Effects of beta3-integrin blockade (c7E3) on the response to angioplasty and intra-arterial stenting in atherosclerotic nonhuman primates

Because the beta3-antagonist abciximab (c7E3 Fab) has significantly improved late outcomes after coronary angioplasty, the beta3 integrins have been implicated in the arterial response to injury. However, the mechanisms underlying this benefit are unknown. The observation that c7E3 binds beta3 integrins on vascular cells (alphavbeta3) with affinity equal to that for the platelet glycoprotein IIb/IIIa integrin has led to the hypothesis that c7E3 may act directly on the artery wall to prevent restenosis after angioplasty. To test this hypothesis, we studied the effects of c7E3 on structural changes within the artery wall after angioplasty or stent angioplasty in 23 male cynomolgus monkeys with established atherosclerosis. Animals were randomly assigned to receive either a bolus of c7E3 (0.4 mg/kg IV, n=11) followed by a 48-hour infusion (0. 2 microg. kg-1. min-1) or an equal volume of vehicle (n=12). Animals received weight-adjusted aspirin and heparin and then underwent unilateral iliac artery experimental angioplasty and subclavian artery stent angioplasty (Palmaz). Iliac artery lumen diameter (LD) was determined by angiography at baseline (LDPre), after angioplasty (LDPost), and 35 days later (LDDay35). Arteries were then fixed by perfusion and removed for analysis. Lumen, intima, media, and external elastic lamina (EEL) areas were measured in iliac artery cross sections. Values from each injured iliac artery were normalized to the contralateral uninjured iliac artery to control for interanimal variability in baseline artery size and atherosclerosis extent. Intimal area was also measured in subclavian stent cross sections. c7E3 blocked platelet aggregation and prolonged the bleeding time from 2.8+/-1.1 to 19.8+/-2.5 minutes, P<0.001. Experimental angioplasty increased LDPost an average of 28%, and the initial gain was similar in both groups (P=NS). Despite an anti-platelet effect, c7E3 did not inhibit iliac lumen narrowing (LDDay35-LDPost: c7E3, -0.69+/-0.17 versus vehicle, -0.99+/-.17 mm, P=0.35); intimal hyperplasia (neointima area: c7E3, 1.12+/-.28 versus vehicle, 1.22+/-.20 mm2, P=0.77); or decrease in artery wall size (EEL area [percent of uninjured control]: c7E3, 101+/-7% versus vehicle, 121+/-7%). Stent intimal hyperplasia was also unaltered by c7E3 treatment (neointimal area: c7E3, 1.09+/-0.16 versus vehicle, 1. 28+/-0.11 mm2, P=0.36). These results suggest that the benefits of c7E3 treatment in coronary angioplasty were not from inhibition of intimal hyperplasia or improved artery wall remodeling. Alternative mechanisms should be explored to explain improved late outcomes after angioplasty in patients treated with c7E3.     

Single dose pharmacokinetics of manidipine in hepatic impaired patients and healthy controls

The pharmacokinetics and safety of a single oral dose of 20 mg manidipine dihydrochloride have been studied in 8 patients with mild to moderate hepatic impairment (grade A or B in Child's classification, or score < or = 7 in Pugh's modification of Child's classification), and in 12 healthy subjects. They received one 20 mg manidipine dihydrochloride tablet with 100 ml of tap water after a standard breakfast. Manidipine was determined using HPLC with electrochemical detection from plasma samples taken up to 24 or 36 h after dosing. The medication was well tolerated. A trend toward higher Cmax, AUC, and MRT was observed in patients with a more severe hepatic impairment, as a consequence of reduction in the liver metabolic function. Patients with grade A hepatic impairment did not exhibit significantly altered pharmacokinetics with respect to healthy subjects, while grade B impairment patients had significantly higher AUC and MRT. Tmax values pointed to reduced absorption rate in patients compared to healthy subjects; the changes were more evident in grade B than grade A patients, although statistical significance was not reached. The reduction in absorption rate in grade B patients is probably related to their higher mean age, since this effect has been reported for manidipine. The pharmacokinetics of manidipine seem only modified in patients with a certain degree of hepatic impairment (at least Pugh grade 6 and Child grade B); therefore, adaptation of the dosing regimen does not seem to be generally recommendable, but should be modulated according to the liver status of the patient.     

Equating the MOS SF36 and the LSU HSI Physical Functioning Scales

This study equates the physical functioning subscales of the Medical Outcomes Study Short Form 36 (SF36) and the Louisiana State University Health Status Instruments (LSU HSI). Data from the SF36's 10-item physical functioning scale, the PF10, and the LSU HSI's 29-item Physical Functioning Scale (PFS), were fit to separate and mixed Rasch rating scale models. Data were provided by a convenience sample of 285 patients waiting for appointments in a public hospital general medicine clinic. Difficulty estimates for a subset of similar items from the two instruments were highly correlated (.95), indicating that the items from the two scales are working together to measure the same variable. The measures from the two equated instruments correlate .80 (.86 when disattenuated for error). Of the two instruments, the PFS's error is lower, model fit is better, and reliability coefficients are higher. Both instruments measure physical functioning, and can do so in a common unit of measurement. Conversion tables are provided for transforming raw scores from either instrument into the common metric.     

Iron-dependent oxidation, ubiquitination, and degradation of iron regulatory protein 2: implications for degradation of oxidized proteins

The ability of iron to catalyze formation of reactive oxygen species significantly contributes to its toxicity in cells and animals. Iron uptake and distribution is regulated tightly in mammalian cells, in part by iron regulatory protein 2 (IRP2), a protein that is degraded efficiently by the proteasome in iron-replete cells. Here, we demonstrate that IRP2 is oxidized and ubiquitinated in cells before degradation. Moreover, iron-dependent oxidation converts IRP2 into a substrate for ubiquitination in vitro. A regulatory pathway is described in which excess iron is sensed by its ability to catalyze site-specific oxidations in IRP2, oxidized IRP2 is ubiquitinated, and ubiquitinated IRP2 subsequently is degraded by the proteasome. Selective targeting and removal of oxidatively modified proteins may contribute to the turnover of many proteins that are degraded by the proteasome.     

Effect of GABA on the processing of interaural time differences in nucleus laminaris neurons in the chick

Neurons in the avian nucleus laminaris (NL) are the first to receive binaural information and are presumed to play a role in encoding interaural time differences (ITD). NL not only receives excitatory projections from the ipsi- and contralateral nucleus magnocellularis, but also receives inhibitory (GABAergic) input. This study investigates how GABA (gamma-aminobutyric acid) influences ITD coding in NL. Intracellular responses of chick NL neurons were studied in a brain slice preparation. Both excitatory inputs to NL were electrically activated and the delay between trains of bilateral stimuli (simulated-interaural time difference [s-ITD]) was varied. The resulting s-ITD functions were recorded in the presence of 0-75 microM GABA. The discharge rate of NL neurons varied with s-ITD. Cells responded maximally using s-ITDs at which the peak of the ipsi- and contralateral excitatory postsynaptic potentials occurred simultaneously (favourable s-ITD). At unfavourable s-ITDs, the discharge rates usually fell below unilateral levels. GABA had contrary effects on the s-ITD functions depending on the drug concentration. A low GABA dose enhanced excitability at favourable s-ITD, but not at unfavourable s-ITDs. In contrast, higher GABA concentrations diminished excitability. Moderate GABA concentrations had no consistent effect. These results suggest that the GABAergic input to NL will either increase or decrease the excitability of the NL neuron depending on the degree to which this GABAergic input is activated. A gain control hypothesis is presented in which the GABAergic input makes ITD processing in NL independent of the stimulus intensity by adjusting the excitability of NL neurons.     

The relative contributions of scatter and attenuation corrections toward improved brain SPECT quantification

Mounting evidence indicates that scatter and attenuation are major confounds to objective diagnosis of brain disease by quantitative SPECT. There is considerable debate, however, as to the relative importance of scatter correction (SC) and attenuation correction (AC), and how they should be implemented. The efficacy of SC and AC for 99mTc brain SPECT was evaluated using a two-compartment fully tissue-equivalent anthropomorphic head phantom. Four correction schemes were implemented: uniform broad-beam AC, non-uniform broad-beam AC, uniform SC + AC, and non-uniform SC + AC. SC was based on non-stationary deconvolution scatter subtraction, modified to incorporate a priori knowledge of either the head contour (uniform SC) or transmission map (non-uniform SC). The quantitative accuracy of the correction schemes was evaluated in terms of contrast recovery, relative quantification (cortical:cerebellar activity), uniformity ((coefficient of variation of 230 macro-voxels) x 100%), and bias (relative to a calibration scan). Our results were: uniform broad-beam (mu = 0.12 cm(-1)) AC (the most popular correction): 71% contrast recovery, 112% relative quantification, 7.0% uniformity, +23% bias. Non-uniform broad-beam (soft tissue mu = 0.12 cm(-1)) AC: 73%, 114%, 6.0%, +21%, respectively. Uniform SC + AC: 90%, 99%, 4.9%, +12%, respectively. Non-uniform SC + AC: 93%, 101%, 4.0%, +10%, respectively. SC and AC achieved the best quantification; however, non-uniform corrections produce only small improvements over their uniform counterparts. SC + AC was found to be superior to AC; this advantage is distinct and consistent across all four quantification indices.     

Agonists for neuropeptide Y receptor subtypes NPY-1 and NPY-2 have opposite actions on rat nodose neuron calcium currents

1. The whole-cell variation of the patch-clamp technique was used to study the effect of neuropeptide Y (NPY) and preferential agonists for the NPY-1 and NPY-2 receptor subtypes on voltage-dependent calcium currents in acutely dissociated postnatal rat nodose ganglion neurons. 2. Both low- and high-threshold calcium current components were present. NPY altered voltage-dependent calcium currents in approximately 50% of neurons studied. NPY (0.1-100 nM, ED50 6 nM) decreased the peak amplitude of transient high-threshold calcium currents in approximately 45% of the neurons. NPY (100 nM) decreased the peak amplitude of these currents 31 +/- 5% (mean +/- SE). However, in approximately 5% of the neurons NPY (100 nM) caused a reversible and reproducible increase in transient high-threshold calcium currents of 21 +/- 4%. NPY did not affect either transient low-threshold or slowly inactivating high-threshold calcium current components. 3. Application of the C-terminal fragment NPY 13-36 (100 nM), a preferential agonist for NPY-2 receptors, reversibly decreased the peak amplitude of transient high-threshold calcium currents by 26 +/- 5% in 9 of 20 cells (45%). Application of [Pro34]-NPY (100 nM), a preferential agonist for NPY-1 receptors, reversibly increased the peak amplitude of transient high-threshold calcium currents 20 +/- 4% in 23 out of 48 neurons (48%). Six of 20 neurons (30%) responded to application of both agonists. Neither the NPY-1 nor NPY-2 agonists affected transient low-threshold or slowly inactivating high-threshold calcium current components.(ABSTRACT TRUNCATED AT 250 WORDS)     

Vitamin E levels in human atherosclerotic plaque: the influence of risk factors

Recent studies suggest that vitamin E may be an important preventative factor in the development and progression of atherosclerosis. In order to more clearly define the role of vitamin E in atherosclerosis, we measured vitamin E, conjugated diens, and lipid flurochromes, as well as cholesterol, triglycerides and phospholipid in arterial and venous tissue of 83 patients. Serum cholesterol and triglyceride levels were significantly higher (P < 0.05) in patients with aortic occlusive (AIOD) and aneurysmal (AAA) disease than in control organ donors (OD). Tissue cholesterol concentrations were significantly elevated in AAA tissue when compared to OD and tissue from patients with peripheral occlusive disease (POD). Tissue from patients with AIOD contained greater concentrations of phospholipid (PL) than were measured in patients with POD and in OD. Vitamin E concentrations were highest in POD tissue and approximately 3.0, 2.0, and 1.6 fold greater than OD, AIOD and AAA tissue respectively. Diene conjugates and lipid flurochromes, measures of early and intermediate products of lipid peroxidation, were markedly elevated in all diseased arterial tissue compared to controls. There were no significant differences in tissue or serum lipid levels between saphenous vein (SVBG) and diseased vein grafts (DVG). However, conjugated diene concentrations were elevated in DVG compared to SVBG. Vitamin E levels were significantly elevated in diseased arterial and venous tissue (AIOD, AAA, POD, DVG) removed from patients with diabetes (P = 0.013) and hypertension (P = 0.049) compared to those without these risk factors. Diabetes was the only risk factor associated with significantly increased (P = 0.005) levels of vitamin E when only data from atherosclerotic arterial tissue (AAA, POD, AIOD) were analyzed. These preliminary data provide additional evidence of altered vitamin E metabolism and free radical processes in the tissues of patients with various manifestations of atherosclerosis.