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Biomedical subjects

C Liu

Publications and source records attributed to C Liu.

At least 757 records · Page 42Linked to original sources
PubMed1993

The flanking amino acids of the human follitropin beta-subunit 33-53 region are involved in assembly of the follitropin heterodimer.

Previous analyses of the topology of human follitropin (hFSH) with monoclonal antibodies and antipeptide antibodies have led to a current operating hypothesis that some amino acids within the hFSH beta 33-53 region are surface oriented, and others participate in subunit contact. Protein structural analysis predicts beta-turns within this region, and the immunochemical studies indicate that the ends may be involved in subunit contact. In this study, hFSH beta was mutagenized to change 34TRDL37 to 34AAAA37 or 48QKTCT52 to 48AAACA52, allowing us to study the ends of the hFSH beta 33-53 sequence contiguous with the hFSH beta sequence. Wild-type and mutant cDNAs were coexpressed with alpha-subunit cDNA in CHOPro-5 cells. Wild-type hFSH was secreted from cells cotransfected with wild-type hFSH alpha and hFSH beta cDNAs, as expected. However, heterodimeric hFSH was minimally detected in the medium from cells transfected with the 34TRDL37 mutant and was not detected in the case of the 48QKTCT52 mutant. Analysis of cell lysates (intracellular FSH) by immunoprecipitation and polyacrylamide gel electrophoresis showed that wild-type and mutant beta-subunits were indistinguishable and recoverable intact from each cell line. Additionally, analysis of lysates with a conformation-specific monoclonal antibody 3G3 revealed that similar levels of properly folded beta-subunit were produced in cells expressing wild-type or either mutated beta-subunit. These data indicate that the flanking amino acids of the hFSH beta 33-53 region, in particular 48QKTCT52, are critical for assembly of hFSH heterodimer.

Amino Acid Sequence↗
PubMed1993

The organization of the suprachiasmatic circadian pacemaker of the rat and its regulation by neurotransmitters and modulators.

The long-term goal of our research is to understand how cells of the suprachiasmatic nucleus (SCN) are organized to form a 24-hr biological clock, and what roles specific neurotransmitters and modulators play in timekeeping and resetting processes. We have been addressing these questions by assessing the pattern of spontaneous neuronal activity, using extracellular and whole-cell patch recording techniques in long-lived SCN brain slices from rats. We have observed that a robust pacemaker persists in the ventrolateral region of microdissected SCN, and have begun to define the electrophysiological properties of neurons in this region. Furthermore, we are investigating changing sensitivities of the SCN to resetting by exogenous neurotransmitters, such as glutamate, serotonin, and neuropeptide Y, across the circadian cycle. Our findings emphasize the complexity of organization and control of mammalian circadian timing.

Animals↗
PubMed1993

Effect of pentobarbital on normal brain protection and on the response of 9L rat brain tumor to radiation therapy.

The authors attempted to confirm published reports that pentobarbital protects against radiation-induced damage to normal rat brain, as well as enhances radiotherapeutic efficacy in a rat brain tumor model. They evaluated animal survival in 9L gliosarcoma-burdened rats that received whole-brain radiation therapy (16, 24, 32, or 40 Gy) while under intraperitoneal pentobarbital (60 mg/kg) or intramuscular ketamine (60 mg/kg) sedation. The animals were examined at autopsy to attribute death to either intracranial tumor growth or normal brain toxicity in the absence of discernible tumor. There was no difference between the two anesthesia groups regarding the survival of unirradiated animals. Radiation therapy produced a significant dose-dependent prolongation in animal survival, which was limited by the development of normal tissue toxicity at the higher doses. When compared to ketamine anesthesia, pentobarbital anesthesia appeared to offer some protection (not statistically significant) against early (but not late) toxicity at selected radiation doses. A reduction in the number of deaths from tissue toxicity suggested an increased antitumor effect, but again this was not statistically significant. Only in one case was there even a marginal significant difference (p = 0.045) between overall therapeutic efficacy in rats sedated with pentobarbital versus ketamine. While there may be a radioprotective effect of pentobarbital in rat brains without intracranial tumor, there is no conclusive evidence for either radioprotection or significant improvement of radiotherapeutic efficacy in this 9L rat brain tumor model.

Animals↗
PubMed1993

Transformation of wheat protoplasts mediated by cationic liposome and regeneration of transgenic plantlets.

E. coli plasmid pCGN1055 containing the hygromycin phosphotransferase (Hpt) gene under the control of the plant promoter was introduced into wheat protoplasts by cationic liposome (lipofectin)-mediated transformation, and transgenic albino plantlets were obtained. The transformation frequencies were 6.0% and 8.8% according to hygromycin resistance and DNA molecular hybridization. The assay of Hpt enzyme activity and Southern blot indicated the foreign gene existed and expressed in transgenic plantlets.

Cations↗
PubMed1993

In vitro and in vivo expressions of transforming growth factor-alpha and tyrosine kinase receptors in human non-small-cell lung carcinomas.

The mRNA expression of transforming growth factor-alpha (TGF-alpha), epidermal growth factor receptor (EGFR), c-erbB-2 and c-met proto-oncogenes in eight newly established cell lines and 29 primary tumors of human non-small-cell lung carcinoma (NSCLC) have been investigated. In vitro, the expressions of TGF-alpha, c-erbB-2, and c-met were consistently high in adenocarcinomas, while EGFR was expressed highest in a squamous cell carcinoma cell line. There was linear correlation between the levels of expression of TGF-alpha and EGFR or c-erbB-2, and between EGFR and c-erbB-2. The c-met expression was also correlated with those of TGF-alpha, EGFR, and c-erbB-2. In vivo, The mean mRNA levels of TGF-alpha, EGFR, and c-met, but not c-erbB-2, were higher in carcinomas than in normal lung tissues (2.8, 1.7, and 3.0 times, respectively); however, only adenocarcinomas expressed a significantly higher level of c-erbB-2 than their corresponding normal tissues (2.2 times). In 20 patients whose paired normal and tumor tissue were examined, the percentage of cases with greater than twofold increase in expression in carcinomas than normal were 55% for both TGF-alpha and EGFR, 30% for c-erbB-2, and 47% for c-met. Among the histological subtypes of NSCLC, a higher percentage of adenocarcinomas than squamous cell carcinomas over-expressed these genes, especially c-erbB-2 and c-met. Over-expression is rarely the result of gene amplification. The results suggest a differential expression of growth factor and receptor genes among the various histological subtypes of NSCLCs.

Blotting, Northern↗
PubMed1993

Inositol-1,3,4,5-tetrakisphosphate induces calcium mobilization via the inositol-1,4,5-trisphosphate receptor in SH-SY5Y neuroblastoma cells.

myo-Inositol-1,3,4,5-tetrakisphosphate [Ins(1,3,4,5)P4]-induced Ca2+ mobilization was examined in saponin-permeabilized SH-SY5Y cells using myo-inositol hexakisphosphate-supplemented buffer to prevent Ins(1,3,4,5)P4-3-phosphatase-catalyzed back-conversion of exogenous Ins(1,3,4,5)P4 to myo-inositol-1,4,5-trisphosphate [Ins(1,4,5)P3]. The Ins(1,3,4,5)P4 concentration-response curve for Ca2+ release in SH-SY5Y cells exhibited an EC50 of 2.5 microM, compared with 52 nM for Ins(1,4,5)P3, with the maximally effective concentration of Ins(1,3,4,5)P4 (100 microM) mobilizing the entire Ins(1,4,5)P3-sensitive pool. Both Ins(1,3,4,5)P4- and Ins(1,4,5)P3-induced Ca2+ mobilizations were heparin sensitive. Further, L-chiro-inositol-2,3,5-trisphosphorothioate, a recently identified low intrinsic activity Ins(1,4,5)P3 receptor partial agonist, shifted both the Ins(1,4,5)P3 and Ins(1,3,4,5)P4 concentration-response curves significantly rightward, with similar potencies. However, binding studies demonstrate that L-chiro-inositol-2,3,5-trisphosphorothioate interacts very poorly (IC50 > 30 microM) with specific Ins(1,3,4,5)P4 binding sites that have been previously characterized in pig cerebellum. Carbachol-pretreated SH-SY5Y cells (1 mM, > or 6 hr) exhibit a decrease in Ins(1,4,5)P3 receptor number, accompanied by both a rightward shift and a reduced maximal Ca2+ release in their Ins(1,4,5)P3 concentration-response curve. Here both Ins(1,4,5)P3 and Ins(1,3,4,5)P4 concentration-response curves were found to exhibit identically reduced maximal Ca2+ release responses and about 4-fold rightward shifts in EC50 values. Together, these observations provide compelling evidence for our hypothesis that Ins(1,3,4,5)P4 exhibits weak but full agonist status at Ins(1,4,5)P3 receptor-operated Ca2+ channels in SH-SY5Y cells.

Calcium↗
PubMed1993

Effect of acupuncture and point-injection treatment on immunologic function in rheumatoid arthritis.

The results of treatment of 54 cases of rheumatoid arthritis (RA) by warm needling (WN) and point-injection (PI) with Zhuifengsu are reported. Good clinical results were observed with an effective rate of 100%. At the same time, changes in cellular and humoral immunity and other parameters in peripheral blood were noted before and after treatment. The NK activity and IL-2 value in RA patients were found to be lower than those of normal individuals; both increased after treatment (P < 0.01). This suggests that the WN and PI with Zhuifengsu exert a regulatory effect on the cellular immunological function.

Acupuncture Points↗
PubMed1993

[Application of in situ hybridization using digoxigenin--labeled HBV DNA probe and comparison with biotinylated probe].

A method of in situ hybridization for HBV DNA on liver tissue with digoxigenin-labeled probe is described. We have detected the HBV DNA of sixteen liver biopsies. The results showed that the sensitivity and specificity of digoxigenin-labeled probe for in situ hybridization were hig er and stronger then those of biotinylated probe. The practicality of digoxigenin-labeled probe is better. It is an excellent non-radioactive probe for in situ hybridization, which may eventually replace the biotinylated probe. The localization of HBV DNA in hepatocytes could be classified into 4 types, namely, the whole cytoplasmic, focal cytoplasmic, whole nucleic and nuclear membranous-nucleolus. The results of in situ hybridization using digoxigenin-labeled probe could reflect the free or integrated status of HBV genome and the levels of its genomic replication in hepatocytes. The procedure of in situ hybridization using digoxigeninlabeled probe was also discussed.

Biotin↗
PubMed1993

Bronchiolitis following infection in adults and children.

Since its recognition as a clinical entity in the 1940s, our knowledge of bronchiolitis has grown with respect to the breadth of disease, epidemiology, treatment, and long-term effects. Bronchiolitis occurs most commonly in infants and children in association with a predictably small number of respiratory pathogens. Our knowledge of the association of bronchiolitis to subsequent wheezing is in a state of evolution. Rarely, bronchiolitis may progress to a chronic obstructive process, bronchiolitis obliterans, seen most often following adenovirus infection. The diagnosis of bronchiolitis in adults is relatively rare and although specific information on etiologic agents is lacking, it is not unlikely that the implicated infectious agents in infant bronchiolitis may play a role in the adult form of the disease. Bronchiolitis obliterans in adults occurs as a result of many possible causes, including infection. Although infection probably contributes to the pathogenesis of bronchiolitis obliterans in the post-organ-transplant population, this process appears to be a complex interaction centering around graft rejection.

Adenovirus Infections, Human↗
PubMed1993

Proto-oncogene and growth factor/receptor expression in the establishment of primary human non-small cell lung carcinoma cell lines.

In our effort to delineate factors that govern the ability of non-small cell lung carcinoma (NSCLC) to form monolayer cell lines, we have attempted to derive monolayer cell lines from the primary cultures of 29 unselected human NSCLCs. Eight new lines were obtained. Cell lines were easier to establish from poorly differentiated tumors, especially adenocarcinomas. One cell line was from a large cell neuroendocrine carcinoma. All cell lines were aneuploid, and they exhibited heterogeneous nutritional requirements for growth in vitro. Cell line-forming primary tumors demonstrated higher mean messenger RNA expression levels for transforming growth factor-alpha and c-met proto-oncogene than did tumors that failed to form cell lines. Although a high level of c-myc expression was correlated with the ability of NSCLC cell lines to form xenograft tumors in nude mice, it was not correlated with the ability of primary tumors to establish cell lines. The results suggest that autocrine growth loops play important roles in the ability of NSCLC cells to proliferate continuously in monolayer culture. The fact that the overexpression of transforming growth factor-alpha in NSCLCs has been negatively correlated with patient survival and that most cell lines can be established only from poorly differentiated carcinomas may provide the explanation for a previous report that the capability for cell line establishment constitutes a negative prognostic indicator for patient survival. However, when the genotype and phenotype of the cell lines were compared with those of their corresponding primary or xenograft tumors, the tumor cells that grew continuously as a cell line often represented a selective subpopulation of the heterogeneous neoplastic cells in the primary tumors. This finding should be taken into consideration when cell lines are used to evaluate the chemo- and radiosensitivity of tumor cells.

Animals↗
PubMed1993

Identification of partial agonists with low intrinsic activity at the inositol-1,4,5-trisphosphate receptor.

The interactions of synthetic L-chiro-inositol-2,3,5-trisphosphorothioate [L-ch-Ins(2,3,5)PS3] and D-6-deoxy-myo-inositol-1,4,5-trisphosphorothioate [D-6-deoxy-Ins(1,4,5)PS3] with D-myo-inositol-1,4,5-trisphosphate [Ins(1,4,5)P3] receptors have been examined using radioligand binding assays and Ca2+ mobilization from permeabilized SH-SY5Y cells. The ability of these analogues to compete with [3H]Ins(1,4,5)P3 for specific sites on adrenal cortical membranes indicated that, although weaker than Ins(1,4,5)P3, both ligands competed fully for these sites [L-ch-Ins(2,3,5)PS3,Ki = 0.5 microM; D-6-deoxy-Ins(1,4,5)PS3,Ki = 5.3 microM]. However, in assays examining the amount of Ca2+ mobilized from the stores of permeabilized SH-SY5Y cells, both of these synthetic analogues displayed low intrinsic activity [L-ch-Ins(2,3,5)PS3, 34%; D-6-deoxy-Ins(1,4,5)PS3, 42% of that of Ins(1,4,5)P3]. Moreover, L-ch-Ins(2,3,5)PS3 and D-6-deoxy-Ins(1,4,5)PS3 were able to inhibit the response to Ins(1,4,5)P3 with Ki values (6 microM and 33 microM, respectively) virtually identical to their EC50 values for Ca2+ release. This is consistent with partial agonist behavior, because these compounds exhibit low maximal responses when the extent of Ca2+ release is examined. These compounds represent the first examples of inositol-based analogues with low intrinsic activity and may point the way towards the design of selective antagonists at Ins(1,4,5)P3 receptors. It also seems probable that these may represent the first true affinity values of inositol phosphates at the active receptor.

Adrenal Cortex↗
PubMed1992

The role of the 2- and 3-hydroxyl groups of 1D-myo-inositol 1,4,5-trisphosphate in the mobilisation of calcium from permeabilised human 1321N1 astrocytoma cells.

The functional significance of the 2- and 3-hydroxyl groups of 1 D-myo-inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] was probed by using Ins(1,4,5)P3 analogues variously modified at positions 2 and 3 or elsewhere. The intrinsic activities of these compounds were compared to that of Ins(1,4,5)P3, using the calcium-mobilising receptor of the 1321N1 human astrocytoma cell line. The ligand-binding affinities were also determined using membrane preparations from rat cerebellum and bovine adrenal cortex. The results show that HO-2 and HO-3 of Ins(1,4,5)P3 have a relatively insignificant role in receptor binding and calcium release. However, the possibility of a regulatory role for the 3-position of Ins(1,4,5)P3 in these processes is proposed.

Adrenal Cortex↗
PubMed1992

Sequence and variability of the 5.8S and 26S rRNA genes of Pneumocystis carinii.

The sequence of the coding region of the rRNA operon of rat-derived Pneumocystis carinii has been completed, including the genes for 5.8S and 26S rRNA. These genes show homology to the rRNA genes of yeast, and an apparent group I self-splicing intron is present in the 26S rRNA gene. Like a similar intron in the 16S rRNA gene, this intron is in a phylogenetically conserved region. Variation in the 26S rRNA sequence was noted between P. carinii organisms isolated from two different sources.

Base Sequence↗
PubMed1992

3-position modification of myo-inositol 1,4,5-trisphosphate: consequences for intracellular Ca2+ mobilisation and enzyme recognition.

The ability of the novel D-myo-inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) analogues, L-chiro-inositol 2,3,5-trisphosphate (L-ch-Ins(2,3,5)P3) and D-3-deoxy-3-fluoro-myo-inositol 1,4,5-trisphosphate (3F-Ins(1,4,5)P3), to bind to the Ins(1,4,5)P3 receptor, mobilise intracellular Ca2+ stores and interact with metabolic enzymes has been investigated. L-ch-Ins(2,3,5)P3 and 3F-Ins(1,4,5)P3 were bound by the Ins(1,4,5)P3 receptor from bovine adrenal cortex with relatively high affinity (Ki values 60.4 and 8.0 nM respectively) but with lower affinity than Ins(1,4,5)P3 (KD = 5.9 nM). Both analogues were apparent full agonists at the Ca2+ mobilising receptor in SH-SY5Y cells, but were less potent than Ins(1,4,5)P3 (EC50 L-ch-Ins(2,3,5)P3 = 1.4 microM, 3F-Ins(1,4,5)P3 = 0.37 microM and Ins(1,4,5)P3 = 0.12 microM). L-ch-Ins(2,3,5)P3 and 3F-Ins(1,4,5)P3 were resistant to Ins(1,4,5)P3 3-kinase, and were potent inhibitors of the enzyme (Ki values 7.1 and 8.6 microM respectively). 3F-Ins(1,4,5)P3 was hydrolysed by Ins(1,4,5)P3 5-phosphatase at a similar rate to Ins(1,4,5)P3, but inhibited dephosphorylation of [3H]Ins(1,4,5)P3 with high potency (apparent Ki = 3.9 microM) L-ch-Ins(2,3,5)P3 was also recognised by the enzyme with high affinity (Ki = 7.7 microM) but was resistant to hydrolysis. These results suggest that the environment around C-3 is of major importance for recognition not only by Ins(1,4,5)P3 3-kinase but also by Ins(1,4,5)P3 5-phosphatase.

Adrenal Glands↗