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Biomedical subjects

Y Gao

Publications and source records attributed to Y Gao.

At least 451 records · Page 25Linked to original sources
PubMed1994

[The study of mechanisms and effects of prophylaxis and cure of electroacupuncture against ischemia injury in brain].

In order to observe the influence of electroacupuncturing (EA) "Ren Zhong" point on acute ischemia injury in brain, an experimental model of acute ischemia injury in brain was produced by antidromically blocking double common carotid arteries in 18 rabbits. The basic arteries' pressure will be increased by EA, RA and the contents of AI, A II increased and the content of LA reduced obviously in brain. An experimental evidence was given for the safety of EA anesthesia and the curative effect of EA on ischemia in brain.

Angiotensin II↗
PubMed1994

Synthesis and separation of optically active compounds. Part I.

Biological processes involve a high degree of stereoselectivity. Considering that pharmacological activity is very often associated with only one enantiomer, regulation authorities have defined new guidelines in requiring chiral drugs to be marketed as pure individually safe and effective enantiomers. If large scale production of pure stereoisomers has met until recently a great difficulty to become economically acceptable, the current state of the art in asymmetric synthesis and chiral separation, provides however many industrial applications. Among the methods currently used, asymmetric synthesis, using chiral auxiliaries or chiral catalysts such as enzymes or metal complexes, allows to create new asymmetric centers, starting from prochiral molecules. Regarding racemate resolution, asymmetric synthesis offers the real economical advantage to produce exclusively the targeted enantiomer. However, resolution methods allowing access to both enantiomers, are very useful at preparative scale for new chiral drugs when preclinical studies are requested for each enantiomer. Large scale racemate resolution can be achieved by crystallization, enzymatic resolution and even more recently by liquid chromatography. Although the "unwanted" enantiomer is also produced, the feasibility of its racemization for recycling has made resolution methods widely used in industry. It is clear today that in most cases, pharmacologically active molecules having an asymmetric center will have to be marketed as optically pure drugs.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1994

Synthesis and separation of optically active compounds. Part II.

This review is the second part of an article devoted to the synthesis and separation of optically active compounds. This article deals mainly with chiral chromatography which represents an important component of the state of art for the preparation of enantiomers, as illustrated by a description and a classification of the main packing materials available to date. The various phases are based on different principles of molecular recognition and show advantages and drawbacks according to the molecules to separate. The preparative aspect of this method is particularly emphasized here and in the same context, trends and future developments are mentioned.

Chromatography, High Pressure Liquid↗
PubMed1994

[Dietary factors and cancer of the colon and rectum in a population based case-control study in Shanghai].

The study was a population-based case control one, to compare possible difference in the risk factors between colonic and rectal cancer. This study showed that: (1) High intake of pork and saturated fat was an important risk factor for colon cancer, and only slightly related to rectal cancer. (2) Low consumption of vegetables especially cruciferous vegetables, rhizome vegetables, sea weeds, legume vegetables, dietary fiber and some vitamins mainly derived from vegetables, e.g. vitamin c and carotene, was associated with an increased risk for both colonic and rectal cancer, and these factors were closer relationship with rectal cancer than colon cancer. (3) High intake of the fried and pickled foods significantly increase the risk of occurrence of these cancers. (4) The ratio of bowel cancer in first degree relatives of colon cancer cases was 2.9 times of control group (P < 0.01), but the ratio for rectal cancer was only 1.6 times (P > 0.05) compared with control group.

Adult↗
PubMed1994

[Study on the pelvic stomata and computer image processing].

A medical image processing system attached to electron microscope was used to study the pelvic stomata of fetuses quantitatively. Two kinds of the mesothelial cells were found on the pelvic peritoneum of fetuses and mice, i.e. flattened and cuboidal cells. The pelvic stomata, arranged in clusters, only were located among the cuboidal cells with skewed distribution. Discrete scale of the pelvic stomata area varied greatly. The average area of a stoma was 10.00 +/- 9.44 microns2. Coefficient of variation was 94.40. Standard deviation and standard error were 9.44 and 0.98, respectively. Most of the pelvic stomata present were 1.34 microns2 to 32.11 microns2, and the maximum and the minimum areas of stomata were 43.4 microns2 and 0.8 micron2. The average percentage of the pelvic stomata was 7.2%.

Animals↗
PubMed1994

[Comparison of risk factors between left and right-sided colon cancer].

To compare differences of risk factors between left-sided and right-sided colon cancer, a population-based comparative case-control study involving 267 patients with left colon cancer, 247 with right colon cancer and 1451 population controls matched by age (+/- 5 yrs) and sex was carried out in Shanghai. The major causes in the two cancer groups were dietary and nutritional factors. Vegetables, ascorbic acid, riboflavin, tocopherol and carotenes played a protective role in the two groups, but various other foods and some vitamins displayed different relations with the two types of cancer. A negative association was observed between dietary fiber and right colon cancer. Animal fat and some fatty acids (e.g. saturated fatty acids, mono-unsaturated fatty acids and oleic acid) significantly elevated the risk for left colon cancer, but only slightly for right colon cancer. Physical activity and familial history of colorectal cancer in first degree relatives showed a more remarkable relationship with left- than right-sided colon cancers.

Adult↗
PubMed1994

[The causes responsible for recurrence of pituitary adenomas and an evaluation of reoperation effects].

Four hundred and twenty one cases of transfrontal removal of pituitary adenomas were presented. Of these 23 had recurrence of tumor which was confirmed by reoperation and histopathological examination. The rate of recurrence decreased while the patients' age increased. Incomplete removal of the tumor tissue was one of the most important causes of recurrence. Invasiveness was another important cause. Most of the tumors in this series were large and had pathologically proven invasiveness. At the reoperations, there were evidences of worse invasiveness, especially the infiltration of adenomas into the capsules and adjacent structures. There was a case of Nelson's syndrome, suggesting the endocrine causes of recurrence. Apparent adhesion and topographic disorders were found during reoperation, improvement of visual impairment decreased obviously, and the mortality rate increased; therefore, the reoperations should be decided with great deliberation.

Adenoma, Chromophobe↗
PubMed1994

[Grouped Cox regression model and its application in study of prognostic factors on cancer].

Cox proportional hazards regression model is the most popular multivariate regression model for analysis of survival data in medical follow-up studies and clinical trials, but it is unable to handle grouped survival data or large data sets with many tied failure times adequately. This paper explores the grouped proportional hazards regression model (GPH model) and its use in analysis of large data sets presented in life tables. By use of the data in a lung cancer follow-up study conducted in urban area of Shanghai, the authors give an example in detail for analysing prognostic factors of lung cancer by using GLIM.

Adult↗
PubMed1994

Whole-body biodistribution, radiation absorbed dose and brain SPECT imaging with iodine-123-beta-CIT in healthy human subjects.

UNLABELLED: SPECT imaging with 123I-labeled methyl 3 beta-(4-iodophenyl)tropane-2 beta-carboxylate ([123I]beta-CIT) in nonhuman primates has shown brain striatal activity, which primarily reflects binding to the dopamine transporter. The biodistribution and calculated radiation-absorbed doses of [123I]beta-CIT administered to eight healthy subjects were measured with attention to the accurate determination of organ time-activity data. METHODS: Whole-body transmission images were obtained with a scanning line source for attenuation correction of the emission images. Following administration of 92.5 +/- 22.2 MBq (2.5 +/- 0.6 mCi) of [123I]beta-CIT, subjects were imaged with a whole-body imager every 30 min for 3 hr, every 60 min for the next 3 hr and at 12, 24 and 48 hr postinjection. Regional body conjugate counts were converted to microcuries of activity, with a calibration factor determined in a separate experiment using a distributed source of 123I. RESULTS: The peak brain uptake represented 14% of the injected dose, with 2% of the activity approximately overlying the striatal region. Highest radiation-absorbed doses were to the lung (0.1 mGy/MBq, 0.38 rads/mCi), liver (0.087 mGy/MBq, 0.32 rads/mCi) and lower large intestine (0.053 mGy/MBq, 0.20 rads/mCi). CONCLUSIONS: Iodine-123-beta-CIT is a promising SPECT agent for imaging of the dopamine transporter in humans with favorable dosimetry and high brain uptake.

Adult↗
PubMed1993

Eukaryotic cytosolic chaperonin contains t-complex polypeptide 1 and seven related subunits.

We have characterized the cytosolic chaperonin from both rabbit reticulocyte lysate and bovine testis. The heteromeric complex contains eight subunits. Partial amino acid sequence data reveal that one of these is t-complex polypeptide 1 (TCP-1), while the other seven are TCP-1-related polypeptides, implicating the existence of a multigene family of TCP-1 homologues. We provide evidence that TCP-1 ring complex from bovine testis can facilitate the folding of both actin and tubulin, although, as in the case of chaperonin from reticulocyte lysate, two cofactors are required for the generation of properly folded tubulin. An additional molecule of TCP-1 may associate with the chaperonin depending on the purification procedure used. We propose that a highly conserved region in these polypeptides and in other chaperonins of the cpn60 chaperone family participates in ATP binding.

Actins↗
PubMed1993

Structural effects of the C2-methylhypoxanthine:cytosine base pair in B-DNA: A combined NMR and X-ray diffraction study of d(CGC[m2I]AATTCGCG).

C2-Methylhypoxanthine (m2I) is a synthetic analog of guanine with the N2-amino group replaced by a methyl group. We have studied the structural consequence of the m2I incorporation in DNA by a combination of X-ray crystallographic, NMR, and enzymatic analyses. The crystal structure of d(CGC[m2I]AATTCGCG) has been solved and refined to an R factor of 20.7% at 2.25-A resolution. In the DNA duplex, the two independent m2I:C base pairs maintain the Watson-Crick scheme. While the C2-methyl group of m2I is in van der Waals contact with the O2 of the base-paired cytosine, it only causes the base pair to have slightly higher propeller twist and buckle angles. Its solution structure was analyzed by the NMR refinement procedure SPEDREF [Robinson, H., & Wang, A. H.-J. (1992) Biochemistry 31, 3524-3533] using 2D nuclear Overhauser effect data. Two starting models, a relaxed fiber model and an X-ray model, were subjected to the NOE-constrained refinement using 1518 NOE cross-peak integrals to arrive at the final models with (NOE) R factors of 13.8% and 14.3%, respectively. The RMSD between the two refined models (all atoms included) is 1.23 A, which presently seems to be near the limit of convergence of NOE-based refinement. The local structures of the two models are in better agreement as measured by the RMSD of the dinucleotide steps, falling in the range 0.54-0.98 A. Both refined solution structures confirm that the m2I dodecamer structure is of the B-DNA type with a narrow minor groove at the AT region, as observed in the crystal. However, significant differences exist between the crystal and solution structures in parameters such as pseudorotation angles, propeller twist angles, etc. The solution structure tends to have a more uniform backbone conformation, an observation consistent with that concluded from the laser Raman study of d(CGCAAATTTGCG) [Benevides, J. M., Wang, A. H.-J., van der Marel, G. A., van Boom, J. H., & Thomas, G. J., J. (1988) Biochemistry 27, 931-938]. Three related dodecamers, d(CGCGAATTCGCG), d(CGC[m2I]AATTCGCG), and d(CGC[e6G]AATTCGCG), were tested as substrates for the restriction endonuclease EcoRI. The m2I dodecamer was active, but the e6G dodecamer was not. Our results illustrate the complementarity in terms of the structural information provided by the two methods, X-ray diffraction and NMR.

Base Composition↗
PubMed1993

Effects of staurosporine on transcription by vesicular stomatitis virus.

The protein kinase inhibitor staurosporine has been found to inhibit vesicular stomatitis virus transcription in infected BHK cells. Both primary and secondary transcription were virtually abolished by 10 microM staurosporine. In contrast, transcription by purified virions, or by nucleocapsids isolated from them, was unaffected by staurosporine. Staurosporine inhibition did not occur at or prior to the uncoating step, since: (i) the drug was equally effective if added at t = 0 or at t = 1 hr after infection; (ii) immunofluorescence microscopy of infected cells in the presence of staurosporine showed that M protein was diffusely present in the cytoplasm, indicative of normal uncoating. Staurosporine caused a modest (< 25%) reduction in virus internalization from the cell surfaces. This was not sufficient to account for the transcription inhibition, however. Inhibition of transcription by staurosporine was not observed in extracts from infected cells, nor could it be induced by addition of uninfected cell cytosol to purified nucleocapsids. This suggests that inhibition of transcription in infected cells is secondary to substrate depletion or other cytotoxic effects of the drug. The addition of staurosporine to purified nucleocapsids, while not affecting cell-free transcription, inhibited phosphorylation of L protein completely and of P (NS) protein partially, providing addition evidence that at least two different kinases are present in nucleocapsids, and that the staurosporine inhibited ones are unnecessary for cell-free viral transcription.

Alkaloids↗
PubMed1993

The effect of vasopressin on the cytoskeleton of the epithelial cell.

Vasopressin (AVP) promotes the fusion of vesicles containing water channels with the apical membrane of receptor cells in the amphibian bladder and mammalian kidney. Fusion is accompanied by depolymerization of the actin cytoskeleton. In this review, we present the evidence for actin depolymerization by AVP in the whole cell, and the application of confocal microscopy and immunogold electron microscopy in localizing depolymerization to the apical region of the receptor cell.

Actins↗
PubMed1993

Beta-adrenoceptors and the epithelial layer in airways.

As an inflammatory disorder of the respiratory system, asthma is characterized by bronchial hyper-responsiveness that appears to involve alterations of the bronchial epithelium. The existence of epithelial beta-receptors is of particular importance to respiratory function, and epithelial dysfunction in asthma may impair beta-adrenoceptor function and lead to bronchial hyper-responsiveness. After reviewing the structure and function of the respiratory epithelium and the role of epithelial beta-adrenoceptors, an in vitro model allowing the detailed study of the regulation of airway smooth muscle by epithelial cells is described. Studies with this model have demonstrated that epithelial beta-adrenoceptors participate in modulating the tone of bronchial smooth muscle cells. Activation of these beta-adrenoceptors leads to bronchial myorelaxation, probably mediated by one or more inhibitory substances generated within the epithelium. In addition, beta-adrenoceptor activity may affect smooth muscle tone indirectly by regulating mucociliary clearance and the paracellular exchange of inflammatory mediators. Since some respiratory diseases seem to be associated with beta-adrenoceptor dysfunction, therapy with beta-agonists may be beneficial by acting on beta-adrenoceptors located both on smooth muscle cells and on epithelial cells.

Animals↗
PubMed1993

Reconstitution of wild type viral DNA in simian cells transfected with early and late SV40 defective genomes.

The DNAs of polyomaviruses ordinarily exist as a single circular molecule of approximately 5000 base pairs. Variants of SV40, BKV and JCV have been described which contain two complementing defective DNA molecules. These defectives, which form a bipartite genome structure, contain either the viral early region or the late region. The defectives have the unique property of being able to tolerate variable sized reiterations of regulatory and terminus region sequences, and portions of the coding region. They can also exchange coding region sequences with other polyomaviruses. It has been suggested that the bipartite genome structure might be a stage in the evolution of polyomaviruses which can uniquely sustain genome and sequence diversity. However, it is not known if the regulatory and terminus region sequences are highly mutable. Also, it is not known if the bipartite genome structure is reversible and what the conditions might be which would favor restoration of the monomolecular genome structure. We addressed the first question by sequencing the reiterated regulatory and terminus regions of E- and L-SV40 DNAs. This revealed a large number of mutations in the regulatory regions of the defective genomes, including deletions, insertions, rearrangements and base substitutions. We also detected insertions and base substitutions in the T-antigen gene. We addressed the second question by introducing into permissive simian cells, E- and L-SV40 genomes which had been engineered to contain only a single regulatory region. Analysis of viral DNA from transfected cells demonstrated recombined genomes containing a wild type monomolecular DNA structure. However, the complete defectives, containing reiterated regulatory regions, could often compete away the wild type genomes. The recombinant monomolecular genomes were isolated, cloned and found to be infectious. All of the DNA alterations identified in one of the regulatory regions of E-SV40 DNA were present in the recombinant monomolecular genomes. These and other findings indicate that the bipartite genome state can sustain many mutations which wtSV40 cannot directly sustain. However, the mutations can later be introduced into the wild type genomes when the E- and L-SV40 DNAs recombine to generate a new monomolecular genome structure.

Animals↗