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Biomedical subjects

E Wong

Publications and source records attributed to E Wong.

At least 199 records · Page 11Linked to original sources
PubMed1988

Repetitive nucleotide sequence insertions into a novel calmodulin-related gene and its processed pseudogene.

A gene containing a transposon-like human repeat element, called THE 1, has been isolated and characterized. The gene, termed T+, encodes a polypeptide resembling known calcium-binding proteins. The THE 1 element is present in the 3'-untranslated region of its message. The cDNA clone corresponding to the gene's mRNA product led to the identification of this gene. A processed RNA pseudogene related to the authentic gene has also been isolated. In addition to intron processing, this pseudogene differs from the gene in that it contains an interspersed Alu repeat instead of a THE 1 element in the 3'-untranslated region. Thus, we compare a site containing a THE 1 element to an ancestrally related transposon-less target site. The comparison suggests a retroviral-related mechanism of THE 1 insertion. This system is unusual in that the parent gene is associated with three distinct retrotransposition events: the parent gene was converted to a processed RNA pseudogene, an Alu repeat inserted into the pseudogene, and a THE 1 element inserted into the parent gene.

Amino Acid Sequence↗
PubMed1988

Studies on uptake of gamma-aminobutyric acid by mouse brain particles; toward the development of a model.

Several substances were studied for their effect on enhancement and/or inhibition of uptake of GABA into a mouse brain microsomal fraction (P3) at pH 7.3 in the presence and absence of buffer. These were diverse: Na+, K+, NH4+, Hg2+, Cl-, and HCO3-; beta-guanidinopropionic and L-2,3-diaminopropionic acids and 1,2-diaminoethane; pyridine and several methylated pyridines; chlorpromazine and ketamine; and melittin. Kinetic experiments tested these substances for competition with GABA and Na+. Assuming the GABA transporter to consist of a GABA recognition entity and a Na+- and Cl-dependent protein required for its activity, a minimal provisional model for the GABA uptake process is proposed that is consistent with all current data and with relevant observations in the literature. It accounts for the activational effects of proton removal on GABA uptake, the stoichiometry of 2 Na+ and 1 Cl- associated with uptake of one GABA molecule, and the types of inhibition of uptake shown by the substances listed above. Factors are considered that may be necessary to maintain the transporter in a GABA-receptive configuration and that allow it the freedom of movement to undergo the structural variations necessary for the transport process to take place at rates that may be regulated by environmental factors.

Animals↗
PubMed1988

Human transposon-like elements insert at a preferred target site: evidence for a retrovirally mediated process.

Members of the human transposon-like family of repetitive sequences (called THE 1 repeats) like many other repetitive DNA sequences are flanked by short direct repeats. Comparison of the base sequences of twelve examples of these flanking direct repeats indicates that THE 1 repeats insert into a preferred genomic target site. In one case, we have identified the sequence of an empty site into which a THE 1 element inserted. The sequence of this empty site and sequences of truncated THE 1 LTRs are consistent with a retroviral mechanism for the insertion of THE 1 elements. Truncated transposon structures illustrate for the first time that intermediate structures of retrotransposition may also be integrated into the genome.

Base Sequence↗
PubMed1988

Clinical applications of electron microscopy in the analysis of collagenous biomaterials.

Scanning and transmission electron microscopy are of clinical value in assessing the interaction between biomaterials and ingrowing tissues. Ultrastructural information allows the clinician and biomaterials specialist to determine events occurring during wound healing and the biocompatibility of prosthetic devices. This paper reviews some of the experimental and clinical studies done in our laboratory on the use of natural and reconstituted collagen as replacements for connective tissues. Consideration is given to collagen flakes used for the treatment of dermal ulcers, a collagen fiber prosthesis used for tendon and ligament replacement, the effects of chemical preservatives on cartilage used for replacement of tissues during plastic surgery and the growth and orientation of nerve cells on reconstituted collagen fibers. Our results show that reconstituted collagen can be prepared into prosthetic devices which encourage cell attachment and orientation thereby facilitating healing of injured tissues. Furthermore chemical preservation of cartilagenous tissues kills chondrocytes resulting in eventual resorption by inflammatory cells.

Biocompatible Materials↗
PubMed1987

Cloned extrachromosomal circular DNA copies of the human transposable element THE-1 are related predominantly to a single type of family member.

The 2300 base-pair transposon-like human element, THE-1, has been identified in the extrachromosomal circular DNA of the established human cell line HeLa as a relatively homogeneous population of covalently closed 1900 base-pair molecules. THE-1, which has been classified tentatively as a retroviral-like transposable element (a retrotransposon), is present in the extrachromosomal circular DNA of African green monkey (BSC-1) and human lymphoblastoid (Jurkat) cell lines. The 1900 base-pair extrachromosomal elements isolated and cloned from HeLa cells (1) appear to contain only THE-1-specific nucleotide sequences, (2) are circularized versions of the linear chromosomal sequence, and (3) are related predominantly to a single, or single type of, family member.

Autoradiography↗
PubMed1987

Sex difference of antifertility effect by passively immunized monoclonal sperm antibodies.

Sperm-specific monoclonal antibodies (MS 204, MS 207, HS 11, and HS 63) that had been shown to inhibit fertilization of mouse oocytes in vitro were used to passively immunize male and female mice. In vitro and in vivo fertilization experiments were performed to compare the efficacy of resulting antifertility effects owing to the presence of circulating sperm antibodies. When the sperm from the antibody-treated mice were recovered for insemination, a partial inhibition of fertilization of mouse oocytes in vitro was observed. However, under the same antibody dose that effectively inhibits the in vivo fertilization of treated female mice the fertilization rate of the treated male was not significantly reduced, when they were mated with normal superovulated females followed by in vitro embryo culture. Similarly, on day 9 after mating with the antibody-treated males, the number of fetuses in mated females was not significantly different from that of the control. In contrast, when the antibody-treated females were mated with the proven fertile males, the number of fetuses was significantly reduced in response to the antibody treatment. When I-125-labeled monoclonal sperm antibodies were used to passively immunize male mice, the percentage of antibodies recovered from epididymis (relative to that of blood) was not much different from that of other organs, except for lower percentages detected in brain and testis. In treated females, oviduct and uterus revealed the presence of relatively high percentages of antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

The chemokinetic response of psoriatic and normal polymorphonuclear leukocytes to arachidonic acid lipoxygenase products.

Polymorphonuclear leukocytes (PMN) from ten patients with chronic stable plaque psoriasis, five of whom had more than 40% skin involvement and five with less than 20% involvement, responded in a dose-related fashion to stimulation with the arachidonic acid lipoxygenase products 5- and 12-hydroxyeicosatetraenoic acid (5- and 12-HETE) and leukotriene B4 (LTB4) in an in vitro chemokinesis assay. There was no significant difference in either the random migration or the chemokinetic response of psoriatic PMN to LTB4 when compared to the responses of PMN from a group of age- and sex-matched healthy controls. Psoriatic PMN migrated further in response to low doses of 5- and 12-HETE although the distance moved after maximal stimulation was no different to that observed in controls. No significant difference was observed in the responses of PMN obtained from patients with less than 20% skin involvement when compared to those with more extensive psoriasis. The small differences measured between the chemokinetic responses of psoriatic and control PMN to the lipoxygenase products tested are unlikely to be of pathogenetic significance.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1986

Inhibitory effects of monoclonal sperm antibodies on the fertilization of mouse oocytes in vitro and in vivo.

The inhibitory effects of monoclonal antibodies on the fertilization of mouse oocytes were evaluated in vitro and in vivo. Among the 40 sperm-specific monoclonal antibodies that had been examined, nine showed significant inhibition of the fertilization of mouse oocytes in vitro. MS 204 was shown to cause a high incidence of penetration of the zona pellucida of mouse eggs by multiple sperm, when the sperm concentration for insemination exceeds 1 X 10(5)/ml. This antibody prevented further penetration of the vitelline membrane by sperm. On the other hand, sperm penetration to zona was inhibited in the presence of MS 207. However, neither MS 204 nor MS 207 caused significant inhibition of penetration of zona-free mouse or hamster eggs by sperm. MS 204 and MS 207 were also found to inhibit the fertilization of mouse oocytes in vivo and embryo development in vitro, when superovulated mice were injected intraperitoneally with given doses of antibodies prior to the mating. Further in vitro culture of the recovered 2-cell oocytes revealed little or no further embryo development beyond two- to four-cell stages. In the controls, greater than 80% of the retrieved oocytes were fertilized and successively developed to the blastocyst stages in vitro when the ascites fluid from NS-1 cells was administered. Two of the monoclonal antibodies generated against human sperm antigens, HS 11 and HS 63, were shown to cross-react specifically with mouse sperm acrosomal antigens and also inhibited the fertilization of mouse oocytes in vitro and in vivo. The results of this study suggest that some monoclonal antibodies to sperm acrosomal antigens exhibit strongly inhibitory effects on the in vitro and in vivo fertilization of mouse oocytes as well as subsequent development of early embryos. As a comparative control, rabbit antisera against sperm-specific enzymes, lactate dehydrogenase-X and 3-phosphoglycerate kinase-2, showed little or no inhibition on the fertilization of mouse oocytes in vitro or in vivo or the subsequent embryo development.

Animals↗
PubMed1986

Developmental studies of sperm surface antigens using sperm-specific monoclonal antibodies.

Sperm-specific monoclonal antibodies generated against mouse sperm isoantigens were used to analyze the developmental expressions of sperm surface antigens during different stages of spermatogenesis. Indirect immunofluorescent assays using the freshly isolated testicular cells from mature and immature mice revealed that a number of monoclonal antibodies did not stain the surface of spermatogenic cells in testis. Instead these antibodies reacted with the sperm surface antigens in testis and/or epididymis. Further analysis was performed using frozen testicular sections from mice of day 14 to day 30 after birth. It was generally observed that a significant number of these antibodies reacted with the cytoplasmic components of spermatogenic cells in testis at the postmeiotic stages (e.g. day 22 after birth). After meiosis, the percentage of seminiferous tubules that were stained by immunofluorescence was found to increase with the ages of the mice. The results of this study suggest that some cytoplasmic components (especially acrosomal) of spermatogenic cells are expressed postmeiotically in testis, but later translocated to the sperm surface during very late stages of spermatogenesis.

Animals↗
PubMed1986

Topical steroid treatment reduces arachidonic acid and leukotriene B4 in lesional skin of psoriasis.

Topical clobetasol propionate or vehicle ointment was applied daily for 3 days to psoriatic plaques on eight patients. Skin chamber exudates from untreated, steroid and vehicle treated lesions were assayed for arachidonic acid (AA), leukotriene B4 (LTB4), prostaglandin E2 (PGE2) and 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) before, and at 24 h and 72 h after treatment. Significant reductions in AA and LTB4 were observed at 72 h in steroid treated lesions. The reduction in 12-HETE levels observed after steroid treatment was not statistically significant. PGE2 levels in lesional psoriatic skin were unaltered. The reduction of AA, and LTB4 was associated with clinical improvement of psoriasis.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1985

Verapamil is a competitive inhibitor of gamma-aminobutyric acid and calcium uptakes by mouse brain subcellular particles.

We found that verapamil and its methoxy analogue, D600, were relatively potent (micromolar) inhibitors of Na+-dependent GABA uptake by a mouse brain microsomal subfraction (P3). Verapamil was competitive with GABA and uncompetitive with Na+ in the uptake assay with the P3 fraction. These substances were much less effective in inhibiting GABA binding in a receptor-related assay system with synaptosomal membranes. Inhibition by verapamil of Na+-dependent 45Ca++ uptake by the P3 particles was competitive with Ca++. A consideration of our results with those in the literature led to the suggestion that the interaction of verapamil and related substances with GABA and 45Ca uptake processes by the P3 fraction, as well as with many other membrane activities, may be allosteric in nature rather than directly competitive with specific ligands at their binding sites.

Animals↗
PubMed1985

Potentiation of Na+-dependent uptake of gamma-aminobutyric acid in mouse brain particles by buffer-mediated proton removal.

A number of buffers showed a remarkable facilitatory effect on the uptake of GABA into a mouse brain microsomal subfraction (P3) at 0 degrees C and pH 7.3 in the presence of 80 mM NaCl. Complete dose-response curves were obtained for 21 buffers, ranging in pKa values from 6.2 to 9.9. The data are consistent with the interpretation that the unprotonated forms of the buffers are responsible for the enhancement of GABA uptake by P3 particles and that this is a result of the removal of protons from a membrane site (or sites) in such a manner as to allow the GABA transporter to function. However, the enhancing effects of the buffers could not solely be attributable to unhindered interaction of protonated membrane sites with unprotonated forms of the buffer. Additional factors related to structures of the buffers and membrane properties which might be importantly operative in the enhancement are discussed.

Animals↗
PubMed1985

Comparison of human and chimpanzee zeta 1 globin genes.

The DNA base sequences of the entire chimpanzee zeta 1 globin gene and an additional 1 kb of DNA flanking both the human and chimpanzee genes have been determined. Whereas the human zeta 1 gene contains a termination codon in the sixth position, the chimpanzee gene appears to be functional. This finding confirms Proudfoot et al.'s suggestion that the human zeta 1 gene was recently inactivated. Like the corresponding human zeta 1 and zeta 2 genes, the first and second introns of the chimpanzee zeta 1 gene are occupied largely by tandem repeats of short oligonucleotides. These tandem repeats have undergone several rearrangements since the divergence of the human and chimpanzee zeta 1 genes.

Amino Acid Sequence↗