 arcs are examined. (Author)
TL;DR: The incidence of coronavirus infection in patients with pneumonia and bronchiolitis was higher than the incidences of adenoviruses, influenza, parainfluenza viruses types 1 and 2, and rhinovirus type 3 and respiratory syncytial virus, and lower only than theincidences of parain fluenza virus type 3.
Abstract: A serologic surveillance of lower respiratory tract disease in 417 hospitalized children under 18 months of age revealed infection with coronaviruses (strains OC43 and/or 229E) in 34 (8.2%). During the same interval, one of 13 control infants was infected. There were two distinct periods lasting six and 14 weeks, respectively, during which the incidence rose to as high as 18.9% of patients with lower respiratory tract disease. The incidence of coronavirus infection in patients with pneumonia and bronchiolitis was higher than the incidences of adenoviruses, influenza, parainfluenza viruses types 1 and 2, and rhinoviruses, and lower only than the incidences of parainfluenza virus type 3 and respiratory syncytial virus. Coronaviruses serologically similar or identical to strain 229E were recovered from frozen nasal washes obtained during the acute phase of pneumonia in two children. Continuing programs of surveillance during the past decade have provided evidence that viral infection is the major identifiable cause of acute lower respiratory tract disease (LRTD) in chil dren. Nevertheless, in every published study be tween one-third and two-thirds of serious illnesses cannot be associated with infection by known viruses [1-4]. When the human coronaviruses were first discovered [5-7] and were shown to be of importance in upper respiratory disease in adults [8, 9], it was hoped that they might account for a proportion of these unexplained illnesses. However, a seroepidemiologic study of their role in LRTD showed no statistically significant corre lation with illness [8]. Nevertheless, in the young est group examined (children less than one year
TL;DR: The response of the uterusine vascular bed to various estrogens was investigated in nonpregnant, oophorectomized sheep utilizing electromagnetic flow probes chronically implanted around the uterine arteries.
Abstract: The response of the uterine vascular bed to various estrogens was investigated in nonpregnant, oophorectomized sheep utilizing electromagnetic flow probes chronically implanted around the uterine arteries. One M.g estradiol-β injected directly into the uterine artery produces a maximum flow response, approximately ten times baseline levels, which is reproducible on a daily basis for periods greater than 30 days. A family of dose response curves demonstrated the following potency for increasing uterine blood flow to 50% of maximum: estradiol-β > estriol > diethylstilbestrol > estradiol-17α > estrone > ent-estradiol- 17β. (Endocrinology 94: 1192, 1974)
TL;DR: In this paper, a theory of broadening of He I lines with forbidden components is developed, which takes into account the effects of dynamic ion broadening and is valid at low densities where the forbidden line is reasonably well isolated.
Abstract: A theory of the broadening of He I lines with forbidden components is developed. The theory takes into account the effects of dynamic ion broadening and is valid at low densities where the forbidden line is reasonably well isolated. Good agreement with experiment and with calculations by Lee (1972) was obtained when the theory was applied at a wavelength of 4471 A. Tables of these data are given and are extended into the line wings beyond the extent of previous tabulations. Reasons for agreement with Lee data are discussed in detail. The density level above which the static ion theory is adequate is defined. A simple numerical profile of allowed lines is also obtained, taking into account dynamic ion effects.
TL;DR: The steroid dose-reducing capacity of troleandomycin (Tao), a macrolide antibiotic, was substantiated by a double-blind crossover study of 74 corticosteroid-dependent asthmatic and bronchitic subjects and the antibiotic property of Tao did not explain improvement.
Abstract: The steroid dose-reducing capacity of troleandomycin (Tao), a macrolide antibiotic, was substantiated by a double-blind crossover study of 74 corticosteroid-dependent asthmatic and bronchitic subjects. Fifty were marked responders, 13 probable responders, and 11 nonresponders. Responders also improved in their sputum production, pulmonary function measurements, need for aerosolized bronchodilators, and subjective evaluations. Tao was effective when used concomitantly with methylprednisone. At a dose of up to 16 mg. of methylprednisolone per day, along with 250 to 500 mg. of Tao per day, patients could either retain a normal serum cortisol level or increase this to normal values 24 to 48 hours after the last dose. Hepatic function abnormalities were usually mild and transient but 10 had increased alkaline phosphatase levels, prompting discontinuation in some patients. The mechanism of action is not known, but in 11 of 14 marked responders on Tao, the threshold dose of methacholine required to produce a 20 per cent fall in Fev 1 was substantially increased. The antibiotic property of Tao did not explain improvement.
TL;DR: In this article, it was shown that even if the eigenvalues of the system A -matrix A(t) of a linear time-varying system are independent of t and some of them have positive real parts, the system is asymptotically stable.
Abstract: An example is given to show that even if the eigenvalues of the system A -matrix A(t) of a linear time-varying system \dot{x}(t) = A(t)x(t) are independent of t and some of them have positive real parts, the system is asymptotically stable.
TL;DR: An attribute frequency model for the abstraction of prototypes is proposed as an alternative to the prototype-plus-transformation model and tested in a Franks and Bransford visual pattern paradigm under conditions in which the two models generate contrasting predictions.
Abstract: An attribute frequency model for the abstraction of prototypes is proposed as an alternative to the prototype-plus-transformation model. A specific model is tested in a Franks and Bransford visual pattern paradigm under conditions in which the two models generate contrasting predictions. The results support the attribute frequency model. Application of the model to reported data obtained in other paradigms is illustrated and discussed.
TL;DR: Since macronuclear DNA from five different syngens of paramecia differed only slightly in their 6 N- methyladenine content, it has been concluded that intersyngen differences can not be attributed to the level of methyl group content.
TL;DR: The results suggest that this interconnection between xyloglucan and cellulose is unlikely to be the point within the wall which regulates the rate of cell elongation, and the hypothesis that, within the cell wall, xylogucan chains are connected to cellulose fibers by hydrogen bonds is supported.
Abstract: Cell wall strength is decreased by both auxin treatment and low pH. In a recently proposed model of the plant cell wall, xyloglucan polymers are hydrogen-bonded to cellulose fibrils, forming the only noncovalent link in the network of polymers which cross-link the cellulose fibers. The decreased strength of the cell wall seen upon lowering the pH might be due to an effect of hydrogen ions on the rate of xyloglucan creep along cellulose fibers. This paper investigates binding of xyloglucan fragments to cellulose. At equilibrium, the per cent of nine- and seven-sugar xyloglucan fragments which are bound to cellulose is sensitive to both temperature and the concentration of nonaqueous solvents. However, neither the per cent of xyloglucan fragments bound to cellulose at equilibrium, nor the rate at which the xyloglucan fragments bind to cellulose, is sensitive to changes in hydrogen ion concentration. These results support the hypothesis that, within the cell wall, xyloglucan chains are connected to cellulose fibers by hydrogen bonds, but these results suggest that this interconnection between xyloglucan and cellulose is unlikely to be the point within the wall which regulates the rate of cell elongation.
TL;DR: These experiments strongly suggest that the accumulation driven by an artificial membrane potential is mediated by the physiological transport systems, and are consistent with the chemiosmotic interpretation of metabolite transport by membrane vesicles.
TL;DR: The pitfalls concealed in some af the Histochemical methods, the histochemical profiles of the muscle fiber types, and the use of histochemistry in the evaluation of developing and diseased muscle will be discussed.
Abstract: Muscle histochemistry has come to be widely used as an investigative tool not only at a laboratory level in the investigation of the basic behavior of muscle, but also in the clinical laboratory as a tool in the investigation of muscle diseases. With the acceptance of histochemistry an assumption has been made that histochemistry is the equivalent of biochemistry in investigating the function of muscle fibers. This attitude has certain drawbacks, and the dangers attendant upon the unquestioning acceptance of liistochemical techniques should be realized. Perhaps the main role that histochemistry has found is as a marker for the delineation of the different types of muscle fibers, so that their behavior may be observed in experimental situations and in disease. For the purpose of the present communication certain aspects of enzyme histochemistry will be considered. The pitfalls concealed in some af the histochemical methods, the histochemical profiles of the muscle fiber types, and the use of histochemistry in the evaluation of developing and diseased muscle will be discussed.