Variable selection in near infrared spectra for the biological characterization of soil and earthworm casts

Near infrared reflectance spectroscopy (NIRS) was used to predict six biological properties of soil and earthworm casts including extracellular soil enzymes, microbial carbon, potential nitrification and denitrification. Partial least squares regression (PLSR) models were developed with a selection of the most important near infrared wavelengths. They reached coefficients of determination ranging from 0.81 to 0.91 and ratios of performance-to-deviation above 2.3. Variable selection with the variable importance in the projection (VIP) method increased dramatically the prediction performance of all models with an important contribution from the 1750–2500 nm region. We discuss whether selected wavelengths can be attributed to macronutrient availability or to microbial biomass. Wavelength selection in NIR spectra is recommended for improving PLSR models in soil research.     

SMEDWI-2 is a PIWI-like protein that regulates planarian stem cells

We have identified two genes, smedwi-1 and smedwi-2, expressed in the dividing adult stem cells (neoblasts) of the planarian Schmidtea mediterranea. Both genes encode proteins that belong to the Argonaute/PIWI protein family and that share highest homology with those proteins defined by Drosophila PIWI. RNA interference (RNAi) of smedwi-2 blocks regeneration, even though neoblasts are present, irradiation-sensitive, and capable of proliferating in response to wounding; smedwi-2(RNAi) neoblast progeny migrate to sites of cell turnover but, unlike normal cells, fail at replacing aged tissue. We suggest that SMEDWI-2 functions within dividing neoblasts to support the generation of cells that promote regeneration and homeostasis.     

Phenological and physiological evaluation of first and second cropping periods of sorghum and maize crops

Environmental conditions influence phenology and physiological processes of plants. It is common for maize and sorghum to be sown at two different periods: the first cropping (spring/summer) and the second cropping (autumn/winter). The phenological cycle of these crops varies greatly according to the planting season, and it is necessary to characterize the growth and development to facilitate the selection of the species best adapted to the environment. The aim of this study was to characterize phenological phases and physiological parameters in sorghum and maize plants as a function of environmental conditions from the first cropping and second cropping periods. Two parallel experiments were conducted with both crops. The phenological characterization was based on growth analyses (plant height, leaf area and photoassimilate partitioning) and gas exchange evaluations (net assimilation rate, stomatal conductance, transpiration and water-use efficiency). It was found that the vegetative stage (VS) for sorghum and maize plants was 7 and 21 days, respectively, longer when cultivated during the second cropping. In the first cropping, the plants were taller than in the second cropping, regardless of the crop. The stomatal conductance of sorghum plants fluctuated in the second cropping during the development period, while maize plants showed decreasing linear behaviour. Water-use efficiency in sorghum plants was higher during the second cropping compared with the first cropping. In maize plants, in the second cropping, the water-use efficiency showed a slight variation in relation to the first cropping. It was concluded that the environmental conditions as degree-days, temperature, photoperiod and pluvial precipitation influence the phenology and physiology of both crops during the first and the second cropping periods, specifically cycle duration, plant height, leaf area, net assimilation rate, stomatal conductance and water-use efficiency, indicating that both crops respond differentially to environmental changes during the growing season.     

Replication and transmission of porcine circovirus type 2 in mice

Little information is known about infection, replication and transmission of porcine circovirus type 2 (PCV2) in species other than swine. Two sets of animal experiments were carried out to investigate the susceptibility of mice to PCV2 and to study their possible role in maintaining and transmitting the virus. In the first experiment 14 mice were inoculated with PCV2 by the intraperitoneal route with 5 x 10(2) TCID50 of the PCV2-ROM strain (Cadar et al., 2007). In a second experiment 24 mice were divided into two groups (A and B); mice in Group A (n = 18) were inoculated orally with 1 x 10(5) TCID50 PCV2-ROM and mice in Group B (n = 6) were left uninoculated until day 12 post inoculation (p.i.), when they were mixed with Group A. The animals were sacrificed at intervals for postmortem investigation and virus genome detection by polymerase chain reaction (PCR). The PCR results indicated that PCV2 could replicate in mice infected intraperitoneally or by the oral route, and that the virus can be transmitted directly from mouse to mouse.     

Use of real-time PCR to detect Mycoplasma haemofelis and 'Candidatus Mycoplasma haemominutum' in the saliva and salivary glands of haemoplasma-infected cats

Feline haemoplasma infection can cause haemolytic anaemia. The natural method of transmission of haemoplasmas between cats is currently unknown but the nature of some of the risk factors for infection suggests that saliva may act as a mode of transmission. The aim of this study was to determine if Mycoplasma haemofelis (Mhf) and 'Candidatus Mycoplasma haemominutum' (CMhm) DNAs could be amplified from saliva and salivary gland samples collected from haemoplasma-infected cats.     

Sheep performance under intensive continuous grazing of native grasslands of <Emphasis Type="Italic">Paspalum notatum</Emphasis> and <Emphasis Type="Italic">Axonopus compressus</Emphasis> in the subtropical region of the Highlands of Central Mexico

Liveweight gain was evaluated in tropical Dorper X Pelibuey lambs under intensive continuous grazing of native grasslands dominated by Paspalum notatum (PN) or Axonopus compressus (AC) in the subtropics of Central Mexico. Two trials were undertaken. Trial 1 lasted 12 weeks with 10 lambs (initial weight 18 +/- 2.57 kg, 3 months old) per treatment in 2002, and Trial 2 for 13 weeks with 8 lambs (initial weight 24.0 +/- 2.0 kg, 4 months old) per treatment. Lambs were weighed once per week, and liveweight change was estimated by linear regression over day of the experiment, using individual regression coefficients as unbiased estimates of daily liveweight change; analysed in a random block design. Lambs on Trial 1 gained 0.061 kg/lamb/day on PN and 0.047 kg/lamb/day on AC (P > 0.05) at an overall mean stocking rate of 25 lambs/ha. In Trial 2, liveweight gain was significantly larger in PN (0.060 kg/lamb/day) than on AC (0.043 kg/lamb/day) (P < 0.05), at a mean stocking rate of 21.5 lambs/ha. It is concluded that intensive continuous grazing of native grasslands in the subtropics of the highlands of Central Mexico enables moderate liveweight gains for weaned lambs during the rainy season; with better results in grasslands dominated by Paspalum notatum.     

Hepatic encephalomyelopathy in a calf with congenital portosystemic shunt (CPSS)

A 4-month-old female Holstein Friesian calf was referred to the Veterinary Teaching Hospital, University of Berne, Switzerland for evaluation of ataxia, weakness, apathy and stunted growth. Clinical examination revealed generalized ataxia, propioceptive deficits, decreased menace response and sensibility. Postmortem examination did not reveal macroscopic changes of major organs. Histologically, the brain and the spinal cord lesions were characterized by polymicrocavitation, preferentially affecting the white matter fibers at the junction of grey and white matter and by the presence of Alzheimer type II cells. The liver revealed lesions consistent with a congenital portosystemic shunt, characterized by increased numbers of arteriolar profiles and hypoplasia to absence of portal veins. The pathological investigations along with the animal history and clinical signs indicated a hepatic encephalomyelopathy due to a congenital portosystemic shunt.     

Effects of pre-natal glucocorticoids on testicular development in sheep

We tested the hypothesis that acute pre-natal exposure to high levels of synthetic glucocorticoid (betamethasone) would alter fetal testicular development through actions on gonadal glucocorticoid receptors (GRs). Pregnant Merino ewes bearing singleton male fetuses (n = 24) were allocated randomly among four equal groups to be injected intramuscularly with saline or betamethasone (0.5 mg/kg) either on day 109 of gestation or on both day 109 and day 116 of gestation. Fetal testes were collected at post-mortem, 5 days after each treatment. The volume of interstitial tissue and the volume, length and diameter of the sex cords were measured, and Sertoli cells and gonocytes were counted. For cord volume and interstitial tissue volume, control testes demonstrated maturational changes as fetal age advanced from 109 to 116 days of gestation. For that period, the single injection of betamethasone significantly reduced Leydig cell proliferation (P < 0.05), but had no effect on Sertoli cell numbers. Immunohistochemistry was used to localize GR and proliferating cell nuclear antigen in testicular cells. GR immunoexpression in Leydig cells was higher in fetuses exposed to betamethasone at 109 days of gestation than in control fetuses. Sertoli cells showed low levels of GR. It was concluded that, during mid-gestation, a brief period of glucocorticoid treatment could affect testicular development in male sheep fetuses. The mechanism probably involves direct effects on Leydig cells, as these cells express extra-GR in response to the treatment. Sertoli cells seem to produce less GR than Leydig cells, perhaps explaining their lack of response to betamethasone. These outcomes may have important implications for future fertility in male offspring.