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At least 1,189 records · Page 66Linked to original sources
PubMed1991

Methylmalonic acid metabolism and nervous-system fatty acids in cobalamin-deficient fruit bats receiving supplements of methionine, valine and isoleucine.

Cobalamin neuropathy was produced in Cape fruit bats (Rousettus aegyptiacus) by a cobalamin-free diet combined with intermittent exposure to nitrous oxide, which inactivates cobalamin. Cobalamin-deficient bats had low hepatic methylmalonyl-CoA mutase holoenzyme activity, with elevated plasma and urinary methylmalonic acid levels. No significant changes could be demonstrated in the concentration of odd- or branched-chain fatty acids in the nervous system. Supplementation of the cobalamin-free diet with methionine, valine or isoleucine delayed the onset of neuropathy, despite persistence of methylmalonic acid accumulation. Supplementation with any of the three amino acids was associated with elevation of hepatic methionine concentration. The action of valine and isoleucine in delaying the onset of neuropathy can be explained by their methionine-sparing effect. These results emphasize the central role of methionine in the cobalamin neuropathy and do not support the hypothesis that the neuropathy is related to an effect of cobalamin deficiency on the propionic acid pathway.

Amino Acids↗
PubMed2001

Motion processing in the auditory cortex of the rufous horseshoe bat: role of GABAergic inhibition.

This study examined the influence of inhibition on motion-direction-sensitive responses of neurons in the dorsal fields of auditory cortex of the rufous horseshoe bat. Responses to auditory apparent motion stimuli were recorded extracellularly from neurons while microiontophoretically applying gamma-aminobutyric acid (GABA) and the GABAA receptor antagonist bicuculline methiodide (BMI). Neurons could respond with a directional preference exhibiting stronger responses to one direction of motion or a shift of receptive field (RF) borders depending on direction of motion. BMI influenced the motion direction sensitivity of 53% of neurons. In 21% of neurons the motion-direction sensitivity was decreased by BMI by decreasing either directional preference or RF shift. In neurons with a directional preference, BMI increased the spike number for the preferred direction by a similar amount as for the nonpreferred direction. Thus, inhibition was not direction specific. BMI increased motion-direction sensitivity by either increasing directional preference or magnitude of RF shifts in 22% of neurons. Ten percent of neurons changed their response from a RF shift to a directional preference under BMI. In these neurons, the observed effects could often be better explained by adaptation of excitation rather than inhibition. The results suggest, that adaptation of excitation, as well as cortex specific GABAergic inhibition, contribute to motion-direction sensitivity in the auditory cortex of the rufous horseshoe bat.

Acoustic Stimulation↗
PubMed2001

Cortical representation of acoustic motion in the rufous horseshoe bat, Rhinolophus rouxi.

Responses of neurons to apparent auditory motion in the azimuth were recorded in three different fields of auditory cortex of the rufous horseshoe bat. Motion was simulated using successive stimuli with dynamically changing interaural intensity differences presented via earphones. Seventy-one percent of sampled neurons were motion-direction-sensitive. Two types of responses could be distinguished. Thirty-four percent of neurons showed a directional preference exhibiting stronger responses to one direction of motion. Fifty-seven percent of neurons responded with a shift of spatial receptive field position depending on direction of motion. Both effects could occur in the same neuron depending on the parameters of apparent motion. Most neurons with contralateral receptive fields exhibited directional preference only with motion entering the receptive field from the opposite direction. Receptive field shifts were opposite to the direction of motion. Specific combinations of spatiotemporal parameters determined the motion-direction-sensitive responses. Velocity was not encoded as a specific parameter. Temporal parameters of motion and azimuth position of the moving sound source were differentially encoded by neurons in different fields of auditory cortex. Neurons with a directional preference in the dorsal fields can encode motion with short interpulse intervals, whereas direction-preferring neurons in the primary field can best encode motion with medium interpulse intervals. Furthermore, neurons with a directional preference in the dorsal fields are specialized for encoding motion in the midfield of azimuth, whereas direction-preferring neurons in the primary field can encode motion in lateral positions. The results suggest that motion information is differentially processed in different fields of the auditory cortex of the rufous horseshoe bat.

Acoustic Stimulation↗
PubMed2000

A population genetic analysis of migration: the case of the noctule bat (Nyctalus noctula).

Although rarely assessed, the population genetics of hibernating colonies can help to understand some aspects of population structure, even when samples from nursery or mating colonies are not available, or in studies of migration when both types of samples are available and can be compared. Here we illustrate both points in a survey of mitochondrial DNA (mtDNA) control region sequences used to study the population genetics of hibernating colonies of a migrating species, the noctule bat (Nyctalus noctula). Lacking samples from Scandinavian nursery colonies, we use a North European hibernacula to suggest that Scandinavian populations are isolated from Central and East European colonies. Then, we compare genetic diversities of nursery and hibernating colonies. We find a significantly higher haplotype diversity in hibernacula, confirming that they consist of individuals from different nursery colonies. Finally, we show that pairwise comparisons of the haplotype frequencies of nursery and hibernating colonies contain some information on the migration direction of the noctule bat.

Animals↗
PubMed2000

Genetic variation and population structure in the endangered greater horseshoe bat Rhinolophus ferrumequinum.

Following a dramatic decline last century, the British population of the endangered greater horseshoe bat Rhinolophus ferrumequinum is highly fragmented. To examine the consequences of fragmentation and limited dispersal on patterns of genetic structure and variation, we used microsatellite markers to screen bats from around 50% of the known maternity colonies in Britain, and two areas from continental Europe. Analyses revealed that Welsh and English colonies were genetically isolated. This, and lower variability in Britain than north France, may result from either genetic drift, or the species' colonization history. Gene flow among most neighbouring colonies was not generally restricted, with one exception. These findings have important implications for the ongoing conservation management of this species.

Animals↗
PubMed2001

Mating patterns, relatedness and the basis of natal philopatry in the brown long-eared bat, Plecotus auritus.

The brown long-eared bat, Plecotus auritus, is unusual among temperate zone bats in that summer maternity colonies are composed of adult males and females, with both sexes displaying natal philopatry and long-term association with a colony. Here, we describe the use of microsatellite analysis to investigate colony relatedness and mating patterns, with the aim of identifying the evolutionary determinants of social organization in P. auritus. Mean colony relatedness was found to be low (R=0.033 +/- 0.002), with pairwise estimates of R within colonies ranging from -0.4 to 0.9. The proportion of young fathered by males in their own colony was investigated using a Bayesian approach, incorporating parameters detailing the number of untyped individuals. This analysis revealed that most offspring were fathered by males originating from a different colony to their own. In addition, we determined that the number of paternal half-sibs among cohorts of young was low, inferring little or no skew in male reproductive success. The results of this study suggest that kin selection cannot account for colony stability and natal philopatry in P. auritus, which may instead be explained by advantages accrued through the use of familiar and successful roost sites, and through long-term associations with conspecifics. Moreover, because the underlying causes of male natal dispersal in mammals, such as risk of inbreeding or competition for mates, appear to be avoided via extra-colony copulation and low male reproductive skew, both P. auritus males and females are able to benefit from long-term association with the natal colony.

Animals↗
PubMed2003

Genetic consequences of the ice ages on nurseries of the bat Myotis myotis: a mitochondrial and nuclear survey.

Analyses of mitochondrial DNA (mtDNA) control region polymorphism and of variation at 10 nuclear microsatellite loci were used to investigate the mechanisms and genetic consequences of postglacial expansion of Myotis myotis in Europe. Initial sampling consisted of 480 bats genotyped in 24 nursery colonies arranged along a transect of approximately 3000 km. The phylogeographical survey based on mtDNA sequences revealed the existence of major genetic subdivisions across this area, with several suture zones between haplogroups. Such zones of secondary contact were found in the Alps and Rhodopes, whereas other potential barriers to gene flow, like the Pyrenees, did not coincide with genetic discontinuities. Areas of population admixture increased locally the genetic diversity of colonies, which confounded the northward decrease in nucleotide diversity predicted using classical models of postglacial range expansion. However, when analyses were restricted to a subset of 15 nurseries originating from a single presumed glacial refugium, mtDNA polymorphism did indeed support a northwards decrease in diversity. Populations were also highly structured (PhiST = 0.384). Conversely, the same subset of colonies showed no significant latitudinal decrease in microsatellite diversity and much less population structure (FST = 0.010), but pairwise genetic differentiation at these nuclear markers was strongly correlated with increasing geographical distance. Together, this evidence suggests that alleles carried via male bats have maintained enough nuclear gene flow to counteract the effects of recurrent bottlenecks generally associated with recolonization processes. As females are highly philopatric, we argue that the maternally transmitted mtDNA marker better reflects the situation of past, historical gene flow, whereas current levels of gene flow are better reflected by microsatellite markers.

Animals↗
PubMed2003

Male dominance, paternity, and relatedness in the Jamaican fruit-eating bat (Artibeus jamaicensis).

We analysed variation at 14 nuclear microsatellite loci to assess the genetic structure, relatedness, and paternity of polygynous Jamaican fruit-eating bats. A total of 84 adults captured in two caves exhibited little genetic differentiation between caves (FST = 0.008). Average relatedness among adult females in 10 harem groups was very low (R = 0.014 +/- 0.011), providing no evidence of harem structure. Dominant and subordinate males shared paternity in large groups, while dominant and satellite males shared paternity in smaller groups. However, our results suggest that male rank influences paternity. Dominant males fathered 69% of 40 offspring, followed by satellite (22%) and subordinate males (9%). Overall adult male bats are not closely related, however, in large harem groups we found that subordinate and dominant males exhibited relatedness values consistent with a father-offspring relationship. Because dominant and subordinate males also sired all the pups in large groups, we propose that their association provides inclusive fitness to them.

Alleles↗
PubMed2006

The infective larva of Litomosoides yutajensis Guerrero et al., 2003 (Nematoda: Onchocercidae), a Wolbachia-free filaria from bat.

The infective larva of Litomosoides yutajensis Guerrero et al., 2003, a parasite of the bat Pteronotus pamellii, is described; it is distinct from congeneric infective larvae by the absence of caudal lappets. The life cycles of five other species of Litomosoides are known; three are parasites of rodents, one of a marsupial and one of a bat. As with these species, the experimental vector of L. yutoajensis used was the macronyssid mite Ornithonyssus bacoti. In nature, the main vectors are probably other macronyssids but transmission by O. bacoti, with its large host-range, could account for the characteristic host-switchings in the evolution of Litomosoides. Unlike the murine model L. sigmodontis Chandler, 1931, L. yutajensis is devoid of the endosymbiontic bacteria Wolbachia and may be of great interest.

Animals↗
PubMed2001

Altered trophoblastic differentiation and increased trophoblastic invasiveness during delayed development in the short-tailed fruit bat, Carollia perspicillata.

During pregnancy in the short-tailed fruit bat, lengthy post-implantational delays in conceptus development can occur in response to stress in captivity and seasonally in the wild. When comparisons were made between uteri carrying embryos in delay at the primitive streak stage and those growing more rapidly, many differences were noted. During delay the developing chorioallantoic placenta was generally smaller, contained a higher ratio of cytotrophoblast to syncytiotrophoblast, and had been invaded only to a limited extent on its embryonic side by mesoderm. Furthermore, much of the cytotrophoblast appeared relatively undifferentiated, randomly-oriented, linked primarily by primitive junctions, and lacked a basal lamina. In contrast, in placentae serving somite and limb-bud stage embryos, sizeable areas were noted that consisted only of more highly differentiated syncytiotrophoblast perforated by maternal vascular spaces (trophospongium). The first contact of the allantois with the developing placenta was also noted at the somite stage, and this initiated widespread invasion of the placenta by mesenchyme and allantoic blood vessels. Wherever this invasion had occurred, the cytotrophoblast between the mesenchyme and syncytiotrophoblast of the interhaemal barrier consisted of a single, polarized layer of more differentiated cells with an associated basal lamina. Eventually, all of the trophospongium was invaded by cytotrophoblast and vascularized fetal mesenchyme. These observations suggest that in addition to its germinal function, cytotrophoblast in this bat may play a major role in controlling mesenchymal invasion and angiogenesis on the embryonic side of the placenta. During the period of delay, highly invasive trophoblast is also released by the placenta. This invades the myometrium and sometimes extrauterine tissues via interstitial migration along maternal capillaries and veins.

Animals↗
PubMed2002

[Histoplasmosis group disease in bat researchers returning from Cuba].

CASE HISTORY: Four males (age 25 to 40 years) and one female (age 25) were admitted to our hospital almost simultaneously with symptoms of fever up to 38 degrees C, dry cough, thoracodynia, dyspnoea, myalgia and arthralgia. All patients belonged to a team of eight German bat researchers who had returned from Cuba 10 days before, where they had investigated bats in caves. Another member of the team had only mild histoplasmosis and was followed in our outpatient clinic. Two scientists who wore their breathing masks continuously during their work in the caves did not fall ill. EXAMINATIONS: Chest X-rays of all in-patients showed pulmonary infiltrates correlating with the severity of their illness. In all patients specific IgG antibodies against Histoplasma capsulatum-antigen were found in the Western Blot assay, confirming the diagnosis of histoplasmosis. TREATMENT: Treatment with oral itraconazole 200 mg b.d was given to four inpatients for 6 weeks, in the fifth patient itraconazole was discontinued because of an increase of liver transaminases. CONCLUSION: Antimycotic treatment of advancing histoplasmosis seems appropriate also in immunocompetent patients. The high number of patients within this group suggests high numbers of Histoplasma capsulatum in the caves. Wearing breathing masks throughout the work in the caves may prevent histoplasmosis even in case of high infectious doses. Pre-travel recommendations for cave researchers have to emphasize the continuous use of breathing masks and vaccination against tetanus and rabies.

Adult↗
PubMed2003

BAT and BEP as instruments for reducing emissions of unintentionally produced POPs and development of guidelines under the Stockholm Convention.

The 6th Intergovernmental Negotiating Committee (INC 6), under the Stockholm Convention on POPs, gave an expert group the mandate to develop guidelines for the application and implementation of best available techniques (BAT) and best environmental practices (BEP) for the prevention and reduction of unintentionally produced and emitted POPs, including polychlorinated dibenzodioxins/-furans (PCDD/Fs), polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB). Measures to reduce or eliminate the release of these POPs to the environment can be found in Article 5 of the Convention. BAT and BEP are already being applied as emission reduction instruments in a number of industrialised countries and are elements of other major international treaties, e.g. the UN ECE Protocol on POPs and the Marine Convention's OSPAR and HELCOM, and of the EU Directive for Integrated Pollution Prevention and Control (IPPC Directive). Existing concepts are presented and compared with the requirements of the Stockholm Convention. Consequences, perspectives and questions for the future intersessional work of the above-mentioned Expert Group are discussed.

Air Pollution↗
PubMed2002

Reorganization of the cochleotopic map in the bat's auditory system by inhibition.

The central auditory system of the mustached bat shows two types of reorganization of cochleotopic (frequency) maps: expanded reorganization resulting from shifts in the best frequencies (BFs) of neurons toward the BF of repetitively stimulated cortical neurons (hereafter centripetal BF shifts) and compressed reorganization resulting from the BF shifts of neurons away from the BF of the stimulated cortical neurons (hereafter centrifugal BF shifts). Facilitation and inhibition evoked by the corticofugal system have been hypothesized to be respectively related to centripetal and centrifugal BF shifts. If this hypothesis is correct, bicuculline (an antagonist of inhibitory GABA-A receptors) applied to cortical neurons would change centrifugal BF shifts into centripetal BF shifts. In the mustached bat, electric stimulation of cortical Doppler-shifted constant-frequency neurons, which are highly specialized for frequency analysis, evokes the centrifugal BF shifts of ipsilateral collicular and cortical Doppler-shifted constant-frequency neurons and contralateral cochlear hair cells. Bicuculline applied to the stimulation site changed the centrifugal BF shifts into centripetal BF shifts. On the other hand, electric stimulation of neurons in the posterior division of the auditory cortex, which are not particularly specialized for frequency analysis, evokes centripetal BF shifts of cortical neurons located near the stimulated cortical neurons. Bicuculline applied to the stimulation site augmented centripetal BF shifts but did not change the direction of the shifts. These observations support the hypothesis and indicate that centripetal and centrifugal BF shifts are both based on a single mechanism consisting of two components: facilitation and inhibition.

Acoustic Stimulation↗
PubMed1998

Experience-dependent corticofugal adjustment of midbrain frequency map in bat auditory system.

Recent studies of corticofugal modulation of auditory information processing indicate that cortical neurons mediate both a highly focused positive feedback to subcortical neurons "matched" in tuning to a particular acoustic parameter and a widespread lateral inhibition to "unmatched" subcortical neurons. This cortical function for the adjustment and improvement of subcortical information processing is called egocentric selection. Egocentric selection enhances the neural representation of frequently occurring signals in the central auditory system. For our present studies performed with the big brown bat (Eptesicus fuscus), we hypothesized that egocentric selection adjusts the frequency map of the inferior colliculus (IC) according to auditory experience based on associative learning. To test this hypothesis, we delivered acoustic stimuli paired with electric leg stimulation to the bat, because such paired stimuli allowed the animal to learn that the acoustic stimulus was behaviorally important and to make behavioral and neural adjustments based on the acquired importance of the acoustic stimulus. We found that acoustic stimulation alone evokes a change in the frequency map of the IC; that this change in the IC becomes greater when the acoustic stimulation is made behaviorally relevant by pairing it with electrical stimulation; that the collicular change is mediated by the corticofugal system; and that the IC itself can sustain the change evoked by the corticofugal system for some time. Our data support the hypothesis.

Acoustic Stimulation↗
PubMed1987

Tissue folates in fruit bats (Rousettus aegyptiacus) with nitrous oxide-induced vitamin B12 deficiency and neurological impairment.

1. Long-term exposure of the fruit bat Rousettus aegyptiacus to nitrous oxide, which inactivates methylcobalamin, leads to neurological impairment and ataxia. 2. In N2O-exposed animals, liver concentrations of total folates and methyl folates decreased to less than one-fifth that of control animals. Pediococcus cerevisiae-active folates were also reduced. 3. In brain, there were no changes in total or methyl folates, but P. cerevisiae-active folates were lower in N2O-exposed animals. 4. Supplementation with methionine retarded the development of neurological impairment and the fall in liver total and methyl folates, but not that in P. cerevisiae-active folates. 5. Supplementation with serine failed to retard the development of neurological impairment or fall in hepatic folates. 6. The present results suggest that the N2O-induced neurological impairment in the bat is not related to depletion of cerebral folates, but do not exclude changes in the subcellular distribution of folates.

Animals↗
PubMed1962

The sarcoplasmic reticulum of the bat cricothroid muscle.

The bat cricothyroid muscle is believed to participate in the production of the short bursts of frequency modulated ultrasound which these animals use as an echolocation device. The evidence seems to indicate that this muscle must be extremely fast acting. It possesses a very well developed sarcoplasmic reticulum, consisting of intercommunicating longitudinal and transverse tubular elements. The transverse elements, situated at the level of the junction between the A and the I bands, are tripartite complexes of tubules called triads, and these are sometimes replaced by more complex structures, the pentads. The intermediate element of the triad appears as a slender continuous tubule, which can be shown to come into close contact with the sarcolemma and also to share with it certain common staining properties. The longitudinal components of the reticulum consist of very numerous tubules which link successive triads to each other and anastomose to form multiple layers of close-meshed reticula in the interfibrillar sarcoplasm. Both the longitudinal and the transverse elements of the sarcoplasmic reticulum form a continuous network across the muscle fiber. It is suggested that the extraordinary development of the sarcoplasmic reticulum in the bat cricothyroid is related to the unusual physiological properties of this muscle.

Animals↗
PubMedDate not supplied

Effects of body mass and reproduction on the basal metabolic rate of brown long-eared bats (Plecotus auritus).

We measured basal metabolic rate (BMR) of nonreproductive and of breeding (pregnant and lactating) female brown long-eared bats (Plecotus auritus) to investigate the effects of intra- and interindividual variation in body mass and of reproduction on metabolism. The BMR of six nonreproductive females was measured between five and seven times at approximately 2-wk intervals over a period of 2.5 mo. There was a highly significant effect (P<0.001) of body mass on BMR of these nonreproductive females. The pooled within-individual scaling exponent (1.88) significantly exceeded the established mammalian interspecific exponent (0.75). In addition, we made single observations on 14 nonreproductive females to establish the effects of differences in mass between individuals. The mean BMR across all 14 individuals was 82 mW (+/-24 SD). There was a significant positive relationship between BMR and body mass across these individuals (r2=0.39), with a between-individual scaling exponent of 0.75. Inter- and intraindividual effects of mass on BMR were combined in a regression analysis that included mean body mass and deviation from mean mass on any given day as predictors. This regression model explained 55% of the variation in BMR. We made longitudinal measurements of BMR throughout reproduction and compared these with the predicted BMR of nonreproductive bats of the same body mass. Reproductive females exhibited temporal flexibility in BMR. BMR during pregnancy increased on a whole-animal basis but was significantly lower (by, on average, 15%) than BMR predicted for nonreproductive females of the same mass. Over a period of 1-75 d following birth, whole-animal BMR was greater than that during pregnancy, even though body mass declined after parturition. Hence, postbirth BMR was greater than the level predicted for nonreproductive females of the same mass. This study indicates that the scaling of BMR with body mass differs significantly within and between individuals and that there is a reduction of BMR in pregnancy and an elevation of BMR during lactation.

Animals↗
PubMed2002

Emerging epidemiology of bat-associated cryptic cases of rabies in humans in the United States.

In the United States, during the past half-century, the number of humans to die of rabies dramatically decreased to an average of 1-2 per year. Although the number of deaths is low, most deaths occur because individuals are unaware that they had been exposed to and infected with rabies virus, and, therefore, they do not seek effective postexposure treatment. Molecular epidemiological studies have linked most of these cryptic rabies exposures to rabies virus variants associated with insectivorous bats. In particular, virus variants associated with 2 relatively reclusive species, the silver-haired bat (Lasionycteris noctivagans) and the eastern pipistrelle (Pipistrellus subflavus), are the unexpected culprits of most cryptic cases of rabies in humans.

Animals↗