Bottom-up Gamma: the Pedunculopontine Nucleus and Reticular Activating System

Gamma rhythms have been proposed to promote the feed forward or "bottom-up" flow of information from lower to higher regions in the brain during perception. On the other hand, beta rhythms have been proposed to represent feed back or "top-down" influence from higher regions to lower. The pedunculopontine nucleus (PPN) has been implicated in sleep-wake control and arousal, and is part of the reticular activating system (RAS). This review describes the properties of the cells in this nucleus. These properties are unique, and perhaps it is the particular characteristics of these cells that allow the PPN to be involved in a host of functions and disorders. The fact that all PPN neurons fire maximally at gamma band frequency regardless of electrophysiological or transmitter type, make this an unusual cell group. In other regions, for example in the cortex, cells with such a property represent only a sub-population. More importantly, the fact that this cell group's functions are related to the capacity to generate coherent activity at a preferred natural frequency, gamma band, speaks volumes about how the PPN functions. We propose that "bottom-up" gamma band influence arises in the RAS and contributes to the build-up of the background of activity necessary for preconscious awareness and gamma activity at cortical levels.

Implications of gamma band activity in the pedunculopontine nucleus

The fact that the pedunculopontine nucleus (PPN) is part of the reticular activating system places it in a unique position to modulate sensory input and fight-or-flight responses. Arousing stimuli simultaneously activate ascending projections of the PPN to the intralaminar thalamus to trigger cortical high-frequency activity and arousal, as well as descending projections to reticulospinal systems to alter posture and locomotion. As such, the PPN has become a target for deep brain stimulation for the treatment of Parkinson's disease, modulating gait, posture, and higher functions. This article describes the latest discoveries on PPN physiology and the role of the PPN in a number of disorders. It has now been determined that high-frequency activity during waking and REM sleep is controlled by two different intracellular pathways and two calcium channels in PPN cells. Moreover, there are three different PPN cell types that have one or both calcium channels and may be active during waking only, REM sleep only, or both. Based on the new discoveries, novel mechanisms are proposed for insomnia as a waking disorder. In addition, neuronal calcium sensor protein-1 (NCS-1), which is over expressed in schizophrenia and bipolar disorder, may be responsible for the dysregulation in gamma band activity in at least some patients with these diseases. Recent results suggest that NCS-1 modulates PPN gamma band activity and that lithium acts to reduce the effects of over expressed NCS-1, accounting for its effectiveness in bipolar disorder.

Arousal, motor control, and parkinson's disease

This review highlights the most important discovery in the reticular activating system (RAS) in the last 10 years, the manifestation of gamma (γ) band activity in cells of the RAS, especially in the pedunculopontine nucleus (PPN), which is in charge of the high frequency states of waking and rapid eye movement sleep. This discovery is critical to understanding the modulation of movement by the RAS and how it sets the background over which we generate voluntary and triggered movements. The presence of γ band activity in the RAS is proposed to participate in the process of preconscious awareness, and provide the essential stream of information for the formulation of many of our actions. Early findings using stimulation of this region to induce arousal, and also to elicit stepping, are placed in this context. This finding also helps explain the novel use of PPN deep brain stimulation for the treatment of Parkinson’s disease, although considerable work remains to be done.

[Psychotropic-associated sexual dysfunctions: a survey of clinical pharmacology and medication-associated practice]

Epidemiological and clinical studies show that often persons affected by depression and schizophrenia can suffer of impairment of the sexual function. Most antidepressant and antipsychotic drugs have adverse sexual effects but it is difficult to identify if the impairment of the sexual function can be attributed to clinical picture or to the psychopharmacological treatments. Both antidepressants and novel and conventional antipsychotics are associated with significant sexual side effects and the presence of sexual side effects may affect compliance and adherence to treatment. In some specific clinical populations (e.g. youths), these specific side-effects turn out to be one of the most annoying and promote increased drop-out rates and poor adherence to treatment. Nevertheless, these clinical variables are often underestimated or not investigated in the course of follow-up of persons suffering from psychiatric disorders in treatment with psychotropic medications. Growing awareness of the adverse effects of psychotropic drugs has led to attempts to use adjuvants or substitute treatments to resolve sexual dysfunction. Effects on sexual function should be carefully diagnosed and treated; it should clearly discuss with patients in order to preserve an adequate quality of life, promote greater adherence to treatment and promote a good remission and recovery. The aim of this study is to review the most recent and significant literature data regarding association between sexual dysfunction and psychotropic medications, especially highlighting neurobiological and clinical data in order to improve the clinical pratice.

Gamma band activity in the RAS-intracellular mechanisms

Gamma band activity participates in sensory perception, problem solving, and memory. This review considers recent evidence showing that cells in the reticular activating system (RAS) exhibit gamma band activity, and describes the intrinsic membrane properties behind such manifestation. Specifically, we discuss how cells in the mesopontine pedunculopontine nucleus, intralaminar parafascicular nucleus, and pontine SubCoeruleus nucleus dorsalis all fire in the gamma band range when maximally activated, but no higher. The mechanisms involve high-threshold, voltage-dependent P/Q-type calcium channels, or sodium-dependent subthreshold oscillations. Rather than participating in the temporal binding of sensory events as in the cortex, gamma band activity in the RAS may participate in the processes of preconscious awareness and provide the essential stream of information for the formulation of many of our actions. We address three necessary next steps resulting from these discoveries: an intracellular mechanism responsible for maintaining gamma band activity based on persistent G-protein activation, separate intracellular pathways that differentiate between gamma band activity during waking versus during REM sleep, and an intracellular mechanism responsible for the dysregulation in gamma band activity in schizophrenia. These findings open several promising research avenues that have not been thoroughly explored. What are the effects of sleep or REM sleep deprivation on these RAS mechanisms? Are these mechanisms involved in memory processing during waking and/or during REM sleep? Does gamma band processing differ during waking versus REM sleep after sleep or REM sleep deprivation?

Virtual navigator automatic registration technology in abdominal application

Real-time Ultrasound (US) image fusion with a pre-acquired second imaging dataset - Computed Tomography (CT), Magnetic Resonance Imaging (MRI) and/or CT/PET - has become widely used in recent years for both diagnosis and image-guided interventional procedures. Liver and kidneys are the main focused anatomical districts, related to abdominal application. There are still nowadays some drawbacks, regarding the adoption of the fusion imaging technique in everyday practice especially regarding its ease of use and the time needed in order to obtain a precise real-time fusion between US and the second imaging modality. The present work is a preliminary study on the feasibility and practical use of an Automatic registration algorithm for CT-US real-time fusion imaging. Data obtained by tests performed on a Doppler phantom, for the assessment of the precision of the registration procedure and in-vivo Automatic registration tests, are presented.

The Use of First Generation versus Second Generation Antipsychotics as Add-on or as Switch Treatment and its Effect on QTc Interval: The Italian Experience in a Real-World Setting

Some psychotropic drugs are connected with prolongation of the QT interval, torsade de pointes and sudden death. Recent data suggest that with regard to this adverse effect, the atypical antipsychotic drugs are no safer than the older drugs. The purpose of this study is to evaluate the different use of first generation versus second generation antipsychotics as add-on (Group I) or switch treatment (Group II) and its effect on QTc interval in a sample of schizophrenic and bipolar inpatients without medical illness. All patients had been evaluated twice by using ECG: on admission and after two weeks of hospitalization. Exclusions criteria were: abnormalities in levels of potassium, magnesium and calcium, cardiovascular and metabolic diseases, alcohol or drug abuse. We found a significant (p < 0.01) greater use of first generation antipsychotic in Group I (73.80%) than in the Group II (33.33%). Also Group I showed a significant increase (p < 0.0001) in total chlorpromazine equivalent (476. 78 ± 448.80 mg/day vs 845.48 ± 491.64 mg/day) and in QTc interval (369.14 ± 33.75 ms vs 387.09 ± 31.97 ms), while we did not find any statistical difference in Group II during hospitalization. Our results, in spite of the small sample size, indicate that antipsychotic add-on can increase QTc interval more than switching to other antipsychotic in psychiatric patients without other risk factors.

Human amniotic fluid stem cells culture onto titanium screws: a new perspective for bone engineering

The use of titanium plates and screws for osteosynthesis is considered to be an effective treatment for different kinds of fractures in orthopedic surgery. The aim of the present study is to test the ability of titanium screws to promote the growth of osteoblasts obtained from human amniotic fluid stem cells (AFS). Osteoblastic differentiation was assessed by RT-PCR of specific markers such as COL1, ONC, OPN, OCN, OPG, BMP-4 and Runx2. Mineralization was demonstrated by the presence of red depositions. Adherent cells were found to cover the whole surface of titanium screw by Scanning Electron Microscopy (SEM). The result indicates the excellent growth of osteoblasts obtained from amniotic fluid on a titanium surface and could represent an important point in view of a possible therapeutic application of AFS cells.

Monte Carlo dose calculations using MCNP4C and EGSnrc/BEAMnrc codes to study the energy dependence of the radiochromic film response to beta-emitting sources

The energy dependence of the radiochromic film (RCF) response to beta-emitting sources was studied by dose theoretical calculations, employing the MCNP4C and EGSnrc/BEAMnrc Monte Carlo codes. Irradiations with virtual monochromatic electron sources, electron and photon clinical beams, a (32)P intravascular brachytherapy (IVB) source and other beta-emitting radioisotopes ((188)Re, (90)Y, (90)Sr/(90)Y,(32)P) were simulated. The MD-55-2 and HS radiochromic films (RCFs) were considered, in a planar or cylindrical irradiation geometry, with water or polystyrene as the surrounding medium. For virtual monochromatic sources, a monotonic decrease with energy of the dose absorbed to the film, with respect to that absorbed to the surrounding medium, was evidenced. Considering the IVB (32)P source and the MD-55-2 in a cylindrical geometry, the calibration with a 6 MeV electron beam would yield dose underestimations from 14 to 23%, increasing the source-to-film radial distance from 1 to 6 mm. For the planar beta-emitting sources in water, calibrations with photon or electron clinical beams would yield dose underestimations between 5 and 12%. Calibrating the RCF with (90)Sr/(90)Y, the MD-55-2 would yield dose underestimations between 3 and 5% for (32)P and discrepancies within +/-2% for (188)Re and (90)Y, whereas for the HS the dose underestimation would reach 4% with (188)Re and 6% with (32)P.

[Fractures of the calcaneus. The indications for surgical treatment]

The authors report the results obtained from a study of 41 cases of calcaneal fractures. Surgical treatment, when possible, is to be applied because it allows a satisfactory reconstruction of the subtalar and calcaneocuboid joint. The choice of various surgical methods is facilitated by computerised tomography which allows a precise assessment of the calcaneum. The quality and the stability of the reduction determine in a significant way the functional result.

[The carpal tunnel syndrome in hemodialysis patients]

The authors describe etiopathogenetic and anatomopathological characteristics of the carpal tunnel syndrome in patients undergoing chronic hemodialysis. In light of clinical experience early surgical treatment, which resolves the syndrome, is recommended.

[The rectus-adductor syndrome. The nosographic picture and treatment criteria]

The authors present a detailed study on the rectum-adductor syndrome, describing etiopathogenesis, physiotherapy, medical clinical and surgical treatment. They point out the importance of a wide knowledge of this syndrome commonly occurring to football players but occasionally found in players of other sports.

[Osteoarticular lesions from parachuting]

Based on personal experience gained in a parachuting centre (Pescara Aero-club) from 1975 up to 1988, the authors report their evaluation on chronic and acute osteoarticular lesions. The review of the cases was not based on the incidence of the lesions nor on their characteristics, normally found in common traumatology, but it was related to the dynamics of the trauma during the landing and to painful syndromes following a prolonged parachuting activity.

[Bifocal fractures of the leg]

The authors present the results obtained on 28 tibial bifocal fractures surgically treated with Kuntschers' intramedullary nailing and P.T.B. functional plastering. Among these cases, 21 occurred at the orthopaedic and traumatologic Clinic of Siena University, while the remaining 7 patients were treated at Chieti University. The authors point out the validity of this method comparing in with other different techniques (Grosse-Kempf method, intramedullary fixation obtained with Ender nails, both associated with functional treatment).

[Solitary chondromas of the hand: treatment indications]

The authors report their own experience on eleven cases of solitary chondroma of the hand, that occurred at the orthopaedic and traumatologic clinic of Chieti University. The patients were treated with curettage and spongy-cortical autoplastic bone-grafting or with injection of calcitonin and spongostan. No case had relapsing symptoms and the results obtained showed satisfactory improvements, even though with short-medium follow-up.