Biomedical subjects

Y Luo

Publications and source records attributed to Y Luo.

At least 451 records · Page 25Linked to original sources

PubMed1994

[Direct determination of tin in water by oscillopolarography].

Sn(IV) has a sensitive polarographic wave in the system of H2SO4-KI-VitC-V (IV). We examined the factors influencing the polarographic wave and found that the concentration of sulfuric acid and temperature were critical factors for the determination. The sensitivity of the method was increased nearly 50-fold by decreasing the concentration of sulfuric acid from 0.8 mol/L to 0.1 mol/L. The coefficient of variation (CV) percentages of the method were less than 5% and 8% for 6-7 determinations of Sn (IV) standard and sample respectively. The recovery ranged from 97.3% to 101%. The proposed method is suitable for direct determination of trace Sn (IV) in most natural water samples.

Polarography↗

PubMed1994

[The effects of brain ischemia and electroacupuncture on cortical somatosensory evoked potential in rats].

The dynamic changes of cortical somatosensory evoked potential during occluding bilateral common carotid arteries and electroacupuncturing "Hegu" point were recorded and observed IN 30 wistar rats anesthetized with chloralose and urethane, The main results were as follows: After brain ischemia, P. N. amplitudes of SEP were significantly depressed, and the spike latency of SEP is obviously increased. The decreased amplitude of SEP during brain ischemia could be obviously increased by electroacupuncturing "Hegu" point. It is suggested that SEP may be an indicator to show brain ischemia and acupuncturing "Hegu" point could improve brain ischemia.

Animals↗

PubMed1994

[The mechanism and clinical significance of decreased anion gap in patients with COPD and acid-base imbalance].

The blood-gas and electrolytes of 427 blood samples from patients with COPD and acid-base imbalance were analysed. The results showed that 14 types of acid-base imbalance were present in patients with COPD and the anion gap decreased in 8 types of acid-base imbalance, especially in respiratory acidosis, metabolic alkalosis and coexistence of both. The anion gap in respiratory acidosis and metabolic alkalosis were 0.8 +/- 6.6mmol/L and 2.1 +/- 7.3mmol/L, respectively. The anion gap in respiratory acidosis with metabolic alkalosis was negative. In all patients the HCO3- increased, and the total anion and total cation diminished. The anion gap decreased owing to the diminution of unmeasured anion. Clinically, the criterion for judging metabolic acidosis with increased anion gap is a value of anion gap over 16 mmol/L. But in case respiratory acidosis (or metabolic alkalosis) and metabolic acidosis coexist in a patient, the anion gap for judging metabolic acidosis should be decreased appropriately.

Acid-Base Equilibrium↗

PubMed1994

[Relationship between airway obstruction and inspiratory muscle function].

Measurement of Pimax (maximal static inspiratory mouth pressure), Pi (static inspiratory mouth pressure) and 5 routine pulmonary function tests, which inspect the degree of airway obstruction, was done in 157 patients with COPD and 55 normal subjects. The results indicated that along with the deterioration of COPD, the Pimax was getting decreased and the Pi/Pimax was getting increased. In the mild and moderate COPD groups, however, the Pi and Pi/Pimax showed no statistical significance, which was the only exception. Our results suggested that (1) the airway obstruction could reduce the inspiratory muscle strength; and (2) the Pi/Pimax might be useful in clinical practice for early diagnosis of inspiratory muscle insufficiency.

Adult↗

PubMed1994

[Polarographic determination of N,N'-methylene-bis(2-amino-1,3,4-thiadiazole) in water].

The polarographic behavior of the product of N,N'-methylene-bis(2-amino-1,3,4-thiadiazole) (I) with nitrite and N-(1-naphthyl)-ethylendiamine is reported. The effects of acidity and reagents on the polarography was studied, and a polarographic method was established for the determination of (I). The relative standard deviation was 2.2-8.4%, and the recovery in the range of 80-103%. The proposed method was sensitive, accurate, reproducible and suitable for the determination of microamount of (I) in water.

Insecticides↗

PubMed1994

[Monitoring of dihydroetorphine hydrochloride in biological fluid].

A method for the monitoring of dihydroetorphine hydrochloride, a powerful anesthetic and analgesic drug, in biological fluid was developed by means of GC-MS with selected ion monitoring. Dihydroetorphine was extracted from human blood and urine with dichloromethane, and then was derivatized with N-heptafluorobutyrylimidazole after it was concentrated to dryness. A dihydroetorphine monoheptafluorobutyl derivative was formed, which showed good characteristics on GC-MS with electronic impact mode. Its M+ was m/z 609. Besides this, its main fragments included m/z 576, 534, 522 and 508. These main ions were all selected as the ions of identification due to their relative peak intensity and stability. The detection limit was 1 pg. The target drug was identified based on its retention time multiple ion monitoring and relative peak intensity. This method has been successfully used for detection of dihydroetorphine hydrochloride in blood and urine from dihydroetorphine addict and poisoned patient, respectively. Good results have been obtained.

Etorphine↗

PubMed1994

Sensitivity to nicotine and brain nicotinic receptors are altered by chronic nicotine and mecamylamine infusion.

DBA/2 mice were chronically infused with saline (control), 4 mg/kg/hr of nicotine, 4 mg/kg/hr of mecamylamine or nicotine+mecamylamine for 7 days. The binding of L-[3H]nicotine was significantly increased in seven of eight brain regions dissected from mice 5 hr after cessation of drug treatment. Similarly, [3H]nicotine binding was increased in six of eight regions by chronic mecamylamine treatment. Treatment with both drugs led to increases in [3H]nicotine binding that were at least the sum of the those observed with either drug alone. These increases were partially reversed 48 hr after cessation of treatment. No significant effects of nicotine or mecamylamine treatment on alpha-[125I]bungarotoxin binding were observed 5 hr after treatment was stopped when assayed using a single ligand concentration. However, saturation analyses of the cerebral cortex detected small increases from control after treatment with nicotine or both drugs. No effects of chronic treatment on alpha-[125I]bungarotoxin binding were evident 48 hr after treatment was stopped. Mice treated with nicotine, mecamylamine or both drugs tested 5 hr after withdrawal were less sensitive to acute injection with nicotine than were saline-infused mice. However, the effects of mecamylamine may have been influenced by continued presence of this drug at the time of testing. Mice tested 48 hr after cessation of treatment were more sensitive to nicotine than those tested after 5 hr, but some tolerance to the effects of nicotine persisted in the nicotine-treated mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Determination of methaqualone and its metabolites in urine and blood by UV, GC/FID and GC/MS.

A systematic procedure for the determination of methaqualone and its metabolites in blood and urine by UV spectrophotometry, GC and GC/MS was developed. Urine and blood samples were from a suicidal patient who ingested 18 tablets of methaqualone. Both solid phase and liquid-liquid extractions were used in the extraction and clean-up of the samples. The total amount of methaqualone and its metabolites was measured by UV spectrophotometry. The amount of parent methaqualone was quantitated by GC/FID. Methaqualone and its 10 metabolites including two acetyl metabolites were found in urine and blood. This procedure is useful for monitoring drugs in emergency treatment.

Chromatography, Gas↗

PubMed1994

[Analysis of meperidine and its metabolites in urine of an addict by GC/FID and GC/MS].

Analytical methods of GC/FID and GC/MS for identification and determination of meperidine, an analgesic drug, and its metabolites were established. The determination of meperidine spiked in urine was shown to have a good linear relationship in the range of 0.1-8.0 micrograms/ml urine (Y = 0.4995X + 0.1201, r = 0.9996). The detection limit was 20 ng/ml urine. With the developed methods, meperidine and its metabolites in urine collected from a meperidine addict were identified and determined. Meperidine, normeperidine, meperidinic acid in free and conjugate forms, normeperidine acid in free and conjugate forms, and acetyl-normeperidine were detected. Among these metabolites, acetyl-normeperidine was reported for the first time.

Cholinesterase Inhibitors↗

PubMed1994

DNA polymorphisms and conditions for SSCP analysis of the 20 exons of the ret proto-oncogene.

Recently identified mutations affecting different domains of the RET proto-oncogene are associated with Multiple Endocrine Neoplasia type 2A (MEN 2A) and type 2B (MEN 2B), familial and sporadic Medullary Thyroid Carcinomas (MTC) and Hirschsprung disease (HSCR). In order to facilitate the screening for RET mutations, and to study possible genotype-phenotype correlations, we established exon-intron junctions and extended the intronic sequences flanking the 20 exons of this gene. This made it possible to design primers and to develop PCR conditions useful for SSCP analysis of the whole RET coding sequence. Nine conformational variants were observed which after sequencing turned out to be 8 silent mutations and a conservative amino acid substitution. Restriction analysis performed on DNA samples from unrelated controls confirmed the polymorphic nature of six of these nucleotide changes and made it possible to estimate the frequency of the corresponding alleles.

Base Sequence↗

PubMed1993

Exon structure and flanking intronic sequences of the human RET proto-oncogene.

Using a PCR strategy based on an initial set of 15 couples of primers designed from the known cDNA sequence, we identified 18 introns in the human RET proto-oncogene and sequenced the corresponding 5' and 3' exon-intron junctions. This approach was successful in locating all the introns contained in fragments short enough to be amplified by PCR. Thus 19 exons were identified which, together with the previously reported exon subjected to alternative splicing, brings the total number of RET exons to 20. This information is relevant for the screening of recently reported missense mutations of RET which cause Multiple Endocrine Neoplasia 2A (MEN2A) and for the search of additional point mutations of the same gene which might cause two other neural crest disorders, MEN2B and Hirschsprung disease, mapping in the same region as MEN2A.

Amino Acid Sequence↗

PubMed1993

Collapsin: a protein in brain that induces the collapse and paralysis of neuronal growth cones.

Repulsive guidance cues can steer neuronal growth cones during development and prevent mature axons from regenerating. We have identified a 100 kd glycoprotein in the chick brain that is a good candidate for a repulsive cue. Since it induces the collapse and paralysis of neuronal growth cones in vitro, we have named it collapsin. It is effective at concentrations of approximately 10 pM. The C-terminal half of collapsin contains a single immunoglobulin-like domain and an additional highly basic region. The N-terminal half of collapsin shares significant homology with fasciclin IV, a growth cone guidance protein in grasshopper. Recombinant collapsin causes sensory ganglion growth cones to collapse but not retinal ganglion cell growth cones. We propose that collapsin could serve as a ligand that guides specific growth cones by a motility-inhibiting mechanism.

Amino Acid Sequence↗

PubMed1993

RNA binding properties of vaccinia virus capping enzyme.

Vaccinia virus capping enzyme, a heterodimer of 95-kDa and 33-kDa subunits, modifies the 5' RNA end and also acts as a transcription termination factor during synthesis of viral early mRNAs. Termination occurs in response to a specific signal, UUUUUNU, in the nascent RNA chain. We now report that purified capping enzyme binds to defined RNAs in solution to form complexes that are stable during native gel electrophoresis. Multiple enzyme molecules can bind to a single RNA. No particular 5' end structure is required for RNA binding, suggesting that the observed protein-RNA interaction is unrelated to the triphosphatase, guanylyltransferase, or methyltransferase functions of capping enzyme. Although binding does not require a UUUUUNU element in the RNA, complex formation is competed preferentially by poly(U) compared to poly(C). Capping enzyme binds to the synthetic 30-mer homopolymers to form a single protein-RNA complex; affinity for U-30 is 10-fold higher than for A-30. The sites of protein-RNA contact, as detected by UV cross-linking, are located predominantly within the 95-kDa capping enzyme subunit, which is itself sufficient to bind and cross-link to RNA in the absence of the small subunit.

Base Sequence↗

PubMed1993

Isolation, crystallization and preliminary diffraction analyses of human pancreatic alpha-amylase.

Human pancreatic alpha-amylase has been isolated using a glycogen affinity precipitation procedure and crystallized in a form suitable for high resolution three-dimensional X-ray crystallographic analyses. Crystals are of the orthorhombic space group P2(1)2(1)2(1), with unit cell dimensions of a = 53.04 A, b = 74.80 A and c = 137.34 A, and contain only one protein molecule per asymmetric unit. Diffraction data have been collected and found to extend to 1.6 A resolution. These studies form the basis for elucidating the full atomic structure of human pancreatic alpha-amylase and thereby providing insight into the catalytic mechanism of this enzyme.

Crystallization↗

PubMed1993

Serologic analysis of a murine chemokine, TCA3.

The TCA3 gene encodes a proinflammatory cytokine related to IL-8 and MCP-1 (JE). TCA3 mRNA is produced by T cells in response to stimulation with Ag or Con A. Glycosylated and nonglycosylated forms of rTCA3 produced by transfected Chinese hamster ovary cells were purified. rTCA3 was used to immunize hamsters and produce mAb. Four mAb were characterized; each was specific for TCA3, failing to react with the closely related molecule MCP-1 (JE). Western blotting also demonstrated that all four mAb specifically recognize rTCA3, native TCA3 produced by activated mouse T cells, and the nonglycosylated TCA3 core protein. A sensitive and specific capture ELISA for TCA3 quantitation was developed, allowing measurement of TCA3 levels in the supernatants from activated murine splenocytes and T cell clones. In addition, two mAb demonstrated dose-dependent neutralization of TCA3 inflammatory activity. Thus, the results directly demonstrate that TCA3 is expressed in an activation-specific manner by mouse T cells. The data also provide characterization of mAb reagents specific for this new cytokine.

Animals↗

PubMed1993

Three new monoclonal antibodies that define a unique antigen associated with prolymphocytic leukemia/non-Hodgkin's lymphoma and are effectively internalized after binding to the cell surface antigen.

Prolymphocytic leukemia (PLL) is closely related to chronic lymphocytic leukemia (CLL), but present with distinctive clinical/laboratory features and associated with much worse prognosis. In this study, we generated three new IgG1-kappa monoclonal antibodies (MoAbs), termed SN8, SN8a and SN8b, by use of an unconventional approach, ie, by using an isolated B PLL antigen preparation to immunize mice. These MoAbs, particularly SN8, showed a highly selective reactivity to B PLL and B non-Hodgkin's lymphoma (NHL) among various human leukemia-lymphoma specimens tested; eg, SN8 was capable of effectively distinguishing B PLL from B CLL as well as from hairy cell leukemia (HCL) cell specimens. The cell surface antigen defined by the three MoAbs was determined to be a covalently linked heterodimeric glycoprotein complex (gp49/40) consisting of a 49,000 dalton (alpha-chain) and a 40,000-dalton component (beta-chain). Epitope comparison showed that the epitope defined by SN8 (SN8 epitope) is in close proximity to SN8a epitope but in a distant position from SN8b epitope. Western blot analysis showed that both SN8 and SN8a epitopes are on the beta-chain, but SN8b epitope was not detected on either the alpha- or the beta-chain of the reduced antigen in the same analysis. Binding of either SN8 or SN8b to the cell surface gp49/40 did not cause significant downregulation of the antigen expression whereas binding of SN8a to the antigen caused small (approximately 20%) decrease in the antigen expression. Among the various normal peripheral blood cells, only a subpopulation (6.0% to 24.2% among different specimens derived from different donors) of B cells reacted with the SN8 series MoAbs; these MoAbs showed no significant reactivity against T cells, granulocytes, monocytes, erythrocytes, and platelets. Minimal or no significant reactivity (0 to 2.6% among different specimens) was detected against normal bone marrow cells. Ricin A-chain conjugates of the three MoAbs are all strongly effective for specific killing of SN8 antigen-expressing leukemia cells in the absence of any potentiators; furthermore, the addition of 10 mmol/L NH4Cl, a potentiator, enhanced strongly the cytotoxic activities of the SN8, SN8a, and SN8b conjugates. Thus, each of the three MoAbs was effectively internalized after binding to the cell surface antigen.

Animals↗

PubMed1993

A microsatellite genetic linkage map of human chromosome 18.

We isolated nine new microsatellite markers from chromosome 18 and further characterized and mapped eight microsatellites developed in other laboratories. We have constructed a framework linkage map of chromosome 18 that includes 14 microsatellite markers (12 dinucleotide and 2 tetranucleotide) and 2 RFLP markers. Cytogenetic localization for the microsatellites was performed by PCR amplification of 18 somatic cell hybrids containing different deletions of chromosome 18. Twelve of the microsatellites and one of the RFLPs have heterozygosites greater than 70%. The average heterozygosity of the markers included in the map is 72%. In addition, we have made provisional placements of 3 more microsatellite markers and 2 more RFLP markers. The map lengths (in Kosambi centimorgans) are as follows: sex-averaged, 109.3 cM; male, 72.4 cM; female, 161.2 cM. The average distance between markers in the sex-averaged map is 7.3 cM, and the largest gap between markers is 16.7 cM. Analysis of the data for differences in the female:male map distance ratio revealed significant evidence for a constant difference in the ratio (chi 2 = 32.25; df = 1; P < 0.001; ratio = 2.5:1). Furthermore, there was significant evidence in favor of a variable female:male map distance ratio across the chromosome compared to a constant distance ratio (chi 2 = 27.78; df = 14; P = 0.015). To facilitate their use in genomic screening for disease genes, all of the microsatellite markers used here can be amplified under standard PCR conditions, and most can be used in duplex PCR reactions.

Base Sequence↗

PubMed1993

Immunological status of patients with obstructive jaundice and immunostimulatory effect of arginine.

Sepsis is a major factor in the high mortality and morbidity following diagnostic and therapeutic procedures in patients with obstructive jaundice. The reasons for this increased susceptibility to infection are not fully understood. We therefore observed prospectively changes in immunological status of patients with obstructive jaundice in the perioperative period and studied immunological effects of perioperative arginine therapy. The results showed that there was a significant reduction in interleukin 2 (IL-2) production, interleukin 2 receptor (IL-2R) expression and lymphocyte response to phytohemagglutinin (PHA) mitogen in patients with obstructive jaundice compared with normal controls. After operation, the immune suppression in patients with obstructive jaundice was more significant. Arginine is a known T lymphocyte stimulator. Perioperative supplement with arginine significantly enhanced the immune function of patients with obstructive jaundice, the mechanism being related to increased IL-2 production and IL-2R expression.

Adjuvants, Immunologic↗