Ultrastable mesostructured silica vesicles

A family of mesoporous molecular sieves (denoted MSU-G) with vesiclelike hierarchical structures and unprecedented thermal (1000 degreesC) and hydrothermal stabilities (more than 150 hours at 100 degreesC) associated with high SiO4 cross-linking was prepared through a supramolecular assembly pathway that relies on hydrogen bonding between electrically neutral gemini surfactants of the type CnH2n+1NH(CH2)2NH2 and silica precursors derived from tetraethylorthosilicate. The vesicle shells are constructed of one or more undulated silica sheets that are about 3 nanometers thick with mesopores (average diameters from 2.7 to 4.0 nanometers) running both parallel and orthogonal to the silica sheets, which makes the framework structure bicontinuous and highly accessible. Catalytic metal ion centers [for example, Ti(IV) and Al(III)] have been incorporated into the framework with the retention of hierarchical structure.     

Time delay, temperature effects and assessment of positive controls on whole blood for the gamma interferon ELISA to detect paratuberculosis

Our objective was to evaluate the effects of time and temperature on whole blood used in the gamma interferon enzyme-linked immunosorbent assay (IFN-gamma ELISA) for paratuberculosis along with evaluating four potential positive controls, and four different mycobacterial antigens for the ELISA. Nine adult Holstein cattle naturally infected with Mycobacterium avium ssp. paratuberculosis were used in a randomized complete block design. Forty-nine blood tubes were collected from each animal and held at 48.9, 37.8, 26.7, 21.1, 15.6 and 4.4 degrees C for 0, 4, 8, 12, 18, 24, 32, 48 and 72 h. Each blood tube was tested with four mycobacterial antigens (two johnin PPDs, an avain PPD and a whole cell sonicate) and four potential positive controls [concanavalin A (conA), phytohaemagglutinin A (PHA), pokeweed mitogen (PWM) and Staphylococcus enterotoxin A (SEA)]. After incubation for 24 h, the plasma was assayed with a commercial IFN-gamma ELISA. Blood stored at 21.1 and 15.6 degrees C maintained the highest ELISA optical densities (OD) over time with severe reduction in OD values at or above 37.8 degrees C. None of the potential positive controls exactly mimicked the antigen response. SEA and PWM were able to elicit a response after the whole blood quit responding to the antigen and conA underestimated the responsiveness. Phytohemagglutinin A was similar to the antigens on an average, but there was significant disagreement among samples. The PPDs were more potent at stimulating IFN-gamma production than the whole cell sonicate. In conclusion, whole blood should be stored/transported at ambient room temperature and stimulated within 12 h of collection.     

Quantitative relationship of systemic virus concentration on growth and immune response in pigs

Ninety-six pigs from a herd naive for porcine reproductive and respiratory syndrome (PRRS) virus were weaned (10 +/- 3 d of age), penned individually in isolation rooms, and, at 29 +/- 4 d of age, oronasally inoculated with a 2-mL dose of 10(4.3) JA142 PRRS virus/ mL. Body weight; feed intake; and serum concentrations of PRRS virus, interferon, and alpha1-acylglycoprotein were determined for each pig every 4 d on d -8 to 24 postinoculation to quantify the effect of PRRS exposure on the immune response and growth of pigs. Another objective was to determine whether a quantitative relationship between a measure of systemic (serum) virus concentration and pig growth exists. Serum PRRS virus and interferon peaked at 10(5) virus/mL and 69% protection, respectively, at 4 d postinoculation and then declined steadily. Serum alpha1-acylglycoprotein concentration peaked at 12 d postinoculation. Pig weight gains and feed intake were reduced sharply in the initial 8 d postinoculation and to a lesser degree for 24 d postinoculation. The serum concentration of virus and to a lesser degree serum concentrations of interferon and alpha1-acylglycoprotein were quantitatively related to body weight gain and feed intake. The magnitude of the relationship was dependent on the stage of recovery from PRRS infection. Specifically, each log increase in serum virus concentration was associated with a reduction of 4-d pig gain and feed intake of .047 kg and .189 kg, respectively, in 5.5-kg pigs 4 d postinoculation and .085 kg and .036 kg, respectively, in 12.5-kg pigs at 20 d postinoculation. Based on these data, factors that minimize the systemic presence of a virus in pigs result in improvements in pig growth that are quantitatively related to the degree of systemic virus elimination or minimization.     

Expression of adhesion molecules on milk and blood lymphocytes from periparturient dairy cattle with Johne's disease

Twelve dairy cows infected with Mycobacterium avium subsp. paratuberculosis were monitored for lymphocyte subsets and expression of adhesion molecules on cells in blood and milk at parturition and at intervals up to 21 days post-partum. Using fluorescent antibody labeling of cells and analysis by flow cytometry, we determined percentages of T cell subsets (CD4+, CD8+, gammadelta+) and expression of adhesion molecules (CD62L, LFA-1, LPAM-1, and CD44) on cells from blood and milk of these cows. Significantly higher percentages of CD8+ cells were found in milk than in blood at all time points; there were no significant differences in percentages of CD4+ or gammadelta+ cells. CD62L, LFA-1, and LPAM-1 were expressed on a significantly higher percentage of all T cell subsets in milk than in blood at various times after parturition. No differences were seen in expression of CD44. Increased percentages of T lymphocytes expressing adhesion molecules in milk compared to blood suggest that a migratory population of cells is being selectively recruited to the mammary gland from the circulation.     

Strategies for mastitis control: dry cow therapy and culling

SUMMARY The effects of three selection strategies for dry cow therapy on prevention of new infections and rate of antibiotic usage were compared. Quarter infection status of 1044 cows in 12 herds was determined by bacteriological methods at drying off, calving and three to five months into the following lactation. Cows that were uninfected at drying off were randomly allocated to treatment (whole udder, dry cow therapy) and non-treatment groups. Infected cows were randomly allocated to whole udder or infected quarter only treatments. The strategies compared were blanket treatment (treat all quarters of all cows), selective cow treatment (treat all quarters of any cow infected in one or more quarters) and selective quarter treatment (treat infected quarters only). Selective cow treatment was identified as the preferred strategy. Blanket treatment resulted in increased antibiotic usage (15.5 vs 6.4 tubes per infection eliminated) with no additional benefit, and selective quarter treatment resulted in a higher new infection rate (6.4%vs 3.9% quarters) in the dry period. The prevalence of infection within a herd at drying off had no influence on new infection rates in the dry period or early lactation. The cure rate after dry cow treatment (mean of 66%) decreased significantly with increasing age (P < 0.001). Cows infected in the previous lactation contributed over 76% of infections at calving and nearly 70% at mid-lactation. To lower the incidence of mastitis in a herd, a greater emphasis on culling of older infected cows and prevention of new infections during lactation is needed.     

An immuno-epidemiological model for Johne’s disease in cattle

To better understand the mechanisms involved in the dynamics of Johne’s disease in dairy cattle, this paper illustrates a novel way to link a within-host model for Mycobacterium avium ssp. paratuberculosis with an epidemiological model. The underlying variable in the within-host model is the time since infection. Two compartments, infected macrophages and T cells, of the within-host model feed into the epidemiological model through the direct transmission rate, disease-induced mortality rate, the vertical transmission rate, and the shedding of MAP into the environment. The epidemiological reproduction number depends on the within-host bacteria load in a complex way, exhibiting multiple peaks. A possible mechanism to account for the switch in shedding patterns of the bacteria in this disease is included in the within-host model, and its effect can be seen in the epidemiological reproduction model.     

Expression of Heparin‐Binding EGF‐Like Growth Factor (HB‐EGF) in Bovine Endometrium: Effects of HB‐EGF and Interferon‐τ on Prostaglandin Production

Heparin‐binding EGF‐like growth factor (HB‐EGF) regulates several cell functions by binding to its membrane receptor (ErbB1 and ErbB4). Experimental evidences suggest that HB‐EGF, prostaglandins (PGs) and interferon‐τ (IFN‐τ) regulate uterine function for pregnancy establishment in ruminants. In this study, the mRNA expressions of HB‐EGF, ErbB1 and ErbB4 in bovine endometrium and the effects of HB‐EGF and IFN‐τ on PGE2 and PGF2‐α production by endometrial cells were investigated. RT‐PCR analysis revealed that HB‐EGF mRNA was greater at the mid‐luteal stage than at the early and regressed luteal stages (p < 0.05). ErbB1 mRNA expression was greater at the mid‐ and late luteal stages than at the other luteal stages (p < 0.05). IFN‐τ increased the expression of HB‐EGF, ErbB1 and ErbB4 mRNA in epithelial cells (p < 0.05). HB‐EGF did not affect PGF2‐α or PGE2 production by bovine endometrial epithelial cells, but increased PGF2‐α and PGE2 production by bovine endometrial stromal cells (p < 0.05). IFN‐τ significantly decreased HB‐EGF‐stimulated PGF2‐α (p < 0.05), but not PGE2 (p > 0.05) production by stromal cells. These results indicate that HB‐EGF and its receptors expression changed in bovine endometrium throughout the oestrous cycle. IFN‐τ increased their expression in cultured endometrial cells. HB‐EGF and IFN‐τ have the ability to regulate PGs production by stromal cells and therefore may play a role in the local regulation of uterine function at the time of implantation in cattle.     

A longitudinal study of veterinary students and recent graduates: 1. Backgrounds, plans and subsequent employment

Objective To examine factors that influence career choies by veterinary graduates.
Design Longitudinal study.
Population Students – 77 female and 77 males - who began studying veterinary science at The University of Queensland in 1985 and 1986.
Procedure Questionnaires were completed in the first and fifth year of the course, and in the second year after graduation. The data were arranged into an aggregated data set, then analysed using the SAS System for Windows.
Results These students chose veterinary science, many cases at an early age, because of their attitude towards animals rather than advice from other people. Most had extensive experience with animals, and many gained this in cities rather than on farms. Between half and two-thirds of them looked forward to a career in private practice when they were in first year. The proportion planning a career in private practice was highest for those who chose veterinary science before they were 12 years old. One-quarter of those in first year were undecided about what they would do after graduation. When they were surveyed in fifth year, most planned to enter mixed private practice at least initially. In fact, 59% entered mixed practice and 28% small animal practice. There were no significant relationships between prior experience with animals and either career plans or success in the job market. When asked in their second year after graduation, about half planned to continue in private practice over the longer term, and a quarter were undecided.
Conclusions The decision to study veterinary science is often made at a young age, and is influenced mainly by attitudes towards animals. The career path planned by the majority involves private practice, but for about a quarter the future is unclear, both when they enter the course and after they have worked as veterinarians.     

Role of nitric oxide production in dairy cows naturally infected with Mycobacterium avium subsp. paratuberculosis

Nitric oxide (NO) is a crucial mediator in host defense and is one of the major killing mechanisms within macrophages. Its induction is highly affected by the types of cytokines and the infectious agents present. In the current study, NO production was evaluated after in vitro infection of unfractionated peripheral blood mononuclear cells (PBMCs) with Mycobacterium avium subsp. paratuberculosis (MAP) after 8 h, 3 and 6 days of culture for cows in different stages of disease. In addition, the effects of in vitro exposure to inhibitory cytokines such as interleukin-10 (IL-10) and transforming growth factor β (TGF-β) as well as the pro-inflammatory cytokine IFN-γ were correlated with the level of NO production. Nitric oxide production was consistently higher in cell cultures from subclinically infected animals at all time points. An upregulation of NO production was demonstrated in unfractionated cell cultures from healthy control cows after exposure to MAP infection as compared to noninfected cell cultures. A similar increase in NO due to the addition of MAP to cell cultures was also noted for clinically infected cows. NO level among subclinically infected cattle was greater at all time points tested and was further boosted with the combination of both in vitro MAP infection and IFN-γ stimulation. Alternatively, nonspecific stimulation with LPS from Escherichia coli O111:B4-W resulted in an upregulation of NO production in all infected groups at 3 and 6 days after in vitro infection. Finally, the in vitro exposure to inhibitory cytokines such as IL-10 and TGF-β prior to MAP infection or LPS stimulation resulted in the downregulation of this inflammatory mediator (NO) in all experimental groups at all time points. In summary, a higher level of NO production was associated with cows in the subclinical stage of MAP infection. As well, the results demonstrated an increase in NO production upon infection with MAP and in the presence of exogenous IFN-γ. Finally, the results suggest an important role of IL-10 and TGF-β on the profile of NO production which may explain the low NO production in MAP clinically infected cows.     

Insulin‐Like Growth Factor‐1 Regulates the Expression of Luteinizing Hormone Receptor and Steroid Production in Bovine Granulosa Cells

Luteinizing hormone LH plays important roles in follicular maturation and ovulation. The effects of LH are mediated by LH receptor (LHR) in the ovary. However, the factors that regulate the expression of LHR in bovine granulosa cells (GCs) are not well known. Insulin‐like growth factor‐1 (IGF‐1) is known to play a key role in the acquisition and maintenance of functional dominance. To better understand the roles of LHR expression and IGF‐1, we conducted three experiments to determine (i) mRNA expression of LHR in the GCs of developing follicles, (ii) the effects of IGF‐1 on LHR mRNA expression in cultured GCs and (iii) the effects of IGF‐1 on estradiol (E2), progesterone (P4) and androstenedione (A4) production by non‐luteinized GCs. In experiment 1, small follicles (<6 mm Ø) expressed lower levels of LHR than mid‐sized follicles (6–8 mm Ø) and large follicles (≥9 mm Ø) expressed the highest levels of LHR mRNA (p < 0.05). In experiment 2, IGF‐1 (1 and 100 ng/ml) increased (p < 0.05) the expression of LHR mRNA in GCs from small and large follicles. In experiment 3, IGF‐1 (0.1–100 ng/ml) increased A4 and E2 in GCs from both small and large follicles but increased P4 only in large follicles. IGF‐1 in combination with LH (0.1 and 1 ng/ml) increased P4 and A4 in large follicles, and increased E2 and A4 in GCs of small follicles. These findings strongly support the concept that IGF‐1 upregulates LHR mRNA expression as well as A4 and E2 production in GCs and that IGF‐1 is required for determining which follicle becomes dominant and acquires ovulatory capacity.