Diverse physiological properties of hypoglossal motoneurons innervating intrinsic and extrinsic tongue muscles.

The mammalian tongue contains eight muscles that collaborate to ensure that suckling, swallowing, and other critical functions are robust and reliable. Seven of the eight tongue muscles are innervated by hypoglossal motoneurons (XIIMNs). A somatotopic organization of the XII motor nucleus, defined in part by the mechanical action of a neuron's target muscle, has been described, but whether or not XIIMNs within a compartment are functionally specialized is unsettled. We hypothesize that developing XIIMNs are assigned unique functional properties that reflect the challenges that their target muscle faces upon the transition from in utero to terrestrial life. To address this, we studied XIIMNs that innervate intrinsic and extrinsic tongue muscles, because intrinsic muscles play a more prominent role in suckling than the extrinsic muscles. We injected dextran-rhodamine into the intrinsic longitudinal muscles (IL) and the extrinsic genioglossus, and physiologically characterized the labeled XIIMNs. Consistent with earlier work, IL XIIMNs (n = 150) were located more dorsally within the nucleus, and GG XIIMNs (n = 55) more ventrally. Whole cell recordings showed that resting membrane potential was, on average, 9 mV more depolarized in IL than in GG XIIMNs (P = 0.0019), and the firing threshold in response to current injection was lower in IL (-31 ± 23 pA) than in GG XIIMNs (225 ± 39 pA; P < 0.0001). We also found that the appearance of net outward currents in GG XIIMNs occurred at more hyperpolarized membrane potentials than IL XIIMNs, consistent with lower excitability in GG XIIMNs. These observations document muscle-specific functional specializations among XIIMNs.NEW & NOTEWORTHY The hypoglossal motor nucleus contains motoneurons responsible for innervating one of seven different muscles with notably different biomechanics and patterns of use. Whether or not motoneurons innervating the different muscles also have unique functional properties (e.g., spiking behavior, synaptic physiology) is poorly understood. In this work we show that neonatal hypoglossal motoneurons innervating muscles that shape the tongue (intrinsic longitudinal muscles) have different electrical properties than those innervating the genioglossus, which controls tongue position.

"Conversational Advice": A mixed-methods analysis of medical residents' experiences co-managing primary care patients with behavioral health providers.

OBJECTIVE: When integrated behavioral health clinicians (IBHCs) and residents co-manage patients, residents may learn new approaches. We aimed to understand the effect of co-management on residents' behavioral health (BH) management learning. METHODS: Residents completed a web-based survey enquiring: whether co-management included a shared visit and/or face-to-face meeting with an IBHC, whether residents received feedback from the IBHC, and what they learned. Qualitative responses were coded thematically using a constant comparative method. RESULTS: Among 117 respondents (overall response rate 72%, 117/163), from five residencies recruited from 40 residencies with BH integration, residents were significantly more likely to receive feedback if they had a shared visit with the patient and an IBHC (yes 69% vs. no 33%; adjusted OR 3.0, 95% CI 1.2-7.6). Residents reported three major learning themes: interpersonal communication skills awareness, BH skills awareness, and newly adopted attitudes toward BH. Residents who received feedback were more likely to report themes of interpersonal communication skills awareness (yes 26.6% vs. no 9.4%). CONCLUSION: BH integration promotes increased feedback for residents practicing face-to-face co-management with IBHCs, and a positive influence regarding residents' attitudes and perceived skills. PRACTICAL IMPLICATIONS: Residency programs can meaningfully improve residents' learning by promoting face-to-face co-management with IBHCs.

Residents' Confidence Providing Primary Care With Behavioral Health Integration.

BACKGROUND AND OBJECTIVES: Behavioral health integration (BHI) entails integrated behavioral health clinicians (IBHCs) providing care-generally for mental health and substance abuse disorders and behavioral comorbidity- within the operational functioning of primary care. Because limited data exist regarding BHI in residency, we studied its impact on resident education by examining whether increased behavioral health (BH) co-management improved residents' perceived ability to treat BH conditions. METHODS: We included residents from internal and family medicine training programs using BHI in residents' continuity clinics and assessed the level of co-management between primary care and IBHCs and the following domains: (1) confidence in managing BH conditions, (2) barriers to BH provision, (3) perception of autonomy when working with IBHCs, (4) satisfaction with the clinic, and (5) perceived educational value of BH learning modes. RESULTS: Altogether, 117 residents participated in our survey (73.1% response rate). Residents who had co-managed ≥ five patients alongside IBHCs reported significantly higher confidence than those who had co-managed < five patients with BH conditions. The association remained significant after adjustment for residents' level of training and specialty. In rating BH learning modes, residents rated most highly active collaboration with IBHCs and observation with feedback from clinic preceptors. CONCLUSIONS: BHI training within residency enhances perceived learning and confidence in providing BH care.

Steroid hormone effects on neurons subserving behavior.

Recent advances in understanding effects of steroid hormones at the level of individual neurons have been achieved using model systems. Steroid hormone effects on dendritic morphology, synaptic function and ionic conductances have been implicated in the regulation of behavior in both vertebrates and invertebrates. Particularly exciting are studies demonstrating steroid hormone effects on specific synaptic connections and ionic currents. There also has been important progress in understanding the diversity of sites and mechanisms of hormone action, encompassing both genomic and non-genomic effects of steroids on neuronal properties.

Remodeling of the insect nervous system.

Our nervous systems and behavior are shaped by hormonally driven developmental changes that continue beyond the embryonic period. Key insights into this process have emerged from studies of the insect nervous system. During insect metamorphosis, the nervous system is remodeled through postembryonic neurogenesis, programmed cell death and the modification of persistent neurons. These changes are regulated to a large degree by gene cascades that are triggered by steroid hormones, the ecdysteroids. Current studies are attempting to reveal the molecular mechanisms involved in regulating these dramatic examples of developmental plasticity.

Neural control of leg movements in a metamorphic insect: sensory and motor elements of the larval thoracic legs in Manduca sexta.

During the metamorphosis of the hawkmoth Manduca sexta the larval thoracic legs degenerate to be replaced in the adult by legs of very different form and function. This change must be accompanied by a reorganization of the neural circuits controlling leg movements. As an initial step in the study of this reorganization we describe here the sensory and motor elements of this circuitry in the larval stage of life. Sensory neurons innervating mechanoreceptive hairs on the thoracic surface were stained individually with cobalt. Those innervating hairs on the general thoracic surface project topographically into two ventral regions of the segmental ganglia. Sensory neurons innervating leg sensilla also map topographically to the more ventral of these regions but in addition have arborizations in a midlateral region. The density of branching within this lateral "leg neuropil" is greatest for sensory neurons form sensilla on the more distal leg segments. Leg motor neurons were identified with intracellular recording and cobalt injection techniques. Those innervating muscles controlling distal leg segments have dense dendritic arbors in the lateral "leg neuropil," while motor neurons controlling more proximal segments and muscles of the ventral body wall have extensive arborizations in a dorsomedial region of the ganglion. In general, flexor motor neurons are excited by medial and inhibited by lateral leg sensilla, while the opposite is true of extensors. Distal segment motor neurons respond most strongly to sensory neurons from distal segments, thus suggesting some interaction within the lateral "leg neuropil." Thus, in the larval nervous system a highly ordered array of of sensory and motor elements underlies the specific behavioral responses of the legs to tactile stimulation.

Neural control of leg movements in a metamorphic insect: persistence of larval leg motor neurons to innervate the adult legs of Manduca sexta.

During metamorphosis of the hawkmoth Manduca sexta, the larval thoracic legs along with their associated sensory organs and muscles degenerate and new adult legs develop. The larval legs are small and relatively simple structures capable of lateral extension and medial flexion allowing them to grasp the substrate as the caterpillar crawls along. By contrast, the adult legs are used for walking with an alternating gait. They are much larger than the larval legs and articulate such that they are capable of movement in several directions. This change in form and function is accompanied by a reorganization of the neural circuits controlling leg movements. In a previous report (Kent and Levine: J. Comp. Neurol. 271:559-576, '88) we described motor neurons innervating the larval prothoracic legs, and here we describe motor neurons innervating the prothoracic legs of the adult. Using a combination of cobalt staining methods and the persistent fluorescent dye Fluoro-Gold, we have found that some, if not all, larval leg motor neurons are retained and innervate the new adult leg muscles. Moreover, we have been able to discover the fate of individual larval leg motor neurons by marking a single larval neuron with Fluoro-Gold and using a second fluorescent dye to double label the same neuron in the adult. Our results suggest that specific larval leg motor neurons innervate corresponding muscles in the adult stage, although their apparent function is significantly different. In addition, the motor neurons undergo significant remodeling of their dendritic branching patterns during metamorphosis, alterations which doubtless contribute to their new roles in adult behavior.

Remodeling of the femoral chordotonal organ during metamorphosis of the hawkmoth, Manduca sexta.

During metamorphosis of the moth, Manduca sexta, the larval legs degenerate and are replaced by adult legs with a diverse array of new sensory organs. The majority of the larval sensory neurons degenerate but some hair sensilla and chordotonal organ sensory neurons survive metamorphosis (Consoulas [2000] J. Comp. Neurol. 419:154-174). In the present study nerve-tracing techniques, birth-date labeling (5-bromodeoxyuridine), and electrophysiology were used to describe the remodeling of the femoral chordotonal organ (FCO) in the prothoracic legs. The larval FCO is composed of two scoloparia, which are associated with separate apodemes. At the onset of metamorphosis, some of the 13 larval neurons degenerate, together with the larval FCO apodemes. The remaining larval FCO sensory neurons persist in the imaginal leg to become the precursors of the adult femoral and tibial chordotonal organs respectively. Early in the pupal stage, 45 to 60 new sensory neurons are generated de novo and become associated with 6 persistent larval neurons in the imaginal femur to compose the adult FCO. Two clusters of persistent and new neurons are enclosed into two scoloparia with short apodemes that eventually become fused. In both larval and adult stages, the FCO contains units that respond phasically and others that respond tonically to femorotibial movements. Nerve activity from the FCO neurons can be recorded continuously during the remodeling of the organ. A persistent leg flexor motoneuron receives inputs from the FCO sensory neurons in both larval and adult stages, offering the opportunity to investigate the remodeling of the neural circuits underlying the proprioceptive control of the femorotibial joint.

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.

Postembryonic development of the dorsal longitudinal flight muscle and its innervation in Manduca sexta.

The neuromuscular systems of holometabolous insects must be remodeled during metamorphosis to allow striking behavioral changes, such as the acquisition of flight. The fast contracting dorsal longitudinal flight muscle (DLM) of Manduca arises from an anlage containing both remnants of specific larval dorsal body wall muscles and extrinsic myoblasts. In the mesothorax, the DLM is innervated by five persisting larval motoneurons: one in the mesothoracic and four in the prothoracic ganglion. These motoneurons innervate two slowly contracting body wall muscles in the larva. 2 days before pupation, the DLM template fibers begin to degenerate, whereas other muscles remain intact until pupation. Correspondingly, the motor terminals retract from the template fibers while they remain on other muscle fibers until pupation. Accumulation and proliferation of putative myoblasts also starts 2 days before pupation in close spatial relationship to the retracted motor tufts around the degenerating larval template fibers. Proliferation increases through the early pupal stages, and is detected within the anlage until the ninth day after pupation. 2 days after pupation, the anlage splits into five bundles, each innervated by one motoneuron. Striations occur on the seventh day after pupation when the growing motor axons reach the attachment sites. Subsequently, the muscle grows in volume and higher-order motor branches are formed. Within the central nervous system, there is dramatic regression of larval dendrites followed by growth of new dendrites as the persistent motoneurons assume their new role in flight behavior. Both central and peripheral remodeling follow similar time courses.

Fate of abdominal ventral unpaired median cells during metamorphosis of the hawkmoth, Manduca sexta.

Each of the unfused abdominal ganglia in the larval, pupal, and adult stages of the hawkmoth, Manduca sexta, has two large ventral median neurons with axons that bifurcate to innervate targets on both sides of the abdomen. Although the dendritic structures of the two neurons are similar, their axons branch to innervate distinct sets of target muscles. During metamorphosis both neurons undergo dendritic regression, followed by growth of new arborizations during adult development. The neurons must innervate different targets in the larva and adult, since many larval muscles degenerate and are replaced during metamorphosis. Both neurons were reactive with an antibody to the neuromodulatory compound, octopamine, in the larval and adult stages. Pairwise intracellular recordings in isolated nerve cords revealed spontaneous excitatory synaptic potentials that occurred in the ventral median neurons of each ganglion in an anterior-to-posterior sequence. The synaptic potentials were eliminated when the interganglionic connective was interrupted posterior to the subesophageal ganglion. The ventral median neurons were also excited by tactile stimulation of the body surface in larvae, pupae and adults.

Peripheral distribution of presynaptic sites of abdominal motor and modulatory neurons in Manduca sexta larvae.

Insect muscle fibers are commonly innervated by multiple motor neurons and efferent unpaired median (UM) neurons. The role of UM neurons in the modulation rather than rapid activation of muscle contraction (Evans and O'Shea [1977] Nature 270:257-259) suggests that their terminal varicosities may differ structurally and functionally from the presynaptic terminals of motor neurons. Furthermore, differences in the characteristics of UM neuron terminal varicosities may be correlated with functional differences among their diverse target muscles. Larval abdominal body wall muscles in the hawkmoth, Manduca sexta, consist of large, elongated fibers that are multiterminally innervated by one and occasionally two motor neurons (Levine and Truman [1985] J. Neurosci. 5:2424-2431). The fibers are also innervated by one of two efferent UM neurons that bifurcate to innervate targets on both sides of the abdomen (Pflüger et al. [1993] J. Comp. Neurol. 335:508-522). In this study, the intracellular tracer biocytin was used to identify the targets of the UM neurons and to distinguish their terminal axonal varicosities on the muscle fibers. An antiserum to the synaptic vesicle protein, synaptotagmin, was used to label synaptic vesicles, and the styryl dye FM1-43 was used to demonstrate release and recycling. Most of the abdominal muscles in a given hemisegment were found to be supplied by one of the two UM neurons. Terminal varicosities of the excitatory motor neurons were large (3-7 pm) and were found in rows of rosettes that extended to every aspect of the muscle fiber; these varicosities were designated as type I terminals. The UM neuron terminal varicosities also occupied every aspect of the fiber but were smaller (1-3 microm) and more separated from each other; these were designated as type II terminals. Both type I and type II terminals are synaptotagmin immunoreactive and, as shown by FM1-43 staining, are sites of synaptic vesicle recycling. The excitatory motor neuron terminals (type I) could easily be loaded and unloaded with FM1-43, which indicates their capacity for repeated vesicular exocytosis and recycling. In contrast, the dye could not as readily be unloaded from UM neuron terminals (type II), which may indicate that they have a slower turnover of synaptic vesicles.

Crustacean cardioactive peptide-immunoreactive neurons in the hawkmoth Manduca sexta and changes in their immunoreactivity during postembryonic development.

An antiserum against crustacean cardioactive peptide was used, in indirect immunocytochemistry on whole-mounts and Vibratome sections, to map immunoreactive neurons at various stages of postembryonic development of the hawkmoth Manduca sexta. About 90 immunoreactive neurons were identified. Many of these cells are immunoreactive at hatching and persist into the adult stage; others become immunoreactive late in postembryonic development. During adult development, transient immunoreactivity is expressed in several cells in the subesophageal and thoracic ganglia. Two sets of immunoreactive neurons are found in the protocerebrum of larvae, but only one of these sets persists into the adult stage. Paired lateral interneurons and neurosecretory neurons are segmentally repeated in the abdominal ganglia and are present from the first larval stage to the adult; the abdominal interneurons project contralaterally to arborizations in adjacent ganglia, and some ascend to tritocerebral arborizations. The abdominal neurosecretory cells, which correspond to a pair of cells reported to contain bursicon, project posteriorly to neurohemal release organs. Motor neurons of dorsal external oblique abdominal muscles become immunoreactive in the fourth larval stage. Paired median neurosecretory cells of abdominal ganglia become immunoreactive during the fifth larval stage. The immunoreactive median and lateral abdominal neurosecretory cells are a subset of a group of cells known to contain cardioactive peptides. Paired lateral neurosecretory cells of the subesophageal ganglion become immunoreactive during pupation and project to the corpora cardiaca and aorta of the adult. Many of the neurons identified here are comparable to crustacean cardioactive peptide-immunoreactive cells described previously in locusts and the mealworm beetle.

An outbreak of gram-negative bacteremia in hemodialysis patients traced to hemodialysis machine waste drain ports.

OBJECTIVE: To investigate an outbreak of gram-negative bacteremias at a hemodialysis center (December 1, 1996-January 31, 1997). DESIGN: Retrospective cohort study. Reviewed infection control practices and maintenance and disinfection procedures for the water system and dialysis machines. Performed cultures of the water and dialysis machines, including the waste-handling option (WHO), a drain port designed to dispose of saline used to flush the dialyzer before patient use. Compared isolates by pulsed-field gel electrophoresis. SETTING: A hemodialysis center in Maryland. RESULTS: 94 patients received dialysis on 27 machines; 10 (11%) of the patients had gram-negative bacteremias. Pathogens causing these infections were Enterobacter cloacae (n = 6), Pseudomonas aeruginosa (n = 4), and Escherichia coli (n = 2); two patients had polymicrobial bacteremia. Factors associated with development of gram-negative bacteremias were receiving dialysis via a central venous catheter (CVC) rather than via an arterio-venous shunt (all 10 infected patients had CVCs compared to 31 of 84 uninfected patients, relative risk [RR] undefined; P<.001) or dialysis on any of three particular dialysis machines (7 of 10 infected patients were exposed to the three machines compared to 20 of 84 uninfected patients, RR = 5.8; P = .005). E cloacae, P aeruginosa, or both organisms were grown from cultures obtained from several dialysis machines. WHO valves, which prevent backflow from the drain to dialysis bloodlines, were faulty in 8 (31%) of 26 machines, including 2 of 3 machines epidemiologically linked to case-patients. Pulsed-field gel electrophoresis patterns of available dialysis machine and patient E cloacae isolates were identical. CONCLUSIONS: Our study suggests that WHO ports with incompetent valves and resultant backflow were a source of cross-contamination of dialysis bloodlines and patients' CVCs. Replacement of faulty WHO valves and enhanced disinfection of dialysis machines terminated the outbreak.

Peptide activation of a simple neural circuit.

Pupae of the tobacco hornworm moth display a characteristic reflex response to tactile stimulation of sensory hairs located in the gin-trap. The reflex is not functional in the prepupa, but is activated abruptly as the animal enters the pupal stage by the direct action of an identified peptide hormone. The neuronal pathway between the sensory and motor neurons involved in the reflex is not direct, and the site of hormone action was localized to the connection between an interganglionic interneuron, and the motorneurons.

Breast cancer screening and compliance and evaluation of lesions.

It appears that screening mammography certainly is of value in women over age 50, and although controversy exists regarding screening of women under 50 years of age for breast cancer, the authors believe that this strategy is the most reasonable one for women 40 to 64 years of age at this time. Additionally, it is important for physicians to remember to encourage their patients to undergo cancer screening evaluation. Encouragement by physicians is an important factor in increasing cancer screening rates.

Behavioral transformations during metamorphosis: remodeling of neural and motor systems.

During insect metamorphosis, neural and motor systems are remodeled to accommodate behavioral transformations. Nerve and muscle cells that are required for larval behavior, such as crawling, feeding and ecdysis, must either be replaced or respecified to allow adult emergence, walking, flight, mating and egg-laying. This review describes the types of cellular changes that occur during metamorphosis, as well as recent attempts to understand how they are related to behavioral changes and how they are regulated. Within the periphery, many larval muscles degenerate at the onset of metamorphosis and are replaced by adult muscles, which are derived from myoblasts and, in some cases, remnants of the larval muscle fibers. The terminal processes of many larval motoneurons persist within the periphery and are essential for the formation of adult muscle fibers. Although most adult sensory neurons are born postembryonically, a subset of larval proprioceptive neurons persist to participate in adult behavior. Within the central nervous system, larval neurons that will no longer be necessary die and some adult interneurons are born postembryonically. By contrast, all of the adult motoneurons, as well as some interneurons and modulatory neurons, are persistent larval cells. In accordance with their new behavioral roles, these neurons undergo striking changes in dendritic morphology, intrinsic biophysical properties, and synaptic interactions.

Development of a case report review instrument.

Case reports are valued components of the medical literature. The assessment of case reports by editors of medical journals and peer reviewers is largely subjective. The purpose of this study was to develop a reliable instrument to evaluate the quality of written case reports. Instrument development involved review of the literature and the materials provided to peer reviewers who review manuscripts, communications with journal editors and discussions of the study team. After multiple amendments, the instrument was pilot tested on both published and unpublished case reports. Further revisions resulted in the final 11-item tool. Four independent reviewers evaluated 28 case reports in their original submission format that had been submitted to five medical journals. The reviewers were blinded to the specific journal that the manuscripts had been submitted and to whether the case reports had been accepted for publication. Inter-rater reliability was assessed using multirater kappa. Inter-rater reliability ranged from 0.03 to 0.90. The four variables with the highest agreement between raters were (i) rationale for writing the case report; (ii) implications of the case report; (iii) adequacy of the literature review; and (iv) overall impression about whether to accept or reject the manuscript (kappas of 0.67, 0.67, 0.90 and 0.67, respectively). Six of the instrument's first 10 variables were highly correlated with the reviewers' decision about whether to accept or reject the case report for publication (item 11) (all p < 0.001). No correlation existed between the reviewers' decision to accept or reject the manuscript and the actual decision that had been made by the various journals. The case report review instrument is the first such tool for objectively evaluating case reports and appears to have reasonable reliability. Medical journals may wish to incorporate the use of this instrument into the decision making about a case report's suitability for publication.

Expansion of the central arborizations of persistent sensory neurons during insect metamorphosis: the role of the steroid hormone, 20-hydroxyecdysone.

During insect metamorphosis many larval neurons persist but are modified to serve new behavioral roles at later stages of life. For example, certain larval mechanosensory neurons expand their central arborizations during pupal development and evoke a different behavioral response, the gin trap reflex. The role of the insect steroid hormone, 20-hydroxyecdysone (20-HE) in this developmental change was investigated by removing the normal source of the hormone, followed by topical application of 20-HE to the peripheral somata of the sensory neurons. In prepupal animals that were ligated between the abdomen and thorax to remove the source of ecdysteroids the sensory neurons retained a larval arborization pattern. Topical application of 20-HE to the peripheral sensory neuron somata caused the treated neurons to undergo terminal arbor expansion within the CNS. The treated sensory neurons were not able to evoke the normal pupal behavioral response, but instead caused a larval-like reflex response. In a previous study, sensory neurons that were treated peripherally with a juvenile hormone analog during the commitment peak of ecdysteroids were shown to retain a larval arborization pattern at pupation and to not evoke the gin trap reflex (Levine et al., 1986). Within 4 d of pupation, however, these neurons belatedly developed expanded terminal arbors and evoked the pupal reflex. In the present study, similarly treated animals were ligated at pupation to block the surge in ecdysteroids that normally occurs at this time. This treatment prevented both the delayed expansion and the reflex, whereas topical 20-HE application induced growth and allowed the treated sensory neurons to evoke the gin trap reflex. It is concluded that both 20-HE and juvenile hormone act directly on the cell bodies of the sensory neurons to regulate the growth of their central processes. This growth is necessary but not sufficient for the development of the gin trap reflex, suggesting that other steroid-dependent changes must also occur within the CNS. Thus, as in the vertebrates, steroid hormones direct important developmental events within the insect nervous system.