Spectrum of neuroradiological manifestations in primary hemophagocytic lymphohistiocytosis: a comparative study of EBV-induced versus non-EBV-induced forms in 75 genetically confirmed pediatric cases

OBJECTIVES

Hemophagocytic lymphohistiocytosis (HLH) is a rare and life-threatening condition affecting young children. It is potentially triggered by Epstein-Barr virus (EBV). This study describes the neuroradiological features observed in 75 children with genetically confirmed primary HLH, comparing EBV-induced with non-EBV-induced HLH forms.

METHODS

Brain MRIs between 2007 and 2021 from 75 children with HLH according to the 2004 Histiocyte Society criteria and with a confirmed HLH-related mutation, were retrospectively reviewed by two pediatric neuroradiologists blinded to EBV status and to mutation status. At diagnosis, 17 children with EBV viremia above a threshold of 1000 copies/mL were included in the EBV-induced HLH group. The remaining 58 patients were included in the non-EBV-induced HLH group.

RESULTS

Of the 75 children initially included, 21 had abnormal MRI (21/75 (28%); 9/17 in the EBV-induced HLH group and 12/58 in the non-EBV-induced HLH group). All patients with abnormal MRI had neurological symptoms. Abnormal MRIs showed white matter lesions; the posterior fossa was affected in all but one case. There was no significant difference between groups regarding the localization or morphology of white matter lesions. The striatum was more frequently affected in the EBV-induced HLH group (8/9 (89%) versus 1/12 (8%), p = 0.00037). All lesions, whether in the white matter or in the basal ganglia, presented increased ADC values on diffusion weighted imaging (DWI).

CONCLUSION

In this study of 75 children with genetically confirmed HLH, only children with neurological signs had abnormal brain MRI. Bilateral striatum involvement suggested an EBV-induced form of HLH.

KEY POINTS

• In children with genetically proven HLH, only those with neurological signs did have brain abnormalities at MRI. • All patients with abnormal brain MRI had multiple white matter lesions with increased ADC values, including in the posterior fossa in almost all cases. • Basal ganglia and in particular the striatum were bilaterally and symmetrically affected in almost all EBV-induced HLH patients, in contrast to the non-EBV-induced HLH patients.

[Late steroid-induced ocular hypertension after intravitreal dexamethasone implants: A series of 20 cases]

INTRODUCTION

Steroid-induced ocular hypertension (OHT) occurs in approximately one third of cases after dexamethasone implant (DEXi) injection. Among these, more than one fifth occur after the third DEXi intravitreal injection (IVI). Our goal was to analyze the clinical profiles of these late responders.

MATERIAL AND METHODS

A real-life, retrospective, observational study was conducted to assess demographic characteristics and intraocular pressure (IOP) responses in late responders (IOP ≥ 21mmHg, n DEXi ≥ 4). The following parameters were analyzed: IOP 2 months after IVI and number of glaucoma medications needed. The IOP response compared to baseline was defined as low (< +6mmHg), moderate (≤ +15mmHg) or high (> 15mmHg).

RESULTS

Late steroid-induced OHT occurred in 20.8% of cases. Twenty eyes (18 patients) were included. The mean duration of follow-up was 3.8±1.9 years. They received a mean number of 9.5±4.2 IVI. The first OHT peak, measured at 25.3±3.2mmHg (21-31), occurred after 6.8±2.3 IVI. Approximately 65% of OHT spikes occurred between the fourth and sixth IVI; 35% occurred later. At maximum, 1.7±1.0 glaucoma medications and 0.75±0.79 SLT procedures were required to control the OHT, with no filtering surgery required. The ratio of "low," "moderate," and "high" responders was 5%, 85% and 10% respectively.

CONCLUSION

Late steroid-induced OHT occurs after at least 3 DEXi in one fifth of multi-injected patients, requiring long-term IOP monitoring. This case series identifies mostly moderate responder profiles, whose IOP rise often remains well-controlled with medical management or laser treatment (SLT).

Biological differences between FIM2 and FIM3 fimbriae of Bordetella pertussis: not just the serotype

INTRODUCTION

Bordetella pertussis still circulates worldwide despite vaccination. Fimbriae are components of some acellular pertussis vaccines. Population fluctuations of B. pertussis fimbrial serotypes (FIM2 and FIM3) are observed, and fim3 alleles (fim3-1 [clade 1] and fim3-2 [clade 2]) mark a major phylogenetic subdivision of B. pertussis.

OBJECTIVES

To compare microbiological characteristics and expressed protein profiles between fimbrial serotypes FIM2 and FIM3 and genomic clades.

METHODS

A total of 19 isolates were selected. Absolute protein abundance of the main virulence factors, autoagglutination and biofilm formation, bacterial survival in whole blood, induced blood cell cytokine secretion, and global proteome profiles were assessed.

RESULTS

Compared to FIM3, FIM2 isolates produced more fimbriae, less cellular pertussis toxin subunit 1 and more biofilm, but auto-agglutinated less. FIM2 isolates had a lower survival rate in cord blood, but induced higher levels of IL-4, IL-8 and IL-1β secretion. Global proteome comparisons uncovered 15 differentially produced proteins between FIM2 and FIM3 isolates, involved in adhesion and metabolism of metals. FIM3 isolates of clade 2 produced more FIM3 and more biofilm compared to clade 1.

CONCLUSION

FIM serotype and fim3 clades are associated with proteomic and other biological differences, which may have implications on pathogenesis and epidemiological emergence.

Revealing Large-Scale Homogeneity and Trace Impurity Sensitivity of GaAs Nanoscale Membranes

III-V nanostructures have the potential to revolutionize optoelectronics and energy harvesting. For this to become a reality, critical issues such as reproducibility and sensitivity to defects should be resolved. By discussing the optical properties of molecular beam epitaxy (MBE) grown GaAs nanomembranes we highlight several features that bring them closer to large scale applications. Uncapped membranes exhibit a very high optical quality, expressed by extremely narrow neutral exciton emission, allowing the resolution of the more complex excitonic structure for the first time. Capping of the membranes with an AlGaAs shell results in a strong increase of emission intensity but also in a shift and broadening of the exciton peak. This is attributed to the existence of impurities in the shell, beyond MBE-grade quality, showing the high sensitivity of these structures to the presence of impurities. Finally, emission properties are identical at the submicron and submillimeter scale, demonstrating the potential of these structures for large scale applications.

Ketamine alters cortical integration of GABAergic interneurons and induces long-term sex-dependent impairments in transgenic Gad67-GFP mice

Ketamine, a non-competitive N-methyl-D-aspartate (NMDA) antagonist, widely used as an anesthetic in neonatal pediatrics, is also an illicit drug named Super K or KitKat consumed by teens and young adults. In the immature brain, despite several studies indicating that NMDA antagonists are neuroprotective against excitotoxic injuries, there is more and more evidence indicating that these molecules exert a deleterious effect by suppressing a trophic function of glutamate. In the present study, we show using Gad67-GFP mice that prenatal exposure to ketamine during a time-window in which GABAergic precursors are migrating results in (i) strong apoptotic death in the ganglionic eminences and along the migratory routes of GABAergic interneurons; (ii) long-term deficits in interneuron density, dendrite numbers and spine morphology; (iii) a sex-dependent deregulation of γ-aminobutyric acid (GABA) levels and GABA transporter expression; (iv) sex-dependent changes in the response to glutamate-induced calcium mobilization; and (v) the long-term sex-dependent behavioral impairment of locomotor activity. In conclusion, using a preclinical approach, the present study shows that ketamine exposure during cortical maturation durably affects the integration of GABAergic interneurons by reducing their survival and differentiation. The resulting molecular, morphological and functional modifications are associated with sex-specific behavioral deficits in adults. In light of the present data, it appears that in humans, ketamine could be deleterious for the development of the brain of preterm neonates and fetuses of addicted pregnant women.

Transient expression of somatostatin receptors in the brain during development

The study of somatostatin receptors by means of autoradiography in tissue sections revealed high densities of binding sites in the immature central nervous system. In rat cerebral cortex, the receptors are present in the intermediate zone and in association with cells migrating through the cortical plate. Somatostatin receptors in the intermediate zone of fetuses and in the cortical plate of postnatal rats exhibit high and low affinities respectively for the somatostatin analogue MK 678. In the rat cerebellum, the external granule cell layer, a germinal matrix containing interneuron precursors, contains a high density of receptors. These receptors exhibit high affinity for MK 678 throughout the period of cell multiplication. In granule cell cultures from eight-day-old rats, MK 678, octreotide and somatostatin are able to inhibit cAMP formation induced by forskolin or pituitary adenylyl cyclase-activating polypeptide. Somatostatin reduces the intracellular Ca2+ concentration in cultured granule cells; this response desensitizes rapidly. These results suggest that the somatostatin receptors in the external granule cell layer are type 2 receptors (sstr2). A low density of receptors with low affinity for MK 678 was also detected in the external granule cell layer and in the granule cell layer of neonatal rats. In adult rats the cerebellum is devoid of somatostatin receptors. These observations indicate that somatostatin probably exerts morphogenetic activities through different receptor types in several structures of the central nervous system.

Role of tissue-plasminogen activator (t-PA) in a mouse model of neonatal white matter lesions: interaction with plasmin inhibitors and anti-inflammatory drugs

Ibotenic acid injected intracerebrally over a broad dose range to 5-day-old mice induces cystic white matter (WM) lesions that mimic periventricular leukomalacia (PVL) of preterm infants. With both low (0.1 mug) and high (5 mug) ibotenic acid doses, tissue-plasminogen activator (t-PA) is involved in cyst formation. Subsequent cyst growth depends on high doses. We evaluated the effects of human recombinant tissue-plasminogen activator (hrt-PA), plasmin inhibitors (tranexamic acid, alpha2-antiplasmin, and aprotinin), and anti-inflammatory drugs (betamethasone, NS-398) in wild-type and t-PA(-/-) mice given high-dose or low-dose ibotenic acid. Intracerebral hrt-PA induced WM cystic lesions in t-PA(-/-) mice and had an additive effect when co-injected with high-dose ibotenic acid. Plasmin inhibitors reduced lesion growth in wild-type mice given high-dose, but not low-dose, ibotenic acid but had no effect in t-PA(-/-) mice. Similarly the anti-inflammatory drugs betamethasone and NS-398 (a cyclooxygenase 2 and NFkappaB inhibitor) were neuroprotective in wild-type animals exposed to high-dose, but not low-dose, ibotenic acid. Thus, the t-PA-dependent effect of low-dose ibotenic acid on cyst formation appeared independent from plasmin activity or inflammation. Conversely, a t-PA-dependent inflammatory process occurred with high-dose ibotenic acid. Potential strategies for PVL in preterm neonates may include fibrinolytic monitoring for prevention and anti-inflammatory agents for treatment.

[Disseminated tuberculosis and profound thrombopenia]

Thrombocytopenia within the context of disseminated tuberculosis can lead to complications requiring rapid treatment. Although the origin is generally central, thrombocytopenia can arise from an immune disorder. We hereby report a case of disseminated tuberculosis associated with thrombocytopenia, which required, in addition to antituberculosis therapy initiated before bacteriological proof, corticosteroid treatment and multiple platelet transfusions. The discovery of anti-platelet antibodies along with the success of immunomodulator therapy confirmed the auto-immune origin of this thrombocytopenia.

Ontogenic study of the influence of tissue plasminogen activator (t-PA) in neonatal excitotoxic brain insult and the subsequent microglia/macrophage activation

Intracerebral injections of ibotenic acid in neonatal mice produced white and gray matter lesions that mimic some aspects of the acquired cerebral injuries observed in human newborns (i.e. periventricular leukomalacias in preterm newborns and post-ischemic cortical necrosis in at term infants). We have evaluated the effects of tissue plasminogen activator inactivation (t-PA-/-) on the effects of ibotenic acid (0.01-20 microg), and on F4/80 labeling of microglia/macrophages at different stages. Three ontogenic periods have been identified. In mice injected the day of birth, postnatal (P) day 0, ibotenic acid induced neuronal migration disorders together with low local microglial activation in wild-type and t-PA-/- mice. In P2 and P5 mice, ibotenic acid induced diffuse microglial activation in the whole cortex and subcortical areas; e.g. caudate nucleus and septum. In wild-type mice, cystic lesions of the white matter were consistently observed, surrounded by macrophages. In t-PA-/- mice, noncystic lesions filled of macrophages were more frequent than cysts. Macrophages were virtually absent in the gray matter. White and gray matter lesions were reduced in t-PA-/- mice. The plasmin inhibitor aprotinin reduced white and gray matter lesions only in wild-type mice injected with high ibotenic acid doses (2.5-5 microg). During this period, a transient F4/80 immunoreactive cell population was detected in the cingulum. At P10, the salient lesion characteristic was a large gray matter lesion containing macrophage accumulation. Microglial activation was confined to the injection site in the white matter. t-PA-/- mice showed reduced lesion size under high doses (>5 microg) of ibotenic acid. Similarly, aprotinin diminished the lesion in wild-type animals exposed to 10 microg ibotenic acid. These data demonstrate that t-PA and microglia do not actively participate in the migration disorders induced in P0 mice. Conversely, t-PA was implicated in cyst formation in older (P2-P10) mice, and in their subsequent growth. t-PA was also involved in GM lesions, probably through an inflammatory process involving macrophages.

Methylphenidate and MK-801, an N-methyl-d-aspartate receptor antagonist: shared biological properties

Methylphenidate (MPH), a dopamine reuptake inhibitor, is used increasingly to treat attention deficit and hyperactivity disorders in children. Given that dopaminergic mechanisms, contribute to the structural and functional maturation of brain circuitry, consideration of the potential influence of MPH in disrupting such processes seems warranted. Following a similar logic regarding the relevance of glutamate neurotransmission in mediating aspects of brain maturation, we and others have previously utilized in vivo and in vitro studies of the developing rodent brain to establish that MK-801, an N-methyl-d-aspartate (NMDA) receptor antagonist has both neuroprotective and pro-apoptotic actions. In this study we used a neonatal murine model of excitotoxin-induced cortical injury to compare such actions between MPH and MK-801, and found that MPH shared some biological properties with MK-801. Specifically, both drugs were neuroprotective against excitotoxic challenge resulting in neonatal brain lesions and in vitro neuronal death, but both drugs also exacerbated programmed neural cell death. However, this profile of action was not shared by the dopamine reuptake blocker GBR-12783, a molecule which like MPH binds to and blocks the dopamine transporter, but which is structurally dissimilar to MPH, suggesting that inhibition of dopamine reuptake alone cannot explain the results from our MPH studies. The implications of our findings are that when studied in our developmental mouse model both drugs demonstrate similar capacities to be either neuroprotective or pro-apoptotic, depending on the specific biologic setting in which they act. Additional studies to identify some potential positive as well as negative consequences of exposure to these drugs during brain development in clinical settings are warranted.

The hydroxyanilide fenhexamid, a new sterol biosynthesis inhibitor fungicide efficient against the plant pathogenic fungus Botryotinia fuckeliana (Botrytis cinerea)

Fenhexamid, a recently developed botryticide, is shown here to inhibit sterol biosynthesis. When the fungus Botryotinia fuckeliana was grown in the presence of fenhexamid, the ergosterol content was reduced, and three 3-keto compounds, 4 alpha-methylfecosterone, fecosterone and episterone, accumulated, suggesting an inhibition of the 3-keto reductase involved in C-4 demethylation. Thus, fenhexamid belongs to a new, promising class of sterol biosynthesis inhibitors not previously used in agriculture or in medicine.

Pseudomonas fluorescens as a potential pathogen: adherence to nerve cells

In order to determine the infectious potential of the psychrotrophic bacterium Pseudomonas fluorescens, a species closely related to the opportunistic pathogen P. aeruginosa, we investigated the binding activity of this bacterium on primary cultures of rat neonate cortical neurons and glial cells, adrenal paraneurons and NG108-15 neuroblastoma cells. Incubated at concentrations of 10(6) and 10(8) CFU/mL, P. fluorescens MF37 exhibited a high binding activity on neurons in the same range as that of P. aeruginosa PAO1. A significant, but lower, adherence of P. fluorescens was also detected on glial cells and adrenal paraneurons. In contrast, when P. fluorescens MF37 or P. aeruginosa PAO1 were incubated with neuroblastoma cells, no binding was observed. In neurons, the association of P. fluorescens with the plasma membrane occurred both on neurites and cell body. Leakage of the cytoplasmic content was frequently noted. Studies performed using the fluorescent probe Hoechst 33258 revealed that in 10% of neurons, P. fluorescens induced the appearance of densely stained clusters of DNA that was typical of an early step of apoptosis. In glial cells exposed to P. fluorescens, marked changes in the morphology of the nucleus, including fragmentation into lobular structures and aggregation of DNA, were also reminiscent of the existence of a possible apoptotic mechanism. Taken together, these results reveal that P. fluorescens can bind to nerve cells and affect their physiology and, in agreement with recent clinical observations, suggest that P. fluorescens could behave as a pathogen.

Central role of microglia in neonatal excitotoxic lesions of the murine periventricular white matter

Periventricular leukomalacia (PVL) is the main cause of neurologic handicap in pre-term infants. The understanding of cellular and molecular mechanisms leading to white matter damage is critical for development of innovative therapeutic strategies for PVL. The pathogenesis of PVL remains unclear but possibly involves glutamate excitotoxicity as an important molecular pathway. We previously described a neonatal mouse model of excitotoxic white matter lesion mimicking human PVL. In the present study, we used this experimental tool to investigate the cellular populations and the glutamate receptor subtypes involved in excitotoxic white matter lesions. Combined immunohistochemical, electron microscopic, and cell death detection data revealed that microglial activation and astrocytic death were the primary responses of white matter to excitotoxic insult. In vitro experiments suggested that microglia activated by ibotenate released soluble factors that kill astrocytes. The use of selective agonists and antagonists of glutamate receptors revealed that N-methyl-D-aspartate (NMDA) receptor activation was essential and sufficient to produce cystic white matter lesions. NMDA receptor immunohistochemistry labeled microglial cells in the neonatal periventricular white matter. The developing white matter displayed a window of sensitivity to excitotoxic damage that was paralleled by the transient presence of NMDA receptor-expressing white matter cells. Assuming that similar pathophysiologic mechanisms are present in human pre- term infants, microglia and NMDA receptors could represent key targets for treatment of PVL.

Neuronal migration disorder in Zellweger mice is secondary to glutamate receptor dysfunction

Disorders of neuronal migration in cerebral cortex are associated with neurological impairments, including mental retardation and epilepsy. Their causes and pathophysiology remain largely unknown, however. In patients with Zellweger disease, a lethal panperoxisomal disorder, and in mice lacking the Pxr1 import receptor for peroxisomal matrix proteins, the absence of peroxisomes leads to abnormal neuronal migration. Analysis of Pxr1-/- mice revealed that the migration defect was caused by altered N-methyl-D-aspartate (NMDA) glutamate receptor-mediated calcium mobilization. This NMDA receptor dysfunction was linked to a deficit in platelet-activating factor, a phenomenon related to peroxisome impairment. These findings confirm NMDA receptor involvement in neuronal migration and suggest a link between peroxisome metabolism and NMDA receptor efficacy.

Identification of multiple somatostatin receptors in the rat somatosensory cortex during development

The present study was aimed at identifying somatostatin receptor subtypes on the basis of their ligand-binding properties in the rat somatosensory cortex during fetal and postnatal development. Characterization of somatostatin-binding sites was performed in individual cortical layers by using three radioligands and eight competitors with known selectivities for the five somatostatin receptor subtypes. Binding sites sensitive to sst2-selective ligands were detected with high densities in the intermediate zone of the fetal cortex. From embryonic day 21 to 21 days postnatal (P21), mixed populations of receptors were detected in the cortical plate and emerging layers I-VI. Putative sst2 receptors were detected throughout the entire period but displayed different affinities for somatostatin and analogs, and a different sensitivity to GTP, depending on the developmental stage and the cortical layer considered. High densities of binding sites exhibiting characteristics of the sst1, sst3/5, and sst4 receptor subtypes were observed from P4 to P7, P7 to P14, and P7 to P21, respectively. In addition, each type of site exhibited a particular distribution pattern across the cortical layers that varied during the development. In the adult cortex, binding sites with sst1 and sst2 receptor characteristics were predominant. This study provides evidences of developmental expression windows of four sst receptor subtypes in selected areas of the rat cerebral cortex.

[Late revealing of congenital diaphragmatic hernia: diagnostic difficulties]

Two patients, aged four and six months, with congenital diaphragmatic hernias, and who presented outside of the neonatal period, are reported. Clinical presentation was a progressive respiratory failure, and radiographic findings showed a consolidation of the left lung, associated with a pneumothorax in one and an ascites in the other. One had previous normal chest X-rays. All cases with herniated bowel showed connecting bowel segments passing through the diaphragmatic defect. All were repaired via an abdominal approach. Delay in presentation of congenital diaphragmatic hernias is not uncommon. Long-term prognosis is favourable and postoperative morbidity is minimal, despite late presentation and undesirable time delay between first sign and surgery.

Two Sibling Species of the Botrytis cinerea Complex, transposa and vacuma, Are Found in Sympatry on Numerous Host Plants

ABSTRACT Strains of Botrytis cinerea (the anamorph of Botryotinia fuckeliana) were collected from 21 different plant species around vineyards in the Champagne region (France). Strains were analyzed using three new polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) markers that were found by SWAPP (sequencing with arbitrary primer pairs), in addition to 15 other markers (PCR-RFLP, transposable elements, and resistance to fungicides). The markers revealed a high degree of genetic diversity and were used to investigate population structure. The two sympatric species transposa and vacuma, previously identified on grapes in these vineyards, were also detected on many of the plant species sampled. A new type of strain was also detected, having only the transposable element Boty. We did not detect any differentiation between strains from different organs or locations, but the prevalences of transposa and vacuma were significantly different on the different host plants. Fungicide resistance frequencies were significantly different in transposa and vacuma species. This study confirms that B. cinerea is a complex of sibling species and shows that the sibling species occur sympatrically on many host plants. However, the two species seemed to have different pathogenic behaviors. These findings contradict the traditional view of B. cinerea as a clonal population without specialization.

Transient expression of somatostatin sst2 receptors in rat cerebellar nuclei during development

Adult rat cerebellar nuclei contain a single population of [125I][Leu8,D-Trp22,Tyr25]somatostatin-28 binding sites characterized as sst1 receptors. In the present study, we have investigated the evolution of somatostatin receptors in rat cerebellar nuclei during development by means of quantitative autoradiography on tissue sections. The binding of [125I][Leu8,D-Trp22,Tyr25]somatostatin-28, observed in the primordium of the medial cerebellar nuclei at embryonic day 17, reached a maximum at postnatal day 7 or 10 in the different nuclei. Thereafter, the density of binding sites gradually decreased to the adult level. Competition studies were performed using the somatostatin analogues CH-288 and MK-678 as specific sst1 and sst2 ligands, respectively. Partial inhibition of the radioligand binding by CH-288 and MK-678 revealed the presence of a predominant population of sst1 from embryonic day 19-28 day postnatal and a minor population of sst2 receptors. The use of [125I]MK-678 as a radioligand confirmed the presence of a transient population of sst2 receptors, suggesting that somatostatin could act on rat cerebellar nuclei via sst1 and/or sst2 receptors during development.

Somatostatin binding sites in the white matter of the developing human brainstem: inverse relationship with the myelination process

The ontogeny of somatostatin binding sites was studied in eight fiber tracts of the human lower brainstem in 18 fetuses and infants aged from 21 weeks postconceptional to 6 months postnatal, and in two adults. The study was performed by means of quantitative autoradiography using [125I-Tyr0,DTrp8]somatostatin-14 as a radioligand. For all structures examined, the highest densities of binding sites were detected in the younger stages and the density of sites decreased during development. These results reveal the existence of a close inverse relationship between the density of somatostatin receptors and the myelination process in the fiber tracts of the human brainstem.

Increased density of somatostatin binding sites in respiratory nuclei of the brainstem in sudden infant death syndrome

Sudden infant death syndrome is the primary cause of mortality in children aged one to six months in industrialized countries. Although the etiology of this syndrome is still unknown, subtle abnormalities in the neuronal circuitry involved in the control of respiratory activity are suspected. Since stereotaxic administration of somatostatin in the brainstem of rat and cat produces fatal apnea, we have compared the densities of somatostatin binding sites in the respiratory centers of 11 cases of sudden infant death syndrome and six control infants without neuronal disease. The density of binding sites was measured in 17 structures of the pons and medulla oblongata by means of quantitative in vitro autoradiography using iodinated [Tyr0,D-Trp8]somatostatin-14 as a radioligand. The density of somatostatin binding sites was significantly higher in the medial and lateral parabrachial nuclei in the sudden infant death syndrome group than in the control group. In six other nuclei, the median of the receptor density was higher in the sudden infant death syndrome group than the maximum values measured in the control group. The presence of high concentrations of somatostatin binding sites in several respiratory nuclei of the brainstem in approximately half of the sudden infant death syndrome victims suggests that the decrease in receptor density that normally occurs during ontogeny was delayed in these infants. In particular, the high level of somatostatin binding sites in the medial and lateral parabrachial nuclei of sudden infant death syndrome suggests that the delayed maturation of these receptors may be associated with a deficit of the hyperventilatory response to hypoxia.

[Endoscopes in urology: disinfection, sterilization, labeling and tracking. Circulars and decrees. Modes of application and commentary. The Committee of Infectious Diseases of the French Association of Urology. Congressional forum UFA--Paris, November 1996. DGS Circular 20 October 1997]

Administrative texts published in 1995, 1996 and 1997, have reinforced materiovigilance and impose disinfection precautions for endoscopes. The steps of disinfection of non-sterilizable endoscopes are: preliminary treatment, rinsing, actual disinfection, final rinsing, storage (see: Progrès en Urologie, 1997, 7, 505-507). Each procedure from collection of the endoscope until storage must be defined by written standard operating procedures validated by CLIN. The risk of transmission of Creutzfeld-Jakob disease requires autoclaving, which is only possible, at the present time, with the most recent rigid endoscopes. Until disinfection has become generalized, the traceability of endoscopes (labelling, utilization files) must be established on the model recommended for haemovigilance (circular of 02/04/96).

RFLP markers show genetic recombination in Botryotinia fuckeliana (Botrytis cinerea) and transposable elements reveal two sympatric species

Molecular markers revealed that Botryotinia fuckeliana (the teleomorph of Botrytis cinerea), a haploid, filamentous, heterothallic ascomycete, contained a large amount of intrapopulation genetic variation. The markers were used to determine the mode of reproduction and the population structure of this fungus. We did not detect any differentiation between isolates from different organs, collection dates, varieties of grape, or locations in the Champagne region of France, but two unexpected sympatric populations were identified. One group of isolates (transposa) contained the transposable elements Boty and Flipper; the other (vacuma) did not. These groups differed from one another for all the other markers. RFLP markers showed that there was genetic recombination in both groups of isolates. We conclude that there are two sympatric populations of B. fuckeliana in Champagne. One species (transposa) seems to be local and well adapted, while the other one (vacuma) is presumably a heterogeneous migrant population.

des-AA-1,2,5[D-Trp8, IAmp9]somatostatin-14 allows the identification of native rat somatostatin sst1 receptor subtype

Somatostatin exerts multiple activities by interacting with at least five different receptor subtypes (sst[1-5]). The affinity of des-AA(1,2,5)-[D-Trp8, IAmp9]somatostatin-14 (CH-275) was studied by competition experiments using the non-selective radioligand [125I][Leu8, D-Trp22, Tyr25]somatostatin-28 in areas of the rat brain and pituitary known to express identified receptor subtypes. In the cerebellar nuclei and cerebral cortex, which possess the somatostatin sst1 receptor subtype, CH-275 exhibited a moderate affinity (IC50: 10-50 nM). Conversely, in the hippocampus, immature cerebellum and pituitary which contain different subsets of receptors mRNAs (sst[2-5]), the IC50 values were > 1 microM. These data indicate that CH-275 is an appropriate ligand for the identification of native rat somatostatin sst1 receptor subtype.

Tracheobronchopathia osteochondroplastica presenting at the time of a difficult intubation

Tracheobronchopathia osteochondroplastica (TO) is a rare and usually benign disorder affecting the trachea and occasionally the bronchi. We describe the case of a 46-year-old woman who was discovered to have TO at the time of a difficult intubation. This case was also unusual since the patient had presented no previous symptoms despite the presence of extensive endotracheal and bronchial lesions. The incidence of TO appears to be underestimated in the literature in view of the fact that it is usually benign. However, a more accurate estimate of its true prevalence may become available through the use of bronchoscopy and computerized tomographic scanning.

Differential expression of multiple somatostatin receptors in the rat cerebellum during development

The present study describes the expression pattern of somatostatin receptor genes during the development of rat cerebellum. Characterization of somatostatin receptors was carried out by binding studies using receptor subtype-selective ligands in the germinative epithelium and granule cell layer of the cerebellum from postnatal day 4 (P4) to P21 and in granule cell cultures. Quantitative reverse transcription-PCR carried out for the five receptor subtype mRNAs in cerebellar extracts showed that sst1 mRNAs are predominant at the end of gestation. A transient high expression of the sst2 gene was observed from P7 to P14. In parallel, high levels of binding sites sensitive to sst2 ligands were detected in the granule cell germinative epithelium and in granule cell cultures. sst3 mRNAs rapidly increased from P14 and became the predominant form at P21, but respective binding sites were not detected. Whereas sst4 mRNA levels were generally low, those of sst5 were nearly undetectable. Reverse transcription-PCR carried out in granule cell cultures revealed the relative abundance of sst mRNAs as follows: sst2 > sst1 > sst3 = sst4. sst5 mRNA was undetectable. The results show the expression of four somatostatin receptor genes, but only three receptors (sst1, sst4, and mainly sst2) were detected as binding sites during cerebellar development.

Ontogeny of somatostatin binding sites in respiratory nuclei of the human brainstem

The ontogeny of somatostatin binding sites was studied in 16 respiratory nuclei of the human brainstem, from 19 postconceptional weeks to 6 months postnatal, by quantitative autoradiography using [(125)I-Tyr0,DTrp8]S14 as a radioligand. In the early gestational stages (19-21 postconceptional weeks), moderate to high concentrations of [(125)I-Tyr0,DTrp8]S14 binding sites were found in all nuclei, the highest density being measured in the locus coeruleus. From 19 weeks of fetal life to 6 months postnatal, a decrease in the density of labeling was observed in all nuclei. The most dramatic reduction in site density (80-90%) was found in the ventral part of the nucleus medullae oblongata lateralis and in the nucleus paragigantocellularis lateralis. A 70-80% decrease was detected in the dorsal part of the nucleus tractus solitarius, the nucleus nervi hypoglossi, the ventral part of the nucleus medullae oblongatae centralis, the nucleus ambiguus, the nucleus paragigantocellularis dorsalis, and the nucleus gigantocellularis, and a 60-70% decrease in the nucleus parabrachialis medialis, the ventrolateral and ventromedial parts of the nucleus tractus solitarius, and the nucleus praepositus hypoglossi. A 50-60% decrease was observed in the caudal part of the nucleus tractus solitarius, the nucleus dorsalis motorius nervi vagi, and the nucleus parabrachialis lateralis, whereas in the nucleus locus coeruleus, the concentration of recognition sites decreased by only 30%. The profiles of the decrease in site density differed in the various structures. In the majority of the nuclei, a gradual diminution of binding density was observed either throughout the developmental period studied or mainly during fetal life. Conversely, in two nuclei, i.e., the nucleus parabrachialis lateralis and the locus coeruleus, an abrupt decrease occurred around birth. The differential decrease in the density of somatostatin binding sites observed in respiratory nuclei during development, together with the observation that microinjection of somatostatin in some of these nuclei causes ventilatory depression and apnea, strongly suggests that the somatostatinergic systems of the human brainstem are involved in the maturation of the respiratory control.

Somatostatin does not affect multiplication of granule cells in the rat cerebellum

Somatostatin receptor are transiently expressed by immature granule cells of rat cerebellum. The effects of somatostatin and octreotide on cell proliferation were studied in cultured cerebellar explants from 10-day-old rats. Cell multiplication was measured using [3H]thymidine incorporation and flow cytometric analysis of cell cycle parameters. [3H]Thymidine incorporation occurred exclusively in neuroblasts of the external granule cell layer in the presence of insulin (1 microM). The labeling index, the length of the S phase, and the potential doubling time were similar in vivo and in explants. Octreotide (10(-12) to 10(-6)M) had no effect on [3H]thymidine incorporation in cerebellar explants. In addition, somatostatin and octreotide did not modify the proportion of cells in the S, G0-G1, and G2-M phases. The present results demonstrate that somatostatin does not affect cell multiplication in neurons of the external granule cell layer.

Distribution of somatostatin receptors in the adult human brainstem

The neuropeptide somatostatin is widely distributed in the central nervous system of rat and human. Somatostatin-containing neurons are particularly abundant in the hypothalamus, the cerebral cortex and the limbic system. Somatostatin is also present in a number of discrete structures in the brainstem and spinal cord. The localization of somatostatin receptors provides valuable information regarding the possible roles of the peptide in the brain. In the present study, we have investigated the precise distribution of somatostatin binding sites in the human lower brainstem by quantitative autoradiography, using [125I- Tyr0,DTrp8]S14 as a radioligand. The tissues were collected from two individuals, aged 50 and 67 years, who had no antecedent of neurological disorders. The binding of the radioligand was visualized in 73 distinct anatomical regions of the medulla and pons and quantified by computer-assisted image analysis. Somatostatin binding sites were present in sensory nuclei, the highest densities being observed in the trigeminal complex (spinalis oralis and interpolaris) and in the nucleus (N.) tractus solitarii. Moderate to low densities of binding sites were detected in the N. vestibularis medialis and spinalis, and in the N. nervus trigemini sensibilis principalis. Many relay nuclei of the ascending somatosensory pathways contained moderate to high densities of binding sites: the inferior olivary complex, the N. arcuatus and the N. praepositus hypoglossi. Binding sites were also present in several motor nuclei such as the N. nervi hypoglossi, the N. dorsalis motorius nervi vagi, the N. nervi facialis and the N. nervi abducentis. Moderate to low concentrations of binding sites were detected in nuclei related to the reticular formation including the N. raphae pallidus, the N. parabrachialis and the N. supratrochlearis. The N. locus coeruleus exhibited a very high concentration of somatostatin binding sites in both individuals. The present data, together with previous studies on the distribution of somatostatin-immunoreactive fibers in the human brainstem, suggest that somatostatin may be involved in (i) sensory processes including vestibular sensitivity, somatosensoriality and proprioception, (ii) sleep-waking cycle and arousal and (iii) control of various neurovegetative functions including regulation of cardiovascular and respiratory activities as well as gastric acid secretion.

Anatomical distribution of somatostatin receptors in the brainstem of the human fetus

The distribution of somatostatin binding sites was studied in the pons and medulla oblongata of three human fetuses (gestional ages 26, 28 and 30 weeks). The study was carried out by in vitro quantitative autoradiography using either [125I-Tyr0,D-Trp8]somatostatin-14 or [125I-Tyr11]somatostatin-14 as radioligands. Somatostatin binding sites were observed in a number of nuclei subserving sensory, motor or integrative functions within the pons and medulla. In addition, discrete tracts also contained significant amounts of binding sites. Among structures involved in sensory processes, a high density of binding sites (40-60 fmol/ mg wet tissue) was measured in the dorsal cochlear nucleus and in the nucleus tractus spinalis trigemini caudalis. Moderate to high levels of binding sites (30-40 fmol/mg wet tissue) were detected in the other sensory cranial nerve nuclei. A moderate density of sites (15-30 fmol/mg wet tissue) was measured in most motor nuclei, the highest concentrations being observed in the dorsal motor nucleus of the vagus nerve, the facial nucleus, the hypoglossal nucleus and the nucleus ambiguus. The griseum pontis and the nucleus corporis pontobulbaris contained very high (> 60 fmol/mg wet tissue) and high concentrations of somatostatin binding sites, respectively, while the other relay nuclei contained low to moderate levels of binding. In monoaminergic nuclei, very high and moderate to high concentrations of somatostatin binding sites were measured in the nucleus locus coeruleus and in its dorsal subnucleus, respectively. Moderate densities of sites were detected in the ventral subnucleus of the nucleus locus coeruleus and in the different parts of the raphe. In the white matter, low levels of binding were measured in the inferior cerebellar peduncle, the lateral and median lemnisci and the tractus solitarius. Conversely, moderate to high concentrations of somatostatin binding sites were measured in the median and superior cerebellar peduncles. The pyramis contained a very high density of recognition sites. A marked heterogeneity in the density of binding sites was observed within a few structures particularly in the medial accessory olivary of nucleus and the medial longitudinal fasciculus. Selective ligands were used to determine the pharmacological profile of the [Tyr11]somatostatin-14 binding sites in various brainstem regions. In the dorsal cochlear nucleus and the pyramis, all somatostatin binding sites belonged to the SSA subtype. Conversely, in the lateral paragigantocellular nucleus, all somatostatin binding sites belonged to the SSB subtype. The other regions studied contained various proportions of SSA and SSB subtypes. In conclusion, the present study shows that high concentrations of somatostatin receptors are present in many regions of the human fetus brainstem. These data support the concept that somatostatin could be involved in the maturation of brain structures.

Characterization of the somatostatin receptor subtype in a bronchial carcinoid tumor responsible for Cushing's syndrome

Small ACTH-secreting carcinoid tumors responsible for Cushing's syndrome are often difficult to localize using available radiological investigations. Somatostatin receptors have been found in about 90% of carcinoid tumors studied, leading to a new approach for the localization of tumors or metastasis by using radiolabeled somatostatin analogs. We report a case of Cushing's syndrome due to an ACTH-secreting bronchial carcinoid tumor, completely suppressible with octreotide treatment and evidenced by body scintigraphy with 111In-labeled pentreotide. After removal, which led to patient recovery, the tumor was studied in vitro. In situ hybridization, using a complementary DNA probe, revealed POMC messenger ribonucleic acid in a subpopulation of tumor cells. These cells were labeled by immunochemistry using an antiserum directed against ACTH. Confocal laser scanning microscopy analysis showed that the ACTH-immunoreactive peptide was sequestered in secretory granules. Autoradiographic labeling using [125I-Tyrzero,D-Trp8]somatostatin-14 demonstrated the presence of somatostatin-binding sites in the whole tumor tissue. The relative affinities of various selective somatostatin analogs and the ability of GTP to inhibit radioligand binding suggested that the receptor expressed in the tumor cells belonged to the SSTR-2 subtype.

Pharmacological characterization of somatostatin receptors in rat cerebellar nuclei

Rat cerebellar nuclei contain somatotropin release-inhibiting factor (SRIF) receptors that bind [125I][Leu8,D-Trp22,Tyr25]SRIF-28 but do not bind [125I][Tyr0,D-Trp8]SRIF-14. The aim of the present study was to investigate the pharmacological profile of these receptors by means of binding experiments on tissue sections and quantitative autoradiography. Competition experiments indicated the presence of a single class of [125I][Leu8,D-Trp22,Tyr25]SRIF-28 binding sites in the lateral cerebellar nuclei, showing similar affinities for SRIF-14 and SRIF-28, but low affinity for short-chained analogs. The IC50 values for somatostatin analogs to compete with the binding of [125I][Leu8,D-Trp22,Tyr25]SRIF-28 in the lateral cerebellar nuclei ranked as follows: [Leu8,D-Trp22,Tyr25]SRIF-28 approximately SRIF-14 approximately SRIF-28 < CGP 23996 < D-Phe-Phe-Phe-D-Trp-Lys-Thr-Phe-Thr-NH2 (BIM 23052) < SMS 201-995 approximately N-Ahep-(7-10)SRIF-14-Bzl << MK 678 < D-Phe-Phe-Tyr-D-Trp-Lys-Val-Phe-D-Nal-NH2 (BIM 23056) < D-Phe-c[Cys-Tyr-D-Trp-Lys-Abu-Cys]Nal-NH2 (NC 8-12). Optimum binding of [125I][Leu8,D-Trp22,Tyr25]SRIF-28 did not require divalent cations, and was partly inhibited by guanosine 5' triphosphate. It appears from this study that the rat lateral cerebellar nuclei contain a pure population of receptors exhibiting the same binding characteristics as the recently cloned sstr1 somatostatin receptor. These nuclei could thus provide a useful model in which to investigate the characteristics of native sstr1.

Quantitative autoradiographic study of somatostatin receptors in the adult human cerebellum

The evolution of the distribution and density of somatostatin receptors was studied in the human cerebellum during ageing. The brain tissues were collected 3-30 h after death from 20 individuals aged from 28 to 86 years. In vitro autoradiographic experiments were performed on blocks of vermis and of right and left cerebellar hemispheres, using [125I-Tyr0,DTrp8]S14 as a radioligand. In the vermis, the mean concentrations of somatostatin receptors in the molecular layer, the granular layer and the medulla were 140 +/- 9, 150 +/- 22 and 61 +/- 13 fmol/mg proteins, respectively. For each individual, the density of sites in the two lateral lobes was similar. The mean concentrations of somatostatin receptors in the molecular layer, the granular layer and the medulla were 152 +/- 17, 190 +/- 20 and 56 +/- 11 fmol/mg proteins, respectively. The mean level of somatostatin receptors and the type of distribution of the receptors were not correlated to the age of the patients. Different distribution patterns of somatostatin receptors were noted among the patients studied. In the majority of patients (11/20), the density of somatostatin receptors was higher in the granular layer than in the molecular layer. Conversely, in four patients, the density of somatostatin receptors was higher in the molecular layer. The other individuals exhibited similar concentrations of somatostatin receptors in the granular and molecular layers. The present study indicates that the adult human cerebellum contains a high concentration of somatostatin receptors (> 100 fmol/mg proteins) and that the receptor level does not decline during ageing.(ABSTRACT TRUNCATED AT 250 WORDS)

Localization and characterization of PACAP receptors in the rat cerebellum during development: evidence for a stimulatory effect of PACAP on immature cerebellar granule cells

Pituitary adenylate cyclase-activating polypeptide (PACAP) and its receptors are abundant in the brain and particularly in the cerebellum of adult rats. In contrast, the occurrence of PACAP binding sites has not been investigated during ontogenesis. The aim of the present study was to determine the distribution and biochemical characteristics of PACAP binding sites in the rat cerebellum during postnatal development, and to examine the effect of PACAP on immature cerebellar granule cells. Autoradiographic studies revealed that PACAP binding sites are transiently expressed in a germinative matrix of the cerebellar cortex, the external granule cell layer, and in the medulla, from postnatal days 8 to 25. A population of PACAP binding sites persisted in the internal granule cell layer in the mature cerebellum. Emulsion-coated cytoautoradiography, performed on cultured immature granule cells from eight-day-old rat cerebellum, demonstrated that transient PACAP binding sites are expressed by cerebellar immature granule cells. Biochemical characterization of binding revealed the occurrence of two classes of PACAP recognition sites exhibiting, respectively, high (Kd = 0.39 +/- 0.08 nM) and low (Kd = 21.2 +/- 9.4 nM) affinity for PACAP27. The two naturally occurring forms PACAP38 and PACAP27 were equipotent in competing for [125I]PACAP27 binding. In contrast, the [Des-His1]PACAP38 analog was eight times less efficient and vasoactive intestinal polypeptide only induced weak displacement of the binding. Exposure of cultured immature granule cells to PACAP27 resulted in a dose-dependent stimulation of the production of cAMP, indicating that PACAP binding sites represent authentic receptors positively coupled to adenylate cyclase. These results show that PACAP receptors are actively expressed in the cerebellum of rats during postnatal development. The presence of functional PACAP receptors in the external granule cell layer suggests that PACAP may play a role in the control of proliferation and/or differentiation of granule cells.

Quantitative autoradiography of somatostatin receptors in the rat limbic system

The distribution of somatostatin receptors (SRIF-R) was analyzed in the limbic system of the adult rat by in vitro autoradiography with [125I-Tyr0,DTrp 8]S14 as a radioligand. Precise quantification of the density of binding sites, at 0.2 mm intervals throughout the different areas revealed a marked heterogeneity of labeling in most structures. In particular, SRIF-R were concentrated in the basal (104.4 +/- 3.3 fmol/mg proteins) and basolateral amygdaloid nuclei (94.8 +/- 4.3 fmol/mg proteins), and in the nucleus of the lateral olfactory tract (121.6 +/- 2.4 fmol/mg proteins), whereas moderate densities were detected in the amygdalo-hippocampal nucleus (76.4 +/- 2.8 fmol/mg proteins). The medial (41.3 +/- 1.9 fmol/mg proteins) and the central (24.0 +/- 1.4 fmol/mg proteins) amygdaloid nuclei contained lower SRIF-R concentrations. It appears from these observations, in the light of the anatomical pathways of the amygdala, that intra-amygdalian SRIF-containing neurons project to the amygdalo-hippocampal nucleus, and that SRIF-R in the basolateral complex are the target of afferents from limbic cortical areas. SRIF-R were detected at different levels of the hippocampal formation but their distribution was more restricted than that of SRIF-containing fibers. The maximal density of sites was detected in the ventral and dorsal parts of the subiculum (115.0 +/- 3.4 and 87.0 +/- 2.8 fmol/mg proteins, respectively) and in the parasubiculum (100.1 +/- 5.4 fmol/mg proteins). In Ammon's horn, the stratum oriens and stratum radiatum of the CA1 field were the only sites enriched in SRIF-R (74.1 +/- 2.0 and 74.6 +/- 1.9 fmol/mg proteins, respectively). The apparent lack of receptors in the pyramidal cell layer indicated that, in Ammon's horn, SRIF is involved in intra-hippocampal communication. Low levels of receptors were found in the hippocampal CA2 and CA3 fields. SRIF-R in the dentate gyrus were mainly concentrated in the molecular layer (57.3 +/- 1.2 fmol/mg proteins). A very high density of sites was also observed in the entorhinal cortex (up to 123.1 +/- 1.5 fmol/mg proteins). A clear mismatch between SRIF and SRIF-R was detected in the septum and the habenula. In the profound layers of the cingulum and retrosplenial cortex, a heterogeneous distribution of SRIF-R was observed. High concentrations of sites were detected in the rostral zone of the cingulate cortex (93.4 +/- 2.0 fmol/mg proteins) while the posterior cingulate only exhibited moderate concentrations of sites (66.5 +/- 0.7 fmol/mg proteins).(ABSTRACT TRUNCATED AT 400 WORDS)

Localization of somatostatin receptors in subcortical visual centres of the rat during development. Effect of neonatal enucleation on the expression of somatostatin receptors

Previous studies have shown that both somatostatin and somatostatin receptors are expressed in the visual system of the rat early during ontogenesis, suggesting that somatostatin plays a role in the development of visual functions. In the present study, we have examined the localization of somatostatin receptors in the lateral geniculate nucleus and the superior colliculus of the developing rat by autoradiography, and we have investigated the effect of neonatal enucleation on the density of receptors in young and adult animals. In the dorsal part of the lateral geniculate nucleus, somatostatin receptors were transiently expressed during the first two postnatal weeks, while in the ventral part, receptors were detected during the whole developmental period. In the superior colliculus, a high density of somatostatin receptors was measured before eye opening; thereafter the concentration of receptors decreased markedly in the whole structure to reach the adult level. Uni- or bilateral enucleation one day after birth only induced minor modifications of the expression of somatostatin receptors in the lateral geniculate nucleus and colliculus. Conversely, bilateral enucleation caused a significant reduction of the density of receptors in the inter-geniculate leaflet and the medial zone of the ventral lateral geniculate nucleus. Taken together, these results indicate that, in the relay nuclei, somatostatin receptors are not borne by retinal afferents. The presence of high densities of receptors in the lateral geniculate nucleus and superior colliculus during development suggests that somatostatin exerts trophic activities in these structures. In adult rat, somatostatin is probably involved in the modulation of visual information in the superior colliculus, but not in the dorsal lateral geniculate nucleus.

Dose-effect and evidence of escape of inhibition after indomethacin treatment in a synchronized model of bone resorption

We previously showed that cyclooxygenase inhibition by indomethacin (7.5 mg/kg/d) prevented resorption in a model of synchronized remodeling. In the present paper, we (i) tested the effectiveness of three doses of indomethacin (2, 4, 7.5 mg/kg/d) in this model, and (ii) verified whether indomethacin action was sustained in time. For that purpose, on day 6 after induction, untreated controls were compared with a group treated for six days with indomethacin (7.5 mg/kg/d), and an interrupted treatment group (4 days indomethacin + 2 days free). Indomethacin inhibited resorption and total number of osteoclasts in a dose-dependent manner. In the second experiment in the discontinued group, the resorption and total number of osteoclasts were similar to sham-treated animals. Indomethacin was still effective in the continuous treatment group; however, resorption was distinctly higher than in the rats treated for four days. These data indicate that despite cyclooxygenase inhibition, another metabolic pathway started resorption. The stoppage of prostanoid inhibition permitted the rapid and complete restoration of resorption.

Somatostatin receptors are expressed by immature cerebellar granule cells: evidence for a direct inhibitory effect of somatostatin on neuroblast activity

Somatostatin and somatostatin receptors are transiently expressed in the immature rat cerebellar cortex but virtually undetectable in the cerebellum of adults. Although somatostatin binding sites have been visualized during the postnatal period in the external granule cell layer, the type of cell that expresses somatostatin receptors has never been identified; thus, the potential function of somatostatin in the developing cerebellum remains unknown. In the present study, we have taken advantage of the possibility of obtaining a culture preparation that is greatly enriched in immature cerebellar granule cells to investigate the presence of somatostatin receptors and the effect of somatostatin on intracellular messengers on cerebellar neuroblasts in primary culture. Autoradiographic labeling revealed the occurrence of a high density of binding sites for radioiodinated Tyr-[D-Trp8]somatostatin-(1-14) on 1-day-old cultured immature granule cells. Saturation and competition studies showed the existence of a single class of high-affinity binding sites (Kd = 0.133 +/- 0.013 nM, Bmax = 3038 +/- 217 sites per cell). Somatostatin induced a dose-dependent inhibition of forskolin-evoked cAMP formation (ED50 = 10 nM), and this effect was prevented by preincubation of cultured immature granule cells with pertussis toxin. Somatostatin also caused a marked reduction of intracellular calcium concentration. These results show the presence of functionally active somatostatin receptors on immature granule cells. Our data suggest the possible involvement of somatostatin in the regulation of proliferation and/or migration of neuroblasts during the development of the cerebellar cortex.