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Biomedical subjects

M H Friedman

Publications and source records attributed to M H Friedman.

At least 109 records · Page 6Linked to original sources
PubMed1976

The toxicity of brominated sesame oil and brominated soybean oil in miniature swine.

Miniature swine were fed brominated sesame oil at dietary levels of 0, 5, 25, 50 or 500 mg/kg of body weight for 17 weeks and brominated soybean oil at levels of 0, 5, 50 or 500 mg/kg of body weight for 28 weeks. Growth rate and food intake were decreased only at the high dose level in the brominated sesame oil study. In both studies, signs of lethargy and ataxia occurred in pigs fed the highest dose, and were probably due to a dose-related increase in serum bromine concentrations. Marked elevations in lactic dehydrogenase (LDH), serum glutamic-oxalacetic transaminase (SGOT) and serum glutamicpyruvic transaminase (SGPT) values were seen at the highest dose level with both substances and these enzyme activities were increased at the 50 mg/kg dose level in the brominated sesame oil study. Histopathologic lesions were confined to animals given the highest dose level of either oil. Marked fatty degeneration of the hepatic plate cells and renal tubular epithelial cells were seen in both studies. In the brominated sesame oil study, neutral fat was moderately increased in the myocardium of the pigs fed 500 mg/kg. However, marked diffuse accumulation of LDH, marked diffuse fatty degeneration and focal degeneration, and/or necrosis of individual or small groups of cardiac muscle fibers were seen in the group fed brominated soybean oil at 500 mg/kg. A moderate to marked testicular atrophy was also observed in this group. A dose-related accumulation of total and hexane-soluble bromine was observed in all tissues examined in both studies; the highest concentrations occurred in adipose tissue of the pigs given the highest dose level. Kidneys, livers, hearts and thyroids of these groups also contained large amounts of bromine. In pigs given the 50 mg/kg dose level, total and hexane-soluble bromine concentrations were higher in the brominated sesame oil study than in the longer brominated soybean oil study and may be responsible for the elevations in LDH, SGPT and SGOT activities in this group.

Animals↗
PubMed1975

Calculations of pulsatile flow through a branch: implications for the hemodynamics of atherogenesis.

Numerical simulations of pulsatile blood flow through a symmetrical branch modeling the aortic bifurcation were carried out to assess several hemodynamic theories of atherogenesis by comparing the distribution of hemodynamic variables with that of early lesions in arterial branches. Considerable spatial and temporal variations in wall shear were found when the flow was pulsatile; the highest values occurred at the convex corner on the outer wall of the branch and in the neighborhood of the flow divider tip, and the lowest shears were experienced by the outer wall of the daughter vessel a short distance distal to the corner. Transient flow reversal occurred almost everywhere in the branch, and a transient separated region was found corresponding to the low-shear region in the daughter vessel. The shear profiles and the calculated separated region were influenced to some degree by the extent of flow development at the branch inlet and markedly by the branch area ratio. All of the proposed hemodynamic promoters of atherosclerosis that were examined--high shear, low shear, and separation--were found at sites in the branch where lesions commonly develop. Comparisons with a steady-flow calculation at the same mean flow rate showed that the severity of all of these proposed hemodynamic determinants was increased by pulsatility.

Arteries↗
PubMed1975

Effect of spatial variations in shear on diffusion at the wall of an arterial branch.

The effect of spatially varying shear on transport to the wall of a two-dimensional branch was examined, using oxygen as the test solute and the results of earlier fluid mechanical calculations to provide the shear profiles in a region characterizing the aortic bifurcation. The numerical technique employed allowed both blood-phase and mural resistances to solute uptake to be treated simultaneously and self-consistently. The calculated profiles of wall concentration and mural flux were significantly different from those which would have obtained if the shear had been uniform. The calculations suggest that, even when solute is rapidly taken up from the blood, the occasional high-shear and flow-development sites encountered along the arterial tree prevent the diffusion boundary layer adjacent to the wall from thickening to the point at which nutrition is compromised. The indirect effect of arterial geometry on transport, consequent to its direct effect on the magnitude and the distribution of the relevant hemodynamic variables, was illustrated using the branch area ratio as the geometric parameter. The shapes of the flux and interfacial concentration profiles along the branch wall were markedly dependent on the extent to which wall shear affected intimal permeability.

Animals↗
PubMed1973

Unsteady transport and hydration dynamics in the in vivo cornea.

The unsteady response of the rabbit cornea to the normal periodic variations in tear tonicity which accompany the sleep-wake cycle is examined quantitatively in terms of a physical description of corneal mechanics and transport. Two different sets of experimental epithelial and endothelial flow conductivities and reflection coefficients are used, and the effect of variations in epithelial solute permeability and sodium pump rate is examined. The use of a set of experimental corneal parameters chosen earlier provides good agreement between calculated and observed in vivo corneal thickness dynamics when the tear tonicity is within the physiologic range. The factors affecting the time-course of corneal thickness dynamics are discussed, including the osmometric quality of the corneal stroma, the role of the epithelial sodium pump, the flow resistance of the limiting corneal layers, and cyclic changes in aqueous tonicity. The unsteady solutions presented here are related to the steady-state solutions given in earlier papers through the concept of the time-average steady state. Any realistic description of the normal in vivo cornea must recognize its unsteady character and the potential for transepithelial flow. On the average, the hypertonicity of the tears relative to the stromal fluid can be sufficient to account for rabbit corneal deturgescence. The absence of endothelial "pumping" from the in vivo rabbit cornea cannot be proven; neither is there any certain need to postulate such transport in the normal state.

Animals↗
PubMed1972

Mercury content of common foods determined by neutron activation analysis.

The mercury contents in samples of flour, sugar, nonfat dry milk, potatoes, hamburger, chicken breast, shrimp, liver, eggs, and whole milk were determined by neutron activation analysis. The mercury was separated by anion exchange chromatography and precipitated as the sulfide. The mercury concentrations for all these foods were below 50 parts per billion.

Activation Analysis↗
PubMed1972

Mass transfer in the cornea. II. Ion transport and electrical properties of a series membrane tissue.

The electrical and active transport properties of isolated rabbit cornea are investigated by computer experimentation. The tissue is modeled as a series membrane system and the passive ion fluxes through it are described by the frictional formulation of irreversible thermodynamics. From short-circuit current (SCC) data, it is found that the epithelial sodium pump rate (P) is not appreciably changed when much of the sodium in the solution bathing the anterior corneal surface (concentration = c(11)) is replaced by choline, with choline-free medium posteriorly. Simulations of open-circuited corneas, using the mean P computed from the SCC data, yield corneal and stromal potentials in agreement with experiment. The stromal fluid is calculated to become more hypotonic as c(11) is diminished, a result consistent with posttest measurements of the sodium content of experimental stromata. The apparent decrease in "bound sodium" which accompanies the reduction of c(11) is a result of the associated changes in steady stromal hydration; the epithelial sodium pump does not contribute to corneal deturgescence. The inclusion of a simple epithelial structure in the computations changes the value of P but affects neither its constancy nor the calculated behavior of the cornea under open-circuit conditions. A general algebraic relation among pump rates and ion fluxes in short-circuited series membrane systems bathed in complex media is derived and used to construct a relation between P and SCC for the cornea. This equation yields pump rates in good agreement with the computer results and is used to show that (a) P is independent of c(11) if d(SCC)/dc(11) is a constant related to the over-all corneal permeability to sodium, and (b) a Lineweaver-Burke plot of 1/SCC vs. 1/c(11) can appear to be linear at constant P.

Animals↗