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D Fong

Publications and source records attributed to D Fong.

At least 37 records · Page 2Linked to original sources
PubMed1997

Lack of correlation between growth of TF-1 cells and tyrosine phosphorylation signals in response to IL-3, IL-5 and GM-CSF.

The human cell line, TF-1, was used to compare responses to interleukin 3 (IL-3), IL-5 and granulocyte-macrophage colony-stimulating factor (GM-CSF). TF-1 cells grew well in the presence of any one of the cytokines in early passages. However, the level of tyrosine phosphorylation was minimal in response to IL-5, and detection of a tyrosine phosphorylation signal required high concentrations of IL-5. When grown for longer periods of time in the presence of one of the cytokines, there were dramatic difference in the cells' responses. IL-3 or GM-CSF-grown cells showed only half of the original bioassay response to IL-5. However, cells grown in IL-5 alone kept the same response, and all cells showed the same response to IL-3 and GM-CSF. IL-5-grown cells also had an increased tyrosine phosphorylation signal, along with increased sensitivity to IL-5, yet there was no difference in an IL-5 bioassay. The relative level of detection of tyrosine phosphorylated JAK-2, STAT-5, SHC, and other substrates corresponded to the overall tyrosine phosphorylation signal. IL-5-grown cells had approximately 10-fold more IL-5 receptor alpha subunit message compared to IL-3-grown. These results suggest that response of TF-1 cells to IL-5 may be deceiving in that a good response in a bioassay can be observed with relatively little tyrosine phosphorylation, but an increase in tyrosine phosphorylation can be correlated with an increase in the expression of IL-5 receptor alpha subunit.

Cell Division↗
PubMed1997

Epidural haematoma and stroller-associated injury.

We present a severe case of head injury in an infant associated with stroller use and review similar reports from the literature. A case report and a literature search of the Medline database from 1966 to 6/1996 using the terms 'perambulator', 'parm', 'stroller', or 'baby carriage'. Reports in English describing injuries associated with their use are reviewed. We report a case of epidural haematoma in a 10 months old girl who sustained the injury after falling from a stroller. Safety harnesses were not worn during the incident. There was no skull fracture. Complete recovery followed surgical evacuation of the blood clot. Five reports describing stroller-related injuries were found in the English literature. Most injuries were mild. Three cases of death were reported of which two were classified as child abuse. The prevalence of unintentional stroller-associated injury is not clear. Mild injury, mostly to the head region, is probably common. Life-threatening injuries are rare but these are potentially preventable if strollers are properly designed and safety recommendations are followed.

Craniocerebral Trauma↗
PubMed1996

Response of digestive cysteine proteinases from the Colorado potato beetle (Leptinotarsa decemlineata) and the black vine weevil (Otiorynchus sulcatus) to a recombinant form of human stefin A.

The effects of the cystatins, human stefin A (HSA) and oryzacystatin I (OCI) on digestive cysteine proteinases of the Colorado potato beetle (CPB), Leptinotarsa decemlineata, and the black vine weevil (BVW), Otiorynchus sulcatus, were assessed using complementary inhibition assays, cystatin-affinity chromatography, and recombinant forms of the two inhibitors. For both insects, either HSA and OCI used in excess (10 or 20 microM) caused partial and stable inhibition of total proteolytic (azocaseinase) activity, but unlike for OCI the HSA-mediated inhibitions were significantly increased when the inhibitor was used in large excess (100 microM). As demonstrated by complementary inhibition assays, this two-step inhibition of the insect proteases by HSA was due to the differential inactivation of two distinct cysteine proteinase populations in either insect extracts, the rapidly (strongly) inhibited population corresponding to the OCI-sensitive fraction. After removing the cystatin-sensitive proteinases from CPB and BVW midgut extracts using OCI- (or HSA-) affinity chromatography, the effects of the insect "non-target" proteases on the structural integrity of the two cystatins were assessed. While OCI remained essentially stable, HSA was subjected to hydrolysis without the accumulation of detectable stable intermediates, suggesting the presence of multiple exposed cleavage sites sensitive to the action of the insect proteases on this cystatin. This apparent susceptibility of HSA to proteolytic cleavage may partially explain its low efficiency to inactivate the insect OCI-insensitive cysteine proteinases when not used in large excess. It could also have major implications when planning the use of cystatin-expressing transgenic plants for the control of coleopteran pests.

Animals↗
PubMed1996

Emergency contraceptive pills: a survey of use and experiences at College Health Centers in the mid-Atlantic United States.

The authors conducted a telephone survey to investigate the availability of the emergency contraceptive pill (ECP) at college health centers in the mid-Atlantic region of the United States. Related issues, such as distribution procedure, existence of an ECPs protocol, personnel involved, contraindications, follow-up procedures, methods of advertising, and staff attitudes were examined. Of the 124 completed responses, 43 schools (35%) reported distributing ECPs. The major reasons the schools listed for not distributing ECPs (n = 81, 65%) were inadequate staffing, religious convictions, no perceived need, and the service was available from a source in the local community.

Attitude of Health Personnel↗
PubMed1996

Feasibility of a telephone follow-up on use of emergency contraceptive pills in a college health center.

The authors examined the feasibility and effectiveness of a telephone follow-up procedure on use of emergency contraceptive pills (ECP) at a college health center. They made 264 telephone calls to the 97 women who had received ECPs during one 16-week academic semester and were successful in reaching 65 (67%) of the women, who responded with information about their experiences with ECPs. The women demonstrated a high rate of adherence to the medical regimen and reported very few side effects from ECPs; a majority said that ECPs did not affect their ability to carry out daily activities. On weighing the relative absence of problems following ECP distribution against the time, effort, and cost required to reach just over two thirds of the women, the researchers concluded that an ECP telephone follow-up procedure was neither cost-effective nor particularly useful.

Contraceptives, Postcoital↗
PubMed1995

Identification of two new exons and multiple transcription start points in the 5'-untranslated region of the human cathepsin-B-encoding gene.

Transcripts for cysteine protease cathepsin B (CTSB) were found to be highly variable in the 5'-UTR (untranslated region). In cDNA clones from a human gastric adenocarcinoma cDNA library, we have identified two new exons (designated 2a and 2b) between exons 2 and 3 in the 5'-UTR of the gene. All of the exons of the 5'-UTR could be alternatively spliced to produce several transcript species. In addition, transcription was initiated from more than one promoter region. Using RT-PCR (reverse transcription-polymerase chain reaction) and primer extension assays, CTSB mRNA species were found to differ among tissues and between a glioblastoma sample and a cell line derived from it. Exons 2a and 2b were detected more frequently in tumor samples than in matched normal samples. Thus, factors related to the cell differentiation and environment seem likely to determine the types of transcripts that are expressed which in turn could influence the overall steady-state level of CTSB mRNAs and their rate of translation. Interestingly, at least three upstream translation initiation codons were observed and could constitute a means of controlling translation initiation.

Adenocarcinoma↗
PubMed1995

Efficacy of the herbicide trifluralin against four P-glycoprotein-expressing strains of Leishmania.

Drug resistance has emerged as a major obstacle to chemotherapy for many infectious diseases. Trifluralin, an antimicrotubule herbicide, is a new experimental drug for treatment of leishmaniasis. Here, we found that it was effective against two strains of Leishmania that express the multidrug-resistant genes ldmdr1 and lmpgpA and two strains that express proteins that are immunologically cross-reactive with mammalian P glycoproteins. These results suggest that trifluralin is not subject to counteractions of these multidrug resistance mechanisms of Leishmania species.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Characterization of the small subunit ribosomal RNA gene of the oyster parasite Haplosporidium costale.

The small subunit ribosomal RNA (SSU rRNA) gene of the oyster parasite Haplosporidium costale was characterized from spore DNA by polymerase chain reaction (PCR) and molecular cloning. Sequence analysis showed that identical clones were obtained from separate batches of spore samples. The gene is 1791 nucleotides in size. It has 84.5% sequence similarity to that of a related oyster parasite, Haplosporidium nelsoni, 71.8% similarity to that of its oyster host, Crassostrea virginica, and 75.4% similarity to that of another oyster parasite, Perkinsus marinus. Among the variable regions of these SSU rRNA genes, H. costale-specific primers were designed and used to confirm parasite identity by the PCR technique. A common 150 base pair amplification product was obtained from DNA samples of H. costale spore DNA, DNA prepared from tissue sections of oysters infected with H. costale plasmodia, and the H. costale SSU rRNA clone. There was no detectable product from DNA samples isolated from tissue sections of oysters infected with H. nelsoni plasmodia.

Animals↗
PubMed1994

Human gastric adenocarcinoma cathepsin B: isolation and sequencing of full-length cDNAs and polymorphisms of the gene.

Four full-length cDNA clones coding for preprocathepsin B were isolated from a human gastric adenocarcinoma cDNA library (AGS 1-6-30-1) and analyzed for possible sequence modifications that might be linked to altered intracellular trafficking and secretion of cathepsin B (CTSB) in malignant tumors. Comparison of AGS 1-6-30-1 cDNAs with human kidney/hepatoma cDNAs revealed: (1) three potential N-glycosylation sites instead of two, (2) a nucleotide (nt) substitution in the coding region for the propeptide from GTG to CTG which would result in a Val26-->Leu change, (3) three silent nt replacements in the coding region for the mature protein, (4) five single-nt differences in the 5'- and 3'-UTR (untranslated regions), (5) heterogeneity in the 5'-UTR, and (6) a 10-bp insertion in the 3'-UTR. The 10-bp insertion in the 3'-UTR may alter the stability of CTSB mRNA transcripts and thereby the expression of CTSB. These clones should be useful for expressing human tumor CTSB and analyzing the function of this enzyme in malignant progression. Two restriction-fragment length polymorphisms (RFLPs), EcoRI and TaqI, were detected by Southern blot analysis of genomic DNA from 36 unrelated Caucasians. Inheritance and distribution of the EcoRI alleles (13.0 and 11.0 kb) and the TaqI alleles (5.7 and 4.6 kb) indicated they were independent polymorphisms. In contrast to the EcoRI alleles of 13.0 and 11.0 kb observed in the population survey, genomic DNA from two AGS gastric adenocarcinoma subclones revealed two EcoRI alleles of 13.0 and 7.8 kb.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗
PubMed1994

Plant microtubule inhibitors against trypanosomatids.

Trypanosomatid protozoa are etiologic agents of several prevalent tropical diseases. Tubulins constitute 10% of the total proteins of these organisms. In addition, they are conserved within the Trypanosomatidae family but are different from that of the mammalian hosts. Since current chemotherapy has severe side effects, new compounds are urgently needed. The microtubular system provides a target for selective chemotherapy. Plant microtubule inhibitors, trifluralin and its analogues, inhibits Leishmania and Trypanosoma brucei, and Marion Chan and Dunne Fong here discuss the biosafety and potential for development of drug resistance to these compounds.

Journal Article↗
PubMed1994

Paromomycin resistance in Leishmania tropica: lack of correlation with mutation in the small subunit ribosomal RNA gene.

The aminoglycoside antibiotic paromomycin is a potentially useful anti-leishmanial chemotherapeutic agent. Resistance to this antibiotic was studied using Leishmania tropica. Promastigotes resistant to 210 micrograms/ml of paromomycin were selected by exposing them to gradual increments of this drug. Previous work in Escherichia coli, Tetrahymena, and yeast mitochondrial mutants has demonstrated mutations in the E. coli small subunit ribosomal RNA at the 1409:1491 basepair position, or equivalent positions in other organisms, resulting in basepair disruption. When the nucleotide sequence at both the DNA and RNA levels of the resistant L. tropica promastigotes cultured in the presence of paromomycin was compared with those of the drug-sensitive parent, there was no sequence change at the putative mutation site. Paromomycin resistance in L. tropica is apparently due to other mechanisms.

Animals↗
PubMed1993

Herbicides to curb human parasitic infections: in vitro and in vivo effects of trifluralin on the trypanosomatid protozoans.

Leishmaniasis is a major tropical disease for which current chemotherapies, pentavalent antimonials, are inadequate and cause severe side effects. It has been reported that trifluralin, a microtubule-disrupting herbicide, is inhibitory to Leishmania amazonensis. In this study, the in vitro effect of trifluralin on different species of trypanosomatid protozoans was determined. In addition to L. amazonensis, trifluralin is effective against Leishmania major and Leishmania tropica, which cause cutaneous infections, Leishmania donovani, which causes visceral disease, Leishmania panamensis, which may cause mucocutaneous infection, and Trypanosoma brucei, an important human and veterinary pathogen. Moreover, most encouragingly, trifluralin is effective in vivo as a topical ointment against L. major and Leishmania mexicana murine cutaneous leishmaniasis. Thus, trifluralin is a promising lead drug for several related, prevalent tropical diseases: leishmaniasis, trypanosomiasis of animals, and, possibly, African trypanosomiasis in humans.

Animals↗
PubMed1993

Effect of the anti-microtubule compound tubulozole on Leishmania protozoan parasites in vitro.

For the cis and trans stereoisomers of the synthetic anti-microtubule compound tubulozole, at micromolar concentrations, tubulozole-C is cytotoxic to mammalian cells whereas tubulozole-T is not. The effect of tubulozoles on the parasitic protozoan Leishmania was tested. For the promastigote stage of L. mexicana amazonensis, both isomers inhibited parasite growth. For the amastigote stage of L. mexicana amazonensis and L. major, within murine J774 macrophage line as host cells in vitro, tubulozole-T reduced the infective index. Despite the observation of macrophage cytotoxicity of tubulozole-T, this compound may be a potentially useful and novel anti-leishmanial drug.

Animals↗
PubMed1993

Adhesion and costimulation of proliferative responses of human gamma delta T cells by interaction of VLA-4 and VLA-5 with fibronectin.

The very late antigens, VLA-4 and VLA-5 belong to the beta 1 subfamily of integrins and have been identified as receptors for different binding regions of fibronectin (FN). We have detected VLA-4 and VLA-5, but not VLA-3 and VLA-6 expressed on human CD3+CD4-CD8- gamma delta TCR T cells by flow cytometry. Binding assays, performed on FN-coated plates, showed that activated CD25high (IL-2 receptor) but not resting CD25low gamma delta T cells specifically adhere to FN. The binding capacity is inhibited by the synthetic peptide GRGDSP which inhibits adhesion mediated by VLA-5 and a functional mAb directed against the alpha 4 subunit. Most FN binding is mediated by VLA-4. Additionally, resting gamma delta T cells cultured on coimmobilized anti-TCR delta 1 mAb and FN or the 40 kDa fragment (which contains the adhesion site in the IIICS domain recognized by VLA-4) for 96 h in the absence of exogeneous IL-2 showed significant increase in proliferation when compared to that of resting gamma delta T cells cultured on immobilized anti-TCR delta 1 mAb alone. Also expression of CD25 was significantly enhanced on cells cultured on coimmobilized anti-TCR delta 1 mAb and FN, indicative of T cell activation. Cross-linking of VLA-4 and VLA-5 molecules costimulated expansion of resting gamma delta T cells induced by cross-linked TCR delta 1. These results suggest that the gamma delta T cell beta 1 integrins, VLA-4 and VLA-5, may function in a dual capacity as signalling and adhesion molecules.

Antibodies, Monoclonal↗
PubMed1993

Structure-function analysis of antimicrotubule dinitroanilines against promastigotes of the parasitic protozoan Leishmania mexicana.

Although leishmaniasis is a major tropical disease, the currently available drugs are toxic and inadequate. We show that the antimicrotubule herbicide trifluralin has antileishmania activity. The present study aimed at deducing the relationship between the structure of the molecule and its antiprotozoan activity. Nine dinitroanilines, all of which were analogs of trifluralin, were compared. We found that pendimethalin was 2.5-fold more potent than trifluralin, and the higher efficacy may be correlated with molecular structural features that increase the accessibility to one nitro group. This association was further supported by molecular modeling. Moreover, trifluralin samples from two sources differed in their activities by more than threefold, and gas column chromatography showed that impurities were present in the more potent sample.

Aniline Compounds↗