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Biomedical subjects

R G Zhang

Publications and source records attributed to R G Zhang.

At least 37 records · Page 2Linked to original sources
PubMed1990

Measurement of intracellular pH in hamster diaphragm by absorption spectrophotometry.

The regulation of intracellular pH (pHi) is important in controlling muscle contraction. In these experiments, a spectrophotometric method of determining pHi was developed, and the method was then used to study muscle pHi regulation during CO2-induced changes in extracellular pH (pHb). Studies were performed in vitro on 27 diaphragm muscle strips obtained from adult hamsters. pHi was measured from the ratio of the absorbances of the acid (lambda = 530 nm) and alkaline (lambda = 460 nm) forms of a vital dye, neutral red, using the unstained diaphragm spectrum as a reference blank. A standard neutral red calibration curve constructed from eight diaphragm muscle homogenates indicated that the absorbance ratio was highly linear, with pH over the range 6.00-8.00. In intact muscle strips gassed with 95% O2-5% CO2, pHb was 7.45 +/- 0.03 (SE) and pHi was 7.00 +/- 0.01 (SE). When the muscle was aerated with CO2 concentrations from 3 to 30%, pHb and pHi changed rapidly and reached a steady state in 10-15 min. However, when pHb ranged from 6.80-7.80, pHi changed little from the value observed when pHb was 7.40. When pHb was less than 6.80 or greater than 7.80, changes in pHi and pHb were quantitatively similar. The results suggest that, in the isolated diaphragm, overall pHi is stable and effectively buffered over a wide range of CO2-induced changes in buffer solution pH.

Animals↗
PubMed1989

Crystallographic studies on E. coli Trp aporepressor.

Two crystal forms of Trp aporepressor, an inactive, unliganded form of Trp repressor have been obtained which are suitable for high resolution X-ray diffraction analysis. Trp aporepressor crystallizes in two forms: orthorhombic, P 2(1)2(1)2 and tetragonal P 4(1) (or P 4(3] which diffract to 1.8 A and 2.4 A, respectively. The orthorhombic crystals contain one monomer in the asymmetric unit, therefore the twofold axis relates two subunits of the dimer as in the case of the previously described Trp repressor (R. Schevitz et al., 1985, Nature, 317, 782-786) and Trp pseudorepressor (C. Lawson & P. B. Sigler, 1988, Nature, 333, 869-871). The tetragonal crystals have two dimers in the asymmetric unit and are nearly isomorphous with the tetragonal crystals of Trp repressor and Trp pseudorepressor grown under similar conditions but in the presence of an activator or inhibitor, respectively.

Apoproteins↗
PubMed1988

Crystal structure of trp repressor/operator complex at atomic resolution.

The crystal structure of the trp repressor/operator complex shows an extensive contact surface, including 24 direct and 6 solvent-mediated hydrogen bonds to the phosphate groups of the DNA. There are no direct hydrogen bonds or non-polar contacts to the bases that can explain the repressor's specificity for the operator sequence. Rather, the sequence seems to be recognized indirectly through its effects on the geometry of the phosphate backbone, which in turn permits the formation of a stable interface. Water-mediated polar contacts to the bases also appear to contribute part of the specificity.

Crystallography↗
PubMed1988

Flexibility of the DNA-binding domains of trp repressor.

An orthorhombic crystal form of trp repressor (aporepressor plus L-tryptophan ligand) was solved by molecular replacement, refined to 1.65 A resolution, and compared to the structure of the repressor in trigonal crystals. Even though these two crystal forms of repressor were grown under identical conditions, the refined structures have distinctly different conformations of the DNA-binding domains. Unlike the repressor/aporepressor structural transition, the conformational shift is not caused by the binding or loss of the L-tryptophan ligand. We conclude that while L-tryptophan binding is essential for forming a specific complex with trp operator DNA, the corepressor ligand does not lock the repressor into a single conformation that is complementary to the operator. This flexibility may be required by the various binding modes proposed for trp repressor in its search for and adherence to its three different operator sites.

Apoproteins↗
PubMed1987

Comparative data on cytophotometric DNA in malignant lesions of the esophagus in the Chinese and Japanese.

Cell DNA content was microspectrophotometrically determined in tissues of advanced esophageal carcinoma of 50 Chinese and 82 Japanese subjects. DNA distribution patterns were classified into Types I, II, III, and IV, according to the degree of dispersion and the peak value on the DNA histogram. The proportions of high ploidy (Types III and IV) in Chinese and Japanese patients were 68% and 81.7%, respectively. Overall 5-year survival rates of the Chinese and Japanese were 25.3% and 19.8%, respectively. Five-year survival rates of patients with Types II, III and IV were 45.7%, 23.8% and 0% in Chinese patients and 57.1%, 16.1%, and 0% in Japanese patients, respectively. Thus, differences in nationality were not related to the prognosis. The incidences of high ploidy group in those with an advanced esophageal carcinoma were high and were associated with a poor prognosis in both races. DNA distribution pattern of esophageal carcinoma reflected the outcome and malignant potential in the Chinese and the Japanese.

Carcinoma, Squamous Cell↗
PubMed1987

Crystal structure determination of mung bean trypsin inhibitor Lys fragment-bovine trypsin complex--molecular replacement, electron density map at 3.0 angstron resolution.

The orientation and position of the trypsin molecule in the complex crystal cell mung bean trypsin inhibitor Lys fragment (MBILF)-bovine trypsin (BTRY) have been successfully determined by molecular replacement method with the model of the refined bovine trypsin molecule. Starting from the BTRY coordinates which were oriented and located in the correct azimuth and position in the complex cell according to the result from rotation function and translation function, sim-weighted Fourier map with coefficients 2/Fo/-/Fc/ at 3.0 A resolution was calculated. Besides the electron density which is obviously attributed to itself, in the vicinity of the active site of BTRY the dense contour levels corresponding to the MBILF and and its boundary could be clearly seen in this map. The size of MBILF was approximately estimated at 15 x 15 x 25 A.

Crystallography↗
PubMed1986

[Resection and reconstruction of the carina].

A case of recurrent adenoid cystic carcinoma after right middle lobectomy is reported. A right lower lobectomy with resection of carina was performed as the lesion involved the right main bronchus, the carina and the orifice of right lower lobe. The carina was reconstructed by the anastomosis of right upper lobe bronchus to the left main bronchus. The postoperative course was uneventful. After two months, the stitch granuloma at the site of anastomosis developed and it was satisfactorily managed by local palliative measures. No recurrence has been found during a follow-up of 1.5 years.

Bronchial Neoplasms↗
PubMed1986

[Experience in the surgical treatment of 748 patients with lung cancer].

A series of 748 patients with lung cancer as treated by surgery from 1961 to 1984 is reported. Regular lobectomy was done in 445 (74%) patients, bronchoplastic lobectomy in 67 (11.2%), segmental or wedge excision in 15 (2.5%) and pneumonectomy in 74 (12.3%) in which the ratio of left to right pneumonectomy was 2.9:1. Overall resection rate was 80.4% (601/748) and resection mortality was 1.2% (7/601) (death within 30 days of operation). Overall 5 year survival rate was 42% (169/402). The 5 year survival rate was 35.3% for pneumonectomy, 54.1% for bronchoplastic lobectomy, 42.3% for regular lobectomy and 16.7% for segmental or wedge excision. In this analysis, emphasis is laid to the therapeutic validity of the different modes of surgery. Statistical data show that only when the indication of different surgical interventions are strictly adhered to and the reasonable procedures are carried out, could better results be obtained. In surgical treatment of lung cancer, it is an important principle to eradicate the tumor and its metastatic foci as thorough as possible and to conserve the respiratory function as much as possible. Regular lobectomy has now become the "standard" and first choice operation. Pneumonectomy should be reserved for the patients with absolute necessity due to the extent of the lesion, adequate cardiopulmonary function and possibility of a permanent cure. Pneumonectomy is substituted by bronchoplastic lobectomy to a certain degree, preserving more of the lung function and improving the living quality after operation and long term results. Extensive practice of this surgical modality is advised.

Adenocarcinoma↗
PubMed1985

Surgery of esophageal carcinoma.

The experience of surgical treatment in 1,874 patients with carcinoma of the esophagus seen at the Cancer Institute and Hospital of the Chinese Academy of Medical Sciences, Beijing, People's Republic of China, between 1958 and 1982, is reported. Despite the prevalence of this malignancy in this part of China, only 3% of the patients in this series had stage I disease, while 80% of the patients had either stage III or stage IV disease with extraesophageal tumor invasion and regional or distant metastases. Of the entire series there was an overall resectability rate of 83.9%, being 77.6% between 1958 and 1969 and 89.0% between 1970 and 1982. Among the 1,572 resections of the entire series, there were 66 deaths within 30 days of operation, for a resection mortality rate of 4.2%, being 4.9% between 1958 and 1969 and 3.7% between 1970 and 1982. Anastomotic leakage occurred in 67 cases of the 1,572 resections, for an incidence of 4.3%. Of the 67 cases with anastomotic leaks, 38 recovered after intensive treatment; the remaining 29 died eventually of the complication, giving a death rate of 43.3%. Pathologic studies of the 1,572 specimens showed lymph node metastasis in 46.1% of the cases. It is obvious that practically all the unresectable cases showed more extensive lymph node involvement at operation, although fixation of the tumor with severe invasion to the surrounding organs usually constituted the chief cause of unresectability. The postresection long-term survivals as calculated by the number of resections at 5, 10, and 15 years were 30.2% (390/1293), 22.4% (196/876), and 18.9% (112/594), respectively. Over one-third, or 36.8%, of the 1,874 patients in the present series were treated with a combination therapy of preoperative irradiation and surgery. The results in the group of 408 selective patients and those in the group of 83 randomized patients with midthoracic esophageal carcinomas were gratifying. In the latter group there was a resectability rate of 95.2%, a resection mortality rate of 3.8%, an incidence of intrathoracic anastomotic leakage of 0%, and a 5-year survival rate of 45.5%, as compared to 89.6%, 4.3%, 1.7%, and 25%, respectively, in the control group treated by surgery alone. From these findings it is concluded that preoperative irradiation as an adjunct can promote both the immediate and long-term results of surgery for carcinoma of the esophagus. Recent advances in the surgical treatment of carcinoma of the esophagus may change the pessimistic philosophy for this malignancy.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1985

The crystallographic study of the complex of the Lys active fragment of the mung bean trypsin inhibitor with bovine trypsin.

The Lys fragment of mung bean trypsin inhibitor can combine with bovine trypsin to form a complex at an equal molar ratio. The single crystals of the complex were obtained by using the micro-still-setting method and the X-ray diffraction extended to 1.8A resolution. Its space group is P212121 with cell dimensions a = 62.9(1)A, b = 63.4(1)A and c = 69.7 (2)A. There is one complex molecule in a crystallographic asymmetric unit.

Animals↗
PubMed1984

Multiple-hole needle for puncture biopsy. An analysis of 420 cases.

A multiple-hole needle for biopsy was designed. Use of needle diagnoses were obtained for 420 cases. Some of these were not diagnosed previously with other biopsy methods. This report describes biopsy procedure with case presentation, showing the advantage of this technique. The overall rate of successful diagnosis by biopsy method is 90.2%, and the rate of success in the thoracic cavity is 81.6%. Only 3 pneumothoraxes developed in 125 cases of thorax puncture using the multiple-hole needle.

Adult↗