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At least 1,657 records · Page 92Linked to original sources
PubMed2000

On Eimeria bragancaensis n. sp. (Apicomplexa: Eimeriidae) and tissue-cysts of an unidentified protozoan in the bat Peropteryx macrotis (Chiroptera: Emballonuridae) from Amazonian Brazil.

A description is given of the mature oocysts and endogenous stages of Eimeria bragancaensis n. sp., from the small intestine of the bat Peropteryx macrotis from north Brazil. Oocysts are spherical to subspherical, 15.9 x 14.6 microns (range 14-17 x 14-17.7). The wall is of two layers: an outer, thicker one which is of a brownish-yellow colour and striated (pitted), and an inner one which is thin and colourless. The outer layer is frequently lost. No micropyle or oocyst residuum present, but the oocyst usually contains one or two polar bodies. Sporocysts 8.4 x 5.3 microns (range 6.25-9 x 4-6) with inconspicuous Stieda and substiedal bodies. Endogenous stages are intracytoplasmic in the epithelial cells of the small intestine, above the host-cell nucleus. Stages of merogony and gametogony are described. Abundant tissue-cysts of an unidentified protozoan, containing from 1-4 zoites, were found in the parenchyma cells of the liver and, less frequently, in the lamina propria of the small intestine. Their possible nature is discussed.

Animals↗
PubMed2002

[A new flea species of the genus Allopsylla Beaucournu et Fain, 1982 (Siphonaptera: Ischnopsyllidae) from Central African Republic, found on a little known molossid bat].

A pair of Allopsylla lobayensis Beaucournu & Barrière, new species were collected the first of November 1999 in Ngotto forest, in the south-western part of the Lobaye basin, Central African Republic (CAR). The host specimen, a little known molossid bat (Myopterus whitleyi), constitutes the first record of this species in CAR. The new flea species appears taxonomically close to A. hetera Beaucournu & Fain, 1982, one of the two other Allopsylla species, previously know from other faunal regions (A. alloides in Nigeria and A. hetera in Democratic Republic of the Congo). The parasitism of three distinctly different hosts by the three known Allopsylla species raises questions regarding the host-parasite specificity of this group.

Animals↗
PubMed2006

First report of Litomosa spp. (Nematoda: Filarioidea) from Malagasy bats; review of the genus and relationships between species.

The presence of the filarial genus Litomosa in Malagasy bats is demonstrated by the finding of L. goodmani n. sp. from Miniopterus gleni and Litomosa sp. (male unknown) from M. manavi, both in the Special Reserve of Ankarana. These materials are compared to the 22 Litomosa species, including two Indian species originally placed in the genus Litomosoides, L. fotedari (Gupta and Trivedi, 1989) n. comb. and L. tewarii (Gupta and Trivedi, 1989) n. comb., and the new taxon L. seurati n. sp. (= L. beaucournui Bain, 1966 pro parte), type-host Rhinolophus ferrum-equinum, Algeria, distinguished by the narrow area rugosa and the female caudal extremity with two conspicuous points, instead of several small ones. The Malagasy material belongs to a group of species close to the type, L. filaria, which have a male area rugosa composed of cuticular bosses and microfilariae folded within the sheath, and which are parasitic in Vespertilionidae, Hipposideridae and Rhinolophidae from Africa and Europe. The two Malagasy species resemble L. seurati n. sp., L. beshkovi Jancev, 1971, L. chiropterum Ortlepp, 1932, L. adami Petit, 1980 and L. ottavianii Lagrange et Bettini, 1948, with the enlarged third segment of the buccal capsule. L. goodmani n. sp. is distinct with its small size and female caudal extremity with a single point, which is suppressed in old mature worms; the females of Litomosa sp. have two conical points. Relationships among Litomosa species appear to be dependent upon both the chiropteran host groups and the geographical region.

Animals↗
PubMedDate not supplied

Relationships between orientation of the blastocyst during implantation, position of the chorioallantoic placenta, and vascularization of the uterus in the noctilionoid bats Carollia perspicillata and Noctilio sp.

In most eutherian mammals, the inner cell mass (ICM) of the blastocyst assumes an almost constantly specific orientation to the uterus at the time of implantation, and this is usually correlated with subsequent positioning of the fetal membranes and chorioallantoic placenta. Although these relationships tend to be conserved between closely related species, this is not the case in the noctilionoid bats. In Carollia perspicillata, which has a simplex uterus, the ICM of the single blastocyst becomes oriented towards the uterotubal junction on the side of ovulation, and the discoidal placenta develops in a fundic position. In Noctilio sp., which have partially bicornuate uteri, the ICM becomes oriented instead towards an endometrial ridge that runs along the antimesometrial to lateral side of the gravid horn. As development proceeds, however, the blastocyst rotates almost 180 degrees, and the discoidal placenta eventually assumes a mesometrial to lateral position. In these species, implantation and subsequent development of the discoidal placenta clearly seem to be targeting major maternal vessels supplying the uterus, rather than exhibiting a consistent pattern of orientation relative to its mesenteric attachments. This permits their chorioallantoic placentae to develop a dual maternal blood supply that may be essential for the development of relatively large, precocious infants.

Allantois↗
PubMed2000

Unusual patterns of intermediate filament protein expression by the trophoblast and decidual cells of the short-tailed fruit bat, Carollia perspicillata.

In the short-tailed fruit bat (Carollia perspicillata) pregnancy can be prolonged by the occurrence of lengthy delays after implantation. This is associated with the development of highly invasive trophoblast that can penetrate the myometrium, mesenteries of the reproductive tract and the oviducts via perivascular (interstitial) routes. In order to confirm the identity and distribution of this trophoblast, intermediate filament protein immunocytochemistry was utilized. In some respects the expression of these proteins differed from what has been reported for more commonly-studied species. Cytotrophoblast in the placenta, its cytotrophoblastic shell and the highly invasive trophoblast strongly expressed cytokeratins. As pregnancy progressed, however, cytokeratin expression by syncytiotrophoblast lining much of the placental labyrinth became very weak. The cytotrophoblastic shell and highly invasive trophoblast also expressed vimentin. The highly invasive trophoblast was unusual in that it developed dendritic processes that sometimes extended out into adjacent tissues in great profusion. Decidual cells generally expressed desmin and vimentin; however, some also coexpressed cytokeratins. These observations indicate that some of the trophoblast in Carollia undergoes a significant epithelial-mesenchymal transformation. They also suggest that caution should be exercised in relying upon intermediate filament proteins as markers for cell identification purposes in exotic species, or when the patterns of protein expression by fetal and maternal cells might be altered in pathological or experimental situations.

Animals↗
PubMed2001

Comparative studies on limb morphogenesis in mice and bats: a functional genetic approach towards a molecular understanding of diversity in organ formation.

The basis of species-specific morphogenesis has been a topic of fascination and speculation for centuries. In 1828, Karl Ernst von Baer noted that at the pharyngula stage of development all vertebrate embryos are morphologically very similar. Most subsequent hypotheses have proposed that the vertebrate body plan develops by a conserved mechanism, and that divergent forms develop by differential elaboration on this basic plan. Gene cloning and expression studies have largely confirmed that the genetic pathways of embryonic patterning are highly conserved. The finding that the proteins encoded by paralogous and orthologous genes within and between species can functionally replace each another is no longer novel; in most cases this is the expected result. How, then, does divergent morphology arise between species? One hypothesis that fits well with comparative data is that divergent morphogenesis arises from genetic differences in the timing, level and pattern of orthologous gene expression during development. This idea is being tested using a functional genetic approach comparing limb morphogenesis between the mouse and bat.

Animals↗
PubMed1989

Sex steroid levels and Leydig cell ultrastructure of the male common sheath-tail bat, Taphozous georgianus.

Male sheath-tail bats were collected from central Queensland over a 12-month period. Plasma testosterone levels peaked in August, coincident with an increase in the volume of the accessory glands and ampulla/seminal vesicle secretion. Peak spermatogenesis occurred in summer and autumn and declined in the face of maximal testosterone levels in winter. Levels of androstenedione and 5 alpha-dihydrotestosterone were high compared with testosterone levels and showed no significant seasonal changes. Ultrastructural examination of Leydig cell cytoplasm revealed numerous lipid droplets and mitochondria, and an abundant smooth endoplasmic reticulum. There were no seasonal changes in Leydig cell ultrastructure. The anomalous reproductive pattern in this species is consistent with the imposition of a cold-induced winter spermatogenic shutdown, on a framework of continuous spermatogenesis, with spring peaks in testosterone and accessory gland activity.

Androgens↗
PubMed2004

Reorganization of the auditory cortex specialized for echo-delay processing in the mustached bat.

Focal excess sensory stimulation evokes reorganization of a sensory system. It is usually an expansion of the neural representation of that stimulus resulting from the shifts of the tuning curves (receptive fields) of neurons toward those of the stimulated neurons. The auditory cortex of the mustached bat has an area that is highly specialized for the processing of target-distance information carried by echo delays. In this area, however, reorganization is due to shifts of the delay-tuning curves of neurons away from those of the stimulated cortical neurons. Elimination of inhibition in the target-distance processing area in the auditory cortex by a drug reverses the direction of the shifts in neural tuning curves. Therefore, such unique reorganization in the time domain is due to strong lateral inhibition in the highly specialized area of the auditory cortex.

Acoustic Stimulation↗
PubMed2005

Asymmetry in corticofugal modulation of frequency-tuning in mustached bat auditory system.

Focal electric stimulation of the auditory cortex is well suited for exploration of the function of the corticofugal (descending) system and the neural mechanism of plasticity in the central auditory system, because it evokes changes in frequency-tuning, called best frequency (BF) shifts, as does auditory fear conditioning. The Doppler-shifted constant frequency (DSCF) area of the primary auditory cortex of the mustached bat is highly specialized for fine frequency analysis. Focal electric stimulation of the DSCF area evokes the BF shifts of ipsilateral cortical and collicular neurons away from the BF of stimulated neurons, whereas the stimulation evokes the BF shifts of contralateral cortical and collicular neurons either toward or away from the stimulated BF. The direction of contralateral BF shifts shows a flip-flop, depending on the spatial relationship between the stimulated and recorded neurons. This asymmetry in corticofugal modulation is mostly, if not totally, created by two subdivisions of the stimulated DSCF area that transmit signals to the contralateral DSCF area, presumably through the corpus callosum. This intriguing asymmetry in corticofugal modulation presumably functions for equalization of the reorganization of the frequency maps of the DSCF areas and subcortical auditory nuclei on both sides.

Acoustic Stimulation↗
PubMed2001

Corticofugal modulation of duration-tuned neurons in the midbrain auditory nucleus in bats.

Animal sounds, as well as human speech sounds, are characterized by multiple parameters such as frequency, intensity, duration, etc. The central auditory system produces neurons tuned to particular durations and frequencies of sounds emitted by a species. In bats, "duration-tuned" neurons are mostly sensitive to short durations and high frequencies of sounds used for echolocation. They are scattered in the frequency maps of the inferior colliculus and auditory cortex. We found that electric stimulation of cortical duration-tuned neurons modulates collicular duration-tuned neurons in both duration and frequency tuning only when collicular and cortical neurons paired for studies are within +/-4 ms in best duration and within +/-6 kHz in best frequency. There are four types of modulations: sharpening or broadening of duration tuning, and lengthening or shortening of best duration. Sharpening is observed in "matched" collicular neurons whose best durations are the same as those of stimulated cortical neurons, and it is accompanied by augmentation of the auditory responses at their best durations. The other three types of modulations are observed in "unmatched" collicular neurons whose best durations are different from those of stimulated cortical neurons. Lengthening or shortening of best duration is linearly related to the amount of the difference in best duration between collicular and cortical neurons. Corticofugal modulation is specific and systematic according to relationships in both duration and frequency between stimulated cortical and recorded collicular neurons.

Animals↗
PubMed1994

The bat gene of Halobacterium halobium encodes a trans-acting oxygen inducibility factor.

Oxygen and light affect the expression of the bacterioopsin gene (bop), which encodes a light-driven proton pump in the purple membrane of Halobacterium halobium. This response is thought to be mediated by a set of genes located adjacent to the bop gene. DNA fragments containing either the bop gene or the entire bop gene cluster reversed the phenotype of purple membrane-deficient strains with mutations in the bop gene. Purple membrane synthesis was constitutive in one of these strains transformed with the bop gene alone. The same strain transformed with the bop gene cluster was inducible by low oxygen tension. Moreover, another strain that constitutively expresses purple membrane remained constitutive when transformed with the bop gene alone but the phenotype of the strain changed to inducible when transformed with the bop gene cluster. Additional experiments have confirmed that one of the genes of the bop gene cluster, the bat gene, encodes a trans-acting factor that is necessary and sufficient to confer inducibility of purple membrane synthesis by low oxygen tension.

Bacteriorhodopsins↗
PubMed1995

Basilar membrane resonance in the cochlea of the mustached bat.

The mustached bat (Pteronotus parnellii) detects the wing beats of prey insects by resolving small frequency modulations in the return echoes to the constant frequency component of its echolocation call at about 61 kHz. The fine frequency discrimination required for this task is due largely to the mechanical properties of the cochlea, as indicated indirectly by the presence of large otoacoustic emissions at 61 kHz. A laser diode interferometer was used to measure basilar membrane displacements in the basal turn of the cochlea at a location that is 4-6 mm basal to the 61-kHz place on the basilar membrane. The region of the basilar membrane from which the measurements were made was tuned not only to those characteristic of this location (88-98 kHz) but also very sharply tuned to 61 kHz. The 61-kHz tuning was labile and could be modeled as a simple resonance. The resonance is not restricted to the 61-kHz place but involves more basal regions. We also provide direct evidence to show that otoacoustic emissions from the ear propagate along the basilar membrane.

Acoustic Stimulation↗
PubMed1996

Characterization of a unique variant of bat rabies virus responsible for newly emerging human cases in North America.

The silver-haired bat variant of rabies virus (SHBRV) has been identified as the etiological agent of a number of recent human rabies cases in the United States that are unusual in not having been associated with any known history of conventional exposure. Comparison of the different biological and biochemical properties of isolates of this virus with those of a coyote street rabies virus (COSRV) revealed that there are unique features associated with SHBRV. In vitro studies showed that, while the susceptibility of neuroblastoma cells to infection by both viruses was similar, the infectivity of SHBRV was much higher than that of COSRV in fibroblasts (BHK-21) and epithelial cells (MA-104), particularly when these cells were kept at 34 degrees C. At this temperature, low pH-dependent fusion and cell-to-cell spread of virus is seen in BHK-21 cells infected with SHBRV but not with COSRV. It appears that SHBRV may possess an unique cellular tropism and the ability to replicate at lower temperature, allowing a more effective local replication in the dermis. This hypothesis is supported by in vivo results which showed that while SHBRV is less neurovirulent than COSRV when administered via the intramuscular or intranasal routes, both viruses are equally neuroinvasive if injected intracranially or intradermally. Consistent with the above findings, the amino acid sequences of the glycoproteins of SHBRV and COSRV were found to have substantial differences, particularly in the region that contains the putative toxic loop, which are reflected in marked differences in their antigenic composition. Nevertheless, an experimental rabies vaccine based on the Pittman Moore vaccine strain protected mice equally well from lethal doses of SHBRV and COSRV, suggesting that currently used vaccines should be effective in the postexposure prophylaxis of rabies due to SHBRV.

Animals↗
PubMed1997

Syntax processing by auditory cortical neurons in the FM-FM area of the mustached bat Pteronotus parnellii.

Syntax denotes a rule system that allows one to predict the sequencing of communication signals. Despite its significance for both human speech processing and animal acoustic communication, the representation of syntactic structure in the mammalian brain has not been studied electrophysiologically at the single-unit level. In the search for a neuronal correlate for syntax, we used playback of natural and temporally destructured complex species-specific communication calls-so-called composites-while recording extracellularly from neurons in a physiologically well defined area (the FM-FM area) of the mustached bat's auditory cortex. Even though this area is known to be involved in the processing of target distance information for echolocation, we found that units in the FM-FM area were highly responsive to composites. The finding that neuronal responses were strongly affected by manipulation in the time domain of the natural composite structure lends support to the hypothesis that syntax processing in mammals occurs at least at the level of the nonprimary auditory cortex.

Animal Communication↗
PubMed2000

Experience-dependent plasticity in the auditory cortex and the inferior colliculus of bats: role of the corticofugal system.

In the big brown bat, Eptesicus fuscus, the response properties of neurons and the cochleotopic (frequency) maps in the auditory cortex (AC) and inferior colliculus can be changed by auditory conditioning, weak focal electric stimulation of the AC, or repetitive delivery of weak, short tone bursts. The corticofugal system plays an important role in information processing and plasticity in the auditory system. Our present findings are as follows. In the AC, best frequency (BF) shifts, i.e., reorganization of a frequency map, slowly develop and reach a plateau approximately 180 min after conditioning with tone bursts and electric-leg stimulation. The plateau lasts more than 26 h. In the inferior colliculus, on the other hand, BF shifts rapidly develop and become the largest at the end of a 30-min-long conditioning session. The shifted BFs return (i. e., recover) to normal in approximately 180 min. The collicular BF shifts are not a consequence of the cortical BF shifts. Instead, they lead the cortical BF shifts. The collicular BF shifts evoked by conditioning are very similar to the collicular and cortical BF shifts evoked by cortical electrical stimulation. Therefore, our working hypothesis is that, during conditioning, the corticofugal system evokes subcortical BF shifts, which in turn boost cortical BF shifts. The cortical BF shifts otherwise would be very small. However, whether the cortical BF shifts are consequently boosted depends on nonauditory systems, including nonauditory sensory cortices, amygdala, basal forebrain, etc., which determine the behavioral relevance of acoustic stimuli.

Acoustic Stimulation↗
PubMed1995

Structural features mediating fibrin selectivity of vampire bat plasminogen activators.

The distinguishing characteristic of vampire bat (Desmodus rotundus) salivary plasminogen activators (DSPAs) is their strict requirement for fibrin as a cofactor. DSPAs consist of structural modules known from urokinase (u-PA) and tissue-type plasminogen activator (t-PA) such as finger (F), epidermal growth factor (E), kringle (K), and protease (P), combining to four genetically and biochemically distinct isoenzymes, exhibiting the formulas FEKP (DSPA alpha 1 and alpha 2) and EKP and KP (DSPA beta and DSPA gamma). Only DSPA alpha 1 and alpha 2 bind to fibrin. All DSPAs are single-chain molecules, displaying substantial amidolytic activity. In a plasminogen activation assay, all four DSPAs are almost inactive in the absence of fibrin but strongly stimulated by fibrin addition. The catalytic efficiency (kcat/Km) of DSPA alpha 1 increases 10(5)-fold, whereas the corresponding value of t-PA is only 550. The ratio of the bimolecular rate constants of plasminogen activation in the presence of fibrin versus fibrinogen (fibrin selectivity) of DSPA alpha 1, alpha 2, beta, gamma, and t-PA was found to be 13,000, 6500, 250, 90, and 72, respectively. Whereas all DSPAs are therefore more fibrin dependent and fibrin selective than t-PA, the extent depends on the respective presence of the various domains. The introduction of a plasmin-sensitive cleavage site in a position akin to the one in t-PA partially obliterates fibrin cofactor requirement. Fibrin dependence and fibrin selectivity of DSPAs are accordingly mediated by fibrin binding, which involves the F domain, as yet undefined determinants within the K and P domains, and by the absence of a plasmin-sensitive activation site. These findings transcend the current understanding of fibrin-mediated stimulation of plasminogen activation: in addition to fibrin binding, specific protein-protein interactions come into play, which stabilize the enzyme in its active conformation.

Aminocaproic Acid↗
PubMed1998

Characterization of the interactions of plasminogen and tissue and vampire bat plasminogen activators with fibrinogen, fibrin, and the complex of D-dimer noncovalently linked to fragment E.

Vampire bat plasminogen activator (b-PA) causes less fibrinogen (Fg) consumption than tissue-type plasminogen activator (t-PA). Herein, we demonstrate that this occurs because the complex of D-dimer noncovalently linked to fragment E ((DD)E), the most abundant degradation product of cross-linked fibrin, as well as Fg, stimulate plasminogen (Pg) activation by t-PA more than b-PA. To explain these findings, we characterized the interactions of t-PA, b-PA, Lys-Pg, and Glu-Pg with Fg and (DD)E using right angle light scattering spectroscopy. In addition, interactions with fibrin were determined by clotting Fg in the presence of various amounts of t-PA, b-PA, Lys-Pg, or Glu-Pg and quantifying unbound material in the supernatant after centrifugation. Glu-Pg and Lys-Pg bind fibrin with Kd values of 13 and 0.13 microM, respectively. t-PA binds fibrin through two classes of sites with Kd values of 0.05 and 2.6 microM, respectively. The second kringle (K2) of t-PA mediates the low affinity binding that is eliminated with epsilon-amino-n-caproic acid. In contrast, b-PA binds fibrin through a single kringle-independent site with a Kd of 0.15 microM. t-PA competes with b-PA for fibrin binding, indicating that both activators share the same finger-dependent site on fibrin. Glu-Pg binds (DD)E with a Kd of 5.4 microM. Lys-Pg binds to (DD)E and Fg with Kd values of 0.03 and 0.23 microM, respectively. t-PA binds to (DD)E and Fg with Kd values of 0.02 and 0.76 microM, respectively; interactions were eliminated with epsilon-amino-n-caproic acid, consistent with K2-dependent binding. Because it lacks a K2-domain, b-PA does not bind to either (DD)E or Fg, thereby explaining why b-PA is more fibrin-specific than t-PA.

Aminocaproic Acid↗
PubMed1996

Season related ultrastructural features of the parotid, submandibular and von Ebner's glands in hibernating bats.

The parotid, submandibular and the von Ebner's salivary glands of hibernating insectivorous bats (Pipistrellus pipistrellus, Rhinolophus f. e. and Eptesicus serotinus) were studied by transmission electron microscopy and by histochemical methods during various seasons of the year. We report the seasonal ultrastructural changes that occur in the cytoplasmic organelles and the secretory granules of the serous and mucous cells and in the intercalated and striated ducts of the major glands. It previously has been hypothesized that the heterogeneity of the inclusions in the serous granules is closely related to the varying seasonal levels of proteinaceous and glycidic constituents. Lymphatic vessels are present only in the perivascular and periductal connective tissue. Morphofunctional and comparative studies seem to confirm a relationship between secretory activity and nutritional status as well as a likely involvement of the intercalated and striated ducts in determining the composition of the saliva.

Animals↗