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At least 829 records · Page 46Linked to original sources
PubMed1983

Determinants of bumetanide response in the dog: effect of indomethacin.

Four male unanesthetized dogs each weighing 22.0-29.0 kg received 0.250 mg/kg iv of bumetanide before (treatment I) and after (treatment II) indomethacin pretreatment. Lactated Ringer's solution was administered intravenously throughout both treatments at a flow rate of 2 ml/min to avoid fluid and electrolyte depletion. Unchanged bumetanide and indomethacin concentrations were analyzed using high-performance liquid chromatography. Sodium was measured by flame photometry and creatinine by colorimetry. Indomethacin pretreatment did not significantly change the pharmacokinetics of bumetanide, affecting neither the total amount of drug nor time course of drug delivered into the urine. In contrast, indomethacin pretreatment resulted in a dramatic reduction in the 4-hr sodium excretion and urine volume. Therefore, a pharmacokinetic interaction may be eliminated as a possible mechanism for the attenuation, by indomethacin, of the natriuretic and diuretic response of bumetanide. Instead, it appears that indomethacin diminishes the response to bumetanide via prostaglandin inhibition.

Animals↗
PubMed1990

NMR visibility of 39K and 35Cl in erythrocytes and kidney tubules.

The NMR visibility of 39K and 35Cl has been investigated in erythrocytes and in dog renal tubules. In erythrocytes, the 39K NMR visibility was determined by comparing the signal intensities before and after hemolysis with water and by comparing the NMR and flame photometry results. Both procedures showed a NMR visibility of 100% for intracellular potassium. The visibility of intracellular chloride in erythrocytes was estimated at 40% by monitoring the intensity of the 35Cl signal as a function of the hematocrit value. In the case of kidney proximal tubules, the 39K visibility appeared to be very low but could not be accurately determined due to the low sensitivity of the nucleus. The 35Cl signals for intracellular chloride in renal tubules were too broad to be detected.

Animals↗
PubMed1990

Sodium-23 MR imaging of the kidney in guinea pig at 2.1 T, following arterial, venous, and ureteral ligation.

In vivo 23Na magnetic resonance images of guinea pig kidney were obtained at 2.1 T using a spin-echo sequence with an echo time of 19 ms. The intact kidney showed a very strong signal intensity in the sodium image. The signal intensity of the kidney decreased to 55% after ligation of the renal artery together with the vein and the ureter. The total sodium content in the excised kidney after arterial occlusion, measured by flame photometry, was 24% higher than that in the intact kidney. The transverse relaxation time (T2) of the extracellular sodium in the isolated kidney decreased to one-third of that in the intact kidney. This shortening of T2 may be partly responsible for the decrease in the 23Na signal intensity from the kidney after arterial occlusion.

Animals↗
PubMed1985

The glomerular ultrastructural distribution of immunoglobulin G in hyperalbuminaemic (protein-overload) proteinuria.

Female Munich-Wistar rats were given intraperitoneal injections either of bovine serum albumin to induce proteinuria or of water as a control. Their kidneys were fixed in situ. An ultrastructural technique was used to demonstrate IgG antiperoxidase antibodies either injected from a heterologous species or autologous, induced by immunization with horseradish peroxidase. Photometry of electron micrographic negative was used to determine the distribution of antiperoxidase antibodies. In glomeruli of control animals IgG was present in the basement membrane. There were three sites at which the passage of IgG across the basement membrane was hindered: between blood plasma and the lamina rara interna, between the lamina densa and the lamina rara externa, and between the lamina rara externa and the urinary space. Glomeruli of proteinuric animals were variable in appearance, some showing little structural damage and others showing marked changes with loss of epithelial foot processes and accumulation of vacuoles and protein droplets in epithelial cells. Both types of glomeruli contained IgG in the urinary space. The distribution of IgG in the basement membrane of both types was similar. Compared with control animals there was less IgG in the basement membrane and IgG was distributed uniformly across the basement membrane. The proteinuria in hyperalbuminaemia (protein-overload) is associated with a diffuse change in the barrier function of the glomerular basement membrane to IgG which is, at least in the initial stages, not related to structural changes in glomerular epithelial cells.

Albuminuria↗
PubMed1998

Modifications of intracellular calcium release channels and calcium mobilization following 70% hepatectomy.

The aim of this study was to investigate the properties of ryanodine and IP3 receptors in regenerating liver following 70% hepatectomy, and to evaluate the hepatic Ca2+ distribution and mobilization during this process. Specific [3H]ryanodine and [3H]IP3 binding to hepatic smooth endoplasmic reticulum membranes, as well as subcellular Ca2+ determination by atomic absorption flame photometry and Ca2+ mobilization by INDO-1 AM spectrofluorescence in hepatocytes, was performed in regenerating livers after surgical 70% hepatectomy. Incorporation of 14C amino acids into proteins and of 32P into phospholipids was done in subcellular fractions. Ryanodine receptor Kd presented a dramatic increase after 12 h of surgery and remained high up to 2 days of treatment. IP3 receptor Bmax showed a significant augmentation starting at 6 h after hepatectomy and returning to normal values after 1 week. Cytosolic total calcium content decreased from 12 h until 4 days after hepatectomy whereas the microsomal and mitochondrial total calcium increased at 1 and 2-4 days of liver regeneration, which coincided with the differential turnover of proteins and phospholipids in these fractions. ATP-induced Ca2+ transients in hepatocytes of 24-h-hepatectomized rats confirmed the altered sensitivity of the ryanodine receptor toward its ligand, since 10 times more ryanodine was necessary to alter the ATP-induced Ca2+ transient. The data support the notion that the calcium release channels are targets of mechanisms of metabolic control during the proliferative response following 70% hepatectomy and might be part of the modified intracellular Ca2+ dynamics during liver regeneration.

Animals↗
PubMed1993

Method for determination of intracellular sodium in perfused cancer cells by 23Na nuclear magnetic resonance spectroscopy.

Changes of intracellular sodium concentrations are often an indication of disease or malfunction. In this work, shift reagent-aided 23Na NMR spectroscopic determination of intracellular sodium was adapted to measurements with perfused cells embedded in agarose gel threads. Ehrlich ascites tumor cells (EHR2) and their multidrug-resistant counterparts (EHR2/DNR+) were immobilized and perfused until the metabolic steady state had been reached as shown by 31P NMR spectroscopy. Subsequent addition of 5 mM dysprosium(III) bis(tripolyphosphate) to the perfusion medium caused a separation of extracellular and intracellular 23Na NMR signals, making quantification of the intracellular sodium possible. The dysprosium shift reagent was apparently nontoxic to the cells, as shown by the unchanged level of ATP and other intracellular phosphates. NMR visibility of the intracellular sodium was determined in suspensions of EHR2 and EHR2/DNR+ cells by treatment with digitonin; the increase of intensity of the extracellular sodium resonance observed after the digitonin treatment corresponded well (97 +/- 3%) to the sum of intracellular and extracellular sodium observed with intact cells prior to the digitonin treatment. The resistant EHR2/DNR+ cells contained a moderately higher intracellular sodium level than the wild-type EHR2 cells, 1.02 +/- 0.10 and 0.77 +/- 0.07 mumol Na/mg protein, respectively. Closely similar levels of intracellular sodium were found by flame photometry. Thus, 23Na NMR offers a reliable method for noninvasive quantification of intracellular sodium in perfused cancer cells.

Animals↗
PubMed1997

Direct and indirect methods for molar-mass analysis of fragments of the capsular polysaccharide of Haemophilus influenzae type b.

Two methods are described for direct molar-mass measurement of low-molar-mass fragments obtained by oxidative cleavage of the capsular polysaccharide of Haemophilus influenzae type b. Absolute molar masses were determined by size-exclusion chromatography (SEC) with detection by multiangle laser-light-scattering photometry (MALLS) and differential refractometry (RI). The end-group structure of the polysaccharide fragments allowed the direct measurement of average chain length by quantitative 1H NMR, from which molar masses were derived. Variation between the molar masses obtained by the two methods ranged from 5 to 7%. When molar masses estimated by indirect methods were compared to SEC-MALLS/RI data, significant deviations were observed. Analysis by SEC with secondary calibration with dextran standards gave molar masses that exceeded the SEC-MALLS/RI data by as much as 2.5-fold. Molar masses estimated by a combination of colorimetric assays varied from the SEC-MALLS/RI data by as much as 50%. These results demonstrated the applicability and superior accuracy of the direct methods of molar-mass determination of the polysaccharide fragments.

Bacterial Capsules↗
PubMed1999

A dye binding assay for the quantification of soluble and cell-bound acidic polysaccharides produced by red algae.

Polysaccharides produced in technical scale from red algae serve in a variety of industrial applications. Ruthenium red (RR) is a cytochemical stain which has been used to visualize these mostly acidic polysaccharides in light microscopy. The binding of RR to algal polysaccharides is highly dependent on the ionic strength of the surrounding medium. The dye is firmly bound at low ionic strength, but is released at increasing salt concentrations. These properties were exploited to develop a new method to quantify the amount of cell wall material synthesized by algal cells under different physiological conditions. Soluble or extracted polysaccharides are quantified by a dot-blot procedure with subsequent image analysis, while cell-bound polysaccharides are determined in situ by a dye-binding assay followed by photometry. In comparison to the current methods of quantification, the new assay is quick, reliable, and avoids extensive use of hazardous chemicals.

Calibration↗
PubMed1993

Wall shear stress rather than shear rate regulates cytoplasmic Ca++ responses to flow in vascular endothelial cells.

Recent evidence suggests that the vascular endothelial cell (EC) can sense the flow-rate over its surface and according to the information, regulates not only its own morphology and functions but also those of the surrounding smooth muscle and other tissues. There is now a discussion over which of the following mechanisms actually initiates the signal-transacting response of EC against flow: the mechanical shear deformation of the cell due to flow-oriented wall shear stress (tau), or the diffusional accumulation of vasoactive agonists on the cell surface modulated by wall shear rate (gamma) or both. To identify the relative importance of each mechanism, we examined quantitative changes in the cytoplasmic free Ca++ concentration ([Ca++]i) in cultured EC in the presence of the Ca++ mobilizing agonist ATP, i.e., a second messenger response of the internal signalling system, following the perfusion of two buffers with different viscosities (mu), which relates these factors as tau = mu gamma. The results of in vitro fluorescence photometry in EC with Fura-2 showed that the [Ca++]i level was enhanced with increase in the shear rate but to a greater extent with higher viscosity, and that the [Ca++]i levels at the same calculated level of shear stress were virtually identical, regardless of difference in shear rate and viscosity. This quantitative one-to-one relationship between the shear stress and the second messenger response suggests that wall shear stress rather than wall shear rate is the principal physical factor eliciting EC responses to flow.

Animals↗
PubMed1996

Iris color and macular pigment optical density.

The present study was designed to assess the relationship between iris color and macular pigment optical density. Both melanin and carotenoids (responsible for iris color and macular pigment composition, respectively) appear to protect the retina through similar mechanisms and higher concentrations may reduce the incidence of retinal degenerations. To evaluate this relationship, 95 subjects were examined and the following variables were measured: iris color; macular pigment optical density (MP); plasma concentrations of lutein and zeaxanthin and beta-carotene; dietary intake of lutein and zeaxanthin and beta-carotene; and total fat intake. Iris color was determined by self assessment and classified as blue or gray (group I), green or hazel (group II) or brown or black (group III). MP density was measured psychophysically by measuring foveal and parafoveal sensitivities to lights of 460 and 550 nm, using the method of heterochromatic flicker photometry. Plasma carotenoid concentrations were measured using reverse-phase high-performance liquid chromatography. Dietary intake was determined by a detailed food-frequency questionnaire. Despite similarities in diet and in blood concentrations of carotenoids, significant differences in macular pigment density (P < 0.02) were found for different colored irises (group I, n = 38, MP = 0.25; group II, n = 26, MP = 0.32; group III, n = 31, MP = 0.38). The covariation of iris color and MP indicates that past epidemiologic studies have not adequately determined the independent effects of either factor. The relationship of MP and iris color may be the result of one or two factors: the evolution of a shared tendency to accumulate melanin and carotenoids due to similar environmental pressures (e.g. light and oxygen); and/or MP might be depleted due to the tendency for eyes with light irises to transmit more light than eyes with dark irises, thus causing increased oxidative stress.

Adult↗
PubMed1997

A one year study of the macular pigment: the effect of 140 days of a lutein supplement.

A low density of macular pigment may represent a risk factor for age-related macular degeneration (AMD) by permitting greater blue light damage. This study was carried out to determine the effects on macular pigment optical density of dietary supplementation with lutein, one of the pigment constituents. Two subjects consumed lutein esters, equivalent to 30 mg of free lutein per day, for a period of 140 days. Macular pigment optical density was determined by heterochromatic flicker photometry before, during, and after the supplementation period. Serum lutein concentration was also obtained through the analysis of blood samples by high-performance liquid chromatography. Twenty to 40 days after the subjects commenced taking the lutein supplement, their macular pigment optical density began to increase uniformly at an average rate of 1.13+/-0.12 milliabsorbance units/day. During this same period, the serum concentration of lutein increased roughly tenfold, approaching a steady state plateau. The optical density curve eventually levelled off 40 to 50 days after the subjects discontinued the supplement. During the same 40 to 50 days, the serum concentration returned to baseline. Thereafter, little or no decrease in optical density was observed. The mean increases in the macular pigment optical density were 39% and 21% in the eyes of the two subjects respectively. In conclusion, the modest period of supplementation has been estimated to have produced in the subjects a 30 to 40% reduction in blue light reaching the photoreceptors, Bruch's membrane, and the retinal pigment epithelium, the vulnerable tissues affected by AMD.

Adult↗
PubMed2002

Macular pigment and lutein supplementation in choroideremia.

Choroideremia is an incurable X-linked retinal degeneration caused by mutations in the gene encoding Rab escort protein-1. A group of clinically defined and genotyped patients were studied to determine: (1) the degree of rod and cone dysfunction and structural abnormality in the central retina and the level of macular pigment; and (2) the response of macular pigment and foveal vision to a 6 month trial of supplementation with oral lutein (at 20 mg per day). Rod and cone-mediated function was measured with dark-adapted static perimetry; in vivo retinal structure was determined with optical coherence tomography; and macular pigment optical density was measured with heterochromatic flicker photometry. In this cohort of patients (ages 15-65 years), both rod- and cone-mediated central function declined with age as did central retinal thickness. Macular pigment levels did not differ between patients and male control subjects. Supplementation of oral lutein in a subset of patients led to an increase in serum lutein and macular pigment levels; absolute foveal sensitivity did not change. It is concluded that macular pigment density can be augmented by oral intake of lutein in patients with choroideremia. There was no short-term change in the central vision of the patients on the supplement, but long-term influences of lutein supplementation on disease natural history warrant further study.

Adolescent↗
PubMed2002

Reaction mechanism of GTP cyclohydrolase I: single turnover experiments using a kinetically competent reaction intermediate.

GTP cyclohydrolase I catalyses the transformation of GTP into dihydroneopterin 3'-triphosphate, which is the first committed precursor of tetrahydrofolate and tetrahydrobiopterin. The kinetically competent reaction intermediate, 2-amino-5-formylamino-6-ribosylamino-4(3H)-pyrimidinone, was used as substrate for single turnover experiments monitored by multiwavelength photometry. The early reaction phase is characterized by the rapid appearance of an optical transient with an absorption maximum centred at 320. This species is likely to represent a Schiff base intermediate at the initial stage of the Amadori rearrangement of the carbohydrate side-chain. Deconvolution of the optical spectra suggested four linearly independent processes. A fifth reaction step was attributed to photodecomposition of the enzyme product. Pre-steady state experiments were also performed with the H179A mutant which can catalyse a reversible conversion of GTP to 2-amino-5-formylamino-6-ribosylamino-4(3H)-pyrimidinone but is unable to form the final product, dihydroneopterin triphosphate. Optical spectroscopy failed to detect any intermediate in the reversible reaction sequence catalysed by the mutant protein. The data obtained with the wild-type and mutant protein in conjunction with earlier quenched flow studies show that the enzyme-catalysed opening of the imidazole ring of GTP and the hydrolytic release of formate from the resulting formamide type intermediate are both rapid reactions by comparison with the subsequent rearrangement of the carbohydrate side-chain which precedes the formation of the dihydropyrazine ring of dihydroneopterin triphosphate.

Catalysis↗
PubMed1998

Angiotensin II and intracellular calcium of adult cardiac fibroblasts.

In various cardiovascular disorders, circulating or myocardial angiotensin II (Ang II) levels are increased, leading to excess collagen synthesis of cardiac fibroblasts. To characterize signal transduction mechanisms of Ang II, we examined changes in intracellular Ca2+ concentration ([Ca2+]i) of fura-2-loaded cultured adult rat cardiac fibroblasts by fluorescence photometry. [Ca2+]i was increased by Ang II via AT1 receptors in a dose-dependent manner (EC50 = 2.4 x 10(-8) mol/l) involving two distinct phases, an initial Ca2+ peak and a sustained elevated plateau phase. The initial Ca2+ peak occurred transiently and independently of the duration of Ang II application. While the magnitude of the transient Ca2+ peak did not differ in a nominally Ca(2+)-free (3 mmol/l EGTA) solution, the Ang II-mediated sustained plateau phase of [Ca2+]i was dependent on extracellular Ca2+. Thus, the initial transient Ca2+ peak appears to arise from intracellular Ca2+ stores, whereas the plateau phase involves an external Ca2+ influx. Since collagen synthesis of cardiac fibroblasts is maximally stimulated by Ang II or by fetal bovine serum (FBS), the effects of Ang II and FBS on [Ca2+]i were compared. The magnitude of the transient Ca2+ peak induced by 10(-7) mol/l Ang II was comparable to that of 10% FBS indicating that the rise in [Ca2+]i might be involved in the signal transduction pathway of Ang II-mediated collagen synthesis of cardiac fibroblasts.

Angiotensin II↗
PubMed2002

Vascular smooth muscle cells derived from atherosclerotic human arteries exhibit greater adhesion, migration, and proliferation than venous cells.

BACKGROUND: Phenotypic variation of vascular smooth muscle cells (VSMC) may result in altered biological behavior and responses. Within the vessel wall, arterial VSMC have a greater propensity to form atherosclerotic lesions as compared to venous VSMC. In this study the rates of proliferation, adhesion, and migration were compared between VSMC of atherosclerotic arterial and venous origin. MATERIALS AND METHODS: Human VSMC cultures were isolated from 18 infragenicular arteries at the time of below knee amputation and from 20 saphenous veins during lower extremity revascularization surgery. Cell cultures were isolated from the media of each specimen and maintained in distinct cell lines for all assays. Cells from passages 2 and 3 were assayed for their proliferative capacity using total DNA fluorescence photometry and for adhesion and migration using a modified Boyden chamber. RESULTS: Patient age and the incidence of atherosclerotic risk factors did not vary significantly between the arterial and the venous patient groups. VSMC of atherosclerotic arterial origin demonstrated greater proliferation (arterial, 162 +/- 59 absorption units, vs. venous, 106 +/- 56 absorption units, P < 0.001), adhesion (arterial, 74.1 +/- 22.6 cells/microscopic field, vs. venous, 41.3 +/- 12.8 cells/microscopic field, P < 0.001) and migration (arterial, 427 +/- 185 cells/microscopic field, vs venous, 119 +/- 101 cells/microscopic field, P < 0.001) than VSMC of venous origin. CONCLUSION: Human atherosclerotic arterial VSMC exhibit significantly increased rates of proliferation, adhesion, and migration as compared to human venous VSMC. These observations of VSMC in culture are consistent with the clinical predilection for the hyperplasic responses that result in the development of atherosclerosis in the arterial wall. Possible intrinsic differences in VSMC phenotype should be considered in designing methods to limit atherosclerosis.

Aged↗
PubMed1999

Copper effects on ion transport across lamprey erythrocyte membrane: Cl(-)/OH(-) exchange induced by cuprous ions.

We studied the effects of prelytic copper concentrations on cell volume, intracellular pH, and ion transport in lamprey erythrocytes. Ion fluxes and pH were measured by radioactive tracer technique, patch clamp, and flame photometry. Prelytic CuSO(4) concentration of 100 microM caused anion-dependent intracellular acidification and increase in Cl(-) influx after 2 min lag-phase. In the presence of ascorbate copper effect was amplified and lag-phase was skipped. Pretreatment of the cells with N-phenyl maleimide abolished copper-induced changes completely. Copper treatment caused an increase in Na(+) fluxes in both directions and a net Na(+) uptake. Copper-induced Na(+) transport was partially amiloride(MIA)-sensitive representing Na(+)/H(+) exchange. The nature of the amiloride-insensitive fraction of copper-activated Na(+) influx remains unknown. Cell swelling after 15 min of copper exposure induced regulatory volume decrease response involving KCl extrusion via K(+) and Cl(-) volume-sensitive channels. We suggest that the effects of copper on ion transport fit the following sequence of events: (i) cupric ions are reduced to cuprous state on the membrane surface, (ii) electroneutral pairs CuCl and CuOH mediate chloride/hydroxyl exchange, as shown before for trialkyltin, dissipating transmembrane pH gradient, and (iii) changes in intracellular pH result in the activation of the Na(+)/H(+) exchange and consecutive volume changes cause the RVD response.

Animals↗
PubMed1988

The simultaneous measurements of tissue oxygen concentration and energy state by near-infrared and nuclear magnetic resonance spectroscopy.

The oxygenation and energy states of brain tissues were measured simultaneously by near-infrared photometry and nuclear magnetic resonance spectroscopy in situ. In both cat and dog, the critical hemoglobin oxygenation was 10%, below which the ratio of phosphocreatine (PCr) to inorganic phosphate (Pi) started to fall. The fall of PCr/Pi paralleled the reduction of copper in cytochrome aa3. The separation of the cytochrome aa3 signal from that of hemoglobin by our optical method was confirmed by the substitution of blood by fluorocarbon solution. The energy-oxygen diagram (PCr/Pi against hemoglobin oxygenation, HbO2) was the same in normal- and fluorocarbon substituted cats, but energy curve shifted to the right in the latter when PCr/Pi plotted against the inspired oxygen, FiO2.

Animals↗
PubMed1987

Infrared emission from P/Halley's dust coma during March 1986.

2 to 20 micrometers photometry of the inner dust coma of comet Halley was obtained at the NASA IRTF on Mar 6.85, 12.8, 13.75, 17.7, and 24.8. Positions offset 10" were measured as well as the central brightness. The strength of the 10 micrometers emission feature was observed to vary with location in the coma. The infrared emission is in general agreement with the dust size distribution measured from the Vega and Giotto spacecraft. Mar 6.8, 17.7, and 24.8 corresponded to strong dust jet activity. The strength of the 10 micrometers silicate emission is shown to be a sensitive indicator of grain size and thus of jet activity. Dust production rate on March 13.75, 6 h before Giotto encounter, was approximately 10(7) gm s-1.

Astronomy↗