Functional zones in the auditory cortex of the echolocating bat, Myotis lucifugus

Neurophysiological mapping experiments in the auditory cortex of the frequency-modulated bat, Myotis lucifugus, reveal 3 functional subregions: a tonotopic zone located dorsally, a delay-sensitive zone more ventrally, and an intermediate zone of major overlap. The unique finding of an overlapping cortical region representing both spectral and time-delay information of echoes is intriguing in view of a recent behavioral study suggesting the convergence of such echo cues in auditory perception. (Simmons et al., Soc. Neurosci. Abstr., 13 [1987] 870).     

A neuroanatomical study of the cochlea of the little brown bat (Myotis lucifugus)

The population and density of the bipolar ganglion cells and sensory hair cells were determined from serial sections and graphic reconstructions of the cochlea and spiral ganglion of four little brown bats. The spiral ganglion lacks a bony canal and is a one and one-half turn spiral of almost uniform thickness which ends in a broad flat nodule at its apex. The average length of the nerve cell body is 7.4 μ (range: 5–15 μ) and it is 6.4 μ wide (5–10 μ). The average number of ganglion cells enumerated was 63.2 × 10³ (range: 60.6 × 10³–65.2 × 10³) and following correction for “split cell error,” the total number was 55.3 × 10³ ganglion cells. The ganglion cell density curve increases gradually to a maximum value of 11.7 × 10³ cells/mm² at 2.4–3.2 mm from the basal end. The two and one-half turn cochlea is 6.9 mm long (6.8–7.1 mm) with an estimated total of 700 inner and 2,800 outer sensory hair cells. The densities of outer and inner hair cells increase from the base to the apex by 21% and 32%, respectively. However, the density of sensory cells per unit of sensory epithelium decreases from base to apex. The ratio increases to a maximum value of 22:1 at 2.4 mm and then declines toward the apex. The significance of these findings is discussed and compared to similar studies on other high-frequency hearing mammals.     

Stimulation rate influences frequency tuning characteristics of inferior colliculus neurons in the little brown bat, Myotis lucifugus.

Previous studies of frequency selectivity have investigated unit's responses to tonal stimuli widely separated in time to minimize inter-stimulus interaction. The results of such studies are assumed to accurately portray the cell's frequency selectivity. The goal of the present study was to investigate the frequency tuning characteristics of neurons in the inferior colliculus (IC) of the little brown bat (Myotis lucifugus) to tone pulses presented at higher rates. Our results indicate that the frequency response properties of central auditory neurons at low stimulation rates do not necessarily reflect the units' frequency response properties to sounds presented at higher, more behaviorally relevant rates. Specifically, IC neurons often show greater frequency selectivity at higher stimulation rates, which presumably confers a greater perceptual frequency resolution.     

Cholecystokinin (CCK)-like immunoreactivity in the brain of the little brown bat (Myotis lucifugus)

The distribution of Cholecystokinin (CCK-8)-like immunoreactivity was mapped in the brain of the little brown bat, Myotis lucifugus, at three different and discrete levels of physiological activity: euthermic, hypothermic, and hibernating. Immunoreactive perikarya were present in the cerebral cortex, hippocampal formation, several nuclei of the olfactory and limbic systems, the ventral lateral geniculate nucleus, suprachiasmatic nucleus, medial geniculate nucleus, and caudate-putamen. Immunoreactive fibers were present in plexuses throughout the brain and in three major projection pathways: the medial forebrain bundle, the mammillary peduncle, and dorsal longitudinal fasciculus. Our data suggest two possible loci for CCK regulation of feeding behavior: a hypothalamic locus in the dorsomedial nucleus and a brainstem locus in the nucleus tractus solitarius.     

Neuromorphometric features and dimensional analysis of the vestibular end organ in the little brown bat (Myotis lucifugus)

Neuromorphometric parameters of the vestibular system were determined from serial sections of temporal bones from four little brown bats. Well-developed eminentiae cruciatae project from the cristae ampullares of the anterior and posterior membranous ampullae. A total of 4,500 bipolar ganglion cells were enumerated within the vestibular ganglion. The widths of the cell somas varied from 2.5 to 20 micrometers, with 70% of them having widths between 5.0 and 12.5 micrometers. Two maxima were observed in a curve of ganglion cell density as a function of the length of the ganglion. The first maximum indicated a density of 4,800 cells per mm2 at a length 0.20 from the apex of the ganglion (in the pars dorsalis); the second, a density of 4,750 cells per mm2 at 0.38 mm (in the pars ventralis). The morphometric parameters studied were the radii of curvature of the semicircular ducts, the cross-sectional diameters of the semicircular canals and ducts, the dimensions of the cristae ampullares and their membranous ampullae, and dimensions pertaining to the statoconial organs. Surface areas (measured from graphic projections) were determined as 0.098 mm2 and 0.016 mm2 and hair cell count 500 and 1,300 cells for the saccular and utricular maculae, respectively. The radii of curvature of the three semicircular ducts, R, were dissimilar, with the anterior duct having the largest radius (R = 0.91 mm) and the posterior duct the smallest one (R = 0.69 mm). The average cross-sectional diameters of the anterior, lateral, and posterior ducts were measured as 0.11 mm, 0.14 mm, and 0.13 mm, respectively. Some of the morphological parameters were used to ascertain information regarding the dynamics of semicircular--canal function. In particular, the coefficients theta and II in the torsion pendulum model (Steinhausen, '31; Egmond et al., '49), and the time constants xi L congruent to II/delta and xi S congruent to theta/II of the torsion pendulum model were estimated for the little brown bat from these parameters. Where appropriate, comparisons were made to time constants obtained for other species.     

Characterization of 11 tetranucleotide microsatellite loci for the little brown bat (Myotis lucifugus) based on in silico genome sequences

Using an in silico approach, we identified tetranucleotide microsatellite loci from an existing whole genome shotgun DNA sequence of the little brown bat (Myotis lucifugus). Eleven loci were polymorphic, and exhibited a range from 4 to 25 alleles per locus (mean?=?11). Observed heterozygosities ranged from 46 to 94%. Primers for the 11 loci were also tested for cross-species amplification in Myotis septentrionalis. These microsatellites will be useful for genetics-based studies of M. lucifugus, which are of increasing importance due to their conservation concern regarding the spread of white-nose syndrome.     

Neuropeptide Y-like immunoreactivity in the diencephalon of the little brown bat (Myotis lucifugus): localized variations with physiological state.

The current study used light microscopic immunocytochemistry to demonstrate and compare neuropeptide Y-like immunoreactivity (NPY-IR) in the diencephalon of the little brown bat (Myotis lucifugus) at different stages in its annual cycle of activity and hibernation. Animals were sacrificed in each of three discrete physiological states: euthermic, hypothermic, and hibernating. In general, NPY-IR was abundant in the hypothalamus and sparse in other diencephalic areas. Immunoreactivity was present in a number of pathways which project to or originate from diencephalic nuclei; these include the ansa peduncularis, medial forebrain bundle, inferior thalamic peduncle, stria terminalis, stria medullaris, mammillary peduncle, and dorsal longitudinal fasiculus. Dense fiber plexuses were present throughout the hypothalamus; however, NPY-IR was conspicuously absent from the suprachiasmatic nucleus. Immunoreactive perikarya were located in the supraoptic, dorsomedial, ventromedial, and arcuate nuclei, in the external division of the ventral lateral geniculate nucleus, and in the pineal gland. Localized changes in density and/or distribution of NPY-IR were correlated with changes in physiological state.     

Cerebral cortical concentrations of bioamines and their metabolites during arousal and after feeding in the little brown bat (Myotis lucifugus)

The concentrations of bioamines and their metabolites have been determined in March and April during arousal from hibernation in the cerebral cortex of the little brown bat (Myotis lucifugus). The patterns during arousal for dopamine and serotonin (5-HT) were similar with a significant fall in concentrations by 1 h of arousal, and an inverse relationship with their respective metabolites, 3,4-dihydroxyphenylacetic acid and 5-hydroxyindolacetic acid (5-HIAA). This suggests an acute release and metabolism of these bioamines with onset of arousal. During arousal, cerebral cortical concentrations of norepinephrine (NE) were not significantly changed. Levels of homovanillic acid were markedly depressed during hibernation and rose acutely with arousal. After arousal and 4 days of feeding in April, there was an increase in all bioamines and their metabolites studied except for NE. Of note is the marked decrease in the hibernating level of 5-HT and increase in its metabolite 5-HIAA from March to April, which may herald the natural termination of hibernation. Our results suggest that the brain of hibernators undergoes complex changes in the modulation of neurotransmitter systems which are consistent with both down- and up-regulation of neuronal activity in the maintenance of hibernation and the initiation of the arousal process.     

Ultrastructural development of raphe nuclei in the bat (Myotis myotis)

The development and ultrastructural features of the raphe nuclei of Microchiroptera Myotis myotis have been studied. Fetuses of different ages, newborn, young and adult bats were examined. Important fetal features were abundant mitoses and an incomplete cytokinesis between daughter cells. A medialward migration of reticular formation neurons was observed. The migration began in the third week of intrauterine life and continued through the sixth week of intrauterine life. In six-week-old fetuses it was possible to distinguish neuronal groups, although the delineation of borders for specific raphe nuclei was still arbitrary. Two types of neurons were distinguished at this stage and at all later stages, and both were present at all levels of the raphe complex. In the nine-week-old fetus the eight raphe nuclei were well-delineated. Newborn bats showed a great increase in cytoplasmic organelles and, also, in the myelination of neuronal fibers. No essential differences between young and adult bats were found.     

不同的频率调谐与递质特异性神经元在鼠耳蝠听觉脑干的空间分布

分别用频率为２０,６０kHz,强度为５９－６３或７１－７３dB SPL(Sound pressure level)的纯音（时程４ms,升降时间各0.5ms,重复速率２pulses/s)对9只鼠耳蝠双耳或单耳进行暴露。采用Ｆos免疫组化重标记技术,考察了Ｆos、Fos／谷氨酸（Ｇlu)和Ｆos/γ－氮基丁酸（ＧＡＢＡ）阳性神经元的空间分布。结果表明,在其脑干听核团中,耳蜗核,斜方体核,上橄榄核,外侧丘系核以及下丘分别有不同数量的Ｆos、Fos/Glu或Fos/GABA阳性神经元分布。两和睦 怕频率暴露条件下Ｆos、Fos/Glu和Fos/GABA都具有特定的空间分布模式,从一个侧面证实脑干频率－幅度轴的存在,并提示Ｇlu能和ＧＡＢＡ能神经元在脑干不同层次对听觉信息加工,特别是对频率编码的作用既表现在参与的神经细胞数量上,也表现在参与神经元的空间分布模式上。     

Novel microsatellite loci to investigate population structure in the endangered gray bat (Myotis grisescens)

We isolated and characterized 16 polymorphic microsatellite loci in the endangered gray bat (Myotis grisescens). This set of loci will be used to investigate patterns of genetic structure in hibernacula and maternity colonies of the gray bat across their range, ultimately combining multiple lines of evidence (mtDNA data, stable isotope signatures, etc.) to develop a spatial network for the species.     

Seasonal changes in methionine-enkephalin immunoreactivity in the brain of a hibernator, Spermophilus columbianus

To identify the actual location of central endogenous opioid systems which may be involved in regulating the hibernation cycle, differences in the pattern of central methionine-enkephalin (Met-EK) immunoreactivity were compared between hibernating (body temperature, Tb = 7 degrees C) and non-hibernating (Tb = 37 degrees C) Columbian ground squirrels using the peroxidase-antiperoxidase technique. In non-hibernating animals, Met-EK-immunoreactive perikarya were observed in telencephalic (putamen, caudate nucleus, medial septum-diagonal band complex, amygdala) and diencephalic (periventricular hypothalamic nucleus, lateral hypothalamic area) regions, whereas immunoreactive fibers were found in the lateral septum, stria terminalis nucleus, various hypothalamic areas, arcuate nucleus, median eminence, thalamic intralaminar, periventricular nucleus and lateral habenular nucleus. Compared to the non-hibernating animal, a marked increase in the number of Met-EK-immunoreactive fibers was found in the lateral septal nucleus, the periventricular nucleus, the intralaminar thalamus and the paraventricular hypothalamus of hibernating ground squirrels. Since these changes in immunoreactivity were not observed in the artificially induced hypothermic ground squirrels (Tb = 7 degrees C), it is unlikely that the dissimilarity in immunoreactivity between animals from different hibernating phases is due to differences in their Tb. In combination with our previous studies, these results tend to suggest that hibernation may be brought about by an increase in endogenous opioid activity, especially in the lateral septal region.     

Adrenergic innervation of vasa and nervi nervorum of optic, sciatic, vagus and sympathetic nerve trunks in normal and streptozotocin-diabetic rats

Adrenergic nerves were studied in nervi nervorum and perivascular nerve plexus of vasa nervorum in whole-mount nerve sheath preparations of optic, sciatic and vagus nerves and in the paravertebral sympathetic chain in normal and streptozotocin-treated diabetic rats. A substantial or complete loss of fluorescent adrenergic fibres around blood vessels in the optic nerves was observed 8 weeks after induction of diabetes. This was in marked contrast to the increase in perivascular adrenergic fibres in the sciatic, vagus and sympathetic chain nerve trunks of the same animals at the same time. Assays of noradrenaline levels in whole nerve segments also showed that they were not biochemically detectable in the optic nerves but were significantly higher in the vagus of diabetic animals (P less than 0.05). There was also an increase in numbers of mast cells in the vicinity of vasa nervorum of diabetic nerves.     

Characterization of small microsatellite loci isolated in endangered Indiana bat (Myotis sodalis) for use in non-invasive sampling

Primers for 10 microsatellite loci were developed specifically to amplify low quantity and quality DNA in the endangered Indiana Bat (Myotis sodalis). In a screen of 20 individuals from a population in Missouri, the 10 loci were found to have levels of variability ranging from seven to 18 alleles. No loci were found to be linked, although two loci revealed significant departures from Hardy–Weinberg equilibrium. These microsatellite loci will be applicable for population genetic analyses and for use in mark-recapture studies that utilize DNA collected non-invasively from fecal pellets, which will ultimately aid in management efforts.     

The B cell,arthritis, and the sympathetic nervous system

The pathogenesis of rheumatoid arthritis (RA) is still an unresolved puzzle. Many factors and inflammatory cells play together to initiate a chronic inflammatory process that, if untreated, leads to complete destruction of involved joints. Recent success in treating severe forms of RA with B cell-depleting or -modifying agents revived the concept that the B cell might play a pivotal role in the pathogenesis of some forms of arthritis. However, the rather unspecific treatment approach affecting all B cells, no matter if autoreactive or not, leads to potential harmful side-effects, e.g., severe infections. Therefore, finding regulatory systems that more specifically modulate B cell function is important to improve current treatment options. One such regulatory system is the sympathetic nervous system (SNS), which is known to modulate B cell function, but also profoundly influences arthritis development and severity. This review develops the hypothesis that the SNS via modulating B cell function influences arthritis development and progression. For this purpose data is presented that shows (1) how the SNS influences B cell function, (2) how the SNS influences arthritis development and severity, and (3) how B cells are involved in the disease process with an emphasis on possible contact points for SNS neuromodulation.     

The absence of nodal sprouts from partially denervated nerve trunks

Nodal sprouts were absent from partially denervated, silver-stained, mouse superior gluteal (SG) nerves examined between 4 and 20 days after partial denervation. Nodal sprouts were also absent from electron micrographs of partially denervated SG nerves. We conclude that an earlier report describing profuse nodal sprouting in partially denervated nerve trunks mistakenly identified fine Schwann cell processes as nodal sprouts.