Biomedical subjects

W T Chang

Publications and source records attributed to W T Chang.

52 records · Page 3Linked to original sources

PubMed1993

Endothelin-mediated calcium response and inositol 1,4,5-trisphosphate release in neuroblastoma-glioma hybrid cells (NG108-15): cross talk with ATP and bradykinin.

Addition of endothelins (ETs) to neuroblastoma-glioma hybrid cells (NG108-15) induced increases in cytosolic free Ca2+ ([Ca2+]i) levels of labeled inositol monophosphates and inositol 1,4,5-trisphosphate [Ins(1,4,5)P3]. The increases in [Ca2+]i elicited by the three ETs (ET-1, ET-2, and ET-3) were transient and did not show a sustained phase. Chelating extracellular Ca2+ in the medium by adding excess EGTA decreased the ET-mediated Ca2+ response by 40-50%. This result indicates that a substantial portion of the increase in [Ca2+]i was due to influx from an extracellular source. However, the increase in [Ca2+]i was not affected by verapamil or nifedipine (10(-5) M). A rank order potency of ET-1 > ET-2 > ET-3 is shown for the stimulated increase in [Ca2+]i, as well as labeled inositol phosphates, in these cells. ATP (10(-4) M) and bradykinin (10(-7) M) also induced the increases in [Ca2+]i and Ins(1,4,5)P3 in NG108-15 cells, albeit to a different extent. When compared at 10(-7) M, bradykinin elicited a five- to sixfold higher increase in the level of Ins(1,4,5)P3, but less than a twofold higher increase in [Ca2+]i than those induced by ET-1. Additive increases in both Ins(1,4,5)P3 and [Ca2+]i were observed when ET-1, ATP, and bradykinin were added to the cells in different combinations, suggesting that each receptor agonist is responsible for the hydrolysis of a pool of polyphosphoinositide within the membrane. ET-1 exhibited homologous desensitization of the Ca2+ response, but partial heterologous desensitization to the Ca2+ response elicited by ATP. On the contrary, ET-1 did not desensitize the response elicited by bradykinin, although bradykinin exhibited complete heterologous desensitization to the response elicited by ET-1. Taken together, these results illustrate that, in NG108-15 cells, a considerable amount of receptor cross talk occurs between ET and other receptors that transmit signals through the polyphosphoinositide pathway.

Adenosine Triphosphate↗

PubMed1993

Biased T-cell receptor delta element recombination in scid thymocytes.

Thymocytes in mutant mice with severe combined immunodeficiency (scid thymocytes) show ongoing recombination of some T-cell receptor delta gene elements, generating signal joints quantitatively and qualitatively indistinguishable from those in wild-type fetal thymocytes. Excised D delta 2-J delta 1 and D delta 1-D delta 2 rearrangements are detectable at levels equivalent to or greater than those in thymocytes from wild-type mice on fetal day 15. Signal junctional modification, shown here to occur frequently in wild-type adult but not newborn excised D delta 2-J delta 1 junctions, can occur normally in adult scid thymocytes. Excised D delta 1-D delta 2 scid junctions, similar to wild-type thymocytes, include pseudonormal coding junctions as well as signal junctions. Inversional D delta 1-D delta 2 rearrangements, generating conventional hybrid junctions, are also reproducibly detectable in scid thymus DNA. These hybrids, unlike those reported for artificial recombination constructs, do not show extensive nucleotide loss. In contrast to the normal or high incidences of D delta 1-, D delta 2-, and J delta 1-associated signal junctions in scid thymocytes, V delta 1, V gamma 3, and V gamma 1.2 signal products are undetectable in scid thymocytes or are detectable at levels at least 10-fold lower than the levels in wild-type fetal thymocytes. These findings confirm biased T-cell receptor element recombination by V(D)J recombinase activity of nontransformed scid thymocytes and indicate that analysis of in vivo-mediated gene rearrangements is important for full understanding of how the scid mutation arrests lymphocyte development.

Aging↗

PubMed1993

Congenital short small intestine: report of three cases.

Three cases are presented in which the recognized syndrome of functional small bowel obstruction with malrotation and short small bowel was diagnosed. Each patient underwent an exploratory laparotomy for intestinal obstruction, which revealed short small intestines with malrotation, measuring 30 cm to 39 cm. Ladd's procedure was performed in each case and gastrointestinal patency was assured during the operations. Two patients received long-term parenteral nutrition and one, in addition, received bowel lengthening using Bianchi's method. However, the symptoms persisted. The third patient received a prokinetic agent (cisapride) but with no effect; the parents withdrew further management. All three patients subsequently died. Although autopsies were performed in two cases, the exact deficits of intestinal motility are unknown.

Female↗

PubMed1993

The multicystic dysplastic kidney in children.

Multicystic dysplastic kidney (MCDK) is the most common renal cystic disease in infancy and the second most common neonatal abdominal mass. It represents an extreme form of renal dysplasia. The key features in MCDK include variability in size, loss of kidney shape, absence of function and obstruction of ureter. Current management is still controversial. The prognosis is largely depended upon the problems of associated anomalies and the condition of the contralateral kidney. From September '82 to September '91, twelve patients with multicystic kidney have been treated at Taichung Veterans General Hospital. Ten of them received elective nephrectomy. The postoperative condition was uneventful. However, there was a high frequency of associated anomalies (41.6%) and pathologic contralateral kidney (50%). Two patients who refused operation were put on close observation and follow-up with ultrasound. During the surgical patients' follow-up period, one suffered from repeated urinary tract infection and the other died of multiple congenital anomalies.

Female↗

PubMed1993

Recurrent pneumonia resulting from retained esophagus following esophageal replacement for corrosive stricture: a case report.

Benign corrosive stricture of the esophagus rarely requires esophageal replacement due to failed dilatation. A patient is presented with severe esophageal stricture from corrosive injury; the native esophagus was eventually replaced with an ileocolon interposition graft. He suffered from recurrent pneumonia one year after operation. Mucocele formation from the retained esophagus with compression of the tracheobronchial tree, was diagnosed by computerized tomographic (CT) scan, and was resected. The clinical status improved dramatically after the procedure. Tracheobronchial compression by mucocele from the retained esophagus should be considered in the differential diagnosis of recurrent pneumonia after esophageal replacement.

Burns, Chemical↗

PubMed1992

Analysis of the genes and gene products of Xanthomonas transposable elements ISXc5 and ISXc4.

A series of deletion mutants have been constructed for the gene analyses of transposable elements, ISXc5 and ISXc4, derived from Xanthomonas. At least two element-encoded polypeptides of 48 kDa and 40 kDa have been identified in the minicell-producing Escherichia coli strain, TC410. A study of the element transposition and cointegrate resolution revealed that the 48-kDa and 40-kDa polypeptide are both involved in translocation of the elements, the 48-kDa product being involved in transposition of the elements and the 40-kDa product being involved in cointegrate resolution.

DNA Mutational Analysis↗

PubMed1992

Possible existence of two subsets of platelet-activating factor receptor to mediate polyphosphoinositide breakdown and calcium influx in neuroblastoma x glioma hybrid NG 108-15 cells.

Platelet-activating factor (PAF) initiated polyphosphoinositide (polyPI) breakdown and a rise of intracellular calcium concentration ([Ca2+]i) in neuroblastoma x glioma hybrid NG 108-15 cells. The accumulation of [3H]inositol trisphosphate and [3H]inositol bisphosphate was evident within 15 s after PAF stimulation, peaked at 1 min, and then gradually decayed. The increase in [3H]inositol monophosphate level was observed at 30 s, plateaued in 5 min, and was sustained up to 10 min in the presence of 10 mM LiCl. On the other hand, the rise of [Ca2+]i evoked by PAF reached a peak within 8-12 s and returned to basal levels within 1 min as measured in fura 2-loaded cells. When cells were suspended in Ca(2+)-depleted medium, the PAF-induced [Ca2+]i rise was reduced by 80%, indicating that the increase of [Ca2+]i was predominantly due to the Ca2+ influx from an extracellular source. Both PAF-induced accumulation of 3H-labeled inositol phosphates and [Ca2+]i elevation were concentration dependent with EC50 values of approximately 1 x 10(-10) and 5 x 10(-8) M, respectively. The PAF analogs 1-O-hexadecyl-2-hydroxy-sn-glycero-3-phosphocholine and 1-O-hexadecyl-2-O-methyl-rac-glycerol-3-phosphocholine were much poorer agonists at eliciting the same responses in these cells. Pretreatment of cells with pertussis toxin caused a substantial inhibition of PAF-induced accumulation of 3H-inositol phosphates. In contrast, the rise in [Ca2+]i was not significantly affected by toxin treatment at the same concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Evaluation of anorectal malformations using magnetic resonance imaging.

Demonstration of the anatomy of the anal sphincter muscles in patients with anorectal malformations is important. The information can help us in preoperative planning for surgical repair and in predicting a patient's prognosis. For patients with postoperative incontinence, the anatomic imaging is especially useful. Magnetic resonance imaging (MRI) is a relatively new diagnostic tool that generates images of sections of the body taken in any plane. From Oct. 1989 to Dec. 1990, twelve patients received MRI examination, imaging the pelvis and lumbosacral spine in the sagittal, transverse, and coronal planes. Normal anorectum in 2 cases was recorded for comparison. The other ten cases included three of postoperative incontinence, three of cloacal anomaly, and four of questionable level of anorectal anomaly before MRI evaluation. Our experience proved that MRI is a useful examination in selected patients with anorectal malformation. To be cost-effective, we suggest that MRI is performed only in patients with postoperative incontinence and some questionable cases.

Anal Canal↗

PubMed1990

Solitary spinal cord metastasis of Wilms' tumor.

Wilms' tumor metastasis to the spinal cord is very rare at any age. We recently encountered a case of a 4-year-old girl, who had a solitary lumbar spinal cord metastasis about 1 year following the initial nephrectomy and an incomplete course of chemotherapy for a stage I Wilms' tumor. The patient recovered uneventfully after decompressive laminectomy, removal of the extradural spinal cord tumor, adjuvant chemotherapy, and radiotherapy according to the National Wilms' Tumor Study (NWTS)-IV protocol.

Child, Preschool↗

PubMed1988

Effect of root agglutinin on microbial activities in the rhizosphere.

A total of 220 bacterial isolates were obtained from pea rhizosphere and nonrhizosphere samples. Of these samples, 100 isolates were chosen randomly to test for their agglutinative reaction against pea root exudate. The percentage of positive agglutination of bacteria isolated from the nonrhizosphere sample was significantly lower than that of bacteria isolated from the rhizosphere sample. Moreover, this agglutinative reaction could not be blocked either by treating the bacterial cells or root exudate with different carbohydrates before they were mixed or by boiling the root exudate first. Bacteria that could be agglutinated by pea root exudate followed the downward growth of the pea root through the soil profile. The greater abilities of such bacteria to colonize the pea rhizosphere were indicated by their higher rhizosphere-colonizing (rhizosphere/nonrhizosphere) ratios, whether the bacteria were added alone or together with nonagglutinating bacteria. However, bacteria did show different agglutinative reactions toward root exudates obtained from different plants.

Journal Article↗

PubMed1986

Prophylactic action of hexamethonium, trimethaphan, and mecamylamine against diisopropyl fluorophosphate poisoning in mice.

Prophylactic Action of Hexamethonium, Trimethaphan, and Mecamylamine against Diisopropyl Fluorophosphate Poisoning in Mice. Chiou, G. C. Y., Chang, W. T. S., and Aimoto, T. (1986). Fund. Appl. Toxicol. 6, 35-43. Hexamethonium, trimethaphan, and mecamylamine are ganglionic blockers which can reduce acetylcholine (ACh) release presynaptically. All these agents are capable of protecting mice from diisopropyl fluorophosphate (DFP) intoxication by prolonging the latent period of death or by completely preventing death. Combinations of these agents with 2-pyridine aldoxime methochloride (2-PAM) (50 mg/kg) improved prophylactic action even further. These results indicate that reduction of ACh release presynaptically plus neutralization of organophosphates with 2-PAM could be an effective way to reduce mortality in patients exposed to organophosphorus poisons.

Animals↗

PubMed1980

Mechanistic studies of carboxypeptidase Y from Saccharomyces cerevisiae. pH and pD profiles and inactivation at low pH (pD) values.

Steady-state kinetics of carboxypeptidase Y, a proteinase from yeast, were studied by using the reaction of 4-nitrophenyl trimethylacetate as a probe. The pH profile of kcat. is sigmoidal in H2O-based buffers for the carboxypeptidase Y-catalysed hydrolysis of this ester (kcat. referring to the rate of deacylation of trimethylacetyl-carboxypeptidase Y). The corresponding pD profile in 2H2O is doubly sigmoidal, with inflexions at pD approximately 3.8 and approximately 6.8. The ionization of pKDapp. approximately 3.8 is caused by a rapid inactivation in 2H2O media by a process that is only slowly reversed on transfer to pH 7.00 phosphate buffer in H2O. The corresponding inactivation in H2O-based buffers of low pH is considerably slower (approximately 30-fold), follows a first-order rate-dependence and is very strongly pH-dependent, indicating some form of co-operative change in enzyme tertiary structure.

Carboxypeptidases↗

PubMed1977

The cellulase system of a Cytophaga species.

Cellulases (EC 3.2.1.4) of a Cytophaga species WTHC 2421 (ATCC 29474) were found in the soluble portion of the cell (the periplasm and the cytoplasm) and on the membrane. Cell-free cellulases were not found. Most of the carboxymethylcellulase activity associated with reduction of viscosity was membrane bound, whereas most of the carboxymethylcellulose (CMC) saccharifying activity was soluble. The CMC-saccharifying activity was increased 534 X by purification procedures which included ammonium sulfate precipitation and molecular exclusion chromatography with Sephadex G-75 and Biogel p-100. Periplasmic carboxymethycellulase had a molecular weight of 6250 and cytoplasmic carboxymethylcellulase had a molecular weight of 8650. Analytical ultracentrifugation of the periplasmic carboxymethylcellulase (CMCase) indicated that it had a low molecular density. The chromatographic fraction containing periplasmic CMCase also contained enzyme activity against crystalline cellulose. The activity against crystalline cellulose was 238 X higher than the activity shown by the whole cell. The reaction of the enzyme with either CMC or dewaxed cotton produced only glucose. The enzyme was slightly inhibited by the presence of 0.01% (w/v) glucose, lactose, or cellobiose, but it was not affected by sucrose, and exhibited increased activity in the presence of xylose and fructose.

Carbohydrates↗

PubMedDate not supplied

Chemical derivatization and the selection of deuterated internal standard for quantitative determination--methamphetamine example.

Use of an isotopic analogue of the analyte as the internal standard in a quantitative gas chromatography-mass spectrometry targeted-compound-analysis protocol is often hindered by the availability of an adequate number (typically three for the drug/metabolite and two for the isotopic analogue) of sufficiently high mass ions that can be attributed to each member of the pair and are sufficiently free of interference by the contribution from the other component of the pair, a phenomenon termed "cross-contribution". Methamphetamine (MA) is selected as the exemplar compound to examine the effectiveness in using different chemical derivatization routes to produce derivatized analyte-isotopic analogue pairs that can generate more favorable mass spectrometric data to meet this analytical requirement. Trimethylsilyl-, trichloroacetyl-, and pentafluoropropionyl-derivatization and MA-d5, MA-d8, and MA-d9 are studied. Data resulting from this study indicate that the number of ion pairs suitable for quantitation and the degree of cross-contribution of these ions vary significantly. These data empirically demonstrate that derivatization methods play a significant role in deciding which deuterated analogue of the analyte provides the most suitable ion pairs that cause the least cross-contribution. The most suitable internal standard varies with the derivatization route adapted for an analytical protocol.

Central Nervous System Stimulants↗

PubMedDate not supplied

Mechanistic studies on the use of 2H- and 13C-analogues as internal standards in selected ion monitoring GC-MS quantitative determination--butalbital example.

As a part of our study on the use of isotopic analogues as the internal standard (IS) for the quantitation of drug analytes, this article reports on the performance characteristics of 2H5-butalbital and 13C4-butalbital with particular focus on (1) determining and comparing the effectiveness of the 2H- and 13C-analogues in serving as the ISs for quantitation; (2) understanding the "cross-contribution" phenomenon underlying the effectiveness of selected ion pairs used for quantitation purpose; and (3) examining whether the same characteristics, observed in our preliminary report for the secobarbital/2H5-secobarbital/13C4-secobarbital system, also exist in the butalbital/2H5-butalbital/13C4-butalbital system. Adapting similar procedures applied to our previous study on the secobarbital system, we observed that (1) both labeled analogues (13C4-butalbital and 2H5-butalbital) cause more significant cross-contributions to ions designated for butalbital than butalbital to the labeled analogues; (2) compared to 2H5-butalbital, 13C4-butalbital appears to cause less cross-contributions to ions designated for butalbital; (3) cross-contribution between the following ion pairs are minimal: m/z 200/196, 199/195, 185/181 (13C4-butalbital as the IS) and m/z 201/196 (2H5-butalbital as the IS). It is also concluded that the butalbital/2H5-butalbital system exhibits the same concentration dependency phenomenon observed in the secobarbital/ 2H5-secobarbital system, that is, ratios of ion pairs designated for these two isotopic analogues (resulting from routine gas chromatography-mass spectrometry protocol) increase as their concentrations are diluted. (In parallel with the secobarbital/13C4-secobarbital system, the butalbital/13C4-butalbital system does not exhibit this phenomenon.)

Barbiturates↗

PubMedDate not supplied

Isolation of biologically functional RNA during programmed death of a colonial ascidian.

The blastogenic (asexual) cycle of the colonial ascidian Botryllus schlosseri (Tunicata, Ascidiaceae) concludes in a cyclical phase of programmed cell and zooid death called takeover, in which all asexually derived adults die synchronously by apoptosis. The characterization of developmentally regulated genes whose expression patterns are selectively modulated during this process could pave the way to understand how this model organism dies. However, isolation of biologically functional RNA in this and other colonial ascidians with conventional phenol/chloroform-based procedures is hampered by extensive contamination of RNA preparations by pigments. Upon cell lysis, pigments that normally reside within specialized cells in the mantle wall of the adult are released and tightly associate with nucleic acids. Here, we report on the usefulness of a single-step RNA isolation method in which acid guanidinium isothiocyanate is used as an extraction medium, followed by preparative cesium chloride ultracentrifugation. This procedure successfully isolated biologically active, high-purity total RNA (OD260/OD280 = 1.9-2.1) from Botryllus colonies during takeover, as well as other species of colonial ascidians (Diplosoma macdonaldii, Botrylloides diegense) irrespective of pigmentation. Northern blot analysis performed with a 32P-labeled tunicate actin probe detected two polyadenylated transcripts of 1.5 and 1.7 kilobases in length from both growth phase and takeover colonies. Two-dimensional protein gel assays from in vitro translated mRNA preparations further revealed that specific transcripts were up-regulated during takeover, while others were repressed or down-regulated. Growth phase and takeover-specific cDNA libraries were constructed from pooled poly(A)+ RNA with a complexity of 1.0 x 10(7) and 1.2 x 10(7) recombinants respectively per 100 ng of cDNA before amplification.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗