Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The eardrum and the auditory ossicles of the middle ear, and the population of cochlear receptors in subterranean mole-rats of Spalax ehrenbergi complex were qualitatively and quantitatively analyzed. The area of the eardrum was 10.2 (S.D. = 0.9) mm2, that of the stapedial footplate 0.6 (S.D. = 0.07) mm2, the malleus: incus lever ratio was 1.25:1. The malleus is simply built, not attached to the tympanic ring. The incus is large; its long process is almost parallel to the manubrium of the malleus. The short process of the incus is provided with a peculiar bony cap, a structure thus far undescribed in mammalian auditory ossicles. Firmness of mutual connection of the ossicles may vary among different forms of Spalax. The size and form of the stapes are characterized by a large variability as well. The length of the basilar membrane was 12.6 (S.D. = 0.7) mm. The mean density of inner hair cells amounted to 93.3 that of outer hair cells to 386.4 cells per mm of the basilar membrane length. In general, the density increased from the base towards the apex. On average there were 415 outer, 100 inner hair cells in the organ of Corti; the ratio being constant along the basal 65% of the length and decreasing in the apical part of the organ of Corti. The radial width of the triad of outer hair cells increased and remained constant along the apical half of the Corti organ. Based on available findings of comparative and functional morphology, most of the studied features may be considered correlates of low-frequency tuning of the hearing organ in mole-rats.
 ...
PMID:Middle ear and cochlear receptors in the subterranean mole-rat, Spalax ehrenbergi. 275 27

Behavioral adaptations exhibited by two African fossorial mammals for the reception of vibrational signals are discussed. The Namib Desert golden mole (Eremitalpa granti namibensis) is a functionally blind, nocturnal insectivore in the family Chrysochloridae that surface forages nightly in the Namib desert. Both geophone and microphone recordings in the substrate suggest that the golden mole is able to detect termite colonies and other prey items solely using seismic cues. This animal exhibits a hypertrophied malleus, an adaptation favoring detection of low-frequency signals. In a field study of the Cape mole-rat (Georychus capensis), a subterranean rodent in the family Bathyergidae, both seismic and auditory signals were tested for their propagation characteristics. This solitary animal is entirely fossorial and apparently communicates with its conspecifics by drumming its hind legs on the burrow floor. Auditory signals attenuate rapidly in the substrate, whereas vibratory signals generated in one burrow are easily detectable in neighboring burrows. The sensitivity to substrate vibrations in two orders of burrowing mammals suggests that this sense is likely to be widespread within this taxon and may serve as a neuroethological model for understanding the evolution of vibrational communication. Neuroethological implications of these findings are discussed.
 ...
PMID:The use of seismic signals by fossorial southern African mammals: a neuroethological gold mine. 936 10

Beckwith-Wiedemann syndrome is a rare genetic overgrowth syndrome presenting with organomegaly, abdominal wall defects, macroglossia, and postnatal hypoglycemia. Head and neck manifestations of this abnormality include flame nevus of the forehead and characteristic sulci of the ear lobe. We present a 7-year-old child with Beckwith-Wiedemann syndrome and a rare finding of conductive hearing loss on both sides due to congenital malleus and stapedial fixation. Small fenestra stapedotomy and mobilization of malleus fixation in the epitympanum improved the child's hearing. The bony fixation of the malleus and stapes is explained as atavism of the processus anterior mallei and peripheral lamina stapedialis in embryological development.
 ...
PMID:Conductive hearing loss in Beckwith-Wiedemann syndrome. 1037 44

Behavioral and anatomical studies relating to possible seismic sensitivity in the desert golden mole (Eremitalpa granti) are reviewed. Field studies in the Namib desert have shown that isolated hummocks of dune grass generate low-frequency vibrations, distinct from the background noise at a distance of many meters. The golden mole apparently uses these cues to orient itself toward the hummocks and the prey species within. An analysis of middle ear morphology suggests that the massive malleus of the golden mole is adapted toward a form of inertial bone conduction, suitable for the detection of seismic cues obtained in this manner. The significance of seismic sensitivity in this golden mole is briefly discussed.
 ...
PMID:Seismic sensitivity in the desert golden mole (Eremitalpa granti): a review. 1208 10

Functionally relevant features and parameters of the outer, middle, and inner ear were studied morphologically and morphometrically in two species of voles, smaller Microtus arvalis and larger Arvicola terrestris. The findings in these fossorial (i.e., burrowing) rodents with components of surface activity were compared with respective findings reported for taxonomically related muroid rodents representing the same size classes but different eco-morphotypes: obligate subterranean rodents (Ellobius talpinus and Spalax ehrenbergi superspecies) and generalized rodents (Mus domesticus and Rattus norvegicus). The ear in voles was characterized by traits reported for subterranean rodents. The eardrum was round, without a distinct pars flaccida, and had an area of 5.4 mm2 in M. arvalis and 9 mm2 in A. terrestris. The middle ear exhibited reduced goniale, enlarged incus nearly parallel to the manubrium of the malleus. The malleus-incus lever ratio amounted to 2.1 (M. arvalis) and 2.0 (A. terrestris). The malleus-incus complex weighed about 0.8 mg in both vole species. The stapedial footplate had an area of 0.3 mm2 in M. arvalis and 0.4 mm2 in A. terrestris. The cochlea had 2.3 coils in both vole species; the basilar membrane was 8.5 mm and 10.5 mm long in M. arvalis and A. terrestris, respectively. There were on average 1,030 (M. arvalis) and 1,220 (A. terrestris) inner hair cells, and 3,760 (M. arvalis) and 4,250 (A. terrestris) outer hair cells in the organ of Corti. In quantitative terms, all these (as well as some further) traits and parameters were intermediate (related to body size) between those reported for generalized rodents on the one hand and subterranean ones on the other. The sound transmission system of the ear seems to be best tuned to frequencies of about 8-16 kHz with a high-frequency cut-off at about 50-60 kHz. The ear of A. terrestris seems to be tuned to somewhat lower frequencies than that in M. arvalis. In this aspect as well as regarding hearing sensitivity (as judged from the mechanical transmission parameters), voles can be considered intermediate not only in their lifestyle but also in their hearing abilities between the subterranean rodents (mole-vole and blind mole-rat) and the surface dwellers (house mouse and Norway rat).
 ...
PMID:Functional morphology of the ear in fossorial rodents, Microtus arvalis and Arvicola terrestris. 1548 5

Comparison between the middle ear anatomy of the Cape golden mole (Chrysochloris asiatica), which exhibits a club-shaped malleus head, and the Desert golden mole (Eremitalpa granti), with a ball-shaped malleus head, suggests differences in sensitivity to airborne sound. Scanning laser Doppler vibrometric measurements of the ossicular behavior in response to both vibration and airborne sound were made in C. asiatica. Two distinct vibrational modes were observed. In response to low-frequency vibration (70-200 Hz), the malleus oscillates about the ligament of the short process of the incus, whereas in response to high-frequency airborne sound (1-6 kHz) the ossicular chain rotates about the long axis of malleus. It is proposed that the club-shaped malleus head in C. asiatica constitutes an adaptation towards bimodal hearing-sensitivity to substrate vibrations and airborne sound. Possible functional differences between these two middle ear types are discussed.
 ...
PMID:Ossicular differentiation of airborne and seismic stimuli in the Cape golden mole (Chrysochloris asiatica). 1628 29

The hypertrophied malleus in the middle ear of some golden moles has been assumed to be an adaptation for sensing substrate vibrations by inertial bone conduction, but this has never been conclusively demonstrated. The Cape golden mole (Chrysochloris asiatica) exhibits this anatomical specialization, and the dynamic properties of its middle ear response to vibrations were the subjects of this study. Detailed three-dimensional middle ear anatomy was obtained by x-ray microcomputed tomography (muCT) at a resolution of 12 microm. The ossicular chain exhibits large malleus mass, selective reduction of stiffness and displacement of the center of mass from the suspension points, all favoring low-frequency tuning of the middle ear response. Orientation of the stapes relative to the ossicular chain and the structure of the stapes footplate enable transmission of substrate vibrations arriving from multiple directions to the inner ear. With the long axes of the mallei aligned parallel to the surface, the animal's head was stimulated by a vibration exciter in the vertical and lateral directions over a frequency range from 10 to 600 Hz. The ossicular chain was shown to respond to both vertical and lateral vibrations. Resonant frequencies were found between 71 and 200 Hz and did not differ significantly between the two stimulation directions. Below resonance, the ossicular chain moves in phase with the skull. Near resonance and above, the malleus moves at a significantly larger mean amplitude (5.8+/-2.8 dB) in response to lateral vs vertical stimuli and is 180 degrees out of phase with the skull in both cases. A concise summary of the propagation characteristics of both seismic body (P-waves) and surface (R-waves) is provided. Potential mechanisms by which the animal might exploit the differential response of the ossicular chain to vertical and lateral excitation are discussed in relation to the properties of surface seismic waves.
 ...
PMID:Middle ear dynamics in response to seismic stimuli in the Cape golden mole (Chrysochloris asiatica). 1639 52

The middle ear structures of eight species of mole in the family Talpidae (Mammalia: Eulipotyphla) were studied under light and electron microscopy. Neurotrichus, Parascalops, and Condylura have a simple middle ear cavity with a loose ectotympanic bone, ossicles of a "microtype" morphology, and they retain a small tensor tympani muscle. These characteristics are ancestral for talpid moles. Talpa, Scalopus, Scapanus, and Parascaptor species, on the other hand, have a looser articulation between malleus and ectotympanic bone and a reduced or absent orbicular apophysis. These species lack a tensor tympani muscle, possess complete bullae, and extensions of the middle ear cavity pneumatize the surrounding basicranial bones. The two middle ear cavities communicate in Talpa, Scapanus, and Parascaptor species. Parascaptor has a hypertrophied malleus, a feature shared with Scaptochirus but not found in any other talpid genus. Differences in middle ear morphology within members of the Talpidae are correlated with lifestyle. The species with middle ears closer to the ancestral type spend more time above ground, where they will be exposed to high-frequency sound: their middle ears appear suited for transmission of high frequencies. The species with derived middle ear morphologies are more exclusively subterranean. Some of the derived features of their middle ears potentially improve low-frequency hearing, while others may reduce the transmission of bone-conducted noise. By contrast, the unusual middle ear apparatus of Parascaptor, which exhibits striking similarities to that of golden moles, probably augments seismic sensitivity by inertial bone conduction.
 ...
PMID:Evolution of the middle ear apparatus in Talpid moles. 1651 63

The densities of middle ear ossicles of golden moles (family Chrysochloridae, order Afrosoricida) were measured using the buoyancy method. The internal structure of the malleus was examined by high-resolution computed tomography, and solid-state NMR was used to determine relative phosphorus content. The malleus density of the desert golden mole Eremitalpa granti (2.44 g/cm3) was found to be higher than that reported in the literature for any other terrestrial mammal, whereas the ossicles of other golden mole species are not unusually dense. The increased density in Eremitalpa mallei is apparently related both to a relative paucity of internal vascularization and to a high level of mineralization. This high density is expected to augment inertial bone conduction, used for the detection of seismic vibrations, while limiting the skull modifications needed to accommodate the disproportionately large malleus. The mallei of the two subspecies of E. granti, E. g. granti and E. g. namibensis, were found to differ considerably from one another in both size and shape.
 ...
PMID:Ossicular density in golden moles (Chrysochloridae). 1694 64

Although increasingly popular as a laboratory species, very little is known about the peripheral auditory system of the naked mole-rat, Heterocephalus glaber. In this study, middle and inner ears of naked mole-rats of a range of ages were examined using micro-computed tomography and dissection. The ears of five other bathyergid species (Bathyergus suillus, Cryptomys hottentotus, Fukomys micklemi, Georychus capensis and Heliophobius argenteocinereus) were examined for comparative purposes. The middle ears of bathyergids show features commonly found in other members of the Ctenohystrica rodent clade, including a fused malleus and incus, a synovial stapedio-vestibular articulation and the loss of the stapedius muscle. Heterocephalus deviates morphologically from the other bathyergids examined in that it has a more complex mastoid cavity structure, poorly-ossified processes of the malleus and incus, a 'columelliform' stapes and fewer cochlear turns. Bathyergids have semicircular canals with unusually wide diameters relative to their radii of curvature. How the lateral semicircular canal reaches the vestibule differs between species. Heterocephalus has much more limited high-frequency hearing than would be predicted from its small ear structures. The spongy bone forming its ossicular processes, the weak incudo-stapedial articulation, the columelliform stapes and (compared to other bathyergids) reduced cochlear coiling are all potentially degenerate features which might reflect a lack of selective pressure on its peripheral auditory system. Substantial intraspecific differences were found in certain middle and inner ear structures, which might also result from relaxed selective pressures. However, such interpretations must be treated with caution in the absence of experimental evidence.
 ...
PMID:Ear Structures of the Naked Mole-Rat, Heterocephalus glaber, and Its Relatives (Rodentia: Bathyergidae). 2792 45


1 2 Next >>