Ocular and systemic toxicity of high-dose intravitreal topotecan in rabbits: Implications for retinoblastoma treatment.

Although many more eyes of children with retinoblastoma are salvaged now compared to just 10 years ago, the control of vitreous seeding remains a challenge. The introduction of intravitreal injection of melphalan has enabled more eyes to be salvaged safely but with definite retinal toxicity. Intensive treatment with high-dose intravitreal topotecan may be a strategy to control tumor burden because of its cell cycle-dependent cytotoxicity and the proven safety in humans. Therefore, we evaluated the ocular and systemic safety of repeated high-dose intravitreal injections of topotecan in rabbits. Systemic and ocular toxicity was assessed in non-tumor-bearing rabbits after four weekly injections of three doses of topotecan (10 µg, 25 µg, and 50 µg) or vehicle alone. Animals were evaluated weekly for general and ophthalmic clinical status. One week after the last injection, vitreous and plasma samples were collected for drug quantification and the enucleated eyes were subjected to histological assessment. Weight, hair loss, or changes in hematologic values were absent during the study period across all animal groups. Eyes injected with all topotecan doses or vehicle showed no signs of anterior segment inflammation, clinical or histologic evidence of damage to the retina, and ERG parameters remained unaltered throughout the study. Vitreous and plasma topotecan lactone concentrations were undetectable. Four weekly intravitreal injections of topotecan up to 50 µg in the animal model or a 100 µg human equivalent dose were not toxic for the rabbit eye. High doses of topotecan may show promising translation to the clinic for the management of difficult-to-treat retinoblastoma vitreous seeds.

Mutations of the beta myosin heavy chain gene in hypertrophic cardiomyopathy: critical functional sites determine prognosis.

OBJECTIVES: To assess patients with different types of mutations of the beta myosin heavy chain (beta MHC) gene causing hypertrophic cardiomyopathy (HCM) and to determine the prognosis of patients according to the affected functional domain of beta MHC. DESIGN AND SETTING: Cohort study of subjects referred to an HCM clinic at an academic hospital. PATIENTS: 70 probands from the HCM clinic were screened for mutations of the beta MHC gene and 148 family members of the genotype positive probands were further assessed. The control group for the genetic studies consisted of 106 healthy subjects. MAIN OUTCOME MEASURES: Direct DNA sequencing was used to screen 70 probands for mutations of the beta MHC gene. Family members underwent genotypic and detailed clinical, ECG, and echocardiographic assessments. The survival of genotype positive subjects was evaluated according to the type of functional domain affected by the missense mutation and according to phenotypic characteristics. RESULTS: A mutation of the beta MHC gene was detected in 15 of 70 probands (21%). Of 148 family members studied in these 15 families, 74 were identified with a beta MHC defect. Eleven mutations were detected, including four novel mutations: Ala196Thr, Pro211Leu, Val404Leu, and Arg870Cys. Median survival was 66 years (95% confidence interval (CI) 64 to 77 years) in all affected subjects. There was a significant difference in survival between subjects according to the affected functional domain (p = 0.02). Significant independent predictors of decreased survival were the non-conservative (that is, associated with a change in the amino acid charge) missense mutations that affected the actin binding site (hazard ratio 4.4, 95% CI 1.6 to 11.8; p = 0.003) and those that affected the rod portion of beta MHC (hazard ratio 4.8, 95% CI 1.2 to 19.4; p = 0.03). No phenotypic characteristics were associated with decreased survival or cardiovascular morbidity. CONCLUSIONS: The type of beta MHC functional domain affected by the missense mutation is predictive of overall prognosis in HCM.

Conditioned nutritional deficiencies in the cardiomyopathic hamster heart.

BACKGROUND: Evidence indicates that nutritional factors may be important in the maintenance of myocyte structure and energetics. The failing myocardium has been reported to exhibit a depletion of several nutrients that are important for the maintenance of intracellular calcium homeostasis and cellular energetics, and levels of oxidative stress. This nutrient depletion may contribute to the progressive deterioration in myocardial structure and function observed in heart failure. OBJECTIVE: To examine the extent to which advanced cardiomyopathy results in a depletion of nutrients and/or metabolites and antioxidants, and whether supplementation with these nutrients may influence cellular structure or function. SUBJECTS AND METHODS: Cardiomyopathic hamsters were randomly placed to one of the three following diet groups: chow; control gelled diet; or a supplemented gelled diet that provided taurine, carnitine, coenzyme Q10, selenium, vitamins E and C, creatine, thiamine and L-cysteine. After approximately three months of supplementation, one group of hamsters underwent functional testing using a modified Langendorff technique with biopsy samples taken for electron microscopy. Myocardial nutrient concentrations were determined in a second group of diseased and nondiseased hamsters of the same age. RESULTS: Cardiomyopathy resulted in a depletion of vitamin E, creatine, carnitine, taurine and coenzyme Q10. Supplementation resulted in improved cardiac ultrastructure, function and contractility compared with nonsupplemented hamsters. CONCLUSIONS: These studies suggest that heart failure results in 'condition-related nutrient deficiencies' that, once corrected, can significantly impact on heart function and structure.

Blood pressure variability in Binswanger's disease and isolated lacunar infarction.

UNLABELLED: To determine whether blood pressure (BP) variability is increased in hypertensive patients with Binswanger's disease (BD), we studied two samples of consecutive treated hypertensive patients: (1) 11 with BD (mean age 71.3 +/- 5.2 years); (2) 16 with lacunar infarction (mean age 65.2 +/- 8.3 years) without cognitive impairment. An averaged baseline office BP was obtained for 3 consecutive weeks. Ambulatory BP monitoring was then carried out to obtain the averaged mean systolic (SBP) and diastolic BP, and BP variability was defined as the standard deviation of consecutive BP values. RESULTS: Diurnal SBP variability was significantly increased in the BD group (p = 0.04). However, with the analysis of covariance for age and baseline office BP, the difference was no longer significant (p = 0.17 and p = 0.09, respectively). We conclude that increased BP variability in BD patients is probably due to older age and increased baseline office BP. Increased BP variability may be a risk factor for small-vessel disease, but not for cognitive impairment.

A controlled clinical trial of vitamin E supplementation in patients with congestive heart failure.

BACKGROUND: Oxidative stress is increased in patients with congestive heart failure and can contribute to the progressive deterioration observed in these patients. Increased oxidative stress is the result of either an increased production of free radicals or a depletion of endogenous antioxidants, such as vitamin E. OBJECTIVE: We aimed to determine whether vitamin E supplementation of patients with advanced heart failure would modify levels of oxidative stress, thereby preventing or delaying the deterioration associated with free radical injury. DESIGN: Fifty-six outpatients with advanced heart failure (New York Heart Association functional class III or IV) were enrolled in a double-blind randomized controlled trial for 12 wk. At a baseline visit and at 2 follow-up visits, blood and breath samples were collected for the measurement of indexes of heart function and disease state, including malondialdehyde, isoprostanes, and breath pentane and ethane. Quality of life was also assessed at baseline and after 12 wk of treatment. RESULTS: Vitamin E treatment significantly increased plasma concentrations of alpha-tocopherol in the treatment group but failed to significantly affect any other marker of oxidative stress or quality of life. In addition, concentrations of atrial natriuretic peptide (a humoral marker of ventricular dysfunction), neurohormonal-cytokine markers of prognosis, tumor necrosis factor, epinephrine, and norepinephrine were unchanged with treatment and were not significantly different from those in the control group. CONCLUSION: Supplementation with vitamin E did not result in any significant improvements in prognostic or functional indexes of heart failure or in the quality of life of patients with advanced heart failure.

Blood pressure variability and leukoaraiosis amount in cerebral small-vessel disease.

OBJECTIVES: To analyze the correlation between blood pressure (BP) variability and leukoaraiosis (LA) amount in patients with symptomatic cerebral small-vessel disease. MATERIALS AND METHODS: We included 25 hypertensive patients: 13 with Binswanger's disease (BD) and 12 with a first-ever lacunar infarction (LI). Baseline office BP was obtained for 3 consecutive weeks. From a 24-h ambulatory BP monitoring performed 1 week later we obtained average systolic (SBP) and diastolic (DBP) BP for daytime, nighttime and 24-h periods. SBP and DBP variability was defined as the within-subject standard deviation of all readings. A standardized cerebral MR was performed in each patient and an LA score was calculated. RESULTS: No statistically significant correlation was obtained between the LA score and any of the following BP values: 1) Baseline SBP and DBP; 2) 24-h, daytime or nighttime SBP and DBP, and 3) 24-h, daytime or nighttime SBP and DBP variability. CONCLUSION: Increased BP variability is not associated with greater amounts of leukoaraiosis.

Variants of trophic factors and expression of cardiac hypertrophy in patients with hypertrophic cardiomyopathy.

Patients with hypertrophic cardiomyopathy (HCM) exhibit variable expression of left ventricular hypertrophy (LVH), a major determinant of mortality and morbidity, which is partly due to the diversity of causal mutations, genetic background (modifier genes), and probably environmental factors. We determined association of functional variants of tumor necrosis factor (TNF)- alpha, interleukin-6 (IL6), insulin-like growth factor-2 (IGF2), transforming growth factor- beta 1 (TGFB1), and aldosterone synthase (CYP11B2) genes, all previously implicated in cardiac hypertrophy, with the severity of LVH in patients with HCM. Two-dimensional echocardiography was performed and demographic variables were recorded in 142 genetically independent patients. Indices of LVH including interventricular septal thickness (IVST), left ventricular mass index (LVMI), and LVH score were measured/calculated. TNF-alpha-308G/A, IL6-174G/C, IGF2 820G/A, TGFB1-509C/T, and CYP11B2-344T/C genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Genotypes were identified by the presence of specific electrophoretic patterns and their distributions were according to the Hardy-Weinberg equilibrium. Demographic variables were not significantly different among the genotypes. Subjects with the AA genotype of TNF-alpha (n=8) were approximately 13 years younger at the time of clinical diagnosis. Despite a younger age, they had a greater mean LVMI than those with the GG (n=94) or GA (n=33) genotypes (191.8+/-59.5 v 139.1+/-47.3 v 132.1+/-34.3, respectively, P=0.004). TNF-alpha-308G/A genotypes accounted for 6.0% of variability of LVMI (P=0.002). Mean IVST, LVEDD, and LVH score were not significantly different. Variants of IL6, IGF2, TGFB1, and CYP11B2 were not associated with indices of LVH. The uncommon allele of TNF-alpha-308G/A polymorphism, known to produce more TNF- alpha, was associated with greater LVMI and clinical diagnosis at a younger age in patients with HCM. Functional variants of other trophic factors, previously implicated in cardiac hypertrophy, were not associated with the indices of LVH. These results suggest that TNF-alpha is a modifier gene for HCM.

Conditioned nutritional requirements and the pathogenesis and treatment of myocardial failure.

The majority of symptomatic patients with congestive heart failure have been shown to be significantly malnourished. Myocardial and skeletal muscle energy reserves are also diminished. Total daily energy expenditure in these patients is less than that in control individuals, and high protein-calorie feeds do not reverse the abnormalities; thus, the wasting that occurs in patients with congestive heart failure is metabolic rather than because of negative protein-calorie balance. Several specific deficiencies have been found in the failing myocardium: a reduction in the content of L-carnitine, coenzyme Q10, creatine and thiamine, nutrient cofactors that are important for myocardial energy production; a relative deficiency of taurine, an amino acid that is integral to the modulation of intracellular calcium levels; and an increase in myocardial oxidative stress, and a reduction of both endogenous and exogenous antioxidant defences. In addition, these processes may influence skeletal muscle metabolism and function. Cellular nutritional requirements conditioned by metabolic abnormalities in heart failure are important considerations in the pathogenesis of the skeletal and cardiac muscle dysfunction. A comprehensive restoration of adequate myocyte nutrition would seem to be essential to any therapeutic strategy designed to benefit patients suffering from this disease.

Usefulness of the I/D angiotensin-converting enzyme genotype for detecting the risk of left ventricular hypertrophy in pharmacologically treated hypertensive men.

The insertion/deletion polymorphism (I/D) of the angiotensin-converting enzyme (ACE) gene has been associated in some studies with a higher prevalence of left ventricular hypertrophy (LVH), but few of them were performed on pharmacologically treated hypertensive patients. The present study was undertaken to determine whether ACE genotype determination could help in the identification of pharmacologically treated hypertensive patients at a higher risk of LVH. Ninety-six consecutive men with essential hypertension were selected for the study. Left ventricular mass (LVM) was assessed by echocardiography and indexed by body surface area and 82 patients were considered suitable for the study. Three groups of patients were defined on the basis of their I/D ACE genotype: DD (n = 39), ID (n = 33) and II (n = 10). There were no statistically significant differences between the three groups regarding to the severity of hypertension at diagnosis, degree of control of blood pressure or type of antihypertensive drug therapy used. No statistically significant differences were found between the three groups regarding to LVM index (total 124 +/- 31, DD 121 +/- 29, ID 127 +/- 35 and II 122 +/- 18 g/m2), relative wall thickness (total 0.5 +/- 0. 2, DD 0.5 +/- 0.3, ID 0.48 +/- 0.07 and II 0.47 +/- 0.04) or prevalence of LVH (total 34%, DD 31%, ID 39% and II 30% by Cornell criteria and total 39%, DD 33%, ID 45% and II 40% by Framingham criteria). Furthermore, the I and D allele frequency distribution was similar in the whole group of patients, in patients with LVH, and in a control group of healthy volunteers. Our data do not support that the I/D ACE genotype determination helps in identifying treated hypertensive patients at higher risk of LVH. Journal of Human Hypertension (2000) 14, 327-331

A biochemical, histochemical, and electron microscopic study on the effects of iron-loading on the hearts of mice.

Acute iron poisoning and chronic iron overload are well-known causes of myocardial failure. Although the exact mechanism is not known, excess iron-catalyzed free radical generation is conjectured to play a role in damaging the myocardium and altering cardiac function. We report here on the effects of acute and chronic iron-loading on the total iron concentration, glutathione peroxidase activity, and cytotoxic aldehyde production in the heart of a murine model (n = 35). Light microscopic examination for the presence of ferrous and ferric iron was undertaken following histochemical staining for these species. In addition, examination of representative samples by transmission electron microscopy was performed. Our findings show that iron-loading can result in significant increases in total iron concentrations, alterations to glutathione peroxidase activity, and increases in cytotoxic aldehyde concentrations in the hearts of mice. Furthermore, we observe that iron-loading can significantly alter and damage various cellular constituents (e.g., mitochondria, lysosomes, sarcoplasmic reticulum) and this may have bearing on the mechanism of iron-induced heart failure.

What is the relevance of apoptosis to the myocardium?

Direct and indirect evidence from a number of studies demonstrates that apoptosis is an important process in heart failure in humans. It is thought that a proapoptotic shift in conditions occurs during heart failure, involving the entire population of cardiac myocytes. A complex mechanism of programmed cell death has been postulated, involving such factors as Fas, Bax and Bcl-2; tumour necrosis may also play a role. Given the myriad apoptotic pathways, a number of opportunities for treatment have been identified.

Effect of a single bolus of intracoronary basic fibroblast growth factor on perfusion in an ischemic porcine model.

Basic fibroblast growth factor (bFGF) has been shown to induce angiogenesis in various animal models, but the methods of administration used experimentally are not clinically feasible. The objective of this study was to determine whether a single intracoronary bolus injection of bFGF would improve coronary perfusion in a porcine ischemic model that mimics clinical chronic ischemia. A copper coil studded with gold was delivered into the proximal right coronary artery of juvenile Yorkshire pigs and deployed by interventional techniques. After a four-week interval for stenosis maturation, bFGF (100 micrograms) was administered by bolus injection into the left coronary artery in five animals, and vehicle alone was administered in four animals. Angiogenesis and change in right coronary perfusion area were assessed two weeks later by angiography, myocardial contrast echocardiography and immunohistochemistry. The right coronary perfusion area increased significantly after treatment in all but one of the animals that received bFGF but not in any of the controls. Intimal hyperplasia was not induced by bFGF. Capillary density determined histochemically was not different in the two groups. In conclusion, in a porcine ischemic model, bFGF administered by a single bolus intracoronary injection into the contralateral artery improved antegrade perfusion into the ischemic territory although without histological evidence of angiogenesis. This preliminary work merits further investigation.

The synergistic effects of vitamin E and selenium in iron-overloaded mouse hearts.

OBJECTIVES: To determine whether supplementation with vitamin E and selenium can improve myocardial antioxidant defenses in iron-overloaded mouse hearts. INTERVENTIONS: Iron-overload state was created in B6D2F1 mice (n = 20) by daily injection of iron dextran (5 mg intraperitoneally/mouse) for four weeks. The mice were also simultaneously randomly assigned to receive vitamin E (alpha-tocopherol acetate, 40 mg intraperitoneally, n = 5), selenium (sodium selenite, 1 part/million orally, n = 5), both (vitamin E + selenium, n = 5) or iron-only treatment (n = 5). The hearts were harvested for determination of selenium concentration and glutathione peroxidase activity. In a subsequent study, 15 B6D2F1 mice were randomly assigned to receive daily injections of iron (n = 5) or iron and combined antioxidant treatment (vitamin E + selenium, n = 5), or to serve as controls (n = 5) for four weeks. The hearts were harvested for determination of total iron concentrations. MAIN RESULTS: Significantly greater concentrations of heart selenium and glutathione peroxidase activity were observed in groups supplemented with both agents, as opposed to iron-only treated or single supplemented mice. Significantly lower concentrations of iron were found in controls and in those receiving combined iron and antioxidant treatment (vitamin E + selenium) than in iron-only treated mice. CONCLUSIONS: Vitamin E and selenium function synergistically in the myocardium to provide important antioxidant defenses in iron-overload states, including increased concentrations of selenium, increased glutathione peroxidase activity and decreased concentrations of iron.

Increased oxidative stress in patients with congestive heart failure.

OBJECTIVES: We sought to study the markers of lipid peroxidation and defenses against oxidative stress in patients with varying degrees of heart failure. BACKGROUND: Despite advances in other areas of cardiovascular disease, the morbidity and mortality from congestive heart failure (CHF) are increasing. Data mainly from animal models suggest that free radical injury may promote myocardial decompensation. However, there are no studies in humans correlating the severity of heart failure with increased free radical injury and antioxidants. METHODS: Fifty-eight patients with CHF and 19 control subjects were studied. In addition to complete clinical and echocardiographic evaluations, the prognosis of these patients was established by measuring the levels of soluble tumor necrosis factor-alpha receptors 1 and 2 (sTNF-R1 and sTNF-R2). Oxidative stress was evaluated by measuring plasma lipid peroxides (LPO), malondialdehyde (MDA), glutathione peroxidase (GSHPx) and vitamin E and C levels. RESULTS: The patients' age range, cause of heart failure and drug intake were comparable across the different classes of heart failure. Heart failure resulted in a significant increase in LPO (p < 0.005), MDA (p < 0.005), sTNF-R1 (p < 0.005) and sTNF-R2 (p < 0.005). There was a significant positive correlation between the clinical class of heart failure and LPO, MDA, sTNF-R1 and sTNF-R2 levels. There was an inverse correlation between GSHPx and LPO. With increased lipid peroxidation in patients with CHF, the levels of vitamin C decreased, but vitamin E levels were maintained. CONCLUSIONS: These data demonstrate a progressive increase in free radical injury and encroachment on antioxidant reserves with the evolution of heart failure; they also suggest that oxidative stress may be an important determinant of prognosis. The therapeutic benefit of administering antioxidant supplements to patients with CHF should be evaluated.

Vitamin E and oxidative stress in the heart of the cardiomyopathic syrian hamster.

Myocardial deterioration is relentlessly progressive in almost all patients who develop overt symptoms. Many dilated cardiomyopathies are associated with a marked increase in cardiac sympathetic tone which may be toxic to myocytes. Microvascular spasm, leading to diffuse, focal reperfusion injury, also appears to be an important mechanism of cardiomyocyte loss in many models of dilated cardiomyopathy. Free radicals may mediate both catecholamine-induced damage and reperfusion injury. We hypothesized that myocardial antioxidant reserve may be significantly reduced in dilated cardiomyopathy and that alpha-tocopheryl acetate may be of benefit. The enzymes superoxide dismutase, catalase and glutathione peroxidase were measured in the myocardial tissue of control and cardiomyopathic hamsters in early (25-50 days) and late (275-320 days) stages of the cardiomyopathy. In another study, myocardial glutathione peroxidase activity and protein oxidation was measured in control and late stage cardiomyopathic hamsters receiving alpha-tocopheryl (70 mg/kg/day) or vehicle for 1 month. There were no significant differences in glutathione peroxidase activity between control and cardiomyopathic hamsters in the early stage of the cardiomyopathy. Superoxide dismutase and catalase activities did not change with aging; however, glutathione peroxidase decreased over 30%, alpha-tocopherol was reduced by approximately 50% and protein oxidation increased more than 2-fold in the hearts of late stage cardiomyopathic hamsters. Alpha-tocopheryl acetate administration restored alpha-tocopherol levels, glutathione peroxidase activity and protein oxidation to normal. We conclude that the decompensating heart has significantly limited antioxidant reserve and that this reserve is sensitive to the intake of antioxidant supplements.

Oxidative stress and the pathogenesis of heart failure.

There is strong evidence for an adverse role of oxidative stress in CHF in both animals and humans. Antioxidant supplement have been very effective in the treatment of animal paradigms; however, the data for the possible benefits of treatment for patients with CHF is either retrospective or inferential. Such information is important and should be the subject of prospective randomized trials.

Shifting the paradigm for the treatment of dilated cardiomyopathy.

Dilated cardiomyopathy (DCM) has emerged as a major health problem during the past two decades. In spite of recent advances, it has become clear that the underlying heart disease is relentlessly progressive in almost all patients who develop symptoms of overt failure; morbidity and mortality continues to be unacceptably high with an incidence of approximately 30% for death or hospital admission at one year. Cardiac transplantation remains the only current prospect for dramatically improving survival in many patients. Trying to enhance cardiac function during the later stages of heart failure is ultimately fruitless; it cannot be done over the long term. The solution to failure lies in defining and preventing its causes or arresting and reversing its evolution. We propose a model where the target for therapeutic intervention becomes the arrest of progressive myocardial disease throughout the course of the cardiomyopathy. In this paradigm, the selection of therapeutic agents for the treatment of heart failure takes into consideration both the stage of the disease and differences in pathogenesis. In addition it broadens our approach from one which focuses on enhancing myocardial function to one which encompasses strategies which are designed to inhibit the progressive loss of myocytes and the inexorable deterioration of the failing myocardium.

Concerted evolution of mammalian cardiac myosin heavy chain genes.

We have recently determined the complete nucleotide sequences of the cardiac alpha- and beta-myosin heavy chain (MyHC) genes from both human and Syrian hamster. These genomic sequence data were used to study the molecular evolution of the cardiac MyHC genes. Between the alpha- and beta-MyHC genes, multiple gene conversion events were detected by (1) maximum parsimony tree analyses, (2) synonymous substitution analyses, and (3) detection of pairwise identity of intron sequences. Approximately half of the 40 cardiac MyHC exons have undergone concerted evolution through the process of gene conversion with the other half undergoing divergent evolution. Gene conversion occurred more often in exons encoding the alpha-helical myosin rod domain than in the globular head domain, and an apparent directional bias was also observed, with transfer of genetic material occurring more often from beta to alpha.

Characterization and structural organization of the cardiac beta-myosin heavy chain gene from Syrian hamster.

In order to perform comparative studies of the cardiac myosin heavy chain (MyHC) genes, we determined the sequence of the Syrian hamster beta-MyHC gene and its 5' flanking region. This 33,960 basepair (bp) sequence contains 12,196 bp of the 5' flanking region as well as 21,731 bp of the complete beta-MyHC gene, with its 3' end overlapping with the alpha-MyHC gene. All the exon/intron boundaries were determined and relative to the human beta-MyHC gene, an extra 5' untranslated exon was identified. The isolation and sequencing of the Syrian hamster beta-MyHC gene may further the understanding about the regulation and the evolution of the cardiac MyHC genes.

Spatio-temporal patterns of velopharyngeal action in phonetic and phonological nasalization.

The aim of this paper is to differentiate between effects of phonetic implementation and effects of phonological structure in the adjustment of articulatory trajectories to varying speech rate. Cross-linguistic data on coarticulatory nasalization of vowels preceding a nasal consonant at different speech rates were analyzed in American English and Spanish. The two languages show different patterns of timing, magnitude, duration, and velocity of velopharyngeal movements. In Spanish the velocity of velar port (VP) opening and closing gestures is not affected by differences in speech rate, which suggests that these trajectories reflect the default articulatory movements automatically implemented by the phonetic component. In American English, VP closing velocity is not affected by speech rate whereas opening velocity adjusts to variations in speech rate to ensure vowel nasalization across rates. The careful regulation of VP opening velocity suggests that it is centrally controlled. Interarticulatory timing data support this interpretation: In Spanish, vowels are oral for most of their duration; onset of VP opening is timed relative to the following nasal consonant and peak VP size occurs at nasal consonant onset across rates, which suggests that the motor commands for opening the velar port are part of the instructions for the nasal consonant. In American English, on the other hand, VP opening onset coincides with vowel onset and peak VP size occurs in the middle of the vowel across rates, which indicates that opening movements are part of the programming instructions for the vowel. It is argued that, in Spanish, vowels followed by a nasal consonant are targeted as oral and are nasalized as a result of a coarticulatory effect, whereas, in American English, vowels are targeted as nasalized as a result of a phonological rule.