Biomedical subjects

Y Liu

Publications and source records attributed to Y Liu.

At least 523 records · Page 29Linked to original sources

PubMed2001

Barriers to getting needed services for Ryan White CARE clients.

To determine why HIV-infected persons do not access needed services, we interviewed clients of Ryan White CARE-funded agencies in San Francisco, San Mateo and Marin Counties. From July to September 1996, we interviewed 519 clients receiving services at 65 CARE-funded sites. Just over half the clients (54.5%) had at least one unmet service need in the previous four months; persons in an unstable living situation and those with lower perceived health status were significantly more likely to have an unmet need. For persons with unmet needs, agency barriers were most common (54.0%), followed by emotional issues (44.8%), lack of information (44.0%) and financial/practical barriers (19.4%). None of the client characteristics (sex, race/ethnicity, age, living situation, perceived health status and risk group) were consistently or significantly (p < 0.05) associated with specific barriers. We believe that the similarity between clients with and without unmet needs reflects the success of CARE in eliminating many barriers. However, the persistence of certain barriers and lack of sub-group-specific barriers suggests the need for individualized interventions to improve service delivery, publicize service availability and address the emotional barriers to accessing HIV-related care.

Adult↗

PubMed2001

Factors affecting nitrite build-up in nitrifying biofilm reactor.

Nitrite build-up in a nitrifying biofilm reactor for direct denitrification from the nitrite stage was investigated. At least three factors were found to influence the nitrite build-up: (i) the relative specific growth rates of Nitrosomonas to Nitrobacter, microNs/microNb in the biofilm; (ii) the relative initial ratio between Nitrosomonas and Nitrobacter on the support surface, (Mao)Ns/(Mao)Nb; (iii) the level of free ammonia, particularly at greater than 0.1 mg N/l that can be inhibitory to Nitrobacter. Results showed that without free ammonia inhibition, the first two factors determined the degree of nitrite build-up. The effect of (Mao)Ns and (Mao)Nb on nitrification kinetics were more significant than the specific growth rates of Nitrosomonas and Nitrobacter. By regulating effects of these three factors, extremely high concentrations of nitrite build-up could occur in a biofilm reactor. This offers a potential for achieving direct denitrification through a nitrate shunt.

Ammonia↗

PubMed2001

Talampanel, a novel noncompetitive AMPA antagonist, is neuroprotective after traumatic brain injury in rats.

Talampanel [(R)-7-acetyl-5-(4-aminophenyl)-8,9-dihydro-8-methyl-7H-1,3-dioxolo[4,5-h][2,3] benzodiazepine] is an orally active noncompetitive antagonist of the AMPA subtype of glutamate excitatory amino acid receptors. The purpose of this study was to determine whether treatment with talampanel would protect in a rat model of traumatic brain injury (TBI). Twenty-four hours prior to TBI, a fluid-percussion interface was positioned parasagittally over the right cerebral cortex. On the following day, fasted rats were anesthetized with 3% halothane, 70% nitrous oxide, and a balance of oxygen; mechanically ventilated and physiologically regulated; and subjected to right parieto-occipital parasagittal fluid-percussion injury (1.5-2.0 atm). The agent (talampanel, bolus infusion of 4 mg/kg followed by infusion of 4 mg/kg/h over 72 h) or vehicle was administered i.v. starting at either 30 min or 3 h after trauma. Seven days after TBI, brains were perfusion-fixed, coronal sections at various levels were digitized, and contusion areas were measured. Treatment with talampanel, when instituted 30 min after trauma, significantly reduced total contusion area compared to vehicle-treated rats (0.54 +/- 0.25 vs. 1.79 +/- 0.42 mm2, respectively). When talampanel treatment was begun at 3 h, the neuroprotective effect of the drug was lost. In addition, treatment with talampanel starting at 30 min significantly attenuated neuronal damage in all three subsectors of the hippocampal CA1 sector compared to vehicle-treated rats (normal-neuron counts, right (ipsilateral) medial CA1: 80.3 +/- 2.0 [talampanel] vs. 66.3 +/- 2.1 [vehicle] (mean +/- SEM); middle CA1: 71.5 +/- 2.0 vs. 60.3 +/- 2.2; lateral CA1: 74.5 +/- 3.0 vs. 63.0 +/- 3.2, respectively). By contrast, when talampanel treatment was begun at 3 h, normal pyramidal-neuron counts were almost identical in both groups. Our findings document that talampanel therapy instituted 30 min after trauma significantly reduces histological damage.

Animals↗

PubMed2001

Immune response to intragraft antigen in draining lymph nodes after corneal transplantation is mediated by interleukin-12.

To examine the molecular basis of immunity generated to intragraft antigens and determine whether it differs between acceptor and rejector hosts, we used a novel in vitro system to assay the T cell response to a specific antigen, ovalbumin (OVA), in the graft. OVA-containing corneas were orthotopically grafted into syngeneic or allogeneic hosts. Draining cervical lymph nodes (cLN) were assayed for OVA-specific T cell proliferation and cytokine production. In addition, cytokine production was assayed in cultures of antigen-presented cells (APC) isolated from cLN cultured with OVA-specific DO11.10 T cells and OVA. OVA-specific immunity was detected only in the draining cLN of mice following allogeneic, but not syngeneic, grafting, and this immunity was evident well before any demonstrable alloresponse in the graft. In addition, cLN cells from mice that accepted their corneal allografts produced significantly less interferon-gamma (IFN-gamma) when stimulated in culture than cells harvested from cLN of rejector hosts. Moreover, APC isolated from cLN of acceptor hosts produced significantly lower levels of IL-12. These data suggest that the induction of immunity to corneal antigens in the draining cLN occurs via an interleukin-12 (IL-12) and IFN-gamma-dependent mechanism. Targeting this process may serve as an effective immunomodulatory strategy in corneal transplantation.

Animals↗

PubMed2001

Improved intracellular delivery of oligonucleotides by square wave electroporation.

Prior studies have shown that electroporation is a simple and effective method for the introduction of oligonucleotides (ODN) into cells. In ex vivo bone marrow purging models, electroporation of ODN into cells has been associated with selective killing of human neoplastic cells while sparing hematopoietic stem cells. Prior studies used conventional electroporation methods (i.e., exponential decay) to introduce ODN into cells. Square wave electroporation allows the delivery of a more defined and regulated electrical pulse and is associated with high transfection efficiencies in a variety of systems. The current study was undertaken to determine whether square wave electroporation was more effective than exponential decay electroporation for the delivery of ODN into hematopoietic cells. Using fluorescein-tagged ODN and K562, chronic myelogenous leukemia (CML) cells, higher transfection rates were observed after square wave electroporation. In addition, c-myc antisense ODN were more effective in reducing c-myc protein when introduced by square wave electroporation, as compared with introduction by exponential decay electroporation. Square wave electroporation is thus identified as the optimal method for delivering ODN into hematopoietic cells.

Base Sequence↗

PubMed2001

Imaging in vivo brain-hormone interaction in the control of eating and obesity.

The field of neuroimaging has made great progress in the mapping of human brain function. In this article, we present a functional magnetic resonance imaging (fMRI) study on the hypothalamic regulation of satiety and its relationship with obesity. The fMRI techniques have been proven invaluable for analyzing changes in brain activity that are associated with most sensorimotor and cognitive functions. However, few studies have been successful in the delineation of the interaction between the central nervous system and the endocrine system, due to the lack of suitable mapping methods which can pinpoint the onset of changes in neuronal activity (e.g., those following eating or drug intake). We have recently introduced a new fMRI method known as temporal clustering analysis (TCA) for dynamically tracking the time course of brain activation. Along with simultaneous blood sampling for the circulating hormone levels, the fMRI techniques with TCA may provide an integrated view of the nervous and endocrine systems in vivo, and thus greatly enhance our understanding of the complex interplay between neural events and hormonal signals.

Cluster Analysis↗

PubMed2001

A Western-style diet induces benign and malignant neoplasms in the colon of normal C57Bl/6 mice.

Decreased dietary intakes of calcium, vitamin D and folic acid have been suggested as risk factors for human colon cancer. We previously fed a Western-style diet (WD) containing reduced calcium, vitamin D and increased fat content to normal C57/Bl6 mice: hyperproliferation, hyperplasia and whole crypt dysplasias developed in the colon following WD administration. Utilizing the same diet, we now also decreased the levels of several nutrients that are required for biochemical reactions involving methyl group inadequacy, i.e. folic acid, methionine, choline and vitamin B(12). Dietary levels of these nutrients were reduced to nutrient-density levels approximating those consumed by large segments of human Western populations. This further modification of the WD resulted in adenoma and carcinoma development in normal mouse colon (P < 0.04 compared with AIN-76A diet). The results indicate, for the first time, that a semi-purified rodent diet designed to mimic the human Western diet can induce colonic tumors in normal mice without carcinogen exposure.

Adenoma↗

PubMed2001

Dietary energy restriction inhibits ERK but not JNK or p38 activity in the epidermis of SENCAR mice.

Ongoing studies in our laboratory have demonstrated that dietary energy restriction (DER) inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced AP-1 transcription factor binding to DNA in the epidermis of SENCAR mice. To dissect the specific signal transduction pathways through which DER inhibits the AP-1:DNA binding, we analyzed the activities of three major MAP kinases that lead to the induction of AP-1. The changes in ERK1 and ERK2 protein expression and phosphorylation were further characterized by western blot analysis. Female SENCAR mice were pre-fed ad libitum (AL) or 40% DER diet for 8-10 weeks. The kinase activities in mouse epidermis were determined by immune complex kinase assays at 0.5, 1, 4, or 6 h following treatment with 3.2 nmol TPA to the shaved dorsal backs. ERK activity at 1 h post-TPA treatment was nearly 5-fold (P< 0.005) above basal levels in AL mice while the increase was abolished in DER mice. The TPA-induced ERK activity in AL mice was accompanied by increased phosphorylation of ERK1 and ERK2 (P< 0.05), which was abrogated in DER mice. In addition, DER mice exhibited reduced expression of total ERK1 and ERK2 and higher proportions of ERK1 and ERK2 phosphorylation in comparison with AL mice (P<0.05). JNK activity was decreased at 1 and 6 h but increased at 4 h (P<0.05) post-TPA treatment. TPA did not change p38 kinase activity at the time points tested. Neither JNK nor p38 activity was altered by DER. Taken together, our results indicated for the first time that DER blocked the TPA stimulation of ERK activity and suggested that the inhibition of TPA-induced AP-1 activity by DER is likely through inhibition of ERK but not JNK or p38 kinase pathway.

Animals↗

PubMed2001

p53 protein at the hub of cellular DNA damage response pathways through sequence-specific and non-sequence-specific DNA binding.

Our environment contains physical, chemical and pathological agents that challenge the integrity of our DNA. In addition to DNA repair, higher multicellular organisms have evolved multiple pathways of response to damage including programmed cell death-apoptosis. The p53 protein appears to sense multiple types of DNA damage and coordinate with multiple options for cellular response. The p53 protein activities depend upon its DNA binding. Specific p53 protein post-translational modifications are required for efficient sequence-specific binding and transcriptional activities. Non-sequence-specific DNA binding may involve a wide spectrum of p53 proteins and predominate as DNA damage is more severe or p53 protein is more highly induced. p53 protein is not strictly required for DNA damage sensing and repair. Rather, p53 protein may govern an apoptosis checkpoint through competition with DNA repair proteins for non-sequence-specific binding to exposed single-stranded regions in the DNA duplex. This model provides a framework for testing mechanisms of p53-mediated apoptosis dependent upon the p53 protein modification state, the level of p53 protein accumulation, the level of DNA damage and the capacity of the damaged cell to repair.

Animals↗

PubMed2001

Contrasting patterns of polymorphisms at the ABO-secretor gene (FUT2) and plasma alpha(1,3)fucosyltransferase gene (FUT6) in human populations.

The coding sequences ( approximately 1 kb) of FUT2 [ABO-Secretor type alpha(1,2)fucosyltransferase] and of FUT6 [plasma alpha(1,3)fucosyltransferase] were analyzed for allelic polymorphism by direct sequencing in five populations. The nucleotide diversities of FUT2 estimated from pairwise sequence differences were 0.0045, 0.0042, 0.0042, 0.0009, and 0.0008 in Africans, European-Africans, Iranians, Chinese, and Japanese, respectively. The nucleotide diversities of FUT6 were 0.0024, 0.0016, 0.0015, 0.0017, and 0.0020 in Africans, European-Africans, Iranians, Chinese, and Japanese, respectively. At FUT2, excesses in pairwise sequence differences compared to the number of polymorphic sites as indicated by a significantly positive Tajima's D were observed in European-Africans and in Iranians. The data do not fit expectations of the equilibrium neutral model with an infinite number of sites. On the other hand, Tajima's D's at FUT6 in each of the five populations and at FUT2 in Africans, Chinese, and Japanese were not significantly different from zero. F(ST) between the Asians and the others measured at FUT2 was higher than at FUT6. These results suggest that natural selection was responsible for the generation of the FUT2 polymorphism in European-Africans and in Iranians.

Alleles↗

PubMed2001

Changes in postural sway during a period of sustained wakefulness in male adults.

Nocturnal variations in postural sway during a period of sustained wakefulness were studied in seven healthy male adults. Postural sways with the subject's eyes open and with them closed were measured every hour from 22:00 to 04:00 h the following day. Parameters of postural sway [rectangle area (RA), root mean square of length in the anterior-posterior direction (RMSL-y), and medium-frequency-band (0.2-1.0 Hz) power of postural sway in the lateral (MF-x) and anterior-posterior (MF-y) directions] showed significant nocturnal variations. RA, RMSL-y, MF-x and MF-y increased after midnight and reached peaks at 04:00 h. Moreover, changes in RA and MF-y depended on visual conditions. The increases in RA and MF-y were larger with the eyes closed than with them open. These postural sway parameters showed positive correlations with subjectively rated sleepiness and negative correlations with electroencephalographic alpha activity. The results suggest that changes in postural sway during the night are influenced by the increase in sleepiness.

Activity Cycles↗

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

Similar pelvic abnormalities on FDG positron emission tomography of different origins.

Fluorodeoxyglucose positron emission tomography (FDG PET) has been used extensively to detect and stage various cancers. However, normal variation and inflammatory lesions may lead to false-positive interpretations of PET findings. The authors report three cases of increased pelvic FDG uptake with differing origins. Although the findings are similar, a postpartum uterus, lymphoma, and a bleeding uterus caused pelvic FDG uptake in these patients. Interestingly, of these three patients, the patient with lymphoma had the lowest level of FDG uptake. Clinical correlation is needed for the accurate interpretation of FDG-PET findings.

Adult↗

PubMed2001

Pulsed electromagnetic fields increase growth factor release by nonunion cells.

The mechanisms involved in pulsed electromagnetic field stimulation of nonunions are not known. Animal and cell culture models suggest endochondral ossification is stimulated by increasing cartilage mass and production of transforming growth factor-beta 1. For the current study, the effect of pulsed electromagnetic field stimulation on cells from human hypertrophic (n = 3) and atrophic (n = 4) nonunion tissues was examined. Cultures were placed between Helmholtz coils, and an electromagnetic field (4.5-ms bursts of 20 pulses repeating at 15 Hz) was applied to 1/2 of them 8 hours per day for 1, 2, or 4 days. There was a time-dependent increase in transforming growth factor-beta 1 in the conditioned media of treated hypertrophic nonunion cells by Day 2 and of atrophic nonunion cells by Day 4. There was no effect on cell number, [3H]-thymidine incorporation, alkaline phosphatase activity, collagen synthesis, or prostaglandin E2 and osteocalcin production. This indicates that human nonunion cells respond to pulsed electromagnetic fields in culture and that transforming growth factor-beta 1 production is an early event. The delayed response of hypertrophic and atrophic nonunion cells (> 24 hours) suggests that a cascade of regulatory events is stimulated, culminating in growth factor synthesis and release.

Adult↗

PubMed2001

Interplay between inhibition of adenosine uptake and phosphodiesterase type 3 on cardiac function by cilostazol, an agent to treat intermittent claudication.

The authors have recently shown that cilostazol, a type 3 cyclic nucleotide phosphodiesterase (PDE3) inhibitor, has a much weaker positive inotropic effect than milrinone, a PDE3 inhibitor of similar potency. They have also shown that cilostazol inhibits adenosine uptake, whereas milrinone has no such effect. This study investigated the possible cardiac functional significance of cilostazol on adenosine uptake inhibition. In isolated rabbit hearts, 10 microM of cilostazol elevated adenosine concentration in interstitial dialysate (0.16 +/- 0.01 microM, or approximately 0.81 microM in the interstitial space when adjusted for recovery rate of microdialysis) and coronary effluent (0.69 +/- 0.03 microM ). The values are significantly higher than those for 10 microM of milrinone (0.11 +/- 0.1 microM in interstitial dialysate and 0.2 +/- 0.04 microM in coronary effluent). Although cilostazol increased contractility, heart rate, and coronary flow in isolated rabbit hearts, the effect on contractility and heart rate was significantly augmented in the presence of an adenosine A 1 receptor antagonist. Conversely, an adenosine A 1 receptor agonist or an adenosine uptake inhibitor attenuated the positive inotropic effect of milrinone. These results indicate that adenosine uptake inhibition by cilostazol increases interstitial and circulatory adenosine concentration, and antagonizes PDE3 inhibition-induced contractility and heart rate increases through an adenosine A 1 receptor-mediated mechanism.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2001

Insulin-leptin-visceral fat relation during weight loss.

INTRODUCTION: The relation between insulin-leptin-visceral fat axis during weight loss has not been studied previously. AIMS: To evaluate the insulin, leptin, and abdominal adiposity relation during weight loss in patients with upper body obesity. METHODOLOGY: Twenty volunteers (7 men, 13 women) with mean age 50.6+/-6.3 (SD) and upper body obesity (weight 105.4+/-12.3 kg, BMI 35.9+/-2.5 kg/m2) were recruited. Participants were enrolled in a one-arm clinical study using a calorie-deficient diet and an escalating dose regimen of sibutramine, starting with 5 mg daily and increasing in 5-mg increments to 20 mg per day. Body weight, insulin, leptin, glucose, lipids, abdominal computed tomography (CT), and total body electrical conductance (TOBEC) were measured serially at weeks 0, 4, 8, 12, and 24. RESULTS: Eighteen patients completed the 6-month study: one man and one woman discontinued because of adverse events. With diet and sibutramine, body weight was significantly and continuously reduced throughout the 6-month study. There was a 16.0% (p = 0.0001) reduction in body weight (p < 0.001) and 22.5% (p = 0.0001) decrease in total body fat mass. Abdominal CT scans showed a 28.3% (p = 0.0001) reduction in total abdominal fat, a 26.0% (p = 0.0001) reduction in subcutaneous fat (p < 0.001), and a 31.0% (p = 0.0003) reduction in visceral fat (p < 0.001). There was a 32.0% (p = 0.0008) reduction in leptin levels and 37.9% (p = 0.0001) reduction in insulin levels between baseline and week 4, but no further significant reduction in leptin and insulin levels was observed for the duration of the study. There was a significant correlation between insulin and leptin concentrations throughout the study (p = 0.0001). Leptin was presented as a function of insulin measured at the same time. Significant associations between visceral abdominal fat, subcutaneous fat, and leptin were also observed. CONCLUSION: In this study, we found that leptin and insulin were related in weight loss. The data suggest that insulin may act as a strong regulator of leptin secretion during weight loss and that circulating leptin levels can be predicted by insulin level. Using sibutramine in conjunction with hypocaloric diet reduced body weight and decreased fat mass significantly. Visceral and subcutaneous abdominal fat depots were shown to decrease. Whether sibutramine exerts any selective reduction of visceral abdominal fat as opposed to total body fat mass will require further clinical investigation.

Adipose Tissue↗

PubMed2001

p53: a good diagnostic marker for intratubular germ cell neoplasia, unclassified.

Intratubular germ cell neoplasia, unclassified (IGCNU) is a precursor of germ cell tumors (GCT) of the testis. In routine histologic sections, neoplastic intratubular germ cells may be very few and easily overlooked. The aim of this study is two-fold: to establish the immunohistochemical pattern of expression of p53 in IGCNU and GCT and to determine whether p53 can be used as a marker for IGCNU. Resection specimens from 14 seminomas, 14 mixed germ cell tumors (MGCT), 3 embryonal carcinomas, 2 mature teratomas, 7 IGCNUs, and 11 normal testes were stained for p53. Normal germ cells and Sertoli cells of the seminiferous tubules in all normal testes were negative for p53. The tumor cells of all IGCNU cases were positive for p53. All invasive components of mixed germ cell tumors, embryonal carcinomas, and seminomas exhibited expression of p53. Mature teratoma components were negative for p53. These findings indicate that p53 is a highly sensitive marker of IGCNU and highly specific in distinguishing lesional tissue from normal seminiferous tubules. The current findings also suggest that p53 may be involved as an early step in the malignant progression of most germ cell neoplasias.

Biomarkers, Tumor↗

PubMed2001

Thermoanaerobacter tengcongensis sp. nov., a novel anaerobic, saccharolytic, thermophilic bacterium isolated from a hot spring in Tengcong, China.

A new, extremely thermophilic bacterium, designated strain MB4T, was isolated from a Chinese hot spring. The new isolate was an obligately anaerobic, rod-shaped, gram-negative, saccharolytic bacterium. Spore formation was not observed. Growth occurred at temperatures between 50 and 80 degrees C, with an optimum of around 75 degrees C; at pH values between 5.5 and 9.0, with an optimum of 7.0-7.5; and at salinities between 0 and 2.5% NaCl, with an optimum of around 0.2% NaCl. The organism utilized glucose, galactose, maltose, cellobiose, mannose, fructose, lactose, mannitol and starch. Acetate was the main end product from glucose fermentation. Thiosulfate and sulfur were reduced to hydrogen sulfide. Sulfate, sulfite and nitrate were not reduced. Growth was inhibited by hydrogen. The G+C content of the DNA was 33 mol%. Phylogenetic analyses based on the 16S rDNA sequence indicated that the isolate was a new member of the genus Thermoanaerobacter and formed a monophyletic unit within the Thermoanaerobacter cluster. Based on its phenotypic and phylogenetic characteristics, the isolate was proposed as a new species, Thermoanaerobacter tengcongensis. The type strain is MB4T (= Chinese Collection of Microorganisms AS 1.2430T = JCM 11007T).

Anaerobiosis↗