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At least 37 records · Page 2Linked to original sources
PubMed1998

Genetic variation of HIV type 1: relevance of interclade variation to vaccine development.

Accumulating data in human immunodeficiency virus (HIV)-infected individuals support the hypothesis that in primary human immunodeficiency virus type 1 (HIV-1) isolates of different clades and phenotype (syncytium inducing [SI] and nonsyncytium inducing [NSI]) common antigenic structures must exist that can stimulate the immune response to produce a broad spectrum (cross-clade and cross SI and NSI) neutralization response. Certain vaccination regimens in chimpanzees and human volunteers with clade B SI type HIV-1 derived candidate vaccines induce neutralizing antibodies against intraclade B SI type primary HIV-1 isolates, but not against intraclade B NSI type of viruses. To be effective against the full antigenic spectrum of primary HIV-1 isolates (cross-clade--SI and NSI) candidate vaccines should contain immunogens of primary isolates representative of the whole antigenic spectrum of HIV-1. There is an urgent need to identify these immunogens and to improve their immunogenicity. As long as we have not yet characterized these cross-HIV-1 spectrum conserved immunogens, candidate vaccines against the more prevalent clades C, A, and E should be developed for evaluation in developing countries. In support of the follow-up and evaluation of the hopefully increasing number of phase 1, 2, and 3 HIV-1 vaccine trials in humans, it is considered a high priority to develop a high throughput neutralization assay, to further expand the use of a limited number of key primary HIV-1 isolates as a surrogate for neutralization of the entire HIV-1 antigenic spectrum (cross-clade--SI and NSI), to develop high throughput subtyping as well as a rapid system to monitor the immunogenic relatedness of different HIV-1 clades.

AIDS Vaccines↗
PubMed1989

Fast hyperpolarization following an excitatory postsynaptic potential in cat bladder parasympathetic neurons.

Intracellular recording techniques were used to study a fast hyperpolarizing potential following the fast excitatory postsynaptic potential evoked by an orthodromic nerve stimulation in cat bladder parasympathetic ganglion cells. In the 61 ganglion cells examined, two types of responses were recorded on stimulating the preganglionic nerve; one had only a fast excitatory postsynaptic potential (type SI, n = 20) and the other had a fast excitatory postsynaptic potential followed by a fast hyperpolarizing potential (type SII, n = 41). In type SII neurons, the half-maximum duration of the afterhyperpolarizing potential following an orthodromic spike was longer than that of a direct spike produced by injecting a depolarizing current pulse through the recording electrode; the half-maximum durations for afterhyperpolarizing potentials following orthodromic and direct action potentials were comparable in type SI cells. Blocking the initiation of an orthodromic spike by hyperpolarizing the membrane in type SII cells revealed a fast excitatory postsynaptic potential followed by a fast hyperpolarizing potential which was similar to that observed at the resting potential. The fast hyperpolarizing potential had a duration comparable to that of an afterhyperpolarizing potential following an orthodromic action potential. The fast excitatory postsynaptic potential-fast hyperpolarizing potential sequence was blocked completely and reversibly by nicotinic receptor antagonists (hexamethonium and D-tubocurarine). Atropine, alpha-2 noradrenergic (yohimbine and phentolamine), and purinergic (caffeine) antagonists had no effect on the fast hyperpolarizing potential. In cells which show type SII responses, spontaneous excitatory postsynaptic potentials were not followed by a hyperpolarization. Depolarizing the membrane (by passing a cathodal current through the recording electrode) to an amplitude comparable to that of a fast excitatory postsynaptic potential also did not elicit a membrane hyperpolarization in type SII cells. In some cells, stimulating one preganglionic nerve trunk elicited a fast hyperpolarizing potential, but activating another nerve trunk innervating the same ganglion cell did not. There was no correlation between the variations in the amplitudes of the fast excitatory postsynaptic potential and the fast hyperpolarizing potential in type SII cells, but increasing the stimulus intensity applied to the presynaptic nerve fiber potentiated the amplitude of the fast excitatory postsynaptic potential and the fast hyperpolarizing potential. The fast hyperpolarizing potential was not associated with appreciable changes in input resistance.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed2002

Formation of vacancy-impurity complexes by kinetic processes in highly As-doped Si.

Positron annihilation experiments have been applied to verify the formation mechanism of electrically inactive vacancy-impurity clusters in highly n-type Si. We show that the migration of V-As pairs at 450 K leads to the formation of V-As2 complexes, which in turn convert to stable V-As3 defects at 700 K. These processes manifest the formation of V-As3 as the dominant vacancy-impurity cluster in highly n-type Si. They further explain the electrical deactivation and clustering of As in epitaxial or ion-implanted Si during postgrowth heat treatment at 700 K.

Journal Article↗
PubMed2002

Developmental difference of neural functions in the song and call control system in Bengalese finches.

In Bengalese finches, the maturation of distance calls and the stabilization of their song are obtained through developmental learning stages. In this study, whole cell patch clamp recordings were made from neurons in the robust nucleus of the archistriatum (RA), which is a motor control nucleus of male-specific vocalization in male birds of different developmental stages. The neurons in the RA were categorized into three types according to their electrophysiological properties under voltage clamp recordings. Distribution ratios of the neuron types changed during development. The firing pattern of these neurons was highly co-related with the expression of slow-inactivated (SI) type outward current. In this study, we first showed that the developmental change of the neural circuit in the RA was induced by the expression of the SI-type outward current.

Animals↗
PubMed2006

Scanning electrochemical microscopy investigations of monolayers bound to p-type silicon substrates.

p-Si type electrodes modified with different organic monolayers were investigated by reaction with radical anion and cation electrogenerated at a microelectrode operating in the configuration of a scanning electrochemical microscope. The method proves to be a convenient tool for investigating both the quality and the redox properties of the layer as previously demonstrated on metallic electrodes especially when the sample cannot be electrically connected. Approach curves recorded with the different mediators were used to investigate the electron-transfer rates across alkyl monolayers bound to p-type silicon substrates. Preliminary results indicate that the interfacial electron transfer occurs via electron tunneling through the organic layer as generally described for SAMs grafted on gold electrodes.

Journal Article↗
PubMed1997

Inhibition of plating of human T cell leukemia virus type I and syncytium-inducing types of human immunodeficiency virus type 1 by polycations.

We examined the effects of polycations, namely, diethylaminoethyl-dextran (DEAE-dextran) and hexadimethrine bromide (Polybrene), on infection with the retroviruses human T cell leukemia virus types I and II (HTLV-I and HTLV-II) and human immunodeficiency virus type 1 (HIV-1). The plating of vesicular stomatitis virus (VSV) pseudotype bearing envelope antigens of HTLV-I [VSV(HTLV-I)] was inhibited about 2- and 10-fold by treatment with DEAE-dextran and Polybrene, respectively. The formation of HTLV-I viral DNA detected 1 day after infection was also inhibited by these polycations. In contrast, polycations enhanced the plating of the VSV (HTLV-II) pseudotype two- to threefold. The polycations did not affect the plating efficiency of HTLV-I or HTLV-II when added after virus adsorption. Infection of human T cell lines, peripheral blood lymphocytes (PBLs), or brain-derived cells with syncytium-inducing (SI) types of HIV-1 strains (GUN1 and IIIB) was inhibited 3- to 20-fold by polycations. However, infection of PBLs or monocyte-derived macrophages with the macrophage-tropic Ba-L or SF162 strain was enhanced 1.5- to twofold by polycations. On the other hand, syncytium formation in coculture induced by HTLV-I, HTLV-II, or HIV-1 was enhanced two- to threefold unanimously by DEAE-dextran or Polybrene. Although polycations have been used to potentiate human retrovirus adsorption, they inhibited infection of cell-free HTLV-I or SI-type HIV-1 strains.

Animals↗
PubMed2002

Atomic-scale imaging of individual dopant atoms and clusters in highly n-type bulk Si.

As silicon-based transistors in integrated circuits grow smaller, the concentration of charge carriers generated by the introduction of impurity dopant atoms must steadily increase. Current technology, however, is rapidly approaching the limit at which introducing additional dopant atoms ceases to generate additional charge carriers because the dopants form electrically inactive clusters. Using annular dark-field scanning transmission electron microscopy, we report the direct, atomic-resolution observation of individual antimony (Sb) dopant atoms in crystalline Si, and identify the Sb clusters responsible for the saturation of charge carriers. The size, structure, and distribution of these clusters are determined with a Sb-atom detection efficiency of almost 100%. Although single heavy atoms on surfaces or supporting films have been visualized previously, our technique permits the imaging of individual dopants and clusters as they exist within actual devices.

Journal Article↗
PubMedDate not supplied

Demographic correlates of SI assessments of type A behavior.

A survey interview and the structured Type A interview (SI) were administered to 903 residents of Washtenaw County, Michigan aged 18 or older selected by a multistage probability sample of households. No bivariate relationship was found between Type A behavior and sex or marital status. Type A behavior was positively related to income and education. The prevalence of Type A behavior was highest among those who were employed in white-collar occupations. There was an inverted U-shaped relationship between age and Type A behavior. A slightly higher prevalence of Type A behavior was noted among whites than among nonwhites. Multivariate analysis showed the seven demographic variables to account for 6.8% of the overall variation in Type A behavior, with family income being the strongest demographic predictor.

Adolescent↗
PubMed2006

Effect of orofacial motor cortex stimulation on neuronal activity in the red nucleus.

We studied modulation of the activities of the red nucleus (RN) neurons under to electrical stimulation of the orofacial motor cortex (OfM) in urethane-anesthetized rats. Of 57 neurons studied, 30 (53%) neurons modulated the firing patterns. The firing patterns of the RN neurons were classified into four types: an excitation (E) type (n=4), a long inhibition (LI) type (n=4), a short inhibition (SI) type (n=22), and a no-effect type (n=27). These modulated neurons were intermingled in the dorso-ventral part of the RN. Our results suggest that the RN neurons receive excitatory or inhibitory inputs from the OfM.

Animals↗
PubMed1997

Dynamics of syncytium-inducing and non-syncytium-inducing type 1 human immunodeficiency viruses during primary infection.

Syncytium-inducing (SI) type 1 human immunodeficiency viruses (HIV-1) replicate faster in vitro and are generally more cytopathic to T cells than non-syncytium-inducing (NSI) HIV-1. Early in infection, the virus population typically consists of NSI viruses, with SI viruses appearing later. This is true even when both SI and NSI viruses are transmitted, and when SI viruses dominate the virus population peak seen during primary infection. Here, Phillips's model of HIV dynamics during primary infection (Science 271:497-499) is modified to map the growth trajectories of SI and NSI subpopulations. The model predicts that with certain rate constants, SI viruses may show a more precipitous decline in their numbers during primary infection than NSI viruses, and this may account for the observed dominance of NSI viruses early in infection.

Giant Cells↗
PubMed2003

Time-dependence of SI RA neuron response to cutaneous flutter stimulation.

Spike discharge activity of RA-type SI cortical neurons was recorded extracellularly in anesthetized monkeys and cats. Multiple applications (trials) of 10-50 Hz sinusoidal vertical skin displacement stimulation ("flutter") were delivered to the receptive field (RF). Analysis revealed large and systematic temporal trends not only in SI RA neuron responsivity (measured as spikes/s and as spikes/stimulus cycle), but also in entrainment, and in phase angle of the entrained responses. In contrast to SI RA neurons, the response of RA skin afferents to comparable conditions of skin flutter stimulation exhibited little or no dynamics. The occurrence and form of the SI RA neuron response dynamics that accompany skin flutter stimulation are shown to depend on factors such as stimulus frequency and the locus of the recording site in the global cortical response pattern. Comparison of recordings obtained in near-radial vs tangential microelectrode penetrations further reveals that the SI RA neuron response dynamics that occur during skin flutter stimulation are relatively consistent within, but heterogeneous across column-sized regions. The observed SI RA neuron response dynamics are suggested to account, in part, for the improved capacity to discriminate stimulus frequency after an exposure ("adaptation") to skin flutter stimulation (Goble and Hollins, J Acoust Soc Am 96: 771-780, 1994). Parallels with recent proposals about the contributions to visual perception of short-term primary sensory cortical neuron dynamics and synchrony in multineuron spike activity patterns are identified and discussed.

Anesthesia↗
PubMed2000

Local chemical states and microstructure of photoluminescent porous silicon studied by means of EELS and TEM

Photoluminescent porous Si (PS) layers were formed on low resistivity p-type Si(100) wafers by anodization at a current density (Ia) of 100-350 mA cm(-2) at room temperature. The local chemical states and the microstructures of the PS layers were studied by means of electron energy loss spectroscopy (EELS) and transmission electron microscopy (TEM), and were correlated to the red photoluminescence (PL). The PS layer consists of sponge-like and tree-like structures. The tree-like structure becomes finer with increase of Ia. The fine tree-like structure is shown to be favorable for intensive PL. The EELS analysis reveals that the Si-4O structure, namely the basic structure of SiO2, and Si crystals coexist in the PS layers. The relative content of SiO2 to Si crystallites (R) increases with increase in Ia and decreases with the depth from the top surface of the PS layer. High R corresponds to intensive PL. These results suggest that PL may be connected with some kind of defects in SiO2 and/or defects in the boundary between Si crystallites and SiO2 structure in anodized PS layers, and that PL may be mainly emitted from the layer near the top surface of the PS layers.

Journal Article↗