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Biomedical subjects

N R Hunter

Publications and source records attributed to N R Hunter.

At least 55 records · Page 3Linked to original sources
PubMed1987

The reliability of cytopathologists' classifications of bronchial epithelial atypias from Kodachrome slides.

The accuracy of computerized cell image analysis techniques for classification of atypical cells is determined by comparing computer-generated classifications with those made by cytopathologists. This measure of accuracy depends not only on the reliability of the computer classifications but also on the reliability of the cytopathologists' classifications. This study reports on the observed reliability of cytopathologists' classifications of squamous epithelial atypias in sputum across cytopathologists and two different classification times. Results indicated the percentage agreement among cytopathologists and computerized cell image analysis techniques. It is recommended that, in the future, all analyses of computerized classification schemes by interpreted in light of the consistency of the cytopathologists' classifications.

Diagnosis, Computer-Assisted↗
PubMed1987

Morphometric markers for the evaluation of preneoplastic lesions in the lung. Diagnostic evaluation by high-resolution image analysis of atypical cells in sputum specimens.

A review is presented of the Baylor College of Medicine/NASA/Lyndon Johnson Space Center high-resolution image analysis system for the detection of preneoplastic lesions of the lung in sputum specimens. For each specimen, 200 cells are graded as to their Atypia Status Index (ASI), a numerical classification based on a weighted composite of morphometric markers identified in the digitized images. The ASI values, which place individual cells within categories ranging from squamous metaplastic to carcinomatous, form the basis of the Cell Atypia Profile (CAP), which reflects the overall status of the patient's bronchial epithelium and can be used to diagnose and monitor epithelial atypias. Initial studies have shown the ASI and CAP to be accurate indices, whose application in the studies of sputum of individuals at high risk for the development of lung cancer (cigarette smokers over 45 years of age and industrially exposed workers) could lead to the early detection of preneoplastic lung lesions and to effective early clinical intervention, including the cessation of smoking or the application of beta-carotone or retinoids, which reportedly arrest the progression of bronchial epithelial atypias. Computer-assisted cell image analysis of morphometric markers in cells in sputum specimens appears to be uniquely applicable for surveillance of individuals at risk for carcinoma of the lung.

Bronchi↗
PubMed1986

Structural and immunological comparison of human thrombospondins isolated from platelets and from culture supernatants of endothelial cells and fibroblasts. Evidence for a thrombospondin polymorphism.

Thrombospondin is a 450-kDa glycoprotein secreted by a variety of cells including endothelial cells, fibroblasts and platelets. The aim of this study was to compare the structural and immunological properties of human endothelial, fibroblast and platelet thrombospondins. All three thrombospondins were purified, digested with thermolysin, and the subsequent thermolysin-generated fragments isolated on a Superose 12 gel-permeation column using non-denaturating conditions. Each isolated proteolytic fragment of thrombospondins was then detected using either a radioimmunoassay with a polyclonal antibody or an enzyme-linked immunosorbent assay with three monoclonal antibodies (P10, MA-I, MA-II) directed against different epitopes of whole platelet thrombospondin. The fragmentation pattern of human endothelial thrombospondin consists of six major thermolysin-generated fragments (135-110, 98-82, 54-47, 25-20, 18-15 and 10 kDa) having molecular masses very similar to those observed with human fibroblast thrombospondin (115-100, 92-80, 54-49, 27-21, 17-13 and 12-10 kDa). Treatment of platelet thrombospondin with thermolysin only generated four proteolytic fragments having molecular masses of 110, 50, 25 and 12/10 kDa respectively. All these proteolytic fragments of endothelial, fibroblast and platelet thrombospondins were recognized by a polyclonal antibody. Monoclonal antibodies MA-I and P10 essentially recognized two proteolytic fragments (135-110, 98-82 kDa) of endothelial and fibroblast (115-100, 92-80 kDa) thrombospondins, and the 110-kDa fragment of platelet thrombospondin. Monoclonal antibody MA-II recognized three proteolytic fragments (54-47, 25-20, 18-15 kDa) of endothelial and fibroblast (54-49, 27-21, 17-13 kDa) thrombospondins, and two fragments (50, 25 kDa) of platelet thrombospondin, different from those detected by P10 an MA-I. The results clearly demonstrate that, under non-denaturating conditions, endothelial and fibroblast thrombospondins are structurally different from platelet thrombospondin since two fragments of endothelial thrombospondin (98-82, 18-15 kDa), equivalent to those of fibroblast thrombospondin (92-80, 17-13 kDa), are not released from platelet thrombospondin after thermolysin treatment. These three forms of thrombospondin are, however, immunologically indistinguishable. To investigate further the structural differences observed between platelet and the two other forms of thrombospondin, their degree of polymerization was compared. Prior to thermolysin treatment, the three forms of thrombospondin were separated into several oligomers ranging from 450 kDa to 3300 kDa when injected onto a Superose 6 gel-permeation column.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1986

Tandem purification of mouse IgM monoclonal antibodies produced in vitro using anion-exchange and gel fast protein liquid chromatography.

A tandem chromatographic procedure was used to isolate rapidly mouse IgM monoclonal antibodies produced by cultivation of hybridomas in vitro. Hybridoma culture supernatants containing mouse IgM monoclonal antibodies were first chromatographed on an anion-exchange Mono Q column connected to a fast protein liquid chromatography system. This anion-exchange step offers the advantage of obtaining IgM antibodies in a concentrated form. The IgM-rich fractions from the Mono Q column were then injected on a gel filtration Superose 6 column equilibrated with a low-ionic strength buffer and eluted with a high-ionic strength buffer. Assessment of the purity of isolated IgM monoclonal antibodies was performed by sodium dodecyl sulphate polyacrylamide gel electrophoresis together with a Coomassie Brillant Blue R 250 staining technique. Assessment of the immunoreactivity of isolated IgM monoclonal antibodies was performed by an enzyme linked immunosorbent assay using a solid phase adsorbed antigen against which IgM monoclonal antibodies were directed. The chromatographic procedures described allows the rapid isolation of mouse IgM monoclonal antibodies produced in vitro at a high degree of purity and in an immunoreactive state.

Animals↗
PubMed1986

Structural and immunological differences between human platelet and endothelial thrombospondins.

The structural and immunological properties of human thrombospondins isolated from platelets and from endothelial cells were compared. Both thrombospondins were digested with either trypsin or thermolysin, in the presence or absence of calcium, then injected onto a Superose 12 gel filtration column. The isolated thermolysin-generated fragments of thrombospondins were identified by radioimmunoassays using either different monoclonal antibodies or a polyclonal antibody directed against platelet thrombospondin. The results show that platelet and endothelial thrombospondins are both partially protected from trypsin digestion in the presence of calcium but have different trypsin and thermolysin fragmentation patterns. The thermolysin-generated fragments from platelet and endothelial thrombospondins are recognized differently by a monoclonal antibody whereas all of them are identified by a polyclonal antibody.

Antibodies, Monoclonal↗
PubMed1985

Comparison of secretion and subcellular localization of von Willebrand protein with that of thrombospondin and fibronectin in cultured human vascular endothelial cells.

Cultured human vascular endothelial cells synthesize von Willebrand protein, thrombospondin and fibronectin. These proteins are secreted in the culture medium and incorporated into the extracellular matrix. We have compared the subcellular localization and the secretion of these proteins in response to stimulants in cultured human umbilical vein endothelial cells. Density gradient centrifugation using colloidal silica showed that the storage and secretion organelle with von Willebrand protein did not contain thrombospondin or fibronectin. Indirect immunofluorescence microscopy indicated that thrombospondin and fibronectin are not located in the rod-shaped organelles containing von Willebrand protein. Thrombin, ionophore A23187 and phorbol myristate acetate did not affect secretion of thrombospondin and fibronectin, while von Willebrand protein secretion was stimulated upon incubation of cells with these agents for 30 min. Prolonged incubation of cultured endothelial cells after a 1-h treatment with phorbol myristate acetate resulted in an increased secretion of von Willebrand protein into the conditioned medium; in contrast, accumulation of thrombospondin and fibronectin in endothelial cell-conditioned medium was decreased. These findings indicate that, unlike in platelets, these major endothelial proteins are not located in the same subcellular compartments. Von Willebrand protein is distinguished from thrombospondin and fibronectin both by its unique subcellular localization and its secretion rate in response to stimuli.

Blood Coagulation Factors↗
PubMed1984

Quantitation by radioimmunoassay of thrombospondin synthesised and secreted by human endothelial cells.

Synthesis and secretion of thrombospondin by cultured human endothelial cells was quantified using a sensitive radioimmunoassay. Two endothelial lines were examined; those from umbilical veins and those from saphenous veins. The foetal line secreted approximately 17 micrograms/10(6) cells of the antigen at 24 hr, whereas the saphenous line secreted five times less in the same period. Intracellular values were similar in both lines. Thrombin and calcium ionophore A23187 were added to umbilical vein endothelial cultures. In contrast to platelets where both agents cause a rapid release reaction, no such thrombospondin release was observed in endothelial cells.

Calcimycin↗
PubMed1984

Precision cell location and relocation techniques. An application for cell image analysis.

Two methods for precise cell location and relocation were developed at the Cell Image Analysis Laboratory, NASA, to increase the efficiency of the cell image acquisition process. The first method uses a Zeiss Zonax with a 10 micron scanning stage and automatically records cell coordinates on 5.25-inch floppy disks. The second method uses a Digital Positioning Device with a 10 micron scanning stage, and the cell coordinates displayed on light-emitting diodes (LEDs) are recorded manually. Because of its superior speed and automation, the Zonax was selected as the method of choice. By using a Zonax for off-line cell location and another Zonax for on-line cell relocation, more than three times the number of digitized images were collected in ten months than in the previous three years. Other beneficial applications of the cell location and relocation methods were realized in photomicrography, data base verification and cytopathology.

Computers↗
PubMed1983

Nuclear segmentation of bronchial epithelial cells by minimax and thresholding techniques. A comparison.

Two nuclear segmentation methods, Baky's minimax algorithm and thresholding, were compared on a sample of 879 atypical bronchial epithelial cells in sputum. Nuclear-cytoplasmic (N/C) ratios for all cells were determined by each segmentation method and compared to a visually determined value. Cells were categorized by atypia class (from metaplastic through malignant), by staining characteristics (orangeophilic and nonorangeophilic) and by method of digitization (either scanning microphotometry or video system). The method of digitization was confounded by subject differences. The results indicated that with most classes of atypia, N/C ratios determined by minimax were closer to the visually derived values than were those of thresholding, particularly with orangeophilic cells. Both methods become progressively less accurate, as compared to the visual procedure, as the degree of atypia increases.

Bronchi↗
PubMed1983

Classification of bronchial epithelial atypias by the atypia status index.

The atypia status index (ASI) is a categorization method of classifying digitized images of atypical bronchial epithelial cells in sputum. The ASI is defined as a linear composite of features linearly related to atypia stage. Over 200 features were examined for more than 3,000 cells that had been classified by atypia stage (squamous metaplasia, mild, moderate or severe atypia and malignant) and staining characteristic (orangeophilia and nonorangeophilia). We reduced the number of features by using a selection process to minimize redundancy. The feature weights were optimized via a least-squares procedure. The 14 features selected accounted for over 60% of the variation of atypia stage and produced ASI values that were within one atypia stage of the criterion classification for over 90% of the cells. The results are consistent with the hypothesis of a progressive pattern in bronchial epithelial atypia and indicate the feasibility of using image analysis for mass screening of premalignant atypias in sputum from subjects considered to be at high risk for lung cancer.

Adult↗
PubMed1981

Nuclear boundary detection algorithm based on a minimax derivative statistic for atypical bronchial squamous epithelial cells.

The thresholding approach in scene segmentation of digitized cell images was found to be unreliable for use with squamous epithelial cells characterized by chromatin condensation within the nucleus. It was observed that the nuclear boundaries of such cells were visually distinguishable. An algorithm was developed for detecting nuclear boundaries in digitized cell images. This algorithm is based on a minimax derivative statistic that has maximum values at nuclear boundaries and low values elsewhere. The statistical properties of the confusion matrix of cellular scene segmentation are outlined. A measurement and a test statistic for scene segmentation errors based on those properties are presented.

Bronchi↗
PubMed1981

Image analysis of atypical bronchial squamous epithelial cells. A quantitative and qualitative examination of squamous cell carcinogenesis.

Atypical bronchial squamous epithelial cells from cigarette smokers were digitized using a high-resolution microphotometric scanning system operating at a wavelength of 530 nm. All cells used for the purpose of developing a training set as well as those used as a test set were classified by a team of three cytopathologists. Reduction in the dimensionality of the feature space and cell classification were performed using a new system known as the atypia status index (ASI); this dual-purpose system will specifically classify cells into five distinct classes of progressive atypia as well as quantitate the degree of atypicality of each individual cell. The distribution of cellular ASI values was arranged from lowest to highest and plotted for each subject as a profile. The ASI range has well-defined intervals, representing the five different atypia classes used in the study (squamous metaplasia, mild atypia, moderate atypia, severe atypia and carcinoma). Subjects at different stages of carcinogenesis were found to have significantly different profiles (P less than 0.01). Changes in visual morphologic characteristics and their relation to changes in ASI values for the five different classes of atypia are presented.

Bronchi↗
PubMed1980

Aytpia status index of respiratory cells: a measurement for the detection and monitoring of neoplastic changes in squamous cell carcinogenesis.

A statistical procedure was developed for calculating an atypia status index (ASI) for cells from the bronchial mucosa. These indices represent the degree of abnormal changes in these cells and classify them as squamous metaplasia, mild atypia, moderate atypia, servere atypia or carcinoma. The classification accuracy of the procedure was more than 99% on trained data and was accomplished by minimizing the overlapping areas between the adjacent multivariate distributions of cell groups for selected features whose group means represent a monotonic function and for which the cell categories are distinguishable. The calculated ASI may reflect abnormal changes in the cell that may not be clearly evident visually. It appears that progression or reversal of bronchial epithelial atypia can be accurately monitored by studying the changes in the ASI, not only for preneoplasia but also for reactions to chemotherapy and various pulmonary infectious disease processes, such as influenza.

Adult↗
PubMed1979

Cyclic amidine inhibitors of indolamine N-methyltransferase.

Syntheses of a large number of mono- and bicyclic, as well as a few tricyclic, amidine derivatives related to 2,3,4,6,7,8,-hexahydropyrrolo[1,2-a]pyrimidine (DBN) are reported. In vitro potencies for inhibition of the enzyme indolamine N-methyltransferase (INMT) from rabbit and human lung are presented. Four bicyclic amidine derivatives and 11 monocyclic derivatives were found to be equal or superior to DBN in in vitro potencies. With the bicyclic amidines, increasing ring size or introduction of substituents reduced activity. Among the monocyclic analogues, the most potent representatives were five- or six-membered systems with an exocyclic imino group, combined with methyl of ethyl substituents on the endocyclic nitrogen. Introduction of additonal substituents decreased inhibitory potency. 2,3,5,6-Tetrahydro-8H-imidazo[2,1-c][1,4]thiazine and 3-methyl-2-iminothiazolidine have been shown to cause inhibition of lung INMT when administered orally to rabbits.

Amidines↗