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Biomedical subjects

A Li

Publications and source records attributed to A Li.

At least 73 records · Page 4Linked to original sources
PubMed2001

CO2 dialysis in the medullary raphe of the rat increases ventilation in sleep.

Central chemoreceptors are widespread within the brain stem. We hypothesize that function at different sites varies with arousal state. In unanesthetized rats, we produced focal acidification at single sites by means of microdialysis using artificial cerebrospinal fluid equilibrated with 25% CO2. Tissue acidosis, measured under anesthesia, is equivalent to that observed with 63 Torr end-tidal PCO2 and is limited to 600 microm. Focal acidification of the retrotrapezoid nucleus increased ventilation by 24% only in wakefulness via an increase in tidal volume (Li A, Randall M, and Nattie E. J Appl Physiol 87: 910-919, 1999). In this study of the medullary raphe, the effect of such focal acidification was in sleep (defined by electroencephalographic and electromyographic criteria): ventilation and frequency increased by 15-20% in non-rapid eye movement sleep, and frequency increased by 15% in rapid eye movement sleep. There was no effect in wakefulness. Chemoreception in the medullary raphe appears to be responsive in sleep. Central chemoreceptors at two different locations appear to vary in effectiveness with arousal state.

Acidosis↗
PubMed2001

Importance of color in the segmentation of variegated surfaces.

We examined how variations in color and brightness are used by the visual system in distinguishing textured surfaces that differed in their first- or second-order statistics. Observers viewed a 32 x 32 array containing two types of square elements differing in chromaticity or luminance or both. The spatial distributions of the two kinds of elements were varied within the array until observers could distinguish two juxtaposed regions. At low but not at high contrast, observers are better able to distinguish regions when the elements differ only in chromaticity than when they differ only in luminance. The advantage of color at low contrasts results from the greater visibility of the arrays defined by color variation. An observer's capacity to distinguish textures defined by variations in first-order chromatic statistics is little affected by the addition of achromatic noise but is more affected by the addition of chromatic noise. The relative robustness of chromatic cues in the face of achromatic noise leaves the visual system well equipped to exploit color variations in segmenting complex scenes, even in the presence of variations in brightness. This capacity seems to depend on mechanisms that sum over large regions: When surfaces differ in their second-order statistics and cannot be distinguished by mechanisms that sum over large regions, the advantage of color is much diminished.

Artifacts↗
PubMed2001

Veridicality of three-dimensional shape perception predicted from amplitude spectra of natural textures.

We show that the amplitude spectrum of a texture pattern, regardless of its phase spectrum, can be used to predict whether the pattern will convey the veridical three-dimensional (3-D) shape of the surface on which it lies. Patterns from the Brodatz collection of natural textures were overlaid on a flat surface that was then corrugated in depth and projected in perspective. Perceived ordinal shapes, reconstructed from a series of local relative depth judgments, showed that only about a third of the patterns conveyed veridical shape. The phase structure of each pattern was then randomized. Simulated concavities and convexities were presented for both the Brodatz and the phase-randomized patterns in a global shape identification task. The concordance between the shapes perceived from the Brodatz patterns and their phase-randomized versions was 80-88%, showing that the capacity for a pattern to correctly convey concavities and convexities is independent of phase information and that the amplitude spectrum contains all the information required to determine whether a pattern will convey veridical 3-D shape. A measure of the discrete oriented energy centered on the axis of maximum curvature was successful in identifying textures that convey veridical shape.

Contrast Sensitivity↗
PubMed2001

[Study on the effects of DNA damage induced by cigarette smoke in male mice testicular cells using comet assay].

The mainstream whole smoke was collected using atmosphere collector-U shape glass plate absorption tube with poly-hole, and both dimethyl sulfoxide(DMSO) and phosphate buffer solution (PBS) were used as absorbents respectively. Comet assay was used to detect the effects of DNA damage of the two solutions of cigarette smoke in male mice testicular cells. The results showed that both the two solutions of cigarette smoke contained some DNA damage agents that could induce the DNA single strand breakage in male mice testicular cells. Besides, the solution of cigarette smoke absorbed by DMSO had stronger cytotoxicity and genotoxicity than the solution of cigarette smoke absorbed by PBS. The research also suggested that collecting cigarette smoke like this paper and detecting DNA damage effects using comet assay might be an ideal measure in studying male reproducible toxicity.

Animals↗
PubMed2001

[Extraction technology of Fructus Psoraleae with orthogonal test].

The extraction conditions of Fructus Psoraleae were studied with orthogonal test, taking the contents of psoralen and isopsoralen as indexes and smesh degree, alcohol concentration, alcohol volume, immersion time and immersion times as factors. The results showed the optimal extraction process is pulverizing the herbs into 20 meshes powder, 6 times volume of 55% alcohol immersed three times and two days every time.

Chemistry, Pharmaceutical↗
PubMed2001

Recombinant tissue factor pathway inhibitor enhances the binding of factor Xa to human monocytes.

Tissue factor pathway inhibitor (TFPI) is a kunitz-type inhibitor of activated factor X (Xa). TFPI was reported to mediate Xa binding to a few of carcinoma cell lines. In this study it was observed that the Xa activity associated with human peripheral blood mononuclear cells (PBMC) incubated with Xa in the presence of recombinant TFPI (rTFPI) was much higher than with Xa alone. Xa activity on PBMC was also observed after whole blood was incubated with pre-formed Xa/TFPI complex. Further studies with flow cytometric analysis demonstrate that rTFPI enhances the binding of Xa to human monocytes. Western blot analysis showed that rTFPI was cleaved into a few of fragments after its incubation with monocytes either in the presence or absence of Xa. Based on these results and the observations reported by others, we speculate that Xa/TFPI complex may bind to human monocytes by a yet unidentified mechanism. The recovery of Xa activity from Xa/TFPI complex on PBMC may be related to the cleavage of rTFPI by Xa and/or monocyte proteases. This observation suggests a new mechanism by which monocytes become procoagulant in some pathological conditions in addition of the well known tissue factor expression on proinflammatic monocytes.

Anticoagulants↗
PubMed2001

[Effects of yinchenhao decoction on normal animals and animal models of diabetes mellitus].

OBJECT: To study the effects of yinchenhao Decoction on the blood glucose level in a variety of animal models and its mechanism. METHODS: Normal mice, rats model of ailoxan (ALX)-induced diabetes mellitus (DM), mice model of ALX-DM and rats model of dexamethasone (DX)-induced insulin resistance (IR) were used. RESULTS: yinchenhao Decoction was able to inhibit the hyperglycemia by ALX-induced mice(P < 0.01), significantly reduce level of FBG in normal mice, ALX-DM mice and rats (P < 0.05-0.01), improve IGT and lower 2hBG (P < 0.01) after OGTT in DX-induced insulin-resistant rats. CONCLUSIONS: The results suggest that yinchenhao Decoction possesses similar hypoglycemic action to meftormin and gliclazied.

Animals↗
PubMed2001

Inhibitors of von Willebrand factor-cleaving protease in thrombotic thrombocytopenic purpura.

Thrombotic thrombocytopenic purpura (TTP), characterized by platelet thrombi in the arterioles and capillaries, is associated with antibodies that inhibit the activity of von Willebrand factor (vWF)-cleaving protease. Using a modified Bethesda method, we studied the inhibitor titers in patients who participated in the trial conducted by the Canadian Apheresis Group. Among the 41 patients investigated, the inhibitor titers at presentation were 1.4 +/- 1.7 U/mL (range -0.2-6.2 U/mL). Thirty-one patients (76%) had a titer > or = 0.2 U/mL, 8 patients (20%) had a titer > or = 2.0 U/mL but none had a titer > or = 10 U/mL. Among the 33 patients with an inhibitor titer < 2.0 U/mL (low titer group) and the 8 patients with an inhibitor titer > or = 2 U/mL (high titer group), 20 (61%) and 8 (100%) respectively had a platelet count < 25x10(9)/L (P = 0.04). Neurological abnormalities were among the presenting problems in 19 (58%) of the low titer and 6 (75%) of the high titer groups. Among the 23 patients who were randomized to plasma exchange, 5 patients had an inhibitor titer > or = 2 U/mL and none responded at the end of the first treatment cycle, while 8 of the 18 patients (44%) with a titer < 2 U/mL responded. This study shows that inhibitors of vWF-cleaving protease are of low titers in most cases of acquired TTP. A higher inhibitor titer is associated with a more advanced stage of the disease and may delay the response to plasma exchange.

ADAM Proteins↗
PubMed2001

Breast cancer: a socioeconomic and racial comparison in northwest Louisiana.

A tumor registry data review on breast cancer populations seen at two hospitals in North Louisiana was completed in order to determine if race is independent of socioeconomic status (SES) factors related to breast cancer stage at diagnosis. The North Louisiana tumor registry identified 1183 patients diagnosed with breast cancer between 1987 and 1991, 304 patients from Louisiana State University Health Science Center (LSUHSC), a state supported hospital providing predominantly indigent care, and 879 patients from a private hospital (PH) serving predominantly insured patients. Hospital site was used as a proxy for SES (LSUHSC low, PH high). The patient populations differed significantly by age, racial makeup, and stage at presentation. Both white and African-American patients seen at PH had more stage 0 disease compared with LSUHSC (9.2% and 2.7%). White patients seen at PH had more stage I cancer as compared to white patients at LSUHSC (31.3% and 19.2%) or African-American patients at either PH or LSUHSC (19.4% and 19.9%). The frequency of stage III/IV cancer was higher in African-American patients at both LSUHSC (30.1%) and PH (29.0%) and white patients at LSUHSC (24.0%) as compared to white patients at PH (14.7%). Two hundred and nine patients were available for individual interview and specific definition of SES. LSUHSC patients were predominantly indigent (83% indigent and without insurance), while only 10% of PH patients lacked insurance. This study provides further support that the SES of white patients influences breast cancer stage at presentation. African-American patients, however, presented with more advanced breast cancer stages regardless of SES. Factors influencing African-American patient's disease stage are not limited to defined SES factors. Further studies are needed to define barriers and develop intervention strategies.

Breast Neoplasms↗
PubMed2001

Expression of interleukin 8 and its receptors in human colon carcinoma cells with different metastatic potentials.

PURPOSE: In the present study, we examined the expression of a multifunctional cytokine, interleukin 8 (IL-8), and its receptors, CXCR1 and CXCR2, in human colon carcinoma cells with different metastatic potentials and determined their role in modulating phenotypes associated with metastasis. EXPERIMENTAL DESIGN: IL-8, CXCR1, and CXCR2 protein and mRNA expression were examined using ELISA, immunocytochemistry, and reverse transcription-PCR in human colon carcinoma cells with different metastatic potentials. IL-8-mediated proliferation, migration, and tumor-endothelial cell interaction were analyzed. RESULTS: IL-8 mRNA and protein expression was very low in Caco2 cells but elevated in KM12C cells and very high in KM12L4 cells, suggesting an association between the IL-8 production and metastatic potential. Similarly, CXCR1 and CXCR2 expression was lower in Caco2 cells than in low and high metastatic KM12C and KM12L4 cells. The recombinant human IL-8 enhanced the proliferation of colon carcinoma cells. Furthermore, proliferation of low and high metastatic cells expressing different levels of IL-8 was inhibited by neutralizing antibodies to IL-8, CXCR1, and CXCR2. We observed significant differences in the invasive potential of colon carcinoma cells expressing different levels of IL-8. In addition, we observed that IL-8 modulates adhesion of tumor cells to endothelial cells in an autocrine and paracrine manner. CONCLUSION: Our present data suggest an association between constitutive expression of IL-8 and aggressiveness in human colon carcinoma cells and the possible role of IL-8 in modulating different metastatic phenotypes associated with progression and metastasis.

Animals↗
PubMed2001

Abnormal activation of glial cells in the brains of prion protein-deficient mice ectopically expressing prion protein-like protein, PrPLP/Dpl.

BACKGROUND: Some lines of mice homozygous for a disrupted prion protein gene (Prnp), including Ngsk Prnp(0/0) mice, exhibit Purkinje cell degeneration as a consequence of the ectopic overexpression of the downstream gene for prion protein-like protein (PrPLP/Dpl) in the brain, but others, such as Zrch I Prnp(0/0) mice, show neither the neurodegeneration nor the expression of PrPLP/Dpl. In the present study, we found that Ngsk Prnp(0/0), but not Zrch I Prnp(0/0) mice, developed gliosis involving both astrocytes and microglia in the brain. MATERIALS AND METHODS: The brains from wild-type (Prnp(+/+)), Ngsk Prnp(0/0), Zrch I Prnp(0/0), and reconstituted Ngsk Prnp(0/0) mice carrying a mouse PrP transgene, designated Tg(P) Ngsk Prnp(0/0) mice, were subjected into Northern blotting and in situ hybridization using probes of glial fibrillary acidic protein (GFAP) and lysozyme M (LM) specific for astrocytes and microglia, respectively. Immunohistochemistry was also performed on the brain sections using anti-GFAP and anti-F4/80 antibodies. RESULTS: Northern blotting demonstrated upregulated expression of the genes for GFAP and LM in the brains of Ngsk Prnp(0/0), but not in Zrch I Prnp(0/0) mice. A transgene for normal mouse PrP(C) successfully rescued Ngsk Prnp(0/0) mice from the glial activation. In situ hybridization and immunohistochemistry revealed activated astrocytes and microglia mainly in the white matter of both the forebrains and cerebella. In contrast, there was no evidence of neuronal injury except for the Purkinje cell degeneration. Moreover, the glial cell activation was notable well before the onset of the Purkinje cell degeneration. CONCLUSIONS: These findings strongly suggest that ectopic PrPLP/Dpl in the absence of PrP(C) is actively involved in the glial-cell activation in the brain.

Aging↗
PubMed2001

[An experimental study of the effects of thrombin receptor activating peptide (TP508) on healing of ischemic wound and flap survival in rats].

OBJECTIVE: To investigate the effects of the thrombin receptor activating peptide (TP508) on healing of ischemic wound and flap survival in rats. METHODS: Sixty-six Sprague-Dawley rats were employed as the model. On the back of the rats, three kinds of wound and flap were made to establish four groups as follows: partial ischemic wound in 16, full ischemic wound in 16, routine wound in 18 and flap in 16 rats. Each group was further divided into TP508 treating group and isotonic saline control group. The total and necrotic areas of the wounds and flaps were daplicated on acetate papers and calculated with a computer on the 3rd, 7th, 10th and 14th post-operation days (PODs). RESULTS: In routine wounds, the ischemic wound area treated by TP508 was 73.7% and 45.4% in saline control groups on 7 and 14 (PODs), respectively. While in the flap model, the necrotic flap area treated by TP508 was 80.4% and 56.8% in control groups on 7 and 14 (PODs), respectively. CONCLUSION: TP508 could accelerate healing of ischemic wound and improve flap survival in rats.

Animals↗
PubMed2001

[An experimental study of the effects of early enteral feeding of L--arginine enriched food on postburn intestinal mucosal proliferation in rats].

OBJECTIVE: To investigate the effects of early enteral feeding of L -- arginine enriched food on postburn intestinal mucosal proliferation in rats. METHODS: Twenty Wistar rats prepared with gastrostomy 7 days before the experiment were inflicted by 30% TBSA flame burn, and were divided into early enteral feeding (EF), L -- arginine enriched early enteral feeding group (AEF) receiving feeding from 2 PBHs and delayed feeding (DF) group, receiving feeding from 48 PBHs. The changes in intestinal mucosal DNA content and intestinal mucosal proliferating cell nuclear antigen labeling index (PCNALI) were determined on the 1st, 3rd, 6th and 9th postburn days (PBDs) respectively in rats. RESULTS: There were rare intestinal mucosal PCNA positive cells on the 1st PBD in all groups. Compared with that in DF group, the intesinal mucosal PCNALI in AEF group increased obviously on 3 PBD, while that in EF group increased evidently on 6 PBD. (P < 0.05). CONCLUSION: There existed intestinal mucosal injury postburn as shown by the inhibition of intestinal epithelial proliferation. Early enteral feeding with L -- arginine enriched food could not only ameliorate intestinal mucosal injury, but also enhance the proliferation of intestinal mucosal epithelium.

Animals↗
PubMed2001

[Detection of enterovirus RNA in cerebrospinal fluid from patients with aseptic meningitis and encephalitis and its clinical significance].

BACKGROUND: To study the pathogenicity of enterovirus (EV) infection in central nervous system and the method for its detection. METHODS: Using reverse transcription polymerase chain reaction (RT-PCR) and viral culture techniques to detect EV from 46 cerebrospinal fluid (CSF) samples of aseptic meningitis and encephalitis patients. The sensitivity and specificity of RT-PCR for EV RNA detection was affirmed by specific RNA identification of 40 strains of prototype enterovirus. RESULTS: By the virus culture method, 14 out of the 46 CSF sample were tested to beEV positive (26.1%) including 6 Echovirus type 2 (ECV2), 2 Coxackie virus type B2 (CVB2), 2CVB6, 1 ECV3 and 1 ECV11. By RT-PCR method, 31 of 46 CSF sample were tested EV RNA positive (67.4%) through amplified product agarose electrophoresis and northern blot hybridizition. The positive CSF included 14 samples that had been tested positive by virus culture and 17 samples that accounted for 53.9% of the 32 CSF samples which were negetive by virus culture. The sensitivity of RT-PCR was statistically higher than that of the virus culture method, Chi(2) =12.57, P <0.01. CONCLUSIONS: EV is known as important etiological agents of aseptic meningitis and encephalitis. RT-PCR is sensitivity, specificity and rapidity, it may be popularized as an effective method to the detection of enterovirus.

Adolescent↗
PubMed2001

[Studies on the methods of mating test for Cryptococcus neoformans].

Six media (MA:Mating agar, HA:Hay agar, HCA:Hay cube agar, RSA:Rice shell agar, IHA:additional nutrition in HA and SDA:Sabouraudia dextrose agar) were compared for their efficiencies of the mating test for Cryptococcus neoformans. The positive rates in 2-week-cultivation were 95% (HCA and RSA), 86% (HA), 38% (MA and SDA) and 24% (IHA). The streaking inoculation was equally replaced by the dot inoculation for the mating tests. However, the dot method saves much more materials, and is suitable for testing in large number of isolates. Additionally, the precultivation of the tester and tested isolates in broth medium (YMPDB) could enhance the positive mating rates.

Agar↗
PubMed2001

[Studies on the specificity of target organs and repair dynamics of DNA damage induced by 1,2-dichloroethane].

In order to investigate the genotoxicity of 1,2-dichloroethane (DCE) and to determine its carcinogenic targets, the DNA damage and repair dynamics were detected by using comet assay in the isolated nuclei with tissue-homogenization. Liver, lung, kidney, spleen, bone marrow, testicle, stomach, colon, bladder, and peripheral lymphocytes of mice were isolated at 3 h, 8 h, 24 h after DCE being gavaged. The results showed that: a) liver, lung, kidney, bone marrow, colon, stomach and peripheral lymphocytes were the genotoxic target organs of DCE in mice; b) DNA damage and repair dynamics were obviously different among the test organs, and the organs with DNA damage and slow repaired (lung, stomach and hemocyte) were in accordance with the carcinogenic targets. The results indicate that multiple organ comet assay in vivo is very useful for the evaluation of genotoxicity and prediction of carcinogenic target organ. The comet tail of peripheral lymphocyte is suitable as a biomarker for DNA damage in the target organs of living creatures and population exposed to DCE. It is suggested that in vivo comet assay is also very important to select right marker cells and biomarker in the epidemiological studies on genotoxicity.

Animals↗
PubMed2001

[Transforming growth factor-beta can induce differentiation of hypertrophic chondrocytes into osteoblast-like cells in epiphyseal plate].

OBJECTIVE: To investigate the effect of transforming growth factor-beta (TGF-beta) on the differentiation of hypertrophic chondrocytes in epiphyseal plate in order to understand its role in the mechanism of bone and cartilage formation. METHODS: We observed the effect of TGF-beta in varied time and dosage on the differentiation of hypertrophic chondrocytes in embryonic chick femora which were cultured in serum-free medium, using histochemical staining to detect the expression of alkaline phosphatase (ALP) and immunohistochemical staining to detect the expression of type I collagen and fibronectin. RESULTS: TGF-beta enabled the chondrocytes to express type I collagen and fibronectin, and it enhanced the expression of ALP in hypertrophic zone. Time-effect and dosage-effect relationships were observed. CONCLUSION: TGF-beta can induce the differentiation of hypertrophic chondrocytes into osteoblast-like cells in epiphyseal plate of embryonic chick femora. The inducing effect might be closely related to time and dosage of TGF-beta.

Animals↗