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PubMed1991

Spontaneous decidual reactions and menstruation in the black mastiff bat, Molossus ater.

Uterine function was assessed histologically in nonpregnant Molossus ater removed from a laboratory breeding colony. During the luteal phase of the cycle, bilateral decidual reactions were found to develop spontaneously in the absence of either embryos or experimental manipulation of the uterus. These included the formation of early decidual giant cells, closure of the uterine lumina, and morphological changes in the endometrial blood vessels. Some endothelial cell hypertrophy was noted in much of the decidua, but this was most pronounced in vessels associated with an unusual vascular tuft that formed in the endometrium surrounding the cranial end of the uterine lumen. These latter vessels also developed very prominent basal laminae. In pregnant bats, this tuft played a central role in the morphogenesis of the definitive discoidal chorioallantoic placenta. At the end of nonpregnant cycles, the decidua became necrotic and was sloughed off with associated bleeding. As in menstruating catarrhine primates, the endometrium of M. ater is vascularized by spiral arterioles and populated by distinctive granulocytes containing large, acidophilic granules. Increased coiling of these arterioles did not appear to be an essential element in the mechanism of mensturation in this species. M. ater is a monotocous, seasonal breeder, with a relatively long gestation period. Although it has a bicornuate uterus, ovulation and implantation appear to occur only on the right side of the tract. The ability to menstruate probably affords this bat an efficient mechanism for eliminating a highly differentiated endometrium from the usual implantation site in the event of a reproductive failure. In the wild, this may provide M. ater with another chance to establish a pregnancy at a still opportune time during the same breeding season.

Animals↗
PubMed1975

Early embryology and implantation in the California leaf-nosed bat, Macrotus californicus.

Female reproductive tracts from 84 bats were examined by light and/or electron microscopy to electron microscopy to observe early embryology and implantation in Macrotus. The earliest pregnancy was observed in October and by the end of October all bats were pregnant. Implantation had begun in most specimens from late October. In late November females were carrying implanted blastocysts in which differentiation of endoderm was noted. Reichert's membrane was first observed in November. In early December the trophoblast had begun to differentiate into cytotrophoblast and syncytiotrophoblast and by the end of January this differentiation was most evident. Reichert's membrane persisted until late January. Endoderm in the January sample completely surrounded the yolk sac cavity. By late February the embryos were at the embryonic disc stage had differenitated mesoderm. The uterine-fetal relationship was complex and an early placenta was recognized. In late March the embryos spanned a range of development from neural plate to limb-bud stages. Parturition occurred in June. This lengthy gestation period is characterized by an embryonic diapause of approximately four and one-half months. The roles of food supply and/or temperature in controlling this growth rate and the evolutionary implications of this development are discussed.

Amnion↗
PubMed1976

Erythropoiesis in the yolk sac of the bat Tadarida brasiliensis cynocephala.

The process of erythropoiesis and vasculogenesis in the yolk sac of the bat (Tadarida brasiliensis cynocephala) has been studied through the use of both light and electron microscopy. Stem cells arise from the leading edge of the migrating splanchnic mesoderm and transform into primitive erythroblasts. Differentiation involves either contact or association with the endodermal cells, since all erythropoietic activity occurs on the endodermal side of the expanding vascular bed, and many of the cells are in close apposition to the lateral or basal plasma membranes of the endodermal cells. Endodermal cells also phagocytize developing primitive erythroblasts during the later stage of the process when erythropoiesis is subsiding in the yolk sac. Cells destined to become the endothelium of the expanding vascular bed also arise from the leading edge of the migrating splanchnic mesoderm. Their process of differentiation involves the development of cytoplasmic extensions that may surround a group of differentiating erythroblasts, enclosing them in the newly formed lumen of the blood vessel. The cytoplasmic extensions make contact and develop junctional complexes with similar processes from other cells to complete the lumen of the lengthening vascular bed. Cells of the granulocyte series or megakaryocytes are not observed in the yolk sac of the bat as has been described in certain other species.

Animals↗
PubMed1984

Ultrastructure of the parotid gland in the little brown bat.

The ultrastructure of the parotid gland was examined in the little brown bat. The seromucous acinar cells contained abundant granules of variable morphology. These granules were characterized by a submembranous dense layer consisting of fine parallel slats. In some bats, the matrix of the granules was structureless, whereas in others it consisted of closely packed but randomly arranged bundles of tubules. The intercalated ducts had a highly developed rough endoplasmic reticulum, often containing large numbers of intracisternal granules. In contrast, only a few secretory granules were present in the supranuclear cytoplasm. The striated ducts, which exhibited the characteristic basal striations consisting of vertically oriented mitochondria and highly folded plasmalemmas, contained numerous small dense granules in a subluminal band. These granules had a paracrystalline substructure with a periodicity of 8 nm. Excretory ducts strongly resembled striated ducts. They showed the same kind of basal striations and about half their constituent cells contained small paracrystalline granules.

Animals↗
PubMed1995

Special relationship between mitochondria and hypolemmal nerve terminals in salivary glands of some bats.

BACKGROUND: Hypolemmal nerve terminals, which are abundant in many types of salivary glands, are naked axons that have penetrated the basement membrane to take up a position between adjacent parenchymal cells. Although they may form vesicle-filled varicosities, there usually are no obvious morphological indications as to which cell actually is being innervated. METHODS: Specimens of over 200 species of bats were live-trapped and their major salivary glands extirpated and prepared for electron microscopic examination. RESULTS: In 13 species of bats out of the more than 200, mitochondria-hypolemmal nerve terminal complexes were observed in different sites in different salivary glands. In these 13 species, mitochondria in epithelial cells that abut nerve varicosities are closely applied to the plasma membranes of their cells to follow the contours of these nerve elements. The complexes so formed often consist of a varicosity flanked by two mitochondria in separate cells. In intensely innervated glandular segments, mitochondria may be opposed not only to varicosities, but to the axonal portions of these nervous elements as well. CONCLUSIONS: The physiological significance of such complexes is unknown; it is conceivable that the mitochondria facilitate signal transmission or play a role in local calcium homeostasis related to nerve function.

Animals↗
PubMed2006

Terminal nerve in the mouse-eared bat (Myotis myotis): ontogenetic aspects.

As in other mammals, ontogenesis of the terminal nerve (TN) in the mouse-eared bat (Myotis myotis) starts shortly after the formation of the olfactory placode, a derivative of the ectoderm. During development of the olfactory pit, proliferating neuroblasts thicken the placodal epithelium and one cell population migrates toward the rostroventral tip of the telencephalon. Here they accumulate in a primordial terminal ganglion, which successively divides into smaller units. Initial fibers of the TN can be distinguished from olfactory fibers in the mid-embryonic period. The main TN fiber bundle (mfb) originates from the anteriormost ganglion in the nasal roof, whereas one or more inconstant smaller fiber bundles (sfb) originate from one or more smaller ganglia in the basal part of the rostral nasal septum. The fibers of the mfb and sfbs join in the posterior quarter of the nasal roof before reaching the central ganglion (M) located in the meninges medial to the olfactory bulb. From the mid-fetal period onward, a thin TN fiber bundle with some intermingled perikarya connects M to the brain by penetrating its wall rostral to the olfactory tubercle. Additional smaller ganglia may occur in this region. The TN and its ganglia persist in postnatal and adult bats but the number of perikarya is reduced here. Moreover, the different potential functions of the TN are discussed briefly.

Aging↗
PubMed2004

Organization of the main olfactory bulbs of some mammals: musk shrews, moles, hedgehogs, tree shrews, bats, mice, and rats.

We immunohistochemically examined the organization of the main olfactory bulbs (MOBs) in seven mammalian species, including moles, hedgehogs, tree shrews, bats, and mice as well as laboratory musk shrews and rats. We focused our investigation on two points: 1) whether nidi, particular spheroidal synaptic regions subjacent to glomeruli, which we previously reported for the laboratory musk shrew MOBs, are also present in other animals and 2) whether the compartmental organization of glomeruli and two types of periglomerular cells we proposed for the rat MOBs are general in other animals. The general laminar pattern was similar among these seven species, but discrete nidi and the nidal layer were recognized only in two insectivores, namely, the mole and laboratory musk shrew. Olfactory marker protein-immunoreactive (OMP-IR) axons extended beyond the limits of the glomerular layer (GL) into the superficial region of the external plexiform layer (EPL) or the nidal layer in the laboratory musk shrew, mole, hedgehog, and tree shrew but not in bat, mouse, and rat. We observed, in nidi and the nidal layer in the mole and laboratory musk shrew MOBs, only a few OMP-IR axons. In the hedgehog, another insectivore, OMP-IR processes extending from the glomeruli were scattered and intermingled with calbindin D28k-IR cells at the border between the GL and the EPL. In the superficial region of the EPL of the tree shrew MOBs, there were a small number of tiny glomerulus-like spheroidal structures where OMP-IR axons protruding from glomeruli were intermingled with dendritic branches of surrounding calbindin D28k-IR cells. Furthermore, we recognized the compartmental organization of glomeruli and two types of periglomerular cells in the MOBs of all of the mammals we examined. These structural features are therefore considered to be common and important organizational principles of the MOBs.

Animals↗
PubMed2007

Connections of functional areas in the mustached bat's auditory cortex with the auditory thalamus.

The auditory thalamus is the major target of the inferior colliculus and connects in turn with the auditory cortex. In the mustached bat, biosonar information is represented according to frequency in the central nucleus of the inferior colliculus (ICc) but according to response type in the cortex. In addition, the cortex has multiple areas with neurons of similar response type compared to the single tonotopic representation in the ICc. To investigate whether these transformations occur at the level of the thalamus, we injected anatomical tracers into physiologically defined locations in the mustached bat's auditory cortex. Injections in areas used for target ranging labeled contiguous regions of the auditory thalamus rather than separate patches corresponding to regions that respond to the different harmonic frequencies used for ranging. Injections in the two largest ranging areas produced labeling in separate locations. These results indicate that the thalamus is organized according to response type rather than frequency and that multiple mappings of response types exist. Injections in areas used for target detection labeled thalamic regions that were largely separate from those that interconnect with ranging areas. However, injections in an area used for determining target velocity overlapped with the areas connected to ranging areas and areas involved in target detection. Thus, separation by functional type and multiplication of areas with similar response type occurs by the thalamic level, but connections with the cortex segregate the functional types more completely than occurs in the thalamus.

Acoustic Stimulation↗
PubMed1980

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.

Animals↗
PubMed1986

Somatosensory cortical representation in the Australian ghost bat, Macroderma gigas.

Bats of the two suborders Microchiroptera and Megachiroptera have a modified hand in which the digits of the forelimb are caudally oriented to form the wing. In a previous study of a megachiropteran species, this modification of body plan was found to be reflected in the somatosensory cortical representation such that the orientation of the digit representation was reversed compared with walking mammals. This finding suggests that the precise details of arrangement of topographical maps are functionally significant and do not merely reflect an order imposed by peripheral innervation. Recent evidence for separate origins of Microchiroptera and Megachiroptera raises the question of whether the cortical somatosensory representation in Microchiroptera will also have a reversal of digit orientation compared with walking mammals. We recorded multiunit activity from the somatosensory cortex of a microchiropteran bat, Macroderma gigas. We found two orderly representations of the body surface, SI and SII, in both of which the digit orientation was opposite to the head orientation in accordance with adaptation for flight, and reversed with respect to equivalent maps in other mammals. We also found minor variations in body surface representation compared with Megachiroptera, in line with their proposed independent evolution.

Animals↗
PubMed1987

Subcortical connections of the superior colliculus in the mustache bat, Pteronotus parnellii.

The mustache bat, Pteronotus parnellii, depends on echolocation to navigate and capture prey. This adaptation is reflected in the large size and elaboration of brainstem auditory structures and in the minimal development of visual structures. The superior colliculus, usually associated with orienting the eyes, is nevertheless large and well developed in Pteronotus. This observation raises the question of whether the superior colliculus in the echolocating bat has evolved to play a major role in auditory rather than visual orientation. The connections of the superior colliculus in Pteronotus were studied with the aid of anterograde and retrograde transport of wheat germ agglutinin conjugated to HRP. These results indicate that the superior colliculus of Pteronotus is composed almost entirely of the layers beneath stratum opticum. The retinal projection is restricted to a very thin zone just beneath the pial surface. Prominent afferent pathways originate in motor structures, particularly the substantia nigra and the deep nuclei of the cerebellum. Sensory input from the auditory system originates in three brainstem nuclei: the inferior colliculus, the anterolateral periolivary nucleus, and the dorsal nuclei of the lateral lemniscus. The projections from these auditory structures terminate mainly in the central tier of the deep layer. The most prominent efferent pathways are those to medial motor structures of the contralateral brainstem via the predorsal bundle and to the ipsilateral midbrain and pontine tegmentum via the lateral efferent bundle. Ascending projections to the diencephalon are mainly to the medial dorsal nucleus and zona incerta. Thus, the superior colliculus in Pteronotus possesses well-developed anatomical connections that could mediate reflexes for orienting its ears, head, or body toward objects detected by echolocation.

Afferent Pathways↗
PubMed1987

Different origins of cochlear efferents in some bat species, rats, and guinea pigs.

The origin of olivocochlear efferents was studied in the rat, the guinea pig, and the bats Rhinolophus, Rhinopoma, Tadarida, and Phylostomus by retrograde labeling with HRP and the fluorescent dye fast blue. In all species with the exception of Rhinolophus rouxi two types of cochlear efferents could be found: small neurons located in the lateral superior olive (LSO) and larger ones located bilaterally in the periolivary region. In bats and rats small olivocochlear neurons (OCN) were found only in the ipsilateral LSO. In guinea pigs some small OCN were found also in the contralateral LSO. Large OCN were found in all animals except Rhinolophus. They were organized in a horseshoelike nucleus that extended in a rostrocaudal direction and bent rostrally around the medial superior olive (MSO). This nucleus contains several periolivary nuclei described separately by other authors. In Rhinol. rouxi somata of all olivocochlear efferents are concentrated in a single nucleus between the MSO and LSO, which we therefore call the nucleus olivocochlearis. This nucleus stains for acetylcholinesterase. We consider its neurons to be similar to small OCN, because they are small, associated with the LSO, and only ipsilaterally labeled. This fits well with the fact that Rhinolophus lacks an efferent innervation of outer hair cells (Bishop: Ph.D. Thesis, University of North Carolina, Chapel Hill, '86; Bruns and Schmieszek: Hear. Res. 3:27-43, '80), which are normally innervated by large OCN (Guinan et al: J. Comp. Neurol. 221:358-370, '83).

Amidines↗
PubMed1989

Central acoustic tract in an echolocating bat: an extralemniscal auditory pathway to the thalamus.

To determine the sources and targets of auditory pathways that bypass the inferior colliculus in the mustache bat, we injected WGA-HRP in the medial geniculate body and related auditory nuclei of the thalamus as well as in the lower brainstem. We used electrophysiological methods to verify that the injection electrode was in an area responsive to sound. The only thalamic injections that produced retrograde transport to cells in auditory nuclei caudal to the inferior colliculus were those that included the suprageniculate nucleus. These injections labeled a group of large multipolar cells lying between the ventral nucleus of the lateral lemniscus and the superior olivary complex. Neurons in this cell group have also been shown to project to the deep layers of the superior colliculus in the mustache bat. The pathway revealed by these studies is almost identical to the "central acoustic tract" in which fibers course medial to the lateral lemniscus and bypass the inferior colliculus to reach the deep superior colliculus and the suprageniculate nucleus.

Animals↗
PubMed1992

Frequency tuning properties of neurons in the inferior colliculus of an FM bat.

We examined frequency tuning characteristics of single neurons in the inferior colliculus of the echolocating bat, Eptesicus fuscus, in order to determine whether there are different classes of spectral selectivity at this level and to relate frequency tuning properties to the design of the echolocation signal. In unanesthetized but tranquilized animals, we recorded responses from 363 single units to pure tones, frequency-modulated (FM) sweeps, or broad-band noise. Most units were selective for stimulus type; 50% responded only to pure tones, 14% responded only to FM sweeps, and 5% responded only to noise. The remainder responded to two or more types of stimuli. Tuning curves could be classified as follows: 1) V-shaped tuning curves (57%) were the most common type; 2) closed tuning curves (20%) had thresholds at both low and high sound levels; 3) narrow filters (14%) had Q values above 20 at 10 dB and 30 dB above threshold or 10 dB and 40 dB above threshold; 4) frequency-opponent tuning (6%) was found in units with high spontaneous activity; within a center range of frequencies, firing rate increased above spontaneous level, but at higher or lower frequencies, firing rate decreased below spontaneous level; 5) double-tuned units (3%) had two best frequencies (BF). The most clear evidence of topographic distribution was seen for filter units, which were only found in the dorsal part of the 20-30 kHz isofrequency contour. Filter units were also the most clearly related to the echolocation signal of the bat. Their BFs were all within the range of the dominant frequency (approximately 20-30 kHz) that Eptesicus uses during the searching phase of echolocation.

Acoustic Stimulation↗
PubMed1994

Projections of physiologically defined subdivisions of the inferior colliculus in the mustached bat: targets in the medial geniculate body and extrathalamic nuclei.

This study examined the output of the central nucleus of the inferior colliculus to the medial geniculate body and other parts of the nervous system in the mustached bat (Pteronotus parnellii). Small deposits of anterograde tracers (horseradish peroxidase, [3H]leucine, Phaseolus vulgaris leucoagglutinin, wheat germ agglutinin conjugated to horseradish peroxidase, or biocytin) were made at physiologically defined sites in the central nucleus representing major components of the bat's echolocation signal. The topography, frequency specificity, and axonal morphology of these outputs were studied. The medial geniculate body was a major target of inferior collicular neurons, with three distinct input patterns. The projection to the ventral division was tonotopically organized, but had a relatively sparse contribution from neurons representing frequency modulated components of the biosonar pulse. The second input was to the rostral medial geniculate body, in which projections from inferior collicular neurons representing constant frequency sonar components were separated from those representing frequency modulated components. A third input was to the suprageniculate nucleus, which received strong, topographically arranged projections. Inputs to the dorsal nucleus and medial division were also observed. Extrathalamic regions receiving input included the pontine gray, external nucleus of the inferior colliculus, pericollicular tegmentum, nucleus of the brachium of the inferior colliculus, and pretectum. These central nucleus projections differed in organization and the structure of axon terminals, suggesting different physiological influences on their target nuclei. These results demonstrate that the central nucleus has divergent projections to various sensory and premotor nuclei, besides its well-established projection to the medial geniculate body.

Acoustic Stimulation↗
PubMed1990

The black mastiff bat (Molossus ater): a novel, mammalian model for studies of ovarian, uterine, and placental biology.

The reproductive biology of the black mastiff bat has been examined using animals maintained in a laboratory colony. Ovulation was found to be spontaneous and occurred only from the right ovary. The corpora lutea appeared to be functional, and decidual reactions developed in the uterus during the luteal phase of the cycle even in the absence of an implanting blastocyst. At the end of nonpregnant, ovulatory cycles much of the endometrium became necrotic and was desquamated with associated bleeding. In the event of pregnancy only a single blastocyst implanted in the right uterine horn, and the discoidal chorioallantoic placenta then developed at the cranial end of that horn. This was preceded by the development of an unusual vascular tuft in the endometrium in that region. The endothelial cells of the tuft vessels became hypertrophied during early pregnancy and developed more prominent basal laminae. Trophoblast then grew preferentially around these vessels. These observations suggest that factors secreted by endometrial endothelial cells and incorporated at least in part into their basal laminae may play a central role in controlling early trophoblastic growth during the morphogenesis of the discoidal chorioallantoic placenta in this bat.

Animals↗
PubMed1993

Basal, diurnal, and stress-induced levels of glucose and glucocorticoids in captive bats.

Plasma levels of glucocorticoids and glucose were measured in three species of fruit bats (Chiroptera) sampled from captive populations. Three species of Old World bats (Pteropus vampyrus, P. Hypomelanus, and Rousettus aegyptiacus) had plasma levels of glucose that were within the normal mammalian range (80-100 mg/dl), with no difference between males and females. All animals had detectable levels of one or both of the major glucocorticoids (cortisol and corticosterone) found in mammals. Steroid levels were highest in P. hypomelanus (cortisol: 1,269 +/- 207 ng/ml; corticosterone; 590 +/- 154 ng/ml) and lowest in R. aegyptiacus (corticosterone: 36 +/- 4 ng/ml; cortisol not determined). Diurnal changes in these steroids and the effects of handling and restraint stress were further investigated in P. hypomelanus. Experimental animals were captured in their roost quarters, bled once by venupuncture within 3 min, placed singly into a small holding chamber for 50-60 min, and bled again. This procedure was performed at four different times over the course of 24 h with different groups of animals. Glucose was at a minimum just before and a maximum just after the period of food presentation. Cortisol levels remained relatively constant throughout the day-roosting period and significantly declined to their lowest level in the period following food presentation. As expected, the effects of handling and isolation caused a significant increase in both plasma cortisol and glucose levels. When individual P. hypomelanus were subjected to 3 h restraint stress in small plastic wire-mesh restraining devices, cortisol levels rose approximately 800% by 2 h, with the first significant increase at 20 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Cortex↗
PubMed2006

Differential expression of selected mitochondrial genes in hibernating little brown bats, Myotis lucifugus.

High rates of non-shivering thermogenesis by brown adipose tissue accompanied by additional shivering thermogenesis in skeletal muscle provide the powerful reheating of body organs that allows hibernating mammals to return from their state of cold torpor back to euthermic function. Previous studies have suggested that changes to brown adipose mitochondria occur during hibernation and are partially responsible for its capacity for non-shivering thermogenesis. The current study shows that selected mitochondrial enzyme activities are elevated and selected genes and proteins are induced during torpor in brown adipose tissue of the little brown bat, Myotis lucifugus. Cytochrome oxidase activity in brown adipose tissue was more than 3-fold higher during torpor than in euthermic animals. Transcript levels of mitochondria-encoded genes, coxII and nad4, were also 3-4-fold higher during torpor, as evidenced by northern blotting. By contrast, transcripts of these genes were unchanged in skeletal muscle during torpor. Protein levels of carnitine palmitoyl transferase-1beta, an enzyme embedded in the outer membrane of the mitochondria that is the rate-limiting step enzyme in beta-oxidation, were also elevated by 2-fold during torpor in brown adipose but were unchanged in skeletal muscle. Cloning and sequencing of a 624 bp segment of cpt-1beta revealed a number of amino acid substitutions in the bat protein as compared to CPT-1beta from other mammals; these may be beneficial for enzyme function at low body temperatures during torpor. This study provides further evidence for a key role of mitochondria in hibernation.

Adipose Tissue, Brown↗