Biomedical subjects

D S Yang

Publications and source records attributed to D S Yang.

At least 73 records · Page 4Linked to original sources

PubMed1989

Structure-function relationship in a winter flounder antifreeze polypeptide. II. Alteration of the component growth rates of ice by synthetic antifreeze polypeptides.

Using synthetic analogs of an alpha-helical winter flounder antifreeze polypeptide (AFP) we investigated some important molecular details of the mechanism of action of this AFP. Of the seven peptides synthesized, all but one were amino-terminal deletions of the native AFP. Three of the seven synthetic analogs possessed the same antifreeze activity as the native polypeptide; the other analogs were devoid of antifreeze activity. The growth rates along the a and c axes of ice in solutions of varying concentrations of the three active AFP analogs were examined. The a axis growth rates of ice were inversely proportional to the concentration of the active peptides. The c-axis growth rates of ice were also dependent on peptide concentration. The active peptides enhanced c-axis growth at lower concentrations, while at higher concentrations they inhibited c axis growth. The ability of the peptides to develop antifreeze activity and to alter the a and c axis growth rates of ice depended on the presence of appropriately positioned amino acid residues with hydrogen bonding side chains. From these observations we propose that at low concentrations the AFP, through dipolar interactions and hydrogen bonding, interact with the prism faces of ice retarding a axis growth. At these concentrations, the electrical field of the AFP helix-dipole, like an externally applied field (Bartlett, J.T., van der Heuval, A.P., and Mason, B.J. (1963) Z. Angew. Math. Phys. 14, 599-610), can enhance ice c axis growth. At higher concentrations, the AFP interact with all ice crystal planes and retard both a and c axis growth.

Animals↗

PubMed1989

Effects of 3,4-dihydroxyacetophenone on the biosynthesis of TXA2 and PGI2 in human placental villus and umbilical artery segments in vitro.

In this paper, the effects of 3,4-dihydroxyacetophenone, DHAP (Qingxintong), an active constituent of traditional Chinese medicine, on the biosynthesis of TXA2 and PGI2 in human placental villi and umbilical artery segments of normal term pregnancy in vitro were studied by a perifusion technique. The collected fractions were assayed by radioimmunoassay for TXB2 and 6-keto-PGF1 alpha. The results showed that DHAP inhibited TXA2 and PGI2 production by umbilical artery segments in a dose dependent fashion and in both tissues TXA2 was more sensitive to inhibition than was 6-keto-PGF1 alpha. According to these data it is suggested that DHAP might be useful in treatment of pathologic pregnancies with chronic defective utero-placental circulation such as PIH and IUGR to improve this circulation.

6-Ketoprostaglandin F1 alpha↗

PubMed1989

[(1H-imidazol-1-yl)methyl]- and [(3-pyridinyl)methyl]pyrroles as thromboxane synthetase inhibitors.

Several [(1H-imidazol-1-yl)methyl]- and [(3-pyridinyl)methyl] pyrroles were prepared and evaluated in vitro as thromboxane synthetase inhibitors in human platelet aggregation studies. A number of structures, e.g. 10b,f,g,i (respective IC50 values: 1 microM, 50 nM, 42 nM, 44 nM) showed superior in vitro inhibition of TXA2 synthetase when compared to the standard dazoxiben (1). However, it was found that in vitro potency did not translate into nor correlate with in vivo activity when these compounds were evaluated in mice in a collagen-epinephrine-induced pulmonary thromboembolism model. (E)-1-Methyl-2-[(1H-imidazol-1-yl)methyl]-5-(2-carboxyprop-1-enyl) pyrrole (10b) was found to offer protection against collagen-epinephrine-induced mortality in mice, thereby demonstrating that oral administration is an effective route for absorption of this drug. Additional evidence for the oral effectiveness of 10b in lowering serum TXB2 levels was obtained by performing ex vivo radioimmunoassay experiments with rats. A 13-week study of 10b in rats with reduced renal mass was conducted in order to evaluate the role of TXA2 production in hypertension and renal dysfunction. Although serum and urinary TXB2 levels in rats were found to be lowered during this study by 10b, the levels of urinary protein excretion remained comparable to that of the control group.

Animals↗

PubMed1989

Foreign body epithelioid granuloma after cosmetic eyebrow tattooing.

We describe two patients with epithelioid granulomatous inflammation on the eyebrows after undergoing cosmetic eyebrow tattooing. We tried to analyze the causative elements from biopsy specimens and tattoo inks with x-ray microanalysis. We suggest that granuloma caused by cosmetic eyebrow tattooing is a complication worthy of mention.

Adult↗

PubMed1989

[The result of extended thymectomy in patients with myasthenia gravis of pure ocular type].

We studied postoperative status of 14 patients with myasthenia gravis of ocular type who underwent extended thymectomy. Nine patients were in remission, three improved, and two unchanged. No patient became worse and died. The remission rates at one, three, five, and ten years after operation were 50.0%, 58.3%, 60.0%, and 80.0%. The palliation rates at one, three, five, and ten years after operation were 64.3%, 75.0%, 80.0%, and 100%. The remission rate at one year after operation in patients of ocular type was significantly (p less than 0.05) higher than that in generalized type (191 patients). The mean preoperative duration of symptoms in patients who obtained remission after surgery was 7.2 +/- 6.5 months, while mean duration was 85.6 +/- 45.8 months in those patients who could not obtain remission, indicating a significant difference (p less than 0.05) of duration of symptoms between two groups. Among 89 patients with generalized as well as ocular symptoms before extended thymectomy, 62 patients (69.7%) still complained of ocular symptoms and 48 patients (53.9%) had generalized symptoms with or without ocular symptoms in 1 to 12 years after operation. This result shows that ocular symptoms do not disappear more easily than generalized ones. We conclude that extended thymectomy should be performed even in patients with myasthenia gravis of pure ocular type.

Adult↗

PubMed1989

[The discussion of the need of mediastinal lymph node dissection in the surgical treatment of lung cancer].

The need of lymph node dissection in the case of operative lung cancer with negative mediastinoscopy was discussed. As a preliminary study, the N-number obtained from the mediastinoscopy and that of postoperative examination was compared. The rate of agreement of N-number was as high as 96%. Secondary, 183 cases of lung cancer with squamous-or adenocarcinoma pathologically T-1 or 2. N-0 and P-0 or 1 were picked up and examined. In those cases, the result of 3 years survival rate was 80% in the cases of absolute curative operation and 60% in that of relative non-curative cases, and 5 years survival rate was 70% and 52% respectively, and the cases of absolute curative operation was statistically excellent than that of another group. However, the background of the two groups was different to some degree on account of the advancement of the cancer and the age of the patients. Therefore, the randomized study as for the lymph node dissection in the cases of negative mediastinoscopy was finally performed. In the 30 cases of squamous cell carcinoma where dissection was carried out in 13 cases and not done in 17 cases, the result of 3 years survival was 84% (dissecting group) and 89% (non-dissecting group), and 5 years survival was 73% and 63% respectively. In 23 cases of adenocarcinoma (13; dissecting, 10; non-dissecting), the result of 3 years survival was 100%, 63% and that of 5 years survival rate was 100%, 63% respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗

PubMed1988

Crystal structure of an antifreeze polypeptide and its mechanistic implications.

The X-ray crystallographic structure of an antifreeze polypeptide from the fish winter flounder, has been determined at 2.5 A by an analysis of the Patterson function. This is the first report of a polypeptide of this size that is a single alpha-helix. A proposed mechanism of antifreeze binding to ice surfaces is given which requires: first, that the dipole moment from the helical structure dictates the preferential alignment of the peptide to the c-axis of ice nuclei; second, amphiphilicity of the helix; and third, torsional freedom of the side chains to facilitate hydrogen bonding to ice surfaces.

Amino Acid Sequence↗

PubMed1988