PubMed Health⌕ Search

Biomedical subjects

C M Chen

Publications and source records attributed to C M Chen.

At least 19 recordsLinked to original sources

Molecular characterization of a family of tandemly repeated DNA sequences, TR-1, in heterochromatic knobs of maize and its relatives.

Two families of tandem repeats, 180-bp and TR-1, have been found in the knobs of maize. In this study, we isolated 59 clones belonging to the TR-1 family from maize and teosinte. Southern hybridization and sequence analysis revealed that members of this family are composed of three basic sequences, A (67 bp); B (184 bp) or its variants B' (184 bp), 2/3B (115 bp), 2/3B' (115 bp); and C (108 bp), which are arranged in various combinations to produce repeat units that are multiples of approximately 180 bp. The molecular structure of TR-1 elements suggests that: (1) the B component may evolve from the 180-bp knob repeat as a result of mutations during evolution; (2) B' may originate from B through lateral amplification accompanied by base-pair changes; (3) C plus A may be a single sequence that is added to B and B', probably via nonhomologous recombination; and (4) 69 bp at the 3' end of B or B', and the entire sequence of C can be removed from the elements by an unknown mechanism. Sequence comparisons showed partial homologies between TR-1 elements and two centromeric sequences (B repeats) of the supernumerary B chromosome. This result, together with the finding of other investigators that the B repeat is also fragmentarily homologous to the 180-bp repeat, suggests that the B repeat is derived from knob repeats in A chromosomes, which subsequently become structurally modified. Fluorescence in situ hybridization localized the B repeat to the B centromere and the 180-bp and TR-1 repeats to the proximal heterochromatin knob on the B chromosome.

Base Sequence↗

Gene frequencies of the HPA-1 to HPA-13, Oe and Gov platelet antigen alleles in Taiwanese, Indonesian, Filipino and Thai populations.

Human platelet antigen (HPA) systems consist of more than twelve bi-allelic antigen polymorphisms in which a base pair substitution leads to change in an amino acid of a glycoprotein expressed on the platelet. The neonatal alloimmune thrombocytopenia (NAIT), post transfusion purpura, and refractoriness to platelet transfusion can be induced by antibodies against human platelet antigens: e.g. HPA-1a, 3a, 4a, 5a, and Gova. HPA typing is essential for the diagnosis and treatment of a variety of diseases. We developed a PCR-based method to detect HPA-1 to HPA-13, Oe and Gov platelet alloantigens. In this method, the amplified PCR products were used to recognize the polymorphism after restriction enzyme digestions. Among 566 Taiwanese, 107 Indonesian, 100 Filipino and 137 Thai subjects studied, HPA-1a, 2a, 4a, 5a, 6a, 7aW, 8aW, 9a, 10a, 11a, 12a, 13a, Oea genes were present in every sample; while HPA-1b, 2b, 4b, 5b and 6b were rarely found. HPA-7aW, 8aW, 9, 10, 11, 12, 13, and Oea alleles were noted to be monomorphic only. HPA-3a/3b alleles had frequencies of 0.595/0.405, 0.505/0.495, 0.507/0.493, 0.530/0.470, while Gova/Govb of 0.462/0.538, 0.450/0.550, 0.463/0.537, 0.520/0.480 among Taiwanese, Indonesians, Thais and Filipinos respectively. The prevalence rates of HPA-1 to 13 in this study were also consistent with other previous reports using different methods. The alloimmunization due to Gov and HPA-3 antigens need to be emphasized in these populations.

Alleles↗

Gene frequencies of the HPA-1 to HPA-8w platelet antigen alleles in Taiwanese, Indonesian, and Thai.

Human platelet antigen (HPA) systems consist of more than eight biallelic antigen polymorphisms in which a base pair substitution leads to change in an amino acid of a glycoprotein expressed on the platelet. HPA typing is essential in the diagnosis and treatment for a variety of diseases. We developed a polymerase chain reaction (PCR)-based method to detect HPA-1 through HPA-8w. In this method, the amplified PCR products were used to recognize the polymorphism after restriction enzyme digestions. Among 295 Taiwanese, 107 Indonesian, and 137 Thai subjects studied, HPA-1a, 2a, 4a, 5a, 6a, 7aw, and 8aw genes were present in every sample tested. HPA-1b, 2b, 4b, 5b, and 6b were rarely found among subjects. Only monomorphic HPA-7aw and 8aw alleles were noted in the samples. HPA-3a and 3b alleles showed frequencies of 0.595/0.405, 0.504/0.496, and 0.507/0.493 in Taiwanese, Indonesian, and Thai subjects, respectively. Our report is the first PCR-based method to detect most of the HPA antigen variants in Taiwanese, Indonesian, and Thai. The genomic typing results were also confirmed by direct sequencing for uncertain and some representative cases. The prevalence rates of HPA-1, 2, 3, 4, and 5 in this study were also consistent with other previous reports using different methods.

Alleles↗

Toxicity of different industrial effluents in Taiwan: a comparison of the sensitivity of Daphnia similis and Microtox.

Industrial effluents are known to exhibit toxicity toward different aquatic organisms. In Taiwan management of these discharges still relies on chemical and physical and physical characteristics of water, although various standard method for assessing aquatic toxicity have been proposed by the Taiwan Environmental Protection Administration. In this study we examined the toxicity and compared the sensitivity of different types of industrial effluents using two proposed toxicity tests: the Daphnia similis acute toxicity test and the Microtox acute assay (Vibrio fischeri). Results showed that electroplating effluents were the most toxic of all the effluents tested, followed by acrylonitrile manufacturing, pulp/paper, and tannery effluents. The EC50 of an electroplating effluent for D. similis and V. fischeri (15 min) was as low as, respectively, 2.9% and 3.9% of the whole effluent. The other effluents were not acutely toxic to either organism tested. However, the tests exhibited different sensitivity toward various discharges. Only the electroplating and acrylonitrile manufacturing effluents had effects on both organisms. These results indicate the importance of the incorporation of aquatic toxicity tests into the management scheme for treated wastewaters.

Animals↗

A novel technique for the identification of CpG islands exhibiting altered methylation patterns (ICEAMP).

Aberrant CpG methylation changes occurring during tumour progression include the loss (hypomethylation) and gain (hypermethylation) of methyl groups. Techniques currently available for examining such changes either require selection of a region, then examination of methylation changes, or utilise methylation-sensitive restriction enzymes to identify an alteration. We describe here a novel method that identifies genomic regions as a consequence of altered methylation during tumourigenesis. A methyl-CpG binding domain column isolates methylated GC-rich sequences from both tumours and surrounding normal tissue. Subsequent subtractive hybridisation removes sequences common to both, leaving only methylated sequences unique to the tumour. Libraries of sequences generated using DNA derived from a breast tumour (histological grade; poorly differentiated) as 'tester' and from matched normal tissue as 'driver' were examined; 26% of clones had the sequence criteria of a CpG island (CGI). Analysis using the bisulfite technique revealed that a number of these sequences were methylated in tumour DNA relative to the normal control. We have therefore demonstrated the ability of this technique, the identification of CGI exhibiting altered methylation patterns (ICEAMP), to isolate tumour-specific methylated GC-rich sequences. This will allow a comprehensive identification of methylation changes during tumourigenesis and will lead to a better understanding of the processes involved.

Base Composition↗

Dissecting complex epigenetic alterations in breast cancer using CpG island microarrays.

It is now clear that aberrant DNA methylation observed in cancer cells is not restricted to a few CpG islands, but affects multiple loci. When this epigenetic event occurs at the 5'-end of the regulatory region of genes, it is frequently associated with transcriptional silencing. To investigate further this widespread event in the tumor genome, we developed a novel microarray containing 7776 short GC-rich tags tethered to glass slide surfaces. This DNA chip was used to study 17 paired tissues of breast tumors and normal controls. Amplicons, representing differential pools of methylated DNA fragments between tumors and normal controls, were cohybridized to the microarray panel. Hypermethylation of multiple CpG island loci was then detected in a two-color fluorescence system. Approximately 1% (on average, 83 loci) of these CpG islands examined were hypermethylated in this patient group. Hierarchical clustering segregated these tumors based on their methylation profiles and identified a group of CpG island loci that corresponds to the hormone-receptor status of breast cancer. This observation was independently confirmed by examining a single locus, the promoter of the human glypican 3 gene, which was predominately hypermethylated in the hormone receptor-negative tumors. Our findings support the notion that hypermethylation of critical CpG island loci influences cancer development and produces distinct epigenetic signatures for particular tumor subtypes.

Breast Neoplasms↗

Instability of myelin tubes under dehydration: deswelling of layered cylindrical structures.

We report experimental observations of an undulational instability of myelin figures. Motivated by this, we examine theoretically the deformation and possible instability of concentric, cylindrical, multilamellar membrane structures. Under conditions of osmotic stress (swelling or dehydration), we find a stable, deformed state in which the layer deformation is given by deltaR infinity r(square root[B(A)/(hB)]), where B(A) is the area compression modulus, B is the interlayer compression modulus, and h is the repeat distance of layers. Also, above a finite threshold of dehydration (or osmotic stress), we find that the system becomes unstable to undulations, first with a characteristic wavelength of order square root[xi(d)0], where xi is the standard smectic penetration depth and d0 is the thickness of dehydrated region.

Biophysical Phenomena↗

Different risks of symptomatic brain necrosis in NPC patients treated with different altered fractionated radiotherapy techniques.

PURPOSE: To report our observation of excessive temporal lobe necrosis in nasopharyngeal carcinoma (NPC) patients treated with 160 cGy b.i.d. radiotherapy technique. During the same period, patients treated with 120 cGy b.i.d. have not shown a similar tendency. Our experience may be useful for designing unconventional radiotherapy regimens for NPC patients. METHODS AND MATERIALS: During the period from October 1991 to January 1998, 81 M0, previously untreated NPC patients completed altered fractionated radiotherapy. Seventy patients were treated with the hyperfractionated technique, and 11 were treated using the accelerated-hyperfractionated scheme. Hyperfractionated radiotherapy was delivered using 120 cGy b.i.d. separated by 6-h intervals throughout the course. A minimum tumor dose of 8000 cGy was the standard dose over an 8-week period. With the accelerated-hyperfractionated scheme, 160 cGy was given twice daily, also with an interval of 6 h. The minimum tumor dose ranged between 6840 and 7640 cGy, with 7 of the 11 patients receiving 7000 cGy. The arrangement of portals was the same for both regimens. The follow-up period for patients alive was from 32 to 102 months with a median of 61 months for the hyperfractionated patients. For the accelerated-hyperfractionated group, it ranged from 67 to 82 months with a median of 72 months. No patient was lost to follow-up. RESULTS: At the time of analysis, 49 of the 70 patients in the hyperfractionated group were alive. In the accelerated group, 8 of the 11 patients were alive. The estimated radiation dose to the temporal lobe for the hyperfractionated group was 6000-7440 cGy with a median of 7080 cGy. For the accelerated-hyperfractionated group, the dose range was 4480-6700 cGy with a median of 6400 cGy. Of the 70 patients treated with hyperfractionated radiotherapy, none developed symptomatic brain necrosis, despite the higher total dose to the temporal lobe in general. In contrast, 3 of the 11 (27%) patients irradiated using the accelerated-hyperfractionated regimen suffered from temporal lobe necrosis at 16, 19, and 40 months after completion of radiotherapy. CONCLUSION: An excessive incidence of temporal lobe necrosis was noted when an accelerated-hyperfractionated regimen with 160 cGy b.i.d. was used in NPC patients with a median brain dose of 6400 cGy. There has been no such event in patients treated using a hyperfractionated regimen with 120 cGy and a median brain dose of 7000 cGy. The real causes of this discrepancy are not known. However, a high sensitivity of the human brain to a change in fraction size may play a role.

Adolescent↗

Cloning, sequencing, heterologous expression, purification, and characterization of adenosylcobalamin-dependent D-ornithine aminomutase from Clostridium sticklandii.

D-Ornithine aminomutase from Clostridium sticklandii catalyzes the reversible rearrangement of d-ornithine to (2R,4S)-2,4-diaminopentanoic acid. The two genes encoding d-ornithine aminomutase have been cloned, sequenced, and expressed in Escherichia coli. The oraS gene, which encodes a protein of 121 amino acid residues with M(r) 12,800, is situated upstream of the oraE gene, which encodes a protein of 753 amino acid residues with M(r) 82,900. The holoenzyme appears to comprise a alpha(2)beta(2)-heterotetramer. OraS shows no significant homology to other proteins in the Swiss-Prot data base. The deduced amino acid sequence of OraE includes a conserved base-off/histidine-on cobalamin-binding motif, DXHXXG. OraE was expressed in E. coli as inclusion bodies. Refolding experiments on OraE indicate that the interactions between OraS and OraE and the binding of either pyridoxal phosphate or adenosylcobalamin play important roles in refolding process. The K(m) values for d-ornithine, 5'-deoxyadenosylcobalamin (AdoCbl), and pyridoxal 5'-phosphate (PLP) are 44.5 +/- 2.8, 0.43 +/- 0.04, and 1.5 +/- 0.1 microm, respectively; the k(cat) is 6.3 +/- 0.1 s(-1). The reaction was absolutely dependent upon OraE, OraS, AdoCbl, PLP, and D-ornithine being present in the assay; no other cofactors were required. A red-shift in UV-visible absorption spectrum is observed when free adenosylcobinamide is bound by recombinant D-ornithine aminomutase and no significant change in spectrum when free adenosylcobinamide is bound by mutant OraE-H618G, demonstrating that the enzyme binds adenosylcobalamin in base-off/histidine-on mode.

Amino Acid Motifs↗

Molecular analysis of SMN, NAIP and P44 genes of SMA patients and their families.

Mutations of the telomeric survival motor neuron gene (SMN1) are related to spinal muscular atrophy (SMA). However, no phenotype-genotype correlation has been observed since the SMN1 gene is lacking in the majority of patients affected with either the severe form (type I) or the milder forms (types II and III). Here, we analyze the SMN, NAIP and P44 genes in 132 Chinese SMA patients and their families. At least three types of normal allele, and four types of mutant allele were found in this study. The combination of one normal allele with one mutant allele resulted in carriers of different types, and the combination of different mutant alleles accounted for the different genotypes among different types of SMA. Deletions of mutant alleles can be further subgrouped into four types, which includes involving SMN1, SMN1 and NAIP(T) (telomeric portion of NAIP gene), SMN1 and NAIP(T) and P44(T) (telomeric portion of P44 gene), and SMN1 and SMN2 (centromeric portion of SMN gene). Some of the severe (type I) SMA cases correlated with the extent of deletions in the SMN, NAIP and P44 genes or the dosage of SMN gene when both SMN1 and SMN2 are deleted. We also found two novel point mutations, an A insertion at codon 8 (AGT-->AAGT) and an A substitution at codon 228 (TTA-->TAA).

Anterior Horn Cells↗

Cloning, structure, and expression of the mouse Ovca1 gene.

We report the isolation of the mouse Ovca1 gene, the orthologue of human OVCA1/DPH2L1, a putative tumor suppressor associated with ovarian cancer. Mouse Ovca1 contains at least 13 exons and spans approximately 17 kb. Northern analysis showed that Ovca1 is expressed in most adult mouse tissues. The most predominant Ovca1 transcript is 2.1 kb. RT-PCR analysis demonstrated Ovca1 expression in embryos from 8.5 days postcoitum (d.p.c.) to 10.5 d.p.c., and various organs of 14.5 d.p.c. embryos. Mouse Ovca1 encodes a protein of 438 amino acids and has high identity with human OVCA1. Western blot and immunohistochemistry revealed that mouse OVCA1 is a 50-kDa protein that is predominately localized in a punctate pattern in the nucleus. Based on gene homology, structure, and expression patterns, these findings indicate that mouse Ovca1 is the orthologue of human OVCA1/DPH2L1. This study will facilitate experiments to elucidate the in vivo role of Ovca1 in cancer.

Amino Acid Sequence↗

A plant gene encoding a Myb-like protein that binds telomeric GGTTTAG repeats in vitro.

A gene (AtTRP1) encoding a telomeric repeat-binding protein has been isolated from Arabidopsis thaliana. AtTRP1 is a single copy gene located on chromosome 5 of A. thaliana. The protein AtTRP1 encoded by this gene is not only homologous to the Myb DNA-binding motifs of other telomere-binding proteins but also is similar to several initiator-binding proteins in plants. Gel retardation assay revealed that the 115 residues on the C terminus of this protein, including the Myb motif, are sufficient for binding to the double-stranded plant telomeric sequence. The isolated DNA-binding domain of AtTRP1 recognizes each telomeric repeat centered on the sequence GGTTTAG. The almost full-length protein of AtTRP1 does not form any complex at all with the DNA fragments carrying four or fewer GGTTTAG repeats. However, it forms a complex with the sequence (GGTTTAG)(8) more efficiently than with the sequence (GGTTTAG)(5). These data suggest that the minimum length of a telomeric DNA for AtTRP1 binding consists of five GGTTTAG repeats and that the optimal AtTRP1 binding may require eight or more GGTTTAG repeats. It also implies that this protein AtTRP1 may bind in vivo primarily to the ends of plant chromosomes, which consist of long stretches of telomeric repeats.

Amino Acid Sequence↗

In situ detection of hTERT mRNA relates to Ki-67 labeling index in papillary thyroid carcinoma.

BACKGROUND: Telomerase is activated in most human cancers but is inactivate in adult somatic tissues except for some proliferating cell lineages. The maintenance of telomerase activity may be a critical step of cellular immortalization and transformation. MATERIALS AND METHODS: We analyzed the expression of human telomerase reverse transcriptase (hTERT) using in situ hybridization and compared it to Ki-67 immunoreactivity in 29 cases of papillary thyroid carcinoma (PTC) and 17 cases of benign thyroid disease. RESULTS: The hTERT messenger RNA (mRNA) was expressed in the cytoplasm of carcinoma cells with moderate (n = 10) to strong intensity (n = 10) in 69% (20 of 29) PTC cases. Human TERT was found in only 29% (5 of 17) cases of benign thyroid disease. Human TERT gene expression was preferentially detected in PTC (P = 0.021). The Ki-67 labeling index was observed in 16 cases of PTC (16 of 29; 55.2%). This result was significantly different from that of benign thyroid disease (P = 0.014). The Ki-67 labeling index related to the intensity of hTERT mRNA expression (r = 0.51; P = 0.005) and was inversely associated with the follicular variant of PTC (r = -0.413; P = 0.026). No statistically significant difference was found between hTERT expression and histological subtype of PTC. CONCLUSIONS: Our results demonstrated that expression of hTERT could be detected using in situ hybridization in PTCs and was significantly distinguishable from that of benign thyroid disease. Human TERT expression was related to the Ki-67 labeling index, indicating that coupling of telomerase activation with cell proliferation was the associated mechanism for tumorigenesis.

Adolescent↗

Use of Japanese medaka (Oryzias latipes) and Tilapia (Oreochromis mossambicus) in toxicity tests on different industrial effluents in Taiwan.

In Taiwan, aquatic toxicity tests for industrial effluents are not required for discharge permits. However, relying on traditional chemical and physical characteristics of an effluent to monitor and regulate such discharges to manage water quality of a receiving water is insufficient. In this study, we used two fish species, Japanese medaka (Oryzias latipes) and tilapia (Oreochromis mossambicus), and three toxic endpoints, including acute and subacute toxicity, to determine toxicity of seven different types of industrial effluents. Prior to the study, two reference toxicants were tested on two fish species. The LC50s of CdCl2 for tilapia and medaka juveniles were 29.6 +/- 15.3 mg/L and 2.2 +/- 1.2 mg/L, respectively. The sensitivity of medaka embryo mortality and hatching inhibition to CdCl2 were about the same, with the LC50 and EC50 of 0.3 +/- 0.1 mg/L and 0.1 +/- 0.1 mg/L, respectively. The LC50s for tilapia and medaka juveniles to sodium dodecyl sulfate (SDS) were 19.7 +/- 10.6 mg/L and 12.5 +/- 5.9 mg/L. The medaka embryo was less sensitive to SDS than to CdCl2. The embryo's LC50 for SDS was 5.8 +/- 2.8 mg/L and the hatching inhibition EC50 was 1.3 +/- 1.1 mg/L. Results of toxicity tests on different effluents showed that the electroplating effluent was the most toxic, followed by acrylonitrile manufacturing and pulp/paper mill discharges. The LC50s of the electroplating effluent to different assays were in the range of several percents of the whole effluent. The pulp/paper effluent was toxic only to the medaka embryo. The rest of the industrial effluents tested showed either moderate or no toxicity to the animals.

Animals↗

Intertrochanteric fractures in adults younger than 40 years of age.

This study reviewed 66 intertrochanteric fractures in patients younger than 40 years old (average 33.0 years old; range 17-40 years old). In contrast to the usual population with intertrochanteric fractures, the factors male predominance (46/66), less pre-injury comorbidity (9/66), more outdoor high energy trauma (47/66), and more associated injuries (32/66) were evident. The distribution of associated injuries was wide. Some of them were life threatening. According to Boyd's classification, 20 were type I, 24 were type II, 13 were type III, and 9 were type IV. Twenty-nine were stable, and 37 were unstable. Stratified by the mechanism of injury, the difference in distribution between the subgroups was significant (p = 0.027, two-tail Fisher's exact test). Simple falls only caused Boyd type I and II fractures. Boyd type III or IV fractures were found more often after vehicular trauma or falls from a height. All the intertrochanteric fractures healed on average 70.5 days (range 31-213 days) after operation. The fractures resulting from vehicular trauma or fall from a height healed significantly more slowly (p = 0.02, univariant log-rank test). There were 6 intertrochanteric fracture-related complications. The mechanism of injury determines the character of intertrochanteric fractures in young adults. Given tougher bone stock, better healing ability, and less co-morbidity, proper management can lead to healing of all intertrochanteric fractures. The extent of functional recovery was also determined by the associated injuries.

Adolescent↗

Avascular necrosis of femoral head after gamma-nailing for unstable intertrochanteric fractures.

We reported on 7 cases of avascular necrosis of the femoral head after treatment of an unstable intertrochanteric fracture with the Asian Pacific gamma-nail. The incidence was about 1.16% (7 of 604) in our series. Good reduction and good implant position were achieved in all 7 men. Avascular necrosis was found about 6 months to 3 years after the initial operation, and all the fractures were solidly united at the final diagnosis. The possible etiologies were initial high energy trauma and combining basal neck fracture and iatrogenic damage of the blood supply to the femoral head.

Adult↗

Cerclage wiring in displaced both-column fractures of the acetabulum.

We evaluated the effect of cerclage wiring in the open reduction and internal fixation of displaced both-column fractures of the acetabulum. This was a prospective clinical evaluation of such cases where the main surgical strategy was open reduction and internal fixation with cerclage wire and supplemental reconstruction plates. Data on 35 cases treated by open reduction (all via the triradiate approach)/internal fixations with cerclage wire and reconstruction plates were collected. The follow-up period was 40 months (18-69). Reduction with a fracture gap of less than 2 mm without articular stepping was achieved in all 35 cases. Postoperative complications developed in seven cases, including subcutaneous haematoma in two, wound infection in two and heterotopic ossification in three. All the complications had no adverse effect on the clinical outcome, and all the cases had good to excellent final results. Cerclage wiring is very useful and effective in the reduction and fixation of displaced both-column fractures of the acetabulum, and supplemental fixation with reconstruction plates and screws is necessary.

Acetabulum↗

Microsomal monooxygenase activity in Tilapia (Oreochromis mossambicus) exposed to a bleached kraft mill effluent using different exposure systems.

Bleached kraft pulp and paper mill effluents (BKMEs) are known to have adverse effects on aquatic organisms. One of the effects of BKMEs is its ability to induce cytochrome P4501A activity in exposed fish. 7-Ethoxyresorufin O-deethylase (EROD) activity is the most common biomarker used to measure the mixed-function monooxygenase activity. In this study, Tilapia were exposed to BKMEs using different exposure systems and their hepatic EROD activity, as well as liver/somatic index (LSI), were determined. In the Phase I study, Tilapia treated with betaNF and a whole (100%) BKME using a static, non-renewal system exhibited statistically significant EROD induction, but LSI values were not altered. In the Phase II study, fish were either caged in the mill's fishpond with the whole effluent passing through or cultured in tanks receiving 100% of the BKME continuously using a flow-through system in the laboratory. Their EROD activities were then compared with the non-exposed fish (control). The EROD activities in both groups of fish were elevated significantly with the greatest induction being observed in the field-exposed group. The LSI values in all of the field-exposed fish were significantly greater than the control Tilapia. The EROD assay was sensitive in detecting biological changes in fish exposed to the BKME. Further studies are warranted to better understand the impacts of BKMEs on aquatic organisms in Taiwan.

Animals↗