Linear and cyclic synthetic peptides related to the main autophosphorylation site of the Src tyrosine kinases as substrates and inhibitors of Lyn †

Tyrosine protein kinases (TPKs) of the src family contain two major phosphoacceptor sites which are homologous to the Tyr 416 and Tyr 527 of pp60^c-src. The former represents the main autophosphorylation sites of these enzymes, and its phosphorylation correlates with increased kinase activity. It has previously been demonstrated that the Src-like tyrosine kinase expressed by the oncogene lyn displays a high affinity toward the heptapeptide H-Glu-Asp-Asn-Glu-Tyr-Thr-Ala-OH, which reproduces the main autophosphorylation site of the Src family enzymes [Donella-Deana, A., Marin, O., Brunati, A.M. & Pinna, L.A. (1992) Eur. J. Biochem. 204 , 1159–1163]. Our study was addressed to the synthesis of some derivatives of this sequence in order to obtain both peptide substrates suitable for the detection of the Src-like tyrosine kinase activity and active site-directed inhibitors specific for this class of enzymes. For this purpose we synthesized by classical solution methods the heptapeptide and its dimeric form. Moreover, in order to improve the proteolytic resistance of these peptides we also synthesized their cyclic derivatives and their N-terminal acetylated and C-terminal amidated analogs. The correlation between the different structural properties induced by the modifications of the native sequence and the propensity of the peptides to act as Lyn substrates was examined. The kinetic data obtained indicate that the extent of the peptide phosphorylation varies considerably depending on the flexibility and length of the analogs. While the cyclization and the C-terminal amidation of the heptapeptide are detrimental for the Lyn activity, dimeric derivatives display very favourable kinetic constants. In particular the cyclic dimer is an especially suitable substrate for the tyrosine kinase and a powerful inhibitor of both the phosphorylation activity of Lyn and the enzyme autophosphorylation. © Munksgaard 1995.     

A sex difference in the interaction between promethazine and morphine in the mouse

The effects of promethazine on the antinociceptive and respiratory actions of morphine have been examined in the mouse. Moderate doses of promethazine (5 and 10 mg kg^?1) potentiated morphine's action in male mice but inhibited it in female mice. Gonadectomy abolished the interaction between promethazine and morphine in both sexes, although the intensity and duration of morphine's activity was greatly enhanced in these mice. Replacement of oestradiol in ovariectomized mice restored morphine's activity to intact female control values. However, interactions between promethazine and morphine required progesterone, as well as oestradiol, replacement to obtain results approaching those obtained in intact female mice.     

Comparison of Cryoballoon and Radiofrequency Ablation of Pulmonary Veins in 40 Patients with Paroxysmal Atrial Fibrillation: A Case‐Control Study

Introduction: Ablation of pulmonary veins (PV) is an established therapeutic option for patients with symptomatic drug‐refractory paroxysmal atrial fibrillation (AF). Radiofrequency (RF) is currently the most widespread energy source for PV ablation. Cryothermal energy applied with a cryoballoon technique as an alternative has recently evolved. Methods and Results: In a case‐control setting, we compared 20 patients with paroxysmal AF who underwent their first PV ablation with the cryoballoon technique to 20 matched patients with conventional RF ablation. In the case of persistent electrical potentials after cryoballoon ablation, it was combined with ablation with a conventional cryocatheter. All patients performed daily event recording for 3 months after ablation procedure. Ablation parameters and success rate after 3 and 6 months were compared. In the cryoballoon group, the overall success rate was 55% (50% in the cryoballoon only group [14 patients] and 66% in the combination group [6 patients]), as opposed to the RF group with 45%. AF episode burden was lower after cryoballoon ablation. There was no significant difference between cryoballoon and RF ablation regarding procedure parameters. In the cryoballoon group, 3 phrenic nerve palsies occurred using the 23 mm balloon that resolved spontaneously. Conclusion: PV ablation with the cryoballoon technique is feasible and seems to have a similar success rate in comparison to RF ablation. Procedure‐ and fluoroscopy duration are not longer than in conventional RF ablation.     

Anxiety in adolescents born preterm or with very low birthweight: a meta‐analysis of case–control studies

Aim To determine if adolescents who are born very preterm (<32wks; of gestation) and/or with very low birthweight (VLBW; <1500g) have a higher risk of experiencing clinically significant anxiety problems. Method We used a systematic review and meta‐analysis. We searched the databases ISI Web of Knowledge, PubMed, PsycNET, Educational Resources Information Center (ERIC), Latin American and Caribbean Literature on the Health Sciences (LILACS), and Virtual Health Library (VHL) with equivalent search expressions (from the databases’ inception to June 2011). Also, we screened reference lists of identified articles. We selected case–control studies of adolescents 11 to 20 years old who were very preterm/VLBW and had a matched reference group born at term with normal birthweight that reported a validated anxiety outcome measure. For data extraction, two authors independently reviewed titles, abstracts, and full articles identified through the searches. Subsequently two authors independently extracted data. Results We included six studies with 1519 adolescents (787 very preterm/VLBW, 732 comparisons). The general risk of developing clinically significant anxiety problems was nearly doubled (p<0.05) in the very preterm/VLBW population (OR 2.27, 95% confidence interval 1.15–4.47). The overall prevalences were 9.9% in the very preterm/VLBW group and 5.5% in the comparison group. Interpretation Those born very preterm/VLBW have an increased risk of developing clinically significant anxiety problems in adolescence.     

Epicardial, Biatrial Synchronous Pacing for Prevention of Atrial Fibrillation after Cardiac Surgery

About 30% of patients develop AF after open heart surgery. Biatrial synchronous pacing (BSP) has been shown to promote sinus rhythm in patients with paroxysmal AF refractory to drug therapy. We conducted a prospective, randomized study to test the effect of BSP via epicardial electrodes on the incidence of AF after heart surgery, as compared to conventional therapy. To apply BSP, we attached two epicardial electrodes to the right and one to the left atrium. Immediately following surgery, BSP was initiated in the AAI-Mode at a rate of 10 beats/min above the underlying rhythm (maximum 110 beats/min) and continued for 3 days, during which the rhythm was continually monitored. After 21 (age 63 +/- 9 years) of the planned 200 patients, the study was prematurely aborted because of the proarrhythmic effect of BSP: 6 of the 12 patients treated with BSP developed sensing failure (P amplitude < 1 mV), which provoked AF in 5 of these 6 patients. BSP was discontinued due to diaphragmal stimulation in two patients and due to ventricular stimulation by a dislocated left atrial electrode in one patient. Two patients in the control group (n = 9) developed AF. Using the available standard technology, BSP via epicardial electrodes is not suitable to suppress AF after heart surgery, primarily due to postoperative deterioration of atrial sensing and its profibrillatory effect. In patients requiring atrial pacing after heart surgery, sensing thresholds must be closely monitored to prevent induction of AF.     

MICROVASCULAR ANGIOPATHY IN ADVANCED PERIODONTAL DISEASE

Previous studies have shown a perivascular hyaline thickening affecting restricted regions of the microcirculation in gingivitis and moderate periodontitis and in the pulpal vessels in chronic pulpitis. In the present study of the lesion of advanced periodontitis, immunostaining for type IV collagen and laminin demonstrated widespread deposition of basement membrane material, with manifest involvement of the venous network. Some vessels were associated with an increased deposition of both basement membrane proteins, while others showed preferential deposition of either laminin or type IV collagen. Immunostaining also revealed an extensive trabecular network of type IV collagen throughout the affected gingival tissue that was not related to recognizable vessels but was co-extensive with less intense staining for laminin. This network was not associated with viable endothelial cells demonstrable by staining with the endothelial marker Ulex agglutinin (UEA-1). The results indicate extensive vascular pathology in advanced periodontitis that could explain the attenuation of the inflammatory reaction and the restricted ability to develop reparative granulation tissue in this disease.