Decrease in catalase activity of cultured cells by Mycoplasma gallisepticum infection

The effect of Mycoplasma gallisepticum infection on the host cell catalase activity was histochemically examined in cultured chicken embryo fibroblasts (CEF) and kidney cells. The activity in normal cells was detected as fine, brown granules in the cytoplasm, which appeared ultrastructurally to correspond to anucleoid microbodies. By infecting cultured cells with a CEF-passaged strain of M. gallisepticum, the catalase-positive granules clearly decreased in amount, whereas the UV light-killed mycoplasma and the original strain failed to decrease the granules. The cell-passaged strain was able to induce cytopathic effects and this appeared to be due to its enhanced adherent ability as compared with the original strain. These findings suggest that attachment of viable organisms to cells is crucial to decrease the catalase activity and that the decreased activity may be an important process for the subsequent development of cytopathic effects.     

Evaluation of an indirect enzyme-linked immunosorbent assay (ELISA) for detection of antibodies to the Apx toxins of Actinobacillus pleuropneumoniae

The reference strains of the 12 serotypes of Actinobacillus pleuropneumoniae express one or two of three different RTX exotoxins designated Apx I, Apx II and Apx III. The toxins are important virulence factors. In the present study, ELISAs with purified Apx I, Apx II and Apx III, respectively, as antigen were evaluated as candidates for serological diagnosis of Actinobacillus pleuropneumoniae infection in pigs. The pigs were inoculated with biotype 1, serotypes 1-12, and biotype 2, serotype 14, respectively. A strong humoral antibody response was seen to all the three antigens in most pigs irrespective of the serotype used for inoculation. However, titers to the exotoxins secreted by the serotype used for inoculation were generally highest. The results show that toxin proteins of Actinobacillus pleuropneumoniae are antigenically related and that a correlation between serotype and secretion of exotoxin is not revealed serologically in the ELISA test.     

Feeding 5-hydroxy-l-tryptophan during the transition from pregnancy to lactation increases calcium mobilization from bone in rats

An increasing demand for calcium during pregnancy and lactation can result in both clinical and subclinical hypocalcemia during the early lactation period in several mammalian species, in particular the dairy cow. Serotonin (5-HT) was recently identified as a regulator of lactation and bone turnover. The purpose of this study was to determine whether supplementation of the maternal diet with a 5-HT precursor would increase maternal bone turnover and calcium mobilization to maintain appropriate circulating maternal concentrations of ionized calcium during lactation. Female Sprague-Dawley rats (n = 30) were fed either a control diet (n = 15) or a diet supplemented with the 5-HT precursor 5-hydroxytryptophan (5-HTP, 0.2%; n = 15) from day 13 of pregnancy through day 9 of lactation. Maternal serum and plasma (day 1 and day 9 of lactation), milk and pup weight (daily), mammary gland and bone tissue (day 9 of lactation) were collected for analysis. The 5-HTP diet elevated circulating maternal concentrations of 5-HT on day 1 and day 9 of lactation and parathyroid hormone related-protein (PTHrP) on day 9 of lactation (P < 0.033). In addition, 5-HTP supplementation increased total serum calcium concentrations on day 1 of lactation and total milk calcium concentration on day 9 of lactation (P < 0.032). Supplemental 5-HTP did not alter milk yield, maternal body weight, mammary gland structure, or pup litter weights (P > 0.05). Supplemental 5-HTP also resulted in increased concentrations of mammary 5-HT and PTHrP, as well as increased mRNA expression of rate-limiting enzyme in 5-HT synthesis, tryptophan hydroxylase 1, and Pthrp mRNA on day 9 of lactation (P < 0.028). In addition, supplementation of 5-HTP resulted in increased mRNA expression of maternal mammary calcium transporters and resorption of bone in the femur, indicated by increase osteoclast number and diameter as well as mRNA expression of classical markers of bone resorption on day 9 of lactation (P < 0.048). These results show that increasing 5-HT biosynthesis during the transition from pregnancy to lactation could be a potential therapeutic target to explore for prevention of subclinical and clinical hypocalcemia.     

Identification and cornification-related gene expression of canine keratinocyte differentiation-associated protein, Kdap

The outermost layer of skin, the epidermis, is cornified epithelial tissue composed of keratinocytes. To maintain the structure and function of the epidermis, the regulation of proliferation, differentiation, and cornification of keratinocytes is crucial, and various soluble factors secreted by keratinocytes are involved in these regulations. Previously, work has shown that keratinocytes secreted the protein Kdap (keratinocyte differentiation-associated protein) associated with the formation of cornified cell envelopes, a specialized protective barrier structure on the periphery of terminally differentiating keratinocytes. In the present report, the canine counterpart of human Kdap is identified and an attempt has been made to define its physiological role in canine keratinization. Canine Kdap (cKdap) showed structural features commonly observed in other counterparts and is secreted from transfected cells. The expression profile of cKdap mRNA, which was restrictively expressed in cornified epithelial tissues besides skin has also been determined. These findings indicate that there is a strong association between cKdap expression and cornification, which supports previous observations that Kdap is involved in the synthesis and/or degradation of cornified cell envelopes in humans and mice.     

The Effect of Angiotensin‐Converting Enzyme Inhibitors of Left Atrial Pressure in Dogs with Mitral Valve Regurgitation

Background: Despite many epidemiological reports concerning the efficacy of angiotensin‐converting enzyme (ACE) inhibitors in dogs with mitral regurgitation (MR), the hemodynamic effects of ACE inhibitor administration have not been fully evaluated. Objectives: To document left atrial pressure (LAP) in dogs with MR administered ACE inhibitors, in order to obtain interesting information about daily LAP changes with administration of ACE inhibitors. Animals: Five healthy Beagle dogs weighing 9.8 to 14.2 kg (2 males and 3 females; aged 2 years). Methods: Experimental, crossover, and interventional study. Chordae tendineae rupture was induced, and a radiotelemetry transmitter catheter was inserted into the left atrium. LAP was recorded for 72 consecutive hours during which each of 3 ACE inhibitors—enalapril (0.5 mg/kg/d), temocapril (0.1 mg/kg/d), and alacepril (3.0 mg/kg/d)—were administered in a crossover study. Results: Averaged diurnal LAP was significantly, but slightly reduced by alacepril (P= .03, 19.03 ± 3.01–18.24 ± 3.07 mmHg). The nightly drops in LAP caused by alacepril and enalapril were significantly higher than the daily drops (P= .03, ?0.98 ± 0.19 to ?0.07 ± 0.25 mmHg, and P= .03, ?0.54 ± 0.21–0.02 ± 0.17 mmHg, respectively), despite the fact that the oral administrations were given in the morning. Systolic blood pressure (122.7 ± 14.4–117.4 ± 13.1 mmHg, P= .04) and systemic vascular resistance (5800 ± 2685–5144 ± 2077 dyne × s/cm⁵, P= .03) were decreased by ACE inhibitors. Conclusions and Clinical Importance: ACE inhibitors decrease LAP minimally, despite reductions in left ventricular afterload. ACE inhibitors should not be used to decrease LAP.     

Prevalence of four enteropathogens in the faeces of young diarrhoeic dairy calves in Switzerland

The prevalences of Cryptosporidium parvum, rotavirus, bovine coronavirus (bcv), and enterotoxigenic Escherichia coli (E coli k99) were determined in diarrhoeic dairy calves aged one to 21 days on 71 dairy farms in western Switzerland during the winter of 2005 to 2006. Faecal samples from 147 untreated calves suffering from acute diarrhoea were analysed by standardised diagnostic methods, and the immunoglobulin status of each calf was evaluated. The prevalences of C parvum, rotavirus, bcv and E coli k99 were 55.0 per cent, 58.7 per cent, 7.8 per cent and 5.5 per cent, respectively. The proportions of herds positive for the respective pathogens among the herds with diarrhoeic calves were 41.7 per cent, 52.1 per cent, 2.1 per cent and 2.1 per cent. The immunoglobulin concentration in the serum of 90.5 per cent of the diarrhoeic calves was below 8 g/l.     

An assay for quantitative virulence in Rhynchosporium commune reveals an association between effector genotype and virulence

Detailed knowledge of the evolutionary genetics of virulence is needed to understand and predict host–pathogen dynamics. This study used a virulence assay based on digital image analysis and treated virulence as a quantitative rather than a binary trait. Such quantitative data may better reflect the genetic underpinning of virulence in many pathogen systems and provide better resolution in statistical investigations. A greenhouse experiment based on a common garden design was conducted to measure virulence (% of leaf area covered by lesions) of 126 genetically distinct isolates of the barley scald pathogen, Rhynchosporium commune, originating from nine field populations around the world. Virulence in this pathosystem was found to be a quantitative trait with a continuous distribution in all populations. By comparing population genetic differentiation for virulence and neutral microsatellite markers (i.e. a Q_ST/G_ST comparison), evidence that virulence is under stabilizing selection across populations was found. Heritability values were high and ranged from 0·52 to 0·96 with a mean heritability of 0·84. Virulence was positively correlated with spore production as predicted by the trade‐off theory of virulence evolution. Furthermore, an association analysis between virulence and sequence haplotypes of three known necrosis‐inducing effector genes (NIP1, NIP2 and NIP3) revealed a significant effect of NIP2 haplotypes and NIP1 deletions. Overall, the results support a quantitative model for virulence in the R. commune–barley pathosystem and very high evolutionary potential for this trait.     

Poultry science: The next 20 years?

1. The theme of the lecture is that research in poultry science has moved too far in the direction of molecular biology and away from studies with whole animals. This has happened partly because exciting prospects are opening up in the field of gene manipulation but mainly because of the use of inappropriate referees to evaluate research proposals.

2. Agricultural research is defined as work intended to benefit agriculture and directed towards those problems which seem capable of solution. Science research is something else. Too much of the money allocated for agricultural and biotechnology research is being spent on science research. The system of rewarding agricultural scientists needs to be adjusted away from counting papers published.

3. Some examples are given of problems in poultry science which seem likely to be soluble by gene manipulation. These include “essential” amino acid synthesis within the chicken, improvement of shell strength, the prevention of many diseases, but probably not the improvement of quantitative traits or of behavioural adaptation to intensive husbandry.

4. Examples are also given of problems likely to require empirical solutions, such as the benefits of acclimatisation or the long‐term response to a lighting programme. Here the need is to develop better theories to guide modelling activities.

5. The author concludes that there is much research that can and should be done in poultry science in the next 20 years but calls for a recognition that some problems cannot be solved by a “fundamental” approach but will need experiments with whole animals coupled with model‐building activities.