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T T Chen

Publications and source records attributed to T T Chen.

At least 19 recordsLinked to original sources
PubMed1992

Identification of a second insulin-like growth factor in a fish species.

An internal portion of insulin-like growth factor (IGF) amplified from the total cDNA of rainbow trout (Oncorhynchus mykiss) liver by a PCR was used to screen a rainbow trout liver cDNA library, and recombinant clones encoding two distinct IGFs were isolated. On the basis of a 98.7% nucleotide and 98.3% predicted amino acid identity to coho salmon IGF-I, one cDNA sequence was identified as rainbow trout preproinsulin-like growth factor I (rtIGF-I). The second cDNA sequence shared 46.1% and 43.3% identity with rtIGF-I at the nucleotide and predicted amino acid levels, respectively, and was identified as rainbow trout preproinsulin-like growth factor II (rtIGF-II). Predicted amino acid sequence comparisons of rtIGFs with those of human IGFs indicate that rtIGF-I is more similar to human IGF-I than to human IGF-II, and that rtIGF-II is more similar to human IGF-II than to human IGF-I. Southern blot analysis of rainbow trout genomic DNA probed with rtIGF-I and -II cDNA suggests that these two forms of IGF originate from separate genes. The presence of a teleost IGF-II suggests that the divergence of IGFs occurred early in vertebrate evolution.

Actins↗
PubMed1992

Clonal expansion in follicular lymphoma occurs subsequent to antigenic selection.

The genesis of human follicular lymphoma (FL) is a multistep process. The initial event is thought to be the chromosomal translocation t(14;18)(q32;q21) juxtaposing the bcl-2 proto-oncogene with the immunoglobulin (Ig) H chain locus joining segment (JH) as an error of D-J or V-D joining in the pre-B cell. However, FL is recognized clinically as a tumor of surface Ig (sIg)-positive B cells with morphologic and phenotypic similarities to the centrocyte of the secondary immune response. Thus, additional steps must be involved in the clonal expansion of the FL tumor cell beyond the activation of bcl-2 as a consequence of the t(14;18) translocation. Like the normal centrocyte, somatic mutations accumulate in the variable (V) genes of FL tumor B cells. To determine if clonal expansion of FL occurs before or after the development of the malignant follicle, we sought to examine the evolution of the FL V gene from its unmutated germline (GL) counterpart. To obtain the GL gene we first cloned the productively rearranged V gene of patient MT FL and obtained the clone rMTF. A hybridization probe derived from the 2.1-kb region upstream of the V gene in clone rMTF identified a single band in Southern blot hybridization of GL DNA. This probe was used to screen a size-selected library, and candidate GL V genes were isolated. Two identical clones, MTGL1 and 2, proved to have upstream regions (USRs) that were colinear with the USR of the rMTF. Thus, the MTGL clones represent the unmutated GL V genes, which were productively rearranged in the MT FL. Comparison of the GL V gene sequence to a consensus of MT FL V gene sequences revealed 42 mutations, demonstrating that malignant clonal expansion occurred subsequent to the activation of somatic mutation, presumably in the malignant follicle. Furthermore, the individual FL V gene sequences segregated into two distinct patterns of mutation. The major population represented 71% of the clones, and the minor population 29%. To investigate possible mechanisms for the parallel selection of distinct tumor cell populations, we analyzed the pattern of silent and replacement mutations within the V gene sequences. We found that in the framework regions (FRs) of both populations there were significantly fewer replacement changes than expected, suggesting that negative selective pressure was maintaining the structural integrity of the sIg. In contrast, the complementarity determining regions (CDRs), which make up the antigen binding domain of Ig, had an excess of replacement changes, suggesting positive selection for altered ligand binding.

Base Sequence↗
PubMed1992

Antigen selection in human lymphomagenesis.

Although surface immunoglobulin plays a central role in the differentiation and growth of normal B-cells, its role in the growth of human B-cell malignancies is largely a matter of conjecture. Human follicular lymphomas are attractive systems to study in part because they are clones of cells sharing many similarities with germinal center B-cells which are critically dependent on antigen selection for survival. Nucleotide sequence information was determined for the immunoglobulin heavy chain variable genes expressed by two cases of follicular lymphoma. In addition, the germ line variable gene counterparts were also cloned and sequenced from biopsy material obtained from both of these patients. Numerous mutations from germ line were present in the variable genes from both of these cases, many of which accumulated during expansion and growth of these lymphomas. Moreover, the mutations that accumulated during tumor expansion were distributed in a manner that almost certainly was dependent on positive selection presumably mediated by contact with an antigen. These data indicate that antigen selection is probably important for the growth and clonal evolution of follicular lymphomas.

Antigens, Neoplasm↗
PubMed1992

Primary-structural and evolutionary analyses of the growth-hormone gene from grass carp (Ctenopharyngodon idellus).

The growth-hormone (GH) gene of grass carp, one of the fastest-growing species of farmed fish, was isolated and the DNA sequenced. Only one GH gene is found in this species. This gene, which is 2.5 kb in length, has five exons and four introns, in common with all of the mammalian and the recently published common-carp GH genes. In the course of vertebrate evolution, the total lengths of the intron and the non-coding region of exon 5 of the GH gene have been shortened by 40-70%, whereas the encoding exons of the gene have been slightly increased. The more closely related species exhibit the closest sequence similarity in their GH genes. For example, the similarity of the exons is 84.1-93.2% between grass carp and common carp (within the same family of Syprinedae), 43.5-82.1% between grass carp and rainbow trout (in different orders of Teleostei) and 45.8-58.6% between grass carp and rat (in different grades of Vertebrata). In addition, similar DNA domains, such as thyroid-hormone-receptor-complex-binding site and cell-type-specific cis elements involved in regulation of expression of rat and human GH genes, have been localized in the corresponding regions of the grass-carp GH gene.

Amino Acid Sequence↗
PubMed1992

Biological actions of monoclonal luteinizing hormone/human chorionic gonadotropin receptor antibodies.

Several recent studies have elucidated the structure of the mammalian LH/hCG receptor; as reported in the present work, we have developed a series of monoclonal antibodies (mAbs) against the rat ovarian LH/hCG receptor using highly purified receptor as immunogen and by screening hybridomas with purified LH/hCG receptors. The mAbs were able to specifically immunoprecipitate LH/hCG receptors from solubilized preparations of rat ovarian membranes as well as from partially purified preparations. Western blotting with mAb P1B4 detected a probable receptor dimer and a receptor fragment in rat and porcine ovarian tissue but not in other tissues. This mAb also partially inhibited hCG binding to rat and porcine ovarian tissues. The receptor mAbs were able to inhibit hCG-induced progesterone synthesis in cultured human and porcine granulosa cells without affecting cAMP- and FSH-induced progesterone synthesis. The mAb P1B4 was used to demonstrate that the majority of ovarian receptors are internalized after hCG treatment and that in pseudopregnant rats receptors are present in the rough endoplasmic reticulum and in microvesicles. Bovine corpus luteal cells also contained P1B4 binding sites, as detected by immunohistochemical technique. Taken together, these results suggest that the mAbs are specific for the LH/hCG receptor, mAb P1B4 recognizes an epitope that is highly conserved among mammals, and this epitope is probably in the extracellular domain.

Animals↗
PubMed1992

The effect of peritoneal macrophage-derived factor(s) on ovarian progesterone secretion and LH receptors: the role of calcium.

Macrophages and their secretory products, cytokines, play an integral role in many reproductive processes. In this study we examined the effect of conditioned media from cultured human peritoneal macrophages on progesterone production by granulosa cells and the role of calcium in this process. Macrophages were pretreated with various concentrations of a calcium channel blocker (verapamil) or a calcium ionophore (A23187). Macrophage-conditioned media (MCM) or cell-free media that contained calcium channel modifiers were added at three dose levels to cultured porcine granulosa cells. Progesterone production and LH receptor content were determined. Macrophage-conditioned media alone elevated basal progesterone production, but significantly attenuated granulosa cell LH receptor content. These effects were neither potentiated nor suppressed by pretreating macrophages with verapamil. However, production of the LH receptor lowering factor(s) appeared to be suppressed by calcium ionophore. We conclude that (1) one or more factors produced by macrophages have a net stimulatory effect on basal progesterone production and these factor(s) may not be calcium-dependent and (2) macrophage-derived secretory products reduce granulosa cell LH receptor content. The production of these factor(s) may be calcium-dependent.

Animals↗
PubMed1992

Temporomandibular joint innervation in rats: a horseradish peroxidase study.

In the present study, we have used the horseradish peroxidase (HRP) retrograde transport technique to map the trigeminal primary afferent and motor neurons that innervate the temporomandibular joint (TMJ) and the lateral pterygoid muscle (LPM). One to 3.0 microL of 4% wheatgerm agglutinin conjugated horseradish peroxidase (HRP-WGA) solution was introduced unilaterally into the joint cavity of twelve Sprague-Dawley rats. Injections were made from the above, following trephining of the zygomatic arch with a dental bur. Seventy-two hours after surgery, the animals were sacrificed via perfusion-fixation through the left ventricle. The TMJ, both trigeminal ganglia and brain stem were removed, sectioned serially at 50 microns, and reacted according to the tetramethyl benzidine (TMB) technique of Mesulam. Tissues were then examined at the light microscopic level. The injection site showed that the HRP-WGA filled the upper chamber of the TMJ cavity and extended anteriorly to include the LPM. HRP injected into the joint cavity was transported retrogradely to the ipsilateral trigeminal ganglion, where numerous HRP labeled neurons were found. The greatest number of cells were localized in the dorsolateral posterior portion of the ganglion. In the brain stem, numerous labeled cells representing the motor innervation of the LPM were found in a crescent-shaped array on the ventral side of the trigeminal motor nucleus. No labeled cells were found in the mesencephalic nucleus. The results show substantial trigeminal sensory innervation of the TMJ and LPM with no central projection to the mesencephalic nucleus.

Animals↗
PubMed1992

Radial keratotomy: eleven-year experiences.

During the period from 1980 to 1991, Radial Keratotomy (RK) had been done by the author under topical anesthesia in more than 10,000 cases, mostly on both eyes at the same time. Those patients had myopia with a preoperative refractive error between 1.5 and 20.0 diopters (D). The surgical technique consisted of 4, 8, 16 incisions using a diamond knife with micrometer and the diameter of the central clear zone was mostly 3.0 mm and determined by preoperative refractive error. Many different procedures were tried to improve the effect of RK, including redeepening intentional microperforations at 1.5 mm, 3 mm, 5 mm distance from the corneal center. But these procedures had no significant effect 6 months after the operation. Complications such as infection, glaucoma, cataract, etc. were almost none. Results of RK on long term follow up showed hyperoptic tendency, and the visual fluctuation were none or minimal.

Follow-Up Studies↗
PubMed1992

Chemical identification of catfish growth hormone and prolactin.

Isolation and primary structure of growth hormone (GH) and prolactin (PRL) from the pituitary gland of catfish (Ictalurus punctatus) are described. Alkaline extract of the pituitary glands was fractionated by gel filtration on Sephadex G-75, ion-exchange chromatography on DEAE-cellulose, and reversed-phase high-performance liquid chromatography on Octadecyl silica ODS. Catfish GH and PRL were identified by Western blotting with antisera against chum salmon GH and PRL. The catfish GH consists of 178 residues and is the most similar to carp GH, with sequence identity of 77%, although there is an uninterrupted deletion of 10 amino acid residues that corresponds to carp GH (90-99). The PRL is composed of 187 residues, which also exhibits the highest identity (79%) with carp PRL. Sequence identity between catfish GH and PRL is only 27%.

Amino Acid Sequence↗
PubMed1990

Transgenic fish.

A range of transgenic animal species have been generated using DNA microinjection, and application of this technique to fish is now showing some degree of success. Studies to optimize microinjection techniques specifically for use with fish, and to investigate possible alternative methods for mass culture, should lead to the commercial production of transgenic fish able to transmit desirable characteristics, such as enhanced growth or disease resistance, to their progeny.

Animals↗
PubMed1990

Molecular cloning of a transcription factor, AGP/EBP, that belongs to members of the C/EBP family.

A C/EBP-like transcription factor, AGP/EBP, that binds to three distinct motifs in the 5'-flanking region of alpha 1-acid glycoprotein gene (AGP) has been identified. Here we report the cloning and properties of cDNA corresponding to mouse AGP/EBP. AGP/EBP and C/EBP share 87% amino acid sequence homology in the "leucine zipper" and its associated DNA-binding domains, while their sequences outside these domains and the sizes of their mRNAs are different. Unlike the limited expression of C/EBP in tissues and cells, AGP/EBP appears to be ubiquitously expressed in tissues like lung, spleen, kidney, heart, testis, and liver and cell lines like p388D1, 129P (hepatoma cell line of C3H/HeJ), FO (mouse myeloma), and L929. Antibody against cloned and expressed AGP/EBP which was raised in rabbits could recognize AGP/EBP from nuclear extract of a number of cells and tissues. On the basis of our findings about the structural relationship and the similarity of motif recognition, we propose that a family of C/EBP-like transcription factors exists.

Amino Acid Sequence↗
PubMed1979

Double Latin square study to determine variability and relative bioavailability of methylprednisolone.

The variability and relative bioavailability of methylprednisolone tablets were evaluated utilizing a double Latin square crossover design in which each of 20 subjects was given four of five treatments. Three different lots of methylprednisolone tablets exhibited virtually identical absorption, with similar ranges and coefficients of variation of some selected bioavailability parameters indicative of lot-to-lot uniformity in bioavailability. Within-lot and between-lot uniformities in bioavailability also were similar, suggesting that the observed variability in serum methylprednisolone levels was not due to manufacturing process variables. With respect to intra-versus intersubject variability, no differences were found for the absorption rate or terminal half-life. In contrast, between-subject variability associated with extent of absorption was greater than that within subjects. Relative to an aqueous suspension, methylprednisolone tablets were fully bioavailable.

Adult↗
PubMed1979

The effects of ibuprofen, indomethacin, aspirin, naproxen, and placebo on the gastric mucosa of normal volunteers: a gastroscopic and photographic study.

The effects of various nonsteroidal antiinflammatory drugs on the gastric mucosa were endoscopically evaluated in 40 normal volunteers. Eight groups, each containing five subjects were designed: aspirin (3600 mg/d); placebo; ibuprofen (1600 mg/d); ibuprofen (2400 mg/d); indomethacin (100 mg/d); indomethacin (150 mg/d); naproxen (500 mg/d); and naproxen (750 mg/d). All volunteers took medication for seven days and gastroscopy was carried out on day one and day eight. All findings were documented by photography. Severe gastric mucosal injury occurred with aspirin (P less than 0.05), both doses of indomethacin, and the higher dose of naproxen. Lesser changes were seen with the lower dose of naproxen, both doses of ibuprofen and placebo. The higher doses of ibuprofen, indomethacin, and naproxen caused a greater degree of gastric mucosal injury, but statistical significance was achieved only with naproxen (P less than 0.01). Subjective gastrointestinal complaints generally correlated with endoscopic pathology; however, nine volunteers had evidence of severe injury to the gastric mucosa with no symptomatology. This was confined to the patients on indomethacin, naproxen, and ibuprofen. Aspirin patients all had some degree of symptomatology but to a lesser degree than expected in view of the endoscopic findings.

Adult↗
PubMed1975

Quantitative cloning of malignant human glioma cells by conditioned medium.

The use of conditioned medium (CM) obtained from monolayer cultures of human glioma cells induced colony formation from single glioma cells in culture. In contrast, no colonies were observed in cultures incubated with nonconditioned standard Eagle's basal medium. The number of colonies formed closely depended on the concentration of CM. The glioma CM not only stimulated colony formation but also induced the formation of fibrillary cell extensions. Culture conditions influencing the production of colony-stimulating factors included cell density and duration of culture medium contact with glioma cells. The colony-stimulating activity (CSA) was stable after freezing and thawing, but decreased 30-40% when CM was exposed to temperatures over 66 degrees C for 30 minutes. In addition, the CSA was filtratable (0.45 mu), dialyzable, and passable through an Amicon PM10 filter, which indicated a molecular weight less than 10,000. The use of CM provided an improved method for quantitative assays of neural tumor cells, based on their colony formation in culture.

Cell Line↗