O-(fluoresceinylmethyl)hydroxylamine (OFMHA): a fluorescent reagent for detection of damaged nucleic acids

5- and 6-O-(Fluoresceinylmethyl)hydroxylamine (OFMHA, 5a, b) were prepared from the corresponding bis-pivaloyl-protected hydroxymethylfluoresceins (1a, b) in 50-70% yield. The hydroxylamine derivatives reacted smoothly with the abasic sites present in acid/heat stressed calf thymus DNA.

Structural characteristics of low-molecular-mass displacers for cation-exchange chromatography. II. Role of the stationary phase

The relative efficacy of a variety of low-molecular-mass displacers was examined on three different stationary phase materials. Several homologous series of displacer molecules were evaluated on these ion-exchange resins using a displacer ranking plot based on the steric mass action model. The results demonstrate that while aromaticity and hydrophobicity can play a significant role in the affinity of displacer molecules on polymethacrylate based and hydrophilized polystyrene-divinylbenzene based materials, this effect is much less pronounced on an agarose based resin. The work presented in this paper demonstrates that different structural features of low-molecular-mass displacers can dominate their affinity on various stationary phase materials employed and provides rules of thumb for the design of high affinity, low-molecular-mass displacers for a variety of commercial cation-exchange materials.

Pseudoaneurysm of the ulnar artery occurring after fracture of the distal radius and ulna: a case report

A case of pseudoaneurysm of the ulnar artery occurring after distal radius and ulna fracture is presented. This case illustrates an uncommon complication following a fairly common injury.

Structural characteristics of low-molecular-mass displacers for cation-exchange chromatography

The relative efficacy of a variety of low-molecular-mass displacers was examined using a displacer ranking plot. This method enables an evaluation of the dynamic affinity of a variety of displacers over a range of operating conditions. Several homologous series of molecules were evaluated to provide insight into the effects of various structural features on displacer efficacy. The results indicate that linear flexible geometries may have advantages over branched or cyclic structures. Data also indicate that the spreading out of charges may increase affinity. The incorporation of aromatic moieties in these displacers, particularly near the surface of the molecules, appears to result in a dramatic increase in displacer affinity. The ability of several high-affinity low-molecular-mass displacers a very strongly bound cationic protein is also examined. The results confirm the predictions of the theory and indicate that it is indeed possible to displace highly bound macromolecules with low-molecular-mass dispatchers. The work presented in this paper indicates that non-specific interactions can be exploited for producing high-affinity low-molecular-mass displacers.

Hemodynamics of human carotid artery bifurcations: computational studies with models reconstructed from magnetic resonance imaging of normal subjects

PURPOSE

The precise role played by hemodynamics, particularly wall shear stress, in the development and progression of vascular disease remains unclear, in large part because of a lack of in vivo studies with humans. Although technical challenges remain for noninvasively imaging wall shear stresses in humans, vascular anatomy can be imaged with sufficiently high resolution to allow reconstruction of three-dimensional models for computational hemodynamic studies. In this paper we present an entirely noninvasive magnetic resonance imaging (MRI) protocol that provides carotid bifurcation geometry and flow rates from which the in vivo hemodynamics can be computed. Maps of average, oscillatory, and gradients of wall shear stress are presented for two normal human subjects, and their data are compared with those computed for an idealized carotid bifurcation model.

METHODS

An MRI protocol was developed to acquire all necessary image data in scan times suitable for patient studies. Three-dimensional models of the carotid bifurcation lumen were reconstructed from serial black blood MR images of two normal volunteers. Common and internal carotid artery flow rate waveforms were determined from MRI phase-contrast velocity imaging in the same subjects and were used to impose fully developed velocity boundary conditions for the computational model. Subject-specific time-resolved velocities and wall shear stresses were then computed with a finite element-based Navier-Stokes equation solver.

RESULTS

Models reconstructed from in vivo MRI of two subjects showed obvious differences in branch angle, bulb size and extent, and three-dimensional curvature. Maps of a variety of wall shear stress indices showed obvious qualitative differences in patterns between the in vivo models and between the in vivo models and the idealized model. Secondary, helical flow patterns, induced primarily by the asymmetric and curved in vivo geometries, were found to play a key role in determining the resulting wall shear stress patterns. The use of in vivo flow rate waveforms was found to play a minor but noticeable role in some of the wall shear stress behavior observed.

CONCLUSIONS

Conventional "averaged" carotid bifurcation models mask interesting hemodynamic features observed in realistic models derived from noninvasive imaging of normal human subjects. Observation of intersubject variations in the in vivo wall shear stress patterns supports the notion that more conclusive evidence regarding the role of hemodynamics in vascular disease may be derived from such individual studies. The techniques presented here, when combined with subject-specific MRI measurements of carotid artery plaque thickness and composition, provide the tools necessary for entirely noninvasive, prospective, in vivo human studies of hemodynamics and the relationship of hemodynamics to vascular disease.

Comparative carcinogenicity in Sprague-Dawley rats of the polychlorinated biphenyl mixtures Aroclors 1016, 1242, 1254, and 1260

A comprehensive chronic toxicity and carcinogenicity study was conducted on a series of Aroclors (1016, 1242, 1254, and 1260). Each Aroclor was assessed at multiple dietary concentrations, ranging from 25 to 200 ppm, for 24 months in male and female Sprague-Dawley rats. Liver toxicity was indicated by elevated serum enzyme activity (AST, ALT, and GGT), elevated serum cholesterol concentration, decreases in hematologic parameters (RBC, Hb, and Hct), hepatocellular hypertrophy, an increased incidence of altered hepatocellular foci, and an increased incidence of hepatocellular neoplasms (primarily adenomas). Liver toxicity was distinctly more severe in females than in males. The incidence of hepatocellular neoplasms was highly sex-dependent (females > males), differed between Aroclor mixtures and, for females, increased with dose and followed the general incidence pattern of Aroclor 1254 > Aroclor 1260 ≈ Aroclor 1242 > Aroclor 1016. A significant response (p < 0.05) in males was seen only for the high dose of Aroclor 1260. A small increase in the incidence of thyroid gland follicular cell adenomas was noted in males for Aroclors 1242, 1254, and 1260, with the incidence being uniform across dose groups and Aroclor mixtures. For females, increased survival relative to controls was observed for all Aroclor treatment groups. A significantly decreased trend in the incidence of mammary gland neoplasms compared to control was also noted for females receiving Aroclors 1242, 1254, and 1260.

Estradiol-mimetic probes. Preparation of 17 alpha-(6-aminohexynyl)estradiol biotin, fluorescein and acridinium conjugates

3-O-tert-Butyldimethylsilyl-17 alpha-(6-mesyloxyhexynyl)estradiol was converted to the azide in 60-70% yield with NaN3/DMPU, then reduced to the corresponding amine (> 95% yield). Acylation with the N-hydroxysuccinimide esters of biotin, 5-carboxyfluorescein and 10-(3-sulfopropyl)-N-tosyl-N-(3- carboxypropyl)acridinium-9-carboxamide gave the title conjugates. The KDs of the tracers with an estradiol antibody ranged from 97-197 nM.

The catalytic mechanism of kynureninase from Pseudomonas fluorescens: insights from the effects of pH and isotopic substitution on steady-state and pre-steady-state kinetics

The effects of pH and isotopic substitution of substrate and solvent on the reaction of kynureninase from Pseudomonas fluorescens have been determined. The pH dependence of kcat/Km for L-kynurenine is bell-shaped, with apparent pKa's of 6.25 +/- 0.05 on the acidic limb and 8.9 +/- 0.1 on the basic limb, and with a pH-dependent value of kcat/Km of 2 x 10(5) M-1 s-1. The pH dependence of kcat/Km for 3-hydroxykynurenine is also bell-shaped, with apparent pKa's of 6.49 +/- 0.07 and 8.55 +/- 0.09, and with a pH-dependent value of 2.5 x 10(3) M-1 s-1. The kcat for L-kynurenine decreases at acidic pH values, with an apparent pKa of 6.43 +/- 0.06 and a pH-dependent value of 7 s-1. The solvent kinetic isotope effect on kcat for the reaction of kynurenine in [2H]H2O is 6.56 +/- 0.59, whereas there is no normal kinetic isotope effect on kcat/Km, at pH 8.1. The proton inventory of kcat fits very well to the Gross-Butler equation, with x = 0.825 +/- 0.08, suggesting that only a single proton is transferred in the rate-determining step. In contrast, there is no significant kinetic isotope effect on either kcat or kcat/Km with alpha-[2H]-L-kynurenine as the substrate. There is a "burst" of anthranilate (0.7 mol/mol of enzyme) formed in the pre steady state of the reaction of kynureninase, with a rate constant of 54 s-1 which is not affected by [2H]H2O. The partition ratio of alanine to pyruvate formation is 2.3 x 10(4) in H2O and 6.9 x 10(3) in [2H]H2O. Taken together, these data indicate that the rate-limiting step in the reaction of kynureninase occurs subsequent to the first irreversible step, which is anthranilate release, is general base catalyzed, and involves transfer of only a single proton. On the basis of these observations, we propose that the rate-limiting step in the reaction of kynureninase is C-4' deprotonation of the pyruvate pyridoxamine 5'-phosphate ketimine intermediate.

Computational blood flow modelling: errors associated with reconstructing finite element models from magnetic resonance images

Construction of computational blood flow models from magnetic resonance (MR) scans of real arteries is a powerful tool for studying arterial hemodynamics. In this report we experimentally determine a lower bound for errors associated with such an approach, and present techniques for minimizing such errors. A known, simple three-dimensional geometry (cylindrical tube) was imaged using a commercial MR scanner, and the resulting images were used to construct finite element flow models. Computed wall-shear stresses were compared to known values and peak errors of 40-60% were found. These errors can be attributed to limited spatial resolution, image segmentation and model construction. A simple smoothing technique markedly reduced these peak errors. We conclude that smoothing is required in the construction of arterial models from in vivo MR images. If used appropriately, such images can be used to construct acceptably accurate computational models of realistic arterial geometries.

Immunoassay reagents for thyroid testing. 3. Determination of the solution binding affinities of a T4 monoclonal antibody Fab fragment for a library of thyroxine analogs using surface plasmon resonance

A library of thyroxine analogs and tracers was prepared, and their solution binding affinities for an anti-T4 Fab fragment were determined using a single high-density L-T4 biosensor surface in a BIAcore surface plasmon resonance instrument. The high-density L-T4 analog biosensor was calibrated by determination of the initial binding rate was of known concentrations of free anti-T4 Fab fragment in solution to the biosensor surface. A range of individual thyroxine analog and tracer concentrations was subsequently mixed with a fixed concentration of anti-T4 Fab fragment. The concentration of free anti-T4 Fab fragment in each solution at equilibrium was determined, and the equilibrium dissociation constant (KD) for each case was derived. The KD values determined in solution are compared to values determined by a direct kinetic analysis on the BIAcore instrument using individual biosensor surfaces.

Comparative carcinogenicity in Sprague-Dawley rats of the polychlorinated biphenyl mixtures Aroclors 1016, 1242, 1254, and 1260

A comprehensive chronic toxicity and carcinogenicity study was conducted on a series of Aroclors (1016, 1242, 1254, and 1260). Each Aroclor was assessed at multiple dietary concentrations, ranging from 25 to 200 ppm, for 24 months in male and female Sprague-Dawley rats. Liver toxicity was indicated by elevated serum enzyme activity (AST, ALT, and GGT), elevated serum cholesterol concentration, decreases in hematologic parameters (RBC, Hb, and Hct), hepatocellular hypertrophy, an increased incidence of altered hepatocellular foci, and an increased incidence of hepatocellular neoplasms (primarily adenomas). Liver toxicity was distinctly more severe in females than in males. The incidence of hepatocellular neoplasms was highly sex-dependent (females >> males), differed between Aroclor mixtures and, for females, increased with dose and followed the general incidence pattern of Aroclor 1254 > Aroclor 1260 approximately Aroclor 1242 > Aroclor 1016. A significant response (p < 0.05) in males was seen only for the high dose of Aroclor 1260. A small increase in the incidence of thyroid gland follicular cell adenomas was noted in males for Aroclors 1242, 1254, and 1260, with the incidence being uniform across dose groups and Aroclor mixtures. For females, increased survival relative to controls was observed for all Aroclor treatment groups. A significantly decreased trend in the incidence of mammary gland neoplasms compared to control was also noted for females receiving Aroclors 1242, 1254, and 1260.

First trimester of pregnancy laparoscopic procedures

Laparoscopic procedures are being performed during pregnancy with increasing frequency; however, few first-trimester operations have been published. Two first-trimester procedures are here reported, both performed with uneventful recoveries.

Oxygen mass transfer calculations in large arteries

The purpose of this study was to model the transport of oxygen in large arteries, including the physiologically important effects of oxygen transport by hemoglobin, coupling of transport between oxygen in the blood and in wall tissue, and metabolic consumption of oxygen by the wall. Numerical calculations were carried out in an 89 percent area reduction axisymmetric stenosis model for several wall thicknesses. The effects of different boundary conditions, different schemes for linearizing the oxyhemoglobin saturation curve, and different Schmidt numbers were all examined by comparing results against a reference solution obtained from solving the full nonlinear governing equations with physiologic values of Schmidt number. Our results showed that for parameters typical of oxygen mass transfer in the large arteries, oxygen transport was primarily determined by wall-side effects, specifically oxygen consumption by wall tissue and wall-side mass transfer resistance. Hemodynamic factors played a secondary role, producing maximum local variations in intimal oxygen tension on the order of only 5-6 mmHg. For purposes of modeling blood-side oxygen transport only, accurate results were obtained through use of a computationally efficient linearized form of the convection-diffusion equation, so long as blood-side oxygen tensions remained in the physiologic range for large arteries. Neglect of oxygen binding by hemoglobin led to large errors, while arbitrary reduction of the Schmidt number led to more modest errors. We conclude that further studies of oxygen transport in large arteries must couple blood-side oxygen mass transport to transport in the wall, and accurately model local oxygen consumption within the wall.

Intraaortic balloon pump insertion after percutaneous revascularization in patients with severe peripheral vascular disease

Severe aortoiliac peripheral vascular disease (PVD) is considered a contraindication for the placement of an intraaortic balloon pump (IABP) because of a high risk of limb ischemia. Recent advances in percutaneous transluminal angioplasty (PTA) and stenting have altered the treatment of iliac stenoses such that the results of PTA with stenting compare favorably with surgery. We reviewed our experience with placement of IABP between July 1994 and February 1996. Of 64 patients receiving IABP, 17 had known or suspected peripheral vascular disease. Severe iliac or distal aortic stenoses were present in 9. These 9 patients underwent PTA with or without stenting prior to 10 IABP insertions. Limb ischemia occurred in 10% of PVD patients treated with percutaneous revascularization, compared to 11% in patients without PVD. No patient had a serious vascular complication or required vascular surgery. We conclude that percutaneous revascularization in patients with severe aortoiliac PVD, for whom this IABP insertion had previously been considered contraindicated, results in a low rate of limb ischemia.

U.S. experience of transradial coronary stenting utilizing Palmaz-Schatz stents

Transradial coronary stenting has been associated with a low frequency of vascular complications and shortened hospital length of stay, but few reports of safety and feasibility are available. To determine the safety and efficacy of transradial coronary stenting, our initial experience in 38 patients was reviewed. Palmaz-Schatz stents hand-mounted on Predator (Cordis Corp., Miami Lakes, FL) balloons were delivered through 6 Fr guide catheters. In 1 of 38 patients (3%) radial access could not be achieved. Fifty-five stents were implanted in 44 lesions (3 total occlusion, 18 type A, 19 type B, 9 type C, National Heart Lung Blood Institute Classification). Access time was 7.7 +/- 4.6 min. Procedural success was achieved in 36 patients (97%). In one patient, a stent could not be delivered to a distal circumflex lesion due to marked proximal tortuosity and calcification. Poststenting residual stenosis was 0 +/0 10%. No access-related complications occurred. One patient had stent thrombosis and required repeat angioplasty and stenting. We conclude that transradial coronary stenting is both feasible and safe with a low risk of access complications and with excellent procedural results.

Escherichia coli dimethylallyl diphosphate:tRNA dimethylallyltransferase: a binding mechanism for recombinant enzyme

Escherichia coli dimethylallyl diphosphate:tRNA dimethylallyltransferase (DMAPP-tRNA transferase) catalyzes the first step in the biosynthesis of the hypermodified A37 residue in tRNAs that read codons beginning with uridine. The enzyme, encoded by the miaA gene, was overproduced and purified to apparent homogeneity in three steps by ion-exchange (DE52 and Mono-Q) and size exclusion chromatography. Affinity-tagged DMAPP-tRNA transferase containing a C-terminal tripeptide alpha-tubulin epitope also was overproduced and purified to apparent homogeneity in two steps by ion-exchange and immunoaffinity chromatography. Addition of the C-terminal tripeptide alpha-tubulin epitope to DMAPP-tRNA transferase did not affect the activity of the enzyme. Undermodified tRNA(Phe) used as substrate in the DMAPP-tRNA transferase-catalyzed reaction was isolated and purified from an overexpressing clone in a miaA deficient strain of E. coli. Active recombinant E. coli DMAPP-tRNA transferase is monomeric. The enzyme transferred the dimethylallyl moiety of DMAPP to A37, located adjacent to the anticodon in undermodified tRNA(Phe). The enzyme required Mg2+ for activity and exhibited a broad pH optimum. Michaelis constants for tRNA(Phe) and DMAPP are 96 +/- 11 nM and 3.2 +/- 0.5 microM, respectively, and Vmax = 0.83 +/- 0.02 micromol min-1 mg-1. DMAPP-tRNA transferase bound tRNA(Phe) with a dissociation constant of 5.2 +/- 1.2 nM. In contrast, DMAPP did not bind to the enzyme in the absence of tRNA. However, DMAPP was bound with a dissociation constant of 3.4 +/- 0.6 microM in the presence of a minihelix analogue of the anticodon stem-loop of tRNA(Phe) where the base corresponding to A37 was replaced by inosine. These results suggest an ordered sequential mechanism for substrate binding.

An assessment of boric acid and borax using the IEHR Evaluative Process for Assessing Human Developmental and Reproductive Toxicity of Agents. Expert Scientific Committee

BACKGROUND

Boron is a ubiquitous element widely distributed in nature in the form of borates at low concentrations in soils and rocks. Boron is released from these minerals by the natural weathering processes in the form of boric acid, which is water soluble and biologically available. High levels of boric acid are naturally found in sea water. Boric acid and borax are used in the greatest quantities and represent the major boron chemical exposures to humans and the environment. The principal use of boric acid and borax is in the manufacture of various types of glass products that do not result in exposure to the consumer. Boric acid and borax are also found in an array of consumer goods including fireproofing for fabrics and wood, insecticides, and in many cosmetics and personal care products as well. Boron may be an essential element for higher animals including humans.

HUMAN EXPOSURE

Boric acid and borax are considered to be completely absorbed by the oral route of exposure. Absorption through intact skin is considered negligible, although absorption can occur through denuded or irritated skin. Boron levels in the body do not persist upon cessation of exposure. People may be exposed to boron through three primary sources: 1) consumption of private, municipal, or commercial (bottled) sources of drinking water; 2) dietary consumption of crops and other foodstuffs (including dietary supplements for body building); and 3) inhalation of boron compounds during their mining, manufacturing, and other industrial processing. While boron has been detected in 81.8% of the municipal water systems, it is a minor source of boron in most parts of the U.S. The mean boron concentration is reported as 0.2 mg B/L. However, residents of California and other western states with boron-rich geologic deposits may be regularly exposed to higher levels in drinking water. Individuals who drink bottled mineral water may also increase their exposure to boron. An EPA health advisory, recommends boron concentrations in drinking water not exceed 0.6 mg B/L [0.06 mM B] over a lifetime of exposure. Dietary exposure to boron for an adult typically ranges from ranges from 0.25 to 3.1 mg B/d with an average of 1.5 mg B/d. The high end of the exposure range, 3.1 mg B/d, was selected by the Expert Committee as best estimate of exposure. It should be noted that a diet high in fruits, vegetables, grains, legumes, and other food stuffs with high boron contents may lead to daily exposures as high as 10 mg B/d from diet alone. Some body building supplements contain boron at levels ranging from 1.5 to 10 mg B, with a median of 4 mg B. Use of the supplements containing the median concentration of boron could equal the daily intake an individual receives from diet and drinking water combined. Adults in the U.S. at the high end of the food exposure range may typically ingest up to 3.5 mg B/d, or a daily dose of 0.005 mmol B/kg b.wt., through exposure from diet (3.1 mg B/d) and drinking water (0.4 mg B/d). Individuals who also use body-building supplements may have a total daily boron intake of 7.5 mg B resulting in a daily dose of 0.01 mmol B/kg b.wt./d. Occupational exposure to boron is mainly through inhalation of borate containing dust during mining and manufacturing processes. Current occupational exposures to boron are reported to result in a daily dose of < 0.0001 to 0.2 mmol B/kg b.wt./d. Current U.S. OSHA permissible exposure limit (PEL) for sodium tetraborates is 10 mg/m3, and the California Occupational Safety and Health Administration PEL is 5 mg/m3. An exposure of 5 mg B/m3 translates to approximately 0.01 mmol B/kg b.wt./d that, coincidentally, is the same as exposure levels associated with combined municipal drinking water, diet, and body building supplement consumption. Infants may receive exposures to boric acid when it is used as a household insecticide for cockroach control. Exposure from boric acid-containing cosmetic and personal care products applie

Determination of angiographic (TIMI grade) blood flow by intracoronary Doppler flow velocity during acute myocardial infarction

BACKGROUND

This study compared angiographically graded coronary blood flow with intracoronary Doppler flow velocity in patients during percutaneous transluminal coronary angioplasty (PTCA) for acute myocardial infarction. Different TIMI angiographic flow grades (flow grades based on results of the Thrombolysis in Myocardial Infarction trial) have been associated with different clinical results after reperfusion for acute myocardial infarction. However, intracoronary blood flow velocity has not been compared with the angiographic method of determining flow grade in patients.

METHODS AND RESULTS

Coronary flow velocity (measured by use of a Doppler guidewire) during primary or rescue PTCA in 41 acute myocardial infarction patients was compared with TIMI grade and cineframes-to-opacification count. Before PTCA, 34 patients had TIMI grade 0 or 1, 5 had TIMI grade 2, and 2 had TIMI grade 3 flow in the infarct artery. Flow velocity was similar among patients with TIMI grades 0, 1, or 2 but was lower than in those with TIMI grade 3 flow (9.4 +/- 5.4 versus 16.0 +/- 5.4 cm/s for TIMI grades < or = 2 versus TIMI grade 3, respectively; P < .05). After PTCA, 1 patient had TIMI grade 1, 5 had TIMI 2, and 35 had TIMI 3 flow. Poststenotic flow velocity increased from 6.6 +/- 6.1 to 20.0 +/- 11.1 cm/s (P < .01). TIMI grade 3 flow increased to 21.8 +/- 10.9 cm/s (P < .05 versus before PTCA). Although post-PTCA flow velocity correlated with angiographic cineframes-to-opacification count (r = .45; P < .02) for TIMI grade 3, there was a large overlap with TIMI grades < or = 2 that had low flow velocity (< 20 cm/s). Nine of 11 clinical events (unstable angina and coronary artery bypass graft surgery) occurred in patients with low coronary flow velocity.

CONCLUSIONS

Determination of flow velocity after reperfusion may enhance patient characterization and provide the physiological rationale for clinical variations after reperfusion therapy.

Identification of the gltX gene encoding glutamyl-tRNA synthetase from Methanobacterium thermoautotrophicum

The gltX gene encoding glutamyl-tRNA synthetase from Methanobacterium thermoautotrophicum has been cloned, sequenced, and identified. The gene is located immediately downstream of idsA in an operon containing at least three additional ORFs. The deduced protein sequence from gltX contains conserved regions (HIGH and KMSKS) indicative of a class I aminoacyl-tRNA synthetase.

Translesional pressure and flow velocity after thrombolysis: assessment of suboptimal angioplasty for serial lesions

Translesional pressure and flow velocity observations in the right coronary artery remain among the most difficult data to interpret because of variation in the location and relative size of branches, and unsuspected diffuse disease. Use of distal hyperemic response and translesional pressure gradients provides the most accurate assessment of serial lesions in such patients. In addition, the use of intracoronary thrombolysis can improve the angiographic appearance of lesions and facilitate later successful interventions. The post-infarction distal microvascular responsiveness may be impaired and, thus, abnormal coronary reserve values in this particular setting should be considered with lesion specific indicators of successful recanalization.

Patterns of phasic coronary collateral flow velocity in patients

Antegrade or retrograde collateral flow velocity Doppler signals, acquired with the flowire, permit the quantitation of collateral blood flow and its phasic patterns. The velocity spectra are easily visualized, and reproducible alterations during balloon occlusion may be directly related to coronary collateral flow-dependent variables of ischemia and left ventricular wall motion. The effects of pharmacologic stimulation on collateral flow remain under study.