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Biomedical subjects

D Li

Publications and source records attributed to D Li.

At least 379 records · Page 21Linked to original sources
PubMed1999

[Application of amanita toxic peptides in life sciences research].

Amanita toxic peptides are the main toxins in wild mushrooms and often result in animal and human intoxication and death. Due to the specific inhibition to eukaryotic cell RNA polymerases II by amatoxins and the binding to actin by phallotoxins, amanita toxic peptides play important roles in life science researches. This paper presents a latest review of applications of amanita toxic peptides in life scientific researches.

Amanita↗
PubMed1999

Accuracy of T1 measurements at high temporal resolution: feasibility of dynamic measurement of blood T1 after contrast administration.

The purpose of this work was to optimize a technique to measure blood T1 dynamically after contrast agent administration with a high temporal resolution. This technique uses a 90 degrees prepared gradient-echo sequence and has a temporal resolution of one T1 measurement per cardiac cycle. The non-ideal excitation slice profiles on the estimation of T1 were evaluated by theoretical simulations and used to obtain corrected blood T1 values. The technique was validated on phantom and in vivo pig studies, which demonstrated significant improvement on the accuracy of the dynamic T1 measurement method after slice profile correction. This technique may find important applications in studying the dynamic blood T1 after injection of various contrast agents. J. Magn. Reson. Imaging 1999;10:576-581.

Animals↗
PubMed1999

Efficacy of slow infusion of gadolinium contrast agent in three-dimensional MR coronary artery imaging.

The impact of the contrast infusion scheme on contrast-enhanced coronary artery imaging was investigated. The imaging technique was a retrospective respiratory-gated gradient-echo sequence. To improve the contrast between blood vessels and myocardium, an inversion pulse was applied to null the myocardial signal. Extravascular contrast agent was infused slowly during data acquisition. Two contrast infusion schemes were compared in animal and volunteer studies and with simulations. One scheme enhanced blood signals during acquisition of both peripheral and central k-space data, which resulted in a relatively flat low-pass k-space filter. The other scheme mainly enhanced blood signals during acquisition of central k-space data, which resulted in a sharp low-pass k-space filter. It is concluded that the former scheme improves the signal-to-noise ratio and edge definition of coronary arteries compared with the latter scheme. J. Magn. Reson. Imaging 1999;10:800-805.

Adult↗
PubMed1999

Inhibitory effect of recombinant FN polypeptide CH50 on the metastasis and tumor growth.

The inhibition of CH50, a recombinant polypeptide of human fibronectin, on the formation of tumor metastases in vivo was studied by inoculation of melanoma B16/F1 cells by hypodermic or intraperitoneal injection, and the size and amount of tumor nodes after therapy were measured. In the treatment of hypodermic tumor, local injection of CH50 produced much better efficacy than distance injection of CH50 did. The inhibitory effect of CH50 on the growth of tumor reached 50%. In the treatment of peritoneal metastasis, the inhibition of CH50 on metastases smaller than 1 mm was above 80%, and above 50% on metastases larger than 1 mm. A better efficacy was achieved if CH50 was used in combination with hydroxycamptothecine (HCPT), a chemotherapeutic agent. CH50 displayed a strong inhibitory effect on the formation of small metastasis and growth of larger nodes of tumor, suggesting that CH50 plays a very important role in combined treatment of tumor therapy.

Fibronectins↗
PubMed1999

The nucleotide sequence of a chinese isolate of wheat yellow mosaic virus and its comparison with a Japanese isolate. Brief report.

The nucleotide sequences of wheat yellow mosaic virus isolated in China were determined and compared with a Japanese isolate of the same virus. Results showed that the viral genome had 7629 nucleotides for RNA1 and 3639 nucleotides for RNA2, which shared 97. 1% and 94.6% of identities to the RNAs of Japanese isolate. The single open reading frames in RNA1 and RNA2 encoded polyproteins with 2407 amino acids and 903 amino acids respectively, from which ten proteins may be produced by autolytic cleavage processing as the Japanese isolate. Since the sequence of WYMV RNA1 showed identity of less than 70% with that of WSSMV, it is further confirmed that WYMV is a distinct species within Bymovirus.

Base Sequence↗
PubMed1999

The metabolism of native and randomized butterfat chylomicrons in the rat is similar.

Reportedly, randomly rearranging the position of fatty acids (FA) in butterfat triacylglycerol (TAG) by interesterification, thereby lowering the proportion of saturated FA in the sn-2 position, reduces its hypercholesterolemic and hypertriglyceridemic properties when fed to humans. The aim of this work was to determine if these reductions in plasma cholesterol and TAG could be explained by an improved rate of clearance from the plasma of chylomicrons composed of randomized butterfat, using a rat model. Acute chylomicron clearance studies demonstrated no differences in fractional clearance rates of cholesteryl esters and TAG from the plasma of rats infused with chylomicrons produced from gastric feeding of either native (NBF) or randomized (RBF) butterfat. Although there was a 14% decrease in the level of saturated FA occupying the sn-2 position of TAG in RBF compared with NBF, this difference became negligible (approximately 5%), following digestion of the fat and subsequent repackaging of TAG into chylomicrons. These observations suggest that the previously observed reduction in hypercholesterolemic properties of randomized butterfat in rat is unlikely to be explained by improved clearance of chylomicron TAG.

Animals↗
PubMed1999

Kinetics of tumor necrosis factor alpha in plasma and the cardioprotective effect of a monoclonal antibody to tumor necrosis factor alpha in acute myocardial infarction.

BACKGROUND: Inflammation plays a critical role in acute myocardial infarction (AMI) and tumor necrosis factor alpha (TNF-alpha) is a potent inflammatory trigger. This study was designed to examine the kinetics of TNF-alpha in plasma in patients with AMI and the potential benefit of inhibition of TNF-alpha monoclonal antibody in AMI. METHODS AND RESULTS: TNF-alpha levels in plasma were measured in 42 patients with AMI. TNF-alpha levels were elevated at 4 hours after onset of chest pain and declined to control values at 48 hours. TNF-alpha levels were higher in patients with Killip III and IV than in those with Killip I and II (P <.01). To examine the pathogenic role of TNF-alpha, New Zealand White rabbits were treated with buffer or a TNF-alpha monoclonal antibody before left anterior descending artery (LAD) ligation. Treatment with the TNF-alpha monoclonal antibody decreased area of necrosis, number of circulating endothelial cells, and lipid peroxidation product malonaldehyde bis(dimethyl acetal). There was a significant correlation of TNF-alpha levels with peak CK-MB in AMI patients, and area of necrosis, MDA, and circulating endothelial cells in rabbits (all P <.05). CONCLUSIONS: TNF-alpha release early in the course of AMI contributes to myocardial injury and dysfunction. Treatment with the monoclonal antibody against TNF-alpha can be cardioprotective, particularly in the setting of heart failure in patients with AMI.

Adult↗
PubMed1999

Modulation of constitutive nitric oxide synthase, bcl-2 and Fas expression in cultured human coronary endothelial cells exposed to anoxia-reoxygenation and angiotensin II: role of AT1 receptor activation.

BACKGROUND: Angiotensin II (Ang II) plays a critical role in the pathophysiology of myocardial ischemia-reperfusion injury. We have recently shown that reoxygenation following a period of anoxia causes apoptosis of cultured human coronary artery endothelial cells (HCAECs). Ang II further enhances apoptosis of HCAECs via Ang II type 1 receptor (AT1R) activation. Recent studies suggest an important role of constitutive nitric oxide synthase (cNOS), Fas and bcl-2 proteins in apoptosis. This study was designed to examine the modulation of cNOS, and Fas and bcl-2 expression in HCAECs during exposure to anoxia-reoxygenation and Ang II. METHODS AND RESULTS: HCAECs were exposed to anoxia-reoxygenation and Ang II. Anoxia-reoxygenation significantly decreased cNOS mRNA, protein and activity in cultured HCAECs (P < 0.05 vs. control). Anoxia-reoxygenation also caused an increase in Fas and a decrease in bcl-2 protein expression in cultured HCAECs (both P < 0.05 vs. control). The presence of Ang II (0.3 microM) further enhanced these effects of anoxia-reoxygenation on cNOS, Fas and bcl-2 expression. The effects of Ang II were significantly attenuated by the AT1R inhibitor losartan (10 microM). CONCLUSION: During exposure of HCAECs to anoxia-reoxygenation and Ang II, AT1R activation induces important changes in cNOS mRNA, protein expression and activity, as well as bcl-2 and Fas protein expression which may have a bearing on the development of apoptosis.

Analysis of Variance↗
PubMed1999

Tumor necrosis factor-alpha enhances hypoxia-reoxygenation-mediated apoptosis in cultured human coronary artery endothelial cells: critical role of protein kinase C.

BACKGROUND: Ischemia and tumor necrosis factor-alpha (TNF alpha) released during ischemia both cause apoptosis and necrosis of myocardial tissues. Since endothelium may be critically important in determination of cardiac function, we examined the interaction between TNF alpha and hypoxia-reoxygenation with regard to induction of apoptosis and underlying signaling pathway in cultured human coronary artery endothelial cells (HCAECs). METHODS AND RESULTS: HCAECs were cultured and exposed to hypoxia alone, hypoxia-reoxygenation, TNF alpha alone, TNF alpha plus hypoxia-reoxygenation, or TNF alpha only during the period of reoxygenation. Apoptosis was evaluated by transmission electron microscopy, DNA nick-end labeling and DNA laddering. Hypoxia alone caused modest time-dependent apoptosis of cultured HCAECs, and reoxygenation increased the number of apoptotic cells (P < 0.01 vs. hypoxia alone). TNF alpha induced concentration-dependent apoptosis, and enhanced reoxygenation-mediated apoptosis in cultured HCAECs (P < 0.01 vs. hypoxia-reoxygenation alone). As expected, monoclonal antibody to TNF alpha significantly blocked the pro-apoptotic effect of TNF alpha-induced apoptosis (P < 0.01). TNF alpha-induced apoptosis was found to be associated with marked activation of protein kinase C (PKC), and pretreatment of cells with a specific PKC inhibitor markedly reduced TNF alpha-mediated PKC activity and apoptosis. CONCLUSION: These observations indicate that hypoxia alone causes modest apoptosis, reoxygenation increases apoptosis beyond that caused by hypoxia in cultured HCAECs. TNF alpha alone causes apoptosis, and further enhances apoptosis caused by hypoxia-reoxygenation. The activation of PKC plays a critical role in TNF alpha-induced apoptosis of cultured HCAECs.

Antibodies, Monoclonal↗
PubMed1999

Is the surface of endoparasitic wasp eggs and larvae covered by a limited coagulation reaction?

Evidence is presented for the existence of a Venturia homologue of hemomucin, a surface mucin that was recently described in Drosophila. Venturia hemomucin is part of the mucinous layer on the egg and larval surface of the parasitoid. Venturia hemomucin forms a complex with lipophorin and other host hemolymph components, that is similar to a hemomucin-lipophorin complex which is part of the coagulation reaction. The possible formation of a specific layer against the host defence system is discussed for eggs and larvae that develop inside another insect.

Journal Article↗
PubMed1999

Distortion product otoacoustic emissions and outer hair cell defects in the hyt/hyt mutant mouse.

Thyroid hormone plays an important role in hearing development. Hereditary hypothyroidism is frequently associated with sensorineural hearing loss as identified in both animal models and human patients. Building upon our original demonstration of congenital deafness and hair cell abnormality in a hyt/hyt mouse model which carries an autosomal recessive mutation causing hereditary hypothyroidism, we investigated the functional capacity of the outer hair cell (OHC) system in these animals using distortion product otoacoustic emissions (DPOAEs). In particular, the amplitude and detection features of DPOAEs were correlated with measures of the auditory brainstem response (ABR) as well as the cellular structure and ultrastructure of the organ of Corti. Input-output (I/O) functions for the 2f(2)-f(1) DPOAEs were obtained for frequencies from 2 to 18 kHz. The thresholds were significantly higher and amplitudes were significantly lower in the homozygous mice (hyt/hyt) than in both heterozygous mice (hyt/+) and wild-type controls at DPOAE frequencies recorded above 6 kHz. Hearing thresholds were significantly elevated in the mutant compared to control mice. In addition, morphological studies revealed consistent inner ear defects in hyt/hyt animals including distortion of the tectorial membrane, dysplasia of the tunnel of Corti and distinct OHC abnormalities. The most striking histopathological finding was a contiguous membrane along the apices of all of the OHC stereocilia. Such ultrastructural changes in the stereocilia of the OHC may limit the deflection of the stereocilia and therefore affect an active cochlear function that produces otoacoustic emissions as well as cause a failure to evoke the normal action potentials in the auditory nerve. From both functional and morphologic evaluations, it was concluded that the OHC system is the most susceptible to the developmental effects of congenital hypothyroidism in the hyt/hyt mouse. The normal OHCs with well-developed ciliary bundles are crucial to maintain the activity of biological mechanisms within the cochlea.

Animals↗
PubMed1999

Differential effects of alpha- and gamma-tocopherol on low-density lipoprotein oxidation, superoxide activity, platelet aggregation and arterial thrombogenesis.

OBJECTIVES: This study was designed to examine the differential effects of alpha- and gamma-tocopherol on parameters of oxidation-antioxidation and thrombogenesis. BACKGROUND: Experimental studies have shown that antioxidants, such as vitamin E (alpha-tocopherol), improve atherosclerotic plaque stability and vasomotor function, and decrease platelet aggregation and tendency to thrombus formation. METHODS: Sprague Dawley rats were fed chow mixed with alpha- or gamma-tocopherol (100 mg/kg/day) for 10 days. A filter soaked in 29% FeCl3 was applied around the abdominal aorta to study the patterns of arterial thrombosis. The aortic blood flow was observed and continuously recorded using an ultrasonic Doppler flow probe. ADP-induced platelet aggregation, low-density lipoprotein oxidation induced by phorbol 12-myristate 13-acetate (PMA)-stimulated leukocytes, superoxide anion generation and superoxide dismutase (SOD) activity were also measured. RESULTS: Both alpha- and gamma-tocopherol decreased platelet aggregation and delayed time to occlusive thrombus (all p < 0.05 vs. control). Both alpha- and gamma-tocopherol decreased arterial superoxide anion generation, lipid peroxidation and LDL oxidation (all p < 0.05 vs. control), and increased endogenous SOD activity (p < 0.05). The effects of gamma-tocopherol were more potent than those of alpha-tocopherol (p < 0.05). CONCLUSIONS: This study indicates that both alpha- and gamma-tocopherol decrease platelet aggregation and delay intraarterial thrombus formation, perhaps by an increase in endogenous antioxidant activity. Gamma-tocopherol is significantly more potent than alpha-tocopherol in these effects.

Animals↗
PubMed1999

A maternal gene mutation correlates with an ovary phenotype in a parthenogenetic wasp population.

Endoparasitoid wasps rely on maternal protein secretions, including viruses and virus-like particles (VLPs), to overcome host defense reactions. In the ichneumonid Venturia canescens, VLPs are assembled in the nuclei of ovarian calyx gland cells, secreted into the lumen of the gland, and eventually transmitted into the host caterpillar together with the parasitoid egg. One of the genes coding for VLP proteins, termed VLP1, exists in two alleles producing two structurally different proteins. Here we describe the establishment and initial phenotypic characterisation of two parthenogenetic laboratory strains, which differ in VLP1 as well as in other genetic markers. A comparison of calyx tissues from the two strains revealed morphological differences that seem to affect egg movement from the ovarioles into the oviduct. The observed histological changes are correlated with differences in egg maturation and embryonic development causing a delay in larval hatching in one of the strains. Under conditions that favour superparasitism, the two strains differ in the number of offspring produced.

Amino Acid Sequence↗
PubMed1999

Immunosuppressive diterpenoids from Tripterygium wilfordii.

A clinically used extract of Tripterygium wilfordii afforded three new diterpenoids-3beta,19-dihydroxyabieta-8,11,13-triene (triptobenzene L) (1); 12,19-dihydroxy-3-oxoabieta-8,11,13-triene (triptobenzene M) (2); and 19-hydroxy-3,7-dioxo-abieta-8,11, 13-triene (triptobenzene N) (3)-along with 14 known diterpenoids. The structures of 1-3 were established on the basis of spectroscopic studies. Of the known compounds, the stereochemistry at C-4 of triptonediol (4) was reassigned. Tripterifordin (8) and 13-epi-manoyl oxide-18-oic acid (9) showed significant inhibitory effects on cytokine production.

Abietanes↗
PubMed1999

Squarroside C, a new cycloartene bisdesmoside from Thalictrum squarrosum.

Squarroside C (1), a new cycloartane 3,21-bisdesmoside, was isolated from the above-ground parts of Thalictrum squarrosum. The structure of 1 was established as 3-O-[O-alpha-L-rhamnopyranosyl-(1-->6)-beta-D-glucopyranosyl]-21-O-be ta-D-glucopyranosyl-21(S),22(S),23(R),3beta,21alpha,22beta, 30-tetrahydroxy-21,23-epoxycycloart-24-ene by 2D NMR spectroscopy and FABMS.

Carbohydrate Sequence↗
PubMed1999

The inter-ligand Overhauser effect: a powerful new NMR approach for mapping structural relationships of macromolecular ligands.

NMR experiments that transfer conformational information from the bound to the uncomplexed state via exchange have been utilized for many years. It is demonstrated here that inter-ligand NOEs ('ILOEs'), which exist in ternary complexes with enzymes or other macromolecular receptors, can be transferred via exchange to pairs of uncomplexed ligands. This approach is illustrated by studies of glycolate + NAD+ in the presence of porcine heart lactate dehydrogenase, and by glucose-6-phosphate + NADPH in the presence of L. mesenteroides glucose-6-phosphate dehydrogenase. This strategy opens up a general methodology for exploring the active sites of enzymes and for the development of artificial ligands which can function as inhibitors, or more generally as modifiers of protein function.

Animals↗
PubMed1999

Different cytokine profiles in cryptogenic fibrosing alveolitis and fibrosing alveolitis associated with systemic sclerosis: a quantitative study of open lung biopsies.

Differences in the inflammatory response and prognosis of cryptogenic fibrosing alveolitis (CFA) and that associated with systemic sclerosis (FASSc) are beginning to emerge. It is hypothesized that these differences may be reflected in a distinct pattern of T-helper (Th)-1 and Th-2-type cytokines. Open lung biopsies were obtained from clinically well-documented cases of CFA and FASSc and, as a control, compared with grossly and histologically normal parenchyma obtained from smokers whose lungs were resected for cancer (n=5 in each group). In situ hybridization (ISH) was applied to the samples using anti-sense and sense 35S-labelled riboprobes to detect messenger ribonucleic acid (mRNA) for interleukins (IL)-2, IL-4, IL-5 and interferon (IFN)-gamma. Between 52-91% of cells expressing the cytokines studied were present in the alveolar interstitium rather than in lumenal cells or the alveolar epithelial lining. The highest values for all four cytokines were present in the patients with FASSc, i.e., 22-39 ISH positive cells x mm(-2) alveolar tissue compared with 1-19 cells x mm(-2) and 4-5 cell x mm(-2) in CFA and control subjects, respectively. Whereas the proportions of the four cytokines in FASSc were similar to the control subjects, IL-4 and IL-5 predominated significantly in CFA (p<0.001). For example, the ratio of IL-5 to IFN-gamma was 22:1 in CFA, significantly higher than in the cases with FASSc (2:1) or the control subjects (4:1) (p<0.05). In conclusion, cryptogenic fibrosing alveolitis is an inflammatory condition which is characterized, like asthma, by a predominance of gene expression for T-helper-2-type regulatory cytokines, whereas cryptogenic fibrosing alveolitis associated with systemic sclerosis appears to have a distinct mixed T-helper-1/T-helper-2 functional phenotype and a greater number of cells expressing each of these pro-inflammatory cytokines.

Adult↗