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Biomedical subjects

R R Anderson

Publications and source records attributed to R R Anderson.

At least 145 records · Page 8Linked to original sources
PubMed1988

Effect of pulse duration on selective ablation of atherosclerotic plaque by 480- to 490-nanometer laser radiation.

The effect of varying pulse duration on selective ablation of human arterial plaque was evaluated by measuring ablation thresholds and ablation efficiencies on fresh human fibrofatty plaque, calcified plaque, normal intima, deep media, and adventitia using 480- to 490-nm laser radiation at 1, 8, and 50-microseconds pulse durations. For all tissues examined, the ablation threshold energy increased with increasing pulse duration, but the threshold for normal tissue ablation was approximately twice that of plaque at all pulse durations. Ablation efficiency was studied at a fluence that was twice the ablation threshold for plaque. For those fluences, normal intima had detectable ablation only at 50 microseconds. The ablation efficiency of fibrofatty plaque was minimally reduced with prolongation of pulse duration; however, there was a substantial decrease in the ablation efficiency of calcified plaque when the pulse duration was lengthened from 8 to 50 microseconds. These data show significant selective ablation of fibrofatty and calcified plaque at 1, 8, and 50 microseconds and suggest that the optimal pulse width for selective ablation of all plaque in the 480- to 490-waveband is less than 50 microseconds.

Aortic Diseases↗
PubMed1988

Pulsed CO2 laser tissue ablation: effect of tissue type and pulse duration on thermal damage.

Tissue removal by infrared lasers is accompanied by thermal damage to nonablated tissue. The extent of thermal damage can be controlled by a choice of laser wavelength, irradiance, and exposure duration. The effect of exposure duration has been studied in vivo by using CO2 lasers with pulse widths that vary from 2 microseconds to 50 msec. Pulse widths of 50 msec, typical of a shuttered, continuous-wave CO2 laser, produce damage regions 750 micron wide in normal guinea pig skin; the use of a 2-microseconds-long pulse reduced this damage zone to as little as 50 micron. Using 2-microseconds-long pulses, in vitro studies showed that the minimum zone of thermal damage varied significantly with tissue type. The thermal denaturation of these tissues has been studied and correlated with damage. The effect of denaturation temperature and pulse duration on the width of the damage zone is explained by a simple model.

Animals↗
PubMed1988

Laser lithotripsy: animal studies of safety and efficacy.

The safety and efficacy of pulsed tunable dye laser fragmentation of common bile duct stones was assessed in pigs. Laser pulses were conducted through a flexible quartz fiber that was in direct contact with stones that had been surgically implanted into the common bile duct. All calculi were rapidly fragmented into small pieces without significant damage to the common bile duct. The immediate and delayed effects of pulsed lasers on the common bile duct were also evaluated. The common bile duct demonstrated a high tolerance to laser-induced damage even when the laser was discharged directly into the bile duct wall. These results suggest that laser lithotripsy can be performed in humans with a high degree of safety and efficacy.

Animals↗
PubMed1988

Selective laser ablation of venous thrombus: implications for a new approach in the treatment of pulmonary embolus.

Laser radiation was employed to ablate venous thrombus or emboli with parameters that would not injure endovascular tissues. Output from a 482-nm, 1-microsec pulsed dye laser was delivered through a 320-microns-diameter fiber to in vitro samples of fresh thrombus (T), venous or pulmonary emboli (VE), inferior vena cava (IVC), pulmonary artery (PA), pulmonary valve, and endocardium (atrial and ventricular). The mean threshold fluences for ablation of T and VE were 1.1 and 5.1 J/cm2, respectively. In contrast, the mean threshold fluences for IVC and PA were significantly higher (P less than 0.0001), at 120 and 124 J/cm2, respectively. Ablation efficiency of thrombus was in excess of 100 mg/J, under conditions that caused no histologic injury to the pulmonary artery. To correlate ablation studies with optical absorption by the tissues, optical properties of fresh T, VE, IVC, and PA were studied. Hemoglobin species accounted for the more than 10 times higher 482-nm absorption by T and VE compared to IVC and PA. This explains the differences in ablation thresholds and, thus, the selectivity encountered. These observations demonstrate, more than any other study in the vascular system, that with pulsed optical radiation, efficient laser ablation of venous thrombus is feasible with a wide margin of safety, and without damage to the surrounding vascular tissue.

Hemoglobin A↗
PubMed1988

Reflection and transmission of laser light from the esophagus: the influence of incident angle.

The application of lasers in gastrointestinal endoscopy is rapidly expanding. Because of the tubular configuration of the gastrointestinal tract, endoscopists often deliver laser energy at large angles of incidence. As incident angle affects the fraction of radiation reflected from the tissue surface, we measured the transmittance and reflectance of laser light from in vitro esophagus as a function of incident angle, using integrating sphere and goniometric techniques. At a wavelength of 633 nm and angles of incidence less than 50 degrees, the total transmittance of the esophagus is approximately 25% and the total reflectance is approximately 45%; both are isotropically distributed. At larger angles of incidence, a specularly reflected component becomes evident and the total reflectance increases. The absorbed light per unit area illuminated decreases with increasing angle, because the area illuminated by the laser beam is proportional to the secant of the incident angle. The data suggest that during endoscopic laser procedures the incident laser beam should be directed within 50 degrees of normal for optimal performance and safety.

Biophysical Phenomena↗
PubMed1988

Selective vascular coagulation of rabbit colon using a flashlamp-excited dye laser operating at 577 nanometers.

Previous studies have demonstrated that brief pulses of selectively absorbed optical radiation can be used to confine thermal injury to pigmented targets within tissues. We performed studies in rabbits to assess the usefulness of this technique for selectively coagulating the colonic vasculature. By measuring the optical absorbance of rabbit colon with a spectrophotometer, it was determined that hemoglobin exhibits strong absorption relative to the rabbit colon at a wavelength of 577 nm. Because light must be absorbed to affect tissue, it was hypothesized that laser pulses of this wavelength would selectively damage blood vessels. This hypothesis was tested by examining the effect of 300-microseconds-long 577-nm laser pulses on rabbit colon in vivo. For delivered radiant exposures between 4 and 8 J/cm2, selective coagulation of the colonic vasculature could be produced without damage to the surrounding colon. At greater radiant exposures, vessel hemorrhage was occasionally noted but no transmural thermal injury was produced with delivered radiant exposures as high as 22 J/cm2. This technique may form the basis of a safe and simple treatment of vascular lesions of the colon such as angiodysplasia.

Animals↗
PubMed1988

Total and free thyroxine and triiodothyronine in blood serum of mammals.

1. Blood samples were obtained from seven species of mammals: horses, cattle, sheep, goats, pigs, guinea pigs and rats for determination of total and free thyroxine and triiodothyronine. Total thyroxine in the order listed above in ng/ml was: 15, 60, 79, 185, 53, 45 and 79. Free thyroxine in pg/ml was: 5.9, 10.0, 19.2, 32.1, 21.7, 6.7 and 51.3. 2. Total triiodothyronine in pg/ml was: 677, 1290, 979, 3170, 760, 317 and 1747. Free triiodothyronine in pg/ml was: 3.22, 4.40, 2.60, 6.74, 2.74, 2.42 and 10.88. 3. Percent free thyroxine was high in rats and low in guinea pigs, while percent free triiodothyronine was high in guinea pigs and low in goats. 4. Free thyroxine and percent free thyroxine were higher in some groups of horses, particularly stallions, than in other groups.

Animals↗
PubMed1988

Viability maintenance of mammary epithelial cells in vitro.

Mammary epithelial cells were isolated from mice lactating for 6 to 10 days and incubated in plastic culture dishes for 10 days. Viability of the cells was tested daily for 8 different treatment regimens including control (Minimum Essential Medium and antibiotics). Tested in cultures were horse serum, a collagen gel matrix, the lactogenic hormones prolactin, insulin, cortisol and all combinations of the above. Effectiveness of treatment was compared each day using the Duncan's New Multiple Range Test (DNMRT) and over the entire 10 day experimental period using regression analysis. After 1 day the collagen gel matrix was the most effective treatment followed by lactogenic hormones and horse serum. On days 2, 4 and 5, horse serum alone was the best treatment while day 3 demonstrated a slight superiority for hormones only. By day 6, and until day 10, a combination of horse serum and hormones maintained viability most successfully. The second and third most effective treatments during this portion of the experimental period were a combination of all three components and hormones alone, respectively. These data support the concept of complex support for mammary epithelial cell viability by a collagen gel matrix accompanied by three known hormones and unknown factors in horse serum.

Animals↗
PubMed1988

An action spectrum for photoinduction of prolonged cutaneous photosensitivity by topical 8-MOP.

Suberythemogenic exposure of human skin treated with aqueous 8-MOP to radiation greater than 380 nm prolongs photosensitization to subsequent UVA from 6 to 24-72 h. One hypothesis for prolonged photosensitization is that greater than 380 nm irradiation forms 8-MOP-DNA monoadducts, which are removed more slowly than free 8-MOP and serve as a substrate for crosslinking by further UVA exposure. Sufficient DNA crosslinking results in erythema. We have examined this hypothesis by measuring the action spectrum for induction of prolonged photosensitization. Skin of normal volunteers was treated with aqueous 8-MOP (0.003%) and immediately received suberythemogenic monochromatic exposures between 334 and 430 nm. twenty-four hours later, the presence of prolonged sensitization was tested by small exposures of UVA. Erythema was evaluated 3 and 5 d later, and an action spectrum for prolonged sensitization was determined. The minimum phototoxic dose (MPD) was also determined at each wavelength. The action spectrum for prolonged photosensitization declined gradually between 334 and 425 nm. The action spectrum for delayed erythema induced by a single exposure of 8-MOP-treated skin declined rapidly from 334-390 nm. These findings are consistent with prolonged binding of 8-MOP in the skin by an initial exposure, possibly as 8-MOP-DNA monoadducts, allowing the second exposure to induce an erythemogenic event, possibly crosslinking of DNA.

Cross-Linking Reagents↗
PubMed1988

Macrominerals in guinea pig milk during 21 days of lactation.

Milk samples were obtained daily from English short-hair albino guinea pigs for 21 d. Analyses included six macrominerals: Ca, P, K, chloride, Na, and Mg (in order of decreasing concentration). All minerals except K gradually increased in concentration from the beginning to the end of lactation. Calcium concentration began at 38 mM on d 1 and was 78 mM on d 21. The pattern of increase was quadratic: Y (mM) = 39 -.48X (day of lactation) + .11 X2. Phosphorus concentration was 38 mM on d 1 and highest at 51 mM on d 21. Chloride was 19 mM on d 1 and 68 mM on d 21. Sodium was 13 mM on d 1 and highest at 42 mM on d 21. Magnesium was 11 mM on d 1 and was highest on d 18 (13 mM). However, K was 31 mM on d 1, reached a high of 33 mM on d 3, and was lowest on d 19 (12 mM). These changes in concentration and previously reported volume changes suggest alterations in functional capacities of ionic transport mechanisms of secretory cell membranes in this species.

Animals↗
PubMed1988

Free and total thyroid hormones in serum of Holstein cows.

Basic parameters are reported for free thyroxine and triiodothyronine in blood serum of dairy cattle. Free thyroxine ranged from a low of 1.47 ng/dl in the summer to 1.86 ng/dl in the spring and from 1.37 ng/dl in early lactation to 1.85 ng/dl in midlactation. The average free triiodothyronine went from a low of 2.98 pg/ml in winter to a high of 6.23 pg/ml in the fall and from 3.45 pg/ml in early lactation to 5.37 pg/ml in midlactation. The free fraction of the serum compared with the total fraction averaged .0267% for thyroxine and .291% for triiodothyronine. Free and total thyroxine were high in fall, low in winter, and intermediate in spring and summer. Free and total triiodothyronine showed a similar pattern with a greater magnitude in the variations. Even though the thyroid hormone secretion rate was higher in winter (earlier studies), increased tissue utilization kept serum concentrations low. Free and total thyroxine and triiodothyronine were low in early lactation due to high demands from peak milk production. Stage of lactation had a much greater influence on changes in serum thyroid hormones than did season.

Animals↗
PubMed1988

Orotic acid in guinea pig milk: changes in concentration during lactation.

The orotic acid concentration in guinea pig milk decreased rectilinearly beginning on d 1 through a lactation duration of 21 d. Concentration was 29 micrograms/ml on d 1 and 5 micrograms/ml on d 17. On d 18 to 21 it was less than 1 microgram/ml. The regression equation of orotic acid on day of lactation was: Y(micrograms orotic acid per milliliter milk) equals 32.3 - 1.6X (day of lactation) with a correlation coefficient of .94. Total orotic acid on a daily basis peaked on d 6 at 950 micrograms and declined to less than 5 micrograms by d 21. The rectilinear regression equation from d 6 to 21 was as follows: Y(micrograms orotic acid per milliliter milk) equals -1.64 + .68X (grams of milk production per day) with a correlation coefficient of .97. This may be used as a marker for persistency of lactation.

Animals↗
PubMed1987

Recanalization of occluded biliary endoprostheses with pulsed laser radiation.

The use of pulsed laser radiation to recanalize occluded biliary endoprostheses was examined. In vitro measurements demonstrated that a repetitively pulsed organic dye laser transmitted through a small diameter quartz fiber can recanalize an occluded stent in less than 10 sec without causing visible damage to the stent. The laser parameters required for recanalization do not result in significant damage to the common bile duct of a pig even when the laser energy is delivered directly into the tissue, indicating that biliary endoprostheses can be cleared with a large margin of safety. Although the duration of this effect is unknown, pulsed laser radiation is a simple, safe, and effective means of recanalizing occluded biliary endoprostheses and may be an alternative to stent replacement.

Animals↗
PubMed1987

Microsecond-long flash photography of laser-induced ablation of biliary and urinary calculi.

High-speed flash photographs of laser-induced fragmentation of biliary and renal calculi under water were obtained using one-microsecond-long dye-laser pulses for both illumination and ablation. The photographs show the presence of a bubble with irregularities on the surface that suggest the early presence of debris or microbubbles. Fragmentation occurs before the bubble collapses, suggesting that fragmentation is due to laser-induced acoustic transients rather than to collapse of a laser-induced cavitation bubble.

Cholelithiasis↗
PubMed1987

Thermal injury by laser pulses: protection by heat shock despite failure to induce heat-shock response.

Pulsed lasers produce a variety of therapeutically useful effects in tissues by thermal mechanisms. In contrast with conventional hyperthermia, pulsed lasers rapidly induce extremely high temperatures confined to small areas within the tissues. It is not established, however, how cellular damage and repair responses differ between conventional and pulsed laser-induced hyperthermia. We have addressed this question by examining the induction of cellular heat-shock proteins (HSPs) and protection by heat-shock response against pulsed laser vs conventional hyperthermia. Cultured human dermal fibroblasts at confluency were exposed to single microsecond, 10.6-microns-wavelength pulses from a pulsed CO2 laser at radiant exposures between 0 and 1.3 J/cm2. Cell monolayers were directly exposed after removal of overlying medium. Positive control for the ability of the cells to synthesize of HSPs was obtained by heating the cells for 20 min in a water bath at 45 degrees C or 47 degrees C. The cultures were then labeled with L-[35S] methionine (Met), and proteins analyzed by sodium dodecyl sulfate polyacrylamide and two-dimensional gel electrophoresis 2 hr after exposure. The morphological alterations induced by laser or heat were similar under phase contrast microscopy. Conventional heating induced a heat-shock response, with the appearance of HSPs 2 hours after heating. In contrast, synthesis of HSPs could not be detected following laser irradiation, even at exposures decreasing both cell viability and incorporation of [35S] Met into cellular protein. Pre-exposure of cells to temperatures which induced synthesis of HSPs, however, significantly decreased cell death induced by subsequent laser irradiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Line↗
PubMed1987

Fragmentation of biliary calculi with tunable dye lasers.

The feasibility of using lasers to fragment biliary calculi was examined in vitro. Flashlamp-pumped tunable dye lasers were coupled to small-diameter flexible quartz fibers that were placed in direct contact with biliary calculi. The minimum laser energy necessary to damage a calculus was measured for wavelengths between 450 and 700 nm and for pulse durations between 0.8 and 360 microseconds. This threshold energy increased with increasing wavelength but was not significantly affected by pulse duration. Cholesterol stones had uniformly higher thresholds than pigmented ones. When a repetitively pulsed laser was used, complete fragmentation required fewer than 500 pulses and fragments were predominantly less than 2 mm. The pulsed dye laser can effectively fragment biliary calculi when transmitted through a small-diameter quartz fiber and may be useful as a tool for fragmenting retained common duct stones.

Cholelithiasis↗