SEARCH · PubMed Health

Results for “Strigiformes”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources

PubMed2005

Noninvasive measures of reproductive function and disturbance in the barred owl, great horned owl, and northern spotted owl.

There is an urgent need for noninvasive methods to study reproduction and environmental stress in at-risk species such as the northern spotted owl (Strix occidentalis caurina). Two related owl species (barred owl and great horned owl) were used as surrogates to validate hormone assays for fecal metabolites of progesterone, 17beta-estradiol, testosterone, and corticosterone. Infusions of radiolabeled hormones showed that the owls excreted most hormone within 6 h. Feces and urine contained roughly equal amounts of hormone, and most fecal hormone metabolites were quite polar. The testosterone and corticosterone assays in this study bound to the major excreted metabolites of these hormones, but two progesterone assays did not appreciably bind to the major progesterone metabolites. All assays showed excellent parallelism with hydrolyzed and unhydrolyzed samples and with previously dried or undried fecal samples. Thus, samples do not require hydrolysis or prior drying. Samples from a female barred owl had significantly higher fecal estrogen, lower fecal testosterone, and higher fecal estrogen/testosterone ratio than samples from two male barred owls. The fecal estrogen/testosterone ratio was the most accurate predictor of owl gender, particularly if two or more samples are available from the same individual. Fecal corticosterone metabolites also demonstrated considerable utility for wild northern spotted owls. Fecal glucocorticoid levels varied by gender and breeding stage, being highest in male northern spotted owls early in the breeding season and highest in females when nestlings were fledging. Collectively, these studies show that noninvasive fecal hormone measurements show great promise for noninvasive assessment of reproduction and stress in wild owls.

Animals↗

PubMed2001

Allometric relationships between embryonic heart rate and fresh egg mass in birds.

Previously, we have measured daily changes (developmental patterns) in embryonic heart rate (fh) in altricial and semi-altricial (ASA) birds (range of mean fresh egg mass approximately 1-20 g), semi-precocial seabirds (egg mass approximately 38-288 g) and precocial birds (egg mass approximately 6-1400 g). An allometric relationship between embryonic fh at 80 % of incubation duration (ID) and fresh egg mass (M) has been derived for six species of precocial bird (fh at 80 % ID=429M(-0.118)). In the present study, additional measurements of embryonic fh in three ASA species, the barn owl Tyto alba, the cattle egret Bubulcus ibis and the lanner falcon Falco biarmicus, were made to extend the egg mass range (20-41 g), and the allometric relationships of embryonic fh for these ASA birds and the precocial and semi-precocial (PSP) groups were investigated from published data. The developmental patterns of embryonic fh in three relatively large ASA species did not show a significant increase prior to the pipping period, unlike those in small ASA birds, but tended to be constant, with a subsequent increase during pipping. The allometric relationship derived for ASA birds was fh at 80 % ID=371M(-0.121) (r=-0.846, P<0.001, N=20) and that for PSP birds was fh at 80 % ID=433M(-0.121) (r=-0.963, P<0.001, N=13). The slopes were parallel, but fh of ASA embryos was low compared with that of PSP embryos with the same egg mass. In ASA birds, embyronic fh was maximal during the pipping (perinatal) period, and the maximum fh (fh(max)) was significantly related to fresh egg mass: fh(max)=440M(-0.127) (r=-0.840, P<0.001, N=20). The allometric relationships for fh at 80 % ID in PSP and fh(max) in ASA embryos were statistically identical. Accordingly, embryonic fh at 80 % ID in PSP birds and fh(max) during pipping in ASA birds can be expressed by a single allometric equation: fh=437M(-0.123) (r=-0.948, P<0.001, N=33).

Animals↗

PubMed1999

Restriction fragment length polymorphism analysis of the F gene of Newcastle disease viruses isolated from chickens and an owl in Taiwan.

To provide information on the epidemiology of Newcastle disease (ND) of poultry in Taiwan, ND virus isolates from chickens and an owl were investigated by restriction site analysis and sequencing of their gene. A 1,349 base fragment of the F (fusion protein) gene was amplified by reverse transcription-polymerase chain reaction (RT-PCR). The PCR products were analyzed using restriction endonucleases, HinfI, BstOI, and RsaI. Three strains isolated from chickens during the 1995 epidemic outbreak had the same restriction sites as that of a 1994 isolate; the number of the restriction sites of HinfI, BstOI, and RsaI were 4, 2, and 4, respectively. In the F gene of the strain isolated from an owl during the same outbreak an additional restriction site of HinfI was found. The 1991 isolate had only 3 restriction sites. The F gene of the owl isolate was amplified by RT-PCR and followed by direct sequencing. The deduced amino acid sequence at the cleavage site of the F protein was of virulent strains, 112R-R-Q-K-R-F117. The F gene of Ow/Tw/2209/95 was phylogenetically most closely related to that of Ck/Tw/2137/95 isolated from the same outbreak. The present results indicate that the causative virus of the 1995 ND outbreak had already been present in Taiwan.

Animals↗

PubMed2004

The complete mitochondrial genomes sequences of Asio flammeus and Asio otus and comparative analysis.

The complete mitochondrial genomes of Asio flammeus and Asio otus were sequenced and found to span 18858 bp and 18493 bp, respectively. It is surprising to find the former to be the largest among all avian mitochondrial genomes sequenced so far. The two genomes have very similar gene order with that of Gallus gallus, neither contains the pseudo control region, but both have a single extra base, namely Cytidine, at position 174 in ND3 gene. The control regions of Asio flammeus and Asio otus' mitochondrial genomes span 3288 bp and 2926 bp respectively, which are the longest among vertebrates except for Myxine glutinosa and contribute to the large size of two genomes. The 3' end of the control region of Asio flammeus and Asio otus contains many tandemly repeated sequences, which are highly similar to a putative control element, i.e. Mt5, and may form stable stem-loop secondary structures. Such repeated sequences probably play an important role in regulating transcription and replication of mitochondrial genome. Our results may provide important clues for uncovering the origin and evolution mechanisms of mitochondrion genome.

Animals↗

PubMed2006

Noise reduction of coincidence detector output by the inferior colliculus of the barn owl.

A recurring theme in theoretical work is that integration over populations of similarly tuned neurons can reduce neural noise. However, there are relatively few demonstrations of an explicit noise reduction mechanism in a neural network. Here we demonstrate that the brainstem of the barn owl includes a stage of processing apparently devoted to increasing the signal-to-noise ratio in the encoding of the interaural time difference (ITD), one of two primary binaural cues used to compute the position of a sound source in space. In the barn owl, the ITD is processed in a dedicated neural pathway that terminates at the core of the inferior colliculus (ICcc). The actual locus of the computation of the ITD is before ICcc in the nucleus laminaris (NL), and ICcc receives no inputs carrying information that did not originate in NL. Unlike in NL, the rate-ITD functions of ICcc neurons require as little as a single stimulus presentation per ITD to show coherent ITD tuning. ICcc neurons also displayed a greater dynamic range with a maximal difference in ITD response rates approximately double that seen in NL. These results indicate that ICcc neurons perform a computation functionally analogous to averaging across a population of similarly tuned NL neurons.

Acoustic Stimulation↗

PubMed2004

Multiple sites of adaptive plasticity in the owl's auditory localization pathway.

In the midbrain auditory localization pathway of the barn owl, a map of auditory space is relayed from the external nucleus of the inferior colliculus (ICX) to the deep and intermediate layers of the optic tectum (OT) and from these layers to the superficial layers. Within the OT, the auditory space map aligns with a visual map of space. Raising young barn owls with a prismatic displacement of the visual field leads to progressive changes in auditory tuning in the OT that tend to realign the auditory space map with the prismatically displaced visual space map. The only known site of this adaptive plasticity is in the ICX, in which the auditory system first creates a map of space. In this study, we identified an additional site of plasticity in the OT. In owls that experienced prisms beginning late in the juvenile period, adaptive shifts in auditory tuning in the superficial layers of the OT exceeded the adaptive shifts that occurred in the deep layers of the OT or in the ICX. Anatomical results from these owls demonstrated that the topography of intrinsic OT connections was systematically altered in the adaptive direction. In juvenile owls, plasticity in the OT increased as plasticity in the ICX decreased. Because plasticity at both sites has been shown to decline substantially in adults, these results suggest that an age-dependent decrease in auditory map plasticity occurs first in the ICX and later at the higher level, in the OT.

Acoustic Stimulation↗

PubMed2005

Localization and identification of concurrent sounds in the owl's auditory space map.

In nature, sounds from multiple sources sum at the eardrums, generating complex cues for sound localization and identification. In this clutter, the auditory system must determine "what is where." We examined this process in the auditory space map of the barn owl's (Tyto alba) inferior colliculus using two spatially separated sources simultaneously emitting uncorrelated noise bursts, which were uniquely identified by different frequencies of sinusoidal amplitude modulation. Spatial response profiles of isolated neurons were constructed by testing the source-pair centered at various locations in virtual auditory space. The neurons responded whenever a source was placed within the receptive field, generating two clearly segregated foci of activity at appropriate loci. The spike trains were locked strongly to the amplitude modulation of the source within the receptive field, whereas the other source had minimal influence. Two sources amplitude modulated at the same rate were resolved successfully, suggesting that source separation is based on differences of fine structure. The spike rate and synchrony were stronger for whichever source had the stronger average binaural level. A computational model showed that neuronal activity was primarily proportional to the degree of matching between the momentary binaural cues and the preferred values of the neuron. The model showed that individual neurons respond to and synchronize with sources in their receptive field if there are frequencies having an average binaural-level advantage over a second source. Frequencies with interaural phase differences that are shared by both sources may also evoke activity, which may be synchronized with the amplitude modulations from either source.

Acoustic Stimulation↗

PubMed2005

Hunting increases adaptive auditory map plasticity in adult barn owls.

The optic tectum (OT) of barn owls contains topographic maps of auditory and visual space. Barn owls reared with horizontally displacing prismatic spectacles (prisms) acquire a novel auditory space map in the OT that restores alignment with the prismatically displaced visual map. Although juvenile owls readily acquire alternative maps of auditory space as a result of experience, this plasticity is reduced greatly in adults. We tested whether hunting live prey, a natural and critically important behavior for barn owls, increases auditory map plasticity in adult owls. Two groups of naive adult owls were fit with prisms. The first group was fed dead mice during 10 weeks of prism experience, while the second group was required to hunt live prey for an identical period of time. When the owls hunted live prey, auditory maps shifted substantially farther (five times farther, on average) and the consistency of tuning curve shifts within each map increased. Only a short period of time in each day, during which the two groups experienced different conditions, accounts for this effect. In addition, increased map plasticity correlated with behavioral improvements in the owls' ability to strike and capture prey. These results indicate that the experience of hunting dramatically increases adult adaptive plasticity in this pathway.

Acoustic Stimulation↗

PubMed2004

Robustness of multiplicative processes in auditory spatial tuning.

Auditory space-specific neurons in the owl's inferior colliculus selectively respond to the direction of sound propagation, which is defined by combinations of interaural time (ITD) and level (ILD) differences. Mathematical analyses show that the amplitude of postsynaptic potentials in these neurons is a product of two components that vary with either ITD or ILD. Temporal correlation in the fine structure of signals between the ears is essential for detection of ITD. By varying the degree of binaural correlation, we could accurately change the amplitude of the ITD component of postsynaptic potentials in the space-specific neurons. Multiplication worked for the entire range of postsynaptic potentials created by manipulation of ITD.

Animals↗

PubMed2006

Auditory and visual space maps in the cholinergic nucleus isthmi pars parvocellularis of the barn owl.

The nucleus isthmi pars parvocellularis (Ipc) is a midbrain cholinergic nucleus that shares reciprocal, topographic connections with the optic tectum (OT). Ipc neurons project to spatially restricted columns in the OT, contacting essentially all OT layers in a given column. Previous research characterizes the Ipc as a visual processor. We found that, in the barn owl, the Ipc responds to auditory as well as to visual stimuli. Auditory responses were tuned broadly for frequency, but sharply for spatial cues. We measured the tuning of Ipc units to binaural sound localization cues, including interaural timing differences (ITDs) and interaural level differences (ILDs). Units in the Ipc were tuned to specific values of both ITD and ILD and were organized systematically according to their ITD and ILD tuning, forming a map of space. The auditory space map aligned with the visual space map in the Ipc. These results demonstrate that the Ipc encodes the spatial location of objects, independent of stimulus modality. These findings, combined with the precise pattern of projections from the Ipc to the OT, suggest that the role of the Ipc is to regulate the sensitivity of OT neurons in a space-specific manner.

Acoustic Stimulation↗

PubMed2005

Axodendritic contacts onto calcium/calmodulin-dependent protein kinase type II-expressing neurons in the barn owl auditory space map.

In the owl midbrain, a map of auditory space is synthesized in the inferior colliculus (IC) and conveyed to the optic tectum (OT). Ascending auditory information courses through these structures via topographic axonal projections. Little is known about the molecular composition of projection neurons or their postsynaptic targets. To visualize axodendritic contacts between identified cell types, we used double-label immunohistochemistry, in vivo retrograde tracing, in vitro anterograde tracing, high-resolution confocal microscopy, three-dimensional reconstruction and fly-through visualization. We discovered a major class of IC neurons that strongly expressed calcium/calmodulin-dependent protein kinase type II, alpha subunit (CaMKII). The distribution of these cells within the IC was mostly restricted to the external nucleus of the IC (ICX), in which the auditory space map is assembled. A large proportion of ICX-OT projection neurons were CaMKII positive. In addition to being the principal outputs, CaMKII cells were in direct contact with axonal boutons emanating from the main source of input to ICX, the lateral shell of the central nucleus of the inferior colliculus (ICCls). Numerous sites of putative synaptic contact were found on the somata, proximal dendrites, and distal dendrites. Double-label immunoelectron microscopy confirmed the existence of synapses between ICCls axons and the dendrites of CaMKII cells. Collectively, our data indicate that CaMKII ICX neurons are a cellular locus for the computation of auditory space-specific responses. Because the ICCls-ICX projection is physically altered during experience-dependent plasticity, these results lay the groundwork for probing microanatomical rearrangements that may underlie plasticity and learning.

Animals↗

PubMed2005

Tonotopic specialization of auditory coincidence detection in nucleus laminaris of the chick.

The interaural time difference (ITD) is a cue for localizing a sound source along the horizontal plane and is first determined in the nucleus laminaris (NL) in birds. Neurons in NL are tonotopically organized, such that ITDs are processed separately at each characteristic frequency (CF). Here, we investigated the excitability and coincidence detection of neurons along the tonotopic axis in NL, using a chick brainstem slice preparation. Systematic changes with CF were observed in morphological and electrophysiological properties of NL neurons. These properties included the length of dendrites, the input capacitance, the conductance of hyperpolarization-activated current, and the EPSC time course. In contrast to these gradients, the conductance of low-threshold K+ current and the expression of Kv1.2 channel protein were maximal in the central (middle-CF) region of NL. As a result, the middle-CF neuron had the smallest input resistance and membrane time constant, and consequently the fastest EPSP, and exhibited the most accurate coincidence detection. The specialization of middle-CF neurons as coincidence detectors may account for the high resolution of sound-source localization in the middle-frequency range observed in avians.

Action Potentials↗

PubMed2001

A reproductive phase-dependent effect of dietary L-tryptophan on pineal gland and gonad of a nocturnal bird, Indian spotted owlet Athene brama.

Unlike other temperate owls, Indian spotted owlet Athene brama possesses a well-developed pineal gland that secrets moderate amount of hydroxy- (serotonin) and methoxy- (melatonin) indoles in circulation. However, in this study, we have reported the response of this endocrine gland to exogenous L-Tryptophan (precursor of the above indoles), and also its effect on gonads of this nocturnal bird. During breeding phase or pineal inactive phase (March), oral treatment of L-Trp (0.5 mg/100 g Bwt/day) significantly increased the pineal gland wt and plasma melatonin (MEL) level, while decreased the gonadal wt and plasma sex steroids levels (estradiol and progesterone in female and testosterone in male). Interestingly, during reproductively quiescent phase or pineal active phase (August), similar amount of L-Trp significantly decreased the plasma MEL level, while increased the above sex steroid levels in plasma. Finally, the results show a clear reproductive phase-dependent inverse effect of L-Trp on pineal gland and gonads for both sexes of the spotted owlets, and suggest that the therapeutic use of this amino acid would be a great advantage for controlling the reproduction of these economically important birds.

Animals↗

PubMed2006

Effects of environmental temperature on thyroid hormones in the barn owl (Tyto alba).

The basic patterns of thyroid hormones [thyroxine (T4) and 3,3',5-triiodothyronine (T3)] and the T4 and T3 responses induced by thyrotropin releasing hormone (TRH) are reported in captive female barn owls (Tyto alba) during the non-breeding period. The main findings of the study, conducted on a total of 10 owls, are as follow: (1) The thyroid gland of barn owl can be stimulated by the classical TRH stimulation test. (2) T3 response was much more pronounced both under cold (around 10 degrees C) and warm (around 20 degrees C) conditions, whereas T4 response ranged so widely that we could not point out any significant change in it. (3) Basal T3 plasma level was significantly (p = 0.036) higher in birds exposed to cold temperature, and they responded to TRH treatment with a lower plasma T3 elevation than the birds kept in a warm chamber. This pattern, however, cannot be explained by increased food intake, but is in agreement with the fact that enhanced T3 level may account for higher avUCP mRNA expression, which results in higher heat production on the cell level. From the results it is concluded that altering T3 plasma level plays a significant role in cold-induced thermoregulation.

Animals↗

PubMedDate not supplied

Congenital skeletal abnormalities in a tawny owl chick (Strix aluco).

In this case report, we describe a tawny owl chick (Strix aluco) coming from a Wild Fauna Recovery Center with multiple congenital malformations in the limbs. The animal was unable to fly and showed marked malnutrition and poor general appearance. Physical, radiologic, and anatomic examinations showed osseous malformations including dislocation of radius and carpometacarpus with abnormal nonfunctional fixation of ligamentum propatagialis, absence of most parts of the bones of the manus in both wings, and twisted nonfused left tarsometatarsus with marked griphosis of digits. Routine toxicologic and pathologic examinations did not reveal a specific etiology.

Animals↗

PubMed2005

Pathologic and immunohistochemical findings in goshawks (Accipiter gentilis) and great horned owls (Bubo virginianus) naturally infected with West Nile virus.

The carcasses of 25 great horned owls and 12 goshawks were investigated for West Nile virus (WNV) infection by immunohistochemistry (IHC) performed on various organs, including brain, spinal cord, heart, kidney, eye, bone marrow, spleen, liver, lungs, pancreas, intestine, and proventriculus, using a WNV-antigen-specific monoclonal antibody and by WNV-specific reverse transcriptase-polymerase chain reaction (RT-PCR), performed on fresh brain tissue only. WNV infection was diagnosed by IHC in all owls and all goshawks. WNV-specific RT-PCR amplified WNV-RNA in the brain of all goshawks but only 12 owls (48%). Cachexia was a common macroscopic finding associated with WNV infection in owls (76%). Myocarditis was occasionally macroscopically evident in goshawks (33%). Microscopically, inflammatory lesions, including lymphoplasmacytic and histiocytic encephalitis, myocarditis, endophthalmitis, and pancreatitis were present in both species but were more common and more severe in goshawks than in owls. The most characteristic brain lesion in owls was the formation of glial nodules, in particular in the molecular layer of the cerebellum, while encephalitis affecting the periventricular parenchyma of the cerebral cortex was common in the goshawks. In owls, WNV-antigen-positive cells were present usually only in very small numbers per organ. Kidney (80%), heart (39%), and cerebellum (37%) were the organs that most commonly contained WNV antigen in owls. WNV antigen was frequently widely distributed in the organs of infected goshawks, with increased amounts of WNV antigen in the heart and the cerebrum. Spleen (75%), cerebellum (66%), heart (58%), cerebrum (58%), and eye (50%) were often WNV-antigen positive in goshawks. In contrast with the goshawks, WNV antigen was not present in cerebral and retinal neurons of owls. WNV infection appears to be capable of causing fatal disease in great horned owls and goshawks. However, the distribution and severity of histologic lesions, the antigen distribution in the various organs, and the amount of antigen varied among both species. Therefore, the diagnostician may choose organs for histology and immunohistochemistry as well as RT-PCR depending on the investigated species in order to avoid false-negative results.

Animals↗

PubMed2005

Malaria in an eastern screech owl (Otus asio).

Owls are frequent carriers of blood parasites but clinical malaria infections are rare. Various stages of Plasmodium subpraecox were seen in 90% of the erythrocytes of an Eastern screech owl (Otus asio) showing symptoms consistent with malaria 1 wk after admission for traumatic injuries. An additional unidentified blood parasite, either a Plasmodium or a Haemoproteus spp. was found in small numbers of red blood cells on blood films examined at admission and at day 7 postadmission. Combined infestation, trauma-induced stress, and iatrogenic corticosteroid administration are possible factors that could have induced disease. Oral treatment with mefloquine at 30 mg/kg, repeated after 12, 24, and 48 hr, proved successful in eliminating both organisms and signs of clinical disease.

Animals↗

PubMed2006

Experimental West Nile virus infection in Eastern Screech Owls (Megascops asio).

Eastern Screech Owls (EASOs) were experimentally infected with the pathogenic New York 1999 strain of West Nile virus (WNV) by subcutaneous injection or per os. Two of nine subcutaneously inoculated birds died or were euthanatized on 8 or 9 days postinfection (DPI) after <24 hr of lethargy and recumbency. All subcutaneously inoculated birds developed levels of viremia that are likely infectious to mosquitoes, with peak viremia levels ranging from 10(5.0) to 10(9.6) plaque-forming units/ml. Despite the viremia, the remaining seven birds did not display signs of illness. All birds alive beyond 5 DPI seroconverted, although the morbid birds demonstrated significantly lower antibody titers than the clinically normal birds. Cagemates of infected birds did not become infected. One of five orally exposed EASOs became viremic and seroconverted, whereas WNV infection in the remaining four birds was not evident. All infected birds shed virus via the oral and cloacal route. Early during infection, WNV targeted skin, spleen, esophagus, and skeletal muscle. The two morbid owls had myocardial and skeletal muscle necrosis and mild encephalitis and nephritis, whereas some of the clinically healthy birds that were sacrificed on 14 DPI had myocardial arteritis and renal phlebitis. WNV is a significant pathogen of EASOs, causing pathologic lesions with varying clinical outcomes.

Animals↗