Biomedical subjects

R S Li

Publications and source records attributed to R S Li.

At least 19 recordsLinked to original sources

PubMed2001

Diagnosis and current management of gastrojejunocolic fistula.

Gastrojejunocolic fistula is a late complication of gastroenterostomy and is associated with inadequate gastric resection and incomplete vagotomy. In the past, attempted primary repair had high mortality and staged operations were normally performed. We present two cases of gastrojejunocolic fistula and discuss the modern management of this condition. In both cases, improved nutritional support allowed successful one-stage surgical repair to be performed.

Adult↗

PubMed1999

Ornithine decarboxylase is a transcriptional target of tumor suppressor WT1.

The product of the Wilm's tumor suppressor gene, WT1, is a zinc-finger DNA-binding protein, which is thought to be a transcription factor. Two genes, those encoding epidermal growth factor receptor and syndecan-1, are known to be endogenous targets of WT1. Previous studies had identified binding sites for WT1 in the promoter of the ornithine decarboxylase (ODC) gene. In this paper, we tested whether the endogenous ODC gene might be a target of WT1 by establishing lines of baby hamster kidney (BHK) cells that expressed WT1 isoform A under control of a tetracycline-regulated expression system. When expression of WT1 was activated in BHK cells, the cellular level of ODC mRNA declined, with kinetics that correlated with the increase in WT1 level, demonstrating that the endogenous ODC gene was indeed responsive to cellular level of WT1. WT1 isoforms A and B inhibited the activity of the ODC promoter by approximately fivefold in transiently transfected BHK cells, while isoforms C and D, which have altered DNA binding domains, had no significant effect. The sequence CTCCCCCGC, located at nucleotides -106 to -98 relative to the site of transcriptional initiation in the ODC gene, interacted with the zinc-finger domain of isoforms A and B of WT1 with high affinity and specificity. A mutation in the binding site that disrupted this interaction partially removed the inhibition of ODC promoter activity by WT1, as did mutation of the two E-box sequences in intron I of the ODC gene. Simultaneous mutation of the WT1-binding motif and the two E-boxes completely abolished inhibition by WT1 of ODC promoter activity. These results, taken together, implicate the ODC gene as a downstream target of the tumor suppressor WT1.

3T3 Cells↗

PubMed1995

[Effects of zhengda zhenhua 851 on improvement of memory and fluency of language of kidney deficiency patients].

A study was conducted on the effects of Zhengda Zhenhua 851-R oral liquor on the improvement of memory and fluency of language of patients suffering from Kidney Deficiency and control group. It was found that the treated group did better in memory tests and the index of mental quotient (MQ) was higher than that of control group. They had markedly higher scores in the tests of directional memory which requires one's initiative and the free recollection of pictures. The scores achieved by the treated group were significantly higher than that of control on the tests of the fluency of language and expressions, particularly with words of different categories. The results showed that Zhengda Zhenhua 851-R oral liquor obviously had the function of improving the memory and fluency of language for Kidney Deficiency patients.

Aging↗

PubMed1995

Influence of 3,4',5-trihydroxystibene-3-beta-mono-D-glucoside on vascular endothelial epoprostenol and platelet aggregation.

AIM: To study the relationship between the inhibiting effect on platelet aggregation and the enhancing effect on epoprostenol (PGI2) released from vascular endothelium with 3,4',5-trihydroxystibene-3-beta-mono-D-glucoside (polydatin, Pol). METHODS: After having been incubated with Pol, the incubating medium was withdrawn from the bottles with newborn umbilical vein endothelial cells (VEC group, trypsin digesting method) and added to the platelets (washing method). The medium withdrawn from the bottles without VEC was designated as control group. Reduction of platelet aggregation rates (PAR, turbidity method) and changes of 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha) and thromboxane B2 (TXB2) (radioimmunoassay method) in the supernatant of the aggregated platelets induced by thrombin were scrutinized. RESULTS: PAR in the control group showed no reduction, whereas PAR reduction (-10 +/- 10) and 6-keto-PGF1 alpha increase (108 +/- 30 ng.L(-1)) in the VEC group treated 10 min with Pol 0.41 mmol.L(-1) (vs that of distilled water, ie, 2 +/- 12 and 54 +/- 20 ng.L(-1)) occurred. CONCLUSION: Increase of PGI2 from VEC by Pol was involved in its (Pol's) inhibition effect of platelet aggregation.

6-Ketoprostaglandin F1 alpha↗

PubMed1995

[Clinical study of effect of zhengda zhenhua 851-R oral liquor on delayed aging process].

A study was conducted on the effects of Zhengda Zhenhua 851-R (ZZ-851-R) oral liquor on middle aged-old patients with Kidney and Spleen Deficiencies. It was found that ZZ-851-R was able to relieve the symptoms of aging, improve the memory and fluency of speech, the activity of superoxide dismutase (SOD) GSH and GSH-peroxidase (GSH-Px) increased remarkably and serum lipid peroxide (LPO) level decreased significantly. Improvements of immunity, function of the pituitary-gonad axis were also noticed in the study, with decreased E2/T ratio and improved ability of total antioxydation. In summary, the ZZ-851-R has the effect of antisenility, without obvious side-effect.

Aged↗

PubMed1994

Complex interactions at a GC-rich domain regulate cell type-dependent activity of the ornithine decarboxylase promoter.

Regulation of ornithine decarboxylase (ODC) is critical to the control of cellular growth, differentiation, and carcinogenesis. A GC-rich region in the ODC promoter contains two overlapping protein binding sites that interact to regulate basal level expression in some cell types. A perfect binding motif for transcription factor Sp1 (CCCCGCCCC) is located at nucleotides -114 to -106 relative to the site of transcriptional initiation, binds strongly to purified Sp1 protein, and forms several complexes when incubated with nuclear extracts. Only one of these complexes is recognized by Sp1-specific antibody. A new protein-binding motif (GCCCCTCCCC, located at -110 to -100) partially overlaps with the Sp1 site and analyses by DNase I protection showed that a new protein ("NF-ODC1") and the Sp1-like proteins interact with the ODC promoter in a mutually exclusive manner. Mutation of the NF-ODC1 binding motif strongly enhanced ODC promoter strength in some cell types, but had little or no influence in others. The effect of mutating the Sp1 site also varied with cell type. These cell type specificities did not correlate with the levels of Sp1 and NF-ODC1 binding activities in nuclear extracts. These results show that regulation of the ODC promoter by the Sp1 family is cell type-specific and modulated by a negative effector that we have termed NF-ODC1.

Animals↗

PubMed1993

The sartorius myocutaneous island flap.

The vascular supply to the distal part of sartorius m. was studied in 37 limbs by dissection under magnification and after black ink and latex injections. The muscle or myocutaneous island flap pedicled on the saphenous artery (SA) is supplied by a retrograde circulation through anastomoses of the SA with the perforating branches of the posterior tibial artery and the medial inferior genicular artery. Three different vascular patterns were defined. Retrograde injection also showed good perfusion of the SA. The flap is useful for covering around the knee, the proximal and middle thirds of the lower leg, and the end of the amputation stump. Raising of the flap has not resulted in any functional or cosmetic defect. Eighteen operations have so far been performed, six using the muscle island flap and twelve using the myocutaneous island flap, and all survived completely.

Humans↗

PubMed1993

[The effect of low doses of recombinant human erythropoietin on renal anemia in predialysis patients with chronic renal failure].

Subcutaneous (s.c.) administration of recombinant human erythropoietin (rHuEPO) has been proven to be effective in anemia of predialysis patients with chronic renal failure (CRF). However, the optimal dosage and frequency of administration have not been established. We use low dose (< 100U.kg-1.w-1) of s.c. rHuEPO to treat renal anemia in two groups (group A: n = 18, twice a week; group B; n = 14, once a week) of nondialytic CRF patients. Hb and Hct gradually increased 1-3 months aftes rHuEPO treatment in the two groups. The incidence of hypertension, one of the main side effects, was lower (4/18 in Group A, 4/14 in Group B) than that reported in the literature. These results showed that either twice weekly or once weekly s.c. injection of low dose rHuEPO is effective and there will be less side effects treating predialysis patients with CRF.

Adult↗

PubMed1992

Multiple DNA elements responsible for transcriptional regulation of the ornithine decarboxylase gene by protein kinase A.

Transcription of the ornithine decarboxylase (ODC) gene is rapidly elevated by activation of protein kinase A (PKA). The additive influence of three cis-acting elements is responsible for this regulation in an adrenal carcinoma cell line. Two sites, CRE2 at -48 base pairs (bp) relative to the start of transcription and CRE3 at +95 bp, are identical to the core motif of the cAMP-responsive element (CRE) of the somatostatin gene and are conserved in the mouse, rat, and human ODC genes. Mutation of CRE2 resulted in a substantial decrease in basal promoter activity, as well as a 5-fold decrease in inducibility of the ODC promoter by PKA. CRE3 did not contribute to the basal activity of the ODC promoter, but mutation of this site resulted in a 2-fold decrease in inducibility by PKA. Deletion of a 45-bp sequence (GC-box) located 5' of CRE2, also resulted in a 2-fold decrease in inducibility of the ODC promoter. DNase I protection revealed the presence of protein binding at CRE2, the TATA box, and the GC-box of the ODC promoter. Mutation of CRE2 resulted in loss of protection of this sequence, as well as the 3' extension of the footprint over the TATA box, without affecting interactions at the GC box. Antibodies to the well characterized CRE-binding protein CREB recognized proteins binding to CRE2, suggesting that binding of CREB, or an antigenically related protein, is important for the activity of CRE2. Additionally, recombinant CREB bound to a DNA probe containing the CRE2 sequence.

Adrenal Gland Neoplasms↗

PubMed1992

Characterization of amelogenin mRNA from secretory- and maturation-stage rat incisor enamel.

Amelogenins are extracellular matrix proteins expressed at the secretory and the maturation stages of enamel formation. To characterize amelogenin transcripts from these two stages, rat incisor enamel-organ mRNA was hybridized to a mouse amelogenin cDNA. Northern analysis of the mRNA showed four amelogenin transcripts at the secretory stage. Two of these were larger than previously described, and would code for high molecular-weight amelogenins (> 40 kDa). These transcripts were similar in size to at least three bovine amelogenin mRNAs. At the maturation stage, one transcript slightly smaller than the major amelogenin transcript from the secretory stage was apparent. These differences may indicate a selective splicing of amelogenin mRNA in the maturation stage as compared to the secretory stage of enamel development.

Ameloblasts↗

PubMed1992

Two polyhydroxylated steroids from the Chinese soft coral Sinularia microclavata.

Two polyhydroxylated steroids have been isolated from the South China Sea soft coral Sinularia microclavata, and their structures were established as 24-methylenecholestane-1 alpha,3 beta,5 alpha,6 beta-tetrol and 1 alpha,3 beta,5 alpha-trihydroxy-24-methylenecholestan-6-one from spectral evidence and from comparison with two reference compounds, numersterol A and 24-methylenecholestane-1 alpha,3 beta,5 alpha,6 beta, 25-pentol, which were isolated from the soft corals, Simularia numerosa and Sarcophyton glaucum, respectively.

Animals↗

PubMed1991

Mechanism of the reaction catalyzed by mandelate racemase. 2. Crystal structure of mandelate racemase at 2.5-A resolution: identification of the active site and possible catalytic residues.

The crystal structure of mandelate racemase (MR) has been solved at 3.0-A resolution by multiple isomorphous replacement and subsequently refined against X-ray diffraction data to 2.5-A resolution by use of both molecular dynamics refinement (XPLOR) and restrained least-squares refinement (PROLSQ). The current crystallographic R-factor for this structure is 18.3%. MR is composed of two major structural domains and a third, smaller, C-terminal domain. The N-terminal domain has an alpha + beta topology consisting of a three-stranded antiparallel beta-sheet followed by an antiparallel four alpha-helix bundle. The central domain is a singly wound parallel alpha/beta-barrel composed of eight central strands of beta-sheet and seven alpha-helices. The C-terminal domain consists of an irregular L-shaped loop with several short sections of antiparallel beta-sheet and two short alpha-helices. This C-terminal domain partially covers the junction between the major domains and occupies a region of the central domain that is filled by an eight alpha-helix in all other known parallel alpha/beta-barrels except for the barrel domain in muconate lactonizing enzyme (MLE) [Goldman, A., Ollis, D. L., & Steitz, T. A. (1987) J. Mol. Biol. 194, 143] whose overall polypeptide fold and amino acid sequence are strikingly similar to those of MR [Neidhart, D. J., Kenyon, G. L., Gerlt, J. A., & Petsko, G. A. (1990) Nature 347, 692]. In addition, the crystal structure reveals that, like MLE, MR is tightly packed as an octamer of identical subunits. The active site of MR is located between the two major domains, at the C-terminal ends of the beta-strands in the alpha/beta-barrel domain. The catalytically essential divalent metal ion is ligated by three side-chain carboxyl groups contributed by residues of the central beta-sheet. A model of a productive substrate complex of MR has been constructed on the basis of difference Fourier analysis at 3.5-A resolution of a complex between MR and (R,S)-p-iodomandelate, permitting identification of residues that may participate in substrate binding and catalysis. The ionizable groups of both Lys 166 and His 297 are positioned to interact with the chiral center of substrate, suggesting that both of these residues may function as acid/base catalysts.(ABSTRACT TRUNCATED AT 400 WORDS)

Binding Sites↗

PubMed1991

Activation of p34cdc2 kinase by cyclin A.

Functional clam cyclin A and B proteins have been produced using a baculovirus expression system. Both cyclin A and B can induce meiosis I and meiosis II in Xenopus in the absence of protein synthesis. Half-maximal induction occurs at 50 nM for cyclin A and 250 nM for cyclin B. Addition of 25 nM cyclin A to activated Xenopus egg extracts arrested in the cell cycle by treatment with RNase or emetine activates cdc2 kinase to the normal metaphase level and stimulates one oscillatory cell cycle. High levels of cyclin A cause marked hyperactivation of cdc2 kinase and a stable arrest at the metaphase point in the cell cycle. Kinetic studies demonstrate the concentration of cyclin A added does not affect the 10 min lag period required for kinase activation or the timing of maximal activity, but does control the rate of deactivation of cdc2 kinase during exit from mitosis. In addition, exogenous clam cyclin A inhibits the degradation of both A- and B-type endogenous Xenopus cyclins. These results define a system for investigating the biochemistry and regulation of cdc2 kinase activation by cyclin A.

Animals↗

PubMed1990

Influence of latent iron deficiency on generation of oxygen species in polymorphonuclear leucocytes.

Measurement of luminol-dependent chemiluminescence (CL) was employed to estimate the generation of reactive oxygen species (ROS) in polymorphonuclear leukocytes (PMN) in patients with latent iron deficiency. There were no differences in the resting value of PMN CL among 20 patients with iron deficient erythropoiesis (2.92 + 0.38 number of pulses) and 20 normal controls (3.07 + 0.52; P greater than 0.05), but a significant decrease of peak value of PMN CL was observed in patients (45.82 + 7.41) as compared with controls (76.08 + 10.12; P less than 0.01). CL production by PMN in 6 patients with storage iron depletion was similar to that of 6 healthy controls. As a good correlation was found between the peak value of PMN CL and free erythrocyte protoporphyrin (FEP) level, increase of FEP could serve as a clinical indicator in the evaluation of decrease of ROS generation in PMN of patients with iron deficiency. Oral iron supplementation could effectively improve the impaired PMN ROS generation.

Adult↗

PubMed1990

[Increased ornithine decarboxylase activity is not essential for progesterone-induced Bufo oocyte maturation].

Ornithine decarboxylase (ODC) activity increases by 2 times in the process of progesterone-induced Bufo oocyte maturation (Table 1). Tumor promotor phorbol ester (PMA) is unable to affect both basal and stimulated ODC activity (Fig. 5) although it is capable of elevating the rate of steroid-induced maturation (Fig. 4). Spermine can inhibit significantly ODC activity of oocytes (Fig. 3). Hormone-stimulated ODC activity falls by 17% when Bufo oocytes are cultured in the alkaline Ringer's solution containing 5 mM spermine (pH 11.6) (Fig. 2). The period, however, is shortened by more than 50% during which the oocytes undergo GVBD (Fig. 1). Otherwise, spermine is found to repress ODC activity in dose dependent manner when microinjected in Bufo oocytes (Fig. 3). But oocytes undergo GVBD with a frequency of more than 80% when progesterone-induced increment of the enzyme activity is totally inhibited in the oocytes injected with approximately 50 nl 4.0 mM spermine. The conclusion may emerge from the above-stated results that increased ornithine decarboxylase activity is not essential for progesterone-induced Bufo oocyte maturation. In addition, ODC activity begins to increase rapidly when endogenous spermine level has been lowered to the largest extent in the maturation process. Therefore the endogenous spermine probably acts as a physiologically negative regulator of ODC activity since exogenous spermine inhibits seriously ODC activity of Bufo oocytes.

Animals↗

PubMed1990

[Studies on the synthesis and bioactivity of some new shikimic acid derivatives].

Ten new shikimic acid derivatives, some of which are analogs of dioxolamycin were synthesized from methyl shikimate because the bioactivity of shikimic acid derivatives has received considerably less attention to date. Compounds 4-10, 12, 16 were subjected to antimicrobial test in vitro, and showed no activity (MIC greater than 25 micrograms/ml). Compounds 4-10, 12, 13, and 16 were subjected to cytostatic activity test against cultured L 1210 Leukemia cells in vitro. Compounds 4, 6, 13 and 16 showed cytostatic activity like dioxolamycin.

Animals↗

PubMed1990

[Various transformations of polycythemia vera].

90 cases of polycythemia vera (PV) were diagnosed and followed up more than 3 years in PUMC Hospital from 1957 to 1986. 15 cases (16.7%) had various transformations during their courses. 4 cases had more than one kind of transformation. As a rare event, one case transformed to chronic lymphocytic leukemia. For illustration, some typical cases were presented, and the related fetuses discussed.

Adult↗

PubMed1989

[Proteins and proteinase-resistant polypeptides of delta-endotoxins from Bacillus thuringiensis and their insecticidal activity].

Proteins, solubility in alkaline buffer and proteinase-resistant polypeptides (PRP) of parasporal crystals (delta-endotoxin) from Bacillus thuringiensis were investigated. 19 sorts of crystals were divided into 7 types. Difference of crystalline proteins were coincident with their solubility and PRP. The characters of the protein, solubility and PRP were subspecies-specific basically, but in a few of crystals they were strain-specific. There was a closed relation between the biochemistry property of crystal protein and the toxicity in 2 species of insects. Crystal with protein of MW 130-138 kD kD or MW 130-138 kD and 60-65 kD, and PRP of MW 68-75 kD were high toxic in Bombyx mori (Lepidoptera), but most of them only showed weak or no toxicity in Culex fatigans (Diptera). Crystals containing more than 3 sorts of proteins with MW 15-138 kD in major protein and MW 35-75 kD in minor protein and PRP of 35-65 kD had very strong toxicity in Culex fatigans, but no toxicity in Bombyx mori. The construct of the crystal protein and the importance of the character in protein and PRP for the selection of expected strain and for the work of genetic engineering in Bacillus thuringiensis were discussed.

Animals↗