bluuebunny/crossref_metadata_2025 huggingface dataset:
Constructing Subscores That Add Validity: A Case Study of Identifying Students at Risk
Authors: Biancarosa Gina , Kennedy Patrick C. , Carlson Sarah E. , Yoon HyeonJin , Seipel Ben , Liu Bowen , Davison Mark L.
Published: March 2018

Prior research suggests that subscores from a single achievement test seldom add value over a single total score. Such scores typically correspond to subcontent areas in the total content domain, but content subdomains might not provide a sound basis for subscores. Using scores on an inferential reading comprehension test from 625 third, fourth, and fifth graders, two new methods of creating subscores were explored. Three subscores were based on the types of incorrect answers given by students. The fourth was based on temporal efficiency in giving correct answers. All four scores were reliable. The three subscores based on incorrect answers added value and validity. In logistic regression analyses predicting failure to reach proficiency on a statewide test, models including subscores fit better than the model with a single total score. Including the pattern of incorrect responses improved fit in all three grades, whereas including the comprehension efficiency score only modestly improved fit in fourth and fifth grades, but not third grade. Area under the curve (AUC) statistics from receiver operating characteristic (ROC) curves based on the various models were higher for models including subscores than those without subscores. Implications for using models with and without subscores are illustrated and discussed.
Survivorship and walking behavior of Inquilinitermes microcerus (Termitidae: Termitinae) in contact with host workers and walls from host nest
Authors: Cruz Joseane Santos , Cristaldo Paulo Fellipe , Sacramento Jailton Jorge Marques , Cruz Marcos Leandro Da Rocha , Ferreira Dinamarta Virginio , Araujo Ana Paula Albano
Published: March 2018

Constrictotermes sp. nests are frequently inhabited by colonies of Inquilinitermes microcerus. In this association, I. microcerus colonies usually establish their colonies spatially isolated from Constrictotermes colonies. Here, we investigated whether the apparent spatial isolation of I. microcerus colonies in Constrictotermes nests should be related to their needs (e.g. feeding) in relation to the central part of the nest or to a possible stress provoked by the presence of the host. For this, survival and walking behavior bioassays were performed to test the hypothesis that the survivorship of inquilines is: (i) reduced in the presence of host, mainly of those from different nests, (ii) increased in contact with inner walls compared with external walls; and that the distance walked and walking velocity of inquiline is: (iii) increased in the presence of the host and (iv) reduced in contact with the internal walls compared with external walls of host nest. The mean time to death of inquiline workers is lower in contact with host (independently from the same or different nest) compared with control and the mean time to death of inquiline workers is lower in contact with external walls of host nest compared with control group and the inner walls. The distance walked and walking velocity of inquiline workers in contact with their hosts (from the same or different nest) did not differ from control, however, these parameters were reduced when workers were in contact with inner and external walls compared with control. In general, our results showed that I. microcerus adopt behavioral strategies to avoid perception by its host.
Termites of Iranian Date Palm Orchards And Their Spatial and Temporal Distribution
Authors: Latifian Masoud , Rad Bahar , Habibpour Behzad
Published: March 2018

This study was conducted during 2013-2014 to determine the dominant species and behavior of termites foraging in date palm orchards in Khuzestan province, Iran. Starting in early March, the ‘cluster random sampling’ method was used within sixty-five sampling plots. Termite species were sampled by breaking open mud tubing and collecting different castes, then bringing them to the laboratory for identification using scientific keys. Glass microscope slides of different body parts, especially the labium, maxillae, palps, mandibles, labrum, and clypeus. The Simpson Diversity Index was used to determine the level of dominance. Results showed three species of termites, Microcerotermes diversus Silvestri, Microcerotermes buettikeri Chhotani and Bose and Amitermes vilis Hagen, all family Termitidae, are active in Khuzestan date palm plantations. Microcerotermes diversus was dominant with a correlation coefficient 0.997 and 8.87, respectively.  Seasonal population fluctuations of workers, nymphs, soldiers and winged castes had two, four, four and four peaks, respectively, over the years.  According to Kriging map spatial distribution, four geographic severity groupings for M. diversus can be considered.  These groups include low, medium, and high risk, and hotspot infestation geographic regions, with severity indices of 2.3 to 3.96, 3.97 to 4.82, 4.83 to 5.68, and 5.96 to 6.53, respectively.
Changes in the Contribution of Termites to Mass Loss of Dead Wood among Three Tree Species during 23 Months in a Lowland Tropical Rainforest
Authors: Roh Yujin , Lee Sohye , Li Guanlin , Kim Seongjun , Lee Jongyeol , Han Seung Hyun , Chang Hanna , Salim Kamariah Abu , Son Yowhan
Published: March 2018

This study investigated the contribution of termites to mass loss of dead wood (Macaranga bancana, Elateriospermum tapos, and Dillenia beccariana) in a lowland tropical rainforest, Brunei Darussalam. Mesh bag method was used to exclude termites, and the mass remaining was monitored after 3, 7, 13, and 23 months. C/N ratio of the samples was analyzed after 13 and 23 months. Initial wood density was 0.63, 0.92, and 1.02 g/cm3 for M. bancana, E. tapos, and D. beccariana, respectively, and the termite contribution to mass loss was an average (range) of 13.05±5.68 (4.17-29.59%), 3.48±1.13 (2.20-6.49), and 3.40±1.92% (0.74-10.78), respectively. Until 7 months, termites contributed highly to mass loss, given the low initial wood density, and interaction effect of species and treatment was significant. After 7 months, the contribution decreased in M. bancana and E. tapos, whereas it increased consistently in D. beccariana. The interaction effect was not significant, whereas differences in C/N ratio among the species were significant, with a lower C/N ratio in M. bancana and E. tapos than in D. beccariana. After 23 months, the differences in C/N ratio were not significant, and ants were present at 40% of control samples in M. bancana and E. tapos. Our results suggest that the contribution of termites to mass loss varies by dead wood species and is temporally variable. Initial wood traits could affect the termite feeding in the beginning, however, termites thereafter could forage in response to the varying C/N ratio among species and predators.
On the Chemical Disguise of a Physogastric Termitophilous Rove Beetle
Authors: Rosa Cassiano Sousa , Cristaldo Paulo Fellipe , Florencio Daniela Faria , Marins Alessandra , Lima Eraldo R , DeSouza Og
Published: March 2018

Inter-specific symbiotic links are often reinforced by morphological, physiological, or behavioural trait modification undergone by the associated species. In some cases, such as in physogastric termitophile staphylinids, such modifications do facilitate the social interaction. Here we inspect chemical traits of the physogastric staphylinid Corotoca melantho (Insecta: Coleoptera) and its termite host Constrictotermes cyphergaster (Insecta: Blattodea: Isoptera), aiming to verify whether staphylinids resemble their host. First, we compared CHC profiles of hosts and guests within and among termitaria, to gather evidence on the origin of such profiles in guests. Then, we examined nitrogen and carbon isotopic signatures of these cohabitants to inspect whether chemical disguise is achieved by predation of host workers by staphylinids. Beetles presented CHC more similar to the CHC of their cohabiting termites than to (i) their conspecifics and (ii) termites from another nest, thereby favouring the hypothesis on CHC acquisition by guests. Isotopic signatures revealed that such similarities could not be majorly determined by share nutrition between these cohabitants. In general, our results evidenced that chemical disguise in termitophiles may function as a strategy for social integration in morphological mimics.
Relative occurrence of the family Kalotermitidae (Isoptera) under different termite sampling methods
Authors: Scheffrahn Rudolf H , Chase James A , Mangold John R. , Hochmair Henry H
Published: March 2018

The termite family Kalotermitidae constitutes a wood-nesting termite family that accounts for about 15% of all extant termite species. In recent decades, field studies have been carried out to assess termite diversity in various wooded habitats and geographic locations. Three sampling methods have been favored expert, transect, and alate light-trap surveys. Expert collecting is not spatially quantifiable but relies on field personnel to recognize and sample termite niches. The transect method aims to standardize and quantify termite abundance and diversity. Light trapping is a passive method for sampling nocturnal alate flights. We compared our expert survey results and results of published sampling methods for their proportional yields of kalotermitid versus non-kalotermitid encounters. Using an odds ratio statistic, we found that worldwide, there is about a 50.6-fold greater likelihood of encountering a kalotermitid sample versus a non-kalotermitid using the expert survey method and a 15.3-fold greater likelihood using alate trapping than using the transect method. There is about a 3.3 -fold greater likelihood of collecting a kalotermitid specimen versus a non-kalotermitid sample using the expert survey method than using the alate trap method. Transect studies in which only termite species diversity was reported gave similar low Kalotermitidae yields. We propose that multiple biases in sampling methodology include tools, time constraints, habitat type, geographical location, topographical conditions, and human traits account for the divergent outcomes in sampling the abundance and diversity of Kalotermitidae compared to other termite families.
Health Care Provider Perceptions of the Safety of IUDs for Women with HIV
Authors: Simmons Katharine B. , Zapata Lauren , Curtis Kathryn M.
Published: March 2018

CONTEXT

Women who are living with HIV use IUDs at a lower rate than the general population, and it is unclear whether health care providers’ misconceptions about IUD safety contribute to this disparity.

METHODS

A 2013–2014 nationwide survey of 1,998 U.S. family planning providers assessed perceptions of IUD safety for women with HIV or other medical conditions. Multivariable logistic regression was used to examine associations between provider characteristics and whether individuals believed IUDs were safe for HIV‐positive women. Data from public‐sector providers and office‐based physicians were analyzed separately.

RESULTS

Seven in 10 providers considered IUDs safe for women with HIV, and there were no differences by provider type. Among public‐sector providers, some of the characteristics associated with believing that IUDs were unsafe for seropositive women were working at a clinic without Title X funding (odds ratio, 1.5), not being trained in IUD insertion (2.1) and not using the U.S. Medical Eligibility Criteria for Contraceptive Use (U.S. MEC) for clinical guidance (1.8). Office‐based physicians who did not use the guidelines also had an increased likelihood of believing that IUDs were unsafe for women with HIV (2.9), and physicians who had completed training 25 or more years ago were more likely than those who had done so less than five years ago to consider IUDs unsafe (3.3).

CONCLUSIONS

Greater use of evidence‐based contraceptive guidance such as the U.S. MEC may help inform provider perceptions of IUD safety and hence contribute to increased contraceptive choice for women with HIV.
Assessment of heavy metals with ecological risk of soils in the industrial vicinity of Tangail district, Bangladesh
Authors: Proshad Ram , Islam Md. Saiful , Kormoker Tapos
Published: March 2018

This study was conducted to assess the ecological risk of heavy metals in soils collected from the industrial vicinity of Tangail district in Bangladesh. In this study, the levels of six heavy metals namely chromium (Cr), nickel (Ni), copper (Cu), arsenic (As), cadmium (Cd), and lead (Pb) in 15 sampling sites around the industrial vicinity of Tangail district in Bangladesh were assessed. The mean concentration of Cr, Ni, Cu, As, Cd and Pb in studied soils were 11.56, 23.92, 37.27, 6.11, 2.01, and 17.46 mg/kg, respectively. Certain indices, including the enrichment factor (EF), contamination factor (Cif), geoaccumulation index (Igeo), pollution load index (PLI), toxic unit analysis, and principal component analysis (PCA) were used to assess the ecological risk. The enrichment factor of all the studied metals for all sampling sites were in the descending order of Cd > Cu > As > Pb >Ni > Cr. The contamination factor values revealed that the studied soils were highly impacted by Cd. The pollution load index (PLI) values of Cd were higher than 1, indicating the progressive deterioration of soil due to Cd contamination. In the context of potential ecological risk (PER), soils from all sampling sites showed moderate to very high potential ecological risk.
Formulation, method development and validation of water soluble vitamins B1, B2 & B6 in bulk and tablet dosage form by HPTLC method
Authors: Velmurugan Devi , Munusamy Jambulingam , Subramaniam Ananda Thangadurai , Karunakaran Anandkumar , Latiff MKM Abdul , Dhanapal Kamalakannan
Published: March 2018

In the present study we are reportingÂ  dissolution, method development and validation of water soluble vitamins B1, B2 & B6 in bulk and tablet dosage form by HPTLC method. The method is based on separation of the three vitamins using HPTLC. Thin layer chromatographic plates coated with silica gel 60F254 as the stationary phase and acetonitrile:water (6:4 v/v) as mobile phase. The chromatographic analysis was carried out in the reflectance and absorbance mode at 280 nm. The method was validated with respect to linearity, accuracy and precision, limit of detection and limit of quantitation. It was then applied for analysis of vitamins B1, B2 & B6 in combined tablet dosage form. The above method developed was reproducible with good resolution and the results of analysis have been validated with correlation coefficient of 0.9990
Developmental and neural regulation of a subsarcolemmal component of the rat neuromuscular junction
Authors: Astrow SH , Sutton LA , Thompson WJ
Published: March 2018

We have generated a monoclonal antibody, designated mAb 3G2, which reacts with a subsarcolemmal component of the neuromuscular junction in adult rats. mAb 3G2 immunoreactivity lies beneath and between the ACh receptor-rich synaptic gutters, around the sole plate nuclei, and at/near sarcomeric Z-disks in the vicinity of the synapse. Localization of mAb 3G2 immunoreactivity to neuromuscular junctions begins postnatally and gradually increases to adult levels. The establishment of this synaptic localization is neurally regulated, as neonatal denervation prevents its occurrence. In adults, denervation results in a loss of synaptic immunoreactivity that returns upon reinnervation. The antigen is also found at the myotendinous junction; its localization here is innervation independent. mAb 3G2 recognizes a 41 kDa protein on immunoblots of extracts of newborn muscle. Based on its distribution within muscle fibers, its developmental and neural regulation, and its molecular weight, the protein recognized by mAb 3G2 can be distinguished from other known postsynaptic proteins. Its neural dependence and developmental regulation suggest that it may participate in synaptic stabilization, perhaps as the intracellular component in a chain of proteins that serve to tether the nerve terminal to the perijunctional region of the muscle fiber.
Identified FMRFamide-immunoreactive neuron LPL16 in the left pleural ganglion of Aplysia produces presynaptic inhibition of siphon sensory neurons
Authors: Small SA , Cohen TE , Kandel ER , Hawkins RD
Published: March 2018

The gill- and siphon-withdrawal reflex of Aplysia undergoes transient inhibition following noxious stimuli such as tail shock. This behavioral inhibition appears to be due in part to transient presynaptic inhibition of the siphon sensory cells, which can be mimicked by application of the peptide FMRFamide. Although FMRFamide is widespread in the Aplysia nervous system, an FMRFamide-containing inhibitory neuron has not previously been identified. We have searched for such a neuron by combining FMRFamide immunofluorescence with fluorescent dye backfilling from the abdominal ganglion, the location of the siphon sensory cells. These methods localized a neuron in the left pleural ganglion, which we have named LPL16. LPL16 is FMRFamide immunoreactive; it is excited by tail shock; and stimulation of LPL16 produces inhibition of siphon sensory cell-to-motor cell postsynaptic potentials and narrowing of action potentials in the sensory cells in tetraethylammonium solution. These results indicate that LPL16 participates in the inhibitory effects of tail shock, and support the idea that FMRFamide plays a physiological role in the inhibition.
Transgenic mice with increased Cu/Zn-superoxide dismutase activity are resistant to N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced neurotoxicity
Authors: Przedborski S , Kostic V , Jackson-Lewis V , Naini AB , Simonetti S , Fahn S , Carlson E , Epstein CJ , Cadet JL
Published: March 2018

Administration of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to mammals causes damage to the nigrostriatal dopaminergic pathway similar to that observed in Parkinson's disease. It has been suggested that the mechanism by which MPTP kills dopamine (DA) neurons involves an energy crisis due to the inhibition of mitochondrial complex I. In addition, superoxide radicals (O2-), generated subsequent to the blockade of mitochondrial complex I, may also be involved in MPTP- induced neurotoxicity. Superoxide dismutase (SOD) is a scavenger enzyme that protects cells from the hazard of O2- radicals. To evaluate further the role of O2- radical in MPTP-induced toxicity, we tested the effects of MPTP in transgenic mice with increased SOD activity. In nontransgenic littermates with normal SOD activity, MPTP injection causes a marked reduction in striatal levels of DA and its metabolites as well as in striatal and nigral 3H-DA uptake; these findings are consistent with a loss in dopaminergic neurons. In contrast, in transgenic mice with increased SOD activity, MPTP injection does not cause any significant changes either in levels of DA and metabolites or in 3H-DA uptake. We show that this lack of toxicity is not due to a lower delivery of MPTP to the brain following its intraperitoneal injection, to reduced brain biotransformation of MPTP to N-methyl-4- phenylpyridinium ion (MPP+), to diminished striatal mitochondrial monoamine oxidase B activity, to decreased synaptosomal uptake of MPP+, to lower potency of MPP+ to inhibit the complex I of the mitochondrial electron transport chain, or to faster brain elimination of MPP+. These results suggest that increased SOD activity is, most likely, the protective factor that confers resistance to transgenic mice against MPTP-induced neurotoxicity. Thus, this study provides further evidence that some of the deleterious effects of MPTP may be mediated by O2- radicals. The similarity between the MPTP model and Parkinson's disease further raises the possibility that oxy-radicals may play a significant role in the etiology of this neurodegenerative disorder.
Basic FGF in astroglial, microglial, and neuronal cultures: characterization of binding sites and modulation of release by lymphokines and trophic factors
Authors: Araujo DM , Cotman CW
Published: March 2018

The present study characterizes whether basic fibroblast growth factor (bFGF) is present and released from astroglia, microglia, and hippocampal neurons in vitro. For cell content, bFGF-like immunoreactivity (IR) of cell extracts was measured, whereas release was determined by assessing the levels of bFGF-like IR in media. In addition, the effects of lymphokines and trophic factors that are known to be released from these cells on bFGF release were examined. For all three cell types, bFGF-like IR in extracts of cell lysates was detectable. In addition, media content was highest in astroglial cultures and lowest in neuronal cultures. Although bFGF-like IR of neuronal and microglial media appeared to increase with time in culture, this was likely due to significant astroglial proliferation. Thus, notable levels of bFGF are released by astroglia in vitro. In astroglia, bFGF release was enhanced by interleukin-1 (IL-1), IL-6, and epidermal growth factor (EGF), but not by other lymphokines or NGF. In contrast, bFGF in microglial media was reduced by IL-3, EGF, and NGF, but slightly augmented by gamma-interferon (IFN); other lymphokines were ineffective. In addition, no effects were seen in the neuronal cultures. It is likely that the bFGF found in glial media interacts with bFGF receptors since in both glial and neuronal cell types, a single class of low-capacity (Bmax), high-affinity (Kd) bFGF binding sites was evident. The possibility that endogenous bFGF acts as an autocrine factor for astroglia was further supported by experiments that tested the mitogenic effects of exogenous bFGF on glial cells. bFGF significantly enhanced 3H-thymidine uptake into astroglial, but not microglial, cells in vitro. Thus, the present study demonstrates that a complex regulation of glial bFGF release by astroglia and microglia occurs in vitro. Moreover, the results are consistent with an autocrine role for bFGF in astroglial cultures.
The neurotoxic carboxy-terminal fragment of the Alzheimer amyloid precursor binds specifically to a neuronal cell surface molecule: pH dependence of the neurotoxicity and the binding
Authors: Kozlowski MR , Spanoyannis A , Manly SP , Fidel SA , Neve RL
Published: March 2018

One of the hallmarks of Alzheimer's disease neurodegeneration is the accumulation of deposits of amyloid in neuritic plaques and in the cerebral vasculature. Recent studies have implicated carboxy-terminal fragments of the Alzheimer amyloid precursor protein (beta APP) in the processes of amyloidogenesis and neurodegeneration. In particular, the carboxy-terminal 104 amino acids of beta APP (beta APP-C104) have been shown to cause amyloid-like fibrils when expressed in non-neuronal cells and to cause the degeneration of neuronal cells. These data suggest that it may play a role in the development of the progressive neuropathology of Alzheimer's disease. We hypothesized that beta APP- C104 may cause the degeneration of neurons by interacting with a cell surface receptor. In the present report, we show that beta APP-C104 synthesized in vitro binds specifically and with high affinity to the surface of NGF-treated PC12 cells. Both the cell surface binding and the neurotoxicity of beta APP-C104 are pH dependent and are not inhibited by tachykinins. Mutational analysis suggests that both the binding and the neurotoxicity are dependent at least in part on the presence of a tyrosine residue that is a potential site of phosphorylation at the carboxy terminus of the fragment.
Neonatal capsaicin treatment attenuates spinal Fos activation and dynorphin gene expression following peripheral tissue inflammation and hyperalgesia
Authors: Hylden JL , Noguchi K , Ruda MA
Published: March 2018

An animal model of nociception involving unilateral hindpaw inflammation has been used to examine behavioral, molecular, and biochemical aspects of well-characterized spinal cord neural circuits involved in pain transmission. The neurotoxin capsaicin administered neonatally was used to modify this neuronal system by producing a selective destruction of most small, unmyelinated primary afferent axons. Capsaicin had minimal effects on the behavioral hyperalgesia and edema associated with the hindpaw inflammation and on the constitutive expression of preprodynorphin (PPD) mRNA and preproenkephalin mRNA in the spinal cord. However, the inflammation-induced increases in Fos- like immunoreactivity (Fos-LI) and in PPD mRNA were greatly attenuated by neonatal capsaicin treatment. The data indicate that input from small-diameter unmyelinated primary afferents is important for the stimulus-induced increase in Fos-LI and PPD mRNA. Our finding that neonatal capsaicin reduces the levels of Fos-LI and PPD mRNA in a related fashion in the spinal dorsal horn provides further evidence for a relationship between the protein product of the c-fos protooncogene and regulation of dynorphin gene transcription.
Long-term regulation of neuronal calcium currents by prolonged changes of membrane potential
Authors: Franklin JL , Fickbohm DJ , Willard AL
Published: March 2018

Although rapid-onset, short-term regulation of neuronal Ca currents by neurotransmitters and second messengers is well documented, little is known about conditions that can cause longer-lasting changes in Ca channel function. We report here that persistent depolarization is accompanied by slowly developing long-term reduction of neuronal Ca currents. Rat myenteric neurons grown in cell culture for 1–7 d were studied with the tight-seal whole-cell recording technique. Macroscopic Ca-channel currents had decaying and sustained components at all days studied. When the neurons were grown in medium containing 25 mM KCl, which depolarized them to -40 mV and caused significant elevation of intracellular Ca, the densities of both components of Ca-channel current decreased by 40–80%. Several results suggest that different mechanisms underlie the downregulation of the two components. (1) The density of the decaying component decreased approximately four times faster than did that of the sustained component. (2) When neurons were returned to control medium, which contained 5 mM KCl, the density of the sustained component returned to control levels within 24 hr, while that of the decaying component did not recover significantly. (3) Inhibitors of RNA and protein synthesis reduced or prevented downregulation of the sustained but not of the decaying component. (4) The dihydropyridine antagonist nitrendipine, which prevented the sustained elevation of intracellular Ca in neurons grown in 25 mM KCl, prevented downregulation of the sustained component but had no effect on downregulation of the decaying component. We suggest that these forms of regulation of Ca current density could help neurons adapt to altered levels of electrical activity and may contribute to changes in synaptic strength that occur during periods of increased or decreased electrical activity.
Differential expression of synapsins I and II among rat retinal synapses
Authors: Mandell JW , Czernik AJ , De Camilli P , Greengard P , Townes-Anderson E
Published: March 2018

The synapsins are a family of synaptic vesicle-associated phosphoproteins thought to regulate the availability of vesicles for neurotransmitter release. In order to assess variability of synapsin isoform expression, we compared the localization of synapsins Ia, Ib, IIa, and IIb in the inner plexiform layer of the rat retina. Double labeling in conjunction with confocal fluorescence and electron microscopy allowed imaging of synapsin I and II immunoreactivity within single presynaptic terminals. No qualitative differences were observed between expression of the a and b isoforms of synapsin I in individual terminals; likewise, the a and b isoforms of synapsin II were identically distributed. In contrast, marked differences were seen upon comparison of synapsin I and synapsin II expression in single terminals. Our results indicate the existence of three classes of presumed amacrine cell synaptic terminals: synapsin I+/synapsin II-, synapsin I-/synapsin II+, and synapsin I+/synapsin II+. Each class of synapse has a different distribution among five IPL sublayers, suggesting that they represent different subpopulations of amacrine cells. Double labeling with an antibody to choline acetyltransferase indicates that synapsin I-/II+ terminals may be those of cholinergic amacrine cells. Furthermore, all synapsin II+ terminals appear to be distinct from those expressing the GABA synthetic enzyme glutamic acid decarboxylase. The observed variations in synapsin content suggest the existence of presynaptic terminal heterogeneity that is not apparent from conventional morphological studies.
Emergent properties of odor information coding in a representational model of the salamander olfactory bulb
Authors: White J , Hamilton KA , Neff SR , Kauer JS
Published: March 2018

In the salamander olfactory bulb, mitral output cells exhibit a variety of responses to electrical and odor stimulation, but the cellular interactions within the bulb that give rise to these responses are not completely understood. We have developed a computer model to investigate whether available data are sufficient for formulating a simulated bulb circuit that can generate realistic mitral cell output. A set of coupled difference equations incorporating mathematical descriptions of anatomical and physiological data was used to calculate changes in membrane potentials of olfactory bulb neurons over time. Model mitral cells showed responses to simple orthodromic and antidromic electrical stimuli that were similar to salamander intracellular responses. Without changing the parameters of the equations, simulated odor stimuli were applied that elicited complex patterns of mitral depolarization, spike activation, and hyperpolarization that emerged from the interactions among the numerous elements in the model. As with the electrical stimuli, model mitral responses to odor were also strikingly similar to those of real mitral cells. As an initial test of how different circuit components contribute to the responses, the lateral interactions between mitral cells and bulbar interneurons were manipulated. Tests with reduced lateral interactions and other tests with no inhibitory synaptic connections both produced mitral cell outputs that were uncharacteristic of salamander recordings. The similarity of the model's output to the complex properties of salamander single-cell recordings suggests that several critical features of the bulb circuit responsible for shaping mitral cell responsivity have been captured.(ABSTRACT TRUNCATED AT 250 WORDS)
Voltage-activated K+ currents in acutely isolated hippocampal astrocytes
Authors: Tse FW , Fraser DD , Duffy S , MacVicar BA
Published: March 2018

Hippocampal astrocytes were acutely isolated by papain treatment and mechanical trituration. Astrocytes were identified by their distinctive stellate morphology and immunocytochemical staining for glial fibrillary acidic protein. The electrophysiological properties of these cells were investigated using whole-cell voltage-clamp techniques. Three kinetically and pharmacologically distinct voltage-activated K+ currents were identified in most cells; they resembled the neuronal A- current, delayed rectifier, and inward rectifier. The activation threshold of the A-current was -40 mV with a time to peak that ranged from 10 msec at -20 mV to 6 msec at 100 mV. Steady-state inactivation was observed when the holding potential was positive to -100 mV. The current was half-inactivated at -60 mV and totally inactivated at -20 mV. The A-current was suppressed by 4-aminopyridine (4-AP). The delayed rectifier was activated by depolarizing pulses more positive than -40 mV and had a half time of activation that ranged from 18 msec at -20 mV to 10 msec at potentials more positive than 40 mV. This current did not inactivate during a 100 msec pulse and was suppressed by extracellular tetraethylammonium (TEA). An inwardly rectifying current was elicited by hyperpolarizing pulses more negative than -80 mV. This current was not blocked by extracellular TEA or 4-AP and was never observed in the presence of external Ba2+. Voltage-activated inward Na+ currents were never observed. Voltage-activated K+ channels may enhance the local K+ spatial buffering capabilities of the astrocyte syncytium when extracellular [K+] increases during neuronal activity.
Multiple Ca2+ currents elicited by action potential waveforms in acutely isolated adult rat dorsal root ganglion neurons
Authors: Scroggs RS , Fox AP
Published: March 2018

Ca2+ entry into different diameter cell bodies of dorsal root ganglion (DRG) neurons depolarized with action potential (AP) waveform commands was studied using the whole-cell patch-clamp technique and pharmacological probes. We have previously shown that Ca2+ current expression in DRG neuron cell bodies depends on cell diameter. In small diameter DRG neurons, L- and N-type Ca2+ currents usually accounted for most Ca2+ entry during APs as determined by blockade with nimodipine and omega-conotoxin GVIA (omega-CgTx). In medium- diameter DRG neurons, T-type Ca2+ currents accounted for 29% or 54% of Ca2+ entry in cells held at -60 mV or -80 mV, respectively, based on blockade by amiloride. T-type Ca2+ currents did not usually contribute to Ca2+ entry in large diameter DRG neurons. An amiloride/omega-CgTx/nimodipine-resistant Ca2+ current was prominent in medium diameter DRG neurons, while L- and N- type Ca2+ currents played a relatively small role in Ca2+ entry. In all DRG neuron sizes, AP-generated currents were large in amplitude, resulting in significant Ca2+ entry. APs with slower rates of repolarization increased Ca2+ entry. In DRG neurons that expressed T- type Ca2+ currents, the duration of Ca2+ current entry during APs was prolonged, and this prolongation was reduced by amiloride. Thus, antagonists selective for different Ca2+ channels produced different patterns of blockade of AP-generated Ca2+ entry in different diameter DRG cell bodies. Selective Ca2+ channel modulation by neurotransmitters might be expected to have similar effects.
Pure, postmitotic, polarized human neurons derived from NTera 2 cells provide a system for expressing exogenous proteins in terminally differentiated neurons
Authors: Pleasure SJ , Page C , Lee VM
Published: March 2018

NTera 2/cl.D1 (NT2) cells, a human teratocarcinoma cell line, were manipulated following retinoic acid treatment to yield greater than 95% pure cultures of neuronal cells (NT2-N cells). The commitment of NT2-N cells to a stable neuronal phenotype is irreversible as judged by the lack of mitotic activity or phenotypic reversion over a period of 2 months in culture. Furthermore, NT2-N cells express a variety of neuronal markers including many neuronal cytoskeletal proteins, secretory markers, and surface markers. NT2-N cells resemble primary neuronal cultures from rodents morphologically and in density of process outgrowth and, like primary neurons, go on to elaborate processes that differentiate into axons and dendrites. This culture method yields sufficient highly differentiated postmitotic NT2-N cells for both biochemical and molecular biological studies. Indeed, when undifferentiated NT2 cells were stably transfected with a beta- galactosidase (beta-gal) expression plasmid, beta-gal expression was shown to be present in both undifferentiated NT2 and postmitotic NT2-N cells. Thus, the ability to transfect expression plasmids into undifferentiated NT2 cells will allow the introduction of normal and mutant gene products into cells that can then be induced to become stable, postmitotic human neurons. We conclude that NT2 cells and NT2-N cells represent a unique model system for studies of human neurons, and a novel vehicle for the expression of diverse gene products in terminally differentiated polarized neurons.
GABA-induced inactivation of functionally characterized sites in cat visual cortex (area 18): effects on orientation tuning
Authors: Crook JM , Eysel UT
Published: March 2018

Microiontophoresis of the inhibitory transmitter GABA was used to reversibly inactivate small sites of defined orientation specificity at a horizontal distance of some 600 microns from single cells recorded in area 18 of cat visual cortex, and the effects on orientation tuning were studied. The receptive fields of cells at the recording and inactivation sites overlapped extensively. During the inactivation of sites where the orientation preference differed by 45 degrees or more from that of a recorded cell (“cross-orientation” sites), 65% of 54 cells tested showed significant broadening of orientation tuning, with a mean increase in tuning width (measured at half the maximum response) of 93%, and an almost fourfold increase in the relative response to the orientation orthogonal to the optimum, compared with the response to the optimum; four cells essentially lost their orientation tuning. Broadening of tuning reflected an increase in response to nonoptimal orientations and was reversible upon termination of GABA application. The effects on orientation tuning typically peaked within 10–15 min of the onset of GABA iontophoresis with 50–100 nA ejecting currents, and could not be replicated by inactivating sites where the orientation preference was similar to that of a recorded cell; when the orientation preference at the inactivation sites was within 22.5 degrees of that of a recorded cell (“iso-orientation” sites), only 3 of 22 cells showed significant broadening of tuning, and in these cases, the effects were relatively weak (mean increase in tuning width of 39% and a negligible change in the relative response to the orientation orthogonal to the optimum). The effect of inactivating “iso-orientation” sites consisted primarily in an increase in response magnitude. The difference in the magnitude of the effects on orientation tuning elicited by inactivating “cross-orientation” and “iso-orientation” sites was highly statistically significant. Additionally, inactivation of “cross- orientation” or “iso-orientation” sites elicited differential effects on orientation tuning in 10 of the 13 cells in which direct comparisons were made. It is argued that the observed broadening of tuning was due to the loss of a “cross-orientation” inhibitory input, which normally sharpens orientation tuning by suppressing responses to nonoptimal orientations.
Selective regulation of Gi alpha 1 expression and function in PC12 cells by cAMP
Authors: Morton ME , Street VA , Nathanson NM
Published: March 2018

Hormone and neutrotransmitter receptor systems regulate both the activity and expression of GTP-binding proteins (G-proteins). However, relatively little is known about the mechanism by which this regulation occurs. One G-protein subtype, Gi alpha 1, is expressed primarily in neuronal cells. Here, we demonstrate the selective regulation of Gi alpha 1 mRNA and protein levels by cAMP. Treatment of PC12 cells with forskolin increases Gi alpha protein levels. Similarly, incubation of PC12 cells with agents that increase intracellular levels of cAMP, including forskolin, dibutyryl-cAMP, and 8-bromo-cAMP, induce a two- to fourfold increase in Gi alpha 1 mRNA levels. Furthermore, the effect of increased intracellular cAMP is specific for Gi alpha 1 mRNA expression; the levels of mRNA encoding other G-protein subtypes remain unaltered. cAMP-stimulated Gi alpha 1 expression occurs within hours of treatment and is sustained for days. Increasing intracellular cAMP by activation of cell surface adenosine receptors also increases Gi alpha 1 mRNA levels. Treatment of PC12 cells with phorbol esters, NGF, or depolarizing concentrations of KCl did not increase Gi alpha 1 mRNA expression, demonstrating that Gi alpha 1 expression is specifically regulated by cAMP. Guanine nucleotide-mediated inhibition of adenylate cyclase activity was measured in order to determine if the change in Gi alpha protein expression was accompanied by a change in G-protein function. Adenylate cyclase activity in PC12 cells treated with an adenosine analog and therefore expressing higher levels of Gi alpha protein is more sensitive to inhibition by guanine nucleotides than in nontreated PC12 cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Synapses formed by identified retinogeniculate axons during the segregation of eye input
Authors: Campbell G , Shatz CJ
Published: March 2018

The synaptic organization of identified retinogeniculate axons was studied during the prenatal development of eye-specific layers in the LGN of the cat. During this period, retinogeniculate axons undergo stereotyped morphological changes. Retinogeniculate axons originating from one eye and passing through LGN territory destined to be solely innervated by the other eye (inappropriate territory) initially give rise to many side branches. As the eye-specific layers emerge, these axons elaborate extensive terminal arbors within territory appropriate to their eye of origin and concurrently retract their side branches from inappropriate territory (Sretavan and Shatz, 1986). These transient side branches may therefore represent a morphological substrate for the observed functional convergence of inputs from the two eyes onto common LGN neurons during prenatal development (Shatz and Kirkwood, 1984). This possibility was investigated by examining whether identified axons and their side branches form synapses in inappropriate territory. Three retinogeniculate axons from two fetuses aged embryonic day 53 (E53) and E57 were filled with HRP in an in vitro preparation, prior to being processed for electron microscopy (EM). The HRP-filled axons, originating from the contralateral eye, were first reconstructed at the light microscope level. The portion of axon passing through the center of ipsilaterally innervated layer A1 was then serially sectioned and reconstructed by EM. Two sets of 450 serial EM sections revealed that all three contralateral axons established synaptic contacts in ipsilateral territory. Many of these synapses were made by side branches and a few were even formed by the main axon trunks. Both side branches and trunks formed mainly en passant asymmetrical contacts that were associated with spherical synaptic vesicles and that were apposed to immature dendritic elements and dendritic shafts. For comparison, a portion of the same E53 axon within the future contralateral layer A was also serially sectioned and reconstructed for EM. Within this contralateral zone, the E53 axon formed synaptic contacts similar to those established in the ipsilateral region, except that in the appropriate zone they contained significantly more synaptic vesicles. These results demonstrate that axons from the contralateral eye can establish synapses in territory simultaneously innervated by the ipsilateral eye, both via side branches and by means of contacts along the main axon trunk. Thus, the development of eye-specific layers is accompanied by the formation and subsequent elimination of synapses that almost certainly represent a morphological substrate for the known transient functional convergence of inputs from the two eyes.
On the role of nerve growth factor in the development of myelinated nociceptors
Authors: Lewin GR , Ritter AM , Mendell LM
Published: March 2018

We have previously demonstrated that administration of antisera against NGF (anti-NGF) can have profound effects on developing primary afferents (Ritter et al., 1991). Chronic administration of anti-NGF to rats beginning on the day of birth results in a severe depletion of cutaneous A delta high-threshold mechanoreceptors (HTMRs) from the sural nerve. Here we have carried out further experiments in order to define the period of time over which this change in the cutaneous afferent population can be produced, and to investigate a possible mechanism for the change. Treatment with anti-NGF from postnatal day (PND) 0–14 resulted in a depletion of cutaneous A delta HTMRs from the sural nerve and also a 20% loss of sensory neurons. However, treatment from PND 2–14 produced an identical deficit of HTMRs without any accompanying cell death. Thus, the depletion of cutaneous A delta HTMRs can be achieved in the absence of cell death induced by anti-NGF treatment. It was also found that a 7 d treatment from PND 4–11 was sufficient to reproduce this effect, but that 7 d treatments earlier (PND 2–9) or later (PND 7–14) within the first 2 weeks were much less effective. This critical period, PND 4–11, corresponds to a period of anatomical change in the innervation of the skin, from epidermal innervation to primarily dermal innervation (Fitzgerald, 1967; Reynolds et al., 1991). In every case where anti-NGF treatment reduced the proportion of HTMRs, there was a reciprocal increase in the proportion of sensitive A delta hair follicle (D-hair) afferents. We hypothesize that in the absence of NGF, developing cutaneous A delta HTMRs do not die but innervate novel targets in the dermis and become D-hair afferents instead.
Prostaglandin E2 increases calcium conductance and stimulates release of substance P in avian sensory neurons
Authors: Nicol GD , Klingberg DK , Vasko MR
Published: March 2018

Prostaglandins are known to lower activation threshold to thermal, mechanical, and chemical stimulation in small-diameter sensory neurons. Although the mechanism of prostaglandin action is unknown, agents known to elevate intracellular calcium produce a sensitization that is similar to that produced by prostaglandins. Consistent with the idea of prostaglandin-induced elevations in calcium, prostaglandins might also stimulate the release of neurotransmitter from sensory neurons. We therefore examined whether prostaglandin E2 (PGE2) could enhance the release of the putative sensory transmitter substance P (SP) from isolated neurons of the avian dorsal root ganglion grown in culture. Utilizing the whole-cell patch-clamp recording technique, we also examined whether PGE2 could alter calcium currents in these cells. Exposure of sensory neurons to PGE2 produced a dose-dependent increase in the release of SP. One micromolar PGE2 increased release approximately twofold above basal release, whereas 5 and 10 microM PGE2 increased release by about fourfold. The release evoked by these higher concentrations of PGE2 was similar in magnitude to the release induced by 50 mM KCl. Neither arachidonic acid (10 microM), prostaglandin F2 alpha (10 microM), nor the lipoxygenase product leukotriene B4 (1 microM) significantly altered SP release. The addition of 1 microM PGE2 increased the peak calcium currents by 1.8-fold and 1.4-fold for neurons held at potentials of -60 and -90 mV, respectively. The action of PGE2 was rapid with facilitation occurring within 2 min. As with release studies, arachidonic acid, prostaglandin F2 alpha, and leukotriene B4 had no significant effect on the amplitude of the calcium current. These results suggest that PGE2 can stimulate the release of SP through the activation or facilitation of an inward calcium current. The capacity of PGE2 to facilitate the calcium current in these sensory neurons may be one mechanism to account for the ability of prostaglandins to sensitize sensory neurons to physical or chemical stimuli.