Long-term hyperexcitability of sensory and motor axons in Aplysia californica: Induction by axotomy, serotonin, and transient depolarization

Neuropathic pain is a debilitating neurological disorder that may appear after peripheral nerve trauma and is characterized by persistent, intractable pain. The well-studied phenomenon of long-term hyperexcitability (LTH), in which sensory somata become hyperexcitable following peripheral nerve injury may be important for both chronic pain and long-lasting memory formation, since similar cellular alterations take place after both injury and learning. Though axons have previously been considered simple conducting cables, spontaneous afferent signals develop from some neuromas that form at severed nerve tips, indicating intrinsic changes in sensory axonal excitability may contribute to this intractable pain. Here we show that nerve transection, exposure to serotonin, and transient depolarization induce long-lasting sensory axonal hyperexcitability that is localized to the treated nerve segment and requires local translation of new proteins. Long-lasting functional plasticity may be a general property of axons, since both injured and transiently depolarized motor axons display LTH as well. Axonal hyperexcitability may represent an adaptive mechanism to overcome conduction failure after peripheral injury, but also displays key features shared with cellular analogues of memory including: site-specific changes in neuronal function, dependence on transient, focal depolarization for induction, and requirement for synthesis of new proteins for expression of long-lasting effects. The finding of axonal hyperexcitability after nerve injury sheds new light on the clinical problem of chronic neuropathic pain, and provides more support for the hypothesis that mechanisms of long-term memory storage evolved from primitive adaptive responses to injury. ^

Exploring parents' memories of their child's death related sensory experiences as a dimension of grieving

Little is known about how dying children and their parents experience death. Dying children have reported death related sensory experiences (DRSEs), defined as seeing or hearing someone or something not visible or audible to others, associated with dying. Although parents report that they and the dying child benefit from these experiences, healthcare providers often unknowingly dismiss them. The aims of this phenomenological inquiry were to describe children's DRSEs and their meaning from the parents' perspectives. Four fathers and six mothers of African American, Caucasian, or Hispanic ethnicity, all Christian, ranging in age from 35 to 59 years, whose child died 23 to 52 months prior and was treated at a children's cancer center, were interviewed in the home or hospital setting of their choice. Children's ages at the time of their death ranged from 4 to 13 years. A modification of van Kaarn's phenomenological method of analysis was used to analyze data. Themes emerging from the data for the first aim were: perceiving someone or something from a spiritual realm others could not, expressing awareness tempered by parental reactions, and embracing transcendence. Themes emerging from the data for the second aim were: spiritual beings prepared child; child revealed reality, preparing parents; and child transcended wholly, easing parents' grief. Post-interview surveys revealed that parents found participating in this study a "very positive" or "positive" experience, particularly being able to tell the story of their child. Children's DRSEs have clinical implications for all who provide care near the end of life. Informing parents of DRSEs, cautioning that not all dying children express them, may help parents to anticipate this phenomenon, which may decrease anxiety when their child expresses them, increasing the opportunity for open dialogue between parent and child about dying and death, and decrease regrets associated with being unreceptive to their child's expressions of death awareness. Validating a child's DRSE can have profound effects on bereaved parents. Examining DRSEs from the child's perspective and the influence of informing parents of DRSEs on the dying experience of the child and the parental grieving process are recommended. ^

Molecular interactions and signal transfer between sensory rhodopsin-I and its cognate transducer

SRI is unique among known photoreceptors in that it produces opposite signals depending on the color of light stimuli. Absorption of orange light (587 nm) triggers an attractant response by the cell, whereas absorption of orange light followed by near-UV light (373 run) triggers a repellent response. Using behavioral mutants that exhibit aberrant color-sensing ability, we tested a two-conformation equilibrium model, using FRET and EPR spectroscopy. The essence of the model applied to SRI-HtrI is that the complex exists in a metastable two-conformer equilibrium which is shifted in one direction by orange light absorption (producing an attractant signal) and in the opposite direction by a second UV-violet photon (producing a repellent signal). First, by FRET we found that the E-F cytoplasmic loop of SRI moves toward the RAMP domain of the HtrI transducer during the formation of the orange-light activated signaling state of the complex. This is the first localization of a change in the physical relationship between the receptor and transducer subunits of the complex and provides a structural property of the two proposed conformers that we can monitor. Second, EPR spectra of a spin label probe at this cytoplasmic position showed shifts in the dark in the mutants toward shorter or longer EF loop-RAMP distances, explaining their behavior in terms of their mutations causing pre-stimulus shifts into one or the other conformer. ^ Next, we applied a novel electrophysiological method for monitoring the directionality of proton movement during photoactivation of SRI, to investigate the process of proton transfer in the photoactive site from the chromophore to proton acceptors on both the wildtype and aberrant color-response mutants. We observed an unexpected and critical difference in the two signaling conformations of the SRI-HtrI complex. The finding is that the vectoriality (i.e. movement away or toward the cytoplasm) of the light-induced proton transfer from the chromophore to the protein is opposite in formation of the two conformations. Retinylidene proton transfer is a common critical process in rhodopsins and these results are the first to show differences in vectoriality in a rhodopsin receptor, and to demonstrate functional importance of the direction of proton transfer. ^

The impact of functional impairment on the survival of patients with Alzheimer's disease

Alzheimer's disease (AD), the most common form of dementia, is the fifth leading cause of death among U.S. adults aged 65 or older. Most AD patients have shorter life expectancy compared with older people without dementia. This disease has become an enormous challenge in the aging society and is also a global problem. Not only do families of patients with Alzheimer's disease need to pay attention to this problem, but also the healthcare system and society as a whole have to confront. In dementia, functional impairment is associated with basic activities of daily living (ADL) and instrumental activities of daily living (IADL). For patients with Alzheimer's disease, problems typically appear in performing IADL and progress to the inability of managing less complex ADL functions of personal care. Thus, assessment of ADLs can be used for early accurate diagnosis of Alzheimer's disease. It should be useful for patients, caregivers, clinicians, and policy planners to estimate the survival of patients with Alzheimer's disease. However, it is unclear that when making predictions of patient outcome according to their histories, time-dependent covariates will provide us with important information on how changes in a patient's status can effect the survival. In this study, we examined the effect of impaired basic ADL as measured by the Physical Self-Maintenance Scale (PSMS) and utilized a multistate survival analysis approach to estimate the probability of death in the first few years of initial visit for AD patients taking into consideration the possibility of impaired basic ADL. The dataset used in this study was obtained from the Baylor Alzheimer's Disease and Memory Disorders Center (ADMDC). No impaired basic ADL and older age at onset of impaired basic ADL were associated with longer survival. These findings suggest that the occurrence of impaired basic ADL and age at impaired basic ADL could be predictors of survival among patients with Alzheimer's disease. ^

Folate pathway polymorphisms and neuropsychological impairment after leukemia therapy

Neuropsychological impairment occurs in 20%-40% of childhood acute lymphoblastic leukemia (ALL) survivors, possibly mediated by folate depletion following methotrexate chemotherapy. We evaluated the relationship between two folate pathway polymorphisms and neuropsychological impairment after childhood ALL chemotherapy. Eighty-six childhood ALL survivors were recruited between 2004-2007 at Texas Children's Hospital after exclusion for central nervous system leukemia, cranial irradiation, and age<1 year at diagnosis. Neuropsychological evaluation at a median of 5.3 years off therapy included a parental questionnaire and the following child performance measures: Trail Making Tests A and B, Grooved Pegboard Test Dominant-Hand and Nondominant-Hand, and Digit Span subtest. We performed genotyping for polymorphisms in two folate pathway genes: reduced folate carrier (RFC1 80G>A, rs1051266) and dihydrofolate reductase (DHFR Intron-1 19bp deletion). Fisher exact test, logistic regression, Student's t-test, and ANOVA were used to compare neuropsychological test scores by genotype, using a dominant model to group genotypes. In univariate analysis, survivors with cumulative methotrexate exposure ≥9000 mg/m2 had an increased risk of attention disorder (OR=6.2, 95% CI 1.2 – 31.3), compared to survivors with methotrexate exposure <9000 mg/m2. On average, female survivors scored 8.5 points higher than males on the Digit Span subtest, a test of working memory (p=0.02). The RFC1 80G>A and DHFR Intron-1 deletion polymorphisms were not related to attention disorder or impairment on tests of attention, processing speed, fine motor speed, or memory. These data imply a strong relationship between methotrexate dose intensity and impairment in attention after childhood ALL therapy. We did not find an association between the RFC1 80G>A or DHFR Intron-1 deletion polymorphisms and long-term neuropsychological impairment in childhood ALL survivors.^

Neurocognitive impairment in relation to glutathione S-transferase enzyme polymorphisms among medulloblastoma patients

Background. Medulloblastoma is a type of brain cancer that accounts for approximately 7-8% of all intracranial tumors and 20-30% of pediatric brain tumors. It is the most common type of malignant brain tumor in childhood. It was reported that majority of survivors with medulloblastoma have social problems, endocrine deficits, and neurological complications. Furthermore, all had significant deficits in neurocognitive functioning. Glutathione S-transferases belong to a family of isoenzymes that catalyze the glutathione conjugation of a variety of electrophilic compounds. ^ Objective. We aimed to determine whether the development of neurocognitive impairment is associated with GST polymorphisms among children and adolescents diagnosed with medulloblastoma (MB) after radiation therapy. ^ Methods. A pilot study composing of 16 children and adolescents diagnosed with MB at Texas Children's Cancer Center was conducted. The t-test was used to determine if the GST polymorphisms were related to neurocognitive impairment and logistic regression was performed to explore association between GST polymorphisms and gender, age at diagnosis, race/ethnicity, and risk group. ^ Results. An association was observed between GSTT1 polymorphism and cognitive impairment one year after radiation and GSTM1 polymorphism two years after radiation. It was observed that patients with GSTT1 null genotype have lower performance IQ (p=0.03) and full scale IQ (p=0.02) one year after radiation and patients with GSTM1 null genotype have lower verbal IQ (p=0.02) two years after radiation. Patients under age 8 have a statistically non-significant higher risk of having not null genotypes compared to those older than age 8 (OR= 7.5, 95%CI: 0.62-90.65 and OR= 2.63, 95%CI: 0.30-23.00 for GSTT1 and GSTM1 respectively). ^ Conclusion. There was a significant association between GSTT1 polymorphism and cognitive impairment one year after radiation and between GSTM1 polymorphism and cognitive impairment two years after radiation. Further large scale studies may be needed to confirm this finding and to examine the underlying mechanism of neurocognitive impairments after treatment of medulloblastoma patients.^

The feasibility of self-report advance directives among elderly patients with cognitive impairment

The central objective of this dissertation was to determine the feasibility of self-completed advance directives (AD) in older persons suffering from mild and moderate stages of dementia. This was accomplished by identifying differences in ability to complete AD among elderly subjects with increasing degrees of dementia and cognitive incompetence. Secondary objectives were to describe and compare advance directives completed by elders and identified proxy decision makers. Secondary objectives were accomplished by measuring the agreement between advance directives completed by proxy and elder, and comparing that agreement across groups defined by the elder's cognitive status. This cross-sectional study employed a structured interview to elicit AD, followed by a similar interview with a proxy decision maker identified by the elder. A stratified sampling scheme recruited elders with normal cognition, mild, and moderate forms of dementia using the Mini Mental-State Exam (MMSE). The Hopkins Competency Assessment Test (HCAT) was used for evaluation of competency to make medical decisions. Analysis was conducted on "between group" (non-demented $\leftrightarrow$ mild dementia $\leftrightarrow$ moderate dementia, and competent $\leftrightarrow$ incompetent) and "within group" (elder $\leftrightarrow$ family member) variation.^ The 118 elderly subjects interviewed were generally male, Caucasian, and of low socioeconomic status. Mean age was 77. Overall, elders preferred a "trial of therapy" regarding AD rather than to "always receive the therapy". No intervention was refused outright more often than it was accepted. A test-retest of elders' AD revealed stable responses. Eleven logic checks measured appropriateness of AD responses independent of preference. No difference was found in logic error rates between elders grouped by MMSE or HCAT. Agreement between proxy and elder responses showed significant dissimilarity, indicating that proxies were not making the same medical decisions as the elders.^ Conclusions based on these data are: (1) Self reporting AD is feasible among elders showing signs of cognitive impairment and they should be given all opportunities to complete advance directives, (2) variation in preferences for advance directives in cognitively impaired elders should not be assumed to be the effects of their impairment alone, (3) proxies do not appear to forego life-prolonging interventions in the face of increasing impairment in their ward, however, their advance directives choices are frequently not those of the elder they represent. ^

The role of the intracellular second messenger cAMP in the induction of long-term morphological changes in sensory neurons of {\it Aplysia\/}

The present work examines the role of cAMP in the induction of the type of long-term morphological changes that have been shown to be correlated with long-term sensitization in Aplysia.^ To examine this issue, cAMP was injected into individual tail sensory neurons in the pleural ganglion to mimic, at the single cell level, the effects of behavioral training. After a 22 hr incubation period, the same cells were filled with horseradish peroxidase and 2 hours later the tissue was fixed and processed. Morphological analysis revealed that cAMP induced an increase in two morphological features of the neurons, varicosities and branch points. These structural alterations, which are similar to those seen in siphon sensory neurons of the abdominal ganglion following long-term sensitization training of the siphon-gill withdrawal reflex, could subserve the altered behavioral response of the animal. These results expose another role played by cAMP in the induction of learning, the initiation of a structural substrate, which, in concert with other correlates, underlies learning.^ cAMP was injected into sensory neurons in the presence of the reversible protein synthesis inhibitor, anisomycin. The presence of anisomycin during and immediately following the nucleotide injection completely blocked the structural remodeling. These results indicate that the induction of morphological changes by cAMP is a process dependent on protein synthesis.^ To further examine the temporal requirement for protein synthesis in the induction of these changes, the time of anisomycin exposure was varied. The results indicate that the cellular processes triggered by cAMP are sensitive to the inhibition of protein synthesis for at least 7 hours after the nucleotide injection. This is a longer period of sensitivity than that for the induction of another correlate of long-term sensitization, facilitation of the sensory to motor neuron synaptic connection. Thus, these findings demonstrate that the period of sensitivity to protein synthesis inhibition is not identical for all correlates of learning. In addition, since the induction of the morphological changes can be blocked by anisomycin pulses administered at different times during and following the cAMP injection, this suggests that cAMP is triggering a cascade of protein synthesis, with successive rounds of synthesis being dependent on successful completion of preceding rounds. Inhibition at any time during this cascade can block the entire process and so prevent the development of the structural changes.^ The extent to which cAMP can mimic the structural remodeling induced by long-term training was also examined. Animals were subjected to unilateral sensitization training and the morphology of the sensory neurons was examined twenty-four hours later. Both cAMP injection and long-term training produced a twofold increase in varicosities and approximately a fifty percent increase in the number of branch points in the sensory neuron arborization within the pleural ganglion. (Abstract shortened by UMI.) ^

The cGMP -PKG pathway is critical for inducing long-term sensitization of identified nociceptive sensory neurons

In various species, peripheral injury produces long-lasting sensitization of central and peripheral neurons representing the affected area. In Aplysia, memory-like traces (lasting days or weeks) of noxious peripheral stimulation include enhancement of central synaptic transmission and enhanced excitability of the central soma and peripheral branches of nociceptive sensory neurons. An important role for the cAMP-PKA-CREB pathway in consolidating long-term memory and inducing transcription-dependent synaptic potentiation has also been indicated by studies in rodents and Drosophila. ^ Much less attention has been paid to the cGMP-PKG pathway for transcription-dependent plasticity. Nevertheless, the cGMP-PKG pathway has been implicated in activity-dependent neural alterations lasting hours, and may trigger some forms of persistent pain. Recent evidence indicates PKG can regulate gene expression in the brain and several properties make it an attractive candidate for inducing long-term memories. ^ This dissertation reports that brief, noxious stimulation of a behaving, semi-intact preparation from mollusc, Aplysia californica, produces transcription-dependent, long-term hyperexcitability (LTH) of nociceptive sensory neurons that requires a nitric oxide (NO)-cGMP-protein kinase G (PKG) pathway and which lasts for at least 24 hours. Intracellular injection of cGMP is sufficient to induce LTH. Similarly, body wall injury induces LTH which can be blocked with specific inhibitors of the NO-cGMP-PKG pathway such as L-NMMA, ODQ, Rp-8-cGMPS, PKI-G and KT5823 by isolated perfusion of pleural ganglion sensory cells in or directly by intracellular injection. In contrast, specific inhibitors of the cAMP-PKA pathway (Rp-8-cAMPS, PKI-A and H-89) failed to block injury-induced LTH. Interestingly, co-injection of the cAMP-responsive element (CRE) blocked the induction of both cAMP and injury-induced LTH, but not cGMP-induced LTH. Furthermore, co-injection of cAMP and cGMP with the Ca2+ buffer BAPTA in reduced Ca2+ seawater blocked cAMP-, but not cGMP-induced LTH. These findings demonstrate that the NO-cGMP-PKG pathway and at least one other pathway (perhaps mediated by Ca2+), but not the cAMP-PKA pathway, are critical for inducing LTH during transient, noxious stimulation.^

Vocational guidance in people with special educational needs as the result of visual impairment during the transition stage from high school to advanced education

This work proposes to seek for the factors related to the choices that people with special educational needs make as the result of the visual impairment, during the transition stage from high school to advanced education. Therefore, we have taken into consideration that Vocational Guidance and the transition towards adulthood get specific characteristics in case of visually impaired young people, particularly in what's related to continue with advanced education. The focus of this work is to be able to clarify the existence of factors that make this transition stage easier or harder, through the observation of visually impaired and blind people who complete high school. This matter has aroused interest and concern about the strategies to follow to ensure the successful entrance and remaining in the selected advanced education. However, if we don?t know the factors involved in the described fact, it's difficult to design an appropriate intervention strategy. Then, in order to take acknowledge about the specific issues of visually impaired young people who complete high school, we chose a special school for this disability and some students who will join this project

Vocational guidance in people with special educational needs as the result of visual impairment during the transition stage from high school to advanced education

This work proposes to seek for the factors related to the choices that people with special educational needs make as the result of the visual impairment, during the transition stage from high school to advanced education. Therefore, we have taken into consideration that Vocational Guidance and the transition towards adulthood get specific characteristics in case of visually impaired young people, particularly in what's related to continue with advanced education. The focus of this work is to be able to clarify the existence of factors that make this transition stage easier or harder, through the observation of visually impaired and blind people who complete high school. This matter has aroused interest and concern about the strategies to follow to ensure the successful entrance and remaining in the selected advanced education. However, if we don?t know the factors involved in the described fact, it's difficult to design an appropriate intervention strategy. Then, in order to take acknowledge about the specific issues of visually impaired young people who complete high school, we chose a special school for this disability and some students who will join this project

Vocational guidance in people with special educational needs as the result of visual impairment during the transition stage from high school to advanced education

This work proposes to seek for the factors related to the choices that people with special educational needs make as the result of the visual impairment, during the transition stage from high school to advanced education. Therefore, we have taken into consideration that Vocational Guidance and the transition towards adulthood get specific characteristics in case of visually impaired young people, particularly in what's related to continue with advanced education. The focus of this work is to be able to clarify the existence of factors that make this transition stage easier or harder, through the observation of visually impaired and blind people who complete high school. This matter has aroused interest and concern about the strategies to follow to ensure the successful entrance and remaining in the selected advanced education. However, if we don?t know the factors involved in the described fact, it's difficult to design an appropriate intervention strategy. Then, in order to take acknowledge about the specific issues of visually impaired young people who complete high school, we chose a special school for this disability and some students who will join this project

Elevated CO2 affects the behavior of an ecologically and economically important coral reef fish

We tested the effect of near-future CO2 levels (= 490, 570, 700, and 960 µatm CO2) on the olfactory responses and activity levels of juvenile coral trout, Plectropomus leopardus, a piscivorous reef fish that is also one of the most important fisheries species on the Great Barrier Reef, Australia. Juvenile coral trout reared for 4 weeks at 570 µatm CO2 exhibited similar sensory responses and behaviors to juveniles reared at 490 µatm CO2 (control). In contrast, juveniles reared at 700 and 960 µatm CO2 exhibited dramatically altered sensory function and behaviors. At these higher CO2 concentrations, juveniles became attracted to the odor of potential predators, as has been observed in other reef fishes. They were more active, spent less time in shelter, ventured further from shelter, and were bolder than fish reared at 490 or 570 µatm CO2. These results demonstrate that behavioral impairment of coral trout is unlikely if pCO2 remains below 600 µatm; however, at higher levels, there are significant impacts on juvenile performance that are likely to affect survival and energy budgets, with consequences for predator-prey interactions and commercial fisheries.

Seawater carbonate chemistry and survival, impairment of three phytoplankton species in a laboratory experiment

Sodium hypochlorite (NaOCl) is widely used to disinfect seawater in power plant cooling systems in order to reduce biofouling, and in ballast water treatment systems to prevent transport of exotic marine species. While the toxicity of NaOCl is expected to increase by ongoing ocean acidification, and many experimental studies have shown how algal calcification, photosynthesis and growth respond to ocean acidification, no studies have investigated the relationship between NaOCl toxicity and increased CO2. Therefore, we investigated whether the impacts of NaOCl on survival, chlorophyll a (Chl-a), and effective quantum yield in three marine phytoplankton belonging to different taxonomic classes are increased under high CO2 levels. Our results show that all biological parameters of the three species decreased under increasing NaOCl concentration, but increasing CO2 concentration alone (from 450 to 715 µatm) had no effect on any of these parameters in the organisms. However, due to the synergistic effects between NaOCl and CO2, the survival and Chl-a content in two of the species, Thalassiosira eccentrica and Heterosigma akashiwo, were significantly reduced under high CO2 when NaOCl was also elevated. The results show that combined exposure to high CO2 and NaOCl results in increasing toxicity of NaOCl in some marine phytoplankton. Consequently, greater caution with use of NaOCl will be required, as its use is widespread in coastal waters.

CO2-induced fertilization impairment in Strongylocentrotus droebachiensis collected in the Arctic

Fertilization depends on distribution and aggregation patterns of sea urchins which influence gamete contact time and may potentially enhance their vulnerability to ocean acidification. In this study, we conducted fertilization experiments to assess the effects of selected pH scenarios on fertilization success of Strongylocentrotus droebachiensis, from Spitsbergen, Arctic. Acidification was achieved by aerating seawater with different CO2 partial pressures to represent pre-industrial and present conditions (measured ~180-425 µatm) and future acidification scenarios (~550-800, ~1,300, ~2,000 µatm). Fertilization success was defined as the proportion of successful/unsuccessful fertilizations per treatment; eggs were classified according to features of their fertilization envelope (FE), hyaline layer (HL) and achievement of cellular division. The diagnostic findings of specific pathological aberrations were described in detail. We additionally measured intracellular pH changes in unfertilized eggs exposed for 1 h to selected acidification treatments using BCECF/AM. We conclude that (a) acidified conditions increase the proportion of eggs that failed fertilization, (b) acidification may increase the risk of polyspermy due to failures in the FE formation supported by the occasional observation of multiple sperms in the perivitelline space and (c) irregular formation of the embryo may arise due to impaired formation of the HL. The decrease in fertilization success could be also related to the observed changes in intracellular pH at pCO2 ~ 1,000 µatm or higher.