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Biomedical subjects

J H Yang

Publications and source records attributed to J H Yang.

At least 109 records · Page 6Linked to original sources
PubMed1991

Relationship between 2'-hydroxyls and magnesium binding in the hammerhead RNA domain: a model for ribozyme catalysis.

The use of deoxyribonucleotide substitution in RNA (mixed RNA/DNA polymers) permits an evaluation of the role of 2'-hydroxyl groups in ribozyme catalysis. Specific deoxyribonucleotide substitution at G9 and A13 of the ribozyme decreases the catalytic activity (kcat) of the ribozyme by factors of 14 and 20, respectively. The reduction of the reaction rate concomitant with the absence of these 2'-OHs or the 2'-OH of the substrate U7 position can be partially compensated by increasing the Mg2+ concentration above 10 mM. The KMg of the all-RNA ribozyme is 5.3 mM, and the lack of either of the three influential 2'-OHs increases this value by a factor of approximately 3. These and other reaction constants for the ribozyme and the deoxy-substituted analogues have been determined by assuming a three-step mechanism. The data presented here provide the basis for the formulation of a molecular model of ribozyme activity.

Base Sequence↗
PubMed1991

Synthesis and anticancer activity of various 3'-deoxy pyrimidine nucleoside analogues and crystal structure of 1-(3-deoxy-beta-D-threo-pentofuranosyl)cytosine.

Various 3'-deoxy pyrimidine nucleoside analogues have been synthesized for evaluation as potential anticancer and antiviral agents. Among these compounds, 1-(3-deoxy-beta-D-threo-pentofuranosyl)cytosine (10, 3'-deoxy-ara-C) and 3'-deoxycytidine (22) had significant anticancer activity against CCRF-CEM, L1210, P388, and S-180 cancer cell lines in vitro, producing ED50 values of 2, 10, 5, and 34 microM, respectively, for 3'-deoxy-ara-C (10); and 25, 5, 2.5, and 15 microM, respectively, for 3'-deoxycytidine (22). Thus, 3'-deoxy-ara-C (10) was 12.5 times more active against CCRF-CEM cells than 3'-deoxycytidine (22). The 2'-O-acetyl, 5'-O-acetyl, and 2',5'-di-O-acetyl derivatives of 3'-deoxy-ara-C (10), compounds 34, 31, and 30, demonstrated anticancer activity in the same range as 3'-deoxy-ara-C (10) against CCRF-CEM, L1210, P388, and S-180 cells. The 5'-O-acetyl derivative (31) had significantly greater activity against CCRF-CEM with an ED50 value of 0.4, but this compound also showed similar activity, as did 3'-deoxy-ara-C, against L1210, P388, and S-180 with ED50 values of 3, 3, and 13 microM, respectively. 3'-Deoxy-ara-C was also evaluated in vitro against HSV-2, HCMV, and GPCMV viruses and was found to be not very active with respective IC50 values of 110, 220, and 1000 microM. The single-crystal structure of 3'-deoxy-ara-C (10) was determined by X-ray crystallography. There are two molecules of the nucleoside and one molecule of water in the asymmetric unit. The sugar moieties of the two nucleoside molecules adopt different conformations. In molecule A, the ring pucker is C3'-endo with P = 18.7 degrees and tau m = 37.3 degrees, while the CH2OH side chain is gauche+. In molecule B, the ring pucker is C2'-endo with P = 156.8 degrees and tau m = 37.8 degrees and the side chain is trans.

Animals↗
PubMed1991

Dyschromatosis universalis with X-linked ocular albinism.

A 10-year-old Chinese boy with the characteristic skin manifestations of dyschromatosis universalis is described. In addition, the patient had congenital nystagmus with poor visual acuity, and ophthalmological examination revealed foveal hypoplasia and albino-like fundi. Histopathology showed giant pigment granules in the skin. Based upon the finding of giant pigment granules in clinically normal skin of the patient's mother, the patient was diagnosed as a case of dyschromatosis universalis with X-linked ocular albinism. To the best of our knowledge, this is the first documented case of this combination.

Albinism, Ocular↗
PubMed1991

[Synthesis of baogongteng A analogs].

In order to search for antiglaucoma drugs, three analogs (5, 12 and 10) of Baogongteng A were synthesized. The analog 12 shows myotic and reducing intraocular pressure activities in rabbit.

Animals↗
PubMed1990

Mixed DNA/RNA polymers are cleaved by the hammerhead ribozyme.

A series of chemically synthesized oligodeoxyribonucleotides containing one or two ribonucleotides (DNA/RNA mixed polymers) at and/or adjacent to the cleavage site of the substrate can be cleaved by the "hammerhead" ribozyme. In comparison with the all-RNA substrate, the predominantly deoxyribonucleotide substrates have (1) lower optimal temperatures of cleavage, (2) approximately 6-fold higher Km's and 7-fold lower kcat's at 30 degrees C, and (3) 15-fold higher Km's and 8-fold lower kcat's at 37 degrees C. The extent to which the RNA substrate cleavage is inhibited in the presence of an all-DNA (KI = 13 microM) and an RNA substrate analogue with a dC at the cleavage site (KI = 0.96 microM) supports the contention that the formation of the ribozyme-substrate complex with the predominantly deoxyribonucleotide substrates (D substrates) is impaired. The weaker binding of D substrates was confirmed by thermal denaturation and determination of the Tm of the complex. Analysis of the kinetic data also suggests that the conformation of the catalytic core of the ribozyme-substrate complex differs from that of the all-RNA complex, a change that results from the presence of a DNA/RNA heteroduplex in the complex.

Base Sequence↗
PubMed1990

Induction of peroxisome proliferation in rainbow trout exposed to ciprofibrate.

Rainbow trout (Salmo gairdneri), average body weight of 450 g, were treated with 15, 25, or 35 mg/kg of ciprofibrate via intraperitoneal injection every other day for 2 to 3 weeks. The effects on hepatic peroxisomal acyl-CoA oxidase, polypeptide PPA-80, catalase, and liver weight were measured. The treatment of trout with ciprofibrate showed significant dose-related increases in peroxisomal acyl-CoA activity, polypeptide PPA-80, and catalase after 3 weeks of exposure. Peroxisomal oxidase activity showed a significant (p = 0.0008) increase (78%) at 35 mg/kg and a marginal (p = 0.1) increase (27%) at 25 mg/kg after 3 weeks of exposure. Densitometric analysis of polypeptide PPA-80 and catalase showed increases up to 48 and 236% at 35 mg/kg, respectively. Morphometric analysis on livers of trout administered 35 mg/kg for 3 weeks showed a 2.3-fold increase of peroxisomal volume density, as compared to control. This study demonstrates the induction of peroxisome proliferation in rainbow trout administered ciprofibrate, a known peroxisome proliferator in rodents.

Acyl-CoA Oxidase↗
PubMed1990

[Clinical observation of free-standing Core-Vent dental implant to replace premolar (1)].

According to Dr. Niznick's alternative two-stage surgical technique, the author installed 3.5 mm x 8 mm Core-Vent Implant (Core-Vent Corporation, Encino, CA, U.S.A.) as a free standing abutment to replace lower left second premolar of 50-year-old male patient. From the foregoing procedure the author obtained the following results: 1. Free-standing Core-Vent Implants can be used to replace single premolar effectively without reduction of adjacent natural teeth. 2. Rotation of screw-in titanium insert (abutment) was observed under occlusal force. 3. Adjustment of height of titanium coping insert was necessary. 4. From the oral examination, patient comments, panoramic and periapical radiograph, there were no evidences in gingival inflammation, pain, reduction of alveolar bone level during the observation period of 13 months postoperatively.

Crowns↗
PubMed1990

Treatment of experimental Coxsackie B-3 viral myocarditis with Astragalus membranaceus in mice.

A murine model system for observing the effect of Astragalus Membranaceus (AM) on experimental myocarditis caused by Coxsackie B-3 virus (CB3V) was developed in 4-week-old male BALB/C mice. Gross, histopathologic and ultrastructural examinations of the infected-AM treated group showed that the severity and involved area of the myocardial lesions became milder and smaller than those in the infected-NS treated mice. The total lesion area, and the total lesion area/total myocardial area examined (%) and virus titer in the former group were also smaller and lower than those in the latter group. The results suggest that AM is effective in the inhibition of Coxsackie B virus propagation and protection of myocardium in mouse myocarditis.

Animals↗
PubMed1990

Gene rearrangement of cutaneous T-cell lymphoma.

Gene Rearrangement is considered to be a helpful tool for diagnosis of cutaneous T-cell lymphoma. In this study five patients with clinical diagnosis of cutaneous T-cell lymphoma were reviewed for their clinical presentation, skin biopsies and surface marker phenotypes. Southern blot analysis of DNA extracted from their skins revealed that rearrangement of T-cell receptor beta chain (TCRB) genes happened in three patients but rearrangement of immunoglobulin heavy chain genes was absent. TCRB rearrangement could also detect lymphoma involvement of lymph nodes, peripheral blood and bone marrow in our patients. In these conditions, systemic therapy is suggested.

Adult↗
PubMed1989

[Bond strength of an etched Co-Cr alloy].

The purpose of this study was to test the bond strength of a Co-Cr alloy. 40 cylindrical specimens (4 mm in diameter) were made of non-surgical Vitallium, and tensile bond strength was measured after etching and bonding. Etching was done with Oxy-Etch, and etching conditions were as follows: Composition of etching solution: Cone. nitric acid; 1 part glacial acetic acid; 1 part distilled water; 2 parts Current: 300 ma/cm2 Etching time: 3 min. The results were as follows: 1. Tensile bond strength was 435 +/- 116 kg/cm2 2. The result of this study shows that this etching method could be clinically applicable.

Acid Etching, Dental↗
PubMed1989

[Study on mandibular movements by Saphon Visitrainer Model 3].

The purpose of this study was to obtain the basic data of mandibular movements for prosthodontic treatment including craniomandibular dysfunction. The author measured the ranges of movements of mandible in the frontal, sagittal and horizontal trajectory using Saphon VisiTrainer Model 3 (Tokyo Shizaisha Inc.) in 8 male dental students of Seoul National University with normal occlusal relationship. The author obtained the following results; 1. The mean for maximal right and left laterotrusion in the frontal trajectory were 11.55mm and 10.51mm, and did not differ significantly (P greater than 0.05). 2. The mean for maximal protrusion from centric relation occlusion in the sagittal trajectory was 12.63mm and antero-posterior distance between CRO and CO was 1.51 mm. Maximum opening could not be trajected in 3 of 8 subjects. 3. The means of right, left laterotrusion and maximum protrusion were 10.97mm, 11.14mm and 10.31mm, and did not differ significantly (P greater than 0.05).

Dental Occlusion, Centric↗
PubMed1989

[Use of double McAb sandwich ELISA to detect circulating antigen of Toxoplasma in infected rabbits].

This paper reports on the cumulative positive frequencies of circulating antigen (CAg) detected in the sera of rabbits infected with Toxoplasma by using double-McAb sandwich ELISA. The positive frequencies of rabbits with heavy and medium infection in the incubation period are 30.8% and 11.1%. Those with medium infection in acute, subacute and early chronic period are 86.1% and 76.7%, 43.3% and 32.0% with light infection. The positive rates of CAg in rabbits of medium and light infection rose progressively in acute period, but declined in subacute and early chronic period. Cross reaction with schistosomiasis and coccidiosis was all negative. This method of high specificity, sensitivity and duplication possesses certain value in the diagnosis of acute or active Toxoplasma infection and may be useful for the diagnosis in the early period.

Animals↗
PubMed1987

Effect of axillary nodal status on the long-term survival following mastectomy for breast carcinoma: nodal metastases may not always suggest systemic disease.

Records of 215 patients receiving radical mastectomies from 1958 to 1968 at Roswell Park Memorial Institute were reviewed for the significance of axillary nodal status on long-term survival and recurrence. Ten-year disease-free interval rates were 83%, 47%, and 17%, respectively, for patients with negative nodes, 1-3 positive nodes, and greater than or equal to 4 positive nodes. Fifteen-year rates were 80%, 37%, and 8%, respectively. Survival and disease-free interval curves for the 3 nodal status groups were significantly different from each other (P less than 0.0001). Curves for three subclasses of the greater than or equal to 4 positive node group (4-6, 7-12, and greater than or equal to 13) were similar in overall survival, but were significantly (P = 0.04) different for disease-free interval, due to a rapid rate of recurrence in the greater than or equal to 13 positive node group. Hazard rates of treatment failure during each successive 3-year period for 9 years following mastectomy for those with 1-3 positive nodes or greater than or equal to 4 positive nodes decreased with time, whereas the rates for those with negative nodes were low and relatively constant throughout follow-up. These findings support the thesis that a significant proportion of negative nodes patients are cured by mastectomy and that a smaller group of node-positive patients have regional disease with a chance of cure by mastectomy.

Axilla↗