Fostering diversity in mathematics cognition

Integrating diverse perspectives in psychological science can enhance innovation in research and allow research teams to better study diverse populations of individuals through an authentic lens. Despite recent efforts to better address issues of race and ethnicity in research samples, the field of psychology broadly-and the area of mathematics cognition specifically-has largely failed to support scientists from diverse racial and ethnic backgrounds. In this essay, we consider the unique contributions that scholars of color can make to psychological research in mathematics cognition. Next, we reveal common challenges faced by scholars of color and challenges to recruiting and maintaining scholars of color in our community with a focus on Black scholars. Finally, we propose actions for diversifying the "pipeline" of promising scholars.

Building fraction magnitude knowledge with number lines: Partitioning versus analogy

Understanding fraction magnitudes is foundational for later math achievement. To represent a fraction x/y, children are often taught to use partitioning: Break the whole into y parts and shade in x parts. Past research has shown that partitioning on number lines supports children's fraction magnitude knowledge more than partitioning on area models. However, partitioning may not take full advantage of children's prior knowledge or the structure of the number line. We tested an alternative fraction number line lesson that leveraged children's preexisting whole number knowledge using a domain-general learning tool: analogy. In a preregistered online experiment, second and third graders (N = 84, M = 8.83 years) were randomly assigned to an analogy lesson (e.g., if I know how big 3 is on a 0-4 line, I know how big ¾ is on a 0-1 line), a partitioning lesson on number lines, or a control lesson using square area models. Results showed that the analogy lesson was more effective for promoting fraction magnitude understanding than the control lesson, and it was at least as effective as the partitioning lesson. The analogy group, but not the partitioning group, significantly outperformed the control group with large-denominator fractions at retention (i.e., 1-week delayed posttest) and on transfer tests (i.e., fraction comparison). We also replicated past findings that fraction partitioning lessons are more effective on number lines than on area models, and this advantage was partially sustained after a 1-week delay. Overall, these findings highlight the power of domain-general analogy to support mathematical development. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Number lines can be more effective at facilitating adults' performance on health-related ratio problems than risk ladders and icon arrays

Visual displays, such as icon arrays and risk ladders, are often used to communicate numerical health information. Number lines improve reasoning with rational numbers but are seldom used in health contexts. College students solved ratio problems related to COVID-19 (e.g., number of deaths and number of cases) in one of four randomly assigned conditions: icon arrays, risk ladders, number lines, or no accompanying visual display. As predicted, number lines facilitated performance on these problems-the number line condition outperformed the other visual display conditions, which did not perform any better than the no visual display condition. In addition, higher performance on the health-related ratio problems was associated with higher COVID-19 worry for oneself and others, higher perceptions of COVID-19 severity, and higher endorsement of intentions to engage in preventive health behaviors, even when controlling for baseline math skills. These findings have important implications for effectively presenting health statistics. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Is a substitute the same? Learning from lessons centering different relational conceptions of the equal sign

Understanding of the equal sign is associated with early algebraic competence in the elementary grades and equation-solving success in middle school. Thus, it is important to find ways to build foundational understanding of the equal sign as a relational symbol. Past work promoted a conception of the equal sign as meaning "the same as". However, recent work highlights another dimension of relational understanding-a substitutive conception, which emphasizes the idea that an expression can be substituted for another equivalent one. This work suggests a substitutive conception may support algebra performance above and beyond a sameness conception alone. In this paper, we share a subset of results from an online intervention designed to foster a relational understanding of the equal sign among fourth and fifth graders (n = 146). We compare lessons focused on a sameness conception alone and a dual sameness and substitutive conception to each other, and we compare both to a control condition. The lessons influenced students' likelihood of producing and endorsing sameness and substitutive definitions of the equal sign. However, the impact of the lessons on students' approaches to missing value equations was less clear. We discuss possible interpretations, and we argue that further research is needed to explore the roles of sameness and substitutive views of the equal sign in supporting structural approaches to algebraic equation solving.

What Can Cognitive Science Do for People?

The critical question for cognitive scientists is what does cognitive science do, if anything, for people? Cognitive science is primarily concerned with human cognition but has fallen short in continuously and critically assessing the who in human cognition. This complacency in a world where white supremacist and patriarchal structures leave cognitive science in the unfortunate position of potentially supporting those structures. We take it that many cognitive scientists operate on the assumption that the study of human cognition is both interesting and important. We want to invoke that importance to note that cognitive scientists must continue to work to show how the field is useful to all of humanity and reflects a humanity that is not white by default. We wonder how much the field has done, and can do, to show that it is useful not only in the sense that we might make connections with researchers in other fields, win grants and write papers, even of the highest quality, but useful in some material way to the billions of non-cognitive scientists across the globe.

Math matters: A novel, brief educational intervention decreases whole number bias when reasoning about COVID-19

At the onset of the coronavirus disease (COVID-19) global pandemic, our interdisciplinary team hypothesized that a mathematical misconception-whole number bias (WNB)-contributed to beliefs that COVID-19 was less fatal than the flu. We created a brief online educational intervention for adults, leveraging evidence-based cognitive science research, to promote accurate understanding of rational numbers related to COVID-19. Participants from a Qualtrics panel (N = 1,297; 75% White) were randomly assigned to an intervention or control condition, solved health-related math problems, and subsequently completed 10 days of daily diaries in which health cognitions and affect were assessed. Participants who engaged with the intervention, relative to those in the control condition, were more accurate and less likely to explicitly mention WNB errors in their strategy reports as they solved COVID-19-related math problems. Math anxiety was positively associated with risk perceptions, worry, and negative affect immediately after the intervention and across the daily diaries. These results extend the benefits of worked examples in a practically relevant domain. Ameliorating WNB errors could not only help people think more accurately about COVID-19 statistics expressed as rational numbers, but also about novel future health crises, or any other context that involves information expressed as rational numbers. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

More than the sum of its parts: Exploring the development of ratio magnitude versus simple magnitude perception

Humans perceptually extract quantity information from our environments, be it from simple stimuli in isolation, or from relational magnitudes formed by taking ratios of pairs of simple stimuli. Some have proposed that these two types of magnitude are processed by a common system, whereas others have proposed separate systems. To test these competing possibilities, the present study examined the developmental trajectories of simple and relational magnitude discrimination and relations among these abilities for preschoolers (n = 42), 2nd-graders (n = 31), 5th-graders (n = 29), and adults (n = 32). Participants completed simple magnitude and ratio discrimination tasks in four different nonsymbolic formats, using dots, lines, circles, and irregular blobs. All age cohorts accurately discriminated both simple and ratio magnitudes. Discriminability differed by format such that performance was highest with line and lowest with dot stimuli. Moreover, developmental trajectories calculated for each format were similar across simple and ratio discriminations. Although some characteristics were similar for both types of discrimination, ratio acuity in a given format was more closely related with ratio acuities in alternate formats than to within-format simple magnitude acuity. Results demonstrate that ratio magnitude processing shares several similarities to simple magnitude processing, but is also substantially different.

Taking the Relational Structure of Fractions Seriously: Relational Reasoning Predicts Fraction Knowledge in Elementary School Children

Understanding and using symbolic fractions in mathematics is critical for access to advanced STEM concepts. However, children and adults consistently struggle with fractions. Here, we take a novel perspective on symbolic fractions, considering them within the framework of relational structures in cognitive psychology, such as those studied in analogy research. We tested the hypothesis that relational reasoning ability is important for reasoning about fractions by examining the relation between scores on a domain-general test of relational reasoning (TORR Jr.) and a test of fraction knowledge consisting of various types of fraction problems in 194 second grade and 145 fifth grade students. We found that relational reasoning was a significant predictor of fractions knowledge, even when controlling for non-verbal IQ and fractions magnitude processing for both grades. The effects of relational reasoning also remained significant when controlling for overall mathematics knowledge and skill for second graders but was attenuated for fifth graders. These findings suggest that this important subdomain of mathematical cognition is integrally tied to relational reasoning and opens the possibility that instruction targeting relational reasoning may prove to be a viable avenue for improving children's fractions skills.

The Relational SNARC: Spatial Representation of Nonsymbolic Ratios

Recent research in numerical cognition has begun to systematically detail the ability of humans and nonhuman animals to perceive the magnitudes of nonsymbolic ratios. These relationally defined analogs to rational numbers offer new potential insights into the nature of human numerical processing. However, research into their similarities with and connections to symbolic numbers remains in its infancy. The current research aims to further explore these similarities by investigating whether the magnitudes of nonsymbolic ratios are associated with space just as symbolic numbers are. In two experiments, we found that responses were faster on the left for smaller nonsymbolic ratio magnitudes and faster on the right for larger nonsymbolic ratio magnitudes. These results further elucidate the nature of nonsymbolic ratio processing, extending the literature of spatial-numerical associations to nonsymbolic relative magnitudes. We discuss potential implications of these findings for theories of human magnitude processing in general and how this general processing relates to numerical processing.

Task Constraints Affect Mapping From Approximate Number System Estimates to Symbolic Numbers

The Approximate Number System (ANS) allows individuals to assess nonsymbolic numerical magnitudes (e.g., the number of apples on a tree) without counting. Several prominent theories posit that human understanding of symbolic numbers is based – at least in part – on mapping number symbols (e.g., 14) to their ANS-processed nonsymbolic analogs. Number-line estimation – where participants place numerical values on a bounded number-line – has become a key task used in research on this mapping. However, some research suggests that such number-line estimation tasks are actually proportion judgment tasks, as number-line estimation requires people to estimate the magnitude of the to-be-placed value, relative to set upper and lower endpoints, and thus do not so directly reflect magnitude representations. Here, we extend this work, assessing performance on nonsymbolic tasks that should more directly interface with the ANS. We compared adults’ (n = 31) performance when placing nonsymbolic numerosities (dot arrays) on number-lines to their performance with the same stimuli on two other tasks: Free estimation tasks where participants simply estimate the cardinality of dot arrays, and ratio estimation tasks where participants estimate the ratio instantiated by a pair of arrays. We found that performance on these tasks was quite different, with number-line and ratio estimation tasks failing to the show classic psychophysical error patterns of scalar variability seen in the free estimation task. We conclude the constraints of tasks using stimuli that access the ANS lead to considerably different mapping performance and that these differences must be accounted for when evaluating theories of numerical cognition. Additionally, participants showed typical underestimation patterns in the free estimation task, but were quite accurate on the ratio task. We discuss potential implications of these findings for theories regarding the mapping between ANS magnitudes and symbolic numbers.

Keys to the Gate? Equal Sign Knowledge at Second Grade Predicts Fourth-Grade Algebra Competence

Algebraic competence is a major determinant of college access and career prospects, and equal sign knowledge is taken to be foundational to algebra knowledge. However, few studies have documented a causal effect of early equal sign knowledge on later algebra skill. This study assessed whether second-grade students' equal sign knowledge prospectively predicts their fourth-grade algebra knowledge, when controlling for demographic and individual difference factors. Children (N = 177; M_age  = 7.61) were assessed on a battery of tests in Grade 2 and on algebraic knowledge in Grade 4. Second-grade equal sign knowledge was a powerful predictor of these algebraic skills. Findings are discussed in terms of the importance of foregrounding equal sign knowledge to promote effective pedagogy and educational equity.

Natural Alternatives to Natural Number: The Case of Ratio

The overwhelming majority of efforts to cultivate early mathematical thinking rely primarily on counting and associated natural number concepts. Unfortunately, natural numbers and discretized thinking do not align well with a large swath of the mathematical concepts we wish for children to learn. This misalignment presents an important impediment to teaching and learning. We suggest that one way to circumvent these pitfalls is to leverage students' non-numerical experiences that can provide intuitive access to foundational mathematical concepts. Specifically, we advocate for explicitly leveraging a) students' perceptually based intuitions about quantity and b) students' reasoning about change and variation, and we address the affordances offered by this approach. We argue that it can support ways of thinking that may at times align better with to-be-learned mathematical ideas, and thus may serve as a productive alternative for particular mathematical concepts when compared to number. We illustrate this argument using the domain of ratio, and we do so from the distinct disciplinary lenses we employ respectively as a cognitive psychologist and as a mathematics education researcher. Finally, we discuss the potential for productive synthesis given the substantial differences in our preferred methods and general epistemologies.

Making Space for Spatial Proportions

The three target articles presented in this special issue converged on an emerging theme: the importance of spatial proportional reasoning. They suggest that the ability to map between symbolic fractions (like 1/5) and nonsymbolic, spatial representations of their sizes or magnitudes may be especially important for building robust fractions knowledge. In this commentary, we first reflect upon where these findings stand in a larger theoretical context, largely borrowed from mathematics education research. Next, we emphasize parallels between this work and emerging work suggesting that nonsymbolic proportional reasoning may provide an intuitive foundation for understanding fraction magnitudes. Finally, we end by exploring some open questions that suggest specific future directions in this burgeoning area.

Fractions We Cannot Ignore: The Nonsymbolic Ratio Congruity Effect

Although many researchers theorize that primitive numerosity processing abilities may lay the foundation for whole number concepts, other classes of numbers, like fractions, are sometimes assumed to be inaccessible to primitive architectures. This research presents evidence that the automatic processing of nonsymbolic magnitudes affects processing of symbolic fractions. Participants completed modified Stroop tasks in which they selected the larger of two symbolic fractions while the ratios of the fonts in which the fractions were printed and the overall sizes of the compared fractions were manipulated as irrelevant dimensions. Participants were slower and less accurate when nonsymbolic dimensions of printed fractions were incongruent with the symbolic comparison decision. Results indicated a robust basic sensitivity to nonsymbolic ratios that exceeds prior conceptions about the accessibility of fraction values. Results also indicated a congruity effect for overall fraction size, contrary to findings of prior research. These findings have implications for extending theory about the nature of human number sense and mathematical cognition more generally.

Individual Differences in Nonsymbolic Ratio Processing Predict Symbolic Math Performance

What basic capacities lay the foundation for advanced numerical cognition? Are there basic nonsymbolic abilities that support the understanding of advanced numerical concepts, such as fractions? To date, most theories have posited that previously identified core numerical systems, such as the approximate number system (ANS), are ill-suited for learning fraction concepts. However, recent research in developmental psychology and neuroscience has revealed a ratio-processing system (RPS) that is sensitive to magnitudes of nonsymbolic ratios and may be ideally suited for supporting fraction concepts. We provide evidence for this hypothesis by showing that individual differences in RPS acuity predict performance on four measures of mathematical competence, including a university entrance exam in algebra. We suggest that the nonsymbolic RPS may support symbolic fraction understanding much as the ANS supports whole-number concepts. Thus, even abstract mathematical concepts, such as fractions, may be grounded not only in higher-order logic and language, but also in basic nonsymbolic processing abilities.

Fractions as percepts? Exploring cross-format distance effects for fractional magnitudes

This study presents evidence that humans have intuitive, perceptually based access to the abstract fraction magnitudes instantiated by nonsymbolic ratio stimuli. Moreover, it shows these perceptually accessed magnitudes can be easily compared with symbolically represented fractions. In cross-format comparisons, participants picked the larger of two ratios. Ratios were presented either symbolically as fractions or nonsymbolically as paired dot arrays or as paired circles. Response patterns were consistent with participants comparing specific analog fractional magnitudes independently of the particular formats in which they were presented. These results pose a challenge to accounts that argue human cognitive architecture is ill-suited for processing fractions. Instead, it seems that humans can process nonsymbolic ratio magnitudes via perceptual routes and without recourse to conscious symbolic algorithms, analogous to the processing of whole number magnitudes. These findings have important implications for theories regarding the nature of human number sense - they imply that fractions may in some sense be natural numbers, too.

Outcome of endovascular intervention for infrainguinal vein graft stenosis

Assisted graft patency rate following revision of a graft stenosis is far better than that following thrombectomy of an occluded graft. Graft revision by endovascular means has been proposed as a suitable alternative to more invasive surgery. This study reports our experience with endovascular treatment of vein graft stenosis. Between December 1992 and September 2000, percutaneous transluminal balloon angioplasty (PTA) was performed on 90 vein graft stenoses in 87 infrainguinal vein bypass grafts identified by routine graft duplex scan (peak systolic velocity, PSV > 300 cm/sec). All 90 stenoses treated by PTA were retrospectively analysed for stenosis-free patency rate (life-table analysis). Re-stenosis was defined by PSV exceeding 300 cm/sec at the same site of the vein graft where a stenosis was dilated. Ninety vein graft stenoses (72 primary stenoses and 18 recurrent stenoses) in 33 femoropopliteal (above knee), 30 femoropopliteal (below knee) and 24 femorotibial vein bypass grafts were treated by PTA. The timing of PTA ranged from one to 252 months (mean, 23.9 months) from the initial surgery. Cumulative stenosis-free patency rate after PTA was 55.8% at 6 months, 54.0% at one year and 45.0% at three years. Stenosis-free patency rate at six months was significantly lower for revision of recurrent stenosis (25.9%) than for primary stenosis (61.6%) (P = 0.01). The revision of duplex scan detected vein graft stenosis with endovascular intervention was associated with an acceptable stenosis-free patency rate. However, recurrent stenosis treated by PTA had a significantly inferior outcome. Direct surgical revision would be more appropriate for recurrent lesions.

Lipid levels and peripheral vascular disease in diabetic and non-diabetic subjects

Non-insulin dependent diabetes (NIDDM) is associated with an increased risk of peripheral vascular disease (PVD), but within the diabetic population the relationship between lipid profile and PVD has not been clearly defined. In this study we examined the association of lipid parameters and in particular low density lipoprotein (LDL) particle size, with the presence of PVD in subjects with and without NIDDM. 41 NIDDM patients and 31 non-diabetic subjects with PVD in the absence of rest pain or ulceration, defined by ankle-brachial index measurements and duplex scanning, were compared with 41 NIDDM and 31 euglycemic control subjects of comparable age and sex, without PVD. In both groups those with PVD were found to have significantly elevated triglycerides (2.7 [2.2-3.3] versus 1.9 [1.6-2.2] mmol/l; P < 0.05 in the diabetic group and 2.0 [1.6-2.3] versus 1.4 [1.1-1.5] mmol/l; P < 0.05 in the non-diabetic group), decreased apolipoprotein A1 (124 +/- 3 versus 139 +/- 5 mg/dl; P < 0.01 in the diabetic group and 133 +/- 4 versus 147 +/- 4 mg/dl; P < 0.05 in the non-diabetic group) and decreased LDL particle size (25.4 +/- 0.1 versus 25.8 +/- 0.1 nm; P < 0.01 in the diabetic group and 26.0 +/- 0.1 versus 26.3 +/- 0.1 nm; P < 0.05 in the non diabetic group). In the non-diabetic group apolipoprotein[a] (365 [239-554] versus 184 [17-266] U/l; P < 0.01), total cholesterol (6.3 +/- 0.2 versus 5.6 +/- 0.2 mmol/l; P < 0.05), LDL cholesterol (4.1 +/- 0.2 versus 3.6 +/- 0.2 mmol/l; P < 0.05) and apolipoprotein B (146 +/- 8 versus 117 +/- 5 mg/dl; P < 0.05) were also found to be associated with PVD although these associations were not observed in the group with diabetes. In addition, 11 NIDDM subjects and 11 non-diabetic subjects with rest pain or ulceration were compared to the corresponding groups with uncomplicated PVD and had lipid profiles with significantly lower levels of total cholesterol and LDL cholesterol. We conclude that the dyslipidemic profile characterized by increased triglyceride level, decreased apolipoprotein A1 level and small dense LDL is associated with uncomplicated PVD in both NIDDM and non-diabetic subjects.

Clinical and vascular laboratory determinants for outcome after infrainguinal atherectomy

Three surgeons performed 180 atherectomy procedures in 161 patients using the Transluminal Extraction Catheter in 144 and the Auth Rotablator in 36. The primary patency rate was 55% at 1 year and 46% at 2 years, and failure was caused by stenosis in 28 (15.6%) and occlusion in 61 (33.7%) limbs. Multivariate Cox regression analysis showed significantly better outcome if the indication was claudication, the lesion was short or there was associated stenting. Vascular laboratory surveillance was performed in 93 limbs in 83 patients. Cox regression analysis in this subgroup also showed a significant relationship between outcome and the maximum peak systolic velocity from a duplex scan at the last study performed. Receiver operating characteristics curves showed that a raised maximum peak systolic velocity best predicted late failure (sensitivity 84%, specificity 66% for > 200 cm/s; sensitivity 72%, specificity 84% for > 250 cm/s); the velocity ratio at the stenosis to that in the segment above or the resting ankle/brachial pressure index were less predictive. For 50 procedures studied in the vascular laboratory which remained successful to the end of the study, maximum peak systolic velocities were > 250 cm/s from the first postoperative study, suggesting residual stenosis in 6%, or increased to become > 250 cm/s by the last study, suggesting recurrent stenoses in 12%. For 43 procedures which were studied and later failed, velocities were > 250 cm/s from the first test in 26% or increased to > 250 cm/s by the last test before failure in 40%. Vascular laboratory surveillance helps to predict outcome after atherectomy. Failure may be a result of residual disease from the time of the procedure or from restenosis. The apparent high incidence of clinically manifest or developing stenoses raises doubts as to the benefit of atherectomy over balloon dilatation alone.

Duplex ultrasonography scanning for chronic venous disease: patterns of venous reflux

PURPOSE

Patterns of flow in superficial and deep veins and outward flow in medial calf perforators were studied by duplex ultrasonography scanning in 1653 lower limbs in 1114 consecutive patients. This study compares results in 776 limbs with primary uncomplicated varicose veins with those in 166 limbs with the complications of lipodermatosclerosis or past venous ulceration.

METHODS

Duplex scanning determined whether superficial and deep veins were occluded or showed reflux and whether outward flow occurred in medial calf perforators with calf muscle contraction.

RESULTS

Two proximal deep veins were occluded. When limbs with primary uncomplicated varicose veins, lipodermatosclerosis, or past ulceration were compared, superficial reflux alone was seen in 55%, 39%, and 38%, deep reflux alone was seen in 2%, 7%, and 8%, and combined superficial and deep reflux was seen in 18%, 34%, and 48%, respectively. Superficial reflux affected the long saphenous system alone in 58%, 57%, and 40%, the short saphenous system alone in 18%, 18%, and 26%, and both the long and short saphenous systems in 24%, 25%, and 34%, respectively. Limbs with ulceration more frequently showed superficial reflux (p < 0.05), and all limbs with complications more frequently showed short saphenous reflux (p < 0.05) and deep reflux (p < 0.01) specifically in the posterior tibial veins (p < 0.01). Outward flow was seen in medial calf perforators in 57%, 67%, and 66%, respectively; it occurred more frequently in all limbs with complications (p < 0.05). Isolated outward flow in perforators without superficial or deep reflux was seen in 10%, 10%, and 2%, respectively.

CONCLUSIONS

Most limbs with complications had superficial reflux either alone or combined with deep reflux, and few had deep reflux alone. Reflux was more frequent in posterior tibial veins for limbs with complications compared with those with uncomplicated primary varicose veins. Outward flow in perforators was common in limbs with complications and with uncomplicated primary varicose veins, but isolated outward flow in perforators was uncommon. Treatment directed to the superficial veins alone may be sufficient for most patients with complications.

Improvement in arterial stiffness during hypolipidaemic therapy is offset by weight gain

Fourteen patients with familial hypercholesterolaemia were managed with dietary advice and simvastatin for 12 months. Either nicotinic acid or cholestyramine resin was added to the regimen if serum cholesterol was not less than 5.5 mmol/l within 18 weeks. After dietary advice but before commencing pharmacotherapy for hyperlipidaemia, arterial stiffness was measured in the common carotid and common femoral arteries. These studies were repeated after 12 months on pharmacotherapy. The primary objective of this study was to determine whether arterial stiffness could be altered with total cholesterol and low density lipoprotein (LDL) cholesterol lowering. Over the 12 month interval, serum total cholesterol, LDL cholesterol and triglycerides fell significantly, whereas high density lipoprotein (HDL) cholesterol and body mass index (BMI) rose significantly. Mean supine blood pressure did not change significantly. Arterial stiffness in the common carotid artery decreased from 1.04 +/- 0.21 x 10(5) N/m2 to 0.63 +/- 0.06 x 10(5) N/m2 (T = -2.67, P < 0.01) over the interval. Stiffness of the common femoral artery decreased from 2.10 +/- 0.57 x 10(5) N/m2 to 0.83 +/- 0.15 x 10(5) N/m2 (T = -2.73, P < 0.01). The change in arterial stiffness was not directly related to changes in circulating lipids or supine blood pressure. Increase in BMI, however, correlated with change in arterial stiffness in the common femoral artery (Rs = 0.53, P < 0.05) but not in the common carotid artery. An increase in BMI was associated with a smaller decrease in common femoral arterial stiffness. Aggressive hypolipidaemic therapy was therefore associated with a favourable effect on arterial wall stiffness.(ABSTRACT TRUNCATED AT 250 WORDS)

Early post-operative ankle pressure indices help predict late patency rates after femoro-distal vein bypass grafting

A prospective graft surveillance programme included 115 femorodistal autogenous vein bypass grafts that were patent when studied by measurements of ankle/brachial pressure indices (ABIs) at 3-5 weeks after operation. The grafts were followed for up to 3 years to determine whether early ABIs helped to predict subsequent failures, defined as graft thrombosis or graft or anastomotic stenosis causing diameter reduction greater than 75% treated by surgery or balloon dilatation. Receiving operating characteristics curves showed that resting ABIs predicted failure better than post-exercise ABIs or the differences between the two, and that an early resting ABI less than 0.85 was the optimal value to predict failure. Primary patency rates at 2 years were 88% for resting ABI greater than or equal to 0.85 and 36% for resting ABI less than 0.85 (p less than 0.0005). Most stenoses occurred in the grafts and not at anastomoses. Arteriographic grading of crural artery outflow was not significantly different for successful or failed grafts or for grafts with resting ABI greater than or equal to 0.85 or less than 0.85. The observation that late graft failure was 3-4 times more likely if the early post-operative ABI was low suggests that most graft failures result from faults relating to the operation.

Double-blind study of dilevalol and captopril, both in combination with hydrochlorothiazide, in patients with moderate to severe hypertension

Sixty-one patients (41 men, 20 women) aged 29-73 years, with moderate to severe hypertension, were enrolled in a multicentre study to compare the efficacy, safety, and tolerability of dilevalol (D) and captopril (C). At the end of the baseline period, supine diastolic blood pressure (SuDBP) was 105-140 mm Hg on hydrochlorothiazide (HCTZ) 25 mg once daily and placebo t.i.d. Patients were randomly assigned to D + HCTZ (n = 29) or C + HCTZ (n = 32) and entered phase II titration of D (100-800 mg b.i.d.) or C (12.5 mg b.i.d. to 50 mg t.i.d.). If SuDBP was greater than 99 mm Hg, hydralazine was added (25 mg once daily to 50 mg b.i.d.). If SuDBP was less than or equal to 99 mm Hg, patients entered phase III, a 3-month maintenance period. Demographic profiles were not significantly different between the two groups. Baseline supine BP (mean +/- SEM) was similar in the two groups (D + HCTZ: 182 +/- 3/112 +/- 1; C + HCTZ: 179 +/- 4/113 +/- 1 mm Hg), as was baseline standing BP (D + HCTZ: 175 +/- 3/114 +/- 2; C +/- HCTZ: 173 +/- 4/113 +/- 1 mm Hg). At the end of phase II, there were no significant differences between treatments with respect to the changes in BP from baseline.(ABSTRACT TRUNCATED AT 250 WORDS)

Risk factors for coronary heart disease in a self-referred population compared with a general population

Screening programmes for community coronary heart disease risk factors aim to identify persons who are at a high risk of the development of coronary heart disease by screening the population for the prevalence of smoking, obesity, high blood pressure and high blood cholesterol concentrations. The effectiveness of such screening programmes is dependent on a number of factors. The characteristics of individuals who attend such screening programmes voluntarily, and the prevalence of abnormal coronary heart disease risk factors that is detected, give a strong indication of the population reach and the potential benefits of the preventive strategy. In this study, persons who attended a self-referred risk-factor screening programme for coronary heart disease were compared with a random sample of the Australian urban population. A disproportionately high number of older persons and of women presented for the self-referred screening programme while smokers were underrepresented. In general, the risk-factor levels of those in the older age-groups who attended the screening programme were lower than were the corresponding measurements that were found in the random sample; the opposite was true for those in the younger age-groups. These results suggest that coronary heart disease risk-factor screening programmes in the community appeal more to those in the health-conscious older age-groups and to women. For heart disease prevention programmes to be more effective, it will be necessary to design screening programmes to attract more men, those in younger age-groups and smokers.

Comparison of felodipine extended release and conventional tablets in essential hypertension using ambulatory blood pressure monitoring

Two formulations of felodipine, conventional and extended release (ER) tablets, were compared in a double-blind, crossover study of patients whose blood pressure was not being controlled using metoprolol 100 mg once daily. Nineteen patients with a supine diastolic blood pressure greater than or equal to 95 mmHg after 4 weeks of taking metoprolol and placebo were randomly assigned to felodipine conventional (5 mg twice a day) or ER (10 mg once daily) for 4 weeks. A 2-week washout period was then followed by 4 weeks of treatment with the alternative formulation. Metoprolol once daily was taken concomitantly throughout the study. Clinic blood pressure was measured at 0 h (i.e. 12 h after the last dose of conventional, and 24 h after the last ER felodipine dose), and then 2 and 5 h after the following dose had been taken. Ambulatory blood pressure and the heart rate were monitored over 24 h using an Accutracker (Suntech Medical Instruments, Raleigh, North Carolina, USA). During the final treatment, both felodipine formulations caused similar substantial falls in supine blood pressure compared with pressures prior to randomized treatment. The falls in clinic blood pressures (systolic/diastolic) were similar with the conventional and ER formulations at all time points, i.e. 0 h (21/13; 19/11 mmHg), 2 h (39/18; 36/18 mmHg) and 5 h (30/12; 35/11 mmHg) after the morning dose was taken. Both formulations also produced similar falls in blood pressures over 24 h and during the daytime (21/12; 20/12 mmHg).(ABSTRACT TRUNCATED AT 250 WORDS)

Lack of cross sensitivity between captopril and enalapril

Oral inhibitors of angiotensin converting enzyme (ACE) now have an established place in the treatment of hypertension and heart failure. Captopril, the first of these agents, was initially used in high doses and was associated with adverse effects including proteinuria, skin rash and taste disturbance. We report 11 patients who developed side effects during captopril therapy (proteinuria two, rash four, taste disturbance four and taste disturbance with rash one) who were subsequently treated with enalapril, a second generation angiotensin converting enzyme inhibitor. Proteinuria did not recur in either patient, skin rash resolved in all five cases and taste disturbance resolved in four of five during enalapril therapy. We conclude that the side effects of proteinuria, skin rash and taste disturbance are consequences of captopril idiosyncrasy rather than inhibition of the angiotensin converting enzyme. The reported incidence of these side effects with the current recommended dosage of captopril is low.

Differential renal function during angiotensin converting enzyme inhibition in renovascular hypertension

Renal function was measured sequentially in 32 patients with proven renovascular hypertension who were treated with the oral angiotensin converting enzyme inhibitor captopril. Renal function was assessed by serial measurement of serum creatinine. Six patients showed acute rises in serum creatinine concentration compatible with acute renal failure. Acute renal failure was confined to those patients with stenosis to a solitary kidney (transplant or native, occurring in 3 of 8 patients) or bilateral renal artery stenosis (occurring in 3 of 13 patients). No rise in serum creatinine concentration was observed in 11 patients with unilateral renal artery stenosis during long-term angiotensin converting enzyme inhibitor therapy. Acute renal failure during angiotensin converting enzyme inhibitor therapy was not related to the degree of blood pressure fall or the plasma angiotensin II level. Eleven patients with renovascular hypertension were followed prospectively with estimation of renal function by 99mTc-diethylenetriaminepentaacetic acid (DTPA) clearance (determined by computer analysis of scintillation camera renography). In six patients with unilateral renal artery stenosis, total 99mTc-DTPA clearance and serum creatinine level remained constant following angiotensin converting enzyme inhibitor therapy, while in five patients with bilateral renal artery stenosis 99mTc-DTPA clearance fell from 40 +/- 9 to 27 +/- 5 ml/min (p less than 0.05). Split renal function studies revealed that 99mTc-DTPA clearance fell in most kidneys with stenosed arteries during angiotensin converting enzyme inhibition, including the stenosed kidney from patients with unilateral renal artery stenosis (16 stenosed kidneys studied; change in Tc-DTPA clearance, -7.5 +/- 2.7 ml/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Controlled trial of enalapril in congestive cardiac failure

Twenty five patients with chronic congestive cardiac failure had enalapril (n = 13) or placebo (n = 12) added to their existing regimen of digoxin and frusemide in a randomised double blind trial. Four hours after the first 5 mg dose, the enalapril group showed significant falls in blood pressure, heart rate, and concentrations of plasma angiotensin II, angiotensin converting enzyme, and noradrenaline. During the 12 week trial heart failure became worse in one enalapril treated patient (8%) and in seven placebo treated patients (58%). There were no significant changes in cardiac ejection fraction or exercise duration in either group. Plasma noradrenaline response to graded exercise and maximum exercise rate-pressure product were significantly reduced after four and 12 weeks of active treatment but unchanged with placebo treatment. There was a sustained increase in plasma potassium and a slight rise in plasma creatinine in the enalapril group. Plasma concentrations of the active drug, enalaprilate, were dose related and log enalaprilate correlated significantly with percentage of plasma angiotensin converting enzyme activity (r = -0.66). Enalapril was well tolerated and produced no adverse effects. The drug appears to be superior to placebo and offers considerable promise for the treatment of this condition.

Hypotensive effect of captopril and decreased rat uterine bradykinin receptors

To determine the role of local bradykinin at the level of the vascular smooth muscle receptors in the hypotensive effect of captopril, we assessed the effects of prolonged intravenous infusions for up to 7 days of bradykinin (0.1 microgram/min) and captopril (1.7 micrograms/min) on systolic blood pressure and uterine bradykinin receptors in normotensive rats. Bradykinin infusion was associated with a transient fall in systolic blood pressure at Day 1 (117.5 +/- 2.8 mmHg vs. 125.8 +/- 1.7, p less than 0.05) and returned to control levels by Day 3. Following captopril infusion there was a similar but more persistent fall in systolic blood pressure (115.3 +/- 2.4 mmHg vs. 125.8 +/- 1.7, p less than 0.01 at Day 1 and 111.0 +/- 2.4 mmHg vs. 125.0 +/- 1.9, p less than 0.001 at Day7). After 2 days of bradykinin infusion the number of bradykinin receptors was decreased (39.9 +/- 2.1 fmol/mg protein vs. 49. 9 +/- 2.4, p less than 0.01) and returned to controls at Day 7, while captopril infusion induced a prolonged decrease (42.3 +/- 1.8 fmol/mg protein vs. 49.9 +/- 2.4, p less than 0.05 at Day 2 and 38.8 +/- 2.4 fmol/mg protein vs. 44.5 +/- 1.3, p less than 0.05 at Day 7). Present results suggest that the increased vascular tissue level of bradykinin can contribute directly to the acute hypotensive effect of captopril. However, it may play only a minor role for the chronic hypotensive effect of captopril.

Bradykinin receptors in rat uterine smooth muscle: studies using radiolabeled ligand binding

Direct binding of 125I-Tyr8-bradykinin to a microsomal fraction prepared from rat uterine smooth muscle, showed an apparent dissociation constant (KD) at 29 degrees C of 5.0 X 10(-10) M calculated from kinetic studies and 6.6 X 10(-10) M from Scatchard plot analysis. The binding of 125I-Tyr8-bradykinin was reversible and saturable, and demonstrated high specificity for Tyr8-bradykinin, bradykinin and Lys-bradykinin, but was not displaced by unrelated peptides angiotensin I, angiotensin II, Arg8-vasopressin and oxytocin. The binding sites were copurified by differential centrifugation and on a discontinuous sucrose density gradient with 5'-nucleotidase activity, a plasma membrane marker enzyme. Prolonged intravenous infusion of bradykinin (5 nmol/h for 2 days) induced a 20% decrease in the number of bradykinin binding sites without a change in the equilibrium dissociation constant. The present results demonstrate that receptors mediating the effect of bradykinin on rat uterine smooth muscle are situated on plasma membranes and the regulation of the receptors is in part under the control of endogenous bradykinin levels.

Influences of low sodium diets on vascular effects of bradykinin and on bradykinin receptors in the uterine smooth muscle in the rats

A low sodium diet for 7 days in the rat induced an enhancement of the vascular effects of bradykinin, determined as the blood pressure response, by 56%. However, this enhancement reverted after 28 days of a low sodium diet. A sustained increase in the number of uterine smooth muscle bradykinin receptors during low sodium diets was observed, 1.3 times of the control on the 7th day and 1.7 times on the 28th day. No change in binding affinity was found in any of the studies. These results suggest that the vascular effects of bradykinin after low sodium diets may be regulated by homeostatic mechanisms via the change in the number of vascular smooth muscle bradykinin receptors at subcellular levels, and that the number of uterine smooth muscle bradykinin receptors may be affected by sodium status per se.

Regulation of uterine smooth muscle bradykinin receptors by bradykinin levels and angiotensin converting enzyme inhibitor in the rat

1. Bradykinin infusion (0.1 microgram/min i.v.) decreased the number of uterine bradykinin receptors by 20% at Day 2. Bradykinin receptors returned to control levels at Day 7. 2. Captopril infusion (1.7 micrograms/min i.v.) induced prolonged decreases in the number of uterine bradykinin receptors of 15% at Day 2 and of 13% at Day 7, respectively. 3. The number of uterine bradykinin receptors was increased in two-kidney, one clip hypertensive rats by 19%. 4. These results suggest that endogenous bradykinin participates in the regulation of uterine bradykinin receptors. 5. Decreased uterine bradykinin receptors induced by captopril might reflect increased endogenous bradykinin.

Use of captopril in the diagnosis of renal hypertension

1. The effects of a single 25 mg oral dose of captopril on blood pressure, heart rate and circulating renin, angiotensin I, angiotensin II, bradykinin and catecholamine levels were examined in untreated patients with essential (n = 10, Group I), accelerated (n = 6, Group II) and renal hypertension (n = 8, Group III) studied on a normal sodium diet. 2. Mean blood pressure fell only slightly in Group I patients, (113 +/- 3 to 109 +/- 3 mmHg at 60 minutes) but a greater fall was observed in Group II (153 +/- 8 to 135 +/- 11 mmHg) and a marked fall in Group III, (136 +/- 3 to 114 +/- 5 mmHg). There were no significant changes in heart rate in any group. 3. Plasma angiotensin II levels were significantly reduced 30 minutes after captopril in all three groups and returned toward resting values after four hours. The falls in plasma angiotensin II levels were accompanied by reciprocal increases in blood angiotensin I and plasma renin, but blood bradykinin and plasma catecholamine concentrations remained unchanged. 4. Resting plasma renin levels showed considerable overlap in the three groups and the mean renin values were not significantly different in the three groups. After captopril a marked rise in plasma renin concentration (greater than 2.5 ng/ml/hr) was observed in seven patients in Group III, including all six patients with renovascular disease. In contrast, none of the patients with essential hypertension and only one patient with accelerated hypertension had such an increase. Determination of the acute renin and blood pressure responses to converting enzyme inhibition with a single oral dose of captopril appears to be useful in identifying patients with renovascular hypertension.

Acute effects of captopril on blood pressure and circulating hormone levels in salt-replete and depleted normal subjects and essential hypertensive patients

1. The acute effects of a single oral dose of captopril on blood pressure, pulse rate and circulating levels of angiotensin I (ANG I), angiotensin II (ANG II), renin, bradykinin and catecholamines were studied in three groups: eight normal subjects, six salt-depleted normal subjects and 16 patients with essential hypertension. 2. Captopril treatment did not cause any significant fall in supine blood pressure in salt-replete normal subjects or patients with untreated essential hypertension but was associated with a fall in mean blood pressure from 85 +/- 2 to 75 +/- 2 mmHg in salt-depleted normal subjects and from 131 +/- 7 to 117 +/- 5 mmHg in patients with essential hypertension treated with diuretics. There was no change in pulse rate in any group. 3. Hormonal responses to captopril were qualitatively similar in the three groups and consisted of significant falls in ANG II with corresponding increases in ANG I and plasma renin concentration. The changes in plasma renin concentration and ANG I were greater in salt-depleted normal subjects (mean values at 90 min were 1140% and 990% of basal levels respectively) than in salt-replete normal subjects (410%, 190%) and were blunted in patients with essential hypertension (140%, 120%). Blood bradykinin, noradrenaline and adrenaline concentrations did not change after captopril in any group. 4. The parallel fall in blood pressure and ANG II levels in salt-depleted normal subjects is consistent with maintenance of blood pressure by increased levels of ANG II in sodium depletion. 5. The failure of captopril to reduce acutely blood pressure in patients with essential hypertension despite suppression of plasma ANG II and without change in circulating bradykinin confirms that the renin-angiotensin system does not play a primary role in essential hypertension.

Acute changes in blood pressure and vasoactive hormones after captopril in hypertensive patients

1. The acute effects of captopril on blood pressure, renin, angiotensin, bradykinin and catecholamines were examined in patients with essential (n = 10, Group 1), accelerated (n = 6, Group 2) and renal hypertension (n = 14, Group 3). 2. Blood pressure showed little change in Group 1, fell significantly in Group 2, with a marked fall in Group 3. Heart rate did not change. 3. The fall in blood pressure was positively correlated with pretreatment renin and angiotensin II. 4. Angiotension II fell, with reciprocal increases in renin and angiotensin I. No changes occurred in bradykinin or catecholamines. 5. The rise in renin after captopril was greatest in renovascular hypertension which may prove useful as a screening test for such patients.

Hormonal changes with long-term converting-enzyme inhibition by captopril in essential hypertension

1. Captopril was shown to be as effective as hydrochlorothiazide in lowering the blood pressure in patients with moderately severe essential hypertension. 2. With the combination of captopril and hydrochlorothiazide satisfactory control of blood pressure was maintained over 8 months. 3. Inhibition of angiotensin converting enzyme by captopril in man was associated with falls in plasma angiotensin II and urinary aldosterone and rises in angiotensin I and plasma renin. 4. No change in venous concentrations of bradykinin could be demonstrated during therapy. 5. Captopril attenuated the hyperaldosteronism and hypokalaemia associated with diuretic therapy.

Long-term effects of captopril (SQ14 225) on blood-pressure and hormone levels in essential hypertension

Captopril, an orally active angiotensin-converting enzyme (ACE) inhibitor, was effective in the long-term reduction of blood-pressure in 17 patients with essential hypertension. The addition of hydrochlorothiazide produced a further hypotensive effect, and the combined treatment produced satisfactory control of the blood-pressure for eight months. Captopril prevented and reversed the secondary hyperaldosteronism and hypokalaemia induced by simultaneous diuretic administration, thus eliminating the need for potassium supplements. The fall in plasma-angiotensin-II and urinary aldosterone and rise in angiotensin I and plasma-renin provide biochemical evidence that captopril inhibits ACE in vivo. No change in circulating venous bradykinin levels could be detected. The hypotensive action of captopril is not mediated by changes in blood-bradykinin but may involve inhibition of the renin-angiotensin and kallikrein-kinin systems locally within the kidneys or blood vessels.

Sodium intake and plasma angiotensin level as modulators of adrenal and uterine angiotensin II receptors in the rat

Angiotensin II receptors from rat adrenal cortex and myometrium were studied with the use of tritiated angiotensin under conditions where the sensitivity of the target organs for angiotensin II is modified. Sodium status was found to modulate the number of angiotensin receptors both in adrenal gland and uterus. In both target tissues low Na+ diet increases the number of receptors, while a high Na+ diet results in an increase in uterine receptors without modifying adrenal cortical receptors. However, a more markedly positive sodium balance, such as that observed in deoxycorticosterone acetate (DOCA) hypertension and in one-kidney Goldblatt hypertension, resulted in a reduction of the adrenocortical angiotensin II binding capacity. The endogenous angiotensin II level may also regulate the number of receptor sites as demonstrated by an increased number of receptors after suppression of circulating angiotensin II. It is proposed that the number of angiotensin II receptors is determined by the combined influences of sodium status and angiotensin II concentration. Some changes in the sensitivity of the target organ can be secondary to variations in the number of angiotensin receptors. However, others cannot be so explained and stem, therefore, from events occurring beyond the hormone-receptor interaction.

Alterations of adrenal and uterine angiotensin II receptors during variation of sodium intake and/or experimental hypertension

1. Angiotensin II receptors from rat adrenal gland and myometrium were studied during variation of sodium intake. 2. In both target-tissues low Na+ diet increased the number of receptors whereas a high Na+ diet did not modify the adrenocortical receptors but increased the number of uterine receptors. 3. Deoxycorticosterone and one kidney Goldblatt hypertension were associated with a decrease in the number of adrenal receptors. 4. Alterations of angiotensin II receptors alone cannot explain satisfactorily the variations of sensitivity of target-cells to angiotensin II during sodium balance changes.

Emergency treatment of severe hypertension with intravenous labetalol

The effects of intravenously administered labetalol on blood pressure and pulse rate were examined in 17 patients with severe hypertension. Prompt and sustained falls in supine blood pressure and pulse rate occurred in ten patients (responders), but seven patients showed little or no change in either measurement (non-responders). Labetalol had a more marked effect on standing than on supine blood pressure. Only two of the responders, but all of the non-responders were concurrently receiving antihypertensive drugs. Plasma renin activity, plasma renin concentration and plasma angiotensin II concentration fell slightly over the one-hour period of observation in ten patients in whom serial measurements were made, but the changes were independent of the blood pressure response.

Specific receptors for des-Asp1-angiotensin II (("angiotensin III") in rat adrenals

The specific binding of angiotensin II and des-Asp1-angiotensin II ("angiotensin III") III") to rat adrenals was studied with the use of the tritiated peptides. The binding sites having maximal affinity for angiotensin II were characterized by an equilibrium dissociation constant of 3.3 to 5.2 X 10(-9) M. Angiotensin III was able to interact with these sites, and also with a class of sites with very high affinity, characterized by an equilibrium dissociation constant of 1 to 2 X 10(-10) M. These sites exhibited a greater affinity for the heptapeptide angiotensin III than for the octapeptide angiotensin II. These findings, together with the known potent aldosterone stimulating effect of angiotensin III and its presence in rat plasma, suggest that this heptapeptide could be the physiologically important steroidogenic angiotensin in this species.