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Biomedical subjects

S Li

Publications and source records attributed to S Li.

At least 1,279 records · Page 71Linked to original sources
PubMed1996

[Detection of multidrug resistance in patients with leukemia by using flow cytometry and RNA in situ hybridization].

Multidrug resistance (MDR) in leukemia and the reversal of MDR by cyclosporin A (CsA) in vitro have been studied through intracellular accumulation of daunorubicin (DNR) in leukemic myeloblasts. The study was carried out with real-time flow cytometry and relative expression levels of MDR, which is estimated by RNA in situ hybridization in 26 patients suffering from leukemia. The change of intracellular DNR accumulation in vitro after adding CsA was also analyzed. The results showed that intracellular DNR accumulation in newly diagnosed and treated patients (MDR1 negative) with remission increased significantly than that in refractory and relapsing patients (P < 0.01). Good reversal effect was obtained in refractory patients and MDR1 positive relapsing patients by adding CsA (P < 0.01). It is suggested that MDR detection by the two above-mentioned methods could help to project the chemotherapy schedule clinically, CsA had obvious reversal effect on the drug-resistant leukemic cells in vitro.

Adult↗
PubMed1996

The visual deprivation and increase in axial length in patients with cataracts.

PURPOSE: To investigate the relationship between axial myopia and visual deprivation in patients with cataracts in their youth. METHODS: Forty myopic eyes of 25 cases had long deprivation of form vision due to cataracts during their youth. The axial length was measured by A-Scan ultrasound. RESULTS: The axial length is 2-6mm (mean: 3.7mm) longer than the other eyes in 10 patients with unilateral cataracts. Fifteen cases with bilateral cataracts had 25-29mm of axial length (mean of the right eyes 26.8mm and the left eyes: 26.7mm). Six cases with unilateral cataract had traumatic history at age from 2-9 years (mean: 5.1 years) and the duration of visual deprivation due to cataract was from 8 to 30 years (mean: 12 years). Thirteen cases with dilateral congenital cataract had 17.4 years (from 3 to 37 years) of visual deprivation. CONCLUSION: The deprivation of form vision due to cataracts in childhood leads to increase in axial length and myopia.

Adolescent↗
PubMed1996

[Evaluation for grading standard of oblique flashlight test].

PURPOSE: We try to study the validity and reliability of grading standard of oblique flashlight test in this paper. METHODS: The validity of the grading standard of the oblique flashlight test was evaluated in 251 eyes. Based on anterior chamber angle as the gold standard, different grades of oblique flashlight test can find capable of closure angle sensitivity and specificity. The reliabilities (interobserver agreement and intraobserver agreement) also were evaluated in 250 and 88 eyes. RESULTS: 1. Validity of grading standard of oblique flashlight test: the results showed that it can find capable of closure angle sensitivity is 96.67%, specificity is 74.53% and Youden's index is 0.712, when the grades cutoff point on grade II. 2. Reliability of grading standard of oblique flashlight test: the results showed that the intraobserver agreement was observed agreement (Po) = 0.8, Kappa value (K) = 0.74 , Z = 22.48 and the intraobserver agreement was Po = 0.909, K = 0.875, Z = 16.08. CONCLUSIONS: The results of this research showed there are satisfactory validity and reliability for grading standard of oblique flashlight test. The test may be applied widely to estimate shallow anterior chamber and narrow angle.

Anterior Chamber↗
PubMed1996

[Detection of konjac glucomannan in seven Amorphophallus Blume species].

Seven Amorphophallus species were detected for konjac glucomananam (KGM). It has been found out that A. albus, A. konjac, A. yuloensis, A. xemengensis and A. dunnii are of higher contents of KGM (30%), but A. sinensis and A. yunnanensis are not as further comfirmed by TLC analysis. It follows that A. albus, A. konjac, A. yuloensis, A. xemengensis and A. dunnii are high quality resources of KGM, but A. sinensis and A. yunanensis cannot be used as substitutes for the above-cited five species.

Chromatography, Thin Layer↗
PubMed1995

Yeast artificial chromosome contigs reveal that distal variable-region genes reside at least 3 megabases from the joining regions in the murine immunoglobulin kappa locus.

The immunoglobulin kappa gene locus encodes 95% of the light chains of murine antibody molecules and is thought to contain up to 300 variable (V kappa)-region genes generally considered to comprise 20 families. To delineate the locus we have isolated 29 yeast artificial chromosome genomic clones that form two contigs, span > 3.5 megabases, and contain two known non-immunoglobulin kappa markers. Using PCR primers specific for 19 V kappa gene families and Southern analysis, we have refined the genetically defined order of these V kappa gene families. Of these, V kappa 2 maps at least 3.0 Mb from the joining (J kappa) region and appears to be the most distal V kappa gene segment.

Animals↗
PubMed1995

A regulatory mechanism that detects premature nonsense codons in T-cell receptor transcripts in vivo is reversed by protein synthesis inhibitors in vitro.

Gene rearrangement during the ontogeny of T- and B-cells generates an enormous repertoire of T-cell receptor (TCR) and immunoglobulin (Ig) genes. Because of the error-prone nature of this rearrangement process, two-thirds of rearranged TCR and Ig genes are expected to be out-of-frame and thus contain premature terminations codons (ptcs). We performed sequence analysis of reverse transcriptase-polymerase chain reaction products from fetal and adult thymus and found that newly transcribed TCR-beta pre-mRNAs (intron-bearing) are frequently derived from ptc-bearing genes but such transcripts rarely accumulate as mature (fully spliced) TCR-beta transcripts. Transfection studies in the SL12.4 T-cell line showed that the presence of a ptc in any of several TCR-beta exons triggered a decrease in mRNA levels. Ptc-bearing TCR-beta transcripts were selectively depressed in levels in a cell clone that contained both an in-frame and an out-of-frame gene, thus demonstrating the allelic specificity of this down-regulatory response. Protein synthesis inhibitors with different mechanism of action (anisomysin, cycloheximide, emetine, pactamycin, puromycin, and polio virus) all reversed the down-regulatory response. Ptc-bearing transcripts were induced within 0.5 h after cycloheximide treatment. The reversal by protein synthesis inhibitors was not restricted to lymphoid cells, as shown with TCR-beta and beta-globin constructs transfected in HeLa cells. Collectively, the data suggest that the ptc-mediated mRNA decay pathway requires an unstable protein, a ribosome, or a ribosome-like entity. Protein synthesis inhibitors may be useful tools toward elucidating the molecular mechanism of ptc-mediated mRNA decay, an enigmatic response that can occur in the nuclear fraction of mammalian cells.

Animals↗
PubMed1995

Phosphatidylcholines with sn-1 saturated and sn-2 cis-monounsaturated acyl chains. Their melting behavior and structures.

Recently, we have shown by high resolution differential scanning calorimetry that the position of a cis double bond (delta-bond) in a series of 1-stearoyl-2-octadecenoyl- phosphatidylcholines can affect the phase transition temperature (Tm) or enthalpy (delta H) of the gel-to-liquid crystalline phase transition of this series of lipids in the following manner. The value of Tm (or delta H) is minimal when the delta-bond is positioned at C(11) in the sn-2 acyl chain; in addition, this value increases steadily as the delta-bond migrates toward either end of the acyl chain, resulting in a symmetrical, inverted bell-shaped profile (Wang, Z.-q., Lin, H.-n., Li, S., and Huang, C. (1995) J. Biol. Chem. 270, 2014-2023). In this communication, we have further demonstrated the inverted bell-shaped profile of Tm using 1-arachidoyl-2-eicosenoyl-phosphatidylcholines. In addition, we have extended the lipid series of 1-stearoyl-2-octadecenoyl-phosphatidylcholines to include 1-arachidoyl-2-octadecenoyl- phosphatidylcholines and 1-behenoyl-2-octadecenoyl-phosphatidylcholine, each series with a delta-bond at varying carbon position of 6, 7, 9, 11, 12, and 13. Calorimetric results obtained with these three series of lipids indicate that the inverted bell-shaped curve shifts toward higher temperatures in a nonuniform manner as the saturated sn-1 acyl chain length increases from 17 to 19 and then to 21 C-C bond lengths. Specifically, the Tm (or delta H) values are nearly identical for these cis-monoenoic lipids when their delta-bonds are positioned at C(13). Based on the height of the rotational energy barrier obtained with molecular mechanics calculations, it is evident that the rotational flexibility of the single C-C bond adjacent to the delta-bond in 1-stearoyl-2-octadecenoyl-phosphatidylcholine increases as the delta-bond migrates from C(9) to C(13). The differential scanning calorimetry results obtained with the three series of lipids can thus be attributed to an increase in the rotational flexibility of the short chain segment succeeding the C(14) atom in the sn-2 octadecenoyl chain. In this communication, we also propose that in the gel-state bilayer of sn-1 saturated/sn-2 cis-monounsaturated phosphatidylcholine the entire length of the shorter segment of the sn-2 acyl chain acts as a structural perturbing element; hence, it is mainly responsible for the large lower Tm of the monoenoic lipid relative to the saturated counterpart. Finally, two general equations relating Tm with the structural parameters of cis-monoenoic phosphatidylcholines are presented.(ABSTRACT TRUNCATED AT 400 WORDS)

Calorimetry, Differential Scanning↗
PubMed1995

The cdc-2-related kinase, PISSLRE, is essential for cell growth and acts in G2 phase of the cell cycle.

Mammalian cell cycle progression is regulated by several protein kinases that are activated by cyclically expressed proteins called cyclins. These cyclin-dependent kinases, the prototype of which is the cdc2 mitosis-promoting kinase, are known to phosphorylate substrates the modified status of which is critical for the cell to progress into sequential phases of the cycle. Recently, a new cdc2-related protein kinase has been discovered. PISSLRE, named with respect to its homology to the cdc2 PSTAIRE amino acid domain. Here we report that by using both antisense and dominant-negative mutant constructs of PISSLRE when overexpressed in U2OS cells, a growth suppression is found. Furthermore, the dominant negative forms of PISSLRE halt cell cycle progression in G2-M. Therefore, PISSLRE is essential for cellular proliferation, and its effect is exerted in G2-M. This describes the first evidence since cdc2 of a cdc2-related kinase acting through G2-M.

Amino Acid Sequence↗
PubMed1995

Synthetic chemical diversity: solid phase synthesis of libraries of C2 symmetric inhibitors of HIV protease containing diamino diol and diamino alcohol cores.

Solid phase synthesis of non-oligomeric organic compounds has been pursued for high-efficiency generation of large numbers of structurally diverse compounds for drug screening. Known as chemical diversity libraries or combinatorial libraries (when the synthesis is carried out in a combinatorial fashion), these compounds can be used for de novo discovery of drug leads or for expedient structure--activity relationship (SAR) studies. To expand the scope of solid phase synthesis beyond the capability of the traditional method of solid phase synthesis for peptides, a strategy was developed for bi-directional solid phase synthesis starting with diamino alcohol or diamino diol core structures. The strategy relies on using bifunctional linkers to modify the core structures, simultaneously protecting the hydroxyl group or the diol moiety of the core and providing a carboxyl group for attachment of the modified cores to a solid support. The two NH2 groups of the modified cores attached to the solid support were then deprotected and reacted with a wide variety of amine-reactive reagents (carboxylic acids, sulfonyl chlorides, isocyanates, chloroformates, etc.) to extend the molecule in both directions. This strategy was successfully applied to automated parallel synthesis of a library of C2 symmetric inhibitors of HIV protease containing the known symmetry-based diamino diol and diamino alcohol core structures, thus enabling expedient access of large numbers of analogs in this series. A library of over 300 discrete compounds was synthesized using this methodology in order to identify potent (IC50 < 100 nM) HIV protease inhibitors with reduced size. This paper describes the technical aspects of this technology.

Alcohols↗
PubMed1995

Inhibition of protein phosphatase 1 and 2A down-regulates beta-tubulin gene expression in Trypanosoma rhodesiense.

We studied the effect of okadaic acid, a specific inhibitor of serine/threonine protein phosphatase types 1 and 2A, on the expression of beta-tubulin and procyclin genes in Trypanosoma rhodesiense. Okadaic acid was found to decrease the steady-state level of beta-tubulin mRNA about 5-fold in differentiating bloodstream trypanosomes and about 3-fold in established procyclic trypanosomes. No effect was observed on the expression of the procyclin gene. The down-regulation of beta-tubulin gene expression by okadaic acid in procyclic trypanosomes occurs at the post-transcriptional level. These results demonstrate the involvement of protein phosphatase 1 and/or 2A activity in maintaining the steady-state level of beta-tubulin mRNA in African trypanosomes.

Animals↗
PubMed1995

Secondary organ allografting after a primary "bridging" xenotransplant.

It remains uncertain whether xenotransplantation can sensitize the recipient to alloantigens, rendering subsequent allotransplantation unsuccessful. This is of considerable importance if a xenograft is to be used as a "bridge" to support the patient until a suitable allograft becomes available. When sera from 9 baboons that had received pig or African green monkey heart or liver xenografts were tested against a panel of lymphocytes from 5 or 6 potential donor baboons, positivity was seen in only 1 baboon (and then to only 2 of the potential 5 donors). In 4 baboons that had undergone previous xenotransplants (1 from this series of 9 baboons and 3 others), subsequent organ allografting was not followed by hyperacute, antibody-mediated, or accelerated cellular rejection. We conclude that organ xenotransplantation using discordant or concordant donor species does not prohibit subsequent allotransplantation.

Animals↗
PubMed1995

Evidence for a regulated interaction between heterotrimeric G proteins and caveolin.

Caveolae are flask-shaped plasma membrane specializations. A 22-kDa protein, caveolin, is a principal component of caveolar membranes in vivo. As recent evidence suggests that caveolae may participate in G protein-coupled signaling events, we have investigated the potential interaction of caveolin with heterotrimeric G proteins. Using cell fractionation techniques, we found that mutational or pharmacologic activation of Gs alpha prevents its cofractionation with caveolin. In a second independent approach, we directly examined the interaction of G proteins with caveolin. For this purpose, we recombinantly expressed caveolin as a glutathione S-transferase fusion protein. Using an in vitro binding assay, we found that caveolin interacts with G protein alpha subunits (Gs, Go, and Gi). Mutational or pharmacologic activation (with guanosine 5'-O-(thiotriphosphate)) of G alpha subunits prevents this interaction, indicating that the inactive GDP-bound form of G alpha subunits preferentially interacts with caveolin. This G protein binding activity is located within a 41-amino acid region of caveolin's cytoplasmic N-terminal domain (residues 61-101). Further functional analysis shows that a polypeptide derived from this region of caveolin (residues 82-101) effectively suppresses the basal activity of purified G proteins, apparently by inhibiting GDP/GTP exchange. This caveolin sequence is homologous to a region of the Rab GDP dissociation inhibitor, a known inhibitor of GDP/GTP exchange for Rab proteins. These data suggest that caveolin could function to negatively regulate the activation state of heterotrimeric G proteins.

Amino Acid Sequence↗
PubMed1995

Inhibitory effect of the potential endogenous benzodiazepine receptor ligand, octadecaneuropeptide (ODN), on gonadotropin-releasing hormone gene expression in the male rat brain.

It has been reported that activation of the GABAA receptor complex by different agents such as barbiturates and neurosteroids can negatively regulate the hypothalamopituitary-gonadal axis. Recently, an 86-amino acid polypeptide with high affinity for diazepam binding sites, termed diazepam-binding inhibitor (DBI), has been found in the rat brain. DBI as well as a peptide derived from DBI, the octadecaneuropeptide DBI[33-50] (ODN), can interact with the GABAA receptor complex. In order to investigate the role of these endogenous ligands for GABAA receptors on GnRH gene expression, we studied the effects of the acute administration (4 h before sacrifice) of ODN injected alone or in combination with the GABAA agonist muscimol on GnRH mRNA levels. Treatment with ODN produced a 31% decrease in the number of silver grains overlying labelled neurones. This effect was not modified by the concomitant administration of muscimol. The administration of the GABAA antagonist picrotoxin not only reversed the inhibitory effect of ODN but induced a 24% increase in the hybridization signal. This stimulating influence of picrotoxin was less striking (15% over control levels) when muscimol was administered with ODN. These data clearly indicate that a potential endogenous neuropeptide can positively interact with the GABAA receptor complex to modulate GnRH neuronal activity.

Animals↗
PubMed1995

A calorimetric study of binary mixtures of 1-octadecanoyl-2-decanoyl-sn-glycero-3-phosphoethanolamine and dimyristoyl phosphatidylethanolamine.

Model membranes composed of 1-octadecanoyl-2-decanoyl-sn-glycero-3- phosphoethanolamine and dimyristoyl phosphatidylethanolamine have been studied calorimetrically. 1-Octadecanoyl-2-decanoyl-sn-glycero-3- phosphoethanolamine is a highly asymmetric mixed-chain lipid, whereas dimyristoyl phosphatidylethanolamine is an identical-chain lipid with the same molecular weight. Calorimetric results indicate that these two lipids with a common molecular weight are completely miscible in the two-dimensional plane of the lipid bilayer in the liquid-crystalline state and that they are only partially miscible in the gel-state bilayer. Specifically, binary mixtures of these two lipids form eutectic phase diagrams at pH 7.4 and 10.0.

Calorimetry, Differential Scanning↗