Biomedical subjects

Y X Liu

Publications and source records attributed to Y X Liu.

At least 73 records · Page 4Linked to original sources

PubMed1994

[Characterization and quantification of dermatan sulfate from donkey skin].

Dermatan sulfate (DS), a recently known antithrombotic glycosaminoglycan, was isolated and purified from donkey skin. Physiochemical characteristics of the glycan, including constituent analysis, electrophoretic behaviour, molecular mass, specific lyase degradations, IR and PMR spectra were described, using porcine skin-origin dermatan sulfate as a standard reference. Contents of DS in donkey skin and its gelatinized preparations (Ejiao) were also measured. Results indicate that the presence of DS may explain the long reputed clinical efficacy of donkey skin and Ejiao in treating serious symptoms associated with what has been called endogenous wind in traditional Chinese medicine.

Animals↗

PubMed1994

Secretion of plasminogen activator inhibitor type 1 by cultured ovarian cells obtained from gonadotropin-treated immature rats.

It is demonstrated that i) theca-interstitial compartment synthesizes the majority of plasminogen activator inhibitor type 1 (PAI-1) in the ovary before ovulation, and the follicular wall may therefore serve as a specific barrier with the presence of PAI-1 activity to prevent the secretion of tPA into the extrafollicular compartments; ii) granulosa cells secrete only a small amount of ovarian PAI-1, but synthesize the most of tissue-type plasminogen activator tPA involved in the processes leading to ovulation; iii) since only matured cumulus-oocyte complexes secrete a large amount of tPA and PAI-1, both tPA and PAI-1 activity in the conditioned medium may be used as reliable markers for evaluating oocyte quality for in vitro fertilization.

Animals↗

PubMed1994

[Effects of selective hepatic duct embolization on normal, cirrhotic livers and hepatocellular carcinomas].

Variant gross and pathology features were observed on effects of selective hepatic duct embolization (SHDE) in contrast to selective hepatic duct ligation (SHDL). Glue TH was used in SHDE that performed on normal liver, induced cirrhotic liver and hepatocellular, carcinoma. The results demonstrated that SHDL has weak effected, while SHDE causes the embolized liver lobes to acute ischemic necrosis, followed by atrophy and fibrosis, accompanied by quickly hypertrophy of the uninvolved lobes. All tumors on the embolized liver lobes also showed acute tumors on the embolized liver lobes also showed acute tumor ischemic necrosis, atrophy and fibrosis. The reason for the above variations is that pressure and tension of SHDE expand the embolized bile duct tree, especially the Hering duct, which will continuously obstruct the dual blood supply to the liver tumor. Effectively and thoroughly annihilating or restricting the tumor, SHDE may lead the tumors to "spontaneous excision", with the unoperated lobes hypertrophy to compensate liver functions simultaneously. These studies indicated that SHDE will be a new method in liver cancer clinic.

Animals↗

PubMed1994

Hormonal regulation of expression of tissue type plasminogen activator and plasminogen activator inhibitor type 1 in cultured rat granulosa cells.

In the present study, gonadotropin and gonadotropin-releasing hormone (GnRH) regulation of tPA and PAI-1 expression in PMSG-primed granulosa cells has been investigated. (i) Addition of gonadotropins (FSH and LH) and GnRH agonist (GnRHa) or PMA to the culture increases tPA activity; FSH (or LH) plus GnRHa (or PMA) in the culture further enhances the enzyme production to such an extent that a more obvious effect than the additive effect caused by these hormones used alone has been observed; (ii) in contrast, FSH and LH decrease PAI-1 activity, whereas GnRHa and PMA alone markedly increase PAI-1 mRNA level and PAI-1 activity. Because FSH and LH stimulate tPA production and have no significant effect on PAI-1 mRNA induction, the observed inhibition of PAI-1 activity by gonadotropins may be due to the occurrence of neutralization of PA and PAI-1 proteins in the conditioned media by the formation of complexes between PA and PAI-1; (iii) increases in PAI-1 mRNA level and activity by GnRH and PMA are completely inhibited by the co-addition of FSH or LH to the culture. It is, therefore, suggested that the mechanism of gonadotropin and GnRHa regulation of tPA and PAI-1 expression in granulosa cells is different.

Animals↗

PubMed1993

The top2-5 mutant of yeast topoisomerase II encodes an enzyme resistant to etoposide and amsacrine.

We have characterized a temperature-sensitive mutant in the yeast TOP2 gene that shows resistance to the anti-topoisomerase II agents amsacrine and etoposide. Cells carrying the top2-5 mutant have a minimum lethal concentration of amsacrine of greater than 100 micrograms/ml, compared to 10 micrograms/ml in isogenic wild-type cells, and a minimum lethal concentration of greater than 100 micrograms/ml etoposide, compared with 50 micrograms/ml for cells carrying wild-type topoisomerase II. We have cloned the top2-5 allele into a yeast vector that allows high level overexpression of the protein. As expected, the purified top2-5 activity is temperature-sensitive. The protein shows a 3-fold reduction of amsacrine-stabilized cleavage at the permissive temperature, confirming that the top2-5 protein is resistant to amsacrine in vitro. The protein also exhibits reduced cleavage in the presence of etoposide, with the largest effect at low concentrations of the drug. These results suggest that the top2-5 protein is altered in its sensitivity to anti-topoisomerase II agents. The relevant portion of the mutant allele has been sequenced, and several tightly clustered mutations have been identified. The location of the mutations identify a domain of the topoisomerase II protein that may be important in the interaction of the protein with anti-topoisomerase II anti-cancer drugs.

Alleles↗

PubMed1993

A temperature sensitive topoisomerase II allele confers temperature dependent drug resistance on amsacrine and etoposide: a genetic system for determining the targets of topoisomerase II inhibitors.

We have developed a simple system for determining the specific contribution of topoisomerase II targeting to the cytotoxic activity of a drug. We have constructed yeast strains that are permeable to anti-topoisomerase II drugs, carry a DNA repair mutation, rad52, and also have a temperature sensitive topoisomerase II mutation, top2-1. Strains carrying the top2-1 mutation have nearly normal topoisomerase II activity at 25 degrees C but less than 10% of wild type activity at 36 degrees C. We find that at a semi-permissive temperature (30 degrees C), there is sufficient topoisomerase II activity for viability; but since the topoisomerase II activity is greatly reduced, the cells are very resistant to anti-topoisomerase II drugs. Conversely, such cells are hypersensitive to the topoisomerase I inhibitor camptothecin. These results provide strong support for the model that drug stabilized DNA cleavage, rather than a lack of enzyme activity, is responsible for cell killing by eukaryotic anti-topoisomerase II agents. They also show that there is a minimum level of topoisomerase II activity in yeast that is consistent with viability but also allows a high degree of resistance to anti-topoisomerase II agents.

Alleles↗

PubMed1993

[Prolactin inhibits gonadotropin-induced increase in ovarian plasminogen activator activity and ovulation in mouse].

We have demonstrated in this study that prolactin inhibits hCG-induced ovulation in PMSG-primed mice. At 18 h after the hormone treatment the number of ova in the oviducts was found to be 31.7 +/- 6.7 (mean +/- SE) in hCG treated group. The number was significantly decreased (19.7 +/- 4.9) when 100 micrograms of prolactin was injected simultaneously. The same effect of PRL on hCG induced ovulation could be also observed at 24 h after the hormone treatment; the values reached respectively to 32.3 +/- 10.8 and 20.3 +/- 5.4. Both in vivo and in vitro experiments further showed that the inhibition of the gonadotropin-induced ovulation by PRL is mediated through decreasing in the ovarian plasminogen activator activity.

Animals↗

PubMed1993

[Effects of anisodamine and ampicillin on cerebrospinal fluid in experimental E coli meningitis].

24 hr and 27 hr after K1-positive E coli suspended in 0.25 ml of saline (E coli 8 x 10(7)/ml) was injected into the cisterna magna of Chinese rabbits, the levels of bacterial titer, endotoxin, malondialdehyde (MDA), lactate and lactic dehydrogenase (LDH) of the cerebrospinal fluid (CSF) were increased significantly. After ampicillin therapy alone for 3 hr, the level of CSF bacterial titer was decreased and that of LDH increased, but the others didn't change significantly. After anisodamine and ampicillin therapy for 3 hr, the levels of CSF endotoxin and lactate concentrations were decreased from 3.2 +/- 0.6 to 2.1 +/- 0.9 log 10 IU/ml and from 8.6 +/- 2.0 to 6.5 +/- 1.8 mmol/L respectively. The CSF MDA concentration (0.31 +/- 0.07) was lower than that of the nontreatment group (0.59 +/- 0.25) or the ampicillin treatment group (0.59 +/- 0.21 nmol/ml) (P < 0.01 or 0.05). These results suggest that anisodamine combined with antibacterial therapy for experimental E coli meningitis is superior to antibacterial treatment in efficacy.

Ampicillin↗

PubMed1993

The possible involvement of tissue type plasminogen activator in luteolysis of rhesus monkey.

Changes of plasminogen activators (PA) during different stages of development of the corpus luteum, and their possible physiological role in luteolysis were studied in rhesus monkeys. It was demonstrated for the first time that monkey corpus luteal cells not only produce PA, but that the function of the corpus luteum is also closely related to the activity of this enzyme system. Generally, the life span for a corpus luteum in monkey is approximately 14-16 days, its demise beginning thereafter. In the present study, we found that urokinase in the corpus luteum is higher on day 5 and day 10 after human chorionic gonadotrophin injection, while the tissue type (t) PA is mainly produced on day 13 when luteolysis may take place. Progesterone production remained high on day 5 and day 10 and decreased dramatically from day 13, indicating the important role of tPA but not urokinase (u) PA in suppressing luteal function. When purified tPA (but not uPA) monoclonal antibody was added to luteal cell culture to neutralize endogenously produced tPA activity, progesterone production in the cells was increased significantly. Interestingly, prolactin alone was capable of increasing PA production by luteal cells; prolactin together with luteinizing hormone, however, had a synergistic luteotrophic effect.

Animals↗

PubMed1993

Hormonal regulation of tissue-type plasminogen activator and plasminogen activator inhibitor type-1 gene expression in cultured mouse Sertoli cells.

We have demonstrated for the first time that (i) mouse Sertoli cells predominantly secrete tPA under the action of FSH and cAMP-generating agents, whereas Leydig cells mainly produce uPA; (ii) Sertoli cells are also capable of secreting PAI-1, as well as FSH, growth factors and GnRH increase PAI-1 gene expression; (iii) the increases in tPA and PAI-1 activities by different hormones in the conditioned media of Sertoli cells correspond to the increases in the levels of tPA and PAI-1 mRNA in the cultured cells, suggesting that the synthesis of the activator-inhibitor in mouse Sertoli cells is regulated at a transcriptional level and the tPA secreted by Sertoli cells may be involved in the spermatogenesis.

Animals↗

PubMed1992

Amsacrine and etoposide hypersensitivity of yeast cells overexpressing DNA topoisomerase II.

Increasing the cellular concentration of DNA topoisomerase II in yeast by expressing constitutively a plasmid-borne TOP2 gene encoding the enzyme greatly increases the sensitivity of the cells to amsacrine and etoposide (VP-16). This increased drug sensitivity at a higher intracellular DNA topoisomerase II level is observed in both RAD52+ repair-proficient strains and rad52 mutants that are defective in the repair of double-stranded breaks. These results provide strong support of the hypothesis that the cellular target of these drugs is DNA topoisomerase II, and that these drugs kill cells by converting DNA topoisomerase II into a DNA damaging agent.

Amsacrine↗

PubMed1992

Mutational specificities of N-nitrosamines in a host-mediated assay: comparison with direct-acting N-nitroso compounds in vitro and an approach to deducing the nature of ultimate mutagens in vivo.

The mutational activities and specificities of several N-nitrosamines in Salmonella recovered from mouse liver in the host-mediated assay (HMA) were compared with the specificities of related direct-acting N-nitroso compounds in vitro. The specificities of the direct-acting methyl, ethyl, propyl, and 2-hydroxypropyl compounds were all different and presumably are attributable to the DNA adducts resulting from the corresponding alkyldiazonium or carbonium ions. Introduction of a 2-hydroxyl group greatly influenced the mutational specificity. The 2-oxopropyl compound showed the same specificity as the methyl compound. This result is consistent with one of the known breakdown pathways of the oxopropyl diazonium ion (or related reactive species), which leads to a methyl diazonium ion. The N-nitrosodialkylnitrosamines N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), and N-nitrosodipropylamine (NDPA), which all require metabolic activation, showed specificities in the HMA similar to those of their direct-acting counterparts. The cyclic nitrosamine N-nitrosopyrrolidine was weakly active in the HMA, although its direct-acting derivative was a potent mutagen in vitro. The results for NDMA and NDEA were consistent with most previous studies of the metabolism of these compounds in vivo. However, NDPA can yield methylating, and probably hydroxypropylating, species in addition to propyldiazonium ion. As the specificity of NDPA was similar to that of a propylating agent, NDPA appears to lead to genotoxic products in the mouse liver mainly by direct alpha-hydroxylation. The initial results described here indicate that mutational specificity in the HMA can be used to deduce metabolic pathways leading to genotoxic products when the appropriate proximate mutagens are available as standards. Furthermore, we observed a reasonable correlation between potency in the HMA and hepatocarcinogenesis.

Animals↗

PubMed1992

The bacterial hemoglobin from Vitreoscilla can support the aerobic growth of Escherichia coli lacking terminal oxidases.

Two Escherichia coli mutants that lack both cytochrome o and d terminal oxidases are able to grow with glucose as the carbon source but not with the aerobic substrates succinate or lactate. One of these, GV101, is a deletion mutant of cytochrome o and a point mutation of cytochrome d. The other, GK100, is a total deletion mutant of all the genes for both cytochromes. When these mutants were transformed with a plasmid containing the gene for the bacterial hemoglobin from Vitreoscilla, they were capable of growth in the presence of succinate or lactate and showed aerobic respiration in the presence of these substrates, unlike the parent strains. Cells transformed with a plasmid containing the gene for the hemoglobin but lacking the native promoter did not express the hemoglobin and did not respire. Membrane vesicles prepared from the cells consumed oxygen in the presence of succinate. This succinate-supported respiration decreased with successive washings of the vesicles but was restored by adding E. coli cytosol containing the hemoglobin or by adding the hemoglobin purified from Vitreoscilla. This respiration was inhibited by cyanide.

Aerobiosis↗

PubMed1992

[Plasminogen activators and plasminogen activator inhibitor type-1 in human endometrium].

Two types of plasminogen activator (PAs) are present in human endometrium, and their contents vary with the different phases of menstrual cycle, i.e. high in the proliferative phase and low in the secretory phase. In the present study by immunohistochemical technique, both uPA and tPA antigens were demonstrated in the stromal and glandular cells of the endometrium. In cell culture, tPA was released only from stromal cells and uPA only from glandular cells as determined by SDS-PAGE followed by fibrin overlay technique, but PA inhibitor type-1 (PAI-1) was secreted by both stromal and glandular cells. Furthermore, secretion of PAs from endometrial cells was enhanced by adding estradiol and markedly inhibited by progesterone in a dose dependent manner, while the PAI reacted just in the opposite way. The effect of the peptide hormones, hCG, GnRH, PRL, as well as cAMP in cell culture on the secretion of PAs and PAI was similar to that of estradiol, while forskolin demonstrated definitely more stimulative effect on tPA than uPA. Taking into account of the finding of the present study, it appears that, under hormonal control, a balance between PAs and PAI in the endometrium exists. The physiological roles of the PAs and PAI in the endometrium were discussed.

Adult↗

PubMed1992

[Transcatheter chemoembolization combined with hepatectomy for primary hepatic carcinoma. A clinical and pathological study].

Transcatheter chemoembolization (TCE) followed by laparotomy was performed in 12 patients with primary hepatic carcinoma (HCC). Each patient received TCE for 1-5 times with an interval of 4-6 weeks. The embolizing reagents included mitomycin C (20-40 mg), adriamycin (20-60 mg) and 40% lipiodol (2-10 ml). Results showed that the AFP level remarkably decreased even became normal and tumor size reduced. Partial hepatectomy was carried out in all 12 patients undergoing laparotomy except one with extensive abdominal metastasis. Histopathological study showed tissue necrosis and fibrosis at different stages in the surrounding liver parenchyma especially in the tumour area. Apart from sclerotic lesions, one or two daughter nodules were found in 2 patients. residual liver cancer was found in all of the 11 patients. Reexploration was made one year after liver resection in one patient for local recurrence and metastasis. The other two with right lung metastatic tumour 4-6 months after operation were given transcatheter pulmonary arterial embolization. We consider TCE as an effective adjuvant therapy to the combined treatment of liver carcinoma. It is suggested that TCE is indicated for unresectable HCCs, resectable HCCs with poor liver function, those associated with portal hypertension, and recurrent HCCs.

Adult↗

PubMed1992

[Hormonal regulation of PAI-1 secretion by cultured rat ovarian cells].

Rat ovarian cells produce not only plasminogen activator (tPA) but also plasminogen activator inhibitor type 1 (PAI-1), and their coordinated geneexpression induced by gonadotropins are thought to be responsible for follicular rupture. In this study, it was demonstrated that (1) theca-interstitial compartment synthesizes the majority of PAI-1 activity in the ovary before ovulation, the follicular wall may therefore serve as a specific barrier to prevent the secretion of PA into the extrafollicular compartment; (2) Granulosa cells contribute only small amount of ovarian PAI-1 activity, but synthesize most of tissue-type plasminogen activator activity involved in the process leading to ovulation: (3) Since only matured cumulus-oocyte complexes secrete high level of tPA and PAI-1, both tPA and PAI-1 activity in the conditioned medium may be used as reliable markers for evaluating oocyte quality for in vitro fertilization.

Animals↗

PubMed1992

Surgical treatment of hilar bile duct carcinoma. Clinical and pathological studies.

Resection of the extrahepatic bile tract for hilar bile duct carcinoma was performed at the PLA General Hospital, with a resectability rate of 62% (31/50) and no operative mortality. Hepatic lobectomy was performed at the same time in 16 cases (51.6%). Reoperative resections were successfully done in 5 cases; 4 cases are still living 1-4 years after the second operation. The cause of late death was mainly biliary infection due to local recurrence and bile duct obstruction. The median survival period was 15 months. 32 cases were studied pathologically, of which 27 were resected surgical specimens and 5 autopsies. The tumors were histologically classified into 4 types: papillary adenocarcinoma (6 cases); well differentiated adenocarcinoma (21); poorly differentiated adenocarcinoma (3); and simple carcinoma (2). The importance of early diagnosis of hilar bile duct carcinoma at its subclinical stage before appearance of clinical jaundice is stressed.

Adenocarcinoma↗

PubMed1991

Purification and characterization of a new isozyme of thiol:protein-disulfide oxidoreductase from rat hepatic microsomes. Relationship of this isozyme to cytosolic phosphatidylinositol-specific phospholipase C form 1A.

Thiol:protein-disulfide oxidoreductase catalyzes the GSH reduction of protein disulfides to sulfhydryls. Chromatography of solubilized hepatic microsomes on Mono Q yielded two peaks, Q-2 and Q-5, which contained all the thiol:protein-disulfide oxidoreductase activity. These were further purified by chromatofocusing giving specific activities of 14.4 and 45.9 nmol/mg of protein/min, respectively with purifications of 45.0- and 143.6-fold. Amino acids 1-18 of Q-5 were the same as previously reported for Thiol:protein-disulfide oxidoreductase (Edman, J. C., Ellis, L., Blacher, R. W., Roth, R. A., and Rutter, W. J. (1985) Nature 317, 267-270), except amino acid 1 was leucine instead of aspartate and amino acid 6 was asparagine instead of glutamate. The N-terminal amino acid sequence of Q-2 differed markedly from Q-5 but Q-2 showed 100% identity at amino acids 25-54, 258-269, 285-310, 347-350, 412-419, and 434-463 for the reported sequence of rat, hepatic, cytosolic phosphatidylinositol-specific phospholipase C form 1a (PLC) (Bennett, C. F., Balcarek, J. M., Varrichio, A., and Crooke, S. T. (1988) Nature 334, 268-270). PLC activity was found in the elution from the Mono Q column, but none was found in purified Q-2 or Q-5. Antibodies to Q-5 reacted with Q-2, but anti-Q-2 did not react with Q-5. Anti-Q-2 antibody showed immunoreactivity with 55- and 60-kDa microsomal proteins, whereas Q-5 antibody reacted with a number of microsomal proteins. Although Q-2 was immunoreactive with a polyclonal antibody to guinea pig, uterine cytosolic PLC, partially purified PLCs from rat liver cytosol did not react to this antibody. Our data would suggest that the published sequence for PLC form 1a may actually be the sequence for Q-2.

Amino Acid Sequence↗