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Biomedical subjects

L Y Li

Publications and source records attributed to L Y Li.

At least 73 records · Page 4Linked to original sources
PubMed1995

Human papillomavirus 11 E5a delays the growth restriction induced by temperature shift in temperature-sensitive simian virus 40 T antigen-immortalized keratinocytes.

The transfection with human papillomavirus type 11 E5a oncoprotein can cause longer and more active proliferation in the human keratinocytes previously transfected stably with temperature sensitive SV40 T antigen at 39 degrees C. Also, after the E5a transfection in parental temperature sensitive SV40 T antigen gene transfected cells, we observe a delay in the accumulation of p21 gene at 39 degrees C. Moreover, T antigen degradation did not occur at 39 degrees C in the E5a transfected cells as it did in the parental cells. We draw from these observations that E5a may transiently stabilize temperature sensitive T antigen and/or repress p21 synthesis.

Antigens, Polyomavirus Transforming↗
PubMed1995

Asian hereditary neuropathy patients with peripheral myelin protein-22 gene aneuploidy.

Japanese hereditary neuropathy with liability to pressure palsy (HNPP) patients have a deletion of one peripheral myelin protein-22 (PMP22) gene region in distal chromosome band 17p11.2 as do Caucasian patients. Japanese and Asiatic Indian CMT1A patients have a PMP22 gene duplication that results in Charcot-Marie-Tooth disease type IA (CMT1A; HMSNIA) in patients of European and Middle Eastern ancestry. About 70% of Japanese CMT1 patients have a PMP22 duplication as do Caucasians, while Japanese CMT1B, CMT2 and Dejerine-Sottas patients to not have PMP22 gene region aneuploidy. Although HNPP and CMT1A genotypes are generated simultaneously by unequal recombination that results in PMP22 gene aneuploidy in each daughter cell, only 3 Japanese HNPP probands with PMP22 deletion from a large patient population were referred to a single center compared to 18 referred CMT1A probands with PMP22 duplication. This lower HNPP frequency more likely reflects lower HNPP reproductive fitness than patient ascertainment bias because disease severity and variation in severity is about the same in CMT1A and HNPP patients and because all patients of both types were referred regardless of disease severity. These results, along with an apparently high de novo CMT1A mutation rate, suggest that common ancestors of Japanese, Asian Indians, and Caucasians carried PMP22 geneflanking sequences that enhance unequal crossing over.

Aneuploidy↗
PubMed1995

Engineering of fibroblast growth factor: alteration of receptor binding specificity.

A five-residue loop structure in basic fibroblast growth factor (FGF-2) which extends from amino acid residue 118 to residue 122 was replaced, by cassette mutagenesis, with the corresponding seven-residue loop structure from the structural homologue acidic fibroblast growth factor (FGF-1) or the corresponding five-residue loop from interleukin-1 beta to give FGF-2LA and FGF-2LI, respectively. The mutants were expressed in Escherichia coli and purified to homogeneity, and their heparin and receptor binding and biological properties were examined. The ability of FGF-2LA to induce endothelial cell proliferation was the same as that of FGF-2. Affinities of the mutants to heparin and to cells that express FGF receptor-1 (FGFR-1) were identical to those of the wild-type protein. The role of the loop structure in FGF-1 and FGF-2 was elucidated by using soluble FGF receptor systems, which display distinct ligand binding specificities. Thus, FGF-2LA bound, with the same affinity as FGF-1 and FGF-2, to FGFR-1 and FGFR-2, whereas only FGF-1 and the FGF-1 loop-containing mutant, FGF-2LA, bound to the keratinocyte growth factor receptor. A change in receptor binding specificity was not observed with the FGF-2LI engineered mutant. That the binding specificity of FGF-2 was dramatically altered by transfer of a loop structure from FGF-1 to resemble the binding profile of the donor protein provides strong evidence that this motif is a receptor binding specificity determinant of fibroblast growth factors.

3T3 Cells↗
PubMed1995

The mobilization regions of two integrated Bacteroides elements, NBU1 and NBU2, have only a single mobilization protein and may be on a cassette.

Bacteroides conjugative transposons can act in trans to excise, circularize, and transfer unlinked integrated elements called NBUs (for nonreplicating Bacteroides units). Previously, we localized and sequenced the mobilization region of one NBU, NBU1, and showed that this mobilization region was recognized by the IncP plasmids RP4 and R751, as well as by the Bacteroides conjugative transposons. We report here that the single mobilization protein carried by NBU1 appears to be a bifunctional protein that binds to the oriT region and catalyzes the nicking reaction that initiates the transfer process. We have also localized and sequenced the mobilization region of a second NBU, NBU2. The NBU2 mobilization region was 86 to 90% identical at the DNA sequence to the oriT-mob region of NBU1. The high sequence similarity between NBU1 and NBU2 ended abruptly after the stop codon of the mob gene and about 1 kbp upstream of the oriT region, indicating that the oriT-mob regions of NBU1 and NBU2 may be on some sort of cassette. A region on NBU1 and NBU2 which lies immediately upstream of the oriT region had 66% sequence identity to a region upstream of the oriT region on a mobilizable transposon, Tn4399, an element that had previously appeared to be completely unrelated to the NBUs.

Amino Acid Sequence↗
PubMed1995

Location and characteristics of the transfer region of a Bacteroides conjugative transposon and regulation of transfer genes.

Many Bacteroides clinical isolates contain large conjugative transposons, which excise from the genome of a donor and transfer themselves to a recipient by a process that requires cell-to-cell contact. It has been suggested that the transfer intermediate of the conjugative transposons is a covalently closed circle, which is transferred by the same type of rolling circle mechanism used by conjugative plasmids, but the transfer origin of a conjugative transposon has not previously been localized and characterized. We have now identified the transfer origin (oriT) region of one of the Bacteroides conjugative transposons, TcrEmr DOT, and have shown that it is located near the middle of the conjugative transposon. We have also identified a 16-kbp region of the conjugal transposon which is necessary and sufficient for conjugal transfer of the element and which is located near the oriT. This same region proved to be sufficient for mobilization of coresident plasmids and unlinked integrated elements as well as for self-transfer, indicating that all of these activities are mediated by the same transfer system. Previously, we had reported that disruption of a gene, rteC, abolished self-transfer of the element. rteC is one of a set of rte genes that appears to mediate tetracycline induction of transfer activities of the conjugative transposons. On the basis of these and other data, we had proposed that RteC activated expression of transfer genes. We have now found, however, that when the transfer region of TcrEmr DOT was cloned as a plasmid that did not contain rteC and the plasmid (pLYL72) was tested for transfer out of a Bacteroides strain that did not have a copy of rteC in the chromosome, the plasmid was self-transmissible without tetracycline induction. This and other findings suggest that RteC is not an activator transfer genes but is stimulating transfer in some other way.

Bacterial Proteins↗
PubMed1995

Conjugative transposons: an unusual and diverse set of integrated gene transfer elements.

Conjugative transposons are integrated DNA elements that excise themselves to form a covalently closed circular intermediate. This circular intermediate can either reintegrate in the same cell (intracellular transposition) or transfer by conjugation to a recipient and integrate into the recipient's genome (intercellular transposition). Conjugative transposons were first found in gram-positive cocci but are now known to be present in a variety of gram-positive and gram-negative bacteria also. Conjugative transposons have a surprisingly broad host range, and they probably contribute as much as plasmids to the spread of antibiotic resistance genes in some genera of disease-causing bacteria. Resistance genes need not be carried on the conjugative transposon to be transferred. Many conjugative transposons can mobilize coresident plasmids, and the Bacteroides conjugative transposons can even excise and mobilize unlinked integrated elements. The Bacteroides conjugative transposons are also unusual in that their transfer activities are regulated by tetracycline via a complex regulatory network.

Anti-Bacterial Agents↗
PubMed1994

Diminished heparin binding of a basic fibroblast growth factor mutant is associated with reduced receptor binding, mitogenesis, plasminogen activator induction, and in vitro angiogenesis.

Using modeling of heparin-fibroblast growth factor interactions, we replaced four basic residues of basic fibroblast growth factor (FGF-2) with neutral glutamine residues by site-specific mutagenesis to give the mutants K128Q, K138Q, K128Q-K138Q, R129Q, K134Q, and R129Q-K134Q. The FGF mutants were characterized for their receptor and heparin binding affinities, mitogenic and cell proliferation activities, and their ability to induce plasminogen activator (PA) production and in vitro angiogenesis by cultured endothelial cells. Heparin binding properties and biological activities of the three mutants involving R129 and K134 remained essentially unchanged; however, significant changes for three mutants involving K128 and K138 were found. The KD values for heparin binding for K128Q and K138Q mutants were increased about 10-fold, and that for the K128Q-K138Q double mutant was increased by about 100-fold. The mutant K128Q-K138Q required a 10-fold higher concentration of heparin to promote binding to heparan sulfate proteoglycan (HSPG)-deficient CHO cells transfected with fibroblast growth factor receptor-1 (FGFR1) or to induce DNA synthesis in HSPG-deficient myeloid cells transfected with FGFR1. Binding affinities of the mutants to cell surface receptors on BHK-21 cells, however, were similar to that of wild-type FGF-2. In endothelial cell proliferation assays the activities of K128Q and K128Q-K138Q were about 10-fold lower than that of the wild-type protein, whereas the K138Q mutant exhibited wild-type activity. In addition, the K128Q-K138Q mutant displayed a markedly lowered capacity to induce PA activity in cultured endothelial cells and to form capillary-like structures in an in vitro angiogenesis model.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

An unusual type of cointegrate formation between a Bacteroides plasmid and the excised circular form of an integrated element (NBU1).

Evidence for an unusual type of cointegrate formation was found as the result of analyzing three integration events that fused a mobilization-deficient Bacteroides plasmid (pEG920) with the excised circular form of a nonreplicating Bacteroides element (NBU1). NBU1 is capable of inserting itself into DNA segments, but the cointegrates were the result of invasion of NBU1 by pEG920, not vice versa. The same site on pEG920 was involved in all cases. Sequence analysis of the cointegrates suggested that the integration events may have been the result of a multistep process in which a conjugative transposon was involved.

Bacteroides↗
PubMed1994

Fluorospectrometric analysis of heparin interaction with fibroblast growth factors.

The fluorescence emission of a single tryptophan residue present in both FGF-1 and FGF-2 was used as a structural probe to directly assess the interaction of the growth factors with heparin or beta-cyclodextran tetradecasulfate. About 20-25% of the fluorescence of either FGF-1 or FGF-2 is quenchable, and is dependent on sulfation of the ligands. The quenchable fluorescence is associated with about 20% of total FGF, suggesting the presence of two fluorospectrometric forms of the protein. The equilibrium dissociation constants, determined by this method, for heparin or beta-cyclodextrin tetradecasulfate binding to FGF-1 are about 1 nM, whereas the values for FGF-2 are 1 and 23 nM, respectively. The method provides a direct tool to evaluate FGF-ligand interaction and assess the structural integrity of the proteins.

Animals↗
PubMed1994

[Superinfection of hepatitis viruses].

Using ELISA method, anti-HAV-IgM and anti-HCV were determined in 493 blood donors and 192 patients with HBV infection. The positive rate of anti-HCV in blood donors was 1.62%. The superinfection rates of HBV and HAV, HBV and HCV, HBV, HAV and HCV in patients with HBV infection were 16.7%, 3.13% and 0.52%, respectively. The incidence of hepatitis B viral replication marker was found to be lower in patients with superinfection of types A and B and/or C hepatitis viruses than in those with HBV infection alone. The prolonged course was found to be longer and the degree severer in patients with superinfection of types A and B and/or C hepatitis viruses than in those with HAV or HBV or HCV infection alone. The results suggest that those patients with superinfection of types A and B and/or C hepatitis viruses showed poor prognosis and prolonged course, and many patients with chronic Type A hepatitis resulted from superinfection HBV and/or HCV.

Adolescent↗
PubMed1994

[The clinical significance serum N-POMC level in lung cancer patients].

Serum N-POMC level of 103 cases of lung cancer were measured in our hospital. The results were as follows: The lung cancer group, 50.5%, of patienst has an N-PONC level above the normal upper limit. The percentages of the N-POMC levels above the normal limit in lung cancers, such as: squamous-cell carcinoma, adenocarcinoma, SCLC and undifferentiated carcinoma were 52.2%, 50.0%, 47.3% and 57.1%, respectively. There was no statistically significant difference of N-POMC levels among these kinds of lung cancers, Eleven of 18 cases of SCLC patients in stage IIIb or IV, and 3 of 9 cases of SCLC patients in stage IIIa had N-POMC levels above the upper normal limit. Could serum N-POMC be one of the indexes for assisting the diagnosis and prognosis of lung cancer needs further investigation. Cases with carcinoid, thymoma and neurofibroma had higher N-POMC levels too. Six patients had Cushing syndrome.

Adenocarcinoma↗
PubMed1994

[Effect of Leontopodium leontopodioides (Willd.) Beauv. on inflammation induced by animal reversed passive arthus (RPA)].

The extract from Leontopodium leontopodioides 50-100mg/kg ip has been proved able to suppress the swelling of normal or adrenalectomised rat hind paws induced by RPA, and strongly inhibit the cutaneous hemorrhage of animals induced by RPA, lysosome or lysosome of broken membrane. It has also been shown that the extract 100 mg/kg ip can markedly inhibit the migration of leukocytes. These suggest that the anti-inflammatory properties of the extract are not dependent on the pituitary-adrenal system or membrane of lysosome.

Animals↗
PubMed1994

[Culture techniques of Asarum sieboldii Miq].

Asarum sieboldii was domesticated in Sichuan, China. The rational planting density was selected according to this study. In the deep, loose and fertile soil, it grows well under semisunlight. Seedlings are raised in the seedling bed for two or three years, and then transplanted to the field, Harvest is started after three of four years of growth. Fertilizer is applied at the beginning of March and the beginning or middle of July.

Drugs, Chinese Herbal↗
PubMed1994

[Protective effect of 1,6-diphosphate fructose in ischemic renal failure in elderly rats].

To study the protective effect of 1,6-diphosphate fructose (FDP) on acute ischemia damage in brain, heart and liver, we observed its effect on acute ischemic renal failure (AIRF). AIRF in male Wistar rats was produced by renal arterial clamping for 45 minutes and reperfusion for 90 minutes. The rats were divided into 4 groups according to their age and FDP therapy: G1: young (3-4 months) AIRF rats without FDP; G2: old (26-27 months) AIRF rats without FDP; G3: young AIRF rats with FDP (0.5g/kg) i.v. infusion; G4: old AIRF rats with FDP. Inulin clearance (CIn), PAH clearance (CPAH), urinary sodium (UNA) were examined before ischemia and 30, 60 and 90 minutes after reperfusion. After reperfusion for 90 minutes, renal cortex was taken for the examination of renal mitochondrial ATP synthetic content (miATPs). CIn and CPAH were lower in G2 than in G1 (0.24 +/- 0.12 vs. 1.75 +/- 0.79, P < 0.01; 0.87 +/- 0.42 vs 7.12 +/- 4.04, P < 0.05, at 90 minutes reperfusion). CIn and CPAH in G1 showed an auto-recovery up to 40.1% and 33.7% of the level in contrast to G2. In G3 and G4 original FDP infusion resulted in a significant increase in miATPs and CIn (609 +/- 145 vs 389 +/- 97; 569 +/- 77 vs 338 +/- 61, P < 0.02; 2.47 +/- 0.58 vs 1.75 +/- 0.79, 1.29 +/- 0.42 vs 0.24 +/- 0.12, P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Kidney Injury↗