DIFFERENTIAL NEURAL CREST CELL ATTACHMENT AND MIGRATION ON AVIAN LAMININ ISOFORMS

A number of laminin isoforms have recently been identified and proposed to exert different functions during embryonic development. In the present study, we describe the purification and partial characterization of several isoforms isolated from chick heart and gizzard, and provide data on the molecular mechanisms underlying the interaction of avian neural crest cells with these molecules in vitro. Laminins extracted from heart and gizzard tissues were separated by gel filtration and purified to homogeneity by sequential lectin and immunoaffinity chromatography by utilizing monoclonal antibodies directed against the avian α2, β2 and γ1 laminin chains. The sodium dodecyl sulfate—polyacrylamide gel electrophoresis (SDS—PAGE) banding pattern of the polypeptide complexes obtained and immunoblotting with polyclonal antisera allowed the identification of Laminin-2 (α2β1γ1), Laminin-4 (α2β2γ1), and laminins comprising the β1, β2 and γ1 chains associated with a shorter α chain which, in SDS—PAGE, co-migrate with the β/γ complex in the 200 kDa region. These latter laminins, which are here arbitrarily denoted Laminin-αχ (heart tissue) and Laminin-G (gizzard tissue), are somewhat distinct in their apparent molecular weight, are differentially associated with nidogen, and appear as “T”-shaped particles similar to Laminin-6 and Laminin-7 when analyzed by transmission electron microscopy following rotary shadowing. In contrast, the avian Laminin-2 and Laminin-4 isoforms exhibit the characteristic cruciform shape described previously for their mammalian counterparts. Isolated neural crest cells differentially attached and migrated on these laminin isoforms, showing a clear preference for Laminin-G. Similarly to the EHS Laminin-1, neural crest cells recognized all avian isoforms through their α1β1 integrin, shown previously to be the primary laminin-binding receptor on these cells. Neural crest cell interaction with the avian laminins was dependent upon maintenance of the secondary and tertiary structure of the molecules, as shown by the marked reduction in cell attachment and migration upon disruption of the α-helical coiled-coil structure of their constituent chains. The results demonstrate that different laminin isoforms may be differentially involved in the regulation of neural crest cell migration and suggest that this regulation operates through interaction of the cells with a structurally conserved cell binding site recognized by the α1β1 integrin. Copyright © 1996. Published by Elsevier Science Ltd.     

Inflammatory Bowel disease in Saudi Arabia: Presentation and initial management

Non-specific Inflammatory Bowel disease (IBD) is infrequently seen in the Arabs of the Arabian Peninsula. This paper documents the presentation and initial management of 101 such Arabs treated for inflammatory bowel disease between 1976 and 1994. Medical records were examined and patients were classified according to the Organisation Mondiale de Gastroenterologie diagnostic scoring system. Sixty-seven patients had mucosal ulcerative colitis, 28 Crohn's disease (CD) and six indeterminate colitis; age range 2–71 years. Three patients had a family history of (IBD). The diagnosis was made by a combination of the patients' history, physical, radiological, endoscopic and histological examination; however, eight patients were not examined endoscopically and one in four patients was not biopsied at presentation. Thirty-nine patients did not receive any treatment prior to referral. One in three patients was first treated as inpatients. Giardia, Amoeba, Salmonella, Shigella or Schistosoma were detected in the stools of 36 patients at presentation. Following appropriate treatment, these infections were eliminated but the patients' symptoms persisted. Six patients who were thought to have gastrointestinal tuberculosis were subsequently diagnosed with CD. Ten patients had extraintestinal manifestations of their IBD and 11 had side effects (osteoporosis, Cushingoid features and growth retardation) from steroid treatment at other hospitals. Diagnosis was often delayed because infectious diarrhoea was common and awareness was low. Patients were referred late and some had developed complications of therapy.     

Cryoablation at Growing Myocardium: No Evidence of Coronary Artery Obstruction or Intimal Plaque Formation Early and Late after Energy Application

Background: Animal studies and clinical observations have demonstrated that radiofrequency current application at growing myocardium may result in coronary artery obstruction. Recently, cryoenergy has emerged as an effective alternative to radiofrequency ablation of arrhythmogenic substrates in pediatric patients. Up to now, there has been a lack of experimental data concerning the effects of cryoenergy application at growing myocardium.
Methods: During general anesthesia, selective coronary angiography of the right and left coronary artery was performed in 10 piglets (age: 6 weeks, body weight: 14–18 kg). Subsequently, cryoenergy was delivered at −75°C for 4 minutes using a 7-F catheter with a 6-mm-tip electrode at the atrial aspect of the tricuspid valve annulus in a posterior and lateral position. Additional cryoenergy lesions were induced via a retrograde approach at the lateral and posterior atrial and ventricular aspect of the mitral valve annulus, respectively. Five animals were restudied after 48 hours by coronary angiography and intracoronary ultrasound and in the remaining five piglets after 3 and 6 months, respectively.
Results: Selective coronary angiography and intracoronary ultrasound studies did not demonstrate any evidence for coronary artery obstruction after 48 hours, 3 months, or 6 months after cryoenergy application. In addition, histological examinations of the cryolesions after 48 hours and after 6 months did not demonstrate any intimal proliferations of the coronary arteries, respectively.
Conclusions: By means of the present study, we did not observe any affection of the coronary arteries after cryoenergy application at growing myocardium in young piglets.     

Electrophysiology of the Atrio-AV Nodal Inputs and Exits in the Normal Dog Heart

Ablation of Atrionodal Connections. Introduction : We studied the effects of selective and combined ablation of the fast (FP) and slow pathway (SP) on AV and VA conduction in the normal dog heart using a novel epicardial ablation technique.
Methods and Results : For FP ablation, radiofrequency current (RFC) was applied to a catheter tip that was held epicardially against the base of the right atrial wall. SP ablation was performed epicardially at the crux of the heart. Twenty-three dogs were assigned to two ablation protocols: FP/SP ablation group (n = 17) and SP/FP ablation group (n = 6). In 12 of 17 dogs, FP ablation prolonged the PR interval (97 ± 10 to 149 ± 22 msec. P < 0.005) with no significant change in anterograde Wenckebach cycle length (WBCL), Subsequent SP ablation performed in 8 dogs further prolonged tbe PR interval and the anterograde WBCL (117 ± 22 to 193 ± 27, P < O.(M)5). Complete AV block was seen in I of 8 dogs, whereas complete or high-grade VA block was seen in 6 of 8 dogs. In the SP/FP ablation group, SP ablation significantly increased WBCL with no PR changes. Combined SP/FP ablation in A dogs prolonged the PR interval significantly, but no instance of complete AV block was seen. VA block was found in 50% of these cases. Histologic studies revealed that RFC ablation affected the anterior and posterior atrium adjacent to the undamaged AV node and His bundle.
Conclusion : Using an epicardial approach, combined ablation of tbe FP and SP AV nodal inputs can be achieved with an unexpectedly low incidence of complete A V block, although retrograde VA conduction was significantly compromised.