Search PubMed⌕ Search

Biomedical subjects

S Yu

Publications and source records attributed to S Yu.

At least 487 records · Page 27Linked to original sources
PubMedDate not supplied

Ascorbic acid feeding of rats reduces copper absorption, causing impaired copper status and depressed biliary copper excretion.

The feeding of diets enriched with ascorbic acid (10 g/kg) to rats has previously been shown to lower plasma and liver copper concentrations. The present studies corroborate this. We hypothesized that ascorbic acid initially reduces copper absorption, this effect being masked later by the stimulatory effect on copper absorption of the impaired copper status. We also hypothesized that the impaired copper status as induced by ascorbic acid feeding is followed by a diminished biliary excretion of copper in an attempt to preserve copper homeostasis. Our hypotheses are supported by the present studies. Ascorbic acid feeding initially reduced apparent copper absorption, and in the course of the experiment this effect tended to turn over into a stimulatory effect. Copper deficiency, as induced by feeding a diet containing 1 mg Cu/kg instead of 5 mg Cu/kg, systematically increased copper absorption. Biliary excretion of copper in rats given ascorbic acid was unaffected initially but became depressed after prolonged ascorbic acid feeding. A similar time course was seen for fecal endogenous copper excretion that was calculated as the difference between true and apparent copper absorption. Copper deficiency systematically reduced biliary copper excretion and fecal endogenous copper loss.

Animals↗
PubMedDate not supplied

Effects of acute barbiturate administration, tolerance and dependence on brain GABA system: comparison to alcohol and benzodiazepines.

Central nervous system depressants, e.g., barbiturates, alcohol and benzodiazepines, have a wide spectrum of activity in humans and animals. Evidence accumulated suggests that some of the pharmacological actions exerted by these agents may be mediated through GABA system by mimicking GABAergic transmission. This review attempts to summarize the evidence available as to how the GABA system plays a part in the barbiturate actions and the development of tolerance to and physical dependence on barbiturates. The comparisons of the effects of alcohol, barbiturates and benzodiazepines at different steps of GABA synapse are also presented. Furthermore, the results which have been reported in the literature are inconsistent. This may be due to differences in: (a) animal models used; (b) brain regions used; (c) protocols (dose, duration, form and route of administration, etc.) used in treating animals and/or (d) techniques (pharmacological, biochemical, physiological, etc.) used.

Animals↗
PubMedDate not supplied

A candidate Ross River virus vaccine: preclinical evaluation.

A killed Ross River virus vaccine is being developed in an effort to prevent the, ca 5000 cases of epidemic polyarthritis which occur in Australia each year. The symptoms of epidemic polyarthritis commonly last 30-40 weeks and 25% of patients have symptoms for a year or more. There is no cure. Although there was some strain to strain variation, particularly after a single injection, outbred and inbred strains of mice all produced significant levels of anti-Ross River virus antibody after intramuscular (i.m.) injection with 24 h BEI inactivated, sucrose gradient purified, Ross River virus vaccine. Mice immunized i.m. with two 20 micrograms doses of vaccine or live virus produced similar levels of neutralizing antibody but the reaction of IgG 2a and IgG 2b antibody from these two groups of mice to Ross River virus proteins in western blots differed. Antibody from BALB/c mice immunized with this vaccine neutralized all strains of Ross River virus tested, in vitro, albeit to different degrees.

Animals↗
PubMedDate not supplied

Rapid esterification of nucleosides to solid-phase supports for oligonucleotide synthesis using uronium and phosphonium coupling reagents.

Nucleosides can be esterified to solid-phase supports using uronium or phosphonium coupling reagents and a coupling additive, such as 1-hydroxybenzotriazole (HOBT), 7-aza-1-hydroxybenzotriazole (HOAT), N-methylimidazole (NMI), or 4-(dimethylamino)pyridine (DMAP). However, DMAP was far superior to other additives and high nucleoside loadings (up to 60 micromol/g) and rapid coupling reactions (< or = 10 min) were possible. Hydroxyl-derivatized CPG was attached to nucleosides with 3'-succinyl or 3'-hydroquinone-O, O'-diacetic acid (HQDA or Q-Linker) carboxyl groups through a primary ester linkage. Alternatively, supports derivatized with succinic acid or the Q-Linker were attached directly to the 3'-OH group of nucleosides through a secondary ester linkage. Uronium reagents (HATU or HBTU) gave the best results with the HQDA linker arm, while the bromophosphonium (BrOP or PyBrOP) reagents were best with the succinyl linker arm. In all cases, the coupling reactions were much faster than previous methods using carbodiimide coupling reagents. The ease and speed of the reaction make this support derivatization procedure suitable for automated in situ couplings on DNA synthesizers.

4-Aminopyridine↗
PubMedDate not supplied

Solid-phase oligonucleotide synthesis and flow cytometric analysis with microspheres encoded with covalently attached fluorophores.

A novel combinatorial approach to synthesize oligonucleotides on fluorescently encoded microspheres based on flow sorting and segmental solid-phase synthesis is described. BODIPY dyes were covalently attached to polystyrene (8.8 microm, 55% DVB) microsphere particles to generate four fluorescently encoded sets. 20-mer oligonucleotide sequences can be synthesized on these microspheres with yields comparable to conventional CPG supports (80% overall yield, average stepwise yield = 99%). The concept of segmental solid-phase synthesis by flow sorting was demonstrated by synthesizing unique 20-mer oligonucleotide sequences on each of four fluorescently encoded microsphere sets by including a flow sorting step (after first eight base additions) and flow cytometric detection of sequences synthesized on each microsphere set by hybridization with fluorescently labeled complementary sequence.

Boron Compounds↗
PubMedDate not supplied

Multiple oligonucleotide synthesis in tandem on solid-phase supports for small and large scale synthesis.

Multiple oligonucleotides linked end-to-end in tandem can be synthesized by adding a nucleoside to the 5'-OH end of a prior sequence. Nucleosides with 3'-succinyl or Q-Linker arms are coupled with HBTU/DMAP. Alternatively, new phosphoramidite reagents with 3'-ester linkages can be used. Hydroxyl or amino supports can also be used as universal starting materials. Treatment with NH4OH cleaves the 3'-ester to yield only 3'-OH groups and no unwanted 3'-phosphorylated products occur.

Cross-Linking Reagents↗
PubMedDate not supplied

Incidence of unfused ossicles in the lumbar facet joints: CT, MR, and cryomicrotomy study.

The incidence of unfused ossicles in the lumbar spine, in radiographic studies, is 0.7-1.5%. With a sledge cryomicrotome, we sectioned 273 lumbar facet joints in 38 adult cadavers and correlated the anatomic appearance of the joints with CT and magnetic resonance (MR) images. Ossicles were present in 13% of the cadavers and 2.6% of the facet joints and were demonstrated effectively by MR. The incidence of ossicles, which can be confused with fractures, in the facet joints is higher than previously reported.

Aged↗
PubMedDate not supplied

Dentin bond shear strength and microleakage for Syntac/Heliomolar: a comparison between the manufacturer's and total etch technique.

Recent improvements in formulation have led to significant improvements in the bond strength and clinical performance of dentin bonding agents. The growing interest in the concept of total etch prompted a comparison between manufacturer-recommended procedure and that of total etch for the product Syntac. An in vitro study to examine shear bond strength to dentin and microleakage and an in vivo component to investigate the micromorphologic relationship between restoration and tissue was conducted. No statistical significance was observed in bond strength values for the nonetched versus the etched group. Significantly, however, a larger number of specimens in the nonetched group exhibited microleakage. In vivo, only the etched group exhibited a zone of hybridization although both nonetched and etched restorations showed no interfacial gaps. It was concluded that total etch does not compromise the shear bond strength of Syntac but it appears to significantly reduce microleakage possibly due to the formation of a hybrid zone and may have merit clinically.

Acid Etching, Dental↗
PubMedDate not supplied

Haptoglobin types in Chinese ethnic groups.

The distribution of haptoglobin (HP) types was examined in six different Chinese ethnic groups. The gene frequencies were compared among these groups and to those reported in other Chinese Han populations. The effects of sex and age on the distribution of HP types are also discussed.

Adolescent↗
PubMedDate not supplied

Adsorption-desorption behavior of copper at contaminated levels in red soils from China.

Adsorption-desorption of copper (Cu2+) at contaminated levels in two red soils was investigated. The red soil derived from the Quaternary red earths (clayey, kaolinitic thermic plinthite Aquult) (REQ) adsorbed more Cu2+ than the red soil developed on the Arenaceous rock (clayey, mixed siliceous thermic typic Dystrochrept) (RAR). The maximum adsorption values (M(A)) that are obtained from the simple Langmuir model were 25.90 and 20.17 mmol Cu2+ kg(-1) soil, respectively, for REQ and RAR. Adsorption of Cu2+ decreased soil pH, by 0.8 unit for the REQ soil and 0.6 unit for the RAR soil at the highest loadings. The number of protons released per Cu2+ adsorbed increased sigmoidally with increasing initial Cu2+ concentration for the RAR soil, but the relationship was almost linear for the REQ soil. The RAR soil released about 2.57 moles of proton per mole of Cu2+ adsorbed at the highest Cu2+ loading and the corresponding value for the REQ soil was 1.12. The distribution coefficient (Kd) decreased exponentially with increasing Cu2+ loading. Most of the adsorbed Cu2+ in the soils was readily desorbed in the NH4Ac. After five successive extractions with 1 mol L(-1) NH4Ac (p 5.0), 61 to 95% of the total adsorbed Cu2+ in the RAR soil was desorbed and the corresponding value for the REQ soil was 85 to 92%, indicating that the RAR soil had a greater affinity for Cu2+ than the REQ soil at low levels of adsorbed Cu2+.

Adsorption↗
PubMedDate not supplied

Haemophilus influenzae type b and Streptococcus pneumoniae as causes of pneumonia among children in Beijing, China.

To determine if Haemophilus influenzae type b (Hib) and Streptococcus pneumoniae could be identified more often from the nasopharynx of patients with pneumonia than from control patients, we obtained nasopharyngeal swab specimens from 96 patients with chest x-ray-confirmed pneumonia and 214 age-matched control patients with diarrhea or dermatitis from the outpatient department at Beijing Children's Hospital. Pneumonia patients were more likely to be colonized with Hib and S. pneumoniae than control patients, even after the data were adjusted for possible confounding factors such as day-care attendance, the presence of other children in the household, and recent antibiotic use. In China, where blood cultures from pneumonia patients are rarely positive, the results of these nasopharyngeal cultures provide supporting evidence for the role of Hib and S. pneumoniae as causes of childhood pneumonia.

Case-Control Studies↗