Transplantation of Cultured Olfactory Bulb Cells Prevents Abnormal Sensory Responses During Recovery From Dorsal Root Avulsion in the Rat

The central branches of the C7 and C8 dorsal roots were avulsed close to their entry point into the spinal cord in adult rats. The forepaw responses to heat and cold stimuli were tested at 1, 2, and 3 weeks after injury. Over this period, the paws were sensitive to both stimuli at 1-2 weeks and returned toward normal at 3 weeks. Immunohistology showed no evidence of axonal regeneration into the spinal cord in a control group of rats with avulsion only, implying that adjacent dorsal roots and their corresponding dermatomes were involved in the recovery. In a further group of rats, a mixture of bulbar olfactory ensheathing cells and olfactory nerve fibroblasts were transplanted into the gap between the avulsed roots and the spinal cord at the time of avulsion. These rats showed no evidence of either loss of sensation or exaggerated responses to stimuli at any of the time points from 1 to 3 weeks. Immunohistology showed that the transplanted cells formed a complete bridge, and the central branches of the dorsal root fibers had regenerated into the dorsal horn of the spinal cord. These regenerating axons, including Tuj1 and CGRP immunoreactive fibers, were ensheathed by the olfactory ensheathing cells. This confirms our previous demonstration of central regeneration by these transplants and suggests that such transplants may provide a useful means to prevent the development of abnormal sensations such as allodynia after spinal root lesions

Methodology for quantifying excitability of identified projection neurons in the dorsal horn of the spinal cord, specifically to study spinal cord stimulation paradigms

BACKGROUND: Using in and ex vivo preparations, electrophysiological methods help understand the excitability of biological tissue, particularly neurons, by providing microsecond temporal resolution. However, for in vivo recordings, in the context of extracellular recordings, it is often unclear precisely which type of neuron the tip of the electrode is recording from. This is particularly true in the densely-populated central nervous system, such as the spinal cord dorsal horn at both superficial and deep levels. / NEW METHOD: Here, we present a detailed protocol for the identification of superficial dorsal horn spinal cord neurons that receive peripheral input and project to the brain, using multiple surgical laminectomies and the careful placement of electrodes. Once a superficial projection unit was found, quantification to electrical peripheral stimulation was performed using a Matlab algorithm to form a template of projection neuron response to controlled C2 stimulation and accurately match this to the responses from peripheral stimulation. / RESULTS: These superficial spinal projection neurons are normally activated by noxious peripheral stimuli, so we adopted a well-characterised wind-up protocol to obtain a neuronal excitability profile. Once achieved, this protocol allows for testing specific interventions, either pharmacological or neuromodulatory (e.g., spinal cord stimulation) to see how these affect the neuron's excitability. This preparation is robust and allows the accurate tracking of a projection neuron for over 3-h. / COMPARISON WITH EXISTING METHOD(S): Currently, most existing methods record from dorsal horn neurons that are often profiled based on their excitability to different peripherally-applied sensory modalities. While this is well-established, it fails to discriminate between interneurons and projection neurons, which is important as these two populations signal via distinctly different neuronal networks. Using the approach detailed here will result in studies with improved mechanistic understanding of the signal integration and processing that occurs in the superficial dorsal horn. CONCLUSIONS: The refinements detailed in this protocol allow for more comprehensive studies to be carried out that will help understand spinal plasticity, in addition to many considerations for isolating the relevant neuronal population when performing in vivo electrophysiology

Does a SLAP lesion affect shoulder muscle recruitment as measured by EMG activity during a rugby tackle?

Background: The study objective was to assess the influence of a SLAP lesion on onset of EMG activity in shoulder muscles during a front on rugby football tackle within professional rugby players. Methods: Mixed cross-sectional study evaluating between and within group differences in EMG onset times. Testing was carried out within the physiotherapy department of a university sports medicine clinic. The test group consisted of 7 players with clinically diagnosed SLAP lesions, later verified on arthroscopy. The reference group consisted of 15 uninjured and full time professional rugby players from within the same playing squad. Controlled tackles were performed against a tackle dummy. Onset of EMG activity was assessed from surface EMG of Pectorialis Major, Biceps Brachii, Latissimus Dorsi, Serratus Anterior and Infraspinatus muscles relative to time of impact. Analysis of differences in activation timing between muscles and limbs (injured versus non-injured side and non injured side versus matched reference group). Results: Serratus Anterior was activated prior to all other muscles in all (P = 0.001-0.03) subjects. In the SLAP injured shoulder Biceps was activated later than in the non-injured side. Onset times of all muscles of the noninjured shoulder in the injured player were consistently earlier compared with the reference group. Whereas, within the injured shoulder, all muscle activation timings were later than in the reference group. Conclusions: This study shows that in shoulders with a SLAP lesion there is a trend towards delay in activation time of Biceps and other muscles with the exception of an associated earlier onset of activation of Serratus anterior, possibly due to a coping strategy to protect glenohumeral stability and thoraco-scapular stability. This trend was not statistically significant in all cases

Repeat pneumococcal polysaccharide vaccination does not impair functional immune responses among Indigenous Australians.

Indigenous Australians experience one of the highest rates of pneumococcal disease globally. In the Northern Territory of Australia, a unique government-funded vaccination schedule for Indigenous Australian adults comprising multiple lifetime doses of the pneumococcal polysaccharide vaccine is currently implemented. Despite this programme, rates of pneumococcal disease do not appear to be declining, with concerns raised over the potential for immune hyporesponse associated with the use of this vaccine. We undertook a study to examine the immunogenicity and immune function of a single and repeat pneumococcal polysaccharide vaccination among Indigenous adults compared to non-Indigenous adults. Our results found that immune function, as measured by opsonophagocytic and memory B-cell responses, were similar between the Indigenous groups but lower for some serotypes in comparison with the non-Indigenous group. This is the first study to document the immunogenicity following repeat 23-valent pneumococcal polysaccharide vaccine administration among Indigenous Australian adults, and reinforces the continued need for optimal pneumococcal vaccination programmes among high-risk populations

Horizontal DNA transfer mechanisms of bacteria as weapons of intragenomic conflict

Horizontal DNA transfer (HDT) is a pervasive mechanism of diversification in many microbial species, but its primary evolutionary role remains controversial. Much recent research has emphasised the adaptive benefit of acquiring novel DNA, but here we argue instead that intragenomic conflict provides a coherent framework for understanding the evolutionary origins of HDT. To test this hypothesis, we developed a mathematical model of a clonally descended bacterial population undergoing HDT through transmission of mobile genetic elements (MGEs) and genetic transformation. Including the known bias of transformation toward the acquisition of shorter alleles into the model suggested it could be an effective means of counteracting the spread of MGEs. Both constitutive and transient competence for transformation were found to provide an effective defence against parasitic MGEs; transient competence could also be effective at permitting the selective spread of MGEs conferring a benefit on their host bacterium. The coordination of transient competence with cell-cell killing, observed in multiple species, was found to result in synergistic blocking of MGE transmission through releasing genomic DNA for homologous recombination while simultaneously reducing horizontal MGE spread by lowering the local cell density. To evaluate the feasibility of the functions suggested by the modelling analysis, we analysed genomic data from longitudinal sampling of individuals carrying Streptococcus pneumoniae. This revealed the frequent within-host coexistence of clonally descended cells that differed in their MGE infection status, a necessary condition for the proposed mechanism to operate. Additionally, we found multiple examples of MGEs inhibiting transformation through integrative disruption of genes encoding the competence machinery across many species, providing evidence of an ongoing "arms race." Reduced rates of transformation have also been observed in cells infected by MGEs that reduce the concentration of extracellular DNA through secretion of DNases. Simulations predicted that either mechanism of limiting transformation would benefit individual MGEs, but also that this tactic's effectiveness was limited by competition with other MGEs coinfecting the same cell. A further observed behaviour we hypothesised to reduce elimination by transformation was MGE activation when cells become competent. Our model predicted that this response was effective at counteracting transformation independently of competing MGEs. Therefore, this framework is able to explain both common properties of MGEs, and the seemingly paradoxical bacterial behaviours of transformation and cell-cell killing within clonally related populations, as the consequences of intragenomic conflict between self-replicating chromosomes and parasitic MGEs. The antagonistic nature of the different mechanisms of HDT over short timescales means their contribution to bacterial evolution is likely to be substantially greater than previously appreciated

The impact of bone cancer on the peripheral encoding of mechanical pressure stimuli

Skeletal metastases are frequently accompanied by chronic pain that is mechanoceptive in nature. Mechanistically, cancer-induced bone pain (CIBP) is mediated by peripheral sensory neurons innervating the cancerous site, the cell bodies of which are housed in the dorsal root ganglia (DRG). How these somatosensory neurons encode sensory information in CIBP remains only partly explained. Using a validated rat model, we first confirmed cortical bone destruction in CIBP but not sham-operated rats (day 14 after surgery, designated “late”-stage bone cancer). This occurred with behavioural mechanical hypersensitivity (Kruskal–Wallis H for independent samples; CIBP vs sham-operated, day 14; P < 0.0001). Next, hypothesising that the proportion and phenotype of primary afferents would be altered in the disease state, dorsal root ganglia in vivo imaging of genetically encoded calcium indicators and Markov Cluster Analysis were used to analyse 1748 late-stage CIBP (n = 10) and 757 sham-operated (n = 9), neurons. Distinct clusters of responses to peripheral stimuli were revealed. In CIBP rats, upon knee compression of the leg ipsilateral to the tumour, (1) 3 times as many sensory afferents responded (repeated-measures analysis of variance: P < 0.0001 [vs sham]); (2) there were significantly more small neurons responding (Kruskal–Wallis for independent samples (vs sham): P < 0.0001); and (3) approximately 13% of traced tibial cavity afferents responded (no difference observed between CIBP and sham-operated animals). We conclude that an increased sensory afferent response is present in CIBP rats, and this is likely to reflect afferent recruitment from outside of the bone rather than increased intraosseous afferent activity

Leishmania isoenzyme polymorphisms in Ecuador: Relationships with geographic distribution and clinical presentation

Background: Determinants of the clinical presentation of the leishmaniases are poorly understood but Leishmania species and strain differences are important. To examine the relationship between clinical presentation, species and isoenzyme polymorphisms, 56 Leishmania isolates from distinct presentations of American tegumentary leishmaniasis (ATL) from Ecuador were analyzed. Methods: Isolates were characterized by multilocus enzyme electrophoresis for polymorphisms of 11 isoenzymes. Patients were infected in four different ecologic regions: highland and lowland jungle of the Pacific coast, Amazonian lowlands and Andean highlands. Results: Six Leishmania species constituting 21 zymodemes were identified: L. (Viannia) panamensis (21 isolates, 7 zymodemes), L. (V.) guyanensis (7 isolates, 4 zymodemes), L. (V.) braziliensis (5 isolates, 3 zymodemes), L. (Leishmania) mexicana (11 isolates, 4 zymodemes), L. (L.) amazonensis (10 isolates, 2 zymodemes) and L. (L.) major (2 isolates, 1 zymodeme). L. panamensis was the species most frequently identified in the Pacific region and was associated with several clinical variants of cutaneous disease (CL); eight cases of leishmaniasis recidiva cutis (LRC) found in the Pacific highlands were associated with 3 zymodemes of this species. Mucocutaneous leishmaniasis found only in the Amazonian focus was associated with 3 zymodemes of L. braziliensis. The papular variant of CL, Uta, found in the Andean highlands was related predominantly with a single zymodeme of L. mexicana. Conclusion: Our data show a high degree of phenotypic variation within species, and some evidence for associations between specific variants of ATL (i.e. Uta and LRC) and specific Leishmania zymodemes. This study further defines the geographic distribution of Leishmania species and clinical variants of ATL in Ecuador

Search For Heavy Pointlike Dirac Monopoles

We have searched for central production of a pair of photons with high transverse energies in $p\bar p$ collisions at $\sqrt{s} = 1.8$ TeV using $70 pb^{-1}$ of data collected with the D\O detector at the Fermilab Tevatron in 1994--1996. If they exist, virtual heavy pointlike Dirac monopoles could rescatter pairs of nearly real photons into this final state via a box diagram. We observe no excess of events above background, and set lower 95% C.L. limits of $610, 870, or 1580 GeV/c^2$ on the mass of a spin 0, 1/2, or 1 Dirac monopole.Comment: 12 pages, 4 figure

Search for High Mass Photon Pairs in p-pbar --> gamma-gamma-jet-jet Events at sqrt(s)=1.8 TeV

A search has been carried out for events in the channel p-barp --> gamma gamma jet jet. Such a signature can characterize the production of a non-standard Higgs boson together with a W or Z boson. We refer to this non-standard Higgs, having standard model couplings to vector bosons but no coupling to fermions, as a "bosonic Higgs." With the requirement of two high transverse energy photons and two jets, the diphoton mass (m(gamma gamma)) distribution is consistent with expected background. A 90(95)% C.L. upper limit on the cross section as a function of mass is calculated, ranging from 0.60(0.80) pb for m(gamma gamma) = 65 GeV/c^2 to 0.26(0.34) pb for m(gamma gamma) = 150 GeV/c^2, corresponding to a 95% C.L. lower limit on the mass of a bosonic Higgs of 78.5 GeV/c^2.Comment: 9 pages, 3 figures. Replacement has new H->gamma gamma branching ratios and corresponding new mass limit