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L Wong

Publications and source records attributed to L Wong.

At least 145 records · Page 8Linked to original sources
PubMed1994

Protein-DNA interactions in the promoter region of the amyloid precursor protein (APP) gene in human neocortex.

We have investigated protein-DNA interactions in the proximal promoter of the human amyloid precursor protein (APP) gene in temporal lobe neocortical nuclei isolated from control and Alzheimer disease (AD) affected brains. We report that the human APP 5' promoter sequence from -203 to +55 bp, which has been previously reported to contain essential regulatory elements for APP gene transcription, lies in a deoxyribonuclease I, micrococcal nuclease- and restriction endonuclease-sensitive, G+C-rich nucleosome-free gap flanked both 5' and 3' by typical nucleosome structures. As analyzed by electrophoretic mobility shift assay, this extended internucleosomal linker DNA is heavily occupied by nuclear protein factors, and interacts differentially with nuclear protein extracts obtained from HeLa and human brain neocortical nuclei. This suggests that the chromatin conformation of the APP gene promoter may vary in different cell types, and may correlate with differences in APP gene expression. Human recombinant transcription factors AP1, SP1 and TFIID (but not AP2 or brain histones H1, H2B and H4) interact with the -203 to +55 bp of the human APP promoter sequence. Only minor differences were observed in the chromatin structure of the immediate APP promoter between non-AD and AD affected neocortical nuclei, suggesting either that post-transcriptional processes, or that regulatory elements lying elsewhere in the APP gene may be important in the aberrant accumulation of the APP gene product.

Aged↗
PubMed1994

Concentration of intracellular hepatic apolipoprotein E in Golgi apparatus saccular distensions and endosomes.

The intrahepatic distribution of apolipoprotein E has been assessed by immunogold labeling of cryosections as well as by Western blotting of organelles isolated from liver homogenates. Both techniques supported the prior analytical fractionation studies of Wong (1989) who concluded that intrahepatic apoE was largely endosomal. All endosomal components decorated by gold particles indicative of apoE antigenicity in cryosections appeared filled with lipoprotein-like particles thereby accounting for this prominent morphological feature of isolated liver endosomes. The distribution of gold particles about the hepatic Golgi apparatus revealed a high content of apoE in closely apposed endosomes, ca. 400 nm in diameter, double labeled for apoE and internalized HRP. Remarkably, apoE (but not internalized HRP) was also observed within saccular distensions of all saccules of stacked Golgi cisternae but absent from the flattened saccular components as was also observed for apoB. This contrasted with albumin, the major secretory protein, which was uniformly distributed throughout the hepatic Golgi apparatus. These observations support a growing body of evidence for intra-Golgi sorting of secretory material in hepatic Golgi apparatus. The lack of any immunoreactive apoE or albumin in small 70-90 nm vesicles about the Golgi cisternae suggests limits to current models of vesicle-mediated intra-Golgi transport.

Albumins↗
PubMed1994

Keratin 19-like immunoreactivity in receptor cells of mammalian taste buds.

Three monoclonal antibodies, 4.62, LP2K and 170.2.14, were used to evaluate keratin 19-like immunoreactivity in gustatory epithelia. Keratin 19-like immunoreactivity was restricted to the intragemmal cells for all types of mammalian taste buds examined. These taste buds included fungiform, foliate and vallate taste buds in rat, gerbil and rabbit, and nasopalatine, epiglottal and palatine taste buds in rat. There was no keratin 19-like immunoreactivity in basal cells or in perigemmal cells lateral to the immunoreactive taste receptor cells. Denervation of the rat vallate papilla eliminated all taste buds, as well as all immunoreactive taste cells. That the immunoreactive material in the taste cells was keratin 19 was supported by the comparable staining of rat taste buds with each of three monoclonal antibodies specific for keratin 19. Furthermore, as predicted, these antibodies selectively stained luminal cells of rat bile ducts, bladder, salivary ducts, trachea, ureter and uterus. It was concluded that monoclonal antibodies against keratin 19 can usefully distinguish intragemmal taste receptor cells from keratinocytes, and from the perigemmal and basal cells of gustatory epithelia. Anti-keratin 19 antibodies may serve to identify differentiated taste cells in gustatory epithelia undergoing taste bud development, renewal, degeneration or regeneration.

Animals↗
PubMed1994

Rigid mesh fixation for alloplastic cranioplasty.

The evolution of cranioplasty techniques is described. A cranioplasty technique is presented that incorporates metallic mesh within acrylic and utilizes the principle of rigid fixation to avoid micromotion at the alloplastic-bone interface. Six procedures have been completed without complications.

Humans↗
PubMed1994

Induction of beta-platelet-derived growth factor receptor in rat hepatic lipocytes during cellular activation in vivo and in culture.

A consistent response to liver injury is the activation of resident mesenchymal cells known as lipocytes (Ito, fat-storing cells) into a proliferating cell type. In cultured lipocytes, platelet-derived growth factor (PDGF) is the most potent proliferative cytokine, but requires the activation-dependent expression of its receptor protein (Friedman, S. L., and M. J. P. Arthur. 1989. J. Clin. Invest. 84:1780-1785); the role of PDGF receptor (PDGFR) in liver injury is unknown. We have examined PDGFR gene expression in freshly isolated lipocytes during liver injury and correlated these findings with a culture model of cellular activation. Whereas lipocytes from normal rats had no detectable transcript for the beta-PDGFR subunit, this mRNA was induced within 1 h after a dose of carbon tetrachloride (CCl4). In contrast, alpha subunit mRNA was detected in normal cells, but was unchanged after liver injury. Similar results were observed in lipocytes from bile duct-obstructed rats, although beta-PDGFR induction was less marked. By immunoblot, induction of beta-PDGFR protein in lipocytes isolated from CCl4-treated animals correlated with mRNA increases. In contrast to lipocytes, endothelial cells from normal liver expressed low levels of alpha- and beta-receptor subunit mRNA, which did not increase with injury. Using a beta-PDGFR antibody, receptor protein could be identified within fibrotic septa in CCl4-treated animals in regions where cells expressed proliferating cell nuclear antigen (PCNA). In cultured lipocytes activated by growth on uncoated plastic, beta-PDGFR transcripts appeared within 3 d after plating, which coincided with the onset of cellular proliferation. In contrast, quiescent cells in suspension culture had no detectable beta-PDGFR mRNA. These results indicate that beta-PDGF receptor induction by lipocytes is an early event during hepatic injury in vivo and in primary culture.

Adipocytes↗
PubMed1994

Heterosexual transmission of human immunodeficiency virus type 1 from transfusion recipients to their sex partners.

Using lookback procedures and other methods, we identified and then prospectively followed human immunodeficiency virus type 1 (HIV-1)-infected transfusion recipients and their sex partners to determine AIDS incidence and risks of heterosexual transmission of HIV-1. At enrollment, 7 of 32 (21.9%) female partners of male recipients were themselves infected with HIV-1, as compared with none of 14 male partners of female recipients (p = 0.08). No additional episodes of transmission were observed. The prevalence of advanced immunodeficiency at enrollment was similar in male and female recipients. Male recipients with advanced immunodeficiency (CD4+ lymphocyte count < or = 0.20 x 10(9)/L or a history of clinical AIDS) at enrollment were more likely to have infected their female partners (odds ratio = 7.9; p = 0.03) than men with neither condition. Similarly, AIDS-free survival, as estimated by the product-limit method, was lower among male transmitters than among male nontransmitters (p = 0.01). Transmission was not associated with frequency of unprotected vaginal intercourse. Our data suggest that HIV-1-infected men who develop immunodeficiency rapidly are more likely to infect their sex partners and that the greater efficiency of male-to-female HIV-1 transmission is not explained by a greater number of sexual contacts or more advanced immunodeficiency in index subjects.

Adult↗
PubMed1993

Two-dimensional electrophoresis of plasma lipoproteins: recognition of new apo A-I-containing subpopulations.

Two-dimensional electrophoresis has been used to resolve 12 distinct apo A-I-containing high-density lipoprotein (HDL) subpopulations in human plasma. The subpopulations were quantitated by 125I-labeled, monospecific antibody and phosphor-imaging. Modification and standardization of the agarose electrophoresis (first dimension) enabled us to recognize new HDL subpopulations. Lipoprotein mobilities in agarose were expressed relative to the mobility of the sample's endogenous albumin. We demonstrated the presence of lipoproteins with mobilities faster than and similar to albumin, as well as subpopulations with mobilities slower than albumin. We refer to these as pre alpha, alpha and pre beta, respectively. Lipoprotein molecular sizes were determined with a non-denaturing polyacrylamide gradient gel electrophoresis (PAGE) (2% to 36%) in the second dimension. Internal standard of 125I-labeled proteins of known molecular size was run simultaneously in each gel permitting accurate size determination. We have demonstrated that ultracentrifugally-isolated lipoproteins are different from the native apo A-I-containing subpopulations. The major difference observed was the loss of pre beta 1 and pre beta 2 particles from the d < 1.21 g/ml fractions to the d > 1.21 g/ml fractions. Possible physiologic and pathologic implications of these findings are also discussed.

Albumins↗
PubMed1993

Comparison of apo A-I-containing subpopulations of dog plasma and prenodal peripheral lymph: evidence for alteration in subpopulations in the interstitial space.

To study in vivo reverse cholesterol transport, dog plasma and lymph apo A-I-containing subpopulations were compared by two-dimensional electrophoresis. Charge and size of subpopulations were similar in plasma and lymph, but the distribution of subpopulations varied considerably. An increase in pre-beta and pre-alpha particles in lymph suggests these changes are a reflection of in vivo reverse cholesterol transport.

Animals↗
PubMed1993

Comparison of the lipid and apolipoprotein composition of skeletal muscle and peripheral lymph in control dogs and in dogs fed a high fat, high cholesterol, hypothyroid-inducing diet.

Most studies of peripheral interstitial fluid lipoprotein composition have been made on interstitial fluid-derived from skin and connective tissue. We developed techniques which allowed simultaneous comparison of lymph (a model of interstitial fluid) from skeletal muscle and skin in control (C) and cholesterol-fed (CF) dogs. Lipoprotein fractions were separated by ultracentrifugation. Skeletal muscle interstitial fluid HDL concentrations were approximately twice those of skin. However, the concentration of VLDL-LDL particles was similar in both interstitial spaces. HDL particles from both microvascular beds showed evidence of extensive remodelling when compared to plasma HDL from the same animal. Relative to apo A-I, skeletal muscle HDL was enriched in free cholesterol and apo E (C and CF dogs) and apo A-IV (CF dogs). Skin-derived HDL was consistently enriched in free cholesterol, apo E and A-IV in both C and CF dogs. These studies indicate that similar remodeling of plasma HDL occurs in widely different tissues which together constitute approximately 70% of the total interstitial space. The relatively high concentration of plasma-derived and remodeled HDL within the interstitial space of skeletal muscle is consistent with that tissue's importance in reverse cholesterol transport.

Animals↗
PubMed1993

Mutation of the gene for the human lysosomal serine protease cathepsin G is not the cause of aberrant APP processing in familial Alzheimer disease.

Recent genetic linkage studies have implicated a gene on chromosome 14 in the pathogenesis of FAD. The identity of this gene remains unknown but it has been speculated that it may be involved in the cellular processing of the amyloid precursor protein (APP). We have analyzed the nucleotide sequence of the entire open reading frame of the cathepsin G gene located on chromosome 14q. No mutations were observed, suggesting that defects in this lysosomal protease are not responsible for aberrant accumulation of proteolytic products of APP in FAD brain tissue.

Alzheimer Disease↗
PubMed1993

Further clinical use of the interposition arteriovenous loop graft in free tissue transfers.

The use of an arteriovenous fistula (AVF) to afford vascular access for free tissue transfer is described in 11 consecutive patients from a 1 year period. The leg was the site of pathology in six cases, and a reversed saphenous AVF to the femoral vessels was created. In the remaining five cases, those in the head and neck and arm regions, the recipient vessels varied. The mean patient age was 37.7 years, and ten of 11 patients were male. Etiologies of defect were automobile accidents in six cases, neoplasm in three, and gunshot wound and electrical injury in one patient each. Mean ischemia time was 113 +/- 15 min. Mean length of AVF was 27.3 +/- 2.1 cm. All flaps survived. AVF was a useful technique in the current study. Several maneuvers were undertaken to minimize the risk of thrombosis. All patients were given aspirin prior to AVF creation. Patients received dextran 40 in the postanastomosis period for 5 days. Finally, every effort was made to create the AVF between large vessels, especially in the leg, to maximize blood flow.

Adolescent↗
PubMed1993

Bcl-2 expression in adult and embryonic non-haematopoietic tissues.

The B-cell leukaemia/lymphoma-2 (bcl-2) proto-oncogene is unusual as its product appears to provide survival advantage to B cells by blocking apoptosis. In this study, the expression of bcl-2 has been examined in normal non-haematopoietic tissues, embryos, and psoriatic skin by immunohistochemical staining. Bcl-2 protein expression is mainly observed in cell populations with a long life and/or proliferating ability such as duct cells in exocrine glands, basal keratinocytes, cells at the bottom of colon crypts, and neurons. In the skin of both adult and embryo and also embryonic kidney and cartilage, bcl-2 expression was observed in cells which were undergoing morphological transition from undifferentiated stem cells to committed precursor cells. The finding of bcl-2 expression in the terminal differentiated syncytial trophoblast, but not cytotrophoblast, and in some cells responsive to hormone stimulation such as in the endometrium and myometrium suggests that the gene expression may be related to hormone responsiveness. As no bcl-2 localization was seen in the benign hyperproliferative skin condition psoriasis, this does not suggest a straight-forward link to proliferation. These observations support the view that the bcl-2 gene may have an important role in cell development, maturation, and the path to terminal differentiation.

Adult↗
PubMed1993

The amiloride resistance gene, car1, of Schizosaccharomyces pombe.

Amiloride, an inhibitor of various sodium transporters, is toxic to Schizosaccharomyces pombe at low concentration in minimal but not in rich media. Amiloride-resistant mutants were isolated and shown to represent a new locus (car1 for changed amiloride resistance) on chromosome I. The car1 gene was cloned and sequenced. Sequence analysis revealed an open reading frame of 526 amino acids with a predicted molecular weight of 58,545 Da. It has 52% hydrophobic residues and belongs to the class of 12-transmembrane-domain transport proteins. Gene disruption of car1 results in increased amiloride resistance. car1 has sequence similarity to proteins from Candida associated with resistance to benomyl, methotrexate and cycloheximide. No single physiologically identifiable component of sodium transport appeared to be lost. We propose that car1 serves an uptake function, perhaps as a symport with an unknown substrate and this carrier may transport amiloride into the cell. Further, we suggest that amiloride toxicity at low concentrations is not due to its effect on sodium transport but, rather, depends on intracellular interference with an unknown biosynthetic pathway.

Alleles↗
PubMed1993

Reduction of calbindin-28k mRNA levels in Alzheimer as compared to Huntington hippocampus.

Disturbances in calcium homeostasis have been observed to be associated with Alzheimer's and other neurodegenerative diseases. Increased total calcium levels and decreased levels of calcium binding proteins have been found in Alzheimer brain tissue. However, the mechanism behind these disturbances remain unknown. In situ hybridization with tritiated antisense RNA probes for the calcium binding proteins, calbindin-28k and calmodulin, was used to examine the expression of genes coding for these proteins in Alzheimer and Huntington brain tissues matched for age, agonal process and autopsy interval. mRNA levels for calbindin-28k were reduced by 35% in CA1 and CA2 regions of Alzheimer hippocampus, as compared to Huntington control. In contrast, calmodulin expression was unchanged in CA1 but reduced by 30% in CA2. mRNA expression of calbindin-28k and calmodulin in Alzheimer temporal cortex did not differ from control. There were no significant differences in calcium binding protein message levels in cerebellar Purkinje cells between Alzheimer and Huntington control. There was no correlation between calcium binding protein message levels and brain weight, autopsy interval, patient age or the extent of neurofibrillary degeneration. Instead, decreased calbindin-28k expression in Alzheimer-affected hippocampus was due to an increase in the percentage of neurons expressing lower message levels for these proteins.

Aged↗
PubMed1993

The effect of a variable dielectric coefficient and finite ion size on Poisson-Boltzmann calculations of DNA-electrolyte systems.

The results of variable dielectric coefficient Poisson-Boltzmann calculations of the counter-ion concentration in the vicinity of an all-atom model of the B-form of DNA are presented with an emphasis on the importance of spatial variations in the dielectric properties of the solvent, particularly at the macro-ion-solvent interface. Calculations of the distribution of hard-sphere electrolyte ions of various dimensions are reported. The presence of a dielectric boundary significantly increases the magnitude of the electrostatic potential with a concomitant increase in the accumulation of small counter-ions in the groove regions of DNA. Because ions with radii greater than 2 A have restricted access to the minor groove, the effect there is less significant than it is within the major groove. Changes in the dielectric coefficient for the electrolyte solution, allowing variation from 10 to 25, 40, 60, and 78.5 within the first 7.4 A of the surface of DNA, substantially increases the calculated surface concentration of counter-ions of all sizes. A lower dielectric coefficient near the macro-ion surface also tends to increase the counter-ion density in regions where the electrostatic potential is more negative than -kT. Regardless of the choice of dielectric coefficient, the number of ions in regions where the electrostatic potential is less than -kT remains the same for 0.153 M added 1-1 monovalent electrolyte as for the case without added salt. The strong dependence of the calculated distribution of counter-ion density on the choice of dielectric coefficients representing the solvent continuum suggests that care must be taken to properly characterize the physical system when studying electrostatic properties using these methods.

Biophysical Phenomena↗
PubMed1993

New techniques in burn wound management.

The critical care management of the burn patient has advanced such that those patients with larger burned surface areas are surviving for longer periods. Wound management and closure thus become critical to the patient's ultimate outcome. New techniques for modifying the extent of the burn injury and for replacing the skin cover are described in this article.

Burns↗