Fractured Whiteside Ortholoc II knee components

A comprehensive failure analysis was performed on 6 femoral components and 1 tibial component that fractured in service. All were Whiteside Ortholoc II total knee arthroplasty components, manufactured from cast cobalt-chromium-molybdenum alloy and porous coated. Fracture surface analysis revealed fatigue-induced failure in all cases. Most fractures occurred at regions of high stress concentration, such as sharp corners, sintered beads, and thin sections. Metallurgical examination showed significant variation in grain size, interdendritic carbides, and hardness between samples. In some cases, continuous carbide networks and voids were prominent at the bead-substrate interface. Patient weight and surgical placement were identified as contributory factors in component failure. Limitations of cast cobalt-chromium-molybdenum alloy in weight-bearing applications must be emphasized, particularly when important determinants, such as design, metallurgy, and specific clinical factors, are less than optimal.

Pyridoxine and pyridoxamine inhibits superoxide radicals and prevents lipid peroxidation, protein glycosylation, and (Na+ + K+)-ATPase activity reduction in high glucose-treated human erythrocytes

Vitamin B(6) (pyridoxine) supplementation has been found beneficial in preventing diabetic neuropathy and retinopathy, and the glycosylation of proteins. Oxygen radicals and oxidative damage have been implicated in the cellular dysfunction and complications of diabetes. This study was undertaken to test the hypothesis that pyridoxine (P) and pyridoxamine (PM) inhibit superoxide radical production, reduce lipid peroxidation and glycosylation, and increase the (Na+ + K+)-ATPase activity in high glucose-exposed red blood cells (RBC). Superoxide radical production was assessed by the reduction of cytochrome C by glucose in the presence and absence of P or PM in a cell-free buffered solution. To examine cellular effects, washed normal human RBC were treated with control and high glucose concentrations with and without P or PM. Both P and PM significantly lowered lipid peroxidation and glycated hemoglobin (HbA(1)) formation in high glucose-exposed RBC. P and PM significantly prevented the reduction in (Na+ + K+)-ATPase activity in high glucose-treated RBC. Thus, P or PM can inhibit oxygen radical production, which in turn prevents the lipid peroxidation, protein glycosylation, and (Na+ + K+)-ATPase activity reduction induced by the hyperglycemia. This study describes a new biochemical mechanism by which P or PM supplementation may delay or inhibit the development of complications in diabetes.

Overcoming challenges in newborn hearing screening

Retrospective hearing screening data were analyzed on 66,292 newborns to assess factors which contribute to overall program success, especially those related to tracking and follow-up of positive initial hearing screens. Newborn hearing screens were performed in 46 sites within five regions utilizing automated auditory brainstem response (AABR) technology. Pediatrix Medical Group managed all 46 sites and tracked all positive screens under the direction of the national program director. One hundred and fourteen newborns were confirmed with hearing loss, with 60% exhibiting no known risk factors. The five regions collectively yielded a final refer rate of 1.01% over a 1-year period, whereas two of the five regions boasted capture rates of 98%. Fifty percent of the confirmed hearing losses was bilateral in nature. Several key factors were noted to have a positive impact on the overall success of the program as related to follow-up. This paper demonstrates that tracking and follow-up can be successful if program management and implementation are considered when establishing a newborn hearing screening program. The protocol presented can be viewed as a model for existing programs by those who are interested in overcoming challenges related to follow-up and can ensure program success.

Lipoic acid decreases lipid peroxidation and protein glycosylation and increases (Na(+) + K(+))- and Ca(++)-ATPase activities in high glucose-treated human erythrocytes

Lipoic acid supplementation has been found to be beneficial in preventing neurovascular abnormalities in diabetic neuropathy. Insufficient (Na(+) + K(+))-ATPase activity has been suggested as a contributing factor in the development of diabetic neuropathy. This study was undertaken to test the hypothesis that lipoic acid reduces lipid peroxidation and glycosylation and can increase the (Na(+) + K(+))- and Ca(++)-ATPase activities in high glucose-exposed red blood cells (RBC). Washed normal human RBC were treated with normal (6 mM) and high glucose concentrations (45 mM) with 0-0.2 mM lipoic acid (mixture of S and R sterioisomers) in a shaking water bath at 37 degrees C for 24 h. There was a significant stimulation of glucose consumption by RBC in the presence of lipoic acid both in normal and high glucose-treated RBC. Lipoic acid significantly lowered the level of glycated hemoglobin (GHb) and lipid peroxidation in RBC exposed to high glucose concentrations. High glucose treatment significantly lowered the activities of (Na(+) + K(+))- and Ca(++)-ATPases of RBC membranes. Lipoic acid addition significantly blocked the reduction in activities of (Na(+) + K(+))- and Ca(++)-ATPases in high glucose- treated RBC. There were no differences in lipid peroxidation, GHb and (Na(+) + K(+))- and Ca(++)-ATPase activity levels in normal glucose-treated RBC with and without lipoic acid. Thus, lipoic acid can lower lipid peroxidation and protein glycosylation, and increase (Na(+) + K(+))- and Ca(++)-ATPase activities in high-glucose exposed RBC, which provides a potential mechanism by which lipoic acid may delay or inhibit the development of neuropathy in diabetes.

Tunable stimulated-Brillouin-scattering resonator started by feedback provided by Bragg scattering from the dynamic grating within an active medium

We report a tunable stimulated-Brillouin-scattering resonator that does not require a starting mirror or a wavelength selector. The resonator is based on the Bragg scattering from the dynamic grating within the active medium itself. The laser dye (Rhodamine 6G dissolved in ethanol) was utilized as the active medium and was pumped by a frequency-doubled Nd:YAG laser. The quality factor (M(2)) of the output beam was 2.2. A single short pulse (<1 ns) with a pumping efficiency of ~4% was observed.

An application of polarized domains in ferroelectric thin films using scanning probe microscope

The feasibility of utilizing PZT films as future data storage media was investigated using a modified AFM. Applying voltages between a conductive AFM tip and the PZT films causes the switching of ferroelectric domains. The domains are observed using an EFM imaging technique. The experimental results and calculations revealed that the electrostatic force generated between the polarized area and the tip is a main contributor for the imaging of the polarized domains. The written features on ferroelectric films were less than 100 nm in diameter, implying the possibility of realizing data storage devices with ultra-high area density. The disappearance of the polarized images without any applied voltage was observed, which is a drawback in this application of PZT thin films.

Transbuccal permeation of a nucleoside analog, dideoxycytidine: effects of menthol as a permeation enhancer

The use of a safe and effective permeation enhancer is paramount to the success of a buccal drug delivery system intended for systemic drug absorption. The enhancing effects of menthol (dissolved in an aqueous buffer in the absence of co-enhancers) on buccal permeation of a model hydrophilic nucleoside analog, dideoxycytidine (ddC), were investigated. In vitro transbuccal permeation of ddC was examined using freshly obtained porcine buccal mucosa. The experiments were carried out in side-bi-side flow through diffusion cells. Permeation enhancement studies were performed with varying concentrations of l-menthol dissolved in Krebs buffer solutions containing ddC. Partition coefficient experiments were carried out to probe into the mechanism of permeation enhancing properties of l-menthol and DSC studies were conducted to determine if there is a eutectic formation between ddC and l-menthol at various concentrations. Permeation of ddC increased significantly (P<0.05) in the presence of l-menthol independent of the concentration of the terpene. The apparent 1-octanol/buffer partition coefficient (log K(p)) of ddC was significantly (P<0.05) increased in presence of l-menthol and was also independent of the enhancer concentration. However, the tissue/buffer partition coefficient (log K'(p)) data showed a concentration dependent increase of log K'(p) in presence of l-menthol. Since log K'(p) is a measure of drug binding to the tissue in addition to drug partitioning, binding of ddC to the buccal tissue may provide an explanation for the concentration dependent increase in these values.

Effect of hyperketonemia on plasma lipid peroxidation levels in diabetic patients

OBJECTIVE

This study was undertaken to examine the effect of ketosis on plasma lipid peroxidation levels in diabetic patients.

RESEARCH DESIGN AND METHODS

Plasma levels of lipid peroxidation products (malondialdehyde) and ketone bodies (acetoacetate and beta-hydroxybutyrate) were determined in diabetic patients (n = 70) and age-matched normal volunteers (n = 25). Diabetic patients with total ketone body levels > 1.0 mmol/l were considered hyperketonemic, and those with levels < or = 1.0 mmol/l were considered normoketonemic.

RESULTS

After normalization versus total lipids, levels of lipid peroxidation were significantly higher in the plasma of hyperketonemic diabetic patients (P < 0.05), but not in normoketonemic diabetic patients, compared with age-matched normal volunteers. In addition, low ketonemia was associated with lower lipid peroxidation levels when lipid peroxidation and ketonemia were determined in the same patient (n = 7) at two different clinic visits.

CONCLUSIONS

This study demonstrated an association between hyperketonemia and increased lipid peroxidation levels in diabetic patients, which suggests that ketosis is a risk factor in the elevated lipid peroxidation levels associated with diabetes. Further investigation is needed to determine whether antioxidant supplementation can be particularly beneficial in reducing lipid peroxidation and complications in type 1 diabetic patients who frequently encounter ketosis.

Ketosis (acetoacetate) can generate oxygen radicals and cause increased lipid peroxidation and growth inhibition in human endothelial cells

Elevated level of cellular lipid peroxidation can increase the incidence of vascular disease. The mechanism by which ketosis causes accelerated cellular damage and vascular disease in diabetes is not known. This study was undertaken to test the hypothesis that elevated levels of ketone bodies increase lipid peroxidation in endothelial cells. Human umbilical venous endothelial cells (HUVEC) were cultured for 24 h at 37 degrees C with ketone bodies (acetoacetate, beta-hydroxybutyrate). Acetoacetate, but not beta-hydroxybutyrate, caused an increase in lipid peroxidation and growth inhibition in cultured HUVEC. To determine whether ketone bodies generate oxygen radicals, studies using cell-free buffered solution were performed. They showed a significant superoxide dismutase (SOD) inhibitable reduction of cytochrome C by acetoacetate, but not by beta-hydroxybutyrate, suggesting the generation of superoxide anion radicals by acetoacetate. Additional studies show that Fe2+ potentiates oxygen radical generation by acetoacetate. Thus, elevated levels of ketone body acetoacetate can generate oxygen radicals and cause lipid peroxidation in endothelial cells, providing a possible mechanism for the increased incidence of vascular disease in diabetes.

Overlay blot identification of GTP-binding proteins in mitochondria from human placenta

In this study, an overlay blot method was used to identify GTP-binding proteins in fractions of human placenta. Human placenta were fractionated by centrifugation into preparations containing (1) mitochondria, (2) nucleoli and (3) microsomes, plasma membrane and cytosol. GTP-binding proteins were detected by overlay blot using alpha32P-GTP. Proteins of 23 and 25 kDa were identified in all fractions and GTP binding was higher in the presence of 1.0, 2.5, 5.0 and 10.0 mM MgCl2 as compared to equivalent concentrations of CaCl2. In mitochondrial preparations binding of alpha32P-GTP to 23 and 25 kDa was displaced significantly by GDP and GTP but not ADP or ATP. Fractions containing microsomes, plasma membrane and cytosol displayed two labelled bands of 14 and 18 kDa that were not present in other fractions. These data indicate that the placenta contains specific GTP-binding proteins of molecular weights that are consistent with the small monomeric GTP binding protein family (18-36 kDa). Two of these are located in the mitochondria and may regulate the function of these organelles in the placenta.

Dual-wavelength operation of a self-seeded dye laser oscillator

We demonstrate simultaneous dual-wavelength operation of a self-seeded dye laser. The laser cavity consists of one dye cell, two pairs of grating and tuning mirrors, and two reflecting mirrors. This configuration can be decomposed with two grazing-incidence cavities and a standing-wave cavity. The self-seeded dual-wavelength output beams are collinear and independently tunable. We were able to vary the output powers at the two wavelengths smoothly by changing the cavity length of a master oscillator.

Characterization of the protease processing sites in a multidomain proteinase inhibitor precursor from Nicotiana alata

A gene encoding a 40.3-kDa serine proteinase inhibitor (PI) precursor is expressed at high levels in the stigma of the ornamental tobacco, Nicotiana alata. The precursor is processed proteolytically in vivo to release five homologous proteinase inhibitors of approximately 6 kDa, as well as two flanking peptides. The five PIs have been purified from stigmas and identified by N-terminal sequencing, electrospray mass spectrometry and inhibition activity against chymotrypsin or trypsin. One of the PIs inhibits chymotrypsin and the other four are most active on trypsin. Cleavage occurs in a linker region (EEKKND) that is repeated six times in the precursor molecule. In the plant, the initial cleavage probably occurs between asparagine and the aspartate residues and ragged ends are formed by subsequent trimming. In vitro, the protease-sensitive linker region is selectively cleaved by the endoproteinases Asp-N, Glu-C and Lys-C to release fully active approximately 6-kDa PIs that are resistant to further proteolytic digestion. The precursor, produced by a recombinant baculovirus, inhibits chymotrypsin more effectively than trypsin. The stoichiometry of 2.6 trypsin molecules/1 precursor molecule indicates that processing is required to activate or expose all of the four trypsin inhibitory sites.

Self-seeding in a dual-cavity-type pulsed Ti:sapphire laser oscillator

We have constructed a self-seeded Ti:sapphire laser oscillator by using a dual-cavity configuration that consists of a Littman configuration cavity and a partially reflecting feedback mirror. This configuration can be decomposed with two kinds of cavity, a grazing-incidence cavity and a standing-wave cavity. The former behaves as an injection seeder and the latter as a slave oscillator. This Ti:sapphire laser system is capable of delivering a continuously tunable laser pulse with a narrow linewidth. Injection at the laser emission region of the free-running Ti:sapphire laser resulted in essentially complete energy extraction.