scispace - formally typeset
Search or ask a question

Showing papers by "University of Virginia published in 1977"


Journal ArticleDOI
01 Oct 1977

1,016 citations


Journal ArticleDOI
03 May 1977-Nature
TL;DR: In this paper, the formal and physical elements of the indicated nucleation and growth criterion for melting are discussed and the existence of upper and lower limits on the melting temperature is outlined.
Abstract: The way that small particles melt is a crucial clement in the construction of a thermodynamic treatment of the relation between particle size and melting temperature. There are indications that melting is initiated at the surface and that the solid–liquid interface sweeps rapidly through the solid at the melting temperature. The formal and physical elements of the indicated nucleation and growth criterion for melting are discussed and the existence of upper and lower limits on the melting temperature is outlined. Theoretical predictions show satisfactory agreement with experimental observations.

545 citations



Journal ArticleDOI
TL;DR: Large doses of cortisone were given to growing and adult rabbits over a five-month period to produce avascular necrosis of the femoral head to cause an increase in the serum cholesterol, fatty metamorphosis of the liver, and fat emboli visible in sections of the Femur and humerus.
Abstract: Large doses of cortisone were given to growing and adult rabbits over a five-month period to produce avascular necrosis of the femoral head. The cortisone caused an increase in the serum cholesterol, fatty metamorphosis of the liver, and fat emboli visible in sections of the femur and humerus. These emboli partially obliterated the microcirculation of the subchondral vessels of both femoral and humeral heads. The average diameter of the marrow fat cells also increased more than ten micrometers. This increase in cell volume might be significant because in the closed chamber of the femoral head it could increase tissue pressure, diminish perfusion, and be the mechanism for avascular necrosis induced by cortisone.

330 citations


Journal ArticleDOI
TL;DR: In this article, the redox potential of ZoBell's solution, consisting of 3.33 × 10 −3 molar K4Fe(CN)6, 3.5157 × 10−3 (t − 25) − 3.7979 − 6 (t−25) 2 relative to the standard hydrogen potential, has been measured by a polished platinum electrode vs a saturated KCl, Ag/AgCl reference electrode.

329 citations


Journal Article
TL;DR: The hypothesis that cyclic AMP plays a role in relaxation of tracheal muscle induced by adrenergic agents is supported; with a variety of other agents, it is found that contraction or relaxation occurred with increases either in cyclic GMP alone or in both cyclicAMP and cyclicGMP.
Abstract: The effects of various agents on cyclic 3',5'-AMP and cyclic 3',5'-GMP levels and mechanical activity of bovine tracheal smooth muscle were examined. Carbachol, acetylcholine, and histamine caused muscle contraction and increased cyclic GMP levels several fold in a dose-dependent manner; contraction preceded the increase in cyclic GMP. Serotonin and high K+ concentrations contracted muscle to the same degree as carbachol, while cyclic GMP increases were smaller than that due to carbachol. The effects of carbachol and histamine were blocked by atropine and diphenhydramine, respectively. The calcium ionophore A-23187 also increased cyclic GMP levels and caused contraction. Guanylate cyclase activators-sodium azide, hydroxylamine, sodium nitrite, nitroglycerin, and sodium nitroprusside-increased cyclic GMP levels and relaxed tracheal smooth muscle. None of these agents had any effect on cyclic AMP levels. The presence of Ca2+ in the incubation medium was not required for cyclic GMP increases with these latter agents. However, it was required in order to see increases in cyclic GMP with carbachol, histamine, and A-23187. Adremergic agonists relaxed muscle preparations and increased cyclic AMP levels 2-3-fold. Both these effects were blocked by propranolol. Inhibitors of cyclic nucleotide phosphodiesterases relaxed muscle preparations and were associated with increases in both cyclic AMP and cyclic GMP. Prostaglandins E1 and F2α had little or no effect on mechanical activity or cyclic nucleotide levels. The addition of 1 mM 8-bromo-cyclic GMP or 8-bromo-AMP relaxed muscle preparations. A variety of other nucleotides had no effect. These results support the hypothesis that cyclic AMP plays a role in relaxation of tracheal muscle induced by adrenergic agents. However, with a variety of other agents, we found that contraction or relaxation occurred with increases either in cyclic GMP alone or in both cyclic AMP and cyclic GMP. Thus the roles of cyclic AMP and cyclic GMP in smooth muscle mechanical activity remain obscure. ACKNOWLEDGMENTS We thank Daniel Macklin and Joanne Holmes for their technical assistance, and Cathy Bostron for typing this manuscript.

293 citations


Journal ArticleDOI
TL;DR: In this article, the authors apply recent advances in understanding mechanisms of unidirectional deformation to fatigue and propose reinterpretations or new mechanisms for the following: the formation of dislocation veins and of persistent slip bands (PSB's), the behavior of dislocations in established PSB's, and the transformation of PSB dipolar walls into dislocation cells.

280 citations


Journal ArticleDOI
TL;DR: It is suggested that at least two proteins are necessary for adenylate cyclase activity and that one of these is retained in the phenotypically adenYLate Cyclase-deficient variant.

262 citations


Journal ArticleDOI
23 Jun 1977-Nature
TL;DR: The results presented here provide direct evidence derived from the mammalian nervous system that the convulsant action of PTZ and PCN may be due to a specific pharmacological action on GABA-mediated inhibitory synaptic transmission.
Abstract: PENTYLENETETRAZOL (PTZ) and penicillin (PCN) are potent convulsants commonly used to produce focal or generalised epileptiform discharges in the mammalian central nervous system1. Investigations of the cellular basis for their con-vulsant effects have been performed in various vertebrate and invertebrate preparations wtih two basic hypotheses dominating the literature: (1) that the convulsant effect is produced by pharmacological actions on synaptic transmissions to reduce inhibition2–8 and/or to enhance excitation9, or (2) that the convulsants directly enhance the excitability of neuronal membranes apart from effects on synaptic transmission10–16. We have studied the mechanism of their convulsant action in a mammalian tissue culture system and report here that both PTZ and PCN selectively antagonise post-synaptic responses to γ-aminobutyric acid (GABA), a putative inhibitory neurotransmitter17. The results presented here provide direct evidence derived from the mammalian nervous system that the convulsant action of PTZ and PCN may be due ito a specific pharmacological action on GABA-mediated inhibitory synaptic transmission.

260 citations


Book ChapterDOI
TL;DR: The common forms of emotional stress experienced by the child with a long-term illness and by his parents are reviewed and the major adaptational techniques enabling the sick child and his family to achieve a satisfactory psychosocial adaptation are described.
Abstract: Robert Louis Stevenson, a victim of pulmonary tuberculosis, once wrote, “Life is not a matter of holding good cards, but of playing a poor hand well.” Children with a chronic physical disorder who have successfully mastered the physical, social, and emotional hardships associated with their illness well illustrate his point. This paper intends to review the common forms of emotional stress experienced by the child with a long-term illness and by his parents. It also describes the major adaptational techniques enabling the sick child and his family to achieve a satisfactory psychosocial adaptation.

251 citations


Journal ArticleDOI
TL;DR: It is suggested that intact B-cell function is essential for eradication of ECHOvirus infection of the central nervous system.
Abstract: We observed persistent ECHOvirus infection of the central nervous system, as defined by continued presence of isolatable virus in cerebrospinal fluid, in five patients with agammaglobulinemia. The immunologic deficit in each was characterized by absence of surface-immunoglobulin-bearing B lymphocytes and of lymph-node cortical follicles, but normal T-cell function. ECHOviruses 30, 19, 9 and 33 were recovered from cerebrospinal fluid for periods varying from two months to three years. The patients had few signs of acute central-nervous-system infection. Three of the five patients had a dermatomyositis-like syndrome, with peripheral lymphocytes that reacted with anti-human leukemia-specific primate and rabbit serums in a cytotoxicity assay. These data suggest that intact B-cell function is essential for eradication of ECHOvirus infection of the central nervous system.

Journal ArticleDOI
TL;DR: The deprived eye was consistently and considerably myopic with respect to either the open eye or the eyes of normally reared tree shrews, indicating myopia in the deprived eyes since the values for the non-deprived eyes were in the normal range.

Journal ArticleDOI
TL;DR: The time course of the recovery, the results following bilateral lesions, and the results of secondary lesions are all consistent with the hypothesis that recovery of alternation performance following unilateral E.C. lesions may depend upon the reinnervation of the dentate gyrus by the contralateral E. C.

Journal ArticleDOI
01 Apr 1977-Primates
TL;DR: Data indicate that female baboons in Amboseli are older at birth of first infant, and have, on the average, a somewhat shorter interbirth interval than was estimated from earlier crossectional field data, and therefore spend a larger portion of their adult life pregnant, but have a much longer interval between the birth of an infant and theBirth of that infant’s next older surviving sibling.
Abstract: Longitudinal data from a population of yellow baboons,Papio cynocephalus, in the Amboseli National Park, Kenya, provide life history parameter estimates. Females reached menarche at approximately four-and-a-half years of age and then cycled for approximately a year before first conception. Postpartum anestrum averaged 12 months but ranged from six to 16 months. In cases of still births or infant death during postpartum amenorrhea, females commenced cycling after approximately one month. In mature females the time spent cycling before conception was five months on the average with a range from one to over 18 months. Only half of all full-term pregnancies resulted in infants who survived the first year of life; only a third, in infants who survived until the birth of their mother’s next infant. In comparison with data from laboratory colonies, our data indicate that female baboons in Amboseli are older at birth of first infant. They have, on the average, a somewhat shorter interbirth interval than was estimated from earlier crossectional field data, and therefore spend a larger portion of their adult life pregnant, but have a much longer interval—at least three years on the average—between the birth of an infant and the birth of that infant’s next older surviving sibling. A number of morphological changes in immature baboons are described.

Journal ArticleDOI
TL;DR: In this article, it was shown that rational cohomology takes a stable value relative to twisting, i.e., for sufficiently large q and e (depending on I' and n), there are isomorphisms H 2(G, V(e))gH'(G(q), V'(e)), rH'((G, q), V') where the first map is restriction.
Abstract: Let G be a semisimple algebraic group defined and split over k,=GF(p). For q=p”, let G(q) be the subgroup of GF(q)-rational points. The main objective of this paper is to relate the cohomology of the finite groups G(q) to the rational cohomology of the algebraic group G. Let I/ be a finite dimensional rational G-module, and, for a non-negative integer e, let V(e) be the G-module obtained by “twisting” the original G-action on V by the Frobenius endomorphism x++xtPel of G. Theorem (6.6) states that, for sufficiently large q and e (depending on I’ and n), there are isomorphisms H”(G, V(e))gH’(G(q), V(e))rH”(G(q), V) where the first map is restriction. In particular, the cohomology groups H”(G(q), V) have a stable or “generic” value H;,,(G, V). This phenomenon had been observed empirically many times (cf. [6, 203). The computation of generic cohomology reduces essentially to the computation of rational cohomology. One (surprising) consequence is that Hi,,(G, V) does not depend on the exact weight lattice for a group G of a given type cf. (6.10), though this considerably affects the structure of G(q). We also obtain that rational cohomology takes a stable value relative to twisting i.e., for sufficiently large E, we have semilinear isomorphisms H”(G, V(E)) % H”(G, V(e)) for all e 2 F. This paper contains many new results on rational cohomology beyond those required for the proof of the main theorem. We mention in particular the vanishing theorems (2.4) and (3.3), and especially the results (3.9) through (3.11) which relate H2(G, V) and Extk( K W) to the structure of Weyl modules. These results explain for example the generic values of H’ determined in [6], cf. (7.6). Also, it is shown in Theorem (3.12) that every finite dimensional rational G-module has a finite resolution by finite dimensional acyclic G-modules. A key ingredient in the proofs is an important theorem of G. Kempf [I93 on the vanishing of cohomology of certain homogeneous line bundles. This result is translated into the language of rational cohomology in (1.2), and is used in

Journal ArticleDOI
TL;DR: In this article, a mathematical two-dimensional hydrostatic model was employed for the study of mesoscale circulations which developed over a mountain barrier, a flat coastline and a mountainous coastline when the prevailing flow is zero.
Abstract: A mathematical two-dimensional hydrostatic model has been employed for the study of mesoscale circulations which develop over a mountain barrier, a flat coastline and a mountainous coastline when the prevailing flow is zero. One of the main features of the model is the inclusion of the parameterization of the surface heat budget, and shortwave and longwave radiative fluxes. Results show that the combined sea breeze and mountain circulations produce a more intense circulation during both day and night than when they act separately. The mountainous coastline case generates an inland penetrating sea breeze which develops a leeside cell of upward vertical velocity. The predictions are in qualitative agreement with the observed phenomenon.

Journal ArticleDOI
TL;DR: In this paper, the diffraction of electromagnetic waves from the rough surface of a material of finite permittivity is examined for the case where the wavelength of the incident radiation is comparable to the dimensions of the surface roughness.
Abstract: The diffraction of electromagnetic waves from the rough surface of a material of finite permittivity is examined for the case where the wavelength of the incident radiation is comparable to the dimensions of the surface roughness. Two methods of calculation studied are the Rayleigh method and the extinction-theorem integral-equation method. The latter is shown to have a unique exact solution. This property is, in turn, used to show how the Rayleigh method can be modified to give convergent results. The extinction theorem is also used to reduce the Rayleigh equations to a simpler form. These reduced equations, which are extremely convenient to use in the case of small roughness, are applied in this case to find perturbative expressions for the reflected field and for the surface-plasmon dispersion relation.

Journal ArticleDOI
01 Nov 1977-Cell
TL;DR: Transmission electron microscopic techniques used to study the spatial distribution of replicons and the ultrastructure of chromatin in the S phase genome of cellular blastoderm Drosophila melanogaster embryos concluded that histones are not disassociated from the DNA significantly prior to DNA replication, and that a very rapid reassociation of nucleosomes occurs on both daughter DNA molecules following replication.

Journal ArticleDOI
TL;DR: Three hundred sixty‐four patients who suffered a subarachnoid hemorrhage from an aneurysm in either the posterior communicating or anterior communicating artery and who were not surgically treated have been followed for up to 21 years in order to determine the frequency of subsequent hemorrhage.
Abstract: Three hundred sixty-four patients who suffered a subarachnoid hemorrhage from an aneurysm in either the posterior communicating or anterior communicating artery and who were not surgically treated have been followed for up to 21 years in order to determine the frequency of subsequent hemorrhage. For patients surviving six months: (1) rebleeding occurs on the average of 3.5% per year during the first decade; (2) the mortality associated with a late rebleed is 67%; (3) high blood pressure and female sex predispose to late rebleeding in posterior communicating artery aneurysms; (4) young patients take longer to rebleed than older patients but do so at the same rate; and (5) increase in aneurysm size as judged by routine arteriography six months after the initial hemorrhage did not correlate with rebleeding, although an increase in size had occurred in all patients who were studied angiographically at the time of their late rebleed.

Journal ArticleDOI
TL;DR: By increasing the sensitivity of a recently developed horseradish peroxidase (HRP) method, long axon-collaterals of a retrogradely labeled cell population can be successfully displayed by injecting HRP in one of its terminal fields.

Journal ArticleDOI
01 Jul 1977
TL;DR: Techniques are introduced which are applicable to machine construction of digraph maps and oriented toward reduction of the number of crossings in a map as a means of improving the readability of hierarchical structures.
Abstract: Techniques are introduced which are applicable to machine construction of digraph maps. These techniques are oriented toward reduction of the number of crossings in a map as a means of improving the readability of hierarchical structures. Permuting, psi-factoring, rotating, twirling, and absorbing are among the techniques considered. Examples are given to illustrate these techniques. When these and related procedures are fully developed for use with machine-interactive processes, they will facilitate group modeling efforts.


Journal ArticleDOI
01 Apr 1977-Lipids
TL;DR: A model for the cholesterol-phosphatidylcholine complex is proposed, in which the 3β-hydroxyl group of cholesterol is assumed to engage in hydrogen bonding with the carbonyl oxygen of the fatty acyl groups in phospholipids.
Abstract: Based on the structural properties of phospholipid and cholesterol molecules, and making use of the known structural and motional effects of cholesterol and its analogs on phospholipid bilayers, a model for the cholesterol-phosphatidylcholine complex is proposed. In this model, the 3β-hydroxyl group of cholesterol is assumed to engage in hydrogen bonding with the carbonyl oxygen of the fatty acyl groups in phospholipids. Some specific configurations of the saturated and unsaturated fatty acyl chains of the phospholipid are suggested to participate in van der Waals attractive interactions with the α and β surface of the steroid nucleus.

Journal ArticleDOI
TL;DR: In this paper, the elastic-electron scattering cross sections from nucleon-nucleon scattering were measured at incident electron energies between 170 and 750 MeV and the Rosenbluth formula was used to separate the cross sections into their longitudinal (charge) and transverse (magnetic) contributions.
Abstract: The elastic-electron scattering cross sections from $^{3}\mathrm{He}$ and $^{4}\mathrm{He}$ have been measured at incident electron energies between 170 and 750 MeV. Cross sections were separated into their longitudinal (charge) and transverse (magnetic) contributions using the Rosenbluth formula. Values of the $^{3}\mathrm{He}$ charge form factor have been extracted to ${q}^{2}=20$ ${\mathrm{fm}}^{\ensuremath{-}2}$ and for the $^{3}\mathrm{He}$ magnetic form factor to ${q}^{2}=16$ ${\mathrm{fm}}^{\ensuremath{-}2}$. The $^{4}\mathrm{He}$ form factor has been determined up to 6.2 ${\mathrm{fm}}^{\ensuremath{-}2}$. Densities for the charge and magnetization have been deduced from phenomenological models used in a phase-shift solution of the Dirac equation. A model-independent determination of the nuclear densities has been performed in order to obtain realistic errors on the extracted distributions. After unfolding the nucleon size from the distributions the point density is shown to have a significant central depression for a radius 0.8 fm for both $^{3}\mathrm{He}$ and $^{4}\mathrm{He}$. Comparison of the form factors is made with Faddeev and variational three-body calculations that use realistic two-body $\mathrm{NN}$ interactions. The influence of off-shell effects, three-body forces, meson-exchange corrections, and short-range correlations are discussed. At present no theoretical calculation that uses input derived entirely from nucleon-nucleon scattering is able to reproduce the experimental data.NUCLEAR REACTIONS $^{3,4}\mathrm{He}(e, {e}^{\ensuremath{'}})$, $E=170, 200, 250, 300, 350, 400, 450, 500, \mathrm{and} 750$ MeV; measured $\ensuremath{\sigma}(E, \ensuremath{\theta})$. Measured charge form factor $^{3}\mathrm{He}$ to ${q}^{2}=20$ ${\mathrm{fm}}^{\ensuremath{-}2}$ and magnetic form factor to ${q}^{2}=16$ ${\mathrm{fm}}^{\ensuremath{-}2}$. Measured $^{4}\mathrm{He}$ form factor to ${q}^{2}=6.2$ ${\mathrm{fm}}^{\ensuremath{-}2}$. Deduced nuclear charge, magnetic and point-nucleon distributions from model-independent analysis.

Journal ArticleDOI
TL;DR: In this article, children traditionally labeled learning disabled, mildly emotionally disturbed, and mildly mentally retarded are considered within a behavioral rather than a categorical framework and no behavioral characteristics can be found that are associated exclusively with any one of the three areas.
Abstract: Children traditionally labeled learning disabled, mildly emotionally disturbed, and mildly mentally retarded are considered within a behavioral rather than a categorical framework. A historical analysis reveals that the three areas have evolved from highly similar foundations. In addition, no behavioral characteristics can be found that are associated exclusively with any one of the three areas. Children who are usually identified as learning disabled, mildly disturbed, or mildly retarded reveal more similarities than differences. Consequently, successful teaching techniques do not differ among the three areas. A noncategorical orientation is recommended in which children are grouped for instruction according to their specific learning deficits rather than their assignment to traditional categories.

Journal ArticleDOI
TL;DR: A novel variant of the S49 mouse lymphoma selected from wild-type cells by growth in medium containing the beta-adrenergic agonist terbutaline and inhibitors of cyclic nucleotide phosphodiesterase, designated as uncoupled (UNC), has been stable for more than 100 generations without exposure to the drugs used for selection.
Abstract: A novel variant of the S49 mouse lymphoma has been selected from wild-type cells by growth in medium containing the beta-adrenergic agonist terbutaline and inhibitors of cyclic nucleotide phosphodiesterase. In contrast to the situation in the wild-type clone, synthesis of adenosine 3':5'-monophosphate (cyclic AMP) is not stimulated by beta-adrenergic agonists or by prostaglandin E1 either in intact variant cells or in membrane preparations of such clones. However, basal and NaF-stimulated activities of adenylate cyclase [ATP pyrophosphate-lyase (cyclizine), EC 4.6.1.1] are normal, enzyme activity is stimulated by guanyl-5'-yl imidodiphosphate [Gpp(NH)p], and intact cells accumulate cyclic AMP when exposed to cholera toxin. Furthermore, variant cell membranes possess ligand-binding activity consistent with the conclusion that a normal or an excessive number of beta-adrenergic receptors is present. Thus, interaction between the hormone-binding and the catalytic moieties of the adenylate cyclase system is lost. This variant phenotype, designated as uncoupled (UNC), has been stable for more than 100 generations without exposure to the drugs used for selection. Such cells should be useful for the elucidation of methanisms of transmission of information from hormone receptors to adenylate cyclase.

Journal ArticleDOI
TL;DR: The uncoupled and adenylate cyclase-deficient variants of the S49 cell are not complementary and the effects of beta-adrenergic agonists and antagonists on the reconstituted system reproduce those that are characteristic of the wild-type S49 lymphoma cell.
Abstract: Membranes of mouse L cells that contain adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] but lack beta-adrenergic receptors have been solubilized with Lubrol 12A9. Addition of such adenylate cyclase-containing extracts to beta-adrenergic receptor-replete membranes from adenylate cyclase-deficient S49 lymphoma cells results in the production of a catecholamine-sensitive adenylate cyclase system. The effects of beta-adrenergic agonists and antagonists on the reconstituted system reproduce those that are characteristic of the wild-type S49 lymphoma cell. The uncoupled variant of the S49lymphoma contains adenylate cyclase, but donor extracts from this clone fail to reconstitute the hormone-sensitive enzyme activity when added to adenylate cyclase-deficient membranes. Thus, the uncoupled and adenylate cyclase-deficient variants of the S49 cell are not complementary.

Book
01 Jan 1977
TL;DR: In this article, a New Guinea relational system is analyzed in terms of kinship in symbolic terms, and a set of operant concepts for the understanding of kinships are presented.
Abstract: Kin relationship may be approached in the traditional manner as the classification or the sociopolitical “relating” of genealogically differentiated relatives, or it may be seen as the purposive differentiation of relational categories to compel a “flow” of analogical “relatedness” among them. Analysis of a New Guinea relational system in the latter terms, beginning with the “interdict” on relations with the wife's mother, reveals a set of operant concepts for the understanding of kinship in symbolic terms, as well as a set of general conclusions as to the nature of kinship.

Journal ArticleDOI
TL;DR: At clinically common concentrations of lidocaine, significant decreases in anesthetic requirements should be anticipated.
Abstract: The effects of various plasma concentrations of lidocaine on nitrous oxide anesthesia in man and halothane requirements in the dog were studied The response to incision of the skin was observed in 20 patients who were anesthetized with nitrous oxide, 70% inspired, and oxygen, 30%, plus various plasma levels of lidocaine In addition, changes in the MAC of halothane in dogs were observed at various levels of lidocaine In both circumstances lidocaine concentrations of 3 to 6 microgram/ml decreased anesthetic requirements approximately 10 to 28% At clinically common concentrations of lidocaine, significant decreases in anesthetic requirements should be anticipated

Journal ArticleDOI
01 Nov 1977-Cell
TL;DR: This experiment shows that new histone does not mix with old histone in the new nucleosomes, since the labeling protocol allows density labeling of only one histone for every seven preexisting unlabeled histones, and that old and new hist one octamers segregate conservatively over 2-3 generations.