Mycobacterium avium subspecies paratuberculosis and Mycobacterium avium subsp. avium infections in a tule elk (Cervus elaphus nannodes) herd

Between 2 August and 22 September 2000, 37 hunter-killed tule elk (Cervus elaphus nannodes) were evaluated at the Grizzly Island Wildlife Area, California, USA, for evidence of paratuberculosis. Elk were examined post-mortem, and tissue and fecal samples were submitted for radiometric mycobacterial culture. Acid-fast isolates were identified by a multiplex polymerase chain reaction (PCR) that discriminates among members of the Mycobacterium avium complex (MAC). Histopathologic evaluations were completed, and animals were tested for antibodies using a Johne's enzyme-linked immunosorbent assay (ELISA) and agar gel immunodiffusion. In addition, 104 fecal samples from tule elk remaining in the herd were collected from the ground and submitted for radiometric mycobacterial culture. No gross lesions were detected in any of the hunter-killed animals. Mycobacterium avium subsp. paratuberculosis (MAP) was cultured once from ileocecal tissue of one adult elk and was determined to be a strain (A18) found commonly in infected cattle. One or more isolates of Mycobacterium avium subsp. avium (MAA) were isolated from tissues of five additional adult elk. Gastrointestinal tract and lymph node tissues from 17 of the 37 elk (46%) examined had histopathologic lesions commonly seen with mycobacterial infection; however, acid-fast bacteria were not observed. All MAC infections were detected from adult elk (P = 0.023). In adult elk, a statistically significant association was found between MAA infection and ELISA sample-to-positive ratio (S/P) > or = 0.25 (P=0.021); four of five MAA culture-positive elk tested positive by ELISA. Sensitivity and specificity of ELISA S/P > or = 0.25 for detection of MAA in adult elk were 50% and 93%, respectively. No significant associations were found between MAC infection and sex or histopathologic lesions. Bacteriologic culture confirmed infection with MAP and MAA in this asymptomatic tule elk herd. The Johne's ELISA was useful in signaling mycobacterial infection on a population basis but could not discriminate between MAA and MAP antibodies. The multiplex PCR was useful in discriminating among the closely related species belonging to MAC.     

Standardising bull breeding soundness evaluations and reporting in Australia

There is substantial variation in bull breeding soundness evaluation procedures and reports in Australia; the situation is compounded by difficulties in interpretation and the validity of many reports. In an effort to overcome this, the scientific literature was reviewed [Fordyce G. In: Fordyce G, editor. Bull fertility: selection and management in Australia. Eight Mile Plains, Australia: Australian Cattle Vets; 2002] and the needs of stakeholders were considered in preparing a manual, Evaluating and Reporting Bull Fertility [Entwistle KW, Fordyce G. Evaluating and reporting bull fertility. Eight Mile Plains, Australia: Australian Cattle Vets; 2003.] that outlined standards for assessing and reporting bull breeding soundness. A new recording and reporting system, called Bull Reporter, is based on standards from this manual and groups bull fertility traits into five summary categories: Scrotum, Physical, Crush-side Semen, Sperm Morphology, and Serving. The client will generally select which categories they wish to have included in the evaluation to suit their specific purposes. While there is adequate room for comments, the veterinarian is not required to make an overall judgment of whether the bull has normal capacity to sire calves under natural mating management, but ensures the standards for each selected category are met. Professional, standardised, easy-to-read reports are produced either electronically [Entwistle KW, Fordyce G. Evaluating and reporting bull fertility. Eight Mile Plains, Australia: Australian Cattle Vets; 2003.] or manually. A bull owner or their agent signs the certificate to affirm that bulls have not undergone procedures to rectify faults which may have otherwise caused them to fail the standards. An accreditation system for assessing sperm morphology was established because of its demonstrated relationship with pregnancy rates and because of the difficulties in achieving consistent and accurate assessments among laboratories. It is considered that Bull Reporter is applicable to beef and dairy bulls across all levels of management, genotypes and environments throughout Australia, with substantial potential for application elsewhere in the world.     

Herbicide-resistance conferred by expression of a catalytic antibody in Arabidopsis thaliana

Engineering herbicide resistance in crops facilitates control of weed species, particularly those that are closely related to the crop, and may be useful in selecting lines that have undergone multiple transformation events. Here we show that herbicide-resistant plants can be engineered by designing an herbicide and expressing a catalytic antibody that destroys the herbicide in planta. First, we developed a carbamate herbicide that can be catalytically destroyed by the aldolase antibody 38C2. This compound has herbicidal activity on all three plant species tested. Second, the light chain and half of the heavy chain (Fab) of the catalytic antibody were targeted to the endoplasmic reticulum in two classes of Arabidopsis thaliana transformants. Third, the two transgenic plants were crossed to produce an herbicide-resistant F1 hybrid. The in vitro catalytic activity of the protein from F1 hybrids corroborates that catalytic antibodies can be constitutively expressed in transgenic plants, and that they can confer a unique trait.     

Sunlight-activated insecticides: historical background and mechanisms of phototoxic activity

Several photosensitizing agents, which are activated by illumination with sunlight or artificial light sources, have been shown to be accumulated in significant amounts by a variety of insects when they are administered in association with suitable baits. The subsequent exposure of such insects to UV/visible light leads to a significant drop in survival. Of the photosensitizers tested so far, xanthenes (e.g. phloxin B) and porphyrins (e.g. haematoporphyrin) appear to be endowed with the highest photoinsecticidal activity. In particular, porphyrins absorb essentially all the UV/visible light wavelengths in the emission spectrum of the sun; hence they are active at very low doses. Thus, 1 h irradiation of Ceratitis capitata, Bactrocera oleae (also known as Dacus oleae) or Stomoxys calcitrans which ingested a few nanomoles of porphyrin per fly with light intensities of the order of 1000 microE s(-1) m(-2) causes about 100% death in laboratory tests. Present evidence suggests that such photosensitizers act on the membranes of the midgut with consequent feeding inhibition, as well as on the neuromuscular sheath. No apparent onset of photoresistance has been observed. The rapid photobleaching of xanthenes and porphyrins when illuminated by visible light, as well as the lack of significant toxicity of such compounds in the dark, minimizes the risk of an important environmental impact of such photoinsecticidal agents.     

Plant patterning: TRY to inhibit your neighbors

Two regulators of hair-cell patterning in Arabidopsis act in the cells where they are produced to inhibit primary cell fate in neighboring cells. Their relationship to the activators of the primary cell fate suggests a classical activator-inhibitor model for patterning that can now be analyzed in detail.     

Purification of the autotransporter protein Hbp of Escherichia coli

The enzyme Hbp (hemoglobin protease) of the pathogenic Escherichia coli strain EB1 has been purified to homogeneity by gel filtration chromatography. The purified protein is capable of binding heme and shows hemoglobin protease activity. Our method of purification is applicable not only to Hbp but also to other autotransporter proteins and will contribute to a better understanding of the function-structure relationship of this family of proteins.     

Steroid 21-hydroxylase gene mutational spectrum in 50 Tunisian patients: Characterization of three novel polymorphisms

Congenital adrenal hyperplasia (CAH) is an autosomal recessive disease of steroid biosynthesis in humans. More than 90% of all CAH cases are caused by mutations of the 21-hydroxylase gene (CYP21A2), and approximately 75% of the defective CYP21A2 genes are generated through an intergenic recombination with the neighboring CYP21A1P pseudogene. In this study, the CYP21A2 gene was genotyped in 50 patients in Tunisia with the clinical diagnosis of 21-hydroxylase deficiency. CYP21A2 mutations were identified in 87% of the alleles. The most common point mutation in our population was the pseudogene specific variant p.Q318X (26%). Three novel single nucleotide polymorphism (SNP) loci were identified in the CYP21A2 gene which seems to be specific for the Tunisian population. The overall concordance between genotype and phenotype was 98%. With this study the molecular basis of CAH has been characterized, providing useful results for clinicians in terms of prediction of disease severity, genetic and prenatal counseling.     

Centromeric chromatin and the pathway that drives its propagation

The centromere is the locus that directs chromosomal inheritance at cell division. While centromeres in diverse eukaryotes are commonly found at sites of repetitive DNA, their location is epigenetically specified. The histone H3 variant CENP-A is the prime candidate for epigenetically marking the centromere, and recent work has uncovered several additional proteins that play key roles in centromere assembly and maintenance. We describe advances in the identification and characterization of proteins that form the centromere, and focus on recent findings that have advanced our understanding of the assembly of functional centromeric chromatin. This article is part of a Special Issue entitled: Histone chaperones and chromatin assembly.     

Galactose recognition by the apicomplexan parasite Toxoplasma gondii

Toxosplasma gondii is the model parasite of the phylum Apicomplexa, which contains numerous obligate intracellular parasites of medical and veterinary importance, including Eimeria, Sarcocystis, Cryptosporidium, Cyclospora, and Plasmodium species. Members of this phylum actively enter host cells by a multistep process with the help of microneme protein (MIC) complexes that play important roles in motility, host cell attachment, moving junction formation, and invasion. T. gondii (Tg)MIC1-4-6 complex is the most extensively investigated microneme complex, which contributes to host cell recognition and attachment via the action of TgMIC1, a sialic acid-binding adhesin. Here, we report the structure of TgMIC4 and reveal its carbohydrate-binding specificity to a variety of galactose-containing carbohydrate ligands. The lectin is composed of six apple domains in which the fifth domain displays a potent galactose-binding activity, and which is cleaved from the complex during parasite invasion. We propose that galactose recognition by TgMIC4 may compromise host protection from galectin-mediated activation of the host immune system.