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Biomedical subjects

S Hsieh

Publications and source records attributed to S Hsieh.

At least 19 recordsLinked to original sources
PubMed1998

Separation and identification of peptides in single neurons by microcolumn liquid chromatography-matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and postsource decay analysis.

Microcolumn liquid chromatography (LC) was interfaced with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) for separation and identification of peptides present in single neurons from the brain of the snail Lymnaea stagnalis. The nanoliter microcolumn LC effluent, mixed off-line with nanoliter matrix solution, was deposited onto the sample target every 60 s, producing fractions of approximately 145 nL in volume, which, upon drying, produced spots of approximately 1 mm in size. At the end of the chromatographic separation, fractions from the sample target were scanned by MALDI-TOF-MS. Identification of peptide peaks was achieved on the basis of LC elution order and mass information. Further identification based on sequence information was carried out for a native peptide fractionated by microcolumn LC from a single neuron with the postsource decay technique.

Animals↗
PubMed1998

Quantal corelease of histamine and 5-hydroxytryptamine from mast cells and the effects of prior incubation.

Corelease of histamine and 5-hydroxytryptamine from individual mast cells has been measured with fast-scan cyclic voltammetry using a carbon-fiber electrode placed next to a single cell. Release events, induced by exposure of the cells to the calcium ionophore, A23187, were resolved at the level of individual exocytotic events. Changes in the relative concentrations secreted from individual granules were observed after incubation with 5-hydroxytryptamine, histamine, and tryptophan. In contrast, an alteration in individual cell content after such incubations, analyzed with capillary chromatography, was only found after incubation with 5-hydroxytryptamine. Cells incubated with 5-hydroxytryptamine or its precursor, tryptophan, released more 5-hydroxytryptamine and less histamine per secretory event relative to controls. Coincubation of the cells with pargyline and 5-hydroxytryptamine further reduced the release of histamine. Since cell content of histamine is unchanged, the reduction in its release must be due to its displacement to a nonreleasable compartment induced by 5-hydroxytryptamine granular uptake. Incubation with histamine increased histamine secretion and, surprisingly, also increased 5-hydroxytryptamine release without changing its cell content. This result is consistent with a relaxation of the storage matrix accompanying histamine granular uptake allowing more 5-hydroxytryptamine to be released. These results demonstrate that the intragranular mode of storage as well as granular uptake of biogenic amines affects the stoichiometry of their release.

Animals↗
PubMed1997

Determination of enzyme activity in single bovine adrenal medullary cells by separation of isotopically labeled catecholamines.

A microcolumn liquid chromatography method for determining norepinephrine (NE), epinephrine (E), and phenylethanolamine N-methyltransferase (PNMT) enzyme activity in single bovine adrenal medullary cells is presented. Single cells were isolated and treated with excess deuterated substrate, D3-NE (0.05 mM) for enzyme reaction. After 6 h, the reaction was quenched and the product, D3-E, was quantified along with endogenous NE and E. Separation and detection of deuterated and protiated NE and E were achieved with microcolumns (110-125 cm long, 25 microns inner diameter) packed with 3 microns octadecylsilane-modified particles and operated with amperometric detection. Of the 33 cells reported, most cells containing predominantly E have enzyme activity while cells containing predominantly NE and cells containing a mixture of both NE and E show no enzyme activity. After incubation with 10 microM hydrocortisone, of the 17 cells reported, most cells containing predominantly E and cells containing a mixture of both NE and E have enzyme activity while cells containing predominantly NE have no enzyme activity. Detection limits for NE and E were 42 and 48 amol, respectively.

Adrenal Medulla↗
PubMed1996

Organization and chromosomal localization of the gene encoding the mouse acid labile subunit of the insulin-like growth factor binding complex.

After birth, most of insulin-like growth factor I and II (IGFs) circulate as a ternary complex formed by the association of IGF binding protein 3-IGF complexes with a serum protein called acid-labile subunit (ALS). ALS retains the IGF binding protein-3-IGF complexes in the vascular compartment and extends the t1/2 of IGFs in the circulation. Synthesis of ALS occurs mainly in liver after birth and is stimulated by growth hormone. To study the basis for this regulation, we cloned and characterized the mouse ALS gene. Comparison of genomic and cDNA sequences indicated that the gene is composed of two exons separated by a 1126-bp intron. Exon 1 encodes the first 5 amino acids of the signal peptide and contributes the first nucleotide of codon 6. Exon 2 contributes the last 2 nt of codon 6 and encodes the remaining 17 amino acids of the signal peptide as well as the 580 amino acids of the mature protein. The polyadenylylation signal, ATTAAA, is located 241 bp from the termination codon. The cDNA and genomic DNA diverge 16 bp downstream from this signal. Transcription initiation was mapped to 11 sites over a 140-bp TATA-less region. The DNA fragment extending from nt -805 to -11 (ATG, +1) directed basal and growth hormone-regulated expression of a luciferase reporter plasmid in the rat liver cell line H4-II-E. Finally, the ALS gene was mapped to mouse chromosome 17 by fluorescence in situ hybridization.

Amino Acid Sequence↗
PubMed1996

Preparation and evaluation of slurry-packed liquid chromatography microcolumns with inner diameters from 12 to 33 microns.

Fused silica capillary liquid chromatography columns with inner diameters between 12 and 33 microns were slurry packed with 5 microns octadecylsilane-modified silica particles. Column efficiencies and van Deemter coefficients were compared. A linear decrease of the A term as column diameter was decreased was the most significant contributor to a lower overall plate height at the optimum velocity.

Chemical Phenomena↗
PubMed1996

Visuospatial orienting of attention in Parkinson's disease.

Orienting attention to visual stimuli was studied in 13 patients with Parkinson's disease whose responses were compared to those of a matched control group using a cued reaction-time task which measured cost and benefit effects of orienting of attention. Both groups were screened to exclude dementia, psychiatric disease, and other neurological abnormalities. Although Parkinson patients showed overall slow mean reaction time, responses showed a pattern of cost and benefit effects similar to that of the control group. The results suggested that Parkinson patients are not impaired on visuospatial orienting of attention on this task.

Aged↗
PubMed1996

Precued shifting of attention between cognitive sets in Parkinson patients.

The precueing paradigm developed by Posner has been used to examine visuospatial shifting of attention. In the current study, we modified such a paradigm so that it could be studied in nonvisuospatial domains and its component processes of disengagement, movement, and engagement could be analyzed in a similar fashion to the visuospatial domains. 14 patients with Parkinson's disease and 14 normal controls matched for age, sex, handedness, and years of education served as subjects. The speed of shifting attention was measured using the cost and benefit analysis. Analyses showed an over-all slowness in reaction time of patients with Parkinson's disease compared to the control group but without a concomitant slowness to engage, shift, and disengage their attention.

Aged↗
PubMed1995

Electrochemical detection of histamine and 5-hydroxytryptamine at isolated mast cells.

The electrochemical oxidation of histamine has been investigated as an analytical tool. In a physiological buffer, histamine is oxidized at carbon fiber microelectrodes at potentials close to the background in a chemically irreversible process. Cylindrical carbon fiber electrodes were used as amperometric detectors for histamine separated with a reversed-phase capillary column, and detection limits of 240 amol were achieved. Electrodes with beveled tips were used as real-time sensors by monitoring with repetitive cyclic voltammograms at a scan rate of 800 V/s with a 16.7-ms repetition rate, and detection limits of 1.4 microM were achieved. Both techniques were used to probe histamine and 5-hydroxytryptamine (5-HT) stored in rat peritoneal mast cells. The content in single cells was measured by capillary HPLC, and both substances were found in single cells. Although the analysis revealed a large cell-to-cell variation in the amount of histamine and 5-HT, the average amount was 150 and 4 fmol of histamine and 5-HT, respectively. Release of histamine and 5-HT was measured with the electrode placed 1 microm from the cell surface. Release was observed as a series of sharp concentration spikes, consistent with corelease of the two substances from individual vesicles following exocytosis.

Animals↗
PubMed1995

Structure and regulation of the ALS gene.

The mouse ALS gene spans at least 6 kb. It contains 2 exons which encode a protein highly homologous to human and rat ALS. It was localized to mouse chromosome 17 by flourescent in situ hybridization. The 5' flanking region lacks a TATA box but contains GC boxes that may be recognised by transcription factors such as Spl. Hepatic ALS mRNA is decreased in rats following hypophysectomy, and restored by stimulated ALS promoter activity in a rat hepatoma cell line, but not in 3T3-F442A mouse preadipocyte fibroblasts, suggesting that utilisation of the ALS promoter is cell-type specific. The rat hepatoma system is a promising system to study the regulation of ALS gene expression, and the signalling pathways of CH regulation.

Animals↗
PubMed1995

Stimulus-driven or autonomous shift or attention?

Hsieh and Allport studied shifts of attention in semantic space, using a semantic monitoring task based on rapid, serial, visually presented sequences of words. They reported that following a shift of criterion, accuracy of semantic monitoring dropped abruptly to a low level, then gradually recovered to reach the preshift level over successive stimuli in the sequence. They further examined the nature of the recovery of accuracy following a shift of criterion. Despite the striking results they obtained, some problems of their design remained. Hence, the current research replicated Hsieh and Allport's experiments with some modifications and showed that a shift of semantic criterion in a rapidly presented sequence indeed appears to be stimulus-driven rather than an autonomous process.

Adult↗
PubMed1995

Set-shifting aptitude in Parkinson's disease: external versus internal cues.

A modified version of the odd-man-out test was used to investigate set-shifting aptitude in 12 patients with Parkinson's disease. We asked subjects to execute in alternation two different sorting rules over successive items. External and internal cueing conditions were employed. Patients with Parkinson's disease were impaired on the tasks with internal cues but were normal on the tasks with external cues. Moreover, the shift costs were consistently larger for the shift to the easier task than the shift to the more difficult task. These findings indicated that the model of 'Supervisory Attentional System' may not be sufficient to explain the data as Brown and Marsden (1988) originally suggested.

Aged↗
PubMed1995

Ifosfamide/carboplatin/etoposide chemotherapy in patients with metastatic non-small cell lung cancer.

We have evaluated the combination of ifosfamide, carboplatin, and etoposide (ICE) along with mesna in 46 patients with stage IV non-small cell lung cancer. Treatment consisted of ifosfamide (1.25 g/m2/d with mesna) and etoposide (80 mg/m2/d) given intravenously on days 1 to 3 and carboplatin (300 mg/m2) given intravenously on day 1 every 4 weeks. Eligibility criteria included measurable disease; adequate hematologic, hepatic, and renal functions; no prior chemotherapy; and an Eastern Cooperative Oncology Group performance status (PS) of 0 to 3. Two patients were lost to follow-up and one had received prior chemotherapy, leaving 43 patients evaluable for response and toxicities. There were 27 male and 16 female patients. Twenty-three patients had a PS of 0 or 1 and 20 had a PS of 2 or 3. Eighteen patients had received prior radiotherapy. There were two complete responses and nine partial responses. The response rate was 35% in PS 0 or 1 patients and 15% in PS 2 or 3 patients. The most frequent toxicity was myelosuppression; 44% of patients experienced grade 3 or 4 leukopenia and 14%, grade 3 or 4 thrombocytopenia. Patients receiving prior radiation were significantly more prone to develop leukopenia (P = .01). Five patients developed leukopenic fever, and three died of sepsis. Gastrointestinal toxicities were mostly mild. No neurologic or genitourinary toxicities were observed. The median length of survival was 209 days for patients with a PS of 0 or 1 and 123 days for the entire group. The 1-year survival rate was 22% and 19%, respectively, in these two patient subgroups. ICE is an active regimen in patients with metastatic non-small cell lung cancer and a good PS. Myelosuppression is the major dose-limiting toxicity. Hematopoietic growth factors may be indicated in subsequent studies, especially in patients who had prior radiation therapy. The therapeutic effect of ICE on patients with a poor PS remains unsatisfactory and requires further investigation.

Adult↗
PubMed1994

Recombinant human insulin-like growth factor (IGF)-binding protein-6 inhibits IGF-II-induced differentiation of L6A1 myoblasts.

Insulin-like growth factor-binding protein-6 (IGFBP-6) is an O-linked glycoprotein that binds insulin-like growth factor-II (IGF-II) with marked preferential affinity over IGF-I. Recombinant human IGFBP-6 (rhIGFBP-6) was synthesized by COS-7 monkey kidney cells that were transiently transfected with a eukaryotic expression vector into which a complementary DNA for IGFBP-6 modified for optimal translation had been inserted. rhIGFBP-6 was similar to IGFBP-6 purified from human cerebrospinal fluid with respect to IGF binding and O-glycosylation. The effect of rhIGFBP-6 on IGF-induced L6A1 myoblast differentiation was studied using creatine kinase activity as an index of differentiation. rhIGFBP-6 inhibited differentiation initiated by IGF-II in a dose-dependent manner, inhibition was complete when rhIGFBP-6 was present in a slight molar excess. In contrast, rhIGFBP-6 had no effect on IGF-I-induced differentiation, even when coincubated in a 5-fold molar excess. These results are consistent with the preferential affinity of IGFBP-6 for IGF-II. As cell association and proteolysis have been associated with the potentiation, rather than the inhibition, of IGF action by IGFBPs, we investigated whether they occurred in the L6A1 myoblast system. After incubation of L6A1 myoblasts with rhIGFBP-6, IGFBP-6 was recovered from the medium, but not from cell lysates or extracellular matrix. In addition, [125I]IGFBP-6 did not bind to myoblast monolayers, and there was no evidence that proteolysis had occurred. Together, these results indicate that rhIGFBP-6 remains intact and soluble and, hence, inhibits IGF-II-induced differentiation. The fidelity of the IGFBP-6 expression system used for these studies will enable us to use this system to determine how structural modifications of the protein affect the modulation of IGF action by IGFBP-6.

Animals↗
PubMed1994

Shifting attention in a rapid visual search paradigm.

A method is introduced for studying shifts of attention in semantic space, testing 56 subjects in four experiments on a semantic monitoring task based on rapid, serial, visually presented (RSVP) word-sequences. Following a cue to shift attention, accuracy of semantic monitoring drops abruptly to a low level, then gradually recovers to reach preshift levels over successive stimuli in the RSVP sequence. Using this method, we compared two kinds of criterion-shifts, one requiring a set-reversal ('reversal shifts'), the other involving a shift between orthogonally defined categories ('orthogonal shifts'); no differences were found. We have also examined the difference in a shift between two different processing domains (semantic vs typographic) compared with a shift of criterion within the same processing domain. The results showed no differences for within- vs between-domain shifts. Finally, we studied the time-course of a semantic attention shift. Execution of a semantic shift did not follow an internally controlled time-course but was a direct function of the rate of stimulus presentation. No evidence was found for the operation of a 'supervisory attentional system' independent of external stimulus triggering.

Attention↗
PubMed1993

Binding of mutants of human insulin-like growth factor II to insulin-like growth factor binding proteins 1-6.

A family of six specific insulin-like growth factor binding proteins (IGFBPs) modulates the biological actions of the insulin-like growth factors, IGF-I and IGF-II. In the present study, we determined the binding affinity of purified human IGFBPs 1-6 for recombinant human IGF-II mutants whose binding to IGF-I, IGF-II/mannose 6-phosphate, and insulin receptors was previously reported (Sakano, K., Enjoh, T., Numata, F., Fujiwara, H., Marumoto, Y., Higashihashi, N., Sato, Y., Perdue, J. F., and Fujita-Yamaguchi, Y. (1991) J. Biol. Chem. 266, 20626-20635). Of the regions studied, the most important determinants of IGF-II binding to the IGFBPs were A-domain residues 48-50 and B-domain residue 26. Substitution of residues 48-50 with the analogous residues from human insulin (Thr-Ser-Ile) reduced binding to IGFBP-1, -5, and -6 more than 50-fold and to IGFBP-4 by 15-50-fold; binding to IGFBP-2 and -3 was reduced 6-12-fold. The same substitution markedly reduced binding to the IGF-II/mannose 6-phosphate receptor but not to IGF-I or insulin receptors. Although substitution of residues 54 and 55 with the analogous residues from IGF-I (Arg-Arg) abolished binding to the IGF-II/mannose 6-phosphate receptor, binding to IGFBPs was not substantially affected. Substitution of Phe26 with Ser or Leu, which decreased binding to the IGF-I and insulin receptors, reduced binding to IGFBP-1 and -6 up to 80-fold, but had lesser effects on the other IGFBPs. [Leu27]IGF-II and [Leu43]IGF-II, which had a more markedly reduced affinity for the IGF-I and insulin receptors than did [Ser26]IGF-II, were bound by the IGFBPs with relatively unchanged affinity compared with IGF-II. Thus, the determinants of IGF-II binding to IGFBPs partially overlap those for the IGF-II/mannose 6-phosphate receptor and overlap those for the IGF-I receptor to a lesser extent. IGFBP-1 and IGFBP-6 are most sensitive to changes in IGF-II structure, although IGFBP-1 binds IGF-I and IGF-II with equal affinity, whereas IGFBP-6 has a marked preferential binding affinity for IGF-II. IGF-II mutants with selective impairment in recognition by specific IGFBPs or receptors will provide a useful tool for dissecting the role of the different IGF binding macromolecules in the mediation of IGF-II actions.

Amino Acid Sequence↗
PubMed1993

Ethnic and gender differences in drug users' perceived need for treatment.

Little is known about ethnic and gender variation in drug users' perceived need for treatment or about the predisposing factors that might account for such variation. Among 1,170 drug-using arrestees in Los Angeles, perceived need for treatment is positively related to these predisposing factors: self-reported drug dependence, attitude toward treatment for drug use, and occurrence of drug-related problems other than dependence. Self-reported drug dependence is higher among women and accounts for the greater perceived need reported by women. Hispanics are less likely to perceive a need for treatment. Among daily drug users, both Hispanics and Africans Americans are less likely to do so. These ethnic differences are not explained by self-reported drug dependence or any other predisposing factor. Implications for treatment referral, intake, and counseling are discussed.

Adolescent↗
PubMed1993

Methadone maintenance and needle/syringe sharing.

Drug users who inject drugs while in treatment share needles/syringes less often than users not in treatment. This relationship may reflect treatment processes, such as cognitive or normative change, by which treatment clients are influenced to lower their HIV infection risk. However, reduced needle/syringe sharing among treatment clients may instead be simply a collateral result of reduced injection frequency. In this sample of injection drug users, those who continued to inject while in methadone maintenance treatment reported less sharing than users not in methadone maintenance. This relationship persisted after injection frequency and drug-user background characteristics were controlled. Efforts to identify explanatory treatment processes were, however, not successful.

Adult↗