Biomedical subjects

L Liu

Publications and source records attributed to L Liu.

At least 685 records · Page 38Linked to original sources

PubMed1998

RT-PCR study of the distribution of connexin 43 mRNA in the glomerulus and renal tubular segments.

An RT-PCR study of the distribution of connexin 43 (Cx43) mRNA in glomeruli and along the rat tubular segments was carried out to establish the differential expression of Cx43 in the different segments of the tubule, in renal regions, in isolated glomerular preparations (IGP), and in microdissected glomeruli. The mRNA level of Cx43 in macrodissected renal regions appeared in the following order: inner papilla > outer papilla and IGP > outer medulla and cortex. Among the microdissected tubules, inner medullary collecting ducts (IMCD) expressed the highest level of Cx43 mRNA, followed by the cortical collecting ducts (CCD). The proximal convoluted tubules and proximal straight tubules expressed significantly less Cx43 than the IMCD, glomeruli, and CCD. Medullary thick ascending limb and distal convoluted tubules showed the lowest level of Cx43 mRNA. The RT-PCR results of the microdissected segments correlate well with those obtained by RT-PCR of the renal regions. The high concentration of Cx43 mRNA in the IMCD together with the observation of abundant punctate immunofluorescence for Cx43 suggests that the IMCD not only expresses Cx43 mRNA but also that the mRNA is translated to Cx43 protein.

Animals↗

PubMed1998

Role of the cyclin-dependent kinase inhibitor CDKN2A in familial melanoma.

BACKGROUND: Approximately 8 to 12% of melanoma appears to be inherited in an autosomal dominant form. Although most early stage melanomas can be treated successfully by simple surgical excision, patients with advanced disease are rarely cured even with aggressive chemotherapy and/or immunotherapy. OBJECTIVE: There is now compelling evidence that germline mutations of the CDKN2A gene on chromosome 9p21 predispose to melanoma in a subset of melanoma-prone families. In this article the evidence for the role of CDKN2A in the genesis of familial melanoma is reviewed and the implications of genetic testing in families with this disease are discussed. CONCLUSION: The identification and subsequent surveillance of unaffected individuals who have a genetic predisposition to melanoma may lead to the detection of early (curable) melanomas and to a reduction in mortality.

Cell Cycle↗

PubMed1998

Compensation for D-glutamate auxotrophy of Escherichia coli WM335 by D-amino acid aminotransferase gene and regulation of murI expression.

D-glutamate, an indispensable component of peptidoglycans of bacteria, is provided by glutamate racemase in E. coli cells. Compensation for D-glutamate auxotrophy of E. coli WM335 cells lacking the glutamate racemase gene, murI, with the D-amino acid aminotransferase gene suggests that presence of a threshold concentration for the D-glutamate required by E. coli cells, as well as a regulation system for murI expression.

Alanine Transaminase↗

PubMed1998

Antagonism of central CRF systems mediates stress-induced changes in noradrenaline and serotonin turnover in rat brain regions.

The present study was conducted to test the hypothesis that central corticotropin-releasing factor (CRF) systems mediate the changes in the dynamics of brain noradrenergic and serotonergic systems induced by electric footshock stress. Serum corticosterone concentrations were determined fluorometrically and brain monoamine contents (noradrenaline, serotonin and their metabolites) in five brain regions in rats were measured by high-performance liquid chromatography with electrochemical detection 10 and 40 min after exposure to electric footshock stress for 1 hour. Intracerebroventricular administration of a CRF antagonist, alpha-helical CRF (100 micrograms), had no effect on serum corticosterone concentrations in either normal or stressed animals. However, electric footshock stress-induced increases in noradrenaline turnover were significantly reduced by the administration of alpha-helical CRF9-41, in the amygdala and septum at both time points after exposure to electric footshock stress. In contrast, electric footshock stress-induced increases in serotonin turnover in all of the brain regions were further elevated by the administration of alpha-helical CRF 9-41, in almost all of the brain regions examined. These results suggest that central CRF neuronal systems are involved in mediating the electric footshock stress-induced changes in the dynamics of brain noradrenergic and serotonergic systems in rats.

Animals↗

PubMed1998

Functional division of the retina and binocular correspondence.

Spatial vision relies on a spatial coding of object directions sensed by the retinal photoreceptors. An empirically measured constant error in this coding of perceived space is described classically as a barrel distortion involving long horizontal lines. A Cartesian retinal coordinate system is constructed to describe the transformation from object space to perceived space. This system establishes a subjective horizontal and vertical (isoelevation and isoazimuth) grid for each eye. The retinal entities that mediate subjective sense of constant elevation (horizontal) and constant azimuth (vertical) constitute the functional division of the retina, and they are described by a model with a single parameter zp, which determines the curvatures of a set of hyperbolic isopters. Empirical isoelevation positions were measured, which were described by this model. The best-fitting zp values appeared to be independent of viewing distance, similar for the two eyes of the same observer but differing significantly among observers. The functional-retinal-division model and horizontal retinal shear, as described by Helmholtz, were used to predict the spatial distributions of binocular corresponding points. The disparity field on a frontoparallel plane at a finite viewing distance showed marked asymmetry between the upper and the lower visual fields. The hyperbolic isoelevation and isoazimuth curves dramatically exaggerated this asymmetry. This theoretical disparity field provides a guideline for experiments that attempt to show the effect of binocular disparity in the periphery.

Humans↗

PubMed1998

Tricyclic pyrone analogs: a new class of microtubule-disrupting anticancer drugs effective against murine leukemia cells in vitro.

Novel 1H,7H-5a,6,8,9-tetrahydro-1-oxopyrano [4,3-b][1]benzopyrans were synthesized in Hua's laboratory (code names H5, H10, H14 and H15) and tested for their ability to prevent L1210 leukemic cells from synthesizing macromolecules and growing in vitro. The aryl groups of these tricyclic pyrone (TP) analogs are either 3, 4-dimethoxyphenyl in H5 and H15 or 3-pyridyl in H10 and H14. Since 50 M H5 and H10 both inhibit DNA synthesis and tumor cell growth by 79-100%, concentrations 25 M were used in this study to assess the structure-activity relationships for this class of compounds. At 10-25 M, H5 and H14 are more potent inhibitors of DNA, RNA and protein synthesis than H10. In contrast, at 5-25 M, H10 is much more effective than H5 and H14 at inhibiting the growth of L1210 cells over a 4-day period. Interestingly, H15 inhibits DNA synthesis as much as H10 but fails to alter tumor cell growth. This discrepancy between the ability of TPs to inhibit macromolecule synthesis and leukemic cell growth suggests that other molecular targets may be involved in the antitumor action of these drugs. Their short-term inhibition of nucleic acid synthesis is reversible following drug removal but their long-term inhibition of tumor cell growth is not. Moreover, 25 M H5 and H10 are not cytotoxic at 2 days but equally decrease cell viability at 4 days, suggesting that the potent and irreversible inhibition of cell proliferation observed 1-4 days after H10 treatment is not solely caused by drug cytotoxicity. The effectiveness of H10 as inhibitor of L1210 cell growth is comparable to that of a spectrum of representative anticancer drugs. A critical finding is that 5 M H10 blocks the polymerization of purified tubulin by 90% and, therefore, may be a novel microtubule de-stabilizing drug. Indeed, H10 inhibits tubulin polymerization and L1210 cell growth as much as 5 M of vincristine (VCR). In contrast, 5 M H5 alters neither tubulin polymerization nor tumor cell growth. The ability of H10 to disrupt microtubule dynamics indirectly suggests that TPs may be novel cell cycle-specific anticancer drugs useful for arresting mammalian cells in mitosis.

Animals↗

PubMed1998

Nutritional habits and serum lipid levels in a low-fat intake Chinese population sample.

The dietary intake of macronutrients and of specific minerals and vitamins was measured in a low-fat intake adult population living in a rural area in northwestern China. The total intake of fat amounted to +/- 12% of total energy. The P/S ratio was 2.5 and the U/S ratio 3.8. Carbohydrates provide about 75% of total energy. The mean total serum cholesterol was 148 mg/dl in men and 163 mg/dl in women. The mean HDL-cholesterol level was 38.6 mg/dl in men and 39.4 mg/dl in women, confirming the absence of a significant sex difference in HDL-cholesterol in low-fat consuming populations. Triglyceride levels were similar to those of Western populations. For both sexes taken together a positive correlation was found between the serum cholesterol level and saturated fat intake (p < 0.001) and a negative correlation with the P/S ratio (p < 0.05). Calcium intake was low: 346 mg/d in men and 245 mg/d in women.

Adult↗

PubMed1998

Discovery of ascomycin analogs with potent topical but weak systemic activity for treatment of inflammatory skin diseases.

Drug therapy for the major inflammatory skin diseases, which include atopic dermatitis, psoriasis and allergic contact dermatitis, is often inadequate due to poor efficacy, toxicity, or both. Much research has focused on the macrolactam T cell inhibitors as a promising new class of agents for immunotherapy, and medicinal chemistry efforts to design novel ascomycin analogs have produced clinically promising agents. A synthetic program to modify the ascomycin nucleus to alter its physicochemical properties and promote systemic clearance is described. A biologic screening strategy to identify analogs with reduced systemic activity and rapid pharmacokinetic elimination led to identification of the clinical candidate, ABT-281. A swine contact hypersensitivity model was used as a stringent indicator of skin penetration as human doses of topical corticosteroids produced inhibition only in the 50% range and ED50 values were 100-fold less potent than in rat. Also, cyclosporine was confirmed to be topically inactive in swine, as seen in human. ABT-281 had topical potency equal to tacrolimus (FK506) despite a severalfold lower potency for inhibiting swine T cells in vitro, consistent with superior skin penetration. ABT-281 was found to have a shorter duration of action after i.v. dosing in monkeys using an ex vivo whole blood IL-2 production assay. Systemic potency was reduced by 30-fold or more in rat popliteal lymph node hyperplasia and contact hypersensitivity assays. Following i.v. or i.p. administration in the swine contact hypersensitivity model, ABT-281 was 19- and 61-fold less potent, respectively, than FK506. Pharmacokinetic studies showed that ABT-281 had a shorter half life and higher rate of clearance than FK506 in all three species. The potent topical activity and reduced systemic exposure of ABT-281 may thus provide both efficacy and a greater margin of safety for topical therapy of skin diseases.

Administration, Topical↗

PubMed1998

[Effects of excessive zinc in fodder on brain development and abilities of learning and memory and their mechanisms in young rats].

OBJECTIVE: To study the effects of excessive zinc in fodder on brain development and abilities of learning and memory and to explore their mechanisms in young rats. METHODS: Animal models with excessive zinc were established in young Wistar rats during their lactation period. Rats were divided into five groups, Groups ZE1 and ZE2 were fed with excessive zinc, Group AL was freely fed with Flanagna fomula fodder added with zinc sulfate, Group PF was matched pair of Group ZE2 and Group ZE2R was fed with fodder same as Group AL after weaning. Ultrastructure was observed with electron microscopy, their free amino acids, nitrous oxide and somatostatin were measured with neurobiochemical methods, and their abilities to learn and memorize were examined. RESULTS: Weight of cerebrum and hippocampus in the rats reduced and zinc levels in their serum and hippocampus raised with the increase of zinc content in their fodder. Acute avoidance response (AAR) and movement in the young rats fed with excessive zinc in Groups ZE1 and ZE2 were obviously lower than in Groups AL and PF. AAR was significantly lower in Group ZE2R than that in Groups AL and PF, but significantly higher than that in Group ZE2. There was no significant difference in AAR between Groups PF and AL, but more movement was observed in them. Nitrous oxide in hippocampus raised and somatostatin decreased in Group ZE2, and total amount of excitatory and inhibitory amino acids in brain tissues raised, especially for glutamic acid. Neurones, gliocytes and organella in the CA1 region of hippocampus in the Group ZE2 showed degeneration, necrosis and rupture of synaptic bolus to varied extent. CONCLUSION: Excessive zinc in fodder could significantly affect brain development and functions in young rats with multiple mechanisms.

Animals↗

PubMed1998

Induction of immune tolerance in adult rabbits undergoing heterotopic cardiac transplantation.

OBJECTIVE: To induce experimental immune tolerance in rabbits and observe its effects on heterotopic cardiac transplantation. METHODS: Donor's splenic lymphocytes pretreated with platinum metal chelator were injected into the recipient's mesenteric-portal vein. Cyclosporin A was perfused through the donor's heart. RESULTS: The injection of donor's splenic lymphocytes before transplantation could significantly prolong the survival time of the heterotopically transplanted heart. The effect of two injections was better than that of one. Radioactive tracer studies showed that the 99mTc-HMPAO tagged lymphocytes injected into the recipient rabbit were later concentrated in the liver, though initially they were distributed in multiple organs. The induced immune tolerance was antigen-specific, and it neither affect the other immune functions of the lymphatic system prominently nor exert any harmful effect on the recipient's liver and renal functions. The perfusion of cyclosporin A through the donor heart could block the glycosyl groups, such as D-glucose, D-mannose or N-acetyl-galactosamine on the surface of the myocardial cells, thus might change the antigenic expression, effectively preventing rejection of the graft by the host, and might be considered as a new method to block graft rejection in cardiac transplantation. The combined use of the above-mentioned two methods acted on both the host and the donor, thus reducing the exposed antigens on the donor organ as well as the immune reaction against the donor antigens, and resulting in synergistic effect in inducing immune tolerance in adult rabbits, and resulting in relatively long-term survival of transplanted hearts. CONCLUSION: This report may provide the experimental basis for inducing immune tolerance in clinical transplantation.

Animals↗

PubMed1998

Detection of Fas/APO-1 in six human urogenital malignant cell lines with flow cytometry.

OBJECTIVE: To investigate the expression of Fas/APO-1 in urogenital tumor cell lines. METHODS: With direct immunofluorescence, the expression of Fas/APO-1 in six urogenital malignant cell lines and one primary in vitro cultured normal renal fibroblast was detected by flow cytometry. RESULTS: Expression of Fas/APO-1 was detected in all six urogenital tumor cell lines, but with limited positive cell percentage and relatively lower fluorescence intensity, compared with expression of Fas/APO-1 in normal control of primary in vitro cultured renal fibroblast. CONCLUSIONS: Lower expression of Fas/APO-1 in urogenital malignant cell lines than that in normal cells might be the reason for occurrence and progression of urogenital malignant tumors.

Apoptosis↗

PubMed1998

[An experimental study of prevention of peridural adhesion following laminectomy].

In order to find an ideal biological material to prevent peridural adhesion following laminectomy, 30 rabbits were used as animal model, in each of which 2 defects with a size of 1 cm x 0.5 cm were made following laminectomy of L3, L5 spine. One of the defects was covered extradurally with chitosan, gelatin foam or PLA membrane respectively, while the other defect was exposed as control. All of these animals were sacrificed on the 2nd, 4th, 6th, 8th and 10th week after operation, and the extradural fibrosis and adhesion of every animal were evaluated by gross observation and histological examinations. It was revealed that in the chitosan and PLA membrane groups, the extradural tissue was smooth without thickening and there was no fibrous proliferation or adhesion in the epidural cavity, and that in the chitosan group, the growth of fibroblast was restrained but the growth of the epithelial cells was promoted significantly, thus, wound healing was rapid. In the control group and gelatin foam group, obvious extradural fibrosis and adhesion were observed and the extradural space had almost disappeared. Therefore, it was concluded that the biodegradable PLA membrane and chitosan were both an ideal material in the prevention of postoperative epidural adhesion.

Animals↗

PubMed1998

Construction of a YAC contig encompassing G200 locus of rice via chromosome walking.

Map-based gene cloning is now widely used to isolate genes of unknown products. After fine mapping of a target gene is completed, the key step to head forward is to construct series of contigs covering the target gene through chromosome walking. To approach the final goal of cloning a wide compatible gene of rice (S5 locus), the flanking G200 marker was used as a starting point to walk. Four positive clones ranging from 240 approximately 650 kb were obtained from the rice genomic YAC library (RGP, Japan). With the ends of YAC inserts isolated by inverse-PCR, a YAC contig of 3 cM was initially built. Next, chromosome walking was performed with the two distal ends of the contig and another seven positive YAC clones were screened out, leading to the contig extending to about 8 cM.

Chromosome Walking↗

PubMed1998

[Changes of tissue oxygenation and relationship between oxygen delivery and consumption in patients with poor cardiac function undergoing valve replacement].

To study the relationship between oxygen delivery(DO2) and consumption(VO2) and tissue oxygenation in patients during cardiac valve replacement, DO2, VO2, arterial blood lactate (ABL) SvO2 were measured. The results showed a poor correlation between DO2 and VO2 and a normal tissue oxygenation before CPB. There was a good positive correlation between DO2 and VO2 within 20 h after the end of CPB(P < 0.01), and changes of ABL and SvO2 showed tissue hypoxia. The level of ABL in patients showing O2 supply-dependency was lower, and SvO2 was higher than those in 15 patients showing O2 supply-independency, respectively (P < 0.05). These data suggest that O2 supply-dependency was existed after the end of CPB, and there was a good correlation between O2 supply-dependency and ABL. It might not exclude tissue hypoxia in O2 supply-independency and normal level of SvO2.

Adult↗

PubMed1998

[Expression of telomerase in acute leukemia].

To understand the expression patterns of telomerase activity in different types of acute leukemia(AL) and during remission state, the mono-nuclear cells of different bone marrow samples were isolated by desity gradient centrifugation. Telomerase activity of the samples was assayed by telomeric repeat amplification protocol(TRAP) with the cell extracts and the TRAP products were resolved in PAGE. The results showed that the telomerase activity was at higher levels in the acute leukemia compared with the normal controls. Of the acute nonlymphocytic leukemia(ANLL), the telomerase activity presented as M2a > M5b > M1 > M3b. Of the acute lymphocytic leukemia(ALL), the activity presented as L1 > L2. The activity assayed in M2a and L2 remission was as high as that in the normal group. It indicated that the expression of telomerase was enhanced differently among the subtypes of ANLL and ALL, and was down-regulated during the AL remission. It implicates that the expression patterns of telomerase activity in AL is associated with the different proliferation states and differentiation properties of the AL cells.

Adolescent↗

PubMed1998

[Treatment of 129 patients with advanced and recurrent malignant ovarian germ cell tumor].

OBJECTIVE: To investigate the improved treatment for advanced malignant germ cell tumors of the ovary. METHODS: 129 patients with advanced and recurrent germ cell tumor of the ovary treated from 1958 to 1993 were retrospectively analyzed. The results of malignant nondysgerminomatous germ cell tumor of the ovary treated from 1958-1983 were compared with those treated with the supplement of VAC (Vincristine + ActinomycinD + Cyclophosphamide), PVB (Cisplatin + Vinblastine + Bleomycin) or BEP (Bleomycin + Etoposide + Cisplatin) combined chemotherapy from 1984-1993. RESULTS: The overall 5-year survival rate was 30% (39/129) of advanced and recurrent germ cell tumor of the ovary. The 5-year survival rates of dysgerminoma and nondysgerminomatous germ cell tumor of the ovary were 68% (19/28) and 20%(20/101), respectively. The 5-year survival rate of patients with malignant nondysgerminomatous germ cell tumor of the ovary was raised from 3% (1/40) to 42% (15/36) in the recent years. The institution of combination chemotherapy is critical for the improvement with BEP regimen as the best among the three. CONCLUSIONS: The endodermal sinus tumor of the ovary stands first in the incidence of malignant germ cell tumors of the ovary in China. To improve the prognosis of advanced malignant germ cell tumor of the ovary, BEP regimen is the most effective at present.

Adolescent↗

PubMed1998

[Short-term screening of anticarcinogenic ingredients of tea by cell biology assays].

By using a panel of short term cell biology assays, several ingredients of tea (tea pigments, caffeine, tea polysaccharide, tea polyphenols tablet and mixed tea) were screened in order to investigate their anticarcinogenic effects. The cytokinesis block micronuclei test in V79 cells induced by mitomycin, the test of metabolic cooperation between V79 and M cells and the test of growth ability of Hela cells in soft agar were used in the screening. The results showed that the six kinds of tea ingredients tested were effective in the test involved in different stages of carcinogenesis, i.e. initiation, promotion and progression. The effects of mixed tea and tea pigments were the strongest among the ingredients tested.

Animals↗

PubMed1998

[Effects of propyl gallate on histopathology of liver from mice exposed to trinitrotoluene].

In addition to the hepatocellular edema and cytoplasmic eosinophilia, sludging of blood was present in liver of mice exposed to trinitrotoluene(TNT). Single necrosis of the partical liver cell was seen occasionally. Liver damage induced by TNT was significantly alleviated by orally administrated propyl gallate(PG). Futhermore, PG can promote the regeneration of the hepatocytes following TNT-exposed mice. The results suggest that PG showed a protective effect on the histopathologic changes of liver injury induced by TNT.

Animals↗