Search PubMed⌕ Search

Biomedical subjects

J L Bert

Publications and source records attributed to J L Bert.

43 records · Page 3Linked to original sources
PubMed1982

Lymph flow characteristics and microvascular exchange: an analog computer simulation.

Lymphatic flow characteristics, which include both progressive lymphatic blockage and plateau of lymph flow with increasing interstitial fluid volume, were incorporated into an analog computer simulation of microvascular exchange, and their effects on interstitial fluid volume and protein content were investigated. The steady state and transient response of the microcirculation to changes in the properties of the lymph flow system are reported. The interstitial fluid and protein content is investigated as a function of venous pressure and for changes associated with the lymph flow characteristics. The interstitial protein content is generally more sensitive to changes in the lymph flow properties than is interstitial fluid volume. Properties of lymphatic drainage of tissues as they effect microvascular exchange are discussed.

Computers↗
PubMed1980

Characterization of collagenous meshworks by volume exclusion of dextrans.

The volumes from which 3H-labelled dextrans are excluded by dermal collagenous fibres were calculated by dilution of dextran probes. Five dextrans, of average Stokes' radii 1.72, 2.53, 3.92, 4.54 and 14.24nm, were investigated at concentrations between 0.1 and 3% (w/w). The excluded volume was dependent on dextran concentration only for the two smaller probes. The largest dextran was shown not to bind to the fibres. A plot of the square root of excluded volume against Stokes' radius was linear for the four smallest dextrans, corresponding to the predictions of Ogston's [(1958) Trans. Faraday Soc. 54, 1754--1757] rod-and-sphere model of fibrous exclusion, and suggesting that dextrans of Stokes' radius between 1.72 and 4.54 nm were excluded by a cylindrical solid fibre of radius 2.90 +/- 0.72 nm. Larger molecules were excluded by a structure of much greater size, since the volume exclusion for the largest dextran was only slightly greater than that of the dextran less than one-third its radius. The excluded volume of 3H2O fell slightly below the line describing the dextran data, indicating that water had access to most of the volume not occupied by the collagenous fibres.

Chemical Phenomena↗
PubMedDate not supplied

Preliminary model of fluid and solute distribution and transport during hemorrhage.

The distribution and transport of fluid, ions, and other solutes (plasma proteins and glucose) are described in a mathematical model of unresuscitated hemorrhage. The model is based on balances of each material in both the circulation and its red blood cells, as well as in a whole-body tissue compartment along with its cells. Exchange between these four compartments occurs by a number of different mechanisms. The hemorrhage model has as its basis a validated model, due to Gyenge et al., of fluid and solute exchange in the whole body of a standard human. Hypothetical but physiologically based features such as glucose and small ion releases along with cell membrane changes are incorporated into the hemorrhage model to describe the system behavior, particularly during larger hemorrhages. Moderate (10%-30% blood volume loss) and large (> 30% blood loss) hemorrhage dynamics are simulated and compared with available data. The model predictions compare well with the available information for both types of hemorrhages and provide a reasonable description of the progression of a large hemorrhage from the compensatory phase through vascular collapse.

Animals↗
PubMedDate not supplied

Flow conductivity of rat dermis is determined by hydration.

The flow rate of phosphate buffered saline through dermis was measured as a function of applied pressure. Hyaluronan and collagen, the two principal materials which confirm resistance to flow in dermis, were not lost from the tissue during the experiments which lasted up to two days. From Darcy's Law, the average flow conductivities were 2 to 6 x 10(-12) cm4/dyn x s and decreased with increasing applied pressure. We conclude that the tissue is compacted in proportion to the applied pressure during the flow experiments. The hydraulic flow conductivity is described mathematically as a function of compaction induced by the applied pressure.

Animals↗