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At least 973 records · Page 54Linked to original sources
PubMed2004

Short-term variations in delta(13)C of ecosystem respiration reveals link between assimilation and respiration in a deciduous forest.

We present a comprehensive dataset of hourly, daily, and monthly measurements of carbon isotope measurements of CO(2) in canopy air from a temperate deciduous forest with the aim to identify the relevance of short-term variations in the isotopic signature of ecosystem respiration (delta(13)C(R)) and to understand its underlying physiological processes. We show that during daytime low vertical mixing inside the canopy can lead to decoupling of the air in the lower and upper canopy layer resulting in large spatial variation of delta(13)C in CO(2) of canopy air. Intercept of Keeling Plots also showed large temporal variation (3.8 per thousand) over the course of the day demonstrating that intercepts can differ between day and night and suggesting that choosing the right time for sampling is essential to capture the isotopic signature of ecosystem respiration (delta(13)C(R)). delta(13)C(R) as obtained from night-time measurements showed large variation of up to 2.65 per thousand on a day-to-day basis, which was similar to the observed variation of delta(13)C(R) over the seasonal cycle (3.08 per thousand). This highlights the importance of short-term physiological processes within ecosystems for the isotopic composition of CO(2) in the atmosphere, not reflected by bulk plant and soil organic samples. At daily and monthly time scales, delta(13)C(R) increased with increasing ratio of vapour pressure deficit to photosynthetically active radiation, measured 4-5 days before. This suggests that ecosystem respiration was isotopically linked to assimilation. Furthermore, assimilates recently fixed in the canopy seem to form a labile carbon pool with a short mean residence time that is respired back to the atmosphere after 4-5 days.

Air↗
PubMed2006

Solar furnaces or swamp coolers: costs and benefits of water use by solar-tracking flowers of the alpine snow buttercup, Ranunculus adoneus.

Solar tracking or heliotropism simultaneously raises organ temperature and light interception. For leaves and flowers carbon gain is maximized at the expense of water loss. In this study I explore how costs and benefits associated with water use by solar-tracking flowers of the alpine snow buttercup, Ranunculus adoneus change with ambient temperature. First, I test whether heliotropism increases the water cost of reproduction in the snow buttercup under extant alpine conditions. I then explore whether water use for evaporative cooling in solar-tracking flowers reduces the risk of over-heating as temperatures increase. Solar tracking, by elevating floral temperature and irradiance causes a 29% increase in water uptake by flowers. Gas exchange measurements suggest that the extra water taken up by solar-tracking flowers is released through transpiration. Transpirational cooling in turn allows solar-tracking flowers to gain advantages of enhanced light interception and warmth while reducing the risk of over-heating. Transpiration reduces excess temperature in solar-tracking flowers, but at a water cost. Results show that even in cool alpine habitats, flower heliotropism has water costs to balance its reproductive advantages. Plants with solar-tracking flowers may tolerate hotter conditions if soil moisture is plentiful, but not under drought.

Feedback, Physiological↗
PubMed2005

Comparison of neutron activated and radiolabeled microsphere methods for measurement of transmural myocardial blood flow in dogs.

BACKGROUND: The 'gold standard' radioactive microsphere (RM) technique for measurement of organ blood flow under various experimental conditions is inaccessible to many researchers due to increasing environmental concerns regarding safety and disposal of low-level radioactive waste materials. A new method using neutron activated microspheres (NAM) has recently been described. METHODS: We compared regional myocardial blood flows using the new formulation STERIspheres (NAM; 15.0 +/- 0.1 [SD] microm; density 1.5 gr/mL) with RM (15.0 +/- 0.1 [SD] microm; density 1.5 gr/mL) under different experimental conditions during acute ischemia-reperfusion injury in dogs. Random paired combinations of four different RM and NAM were co-injected into the left atrium during autoregulation, coronary occlusion and flow-mediated hyperemia (reperfusion) in the same animal. The left ventricle was divided into non-ischemic and ischemic regions and further subdivided into endocardial, mid-myocardial and epicardial portions. After gamma-counting, blood and myocardial tissue samples (n = 180) were dried and then shipped to a core facility for neutron activation and analysis. NAM-RM blood flow data were directly compared by ANOVA and regression analysis; Bland and Altman analysis was also performed to assess mean differences in blood flow with NAM-RM. RESULTS: A direct relation for blood flow between NAM-RM was observed; the slope of the relation (1.17 RM +/- 0.04 [SEE]) was different from unity but the intercept (0.06 +/- 0.06 [SEE]) was not different from the origin. Intermethod mean differences were minimal between NAM-RM in the low to normal range of blood flow and were increased at the higher blood flow levels the latter being of minor physiological consequence. A direct relation for endo/epicardial blood flow ratios between NAM-RM was also observed; the slope of the relation (0.98 RM +/- 0.04 [SEE]) and the intercept (0.03 +/- 0.06 [SEE]) were not different from unity or the origin, respectively. CONCLUSIONS: RESULTS show that in addition to limiting production of radioactive waste materials, NAM accurately measure myocardial blood flow, endocardial/epicardial and ischemic/non-ischemic blood flow distributions over a wide range. We compared myocardial blood flows using paired combinations of neutron activated (NAM) and the 'gold standard' radiolabeled microspheres (RM) co-injected during autoregulation, coronary occlusion and flow-mediated hyperemia in an in situ canine ischemia-reperfusion preparation. A direct relation for blood flow and endo/epicardial blood flow ratios between NAM-RM was observed; intermethod mean differences between NAM-RM were minimal in the low to normal blood flow range but increased at higher blood flow levels. These results indicate that NAM accurately measure myocardial blood flow and its transmural distribution in addition to limiting unnecessary production of radioactive laboratory waste products.

Animals↗
PubMed2026

Genetic Evidence That Stroke Causally Increases Circulating PDGFB Levels: a Two-Sample Mendelian Randomization Study.

Platelet-derived growth factor subunit B (PDGFB) is a key regulator of vascular remodeling, angiogenesis, and blood-brain barrier integrity. Although elevated PDGFB levels have been reported after ischemic injury, whether stroke liability itself causally influences circulating PDGFB levels remains unclear. We performed a two-sample Mendelian randomization (MR) analysis to assess the causal effects of genetically predicted all stroke, ischemic stroke, and cardioembolic stroke on plasma PDGFB concentrations. Genetic instruments were obtained from large-scale GIGASTROKE genome-wide association studies, and outcome data were derived from a proteomics GWAS. Instruments were then filtered by removing variants associated with established cardiovascular risk factors in a phenome-wide screen and outliers identified by RadialMR. The inverse variance-weighted (IVW) method was used as the primary analysis, complemented by weighted median, weighted mode, and MR-Egger approaches. Sensitivity analyses included Cochran's Q statistics, MR-Egger intercept tests, single-SNP analyses, leave-one-out analyses, and MR-PRESSO. IVW analysis demonstrated a significant positive causal association between genetic liability to all stroke and plasma PDGFB levels (β = 0.209, SE = 0.062, 95% CI 0.088 to 0.331, p = 7.3 × 10-4). A similar association was observed for ischemic stroke (β = 0.155, SE = 0.059, 95% CI 0.039 to 0.270, p = 0.009), with directionally consistent results across sensitivity analyses. MR-Egger regression for ischemic stroke initially suggested pleiotropy.After removal of a radial-MR outlier (rs2289252), the intercept was attenuated and no longer statistically significant (- 0.0190, p = 0.282). In contrast, no evidence of a causal association was found between cardioembolic stroke liability and plasma PDGFB levels across all MR methods (β = - 0.078, SE = 0.087, 95% CI - 0.248 to 0.092, p = 0.368). These findings provide genetic evidence that liability to stroke, particularly ischemic stroke, is causally associated with increased circulating PDGFB levels, whereas cardioembolic stroke does not show such an effect. This suggests that elevated PDGFB reflects vascular responses specific to ischemic stroke rather than a general consequence of all stroke subtypes.

Humans↗
PubMed1986

Can the technique for Doppler estimate of pulmonary stenosis gradient be simplified?

Although Doppler echocardiography has been demonstrated to accurately predict the pressure drop across the pulmonary valve in patients with pulmonary valve stenosis, prior reports have stressed the need to correct for beam-flow intercept angles, to use simultaneous imaging, and to utilize the subcostal approach. The purpose of this study was to determine the accuracy of estimating the pressure drop in pulmonary stenosis patients by means of nonimaging Doppler applied without angle correction from precordial examination. Pressure drop estimated by Doppler was compared to that measured by strain gauge manometry at catheterization. Data for 39 patients (21 simultaneous measurements; 18 nonsimultaneous) were evaluated. Results for the entire group showed a good correlation (r = 0.94; SEE = 7.9 mm Hg). The correlation for simultaneous measurement improved somewhat (r = 0.95; SEE = 5.9), but the difference was not significant. Comparison of the slope and intercept of data of this study to those of prior studies, which advocated more complex methodology, indicated that results were essentially similar and that use of the additional steps did not confer a significantly improved result. We conclude that the simplified methodology utilized in this study provides accurate Doppler estimates of pressure gradient in patients with pulmonary stenosis.

Adolescent↗
PubMed1987

Accuracy of digital angiography for quantitation of normal coronary luminal segments in excised, perfused hearts.

The accuracy of coronary artery diameter determination by digital angiography was assessed by imaging 39 coronary segments of excised dog and human hearts and comparing these segments with pathologic sections 0.76 to 3.31 mm in luminal diameter. Digital images were obtained postmortem both during contrast injection using a fixed-pressure coronary perfusion system and after fixation when the coronary size was maintained by injection of a barium-gelatin casting mixture. Digital data were analyzed with commercially available, automated edge-detection software using a coronary catheter as the calibration standard. Coronary diameter measured during contrast injection was not significantly different from that measured after casting and fixation. Digital data from both methods correlated well with diameters from pathologic sections (injected, r = 0.85; fixed, r = 0.91). Linear regression parameters comparing pathologic diameters with the contrast injection method were slope = 0.82, intercept = 0.42 mm, and standard error of the estimate = 0.27 mm. Parameters for the comparison of pathology with casted coronary data were slope = 0.95, intercept = 0.16 mm, and standard error of the estimate = 0.23 mm. Intra- and interobserver variability were 3% (0.05 mm) and 4% (0.07 mm), respectively. These data indicate that when a coronary catheter as a calibration standard is used, coronary artery dimensions can be accurately measured by automated digital angiography techniques.

Angiography↗
PubMed1988

Comparison of coronary stenosis quantitation results from on-line digital and digitized cine film images.

To examine the effects of digital image acquisition mode and subtraction techniques on the results of coronary stenosis quantitation, 100 discrete lesions from 45 patients undergoing routine diagnostic angiography were analyzed in each of 3 image types: direct on-line digital, electrocardiogram-gated digital subtraction and digitized cine film images. For the geometric measurements (minimal lumen diameter and percent diameter stenosis) correlation coefficients for 2-way comparisons among the image types ranged from 0.90 to 0.96. Linear regression slopes ranged from 0.93 to 1.00, with intercepts from 0.03 to 0.07 mm for minimal diameter and -0.5 to 4.4% for percent diameter stenosis. For the videodensitometric percent area stenosis data, the correlation coefficients ranged from 0.80 to 0.89, with linear regression slopes from 0.84 to 0.89 and intercepts from 8.3 to 12.8%. Thus, the results of quantitative geometric measurements of coronary stenosis severity were not strongly affected by image acquisition mode (on-line versus cine film digitization) or by electrocardiogram-gated digital subtraction, while densitometric data correlated less well when on-line digital and digitized cine film acquisition methodology were compared.

Angiography↗
PubMed1991

Age-related variation in contractility estimate in patients less than or equal to 20 years of age.

The relation between velocity of circumferential fiber shortening (VCF) and wall stress (WS) is being used to estimate contractile state in a variety of disease states and patient ages more frequently. However, its relation to age has not been established. To determine reproducibility and age and sex dependence of this relation, 204 normal children (113 boys, 91 girls) underwent echographic determination of VCF and WS. The children were enrolled in 3 groups: group 1 less than 6 months old (n = 27); group 2 greater than 6 months and less than 3 years old (n = 38); and group 3 greater than 3 and less than 20 years old (n = 139). Twenty-five children also underwent serial echocardiography (n = 44) to determine reproducibility of the relation. Only 1 of the 44 repeat data pairs of VCF and WS was outside the 95% confidence limits of that relation. In all 3 groups, VCF was significantly inversely and linearly related to WS (p less than 0.001). The regression equation in the oldest group was very similar to previous reports (VCF = -0.0031 [WS] + 1.21). The regression lines in the 2 younger groups were significantly steeper and had a significantly higher y-intercept (p less than 0.01). Group 1 had the steepest slope and highest y-intercept. There was no difference in the regression lines of different sexes in any of the patient groups. It is concluded that the relation of VCF to WS is reproducible over time. It is age-dependent but has no relation to gender. VCF in patients less than 6 months old is more highly dependent on WS.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Ultrasonographic fetal weight estimation by an integrated computer-assisted system: can each laboratory improve its accuracy?

Estimated fetal weights from 1684 cases with singleton, live infants born within 7 days of an ultrasonographic examinations were compared with their birth weights, which ranged from 520 to 5920 gm. Estimated weight calculated from Shepard's equation produced a linear relationship of birth weight against estimated weight with an intercept and slope of 209.5 gm and 0.929. Overall, 75% of the estimated weights were within 15% of the actual weight. A separate regression model that used the same variables from Shepard's equation failed to improve the comparison between estimated and actual weights. All cases were reevaluated with multiple regression modeling. Various examination-to-birth intervals were analyzed; intervals less than or equal to 3 days appeared optimal. The best equation increased the percent of cases that were within 15% of the actual birth weight to 80%. The plot of birth weight against estimated weight had an intercept and slope of 33.1 gm and 0.994. Unlike Shepard's equation, the best equation was not statistically different from the ideal one-to-one relationship between estimated and actual weight. When the new equation was applied to an additional 339 new cases, equally accurate results were obtained. Customizing a laboratory's ultrasonographic weight estimation equations may be necessary to obtain the best estimate of fetal weight.

Birth Weight↗
PubMed1981

Morphologic changes in the sagittal dimension using the Fränkel appliance.

Interceptive orthodontic treatment of four patients with the Fränkel appliance is presented. The Fränkel appliance is but one of many appliances available using the principle of functional jaw orthopedics. However, the Fränkel appliance seems to offer a broad range of potential corrections and appears worthy of consideration for early treatment by any orthodontist. The cases presented show various combinations of condylar growth, maxillary retraction, and dentoalveolar changes in the correction of Class II, Division I malocclusions with varying degrees of mandibular retrognathia. In all patients facial improvement was noted. Lateral expansion was also noted and offers another possibility in orthodontic treatment. It appears that the Fränkel appliance may be capable of taking advantage of three types of orthopedic correction: condylar growth, maxillary retraction, and lateral expansion. The possibilities of these changes occurring on a routine clinical level are discussed, and further studies of the Fränkel appliance are encouraged. It seems that, regardless of the orthodontist's choice of bands or bonds, the Fränkel appliance could be incorporated into any practice and offer potential orthopedic and/or orthodontic benefits for interceptive orthodontic treatment.

Activator Appliances↗
PubMed1983

Measurement of rate constants for actin filament elongation in solution.

This paper describes a simple method to measure the rate constants for actin filament elongation using pyrene-actin fluorescence as a measure of the polymer concentration and unlabeled actin filaments as nuclei. With careful selection of conditions, the initial rate of polymerization is directly proportional to the actin monomer concentration above the critical concentration. Plots of initial rate versus actin concentration give the critical concentration (x intercept), the association rate constant, k+ (slope), and the dissociation rate constant, k-(y intercept). By calibrating the system under conditions where the absolute values of these rate constants are known from previous electron microscopic experiments [T. D. Pollard and M. S. Mooseker (1981) J. Cell Biol. 88, 654-659; J. A. Cooper, S. B. Walker, and T. D. Pollard (1983) J. Muscle Res. Cell Motil. 4, 253-262], one can calculate the absolute values of the rate constants under other conditions as well as the length of the filaments used as a nuclei. This approach has proven useful for evaluating the effect of actin-binding proteins on the polymerization process.

Actins↗
PubMed1990

Kinetics of the reaction of prostaglandin H synthase compound II with ascorbic acid.

The reduction of prostaglandin H synthase compound II by ascorbic acid in the presence of diethyldithiocarbamate was studied in 0.1 M phosphate buffer (pH 8.0) at 4.0 +/- 0.5 degrees C, by rapid scan spectrometry and transient state kinetics. A saturation effect and nonzero intercept were observed in the plot of pseudo-first-order rate constant versus ascorbic acid concentration. The saturation behavior suggests formation of a complex between prostaglandin H synthase compound II and ascorbic acid, whereas the nonzero intercept is attributable to the reaction of compound II of prostaglandin H synthase with diethyldithiocarbamate present in the system as a stabilizing agent. A rate equation has been derived which includes all pathways for the conversion of prostaglandin H synthase compound II back to native enzyme. Kinetic parameters for the reduction of compound II by ascorbic acid were obtained. They are the second-order rate constant of (1.4 +/- 0.5) X 10(5) M-1, S-1, for the formation of the compound II-ascorbic acid complex, the first-order rate constant of (14 +/- 4) S-1 for the oxidation-reduction reaction of the complex and its dissociation, and a parameter, Km of 92 +/- 10 microM analogous to the Michaelis-Menten constant. Thus we demonstrate that a quantitative kinetic study on the prostaglandin H synthase reactions can be performed in the presence of diethyldithiocarbamate.

Alkenes↗
PubMed1990

Effects of trauma to the mandibular nerve on human perioral directional sensitivity.

The capacity of 4 patients who had previously experienced trauma to their mandibular nerves to distinguish opposing directions of tactile motion over the distribution of the mental nerve was compared to that of 8 neurologically normal adults. Brushing stimuli were delivered to the perioral region and were precisely controlled for their velocity, the length of skin traversed, the width of skin contacted, and the orientation and direction of motion. A temporal, 2-alternative, forced choice method was used to obtain estimates of directional sensitivity, d'. It was discovered that impairment in cutaneous directional sensitivity could be readily detected within areas of hypaesthesia. Although directional sensitivity was found to increase linearly with the length of skin traversed for both the patients and the neurologically normal adults, the slope and the x-intercept of the linear relationship differed between the two groups. The difference in the slope suggests that direction discrimination within the hypaesthetic areas is relatively insensitive to changes in the length of skin traversed. The difference in the x-intercept suggests that a greater length of skin must be traversed before any information about direction is made available at the hypaesthetic sites. The dependency of the capacity of neurologically normal and impaired individuals to process information about direction of tactile motion on the length of skin traversed and the velocity of stimulation suggests that a high degree of stimulus control is required for the detection and quantification of subtle neurosensory deficits.

Adolescent↗
PubMed1979

Studies on the succinate dehydrogenating system. I. Kinetics of the succinate dehydrogenase interaction with a semiquindiimine radical of N,N,N',N'-tetramethyl-p-phenylenediamine.

1. The activities of the soluble reconstitutively active succinate dehydrogenase (EC 1.3.99.1) measured with three artificial electron acceptors, e.g. ferricyanide, phenazine methosulfate and free radical of N,N,N',N'-tetramethyl-p-phenylenediamine (WB), have been compared. The values estimated by extrapolation to infinite acceptor concentration using double reciprocal plots 1/v versus 1/[acceptor] are nearly the same for ferricyanide and phenazine methosulfate and about twice as high for the WB. 2. The double reciprocal plots 1/v versus 1/[succinate] in the presence of malonate at various concentrations of WB give a series of straight lines intercepting in the third quadrant. The data support the mechanism of the overall reaction, in which the reduced enzyme is oxidized by WB before dissociation of the enzyme-product complex. 3. The dependence of the rate of the overall reaction on WB concentration shows that only one kinetically significant redox site of the soluble succinate dehydrogenase is involved in the reduction of WB. 4. Studies of the change of V and Km values during aerobic inactivation of the soluble enzyme suggest that only 'the low Km ferricyanide reactive site' (Vinogradov, A.D., Gavrikova, E.V. and Goloveshkina, V.G. (1975) Biochem. Biophys, Res. Commun. 65, 1264--1269) is involved in reoxidation of the reduced enzyme by WB. 5. The pH dependence of V for the succinate-WB reductase reaction shows that the group of the enzyme with the pKa value of 6.7 at 22 degrees C is responsible for the reduction of dehydrogenase in the enzyme-substrate complex. 6. When WB interacts with the succinate-ubiquinone region of the respiratory chain, the double reciprocal plot 1/v versus 1/[WB] gives a straight line. The thenoyltrifluoroacetone inhibition of succinate-ubiquinone reductase or extraction of ubiquinone alter the 1/v versus 1/[WB] plots for the curves with a positive initial slope intercepting the ordinate at the same V as in the native particles. The data support the mechanism of succinate-ubiquinone reduction, in which no positive modulation of succinate dehydrogenase by ubiquinone exist in the membrane.

Aerobiosis↗
PubMed1995

Kinetics of the mitochondrial three-subunit NADH dehydrogenase interaction with hexammineruthenium(III).

The steady-state kinetics of the NADH dehydrogenase activity of the three-subunit flavo-iron-sulfur protein (FP, Type II NADH dehydrogenase) in the presence of the one-electron acceptor hexammineruthenium(III) (HAR) were studied. The maximal catalytic activities of FP with HAR as electron acceptor calculated on the basis of FMN content were found to be approximately the same for the submitochondrial particles, Complex I and purified FP. This result shows that the protein structure responsible for the primary NADH oxidation by FP is not altered during the isolation procedure and the lower (compared with Complex I) catalytic capacity of the enzyme previously reported was due to the use of inefficient electron acceptors. Simple assay procedures for NADH dehydrogenase activity with HAR as the electron acceptor are described. The maximal activity at saturating concentrations of HAR was insensitive to added guanidine, whereas at fixed concentration of the electron acceptor, guanidine stimulated oxidation of low concentrations of NADH and inhibited the reaction at saturating NADH. The inhibitory effect of guanidine was competitive with HAR. The double-reciprocal plots 1/v vs. 1/[NADH] at various HAR concentrations gave a series of straight lines intercepting on the ordinate. The plots 1/v vs. 1/[HAR] at various NADH concentrations gave a series of straight lines intercepting in the fourth quadrant. The kinetics support the mechanism of the overall reaction where NADH is oxidized by the protein-Ru(NH3)3+(6) complex in which positively charged electron acceptor is bound at the specific site close to FMN, thus stabilizing the flavosemiquinone intermediate.

Animals↗
PubMed1980

Large vesicle contamination in small, unilamellar vesicles.

Small, unilamellar phospholipid vesicles have been prepared using a new, high-powdered cup sonifier that avoids contact of the sample with a titanium probe. These vesicles have been characterized by gel filtration chromatography both before and after fractionation by high-speed centrifugation. Plots of the turbidity of centrifuged vesicles between 300 and 650 nm against the reciprocal fourth power of the scattering wavelength were linear with zero intercepts (extrapolated to infinite wavelength). In the presence of minute quantities of large, multilamellar vesicles, these plots remained linear but had intercepts quantitatively proportional to the amount of contaminating large vesicles. Since this measurement requires only a standard spectrophotometer and very small quantities of lipid, this method is suggested as a useful assay for determining contamination of small vesicle preparations by large vesicles. Two applications of this method as well as a practical limitation are discussed.

Liposomes↗
PubMed1975

An extended Scatchard analysis for competitively bound ligands and its application to cyclic adenosine-3',5'-monophosphate and cyclic 5'-amido-5'-deoxyadenosine-3', 5'-monophosphate binding to beef skeletal muscle protein.

A method for determining the dissociation constants of ligands and ligand analogs is described. It is based on competition binding studies in the presence of an isotope-labeled, or otherwise measurable, ligand and suitable analog concentrations. The steps used are determination of (1) the maximal amount of radioactive ligand that can be bound, (2) the slopes and intercepts from Scatchard plots at different analog concentrations and (3) the values for the dissociation constants of radioactive ligand and ligand analog from replots of the reciprocals of the slopes and intercepts obtained from the Scatchard plots. Application of the method to a cyclic AMP-binding protein from beef muscle is demonstrated, yielding dissociation constants of 2.10-9 M for cyclic (3H) AMP and cyclic AMP, and 3.10-5 M for cyclic 5'-amido-5'-deoxyadenosine-3', 5'-monophosphate.

Amides↗
PubMed1979

Brain sodium uptake after choroid plexectomy.

When in a (control) series of rats brain sodium uptake (BSU) -- as calculated from estimated radioactivities of brain and blood following the injection of [24Na]sodium chloride 30 min and [22Na]sodium chloride one minute before killing -- was plotted against average arterial blood pressure of the animals during the 30 min survival period, a linear dependence of BSU on blood pressure was observed. In another series of animals, in which the choroid plexuses of the fourth and both lateral ventricles had been removed, the regression line showed the same slope, but a significantly lower intercept. On the other hand, a series of rats which had been subjected to a sham operation without removal of the choroid plexuses, showed a regression line not different from the control series. The results indicate that probably the blood pressure independent component of brain sodium uptake, as represented by the intercept of the regression line, for the greater part constitutes cerebrospinal fluid secretion by the choroid plexus.

Animals↗