Biomedical subjects

F Li

Publications and source records attributed to F Li.

At least 397 records · Page 22Linked to original sources

PubMed1997

Endothelial cells exhibit differential chemokinetic and mitogenic responsiveness to alpha-thrombin.

Rapid regeneration of the endothelium is a critical component of vascular wall repair because limitations of this process enhance early thrombotic and vasospastic complications, as well as late sequelae of recurrent lesion formation. We have postulated that direct activation of the thrombin receptor initiates both mitogenic and chemokinetic endothelial behavior which facilitates intimal repair. To characterize the role of the thrombin receptor in human endothelial cell (EC) proliferation and migration, we investigated the effects of both alpha-thrombin (0.5-10 U/ml) and its receptor-activating peptide (TRAP; 1-100 microM). Responses of human aortic (HAEC) and umbilical vein (HUVEC) were characterized using [3H]thymidine and 61Cr microcarrier bead assays of proliferation and migration, respectively. Expression of motility-related genes was evaluated using a ribonuclease protection assay. Thrombin exerts both of its chemokinetic and mitogenic effects differentially in human endothelial cells. Following 2 or 4 days in culture, HUVEC proliferation increased two- to threefold after exposure to thrombin, primarily in the low concentration range (P < 0.05). However, HACE proliferation was inhibited up to 50% after a 4-day incubation period (P < 0.005). These mitogenic effects, including the inhibition of aortic endothelial cell proliferation, were reproduced, in part, by thrombin receptor activation with TRAP. In contrast, thrombin stimulates migratory responses in HAEC, but not HUVEC. However, this behavior was not reproduced by TRAP. It is noteworthy that urokinase-plasminogen activator (u-PA) expression was much more strongly expressed in migrating HAEC than in the HUVEC population. Moreover, when stimulated with thrombin, u-PA gene expression was significantly augmented in HAEC. It has been speculated that an effective human thrombin receptor (HTR) antagonist may reduce the proliferation of vascular smooth muscle cells and the development of a restenotic lesion following arterial wall injury. Our data suggest that such an inhibitor will likely also accelerate intimal regeneration through a dominant effect on limiting the HTR inhibitory effect on endothelial proliferation.

Amino Acid Sequence↗

PubMed1997

Hippocampal pathology in diffuse Lewy body disease using ubiquitin immunohistochemistry.

Various ubiquitin-positive structures in the hippocampus in diffuse Lewy body disease (n=12) and non-demented aged subjects (n=3) were investigated immunohistochemically. These structures were composed of ubiquitin-positive granular structures (UPG), ubiquitin-positive neuritic structures (UPN), spheroidal structures, neuritic plaques, neurofibrillary tangles (NFT), Lewy bodies (LB) and ubiquitin-positive neurons. UPG, UPN, spheroidal structures and neuritic plaques were distributed with special reference to the hippocampal pathway assumed in this study. This pathway was thought to run along the stratum oriens, mostly perforating the stratum pyramidale at many sites of the subiculum and CA1-3, and to end partly in the CA2-3 and the subiculum of the uncus (UPG or UPN). After perforating the stratum pyramidale and giving off terminal branches (ubiquitin-positive neurons or neuritic plaques with degenerative neurites), it was thought to run along the stratum radiatum and continue along the stratum moleculare of the dentate gyrus, forming synapses with the apical dendrites from the stratum pyramidale and the stratum granulosum (spheroidal structures or neuritic plaques). These findings suggest that many of the ubiquitin-positive structures may be caused by degeneration of terminal or distal axons of this pathway. NFT and LB also had a somewhat orderly distribution with reference to this pathway.

Aged↗

PubMed1997

Synthesis and progestational activity of 16-methylene-17 alpha-hydroxy-19-norpregn-4-ene-3,20-dione and its derivatives.

16-Methylene-17 alpha-hydroxy-19-norpregn-4-ene-3,20-dione 1 and its 17 alpha-acylated derivatives were synthesized. The length of the 17 alpha-side-chain ranges from C2-C6. As anticipated, compound 1 did not show any progestational activity or receptor binding activity; whereas, the acylated compounds, especially the butyrate, showed remarkable ability to bind to progesterone receptors. These compounds also showed progestational activity in an in vitro T47D cell culture assay in which progestins increase alkaline phosphatase activity and in an in vivo ovulation inhibition assay. All of the compounds synthesized were without estrogenic activities. The results showed that acylation of 16-methylene-17 alpha-hydroxy-19-norprogesterone can increase progestational activity. The progestational activities of these compounds varied with the 17 alpha-side chain.

Animals↗

PubMed1997

High level expression of the capsid protein of hepatitis E virus in diverse eukaryotic cells using the Semliki Forest virus replicon.

The capsid protein of hepatitis E virus (HEV) is encoded by open reading frame 2 (ORF 2) and exhibits variable processing when expressed in insect and COS cells, but nothing is known of its processing in cells relevant to its replication. The full-length ORF 2 protein was expressed at high levels in mammalian cells by insertion of ORF 2 in the Semliki Forest virus (SFV) replicon to generate rSFV/HEV ORF 2K. Expression of the capsid protein was detected readily by metabolic labelling and indirect immunofluorescence in BHK-21 cells transfected with RNA transcripts derived from rSFV/HEV ORF 2K. ORF 2 protein was also expressed at high levels in cells of diverse origin, including liver-derived cell lines Huh7 and HepG2, following infection with recombinant virus derived from cotransfection of BHK-21 cells with the rSFV/HEV ORF 2K and helper SFV replicon RNAs. The addition of hypertonic KCl during metabolic labelling reduced the level of host cell protein synthesis and enhanced the detection of intermediates in ORF 2 protein processing. The wide host range and high level expression directed by SFV replicon particles has particular utility in the analysis of cell-specific factors in the protein processing and assembly of non-cultivable viruses such as HEV.

Animals↗

PubMed1997

Mucosal immunization with a DNA vaccine induces immune responses against HIV-1 at a mucosal site.

Mucosal immunity is the first defense system in protection against mucosal infection by sexually transmitted diseases and subsequent systemic dissemination of infection. Development of vaccines which can induce protective mucosal immunity would have great promise for preventing sexually transmitted diseases including AIDS. DNA vaccines have recently shown certain advantages over other types of vaccines in safety and elicitation of specific immune responses. We have hypothesized that direct delivery of a DNA plasmid coding the HIV-1 envelope (pcMN160) via mucosal routes will stimulate mucosal immunity against HIV-1. The expression of DNA plasmid inoculated intravaginally was detected in various tissues. Intravaginal inoculation of pcMN160 elicits production of vaginal immunoglobulins which specifically bind to the HIV-1 envelope and neutralize HIV-1 infectivity in vitro. These results indicate the feasibility of inducing mucosal immunity following mucosal inoculation of DNA vaccines. When coupled with systemic inoculation of appropriate DNA constructs, effective mucosal and systemic immunity may be generated.

AIDS Vaccines↗

PubMed1997

Frequency of food intake and natural dietary components are potent modulators of bone resorption and bone mass in rats.

Prevention of low bone mass is important to reduce the incidence of osteoporotic fractures. In this report evidence is provided that feeding habits per se, that is, increased frequency of food intake as well as a diet containing soy and other raw components, decrease bone resorption and increase bone mass in growing rats. Interim results after 6 weeks indicate that food fractionation and natural dietary components are both capable of inhibiting trabecular bone loss in aged rats. These interim results indicate that the effect of both dietary interventions are additive and together are capable of nearly completely blunting the age-dependent loss of trabecular bone mineral density. These dietary manipulations are, however, only partially effective in inhibiting the strongly increased loss of trabecular bone mineral density induced by estrogen deprivation. The fact that the natural dietary components are not more effective in ovariectomized rats as compared to intact females confirms our contention that these components may not operate by mimicking the effect of estradiol. Whether bone mass in humans is also under the control of dietary habits is not known. If so, an increased frequency of meals of appropriate composition may be used to prevent osteoporosis.

Animals↗

PubMed1997

Application of a novel fluorescence probe in the determination of nucleic acids.

A novel fluorimetric method has been developed for rapid determination of DNA and RNA with hypocrellin A (HA) as a fluorescence probe, based on the fluorescence enhancement of HA in the presence of DNA or RNA. Maximum fluorescence is produced in the pH range 3.4-4.0, with maximum excitation and emission wavelengths at 470 and 600 nm, respectively. Under optimal conditions, the calibration graphs are linear over the range 0-200.0 ng cm-3 for calf thymus DNA and 13.0-200.0 ng cm-3 for yeast RNA, respectively. The corresponding detection limits are 5.0 ng cm-3 for calf thymus DNA and 13.0 ng cm-3 for yeast RNA. The relative standard deviation of six replicate measurements is 4.5% for 100 ng cm-3 calf thymus DNA. DNA could be determined in the presence of 20% m/m yeast RNA. The mechanism for the binding of HA to DNA is also studied.

DNA↗

PubMed1997

Helping behaviors and the perception of helping intentions among Chinese students.

A questionnaire survey explored the kinds of helping behaviors given and received by Chinese college students and the kinds of explanations offered for these behaviors. Helping behaviors reported by the Chinese students paralleled those of U.S. college students in McGuire (1994); the behaviors were sorted, according to her typology, into casual, substantial personal, emotional, and emergency helping. Four categories of perceived intentions behind helping behaviors were identified: altruistic, normative, relationship, and exchange.

Adolescent↗

PubMed1997

Lung nodule conspicuity using unsharp mask filters with storage-phosphor-based computed radiography.

PURPOSE: To compare the performance of various types of unsharp mask filter applied in storage-phosphor-based computed radiography (SR), and to improve the detection of faint nodules of the lung cancer type. MATERIAL AND METHODS: A total of 120 SR radiographs were obtained by means of an anthropomorphous chest phantom and a combination of 3 types of small simulated nodule (5-mm sphere-shaped, and 5-mm and 10-mm hemisphere-shaped) placed on the phantom's surface. Eight combinations of nodule site were selected from 16 predetermined chosen sites, and 5 types of parameter were used for unsharp mask filtering. Eight observers evaluated the images, and the detectability of the lung nodules was evaluated from the images by a ROC analysis. RESULTS: The visibility of the 10-mm hemispherical nodules was nearly equivalent at each site when 5 types of unsharp mask filter were used. The detection of the 5-mm nodules with mid-frequency suppressing and very-low-frequency enhancing filters was better than with a conventional (department standard) mid-frequency enhancing filter. CONCLUSION: Mid-frequency suppressing versions of the filter helped to demonstrate faint nodular opacity, which is often shown by early bronchogenic carcinoma. This filter could replace conventional filters in the detection of lung nodules.

Carcinoma, Bronchogenic↗

PubMed1997

Effect of calcium intake and physical activity level on bone mass and turnover in healthy, white, postmenopausal women.

Calcium intake and physical activity level (PAL) were assessed by questionnaire in 124 healthy women aged 52-62 y to determine the effect of calcium intake and PAL on bone mass and turnover. Four groups were identified according to their different reported calcium intakes and PALs. Bone mineral density (BMD) at the spine, hip, and left os calcis was measured together with total bone mineral content (TBMC) with dual-energy X-ray absorptiometry. Bone formation and resorption biochemical markers were measured in fasting samples of blood and urine. Women with the highest calcium intakes and PALs had the highest BMD at all sites compared with those with the lowest calcium intakes and PALs (P < 0.001). Calcium intake and PAL were positively correlated with BMD at all sites. Bone turnover markers did not explain the variation in bone mass between groups. In stepwise-multiple-regression analysis only calcium intake, physical activity, age, or weight remained as independent predictors of BMD and TBMC. When subjects were divided by past PALs, calcium intake and PAL were second to age and weight in their influence on spinal and hip BMD, but remained influential on the os calcis and whole body. We conclude that current high calcium intakes and PALs influence BMD at the os calcis and TBMC and protect bone mass in women 5-12 y postmenopausal at all measured sites, including the spine and hip. This finding does not exclude the possibility of past influences of calcium and activity on bone mass.

Biomarkers↗

PubMed1997

Delayed triphenyltetrazolium chloride staining remains useful for evaluating cerebral infarct volume in a rat stroke model.

Sixteen of 24 Sprague-Dawley rats with permanent middle cerebral artery occlusion for 24 hours were subjected to immediate or 8-hour delayed 2,3,5-triphenyltetrazolium chloride (TTC) staining (n = 8 at each time point); the other 8 animals were subjected to immediate or 8-hour delayed measurement of succinate dehydrogenase activity (n = 4 at each time point). The TTC staining was of good quality good in all animals, and the infarcted region could be distinguished easily from normal tissue. There was no significant difference in corrected infarct volume between the two groups (263.8 +/- 43.1 versus 264.4 +/- 54.8 mm3 [mean +/- standard deviation]). The activity of succinate dehydrogenase was not significantly different when normal or infarcted tissue was measured immediately after death or with an 8 hour delay, although less activity was detected at both time points in the infarcted tissue. These results demonstrate that an 8-hour delay of TTC staining is reliable for evaluating brain infarct volume in a rat stroke model and this probably is attributable to the slow deterioration of mitochondrial enzyme activity in nonischemic brain over this time period.

Animals↗

PubMed1997

Factors affecting the radiologic appearance of peripheral bronchogenic carcinomas.

The use of high-resolution computed tomography and magnetic resonance imaging have allowed the detailed description of morphologic findings associated with lung cancer. In particular, the desmoplastic response of lung tissue to tumor growth has not been adequately described. This article reviews roentgenologic and pathologic correlations of primary lung carcinomas. An irregular or indistinct tumor margin may be caused by tumor infiltration, an irregular desmoplastic response to the tumor growth, or irregular contraction in the central portion of the tumor. Solid tumor growth, on the other hand, may be associated with a well-defined tumor margin, with or without displacement of adjacent anatomical structures.

Adenocarcinoma↗

PubMed1997

Identification of noncytopathic equine rhinovirus 1 as a cause of acute febrile respiratory disease in horses.

Equine rhinovirus 1 (ERhV1) is a recognized cause of acute febrile respiratory disease in horse, although the virus is rarely isolated from such animals, despite seroprevalence rates as high as 50% in some horse populations. Recently, ERhV1 has been shown to be most closely related to foot-and-mouth disease virus, raising questions as to its disease associations in horses. We report that ERhV1 infection was the likely cause of two separate outbreaks of severe febrile respiratory disease which involved more than 20 horses. Attempts to isolate ErhV1 from nasopharyngeal swabs by conventional cell culture methods were unsuccessful, in that cytopathology was not observed. Viral antigen was detected by immunofluorescence assay in the cytoplasm of cells infected with 10 of 15 nasopharyngeal swab samples, indicating the presence and presumably replication of ERhV1. A rise in serum neutralizing antibody titer between acute- and convalescent-phase sera confirmed that ERhV1 was causatively associated with one of the outbreaks. ERhV1 RNA was detected in nasopharyngeal swabs collected from all horses during the acute phase of disease by reverse transcription-PCR. Nucleotide sequencing of amplified products showed that within each outbreak a single strain of ERhV1 was involved but that distinct viruses were involved in each outbreak. A retrospective study of samples from nine other outbreaks of respiratory disease in horses suggested ERhV1 etiology in at least two of these. We conclude that the relative importance of ERhV1 as a cause of acute febrile respiratory disease in horses has been underestimated due to failure in many instances to isolate virus by conventional cell culture methods.

Acute Disease↗

PubMed1997

Hyperplasia and hypertrophy of chicken cardiac myocytes during posthatching development.

For characterization of the growth pattern of cardiac myocytes during posthatching development, cardiac myocytes were enzymatically isolated from the ventricles of 1-, 15-, 29-, and 42-day-old chickens for measurement of myocyte nucleation, length, width, volume, and number, and for immunolabeling of cytoskeletal proteins. Ventricular myocyte number increased 156% from day 1 to day 42. Average cell volume increased more than 400%, and myocytes lengthened 125%, but cell width only increased 53% during this period. All myocytes were mononucleated at day 1. At day 15, 18% of myocytes became binucleated with < 1% of myocytes containing more than two nuclei. Interestingly, binucleated myocytes were able to divide with two nuclei going through mitosis at the same time. As demonstrated by staining with tubulin and alpha-actinin antibodies, two mitotic spindles and two cleavage furrows were formed in dividing binucleated myocytes. At day 42, binucleated myocytes increased to 44% with 11% of myocytes containing more than two nuclei. Sarcomeric alpha-actinin was partially disassembled in prometaphase and was reorganized into regular Z lines of sarcomeres in telophase. Desmin was disassembled in prophase and was reassembled during late telophase. These results suggest that chicken myocytes undergo hypertrophy and continue to proliferate during posthatching maturation, although it is currently believed that myocytes of all vertebrates withdraw from the cell cycle shortly after birth. We provide direct evidence for the first time of in vivo myocyte division in 6-wk-old chicken hearts.

Aging↗

PubMed1997

Differing regulation of major histocompatibility class II and adhesion molecules on human umbilical vein endothelial cells by serotonin.

Major histocompatibility class II molecules (MHC class II), whose biosynthesis and expression by endothelial cells can be induced by gamma-interferon (IFN-gamma), play a major role in antigen recognition and subsequent cell-cell interactions involved in the initiation of immune responses. Adhesion molecules such as E-selectin and intercellular adhesion molecules (ICAM-1), whose biosynthesis and membrane expression by endothelial cells is regulated by proinflammatory cytokines (IL-1 and TNF), are necessary for the attachment and subsequent extravasation of leukocytes into the surrounding tissue. In the present study, the effects of preformed inflammatory mediators (histamine and serotonin) on the induction and expression of MHC class II, E-selectin, and ICAM-1 molecules by human umbilical vein endothelial cells were examined. Serotonin but not histamine was found to significantly inhibit in a dose-response fashion the induction and expression of MHC class II molecules. Inhibition occurred when it was added 24 h before, at the same time (most effective), or 24 h after IFN-gamma stimulation. No enhancement or stimulation of MHC class II biosynthesis could be detected using moderate or low concentration of either histamine or serotonin alone. In contrast to MHC class II molecules, neither serotonin nor histamine blocked the induction and biosynthesis of E-selectin and ICAM-1 molecules as detected by specific H18/7 and RR1/1 monoclonal antibodies, respectively, using flow cytometry. These findings suggest that serotonin but not histamine can assist in regulating the induction and expression of MHC class II molecules. Failure to block biosynthesis of E-selectin and ICAM-1 induced by TNF-alpha and IL-1 beta indicates the inhibitory effect exerted by serotonin was selective in nature.

Cell Adhesion Molecules↗

PubMed1997

Synergistic effects of citicoline and MK-801 in temporary experimental focal ischemia in rats.

BACKGROUND AND PURPOSE: Citicoline, a naturally occurring precursor of phosphatidylcholine, is neuroprotective and is currently being assessed in clinical trials. To evaluate potential synergistic neuroprotective effects of prolonged citicoline treatment and early N-methyl-D-aspartate (NMDA) antagonist therapy, suboptimal treatment regimens of citicoline and MK-801 were tested alone and in combination in a rat model of temporary focal ischemia. METHODS: Four groups of Sprague-Dawley rats (n = 12 per group) underwent 90 minutes of temporary middle cerebral artery occlusion (MCAO) with the suture model. Animals were randomly and blindly assigned to one of four treatment groups: (1) saline, vehicle; (2) MK-801, 0.5 mg/kg IV bolus at 60 minutes after MCAO followed by saline 1 mL/kg IP daily for 7 days; (3) saline IV at 60 minutes after MCAO followed by citicoline 250 mg/kg IP daily for 7 days; or (4) both MK-801 and citicoline (daily for 7 days) active treatment. Triphenyltetrazolium chloride staining was used to assess postmortem infarct volume. Neurological scores were determined daily. RESULTS: Premature mortality between days 2 and 4 was 33.3% in group 1, 41.7% in groups 2 and 3, and 25.0% in group 4. Mean corrected infarct volume was significantly reduced in group 4 compared with the others (175.2 +/- 89.3 mm3 in group 1, 179.1 +/- 78.5 mm3 in group 2, 163.9 +/- 73.7 mm3 in group 3, and 84.7 +/- 56.8 mm3 in group 4 [P < .02, ANOVA and P < .05, Scheffé's test for group 1 versus group 4]). Mean infarct volume in animals dying prematurely was significantly (P < .05, Student's t test) larger in group 1 than those surviving for 7 days (247.2 +/- 89.5 versus 139.2 +/- 68.2 mm3), but there was no significant difference in infarct volume in groups 2, 3, and 4 between animals dying prematurely and those surviving for 7 days. CONCLUSIONS: These results demonstrate synergistic neuroprotective effects of citicoline and an NMDA antagonist in temporary experimental focal ischemia.

Animals↗

PubMed1997

Age differences in locus of control and self-monitoring in China.

Locus of control and self-monitoring were measured in three age groups in Changchun, northeastern China: 164 junior high school students (12-15 yr.), 121 college students (16-26 yr.), and 46 adults (29-57 yr.). Analysis indicated that adults and college students scored higher on locus of control (Ms = 10.0 and 9.2, scores indicating the number of external control beliefs affirmed) than high school students (M = 6.1) and that adults scored lower on self-monitoring (M = 8.7) than college and high school students (Ms = 11.6 and 10.6). Such differences seem attributable to the interaction between individual development and some societal factors that are believed to foster external control beliefs and propensity to self-monitoring.

Adolescent↗

PubMed1997

[Effects of exposure to hypoxia on the skin temperature and glycogen content of frostbitten feet in rabbits].

Effect of exposure to acute hypoxia and hypoxia for 2 weeks on the skin temperature and content of glycogen of frostbitten feet in rabbits were observed. The results showed that the skin temperatures and content of glycogen were decreased in frostbite at normoxia (FN) group frostbite during acute hypoxia (FAH) group and frostbite hypoxia for 2 weeks (FH-2w) group. After treatment with warm chlorhexidine immersion the skin temperature and glycogen content in treated feet of FN and FAH group were increased, as compared with untreated feet. However, there was no difference between treated and untreated feet in FH-2w group, suggesting that there may be severe disturbance of blood circulation on frostbitten feet under this condition.

Animals↗