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T L Huang

Publications and source records attributed to T L Huang.

At least 73 records · Page 4Linked to original sources
PubMed1997

Three-dimensional helical computed tomographic cholangiography: application to living related hepatic transplantation.

Variations in the anatomy of intrahepatic bile ducts complicate operations in living related hepatic transplantation (LRHT). Preoperative delineation of the biliary system is important to achieve successful results. The purpose of this study was to assess the utility and accuracy of three-dimensional helical computed tomographic cholangiography (3DHCTC) as a replacement for endoscopic retrograde cholangiography (ERC) in evaluating the anatomy of the intersegmental biliary connection of the potential donors in LRHT. Helical CT was performed in 16 potential donors after a slow infusion of 100 cm3 meglumine iodipamide. By using the maximum intensity projection and shaded surface displaced image reconstruction technique, three-dimensional images of the bile ducts were isolated from the surrounding hepatic parenchyma. Among the 16 potential donors, 3 cases underwent an ERC study and another 7 cases donated liver graft during LRHT. In all 16 cases the anatomy of the bilateral essential intrahepatic ducts was well displayed with and without the liver parenchyma background in an axial and three-dimensional fashion which had good correlation with images from ERC and intra-operative cholangiography. Two variants were found, including drainage of the right posterior intrahepatic duct into the left hepatic duct and direct drainage of the segment II bile duct into the common hepatic duct, respectively. It is concluded that unusual routes of intrahepatic ducts may necessitate a change in the cutting plane during graft retrieval and patterns of ductoenteral anastomosis to avoid potential complications to both donors and recipients. With the advantages of non-invasiveness and comparable accuracy in demonstrating biliary anatomy, 3DHCTC may replace the traditional ERC in the pre-transplant survey of potential donors for LRHT.

Adult↗
PubMed1997

Variations of the intrahepatic bile ducts: application in living related liver transplantation and splitting liver transplantation.

The variations in the anatomy of intrahepatic bile ducts complicate operations in living related liver transplantation (LRLT) and therefore preoperative delineation of the biliary system is important to achieve a successful outcome. The aim of this study was to establish a standard relationship between the biliary variations and the methods of the graft splitting and anastomosis. Of 958 endoscopic retrograde cholangiographies with good visualization of bile duct branches were selected and were available for evaluation of their ramifications and variants. According to drainage of right hepatic duct and left hepatic duct, we classified the bile ducts into two major groups. Unusual routes of the intrahepatic ducts were present in 105 cases (11% in group A) the right sectoral duct drained into the left hepatic duct directly; in 200 cases (21% in groups B) the duct of segment IV drained into right side or common hepatic duct; and in 29 cases (3% in groups B) the duct of segment: II and III drained into the CBD and right hepatic duct separately. There is no specific bile duct variation that forbids someone from LRLT and SLT, but unusual intrahepatic ducts routes may require a change both in the cutting plane during graft retrieval and pattern of ductoenteral anastomosis to avoid potential complications to both donors and recipients. Cholangiography for screening intrahepatic duct variations is therefore important for safe bile drainage for both donors and recipients.

Adolescent↗
PubMed1996

Variations of the left and middle hepatic veins: application in living related hepatic transplantation.

The anatomic variations of the middle hepatic vein (MHV) and left hepatic vein (LHV) in 200 patients with normal liver function were analyzed using ultrasonography to clarify the feasibility of resecting the left lobe or left lateral segment in living subjects for living related hepatic transplantation (LRHT). The MHV and LHV form a common trunk in 70% of cases but drain independently into the inferior vena cava (IVC) in 30%. In 7% of cases, the left median vein (LMV) drains into the MHV, in 32% of cases the anterior superior segmental vein (ASSV) that drains segment 8 flows into the MHV. The distance between the two confluence points (LHV flows into MHV or IVC and LMV flows into the MHV) ranged from 0.3 cm to 2.5 cm with an average of 0.75 cm. The diameter of the LMV at the point that flows into MHV ranged from 0.3 cm to 0.9 cm. with an average of 0.61 cm. The distance from the IVC to the confluence of the MHV and LHV ranged from 0 cm to 3.5 cm with an average of 1.5 cm in those cases whose MHV and LHV presented as common trunks. Preoperative delineation of this complex venous anatomy is of paramount importance because the hepatic veins have to be transected in the cutting plane of the liver. The location of this plane is determined by the optimal graft volume required, and both the graft and the remnant liver have to retain perfect function. The venous anatomy would change the cutting plane in the living donor and the surgical method of anastomosis for the recipient.

Adult↗
PubMed1996

Structure-activity relationships for substrates and inhibitors of mammalian liver microsomal carboxylesterases.

PURPOSE: Carboxylesterases are important in the detoxification of drugs, pesticides and other xenobiotics. This study was to evaluate a series of substrates and inhibitors for characterizing these enzymes. METHODS: A series of novel aliphatic esters and thioesters were used in spectral assays to monitor human, murine and porcine esterases. A series of transition state mimics were evaluated as selective esterase inhibitors. RESULTS: Several alpha-alkyl thioacetothioates were found to be approximately 2 to 11-fold superior to commonly used substrates for monitoring carboxylesterase activity. Insertion of a heteroatom in the acid portion of these esters in the beta or gamma position relative to the carbonyl had a dramatic effect on enzyme activity with S or O substituents often improving the kCAT/K(M) ratio of the substrate and N decreasing it. Several alpha,alpha'-bis (2-oxo-3,3,3-trifluoropropylthio)alkanes proved to be potent selective transition state mimics of the esterase activity with IC50's from 10(-5) to 10(-9)M. CONCLUSIONS: This library of substrates and inhibitors are useful research tools for characterizing the numerous isozymes of carboxylesterases present in mammalian tissues.

Animals↗
PubMed1996

Total knee arthroplasty in tuberculous arthritis.

Sixteen cases of tuberculosis of the knee treated by total knee arthroplasty with followup of 3.4 to 11 years were reviewed. Eight cases were treated with antituberculous chemotherapy for 2 to 20 months before and 1 year after the arthroplasty. Another 8 cases were not diagnosed primarily and therefore received only postoperative antituberculous chemotherapy. Five cases had a recurrence of tuberculosis. Four of these 5 cases did not receive preoperative antituberculous treatment. The infection in 1 case was controlled satisfactorily with chemotherapy alone, and for the other 3 cases, chemotherapy was supported by surgical debridements. The last case of recurrent infection occurred in a patient who had received long- standing corticosteroid therapy. He required an excisional arthroplasty to control the infection. The mean functional knee score was 30.5 points before surgery and 82.6 points at the time of the last followup. These results suggest that arthroplasty may be formed for knees badly damaged with tuberculous infection, and good results may be expected for those patients who have received effective antituberculous chemotherapy both before and after surgery. There is a substantial risk of reactivation of tuberculous infection for those patients not treated before surgery or for patients dependent on corticosteroids.

Adult↗
PubMed1996

Paediatric liver transplantation: a 10 year experience in Taiwan.

Between March 1984 and August 1994, 13 orthotopic liver transplantations were performed in 13 patients < or = 25 years of age. The indications included Wilson's disease (n = 7), biliary atresia (n = 4), choledochal cyst (n = 1) and hepatitis C cirrhosis (n = 1). Technical variants included full-size (n = 11), reduced-size (n = 1) and living-related (n = 1) liver transplantation. These recent technical innovations have offered an expanded donor pool for earlier transplantation, shorter waiting times and excellent quality grafts. Surgical complications occurred in six patients; all required additional surgery. Biliary complications were encountered more commonly in our earlier patients. Our actuarial patient and graft survival rate is 92% at 2 years. The long-term follow-up of our liver-transplanted Wilson's disease patients provides confirmatory evidence that orthotopic liver transplantation cures the underlying metabolic defect with complete normalization of biochemical abnormalities of copper metabolism, reversal of neurological impairments and the disappearance of Kayser-Fleischer corneal rings. The high rate of patient survival and excellent rehabilitation indicate that with prudent clinical judgement, liver transplantation can be achieved with an acceptable rate of morbidity, mortality and cost in a setting where manpower and donor organs are very limited.

Adolescent↗
PubMed1995

Characterization of a spectrophotometric assay for juvenile hormone esterase.

Two surrogate substrates, methyl 1-heptylthioacetothioate (HEPTAT) and methyl 1-hexylthioacetothioate (HEXTAT) were utilized to compare a new spectrophotometric assay with the standard radiochemical partition assay used to quantify juvenile hormone esterase (JHE) activity. The surrogate substrates were made with one common factor being a thiol ester moiety substituting for the ester moiety found in juvenile hormones (JHs) and a thioether replacing the 2,3-olefin of the JHs. As a result, nucleophilic attack by the serine residue of JHE at the carbonyl functional group results in a hydrolytic reaction and release of methanethiol. In the presence of Ellman's Reagent (DTNB) methanethiol will cleave the disulfide bond of DTNB resulting in a chromophore detectable at 405 nm. Methyl 1-hexylthioacetothioate and its oxygen ester analogue, methyl-1-hexylthioacetate, were compared for JHE activity. Statistical analysis of the slopes indicated a very small but significant difference between the hydrolytic rates for the thiol ester and oxygen ester. However, the data indicate that thiol esters can replace oxygen esters to quantify hydrolytic activity by the JHEs examined. Results gathered from different preparations of JHE including tissue culture media from a baculovirus expression system, affinity- and DEAE-purified enzyme, as well as insect hemolymph indicate an excellent correlation between the two assays. Isoelectric focusing of pure and crude JHE preparations resulted in coinciding peaks of hydrolytic activity when using the standard partition assay and the spectrophotometric assay, with no other peaks of activity found in the crude preparations with either substrate. Several esterase bands were found at different isoelectric points when gels were stained with alpha-naphthyl acetate.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗
PubMed1994

Juvenile hormone esterase purified by affinity chromatography with 8-mercapto-1,1,1-trifluoro-2-octanone as a rationally designed ligand.

Trifluoromethyl ketones are potent inhibitors of a variety of serine hydrolases. Based on this chemistry improved affinity chromatography procedures were developed for juvenile hormone esterase from insects. New affinity gels were prepared by binding rationally designed ligands to epoxy-activated Sepharose. One ligand is 8-mercapto-1,1,1-trifluoro-2-octanone which has a methylene group replacing a sulfide sulfur beta to the carbonyl of the trifluoromethyl ketone of the previously reported ligand, 3-(4-mercaptobutylthio)-1,1,1-trifluoro-2-propanone. With many loading levels and esterases, the original gel bound enzymes too tightly, resulting in elution difficulties. This replacement of the sulfur beta to the ketone thought to interact with the catalytic serine decreases the binding capacity of the gel at similar loading by approximately 56% compared to the affinity gel with the thioether. However, elution of the enzyme from the column can be accomplished with less potent inhibitors such as 3-n-butylthio- or 3-n-pentylthio-1,1,1-trifluoro-2-propanone, which can easily be removed from the enzyme by dialysis in the presence of the detergent n-octyl beta-D-glucopyranoside. An alternative approach allowing elution with less potent inhibitors involved varying concentrations of the previous high-affinity ligand to optimize the concentration of ligand on the column. Low concentrations of the high-affinity ligand also allowed the use of less potent eluting agents. These two improved affinity chromatography systems have been successfully used to purify juvenile hormone esterase of Heliothis virescens to near homogeneity with a 30-90% recovery of recombinant esterase secreted into the cell media in a baculovirus expression system. The purity of the esterase after affinity chromatography with newly prepared gel was comparable to that produced using the original affinity system based on analyses by SDS-PAGE and isoelectric focusing. A library of affinity gels with ligands of different affinities used at several loading levels and a library of eluting inhibitors of varying potency facilitate the rational selection of conditions for the affinity purification of esterases.

Animals↗
PubMed1993

Development of surrogate substrates for juvenile hormone esterase.

Twenty-nine thioester compounds were synthesized to test their effectiveness as surrogate substrates for the insect enzyme, juvenile hormone esterase (JHE). Substrates were designed that resembled the endogenous substrate juvenile hormone (JH), with one common factor being a thioester instead of carboxyl ester found in JH. The principle of the spectrophotometric assay is based on a modification of Ellman's method. Characterization of the substrates showed that replacement of the carbon atom by a sulfur or oxygen beta to the carbonyl of the acyl group of the substrates resulted in an approximate five- to sixfold increase in the rate of hydrolysis by JHE. The specific activities of JHE, porcine liver carboxylesterase, and acetylcholinesterase were determined for the surrogate substrates. While JHE and porcine liver carboxylesterase hydrolyzed several of the substrates, acetylcholinesterase did not produce any detectable hydrolysis of the substrates. Michaelis-Menten kinetic parameters of the surrogate substrates when compared to a previously reported partition assay, utilizing radiolabeled [3H]JH III, indicated that the surrogate substrates have lower affinity as indicated by higher Km values but are more easily hydrolyzed (Vmax) by JHE. Furthermore, optimal reaction conditions for substrate hydrolysis and the spectrophotometric reaction were determined. In addition, first order rate constants for base hydrolysis and critical micelle concentrations were determined for several surrogate substrates. The spectrophotometric assay was also compared with a Vmax and research spectrophotometer, and these two instruments produced almost identical slopes. The relative potency of four transition state inhibitors of JHE was found to be similar with those of the surrogate substrates and the [3H]JH III substrate.

Acetylcholinesterase↗
PubMed1993

Hydrolysis of carbonates, thiocarbonates, carbamates, and carboxylic esters of alpha-naphthol, beta-naphthol, and p-nitrophenol by human, rat, and mouse liver carboxylesterases.

Thirty carbonates, thiocarbonates, carbamates, and carboxylic esters of alpha-naphthol, beta-naphthol, and p-nitrophenol were synthesized and tested as substrates for liver carboxylesterases from the crude microsomal fractions of human and mouse, and purified isozymes, hydrolases A and B, from rat liver microsomes. The carbonates, thiocarbonates, and carboxylic esters of alpha-naphthol were cleaved more rapidly than the corresponding beta-naphthol isomers by the mammalian liver esterases. alpha-Naphthyl esters of acetic, propionic, and butyric acids were among the best substrates tested for these enzymes. The majority of the substrates was consistently hydrolyzed at higher rates by hydrolase B compared with hydrolase A, although the Michaelis-Menten constant (Km) values of selected substrates differed widely with these two isozymes. Malathion was a 15-fold better substrate for hydrolase B than for hydrolase A. Compared with the corresponding carboxylates, the carbonate moiety of alpha- and beta-naphthol and p-nitrophenol lowered the specific activities of the enzymes by about fivefold but improved stability under basic conditions. The optimum pH of mouse liver esterase with the acetate, methyl-carbonate, and ethylthiocarbonate of alpha-naphthol was between pH 7.0 and pH 7.6. Human and mouse liver microsomal esterase activities were about five orders of magnitude lower than the esterase activities of purified rat liver hydrolase B. A relationship between the catalytic activity of the enzymes and the lipophilicity of the naphthyl substrates indicated that (i) in the alpha- and beta-naphthyl carbonate series, an inverse relationship between enzyme activity and lipophilicity of the substrates was observed, whereas (ii) in the alpha-naphthyl carboxylate series, an increase in enzyme activity with increasing lipophilicity of the substrates up to a logP value of about 4.0 was observed, after which the enzyme activity decreased.

Animals↗