Showing papers by "University of California, San Diego published in 1976"

Antibody to acetylcholine receptor in myasthenia gravis Prevalence, clinical correlates, and diagnostic value

Abstract: Elevated amounts of antibodies specific for acetylcholine receptors were detected in 87 percent of sera from 71 patients with myasthenia gravis but not in 175 sera from individuals without myasthenia gravis, including those with other neurologic or autoimmune diseases. Antireceptor antibodies were not directed at the acetylcholine binding site of the receptor. Presence or titer of antibody did not appear to correlate with age, sex, steroid therapy, or duration of symptoms. Myasthenia gravis patients with only ocular symptoms had lower antibody titers, while the majority of titers in myasthenia gravis patients with thymoma exceeded the median titer of the myasthenia gravis group as a whole. Assay of antireceptor antibody should prove a useful test in the diagnosis of myasthenia gravis.

Predictability of Sea Surface Temperature and Sea Level Pressure Anomalies over the North Pacific Ocean

Abstract: Nonseasonal variability of sea level pressure (SLP) and sea surface temperature (SST) in the mid-latitude North Pacific Ocean is examined. The objective is examination of the basic scales of the variability and determination of possible causal connections which might allow prediction of short-term climatic (time scales between a month and a year) variability. Using empirical orthogonal function descriptions of the spatial structure, it is found that SLP variability is concentrated in a few large-scale modes but has a nearly white frequency spectrum. SST variability is spatially complex (being spread over many spatial modes, some of which have small-scale changes) but is dominated by low-frequency changes. The use of linear statistical estimators to examine predictability is discussed and the importance of limiting the number of candidate data used in a correlation starch is underscored. Using linear statistical predictors, it is found that (A) SST anomalies can be predicted from SST observations ...

Endorphins: profound behavioral effects in rats suggest new etiological factors in mental illness.

Abstract: The endogenous morphinomimetic brain peptides Met5-enkephalin and alpha-, beta-, and gamma-endorphins have been evaluated in rats after intracerebrospinal fluid injection. beta-Endorphin produces marked, prolonged muscular rigidity and immobility similar to a catatonic state, counteracted by the opiate antagonist naloxone; this effect occurs at molar doses 1/100 to 1/400 that at which the other peptides or morphine block the response to painful stimuli. All peptides evoked dose-related, naloxone-reversible, wet-dog shakes in rats that had not been exposed to drugs. beta-Endorphin produced hypothermia, whereas gamma-endorphin produced hyperthermia. Such potent and divergent responses to naturally occurring subtances suggest that alterations in their homeostatic regulation could have etiological significance in mental illness.

Atmospheric carbon dioxide variations at Mauna Loa Observatory, Hawaii

Abstract: The concentration of atmospheric carbon dioxide at Mauna Loa Observatory, Hawaii is reported for eight years (1964-1971) of a long term program to document the effects of the combustion of coal, petroleum, and natural gas on the distribution of CO, in the atmosphere. The new data, when combined with earlier data, indicate that the annual average CO, concentration rose 3.4 '% between 1959 and 1971. The rate of rise, however, has not been steady. In the mid-1960's it declined. Recently it has accelerated. Similar changes in rate have been observed at the South Pole and are evidently a global phenomenon.

Intracellular pH and activation of sea urchin eggs after fertilisation.

Abstract: The intracellular pH of the sea urchin embryo increases 0.3 pH units between 1 and 4 min after fertilisation. The increase in pH is required for initiating development. The increase results from an exchange of extracellular Na+ for intracellular H+.

Van der Waals interaction between an atom and a solid surface

Abstract: : This paper contributes to the theory of the long-ranged attractive polarization force between a neutral atom and a crystalline solid surface in the non-relativistic limit. The first two terms in the asymptotic expansion of the polarization energy are used to define an atom-solid potential of the form V(pol) = -C(Z - Zo) to the (-3) power. The constant C appearing in this expression is known from the earlier work of E. M. Lifshitz. The present paper gives a theory of the position of the 'reference plane,' Z(o), which is important in applications to physisorption. An explicit expression for Z(o) is first derived for atoms interacting with a jellium metal and with an insulating crystal consisting of atoms which interact via dipole-dipole forces. These model calculations are then incorporated into a computation of the polarization energies of rare gas atoms physisorbed on noble metal surfaces. The computed energies are found to be consistent with observed adsorption energies.

Replacement of serum by hormones permits growth of cells in a defined medium

Abstract: MOST cell cultures require the addition of serum to synthetic media for their maintenance and growth, and we believe that the primary role of the serum is to provide hormones1. We have been led to this hypothesis by a series of experiments showing that serum depleted of certain hormones no longer supports growth of cells, unless the medium is supplemented with the hormones that were removed2–4. Clear evidence for the validity of this hypothesis has not yet been obtained because it is difficult to grow cells in the absence of serum. Recently, however, we have succeeded in growing an established rat pituitary cell line, GH3, in a defined serum-free medium supplemented with physiological concentrations of four hormones together with the iron transport protein, transferrin. Preliminary investigation shows that serum-free medium supplemented with hormone will also support the growth of several other cell lines.

The wick catheter technique for measurement of intramuscular pressure. A new research and clinical tool.

Abstract: The wick catheter technique was developed in 1968 for measurement of subcutaneous pressure and has been modified for easy intramuscular insertion and continuous recording of interstitial fluid pressure in animals and humans. Studies in dogs of the anterolateral compartment of the leg in simulation of the compartment syndrome showed the technique to be accurate and reproducible. The wick catheter technique is capable of important clinical applications in the diagnosis and treatment of acute and chronic compartment syndromes.

Time Series Modelling and Interpretation

Abstract: SUMMARY By considering the model generating the sum of two or more series, it is shown that the mixed ARMA model is the one most likely to occur. As most economic series are both aggregates and are measured with error it follows that such mixed models will often be found in practice. If such a model is found, the possibility of resolving the series into simple components is considered both theoretically and for simulated data. 1. INrRODUCTION THE recent publication of the book by Box and Jenkins has greatly increased interest by time series analysts and econometricians in more complicated, even if more "parsimonious", time series models. However, the intuitive interpretation of the models that arise is not always simple and an applied research worker may well ask how such a model could have arisen in practice. In this paper, the possibility that a complicated looking model could have arisen from a simpler situation is explored and some suggestions made about the possible interpreta- tion of some models that appear to arise in practice. The only series to be considered are those with zero means and generated by models with time-invariant parameters. Thus, possibly after an appropriate linear transformation, the series will be taken to be second-order stationary. Let Xi be such a series, so that E{X} =O, all t.

Moment Tensors and other Phenomenological Descriptions of Seismic Sources—I. Continuous Displacements

Abstract: Summary. In most seismic calculations the real physical stress tensor S is replaced by a linearized isentropic elastic model stress tensor 9. Backus & Mulcahy showed how the stress glut r = 9- S gives rise to all the usual phenomenological descriptions of earthquake sources, the equivalent forces, the moment tensor densities, the stress-free strain and the seismic moment tensors of various types and degrees. In our earlier paper the displacement field s was supposed to be continuously differentiable, so discontinuous faulting could not be discussed. The present work extends our earlier paper to cover the possibility that 9 is a singular generalized function, so that s can be discontinuous or singular. Even when s is smooth, generalized functions simplify the notation. Surface and volume forces, real or equivalent, can be combined in a single distribution; boundary conditions are automatically included in the field equations; and representing a localized source by certain moment tensors of low degree amounts to approximating the source by a point source with the same moments of low degree. It is shown that all the results in our earlier paper can be extended to discontinuous s and singular 9. New results, not obtainable in our earlier paper, include these: a simple description of the most general seismic point source; a proof that every tensor with the obvious appropriate index symmetries is a forcemoment or glut-moment tensor of a seismic point source; a catalogue of point sources with no seismic effects; a new, direct derivation of the classical phenomenological descriptions of ideal fault sources which Burridge & Knopoff, Dahlen and Walton obtained from the reciprocity theorem and the impulse response; a discussion of how, unlike ideal faults, a real fault might have a seismic moment tensor with non-zero trace; and a description of a source type, the simple surface source, which may be a more accurate phenomenological description of real faults than are the classical ideal fault descriptions. It can be shown that a simple surface source with fault surface Z is uniquely determined by the motion it produces if it is developable or if the Gaussian curvature of Z never vanishes, but not if Z contains a piece of a plane.

Aspartic acid racemisation in dentine as a measure of ageing.

Abstract: THE L-amino acids initially present in bone protein undergo slow racemisation over geological time at a rate which is proportional to temperature1,2. We have shown3 that at the human body temperature of ∼37°C aspartyl residues in tooth enamel protein also undergo racemisation at a rate which corresponds to an enrichment in the D-aspartic acid content of ∼0.1% per year. No D-aspartic acid increase was detected in haemoglobin, a protein with a more rapid turnover. We concluded that D-aspartyl residues accumulate in the metabolically stable protein in tooth enamel during the human lifetime as a result of in situ racemisation. We proposed that the irreversible first-order rate equation calculated from the enamel results could be used to deduce the age of any stable protein from a long lived mammal and thus the age of the organism itself. The error among samples from old individuals was large, however, probably because attrition and caries reduce the amount of uncontaminated enamel, and thus tend to limit the usefulness of tooth enamel for age determinations. In this report, we show that tooth dentine is a more suitable material, and the extent of aspartic acid racemisation in this fraction can be used as a reliable indicator of mammalian age.

Dynamic changes in left ventricular wall thickness and their use in analyzing cardiac function in the conscious dog.

Abstract: The thickness of the left ventricular free wall and internal chamber diameter were continuously measured by pairs of ultrasonic crystals together with left ventricular pressure in normal conscious dogs. During the resting state, wall thickness decreased abruptly with the onset of atrial contraction from 10.5 mm to an average end-diastolic valueof9.8 mm. In contrast to most previous studies, there was no change in wall thickness during isovolumic systole, and with ejection the wall thickened by 31.3 percent of end-diastolic wall thickness. Atrial pacing, phenylephrine, isoproterenol and propranolol produced significant changes in chamber size with reciprocal changes in wall thickness. In addition, changes in the extent and velocity of left ventricular chamber shortening in the minor equator were associated with comparable reciprocal changes in the extent and velocity of free wall thickening (correlation coefficients 0.97 to 0.99). During acute coronary occlusion, progressive reductions in the extent and velocity of regional wall shortening with partial ischemia were associated with comparable changes in systolic wall thickening characteristics (r = 0.96 and 0.95), and holosystolic elongation in fully ischemic areas was associated with holosystolic wall thinning. During chronic pressure overload, despite wall thickening, the relation between chamber shortening and wall thickening were retained and direct computation of dynamic wall stress variations was possible. These measurements allowed precise definition of the dynamics of the left ventricular wall during normal and abnormal cardiac states. The demonstration that in the absence of regional dysfunction analysis of wall thickness in a single region of ventricular free wall can be used to describe myocardial and overall left ventricular function, as well as regional function in the presence of ischemia, constitutes a new approach to the assessment of cardiac function that has potential for echocardiographic applications.

Lowering of Dimensionality in Phase Transitions with Random Fields

Abstract: We prove that to all orders in perturbation expansion, the critical exponents of a phase transition in a $d$-dimensional ($4ldl6$) system with short-range exchange and a random quenched field are the same as those of a ($d\ensuremath{-}2$)-dimensional pure system. Heuristic arguments are given to discuss both this result and the random-field Ising model for $2ldl6$.

Superconducting and normal state properties of Li 1+x Ti 2−x O 4 spinel compounds. I. Preparation, crystallography, superconducting properties, electrical resistivity, dielectric behavior, and magnetic susceptibility

Abstract: LiTi 2 O 4 is one end member of the homogeneity range of the spinel phase Li 1+x Ti 2−x O 4 (0≤x≤1/3) and is superconducting at temperatures up to 13.7 K. Various measurements were carried out in order to characterize the superconducting and normal state properties of LiTi 2 O 4 and of other compositions within the homogeneity range of the spinel phase. These measurements establish LiTi 2 O 4 as ad-band superconductor and show thatT c decreases to <1.5 K forx≳0.1. This disappearance of superconductivity with increasingx was found to be correlated with anomalous changes in the lattice parameter with composition, and, from electrical resistivity measurements, is tentatively attributed to the occurrence of a composition-induced metal-semiconductor transition atx≈0.1. The metallic character of LiTi 2 O 4 and the composition dependence of the observed electrical properties are shown to follow from crystallographic considerations.

Effects of Dopamine Infusion on Pituitary Hormone Secretion in Humans

Abstract: Dopamine, infused at a rate of 4 mug/kg/min for 3-4 h unaccompanied by any significant changes in cardiovascular dynamics, induced a prompt and sustained suppression of circulating prolactin (PRL) levels in normal men and women as well as in patients with hyperprolactinemia At the discontinuation of the infusion, there was a marked rebound in PRL levels in normal subjects and a rapid return to basal levels in hyperprolactinemic patients Dopamine infusion also induced a significant fall in LH levels in the normal subjects with a marked rebound in LH levels following the infusion No significant changes in GH, TSH, and FSH levels were observed These data indicate that in man a dopaminergic mechanism ixists in the regulation of PRL secretion and that dopamine also exerts an inhibitory effect of LH release

Stimulus Filtering and Electroreception: Tuberous Electroreceptors in Three Species of Gymnotoid Fish

Abstract: Electroreceptive neurons in the posterior branch of the anterior lateral line nerve of three species of electric fish (Gymnotoidei):Sternopygus macrums, Eigenmannia virescens, andApteronotus albifrons, show speciesspecific differences in the filtering of electrical stimuli. All of the tuberous electroreceptor fibers of an individual are tuned to the same frequency: that of the electric organ discharge (EOD) of the species, more specifically, to that of the individual. The fibers inSternopygus are tuned to 50–150 Hz; those inEigenmannia to 250–500 Hz, and those inApteronotus to 800–1,200 Hz (Figs. 3, 5, 8). Two classes of organs inSternopygus andEigenmannia, P and T units, respond to sinusoidal stimuli at the unit's best frequency (BF) with a phase-locked partially-adapting (P), or tonic (sustained) (T) discharge. T-units are more sharply tuned and are more sensitive than P-units. Only one class of organs,P or partially adapting units, have been found inApteronotus and phase-locking is less evident than it is in other species.

The Effect of Small, Aspherical Perturbations on Travel Times and a Re-examination of the Corrections for Ellipticity

Abstract: Summary We use the stationarity of the Fermat ray path to develop theoretical expressions that relate small, aspherical perturbations in velocity to small perturbations in travel times. For the Earth's ellipticity of figure we derive a compact expression for the perturbation in travel time. If the ellipticity is hydrostatic and is the dominant perturbation, then anomalies in travel times are linear constraints on the radial gradient of velocity. Otherwise, the anomalies are constraints on the (unknown) aspherical perturbations. We are led to an inverse problem in either case. Using recently derived models of the Earth we present calculations of the effect of ellipticity. If the effect of focal depth is neglected in the calculations, then mislocations in both epicentre and origin time can result. Differences between our calculations and those predicted by the approximate formula 6t = (h+H)f(A) are as large as 0-25 s for P at 90". Nowadays, seismologists are prone to attach significance to anomalies as small as 0.10 s. Consequently, we advocate that the effect of focal depth be considered and that traditional approximations be replaced by the more accurate calculations tabulated in this report. Theoretical development The effect of the Earth's ellipticity of figure on travel times was first studied more than 40 years ago by Comrie and by Gutenberg and Richter. Bullen (1965, p. 173176) has presented a concise theoretical derivation of the effect. Recent improvements in our knowledge of the mechanical structure of the Earth make it desirable not only to re-examine the effect of ellipticity, but also to consider other small, aspherical perturbations as well. We follow the derivation of Bullen A source is located a (r,,, ,!lo, &) in spherical polar co-ordinates, and a receiver at

Demonstration of a mental analog of an external rotation

Abstract: Subjects imagined a designated two-dimensional shape rotating within a blank, circular field at a self-determined rate. At some point during the mental rotation, a test shape was presented at one of 12 picture-plane orientations, and the subject was required to determine as rapidly as possible whether the test shape was the same as the originally designated shape or was its mirror image. When the test shape was presented in the expected orientation (the orientation assumed to correspond to the current orientation of the rotating internal representation), reaction time was short and constant, regardless of the angular departure of that orientation from a previously trained position. This was true even when the test shape was presented in an orientation which had not previously been tested. When the test shape was presented at some other, unexpected orientation, reaction time increased linearly with the angular difference between the expected orientation and the orientation of the test shape. It is argued that these results provide a demonstration of the \ldanalog\rd nature of mental rotation.