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Biomedical subjects

Z Liu

Publications and source records attributed to Z Liu.

At least 1,171 records · Page 65Linked to original sources
PubMed1994

Erythropoietin receptor mRNA expression in human endothelial cells.

A previous report demonstrated that endothelial cells have erythropoietin receptors and respond to this hormone with enhanced proliferation. The present study demonstrates the existence of mRNA for erythropoietin receptor in human umbilical vein endothelial cells. We have reverse transcribed mRNA of endothelial cells and then used different PCR primers to amplify erythropoietin receptor target cDNA between exons 5 and 6 as well as 3-5 in addition to an internal standard DNA fragment. Correspondence of size as well as location of restriction endonuclease scission (Ava II) was used in comparing the amplified fragments of human endothelial cell erythropoietin receptor to those of two human erythroleukemia cell lines, OCIM1 and K562. No alpha- or gamma-globin mRNA was detected in endothelial cells but was readily demonstrable in OCIM1 cells. In addition, to determine whether the expression of human erythropoietin receptor on endothelial cells occurs in vivo, sections of umbilical cord and placenta were immunostained with antibodies against the extracellular portion of the receptor; the results showed strong positive staining of the vascular endothelium.

Base Sequence↗
PubMed1994

Evidence of a selective free radical degradation of heparin, mediated by cupric ion.

A free radical reaction generated by a mixture of Cu2+, hydrogen peroxide, and ascorbate causes an abrupt reduction in the anti Xa activity of heparin by about one-half, and in molecular weight by about one-third. The product, which has the characteristics of a "low molecular weight" heparin, differs little in constitution from the intact heparin, on the basis of NMR evidence that includes data for fractions of the polymers. The free radical attack appears to occur adjacent to, rather than directly upon, some residues of alpha-L-iduronic acid 2-sulfate. Substitution of the Cu2+ with Fe2+, results in a less selective alteration of the heparin. Dermatan sulfate undergoes more extensive degradation than heparin with the Cu-reagent, although its anti Xa a potency is less drastically reduced. Overall, the results are more consistent with a high degree of regioselectivity in the interaction between heparin and Cu2+ ion, than with a delocalized counter-ion interaction.

Ascorbic Acid↗
PubMed1994

A long-lasting vitamin C derivative, ascorbic acid 2-phosphate, increases myogenin gene expression and promotes differentiation in L6 muscle cells.

Hormones and growth factors are important regulators of myogenic cell differentiation, but little is known about the effect of vitamins on muscle differentiation and development. We recently showed that L-ascorbic acid 2-phosphate, a stable form of vitamin C, increased the expression of muscle-specific glucose and ion transporters. We now show the effect of L-ascorbic acid 2-phosphate on the kinetics of myogenin expression at both the mRNA and protein levels during differentiation of L6 muscle cells. At the fully differentiated stage, control and L-ascorbic acid 2-phosphate treated cultures showed the same degree of cell fusion, but L-ascorbic acid 2-phosphate treated myotubes had a larger diameter than control myotubes. During L6 cell differentiation, the amount of both myogenin mRNA and protein reached a maximal level on day 4 before full myotube formation and then declined. L-ascorbic acid 2-phosphate treated cells expressed a higher amount of myogenin at both the mRNA and protein levels on day 4 compared to untreated cultures. Ethyl-3,4-dihydroxybenzoate, an inhibitor of collagen synthesis, prevented expression of myogenin mRNA and protein in both the control and L-ascorbic acid 2-phosphate treated cells. These results demonstrate that vitamin C can promote muscle differentiation likely through the increase of myogenin expression in myogenic cells, which may in turn regulate muscle differentiation in vivo.

Animals↗
PubMed1994

Generation of selenium-containing abzyme by using chemical mutation.

A new strategy for generating abzyme was developed. Glutathione peroxidase (GPX, EC 1.11.1.9) is one of the important members of antioxidation enzyme system; it catalyzes the reductions of a variety of hydroperoxides in presence of glutathione(GSH). We have first prepared the monoclonal antibody (McAb) with GSH binding sites, then incorporated GPX catalytic group selenocystein (SeCys) into the antibody combining sites by using chemical mutation. Thus the mutated antibody displays high GPX activity, which approaches the magnitude level of native GPX, exhibits the kinetic behavior similar to native GPX, and has some advantages over native GPX.

Animals↗
PubMed1994

Tracheal autograft revascularization and transplantation.

OBJECTIVE: No vascular pedicle can be obtained reasonably to provide revascularization of a tracheal graft by direct microvascular suture. This study is a morphometric analysis of epithelial regeneration, submucosal revascularization, and mucosal thickness of isolated, tracheal segments revascularized by a lateral thoracic fascial flap. The purpose of the first part of the study is to determine the optimal period of tracheal viability after isolation and revascularization. The second part consisted of a reimplantation of the revascularized autograft into its original tracheal location. DESIGN: A tracheal segment was excised in 30 animals, and the segment was wrapped in the lateral thoracic fascia. The segments were reviewed histologically and morphometrically 2 to 28 days after graft isolation and after injection of the lateral thoracic artery with a blue silicone dye. Twelve grafts were reimplanted. Six segments were reinserted in the original direction and six segments were reinserted in the opposite direction. Tracheal airway clearance was studied by observation of the movement of carbon particles placed at different locations on the native and transplanted tracheal mucosa. MEAN OUTCOME MEASURES: Tracheal autograft revascularization and reepithelialization. RESULTS: Histologic evaluation of the revascularized grafts revealed an optimal viability of the autograft 16 to 20 days after isolation. The autografts could be reimplanted successfully after this period. This demonstrated the viability of the isolated grafts after a revascularization period of 16 days. The original direction of the mucosal clearance was preserved after reimplantation. The clearance in the opposite direction, with the 180 degrees rotated segments, however, had no influence on survival.

Anastomosis, Surgical↗
PubMed1994

Phenobarbital modifies seizure-related brain injury in the developing brain.

To investigate the potential role of drug therapy in preventing or exacerbating seizure-related brain injury in the prepubescent brain, we administered kainic acid to rats at postnatal day 35. Therapy with daily phenobarbital was started directly before or 1 day after kainic acid was administered, and was continued through postnatal day 153. Rats receiving phenobarbital had therapeutic concentrations during most of the 24-hour dosing period, but also experienced supratherapeutic peak concentrations. The animals were subsequently tested using the water maze (a measure of visuospatial memory), open field (a measure of activity level), and handling tests (a measure of emotionality). The frequency of spontaneous recurrent seizures was monitored during and after phenobarbital therapy. Kainic acid resulted in status epilepticus on postnatal day 35 in all the rats that received it but those receiving phenobarbital first manifested a shorter and less severe status epilepticus as compared to the rats given kainic acid alone. Rats starting phenobarbital immediately before kainic acid was administered did not differ from control rats on behavioral testing and had no subsequent spontaneous recurrent seizures and no histological lesions. Rats receiving kainic acid alone performed significantly poorer than did control rats in the water maze, were more aggressive, had histological lesions, and manifested spontaneous recurrent seizures. As compared to the group treated only with kainic acid, rats receiving kainic acid followed by phenobarbital at postnatal days 36 to 153 manifested similar aggressiveness and histological lesions, similar frequency of spontaneous recurrent seizures after phenobarbital taper, and even greater disturbances in memory, learning, and activity level.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1994

Cytogenetic analysis of 63 non-small cell lung carcinomas: recurrent chromosome alterations amid frequent and widespread genomic upheaval.

A detailed cytogenetic analysis of 63 non-small cell lung carcinomas (NSCLCs) was carried out for identification of recurrent chromosomal alterations. Most specimens displayed very complex karyotypes with multiple numerical and structural changes (median number, 31). Losses of chromosomes 9 (65% of cases) and 13 (71%) were the most frequent numerical changes. Loss of the Y was often observed in tumors from males. Gain of chromosome 7 was also frequent (41%). Chromosome arms 1p, 1q, 3p, 3q, 6q, 7q, 8q, 9p, 11q, 17p, and 19q were particularly prone to rearrangement. The chromosome arm most often contributing to losses was 9p (79%). Other arms that were frequently lost included 3p, 6q, 8p, 9q, 13q, 17p, 18q, 19p, 21q, 22q, and the short arm of each acrocentric chromosome. The percentage of cases with loss of 3p was significantly higher in squamous cell carcinomas (94%) than in adenocarcinomas (60%). There was also a statistically significant increase in the proportion of cases with gains of 1q, 7p, and 11q in adenocarcinomas compared to squamous cell carcinomas. Several recurrent isochromosomes and unbalanced exchanges were found. Among these was i(5p), which was observed in nine tumors, eight of which displayed adenomatous features. An i(8q) was identified in six cases, including five adenocarcinomas. Double minutes and/or homogeneously staining regions were seen in seven specimens. These data indicate that numerous chromosome alterations contribute to the pathogenesis of NSCLC and that, amid this widespread genomic disarray, recurrent abnormalities exist that could have biological and clinical implications.

Adult↗
PubMed1994

The E6 gene of human papillomavirus type 16 is sufficient for transformation of baby rat kidney cells in cotransfection with activated Ha-ras.

The transforming potential of the E6 open reading frame (ORF) of the human papillomavirus type 16 was investigated with transformation assays in cotransfections with an activated ras gene. The E6 ORF driven by the heterologous CMV promoter could fully transform baby rat kidney cells (BRK) in cooperation with ras. The transformed cells grew in soft agar and induced tumors in athymic nude mice. The E6 ORF with mutations at the splicing donor site, which only encodes the full length E6 but not E6*s, could also fully transform the BRK cells at a similar efficiency as the wild-type E6 ORF, indicating that the full-length E6 was sufficient for the transformed phenotype.

Animals↗
PubMed1994

Inhibition of CNS myelin development in vivo by implantation of anti-GalC hybridoma cells.

Implantation of hybridoma cells that secrete a monoclonal antigalactocerebroside into the dorsal columns of < or = 9-day-old rat spinal cord results in failure of development of dorsal column myelin in the vicinity of the implant. Clusters of apparently undamaged amyelinated axons remain among the hybridoma cells. Ventral myelin is unaffected. These in vivo results support antibody-mediated inhibition of myelin formation as a potential mechanism underlying failure of remyelination in multiple sclerosis.

Animals↗
PubMed1994

Nuclear antisense RNA. An efficient new method to inhibit gene expression.

We describe an efficient new antisense RNA method to inhibit gene expression. Antisense RNAs that are retained in the nucleus bind to target transcripts and appear to lead to the degradation of their targets. Antisense RNAs can be expressed and accumulated specifically in the nucleus if they are not polyadenylated at their 3' ends. In antisense expression vectors we use a cis-acting ribozyme to generate 3'-ends independently of the polyadenylation machinery and thereby inhibit transport of RNA molecules from the nucleus to the cytoplasm. We have evaluated this method in the mouse polyoma virus model system, where nuclear antisense transcripts to the viral early transcription region efficiently reduced the level of viral early-strand RNAs. Nonspecific antisense RNA had no effects on viral gene expression. In comparative studies, nuclear antisense RNAs were significantly more effective in downregulating polyoma virus early RNAs than were conventional antisense molecules, which were processed by polyadenylation.

3T3 Cells↗
PubMed1994

Regulation of glucose transport and expression of GLUT3 transporters in human circulating mononuclear cells: studies in cells from insulin-dependent diabetic and nondiabetic individuals.

We have previously shown that human circulating mononuclear cells (CMCs) respond to physiological concentrations of insulin with a rapid increase in glucose transport rate. The responding cells were found to be the monocytes, and cells derived from individuals with insulin-dependent diabetes mellitus (IDDM) had lower basal and insulin-stimulated glucose transport rates. Of interest, both cell types were found to express the GLUT1 but not the typical insulin-responsive GLUT4 transporter isoform. To further study the mechanisms responsible for stimulation of transport in these cells, we investigated (1) the response to insulin-like growth factor-I (IGF-I) and insulin-mimetic agents, and (2) the expression of other glucose transporter isoforms in CMCs of nondiabetic and IDDM individuals. The time course of insulin-stimulated glucose uptake in CMCs was rapid, reaching a plateau within 30 minutes. CMCs showed a dose-dependent and highly sensitive increase in glucose uptake to IGF-I (maximal response reached at 0.1 to 0.5 nmol/L IGF-I). The IGF-I dose-response curve was similar for CMCs of control and IDDM individuals, but both the basal and maximal response to IGF-I were lower in the diabetic group (P < .01). CMCs did not respond to vanadate, lithium, hydrogen peroxide, or short incubation (1 hour) with metformin, but glucose uptake increased in response to peroxides of vanadate and longer-duration (14 hours) metformin incubations. The glucose transporter isoforms of separated monocytes and lymphocytes were further investigated by Northern blotting of total RNA with a GLUT3-specific cDNA probe and by Western blotting of total membranes using GLUT3-specific antiserum.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Topical CTC-96 accelerates wart growth in rabbits infected with cottontail rabbit papillomavirus.

CTC-96, a cobalt containing complex, was tested as a putative topical therapeutic agent for the treatment of papillomavirus-induced tumors in our cottontail rabbit papillomavirus (CRPV)-rabbit model system. Following experimental infection of domestic rabbits with CRPV, CTC-96 was applied to infection sites twice daily, 5 days a week for a total of 8 weeks. Two levels of concentrations of aqueous CTC-96 were compared to placebo control-treated animals. With increasing dose of CTC-96 we observed tumors earlier, larger, and more often across eight infected sites on each animal.

Administration, Topical↗
PubMed1994

Mutagenic effects of heavy ion radiation in plants.

Genetic and developmental effects of heavy ions in maize and rice were investigated. Heavy particles with various charges and energies were accelerated at the BEVALAC. The frequency of occurrence of white-yellow stripes on leaves of plants developed from irradiated maize seeds increased linearly with dose, and high-LET heavy charged particles, e.g., neon, argon, and iron, were 2-12 times as effective as gamma rays in inducing this type of mutation. The effectiveness of high-LET heavy ion in (1) inhibiting rice seedling growth, (2) reducing plant fertility, (3) inducing chromosome aberration and micronuclei in root tip cells and pollen mother cells of the first generation plants developed from exposed seeds, and (4) inducing mutation in the second generation, were greater than that of low-LET gamma rays. All effects observed were dose-dependent; however, there appeared to be an optimal range of doses for inducing certain types of mutation, for example, for argon ions (400 MeV/u) at 90-100 Gy, several valuable mutant lines with favorable characters, such as semidwarf, early maturity and high yield ability, were obtained. Experimental results suggest that the potential application of heavy ions in crop improvement is promising. RFLP analysis of two semidwarf mutants induced by argon particles revealed that large DNA alterations might be involved in these mutants.

Argon↗
PubMed1994

Quantitative evaluation of neuronal loss in the dorsal hippocampus in rats with long-term pilocarpine seizures.

Systemic administration of the cholinergic agonist pilocarpine (350-400 mg/kg, i.p.) to rats induces acute behavioral and EEG status epilepticus followed by apparent complete neurological recovery. In rats receiving higher doses of pilocarpine (i.e., 380-400 mg/kg), recurrent seizures reappear 2-2.5 weeks later and continue to occur as long as the rats are kept alive. Stereological estimates of neurons in regions CA1, CA3 and the dentate granule cell layer in the dorsal hippocampus show a dose-dependent neuronal loss in the CA3 and CA1 subregions. The granule cell layer of the dentate gyrus is not affected. No progressive neuronal loss was observed in the regions studied after 3, 6 and 12 weeks during which the animals displayed spontaneous recurrent seizures. The temporal profile of the epileptic condition induced by pilocarpine and the resulting pattern of neuronal loss in the rat hippocampus are similar to those seen in many cases of human temporal lobe epilepsy. The neuronal loss is dose-dependent and primarily results from the acute pilocarpine-induced seizures as chronic seizures do not produce any measurable additional cell loss in the regions examined in the experimental model used in this study.

Animals↗
PubMed1994

Long-term behavioral deficits following pilocarpine seizures in immature rats.

The effect of seizures on subsequent long-term behavior was studied in immature rats. A similar severity of seizures were induced in 20-day old rats (P20) and 45-day old rats (P45) by intraperitoneal injections of pilocarpine at doses of 200 mg/kg and 380 mg/kg, respectively. Immediately after injection of pilocarpine, prolonged seizures with electroencephalographic ictal discharges were observed in both groups of rats. These seizures were followed by seemingly complete neurological recovery. In rats that received pilocarpine at P45 spontaneous recurrent seizures appeared after 4-10 days and persisted until completion of the study at P100. Behavioral tests performed when the rats were fully mature demonstrated that they were more aggressive when handled, more active in open field, and had deficits in learning platform position in the water maze as compared to controls. Furthermore, flurothyl seizure latency was significantly lower in pilocarpine-treated P45 rats than controls. Histology examination showed gross cell loss in the CA3 subfield of the hippocampus in four out of six pilocarpine-treated rats while no cell loss was found in control rats. Rats that received pilocarpine at P20, despite having more severe seizures than the P45 rats, had no histological lesions, did not develop spontaneous recurrent seizures, and had no significant difference in the flurothyl seizure latency test when compared to their controls. While there was no difference between the control and pilocarpine-treated rats in the handling and open field test, P20 rats receiving pilocarpine were slower in learning platform position in the water maze than the controls. Rats receiving pilocarpine at P45 performed significantly more poorly than rats treated at P20 in the water maze. These results suggest that prolonged seizures in immature rats can cause long-term behavioral deficits. However, the severity and nature of these deficits are highly age dependent.

Animals↗
PubMed1994

Semi-automatic quantitation of nucleolar organizer regions in non-Hodgkin's lymphomas.

Nucleolar organizer regions may be useful in the diagnosis and classification of non-Hodgkin's lymphomas. In this study of 46 cases we applied morphometric analysis with quantitation of physical descriptors of the nuclear profile (area, perimeter) and both number and area of stained nucleolar organizers therein enclosed to a series of lymphomas and benign lymphoid infiltrates. While nuclear outlines were manually traced small organizer regions within the nuclear profiles were semi-automatically outlined by a thresholding procedure subjected to manual override. This results in determination of number, area and perimeter of organizer regions. Data were corrected for section thickness effects and a stereologic (three-dimensional) analysis was additionally performed. We found an increase in mean number and area of nucleolar organizers per nucleus in high grade lymphomas compared to benign infiltrates and lower grade lymphomas. Volume and thickness corrected data showed a decrease in organizer number with concomitant increase in organizer volume in the higher grade lymphomas. Multivariate analysis of the cases, previously classified histologically, showed that clear resolution could be obtained, on the basis of physical descriptors, both between as well as within groups of the three tumor grades.

Humans↗
PubMed1994

Persistent cytomegalovirus infection of semen increases risk of AIDS.

To evaluate if persistent cytomegalovirus (CMV) infection of semen in human immunodeficiency virus type 1 (HIV-1) antibody-positive men increases AIDS risk, serial cultures for CMV every 3-6 months were attempted four or more times from 164 men followed 3 years. CMV was never isolated from 58 men, in 1 or 2 samples from 54 (intermittently positive), and in > or = 3 samples from 52 (persistently positive). The Cox model was used to estimate relative hazards while controlling for CD4 cell number. The relative hazard was 2.9 for those intermittently and 4.0 for those persistently positive (P < .001). No Kaposi's sarcoma occurred in culture-negative men, 3 cases (5.6%) in intermittently positive men, and 4 cases (7.7%) in persistently positive men (P < .04). Persistent CMV in semen increases the hazard of AIDS in HIV-1 antibody-positive men, possibly by activating CD4 cells to produce HIV-1. Thus, control of CMV in HIV-1-infected persons may slow progression to AIDS.

Acquired Immunodeficiency Syndrome↗