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At least 91 records · Page 5Linked to original sources
PubMed1998

Role of CCR2 genotype in the clinical course of syncytium-inducing (SI) or non-SI human immunodeficiency virus type 1 infection and in the time to conversion to SI virus variants.

The effect of a valine to isoleucine switch in the CCR2 first transmembrane domain (CCR2 64I) on the clinical course of human immunodeficiency virus type 1 (HIV-1) infection was analyzed in relation to the presence or absence of syncytium-inducing (SI) HIV-1 variants. Compared with persons with a wild-type genotype for CCR2 and CCR5, subjects with a CCR2-64I/+ or 64I/64I (but CCR5 wild-type homozygous genotype) had significantly delayed disease progression (relative hazard, 0.66; 95% confidence interval, 0.44-0.99) with a 1. 5-fold slower CD4 T lymphocyte decline and a 1.2-fold lower RNA virus load. The delay in disease progression was more pronounced when only non-SI (NSI) HIV-1 variants were present and was not observed after conversion to SI HIV-1 in CCR2-64I/+ persons. In CCR2-64I/+ subjects, a higher conversion rate to and a higher prevalence of SI HIV-1 was observed. These findings suggest that the mechanism of action of the CCR2 polymorphism is mediated via CCR5-restricted NSI HIV-1 variants.

Cells, Cultured↗
PubMed1998

Lanthanum Nickel Silicides with the General Formula La(()(n)()(+1)()(n)()(+2))Ni(n)()(()(n)()(-)(1)+2)Si(n)()(()(n)()(+1)) and Other Series of Hexagonal Structures with Metal:Metalloid Ratios Close to 2:1.

The closely related crystal structures of the compounds La(6)Ni(2)Si(3) (La(12)Ni(4)Si(6), n = 2) and La(5)Ni(2)Si(3) (La(20)Ni(8)Si(12), n = 3) as well as those of the new compounds La(15)Ni(7)Si(10) (La(30)Ni(14)Si(20), n = 4) and La(21)Ni(11)Si(15) (La(42)Ni(22)Si(30), n = 5) were determined from single-crystal X-ray diffractometer data. In these hexagonal silicides (space group P6(3)/m) almost all atoms are situated on mirror planes, which extend perpendicular to the short c axes. The only exceptions are nickel atoms located on the 6(3) axes, which show some disorder resulting in the exact compositions La(6)Ni(1.54(2))Si(3) [a = 1224.3(1) pm, c = 438.3(1) pm, Z = 2, Ce(6)Ni(2)Si(3) type structure], La(5)Ni(1.75(1))Si(3) [a = 1624.4(3) pm, c = 434.2(2) pm, Z = 4, Ce(5)Ni(2)Si(3) type], La(15)Ni(6.62(2))Si(10) [a = 2021.2(3) pm, c = 435.1(1) pm, Z = 2, Pr(15)Ni(7)Si(10) type], and La(21)Ni(10.49(3))Si(15) [a = 2427.7(3) pm, c = 435.2(1) pm, Z = 2, a new structure type]. All of these structures have building elements which resemble the AlB(2) type structure. In these the lanthanum atoms correspond to the aluminum atoms of AlB(2), while the nickel and silicon atoms occupy the boron positions in an ordered manner. Other series of ternary hexagonal lanthanoid and actinoid transition metal silicides and phosphides, e.g., the series with the general formula R(n)()(()(n)()(-)(1))Ni(()(n)()(+1)()(n)()(+2))P(n)()(()(n)()(+1)+1) (R = Th, U), are briefly reviewed, and the systematics in the space groups and the diffraction patterns of these compounds are pointed out.

Journal Article↗
PubMed2000

Atomic and electronic origins of a type- C defect on Si(001)

We present an extensive set of ab initio calculations for a type- C defect on Si(001). Various models belonging to subsurface defects are studied. A substitutional B in the second surface layer is predicted as a possible atomic origin of this defect. However, H and O coupled with second-layer vacancies and a substitutional C are not responsible for a type- C defect. We also discuss how the electronic structure of a type- C defect contributes to its specific scanning tunneling microscopy images.

Journal Article↗
PubMed2006

Altered folding, turnover, and polarized sorting act in concert to define a novel pathomechanism of congenital sucrase-isomaltase deficiency.

Naturally occurring mutants of membrane and secretory proteins are often associated with the pathogenesis of human diseases. Here, we describe the molecular basis of a novel phenotype of congenital sucrase-isomaltase deficiency (CSID), a disaccharide malabsorption disorder of the human intestine in which several structural features and functional capacities of the brush-border enzyme complex sucrase-isomaltase (SI) are affected. The cDNA encoding SI from a patient with CSID reveals a mutation in the isomaltase subunit of SI that results in the substitution of a cysteine by an arginine at amino acid residue 635 (C635R). When this mutation is introduced into the wild type cDNA of SI a mutant enzyme, SI(C635R), is generated that shows a predominant localization in the endoplasmic reticulum. Nevertheless, a definite localization of SI(C635R) in the Golgi apparatus and at the cell surface could be also observed. Epitope mapping with conformation-specific mAbs protease sensitivity assays, and enzymatic activity measurements demonstrate an altered folding pattern of SI(C635R) that is responsible for a substantially increased turnover rate and an aberrant sorting profile. Thus, SI(C635R) becomes distributed also at the basolateral membrane in contrast to wild type SI. Concomitant with the altered sorting pattern, the partial detergent extractability of wild type SI shifts to a complete detergent solubility with Triton X-100. The mutation has therefore affected an epitope responsible for the apical targeting fidelity of SI. Altogether, the combined effects of the C635R mutation on the turnover rate, function, polarized sorting, and detergent solubility of SI constitute a unique and novel pathomechanism of CSID.

Adult↗
PubMed1987

Dimensions of social insecurity and their relation to coronary-prone behaviour in college undergraduates.

Research suggests that Type A behaviour and 'social insecurity' (SI) may represent independent additive task factors for coronary disease. Research examining SI and Type A behaviour, however, has not rigorously evaluated the structure of the SI scale. The present study examined the structure of a previously used eight-item SI scale, and its relation to a questionnaire measure of Type A (the student Jenkins Activity Survey), for a sample of 504 undergraduates. Exploratory and confirmatory factor analyses of responses to the SI items revealed a three-factor solution was most appropriate for Type As, and a two-factor solution for Type Bs. For both As and Bs, the first factor reflected insecurity regarding one's own capabilities and worth (self-specific insecurity), and the second factor reflected insecurity specific to a group or social context (group-specific insecurity). A third factor emerging only for Type As reflected insecurity regarding others' capabilities (other-directed insecurity). Semipartial correlations revealed Type A total score was marginally negatively related to group-specific insecurity and marginally positively related to other-directed insecurity, corroborating previous angiographic and prospective medical research. The hard-driving/competitive subscale was significantly negatively related to self-specific insecurity, supporting evidence regarding Type A and interpersonal dominance, competitiveness, and aggression.

Adolescent↗
PubMed2004

Characteristics of saccadic intrusions.

Primary fixation is never perfectly stable, but is frequently interrupted by slow drifts, microsaccades and saccadic intrusions (SI). SI are involuntary, conjugate movements which take the form of an initial fast movement away from the desired eye position and followed after a short duration, by either a return secondary saccade or a drift. The purpose of this study was to examine the prevalence and metrics of SI in a population of 50 healthy subjects. Using both one and two dimensional recordings we find that all 50 members of the subject group exhibited SI. The SI were bilateral, conjugate and horizontal. No purely vertical SI were detected when examined in three subjects. SI amplitude mean and range was 0.6 degrees +/-0.5 degrees, 0.1 degrees -4.1 degrees; SI frequency mean and range was 18.0+/-14.3 per min, 1.0-54.8 per min; SI duration mean and range was 225+/-150, 20-870 ms. The mean SI amplitude and frequency when SI<0.5 degrees were removed was 0.97 degrees +/-0.56 degrees and 7.0+/-11.4 per min respectively. Age was positively correlated with SI amplitude (p<0.01), but there was no correlation between age and SI frequency. Three of four types of SI monophasic square wave intrusions (MSWI), biphasic square wave intrusions (BSWI) and double saccadic pulses (DSP) were found to be exclusively saccadic, whilst the fourth type, the single saccadic pulses (SSP), were confirmed to exhibit a slow secondary component. MSWI were the most frequently observed SI occurring in 47 out of 50 (94%) of the subjects with a mean amplitude, frequency and duration of 0.7 degrees +/-0.5 degrees, 11.5+/-11.6 per min, and 255+/-147 ms respectively. Mean amplitudes and frequencies for BSWI (n=20), SSP (n=11) and DSP (n=34) were found to be 0.50 degrees +/-0.2 degrees, 1.2+/-2.5 per min; 0.40 degrees +/-0.20 degrees, 0.4+/-1.0 per min and 0.3 degrees +/-0.4 degrees, 5.0+/-8.7 per min respectively. No differences in MSWI characteristics were found between binocular and monocular viewing. Possible explanations for SI occurrence include experimental viewing conditions, subject fatigue and covert shifts in attention.

Adult↗
PubMed1999

Conversion rate towards a syncytium-inducing (SI) phenotype during different stages of human immunodeficiency virus type 1 infection and prognostic value of SI phenotype for survival after AIDS diagnosis.

The presence of syncytium-inducing (SI) human immunodeficiency virus type 1 (HIV-1) variants is predictive for accelerated progression to AIDS. This study showed that a 4-year survival with AIDS also occurred significantly more often for patients who lacked SI variants. However, multivariate Cox analysis excluded the predictive value of SI viruses for rapid death as being independent from low CD4+ T cell counts. Incidence of appearance of SI variants was increased in persons with CD4+ T cell counts <500/microliter but remained constant in the strata of CD4+ T cell counts <500/microliter, excluding the possibility that loss of immune control is the only prerequisite for the development of SI HIV-1 variants.

Acquired Immunodeficiency Syndrome↗
PubMed1976

Control of Fc and C3 receptors on myeloid leukemic cells.

An experimental system has been developed to study in cloned lines of cells the control of Fc and C3 receptors by different compounds. The cells used were clones of mouse myeloid leukemic cells and the compounds used were the protein MGI2 (macrophage and granulocyte inducer) in serum from mice injected with bacterial endotoxin and the steroid inducer (SI) dexamethasone. Eight clones were isolated which could be divided into three groups. One group (MGI+SI+) was induced to form EA and EAC rosettes by MGI and only EAC rosettes by SI, the second group (MGI-SI+) was not inducible by MGI but was induced by SI to form EA or EA and EAC rosettes, and the third group (MGI-SI-) was not inducible for EA or EAC by MGI or SI. There were two types of MGI+SI+ clones, one type (D+) could be induced by MGI to differentiate to mature macrophages and granulocytes, and the other type (D-) could not be induced to differentiate to mature cells. The MGI-SI+ and MGI-SI- clones were all D-. The results indicate that there are different cellular sites for MGI and SI and that induction of EA and EAC rosettes did not seem to be mediated by cyclic AMP. Experiments with specifically bound 3H-BSA-anti-BSA complexes have indicated that there was an increase in the amount of 3H-BSA-anti-BSA bound per rosette-forming cell following induction by MGI or SI, and there were differences in the amount of 3H-BSA-anti-BSA bound per rosette-forming cell in different clones. These clones also showed differences in the shape of the curve for the number of EA rosette-forming cells obtained with erythrocytes coated with decreasing concentrations of antibody. The results suggest that such curves and those obtained with EAC rosettes can be used to determine the relative abundance of EA and EAC receptors on rosette-forming cells. EA rosettes on the myeloid leukemic cells, like those on normal macrophages and granulocytes, were specifically inhibited by IgG2a and by the Fc but not the Fab fragment of IgG. The EAC rosettes were inhibited by destroying the C3 component of complement. The different clones maintained their specific properties for at least 6 months in culture. The present system should, therefore, also be useful for studies on the genetic control of the regulation of Fc and C3 receptors.

Animals↗
PubMed2003

Seeing the atomic orbital: first-principles study of the effect of tip termination on atomic force microscopy.

We perform extensive first-principles calculations to simulate the topographical atomic-force-microscope image of an adatom on the Si(111)-(7 x 7) surface, demonstrating the feasibility of imaging not only the atoms but also the atomic orbitals. Our comparative study of tip terminations shows that two subatomic features can appear for a single adatom when it is imaged by a Si(001)-type tip having two dangling bonds on its apex, while only one feature would appear if it were imaged by a Si(111)-type tip having one dangling bond on the apex. The key condition for seeing the atomic orbitals is to bring the tip so close to the surface that the angular-dependent force dominates the tip-surface interaction.

Journal Article↗
PubMed2006

Atomic-scale sharpening of silicon tips in noncontact atomic force microscopy.

The atomic-scale stability of clean silicon tips used in noncontact atomic force microscopy (NC-AFM) is simulated by ab initio calculations based on density functional theory. The tip structures are modeled by silicon clusters with and termination. For the often assumed Si(111)-type tip we observe the sharpening of the initially blunt tip via short-range chemical forces during the first approach and retraction cycle. The structural changes corresponding to this intrinsic process are irreversible and lead to stable NC-AFM imaging conditions. In opposition to the picture used in literature, the Si(001)-type tip does not exhibit the so-called "two-dangling bond" feature as a bulklike termination suggests.

Journal Article↗
PubMed1968

Mutation in pneumococcus type 3 affecting multiple cistrons concerned with the synthesis of capsular polysaccharide.

The genetic behavior in transformation reactions of 20 noncapsulated mutants of pneumococcus type III suggests that each has a single-site mutation in the locus controlling the synthesis of uridine diphosphate glucose (UDPG) dehydrogenase. Each strain is capable of yielding transformants of the binary capsular type SI-III when exposed to deoxyribonucleic acid (DNA) from type I cells. One additional mutant reacted differently and behaved as if it were a multisite mutant with the mutation affecting both the locus for UDPG dehydrogenase and that controlling the synthesis of high molecular weight type III capsular polysaccharide. When exposed to DNA from type I pneumococci, this strain yielded transformants which were genotypically binary but which expressed only the type I capsular phenotype.

DNA, Bacterial↗
PubMed2005

Determining the geometry of strongly hydrogen-bonded silanols in a layered hydrous silicate by solid-state nuclear magnetic resonance.

High-resolution solid-state NMR spectroscopy is exploited to obtain structural constraints involving strongly hydrogen-bonded silanols in octosilicate, a prominent member of the layered hydrous sodium silicates. Proton-silicon cross-polarization dynamics reveals that octosilicate contains two types of Q(3) silicons present in hydrogen-bonded -Si-O-Hcdots, three dots, centeredO-Si- and -Si-O(-)-type sites which can only be distinguished by their different abilities to cross polarize and the different mobilities of neighboring hydrous species. The theoretical analysis of the oscillating components of the polarization transfer buildup curves suggests that the model of heteronuclear pairs is an adequate description of the quantum spin system within hydrogen-bonded -Si-O-Hcdots, three dots, centeredO-Si- fragments. We also show that dipolar modulated, slow speed magic-angle (29)Si NMR spectrum provides unique geometric information on strongly hydrogen-bonded silanols. The dipolar modulated spinning sidebands contain all the information necessary to determine the internuclear Sicdots, three dots, centeredH distances as well as the magnitude and orientation of the principal elements of the (29)Si chemical shielding tensor in the molecular frame. The data provide definite proof of the intralayer character of strongly hydrogen-bonded silanol groups in a bridging, albeit not symmetric, position between neighboring tetrahedra. The approach developed in this work may be useful to obtain structural information on related layered alkali metal silicates, silica gels as well as on other classes of microporous materials.

Journal Article↗
PubMed1997

Applications of boundary theory to the concept of service integration in the human services.

Service integration (SI) is an aspect of theorizing about organizations and governance. To discover questions for future practice and theory-building, the analysis here reframes the SI concept in the human services from the typical starting point of fragmentation-integration to the imperatives of boundary theory. Extant SI discourse is a confused array of descriptive, normative, and explanatory theory. An action-reflection interplay with conflicting and missing values is revealed. Boundary spanning and boundarylessness, defined in five metaphors, illustrate boundary theory. Selected literature on SI in the human services is translated into boundary theory (e.g., types of SI boundaries, SI boundary values and roles) and a research agenda is posed.

Community Health Services↗