Biomedical subjects

T H Huang

Publications and source records attributed to T H Huang.

At least 19 recordsLinked to original sources

PubMed2004

Antibody-cytokine fusion proteins: innovative weapons in the war against cancer.

Cancer patients who are administered therapeutic doses of cytokines (e.g., interleukin-2, granulocyte macrophage colony stimulating factor, interleukin-12, and tumor necrosis factor-alpha) frequently develop devastating toxic side effects that can lead to discontinuation of therapy. This problem has compelled numerous investigators to design innovative strategies that will reduce prolonged systemic cytokine exposure and promote cytokine accumulation at the site of the tumor. One such strategy involves the use of antibody-cytokine fusion proteins consisting of immunoenhancing cytokines genetically fused to antibodies that are able to target specific antigens exclusively expressed or overexpressed on the surface of tumor cells. Preclinical studies examining their therapeutic efficacy demonstrate that they posses potent tumoricidal activity, suggesting that they may be clinically useful as novel cancer therapeutic agents.

Antibodies↗

PubMed2003

Effects of different exercise modes on mineralization, structure, and biomechanical properties of growing bone.

Weight bearing during exercise plays an important role in improving the mechanical properties of bone. The effect on bone of non-weight-bearing exercise such as swimming remains controversial. To investigate the effects of exercise mode on growing bone, 29 male Wistar rats (7 wk old) were randomly assigned to a running exercise group (Run, n = 9), a swimming exercise group (Swim, n = 10), or a nonexercise control group (Con, n = 10). During an 8-wk training session (20-60 min/day, 5 days/wk), the Run rats were trained at progressively increasing running speeds (12-22 m/min), and weights attached to the tail of the Swim rats were progressively increased from 0 to 2% of their body weight. The bone mineral density of the proximal tibiae of the Run rats was significantly higher than in the Swim (P < 0.05). Femoral wet weights of the two exercise groups were significantly higher than in the control group (P < 0.05). Interestingly, the percent difference between the tissue wet weight and dry weight (water content ratio), which is related to bone mechanical properties, was significantly higher in the tibiae of the Swim rats and the femora of both exercise groups compared with controls (P < 0.05). Extrinsic as well as intrinsic biomechanical material properties were measured in a three-point bending test. Bone mechanical properties of the tibiae and femora of rats in the Swim and Run groups were significantly greater than those in the control group (P < 0.05). In summary, different modes of exercise may benefit bone mechanical properties in different ways. The specific effects of swimming exercise (non-weight-bearing exercise) on bone require further study.

Algorithms↗

PubMed2002

Effects of caffeine and exercise on the development of bone: a densitometric and histomorphometric study in young Wistar rats.

High doses of caffeine will induce calcium loss and influence the normal development of bone, whereas the proper exercise has positive effects on bone metabolism. This study investigated the possible effects of exercise to antagonize the caffeine-induced impairment of bone development in young male Wistar rats. A total of 32 male rats (5 weeks old) were divided randomly into four groups: group 1 rats were fed caffeine; group 2 rats were prescribed an exercise program; group 3 rats were fed caffeine and prescribed an exercise program; and group 4 rats served as the control group. The caffeine was fed via the animals' dietary water and the dosage was 10 mg/100 g body weight per day, 3 days a week. The exercise program was carried out on a treadmill for 10 weeks (5 days/week, 1 h/day, 70% VO(2)max). Body weight was measured weekly. After sacrifice, the tibia length was measured and the tibia was processed for histomorphometric analysis. Bone mineral density was measured by dual-energy X-ray absorptiometer at three different sites of the tibia. In addition, the calcium content of the right femur was measured by atomic absorptiometry. The results showed that both exercise and caffeine significantly lowered the body weight gain. Rats fed with caffeine (groups 1 and 3) had a significantly longer tibia as compared with the non-caffeine-fed rats (groups 2 and 4) (p = 0.0149). The histomorphometry study showed that thickness of the growth plate in the proliferative zone, the hypertrophic zone, and total growth plate was greater in caffeine-fed groups than in non-caffeine-fed groups. The cell number in the proliferative zone was higher in the caffeine-fed groups. Area ratio of trabeculae in the primary spongiosa of rats in groups 1 and 2 were significantly greater than the control group. Caffeine feeding (groups 1 and 3) induced a lower area ratio of bone trabeculae in the secondary spongiosa, whereas exercise training (groups 2 and 3) increased the thickness of the trabeculae. The exercise program counteracted the negative effect of caffeine on the trabecular thickness, but did not correct the trabecular bone ratio. The bone mineral density (BMD) of the tibia was significantly lower in caffeine-fed rats, and the exercise program did not show any counteracting effect on the caffeine-induced BMD reduction. The calcium content assay showed that caffeine feeding decreased the weight and total calcium content of the femur. Again this exercise program did not counterbalance the negative effects of caffeine. In conclusion, high doses of caffeine seemed to stimulate the growth of long bone. However, it caused more serious negative effects on bone, including bone mineral loss, lower BMD, and lower calcium content. Exercise training at 70% VO(2)max had little antagonizing effect on caffeine-induced impairment of bone formation. Therefore, the best way to prevent caffeine-induced negative effects on bone development is to lower caffeine exposure.

Animals↗

PubMed2001

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↗

PubMed2001

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↗

PubMed2001

[Ultrasonographic evaluation of adrenal masses].

OBJECTIVE: To identify the diagnostic value of ultrasonography on adrenal masses. METHOD: Retrospectively analyzed the ultrasonographic features of 116 patients who suffered from adrenal masses, which were verified histologically after operation. RESULTS: Of all patients, the correct rate of localization and determination is 94.8% and 93.6%, respectively. CONCLUSION: Ultrasonography can be considered as an accurate means of scanning adrenal masses.

Adenoma↗

PubMed2001

Backbone dynamics of Escherichia coli thioesterase/protease I: evidence of a flexible active-site environment for a serine protease.

Escherichia coli thioesterase/protease I (TEP-I) is a member of a novel subclass of the lipolytic enzymes with a distinctive GDSLS motif. In addition to possessing thioesterase and protease activities, TEP-I also exhibits arylesterase activity. We have determined the (15)N nuclear magnetic spin relaxation rates, R(1) and R(2), and the steady state (1)H-(15)N heteronuclear Overhauser effect, measured at both 11.74 T and 14.09 T, of (u-(15)N) TEP-I. These data were analyzed using model-free formalism (with axially symmetric rotational diffusion anisotropy) to extract the backbone dynamics of TEP-I. The results reveal that the core structure of the central beta-sheet and the long alpha-helices are rigid, while the binding pocket appears to be rather flexible. The rigid core serves as a scaffold to anchor the essential loops, which form the binding pocket. The most flexible residues display large amplitude fast (ps/ns time-scale) motion and lie on one stripe whose orientation is presumed to be the ligand-binding orientation. We also detected the presence of several residues displaying slow (microseconds/ms time-scale) conformational exchanging processes. These residues lie around the binding pocket and are oriented perpendicularly to the orientation of the flexible stripe. Two of the putative catalytic triads, Ser10 and His157, and their neighbors show motion on the microseconds/ms time-scale, suggesting that their slow motion may have a role in catalysis, in addition to their possible roles in ligand binding. The presence of a flexible substrate-binding pocket may also facilitate binding to a wide range of substrates and confer the versatile functional property of this protein.

Anisotropy↗

PubMed2001

DNA methylation and ovarian cancer. I. Analysis of CpG island hypermethylation in human ovarian cancer using differential methylation hybridization.

OBJECTIVE: The aim of this study was to examine CpG island methylation patterns in ovarian cancer and determine whether epigenetic information can be related to clinical data of patients. CpG island (CpGI) hypermethylation is commonly associated with cancer progression, but little is currently known about the role of methylation in ovarian cancer. METHODS: Differential methylation hybridization (DMH) analysis at 742 loci was performed to determine methylation signatures for 20 primary epithelial ovarian carcinomas (Stages II, III, and IV adenocarcinomas, serous papillary), 6 ovarian cancer cell lines, and normal ovarian surface epithelial cells. RESULTS: Between 23 and 108 methylated CpGIs were seen in the ovarian carcinomas. Fewer (P < 0.05) methylated CpGIs were observed in the ovarian cancer cell lines; however, a number of CpGIs were commonly hypermethylated in both the cell lines and the tumor samples. A methylation signature, consisting of frequently (P < 0.05) methylated CpGIs, was determined for the samples. The observed pattern of methylation in ovarian cancers included several (11) CpGI tags that were previously reported to be hypermethylated in human breast cancer. CONCLUSIONS: Epigenetic signatures in ovarian cancer were determined using DMH. This proof-of-concept study lays the foundation for genome-wide screening of methylation to examine epigenotype-phenotype relationships in ovarian cancer.

Adult↗

PubMed2001

Comparison of ion release from new and recycled orthodontic brackets.

Bracket corrosion can occur in the oral environment. The purpose of this study was to compare the release of metal ions from new and recycled brackets in artificial saliva and buffers with different pH values over a 12-week immersion period. The brackets were divided into 2 groups: new and recycled. The recycled bracket bases were coated with adhesive and the brackets were heat treated. Nickel, chromium, iron, and manganese ions were detected by atomic absorption. The surface characteristics of the brackets were examined by energy dispersive radiographic analysis. The results were as follows: (1) Recycled brackets released more ions than did the new brackets. (2) Greater amounts of nickel, iron, and manganese ions were released in artificial saliva than in the other buffers tested. (3) Ion release from brackets in a pH 4 buffer was greater than that observed in pH 7 or pH 10 buffers. (4) The total amount of ion release increased with time. (5) After a 12-week immersion, the total ion release averaged over the period did not exceed the recommended daily intake.

Adhesives↗

PubMed2001

The shear bond strength of composite brackets on porcelain teeth.

Recent advances in materials and techniques suggest that direct bonding of orthodontic attachments to surfaces other than enamel may now be possible. To test the effectiveness of bonding orthodontic attachments to porcelain teeth, composite brackets (Spirit MB) were bonded to 64 porcelain teeth by means of a self-cure non-mixed resin system (Unite). The 64 porcelain teeth were divided into groups of eight and after roughening with a green stone they were subjected to a combination of treatments. Some were etched, some primed with a silane coupling agent and some received both treatments before the brackets were bonded to them. Half of the teeth were then thermally-cycled 500 times between 4 and 60 degrees C before all the brackets were removed in a shear test. The shear data was analysed by one way analysis of variance and the Student-Newman-Keul test. The results showed that the highest bond strength existed in the group which had been both etched and primed but not thermocycled (P < 0.05). The factors that affected the bond strength, beginning with the most significant, were acid etching, primer application, and then thermocycling. A mechanical based composite bracket can offer good bond strength to porcelain teeth.

Acid Etching, Dental↗

PubMed2001

Evaluation of the genotoxicity of zinc oxide eugenol-based, calcium hydroxide-based, and epoxy resin-based root canal sealers by comet assay.

Three main types of root canal sealer are currently commonly used in pulp treatment: zinc oxide eugenol-based, calcium hydroxide-based, and epoxy resin-based sealers. In the present study, the genotoxicity of sealer on oral carcinoma cells was evaluated by single-cell gel electrophoresis assay (comet assay). The whole length of the comet and the diameter of the head were measured using an image analysis system. The results were analyzed by one-way analysis of variance to compare the various means. The zinc oxide eugenol-based sealers (Canals, Canals-N, and Tubilseal) did not always cause a dose-dependent increase in genotoxicity. The resin-based sealers (Topseal, AH 26, and AH Plus) caused a dose-dependent increase in genotoxicity, but no such effect was seen with the calcium hydroxide-based sealer (Sealapex). The highest level of DNA damage was induced by the resin-based sealers.

Analysis of Variance↗

PubMed2001

Wilms' tumor: a paradigm for the new genetics.

Carcinogenesis can be triggered by a diverse range of molecular lesions, a variety of which can be illustrated by Wilm's tumor (WT), a pediatric kidney cancer. Molecular defects observed in WTs include several independent targets and mechanisms best exemplified by changes on the short arm of chromosome 11. This article will review the molecular pathology of WT and emphasize the broader ramifications for cancer genetics. Consideration will be given to carcinogenic pathways, novel cellular molecules, and technologies that will assist in the rapid interpretation and assimilation of DNA sequence data arising from the sequencing of the human genome.

Genes, Wilms Tumor↗

PubMed2001

The genetic events of HPV-immortalized esophageal epithelium cells.

We studied cytogenesis, telomere and telomerase, and c-myc, ras, bcl-2, and p53 genes of cells in the progressive process of immortal epithelial cells from embryonic esophagus induced by human papillomavirus (HPV). The SHEE cell line, established by us, consist of immortalized epithelial cells from the embryonic esophagus induced by genes E6E7 of HPV type 18. It was in initial malignant transformation when cultivated over 60 passages without co-carcinogens. Cells of the 10th, 31st, and 60th passages were represented in the progressive process within the immortal period. In these three stages of the cell line, the modal number of chromosome and karyotypes were analyzed. The telomere length was assayed by Southern blot methods, and the telomerase activity was analyzed by hTR and hTERT assay. C-myc, p53, bcl-2, ras genes were assayed by the multi-PCR method. The morphology of the 10th passage cells exhibited good differentiation, the 60th passage cells were relatively poorly differentiated, and the 31st passage cells differentiated in two distinct ways. The growth characteristics of the 31st and 60th passage cells were weakened at contact-inhibition and anchorage-dependent growth. Karyotypes of three cell passages belonged to hyperdiploid and hypotriploid with abnormal chromosomes +1, +3, +7, +9, +17, +18; del(1)(p32); der(4), t(4;?)(q31;?); der(5),t(5;?)(q31;?); der(13),t(13;13)(p11;q11) and others. Bimodal distribution of chromosomes with more aberrant chromosomes appeared in the 31st and 60th passage cells. Telomere length sharply shortened from normal fetal esophagus to the 10th and 31st passage step by step, but was stable from the 31st to the 60th passage and the telomerase activities measured were expressed at late two passages. p53 mutant was positive in three passages, c-myc was positive in the 31st and the 60th passage K-ras only in the last. The results reveal that changes of chromosomes, telomere length, telomerase activity and certain gene expressions are important events of HPV-immortalized esophageal epithelium cells. All of these changes occurred in dynamic progressive process. This cell line may be useful for the elucidation of the genetic mechanism of cellular immortalization.

Cell Line, Transformed↗

PubMed2000

Enhanced antitumor immunity by fusion of CTLA-4 to a self tumor antigen.

The idiotypic determinant (Id) of the immunoglobulin expressed by a B-cell malignancy can serve as an effective tumor-specific antigen but is only weakly immunogenic. This study demonstrates that the immunogenicity of the tumor Id protein can be dramatically increased by directing it to antigen-presenting cells (APCs). Cytotoxic T-lymphocyte antigen 4 (CTLA-4) present on activated T cells has a strong binding affinity to both B7-1 and B7-2 molecules, which are primarily expressed on APCs. After construction of a fusion protein consisting of Id and CTLA-4 (Id-CTLA4), mice immunized with the fusion protein induced high titers of Id-specific antibody and T-cell proliferative responses without adjuvants and were protected from lethal tumor challenge. The Id-CTLA4 fusion protein was so potent that even low doses (down to 0.1 microg) of the immunogen were able to elicit strong antibody responses. By using an Id-CTLA4 mutant protein, the ability to bind B7 molecules on APCs was shown to be required for the enhanced immunogenicity of Id-CTLA4. These findings demonstrate that fusing CTLA-4 to a potential tumor antigen represents an effective approach to prime antitumor immunities in vivo and may be applicable to the design of vaccines for a variety of other diseases. (Blood. 2000;96:3663-3670)

Abatacept↗

PubMed2000

Alternate aggregation pathways of the Alzheimer beta-amyloid peptide. An in vitro model of preamyloid.

Deposition of amyloid-beta (Abeta) aggregates in the brain is a defining characteristic of Alzheimer's disease (AD). Fibrillar amyloid, found in the cores of senile plaques, is surrounded by dystrophic neurites. In contrast, the amorphous Abeta (also called preamyloid) in diffuse plaques is not associated with neurodegeneration. Depending on the conditions, Abeta will also form fibrillar or amorphous aggregates in vitro. In this present study, we sought to characterize the properties of the amorphous aggregate and determine whether we could establish an in vitro model for amorphous Abeta. CD data indicated that Abeta40 assembled to form either a beta-structured aggregate or an unfolded aggregate with the structured aggregate forming at high peptide concentrations and the unstructured aggregate forming at low Abeta40 levels. The critical concentration separating these two pathways was 10 microm. Fluorescence emission and polarization showed the structured aggregate was tightly packed containing peptides that were not accessible to water. Peptides in the unstructured aggregate were loosely packed, mobile, and accessible to water. When examined by electron microscopy, the structured aggregate appeared as protofibrillar structures and formed classic amyloid fibrils over a period of several weeks. The unstructured aggregate was not visible by electron microscopy and did not generate fibrils. These findings suggest that the unstructured aggregate shares many properties with the amorphous Abeta of AD and that conditions can be established to form amorphous Abeta in vitro. This would allow for investigations to better understand the relationship between fibrillar and amorphous Abeta and could have significant impact upon efforts to find therapies for AD.

Alzheimer Disease↗

PubMed2000

Tertiary trisomy due to a reciprocal translocation of chromosomes 5 and 21 in a four-generation family.

Tertiary trisomy, or double trisomy, is a rare occurrence. We present two individuals with a previously unreported tertiary trisomy for chromosomes 5p and 21q in an eight-generation pedigree. Their phenotypes are compared with other partial trisomies of either 5p or 21q from the literature. The propositus was diagnosed with trisomy 21 at 2 years of age after a karyotype study for short stature and developmental delay. His phenotype was described as atypical for Down syndrome. He presented at 9 years of age because of pervasive behavioral problems and obesity. He was brachycephalic with a flattened nasal bridge, but he lacked other characteristics of trisomy 21. Because of lack of phenotypic evidence of Down syndrome, a repeat karyotype was obtained and showed 47,XY, +der(21)t(5;21)(p15.1; q22.1), incorporating partial trisomies of both chromosomes 5 and 21. Mother had a balanced translocation, 46, XX,t(5;21)(p15.1; q22.1); 8 other relatives were examined. The translocation originated from the maternal great-grandmother, but only the propositus and his mentally retarded aunt had a similar phenotye and the derivative chromosome. Fluorescence in situ hybridization showed absence of band 21q22.2 in the derivative chromosome of the propositus and his aunt, indicating that neither had trisomy for the Down syndrome critical region. These cases represent a unique double partial trisomy of chromosome arms 5p and 21q that occurred because of 3:1 malsegregation of a reciprocal translocation. These cases further demonstrate that phenotypic discordance with cytogenetic results dictate further investigation using advanced cytogenetic hybridization.

Adolescent↗

PubMed2000

Structural studies of soluble oligomers of the Alzheimer beta-amyloid peptide.

Recent studies have suggested that non-fibrillar soluble forms of Abeta peptides possess neurotoxic properties and may therefore play a role in the molecular pathogenesis of Alzheimer's disease. We have identified solution conditions under which two types of soluble oligomers of Abeta40 could be trapped and stabilized for an extended period of time. The first type of oligomers comprises a mixture of dimers/tetramers which are stable at neutral pH and low micromolar concentration, for a period of at least four weeks. The second type of oligomer comprises a narrow distribution of particles that are spherical when examined by electron microscopy and atomic force microscopy. The number average molecular mass of this distribution of particles is 0.94 MDa, and they are are stable at pH 3 for at least four weeks. Circular dichroism studies indicate that the dimers/tetramers possess irregular secondary structure that is not alpha-helix or beta-structure, while the 0.94 MDa particles contain beta-structure. Fluorescence resonance energy transfer experiments indicate that Abeta40 moieties in amyloid fibrils or protofibrils are more similar in structure to those in the 0.94 MDa particles than those in the dimers/tetramers. These findings indicate that soluble oligomeric forms of Abeta peptides can be trapped for extended periods of time, enabling their study by high resolution techniques that would not otherwise be possible.

Alzheimer Disease↗

PubMed2000

Assessment of zinc finger orientations by residual dipolar coupling constants.

Residual dipolar coupling constants measured in anisotropic solution contain information on orientations between internuclear vectors and the magnetic field, providing long-range information that may help determine the relative orientations of distinct domains in biomolecules. Here we describe the measurement and use of residual dipolar coupling restraints in the refinement of the structure of the complex of DNA with three zinc fingers of transcription factor IIIA (TFIIIA), measured in a DMPC/DHPC bicelle solution. These dipolar restraints were applied on a variety of orientations of the zinc finger domains (derived from crystallography, previous NMR studies, and systematic modeling) in order to examine the validity and sensitivity of using residual dipolar splittings to study interdomain orientations. The spread in interdomain angles between zinc fingers is reduced from 24 degrees to 9 degrees upon incorporation of dipolar restraints. However, the results also show that the ability to determine relative orientations is strongly dependent on the structural accuracy of the local domain structures.

Computer Simulation↗