Apoptosis in interface membranes of aseptically loose total hip arthroplasty.

The terminal events leading to periprosthetic osteolysis are multifactorial in nature and modulation of this process after the stage of osteolytic mediator release has been futile. Recently, the demonstration of the ability of bisphosphonates to inhibit bone resorption that is mediated by particle-stimulated macrophages and their induction of osteoclast apoptosis suggests a potent area for modulation of osteolysis at the prosthesis-bone interface. The purpose of this study was to determine the mode of cell death that occurs at the osteolytic interface of failed total hip arthroplasty (THA). TUNEL staining, DNA laddering, and immunodetection of poly(ADP-ribose)polymerase (PARP) protein were used to identify the presence of apoptosis in interface membranes from 25 patients aged 28-88 years old (mean, 58 years) harvested at the time of hip revision surgery. Our results demonstrated positive TUNEL stain in 100% of specimens with an average 37% of cells (range 12-60%) positively stained for TUNEL whereas less than 8% of control tissue cells showed positive staining. DNA laddering, a characteristic feature of apoptotic cells, was observed in 82% (28/34) of specimens studied at both the acetabular and femoral side of aseptically loose THAs. No laddering was observed in control tissues. Finally, using Western blot analysis, we observed the appearance of the 89 kDa PARP fragment associated with apoptosis in 92% of specimens (30/33). Our results demonstrate the presence of apoptotic cell death in interface membranes of THAs suggesting that apoptosis-related events are indeed associated with periprosthetic osteolysis and could serve as a specific target point for therapeutic modulation.

Pharmacokinetics of ICG and HPPH-car for the detection of normal and tumor tissue using fluorescence, near-infrared reflectance imaging: a case study.

We present in vivo fluorescent, near-infrared (NIR), reflectance images of indocyanine green (ICG) and carotene-conjugated 2-devinyl-2-(1-hexyloxyethyl) pyropheophorbide (HPPH-car) to discriminate spontaneous canine adenocarcinoma from normal mammary tissue. Following intravenous administration of 1.0 mg kg-1 ICG or 0.3 mg kg-1 HPPH-car into the canine, a 25 mW, 778 nm or 70 mW, 660 nm laser diode beam, expanded by a diverging lens to approximately 4 cm in diameter, illuminated the surface of the mammary tissue. Successfully propagating to the tissue surface, ICG or HPPH-car fluorescence generated from within the tissue was collected by an image-intensified, charge-coupled device camera fitted with an 830 or 710 nm bandpass interference filter. Upon collecting time-dependent fluorescence images at the tissue surface overlying both normal and diseased tissue volumes, and fitting these images to a pharmacokinetic model describing the uptake (wash-in) and release (wash-out) of fluorescent dye, the pharmacokinetics of fluorescent dye was spatially determined. Mapping the fluorescence intensity owing to ICG indicates that the dye acts as a blood pool or blood persistent agent, for the model parameters show no difference in the ICG uptake rates between normal and diseased tissue regions. The wash-out of ICG was delayed for up to 72 h after intravenous injection in tissue volumes associated with disease, because ICG fluorescence was still detected in the diseased tissue 72 h after injection. In contrast, HPPH-car pharmacokinetics illustrated active uptake into diseased tissues, perhaps owing to the overexpression of LDL receptors associated with the malignant cells. HPPH-car fluorescence was not discernable after 24 h. This work illustrates the ability to monitor the pharmacokinetic delivery of NIR fluorescent dyes within tissue volumes as great as 0.5-1 cm from the tissue surface in order to differentiate normal from diseased tissue volumes on the basis of parameters obtained from the pharmacokinetic models.

Gadolinium(III) di- and tetrachelates designed for in vivo noncovalent complexation with plasma proteins: a novel molecular design for blood pool MRI contrast enhancing agents.

A new series of gadolinium chelates designed as blood pool contrast enhancing agents for magnetic resonance imaging applications is described. Complexes having four Gd(III) chelate units display a significant increase in molecular relaxivity per gadolinium ion in water (9-13 L x mmol(-1) x (s-1) compared to Gd(III)-DTPA (5 L x mmol(-1) x s(-1). A further jump in relaxivity (25 L x mmol(-1) x sec(-1) in 4% BSA solution was observed in the case of a fatty acid-containing tetrachelate and is attributed to noncovalent binding of the tetrachelate to serum albumin. This agent was successfully used for imaging the rat circulatory system.

Hemodynamic effects of ioversol in the dog and rat.

The hemodynamic effects of selectively administered ioversol were examined in the dog and rat. At concentrations ranging from 32% to 37% I, wt/vol, ioversol was compared with nonionic (iohexol, iopamidol) and ionic (diatrizoate) contrast media for cardiovascular responses following injections into the femoral vein, right and left coronary arteries, left ventricle, and the pulmonary and femoral arteries of the dog, and into the carotid artery of the rat. Regardless of the intravascular route of injection, ioversol generally caused minimal effects on the heart rate, minimal to moderate decreases in myocardial contractility, left ventricular pressure, mean arterial pressure, pulmonary vascular resistance, and systemic vascular resistance. These effects of ioversol were comparable to those of iohexol and iopamidol, and were relatively less profound than those of diatrizoate. Under experimental conditions injections of ioversol exerted hemodynamic effects comparable to those of other nonionic agents, yet relatively diminished as compared with a representative high-osmolality ionic contrast agent. These results suggest that the nonionic contrast agent, ioversol, should be well tolerated in patients following injections via similar intravascular routes.

Reproductive, developmental, and genetic toxicology of ioversol.

The authors examined the reproductive, developmental, and genetic toxicity of ioversol in several in vivo and in vitro systems. In Segments I, II, and III reproductive toxicity studies, ioversol did not produce teratogenic effects in either rats or rabbits at daily intravenous dose levels of up to 3.2 g I/kg/day. Daily intravenous injections in male and female rats did not adversely affect fertility or reproductive function. Offspring derived from dams treated with ioversol also developed and reproduced in a normal fashion. Four genetic toxicity studies employing bacterial and mammalian assay systems, and using both in vitro and in vivo methods, indicated that ioversol did not possess mutagenic or clastogenic activity.

Acute and subacute toxicity studies of ioversol in experimental animals.

The authors examined the acute and subacute toxicity of the low-osmolality nonionic radiographic contrast agent, ioversol. The median lethal dose (LD50) of ioversol administered intravenously to mice, rats, rabbits, and dogs was more than 12 g I/kg, which exceeds the maximal anticipated clinical dose by at least tenfold. When the acute intravenous toxicity of 35% I, wt/vol, ioversol was compared with 35% I, wt/vol, iohexol and 37% I, wt/vol, iopamidol in mice, no significant differences in LD50 values or general toxicity were found. Ioversol also was administered via intrathecal routes to rats, dogs, and monkeys. In a comparative study, acute intracisternal injections of 35% I, wt/vol, ioversol in rats demonstrated far less toxicity than 35% I, wt/vol, iohexol and 37% I, wt/vol, iopamidol, a result that may be due to the increased hydrophilic tendency of ioversol relative to iohexol and iopamidol. Acute intracisternal injections of 43% I, wt/vol, ioversol, 35% I, wt/vol, iohexol, and 37% I, wt/vol, iopamidol into dogs at 160 or 240 mg I/kg, demonstrated comparable, but only minimal, toxicity. Monkeys given lumbar intrathecal injections of ioversol tolerated 60 mg I/kg well with no resulting arachnoiditis. Subacute toxicity studies involving 4-week daily intravenous injections (0.2, 0.8, and 3.2 g I/kg/day) in rats and dogs showed ioversol to be well tolerated. The signs of toxicity included a reversible renal cytoplasmic tubular vacuolation in the rat at high doses and a reversible hepatocyte vacuolation in the dog at the same high dose. However, clinical chemistry tests showed no signs of renal or hepatic dysfunction, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of sodium on the fibrillatory potential of ioversol.

The spontaneous ventricular fibrillation (VF) potential of the nonionic contrast media, ioversol (IOV), with and without the addition of sodium was examined during right coronary artery (RCA) injections into anesthetized closed-chest dogs. Protocols included fixed volume (6 mL) and fixed rate (0.4 and 0.6 mL/sec) injections to compare two or more of the following: IOV, IOV + (0.075-0.9% wt/vol) NaCl, and sodium/meglumine diatrizoate (DIA). In these studies, the incidence of VF for IOV alone was either greater that with IOV + NaCl formulations or, if equivalent, the incidence of other arrhythmias was greater with IOV alone than with the sodium formulations. When DIA was included in the comparisons, the incidence of VF was always greater than IOV with or without sodium. There was a sodium-related concentration prolongation in QT interval that, at 0.9% NaCl, approximated that with DIA, even though the incidence of VF for the sodium formulation was 0/15 vs. 6/12 for DIA. Thus, the addition of sodium to IOV appears to reduce the propensity for sponteneous VF in the canine model.

Potentiation of 2,5-hexanedione neurotoxicity by methyl ethyl ketone.

Chronic oral administration of a combination of 2.2 mmol methyl ethyl ketone (MEK) and 2.2 mmol 2,5-hexanedione (2,5-HD)/kg/day, 5 days/week resulted in more rapid onset of motor deficits than did chronic dosing with 2.2 mmol 2,5-HD/kg/day alone. In kinetic studies blood time courses of 2,5-HD were determined in rats in the presence and absence of MEK. Concomitant administration of MEK reduced blood 2,5-HD clearance and increased the area under the curve (AUC) for the blood 2,5-HD. In companion experiments with 2,5-[1,6-14C]HD as a tracer, neural and nonneural tissues were examined 72 hr following the last treatment at Weeks 1, 2, and 3 of chronic administration of 2,5-HD alone or in combination with an equimolar dose of MEK. Rats treated with 2,5-[14C]HD alone or in combination with MEK demonstrated no difference in total or trichloroacetic acid-precipitable radioactivity in blood, in liver homogenates, or in neurofilament-enriched fractions from sciatic nerve and spinal cord. The data support a suggestion that the potentiation of hexacarbon neurotoxicity by MEK is the result of the persistence of the neurotoxic metabolite in the blood and not the enhanced metabolism of parent hexacarbon to 2,5-HD.