Specific serum antibody responses in channel catfish (Ictalurus punctatus) provide limited protection against Streptococcus ictaluri challenge

Passive immunization studies were conducted to determine the role of specific antibodies in immunity to Streptococcus ictaluri. Adult channel catfish (Ictalurus punctatus) were injected i.p. with tryptic soy broth as control or with 1.5 × 10(7)colony-forming units (cfu) S. ictaluri/fish at 0, 30, and 60 d, and serum was collected 90 d after the original challenge. Fish were passively immunized by i.p. injection with serum from the tryptic soy broth (TSB) control group, anti-S. ictaluri serum from fish immunized three times and sampled at 90 d (SSI), or heat-inactivated anti-S. ictaluri serum from fish immunized three times and sampled at 90 d (HISSI). These passively immunized fish were then challenged 72 h later with 1.5 × 10(8)cfu S. ictaluri/fish. Over 21 d, the mean cumulative percent survival was 43.3 (TSB), 63.3 (SSI), and 50.0 (HISSI). A significant difference in cumulative percent survival was noted between the TSB and the HISSI groups, and significant differences were noted between these groups and the SSI group. Serum obtained from immunized fish 72 h after passive immunization exhibited increased anti-S. ictaluri antibody levels. Twenty-one days after the challenge, the HISSI and SSI group antibody levels significantly increased above their corresponding pre-challenge levels. No significant (r(2)=0.0806; P<0.5985) correlation between increased pre-challenge specific serum antibody levels and survival after challenge was demonstrated when analyzing the control and passive immunization groups. The results indicate that both specific anti-S. ictaluri antibodies and non-specific immune responses are important for protection against S. ictaluri.     

Relationships between genetic distance measured by RAPD-PCR and heterosis in inbred lines of white clover (Trifolium repens L.)

The RAPD-PCR technique has been used to generate DNA amplification profiles from a set of advanced generation inbred lines of white clover ( Trifolium repens L.). The genetic distances between lines have been estimated and have been compared with the extent of positive heterosis for dry matter yield in hybrid crosses. The analysis clearly separated the four major groups (H, J, R and S), with little within group variation. Heterosis, previously shown to be positively correlated with the extent of phenotypic variation between parental lines, was greatest between lines from groups showing the least genetic distance. The lack of correlation between heterosis and genetic divergence is discussed in the context of results from other systems. Additionally, the data allow a comparison of the extent of phenotypic variation for a trait under selective pressure with the degree of variation at the DNA level detected with the RAPD technique. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Influence of Castration on the Development of Prostatic Carcinoma in the Dog 43 Cases (1978–1985)

Prostatic carcinoma (PC) was diagnosed in 43 dogs at the Michigan State University Veterinary Clinical Center (MSU-VCC) between 1978 and 1985. Of the 43 dogs with histologically confirmed PC, 19 (44.19%) had been castrated at least three years prior to the development of any prostatic disease. Seven of the castrates had been neutered at less than 12 months of age. Fourteen dogs (32.55%) were presented as intact males at the time of diagnosis. The remaining ten dogs (23.62%) had been castrated as treatment for presumptive prostatic disease prior to referral to the MSU-VCC. Dates of castration were known in all cases. In this study, therefore, castration at any age showed no sparing effect on the risk of development of PC in the dog. The etiology of PC in the dog may not be exclusively related to testicular hormones. Work in humans suggests that the adrenal and pituitary glands play a significant role in the disease. Preliminary work in dogs supports that nontesticular androgens exert a significant influence on the canine prostate.     

Forest roads and landscape structure in the southern Rocky Mountains

Roadless areas on public lands may serve as environmental baselines against which human-caused impacts on landscape structure can be measured. We examined landscape structure across a gradient of road densities, from no roads to heavily roaded, and across several spatial scales. Our study area was comprised of 46,000 ha on the Roosevelt National Forest in north-central Colorado. When forest stands were delineated on the basis of seral stage and covertype, no relationship was evident between average stand size and road density. Topography appeared to exert a greater influence on average stand size than did road density. There was a significant positive correlation between the fractal dimension of forest stands and road density across all scales. Early-seral stands existed in greater proportions adjacent to roads, suggesting that the effects of roads on landscape structure are somewhat localized. We also looked at changes in landscape structure when stand boundaries were delineated by roads in addition to covertype and seral stage. Overall, there was a large increase in small stands with simple shapes, concurrent with a decline in the number of stands > 100 ha. We conclude that attempts to quantify the departure from naturalness in roaded areas requires an understanding of the factors controlling the structure of unroaded landscapes, particularly where the influence of topography is great. Because roads in forested landscapes influence a variety of biotic and abiotic processes, we suggest that roads should be considered as an inherent component of landscape structure. Furthermore, plans involving both the routing of new roads and the closure of existing ones should be designed so as to optimize the structure of landscape mosaics, given a set of conservation goals.     

Cytologic identification of fungal arthritis in a Labrador Retriever with disseminated Talaromyces helicus infection

An 8‐year‐old, neutered male Labrador Retriever presented with acute forelimb lameness. Clinical signs progressed over one week. On physical examination, right cubital joint effusion and bilateral axillary lymphadenomegaly were noted, and severe internal lymphadenomegaly was observed ultrasonographically. Granulomatous lymphadenitis with intralesional fungi was noted cytologically, and the dog was ultimately diagnosed with disseminated Talaromyces helicus infection via PCR of a pure isolate. Extensive medical therapy was pursued, and months later, an arthrocentesis was performed due to continued lameness and severe cubital joint effusion. The synovial fluid contained increased numbers of neutrophils, macrophages, and multinucleated giant cells. Frequent fungal hyphae were found both intracellularly and extracellularly. These basophilic organisms were 2‐4 µm in width with internal eosinophilic granules, roughly parallel walls, and occasional to frequent septa. Round to oval yeast‐like forms with thin, clear halos were also occasionally identified. Due to the severity of clinical signs, the right thoracic limb was amputated. Histologic examination of the cubital joint revealed marked granulomatous synovitis, fasciitis, panniculitis, and osteomyelitis, all with intralesional fungi. Talaromyces helicus is a very rare cause of disease, reported only in one other dog. Granulomatous lymphadenitis appears to be a feature of this disease, but this report is the first to describe a significant synovial component.     

Physiology and quality response of harvested banana fruit to cold shock

Experiments were conducted to examine softening and quality responses of harvested banana fruit to cold shock treatment intended to extend shelf-life. Fruit were immersed in ice-water for 1 h, then treated with or without 100 μL L^?1 ethylene for 24 h at 24 °C, and finally stored at 20 °C. Fruit firmness, chlorophyll content, ethylene production, respiration rates, contents of pectin, starch and sugar, and the activities of the cell wall modifying enzymes polygalacturonase (PG), pectin methylesterase (PME) and CMCase (cellulase, endo-1,4-β-glucanase) were analyzed. Total amylase activity was also measured. Immersion in ice-water for 1 h effectively inhibited ripening-associated processes, including peel de-greening and pulp softening during storage or ripening. The delay in ripening was also manifest in reduced ethylene production and respiration rates. The inhibition of softening by cold shock treatment was related to decreased PG and PME activities, that is, retardation of pectin solubilization/degradation. Reduced activities of CMCase and total amylase and conversion of starch to sugar by ice-water immersion also contributed to the delay in softening of harvested banana fruit.