Dynamic spatiotemporal synaptic integration in cortical neurons: neuronal gain, revisited

Gain modulation is a ubiquitous phenomenon in cortical neurons, providing flexibility to operate under changing conditions. The prevailing view is that this modulation reflects a change in the relationship between mean input and output firing rate brought about by variation in neuronal membrane characteristics. An alternative mechanism is proposed for neuronal gain modulation that takes into account the capability of cortical neurons to process spatiotemporal synaptic correlations. Through the use of numerical simulations, it is shown that voltage-gated and leak conductances, membrane potential, noise, and input firing rate modify the sensitivity of cortical neurons to the degree of temporal correlation between their synaptic inputs. These changes are expressed in a change of the temporal window for synaptic integration and the range of input correlation over which response probability is graded. The study also demonstrates that temporal integration depends on the distance between the inputs and that this interplay of space and time is modulated by voltage-gated and leak conductances. Thus, gain modulation may reflect a change in the relationship between spatiotemporal synaptic correlations and output firing probability. It is further proposed that by acting synergistically with the network, dynamic spatiotemporal synaptic integration in cortical neurons may serve a functional role in the formation of dynamic cell assemblies.     

SKAP-55 regulates integrin adhesion and formation of T cell-APC conjugates

Src kinase-associated phosphoprotein of 55 kDa (SKAP-55; encoded by SCAP1) is a T cell adaptor protein of unknown function that contains a pleckstrin homology and an SH3 domain. Here we show that SKAP-55 regulates integrin-mediated adhesion and conjugate formation between T cells and antigen-presenting cells (APCs). SKAP-55 enhances adhesion to fibronectin and intercellular adhesion molecule-1 (ICAM-1), colocalizes with actin at the T cell-APC synapse and promotes the clustering of lymphocyte-associated antigen-1 (LFA-1). Enhanced conjugation is comparable to that induced by adhesion and degranulation-promoting adaptor protein (ADAP), a binding partner of SKAP-55, and is abrogated by deletion of the SKAP-55 SH3 domain. Conjugate formation is accompanied by the translocation of SKAP-55 to membrane rafts, an event that is regulated by both LFA-1 and T cell receptor ligation. Our findings identify a mechanism by which SKAP-55 modulates T cell responses to antigen.     

Dracunculosis or Medina worm filariasis. Apropos of 2 cases

We report two patients with calcified Medina worms. With the considerable increase in international travel and exchange, it is important that radiologists in non-endemic areas be familiar with this type of parasitic calcification.     

SMN2‐deletion in childhood‐onset spinal muscular atrophy

We report a 27‐year‐old man with an apparently new syndromic form of progressive erosive arthropathy and contractures of small and large joints associated with mild epiphyseal changes, normal vertebrae, and generalized osteopenia. The patient had a characteristic craniofacial appearance, dermatological abnormalities, and normal intelligence. The head was large with frontal bossing. The face was elongated with malar hypoplasia, thin upper lip, prominent lower jaw, high arched palate, dental malocclusion, and prominent ears with absent ear lobules. Dermatological abnormalities included malar erythema and facial telangiectasia together with multiple nevi and lentigenes all over the body. Pseudorheumatoid arthropathy, spondyloarthropathy, and Borrone dermatocardioskeletal syndrome were considered in the differential diagnosis and were excluded. Also, no similar cases have been found in POSSUM or the London Dysmorphology databases. © 2001 Wiley‐Liss, Inc.     

Hyperplastic callus formation in osteogenesis imperfecta type V: follow-up of three generations over ten years

Hyperplastic callus (HPC) formation is a prominent feature of osteogenesis imperfecta (OI) type V; however, little is known about its long-term outcome. In this case report we describe the occurrence, appearance and course of a femoral HPC in a patient with OI type V during 10 years of follow-up. Radiographs of HPC in this child were compared and contrasted with HPC formation in the femur of his father and paternal grandfather, who also were affected with OI type V. This case report makes it clear that HPC can lead to significant morbidity, not only in the acute phase but also long term as a result of residual alteration in bone architecture. This study was supported by the Shriners of North America and the Fonds de la Recherche en Santé du Québec.     

CT and ultrasound imaging of pelvic rhabdomyosarcoma in children

We have retrospectively reviewed the radiographic and clinical features of 56 cases of pelvic rhabdomyosarcoma seen in three Pediatric Hospitals between 1960 and 1986. There were 35 boys and 21 girls. The study aimed at better defining the role played by the various imaging techniques in the investigation of these tumors. The role of diagnostic radiology is the detection and delineation of the primary tumor, its local spread and distant metastases at the time of diagnosis and on follow-ups. Intravenous urography (IVU) and to a lesser extent barium enema (BE) and cystography (VCUG) were used even after the availability of ultrasonography (US) and computed tomography (CT). These two modalities have only partly replaced the traditional radiographic techniques. All patients seen or followed after 1977 (28 patients) had both US and CT examinations. We have focused our discussion on these relatively new imaging modalities namely US and CT. Magnetic resonance was not utilized in any patient in this series. US was by far the best imaging technique available for lesions of the urinary bladder and those invading the bladder wall in children as it was possible to visualize, measure and follow these tumors. Scrotal US was used to confirm the clinical diagnosis of a paratesticular mass. CT showed to best advantage the tumour and its relationship to pelvic organs, musculature and bones.     

Traumatised ischial apophysis (report of six cases)

Six boys with traumatic ischial apophysis are reported. Two cases were diagnosed as stress apophysis and four as apophyseolysis. Two of our patients were referred to the hospital as malignant bone tumours--Ewing sarcoma and osteosarcoma.