Directional Variability of Stimulation Threshold Measurements in Isolated Guinea Pig Cardiomyocytes: Relationship with Orthogonal Sequential Defibrillating Pulses

BARDOU A.L., ET AL.: Directional Variability of Stimulation Threshold Measurements in Isolated Guinea Pig Cardiomyocytes: Relationship with Orthogonal Sequential Defibrillating Pulses. Reports on delivery of separated orthogonal pulses markedly improving cardiac defibrillation have suggested that the stimulation threshold of heart fibers varies in accordance with their orientation within the electric field. The present work was aimed at investigating the directional variability of stimulation thresholds in isolated guinea pig cardiomyocytes. This variability was measured in 48 single myocytes by rotating each one through a theta (θ) angle between two-fixed parallel electrodes 1.1 cm apart, thus making θ vary between the electric field and the myocyte axis. For θ= 0°, the mean longitudinal current stimulation threshold was 16.92 ± 4.20 mA (n = 48). When θ was increased by increments of 10° up to 90°, the stimulation threshold increased in an exponential way. For θ= 90°, the mean transverse stimulation threshold was 63.23 ± 13.30 mA. These results clearly demonstrate the dependence of isolated cardiomyocyte stimulation thresholds on their orientation within the electric field and may account for the improved efficacy of defibrillation previously observed after delivery of orthogonal pulses.     

A glucose transfer from membrane glycoconjugates to haemoglobin in isolated young red blood cells: another biosynthetic way for glycosylated haemoglobins

Abstract. Human red blood cells (RBC) are separated by centrifugation into young and old ones, as demonstrated by lower enzymatic activities and lower potassium content of the older ones. The young RBC fraction represents 5% of total RBC. After incubation for 24 h in a neutral buffer, the young RBC HbA_1c content increases significantly from 4·2 to 5·2% of total Hb. No increase is found in the case of old RBC. When young RBC have been extracted for 1 h by a neutral buffer prior to incubation, there is no more increase of HbA_1c.
The extract contains a glycoconjugate that is both soluble in neutral buffers and in chloroform. A glycolipid extractable from the young RBC membrane contributes to HbA_1c formation but disappears from old RBC, in which glycosylation by free glucose occurs. These processes are stereospecific.     

Combined immunophenotyping and in situ hybridization (FICTION): a rapid method to study cell lineage involvement in myelodysplastic syndromes

Summary. We present a study in which we used a recently described method combining fluorescence in situ hybridization (FISH) and immunophenotyping, i.e. FICTION, to assess the involvement of different cell lineages in myelodysplastic syndrome (MDS) with monosomy 7 (–7), trisomy 8 (+8) or loss of Y chromosome (–Y). Blood or marrow smears or cytocentrifuge preparations were stained both by antibodies to granulocytes (CD₁₅), monocytes (CD₁₄), T lymphocytes (CD₃), B lymphocytes (CD₂o) and by probes specific for chromosomes 7, 8 or Y. Of nine cases of MDS with –7, four with +8 and two with – Y studied, none showed lymphocytic involvement by the chromosome abnormality. In contrast, -7,-1-8 and – Y were found in granulocytes and monocytes in all patients studied, but they involved a variable proportion of those cells. The partial involvement by –7 and +8 seen in some cases suggests that myelopoi'esis was only partially clonal in those cases, or that the chromosome abnormality was a secondary event in the MDS process. FICTION therefore appears to be a simple and easily reproducible method that can be used for the assessment of lineage involvement in MDS and other haematological malignancies.     

Applications of BOP reagent in solid phase peptide synthesis III. Solid phase peptide synthesis with unprotected aliphatic and aromatic hydroxyamino acids using BOP reagent

The BOP reagent [benzotriazol-1-yl-oxy-tris-(dimethylamino)phosphonium hexafluorophosphate], which has been shown to be ideally suited for solid phase synthesis, has now been found to be useful for solid phase synthesis using a minimal side-chain protection scheme. This new application of the BOP reagent was exemplified by the successful synthesis of the CCK-7 analog, Ac-Tyr(SO₃H)-Met-Gly-Trp-Met-Thr(SO₃H)-Phe-NH₂, using unprotected Boc(hydroxy)-amino acids [Boc-Thr-OH and Boc-Tyr-OH]. N-Terminal acetylation was achieved under mild conditions by using the BOP coupling reaction with acetic acid. This procedure provided the unprotected (Tyr²⁷, Thr³²)-peptide-resin which is ready for the required sulfation on the solid support without selective side-chain deprotection of Ty²⁷ and Thr³². Solid phase sulfation was evaluated under a variety of conditions and it was determined that disulfation was optimal using pyridine acetyl sulfate (38 equiv.) in pyridine at 45° for 4 h. Shorter reaction times or milder conditions lead to the formation of the Thr³² monosulfated analog. Cleavage of the disulfated analog from the PAM-resin was achieved using liquid ammonia and the product was purified by preparative hplc and fully characterized. The advantages of the new procedure are compared with the reported synthesis of CCK-7.     

Review of Immunomodulation by Photopheresis: Treatment of Cutaneous T–Cell Lymphoma, Autoimmune Disease, and Allograft Rejection

Abstract: Photopheresis is an apheresis–based therapy that is currently available at approximately 70 medical centers worldwide. Recent evidence indicates that extracorporeal photopheresis can significantly prolong life as well as induce a 60–75% response rate among individuals with advanced cutaneous T–cell lymphoma (CTCL). Moreover, a 10–15% cure rate, in response to photopheresis alone, or in combination with interferon–a, has been obtained at our institution. These complete responses have been characterized by the complete disappearance of morphologically atypical cells from the skin and blood. Southern blot analysis of peripheral blood specimens has also confirmed the indefinite disappearance of the malignant T–cell clone from the blood of patients with complete responses. Current immunological data obtained from in vitro human studies and from animal models suggest that the basis for the responses of CTCL patients are related to activation of treated macrophages resulting in release of cytokines, including substantial levels of tumor necrosis factor a (TNF-α), and perhaps, to the induction of anticlonotypic immunity directed against pathogenic clones of T lymphocytes. In addition to the treatment of CTCL, a potential role for photopheresis in the therapy of autoimmune disease has been suggested by recent pilot studies of pemphigus vulgaris, rheumatoid arthritis, and systemic lupus erythematosus. Furthermore, a randomized, single–blinded trial involving 79 patients with early onset, aggressive systemic sclerosis suggested that photopheresis could beneficially affect the course of the cutaneous thickening in this form of the disease. Lastly, two independent pilot studies of cardiac transplantation have indicated that photopheresis can reverse acute cardiac allograft rejection and potentially suppress ongoing chronic rejection. Randomized, controlled trials for these new indications for photopheresis therapy are currently in the early stages of implementation.     

Synthesis and biological activity of a destruxin analogue: d-Lac-6 destruxin E

A general strategy for the synthesis of destruxin analogues is described and applied to a particular example, d -Lac-6 destruxin E. The tetrapeptide Boc-Ile-N-MeVal-N-MeAla-β-Ala-OMe (2) was chosen as the basic starting compound, and its preparation was optimized. This fragment was then coupled with the compound (D)Lac-Pro, and the resulting peptide was cyclized by the DEPC or DPPA/HOBt/DMAP methods at 21 and 30% yield, respectively. The biological activity of the analogue obtained was established by injection to an insect host.     

Surgical Treatment of Ascending Aortic Pathology

Among the first 10,200 valvular replacements performed in our unit, 288 complex repairs of the ascending aorta were done for various aortic pathology. Aneurysms of the ascending aorta were the most frequent; 53 supracoronary artery aneurysms with aortic valvular insufficiency were treated by the separate replacement of the aortic valve and the supracoronary ascending aorta; 206 annulo-aortic ectasia had total and combined replacement of the ascending aorta and the aortic valve with a personal modification of the Bentall's technique using an 8-mm diameter Dacron graft to perform the reimplantation of the coronary arteries on the composite aortic grafts. The operative mortality for the first 100 patients was 4% and for the entire 206 patients, 6%. Late mortality during a follow-up period ranging from 18 months to 8 years was 11%. The actuarial survival rate at 8 years is 75%; 25 patients restudied by angiography demonstrated satisfactory results with neither stenosis nor aneurysm on the coronary graft but a recurrent or persisting chronic distal aortic dissection in four patients. In 26 cases of aortic valvular endocarditis, large abscesses of the aortic annulus involved the aortic root. In 11, the aortic repair consisted of the insertion of a subcoronary valved conduit (two early deaths, two late deaths, one reoperation, seven good results--maximum follow-up of eight years). Twelve patients had a supracoronary valved conduit with four early deaths, one late death, and two reoperations; seven are alive and well, two to six years later. Three patients previously operated had a left ventricular abdominal aorta valved conduit; two of them are alive and well up to six years later. In three patients with iterative aortic paravalvular leak (recurring three or four times), ablation of the aortic insufficiency was obtained by interposition of a composite valved graft in the ascending aorta.     

Applications of BOP reagent in solid phase synthesis

Using a variety of activating agents, a kinetic study was carried out to evaluate the rate of solid phase side-chain to side-chain cyclization of Asp³ to Lys¹² in the model peptide-resin, [Ala¹⁵]-GRF(1–29)-BHA-resin. Asp³ and Lys¹² were introduced in the peptide chain by using N^α-Boc amino acids in conjunction with the OFm/Fmoc side-chain protection scheme. The OFm and Fmoc side-chain protecting groups were shown to be stable to diisopropylethylamine and selectively deprotected on treatment with 20% piperidine in DMF. Solid phase side-chain to side-chain cyclization (lactamization) was shown to proceed to completion within 2 h using benzotriazol-1-yl-oxy-tris(dimethylamino)-phosphonium hexafluorophosphate (BOP reagent) while the reaction was only 55% completed in 24h using DCC/HOBt. Solid phase side-chain to side-chain cyclization by the BOP procedure not only proceeded more rapidly but also gave a purer cyclic product.     

Evaluation of the use of ultrasonography in primary care

Ultrasonography is proposed as a useful diagnostic aid for primarycare physicians. This prospective study describes the demandfor ultrasound examinations, excluding heart, vessels and pregnancymonitoring, in primary care in Switzerland. Eleven independentphysicians requested an average of 2.7 ultrasound examinationsper month and 18 residents 1.9 per month, which was similarto the figure of 2.2 obtained in a population-based study of82 primary care physicians serving a region of 80, 000 inhabitants.Current demand for ultrasound scanning is low and does not indicatesystematic training of primary care physicians until the efficacyof ultrasonography in this setting has been shown.     

Physical and Dynamic Characteristics of DC Ablation in Relation to the Type of Energy Delivery and Catheter Design

We evaluated and compared the in vitro characteristics of direct current ablation using high energy ablation (Hewlett-Packard defibrillator) and a new form of low energy ablation (low energy ablation power supply, Cardiac Recorders, UK). Two new catheters with a large distal electrode have been recently introduced for catheter ablation: a low energy 7F bipolar catheter (Bard) with a contoured distal electrode, and a 7F deflectable catheter with a 4-mm tip (Mansfield). In vitro studies were carried out in a large tank filled with physiological saline while recording voltage, current, and pressure. High speed cinematography at 32,000 frames per second (Cordin, Utah) was done to assess the dynamic behavior of the vapor globe with both systems of energy delivery. We evaluated shocks of 50, 100, 150, 200, and 300 joules with the conventional system, and shocks of 10, 15, 20, 30, and 40 joules with the new system, and also compared the effects of varying catheter design with both systems of energy delivery. The conventional system using high energy showed significant arcing and increases in pressure. Low energy direct current ablation produces nonarcing shocks with 20 joules or less, and significantly less vapor globe and gas formation during arcing shocks, with a shorter duration of increase in pressure. This new system using low energy direct current may reduce the risk and complications reported with high energy ablations.