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Biomedical subjects

D Lee

Publications and source records attributed to D Lee.

At least 325 records · Page 18Linked to original sources
PubMed1996

Hepatocellular and hepatic peroxisomal alterations in mice with a disrupted peroxisomal fatty acyl-coenzyme A oxidase gene.

Peroxisomal genetic disorders, such as Zellweger syndrome, are characterized by defects in one or more enzymes involved in the peroxisomal beta-oxidation of very long chain fatty acids and are associated with defective peroxisomal biogenesis. The biologic role of peroxisomal beta-oxidation system, which consists of three enzymes: fatty acyl-CoA oxidase (ACOX), enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase (HD), and thiolase, has been examined in mice by disrupting ACOX gene, which encodes the first and rate-limiting enzyme of this system. Homozygous (ACOX -/-) mice lacked the expression of ACOX protein and accumulate very long chain fatty acids in blood. However, these homozygous mice are viable, but growth-retarded and infertile. During the first 3-4 months of age, the livers of ACOX -/- mice reveal severe microvesicular fatty metamorphosis of hepatocytes. In such steatotic cells, peroxisome assembly is markedly defective; as a result, they contain few or no peroxisomes. Few hepatocytes in 1-3-month-old ACOX -/- mice contain numerous peroxisomes, and these peroxisome-rich hepatocytes show no fatty change. At this stage, the basal mRNA levels of HD, thiolase, and other peroxisome proliferator-induced target genes were elevated in ACOX -/- mouse liver, but these mice, when treated with a peroxisome proliferator, showed no increases in the number of hepatic peroxisomes and in the mRNAs levels of these target genes. Between 4 and 5 months of age, severe steatosis resulted in scattered cell death, steatohepatitis, formation of lipogranulomas, and focal hepatocellular regeneration. In 6-7-month-old animals, the newly emerging hepatocytes, which progressively replaced steatotic cells, revealed spontaneous peroxisome proliferation. These livers showed marked increases in the mRNA levels of the remaining two genes of the beta-oxidation system, suggesting that ACOX gene disruption leads to increased endogenous ligand-mediated transcription levels. These observations demonstrate links among peroxisomal beta-oxidation, development of severe microvesicular fatty liver, peroxisome assembly, cell death, and cell proliferation in liver.

Acyl-CoA Oxidase↗
PubMed1996

The product of the mouse nude locus, Whn, regulates the balance between epithelial cell growth and differentiation.

Mutations in the winged-helix nude (whn) gene result in the nude mouse and rat phenotypes. The pleiotropic nude phenotype which affects the hair, skin, and thymus suggests that whn plays a pivotal role in the development and/or maintenance of these organs. However, little is known about whn function in these organs. We show here that in skin whn is specifically expressed in epithelial cells and not the mesenchymal cells, and using a hair reconstitution assay, we demonstrate that the abnormal nude mouse hair development is attributable to a functional defect of the epithelial cells. Examination of nude mouse primary keratinocytes in culture revealed that these cells have an increased propensity to differentiate in an abnormal fashion, even under conditions that promote proliferation. Furthermore, nude mouse keratinocytes displayed a 100-fold increased sensitivity to the growth-inhibitory/differentiation effects of the phorbol ester TPA. In parallel with these findings, we directly show that whn functions as a transcription factor that can specifically suppress expression of differentiation/TPA-responsive genes. The region of Whn responsible for these effects was mapped to the carboxy-terminal transactivating domain. These results establish whn as a key regulatory factor involved in maintaining the balance between keratinocyte growth and differentiation. The general implications of these findings for an epithelial self-renewal model will be discussed.

Animals↗
PubMed1996

Photo-induced inactivation of viruses: adsorption of methylene blue, thionine, and thiopyronine on Qbeta bacteriophage.

The adsorption of cationic organic dyes (methylene blue, thionine, and thiopyronine) on Qbeta bacteriophage was studied by UV-visible and fluorescence spectroscopy. The dyes have shown a strong affinity to the virus and some have been used as sensitizers for photo-induced inactivation of virus. In the methylene blue concentration range of 0.1-5 microM and at high ratios of dye to virus (greater than 1000 dye molecules per virion), the dyes bind as aggregates on the virus. Aggregation lowers the efficiency of photoinactivation because of self-quenching of the dye. At lower ratios of dye to virus (lower than 500 dye molecules per virion), the dye binds to the virus as a monomer. Fluorescence polarization and time-resolved studies of the fluorescence support the conclusions based on fluorescence quenching. Increasing the ionic strength (adding NaCl) dissociates bound dye aggregates on the virus and releases monomeric dye into the bulk solution.

Adsorption↗
PubMed1996

Immunostimulatory DNA sequences necessary for effective intradermal gene immunization.

Vaccination with naked DNA elicits cellular and humoral immune responses that have a T helper cell type 1 bias. However, plasmid vectors expressing large amounts of gene product do not necessarily induce immune responses to the encoded antigens. Instead, the immunogenicity of plasmid DNA (pDNA) requires short immunostimulatory DNA sequences (ISS) that contain a CpG dinucleotide in a particular base context. Human monocytes transfected with pDNA or double-stranded oligonucleotides containing the ISS, but not those transfected with ISS-deficient pDNA or oligonucleotides, transcribed large amounts of interferon-alpha, interferon-beta, and interleukin-12. Although ISS are necessary for gene vaccination, they down-regulate gene expression and thus may interfere with gene replacement therapy by inducing proinflammatory cytokines.

Amino Acid Sequence↗
PubMed1996

Genetic progression model for head and neck cancer: implications for field cancerization.

A genetic progression model of head and neck squamous cell carcinoma has not yet been elucidated, and the genetic basis for "field cancerization" of the aerodigestive tract has also remained obscure. Eighty-seven lesions of the head and neck, including preinvasive lesions and benign lesions associated with carcinogen exposure, were tested using microsatellite analysis for allelic loss at 10 major chromosomal loci which have been defined previously. The spectrum of chromosomal loss progressively increased at each histopathological step from benign hyperplasia to dysplasia to carcinoma in situ to invasive cancer. Adjacent areas of tissue with different histopathological appearance shared common genetic changes, but the more histopathologically advanced areas exhibited additional genetic alterations. Abnormal mucosal cells surrounding preinvasive and microinvasive lesions shared common genetic alterations with those lesions and thus appear to arise from a single progenitor clone. Based on these findings, the local clinical phenomenon of field cancerization seems to involve the expansion and migration of clonally related preneoplastic cells.

Carcinoma, Squamous Cell↗
PubMed1996

Initial management of auricular trauma.

The exposed and unprotected position of the auricle makes it susceptible to injuries. Because many of these injuries are initially managed in a primary care setting, family physicians should have an understanding of the management of auricular hematomas, lacerations, abrasions and thermal injuries. Auricular hematoma requires prompt drainage and pressure applied to the site for several days. Treatment of lacerations and abrasions includes meticulous cleaning and minimal debridement of viable tissue. Thermal injuries require recognition of the extent of injury. Prompt treatment of auricular injuries will help avoid aesthetic and functional complications.

Burns↗
PubMed1996

DNA profiling and plant variety registration: 1. The use of random amplified DNA polymorphisms to discriminate between varieties of oilseed rape.

Before they can be marketed in the UK, newly bred varieties of crop species have to undergo a process of statutory testing, part of which involves the examination of the distinctness, uniformity and stability (DUS) of the variety. DUS testing is also used as the basis for the award of Plant Breeders' Rights. This paper examines the potential of DNA polymorphisms, amplified using arbitrary primers (RAPDs) for use in DUS testing of varieties of oilseed rape. RAPDs using suitable primers can produce high levels of discrimination (> 95%) between varieties, although there are certain problems in gel 'scoring' that are only partially resolved by computerised gel scanning/evaluation techniques. Varieties of oilseed rape are also heterogeneous in their RAPD profiles using certain primers, which could cause problems in the DUS testing context. DNA profiling with RAPDs could be used for discrimination between and identification of oilseed rape varieties, but its use for DUS testing needs to be considered carefully.

Base Sequence↗
PubMed1996

Decreased bone mineralization in children with phenylketonuria under treatment.

Children with phenylketonuria (PKU) obtain a great deal of their protein and mineral intakes from synthetic elemental formulae devoid of phenylalanine. To assess the effect of such diets and/or the disease on bone mineralization, children with PKU were compared to normal children for many parameters of mineral homeostasis and bone mineralization. A total of 11 children with PKU of mean age 10.9 +/- 4.2 years were compared to a large group of normal control children mean age 11.4 +/- 4.2, and an age and sex matched subset (n = 11). Children with PKU had lower serum calcium (9.1 +/- 0.9 vs 10.4 +/- 1.9 mg/dl P < 0.01) amd magnesium (1.67 +/- 1.4 vs 2.07 +/- 0.16 mg/ dl, P < 0.001) but normal values for phosphorus, zinc, and copper. The percentage tubular reabsorption of phosphorus was increased in PKU (93 +/- 3% vs 88 +/- 6%, P < 0.05) suggesting a lower phosphorus intake and/or absorption. Serum 25-hydroxyvitamin D, parathyroid hormone and 1,25 dihydroxyvitamin D were similar in PKU and control children. Serum albumin and lean body mass by dual energy X-ray absorption were not different suggesting that protein intake was adequate. In the 11 pairs, a decreased bone mineral density was seen for the lumbar spine (0.61 +/- 0.15 vs 0.72 +/- 0.24 P < 0.05), and lower extremities (1.56 +/- 0.30 vs 1.87 +/- 0.56 P < 0.05) by paired t-test. Compared to the total controls and the paired controls, decreases were seen in markers of bone formation; bone alkaline phosphatase, (72 +/- 30 vs 126 +/- 43 P < 0.001), osteocalcin (10.7 +/- 3.4 vs 13.1 +/- 2.0 P < 0.05) and procollagen type I carboxyterminal propeptide. No differences were seen in the bone resorption markers tartrate resistant acid phosphatase and urine Ca/Cr. The changes noted could not be related after age correction to serum phenylalanine levels, protein intake, or mineral intakes. It is unclear whether deficits in bone mineralization relate to the disease process itself or its treatment.

Adolescent↗
PubMed1996

PATH: a work sampling-based approach to ergonomic job analysis for construction and other non-repetitive work.

A high prevalence and incidence of work-related musculoskeletal disorders have been reported in construction work. Unlike industrial production-line activity, construction work, as well as work in many other occupations (e.g. agriculture, mining), is non-repetitive in nature; job tasks are non-cyclic, or consist of long or irregular cycles. PATH (Posture, Activity, Tools and Handling), a work sampling-based approach, was developed to characterize the ergonomic hazards of construction and other non-repetitive work. The posture codes in the PATH method are based on the Ovako Work Posture Analysing System (OWAS), with other codes included for describing worker activity, tool use, loads handled and grasp type. For heavy highway construction, observations are stratified by construction stage and operation, using a taxonomy developed specifically for this purpose. Observers can code the physical characteristics of the job reliably after about 30 h of training. A pilot study of six construction laborers during four road construction operations suggests that laborers spend large proportions of time in nonneutral trunk postures and spend approximately 20% of their time performing manual material handling tasks. These results demonstrate how the PATH method can be used to identify specific construction operations and tasks that are ergonomically hazardous.

Journal Article↗
PubMed1996

Intimal thickening under shear in a carotid bifurcation--a numerical study.

In the present study, a model for intimal thickening proposed by Friedman and his co-workers is employed to simulate the growth of intima in a carotid bifurcation with a steady flow. The computer code developed is a pressure-based, finite volume method in a boundary-fitted coordinate system. A model bifurcation is used to demonstrate the usefulness of the numerical tool. The predicted results are consistent with the available experimental observations. The localization of plaques is shown. It is found that thicker intima is formed in preferential regions near the junction and the carotid bulb due to relatively low wall shear stresses. The intimal thickening tends to reduce the size of low shear regions. It is also found that the new geometry resulting from the thickening yields a more even stress distribution over the bifurcation. The effect of the branching ratio on the distribution of intimal thickening is also studied. The computer code provides a potential tool for visualization of intimal thickening.

Algorithms↗
PubMed1996

Detection of human cytomegalovirus polymerase chain reaction products using oligonucleotide probes directly conjugated to alkaline phosphatase.

A 24 base pair oligonucleotide probe directly conjugated to alkaline phosphatase has been used to detect immobilised amplicons derived from a cytomegalovirus specific polymerase chain reaction (PCR). The sensitivity of detection using a highly amplified alkaline phosphatase detection system was four genome equivalents and was comparable to the limit of detection using agarose gel methods. The mean optical density at 492 nm of samples not known to contain cytomegalovirus DNA was 0.085 +/- 0.006 and was well separated from the optical density generated from four genome equivalents (absorption at 492 nm: 0.132). The assay was used to identify the presence of cytomegalovirus in blood DNA extracts from immunocompromised patients in whom conventional ethidium bromide stained agarose gel electrophoresis revealed the presence of multiple amplicons. Samples yielding an uninterpretable result at both neat and diluted 1 in 20 in the PCR gave rise to the highest proportion of positive results (68%) whilst samples that produced uninterpretable results neat but were negative at 1 in 20 and vice versa gave positive rates of 33.6 and 21.7%, respectively. The use of this assay for identifying cytomegalovirus specific PCR products in problematic samples is discussed.

Alkaline Phosphatase↗
PubMed1996

Neural mechanisms in primary hypertension. Efficacy of alpha-blockade with doxazosin during stress.

This single-blind study assessed the role of the sympathetic nervous system in primary hypertensives, at rest and during stress, and examined blood pressure responses to an alpha 1-blocker, doxazosin. Twenty patients were selected who had a sitting diastolic blood pressure 95 to 115 mm Hg at the end of the placebo period. Doxazosin was given in doses of 1 mg per day initially, then increased weekly to 2, 4, 8, and 16 mg, until goal blood pressure or maximum dose was reached or side effects limited further increase. Their determined dose of doxazosin was held constant for 16 weeks of the maintenance period. Mental and isometric stress tests were performed at the end of placebo and at the first and last months of maintenance. Diastolic blood pressures were related to baseline plasma norepinephrine, r = 0.61, P < .01. The dose of doxazosin administered was 8.4 +/- 4.1 mg. After 4 months of therapy, doxazosin lowered blood pressure from 147 +/- 16/99 +/- 3 to 135 +/- 5/87 +/- 8 sitting, and from 146 +/- 14/99 +/- 6 to 130 +/- 14/86 +/- 7 standing, respectively. Heart rates were not changed. The reduction of standing systolic blood pressure was related to baseline norepinephrine in the 12 patients who reached goal blood pressure, r = 0.57, P < .05. During mental and isometric stress tests, the percentage changes of blood pressures were related to their baseline plasma norepinephrine. Doxazosin reduced the percentage increments of blood pressure during mental stress 12.2 +/- 5.7/11.8 +/- 4.3% versus 5.7 +/- 1.0/8.1 +/- 7.4%, P < .01/.05. Doxazosin also blunted the diastolic blood pressure response to isometric exercise from 18.3 +/- 12.2% to 9.3 +/- 11.0%, P < .05. Neurogenic factors participate in the elevation of blood pressure in some patients with primary hypertension. The alpha-blocker doxazosin was effective in 60% of the hypertensive patients--it controlled blood pressure during laboratory stress, suggesting particular value in reduction of blood pressure during ambient stress of everyday living.

Adrenergic alpha-Antagonists↗
PubMed1996

Compatibility of propofol, fentanyl, and vecuronium mixtures designed for potential use in anesthesia and patient transport.

STUDY OBJECTIVE: To determine whether propofol emulsion, fentanyl, and vecuronium remain compatible and stable when mixed in clinically appropriate concentrations. DESIGN: Seven separate in vitro experiments. Two different propofol-fentanyl-vecuronium mixtures were formulated. Regular assays of propofol, fentanyl, and vecuronium were performed during a 90-minute infusion period and also during storage of one of the mixtures for 30 days at 4 degrees C, 22 degrees C, and 30 degrees C. Initial and storage pH were determined, and assays of the three drugs were performed when pH of the mixtures was varied between 1.4 and 12.7. Emulsion stability was assessed by measuring immediate and delayed alterations in droplet charge (zeta potential) and size. Finally, samples of the stored mixtures were incubated in culture medium for one week. SETTING: Teaching hospital and university laboratories. MEASUREMENTS AND MAIN RESULTS: Concentrations of the three drugs remained unchanged during infusion. During storage, concentrations of all three drugs were stable for two weeks at 4 degrees C or 22 degrees C, and for several days at 30 degrees C. Initial pH of the two mixtures was 5.1 and 5.3, and pH of the stored mixture increased slowly after 8 days. When the pH of mixtures was greater than or equal to 5.6, concentrations of fentanyl and vecuronium were unstable, but the concentration of propofol remained unchanged. Despite a reduction in zeta potential, immediate droplet size was essentially unchanged. No microbial growth was detected in stored mixtures. CONCLUSION: The propofol, fentanyl, and vecuronium mixtures studied were compatible and stable immediately after mixing. Appropriate in vitro compatibility testing is recommended before clinical evaluation of propofol-opioid or propofol-opioid-muscle relaxant mixtures.

Anesthesia↗