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Biomedical subjects

H C Chang

Publications and source records attributed to H C Chang.

At least 145 records · Page 8Linked to original sources
PubMed1996

Effect of acupuncture at tai-tsih (K-3) on the pulse spectrum.

The frequency specific acupuncture effect on Tai-Tsih (K-3) was examined by investigating pulse variations at the radial artery. The harmonic proportions of the 2nd, 3rd, and the 4th harmonics were increased but the 5th, 6th and 9th harmonics were decreased significantly. The phase angles of all except the 2nd harmonic were increased (wave propagated slower). These results are compared with the frequency specific acupuncture effect on Tsu-San-Li (St-36) which we reported previously (Wang et al., 1995a). This study solidified the weak coupling resonance theory, which successfully explains these frequency specific effects as well as the acupuncture mechanism.

Acupuncture Therapy↗
PubMed1996

The SH2-containing tyrosine phosphatase corkscrew is required during signaling by sevenless, Ras1 and Raf.

The sevenless gene encodes a receptor tyrosine kinase which is required for the development of the R7 photoreceptor cell in each ommatidium of the Drosophila eye. We have previously used a sensitized genetic screen to identify mutations, designated Enhancers of sevenless (E(sev)), which affect genes that encode components of the sevenless signaling pathway. Here, we report that one of these mutations, E(sev)1Ae0P is a dominantly inhibiting allele of corkscrew, which encodes an SH2 domain-containing protein tyrosine phosphatase (Perkins et al., 1992). We show that corkscrew function is essential for sevenless signaling and that expression of a membrane-targeted form of corkscrew can drive R7 photoreceptor development in the absence of sevenless function. Furthermore, we have used the dominantly inhibiting corkscrew allele to examine the role of corkscrew during signaling by activated forms of Ras1 and Raf. Our analysis indicates that corkscrew function is still required during signaling by activated forms Ras1 and Raf proteins. These results define a function for corkscrew that is either downstream of Ras1 activation or in a parallel pathway that acts with activated Ras1/Raf to specify R7 photoreceptor development.

Alleles↗
PubMed1996

Delayed delivery of surviving triplet after fetal reduction and spontaneous abortion.

In multiple pregnancies, survival of remaining fetuses after premature death and delivery of one fetus is uncommon. We report a case of a triplet pregnancy that was reduced to twins at the 14th gestational week and then had preterm premature rupture of membranes and intrauterine fetal death of one twin at the 17th gestational week. To save the surviving fetus, delivery of the dead fetus and ligation of the umbilical cord at the cervical level were performed. We also performed McDonald cervical cerclage to keep the placenta of the dead fetus as well as that of the surviving one in the uterine cavity. After a series of aggressive procedures, including immediate administration of tocolytic agents, and antibiotic prophylaxis to prevent infection and preterm labor, the surviving fetus was delivered vaginally 73 days later due to intractable uterine contractions. After a 10-week hospital stay, the infant boy, weighing 2,500 g, was discharged without any sequelae. To our knowledge, this was the longest interval between deliveries in a triplet pregnancy reported in Taiwan. With adequate intensive management, a satisfactory outcome of the fetus and mother in such cases is possible.

Abortion, Spontaneous↗
PubMed1995

KSR, a novel protein kinase required for RAS signal transduction.

We have identified and characterized two genes in Drosophila whose products are required for activated RAS to signal with normal efficiency, but do not appear to effect signaling by activated RAF. One encodes the beta subunit of type I geranylgeranyl transferase, a prenylation enzyme essential for targeting RAS to the plasma membrane. The other encodes a protein kinase that we have named kinase suppressor of ras (ksr). By genetic criteria, we show that KSR functions in multiple receptor tyrosine kinase pathways. We have isolated mammalian homologs of KSR that, together with the Drosophila gene, define a novel class of kinases. Our results suggest that KSR is a general and evolutionarily conserved component of the RAS signaling pathway that acts between RAS and RAF.

Amino Acid Sequence↗
PubMed1995

Determination of berberine in plasma, urine and bile by high-performance liquid chromatography.

A high-performance liquid chromatographic method for the determination of berberine in plasma, urine and bile samples is described. Plasma samples were pretreated by protein precipitation with acetonitrile and urine and bile samples were pretreated by organic solvent extraction using 5% 2-propanol in methylene chloride. Berberine was determined in all samples using an octyl reversed-phase column with a mobile phase of 60-63% acetonitrile in 0.1% phosphoric acid (pH 6.0) and with UV detection at 267 nm. The detection limits for berberine in plasma, urine and bile were 18.1 ng/ml, 2.3 ng/ml and 90.4 ng/ml, respectively. The recoveries of berberine by simple deproteinization of plasma and by solvent extraction of urine were 78.3 and 82.9%, respectively. The intra-day and inter-day accuracy and precision for plasma reported as coefficients of variation and relative errors were both less then 6%. The applicability of the assay to pharmacokinetic and bioavailability studies was demonstrated by the determination of berberine in plasma, urine and bile after intravenous and intramuscular administration to rabbits at a dose of 2 mg/kg.

Animals↗
PubMed1995

phyllopod functions in the fate determination of a subset of photoreceptors in Drosophila.

phyllopod (phyl) encodes a novel protein required for fate determination of photoreceptors R1, R6, and R7, the last three photoreceptors to be recruited into the ommatidia of the developing Drosophila eye. Genetic data suggests that phyl acts downstream of Ras1, raf, and yan to promote neuronal differentiation in this subset of photoreceptors. Ectopic expression of phyl in the cone cell precursors mimics the effect of ectopic activation of Ras1, suggesting that phyl expression is regulated by Ras1. phyl is also required for embryonic nervous system and sensory bristle development.

Amino Acid Sequence↗
PubMed1995

Liposomal entrapment of suramin(II): interaction of suramin with phospholipids of various chain lengths.

Previously, we reported that the entrapment of suramin in dipalmitoylphosphatidylcholine (DPPC, C16) multilamellar liposomes ranged from 25% to 65% and the addition of 30-50 mol% cholesterol (CHL) greatly reduced entrapment. Entrapment of small molecules similar to suramin, disodium 1,5-naphthalenedisulfonic acid (5.5%) and sodium 3-amino-2,7-naphthalenedisulfonic acid (1.2%), were very low. In the present study, the entrapment and interaction of suramin with dilauroylphosphatidylcholine (DLPC, C12), dimyristoylphosphatidylcholine (DMPC, C14), and distearoylphosphatidylcholine (DSPC, C18) liposomes was investigated. DLPC and DMPC showed 2-3-fold higher entrapment percentages (95.1% and 74.2%, respectively) than DPPC (37%). However, the entrapment with DSPC (29%) was about 25% lower than DPPC. Adding 50 mol% cholesterol greatly reduced suramin entrapment for all phospholipids. The entrapment of polysulfonated dyes such as Evans blue, Direct blue 1, or Trypan blue, which are structurally similar to suramin, was found to be in the same order of DLPC > DMPC > DPPC > DSPC. Differential scanning calorimetry of aqueous dispersions of DLPC and DMPC with suramin showed more apparent interaction than for DPPC and DSPC. These results suggest that a large portion of the associated suramin and other polysulfonated compounds results from binding to the surface of the phospholipid bilayer or intercalation into the liposomal bilayer. The phospholipid chain length effect on entrapment may be due to the lower net van der Waals interaction between hydrocarbon chains for shorter acyl chains which also increases the bilayer intermolecular spacing. Such effects could then increase the ability of suramin to interact with individual phospholipid molecules.

Azo Compounds↗
PubMed1995

Nucleotide sequence of a plasmid pCL2.1 from Lactococcus lactis ssp. lactis ML8.

The nucleotide sequence of a small cryptic plasmid, pCL2.1, from Lactococcus lactis ssp. lactis ML8 was determined. Sequence analysis of the pCL2.1 revealed that it contained 2112 bp, 33.9% GC, and two open reading frames that encoded polypeptides of 26 and 14 kDa. In vitro transcription-translation of the pCL2.1 confirmed the existence of two polypeptides. Based on sequence homology, it is deduced that the ORF2 product functions in plasmid replication by a rolling circle mechanism.

Base Sequence↗
PubMed1995

Sequence analysis of an Erwinia stewartii plasmid, pSW100.

The nucleotide sequence of the smallest plasmid of Erwinia stewartii SW2 was determined. This plasmid, pSW100 (4272 bp), consists of a 702-bp region homologous to the origins of replication of plasmids p15A, ColE1, and ColA. Plasmid pSW100 also contains sequences homologous to the bom region and mobCABD genes of ColE1, except that a single-base deletion in mobA has been detected. This deletion did not affect the mobilization ability of pSW100 by an endogenous conjugative plasmid of E. stewartii SW2, pDC250. Plasmid pSW100 also has a 1596-bp open reading frame with five 132-bp perfect repeats. However, this open reading frame and the repeats are not required for plasmid replication. Furthermore, curing of pSW100 did not cause any phenotypic change, suggesting that this plasmid is not essential for the survival of the organism.

Amino Acid Sequence↗
PubMed1995

Effect of acupuncture at Tsu San Li (St-36) on the pulse spectrum.

Effect of acupuncture at Tsu San Li (St-36) was examined by investigating the pulse variation of the radial artery. Our results indicated that acupuncture at Tsu San Li has a specific effect on the Fourier components of the pulse. The harmonic proportions were redistributed (C2, C4 decreased, C5, C6, C8 and C9 increased), and the phase angle of the 5th and 8th harmonic waves were decreased (propagating faster). This specific frequency effect was not found when acupuncture needle was applied on a non-acupuncture point. These results can be explained by the resonance theory, which provides a scientific explanation of the acupuncture effect from the hemodynamic view point.

Acupuncture Points↗
PubMed1995

Impact of chart reminders on smoking cessation practices of pulmonary physicians.

Cigarette smoking remains one of the most preventable causes of premature death in our society, yet only a third to a half of smokers visiting a physician are counseled to quit. In the primary care setting, chart reminders can increase physician smoking cessation counseling rates. It is unclear, however, whether pulmonary physicians require prompting to discuss smoking cessation with patients. We hypothesized that chart reminders would improve the smoking cessation counseling and referral practices in our pulmonary clinic. Chart reviews were performed for two 1-mo periods and documentation of smoking status, counseling, and referrals to smoking cessation clinic were recorded. After the implementation of chart reminders, charts were reviewed at 1, 3, and 8 mo. Chart reminders increased documentation of smoking status from 33 to 83% (p = 0.0001). The proportion of all patients counseled increased from 6.0 to 13.2% (p = 0.01). The improvement in counseling to quit occurred primarily by increasing the identification of active smokers. Pulmonary physicians counseled 70% of smokers to quit once patients were identified as smokers. Chart reminders, an inexpensive and easily implemented smoking cessation intervention, increased the overall number and proportion of patients counseled to stop smoking by increasing the number of identified smokers. This simple intervention can improve counseling in populations at high risk for smoking related lung disease.

Counseling↗
PubMed1995

In vitro fertilization pregnancy achieved with epididymal caput sperm of a patient with obstructive azoospermia.

A successful epididymal sperm aspiration, in vitro fertilization and embryo transfer in a woman whose husband had previously undergone extensive attempts at recanalization of the spermatic ducts is reported. A twin pregnancy was achieved using sperm obtained from the husband's epididymal caput. This case demonstrates that pregnancy can be achieved by this reproductive technique in cases of obstructive azoospermia, even after extensive surgery.

Adult↗
PubMed1994

A general method for facilitating heterodimeric pairing between two proteins: application to expression of alpha and beta T-cell receptor extracellular segments.

Generation of soluble T-cell receptor (TCR) molecules by a variety of genetic engineering methods has been hampered by inefficient pairing of alpha and beta subunits in the absence of their respective transmembrane regions and associated CD3 components. To overcome this obstacle, we have added 30-amino acid-long segments to the carboxyl termini of alpha and beta extracellular domains via a cleavable flexible linker. These peptide segments (BASE-p1 for alpha and ACID-p1 for beta) have been previously shown to selectively associate to form a stable heterodimeric coiled coil termed a leucine zipper. Homodimeric structures are not permitted due to electrostatic repulsion among amino acid side chains. Expression of a representative TCR-leucine zipper fusion protein in a baculovirus expression system results in production of alpha beta TCR heterodimer at 0.6-1.4 mg/liter. This yield is 5- to 10-fold greater than that of the TCR expressed in the absence of the synthetic leucine zipper sequence. The structure of the TCR component of the fusion heterodimer was judged to be native when probed with a panel of 17 mAbs specific for alpha and beta constant and variable domains. A mAb specific for the isolated BASE-p1/ACID-p1 coiled coil was also generated and shown to react with the TCR fusion protein. The above technology should be broadly useful in the efficient production and purification of TCRs as well as other heterodimeric proteins.

Amino Acid Sequence↗
PubMed1994

Conservation of Hsp90 macromolecular complexes in Saccharomyces cerevisiae.

In higher eukaryotic cells, the Hsp90 chaperone protein is found in complexes with other proteins, in addition to the substrate protein. These other proteins include Hsp70, p60, and several peptidyl-prolyl cis-trans isomerases (immunophilins). We utilized affinity chromatography to investigate whether Hsp82, the Hsp90 of Saccharomyces cerevisiae, is found in similar complexes in that organism. Six histidine residues were fused to the N terminus of Hsp82 to yield a fusion protein (Hsp82FP) with affinity for a nickel-ion matrix. Hsp82FP was shown to have wild-type function. In addition, when mammalian substrates of Hsp90 (glucocorticoid receptor and p60v-src) were expressed in yeast cells, these proteins bound to the affinity matrix only when isolated from cells containing Hsp82FP. Yeast homologs of Hsp70 (in particular, members of the Ssa subfamily), p60 (Sti1), and a 45-kDa immunophilin homolog were also isolated in this manner, by virtue of their specific, stable association with Hsp82. Thus, Hsp90 functions as part of a highly conserved macromolecular complex in eukaryotes.

Amino Acid Sequence↗
PubMed1994

Liposomal entrapment of suramin.

The liposomal entrapment of suramin and similar compounds in phospholipid vesicles was examined. For dipalmitoylphosphatidylcholine (DPPC) liposomes, entrapment percentages ranged from 25 to 65% with 3-25 mM phospholipid for aqueous solutions containing 0.07 mM of suramin. Incorporation of 30-50 mol % cholesterol (CHL) into DPPC liposomes reduced the percentage suramin entrapment. Addition of positively-charged stearylamine (5 mol %) to DPPC/CHL liposomes increased the entrapment from 2.3% to 30.3%. Entrapment was not affected by the incorporation of negatively-charged phosphatidylglycerol into DPPC/CHL liposomes. When the amount of suramin was increased from 0.07 to 0.7 mM, the entrapment percentage decreased from 37% to 11% when DPPC was held constant at 6 mM. The entrapment of 0.07 mM Evans blue, a molecule similar in structure to suramin, was 51.6% in DPPC liposomes for 6 mM phospholipid. The entrapment percentage, however, decreased by about 50% when incorporated into 7:3 (DPPC/CHL) liposomes. The liposomal entrapment of disodium 1,5-naphthalenedisulfonic acid (5.5%) and sodium 3-amino-2,7-naphthalene-disulfonic acid (1.2%) was very low compared to that of suramin or Evans blue. Differential scanning calorimetry studies of suramin and an aqueous dispersion of DPPC showed an apparent interaction between them. These observations suggest that a significant portion of the entrapped suramin results from binding of suramin to the surface of or intercalation into the liposomal bilayer. Surface binding or intercalation into the phospholipid bilayer may be attributed to both ionic and hydrophobic interactions. The ionic interaction would arise from the suramin sulfonate groups associating with the cationic choline portion of the phospholipid.(ABSTRACT TRUNCATED AT 250 WORDS)

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1994

Management for acute corrosive injury of upper gastrointestinal tract.

BACKGROUND: It is imperative that the surgeon promptly determine the severity of any acute injury of the upper gastrointestinal (UGI) tract by caustic material ingested and the definite therapy be instituted. Prognostic factors of such injuries have not been clearly demonstrated in previous reports. Here, some prognostic factors and recommended emergency surgical indications in clinical assessment are discussed. METHODS: Forty-six patients (22 men and 24 women; age range 19 to 77 years), sustaining acute corrosive injuries to the UGI tract, were retrospectively assessed from November 1990 to May 1993. Immediate management was given to prevent shock, to identify any associated injury and to observe patency of the airway. Emergency operation was performed if any signs of peritonitis, mediastinitis or sepsis were present. Age, sex, time interval between ingestion and initial resuscitation, consciousness, peritoneal sign, shock index, pH value and [HCO3-] in arterial blood gas were evaluated as prognostic factors with respect to mortality. Chi-square test with Yates' correction was used. A p value less than 0.05 was regarded as statistically significant. RESULTS: Suicide attempt by caustic ingestion was in 40 patients (87%) and ingestion was accidental in 6 (13%). Acidic injury was specified in 36 patients (78.3%). In 14 severely injured patients, emergency exploratory laparotomy with or without esophagogastrectomy was performed in 9 (19.6%), of whom 2 survived. The other five patients were treated conservatively, and all died. Overall mortality rate was 26.1% (12/46). A significantly higher mortality rate was observed in patients with age > or = 50 years, positive peritoneal sign, shock index > 1, pH below 7.2 and bicarbonate concentration below 16 mEq/L as revealed by arterial blood gas (p < 0.05). CONCLUSIONS: The prognostic factors related to a higher mortality rate included age 50 years old or more, positive peritoneal sign, shock index above 1, pH below 7.2 and [HCO3-] below 16 mEq/L in arterial blood gas. Recognition of these factors indicates further detailed study will be required to propose a caustic injury score for predicting severity. Nevertheless, emergency operation is recommended if there are positive signs of peritonitis or mediastinitis, shock index above 1, pH below 7.0 and [HCO3-] below 10 mEq/L in arterial blood gas.

Acute Disease↗