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Biomedical subjects

G Feng

Publications and source records attributed to G Feng.

137 records · Page 8Linked to original sources
PubMed1993

Dynamic investigation on chromosome aberration of a human retinoblastoma cell line So-Rb50.

G-banding and karyotype analyses of cells in seventeen passages of SO-Rb50 during a long period of culture for about four years were performed. Three chromosome markers 13q14-, 1p36+ and 12p13+ were found. Cells possessed 13q14- reduced to zero after the 200th passage while 1p+ and 12p+ cells increased to 100% after 30 and 200 passages respectively. Abnormal chromosomes, ring chromosomes, chromosome radiuses and double minutes were also observed. These chromosomal changes were more often seen before the 200th passage. The significance of these changes are discussed.

Chromosome Aberrations↗
PubMed1993

[Pathologic, electron microscopic and experimental examination of band keratopathy].

One hundred and thirteen cases previously diagnosed as band keratopathy were reexamined by light microscopy and histochemistry, 10 cases of which were studied by TEM and 2 cases were studied by SEM. We find that the calcium deposition initially occur as fine calcific particles within the cytoplasm of epithelic cells and in the basal membrane and bowman's layer, which aggregated to form calcific spherules and large calcific masses extracellularly. When 3 normal corneal tissues were frozen and cultured, the calcium deposition occur in the superficial layer of bowman's membrane and in the stromal lamellae, Authors suggest that the degeneration and calcific abnormal metabolism of the cell caused by various factors is the main pathogenesis that leads to the calcific deposit. The evaporation and constructive destruction of the corneal surface in the interpiperbral area inhibits the formation of the lacrimal membrane and results in deposition of calcium salts in the superficial tissue of exposed cornea in a band configuration. The combination of glycosaminoglycan with calcium salts is the dynamics of aggregation of the fine calcific particles to form the calcific spherules and calcific masses.

Calcium↗
PubMed1993

Inhibition of brain protein kinase C subtypes by lead.

Protein kinase C (PKC) is an important enzyme in mediating cellular signal transduction and neuronal plasticity. Extremely low concentrations (picomolar range) of Pb++ have been reported to activate partially purified PKC from rat brain (Markovac and Goldstein, 1988). However, the lead activation of PKC at such low concentrations is still a matter of discussion (Simons, 1989). To clarify this point, we have examined the lead effect on highly purified PKC subtypes. Pb++ was found to be a potent inhibitor for all three PKC subtypes (types I, II and III) with IC50 of 2 to 10 microM. Characterization of this lead inhibition of PKC suggests that 1) the inhibition is not due to the competition with Ca++, 2) the site of action of lead is on the catalytic domain of PKC, 3) the inhibition is not dependent on the mode of activation (phosphatidylserine/diacylglycerol vs. cis-unsaturated fatty acid) and 4) the inhibition is totally reversible.

Animals↗
PubMed1991

[Choroidal malignant melanoma (clinical and pathologic studies of 42 cases)].

Clinical and pathologic studies of 42 cases of choroidal malignant melanoma are reported. We discussed: (1) The diagnosis of early stage cases and later cases with complication. (2) The prognosis is related to the size of tumor, the skill level of surgery, and whether tumor cell invades the superficial sclera of venous duct.

Adolescent↗
PubMed1991

[Glycosaminoglycans associate with corneal transparency].

Keratoplasty specimens form 12 patients with macular corneal dystrophy, 1 patient with systemic glycosaminoglycan stored disease and 12 cases of normal cornea were studied by electron-histochemistry. The results showed that the normal cornea contains chondroitin sulfate in the basement membrane and bowman's membrane, Keratan sulfate and chondroitin sulfate between the collagen fibrils of strome, heparan sulfate on the cell membranes of various cells, and hyaluronic acid on the surface of endothelial cell. The chondroitin sulfate of the stroma of macular corneal dystrophy increases, but the keratan sulfate is absent. The keratocytes and endothelial cells of macular corneal dystrophy synthesize fibrillogranular material and abnormal glycosaminoglycan. The heparan sulfate is stored in the cytoplasm of corneal epithelial cell and keratocyte of systemic glycosaminoglycan stored disease and absent on the membrane of involved cells. The authors suggest that glycosaminoglycan play important role in maintaining corneal transparency and the changes of distribution, character and quantity of glycosaminoglycan in the cornea cause corneal opaqueness.

Cornea↗
PubMed1990

[Early and late results of PTA in relation to the patient's age].

506 cases of percutaneous transluminal angioplasty performed between 1983 and 1988 in the iliac, femoropopliteal and crural segments were analyzed with special consideration of the patients' age. The early results were significantly worse only in the age group over 70. The late results were evaluated by the life table method. Relapses within the first 6 months occurred in 13.8% of the patients over 60 and in 8.2% of the younger age group (under 60). After 12 months, however, no significant difference was observed between the two age groups. The rate of complications (overall value 7.9%) was twice as high in the geriatric age group than among the younger patients. Type and extent of the occlusion, clinical stage and run-off conditions determine the early and late results.

Age Factors↗
PubMed1990

[Selection of optimum technological conditions for vinegar-processing of fresh rhizoma Corydalis].

The Total alkaloid contents of chloroform extracts and aqueous decoctions of different vinegar-processed samples of fresh Rhizoma Corydalis were determined and compared using orthogonal experimental design. Two optimum schemes suggested by the results are 1. If aqueous decoction is wanted, the fresh tuber Corydalis should be scalded by hot edible vinegar till the liquid has permeated to its center; 2. If total alkaloid extract is required for making Chinese traditional patent medicine, the fresh Rhizoma should be slightly scalded with edible vinegar which has been diluted with an equal volume of water.

Alkaloids↗
PubMed1989

[Results of percutaneous transluminal angioplasty].

Percutaneous transluminal angioplasty (PTA) can be subdivided into three epochs: 1. from its inception by Dotter and Judkins up to the first coronary artery stenosis dilatation with the Grüntzig balloon catheter system; 2. from the introduction of coronary stenosis dilatation by Grüntzig up to its unequivocal acceptance; 3. the period of influence of low-risk coronary dilatation on peripheral angioplasty and the search for techniques to compliment or obviate the need for balloon dilatation. The Grüntzig double-lumen balloon catheter system contributed to the lower rate of complications and higher success rate. The clinical acceptance appeared greater for the coronary arteries since, in contrast to the peripheral vascular system, the indication for treatment is established by the physician performing the dilatation. PTA implies percutaneous puncture of a vessel with Seldinger technique and introduction of devices such as guidewires, Dotter or Grüntzig catheters among others, catheters with fiberglass for laser conduction and instruments for fractionating, drilling and cutting. The goal of PTA is to completely or partially eliminate, without surgery, intraluminal vascular narrowing in the presence of peripheral arterial disease in stage II, III or IV. Prerequisite to the use of PTA are: 1. adequate fluoroscopic and angiographic facilities; 2. adequate instrumentation; 3. experience with at least 200 procedures; 4. knowledge of the pathophysiology and adjunctive treatment; 5. knowledge of the treatment of complications; 6. cooperation with a vascular surgery service. A number of factors may influence the results of treatment. Adjunctive medical treatment: the use of platelet aggregation inhibitors and heparin influences the rate of early rethrombosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMedDate not supplied

Development of the neuromuscular junction: genetic analysis in mice.

Formation of the skeletal neuromuscular junction is a multi-step process that requires communication between the nerve and muscle. Studies in many laboratories have led to identification of factors that seem likely to mediate these interactions. 'Knock-out' mice have now been generated with mutations in several genes that encode candidate transsynaptic messengers and components of their effector mechanisms. Using these mice, it is possible to test hypotheses about the control of synaptogenesis. Here, we review our studies on neuromuscular development in mutant mice lacking agrin alpha CGRP, rapsyn, MuSK, dystrophin, dystrobrevin, utrophin, laminin alpha 5, laminin beta 2, collagen alpha 3 (IV), the acetylcholine receptor epsilon subunit, the collagenous tail of acetylcholinesterase, fibroblast growth factor-5, the neural cell adhesion molecule, and tenascin-C.

Agrin↗
PubMedDate not supplied

Cystic acoustic schwannomas: MR characteristics.

PURPOSE: To evaluate the spectrum of MR characteristics of cystic acoustic schwannoma and to investigate its incidence. METHODS: We retrospectively reviewed the MR findings and clinical records of 16 patients with cystic acoustic schwannomas. In addition, the MR examinations of 411 consecutive patients referred for clinical suspicion of acoustic schwannomas were reviewed retrospectively to assess the incidence of acoustic schwannomas with cystic lesions arising from the internal auditory canal. RESULTS: Of the 16 acoustic schwannomas with MR evidence of intramural cysts, 11 tumors had single small cysts, and five had multiple intramural cysts of variable size. Intramural cysts in 11 of the 16 tumors exhibited higher signal intensity than that of cerebrospinal fluid; the remainder were isointense to cerebrospinal fluid on both T1- and T2-weighted images. All intramural cysts showed circumferential enhancement after contrast administration. Nine of the 16 cystic acoustic schwannomas also had MR evidence of extramural/arachnoid cysts. Six of the extramural/arachnoid cysts had epicenters away from the dural interface, and the other three cysts were broadly based against the dura. The incidence of cystic acoustic schwannomas was 11.3% and association with extramural/arachnoid cysts 7.5%. CONCLUSION: Our series suggests that cystic changes in acoustic schwannomas and the association with extramural/arachnoid cysts are not as rare as previously reported by other diagnostic methods. The high signal intensity of intramural cysts is probably related to necrotic material, blood, or colloid-rich fluid. The difference in the MR characteristics of extramural/arachnoid cysts associated with acoustic schwannomas and those of typical arachnoid cysts not associated with neoplasia may be related to higher protein and/or colloid contents secreted by the tumor. Most extramural/arachnoid cysts had epicenters between the tumor and brain, suggesting that the most likely mechanism of formation is peritumoral adhesions. It creates a pseudo-duplication caused by the trapping of fluid between the leptomeninges and the mass, resulting in an acquired type of arachnoid cyst.

Adult↗