Near-field acuity changes after visual system lesions in pigeons. II. Telencephalon

Pigeons were trained to perform in a psychophysical task that measured their minimum-separable visual acuity. After their performance stabilized, lesions were made in telencephalic components of the visual system. In one group, lesions were made in the ectostriatum, which is the telencephalic target of the tectofugal visual pathway. These cases showed severe to moderate losses of acuity. The magnitude of the loss was correlated with the extent of ectostriatal damage. In another group, lesions were made in the visual Wulst, a portion of which receives the ascending fibers of the thalamofugal visual pathway. Within this group, only lesions that were large and included all components of the visual Wulst were effective in decreasing visual acuity to a moderate degree. A partial correlation analysis indicated that the components of the visual Wulst that were responsible for the acuity changes were the accessory hyperstriatum and the hyperstriatum ventrale. However, lesions that were generally confined to these regions alone were ineffective. Also ineffective were lesions of the granular components of the visual Wulst, which receive the ascending thalamofugal fibers. The results raise questions about the presumed roles of the tectofugal pathway as a background-vision mechanism and the thalamofugal pathway as a fine-detail vision mechanism.     

Thalamo-hyperstriatal projections in the pigeon(Columba livia) as demonstrated by retograde double-labeling with fluorescent tracers

Thalamo-hyperstriatal projections were studied in the pigeon by retrograde thalamic labeling following bilateral injections of different combinations of fluorescent substances (Fast Blue, Evans Blue, Nuclear Yellow) into the hyperstriatum. The distribution of single and double-labeled neurons within the thalamic nuclei dorsolateralis anterior and superficialis parvocellularis indicated the presence of distinct functional sub-regions containing neuronal populations providing ascending projections which were either ipsilateral, contralateral or bilateral via collateral axon branching.     

Discrepant effects of unilateral and bilateral forebrain lesions on the visual performance of pigeons

The monocular and binocular performance of pigeons with bilateral, unilateral or sham lesions in the telencephalic Wulst was tested with visual discrimination tasks. Unilateral lesions yielded a marked deficit when the animals could only use the eye contralateral to the lesion. Otherwise the accomplishments of the ablated animals did not differ from that of the controls. The reciprocal inhibition of symmetrical visual brain stem centers is thought to have been unbalanced through the one-sided interruption of a known pathway descending from the Wulst.     

Six-year surveillance of Newcastle disease virus in wild birds in north-eastern Spain (Catalonia)

Given that Newcastle disease (ND) is one of the major threats for the poultry industry, testing of Newcastle disease virus (NDV) has been carried out since 2010 in cases of mortality in wild birds (passive surveillance) in Catalonia. The objective is to provide an early warning system to prevent the infection of poultry. Since 2010, 35 episodes of mortality in wild birds were attributed to NDV infection. Throughout this period there was a progressive expansion of NDV to new areas, with an increase in the episodes of mortality, although it is not clear whether they were the result of the spread of the virus, or of the improvement of the surveillance. Phylogenetic analyses indicate that two distinct sublineages of NDV, 4a and 4b, were circulating in Catalonia. Both sublineages seem to be endemic in the wild bird population, affecting mainly Eurasian-collared doves, with a clear pattern in relation to its spatial distribution (coincident with the distribution of this species), and its temporal distribution (with the majority of cases between September and February). So far, endemicity in wild birds has not resulted in ND outbreaks in poultry. However, there are still many uncertainties about, for example, whether NDV may expand to new areas of Catalonia (with higher poultry density), or about the threat that the apparently more novel sublineage 4a may represent. Hence, efforts should be made so that measures to prevent infection of poultry farms (particularly in high-risk areas and periods) are encouraged, and surveillance is maintained.     

Immunization of BALB/c mice with pigeon IgY induces the production of anti-IgG autoantibodies

The breakdown of immunological tolerance due to the activation of autoreactive B and T cells triggers physiopathological processes. An example of such conditions is the production of IgG autoantibodies specific for the Fc portion of IgG (anti-Fcγ IgG). Previous reports have shown that patients with pigeon-related hypersensitivity pneumonitis exhibit an increase in the serum levels of anti-Fcγ IgG. There is no in vivo model for the study of this condition and the immunological mechanisms of tolerance breakdown associated with sensitization by pigeon antigens are still unknown. In this work, we show that the repeated immunization of BALB/c mice with pigeon IgY during 16-weeks induces the production of anti-Fcγ IgG and keeps their high levels for seven weeks. The late appearance of anti-Fcγ IgG autoantibodies in the plasma is similar to what has been reported in other experimental autoimmune models. With the occurrence of anti-Fcγ IgG, there is a reduction in the proportion of Foxp3?+?cells (regulatory T cells, Tregs) within the population of splenic CD4?+?CD25?+?T cells. Thus, our data showed that the immunization of BALB/c mice with IgY promotes the production of anti-Fcγ IgG along with a decrease in Tregs in the spleen. We propose that immunization of mice with pigeon antigens, like IgY can provide a model to study the immunological mechanisms involved in the development of pigeon-related hypersensitivity pneumonitis.     

The primary vestibular projection to the cerebellar cortex in the pigeon (Columba livia)

The cerebellar cortex of the pigeon receiving direct vestibular afferents was delineated by anterograde transport of [3H]-amino acids injected into the vestibular nerve. Labelled mossy fiber rosettes in the granular layer were concentrated in lobule X (nodulus) and to a lesser extent, in the ventral portion of lobule IXd (uvula and paraflocculus). A few solitary labelled rosettes were also found in more dorsal portions of lobule IX, as well as in the anterior lobe between lobule II and IV. The lingula remained unlabelled. Discrete injections of [3H]-leucine into the cristae of each of the three semicircular canals or the utricular macula yielded a similar distribution of fewer labelled rosettes. A few primary mossy fiber terminals labelled after cochlear injections are attributed to afferents from the lagenar macula. Since effective diffusion of label from the injection site was excluded by controls, it is concluded that projection of individual canal and macula nerves to the vestibulocerebellar cortex is not topographically separated. It is proposed that this extensive convergence of various afferents is required by the cerebellum to compute precise and directionally specific control signals during head rotation in all conceivable planes.     

云南省部分地区鸽粪中新型隐球菌的分离与鉴定

目的对云南省部分地区鸽粪中新型隐球菌进行分离鉴定,并对各个地区鸽粪中新型隐球菌带菌率进行调查。方法采集云南省4个城市鸽粪标本共473份,用黑米琼脂培养基对其进行分离,肉眼观察菌落形态、颜色,光学显微镜下观察菌体形态,对疑似菌落进行纯培养后用特异性引物CN4和CN5扩增URA5基因,阳性者鉴定为新型隐球菌,并用SPSS16.0对其结果进行统计分析。结果云南省4个地区473份鸽粪标本中共分离出152株新型隐球菌,平均阳性率为32.13%。其中大理地区阳性率为26.08%,昭通阳性率为30.05%,曲靖阳性率为81.81%,临沧阳性率为37.03%。4个地区阳性率差异有统计学意义（χ^2=41.87,P〈0.01）。结论云南地区鸽粪中新型隐球菌带菌率较高,且不同地区带菌率不同。     

The accessory optic system in pigeons: receptive field properties of identified neurons

Visual receptive fields of neurons in the nucleus of the basal optic root were investigated in pigeons. Their projections could be traced to vestibulo-cerebellum and oculomotor complex by means of antidromic activation. Units in that nucleus showed large peripheral receptive fields and appeared highly sensitive to moving targets, with the majority displaying axis specificity and direction selectivity. The results seem consistent with the proposed role of the accessory optic system in oculomotor reflexes.     

Key word index

Interocular transfer (IOT) of monocularly learned pattern, brightness and color discriminations was studied in normal pigeons and in pigeons with a bilateral ablation of the visual Wulst. No significant differences were found between the two groups in terms of both rate of monocular learning and degree of IOT. Pigeons with a Wulst ablation which had shown a normal capacity for IOT, subsequently lost this capacity following a section of the supra-optic decussation (DSO). It is concluded that IOT in pigeons does not require the presence of the binocular neurons of the visual Wulst, and that in absence of this structure, IOT must rely on other centers for binocular interaction which receive fibers from the DSO.