Epidemiology and Immediate Indirect Effects of Respiratory Viruses in Lung Transplant Recipients: A 5-Year Prospective Study.

The epidemiology of respiratory viruses (RVs) in lung transplant recipients (LTRs) and the relationship of RVs to lung function, acute rejection (AR) and opportunistic infections in these patients are not well known. We performed a prospective cohort study (2009-2014) by collecting nasopharyngeal swabs (NPSs) from asymptomatic LTRs during seasonal changes and from LTRs with upper respiratory tract infectious disease (URTID), lower respiratory tract infectious disease (LRTID) and AR. NPSs were analyzed by multiplex polymerase chain reaction. Overall, 1094 NPSs were collected from 98 patients with a 23.6% positivity rate and mean follow-up of 3.4 years (interquartile range 2.5-4.0 years). Approximately half of URTIDs (47 of 97, 48.5%) and tracheobronchitis cases (22 of 56, 39.3%) were caused by picornavirus, whereas pneumonia was caused mainly by paramyxovirus (four of nine, 44.4%) and influenza (two of nine, 22.2%). In LTRs with LRTID, lung function changed significantly at 1 mo (p = 0.03) and 3 mo (p = 0.04). In a nested case-control analysis, AR was associated with RVs (hazard ratio [HR] 6.54), Pseudomonas aeruginosa was associated with LRTID (HR 8.54), and cytomegalovirus (CMV) replication or disease was associated with URTID (HR 2.53) in the previous 3 mo. There was no association between RVs and Aspergillus spp. colonization or infection (HR 0.71). In conclusion, we documented a high incidence of RV infections in LTRs. LRTID produced significant lung function abnormalities. Associations were observed between AR and RVs, between P. aeruginosa colonization or infection and LRTID, and between CMV replication or disease and URTID.

The corticomotor projection to liminally-contractable forearm muscles in chronic spinal cord injury: a transcranial magnetic stimulation study.

STUDY DESIGN: A cross-sectional study in chronic spinal cord injury with cervical lesions (cSCI). OBJECTIVE: To determine the corticomotor projection and motor cortex organization of paralyzed forearm muscles that presented only liminal voluntary activation. SETTING: Burke Medical Research Institute, White Plains, NY, USA. METHODS: We identified ten people with chronic SCI who had a wrist flexor or extensor muscle with a motor power (MP) of 1 over 5. We recorded motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) over the primary motor cortex of the hemisphere contralateral to the target muscle. We measured resting motor threshold (RMT), corticomotor latency (LTY), MEP amplitude (AMP) and performed cortical motor mapping to determine the optimal site (OPT) and map area (AREA). Results were compared with the data from 18 controls. RESULTS: A MEP in the target muscle was observed for all cSCI cases. LTY was normal, while corticomotor excitability (as determined by RMT and AMP) was reduced in about half of the group. The OPT site of the motor maps was within control range for all cSCI cases, while AREA was reduced in three cases. CONCLUSIONS: Corticomotor conduction and cortical topography were appreciably normal despite only liminal activation of the target muscle with voluntary effort. Muscles with these characteristics may benefit from a targeted rehabilitation program even in the chronic phase after SCI.

Epidemiology of invasive respiratory disease caused by emerging non-Aspergillus molds in lung transplant recipients.

OBJECTIVES: Our aim was to assess the impact of positive cultures for non-Aspergillus molds on the risk of progression to invasive fungal infection (IFI), and the effect of prophylactic nebulized liposomal amphotericin B (n-LAB) on these pathogens. METHODS: This was an observational study (2003-2013) including lung transplant recipients (LTR) receiving lifetime n-LAB prophylaxis, in whom non-Aspergillus molds were isolated on respiratory culture before and after transplantation (minimum 1-year follow-up). RESULTS: We studied 412 patients, with a mean postoperative follow-up of 2.56 years (interquartile range 1.01-4.65). Pre- and post-transplantation respiratory samples were frequently positive for non-Aspergillus molds (11.9% and 16.9% of LTR respectively). Post transplantation, 10 (2.42%) patients developed non-Aspergillus mold infection (4 Scedosporium species, 4 Purpureocillium species, 1 Penicillium species, and 1 Scopulariopsis species); 5 (1.21%) had IFI, with 60% IFI-related mortality. Non-Aspergillus molds with intrinsic amphotericin B (AB) resistance were more commonly isolated in bronchoscopy samples than AB-variably sensitive or AB-sensitive molds (54.5% vs. 25%, P = 0.04) and were associated with a higher risk of infection (56.3% vs. 1.3%%, P < 0.01). CONCLUSIONS: In LTR undergoing n-LAB prophylaxis, pre- and post-transplantation isolation of non-Aspergillus molds is frequent, but IFI incidence (1.21%) is low. Purpureocillium is an emerging mold. AB-resistant non-Aspergillus species were found more often in bronchoscopy samples and were associated with a higher risk of infection.

Assessing Single Upconverting Nanoparticle Luminescence by Optical Tweezers.

We report on stable, long-term immobilization and localization of a single colloidal Er(3+)/Yb(3+) codoped upconverting fluorescent nanoparticle (UCNP) by optical trapping with a single infrared laser beam. Contrary to expectations, the single UCNP emission differs from that generated by an assembly of UCNPs. The experimental data reveal that the differences can be explained in terms of modulations caused by radiation-trapping, a phenomenon not considered before but that this work reveals to be of great relevance.

Neuromuscular Fatigue after Submaximal Intermittent Contractions in Motorcycle Riders.

Highly repetitive submaximal intermittent contractions of the forearm muscles during periods of 30-50 min partially explain why motorcycle races are so demanding for the neuromuscular system. This study investigated the contribution of central and peripheral mechanisms of fatigue on the exerted and contralateral extensor digitorum communis following an intermittent fatigue protocol (IFP) designed for motorcycle riders. 12 riders performed an IFP, which simulates the braking and throttle handle gesture. We examined the time course of recovery of maximal voluntary contraction (MVC), M-wave, motor evoked potential (MEP) to transcranial magnetic stimuli in relaxed and facilitated condition, and the cortical silent period (CSP) at time windows of 1, 3, 5, 10 and 20 min after the IFP. Whereas MVC, M-wave and MEP decreased, CSP lengthened significantly in the fatigued limb after completion of the IFP. Nevertheless, no differences were observed in the contralateral limb. All neurophysiological parameters reverted to baseline values in less than 20 min, while MVC remained lower in the exercised limb. No cross-over effects were observed in the contralateral non-exercised limb. Our results suggest that local factors are those mainly responsible for the incomplete MVC recovery after an intermittent muscle contraction protocol.

Patients' Perceived Valorization Toward Ringing the Cancer Bell at the End of Their Radiation Therapy.

PURPOSE: In recent times, "ringing the bell" at the end of cancer treatment has attracted the attention of health care providers with regard to how this experience impacts patients' mental and emotional health. In this context, a study was conducted at a radiation oncology center in Santiago, Chile, to assess the perceived valorization of patients toward "ringing the bell" at the end of their treatment. It was further determined whether this experience had a positive or negative impact on their mental health. METHODS AND MATERIALS: Two hundred thirty-six patients were invited to respond to a printed anonymous survey that used a Likert scale to evaluate their perceived valorization of "ringing the bell" after radiation therapy. In this survey, patients were also asked questions regarding their background to examine possible trends related to different lifestyles and socioeconomic status. RESULTS: The results showed that 93.6% of participants classified the experience as "positive" or "very positive." There were 6 "negative" responses out of 708 (0.8%) to the 3 questions regarding perceived valorization of the experience and no "very negative" responses. CONCLUSIONS: "Ringing the bell" at the end of radiation therapy can be considered a psychological comfort that positively impacts patients' mental health. No trends related to socioeconomic status were observed.

Comparison of two HIV testing strategies in primary care centres: indicator-condition-guided testing vs. testing of those with non-indicator conditions.

OBJECTIVES: The aim of the study was to compare prospectively indicator-condition (IC)-guided testing versus testing of those with non-indicator conditions (NICs) in four primary care centres (PCCs) in Barcelona, Spain. METHODS: From October 2009 to February 2011, patients aged from 18 to 65 years old who attended a PCC for a new herpes zoster infection, seborrhoeic eczema, mononucleosis syndrome or leucopenia/thrombopenia were included in the IC group, and one in every 10 randomly selected patients consulting for other reasons were included in the NIC group. A proportion of patients in each group were offered an HIV test; those who agreed to be tested were given a rapid finger-stick HIV test (€6 per test). Epidemiological and clinical data were collected and analysed. RESULTS: During the study period, 775 patients attended with one of the four selected ICs, while 66,043 patients presented with an NIC. HIV screening was offered to 89 patients with ICs (offer rate 11.5%), of whom 85 agreed to and completed testing (94.4 and 100% acceptance and completion rates, respectively). In the NIC group, an HIV test was offered to 344 persons (offer rate 5.2%), of whom 313 accepted (90.9%) and 304 completed (97.1%) testing. HIV tests were positive in four persons [prevalence 4.7%; 95% confidence interval (CI) 1.3-11.6%] in the IC group and in one person in the NIC group (prevalence 0.3%; 95% CI 0.01-1.82%; P < 0.009). If every eligible person had taken an HIV test, we would have spent €4650 in the IC group and €396,258 in the NIC group, and an estimated 36 (95% CI 25-49) and 198 persons (95% CI 171-227), respectively, would have been diagnosed with HIV infection. The estimated cost per new HIV diagnosis would have been €129 (95% CI €107-153) in the IC group and €2001 (95% CI €1913-2088) in the NIC group. CONCLUSIONS: Although the number of patients included in the study was small and the results should be treated with caution, IC-guided HIV testing, based on four selected ICs, in PCCs seems to be a more feasible and less expensive strategy to improve diagnosis of HIV infection in Spain than a nontargeted HIV testing strategy.

[Recommendations for the clinical use of motor evoked potentials in multiple sclerosis]. / Recomendaciones para la utilización clínica del estudio de potenciales evocados motores en la esclerosis múltiple.

OBJECTIVE: To establish clinical guidelines for the clinical use and interpretation of motor evoked potentials (MEP) in diagnosing and monitoring patients with multiple sclerosis (MS). Recommendations for MEP use and interpretation will help us rationalise and optimise resources used in MS patient diagnosis and follow up. METHOD: We completed an extensive literature review and pooled our own data to produce a consensus statement with recommendations for the clinical use of MEPs in the study of MS. RESULTS: MEPs, in addition to spinal and cranial magnetic resonance imaging (MRI), help us diagnose and assess MS patients whose disease initially presents as spinal cord syndrome and those with non-specific brain MRI findings, or a normal brain MRI and clinical signs of MS. CONCLUSIONS: Whenever possible, a multimodal evoked potential study should be performed on patients with suspected MS in order to demonstrate involvement of the motor pathway which supports a diagnosis of dissemination in space.

High-sensitivity fluorescence lifetime thermal sensing based on CdTe quantum dots.

The potential use of CdTe quantum dots as luminescence nano-probes for lifetime fluorescence nano-thermometry is demonstrated. The maximum thermal sensitivity achievable is strongly dependent on the quantum dot size. For the smallest sizes (close to 1 nm) the lifetime thermal sensitivity overcomes those of conventional nano-probes used in fluorescence lifetime thermometry.

EFNS guidelines on diagnosis and treatment of primary dystonias.

OBJECTIVES: to provide a revised version of earlier guidelines published in 2006. BACKGROUND: primary dystonias are chronic and often disabling conditions with a widespread spectrum mainly in young people. DIAGNOSIS: primary dystonias are classified as pure dystonia, dystonia plus or paroxysmal dystonia syndromes. Assessment should be performed using a validated rating scale for dystonia. Genetic testing may be performed after establishing the clinical diagnosis. DYT1 testing is recommended for patients with primary dystonia with limb onset before age 30, and in those with an affected relative with early-onset dystonia. DYT6 testing is recommended in early-onset or familial cases with cranio-cervical dystonia or after exclusion of DYT1. Individuals with early-onset myoclonus should be tested for mutations in the DYT11 gene. If direct sequencing of the DYT11 gene is negative, additional gene dosage is required to improve the proportion of mutations detected. A levodopa trial is warranted in every patient with early-onset primary dystonia without an alternative diagnosis. In patients with idiopathic dystonia, neurophysiological tests can help with describing the pathophysiological mechanisms underlying the disorder. TREATMENT: botulinum toxin (BoNT) type A is the first-line treatment for primary cranial (excluding oromandibular) or cervical dystonia; it is also effective on writing dystonia. BoNT/B is not inferior to BoNT/A in cervical dystonia. Pallidal deep brain stimulation (DBS) is considered a good option, particularly for primary generalized or cervical dystonia, after medication or BoNT have failed. DBS is less effective in secondary dystonia. This treatment requires a specialized expertise and a multidisciplinary team.

Excitatory and inhibitory responses to cervical root magnetic stimulation in healthy subjects.

OBJECTIVES: To characterize direct and reflex hand muscle responses to cervical root magnetic stimulation (CRMS) in healthy volunteers during sustained voluntary contraction. METHODS: In 18 healthy volunteers, we recorded from the first dorsal interosseous (FDI) muscle the responses to CRMS of progressively increasing intensity and level of muscle contraction. The compound muscle action potential (CMAP) and the silent period (SP) were compared to those obtained with plexus, midarm and wrist stimulation. Additionally, in a smaller number of subjects, we obtained the peristimulus time histogram (psth) of single motor unit firing in the FDI, examined the effects of vibration and recorded the modulation of sustained EMG activity in muscles of the lower limbs. RESULTS: Increasing CRMS intensity led to larger CMAP with no relevant changes in SP1 or SP2, except for lower amplitude of the burst interrupting the silent period (BISP). Increasing the level of muscle contraction led to reduced CMAP, shorter SP duration and increased BISP amplitude. The psth analysis showed the underlying changes in the motor unit firing frequency that corresponded to the changes seen in the CMAP and the SP with surface recordings. Progressively distal stimulation led to CMAPs of shorter latency and increased amplitude, SPs of longer latency and shorter duration, and a BISP of longer latency. Vibration led to reduction of the SP. CRMS induced SPs in muscles of the lower limb. CONCLUSIONS: CRMS induces excitatory and inhibitory responses in hand muscles, fitting with the expected behavior of mixed nerve stimulation at very proximal sites. SIGNIFICANCE: Characterization of the effects of CRMS on hand muscles is of physiological and potentially clinical applicability, as it is a painless and reliable procedure.

Involvement of the K and I regions of the H-2 complex in resistance to hemopoietic allografts.

Irradiated (H-2b X H-2k)F1 and (H-2b X H-2d)F1 recipients strongly resist the growth of H-2b parental bone marrow cells and do not resist marrow grafts from non-H-2b parents such as C3H and BALB/c. This phenomenon of hybrid resistance has been shown to be under genetic control of the H-2D-linked loci and was interpreted by Cudkowicz (9) as due to the existence of H-2D-linked recessive hemopoietic histocompatibility genes. To check whether the H-2D-linked loci are solely responsible for the fate of bone marrow allografts, we measured the strength of resistance of irradiated (B6 X C3H)F1 and (B6 X BALB/c)F1 recipients toward bone marrow grafts from a set of H-2 recombinant and F1 hybrid donors carrying either the H-2b, H-2d, and H-2k alleles. We found that growth of all H-2b grafts was resisted, although to different degrees. Resistance was minimal when donors shared with the input strain of a corresponding F1 hybrid the H-2K and H-2I regions, or when both F1 donors and F1 recipients formed identical unique hybrid Ia molecules. In addition, H-2b grafts were resisted by congenic, H-2D-identical, H-2K-and H-2I-incompatible recipients. The fate of grafts from H-2Dd donors seemed to depend on the incompatibility of the combinatorial determinant Ia.22. If both donor and recipient expressed such a determinant (either in the cis or in the transposition), or if neither could form such a determinant, grafts were not resisted. The H-2Dk allele is not the main or only factor that confers on the C3H parental bone marrow cells the ability to grow unresisted in (B6 X C3H)F1 recipients. Grafts from congenic C3H.OH donors, carrying the same H-2Dk alleles and differing in the left part of the H-2 complex, were resisted by the F1 recipients. We conclude that both class I (K and D) and class II (I-A and I-E) major histocompatibility complex genes, rather than hypothetical hemopoietic histocompatibility genes control hemopoietic resistance. To reconcile codominant inheritance of classic H-2 antigens with the apparent recessive inheritance of hybrid resistance, we assume that there exist parental determinants that are not formed in some F1 hybrids due to preferential association of either Ia alpha chains with allogeneic beta chains or of class I antigens with allogeneic or hybrid class II restriction elements.

A novel PSEN1 mutation (K239N) associated with Alzheimer's disease with wide range age of onset and slow progression.

OBJECTIVE: To describe a novel mutation (K239N) in the PSEN1 associated with familial Alzheimer's disease (AD). METHODS AND RESULTS: The proband was a man who developed cognitive decline with marked behavioural abnormalities at age 57. At age 70, he was admitted into a psychiatric facility because of aggressiveness and a suicide attempt. Family history was consistent with autosomal dominant AD. One of the two other family members studied presented also with prominent behavioural symptoms at age 42 and has also been forced into a psychiatric facility because of aggressiveness at age 56. The remainder patient has presented a prototypical AD, but starting at age 71. Direct sequencing of PSEN1 in the three living affected members disclosed a heterozygous G to C transition in exon 7 of PSEN1 leading to the K239N mutation. CONCLUSION: The K239N mutation is associated with autosomal dominant AD with a wide range of age of onset and incomplete penetrance at the age of 65, prominent behavioural features and slow progression.

European Federation of Neurological Societies/Peripheral Nerve Society Guideline on the use of skin biopsy in the diagnosis of small fiber neuropathy. Report of a joint task force of the European Federation of Neurological Societies and the Peripheral Nerve Society.

BACKGROUND: Revision of the guidelines on the use of skin biopsy in the diagnosis of peripheral neuropathy, published in 2005, has become appropriate owing to publication of more relevant articles. Most of the new studies focused on small fiber neuropathy (SFN), a subtype of neuropathy for which the diagnosis was first developed through skin biopsy examination. This revision focuses on the use of this technique to diagnose SFN. METHODS: Task force members searched the Medline database from 2005, the year of the publication of the first EFNS guideline, to June 30th, 2009. All pertinent articles were rated according to the EFNS and PNS guidance. After a consensus meeting, the task force members created a manuscript that was subsequently revised by two experts (JML and JVS) in the field of peripheral neuropathy and clinical neurophysiology, who were not previously involved in the use of skin biopsy. RESULTS AND CONCLUSIONS: Distal leg skin biopsy with quantification of the linear density of intraepidermal nerve fibers (IENF), using generally agreed upon counting rules, is a reliable and efficient technique to assess the diagnosis of SFN (Recommendation Level A). Normative reference values are available for bright-field immunohistochemistry (Recommendation Level A) but not yet for confocal immunofluorescence or the blister technique. The morphometric analysis of IENF density, either performed with bright-field or immunofluorescence microscopy, should always refer to normative values matched for age (Recommendation Level A). Newly established laboratories should undergo adequate training in a well-established skin biopsy laboratory and provide their own stratified for age and gender normative values, intra- and interobserver reliability, and interlaboratory agreement. Quality control of the procedure at all levels is mandatory (Good Practice Point). Procedures to quantify subepidermal nerve fibers and autonomic innervated structures, including erector pili muscles, and skin vessels, are under development but need to be confirmed by further studies. Sweat gland innervation can be examined using an unbiased stereologic technique recently proposed (Recommendation Level B). A reduced IENF density is associated with the risk of developing neuropathic pain (Recommendation Level B), but it does not correlate with its intensity. Serial skin biopsies might be useful for detecting early changes of IENF density, which predict the progression of neuropathy, and to assess degeneration and regeneration of IENF (Recommendation Level C). However, further studies are warranted to confirm its potential usefulness as an outcome measure in clinical practice and research. Skin biopsy has not so far been useful for identifying the etiology of SFN. Finally, we emphasize that 3-mm skin biopsy at the ankle is a safe procedure based on the experience of 10 laboratories reporting absence of serious side effects in approximately 35,000 biopsies and a mere 0.19% incidence of non-serious side effects in about 15 years of practice (Good Practice Point).

H reflex modulation by transcranial magnetic stimulation in spinal cord injury subjects after gait training with electromechanical systems.

STUDY DESIGN: Prospective longitudinal study. OBJECTIVES: The aim of this study was to examine the effects of transcranial magnetic stimulation (TMS) on the soleus H reflex in patients with spinal cord injury (SCI) before and after locomotion training. SETTING: Neurorehabilitation hospital in Barcelona, Spain. METHODS: H reflex was elicited in 29 incomplete patients with SCI at 20, 50 and 80 ms after single vertex TMS, and compared with 13 healthy subjects. Patients were subdivided in two groups according to time since injury (<3 months, 3-12 months), and all received training with electromechanical systems. The H reflex modulation pattern to TMS was reassessed and the results were analyzed as a function of change in the patient clinical score. RESULTS: Healthy subjects showed a significant H reflex facilitation at 20 ms (186.1%) and at 80 ms (190.6%) compared with the control H reflex. In patients, the H reflex facilitation at 20 ms was significantly reduced before training (142.5%, P=0.039) compared with healthy subjects. After training, patients with <3 months exhibited an increase in H reflex facilitation at 20 ms (170.7%, P=0.04), a greater gait velocity (P=0.014) and a positive correlation with the walking index for spinal cord injury (WISCI II) scale (P=0.050), compared with those with >3 months. CONCLUSIONS: TMS-induced H reflex modulation may help in the assessment of changes in the descending control of leg reflexes. Our results suggest that the changes on reflex modulation in patients with SCI occur within the first 3 months after injury.

Role of boost radiotherapy for local control of pure ductal carcinoma in situ after breast-conserving surgery: a multicenter, retrospective study of 622 patients.

PURPOSE: To evaluate the effect of boost radiotherapy on ipsilateral breast tumor recurrence (IBTR) for ductal carcinoma in situ (DCIS) after breast-conserving surgery and whole breast radiotherapy (WBRT) with or without boost. METHODS AND MATERIALS: Retrospective, multicentre study of 622 patients (624 tumors) diagnosed with pure DCIS from 1993-2011. RESULTS: Most tumors (377/624; 60.4%) received a boost. At a median follow-up of 8.8 years, IBTR occurred in 64 cases (10.3%). A higher percentage of patients with risk factors for IBTR received a boost (p < 0.05). Boost was not associated with lower rates of IBTR than WBRT alone (HR 0.75, 95% CI 0.42-1.35). On the univariate analyses, IBTR was significantly associated with tumor size (11-20 mm, HR 2.32, 95% CI 1.27-4.24; and > 20 mm, HR 2.10, 95% CI 1.14-3.88), re-excision (HR 1.76, 95% CI 1.04-2.96), and tamoxifen (HR 2.03, 95% CI 1.12-3.70). Boost dose > 16 Gy had a protective effect (HR 0.39, 95% CI 0.187-0.824). Multivariate analyses confirmed the independent associations between IBTR and 11-20 mm (p = 0.02) and > 20 mm (p = 0.009) tumours, and re-excision (p = 0.006). On the margin-stratified multivariate analysis, tamoxifen was a poor prognostic factor in the close/positive margin subgroup (HR 4.28 95% CI 1.23-14.88), while the highest boost dose ( > 16 Gy) had a significant positive effect (HR 0.34, 95% CI 0.13-0.86) in the negative margin subgroup. CONCLUSIONS: Radiotherapy boost did not improve the risk of IBTR. Boost radiotherapy was more common in patients with high-risk disease. Tumor size and re-excision were significant independent prognostic factors.

Controlling Magnetization Reversal and Hyperthermia Efficiency in Core-Shell Iron-Iron Oxide Magnetic Nanoparticles by Tuning the Interphase Coupling.

Magnetic particle hyperthermia, in which colloidal nanostructures are exposed to an alternating magnetic field, is a promising approach to cancer therapy. Unfortunately, the clinical efficacy of hyperthermia has not yet been optimized. Consequently, routes to improve magnetic particle hyperthermia, such as designing hybrid structures comprised of different phase materials, are actively pursued. Here, we demonstrate enhanced hyperthermia efficiency in relatively large spherical Fe/Fe-oxide core-shell nanoparticles through the manipulation of interactions between the core and shell phases. Experimental results on representative samples with diameters in the range 30-80 nm indicate a direct correlation of hysteresis losses to the observed heating with a maximum efficiency of around 0.9 kW/g. The absolute particle size, the core-shell ratio, and the interposition of a thin wüstite interlayer are shown to have powerful effects on the specific absorption rate. By comparing our measurements to micromagnetic calculations, we have unveiled the occurrence of topologically nontrivial magnetization reversal modes under which interparticle interactions become negligible, aggregates formation is minimized and the energy that is converted into heat is increased. This information has been overlooked until date and is in stark contrast to the existing knowledge on homogeneous particles.

The effect of a prepulse stimulus on the EMG rebound following the cutaneous silent period.

The cutaneous silent period (CSP) is a spinal inhibitory reflex mediated by Adelta fibres. The postinhibitory rebound of electromyographic (EMG) activity following the CSP has been mainly attributed to resynchronization of motoneurons, but the possibility of startle reflex activity contributing to the EMG burst has also been suggested. Several types of reflexes may be suppressed by a preceding weak stimulus--a phenomenon called prepulse inhibition (PPI). Our aim was to study whether PPI would diminish the EMG rebound, thereby providing further evidence for excitatory reflex activity contained within the postinhibitory EMG rebound following the CSP. Ten healthy subjects underwent CSP testing following noxious digit II stimulation in two conditions, with and without a prepulse applied to digit III. Rectified surface EMG recordings were obtained from right orbicularis oculi, sternocleidomastoid and thenar muscles of the dominant hand during thumb abduction with 25% of maximum force. The area of the EMG rebound and the EMG reflex responses in orbicularis oculi and sternocleidomastoid were significantly smaller in recordings where a prepulse stimulus was applied 100 ms before the stimulus as compared to control responses without prepulse. CSP onset and end latency, CSP duration, and the degree of EMG suppression were not influenced. Prepulses significantly reduced subjective discomfort as based on visual analog scale scores. Inhibition of the EMG rebound by prepulse stimulation supports the hypothesis that the excitatory EMG activity following the CSP contains not only resynchronization of motoneuronal firing, but also an excitatory reflex component. The most probable type of reflex seems to be a somatosensory startle reflex, a defence reaction which is generated in structures located in the caudal brainstem following an unexpected intense stimulus. Reduction of the discomfort associated with high-intensity electrical fingertip stimulation by a prepulse without affecting CSP parameters underlines the utility of PPI in the context of CSP testing.