Rodolfo Gatto

Inhibition of Fast Axonal Transport by Pathogenic SOD1 Involves Activation of p38 MAP Kinase

Dying-back degeneration of motor neuron axons represents an established feature of familial amyotrophic lateral sclerosis (FALS) associated with superoxide dismutase 1 (SOD1) mutations, but axon-autonomous effects of pathogenic SOD1 remained undefined. Characteristics of motor neurons affected in FALS include abnormal kinase activation, aberrant neurofilament phosphorylation, and fast axonal transport (FAT) deficits, but functional relationships among these pathogenic events were unclear. Experiments in isolated squid axoplasm reveal that FALS-related SOD1 mutant polypeptides inhibit FAT through a mechanism involving a p38 mitogen activated protein kinase pathway. Mutant SOD1 activated neuronal p38 in mouse spinal cord, neuroblastoma cells and squid axoplasm. Active p38 MAP kinase phosphorylated kinesin-1, and this phosphorylation event inhibited kinesin-1. Finally, vesicle motility assays revealed previously unrecognized, isoform-specific effects of p38 on FAT. Axon-autonomous activation of the p38 pathway represents a novel gain of toxic function for FALS-linked SOD1 proteins consistent with the dying-back pattern of neurodegeneration characteristic of ALS.

THE UTILITY OF INTRAOPERATIVE BLOOD FLOW MEASUREMENT DURING ANEURYSM SURGERY USING AN ULTRASONIC PERIVASCULAR FLOW PROBE

OBJECTIVE: Inadvertent vessel compromise is one major cause of unfavorable outcome from aneurysm surgery. Existing strategies for intraoperative assessment of this complication have potential limitations and disadvantages. We assessed the utility of quantitative intraoperative flow measurements using the Transonic ultrasonic flow probe (Transonic Systems, Inc., Ithaca, NY) during aneurysm surgery. METHODS: Of all aneurysms treated surgically at our institution from 1998 to 2003, 103 patients with 106 aneurysms were identified in whom intraoperative flow measurements were available for analysis. We assessed the frequency of flow compromise and clip repositioning and correlated these with postoperative angiography and stroke. RESULTS: Significant (>25%) reduction in flow rate was apparent in 33 (31.1%) cases, and resulted in clip repositioning in 27 (25.5%), with return to baseline flow except for two cases with vessel thrombosis/dissection. In the other six cases, flow reduction was owing to spasm resolving with papaverine (n = 3) or responded to retractor repositioning (n = 3). In another six (5.7%) cases, unnecessary clip repositioning was avoided (n = 3) or safe occlusion of the parent vessel for trapping of the aneurysm was allowed by confirming adequate distal flow (n = 3). Aneurysms of the basilar, middle cerebral, anterior communicating, or carotid terminus were more likely to be associated with flow compromise (odds ratio, 4.3; P = 0.03). Postoperative angiography corroborated vessel patency in all cases, and no unexpected large vessel occlusions or strokes were evident. CONCLUSION: Use of the ultrasonic flow probe provides real-time immediate feedback concerning vessel patency. Vessel compromise is easier to interpret than with Doppler, and faster/less invasive than intraoperative angiography. Intraoperative flow measurement is a valuable adjunct for enhancing the safety of aneurysm surgery

A Novel Method for Extracting Respiration Rate and Relative Tidal Volume from Infrared Thermography

In psychophysiological research, measurement of respiration has been dependent on transducers having direct contact with the participant. The current study provides empirical data demonstrating that a noncontact technology, infrared video thermography, can accurately estimate breathing rate and relative tidal volume across a range of breathing patterns. Video tracking algorithms were applied to frame-by-frame thermal images of the face to extract time series of nostril temperature and to generate breath-by-breath measures of respiration rate and relative tidal volume. The thermal indices of respiration were contrasted with criterion measures collected with inductance plethysmography. The strong correlations observed between the technologies demonstrate the potential use of facial video thermography as a noncontact technology to monitor respiration.

Synergistic benefits of erythropoietin and simvastatin after traumatic brain injury

Simvastatin and recombinant human erythropoietin (rhEpo) are implicated as potential therapeutic candidates for traumatic brain injury (TBI). Prominent effects of simvastatin include its anti-inflammatory, neurotrophic and neuroregenerative actions studied in various models of neuronal injury. On the other hand, rhEpo has been shown to promote cell survival mechanisms by producing anti-apoptotic and cell proliferative actions. Beneficial effects of rhEpo and statin monotherapies have been well studied. However, there are no reports showing combined use of rhEpo and statins after TBI. This investigation examined if combined efficacy of cell proliferative ability of rhEpo along with the neuroregenerative ability of simvastatin will render maximum recovery in a controlled cortical impact (CCI) mouse model of TBI. Results showed that compared to baseline TBI, rhEpo was more effective than simvastatin in promoting cell proliferation while simvastatin was more effective than rhEpo in restoring axonal damage following TBI. Combined treatment with simvastatin and rhEpo maximally restored axonal integrity while simultaneously inducing greater proliferation of newly formed cells resulting in better functional recovery after TBI than either alone. This is the first study showing the efficacy of erythropoietin-simvastatin combinational therapeutic approach in achieving greater structural and cognitive recovery after TBI.

Frequency domain near- infrared spectroscopy technique in the assessment of brain oxygenation : A validation study in live subjects and cadavers

BACKGROUND Studies with continuous wave near infrared spectroscopy (CW-NIRS) have shown little difference in brain oxygenation of dead compared to live subjects. We determined brain oxyhemoglobin (OHb) and deoxyhemoglobin (HHb) concentrations in healthy volunteers and cadavers using frequency domain near infrared spectroscopy (FD-NIRS). METHODS Regional OHb and HHb, brain oxygen saturation (SO2), and total hemoglobin (tHb) were determined. Nine patients who died in the hospital were evaluated by FD-NIRS in the morgue 7-96 h after death was confirmed. Ten volunteers served as a control group. RESULTS Absolute concentrations of brain tissue OHb and HHb were 24.9 +/- 9.1 uM and 13.8 +/- 32 uM, respectively, in live subjects. In dead subjects, OHb was 1.3 +/- 2.1 uM and HHb was 30.8 +/- 14.4 uM (both P < 0.05 compared to live). OHb showed a 90% decrease within 7h of death. There was a significant trend for a continued decrease in OHb from 7 to 96 h. CONCLUSION OHb decreased and HHb increased in dead patients compared to live volunteers. Depletion of OHb primarily occurred within 7 h of death but continued gradually over 96 h. FD-NIRS was a novel technique for determining OHb and HHb changes following death.

Analysis of YFP(J16)-R6/2 reporter mice and postmortem brains reveals early pathology and increased vulnerability of callosal axons in Huntington's disease

Cumulative evidence indicates that the onset and severity of Huntingtons disease (HD) symptoms correlate with connectivity deficits involving specific neuronal populations within cortical and basal ganglia circuits. Brain imaging studies and pathological reports further associated these deficits with alterations in cerebral white matter structure and axonal pathology. However, whether axonopathy represents an early pathogenic event or an epiphenomenon in HD remains unknown, nor is clear the identity of specific neuronal populations affected. To directly evaluate early axonal abnormalities in the context of HD in vivo, we bred transgenic YFP(J16) with R6/2 mice, a widely used HD model. Diffusion tensor imaging and fluorescence microscopy studies revealed a marked degeneration of callosal axons long before the onset of motor symptoms. Accordingly, a significant fraction of YFP-positive cortical neurons in YFP(J16) mice cortex were identified as callosal projection neurons. Callosal axon pathology progressively worsened with age and was influenced by polyglutamine tract length in mutant huntingtin (mhtt). Degenerating axons were dissociated from microscopically visible mhtt aggregates and did not result from loss of cortical neurons. Interestingly, other axonal populations were mildly or not affected, suggesting differential vulnerability to mhtt toxicity. Validating these results, increased vulnerability of callosal axons was documented in the brains of HD patients. Observations here provide a structural basis for the alterations in cerebral white matter structure widely reported in HD patients. Collectively, our data demonstrate a dying-back pattern of degeneration for cortical projection neurons affected in HD, suggesting that axons represent an early and potentially critical target for mhtt toxicity.

Restoration of cognitive deficits after statin feeding in TBI

PURPOSE Traumatic brain injury (TBI) is a global health concern and growing socio-economic burden with limited treatment options. Behavioral assessment in experimental TBI with candidate therapeutic interventions is critical in order to expedite clinical translation. Statins constitute one of the potential treatment options based on their proven beneficial effects in various models of neurotrauma. We compared functional outcome after dietary intervention with representative hydrophilic Pravastatin or lipophilic Simvastatin and Lovastatin to test if different statins will differentially affect cognitive outcomes after injury in a controlled cortical impact injury (CCI) mouse model of TBI. METHODS Mice were subjected to TBI with a controlled cortical impact produced on the left somatosensory-parietal cortex between bregma -1.82 and -2.06, fed with Simvastatin/Lovastatin/Pravastatin (2 mg/kg) for 8 weeks, evaluated for learning, memory and spontaneous exploration behavior followed by immunocytochemistry of an axonal marker. RESULTS Results indicate that feeding of TBI mice with Simvastatin and Lovastatin significantly improved spatial learning and memory, restored spontaneous exploration and restored axonal integrity (Simvastatin > Lovastatin). On the other hand, Pravastatin failed to improve spatial learning or memory or exploration or axonal damage. CONCLUSIONS Current findings confirm maximum benefits rendered by Simvastatin and reinforce Simvastatin as the candidate therapy for treating TBI.

Age effects on brain oxygenation during hypercapnia

Previous studies showed that the cerebrovasodilation response to hypercapnia is attenuated with aging. The purpose of this study was to determine if normal aging attenuates increases in brain oxygenation during hypercapnia. Prefrontal cortex oxyhemoglobin (OHb) and deoxyhemoglobin (HHb) concentrations were measured in 13 healthy subjects ages 26 to 59 years using a frequency domain tissue oximeter. Measurements were obtained under the following conditions: (1) subject awake breathing spontaneously, (2) during mask ventilation with 21% oxygen, (3) mask ventilation with 100% oxygen, (4) 100% oxygen in a rebreathing circuit to increase end-tidal CO(2). Under baseline conditions breathing room air, there was a negative correlation between baseline OHb and age (r=-0.60, P<0.05). Ventilation with 100% oxygen increased OHb without a change in total hemoglobin and no affect of age. During mask rebreathing, end-tidal CO(2) increased from 39.5+/-5.0 mm Hg (millimeters of mercury) to 56.5+/-5.7 mm Hg, which produced significant increases in OHb and total blood volume that were negatively correlated with age (r=-0.67, P<0.05) and positively correlated to baseline OHb (r=0.60, P<0.05). These results indicate that OHb concentrations decreased with age, consistent with attenuated cerebral vasodilation during hypercapnia.

Increased brain oxygenation during intubation-related stress

Background and objectives The purpose of this study was to determine whether brain oxyhaemoglobin‐deoxyhaemoglobin coupling was altered by anaesthesia or intubation‐induced stress. Methods This was a prospective observational study in the operating room. Thirteen patients (ASA I and II) undergoing spinal or peripheral nerve procedures were recruited. They were stabilized before surgery with mask ventilation of 100% oxygen. Anaesthesia was induced with 2 &mgr;g kg−1 fentanyl and 3 mg kg−1 thiopental. Laryngoscopy and intubation were performed 4 min later. After intubation, desflurane anaesthesia (FiO2=1.0) was adjusted to maintain response entropy of the electroencephalogram at 40‐45 for 20 min. Prefrontal cortex oxyhaemoglobin and deoxyhaemoglobin were determined every 2 s using frequency domain near‐infrared spectroscopy. Blood pressure, heart rate and response entropy were collected every 10 s. Results Awake oxyhaemoglobin and deoxyhaemoglobin were 18.9 ± 2.3 &mgr;mol (mean ± SD) and 12.7 ± 0.8 &mgr;mol, respectively, and neither changed significantly during induction. Intubation increased oxyhaemoglobin by 37% (P < 0.05) and decreased deoxyhaemoglobin by 16% (P < 0.05), and both measures returned to baseline within 20 min of desflurane anaesthesia. Blood pressure, heart rate and electroencephalogram response entropy increased during intubation, and the increase in heart rate correlated with the increase in brain oxygen saturation (r = 0.48, P < 0.05). Conclusions Intubation‐related stress increased oxyhaemoglobin related to electroencephalogram and autonomic activation. Stress‐induced brain stimulation may be monitored during anaesthesia using frequency domain near‐infrared spectroscopy.

Effect of age on brain oxygenation regulation during changes in position

INTRODUCTION Reports indicate that brain regulation of oxygenation is inhibited in patients with low baseline oxyhemoglobin concentrations and that brain oxyhemoglobin concentrations are decreased with aging. The purpose of this study was to determine if regulation of brain oxygenation to changes in blood pressure is inhibited by normal aging. METHODS Brain oxyhemoglobin (OHb) and deoxyhemoglobin (HHb) concentrations were determined from the forehead using a frequency domain near infrared spectroscopy in 27 healthy volunteers. Subjects were separated into two groups by age (20-39, n=16; 40-60, n=11). Brain hemoglobin and non-invasive blood pressure were measured in (1) supine, (2) sitting, (3) supine and (4) sitting positions with 10-min equilibration intervals between each determination. Statistical differences were determined by two way repeated measures analysis of variance. RESULTS Young subjects were 28+/-5 years (mean+/-S.D.) and older subjects were 48+/-6 years. In supine position, OHb and HHb were 28.4+/-8.3 and 15.4+/-2.4micromol/L, respectively, in young; 22.4+/-5.7 and 13.4+/-2.9micromol/L, respectively, in older subjects, both P<0.05 between groups. Changing position from supine to sitting decreased OHb 5% and increased HHb 5% with no difference between groups. CONCLUSIONS There was a small but significant decrease in OHb and an increase in HHb from supine to sitting position, and this effect was similar between young and older subjects. Regulation of brain oxygenation during modest decreases in blood pressure did not change in normal aging to 60 years compared to young adults.