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Biomedical subjects

T D Lee

Publications and source records attributed to T D Lee.

At least 91 records · Page 5Linked to original sources
PubMed1994

Mouse liver NAD(P)H:quinone acceptor oxidoreductase: protein sequence analysis by tandem mass spectrometry, cDNA cloning, expression in Escherichia coli, and enzyme activity analysis.

The amino acid sequence of mouse liver NAD(P)H:quinone acceptor oxidoreductase (EC 1.6.99.2) has been determined by tandem mass spectrometry and deduced from the nucleotide sequence of the cDNA encoding for the enzyme. The electrospray mass spectral analyses revealed, as previously reported (Prochaska HJ, Talalay P, 1986, J Biol Chem 261:1372-1378), that the 2 forms--the hydrophilic and hydrophobic forms--of the mouse liver quinone reductase have the same molecular weight. No amino acid sequence differences were found by tandem mass spectral analyses of tryptic peptides of the 2 forms. Moreover, the amino-termini of the mouse enzymes are acetylated as determined by tandem mass spectrometry. Further, only 1 cDNA species encoding for the quinone reductase was found. These results suggest that the 2 forms of the mouse quinone reductase have the same primary sequences, and that any difference between the 2 forms may be attributed to a labile posttranslational modification. Analysis of the mouse quinone reductase cDNA revealed that the enzyme is 273 amino acids long and has a sequence homologous to those of rat and human quinone reductases. In this study, the mouse quinone reductase cDNA was also ligated into a prokaryotic expression plasmid pKK233.2, and the constructed plasmid was used to transform Escherichia coli strain JM109. The E. coli-expressed mouse quinone reductase was purified and characterized. Although mouse quinone reductase has an amino acid sequence similar to those of the rat and human enzymes, the mouse enzyme has a higher NAD(P)H-menadione reductase activity and is less sensitive to flavones and dicoumarol, 2 known inhibitors of the enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Formation of multiply charged ions from large molecules using massive-cluster impact.

Massive-cluster impact is demonstrated to be an effective ionization technique for the mass analysis of proteins as large as 17 kDa. The design of the cluster source permits coupling to both magnetic-sector and quadrupole mass spectrometers. Mass spectra are characterized by the almost total absence of chemical background and a predominance of multiply charged ions formed from 100% glycerol matrix. The number of charge states produced by the technique is observed to range from +3 to +9 for chicken egg lysozyme (14,310 Da). The lower m/z values provided by higher charge states increase the effective mass range of analyses performed with conventional ionization by fast-atom bombardment or liquid secondary ion mass spectrometry.

Animals↗
PubMed1994

Matrix-free desorption of biomolecules using massive cluster impact.

Massive-cluster impact (MCI) ionization was found to be capable of producing high secondary-ion yields from biological samples without the use of a liquid matrix. Dry samples of molecules as large as cytochrome c were observed to be efficiently desorbed without significant fragmentation by the MCI beam of glycerol clusters. In addition, signals from protonated molecules retained a significant proportion of their initial intensity even after several minutes exposure to the primary beam. It was determined that these remarkable phenomena are not the result of the build-up of a layer of glycerol caused by the cluster bombardment.

Amino Acid Sequence↗
PubMed1994

Homogeneous fluorescence detection method for human leukocyte antigen-DR typing following polymerase chain reaction amplification with sequence-specific primer.

A fluorescent homogeneous method for the detection of sequence-specific amplification of human leukocyte antigen (HLA) alleles has been developed. In this approach, polymerase chain reaction sequence-specific primers (PCR-SSP) are used to amplify DRB1, DRB3, and DRB4 alleles. Lambda exonuclease and Exonuclease I are added to reduce background by digesting template DNA, partial primer dimer, and primer. PCR amplicons are then detected following the addition of a fluorescent dye (thiazole yellow dimer) which binds to double-stranded DNA. No transfer or wash steps are required. Thus, the risk of sample contamination, which is a major source of inaccuracy for DNA amplification methods, is greatly reduced. This approach is also faster and more easily automated than the standard approach using gel electrophoresis and ethidium bromide staining. Speed and automation are important considerations for HLA typing since the number of possible alleles for each HLA type is substantial. A homogeneous HLA-SSP typing method may be especially useful for clinical labs doing large numbers of samples and for the eventual automation of HLA DNA typing.

Alleles↗
PubMed1994

Degradation of vasoactive intestinal polypeptide by rabbit gastric smooth muscle membranes.

Crude membrane fractions prepared from rabbit gastric fundic muscle degraded vasoactive intestinal polypeptide (VIP) with an average specific activity of 0.96 nmol/min/mg protein at 37 degrees C, pH 7.5, and at [S]o = 0.05 mM. The relative activities towards [Leu5]enkephalin, substance P, VIP, and neurotensin were approximately 7.7, 2.0, 1.0, and 0.54, respectively. The VIP degradation was inhibited by metal chelators EDTA and o-phenanthroline. CaCl2 at 0.3-1.0 mM enhanced VIP degradation up to twofold. Phosphoramidon, captopril, and bestatin, the specific inhibitors for endopeptidase-24.11, angiotensin-converting enzyme, and aminopeptidase M, respectively, did not affect VIP degradation significantly. However, the complex mixtures of VIP fragments generated implicates action of multiple peptidases including the aforementioned three peptidases and other unidentified peptidase(s).

Amino Acid Sequence↗
PubMed1994

Effects of bandwidth goals and bandwidth knowledge of results on motor learning.

An experiment is reported that contrasted two recent hypotheses about the guiding effects of knowledge of results (KR) on motor learning. Specifically, the purpose was to compare the impact of the nature of the KR itself versus the effect of the information conveyed by the KR on learning. We compared four groups of subjects, comprising a factorial combination of KR conditions (specific or bandwidth) and the movement timing goal (specific or bandwidth). All subjects performed 100 acquisition trials and 20 retention trials. The results revealed that bandwidth KR conditions facilitated learning, regardless of the specificity of the movement goal. These effects support the hypothesis that when error KR is provided, its very provision can block error detection activities that are important for retention performance.

Adult↗
PubMed1994

Red cells, HLA and platelet antibody formation in patients with multiple transfusions.

Totally 436 Chinese patients having received multiple transfusions of red cells and platelets on more than three occasions were screened for red cell antibodies. Twenty-six (6%) of them were positive. Anti-E, -Mia, and -c were the common alloantibodies. Nine patients were immunized during the period of regular transfusions, with a newly immunized rate of 2% (9/436). Among 436 patients, 387 were screened for HLA antibodies by lymphocytotoxicity test (LCT). The overall positive rate was 35%. Most of the antibodies identified were against the high-frequency HLA antigens in the Chinese population. About 10% of the LCT-positive cases reverted to negative state during the follow-up period. After chloroquine stripping of the target platelets, mixed passive hemagglutination assay was used to detect platelet antibodies other than HLA antibody. Fifty-eight of 161 cases (36%) were positive for platelet antibodies, but half of them disappeared within 1 month. Nineteen of the 58 patients had sepsis and 2 had jaundice. These findings suggested that HLA and platelet antibodies are common among Chinese, though their clinical significance and the role in platelet damage are doubtful.

Antibody Specificity↗
PubMed1993

Electrospray ionization mass spectrometry as a mechanistic tool: mass of human leucocyte elastase and a beta-lactam-derived E-I complex.

We have utilized liquid chromatography electrospray ionization mass spectrometry (ESI-MS) to probe the nature of the covalent E-I complex of human leucocyte elastase (HLE) and a beta-lactam. The mass spectrum of HLE isozyme 4 displayed one major and two minor components with masses of 25,202, 25,043, and 24,522 Da, respectively. Isozyme 3 displayed three components, with masses of 25,180, 24,030, and 24,523 Da. These data suggest that the isozymes differ in the type and not the content of carbohydrate. The minor components represent decreases in carbohydrate content. Inactivation of isozyme 4 with trans-4-(ethoxycarbonyl)-3-ethyl-1-[(4-nitrophenyl)sulfonyl]-azetidin -3-one increased the mass of the three components by that of the parent compound. Similar results were obtained with the mixture of HLE isozymes. These observations demonstrate that HLE does not catalyze the beta-elimination of p-nitrophenylsulfinate as Firestone et al. [(1990) Tetrahedron 46, 2255) suggested. In addition, it suggests that a "double hit" of both the active-site serine and histidine is not required to form a stable acyl-enzyme. Noncovalent complexes between HLE and either the tight-binding secretory leucoprotease inhibitor (SLPI) or a slow tight-binding peptide difluoroketone inhibitor were not observed by ESI-MS. SLPI displayed a mass of 11,710 Da in the absence and presence of HLE. These data demonstrate the utility of ESI-MS to probe the mechanism of inhibition of enzymes by mechanism-based inhibitors.

Anti-Bacterial Agents↗
PubMed1993

The use of hydrogen-deuterium exchange to facilitate peptide sequencing by electrospray tandem mass spectrometry.

The utility of hydrogen-deuterium exchange for sequencing peptides by mass spectrometry is demonstrated. The number of exchangeable hydrogens in a peptide is readily obtained by electrospray analysis of the peptide dissolved in deuterated solvents. This information can be used, in conjunction with published computer algorithms for interpreting peptide mass spectra, to reduce significantly the number of candidate sequences that fit the experimental data. This information, when combined with fragment-ion information in the mass spectrum, greatly increases the reliability of sequence determination.

Amino Acid Sequence↗
PubMed1993

Acquiring bimanual skills: contrasting forms of information feedback for interlimb decoupling.

The present experiments addressed the learner's capability to perform different upper-limb actions simultaneously with the help of various sources of information feedback. An elbow flexion movement was made in the left limb together with a flexion-extension-flexion movement in the right limb. Interlimb interactions were assessed at the structural as well as the metrical level of movement specification during acquisition and retention. Despite a strong initial tendency for the limbs to be synchronized, findings revealed that Ss became gradually more successful in interlimb decoupling as a result of practice with augmented feedback. However, detailed knowledge of movement kinematics was no more effective than global outcome information for interlimb decoupling, indicating that knowledge of results may have more potential for acquiring multiple degree-of-freedom tasks than previously believed. Finally, the data support the general notion that learning new coordination tasks involves the suppression of preexisting preferred coordination tendencies, which is often a prerequisite for building new coordination modes.

Adolescent↗
PubMed1993

Contextual interference in movements of the same class: differential effects on program and parameter learning.

Contextual interference effects in motor learning usually were not found when the tasks to be learned presumably required the same generalized motor program (GMP) and differed only with regard to the movement parameters (see Lee, Wulf, & Schmidt, 1992; Magill & Hall, 1990). Thus, tasks requiring different motor programs (e.g., different relative timings) seemed to be a prerequisite for random practice to be more effective than blocked practice. However, the previous studies (that did not find random/blocked differences) used global error measures that confounded errors in relative timing and errors in absolute timing. In the present study, subjects practiced three movement patterns that had the same relative timing (requiring the same GMP) but different overall durations (requiring different parameters). Errors in relative timing and in absolute timing were assessed separately. The results indicate that random practice is more effective for the learning of relative timing (GMP learning) and less effective for the learning of absolute timing (parameter learning) than blocked practice. Preliminary ideas as to the reasons for this effect are discussed.

Journal Article↗
PubMed1993

Variance and invariance in expert and novice triple jumpers.

The purpose of this study was to examine relative timing, relative distance, and effector independence characteristics of the triple jump. We videotaped expert and novice triple jumpers using standing and running starts. On some trials, the triple jumpers were required to take off from their nondominant leg. Gentner's (1987) interaction test was used to assess the proportional duration model in describing the timing of the component submovements. For both experts and novices, the proportional durations varied with the type of start. For experts, the relative timing of the jump components was independent of the take-off leg. The findings were mixed for the novices. Similar results were obtained when relative distance was examined. These results are discussed with respect to constructs related to variability in skilled performance.

Adult↗
PubMed1993

The effect of acidified glucose nutrient solution on preservation of platelet concentrate.

The preservation effect of a new platelet solution--acidified glucose nutrient solution (AGN)--was tested by adding AGN to pooled platelet rich plasma (PRP) prior to preparation of platelet concentrates (PC). Each PRP unit was prepared from a unit of whole blood and four PRP of the same blood group were pooled in 400 ml volume PVC bags. Equal aliquots of each pooled PRP were made prior to preparation of PC. AGN was added to one aliquot and nothing was added to the control aliquot. Equal volume and concentration PC were then prepared and the PC were further aliquoted for storage at 22 degrees C. After five days, the parameters of platelet count, pH, aggregability and hypotonic shock response (HSR) for PC preserved in AGN plasma were better than those of the controls preserved in normal ACD plasma. The aggregability and HSR of AGN platelet concentrates recovered to baseline after two h of incubation with fresh plasma. The results of electron microscopy show that platelets preserved in AGN have less changes in morphology. The results of our work suggest that the preservation effect of AGN on PC is similar to the effect of using second generation containers or preparation of platelets from thrombocytapheresis.

Blood Platelets↗
PubMed1993

Taiwan Blood Donation Program: a model for development.

In 1974, the Taiwan National Blood Program had not yet been fully developed. The volunteer donor base was less than 5% and there was no organized national structure or regulation of blood services. Following the founding of the Blood Donation Association and the Blood Services Foundation, promotion of an all-volunteer blood program, increased utilization of blood components and the standardization of laboratory methods were strategies that led to the development of the Taiwan National Blood Program. In 1991, 1,066,082 units of blood were collected in Taiwan, serving a population of about 20 million. There are currently 6 major blood centers and 13 blood stations. Blood donation is now 100% volunteer and 78% of all blood collected is separated into 10 available components. With national organization and regulation, the transition has taken 17 years and has resulted in a community-based, all-volunteer blood supply.

Blood Component Removal↗
PubMed1993

Potentiation of IgE responses to third-party antigens mediated by Ascaris suum soluble products.

A reductive approach was used to examine the potentiation of IgE responses by nematode infection. Ascaris homogenized extract, Ascaris pseudocoelomic (body) fluid (ABF) and purified Ascaris allergen (ABA) were tested for their ability to act as protein carriers and as mediators of potentiated IgE responses to third-party (ovalbumin; OVA) responses. All three nematode products were excellent protein carriers for the hapten dinitrophenol and showed significantly better activity in this respect than OVA. Neither ABF nor ABA enhanced the level of the IgE response to the third-party antigen but both prolonged the response markedly. ABF, but not ABA, induced high levels of total circulating IgE when given at the same time as OVA with alum. The data suggest that the enhancement and prolongation of IgE responses by nematodes may be two separate but related activities.

Allergens↗