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Biomedical subjects

K R Diller

Publications and source records attributed to K R Diller.

71 records · Page 4Linked to original sources
PubMed1981

Blood freezing to nearly absolute zero temperature: -272.29 degrees C.

Human erythrocytes were collected in ACD anticoagulant, glycerolized with an equal volume of 8.6 M glycerol, 8 percent glucose, 1 percent fructose, and 0.3 percent Na2 EDTA solution, sealed in glass ampules, and frozen to -272.29 degrees C (0.86 degrees K) in liquid helium under high vacuum. Biological assays performed after thawing and three-stage dialysis to remove the glycerol showed less than 1 percent hemolysis. Intracellular potassium, 2,3 DPG, and ATP were within the normal range.

Blood↗
PubMed1980

Volumetric changes in cells during freezing and thawing.

A thermodynamic model is presented to describe the combined freezing and thawing process for living cells. Continuous changes in the cell volume are predicted according to the thermal protocol imposed on the system. Experimental verification of the model is sought by monitoring continuously the volume of cells as frozen on a cryomicroscope. The volumes of individual cells are measured from sequential photomicrographs by a computerized image analysis technique. The model and experimental data are in quite close agreement for the freezing process, but upon thawing the experimentally measured volumes consistently increased much more rapidly than predicted by the model. The model can be made to conform to the data by accounting for a substantial influx of electrolyte to the cell at subfreezing temperatures.

Cell Membrane↗
PubMedDate not supplied

The analysis of biological shape changes from multidimensional dynamic images.

A technique for modeling shape changes in a time series of biological images of arbitrary dimension is described. The technique consists of first segmenting the image to locate the specimen, and then parametrizing the specimen in the initial image with an orthogonal material coordinate system. The deformation of the material coordinate system caused by the changing shape of the specimen is then solved for by minimizing an energy functional. The energy functional is a linear combination of a brightness continuity term and a shape change term. A parameter lambda, weights the brightness continuity against the shape change smoothness. The best value to use for lambda is chosen as the value that minimizes the mean square error between the image derived from the calculated shape change parameters and the corresponding actual image. A two-dimensional implementation by finite differences is given. Results from both two-dimensional confocal images, and two-dimensional synthetic images are presented. Our early work on a three-dimensional implementation is given.

Algorithms↗
PubMedDate not supplied

Analysis of burns caused by long-term exposure to a heating pad.

The potential for creating a second-degree burn by extended exposure to an electric heating pad was evaluated in a simple model. Extrapolation of empirical results from experiments in thermal burns and in hyperthermia indicated that a heating pad at the low power setting can produce a burn within a threshold time of approximately 12 to 20 hours.

Burns↗
PubMedDate not supplied

The effects of epinephrine, ibuprofen, and tetrachlorodecaoxide on cutaneous microcirculation in thermally injured hamsters.

Fluctuations in the diameter of selected arterioles in the cutaneous microcirculation of Syrian golden hamster dorsal skin flap chambers, which ranged in size from 10 to 70 microns at different branching order sites, were measured before burn, at the same sites after burn and after injection of the drug. Three different drugs epinephrine (administered intravenously), ibuprofen (administered intravenously), and tetrachlorodecaoxide (administered intravenously and topically) were evaluated. Results show that the response to thermal injury in the control group involved extensive vasodilation in the arterioles, prolonged flow irregularities including flow obstructions and stasis, and a decrease in the level of vasoactivity of the microvessels. In two treatment groups, the ibuprofen and tetrachlorodecaoxide groups, significant improvement as indicated by reduced vasodilation and edema and improved microcirculatory blood flow after injury were observed. Further testing of tetrachlorodecaoxide as a topically applied wound dressing is indicated.

Animals↗
PubMedDate not supplied

Burn-induced alterations in vasoactive function of the peripheral cutaneous microcirculation.

Alterations in the cutaneous vasomotion function caused by scald burns to a large area on the flank were observed and quantified in a dorsal skin flap window with a hamster model. Subsequent to chronic implantation of the window chamber to provide direct microscopic observation of blood flow for an entire thickness of skin, control measurements of vasoactivity in a defined network of arterioles were taken by means of a digital video image splitter over a period of several days. A 100 degrees C, 5-second water scald was then effected over 17% to 55% of the total body surface area, and the vasoactivity was remeasured in the targeted set of sites at serial time intervals for 2 to 4 days. Data were acquired directly into a computer and analyzed for both the magnitude and time pattern of diameter fluctuations during 3-minute observation periods. Average and standard deviations of diameters were computed, and the Prony power spectral analysis method was applied to identify the presence and strength of fluctuation frequencies. In general, vasomotion was suppressed for several hours subsequent to the burn, and the activity was dominated by much slower contractions than control. No direction of vessel diameter changes prevailed uniformly throughout the peripheral microcirculation. Large alternate constrictions and dilations were also observed for some arteriolar and venular components, but others exhibited no significant change at all. The incidence and magnitude of peripheral microvascular response was proportional to the size of the injured area.

Anesthesia, Inhalation↗
PubMedDate not supplied

Local macromolecular extravasation in thermal burns quantified by fluorescent video microscopy and computer vision.

A dorsal skin flap chamber model was developed for analysis of the microvascular response to moderate intensity local thermal burns. Fluorescein isothiocyanate tagged 70,000 d dextran was introduced to visualize the extravasation and interstitial transport of macromolecules at the burn site. Contact burns 0.5 cm in diameter were affected by touching a thermostated metal rod onto the exposed epidermal side of the chamber preparation. All burns were of 5-second duration at temperatures between 55 degrees C and 70 degrees C. Postburn leakage of the fluorescein-labeled probed was monitored at numerous sites in the preparation on a fluorescent microscope equipped with a low-light-level intensified silicon intensified target video camera and recorded on tape for subsequent quantitative analysis. Selected scenes were digitized and subjected to a sequence of computer-image processing operations to extract quantitative information about the concentration distribution and net accumulation of dextran in the interstitial space as a function of postburn time. A diffusion model based on cylindrical geometry was fit to the concentration profile data at each site analyzed, and an apparent diffusion coefficient describing the interstitial transport process was determined. The interstitial transport increased with burn temperature up to a threshold of 70 degrees C, where other factors resulted in significant reduction in the loss of fluorescent macromolecule from the vasculature.

Animals↗
PubMedDate not supplied

Modeling thermal skin burns on a personal computer.

Mathematic models have been used for several decades to predict the severity of burn injury that would result from application of a given thermal stress to the surface of the skin. Solution of the governing mathematic equations has been achieved either by analytic methods, with required simplifying assumptions that may compromise the rigor with which the results are applied, or by numeric methods, which require programming of finite element or finite difference codes in computer languages. In recent years microcomputer hardware and the associated software have become both powerful and relatively simple to use, and the price per unit of computing capability has dropped dramatically. Thus it is now possible to perform on a desktop machine with relative case calculations that previously might have been prohibitively complex or expensive. Modeling of burn injuries fits into this category. This article presents a straightforward method for implementing a finite difference solution to the burn process through the combination of a Macintosh personal computer and a widely used spreadsheet software program; this hardware and software combination has been used widely for a broad spectrum of general computing activities. This article presents a model for a surface thermal burn, as implemented for solution on a spreadsheet, with example runs to illustrate and verify the method.

Burns↗
PubMedDate not supplied

Development and solution of finite-difference equations for burn injury with spreadsheet software.

This article presents a brief description of a set of equations by which the thermal burn process may be modeled, a formulation of the differential equations into a finite-difference format, and a simple method of solution using a standard commercial spreadsheet software application. A companion article provides a discussion of results that can be obtained with the modeling techniques presented here. A short version of the spreadsheet program is available from the author.

Burns↗
PubMedDate not supplied

Prediction of transient temperature fields and cumulative tissue destruction for radio frequency heating of a tumor.

A therapeutic hyperthermia protocol using a radio frequency (rf) electrode placed adjacent to a bronchial wall tumor has been modeled using the finite element technique. Variable physical properties and variable blood perfusion have been assigned to the tumor and to the surrounding normal lung tissue. The Laplace equation was solved on a curvilinear grid for a single rf source electrode to determine the steady-state electric field, which in turn governs the energy deposition function. The heat generation in the tumor and in the lung tissue is then calculated from the energy deposition profile, and the bioheat equation is solved on the same finite element mesh to determine the transient temperature history. The temperatures are displayed as isothermal contours at designated times during the protocol and as temperature histories at selected points. In addition, an Arrhenius-type injury model has been implemented to predict thermally induced damage, from which equal total amounts of energy are deposited into the tissue using a constant power density for an appropriate time or using a cyclic heating pattern. The cyclic heating pattern consisted of a series of equal duration time periods during which the rf current source is alternately turned on and off (50% duty cycle). This study illustrates how a finite element model could be used to evaluate alternative protocols for heating a tumor of a specific geometry and to evaluate thermally induced damage to surrounding normal tissue.

Humans↗