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Biomedical subjects

J Liu

Publications and source records attributed to J Liu.

At least 415 records · Page 23Linked to original sources
PubMed2001

Structure-activity of inhibition of HIV-1 integrase and virus replication by G-quartet oligonucleotides.

As novel anti-HIV agents, the G-tetrad-forming oligonucleotides have been explored for their structure-activity relations with regard to inhibition of integrase (IN) (N. Jing, Expert Opin. Investig. Drugs (2000) 9, 1777-1785). We have now developed two families of G-quartet oligonucleotides: T40217-T40222, with potential formation of a tail-to-tail G-quartet dimer, and T40224-T40227, with phosphorothioate (PT) linkages in the guanine loops. The results obtained from biophysical measurements and the assays of the inhibition of HIV-1 IN and virus replication demonstrated that an increase in the length of the G-quartet structure from a monomer (15A) to a tail-to-tail dimer (47A) does not distinctly disrupt the inhibition of HIV-1 IN activity or the inhibition of HIV-1 replication in cell cultures. G-quartet oligonucleotides were observed to induce molecular aggregation of HIV-1 IN and interrupt the binding of viral DNA to HIV-1 IN. Also, PT substitutions did not confer any advantages compared with the regular phosphodiesters for the inhibition of HIV-1 replication by intramolecular G-quartets. The G-quartet motif is the primary requirement for the remarkable nuclease resistance and pronounced biological efficacy of these oligonucleotides.

Cell Line↗
PubMed2001

Caveolin-1 expression negatively regulates cell cycle progression by inducing G(0)/G(1) arrest via a p53/p21(WAF1/Cip1)-dependent mechanism.

Caveolin-1 is a principal component of caveolae membranes in vivo. Caveolin-1 mRNA and protein expression are lost or reduced during cell transformation by activated oncogenes. Interestingly, the human caveolin-1 gene is localized to a suspected tumor suppressor locus (7q31.1). However, it remains unknown whether caveolin-1 plays any role in regulating cell cycle progression. Here, we directly demonstrate that caveolin-1 expression arrests cells in the G(0)/G(1) phase of the cell cycle. We show that serum starvation induces up-regulation of endogenous caveolin-1 and arrests cells in the G(0)/G(1) phase of the cell cycle. Moreover, targeted down-regulation of caveolin-1 induces cells to exit the G(0)/G(1) phase. Next, we constructed a green fluorescent protein-tagged caveolin-1 (Cav-1-GFP) to examine the effect of caveolin-1 expression on cell cycle regulation. We directly demonstrate that recombinant expression of Cav-1-GFP induces arrest in the G(0)/G(1) phase of the cell cycle. To examine whether caveolin-1 expression is important for modulating cell cycle progression in vivo, we expressed wild-type caveolin-1 as a transgene in mice. Analysis of primary cultures of mouse embryonic fibroblasts from caveolin-1 transgenic mice reveals that caveolin-1 induces 1) cells to exit the S phase of the cell cycle with a concomitant increase in the G(0)/G(1) population, 2) a reduction in cellular proliferation, and 3) a reduction in the DNA replication rate. Finally, we demonstrate that caveolin-1-mediated cell cycle arrest occurs through a p53/p21-dependent pathway. Taken together, our results provide the first evidence that caveolin-1 expression plays a critical role in the modulation of cell cycle progression in vivo.

Animals↗
PubMed2001

Prediction of volatile anaesthetic solubility in blood and priming fluids for extracorporeal circulation.

Volatile anaesthetics are often used during cardiopulmonary bypass (CPB). To understand the kinetics of inhaled anaesthetics during CPB, anaesthetists should understand changes in blood solubility caused by fluid use. We set out to predict the solubility of three volatile anaesthetics, desflurane, isoflurane and halothane, during CPB by determining: (i) their solubility in fresh whole blood and eight CPB priming fluids at 37 degrees C; (ii) the effect of temperature on the solubility of these anaesthetics in lactated Ringer's, gelofusin, banked blood and plasma; (iii) their solubility in different mixtures of these four priming fluids at different temperatures; and (iv) their estimated and actual solubility in blood during hypothermic CPB. We calculated solubility using a concept of volume fraction partition coefficient and compared estimated and measured solubilities. For the three anaesthetics tested, solubilities are in the order: fresh whole blood approximately = plasma > banked blood > normal saline approximately = lactated Ringer's approximately = gelofusin approximately = Haemaccel approximately = hydroxyethyl starch > mannitol. The solubilities of the anaesthetics in all priming fluids increased logarithmically at lower temperatures (P<0.05). The volume-fraction estimates of the partition coefficients were within approximately +/-20% of the measured values for all values of solubility. The corresponding estimates of solubility for CPB blood samples were between -36% and +24% of the measured values. During normothermic CPB, blood solubility of volatile anaesthetics would be unchanged when using plasma, slightly reduced when using banked blood and markedly reduced when using crystalloids and colloids.

Anesthetics, Inhalation↗
PubMed2001

Analysis of heparan sulfate oligosaccharides by nano-electrospray ionization mass spectrometry.

A highly sensitive method to identify and quantify heparan sulfate (HS) oligosaccharides by using nano-electrospray ionization mass spectrometry (nESI-MS) is described. The new approach allows us to detect approximately 50 nM of a chemically synthesized pentasaccharide with a structure of GlcNS6S-GlcA-GlcNS6S-IdoA2S-GlcNS6SOMe (3-OH pentasaccharide). Typically, solutions were infused for a total of 5 min, at an average flow rate of 30 nl/min, and the remaining sample was recovered from the nanovial. The spectra shown were obtained by summing scans for 1--3 min. Hence, our data indicated that as little as 3 x 10(-15) mole of the pentasaccharide was consumed to obtain a reasonable spectrum at the concentration as low as 50 nM. In addition, we found a linear relationship between the relative response of the molecular ion and the concentration of the analyzed 3-OH pentasaccharide, demonstrating that this approach can be used to determine the amount of HS oligosaccharides. To this end, a 3-O-sulfated pentasaccharide was prepared by incubating the 3-OH pentasaccharide with purified HS 3-O-sulfotransferase-1 and 3'-phosphoadenosine-5'-phospho[(35)S]sulfate. The resulting 3-O-sulfated pentasaccharide was purified and analyzed by nESI-MS. Based on the standard curve constructed with the 3-OH pentasaccharide, we calculated the concentration of the 3-O-sulfated pentasaccharide by the relative response. The result indicates that this value is very close to the value measured by [(35)S]sulfate radioactivity. In conclusion, nESI-MS provides both high sensitivity and the capacity to quantify HSs. This approach is likely to become a very important tool for structural analysis and sequencing of HS and heparin oligosaccharides.

Carbohydrate Sequence↗
PubMed2001

The female-to-male transsexual patient: a source of human ovarian cortical tissue for experimental use.

We demonstrated that ovaries removed from female-to-male transsexuals can be used as research material for ovarian cryopreservation, grafting and culture studies. A 21 year old female-to-male transsexual individual, who had been treated with androgens for 12 months, donated her ovaries removed in the sex reversal operation. She had normal numbers of, and proportions of, primordial (98.6%) and primary (1.4%) follicles in her ovarian cortex. After freezing and thawing the ovarian tissue was grafted to immuno-incompetent mice, which were stimulated by human recombinant FSH for 14 days, 10 weeks after transfer. Initiation of growth had occurred in the grafts in which only 79.4% of follicles were primordial, 17.1% primary, and in which there were also secondary and pre-antral follicles. Because long-term androgen treatment does not appear to cause depletion of the primordial follicle pool or affect the developmental capacity of the follicles, ovaries from individuals who undergo sex-reversal operations are an excellent source of tissue for research and maybe even for oocyte donation in the future.

Adult↗
PubMed2001

High-resolution transmission electron microscopy observation of the cross-sectional structure of reconstructed silicon (5,5,12) surface.

The cross-sectional reconstructed structure of Si (5,5,12) surface was, for the first time, observed using ultrahigh vacuum high-resolution transmission electron microscopy (UHV-HRTEM) profile view method. In the high-index region, two units of the (337) surface combine with one units of the (225) surface to complete one unit cell of (5,5,12) surface. The (337) unit at one side of the (225) unit is distinctly different from that at another side of (225) unit. The observed HRTEM images do not agree with the previous structural models of the (5,5,12) surface. We propose a new structure model of this surface using a TEM image simulation. Our model is agreement with the previously reported scanning tunnelling microscope images.

Letter↗
PubMed2001

Gonadotrophins inhibit and activin induces expression of inhibin/activin beta(B) subunit mRNA in cultured human granulosa-luteal cells.

During the human menstrual cycle, serum inhibin concentrations fluctuate in a cyclic fashion. To examine the regulation of inhibin/activin beta(B) subunit gene expression in ovarian granulosa-luteal cells, the levels of beta(B) subunit mRNA were determined in primary cultures of human granulosa-luteal cells treated with gonadotrophins and protein kinase modulators. Granulosa cells were obtained from women undergoing an IVF programme. The cells were enzymatically dispersed, separated from red blood cells, and maintained in culture for 5--10 days before addition of different agents. Northern blot analysis with specific oligonucleotide probes was performed to study inhibin/activin beta(B) subunit mRNA levels. Both LH and FSH reduced the accumulation of beta(B) subunit mRNA in a dose-dependent manner. The protein kinase A activator, (Bu)(2)cAMP, and the protein kinase inhibitor staurosporine also inhibited beta(B) subunit mRNA expression dose-dependently. Activin A increased dose-dependently beta(B) subunit mRNA expression. Our study suggests that activin-induced and gonadotrophin-inhibited beta(B) subunit expression in granulosa cells might be key factors in the transition from inhibin B to inhibin A dominance during the menstrual cycle.

Activins↗
PubMed2001

Synthesis and DNA binding properties of alkyl-linked bis(benzimidazole) compounds.

We have synthesized novel alkyl-linked bis(benzimidazole) compounds and studied their DNA binding properties by spectroscopic (absorption, CD, flow dichroism and fluorescence) and viscosity measurements. The results indicate that bis(benzimidazole) compounds interact with DNA both by intercalation and by groove binding.

Alkylation↗
PubMed2001

Application of cDNA microarray to the study of arsenic-induced liver diseases in the population of Guizhou, China.

Arsenic is an environmental toxicant and a human carcinogen. Epidemiology studies link human arsenic exposure to various diseases and cancers, including liver diseases and hepatocellular carcinoma. However, the molecular mechanisms for arsenic toxicity and carcinogenicity are poorly understood. To better understand these mechanisms, we used the human cancer cDNA expression array to profile aberrant gene expression in arsenic-exposed populations in Guizhou, China. The selected patients had a history of exposure to environmental arsenic for at least 6-10 years, and had arsenic-induced skin lesions and hepatomegaly. Samples were obtained by liver needle biopsy. Histology showed degenerative liver lesions, such as chronic inflammation, vacuolation, and focal necrosis. The University of North Carolina Hospitals provided normal human liver tissues from surgical resection or rejected transplants. Microarray was performed with total RNA from liver samples, and signal intensities were analyzed with AtlasImage software and normalized with 9 housekeeping genes. Means and SEM were calculated for statistical analysis. Approximately 60 genes (10%) were differentially expressed in arsenic-exposed human livers compared to controls. The differentially expressed genes included those involved in cell-cycle regulation, apoptosis, DNA damage response, and intermediate filaments. The observed gene alterations appear to be reflective of hepatic degenerative lesions seen in the arsenic-exposed patients. This array analysis revealed important patterns of aberrant gene expression occurring with arsenic exposure in human livers. Aberrant expressions of several genes were consistent with the results of array analysis of chronic arsenic-exposed mouse livers and chronic arsenic-transformed rat liver cells. Clearly, a variety of gene expression changes may play an integral role in arsenic hepatotoxicity and possibly carcinogenesis.

Arsenic↗
PubMed2001

Stress-related gene expression in mice treated with inorganic arsenicals.

Arsenic (As) is an environmental chemical of high concern for human health. Acute toxicity of arsenic is dependent on its chemical forms and proximity to high local arsenic concentrations is one of the mechanisms for cell death. This study was designed to define acute arsenic-induced stress-related gene expression in vivo. Mice were injected sc with either sodium arsenite [As(III), 100 micromol/kg], sodium arsenate [As(V), 300 micromol/kg], or saline. To examine stress-related gene expression, livers were removed 3 h after arsenic injection for RNA and protein extraction. The Atlas Mouse Stress/Toxicology array revealed that the expression of genes related to stress, DNA damage, and metabolism was altered by acute arsenic treatments. Expression of heme oxygenase 1 (HO-1), a hallmark for arsenic-induced stress, was increased 10-fold, along with increases in heat shock protein-60 (HSP60), DNA damage inducible protein GADD45, and the DNA excision repair protein ERCC1. Downregulation of certain cytochrome P450 enzymes occurred with arsenic treatment. Multiprobe RNase protection assay revealed the activation of the c-Jun/AP-1 transcription complex after arsenic treatments. Western blot analysis further confirmed the enhanced production of arsenic-induced stress proteins such as HO-1, HSP70, HSP90, metallothionein, the metal-responsive transcription factor MTF-1, nuclear factor kappa B and c-Jun/AP-1. Increases in caspase-1 and cytokines such as tumor necrosis factor-alpha (TNF-alpha) and macrophage inflammatory protein-2 were also evident. In summary, this study profiled the gene expression pattern in mice treated with inorganic arsenicals, which adds to our understanding of acute arsenic poisoning and toxicity.

Animals↗
PubMed2001

Mechanisms of arsenic-induced cross-tolerance to nickel cytotoxicity, genotoxicity, and apoptosis in rat liver epithelial cells.

The purpose of the present study was to investigate the mechanism of cross-tolerance to nickel in arsenic-transformed cells. Chronic arsenite-exposed (CAsE) cells (TRL 1215 cells, which had been continuously exposed to 0.5 microM arsenite for 20 or more weeks) and control TRL 1215 cells were both exposed to nickel for 24 h, and cell viability was determined by metabolic integrity. The LC(50) for nickel was 608 +/- 32 microM in CAsE cells as compared to 232 +/- 16 microM in control cells, a 2.6-fold increase. CAsE and control cells were treated with 200 microM nickel for 4 h and cellular-free radical production was measured using ESR spectrometry. Hydroxyl radical generation was decreased in CAsE cells. Thiobarbituric acid reactive substances, indicative of lipid peroxidation, and 8-oxo-2'-deoxyguanosine, indicative of oxidative DNA damage, were reduced in CAsE cells. Flow cytometric analysis using Annexin/FITC revealed that nickel-induced apoptosis was reduced in CAsE cells. CAsE cells showed generalized resistance to oxidant-induced toxicity as evidenced by a marked reduction in sensitivity to hydrogen peroxide. Interestingly, intracellular reduced glutathione (GSH) levels were significantly increased in CAsE cells, and when GSH was depleted, CAsE cells lost their nickel resistance. The mechanism of arsenic-induced cross-tolerance to cytotoxicity, genotoxicity, and apoptosis induced by nickel appears related to a generalized resistance to oxidant-induced injury, probably based, at least in part, in increased cellular GSH levels.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2001

Live offspring by in vitro fertilization of oocytes from cryopreserved primordial mouse follicles after sequential in vivo transplantation and in vitro maturation.

The objectives of the present study were to achieve 1) oocyte maturation, 2) oocyte competence of fertilization, and 3) oocyte competence of embryogenesis with oocytes from primordial follicles obtained from cryopreserved newborn mouse ovaries by using a two-step method. In the first step, frozen-thawed newborn mouse ovaries were transplanted under the kidney capsule of recipients for the initiation of growth from the primordial follicle stage on. In the second step, growing preantral follicles in the ovarian grafts were recovered and cultured. The results demonstrated that primordial follicles were able to be recruited to preantral follicles during the period of transplantation, and preantral follicles could be mechanically isolated from ovarian grafts. Under the present in vitro culture conditions, 85.8% of the isolated follicles (n = 332) from ovarian grafts survived the 12-day in vitro culture process, 84.9% of the recovered oocytes (n = 285) were germinal vesicle breakdown (GVBD)-competent, and 76% of the oocytes that underwent GVBD (n = 242) developed to the metaphase II (MII) stage. In the in vitro fertilization experiments, 75.4% of 142 inseminated MII oocytes underwent fertilization and cleavage to the 2-cell stage. Subsequently, 79.7% of the 2-cell-stage embryos (n = 69) progressed to the late morula-early blastocyst stage. Transfer of late morula-early blastocyst embryos resulted in the production of live offspring. From our experiments, it may be concluded that in vivo maturation by grafting followed by in vitro maturation of frozen-thawed primordial follicles can restore fertility in mice. This model could be useful for a similar application in the human.

Animals↗
PubMed2001

Molecular characterization of bovine prostaglandin G/H synthase-2 and regulation in uterine stromal cells.

Prostaglandin G/H synthase (PGHS) is a key rate-limiting enzyme in the prostaglandin biosynthetic pathway, and prostaglandins play a central role in the control of the reproductive cycle. The objectives of this study were to clone and characterize the primary structure of bovine PGHS-2 and to study its regulation in uterine stromal cells in vitro. The bovine PGHS-2 cDNA was cloned by a combination of reverse transcription-polymerase chain reaction and cDNA library screening. Results showed that the complete bovine PGHS-2 cDNA is composed of a 5'-untranslated region of 128 bp, an open reading frame of 1815 bp, and a 3'-untranslated region of 1565 bp containing multiple repeats (n = 11) of the Shaw-Kamen sequence 5'-ATTTA-3'. The open reading frame encodes a 604-amino acid protein that is 86-97% identical to other mammalian PGHS-2 homologs. The regulation of PGHS-2 mRNA and protein was studied in primary cultures of bovine uterine stromal cells stimulated with phorbol 12-myristate 13-acetate (PMA; 100 nM). Northern and Western blot analyses reveal a marked induction in PGHS-2 transcript (4.0 kilobases) and protein (M(r) = 72 000) after 3-12 h of PMA stimulation (P < 0.05). However, this induction was transient in nature as levels of PGHS-2 mRNA and protein returned to basal levels after 24 h of PMA stimulation. In contrast, PMA had no effect on levels of PGHS-1 (P > 0.05). The PMA-dependent induction of PGHS-2 was associated with a significant increase in prostaglandin E2 secretion in the culture media (P < 0.05). To study promoter activity of the 5'-flanking DNA region of the bovine PGHS-2 gene, the genomic fragment -1574/-2 (+1 = transcription start site), as well as a series of 5'-deletion mutants, were fused upstream of the firefly luciferase gene and transiently transfected into primary cultures of bovine uterine stromal cells. Results showed that a first promoter region located between -1574 and -492 and a second region between -88 and -39 appear to play important roles in PMA-dependent regulation of PGHS-2 promoter activity in bovine uterine cells. Thus, this study characterizes for the first time the structure of the bovine PGHS-2 transcript and the deduced amino acid sequence of its encoded protein and establishes an in vitro model to study the regulation of PGHS-2 gene expression in bovine uterine tissue.

Amino Acid Sequence↗
PubMed2001

Ovarian 'tumor' of the adrenogenital syndrome: the first reported case.

We report the case of a 36-year-old woman with congenital adrenal hyperplasia from 21-hydroxylase deficiency who had been receiving replacement therapy with corticosteroids since birth. At the age of 35 years, she developed abrupt aggravation of her virilizing symptoms and underwent an adrenalectomy and partial left oophorectomy. Persistent virilization and high testosterone levels led to right oophorectomy and completion left oophorectomy 6 months later. Each adnexa contained ovarian or paraovarian soft brown masses that on microscopic examination were identical to the testicular tumor of the adrenogenital syndrome. This represents the first reported case of this pathology (well known in the testis) in the ovary.

Adrenal Hyperplasia, Congenital↗
PubMed2001

The effect of temperature on solubility of volatile anesthetics in human tissues.

UNLABELLED: Hypothermia often occurs during surgery, a factor influencing anesthetic pharmacokinetics through its influence on solubility. Information on the tissue solubility of volatile anesthetics under hypothermia is limited. The present study supplies this information for the solubility of volatile anesthetics in human tissues. Tissue specimens of brain, heart, liver, muscle, and fat were obtained from 10 postmortem males (27 +/- 8 yr). Tissue/gas partition coefficients of desflurane, sevoflurane, enflurane, isoflurane and halothane were measured at 37 degrees C, 33 degrees C, 29 degrees C, 25 degrees C, 21 degrees C, and 17 degrees C. For each given tissue, the order of tissue/gas partition coefficient was halothane >enflurane >isoflurane >sevoflurane >desflurane. Tissue/gas partition coefficients at 37 degrees C differed significantly (P < 0.05) across drugs, except that liver/gas partition coefficients for isoflurane and enflurane did not differ. The logarithm of all tissue/gas partition coefficients increased linearly with decreasing temperature (P < 0.05). In conclusion, hypothermia increases tissue/gas partition coefficients of volatile anesthetics. The increases are proportional to those for blood/gas partition coefficients, and therefore tissue/blood partition coefficients will not change during hypothermic conditions. IMPLICATIONS: Volatile anesthetics are often used during hypothermic conditions, and tissue solubility of volatile anesthetics is an important determinant for the wash-in and washout of the anesthetics in tissue. Tissue/gas partition coefficients during hypothermia have implications for understanding the pharmacokinetics of volatile anesthetics at hypothermic conditions.

Adult↗
PubMed2001

The effect of hypothermia on isoflurane MAC in children.

BACKGROUND: Hypothermia has been shown to decrease the requirement for inhaled anesthetics in animals, but information in humans is limited. METHODS: Thirty-three unpremedicated children with congenital left-to-right shunt heart diseases undergoing open heart surgeries were assigned to one of three groups, with nasopharyngeal temperatures at the time of skin incision of 37, 34, or 31 degrees C. Anesthesia was induced and maintained with isoflurane in oxygen. End-tidal isoflurane concentration and nasopharyngeal temperature were kept at stable levels for at least 15 min before the skin incision. Isoflurane minimum alveolar concentration was determined by using the Dixon up-and-down approach. RESULTS: Isoflurane minimum alveolar concentration values were 1.69 +/- 0.14%, 1.47 +/- 0.10%, and 1.22 +/- 0.15% (mean +/- SD) at 37, 34, and 31 degrees C, respectively. CONCLUSIONS: Hypothermia decreases the isoflurane requirement in children by 5.1 degrees C.

Anesthesia, Inhalation↗
PubMed2001

Rhenium-188 HEDP to treat painful bone metastases.

PURPOSE: Rhenium-188 hydroxyethylidine diphosphonate (HEDP) is a new and attractive radiopharmaceutical that localizes in skeletal metastases and emits beta particles that may be therapeutically beneficial. In this study, the therapeutic efficacy of Re-188 HEDP was investigated in an uncontrolled initial trial of 61 patients with different types of advanced cancer for the palliation of painful bone metastases. MATERIALS AND METHODS: Sixty-one patients with painful bone metastases of lung, prostate, breast, renal, rhinopharyngeal, and bladder cancers were treated with 1.1 GBq (31 mCi) to 6.9 GBq (188 mCi) Re-188 HEDP. After treatment, the patients were followed at weekly intervals for the first 2 months and monthly thereafter for as long as 1 year. Hematologic function tests were also performed before and after treatment for 6 weeks. Pain responses were scored according to a three-point pain-rating scale as complete, significant, and minimal. RESULTS: Prompt and significant relief of bone pain occurred in 80% of patients overall. Of the specific tumor types, pain relief was achieved in 77% of patients with lung cancer, in 80% with prostate cancer, in 83% with breast cancer, in 100% with bladder cancer, in 50% with renal cancer, in 50% with rhinopharyngeal cancer, and in 87% of patients with other tumor types, with no severe side effects or hematopoietic toxicity. CONCLUSION: This large clinical trial verified that Re-188 HEDP is a useful radiopharmaceutical agent to treat painful bone metastases from various tumor types.

Bone Neoplasms↗