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Biomedical subjects

W L Li

Publications and source records attributed to W L Li.

At least 19 recordsLinked to original sources
PubMed2004

Natural medicines used in the traditional Chinese medical system for therapy of diabetes mellitus.

The rapidly increasing diabetes mellitus is becoming a serious threat to mankind health in all parts of the world. The control and treatment of diabetes and its complications mainly depend on the chemical or biochemical agents, but the fact is that it has never been reported that someone had recovered totally from diabetes. With the distinctive traditional medical opinions and natural medicines mainly originated in herbs, the traditional Chinese medicine performed a good clinical practice and is showing a bright future in the therapy of diabetes mellitus and its complications. Based on a large number of chemical and pharmacological research work, numerous bioactive compounds have been found in Chinese medicinal plants for diabetes. The present paper reviews 86 natural medicines with regards to their origin, anti-diabetic active principles and/or pharmacological test results, which are commonly used in the traditional Chinese medical system and have demonstrated experimental or/and clinical anti-diabetic effectiveness. Among these natural medicines, 82 originate from plants and 4 from animals or insects, which covers 45 families. It is strongly significant to pay close attention to traditional Chinese medical therapeutics and natural medicines for treatment of diabetes mellitus and its complications.

Diabetes Mellitus↗
PubMed2000

[Cloning and sequencing of the maize ribosome-inactivating protein gene].

A gene encoding maize Ribosome-inactivating protein was amplified by means of PCR using mRNA of maize leaves as a template, and cloned into pUC19 vector. The amplified DNA sequence has been determined, which consists of 828 bp and encodes 275 amino acid residues. Comparison with previously reported sequence shows 98.4% homologies in nucleotide sequence and 97.4% in amino acid sequence, respectively.

Amino Acid Sequence↗
PubMed1997

Sterically stabilized anti-HER2 immunoliposomes: design and targeting to human breast cancer cells in vitro.

Liposomes (70-100 nm) of 1-palmitoyl-2-oleoylphosphatidylcholine, cholesterol, and poly(ethylene glycol) (PEG)-modified phosphatidylethanolamine (PEG-DSPE) were conjugated to Fab' fragments of a humanized recombinant MAb against the extracellular domain of HER2/neu to create sterically stabilized immunoliposomes (anti-HER2 SL) as a drug carrier targeting HER2-overexpressing cancers. Conjugation employed maleimide-terminated membrane-anchored spacers of two kinds: a short spacer, providing attachment of Fab' close to the liposome bilayer, or a long spacer, with Fab' attachment at the distal terminus of the PEG chain. Confocal microscopy and spectrofluorometry of HER2-overexpressing breast cancer cells incubated with fluorescently labeled anti-HER2 SL prepared with either spacer showed binding of liposomes (8000-23000 vesicles/cell) followed by endocytosis (rate constant ke = 0.012-0.033 min-1) via the coated-pit pathway, evidenced by intracellular acidification and colocalization with transferrin. Uptake of anti-HER2 immunoliposomes by breast cancer cells with low HER2 expression, or after preincubation of cells with free anti-HER2 Fab', was less than 0.2% and 4.3%, respectively, of the uptake by HER2-overexpressing cells. Increasing PEG-DSPE content (up to 5.7 mol %) in anti-HER2-SL prepared with the short spacer decreased liposome-cell binding affinity 60-100-fold, while ke decreased only 2-fold; however, when Fab' fragments were conjugated via a PEG spacer, both binding affinity and ke were unaffected by PEG-DSPE content. Cell binding and internalization of anti-HER2 immunoliposomes increased at higher surface density of conjugated Fab' fragments, reaching plateaus at approximately 40 Fab'/liposome for binding and approximately 10-15 Fab'/liposome for internalization. Uptake of anti-HER2 immunoliposomes correlated with the cell surface density of HER2 and significantly (p < 0.005) correlated with the antiproliferative effect of the targeting antibody but not with the total level of cellular HER2 expression. The results obtained were used to optimize in vivo preclinical studies of anti-HER2 SL loaded with antineoplastic drugs.

Antibodies, Monoclonal↗
PubMed1997

Detailed analysis of a 17q21 microdissection library by sequence bioinformatics and isolation of region-specific clones.

A region-specific microdissection library originating from human chromosome 17q21, was constructed using the MboI linker-adaptor microcloning technique. DNA sequencing of 241 microclones resulted in the identification of 74 novel coding sequences, paralogs of known genes, and known, but previously unmapped, genes or expressed sequence tags that were "virtually" mapped to chromosome 17q21. By pooling the microclones as multiplexed hybridization probes, and by virtue of their origin on 17q21, we were able to identify approximately 150 P1 clones from the human Reference Library Data Base P1 Library that potentially map to chromosome 17q21. Verification of the 17q21 location of 16 P1 clones was accomplished by PCR analysis with STS primer pairs to known 17q21 genes or by FISH. Our results demonstrate the substantial advantage of combining the sequence analysis of microclones with multiplex hybridization strategies for gene discovery and mapping specific gene rich regions of the genome.

Base Sequence↗
PubMed1995

Human genomic characterization of a novel locus-specific repetitive sequence.

A novel human chromosome locus-specific repetitive sequence was identified and characterized using arbitrary PCR. The repeat monomer consensus sequence is 100 bp long, and there are a minimum of 140 to 160 copies of the repetitive sequence per haploid human genome. The repetitive sequence is highly clustered on 20q12 within a 200- to 400-kb region. The highly polymorphic repeat array is inherited in a stable Mendelian fashion. Hybridization analysis revealed detectable conservation of the repeated element only among hominoids and Old World monkeys, where repeat arrangements are also polymorphic.

Animals↗
PubMed1994

[Staining test with methylene blue during resection of bladder cancer in 30 patients].

From November 1991 to March 1993, staining test with methylene blue was applied in 30 patients with the bladder cancer during operation. Twelve patients (40%) showed positive results, and 27 specimens were obtained from the stained areas. Histological examination proved that they were carcinoma in situ (11), transitional cell carcinoma (7), squamous cell carcinoma (4), dysplasia (3), chronic cystitis (1), and normal mucosa (1). The positive rate of histological results was 96.3%. 21 specimens from the unstained areas showed negative results. Six (33%) of 18 patients with single tumor and 6 (50%) of 12 patients with multiple tumor were positively stained. Follow-up from 10 to 26 months showed one patient (3.3%) had recurrence after 8 months.

Adult↗
PubMed1993

A truncated intracellular HER2/neu receptor produced by alternative RNA processing affects growth of human carcinoma cells.

Cloned sequences encoding a truncated form of the HER2 receptor were obtained from cDNA libraries derived from two HER2-overexpressing human breast cancer cell lines, BT-474 and SK-BR-3. The 5' 2.1 kb of the encoded transcript is identical to that of full-length 4.6-kb HER2 transcript and would be expected to produce a secreted form of HER2 receptor containing only the extracellular ligand binding domain (ECD). The 3' end of the truncated transcript diverges 61 nucleotides before the receptor's transmembrane region, reads through a consensus splice donor site containing an in-frame stop codon, and contains a poly(A) addition site, suggesting that the truncated transcript arises by alternative RNA processing. S1 nuclease protection assays show a 40-fold variation in the abundance of the truncated 2.3-kb transcript relative to full-length 4.6-kb transcript in a panel of eight HER2-expressing tumor cell lines of gastric, ovarian, and breast cancer origin. Expression of this truncated transcript in COS-1 cells produces both secreted and intracellular forms of HER2 ECD; however, immunofluorescent labeling of HER2 ECD protein in MKN7 tumor cells that natively overexpress the 2.3-kb transcript suggests that transcriptionally generated HER2 ECD is concentrated within the perinuclear cytoplasm. Metabolic labeling and endoglycosidase studies suggest that this HER2 ECD (100 kDa) undergoes differential trafficking between the endoplasmic reticulum and Golgi compartments compared with full-length (185-kDa) HER2 receptor. Transfection studies indicate that excess production of HER2 ECD in human tumor cells overexpressing full-length HER2 receptor can result in resistance to the growth-inhibiting effects of anti-HER2 monoclonal antibodies such as muMAb4D5. These findings demonstrate alternative processing of the HER2 transcript and implicate a potentially important growth regulatory role for intracellularly sequestered HER2 ECD in HER2-amplified human tumors.

Alternative Splicing↗
PubMed1993

[Ultrastructural localization of 145/102 kDa antigens in erythrocytic stages of Plasmodium falciparum].

The ultrastructural localization of the 145/102 kDa antigens recognized by the possible protective monoclonal antibody (McAb) M26-32 in erythrocytic stages of Plasmodium falciparum, FCC1/HN, in vitro, was investigated by immuno-electron microscopy with LR White resin embedding and colloidal gold probe cytochemistry techniques. The results showed that the gold particles were mainly localized within the cytoplasm of ring forms, trophozoites, schizonts and merozoites of the Plasmodium. Some gold particles were found to locate on the pellicular complex of the plasmodium surface or in the cytoplasm of the infected erythrocytes. The results indicated that 145/102 kDa antigens were the common cytoplasmic antigens of asexual blood stages of Plasmodium falciparum, FCC1/HN, while a portion of the antigens could be transported to the cytoplasm of the infected erythrocytes via the pellicular complex of the plasmodium surface (Figs. 1-4).

Animals↗
PubMed1992

[Localization of the antigen in erythrocytic stages of Plasmodium yoelii by immuno-electron microscopy].

In this study, the antigen recognized by the protective McAb M26-32 in erythrocytic stages of P. yoelii was localized by immuno-electron microscopy with LR Whithe resin embedding and colloidal gold probe cytochemical techniques. The results indicated that the antigen which reacts specifically to McAb M26-32 was mainly localized within the cytoplasm of early and late trophozoites, schizonts and merozoites, being the common antigen of asexual blood stages of the plasmodium. The amount of the antigen was on the increase during the development of trophozoite, while a portion of the antigen might be transported outward by exocytosis of the parasites and then be localized in the cytoplasm of the infected erythrocytes adjacent to the parasites.

Animals↗
PubMed1991

Tb(III) as a fluorescent probe for the structure of bovine serum albumin.

Tb(III) was used as a fluorescent probe in the study of the calcium-binding sites on Bovine Serum Albumin (BSA). The fluorescence of Tb(III) is enhanced markedly when bound to BSA and nonradiative energy transfer between two fluorescent tryptophan(Trp) residues and Tb(III) bound to calcium-binding sites on BSA occurred. Experimental results show that the major groups in BSA bound to metal ion are the carboxyl side groups of glutamic acid (Glu) and aspartic acid (Asp). The average distance between the bound Tb(III) and the two tryptophan residues in BSA calculated by a Föster dipole-dipole nonradiative energy transfer mechanism is 1.48 nm.

Binding Sites↗
PubMed1991

The accumulation and metabolism of a fluorescent ceramide derivative in Plasmodium falciparum-infected erythrocytes.

We have examined the accumulation and metabolism of N-[7-(4-nitrobenzo-2-oxa-1,3-diazole)]aminocaproyl sphingosine (C6-NBD-cer) in Plasmodium falciparum FCR-3/A2-infected erythrocytes. C6-NBD-cer transferred to live infected erythrocytes at 2 degrees C to label the infected red cell surface and intracellular parasite membranes. Subsequent incubation for 30 min at 2 degrees C, resulted in a depletion of the ceramide label from the red cell membrane and an accumulation of fluorescence in parasite membranes, by an energy independent process. When the cells were subsequently warmed to 37 degrees C for 30 min, virtually all of the ceramide was converted to N-[7-(4-nitrobenzo-2-oxa-1,3- diazole)]aminocaproyl sphingosine-1-phosphocholine (C6-NBD-Sm). Uninfected erythrocytes were incapble of sphingomyelin synthesis. By fluorescence microscopy, sphingomyelin synthesis in infected erythrocytes occurred in compartments morphologically similar to those accumulating ceramide. To examine the intracellular sites of ceramide accumulation glutaraldehyde fixed cells were labeled with C6-NBD-ceramide and subsequently back extracted to remove excess probe. This resulted in a depletion of label at the red cell membrane but prominent fluorescence remained associated with the parasite. Photobleaching in the presence of diaminobenzidine resulted in precipitates in intraerythrocytic cisternae and the vacuolar membrane surrounding the parasite, rather than a perinuclear Golgi apparatus within the organism. The results support a novel organisation of plasmodial membranes regulating the accumulation and metabolism of C6-NBD-cer in infected erythrocytes.

4-Chloro-7-nitrobenzofurazan↗
PubMed1991

Stage-specific expression of plasmodial proteins containing an antigenic marker of the intraerythrocytic cisternae.

A monoclonal antibody, LWLI, recognized 3 proteins of 45, 50 and 102 kDa in Plasmodium falciparum-infected erythrocytes. The 45- and 50-kDa proteins were parasite-encoded and displayed markedly different peptide maps, indicating that they were distinct plasmodial polypeptides with a common antigenic epitope rather than differentially processed forms of a primary translational product. The 45-kDa protein was present throughout intraerythrocytic growth, while the 50-kDa molecule was not detected earlier than 11 h in the life cycle. The 102-kDa protein was only expressed in trophozoite- and schizont-infected red cells: its structural relationship to the 45- and 50-kDa proteins, if any, remains undefined. By indirect immunofluorescence and immunoelectron microscopy, LWLI bound to flattened intraerythrocytic cisternae exported into the erythrocyte cytoplasm. The results support the theory that proteins recognized by the antibody were concentrated in these compartments and their common antigenic epitope may serve as a marker for the cisternae. Stage-specific expression of LWLI reactive proteins implicates developmental regulation of cisternal functions during asexual parasite development.

Animals↗
PubMed1989

Construction and screening of Plasmodium falciparum cDNA library.

The HAINAN isolate of Plasmodium falciparum FCC1/HN was cultured in vitro in large quantities. The total parasite mRNA was purified and reverse transcribed into cDNA. The cDNA fragments were inserted into lambda gt11 to construct a P. falciparum FCC1/HN erythrocytic stage cDNA library. Inhibitory monoclonal antibodies (McAbs) M26-32, F6-C2, and F6-D3 were used to screen the cDNA library expressed in E. coli. A total of 27 positive clones were found to react with M26-32 alone and 34 clones with both M26-32 and F6-C2. These expressed proteins may be candidates for use in malaria vaccine.

Animals↗
PubMed1989

[Manifestations of fluorescein angiography in choroidal melanoma].

This paper reported on the manifestations of fundus fluorescein angiography in 21 patients with choroidal melanoma. According to the findings of fluorescein angiography, we suggest that this disease can be classified into 3 types: type I shows hyperfluorescent mottles (12 cases); type II shows hyperfluorescent spots and patches, (4 cases); type III shows a dark area in the tumor body, (5 cases). The angiographic characteristics of the three types of melanoma and their histopathologic changes are discussed. The differential diagnosis of the three types of melanoma from metastatic choroidal carcinoma, senile macular degeneration with subretinal hemorrhage and choroidal hemangiomas is discussed. For the first time choroid melanoma has been classified into 3 types according to fluorescein angiography. It may contribute to the early diagnosis of this disease.

Adolescent↗
PubMed1989

Studies on the mechanism of anemia in rodent malaria.

The underlying cause of anemia is one of the problems to be solved in malaria research. Many factors are involved in reducing the quantity of uninfected red blood cells (RBC) in addition to those infected RBC destroyed by malaria parasites. In the Plasmodium yoelii (P.y.)-mouse model, the amount of [51Cr]-labelled normal mouse RBC destroyed in peripheral blood as well as the quantity phagocytized by spleen cells during acute and chronic infection in vivo is reported in this paper. Our results show that compensatory enlargement of the spleen, which cleans up a large amount of the damaged uninfected RBC, may be the major cause of anemia in chronic malaria infection. In acute malaria infection destruction of uninfected RBC in peripheral circulation is higher than that in normal mice. Neither malaria antigen, mouse autoantibody nor immune complex was detected on the surface of normal RBC from infected mice using indirect immunofluorescence assay (IFA) or [3H]-isoleucine-labelled P.y. antigen (P.y.Ag) in vitro. This suggests that malaria immune complexes do not play an important part in RBC destruction in circulating blood. Since no obvious hemolysis was observed by mixing RBC with P.y. culture supernatant in vitro, it is possible that physical and chemical changes in uninfected RBC induced by malaria metabolites are the prerequisite for their destruction in circulating blood in vivo. Hemolysis occurs due to external stresses, such as those incurred when damaged RBC run into each other in the blood stream or when they change their shape to pass through capillaries.

Anemia↗