Karla S. Kent

An accessory olfactory pathway in Lepidoptera: the labial pit organ and its central projections in Manduca sexta and certain other sphinx moths and silk moths

SummaryIn the hawkmoth, Manduca sexta, the third segment of each labial palp contains a pit, which houses a densely packed array of sensilla. We have named this structure the labial pit organ (LPO). The sensilla within the pit are typical of olfactory receptors, characterized by a grooved surface, wall pores, and pore tubules. Axons arising from receptor cells that innervate these sensilla project bilaterally to a single glomerulus in each antennal lobe. We have compared this central projection with that in three other species of Manduca (M. quinquemaculata, M. dilucida, and M. lanuginosa) and in the silkmoths Antheraea polyphemus and Bombyx mori. A bilateral projection to a single glomerulus in each antennal lobe is present in all cases. We suggest that the LPO serves as an accessory olfactory organ in adult Lepidoptera.

Herpesviruses in Abscesses and Cellulitis of Endodontic Origin

Acute apical abscesses and cellulitis are severe endodontic diseases caused by opportunistic bacteria with possible coinfection with latent herpesviruses. The objectives of this study are to identify herpesviruses, including human cytomegalovirus (HCMV), Epstein-Barr virus (EBV), herpes simplex virus-1 (HSV-1), and Varicella zoster virus (VZV) in patients (n = 31) presenting with acute apical abscesses and cellulitis of endodontic origin. Primary and nested polymerase chain reaction (PCR) was conducted using virus-specific primers and DNA isolated from cell-free abscess fluid. From patients exhibiting concurrent spontaneous pain (n = 28), nine abscesses contained HCMV, two abscesses contained EBV, one abscess contained HSV-1, and no abscesses contained VZV. Control PCR using genomic or recombinant templates showed detection limits to a single genomic copy of HCMV, 100 genomic copies for EBV, and 1 to 10 copies for HSV-1 with no cross-amplification between herpesviral DNA targets. Nested PCR was required for detection of herpesviral DNA in the abscess specimens, indicating that these viruses were present in low copy number. Filtration of abscess specimens and virus transfer experiments using human fibroblastic MRC-5 cells confirmed the presence of HCMV particles in several abscess specimens. We conclude that herpesviruses are present but not required for the development of acute apical abscesses and cellulitis of endodontic origin.

Remodeling of the peripheral processes and presynaptic terminals of leg motoneurons during metamorphosis of the hawkmoth, Manduca sexta

During metamorphosis of the hawkmoth, Manduca sexta, the muscles, cuticular structures, and most sensory neurons of the larval thoracic legs are replaced by new elements in the adult legs. The thoracic leg motoneurons, however, survive the loss of the larval muscles and persist to innervate new targets in the imaginal legs. Here we have used biocytin staining, immunocytochemistry, and confocal microscopy to follow the fates of the peripheral processes and presynaptic terminals of the leg motoneurons. Although the most distal processes of the motor nerves retract following the degeneration of larval leg muscles, the axon terminals always retain close association with the muscle remnants and the anlagen of the new adult muscles. As the imaginal muscles differentiate and enlarge, the motor terminals expand to form adult presynaptic terminals. An antibody to the presynaptic protein, synaptotagmin, revealed its localization to the terminal varicosities in both larval and adult stages but distribution within pre‐terminal branches during adult development. Electrophysiological methods revealed that functional neuromuscular transmission first occurs quite early during metamorphosis, before the differentiation of contractile elements in the muscle fibers.

Sensory organs of the thoracic legs of the moth Manduca sexta.

SummaryThe thoracic legs of the moth Manduca sexta acquire a new form and develop a new complement of sensory organs and muscles during metamorphosis from larva to adult. Because of our interest in the reorganization of neural circuitry and the acquisition of new behaviors during metamorphosis, we are characterizing sensory elements of larval and adult legs so that we may determine the contribution of new sensory inputs to the changes in behaviors. Here we describe the sensory structures of adult legs using scanning electron microscopy to view the external sensilla and cobalt staining to examine innervation by underlying sensory neurons. We find that, in contrast to larval legs, the adult legs are covered with a diverse array of sensilla. All three pairs of thoracic legs contain scattered, singly innervated scalelike sensilla. Campaniform sensilla occur singly or in clusters near joints. Hair plates, consisting of numerous singly innervated hairs, are also present near joints. Other more specialized sensilla occur on distal leg segments. These include singly innervated spines, two additional classes of singly innervated hairs, and three classes of multiply innervated sensilla. Internal sensory organs include chordotonal organs, subgenual organs, and multipolar joint receptors.

Development of the labial pit organ glomerulus in the antennal lobe of the moth Manduca sexta: The role of afferent projections in the formation of identifiable olfactory glomeruli

Iterated neuropil modules called glomeruli are characteristic of primary olfactory centers in both vertebrates and invertebrates. To gain insight into the developmental mechanisms underlying the formation of such structured, organized neuropil, we have examined the development of an identified glomerulus in the olfactory (antennal) lobe of the moth Manduca sexta. The labial pit organ glomerulus (LPOG) receives bilateral sensory projections from the labial pit organs in the labial palps of the mouthparts, while other glomeruli in the antennal lobe receive unilateral projections from the antenna. Here, we chronicle the development of the LPOG under normal and perturbed conditions. Our findings suggest that the sensory axons of the labial pit organ, like those of the antenna, induce and shape growth of interneuronal arborizations, but specific features of interneuronal arborizations such as the relative position of glomerular arborizations within the antennal lobe are independent of both classes of afferent innervation. Labial pit organ axons and antennal axons exhibit a high degree of specificity for their respective target regions, independent of the presence or absence of the other class of afferent axon or the route taken to the antennal lobe. Specification of glomerular position is intrinsic to the antennal lobe rather than a consequence of competition between afferent axons.

Jelly belly trans‐synaptic signaling to anaplastic lymphoma kinase regulates neurotransmission strength and synapse architecture

In Drosophila, the secreted signaling molecule Jelly Belly (Jeb) activates anaplastic lymphoma kinase (Alk), a receptor tyrosine kinase, in multiple developmental and adult contexts. We have shown previously that Jeb and Alk are highly enriched at Drosophila synapses within the CNS neuropil and neuromuscular junction (NMJ) and postulated a conserved intercellular signaling function. At the embryonic and larval NMJ, Jeb is localized in the motor neuron presynaptic terminal whereas Alk is concentrated in the muscle postsynaptic domain surrounding boutons, consistent with anterograde trans‐synaptic signaling. Here, we show that neurotransmission is regulated by Jeb secretion by functional inhibition of Jeb–Alk signaling. Jeb is a novel negative regulator of neuromuscular transmission. Reduction or inhibition of Alk function results in enhanced synaptic transmission. Activation of Alk conversely inhibits synaptic transmission. Restoration of wild‐type postsynaptic Alk expression in Alk partial loss‐of‐function mutants rescues NMJ transmission phenotypes and confirms that postsynaptic Alk regulates NMJ transmission. The effects of impaired Alk signaling on neurotransmission are observed in the absence of associated changes in NMJ structure. Complete removal of Jeb in motor neurons, however, disrupts both presynaptic bouton architecture and postsynaptic differentiation. Nonphysiologic activation of Alk signaling also negatively regulates NMJ growth. Activation of Jeb–Alk signaling triggers the Ras‐MAP kinase cascade in both pre‐ and postsynaptic compartments. These novel roles for Jeb–Alk signaling in the modulation of synaptic function and structure have potential implications for recently reported Alk functions in human addiction, retention of spatial memory, cognitive dysfunction in neurofibromatosis, and pathogenesis of amyotrophic lateral sclerosis.

Remodeling of motor terminals during metamorphosis of the moth Manduca sexta: expression patterns of two distinct isoforms of Manduca fasciclin II.

During metamorphosis of the moth Manduca sexta, the neuromuscular system of the thoracic legs is reorganized dramatically. Larval leg muscles degenerate at the end of larval life, and new adult leg muscles develop during the ensuing pupal stage. Larval leg motoneurons persist, but undergo substantial remodeling of central and peripheral processes. As part of our on‐going investigation of mechanisms underlying the remodeling of motor terminals, we have used antisera generated against Manduca‐specific isoforms of the homophilic adhesion molecule fasciclin II (MFas II) to label motor terminals during metamorphosis. Antisera generated against the glycosyl‐phosphatidylinositol (GPI) ‐linked isoform of MFas II (GPI‐MFas II) labeled the motor nerves at all stages and seemed to be associated with glial cells ensheathing the peripheral nerves. In addition, the anti–GPI‐MFas II antisera labeled regions associated with synaptic boutons at both larval and adult stages. In contrast, antisera generated against a transmembrane isoform of MFas II (TM‐MFas II) only labeled specific neuronal processes at discrete intervals during remodeling. Identified leg motoneurons (such as the femoral depressor motoneuron) expressed detectable levels of TM‐MFas II in their peripheral processes only during phases of motor‐terminal retraction and initial stages of motor‐terminal re‐growth. Putative modulatory neurons (such as the unpaired median neurons), however, expressed TM‐MFas II in their processes during larval stages as well as during remodeling. Use of the isoform‐specific anti‐MFas II antisera provided a novel method for visualizing remodeling of motor terminals during metamorphosis and helped distinguish different components of the motor nerves and neuromuscular junction. J. Comp. Neurol. 434:69–85, 2001.

The dangers of dental devices as reported in the Food and Drug Administration Manufacturer and User Facility Device Experience Database.

BACKGROUND The authors conducted a study to determine the frequency and type of adverse events (AEs) associated with dental devices reported to the Food and Drug Administration Manufacturer and User Facility Device Experience (MAUDE) database. METHODS The authors downloaded and reviewed the dental device-related AEs reported to MAUDE from January 1, 1996, through December 31,2011. RESULTS MAUDE received a total of 1,978,056 reports between January 1, 1996, and December 31, 2011. Among these reports, 28,046 (1.4%) AE reports were associated with dental devices. Within the dental AE reports that had event type information, 17,261 reported injuries, 7,777 reported device malfunctions, and 66 reported deaths. Among the 66 entries classified as death reports, 52 reported a death in the description; the remaining were either misclassified or lacked sufficient information in the report to determine whether a death had occurred. Of the dental device-associated AEs, 53.5% pertained to endosseous implants. CONCLUSIONS A plethora of devices are used in dental care. To achieve Element 1 of Agency for Healthcare Research and Qualitys Patient Safety Initiative, clinicians and researchers must be able to monitor the safety of dental devices. Although MAUDE was identified by the authors as essentially the sole source of this valuable information on adverse events, their investigations led them to conclude that MAUDE had substantial limitations that prevent it from being the broad-based patient safety sentinel the profession requires. PRACTICAL IMPLICATIONS As potential contributors to MAUDE, dental care teams play a key role in improving the professions access to information about the safety of dental devices.

Leg proprioceptors of the tobacco hornworm, Manduca sexta: organization of central projections at larval and adult stages.

Organization of the central neuropil of the insect ganglion is characterized in part by a modality‐specific layering of afferent projections. This organization has been particularly well described for the central projections of thoracic leg sensory neurons of adult locusts, crickets, and flies. Tactile sensory neurons project into a ventral layer of neuropil, while proprioceptive sensory neurons project into an intermediate layer of neuropil. In order to determine whether a modality‐specific layering exists in the CNS of larval Manduca sexta, we have examined the projections of sensory neurons innervating one class of putative proprioceptors, the campaniform sensilla, of the larval metathoracic legs. We find that campaniform sensory neurons of the larval legs have central projection patterns that generally distinguish them from each other and from the tactile sensory neurons. The campaniform projections, however, are not completely segregated from tactile projections in ventral layers of neuropil, as has been described in other insects. By contrast, the projections of campaniform sensory neurons from the adult legs are more extensive and elaborate than their larval counterparts and dramatically different from projections of nearby adult tactile hairs, having extensive arborizations in more dorsal regions of neuropil while those of tactile sensory neurons are restricted to very ventral layers of neuropil. This difference in organization of the afferent projections in larval and adult ganglia may reflect different functions of the leg sensilla and different functions of the legs at the two stages.

Original ContributionsPatient SafetyThe dangers of dental devices as reported in the Food and Drug Administration Manufacturer and User Facility Device Experience Database

BACKGROUND The authors conducted a study to determine the frequency and type of adverse events (AEs) associated with dental devices reported to the Food and Drug Administration Manufacturer and User Facility Device Experience (MAUDE) database. METHODS The authors downloaded and reviewed the dental device-related AEs reported to MAUDE from January 1, 1996, through December 31,2011. RESULTS MAUDE received a total of 1,978,056 reports between January 1, 1996, and December 31, 2011. Among these reports, 28,046 (1.4%) AE reports were associated with dental devices. Within the dental AE reports that had event type information, 17,261 reported injuries, 7,777 reported device malfunctions, and 66 reported deaths. Among the 66 entries classified as death reports, 52 reported a death in the description; the remaining were either misclassified or lacked sufficient information in the report to determine whether a death had occurred. Of the dental device-associated AEs, 53.5% pertained to endosseous implants. CONCLUSIONS A plethora of devices are used in dental care. To achieve Element 1 of Agency for Healthcare Research and Qualitys Patient Safety Initiative, clinicians and researchers must be able to monitor the safety of dental devices. Although MAUDE was identified by the authors as essentially the sole source of this valuable information on adverse events, their investigations led them to conclude that MAUDE had substantial limitations that prevent it from being the broad-based patient safety sentinel the profession requires. PRACTICAL IMPLICATIONS As potential contributors to MAUDE, dental care teams play a key role in improving the professions access to information about the safety of dental devices.