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Biomedical subjects

Y F Zhao

Publications and source records attributed to Y F Zhao.

At least 37 records · Page 2Linked to original sources
PubMed1993

N-->S phosphoryl migration in phosphoryl glutathion.

It was found that in the case of N-(diisopropylphosphoryl) glutathion (reduced form), 2, N-->S phosphoryl migration took place, but not for N,N-bis(diisopropylphosphoryl) glutathion (oxidized form) or N-diisopropylphosphoryl cysteine. These results were deduced by 31P-NMR tracing experiments. It was shown that phosphoryl migration was catalyzed by an intramolecular carboxyl group, and a mechanism involving a mixed carboxyl-phosphoric anhydride was proposed. A competitive reaction between the amino and thiol group toward diisopropyl phosphite indicated that the phospho-thiol derived from N-(diisopropylphosphoryl) glutathion (reduced form), 2, did not result from direct phosphorylation of the thiol group. N,S-Bis(diisopropylphosphoryl) glutathion provides an authentic sample to confirm the migrated phosphoryl thiol product.

Amino Acid Sequence↗
PubMed1992

Phosphoryl group participation leads to peptide formation from N-phosphorylamino acids.

N-phosphorylated amino acids without a side chain functional group can transfer themselves into peptides after prolonged standing in solvents at warm temperatures. Seven N-phosphorylpeptides and free peptides were isolated and their structures determined. The phosphoryl group participation is the key to the peptide formation. An intramolecular mixed carboxylic-phosphoric anhydride intermediate was proposed for this type of reaction which might provide a clue to the function of the phosphoryl group in the phosphorylated enzymes and in the prebiotic synthesis of protein.

Amino Acid Sequence↗
PubMed1992

[Repair of the extracranial facial nerve defect by autogenous vein graft: an experimental study].

In this study, we repaired the extracranial facial nerve defect of rabbit using an autogenous vein graft and compared the results with conventional autogenous nerve graft in function and morphology. A 1 cm segment of the extracranial morphology. A 1 cm segment of the extracranial facial nerve was removed in 30 rabbits, the defect was repaired by a segment of vein or by a segment of nerve or without repair. The gross observation, histologic and histochemical examination, electrophysiological study and nerve fascicle graphics analysis were performed at 4, 8, 12, 20 weeks. The results of this study demonstrated that an autogenous vein as a non-nervous tissue graft can repair the extracranial facial nerve defect. 20 weeks after operation, the results with vein graft were superior to nerve graft.

Animals↗
PubMed1992

[Changes in the mandibular growth after ramus osteotomy in rats].

A comparison is made between mandibular growth of the operated side and the unoperated side after vertical ramus osteotomy by measurements of the area and linear distances of bilateral mandibles, and digital image processing technique from the radiographs. The results show that slightly retarded growth of the mandible of the experimental side in growing Wistar rats occurs after osteotomy in the mandibular ramus, but obvious asymmetry is not found Deficiencies of mandibular growth in the operated side are similar in both groups of upward and downward repositioning of the proximal segment.

Animals↗
PubMed1991

Cis- and trans-repression of class I major histocompatibility gene expression in Abelson virus-transformed murine leukemia.

Numerous tumor cell lines of leukemic origin are known to modulate cell surface expression of major histocompatibility complex (MHC) class I antigens resulting in alterations in their immune detection and tumorigenicity. We have been studying the mechanisms responsible for attenuation of MHC class I gene expression in an H-2 heterozygous (H-2b x H-2d) Abelson-Murine leukemia virus (A-MuLV)-transformed leukemic cell line (designated R8). Here we report that treatment of the R8 cell line with the protein synthesis inhibitor cycloheximide (CHX) increased H-2Kb steady-state messenger RNA (mRNA) levels several fold. The induced H-2Kb mRNA transcripts were functional, as demonstrated by their ability to be translated into immunoprecipitable H-2Kb alloantigen. H-2Kb null variants derived from the R8 cell line were shown to be the product of both cis- and trans-acting mechanisms, insomuch as the treatment of R8-derived H-2Kb non-expressor lines with CHX re-established expression of H-2Kb mRNA to the same extent as transfection of the variant cell line with the wild-type H-2Kb gene. Such findings indicate that downregulation of MHC class I gene expression is constitutive for the R8 leukemic cell line, a phenomenon that may be related to the immature pre-B-cell phenotype of this A-MuLV transformant.

Abelson murine leukemia virus↗
PubMed1991

A novel reagent, dialkylphosphite, for peptide synthesis.

The same dialkylphosphite reagent can be used for both N protection and C activation of amino acids. Two N-diisopropyloxyphosphinyl (Dipp) tripeptide esters were prepared, and nine N-Dipp-dipeptide acids were synthesized through the activated amide intermediate. The positive ion FAB-MS of N-Dipp-tripeptide showed novel cleavage patterns in that only the N-phosphoryl fragment ions gave intense peaks while the C-terminal series ions did not appear. This novel character might be useful for peptide sequence analysis. In addition, dialkyloxyphosphinyl group can be examined by 31P-NMR for peptide conformational analysis and inspection for the degree of racemization during the coupling reaction.

Amino Acid Sequence↗
PubMed1991

[Relationship between hemodynamics and hemorrheology in chronic cor pulmonale].

Hemodynamics, hemorrheology and blood gases were studied in 20 patients with stable chronic cor pulmonale. Blood viscosity was affected by hematocrit and blood gases, which acted on pulmonary pressure, pulmonary vascular resistance and right cardiac output. Blood viscosity was measured in the shear stress rate of 5.75, 11.5, 23, 46, 115 and 230 s-1. The decrease in plasma pH and PaO2 elevated high shear stress blood viscosity, pulmonary arterial pressure, total pulmonary vascular resistance and decreased right cardiac output, O2 administration decreased in high shear stress blood viscosity, but increased in low shear stress blood viscosity. Blood viscosity was positively correlated with hematocrit, which varied in different shear stress rate, the relative coefficient was the highest when the shear stress rate was in 11.5 s-1 (r = 0.9288 P less than 0.001). Pulmonary arterial pressure and pulmonary vascular resistance were positively correlated with high shear stress blood viscosity but uneffected by low shear stress blood viscosity. The increasing in high shear stress blood viscosity decreased the right cardiac output. Rigidity of red blood cell may play an important role in regulating pulmonary circulation and right heart function.

Adult↗
PubMed1990

[Clinicopathologic observation of 36 cases of basal cell carcinoma of the facial region].

The clinicopathologic features of thirty-six cases of basal cell carcinoma in the facial region are reported. There were 26 men and 10 women. The ages of these patients ranged from 14 to 72 years and the largest number of cases (67.74 percent) were encountered in the fifth and sixth decades of life. The average duration was approximately 6 years before patients were treated. The tumors were most frequent in the nose and upper lip. Most of them were histopathologically classified as the solid type. Moderate and extensive irregular peripheral palisading and squamous differentiation were less frequent in the primary basal cell carcinoma.

Adolescent↗
PubMed1990

Laparotomy ovum pick-up and ultrasonic transvaginal ovum retrieval in an IVF program.

Different methods of ovum pick-up were used in an IVF program from January 1, 1988 to January 31, 1989. In the initial stage of the program, laparotomy ovum pick-up with surgical treatment of pelvic diseases resulted in two cases of clinical pregnancy in 1987 with full-term delivery of two healthy babies. Transvaginal ovum pick-up with a needle using an ultrasonic endovaginal transducer was started in late 1987. In 1988-1989 the transvaginal method was employed more frequently than laparotomy, and it has become a routine practice in the IVF program. The ultrasonic endovaginal approach seemed to give a low ovum recovery rate (70.99%), but the fertilization rate was high (85.10%, P less than 0.05), and the rate of embryo transfer was 89.33%. The average number of pre-embryo per transfer was 2.26. These figures were quite similar in the two groups. The ultrasonic transvaginal approach for egg retrieval was noninvasive, easily accepted by patients. We suggest that it can be done repeatedly on one patient to improve the cumulative pregnancy rate. However, the laparotomy for ovum pick-up has shown some special merits and is still indicated in some cases.

Adult↗
PubMed1989

[Surgical treatment of primary pulmonary cryptococcal granuloma--report of 4 cases].

Primary pulmonary cryptococcal granuloma is not common in Sichuan. The diagnosis of this disease is difficult to make because the patient has no characteristic symptoms and the chest X-ray findings of the mass are not easily differentiated from carcinoma of the lung. The incidence of this disease is apparently increasing. Pulmonary cryptococcosis may be disseminated hematogenously to the meninges and cryptococcal meningitis is very difficult to treat. If the pulmonary lesion is localized, the patient's general condition is good with no evidence of systemic lupus erythematosis, diabetes, leukemia or lymphoma, partial resection of the lung is indicated. But, if the patient has a history of recent cryptococcal meningitis, surgery must be deferred. Four cases of primary pulmonary cryptococcal granuloma have been treated surgically supplemented with medical therapy in the First Affiliated Hospital from 1986 to 1987. Follow-up of more than one year showed good results in each case.

Adult↗
PubMed1989

[The finite element analysis of the bicuspid and molar of mandible].

Recently, the finite element method has been adopted in the study of tooth structure as well as the stress distribution of dental prosthesis. In order to understand the loading state of the supporting tissues and the stress distribution of the teeth in various shapes under the pressure of loading, the author of this essay has applied the two-dimensional finite element method to the study of the stress distribution of the periodontal supporting tissues at the time when the second bicuspid and the second molar are vertically and obliquely loaded. Finally, the results of the quantitative analysis are obtained and a curve of the stress distribution of the teeth is also drawn up. The conclusion is as follows: 1. When the vertical loading is applied to the occlusal surface of the bicuspid and molar, the stress distribution of periodontal supporting tissues is uniform. 2. The stress concentration is on the marginal ridge and thedistal apex of bicuspid under the oblique loading. 3. When the oblique loading is applied to the occlusal surface of the molar, the stress concentration is only on the marginal ridge, and it is small.

Alveolar Process↗
PubMed1989

[Stress distribution analysis of a loaded fixed bridge by finite element method].

The fixed bridge is a common prosthesis widely used in clinical dentistry. In order to design an ideal fixed bridge which can provide the best protection of the abutments, we must study the stress distribution of alveolar bone, when the fixed bridge is under the loading. In this article, we report the application of the finite element method to examine the stress distribution of the alveolar bone of fixed bridge abutments. We have made seven vertical loading models and two oblique loading models. A quantitative analysis result has been obtained and the stress distribution result drawn up by a computer. The results of this analysis are as follows: 1. Under the seven vertical loadings, the bearing compress stress on the mesial apex of the second bicuspid is large. In this area the compress stress is largest, when the vertical loading is applied on the two-abutment tooth and pontic, the sigma 2 is -120.0 but the stress of alveolar bone of the molar is uniform. 2. Under the oblique loading, by the mesial apex of bicuspid are borne the tensile stress and compress stress, the latter is larger than the former, and the sigma 2 is -75.0. 3. The molar is an ideal abutment tooth for the fixed bridge.

Alveolar Process↗
PubMed1987

Improvement in sensitivity of fast atom bombardment mass spectrometry of amino acids by di-isopropylphosphorylation.

Positive ion fast atom bombardment mass spectrometric sensitivities of seven amino acids and the corresponding di-isopropylphosphorylated derivatives were carefully compared. Results showed that an improvement in sensitivity by factors of 4-29, mostly above 10, were achieved after the derivatization. The chemical noise derived from glycerol matrix was also greatly reduced by this derivatization.

Amino Acids↗