An extremely energetic cosmic ray observed by a surface detector array

Cosmic rays are energetic charged particles from extraterrestrial sources, with the highest-energy events thought to come from extragalactic sources. Their arrival is infrequent, so detection requires instruments with large collecting areas. In this work, we report the detection of an extremely energetic particle recorded by the surface detector array of the Telescope Array experiment. We calculate the particle's energy as [Formula: see text] (~40 joules). Its arrival direction points back to a void in the large-scale structure of the Universe. Possible explanations include a large deflection by the foreground magnetic field, an unidentified source in the local extragalactic neighborhood, or an incomplete knowledge of particle physics.

Indications of proton-dominated cosmic-ray composition above 1.6 EeV

We report studies of ultrahigh-energy cosmic-ray composition via analysis of depth of air shower maximum (X(max)), for air shower events collected by the High-Resolution Fly's Eye (HiRes) observatory. The HiRes data are consistent with a constant elongation rate d<X(max)>/d[log(E)] of 47.9+/-6.0(stat)+/-3.2(syst) g/cm2/decade for energies between 1.6 and 63 EeV, and are consistent with a predominantly protonic composition of cosmic rays when interpreted via the QGSJET01 and QGSJET-II high-energy hadronic interaction models. These measurements constrain models in which the galactic-to-extragalactic transition is the cause of the energy spectrum ankle at 4x10(18) eV.

First observation of the Greisen-Zatsepin-Kuzmin suppression

The High Resolution Fly's Eye (HiRes) experiment has observed the Greisen-Zatsepin-Kuzmin suppression (called the GZK cutoff) with a statistical significance of five standard deviations. HiRes' measurement of the flux of ultrahigh energy cosmic rays shows a sharp suppression at an energy of 6 x 10(19) eV, consistent with the expected cutoff energy. We observe the ankle of the cosmic-ray energy spectrum as well, at an energy of 4 x 10(18) eV. We describe the experiment, data collection, and analysis and estimate the systematic uncertainties. The results are presented and the calculation of the statistical significance of our observation is described.

Constraints on cosmic neutrino fluxes from the Antarctic Impulsive Transient Antenna experiment

We report new limits on cosmic neutrino fluxes from the test flight of the Antarctic Impulsive Transient Antenna (ANITA) experiment, which completed an 18.4 day flight of a prototype long-duration balloon payload, called ANITA-lite, in early 2004. We search for impulsive events that could be associated with ultrahigh energy neutrino interactions in the ice and derive limits that constrain several models for ultrahigh energy neutrino fluxes and rule out the long-standing -burst model.

Measurement of the flux of ultrahigh energy cosmic rays from monocular observations by the High Resolution Fly's Eye experiment

We have measured the cosmic ray spectrum above 10(17.2) eV using the two air-fluorescence detectors of the High Resolution Fly's Eye observatory operating in monocular mode. We describe the detector, phototube, and atmospheric calibrations, as well as the analysis techniques for the two detectors. We fit the spectrum to a model consisting of galactic and extragalactic sources.

Experimental modelling of human spinal cord injury: a model that crosses the species barrier and mimics the spectrum of human cytopathology

STUDY DESIGN

Literature review and presentation of an experimental model of human spinal cord injury, (SCI).

OBJECTIVES

Experimental designs seek to mimic and model the physical processes by which human SCI occurs and replicate the variety of chronic pathologies that characterize its long term effects. The variations in biological processes that are present between species have contributed to recent difficulties in generalizing experimental findings to the human condition. In this review, one finds: (1) a discourse on the pathological nature of the chronic human lesion, (2) a consideration of how the physical properties of soft tissue injury result in acute and chronic changes in the spinal substance, (3) a description of a device (ESCID) that is able to replicate and dynamically monitor physical indices of SCI as they take place in experimental models, and (4) a summary of how use of this device in different species has allowed the biomechanical descriptors of such injuries to be easily compared even in murine models.

SETTING

Ohio State University, Ohio, USA.

RESULTS

Careful attention to the details of injury device design has finally allowed a direct comparison of contusion-type injury models in the rat and mouse. Biomechanical outcomes with predictive capabilities have evolved that allow the investigator to create the range of pathologies seen in the human lesion even in these small vertebrates. The predictive cytopathology and our ability to manipulate the mouse genome will allow the testing of specific hypotheses related to cause and effect in experimental spinal cord injuries. Since the biomechanics, pathology, and chronic outcomes appear to be similar to those seen in the human, these animal models should facilitate rapid progress in the design of human therapeutics.

CONCLUSIONS

Biomechanics of certain elements of experimental spinal injury are surprisingly accurate descriptors of acute and chronic pathologies in the spinal cord. This tenet applies across species and has often allowed more accurate design of clinical trials in the past few decades. As molecular approaches to this problem evolve, the use of species with known genomes appear warranted. Models that take advantage of these approaches are likely to produce innovations that quicken the pace of human trial strategies.

Behavioral and histological outcomes following graded spinal cord contusion injury in the C57Bl/6 mouse

A computer-controlled electromagnetic spinal cord injury device (ESCID) has been adapted to develop a mouse model of spinal cord contusion injury. In the present study, we have extended this model in C57Bl/6 mice with behavioral and histopathological outcome assessment. Three groups of mice received a laminectomy at the T(9) vertebral level followed by a contusion injury from a predetermined starting load of 1500 dynes. Contusion was produced by rapid displacement of the spinal cord to a peak distance of 0.3, 0.5, or 0.8 mm, with the entire injury and retraction procedure completed over a 23-ms epoch. Control groups received laminectomy alone or complete transection. Functional recovery was examined for 9 weeks after injury using the BBB locomotor rating scale, grid walking, and footprint analysis. Distinct patterns of locomotor recovery were evident across the five groups. Measurements of spared white matter at the epicenter, lesion length, and cross-sectional area of fibronectin-immunopositive scar tissue were also significantly different between injury groups. The severity of injury corresponded with the biomechanical measures recorded at the time of impact as well as with behavioral and histological parameters. The results demonstrate that graded contusion injuries can be produced reliably in mice using the ESCID. The data provide a thorough and quantitative analysis of the effects of contusion injury on long-term behavioral and histological outcome measures in this strain and species.

Pegylated brain-derived neurotrophic factor shows improved distribution into the spinal cord and stimulates locomotor activity and morphological changes after injury

The neurotrophin brain-derived neurotrophic factor (BDNF) shows promise for the treatment of central nervous system (CNS) trauma and disease. Effective delivery methods are required, however, for BDNF to be useful as a therapeutic agent. To this end, we examined the penetration of intrathecally infused N-terminal pegylated BDNF (peg-BDNF) compared to similar infusion of native BDNF after spinal cord injury (SCI). Pegylation dramatically improved delivery of BDNF to the spinal cord and induced the expression of Fos in spinal cord neurons. To test whether enhanced delivery would improve the modest effects on behavioral recovery and axonal outgrowth observed with native BDNF infusion, we assessed the efficacy of 2-week 25 microg/day peg-BDNF treatment, beginning 12-24 h (early) or 15 days (delayed) after midthoracic spinal contusion. Similar to native BDNF, early treatment with peg-BDNF accelerated the recovery of stepping in the open-field and acutely stimulated locomotor central pattern generator activity, as seen by the activation of hindlimb airstepping during either period of administration. The infusion of peg-BDNF, regardless of the timing of delivery, was related to enhanced sprouting of putative cholinergic fibers, like that observed after high dose native BDNF treatment. Despite improved delivery, however, neither axonal responses nor the extent of locomotor recovery were enhanced compared to native BDNF treatment. This suggests that alternative strategies, such as neurotrophin treatment in conjunction with cell transplantation techniques, or treatment nearer the cell bodies of target neurons might be employed in an attempt to effect significant repair after SCI.

Proliferation of NG2-positive cells and altered oligodendrocyte numbers in the contused rat spinal cord

Given the numerous reparative roles glia may play after spinal cord injury (SCI), glial proliferation and cell number were examined in a model of traumatic SCI. Emphasis was placed on analysis of oligodendrocytes and NG2-positive (NG2+) cells, an endogenous cell population that may be involved in oligodendrocyte replacement. Overall, proliferation (assessed by bromodeoxyuridine incorporation) was markedly elevated during the first 2 weeks after injury and declined thereafter; a large portion of these dividing cells likely consisted of microglia-macrophages. Although the total number of NG2+ cells in the epicenter was reduced by half, we noted protracted proliferation in surviving NG2+ cells, with values sevenfold greater than in uninjured controls. Elevated proliferation of NG2+ cells persisted throughout the first 4 weeks after injury. However, the absolute number of NG2+ cells was not increased over controls, suggesting that the daughter cells either did not survive or they differentiated into other cell types. As expected, oligodendrocyte numbers were drastically altered after SCI. By 7 d after injury, the number of oligodendrocytes at the impact site was reduced by 93%. Despite ongoing tissue loss, the number of oligodendrocytes in spared tissue rose threefold at 14 d after injury. Although the function of NG2+ cells within the spinal cord is not completely understood, several studies suggest that they may differentiate into oligodendrocytes. Thus, proliferating NG2+ cells may contribute to the increased oligodendrocyte number observed at 2 weeks after injury. Future studies are required, however, to definitively determine the role NG2+ cells play in oligodendrocyte genesis, remyelination, and other post-injury events.

Localization of transforming growth factor-beta1 and receptor mRNA after experimental spinal cord injury

Transforming growth factor-beta1 (TGFbeta1) is a cytokine/growth factor found within the pathological central nervous system. TGFbeta1 has been shown to inhibit the release of cytotoxic molecules from microglia and macrophages, decrease astrocyte proliferation, and promote neuron survival. Because of the relevance of these actions to spinal cord injury, we examined TGFbeta1 and its receptors betaRI and betaRII mRNA levels and localization within the contused rat spinal cord using in situ hybridization. At the lesion site, TGFbeta1 mRNA peaked at 7 days postinjury and declined thereafter. Temporal and spatial localization of the betaRI and betaRII receptor mRNA closely mimicked that for TGFbeta1 in the epicenter. TGFbeta1, betaRI, and betaRII mRNAs also were elevated rostral and caudal to the injury, especially in regions known to contain activated microglia and degenerating axon profiles. Immunohistochemical staining of nearby sections confirmed that the highest levels of TGFbeta1 and receptor mRNA corresponded to regions filled with activated microglia and macrophages. The similar expression pattern of TGFbeta1, betaRI, and betaRII mRNA within the injured spinal cord suggests a local site of action. Since TGFbeta1 can act as an immunosuppressant as well as a stimulant for growth factors and neurite sprouting, it likely plays an important role, both temporally and spatially, in orchestrating postinjury events within the spinal cord.

Traumatic spinal cord injury produced by controlled contusion in mouse

Previous work from this laboratory has described a rat spinal cord injury (SCI) model in which the mid-thoracic spinal cord is subjected to a single rapid and calibrated displacement at the site of a dorsal laminectomy. Injury is initiated at the tip of a vertical shaft driven by an electromagnetic shaker. Transducers arranged in series with the shaft record the patterns of displacement and force during the impact sequence. In the present study, this device and the relevant surgical procedures were adapted to produce a spinal contusion injury model in laboratory mice. The signal generator for the injury device has also been converted to a computer-controlled interface to permit extension of the model to other laboratories. Mice were subjected to SCI across a range of severities by varying the amplitude of displacement and the magnitude of measured preload force on the dural surface. A moderate injury produced by displacement of 0.5 mm over 25 msec resulted in initial paralysis and recovery of locomotion with chronic deficits in hindlimb function. The magnitude of the peak force, impulse, power, and energy generated at impact were correlated with behavioral outcome at 1 day postinjury, while peak displacement and impulse were the best predictors of behavioral outcome at 28 days postinjury. The shape of the force recording proved to be a highly sensitive measure of subtle variations in the spinal compartment that were otherwise difficult to detect in this small species. The results demonstrate that the electromagnetic spinal cord injury device (ESCID) can be used to produce a well-controlled contusion injury in mice. The unique features of controlled displacement and monitoring of the biomechanical parameters at the time of impact provide advantages of this model for reducing outcome variability. Use of this model in mice with naturally occurring and genetically engineered mutations will facilitate understanding of the molecular mechanisms of pathophysiology following traumatic spinal cord injury.

Mechanisms through which PDGF alters intracellular calcium levels in U-1242 MG human glioma cells

PDGF-BB induces a rapid, sustained increase in intracellular calcium levels in U-1242 MG cells. We used several calcium channel blockers to identify the types of channels involved. L channel blockers (verapamil, nimodipine, nicardipine, nitrendipine and taicatoxin) had no effect on PDGF-BB induced alterations in intracellular calcium. Blockers of P, Q and N channels (omega-agatoxin-IVA, omega-conotoxin MVIIC and omega-conotoxin GVIA) also had no effect. This indicates that these channels play an insignificant role in supplying the Ca2+ necessary for PDGF stimulated events in U-1242 MG cells. However, a T channel blocker (NDGA) and the non-specific (NS) calcium channel blockers (FFA and SK&F 9365) abolished PDGF-induced increases in intracellular calcium. This indicates that PDGF causes calcium influx through both non-specific cationic channels and T channels. To study the participation of intracellular calcium stores in this process, we used thapsigargin, caffeine and ryanodine, all of which cause depletion of intracellular calcium stores. The PDGF effect was abolished using both thapsigargin and caffeine but not ryanodine. Collectively, these data indicate that in these human glioma cells PDGF-BB induces release of intracellular calcium from caffeine- and thapsigargin-sensitive calcium stores which in turn lead to further calcium influx through both NS and T channels.

Depletion of hematogenous macrophages promotes partial hindlimb recovery and neuroanatomical repair after experimental spinal cord injury

Traumatic injury to the spinal cord initiates a series of destructive cellular processes which accentuate tissue damage at and beyond the original site of trauma. The cellular inflammatory response has been implicated as one mechanism of secondary degeneration. Of the various leukocytes present in the spinal cord after injury, macrophages predominate. Through the release of chemicals and enzymes involved in host defense, macrophages can damage neurons and glia. However, macrophages are also essential for the reconstruction of injured tissues. This apparent dichotomy in macrophage function is further complicated by the overlapping influences of resident microglial-derived macrophages and those phagocytes that are derived from peripheral sources. To clarify the role macrophages play in posttraumatic secondary degeneration, we selectively depleted peripheral macrophages in spinal-injured rats during a time when inflammation has been shown to be maximal. Standardized behavioral and neuropathological analyses (open-field locomotor function, morphometric analysis of the injured spinal cord) were used to evaluate the efficacy of this treatment. Beginning 24 h after injury and then again at days 3 and 6 postinjury, spinal cord-injured rats received intravenous injections of liposome-encapsulated clodronate to deplete peripheral macrophages. Within the spinal cords of rats treated in this fashion, macrophage infiltration was significantly reduced at the site of impact. These animals showed marked improvement in hindlimb usage during overground locomotion. Behavioral recovery was paralleled by a significant preservation of myelinated axons, decreased cavitation in the rostrocaudal axis of the spinal cord, and enhanced sprouting and/or regeneration of axons at the site of injury. These data implicate hematogenous (blood-derived) macrophages as effectors of acute secondary injury. Furthermore, given the selective nature of the depletion regimen and its proven efficacy when administered after injury, cell-specific immunomodulation may prove useful as an adjunct therapy after spinal cord injury.

Operant conditioning of H-reflex increase in spinal cord--injured rats

Operant conditioning of the spinal stretch reflex or its electrical analog, the H-reflex, is a new model for exploring the mechanisms of long-term supraspinal control over spinal cord function. Primates and rats can gradually increase (HRup conditioning mode) or decrease (HRdown conditioning mode) the H-reflex when reward is based on H-reflex amplitude. An earlier study indicated that HRdown conditioning of the soleus H-reflex in rats is impaired following contusion injury to thoracic spinal cord. The extent of impairment was correlated with the percent of white matter lost at the injury site. The present study investigated the effects of spinal cord injury on HRup conditioning. Soleus H-reflexes were elicited and recorded with chronically implanted electrodes from 14 rats that had been subjected to calibrated contusion injuries to the spinal cord at T8. At the lesion epicenter, 12-39% of the white matter remained. After control-mode data were collected, each rat was exposed to the HRup conditioning mode for 50 days. Final H-reflex amplitudes after HRup conditioning averaged 112% (+/-22% SD) of control. This value was significantly smaller than that for 13 normal rats exposed to HRup conditioning, in which final amplitude averaged 153% (+/-51%) SD of control. As previously reported for HRdown conditioning after spinal cord injury, success was inversely correlated with the severity of the injury as assessed by white matter preservation and by time to return of bladder function. HRup and HRdown conditioning are similarly sensitive to injury. These results further demonstrate that H-reflex conditioning is a sensitive measure of the long-term effects of injury on supraspinal control over spinal cord functions and could prove a valuable measure of therapeutic efficacy.

Peroxynitrite production and activation of poly (adenosine diphosphate-ribose) synthetase in spinal cord injury

Peroxynitrite formation and the subsequent activation of the nuclear enzyme, poly (adenosine diphosphate [ADP]-ribose) synthetase (PARS), has been implicated in the pathogenesis of several neurodegenerative disorders. Here, we demonstrate that nitrotyrosine, an indicator of peroxynitrite generation, and poly (ADP) ribose, a marker of PARS activation, were selectively localized within tissues from spinal cord-injured rats. Our data implicate a role for peroxynitrite production and PARS activation in the development of spinal cord trauma.

Assessment of the mechanism by which prolactin stimulates progesterone production by early corpora lutea of pigs

Previously, we reported that administration of prolactin (PRL) during the early luteal phase in sows increases plasma progesterone concentrations. In the current study, we searched for the mechanisms by which PRL exerts this luteotrophic effect. The objectives of the study were (1) to examine the effect of PRL and/or low-density lipoproteins (LDL) on progesterone production by porcine luteal cells derived from early corpora lutea, and (2) to assess the ability of PRL to activate phosphoinositide-specific phospholipase C (PI-PLC) and protein kinase C (PKC) in these luteal cells. Ovaries with early corpora lutea (day 1-2 of the oestrous cycle) were obtained from the slaughterhouse. Progesterone production by dispersed luteal cells was measured after treatment with PRL, phorbol 12-myristate 13-acetate or inhibitors of PKC in the presence or absence of LDL. LDL increased progesterone concentration in the incubation medium (304.5 vs 178.6 ng/ml in control, P<0.05). PRL augmented LDL-stimulated progesterone secretion by luteal cells (to 416 ng/ml, P<0.05), but PRL alone did not affect progesterone production (209.6 ng/ml, P>0.05). Staurosporine, a PKC inhibitor, inhibited progesterone secretion stimulated by the combined action of LDL and PRL; however, such inhibition was not demonstrated when cells were treated with the PKC inhibitor, H-7. PKC activation was assessed by measuring the specific association of [H]phorbol dibutyrate (H-PDBu) with luteal cells after treatment with PRL or ionomycin (a positive control). PRL and ionomycin increased H-PDBu-specific binding in early luteal cells by 28+/-5.5% (within 5 min) and 70.2+/-19.3% (within 2 min) over control binding respectively (P<0.05). In addition, PRL did not augment the LDL-stimulated progesterone production in PKC-deficient cells. In contrast with PKC, total inositol phosphate accumulation, as well as intracellular free calcium concentrations, were not affected by PRL in the current study. We conclude that PRL, in the presence of LDL, stimulates progesterone production by early corpora lutea in vitro. Moreover, PRL appears to activate PKC, but not PI-PLC, in these cells. Thus intracellular transduction of the PRL signal may involve activation of PKC that is not dependent on PI-PLC.

Brain-derived neurotrophic factor stimulates hindlimb stepping and sprouting of cholinergic fibers after spinal cord injury

Neurotrophic factors have been proposed as a therapeutic treatment for traumatic brain and spinal cord injury. The present study determined whether exogenous administration of one such factor, brain-derived neurotrophic factor (BDNF), could effect behavioral recovery and/or histopathological changes after spinal cord injury. Adult rats received a mild or moderate contusion injury or complete transection of the mid-thoracic spinal cord. Immediately thereafter, they were infused intrathecally with vehicle or BDNF for 28 days. Behavioral recovery was evaluated for 6 weeks after injury, at which time the rats were sacrificed and the spinal cord tissue was examined histologically. The infusion of BDNF resulted in acute stimulation of hindlimb activity. These effects included activation of alternating airstepping in injured rats when the hindlimbs were unloaded as well as slight improvements in the rate of recovery in open field locomotion score. BDNF infusion was also associated with enhanced growth of cholinergic fibers at the injury epicenter, but did not affect white matter sparing or density of serotonergic axons at or below the injury site. Based on immunohistochemical detection of BDNF protein distribution, these described effects are likely to be mediated by the activation of cells and axons within the central injury region and the along the peripheral rim of the spinal cord. Together, these findings demonstrate that the exogenous infusion of BDNF after spinal trauma can influence postinjury outcome through mechanisms that include acute stimulation of hindlimb activity and neuritogenesis at the injury site.

Effect of neutrophil depletion in acute cerebritis

Inhibition of the host's neutrophil response has been proposed as one means to reduce tissue damage in acute inflammation. If this approach can be applied in acute central nervous system (CNS) infection, the long-term morbidity, which occurs in CNS infection, might be reduced. Previous studies in models of CNS infection yielded conflicting results whether neutrophil depletion might be protective. To determine whether neutrophil depletion reduces tissue necrosis and cerebrovascular injury in experimental bacterial cerebritis, we depleted circulating neutrophils with an IgM monoclonal antibody, RP3, given after the start of the infection. RP3 treatment successfully depleted circulating neutrophils and reduced the extent of neutrophil influx into the cerebritis region. The extent of tissue necrosis, measured histologically, and the regional increase of blood-brain barrier (BBB) permeability were not inhibited by neutrophil depletion, and in animals treated with RP3 alone, the extent of tissue necrosis and BBB permeability tended to be larger than in S. aureus inoculated controls. We conclude that host neutrophils do not add to the tissue and cerebrovascular damage created by the intracerebral inoculation of a pathogenic bacteria, and the neutrophils serve to diminish local damage in the setting of a cerebritis.

Selective chemokine mRNA accumulation in the rat spinal cord after contusion injury

Following traumatic injury to the spinal cord, hematogenous inflammatory cells including neutrophils, monocytes, and lymphocytes infiltrate the lesion in a distinct temporal sequence. To examine potential mechanisms for their recruitment, we measured chemokine mRNAs in the contused rat spinal cord, using specific and sensitive reverse transcriptase polymerase chain reaction (RT-PCR) dot-blot hybridization assays. The neutrophil chemoattractant GRO-alpha was 30-fold higher than control values at 6 hr postinjury and decayed rapidly thereafter. LIX, a highly related alpha-chemokine, also was elevated early postinjury. Monocyte chemoattractant peptide (MCP)-1 and MCP-5 mRNAs, potent chemoattractants for monocytes, were significantly elevated at the lesion epicenter at 12 and 24 hr postinjury and declined thereafter. Interferon-gamma-inducible protein, 10 kDa (IP-10), chemoattractant towards activated T-lymphocytes, was significantly elevated at 6 and 12 hr postinjury. The dendritic cell chemoattractant MIP-3alpha also was increased, perhaps contributing to the development of T-cell autoreactivity to neural components after spinal cord injury (SCI) in rats. Other beta-chemokines, including MIP-1alpha and RANTES (regulated on expression normal T-cell expressed and secreted), were minimally affected by SCI. Expression of chemokines, therefore, directly precedes the influx of target neutrophils, monocytes, and T-cells into the spinal cord postinjury, as noted previously. Thus, selective chemokine expression may be integral to inflammatory processes within the injured spinal cord as a mechanism of recruitment for circulating leukocytes.

Neurotrophin-3 and brain-derived neurotrophic factor induce oligodendrocyte proliferation and myelination of regenerating axons in the contused adult rat spinal cord

Functional loss after spinal cord injury (SCI) is caused, in part, by demyelination of axons surviving the trauma. Neurotrophins have been shown to induce oligodendrogliagenesis in vitro, but stimulation of oligodendrocyte proliferation and myelination by these factors in vivo has not been examined. We sought to determine whether neurotrophins can induce the formation of new oligodendrocytes and myelination of regenerating axons after SCI in adult rats. In this study, fibroblasts producing neurotrophin-3 (NT-3), brain-derived neurotrophic factor (BDNF), ciliary neurotrophic factor, nerve growth factor, basic fibroblast growth factor, or beta-galactosidase (control grafts) were transplanted subacutely into the contused adult rat spinal cord. At 10 weeks after injury, all transplants contained axons. NT-3 and BDNF grafts, however, contained significantly more axons than control or other growth factor-producing grafts. In addition, significantly more myelin basic protein-positive profiles were detected in NT-3 and BDNF transplants, suggesting enhanced myelination of ingrowing axons within these neurotrophin-producing grafts. To determine whether augmented myelinogenesis was associated with increased proliferation of oligodendrocyte lineage cells, bromodeoxyuridine (BrdU) was used to label dividing cells. NT-3 and BDNF grafts contained significantly more BrdU-positive oligodendrocytes than controls. The association of these new oligodendrocytes with ingrowing myelinated axons suggests that NT-3- and BDNF-induced myelinogenesis resulted, at least in part, from expansion of oligodendrocyte lineage cells, most likely the endogenous oligodendrocyte progenitors. These findings may have significant implications for chronic demyelinating diseases or CNS injuries.

Cytokine mRNA profiles in contused spinal cord and axotomized facial nucleus suggest a beneficial role for inflammation and gliosis

We have studied temporal mRNA expression patterns for interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), macrophage colony stimulating factor (M-CSF), and transforming growth factor-beta1 (TGF-beta1) in two rat injury paradigms with very different cellular inflammatory reactions: contussion of the spinal cord and axotomy of the facial nerve. Our comparative analyses using semiquantitative reverse transcription polymerase chain reaction (RT-PCR) show an early and robust upregulation of IL-1beta, TNF-alpha, IL-6, and M-CSF mRNAs in spinal cord after contusion injury. Peak expression of these mRNAs was transient and returned to control levels by 24 h postinjury. In contrast, expression of IL-1beta and TNF-alpha mRNAs in the axotomized facial nucleus was minimal and delayed, and levels of M-CSF mRNA remained unaltered. Similar to injured spinal cord, the axotomized nucleus showed a dramatic and early upregulation of IL-6 mRNA, but unlike spinal cord, IL-6 mRNA levels subsided only gradually. Both injury paradigms showed gradually increasing levels of TGF-beta1 mRNA which were maximal at 7 days postinjury. RT-PCR analyses were also performed on isolated blood-borne mononuclear cells and neutrophils. The results showed that these cells contain high levels of IL-1beta and M-CSF mRNAs, moderate levels of TGF-beta and TNF-alpha mRNAs, and minimal levels of IL-6 mRNA. The RT-PCR analyses together with histological observations indicate that expression of the proinflammatory cytokines IL-1beta, TNF-alpha, and IL-6 is short-lived and self-limited after contusion injury, and that it occurs primarily within endogenous glial cells. Transient expression of these molecules likely triggers secondary events which may be beneficial to wound repair and regeneration.

Phosphorus-31 magnetic resonance spectroscopy studies of pig spinal cord injury. Myelin changes, intracellular pH, and bioenergetics

RATIONALE AND OBJECTIVES

Phosphorus-31 (31P) nuclear magnetic resonance (NMR) spectroscopy was used to monitor changes in phosphocreatine (PCr), adenosine triphosphate (ATP), inorganic phosphate (Pi), intracellular pH (pHi), and free magnesium in the in vivo pig spinal cord after injury.

METHODS

Phosphorus-31 NMR spectra were acquired from healthy (n = 4) and injured pig spinal cords (n = 8) under in vivo conditions using a 4.7-tesla spectrometer. Spinal cords were injured by dropping a 20-g weight from 20 cm onto the surgically exposed cord surface.

RESULTS

In vivo spectra of injured cords revealed a reduction in ATP, PCr, pHi, and an increase in Pi. In addition, a broad resonance that is likely to arise from myelin phospholipids was reduced significantly after injury.

CONCLUSIONS

Phosphorus-31 NMR can be used to follow in vivo changes in high energy phosphates after injury and may have the potential to follow changes in myelin structure. This technique may prove important in the study of myelin breakdown after secondary, nonreversible spinal cord injury. Changes in high energy phosphates and pHi did not seem to parallel these putative changes in myelin structure.

Purinergic Ca2+ signaling in myenteric neurons via P2 purinoceptors

Fura 2 microfluorimetry was used to test the hypothesis that ATP acts at P1 and P2 purinoceptors to elevate cytosolic free Ca2+ concentrations [Ca2+]i) in calbindin-immunoreactive cultured myenteric neurons from adult guinea pig small intestine. Local "micro-puff" application of ATP or ATP(gamma)S caused an increase in [Ca2+]i in 99% of 200 multipolar neurons. The potency profile of agonists for the rise in [Ca2+]i was ATP(gamma)S = ATP >> ADP >> AMP, adenosine, 5'-(N-ethylcarboxamido)adenosine, and 2-chloro-N(6)-cyclopentyladenosine. Tetrodotoxin-sensitive synaptic transmission could contribute as much as 25% to the ATP response. The P1 antagonist 8-cyclopentyl-1,3-dipropylxanthine blocked 50% of the peakATP Ca2+ response. P2 antagonists blocked the ATP response: pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid > reactive blue 2 > suramin. Suramin enhanced the ATP response in 27.5% of neurons. Some neurons (<15%) displayed distinct multiphasic Ca2+ signatures. About 54% of ATP-responsive neurons expressed calbindin. The data support the following hypotheses: 1) two distinct P2 purinoceptors are linked to the rise in [Ca2+]i in myenteric neurons; 2) purinergic Ca2+ signaling is not restricted to one neuronal phenotype; and 3) intraneuronal Ca2+ is not involved in adenosinergic hyperpolarization in AH/type 2 neurons.

Cellular inflammatory response after spinal cord injury in Sprague-Dawley and Lewis rats

The distribution of microglia, macrophages, T-lymphocytes, and astrocytes was characterized throughout a spinal contusion lesion in Sprague-Dawley and Lewis rats by using immunohistochemistry. The morphology, spatial localization, and activation state of these inflammatory cells were described both qualitatively and quantitatively at 12 hours, 3, 7, 14, and 28 days after injury. By use of OX42 and ED1 antibodies, peak microglial activation was observed within the lesion epicenter of both rat strains between three and seven days post-injury preceding the bulk of monocyte influx and macrophage activation (seven days). Rostral and caudal to the injury site, microglial activation plateaued between two and four weeks post-injury in the dorsal and lateral funiculi as indicated by morphological transformation and the de-novo expression of major histocompatibility class II (MHC II) molecules. Similar to the timing of microglial reactions, T-lymphocytes maximally infiltrated the lesion epicenter between three and seven days post-injury. Reactive astrocytes, while present in the acute lesion, were more prominent at later survival times (7-28 days). These cells were interspersed with activated microglia but appeared to surround and enclose tissue sites occupied by reactive microglia and phagocytic macrophages. Thus, trauma-induced central nervous system (CNS) inflammation, regardless of strain, occurs rapidly at the site of injury and involves the activation of resident and recruited immune cells. In regions rostral or caudal to the epicenter, prolonged activation of inflammatory cells occurs preferentially in white matter and primarily consists of activated microglia and astrocytes. Differences were observed in the magnitude and duration of macrophage activation between Sprague-Dawley (SD) and Lewis (LEW) rats throughout the lesion. Increased expression of complement type 3 receptors (OX42) and macrophage-activation antigens (ED1) persisted for longer times in LEW rats while expression of MHC class II molecules was attenuated in LEW compared to SD rats at all times examined. Variations in the onset and duration of T-lymphocyte infiltration also were observed between strains with twice as many T-cells present in the lesion epicenter of Lewis rats by 3 days post-injury. These strain-specific findings potentially represent differences in corticosteroid regulation of immunity and may help predict a range of functional neurologic consequences affected by neuroimmune interactions.

A quantitative spatial analysis of the blood-spinal cord barrier. II. Permeability after intraspinal fetal transplantation

In previous experiments we utilized quantitative autoradiography to temporally describe vascular permeability of a radiolabeled vascular tracer following spinal contusion injury in the rat. In the present report we compare these findings with permeability assessments following fetal grafting in the contused rat spinal cord. At 10 days postinjury, Embryonic Day 14 spinal tissue was grafted into the lesioned spinal cord of Sprague-Dawley rats. At 7, 14, and 28 days postgrafting the alpha-aminoisobutyric acid (AIB) technique was used to assess blood-to-tissue transfer rates in graft and host tissue over several segments of the injured spinal cord. Regional changes in permeability were assessed using four distinct image analysis techniques. Using these methods, we have previously shown that contusion injury alone results in a chronic relapse in vascular permeability. The present data indicate that fetal transplants at 7 days postgrafting have AIB transfer rates that are significantly above uninjured control levels and are similar in magnitude to neighboring host spinal tissue. In addition, permeability in 14- and 28-day intraspinal grafts decreased relative to that of the 7-day transplant group, but remained significantly elevated at and rostral to the injury epicenter. Alternately, graft and host tissue in regions caudal to the injury epicenter (e.g., T10--L2) acquired a functional barrier to AIB as early as 14 days posttransplantation. These experiments suggest that graft development occurs in a different manner or at a different rate in segments of the injured spinal cord rostral and caudal to the injury site. Additionally, it appears that vascular permeability of the injured spinal cord can be influenced by the process of intraspinal transplantation.

A quantitative spatial analysis of the blood-spinal cord barrier. I. Permeability changes after experimental spinal contusion injury

Blood-spinal cord barrier (BSB) permeability was measured using quantitative autoradiography following contusion injury to the rat spinal cord. Permeability was assessed by calculating blood-to-tissue transfer constants (Ki values) for the vascular tracer [14C]-alpha-aminoisobutyric acid (AIB) in injured (3, 7, 14, and 28 days postinjury), laminectomy control, and uninjured control animals. Permeability was quantitated using four separate imaging techniques in gray and white matter throughout the rostro-caudal extents of the forming lesion. Away from the epicenter, gray matter permeability was further differentiated within discrete spinal lamina using computerized templates. Regardless of the type of analysis used, increased AIB permeability (Ki values) was noted at all survival times in all tissue regions with respect to both uninjured and laminectomy control groups. The data indicate a large increase in individual Ki values throughout the dorsoventral axis of the spinal cord at 3 days postinjury (approximately 6-9 ml/kg/min). By 7 days, Ki values were quantitatively smaller (approximately 4-5 ml/kg/min) in all regions compared with 3-day tissues. Despite further attenuation of AIB uptake in the gray matter at 14 and 28 days postinjury, circumferential white matter tracts showed a secondary increase in permeability compared to 7-day tissue. Permeability in the white matter at 14-28 days postinjury (approximately 5-6 ml/kg/min) was comparable to that at 3 days postinjury (6-7 ml/kg/min). Measurements of the axial distribution of AIB permeability indicate increased BSB permeability over several segments rostral and caudal to the lesion epicenter (approximately 3 cm in both directions). Secondary elevations of AIB transfer in the spinal white matter between 14 and 28 days were colocalized with zones of immunohistochemically defined microglial clusters. The known plasticity of this cell type in response to changes in the extracellular microenvironment suggests that the spinal white matter at later survival times (14-28 days postinjury) is an area of dynamic vascular and/or axonal reconstruction. The implications of increased permeability to both tissue injury and neural regeneration are discussed.

Operant conditioning of H-reflex in spinal cord-injured rats

Operant conditioning of the spinal stretch reflex or its electrical analog, the H-reflex, is a new model for exploring the mechanisms of supraspinal control over spinal cord function. Both rats and primates can gradually increase (HRup conditioning mode) or decrease (HRdown conditioning mode) soleus H-reflex magnitude when exposed to an operant conditioning task. This study used H-reflex operant conditioning to assess and modify spinal cord function after injury. Soleus H-reflexes were elicited and recorded with chronically implanted electrodes from rats that had been subjected to calibrated contusion injuries to the spinal cord at T8. From 18 to 140 days after injury, background EMG, M response amplitude, and initial H-reflex amplitude were not significantly different from those of normal rats. HRdown conditioning was successful in some, but not all, spinal cord-injured rats. The H-reflex decrease achieved by conditioning was inversely correlated with the severity of the injury as assessed histologically or by time to return of bladder function. It was not correlated with the length of time between injury and the beginning of conditioning. The results confirm the importance of descending control from supraspinal structures in mediating operantly conditioned change in H-reflex amplitude. In conjunction with recent human studies, they suggest that H-reflex conditioning could provide a sensitive new means for assessing spinal cord function after injury, and might also provide a method for initiating and guiding functional rehabilitation.

Activation of elements of the phosphatidylinositol pathway in the primate corpus luteum by prostaglandin E2

The current study was designed to examine the effects of prostaglandin (PG) E2 on progesterone production by primate luteal cells collected during the late luteal phase. PGE2 inhibited basal and human chorionic gonadotrophin (HCG)-stimulated progesterone production (P < 0.01) in late luteal phase corpora lutea. The ability of PGE2 to activate a second messenger system (phosphatidylinositol pathway) in corpora lutea of rhesus monkeys was also assessed. PGE2 significantly increased the accumulation of inositol phosphates (P < 0.05). This stimulation was not apparent in the early luteal phase but was manifested in the mid-late luteal phase. PGE2 also caused a rapid, yet transient, increase (P < 0.01) in intracellular free calcium ion concentrations ([Ca2+]i) in a large proportion of primate luteal cells. The proportion of luteal cells that responded to PGE2 with an increase in [Ca2+]i was smaller (P < 0.05) in corpora lutea collected during the early luteal phase (12%) in comparison with those collected during the latter half of the luteal phase (63-66%). Changes in [Ca2+]i in response to PGE2 were similar in small and large luteal cells. This study demonstrates that PGE2 activates elements of the phosphatidylinositol pathway in primate corpora lutea. This activation is augmented as the luteal phase progresses. Thus, the inhibitory effects of PGE2 on luteal progesterone production observed in the late luteal phase are associated with activation of elements of the phosphatidylinositol pathway.

Concept of autoimmunity following spinal cord injury: possible roles for T lymphocytes in the traumatized central nervous system

The effect of immunological activation on the neuropathologic sequelae and neurologic outcome from spinal cord injury is unclear. Similar to models of neuroinflammatory disease (e.g., experimental autoimmune encephalomyelitis; EAE), injury to the spinal cord precipitates the activation of resident microglia and the recruitment of circulating inflammatory cells (e.g., macrophages and lymphocytes). In EAE, these cells are known to cause tissue damage and loss of neurological function via autoimmune reactions to myelin proteins. The role these cells play in the pathology of traumatic injury to the spinal cord has not been clarified. In this review, data are presented that indicate that T cells isolated from spinal-injured rats are capable of causing neurologic deficits and histopathologic changes similar to EAE when injected intravenously into naive animals. These data are consistent with the concept of trauma-induced autoimmune reactions. However, disease transfer was only possible when T cells were obtained from animals at 1 week post-injury. Thus, the encephalitogenic T-cell repertoire appears to be rapidly regulated. It is possible that trauma-induced autoimmunity evolves into a mechanism by which the autoreactive repertoire regulates ongoing central nervous system (CNS) immunologic responses. Similar immunoregulatory networks have been proposed in EAE and are discussed here in the context of CNS trauma and neurodegenerative disease.

Responsiveness to ATP with an increase in intracellular free Ca2+ is not a distinctive feature of calbindin-D28 immunoreactive neurons in myenteric ganglia

The aim of this study was to test the hypothesis that ATP elevates cytosolic free Ca2+ levels ([Ca2+]i) in myenteric neurons expressing the Ca2+ binding protein, calbindin-D28. A laser microbeam marked the location of cultured neurons on coverslips and provided unequivocal relocation of ATP-responsive neurons after immunocytochemistry. All myenteric multipolar neurons displayed ATP Ca2+ transients, and 42% also expressed calbindin-D28 reactivity. Statistical analysis of the kinetics and shape of ATP Ca2+ transients revealed no differences between calbindin and non-calbindin neurons. The identity of other responsive neurons is unknown. Less than 8% of ganglion cells with ATP Ca2+ transients were immunopositive for the glial protein S-100. We conclude that one of the actions of ATP in myenteric ganglia is to increase [Ca2+]i which may activate gKCa leading to membrane hyperpolarization in AH, Dogiel Type II neurons expressing calbindin-D28. An efficient buffering mechanism for handling large purinergic Ca2+ loads is a common feature of all types of myenteric ganglion cells.

Phosphorus-31 nuclear magnetic resonance spectroscopy of the spinal cord in the pig, rat, and rabbit

RATIONALE AND OBJECTIVES

To ensure that contamination-free phosphorus-31 nuclear magnetic resonance (31P-NMR) spectra of the spinal cord could be obtained, a porcine model was adopted that provided a large cord sample and a greater area free from adjacent muscle tissue.

METHODS

Phosphorus-31 NMR spectra were acquired from the porcine spinal cord under in vivo conditions using a 4.7-T spectrometer. Spectra also were collected from perchloric acid and lipid extracts, and excised freeze trapped samples of the rat, rabbit, and pig spinal cord.

RESULTS

The in vivo spectrum showed resonances corresponding to adenosine triphosphate, phosphocreatine, inorganic phosphate, phosphomonoesterase, and phosphodiesterase as confirmed by extracts. In addition, a broad resonance was observed that was assigned to myelin phospholipids.

CONCLUSION

Phosphorus-31 NMR spectra of the spinal cord revealed resonances common to brain tissue. Importantly, the existence of a previously undetected resonance, which is likely to correspond to myelin phospholipids, also is reported. This resonance may prove important in future studies monitoring changes in myelin in response to trauma and ischemia.

Quantitative analysis of vascularization and cytochrome oxidase following fetal transplantation in the contused rat spinal cord

In the normal adult central nervous system, a coupling between energy consumption and vascular density is well established. Likewise, the survival of fetal neural tissue grafts is highly dependent on the establishment of functional vascular integration with the host. However, to what degree graft vascularization and tissue metabolism influence the normal host response to traumatic injury has not been extensively studied. In the present report, embryonic day 14 fetal spinal cord suspension grafts were made into the lesion epicenter of subchronic (10 days) contusion-injured rats. Three months later, intraspinal transplants were analyzed using correlative cytochrome oxidase histochemistry and vascular morphometric analysis. The same approaches were applied to the host spinal cord and injured, non-transplanted animals in order to determine the ability of a graft to alter the level of post-injury vascularization and/or metabolism. In general, graft vascular density was increased over that measured in normal or injured gray matter. Vascular density in gray matter near the host/graft interface was markedly increased when compared to either gray matter of the same spinal level in injured non-grafted animals or normal control spinal gray matter. Vascular changes were not noted in gray matter 3 mm distal to the lesion epicenter (rostral or caudal) in all groups analyzed. Cytochrome oxidase was up-regulated at this time in the graft and gray matter at the host/graft interfaces when compared to either gray matter of the same spinal level in injured, non-grafted animals or that of uninjured controls. These data indicate that an intraspinal transplant placed into the contused adult rat spinal cord reaches a metabolic capacity that is likely to be associated with high levels of oxidative metabolism in the well-vascularized graft neuropil. In addition, transplantation chronically alters vascularization and metabolic patterns of adjacent spinal gray matter following contusion injury.

Analysis of TGF-beta 1 gene expression in contused rat spinal cord using quantitative RT-PCR

We have used northern blot analysis and quantitative reverse transcription polymerase chain reaction (RT-PCR) to determine the postinjury expression profile of the transforming growth factor-beta 1 (TGF-beta 1) gene in the contused rat spinal cord. Spectrophotometric estimates of total sample RNA and quantitative analyses of cyclophilin mRNA using RT-PCR served as controls for comparisons between samples. No changes in cyclophilin gene expression were found at any postinjury survival times. The results of the TGF-beta 1 analyses, which were carried out on spinal cord samples taken at postinjury intervals ranging from 6 h to 10 days, show that the amount of TGF-beta 1 mRNA present in spinal cord increases rapidly following injury, reaching maximum levels 7 days postinjury. Unoperated control samples contained approximately 2 x 10(8) molecules of TGF-beta 1 mRNA/0.5 microgram total RNA. By 1 day postinjury, the amount of TGF-beta 1 mRNA in the cord had increased by a factor of 2.5 to 5 x 10(8) molecules/0.5 microgram total RNA. At 7 days postinjury, there were approximately 15 x 10(8) molecules of TGF-beta 1 mRNA/0.5 microgram total RNA. By 10 days postinjury the amount of TGF-beta 1 mRNA present in the spinal cord had declined to 8 x 10(8) molecules of TGF-beta 1 mRNA/0.5 microgram total RNA, a value similar to that observed at 3 days postinjury. The roles that TGF-beta 1 might play in modifying cellular responses in injured spinal cord are discussed.

Gangliosides inhibit PDGF-induced signal transduction events in U-1242 MG human glioma cells

In this study we investigated the responses of intracellular calcium ([Ca2+]i) and protein kinase C (PKC) to PDGF in U-1242 MG cells. PDGF-BB stimulated [3H]PDBu binding approximately 2-3 fold. This response was inhibited by preincubating the cells with an inhibitor of phospholipase C (PLC), U73122, suggesting that PLC mediates the induction of PKC translocation by PDGF. PDGF also increased the concentration of [Ca2+]i that was attenuated in a calcium-free medium. This indicates that PDGF-induced elevation of [Ca2+]i is mainly due to influx of extracellular calcium. PDGF-stimulated translocation of PKC was inhibited by the intracellular calcium buffer BAPTA/AM. All gangliosides studied except GM3 inhibited these responses with similar efficacy. Collectively, these results indicate that the signal transduction pathway initiated by PDGF leading to PKC translocation in U-1242 MG cells is intact, and this pathway is inhibited by several gangliosides.

Arachidonic acid inhibits hCG-stimulated progesterone production by corpora lutea of primates: potential mechanism of action

Arachidonic acid (AA) is a precursor of metabolites known to affect the corpus luteum (CL) in many species, including primates. We have shown that some of these products (prostaglandins F2 alpha and E2) inhibit pro-gesterone (P4) production and activate the phosphatidylinositol (PI) pathway in CL of rhesus monkeys. A direct role of AA in luteal function has also been suggested. The current experiments were designed to investigate the effect of AA on P4 synthesis and to examine the ability of AA to activate the PI pathway in CL of rhesus monkeys. Basal and hCG-stimulated P4 production by luteal cells collected during the midluteal phase was measured after treatment with AA (1, 5, and 10 microM) or linoleic acid (1, 5, and 10 microM). Dispersed cells (50,000/tube) were incubated at 37 degrees C for 2 h. AA elicited a dose-dependent decrease in hCG-stimulated, but not in basal, P4 production. hCG-stimulated P4 production was reduced (P < 0.01) at AA doses of 5 microM (12.1 +/- 1.5 ng/mL) and 10 microM (8.6 +/- 1.8 mg/mL) to hCG alone (18 +/- 1.6 ng/mL). There was no significant effect of 1 microM AA (15.2 +/- 1.6). Response to linoleic acid was dissimilar and was not dose-dependent. Viability of cells was not affected by any treatment. Indomethacin, a prostaglandin synthesis inhibitor, and nordihydroguaiaretic acid, an inhibitor of lipoxygenase, did not interfere with the inhibitory effect of AA. Activation of the PI pathway was assessed by monitoring the hydrolysis of phosphatidylinositol-4,5-bisphosphate (PIP2) to inositol phosphates and by monitoring increases in intracellular free calcium concentrations ([Ca2+]i) in individual cells. Moreover, the ability of AA to activate protein kinase C (PKC) in luteal cells was measured using a [3H]phorbol dibutyrate (PDBu) binding assay. AA did not alter PIP2 hydrolysis or [Ca2+]i, however, AA (10 microM) increased specific binding of [3H]PDBu to luteal cells (P < 0.05). We conclude that AA inhibits hCG-stimulated P4 production by primate luteal cells. AA exerts this action without being converted to prostaglandins or leukotrienes. This inhibition may be mediated through the activation of PKC. These results suggest a possible role for AA in the regulation of luteal function in primates, and that PKC-activation by AA may promote its effects.

Fetal transplantation following spinal contusion injury results in chronic alterations in CNS glucose metabolism

Glucose utilization of the injured rat spinal cord was determined using the autoradiographic technique of Sokoloff et al. (33). Animals were analyzed chronically (2 and 3 months) after spinal contusion injury alone or when a spinal lesion was followed by subchronic (10-day) intraparenchymal fetal spinal transplantation. At 2 and 3 months postinjury, spinal glucose utilization was reduced in dorsal gray and white matter above and below the lesion site. In addition, sensory regions of the forebrain and brain stem (e.g., nucleus gracilis and ventral posterior medial nucleus of the thalamus) had a lower basal metabolic rate than control animals. Decreased metabolic rates in supraspinal regions were reversed by the presence of a spinal graft at 3 but not at 2 months postinjury. Furthermore, gray matter in animals receiving an intraspinal transplant had elevated glucose utilization rates for several spinal segments rostral and caudal to the lesion epicenter. Graft glucose utilization was higher at 2 months (80-90 mumol/100 g/min) than at 3 months (60-70 mumol/100 g/min) posttransplantation. These data are the first quantitative metabolic imaging of spinal and brain metabolism following spinal contusion injury and fetal transplantation. The study suggests that intraspinal transplants can become functionally integrated with adjacent host gray matter and can chronically alter specific postinjury metabolic patterns.

Staurosporine affects calcium homeostasis in cultured bovine adrenal chromaffin cells

These studies show that the potent, non-specific, protein kinase inhibitor, staurosporine, disrupts Ca2+ homeostasis in cultured bovine adrenal chromaffin cells. Staurosporine treatment reduces basal and A23187-stimulated catecholamine release from chromaffin cells, but does not inhibit activated Ca2+ influx. Furthermore, pretreatment with staurosporine also reduces Ca(2+)-stimulated catecholamine release from digitonin-permeabilized cells (t1/2, 40.6 min; IC50, 66.0 nm). However, staurosporine does not inhibit the rise in intracellular Ca2+ ([Ca2+]i) in response to nicotine stimulation as measured by fura-2 photometry. These studies demonstrate that staurosporine interferes with the secretory process at some step at or after the rise in [Ca2+]i in adrenal chromaffin cells. Examination of the effects of staurosporine on 45Ca2+ movement shows that staurosporine produces a slowly developing basal 45Ca2+ accumulation; after 30 min no significant change is observed, but by 120 min, 45Ca2+ accumulation is increased by 29.5%. Thapsigargin and 2,5-di-(tert-butyl)-1,4-benzohydroquinone (tBHQ), inhibitors of Ca(2+) ATPases, were used to determine whether staurosporine induced 45Ca2+ accumulation results from sequestration of 45Ca2+ within intracellular stores. While thapsigargin has no significant effect, concomitant treatment with tBHQ prevents the increase in 45Ca2+ uptake associated with staurosporine treatment. Therefore, the tBHQ-sensitive Ca2+ store, but not the thapsigargin/inositol 1,4,5-triphosphate-sensitive Ca2+ store, appears to be staurosporine-sensitive. Overall, these studies indicate that staurosporine reduces catecholamine release by interfering with Ca2+ homeostasis. Furthermore, this work suggests that a staurosporine-sensitive phosphoprotein(s) is involved with the regulation of Ca2+ homeostasis in bovine adrenal chromaffin cells.

Procaine, lidocaine, and hypothermia inhibit calcium paradox in glial cells

The purpose of this study was to determine the effects of local anesthetics (lidocaine and procaine) and hypothermic perfusion on Na+/Ca2+ exchanger activity during reperfusion-induced calcium paradox in vitro. Hypothetically, this work provides a mechanism for reperfusion paradox injury in vitro that may relate to a variety of ischemic insults in vivo. Intracellular calcium ([Ca2+]i) in individual cells was measured using a fura-2 photometry system during protocols previously shown to dramatically and persistently increase [Ca2+]i in a manner that replicates certain phases of reperfusion injury in vivo. Our results suggest that short (< 5.0 min) exposure to hypocalcia prompts subsequent, potentially lethal, sodium-dependent calcium entry via the reverse phase of the Na+/Ca2+ exchanger. The local anesthetics lidocaine or procaine are able to block [Ca2+]i increases when added at the time of reperfusion. Furthermore, since [Ca2+]i is normally increased when local anesthetics are added by themselves, the results suggest that local anesthetics promote the forward mode of Na+/Ca2+ exchange (i.e., Na-dependent calcium removal) in addition to reverse Na+/Ca2+ exchanger blockade. Low temperature (18 degrees C) perfusion or reperfusion also affects exchanger dynamics and attenuates calcium entry during such protocols. These experiments further implicate the Na+/Ca2+ exchanger in reperfusion-mediated cell injury and provide potential ways to therapeutically modify such phenomena in vivo.

The effects of gonadotropin on the phosphatidylinositol pathway in the primate corpus luteum

The current study was designed to investigate the effects of gonadotropin on basal and prostaglandin (PG) F2 alpha-induced activity of the phosphatidylinositol pathway in corpora lutea (CL) of rhesus monkeys. Luteal progesterone production in vitro was significantly stimulated (P < 0.05) by human chorionic gonadotropin (hCG). Neither basal nor PGF2 alpha-induced phosphatidylinositol 4,5-bisphosphate hydrolysis was significantly influenced by hCG in CL of various ages (P > 0.10). Gonadotropin did induce a slight, yet sustained, increase (P < 0.05) in [Ca2+]i in approximately 70% of luteal cells. The maximal increase in [Ca2+]i in response to hCG (approximately 100 nM) was about one-tenth that induced by PGF2 alpha (approximately 1000 nM). hCG treatment did not alter (P > 0.10) the increase in [Ca2+]i induced by PGF2 alpha Treatment-induced changes in [Ca2+]i did not differ between small (17-21 microns) and large (23-28 microns) luteal cells. Therefore, luteolytic agents are more potent activators of the phosphatidylinositol pathway than luteotropins. This is consistent with the hypothesis that the phosphatidylinositol pathway is involved in primate luteal regression. The inability of hCG to acutely alter the responsiveness of this pathway to PGF2 alpha suggests that CG may rescue the CL of early pregnancy via a mechanism other than direct inhibition of the luteolytic actions of PGF2 alpha.

Elevation of the neurotoxin quinolinic acid occurs following spinal cord trauma

Excitatory amino acid neurotoxicity and the inflammatory response are suspected as mediators of some of the pathological sequelae occurring as a result of spinal cord injury. Here we report temporal and regional increases of the NMDA receptor agonist, quinolinic acid (QUIN), in an experimental model of spinal contusion injury. These changes occurred at a time when the blood-brain barrier is known to be dysfunctional and the activation state and density of microglia and macrophages are increased. Thus, alterations in tissue QUIN levels may occur as a result of secondary activation of CNS inflammatory cells or from peripherally derived sources across a damaged blood-brain barrier.

Intracellular calcium dynamics and cerebral injury: modeling various insults in vitro

The magnitude and time course of intracellular [Ca2+]i alterations were studied after excitatory amino acid challenge (EAA) or chemical energy depletion in mature spinal cultures. While either cytotoxic event led to prompt increases in [Ca2+]i, the pattern of these changes before and after exposure to the toxin was different. EAA [Ca2+]i changes seem primarily dependent on surface membrane alterations from which the cells rapidly recover while energy depletion effects release of [Ca2+]i from intracellular stores and produces a lasting compromise in the ability of these neurons in culture to recover from the initial insult.

Mechanisms through which gangliosides inhibit PDGF-stimulated mitogenesis in intact Swiss 3T3 cells: receptor tyrosine phosphorylation, intracellular calcium, and receptor binding

Several potential mechanisms through which gangliosides could modulate PDGF-stimulated events in Swiss 3T3 cells were studied using intact cells. Of the gangliosides studied, at low micromolar concentrations GM2 was the only one that inhibited PDGF-stimulated DNA synthesis, but GT1b was the most potent between 25 and 100 microM; GM1 was generally the least effective, and GD1a and GM3 had intermediate effects. All gangliosides tested inhibited the PDGF-stimulated increases in free intracellular calcium concentrations ([Ca2+]i) with the rank order of potency being GM1 > or = GT1b > GM2 > GM3. PDGF stimulated phosphorylation on tyrosine of a protein with apparent M(r) = 170 kDa which was immunoprecipitated by an anti-PDGF receptor (beta) antibody, indicating that it is a PDGF receptor. Preincubating the cells with specific gangliosides inhibited tyrosine phosphorylation of this protein in a dose-responsive fashion with the following rank order of potency GD1a = GT1b > GM1 > GM2 > GM3. Autoradiography showed that this was due to a decrease in the proportion of cells synthesizing DNA, and a time study showed that ganglioside did not delay entry of the cells into S phase. These effects were not due to gangliosides interfering with PDGF binding to its receptor because results of competitive binding studies showed that none of the gangliosides studied had an effect on either receptor number or affinity, and did not bind to PDGF in solution. These results show that gangliosides affect several specific components of the complex responses to PDGF in intact cells. The relative effectiveness of individual gangliosides, however, varied among the different cellular and molecular responses. This is interpreted to mean that specific gangliosides modulate to different degrees several molecular mechanisms which converge on the common biological response of mitogenesis, and suggests that gangliosides as a family of molecules may function as coordinators of different molecular events involved in complex cellular processes.

Myoelectric evoked potentials versus locomotor recovery in chronic spinal cord injured rats

The purpose of this study was to determine the utility of descending evoked potentials in evaluating functional recovery in rats after spinal cord contusion injury. Rats received thoracic contusions at T9 using a controlled-displacement impactor. They were evaluated for 5 weeks postinjury using auditory startle responses (ASR) while alert, or by cerebellar motor evoked potentials (CMEP) while anesthetized. ASR and CMEP were recorded electromyographically from forelimb and hindlimb muscles. Open field locomotor performance was also assessed and recovered to almost normal levels by 3 weeks postinjury. Histologic analysis of the injury site indicated that the contusions destroyed approximately 70% of the cross-sectional area of the cord. Although the remaining 30% was sufficient to preserve nearly normal locomotor behavior, ASR and CMEP amplitudes in hindlimb flexors and extensors were reduced by 90% or more after injury and showed virtually no recovery. Significant ASR and CMEP responses were present in the cutaneous trunk muscles of the lower torso after injury. These muscles are innervated via peripheral nerves originating at cord levels above the injury. Multi-wave field potentials normally recorded from the dorsal cord surface in response to cerebellar stimulation were absent in injured rats, suggesting minimal if any activation of segmental neurons via the pathways normally mediating CMEP. The tracts mediating ASR and CMEP thus appear to be highly sensitive to mild spinal cord trauma but are evidently not essential for support or walking.

Differential expression of MHC class II antigen in the contused rat spinal cord

Following contusion injury to the dorsal surface of thoracic rat spinal cord, major histocompatibility complex (MHC) class II (Ia) antigen expression by microglia was evaluated throughout the developing lesion. Past investigations of various central nervous system (CNS) lesions have examined short-term or acute sequelae of post-traumatic Ia expression. This report demonstrates that in animals allowed to recover for 18 (sub-chronic) and 45 (chronic) days post-injury, MHC class II antigen is expressed differently at rostral and caudal extents of the lesion as compared with the lesion's epicenter. Following contusion injury to the thoracic spinal cord, sub-chronically injured animals demonstrated Ia-positive microglial staining throughout the white matter rostral and caudal to the epicenter of the lesion, whereas Ia-positive microglia and/or perivascular cells are localized within the gray matter adjacent to it. MHC class II immunoreactivity is down-regulated on microglia at chronic survival times but clusters of Ia-positive macrophages are prominent in regions of maximal degeneration at the epicenter of the lesion. Our findings support the theory that two distinct populations of macrophages participate in resolving traumatic injury. One population is the parenchymal CNS microglia and the other is presumably exudate macrophages derived from the blood. Furthermore, the immunocompetence of these cells as measured by MHC expression may be differentially regulated. This hypothesis is based on differences in Ia-positive staining observed between microglia and macrophages over time concomitant with differences in the spatial distribution of these cell types.

Gangliosides inhibit platelet-derived growth-factor-stimulated increases in intracellular calcium in Swiss 3T3 cells

Individual Swiss 3T3 cells stimulated by platelet-derived growth factor delivered by means of a picopump device respond with a brisk, large, and sustained increase in intracellular calcium concentration ([Ca2+]i). Preincubation of cells with either GM1 or GT1b gangliosides inhibited the proportion of responding cells and caused a dose-related diminution in the magnitude of the increase in [Ca2+]i. This effect of ganglioside is probably part of the mechanism through which gangliosides exert their biological effects, including inhibition of platelet-derived growth-factor-induced mitogenesis.

Activation of the phosphatidylinositol pathway in the primate corpus luteum by prostaglandin F2 alpha

The current study was designed to investigate the ability of prostaglandin F2 alpha (PGF2 alpha) to activate a second messenger system (phosphatidylinositol pathway) in corpora lutea (CL) of rhesus monkeys. Activation of this pathway was assessed by monitoring the hydrolysis of phosphatidylinositol to inositol phosphates. Since inositol triphosphate mobilizes intracellular Ca2+, intracellular free calcium concentrations ([Ca2+]i) were also assessed in individual cells by fura-2 fluorescence photometry. These responses to PGF2 alpha were measured in luteal cells collected from nonpregnant rhesus monkeys. CL were collected during the early (days 4-5 after estimated LH surge; n = 4), mid (days 8-9; n = 4), and late (days 13-14; n = 5) luteal phase and 1 day after in vivo hCG treatment (15 IU/dose, morning and evening), which began during the midluteal phase (n = 5). PGF2 alpha significantly increased the accumulation of inositol phosphates in all groups (P less than 0.05), except the midluteal phase (P = 0.07). The luteal sensitivity to PGF2 alpha, judged by phosphatidylinositol hydrolysis, was low in the early to midluteal phase compared to that in the late luteal phase and after in vivo hCG treatment. PGF2 alpha also caused a rapid, yet transient, increase in [Ca2+]i in a large proportion of primate luteal cells. The proportion of luteal cells that responded to PGF2 alpha with an increase in [Ca2+]i was smaller (P less than 0.05) in CL collected during the early luteal phase than in the other groups. Luteal progesterone production was inhibited by PGF2 alpha in CL collected after in vivo hCG. CL treated in vivo with hCG also displayed in vitro the largest increases in phosphatidylinositol hydrolysis and [Ca2+]i in response to PGF2 alpha. Therefore, this study demonstrates that PGF2 alpha is a potent activator of the phosphatidylinositol pathway in the primate CL. This activation is augmented as the luteal phase progresses and is influenced by in vivo hCG treatment. This study also provides evidence that the inhibitory effects of PGF2 alpha on progesterone production are associated with the activation of the phosphatidylinositol pathway.