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Biomedical subjects

S Hsu

Publications and source records attributed to S Hsu.

At least 19 recordsLinked to original sources
PubMed1998

Phosphodiesterase activity in intrapulmonary arteries and veins of perinatal lambs.

The transition from fetal to newborn life is marked by a reduction in pulmonary vascular tone mediated by the intracellular second messengers, cGMP and cAMP. We have compared the rates of phosphodiesterase (PDE)-catalyzed hydrolysis of cGMP and cAMP in intrapulmonary vessels of fetal (146 +/- 2 days gestation) and newborn (3-7-day-old) lambs, each n = 6. Lung vessels of second to sixth generations were dissected and cytosol was prepared by differential centrifugation. PDE activity in cytosol was determined by radiometric assay of the hydrolysis of exogenous nucleotides at 30 degrees C for 10 min. Rates of hydrolysis (pmol/min/mg protein) of cGMP were 225 +/- 38 in fetal arteries and different from 151 +/- 7 in veins. In newborn vessels, the rates were 155 +/- 49 and 63 +/- 13 in arteries and veins, respectively. Rates of cAMP hydrolysis by the fetus were 80 +/- 11 in arteries and 45 +/- 16 veins. In newborn lambs the rates were 69 +/- 10 in arteries and different from 18 +/- 4 in veins. Inhibition of PDE activity by zaprinast, a cGMP-specific PDE inhibitor, and rolipram, a cAMP-specific PDE inhibitor, was more in veins of fetal and newborn lambs. Our data show that rates of hydrolysis of the cyclic nucleotides were faster in fetal vessels than in the newborn. We speculate that this would result in a greater accumulation of the cyclic nucleotides in newborn vessels, particularly the veins, and therefore endow the veins with less vascular tone.

Animals↗
PubMed1998

Spores and mycelia in cutaneous chromomycosis.

In 2 cases of cutaneous chromomycosis, potassium hydroxide preparations of lesional crust/scale easily revealed characteristic Medlar bodies. However, in both instances mycelia were also demonstrated. This contradicts the prevailing belief that concomitant spores and mycelia are found only in cerebral chromomycosis.

Biopsy↗
PubMed1998

Rapid, automated assay for progesterone on the Abbott AxSYM analyzer.

We describe an automated assay for progesterone (P4) in human serum and plasma with the Abbott AxSYM random-access immunoassay analyzer. In this one-step competitive assay, P4 immobilized onto latex microparticles competes with sample P4 for binding to a conjugate of alkaline phosphatase (AP) and anti-P4 antibody. Total CVs ranged from 3.4% to 8.2% in multiple precision studies conducted according to the 20-day NCCLS EP5-T protocol. The detection limit (zero calibrator + 2 SD) was 0.10 microg/L across 36 experiments. Values for diluted samples were 83-116% of expected. Recovery of P4 added to serum specimens was 92-115%. Cross-reactivities with 43 natural and synthetic steroids were 0-6.3%. No significant interference was detected from bilirubin, protein, erythrocytes, hemoglobin, triglycerides, or cholesterol. In a multisite correlation study, AxSYM P4 results compared well with results from a commercial RIA method (n = 1156; r = 0.976; slope = 1.03; y-intercept = 0.04). Assay throughput is >80 tests per hour in batch mode, 60 tests per hour with mixed load list configurations.

Autoanalysis↗
PubMed1997

Transcutaneous multielectrode basket catheter for endocardial mapping and ablation of ventricular tachycardia in the pig.

BACKGROUND: Endocardial mapping using standard electrode catheters is often technically limited in ventricular tachycardia and constitutes a major obstacle to successful ablation. We wished to examine the utility of a basket-shaped multielectrode mapping catheter (MMC) in the mapping and ablation of ventricular tachycardia. METHODS AND RESULTS: This study of sustained monomorphic ventricular tachycardia (SMVT) was conducted in two phases in the postinfarction pig model. In the first phase, the utility of the MMC in providing adequate localization of potential ablation site(s) of SMVT by different techniques (presystolic potentials, pace mapping, and concealed entrainment) was assessed in 21 pigs. In the second phase, ablation of induced SMVT was attempted in 10 pigs. Mapping of SMVT was performed after percutaneous introduction of the MMC to the LV. Comprehensive mapping was performed in 90 episodes of SMVT and required 2.0 to 25 seconds. Diastolic potentials were recorded during 86 episodes; good or identical pace maps (> or = 9 of 12 paced surface ECG leads identical to ventricular tachycardia surface ECG leads) were obtained in 25 of 31 maps, and entrainment was achieved during 28 of 42 SMVTs. In 10 pigs, 10 SMVTs were recorded at least twice and were considered for radiofrequency ablation. An 8-mm tip ablation catheter was advanced to potential ablation sites with a specially designed "homing" device, requiring a median time of 120 seconds. In these 10 pigs, either identical pace map (> or = 11 of 12, 6 SMVTs) or concealed entrainment (4 SMVTs) guided the ablation procedure. After ablation, 8 of 10 SMVTs were rendered noninducible, while 2 pigs died during energy application of degeneration of SMVT to ventricular fibrillation. CONCLUSIONS: The MMC allows rapid, comprehensive, and reliable endocardial mapping during SMVTs, which facilitates successful ablation in the porcine post-myocardial infarction model.

Animals↗
PubMed1997

Characterization of the effects of amphotericin B on ion channels in MDCK cells using the patch-clamp technique.

Cultured Madin-Darby Canine Kidney cells were used as a model to study the mechanism of nephrotoxicity of amphotericin B using the patch-clamp technique. At the whole-cell level, amphotericin B altered potassium conductances in two types of these cells categorized on the basis of whole-cell potassium currents. The first cell type, classified as Type I, exhibited no significant whole-cell potassium currents. The second type, Type II, exhibited depolarization-induced outward potassium currents that rundown over time. In both of these subpopulations, exposure to amphotericin B at a concentration of 68 nM for a prolonged period of time (approximately 30-45 min) led to an increased whole-cell potassium conductance. In Type I cells, it increased by a factor of 16 and in Type II cells, by a factor of 3.5. Furthermore, the potassium currents observed in Type I cells following amphotericin B treatment bore no resemblance to currents through pores formed by amphotericin B in artificial membranes. At the single-channel level, incubation with amphotericin B led to a significantly higher potassium channel activity in both inside-out and outside-out patches. Kinetic studies in inside-out patches revealed that the increases in channel activity were associated with a decrease in the mean closed time and an overall increase in the mean open time. In summary, our data suggest that the direct toxicity of amphotericin B is primarily related to its ability to disturb normal ion channel functioning rather than to formation of pores in cell membranes.

Amphotericin B↗
PubMed1997

Unilateral rotational path removable partial dentures for tilted mandibular molars: design and clinical applications.

This article describes the design of a unilateral rotational path removable partial denture to restore a single edentulous space with a tilted mandibular molar. It is modified from an original bilateral rotational path design and consists of several components, which are (1) the rotation axis, (2) the long occlusal rest, (3) the short bracing arms, (4) the rigid retainer and extended proximal plates, (5) the conventional direct retainer assembly, and (6) optional auxiliary rest. The stability and retention of the denture are controlled anteriorly by the buccal retentive clasp and lingual guide plate of the conventional direct retainer, and posteriorly by the rigid retainer and its buccally and lingually extended proximal plates. The clinical results of the dentures used in strictly selected situations are excellent; however, it is emphasized that a unilateral denture is only an alternative rather than a routine application. The risk of accidental aspiration is also of concern.

Deglutition↗
PubMed1997

On matching compliance between canine carotid arteries and polyurethane grafts.

Compliance mismatch between a host artery and an implanted graft has been suggested as a contributing factor to a small diameter graft failure. In this study, static compliance and dynamic compliance were defined and measured in vitro and in vivo for canine carotid arteries and 2 types of polyurethane grafts. Based on these compliance values, the circumferential modulus (E[theta]) and longitudinal modulus (Ez) were calculated. It was shown that grafts have constant moduli over a wide range of pressure while the moduli of carotid arteries increase significantly with increasing pressure (dynamic E[theta] from 0.20 to 1.32 MPa). Polyurethane grafts are nearly isotropic, with the modulus almost identical in each direction, while carotid arteries are anisotropic (E[theta]/Ez = 2-3). The dynamic moduli are generally higher than static values and are especially pronounced for arteries. Due to these different inherent characteristics, the compliance of a synthetic graft may match that of the host artery only in the circumferential direction and within a small pressure range. A stated limitation is therefore given for complete compliance matching. The results provide a rationale for identifying the degree of compliance match. These efforts may lead to better designed vascular grafts.

Animals↗
PubMed1997

Multiple control elements mediate activation of the murine and human interleukin 12 p40 promoters: evidence of functional synergy between C/EBP and Rel proteins.

Interleukin 12 (IL-12) is a heterodimeric cytokine whose activity is critical for T-helper 1 responses. The gene for the IL-12 p40 subunit is expressed in macrophages following induction by bacterial products, and its expression is augmented by gamma interferon. In this study, we performed a functional analysis of the murine and human p40 promoters in the murine macrophage cell line RAW 264.7. Transcription from the murine p40 promoter was strongly induced by lipopolysaccharide and heat-killed Listeria monocytogenes (HKLM), but promoter activity was not enhanced by gamma interferon. Multiple cis-acting elements involved in activated transcription were identified through an extensive mutant analysis. The most critical element, whose activity is conserved in mice and humans, is located between positions -96 and -88 relative to the murine transcription start site. This element exhibits functional synergy with a previously described NF-kappaB half-site which interacts with Rel proteins. DNase I footprinting and electrophoretic mobility shift assays demonstrated that C/EBP proteins interact with the critical element, but in nuclear extracts, cooperative binding of C/EBP and Rel proteins to their respective sites was not observed. Interestingly, promoter activity was induced by HKLM in the presence of cycloheximide, consistent with induction by posttranslational mechanisms. The results suggest that C/EBP and Rel proteins play important roles in the activation of IL-12 p40 transcription by bacteria. However, many complex interactions will need to be clarified to fully understand p40 regulation.

Animals↗
PubMed1996

Percutaneous multielectrode endocardial mapping during ventricular tachycardia in the swine model.

BACKGROUND: Identification of critical areas within the ventricular tachycardia circuit is a prerequisite for catheter ablation. Currently, mapping during ventricular tachycardia, usually performed with standard catheters, is difficult and time-consuming and can be used only in patients with hemodynamically stable tachycardia. METHODS AND RESULTS: A total of 43 pigs underwent closed-chest induction of myocardial infarction. A basket-shaped catheter carrying 64 electrodes was deployed in the left ventricle during normal sinus rhythm. Unipolar pacing at 3 mA was successful in 78% of the basket catheter electrodes, demonstrating good electrode-tissue contact. Hemodynamic and echocardiographic measurements did not reveal any significant interference with myocardial or valvular function during or after catheter deployment. One hundred eighteen episodes of monomorphic ventricular tachycardia were induced in 28 pigs through right ventricular stimulation, 81 of which were mapped and analyzed. Ventricular tachycardia mapping was rapid, requiring only several beats and < 10 seconds to complete. Presystolic potentials, a possible target for ablation, were identified in 58% of the tachycardia episodes mapped. Pathological examination revealed only minor valvular and endocardial catheter-induced lesions immediately after mapping and none a month later. CONCLUSIONS: The multielectrode catheter enables rapid and safe percutaneous endocardial mapping of ventricular tachycardia in the swine model. Exploration of the clinical potential of the multielectrode catheter seems warranted.

Animals↗
PubMed1996

A one step PCR procedure for analysis of tumor specific T lymphocyte responses.

In an effort to develop optimal conditions for analysis of tumor specific T lymphocyte responses, we have studied the effect of changes in the concentration of oligonucleotide primers on the synthesis of TCR cDNAs in one step PCR procedure using Vbeta10 gene subfamily as a model. It was found that synthesis of the TCR cDNAs increases in a roughly linear fashion at primer concentrations between 0.005-0.05 muM. Evaluation of the use of low concentration (0.005 muM) of primers showed these conditions to be adequate for the analysis of TCR Vbeta subfamilies in the spleen of BALB/c mice, but not in the peritoneal exudate cells (PECs), the latter requiring ten-fold higher concentrations of the variable region primers to compensate for the overall low frequency of T lymphocytes in the PECs in comparison to the spleen. Use of these optimal conditions to detect L1210 tumor specific T lymphocyte responses showed that, in the immunized mice, L1210 specific T lymphocyte responses are detectable in the PECs, but not in the spleen cells from these mice. Thus, upon i.p. immunization of DBA/2 mice with irradiated L1210 lymphoma cells, followed by analysis of the PECs by RT/PCR, three TCR Vbeta subfamilies, including Vbeta8.2, Vbeta15 and Vbeta16 were found to contain specific major TCR cDNA bands. The approach described here is very efficient, as it uses a small amount of the 32P isotope (0.5 muCi) followed by direct analysis of the PCR products on a denaturing acrylamide/urea gel. Furthermore, data is also presented that shows that quantitative differences in the levels of individual TCR cDNAs in a particular Vbeta subfamily are preserved during PCR amplification.

Animals↗
PubMed1996

Characterization of [3H]GR 113808 binding to 5-HT4 receptors in brain tissues from patients with neurodegenerative disorders.

[3H]GR 113808 binding studies in guinea-pig brain tissue revealed a temperature dependency and pharmacological specificity consistent with labelling of a 5-HT4 receptor. Detailed comparison of competition data between brain regions from human and guinea-pig suggest minor differences in the rank order of affinity. Studies in brain tissue from patients with Alzheimer's Huntington's and Parkinson's disease have revealed specific deficits in 5-HT4 receptor densities.

Aged↗
PubMed1996

In vivo effects of tumor necrosis factor-alpha on incised wound and gunshot wound healing.

Recombinant tumor necrosis factor alpha (TNF-alpha) was applied to incised wounds (adult rats, n = 14) and gunshot wounds (dogs, n = 5). The accumulation of RNA and DNA in regenerative tissue, the wound disruption strength (WDS), and histology were examined. The results showed that a single dose of TNF-alpha in saline with highly purified bovine serum albumin increased the WDS and accumulation of RNA and DNA in regenerative tissue in incised wounds 3 days after surgery (p < 0.05). Also, TNF-alpha promoted the inflammatory reaction in the wounded area of gunshot wounds. Histology revealed increased capillary tube-like structures and collagen formation and fibroblast proliferation in both incised and gunshot wounds treated with TNF-alpha. The results indicated that locally applied TNF-alpha benefited the incised and gunshot wound healing. These mitogenic and inflammatory effects of TNF-alpha may be the synergistic effects with other growth factors such as platelet-derived growth factor (PDGF).

Animals↗
PubMed1996

Large-scale DRB and DQB1 oligonucleotide typing for the NMDP registry: progress report from year 2.

DNA typing of HLA class II alleles of the DRB1/3/4/5 and DQB1 loci using sequence-specific oligonucleotide probes and polymerase chain reaction amplified DNA has been used for the large-scale typing of donors for the National Marrow Donor Program unrelated donor registry. The results of quality control analysis for the second year of the project (10/1/939/30/94) show the typing continues to be highly accurate, specific, and reliable. The average percent of correctly classified HLA oligotypes (groups of alleles defined by a hybridization pattern with a panel of sequence-specific oligonucleotide probes) based on 9,244 DRB1 and 7,244 DQB1 assignments was 99.8% (range 99.4%100.0%) for DRB1/DRB3/DRB4/DRB5 and 99.8% (range 99.6%100.0%) for DQB1. This level of accuracy is particularly remarkable because the 4,636 DRB quality control samples were tested blindly and could not be distinguished from 57,580 donor samples tested at the same time by the laboratories.

Alleles↗
PubMed1995

Platelet-derived growth factor-B increases colon cancer cell growth in vivo by a paracrine effect.

PDGF-B released from colon tumor cells regulated tumor growth in athymic mice in a paracrine manner by inducing blood vessel formation. A positive correlation was found between expression of PDGF B-chain in cells grown in vitro and the number of factor VIII-positive blood vessels in tumors induced by three classes of colon carcinoma cell lines. Elevated expression of PDGF-B was also correlated with tumor size. Each cell line had the same mutations in the colon cancer genes APC, DCC, and p53 and had wild type c-K-ras genes (Huang et al. [1994] Oncogene, 9:3701-3706.) eliminating the possibility that any differences in tumor blood vessel formation were due to mutations and/or deletions in these genes. Colon carcinoma cells released biologically active PDGF capable of stimulating the growth of NIH3T3 cells, which was inhibited by neutralizing antisera to PDGF-AB chains. An inverse correlation was found between induction of factor VIII-positive blood vessels and expression of vascular endothelial growth factor (VEGF), while no correlation was seen with expression of either TGF alpha or k-FGF. Basic fibroblast growth factor (FGF) expression was not detected in these tumor cells. TGF beta 1 was capable of inducing PDGF-B expression in the undifferentiated U9 colon carcinoma cell line, but this sensitivity was not seen in differentiated cells. In contrast, TGF beta 1 inhibited VEGF expression in both undifferentiated cells and differentiated colon cancer cells. Thus, TGF beta 1 has two roles in the growth of undifferentiated U9 colon carcinoma cells in vivo: direct stimulation of cell proliferation as we have showed in earlier studies, and an increase in angiogenesis by inducing PDGF-B.

Animals↗
PubMed1995

Colon carcinoma cells with inactive nm23 show increased motility and response to motility factors.

nm23H1 has properties of a metastasis suppressor gene. Although its mechanism of action is unknown, nm23 has been implicated in transforming growth factor beta 1 (TGF beta 1) signal transduction. In an earlier study we decreased nm23 mRNA levels 2- to 8-fold by antisense phosphorothiolated oligonucleotides in two HT29 colon carcinoma sublines at different stages in tumor progression with different responses to TGF beta 1: the HD3 subline, which shows TGF beta 1-induced growth arrest and differentiation; and the more tumorigenic U9 subline, whose growth and invasion are stimulated by TGF beta 1. Only TGF beta 1-mediated responses in HD3 cells were inhibited by nm23 antisense oligos, suggesting that nm23 functions in only one TGF beta 1 signaling pathway. In the current report we have extended this study to cell motility. HD3 motility was increased by nm23 phosphorothiolated antisense oligos which decrease nm23 mRNA levels, while HD3 cell motility was conversely decreased by TGF beta 1 which increases nm23 mRNA levels. HD3 motility was not increased by basic FGF, TGF beta 1 or TGF alpha, while the 13-fold higher basal motility of U9 cells was stimulated 3-fold by basic FGF, 4-fold by TGF beta 1 and 5-fold by TGF alpha, but not by scatter factor. Differences in motility and response to motility factors could not be ascribed to differences in either basal levels of proteases or modulation of their levels by TGF beta 1. Both HD3 and U9 cells displayed equal levels of urokinase activity and mRNA, equal expression of the metalloproteinase inhibitor TIMP-1, and no detectable collagenases by zymography. No differential response to TGF beta 1 was seen in any of these assays. Thus limited cell motility and lack of response to motility factors in HD3 colon cancer cells could be correlated with expression of nm23 active in signal transduction.

Base Sequence↗
PubMed1994

High level of Nm23-H1 gene expression is associated with local colorectal cancer progression not with metastases.

This study aimed to determine the expression of Nm23-H1 in colorectal cancer and liver metastases and to correlate Nm23-H1 expression with clinicopathological variables. Specimens from 59 primary colorectal cancers and five liver metastases were studied using Northern blot hybridisation. The mean +/- s.e. of tumour/normal (T/N) ratio of Nm23-H1 RNA expression was 4.3 +/- 0.4 (P < 0.001) and 5.1 +/- 0.90 (P < 0.01) for colorectal cancer and liver metastases respectively. No significant relationship was observed between the level of Nm23-H1 RNA and the patient's age, sex, tumour location, differentiation, presence of lymph node involvement or distant metastases. Nm23-H1 RNA level was 2.6 +/- 0.5 for tumour size less than 3.0 cm and 4.6 +/- 0.5 for those > or = 3.0 cm (P = 0.05). There appeared to be a trend between increasing relative Nm23-H1 RNA and bowel wall invasion, irrespective of metastatic status (T1 = 1.9 +/- 0.3, T2 = 4.1 +/- 0.6, T3 = 4.1 +/- 0.5 and T4 = 6.4 +/- 1.6). This difference was statistically significant when T1 was compared against > or = T2 lesions (P = 0.01). Western blot analysis reveals two Nm23H-1 bands (17.0 kDa and 18.5 kDa). In 16 colorectal patients, the T/N fold-increase in protein expression was 2.66 +/- 0.46 (P < 0.001) and 2.40 +/- 0.32 (P < 0.001) for the 17.0 and 18.5 kDa band respectively. Both Nm23-H1 RNA and protein levels in primary colorectal cancers do not appear to correlate with synchronous regional or distant metastases. Since Nm23-H1 RNA expression is associated with increasing tumour size and tumour local invasion, Nm23-H1 RNA expression may be associated with local disease progression.

Adult↗