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Biomedical subjects

L Guo

Publications and source records attributed to L Guo.

At least 235 records · Page 13Linked to original sources
PubMed1998

[Studies on the selection of strains producing colominic acid and culture conditions].

One strain E. coli C-8, the highest yield of colominic acid, was selected from 40 E. coli strains in the medium in which glucose and ammonium sulfate were the only carbon and nitrogen resources. An optimum medium for the growth and colominic acid production of E. coli C-8 was studied. The optimum carbon resources for colominic acid production was sorbitol selected from 16 kinds of carbons, and its optimum concentration was 2.5%. The optimum inorganic and organic nitrogen resources for colominic acid production were ammonium sulfate (0.5%) and tryptone (1.5%), respectively. The optimum concentration of K2 HPO4 was 90 mmol/L. The optimum culture temperature was 37 degrees C, but no colominic acid was produced below 20 degrees C. The optimum pH range was 7.5-8.2. The strain growth in the optimum medium kept logarithmic phase in 40 h (maxim A = 22). The colominic acid secreted into medium was much lower before 20 h, but high biosynthetic rate of colominic acid was detected after 40 h, the colominic acid reached the highest level (1,200 micrograms/ml) at 65 h.

Culture Media↗
PubMed1998

Color vision defects with variation in the exon 5 of red and green pigment genes.

PURPOSE: To investigate correlation of variation in the exon 5 of red and green pigment genes with color vision defects. METHODS: Exon 5 of the red and green pigment genes in 11 protans, 19 deutans and 38 normal controls were analyzed by heteroduplux-SSCP analysis. RESULTS: In all 11 protans and 8 of the 19 deutans, defects of the red or green pigment gene could be identified. The C polymorphism (A/C at codon 283) in green pigment gene was present in 8 of 44 trichromats and 5 of 24 dichromats. Specific electrophoretic bands were found in 2 normal controls and a deutan. CONCLUSIONS: Variation in the exon 5 of the red and green pigment genes is the most common cause for color vision defects. Heteroduplex-SSCP analysis is a suitable way in screening specific variation in visual pigment genes.

Chromosomes, Human, X↗
PubMed1998

Comparison of the open-close kinetics of the cloned inward rectifier K+ channel IRK1 and its point mutant (Q140E) in the pore region.

To test whether a single amino-acid residue at the center of pore region can dictate the difference of open-close kinetics in a steady-state at hyperpolarized potentials among members of the inward K+ channel family, the Q140E mutant of the inward rectifier K+ channel (IRK1) was made and its gating properties were compared with those of IRK1 wild type (Wt) in Xenopus oocytes. The distinct differences were observed only at the single channel level. The open time constant of mutant tau(o)(Q140E) at -80 mV was over ten-fold shorter than that of Wt tau(o)(Wt); in Wt, the closed time distribution was fitted with a sum of two exponentials (c-slow and c-fast), whereas it could be fitted with three exponentials (c-slow, c-fast, and additional c-extrafast) in Q140E. However, the time constant of burst duration of mutant tau(b)(Q140E) was close to tau(o)(Wt) and both showed a similarly strong voltage dependence, and a high sensitivity to pH0 in the absence of Mg02+, indicating that tau(b)(Q140E) is closely related to tau(o)(Wt). These results demonstrated that Q140E shortened the channel openings by acquiring an extra-fast closing state. From the analysis of the effects of cations on both Wt and Q140E, it was suggested that the transition from the open state to this extra-fast closing state was not due to the block by H+ or Mg2+ but possibly by extracellular K+.

Amino Acid Sequence↗
PubMed1997

Regulation of lipid A modifications by Salmonella typhimurium virulence genes phoP-phoQ.

Bacterial pathogenesis requires proteins that sense host microenvironments and respond by regulating virulence gene transcription. For Salmonellae, one such regulatory system is PhoP-PhoQ, which regulates genes required for intracellular survival and resistance to cationic peptides. Analysis by mass spectrometry revealed that Salmonella typhimurium PhoP-PhoQ regulated structural modifications of lipid A, the host signaling portion of lipopolysaccharide (LPS), by the addition of aminoarabinose and 2-hydroxymyristate. Structurally modified lipid A altered LPS-mediated expression of the adhesion molecule E-selectin by endothelial cells and tumor necrosis factor-alpha expression by adherent monocytes. Thus, altered responses to environmentally induced lipid A structural modifications may represent a mechanism for bacteria to gain advantage within host tissues.

Acylation↗
PubMed1997

Prevention of preneoplastic mammary lesion development by a novel vitamin D analogue, 1alpha-hydroxyvitamin D5.

BACKGROUND: The form of vitamin D (vitamin D3) in fortified milk and the provitamin D produced by the body undergo metabolic activation to a biologically active form, 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3]. This compound can induce cell differentiation and can prevent proliferation of cancer cells. However, because 1alpha,25(OH)2D3 is hypercalcemic (effective in increasing serum calcium level), it is not suitable for use in cancer prevention or cancer therapy trials. PURPOSE: We synthesized a vitamin D5 series analogue, 1alpha-hydroxy, 24-ethyl-cholecalciferol, or 1alpha-hydroxyvitamin D5 [1alpha(OH)D5], and evaluated its chemopreventive activity in carcinogen-treated mammary glands in organ culture experiments. METHODS: The analogue 1alpha(OH)D5 was synthesized from sitosterol acetate and was characterized by nuclear magnetic resonance. Its purity was evaluated by high-pressure liquid chromatography. The calcemic activities of vitamin D3 and D5 analogues were determined in vitamin D-deficient Sprague-Dawley rats. Mammary glands of BALB/c mice were placed in organ culture and treated with the carcinogen 7,12-dimethylbenz[a]anthracene (DMBA) to induce preneoplastic lesions. Vitamin D analogues were added to the culture medium at four different concentrations, and formation of mammary lesions was evaluated. The effects of 1alpha(OH)D5 and 1alpha,25(OH)2D3 on the expression of vitamin D receptors (VDRs) and transforming growth factor-beta1 (TGF-beta1) were studied by immunohistochemistry. Statistical significance was determined by the chi-squared test. All reported P values were two-sided. RESULTS: 1alpha,25(OH)2D3 was fourfold more calcemic than 1alpha(OH)D5 at a dose of 0.042 microg/kg per day in rats. Both 1alpha,25(OH)2D3 and 1alpha(OH)D5 inhibited the development of DMBA-induced preneoplastic lesions in mouse mammary glands compared with untreated glands. The effect of the vitamin D3 analogue was observed at a much lower concentration (0.01 microM). Treatment with 1alpha(OH)D5 resulted in a dose-related (0.01-10.0 microM) inhibition without any toxicity, whereas the vitamin D3 analogue was highly potent but toxic at concentrations of 1.0 microM or higher. Normal mouse mammary glands poorly express VDR and TGF-beta1; incubation with 1alpha(OH)D5 or 1alpha,25(OH)2D3 dramatically induced their expression. CONCLUSIONS: This is the first report showing the possibility of chemoprevention by a vitamin D5 series compound. We conclude that 1alpha(OH)D5 is less calcemic than 1alpha,25(OH)2D3. It is nontoxic at a wide range of concentrations, but it is potent in inhibiting the development of preneoplastic lesions in mammary glands in organ culture. In addition, we show for the first time the induction of TGF-beta1 in normal mammary tissues by a chemopreventive agent. IMPLICATIONS: 1alpha(OH)D5 is a good candidate for in vivo chemoprevention studies. It may mediate its action by inducing expression of VDR and of TGF-beta1, as is seen in other systems.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1997

A Silicon Single-Electron Transistor Memory Operating at Room Temperature

A single-electron memory, in which a bit of information is stored by one electron, is demonstrated at room temperature. The memory is a floating gate metal-oxide-semiconductor transistor in silicon with a channel width ( approximately 10 nanometers) smaller than the Debye screening length of a single electron and a nanoscale polysilicon dot ( approximately 7 nanometers by 7 nanometers) as the floating gate embedded between the channel and the control gate. Storing one electron on the floating gate screens the entire channel from the potential on the control gate and leads to (i) a discrete shift in the threshold voltage, (ii) a staircase relation between the charging voltage and the shift, and (iii) a self-limiting charging process. The structure and fabrication of the memory should be compatible with future ultralarge-scale integrated circuits.

Journal Article↗
PubMed1997

Characterization of a novel microsomal fatty acid synthetase (FAS) compared to a cytosolic FAS in the housefly, Musca domestica.

A novel membrane-bound fatty acid synthetase (FAS) associated with the microsomal fraction from the housefly, Musca domestica, was solubilized and purified to homogeneity. The microsomal FAS was solubilized by 0.75 M KCl in phosphate buffer and was purified to homogeneity by the sequential use of ammonium sulfate precipitation followed by Sepharose CL-6B, DEAE Sephacel and Red Agarose (dye ligand affinity) chromatography. The specific activity of the microsomal FAS was increased 1,440-fold to 6,522 U/mg during purification. The cytosolic FAS from the housefly was also purified by similar methods and the specific activity increased 183-fold to 7,533 U/mg. The relative molecular mass of the microsomal and cytosolic FAS are 419 +/- 22 kDa and 405 +/- 18 kDa, respectively, for the dimers as determined by gel permeation chromatography. The microsomal and the cytosolic FAS yield different tryptic digestion maps and have slightly different amino acid compositions, which demonstrate structural differences between the two FASs. In addition, there are differences between the two FASs in their kinetic characteristics and their ability to incorporate methylmalonylCoA into the growing fatty acyl chain.

Acyl Coenzyme A↗
PubMed1997

Tolerance to mu-opioid agonists in human neuroblastoma SH-SY5Y cells as determined by changes in guanosine-5'-O-(3-[35S]-thio)triphosphate binding.

1. The agonist action of morphine on membranes prepared from human neuroblastoma SH-SY5Y cells was measured by an increase in the binding of the GTP analogue [35S]-GTPgammaS. Morphine increased the binding of [35S]-GTPgammaS to SH-SY5Y cell membranes by 30 fmol mg(-1) protein with an EC50 value of 76 +/- 10 nM. 2. Incubation of SH-SY5Y cells with 10 microM morphine for 48 h caused a tolerance to morphine manifested by a 2.5 fold shift to the right in the EC50 value with a 31 +/- 6% decrease in the maximum stimulation of [35S]-GTPgammaS binding. The response caused by the partial agonist pentazocine was reduced to a greater extent. 3. Chronic treatment of the cells with the more efficacious mu-ligand [D-Ala2, MePhe4, Gly-ol5]enkephalin (DAMGO, 10 microM) for 48 h afforded a greater effect than treatment with morphine. The maximal agonist effect of morphine was reduced to 58.9 +/- 6% of that seen in control cells while the maximal effect of DAMGO was reduced to 62.8 +/- 4%. There was a complete loss of agonist activity for pentazocine. 4. The development of tolerance was complete within 24 h and was blocked by naloxone and by the nonselective protein kinase inhibitor H7, but not by the putative beta-adrenoceptor kinase (beta-ARK) inhibitor suramin. 5. The observed tolerance effect was accompanied by a down-regulation of mu-opioid receptors determined by a decrease in the maximal binding capacity for the opioid antagonist [3H]-diprenorphine of 66 +/- 4%, but with no change in binding affinity. Binding of the agonist [3H]-DAMGO was similarly reduced. 6. The modulation of [35S]-GTPgammaS binding in SH-SY5Y cell membranes by opioids provides a simple method for the study of opioid tolerance at a site early in the signal transduction cascade.

Drug Tolerance↗
PubMed1997

[Electron microscopy of elastic system fibers in the rat mandibular joint].

We study the Elastic System Fibers (ESFs) in the rat mandibular joint using light microscope and image analyzer system and Electron Microscope. The results showed that the ESFs in the articular disc and capsule were more than in the articular cartilage. In addition, microfibrils and elaunin were the principal ESFs in all the articular components. The microfibrils in the articular surfaces ran at nearly right angle to the collagen fibers. The ESFs beneath the articular surfaces and the other articular components showed no specific directivity. ESFs construct an extensive fibers network in the disc and the capsule.

Animals↗
PubMed1997

Overexpression of p53, EGFR, c-erbB2 and c-erbB3 in endometrioid carcinoma of the ovary.

OBJECTIVES: To determine overexpression of p53, EGFR, c-erbB-2 and c-erbB-3 in endometrioid carcinoma of the ovary and to evaluate the prognostic significance of these results, especially, coexisting overexpression of p53 and one of the member of type I growth factor receptor family. METHODS: Overexpressions of the p53, EGFR, c-erbB-2 and c-erbB-3 protein were studied by immunohistochemistry in paraffin-embedded tumor tissue from 28 patients with endometrioid carcinoma of the ovary. RESULTS: 11 (39.3%), 13 (46.4%), and 14 (50.0%) were stained positively with p53, c-erbB-2 and c-erbB-3 monoclonal antibodies. 13 (46.4%) was stained positively with EGFR polyclonal antibody. There were no relationship between p53, EGFR, C-erbB-2, c-erbB-3 and histologic grade, lymph node metastasis. The percentage of tumors with over expression of p53, EGFR, C-erbB-2 and c-erbB-3 was higher in those with stage II-III tumors compared with those with stage I, in patients with residual tumor after initial surgery compared with those without. A high survival rate was observed in patients without p53, EGFR, c-erbB-2 and c-erbB-3 overexpression respectively than those with. A highest survival rate was observed in patients with both p53 and one of EGFR, c-erbB-2 and c-erbB-3 negative compared with those both positive or either of both positive. CONCLUSION: Overexpression of p53, EGFR, c-erbB-2 and C-erbB-3 resulted in a poorer prognosis respectively. Overexpression of both p53 and one of the EGFR, c-erbB-2 and c-erbB-3 is a worse prognostic indicator in patients with endometrioid carcinoma of the ovary.

Adult↗
PubMed1997

[Binding of oral lactobacilli to collagen].

The present study surveyed the ability, the characters and the influential factors on lactobacilli binding to the collagen. The experiment employed reference strains and fresh isolated strains. Binding of 3H-labeled bacteria to human type I collagen absorbed on hydroxyapatite surface (C-HA) was tested. The results suggested that the lactobacilli had high affinity for collagen. Competitive inhibitory assay indicated the attachment was highly specific. Binding to C-HA occurred in a collagen dose-dependent manner. pH value of reaction mixtures significantly affected the adherence. Below pH 6.5, increasing pH value caused a reduction of binding. Above pH 6.5, the binding was less affected. The ionic strength apparently influenced the binding level. The results of this study revealed one of the mechanisms that oral lactobacilli target dentin and root surfaces caries. This may also be a cariogenic virulent factor of lactobacilli.

Bacterial Adhesion↗
PubMed1997

[Interstitial tubercle in Chinese and Japanese young adults]

A comparative study on the incidence of interstitial tubercle from standardized stone casts of 160 Chinese and 190 Japanese young adults,ages from 20-30.The following results were obtained:(1)No significant difference in the incidence of interstitial tubercle on maxillary first premolar between Chinese and Japanese groups(P>0.05),but on maxillary second premolar,Japanese is higher than Chinese(P<0.05).(2)The incidence of interstitial tubercle on maxillary first premolar is higher than second premolar in two groups(P<0.05).(3)The intestitial tubercle occurs in unilateral more frequently than in bilateral.The incidence of maxillary first premolar in mesial of occlusal is higher than in distal.No difference between mesial and distal on occlusal of maxillary second premolar in the Chinese group,and the incidence in mesial is higher than in distal in the Japanese group.

Journal Article↗
PubMed1997

[Morphological study on occlusal grove of mandibular molar of Chinese adults]

During human evolution,the morphology of mandibular molar occlusal grooves have changed from the pattern "Y" to pattern "+".Six types of occlusal grooves were classified as:Y5,Y4,+5,+5,X5 and X4. Using computer analysis,we get the result.(1)The rate of "Y5" in first mandibular molar is the highest,the rate of "X4" is the lowest.(2)The rate of "+4" in second mandibular molar is the highest,while the rate of "Y5" is the lowest. (3)The rates of each type groove between male and remale have no significant difference.Our conclusion coincides in the evolution of human mandibular molar,that is helpful to direct the clinic and anthropology study.

Journal Article↗
PubMed1997

[Determination of cefotaxime in human serum by high performance liquid chromatography (HPLC)].

A reversed-phase HPLC assay has been developed for measuring cefotaxime (CTX) in human serum. A solid-phase extraction column (Bond Elute C18) was used for the pre-purification of sample. Serum (200 microL) was mixed with 100 microL of internal standard (acetylamino phenol) solution and 200 microL of sodium acetate buffer (0.01 mol/L, pH 5.8), loaded onto the conditioned column and washed with 2 mL of acetate buffer, the compounds were eluted with 0.5 mL x 2 of methanol-acetate buffer (40:60, V/V ). The eluate (20 microL) was injected directly into an Apex ODS column (250 mm x 4.6 mm i.d., 5 microm) with a mobile phase of acetate buffer (0.01 mol/L, pH 5.8)-methanol (80:20, V/V ), detection was achieved at 254 nm. The average extraction recoveries were 96.7% and 97.7% for CTX and internal standard respectively, which were higher than that of CTX (91.0%) obtained by protein precipitation with methanol. The solid-phase extraction method also provided much clearer samples for HPLC analysis. The concern of acid degradation of CTX when an acid is used as a protein precipitation agent was avoided. The calibration curve of CTX was linear between 10 and 150 mg/L of serum concentration with a correlation coefficient of 0.9992, and the minimum detection limit was 2 mg/L. The precision was tested with three sample concentrations, and within-day RSD below 3.0% and day-to-day RSD below 4.1% were achieved. Maximum serum concentrations of 25.95 and 22.89 mg/L were measured at 45 min after intramuscular injection of 1 g CTX to two healthy volunteers respectively. The chromatographic behaviour of CTX was also studied.

Adult↗
PubMed1997

[Studies on the separation method with multiple injection of proteins].

An abrupt change of the eluting curve of proteins in the RPC and HIC was reported in the previous paper. Here, we present a new multi-injection method of proteins in which the sample may be injected for many times in the same chromatographic run. When the composition of mobile phase is far away from the position of the abrupt change, the multi-injection of proteins before and/or after starting a gradient elution for one chromatographic separation in the RPC and HIC can be performed. Thus we may obtain the same chromatogram and retention of proteins as the ordinary one. This method can be used to overcome the difficulty that the loop is too small for injection big volume of sample solution. A larger sample size can be injected by many times in one chromatographic run to save time and to decrease the consumption of the experimental material. If there exist some impure proteins of weak retention, the impure proteins may go through the column with the solution A when the selected concentration of mobile phase is suitable. Therefore, a fixed column size can adsorb more related proteins, that is the effective column capacity is relatively raised. This injection method has an important value in the preparative chromatography of proteins.

Chromatography↗
PubMed1997

Hemofiltration or hemodiafiltration with on-line production of substitution fluid: clinical observation of safety and effectiveness.

OBJECTIVE: To observe the safety and cardiovascular stability of on-line hemofiltration (HF) or hemodiafiltration (HDF) and evaluate the clinical effectiveness of one HF or HDF session in addition to two hemodialysis (HD) sessions weekly. METHODS: Forty patients were randomly divided into four groups: group predilutional (PRD) HF (filtration rate: 259-333 ml/min) group predilutional HDF (filtration rate: 167 ml/min) group postdilutional (POD) HDF (filtration rate: 83 ml/min) and group bicarbonate HD. The reduction rate of parathyroid hormone (PTH), beta 2-microglobulin (beta 2MG), alpha 1-microglobulin (alpha 1MG) and KT/V in the initial treatment of every month was observed, and the incidence of hypotension and pyretic reaction during each treatment was evaluated. RESULTS: After 4-month observation, the KT/V for Group POD HDF is better than that for the other three groups, and for Group PRD HDF is better than that for Group HF and HD. Serum level of PTH and beta 2MG was not decreased after every treatment in Group HD, and so was serum level of alpha 1MG in all groups. Significant removal of PTH and beta 2MG was observed in Group HF, PRD HDF and POD HDF. The monthly serum level of beta 2MG and KT/V were stable in all groups, but the monthly serum level of PTH tended to be decreased in Group HF, PRD, HDF, and POD HDF. The incidence of pyretic reaction in HF or HDF was the same as in HD. Although the ultrafiltration volume was significantly higher during HF or PRD HDF than during HD, the incidence of hypotension in HF or PRD HDF was similar to that in HD. CONCLUSIONS: On-line HF or HDF proved to be a safe and reliable method. POD HDF mode seems to have the best KT/V, HF or PRD HDF offers a better choice for preventing intradialytic hypotension. One HF or HDF session in addition to two HD sessions weekly is similarly effective to decrease the serum level of PTH and the proof of the clinical effectiveness of such a therapy awaits a long-term observation.

Adult↗