Biomedical subjects

L Eng

Publications and source records attributed to L Eng.

17 recordsLinked to original sources

PubMed2005

Stimulated emission of surface plasmons at the interface between a silver film and an optically pumped dye solution.

Surface plasmons (SPs) are surface-bound electromagnetic waves supported by metals, offering the possibility of strong spatial confinement of electromagnetic fields on the micro- and nanoscales. They suffer, however, from strong damping caused by internal absorption and radiation losses. Here we demonstrate amplification of SPs by stimulated emission, which marks a possible solution to this problem. We use an attenuated-total-reflection setup to detect stimulated emission of SPs at the interface between a silver film and an optically pumped dye solution acting as the amplifying medium. Clear evidence of stimulated emission is provided by an excellent agreement of the experimental observations with a theoretical analysis. Amplification of SPs can be considered analogous to photon amplification in a laser, thereby suggesting novel approaches in the field of nano-optics.

Journal Article↗

PubMed2005

ATM gene founder haplotypes and associated mutations in Polish families with ataxia-telangiectasia.

Ataxia-telangiectasia (A-T) is an early onset autosomal recessive ataxia associated with characteristic chromosomal aberrations, cell cycle checkpoint defects, cancer susceptibility, and sensitivity to ionizing radiation. We utilized the protein truncation test (PTT), and single strand conformation polymorphism (SSCP) on cDNA, as well as denaturing high performance liquid chromatography (dHPLC) on genomic DNA (gDNA) to screen for mutations in 24 Polish A-T families. Twenty-six distinct Short Tandem Repeat (STR) haplotypes were identified. Three founder mutations accounted for 58% of the alleles. Three-quarters of the families had at least one recurring (shared) mutation, which was somewhat surprising given the low frequency of consanguinity in Poland. STR haplotyping greatly improved the efficiency of mutation detection. We identified 44 of the expected 48 mutations (92%): sixty-nine percent were nonsense mutations, 23% caused aberrant splicing, and 5% were missense mutations. Four mutations have not been previously described. Two of the Polish mutations have been observed previously in Amish and Mennonite A-T patients; this is compatible with historical records. Shared mutations shared the same Single Nucleotide Polymorphism (SNP) and STR haplotypes, indicating common ancestries. The Mennonite mutation, 5932 G>T, is common in Russian A-T families, and the STR haplovariants are the same in both Poland and Russia. Attempts to correlate phenotypes with genotypes were inconclusive due to the limited numbers of patients with identical mutations.

Adolescent↗

PubMed2001

An amperometric cellobiose dehydrogenase-based biosensor can be used for measurement of cellulase activity.

The hemoflavoenzyme cellobiose dehydrogenase (CDH, EC 1.1.99.18) from Phanerochaete chrysosporium has been used in an amperometric redox polymer-based biosensor. Used in conjugation with a FIA system this biosensor can replace colorimetric assays for measuring cellobiose liberated from cellulose in a series of cellulase-containing samples. The biosensor gave the same result as the Somogyi-Nelson method in a less time-consuming and laborious manner. The two methods showed about the same precision.

Biosensing Techniques↗

PubMed1998

Reconstituted human oral and esophageal mucosa in culture.

We have successfully established monolayer and organotypic culture techniques for growing human oral and esophageal epithelial cells. Cells in monolayer culture were grown in serum-free medium, modified from techniques previously reported by our group. The organotypic cultures were grown in a defined medium supplemented with 10% fetal calf serum. Oral and esophageal cells were maintained in keratinocyte basal medium with pituitary extract and other supplements, and 0.05 mM calcium for 7-9 and 9-11 passages, respectively. Both cell types had similar morphology by phase contrast microscopy. When confluent, the cells were predominantly small, basaloid, and uniform and interspersed with larger, differentiated cells. By immunohistochemistry, both cell types in monolayer were positive to AE1, AE3, and 34BE12 antibodies to keratins of stratified epithelia. Oral epithelial cells in monolayer also were positive to 35BH11, representative of simple epithelial keratins, while esophageal cells were not. The esophageal cells were focally positive to K13, while the oral cells were negative. Both were negative for K19. When comparing monolayer to organotypic cultures and to in vivo specimens, there was a significant difference in the expression of keratins. Using organotypic cultures, AE1, AE3, and 34BE12 were strongly positive in both oral and esophageal cells, similar to in vivo tissues. In contrast to monolayers, both were also focally positive for K19. Esophageal cells were strongly positive for K13, while the oral cells were mildly but uniformly positive. Both were negative for keratins of simple epithelia. These two cell culture techniques offer unique opportunities to study the pathobiology, including carcinogenesis, of stable cell systems from the oral and esophageal epithelia.

Cells, Cultured↗

PubMed1998

Severe insulin resistance in a patient with type 1 diabetes and stiff-man syndrome treated with insulin lispro.

We describe a patient with type 1 diabetes with recurrent diabetic ketoacidosis and severe insulin resistance. Extensive evaluation of the etiology of the insulin resistance did not reveal an etiology, and well over 1000 U of daily insulin did not prevent the ketoacidosis. Her blood glucose and insulin requirements were improved with glucocorticoids and octreotide, but the effects of both of these agents were short-lived. She was given a trial of insulin lispro with immediate and dramatic effects, lowering her HbA1c from 14.6 to 5.1% in 7 months with a decrease in insulin requirements of 1600-100 U per day. Besides her diabetes, she had a history of pain and stiffness affecting numerous muscle groups, and hospitalization was required for pain control. The diagnosis of stiff-man syndrome (SMS) was confirmed with high titers of glutamic acid decarboxylase 65 antibodies in both serum and cerebral spinal fluid. In summary, we describe the first patient with type 1 diabetes, SMS, and severe insulin resistance. Although the etiology of the insulin resistance is unknown, due to the efficacious response to insulin lispro, hydrocortisone, and perhaps octreotide, we propose an immune-mediated etiology. Although rare, this syndrome needs to be considered as an etiology of insulin resistance.

Adult↗

PubMed1998

A novel inward rectifier K+ channel with unique pore properties.

We have cloned a novel K+-selective, inward rectifier channel that is widely expressed in brain but is especially abundant in the Purkinje cell layer of the cerebellum and pyramidal cells of the hippocampus. It is also present in a wide array of tissues, including kidney and intestine. The channel is only 38% identical to its closest relative, Kir1.3 (Kir1-ATP-regulated inward rectifier K+ [ROMK] family) and displays none of the functional properties unique to the ROMK class. Kir7.1 has several unique features, including a very low estimated single channel conductance (approximately 50 fS), low sensitivity to block by external Ba2+ and Cs+, and no dependence of its inward rectification properties on the internal blocking particle Mg2+. The unusual pore properties of Kir7.1 seem to be explained by amino acids in the pore sequence that differ from corresponding conserved residues in all other Kir channel proteins. Replacement of one of these amino acids (Met-125) with the Arg absolutely conserved in all other Kir channels dramatically increases its single channel conductance and Ba2+ sensitivity. This channel would provide a steady background K+ current to help set the membrane potential in cells in which it is expressed. We propose that the novel channel be assigned to a new Kir subfamily, Kir7.1.

Animals↗

PubMed1996

The effect of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) on cultured dog pancreatic duct epithelial cells.

To study the morphologic and genetic events associated with the carcinogenic process in the pancreas, we have isolated and cultured a cell line of dog pancreatic duct epithelial cells and treated these cells with a carcinogen. The pancreatic duct epithelial cells were plated onto Vitrogen-coated Transwell inserts suspended above a feeder layer of human gallbladder myofibroblasts. The epithelial cells grew steadily into polarized monolayers, could be passaged repeatedly, and demonstrated the typical morphologic, immunohistochemical, and flow cytometric profile of normal well-differentiated columnar pancreatic epithelial cells. After being treated with 10(-5) M N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) for 48 h, the treated cells grew on plastic surfaces. When grown in organotypic culture, the MNNG-treated cells were cuboidal with a multilayered, pseudostratified architecture. Flow cytometry demonstrated aneuploidy and a high percentage of the cells in S phase after reaching confluency, in sharp contrast to untreated cells. Cytogenetic analysis of the MNNG-treated cells revealed frequent chromosomal trisomy and tetrasomy. The secretion of mucin was also different in the MNNG-treated cells versus the untreated cells. The cultured pancreatic epithelial cells may be useful as an assay system to study the genotoxicity of known and potential carcinogens.

Animals↗

PubMed1996

Dog pancreatic duct epithelial cells: long-term culture and characterization.

Epithelial cells, isolated from a normal dog pancreatic duct, were grown on collagen-coated culture inserts suspended above a feeder layer of myofibroblasts. The cells were examined by transmission electron microscopy, immunohistochemistry, cytogenetics, and flow cytometry. In addition, the constitutive and agonist-stimulated mucin secretion of these cells was studied using a [3H]N-acetyl-D-glucosamine labeling assay, and the stimulation of intracellular cAMP was measured. Cells grown on inserts with a feeder layer developed into confluent monolayers consisting of strictly polarized columnar epithelial cells with prominent microvilli, intercellular junctions, and normal chromosomal characteristics. They could be passaged repeatedly without a detectable alteration in their morphology. The cells could also be grown on organotypic cultures, resulting in further differentiated cells simulating in vivo morphology. Immunohistochemistry demonstrated the presence of carbonic anhydrase II in these cells. Cells treated with vasoactive intestinal peptide, epinephrine, and dibutyryl-cAMP demonstrated a marked increase in mucin secretion compared with controls. In parallel experiments, VIP and epinephrine significantly increased intracellular cAMP. In conclusion we have developed a pancreatic epithelial cell preparation with morphology, cytokinetics, chromosomal, and DNA analyses characteristic of normal cells. Similar to normal columnar epithelial cells, these pancreatic duct cells secreted mucin constitutively and responded to agonist by increasing secretion via a cAMP-mediated pathway. They also contained carbonic anhydrase, which indicates that the cells are capable of secreting bicarbonate.

Animals↗

PubMed1995

Bovine serum albumin conformation on methyl and amine functionalized surfaces compared by scanning force microscopy.

We investigated the adsorption of albumin on chemically modified gold surfaces by scanning force microscopy operating both in contact and noncontact mode. The surface modification was performed with thiol-based self-assembling molecules carrying amine or methyl groups. The albumin on the aminoethanethiol-coated gold formed a uniform layer and single molecules could be distinguished. On the dodecanethiol-coated surface the protein adsorbed in aggregates or single isolated molecules depending on the incubation time. The width of the albumin molecule on both surface was similar, but the height was much lower on the amine than on the methyl surface. This was interpreted as a difference in the conformation of albumin depending on the substrate, and could explain the promotion of cell adhesion on amine-treated polymers coated with albumin.

Adsorption↗

PubMed1995

Organotypic culture of human gallbladder epithelium.

We have modified methods of growing human gallbladder epithelial cells in monolayer and organotypic culture. These cells were grown in the presence of fetal bovine serum and with coculture of feeder layers of human gallbladder fibroblasts. Human gallbladders were obtained from cholecystectomy specimens, and the cells were dissociated with trypsin/EDTA. Cells, which were grown with feeder layer on collagen-coated plates in the presence of 10% FBS, grew rapidly and formed islands of cuboidal cells with morphology typical of epithelial cells in culture. They could be passaged up to four times. The cells were also successfully grown by organotypic technique producing a monolayer of tall, columnar, palisade, epithelial cells. These cells, both in monolayer and in organotypic culture, were positive to antibodies for simple epithelial keratin and negative to antibody for vimentin or any of the mesenchymal antibodies. These cells respond to agonists (prostaglandin E2, isoproterenol) by the intracellular generation of cAMP. Secreted mucin on the apical surface stained strongly with periodic acid-Schiff. Organotypic culture of human gallbladder epithelium may serve as a cell preparation for the study of pathobiology of columnar epithelial cells.

Adrenergic Agonists↗

PubMed1986

Rat lung and liver microsomal cytochrome P-450 isozymes involved in the hydroxylation of n-hexane.

The primary metabolism of n-hexane in rat lung and liver microsomes was investigated. In liver microsomes from untreated animals the formation of each of the metabolites, 1-, 2- and 3-hexanol, was best described kinetically by a two-enzyme system, whereas for lung microsomes a one-enzyme system was indicated for each metabolite. Cytochrome P-450-PB-B, the major cytochrome P-450 isozyme induced in rat liver by phenobarbital, appeared to be responsible for the formation of 2- and 3-hexanol in lung microsomes from untreated rats as judged by antibody inhibition studies. The presence of this isozyme was confirmed by immunoblotting. In contrast, formation of 1-hexanol in rat lung was catalyzed by a cytochrome P-450 isozyme different from the major isozymes induced by either phenobarbital or beta-naphthoflavone. Similarly, formation of 2,5-hexanediol from 2-hexanol was catalyzed by a P-450 isozyme different from cytochrome P-450-PB-B and present in liver but not in lung microsomes. Furthermore, alcohol dehydrogenase activity with hexanols or hexanediol as the substrate was found exclusively in liver cytosol. These results suggest that inhaled n-hexane must be transported to the liver either intact or in the form of 2-hexanol before the neurotoxic metabolite 2,5-hexanedione can be formed.

Animals↗

PubMed1985

The lens epithelium contains glial fibrillary acidic protein (GFAP).

Both polyclonal and monoclonal antibodies to glial fibrillary acidic protein (GFAP) intensely immunostain the lens epithelium. Two-dimensional gels of mouse lens epithelium protein extracts reveal a protein which co-migrates with GFAP from spinal cord. A lens epithelial protein of approximately 50 000 MW on one-dimensional gels is immunoreactive with antiserum to GFAP (Hatfield et al. 1984). GFAP has been regarded as a protein unique to neuroglial cells but this study indicates that some cells of ectodermal origin (the lens epithelium) express GFAP.

Animals↗

PubMed1985

Human dendritic cells and macrophages. In situ immunophenotypic definition of subsets that exhibit specific morphologic and microenvironmental characteristics.

Using a panel of monoclonal antibodies and antisera in situ, the authors have defined subsets of human dendritic cells and macrophages that exhibit specific morphologic and microenvironmental characteristics. All subsets contained cells that reacted with antibodies directed against HLA-A,B,C, HLA-Dr, leukocyte common, Leu-M3, and Leu-3(T4) antigens. R4/23 and anti-S100 defined three major subsets. R4/23+, S100- cells constituted the B-cell-related follicular dendritic cells, which were identified only within the germinal center/mantle microenvironment of lymphoid follicles. R4/23-, S100+ cells constituted the T-cell-related dendritic cell subset. Anti-Leu-6(T6) further subdivided this group into Leu-6(T6)- interdigitating cells within the T-cell microenvironments of lymphoid organs and Leu-6(T6)+ Langerhans cells found predominantly in epithelial microenvironments, especially the skin. R4/23-, S100- cells constituted the nondendritic tissue macrophage subset which was widely distributed, primarily outside of dendritic-cell microenvironments. These data indicate that although dendritic cells and macrophages share several common antigenic features, morphologically and microenvironmentally distinct subsets express distinct immunologic phenotypes. Such data may provide insight into the ontogeny and function of these subsets and constitute a basis for the comparison of normal dendritic cells and macrophages to various histiocytic proliferative disorders.

Animals↗

PubMed1984

Glial fibrillary acidic protein is localized in the lens epithelium.

The epithelium of the mouse lens stains intensely with antisera to glial fibrillary acidic protein (GFAP). A protein co-migrating with GFAP and immunoreactive with antisera to GFAP can be demonstrated in lens epithelium protein extracts by immunoblots. GFAP has previously been considered unique to cells of neural origin, but this study demonstrates that ectodermally derived cells express GFAP or a highly similar protein.

Animals↗

PubMed1981

Human brain in tissue cultures. VI. Presence of glial fibrillary acidic protein in subcultivated human fetal brain cells as demonstrated by immunofluorescent and immunoperoxidase staining.

Glial fibrillary acidic protein (GFAP) was present in cell cultures derived from human fetal brain tissue as determined by indirect immunofluorescence (IF) and immunoperoxidase (IP) staining using rabbit anti-human GFAP antisera. The IF and IP techniques were comparable in localizing the cytoplasmic distribution and the frequent perinuclear concentration of GFAP in brain cells. The horseradish peroxidase technique was more sensitive and a 1:20-1:40 dilution of anti-GFAP serum could be applied in the initial step of the peroxidase staining as compared to a 1:10 dilution of anti-GFAP serum for IF staining. Sequential studies of subcultivated human fetal brain cell lines by these techniques indicated that some brain cell lines become GFAP-negative rapidly, whereas other cell lines remain GFAP-positive for no less than ten subcultivations in vitro. GFA protein was never present in any PML-SV40-transformed human brain cells.

Animals↗

PubMed1981

Regio-selectivity of purified forms of rabbit liver microsomal cytochrome P-450 in the metabolism of benzo(a)pyrene, n-hexane and 7-ethoxyresorufin.

The specificity of electrophoretically homogeneous preparations of rabbit liver microsomal cytochrome P-450LM2-4 towards oxygenation of n-hexane, 7-ethoxyresorufin and benzo(a)pyrene was examined using a reconstituted system consisting of cytochrome P-450, NADPH-cytochrome P-450 reductase and dilauroylphosphatidylcholine. Epoxide hydrase was included when benzo(a)pyrene was used as substrate. Cytochrome P-450LM2 was most active in n-hexane and benzo(a)pyrene oxygenation especially with regard to the formation of 2-hexanol, B(a)P-4,5-dihydrodiol and B(a)P-phenol metabolites. 7-Ethoxyresorufin was, however, a very poor substrate for cytochrome P-450LM2. Cytochrome P-450LM3 had less activity towards the investigated substrates while cytochrome P-450LM4 preferentially formed 2- and 3-hexanol, resorufin and B(a)P-9,10-dihydrodiol. Cytochrome P-450LM4 isolated after pretreatment with 3-methylcholanthrene or phenobarbital showed roughly the same characteristics except in the formation of 1-hexanol where cytochrome P-450LM4 isolated after phenobarbital treatment was the most effective. The formation of B(a)P-4,5- and -9,10-dihydrodiols was greatly increased by incorporation of epoxide hydrase. Our results indicate a certain specificity of the different forms of cytochrome P-450 in the liver microsomes although some overlap in activities was observed.

Animals↗

PubMed1978

Diazepam, alcohol and drivers.

Fifteen hundred drivers' blood samples have been analysed for the drug diazepam (Valium) over a three-year period. Of 1000 hospitalised drivers whose blood samples were forwarded to DSIR for alcohol analysis, diazepam was detected in 2.0% and alcohol in over 90%. Diazepam was found to a lesser extent in blood samples from 370 fatally injured drivers, and from 130 apprehended drivers who returned low blood alcohol levels. The significance of the levels of diazepam and its major metabolite in blood are discussed in relation to the blood alcohol level and consequent driving impairment.

Accidents, Traffic↗