The Exploitation of Nematode-Responsive Plant Genes in Novel Nematode Control Methods

The molecular interactions between plants and sedentary nematodes are undergoing intense study, not only for reasons of fundamental research but also for the potential benefits to agriculture. The present technology allows the transformation of an increasing number of crop plants, providing new ways to introduce resistance against plant-parasitic nematodes. The ability of sedentary nematodes to induce specialized feeding sites in plant roots is one of the most fascinating aspects of this host–parasite interaction. Molecular approaches have been initiated to identify and characterize plant genes altered in expression after infection by sedentary nematodes. The results obtained indicate that many genes indeed become up-regulated upon nematode infection. Surprisingly, several so-called constitutive promoters that are normally used to achieve high expression in plant cells are completely ‘silenced’ in the feeding sites within days after nematode infection. Generally, there are two options available for the genetic engineering of nematode resistance: the synthesis of anti-nematode proteins or the localized production of a cytotoxic protein that interferes with the development of feeding cells. Nematode-induced promoters are very useful for the production by plants of sufficiently high levels of anti-nematode proteins at feeding sites. Alternatively, interfering with feeding-cell development is somewhat similar to the hypersensitive response evoked by nematodes in a naturally resistant plant. Here, destruction of specific plant cells can be achieved by the localized expression of a cytotoxin such as barnase, a potent ribonuclease. This approach, however, calls for a highly specific ‘non-leaky’ promoter, which is active only in the feeding cells. Another possibility is to use a two-component system, where the leakiness of the promoter in other tissues is counterbalanced by the constitutive expression of a neutralizing gene.     

East Coast fever immunisation field trial in crossbred dairy cattle in Hanang and Handeni districts in northern Tanzania

East Coast fever (ECF) causes considerable mortality and production losses in the Tanzania smallholder dairy sector and limits the introduction of improved dairy breeds in areas where the disease is present. The infection and treatment method (ITM) was adopted by smallholder dairy farms for ECF immunisation in Hanang and Handeni districts of Tanzania. This study recorded incidence rates for ECF and other tick-borne diseases (TBDs) for ECF-immunised and non-immunised cattle between 1997 and 2000. Approximately 80% of smallholder households from both sites (n?=?167) participated in this longitudinal study, with immunisations carried out at the request of the livestock owners. Efficacy of ITM for preventing ECF cases in these crossbred dairy cattle was estimated at 97.6%, while that for preventing ECF deaths was 97.9%. One percent of the cattle developed clinical ECF as a result of immunisation. Since ECF immunisation permits a reduction in acaricide use, an increase in other TBDs is a potential concern. Sixty-three percent of farmers continued to use the same acaricide after immunisation, with 80% of these reducing the frequency of applications. Overall, 78% of farmers increased the acaricide application interval after immunisation beyond that recommended by the manufacturer, resulting in annual savings in the region of USD 4.77 per animal. No statistical difference was observed between the immunised and non-immunised animals in the incidence of non-ECF TBDs. However, immunised animals that succumbed to these diseases showed fewer case fatalities. ITM would therefore appear to be a suitable method for ECF control in Tanzania's smallholder dairy sector.     

Signs of generalized anxiety and compulsive disorders in chimpanzees

Fear and anxiety have been studied extensively in humans and other animals. However, far less attention has been focused on the clinical and ethical implications of nonhuman animals’ susceptibility to psychological disorders. Behavioral signs of psychopathology in nonhuman animals, including our closest phylogenetic relatives, are rarely described as clinical syndromes. In this study, we drew on approaches described in child psychiatry, veterinary medicine, and primatology, to identify behavioral clusters in chimpanzees comparable with human anxiety disorders, such as generalized anxiety disorder and obsessive–compulsive disorder.In phase 1 of this study, we accessed published case reports of 20 chimpanzees subjected to maternal separation, social isolation, experimentation, or similar experiences. We tested the inter-rater reliability of the Diagnostic and Statistical Manual of Mental Disorders (fourth edition; DSM-IV) criteria for generalized anxiety disorder and obsessive–compulsive disorder when applied to chimpanzees in these case studies. Additionally, based on the DSM-IV, veterinary approaches, and ethograms, we defined behaviorally anchored alternative criteria, which proved more reliable than the DSM-IV criteria in phase 1. In phase 2, the new behaviorally anchored criteria were applied to chimpanzees living in wild sites in Africa (n = 196) and those with previous histories of experimentation, orphanage, illegal seizure, or violent human conflict (n = 168) living in sanctuaries. In phase 2, 18% of chimpanzees living in sanctuaries met the set of behaviorally anchored criteria for generalized anxiety disorder, compared with 0.5% of those in the wild (P = 0.036), and 19% of chimpanzees in sanctuaries met the set of behaviorally anchored criteria for obsessive–compulsive disorder, compared with 0% of those in the wild (P = 0.071).Chimpanzees display behavioral clusters similar to anxiety disorders described in humans, underscoring the importance of ethical considerations regarding their use in experimentation and other captive settings.     

Evaluation of oral administration of cortisol as a model for prenatal stress in pregnant sows

OBJECTIVE: To design a treatment that increases plasma corticosteroid concentrations to mimic prenatal stress in pregnant sows. ANIMALS: 24 pregnant sows. PROCEDURE: Sows were assigned to 1 of 4 treatment groups; treatment consisted of twice-daily oral administration of a placebo or 20, 60, or 180 mg of hydrocortisone acetate (HCA)/sow from 7 to 11 weeks of gestation. Blood and saliva samples for determination of cortisol concentrations were obtained hourly on treatment days 3 and 25 and twice weekly for the remainder of the treatment period. The WBC, neutrophil, and lymphocyte counts and concentrations of interleukin (IL)-2 and IL-4 were determined on 4 days during treatment. Litter characteristics were recorded. RESULTS: Plasma and salivary cortisol concentrations were significantly increased in sows that received 60 or 180 mg of HCA (0.30 to 0.37 mg/kg and 0.95 to 1.15 mg/kg, respectively), compared with control sows. Except for the second day of treatment, the number of WBCs and the IL-2:IL-4 ratio did not differ among treatment groups. The neutrophil-to-lymphocyte ratio was significantly higher in sows that received 180 mg of HCA. Gestation duration was significantly shorter in sows that received 180 mg of HCA. CONCLUSIONS AND CLINICAL RELEVANCE: Oral administration of 60 mg of HCA is suitable to increase plasma and salivary cortisol concentrations in pregnant sows in a controlled manner to concentrations comparable to concentrations detected after psychologic stressors. This model seems to be suitable to study the effects of increased maternal corticosteroid concentrations on young pig behavior, physiologic variables, and development.     

Adhesion of Salmonella enterica serotype Enteritidis isolates to chicken isthmal glandular secretions

The ability of Salmonella enterica serotype Enteritidis isolates to adhere to immobilized secretions of the isthmus of the laying hen was determined in an ELISA-type assay. One-third of the 56 isolates tested in the logarithmic growth phase, adhered to the isthmal secretions. Using a binding assay of the isolates to thin paraffin sections of the oviduct, we demonstrated that the receptor of the adhesion was localized inside the tubular gland cells of the isthmus. The adhesion to immobilized isthmal secretions as well as to the paraffin sections was blocked by the addition of mannose. A fimD mutant of S. Enteritidis, lacking type 1 fimbriae, did not adhere, confirming that the adhesion was mediated by type 1 fimbriae. Mannosylated glycoproteins were demonstrated in the isthmus glandular cells using confocal laser scanning microscopy by FITC-labelled Lens culinaris lectins. It is hypothesized that the binding of S. Enteritidis to isthmal secretions could play a role in the contamination of eggs through incorporation of the bacteria in the shell membranes.     

Analysis of ITS of the rDNA to infer phylogenetic relationships among Vietnamese Citrus accessions

This study focused on clarifying phylogenetic relationships among Citrus accessions from Vietnam. Our phylogenetic analysis based on nucleotide sequences from the ITS of the ribosomal DNA included 69 accessions belonging to Citrus and related (sub)genera. Maximum parsimony and Bayesian analysis confirmed a clear separation of the three ‘true’ Citrus species (C. medica, C. maxima and C. reticulata). Confirming recent taxonomic revisions, Fortunella, Poncirus trifoliata and Citrus hystrix are clustered among the accessions of subgenus Citrus. C. × sinensis accessions revealed a close evolutionary relationship to either C. maxima or C. reticulata, thereby confirming their involvement in its hybrid origin. Also, some other hybrid taxa and their proposed parental species were investigated and their origin could in some cases be confirmed using the ITS sequence data.     

Maternal inheritance of cytoplasmic organelles in intergeneric hybrids of Carica papaya L. and Vasconcellea spp. (Caricaceae Dumort., Brassicales)

The mode of inheritance of chloroplast and mitochondrial DNA has been determined in intergeneric hybrids between C. papaya and four different Vasconcellea species by employing a restriction fragment length polymorphism analysis of a PCR-amplified chloroplast and mitochondrial DNA region. Artificial F₁ hybrids were produced between a female specimen of C. papaya and male specimens of either V. parviflora, V. goudotiana, V. cundinamarcensis or V. quercifolia. The hybridization patterns of all hybrids correspond in all cases with that of the C. papaya mother, and are different from that of the paternal Vasconcellea species, thus indicating the maternal inheritance of cpDNA and mtDNA in intergeneric hybrids between C. papaya and wild relatives of the Vasconcellea genus.     

Lower birth weight and attenuated adrenocortical response to ACTH in offspring from sows that orally received cortisol during gestation

Prenatal stress is known to affect several offspring characteristics, but its effects depend among other factors on the period of gestation in which it is applied. In the present study, oral administration of hydrocortisone-acetate (HCA) was used to elevate cortisol concentrations in pregnant sows to levels also observed after psychological stress. HCA was administered during three different periods of gestation (115 days in pigs): period 1: 21-50 (P1, n = 10), period 2: 51-80 (P2, n = 10) and period 3: 81-110 (P3, n = 10) days after insemination. Control sows (n = 11) received vehicle from 21-110 days after insemination. When P1-, P2- and P3-sows did not receive HCA, they also received vehicle. During gestation, weekly saliva samples were taken from the sows to determine salivary cortisol concentrations. Treatment effects on sow, litter and piglet characteristics were determined. In addition, two female piglets per litter were subjected to an ACTH-challenge test at 6 weeks of age to determine the adrenocortical response to ACTH. Pigs were slaughtered at 6 months of age and slaughter weight, back fat thickness and percentage of lean meat were analysed. During the period of treatment with HCA, salivary cortisol concentrations were increased in P1-, P2- and P3-sows compared to control sows (P < 0.01). The total number of piglets born per litter did not differ among treatment groups (P > 0.30), but pooled HCA-litters had a higher percentage of live born piglets (P < 0.05) and fewer mummies than control litters (P < 0.05). Gestation length did not differ among treatment groups (P = 0.21), but did affect treatment effects on birth weight. Overall, HCA-piglets weighed less at birth, and remained lighter until weaning (P < 0.05). The salivary cortisol concentrations after i.m. injection of ACTH (2.5 IU/kg) were lower in P1- and P3-piglets compared to control piglets. At slaughter, HCA-treatment indirectly decreased lean meat percentage and increased back fat thickness. In conclusion, elevated peripheral cortisol concentrations in pregnant sows affect both litter characteristics and piglet physiology, the latter depending on the period of gestation during which concentrations were elevated. Underlying mechanisms require further investigation.