The use of biomedical sensors to monitor capsule formation around soft tissue implants.

Piezoelectric sensors have been shown to respond reproducibly to changes in tissue mechanical properties surrounding an implant over a 4-month period. The vibrational amplitude at a frequency corresponding to the radial resonance shows a statistically significant change over time. The initial period of inflammation is marked by a significant reduction in amplitude, which is indicative of an increase in viscous dissipation of the tissue. As collagen displaces the cellular response, the amplitude continues to decrease. Finally, as the tissue matures, the capsule becomes stiffer, and the viscous dissipation lessens. These results are consistent with qualitative assessments of explanted capsules. Strain gauges encased in a monolithic block of silicone exhibited a greater degree of variability, yet show similar trends over time. The strain increases in the initial 4-week period and remains relatively steady over the following 4 weeks. Beyond 8 weeks, the gauges begin to extrude from the animal or suffer a loss of electrical continuity. Steps are being taken to improve the strain sensor longevity in the animals.

Bridging the gap between macro- and nanotribology: a quartz crystal microbalance study of tricresylphosphate uptake on metal and oxide surfaces.

We report a quartz crystal microbalance study of the nanodynamical properties of tricresylphosphate (TCP) reaction films formed on high purity Fe, Cr, Fe oxide, and Cr oxide surfaces at elevated temperatures. The data reveal trace levels of interfacial slippage, potentially in conjunction with viscoelastic effects, for reaction films characterized by very low macroscopic friction coefficients. In contrast, rigidly attached TCP reaction films are observed in systems characterized by high macroscopic friction coefficients.

Combined atomic force microscopy and scanning tunneling microscopy imaging of cross-sectioned GaN light-emitting diodes.

Cross-sectional scanning tunneling microscopy (STM) was combined with atomic force microscopy (AFM) over the same area to characterize a cross-sectioned GaN light emitting diode. Because GaN is typically grown on a non-native substrate and also forms a wurtzite crystal structure, a cryogenic cleaving technique was developed to generate smooth surfaces. The depletion region surrounding the p-n junction was clearly identified using STM. Furthermore, by imaging under multiple sample biases, distinctions between the n-doped and p-doped GaN could be made.

Unique antithymocyte serum versus OKT3 for induction immunotherapy after heart transplantation.

To determine the efficacy of a unique polyclonal rabbit antithymocyte serum (ATS), we compared 17 consecutive nonrandomized heart transplant recipients (mean age, 38 +/- 15 years) given a 7-day prophylactic postoperative course of locally produced ATS (whole serum, no Freund's adjuvant, IV) with 19 patients (mean age, 42 +/- 17 years) given 14 days of monoclonal antibody OKT3. Cyclosporine, steroid, and azathioprine dosages were similar. At 30 days the event-free incidence of rejection was 66% +/- 11% for OKT3 (2.3 events/100 patient-days) versus 47% +/- 12% for ATS (1.2 events/100 patient-days). At 60 days and thereafter, however, there was no difference in overall number of cumulative rejection episodes. Overall infection rates were similar in both groups: the ATS group tended to have more bacterial infections, whereas the OKT3 group displayed more viral infections. Antiidiotypic antibodies developed in 29% of the ATS group and in 22% of the OKT3 group. This report demonstrates the efficacy of this polyclonal serum preparation made without Freund's adjuvant when used as an adjunct for induction-prophylactic immunotherapy in heart transplant recipients when compared with OKT3.

Molecular stability and function of hemoglobins Hasharon (alpha(2)47 (CD5)Asp----His beta 2) and Hasharon (alpha(2)47 (CD5)Asp----His delta 2).

The molecular stability and function of hemoglobin (Hb) Hasharon (alpha 2 H beta 2) and Hb Hasharon2 (alpha 2 H delta 2) were studied and compared to Hbs A, A2 and S. Hb Hasharon and Hb Hasharon2 had slightly lower P50 values than Hb A and Hb A2 but had normal responses to organic phosphates. The molecular stability of Hb Hasharon and Hb Hasharon2 (as measured by mechanical shaking and heat denaturation at 60 degrees C) were less than Hb A and Hb A2 but greater than Hb S in the oxy- and carbonmonoxy-forms. In the met-form, however, Hb Hasharon and Hb Hasharon2 were less stable than hemoglobins S, A and A2. The oxy-form of Hb Hasharon forms methemoglobin at a faster rate than Hb A and Hb S. The mechanical and heat stabilities and the rate of methemoglobin formation of oxy-Hb Hasharon were studied in the presence of sulfisoxazole. This drug increased the rate of methemoglobin formation, thus causing a further decrease in the stability of Hb Hasharon. The relationship between these laboratory findings and previously observed clinical findings associated with Hb Hasharon are discussed.

Precipitation of oxyhemoglobins A and S by isopropanol.

The isopropanol precipitation test is widely used for the detection of unstable hemoglobins. A method for accurately and easily determining the amount of hemoglobin precipitated is described. This study demonstrates that changes in incubation time, pH, temperature, and isopropanol and hemoglobin concentrations affect the precipitation of oxy Hb A and oxy Hb S. Hb S shows greater precipitation than Hb A with increasing time, temperature, and isopropanol concentrations. Both hemoglobins show equal increases in precipitation, with increases and decreases in pH and decreases in hemoglobin concentration. Comparison of the isopropanol precipitation test with the mechanical shake and heat denaturation tests reveals that the mechanical shake test is the easiest method to study the stability of Hbs A and S. Each of the tests may measure different parameters of stability. The use of all three tests in the evaluation of unstable hemoglobins should be considered.

The effect of VP 16-213 on NBT reduction in the normal polymorphonuclear neutrophil.

VP 16-213, an antineoplastic, semisynthetic podophyllotoxin derivative, inhibits NBT reduction in the polymorphonuclear neutrophil (PMN). In the resting PMN an almost complete inhibition is seen at a concentration of 170 microM and a partial inhibition is seen at 17 microM. In PMN's stimulated with zymosan activated serum, partial inhibition is seen at concentrations of both 170 microM and 17 microM. VP 16-213 shows no significant inhibition of NBT reduction in PMN's stimulated by methylene blue. VP 16-213 may alter normal respiratory function in the PMN as reflected by inhibition of NBT reduction.

Fatal Staphylococcus epidermidis sepsis following bone marrow transplantation.

Staphylococcus epidermidis septicemia and pneumonia developed in an 18-year-old male undergoing bone marrow transplantation. The organism was isolated from multiple blood cultures, sputum cultures, an indwelling catheter tip and post-mortem lung biopsy specimens. The bacterium was resistant to penicillin, erythromycin, clindamycin, chloramphenicol, vancomycin, gentamicin, cephalothin and trimethoprim-sulfamethoxazole, but was sensitive to rifampin. The rapid demise of this patient, as well as the difficulty in achieving effective antibiotic therapy, illustrates the potential pathogenicity of this organism in immunosuppressed patients.

Serum phosphodiesterase I activity in breast cancer patients.

Serum phosphodiesterase I (PDE I) activity was determined in 13 control and 51 breast-cancer patients with various stages of disease. Patients with both localized and metastatic breast cancer had significantly elevated serum PDE I activity. The highest activity was seen in patients with liver metastases. A decline in serum PDE I activity was seen after surgical resection of all known disease.

Angiotensin-I-converting enzyme activity in term and premature infants.

Cord blood angiotensin-I-converting enzyme (ACE) activity was examined in 21 term and 21 premature infants. Values were significantly higher in premature infants than in term infants. Cord blood ACE activity was found to have a significant negative correlation with birth weight and gestational age. ACE activity measured from peripheral blood during the first 24 h of life was higher in premature than term infants but similar to levels in maternal and adult controls. It was not possible to predict those premature infants who would develop respiratory distress syndrome on the basis of cord blood ACE activity. However, ACE may serve as a marker for maturation of the pulmonary vascular endothelial cell.

The reversible reduction of horse metmyoglobin by the iron(II) complex of trans-1,2-diaminocyclohexane-N,N,N,n-tetraacetate.

The reduction of metmyoglobin by the iron(II) complex of trans-1,2-diaminocyclohexane-N,N,N'N'-tetraacetate (FeCDTA2-) has been investigated. The equilibrium constant, measured spectrophotometrically, is 0.21 with a resulting reduction potential of 0.050 V for Mb0. The rate constant for the reduction is 28 M-1 sec-1 with a deltaH ++ of 13 kcal M-1 and deltaS ++ of -11 eu. Both CN- and OH- inhibit the reduction because of the relatively low reactivity of cyanometmyoglobin (Mb+CN-) and ionized metmyglobin (Mb+OH-). The rate constant for the reduction of Mb+CN- by FeCDTA2- is 4.0 X 10(-2) M-1 sec-1 and that for reduction of Mb+OH- is 4.8 M-1 sec-1. The nitric oxide complex of metmyoglobin is reduced with a rate constant of 10 M-1 sec-1. The kinetics of oxidation of oxymyoglobin by FeCDTA- were studied. The data are consistent with a mechanism where oxidation takes place entirely through the deoxy form. A rate constant of 1.45 X 10(2) M-1 sec-1 was calculated for the oxidation of deoxymyoglobin by FeCDTA-, in equilibrium constant and rate constant for reduction. The above data are discussed in terms of a simple outer-sphere reduction reaction.