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In male bats Tadarida brasiliensis spermatogenesis occurs only during winter and spring. Two additional lactate dehydrogenase isozymes appear in testes containing mature spermatozoa. This type of isozymic change implies cyclic activation of genes and affords valuable markers for study of the factors involved.
Macronyssid mites (Radfordiella) have been found in the oral mucosa of the long-nosed bat (Leptonycteris nivalis), which occurs from Texas southward throughout much of Mexico. This is the first report of mites of the suborder Mesostigmata attached in the oral cavity of a mammal. Osteolysis of hard palate and odontolysis of teeth result from infestations of mites adjacent to the upper premolars and molars; destruction of bone, teeth, and Connective tissue often leads to exfoliation of teeth in life. Oral mites have not been found in Leptonycteris sanborni, a species in part sympatric with Leptonycteris nivalis.
Studies in which the Australian bat Myotis adversus was marked and recaptured showed that mature males tend to be solitary, are strongly attached to a particular site, and apparently defend home sites. Harem formation concurrent with mating has been observed, and the bond between the mother and her young extends beyond extends beyond nursing.
In Panama the phyllostomid bat Artibeus jamaicensis is seasonally polyestrous, and young are born in March or April and July or August. Blastocysts conceived after the second birth implant in the uterus but are dormant from September to mid-November, when normal development again resumes.
A vampire bat, Desmodus rotundus, captured in Oaxaca, Mexico, in August 1970, was found to be infected with the epidemic strain of Venezuelan equine encephalomyelitis virus at the same time that an equine epizootic was occurring there.
Scientists are a step closer to unraveling a medical mystery that killed 105 people in Malaysia last year and destroyed the country's pig industry. The Nipah virus, which caused the disease, most likely originated in a native fruit bat species, Malaysian researchers reported here at a meeting last week. They say the findings will help Malaysian health authorities prevent future outbreaks of the Nipah virus. Others see the case as an argument for expanding research into infections that can leap the boundary between animals and humans.
The auditory cortex of the mustache bat, Pteronotus parnellii rubiginosus, is composed of functional divisions which are differently organized to be suited for processing the elements of its biosonar signal according to their biological significance. Unlike the Doppler-shifted-CF (constant frequency) processing area, the area processing the frequency-modulated components does not show clear tonotopic and amplitopic representations, but consists of several clusters of neurons, each of which is sensitive to a particular combination (or combinations) of information-bearing elements of the biosonar signal and echoes. The response properties of neurons in the major clusters indicate that processing of information carried by the frequency-modulated components of echoes is facilitated by the first harmonic of the emitted biosonar signal. The properties of some of these neurons suggest that they are tuned to a target which has a particular cross-sectional area and which is located at a particular distance.
The mustache bat emits a three-harmonic echolocation pulse. At the external ear, large interaural intensity differences are generated only when a sound originates within a limited area of two-dimensional space, and this area is different for each pulse harmonic. As a consequence, the external ear generates pronounced binaural spectral cues containing two-dimensional spatial information. This information is encoded in the inferior colliculus by neurons tuned to one of the harmonics and sensitive to interaural intensity differences.
Some of the neurons in the nucleus intercollicularis and auditory cortex of the echolocating bat Eptesicus fuscus respond selectively to sonar echoes occurring with specific echo delays or pulse-echo intervals. They do not respond for a wide range of other types of sounds or for sonar echoes at longer or shorter pulse-echo intervals; they may, therefore, be specialized for detection and ranging of sonar targets.
Echolocating bats (Eptesicus fuscus) can perceive changes of as little as 3 degrees of arc in the vertical angles separating pairs of horizontal rods. This acuity depends upon modification of sounds entering the external ear canal by the structures of the external ear. Deflection of the tragus degrades the acuity of vertical-angle perception from 3 degrees to about 12 degrees to 14 degrees. The pinna-tragus structure produces a strong secondary echo of sounds entering the external ear canal, and the delay of this echo after the time when the sound directly enters the ear canal apparently encodes the vertical direction of a sound source.
A previously undescribed response pattern has been observed in certain single units in the posterior colliculus of Pteronotus suapurensis. These units, constituting about one-third of those tuned to the region of the dominant constant-frequency (CF) components of the orientation sounds, respond to a tone pip with a burst of spikes at a latency of 3 to 6 milliseconds, within the frequency-intensity domain of a normal V-shaped response area. In these units, however, as intensity is dropped below threshold for this response, a response of 5-to 10-milliseconds longer latency appears and persists throughout another 10 to 30 decibels of attenuation. These late responses can be very vigorous, are sharply tuned to frequencies at or just above the CF components of the signal, and are often strongest and of lowest threshold at stimulus durations of 1.5 to 3 milliseconds--approximately the duration of the CF component. These properties imply that the late responses are concerned with analysis of the CF components of echoes, apparently in ways not as prominent in other bats.
Neurons in the inferior colliculus of echolocating bats responded well to two stimuli presented in close temporal sequence. Favorable recovery of responsiveness was seen with stimuli having durations, intensities, and interpulse intervals similar to the natural biosonar signals reaching the ears during the various phases of echolocation. Some units responded to a subthreshold simulated echo but only when preceded by a loud initial pulse. These units appear to be specialized for echo-detection.
Evidence is presented in support of the hypothesis that fresh bat guano serves as a means of pathogenic fungi dissemination in caves. A total of 371 guano samples were collected from caves in southeastern New Mexico. Each sample was agitated in sterile saline and sand. The supernatant fluid was treated with an antibiotic and streaked on differential media. Cultures were incubated at 25 and 37 C and examined at intervals over a 4-week period. For animal inoculation, highly concentrated inoculum was injected intraperitoneally into white Swiss mice. Animals were sacrificed 4 weeks later, and portions of their lung, liver, and spleen were cultured on selective media, incubated at 25 C, and examined at intervals over a 4-week period. Microsporum gypseum was isolated at all 10 collecting stations with an incidence of 22.4%, Trichophyton mentagrophytes at 7 stations with an incidence of 5%, T. rubrum at 3 stations with an incidence of 3%, and T. terrestre at 1 station with an incidence of 0.5%. From a total of 60 pools of liver-spleen-lung suspensions, 6 pools yielded positive cultures of Histoplasma capsulatum and 1 pool yielded T. mentagrophytes. No significant difference was found among the different selective media with respect to recovery of dermatophytes. Among the human pathogenic fungi isolated were Candida sp., Cladosporium sp., Coccidioides immitis, Cryptococcus neoformans, H. capsulatum, M. gypseum, T. mentagrophytes, T. rubrum, T. terrestre, and Sporotrichum sp.
Rabies is a lethal disease caused by neurotropic viruses that are endemic in nature. When exposure to a potentially rabid animal is recognized, prompt administration of virus-neutralizing antibodies, together with active immunization, can prevent development of the disease. However, once the nonspecific clinical symptoms of rabies appear conventional postexposure treatment is unsuccessful. Over the last decade, rabies viruses associated with the silver-haired bat (SHBRV) have emerged as the leading cause of human deaths from rabies in the United States and Canada as a consequence of the fact that exposure to these viruses is often unnoticed. The need to treat SHBRV infection following the development of clinical rabies has lead us to investigate why the immune response to SHBRV fails to protect at a certain stage of infection. We have established that measurements of innate and adaptive immunity are indistinguishable between mice infected with the highly lethal SHBRV and mice infected with an attenuated laboratory rabies virus strain. While a fully functional immune response to SHBRV develops in the periphery of infected animals, the invasion of central nervous system (CNS) tissues by immune cells is reduced and, consequently, the virus is not cleared. Our data indicate that the specific deficit in the SHBRV-infected animal is an inability to enhance blood-brain barrier permeability in the cerebellum and deliver immune effectors to the CNS tissues. Conceivably, at the stage of infection where immune access to the infected CNS tissues is limited, either the provision or the development of antiviral immunity will be ineffective.
"British American Tobacco strongly believes children should not smoke, and smoking should only be for adults who understand the risks associated with it. Our Group companies support and run programmes worldwide tackling underage smoking, and we are committed to pooling our resources and experience globally with others in the tobacco industry--and with governments and NGOs--to help prevent youth smoking. Along with the other two largest international tobacco groups--Philip Morris International and Japan Tobacco International--our Group companies have funded and supported more than 130 Youth Smoking Prevention (YSP) programmes in more than 70 countries. We fully support laws and regulations on a minimum age for buying tobacco products, and penalties for retailers who break the law. Our company policy worldwide is not to market to anyone under 18 years old, or more if the law in a particular country sets the age higher."--BAT website November 2003.
The effects of hibernation on the expression of Akt (protein kinase B), the peroxisome proliferator-activated receptor gamma isoform (PPARgamma), and the PPARgamma coactivator PGC-1 were assessed in seven tissues of the little brown bat, Myotis lucifugus. Western blotting revealed that the levels of active phosphorylated Akt were strongly reduced in brain, kidney, liver, and white adipose during torpor as compared with aroused animals and that total Akt protein was also reduced in white adipose during torpor. By contrast, both total and phospho-Akt were elevated in brown adipose tissue, the thermogenic organ. PPARgamma and PGC-1 levels showed parallel changes in all organs. Both were strongly suppressed in brain, but levels increased significantly in all other organs during hibernation (except for PGC-1 in heart). Reduced Akt activity is consistent with a probable reduced insulin response during torpor that facilitates the mobilization of lipid reserves for fuel supply and is further supported by increased gene expression of enzymes and proteins involved in lipid catabolism under the stimulation of enhanced PPARgamma and PGC-1 levels.
Echolocating bats use audition to guide much of their behavior. As in all vertebrates, their lower brainstem contains a number of parallel auditory pathways that provide excitatory or inhibitory outputs differing in their temporal discharge patterns and latencies. These pathways converge in the auditory midbrain, where many neurons are tuned to biologically important parameters of sound, including signal duration, frequency-modulated sweep direction, and the rate of periodic frequency or amplitude modulations. This tuning to biologically relevant temporal patterns of sound is created through the interplay of the time-delayed excitatory and inhibitory inputs to midbrain neurons. Because the tuning process requires integration over a relatively long time period, the rate at which midbrain auditory neurons respond corresponds to the cadence of sounds rather than their fine structure and may provide an output that is closely matched to the rate at which motor systems operate.
A mathematical theory of interstitial fluid motion and capillary exchange is developed in order to understand and explain measurements of capillary and interstitial fluid pressure in the bat wing, in which a high degree of vasomotor activity occurs. As a result of precapillary sphincter activity, fluid is alternately filtered and reabsorbed from the capillary, and previous studies of related steady problems by the author suggest that the interstitial fluid pressure should oscillate with time. Wiederhielm and Weston did not observe such fluctuations when they measured tissue pressures near the capillaries. This apparent paradox is resolved in the present paper by including unsteady effects. It is shown that pressure oscillations are predicted, but because of the very high vasomotor frequency they die out within a very short distance from the capillary wall. The capillary pressure measurements of Wiederhielm and Weston are also explained in terms of precapillary sphincter activity.