Evaluation of the efficacy of the crude extracts of Capsicum frutescens, Citrus limon and Opuntia vulgaris against Newcastle disease in domestic fowl in Tanzania.

Prophylactic and therapeutic efficacy of a combination of Capsicum frutescens (red pepper), Citrus limon (lemon) and Opuntia vulgaris (prickly pear) against Newcastle disease (ND) in domestic fowl were evaluated. Eighty-eight broiler chickens were divided into five groups. Birds from three groups were inoculated with velogenic ND virus strain, whereas birds from two groups were left as controls. Two groups received a mixture of the plant extract three days prior to inoculation and birds from one group were given the plant extract for two days following development of clinical signs. Blood samples were collected for haemaglutination inhibition tests (HI) for detection of ND virus antibodies. Body weights were monitored during the experiment. Three birds died from the group that was inoculated with ND virus and treated with the plant extract; two died from the group that received the plant extract as a prophylaxis and inoculated with ND virus; and one bird died from the group that was inoculated with ND virus but not given the plant extract. No death was observed in any of the birds in the control groups. Antibody titers for ND virus rose four-fold in the inoculated birds but remained low in the un-inoculated groups. Mean body weights of birds in group B declined markedly compared to the other groups. The results indicated that there was no prophylactic or therapeutic value of the plant extract against ND. The plant extract showed a negative effect on body weights in birds with ND.

Stereological and allometric studies on mammalian cerebral cortex with implications for medical brain imaging.

Design-based stereological methods (the Cavalieri principle and vertical sectioning) have been used to estimate the volumes, surface areas and thicknesses of the cerebral cortex. Cortices of individual hemispheres were analysed in a selection of 31 adult domestic mammals (horses, oxen, pigs, goats, dogs, cats and rabbits). There were 13 females and 18 males. After correcting for fixation shrinkage effects, results were tested for species, laterality and sex differences using linear regression and analysis of variance. Mean body weights of domestic mammals varied from 4 kg to 460 kg and brain volumes from 11 cm3 to 603 cm3. Hemisphere dimensions varied between species but, except for volume (which exhibited a species x sex interaction effect), no other differences were detected. It is concluded that these mammalian brains are, in terms of their gross anatomy, symmetric and not sexually dimorphic. Apparent cortical thickness (measured directly on slices) proved to be a satisfactory estimate of true thickness (estimated by dividing cortical volume by the mean of outer and inner cortical surfaces). This has implications for medical slice images on which mean cortical thickness can be estimated only from apparent local thicknesses.

The gyrification of mammalian cerebral cortex: quantitative evidence of anisomorphic surface expansion during phylogenetic and ontogenetic development.

Describing the shapes of 3D objects has proved to be as problematical in biology as in other areas. In an attempt to tackle this problem, established stereological methods (the Cavalieri principle and vertical sectioning) have been used to estimate a 3D shape-dependent quantity which can detect anisomorphic changes and is related to the degree of cortical convolution or gyrification. This isomophy factor is employed to assess phylogenetic and ontogenetic changes in the mammalian cerebral cortex. Gross anatomical differences between cerebral hemispheres of adult domestic mammals (horses, oxen, pigs, goats, dogs, cats and rabbits) were tested by paying attention to species, laterality and sex differences. Human fetal brains were also studied. Mean body weights of domestic mammals varied from 4 kg to 460 kg and brain weights from 10 g to 636 g. Fetuses weighed 39-610 g (crown-rump lengths 85-185 mm) and brain volumes were 4-56 cm3. Isomorphy factors were derived from estimates of hemisphere volumes and cortical surface areas. Hemisphere shape varied between species but no lateral or sex differences were detected. It is concluded that these mammalian brains are, in terms of their gross anatomy, symmetric and not sexually dimorphic. Fetal brains became more convoluted during uterine development. The isomorphy factor offers a convenient measure of gyrification which demonstrates that brains become more convoluted as they enlarge.

A canine distemper virus epidemic in Serengeti lions (Panthera leo).

Canine distemper virus (CDV) is thought to have caused several fatal epidemics in canids within the Serengeti-Mara ecosystem of East Africa, affecting silver-backed jackals (Canis mesomelas) and bat-eared foxes (Otocyon megalotis) in 1978 (ref. 1), and African wild dogs (Lycaon pictus) in 1991 (refs 2, 3). The large, closely monitored Serengeti lion population was not affected in these epidemics. However, an epidemic caused by a morbillivirus closely related to CDV emerged abruptly in the lion population of the Serengeti National Park, Tanzania, in early 1994, resulting in fatal neurological disease characterized by grand mal seizures and myoclonus; the lions that died had encephalitis and pneumonia. Here we report the identification of CDV from these lions, and the close phylogenetic relationship between CDV isolates from lions and domestic dogs. By August 1994, 85% of the Serengeti lion population had anti-CDV antibodies, and the epidemic spread north to lions in the Maasai Mara National reserve, Kenya, and uncounted hyaenas, bat-eared foxes, and leopards were also affected.

Dichapetalum spp toxicity in cattle at a farm in Tanzania.

An investigation was carried out to establish the cause of mortalities during the dry season in cattle at a state livestock replacement farm at Kibaha in the Coast Region of Tanzania. Studies included a thorough review of the farm records, interviews with the farm staff, screening for parasites through examination of blood and lymph node smears, clinical examination of sick animals, and a survey of the grazing lands as well as postmortem examinations of the dead cattle. Circumstances incriminated plant poisoning as the cause of the deaths. A systematic survey of the pastures indicated a preponderance of Dichapetalum spp poisonous plants in areas in which most of the affected cattle had been grazing. Leaves of these plants were collected, dried, powdered and fed or drenched to 6 goats and 24 wistar rats. Lesions in animals that died resembled those seen in dead cows--pulmonary congestion and edema, froth in the airways, hemorrhagic gastroenteritis, and variable quantities of serous effusions into serous cavities. Although Dichapetalum spp occur especially in coastal regions, previous cases of poisoning by this plant in Tanzania have not been published. This report documents a systematic toxicological trial to verify the poisonous potency of this plant.

Stereological studies on red corpuscle size produce values different from those obtained using haematocrit- and model-based methods.

The routine methods for estimating erythrocyte size (volume and surface area) are not generally unbiased. Using geometric models introduces a bias determined by the ways in which real red blood corpuscles depart in size and shape from the simplistic ideal. Employing haematocrit and red corpuscle count to estimate mean corpuscular volume relies on an implicit assumption that erythrocytes fill three-dimensional space. However, a biconcave circular disc cannot be space-filling. The bias is positive and its magnitude depends on erythrocyte geometry and packing density within the centrifuge pellet. We have estimated the volumes, surface areas and shape factors of red blood corpuscles in normal adults (three males, three females) using transmission electron microscopy and stereology. We confirm the lack of sexual dimorphism and find that the mean corpuscular volume is 44 fl (between-subject coefficient of variation 5%), mean membrane surface area is 87 microns2 (6%) and the shape factor is 18.4 fl/fl (11%). The surface is 44% greater than that of a sphere of equal volume. The possible reasons for discrepancies with standard haematological values are discussed. On the basis of observed volumes, we predict that red blood corpuscles account for only 51% of the volume of the red column in standard haematocrit pellets.

Purkinje cell complements in mammalian cerebella and the biases incurred by counting nucleoli.

An unbiased stereological counting device (the fractionator) was used to count Purkinje neurons in mammalian cerebella of known weights in order to define the relationship between weight and number. Nucleoli were chosen as the counting unit and numbers were estimated from uniform random samples of wax-embedded tissue sections. For the cerebella of rat, rabbit, cat, dog, goat, sheep, pig, ox, horse and human, there was a significant linear relationship between log number and log weight. The allometric relationship took the form N = 748,500 x W0.627. The relative bias associated with using nucleoli as counting units was assessed separately on disector pairs of sections and amounted to roughly -5% but varied between species. When the brains of females and males were analysed separately (cat, goat, pig, ox, horse, human), there were no significant differences between the regression lines. These results are consistent with earlier findings. They imply that Purkinje neuron packing densities decrease as brain size increases. Moreover, our preliminary findings appear to indicate that, for any given cerebellar weight, females and males have similar numbers of neurons.

Comparative morphometry of the mammalian brain: estimates of cerebral volumes and cortical surface areas obtained from macroscopic slices.

Stereological methods for obtaining unbiased estimates of brain volumes and surface areas are illustrated on fixed brains (cerebrum only) from mammals varying in body weight between 2 kg (cat) and 550 kg (ox). Brain sampling was designed so that Cavalieri estimates of volumes (derived via point counting) could be combined with vertical sectioning estimates of surface areas (via intersection counting). Total volumes, cortical volumes and cortical surface areas were calculated. Each cerebral hemisphere was cut into 3 slabs. Each slab was cut further into macroscopic, parallel vertical slices having a uniform random start position. The term vertical as used here signifies orthogonal to the medial aspect of the hemisphere. The direction of vertical slices also had a random start but was varied systematically across the slabs. Test lattices bearing test points and cycloid test lines were superimposed on vertical slices. Fixed volumes and surfaces were corrected for shrinkage effects. A worked example of the calculation sequence is provided. The experimental design was flexible. Brains of different sizes could be analysed by simply altering the distance between slices and the size of the test lattice. Analyses took 30-45 minutes per hemisphere. Whilst volumes and surfaces increased with body weight, specific values declined. Thus, specific surfaces for the cortex fell from 25 cm2/kg (cat) to 2 cm2/kg or less (pig and ox).