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R Ungar

Publications and source records attributed to R Ungar.

7 recordsLinked to original sources
PubMed1989

Articular cartilage and intervertebral disc proteoglycans differ in structure: an electron microscopic study.

Articular cartilage and the intervertebral disc tissues have different material and biological properties and different patterns of aging and degeneration. To determine if the proteoglycans of these tissues differ in structure, we used the electron microscopic monolayer technique to compare baboon articular cartilage proteoglycans with baboon annulus fibrosus, transition zone, and nucleus pulposus proteoglycans. Intervertebral disc and articular cartilage proteoglycans differed significantly. Articular cartilage contained large proteoglycan aggregates formed from hyaluronic acid central filaments, multiple monomers, and large nonaggregated monomers. These molecules were identical to those of nasal cartilage, growth plate cartilage, chondrosarcomas, or menisci. In contrast, the intervertebral disc tissues contained only nonaggregated proteoglycan monomers and clusters of monomers without apparent central filaments. Intervertebral disc nonaggregated monomers were shorter and more variable in length than those from articular cartilage, and nucleus pulposus nonaggregated monomers were even shorter and more variable in length than transition zone and annulus fibrosus monomers. These observations suggest that significant differences in proteoglycan metabolism exist between articular cartilage and intervertebral disc.

Animals↗
PubMed1987

Changes in proteoglycan aggregates during cartilage mineralization.

The dimensions of proteoglycan aggregates, aggregated monomers, and nonaggregated monomers, and the proportion of aggregated monomers found in the different zones of bovine rib growth plate have been defined by the electron microscopic monolayer technique. Growth plates were divided into the following 1 mm thick transverse slices; the hypertrophic zone, the lower proliferative zone, the upper proliferative zone, a transitional zone, and epiphyseal cartilage. Proteoglycans prepared by associative extraction followed by equilibrium density gradient centrifugation under associative conditions were examined by electron microscopy. Proteoglycan aggregate size decreased sharply in the lower proliferative and hypertrophic zones, as indicated by decreases in hyaluronate filament length and in the number of monomers per aggregate. Aggregated proteoglycan monomers did not show evidence of proteolytic degradation. Nonaggregated monomers were shorter than aggregated monomers, but their mean length did not decrease in the lower proliferative and hypertrophic zones. However, the proportion of nonaggregated monomers increased in these zones. Thus, before the cartilage matrix mineralized in the lower proliferative zone and as the cartilage matrix began to mineralize in the hypertrophic zone, proteoglycan aggregate size decreased and the proportion of aggregated monomers decreased. These changes in matrix proteoglycans may be one of the events that allow cartilage mineralization.

Animals↗
PubMed1986

Morphometric analysis of chondrocyte hypertrophy.

In the hypertrophic zone of the cartilaginous growth plate, chondrocytes enlarge, assume a more spherical shape, and form a population of cells called the hypertrophic chondrocytes. The mechanisms that are involved in the formation of hypertrophic chondrocytes are poorly understood. Cell hypertrophy usually refers to an increase in cell size and volume associated with an increase in organelles. In this study, we sought to determine whether the formation of hypertrophic chondrocytes represents true cell hypertrophy associated with an increase in organelles or whether it is due to swelling and fluid accumulation. Morphometric analyses of electron micrographs were carried out to determine changes in cell number, cell volume, cell organelle volumes, and matrix volumes in the reserve zone, upper proliferative zone, lower proliferative zone, upper hypertrophic zone, and lower hypertrophic zone. Between the upper proliferative zone and the lower hypertrophic zone, the cells increased their mean volume more than 500 per cent. As they enlarged, their matrices altered; territorial matrix volume increased as its collagen content decreased, and interterritorial matrix volume decreased as its collagen content increased between the lower proliferative zone and the lower hypertrophic zone. Between the upper proliferative zone and the lower hypertrophic zone, the absolute volume per cell of endoplasmic reticulum, Golgi membranes, and mitochondria increased 126 per cent, while the volume of cytoplasm and nucleoplasm increased 779 per cent, apparently by accumulation of water. Cell organelles of the lower hypertrophic zone did not show the changes that are associated with cell injury or death. Thus, the synthesis of organelles contributed to chondrocyte enlargement, but the primary mechanism of cell enlargement was cytoplasmic and nuclear swelling.

Animals↗
PubMed1985

Growth-plate-chondrocyte profiles and their orientation.

We studied the proximal tibial physes of mice, seven, fifteen, twenty-two, and twenty-eight days old, to define in mathematical terms the changes in cell profile and profile orientation among growth-plate zones and to determine if cell profile and profile orientation change with changes in the rate of growth. Using electron microscopy, we identified five growth-plate zones: the reserve zone, the upper proliferative zone, the lower proliferative zone, the upper hypertrophic zone, and the lower hypertrophic zone. In transverse sections, cell profiles did not change among growth-plate zones and the degree of cell-profile orientation approached zero in all zones. In longitudinal sections, cell profiles and profile orientations differed significantly among zones. Cell profiles in the upper and lower proliferative zones were eccentric and highly oriented. They became more rounded and the degree of cell orientation decreased between the proliferative and hypertrophic zones. As the rate of longitudinal bone growth decreased, cell profiles and cell-profile orientation changed. The cell profiles in the reserve zone became flatter and in the other zones the cell profiles became more rounded. The degree of cell-profile orientation decreased quadratically in the upper and lower proliferative zones, decreased linearly in the reserve and upper hypertrophic zones, and remained unchanged in the lower hypertrophic zone.

Aging↗
PubMed1975

Detection of neuroelectric signals from multiple data channels by optimum linear filter methods.

A general mathematical formulation for predicting achievable levels of detection of neuroelectric signals in associated background noise is provided for the case where such data are obtainable from multiple recording loci. The formulation depends upon the signal-to-noise ratios and bandwidths of the incorporated data channels and on the degree of noise dependency between channels. The signals are assumed to relate to the same event such as the production of an incipient movement but need not have the same waveshape. The detection technique is based upon passage of the data through a series of optimum linear filters. The outputs of the filters can either be summated in analog fashion prior to making the detection decision, or their separate outputs and separate detection decisions can be treated combinatorially to determine a detection decision for the aggregate. The former method is superior to the latter for small numbers of data channels. The latter method may be preferable where variation in signal latency exists between channels. Incorporation of information from multiple channels with independent noise can result in significant improvement over detection signals from a single channel provided that the signal-to-noise level of each additional channel exceeds that of the aggregate divided by square rootK, K being the total number of added channels. However, the presence of noise dependency between channels may severly restrict the degree of imporvement realizable through the multiple channel detection operation, irrespective of the number of added cha-nels. The implication of this result on the possibility of using EEG signals predicting incipient movement to control the operation of a motor prosthesis is profound. Inter-channel noise dependency with correlation coefficienr filter method of detection levels required for prosthesis operation. Zero lag correlation coefficients between electrical recordings from separate cortical loci both in man a

Animals↗
PubMedDate not supplied

International Training and Research in Central and Eastern Europe: The University of Iowa model.

In 1995, with support from the Fogarty International Center of the National Institutes of Health, The Center for International Rural and Environmental Health (CIREH) at The University of Iowa began developing the multi-level International Training and Research Program in Occupational and Environmental Health, focusing on countries in Central and Eastern Europe that were formerly under socialist control and have particular occupational and environmental health needs after decades of neglect and mismanagement. The purpose of the program is to prepare health science professionals to return to their home countries with new skills, added confidence, and leadership capabilities in public health to lead their colleagues and institutions in meeting the needs in their respective countries and establish active national and international networks and collaborations. By December 1998, 19 trainees had completed the five-month program and returned home to conduct workshops for others in their countries. Details of the program are presented.

Communism↗