Biomedical subjects

G Feng

Publications and source records attributed to G Feng.

At least 127 records · Page 7Linked to original sources

PubMed1996

[The approach of cloned method in a human retinoblastoma cell line SO-Rb50].

PURPOSE: In order to obtain the same characteristic tumor cells in genetical and biological aspect, the cloned human retinoblastoma cell line SO-Rb50 established in our department is reported in this paper. METHOD: SO-Rb50 cells were cloned in multi-well plates. RESULT: Non-rosette Rb cells were successfully cloned while rosette Rb cells failed. CONCLUSION: The result suggested that high differentiated Rb cells were difficult to be cloned.

Clone Cells↗

PubMed1996

[Assessment of the toxicity of TAH on the cell lines of SO-Rb50 and SO-Rb70].

PURPOSE: MTT assay was evaluated on cytoxicity for suspension growing cell lines of SO-Rb50 and SO-Rb70, and the toxicity of TAH (the total alkaloid of peqanum harmala L) on the above cell lines was assessed. METHODS: The relationships between cell number and optical density, between optical density and exposure time of MTT, and the stability of formazan crystal solution in MDSO were determined. And the toxicity of TAH on the cell lines of SO-Rb50 and SO-Rb70 in vitro with MTT assay was assessed. RESULTS: There was a direct proportional relationship between the amount of cell number and its optical density; The optical density increased gradully within 12 hours of the MTT incubation time; The stable time of the formazan crystal solved in DMSO was 11 hours. The IC50 values (micrograms/ml) of TAH on SO-Rb50 were 10.66, 4.82 respectively for 48 and 72 hours; and on SO-Rb70 were 6.38, 4.2 respectively for 48 and 72 hours. CONCLUSION: MTT assay can be used for suspension growing cell lines of SO-Rb50 and SO-Rb70: TAH has obvious toxicity to these two cell lines.

Alkaloids↗

PubMed1995

Cloning and functional analysis of TipE, a novel membrane protein that enhances Drosophila para sodium channel function.

Voltage-dependent sodium channels are involved in the initiation and propagation of action potentials in many excitable cells. Here we report that tipE, a gene defined by a temperature-sensitive paralytic mutation in Drosophila, encodes a novel integral membrane protein that dramatically stimulates functional expression in Xenopus oocytes of the Drosophila sodium channel alpha subunit encoded by the paralytic (para) locus. Using a heat shock promoter to control tipE+ gene expression in transgenic flies, we demonstrate that tipE+ gene expression is required during pupal development to rescue adult paralysis. In addition, we demonstrate a role for the tipE gene product in adults.

Amino Acid Sequence↗

PubMed1995

Discontinuous movements of DNA and RNA in RNA polymerase accompany formation of a paused transcription complex.

A central enigma of transcriptional regulation is how the normally efficient transcription elongation complex stops at pause and termination signals. One possibility, raised by the discovery that RNA polymerase sometimes contracts its DNA footprint, is that discontinuous movements contribute to recognizing these signals. We report that E. coli RNA polymerase responds to sequences immediately downstream and upstream from the his leader pause site by changing neither its downstream DNA contact nor its upstream RNA contact for 8 bp preceding the pause. This compressed complex isomerizes to a paused conformation by an approximately 10 bp jump of its downstream DNA contact and simultaneous extrusion of an RNA hairpin that stabilizes the paused conformation. We suggest pausing and termination could be alternative outcomes of a similar isomerization that depend on the strength of contacts to 3'-proximal RNA remaining after the jump.

Base Sequence↗

PubMed1995

Cytogenetic and molecular localization of tipE: a gene affecting sodium channels in Drosophila melanogaster.

Voltage-sensitive sodium channels play a key role in nerve cells where they are responsible for the increase in sodium permeability during the rising phase of action potentials. In Drosophila melanogaster a subset of temperature-sensitive paralytic mutations affect sodium channel function. One such mutation is temperature-induced paralysis locus E (tipE), which has been shown by electrophysiology and ligand binding studies to reduce sodium channel numbers. Three new gamma-ray-induced tipE alleles associated with either visible deletions in 64AB or a translocation breakpoint within 64B2 provide landmarks for positional cloning of tipE. Beginning with the flanking cloned gene Ras2, a 140-kb walk across the translocation breakpoint was completed. Germline transformation using a 42-kb cosmid clone and successively smaller subclones localized the tipE gene within a 7.4-kb genomic DNA segment. Although this chromosome region is rich in transcripts, only three overlapping mRNAs (5.4, 4.4, and 1.7 kb) lie completely within the smallest rescuing construct. The small sizes of the rescuing construct and transcripts suggest that tipE does not encode a standard sodium channel alpha-subunit with four homologous repeats. Sequencing these transcripts will elucidate the role of the tipE gene product in sodium channel functional regulation.

Alleles↗

PubMed1995

Cloning and characterization of a calcium channel alpha 1 subunit from Drosophila melanogaster with similarity to the rat brain type D isoform.

We report the complete sequence of a calcium channel alpha 1 subunit cDNA cloned from a Drosophila head cDNA library. This cDNA encodes a deduced protein containing 2516 amino acids with a predicted molecular weight of 276,493. The deduced protein shares many features with vertebrate homologs, including four repeat structures, each containing six transmembrane domains, a conserved ion selectivity filter region between transmembrane domains 5 and 6, and an EF hand in the carboxy tail. The Drosophila subunit has unusually long initial amino and terminal carboxy tails. The region corresponding to the last transmembrane domain (IVS6) and the adjacent cytoplasmic domain has been postulated to form a phenylalkylamine-binding site in vertebrate calcium channels. This region is conserved in the Drosophila sequence, while domains thought to be involved in dihydropyridine binding show numerous changes. The Drosophila subunit exhibits 78.3% sequence similarity to the rat brain type D calcium channel alpha 1 subunit, and so has been designated as a Drosophila melanogaster calcium channel alpha 1 type D subunit (Dmca1D). In situ hybridization shows that Dmca1D is highly expressed in the embryonic nervous system. Northern analysis shows that Dmca1D cDNA hybridizes to three size classes of mRNA (9.5, 10.2, and 12.5 kb) in heads, but only two classes (9.5 and 12.5 kb) in bodies and legs. PCR analysis suggests that the Dmca1D message undergoes alternative splicing with more heterogeneity appearing in head and embryonic extracts than in bodies and legs.

Amines↗

PubMed1995

Radiologic manifestations of osteopetrosis.

The clinical radiologic manifestations of 8 patients with osteopetrosis (4 males and 4 females) are analyzed. Six of the cases are benign. The pathologic basis for the radiologic manifestations is discussed, and a classification is suggested. "Broom-like" metaphyses, metaphyses containing three or four dense layers of bone, and ossification of soft tissues around joints were found and differential diagnosis was made.

Adolescent↗

PubMed1995

[Experimental study of survival mechanism of skin flap with subdermal vascular rete].

AIM: To determine the blood supply style and survival mechanism of skin flap with subdermal vascular rete. MATERIAL AND METHODS: The skin flap on trunk of piglets were taken as experimental pattern. The survival length of skin flap was examined and the nuclear element distribution in the skin flap was determined by ECT. RESULTS AND CONCLUSION: This study demonstrated that the distal portion of super-long flap with subdermal vascular rete fail to getting blood supply from its pedicle. This kind of flap is actually a combination of flap and free graft with subdermal vascular rete. This kind of super-long and super-wide flap is actually not a flap but a free skin graft. The survival of super-long and super-wide flaps with subdermal vascular rete rely on the blood supply from the wounds and their edges partially or completely. Their survival style is actually free grafting.

Animals↗

PubMed1995

Single-step purifications of His6-MutH, His6-MutL and His6-MutS repair proteins of escherichia coli K-12.

The MutS, MutH and MutL proteins mediate methyl-directed-mismatch (MDM) repair in Escherichia coli and Salmonella typhimurium. These proteins have been developed into powerful tools for screening genomes for polymorphisms and detecting and localizing mutations. In an ongoing study of the regulation of MDM repair, we developed one-step schemes to purify the E. coli MutS, MutH and MutL proteins fused to a polyhistidine (His6) affinity tag. The E. coli K-12 mutS+, mutH+ and mutL+ genes were cloned from the Clarke-Carbon plasmid or Kohara-phage library into expression vector pET-15b, which allows fusion to the His6 affinity tag. Each of the resulting recombinant plasmids complemented the corresponding mutHLS mutation in the Cupples-Miller CC106 mutator tester strain, indicating that the His6-MutHLS fusion proteins were individually functional in vivo. The His6-MutHLS proteins were separately purified by variations of batch binding to Ni(2+)-chelation affinity resin. The yield of purified His6-MutHLS proteins from these procedures was 0.4-0.6 mg from 40 mL of induced culture. The binding properties of one-step-purified His6-MutS protein were characterized further. His6-MutS exhibited the same mismatch-binding activity and specificity as native MutS in side-by-side bandshift assays. These constructs and purification methods should be useful to laboratories wishing to apply or develop MutS-mismatch mapping and to other applications or studies of the E. coli MutHLS repair proteins.

Adenosine Triphosphatases↗

PubMed1995

[777 cases of the primary conjunctival neoplasms].

PURPOSE: To make a histopathologic analysis of the primary conjuctival neoplasms. METHODS: The light microscopic findings of 777 cases of the primary conjunctival neoplasms were reported. The histochemical and immunohistochemical technologies were used. RESULTS: In a series of 777 primary conjunctival neoplasms, 669(86.1%) were benign and 108 (13.9%) were malignant. The pigmented nevi (247 cases) were the most common in the benign tumors, while the squamous cell carcinoma (58 cases) were the most common tumors among the malignant ones. CONCLUSIONS: The biological characteristics of the benign and malignant tumors can be referred as differential diagnosis. There is the spindle cell and mucoepidermoid type in the squamous cell carcinoma of the conjunctiva. Postoperative recurrent factor of the malignant melanoma of the conjunctiva is numerous.

Carcinoma, Squamous Cell↗

PubMed1995

[An analysis of causes of recurrence, matastasis and death of retinoblastoma].

PURPOSE: To discuss the relationship between diagnosis, treatment and recurrence, metastasis, death of Rb patients. METHODS: To analyse the data of 46 Rb patients treated in our center from July 1967 to May 1992, who had either recurrence, metastasis or died. RESULTS: The main factors affecting Rb prognosis are: 1 early or late diagnosis: 2 the mortality rate increased with the degree of optic nerve involvement: 3 involvement of orbit, cranial cavity and choroid by Rb; 4 clinically, secondary glaucoma often accompanied by optic nerve involvement. CONCLUSIONS: Delay in diagnosis and treatment will result in Rb recurrence, metastasis and death. Early diagnosis and treatment is very important for survival rate.

Child↗

PubMed1994

Termination-altering amino acid substitutions in the beta' subunit of Escherichia coli RNA polymerase identify regions involved in RNA chain elongation.

To identify regions of the largest subunit of RNA polymerase that are potentially involved in transcript elongation and termination, we have characterized amino acid substitutions in the beta' subunit of Escherichia coli RNA polymerase that alter expression of reporter genes preceded by terminators in vivo. Termination-altering substitutions occurred in discrete segments of beta', designated 2, 3a, 3b, 4a, 4b, 4c, and 5, many of which are highly conserved in eukaryotic homologs of beta'. Region 2 substitutions (residues 311-386) are tightly clustered around a short sequence that is similar to a portion of the DNA-binding cleft in E. coli DNA polymerase I. Region 3b (residues 718-798) corresponds to the segment of the largest subunit of RNA polymerase II in which amanitin-resistance substitutions occur. Region 4a substitutions (residues 933-936) occur in a segment thought to contact the transcript 3' end. Region 5 substitutions (residues 1308-1356) are tightly clustered in conserved region H near the carboxyl terminus of beta'. A representative set of mutant RNA polymerases were purified and revealed unexpected variation in percent termination at six different rho-independent terminators. Based on the location and properties of these substitutions, we suggest a hypothesis for the relationship of subunits in the transcription complex.

Amino Acid Sequence↗

PubMed1994

Crystallization of GreA, a transcript cleavage factor from Escherichia coli.

GreA is a 17.6 kDa protein from Escherichia coli that induces cleavage of the nascent transcript in the elongating complex of RNA polymerase, followed by release of the 3'-terminal fragment. Crystals of GreA have been obtained from polyethylene glycol 4000, 2-propanol and sodium citrate, pH 5.6 and have been propagated by a novel seeding procedure. The crystals diffract beyond 2 A resolution and belong to the orthorhombic space group P2(1)2(1)2(1), with cell dimensions a = 101.7 A, b = 42.22 A, c = 40.05 A and with one molecule in the asymmetric unit.

Bacterial Proteins↗

PubMed1994

GreA-induced transcript cleavage is accompanied by reverse translocation to a different transcription complex conformation.

GreA- and GreB-induced transcript cleavage drives reverse translocation of Escherichia coli RNA polymerase on a DNA template in the absence of NTPs (Feng, G.-H., Lee, D. N., Wang, D., Chan, C. L., and Landick, R. (1994) J. Biol. Chem. 269, 22282-22294, accompanying report). During transcript elongation, the sizes of the DNA footprint and the single-stranded transcription bubble vary markedly among transcription complexes halted at different template positions. To test whether transcription complex intermediates formed during transcript cleavage-induced reverse translocation also display heterogeneous conformations at different template positions, we examined the structures of two different transcription complexes before and after GreA treatment. Transcription complexes halted at position +16 after initiation at the T7 A1 promoter or paused at the trpL pause site exhibited strong blocks to transcript cleavage after removal of 6 to 10 nucleotides. In both cases, the down-stream contact between RNA polymerase and DNA moved little during transcript cleavage, thereby increasing its distance from the active site, whereas the upstream DNA contact and the borders of the transcription bubble moved in approximate register with the transcript 3'-end. The backward movements of halted E. coli RNA polymerase are similar to a recently postulated model for discontinuous translocation during transcription, but differ from those reported for arrested RNA polymerase II transcription complexes.

Bacterial Proteins↗

PubMed1994

The mutL repair gene of Escherichia coli K-12 forms a superoperon with a gene encoding a new cell-wall amidase.

We report a molecular genetic analysis of the region immediately upstream from the Escherichia coli mutL DNA repair gene at 94.8 min. An open reading frame ending 9 bp upstream from the start of mutL corresponds to a 48 kDa polypeptide detected previously in minicells. The predicted amino acid sequence of this 48 kDa polypeptide shows homology to the major N-acetylmuramoyl-L-alanine amidase autolysin of Bacillus subtilis, a known amidase of Bacillus licheniformis, and the product of a Salmonella typhimurium gene that maps near 50 min. Insertions in this upstream gene, which we named amiB, or in mutL did not affect cell shape or viability; however, overexpression of the AmiB polypeptide caused cell lysis, hypersensitivity to osmotic shock and treatment with water, and temporary autolysis by low levels of antibiotics, which are all consistent with AmiB acting as a cell-wall hydrolase. Analysis of chromosomal transcription demonstrated that amiB forms a complex operon with mutL and two additional upstream genes. mutL transcripts also originated from an internal promoter, designated PmutL, located in amiB 312 bp upstream from the translational start of mutL. Together, these results suggest that E. coli contains a second amidase possibly involved in cell-wall hydrolysis, septation, or recycling, and that transcription of this amidase is directly linked to a gene central for DNA repair.

Adenosine Triphosphatases↗

PubMed1994

[Clinicopathological analysis of rhabdomyosarcoma of the ocular adenexa].

12 cases including 11 males and 1 female of rhabdomyosarcoma of ocular adenexa were analysed. The average age of the patients was 4.2 years. 9 cases of lesion were located in the orbit, 2 in the eyelid and 1 in conjunctiva. Pathologically 8 cases were embryonal forms, 2 alveolar, 2 polymorphic. Immunohistochemical studies were performed in 8 cases, which showed desmin positive. Myoglobin presented strong or weak positive in 5 cases, suspicious positive in 3 cases. The clinical manifestation, prognosis and treatment were briefly discussed.

Child↗

PubMed1994

[Experimental study and clinical application of end-to-side (transverse incision) anastomosis between small arteries].

The results of end to side anastomoses with longitudinal or transverse incision on the transverse limb were investigated. The anastomosis of the superficial epigastric artery to the femoral artery in rabbits served as the experimental model. The results demonstrated that the microartery end to side anastomosis with transverse arteriotomy is a more preferable anastomosis style with higher patency, easier arteriotomy and suturing, and it effectively prevents anastomotic stoma spasm or stenosis, and in accord with vascular physiological function. It is worthy to be recommended. The clinical successful cases are also reported.

Abdominal Muscles↗

PubMed1993

The natural history of dry type of age-related macular degeneration.

To study the natural history of dry type of age-related macular degeneration (AMD) and search for a sensitive method for detecting the development of the disease, the fundus fluorescein angiography, visual acuity, electroretinogram and FM 100-hue test were used to examine 75 eyes, 147 eyes, 73 eyes, and 94 eyes respectively. These examinations were taken at least twice during the follow-up periods. The average age was 63.2 years (50-80 years). The average follow-up was 29.8 months with a range of 3-74 months. It was shown tht there were not any statistically significant difference in the macular lesions and electroretinogram between the initial examinations and after follow-up (P > 0.05). 91.14% of the eyes maintained good visual acuity during the follow-up. Subretinal neovascularization developed only in one of the eyes. The total error score of FM 100-hue test had a statistically significant difference between the initial test and the test taken two years afterwards (P < 0.01). It was suggested that most of the dry type of AMD had a favorable prognosis and that color visual test was a sensitive method for monitoring the development of dry type of AMD.

Age Factors↗