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PubMed2003

In-field labeling of western corn rootworm adults (Coleoptera: Chrysomelidae) with rubidium.

Field and laboratory studies were conducted in 2000 and 2001 to determine the feasibility of mass marking western corn rootworm adults, Diabrotica virgifera virgifera LeConte, with RbCl in the field. Results showed that application of rubidium (Rb) in solution to both the soil (1 g Rb/plant) and whorl (1 g Rb/plant) of corn plants was optimal for labeling western corn rootworm adults during larval development. Development of larvae on Rb-enriched corn with this technique did not significantly influence adult dry weight or survival. Rb was also highly mobile in the plant. Application of Rb to both the soil and the whorl resulted in median Rb concentrations in the roots (5,860 ppm) that were 150-fold greater than concentrations in untreated roots (38 ppm) 5 wk after treatment. Additionally, at least 90% of the beetles that emerged during the first 3 wk were labeled above the baseline Rb concentration (5 ppm dry weight) determined from untreated beetles. Because emergence was 72% complete at this time, a significant proportion of the population had been labeled. Results from laboratory experiments showed that labeled beetles remained distinguishable from unlabeled beetles for up to 4 d postemergence. The ability to efficiently label large numbers of beetles under field conditions and for a defined period with virtually no disruption of the population provides an unparalleled opportunity to conduct mark-recapture experiments for quantifying the short-range, intrafield movement of adult corn rootworms.

Animals↗
PubMed1971

Sodium and rubidium fluxes in rat red blood cells.

1. The Na content of rat red cells was found to be 4.40 m-mole/l. cells. When incubated in K(Rb)-free Na this value was doubled in 1 hr, whereas in K(Rb)-free choline it was reduced to about 35% in the same period of time.2. In cells with elevated Na (13.70 m-mole/l.) the activation curve of Rb influx by external Rb reached the same V(max) in sodium as in choline. The shape of the curve was sigmoid in the first case (K(m) about 1.05 mM) and hyperbolic in the second (K(m) about 0.20 mM).3. The activation curve of rubidium influx by internal sodium was linear at least up to 12 m-mole/l. cells with a slope of 0.84. From this concentration it could increase more steeply, though the data is insufficient to assure it.4. In normal cells the efflux of Na in K(Rb)-free Na Ringer was 5.64 m-mole/l. cells. hr, and it was reduced to 4.32 m-mole by 10(-4)M ouabain. This was accompanied by a reduction of Na influx by 4.14 m-mole, representing then a Na-Na ouabain-sensitive exchange mechanism.5. At a concentration of 5 mM, external Rb increased Na efflux in 2.32 m-mole/l. cells. hr above the K(Rb)-free levels, and reduced Na influx by 2.13 m-mole.6. It is proposed that the Na pump is able to operate even in the absence of external K(Rb), though at reduced rate and on a Na-Na exchange basis (Na is the only monovalent cation in the bathing solution). External K(Rb) would have two actions: to increase the rate of shuttling of the carrier (catalytic effect) and to switch the Na-Na to a Na-K(Rb) exchange.7. These results raise a question of the real significance of the Na/K(Rb) ;coupling' ratio and the K-free effect on the Na pump mechanism.

Animals↗
PubMed1989

Rubidium ions and the gating of delayed rectifier potassium channels of frog skeletal muscle.

1. Unitary currents were measured through delayed rectifier potassium channels of frog skeletal muscle, under conditions where either potassium or rubidium ions carried current. 2. Unitary currents were reduced in amplitude when Rb+ was the charge carrier, indicating that Rb+ permeated the channel less readily than did K+. On the other hand permeability ratios (PRb/PK) measured from the change in reversal potential upon ionic substitution were 0.92 for the external and 0.67 for the internal mouth of the channel. 3. Ensemble-averaged currents activated under depolarization along a similarly S-shaped time course whether K+ or Rb+ carried current, though slightly more slowly in Rb+. However, under repolarization to a negative level, tail currents were prolonged about tenfold in Rb+. 4. The duration of channel opening was substantially prolonged in Rb+. The distribution of open times was fitted by a single exponential whether K+ or Rb+ was the charge carrier, indicating a single open state. But the mean open time, averaged over all voltages investigated, was 2.65 times greater in Rb+. 5. The prolongation in Rb+ of tail currents under repolarization was associated with increases in the number of openings per burst and in the number of bursts during each tail. 6. The implications of these results for channel gating are discussed. It is argued that an early step in channel activation is more voltage dependent than later steps.

Action Potentials↗
PubMedDate not supplied

Determination of red cell survival in rabbits by fluorescent excitation analysis of stable rubidium.

Nonradioactive rubidium was used to label red cell in rabbits and its concentration was determined by employing a simple version of radioisotope-induced x-ray fluorescence analysis. About 10 ml of red cells were labeled in vitro with 0.5-1 mg of RbCl and subsequently reinjected, resulting in a Rb concentration of about 50 ppm by the red cells. Four milliliters of blood were collected about every week, the concentrated erythrocytes deposited on filter paper disks, and the Rb content analyzed. Except for the first four to seven days, a function of the type N = Noe-kt fitted very well the experimental Rb disappearance curve data. The mean half-time value deduced from the experimental data was 310 +/- 15 days, which should be compared with the values of T1/2 = 260 +/- 20 h and T1/2 = 206 +/- 30 h obtained, respectively, by these authors and by Price et al., employing radioactive 51Cr-labeled red cells. The possibility of labeling human red cells with stable Rb is discussed.

Animals↗
PubMed1970

Brain norepinephrine: enhanced turnover after rubidium treatment.

After biosynthesis of norepinephrine was inhibited, treatment of rats for 10 days with rubidium chloride (0.6 milliequivalent per kilogram of body weight) caused an increase in the rate of disappearance of norepinephrine in the brainstem but not in the telencephalon. Also the utilization of intracisternally injected tritiated norepinephrine was increased and was accompanied by a shift in the pattern of norepinephrine metabolism to normetanephrine. These data suggest that greater amounts of neuronally stored norepinephrine were released to central adrenergic receptors.

Animals↗
PubMed1987

Dihydroxy bile salt-induced secretion of rubidium ion across the rabbit distal colon.

Possible mechanisms of dihydroxy bile salt-induced K+ secretion by the mammalian colon were evaluated by studying the effects of taurochenodeoxycholate (TCDC) on 86Rb+ transport across the isolated, short-circuited rabbit distal colon. Simultaneous measurements of 86Rb+ and 42K+ unidirectional fluxes were highly correlated [r = 0.964 for serosal (s) to mucosal (m) and 0.765 for m to s], indicating that Rb+ is a suitable tracer for K+ transport across the colon. Furthermore, mucosal Ba2+ (4 mM) or serosal ouabain (0.1 mM) decreased serosal to mucosal rubidium flux (JRbs----m) (from 0.24 +/- 0.02 to 0.09 +/- 0.02, and 0.08 +/- 0.01 mu eq X h-1 X cm-2, respectively) without affecting JRbm----s. Dibutyryl cyclic adenosine monophosphate (dBcAMP, 0.5 mM serosal) specifically increased JRbs----m of controls (from 0.21 +/- 0.05 to 0.67 +/- 0.09 mu eq X h-1 X cm-2) through a barium- (4 mM, mucosal) sensitive pathway without affecting JRbs----m. Mucosal addition of 2 mM TCDC increased tissue conductance (GT), reduced short-circuit (Isc) slightly, and reversed JRbnet (from 0.13 +/- 0.05 to -0.29 +/- 0.08 mu eq X h-1 X cm-2) principally by increasing JRbs----m. The TCDC-induced increases in JRbs----m were reduced by 0.1 mM serosal ouabain (from 0.53 +/- 0.03 to 0.11 +/- 0.02 mu eq X h-1 X cm-2) or 4 mM mucosal Ba2+ (from 0.76 +/- 0.07 to 0.32 +/- 0.04 mu eq X h-1 X cm-2).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Serial analysis of renal blood flow by positron tomography with rubidium-82.

To determine whether renal blood flow can be measured by positron-emission tomography (PET) during constant infusion of rubidium-82 (82Rb) using a steady-state kinetic model, studies were performed in 10 dogs at control (n = 10), during mild flow reduction (n = 7), during severe flow reduction (n = 10), and after reperfusion of the kidney (n = 3). PET data were quantified to determine mean concentration of 82Rb (Ct) in each transverse section of the kidney. The arterial concentration (Ca) of 82Rb was measured by well counting of arterial blood samples during the equilibrium scan. 82Rb renal uptake (Ct/Ca) correlated nonlinearly with microsphere renal blood flow according to a steady-state kinetic model (r = 0.90). 82Rb estimated flow was 3.16 +/- 1.36 ml X min-1 X g-1 at control and 1.56 +/- 0.57 and 0.37 +/- 0.59 during mild and severe flow reductions, respectively. Microsphere determined flow was 2.89 +/- 0.77 ml X min-1 X g-1 at control, 1.58 +/- 0.42 at mild reduction, and 0.27 +/- 0.49 at severe reduction. In the occlusion and reperfusion model, the 82Rb estimated flow during occlusion was 0.21 +/- 0.15 ml X min-1 X g-1 and on reperfusion went up to 2.13 +/- 1.08. The contralateral kidney demonstrated reductions in the 82Rb estimated flow of 3.02 +/- 1.62 ml X min-1 X g-1 (63%) and 2.92 +/- 0.89 (61%) during mild and severe flow reductions, respectively. We conclude that PET with 82Rb permits serial quantitative assessment of renal flood flow.

Animals↗
PubMed1997

Kinetic analysis of rubidium and thallium as deposited myocardial blood flow tracers in isolated rabbit heart.

Evaluation of myocardial perfusion with tracers such as thallium and rubidium is based on the assumption that tissue tracer content is proportional to flow. The purpose of this study was to evaluate the relationship between flow and tissue tracer content of 201Tl and 83Rb in the isolated perfused rabbit heart. 83Rb (86-day half-life), an isotope that is not used clinically, was used as a subsitute for 82Rb (76-s half-life) to improve the accuracy and precision of data acquisition. The multiple indicator-dilution technique was employed with two independent computational approaches. The first approach explicitly deconvolved 201Tl and 83Rb venous concentration curves by the intravascular reference tracer curve. The second approach used a conventional analysis. Both approaches showed that there was more early washout of 83Rb than 201Tl and that the heart retained 201Tl better than 83Rb within 2 min after isotope introduction. These data indicate that 201Tl is a better perfusion tracer than 83Rb in the isolated rabbit heart.

Animals↗
PubMed1975

Norepinephrine metabolism in mouse heart after lithium and rubidium treatment.

This report describes the effects of treatment with lithium (Li), rubidium (Rb) and sodium (Na; 1 mEq/kg/day) for 7 days on norepinephrine (NE) turnover in mouse heart. The effects of several drugs which modify the uptake and storage of NE were also studied in similarly pretreated mice. A method based on the combustion of tissue tritium to tritiated water was used to assay tritiated l-norepinephrine (l-NE-3H) concentrations in individual hearts. The rate of decline of tissue tritium concentrations in groups of pretreated mice maintained at ambient temperature (23--24 degrees C) or in the cold (4--5 degrees C) was determined. The results indicate that, compared to Na, Li and Rb did not modify the tritium turnover rate in mouse heart. Pretreatment with Li or Rb did not modify the uptake of tritiated NE in the heart. The effects of desipramine. cocaine, bretylium and chlorpromazine on NE uptake were not altered by the alkali ions. Further, pretreatment did not modify NE release by tyramine, metaraminol and guanethidine. These studies suggest that Li and Rb do not modify NE uptake, release and storage in mouse heart.

Animals↗
PubMed1989

Effect of noradrenaline on rubidium (86Rb) efflux in the rat isolated seminal vesicle.

The effect of noradrenaline (NA) on the efflux of rubidium (86Rb) from the rat isolated seminal vesicle was studied in the absence and presence of phentolamine and papaverine. Strips of spirally cut seminal vesicles were incubated in radioactive 86Rb (10 microCi.ml-1) for 2 h. Radioactivity was measured using an autogamma spectrometer, and the flux data were expressed in terms of rate constants per minute, of the reactive isotope efflux. A concentration-effect curve for the effect of NA on rat seminal vesicles was constructed, alone and in the presence of phentolamine (1 mumol/l) or papaverine (5 mumol/l). The results showed that NA (10-1,000 mumol/l) produced concentration-dependent contractions in the rat seminal vesicle. These responses were greatly reduced by phentolamine but markedly enhanced by papaverine. NA significantly increased 86Rb efflux from rat seminal vesicles (control rate constant 0.0042 +/- 0.001; test 0.0064 +/- 0.002, means +/- SE; n = 8 rats; p less than 0.001). This increase (52%) occurred within an exposure of 7 +/- 1 min to NA. Phentolamine decreased the NA-induced increase in 86Rb efflux, by 75 +/- 2%, whereas papaverine enhanced it by 86 +/- 5% of the control value. The mechanism of NA-induced increase in 86Rb efflux was not further investigated but was interpreted in terms of an increase in intracellular K+ (here represented by 86Rb), which will leave the cell (efflux) after initial membrane depolarization.

Animals↗
PubMed1997

A new chromatographic method for measurement of rubidium transport activities in cultured bovine retinal pigment epithelial cells.

A new method for measuring cellular rubidium (Rb+) uptake activities based on cation chromatography was developed and compared with the standard technique, uptake of the radioisotope 86Rb+, using cultured bovine retinal pigment epithelial (RPE) cells. The Rb+ response was strictly linear from 0.25 nmol (detection limit) to 25 nmol. The Na+/K(+)-ATPase inhibitor ouabain inhibited Rb+ uptake with IC50 values of 128.7 +/- 23.5 nM (n = 8; radioactive method) and 56.6 +/- 9.3 nM (n = 9; non-radioactive method, p < 0.01). The latter value is identical to the IC50 value of 54.4 +/- 16.2 nM (n = 3) for ouabain binding to the intact RPE cells. Ouabain and bumetanide, an inhibitor of the Na+/K+/Cl(-)-cotransporter, each inhibited Rb+ uptake maximally by 66 and 30%, respectively. This new technique allows sensitive measurement of intracellular Rb+, as well as K+ and Na+, and, thus, should prove useful for studying the effects of pharmacologic agents and simulated disease conditions on cation transport and cation balance in RPE and other cell types.

Animals↗
PubMed1975

Noninvasive detection of regional myocardial ischemia using rubidium-81 and the scintillation camera: comparison with stress electrocardiography in patients with arteriographically documented coronary stenosis.

The sensitivity of rest and stress myocardial perfusion studies using scintillation camera imaging of intravenously administered rubidium-81 (81Rb) in the detection of myocardial ischemia was compared to that of stress electrocardiography by relating results in 40 patients to the degree of stenosis delineated by coronary arteriography. Of 33 patients with greater than 75% stenosis of at least one of the three major coronary vessels (significant stenosis), rest and stress 81Rb imaging detected ventricular ischemia in 29 (88%) whereas simultaneous stress electrocardiography was positive (1 mm or greater horizontal ST-segment depression) in only 19 (58%) of the same patients. Five of the 29 patients who developed stress-induced scintigraphic evidence of ischemia did not develop angina or a positive electrocardiogram with stress. In 31 of the 33 patients with significant coronary stenosis, either the stress scintigram or the stress electrocardiogram was positive. In seven patients with less than 50% narrowing of a major coronary vessel on coronary arteriography, the stress scinitigrams were negative, whereas the stress electrocardiograms were positive in the two of these patients with the syndrome of angina with normal coronary arteriograms. It is concluded that high resolution images of the myocardium can be obtained with 81Rb using the scintillation camera with special shielding, and that rest and stress 81Rb scintigraphy appears to provide greater sensitivity and specificity when compared to stress electrocardiography in the nininvasive identification of significant coronary stenosis.

Coronary Angiography↗
PubMed1996

Myocardial rubidium-82 tissue kinetics assessed by dynamic positron emission tomography as a marker of myocardial cell membrane integrity and viability.

BACKGROUND: Recent reports have demonstrated the clinical use of rubidium-82 chloride (Rb-82) in combination with positron emission tomography (PET) not only as a tracer of myocardial blood flow but also as a marker of cell membrane integrity using static imaging early and late after tracer injection. The purpose of this study was to compare myocardial Rb-82 kinetics assessed by dynamic PET imaging as a marker for tissue viability with regional fluorine-18 fluorodeoxyglucose (FDG) uptake in patients with coronary artery disease. METHODS AND RESULTS: Twenty-seven patients with angiographically proven coronary artery disease and 5 subjects with a low likelihood for coronary artery disease underwent dynamic PET imaging under resting conditions using Rb-82 and FDG. Both image sequences served as input data for a semiautomated regional analysis program. This program generated polar maps representing Rb-82 tissue half-life and FDG utilization assessed by Patlak's approach. Myocardial tissue viability was visually determined from static Rb-82 and FDG images. Regions were categorized as normal, ischemically compromised, and scar tissue. Their coordinates were subsequently copied to the functional polar maps for further analyses. In normal subjects, Rb-82 tissue half-life was homogeneous throughout the left ventricle (90 +/- 11 seconds). In coronary patients, differences between Rb-82 tissue half-lives in normal and scar tissue were highly significant (95 +/- 10 and 57 +/- 15 seconds, respectively; P < .0001). FDG uptake in these two tissue groups was 78 +/- 12% and 40 +/- 13%, respectively (P < .0001). Ischemically compromised tissue with reduced perfusion but maintained FDG uptake displayed an Rb-82 half-life of 75 +/- 9 seconds, indicating active cellular tracer retention, which was significantly different from scar tissue. Overall agreement of tissue categorization as either viable or scar was 86% between Rb-82 kinetics and FDG utilization. In a subgroup of 11 patients with all three tissue types within one image set, Rb-82 tissue half-life discriminated between normal, ischemic, and scar tissue (97 +/- 9, 75 +/- 9, and 60 +/- 15 seconds, respectively; P < .01). CONCLUSIONS: This study demonstrated a significant relationship between cell membrane integrity as assessed by dynamic Rb-82 PET imaging and myocardial glucose utilization as a marker for tissue viability. In regions with reduced perfusion, Rb-82 kinetics was different in compromised but metabolically active and irreversibly injured myocardium. The predictive value of this approach must be evaluated in follow-up studies.

Adult↗
PubMed1988

The effect of captopril on renal blood flow in renal artery stenosis assessed by positron tomography with rubidium-82.

The sequence and magnitude of acute changes in renal blood flow following administration of captopril were determined in a canine model of acute unilateral renal artery stenosis using rubidium-82 and positron emission tomography. Data were recorded in each of nine dogs under three conditions: 1) during a baseline control interval, 2) during renal artery stenosis, and 3) during stenosis with intravenous injection of captopril (1.2 mg/kg). Mean arterial blood pressure was 108 +/- 12 mm Hg at control, increased significantly to 125 +/- 13 mm Hg (p less than 0.01) during stenosis, and decreased to 98 +/- 13 mm/Hg (p less than 0.01) after captopril infusion. Mean renal blood flow was calculated using a steady state single compartment model from the images produced by positron emission tomography. The estimated flow to the affected kidney was 3.37 +/- 1.48 ml/min/g at control, 0.86 +/- 0.62 ml/min/g during stenosis (p less than 0.01), and 0.64 +/- 0.57 ml/min/g after captopril administration (p = NS compared with precaptopril value). The estimated flow to the contralateral kidney was minimally reduced from a baseline of 3.84 +/- 0.95 to 3.24 +/- 1.13 ml/min/g (p = NS) during stenosis and increased after captopril infusion (4.08 +/- 0.94 ml/min/g; p = 0.01). These data suggest that repetitive imaging with positron emission tomography can be used to delineate acute changes in renal perfusion following captopril administration.

Animals↗
PubMedDate not supplied

Rubidium-86 uptake and energy metabolism in suspended human erythrocytes monitored by microdialysis.

We aimed to develop a model for studying membrane leakiness. A microdialysis technique was used to investigate rubidium-86 (86Rb) uptake in suspended human erythrocytes in vitro, with the aim of later applying the technique to in vivo studies. Suspensions were prepared from washed erythrocytes and 86Rb administered directly or via the microdialysis probe. The effects on 86Rb uptake of varying the haematocrit were measured. Erythrocytes were also treated with the K+ ionophore valinomycin or the Na+/K+-ATPase inhibitor ouabain. The effects on 86Rb uptake, microdialysate content of lactate and pyruvate, and erythrocyte content of 2,3-bisphosphoglycerate (2,3-BPG) were measured. Valinomycin dissipates the potassium gradient and activates Na+/K+-ATPase, demonstrated by decreased erythrocyte 86Rb uptake with increasing concentrations of valinomycin. This increased ion pump activity enhanced glycolysis, which was demonstrated by accumulation of pyruvate and lactate due to enhanced consumption of 2,3-BPG. The microdialysis technique is appropriate for in vitro studies of ion fluxes across cellular membranes.

2,3-Diphosphoglycerate↗
PubMed1988

Kinetic parameters of rubidium transport pathways are normal in cystic fibrosis red cells.

The abnormalities in ion transport in cystic fibrosis (CF) respiratory and sweat duct epithelia have prompted studies of ion permeability in CF red blood cells (RBC) although previous reports have been contradictory. In this study, the kinetic characteristics of the three major cation transport systems in RBC were evaluated by measuring rubidium (Rb) uptake at various external Rb concentrations. The maximal velocity and affinity for external Rb (K1/2) of the NaK pump were normal in CF RBC, as were the maximal velocity and Km for Rb of the NaK cotransport system. Residual (ouabain and bumetanide insensitive) Rb uptake, and steady state RBC Na and K contents were also normal. These data indicate the NaK pump and cotransport system do not exhibit primary or secondary perturbations in CF RBC, and suggest that the noncarrier-mediated membrane permeability to cations is also normal in these cells.

Adolescent↗
PubMed2005

Efficiency of rubidium marking in Aedes albopictus (Diptera: Culicidae): preliminary evaluation on persistence of egg labeling, survival, and fecundity of marked female.

Rubidium chloride (RbCl) has been used for the study of vector biology and behavior, although the efficacy of marking, egg production, and survivorship of marked females have been poorly studied. Four concentrations of RbCl were tested, among which 0.025 M was the best for marking Aedes albopictus: more than 80% of egg batches of females fed once with blood containing RbCl were marked; Rb-marked egg batches, interspersed with non marked ones were recovered until 61 days after a blood meal containing RbCl followed by non marked meals; RbCl was essentially detected in the abdomen of marked females, whose egg production and survivorship did not differ from non marked ones, at least in the three weeks following the Rb-marked blood meal.

Aedes↗