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Biomedical subjects

D J Harrison

Publications and source records attributed to D J Harrison.

At least 55 records · Page 3Linked to original sources
PubMed2000

Integration of immobilized trypsin bead beds for protein digestion within a microfluidic chip incorporating capillary electrophoresis separations and an electrospray mass spectrometry interface.

A microfluidic device is described in which an electrospray interface to a mass spectrometer is integrated with a capillary electrophoresis channel, an injector and a protein digestion bed on a monolithic substrate. A large channel, 800 microm wide, 150 microm deep and 15 mm long, was created to act as a reactor bed for trypsin immobilized on 40-60 microm diameter beads. Separation was performed in channels etched 10 microm deep, 30 microm wide and about 45 mm long, feeding into a capillary, attached to the chip with a low dead volume coupling, that was 30 mm in length, with a 50 microm i.d. and 180 microm o.d. Sample was pumped through the reactor bed at flow rates between 0.5 and 60 microL/min. The application of this device for rapid digestion, separation and identification of proteins is demonstrated for melittin, cytochrome c and bovine serum albumin (BSA). The rate and efficiency of digestion was related to the flow rate of the substrate solution through the reactor bed. A flow rate of 1 or 0.5 microL/min was found adequate for complete consumption of cytochrome c or BSA, corresponding to a digestion time of 3-6 min at room temperature. Coverage of the amino acid sequence ranged from 92% for cytochrome c to 71% for BSA, with some missed cleavages observed. Melittin was consumed within 5 s. In contrast, a similar extent of digestion of melittin in a cuvet took 10-15 min. The kinetic limitations associated with the rapid digestion of low picomole levels of substrate were minimized using an integrated digestion bed with hydrodynamic flow to provide an increased ratio of trypsin to sample. This chip design thus provides a convenient platform for automated sample processing in proteomics applications.

Animals↗
PubMed2000

Increasing age does not affect good outcome after lumbar disc replacement.

From 1992 to 1998 fifteen Link-Charite SB III disc prostheses were implanted into 14 patients. The main indication was degenerative lumbar disc disease with segmental instability. With a mean follow-up of 48 months (18-68 months); 12 patients had a good (10) or fair (2) outcome regarding pain relief, return to employment and level of general physical activity. In contrast to previous publications we felt that age over 45 years did not appear to adversely affect the outcome.

Activities of Daily Living↗
PubMed2000

Red diode laser induced fluorescence detection with a confocal microscope on a microchip for capillary electrophoresis.

A highly sensitive laser induced fluorescence (LIF) detection system based on a 635 nm laser diode and cyanine-5 (Cy-5) dye, is described for use with a planar, microfluidic, capillary electrophoresis (CE) chip. The CE-chip is able to determine a protein biological threat agent simulant, ovalbumin (Ov), by performing an immunoassay separation of Cy-5 labeled anti-ovalbumin from its complex with Ov, in under 30 s. A confocal, epiluminescent detection system utilizing a photomultiplier tube gave optimum results with a 400 microm pinhole, an Omega 682DF22 emission filter, a 645DRLP02 dichroic mirror, a 634.54 +/- 5 nm excitation filter, and a Power Technology ACMO8 635 nm laser operated at 11.2 mW. Using this detector, a microchip CE device with a separation efficiency of 42,000 plates and an etch depth of 20 microm, gave a concentration detection limit of 9 pM Cy-5. This limit corresponds to the determination of 4560 injected molecules and detection of 900 of these molecules, given a probe volume of 1.6 pl and a probing efficiency of 20%.

Electrophoresis, Capillary↗
PubMed2000

Gene transfer to adult human lung tissue ex vivo.

The potential of gene therapy for treatment of lung disease remains unrealised. Early model systems often resulted in promising efficiency of gene transfer, only to prove irreproducible in the clinic. While problems such as induction of host immune responses and duration of expression also need to be addressed, it is now widely believed that alternative, relevant models which more accurately reflect gene transfer efficiencies in human lungs are urgently required. We report here on a human lung slice culture system to assess gene transfer to adult lung epithelium. A lacZ-expressing adenovirus (AdCA35lacZ) was used as a reporter vector. A solution of AdCA35lacZ was instilled via bronchioles into resected lung tissue, a route analogous to clinical administration. Following a 1 h incubation, the tissue was inflated with a 0.4% agarose solution, instilled via the same bronchioles. Once solidified, 500 microm slices of the tissue were prepared and cultured for 4 days. beta-Galactosidase staining revealed lacZ transgene expression in bronchiolar and alveolar cells of the lung slices throughout the 4 days in culture. This system, which can also be used to study other viral and liposome vectors, could prove to be a useful alternative model for assessing gene delivery to adult human lung epithelium.

Adenoviridae↗
PubMed2000

mRNA isolation in a microfluidic device for eventual integration of cDNA library construction.

mRNA isolation for the purpose of cDNA library construction was performed in a microfluidic chip device using paramagnetic oligo-dT beads. The simple Y-intersection flow design mixes beads and sample on-chip, and uses magnetic trapping to capture, then release the beads. The capillary gel electrophoresis (CGE) detection of the total unamplified mRNA isolated on-chip, and of a reverse transcription-polymerase chain reaction (RT-PCR) amplified rare gene indicated that mRNA could be captured by oligo-dT beads on-chip, had very good integrity and was suitable for constructing a cDNA library. The limit of detection for the rare bicoid gene of Drosophila Melanogaster corresponded to the capture of approximately 2.8 ng of total mRNA from 0.85 microgram of total RNA (TRNA) within the microchip. As much as 34 ng of total mRNA was estimated to be captured from 10 micrograms of TRNA.

Animals↗
PubMed2000

Immunohistochemical assessment of Ki67 and p53 expression assists the diagnosis and grading of ulcerative colitis-related dysplasia.

AIMS: To assess whether Ki67 and p53 immunostaining may assist the diagnosis and grading of ulcerative colitis-related dysplasia. METHODS AND RESULTS: Location of Ki67 staining and location and intensity of p53 staining were assessed in ulcerative colitis (UC) cases showing the features of high-grade dysplasia (HGD, n = 14), low-grade dysplasia (LGD, n = 22), 'indefinite for dysplasia' (n = 12), or regenerative atypia (RA, n = 22). Good intra- and inter-observer reproducibilities were demonstrated in the performance of these assessments. All the dysplasia cases showed extension of Ki67 staining above the basal third of the crypt. Moderate intensity p53 staining was seen in 10/22 RA cases, but strong intensity p53 staining was seen only in cases of dysplasia. All the cases of HGD showed extension of Ki67 and p53 staining above the basal two thirds of the crypt. CONCLUSIONS: Restriction of Ki67 staining to the basal third of the crypt appears to exclude a diagnosis of dysplasia whereas strong intensity p53 staining suggests a diagnosis of dysplasia. Restriction of Ki67 or p53 staining to the basal two-thirds of the crypt appears to exclude a diagnosis of HGD.

Biopsy↗
PubMed2000

Serum hyaluronan--a non-invasive test for diagnosing liver cirrhosis.

INTRODUCTION: Hyaluronan is a glucosaminoglycan synthesized by the mesenchymal cells and degraded by hepatic sinusoidal endothelial cells by a specific receptor-mediated process. Elevated levels are associated with the sinusoidal capillarization that is seen in cirrhosis. METHODOLOGY: Serum hyaluronan was measured, using a radiometric assay (Pharmacia, Sweden) in 221 patients with biopsy-proven chronic liver disease of a variety of aetiologies (alcohol n = 70, autoimmune chronic active hepatitis n = 23, primary biliary cirrhosis n = 17, hepatitis C n = 69, cryptogenic n = 15, various n = 27). All patients were fasted, and their liver function tests, full blood count, prothrombin time and Child-Pugh score were assessed at the time of the liver biopsy. RESULTS: Hyaluronan levels (microg/l) were significantly higher in patients with liver cirrhosis (cirrhosis n = 127, mean 440, 95% CI 367-515) (P < 0.0001) compared with hepatic fibrosis (n = 23, mean 144, 95% CI 69-190), chronic hepatitis (n = 60, mean 63, 95% CI 37-91) and fatty liver (n = 11, mean 107, 95% CI 37-177). Within the cirrhotic population, there was no significant difference in hyaluronan levels between different aetiologies, but hyaluronan level increased proportionally to the severity of cirrhosis. Overall, a hyaluronan level > 100 microg/l had a 78% specificity and 83% sensitivity for diagnosing cirrhosis, while the specificity was increased to 96% for all patients with hyaluronan levels > 300 microg/l. The highest specificity and sensitivity were seen at a cut-off value of 100 microg/l in patients with alcohol-associated liver disease (89%, 87%) and hepatitis C (93%, 72%) respectively. Within patient cohorts, there was a significant correlation (P < 0.01) between hyaluronan and albumin, platelet count and bilirubin, but not with alanine aminotransferase. CONCLUSION: Measurement of fasted serum hyaluronan reliably differentiated cirrhotic from non-cirrhotic liver disease and can be regarded as a useful test in the diagnosis of liver cirrhosis, particularly when a liver biopsy is contraindicated.

Biopsy↗
PubMed2000

Genetic polymorphisms of cytochrome p4502E1 and susceptibility to alcoholic liver disease and hepatocellular carcinoma in a white population: a study and literature review, including meta-analysis.

AIMS: To investigate the associations between the Rsa I, Dra I, and Taq I genetic polymorphisms of cytochrome p4502E1 and susceptibility to alcoholic liver disease or to hepatocellular carcinoma. METHODS: DNA samples isolated from 61 patients with alcoholic liver disease, 46 patients with hepatocellular carcinoma, and 375 healthy controls were subjected to polymerase chain reaction amplification followed by digestion with the endonucleases Rsa I, Dra I, or Taq I. Meta-analysis was performed using data from previous studies of Rsa I polymorphism and the risk of alcoholic liver disease. RESULTS: No association was found between any of the three polymorphisms and susceptibility to hepatocellular carcinoma. The distributions of Rsa I and Dra I alleles among the patients with alcoholic liver disease were not significantly different from those among the control group. Meta-analysis of this data and previous data concerning Rsa I polymorphism and alcoholic liver disease risk failed to demonstrate any significant association between the two. However, the alcoholic liver disease group in this study showed a significantly lower frequency of the less common Taq I allele compared with the healthy control group (odds ratio, 0.33; 95% confidence interval, 0.12 to 0.78). CONCLUSIONS: Possession of the less common Taq I cytochrome p4502E1 allele is associated with reduced susceptibility to alcoholic liver disease. There is no existing evidence that the Taq I polymorphism is directly associated with altered alcohol metabolism, but it might be in linkage disequilibrium with as yet unidentified protective factors.

Adult↗
PubMed1999

Dysregulated expression of beta-catenin marks early neoplastic change in Apc mutant mice, but not all lesions arising in Msh2 deficient mice.

We have analysed the pattern of beta-catenin expression by immunohistochemistry in mice singly or multiply mutant for Apc, p53 and Msh2. We observed increased expression of beta-catenin in all intestinal lesions arising on an ApcMin+/- background. In all categories of lesion studied mosaic patterns of beta-catenin expression were observed, with the proportion of cells showing enhanced expression decreasing with increasing lesion size. p53 status did not alter these patterns. We also show that beta-catenin dysregulation marks pancreatic abnormalities occurring in ApcMin+/- and (ApcMin+/-, p53-/-) mice. In these mice both adenomas and adenocarcinomas of the pancreas arose and were characterized by increased expression of beta-catenin. We have extended these analyses to intestinal lesions arising in mice mutant for the mismatch repair gene Msh2. In these mice, increased expression of beta-catenin was again observed. However, in contrast with ApcMin+/- mice, a subset of lesions retained normal expression. Taken together, these findings show that increased expression of beta-catenin is an efficient marker of early neoplastic change in both murine intestine and pancreas in Apc mutant mice. However, we also show that dysregulation of beta-catenin is not an obligate step in the development of intestinal lesions, and therefore that genetic events other than the loss of Apc function may initiate the transition from normal to neoplastic epithelium.

Adenomatous Polyposis Coli Protein↗
PubMed1999

Major differences exist in the function and tissue-specific expression of human aflatoxin B1 aldehyde reductase and the principal human aldo-keto reductase AKR1 family members.

Complementary DNA clones encoding human aflatoxin B(1) aldehyde reductase (AKR7A2), aldehyde reductase (AKR1A1), aldose reductase (AKR1B1), dihydrodiol dehydrogenase 1 (AKR1C1) and chlordecone reductase (AKR1C4) have been expressed in Escherichia coli. These members of the aldo-keto reductase (AKR) superfamily have been purified from E. coli as recombinant proteins. The recently identified AKR7A2 was shown to differ from the AKR1 isoenzymes in being able to catalyse the reduction of 2-carboxybenzaldehyde. Also, AKR7A2 was found to exhibit a narrow substrate specificity, with activity being restricted to succinic semialdehyde (SSA), 2-nitrobenzaldehyde, pyridine-2-aldehyde, isatin, 1,2-naphthoquinone (1,2-NQ) and 9,10-phenanthrenequinone. In contrast, AKR1A1 reduces a broad spectrum of carbonyl-containing compounds, displaying highest specific activity for SSA, 4-carboxybenzaldehyde, 4-nitrobenzaldehyde, pyridine-3-aldehyde, pyridine-4-aldehyde, 4-hydroxynonenal, phenylglyoxal, methylglyoxal, 2,3-hexanedione, 1, 2-NQ, 16-ketoestrone and d-glucuronic acid. Comparison between the kinetic properties of AKR7A2 and AKR1A1 showed that both recombinant enzymes exhibited roughly similar k(cat)/K(m) values for SSA, 1,2-NQ and 16-ketoestrone. Many of the compounds which are substrates for AKR1A1 also serve as substrates for AKR1B1, though the latter enzyme was shown to display a specific activity significantly less than that of AKR1A1 for most of the aromatic and aliphatic aldehydes studied. Neither AKR1C1 nor AKR1C4 was found to possess high reductase activity towards aliphatic aldehydes, aromatic aldehydes, aldoses or dicarbonyls. However, unlike AKR1A1 and AKR1B1, both AKR1C1 and AKR1C4 were able to catalyse the oxidation of 1-acenaphthenol and, in addition, AKR1C4 could oxidize di- and tri-hydroxylated bile acids. Specific antibodies raised against AKR7A2, AKR1A1, AKR1B1, AKR1C1 and AKR1C4 have been used to show the presence of all of the reductases in human hepatic cytosol; the levels of AKR1B1 and AKR1C1 were markedly elevated in livers with alcohol-associated injury, and indeed AKR1B1 was only detectable in livers with evidence of alcoholic liver disease. Western blotting of extracts from brain, heart, kidney, liver, lung, prostate, skeletal muscle, small intestine, spleen and testis showed that AKR7A2 is present in all of the organs examined, and AKR1B1 is similarly widely distributed in human tissues. These experiments revealed however, that the expression of AKR1A1 is restricted primarily to brain, kidney, liver and small intestine. The AKR1C family members proved not to be as widely expressed as the other reductases, with AKR1C1 being observed in only kidney, liver and testis, and AKR1C4 being found in liver alone. As human kidney is a rich source of AKR, the isoenzymes in this organ have been studied further. Anion-exchange chromatography of human renal cytosol on Q-Sepharose allowed resolution of AKR1A1, AKR1B1, AKR1C1 and AKR7A2, as identified by substrate specificity and Western blotting. Immunohistochemistry of human kidney demonstrated that AKR7A2 is expressed in a similar fashion to the AKR1 family members in proximal and distal convoluted renal tubules. Furthermore, both AKR7A2 and AKR1 members were expressed in renal carcinoma cells, suggesting that these groups of isoenzymes may be engaged in related physiological functions.

Alcohol Oxidoreductases↗
PubMed1999

A zinc finger truncation of murine WT1 results in the characteristic urogenital abnormalities of Denys-Drash syndrome.

The Wilms tumor-suppressor gene, WT1, plays a key role in urogenital development, and WT1 dysfunction is implicated in both neoplastic (Wilms tumor, mesothelioma, leukemias, and breast cancer) and nonneoplastic (glomerulosclerosis) disease. The analysis of diseases linked specifically with WT1 mutations, such as Denys-Drash syndrome (DDS), can provide valuable insight concerning the role of WT1 in development and disease. DDS is a rare childhood disease characterized by a nephropathy involving mesangial sclerosis, XY pseudohermaphroditism, and/or Wilms tumor (WT). DDS patients are constitutionally heterozygous for exonic point mutations in WT1, which include mutations predicted to truncate the protein within the C-terminal zinc finger (ZF) region. We report that heterozygosity for a targeted murine Wt1 allele, Wt1(tmT396), which truncates ZF3 at codon 396, induces mesangial sclerosis characteristic of DDS in adult heterozygous and chimeric mice. Male genital defects also were evident and there was a single case of Wilms tumor in which the transcript of the nontargeted allele showed an exon 9 skipping event, implying a causal link between Wt1 dysfunction and Wilms tumorigenesis in mice. However, the mutant WT1(tmT396) protein accounted for only 5% of WT1 in both heterozygous embryonic stem cells and the WT. This has implications regarding the mechanism by which the mutant allele exerts its effect.

Animals↗
PubMed1999

Effects of injector geometry and sample matrix on injection and sample loading in integrated capillary electrophoresis devices.

The double-T injector design employed in many microchip capillary electrophoresis devices allows for the formation of very small (50-500 pL) sample plugs for subsequent analysis on-chip. In this study, we show that sample plugs formed at the channel junction can be geometrically defined. The channel width and injector symmetry prove to be of great importance to good performance. A unique pushback of solvent into the side channels can be induced when the side channels have a very low resistance to flow, and this helps to better define the injected sample plug. Samples and running buffers of differing ionic strength (e.g., 10 mM KCl buffer and 20 mM KCl sample) can yield widely variable results in terms of plug shape and amount injected (variations of 1.5 to 10x). Applying bias voltages to all the intersecting channels aids in controlling the plug shape. However, when the ionic strengths of buffer and sample are not matched, the actual amount injected (up to 10x variations) can be inconsistent with the appearance of the plug formed in the injector (up to only 30 % variations). Operating at constant pH and ionic strength produced the most consistent results. This report examines the effects of altering the injector geometry and solution ionic strengths, and presents the results of using bias voltages to control plug formation. The observed results should provide a benchmark for modeling of the fluid dynamics in channel intersections.

Electrophoresis, Capillary↗
PubMed1999

Control strategies for aeroallergens in an animal facility.

BACKGROUND: Prevalence of the occupational disease laboratory animal allergy could be reduced if aeroallergen reduction strategies are identified. OBJECTIVE: To reduce worker exposure to Mus m 1, an allergen from laboratory mice, the effect of filter cage tops, increased room ventilation, negatively pressurized ventilated cages, and ventilated cage-changing tables were evaluated. METHODS: Aeroallergen was collected in the ambient air and in the breathing zone and quantified by using a competitive immunoassay. RESULTS: When mice were housed in unventilated cages, ambient allergen was reduced from 5.1 ng/m3 with no cage top to 1.3 ng/m3 with a simple filter-sheet top and 0.8 ng/m3 with a fitted filter-bonnet top (P <. 05). Room ventilation was increased from 6 to 10, 15, and 20 air changes per hour and had little effect on aeroallergen levels and no impact on airborne particulate matter. When mice were housed in ventilated cages, ambient allergen was significantly reduced from 1. 1 ng/m3 at positive cage pressure to 0.3 ng/m3 at negative cage pressure (P <.05). Negative cage pressure combined with handling animals under a ventilated table reduced breathing zone allergen from 28 ng/m3 with neither control strategy in place to 9 ng/m3 (P <. 05). Use of a ventilated table controlled bacterial contamination, measured as colony forming units, found in negatively pressurized cages. CONCLUSION: Three aeroallergen control strategies are use of filter cage tops, operation of negatively pressurized cages, and use of ventilated changing tables.

Air Pollution↗
PubMed1999

Factors influencing capacitance-based monitoring of microbial growth.

Microbiological impedance devices are routinely used by food and manufacturing industries, and public health agencies to measure microbiological growth. Factors contributing to increases and decreases in capacitance at the culture medium-electrode interface are poorly understood. To objectively evaluate the effects of temperature, cell density and medium conductivity on capacitance, admittance values from an impedance device were standardized; capacitance was converted to susceptance to allow unit comparisons with conductance. Although increases in temperature increased susceptance, a linear relationship could not be established between the change of susceptance with temperature and conductance of the medium. Cell density by itself had no measureable effect on susceptance or conductance, indicating that cells did not impede the movement of ions in the medium or around the electrode. In a low conductivity medium, increases in conductance by the addition of ions resulted in a concomitant increase of susceptance values. However, in a high conductivity medium, increases in conductance resulted in little or no increase of susceptance values because ions saturated the electrode surface. Susceptance increased when Escherichia coli, Pseudomonas aeruginosa, Alcaligenes faecalis and Staphylococcus aureus were grown in high conductivity media because protons produced by metabolically active bacteria balance more charge on the electrode than other ions. Increases in susceptance due to bacterial growth and metabolism in low conductivity media were attributed to both increases in protons and ionic metabolites. These results indicate that capacitance may provide a better measure of microbial growth and metabolism than conductance.

Bacteria↗
PubMed1999

Microsomal epoxide hydrolase gene polymorphism and susceptibility to colon cancer.

We examined polymorphisms in exons 3 and 4 of microsomal epoxide hydrolase in 101 patients with colon cancer and compared the results with 203 control samples. The frequency of the exon 3 T to C mutation was higher in cancer patients than in controls (odds ratio 3.8; 95% confidence intervals 1.8-8.0). This sequence alteration changes tyrosine residue 113 to histidine and is associated with lower enzyme activity when expressed in vitro. This suggests that putative slow epoxide hydrolase activity may be a risk factor for colon cancer. This appears to be true for both right- and left-sided tumours, but was more apparent for tumours arising distally (odds ratio 4.1; 95% confidence limits 1.9-9.2). By contrast, there was no difference in prevalence of exon 4 A to G transition mutation in cancer vs controls. This mutation changes histidine residue 139 to arginine and produces increased enzyme activity. There was no association between epoxide hydrolase genotype and abnormalities of p53 or Ki-Ras.

Adolescent↗
PubMed1999

Luteal regression in the primate: different forms of cell death during naturaland gonadotropin-releasing hormone antagonist or prostaglandin analogue-induced luteolysis.

Morphological changes in the corpus luteum following natural and induced luteolysis in the marmoset were investigated by light and electron microscopy. Functional corpora lutea were studied in the mid and late luteal phase, naturally regressed corpora lutea in the early and late follicular phase, and corpora lutea induced to regress by administration of GnRH antagonist or prostaglandin F(2alpha) analogue in the midluteal phase. Natural luteolysis was associated with lutein cell atrophy, condensation of cytoplasmic inclusions and organelles, and accumulation of lipid. GnRH antagonist treatment resulted in aggregations of smooth membranes and myelin-like bodies in the cytoplasm of the lutein cells together with complex aggregations of degenerative cells. After prostaglandin treatment, the lutein cells contained numerous small and large vesicles; as the degenerative changes advanced, these vesicles coalesced into alveolar-type vacuoles, and nuclei involuted. These results show that in the marmoset, natural luteolysis and the two luteolytic treatments reveal different forms of luteal degeneration and cell death, none of which fit the ultrastructural criteria for apoptosis. More emphasis needs to be placed on understanding these predominant nonapoptotic forms of cell death in order to elucidate the process of luteolysis in the primate.

Animals↗
PubMed1999

A functional, discontinuous HIV-1 gp120 C3/C4 domain-derived, branched, synthetic peptide that binds to CD4 and inhibits MIP-1alpha chemokine binding.

This paper describes a branched synthetic peptide [3.7] that incorporates sequence discontinuous residues of HIV-1 gp120 constant regions. The approach was to bring together residues of gp120 known to interact with human cell membranes such that the peptide could fold to mimic the native molecule. The peptide incorporates elements of both the conserved CD4 and CCR5 binding sites. The 3.7 peptide, which cannot be produced by conventional genetic engineering methods, is recognized by antiserum raised to native gp120. The peptide also binds to CD4 and competitively inhibits binding of QS4120 an antibody directed against the CDR2 region of CD4. When preincubated with the CD4+ve MM6 macrophage cell line, which expresses mRNA for the CCR3 and CCR5 chemokine receptors, both 3.7 and gp120 inhibit binding of the chemokine MIP-1alpha. The peptide also inhibits infection of primary macrophages by M-tropic HIV-1. Thus, 3.7 is a prototype candidate peptide for a vaccine against HIV-1 and represents a novel approach to the rational design of peptides that can mimic complex sequence discontinuous ligand binding sites of clinically relevant proteins.

Amino Acid Sequence↗