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At least 1,603 records · Page 89Linked to original sources
PubMed1999

corticofugal regulation of excitatory and inhibitory frequency tuning curves of bat inferior collicular neurons.

Corticofugal regulation of excitatory and inhibitory frequency tuning curves (FTCs) of neurons in the central nucleus of bat inferior colliculus (ICc) was studied by electrical stimulation of the primary auditory cortex (AC stimulation) under free field stimulation conditions using a two-tone inhibition paradigm. AC stimulation narrowed the excitatory FTCs and asymmetrically expanded the lateral inhibitory FTCs of corticofugally inhibited ICc neurons. The opposite results were observed for excitatory and inhibitory FTCs of corticofugally facilitated ICc neurons. These data support previous reports that corticofugal systems work together with widespread lateral inhibition to regulate subcortical frequency processing.

Acoustic Stimulation↗
PubMedDate not supplied

The interhaemal barrier in the chorioallantoic placenta of the greater mustache bat, Pteronotus parnellii, with observations on amplification of its intrasyncytial lamina.

Chorioallantoic placentae were obtained from a reproductively synchronized wild population of greater mustache bats for ultrastructural and immunocytochemical examination. The single discoidal placenta was always located in a lateral to mesometrial position on the right side of the uterus, which in the non-pregnant state is partially bicornuate. The placenta was labyrinthine and haemodichorial in advanced pregnancy. The interhaemal barrier included syncytiotrophoblast that lined the maternal vascular spaces and an underlying, continuous layer of cytotrophoblast. The barrier also contained a discontinuous extracellular layer, the intrasyncytial lamina, that was usually completely surrounded by syncytiotrophoblast. Two lines of evidence suggest that the intrasyncytial lamina may serve, in part, to strengthen the interhaemal barrier: (1) the lamina became significantly thicker as the maternal vascular channels became larger; and (2) the syncytiotrophoblast in the walls of the smallest vascular tubules expressed only very limited amounts of cytokeratins, normally a major component of the cytoskeleton of cells of epithelial origin, while the cytokeratin-rich cytotrophoblast was often highly attenuated. It was not uncommon to see gaps between the ectoplasmic processes of syncytiotrophoblast which exposed portions of the intrasyncytial lamina to the maternal vascular space. As platelet adhesion was never observed in such areas, the intrasyncytial lamina may be augmented in part by material that is non-thrombogenic.

Allantois↗
PubMed2000

Molecular methods to distinguish between classical rabies and the rabies-related European bat lyssaviruses.

A rapid and sensitive reverse transcriptase-polymerase chain reaction (RT-PCR) assay for the detection of classical rabies virus (genotype 1) and the rabies related European bat lyssaviruses (EBLs) (genotypes 5 and 6) was developed. When combined with specific oligonucleotide probes and a PCR-enzyme linked immunosorbent assay (PCR-ELISA), genotype 5 and 6 viruses can be distinguished from each other and from genotype 1 viruses. Ninety-two isolates from the six established genotypes of rabies and rabies-related viruses were screened by RT-PCR and PCR-ELISA to determine the specificity of the assays. All genotype 1, 5 and 6 viruses were detected by RT-PCR while none of the genotype 2, 3 and 4 viruses were detected. All the genotype 5 and 6 viruses were detected by the two PCR-ELISA probes when used in combination while none of the genotype 1-4 viruses were detected. When used individually, the PCR-ELISA probes also distinguished between the genotype 5 and 6 viruses. This new discriminatory test should allow the rapid genotyping of all lyssaviruses likely to be encountered in Europe and as such could provide useful epidemiological information in the event of an outbreak.

Animals↗
PubMed1998

Reduced BAT function as a mechanism for obesity in the hypophagic, neuropeptide Y deficient monosodium glutamate-treated rat.

Neuropeptide Y (NPY) exerts effects on food intake at the level of the paraventricular nucleus (PVN), which receives a dense projection from the arcuate nucleus. Monosodium glutamate (MSG) has been shown to induce hyperadiposity despite hypophagia associated with chemical ablation of the arcuate nucleus. We investigated the mechanism for the excess fat accumulation by studying the time course of changes in brain NPY content, food intake, leptin levels and BAT GLUT4 content after neonatal MSG treatment. Male rat pups were injected with MSG or saline vehicle on days 2, 4, and 6 and examined at 30 and 90 days. Plasma leptin, body mass, length, adipose tissue mass and brown fat GLUT4 were measured and brains dissected for measurement of NPY content. By 30 days, NPY concentrations were reduced in the arcuate nucleus and anterior hypothalamus, and animals tended to be hypophagic. Peripheral adipose tissue levels were less than controls, in line with their low leptin concentrations. At 90 days, MSG treatment was associated with marked reductions in NPY concentrations in several hypothalamic areas, including the PVN and arcuate nucleus, along with increased adiposity and plasma leptin. Animals also displayed marked hypophagia. Levels of GLUT4 transporter were reduced in brown adipose tissue at both ages. The early decrease in brown fat GLUT4 suggests an impairment of the hypothalamic sympathetic input to brown fat which disrupts thermogenesis, contributing to the development of adiposity in the presence of hypophagia.

Adipose Tissue, Brown↗
PubMed2003

Bat lyssaviruses (Aravan and Khujand) from Central Asia: phylogenetic relationships according to N, P and G gene sequences.

Bat lyssaviruses Aravan and Khujand were isolated in southern Kyrgyzstan in 1991 and in northern Tajikistan in 2001, respectively. Preliminary studies with anti-nucleocapsid monoclonal antibodies suggested that the viruses were distinct from other lyssavirus serotypes. These data were supported by sequencing of the N gene of Aravan virus. In the present study, we sequenced the entire N, P and G genes of both Aravan and Khujand viruses and compared them with respective sequences of other lyssaviruses available from GenBank. The results suggested that each virus should be considered as a newly recognized genotype according to the current approaches for genotype definition (amount of nucleotide identity of the N gene and bootstrap support of joining to certain phylogenetic groups). Use of different phylogenetic methods and comparison of different parts of the genomes generally suggested that Khujand virus was mainly related to genotype 6, while Aravan virus, on the one hand, was related to Khujand virus, and, on the other hand, demonstrated moderate similarity to genotypes 4, 5 and 6. The potential significance of these new lyssaviruses for veterinary and public health should not be underestimated.

Amino Acid Sequence↗
PubMed1998

Human diploid cell culture rabies vaccine (HDCV) and purified chick embryo cell culture rabies vaccine (PCECV) both confer protective immunity against infection with the silver-haired bat rabies virus strain (SHBRV).

The demonstration of extensive differences in the antigenic makeups of the silver-haired bat rabies virus (SHBRV) and canine rabies virus (COSRV) strains raised concerns as to whether current licensed rabies vaccines are sufficiently protective against SHBRV. NIH mouse protection test results show that both the human diploid cell culture rabies vaccine (HDCV) and the purified chicken embryo cell rabies vaccine (PCECV) protected against lethal infection with SHBRV as well as the canine rabies strain COSRV. However, in this investigation, the potencies of both vaccines in mice were found to be significantly higher for COSRV than for SHBRV. The in vivo protection data are confirmed by in vitro virus neutralizing antibody (VNA) test results which demonstrate that mice immunized with HDCV or PCECV develop significantly higher VNA titres against COSRV than against SHBRV. In contrast, VNA tests of sera from individuals immunized with HDCV or PCECV showed that humans, as opposed to mice, develop significantly higher VNA titres against SHBRV than against COSRV. These data suggest that HDCV and PCECV will protect humans against infection with the silver-haired but rabies virus strain in addition to canine rabies virus strains.

Animals↗
PubMed2001

Multiple combination-sensitive neurons in the auditory cortex of the mustached bat.

The mustached bat, Pteronotus parnellii, emits biosonar pulses consisting of four constant-frequency (CF(1-4)) and four frequency-modulated (FM(1-4)) components. The FM-FM area of its auditory cortex consists of three subdivisions, containing either FM(1)-FM(2), FM(1)-FM(3) or FM(1)-FM(4) combination-sensitive neurons. The FM-FM area also contains 'multiple combination-sensitive' neurons: FM(1)-FM(2,3), FM(1)-FM(3,4), FM(1)-FM(2,4), and FM(1)-FM(2,3,4) neurons. All FM-FM neurons are tuned to a time delay (echo delay) of FM(n) (n=2-4) from FM(1). In the present study, we made the following four major findings. (1) Multiple combination-sensitive neurons show the strongest response to a combination of more than two signal elements. (2) Multiple combination-sensitive neurons are located in about 100 microm wide bands at the boundaries between two adjacent subdivisions of the FM-FM area. (3) Iso-best-delay contour lines across the three single combination-sensitive subdivisions are not interrupted by multiple combination-sensitive bands. (4) Each subdivision of the FM-FM area has frequency-vs.-frequency coordinates in terms of best FM(1) and best FM(n) frequencies for facilitation, although such coordinates were not obtained with single tone bursts.

Acoustic Stimulation↗
PubMed2000

IPPC, BAT, and voluntary agreements.

It is argued that the current discussion on Best Available Techniques (BAT) may not foster true sustainable production. Other instruments from the Integrated Pollution Prevention and Control (IPPC) Directive, such as reporting, may be more effective in this respect. The Irish Integrated Pollution Control (IPC) system has operated for more than 5 years. Its emphasis is on prevention, environmental management systems (EMS), and reporting. Initial results are encouraging. In this paper, the system is used as a case study to illustrate the potential power of the Directive.EMS, if solely voluntary, may be less than effective. It is thus argued that the regulator can become involved in the process - so that EMS can be 'guided'.

Environmental Pollution↗
PubMed2003

The Australian paralysis tick may be the missing link in the transmission of Hendra virus from bats to horses to humans.

Hendra virus is a new virus of the family Paramyxoviridae. This virus was first detected in Queensland, Australia, in 1994; although, it seems that the virus has infected fruit-eating bats (flying-foxes) for a very long time. At least 2 humans and 15 horses have been killed by this virus since it first emerged as a virus that may infect mammals other than flying-foxes. Hendra virus is thought to have moved from flying-foxes to horses, and then from horses to people. There is a reasonably strong hypothesis for horse-to-human transmission: transmission of virus via nasal discharge, saliva and/or urine. In contrast, there is no strong hypothesis for flying-fox-to-human transmission. I present evidence that the Australian paralysis tick, Ixodes holocyclus, which has apparently only recently become a parasite of flying-foxes, may transmit Hendra virus and perhaps related viruses from flying-foxes to horses and other mammals.

Animals↗
PubMed2000

Bicuculline application affects discharge patterns, rate-intensity functions, and frequency tuning characteristics of bat auditory cortical neurons.

This study examined the effect of bicuculline application on the auditory response properties in the auditory cortex of the big brown bat, Eptesicus fuscus. All auditory cortical neurons studied discharged either 1-2 or 3-7 impulses to 4 ms sound stimuli. Cortical neurons with high best frequencies tended to have high minimum thresholds. Bicuculline application increased the number of impulses and shortened the response latencies of all cortical neurons as well as changing the discharge patterns of half of the cortical neurons studied. Bicuculline application raised the rate-intensity functions but lowered the latency-intensity functions to varying degrees. Threshold-frequency tuning curves (FTCs) were either V-shaped, upper threshold or double-peaked. Threshold-FTCs and impulse-FTCs were mirror-images of each other. Bicuculline application expanded and raised the impulse-FTCs but lowered the threshold-FTCs, resulting in significantly decreased Q(n) values. Threshold-FTCs of cortical neurons determined within an orthogonally inserted electrode were very similar and expanded FTCs during bicuculline application were also very similar. Possible mechanisms for the contribution of GABAergic inhibition to shaping these response properties of cortical neurons are discussed.

Acoustic Stimulation↗
PubMed2001

Cellular and subcellular distribution of AMPA-type glutamate receptor subunits and metabotropic glutamate receptor 1alpha in the cochlear nucleus of the horseshoe bat (Rhinolophus rouxi).

Ionotropic alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) selective glutamate receptors (GluRs) are the main mediators of fast excitatory neurotransmission and composed of a variable combination of four different subunits (GluR1-4). The metabotropic glutamate receptor 1alpha (mGluR1alpha) is involved in plastic synaptic events. Since horseshoe bats strongly depend on temporal cues for acoustic imaging by echolocation and exhibit prominent species specific specializations of the cochlear nucleus (CN), the subunit distribution of AMPA selective GluRs and the distribution of mGluR1alpha was studied at the light and electron microscopic level with preembedding immunocytochemistry. Immunoreactivity to GluR1 was low throughout the CN. All types of projection neurons of the ventral CN expressed distinct GluR2/3 and GluR4 immunoreactivity with GluR4-labeling especially prominent in multipolar and octopus cell-like neurons of the posteroventral CN. The AMPA and metabotropic receptor inventory of the laminated ventral subdivision of the dorsal CN (DCNv) agreed with that reported in other mammals, whereas the specialized dorsal non-laminated subdivision of DCN (DCNd) lacked the prominent labeling for GluR2/3 and mGluR1alpha that characterizes cartwheel cells of DCNv. Distinct GluR2/3 and GluR4 immunoreactivity combined with low expression of mGluR1alpha immunoreactivity was characteristic for fusiform cells of DCNv and DCNd. Tuberculoventral cells of both the deep DCNv and the DCNd exhibited light to moderate GluR2/3 and GluR4 immunoreactivity. The staining patterns in DCNd thus indicate a loss of cerebellar-like microcircuits and a conservation of frequency specific circuitry of the deep and fusiform cell layers of the mammalian DCN.

Animals↗
PubMed2002

The effect of two-tone stimulation on responses of two simultaneously recorded neurons in the inferior colliculus of the big brown bat, Eptesicus fuscus.

This study examined auditory responses of two simultaneously recorded neurons in the central nucleus of bat inferior colliculus (IC) under two-tone stimulation conditions. We specifically examined how a sound within the excitatory frequency tuning curve (FTC) of one IC neuron might affect responses of the other IC neuron in amplitude and frequency domains. Under this specific two-tone stimulation condition, responses of 82% neurons were suppressed and their excitatory FTCs sharpened. Responses of the other 18% neurons were facilitated and their excitatory FTCs broadened. Two-tone suppression was greater at low than at high stimulus amplitudes. Two-tone suppression also decreased with increasing recording depth and best frequency (BF) difference between each pair of neurons. The suppressive or facilitatory FTC of a neuron plotted under two-tone stimulation conditions was always within the excitatory FTC of the other neuron. Two-tone suppression or two-tone facilitation was weak near the BF but became increasingly strong with frequencies away from the BF. Biological significance of these findings is discussed.

Acoustic Stimulation↗
PubMed2002

Interaction between excitation and inhibition affects frequency tuning curve, response size and latency of neurons in the auditory cortex of the big brown bat, Eptesicus fuscus.

Neurons in the auditory cortex (AC) receive convergent excitatory and inhibitory inputs from the lower auditory nuclei. Interaction between these two opposing inputs shapes different response properties of AC neurons. In this study, we examined how this interaction might affect the frequency tuning curves (FTCs), number of impulses and latency of AC neurons in the big brown bat, Eptesicus fuscus, using a probe (excitatory tone) and a masker (inhibitory tone) under different stimulation conditions. Excitatory FTCs of AC neurons were either V-shaped, closed (i.e. upper threshold) or double-peaked. Inhibitory FTCs were obtained either at both flanks or only at the low or high flank of excitatory FTCs. Application of bicuculline, an antagonist for gamma-aminobutyric acid A receptors, produced expansion of excitatory FTCs into predrug inhibitory FTCs. Inhibition of probe-elicited responses occurred when a masker was presented at certain intertone intervals. Maximal inhibition typically took place when a masker was presented within 4 ms prior to the probe. During maximal inhibition, a neuron had the minimal number of impulses and the longest response latency. Inhibition became stronger with increasing masker intensity but became weaker with increasing intertone interval. Biological significance of these data is discussed.

Acoustic Stimulation↗
PubMed2003

Binaural interaction in the inferior colliculus of the big brown bat, Eptesicus fuscus.

Binaural interaction plays an important role in shaping response properties of central auditory neurons. Using single unit recording and iontophoresis, we examined frequency tuning curves (FTCs), interaural intensity difference (IID) curves, and rate-intensity functions of inferior collicular (IC) neurons of the big brown bat, Eptesicus fuscus, under closed system or free field stimulation conditions. We isolated 46 EI (excitation-inhibition), 24 EO (monaural excitation) and 6 EE (excitation-excitation) neurons. Inhibitory FTCs of EI neurons plotted under ipsilateral sound stimulation fell within (n=10, 22%), partly overlapped (n=26, 56%), or almost entirely encompassed (n=10, 22%) excitatory FTCs plotted by contralateral sound stimulation. The discharge rate of EI neurons was a sigmoid function of IID. The peak discharge rate occurred at IIDs at which contralateral sound stimulation was stronger than ipsilateral sound stimulation. Application of bicuculline, an antagonist for gamma-aminobutyric acid A receptors, raised the IID curves and broadened the excitatory FTCs but partly or completely abolished the ipsilateral inhibitory FTCs. For EE neurons, excitatory FTCs and rate-intensity functions plotted by contralateral sound stimulation were always broader and higher than those plotted by ipsilateral sound stimulation. The sharpness of FTCs of EI neurons was significantly greater at ipsilateral 30 degrees than at 30 degrees contralateral. This direction-dependent frequency tuning was effectively abolished by occlusion of the ipsilateral ear. Possible mechanisms underlying these observations are discussed.

Acoustic Stimulation↗
PubMed2003

Spectral directionality of the external ear of the lesser spear-nosed bat, Phyllostomus discolor.

The directional dependence of sound pressure transformation of head and pinna has been measured in the phyllostomid bat Phyllostomus discolor for the frontal hemisphere using a maximum length sequence method. The azimuthal position of the axis of highest pinna gain came closer to the midsagital plane with increasing frequency. The acoustic axis of highest pinna gain was further characterized by an increase of the elevation angle with increasing frequency and a specific decrease at 55 kHz. Additionally, a spectral notch separated two regions of high and low frequency hearing at specific elevation and frequency combinations. The special influence of the tragus on the position of the pinna gain axis and the spectral notches is demonstrated. The functional implications of the spectral notch for hearing in P. discolor are discussed.

Animals↗
PubMed2003

Corticofugal modulation of amplitude domain processing in the midbrain of the big brown bat, Eptesicus fuscus.

Recent studies have shown that the corticofugal system systematically modulates and improves subcortical signal processing in the frequency, time and spatial domains. The present study examined corticofugal modulation of amplitude sensitivity of 113 corticofugally inhibited neurons in the central nucleus of the inferior colliculus (IC) of the big brown bat, Eptesicus fuscus. Cortical electrical stimulation decreased the number of impulses and increased the response latency of these neurons. They had an average of 5.9+/-4.4 kHz best frequency (BF) differences between collicular and electrically stimulated cortical neurons. Cortical electrical stimulation synchronized with sound stimulation for 30 min compressed the rate-amplitude functions of half (56, 49.6%) of these collicular neurons and shifted their minimum thresholds (MT) and dynamic ranges (DR) toward that of electrically stimulated cortical neurons for as long as 40 min. These collicular neurons had an average of 1.6+/-1.4 kHz BF differences. The shift in collicular MT and DR significantly increased with differences in MT and DR between collicular and cortical neurons. Cortical electrical stimulation also shifted the BF and best amplitude (BA) of collicular neurons toward that of cortical neurons. The BF shift increased with BF differences and the BA shift increased with BA differences. These data suggest that the corticofugal system modulates collicular responses on the basis of topographic projections between the IC and auditory cortex. However, corticofugal modulation of collicular amplitude sensitivity is primarily dependent upon the difference but not the absolute amplitude sensitivity between collicular and cortical neurons.

Acoustic Stimulation↗
PubMed2003

Spectral directionality of the external ear of the lesser spear-nosed bat, Phyllostomus discolor.

The directional dependence of sound pressure transformation of head and pinna has been measured in the phyllostomid bat Phyllostomus discolor for the frontal hemisphere using a maximum length sequence method. The azimuthal position of the axis of highest pinna gain came closer to the midsagital plane with increasing frequency. The acoustic axis of highest pinna gain was further characterized by an increase of the elevation angle with increasing frequency and a specific decrease at 55 kHz. Additionally, a spectral notch separated two regions of high and low frequency hearing at specific elevation and frequency combinations. The special influence of the tragus on the position of the pinna gain axis and the spectral notches is demonstrated. The functional implications of the spectral notch for hearing in P. discolor are discussed.

Animals↗
PubMed1997

NMDA-mediated facilitation in the echo-delay tuned areas of the auditory cortex of the mustached bat.

We recorded the responses of single delay-tuned neurons in the dorsal fringe (DF) area and the FM-FM area of the auditory cortex of the mustached bat using multi-barreled carbon-fiber electrodes. An iontophoretic application of N-methyl-D-aspartate (NMDA) or kainate (KA) to a DF neuron evoked a burst of discharges from the neuron. The burst of discharges evoked by NMDA was always smaller than that evoked by KA. Simultaneous application of D-2-Amino-5-phosphonovalerate (APV) with NMDA and KA abolished the NMDA-evoked but not the KA-evoked discharges. APV did not evoke any significant changes in the auditory responses of 43 out of the 47 delay-tuned neurons studied in the DF area, and in all 20 neurons studied in the FM-FM area. In the remaining four DF neurons, however, APV either increased the initial discharges of their auditory response or decreased the late discharges of their response. These results indicate that in the majority of neurons in the DF and FM-FM areas NMDA receptors do not play a significant role in the processing of target-distance information, and that their facilitative auditory responses are basically created by synaptic interactions occurring in the subcortical auditory nuclei.

2-Amino-5-phosphonovalerate↗