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Biomedical subjects

T T Chen

Publications and source records attributed to T T Chen.

At least 127 records · Page 7Linked to original sources
PubMed1987

Clinical experience with soft intraocular lens implantation.

A retrospective study of 205 consecutive, planned extracapsular cataract extractions with posterior chamber silicone elastomer lens implants inserted in the ciliary sulcus region were examined between six and 23 months postoperatively. When the patients with preexisting pathology were excluded, the percentage of patients seeing 20/40 or better was 94.1%. The postoperative complications included intraocular lens dislocation in two cases, cystoid macular edema in one case, and secondary glaucoma in one case.

Aged↗
PubMed1987

Evaluation of cataract-related risk factors using detailed classification systems and multivariate statistical methods.

The well-known different morphological features observed in so-called senile cataract are probably symptoms of various pathogenetic mechanisms in the lens. In order to identify a relationship between type of cataract and special risk factors, a cataract classification system using Scheimpflug photography has been developed. Data of 288 cataract patients (case histories and blood chemistries) have been grouped according to differences in cataract morphology. The multivariate analyses showed the following five variables to be important and to contribute independently to the differentiation of cataract types: cholelithiasis, allergy, heart insufficiency, pneumonia, and age. A case-control study without consideration of cataract morphology showed the following variables to be important and to associate independently with the risk of developing cataracts: age, allergy, diabetes, hypotension, hypertension, use of analgesics, and coronary disease.

Age Factors↗
PubMed1987

Multimodal therapy for limited small-cell lung cancer: a randomized study of induction combination chemotherapy with or without thoracic radiation in complete responders; and with wide-field versus reduced-field radiation in partial responders: a Southwest Oncology Group Study.

In 1979 we initiated a phase III study in the Southwest Oncology Group (SWOG) which was designed to determine the value of chest radiation in limited-stage small-cell lung cancer patients achieving complete response after induction chemotherapy, and to test the use of wide-field v more limited-volume radiation in patients with partial responses (PRs) and patients with stable disease (SD). The induction chemotherapy (VMV-VAC) consisted of vincristine, 2 mg intravenously (IV) every week for six doses; methotrexate, 60 mg/m2 IV days 1 and 43; VP-16, 50 mg/m2/d IV days 1 to 5 and 43 to 47; doxorubicin, 60 mg/m2 IV days 22 and 64; and cyclophosphamide, 1,000 mg/m2 IV days 22 and 64. Four hundred ninety-four patients were registered, of whom 473 were eligible. Of 466 response-evaluable patients, 153 (33%) achieved complete disease remission (CR) with chemotherapy. A total of 387 patients entered the consolidation phase of treatment after chemotherapy and response determination. CR patients were prospectively randomized to receive chest radiation, consisting of 4,800 rad administered in a split-course scheme, or to continue chemotherapy without interruption. The treatment volume was based on tumor extent before the induction chemotherapy. Maintenance chemotherapy consisted of cyclophosphamide and VP-16 administered for four cycles before a period of reinduction chemotherapy consisting of VMV-VAC as described above. Patients receiving chest radiation therapy were given the same maintenance and reinduction chemotherapy programs following completion of the chest radiation. One hundred ninety-one eligible patients achieving PR or SD status after induction chemotherapy were randomized to a preinduction treatment volume or to a postinduction reduced tumor volume, with treatment portals designed according to tumor extent before or after induction chemotherapy, respectively. After completion of the entire treatment plan, there were 218 (47%) CRs and 121 (26%) PRs. These figures represent the greatest response achieved at any point in the treatment program. The median survival for all eligible patients was 57 weeks (74 weeks for CRs). Overall survival for CR patients was not different for patients who did or did not receive chest radiation. However, patterns of tumor relapse were affected by the chest radiation, as 38 of 42 relapsing patients who did not receive radiation had intrathoracic recurrences in comparison to only 20 of 36 radiated patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1986

The porcine ovarian luteinizing hormone/human chorionic gonadotropin receptor II. Is the purified receptor an oligomer of identical subunits?

Purified porcine luteinizing hormone/human chorionic gonadotropin receptors were analyzed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis following reduction and thermal denaturation and stained with Coomassie Brilliant Blue. A major protein of Mr = 77 +/- 4 X 10(3) and a minor protein of Mr = 66 +/- 4 X 10(3) were observed. Iodoreceptor proteins were resolved into a major component of Mr = 77 +/- 3 X 10(3) and a minor component of Mr = 62 +/- 5 X 10(3) after reduction and thermal denaturation. In the absence of reduction, the iodoreceptor had a major component of Mr 63 +/- 3 X 10(3). Purified human chorionic gonadotropin specifically transferred part of the iodoreceptor from the Mr = 63 X 10(3) species to an Mr = 110-120 X 10(3) species. Purified receptors were analyzed by nondenaturing polyacrylamide gel electrophoresis and identified by specific binding of iodo-human chorionic gonadotropin. Three binding species with approximate Mr = 60 X 10(3), 130 X 10(3), and 260 X 10(3) were identified. Iodoreceptors co-migrated with the Mr = 60 X 10(3) species under the same conditions. Similar results were obtained following renaturation of receptors separated by sodium dodecyl sulfate/polyacrylamide gel electrophoresis without reduction and thermal denaturation. These results suggest for the first time that the porcine corpus luteum luteinizing hormone/human chorionic gonadotropin receptor may be a hormone binding monomer of Mr = 60-65 X 10(3), and that the monomer may associate to form hormone binding polymeric receptor complexes.

Animals↗
PubMed1986

Postsplenectomy sepsis and other complications following staging laparotomy for Hodgkin's disease in childhood.

This is a survey of 234 pediatric patients in whom staging laparotomy/splenectomy was carried out (1975 to 1981) in the course of the Intergroup Hodgkin's Disease in Childhood Study (IHDCS). Relapse has occurred in 44 of these patients, and 12 have died, 7 secondary to extension of lymphoma, 2 with herpes or pneumocystis infections, 2 with leukemia, and 1 from an unrelated accident. During the period of surveillance (mean 5.5 yr), five episodes of bacterial sepsis (positive blood cultures) have occurred, including two due to Streptococcus pneumoniae; and three, to Hemophilus influenzae. The former occurred in the small group of patients in this series who had not received the prescribed pneumococcal vaccination. No fatalities were associated with these septic episodes. Intestinal obstruction secondary to adhesions (benign) occurred in eight patients and was managed without intestinal resection or mortality. One patient required operative release of an obstructed ureter following laparotomy, and one, oophorectomy for an infarcted (transposed) ovary.

Adolescent↗
PubMed1986

Cellular myc (c-myc) in fish (rainbow trout): its relationship to other vertebrate myc genes and to the transforming genes of the MC29 family of viruses.

We have isolated, cloned, and sequenced the rainbow trout (Salmo gairdneri) c-myc gene. The presumptive coding region of the trout c-myc gene shows extensive homology to the c-myc genes of chicken, mouse, and human. Comparison of nucleotide sequences reveals that human, mouse, chicken, and trout c-myc genes contain at least two coding exons, interrupted by introns of decreasing size of 1.38 kilobases (kb), 1.2 kb, 0.97 kb, and 0.33 kb, respectively. The exons are clearly delineated by donor-acceptor splice signals. The degree of nucleotide homology between trout, chicken, and human exon II is less than that observed for exon III. However, the greatest homology among these three genes is localized to two specific regions within exon II (myc boxes A and B). At the predicted amino acid level, fish c-myc shows considerable homology to vertebrate c-myc gene products. Trout c-myc is expressed in normal trout cells as a single 2.3-kb mRNA species, similar in size to other vertebrate transcripts.

Amino Acid Sequence↗
PubMed1986

Rainbow trout growth hormone: molecular cloning of cDNA and expression in Escherichia coli.

We have isolated several recombinant clones carrying the complementary DNA (cDNA) sequence of the rainbow trout (rt) Salmo gairdneri growth hormone (GH) mRNA by immunoblot screening using an antiserum to chum salmon (Oncorhyncus keta) GH. The nucleotide sequence of one of the rtGH cDNA clones (pAF51) was determined. The rt cDNA sequence in pAF51 encodes a hybrid polypeptide of 199 amino acid residues containing 9 amino acid residues of the bacterial beta-galactosidase, one residue from the codon at the junction of the beta-galactosidase gene, and the rtGH cDNA sequence, an additional residue from the presumptive signal peptide of the pre-rtGH and the entire sequence of the mature rtGH (188 amino acid residues). Pairwise matrix comparisons of the hydropathy profiles of bovine, human, rat, and rainbow trout GH polypeptides indicate that regions of similarity exist between the rtGH and mammalian GH. In particular, there are two major regions of similarity found near the amino-terminal region and at the carboxy-terminal region. These regions correspond to hydrophilic domains of the GH molecules. The possible significance of these domains is discussed.

Amino Acid Sequence↗
PubMed1986

Effect of alternating combination chemotherapy on survival of ambulatory patients with metastatic large-cell and adenocarcinoma of the lung. A Southwest Oncology Group Study.

Using a randomized prospective trial design, chemotherapy with 5-fluorouracil, vincristine, and mitomycin C (FOMi) was compared with cyclophosphamide, doxorubicin, and cisplatin (CAP) and with FOMi alternating with CAP (FOMi/CAP) in 452 eligible patients with metastatic large-cell undifferentiated and adenocarcinoma of the lung. Objective responses were obtained in 26%, 17%, and 22% of patients treated with FOMi, CAP, and FOMi/CAP, respectively. The median survival was similar for FOMi, CAP, and FOMi/CAP therapies (20, 24, and 23 weeks, respectively), but the overall survival (log rank test), 1-year survival, and remission duration were longer for FOMi/CAP-treated patients. Survival was significantly longer for fully ambulatory FOMi/CAP-treated patients compared with either FOMi (P = .01) or CAP (P = .04). Younger patients treated with full doses of therapy responded more often than older patients receiving reduced drug doses (26% and 11%, respectively; P = .003). A prognostic factor regression analysis of all eligible patients indicates that sex, performance status, stage, and treatment assigned were important independent variables determining survival (P less than .05). Toxicity was comparable in each treatment group.

Adenocarcinoma↗
PubMed1986

Receptor-mediated uptake of lipoproteins by cultured porcine granulosa cells.

Receptor-mediated uptake of low density lipoprotein (LDL) has been shown to provide a major source of cholesterol for a variety of cell types, particularly steroidogenic cells. In this study, the functional significance of lipoproteins in porcine ovarian granulosa cells and their mechanism of uptake by the cell was examined. Porcine LDL and high density lipoprotein (HDL) were isolated using a KBr density gradient, and the purity of both lipoproteins was confirmed by single corresponding bands on agarose gel stained for lipid and protein. Purified LDL and HDL were radioiodinated and labelled with colloidal gold for binding and tracer studies respectively. Both lipoproteins bind to cell surface and are internalized within 30 min at 37 degrees C. The cultured granulosa cells possess more HDL binding sites than LDL binding sites and are more responsive in progesterone production when supplemented with HDL. These results suggest that granulosa cells may preferentially utilize HDL over LDL as a source of cholesterol for steroidogenesis.

Animals↗
PubMed1985

The porcine LH/hCG receptor. Characterization and purification.

Porcine luteal LH/hCG receptor (LH/hCG R) was solubilized with 70-80% recovery from the crude plasma membrane fraction by Triton X-100 in the presence of 25% glycerol and protease inhibitors. The solubilized receptor maintained 90% of original activity at -60 degrees C for 90 days. Equilibrium association constant (Ka) values of 1.92, 2.22, and 2.03 X 10(10) M-1 were observed for the whole homogenate, plasma membrane fraction, and solubilized LH/hCG R preparations, respectively. The specific binding capacity for the same fractions were 49, 70, 55 fmol/mg protein, respectively. Complexes of LH/hCG R and Triton X-100 were resolved into two components with approximate Mr = 2.7 X 10(5) and 5.4 X 10(5) by gel filtration on Sepharose 6B and two glycoprotein components by chromatography on concanavalin A-Sepharose. Solubilized porcine LH/hCG R was purified by two cycles of affinity chromatography on highly purified hCG-Sepharose with an overall recovery of 30-35% of the initial activity in the Triton extract. Purified porcine LH/hCG R had a specific binding capacity of 2300 pmol/mg protein and a Ka = 1.5 X 10(10) M-1. Silver staining of sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels demonstrated that the major protein in porcine LH/hCG R preparations has Mr = 68,000. A weakly staining band at Mr = 45,000 was also observed in the purified receptor preparation. Analysis of iodinated purified LH/hCG R by autoradiography has confirmed these results. Porcine LH/hCG R was purified 40,000-fold by this method.

Animals↗
PubMed1985

Analysis of intraocular lens power calculation.

We performed an analysis of ocular biometry and intraocular lens (IOL) power calculation on 100 eyes that had anterior chamber IOL implantation during 1981 and 1982. Various methods of calculating the IOL power were used, including the standard lens power, presurgical basic refraction, Fyodorov's formula, Colenbrander's formula, Binkhorst's formula, and the SRK formula. In addition, we took the median value of these calculated results as the median power in selecting an appropriate IOL power. The postoperative refraction and actually implanted IOL power were used to determine the IOL power needed for emmetropia. Our regression analysis of the predicted IOL power and power actually needed for emmetropia showed that the methods of standard power and presurgical basic refraction were unreliable while the rest were of satisfactory accuracy. Among the latter, all the predicted IOL powers based on the biometric data had almost the same coefficient of determination and standard error of estimate. However, with the SRK formula and the median power the values of the regression line were closest to the ideal value. With the regression analysis, the accuracy of predicted IOL power from theoretical formulas was comparable to that of the SRK regression formula.

Aged↗