scholarly journals Short periods of bipolar anodal TDCS induce no instantaneous dose-dependent increase in cerebral blood flow in the targeted human motor cortex

2022 ◽  
Author(s):  
Marie Louise Liu ◽  
Anke N Karabanov ◽  
Marjolein Piek ◽  
Esben Thade Petersen ◽  
Axel Thielscher ◽  
...  
Keyword(s):  
Blood Flow ◽  
Short Duration ◽  
Hand Movement ◽  
Current Intensity ◽  
Electrical Field Strength ◽  
Human Motor Cortex ◽  
Individual Level ◽  
The Individual ◽  
Dose Dependent Increase ◽  
Dose Dependent

Background: Anodal transcranial direct current stimulation (aTDCS) of primary motor hand area (M1-HAND) can enhance corticomotor excitability. Yet, it is still unknown which current intensity produces the strongest effect on regional neural activity. Magnetic resonance imaging (MRI) combined with pseudo-continuous Arterial Spin Labeling (pc-ASL MRI) can map regional cortical blood flow (rCBF) and may thus be useful to probe the relationship between current intensity and neural response at the individual level. Objective: Here we employed pc-ASL MRI to map acute rCBF changes during short-duration aTDCS of left M1-HAND. Using the rCBF response as a proxy for regional neuronal activity, we investigated if short-duration aTDCS produces an instantaneous dose-dependent rCBF increase in the targeted M1-HAND that may be useful for individual dosing. Methods: Nine healthy right-handed participants received 30 seconds of aTDCS at 0.5, 1.0, 1.5, and 2.0 mA with the anode placed over left M1-HAND and cathode over the right supraorbital region. Concurrent pc-ASL MRI at 3 T probed TDCS-related rCBF changes in the targeted M1-HAND. Movement-induced rCBF changes were also assessed. Results: Apart from a subtle increase in rCBF at 0.5 mA, short-duration aTDCS did not modulate rCBF in the M1-HAND relative to no-stimulation periods. None of the participants showed a dose-dependent increase in rCBF during aTDCS, even after accounting for individual differences in TDCS-induced electrical field strength. In contrast, finger movements led to robust activation of left M1-HAND before and after aTDCS. Conclusion: Short-duration bipolar aTDCS does not produce instantaneous dose-dependent rCBF increases in the targeted M1-HAND at conventional intensity ranges. Therefore, the regional hemodynamic response profile to short-duration aTDCS may not be suited to inform individual dosing of TDCS intensity.

Dose-Dependent Effects of Meclofenamate on Peripheral Vasculature of Conscious Rabbits

1983 ◽  
Vol 64 (5) ◽  
pp. 471-474 ◽  
Author(s):  
R. A. Banks ◽  
L. J. Beilin ◽  
J. Soltys
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Organ Blood Flow ◽  
Hepatic Circulation ◽  
Peripheral Vasculature ◽  
Conscious Rabbits ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
The Brain ◽  
Intravenous Sodium

1. Changes in systemic haemodynamics and organ blood flow were measured in conscious rabbits after various doses of intravenous sodium meclofenamate, an inhibitor of prostaglandin cyclo-oxygenase. 2. Meclofenamate had no effect on arterial pressure or cardiac output but caused a dose-dependent fall in renal blood flow. 3. Meclofenamate also reduced adrenal perfusion but, in contrast, caused a dose-dependent increase in blood flow to the brain, bronchial and hepatic circulation and to the testis. No effect was demonstrated on other organs studied. 4. The effect on the cerebral circulation was observed at the lowest dose of meclofenamate (0.75 mg/kg). Higher total doses were necessary for an effect on the renal and bronchial (3 mg/kg) and testicular and hepatic arteries (6 mg/kg). 5. The results suggest a variety of local vasomotor influences of renal and non-renal prostaglandins in conscious rabbits.

Effects of intrarenal adenosine on renal function and medullary blood flow in the rat

1988 ◽  
Vol 255 (6) ◽  
pp. F1230-F1234 ◽  
Author(s):  
M. Miyamoto ◽  
Y. Yagil ◽  
T. Larson ◽  
C. Robertson ◽  
R. L. Jamison
Keyword(s):  
Blood Flow ◽  
Sodium Excretion ◽  
Systemic Circulation ◽  
Urinary Flow ◽  
Medullary Blood Flow ◽  
Vasa Recta ◽  
Potent Vasodilator ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
Higher Doses

Adenosine is a potent vasodilator of the systemic circulation. Infusion of adenosine into the aorta causes water and sodium retention and a fall in glomerular filtration rate and renal blood flow. The effect of adenosine on medullary blood flow is unknown. Because systemic vasodilatory effects may confound its renal actions, adenosine was infused into the renal artery of anesthetized Munich-Wistar rats at doses of 2, 6, and 15 micrograms/min. A marked dose-dependent increase in urinary flow and sodium excretion was observed. Inulin and p-aminohippuric acid clearance did not change significantly. Blood flow in vasa recta in the exposed renal papilla, as determined by fluorescence videomicroscopy, increased significantly only with the highest dose of adenosine. In control animals infused with the vehicle only, there was no change in any of the above variables. These results indicate that direct intrarenal infusion of adenosine in the rat increases urinary flow and sodium excretion and at higher doses also increases vasa recta blood flow. The effects on urinary flow and sodium excretion were therefore mediated by a mechanism other than an increase in vasa recta blood flow.

Dopamine stimulates cAMP production in canine afferent arterioles via DA1 receptors

1989 ◽  
Vol 256 (3) ◽  
pp. H626-H629
Author(s):  
T. Tamaki ◽  
C. E. Hura ◽  
R. T. Kunau
Keyword(s):  
Blood Flow ◽  
Sch 23390 ◽  
Fold Increase ◽  
Camp Accumulation ◽  
Afferent Arteriole ◽  
Camp Production ◽  
Receptor Stimulation ◽  
Afferent Arterioles ◽  
Dose Dependent Increase ◽  
Dose Dependent

Dopamine increases renal blood flow and dilates isolated afferent and efferent arterioles preconstricted with norepinephrine via dopamine 1 (DA1) receptors. DA1-receptor stimulation also results in dopamine-induced elevation of adenosine 3'5'-cyclic monophosphate (cAMP) in dog and rat renal arteries. The present study was undertaken to determine the effects of dopamine on cAMP accumulation in isolated canine superficial cortical afferent arterioles. The effect of Sch 23390, a specific DA1-receptor antagonist, on dopamine-stimulated cAMP accumulation was also examined. Forskolin (10(-5) M), a potent stimulator of adenylate cyclase, produced a greater than 11-fold increase in cAMP production compared with control. Dopamine produced a dose-dependent increase in cAMP accumulation in afferent arterioles at concentrations of 10(-4) M and 10(-6) M, Sch 23390 (2 x 10(-4) M) abolished dopamine (10(-4) M)-stimulated cAMP accumulation in afferent arterioles. The dopamine-induced increase in arteriolar cAMP accumulation was unaffected by propranolol (10(-4) M). Our results suggest that dopamine increases cAMP production in afferent arterioles via the DA1 receptor. Increased cAMP production may be responsible for dopamine-induced vasodilation in the afferent arteriole.

Loss of vasomotor responsiveness to the μ-opioid receptor ligand endomorphin-1 in adjuvant monoarthritic rat knee joints

2004 ◽  
Vol 286 (4) ◽  
pp. R634-R641 ◽  
Author(s):  
Jason J. McDougall ◽  
A. Kursat Barin ◽  
Chelsea M. McDougall
Keyword(s):  
Blood Flow ◽  
Opioid Receptor ◽  
Opioid Receptors ◽  
Immunohistochemical Analysis ◽  
Knee Joints ◽  
Μ Opioid Receptor ◽  
Arthritic Joints ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
Μ Opioid Receptors

Endomorphin-1 is a short-chain neuropeptide with a high affinity for the μ-opioid receptor and has recently been localized in acutely inflamed knee joints where it was found to reduce inflammation. The present study examined the propensity of endomorphin-1 to modulate synovial blood flow in normal and adjuvant-inflamed rat knee joints. Under deep urethane anesthesia, endomorphin-1 was topically applied to exposed normal and 1 wk adjuvant monoarthritic knee joints (0.1 ml bolus; 10-12-10-9 mol). Relative changes in articular blood flow were measured by laser Doppler perfusion imaging and vascular resistances in response to the opioid were calculated. In normal knees, endomorphin-1 caused a dose-dependent increase in synovial vascular resistance and this effect was significantly inhibited by the specific μ-opioid receptor antagonist d-Phe-Cys-Tyr-d-Trp-Orn-Thr-Pen-Thr amide (CTOP) ( P < 0.0001, 2-factor ANOVA, n = 5-7). One week after adjuvant inflammation, the hypoaemic effect of endormophin-1 was completely abolished ( P < 0.0001, 2-factor ANOVA, n = 5-7). Immunohistochemical analysis of normal and adjuvant-inflamed joints showed a ninefold increase in endomorphin-1 levels in the monoarthritic knee compared with normal control. Western blotting and immunohistochemistry revealed a moderate number of μ-opioid receptors in normal knees; however, μ-opioid receptors were almost undetectable in arthritic joints. These findings demonstrate that peripheral administration of endomorphin-1 reduces knee joint blood flow and this effect is not sustainable during advanced inflammation. The loss of this hypoaemic response appears to be due to downregulation of μ-opioid receptors as a consequence of endomorphin-1 accumulation within the arthritic joint.

scholarly journals Honeybee colonies compensate for pesticide-induced effects on royal jelly composition and brood survival with increased brood production

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Matthias Schott ◽  
Maximilian Sandmann ◽  
James E. Cresswell ◽  
Matthias A. Becher ◽  
Gerrit Eichner ◽  
...  
Keyword(s):  
Royal Jelly ◽  
Brood Production ◽  
Initiation Rate ◽  
Term Survival ◽  
Individual Level ◽  
Sublethal Doses ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
Colony Level

AbstractSublethal doses of pesticides affect individual honeybees, but colony-level effects are less well understood and it is unclear how the two levels integrate. We studied the effect of the neonicotinoid pesticide clothianidin at field realistic concentrations on small colonies. We found that exposure to clothianidin affected worker jelly production of individual workers and created a strong dose-dependent increase in mortality of individual larvae, but strikingly the population size of capped brood remained stable. Thus, hives exhibited short-term resilience. Using a demographic matrix model, we found that the basis of resilience in dosed colonies was a substantive increase in brood initiation rate to compensate for increased brood mortality. However, computer simulation of full size colonies revealed that the increase in brood initiation led to severe reductions in colony reproduction (swarming) and long-term survival. This experiment reveals social regulatory mechanisms on colony-level that enable honeybees to partly compensate for effects on individual level.

Effect of isoproterenol on phosphorylase activation in the hyperthyroid rat heart

1979 ◽  
Vol 57 (6) ◽  
pp. 567-573 ◽  
Author(s):  
Penelope A. Longhurst ◽  
John H. McNeill
Keyword(s):  
Blood Flow ◽  
Coronary Blood Flow ◽  
Time Dependent ◽  
Force Of Contraction ◽  
Phosphorylase Activity ◽  
Isolated Atria ◽  
Langendorff Hearts ◽  
The Right ◽  
Dose Dependent Increase ◽  
Dose Dependent

Pretreatment of rats for 3 days with triiodothyronine produced an increase in rate in the right atrium and a decrease in force of contraction in the right ventricle and Langendorff heart.Isoproterenol administration produced a time-dependent increase in rate and tension. The increase in rate was consistently greater in atria from hyperthyroid rats, and the increase in tension consistently greater in tissues from euthyroid rats. Isoproterenol also produced a time- and dose-dependent increase in phosphorylase a activity. In the isolated atria and ventricles enzyme activity was similar in the two groups. In the Langendorff hearts, however, there was an enhancement of the isoproterenol-induced increase in phosphorylase activity in hearts from hyperthyroid rats. Reduction of the coronary blood flow to the level found in euthyroid animals did not reduce the potentiation of phosphorylase activation found in hearts from hyperthyroid rats.It is concluded that the potentiation of phosphorylase activation in hearts from hyperthyroid rats is not due to the increase in coronary blood flow.

scholarly journals Toxicity and bioaccumulation of Cadmium, Copper and Zinc in a direct comparison at equitoxic concentrations in common carp (Cyprinus carpio) juveniles

2019 ◽  
Author(s):  
Vyshal Delahaut ◽  
Božidar Rašković ◽  
Marta Satorres Salvado ◽  
Lieven Bervoets ◽  
Ronny Blust ◽  
...  
Keyword(s):  
Common Carp ◽  
Structural Damage ◽  
Gill Tissue ◽  
Specific Pattern ◽  
Zinc Toxicity ◽  
Exposure Experiment ◽  
The Individual ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
Histopathological Effects

AbstractThe individual toxicity and bioaccumulation of cadmium (Cd), copper (Cu) and zinc (Zn) towards common carp juveniles was evaluated in a direct comparison in two experimental setups. First, the fish were exposed for 10 days to different metal concentrations. Accumulated metals were quantified and showed a positive dose dependent uptake for cadmium and copper, but not for zinc. Toxicity was in the order Cd>Cu>Zn with 96h LC50 values (concentration where 50% of the animals dies within 96h) for Cd at 0.20±0.16 μM, Cu at 0.77±0.03 μM, and Zn at 29.89±9.03 μM respectively, and incipient lethal levels (concentration where 50% of the animals survives indefinitely) at 0.16 μM, 0.77 μM and 28.33 μM respectively. Subsequently, a subacute exposure experiment was conducted, where carp juveniles were exposed to 2 equitoxic concentrations (10% and 50% of LC50 96 h) of the three metals. The gill metal content was quantified after 1, 3 and 7 days, and was correlated to electrolyte levels and structural damage of the gill tissue and associated pathological effects. Again a significant dose-dependent increase in gill cadmium and copper, but not in zinc, was observed during the 7-day exposure. Copper clearly affected the sodium levels in the gill tissue, while zinc and cadmium did not significantly alter any of the gill electrolytes. The overall histopathological effects (e.g. hyperemia and hypertrophy) of the metal exposures were mild for most of the alterations, and no metal specific pattern was elucidated for the tested metals except oedema of the primary epithelium which typically occurred in both levels of Zn exposure.

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