Biomedical subjects

W T Chang

Publications and source records attributed to W T Chang.

At least 37 records · Page 2Linked to original sources

PubMed1997

Three-dimensional PET emission scan registration and transmission scan synthesis.

The duration of a positron emission tomography (PET) imaging scan can be reduced if the transmission scan of one patient which is used for emission correction can be synthesized by using the reference transmission scan of another patient. In this paper, we propose a new intersubjects PET emission scan registration method and PET transmission synthesis method by using the boundary information of the body or brain scan of the PET emission scans. The PET emission scans have poor image quality and different intensity statistics so that we preprocess the emission scans to have similar histogram and then apply the point distribution model (PDM) [15] to extract the contours of the emission scan. The extracted boundary contour of every slice is used to reconstruct the three-dimensional (3-D) surface of the reference set and the target set. Our registration is 3-D surface-based which uses the normal flow method [17] to find the correspondence vector field between two 3-D reconstructed surfaces. Since it is difficult to analyze internal organ using the PET emission scan imaging without correction, we assume that the deformation of internal organ is homogeneous. With the corresponding vector field between the two emission scans and the transmission scan of the reference set, we can synthesize the transmission scan of the target set.

Abdomen↗

PubMed1997

Purification and characterization of two bifunctional chitinases/lysozymes extracellularly produced by Pseudomonas aeruginosa K-187 in a shrimp and crab shell powder medium.

Two extracellular chitinases (FI and FII) were purified from the culture supernatant of Pseudomonas aeruginosa K-187. The molecular weights of FI and FII were 30,000 and 32,000, respectively, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 60,000 and 30,000, respectively, by gel filtration. The pIs for FI and FII were 5.2 and 4.8, respectively. The optimum pH, optimum temperature, pH stability, and thermal stability of FI were pH 8, 50 degrees C, pH 6 to 9, and 50 degrees C; those of FII were pH 7, 40 degrees C, pH 5 to 10, and 60 degrees C. The activities of both enzymes were activated by Cu2+; strongly inhibited by Mn2+, Mg2+, and Zn2+; and completely inhibited by glutathione, dithiothreitol, and 2-mercaptoethanol. Both chitinases showed lysozyme activity. The purified enzymes had antibacterial and cell lysis activities with many kinds of bacteria. This is the first report of a bifunctional chitinase/lysozyme from a prokaryote.

Amino Acids↗

PubMed1997

Production of chitinase from shellfish waste by Pseudomonas aeruginosa K-187.

The production of chitinolytic enzyme by Pseudomonas aeruginosa K-187, using shrimp and crab shell powder (SCSP) as the carbon source, was studied. It was observed that chemically treated SCSP induced a significant increase of enzyme production, as compared with untreated SCSP. Spent HCl and NaOH from the chitin production industry was used to process SCSP. Various strategies of SCSP processing are examined and compared in terms of chitinolytic enzyme production. A three-and-one-half-fold increase of enzyme production (0.68 U/ml to 2.4 U/ml) was attained using HCl/NaOH treated SCSP. The microorganism (K-187) was isolated from soil in Taiwan and has been characterized and reported in a previous paper.

Acetylglucosamine↗

PubMed1996

Identification of the cell fate gene stalky in Dictyostelium.

Using insertional mutagenesis, we have isolated a "stalky" mutant in which cells destined to become spores end up as stalk cells. Similar mutants were previously observed after chemical mutagenesis, but the affected gene could not be isolated. Our mutant, like the previous ones, is in stkA. Its defect is cell-autonomous and not overcome by overexpressing cAMP-dependent protein kinase. stkA is strongly expressed in the prespore region of aggregates but not in the anterior prestalk zone. The mutant expresses normal levels of prespore-cell transcripts but fails to produce the spore transcript spiA. stkA encodes a predicted 99 kDa protein (STKA) with two putative C4 zinc fingers, one of which is a GATA-type finger, indicating that it may be a transcription factor. This conclusion is supported by localization of STKA in the nucleus.

Amino Acid Sequence↗

PubMed1996

Evidence for transcriptional modulation but not acid phosphatase expression during programmed cell death in the colonial tunicate Botryllus schlosseri.

Botryllus schlosseri is a clonally modular ascidian in which asexually derived adults (zooids) exhibit developmental synchrony. At the conclusion of the blastogenic (asexual) cycle every 5 days at 21 degrees C, all zooids within a colony die simultaneously in 24 hours and are replaced by a new asexual generation of zooids. This cyclical process, called takeover, involves the selective destruction of the zooid's visceral tissues which include the pharynx, esophagus, stomach, intestine, endostyle, neural complex and heart, whereas bud tissues and mesenchymal components (muscle and blood cells) remain unaffected. Ultrastructural analysis indicates that the most prevalent form of cell death occurs by apoptosis, although necrotic changes are also observed in several tissues (i.e., stomach and intestine). Blood-derived macrophages and neighboring cells subsequently engulf visceral tissues, reducing the zooid to the size of a small vesicle. Here, we have tested the possibility that acid phosphatase, a hydrolase whose presence is associated with cell death in several invertebrate systems, could account for some of the regressive changes observed during takeover. Our observations indicate that acid phosphatase (AP) activity was selectively localized in the gut of parent zooids during the growth phase of the cycle, with the stomach exhibiting the most intense histochemical staining on tissue sections. As zooid regression progressed during takeover, stomach AP staining gradually disappeared. Other visceral tissues never became AP-positive. Therefore, this hydrolase appears to play a minimal role in zooid death. In order to characterize genes whose expression pattern was selectively altered during takeover, we have carried out differential mRNA display analysis. We report on two genes, 790.3 and 790.4, that are down- and upregulated, respectively, during this process. Collectively, these findings indicate that the takeover phase of blastogenesis in Botryllus involves modulated gene expression.

Acid Phosphatase↗

PubMed1996

Surgical management of the buried penis.

BACKGROUND: Buried penis is a congenital abnormality in which the phallus is concealed within the surface of prepubic skin. It is probably more common than is generally recognized. The objective was to describe the pathophysiology, and search for the best management of this disease. METHODS: Over a period of 6 years, a total of 31 cases receiving surgery for buried penis at this hospital were analyzed. According to their major pathophysiology, patients were divided into three groups: in the first, the major mechanism was poor skin suspension; in the second, prominent suprapubic fat pad was the major cause. In the third group, the dartos fascia was abnormally thickened and attached to the penile shaft. Different surgical techniques were applied in the different groups. RESULTS: All 15 children in the first group had satisfactory results after penile skin fixation. In the second group, nine children underwent adjunctive lipectomy but only five had satisfactory results. Seven patients in the third group needed degloving of the penis and the three cases who underwent preputial unfurling had severe lymphedema of the inner preputial layer. One of them received revision. The end results were good in the other six patients after long-term follow up. CONCLUSIONS: The buried penis occurs in a spectrum. Although, there are three major pathophysiology mechanisms, most of the patients had a combination. Surgical management should be individualized, and results are usually satisfactory. For the obese patient, weight loss is important. Preputial unfurling and using inner preputial layer to cover the defect should be avoided because of severe postoperative lymphedema.

Child↗

PubMed1996

Antenatal diagnosis and early surgery for choledochal cyst: a report of two cases.

Since the advent of routine antenatal sonography to detect fetal abnormalities, two cases of choledochal cyst have been found prenatally in our hospital. The first presented when a choledochal cyst was demonstrated at 31 weeks of gestation, and a firm diagnosis established within 2 days of birth. Technetium 99m disofenin (DISIDA) cholescintigram revealed delayed visualization of the small bowel. The second case was found by ultrasound examination at 21 weeks of gestation to have a choledochal cyst, and diagnosis was confirmed within 3 days of birth. DISIDA scintigram demonstrated complete obstruction of the extrahepatic biliary tree. Both infants received early excision of the cyst at the ages of three and four days respectively. The postoperative course was quite smooth, and there were no abnormal symptoms after follow up of four and two years, respectively. Neonates with distal common bile duct obstruction in association with presumed choledochal cyst should have prompt surgical exploration, and early excision of the cyst is a safe procedure in the newborn.

Adult↗

PubMed1996

Detection of k-ras point mutations in codons 12 and 13 in non-small cell lung cancers.

Point mutations of the K-ras gene have been reported in a wide variety of human tumors. By using polymerase chain reaction followed by direct DNA sequencing, we screened for point mutations at codons 12 and 13 of the K-ras gene in specimens obtained from fresh frozen tumors in 38 patients with non-small cell lung cancers. Point mutations were detected in two of 38 (5.3%) resected non-small cell lung cancers. Both of them were G to T transversions. One patient was found to have a K-ras codon 13 point mutation (GGC to TGC, gly to cys), while the other had a codon 12 point mutation (GGT to GTT, gly to val). Based on the limited numbers in this study, we found that the frequency of K-ras point mutations in codons 12 and 13 among Asian patients with lung adenocarcinomas was lower than that detected among Caucasian patients.

Adult↗

PubMed1995

Trapping developmental promoters in Dictyostelium.

Recently an insertional mutagenesis procedure has been developed to permit cloning of genes affected in developmental mutants of Dictyostelium discoideum (Kuspa and Loomis, Proc. Natl. Acad. Sci. USA 89, 8803-8807, 1992). In this procedure a plasmid bearing the URA (pyr5-6) gene is linearized with a restriction enzyme and electroporated into URA- amoebae (auxotrophic for uracil) together with the corresponding restriction enzyme. Transformants that can grow without uracil are screened for developmental defects resulting from insertion of the plasmid into a gene of developmental importance. We have modified this procedure to permit characterization of the promoters and structural sequences of genes that would be missed by the standard procedure because their disruption produces no obvious phenotype. Constructs carrying a promoter-less Escherichia coli lacZ gene were designed so that expression of lacZ requires insertion into an active host transcription unit. By screening restriction enzyme-generated transformants we have isolated several strains in which lacZ is under the control of a developmentally activated promoter and have cloned the 5' flanking DNA adjacent to the insertion site. Sequencing the junction between plasmid and host genome has confirmed in-frame fusion with the lacZ gene, and reintroduction of the cloned plasmids into parental cells has shown that the cloned sequences do actually contain the relevant promoters. This procedure should give ready access to a wide range of developmental promoters without the need for prior identification of the developmental genes involved.

Animals↗

PubMed1995

Jejunoileal atresia in neonates.

BACKGROUND: Jejunoileal atresia is the most common intestinal atresia and the most frequent cause of neonatal intestinal obstruction. The prognosis depends on several important factors. The patients reported were collected for evaluation of the factors contributing to their prognoses. METHODS: In the ten-year period from October 1982 to October 1992, all jejunoileal atresia patients who received treatment in this hospital were entered in this study. Possible factors contributing to prognosis, such as prematurity, low birth weight, apple peel atresia, anastomotic leakage, sepsis, short bowel syndrome were evaluated using Mann-Whitney U-test. RESULTS: Twenty-four patients of jejunoileal atresia had been managed in our hospital in 10 years period. Their ages ranged from one to thirteen days old (mean 3.9 days). The numbers and types of atresia were as follow: type I (n = 4), type II (n = 4), type IIIa (n = 10), type IIIb (n = 5), type IV (n = 1). All patients received surgical correction. Nine complications were found in eight patients, which included four anastomotic leakage, three wound infections and two intestinal obstructions. There were three mortalities from sepsis. Total parenteral nutrition was applied to 14 patients (58.3%). The mean hospital stay was 45.1 days, and the survival rate was 87.5%. Low birth weight and anastomotic leakage contributed to prolonged hospital stays (p < 0.05). CONCLUSIONS: Jejunoileal atresia is a common neonatal surgical condition. The prognosis is generally good, except when a patient presented with factors, such as, low birth weight or anastomotic leakage, which prolonged hospital stays. Moreover, sepsis is the only important factor contributing to mortality.

Female↗

PubMed1995

Production of chitinase by Pseudomonas aeruginosa K-187 using shrimp and crab shell powder as a carbon source.

Shrimp and crab shell powder prepared by treating shrimp and crab processing waste with boiling and crashing was used as a substrate for isolating alkali-tolerant chitinolytic microorganisms. Strain K-187 appeared to be the chitinase-producing strain with the most potential. The organism was identified as a strain of Pseudomonas aeruginosa. Maximum chitinase activity was obtained when the strain was grown aerobically in a medium consisting of 3.0% shrimp and crab shell powder, 0.1% CMC, 0.1% (NH4)2SO4, 0.1% K2HPO4, 0.1% MgSO4.D7H2O and 0.1% ZnSO4 (pH 9), at 45 degrees C after 3 days. The optimum pH and temperature of the enzyme reaction were 7 and 40 degrees C, respectively. The chitinase was stable at pH from 5 to 10 and was stable under 60 degrees C.

Animals↗

PubMed1995

Posterior urethral valves: a report of five cases.

From 1985 to 1993, five male patients with posterior urethral valves were treated at our hospital; they included three newborns, a 32-month-old and a 10-year-old child. On initial examination, all patients showed severe bilateral hydronephrosis and hydroureter on sonographic findings, dilatation of the prostate urethra and trabeculation of the bladder wall in the voiding cystourethrogram; only one patient showed vesicoureteral reflux. Type I urethral valves were present in all patients. Retrograde transurethral ablation of the valves was performed in four patients with good preoperative renal function. The postoperative courses were smooth except for vesicoureteral reflux in one patient and systemic fungus infection in another. Reimplantation of the ureter was done for the vesicoureteral reflux, and the fungus infection was treated by amphotericin B. Cutaneous vesicostomy was performed for a newborn since the urethral orifice was small. He presented with poor renal function and ascites. Delayed antegrade ablation of the valves per vesicostomy and closure of the vesicostomy were done three months later after restoration of the renal function. Renal function returned to normal after operation in all patients, but the function of the upper urinary tract and bladder continence need long-term follow-up.

Child↗

PubMed1994

Studies on the concentrations of arsenic, selenium, copper, zinc and iron in the hair of blackfoot disease patients in different clinical stages.

Flame atomic absorption spectrophotometric methods were developed for, arsenic, selenium, copper, zinc and iron in hair samples. Data from blackfoot disease patients at five clinical stages were compared with those from healthy controls. The copper and zinc concentrations showed only slight differences in all clinical stages, which indicated the less relation to blackfoot disease. The decrease of selenium and iron in all stages was attributed to the antagonistic effect of arsenic; arsenic increased in the first and second stages, but decreased in the later stages. The decrease of selenium and iron during the progression of the disease is thought to be due to persistence of the antagonistic effect of arsenic in the initial stages, so that very low concentrations of selenium are found in the advanced stages, despite the later decrease of arsenic. There was also a progressive decrease of iron with advance of the disease, and the later stages also showed a decrease in haemoglobin. It was shown that arsenic is a major cause of blackfoot disease, and that it antagonises selenium and iron, which decreased in the advanced clinical stages of the disease.

Aged↗

PubMed1994

Stroke-like complication after abdominal surgery: a case report of chronic subdural hematoma.

An 81-year-old patient who developed consciousness change and progressive right limb weakness after low abdominal surgery is reported. Brain computed tomography scan showed a left-sided chronic subdural hematoma; appropriate management was instituted immediately. This case is a reminder of the possibility of chronic subdural hematoma in elderly patients who may develop stroke-like symptoms after non-neurosurgical procedures.

Abdomen↗

PubMed1994

Adrenal adenoma with primary aldosteronism in a child: a case report.

Primary aldosteronism caused by an aldosterone-producing adrenal adenoma was documented in an 11-year-old girl who presented with persistent hypertension, headache, tinnitus and hypokalemia. Elevated plasma aldosterone concentration (PAC) (45.5 ng/dl) and suppressed plasma renin activity (PRA) (< 0.3 ng/ml/hrs) were detected. Saline infusion test and postural test helped to confirm the diagnosis. The tumor site was localized by magnetic resonance imaging (MRI). Surgical removal of the tumor yielded dramatic improvement in blood pressure; PAC and PRA returned to normal range. This rare case illustrates the feasibility of recognition and localization of adrenal adenoma in children. The high cure rate by surgical excision warrants careful screening of hypertensive patients with this entity.

Adenoma↗

PubMed1994

Clinical observation of neonatal gastrointestinal perforation.

BACKGROUND: Gastrointestinal perforation is an infrequent occurrence in neonates. Experience in its management is presented, while also attempting to analyze the factors affecting outcome. METHODS: From 1983 to 1992, 31 neonates with gastrointestinal perforation were treated at Taichung Veterans General Hospital. The medical records of these patients were reviewed thoroughly. In the meantime, Mann-Whitney U and Yates' correction chi square tests were used to analyze the factors predicting the outcomes. RESULTS: There were 21 males and 10 females, among whom 16 were premature births. The median age at diagnosis was 5 day; half (16/31) had occurred during the first 5 days of life. Abdominal distension was the most common manifestation (87%). Hemograms at admission showed leukopenia in 32% (10/31) and thrombocytopenia in 40% (8/20) of the patients. Metabolic acidosis was present in 46% (13/28) of the patients. Peritoneal fluid and preoperative blood cultures were positive in 71% (17/24) and 50% (13/26) of the patients, and both of them had Gram-negative enterobacteriacea as the most common pathogen. The overall mortality rate was 58%. The highest mortality rate was associated with gastric perforation (100%), followed by small bowel (50%) and colon (50%) perforations. The predominant cause of perforation was necrotizing enterocolitis (14/31), with the most common site the terminal ileum (16/29). Four patients with necrotizing enterocolitis had multiple perforations. Others who underwent surgery showed single perforation. The major cause of death in those patients who received operation was sepsis (8/13). An initial arterial pH value higher than 7.25, and surgical procedure performed within two days after disease onset may predict a favorable outcome (p < 0.01). CONCLUSIONS: Gastrointestinal perforation is a life-threatening complication in neonates. A better survival rate can be obtained by cooperation among neonatologists, pediatric surgeons and the nursing staff taking care of these high risk babies.

Chi-Square Distribution↗

PubMed1994

Congenital duodenal web in late infancy and childhood: a report of two cases.

Congenital duodenal webs are rare lesions, usually detected during early infancy because of signs of high intestinal obstruction. The occasional patient escapes both symptoms and detection until adolescence or adulthood. This report concerns two cases of congenital duodenal web at different ages and with different clinical manifestations. Case 1, a six-month-old male, was admitted because of abdominal distention and vomiting. Case 2, a 13-year-old boy, was referred here for further evaluation of recurring seizure attacks, elevated blood urea nitrogen and creatinine and hyponatremia. Duodenotomy and excision of the web performed for both patients. Complete amelioration of all symptoms was then observed at Outpatient Clinic follow-up for one year.

Adolescent↗

PubMed1994

Congenital diaphragmatic hernia.

BACKGROUND: The management of congenital diaphragmatic hernia (CDH) remains a subject of controversy. With the objective to achieve a better future survival rate, clinical analysis of 14 cases during a 10-year period was done. METHODS: From 1983 to 1992, 14 cases with CDH were treated at Taichung Veterans General Hospital. The medical records of these patients were reviewed thoroughly. In the meantime, Mann-whitney U and Fisher's exact tests were used to analyze the factors predicting the outcomes. RESULTS: The overall mortality rate was 36%. Bochdalek hernia represented the most common defect in those patients who were operated upon (10/13, 77%). Ipsilateral pulmonary hypoplasia was present in five patients, four of whom died. Unilateral diaphragm agenesis was noted in two cases and both expired postoperatively. Initial arterial pH < 7.2, PaCO2 > 60 mmHg and early onset of symptoms may predict a poor outcome. There were no significant benefits from preoperative stabilization in those patients whose initial arterial pH values were lower than 7.2. CONCLUSIONS: CDH remains a major challenge for pediatricians and pediatric surgeons. Further studies are needed to deal with this frustrating disorder.

Female↗