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Biomedical subjects

R F Bonner

Publications and source records attributed to R F Bonner.

54 records · Page 3Linked to original sources
PubMed1987

Intraoperative measurement of cortical blood flow adjacent to cerebral AVM using laser Doppler velocimetry.

Standard methods for measurement of cerebral blood flow (CBF) are not optimal for continuous intraoperative recording. Laser Doppler velocimetry has been used for evaluation of microcirculatory flow in a variety of human tissues, including skin, muscle, and retina. The authors report the use of this technique for measuring flow in human cerebral cortex. The physiological changes associated with excision of a cerebral arteriovenous malformation are interpreted using CBF recorded intraoperatively with the laser Doppler probe.

Adult↗
PubMed1987

Use of laser-UV for inactivation of virus in blood products.

Inactivation of virus by UV radiation was examined as a potential method for sterilization of blood products. Samples of attenuated poliovirus, platelets and plasma were uniformly irradiated with a XeCl excimer laser that delivered 40 nsec pulses of UV at 308 nm (UVB308). Intensities and exposure does were varied from 0.11 to 1.40 MW/cm2 and 0.51 to 56.0 J/cm2, respectively. In studies conducted with low intensity UVB308 (less than or equal to 0.17 MW/cm2), using exposure doses greater than or equal to 10.8 J/cm2, it was possible to inactivate poliovirus by 4 to 6 log10. Platelets irradiated with doses less than or equal to 21.5 J/cm2 exhibited minimal damage as assessed by aggregation activity and spontaneous release of serotonin. Examination of the coagulation activity of irradiated plasma indicated that exposure doses less than or equal to 21.5 J/cm2 resulted in less than 20% increase in prothrombin and partial thromboplastin times. The use of UVB308 at a higher intensity (1.4 MW/cm2) over a similar range of exposure doses did not enhance viral inactivation but did result in increased damage to platelet and plasma proteins. These results demonstrate that at 308 nm there exists a "window of efficacy" for exposure doses between 10.8 and 21.5 J/cm2 and peak intensities less than or equal to 0.17 MW/cm2 in which a hardy virus is significantly inactivated and platelets and plasma proteins are, by functional criteria, minimally affected. Increased viral inactivation cannot be accomplished with higher UV intensities and will require additional or alternate measures.

Blood↗
PubMed1986

Posterior vitreous fluorophotometry in normal subjects.

We performed vitreous fluorophotometry using the Fluorotron Master and intravenous fluorescein injection of 14 mg/kg of body weight in 22 normal subjects. Various methods of analysis were used to evaluate vitreous fluorescein concentration at 3 mm from the retina as well as averaged over the posterior 6 mm. The various methods of calculation yielded mean (+/- SD) postinjection values ranging from 1.7 +/- 1.4 to 4.3 +/- 2.3 ng/mL at 30 minutes and from 7.1 +/- 2.4 to 10.8 +/- 2.7 ng/mL at 60 minutes. The permeability index determined 60 minutes after injection ranged from 0.92 +/- 0.40 X 10(-7) to 1.19 +/- 0.30 X 10(-7) cm/s, according to the protocol used. Replicate pairs of measurements in six subjects demonstrated that the procedure was reproducible to within 17% to 49%, depending on the analysis. The results suggest that if the current methods of data analysis are used, fluorescein leakage might be considered abnormally high if at 60 minutes the 3-mm posterior vitreous fluorescein concentration corrected for background fluorescence exceeds 14.3 ng/mL and/or the permeability index exceeds 2 X 10(-7) cm/s.

Adult↗
PubMed1986

Indices of sympathetic vascular innervation in sympathectomized patients.

We measured arterial and venous plasma catecholamines and used laser-Doppler flowmetry to measure cutaneous microcirculatory flow in the sympathectomized and in the intact limbs of 3 patients who had undergone regional sympathectomies. Venous concentrations of norepinephrine, the sympathetic neurotransmitter, exceeded arterial concentrations in the intact limbs--a normal finding--but invariably were less than arterial in the sympathectomized limbs of the same patients, both during baseline conditions and during sympathetic stimulation using tilt, standing and the cold pressor test (mean arteriovenous decrement about 40%). Arterial epinephrine levels exceeded venous levels with or without sympathectomy. Skin microvascular flow rapidly decreased during the cold pressor test and the Valsalva maneuver in the intact but not in the sympathectomized limbs, and spontaneous flow oscillations occurred in the sympathectomized limbs. The results suggest that an arteriovenous increment in plasma norepinephrine reflects local release of norepinephrine from sympathetic nerve endings, whereas removal of circulating catecholamines can occur with or without sympathetic neural impulses. Laser-Doppler flowmetry can measure reflexive sympathetically mediated responses of skin microvascular flow and so can detect sympathetic denervation. Spontaneous oscillations in this flow may not depend exclusively on oscillations in the activity of the sympathetic microvascular innervation.

Adult↗
PubMed1984

Periodic microcirculatory flow in patients with sickle-cell disease.

We have applied the technique of laser-Doppler velocimetry to compare patterns of cutaneous blood flow in the forearms of patients with stable sickle-cell disease, with the patterns in normal subjects matched for age, race, and sex, and in patients with anemia due to beta+-thalassemia. The mean resting blood flow in the patients with sickle-cell disease was comparable to that of the control groups but was associated with large, local oscillations in flow with periods of 7 to 10 seconds and peak-to-trough magnitudes about half the mean flow. Oscillations occurred simultaneously at sites separated by 1 cm but were independent in phase and frequency. Since these laser-Doppler measurements represent the average flow pattern in about 1 mm3 of skin (i.e., in approximately 50 to 70 capillary loops), these results suggest that microcirculatory flow in patients with sickle-cell disease proceeds by synchronization of rhythmic flow in large domains of microvessels. These findings indicate that periodic flow may be a compensatory mechanism to offset the deleterious altered rheology of erythrocytes containing polymerized hemoglobin S, and suggest that laser-Doppler velocimetry may be a useful method to investigate microvascular physiology in patients with sickle-cell disease.

Adult↗
PubMed1984

Response of nasal blood flow to neurohormones as measured by laser-Doppler velocimetry.

Laser-Doppler velocimetry (LDV) has been adapted to measure nasal blood flow (NBF) in the mucosa of human volunteers. Resting NBF was 42.4 +/- 2.1 ml X 100 g-1 X min-1 in 19 nonatopic subjects and 37.9 +/- 1.7 ml X 100 g-1 X min-1 in 24 atopic subjects. Topical saline, but not water, reduced ipsilateral NBF by 15.4 +/- 6.6% (n = 22) without affecting contralateral NBF. Administration of 60 microgram of oxymetazoline reduced NBF by 26.5% (n = 28), whereas 120 microgram resulted in a 54.3% reduction. Phenylephrine produced a dose-related reduction in NBF with an ID50 (dose producing 50% reduction) of 1,456 microgram. Methacholine (0.006 to 12 mg) had no significant effect on NBF when studied alone or after oxymetazoline pretreatment. Therefore, LDV can be employed to monitor NBF, which has been found to be sensitive to alpha-adrenergic, but not cholinergic, stimulation.

Adolescent↗
PubMed1984

Quantitative assessment of platelet morphology by light scattering: a potential method for the evaluation of platelets for transfusion.

Normal fresh platelets are discoid, and platelets that have been stored become spherical. Discoid morphology correlates with normal viability and imparts to a platelet suspension a "streaming" appearance when agitated. We developed a device that quantitates the percent of discoid cells in a suspension by means of laser light scattering at low angles. It performs this assay within 3 minutes on platelets contained in a plastic blood bag. The ability of the device to quantitate discoid platelets was demonstrated in the following ways: (1) comparison of percentage discs calculated from light-scattering data with visually observed optical streaming; (2) correlation of percentage discs from light scattering with the percentage determined by phase microscopy; and (3) observation of changes during room temperature storage. Platelet suspensions containing extreme (dendritic and balloon) forms were examined, and we conclude that these forms do not significantly affect the light-scattering assay. The optical measurements were also used to accurately approximate the total platelet counts of the suspensions. This device may have a role in the evaluation of platelets for transfusion.

Blood Platelets↗
PubMed1983

A continuous-flow detector for cytochrome P-450 and cytochrome P-420.

A spectrophotometric detector for automatically monitoring levels of cytochrome P-450 and cytochrome P-420 in chromatographic column effluents is described. Levels of cytochrome P-450 and P-420 as low as 30 pmol/ml can be detected above an absorbance background noise equivalent to 10 pmol/ml of these heme proteins. Spectra and the concentrations of cytochrome P-450 and cytochrome P-420 are determined every 5 sec. The automatic flow reactor and detector offer the following advantages over existing manual methods: (i) greatly reduced analysis time, (ii) measurement of a larger number of independent samples than is practical manually, (iii) simultaneous measurement of cytochrome P-450 and its degradation product cytochrome P-420 immediately after elution from the column, thus avoiding further sample degradation, and (iv) greatly increased accuracy and threshold resolution due to highly reproducible reaction conditions and constant optics.

Animals↗
PubMed1983

Threshold for retinal damage associated with the use of high-power neodymium-YAG lasers in the vitreous.

Ultrashort, Q-switched or mode-locked, neodymium-YAG laser pulses focused within 2 mm of the retina caused reproducible retinal damage in four eyes of two monkeys and in four eyes of three rabbits. The distance of the laser focus from the retina for clinically observed threshold retinal damage was characterized for pulse energies up to 9 mJ. For the 2- to 6-mJ pulse energies necessary to rupture vitreal membranes in clear media in rabbits, the high-power laser pulses could not be focused within 2 mm of the retina without substantial risk of damaging the underlying retina. These laser pulses did not rupture vitreal membranes in hazy ocular media that prevented precise focusing. The retinal damage was somewhat greater than expected for retinal absorption of 1.06-micron laser energy, suggesting that secondary effects such as self-focusing and shock waves emanating from the focus may be important.

Absorption↗
PubMed1983

Laser Doppler blood flow studies during open muscle biopsy in patients with neuromuscular diseases.

Laser Doppler measurements of skeletal muscle blood flow were performed in 12 patients with neuromuscular disorders and 6 controls. The mean resting blood flows and postocclusive reactive hyperemias were similar for the patients with neuropathic disorders and for controls. The patients with myopathic disorders had higher resting muscle blood flows and reactive hyperemias. Correlation of blood flow results and muscle biopsy characteristics suggested that muscle type grouping was not associated with a change in skeletal muscle blood flow, whereas muscle fiber degeneration was associated with an increased blood flow.

Adult↗
PubMed1982

Retinal irradiance from vitrectomy endoilluminators.

We compared the maximum light output of selected 19- and 20-gauge continuous-fiber and detachable-tip endoilluminators to the retinal damage threshold for intravitreal fiber-optic light in the owl monkey. Because of cumulative light toxicity to the retina there is a substantial risk of retinal damage from endoillumination when the endoilluminator is close to the retina (for example, during membrane peeling procedures) and especially when the continuous-fiber endoilluminator with high light output is used.

Animals↗
PubMed1975

Structural dynamics of frog muscle during isometric contraction.

Intensity fluctuation autocorrelation functions of laser light scattered by actively contracting muscle were measured at points in the scattered field. They were reproducible and showed characteristics which depended on the physiological state of the muscle and the parameters of the scattering geometry. The autocorrelation functions had large amplitudes and decay rates that varied significantly with the phase of the contraction-relaxation cycle. The dependence of the autocorrelation function on scattering geometry indicated many elements with diameters on the order of 0.5 mum (presumed to be myofibrillar sarcomeres or their A bands or I bands) undergo independent random changes in their axial positions and their internal distribution of optical polarizability during the plateau of an isometric tetanus. The experimental results are interpreted in terms of a model in which most of the scattering elements in isometrically contracting muscle have random fluctuating axial velocities of average magnitude 20 nm/ms that persist for a few milliseconds at least. In addition to these axial motions there are local fluctuations in polarizability. Similar intensity fluctuation autocorrelation functions were observed throughout the active state on two muscle preparations, whole sartorius muscle and small bundles of single fibers (three to eight) of semitendinosus muscle. These results imply that the tension developed during an isometric tetanus contains a fluctuating component as well as a constant component.

Animals↗
PubMedDate not supplied

Protection from radiation-induced alopecia with topical application of nitroxides: fractionated studies.

PURPOSE: Hair loss resulting from irradiation of the head and neck or from whole brain irradiation often leads to cosmetic, social, and psychological problems for the radiotherapy patient. Few successful clinical interventions are available. We have shown that nitroxides (stable free radicals) afford radiation protection against single-dose radiation-induced alopecia in a guinea pig model. Here we determine if topical nitroxide application provides protection from fractionated radiation treatment. MATERIALS AND METHODS: Two symmetrical and contralateral areas (3 x 5 cm) of skin on the dorsal trunk of guinea pigs were shaved to a hair length of 0.25 cm. A 2 mL solution containing 70 mg/mL nitroxide (Tempo or Tempol) in 70% ethanol was topically applied to the skin surface of one side; 70% ethanol was applied to the contralateral (control) side 10 minutes before irradiation. Animals were placed in a special jig that held skin without decreasing blood flow to the treatment area and fractionated external beam radiation (7 Gy) was delivered daily for eight fractions over 10 days via a 4 MeV linear accelerator. Alopecia (hair density) was scored weekly for 13 to 14 weeks after radiotherapy, using a standardized reference with respect to hair loss and regrowth in the treatment field. RESULTS: After radiation treatment, dry desquamation and gradual hair loss were observed for both control and nitroxide-treated skin; however, over weeks 4 to 11 postirradiation hair loss was much more pronounced in control animals when compared with nitroxide-treated animals. Hair density measurements for Tempol treatment over weeks 9 to 13 were approximately 75% compared with measurements in controls of approximately 25%. Tempo-treated animals exhibited hair density values of approximately 90% compared with 12% in controls over weeks 11 to 14. Tempol and Tempo treatments resulted in significant radioprotection. Histologic evaluation showed that radiation treatment alone in ethanol controls resulted in a marked decrease in the number of hair follicles and poor development of remaining follicles; however, nitroxide pretreatment resulted in no appreciable decrease in hair follicles and hair follicles appeared mature. This was also observed in unirradiated ethanol controls. Electron paramagnetic resonance studies revealed that topical nitroxide application did not result in measurable systemic concentrations of either drug. CONCLUSIONS: The results of this study suggest that topical application of nitroxides may be useful in a clinical setting to reduce the undesirable toxicity of radiation-induced alopecia.

Administration, Topical↗