Some Laser-Tissue Interactions in 308 nm Excimer Laser Coronary Angioplasty

Some physical concepts of laser-tissue interactions that occur in 308-nm excimer laser angioplasty are addressed. Monte Carlo numerical computations were used to analyze the light fluence rate distributions resulting from finite diameter laser beams incident on tissue, as applied by fiber-optic light delivery catheters. The fluence rate at the inside part of the tissue surface from a 0.2-mm diameter fiber emitting 308-nm light, is increased more than twice relative to the incident power density. The light fluence rate distribution inside the tissue spreads very little outside the incident beam diameter. Therefore, the distributions from different fibers in multifiber catheters will not overlap unless the fibers are very close together. The maximum fluence rate decreases with decreasing beam diameters. Ablation of tissue by a 308-nm excimer laser delivery system in contact with the tissue resulted in a damage zone adjacent to the crater wall, due to expansion of the gaseous debris trapped under the tip of delivery system. In case of contact irradiation, the ablation was more efficient than in case of noncontact irradiation. Direct temperature measurements during excimer laser ablation by an infared (IR) camera showed that temperature accumulation will occur when a sequence of pulses is applied at frequencies of at least 5 Hz. The temperature rise above ambient under circumstances simulating clinical conditions is measured to be 66°± 7°C.     

Ocular Melanoma Metastatic to Skin: The Value of HMB-45 Staining

BACKGROUND: Cutaneous metastatic disease is an important finding that may represent the first sign of systemic cancer, or, if already known, that may change tumor staging and thus dramatically altered therapeutic plans. Although cutaneous metastases are relatively frequent in patients with cutaneous melanoma, they are less so from ocular melanoma. OBJECTIVE: To demonstrate the value of HMB-45, staining in the detection of ocular melanoma metastatic to skin. METHODS: The immunohistochemical stain HMB-45 a monoclonal antibody directed against intact human melanoma cells, was employed on a skin biopsy specimen from a cutaneous tumor. Results: HMB-45 staining was positive in the atypical hyperchromatic cells of the deep dermis. CONCLUSION: HMB-45 may be of value in the detection of ocular melanoma metastatic to skin. Cutaneous metastatic disease is a somewhat common and extremely important diagnosis. Although cutaneous metastases from cutaneous melanoma are relatively frequent, those from ocular melanomas are less so. Use of histochemical staining, especially the HMB-45 stain, allows confirmation of the diagnosis.     

Molluscum Contagiosum Treated with Iodine Solution and Salicylic Acid Plaster

Twenty cases of molluscum have been evaluated for the clinical effectiveness of 10% PVP-iodine solution and 50% salicylic acid plaster therapy. The treatment works well, and the shorter duration of treatment necessary for healing is statistically significant as compared with the duration of treatment for controls who lacked either one of the applications. Although the working mechanism for the effectiveness is not known, the treatment is characterized as a less expensive and less painful procedure. All patients were completely healed after a mean treatment of 26 days; there were no adverse effects. This therapy is recommended for the office patient, young children, diabetic patients, and those with multiple lesions.     

Plasmapheresis in a patient with severe asthma associated with auto-antibodies to platelets

Although the pathogenesis of aspirin-sensitive asthma remains to be specified, it is known that in the presence of acetylsalicylic acid or non-steroidal anti-inflammatory drugs, platelets from aspirin-sensitive asthmatics have been described as generating cytocidal mediators that killed parasite targets such as Schistosoma mansoni larvae. Here we report, in a patient with corticosteroid-dependent asthma associated with aspirin sensitivity, the presence of circulating IgE antibodies against 55 kD and 68 kD platelet antigens. In addition, the serum from this patient was shown to contain a factor able to trigger the release of cytocidal mediators from his platelets as well as from normal individual platelets. This platelet stimulatory activity was presumably supported by IgE antibodies or immune complexes. After informed consent the patient was submitted to plasma exchanges. Plasma removal induced clinical improvement, anti-platelet antibody decrease, and the reduction of the platelet stimulatory activity. All clinical symptoms disappeared within 2 weeks. The disease remained quiescent for 2 months, and daily requirements for prednisone (20-5 mg), and beta-agonist (10-16 to 0-1 inhalations) could be kept at a low level follow-up. The plasma exchanges were delayed by 3 mg kg-1 azathioprine with the maintenance of clinical improvement. A relapse occurred after the arrest of immunosuppressive therapy with the reappearance of both asthma attacks and anti-platelet antibodies, as well as the increase of the platelet stimulatory activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

The Vulnerable Window for Unidirectional Block in Cardiac Tissue:

Vulnerable Window of Unidirectional Block. Introduction: Unidirectional block is a requisite event in the initiation of reentry in cardiac tissue, but its initiation and behavior in the presence of tissue pathologies remain poorly understood. Previous experimental and theoretical reports on vulnerability to unidirectional block under conditions of reduced cellular coupling and reduced membrane excitability have varied due to differences in experimental and simulation protocols. Methods and Results: We have addressed the issue of vulnerability to unidirectional block using the recent Luo-Rudy membrane model and computer simulations of propagation in a one-dimensional cardiac fiber. The vulnerable window (VW) of unidirectional block from premature stimulation is expressed in units of time, VW_time, and as a range of membrane potentials at the stimulus site, VW_pot VW_pot and VW_time, were quantified over a range of membrane excitability and gap junction resistances (intercellular coupling). With normal membrane excitability and intercellular coupling, VW_pot, and VW_time, were small (VW_Pot, = 0.44 mV, VW_time, = 0.39 msec). A uniform reduction (0.25 ×) in the degree of intercellular coupling increased VW_time, and VW_pot, by factors of 3.6 and 4.7, respectively, whereas a uniform decrease (0.25 ×) in membrane excitability (same resulting velocity) increased VW_time, by only a factor of 0.4 and decreased VW_pot, to negligible levels. When inhomogeneities in fiber properties were introduced (intercellular coupling and membrane excitability), VW_time, increased more due to inhomogeneity in membrane excitability (VW_time= 4.5 msec) than to inhomogeneity in intercellular coupling (VW_time, = 1.5 msec). The simulations also clarify the dependence of the VW on the dimensions of the stimulating electrode. The length of the stimulating electrode added a factor, equal to the propagation time across the eiectrode length, to the intrinsic VW of the fiber. Conclusions: VW_pot, and VW_time, are both important parameters for quantifying vulnerability to unidirectional block. In an environment with uniform distribution of fiber and membrane properties, reduced intercellular coupling bas a greater effect on the VW than reduced membrane excitability. Inhomogeneous reduction of membrane excitability can significantly enhance vulnerability to unidirectional block, much more so than inhomogeneous reduction of intercellular coupling. Theoretically, stimulation at a point should be used to define the VW. Finite electrode dimensions introduce a geometrical factor that affects the measurement of the VW.     

Interpretation of Biophysical Profiles by Nurses and Physicians

Objective: To determine the agreement between nurse and physician interpretation of biophysical profile scores.
Design: A prospective evaluation of videotaped biophysical profiles was independently scored by four nurse and four physician interpreters and compared to that of an expert physician.
Setting: The fetal assessment center of a large tertiary-care center; study included women from public and private practices.
Patients: Twenty-three women with high-risk pregnancies who were regularly scheduled for a biophysical profile. Women pregnant with multiple fetuses or whose fetuses were less than 28 weeks' gestational age or had severe fetal anomalies were excluded.
Main Outcome Measure: The proportion of agreement between the physicians and nurses and the physician expert was calculated for each biophysical profile criterion.
Results: The kappa statistic was used to evaluate the proportion of agreement with the "gold standard." When compared with the expert, physicians showed 60% moderate or substantial agreement, and the nurses showed 80% moderate or substantial agreement.
Conclusions: Nurses' interpretations of biophysical profiles were at least as reliable as physicians' when compared with an expert reviewer.