Premature spinal fusion after insertion of magnetically controlled growing rods for treatment of early-onset scoliosis: illustrative case.

BACKGROUND: Magnetically controlled growing rod (MCGR) systems have gained attention for their use in the treatment of early-onset scoliosis. Although traditional growing rods require frequent operations to lengthen the construct, MCGR allows for fewer open procedures and more frequent distractions by externally controlling rod elongation. Despite its appealing advantages, MCGR is not without limitations. OBSERVATIONS: The authors describe a case of premature spinal autofusion before growing rod removal and termination of rod distraction. LESSONS: This case highlights the limitations of MCGR systems, including length of use, body habitus restrictions, and risk of autofusion.

The role of non-placental signals in the adaptation of islets to pregnancy.

It is well established that the maternal ß-cell mass increases during pregnancy in both humans and rodents to compensate insulin resistance and increased metabolic demand, and rapidly returns to normal levels post-partum. However, the mechanisms underlying this adaptation are not well understood. It is established that this process is driven partly by placental signals, but the contribution of non-placental signals is still unclear. This study aimed to differentiate between the role of placental and non-placental signals in regulating the ß-cell mass and glucose homeostasis during and after pregnancy. Pseudopregnant, pregnant and lactating mice were used to study the effects of maternal hormones on ß-cell function during early pregnancy, mid-to-late pregnancy and post-partum, respectively. Pseudopregnant mice, with circulating hormone levels mirroring those during pregnancy but lacking placental signals, had significantly increased ß-cell proliferation compared to non-pregnant controls but no change in glucose homeostasis, suggesting a role for non-placental hormones in increasing ß-cell mass. The rate of ß-cell proliferation rate dropped immediately after parturition, but lactating mice still had a significantly higher rate of ß-cell proliferation compared to non-lactating post-partum mice, suggesting that lactation-related hormones play a role in the controlled involution of ß-cell mass post-partum. These results implicate a role for both non-placental and placental signals in regulating ß-cell mass during and after pregnancy.

The permissive effects of glucose on receptor-operated potentiation of insulin secretion from mouse islets: a role for ERK1/2 activation and cytoskeletal remodelling.

AIMS/HYPOTHESIS: Glucose plays two distinct roles in regulating insulin secretion from beta cells--an initiatory role, and a permissive role enabling receptor-operated secretagogues to potentiate glucose-induced insulin secretion. The molecular mechanisms underlying the permissive effects of glucose on receptor-operated insulin secretion remain uncertain. We have investigated the role of extracellular signal-regulated kinase 1/2 (ERK1/2) activation and consequent cytoskeletal remodelling in this process. METHODS: Insulin release was measured from groups of isolated mouse islets using static incubation experiments and subsequent radioimmunoassay of samples. ERK1/2 activation was measured by western blotting of islet protein samples for both phosphorylated and total ERK1/2. Rhodamine-phalloidin staining was used to measure filamentous actin in dispersed primary beta cells. RESULTS: Inhibition of ERK1/2 blocked potentiation of glucose-induced insulin release by the receptor-operated secretagogues kisspeptin, A568, exendin-4 and JWH015, although the agonists alone had minimal effects on ERK1/2 activation, suggesting a permissive rather than causal role for ERK1/2 activation in receptor-operated insulin release. Following pharmacological activation of ERK1/2 all agonists caused a significant increase in insulin release from islets incubated with sub-stimulatory levels of glucose. ERK1/2 inhibition significantly reduced the glucose-dependent decreases in filamentous actin observed in primary beta cells, while pharmacological dissociation of actin filaments enabled all receptor-operated secretagogues tested to significantly stimulate insulin release from islets at a sub-stimulatory glucose concentration. CONCLUSIONS/INTERPRETATION: Glucose-induced ERK1/2 activation in beta cells mediates the permissive effects of stimulatory glucose concentrations on receptor-operated insulin secretagogues, at least in part through effects on actin depolymerisation and cytoskeletal remodelling.

Cannabinoid receptor agonists and antagonists stimulate insulin secretion from isolated human islets of Langerhans.

AIMS: The role of cannabinoid receptors in human islets of Langerhans has not been investigated in any detail, so the current study examined CB1 and CB2 receptor expression by human islets and the effects of pharmacological cannabinoid receptor agonists and antagonists on insulin secretion. METHODS: Human islets were isolated from pancreases retrieved from heart-beating organ donors. Messenger RNAs encoding human CB1 and CB2 receptors were amplified from human islet RNA by RT-PCR and receptor localization within islets was identified by immunohistochemistry. Dynamic insulin secretion from human islets perifused with buffers supplemented with CB1 and CB2 receptor agonists and antagonists was quantified by radioimmunoassay. RESULTS: RT-PCR showed that both CB1 and CB2 receptors are expressed by human islets and immunohistochemistry indicated that receptor expression co-localized with insulin-expressing ß-cells. Perifusion experiments using isolated human islets showed that insulin secretion was reversibly stimulated by both CB1 and CB2 receptor agonists, with CB1 receptor activation associated with increased basal secretion whereas CB2 receptors were coupled to initiation and potentiation of insulin secretion. Antagonists at CB1 (N-(Piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide) and CB2 (N-(1,3-Benzodioxol-5-ylmethyl)-1,2-dihydro-7-methoxy-2-oxo-8-(pentyloxy)-3-quinoline carboxamide) receptors failed to inhibit the stimulatory effects of the respective agonists and, unexpectedly, reversibly stimulated insulin secretion. CONCLUSIONS: These data confirm the expression of CB1 and CB2 receptors by human islets and indicate that both receptor subtypes are coupled to the stimulation of insulin secretion. They also implicate involvement of CB1/2 receptor-independent pathways in the antagonist-induced stimulatory effects.

Physeal fractures of the distal tibia: predictive factors of premature physeal closure and growth arrest.

BACKGROUND: A retrospective review of 124 patients was undertaken to determine the incidence of physeal growth arrest (premature physeal closure [PPC]) after physeal fractures of the distal end of the tibia in children. We also sought to identify clinical predictors of PPC. METHODS: We defined PPC as radiographic evidence of physeal closure as compared to the uninjured side in this patient population. We reviewed the charts of 124 pediatric patients with distal tibia physeal fractures. All patients were followed up until symmetric growth was noted (by Harris growth lines) for a minimum of 1 year or until physiologic closure of the growth plates had been documented radiographically. We calculated the overall incidence of PPC and the incidence by fracture type. Cox multivariate regression analysis was also performed for a number of clinical variables. RESULTS: The mean follow-up was 57 weeks. Fifteen fractures (12.1%) were complicated by PPC. In our study, 67% of the PPC observed occurred in Salter-Harris II fractures, followed by 13% in Salter-Harris III, 13% in Salter Harris IV, and 7% in triplane fractures. We did not observe any physeal arrest in the Salter-Harris I or Tillaux fractures. Using a Cox multivariate regression analysis, we were able to demonstrate statistically significant correlations between mechanism of injury and PPC and between the amount of initial fracture displacement and the rate of PPC. There was a strong relationship between mechanism of injury and PPC. There were trends seen about residual displacement after reduction and the number of attempted reductions and the rate of PPC, but these correlations were not statistically significant. For each millimeter of initial displacement, there was a relative risk of 1.15 (P < 0.01). CONCLUSIONS: Recent articles have shown a much higher rate of PPC after distal tibia physeal fracture than what was observed in our cohort. The amount of initial fracture displacement and the mechanism of injury have a statistically significant predictive value in determining the likelihood of PPC development after distal tibia physeal fracture. Trends were seen regarding residual displacement and the number of fracture reductions but were not statistically significant in predicting the occurrence of a PPC. LEVEL OF EVIDENCE: Level III: Retrospective Review.

Kisspeptin stimulation of insulin secretion: mechanisms of action in mouse islets and rats.

AIMS/HYPOTHESIS: Kisspeptin is a novel peptide identified as an endogenous ligand of the G-protein-coupled receptor 54 (GPR-54), which plays a crucial role in puberty and reproductive function. High levels of GPR-54 and kisspeptin have been reported in the pancreas and we have previously shown that kisspeptin potentiates glucose-induced insulin release from isolated islets, although the mechanisms underlying this effect were unclear. METHODS: Insulin secretion from isolated mouse islets was measured to characterise the effects of kisspeptin. The effects of kisspeptin on both p42/44 mitogen-activated protein kinase (MAPK) phosphorylation and intracellular Ca(2+)([Ca(2+)](i)) in mouse islets were also investigated. Furthermore, kisspeptin was administered to rats in vivo and effects on plasma insulin levels measured. RESULTS: In the current study, kisspeptin induced a concentration-dependent potentiation of glucose-induced (20 mmol/l) insulin secretion from mouse islets, with maximal effects at 1 micromol/l, but had no effect on insulin secretion at a substimulatory concentration of glucose (2 mmol/l). Activation of GPR-54 by kisspeptin also caused reversible increases in [Ca(2+)](i) in Fura-2 loaded dispersed islet cells. The kisspeptin-induced potentiation of glucose-induced insulin secretion was completely abolished by inhibitors of phospholipase C and p42/44 MAPK, but not by inhibitors of protein kinase C or p38 MAPK. Intravenous administration of kisspeptin into conscious, unrestrained rats caused an increase in circulating insulin levels, whilst central administration of kisspeptin had no effect, indicating a peripheral site of action. CONCLUSIONS/INTERPRETATION: These observations suggest that neither typical protein kinase C isoforms nor p38 MAPK are involved in the potentiation of glucose-induced insulin release by kisspeptin, but intracellular signalling pathways involving phospholipase C, p42/44 MAPK and increased [Ca(2+)](i) are required for the stimulatory effects on insulin secretion. The observation that kisspeptin is also capable of stimulating insulin release in vivo supports the conclusion that kisspeptin is a regulator of beta cell function.

A role for the medial preoptic area in CGRP-induced suppression of pulsatile LH secretion in the female rat.

Calcitonin gene-related peptide (CGRP) is involved in a variety of stress responses and plays a pivotal role in stress-induced suppression of the GnRH pulse generator in the rat. Intracerebroventricular administration of CGRP suppresses luteinizing hormone (LH) pulses and increases Fos expression within the medial preoptic area (mPOA) and paraventricular nucleus (PVN). The aims of the present study were to investigate whether the mPOA or PVN are sites of action for CGRP-induced suppression of LH pulses and whether lipopolysaccharide (LPS), restraint or insulin-induced hypoglycaemia, stressors known to suppress LH pulses, affect mRNA expression for CGRP and its receptor subunits (calcitonin receptor-like receptor (CL) and RAMP-1) in the mPOA and PVN. Micro-infusion of CGRP (50, 250 or 500 pmol) into the mPOA, but not the PVN, dose-dependently suppressed LH pulse frequency. LPS, restraint and hypoglycaemia suppressed RAMP-1 mRNA, but not CL or CGRP mRNA expression in the mPOA. In the PVN, all three stressors suppressed CL mRNA expression, but only LPS or restraint suppressed RAMP-1 mRNA, and CGRP mRNA was unaffected. These results provide evidence that, unlike the PVN, the mPOA might play an important role in the inhibitory effect of CGRP on pulsatile LH secretion. Additionally, CGRP receptor function may be involved in this brain region in stress-induced suppression of the GnRH pulse generator.

The role of corticotrophin-releasing hormone receptors in the calcitonin gene-related peptide-induced suppression of pulsatile luteinising hormone secretion in the female rat.

Corticotrophin-releasing hormone (CRH) plays a pivotal role in the suppression of the gonadotrophin-releasing hormone (GRH) pulse generator in response to stress and intracerebroventricular (i.c.v.) administration of calcitonin gene-related peptide (CGRP). We have previously shown both CRH receptor subtypes, CRH-R1 and CRH-R2, are involved in the stress-induced suppression of LH pulses. The aims of the present study were to examine the role of CRH-R1 and CRH-R2 in CGRP-induced suppression of LH pulses, and to investigate the effects of CGRP on CRH expression in the paraventricular nucleus (PVN) and central nucleus of the amygdala (CeA), which have prominent CRH neurone populations that receive dense CGRP innervations. The suppression of LH pulses by CGRP (1.5 microg i.c.v.) was completely prevented by intravenous administration of the CRH-R1 antagonist SSR125543Q (7.5 mg/rat i.v., 30 min before CGRP), but was not affected by the CRH-R2 antagonist, astressin(2)-B (100 microg i.c.v., 10 min before CGRP). CGRP increased the CRH mRNA expression in PVN and CeA. These results provide evidence of a role for CRH-R1 in mediating the suppressive effects of CGRP on pulsatile LH secretion in the female rat, and additionally raise the possibility of an involvement of PVN and CeA CRH neuronal populations in this suppression.

Neurophysiological detection of impending spinal cord injury during scoliosis surgery.

BACKGROUND: Despite the many reports attesting to the efficacy of intraoperative somatosensory evoked potential monitoring in reducing the prevalence of iatrogenic spinal cord injury during corrective scoliosis surgery, these afferent neurophysiological signals can provide only indirect evidence of injury to the motor tracts since they monitor posterior column function. Early reports on the use of transcranial electric motor evoked potentials to monitor the corticospinal motor tracts directly suggested that the method holds great promise for improving detection of emerging spinal cord injury. We sought to compare the efficacy of these two methods of monitoring to detect impending iatrogenic neural injury during scoliosis surgery. METHODS: We reviewed the intraoperative neurophysiological monitoring records of 1121 consecutive patients (834 female and 287 male) with adolescent idiopathic scoliosis (mean age, 13.9 years) treated between 2000 and 2004 at four pediatric spine centers. The same group of experienced surgical neurophysiologists monitored spinal cord function in all patients with use of a standardized multimodality technique with the patient under total intravenous anesthesia. A relevant neurophysiological change (an alert) was defined as a reduction in amplitude (unilateral or bilateral) of at least 50% for somatosensory evoked potentials and at least 65% for transcranial electric motor evoked potentials compared with baseline. RESULTS: Thirty-eight (3.4%) of the 1121 patients had recordings that met the criteria for a relevant signal change (i.e., an alert). Of those thirty-eight patients, seventeen showed suppression of the amplitude of transcranial electric motor evoked potentials in excess of 65% without any evidence of changes in somatosensory evoked potentials. In nine of the thirty-eight patients, the signal change was related to hypotension and was corrected with augmentation of the blood pressure. The remaining twenty-nine patients had an alert that was related directly to a surgical maneuver. Three alerts occurred following segmental vessel clamping, and the remaining twenty-six were related to posterior instrumentation and correction. Nine (35%) of these twenty-six patients with an instrumentation-related alert, or 0.8% of the cohort, awoke with a transient motor and/or sensory deficit. Seven of these nine patients presented solely with a motor deficit, which was detected by intraoperative monitoring of transcranial electric motor evoked potentials in all cases, and two patients had only sensory symptoms. Somatosensory evoked potential monitoring failed to identify a motor deficit in four of the seven patients with a confirmed motor deficit. Furthermore, when changes in somatosensory evoked potentials occurred, they lagged behind the changes in transcranial electric motor evoked potentials by an average of approximately five minutes. With an appropriate response to the alert, the motor or sensory deficit resolved in all nine patients within one to ninety days. CONCLUSIONS: This study underscores the advantage of monitoring the spinal cord motor tracts directly by recording transcranial electric motor evoked potentials in addition to somatosensory evoked potentials. Transcranial electric motor evoked potentials are exquisitely sensitive to altered spinal cord blood flow due to either hypotension or a vascular insult. Moreover, changes in transcranial electric motor evoked potentials are detected earlier than are changes in somatosensory evoked potentials, thereby facilitating more rapid identification of impending spinal cord injury.

Differential role of corticotrophin-releasing factor receptor types 1 and 2 in stress-induced suppression of pulsatile luteinising hormone secretion in the female rat.

Corticotrophin-releasing factor (CRF) plays a pivotal role in stress-induced suppression of the gonadotrophin-releasing hormone pulse generator. We have previously shown that type 2 CRF receptors (CRF(2)) mediate restraint stress-induced suppression of luteinising hormone (LH) pulses in the rat. The present study aimed: (i) to determine whether type 1 CRF receptors (CRF(1)) are also involved in this response to restraint and (ii) to investigate the differential involvement of CRF(1) and CRF(2) in the suppression of LH pulses in response to the metabolic perturbation of insulin-induced hypoglycemia and the innate immunological challenge of lipopolysaccharide (LPS). Ovariectomised rats with oestrogen replacement were implanted with intracerebroventricular (i.c.v.) and intravenous (i.v.) cannulae. Blood samples (25 microl) were collected every 5 min for 5 h for LH measurement. After 2 h of controlled blood sampling, rats were either exposed to restraint (1 h) or injected intravenously with insulin (0.25 IU/kg) or LPS (5 microg/kg). All three stressors suppressed LH pulses. The CRF(1) antagonist SSR125543Q (11.5 micromol/rat i.v., 30 min before stressor) blocked the inhibitory response to restraint, but not hypoglycaemia or LPS stress. In addition to its effect on restraint, the CRF(2) antagonist astressin(2)-B (28 nmol/rat i.c.v., 10 min before insulin or LPS) blocked hypoglycaemia or LPS stress-induced suppression of LH pulses. These results suggest that hypoglycaemia and LPS stress-induced LH suppression involves activation of CRF(2) while restraint stress-induced inhibition of LH pulses involves both CRF(1) and CRF(2).

Effect of calcitonin gene-related peptide on gonadotrophin-releasing hormone mRNA expression in GT1-7 cells.

Recent evidence has shown calcitonin gene-related peptide (CGRP) to be a key mediator of stress-induced suppression of the gonadotrophin-releasing hormone (GnRH) pulse generator, although little is known about the neural pathways involved. In the present study, we investigated the potential direct action of CGRP on GnRH neurones using GT1-7 cells, an established GnRH cell line. First, we detected expression of the CGRP receptor subunits, calcitonin receptor-like receptor and receptor activity-modifying protein-1 in the GT1-7 cells by reverse transcriptase-polymerase chain reaction. Second, we have shown that CGRP inhibits GnRH mRNA expression in the GT1-7 cells, which was effectively reversed by the CGRP receptor antagonist, CGRP8-37. These results suggest that CGRP down regulates expression of GnRH mRNA, via CGRP receptors in the GT1-7 cell, thus implying that a potential direct action of CGRP may mediate a suppressive effect on the GnRH neural network.

Calcitonin gene-related peptide-induced suppression of luteinizing hormone pulses in the rat: the role of endogenous opioid peptides.

Calcitonin gene-related peptide (CGRP) is involved in a variety of stress responses in the rat. Central administration of CGRP activates the hypothalamo-pituitary-adrenal axis resulting in increased corticosterone secretion. We have previously shown that central CGRP suppresses the gonadotrophin-releasing hormone (GnRH) pulse generator, specifically LH pulses. Endogenous opioid peptides (EOPs) have been shown to play an important role in stress-induced suppression of the reproductive axis. The aim of the present study was to test the hypothesis that EOPs mediate CGRP-induced suppression of pulsatile LH secretion. Ovariectomized rats were implanted with intracerebroventricular (i.c.v.) and i.v. cannulae. Intravenous administration of the opioid antagonist naloxone (250 microg) completely blocked the suppression of LH pulses induced by 1.5 microg i.c.v. CGRP and significantly attenuated the suppression of pulsatile LH secretion induced by 5 microg i.c.v. CGRP. Furthermore, intravenous administration of naloxone was found to immediately restore normal LH pulse frequency in animals treated 90 min earlier with 1.5 microg i.c.v. CGRP. Co-administration (i.c.v.) of CGRP (1.5 microg) with the mu and kappa opioid receptor-specific antagonists naloxone (10 microg) and norbinaltorphimine (5 microg), respectively, blocked the CGRP-induced suppression of LH pulses, whilst i.c.v. co-administration of CGRP (1.5 microg) with the delta opioid receptor-specific antagonist naltrindole (5 microg) did not. These data provide evidence that EOPs play a pivotal role in mediating the inhibitory effects of CGRP on pulsatile LH secretion in the rat. They also suggest that the mu and kappa, but not the delta, opioid receptors may be responsible for mediating the effects of CGRP on LH pulses.

The effects of the phytoestrogen, coumestrol, on gonadotropin-releasing hormone (GnRH) mRNA expression in GT1-7 GnRH neurones.

Phytoestrogens can produce inhibitory effects on gonadotropin secretion in both animals and humans, although little is known about the mechanisms and the role of direct action on oestrogen receptors (ER) in this process. We examined the effect of coumestrol, alone and combined with ER antagonists, on gonadotropin-releasing hormone (GnRH) mRNA expression in GT1-7 cells. Coumestrol was found to have an inhibitory effect compared to controls, which was blocked by R,R-THC, a selective ER beta antagonist. These results suggest that ER beta is involved in the suppression of GnRH mRNA expression by coumestrol.

Physical restraint management of hospitalized adults and follow-up study.

During the winter of 1998 the management of 118 (N = 118) physically restrained adult patients in a 238-bed urban acute care hospital were assessed by 26 registered nurse (RN) data collectors. In the spring of 1999, following a comprehensive hospital-wide staff development program and revised physical restraint protocol, 10 RN data collectors conducted a follow-up study of 53 (N = 53) restrained adults in the same institution. In both studies, data regarding restraints management were gathered using a Restraint Management Improvement Indicator. Following a program of restraint management education, substantial improvements were found for virtually all of the physical restraint indices studied. The findings suggest that future educational efforts should be undertaken to further improve the documentation in hospital medical records regarding medical orders and ongoing observation, assessment, and interventions for physically restrained patients. Future research should further document and study interventions to reduce or eliminate the use of physical restraints.