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Biomedical subjects

L Q Chen

Publications and source records attributed to L Q Chen.

46 records · Page 3Linked to original sources
PubMed1991

SkM2, a Na+ channel cDNA clone from denervated skeletal muscle, encodes a tetrodotoxin-insensitive Na+ channel.

Approximately one third of the Na+ channels expressed in denervated or developing skeletal muscle are tetrodotoxin (TTX) insensitive, with a Kd for channel blockade of approximately 1 microM, similar to that found for cardiac Na+ channels. We have recently reported the cloning of a putative Na+ channel subtype that is characteristic of denervated and developing skeletal muscle (SkM2), the deduced amino acid sequence of which is identical to that of a Na+ channel cDNA isolated from heart. We have now examined the functional properties of SkM2 Na+ channels after expression in Xenopus oocytes. We found that the efficiency of expression of constructs containing the SkM2 clone was strongly dependent on the amount of 5'-untranslated region (5'UTR) included. Constructs containing a 206-nucleotide 5'UTR were expressed poorly, whereas constructs from which most of the 5'UTR was removed were expressed well. The channels showed rapid voltage-dependent activation and inactivation. In addition, SkM2 Na+ channels were insensitive to low concentrations of TTX but were ultimately blocked by this toxin, with a Kd of 1.9 microM. The TTX block exhibited use dependence. Finally, SkM2 Na+ channels were not blocked by 100 nM mu-conotoxin, which blocks Na+ channels in innervated skeletal muscle in the low nanomolar concentration range. These data indicate that SkM2 Na+ channels are the TTX-insensitive Na+ channels found in denervated or developing skeletal muscle and are identical to the TTX-insensitive Na+ channels from heart.

Animals↗
PubMed1991

[Influence of hemoultrafiltration and hemodialysis on endothelin].

In order to study the mechanism of plasma ET increment in CRF patients, we investigated 20 endothelin (CRF) patients undergone hemoultrafiltration for 90 min followed by hemodialysis, and 12 patients subjected to single hemodialysis. The results revealed that 90 min's ultrafiltration along with 2500 ml fluid extraction brought about a significant decrease in plasma ET (from 1132 to 753 pg/ml, P less than 0.05), while the hemodialysis without water extraction of a same period resulted no significant change. In the meantime, the BUN in the ultrafiltration group showed no prominent change. But the hemodialysis group presented a significant decrease (from 34.6 to 22.5 mmol/L P less than 0.05), which showed that the ET falling had no significant relevance to the metabolic products extraction. In the followed 120 min's hemodialysis, ET level in the two groups decreased in a different extend. Therefore, the research suggested that decreased extracellular volume via ultrafiltration can lead to the discretion of ET level.

Adult↗
PubMed1991

Influence of hemoultrafiltration and hemodialysis on endothelin.

To study the mechanism of plasma endothelin (pET) increment in chronic renal failure (CRF) patients, we investigated 20 CRF cases given hemoultrafiltration for 90 min followed by hemodialysis and 12 given hemodialysis only to examine the effect on ET. The results revealed that 90-min ultrafiltration with 2 500ml fluid extraction significantly decreased plasma ET (1 132 +/- 793--753 +/- 702 pg/ml, P less than 0.05), while hemodialysis without water extraction for the same period of time resulted in no significant change (1 195 +/- 891--1 011 +/- 654pg/ml, P greater than 0.05). BUN in the ultrafiltration group showed no marked changes (102 +/- 11.4--83.5 +/- 119 mg/dl), but the hemodialysis group presented a significant decrease (97 +/- 12--63 +/- 7 mg/dl, P less than 0.05), showing that the ET fall had no significant relevance to the metabolic products extracted. In 120 min following hemodialysis, ET levels in both groups decreased by different amounts. MAP decreased in both groups throughout the procedure period. Therefore, it is suggested that decreased extracellular volume via ultrafiltration can lead to lowering of ET levels, showing that extracellular volume may influence the ET level.

Adult↗
PubMed1990

Primary structure and expression of a sodium channel characteristic of denervated and immature rat skeletal muscle.

The alpha subunit of a voltage-sensitive sodium channel characteristic of denervated rat skeletal muscle was cloned and characterized. The cDNA encodes a 2018 amino acid protein (SkM2) that is homologous to other recently cloned sodium channels, including a tetrodotoxin (TTX)-sensitive sodium channel from rat skeletal muscle (SkM1). The SkM2 protein is no more homologous to SkM1 than to the rat brain sodium channels and differs notably from SkM1 in having a longer cytoplasmic loop joining domains 1 and 2. Steady-state mRNA levels for SkM1 and SkM2 are regulated differently during development and following denervation: the SkM2 mRNA level is highest in early development, when TTX-insensitive channels predominate, but declines rapidly with age as SkM1 mRNA increases; SkM2 mRNA is not detectable in normally innervated adult skeletal muscle but increases greater than 100-fold after denervation; rat cardiac muscle has abundant SkM2 mRNA but no detectable SkM1 message. These findings suggest that SkM2 is a TTX-insensitive sodium channel expressed in both skeletal and cardiac muscle.

Amino Acid Sequence↗
PubMed1990

[Image analysis for measuring the rDNA transcriptional activity].

It was clearly demonstrated that the silver stainability of NORs during interphase and metaphase could be inhibited by low doses of AMD concentration. It showed that the AMD concentration could reflect the rDNA transcriptional activity in NORs. In this experiment we used HABM image analysis system to measure the variation of silver stainability of NORs treated by different doses of AMD in order to find the correlation between the rDNA transcriptional activity and the AMD concentration. The data resulted from this experiment were analysed with variance and correlation analysis method. The result showed that the variability of Ag-Nucleoli was significant in different AMD concentration and it was positively correlated with AMD concentration. So, we considered that the size of Ag-Nucleoli is one of the most precise signs when measuring the rDNA transcriptional activity with silver staining method.

Analysis of Variance↗
PubMed1989

A new crystal form of ricin-OR.

Ricin-OR, an antitumor toxin, has been crystallized in space group P2 with cell parameters a = 8.77 nm, b = 4.64 nm, c = 7.64 nm and beta = 101 degrees. There is one molecule in the asymmetric unit and the solvent content is estimated to be 48% by volume. The crystals diffract to 0.25 nm resolution which is higher than that of the previously reported C2 crystal form which had a solvent content of 65%.

Antineoplastic Agents↗
PubMedDate not supplied

Clinicopathologic characteristics and postoperative outcome in Japanese and Chinese patients with thoracic esophageal cancer.

We evaluated the clinicopathologic findings and surgical results of 140 patients with thoracic esophageal cancer treated at Shinshu University, Japan (Shinshu group), and compared them with those from 1164 patients treated at Hebei Medical College, China (Hebei group) to determine if the two groups showed any differences. The Shinshu group had significantly higher incidences of elderly patients (>70 years of age), male patients, and tumors located at the lower esophagus (p < 0.01). In the Hebei group, although the depth of tumor invasion was more advanced, the incidence of nodal metastasis was significantly lower (p < 0.01). Operative death and postoperative complications were more frequent in the Shinshu group. Comparison of the postoperative survival curves revealed significantly longer survival of patients with pT2 or pT3 tumor in the Hebei group (p < 0.01), but there were no significant differences between the two groups when the lesions were classified by pTNM stage. This study demonstrated several differences between the patients in the two areas in regard to the clinicopathologic characteristics of thoracic esophageal cancer. The most important characteristic of the esophageal cancer in the Hebei group appears to be the low incidence of nodal metastasis.

Adult↗