Ecological and landscape effects on genetic distance in an assemblage of headwater fishes

Environmental divergence along hierarchically structured longitudinal gradients may constitute barriers to gene flow in river networks for headwater specialised species. While known, this phenomenon has not been well studied, especially with regard to degree of headwater specialisation. We examined six headwater species that differ in habitat specialisation to assess whether patterns of differentiation vary according to geographic or environmental distance. We also identified regional environmental or anthropogenically induced fragmentation effects by comparing within‐drainage patterns of genetic distance across replicate watersheds. We used a comparative modelling framework to determine whether isolation by distance or isolation by resistance of large river habitats was a better predictor of genetic distance across species. The influence of reservoir presence and regional network characteristics that may influence the hydrology and size of large river habitats were also assessed. Resistance effects from large rivers were closely related to headwater specialisation, with increased specialisation leading to increased resistance and loss of drainagewide population connectivity. These results affirm that dendritic networks naturally fragment headwater specialised species. Further isolation from anthropogenic fragmentation was detected in two of the six drainages, indicating interactions with system‐specific conditions. Landscape variables related to the hydrology of large rivers also affected genetic distance in predicted ways, supporting the importance of large rivers in genetically structuring headwater species in drainage networks.     

Effects of betamethasone treatment on central myelination in fetal sheep: an electron microscopical study

The long-term effect of betamethasone on the myelination of commissural and associational fibres was investigated in fetal sheep. We studied the corpus callosum and subcortical white matter by electron microscopy. Axons were subdivided into classes according to their axonal diameter: class I: < or =0.65 microm; class II: 0.66-0.84 microm; class III: > or =0.85 microm. Under control conditions, the different functions of the white matter tracts examined were reflected by three morphological criteria: (1) there was a diverse percentage of axonal classes in the investigated areas. In corpus callosum the axons of class II predominate (47.1%). In the subcortical white matter, class I axons with small diameter are in majority (40.8%). (2) In the subcortical white matter more axons are present, with especially large diameter and hence of axonal class III. (3) The axons of subcortical white matter have thicker myelin sheaths than those of the corpus callosum. Betamethasone administration caused a significant decrease of class II axons in the corpus callosum (36.9%). In corpus callosum, axons of all classes present thicker myelin sheaths. Betamethasone administration resulted in a change in the formation of the myelin sheath in the commissural fibres of the corpus callosum but not in the associational fibres of the subcortical white matter. This could be the morphological correlate to behavioral and cognitive changes known to occur in humans after prenatal glucocorticoid treatment.     

Experimental infection of domestic pigeons with pigeon circovirus

Pigeon circovirus (PiCV) infection and young pigeon disease syndrome (YPDS), associated with high morbidity and mortality, have been recognized in young racing pigeons from large portions of Central Europe. There exist a number of data indicating that YPDS is a consequence of PiCV infection and subsequent immunosuppression. In order to prove PiCV to be one of the crucial factors of YPDS, an experimental infection with PiCV was performed under controlled conditions. Twenty-four domestic pigeons (Columba livia forma domestica) were divided into two groups with 12 pigeons each; an infection group and a control group. All birds were between their fourth to eighth week of life. Pigeons in the infection group were infected both intramuscularly and orally with PiCV purified from naturally infected birds, while pigeons in the control group received a placebo. To test a possible influence of the PiCV infection on the immune system, the animals in both groups were vaccinated simultaneously, on the same day, against PMV-1 (Lasovac plus, IDT, Dessau-Tornau, Germany). Weekly virologic testing showed a viraemic period, and excretion of the infection virus, in pigeons in the infection group. Replication of PiCV could be proved on the basis of histologic findings of multiglobular inclusion bodies, mainly observed in macrophages of the bursa of Fabricius. A PiCV, genetically distinct from the experimental virus, was detected in the control group by polymerase chain reaction (PCR) testing, but any histologic findings comparable to the infection group were absent. None of the pigeons revealed clinical signs of illness, or hints that immunosuppression had occurred, regardless of their group. The absence of stressful conditions, considered as a trigger for the development of YPDS, may be responsible for the failure of disease reproduction in our infection model.     

Blindness as a sign of proventricular dilatation disease in a grey parrot (Psittacus erithacus erithacus)

An approximately eight-year-old female grey parrot (Psittacus erithacus erithacus) was presented with a two months history of blindness. The radiographic examination showed a dilatation of the proventriculus, ventriculus and gut. Ophthalmoscopy and electroretinography revealed degeneration of the retina. A proventricular dilatation disease was suspected. The bird was euthanased because of deteriorating condition and poor prognosis. The pathological examination showed an atrophy of the ventricular muscles and lymphoplasmacytic infiltrates of the myenteric plexus of the proventriculus, ventriculus and gut as well as moderate lymphoplasmacytic infiltrates of the cerebrum with moderate neuronophagia. Lymphoplasmacytic infiltrates in the retina, indicating proventricular dilatation disease, and subsequent retinal degeneration were found. A potential common aetiology for proventricular dilatation disease and blindness is discussed.     

Ultrasonographic appearance of the craniocervical junction in normal brachycephalic dogs and dogs with caudal occipital (Chiari-like) malformation

Ultrasonographic evaluation of the spine, especially of the spinal cord, has been rarely reported in dogs. The atlanto-occipital junction provides a small acoustic window through which examination of the craniocervical transition can be performed. Normal sonographic findings of this region in 10 normal brachycephalic dogs are presented and compared with sonographic findings from 25 Cavalier King Charles Spaniels with the caudal occipital malformation syndrome. Sonographic findings were compared with magnetic resonance imaging findings to determine the extent of cerebellar herniation and syringohydromyelia. Cerebellar displacement into the foramen magnum was clearly identified sonographically; however, syringohydromyelia was not discernable due to bone overlay.     

The avian thyroid gland.

There has been a considerable amount of research regarding the function of the avian thyroid gland, particularly in chickens. There is also more information on diseases of the avian thyroid gland, although it is usually in the form of case reports. This article covers a limited amount of material on the structure and function of the avian thyroid gland and its diseases.     

Effects of autologous stem cells on immunohistochemical patterns and gene expression of metalloproteinases and their tissue inhibitors in doxorubicin cardiomyopathy in a rabbit model

This study aims to investigate the expression of metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in chronic doxorubicin cardiomyopathy in a rabbit model and to evaluate the effects of bone marrow-derived mesenchymal stem cell (MSC) transplantation in this disease. Thirty-nine 3-month-old New Zealand rabbits were divided into 4 groups: group 1 (n = 9) was the untreated control. Groups 2-4 were treated with 6 weeks of doxorubicin (3 mg/kg). Group 2 (n = 6) received no further treatment. In group 3 (n = 9), animals were treated with culture medium (CM) alone. In group 4 (n = 15), autologous MSCs (1.5-2.0 x 10(6)/ml) were injected in the left ventricular (LV) wall. Hearts were stained with HE and picrosirius red. MMP-1, -2, -3 and -9 and TIMP-2 and -3 were detected immunohistochemically. The mRNA levels were determined by real-time polymerase chain reaction. The results confirmed that doxorubicin treatment resulted in minimal myocardial fibrosis and showed that expression of MMPs increased and TIMP-3 decreased. The injection procedure resulted in increased myocardial fibrosis in groups 3 and 4. After MSC injection, MMP-1, MMP-2, and TIMP-3 expression was higher than that in group 2. CM injection led to more fibrosis, elevated TIMP-3, but diminished MMP-1 and MMP-2 expression compared with MSC injection. The mRNA levels of MMPs and TIMPs were not significantly different among all groups. In conclusion, chronic doxorubicin cardiomyopathy was characterized by increased MMP and decreased TIMP-3 expression. MSCs injection into the LV resulted in marked differences of collagen content and MMP/TIMP expression in the whole heart, although significant numbers of living MSCs were not detected after 4 weeks.