Biomedical subjects

S Holcomb

Publications and source records attributed to S Holcomb.

18 recordsLinked to original sources

PubMed2000

Factors affecting blood pressure responses to diet: the Vanguard study.

To study physiologic factors affecting the blood pressure (BP) response to nonpharmacologic maneuvers, fasting blood glucose, insulin, lipid and mineral levels, urinary mineral excretion, and the calcium regulating hormones parathyroid hormone (PTH) and 1,25 dihydroxyvitamin D (1,25 (OH)2D) were measured in 71 unmedicated hypertensive (26 hypertensive only [HT], 45 hypertensive hyperlipidemic [HTHL]), and 87 normotensive hyperlipidemic (NTHL) control subjects before and during a 10-week multicenter, randomized controlled trial comparing a prepared meal plan (CCNW) with a self-selected diet (SSD) based on nutritionist counseling. Blood pressure fell to a greater extent in hypertensive versus normotensive subjects (-8+/-1/-5+/-1 v -2+/-1/-2+/-1 mm Hg, P < .0001/P < .0001), and on CCNW versus SSD diets (delta systolic BP [SBP]/delta diastolic BP [DBP], P = .033/P = .002). Diet-induced weight change was the strongest correlate of changes in BP (SBP: r = 0.360, P < .0001; DBP: r = 0.414, P < .0001), which, on multivariate analysis for deltaSBP, could partly be accounted for by diet-induced changes in fasting glucose (r = 0.215, P = .009) and cholesterol (r = 0.219, P = .006) levels. Independently of weight, diet-induced changes in SBP also were significantly related to concomitant changes in urinary excretion of potassium (r = -0.285, P = .001), magnesium (r = -0.254, P = .003), and calcium relative to sodium (r = -0.200, P = .021), but not to sodium per se; and to changes in serum potassium (r = -0.249, P = .002), phosphorus (r = -0.279, P = .001), PTH (r = 0.288, P = .0006), and 1,25 D (r = 0.202, P = .017). We conclude that the ability of diet to lower BP successfully may result from the additive contributions of multiple components. Independently of weight loss and the associated changes in circulating glucose and cholesterol, BP is influenced by the increasing provision of minerals such as potassium, magnesium, and calcium, perhaps by virtue of their suppressive effects on circulating vasoactive calcium regulating hormones.

Adult↗

PubMed1999

Nutritionally complete prepared meal plan to reduce cardiovascular risk factors: a randomized clinical trial.

OBJECTIVE: To compare a nutritionally complete prepared meal plan that meets national dietary guidelines to usual-care dietary therapy for hypertension, dyslipidemia, and glycemic control. DESIGN: Randomized, controlled trial. SUBJECTS/SETTING: Outpatients with hypertension, dyslipidemia, or diabetes mellitus (n = 251) were recruited at 6 medical centers in the United States and Canada. INTERVENTION: The prepared meal plan, which was developed by university-based nutrition and cardiovascular scientists and food technologists at Campbell's Center for Nutrition & Wellness (CCNW), provided the optimal levels of macronutrients and micronutrients recommended for cardiovascular risk reduction in a variety of prepackaged meals and snacks. After a 4-week pretrial period to assess baseline state, participants were randomized to the CCNW plan or "usual-care" diet for 10 weeks. MAIN OUTCOME MEASURES: Blood pressure, carbohydrate metabolism, lipoproteins, homocysteine, weight, nutrient intake, compliance. STATISTICAL ANALYSES PERFORMED: Repeated measures analysis of variance. RESULTS: Lipoproteins, carbohydrate metabolism, blood pressure, and weight improved on both plans. Mean differences (+/- standard deviation) between baseline and follow-up for the CCNW plan and the usual-care plan, respectively, were total cholesterol, -0.41 +/- 0.64 and -0.20 +/- 0.50 mmol/L (between-group P < .01); plasma glucose, -0.7 +/- 1.7 and -0.3 +/- 1.3 mmol/L (P < .05); systolic blood pressure, -5.2 +/- 10.0 and -4.7 +/- 9.0 mm Hg (P = .67), diastolic blood pressure, -3.8 +/- 5.9 and -2.2 +/- 5.5 mm Hg (P < .05); and homocysteine, -1.3 +/- 3.8 and 0.2 +/- 3.4 mumol/L (P < .01). The CCNW plan led to greater weight loss than the usual-care diet (-5.5 +/- 3.8 kg vs -3.0 +/- 3.2 kg, P < .0001). APPLICATIONS/CONCLUSION: The nutritionally complete CCNW plan offers greater improvements in lipids, blood sugars, homocysteine, and weight loss than usual-care diet therapy. This prepackaged comprehensive nutrition program can augment both the prescription and practice of optimal dietary therapy.

Adult↗

PubMed1999

Increased dietary micronutrients decrease serum homocysteine concentrations in patients at high risk of cardiovascular disease.

BACKGROUND: Elevated blood homocysteine is a risk factor for cardiovascular disease. A 5-micromol/L increase is associated with an approximately 70% increase in relative risk of cardiovascular disease in adults. For patients with established risk factors, this risk is likely even greater. OBJECTIVE: Effects of increased dietary folate and recommended intakes of vitamins B-12 and B-6 on serum total homocysteine (tHcy) were assessed in individuals at high risk of cardiovascular disease. DESIGN: This trial was conducted at 10 medical research centers in the United States and Canada and included 491 adults with hypertension, dyslipidemia, type 2 diabetes, or a combination thereof. Participants were randomly assigned to follow a prepared meal plan (PMP; n = 244) or a self-selected diet (SSD; n = 247) for 10 wk, which were matched for macronutrient content. The PMP was fortified to provide >/=100% of the recommended dietary allowances for 23 micronutrients, including folate. RESULTS: Mean folate intakes at 10 wk were 601 +/- 143 microgram/d with the PMP and 270 +/- 107 microgram/d with the SSD. With the PMP, serum tHcy concentrations fell from 10.8 +/- 5.8 to 9.3 +/- 4.9 micromol/L (P < 0.0001) between weeks 0 and 10 and the change was associated with increased intakes of folate, vitamin B-12, and vitamin B-6 and with increased serum and red blood cell folate and serum vitamin B-12 concentrations. tHcy concentrations did not change significantly with the SSD. CONCLUSIONS: The PMP resulted in increased intakes and serum concentrations of folate and vitamin B-12. These changes were associated with reduced serum tHcy concentrations in persons at high risk of cardiovascular disease.

Adult↗

PubMed1998

Accuracy of an automated blood pressure device in stable inpatients: optimum vs routine use.

BACKGROUND: Despite widespread use of the automated blood pressure (BP) device (IVAC model 4200, IVAC Corporation, San Diego, Calif), there is little formal validation in the literature on its accuracy. OBJECTIVE: To assess the accuracy of the IVAC 4200 device, both under standardized conditions and as routinely used by ward staff, compared with the true indirect BP measured by mercury manometer (MM). METHODS: One hundred forty-five stable inpatients were randomly selected for BP measurements by 3 randomly ordered protocols: (1) MM performed by certified investigators, (2) IVAC 4200 BP performed by trained investigators (research automated [RA]), and (3) IVAC 4200 BP performed by ward personnel (ward automated [WA]). RESULTS: For RA compared with MM ("true" indirect BP), 59% of systolic and 54% of diastolic readings were within 5 mm Hg and 83% of systolic and 86% of diastolic were within 10 mm Hg for a British Hypertension Society grade C for both. For WA compared with MM, 40% of systolic and 50% of diastolic readings were within 5 mm Hg and 70% of systolic and 80% of diastolic readings were within 10 mm Hg for British Hypertension Society grades D and C, respectively. The presence of arrhythmias and/or low K5 values (fifth phase of Korotkoff sounds <30 mm Hg) significantly increased the inaccuracy for diastolic values. Inappropriate cuff selection significantly increased inaccuracy of systolic BP (WA vs MM). CONCLUSIONS: The IVAC 4200 yields substandard estimates of systolic and diastolic BP even under standardized, thus optimum conditions. The presence of arrhythmias or low K5 values and the selection of inappropriate cuff size by the ward staff also contributed to inaccuracy.

Adult↗

PubMed1998

Comprehensive nutrition plan improves cardiovascular risk factors in essential hypertension.

Increased arterial pressure is known to be influenced by a variety of nutrients. Compliance with dietary recommendations for risk reduction is often limited by the complexity of their implementation. In addition, how improvements in total diet, rather than single nutrients, influence concomitant cardiovascular risk factors has not been thoroughly explored. We assessed the effects of a nutritionally complete prepared meal program, the Campbell's Center for Nutrition and Wellness plan (CCNW), compared with dietary therapy in which participants received a structured nutritional assessment and prescription and selected their own foods, in 101 women and men with mild-to-moderate hypertension. Outcome measures included blood pressure (BP), lipids and lipoproteins, glucose, glycosylated hemoglobin (HbA1c), insulin, homocysteine, nutrient intake, compliance, and quality of life. Both dietary interventions significantly lowered BP (P < .0001), while simultaneously improving the overall cardiovascular risk profile. Significantly greater benefits were observed with the CCNW plan as compared with the participant selected diet in cholesterol and LDL levels (both P < .0001), LDL:HDL (P < .001), HbA1c (P < .05), homocysteine (P < .001), total nutrient intake (P < .0001), compliance (P < .0001), and quality of life (P < .001). This study demonstrates that improving the total diet to include the full array of recommended dietary guidelines, rather than focusing on single nutrients, has significant benefits for the cardiovascular risk profile of hypertensive persons beyond BP control. Compared with typical dietary therapy, the comprehensive CCNW meal plan has significantly greater effects on multiple cardiovascular risk factors while yielding greater compliance and improved quality of life.

Adult↗

PubMed1997

Direct measurement of three-dimensionally reconstructed flow convergence surface area and regurgitant flow in aortic regurgitation: in vitro and chronic animal model studies.

BACKGROUND: Evaluation of flow convergence (FC) with two-dimensional (2D) imaging systems may not be sufficiently accurate to characterize these often asymmetric, complex phenomena. The aim of this study was to validate a three-dimensional (3D) method for determining the severity of aortic regurgitation (AR) in an experimental animal model. METHODS AND RESULTS: In six sheep with surgically induced chronic AR, 20 hemodynamically different states were studied. Instantaneous regurgitant flow rates were obtained by aortic and pulmonary electromagnetic flow meters. Video composite data of color Doppler flow mapping images were transferred into a TomTec computer after computer-controlled 180 degrees rotational acquisition. Direct measurement of the 3D reconstructed FC surface areas as well as measurements of FC areas estimated with 2D methods with hemispherical and hemielliptical assumptions were performed, and values were multiplied by the aliasing velocity to obtain peak regurgitant flow rates. There was better agreement between 3D and electromagnetically derived flow rates than there was between the 2D and the reference values (r=.94, y=1.0x-0.16, difference=0.02 L/min for the 3D method; r=.80, y=1.6x-0.3, difference=1.2 L/min for the 2D hemispherical method; r=.75, y=0.90x+0.2, difference=-0.20 L/min for the 2D hemielliptical method). CONCLUSIONS: Without any geometrical assumption, the 3D method provided better delineation of the FC zones and direct measurements of FC surface areas, permitting more accurate quantification of the severity of AR than the 2D methods.

Animals↗

PubMed1997

Nutritional management of cardiovascular risk factors. A randomized clinical trial.

BACKGROUND: Adherence to dietary recommendations for disease management is often hindered by the complexity of incorporating them into the daily diet. Nutrition and cardiovascular scientists and food technologists collaborated to develop a prepared meal plan that meets national dietary guidelines for cardiovascular risk reduction. OBJECTIVE: To assess the clinical effects of this plan, which incorporates all National Academy of Sciences National Research Council recommended dietary allowances for vitamins, minerals, and macronutrients, compared with a patient-selected American Heart Association Step I and Step II diet plan. METHODS: This multicenter, randomized, parallel-intervention trial was conducted at 10 medical centers in the United States and Canada and involved 560 men and women with hypertension, dyslipidemia, or diabetes. Following calculation of prescriptions to meet individual nutritional requirements based on the Harris-Benedict equation, participants were randomized to the Campbell's Center for Nutrition and Wellness (CCNW) plan, which is composed of prepackaged breakfast, lunch, and dinner meals provided to participants, or a nutritionist-guided American Heart Association Step I and Step II diet, in which participants self-selected foods to meet their nutrition prescription for 10 weeks. MAIN OUTCOME MEASURES: Blood pressure (BP); lipid, glucose, glycosylated hemoglobin (HbA1c), and insulin levels; body weight; dietary intake; and quality of life. RESULTS: Patients' BP, lipid levels, carbohydrate metabolism, weight, and quality of life (P < or = .001 for all findings except low-density lipoprotein-high-density lipoprotein ratio, P = .25) all improved on both nutrition plans. Mean differences (+/-SD) between baseline and treatment clinical values for the CCNW and the self-selected diet groups (between-group P values), respectively, were as follows: systolic BP, -6.4 +/- 9.2 mm Hg and -4.6 +/- 9.0 mm Hg (P = .02); diastolic BP, -4.2 +/- 5.7 mm Hg and -3.0 +/- 5.1 mm Hg (P = .006); cholesterol, -0.32 +/- 0.58 mmol/L and -0.27 +/- 0.56 mmol/L (-12.4 +/- 22.5 mg/dL and -10.4 +/- 21.9 mg/dL) (P = .30); glucose, -0.65 +/- 1.88 mmol/L and -0.75 +/- 2.03 mmol/L (-11.7 +/- 34.0 mg/dL and -13.5 +/- 36.6 mg/dL) (P = .10); and HbA1c, -0.4% +/- 0.8% and -0.3% +/- 0.7% (P = .66). Weight loss with the CCNW and self-selected plans, respectively, was as follows: men, -4.5 +/- 3.6 kg and -3.5 +/- 3.3 kg; and women, -4.8 +/- 3.0 kg and -2.8 +/- 2.8 kg. Quality of life was significantly improved for daily and work activities (P < .05) and nutritional health perceptions (P < .05) with the CCNW plan relative to the self-selected group. Overall nutrient intake and compliance were both significantly (P < .001) better with the CCNW plan. CONCLUSIONS: Nutritionally balanced meals that meet the recommendations of national health organizations improved multiple risk factors for patients with cardiovascular disease. The CCNW plan resulted in greater clinical benefits, nutritional completeness, and compliance than the self-selected diet. The CCNW is a comprehensive nutrition plan, convenient for both prescription and practice, and appears viable for effecting favorable dietary changes in patients at high risk for cardiovascular disease.

Adult↗

PubMed1997

Dietary compliance and cardiovascular risk reduction with a prepared meal plan compared with a self-selected diet.

Noncompliance with therapeutic diets remains a major obstacle to achieving improvements in cardiovascular disease (CVD) morbidity and mortality. This study compared dietary compliance and CVD risk factor response to two dietary interventions designed to treat hypertension, dyslipidemia, and diabetes mellitus. In a multicenter trial, 560 adults were randomly assigned to either a self-selected, mixed-food plan (n = 277), or a nutrient-fortified prepared meal plan (n = 283); each was designed to provide 15-20% of energy from fat, 55-60% from carbohydrate, and 15-20% from protein. Nutrient intake was estimated from 3-d food records collected biweekly throughout the 10-wk intervention. Compliance was determined by evaluating the participants' ability to meet specific criteria for energy intake [+/-420 kJ (100 kcal) from the midpoint of the prescribed energy range], fat intake (< 20%, < 25%, or < 30% of energy from total fat), and the National Cholesterol Education Program/American Heart Association Step 1 and 2 diet recommendations. Compliance with energy, fat, and Step 1 and 2 criteria was better in participants who followed the prepared meal plan than in those who followed the self-selected diet (P < 0.0001). Compliant participants in both groups achieved greater reductions in body weight, systolic and diastolic blood pressure, and total and low-density-lipoprotein cholesterol than noncompliant participants (P < 0.05). In general, better endpoint responses were observed with lower fat intakes regardless of group assignment. The prepared meal plan is a simple and effective strategy for meeting the many nutrient recommendations for CVD risk reduction and improving dietary compliance and CVD endpoints.

Adult↗

PubMed1996

Toward optimal laboratory use. Problems in laboratory testing in primary care.

OBJECTIVE: To examine the frequency and characteristics of problems in laboratory testing in primary care physicians's offices and their impact on health care. DESIGN: Prospective descriptive study in which participating office-based primary care clinicians reported each occurrence of any laboratory incident during a 6-month study. Each identified problem was reported on a structured data collection instrument with an open-ended description of the problem. SETTING: Primary care physicians' offices in North America. PARTICIPANTS: One hundred twenty-four primary care clinicians in 49 practices of the Ambulatory Sentinel Practice Network (ASPN). MAIN RESULTS: A total of 180 problems were reported, yielding a crude rate of 1.1 problems per 1000 patient visits. Problems involving test ordering and specimen handling were the most common (56%), while those attributable to the test analysis itself accounted for 13% of the total. In the judgment of the practice staff, 27% of the reported problems had an impact on patient care. Of the 24 cases for which the specific impact was known and reported, half of the impacts were minor and about half were significant, as judged by whether or not the diagnosis and/or treatment of the patient was measurably affected. CONCLUSIONS: Clinically apparent problems with laboratory testing in primary care were found at a rate of 1.1 problems per 1000 patient visits. Of the laboratory problems that occurred in this study, 27% were judged by the physician to have an effect on patient care.

Clinical Laboratory Techniques↗

PubMed1996

Effective regurgitant orifice area by the color Doppler flow convergence method for evaluating the severity of chronic aortic regurgitation. An animal study.

BACKGROUND: The aim of the present study was to evaluate dynamic changes in aortic regurgitant (AR) orifice area with the use of calibrated electromagnetic (EM) flowmeters and to validate a color Doppler flow convergence (FC) method for evaluating effective AR orifice area and regurgitant volume. METHODS AND RESULTS: In 6 sheep, 8 to 20 weeks after surgically induced AR, 22 hemodynamically different states were studied. Instantaneous regurgitant flow rates were obtained by aortic and pulmonary EM flowmeters balanced against each other. Instantaneous AR orifice areas were determined by dividing these actual AR flow rates by the corresponding continuous wave velocities (over 25 to 40 points during each diastole) matched for each steady state. Echo studies were performed to obtain maximal aliasing distances of the FC in a low range (0.20 to 0.32 m/s) and a high range (0.70 to 0.89 m/s) of aliasing velocities; the corresponding maximal AR flow rates were calculated using the hemispheric flow convergence assumption for the FC isovelocity surface. AR orifice areas were derived by dividing the maximal flow rates by the maximal continuous wave Doppler velocities. AR orifice sizes obtained with the use of EM flowmeters showed little change during diastole. Maximal and time-averaged AR orifice areas during diastole obtained by EM flowmeters ranged from 0.06 to 0.44 cm2 (mean, 0.24 +/- 0.11 cm2) and from 0.05 to 0.43 cm2 (mean, 0.21 +/- 0.06 cm2), respectively. Maximal AR orifice areas by FC using low aliasing velocities overestimated reference EM orifice areas; however, at high AV, FC predicted the reference areas more reliably (0.25 +/- 0.16 cm2, r = .82, difference = 0.04 +/- 0.07 cm2). The product of the maximal orifice area obtained by the FC method using high AV and the velocity time integral of the regurgitant orifice velocity showed good agreement with regurgitant volumes per beat (r = .81, difference = 0.9 +/- 7.9 mL/beat). CONCLUSIONS: This study, using strictly quantified AR volume, demonstrated little change in AR orifice size during diastole. When high aliasing velocities are chosen, the FC method can be useful for determining effective AR orifice size and regurgitant volume.

Animals↗

PubMed1996

Improved quality of life in patients with generalized cardiovascular metabolic disease on a prepared diet.

Current dietary recommendation for cardiovascular disease risk reduction and recommended dietary allowances (RDAs) were used to develop a nutritionally complete prepackaged prepared meal plan specifically designed to reduce the risk of cardiovascular disease. In the current study we tested patient acceptance of the diet as defined by measures of quality of life. In a randomized, parallel-design, multicenter clinical trial, 77 persons with hypertension, diabetes mellitus, dyslipidemia, or a combination of two or more of these conditions were recruited and randomly assigned to either a prepared meal plan (n = 39) or a comparable self-selected diet (n = 38) for 10 wk. The prepared meal plan met both the RDAs for all essential micronutrients and the dietary recommendations of national health organizations for macronutrients, cholesterol, sodium, and fiber. The prescribed self-selected diet was matched for macronutrients. Quality of life, as measured by a battery of instruments, was the major endpoint. Individuals consuming the prepared meal plan had significant improvements in mental health (P < 0.01), general perceived health (P < 0.005), daily activities (P < 0.05), work performance (P < 0.005), affect (P < 0.01), and nutritional health perceptions (P < 0.001), and reductions in nutrition hassles based on a standardized questionnaire (P < 0.001). The self-selected-diet group had significant improvements in nutritional health perceptions (P < 0.001) and affect (P < 0.001). There were significant improvements in weight (P < 0.001), blood pressure (P < 0.001), cholesterol (P < 0.002), low-density lipoproteins (P < 0.001), glucose (P < 0.014), and glycated hemoglobin (Hb A(1c) (P < 0.004) that were comparable in both groups. In summary, this study shows that a nutritionally complete diet, whether prepackaged or self-selected, improves multiple risk factors for cardiovascular disease. The prepackaged prepared meal plan had the added benefit of a greater improvement in quality of life.

Blood Glucose↗

PubMed1996

Matching anonymous pre-posttests using subject-generated information.

Sensitive research issues call for anonymous questionnaires. This makes accurately matching pretests with posttests difficult or impossible. Various subject-generated coding schemes have been developed, but their accuracy has been unknown. This anonymous study, with 745 students, used subject-generated coding to match pretests with posttests. The matching was verified for accuracy with the use of a collateral, anonymous, sticker identification system. The coding system was able to accurately match 75.2% of all the pretest-posttest pairs. An additional 22.1% of the pairs were left unmatched and only 2.7% were matched incorrectly. Subject-generated coding systems can be very effective where confidentiality is important to protect.

Adolescent↗

PubMed1995

Regulation of parathyroid hormone and vitamin D in essential hypertension.

Patients with essential hypertension have been reported to have a higher serum concentration of parathyroid hormone (PTH) than normotensive individuals although this finding is not universal among studies. To further characterize the status of the calcium regulating hormones in essential hypertension, we measured the parathyroid gland response to acute EDTA-induced hypocalcemia and the renal response of 1,25(OH)2-vitamin D to dietary calcium deprivation in 16 hypertensive (H) and 15 normotensive (N) men. The average mean arterial blood pressure once all antihypertensive medications were discontinued was 108 +/- 7 mm Hg for the hypertensive group and 89 +/- 4 mm Hg for the normotensive group (P < .01). There were no group differences in baseline serum concentrations of ionized calcium, creatinine, intact PTH, and 1,25(OH)2-vitamin D, urinary calcium excretion, and creatinine clearance. After a 1-h infusion of EDTA at 12.5 mg/kg/h, the serum concentration of ionized calcium fell (H: 1.25 +/- .03 to 1.17 +/- .04 mmol/L, N: 1.26 +/- .04 to 1.18 +/- .04 mmol/L, P = NS) and PTH increased (H: 36 +/- 9 to 91 +/- 30 pg/mL, N: 40 +/- 14 to 85 +/- 28 pg/mL, P = NS). With an additional hour of EDTA at a dose of 25 mg/kg/h, serum ionized calcium concentration fell further (H: 1.01 +/- .05 mmol/L, N: 1.03 +/- .06 mmol/L, P = NS) and PTH increased to 150 +/- 58 pg/ml in patients and 130 +/- 32 pg/ml in controls (P < .001). The response suggested an increased maximal parathyroid gland secretory capacity in the hypertensive patients relative to the controls. There was no group difference in the serum concentration of 1,25(OH)2-vitamin D at baseline (H: 32 +/- 6 pg/ml, N: 32 +/- 8 pg/ml, P < .90) and following dietary calcium deprivation for three days (H 50 +/- 12, N 48 +/- 14 P < 0.76). The maximal stimulated PTH level was significantly higher in hypertensive than normotensive subjects in the absence of measured differences in serum ionized calcium concentration, serum 1,25(OH)2-vitamin D concentration, and creatinine clearance. These findings suggest an intrinsic alteration of PTH regulation in patients with essential hypertension, manifest as increased parathyroid gland secretory capacity.

Adolescent↗

PubMed1994

Estimation of regurgitant flow volume based on centerline velocity/distance profiles using digital color M-Q Doppler: application to orifices of different shapes.

OBJECTIVES: In this study we investigated the centerline velocity profile method for flow computation as applied to noncircular, as well as circular, orifices using digital color flow data. BACKGROUND: Recently it has been suggested that flow volume through an orifice can be estimated more accurately by computing the axial "centerline" flow velocity/distance profile proximal to the orifice. METHODS: A total of seven different orifices were mounted in a constant-flow model: four circular orifices, two rectangular orifices with a major/minor axis ratio of 4:1 and 8:1 and an ovoid orifice having a major/minor axis ratio of 2:1. Three different flow rates were examined (1.68, 3.48 and 6.48 liters/min). Digital measurements of flow velocity at discrete positions along the centerline progressing toward the orifice were analyzed to yield complete flow velocity profiles for each orifice at each flow rate. RESULTS: A clear separation of the flow profiles for the three different flow rates was observed independent of orifice size for all of the circular orifices. The velocity/distance acceleration curves showed highly significant correlations using multiplicative regression fits (y = ax-b, r = 0.94 to 0.99, all p < 0.0001). An equation for quantitatively correlating the a and b coefficients from the multiplicative regression fits with flow rates was derived from stepwise regression analysis: Flow rate = 23a + 3.3b - 1.5 (r = 0.97, p < 0.0001, SEE 0.46 liter/min). CONCLUSIONS: In view of the various sizes and shapes encountered clinically for regurgitant orifices, the simplicity of this method for the estimation of the severity of regurgitant lesions might be of importance for clinical applications of this method.

Blood Flow Velocity↗

PubMed1994

Vascular mechanisms of cyclosporin-induced hypertension in the rat.

Numerous studies have explored the pathogenesis of cyclosporin A (CysA)-induced hypertension; however, none has assessed the impact of CysA treatment on resistance arteries in the setting of elevated blood pressure. Therefore, we studied the chronic effect of CysA on rat mesenteric artery resistance vessels (ex vivo). CysA (25 mg/kg per d for 7 d), but not vehicle, significantly raised systolic blood pressure (13.4 +/- 2.2 mmHg, P < 0.003, n = 9 per group). The resistance vessels from CysA-treated rats showed a small but significant decrease in norepinephrine sensitivity (P < 0.03) and a pronounced decrease in endothelium-dependent and -independent relaxation (P < 0.001) compared to controls. Endothelin-1 sensitivity tended to be diminished (P = 0.07). The direct (in vitro) effect of CysA was subsequently evaluated in resistance vessels from nontreated animals (n = 8) and exposed to CysA (2 micrograms/ml) for 24 h. As observed in vivo, CysA significantly decreased endothelium-dependent and -independent relaxations (P < 0.05) and attenuated norepinephrine sensitivity (P = 0.06). Methylene blue, a nitric oxide quencher, significantly inhibited the acetylcholine-induced relaxation in control, but not in CysA vessels, suggesting a selective action of CysA on the nitric oxide pathway. We conclude that CysA-induced hypertension is the consequence of a primary effect on resistance vessel relaxation, not increased vasoconstriction, as previously suggested.

Acetylcholine↗

PubMed1993

Mevalonate availability and cardiovascular functions.

Data delineating the relationship between disorders of cholesterol metabolism and elevated blood pressure (BP) do not exist. We postulated that mevalonate, the metabolic precursor of endogenous cholesterol and the direct product of 3-hydroxy-3-methylglutaryl-CoA reductase, was a contributing factor for the maintenance of vascular tone and systemic BP. We conducted in vivo, ex vivo, and in vitro experiments in normotensive and hypertensive rats, where exogenous mevalonate and lovastatin, a competitive inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase, were used, respectively, to increase or limit mevalonate availability. Mevalonate decreased BP in the whole animal without significant change in plasma cholesterol. Incubation of aortas with mevalonate attenuated their reactivity to norepinephrine and increased their response to endothelium-dependent and -independent relaxing factors. Lovastatin, in contrast, had the opposite effect in vivo and in vitro: it increased BP, enhanced vascular response to norepinephrine, and impaired endothelium-dependent and -independent relaxations. Neither agent modified cholesterol vascular content. Alteration of vascular reactivity was also observed in resistance vessels from animals pretreated with lovastatin. Our findings suggest that mevalonate availability is an unrecognized metabolic contributor to vascular tone and BP. They imply that (i) metabolites of the mevalonate pathway other than cholesterol could potentially control vascular functions and cardiovascular hemodynamics, (ii) elevated arterial pressure could be in part the consequence of primary disorders of this pathway, and (iii) pharmacological inhibition of mevalonate production as a means to lower plasma cholesterol may have an adverse impact on other cardiovascular risk factors, such as BP.

Acetylcholine↗

PubMed1993

Tying pay to performance: one critical care unit's approach.

This article describes development and testing of a tool for determining an appropriate reward for staff performance in a critical care area. Outlined is the process of identifying and quantifying appropriate merit increases based on bedside performance as well as participation in other unit, hospital, professional and community activities. Positive results are reported after one- and two-year use.

Career Mobility↗

PubMed1986

Needs analysis for teachers of the visually impaired.

The needs of educators dealing with low vision children were assessed by use of a mailed questionnaire. Teachers of the visually impaired (VH) of the Los Angeles City, Los Angeles County, and Long Beach City districts comprised the sample population. Analysis of the results revealed unmet needs in the following areas: teachers' knowledge in use of low vision aids, lack of low vision assessment by vision care specialists for their students, difficulty with adequacy of eye reports, and lack of communication with their students' eye care specialists. Recommendations are made for improvement of these problem areas.

Blindness↗