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Biomedical subjects

L Wong

Publications and source records attributed to L Wong.

At least 109 records · Page 6Linked to original sources
PubMed1997

Role of free apolipoprotein A-I in cholesterol efflux. Formation of pre-alpha-migrating high-density lipoprotein particles.

This article characterizes products formed by the interaction of purified apolipoprotein (apo) A-I and human fibroblasts. Fibroblasts were incubated with different concentrations of purified apoA-I (1 to 30 micrograms/mL) in tissue culture medium for different periods of time (0 to 24 hours). The medium was then characterized by one- (agarose) and two-dimensional (agarose: polyacrylamide nondenaturing gradient gel) electrophoresis. At any given concentration of apoA-I, the rate of cellular cholesterol efflux appeared linear over 24 hours. Incubating purified apoA-I with fibroblasts for 4 hours, we detected five pre-alpha lipoproteins with particle sizes between 114 and 684 kDa. Formation of pre-alpha lipoproteins was concentration-dependent. At low concentrations (below 5 micrograms/mL apoA-I), all purified apoA-I (with pre-beta mobility) was converted to pre-alpha lipoproteins. At higher concentrations (greater than 5 micrograms/mL apoA-I), more apoA-I remained with pre-beta mobility. The pre-alpha lipoproteins were characterized by colocalization of apoA-I particles with 14C-cholesterol and 32P-phospholipids. Results showed that the pre-alpha particle of lowest molecular weight contained phospholipid and apoA-I but no cholesterol. The remaining pre-alpha particles contained all three substances. When pre-alpha particles were subjected to ultracentrifugation, all particles floated at d < 1.21 g/mL with some of the smallest phospholipid apoA-I only particles being present in the d > 1.21 g/mL fraction. Based on these results, we postulated that in the first stages of reverse cholesterol transport, pre-alpha lipoproteins are formed by the interaction of lipid free apoA-I and peripheral cells.

Apolipoprotein A-I↗
PubMed1997

Mother-infant interactions in two strains of rats: implications for dissociating mechanism and function of a maternal pattern.

Mother-infant interaction was observed in Long-Evans and Fischer 344 rats after fostering within or across strains. Interactions immediately following introduction of foster pups to the cage as well as undisturbed interactions with resident litters were examined. Some differences were related to alien status, some to strain of pups, and others to strain of dams. Greater responsiveness to pups of the maternal strain was exhibited in retrieval and body licking. Long-Evans pups received more crouching from dams of both strains 3-12 days postpartum, perhaps because they are significantly larger. Regardless of pup strain, Long-Evans dams engaged in more maternal licking than did F344 dams, and this was more likely directed to the anogenital region. Dams of both strains were more likely to lick male than female pups, regardless of pup strain. The strain difference in maternal licking is consistent with adult strain differences in water and salt appetite and may contribute developmentally to the superior copulatory performance of Long-Evans males.

Animals↗
PubMed1996

Helicobacter pylori induces gene expression in human gastric cells identified by mRNA differential display.

Changes in gene expression patterns in gastric cells infected with Helicobacter pylori were characterized by means of mRNA differential display. Total RNA preparations were extracted from the H. pylori infected gastric cells and paired non-infected cells, and were probed with candidate clones identified after screening up to 6,000 mRNA species. Among them, four clones, 04G-1, 04G-2, 01G-1, and Cppa-2 show significant expression in the infected cells by Northern blot analysis, and they are 199 bp, 196 bp, 228 bp, and 276 bp in length, respectively. Database search revealed that nucleotide sequences of these clones share very low identity with any known sequence. These results indicate that H. pylori can significantly affect gene expression in gastric cells. Furthermore mRNA differential display can be used in pathogenesis studies to identify new genes in gastric cells in response to insults such as H. pylori.

Adenocarcinoma↗
PubMed1996

Epidermal growth factor induces coupling of protein-tyrosine phosphatase 1D to GRB2 via the COOH-terminal SH3 domain of GRB2.

The Src homology 2 (SH2) and SH3 domain-containing adaptor protein GRB2 and the SH2 domain-containing protein-tyrosine phosphatase 1D (PTP1D, also called SHPTP2, PTP2C, SHPTP3, Syp, or SHP-2) function as positive mediators of growth factor-induced mitogenesis. Epidermal growth factor (EGF) is a potent mitogen for MCF-10A human mammary epithelial cells and EGF receptor-expressing mouse NR6 fibroblasts. Western blot analysis of anti-PTP1D immune complexes derived from EGF-treated cells demonstrated a ligand-dependent coupling between the phosphatase and GRB2 in vivo. Probing of lysates from these cells with glutathione S-transferase (GST) fusion proteins corresponding to the individual domains of GRB2 revealed that this interaction was mediated exclusively by the COOH-terminal SH3 domain of GRB2. Importantly, a GST fusion protein containing the PTP1D SH2 domains was not capable of generating the EGF-induced linkage to GRB2. Additional experiments indicated that neither the binding of the nucleotide exchange factor Sos to GRB2 nor tyrosine phosphorylation of PTP1D was required for EGF-stimulated coupling of PTP1D to GRB2. This is the first demonstration of a growth factor- or cytokine-induced coupling of a protein through an SH3 domain and suggests that GRB2 functions to target PTP1D, in addition to Sos, to the plasma membrane in response to EGF.

Adaptor Proteins, Signal Transducing↗
PubMed1996

STAT activation by epidermal growth factor (EGF) and amphiregulin. Requirement for the EGF receptor kinase but not for tyrosine phosphorylation sites or JAK1.

The epidermal growth factor (EGF) receptor activates several signaling cascades in response to the ligands EGF and amphiregulin (AR). One of these signaling events involves the tyrosine phosphorylation of STATs (signal transducers and activators of transcription), a process believed to require the activation of a tyrosine kinase of the JAK family. In this report we demonstrate that EGF- and AR-induced STAT activation requires the intrinsic kinase activity of the receptor but not the presence of Jak1. We show that both wild type (WT) and truncated EGF receptors lacking all autophosphorylation sites activate STAT 1, 3, and 5 in response to either EGF or AR. Furthermore, relative to cells expressing WT receptor, ligand-induced tyrosine phosphorylation of the STATs was enhanced in cells expressing only the truncated receptor. These results provide the first evidence that (i) EGF receptor-mediated STAT activation occurs in a Jak1-independent manner, (ii) the intrinsic tyrosine kinase activity of the receptor is essential for STAT activation, and (iii) tyrosine phosphorylation sites within the EGF receptor are not required for STAT activation.

Amphiregulin↗
PubMed1996

Inhibition by ethanol of the growth of biofilm and dispersed microcosm dental plaques.

Inhibition of microcosm plaque biofilm growth by periodic application of ethanol was compared with the minimum inhibitory concentration (MIC) and bactericidal effects of ethanol on liquid cultures of dispersed plaque bacteria. Microcosm plaques were cultured from saliva in a multiplaque 'artificial mouth' and their growth in wet weight measured daily. Nutrient conditions included: a continuous supply of a medium containing 0.25 percent mucin, and 8-hourly 5 percent (w/v) sucrose (1.5 ml over 6 min). Plaque biofilm growth was strongly inhibited by exposure to 40 percent (v/v) ethanol applied in volumes of 3.75 ml over 15 min, six times daily. Application of 1.5 ml over 6 min inhibited much less or not at all. Ethanol concentrations lower than 40 percent caused less inhibition, with 10 percent having almost no effect. The pH response to sucrose was unchanged by prior application of 40 percent ethanol for 30 min. Some evidence was obtained for either bacterial adaptation to ethanol or selection of ethanol-resistant bacteria. The MIC and bactericidal effects of ethanol were assessed by growth of dispersed plaque in liquid culture; the bactericidal effect was measured as the induced delay in growth. The aerobic and anaerobic MIC of ethanol for growth was 10 percent and 8 percent; 50 percent inhibition of growth rate occurred at 3.7 percent and 2.8 percent. Ethanol (40 percent) was bactericidal within 1-2 min, but 10 percent had almost no effect. It was concluded that, despite the well-known high ethanol sensitivity of dispersed plaque bacteria, prolonged application of ethanol concentrations in the order of 40 percent are necessary to inhibit growth of plaque biofilms.

Adaptation, Physiological↗
PubMed1996

Early olfactory experience, novelty, and choice of sexual partner by male rats.

After rearing by citral-scented or unscented dams, adult male rats were given simultaneous choices of citral-scented or unscented female partners in approach, contact, and sexual behavior tests. There was no evidence that mate choice had been affected by the early rearing experience. In Experiment 1, both citral and control males approached citral-scented females in a T-apparatus at slightly above chance levels and exhibited no differences in copulatory behavior during successive pairings. In Experiment 2, normally reared males directed their first mount more rapidly to a citral female, but otherwise mated equally with the scented and unscented females. In Experiment 3, citral-reared males approached citral and unscented females equally, whereas controls approached citral females less often. With 2 females in the same arena (Exp. 3), the first mount was more rapid when the odor of the partner matched that of the dam, but no other measure of sexual behavior was affected by the partner's odor. Despite the importance of early olfactory experience for the development of social behavior, a preference for estrous-related odors is evidently not learned before mating experience. Under some circumstances, a novel odor added to familiar conspecific odors may attract naive males to potential partners.

Acyclic Monoterpenes↗
PubMed1996

Use of cytokines in clozapine-induced agranulocytosis.

OBJECTIVE: To report and review the use of cytokines for the treatment of clozapine-induced neutropenia. METHOD: Case report and review of literature. RESULTS: Cytokines, granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF), appear to shorten the duration of clozapine-induced neutropenia. CONCLUSIONS: G-CSF or GM-CSF therapy should be considered in patients with profound neutropenia of prolonged duration (high-risk neutropenia).

Adult↗
PubMed1996

The impact of a gel system on routine work in a general hospital blood bank.

The gel system has been reported to be more sensitive and specific than the conventional tube indirect antiglobulin test (IAT) for antibody screening. However, a major concern about the gel system is its cost. A cost analysis study was therefore conducted at our hospital. The gel system costs more than the conventional tube IAT per test; however, the total staff and reagent costs per year were about equal, because of staff savings. Workload and cost per patient requiring blood were reduced using the gel system.

Journal Article↗
PubMed1995

A YAC-, P1-, and cosmid-based physical map of the BRCA1 region on chromosome 17q21.

A familial early-onset breast cancer gene (BRCA1) has been localized to chromosome 17q21. To characterize this region and to aid in the identification of the BRCA1 gene, a physical map of a region of 1.0-1.5 Mb between the EDH17B1 and the PPY loci on chromosome 17q21 was generated. The physical map is composed of a yeast artificial chromosome (YAC) and P1 phage contig with one gap. The majority of the interval has also been converted to a cosmid contig. Twenty-three PCR-based sequence-tagged sites (STSs) were mapped to these contigs, thereby confirming the order and overlap of individual clones. This complex physical map of the BRCA1 region was used to isolate genes by a number of gene identification techniques and to generate transcript maps of the region, as presented in the three accompanying manuscripts of Brody et al. (1995), Osborne-Lawrence et al. (1995), and Friedman et al. (1995).

BRCA1 Protein↗
PubMed1995

Urban rape survivors: characteristics and prevalence of human immunodeficiency virus and other sexually transmitted infections. Multicenter Crack Cocaine and HIV Infection Study Team.

OBJECTIVE: To determine the prevalence of recent rape, the characteristics or recent rape survivors, and the seroprevalence of human immunodeficiency virus (HIV), syphilis, and genital herpes (HSV-2) among recent rape survivors. METHODS: We surveyed women 18-29 years old who were recruited from places unassociated with medical or drug treatment or the criminal justice system in three urban communities where illicit drug use is common. We compared characteristics and HIV, syphilis, and HSV-2 seroprevalence of women who reported recent rape with those of women who denied recent rape. RESULTS: One hundred fifty-one of 1104 (13.7%) women reported having been raped in the year before our interview. Rape survivors were more likely than women who denied recent rape to smoke crack cocaine (86.8 versus 56.7%; odds ratio [OR] 5.0, 95% confidence interval [CI] 3.2-7.8), to be homeless (17.2 versus 6.1%; OR 3.2, CI 2.0-5.2), to report a recent sexually transmitted disease (38.7 versus 18.7%; OR 2.7, CI 1.9-3.9), and to be infected with syphilis (42.4 versus 28.4%; OR 1.9, CI 1.3-2.6) and HSV-2 (71.9 versus 57.5%; OR 1.9, CI 1.3-2.8). Survivors were more likely to acknowledge any HIV risk behavior (including sex work) (85.4 versus 49.5%; OR 5.9, CI 3.9-9.0) and to be HIV-infected (23.3 versus 13.4%; OR 1.9, CI 1.3-2.9). Rape was not independently associated with HIV (OR 0.8, 95% CI 0.4-1.3), syphilis (OR 0.9, 95% CI 0.6-1.3), or HSV-2 (OR 1.3, 95% CI 0.9-2.0) infections after adjustment for confounding factors. CONCLUSION: One in seven women reported being raped recently. Rape was most common among sex workers, crack smokers, and the homeless. Most survivors reported HIV risk behaviors, and many were HIV-infected. Programs to prevent repeated rape, voluntary HIV counseling and testing, and other medical and social services may benefit survivors in these and similar communities.

Adolescent↗
PubMed1995

Keratins as markers of differentiated taste cells of the rat.

Cytokeratins in taste buds were immunocytochemically evaluated with monoclonal antibodies. In each of six different epithelial sites in the rat oral cavity, intragemmal cells of taste buds were immunoreactive for keratin polypeptides 8, 18, and 19, as well as for keratin 7, which has not been previously reported in taste buds. Keratin-18-like immunoreactivity was present in fewer than half of the intragemmal cells, whereas all intragemmal cells were immunopositive for keratins 7, 8, and 19. Apart from some salivary duct cells, no other cells in the tongue were immunoreactive for any of these four keratins. Morphological and immunocytochemical profiles indicate that taste buds are islets of simple epithelium embedded in an expanse of stratified squamous epithelium. These simple epithelial cells and their keratins are nerve-dependent, since denervation eliminated all four keratins and replaced elongated taste cells of the vallate papilla with stratified squamous epithelium. We conclude that antibodies against keratins 7, 8, or 19 are useful markers for intragemmal cells in studies of taste bud development, degeneration, regeneration, turnover and tissue culture.

Animals↗
PubMed1995

Keratin 18 is associated with a subset of older taste cells in the rat.

All or nearly all intragemmal (elongated) cells of rat taste buds were immunopositive for keratins 7, 8, and 19. In contrast, keratin 18 was detected in 19 +/- 5 cells per taste bud (mean +/- sd), or about 25% of the intragemmal cells. During taste bud development keratins 7, 8, and 19 were evident initially in polygonal cells and later in elongated taste cells. Keratin 8 appeared in vallate taste cells at P0 (postnatal day 0), followed by keratins 7 and 19 at P1, and keratin 18 at P2-P3. Keratin 18 was always limited to elongated cells. The assemblage of elongated taste cells comprising a taste bud began with a single elongated cell, rather than with the synchronous elongation of a cluster of cells. Developmental errors were observed at P2-P3, e.g., some vallate taste cells had a misoriented axis. In order to study the pace of keratin differentiation during cell turnover we injected bromodeoxyuridine (BrdU) into adult rats to monitor taste cell age. Keratin-19-positive intragemmal cells differentiated within 1 day. In contrast, keratin 18 was first detected in cells aged 3 days. Hence, both in taste cell development and replacement, keratin 18 was restricted to the older cells; it was the last taste cell keratin to become expressed during differentiation.

Animals↗
PubMed1995

Evaluation of the gel test for antibody screening in a tertiary hospital in Hong Kong; insensitivity for some cold antibodies that are reactive at 37 degrees C by conventional indirect antiglobulin tests.

The antiglobulin gel test (DiaMed) was compared with conventional IAT methods in pretransfusion antibody screening in a tertiary hospital in Hong Kong. Antibody titrations showed that the gel system was more sensitive than the tube IAT method in detecting anti-D, anti-S, anti-s, but slightly less sensitive with anti-E. The gel tests detected all clinically significant warm reacting allo-antibodies detected by conventional IAT methods except one case of weak anti-E. It detected a case of anti-C missed in conventional screening. The number of serological investigations due to false positive screens, non-specific antibodies and clinically insignificant cold antibodies (anti-P, and anti-Lewis) were reduced. The gel system was fast and easy to use. It would reduce delays and inconvenience caused to patients due to false positive screens and non-specific antibodies without compromising detection of clinically significant antibodies. However, of concern was the failure to detect several cases of anti-Le(a) and anti-P1 that were reactive at 37 degrees C by conventional IAT and one case of anti-H in a patient with Parabombay A.

Blood Grouping and Crossmatching↗