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T C Liu

Publications and source records attributed to T C Liu.

At least 91 records · Page 5Linked to original sources
PubMed1993

Molecular characterization of Hb H disease by polymerase chain reaction.

We utilized the PCR method to amplify the alpha-thalassemia-1 breakpoint area of the Southeast Asia type and several regions of the alpha-globin gene cluster to diagnose rightward deletion (-alpha 3.7), leftward deletion (-alpha 4.2) or nondeletion forms of the Hb H disease. For the nondeletion form, a natural restriction site of MseI was used to detect the Hb Constant Spring (Hb CS) or other termination codon mutations. Another naturally occurring restriction site of MspI was used to detect the Hb Quong-Sze. For the deletion form of the Hb H disease, the differences among nonhomologous I, II and III of the rightward or leftward deletion were used to distinguish the mutations. For further characterization of the subtype of -alpha 3.7 deletion, the same primers for detecting termination codon mutations were used to amplify part of the alpha-globin gene, then the PCR product was digested by the restriction enzyme ApaI. In the 57 cases which were studied, 19 were deletion forms while 38 were nondeletion forms. In the deletion form cases, 13 were rightward deletion (-alpha 3.7) and the other 6 were leftward deletion (-alpha 4.2). However, all of the nondeletion form cases were alpha-thalassemia-1 with Hb CS. After the subtyping of -alpha 3.7 deletion, 11 out of 13 were type I deletions and the other 2 were type II deletions.

Adolescent↗
PubMed1993

Unimpaired postreceptor regulation of luteinizing hormone secretion by gonadotropin-releasing hormone and estrogen in aged rat anterior pituitary cells.

Delayed, attenuated, or absence of the proestrous LH surge occurs in aging rats. To assess how aging affects the positive feedback action of 17 beta-estradiol (E2) on the pituitary, we determined the responsiveness of rat pituitary cells to GnRH and the secretagogues affecting intracellular signal transduction mechanisms in the presence or absence of E2. We also correlated the LH response to pituitary LH content. Anterior pituitaries excised from ovariectomized Sprague-Dawley rats, either young (3-4 months) or old (19-20 months), were enzymatically dispersed and then pretreated with or without E2 (0.6 nM) for 48 h, followed by incubation for 3 h with or without various secretagogues. The secretagogues included GnRH (1 and 10 nM), veratridine (increases Ca2+ influx; 5 and 10 microM), and phorbol 12-myristate 13-acetate (a protein kinase-C activator; 10 and 100 nM). LH in media and cells were measured by RIA and expressed on the basis of cellular DNA. GnRH, veratridine, and phorbol 12-myristate 13-acetate at all doses stimulated (P < 0.01) LH release in cells from both young and old rats. E2 stimulated (P < 0.05 to P < 0.01) all secretagogue-induced LH release in cells from both young and old rats, but only basal LH release (P < 0.05) in cells from young rats. The magnitude of both basal and secretagogue-induced LH release in either the presence or absence of E2 was smaller (P < 0.01) in cells from old than in those from young rats. The initial cellular LH was lower (P < 0.01) in cells from old than in those from young rats. The LH-releasing ability (expressed as a percentage of total cellular LH) of cells from old rats was identical (P > 0.05) to that of cells from young rats under all conditions studied. These results suggest that the reduced magnitude of LH release by cells from old rats may be attributed to reduced cellular LH, rather than to impaired estrogen feedback or impaired signal transduction mechanisms. It remains to be determined whether LH biosynthesis per cell and/or the number of gonadotropes decrease with age.

Aging↗
PubMed1993

Prenatal and molecular diagnosis of beta-thalassemia major in Taiwan by naturally and amplified created restriction sites.

To characterize mutations rapidly in 43 patients with beta-thalassemia major in Taiwan, we utilized a method of natural and amplified created restriction site (ACRS) analysis for detection of beta-globin gene mutation. After analysis, eight different point mutations were found among 86 known chromosomes. IVS-2 nt 654 (C-->T), accounting for 40 of the 86 mutations with mutant beta-globin genes, is the most common mutation, followed by frameshift codons 41/42 (-TCTT) in 28 mutations, -28 mutation (A-->G) in 7 mutations, nonsense codon 17 (A-->T) in 5 mutations, frameshift codons 27/28 (insertion of C) in 2 mutations, IVS-1 nt 1 (G-->T) in 2 mutations, frameshift codons 71/72 (insertion of A) in 1 mutation, and IVS-1 3' end TAG-->GAG in 1 mutation. The first four mutations account for 80 of all 86 mutations of beta-thalassemia major in Taiwan. Furthermore, the beta-globin gene mutation was identified successfully in one chorionic villi biopsy for prenatal diagnosis and in specimen of blood from one patient who had received bone marrow transplantation (BMT). Complete diagnosis is possible in all of the Chinese families with beta-thalassemia in Taiwan, and the first trimester prenatal diagnosis can be achieved simply by using only 13 oligonucleotide primers and 10 restriction endonucleases. This non-radioactive assay was shown to be a rapid, sensitive, precise and safe method in detecting the mutations of beta-thalassemia in Taiwan.

Adolescent↗
PubMed1993

Clear cell chondrosarcoma of bone. A report of three cases with immunohistochemical and affinity histochemical observations.

Clear cell chondrosarcoma, a subtype and separate entity from the traditional chondrosarcoma, is characterized by its special histologic features, site of predilection, slow growth and better prognosis. Three cases are presented with elucidation of clinicopathologic correlation and detection by the ABC immunohistochemical method using several antibodies. The observation of positive reaction to S-100 protein (S-100), vimentin (Vim), alpha 1-antichymotrypsin (AACT) and lysozyme (Lyso) by the tumor cells of clear cell chondrosarcoma, similar to traditional chondrosarcoma and chondroblastoma, proves that this tumor has its origin in the cartilaginous tissue. It was found for the first time that the clear cell chondrosarcoma was positive for wheat germ agglutinin (WGA) and concanavalin A (Con A). The authors believe that clear cell chondrosarcoma may result from the anaplastic changes of chondroblastoma cells into another subtype of that tumor. The osteoclast-like multinucleated giant cells (MGC), retaining the antigens of phagocytes, are not considered to be neoplastic.

Adult↗
PubMed1992

Rapid diagnosis of beta-thalassemia mutations in Chinese by naturally and amplified created restriction sites.

We developed a rapid and simple method to diagnose the molecular defects of beta-thalassemia in Chinese patients. This method involves the selective amplification of a DNA fragment from human beta globin gene with specific oligonucleotide primers, followed by digestion with restriction enzymes that recognize artificially created or naturally occurring restriction sites. To detect the 4-nucleotide deletion of codon 41-42, we introduced a single mismatch nucleotide into the 3' end of the upstream primer to create an artificial Taq I restriction site. With a similar approach, an artificial Rsa I site was generated to detect the nucleotide 654 mutation (C-->T) of IVS-2, and Alu I restriction site was created to detect the codon 17 mutation (A-->T), and EcoRI restriction site was created for the -28 mutation (A-->G), a Rsa I restriction site was created for the nucleotide 5 mutation (G-->C) of IVS-1, and a Spe I restriction site was created to distinguish the codon 71 (+T) and codon 71/72 (+A) mutations from a normal sequence. The other eight rare mutations that occur in the genes of the Chinese people naturally create or abolish restriction sites. Using this kind of approach, we are able to provide a simple, rapid, accurate, and nonradioactive method to detect the genetic defects of beta-thalassemia in the Chinese population. It should be used not only for routine screening but also for prenatal diagnosis.

Base Sequence↗
PubMed1992

Molecular characterization of glucose-6-phosphate dehydrogenase (G6PD) deficiency by natural and amplification created restriction sites: five mutations account for most G6PD deficiency cases in Taiwan.

We have developed a rapid and simple method to diagnose the molecular defects of glucose-6-phosphate dehydrogenase (G6PD) deficiency in Chinese in Taiwan. This method involves the selective amplification of a DNA fragment from human G6PD gene with specific oligonucleotide primers followed by digestion with restriction enzymes that recognize artificially created or naturally occurring restriction sites. Ninety-four Chinese males with G6PD deficiency were studied. The results show that 50% (47 of 94) were G to T mutation at nucleotide (nt) 1376, 21.3% (20 of 94) were G to A mutation at nt 1388, 7.4% (7 of 94) were A to G mutation at nt 493, 7.4% (7 of 94) were A to G mutation at nt 95, 4.2% (4 of 94) were C to T mutation at nt 1024, 1.1% (1 of 94) was G to T mutation at nt 392, and 1.1% (1 of 94) was G to A mutation at nt 487. These results show that the former five mutations account for more than 90% of G6PD deficiency cases in Taiwan. Aside from showing that G to T change at nt 1376 is the most common mutation, our research indicates that nt 493 mutation is a frequent mutation among Chinese in Taiwan. We compared G6PD activity among different mutations, without discovering significant differences between them.

Base Sequence↗
PubMed1992

Leukemic manifestation in a case of alpha-chain disease with multiple polypoid intestinal lymphocytic lymphoma.

We describe a female aborigine from Taiwan with alpha-chain disease associated with multiple polypoid intestinal lymphocytic lymphoma and leukemic manifestation. Initially, the patient experienced intermittent diarrhea, abdominal pain, and leukemic manifestation. No evidence of bone marrow involvement was found. Alpha-chain protein was demonstrated in the serum. Gastroendoscopy and a series of radiographs of the small intestine revealed multiple polypoid tumors involving the entire length of the small intestine. Duodenal biopsy showed diffuse lymphocytic lymphoma. Immunohistochemical staining of tumor samples revealed features typical of alpha-chain disease. Cytogenetic analysis showed the same abnormal karyotypes of neoplastic clones in intestinal tumor cells and in circulating leukemic cells. The data suggest that alpha-chain disease can present initially with intestinal multiple polypoid lymphocytic lymphoma and leukemic manifestation without evidence of bone marrow involvement. The data also support the homing theory of lymphomas from mucosa-associated lymphoid tissue.

Adult↗
PubMed1992

A mutation in the E1 alpha subunit of pyruvate dehydrogenase associated with variable expression of pyruvate dehydrogenase complex deficiency.

Defects in pyruvate dehydrogenase, the first catalytic component of the pyruvate dehydrogenase complex, are the most common cause of pyruvate dehydrogenase complex deficiency. A family with variable pyruvate dehydrogenase complex deficiency had been described in which cultured skin fibroblasts of affected family members had normal pyruvate dehydrogenase complex activity, but different tissues and blood lymphocytes had significantly diminished activities. Enzymatic activity and immunoblot studies indicated that pyruvate dehydrogenase was affected. Further evidence is presented here showing that the defect affecting pyruvate dehydrogenase complex activity is posttranscriptional. Sequencing of the coding region of the alpha-subunit of pyruvate dehydrogenase revealed a point mutation in the codon for amino acid 234 resulting in a substitution of glycine for arginine. Study of other members of the family suggested that this mutation is inherited in a sex-linked mode. The point mutation is located in a highly conserved region of the pyruvate dehydrogenase alpha-subunit gene that contains both hydrophobic and positively charged amino acid residues. Variable expression of pyruvate dehydrogenase complex deficiency in this case may be due to instability of the pyruvate dehydrogenase heterotetramer in specific tissues because of a disruption in subunit-subunit interaction.

Amino Acid Sequence↗
PubMed1992

Divergent roles of protein kinase C in luteinizing hormone biosynthesis versus release in rat anterior pituitary cells.

We previously demonstrated that protein kinase C (PKC) activators, i.e. L-alpha-1,2-dioctanoyl glycerol (C8) and phorbol 12-myristate 13-acetate (PMA), mimic the stimulatory effects of GnRH on both LH glycosylation and release. To further evaluate the roles of PKC, we determined: 1) the interaction between PKC activator and GnRH; and 2) the effects of depleting cellular PKC with a high dose of PMA on LH glycosylation vs. release. Anterior pituitaries excised from ovariectomized rats were enzymatically dispersed and cultured. In series 1 experiments, day 3 monolayer cells were incubated in the presence of radiolabeled precursors and GnRH (0, 1, or 100 nM), with or without C8 (200 microM). In series 2 experiments, day 2 cells were pretreated with either PMA (1 microM) or vehicle (0.08% dimethyl sulfoxide) for 24 h and then incubated with diluent, GnRH (1 nM), or PMA (20 nM), and radiolabeled precursors for 4 h. LH translation and glycosylation were monitored by measuring incorporation of [14C]alanine ([14C]A) and [3H]glucosamine ([3H]GA), respectively, into LH. Immunoreactive LH (IRLH) was measured by RIA. In series 1 experiments, C8 increased basal release of IRLH, potentiated IRLH release stimulated by 1 nM GnRH, but not by 100 nM GnRH. C8 elevated total [3H]GA-LH but had no additive effects with GnRH. In series 2 experiments, PMA pretreatment inhibited subsequent PMA-stimulated IRLH release. However, PMA pretreatment did not affect GnRH-induced IRLH release even though PMA pretreatment decreased cellular IRLH content. In comparison, PMA pretreatment reduced both GnRH- and PMA-stimulated total [3H]GA-LH. PMA pretreatment had no effects on total [14C]A-LH in the presence of GnRH or PMA, but reduced the basal level. In summary, PKC activators had no additive effects on either IRLH release or LH glycosylation stimulated by a maximal dose of GnRH. However, PMA pretreatment decreased GnRH-induced LH glycosylation without depressing LH release. These results suggest differential roles of PKC in the actions of GnRH on LH glycosylation vs. LH release.

Alanine↗
PubMed1992

Rapid molecular diagnosis of hemoglobin variants by RT-PCR of reticulocyte mRNA and direct sequencing.

We have developed a rapid and simple approach for the molecular characterization of hemoglobin variants by a one-step reverse transcription-polymerase chain reaction of reticulocyte mRNA and direct sequencing of the product. This method can selectively amplify the alpha 1- or alpha 2-globin gene or the beta-globin gene transcript. The amino acid substitution of Hb G-Taichung is due to a G----C mutation at codon 74 of the alpha 1-globin gene, that of Hb J-Meinung to a G----A substitution at codon 56 of the beta-globin gene, and that of Hb Kaohsiung (or New York) to a T----A substitution at codon 113 of the beta-globin gene. The amplified segment encompassed the sequence from upstream of the initial codon behind the Cap site to downstream of the terminal codon before the polyadenylation addition signal. Hence, all hemoglobin variants should be able to be characterized by this approach.

Base Sequence↗
PubMed1992

Detection of hemoglobin E heterozygotes by using polymerase chain reaction and direct DNA sequencing: report of a case.

From an overseas Chinese born in Thailand, an extraordinarily high level of A2 + E band (20.2%) was found during routine cellulose acetate Hb electrophoresis. With a suspicion of Hb E, the beta-globin gene was studied by using the polymerase chain reaction (PCR) and direct DNA sequencing method. A 1.4 kb fragment covering the whole beta-globin gene was amplified by PCR. Sequence analysis of the amplified product revealed a GAG > AAG transversion at codon 26, which resulted in an amino acid substitution of lysine for glutamic acid. A normal sequence at the corresponding codon was noted in the other allele; hence, this patient is a heterozygote of Hb E. PCR and direct DNA sequencing provide a rapid method for detection of Hb E from a small amount of DNA.

Adult↗
PubMed1992

Psychiatric syndromes in pernicious anaemia--a case report.

Surveys of psychiatric population had previously shown a high incidence of patients with low serum vitamin B12. A variety of psychiatric syndromes have been described, ranging from mild disturbance in mood state like depression to maniacal excitement; psychotic conditions like paranoid states and schizophrenia; and cognitive dysfunctions such as memory defect, delirium and dementia. A case of a 67-year-old Chinese lady suffering from pernicious anaemia, but presenting with prominent paranoid delusions is reported. Treatment with cyanocobalamine and anti-psychotic medication led to prompt resolution of her psychotic experience. Subsequently she developed a transient depressive syndrome which also responded well to a short course of antidepressant.

Aged↗
PubMed1991

Expression of cDNA sequences encoding mature and precursor forms of human dihydrolipoamide dehydrogenase in Escherichia coli. Differences in kinetic mechanisms.

The cDNA sequences encoding mature and precursor forms of human dihydrolipoamide dehydrogenase (E3) were expressed in Escherichia coli using a lambda PL promoter-driven prokaryotic expression vector. The expressed proteins in total cell extracts were identified by Western blot analysis using anti-pig heart E3 antibody and also by measurement of E3 activity. Most of the expressed human E3 polypeptides (five bands) were found in the insoluble pellet while primarily full-length mature E3 was found in the soluble fraction. About 2% of the total soluble protein was mature human E3 when expressed in wild type E. coli AR120. Since wild type E. coli has its own endogenous E3 activity, the expression of human E3 was performed in a pyruvate dehydrogenase complex-deficient strain of E. coli, JRG1342. The expressed recombinant human E3s in JRG1342 were purified to near homogeneity. The amino-terminal amino acid sequence analysis revealed that the recombinant mature E3 had an expected sequence while the recombinant precursor E3 lost 19 amino acid residues of its 35-amino acid leader sequence presumably due to a proteolytic cleavage. The recombinant mature E3 displayed comparable kinetic properties to those reported for highly purified mammalian E3s. The truncated precursor E3 showed about half of the mature E3 activity. The double-reciprocal plot for the mature E3 in the direction of NAD+ reduction showed parallel lines (ping-pong mechanism) while that for the truncated precursor E3 displayed intersecting lines (sequential mechanism). In the direction of NADH oxidation, the kinetic mechanisms of both E3s were apparently a ping-pong mechanism. These kinetic results showed that the partial 16-amino acid extension in the leader sequence changed the kinetic mechanism of human E3 so that it resembled that of glutathione reductase.

Amino Acid Sequence↗
PubMed1991

HTLV-1 associated T cell lymphoma in South East Asia: case report and family study.

Geographic clustering of human T cell lymphoma/leukaemia virus type 1 (HTLV-1) infection is well recognised, particularly in south western Japan, parts of West and Central Africa, the south eastern United States and the Caribbean islands. Sporadic cases have been reported in many other parts of the world. The first case of HTLV-1 associated leukaemia/lymphoma (ATLL) in South East Asia is reported. Contact tracing showed a high incidence of carriers among the relatives.

Carrier State↗
PubMed1991

Mutation analysis of the ras gene in myelocytic leukemia by polymerase chain reaction and oligonucleotide probes.

Twenty-nine patients with acute myelocytic leukemia (AML) and 14 patients with Philadelphia chromosome-positive chronic myelocytic leukemia (CML) were analyzed to detect the presence of mutations in their ras genes by the polymerase chain reaction and oligonucleotide hybridization methods. Deoxyribonucleic acid (DNA) isolated from blood or bone marrow samples was screened for mutations in codons 12, 13 and 61 of N-ras and in codons 12 and 61 of K-ras and H-ras. We detected mutations of the ras gene in 7 patients with AML (7/29), all in N-ras. The mutations were 3 GGT- greater than GAT transitions in codon 12, 1 GGT- greater than TGT transition in codon 13, and 3 CAA- greater than AAA transitions in codon 61. No correlation has been observed between French-American-British subtypes and the incidence of N-ras mutation, nor between cytogenetic changes and the incidence of N-ras mutation. All ras gene mutations detected by the oligonucleotide hybridization method were further confirmed by direct sequencing. No mutations were detected in ras genes in samples from the 14 Philadelphia chromosome-positive CML patients (12 in chronic phase, 2 in blastic phase). These findings are in line with previous results indicating that ras gene mutations in the codons tested play only a small role in the tumorigenesis of CML.

Adolescent↗