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The adaptor proteins (APs) are a family of five heterotetrameric complexes with important functions in vesicle trafficking. While the roles of APs 1-3 are broadly established, comparatively little is known about AP-4 and AP-5. Current evidence suggests that AP-4 mediates TGN to endosome transport of specific cargo proteins, such as the amyloid precursor protein APP, and that it is involved in basolateral sorting in polarized cells. Furthermore, several independent studies have reported human patients with mutations in AP-4 genes. AP-4 deficiency causes severe intellectual disability and progressive spastic para- or tetraplegia, supporting an important role for AP-4 in brain function and development. The newly discovered AP-5 complex appears to be involved in endosomal dynamics; its precise localization and function are still unclear. Intriguingly, AP-5 deficiency is also associated with progressive spastic paraplegia, suggesting that AP-5, like AP-4, plays a fundamental role in neuronal development and homeostasis. The unexpected phenotypic parallels between AP-4 and AP-5 patients may in turn suggest a functional relationship of the two APs in vesicle trafficking.

Held this autumn on the beautiful Cote d'Azur, the first joint meeting of the BSDB and SFBD provided delegates with the perfect informal setting for discussion spanning a broad cross-section of Developmental Biology. Participants' interests were diverse, ranging from the implementation of genome-wide approaches aimed at identifying all the molecular components of cell proliferation, signalling, patterning, and morphogenesis, to those engaged in capturing mesmerising glimpses of the minute and intricate workings of the cell. The meeting considered a wide spectrum of model organisms, including the simple plant Arabidopsis, the invertebrates Dictyostelium, Caenorhabditis elegans, and Drosophila melanogaster, the ascidian Ciona intestinalis, and the vertebrates Xenopus, zebrafish, chick, and mouse. Such a diverse approach served to highlight both similarities and differences in the molecular mechanisms that govern embryonic development among different species. Here, we highlight a few aspects of the meeting that illustrate this point.

Current evidence suggests that the anterior segment of the vertebrate hindbrain, rhombomere 1, gives rise to the entire cerebellum. It is situated where two distinct developmental patterning mechanisms converge: graded signalling from an organising centre (the isthmus) located at the midbrain/hindbrain boundary confronts segmentation of the hindbrain. The unique developmental fate of rhombomere 1 is reflected by it being the only hindbrain segment in which no Hox genes are expressed. In this study we show that ectopic FGF8 protein, a candidate for the isthmic organising activity, is able to induce and repress gene expression within the hindbrain in a manner appropriate to rhombomere 1. Using a heterotopic, heterospecific grafting strategy we demonstrate that rhombomere 1 is able to express Hox genes but that both isthmic tissue and FGF8 inhibit their expression. Inhibition of FGF8 function in vivo shows that it is responsible for defining the anterior limit of Hox gene expression within the developing brain and thereby specifies the extent of the r1 territory. Previous studies have suggested that a retinoid morphogen gradient determines the axial limit of expression of individual Hox genes within the hindbrain. We propose a model whereby activation by retinoids is antagonised by inhibition by FGF8 in the anterior hindbrain to set aside the territory from which the cerebellum will develop.

The adaptor proteins (APs) are a family of five heterotetrameric complexes with important functions in vesicle trafficking. While the roles of APs 1-3 are broadly established, comparatively little is known about AP-4 and AP-5. Current evidence suggests that AP-4 mediates TGN to endosome transport of specific cargo proteins, such as the amyloid precursor protein APP, and that it is involved in basolateral sorting in polarized cells. Furthermore, several independent studies have reported human patients with mutations in AP-4 genes. AP-4 deficiency causes severe intellectual disability and progressive spastic para- or tetraplegia, supporting an important role for AP-4 in brain function and development. The newly discovered AP-5 complex appears to be involved in endosomal dynamics; its precise localization and function are still unclear. Intriguingly, AP-5 deficiency is also associated with progressive spastic paraplegia, suggesting that AP-5, like AP-4, plays a fundamental role in neuronal development and homeostasis. The unexpected phenotypic parallels between AP-4 and AP-5 patients may in turn suggest a functional relationship of the two APs in vesicle trafficking.

The midbrain-hindbrain interface gives rise to a boundary of particular importance in CNS development as it forms a local signalling centre, the proper functioning of which is essential for the formation of tectum and cerebellum. Positioning of the mid-hindbrain boundary (MHB) within the neuroepithelium is dependent on the interface of Otx2 and Gbx2 expression domains, yet in the absence of either or both of these genes, organiser genes are still expressed, suggesting that other, as yet unknown mechanisms are also involved in MHB establishment. Here, we present evidence for a role for Notch signalling in stabilising cell lineage restriction and regulating organiser gene expression at the MHB. Experimental interference with Notch signalling in the chick embryo disrupts MHB formation, including downregulation of the organiser signal Fgf8. Ectopic activation of Notch signalling in cells of the anterior hindbrain results in an exclusion of those cells from rhombomeres 1 and 2, and in a simultaneous clustering along the anterior and posterior boundaries of this area, suggesting that Notch signalling influences cell sorting. These cells ectopically express the boundary marker Fgf3. In agreement with a role for Notch signalling in cell sorting, anterior hindbrain cells with activated Notch signalling segregate from normal cells in an aggregation assay. Finally, misexpression of the Notch modulator Lfng or the Notch ligand Ser1 across the MHB leads to a shift in boundary position and loss of restriction of Fgf8 to the MHB. We propose that differential Notch signalling stabilises the MHB through regulating cell sorting and specifying boundary cell fate.

The midbrain–hindbrain boundary (MHB) acts as an organiser/signalling centre to pattern tectal and cerebellar compartments. Cells in adjacent compartments must be distinct from each other for boundary formation to occur at the interface. Here we have identified the leucine-rich repeat (LRR) neuronal 1 (Lrrn1) protein as a key regulator of this process in chick. The Lrrn family is orthologous to the Drosophila tartan/capricious (trn/caps) family. Differential expression of trn/caps promotes an affinity difference and boundary formation between adjacent compartments in a number of contexts; for example, in the wing, leg and eye imaginal discs. Here we show that Lrrn1 is expressed in midbrain cells but not in anterior hindbrain cells. Lrrn1 is down-regulated in the anterior hindbrain by the organiser signalling molecule FGF8, thereby creating a differential affinity between these two compartments. Lrrn1 is required for the formation of MHB — loss of function leads to a loss of the morphological constriction and loss of Fgf8. Cells overexpressing Lrrn1 violate the boundary and result in a loss of cell restriction between midbrain and hindbrain compartments. Lrrn1 also regulates the glycosyltransferase Lunatic Fringe, a modulator of Notch signalling, maintaining its expression in midbrain cells which is instrumental in MHB boundary formation. Thus, Lrrn1 provides a link between cell affinity/compartment segregation, and cell signalling to specify boundary cell fate., Research highlights ►Lrrn1 is expressed in midbrain cells but not in anterior hindbrain cells. ►Lrrn1 is down-regulated in anterior hindbrain by FGF8. ►Lrrn1 creates a differential affinity between midbrain and hindbrain compartments. ►This forms a sharp compartment boundary at the midbrain–hindbrain interface. ►Lrrn1 is required for formation of the mid–hindbrain boundary.

The use of intramuscular droperidol to treat acute migraine headache has not been previously reported in the emergency medicine literature. It is a promising therapy for migraine. The authors performed a pilot review of all patients receiving droperidol for migraine in our emergency department (ED) to evaluate its efficacy. We used a retrospective case series, in a suburban ED with an annual patient census of 48,000. All patients with a discharge diagnosis of migraine headache who were treated with i.m. droperidol during a consecutive 5-month period in our ED were identified. All patients received droperidol 2.5 mg intramuscular. As per ED protocol, their clinical progress was closely followed and documented at 30 minutes after drug administration (t30). Demographic and clinical variables were recorded on a standardized, closed-question, data collection instrument. The primary outcome measurement was relief of symptoms at t30 to the point that the patient felt well enough to go home without further ED intervention (symptomatic relief). Thirty-seven patients were treated (84% female), with an ED diagnosis of acute migraine with droperidol during the study period. The mean age was 36 +/- 12 years. Analgesics had been used within 24 hours before ED presentation by 62% of patients. At t30, 30 (81%) patients had symptomatic relief, 2 (5%) felt partial relief but required rescue medication, and 5 (14%) had no relief of symptoms. Drowsiness (14%) and mild akathisia (8%) were the only adverse reactions observed following drug administration. Droperidol 2.5 mg intramuscular may be a safe and effective therapy for the ED management of acute migraine headache. Randomized, controlled trials are warranted to further validate the findings of this preliminary study.

Formation of the trochlear nerve within the anterior hindbrain provides a model system to study a simple axonal projection within the vertebrate central nervous system. We show that trochlear motor neurons are born within the isthmic organiser and also immediately posterior to it in anterior rhombomere 1. Axons of the most anterior cells follow a dorsal projection, which circumnavigates the isthmus, while those of more posterior trochlear neurons project anterodorsally to enter the isthmus. Once within the isthmus, axons form large fascicles that extend to a dorsal exit point. We investigated the possibility that the projection of trochlear axons towards the isthmus and their subsequent growth within that tissue might depend upon chemoattraction. We demonstrate that both isthmic tissue and Fgf8 protein are attractants for trochlear axons in vitro, while ectopic Fgf8 causes turning of these axons away from their normal routes in vivo. Both inhibition of FGF receptor activation and inhibition of Fgf8 function in vitro affect formation of the trochlear projection within explants in a manner consistent with a guidance function of Fgf8 during trochlear axon navigation.

The emergency department (ED) treatment of acute peripheral vertigo (APV) has not been well studied. The purpose of this study was to determine the efficacy of intramuscular (IM) droperidol vs IM dimenhydrinate, in the treatment of ED patients with APV.The study was a randomized, double-blinded clinical trial, performed at a suburban, teaching ED. A convenience sample of adult patients with symptoms and signs consistent with rigid diagnostic criteria for APV were randomized to one of two treatment groups. Patients more than 65 years of age were excluded to reduce the likelihood of diagnostic misclassification. Demographic and historical features were recorded on a standardized data form. Patients recorded their initial level (t0) of discomfort on a 10-centimeter (cm) visual analog scale (VAS). Treatment group 1 received 2.5 mg droperidol IM, while treatment group 2 received 50 mg dimenhydrinate IM. After 30 minutes (t30), patients again recorded the severity of their symptoms on the VAS. Chi-square, t-tests, and Mann-Whitney were used for statistical comparison as appropriate. All tests were two-tailed, with alpha set at 0.05. Primary outcome parameters were the mean change in VAS score from t0 to t30, and the percentage of patients in each treatment group who felt well enough to go home after t30 without further ED intervention.There were 20 patients in the droperidol group and 20 in the dimenhydrinate group. The two groups were similar with respect to mean age (40 +/- 13 years droperidol vs. 42 +/- 13 years dimenhydrinate; p = 0.6), female sex (60% vs. 50%; p = 0.7), and mean median duration of symptoms [3 (interquartile range 2-12) vs 9 (interquartile range 2-30) hours; p = 0.2]. Mean initial t0 VAS scores were 7.2 +/- 2.3 and 7.8 +/- 1.9 (p = 0.47). Both treatment groups had mean reductions in VAS scores at t30 of 3.3 [95% confidence interval (95% CI) = 2.3 to 4.3]. At t30, 42% of patients in the droperidol group and 45% of patients in the dimenhydrinate group felt well enough to go home without further ED intervention.The authors found no difference between the therapeutic efficacies of IM droperidol and dimenhydrinate for the treatment of acute peripheral vertigo.

In this article, an adjunct to a platform presentation at the Winternational 2000 Symposium, we summarize the recent findings of this group concerning the regulation and functions of FGF8 expressed at the isthmus of the developing brain. We show that several different FGF8 isoforms, ectopically expressed in midbrain or posterior forebrain, are able to mimic the proliferative and patterning functions previously attributed to the isthmus in tissue grafting studies. Moreover, we also show that FGF8 protein is sufficient to induce an ectopic isthmic organiser (Fgf-8+, Gbx2+) in anterior midbrain. We also provide evidence that isthmic FGF8 patterns anterior hindbrain, repressing Hox-a2 expression and setting aside a territory of the brain that includes the cerebellar anlage. We show that these effects of FGF8 are likely to be mediated via FGFR1 and be modulated by the putative FGF antagonist, Sprouty2, identified using a differential display screen. Finally, we provide evidence that the onset of Fgf8 expression is regulated by En1 and that its expression at the isthmus is subsequently maintained by a specific and direct interaction between rhombomere 1 and midbrain.

RESUME Abstracts / Resumes 645s / Resumes 645 © 2000 NRC Canada Roles of FGF signalling in regional specification of midbrain and anterior hindbrain Ivor Mason, David Chambers, Carol Irving, Huma Shamim, and Jennifer Walshe MRC Brain Development Programme, Centre for Developmental Neurobiology, King’s College London, New Hunt’s House, Guy’s Campus, London SE1 9RT, U.K. Axial pattern is established along the vertebrate neural tube by both vertical signals from adjacent mesoderm and planar signals from organising centres. One of the best-characterised of the latter is the midbrain-hindbrain boundary, or isthmus. Tissue grafting studies have established that the isthmus is the source of signals that impart regional identity to midbrain and anterior hindbrain. Heterotopic transplants of isthmic tissue into anterior midbrain respecify it to develop posterior midbrain morphological and molecular characteristics, grafts into posterior forebrain convert that tissue to an ectopic midbrain, while grafts into posterior hindbrain cause the development of ectopic cerebellar structures. Fibroblast growth factor 8 (Fgf8) is expressed at the isthmus in all vertebrate classes. We, and others, have shown that ectopic introduction of Fgf8 in the avian embryo is sufficient to cause anterior midbrain to be converted to a posterior character and posterior forebrain to develop as midbrain. Much of this presentation will be devoted to the roles of isthmic Fgf8 in patterning anterior hindbrain; previous reports have suggested that Fgf8 does not participatein this process. Part of the fate of the most anterior hindbrain rhombomere (r), r1, is to give rise to the cerebellum. Data will be presented to show that Fgf8 functions to establish and pattern the r1 territory, thereby setting aside tissue to form the cerebellar anlage. A differential display PCR analysis to identify r1-specific genes has identified a member of a family of intracellular antagonists of Fgf signalling, sprouty2. sprouty2 is rapidly inducible by Fgf8 and its expression domain suggests that it functions as a long range antagonist of the Fgf8 signal within the anterior hindbrain. Finally, the results of studies on regeneration of isthmic tissue will be presented which provide evidence that Fgf8 and the isthmic organiser are induced and (or) maintained by a specific interaction between midbrain and r1 involving a diffusible signal.

A meeting report from the Santa Cruz Developmental Biology Meeting, University of California at Santa Cruz, USA, July 21-25, 2000.

Purpose: The prevalence of asthma in the pediatric population is approximately 9% and the incidence of acute exacerbation in this population has been increasing. The purpose of this study was to determine if there has been a change in the pre-hospital presentation and treatment of pediatric asthma.Methods: This observational study was a retrospective consecutive case series comparing pediatric (#18 yrs) asthmatics treated and transported by an inner city EMS system over two years. (1987, 1992). Data collected included patient demographics, prehospital treatment, and evaluated diagnostic criteria used by paramedics to initiate treatment. Students t test was performed for continuous data and contingency analysis (chisquare) for non-continuous data. A Wilks stepwise discriminant analysis was performed on 1987 and 1992 data to evaluate diagnostic factors.Results: There were 407 transports in 1987 and 652 in 1992, representing a 60% increase. 237(56%) of patients received advanced life support (ALS) in 1987 and 344(53%) in 1992. Mean age of ALS patients in 1987 was 10.25 (±5.3) and was 8.03 (±2.8) in 1992 (p