Animal physiology. Summer declines in activity and body temperature offer polar bears limited energy savings.

Polar bears (Ursus maritimus) summer on the sea ice or, where it melts, on shore. Although the physiology of "ice" bears in summer is unknown, "shore" bears purportedly minimize energy losses by entering a hibernation-like state when deprived of food. Such a strategy could partially compensate for the loss of on-ice foraging opportunities caused by climate change. However, here we report gradual, moderate declines in activity and body temperature of both shore and ice bears in summer, resembling energy expenditures typical of fasting, nonhibernating mammals. Also, we found that to avoid unsustainable heat loss while swimming, bears employed unusual heterothermy of the body core. Thus, although well adapted to seasonal ice melt, polar bears appear susceptible to deleterious declines in body condition during the lengthening period of summer food deprivation.

Transplacental transmission and abortion in cows administered Neospora caninum oocysts.

Neospora caninum infection is a common cause of bovine abortion. One method by which cattle can acquire infection is through ingestion of oocysts; however, this has not yet been proved to cause transplacental infection or abortion. In this study, 19 cows, pregnant between 70 and 176 days, were administered 1500 to 115,000 oocysts through an esophageal tube. Seventeen of the cows became seropositive, indicating acquisition of infection, whereas 8 negative control cows remained seronegative (P < 0.001). Offspring were examined using serology, histology, immunohistochemistry, parasite isolation, and polymerase chain reaction (PCR). Six offspring were infected and 1 of them was aborted. The aborted fetus had typical lesions and positive immunohistochemistry and PCR for N. caninum. All 6 cows with infected offspring had continuously rising antibody titers, whereas 10 of 11 infected cows with uninfected offspring had falling titers after an early apex. The risk of transplacental transmission was increased by later exposure times during gestation and by the dose of oocysts (P < 0.01 for the 2 combined variables). The lowest dose of oocysts, when administered after the 160th day of gestation, caused transplacental infection in 1 of 2 animals. This study demonstrates that infection with N. caninum oocysts can cause transplacental transmission and abortion in cattle.

Neospora caninum in vitro: evidence that the destiny of a parasitophorous vacuole depends on the phenotype of the progenitor zoite.

We previously reported that Neospora caninum can be induced to express BAGI, a bradyzoite antigen, within 3 days of culture under stress conditions. The main goals of the present experiment were to increase the expression of BAGI in vitro (in part by extending cultures for 9 days), to observe parasitophorous vacuoles at various points of stage differentiation, and to test the ability of organisms produced in vitro to function like mature bradyzoites. Expression of BAG1 and of a tachyzoite antigen (NcSAGI) was monitored using a double-label immunofluorescence assay. For the purpose of this study, organisms expressing NcSAG1 were designated as tachyzoites, those expressing BAG1 were designated as bradyzoites, and those expressing both antigens were designated as intermediate zoites. The greatest percentage of intermediate zoites and bradyzoites (14%) occurred in bovine monocytes maintained for 9 days. These bradyzoites did not appear to be functionally mature; they did not induce patent infections in dogs. in contrast to bradyzoites that were produced in chronically infected mice. In vitro, large parasitophorous vacuoles contained either a pure population of tachyzoites or a mixture of tachyzoites and intermediate zoites, which is indicative of asynchronous stage conversion of organisms within a vacuole. Bradyzoites were first observed within small vacuoles on day 6. and bradyzoites never shared vacuoles with tachyzoites. This finding suggests that vacuoles containing bradyzoites may develop only if the cell is invaded by a zoite that has already begun bradyzoite differentiation. An alternative possibility is that cysts may develop if the establishing tachyzoite undergoes bradyzoite differentiation before multiplying. Cysts do not appear to arise from transformation of tachyzoites within large parasitophorous vacuoles.

Evidence of point-source exposure to Neospora caninum and protective immunity in a herd of beef cows.

OBJECTIVE: To determine whether cows with evidence of previous infection with Neospora caninum were less likely to abort or give birth prematurely during an outbreak of neosporosis, compared with herdmates with evidence of primary infection. DESIGN: Cohort study. ANIMALS: 208 pregnant beef cows. PROCEDURES: Aborted fetuses and calves born prematurely were examined during an outbreak of neosporosis in a herd of beef cows. Sera were collected from all cows during the outbreak and again 71 days later. Cows were classified into groups on the basis of normal and abnormal reproductive outcomes. Sera were examined, using an avidity ELISA procedure for N caninum, and results were compared between groups and among time points. RESULTS: Antibody concentrations decreased significantly and IgG avidity values increased significantly over time. During the outbreak, cows with normal reproductive outcomes were significantly more likely to have high IgG avidity values than cows with abnormal reproductive outcomes. CONCLUSIONS AND CLINICAL RELEVANCE: The herd had numerous abortions and premature births with evidence of recent point-source exposure to N caninum. Therefore, to reduce risk of transmission of N caninum to cattle, attempts should be made to prevent canine feces from contaminating feed, especially feedstuffs used to prepare mixed rations for cattle. Cows with evidence of previous exposure to N caninum were less likely to abort or give birth prematurely during the outbreak than cows with primary infections with N caninum; this finding suggests development of protective immunity in previously infected cows.

Antibody responses of cows during an outbreak of neosporosis evaluated by indirect fluorescent antibody test and different enzyme-linked immunosorbent assays.

Serum samples from 70 (33 aborting and 37 non-aborting) dairy cows from a herd in California were analyzed for Neospora caninum antibodies in different laboratories by various serologic assays including enzyme-linked immunosorbent assay (ELISA) with recombinant antigens (Nc4.1 and Nc14.1), kinetic ELISA, whole tachyzoite lysate ELISA, immunostimulating complex (iscom) ELISA, antigen capture competitive inhibition ELISA, and by the indirect fluorescent antibody test. Eighteen percent of pregnant cows in this herd had aborted within 2 mo of the index case. All 70 cows had antibodies to N. caninum by at least 1 of the tests. Antibody levels to N. caninum in aborting cows as a group were higher than in nonaborting cows. However, it was concluded that no serological test could be used to establish definitively that N. caninum caused the abortion in an individual cow.

A protocol for the production of Neospora caninum tissue cysts in mice.

Identification of a definitive host for Neospora caninum has been inhibited by lack of an efficient method for producing bradyzoites, needed for oral infectivity trials. An improved protocol for producing bradyzoite-containing tissue cysts in mouse brains is described. Six variables, including mouse strain (Balb/C, CBA/Ca, and ICR), sex, N. caninum isolate (NC-2 and NC-Liverpool), tachyzoite inoculum dose, immunosuppression with methylprednisolone acetate (MPA), and sulfadiazine treatment were tested. Tissue cyst numbers were estimated using an immunohistologic staining procedure specific for bradyzoites. Male ICR mice (> or = 30 g) that were immunosuppressed with 2 mg MPA 7 days prior to and 2.5 mg MPA at the time of subcutaneous inoculation with 400,000 N. caninum tachyzoites produced the highest numbers of tissue cysts. Significant numbers were produced by methods using the NC-2 strain of N. caninum; however, protocols using NC-Liverpool produced greater numbers of tissue cysts. Sulfadiazine treatment did not appear to contribute to tissue cyst production. The procedure described is superior to previously described methods with regard to numbers of tissue cysts produced, protocol reproducibility, and survival of mice until tissue cyst formation.

Robust estimates of wildlife location using telemetry data.

The location of wildlife is frequently determined using telemetry data gathered at short intervals. If radio transmissions are reflected, as often occurs in mountainous regions, then existing location estimation techniques re unreliable. We explore the effects of gross observation errors upon current analyses and suggest an alternative analysis based on robust state-space time-series modeling. We determine location estimates and their precisions, both for simulated and real mule-deer data, using current and robust procedures. Implementation and specification of filter parameters are also discussed. We conclude that the proposed filter-smoother is similar to the Gaussian filter-smoother when data are not greatly contaminated and that the robust version improves upon location estimates when contamination is large.

Crypt cell thymidine incorporation in ileal urinary pouch. Preliminary report.

This is a brief communication about mucosal change in ileal urinary reservoirs, the earliest reported observations to date. Previous authors described early villous atrophy and crypt elongation, late panmucosal atrophy and metaplasia. Crypt cell proliferation should be a forerunner of these events and therefore warrants quantitative measurement. We studied continent pouches in dogs on postoperative days 42 and 43 using in vivo tritiated thymidine incorporation into crypt cell DNA, a novel application of autoradiography for urinary reservoirs. Adjacent normal ileum provided the internal control. Increased crypt cell thymidine incorporation was confirmed at this early time.

Environmental sampling: a brief review.

Proper application of statistical principles at the onset of an environmental study can make the difference between an effective, efficient study and wasted resources. This review distills some of the thoughts current among environmental scientists from a variety of backgrounds and organizes them according to statistical principles. Collection and review of preliminary information is important for guiding sampling design. Problems must be carefully defined before rational sample selection is possible. Many potential sources of variability exist, and as many of these sources as possible should be identified, assessed, and, ideally, minimized. Sample selection itself will depend on the precise questions that are to be addressed by the study and on what assumptions can be reasonably made about structures and patterns of contaminants in the field. Careful specification of protocols for sample procurement are needed. Choices of statistical analyses will depend on how data are collected, and intended analyses should be predetermined as part of the sampling plan. Proper attention to these principles will substantially increase the quality and efficiency of an environmental sampling program.