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Y T Chang

Publications and source records attributed to Y T Chang.

At least 73 records · Page 4Linked to original sources
PubMed1996

Determination of specificity of a high-affinity inositol 1,3,4,5-tetrakisphosphate binding site at a 42 kDa receptor protein, p42IP4: comparison of affinities of all inositoltris-,-tetrakis-, and -pentakisphosphate regioisomers.

The specificity of the binding site of p42IP4, a high-affinity 42 kDa Ins (1,3,4,5)P4 receptor protein identified by photoaffinity labelling (Reiser et al., Biochem. J. 280, 533, 1991) was analyzed by determining the affinities for all possible inositoltris-, -tetrakis-, and -pentakisphosphate regioisomers. We tested the purified receptor protein displaying a Kd of 2.2 nM for Ins (1,3,4,5)P4 which was unequalled by any of the other inositoltetrakis- and -trisphosphate regioisomers. The affinities of inositoltetrakisphosphates were 25 to 150 times lower, with a substitution at C-2 having the largest effect in reducing the affinity. The inositoltrisphosphate isomers were three orders of magnitude less potent than Ins (1,3,4,5)P4, apart from D/L-Ins (3,4,5)P3. The pentakisphosphate Ins(1,3,4,5,6)P5 had an affinity for the solubilized and purified receptor comparable to that of D-Ins (1,3,4,5)P4. This lack of discrimination was unique for the solubilized receptor, since it was not observed with the membrane-associated receptor protein. Most importantly, D-Ins (1,3,4,5)P4 and D-Gro PtdIns (3,4,5)P3 had identical affinities with the 42 kDa protein. Thus, this protein p42IP4 selectively recognizes two potential second messengers.

Animals↗
PubMed1996

Synthesis and iron binding studies of myo-inositol 1,2,3-trisphosphate and (+/-)-myo-inositol 1,2-bisphosphate, and iron binding studies of all myo-inositol tetrakisphosphates.

The first syntheses of the natural products myo-inositol 1,2,3-trisphosphate and (+/-)-myo-inositol 1,2-bisphosphate are described. The protected key intermediates 4,5,6-tri-O-benzoyl-myo-inositol and (+/-)-3,4,5,6-tetra-O-benzyl-myo-inositol were phosphorylated with dibenzyl N,N-di-isopropylphosphoramidite in the presence of 1H-tetrazole and subsequent oxidation of the phosphite. The crystal structures of the synthetic intermediates (+/-)-1-O-(tert-butyldiphenylsilyl)-2,3,O-cyclohexylidene-myo-inos itol and (+/-)-4,5,6-tri-O-benzoyl-1-O-(tert-butyldiphenylsilyl)-2,3-O-cycl ohexylidene- myo-inositol are reported. myo-Inositol 1,2,3-trisphosphate, (+/-)-myo-inositol 1,2-bisphosphate, and all isomeric myo-inositol tetrakisphosphates were evaluated for their ability to alter HO. production in the iron-catalysed Haber-Weiss reaction. The results demonstrated that a 1,2,3-grouping of phosphates in myo-inositol was necessary for inhibition, also that (+/-)-myo-inositol 1,2-bisphosphate potentiated HO. production. myo-Inositol 1,2,3-trisphosphate resembled myo-inositol hexakisphosphate (phytic acid) in its ability to act as a siderophore by promoting iron-uptake into Pseudomonas aeruginosa.

Binding Sites↗
PubMed1996

Alternative splicing in the coding region of human aromatic L-amino acid decarboxylase mRNA.

Total RNA from human neuroblastoma cells (SK-N-SH) was reverse transcribed and amplified using primers specific for aromatic L-amino acid decarboxylase (AADC). Two polymerase chain reaction (PCR) products were observed following agarose electrophoresis. Cycle sequencing of the PCR products revealed the larger fragment (414 bp) to be identical to the published human cDNA sequence (Type I). Sequencing of the smaller band (300 bp) demonstrated a form missing exon three (Type II). Both types of the mRNA were colocalized in human brain regions (gray matter and white matter) and other human tissues (liver, kidney, adipose, heart, adrenal gland and keratinocytes). The relative concentrations varied in each tissue studied but specific neuronal or non-neuronal patterns were not apparent. The study demonstrates alternative splicing within the coding region of the human AADC mRNA and the results suggest the possibility that two proteins are derived from the AADC gene in human tissues.

Aromatic-L-Amino-Acid Decarboxylases↗
PubMed1996

Computer modeling of 3D structures of cytochrome P450s.

The understanding of structure-function relationship of enzymes requires detailed information of their three-dimensional structure. Protein structure determination by X-ray and NMR methods, the two most frequently used experimental procedures, are often difficult and time-consuming. Thus computer modeling of protein structures has become an increasingly active and attractive option for obtaining predictive models of three-dimensional protein structures. Specifically, for the ubiquitous metabolizing heme proteins, the cytochrome P450s, the X-ray structures of four isozymes of bacterial origin, P450cam, P450terp, P450BM-3 and P450eryF have now been determined. However, attempts to obtain the structure of mammalian forms by experimental means have thus far not been successful. Thus, there have been numerous attempts to construct models of mammalian P450s using homology modeling methods in which the known structures have been used to various extents and in various strategies to build models of P450 isozymes. In this paper, we review these efforts and then describe a strategy for structure building and assessment of 3D models of P450s recently developed in our laboratory that corrects many of the weaknesses in the previous procedures. The results are 3D models that for the first time are stable to unconstrained molecular dynamics simulations. The use of this method is demonstrated by the construction and validation of a 3D model for rabbit liver microsomal P450 isozyme 2B4, responsible for the oxidative metabolism of diverse xenobiotics including widely used inhalation anesthetics. Using this 2B4 model, the substrate access channel, substrate binding site and plausible surface regions for binding with P450 redox partners were identified.

Amino Acid Sequence↗
PubMed1996

Construction and evaluation of a three-dimensional structure of cytochrome P450choP enzyme (CYP105C1).

The purpose of this work was to develop and carefully evaluate improved strategies for constructing reliable 3-D models of P450 isozymes. To this end, a unique combination of steps for building and evaluating a model structure was used to build a homology model of the P450choP isozyme, based on knowledge of the X-ray structures of P450cam, P450terp, P450BM-3 and P450eryF. Specifically, the reliability of this model was examined by systematic comparisons of its conformational, energetic, environmental and packing properties and those of the four reference proteins with corresponding properties from the database of proteins with known structures. The results showed that the examined properties of this model structure are well within the criteria established for reliable structures and are of nearly as good quality as those of the reference proteins. In addition, the result from a 120 ps unconstrained MD simulation of the model with structural waters provided evidence that the model is stable at room temperature. This 3-D model can now be reliably used for explicit characterization of substrate and inhibitor complexes. Most importantly, although it is envisioned that building models for mammalian P450s will be even more challenging, the steps described here should be very useful in future construction of 3-D models of mammalian P450 isozymes.

Amino Acid Sequence↗
PubMed1996

Extramammary Paget's disease: a report of 22 cases in Chinese males.

Extramammary Paget's disease (EMPD) is more frequently seen in Caucasian females than in males (3.2:1 female:male ratio). During the past 14 year period, we have collected 22 patients, all Chinese males, with EMPD. They presented with eczema-like lesions in the early stages in the genital or perianal regions. Histological sections showed Paget cells within the epidermis or skin appendages and even within the dermis. No underlying adnexal carcinoma or adjacent internal carcinoma could be detected after thorough examinations. Mode of therapy and outcome are presented. EMPD seems to affect more males than females in Orientals. The incidence of concomitant malignancy in Chinese male patients with genital Paget's disease seems to be much lower than that in Caucasians. However, if EMPD involves the glans penis or perianal area, a search for internal malignancy is still warranted.

Aged↗
PubMed1996

A new compound heterozygous frameshift mutation in the type II 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) gene causes salt-wasting 3 beta-HSD deficiency congenital adrenal hyperplasia.

We report a new compound heterozygous frameshift mutation in the type II 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) gene in a Pakistanian female child with the salt-wasting form of 3 beta-HSD deficiency congenital adrenal hyperplasia. The child, born with clitoral enlargement, manifesting salt-wasting adrenal crisis, and public hair growth during infancy, was treated with hormonal replacement therapy. The etiology of her congenital adrenal hyperplasia, however, was not defined. Two of her siblings, as well as one paternal cousin with ambiguous genitalia and palpable gonads and another paternal cousin with normal female genitalia, had symptoms of adrenal crisis and died during early infancy. Thus, although the family history suggested possible 3 beta-HSD deficiency disorder, suppressed adrenal function caused by excess glucocorticoid therapy in this child at 7 yr of age did not allow hormonal diagnosis. To confirm 3 beta-HSD deficiency, we sequenced the type II 3 beta-HSD gene in the patient, her family, and the parents of her decreased paternal cousins. The type II 3 beta-HSD gene region of a putative promoter, exons I, II, III, and IV, and exon-intron boundaries were amplified by PCR and sequenced in all subjects. The DNA sequence of the child revealed a single nucleotide deletion at codon 318 [ACA (Thr)-->AA] in exon IV in one allele, and two nucleotide deletions at codon 273 [AAA(Lys)-->A] in exon IV in the other allele. The remaining gene sequences were normal. The codon 318 mutation was found in one allele from the father, brother, and parents of the deceased paternal cousins. The codon 273 mutation was found in one allele of the mother and a sister. These findings confirmed inherited 3 beta-HSD deficiency in the child caused by the compound heterozygous type II 3 beta-HSD gene mutation. Both codon 273 and 318 mutations yielding frameshift and premature stop codons at codons 279 and 367, respectively, are predicted to result in an altered and truncated type II 3 beta-HSD protein, thereby causing salt-wasting 3 beta-HSD deficiency in the patient. The type II 3 beta-HSD gene findings and clinical history of her family members suggest that the patient's deceased siblings were likely affected males with the same compound heterozygous mutations of the gene as in the proband, whereas the deceased cousins were likely affected with the homozygous codon 318 mutation in the gene.

3-Hydroxysteroid Dehydrogenases↗
PubMed1996

Studies of 3 beta-hydroxysteroid dehydrogenase genes in infants and children manifesting premature pubarche and increased adrenocorticotropin-stimulated delta 5-steroid levels.

Classic 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) deficiency congenital adrenal hyperplasia (CAH) results from a mutation in the type II 3 beta HSD gene encoding adrenal and gonadal 3 beta HSD. We investigated the type II and type I 3 beta HSD gene sequences in 15 infants and children with premature pubarche (PP; mean/range of age at PP, 4/0.08-9 yr) and elevated ACTH-stimulated delta 5 precursor steroid levels. Compared to Tanner I control subjects of similar age, ACTH-stimulated hormonal levels were at 2.3-10.7 SD for 17-hydroxypregnenolone (delta 5-17P) in all PP subjects, at 2.2-17 SD for dehydroepi-androsterone (DHEA) and 2.4-5.6 SD for the delta 5-17P/cortisol (F) ratio in all PP subjects except 1 infant, and at 2.3-10 SD for the DHEA/ androstenedione (delta 5-A) ratio in 8 PP subjects. Compared to Tanner II normal children, the hormonal levels were at 3-8 SD for delta 5-17P in all 13 PP children, at 2.3-4.7 SD for the delta 5-17P/F ratio in 6 PP children, and at 2.3-6.5 SD for DHEA and 3.5-9 SD for the DHEA/delta 4-A ratio in 7 PP children. Type II 3 beta HSD gene sequences, including regions of a putative promoter, all exons (I, II, III, and IV), and exon-intron boundaries, were normal in all subjects. Sequences of the type I 3 beta HSD gene encoding extraadrenal and extragonadal 3 beta HSD were normal in the 6 patients tested. The ACTH-stimulated delta 5-17P levels and delta 5-17P/F ratios in the PP children without type II 3 beta HSD gene mutation were exceedingly lower than the respective reported hormonal data for children with 3 beta HSD deficiency CAH with proven type II 3 beta HSD gene mutation. The ACTH-stimulated DHEA levels and DHEA/delta 4-A ratios were not exceedingly different between the children with and without type II 3 beta HSD gene mutation. These findings suggest that the degree of ACTH-stimulated delta 5 precursor steroid abnormality, such as delta 5-17P levels up to 10 SD above the normal mean level found in our PP patients, is not caused by a mild variant of 3 beta HSD deficiency CAH resulting from type II or type I 3 beta HSD gene mutation. The hormonal criterion for ACTH-stimulated delta 5-17P levels in patients with mild variant 3 beta HSD deficiency, therefore, is predicted to be higher than 10 SD above the normal mean value.

17-alpha-Hydroxypregnenolone↗
PubMed1996

Bullous pemphigoid--a report of 86 cases from Taiwan.

We reviewed 86 cases of bullous pemphigoid and the results were compared with those reported in the literature. Seventy-eight per cent of the patients developed generalized blisters and 22% had localized blisters, including three cases of dyshidrosiform pemphigoid and one case of pretibial pemphigoid. Oral mucosal involvement was noticed in 12.8% of the patients. Fifteen per cent of the patients had internal malignancies but the incidence was not significantly different from the control group. Direct immunofluorescence in our series showed a high positive rate of 98.8%. Indirect immunofluorescence was positive in 48.1% of the 54 patients in whom this was carried out. Peripheral blood eosinophilia was observed in 22.1% of the patients. Prednisolone alone or in combination with immunosuppressive agents was the mainstay of treatment. Treatment side-effects was observed in 33% of the patients. Thirty per cent of the patients had a complete remission after a mean follow-up period of 26.9 months. Bullous pemphigoid (BP) is a chronic debilitating autoimmune blistering disease. It is characterized clinically by generalized tense bullae and histologically by subepidermal blisters. Immunofluorescence is crucial in the diagnosis and shows linear deposits of C3 and/or IgG at the basement membrane zone (BMZ). Information regarding this disease in Chinese patients is quite limited. In this study, 86 patients with BP were reviewed. The clinical and histological features, immunofluorescence, modes of therapy and outcome were studied.

Adolescent↗
PubMed1995

Specificity of the purified inositol (1,3,4,5) tetrakisphosphate-binding protein from porcine platelets.

The specificity of the inositol 1,3,4,5-tetrakisphosphate binding protein purified from porcine platelets [Cullen et al. (1995) Biochem. J. 305, 139-143] was examined using all the isomers of myo-inositol tetrakisphosphate. From the relative potencies of these compounds it appears that phosphorylation of the 1, 3 and 5 positions is essential for high affinity binding, that there is some tolerance of phosphorylation of the 6-hydroxyl, but none of a phosphate in the 2-position, and that phosphorylation of the 4-hydroxyl has very little influence. The binding of Ins(1,3,4,5)P4 was not appreciably altered by physiological Mg2+ concentrations, and the pH dependence of binding under physiological conditions showed a decline from pH 5.5 to pH 9.0.

Animals↗
PubMed1995

Penile basal cell carcinoma with eccrine differentiation.

Basal cell carcinoma (BCC) is rare on the penis. There have been only 17 cases of penile BCC reported in the literature. Eccrine differentiation may not be uncommon in BCC but has not been reported in penile BCC. We report here a 75-year-old man with multiple penile BCC with histological features of eccrine differentiation. A brief review of the literature is included. Basal cell carcinoma (BCC) is the most commonly diagnosed malignant skin tumour; it probably originates from pluripotential cells in the epidermis or hair follicle. More than 90% of BCCs are located on the head or neck, and its occurrence on the penis is rare. Seventeen cases of penile BCC have been reported in the literature.

Aged↗
PubMed1995

Absence of molecular defect in the type II 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) gene in premature pubarche children and hirsute female patients with moderately decreased adrenal 3 beta-HSD activity.

To date the molecular basis and hormonal criteria for inherited mild late-onset 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) deficiency congenital adrenal hyperplasia (CAH) have not been defined. We have thus investigated the presence or absence of mutation in the type II 3 beta-HSD gene encoding adrenal/gonadal 3 beta-HSD in each of five premature pubarche children and hirsute female patients manifesting moderately decreased adrenal 3 beta-HSD activity. ACTH-stimulated hormonal levels in all patients compared with mean levels in pubertal stage-matched normal subjects were between 2.5 and 6.5 SD for 17-hydroxypregnenolone levels, and between 2.5 and 7 SD for dehydroepiandrosterone levels in all except one patient. 17-Hydroxypregnenolone to cortisol ratios were between 2.5 and 4.3 SD, and dehydroepiandrosterone to androstenedione ratios were between 3 and 8.6 SD. The type II 3 beta-HSD gene regions of a putative promoter, exons I, II, III, and IV, and exon-intron boundaries in all subjects were amplified by polymerase chain reaction and then sequenced. All patients had normal sequences of the type II 3 beta-HSD gene in both alleles. Three female patients heterozygotic for severe 3 beta-HSD deficiency CAH with one allele mutation of the gene demonstrated normal ACTH-stimulated hormone profiles. These data indicate that moderately decreased adrenal 3 beta-HSD activity resulting in modestly increased delta 5 precursor steroid levels and delta 5 to delta 4 steroid ratios in premature pubarche and hirsute patients is not caused by a mutation in the type II 3 beta-HSD gene.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxysteroid Dehydrogenases↗
PubMed1995

[Swallowing of fixed denture following general anesthesia--a case report].

Dental injury is a common complication associated with endotracheal general anesthesia. According to a study in Japan, the incidence of dental injury caused by endotracheal intubation is 0.69%. In one study in our country, evaluation of the oral condition was performed before, during and after anesthesia, and the frequency of dental trauma is as high as 12.1%. Fragment(s) of tooth or denture may cause serious, or even fatal complications. We report a case of swallowing of fixed denture following endotracheal general anesthesia. Our accident involved a 33-yr-old male who had experienced bilateral auditory impairment as a result of chronic otitis media. The patient underwent right modified radical mastoidectomy under endotracheal general anesthesia. It might well be that the patient's maxillary fixed denture was loosened at the time of endotracheal intubation. However, patient's denture was normal in appearance and not much attention was paid to it. During his stay at the post-anesthesia care unit, he might have unconsciously swallowed his denture. Verification was later made by X-ray. On careful observation, his denture was found in the feces during defecation 30 h post-operatively.

Adult↗
PubMed1994

Enrichment of unlabelled human Langerhans cells by modified discontinuous Ficoll-metrizoate density medium and following Langerhans cell culture.

Highly enriched and specifically unlabelled human Langerhans cells (LC) from epidermal cell suspensions (ECS) are indispensable for the intensive study of LC function. Discontinuous Ficoll-metrizoate density gradient centrifugation was found to be a satisfactory method of enriching LC from ECS. In contrast to a previous study, however, the majority of LC floated on Ficoll-metrizoate with a density of 1.057 g/cm3 instead of 1.068 g/cm3. The concentration of unlabelled LC can be enriched to as high as 92% from the original 1.8-3.1% LC in ECS. Approximately 40-50% of original LC can be harvested. The procedure was also simplified by using a Schick razor instead of a dermatome to obtain thin epidermal sheets (about 0.25 mm in thickness), omitting the density gradients of 1.089 and 1.10 g/cm3 and using the avidin-biotin complex method to identify LC. LC are non-proliferative cells in in vitro culture systems. The viability of LC dropped to 20-30% after 3 days in the culture medium. It was also observed that LC tended to attach to aggregated keratinocytes in the culture system.

Cell Survival↗