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Biomedical subjects

S Schultz

Publications and source records attributed to S Schultz.

At least 37 records · Page 2Linked to original sources
PubMed2000

Studies on the attenuation phenotype of polio vaccines: poliovirus RNA polymerase derived from Sabin type 1 sequence is temperature sensitive in the uridylylation of VPg.

Determinants of temperature sensitivity and/or attenuation in Sabin type 1 poliovirus reside in the 5' NTR and coding sequences of the capsid proteins and viral RNA polymerase, 3D(pol). Previous studies have implicated at least two mutations in 3D(pol) of Sabin 1 vaccine strain [PV1(S)], including a Y73H change, as contributing to these phenotypes. We have used an in vitro assay to test the first step in RNA synthesis, the uridylylation of the terminal protein VPg with 3D(pol) isolated from PV1(S). Wt and two mutant 3D(pol) proteins (Y73H, D53N/Y73H) were expressed in Escherichia coli and were purified, and their activities were measured in the synthesis of VPgpU(pU) and of VPg-linked poly(U) at 30 and 39.5 degrees C. Our results show that at 39.5 degrees C the Y73H mutation leads to a defect in the synthesis of VPgpUp(U) and of VPg-poly(U) but not in the elongation of a (dT)(15) primer. The double mutant protein had the same activities as Y73H 3D(pol). Using the yeast two-hybrid assay, we detected a reduced interaction between 3D(pol) molecules carrying either the single or double mutations. Tyrosine-73 maps to the finger domain in the three-dimensional structure of 3D(pol). A model will be presented in which a change of Y73 to H73 may interfere with an interaction between two polymerase molecules that, in turn, may interfere with VPg uridylylation. Alternative explanations, however, cannot be excluded at the present time.

Amino Acid Sequence↗
PubMed2000

Composite medium with simultaneously negative permeability and permittivity

We demonstrate a composite medium, based on a periodic array of interspaced conducting nonmagnetic split ring resonators and continuous wires, that exhibits a frequency region in the microwave regime with simultaneously negative values of effective permeability &mgr;(eff)(omega) and permittivity varepsilon(eff)(omega). This structure forms a "left-handed" medium, for which it has been predicted that such phenomena as the Doppler effect, Cherenkov radiation, and even Snell's law are inverted. It is now possible through microwave experiments to test for these effects using this new metamaterial.

Journal Article↗
PubMed2000

Single-target molecule detection with nonbleaching multicolor optical immunolabels.

We introduce and demonstrate the use of colloidal silver plasmon-resonant particles (PRPs) as optical reporters in typical biological assays. PRPs are ultrabright, nanosized optical scatterers, which scatter light elastically and can be prepared with a scattering peak at any color in the visible spectrum. PRPs are readily observed individually with a microscope configured for dark-field microscopy, with white-light illumination of typical power. Here we illustrate the use of PRPs, surface coated with standard ligands, as target-specific labels in an in situ hybridization and an immunocytology assay. We propose that PRPs can replace or complement established labels, such as those based on radioactivity, fluorescence, chemiluminescence, or enzymatic/colorimetric detection that are used routinely in biochemistry, cell biology, and medical diagnostic applications. Moreover, because PRP labels are nonbleaching and bright enough to be rapidly identified and counted, an ultrasensitive assay format based on single-target molecule detection is now practical. We also present the results of a model sandwich immunoassay for goat anti-biotin antibody, in which the number of PRP labels counted in an image constitutes the measured signal.

ATP-Binding Cassette Transporters↗
PubMed2000

Memory complaint in a community sample aged 70 and older.

OBJECTIVES: The ability of older people to estimate their own memory, often referred to as "metamemory," has been evaluated in previous studies with conflicting reports regarding accuracy. Some studies have suggested that an older person's metamemory is mostly accurate, whereas others have demonstrated little relationship between memory complaint and actual impairment. This study examines memory complaint in a large national sample of older people aged > or = 70. DESIGN: A longitudinal cohort study with two waves of data collection spaced 2 years apart. SETTING: A nationwide random sample of community-dwelling older persons. PARTICIPANTS: A total of 5,444 community-dwelling persons aged > or = 70 and their spouses. MEASUREMENTS: Participants were asked if they believed their memory was excellent, very good, good, fair, or poor. They were then administered a cognitive assessment derived from the Mini-Mental Status Exam. RESULTS: In general, people's assessment of their memory corresponded with their actual performance on cognitive measures. However, large portions of the sample inaccurately assessed their memory skills. People who reported depressive symptoms and had impairment in activities of daily living were more likely to state that their memory was impaired, although they performed very well on cognitive measures. CONCLUSIONS: The conditions that skew people's self-assessment are the ones most likely to bring them into contact with healthcare professionals. This may give clinicians the general impression that older people cannot assess their own cognitive skills. However, poor metamemory appears to be a characteristic of a specific subgroup of older persons, not necessarily characteristic of the general population.

Activities of Daily Living↗