SUMMARYDuring development, specific cells are eliminated by apoptosis to ensure that the correct number of cells is integrated in a given tissue or structure. How the apoptosis machinery is activated selectively in vivo in the context of a developing tissue is still poorly understood. In the Drosophila ovary, specialised follicle cells [polar cells (PCs)] are produced in excess during early oogenesis and reduced by apoptosis to exactly two cells per follicle extremity. PCs act as an organising centre during follicle maturation as they are the only source of the JAK/STAT pathway ligand Unpaired (Upd), the morphogen activity of which instructs distinct follicle cell fates. Here we show that reduction of Upd levels leads to prolonged survival of supernumerary PCs, downregulation of the pro-apoptotic factor Hid, upregulation of the anti-apoptotic factor Diap1 and inhibition of caspase activity. Upd-mediated activation of the JAK/STAT pathway occurs in PCs themselves, as well as in adjacent terminal follicle and interfollicular stalk cells, and inhibition of JAK/STAT signalling in any one of these cell populations protects PCs from apoptosis. Thus, a Stat-dependent unidentified relay signal is necessary for inducing supernumerary PC death. Finally, blocking apoptosis of PCs leads to specification of excess adjacent border cells via excessive Upd signalling. Our results therefore show that Upd and JAK/STAT signalling induce apoptosis of supernumerary PCs to control the size of the PC organising centre and thereby produce appropriate levels of Upd. This is the first example linking this highly conserved signalling pathway with developmental apoptosis in Drosophila.

Objectives: To develop the first Spanish Pediatric Trauma Registry to collect and evaluate infornation concerning aspects of injuries in our pediatric population. Methods: From January 1995 to August 1998.946 children younger than 16 years were treated in our hospital for acute injury: 1500 were admitted and ineluded in our database. Dur file registry consists of 108 data points ineluding: patient identification, type. place and mechanism of injury, pre-hospital care, transport, assess· ment on admission, severity scores, diagnostic studies, injuries, treatment morbidity and mortality. Results: Aceidents were more frequent in males (68 %) than in fern ales. The predominant age group was 12 -15 years of age (34%). Aceidents were more frequent in the street (35.1 %) than at horne (18.9%) or school (13%). Falls and traffic-related aceidents were the leading cause of injury (39% and 21.2%, respectively). Two hundred and thirty-five (15.7%) had a Pediatric Trauma Score::; 8. Fifty of these sustained multiple trauma (33 %) (Injury Severity Scorẽ 15). Musculoskeletal and head trauma were the most frequent injuries (48.5% and 42.0%, respectively). Surgical or orthopedic procedures were performed in 906 patients (56.5 %). The average Jength of stay was 4.5 days (range 1 -93 days). Functional impairment in children older than 4 years of age was found in 413 children (33.3 %). We encountered 7 deaths in the 1500 patients, or an overall mortality of 0.5%. These 7 deaths were only seen in the I.S.S.~15 group (50 patients) with 14% mortality. Conclusions: The goals of this Registry are to estabJish the epidemiology of our injured pediatric population, to review patient care, to deveJop prevention programs and to compare results with other centers so that potential deficieneies can be corrected.• Key words: Pediatric Trauma -Registry -Epidemiology Resume Objectifs: Developper le premier registre des traumatismes pediatriques espagnol pour appreeier Jes differents aspects des traumatismes dans notre population pediatrique. Methodes:Eur

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