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Biomedical subjects

W C Liu

Publications and source records attributed to W C Liu.

72 records · Page 4Linked to original sources
PubMed1981

Automated synthesis of gene fragments.

The DNA/RNA Synthesizer provides a complete and automated procedure for the synthesis of DNA sequences. Each base unit is added in a 30-minute cycle, permitting a tetradecamer to be constructed in 6 1/2 hours. The complete procedure is described, including a practical procedure for isolation and purification of the desired DNA sequence.

Automation↗
PubMed1981

Tissue and species-specific effects of small molecular weight nuclear RNA's on transcription in isolated mammalian nuclei.

Small molecular weight nuclear RNA's (SnRNA's) purified from the 0.35 M NaCl extract of chromatin from human and monkey tissues have been found to stimulate transcription of chromatin in isolated nuclei in a tissue- and species-specific manner. While SnRNA from normal human cells (WI38 fibroblasts and placenta) stimulates homologous transcription to some extent, it has a greater activity on transcription of heterologous tissue of the same species and no activity on heterologous tissue of a different species (monkey kidney cells). Likewise SnRNA from monkey cells stimulates transcription of homologous chromatin but has no effect on human cells. Fractionation of the RNA's in polyacrylamide gradient slab gels revealed that in all cases the active RNA was 160-175 nucleotides in length. Our results are compatible with the hypothesis that the active RNA's are involved in the determination and maintenance of tissue differentiation by recognizing promoter or regulator sequences in the DNA and act at the level of the nucleosome to induce tissue-specific genes.

Animals↗
PubMed1981

Separation and biologic activities of individual components of S15-1, a streptothricin class antibiotic.

A method is described for isolation of gram quantities of the components of the streptothricin complex S15-1 utilizing CM Sephadex column chromatography eluted with 10% acetic acid as an eluant followed by gradient elution with 10% acetic acid containing 0.02 N approximately 0.03 N HCI. Streptothricins F and E, as well as an unidentified component C1, have been isolated and their comparative biological activities determined. Streptothricins F and E were comparable in taeniacidal activity in mice infected with Hymenolepis nana ia feeding either one at 0.05% in the diet removed 92 approximately 100% of the adult tapeworms. The unidentified component C1 was inactive at the levels tested. In contrast, component C1 was the most active in antimicrobial activity against Bacillus subtilis and in inhibiting the urease activity of proteus mirabilis. In the former test, the ratios of activity were; 1:7:30 for F:E:C1 and in the latter; 1:2:4 for F:E:C1.

Animals↗
PubMed1981

Siderochelin, a new ferrous-ion chelating agent produced by Nocardia.

A new ferrous-ion chelating agent, siderochelin, was isolated from fermentation broths of Nocardia sp. SC 11,340. Siderochelin was produced by conventional submerged culture and purified by solvent extraction and recrystallization. The antibiotic was crystallized from acetonitrile as a mixture of diastereoisomers. The molecular formula of siderochelin was determined as C11H13N3O3 on the basis of elemental analysis and mass spectrometry, and the structure was elucidated by X-ray crystallography. The compound shows a broad spectrum of antimicrobial activity, being active against bacteria, fungi and protozoa.

Anti-Bacterial Agents↗
PubMed1980

Stimulation of transcription of chromatin by specific small nuclear RNAs.

Small molecular weight nuclear RNAs (SnRNA) purified from the chromatin of SV40-transformed W138 human fibroblasts have been found to stimulate transcription of chromatin in homologous isolated nuclei as well as in nuclei of untransformed human and monkey cells. Stimulation in normal cell nuclei involves an increase in both initiation sites and rate of elongation of RNA chains. Fractionation of the SnRNA in polyacrylamide gradient slab gels revealed that the "active" RNA was 160-175 nucleotides in length.

Cell Line↗
PubMed1980

Izumenolide-a novel beta-lactamase inhibitor produced by Micromonospora. I. Detection, isolation and characterization.

Micromonospora chalcea subsp. izumensis produces a novel beta-lactamase inhibitor izumenolide (EM4615). Isolation of izumenolide was performed by extraction into butanol under acidic conditions and then back extraction into water at neutrality. The compound was precipitated from the aqueous phase by the addition of calcium or barium salts. Further purification was achieved by distribution in BuOH - 1 N NaOH. Izumenolide is a macrolide containing sulfate ester groups.

Chemical Phenomena↗
PubMed1978

Ionomycin, a new polyether antibiotic.

Ionomycin, a new polyether antibiotic with a high affinity for calcium ions, is obtained in pure form from fermentation broths of Streptomyces conglobatus sp. nov. Trejo by solvent extraction. It is unique amongst known polyether antibiotics in that it has a UV absorption maximum at 300 nm. thereby distinguishing it from other antibiotics of its class. The Ca salt has the molecular formula C41H70O9Ca. Ionomycin is a narrow spectrum antibiotic being active against Gram-positive bacteria.

Animals↗
PubMedDate not supplied

Water-suppression MRI: role in the evaluation of osseous lesions.

The efficacy of chemical shift based water-suppression MRI in the evaluation of bone marrow lesions has not been previously reported. T1-weighted images without and with water suppression were compared in five patients with 16 lesions. There was a significant improvement in the contrast-to-noise ratio (from 4.32 to 5.95, P < 0.01) and contrast ratio (from 1.71 to 5.69, P < 0.004) with water suppression. Water suppression may be useful clinically by increasing the conspicuity of bone marrow lesions.

Adult↗
PubMedDate not supplied

Intraoperative functional MRI using a real-time neurosurgical navigation system.

A 42-year-old-man had focal left hand motor seizures. MR studies demonstrated a right posterior frontal brain tumor. Functional MRI was performed, localizing the motor cortex posterior to the lesion. The functional images were integrated with a neurosurgical navigation computer. A real-time intraoperative display of the anatomic and functional images was produced, registered to a neurosurgical probe. Excellent correlation was demonstrated between the functional maps and invasive electrophysiologic mapping performed at the time of craniotomy.

Adult↗
PubMedDate not supplied

Tuberculous aneurysm of the abdominal aorta: endovascular repair using stent grafts in two cases.

Tuberculous aneurysm of the aorta is exceedingly rare. To date, the standard therapy for mycotic aneurysm of the abdominal aorta has been surgery involving in-situ graft placement or extra-anatomic bypass surgery followed by effective anti-tuberculous medication. Only recently has the use of a stent graft in the treatment of tuberculous aortic aneurysm been described in the literature. We report two cases in which a tuberculous aneurysm of the abdominal aorta was successfully repaired using endovascular stent grafts. One case involved is a 42-year-old woman with a large suprarenal abdominal aortic aneurysm and a right psoas abscess, and the other, a 41-year-old man in whom an abdominal aortic aneurysm ruptured during surgical drainage of a psoas abscess.

Adult↗
PubMedDate not supplied

Indicine-N-oxide: the antitumor principle of Heliotropium indicum.

Extracts of Heliotropium indicum Linn. (Boraginaceae) showed significant activity in several experimental tumor systems. The active principle is isolated and shown to be the N-oxide of the alkaloid, indicine, previously isolated from this plant. Supporting structural data and anti-tumor data are provided.

Alkaloids↗