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Biomedical subjects

L R Brown

Publications and source records attributed to L R Brown.

At least 73 records · Page 4Linked to original sources
PubMed1989

Detection and characterization of interleukin-1 in human dental pulps.

Pulp tissue was obtained from clinically intact third molars and premolars, and from teeth affected by caries and periodontal disease. After incubation and homogenization, supernatants were centrifuged, sampled and assayed for lymphocyte activating factor-like activity using the thymidine-incorporated D10.G4.1 cell-line assay. Significantly higher levels of mitogenic activity were found in the pulp supernatants of symptomatic carious teeth, and in those of third molars with attendant pericoronitis, than in pulps from symptomatic and asymptomatic periodontally affected teeth and asymptomatic third molars and premolars. As both interleukin-1 (IL-1) and interleukin-2 (IL-2) may be involved in the proliferation of D10.G4.1 cells, supernatants from carious pulps were further tested for IL-2 activity using murine natural killer (NK) cells. Those that had elicited a proliferative response of D10.G4.1 cells did not enhance NK proliferation, indicating that the factor responsible for clonal replication of D10.G4.1 cells was IL-1. To confirm the presence of IL-1, immunohistochemistry using a monoclonal antibody to IL-1 was performed on frozen and paraffin-embedded sections of pulps from each group. IL-1 was immunolocalized within cells in pulps from the caries symptomatic group. The cell type producing IL-1 was further characterized as an alpha-naphthyl-acetate-esterase-positive macrophage within the connective tissue stroma of pulps from the caries symptomatic group. This novel demonstration of IL-1 and IL-1 producing cells in human dental pulp indicates the involvement of this mediator of inflammation in dental disease.

Cells, Cultured↗
PubMed1989

High-resolution computed tomography of the lung.

High-resolution computed tomography (HRCT) and thin-section CT are techniques that are particularly suited for evaluation of the pulmonary parenchyma. These techniques have been found useful in the assessment of bronchiectasis and solitary pulmonary nodules. HRCT offers promise in evaluation of diffuse and focal pulmonary parenchymal disease. The principles and applications of HRCT of the lung are reviewed.

Bronchiectasis↗
PubMed1989

Magnetic resonance imaging of the thorax.

The role of magnetic resonance imaging (MRI) in the evaluation of thoracic disease is emerging amidst much debate and study. Recent technical advances have led to new applications of this modality, and a reappraisal of previous conclusions seems warranted. This article reviews our 5 1/2 years' experience with thoracic MRI.

Contrast Media↗
PubMed1988

Characterization of dodecylphosphocholine/myelin basic protein complexes.

The stoichiometry of myelin basic protein (MBP)/dodecylphosphocholine (DPC) complexes and the location of protein segments in the micelle have been investigated by electron paramagnetic resonance (EPR), ultracentrifugation, photon correlation light scattering, 31P, 13C, and 1H nuclear magnetic resonance (NMR), and electron microscopy. Ultracentrifugation measurements indicate that MBP forms stoichiometrically well-defined complexes consisting of 1 protein molecule and approximately 140 detergent molecules. The spin-labels 5-, 12-, and 16-doxylstearate have been incorporated into DPC/MBP aggregates. EPR spectral parameters and 13C and 1H NMR relaxation times indicate that the addition of MBP does not affect the environment and location of the labels or the organization of the micelles except for a slight increase in size. Previous results indicating that the protein lies primarily near the surface of the micelle have been confirmed by comparing 13C NMR spectra of the detergent with and without protein with spectra of protein/detergent aggregates containing spin-labels. Electron micrographs of the complexes taken by using the freeze-fracture technique confirm the estimated size obtained by light-scattering measurements. Overall, these results indicate that mixtures of MBP and DPC can form highly porous particles with well-defined protein and lipid stoichiometry. The structural integrity of these particles appears to be based on protein-lipid interactions. In addition, electron micrographs of aqueous DPC/MBP suspensions show the formation of a small amount of material consisting of large arrays of detergent micelles, suggesting that MBP is capable of inducing large changes in the overall organization of the detergent.

Animals↗
PubMed1988

The effect of ascorbic acid deficiency on leukocyte phagocytosis and killing of actinomyces viscosus.

The ascorbic acid content of guinea pig leukocytes is reduced by a factor of 16:1 between normal and scorbutic guinea pigs. Ascorbic acid deficiencies do not appear to affect phagocytic activity but do change leukocyte morphology. A deficiency of this vitamin appears to significantly interfere with the in vitro bactericidal effectiveness of circulating leukocytes against ingested, cell-associated, and extracellular bacterial cells of the oral pathogen, Actinomyces viscosus. Leukocytes from scorbutic guinea pigs killed 13% of ingested and cell-associated Actinomyces viscosus compared to 83% killed by normal leukocytes by both acridine orange staining and viable count. Degranulation resulted in extracellular killing in normal but not scorbutic leukocytes. This decreased bactericidal activity can be reversed by adding supplements of the vitamin to the diet of scorbutic animals. Chemotactic responses were much lower in vivo and absent in vitro in scorbutic leukocytes. The acridine orange staining technique is an excellent indicator of leukocyte health. This study supports the important role for ascorbic acid in leukocyte function and also discusses its probable protective and bactericidal activities related to oral pathogens.

Actinomyces↗
PubMed1988

Chyloptysis (chylous sputum) due to thoracic lymphangiectasis with successful surgical correction.

A 73-year-old woman with a two-year history of recurrent episodes of respiratory distress is described. The finding of an elevated triglyceride value of 23.4 mmol/L (2072 mg/dL) and a normal cholesterol value in her sputum led to the correct diagnosis of chyloptysis after lymphangiography was performed. It is thought that congenital incompetence of the lymphatic valves was the cause of chyloptysis.

Aged↗
PubMed1987

Nucleotide sequence and analysis of the coliphage T3 S-adenosylmethionine hydrolase gene and its surrounding ribonuclease III processing sites.

To understand better the characteristics of the coliphage T3 S-adenosyl-L-methionine (AdoMet) hydrolase (AdoMetase, E.C. 3.3.1.2) and its expression in phage-infected Escherichia coli, we determined the DNA sequence of the cloned gene and its surrounding ribonuclease (RNase) III mRNA transcript processing sites. The AdoMetase gene contains two in-frame protein translation initiation sites specifying peptides 17105 and 13978 daltons in size. Both proteins terminate at the same ochre codon making the shorter peptide identical to the carboxy terminal 82% of the 17 kd protein. Our data explain the existence of two AdoMetase-related peptides in preparations of the purified enzyme as well as identify sequences that might serve to regulate the enzyme's expression. Comparisons between this T3 sequence and the homologous 0.3 gene region of the closely related coliphage T7 show both the nucleotide and amino acid sequences to be unrelated. The RNase III mRNA processing sites that bracket these genes in T3 and T7 are highly conserved in both their primary and secondary structures.

Amino Acid Sequence↗
PubMed1987

Computed tomography of benign mature teratomas of the mediastinum.

The computed tomography (CT) findings of five benign, mature teratomas of the anterior mediastinum collected during a ten-year period are described, and their case histories are reviewed. Three of the five were primarily cystic, with only small soft tissue components. One of the five contained equal cystic and solid elements. All cysts had a higher attenuation than water. Three tumors contained small foci of dense calcification or ossification. Only two contained fat. Computed tomography accurately predicted the presence of adherence to adjacent structures in all five. Four of five patients were less than 22 years of age, and benign teratoma of the mediastinum was not a common neoplasm at any age. The origin and pathology of germ cell tumors of the mediastinum are briefly reviewed.

Adolescent↗
PubMed1987

Role of Carbon Dioxide in Catabolism of Propane by "Nocardia paraffinicum" (Rhodococcus rhodochrous).

The catabolism of propane by "Nocardia paraffinicum" (Rhodococcus rhodochrous) has been shown to involve CO(2) fixation after its oxidation to propionic acid. "N. paraffinicum" failed to grow on either propane or 1-propanol in the absence of CO(2). The rate of propane utilization was directly related to the initial CO(2) concentration, and Warburg respirometry suggested that CO(2) was required for the catabolism of 1-propanol, propionaldehyde, and propionate but not for 2-propanol. These data also suggested that the predominant pathway for the utilization of propane by "N. paraffinicum" was through 1-propanol. The use of [2-C]propane and CO(2) confirmed the catabolism of propane and the fixation of CO(2). Through the use of these isotopes and the pyruvate carboxylase inhibitor sodium arsenite, the labeled 2,4-dinitrophenylhydrazine derivative of pyruvate was trapped and isolated via thin-layer chromatography. The trapping of [C]pyruvate in this manner was considered to be indicative of the presence of the methylmalonyl coenzyme A pathway for CO(2) fixation.

Journal Article↗
PubMed1987

Expression of the cloned coliphage T3 S-adenosylmethionine hydrolase gene inhibits DNA methylation and polyamine biosynthesis in Escherichia coli.

We have developed a new research tool for the study of S-adenosylmethionine (AdoMet) metabolism by cloning the coliphage T3 AdoMet hydrolase (AdoMetase; EC 3.3.1.2) gene into the M13mp8 expression vector. The recombinant bacteriophage clones expressed an AdoMetase activity in Escherichia coli like that found in T3-infected cells. High levels of AdoMetase expression impaired AdoMet-mediated activities such as dam and dcm methylase-directed DNA modifications and the synthesis of spermidine from putrescine. Expression vectors containing the cloned AdoMetase gene thus provide an alternate approach to the use of chemical inhibitors or mutants defective in AdoMet biosynthesis to probe the effect of AdoMet limitation.

Cloning, Molecular↗
PubMed1986

Presentation of Candida albicans and purified protein derivative soluble antigens by Epstein-Barr virus-transformed human lymphoblastoid B-cell lines.

Cells other than the macrophage can function as antigen-presenting cells (APCs). These class II-bearing accessory cells include dendritic cells, epidermal Langerhans cells, B cells, murine B-cell tumors, and human Epstein-Barr virus-transformed lymphoblastoid cell lines (EBV-LCL). We investigated the ability of EBV-LCL to present two soluble antigens, Candida albicans and purified protein derivative of tuberculin (PPD). The EBV-LCL derived from B cells of two different individuals can present both antigens to bulk cultures of autologous antigen-primed peripheral blood lymphocytes. The responses of PPD-reactive T-cell clones were weaker to PPD when presented by EBV-LCL than by PBL-APCs, with some clones responding only to PPD presented by PBL-APCs. This suggests that EBV-LCL are not equivalent to PBL monocytes in APC function, and that expression of class II major histocompatibility complex antigen is not sufficient in enabling antigen-presenting capability.

Antigen-Presenting Cells↗
PubMed1986

Intrathoracic lymphangioma.

Of 14 cases of intrathoracic lymphangioma, 4 occurred in the anterior, 5 in the superior, and 4 in the posterior mediastinum. One lesion was diffuse and associated with disappearing bone disease (Gorham's disease). The anterior mediastinal lymphangiomas occurred in adults and seemed to arise from the mediastinum. They could not be distinguished from other anterior mediastinal lesions on plain film roentgenograms. The lesions of the superior mediastinum were extensions from cystic hygromas of the neck and occurred primarily in children. Recurrence was common because complete resection was not possible. Computed tomography was helpful in detecting the cervical extension and cystic nature of these lesions. Although two of the four posterior compartment lesions were isolated lymphangiomas, the other two were part of a much more extensive and generalized lymphangiomatosis that included bone lesions and subdiaphragmatic extension. Both of these latter cases were complicated by chylothorax after attempted removal of the mediastinal lymphangioma. Computed tomography and lymphangiography were helpful in determining the extent of the disease and the cystic and lymphatic nature of the mass. The patient with Gorham's disease had extensive lymphangiomatosis of the thorax and recurrent chylothorax; surgical treatment was unsuccessful. Although lymphangioma is a benign tumor, its infiltrative tendency complicates its removal and contributes to its postoperative recurrence.

Adolescent↗
PubMed1986

Quantitative comparisons of potentially cariogenic microorganisms cultured from noncarious and carious root and coronal tooth surfaces.

Potentially cariogenic microorganisms cultured from noncarious and carious root and coronal (enamel) surfaces were quantitatively compared in patients 22 to 84 years of age (mean, 52 years). We collected 150 plaque specimens from 26 in situ teeth with initial root lesions and from 25 extracted teeth with advanced root lesions. The frequencies of isolation of Streptococcus mutans, Actinomyces viscosus, and Lactobacillus spp. were, respectively, 94, 72, and 51% at the noncarious root site; 98, 71, and 54% at the root lesion; 84, 61, and 44% at the noncarious enamel site; and 100, 66, and 90% at the enamel lesion. The streptococci made up the largest mean proportion of the total anaerobic cultivable microflora, ranging from 31.2% at the noncarious enamel site to 37.6% at the root lesion, while S. mutans varied between 18% at the noncarious enamel and root surfaces and approximately 24% at both the enamel and root lesions. The proportion of actinomyces ranged from 12.3% at the root lesion to 23.6% at the noncarious root site, while A. viscosus varied from 7.8% at the root lesion to 15.1% at the noncarious root site. The largest mean proportion of lactobacilli (4.2%) was recovered at the enamel lesion site. Proportions of Candida spp. made up less than 0.1% at all sites. Proportions of microorganisms did not differ significantly between noncarious enamel and root sites, but the noncarious coronal and root sites had higher (P less than 0.05) proportions of actinomyces than did the root lesion. Also, enamel lesions had a greater (P less than 0.05) percentage of Lactobacillus spp. than did root lesions. The number of streptococci recovered from the root lesion was greater (P less than 0.01) than the number of actinomyces at the same site. S. mutans was recovered from initial root lesions in greater numbers (P less than 0.001) than were actinomyces and lactobacilli. The number of S. mutans recovered at the initial root lesions was greater (P less than 0.01) than that recovered from the advanced root lesions.

Actinomyces↗
PubMed1986

Comparison of mammography and transillumination light scanning in the detection of breast lesions.

A prospective study was done involving 822 women who had both film screen mammography and a breast transillumination light scan examination. The study population was not randomized; a modified phase-2 study was done. Mammography was superior for detecting malignancy: of the 67 pathologically proved breast cancers, 64 (95.5%) were detected by mammography and 45 (67.2%) were detected by transillumination. Biopsy revealed that 74 patients had benign lesions. In this group of patients, the false-positive rate was 12.2% for light scanning and 79.7% for mammography; however, 117 other patients had false-positive light scans.

Breast Neoplasms↗
PubMed1985

Purification and subunit characterization of Rhizobium meliloti RNA polymerase.

The RNA polymerase of the symbiotic, nitrogen-fixing bacterium Rhizobium meliloti was purified, and its subunit composition was determined. The cells were disrupted in the presence of protease inhibitors, and holoenzyme fractions were purified by fractionation by using DEAE-cellulose and DNA-agarose chromatography. The core polymerase was purified by additional chromatography on phosphocellulose. The subunit structure is beta prime (155,000 molecular weight), beta (151,000), alpha (43,000), and sigma (93,000), with an additional polypeptide of 29,000 molecular weight, which we have designated tau, found associated with both core and holoenzyme fractions. The measured stoichiometry of the holoenzyme complex was found to be 2 alpha:1 beta':1 beta:0.7 sigma:1 tau. The 93,000 molecular-weight protein subunit was identified as the sigma subunit based upon stimulation of specific transcription in assays with reconstituted polymerase.

DNA-Directed RNA Polymerases↗