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Biomedical subjects

Tao Guo

Publications and source records attributed to Tao Guo.

51 records · Page 3Linked to original sources
PubMed2003

Ca2+ scraps: local depletions of free [Ca2+] in cardiac sarcoplasmic reticulum during contractions leave substantial Ca2+ reserve.

Free [Ca2+] inside the sarcoplasmic reticulum ([Ca2+]SR) is difficult to measure yet critically important in controlling many cellular systems. In cardiac myocytes, [Ca2+]SR regulates cardiac contractility. We directly measure [Ca2+]SR in intact cardiac myocytes dynamically and quantitatively during beats, with high spatial resolution. Diastolic [Ca2+]SR (1 to 1.5 mmol/L) is only partially depleted (24% to 63%) during contraction. There is little temporal delay in the decline in [Ca2+]SR at release junctions and between junctions, indicating rapid internal diffusion. The incomplete local Ca2+ release shows that the inherently positive feedback of Ca2+-induced Ca2+ release terminates, despite a large residual driving force. These findings place stringent novel constraints on how excitation-contraction coupling works in heart and also reveal a Ca2+ store reserve that could in principle be a therapeutic target to enhance cardiac function in heart failure.

Adrenergic beta-Agonists↗
PubMed2003

Oxidative capacity in failing hearts.

Although high-energy phosphate metabolism is abnormal in failing hearts [congestive heart failure (CHF)], it is unclear whether oxidative capacity is impaired. This study used the mitochondrial uncoupling agent 2,4-dinitrophenol (DNP) to determine whether reserve oxidative capacity exists during the high workload produced by catecholamine infusion in hypertrophied and failing hearts. Left ventricular hypertrophy (LVH) was produced by ascending aortic banding in 21 swine; 9 animals developed CHF. Basal myocardial phosphocreatine (PCr)/ATP measured with 31P NMR spectroscopy was decreased in both LVH and CHF hearts (corresponding to an increase in free [ADP]), whereas ATP was decreased in hearts with CHF. Infusion of dobutamine and dopamine (each 20 microg. kg-1. min-1 iv) caused an approximate doubling of myocardial oxygen consumption (MVO2) in all groups and decreased PCr/ATP in the normal and LVH groups. During continuing catecholamine infusion, DNP (2-8 mg/kg iv) caused further increases of MVO2 in normal and LVH hearts with no change in PCr/ATP. In contrast, DNP caused no increase in MVO2 in the failing hearts; the associated decrease of PCr/ATP suggests that DNP decreased the mitochondrial proton gradient, thereby causing ADP to increase to maintain adequate ATP synthesis.

Adenosine Triphosphate↗
PubMed2003

Determination of ferulic acid and adenosine in Angelicae Radix by micellar electrokinetic chromatography.

A micellar electrokinetic chromatography for determining ferulic acid and adenosine in Angelicae Radix was developed. A buffer solution composed of 50 mmol L(-1) borax, 10 mmol L(-1) sodium deoxycholate, and 2% methanol was found to be the most suitable electrolyte for the separation. The contents of ferulic acid and adenosine in Angelicae Radix were determined within 20 min. Good linearity between peak area ratio and the concentration was found in the range of approximately 20-320 microg mL(-1) for ferulic acid and about 10-160 microg mL(-1) for adenosine ( r >0.998), respectively. The recoveries were approximately 96.8-97.4% and 93.2-95.0%, and the RSD of this proposed method were 4.4% and 3.2% for ferulic acid and adenosine, respectively ( n=5). The contents of ferulic acid and adenosine in Angelicae Radix from different sources were determined.

Adenosine↗
PubMed2003

Privileged structure-based combinatorial libraries targeting G protein-coupled receptors.

Combinatorial chemistry has become a key component of today's drug discovery process. Privileged structures, with their inherent affinity for diverse biological receptors, represent an ideal source of core scaffolds and capping fragments for the design and synthesis of combinatorial libraries targeted at various receptors. GPCRs-distributed widely in the body and involved in many physiological and pathophysiological processes-have been historically among the most popular targets for drug discovery. Numerous privileged structure-based combinatorial libraries have been designed and synthesized, and these libraries have proved to be an extremely powerful tool to aid the rapid discovery and optimization of potent and selective ligands for a wide variety of GPCR targets. This review focuses on recent developments in applying privileged structure-based combinatorial libraries for the discovery and optimization of GPCR ligands and critically evaluates the advantages of the various types of GPCR-targeted libraries.

Combinatorial Chemistry Techniques↗
PubMed2003

[Determination of adenosine, rutin and quercetin in Carthamus tinctorius by HPCE].

AIM: To develop a method for determination of adenosine, rutin and quercetin in Carthamus tinctorius L. by high performance capillary electrophoresis(HPCE). METHODS: A fused silica capillary (66.5 cm x 50 microns ID, an effective length of 58 cm) was used. The running buffer composed of 50 mmol.L-1 borax (pH 9.7) containing 18% methanol. The applied voltage was 24 kV and the capillary temperature was 20 degrees C. The detection wavelength was 210 nm. Rifampicin was used as internal standard. RESULTS: A good linearity between peak area ratio of the common peak to the internal standard and the concentration was found in the range of 10-160 mg.L-1 for adenosine, 100-2,000 mg.L-1 for rutin and 100-1,600 mg.L-1 for quercetin (r > 0.998). The average recoveries were 98.5%-100.5%, 96.9%-99.5% and 99.1%-99.5% for adenosine, rutin and quercetin, respectively. The relative standard deviation was less than 6.5% (n = 5). CONCLUSION: The method is simple, rapid and with satisfactory recoveries and good reproducibilities. It can be used to control the quality of Carthamus tinctorius.

Adenosine↗
PubMed2003

[Comparative study of four GRE sequences in MnDPDP-enhanced magnetic resonance imaging for primary hepatocellular carcinoma].

OBJECTIVE: To assess the value of four T(1)-weighted (T(1)W) gradient-recalled-echo (GRE) sequences in MnDPDP-enhanced magnetic resonance imaging (MRI) for diagnosing primary hepatocellular carcinoma (HCC). METHODS: T(1)W images of fast low-angle shot (FLASH), fat-suppressed (FS) FLASH, in-phase and opposed-phase (IP/OP) FLASH were obtained from 13 HCC patients before and 30 min after the patients were given 5 micromol/kg.b.w. MnDPDP. The delayed (24 h) images were also obtained with the same sequences in addition to the T(2)W turbo spin-echo (TSE) sequence performed before MnDPDP administration. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the liver parenchyma and the tumor foci were calculated for each sequence. RESULTS: No statistical differences were found in SNR and CNR between the images obtained with the four T(1)W sequences (P > 0.05). The fatty degeneration of HCC could be detected by OP imaging, but not by T(1)W FLASH or IP T(1)W imaging. CONCLUSION: IP and OP FLASH produces better and easier performance in characterizing the fatty degeneration of HCC, and are recommended for MnDPDP-enhanced MRI of HCC.

Adult↗
PubMed2003

[Studies on diclofenac sodium pulsatile release pellets].

AIM: To investigate the preparation of diclofenac sodium pulsatile release pellets (DS-PRP), the release in vitro and the pharmacokinetics of the drug. METHODS: Diclofenac sodium (DS) core pellets prepared by extrusion-spheronization technology were coated in a mini-fluidized bed spray coater with swelling material as the inner coating swelling layer and ethylcellulose aqueous dispersion as the outer coating controlled layer. The effects of formulation and medium on pulsatile release of DS were investigated under release rate test. Pharmacokinetic and bioavailability study in eight human subjects were performed by HPLC method. RESULTS: The delayed-release time and release rate of DS from DS-PRP were influenced obviously by the swelling material, the concentration of SDS in medium, the coating level of the inner swelling layer and the outer controlled layer. In vitro, the delayed-release time T0.1 was 3.1 h, and the pulsed-release time T0.1-0.2 was 1.2 h. In vivo, the delayed-release time Tlag was 2.8 h, and the bioavailability was (91 +/- 12)%. CONCLUSION: The release of drug from DS-PRP was shown to be in pulsed way both in vitro and in vivo.

Adult↗
PubMed2002

Proteins with class alpha/beta fold have high-level participation in fusion events.

Now that complete genome sequences are available for a variety of organisms, the elucidation of potential gene products function is a central goal in the post-genome era. Domain fusion analysis has been proposed recently to infer the functional association of the component proteins. Here, we took a new approach to the analysis of the structural features of the proteins involved in fusion events. An exhaustive survey of fusion events within 30 completely sequenced genomes and subsequent structure annotations to the component proteins at a SCOP superfamily level with hidden Markov models was carried out. A domain fusion map was then constructed. The results revealed that proteins with the class alpha/beta fold are frequently involved in fusion events, around 86% of the total 676 assigned single-domain fusion pairs including at least one component protein belonging to the alpha/beta fold class. Moreover, the domain fusion map in our work may offer an attractive framework for designing chimeric enzymes following Nature's lead, and may give useful hints for exploring the evolutionary history of proteins. (c) 2002 Elsevier Science Ltd.

Archaeal Proteins↗
PubMed2002

Mining functional relationships in feature subspaces from gene expression profiles and drug activity profiles.

In an effort to determine putative functional relationships between gene expression patterns and drug activity patterns of 60 human cancer cell lines, a novel method was developed to discover local associations within cell line subsets. The association of drug-gene pairs is an explorative way of discovering gene markers that predict clinical tumor sensitivity to therapy. Nine drug-gene networks were discovered, as well as dozens of gene-gene and drug-drug networks. Three drug-gene networks with well studied members were discussed and the literature shows that hypothetical functional relationships exist. Therefore, this method enables the gathering of new information beyond global associations.

Antineoplastic Agents↗
PubMed2002

Preparation of the traditional Chinese medicine compound recipe heart-protecting musk pH-dependent gradient-release pellets.

In this study a sustained-release formulation of traditional Chinese medicine compound recipe (TCMCR) was developed by selecting heart-protecting musk pills (HPMP) as the model drug. Heart-protecting musk pellets were prepared with the refined medicinal materials contained in the recipe of HPMP. Two kinds of coated pellets were prepared by using pH-dependent methacrylic acid as film-forming material, which could dissolve under different pH values in accordance with the physiological range of human gastrointestinal tract (GIT). The pellets coated with Eudragit L30D-55, which dissolves at pH value over 5.5, were designed to disintegrate and release drug in the duodenum. The pellets coated with Eudragit L100-Eudragit S100 combinations in the ratio of 1:5, which dissolve at pH value 6.8 or above, were designed to disintegrate and release drug in the jejunum to ileum. The pellets coated with HPMC, which dissolves in water at any pH value, were designed to disintegrate and release drug in the stomach. Finally, the heart-protecting musk sustained-release capsules (HPMSRC) with a pH-dependent gradient-release pattern were prepared by encapsulating the above three kinds of coated pellets at a certain ratio in hard gelatin capsule. The results of dissolution of borneol (one of the active compounds of the TCMCR) in vitro demonstrated that the coating load and the pH value of the dissolution medium had little effect on the release rate of borneol from pellets coated with hydroxypropyl methyl cellulose (HPMC), but had a significant effect on the release rate of borneol from pellets coated with Eudragit L30D-55 or Eudragit L100-Eudragit S100 combinations in the ratio of 1:5. The pellets coated with Eudragit L30D-55 at 30% (w/w) coating load or above had little drug release in 0.1 mol/L HCl for 3 hr and started to release drug at pH value over 5.5. The pellets coated with Eudragit L100-Eudragit S100 combinations in the ratio of 1:5 at 36% (w/w) coating load or higher had little drug release in 0.1 mol/L HCl for 3 hr and in phosphate buffer of pH value 6.6 for 2 hr, and started to release drug at pH value 6.8 or above. The release profiles of lipophilic bornoel and hydrophilic total ginsenoside from HPMSRC, consisting of three kinds of pellets respectively coated at a certain ratio with HPMC, Eudragit L30D-55, and Eudragit L100-Eudragit S100 in the ratio of 1:5, showed a characteristic of pH-dependent gradient release under the simulated gastrointestinal pH conditions and no significant difference between them. The results indicated that various components with extremely different physicochemical properties in the pH-dependent gradient-release delivery system of TCMCR could release synchronously while sustained-releasing. This complies with the organic whole concept of compound compatibility of TCMCR.

Chemistry, Pharmaceutical↗
PubMed2002

[Study on the antibacterial activity of ginkgolic acids].

In this article we studied the anti-bacterial activity of the extract from testa of Ginkgo biloba and ginkgolic acids. They can inhibit the growth of Staphylocococus aureus, Escherichia coli, Bacillus subtilis, B. cereus and MRSA. Ginkgolic acids combined with peniciline can enhance their inhibitory activity to MRSA.

Anti-Bacterial Agents↗
PubMed2002

[Studies on heart-protecting musk pH-dependent gradient-release pellets].

AIM: To prepare heart-protecting musk pH-dependent gradient-release pellets and investigate the drug release in vitro and in vivo. METHODS: The pH-dependent gradient-release pellet system was prepared by using HPMC, Eudragit L-30D-55 and Eudragit L100-Eudragit S100 (1:5) combinations as coater. The release of borneol and total ginsenoside from pH-dependent gradient-release pellets were determined according to the method of Pharmacopoeia of the People's Republic of China (2000) in the simulated gastrointestinal pH conditions. The gastrointestinal transit and disintegration of pellets was investigated by using gamma-scintigraphic trace in volunteers. The pharmacokinetics of borneol of heart-protecting musk pH-dependent gradient-release pellets was studied in 6 healthy volunteers by GC methods. RESULTS: The f2 value of release data of borneol and total ginsenoside of the heart-protecting musk pH-dependent gradient-release pellets was 79.6 in the simulated gastrointestinal pH conditions. The gamma-scintigraphic trace evaluation demonstrated that the pellets coated with HPMC, Eudragit L-30D-55 or Eudragit L100-Eudragit S100 (1:5) combinations can disintegrate in stomach, duodenum and jejunum or ileum. The gastrointestinal transit time of pellets was about 5 hours in fasted state and about 6 hours in fed state. The concentration-time curves of borneol of heart-protecting musk pills fit in two-compartment model. The pharmacokinetics data showed that borneol had a short time of absorption and elimination. The mean residence time (MRT) of borneol of heart-protecting musk pills was 2.61 hours. The plasma concentration of borneol of heart-protecting musk sustained-release capsule which consisted of three kinds of pellets coated with HPMC, Eudragit L-30D-55 or Eudragit L100-Eudragit S100 (1:5) combinations was steadier than those of heart-protecting musk pills, its Cmax was lower than and Tmax was near to those of heart-protecting musk pills, its MRT was 4.0 hours, and its relative bioavailability was 96%. CONCLUSION: The lipidsoluble borneol and watersoluble total ginsenoside of heart-protecting musk pH-dependent gradient-release pellets can release simultaneously while sustained-releasing in vitro. The heart-protecting musk pH-dependent gradient-release pellets had the characteristics of pH-dependent gradient-releasing and disintegration while transiting in gastrointestinal tract. A characteristic of gradient sustained-release was shown in the concentration-time curves of borneol of heart-protecting musk sustained-release capsule in volunteers.

Adult↗
PubMed2002

[Study on the preparation of venenum bufonis beta-cyclodextrin inclusion complexes].

OBJECTIVE: To study the preparation of Venenum Bufonis beta-cyclodextrin inclusion complexes. METHOD: An optimal condition was established by the uniform design. Under the optimal conditions the Venenum Bufonis beta-cyclodextrin inclusion complexes were prepared with 5 different methods. RESULT: The ball grinding method was superior to other four methods. The bufadienolide inclusion rate of Venenum Bufonis beta-cyclodextrin prepared with ball grinding method was 85.42%. CONCLUSION: Ball grinding method is the best method for the preparation of Venenum Bufonis beta-cyclodextrin inclusion complexes.

Amphibian Venoms↗
PubMed1997

Design, Synthesis, and Evaluation of a Depsipeptide Mimic of Tendamistat.

The cyclic hexadepsipeptide framework of enniatin B was identified as a template matching the beta-turn tripeptide of tendamistat. The modified analog 1 was synthesized as a tendamistat mimic and compared to the acyclic derivative 2 and the tripeptide Ac-Try-Arg-Tyr-OMe. These compounds were assembled from the dimeric esters 3-5. As an inhibitor of alpha-amylase, 1 is twice as potent as 2 and comparable to the tripeptide. NMR studies of 1 reveal four conformers in equilibrium in a 50:25:15:10 ratio; the ring conformation of the major component is similar to that of the enniatin B template, with the cis geometry of the alpha-hydroxyisovaleryl-N-methylvaline amide linkage; the other conformers differ in the position or presence of the cis amide linkage.

Journal Article↗