L-Ala-substituted rat galanin analogs distinguish between hypothalamic and jejunal galanin receptor subtypes

In order to explore which amino acids or which blocks of amino acids in the 29 amino acid neuropeptide galanin are important for recognition of the endogenous ligand by galanin receptor subtypes present in the jejunum and in the hypothalamus, respectively, we have carried out L-Ala substitutions of individual amino acids or of blocks of amino acids in the rat galanin sequence and examined the binding of the obtained analogs to the rat hypothalamic and jejunal galanin receptor subtypes. This study reveals that the galanin sequence YLLGPH^9–14 is essential for recognition of galanin by both the rat hypothalamic and jejunal galanin receptor subtypes. Substitution of the N-terminal amino acids, GWTL^1–4, leads to total loss of affinity of galanin for both hypothalamic and jejunal galanin receptors. The α-helical C-terminal amino acid (25–29) part of galanin has no greater influence on the affinity of galanin to the hypothalamic galanin receptor subtype. L-Ala substitution of the C-terminal amino acids of galanin KHGLT^25–29 shows, however, that this C-terminal motif is essential for the recognition by the jejunal galanin receptor subtype, whereas amino acids in the middle portion of galanin NSAG^5–8 are of importance for binding to the hypothalamic but not to the jejunal receptor. [Ala^5–8] Galanin thus has a more than 100-fold higher affinity to jejunal receptor than to the hypothalamic receptor, while [Ala^25–29] galanin has a more than 100-fold higher affinity for the hypothalamic than for jejunal galanin receptor subtypes. pH dependence of the galanin binding to these receptor subtypes is also different. © Munksgaard 1997.     

Bradycardiomyopathy: The Case for a Causative Relationship Between Severe Sinus Bradycardia and Heart Failure

Bradycardiomyopathy . A 28‐year‐old man presented with progressive fatigue. Physical examination and ECG revealed severe sinus bradycardia. Echocardiography showed features of noncompaction cardiomyopathy and moderate aortic valve regurgitation. We hypothesized that the chronic volume overload exaggerated by prolonged diastole due to the bradycardia resulted in heart failure and noncompaction cardiomyopathy look‐alike features. After implantation of an AAI pacemaker, his symptoms and signs of cardiomyopathy were fully recovered. (J Cardiovasc Electrophysiol, Vol. pp. 822‐824, July 2010)     

Evaluation of biological activities of new LH-RH antagonists (T-series) in male and female rats

A series of new highly potent LH-RH antagonists (T-series) has been synthesized in our laboratory. Among these analogs, antagonists [Ac-d -Nal(2), d -Phe(4Cl)². d -Pal(3)³, d -Lys(A₂pr(Car)₂)⁶, d -Ala¹⁰LH-RH (T-140); [Ac-d -Nal(2)¹, d -Phe(4Cl)², d -Pal(3)³, d -Lys(A₂pr(Ac)₂)⁶, d -Ala¹⁰]LH-RH (T-148); [Ac-d -Nal(2)¹, d -Phe(4Cl)², d -Pal(3)³, d -Lys(A₂pr(For)₂)⁶, d -Ala¹⁰)]LH-RH (T-151) and [Ac-d -Nal(2)¹, d -Phe(4cl)², d -Pal(3)³, d -Lys(A₂bu(For)₂)⁶, d -Ala¹⁰]LH-RH (T-159) were the most powerful. Antagonists T-140, T-148 and T-151 produced a complete blockade of ovulation in normal cycling rats at a dose of 1.5 μg/rat and antagonist T-159 at a dose of only 0.75 μg/rat. The inhibitory effects of compounds T-148, T-151 and T-159 on gonadotropin and sex steroid secretion were investigated in male and female rats. To determine their effect on LH levels in castrated male and ovariectomized female rats, T-148, T-151 and T-159 were injected subcutaneously in doses of 0.625 and 2.5 μg/rat. Blood samples were taken at different intervals for 48 h. All three compounds at either dose caused a significant (P< 0.01) decrease in LH levels for more than 6 h. Significant (P <0.01) inhibition of LH lasted for more than 24 h following a dose of 2.5 μg sc of all 3 antagonists in both male and female rats. Serum FSH levels were also suppressed significantly for more than 48 h in castrated male rats by all three antagonists at a dose of 5 μg/rat sc. Serum testosterone levels were measured in intact male rates injected with antagonists T-148, T-151 and T-159 in doses of 50 and 100 pg sc. Both doses produced a dramatic fall in testosterone (P<0.01) to castration levels 6 h after injection. The inhibition of serum testosterone lasted for more than 48 h, but only 100 μg of T-148 maintained testosterone in the castration range for more than 48 h. Antagonists T-148, T-151 and T-159 injected at a dose of 100 μg to intact female rats reduced serum estradiol levels significantly (P<0.01) for more than 48 h, as compared to control animals. In the cutaneous anaphylactoid test (CAT), T-148, T-151 and T-159 proved to have very low histamine releasing activities. These data demonstrate a high efficacy of these new LH-RH antagonists in suppressing the pituitary-gonadal axis in male and female rats. These LH-RH antagonists could possibly be used for treatment of sex-hormone sensitive cancers and other disorders and conditions, in which a reduction in circulating sex steroids would be beneficial.     

New antagonists of LHRH II. Inhibition and potentiation of LHRH by closely related analogues

Modifications of the previously described LHRH antagonists, [Ac-d -Nal(2)¹, d -Phe(4Cl)², d -Trp³, d -Cit⁶, d -Ala¹⁰]LHRH and the corresponding d -Hci⁶ analogue, have been made to alter the hydrophobicity of the N-terminal acetyl-tripeptide portion. Substitution of d -Trp³ with the less hydrophobic d -Pal(3) had only marginal effects on the antagonistic activities and receptor binding potencies of the d -Cit/d -Hci⁶ analogues, but it appeared to further improve the toxicity lowering effect of d -Cit/d -Hci⁶ substitution. Antagonists containing d -Pal(3)³ and d -Cit/d -Hci⁶ residues, i.e. [Ac-d -Nal(2)¹, d -Phe(4Cl)², d -Pal(3)³d -Cit⁶, d -Ala¹⁰]LHRH (SB-75) and [Ac-d -Nal(2)¹, d -Phe(4Cl)², d -Pal(3)³, d -Hci⁶, d -Ala¹⁰]LHRH (SB-88), were completely free of the toxic effects, such as cyanosis and respiratory depression leading to death, which have been observed in rats with the d -Trp³, d -Arg⁶ antagonist and related antagonists. Replacement of the N-acetyl group with the hydrophilic carbamoyl group caused a slight decrease in antagonistic activities, particularly in vitro. Introduction of urethane type acyl group such as methoxycarbonyl (Moc) or t-butoxycarbonyl (Boc) led to analogues that showed LHRH-potentiating effect. The increase in potency induced by these analogues, e.g. [Moc-d -Nal(2)¹, d -Phe(4Cl)², d -Trp³, d -Cit⁶, d -Ala¹⁰]LHRH and [Boc-d -Phe¹, d -Phe(4Cl)², d -Pal(3)³, d -Cit⁶, d -Ala¹⁰]LHRH, was 170-260% and persisted for more than 2 h when studied in a superfused rat pituitary system.     

Effects of Septal Pacing on P Wave Characteristics: The Value of Three-Dimensional Echocardiography

SZILI-TOROK, T., et al .: Effects of Septal Pacing on P Wave Characteristics: The Value of Three-Dimensional Echocardiography. Interatrial septum (IAS) pacing has been proposed for the prevention of paroxysmal atrial fibrillation. IAS pacing is usually guided by fluoroscopy and P wave analysis. The authors have developed a new approach for IAS pacing using intracardiac echocardiography (ICE), and examined its effects on P wave characteristics. Cross-sectional images are acquired during pullback of the ICE transducer from the superior vena cava into the inferior vena cava by an electrocardiogram- and respiration-gated technique. The right atrium and IAS are then three-dimensionally reconstructed, and the desired pacing site is selected. After lead placement and electrical testing, another three-dimensional reconstruction is performed to verify the final lead position. The study included 14 patients. IAS pacing was achieved at seven suprafossal (SF) and seven infrafossal (IF) lead locations, all confirmed by three-dimensional imaging. IAS pacing resulted in a significant reduction of P wave duration as compared to sinus rhythm (   99.7 ± 18.7   vs   140.4 ± 8.8  ms; P < 0.01   ). SF pacing was associated with a greater reduction of P wave duration than IF pacing (   56.1 ± 9.9   vs   30.2 ± 13.6  ms; P < 0.01   ). P wave dispersion remained unchanged during septal pacing as compared to sinus rhythm (   21.4 ± 16.1   vs   13.5 ± 13.9  ms; NS   ). Three-dimensional intracardiac echocardiography can be used to guide IAS pacing. SF pacing was associated with a greater decrease in P wave duration, suggesting that it is a preferable location to decrease interatrial conduction delay. (PACE 2003; 26[Pt. II]:253–256)     

Reproducibility of the Dobutamine-Atropine Echocardiography Stress Test

To assess the reproducibility of dobutamine-atropine echocardiography testing, two studies (1 to 20 days apart [mean 3.3 days]) were performed in 23 patients with stable effort angina pectoris or chest pain. During the study, 20 (87%) patients were receiving beta blockers alone or combined with nitrates or calcium antagonists. Dobutamine was infused at doses of 10 μg/kg per minute every 3 minutes up to a maximum of 40 μg/kg per minute and this maximal dose was continued for 6 minutes. In patients not achieving 85% predicted maximal heart rate or myocardial ischemia, atropine (0.25–1 mg) was added and dobutamine continued for another 3 minutes, until either an adequate heart rate was achieved or the test was considered positive. During dobutamine infusion, electrocardiographic, echocardiographic, and blood pressure monitoring were obtained in each patient. Side effects including tremor, nausea, palpitation, dizziness, headache, and nonsustained ventricular tachycardia occurred in three patients. The same symptoms, but no ventricular tachycardia, developed during the same stage of the second test. Angina pectoris (eight patients), electrocardiographic changes (six patients), and ischemic wall-motion abnormalities (six patients) were observed at the same stage of the two tests. The mean values of heart rate, blood pressure, and rate-pressure product were comparable for each stage in duplicate tests. Our data show that pharmacological stress echocardiography using dobutamine-atropine has good reproducibility and provides a useful tool for assessing disease progression and the effects of therapeutic interventions in patients with coronary artery disease.     

Transvenous Cryothermal Catheter Ablation of a Right Anteroseptal Accessory Pathway

In patients with Wolff-Parkinson-White syndrome, right anteroseptal accessory pathways are uncommon and run from the atrium to the ventricle in close anatomic proximity to the normal AV conduction system. Radiofrequency catheter ablation is the first-line therapy for elimination of these accessory pathways. Although the initial success rate is high, there is a potential risk of inadvertent development of complete heart block, and the recurrence rate is relatively high. The capability of cryothermal energy to create reversible lesions (ice mapping) at less severe temperatures provides a potential benefit in ablation of pathways located in a complex anatomic area, such as the mid-septum and anteroseptum.