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Biomedical subjects

M Grossmann

Publications and source records attributed to M Grossmann.

At least 19 recordsLinked to original sources

Reproducibility of dorsal hand vein responses to phenylephrine and prostaglandin F2 alpha using the dorsal hand vein compliance method.

Assessment of drug-induced venodilation by the dorsal hand vein compliance method requires stable constriction of the vein. This study was designed to investigate intra- and intersubject reproducibility of the venous preconstriction technique in response to phenylephrine and prostaglandin F2 alpha and to determine the influence of basal vein size. Twelve healthy male nonsmokers participated in a prospective cross-over study. Inter- and intrasubject variability was tested in response to phenylephrine and PGF2 alpha on different study days in the same hand vein. The dose of the respective constrictor causing approximately 80% constriction of the vein (ED80) was determined and infused for another 100 minutes. Actual vein size was measured every 5 minutes. Coefficient of variation and regression analyses were performed to analyze influence of vessel size on ED80 of the respective constrictor. Adjusted constriction levels were stable and well reproducible in all subjects. The intersubject coefficient of variation of ED80 ranged from 0.9% to 6.7% for phenylephrine and from 0.9% to 6.9% for PGF2 alpha. Whereas responses to phenylephrine were independent of basal vein diameter, there was a positive correlation between ED80 of PGF2 alpha and basal vein size. Thus, the hand vein compliance method is a suitable method to study dilatory responses in phenylephrine- or PGF2 alpha-constricted veins with considerable interindividual but small intraindividual variability. However, in such studies, phenylephrine appears to be a more reliable tool than PGF2 alpha.

Adult↗

Local and systemic effects of Na+/K+ATPase inhibition.

The positive inotropic and electrophysiological effects of cardiac glycosides on cardiac muscle are mediated through inhibition of Na+/K+ ATPase by binding to a specific extracytoplasmic site of the a-subunit of this enzyme. The inhibition of Na+/K+ ATPase affects ionic flux and produces direct local effects on cardiac contractility, electrical excitability and conduction, but also profound systemic effects mainly as a result of haemodynamic changes. These effects are responsible for beneficial therapeutic as well as toxic effects. Inhibition of Na+/K+ ATPase results in potentiation of K+ loss from cells and Na+ entry into cells, so consequently affects action potential generation and propagation. This also underlines the potentiation of certain effects of cardiac glycosides by hypokalemia and hypomagnesaemia, and the effects of changes in calcium homeostasis on the cardiac glycoside pharmacodynamics. Furthermore, inhibition of Na+/Ca++ exchange enhances Ca++ mobilization and promotes contractility. These effects (locally and systemically) differ greatly, depending on the haemodynamic status and myocardial oxygen supply. Cardiac glycosides have less affinity for Na+/K+ ATPases at other sites (e.g. skeletal muscle), but some extracardiac effects (vascular effects, effects on colour vision, CNS and autonomic effects, renal effects) may be related to Na+/K+ ATPase inhibition.

Cardiac Glycosides↗

Effects of cardiac glycosides on 24-h ambulatory blood pressure in healthy volunteers and patients with heart failure.

Blood pressure effects of cardiac glycosides in humans have been infrequently reported. Although direct infusion of ouabain or digoxin causes vasoconstriction, indirect effects of cardiac glycosides may have the opposite effect, owing to changes in sympatho-vagal balance. This paper summarises three studies on the effects of cardiac glycosides on circadian blood pressure, utilizing automatic 24-h ambulatory blood pressure measurement (ABPM). In healthy volunteers, 10 days of oral digoxin or digitoxin caused decreases in diastolic blood pressure and heart rate during overnight sleep. No effect was detectable during daytime activities. In patients with heart failure (NYHA stage II), 7 days of oral digoxin also caused a decrease in diastolic blood pressure but only a small increase in systolic pressure during overnight sleep. Again, no effect was detectable during the day. Cardiac glycosides have significant effects on blood pressure, which only appear during overnight sleep, i.e. a phase when sympathetic background activity is lowest. Regular daytime activities may 'overwrite' these effects. Effects of cardiac glycosides on blood pressure may have therapeutic impact, depending on the stage of heart failure and concomitant diseases.

Blood Pressure↗

Tissue engineering: complete autologous valve conduit--a new moulding technique.

OBJECTIVE: The use of fibrin gel, which can be produced from patients' blood, was investigated as an autologous, biodegradable scaffold. A new moulding technique was developed to create a complete aortic root. METHODS: A new moulding technique was generated for the creation of complete valve conduit. On the basis of biomechanical valve design studies, a tricuspid "ventricular" and "aortic" stamp were developed. A silicone-coated aluminum cylinder was used to circumferentially limit the mould. The cell/gel suspension was filled into the mould and polymerization was started. RESULTS: The creation of complex structures such as complete valve conduits is possible with the moulding technique described. With a layer thickness of up to 2 mm, histological investigations showed excellent tissue development with viable fibroblasts surrounded by collagen bundles. CONCLUSION: Fibrin gel unifies many properties of an ideal scaffold: The formation of complex structures is possible, the degradation and polymerization is controllable and the formation of the extracellular matrix is excellent.

Aortic Valve↗

Heterogeneity in hand veins responses to acetylcholine is not associated with polymorphisms in the G-protein beta3-subunit (C825T) and endothelial nitric oxide synthase (G894T) genes but with serum low density lipoprotein cholesterol.

Vascular responses to acetylcholine (ACh) are notoriously variable, the reason for this phenomenon is unknown. We tested the hypothesis that the variability in venous response to acetylcholine may be associated with two recently identified genetic polymorphisms for proteins involved in the signal transduction pathway, i.e. the G-protein beta3-subunit (GNB3) and endothelial nitric oxide synthase (eNOS). The dorsal hand vein technique was used in 37 healthy subjects. Hand veins were preconstricted with the alpha1-adrenoceptor agonist phenylephrine and the venodilator response to local ACh infusion was measured with and without comedication of acetylsalicylic acid or co-infusion of N(G)-monomethyl-L-arginine (L-NMMA). In addition, all subjects received routine laboratory tests and 26 of them were genotyped for the C825T polymorphism of the GNB3 gene and for the G894T polymorphism of the eNOS gene. A striking variability in venous response to ACh was found with dilation observed in the low ACh concentration range and reduced dilation or even constriction at high concentrations. ACh-induced venodilation was mediated by muscarinic receptors and abolished in the presence of both acetylsalicylic acid and L-NMMA suggesting dependence on endothelium. We did not find any association of the variability in ACh response with GNB3 or eNOS allele status. On the other hand, a significant positive correlation between ACh responsiveness and low density lipoprotein-cholesterol status was detected. Two recently discovered gene polymorphisms are not responsible for the profound heterogeneity in venodilator response to ACh. Surprisingly, this variability appears to relate to the lipid status of the subjects. The exact nature of this new finding requires further study.

Acetylcholine↗

Intensity modulated proton therapy: a clinical example.

In this paper, we report on the clinical application of fully automated three-dimensional intensity modulated proton therapy, as applied to a 34-year-old patient presenting with a thoracic chordoma. Due to the anatomically challenging position of the lesion, a three-field technique was adopted in which fields incident through the lungs and heart, as well as beams directed directly at the spinal cord, could be avoided. A homogeneous target dose and sparing of the spinal cord was achieved through field patching and computer optimization of the 3D fluence of each field. Sensitivity of the resultant plan to delivery and calculational errors was determined through both the assessment of the potential effects of range and patient setup errors, and by the application of Monte Carlo dose calculation methods. Ionization chamber profile measurements and 2D dosimetry using a scintillator/CCD camera arrangement were performed to verify the calculated fields in water. Modeling of a 10% overshoot of proton range showed that the maximum dose to the spinal cord remained unchanged, but setup error analysis showed that dose homogeneity in the target volume could be sensitive to offsets in the AP direction. No significant difference between the MC and analytic dose calculations was found and the measured dosimetry for all fields was accurate to 3% for all measured points. Over the course of the treatment, a setup accuracy of +/-4 mm (2 s.d.) could be achieved, with a mean offset in the AP direction of 0.1 mm. Inhalation/exhalation CT scans indicated that organ motion in the region of the target volume was negligible. We conclude that 3D IMPT plans can be applied clinically and safely without modification to our existing delivery system. However, analysis of the calculated intensity matrices should be performed to assess the practicality, or otherwise, of the plan.

Adult↗

Ascorbic acid-induced modulation of venous tone in humans.

Ascorbic acid appears to have vasodilatory properties, but the underlying mechanisms are not well understood. The aims of this study were to define the acute effects of locally infused ascorbic acid in human veins and to explore underlying mechanisms by using pharmacological tools in vivo. Ascorbic acid was infused in dorsal hand veins submaximally preconstricted with the alpha(1)-adrenoceptor agonist phenylephrine or with prostaglandin F(2alpha) in 23 healthy male nonsmokers, and the venodilator response was measured. Ascorbic acid produced dose-dependent dilation with maximum reversal of constriction of 38+/-4% in phenylephrine-preconstricted veins and of 51+/-13% in prostaglandin F(2alpha)-preconstricted veins. Oral pretreatment with the cyclooxygenase inhibitor acetylsalicylic acid or local coinfusion of ascorbic acid and the nitric oxide synthase inhibitor N:(G)-monomethyl-L-arginine had no effect, but coinfusion of ascorbic acid and methylene blue (to inhibit cGMP generation) abolished venodilation. Coinfusion of ascorbic acid and the nonselective potassium channel blocker quinidine abolished venodilation, whereas the inhibitor of ATP-dependent potassium channels glibenclamide had no effect. In cultured bovine endothelial cells, ascorbic acid did not affect intracellular calcium concentration but blunted the response to ATP or digitonin exposure. Ascorbic acid, in millimolar concentrations, dilates human hand veins, presumably by activation of vascular smooth muscle potassium channels through cGMP. This activation is independent of eNOS-mediated nitric oxide synthesis and cyclooxygenase products and does not involve ATP-dependent potassium channels.

Adult↗

Pharmacokinetic-pharmacodynamic modeling of the electroencephalogram effects of scopolamine in healthy volunteers.

Scopolamine is a muscarinic receptor antagonist commonly used as a pharmacological model substance based on the "cholinergic hypothesis" of memory loss in senile dementia of the Alzheimer type. The objective of the study was to relate pharmacodynamic electroencephalogram (EEG) changes and scopolamine serum concentration using pharmacokinetic-pharmacodynamic (PK-PD) modeling techniques. This was a randomized, three-way crossover, open-label study involving 10 healthy nonsmoking young male volunteers who received either scopolamine 0.5 mg as an intravenous (i.v.) infusion over 15 minutes or an intramuscular (i.m.) injection or a placebo. The pharmacodynamic EEG measure consists of the total power in delta, theta, alpha, and beta bands over frontal, central, and occipital brain areas. The values of the pharmacokinetic parameters of scopolamine after i.v. infusion were clearance (CL) 205 +/- 36.6 L/h, volume of distribution (Vd) 363 +/- 66.7 L, distribution half-life (t1/2 alpha) 2.9 +/- 0.67 min, and terminal half-life (t1/2 beta) 105.4 +/- 9.94 min (mean +/- SEM). Mean peak serum concentrations (Cmax) were 4.66 and 0.96 ng/ml after i.v. and i.m. administration, respectively (p < 0.05). The area under the serum concentration versus time curve (AUC) after i.m. administration (81.27 +/- 11.21 ng/ml/min) was significantly lower compared to the value after i.v. infusion (157.28 +/- 30.86 ng/ml/min) (mean +/- SEM, p < 0.05). Absolute bioavailability of scopolamine after i.m. injection was 57% +/- 0.08% (mean +/- SEM). After both i.v. and i.m. administration, scopolamine induced a decrease in EEG alpha power (7.50-11.25 Hz) over frontal, central, and occipital brain areas compared to placebo (p < 0.05). The individual concentration-EEG effect relationships determined after i.v. infusion of scopolamine were successfully characterized by a sigmoidal Emax model. The averaged values of the pharmacodynamic parameters were E0 = 0.58 microV2, Emax = 0.29 microV2, EC50 = 0.60 ng/ml, and gamma = 1.17. No time delay between serum concentrations and changes in alpha power was observed, indicating a rapid equilibration between serum and effect site. The results provide the first demonstration of a direct correlation between serum concentrations of scopolamine and changes in total power in alpha frequency band in healthy volunteers using PK-PD modeling techniques. As regards the effect on the EEG, 0.5 mg of scopolamine administered i.v. appears to be a suitable dose.

Adult↗

The anti-apoptotic activities of Rel and RelA required during B-cell maturation involve the regulation of Bcl-2 expression.

Rel and RelA, individually dispensable for lymphopoiesis, serve unique functions in activated B and T cells. Here their combined roles in lymphocyte development were examined in chimeric mice repopulated with c-rel(-/-) rela(-/-) fetal liver hemopoietic stem cells. Mice engrafted with double-mutant cells lacked mature IgM(lo)IgD(hi) B cells, and numbers of peripheral CD4(+) and CD8(+) T cells were markedly reduced. The absence of mature B cells was associated with impaired survival that coincided with reduced expression of bcl-2 and A1. bcl-2 transgene expression not only prevented apoptosis and increased peripheral B-cell numbers, but also induced further maturation to an IgM(lo)IgD(hi) phenotype. In contrast, the survival of double-mutant T cells was normal and the bcl-2 transgene could not rectify the peripheral T-cell deficit. These findings indicate that Rel and RelA serve essential, albeit redundant, functions during the later antigen-independent stages of B- and T-cell maturation, with these transcription factors promoting the survival of peripheral B cells in part by upregulating Bcl-2.

Animals↗

Bioengineering of human thyrotropin superactive analogs by site-directed "lysine-scanning" mutagenesis. Cooperative effects between peripheral loops.

We have previously engineered the first superactive analogs of human thyrotropin (hTSH) by using a novel design strategy. In this study, we have applied homology comparisons focusing on the alphaL3 loop of the common alpha-subunit of human glycoprotein hormones. Seven highly variable amino acid residues were identified, and charge-scanning mutagenesis revealed three previously unrecognized modification permissive domains and four gain-of-function lysine substitutions. Such gain-of-function mutations were hormone- and receptor-specific and dependent on location and basic charge. Cooperativity of individual substitutions was established in double and triple lysine mutants. In combinations of the most potent alphaL3 loop analog with two previously characterized loop analogs, a higher degree of cooperativity for the alphaL3 loop analog compared with both the alphaL1 loop analog and the hTSH-betaL3 loop analog was observed. We demonstrated that spatially distinct regions of the common alpha-subunit contribute differentially to the interaction of hTSH with its receptor and that combinations of two modified loops on the same and on opposite sides of the hTSH molecule display similar increases in in vitro biopotency. In addition, combination of all three superactive loops showed cooperativity in receptor binding and activation resulting in the most potent hTSH superactive analog described to date.

Amino Acid Sequence↗

The exchange of radiotherapy data as part of an electronic patient-referral system.

PURPOSE: To describe the implementation and use of an electronic patient-referral system as an aid to the efficient referral of patients to a remote and specialized treatment center. METHODS AND MATERIALS: A system for the exchange of radiotherapy data between different commercial planning systems and a specially developed planning system for proton therapy has been developed through the use of the PAPYRUS diagnostic image standard as an intermediate format. To ensure the cooperation of the different TPS manufacturers, the number of data sets defined for transfer has been restricted to the three core data sets of CT, VOIs, and three-dimensional dose distributions. As a complement to the exchange of data, network-wide application-sharing (video-conferencing) technologies have been adopted to provide methods for the interactive discussion and assessment of treatments plans with one or more partner clinics. RESULTS: Through the use of evaluation plans based on the exchanged data, referring clinics can accurately assess the advantages offered by proton therapy on a patient-by-patient basis, while the practicality or otherwise of the proposed treatments can simultaneously be assessed by the proton therapy center. Such a system, along with the interactive capabilities provided by video-conferencing methods, has been found to be an efficient solution to the problem of patient assessment and selection at a specialized treatment center, and is a necessary first step toward the full electronic integration of such centers with their remotely situated referral centers.

Computer Communication Networks↗

The decision to cancel a preimplantation genetic diagnosis cycle.

It has been suggested that a minimum number (six) of cumulus-oocyte complexes (COCs) should be retrieved for fertilization to offer enough chances to ensure a pregnancy after a preimplantation genetic diagnosis (PGD) procedure. Therefore a decision to cancel a PGD cycle should be adequately weighted to offer the patients the highest chances to obtain a pregnancy. We describe a case where, after retrieving only three COCs suitable for fertilization, a triplet pregnancy was obtained. This case suggests that, although low numbers of COCs can reduce the effectiveness of the PGD procedure, other factors are involved in its final result. Thus, the opportunity of routinely cancelling such cycles should be reconsidered. In addition, this is, to our knowledge, the first case where sex selection was carried out to prevent the birth of carriers of the abnormal gene, and not of affected offspring.

Adult↗

Human thyroid-stimulating hormone: structure-function analysis.

This article provides the reader with an overview of methodological strategies to investigate structure-function relationships of human thyroid-stimulating hormone (hTSH). Various aspects of hTSH production, purification, and characterization described here in more detail are not only relevant to studies on other members of the glycoprotein hormone family, but also applicable to studies of other glycosylated proteins. Knowledge of structure-function relationships of specific hTSH domains is important for a better understanding of the molecular mechanisms of its action. New insights from such studies permit the design of glycoprotein hormone analogs with specific pharmacological properties and potential clinical applications.

Animals↗

N-desethylamiodarone modulates intracellular calcium concentration in endothelial cells.

The main in-vivo metabolite of amiodarone, N-desethylamiodarone (DEAM), possesses clinically relevant class-II antiarrhythmic and vasodilator activities. Vasodilation by DEAM is endothelium dependent and involves a sustained and biphasic increase in cytosolic free Ca2+ concentration ([Ca2+]i). The aims of this study were to explore the mechanisms mediating the DEAM-induced increase in [Ca2+]i in endothelial cells and to determine whether this increase in [Ca2+]i was associated with altered cell proliferation. Cultured bovine aortic endothelial cells were loaded with the Ca2+-sensitive fluorescent dye Fura-2/AM, and [Ca2+]i measured spectrofluorimetrically. DEAM increased [Ca2+]i concentration dependently (EC50 approximately 6 microM) both in the presence and absence of extracellular Ca2+. In the presence of extracellular Ca2+, the response of [Ca2+]i to DEAM (10 microM) consisted of an initial rise to a plateau followed by a second increase to micromolar levels. The initial plateau was reduced by the endoplasmic reticulum Ca2+-ATPase inhibitor thapsigargin (200 nM) and by the antioxidant ascorbic acid (100 microM). The initial rate of rise in [Ca2+]i was decreased by blocking mitochondrial Ca2+ release with cyclosporine A (1 microM). Under Ca2+-free conditions, the response of [Ca2+]i to DEAM (10 microM) was also biphasic, consisting of an initial transient peak and a second slow increase. When extracellular Ca2+ was restored, [Ca2+]i rose to micromolar concentrations. The initial peak was abolished by thapsigargin, but not altered by ascorbic acid or cyclosporine A. Both the second [Ca2+]i increase and that due to restoring extracellular Ca2+ were reduced by ascorbic acid but not affected by thapsigargin or cyclosporine A. The DEAM-induced generation of free radicals and sustained increase in [Ca2+]i might alter cell proliferation and endothelial cell proliferation was indeed concentration-dependently inhibited by DEAM (IC50 approximately 2.5 microM). In conclusion, the DEAM-induced [Ca2+]i increase in endothelial cells is due to Ca2+ influx from the extracellular space and to Ca2+ release from endoplasmic reticulum and mitochondria and involves enhanced generation of free radicals.

Amiodarone↗

Rel/NF-kappaB transcription factors: key mediators of B-cell activation.

The Rel/nuclear factor (NF)-kappaB family of transcription factors have been implicated in the regulation of a wide variety of genes, in particular those encoding proteins crucial to the function of the immune system. Through the use of mutant mice that lack one or more of these proteins, we have begun to examine the individual and combined roles of Rel, RelA and NF-kappaB1 in B-cell development and function. Here we outline and discuss how these transcription factors operate as differentiation stage-specific regulators of B-cell development, survival, division and immunoglobulin expression, emphasizing those Rel/NF-kappaB-regulated genes that mediate these functions.

Animals↗

Effect of digoxin on circadian blood pressure values in patients with congestive heart failure.

BACKGROUND: The aim of the study was to investigate the effect of chronic digoxin treatment on circadian blood pressure profile in normotensive patients with mild congestive heart failure. METHODS: In a randomized double-blind, placebo-controlled cross-over protocol, 12 normotensive patients with mild congestive heart failure took digoxin or placebo for a total of 7 days. Automatic 24-h ambulatory blood pressure measurements were carried out at day 7, of either digoxin or placebo. RESULTS: Diastolic blood pressure significantly decreased and systolic blood pressure significantly increased during overnight sleep in the digoxin phase compared to placebo. Digoxin had no effect on either systolic or diastolic blood pressure during daytime. Heart rate decreased in the overnight sleeping phase but did not differ significantly between placebo and digoxin phase. CONCLUSIONS: Digoxin significantly decreases diastolic blood pressure during overnight sleep in patients with congestive heart failure. This effect is likely to be caused by reduction of sympathetic activity or increase of parasympathetic activity. Increase of systolic blood pressure during sleep is probably caused by the positive inotropic effect of the drug.

Aged↗

Local venous response to N-desethylamiodarone in humans.

OBJECTIVE: Amiodarone, a class III antiarrhythmic agent, is a potent vasodilator in vivo. Its main metabolite, N-desethylamiodarone, contributes to the antiarrhythmic action of amiodarone after long-term treatment. It is unknown whether N-desethylamiodarone has acute vascular effects. The aim of this study was to explore the mechanism of action of N-desethylamiodarone in human hand veins. METHODS: The dorsal hand vein compliance technique was applied in 36 healthy male volunteers. In hand veins preconstricted with the alpha1-adrenergic receptor agonist phenylephrine or prostaglandin F2alpha, N-desethylamiodarone and an inhibitor of nitric oxide formation (N(G)-monomethyl-L-arginine, L-NMMA) were infused in the presence or absence of a cyclooxygenase inhibitor (acetylsalicylic acid), and the venodilator effect was measured. Furthermore, N-desethylamiodarone was infused after oral treatment with hydrocortisone or coinfused with alpha-tocopherol. Additional experiments were carried out in bovine aortic endothelial cells to explore the effects of N-desethylamiodarone on the intracellular Ca2+ concentration ([Ca2+]i). RESULTS: N-Desethylamiodarone produced dose-dependent venodilation (47% +/- 4% maximum). In vitro, 10 micromol/L N-desethylamiodarone caused a sustained increase of the endothelial [Ca2+]i. Pretreatment of the volunteers with acetylsalicylic acid reduced the maximum N-desethylamiodarone-induced venodilation to 22% +/- 8%; L-NMMA reduced the maximum N-desethylamiodarone-induced venodilation to 18% +/- 11%. Pretreatment with acetylsalicylic acid and coinfusion of N-desethylamiodarone and L-NMMA abolished the venodilation, whereas hydrocortisone had no effect. Coinfusion of alpha-tocopherol and N-desethylamiodarone reduced the maximum N-desethylamiodarone-induced venodilation to 11% +/- 4%. CONCLUSIONS: In concentrations estimated to be in the therapeutic range, N-desethylamiodarone dilates preconstricted human hand veins in vivo and increases endothelial [Ca2+]i in vitro. Subsequently the cyclooxygenase (COX-1) and the endothelial nitric oxide synthase pathways are activated. The resulting venodilation does not involve inflammatory cytokines, inducible nitric oxide synthase, or inducible cyclooxygenase (COX-2).

Adult↗

An extract of Petasites hybridus is effective in the prophylaxis of migraine.

OBJECTIVE: Migraine is still an unsolved problem. This clinical trial investigates the efficacy and tolerance of Petasites hydridus in the prophylaxis of migraine. METHODS: A randomized, group-parallel, placebo-controlled, double-blind clinical study was carried out with a special CO2 extract from the rhizome of Petasites hybridus. Following a 4-week run-in phase, 60 patients received either the special Petasites hybridus extract petadolex or placebo at a dosage of 2 capsules (each capsule contains 25 mg) twice daily over 12 weeks. Outcome variables included the frequency, intensity and duration of migraine attacks as well as any accompanying symptoms. RESULTS: The frequency of migraine attacks decreased by a maximum of 60% compared to the baseline. This reduction in migraine attacks with petadolex was significant (p < 0.05) compared to placebo. No adverse events were reported. Petasites was exceptionally well tolerated. CONCLUSIONS: The results suggest that migraine patients can benefit from prophylactic treatment with this special extract. The combination of high efficacy and excellent tolerance emphasizes the particular value that Petasites hydridus has for the prophylactic treatment of migraine.

Adult↗