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Biomedical subjects

W D O'Brien

Publications and source records attributed to W D O'Brien.

At least 73 records · Page 4Linked to original sources
PubMed1981

Dependence of the ultrasonic scatter coefficient on collagen concentration in mammalian tissues.

The difference between literature values of ultrasonic attenuation and absorption coefficients, defined as the scatter coefficient, was related to percent wet weight collagen concentration for brain, heart, liver, kidney, and tendon, in the range of 0.7 to 7 MHz. The comparison shows that as the ultrasonic frequency increases, the scatter coefficient increases, and the dependence of scattering upon collagen concentration decreases.

Acoustics↗
PubMed1981

Quantitative acoustical assessment of wound maturation with acoustic microscopy.

Preliminary results of the ultrasonic characterization of cutaneous wound tissue and surrounding margin, obtained with the scanning laser acoustic microscope, show an increase in the speed of sound and in the acoustic heterogeneity as function of wound age. As the wound age increased, the following results were noted: (1) The wound area, initially quite homogeneous in acoustic appearance, became more heterogeneous; (2) the acoustic appearance of the wound tended to become similar to that of the adjacent tissue; and (3) the ultrasonic velocity of the wound area increased from a range of 1540--1575 m/s at 7 days to a range of 1700--2000 m/s at 35 days.

Animals↗
PubMed1981

Ultrasonically induced, in vivo morphological damage in mouse testicular tissue.

Mouse testes were exposed in vivo to 1 MHz continuous wave ultrasonic energy for 30 sec at spatial peak intensities of either 2 or 5 W/cm2. Following exposure they were surgically removed at times ranging from immediate (within 60 sec) to 63 days, and histologically prepared for optical microscopy examination. The observed alterations can be classified according to the number and type of affected cell layers in the tubule. Leydig cells were unaffected, and some alterations differed from those previously seen at higher ultrasonic exposure intensities or at much longer exposure times.

Animals↗
PubMed1980

Modified assay for determination of hydroxyproline in a tissue hydrolyzate.

A modified assay for the determination of hydroxyproline in tissue is presented. The modifications greatly reduce the time required for analysis of excised tissue as first introduced by Stegemann and Stalder [1]. These modifications include a change in the technique for tissue hydrolysis and a change in the preparation of the hydroxyproline oxidizing agent. The analysis utilizes the standard addition technique, eliminating the need for correction of matrix effects between the specimen and standard. This paper attempts to give a complete detailed description of the assay such that the procedure may be repeated without requiring additional reference material.

Animals↗
PubMed1977

Effects of ultrasound on nucleic acid bases.

To understand the effects of ultrasound in biological systems at the molecular level, sonolysis of nucleic acid bases at sonic intensities less than or equal to 5 W/cm2 was studied. These sonoreactions were followed by UV-spectral decrease and by sonoproduct analysis. The order of reactivity was found to be thymine greater than uracil greater than cytosine greater than guanine greater than adenine. The extent of sonoreactions depends on the exposure time and the rate of the intensity. Aeration was necessary for maintenance of a reasonable reaction rate. "Threshold" intensities for uracil and thymine were observed at approximately 0.5 W/cm2. The effectiveness of the dissolved gases in producing sonoreactions was Ar greater than 02 greater than air greater than N2 greater than He greater than N2O, suggestive of free radicals mediating these reactions since N2O is an effective radical scavenger. Studies of the effects of substituents have shown that electronic rather than steric effects may have a greater influence. Preliminary identification indicates that cis- and trans-uracil glycols are the major products of uracil. Thus, a stepwise mechanism of pyrimidine sonolysis is proposed. Sonolysis of a dilute aqueous solution of uracil yielded pseudo-first-order kinetics in terms of [Ura] with a rate constant of 3.9 X 10(-2) min-1, implying that the rate-limiting step is the reaction of HO- with the base.

Adenine↗
PubMedDate not supplied

The combined effect of ultrasonic exposure and protein restriction on maternal and fetal mice.

This investigation was undertaken to assess the combined effects of protein restriction and ultrasonic energy exposure during pregnancy on the maternal and fetal mouse. Pregnant female mice were fed diets containing either 18% casein (control diet) or 6% casein (restricted protein diet) during gestation. All animals were subjected to the ultrasonic exposure procedure (actual: 2.5 W/cm2 spatial peak; sham: 0 W/cm2; continuous wave for 20 sec at a frequency of 1 MHz) on day 8 of gestation. On day 18 of gestation, the animals were sacrificed. Products of conception were examined, and chemical analysis were performed on maternal liver, placenta and fetus. Our results suggest that there are possible influences of ultrasonic energy exposure to the mouse fetus and placenta, as indicated by the tendency toward decreases of fetal weight, placental weight, and DNA and RNA contents of both fetus and placenta, especially with restricted protein in the maternal diet during gestation. Protein restriction during pregnancy had an adverse influence on both the maternal organism and her products of conception. The nutritional needs for the fetus were not met at the expense of the maternal organism. Parameters of fetal cellular growth were reduced by gestational protein restriction indicating that there is competition for available nutrients between the fetus under time of stress. Results also show that the trends of fetal and placental growth are in the same general direction suggesting the possible usefulness of human placental tissue as a maker for fetal growth in subsequent population studies.

Animals↗
PubMedDate not supplied

Ultrasonically induced morphological damage to mouse ovaries.

Mouse ovaries were exposed in vivo to 1 MHz continuous wave ultrasonic energy at spatial peak intensities ranging from 5 to 100 W/cm2 for times varying from 300 to 15 s depending on the intensity. Following exposure the ovaries were surgically removed at times ranging from immediately (within 60 s) to 7 days and prepared histologically for light microscopic analysis. The observed tissue alterations varied from severe, at the higher intensities to subtle, at the lower intensities. Lesions were manifested by pyknosis of cells, vacuolization of cells and tissue, eosinophilic cytoplasm, and general cellular disruption. Subtle alterations showed large numbers of polyovular follicles and increases in the amount of PAS positive material in the interstitial tissue. Various ovarian structures showed differing sensitivities to the insult with luteinized structures being preferentially altered.

Animals↗
PubMedDate not supplied

Ultrasonically induced temperature elevation in mouse ovary.

Temperature increases, resulting from exposure to 1 MHz ultrasound, were measured in in situ and in exteriorized mouse ovaries. It is concluded that temperature increases from exposure to 10 W/cm2 and less are probably not significant for producing ovarian tissue damage, but that 25 W/cm2 exposures, and greater, are of such magnitude that damaging thermal levels ensue. The significance of blood flow in removing ultrasonically generated heat has been observed quantitatively.

Animals↗