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PubMed1988

Analysis of cold and warm receptor activity in vampire bats and mice.

The response characteristics of facial thermoreceptors of the common vampire bat and of the mouse have been quantitatively studied. Cold receptors were identified in bat and mouse; warm receptors were only established in the bat. Cold and warm receptor populations of the two species share most of their properties with facial thermoreceptor populations of various mammalian species investigated so far. The temporal pattern of activity of cold receptors of the mouse corresponded to that observed in cats, dogs and monkeys: impulse groups at lower, and beating activity at higher temperatures. At maintained temperature, no impulse groups were initiated in cold receptors of the bat. However, cooling steps from various initial temperatures induced a transient grouped discharge in both cold receptor populations. A discharge in regular groups of impulses was occasionally generated in warm receptors of the bat at maintained temperatures and following warming steps. The data indicate that the temperature dependence of periodic activity in warm receptors is not as uniform as it is in cold receptors. It is concluded that cyclic processes are involved in sensory transduction of both warm and cold receptors, and that this cyclic behavior seems to be a general property of thermoreceptors of presumably all vertebrate species.

Animals↗
PubMed1986

The detection of phantom targets in noise by serotine bats; negative evidence for the coherent receiver.

Using a target simulator three serotine bats, Eptesicus serotinus, were trained to judge whether a phantom target was present or absent. The echolocation sounds emitted by the bats during the detection were intercepted by a microphone, amplified and returned by a loudspeaker as an artificial echo, with a delay of 3.2 ms and a sound level determined by the overall gain and cry amplitude. The cry level of each pulse was measured and the echo level received by the bat was calculated. The target was presented in 50% of the trials and the gain adjusted using conventional up/down procedures. Under these conditions between 40 and 48 dB peSPL were required for 50% detection (Figs. 2, 3). In a subsequent experiment the phantom target was masked with white noise (No) with a spectrum level of -113 dB re. 1 Pa X Hz-1/2. The thresholds were increased by 7-14 dB. Energy density (S) of a single pulse was measured and used to estimate S/No, which ranged from 36-49 dB at threshold. Theoretically the coherent receiver model predicts the ratio between hits and false alarms observed for the bats at a S/No of ca. 1-2 dB. Since the bats require 40-50 dB higher S/No (Fig. 3), this is taken as negative evidence for coherent reception (cross correlation). Furthermore, a strong sensitivity to clutter was found since there seemed to exist a fixed relationship between thresholds and clutter level.

Animals↗
PubMed1997

Leptin, corticotropin-releasing hormone (CRH), and neuropeptide Y (NPY)in free-ranging pregnant bats.

Leptin, the product of the obese gene first identified in mice, restores fertility in obese mice, and accelerates puberty in mice. We hypothesized that leptin's putative role in reproduction may extend to pregnancy and lactation. Leptin levels were determined in Myotis lucifugus, the little brown bat, a free-ranging mammal with a seasonal breeding cycle. The present study shows that plasma levels of leptin progressively rise during pregnancy, supporting a potential role for leptin in the maintenancy of pregnancy. In contrast, leptin was significantly lower during lactation, a time when most mammals, including bats, demonstrate reduced fertility. In addition to its possible roles in reproduction, leptin appears important in regulation of energy balance. M. lucifugus spontaneously fasts for up to 16 h each day during the active season, which allowed us to test the hypothesis that acute fasting was associated with decreased leptin. Leptin was significantly lower in fasted (lactating) bats, compared to those that recently returned from nightly foraging. Although postprandial lactating bats had a significantly higher fat index than fasted bats, plasma leptin and body fat were not significantly correlated, and were only weakly correlated (r2 = 0.26) when both pregnant and lactating females were included in the analysis. Similar changes during pregnancy, lactation, and the daily feeding cycle were observed in the hypothalamic neuropeptide, corticotropin-releasing hormone (CRH), which is believed to play an important role in energy balance and reproduction. By contrast, neuropeptide Y (NPY) increased during pregnancy but did not change during fasting. These results suggest that leptin's putative role in reproduction may extend to pregnancy and lactation, and that spontaneous, acute fasting results in decreased circulating levels of leptin in M. lucifugus.

Adipose Tissue↗
PubMed2003

Evolutionary aspects of bat echolocation.

This review is yet another attempt to explain how echolocation in bats or bat-like mammals came into existence. Attention is focused on neuronal specializations in the ascending auditory pathway of echolocating bats. Three different mechanisms are considered that may create a specific auditory sensitivity to echos: (1). time-windows of enhanced echo-processing opened by a corollary discharge of neuronal vocalization commands; (2). differentiation and expansion of ensembles of combination-sensitive neurons in the midbrain; and (3). corticofugal top-down modulations. The second part of the review interprets three different types of echolocation as adaptations to ecological niches, and presents the sophisticated cochlear specializations in constant-frequency/frequency-modulated bats as a case study of finely tuned differentiation. It is briefly discussed how a resonant mechanism in the inner ear of constant-frequency/frequency-modulated bats may have evolved in common mammalian cochlea.

Acoustic Stimulation↗
PubMed1998

The energy cost of flight: do small bats fly more cheaply than birds?

Flapping flight is one of the most expensive activities in terms of metabolic cost and this cost has previously been considered equal for the two extant vertebrate groups which evolved flapping flight. Owing to the difficulty of obtaining accurate measurements without disturbing flight performance, current estimates of flight cost within the group of small birds and bats differ by more than a factor of five for given body masses. To minimize the potential problem that flight behaviour may be affected by the measurements, we developed an indirect method of measuring flight energy expenditure based on time budget analysis in which small nectar-feeding bats (Glossophaginae) could continue their natural rhythm of flying and resting entirely undisturbed. Estimates of metabolic flight power based on 172 24-h time and energy budget measurements were obtained for nine individual bats from six species (mass 7-28 g). Metabolic flight power (PF) of small bats was found to increase with body mass following the relation PF = 50.2 M0.771 (r2 = 0.96, n = 13, PF in W, M in kg). This is about 20-25% below the majority of current predictions of metabolic flight cost for small birds. Thus, either the flight cost of small birds is significantly lower than has previously been thought or, contrary to current opinion, small bats require less energy to fly than birds.

Animal Feed↗
PubMed1984

Luteinizing hormone-releasing hormone (LH-RH) cells and their projections in the forebrain of the bat Myotis lucifugus lucifugus.

Luteinizing hormone-releasing hormone (LH-RH) neurons and their projections were studied by immunocytochemistry in the brains of little brown bats (Myotis lucifugus lucifugus: Chiroptera: Vespertilionidae ) as a first step in the study of relationships between these neurons and the seasonal reproductive events characteristic of this species. The majority of immunoreactive neurons in adult male, adult female, and fetal bats were ovoid bipolar cells with one thin and one thicker process, both of which gave rise to fine varicose fibers. LH-RH-immunoreactive perikarya were concentrated in the region of the arcuate nuclei in all bats examined. Perikarya were also consistently found dispersed in the mammillary region, anterior hypothalamus, preoptic areas, septum, diagonal band of Broca, and olfactory tracts; they were occasionally observed in the dorsal hypothalamus, organum vasculosum of the lamina terminalis (OVLT), habenula, amygdala, and cingulate gyrus. LH-RH-immunoreactive fibers projected heavily to the median eminence, infundibular stalk, and posterior pituitary. In extrahypothalamic areas, these fibers were especially abundant in the stria medullaris/habenula and stria terminalis/amygdala, but also contributed to the diagonal band of Broca and the olfactory tracts. Immunoreactive fibers that may be components of many different pathways clustered in the rostral septum and permeated the medial hypothalamus. LH-RH-containing fibers frequently entered the subfornical organ, but were observed less often in the OVLT and only occasionally in the pineal. The organization of the LH-RH system in the little brown bat resembles that of primates, but differs considerably from that in the rat. Anatomical characteristics of the LH-RH system in bats thus suggest that this animal may be a particularly suitable species for further study of neuroendocrine control of reproductive function as it may relate to primates, including humans.

Amygdala↗
PubMed1981

Blood oxygen transport and organ weights of small bats and small non-flying mammals.

Blood oxygen transport properties and organ weights of five bat species in the weight range between 4.8 and 150 g have been investigated and compared to four similar-size non-flying mammals. In addition allometric organ weight-body weight relations have been compiled for both groups. All bats had higher relative heart weights than the terrestrial mammals. In both groups the relative heart weight increased with decreasing body weight. In bats hemoglobin concentrations (18.2--24.4 g Hb/dl), hematocrits (51--63%), and red blood cell counts (11.0 x 10(6)--26.2 x 10(6) RBC/microliter) were remarkably increased compared to non-flying mammals (15.3--17.4 g Hb/dl, 44--50% Hct, 8.8 x 10(6)--18.3 x 10(6) RBC/microliters). The highest values have been found in the smallest european bat Pipistrellus pipistrellus (4.8 g), they exceeded by far the results of the smallest terrestrial mammal, the shrew Suncus etruscus (2.5 g). Oxygen half saturation pressures and Bohr factors did not show considerable differences between similar-size flying and non-flying mammals. Our results indicate that the higher specific oxygen uptake of flying bats compared to exercising non-flying mammals is mainly enabled by larger hearts and larger blood oxygen capacities.

Animals↗
PubMed1987

Analysis of suppressor factor in delayed immune responses of a bat, Pteropus giganteus.

Bat spleen and mesenteric lymph node cell cultures treated with varying doses of LPS showed significant blastogenic and DNA synthetic responses between 72-96h. Peak responses were not different when the cell culture medium was supplemented either with autologous serum or heterologous serum indicating the absence of any significant suppressor factor in autologous bat serum. In contrast, blastogenesis and DNA synthesis peaks appeared early, at 48h, in lymphocytes depleted of suppressor T cells by pretreatment with cyclophosphamide. Direct antibody producing cells against SRBC were studied in normal spleen and mesenteric lymph node cell cultures. The peak PFC response was lacking even at 120h while CY pretreated bat lymphocytes, showed peak PFC responses at 96h. Thus the delayed immune response in bats seems to be a function of suppressor T cells but serum suppressor factor(s) possibly exerts no significant effect. The function of suppressor cells in bats in relation to their role as carriers of several dreaded bacteria and viruses is discussed.

Animals↗
PubMed1982

Concentrations of lactate and pyruvate and temperature effects on lactate dehydrogenase activity in the tissues of the big brown bat (Eptesicus fuscus) during arousal from hibernation.

1. The rectal temperatures, steady state concentrations of lactate and pyruvate, and the LDH isoenzyme composition in the heart, liver, and pectoral muscle of hibernating and arousing Eptesicus fuscus were measured. 2. Bat rectal temperature increased from 8.86 to 33.1 degrees C during arousal. 3. During arousal, steady state concentrations of pyruvate and lactate increased significantly in the tissues, however they remained generally below the level necessary to saturate LDH at the respective temperature. 4. The activities of the two LDH isoenzymes, M4, the predominant form in bat liver, and H4, the main form in bat heart and pectoral muscle, show substrate-dependent temperature effects described by the equation, mu = (E beta S + E alpha K t)/(K t + S). 5. Temperature effects (mu) on bat LDH activity increased during arousal but remained significantly lower than mu determined at saturating concentrations of substrate (E beta). 6. The parameters E beta-E alpha, E alpha and K tau are particularly important in describing the temperature dependence of LDH activity in tissues of the arousing bat.

Animals↗
PubMed1992

Intestinal disaccharidases in five species of phyllostomoid bats.

1. Intestinal disaccharidases were studied in nectarivorous (Leptonycteris curasoae and Glossophaga soricina), frugivorous (Artibeus jamaicensis and Sturnira lilium), and insectivorous (Pteronotus personatus) adult bats. 2. Adult bats lacked measurable lactase activity. With the exception of trehalase activity, which was present only in P. personatus, nectar- and fruit-eating bats exhibited higher disaccharidase activities standardized by intestinal nominal area than insect-eating P. personatus. 3. Maltase and sucrase activities were significantly linearly correlated. 4. Apparent affinity of sucrase varied almost 5-fold among species. This variation may reflect unstirred layer effects resulting from sucrase being a membrane bound enzyme rather than differences in the "true" affinity of sucrase in solution. 5. Passerine birds showed higher maltase activity per unit of sucrase activity than bats and hummingbirds. Maximal sucrase and maltase activities standardized per intestinal nominal area are 1.5-2 times higher in hummingbirds than in nectar-feeding bats.

Animals↗
PubMed1990

Cochlear resonance in the mustached bat: behavioral adaptations.

Mustached bats, Pteronotus p. parnellii, use complex, multiharmonic biosonar signals with prominent approx. 60 kHz (CF) components. The sense of hearing is especially acute to sounds near 60 kHz and the cochlea shows a number of specializations in the 60 kHz region. Foremost is a remarkable degree of cochlear resonance. In this study it is shown that: 1) any sounds near the resonance frequency elicit a pronounced resonance that continues after the stimulus terminates; 2) Doppler-shifted echoes of the bat's own cries may cause resonance; 3) continuous resonance can be produced by stimulating the ear with broadband noise but such resonance does not interfere with the bat's ability to Doppler-shift compensate during simulated flight; 4) significant changes in the resonance frequency of the cochlea occur during and after flight; 5) the changes in resonance can be dependent or independent of body temperature changes; and 6) mustached bats continuously adjust the CF component of their pulses to keep the second harmonic echoes in a constant frequency band near the resonance frequency. Thus, mustached bats not only compensate for Doppler-shifts imposed by their movements relative to that of a target, but they cochlear resonance compensate to deal with small changes in the micromechanical properties of the cochlea.

Animals↗
PubMed1996

Monaural and binaural spectral cues created by the external ears of the pallid bat.

The acoustic properties of external ears transform the spectra of incident sound in a location-dependent manner, and provide monaural and binaural spectral information used in 2-dimensional localization. Human studies suggest that binaural spectral differences, and spectral peaks and notches in monaural transfer functions, may all provide spatial information. This study examined the acoustic properties of the pallid bat ear to determine directionality, interaural intensity differences spectral peaks and notches in transfer functions, as well as acoustic gain. The pallid bat is a gleaning bat that uses passive sound localization to find prey, and echolocation for general orientation. It is capable of very accurate passive sound localization, and the primary focus of this study was to determine the spectral cues that might support this localization acuity. Results show that the external ears of this bat create spectral maxima and minima that vary systematically with azimuth and elevation. The monaural spectral cues resemble those reported in humans and cats and suggest that similar spectral cues are used across taxa. The ears also create robust interaural spectral differences that vary systematically with both sound azimuth and elevation. These monaural and binaural spectral cues may provide the basis for the 1 degrees angular resolution apparent in it this bat's passive sound localization performance.

Acoustic Stimulation↗
PubMed1991

Preparation, radiolabeling and biodistribution of a new class of bisaminothiol (BAT) ligands as possible imaging agents.

In developing new ligands as potential brain and heart perfusion imaging agents two ligands based upon N2S2 donor atoms with the biphenyl backbone were synthesized. Biphenyl-2,2'-bis(N-1-amino-2-methyl-propane-2-thiol) (BP-BAT-TM) and biphenyl-2,2'-bis(N-1-amino-2-ethyl-butane-2-thiol) (BP-BAT-TE) form stable, neutral and lipid soluble complexes with [99mTc]pertechnetate in the presence of tin(II) tartarate as a reducing agent. The [99mTc]BP-BAT-TM complex penetrates the blood-brain barrier following i.v. injection into rats. Washout from the brain is fast, indicating no retention. The biodistribution of [99mTc]BP-BAT-TE in rats showed an initial heart uptake (0.8%/organ, at 2 min) and a slow washout (0.74% at 15 min). No brain uptake was found (0.05%). Significant uptake and retention in liver was observed. An imaging study of [99mTc]BP-BAT-TE in a monkey showed no brain uptake and a clear indication of liver uptake and gall bladder clearance. These results indicate that this ligand system may be suitable as the basic core structure for the development of new imaging agents. Further studies with structural variations in the biphenyl backbone are warranted to develop new 99mTc imaging agents for clinical applications.

Animals↗
PubMed2005

Is humanlike cytoarchitectural asymmetry present in another species with complex social vocalization? A stereologic analysis of mustached bat auditory cortex.

Considerable evidence suggests that left hemispheric lateralization for language comprehension in humans is associated with cortical microstructural asymmetries. However, despite the fact that left hemispheric dominance for the analysis of species-specific social vocalizations has been reported in several other species, little is known concerning microstructural asymmetries in auditory cortex of nonhumans. To test whether such neuroanatomical lateralization characterizes another species with complex social vocalizations, we performed stereologic analyses of Nissl-stained cells in layer III of area DSCF in mustached bats (Pteronotus parnellii). Area DSCF was selected because it contains neurons which are sensitive to several temporal features of conspecific vocalizations. Primary visual cortex (V1) was also studied as a comparative reference. We measured neuron densities, glial densities, and neuronal volumes in both hemispheres of 10 adult male bats. Results indicate that these variables are not significantly lateralized in area DSCF or V1. Additionally, magnopyramidal cells (i.e., the largest 10% of neurons from both hemispheres) were not asymmetric in their frequency of distribution at the population level. Although several individual bats had asymmetric neuron distributions, consistent hemispheric bias was not evident. Absence of population-level microstructural asymmetry in area DSCF of mustached bats suggests alternative evolutionary scenarios including: (1) microstructural lateralization of auditory cortical circuitry may be a unique adaptation for human language, and (2) the specialized biosonar function of mustached bat auditory cortex may require symmetrical cytoarchitectural structure. Resolution of these alternatives will require further data on the microstructure of auditory cortex in species with lateralized perception of acoustic social communication.

Adaptation, Physiological↗
PubMed2005

BAT monoclonal antibody immunotherapy of human metastatic colorectal carcinoma in mice.

BAT monoclonal antibody exhibited anti-tumor activity mediated by T and NK cells. We have evaluated the efficacy of murine and humanized BAT for the treatment of human colorectal carcinoma liver metastases in nude mice. HM7, a human colorectal carcinoma was injected into the spleen to colonize the liver. A single intravenous administration of both BAT antibodies significantly reduced the number of metastases and liver weights. Histological examinations demonstrated lymphocyte accumulation near remnant tumors and in tumor-free tissues of BAT treated mice. The efficacy of humanized BAT in the regression of hepatic metastases in human colorectal carcinoma has potential clinical use.

Animals↗
PubMed2004

Role of urea in the postprandial urine concentration cycle of the insectivorous bat Antrozous pallidus.

Insectivorous bats, which feed once daily, produce maximally concentrated urine only after feeding. The role of urea as an osmolyte in this process was investigated in pallid bats (Antrozous pallidus) in the laboratory. Following a 24-h fast, plasma and urine were sampled before and 2 h after feeding in postprandial (PP) animals and before and 2 h after similar treatment without feeding in nonfed (NF) animals. Food consumption by PP animals and handling of NF animals had no effect on blood water content as measured by hematocrit and plasma oncotic pressure. Food consumption increased both plasma osmolality (P(osm)) and plasma urea (P(urea)) by as much as 15%. Food consumption also increased urine osmolality (U(osm)) and urine urea (U(urea)) by 50-100%. Feeding increased U(osm) regardless of changes in P(osm), and elevation of U(osm) resulted primarily from increased U(urea). In NF bats, P(osm) and P(urea) were unchanged, while U(osm) and U(urea) increased by as much as 25%. Again, increased U(osm) resulted primarily from increased U(urea). The PP urine concentration cycle of pallid bats resulted from increased urea excretion in response to apparent rapid urea synthesis. Bats rapidly metabolized protein and excreted urea following feeding when body water was most plentiful.

Animals↗
PubMed2006

Effect of fasting on carbohydrate metabolism in frugivorous bats (Artibeus lituratus and Artibeus jamaicensis).

The compensatory changes of carbohydrate metabolism induced by fasting were investigated in frugivorous bats, Artibeus lituratus and Artibeus jamaicensis. For this purpose, plasma levels of glucose and lactate, liver and muscle glycogen content, rates of liver gluconeogenesis and the activity of related enzymes were determined in male bats. After a decrease during the first 48 h of fasting, plasma glucose levels remained constant until the end of the experimental period. Plasma lactate levels, extremely high in fed bats, decreased after 48 h of fasting. Similarly, liver glycogen content, markedly high in fed animals, was reduced to low levels after 24 h without food. Muscle glycogen was also reduced in fasted bats. The expected increase in liver gluconeogenesis during fasting was observed after 48 h of fasting. The activities of liver glucose-6-phosphatase and fructose-1,6-bisphosphatase were not affected by food withdrawn. On the other hand, fasting for 24 h induced an increase in the activity of liver cytosolic phosphoenolpyruvate carboxykinase. The data indicate that liver gluconeogenesis has an important role in the glucose homeostasis in frugivorous bats during prolonged periods of food deprivation. During short periods of fasting liver glycogenolysis seems to be the main responsible for the maintenance of glycemia.

Animals↗
PubMed2006

Integrative models of bat rabies immunology, epizootiology and disease demography.

Bats are natural reservoirs of rabies. We address the maintenance of the disease in bat colonies by developing individual and population models that generate indicators of risk of rabies to bats, that provide dynamic estimates of effects of rabies on population densities, and that suggest consequences of viral exposures and infections in bats relative to physiological and ecological characteristics of bats in different habitats. We present individual models (within host) for the immune responses to a rabies virus challenge, an immunotypic disease model that describes the evolution of the disease and a disease demographics model, which is structured by immunotypic response governed by immune system efficiency. Model simulations are consistent with available data, characterized by relatively low prevalence of the virus in colonies and much higher prevalence of rabies virus-neutralizing antibodies. Under model conditions, there is a robust non-clinical state that can be attained by the exposed individual that allows persistence of the disease in the population.

Animals↗