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S Liang

Publications and source records attributed to S Liang.

At least 91 records · Page 5Linked to original sources
PubMed1997

[Determination of alkylmercuric compounds in human body fluids by gas chromatography--atomic absorption spectrophotometry].

In order to detect trace of alkylmercuric compounds in human body fluids, a highly sensitive, selective and rapid method, based on the coupling of gas chromatography with atomic absorption spectrophotometry, has been developed. The transfer-tube was made up of Teflon, with stainless steel tubes in the two sides. The atomization of alkylmercuric compounds was performed in quartz tube. The quantitative determination of alkylmercuric compounds in urine and blood samples collected from the workers exposing to metallic mercury, has been extensively carried out in this work. The optimal Westoo program was used to enrich methylmercuric chloride in samples, Extracts of methylmercuric chloride in benzene were determined by GC-AAS, with a total recovery of more than 90%. Dimethylmercury in samples was extracted once by xylene. Then the extracts were determined, with a total recovery of 65%-70%. The detectable limit for mercury was 0.01ng. The methylation of mercury was confirmed in our experiment. This method can be used for the determination of other metallic compounds.

Alkylmercury Compounds↗
PubMed1997

Regulation of tRNA suppressor activity by an intron-encoded polyadenylation signal.

A 26-nt sequence from the 3' UTR of the yeast GAL7 mRNA directs accurate and efficient cleavage and polyadenylation to form the 3' end of the GAL7 mRNA in vivo and in vitro. Here we asked whether this polyadenylation signal can function within the context of a tRNA. Insertion of the GAL7 signal into the intron of the dominant SUP4 nonsense suppressor allowed us to judge the effect of the insert on SUP4 function by observation of nonsense suppression efficiency in vivo. The GAL7 signal impairs the function of SUP4 in an orientation-dependent manner in vivo, consistent with its ability to specify cleavage and polyadenylation in this context in vitro. Mutation of a UA repeat within the GAL7 signal restores SUP4 function partially, consistent with the role of this repeat as an efficiency element in polyadenylation. Mutations that impair the mRNA 3' end-processing factors Rna14p and Rna15p restore suppressor function partially. Northern blot analysis, PCR amplification, and DNA sequence analysis show that the GAL7 signal directs polyadenylation within the body of pre-SUP4 and within the terminator, suggesting that polyadenylation inhibits 5' and 3' end processing, as well as removal of the pre-tRNA intron. These findings indicate that the GAL7 polyadenylation signal is capable of targeting a pre-tRNA to the mRNA processing pathway.

Base Sequence↗
PubMed1997

[Comparison of stature growth curves in children and adolescents].

Growth charts of height in Chinese children and adolescents (excluding Taiwan and Hong Kong) in the 1980s and 1990s were fitted to JPA2 model to study their growth and developmental characteristics and their future trend and to compare them with the criteria for growth in the developed countries and areas. Results showed that fitted growth curves were comparable. The difference in body height of children in cities during puberty period was the most significant during the 1980s. Body height of boys and girls aged over seven to maturity period in Beijing during the 1990s was higher than that in Hong Kong and Japan, and reached basically the criteria set by the National Center for Health Statistics (NCHS), United States, but body height of adults was still three to four centimeters lower than that in criteria set by NCHS. Body height in adolescents in Beijing was kept in stable as compared with that in the 1980s.

Adolescent↗
PubMed1996

Heat shock disassembles the nucleolus and inhibits nuclear protein import and poly(A)+ RNA export.

Heat shock causes major positive and negative changes in gene expression, drastically alters the appearance of the nucleolus and inhibits rRNA synthesis. We here show that it causes many yeast nucleolar proteins, including the fibrillarin homolog Nop1p, to relocate to the cytoplasm. Relocation depends on several proteins implicated in mRNA transport (Mtrps) and is reversible. Two observations indicate, surprisingly, that disassembly results from a reduction in Ssa protein (Hsp70) levels: (i) selective depletion of Ssa1p leads to disassembly of the nucleolus; (ii) preincubation at 37 degrees C protects the nucleolus against disassembly by heat shock, unless expression of Ssa proteins is specifically inhibited. We observed that heat shock or reduction of Ssa1p levels inhibits protein import into the nucleus and therefore we propose that inhibition of import leads to disassembly of the nucleolus. These observations provide a simple explanation of the effects of heat shock on the anatomy of the nucleolus and rRNA transcription. They also extend understanding of the path of nuclear export. Since a number of nucleoplasmic proteins also relocate upon heat shock, these observations can provide a general mechanism for regulation of gene expression. Relocation of the hnRNP-like protein Mtr13p (= Npl3p, Nop3p), explains the heat shock sensitivity of export of average poly(A)+ RNA. Strikingly, Hsp mRNA export appears not to be affected.

Cell Nucleolus↗
PubMed1996

A DEAD-box-family protein is required for nucleocytoplasmic transport of yeast mRNA.

An enormous variety of primary and secondary mRNA structures are compatible with export from the nucleus to the cytoplasm. Therefore, there seems to be a mechanism for RNA export which is independent of sequence recognition. There nevertheless is likely to be some relatively uniform mechanism which allows transcripts to be packaged as ribonucleoprotein particles, to gain access to the periphery of the nucleus and ultimately to translocate across nuclear pores. To study these events, we and others have generated temperature-sensitive recessive mRNA transport (mtr) mutants of Saccharomyces cerevisiae which accumulate poly(A)+ RNA in the nucleus at 37 degrees C. Several of the corresponding genes have been cloned. Upon depletion of one of these proteins, Mtr4p, conspicuous amounts of nuclear poly(A)+ RNA accumulate in association with the nucleolus. Corresponding dense material is also seen by electron microscopy. MTR4 is essential for growth and encodes a novel nuclear protein with a size of approximately 120 kDa. Mtr4p shares characteristic motifs with DEAD-box RNA helicases and associates with RNA. It therefore may well affect RNA conformation. It shows extensive homology to a human predicted gene product and the yeast antiviral protein Ski2p. Critical residues of Mtr4p, including the mtr4-1 point mutation, have been identified. Mtr4p may serve as a chaperone which translocates or normalizes the structure of mRNAs in preparation for export.

Amino Acid Sequence↗
PubMed1996

Stretch-induced injury of cultured neuronal, glial, and endothelial cells. Effect of polyethylene glycol-conjugated superoxide dismutase.

BACKGROUND AND PURPOSE: There is abundant evidence that after in vivo traumatic brain injury, oxygen radicals contribute to changes in cerebrovascular structure and function; however, the cellular source of these oxygen radicals is not clear. The purpose of these experiments was to use a newly developed in vitro tissue culture model to elucidate the effect of strain, or stretch, on neuronal, glial, and endothelial cells and to determine the effect of the free radical scavenger polyethylene glycol-conjugated superoxide dismutase (PEG-SOD; pegorgotein, Dismutec) on the response of each cell type to trauma. METHODS: Rat brain astrocytes, neuronal plus glial cells, and aortic endothelial cells were grown in cell culture wells with 2-mm-thick silastic membrane bottoms. A controllable, 50-millisecond pressure pulse was used to transiently deform the silastic membrane and thus stretch the cells. Injury was assessed by quantifying the number of cells that took up the normally cell-impermeable dye propidium iodide. Some cultures were pretreated with 100 to 300 U/mL PEG-SOD. RESULTS: Increasing degrees of deformation produced increased cell injury in astrocytes, neuronal plus glial cultures, and aortic endothelial cells. By 24 hours after injury, all cultures showed evidence of repair as demonstrated by cells regaining their capacity to exclude propidium iodide. Compared with astrocytes or neuronal plus glial cultures, endothelial cells were much more resistant to stretch-induced injury and more quickly regained their capacity to exclude propidium iodide. PEG-SOD had no effect on the neuronal or glial response to injury but reduced immediate posttraumatic endothelial cell dye uptake by 51%. CONCLUSIONS: These studies further document the utility of the model for studying cell injury and repair and further support the vascular endothelial cell as a site of free radical generation and radical-mediated injury. On the assumption that, like aortic endothelial cells, stretch-injured cerebral endothelial cells also produce oxygen radicals, our results further suggest the endothelial cell as a site of therapeutic action of free radical scavengers after traumatic brain injury.

Animals↗
PubMed1996

Immunohistochemical study of epithelioid hemangioendothelioma in the leg: a case report.

Epithelioid hemangioendothelioma is a relatively rare lesion. Although its histogenesis has been well described, its immunohistochemical characteristics remain controversial. A case of epithelioid hemangioendothelioma of the soft tissue of the right leg in a 67-year-old Chinese woman is reported. Histologic findings of intracytoplasmic lumina in the tumor cells and positive immunostaining for vimentin, factor VIII-related antigen. CD34 and Ulex europaeus agglutinin 1 (UEA-1) were obtained, demonstrating differentiation of the tumor cells to endothelial cells, although staining for antibodies to cytokeratins AE1/AE3 and CAM5.2 was weak. CD34 as well as Factor VIII-related antigen is a useful marker of endothelial differentiation in this tumor. A review of the literature is also presented.

Aged↗
PubMed1996

[Percutanous trans-catheter intervention for the diagnosis and treatment of malignant pericardial effusion, with a report of 50 cases].

Diagnosis and treatment of malignant pericardial effusion are difficult in clinical practice. This paper reports the feasibility and reliability of percutanous trans-catheter intervention for the diagnosis and treatment of malignant pericardial effusion. Under echocardiagraphic guidence, pericardial puncture was performed and a heamostasis sheath was placed in situ by Seldinger technique. Through the sheath multiple biopsies of the pericardium were taken for pathological examination. A pigtail catheter was inserted to drain off the effusion. According to pathological report suitable anti-cancer drugs were instilled into the pericardial cavity through indwelling catheter for 3-5 days. The catheter was withdrawn when fluid did not re-accumulate. Diagnosis was made in over 96.0% of the cases. Upon follow-up for 3-6 months, complete remission was seen in 96.0% of the treated patients. No significant complication was found in all patients. Percutaneous trans-catheter intervention is a useful approach for the diagnosis and treatment of malignant pericardial effusion.

Adenocarcinoma↗
PubMed1996

[The surgical treatment for the epiglottic cancer extended to the base of tongue].

26 cases of the epiglottic cancer extended to the base of the tongue were studied retrospectively. Among them, 14 were male and 12 female. The age varied from 43 to 62. Besides two cases who underwent total laryngectomy, the other twenty-four were treated with supraglottic horizontal partial laryngectomy or horizontovertical subtotal laryngectomy and resection of part of base of the tongue. 11 cases received bilateral radical neck dissection (RND) and 10 cases unilateral RND simultenously. The results showed twenty-four cases had resumed speaking ability, twenty had been decannulated and restored the laryngeal functions. The 5-year survival rate was 57.9% (12/19). It was concluded that transpharyngeal approach was reasonable for supraglottic horizontal partial laryngectomy associated with the resection of the base of the tongue.

Adult↗
PubMed1995

Computerized microimage analysis of age-related changes of the human sinoatrial node.

This paper reports the age-related changes in the histological features of the sinoatrial node (SAN). The hearts of 106 persons dying at different ages (2 days-83 years), without clinical or pathological evidence of cardiac disease, were taken and divided into seven age-groups. Serial sections with a thickness of 2 microns, parallel to the long axis of the SAN, were prepared. Sections with the maximal area of the SAN were stained with hematoxylin/eosin (H & E) and Betty's method. The largest area of SAN were calculated by a computerized microimage analysis system. The age-related changes of the human SAN were discussed.

Adolescent↗
PubMed1995

Adenoviral E1B-55kDa protein inhibits yeast mRNA export and perturbs nuclear structure.

The mechanisms of export of RNA from the nucleus are poorly understood; however, several viral proteins modulate nucleocytoplasmic transport of mRNA. Among these are the adenoviral proteins E1B-55kDa and E4-34kDa. Late in infection, these proteins inhibit export of host transcripts and promote export of viral mRNA. To investigate the mechanism by which these proteins act, we have expressed them in Saccharomyces cerevisiae. Overexpression of either or both proteins has no obvious effect on cell growth. By contrast, overexpression of E1B-55kDa bearing a nuclear localization signal (NLS) dramatically inhibits cell growth. In this situation, the NLS-E1B-55kDa protein is localized to the nuclear periphery, fibrous material is seen in the nucleoplasm, and poly(A)+ RNA accumulates in the nucleus. Simultaneous overexpression of E4-34kDa bearing or lacking an NLS does not modify these effects. We discuss the mechanisms of selective mRNA transport.

Adenoviridae↗
PubMed1995

Proton nuclear magnetic resonance studies on huwentoxin-I from the venom of the spider Selenocosmia huwena: 1. Sequence-specific 1H-NMR assignments.

The complete sequence-specific assignments of resonances in the 1H-NMR spectrum of huwentoxin-I from the Chinese bird spider, Selencocosmia huwena, is described. A combination of two-dimensional NMR experiments including 2D-COSY, 2D-NOESY, and 2D-TOCSY has been employed on samples of the toxin dissolved in D2O and in H2O for assignment purposes. Protons belonging to spin systems for each of the 33 amino acids were identified. The sequence-specific assignments were facilitated by the identification of d alpha N connectivities on the fingerprint regions of the COSY and NOESY spectra and were supported by the identification of dNN and d alpha N connectivities in the TOCSY and NOESY spectra. These studies provide a basis for the determination of the solution-phase conformation of this toxin.

Amino Acid Sequence↗
PubMed1995

A new model for rapid stretch-induced injury of cells in culture: characterization of the model using astrocytes.

The purpose of this study was to develop a simple, reproducible model for examining the morphologic, physiologic, and biochemical consequences of stretch-induced injury on tissue-cultured cells of brain origin. Rat cortical astrocytes from 1- to 2-day-old rats were cultured to confluency in commercially available 25-mm-diameter tissue culture wells with a 2-mm-thick flexible silastic bottom. A cell injury controller was used to produce a closed system and exert a rapid positive pressure of known amplitude (psi) and duration (msec). The deformation of the membrane, and thus the stretch of the cells growing on the membrane, was proportional to the amplitude and duration of the air pressure pulse. Extent of cell injury was qualitatively assessed by light and electron microscopy and quantitatively assessed by nuclear uptake of the fluorescent dye propidium iodide, which is excluded from cells with intact membranes. Lactate dehydrogenase (LDH) enzyme release was measured spectrophotometrically. Cell injury was found to be proportional to the extent of the silastic membrane deformation. Increasing cell stretch caused mitochondrial swelling and vacuolization as well as disruption of glial filaments. Stretching also caused increased dye uptake, with maximum dye uptake occurring with a 50 msec pressure pulse duration, whereas deformations produced over longer periods of time (seconds) caused little dye uptake. With increasing postinjury survival fewer cells took up dye, implying cell repair. LDH release was also proportional to the amplitude of cell stretch, with maximum release occurring within 2 h of injury. In summary we have developed a simple, reproducible model to produce graded, strain-related injuries in cultured cells. Our continuing experiments suggest that this model can be used to study the biochemistry and physiology of injury as well as serve as a tool to examine the efficacy of therapeutic agents.

Air Pressure↗