A serial examination of three groups of cattle infected intravenously (iv) (Group 1, n=8) or subcutaneously (sc) (Group 2, n=8) with live Neospora caninum tachyzoites or with VERO cells (Group 3, n=8) at 70 days' gestation was carried out and the nature of the inflammatory responses in the placenta and the presence of parasite antigen were analysed. Immune cells expressing CD3, CD4, CD8, gamma delta (gammadelta) T-cell receptors (TCR), CD79alpha cytoplasmic (cy) (B cells) and NKp46 [natural killer (NK) cells] antigens were identified immunohistochemically and cells expressing mRNA for interferon-gamma (IFN-gamma) were labelled by in-situ hybridization. Intravenous inoculation caused mortality in all fetuses from 28 days post-inoculation (dpi) onwards. Subcutaneous inoculation caused mortality in 50% of the animals by 28dpi. Pathological changes in the placenta consisted of necrosis of fetal placental villi, necrosis and inflammation in adjacent areas of the maternal septum and inflammation at the base of the maternal caruncle. The inflammatory infiltrate consisted mainly of CD3(+) lymphocytes, dominated by CD4(+) and gammadelta TCR(+) cells, with CD8(+) cells present to a lesser extent. The results from the control group indicated fewer NK cells than those occurring in the placenta of human beings or mice. Infiltration of CD4(+) cells and NKp46(+) cells was observed in the caruncular base and septa 14 days after infection, whereas infiltration of gammadelta TCR(+) cells was observed from 28 dpi onwards. To our knowledge this is the first report on the presence and distribution of NK cells in the bovine placenta. Maternal inflammatory cells expressing mRNA for IFN-gamma were identified in animals inoculated with parasites iv or sc at 14 and 28 dpi, respectively. In the sc-inoculated dams with live fetuses at 28, 42 and 56dpi, there was no evidence of parasite antigen, infiltration of immune cells or production of IFN-gamma, suggesting that the parasite had not reached the placenta. The exact cause of fetal death was not established. Tissue destruction by the parasite may have occurred; in addition, there may have been a T helper 1 (Th-1) immune response to the neospora infection at the materno-fetal interface, resulting in infiltrations of CD4T cells, gammadelta T cells and NK cells and the subsequent production of IFN-gamma. It is possible that a pro-inflammatory Th-1 response early in gestation protects the dam by eliminating the parasite; however, it may lead to destruction of the placental tissues themselves and thus be incompatible with fetal survival.

Animals↗

PubMedDate not supplied

The pathogenesis of neosporosis in pregnant cattle: inoculation at mid-gestation.

To investigate the pathogenesis of bovine neosporosis, 14 pregnant cattle were each inoculated subcutaneously with either 10(7) or 5 x 10(8) Neospora caninum (strain NC1) tachyzoites at 140 days' gestation. Serial necropsies were then carried out over an 8-week period. In the placenta, Neospora DNA and histopathological changes were observed in samples taken 14 days post-inoculation (dpi), with focal necrosis of maternal caruncular septa and fetal placental villi, serum leakage, and a maternal and fetal inflammatory response. At subsequent samplings, pathological changes in the placenta showed signs of resolution. No parasitaemia was detected in the dams in the two weeks following inoculation. In the fetus, Neospora DNA was detected at 14 dpi, and histopathological changes in the fetal central nervous system at 28 and 42 dpi consisted of small foci of necrosis and inflammation. Resolution of placental lesions during the experiment indicated that the disease was being controlled, and fetal infection, although established, did not appear to be progressing to a fatal outcome. The two doses of tachyzoites produced similar results, but the higher dose elicited earlier and more extensive lesions in the placenta and fetus. Control animals remained negative for all parameters recorded. It is concluded that in bovine neosporosis the placenta plays a central role in the pathogenesis and epidemiology of the infection, and that while primary tissue destruction by the parasite may endanger the fetus, the maternal and fetal inflammatory responses may also be damaging.

Animals↗

PubMedDate not supplied

Maintenance of optical quality during crystalline lens growth.

Vertebrate lenses grow throughout life by the division of cells at the lens surface. The fibre cells thus produced are gradually covered by newer tissue, giving a layered structure. During growth, the lens must remain transparent and retain its refractile properties. The severity of these constraints is perhaps most evident in teleost fish which have a spherical lens that may increase in volume by a thousandfold during the first year of life. The dioptric power of the teleost fish eye is vested entirely in this spherical lens, as water, the cornea and the intraocular vitreous humour have almost identical refractive indices. Spherical lenses of uniform refractive index produce poor images because rays entering at different distances from the optic axis are focused at different distances from the lens. Teleost fish do not suffer from this imperfection and it has long been presumed that this is because there exists a refractive index gradient having a high value in the centre and decreasing continuously and symmetrically with radius in all directions. Here we demonstrate in the African cichlid fish, Haplochromis burtoni, that a refractive index gradient does exist, although its form is significantly different from that previously postulated.

Animals↗

PubMedDate not supplied

Vision impairment and handicap: The RVIB Employment Survey. The Steering Committee for the RVIB Employment Survey.

PURPOSE: The purpose of this study was to examine the association between type of vision impairment and disability and the handicap or impact of vision loss on functioning. METHODS: Participants were interviewed for the Royal Victorian Institute for the Blind Employment Survey, and asked to self-report whether totally blind or not (vision impaired). Causes of visual impairment were also reported. Eyesight was rated on a scale from 0 (completely blind) to 10 (best possible eyesight). Difficulty with mobility, personal care, household activities, work and hobbies and social interactions were also rated. Participants with vision impairment also rated their level of disability in reading and seeing other people's reactions using the same scale. RESULTS: Of the 250 participants, 39 self-reported total blindness. Participants with vision impairment experienced greater levels of difficulty in almost all areas than people who self-reported total blindness. People with vision impairment due to glaucoma and macular degeneration reported significantly more difficulty with reading newspapers, while there was a borderline significant relationship between difficulty with seeing people's reactions and macular degeneration. CONCLUSIONS: In summary, we found that difficulty associated with everyday tasks was greater than might be expected from self-report of vision. This study confirms the need for visual function tools to supplement the use of objective visual acuity measurements in people with vision impairment.

Activities of Daily Living↗