Biomedical subjects

L Berkwits

Publications and source records attributed to L Berkwits.

6 recordsLinked to original sources

PubMed1989

Probabilistic division systems modeling the generation of mosaic fields.

The explanation of mosaic pattern in chimeric organs analyzed by in situ methods requires modeling of specific hypotheses. The use of computer simulations to achieve this has led to the conclusion that finely variegated mixtures of cell lineage within chimeric tissues does not require extensive cell movement. Cell division models were used to determine the distribution of patch size as mosaic fields are generated. The results establish that these distributions are sensitive to the proportion of the two cell types which comprise the mosaic.

Animals↗

PubMed1988

Mosaic pattern and lineage analysis in chimeras.

Mammalian chimeras have been used in a number of developmental studies over the years. A major limitation in these studies has been the lack of in situ procedures for establishing mosaic pattern in the tissues of these animals. Recently, a number of procedures have become available for the histochemical demonstration of mosaicism in chimeras. These include the elucidation of various enzymes, receptors, or surface antigens, which have variant expression between strains. The observation of pattern in organs of mosaic animals can suggest possible modes of organogenesis and organ maintenance. Experimentation with such animals can be used to establish some mechanisms of pathogenesis as well.

Animals↗

PubMed1987

The clonal nature of carcinogen-induced altered foci of gamma-glutamyl transpeptidase expression in rat liver.

The clonality of tumors has been convincingly established. Because it is generally accepted that tumor formation involves a number of steps, it is important to determine which if any of the precursors of tumors are clonal. A series of chimeric rats produced between congenic strains by morulae aggregation were used to establish the cellular composition of foci of gamma-glutamyl transpeptidase (gamma-GTP; E.C. 2.3.2.2) expression in liver following initiation with N-nitrosodiethylamine and promotion with phenobarbital. The chimeras were produced between congenic rat strains (PVG and PVG-RT1a) genetically distinguished by alleles of the major histocompatibility complex (MHC). Monoclonal antibodies directed to distinctive class I MHC alloantigens were used to detect patterns of mosaicism in the animals. The parental genotypes present in most visceral tissues could be easily distinguished by our method. Analysis of 499 enzyme-altered foci revealed that 474 were comprised solely of either PVG-RT1a or PVG cells. Some apparent mixture of cells from the two lineages was observed in 25 lesions, most of which were very small. The observed pattern of distortion of normal patch distribution clearly indicated the expanding and clonal nature of these lesions.

Animals↗

PubMed1987

A probabilistic model of mosaicism based on the histological analysis of chimaeric rat liver.

The analysis of pattern development in mosaic and chimaeric animals has provided insight into a number of developmental problems. In order to aid the understanding of the dynamics of the development of mosaic tissues, a computer simulation of the generation of a mosaic tissue was created using simple probabilistic decisions. Results of quantitative analysis of the simulated mosaicism were compared with chimaeric liver. Chimaeric animals were produced by morula aggregation between histologically distinguishable strains of congenic rats. The livers of these animals revealed a pattern of patchy mosaicism unrelated to either acinar or lobular architecture of the organ. Independent quantifiable parameters were correlated and compared between the simulation and chimaeric liver tissue. This analysis showed that extensive cell migration is not required to develop finely variegated mosaic tissue and that the patterns of mosaicism observed could have resulted from tissue development in which as few as three reiterated decisions were required. First, the simulation established anlagen of two cell types of various specified proportions with randomly chosen placement. Second, in each generation of the simulation the order in which the cells divided was established randomly. Third, there was a random choice of the direction of placement of the daughter cell. The quantitative relationships between the proportion of cell types, the area of patches and the number of patches per unit area was consistent between the simulation and the chimaeric tissue.

Animals↗

PubMed1986

Marjolin's ulcer complicating a pressure ulcer: case report and literature review.

Fifteen years after spinal cord injury and 14 years after development of a sacral pressure ulcer in a paraplegic man, a squamous cell carcinoma was found on biopsy during surgical reconstruction of the pressure ulcer. The patient refused the extensive surgery necessary to remove the infiltrating tumor, and the wound was closed with a latissimus dorsi flap. Pressure ulcers remain a problem in spinal cord injured and other disabled patients. Malignant degeneration (Marjolin's ulcer) in chronic pressure ulcers and other chronic skin ulcerations may become more widespread as the life span of spinal cord injured patients increases.

Adult↗

PubMed1985

A microcomputer-based quantitative morphometric analysis system for computing areas of amorphous patches.

A method for analysis of irregular areas has been developed for use with histological sections. The analysis is performed utilizing a digitizing tablet and a microcomputer. The advantages of this system are a specialized form of output suited to the analysis of mosaic tissues, disk storage of all data, plotter output for verification, and an inexpensive hardware environment. The program results of determinations of liver patch size in a novel chimeric rat system are described.

Animals↗