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Our aim was to confirm earlier studies showing tcPO2 to be higher under clothing made with polyethylene terephalate (PET) fabric containing ceramic particles (CEL) compared to standard PET fabric. In previous studies PET garments were donned first to avoid possible persistent effects from ceramic particles. This study randomized donning sequence to avoid bias. METHODS: Subjects were randomized to don either PET shirts first (PETF n=73) or CEL first (CELF n=80), switching garments after 90 minutes. Skin temperature (ST), arterial oxygen saturation (O2sat), and tcPO2 were measured every 30 minutes. RESULTS: Baseline ST and O2 sat were nearly identical in the two groups. Baseline tcPO2 was modestly higher in the CELF group than with PETF: 66.4 ± 18.9 vs. 63.9 ± 18.8 mmHg (n.s). Independent of donning sequence, tcPO2 measurements 90 minutes after wearing CEL were 6.7% higher than after 90 minutes wearing PET (p<0.0003). Sequence analysis found tcPO2 in PETF subjects to gradually rise before and after switching garments, but tcPO2 fell immediately after switching garments in CELF subjects. PETF baseline O2sat of 98.1 ± 1.3 increased insignificantly after 90 minutes, and then increased further to 98.6 ± 0.8 after wearing CEL ninety minutes (p=0.0001). CELF baseline O2sat of 97.9 ± 1.7 increased to 98.5 ± 1.1 90 minutes after donning CEL (p=0.0002) and fell to 98.3 ± 1.0 ninety minutes after switching to PET (p=0.0033). CONCLUSIONS: The ability of ceramic-embedded fabric to induce higher tcPO2 measurements is not due to sequence bias.

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BACKGROUND: Although AV fistulas are the preferred access for hemodialysis and have low complication rates, failure to function remains high and time to first dialysis may be several months. METHODS: Data from a Computerized Patient Record System of patients undergoing AV fistula from October 2000 to March 2006 were reviewed for type of fistula, interval from AV fistula construction to first hemodialysis, patency period, and complication rate. RESULTS: 129 patients were identified who underwent 155 autogenous AV fistula constructions. The average age was 62.1 (range 40-84) years old. 114 radiocephalic and 41 brachiocephalic fistulas were performed. 57 (50%) radiocephalic fistulas allowed successful hemodialysis after an average length of 13+/-5 weeks with a primary patency of 13+/-4 months. 24 (42%) fistulas subsequently thrombosed, 7 (12%) developed fistula stenosis, and 2 (4%) developed steal syndrome. 28 (68%) brachiocephalic fistulas reached successful hemodialysis after 6+/-2 weeks with a primary patency of 16+/-7 months. Eleven (42%) of the brachiocephalic fistulas that reached hemodialysis remained patent while four (15%) thrombosed. Two (8%) brachiocephalic fistulas thrombosed before reaching hemodialysis. There were two incidences (5%) of steal syndrome in the brachiocephalic group with one case being severe leading to tissue loss in the hand. CONCLUSION: Brachiocephalic fistulas were superior to radiocephalic in both time to maturity, primary patency, and functional primary patency. Brachiocephalic fistulas had a higher maturation rate and were less likely to fail once hemodialysis began. Vascular surgeons should develop better patient selection to predict which fistulas will function successfully rather than risk complications of prolonged central catheters.

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Natural gene flow is often localised because of gamete dispersal limitations, and the quantity and structure of the genotypic variance in such populations is a key to predicting the advance from selection, in both evolution and artificial breeding programmes. Earlier derivations of this variance have shown that the total dominance variance may increase with inbreeding despite the fact that heterozygosity is decreasing. This anomaly has been corrected following the de novo biometrical derivation presented in this paper. The whole population also subdivides into descendant lineages that differ in allele frequencies and means because of the dispersion caused by genetic drift and continuing localisation of gamodemes. The paper defines for the first time the among-line and within-line partitions of the dominance variance; and corrects anomalies in the total genic (additive genetic) variance, and its underlying inbred average alle-substitution effect. The revisions also clarify the connections between the Fisher-Falconer, Mather-Hayman, and Wright approaches to defining the inbred genotypic variance. Relationships are discussed between the population dispersion structure and genetic efficiency in selection.

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The success rate of percutaneous transluminal coronary angioplasty for chronic total arterial occlusions is still unsatisfactory. Inability to cross the lesion with a guidewire is a major cause of failure. Optical coherent reflectometry (OCR) is a new method of using laser light to measure the depth of tissue from the end of an optic fiber. This study tests whether an OCR prototype guidewire provides a guidance system that might be useful to assist reopening chronic total arterial occlusions. An OCR fiber optic within a 0.014" hypotube was developed using the interference pattern of two reflected light beams (wave length 1,300 nm). To determine if OCR can distinguish different tissue types, plaques of human lower extremity arterial segments were visually divided into three types (calcified, white, or yellow). The slope of the initial reflectance of the OCR curve was calculated and compared between the three groups. In six other arteries, the OCR wire was advanced longitudinally through occluded human artery segments in vitro. Guidewire position was determined by OCR and compared to the position of the guidewire tip observed simultaneously by intravascular ultrasound (IVUS) imaging. In 16 arterial surface segments, calcified plaques had a significantly steeper slope than white or yellow plaques (-227.2 +/- 82.2; -81.5 +/- 12.9; -103.6 +/- 19.6 dB/mm; P < 0.01). For the determination of the guidewire position, IVUS and OCR corresponded correctly in 82% of 28 measurements. Sensitivity and specificity of OCR for detection of plaque versus the media/adventitia boundary were 79% and 89%, respectively (P < 0.001). OCR can distinguish calcified from noncalcified plaque and may distinguish plaque from the media/adventitia boundary. This technology may be useful as a means to help navigate a guidewire safely through an occluded artery.

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HYPOTHESIS: Patency after primary percutaneous transluminal angioplasty (PTA) and stenting of superficial femoral artery (SFA) occlusions is better than historical experience with PTA alone. DESIGN: Consecutive case series of primary PTA with stenting, and follow-up with duplex imaging every 6 months (mean +/- SD follow-up, 32 +/- 15 months). SETTING: Veterans Affairs medical center. PATIENTS AND METHODS: Patients were 57 previously untreated men with 71 limbs having chronic atherosclerotic SFA occlusion with suprageniculate reconstitution and patent tibial runoff. Critical ischemia (Society for Vascular Surgery [SVS] category, 4-6) was present in 7 (10%), the remainder had intermittent claudication only (SVS, 1-3). INTERVENTIONS: Guidewire recanalization followed by PTA, Wallstent deployment, and adjunctive thrombolysis as necessary; 19 limbs (27%) required thrombolysis to manage periprocedural thrombosis. MAIN OUTCOME MEASURES: Cumulative patency, limb salvage, and complications. RESULTS: Length (mean +/- SD) of occlusion was 14.4 +/- 9.9 cm. Length of stented artery was 24.3 +/- 11.1 cm. Ankle brachial index increased from 0.59 +/- 0.14 to 0.86 +/- 0.16 (P<.001) after stenting. One- and 3-year patencies were as follows: primary, 54.6% +/- 6.3% and 29.9% +/- 6.6%; assisted primary, 72.3% +/- 5.6% and 59.0% +/- 6.8%; and secondary, 81.6% +/- 4.8% and 68.3% +/- 6.5%. Three-year secondary patency when periprocedural thrombolysis was required was 35.7% +/- 12.5% compared with 70.6% +/- 7.4% for limbs not requiring periprocedural thrombolysis (P=.02); the differences in occlusion length and severity of ischemia were not significant between these 2 groups. Limbs undergoing adjunctive PTA during angiography 6 to 12 months after initial stenting had 63.0% +/- 13.3% patency at 3 years compared with 100% patency in limbs not requiring PTA at 6 to 12 months angiography (P=.046). Periprocedural mortality and morbidity were 2.8% and 15.5%, respectively. Three of the 7 limbs with critical ischemia underwent amputation during follow-up compared with 2 (3%) of 64 limbs with functional ischemia (chi(2) test, P<.006). A mean of 1.8 endovascular interventions per limb were performed. CONCLUSIONS: Percutaneous transluminal angioplasty and stenting yielded higher patency rates than historical controls undergoing PTA alone. When periprocedural thrombolysis is required, subsequent patency appears to be significantly worse. Poor results after PTA and stenting of limbs with critical ischemia and the need for additional endovascular therapy limit the technique's utility.

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General quantitative genetic properties are derived for the F2 originating from self-fertilisation of hybrid (F1) individuals. These results extend and generalize previous restricted knowledge about this F2. New equations are found for all genotype frequencies, allele frequencies, inbreeding coefficient, genic (additive-genetic) and dominance variances, broadsense and narrowsense heritabilities, and selection potential. The bulk mean is generally lower, and the genotypic variance is generally higher, than those of the F1 and the allogamous F2. Genic and dominance variances for the selfed F2 are very different to the classical counterparts. Their relationships with inbreeding have been investigated, and they are more elaborate than previously considered. The level of inbreeding is constant irrespective of parental combinations, which is different to the inbreeding of an allogamous F2. Selection potential is generally high, and selection advance generally exceeds bulk inbreeding depression. If selection is assisted by dispersion, the autogamous F2 may obtain greater genetic advance than its allogamous counterpart for the same selection pressure. Under conditions of spatially separated F2, swarms, natural selection may be enhanced by selfing.

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PURPOSE: To improve the patency rate for angioplasty in chronic occlusion of the superficial femoral artery by deploying stents after angioplasty. MATERIALS AND METHODS: Angioplasty and stent placement were performed in 61 arteries in 48 male patients. The mean occlusion length was 13.5 cm and the mean stent length was 30 cm. Patency rates were analyzed at 6 months and at 1, 2, 3, and 4 years. The predictors of restenosis were analyzed by univariate and multiple logistic regression. RESULTS: Patency rates were 87% at 6 months, consisting of 74% primary, 6% primary assisted, and 7% secondary; 79% at 1 year, consisting of 47% primary, 19% primary assisted, and 13% secondary; 72% at 2 years, consisting of 36% primary, 26% primary assisted, and 10% secondary; 70% at 3 years, consisting of 26% primary, 22% primary assisted, and 22% secondary; and 63% at 4 years, consisting of 25% primary, 0% primary assisted, and 38% secondary. There was a 15% morbidity rate and one mortality as a result of retroperitoneal bleeding. Better patency rates were noted at all time intervals in diabetic limbs, 7-mm-diameter versus 10-mm-diameter stents, shorter obstructions and shorter stents, nonsmokers, in limbs in which urokinase was not necessary after stent deployment, and in limbs with an International Society of Cardiovascular Surgery (ISCVS) classification under 3. Patency rates were not affected by age, race, number of trifurcation vessels patent, experience in performing the procedures, and procedures requiring less time. By multivariate logistic analysis, the independent predictors of patency at 6 months were postprocedure ankle/brachial index (ABI) and shorter stent length; at 1 year, preprocedure ABI, shorter stent length, and the presence of diabetes; at 2 years, preprocedure ABI and the presence of diabetes; and at 3 years, the preprocedure ABI. CONCLUSIONS: The techniques used to reestablish antegrade flow in these superficial femoral arteries yielded a high success rate. In addition, the use of angioplasty with stents may improve patency rates over angioplasty without stents.

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The quantitative genetic properties are derived for the bulk F2 originating from random fertilization (RF) amongst hybrid (F1) individuals. Only its mean appears to have been derived previously, and that definition is confirmed (by another method). New general equations are found also for all genotype frequencies, allele frequencies, inbreeding coefficient, the genotypic, additive-genetic and dominance variances, and broad-sense and narrow-sense heritabilities. The assumption that such an F2 is a classical RF population is shown to be correct. Indeed, the allogamous F2 is a natural origin for the RF population. The relationships are given between precedent RF populations (parents) and subsequent RF populations following hybridization (allogamous F2). The allogamous F2 is generally inbred with respect to its parental F1, the degree depending on the hybrid's parents' allele frequencies. At the same time, it is outbred with respect to those original parents, and not inbred at all with respect to the equivalent RF population. The genotypic variance is generally more than in the F1, and likewise for heritabilities. These findings make it possible to evaluate the genetic advance from selection and hybridization. The results depend on the allele frequencies of the original parents and the degree of overdominance, but generally, selection is more advantageous than hybrid vigour.

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BACKGROUND: Little is known about the rate at which new abdominal aortic aneurysms (AAAs) develop or whether screening older men for AAA, if undertaken, should be limited to once in a lifetime or repeated at intervals. METHODS: A large population of veterans, aged 50 through 79 years, completed a questionnaire and underwent ultrasound screening for AAA. Of these, 5151 without AAA on the initial ultrasound (defined as infrarenal aortic diameter of 3.0 cm or larger) were selected randomly to be invited for a second ultrasound screening after an interval of 4 years. Local records and national databases were searched to identify deaths and AAA diagnoses made during the study interval in subjects who did not attend the rescreening. RESULTS: Of the 5151 subjects selected for a second screening, 598 (11.6%) had died (none due to AAA), and 20 (0.4%) had an interim diagnosis of AAA. A second screening was performed on 2622 (50.9%), of whom 58 (2.2%; 95% confidence interval, 1.6%-2.8%) had new AAA. Three new AAAs were 4.0 to 4.9 cm, 10 were 3.5 to 3.9 cm, and 45 were 3.0 to 3.4 cm. Independent predictors of new AAA at the second screening included current smoker (odds ratio, 3.09; 95% confidence, 1.74-5.50), coronary artery disease (odds ratio, 1.81; 95% confidence interval, 1.07-3.07), and, in a separate model using a composite variable, any atherosclerosis (odds ratio, 1.97; 95% confidence interval, 1.16-3.35). Adding the interim and rescreening diagnosis rates suggests a 4-year incidence rate of 2.6%. Rescreening only in subjects with infrarenal aortic diameter of 2.5 cm or greater on the initial ultrasound would have missed more than two thirds of the new AAAs. CONCLUSIONS: A second screening is of little practical value after 4 years, mainly because the AAAs detected are small. However, the incidence that we observed suggests that a second screening after longer intervals (ie, more than 8 years) may provide yields similar to those seen in initial screening and therefore warrants further study.

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Estimators for standard errors of heritability for two typical and complex forage breeding models are illustrated with estimates of variance and covariance components from least-squares and restricted maximum likelihood methods. The first experiment (Model 1) is a factorial design (two grazing management factors) with two layers of split plots (populations and grazing periods) and with plants within populations nested beneath the first split. The second model is for a sites pooling of randomized complete block experiments, with plants nested inside plots and with a split in time. One definition of heritability was applied to the plant habit character for both models in a red clover germplasm. Heritability estimates were statistically the same for the two methods for both models.

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Quantitative genetics generally is based on the properties of the randomly fertilized (RF) population or inbred derivatives of it. Simple hybrids and hybrid swarms do not conform to this model; and only some properties of hybrid means appear to have been available. In this paper, several genetical properties are derived, including genotype and allele frequencies, genotypic variance, broad-sense heritability, and outbreeding coefficient. The earlier mean is confirmed, and hybrid vigour is examined critically. These results make it possible to evaluate quantitatively both natural selection and forward selection (in plant breeding) from hybrids. An important finding is that hybrids with maximum hybrid vigour do not maximize genetic advance from forward selection, i.e. evolution is unlikely to enhance hybrid vigour. Another finding is that the concepts of additive genetic variance and narrow-sense heritability are inappropriate for hybrids, owing to the genetic disequilibrium inherent from their origin, and to the ephemeral nature of their population structure.

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Cilostazol is an antiplatelet agent and vasodilator marketed in Japan for treatment of ischemic symptoms of peripheral vascular disease. It is currently being evaluated in the United States for treatment of symptomatic intermittent claudication (IC). Cilostazol has been shown to improve walking distance in patients with IC. In addition to its reported vasodilator and antiplatelet effects, cilostazol has been proposed to have beneficial effects on plasma lipoproteins. We examined the effect of cilostazol versus placebo on plasma lipoproteins in 189 patients with IC. After 12 weeks of therapy with 100 mg cilostazol BID, plasma triglycerides decreased 15% (P<0.001). Cilostazol also increased plasma high density lipoprotein cholesterol (HDL-C) (10%) and apolipoprotein (apo) A1 (5.7%) significantly (P<0.001 and P<0.01, respectively). Both HDL3 and HDL2 subfractions were increased by cilostazol; however, the greatest percentage increase was observed in HDL2. Individuals with baseline hypertriglyceridemia (>140 mg/dL) experienced the greatest changes in both HDL-C and triglycerides with cilostazol treatment. In that subset of patients, HDL-C was increased 12.2% and triglycerides were decreased 23%. With cilostazol, there was a trend (3%) toward decreased apoB as well as increased apoA1, resulting in a significant (9.8%, P<0.002) increase in the apoA1 to apoB ratio. Low density lipoprotein cholesterol and lipoprotein(a) concentrations were unaffected. Cilostazol treatment resulted in a 35% increase in treadmill walking time (P=0.0015) and a 9.03% increase in ankle-brachial index (P<0.001). These results indicate that in addition to improving the symptoms of IC, cilostazol also favorably modifies plasma lipoproteins in patients with peripheral arterial disease. The mechanism of this effect is currently unknown.

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PURPOSE: To assess the effects of age, gender, race, and body size on infrarenal aortic diameter (IAD) and to determine expected values for IAD on the basis of these factors. METHODS: Veterans aged 50 to 79 years at 15 Department of Veterans Affairs medical centers were invited to undergo ultrasound measurement of IAD and complete a pre-screening questionnaire. We report here on 69,905 subjects who had no previous history of abdominal aortic aneurysm (AAA) and no ultrasound evidence of AAA (defined as IAD > or = 3.0 cm). RESULTS: Although age, gender, black race, height, weight, body mass index, and body surface area were associated with IAD by multivariate linear regression (all p < 0.001), the effects were small. Female sex was associated with a 0.14 cm reduction in IAD and black race with a 0.01 cm increase in IAD. A 0.1 cm change in IAD was associated with large changes in the independent variables: 29 years in age, 19 cm or 40 cm in height, 35 kg in weight, 11 kg/m2 in body mass index, and 0.35 m2 in body surface area. Nearly all height-weight groups were within 0.1 cm of the gender means, and the unadjusted gender means differed by only 0.23 cm. The variation among medical centers had more influence on IAD than did the combination of age, gender, race, and body size. CONCLUSIONS: Age, gender, race, and body size have statistically significant but small effects on IAD. Use of these parameters to define AAA may not offer sufficient advantage over simpler definitions (such as an IAD > or = 3.0 cm) to be warranted.

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1. The effect of high-dose adenosine administration on atrial natriuretic peptide (ANP) and antidiuretic hormone (ADH) release is not completely understood, and data concerning the effect of adenosine on renal and systemic hemodynamics in the pig are lacking. Measurements of central hemodynamics, renal blood flow and urine production were made in anesthetized pigs during infusion of adenosine. The relationship between these parameters and the plasma concentrations of ANP, ADH and renal renin production was examined. 2. Adenosine infusion at the rate of 140 mg/kg per minute resulted in a significant decrease in systolic, diastolic and mean arterial blood pressure as well as pulmonary arterial pressure. However, cardiac output and renal blood flow remained unchanged during adenosine infusion. Likewise, heart rate remained unchanged until the end of infusion when it increased significantly, Plasma ANP and ADH concentrations increased significantly within 30 min after adenosine infusion, reaching peak levels at 30 to 60 min. However, despite the significant decrease in arterial blood pressure, renal renin production did not change significantly. 3. The adenosine-induced rise in ANP, which is normally released by atrial stretch, may represent a direct effect of adenosine on the cardiac myocytes. The increase in ADH may be a result of decreased arterial blood pressure triggering stimulatory signals from the aortic arch and carotid body receptors to hypothalamic-pituitary sites of ADH production/release. Urine flow decreased dramatically within 30 min of adenosine infusion. Thus adenosine infusion at the given rate led to marked reduction in systemic and pulmonary arterial pressures without significant change in cardiac output, heart rate and renal blood flow. This was associated with a marked increase in plasma ANP and ADH levels with no significant change in renal renin production despite a marked reduction in arterial blood pressure. 4. Maintenance of renal blood flow despite marked reduction in perfusion pressure suggests that, at high doses, adenosine induces renal vasodilation in pigs as opposed to a combined afferent and efferent vasoconstriction known to occur under different experimental conditions.

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We have observed apparently disproportionate numbers of abdominal aortic aneurysms (AAAs) in chronic spinal cord injury (SCI) patients. To test whether aortic enlargement is more frequent in SCI, we measured maximum infrarenal aortic diameters (AoDmax) by B mode ultrasound in 89 SCI subjects and 223 age and sex matched controls. The average AoDmax in SCI subjects (mean age 60.3 years) was 2.27+/-0.80 cm compared to 2.07+/-0.69cm in the controls. This difference was significant (P = 0.023), as were the proportions of subjects with AoDmax >/- 3cm. A total of 20.2 per cent of the SCI group had AoDmax >/- 3cm compared to 8.9 per cent for the controls (P < 0.0001, chi-square). Race, height, and weight distributions were similar. SCI patients had lower levels of hypertension and cigarette smoking than controls. Within the SCI and control groups, subjects with AoDmax >/- 3cm had increased cigarette consumption compared to /- 3cm group than in the >/- 3cm group, T6 versus T8, but not significantly (P = 0.23)> Based on these results, SCI patients have over a two-fold risk of aortic enlargement as a consequence of spinal cord injury.

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OBJECTIVES: The purpose of this study was to test the hypothesis that in occlusions of the superficial femoral artery, removal of atherosclerotic plaque would result in a higher long-term patency rate compared to balloon dilatation alone. A secondary hypothesis was that long term patency would be proportional to the amount of plaque removed. METHODS: A randomized controlled study of patients with occluded superficial femoral arteries was performed comparing balloon dilatation alone versus a 2.7 mm or a larger (4.0 mm or 4.7 mm) transcutaneous extraction catheter (TEC) atherectomy device followed by balloon dilatation. The effect of these devices on plaque area was assessed directly by intravascular ultrasound imaging. RESULTS: The mean occlusion length was 19.4 cm +/- 11.7 cm. The mean lumen area increased from 4.7 mm2 to 15.1 mm2, primarily due to balloon dilatation, but the mean atheroma area of 19.8 mm2 did not change with either size of TEC device. Although the initial procedure success rate was high (79%), the 6 month patency was only 45%. There was no difference in 6 month patency between the 3 groups. CONCLUSIONS: The data indicate that the TEC atherectomy devices do not remove a significant amount of atherosclerotic plaque in occluded superficial femoral arteries. The 6 month patency is no different with these atherectomy devices than with balloon dilatation alone. The larger (4.0 mm or 4.7 mm) TEC device does not remove any more tissue than the smaller (2.7 mm) device. The use of intravascular ultrasound to quantitate the effects of this atherectomy device provides important insights into the mechanism of action and lack of efficacy of the TEC atherectomy catheter.

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PURPOSE: We wanted to characterize the immediate effect of endarterectomy on flow of the arteries composing the extracranial carotid artery system. METHODS: Transit time ultrasound probes were used to measure flow through the carotid bifurcation in 48 patients undergoing endarterectomy. Maximum single-diameter stenosis affecting the internal carotid artery (ICA) was determined by angiography. The significance of differences between means were determined by t tests and analysis of variance; linear and nonparametric correlation analyses were also applied to analyze the relation between stenosis and several flow-derived parameters. RESULTS: Common carotid artery flow significantly increased (p = 0.0043) from a mean value of 264 +/- 99 ml/min to 314 +/- 98 ml/min, corresponding to an average percent increase of 34.3% +/- 71.3%. ICA flow increased from 128 +/- 69 ml/min to 173 +/- 66 ml/min (p < 0.0001), with an average percent increase of 74.9% +/- 114.9%. External carotid artery (ECA) flow decreased from 129 +/- 61 ml/min to 106 +/- 49 ml/min (p = 0.0098), representing an average percent decrease of -5.2% +/- 48.2%. The difference between ECA and ICA mean flow changes is highly significant (p < 0.001). The percent change in ECA flow did not correlate with preoperative stenosis. We noted, however, a positive correlation between stenosis and the ECA/ICA flow ratio before endarterectomy (Spearman r = 0.31, p = 0.032), indicating that more severe stenosis led to a greater distribution of blood into the ECA. The ECA/ICA flow ratio fell from an initial value (ECFbef/ICFbef) of 1.52 +/- 1.74 before endarterectomy to 0.69 +/- 0.37 (ECFaft/ICFaft) after endarterectomy (p = 0.0006). CONCLUSIONS: The data are consistent, with the ECA being an important collateral path for cerebral perfusion when ICA stenosis exists. When endarterectomy relieves bifurcation stenosis, common carotid artery blood flow is redistributed preferentially to the ICA at the expense of ECA flow, consistent with a change in the relative resistances of the two vessels resulting from operative reconstruction.

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OBJECTIVE: To characterize the relationship between changes in renal blood flow and cardiac output induced by dopamine, hypothesizing that at low doses renal blood flow changes more than cardiac output. DESIGN: Anesthetized swine had renal blood flow and cardiac output measured during either continuous dopamine infusions (2 to 8 micrograms/kg per minute) or bolus dosing (1 to 16 micrograms/kg), and increases in both were compared. Two different fluid protocols were compared using constant dopamine infusions. In the constant pulmonary capillary wedge pressure protocol, intravenous fluids were titrated to keep this parameter constant. In the other protocol, fluid therapy was held constant at 10 mL/kg per hour. RESULTS: With infusions, mean increases in renal blood flow and cardiac output were relatively equal. The maximum increase was 35% at 8 micrograms/kg per minute under the constant pulmonary capillary wedge pressure protocol, with no significant differences (P > .1) found between the change in renal blood flow and cardiac output at any dose in either protocol. With bolus dosing, renal blood flow increased significantly more than cardiac output at 1, 4, and 8 micrograms/kg (P < .05). CONCLUSION: Disproportionate increases in renal blood flow compared with cardiac output at low bolus doses show initial renal responses to be independent of cardiac output. The infusion data suggest that renal responses exhibit tachyphylaxis or that cardiac output slowly accommodates to decreased total peripheral resistance.

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Standard Scatchard analysis of ligand binding to cell receptors requires the use of isotopes and is imprecise at low ligand concentrations. To evaluate the feasibility of Scatchard analysis via fluorescence flow cytometry, the binding of fluorescein isothiocyanate-derivatized concanavalin A (FITC-ConA) to murine lymphocytes at 4 degrees C was compared to 125I-ConA binding. A FACS IV flow cytometer (Becton-Dickinson, Mountain View, CA) was used for analysis of cells after fluorescent ligand binding. A simple spectrophotometric technique was used to calibrate the relation between cytometer-determined fluorescence and ligand binding per cell. As FITC-ConA binding showed a quasi-Gaussian distribution, the mean number of molecules bound per cell was easily calculated. Scatchard analysis of FITC-ConA binding yielded results (1.9 x 10(6) receptors/cell, K = 3.6 x 10(-15)) similar to those obtained with 125I-ConA (1.4 x 10(6) receptors/cell, K = 5.2 x 10(-15)). Cytometric Scatchard plots showed less scatter and seemed more precise, suggesting superiority to radioactive ligand measurements, particularly at low ligand concentrations.

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