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L M Wong

Publications and source records attributed to L M Wong.

51 records · Page 3Linked to original sources
PubMed1988

Mapping of a cell-binding domain in the cell adhesion molecule gp80 of Dictyostelium discoideum.

At the aggregation stage of Dictyostelium discoideum development, a cell surface glycoprotein of Mr 80,000 (gp80) has been found to mediate the EDTA-resistant type of cell-cell adhesion via homophilic interaction (Siu, C.-H., A. Cho, and A. H. C. Choi. 1987. J. Cell Biol. 105:2523-2533). To investigate the structure-function relationships of gp80, we have isolated full length cDNA clones for gp80 and determined the DNA sequence. The deduced structure of gp80 showed three major domains. An amino-terminal globular domain composed of the bulk of the protein is supported by a short stalk region, which is followed by a membrane anchor at the carboxy terminus. Structural analysis suggested that the cell-binding domain of gp80 resides within the globular domain near the amino terminus. To investigate the relationship of the cell-binding activity to this region of the polypeptide, three protein A/gp80 (PA80) gene fusions were constructed using the expression vector pRIT2T. These PA80 fusion proteins were assayed for their ability to bind to aggregation stage cells. Binding of 125I-labeled fusion proteins PA80I (containing the Val123 to Ile514 fragment of gp80) and PA80II (Val123 to Ala258) was dosage dependent and could be inhibited by precoating cells with the cell cohesion-blocking mAb 80L5C4. On the other hand, there was no appreciable binding of PA80III (Ile174 to Ile514) to cells. Reassociation of cells was significantly inhibited in the presence of PA80I or PA80II. In addition, 125I-labeled PA80II exhibited homophilic interaction with immobilized PA80I, PA80II, or gp80. The results of these studies lead to the mapping of a cell-binding domain in the region between Val123 and Leu173 of gp80 and provide direct evidence that the cell-binding activity of gp80 resides in the protein moiety.

Amino Acid Sequence↗
PubMed1988

Molecular mechanisms of cell-cell interaction in Dictyostelium discoideum.

During development of the cellular slime mold Dictyostelium discoideum, cells migrate in response to cAMP to form aggregates, which give rise to fruiting bodies consisting of two major cell types: spores and stalk cells. Multicellularity is achieved by the expression of two types of cell-cell adhesion sites. The EDTA-sensitive binding sites are expressed at the initial stage of development. At the aggregation stage, cells acquire EDTA-resistant binding sites, which are mediated by a cell-surface glycoprotein of Mr80,000 (gp80). gp80 is preferentially associated with cell surface filopodia, which are probably involved in the initiation of contact formation between cells. Covaspheres conjugated with gp80 bind specifically to aggregation-stage cells. The binding can be inhibited by precoating cells with an anti-gp80 monoclonal antibody, thus suggesting that gp80 mediates cell-cell binding via homophilic interaction. The structure of gp80 predicted from its cDNA sequence can be divided into three major domains: a membrane anchor, a hinge, and a globular region. An analysis of fusion proteins containing different gp80 segments shows that the cell-binding activity resides in the globular region. In the postaggregation stages, gp80 is replaced by other surface glycoproteins in maintaining cell-cell adhesion. One of them has a Mr of 150,000 (gp150). Anti-gp150 antibodies have no effect on aggregation-stage cells, but they disrupt cell-cell adhesion at subsequent stages. It becomes evident that the complex phenomena of cell adhesion and tissue organization involve the participation of a number of surface glycoproteins.

Amino Acid Sequence↗
PubMed1986

Cloning of cDNA for the contact site A glycoprotein of Dictyostelium discoideum.

A cell surface glycoprotein of Dictyostelium discoideum with M(r) 80,000 (gp80) has been shown to mediate the formation of the developmentally acquired EDTA-resistant cell-cell binding sites termed contact sites A. We have isolated cDNA clones encoding gp80 by immunological screening of an expression library prepared in Escherichia coli. Double-stranded cDNA was prepared from poly(A)(+) RNA isolated from cells at 8 hr of development and cloned into the bacteriophage expression vector lambdagt11. Two recombinant phages containing cDNA inserts of 1.2 and 0.8 kilobases were isolated and shown to contain sequences coding for gp80 by the immunoselect assay. Partial DNA sequence analysis also confirmed that one of these cDNA clones, lambdaDdgp80c-19, contained the coding sequence for the amino terminus of gp80. DNA-RNA hybridization showed that the insert of lambdaDdgp80c-19 hybridized to a single mRNA transcript of approximately 2.0 kilobases. gp80 mRNA became detectable after 6 hr of development, reached its maximum level at 9 hr, and dropped to a negligible level by 15 hr. This pattern of mRNA accumulation corresponded closely to that of gp80 synthesis in D. discoideum cells, suggesting that gp80 expression is regulated at the transcriptional level.

Journal Article↗
PubMed1985

Multiple-dose study of imipenem/cilastatin in patients with end-stage renal disease undergoing long-term hemodialysis.

Multiple doses of imipenem/cilastatin were administered to patients with end-stage renal disease undergoing long-term hemodialysis. Schedules of 250 mg every six hours, 500 mg every six hours, and 500 mg every 12 hours were studied. Five hundred mg every 12 hours was the most efficient schedule that maintained effective trough antibiotic activity. Twelve volunteers including two patients with clinical infections using the dose schedule of 500 mg every 12 hours received imipenem/cilastatin for two to 14 days without any notable clinical side effects. Imipenem peak and trough concentrations averaged 29 +/- 5 micrograms/ml and 10 +/- 3 micrograms/ml, respectively. No accumulation of imipenem occurred during the trial. Cilastatin peak and trough concentrations were 89 +/- 38 micrograms/ml and 70 +/- 27 micrograms/ml, respectively. The plasma concentration of cilastatin increased with each dose until the next hemodialysis session.

Aged↗
PubMed1983

Marine bacteria complicating seawater near-drowning and marine wounds: a hypothesis.

Of the hundreds of species of bacteria in seawater, in marine sediments, and associated with marine organisms, more than 20 are known human pathogens. Based on published data, wherein a variety of marine bacteria have been cultured from open wounds (eg, coral cuts) and from near-drowning pneumonias, it is hypothesized that these bacteria can provide a primary infectious inoculation of open marine wounds and of the respiratory tract of near-drowners.

Anti-Bacterial Agents↗
PubMedDate not supplied

Effect of later treatment with estrogen on reproductive tract lesions in neonatally estrogenized female mice.

Continuous ethinyl estradiol treatment following ovariectomy at day 38 of BALB/cfC3H mice treated neonatally with estradiol resulted in a more organized vaginal epithelium than that seen in the absence of postnatal estrogen, 30 days after treatment was initiated. Although the epithelium became increasingly disorganized in all neonatally estrogenized groups with age, the later estrogen treatment reduced the incidence and severity of vaginal epithelial lesions and the incidence of vaginal concretions. Uterine epithelial metaplasia was accelerated by the later estrogen treatment.

Animals↗
PubMedDate not supplied

Childhood thrombocytopenia associated with Graves disease is distinct from idiopathic thrombocytopenic purpura.

The authors report a case of thrombocytopenia in a 10-year-old Chinese girl who was also found to have Graves disease 6 months later. The clinical, hematologic, and bone marrow features were indistinguishable from chronic idiopathic thrombocytopenic purpura, but the patient's platelet counts were normalized concurrently with the control of thyrotoxicosis with carbimazole treatment. Childhood thrombocytopenia associated with autoimmune thyroid disease is a rarely reported condition and its management differs from that of idiopathic thrombocytopenic purpura.

Carbimazole↗