Biomedical subjects

J V Bacus

Publications and source records attributed to J V Bacus.

8 recordsLinked to original sources

PubMed2000

Quantitative grading of rat esophageal carcinogenesis using computer-assisted image tile analysis.

Our objective was to grade, by computer-assisted quantitative image tile analysis, the intraepithelial neoplasia (also called dysplasia) that develops in esophagi of rats given N-nitrosomethybenzylamine (NMBA) for 5 weeks. To perform image tile analysis, the computer divides the video image of the neoplastic epithelium into a row of contiguous small rectangular images, or "tiles," 84 x 292 microm in size, and quantitatively measures four selected tissue features within each image tile. The computer then calculates a tile grade for each image tile as the weighted sum of the four feature measurements, transformed into statistical Z-scores, the weights being determined by Fisher linear discriminant analysis of 300 tile grades of the neoplastic epithelium referenced to the mean tile grade (MTG) of 300 image tiles of normal epithelium. The two grading parameters, MTG and the percentage of tile grades exceeding the MTG of normal epithelium by >4 SD units (%TG>4SD), were validated as endpoints for screening chemopreventive agents in the rat NMBA-induced esophageal carcinogenesis model in two ways: (a) after NMBA treatment, %TG>4SD developed in parallel with tumor incidence and tumor multiplicity (number of papillomas/tumor-bearing rat); and (b) placing the chemopreventive phenethylisothiocyanate in the food of NMBA-treated rats produced parallel reductions in MTG, tumor incidence, and tumor multiplicity. Both MTG and %TG>4SD, measured by quantitative image tile analysis, are sensitive and objective continuous parametric response variables expressed to three significant figures, with wide dynamic range, that may be evaluated by t tests to compare tissue neoplastic changes before and after treatment with a chemopreventive agent.

Administration, Oral↗

PubMed2000

Chemoprevention with theaflavins of rat esophageal intraepithelial neoplasia quantitatively monitored by image tile analysis.

The objective of the study was to compare three methods of monitoring the inhibition by dietary theaflavins of N-nitrosomethylbenzylamine (NMBA)-induced rat esophageal intraepithelial neoplasia: the mean tile grade, measured by computer-assisted quantitative image tile analysis; tumor multiplicity; and mean tumor size. A "tile" is defined as a small portion of a microscopic image at x 40, 87 x 292 microm in size. The computer divided the image of esophageal intraepithelial neoplasia into a grid of contiguous tiles and measured four tissue features within each tile based on cytonuclear and tissue architectural changes used by pathologists to diagnose intraepithelial neoplasia. The tile grade is defined as the weighted sum of the four feature measurements within a tile, the weights being determined by Fisher linear discriminant analysis. The mean tile grade of 300 tiles is used to grade rat esophageal intraepithelial neoplasia. NMBA was given s.c., 0.5 mg/kg, three times a week for 5 weeks. Theaflavins were given in the drinking water at 360 ppm (low dose) and 1200 ppm (high dose) throughout the experiment. In a given set of four groups of rats, one group received theaflavins alone, one NMBA alone, one NMBA plus low-dose theaflavins, and one NMBA plus high-dose theaflavins. One set of four groups, four rats/group, was sacrificed at the 15th week and another at the 20th week after starting NMBA; a final set with 15 rats/group was sacrificed at 25 weeks. At the 15th and 20th weeks, the mean tumor grade was the only variable that responded significantly (P < 0.01) to the low dose of dietary theaflavins. In fact, tumor multiplicity and mean tumor size sometimes showed enhancement at these doses. At the 25th week, when there were 15 instead of 4 rats/group, the mean tile grade, tumor multiplicity, and mean tumor size were all significantly (P < 0.01) decreased by both low and high doses of theaflavins. The mean tile grade is a more sensitive and reproducible variable than tumor multiplicity and mean tumor size in detecting the chemopreventive effects of theaflavins on intraepithelial neoplasia in the rat esophagus. This suggests that the mean tile grade may be a useful intermediate end point for use in human chemoprevention trials.

Animals↗

PubMed1999

Image morphometric nuclear grading of intraepithelial neoplastic lesions with applications to cancer chemoprevention trials.

A new image morphometric method of nuclear grading is described and assessed in the context of the evaluation of histological samples from ductal carcinoma in situ of the breast and cervical intraepithelial neoplasia. The method results in a continuous scaled variable, or nuclear grading scale, expressed in SD units from measured normal nuclei from breast or cervix. For a given histological preinvasive neoplastic lesion, the mean nuclear grade of measured nuclei was shown to be analogous to the histopathological nuclear grade of the same lesion assigned subjectively by the pathologist. In a chemoprevention trial of the effect of difluoromethylornithine given for 1 month to subjects with cervical intraepithelial neoplasia grade 3, pathologists could see no difference in 14 histological sections taken before and after difluoromethylornithine treatment. However, the image morphometric method detected a systematic effect of lowered mean nuclear grade and a decrease in the variability of nuclear grade expression. Twelve of 14 samples showed a lower posttreatment mean nuclear grade (P<0.05), and 13 of the 14 samples showed a decrease in the SD of their nuclear grade distributions (P<0.01). This study demonstrates the use of image morphometric nuclear grading in a chemoprevention setting. It may be very useful in supplementing the pathologist's histopathological grading by providing objective, quantitative assessments.

Antineoplastic Agents↗

PubMed1997

Properties of intraepithelial neoplasia relevant to cancer chemoprevention and to the development of surrogate end points for clinical trials.

Cancer chemoprevention is defined as the prevention of cancer by the administration of diet supplements or drugs. A drug discovery effort should therefore focus on finding agents that will avert the process of intraepithelial neoplasia which precedes invasive cancer. Over 30 agents developed by the chemoprevention program at the National Cancer Institute are being tested against intraepithelial neoplasia of many organ sites in more than 80 clinical trials. Two basic mechanisms underlie the onset and development of intraepithelial neoplasia. First is the development of the two precursor lesions of chronic diffuse epithelial hyperplasia and genomic instability, the latter being produced by "mutator" mutations in genes responsible for genomic stability, by gene copy amplification or loss from DNA breakage-fusion-anaphase-bridge cycles, by unequal sister chromatid exchange, and by accumulation of double minutes. Second is the development of multicentric intraepithelial neoplastic lesions which independently progress through each of the following processes at a continuously accelerating rate: clonal evolution, hyperproliferation, production of genomic structural variants, and apoptosis. Recommended chemoprevention strategies based on these mechanisms are (i) the development of better technology for early diagnosis, (ii) the development of multiple agents that block intralesional proliferation at steps along the signal pathway of mitotic signal transduction and along the signal pathway of synthesis of daughter cell components, (iii) the development of nontoxic anti-inflammatory agents, anitoxidants, antimutagens, and proapoptotics, (iv) the avoidance of "clonal escape" through use of drug combinations, and (v) the use of computer-assisted quantitative image analysis to assay modulation of surrogate end points in chemoprevention clinical trials.

Anticarcinogenic Agents↗

PubMed1997

Properties of intraepithelial neoplasia relevant to the development of cancer chemopreventive agents.

Cancer chemoprevention is concerned with the development of drugs or diet supplements that will avert the onset or stop the progression of the intraepithelial neoplasia which precedes invasive cancer. Two basic processes underlie the onset and development of intraepithelial neoplasia. First is genomic instability (often associated with chronic diffuse epithelial hyperplasia), which is the increased production of genomic structural variants due to unrepaired DNA breaks with secondary formation of abnormal structures, including "mutator" mutations in genes responsible for genomic stability, gene copy amplification or loss from DNA breakage-fusion-anaphase bridge cycles, unequal sister chromatid exchange, and accumulation of double minutes. Second is the development within an epithelium having genomic instability of multicentric neoplastic lesions that independently progress through each of the following processes at a continuously accelerating rate: clonal evolution, hyperproliferation, production of genomic structural variants, and apoptosis. Recommended chemoprevention strategies based on these mechanisms are (1) early diagnosis and treatment of genomic instability before the appearance of intraepithelial neoplasia, i.e., during the "predysplastic" or "premorphologic" phase, (2) development of multiple agents that block intralesional proliferation at steps along the "command" pathways of mitotic signal transduction and along the "execute" pathways of synthesis of daughter cell components, (3) development of nontoxic antiinflammatory agents, antioxidants, antimutagens, and proapoptotics, (4) avoidance of "clonal escape" through use of drug combinations, and (5) use of computer-assisted quantitative image analysis to assay modulation of surrogate endpoints in chemoprevention clinical trials.

Carcinoma in Situ↗

PubMed1997

Quantitation of preinvasive neoplastic progression in animal models of chemical carcinogenesis.

An assay method that precisely quantitates the cellular and tissue changes associated with early, preinvasive neoplasia is much needed as a surrogate endpoint biomarker (SEB) in clinical trials to predict the potential efficacy of chemopreventive agents in bringing about cancer incidence reduction. Quantification of histological changes at the tissue level are potentially powerful SEB's since these visually apparent changes are common in all neoplastic development, regardless of tissue type or neoplastic cause. Currently, subjective inspection of the histological appearance of sectioned and stained material, or "grading," by experienced pathologists is used to evaluate neoplastic progression. This has well-known limitations of reproducibility, accuracy, and resolution of grading scale. Since neoplastic changes are visually apparent and morphologic in nature, quantification by image analysis is a measurement modality of choice. Image analysis was implemented through the use of high-resolution "tiled" images of complete tissue sections. A histological grading system, or "scale," was developed that could be expressed in terms of normal deviate units of multiple and different morphometric descriptors. Neoplastic growth was characterized quantitatively with multiple measurements on each tissue image tile, which were combined into a single number for each tile, i.e., a histologic grade per tile, and parameters from the distributions of these measurements were used to represent the histologic grade for the entire region considered. This concept provided a uniform final scale in similar units of measurement, regardless of which tissues were graded. Also, the grading scale automatically adjusted measurement variance for different tissues by using normal tissue for each different type to obtain the normalization to standard deviation (z) units. This further defined a uniform final scale and maintained standard references. Using this method, results from two well-known animal models of carcinogenesis, squamous cell carcinoma of SENCAR mouse skin induced by benzo(a)pyrene (B[a]P), and squamous cell carcinoma of the rat esophagus induced by N-nitrosomethylbenzylamine (NMBA), were compared to each other. Image analysis was performed on skin tissue sections from a total of 64 SENCAR mice, and esophagus tissue sections from 96 Fischer-344 rats. In both cases, a quantitative expression of the preinvasive neoplastic response to the carcinogen as a function of time of exposure was expressed along a continuous grading scale in standard deviation units (z). In the SENCAR mouse skin animal model, similar cohorts of 4 mice at 20 weeks showed significant modulation of B[a]P-induced neoplasia by treatment with the antiproliferative agent difluoromethylornithine, P < .05. In the rat esophagus animal model, similar cohorts of 6 rats at 10 and 15 weeks showed significant modulation of NMBA-induced neoplasia by treatment with the antimutagen phenethyl isothiocyanate, P < .05.

Animals↗

PubMed1994

Quality control in image cytometry: DNA ploidy.

DNA ploidy has become a commonly performed quantitative image cytometry test in microscopic pathology. This has led to the need to develop quality control procedures to aid in assuring uniform and reliable test results. There are a number of unique issues related to the emerging technology of image analysis and its routine use as a quantitative microscopic assay that require consideration before establishing a quality control program. Previous considerations of this topic have primarily related to measurement issues, e.g., accuracy comparisons to other methodologies, calibration of instrumentation, sources of measurement error, and the interpretation of measurements results. Although these issues are critically important, with more routine usage the focus is now turning to quality control of the overall testing process in everyday use. Control charts and methods of controlling the total measurement process such as have been used in clinical chemistry, need to be established. As one of the first image assays in pathology, quality control procedures established now for DNA ploidy measurements could help shape the development of this field, especially as pathology transitions from being a subjective visual microscopic inspection process to a quantitative measurement process. This paper discusses these issues as they relate to overall quality assurance for the DNA ploidy test and describes a quality control program developed for an active breast cancer testing laboratory specializing in image cytometry tests, including DNA ploidy. The quality control program includes calibration control charts, control charts for internal diploid controls, check samples, and computerized individual histogram interpretation.

Biopsy, Needle↗

PubMed1994

A method of correcting DNA ploidy measurements in tissue sections.

A new method of performing DNA ploidy measurements in tissue sections using image cytometry is described. The method involves an image processing "object" filtering operation to remove cut and overlapping nuclei, and DNA correction of larger nuclei for the part of the DNA cut away. The methodology of the technique is developed in detail, and the results of testing using sections of rat liver are presented. The results indicated reliable correction of DNA ploidy histograms to reconstruct the polyploid nature of this material. The sensitivity of the material to sectioning thickness errors and methods to overcome this were shown, along with an example of its use on prostate bioptic gun tissue sections.

Animals↗