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At least 883 records · Page 49Linked to original sources
PubMed1999

First environmental isolation of Cryptococcus neoformans var. neoformans and var. gatti from the Gharbia Governorate, Egypt.

Flowers from two Eucalyptus camaldulensis trees in the Qutur area and one tree from the Tanta area yielded three isolates of Cryptococcus neoformans var. gattii. Pigeon and sparrow droppings were also investigated for the occurrence of C. neoformans within the study area. Ninety five isolates of the neoformans variety of C. neoformans were recovered from 550 samples of avian droppings.

Animals↗
PubMed2002

Yersinia pseudotuberculosis infection in breeding monkeys: detection and analysis of strain diversity by PCR.

In the last three decades, several monkeys reared in outdoor/indoor-outdoor breeding colonies and cages of the Primate Research Institute, Kyoto University, died of yersiniosis caused by Yersinia pseudotuberculosis, necessitating introduction of a method to detect the bacteria rapidly and thus allow preventive measures to be undertaken. A rapid nested polymerase chain reaction (PCR) method for identification of Y. pseudotuberculosis in fecal samples and a random amplified polymorphic DNA (RAPD)-PCR approach for distinguishing between bacterial strains were therefore developed. Yersinia pseudotuberculosis isolates from monkey specimens were found to be classifiable into several types. To determine the source of infection, hundreds of fecal samples of wild rats, pigeons, and sparrows were collected from around the breeding colonies and cages, and subjected to PCR analyses. Yersinia pseudotuberculosis was detected in 1.7% of the fecal samples of wild rats. The DNA fingerprints of the bacteria revealed by RAPD-PCR were the same as that of one strain isolated from macaques, suggesting the wild rat to be a possible source of infection.

Adhesins, Bacterial↗
PubMed1977

Role of auditory feedback in canary song development.

As in other songbirds, early deafening had drastic effects on the song of the roller canary, a cardueline finch, resulting in a song that was much simpler and more variable than the normal. The repertoire of the syllable types, of which the song is made, was reduced from 30 to a mean of 5.0. Loud white noise was successfully used as a reversible method of cutting off auditory feedback from vocal behavior. Although suffering permanent elevation of hearing thresholds, birds reared in noise to 200 days, singing at first like deaf birds, subsequently increased their syllable repertoires significantly. Birds reared in noise to weaning at 40 days, again partly deaf, achieved a normal repertoire size when stimulated with a singing adult. Without such stimulation the repertoire was significantly reduced, showing that canary song is not fully innate, as had been thought. Although abnormal, the song of deaf canaries retained more species-specific features than did the song of emberizine sparrows when the songs developed without auditory feedback. The results are interpreted in terms of a sensory template theory.

Animals↗
PubMed1977

Angiotensin-induced dipsogenesis in domestic fowl (Gallus gallus).

Both systemic (100 mug, 200 mug, and 400 mug im) and intracranial (75 ng, 150 ng, and 300 ng) injections of Val5-angiotensin II-amide produce copious and dose-related drinking in White Leghorn chickens in normal water balance. Angiotensin-induced drinking has been reported in several mammalian species and in Barbary doves and white-crowned sparrows. The findings reported here extend the species generality of angiotensin-induced thirst and are evaluated in light of current biochemical and pharmacological analyses of the renin-angiotensin system in chickens.

Angiotensin II↗
PubMed1980

Ferromagnetic coupling to muscle receptors as a basis for geomagnetic field sensitivity in animals.

Over the past decade several investigators have provided convincing evidence that the orientation of pigeons and other birds during homing and migrational activities is significantly affected by Earth-strength (less than or equal to 0.5 G) magnetic fields. The presumed mediator of such effects would be a highly sensitive magnetoreceptor which the birds would normally use to extract navigational information from the geomagnetic field. The recently reported measurement of magnet remanence in honeybees and in homing pigeons has stimulated interest in the possibility that the magnetically sensitive structure may be constructed from permanently magnetic material. Here we report the detection of permanently magnetic material in the neck musculature of pigeons (Columba livia) and migratory white-crowned sparrows (Zonotrichia leucophrys). We propose that a magnetic field detector might involve the coupling of magnetic particles to a sensitive muscle receptor such as a spindle. A detection mechanism of this kind could account for the difficulties encountered in conditioning immobile homing pigeons to magnetic field changes and for the puzzling requirement of movement in other behavioural experiments involving pigeons and magnetic fields.

Animals↗
PubMed1980

Heterozygosity at enzyme loci and morphological variation.

Two recent reports have concerned the relationship between genic heterozygosity, as indicated by electrophoretically detected enzyme loci, and an individual's tendency to depart from the mean on a variety of morphological traits. Using different methods to assess differences in morphological variances between homozygote and heterozygote classes, both conclude that homozygotes show a significantly higher level of morphological variation. These conclusions are important in that they seem to extend the phenomenon from studies on manipulated stocks of organisms to variation in natural populations. As Eanes points out, it is necessary to determine the generality of of this result. Both these studies consider poikilotherm animals (a fish and an insect), so it would be particularly interesting to look for the relationship in homoiotherms. As a contribution to this end, I present here the results (Table 1) of an analysis of variation in the Rufous-collared sparrow, Zonotrichia capensis. I found no difference in levels of variation either between the homozygote and heterozygote classes or between classes of individuals heterozygous at different numbers of loci. My results thus suggest a difference between homoiotherms and poikilotherms in this phenomenon.

Animals↗
PubMed2002

Visual categorization shapes feature selectivity in the primate temporal cortex.

The way that we perceive and interact with objects depends on our previous experience with them. For example, a bird expert is more likely to recognize a bird as a sparrow, a sandpiper or a cockatiel than a non-expert. Neurons in the inferior temporal cortex have been shown to be important in the representation of visual objects; however, it is unknown which object features are represented and how these representations are affected by categorization training. Here we show that feature selectivity in the macaque inferior temporal cortex is shaped by categorization of objects on the basis of their visual features. Specifically, we recorded from single neurons while monkeys performed a categorization task with two sets of parametric stimuli. Each stimulus set consisted of four varying features, but only two of the four were important for the categorization task (diagnostic features). We found enhanced neuronal representation of the diagnostic features relative to the non-diagnostic ones. These findings demonstrate that stimulus features important for categorization are instantiated in the activity of single units (neurons) in the primate inferior temporal cortex.

Animals↗
PubMed1976

Some examples of double exponential fitness functions.

The advantages of using a double exponential fitness function are pointed out for the analysis of differential survival data. The uses of this type of function are illustrated on Bumpus' (1898) data on the survival of English sparrows after a severe storm and also on Cook and O'Donald's (1971) data on the over-winter survival of a large sample of snails.

Animals↗
PubMed1978

An analysis of errors in estimation of the rate of protein synthesis by constant infusion of a labelled amino acid.

Rates of protein synthesis in tissues can be calculated from the specific radioactivity of free and protein-bound amino acids at the end of a constant infusion of a labelled amino acid (Garlick, Millward & James (1973) Biochem. J. 136, 935--945]. The simplifying assumptions used in these calculations have been criticized [Madsen, Everett, Sparrow & Fowkes (1977) FEBS Lett. 79, 313--316]. A more detailed analysis using a programmable desk-top calculator is described, which shows that the errors introduced by the simplifying assumptions are small, particularly when the specific radioactivity of the free amino acid rises rapidly to a constant value.

Amino Acids↗
PubMed1991

Communication and socialization skills at ages 2 and 3 in "late-talking" young children.

Twenty-one apparently normal children between 18 and 34 months of age with slow expressive language acquisition were compared to a group of normally speaking children matched for age, SES, and sex ratio, on the Vineland Adaptive Behavior Scales (Sparrow, Balla, & Cicchetti, 1984). The late talkers (LTs) scored significantly lower not only in expressive communication, but also in receptive communication and socialization. A follow-up study of the same subjects, seen at age 3, showed nearly half the 3-year-olds with a history of LT remained delayed in expressive communication and socialization, while one third remained behind in receptive language. The data suggest that social skills are particularly vulnerable to disruption in children with late expressive language development, even after communication skills have moved into the normal range. They suggest, further, that receptive deficits do not seem, in themselves, to increase the risk of continued language delay. Clinical implications of these findings are discussed.

Child Language↗
PubMed1999

Shiga toxin-producing Escherichia coli O157 in feedlot cattle and Norwegian rats from a large-scale farm.

A total of 365 faecal samples from different categories of cattle, 12 samples of untreated slurry, 50 samples of fresh droppings of feral domestic pigeons, 20 samples of fresh droppings of domestic sparrows and stool samples of 19 synanthropic rodents were examined for the presence of Escherichia coli by broth enrichment culture and a subsequent immunomagnetic separation. Escherichia coli O157 was found in 72 (20%) bovine samples, six (50%) samples of untreated slurry and four (40%) of 10 rats (Rattus norvegicus). Significant differences were found in the E. coli O157 shedding frequency between different age categories of bulls. Genes stx2 and eaeA were detected in all isolates, and the stx1 gene in all but 10 isolates.

Animals↗
PubMed2003

Migratory birds and West Nile virus.

West Nile virus was first recorded in the New World during August 1999 in New York City. Aetiology of the disease in the Old World indicated birds as the likely introductory and amplifying hosts with ornithophilous mosquitoes, e.g. Culex pipiens, as the principal vectors. Speculation regarding likely agents for movement of the virus in its new environment focused on migratory birds, but evidence to date is equivocal. While spread of the disease has been fairly rapid, at a rate of roughly 70 km a month, it has not shown the kind of long-distance, leap frog movements one might expect if transient birds were the principal introductory hosts. Furthermore, movement of the disease has not been focused southward, but shows a radiating pattern with detection sites located in all directions from New York where terrestrial habitat was available. In addition, tests among potential New World, avian hosts have revealed prolonged viraemia (up to 5 days) only in the relatively non-migratory House Sparrow (Passer domesticus). Dispersal movements by this species could account for the observed pattern of West Nile virus spread in the Western Hemisphere to date. Regardless of whether avian migration, dispersal, or some other agent is responsible, West Nile virus should reach the New World tropics in another 1-2 years, at which time a vast number of new potential introductory and amplifying avian hosts would be exposed to the disease and mosquito vectors would be available throughout most of the year, likely causing serious, long-term threats to human health and vulnerable avian populations in the region.

Animals↗
PubMed1998

Neuroendocrine suppression of female courtship in a wild passerine: corticotropin-releasing factor and endogenous opioids.

During emergencies in their natural environments, vertebrates initiate coping mechanisms that redirect behavior away from nonessential activities and towards survival. Reproductive behaviors are suppressed. Evidence from field studies on passerine birds shows that this inhibition may not depend on the suppression of gonadal sex steroids, since during the breeding season they remain elevated despite activation of the stress response. We hypothesize that an alternate, central mechanism mediates the inhibition of reproductive behavior during stress in passerines. In this study, we tested the intracerebroventricular effects of endogenous opioids and corticotropin-releasing factor (CRF), neuropeptides implicated in the stress response, on courtship behavior in wild-caught female white-crowned sparrows. Beta-endorphin (beta-EN) significantly inhibited copulation solicitation, an estrogen-dependent courtship display, 30 min after treatment. Naloxone, an opioid antagonist, enhanced the behavior. CRF caused a suppression of solicitation that was reversible by pretreatment with naloxone, suggesting an intermediary role for endogenous opioids in CRF-induced suppression of courtship. The effects of beta-EN and CRF on solicitation appear to be independent of any general effects on locomotor activity. These results support our hypothesis that stress neuropeptides orchestrate coping behaviors in wild birds.

Adaptation, Psychological↗
PubMed2003

Morphological and microsatellite differentiation in Melospiza melodia (Aves) at a microgeographic scale.

Geographical variation in microsatellite allele frequencies and morphology were compared for five subspecies of Melospiza melodia (song sparrow; M. m. samuelis, M. m. maxillaris, M. m. pusillula, M. m. gouldii, and M. m. heermanni) in 14 populations in the San Francisco Bay region to (a) assess divergence based on these estimates and (b) test the hypothesis that drift is responsible for morphological and genetic divergence. Morphological differentiation between subspecies was high despite low differentiation at microsatellite loci, indicating high gene flow and large effective population sizes. Low concordance of morphological and genetic estimates of divergence suggests that selection or phenotypic plasticity in morphology has caused morphological differentiation among the subspecies.

Animals↗
PubMed2000

Biosynthesis of a major lipofuscin fluorophore in mice and humans with ABCR-mediated retinal and macular degeneration.

Increased accumulation of lipofuscin in cells of the retinal pigment epithelium (RPE) is seen in several forms of macular degeneration, a common cause of blindness in humans. A major fluorophore of lipofuscin is the toxic bis-retinoid, N-retinylidene-N-retinylethanolamine (A2E). Previously, we generated mice with a knockout mutation in the abcr gene. This gene encodes rim protein (RmP), an ATP-binding cassette transporter in rod outer segments. Mice lacking RmP accumulate A2E in RPE cells at a greatly increased rate over controls. Here, we identify three precursors of A2E in ocular tissues from abcr-/- mice and humans with ABCR-mediated recessive macular degenerations. Our results corroborate the scheme proposed by C. A. Parish, M. Hashimoto, K. Nakanishi, J. Dillon & J. Sparrow [Proc. Natl. Acad. Sci. USA (1998) 95, 14609-14613], for the biosynthesis of A2E: (i) condensation of all-trans-retinaldehyde (all-trans-RAL) with phosphatidylethanolamine to form a Schiff base; (ii) condensation of the amine product with a second all-trans-RAL to form a bis-retinoid; (iii) oxidation to yield a pyridinium salt; and (iv) hydrolysis of the phosphate ester to yield A2E. The latter two reactions probably occur within RPE phagolysosomes. As predicted by this model, formation of A2E was completely inhibited when abcr-/- mice were raised in total darkness. Also, once formed, A2E was not eliminated by the RPE. These data suggest that humans with retinal or macular degeneration caused by loss of RmP function may slow progression of their disease by limiting exposure to light. The precursors of A2E identified in this study may represent pharmacological targets for the treatment of ABCR-mediated macular degeneration.

ATP-Binding Cassette Transporters↗
PubMed2002

Act locally and think globally: intracerebral testosterone implants induce seasonal-like growth of adult avian song control circuits.

There is pronounced seasonal plasticity in the morphology of the neural circuits that regulate song behavior in adult songbirds, primarily in response to changes in plasma testosterone (T) levels. Most song nuclei have androgen receptors. Afferent input from the telencephalic nucleus HVc (also known as the "high vocal center") is necessary for seasonal growth of the direct efferent target nuclei RA and area X. We asked here whether T-stimulated growth of HVc is sufficient to induce growth of its efferent nuclei. Intracerebral T implants were placed unilaterally near HVc or RA in photosensitive adult male white-crowned sparrows for one month. The T implant near HVc produced significant growth of the ipsilateral (but not contralateral) HVc, RA, and area X, and increased neuronal number in the ipsilateral HVc. The T implant near RA did not produce selective growth of ipsilateral RA, HVc, or area X. Intracerebral T implants did not elevate plasma T levels, nor did they stimulate growth of two peripheral androgen sensitive targets, the syrinx and the cloacal protuberance. These results suggest that seasonal growth of the adult song circuits results from T acting directly on HVc, which then stimulates the growth of RA and area X transynaptically.

Animals↗
PubMed2001

Auditory representation of the vocal repertoire in a songbird with multiple song types.

Neural mechanisms for representing complex communication sounds must solve the problem of encoding multiple and potentially overlapping signals. Birdsong provides an excellent model for such processing, in that many songbird species produce multiple song types. Although auditory song representations in single song type species have been studied, how song is represented in the brains of species that sing multiple song types remains unknown. Here we examine song type representations in swamp sparrows (Melospiza georgiana), a multiple song type species, by making in vivo intracellular recordings from the telencephalic nucleus HVc, the major auditory-vocal interface in the songbird brain. These recordings show that single HVc relay neurons often generate action potentials to playback of only a single song type, even though synaptic inputs on these cells can be activated by playback of other song types in the bird's repertoire and songs of other birds. These subthreshold response patterns suggest that the song evoked action potential discharge of a single relay neuron is more selective than its presynaptic network. One component of this presynaptic network is likely to be in HVc, because multiple recordings from single birds show that different relay neurons can respond best to different song types, whereas single interneurons can generate action potentials to all song types in the bird's repertoire. These results show that single HVc neurons can generate song type-specific action potential responses, a feature that may facilitate the selective auditory encoding of multiple learned vocalizations in a single brain area.

Action Potentials↗
PubMed2000

A preference for own-subspecies' song guides vocal learning in a song bird.

In many song birds, males develop their songs as adults by imitating the songs of one or more tutors, memorized previously during a sensitive phase early in life. Previous work using two assays, the production of imitations by adult males and playback-induced calling by young birds during the sensitive phase for memorization, has shown that song birds can discriminate between their own and other species' songs. Herein I use both assays to show that male mountain white-crowned sparrows, Zonotrichia leucophrys oriantha, must learn to sing but have a genetic predisposition to memorize and learn the songs of their own subspecies. Playback tests to young naive birds before they even begin to sing reveal that birds give begging calls more in response to oriantha song than to songs of another species. After 10 days of tutoring with songs of either their own or another subspecies, birds continue to give stronger call responses to songs of their own subspecies, irrespective of whether they were tutored with them, and are more discriminating in distinguishing between different dialects of their own subspecies. The memory processes that facilitate recognition and discrimination of own-subspecies' song may also mediate the preferential imitation of song of a bird's own subspecies. Such perceptual biases could constrain the direction and rate of cultural evolution of learned songs.

Animals↗