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Biomedical subjects

P Shen

Publications and source records attributed to P Shen.

At least 73 records · Page 4Linked to original sources
PubMed1999

[Effect of the coordinate micro-environment on the structure of Hg (II)-serum albumin].

Detailed studies on the UV spectra of Hg (II)-HSA or Hg (II)-BSA complexes nearby isoionic point were carried out in this paper. Compared with the spectra at physiological pH, the band nearby 250 nm of Hg (II)-BSA generally disappeared or widened and weakened,but the band at 290 nm of Hg (II)-BSA and Hg (II)-HSA remained nearly unchanged. These results support that these binding sites of Hg (II)-serum albumin may be located at seven pairs of adjacent disulfide bridges and there might be the structure of HgS4 tetrahedral configuration. For the first time, this paper put forward the solid figure of HgS4 tetrahedral configuration, and further discussed the results using the discrepancy of the coordinate micro-environment.

Animals↗
PubMed1999

[Study on the interaction of human serum albumin and Mn (II), Co (II) by fluorescence method].

The interaction of Mn (II), Co(II) and HSA has been studied by fluorescence method at pH 7.4 and 5.3. Based on Forste non-radiative energy transfer theory, the distance between Trp-214 residue of HSA and the first strong binding site to Mn (II), Co (II) in HSA was determined, and it is much larger than that of reference. This notable different result has been discussed according to the binding site of Mn (II), Co (II ) and domain structure in HSA.

Binding Sites↗
PubMed1998

ATP-dependent copper transport by the Menkes protein in membrane vesicles isolated from cultured Chinese hamster ovary cells.

The Menkes (MNK) protein is a vital component of copper homeostasis in mammalian cells. In this paper we provide the first biochemical evidence that the MNK protein functions as a copper-translocating P-type ATPase in mammalian cells. The enzyme activity in membrane vesicles prepared from Chinese hamster ovary cells overexpressing MNK was ATP-dependent, correlated with the amount of MNK and followed Michaelis-Menten kinetics with respect to copper. The copper transport was observed only under reducing conditions suggesting MNK transports Cu(I). This study opens the way to detailed structure-function studies and assessment of functional MNK derived from patients with Menkes disease.

Adenosine Triphosphatases↗
PubMed1998

Bacteriophage T7 mRNA is polyadenylated.

To determine whether the RNA of bacterial viruses is polyadenylated like bacterial mRNAs, pulse-labelled as well as the steady-state population of bacteriophage T7-specific transcripts were examined for the presence of poly(A) tracts by binding to oligo(dT) cellulose followed by hybridization with specific gene probes. Representatives of all classes of bacteriophage-specific mRNA--early, middle and late--were found to be polyadenylated. This conclusion was confirmed by screening the products of oligo(dT)-dependent cDNA synthesis. A cDNA library was prepared from RNA synthesized after bacteriophage T7 infection and the sequence of bacteriophage-specific clones was determined to define the sites of polyadenylation. About half of the clones were polyadenylated near the end of a protein-coding region, one of them at the site of post-transcriptional processing by RNase III. Other clones were polyadenylated within protein-coding regions. These observations suggest that polyadenylation occurs after the nucleolytic processing of primary transcripts and in some cases also after mRNA degradation has already begun.

Bacteriophage T7↗
PubMed1998

[Trans-ethmoidal optic nerve decompression in traumatic optic neuropathy].

UNLABELLED: To evaluate the outcome of trans-ethmoidal optic nerve decompression (TOND). METHOD: Between November 1984 and May 1996, 35 patients with traumatic optic neuropathy (TON) underwent TOND. While 6 patients were treated with high dose corticosteroids (HDC). RESULTS: 13(37.14%) cases of 35 patients who underwent TOND showed improvement in vision. 1 (16.67%) of 6 patients who were treated with HDC showed improvement in vision. Of the 12 patients with some initial vision, 8 patients underwent TOND and 7(87.5%) patients showed improvement in vision. Another 4 patients treated with HDC, 1(25.0%) patient showed improvement in vision. Of the 29 patients who presented with no light perception, 27 patients underwent TOND and 6(22.22%) patients showed improvement in vision. 2 patients treated with HDC failed to get vision improvement. CONCLUSION: TOND can improve vision in patients with TON. It is rational to perform surgical decompression early. Using of HDC before and after surgery may improve the outcome of TON. No light perception and absence of waveform on visual evoked response is not contradict, some patients may show improvement in vision.

Adolescent↗
PubMed1998

[Study on efficacy of Chinese Kidney-Tonifying Recipe in male rats with osteoporosis induced by dexamethasone and its mechanism].

OBJECTIVE: To study the efficacy of traditional Chinese Kidney-Tonifying Recipe (KTR) in male rats with osteoporosis induced by dexamethasone (DM) and its mechanism. METHODS: Forty-six male Sprague-Dawley rats at 12 months of age were chosen: they were divided into four groups and KTR and DM were administered appropriately for 18 weeks. General bone mineral density, femur bending strength, serum-BGP, serum-PTH and serum-E2 were measured. RESULTS: General bone mineral density, femur bending strength in KTR prevention group were significantly higher than those in DM group (P < 0.01) and the same with those in normal control group (P > 0.05). General bone mineral density, femur bending strength in KTR treatment group were higher than those in DM group (P < 0.05), and lower than those in normal control group. Compared with DM group, level of serum-T in KTR prevention group and KTR treatment group increased (P < 0.05) and level of serum-PTH in those two groups decreased (P < 0.05). But in comparison with DM group, level of serum-E2 and serum-BGP in the above-mentioned two groups was unchanged (P > 0.05). CONCLUSIONS: The data indicated that traditional Chinese Kidney-Tonifying Recipe could prevent and treat osteoporosis in male rats induced by DM.

Animals↗
PubMed1997

Half-life of Escherichia coli polyadenylated lipoprotein mRNA.

In the light of recent evidence that the half-life of bacterial mRNA may be modulated by polyadenylation at the 3' end, we determined the half-life of polyadenylated lpp mRNA, which is an abundant and comparatively stable message encoding a major lipoprotein of the outer membrane. Messenger RNAs were pulse-labeled with [3H] adenosine and poly(A) RNA was isolated at various times after pulse-labeling by affinity chromatography on oligo(dT) cellulose. The amount of lpp mRNA remaining was quantitated by hybridization with the antisense strand of the lpp gene cloned in M13mp18. The observed half-life for polyadenylated lpp mRNA was 12 min. This represents the first half-life measurement for a specific polyadenylated mRNA in E. coli, and is slightly longer than the half-life of total lpp RNA reported earlier. It coincides with the functional half-life for lpp mRNA determined by Inouye and coworkers by measuring the rate of lipoprotein synthesis at various times after rifampicin addition. This suggest that polyadenylated lpp RNA is the predominant and translationally active form of lpp mRNA within the cell.

Adenosine↗
PubMed1996

[The prevalence and risk factors of carotid atherosclerosis in elderly patients].

To assess the prevalence of extracranial carotid artery atherosclerosis and its relation to principal cardiovascular risk factors in Chinese elderly patients, 100 cases aged from 54 to 94 were investigated with B-mode ultrasonography. Arterial intima-media thickening, plaque, mild stenosis (defined as a plaque that obstructed > 20% of the lumen diameter), and clinically significant stenosis (> 50% in cross-sectional area) were found in 79, 49, 40 and 3 patients, respectively. There was no significant correlation between carotid atherosclerosis and coronary heart disease, cerebral infarction, hypertension, hyperlipidemia or diabetes. In contrast, the prevalence of carotid atherosclerosis was increased with age (P < 0.05), so did the severity. Thus, age is a major risk factor for carotid atherosclerosis in the elderly.

Age Factors↗
PubMed1995

An atlas of aromatase mRNA expression in the zebra finch brain.

Neural conversion of androgen to estrogen by aromatase is an important step in the development and expression of masculine behavior in mammals and birds. In contrast to the low telencephalic levels of aromatase in adult mammals and nonsongbirds, the zebra finch telencephalon possesses high aromatase activity. This study maps, by in situ hybridization, cells that express aromatase mRNA in the adult zebra finch telencephalon, diencephalon, midbrain, and pons. High aromatase mRNA expression was observed in the caudal neostriatum, limbic archistriatum, and hypothalamus. The hippocampus, parahippocampal area, and hyperstriatum accessorium contained cells expressing moderate amounts of aromatase message. Weakly labeled cells were found in the rostral neostriatum, lobus parolfactorius, and mesencephalic reticular formation. These findings are consistent with aromatase activity measurements of zebra finch tissue and document with anatomical precision both the widespread expression of aromatase mRNA in the brain and novel sites of brain aromatase. This study identifies the caudal neostriatum as a major site of telencephalic aromatase. A previous survey (Gahr et al., 1993: J. Comp. Neurol. 327:112-122) of several avian species found that the presence of estrogen receptors in parts of the caudal neostriatum is unique to songbirds, which are the only birds to possess the elaborated telencephalic song system. Together, these findings suggest that the heightened estrogen synthesis and estrogen sensitivity of the passerine caudal neostriatum may have some functional relation with the telencephalic circuits responsible for song.

Animals↗
PubMed1995

Chaos in intracellular Ca2+ oscillations in a new model for non-excitable cells.

A new model for intracellular Ca2+ oscillations is presented. The new model reinterprets two previous models, the ICC and CICR mechanisms, and incorporates the bell-shaped dependence of Ca2+ release on cytosolic [Ca2+]. Complex oscillations and chaos are found with this new model, confirming experimental observations of complex oscillations. A rich bifurcation sequence is found for the model as the stimulation due to agonist (R) is varied, including a period doubling route to chaos and a period-adding sequence of mixed-mode states.

Animals↗
PubMed1995

Gene amplification of the Menkes (MNK; ATP7A) P-type ATPase gene of CHO cells is associated with copper resistance and enhanced copper efflux.

Three copper-resistant variants of cultured Chinese hamster ovary (CHO) cells were isolated and each was shown to accumulate less intracellular copper than the parental cells when grown in copper-supplemented media. The reduced copper accumulation was related to enhanced copper efflux. As cultured cells from patients with Menkes disease (mutations in MNK; ATP7A gene) accumulate copper, probably due to defective copper efflux, we investigated the possible role of the MNK gene in the molecular basis of copper resistance. We found increased MNK mRNA and MNK protein in all three resistant variants. The MNK protein, which has not been previously demonstrated experimentally in mammalian cells, was observed to have an apparent molecular weight of 178 kDa on SDS gels. The degree of increase in MNK mRNA and protein correlated well with the level of copper resistance and extent of copper efflux. By Southern blot and FISH analysis we determined that the molecular basis for overexpression of MNK was genomic amplification of the MNK gene. These data, combined with the clinical and cellular phenotype in Menkes disease, provide strong evidence that the MNK protein is involved in transmembrane copper efflux, and demonstrate a new system of gene amplification in mammalian cells.

Adenosine Triphosphatases↗
PubMed1994

Outcomes of pregnancy associated with antiepileptic drugs.

OBJECTIVE: To determine whether exposure to antiepileptic drugs during pregnancy is associated with poor fetal outcomes (anomalies and death) and to assess the relative risks with phenobarbital, phenytoin sodium, and carbamazepine. DESIGN: The design was a prospective case-control cohort study of pregnant women with epilepsy and their offspring. Outcomes were compared with those of a control group of 355 healthy women and their offspring. SETTING: The obstetrics service at Los Angeles County/University of Southern California Medical Center, Los Angeles, a large, inner-city, teaching hospital. PATIENTS: Two hundred eleven subjects who were pregnant during the years 1987 through 1990, 174 of whom were delivered of infants, were available for analysis. A control group of 355 healthy women and their offspring from the same hospital were randomly selected from a computerized database. INTERVENTION: None. MAIN OUTCOME MEASURE: Anomalies and fetal death were the primary outcome measures. RESULTS: Offspring of women with epilepsy who were exposed to antiepileptic drugs had a higher rate of fetal death and anomalies than did the control population (P = .001). Abnormal outcomes were associated with the three major antiepileptic drugs (carbamazepine, phenytoin, and phenobarbital). In terms of abnormal outcome (death and anomalies), phenobarbital was associated with the highest relative risk, phenytoin with intermediate relative risk, and carbamazepine with the lowest relative risk (P = .019). Numbers were insufficient for assessment of risk associated with valproic acid. CONCLUSION: All three major antiepileptic drugs (phenobarbital, phenytoin, and carbamazepine) are associated with an increased risk of fetal death and anomalies. We found phenobarbital to be most associated with poor pregnancy outcome.

Abnormalities, Drug-Induced↗
PubMed1994

Analysis of ribosomal DNA restriction patterns in the genus Kluyveromyces.

Riboprinting was used to determine the relationships among strains belonging to 15 species of the genus Kluyveromyces. The small subunit ribosomal RNA gene (SSU rDNA) was amplified using the Polymerase Chain Reaction (PCR) and subjected to a battery of nine restriction enzymes. Similarity coefficients between strains were calculated based on shared and unique restriction fragments. Cluster analysis revealed three major groups that generally correlated with previously reported relationships based on other molecular data. Variations in SSU rDNA restriction fragments may be used for differentiation of the Kluyveromyces strains included in this study.

Base Sequence↗
PubMed1994

Isolation and characterization of a zebra finch aromatase cDNA: in situ hybridization reveals high aromatase expression in brain.

The brain regions controlling song are much larger in male than in female zebra finches. This sex difference is thought to arise developmentally when the male's brain is exposed to higher levels of estrogen. The synthesis of estrogen from androgen is catalyzed by aromatase, a key enzyme implicated in song development in the zebra finch. To study the role of estrogen synthesis in the organization of brain regions responsible for song, a cDNA encoding aromatase was isolated from a zebra finch ovarian cDNA library. The 3188 bp cDNA contains a 1527 bp open reading frame with 5' and 3' untranslated regions of 116 bp and 1545 bp, respectively. The deduced polypeptide is 509 amino acids in length, and is highly homologous to aromatases reported for chicken (92%), human (72%), mouse (70%), rat (69%) and trout (53%). Northern blot analysis revealed 5.4 kb, 4.8 kb and 3.2 kb aromatase mRNAs in brain and ovary. In situ hybridization histochemistry revealed the expression of aromatase mRNA in ovarian thecal cells of some, but not all, follicles, suggesting that aromatase gene expression is regulated during follicular maturation. In the adult brain, the distribution of aromatase mRNA was surprisingly widespread, and included the preoptic area, hypothalamus, hippocampus and neostriatum. By contrast, little aromatase mRNA expression was noted in the song nuclei (HVC, RA, area X). This study, the first description of aromatase mRNA expression by in situ hybridization in the brain of any species, identifies a surprisingly large number of cells that express aromatase mRNA in the zebra finch telencephalon. This pattern may be a unique feature of all songbirds.

Amino Acid Sequence↗