Real-time monitoring of adhesion and aggregation of platelets using thickness shear mode (TSM) sensor.

Hemostasis is required to maintain vascular system integrity, but thrombosis, formation of a clot in a blood vessel, is one of the largest causes of morbidity and mortality in the industrialized world. Novel clinical and research tools for characterizing the hemostatic system are of continued interest, and the object of this research is to test the hypothesis that clinically relevant platelet function can be monitored using an electromechanical sensor. A piezoelectric thickness shear mode (TSM) biosensor coated with collagen-I fibers to promote platelet activation and adhesion was developed and tested for sensitivity to detect these primary events. Magnitude and frequency response of the sensor were monitored under static conditions at 37 degrees C, using platelet-rich plasma (PRP), and PRP with adenosine diphosphate (ADP), a clinical aggregation inhibitor (abciximab), or a collagen binding inhibitor. Sensors loaded with PRP exhibited a 3-stage response; no significant change in response for the first 20 min (Stage-1), followed by a larger drop in response (Stage-2) and subsequently, response gradually increased (Stage-3). Exogenous ADP stimulated an immediate Stage-2 response, while abciximab delayed and reduced the magnitude change of Stage-2. In the presence of collagen inhibitor, Stage-2 response was similar to that of control but was delayed by an additional 20 min. The obtained results, supported by epifluorescence and complementary SEM studies, demonstrated the selective sensitivity of TSM electromechanical biosensors to monitor platelet function and inhibition, particularly aggregation.

Browpexy: lateral orbicularis muscle fixation as an adjunct to upper blepharoplasty.

Lateral ptosis of the eyebrow is a major part of the complex changes that patients are seeking to improve with an upper blepharoplasty. Two hundred and eight patients have undergone a browpexy procedure at the time of blepharoplasty. This operative maneuver, which is performed through the blepharoplasty incision, prevents the brow from dropping below the superior orbital rim and creates a defined tarsal sulcus to produce a sculptured upper eyelid.

Error and artefact in post mortem toxicological analysis.

The factors which may influence the result of a toxicological analysis on post mortem specimens are presented. These factors are discussed in varying depth and suggestions are made on ways of overcoming the problems.

Image-based three-dimensional finite element modeling approach for upper airway mechanics.

The goal of the project is to investigate new computational tools for understanding normal upper airway mechanics and the pathophysiology of obstructive sleep apnea (OSA), a disorder characterized by repetitive pharyngeal collapse and occlusion during sleep. To relate the airway mechanical parameters to anatomy, and explore the roles of primary muscle properties, airway shape and structure, a new computational system for modeling of rat upper airway passive mechanics based on magnetic resonance imaging (MRI) was developed. The model is capable of computing stress and strain distributions under arbitrary loading, and dynamic animation of three-dimensional airway motion.

Semiautomated spectrophotometry of total phospholipids in plasma.

A one-stage semiautomated method for estimating total phospholipids in plasma is reported. The phospholipids are extracted into aqueous ethanol, combined with a Lewis acid, and the change in pH is monitored colorimetrically. The method, compared with the acid digestion method of Gomori [J. Lab. Clin. Med. 27, 955 (1942)], gives results that are about 0.25 mmol/liter lower, but seems to be a suitable and less hazardous alternative.

Fluid mechanics of vascular systems, diseases, and thrombosis.

The cardiovascular system is an internal flow loop with multiple branches circulating a complex liquid. The hallmarks of blood flow in arteries are pulsatility and branches, which cause wall stresses to be cyclical and nonuniform. Normal arterial flow is laminar, with secondary flows generated at curves and branches. Arteries can adapt to and modify hemodynamic conditions, and unusual hemodynamic conditions may cause an abnormal biological response. Velocity profile skewing can create pockets in which the wall shear stress is low and oscillates in direction. Atherosclerosis tends to localize to these sites and creates a narrowing of the artery lumen--a stenosis. Plaque rupture or endothelial injury can stimulate thrombosis, which can block blood flow to heart or brain tissues, causing a heart attack or stroke. This small lumen and elevated shear rate in a stenosis create conditions that accelerate platelet accumulation and occlusion. The relationship between thrombosis and fluid mechanics is complex, especially in the post-stenotic flow field. New convection models have been developed to predict clinical from platelet thrombosis in diseased arteries. Future hemodynamic studies should address the complex mechanics of flow-induced, large-scale wall motion and convection of semisolid particles and cells in flowing blood.

A mechanistic model of acute platelet accumulation in thrombogenic stenoses.

Thrombosis on an atherosclerotic lesion can cause heart attack or stroke. Thrombosis may be triggered by plaque rupture or erosion, creating a thrombogenic stenosis. To measure and model this situation, collagen-coated stenoses have been exposed to nonanticoagulated blood in a baboon ex vivo shunt. The maximum rate of platelet accumulation, measured using a gamma camera, was highest in the throat region of moderate and severe stenoses, and increased with increasing stenosis severity. A species transport model of platelet accumulation was developed, which included mechanisms of convection, shear-enhanced diffusion, near-wall platelet concentration, and a kinetic model of platelet activation and aggregation. The model accurately reproduced the average spatial pattern and time rate of platelet accumulation in the upstream and throat regions of the stenosis, where shear-enhanced diffusivity increased platelet transport in the stenosis throat. Downstream of the throat where flow is complicated by recirculation, the model computed a transport-limited region with lower than measured platelet accumulation, suggesting that fluid-phase platelet activation may significantly affect both transport and adhesion rates in the poststenotic region. This model may provide an initial quantitative estimate of the likelihood of occlusive thrombus in individual patients due to plaque erosion, artery spasm, incomplete angioplasty, or plaque rupture.

A technic of general anesthesia for blepharoplasty and rhytidectomy.

A series of 66 consecutive cases of blepharoplasty and rhytidectomy are reported, 60 of which were performed with a general anesthesia technic utilizing local anesthesia with epinephrine, in association with enflurane inhalation delivered via bilateral nasopharyngeal airways (BNPA). Six cases were not suitable candidates for the technic because of physical status or for anatomic reasons. The technic has teh advantage of providing airway control without tracheal intubation, light depth of anesthesia, compatibility with epinephrine, and highly acceptable limits of intraoperative bleeding and postoperative hematoma.

Desmoid tumor occurring after reconstruction mammaplasty for breast carcinoma.

We present a case of desmoid tumor associated with prior alloplastic breast reconstruction. Wide local excision that includes chest wall resection, if necessary, is the primary treatment of choice. Patients with extensive nonresectable or recurrent disease may benefit from radiation therapy. Systemic therapy is a possibility in certain cases, but its toxicity generally precludes its use with this nonmetastatic tumor. Although this is the fourth reported case of desmoid tumor arising after implantation of a silicone prosthesis, we cannot claim a causal relationship. Careful follow-up consisting of yearly physical and mammagraphic examinations may facilitate early diagnosis and treatment of locally aggressive desmoid tumors but is not warranted, except in the context of routine screening for breast carcinoma.

Endothelial-dependent vasodilation is associated with increases in the phosphorylation of a small heat shock protein (HSP20).

PURPOSE: Increases in the phosphorylation of a small heat shock protein (HSP20) are associated with cyclic nucleotide-dependent vasorelaxation. The effect of pressure and flow on vessel diameter was studied. We hypothesized that physiologic conditions that induce vasorelaxation would lead to increases in HSP20 phosphorylation. METHODS: Flow-dependent changes in vessel diameter, at different intraluminal pressures, were measured with a laser optical micrometer in intact bovine carotid arteries. Experiments were performed in the presence and absence of norepinephrine (10(-5) mol/L). Increases in the phosphorylation of HSP20 were determined with isoelectric focusing immunoblots. RESULTS: The increase in vessel diameter was most significant at low intraluminal pressures (20 mm Hg), high flow rates (200 mL/min), and in the presence of the vasoconstrictor norepinephrine (10(-5) mol/L). The addition of methylene blue (a guanylate cyclase inhibitor) completely inhibited flow-induced vasodilation. Under conditions in which maximal flow induced vasodilation occurred, there were significant increases in the phosphorylation of HSP20. CONCLUSION: Flow-dependent vasodilation in isolated perfused segments of bovine carotid arteries was maximal when the intraluminal pressures were low and when the vessels were precontracted with norepinephrine. Flow-dependent vasodilation was inhibited by methylene blue and was associated with increases in the phosphorylation of HSP20, suggesting that the vasodilation was mediated by endothelial production of nitric oxide.