Biomedical subjects

D Cai

Publications and source records attributed to D Cai.

At least 55 records · Page 3Linked to original sources

PubMed1999

[The role of nitric oxide on the functional change of interleukin-1 beta and interleukin-6 induced rat pancreatic islets of Langerhans].

OBJECTIVE: To observe the effects of interleukin (IL)-1 beta and IL-6 on nitric oxide (NO) production, islet cell DNA and insulin content, and MTT assay of rat pancreatic islets of Langerhans. METHODS: Isolated pancreatic islet cells from SD rats were cultured in monolayer in vitro. Nitrite production, islet cell DNA and insulin content, and MTT assay in rat pancreatic islet cells incubated with IL-1 beta and IL-6, singly or in combination, were measured. The levels of these parameters of the cytokines in the absence and presence of N(G)-monomethyl-L-arginine (L-NMMA), an inhibitor of nitric oxide synthetase, were compared. RESULTS: IL-1 beta induced a significant increase in nitrite production, a decrease of islet cell DNA and insulin content and reduction of cell activity (MTT, P < 0.001); these changes were blocked by L-NMMA (P < 0.001). IL-6 produced no significant change in those parameters (P > 0.05). The combination of IL-1 beta and IL-6 increased NO production, decreased islet cell DNA and insulin content and reduced cell activity (P < 0.001); the changes were similar to those with IL-1 beta alone (P > 0.05). CONCLUSION: The cytotoxic effects of IL-1 beta on pancreatic islets might be mediated by NO. IL-6 may not be directly cytotoxic to pancreatic islets. It may be related with the fact that IL-6 does not induce NO production.

Animals↗

PubMed1999

[Determination of triflumizole and its metabolite residues in vegetables by high performance liquid chromatography].

Triflumizole (TRI) and its metabolite [4-chloro-alpha,alpha,alpha-trifluoro-N-(1-amino-2-propoxythylidene)- O-toluidine] (MET) were extracted with methanol and reverse-extracted with dichloromethane. After evaporation to dryness, the residue in dichloromethane layer was dissolved in mobile phase for high performance liquid chromatographic determination with external standard method. The total residue content of TRI and MET (calculated as TRI) is reported.

Chromatography, High Pressure Liquid↗

PubMed1998

Co-purification of microsomal epoxide hydrolase with the warfarin-sensitive vitamin K1 oxide reductase of the vitamin K cycle.

Vitamin K1 oxide reductase activity has been partially purified from rat liver microsomes. A three-step procedure produced a preparation in which warfarin-sensitive vitamin K1 oxide reductase activity was 118-fold enriched over the activity in intact rat liver microsomes. A major component of the multi-protein mixture was identified as a 50 kDa protein that strongly cross-reacts with antiserum prepared against homogeneous rat liver microsomal epoxide hydrolase. The reductase preparation also had a high level or epoxide hydrolase activity against two xenobiotic epoxide substrates. The K(m) values for hydrolysis by the reductase preparation were similar to those for homogeneous microsomal epoxide hydrolase itself, and the specific hydrolase activities of the reductase preparation were 25-35% of the specific activities measured for the homogeneous hydrolase preparation. Antibodies prepared against homogeneous microsomal epoxide hydrolase inhibited up to 80% of reductase activity of the reductase preparation. Homogeneous microsomal epoxide hydrolase had no vitamin K1 oxide reductase activity. This evidence suggests that microsomal epoxide hydrolase, or a protein that is very similar to it, is a major functional component of a multi-protein complex that is responsible for vitamin K1 oxide reduction in rat liver microsomes.

Animals↗

PubMed1998

An ergonomic approach to public squatting-type toilet design.

This paper reports a case study on public squatting-type toilet design, which was undertaken with a special emphasis on ergonomic considerations. A field survey on the use of public toilets in Taipei reveals that almost half of the subjects take a non-sitting posture while using the sitting-type public toilets and 86% of the subjects agreed that the squatting-type public toilets better satisfy sanitary requirements. An experiment was conducted to determine relevant anthropometric data for a redesign of squatting-type toilets. One of the variables studied was the effect of the footstep slope on squatting comfort. A total of 80 subjects as tested on four footstep slopes: 0 degrees, 15 degrees, 30 degrees and 45 degrees. Their heart rates were measured before and after the test, and their subjective evaluations of squatting comfort were also recorded. The 15 degrees slope was found to be preferred. These findings were then used in design development where mock-ups were presented to subjects for evaluation, then modifications were made and further tests conducted for verification. The result shows that the ergonomic approach is feasible recommended to be adopted in the process of product design of such facilities.

Adolescent↗

PubMed1998

Structure of double-shelled rice dwarf virus.

Rice dwarf virus (RDV), a member of the Reoviridae family, is a double-stranded RNA virus. Infection of rice plants with RDV reduces crop production significantly and can pose a major economic threat to Southeast Asia. A 25-A three-dimensional structure of the 700-A-diameter RDV capsid has been determined by 400-kV electron cryomicroscopy and computer reconstruction. The structure revealed two distinctive icosahedral shells: a T=13l outer icosahedral shell composed of 260 trimeric clusters of P8 (46 kDa) and an inner T=1 icosahedral shell of 60 dimers of P3 (114 kDa). Sequence and structural comparisons were made between the RDV outer shell trimer and the two crystal conformations (REF and HEX) of the VP7 trimer of bluetongue virus, an animal analog of RDV. The low-resolution structural match of the RDV outer shell trimer to the HEX conformation of VP7 trimer has led to the proposal that P8 consists of an upper domain of beta-sandwich motif and a lower domain of alpha helices. The less well fit REF conformation of VP7 to the RDV trimer may be due to the differences between VP7 and P8 in the sequence of the hinge region that connects the two domains. The additional mass density and the absence of a known signaling peptide on the surface of the RDV outer shell trimer may be responsible for the different interactions between plants and animal reoviruses.

Amino Acid Sequence↗

PubMed1998

[Somastostatin and growth hormone in preventing liver damage due to acute necrotizing pancreatitis].

OBJECTIVE: To study the role of somastostatin and growth hormone in preventing liver damage due to ANP. METHODS: The roles of inflammatory mediators (Endotoxin, Amylase, TNF alpha) were investigated in ANP model by retrograde injection of 3.5% sodium taurocholate 2.5 ml/kg into the pancreatic duct, and TNF alpha mRNA in the liver after ANP was observed by reverse transcriptase-polymerase chain reaction. Besides, the effects of somastostain and growth hormone were also observed. RESULTS: ANP caused remarkable elevation of those inflammatory mediators, being positively correlated with the development of pancreas and liver damage. Somastostain and growth hormone inhibited the inflammatory mediates and TNF alpha mRNA overexpression and reduced the damage to the pancreas and liver. CONCLUSIONS: TNF alpha plays an important role in ANP progression, and somastostatin and growth hormone may prevent the development and progression of liver damage due to ANP.

Animals↗

PubMed1998

[Arthroscopy in diagnosis and treatment of tuberculous synovitis].

OBJECTIVE: To evaluate the role of arthroscopy in the diagnosis and treatment of early tuberculous synovitis. METHOD: Eighteen patients with monoarticular synovitis who underwent arthroscopy and diagnosed as tuberculous synovitis because of arthroscopic findings and synovial biopsies from September 1986 to September 1996 were reviewed. RESULT: Four out of 18 patients were diagnosed on the basis of clinical manifestations and laboratory results before operation, and proved pathologically after operation. The other 14 cases were definitely diagnosed by arthroscopy and pathological examination. With an average of 3 years and 4 months follow-up, the results of the treatment were excellent. Symptoms disappeared, and full joint functions restored in each case. CONCLUSION: Arthroscopy is a useful method in the diagnosis and treatment of early tuberculous synovitis.

Adolescent↗

PubMed1998

[Clinical and experimental research of Epimedium brevicornum in relieving neuroendocrino-immunological effect inhibited by exogenous glucocorticoid].

OBJECTIVE: To study protective effect of Epimedium brevicornum (EB) on hypothalamus-pituitary-adrenal-thymus (HPAT) axis inhibited by exogenous glucocorticoid. METHODS: In clinical research, variation of cortisol, adrenocorticotrophin (ACTH), lymphocyte proliferative reaction were observed before and after medication in 65 patients took prednisone, and were randomly divided into Fufang prednisone group (mixture of prednisone and EB) and prednisone group. An experimental model of HPAT axis inhibited by corticosterone (CORT) was established to observe the effect of EB on relevant indices of HPAT axis. RESULTS: The level of ACTH and CORT in plasma decreased and lymphocyte proliferative reaction reduced in patients (P < 0.05). In experimental study, monoaminic transmitters activated in hypothalamus; weight of pituitary, adrenal and thymus decreased; number of CRH positive neurons in hypothalamic paraventricular nucleus, CRH positive neurofibrilin median eminence and anterior pituitary ACTH positive secretory cells decreased; adrenal fasciculate zone and thymus cortex atrophies; NK cell cytotoxicity and the level of IL-2 and gamma-IFN which were produced by lymphocytes reduced in CORT-rats (P < 0.05). There were significant difference between Fufang prednisone group (clinical research) or EB group (experimental research) and CORT control groups, P < 0.05. CONCLUSION: EB could relieve neuroendocrino-immunological effect inhibited by exogenous glucocorticoid.

Adult↗

PubMed1998

[Clinical and experimental study on treatment of acute cerebral infarction with Acanthopanax Injection].

OBJECTIVE: To evaluate the effect of Radix Acanthopanacis Senticosi in treating acute cerebral infarction and its mechanism. METHODS: Clinical study using single-blind, control trial, in which 60-80 ml of Acanthopanax Injection (AI) added to 500 ml of 0.9% normal saline was given by intravenous drip once a day for 14 days in the AI group(34 patients), while 500 ml of dextra-40 was given by the same way in the control group(26 patients). In experimental study, rabbit model of acute incomplete cerebral ischemia was made by ligation of bilateral common carotid artery. 10 ml of AI were given once daily intravenously for 7 days to the AI group and 10 ml of normal saline was given to the control group in the same way. Clinical effects (in clinical study) and effect of AI on cerebral oxygen free radicals (OFR), superoxide dismutase (SOD), and serum concentration of ACTH and cortisone were observed (in experimental study). RESULTS: Clinical study showed that the total effective rate of AI group (86%) was higher than that of the control group (50%) while nervous functional deficit score was lower in AI group (9.96 +/- 4.66) than that in the control group (13.56 +/- 1.84) significantly. Experimental study showed that the cerebral level of OFR decreased while SOD increased and serum concentration of ACTH and cortisone decreased after treatment in AI group. CONCLUSIONS: AI was effective in treating acute cerebral infarction, the mechanism is probably by ameliorating peroxidation in brain and improving hypothalamic-pituitary-adrenocortical axis function.

Adrenocorticotropic Hormone↗

PubMed1997

Mechanism-based inactivation of a yeast methylamine oxidase mutant: implications for the functional role of the consensus sequence surrounding topaquinone.

The copper-containing yeast methylamine oxidase E406N mutant has an altered consensus sequence surrounding the topaquinone cofactor (residue 405). The mutation has no effect on the final yield of the active-site topaquinone cofactor during biogenesis but causes the enzyme to be inactivated by substrate methylamine [Cai, D., and Klinman, J. P. (1994) Biochemistry 33, 7674-7653]. In this study we show that the inactivation leads to the formation of a covalent adduct, which has a UV/vis spectrum very similar to that of a product Schiff base, an intermediate of topaquinone-catalyzed amine oxidation reactions. The kinetic isotope effects on the second-order rate constant for the inactivation and catalytic turnover are identical, indicating that the two processes share a common intermediate that follows C_H bond cleavage. Resonance Raman spectroscopy provides direct evidence for the accumulation of a neutral product Schiff base species. Removal of excess methylamine leads to recovery of both activity and the native absorption spectrum for E406N, indicating that the cofactor in the inactivated enzyme is chemically competent for hydrolysis. The rate of the reactivation is slow, however; the shortest half-life of the inhibited E406N at 25 degrees C is 5.9 min at pH 6.15. pH effect experiments show that the inactivation and reactivation steps are controlled by a single ionizable group with a pKa of 6.9-7.1; under basic conditions, when this residue is deprotonated, the inactivation is the fastest and the half-life of the inhibited enzyme is the longest. On the basis of the available crystal structures of copper amine oxidases, we propose that a histidine residue in the dimer interface is responsible for the observed ionization. In the wild-type enzyme this histidine is kept protonated by virtue of Glu at position 406. Unlike methylamine, the larger substrates ethylamine and benzylamine give normal turnover with E406N. Disruption of structure at the subunit interface in E406N may allow a rotation of the relatively small topa-product Schiff base complex (formed from methylamine) away from the active-site base to a conformation that is incompetent toward hydrolysis.

Consensus Sequence↗

PubMed1997

Effect of metal on 2,4,5-trihydroxyphenylalanine (topa) quinone biogenesis in the Hansenula polymorpha copper amine oxidase.

Previous studies of wild-type and mutant forms of a recombinant copper amine oxidase from Hansenula polymorpha, expressed in Saccharomyces cerevisiae, have indicated a self-processing mechanism for 2,4,5-trihydroxyphenylalanine (topa) quinone biogenesis involving the active site copper (Cai, D., and Klinman, J. P. (1994) J. Biol. Chem. 269, 32039-32042). In contrast to prokaryotic copper amine oxidases, however, it has not been possible to initiate topa quinone formation by the addition of exogenous copper to precursor H. polymorpha amine oxidase lacking copper. Metal analysis of copper-depleted wild-type enzyme reveals 0.2-0.3 mol copper, together with 0.6 mol zinc. Despite changes in the zinc and copper levels in growth media, the level of zinc in purified enzyme remains fairly constant. Further, we have been unable to displace protein-bound zinc by exogenously added copper. The H. polymorpha amine oxidase gene was subsequently expressed in Escherichia coli and found to be almost completely free of copper and zinc. In vitro reconstitution of this apoprotein confirms that zinc binds to H. polymorpha amine oxidase and prevents reconstitution with copper. By contrast, addition of copper first to apoprotein leads to formation of topa quinone and stable activity in the presence of added zinc. These findings indicate efficient binding of either zinc or copper to a site that undergoes little or no exchange. The data confirm that topa quinone biogenesis in the H. polymorpha system is catalyzed by copper and occurs in the absence of added factors. We conclude that the mechanisms of cofactor biogenesis in pro- and eukaryotic systems are likely to be similar or identical. The results described herein imply different pathways for the in vivo assembly of heterologously expressed amine oxidases in S. cerevisiae and E. coli.

Amine Oxidase (Copper-Containing)↗

PubMed1997

Crystallographic study of yeast copper amine oxidase.

The copper-containing amine oxidase from the yeast Hansenula polymorpha (YAO) has been crystallized and partially solved by molecular replacement. It catalyzes the oxidative deamination of primary amines by molecular oxygen to the corresponding aldehydes, ammonia and hydrogen peroxide. It contains a covalently bound redox cofactor, topa quinone, generated by post-translational modification of a single tyrosine side chain. The crystals of YAO are orthorhombic, with space-group symmetry P2(1)2(1)2(1) and unit-cell dimensions a = 138.8, b = 148.2, c = 234.0 A and diffract X-rays beyond 2.0 A resolution. Solution by molecular replacement using the E. coli amine oxidase structure [Parsons, Convery, Wilmot, Yadav, Blakeley, Corner, Philips, McPherson & Knowles (1995). Structure, 3, 1171-1184] as a search model reveals that there are three dimers in the asymmetric unit in a trigonal arrangement having 32 point-group symmetry. The solution agrees well with the self-rotation function of YAO. The non-crystallographic threefold axis lies parallel to a crystallographic twofold screw axis and each dimer has twofold symmetry. Phases from the refined model based on the molecular-replacement solution were used to solve one heavy-atom derivative. Model building from the unbiased isomorphous replacement phases is in progress.

Journal Article↗

PubMed1997

Positional cloning of a gene for nematode resistance in sugar beet.

The Hs1(pro-1) locus confers resistance to the beet cyst nematode (Heterodera schachtii Schmidt), a major pest in the cultivation of sugar beet (Beta vulgaris L.). The Hs1(pro-1) gene was cloned with the use of genome-specific satellite markers and chromosomal break-point analysis. Expression of the corresponding complementary DNA in a susceptible sugar beet conferred resistance to infection with the beet cyst nematode. The native Hs1(pro-1) gene, expressed in roots, encodes a 282-amino acid protein with imperfect leucine-rich repeats and a putative membrane-spanning segment, features similar to those of disease resistance genes previously cloned from higher plants.

Amino Acid Sequence↗

PubMed1997

Isometric muscle strength of Chinese young males in Taiwan.

This paper represents the results of an anthropometric measurement of the isometric muscle strength of Chinese young males in Taiwan aged from 16 to 20 years. The study uses a sample of 120 male students and measures four types of muscle strength: (1) right arm strength in exerting pull, push, adduction, abduction, lift, and press directions with five elbow angles (60, 90, 120, 150 and 180 degrees) in seated posture; (2) grip strength of both hands; (3) backlift strength: and (4) chest expanding strength. The obtained data are analysed and listed. Comparisons are made between the results of this study and those from domestic and foreign studies available in the literature. In general, their pattern is similar, but values obtained in this study are relatively smaller than those obtained in western countries.

Adolescent↗

PubMed1997

Spatiotemporal receptive field organization in the lateral geniculate nucleus of cats and kittens.

We have studied the spatiotemporal receptive-field organization of 144 neurons recorded from the dorsal lateral geniculate nucleus (dLGN) of adult cats and kittens at 4 and 8 wk postnatal. Receptive-field profiles were obtained with the use of a reverse correlation technique, in which we compute the cross-correlation between the action potential train of a neuron and a randomized sequence of long bright and dark bar stimuli that are flashed throughout the receptive field. Spatiotemporal receptive-field profiles of LGN neurons generally exhibit a biphasic temporal response, as well as the classical center-surround spatial organization. For nonlagged cells, the first temporal phase of the response dominates, whereas for lagged neurons, the second temporal phase of the response is typically the largest. This temporal phase difference between lagged and nonlagged cells accounts for their divergent behavior in response to flashed stimuli. Most LGN cells exhibit some degree of space-time inseparability, which means that the receptive field cannot simply be viewed as the product of a spatial waveform and a temporal waveform. In these cases, the response of the surround is typically delayed relative to that of the center, and there is some blending of center and surround during the time course of the response. We demonstrate that a simple extension of the traditional difference-of-Gaussians (DOG) model, in which the surround response is delayed relative to that of the center, accounts nicely for these findings. With regard to development, our analysis shows that spatial and temporal aspects of receptive field structure mature with markedly different time courses. After 4 wk postnatal, there is little change in the spatial organization of LGN receptive fields, with the exception of a weak, but significant, trend for the surround to become smaller and stronger with age. In contrast, there are substantial changes in temporal receptive-field structure after 4 wk postnatal. From 4 to 8 wk postnatal, the shape of the temporal response profile changes, becoming more biphasic, but the latency and duration of the response remain unchanged. From 8 wk postnatal to adulthood, the shape of the temporal profile remains approximately constant, but there is a dramatic decline in both the latency and duration of the response. Comparison of our results with recent data from cortical (area 17) simple cells reveals that the temporal development of LGN cells accounts for a substantial portion of the temporal maturation of simple cells.

Analysis of Variance↗

PubMed1997

Generation of multiple mRNA fingerprints using fluorescence-based differential display and an automated DNA sequencer.

Differential display is a method for the survey, analysis and comparison of gene expression in eukaryotic cells and tissues. Differential display involves isolation of high-quality nondegraded RNA, selective reverse transcription of polyadenylated mRNA using specific anchored oligopolydeoxythymidine [oligo(dT)] primers, and the subsequent PCR amplification of the cDNA with the same oligo(dT), an arbitrary upstream primer and radioisotopes for labeling the PCR products. The radioisotopically labeled products are then separated on a sequencing gel. In this report, we describe a rapid, specific, nonradioactive fluorescent differential display methodology in which fluorescently differentially labeled anchored oligo(dT) downstream primers are used in the reaction, with subsequent analysis of fluorescently labeled PCR products on an automated sequencer. Complete gene expression profiles, containing multiple mRNA fingerprints are possible by the simultaneous comparison of the multicolored banding patterns of the fluorescently differentially labeled products from several primer combinations. This modification of the differential display technique simplifies the assay and increases the throughput of high sample volumes required for comparative gene expression studies in various clinical applications.

Antibodies↗

PubMed1997

[The actions of nucleating proteins in vesicle aggregation and fusion: a preliminary study].

After investigation of the effects of Con A-binding proteins, the major biliary pronucleating effectors system on the figures and lipid composition of model biliary vesicles, the authors found that Con A-binding proteins accelerate aggregation and fusion of vesicles as a result of increased vesicular cholesterol and decreased vesicular phospholipids as well as cholesterol-saturated vesicles. We also found that vesicular proteins though in small quantity are potent in pronucleating effects. The distribution of several known nucleating proteins between the vesicles and micelles is quite different, and there are higher content and more potent pronucleating effectors in patients with cholesterol gallstone than those with pigment stone. By affinity staining method, con A-binding proteins were shown in native biliary vesicles as lipid-protein complex. These results suggest that the existence and changes in their quantity and quality of vesicular nucleating proteins play an important role in vesicle aggregation and fusion.

Bile↗

PubMed1997

Inhibition of recombinant Ca2+ channels by benzothiazepines and phenylalkylamines: class-specific pharmacology and underlying molecular determinants.

To understand the molecular basis of state-dependent pharmacological blockade of voltage-gated Ca2+ channels, we systematically characterized phenylalkylamine and benzothiazepine inhibition of three molecular classes of Ca2+ channels (alpha1C, alpha1A, and alpha1E) expressed from cDNA clones transfected into HEK 293 cells. State-dependent blockade figures importantly in the therapeutically desirable property of use-dependent drug action. Verapamil (a phenylalkylamine) and diltiazem (a benzothiazepine) were imperfectly selective, so differences in the state dependence of inhibition could be compared among the various channels. We found only quantitative differences in pharmacological profile of verapamil: half-maximal inhibitory concentrations spanned a 2-fold range (70 microM for alpha1A, 100 microM for alpha1E, and 110 microM for alpha1C), and inhibition was state dependent in all channels. In contrast, diltiazem produced only state-dependent block of alpha1C channels; alpha1A and alpha1E channels demonstrated state-independent block despite similar half-maximal inhibitory concentrations (60 microM for alpha1C, 220 microM for alpha1E, and 270 microM for alpha1A). To explore the molecular basis for the sharp distinction in state-dependent inhibition by diltiazem, we constructed chimeric channels from alpha1C and alpha1A and localized the structural determinants for state dependence to repeats III and IV of alpha1C, which have been found to contain the structures required for benzothiazepine binding. We then constructed a mutant alpha1C construct by changing three amino acids in IVS6 (Y14901, A1494S, 11497M) that have been implicated as key coordinating sites for avid benzothiazepine binding. Although these mutations increased the half-maximal inhibitory concentration of diltiazem inhibition by approximately 10-fold, the state-dependent nature of inhibition was spared. This result points to the existence of physically distinct elements controlling drug binding and access to the binding site, thereby favoring a "guarded-receptor" rather than a "modulated-receptor" mechanism of drug inhibition.

Calcium Channel Blockers↗