Social services referral of adolescent trauma patients admitted following alcohol-related injury.

Alcohol screening of severely injured patients should be universal. Hospitalization following alcohol-related injury provides an opportunity for intervention to reduce recidivism. This study examines the frequency of social services referral of an alcohol positive cohort of adolescent trauma patients. This was a retrospective analysis of data collected from 1994 through 1998 by the National Pediatric Trauma Registry. All patients between the ages of 12 and 17 who had a blood alcohol level (BAL) measured were analyzed. Patients receiving referral to the department of social services, family counseling, or addiction services, and those receiving any substance abuse education intervention were considered a positive referral. There were 6006 children age 12 to 17 included in the database during this five-year period, 751 of whom had a BAL measured. Of those screened, 15.5% were positive. Sixty-eight (59%) of the BAL positive patients were referred for intervention through social services. The only statistically significant predictor of referral was whether or not the patient was the operator of a vehicle involved in the motor vehicle collision. Nearly half of the adolescents in this study, who screened positive for alcohol, received no social services support.

Pediatric minor head trauma: indications for computed tomographic scanning revisited.

BACKGROUND: Although the use of computed tomographic (CT) scanning in severe head trauma is an accepted practice, the indications for its use in minor injury remain ill defined and subjective. We sought to define the incidence and identify risk factors for intracranial injury (ICI) after minor head trauma in children who did not have suspicious neurologic symptoms in the field or on presentation. METHODS: From January 1, 1992, until April 1, 2000, 569 blunt trauma patients (age < 16 years) with a Glasgow Coma Scale score of 14 or 15 triaged by American College of Surgeons Pediatric Mechanism Criteria at a Level I trauma center received head CT scan. Loss of consciousness (LOC) status was known for 429. This subgroup was retrospectively reviewed for mechanism, age, Injury Severity Score, LOC status, GCS score, associated injuries, and CT scan findings (normal, fracture only, or intracranial injury). Relative risk values for intracranial injury were generated and statistical significance was assessed. RESULTS: Fourteen percent (62 of 429) of study patients (GCS score of 14 and 15) had ICI. Sixteen percent of patients (35 of 215) with GCS score of 15 and (-)LOC (negative for LOC) had intracranial injury manifesting as subdural hematoma, epidural hematoma, subarachnoid hemorrhage, or brain contusion. Three required surgery for intracranial mass lesions. One patient deteriorated and required intubation and intensive care unit management. Neither (+)LOC (positive for LOC) nor GCS score of 14 increased the likelihood of intracranial injury over those patients without loss of consciousness or with GCS score of 15. Distant injury was also not an independent predictor of ICI for those with GCS scores of 14 or 15, as 84% of the ICI group had head injury only. Skull fracture was a risk factor for ICI but had poor negative predictive value, as 45% of patients with ICI did not have fractures. Similarly, minor craniofacial soft tissue trauma was a significant risk factor (relative risk, 11) that had marginal negative predictive value (0.95), as 14% (9 of 62) of ICI patients did not have superficial craniofacial injury. CONCLUSION: A normal neurologic exam and maintenance of consciousness does not preclude significant rates of intracranial injury in pediatric trauma patients. Contrary to convention, neither LOC nor mild altered mentation is a sensitive indicator with which to select patients for CT scanning. Skull fractures and superficial craniofacial injury are similarly unreliable. Identification of these patients is important for the occasional case requiring intervention and for the tracking of complications. A liberal policy of CT scanning is warranted for pediatric patients with a high-risk mechanism of injury despite maintenance of normal neurologic status in the field and at hospital screening.

Neuronal contact guidance in magnetically aligned fibrin gels: effect of variation in gel mechano-structural properties.

Neurite outgrowth from chick dorsal root ganglia entrapped in isotropic and magnetically aligned fibrin gels was studied, and the dependence on the diameter of the fibrin fibrils was characterized. The fibrin fibril diameter was varied, as inferred from turbidity measurements, by using different Ca2+ concentrations in the fibrin-forming solution, but this variation was accomplished without affecting the degree of magnetic-induced alignment, as directly visualized in fluorescently spiked gels. Magnetically aligned fibrin gels possessing different fibril diameters but similar alignment resulted in drastic changes in the contact guidance response of neurites, with no response in gels formed in 1.2 mM Ca2+ (having smaller fibril diameter, ca. 150 nm), but a strong response in gels formed in 12 and 30 mM Ca2+ (having larger fibril diameter, ca. 510 nm) with an attendant two-fold increase in neurite length. These changes are attributed to variation of the mechano-structural properties of the network of aligned fibrils as the fibril diameter is varied.

Active glottal closure during anoxic gasping in lambs.

The present study was aimed at assessing laryngeal dynamics and their consequences during anoxic gasping in ketamine-sedated lambs. We first verified that the glottis was closed between gasps during anoxic gasping in seven chronically instrumented lambs, aged 11-15 days. Recording of glottal constrictor muscle electrical activity, subglottal pressure and lung volume, together with endoscopic observation, confirmed the presence of active glottal closure with maintenance of a high lung volume between gasps. Secondly, we tested whether maintenance of a high lung volume between gasps improved autoresuscitation efficiency. Six sedated lambs aged 8-11 days underwent two anoxic runs, including one with an open tracheostomy to prevent maintenance of a high lung volume. Access back to air was allowed for gasping. No significant difference was found in time to eupnea resumption, hemodynamic parameters or arterial blood gases. We conclude that a high lung volume is actively maintained by glottal closure between anoxic gasps in sedated lambs. Further studies are however needed to define the importance of laryngeal dynamics during gasping.

Neurotrophins and the dynamic regulation of the neuronal cytoskeleton.

The morphology of neuronal axons and dendrites is dependent on the dynamics of the cytoskeleton. An understanding of neurodevelopment and adult neuroplasticity must therefore include a detailed description of the intrinsic and extrinsic mechanisms that regulate the organization and dynamics of actin filaments and microtubules. In this paper we review recent advances in the understanding of the dynamic regulation of neuronal morphology by interactions among cytoskeletal components and the regulation of the cytoskeleton by neurotrophins.

Stabilization of growing retinal axons by the combined signaling of nitric oxide and brain-derived neurotrophic factor.

The pattern of axonal projections early in the development of the nervous system lacks the precision present in the adult. During a developmental process of refinement, mistargeted projections are eliminated while correct projections are retained. Previous studies suggest that during development nitric oxide (NO) is involved in the elimination of mistargeted retinal axons, whereas brain-derived neurotrophic factor (BDNF) may stabilize retinal axon arbors. It is unclear whether these neuromodulators interact. This study showed that NO induced growth cone collapse and retraction of developing retinal axons. This effect was not attributable to NO-induced neurotoxicity. BDNF protected growth cones and axons from the effects of NO. This effect was specific to BDNF, because neither nerve growth factor (NGF) nor neurotrophin-3 (NT-3) prevented NO-induced growth cone collapse and axon retraction. Exposure to both BDNF and NO, but not either factor alone, stabilized growth cones and axons. Stabilized axons exhibited minimal retraction or extension. This response appears to be a new axon "state" and not simply a partial amelioration of the effect of NO, because lower doses of BDNF or NO allowed axon extension. Furthermore, BDNF/NO-induced growth cone stabilization correlated with the appearance of a cytochalasin D-resistant population of actin filaments. BDNF protection from NO likely was mediated locally at the level of the growth cone, because growth cones or individual filopodia in contact with BDNF-coated beads were protected from NO-induced collapse. These findings suggest a cellular mechanism by which some axonal connections are stabilized and some are eliminated during development.

Embryonic neurons adapt to the inhibitory proteoglycan aggrecan by increasing integrin expression.

The primary mediators of cell migration during development, wound healing and metastasis, are receptors of the integrin family. In the developing and regenerating nervous system, chondroitin sulfate proteoglycans (CSPGs) inhibit the integrin-dependent migration of neuronal growth cones. Here we report that embryonic sensory neurons cultured on the growth-promoting molecule laminin in combination with the inhibitory CSPG aggrecan rapidly adapt to inhibition. Adaptation is associated with a two- to threefold increase in the levels of RNA and surface protein for two laminin receptors, integrin alpha6beta1 and alpha3beta1, indicating that integrin expression is regulated by aggrecan. Increased integrin expression is associated both with increases in neuronal cell adhesion/outgrowth and with decreases in the ability of aggrecan to inhibit cell adhesion. Directly increasing integrin expression by adenoviral infection is sufficient to eliminate the inhibitory effects of aggrecan, indicating that upregulation of integrin receptors may promote neuronal regeneration in the presence of inhibitory matrix components.

Guided neurite elongation and schwann cell invasion into magnetically aligned collagen in simulated peripheral nerve regeneration.

High-strength magnetic fields were used to align collagen gel formed into 4-mm-diameter rods during the self-assembly of type I collagen monomers into fibrils. We developed an in vitro assay to study neurite elongation into the magnetically aligned collagen gel rods from dorsal root ganglia (DRG) explants placed onto one end of the rods. The depth of neurite elongation from chick embryo DRG neurons into these rods was found to be substantially greater than that observed in controls and increased with an increase in magnetic field strength, as did the collagen gel rod birefringence, indicative of collagen fibril alignment along the rod axis. Moreover, the axial bias of neurite elongation became more pronounced with an increase in magnetic field strength, presumably due to a contact guidance response of growth cones at the neurite tips. Coinvasion of Schwann cells from neonatal rat DRG was also studied in these assays using double immunolabeling. In the absence of serum, Schwann cells were highly associated with, and often trailed, elongating neurites. In the presence of serum, Schwann cells showed significantly higher rates of invasion and formed axially aligned chords reminiscent of bands of Büngner. These results may translate into an improved method of entubulation repair of transected peripheral nerves by directing and stimulating axonal growth through a tube filled with magnetically aligned collagen gel.

Radiotelemetry system for apnea study in lambs.

Neonatal apneas are being studied in the laboratory using polysomnographic recordings in lambs. Standard equipment, requiring animal restraint, disrupts sleep and prevents development of spontaneous apneas. The aim of the current work was to develop and validate a wireless recording equipment to study freely moving lambs. Firstly, a radiotelemetry equipment composed of a multichannel FM transmitter and a receiver was developed. Secondly, to test the telemetry equipment, each biopotential - [electroencephalogram (EEG), electrooculogram (EOG), electrocardiogram (ECG), electromyograms (EMGs), nasal airflow] - was recorded simultaneously by standard equipment and by telemetry (5 lambs). The results indicated an excellent concordance between signals obtained by both systems. Finally, the 8-channel telemetry prototype was tested for polysomnographic recordings (16 lambs). Results obtained confirmed the possibility of recording frequent REM sleep periods and spontaneous apneas. In conclusion, this radiotelemetry polysomnographic equipment brings new possibilities for research on neonatal apneas.

Axon guidance: A balance of signals sets axons on the right track.

Axon guidance depends on the transduction of extracellular guidance cues into motile responses by the axonal growth cone. Recent studies in vivo have elucidated mechanisms required for this process that involve kinases and phosphatases, calcium dynamics and remodeling of the actin cytoskeleton.

Thyroarytenoid muscle electrical activity during spontaneous apneas in preterm lambs.

Laryngeal dynamics plays a major role during perinatal life, a period of respiratory control immaturity. Continuous electromyographic (EMG) activity of a laryngeal adductor muscle (thyroarytenoid [TA] muscle), was recently observed throughout provoked central apneas, either isolated or during induced periodic breathing, in full-term lambs. The aim of the present study was to test if continuous TA EMG activity was also present during spontaneous apneas in nonsedated preterm lambs. We studied 7 premature lambs (term 131 +/- 1 d of postconceptional age). Premature birth was induced after acceleration of fetal lung maturation. Electrodes for diaphragm, inferior pharyngeal constrictor (IPC), and TA electromyograms, electrocardiogram, electroencephalogram, eye movement, and airflow recordings were implanted. Radiotelemetry recordings were repeated from 135 to 149 +/- 8 d of postconceptional age. A total of 2,088 apneas (2,020 central and 68 mixed) >/= 3 s were recorded in the lambs, including 57 epochs of periodic breathing. Continuous TA EMG activity was present throughout 88.4% of all apneas and 98.4% of apneas during periodic breathing, regardless of the sleep stage. These results suggest that active glottic closure is frequent during spontaneous central apneas in this model of prematurity. This unique model will allow us to study controlling mechanisms and consequences of glottic closure during neonatal apneas.

Different contributions of microtubule dynamics and transport to the growth of axons and collateral sprouts.

Axonal growth is believed to depend on microtubule transport and microtubule dynamic instability. We now report that the growth of axon collateral branches can occur independent of microtubule dynamic instability and can rely mostly on the transport of preassembled polymer. Raising embryonic sensory neurons in concentrations of either taxol or nocodazole (NOC) that largely inhibit microtubule dynamics significantly inhibited growth of main axonal shafts but had only minor effects on collateral branch growth. The collaterals of axons raised in taxol or nocodazole often contained single microtubules with both ends clearly visible within the collateral branch ("floating" microtubules), which we interpret as microtubules undergoing transport. Furthermore, in these collaterals there was a distoproximal gradient in microtubule mass, indicating the distal accumulation of transported polymer. Treatment of cultures with a high dose of nocodazole to deplete microtubules from collaterals, followed by treatment with 4-20 nM vinblastine to inhibit microtubule repolymerization, resulted in the time-dependent reappearance and subsequent distal accumulation of floating microtubules in collaterals, providing further evidence for microtubule transport into collateral branches. Our data show that, surprisingly, the contribution of microtubule dynamics to collateral branch growth is minor compared with the important role of microtubule dynamics in growth cone migration, and they indicate that the transport of microtubules may provide sufficient cytoskeletal material for the initial growth of collateral branches.

Vagal afferents and active upper airway closure during pulmonary edema in lambs.

The present study was undertaken to gain further insight into the mechanisms responsible for the sustained active expiratory upper airway closure previously observed during high-permeability pulmonary edema in lambs. The experiments were conducted in nonsedated lambs, in which airflow and thyroarytenoid and inferior pharyngeal constrictor muscle electromyographic activity were recorded. We first studied the consequences of hemodynamic pulmonary edema (induced by impeding pulmonary venous return) on upper airway dynamics in five lambs; under this condition, a sustained expiratory upper airway closure consistently appeared. We then tested whether expiratory upper airway closure was related to vagal afferent activity from bronchopulmonary receptors. Five bivagotomized lambs underwent high-permeability pulmonary edema: no sustained expiratory upper airway closure was observed. Finally, we studied whether a sustained decrease in lung volume induced a sustained expiratory upper airway closure. Five lambs underwent a 250-ml pleural infusion: no sustained expiratory upper airway closure was observed. We conclude that 1) the sustained expiratory upper airway closure observed during pulmonary edema in nonsedated lambs is related to stimulation of vagal afferents by an increase in lung water and 2) a decrease in lung volume does not seem to be the causal factor.

Effects of capsaicin pretreatment on expiratory laryngeal closure during pulmonary edema in lambs.

The present study, performed in nonsedated, conscious lambs, consisted of two parts. In the first part, we 1) examined for the first time whether a respiratory response to pulmonary C-fiber stimulation could be elicited in nonsedated newborns and 2) determined whether this response could be abolished by capsaicin pretreatment. Then, by using capsaicin-desensitized lambs, we studied whether pulmonary C fibers were involved in the sustained, active expiratory upper airway closure previously observed during pulmonary edema. Airflow and thyroarytenoid and inferior pharyngeal constrictor muscle electromyographic activities were recorded. In the first set of experiments, a 5-10 microg/kg capsaicin bolus intravenous injection in seven intact lambs consistently led to a typical pulmonary chemoreflex, showing that C fibers are functionally mature in newborn lambs. In the second series of experiments, eight lambs pretreated with 25-50 mg/kg subcutaneous capsaicin did not exhibit any respiratory response to 10-50 microg/kg intravenous capsaicin injection, implicating C fibers in the response. Finally, in the above capsaicin-desensitized lambs, we observed that halothane-induced high-permeability pulmonary edema did not cause the typical response of sustained expiratory upper airway closure seen in the intact lamb. We conclude that functionally mature C fibers are present and responsible for a pulmonary chemoreflex in response to capsaicin intravenous injection in nonsedated lambs. Capsaicin pretreatment abolishes this reflex. Furthermore, the sustained expiratory upper airway closure observed during halothane-induced pulmonary edema in intact nonsedated lambs appears to be related to a reflex involving stimulation of pulmonary C fibers.

Complete glottic closure during central apnea in lambs.

OBJECTIVE: The objectives of this study were threefold: to document complete glottic closure during artificially induced central apnea in lambs; to unequivocally confirm that thyroarytenoid muscle electrical activity during central apneas in lambs reflects complete glottic closure; and to evaluate the physiologic significance of this phenomenon in artificially induced central apneas in lambs. METHODS: We recorded thyroarytenoid (TA) muscle EMG, subglottic pressure, and lung volume simultaneously with direct endoscopic vision of the glottis from beneath on nine 11- to 15-day-old lambs during artificially induced central apneas. RESULTS: Thirty-eight central apneas were induced. Complete glottic closure was present on 35/38 (92%) of these apneas. Complete glottic closure was always paralleled by thyroarytenoid muscle electromyogram (EMG) activity (35/38). In no instance was TA EMG recorded without complete glottic closure. Moreover, positive subglottic pressure and maintenance of lung volume above functional residual capacity were observed in 27/30 (90%) and 18/19 (95%), respectively, of these apneas where complete glottic closure was present. CONCLUSIONS: Complete glottic closure is present throughout most artificially induced central apneas in lambs. Complete glottic closure is paralleled by TA EMG in artificially induced central apneas. Thyroarytenoid muscle electromyographic activity is a reliable way to document complete glottic closure during apneas, especially in the presence of positive subglottic pressure. These observations suggest that complete glottic closure could be a physiologic mechanism aimed at maintaining higher lung volumes to improve gas exchange during central apneas.

Localized sources of neurotrophins initiate axon collateral sprouting.

The sprouting of axon collateral branches is important in the establishment and refinement of neuronal connections during both development and regeneration. Collateral branches are initiated by the appearance of localized filopodial activity along quiescent axonal shafts. We report here that sensory neuron axonal shafts rapidly sprout filopodia at sites of contact with nerve growth factor-coated polystyrene beads. Some sprouts can extend up to at least 60 micro(m) through multiple bead contacts. Axonal filopodial sprouts often contained microtubules and exhibited a debundling of axonal microtubules at the site of bead-axon contact. Cytochalasin treatment abolished the filopodial sprouting, but not the accumulation of actin filaments at sites of bead-axon contact. The axonal sprouting response is mediated by the trkA receptor and likely acts through a phosphoinositide-3 kinase-dependent pathway, in a manner independent of intracellular Ca2+ fluctuations. These findings implicate neurotrophins as local cues that directly stimulate the formation of collateral axon branches.

Axon guidance: GTPases help axons reach their targets.

During development and regeneration of the nervous system, axons must correctly navigate to their specific targets through a complex molecular environment. Recent work has shed light on how GTPases of the Ras family are involved in transducing extracellular signals into responses that lead to directed neurite outgrowth.

Micropatterning gradients and controlling surface densities of photoactivatable biomolecules on self-assembled monolayers of oligo(ethylene glycol) alkanethiolates.

BACKGROUND: Bioactive molecules that are covalently immobilized in patterns on surfaces have previously been used to control or study cell behavior such as adhesion, spreading, movement or differentiation. Photoimmobilization techniques can be used, however, to control not only the spatial pattern of molecular immobilization, termed the micropattern, but also the surface density of the molecules--a characteristic that has not been previously exploited. RESULTS: Oligopeptides containing the bioactive Arg-Gly-Asp cell-adhesion sequence were immobilized upon self-assembled monolayers of an oligo(ethylene glycol) alkanethiolate in patterns that were visualized and quantified by autoradiography. The amount and pattern of immobilized peptide were controlled by manipulating the exposure of the sample to a UV lamp or a laser beam. Patterns of peptides, including a density gradient, were used to control the location and number of adherent cells and also the cell shape. CONCLUSIONS: A photoimmobilization technique for decorating surfaces with micropatterns that consist of variable densities of bioactive molecules is described. The efficacy of the patterns for controlling cell adhesion and shape has been demonstrated. This technique is useful for the study of cell behavior on micropatterns.

Concentration-dependent stimulation and inhibition of growth cone behavior and neurite elongation by protein kinase inhibitors KT5926 and K-252a.

We examined the concentration- and time-dependent effects of two related protein kinase inhibitors, KT5926 and K-252a, on neurite formation and nerve growth cone migration of chick embryo sensory neurons. The effects of these drugs on neurite formation over an 18-h period were dissimilar. KT5926 stimulated neurite formation at concentrations between 100 and 500 nM and inhibited neurite formation at 5 microM. K-252a had no stimulatory effects on neurite formation, and it inhibited neurite formation at concentrations above 50 nM. This difference may occur because K-252a inhibits activation of the nerve growth factor receptor trk A, while KT5926 does not inhibit trk A. Both drugs, however, had similar immediate effects on growth cone migration. Growth cone migration and lamellipodial spreading were rapidly stimulated by 500 nM concentrations of KT5926 and K-252a. At 2 microM levels of either drug, growth cone spreading was still stimulated, but growth cone migration was inhibited by both drugs. These results show that changes in protein phosphorylation/dephosphorylation can rapidly regulate the cellular machinery that is responsible for driving growth cone migration and neurite elongation. The different effects of 2 microM concentrations of either KT5926 or K-252a on growth cone spreading versus migration suggests that the actin-dependent protrusive motility of the growth cone leading margin is regulated differently by changes in protein phosphorylation and dephosphorylation than the cytoskeletal mechanism that drives neurite elongation.