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Biomedical subjects

C Li

Publications and source records attributed to C Li.

At least 1,081 records · Page 60Linked to original sources
PubMed1993

Mechanism of adverse conditions causing lack of flagella in Escherichia coli.

Escherichia coli lacks flagella when grown in tryptone broth in the presence of various adverse conditions (C. Li, C. J. Louise, W. Shi, and J. Adler, J. Bacteriol. 175:2229-2235, 1993). Now, the synthesis, rather than the degradation, of flagellin was shown to be inhibited. Studies of transcriptional fusions of flagellar operons to the lacZ gene revealed that transcription of the flagellar genes was reduced in cells grown under these adverse conditions. Increasing gene dosage of the flhD operon by a plasmid partially suppressed the nonflagellation caused by some adverse conditions. The signal which shuts off the synthesis of flagella under adverse conditions remains to be discovered. This shutting-off process does not result from catabolite repression or from signals from the chemotaxis system.

Chemotaxis↗
PubMed1993

Escherichia coli shows two types of behavioral responses to osmotic upshift.

Behavioral responses to osmotic upshift were characterized by temporal assays of free-swimming cells of Escherichia coli. Small osmotic upshifts (200 to 300 mosM) elicited tumble responses which were chemotaxis dependent, while large osmotic upshifts (400 to 500 mosM) elicited stopping followed by pseudotumbling which was chemotaxis independent.

Cell Movement↗
PubMed1993

Isolation of Helicobacter pylori from saliva.

Helicobacter pylori was grown in low numbers from the saliva of one of nine patients who were positive for gastric H. pylori. The saliva-derived isolate from this patient was identical to the antral biopsy-derived isolate from the same patient and differed from isolates cultured from the antral biopsies of all other patients by soluble-protein electrophoresis, restriction endonuclease DNA analysis, and Southern blot hybridization. This is the first observation, to our knowledge, of the recovery of viable H. pylori from saliva.

Fatty Acids↗
PubMed1993

A highly specific and sensitive DNA probe derived from chromosomal DNA of Helicobacter pylori is useful for typing H. pylori isolates.

HindIII-digested DNA fragments derived from an EcoRI-digested 6.5-kb fragment of chromosomal DNA prepared from Helicobacter pylori ATCC 43629 (type strain) were cloned into the pUC19 vector. A 0.86-kb insert was identified as a potential chromosomal DNA probe. The specificity of the probe was evaluated by testing 166 non-H. pylori bacterial strains representing 38 genera and 91 species which included aerobic, anaerobic, and microaerophilic flora of the upper and lower gastrointestinal tracts. None of the 166 non-H. pylori strains hybridized with this probe (100% specificity), and the sensitivity of this probe was also 100% when H. pylori isolates from 72 patients with gastritis and with the homologous ATCC type strain were tested by dot blot hybridization. The capability of this probe for differentiating between strains of H. pylori was evaluated by Southern blot hybridization of HaeIII-digested chromosomal DNA from 68 clinical isolates and the homologous ATCC type strain of H. pylori. Fifty-one unique hybridization patterns were seen among the 69 strains tested, demonstrating considerable genotypic variation among H. pylori clinical isolates. We propose that this probe would be of significant value for conducting epidemiologic studies.

Bacterial Typing Techniques↗
PubMed1993

Novobiocin forms cation-permeable ion channels in rat fetal distal lung epithelium.

The antibiotic novobiocin has been previously reported to increase Na+ transport in frog skin, presumably by attenuation of Na+ self-inhibition of Na+ channels. To determine whether novobiocin had similar effects and utilized a similar mechanism in mammalian Na(+)-transporting tissues, we studied its effect on ion transport by primary cultures of fetal distal lung epithelium (FDLE) cultured from 20-day gestationally aged rats (term = 22 days). Novobiocin (10 mM) increased short-circuit current and markedly decreased the resistance in FDLE monolayers mounted in Ussing chambers. Fura-2 single-cell studies showed that novobiocin increased intracellular Ca2+ concentration and that this resulted from extracellular sources. Nystatin-perforated patch-clamp techniques demonstrated that novobiocin increased nonrectifying cation whole cell currents without inducing detectable anion currents. Novobiocin created nonrectifying monovalent cation-selective channels in lipid bilayers. These studies demonstrated that novobiocin affects the bioelectric properties of Na+ transporting lung epithelium and that this likely occurs by the formation of ion-permeant channels in their lipid membranes.

Animals↗
PubMed1993

Synthesis of [18F]fluoroalanine and [18F]fluorotamoxifen for imaging breast tumors.

To develop ligands for imaging breast tumors, [18F]fluoro analogue of tamoxifen and [18F]fluoroalanine were radiosynthesized. In vivo biodistribution studies were performed in mammary tumor-bearing rats. In studies on the biodistribution of an [18F]fluoro analogue of tamoxifen, tumor uptake decreased when rats were pretreated with diethylstilbestrol (DES), suggesting that tracer uptake in tumors was receptor-mediated. An estrogen receptor assay indicated that tumors have a receptor density of 7.5 fmol/mg protein. Studies of the distribution of [18F]fluoroalanine in tissue showed that the tumor-to-tissue ratio increases as a function of time. Positron emission tomography (PET) images of tumor-bearing rats demonstrated that tumors can be visualized 1 h after rats are injected with an [18F]fluoro analogue of tamoxifen. PET imaging of pigs after injection of 10 mCi of [18F]fluoro analogue of tamoxifen showed uterine uptake that could be blocked by DES (50 mg). The findings suggest that both radiotracers are useful for imaging breast tumors.

Alanine↗
PubMed1993

[Glutathione S-transferases in carcinogenesis and diagnosis of liver cancer].

We studied the relations between glutathione S-transferases (GSTs) from human liver and hepatic cancer and preneoplastic lesions in high risk area of Qidong city and Beijing. A biotin-avidin enzyme-linked immunoassay (BA-ELISA) for serum level of GSTs was developed. The results showed that the GSTs level of normal controls in Qidong city (0.66 +/- 0.54 ng/ml) was higher than that in Beijing (0.37 +/- 0.27 ng/ml). The members of high cancer families, HBVsAg carries and patients having a low level fluctuating pattern of serum AFP were the population with high risk of liver cancer; their serum level of GSTs was 1.25 +/- 1.46, 1.43 +/- 1.44 and 2.81 +/- 1.76 ng/ml respectively, and it was significantly higher than in the normal controls. The content of GSTs of hepatic cancer patients in Qidong city and Beijing was 3.03 +/- 3.35 and 3.60 +/- 3.70 ng/ml respectively, but the positive rate (97%) of GSTs in Qidong city was higher than that (82%) in Beijing. The results suggested that serum expression of GSTs can be used as an enzyme marker for hepatic cancer and preneoplastic lesions. Possible roles of these forms in hepatic carcinogenesis induced by chemical carcinogenesis were discussed.

Biomarkers, Tumor↗
PubMed1993

[Relationship between the presynaptic depolarization effect of acupuncture and r-aminobutyric acid, opioid peptide and substance P].

The present study was performed on 22 cats to explore whether r-aminobutyric acid (GABA), endogenous opioid peptide and substance P (SP) were involved in the regulation of presynaptic inhibition in acupuncture analgesia. The size of the antidromic compound C action potentials of the sural nerve evoked by the testing stimulation in spinal cord was measured as an indicator of C-afferent terminal excitability. It was found that the electro-acupuncture (EA) at "Huantiao" (GB30) and "Yang lingquan" (GB34) points induced significant enlargement of the antidromic C-waves, showing the depolarization of presynaptic terminals of primary C-afferents was enhanced. The depolarization effect of EA was significantly reduced by bicuculline, naloxone and the antiserum of SP locally applied to the surface of spinal cord respectively. It is supposed that GABA, endogenous opioid peptide and SP may be involved in the regulation of presynaptic inhibition in acupuncture analgesia.

Action Potentials↗
PubMed1993

[Transformation of recombinant plasmid pRK 41 and amplification of full-length coding region of human brain myelin basic protein cDNA].

Transformation of the recombinant plasmid pRK41 containing 2.15 kd human brain myelin basic protein MBP)-coding sequence and 3' untranslated region (1.2 kb) into the E. coli JM109 was made by using Hanahan's method. Positive colonies were screened with digoxigenin oligo labelled rat brain MBP cDNA fragment (1.2 kb). To remove 3' untranslated region and obtain the full-length coding sequence of MBP cDNA, a pair of specific DNA primers was designed and synthesized. A 600 bp fragment was amplified from the recombinant plasmid, extracted from the positive colony by using polymerase chain reaction (PCR). The PCR fragment was isolated, and then digested with BamH I, Kpn I and BamH I + Kpn I. The results of restriction analysis indicate that the PCR amplified fragment is desirable and can be used directly to constract expression vectors.

Base Sequence↗
PubMed1993

[The role of OLS in peripheral acupuncture analgesia in arthritic rats].

Our previous work has shown that opiate-like substance (OLS) is involved in the central mechanism of acupuncture analgesia (AA) in the arthritic rats. In this paper, the role of OLS in peripheral mechanism of AA is further studied. Twenty four hours after a subcutaneous injection of Freund's adjuvant into the right ankles, acute arthritis with typical symptoms developed in all the rats. Following needling at Huantiao points for 10 minutes, the pain threshold (PT) was raised by 42.3% (P < 0.05) in the inflamed ankles and by 5.6% in the non-inflamed ones. When systemically administered a dose of 250 and 100 micrograms, naloxone (Nx) could completely and partially (49.6%) block AA respectively. While locally injected a dose of 100 micrograms even 20 micrograms, Nx could completely antagonize AA. After systemic administration of morphine (10, 5.0, 2.5, 1.25 mg/kg), PT rise was dose-related, and PT was raised by 86.5 +/- 22.7% in the affected ankles and by 32.9 +/- 14.9% in the normal ankles at 5 mg/kg in dose. It is evident that the opiate receptors in the inflamed area should by sensitized. These results demonstrate that activation of endogenous opiate system may also be involved in the peripheral AA. Acupuncture may enhance the release of peripheral OLS which can act at the sensitized opiate receptors, leading to more potent analgesic effect in the inflamed area.

Acupuncture Analgesia↗
PubMed1993

[Horseshoe tears and proliferative vitreoretinopathy].

Eyes at the risk of developing severe PVR postoperatively are limited to those affected with retinal detachment associated with horseshoe tears. This study is conducted to determine the relationship of horseshoe tears and PVR. 101 failure cases following surgery of retinal detachment with simple horseshoe tears were reviewed. The PVR group was compared with the group without PVR. The results indicate that vitreous gel liquefaction and posterior vitreous detachment are essential reasons of retinal detachment with horseshoe tears. Vitreous hemorrhage, uveitis, choroidal detachment and multiple operations are predisposing factors. It is the clinical evidence developed PVR that horseshoe tears with a curled and fixed posterior edge or the anterior flaps are smaller in size than the area of the exposed pigment epithelial cells.

Choroid Diseases↗
PubMed1993

[FeS2 changes in ignited pyritum].

FeS2 changes in Pyritum during igniting process were studied systematically by comparing Pyritum ignited under different conditions in terms of S content, Fe content, yielding ratio of ignited product and appearance features. Calcined Pyritum samples purchased from various parts of China were also compared in regard to their quality.

Hot Temperature↗
PubMed1993

[Isolation and structure of sibirate from Sibiraea angustata].

A new ferulic acid ester, C16H22O9, mp 141-143 degrees C (EtOAc), named sibirate (I), was isolated from the aerial part of Sibiraea angustata (Rchd.) Hand.-Mazz. in addition to a known compound ferulic acid. By means of IR, EI-MS, FAB-MS, 1H NMR, 13C NMR and chemical evidences the structure of sibirate was established as glucityl ferulate.

Cinnamates↗
PubMed1993

[Influence of processing conditions on quality of calcined concha Osterae].

Concha Osterae (the shell of Ostera gigas) ignited under different conditions was compared and discussed in terms of appearance features, yielding ratio of ignited product, Ca content of the ignited product, decocting rate of total component, Ca2+ content of decoction and trace element content. Furthermore, calcined Concha Osterae products obtained commercially from 6 cities of China were also compared in regard to the quality.

Animals↗
PubMed1993

[PCR amplification of nerve growth factor (beta-NGF) gene in human brain].

Nerve growth factor, an important nutrition factor for neuronal survival, growth, development and maintenance of neuronal functions, consists of three kinds of subunit (alpha 2, beta and gamma 2), but only the subunit beta-NGF has the biological activity. beta-NGF coding sequence is located in a single exon of NGF gene. In our study, a pair of specific primers (29 mers) has been designed and synthesized with ABI 318 A DNA synthesizer. The upstream primer includes an initiation codon and the 1st to 20th base of the exon. The downstream primer includes the complementary sequence of 334 to 354 base of the exon and a stop codon. The full-length DNA fragment of beta-NGF gene has been successfully obtained from human brain cDNA library in lambda ZAPII/EcoRI and human brain genomic DNA respectively by using polymerase chain reaction. The reaction program consists of denaturing at 93 degrees C for 1 min, annealing at 55 degrees C for 1 min, and extending at 72 degrees C for 2 min. Both amplified products of 350 bp in length coincide with the exon coding sequence and are enough for the analysis of restriction mapping, DNA sequencing and construction of expression vector.

Brain↗