An approach to acoustic properties of biological tissues using acoustic micrographs of attenuation constant and sound speed.
(57/1535)
OBJECTIVE: To develop a method for two-dimensional measurement of acoustic properties of biological tissue elements at the microscopic level for specimens with a thickness of approximately 10 microm. METHODS: The procedure was developed on the basis of mechanically scanned acoustic microscopic techniques in the frequency range of 100 to 200 MHz and the theory of interference phenomena. Various tissues and samples were prepared to evaluate the method and to interpret sound propagation properties. RESULTS: Tissues with high protein content, low water content, or both had a high attenuation constant and sound speed. The exponent n of attenuation against frequency was almost unity at the microscopic level, whereas it was greater than unity when the specimen thickness was greater. Sound speed dispersion was not observed. CONCLUSIONS: The method was shown to be reproducible, and the data were interpreted acoustically and pathologically with reference to tissue type and specimen thickness. (+info)
Calculation of the optical power of intraocular lenses.
(58/1535)
A rather simple clinical approach has been used to derive formulas necessary to calculate the power of pupillary intracameral prosthetics and these have been applied in 150 eyes. In 136 eyes, the postoperative measurements were within one diopter of preoperative calculations. (+info)
Clinical, histologic, and electron microscopy study of skin exposed to low-frequency ultrasound.
(59/1535)
The use of low-frequency ultrasound has been proposed to enhance the transdermal transport of various drugs, a technique referred to as sonophoresis. The aim of the present study was to determine the safety of low-frequency sonophoresis on human and rat skin by evaluating their structural modifications after ultrasound exposure. Human skin samples and hairless rats were exposed to 20 kHz ultrasound in vitro and in vivo, respectively. Ultrasound was used with average intensities ranging from 0.25 to 7 W/cm(2) in pulsed or continuous mode. Hairless rats were also exposed to a heat source mimicking the temperature versus time profile during sonication. Skin samples were observed under optical and electron microscopy to detect any structural changes. Human skin samples exposed to intensities lower than 2.5 W/cm(2) showed no modification. For hairless rats, slight and transient erythema was observed after 2.5 W/cm(2) exposure, whereas deep lesions (dermal and muscle necrosis) were observed 24 hr later. These lesions were also observed when a plastic film was placed between the coupling medium and the animals' skin during sonication. In contrast, no histologic lesion could be seen when a heat source was applied to animal skin. Low-frequency ultrasound induces delayed and deep lesions in hairless rat skin at 2.5 W/cm(2) which are not only attributable to the increase in temperature at the skin surface during ultrasound exposure. By using the same ultrasound conditions, human skin seems to be less sensitive in vitro. (+info)
Prolactin levels and maternal behavior induced by ultrasonic vocalizations of the rat pup.
(60/1535)
The relationship among ultrasonic vocalization (USV), prolactin and maternal behavior was investigated in lactating rat mothers and their pups. The lactating mother had a cannula inserted into the external jugular vein, and was exposed to USVs emitted from a pup immediately. Changes of prolactin and maternal behavior were determined. Prolactin increased dramatically during exposure to USVs, when maternal search, retrieving and nest building behavior appeared significantly. These results suggested that the relationship among USV, prolactin and maternal behavior was included in communication between lactating mother and pup. (+info)
Incorporation of a cationic aminopropyl chain in DNA hairpins: thermodynamics and hydration.
(61/1535)
We report on the physicochemical effects resulting from incorporating a 5-(3-aminopropyl) side chain onto a 2'-deoxyuridine (dU) residue in a short DNA hairpin. A combination of spectroscopy, calorimetry, density and ultrasound techniques were used to investigate both the helix-coil transition of a set of hairpins with the following sequence: d(GCGACTTTTTGNCGC) [N = dU, deoxythymidine (dT) or 5-(3-aminopropyl)-2'-deoxyuridine (dU*)], and the interaction of each hairpin with Mg(2+). All three molecules undergo two-state transitions with melting temperatures (T(M)) independent of strand concentration that indicates their intramolecular hairpin formation. The unfolding of each hairpin takes place with similar T(M) values of 64-66 degrees C and similar thermodynamic profiles. The unfavorable unfolding free energies of 6.4-6.9 kcal/mol result from the typical compensation of unfavorable enthalpies, 36-39 kcal/mol, and favorable entropies of approximately 110 cal/mol. Furthermore, the stability of each hairpin increases as the salt concentration increases, the T(M)-dependence on salt yielded slopes of 2.3-2.9 degrees C, which correspond to counterion releases of 0.53 (dU and dT) and 0.44 (dU*) moles of Na(+) per mole of hairpin. Absolute volumetric and compressibility measurements reveal that all three hairpins have similar hydration levels. The electrostatic interaction of Mg(2+) with each hairpin yielded binding affinities in the order: dU > dT > dU*, and a similar release of 2-4 electrostricted water molecules. The main result is that the incorporation of the cationic 3-aminopropyl side chain in the major groove of the hairpin stem neutralizes some local negative charges yielding a hairpin molecule with lower charge density. (+info)
Application of electrolyzed acid water to sterilization of denture base part 1. Examination of sterilization effects on resin plate.
(62/1535)
Bactericidal activities of electrolyzed strong and weak acid waters for acrylic denture base resin were evaluated in order to discuss the applicability of these waters for sterilization of denture base. Only 1-minute immersion in the electrolyzed strong or weak acid water could completely eliminate the attached bacteria, Staphylococcus aureus 209P, on the resin plate. When the resin was relined with tissue conditioner, 5-minute immersion or 1- to 2-minute ultrasonic cleaning reduced the number of the bacteria from 10(5)/cm2 level to 10(1)/cm2 and no surviving bacteria could be detected after 10-minute treatment. These findings suggest that both the electrolyzed strong and weak acid waters are well applicable to the disinfectant for acrylic denture base showing excellent bactericidal activities in a significantly shorter treatment as compared with the conventional denture cleaning. (+info)
Effects of diagnostic ultrasound irradiated during fetal stage on development of orienting behavior and reflex ontogeny in rats.
(63/1535)
The physical growth, the development of orienting behavior and neuromotor reflexes of offspring of rats that received an irradiation of a diagnostic level of ultrasound on the 9th day of gestation were estimated and compared with those of two control groups (untreated control and sham-irradiated or immobilized control). Results showed no significant group differences in terms of either physical development or development of orienting behavior. In the reflexological tests, however, a number of those reflexes that developed after 6 days of postnatal life of the offspring of irradiated rats showed significant delays in maturation when compared with those of the untreated control rats, but showed no difference from those of the sham-irradiated group. From these findings it is suggested that under certain circumstances such as in stress, the prenatally irradiated ultrasound of even a low-intensity may affect the development of the brain of offspring. (+info)
Effects of double-chained cationic surfactants n-dimethyldialkylammoniums on skin permeation of benzoic acid through excised guinea pig dorsal skin: comparison of their enhancement effects with hemolytic effects on erythrocytes.
(64/1535)
We examined the effects of the double-chained cationic surfactants dimethyidialkylammoniums (CH3)2N+ (CnH(2n+1))2 on the permeation of benzoic acid through excised guinea pig dorsal skin. Among five dimethyldialkylammoniums tested (n=10-18), dimethyldidecylammonium (n=10) had dose-dependent enhancement effects at concentrations of more than 20 microM. Compared with the marked enhancement effects of dimethyldialkylammoniums with relatively shorter alkyl chains, those of long-chain dimethyldialkylammoniums (n=16, 18) were much less. We compared the enhancement effects of these cationic surfactants on skin permeation with their hemolytic effects on guinea pig erythrocytes. Their enhancement effects corresponded to their hemolytic activity. The findings suggest that dimethyldialkylammoniums with relatively shorter alkyl chains, which form either vesicles with looser molecular packing or micelles and appear to be present as surfactant monomers in higher ratios than those with longer alkyl chains, favor the interaction with skin. Their enhancement mechanism is possibly similar to that of single-chained cationic surfactants. (+info)