Effects of thyroid status on renal calcium and magnesium handling.

Renal calcium and magnesium handling was studied in rats with chronic thyroid hormone deficiency or excess, hyperthyroidism. Mean kidney weight of the thyroid deficient rats was 42% of age matched, euthyroid and hyperthyroid animals and glomerular filtration rate was 71% of normal. Fractional sodium excretion was consistently elevated in thyroid deficient rats (0.26%) as compared to euthyroid (0.07%) and hyperthyroid animals (0.07%). Urinary calcium excretion (0.39%) was also elevated and parallel to sodium excretion in thyroid deficiency. Despite this renal leak of sodium and calcium, thyroid deficient animals conserved magnesium much more efficiently than either euthyroid or hyperthyroid rats (5.7% vs 17.4% respectively). Plasma magnesium concentration was elevated by acute MgCl2 infusions to determine the reabsorptive capacity of magnesium. Thyroid deficient rats reabsorbed 15-30% more of the filtered magnesium at any given plasma concentration. Although these effects on electrolyte reabsorption are modest compared to the hemodynamic alterations, the data suggest that thyroid hormone has a direct effect on the tubule which if chronically absent results in subtle sodium and calcium wasting and renal retention of magnesium. Administration of thyroid hormone to euthyroid or thyroid deficient rats twenty-four hours prior to experimentation had no effect on calcium and magnesium handling.     

Bovine major histocompatibility complex class I specific monoclonal antibodies characterized by flow cytometry, one- and two-dimensional electrophoresis, western blot and inhibition of cytotoxic T lymphocyte function.

To identify and characterize the bovine major histocompatibility complex (MHC) class I molecules, a panel of 11 monoclonal antibodies (mAbs) were analyzed. The mAbs reacted with bovine MHC class I antigens, as assessed by flow cytometry and immunoprecipitation followed by one- and two-dimensional gel electrophoresis. Analysis by flow cytometry revealed that class I molecules were expressed less on a class I mutant B-lymphoblastoid cell line than on the parent cell line. The relative molecular weights of the proteins identified by these mAbs were similar to those reported previously for cattle and humans. Nonequilibrium pH gradient two-dimensional gel electrophoresis showed that RH16C recognized four different class I gene products, indicating this mAb reacts with a conserved epitope present on different class I molecules. These mAbs effectively blocked cytotoxic T lymphocyte killing of allogeneic lymphoblasts, suggesting the functional importance of beta-2m in this process. These mAbs should be useful reagents for studying bovine MHC class I molecules.     

Duration of immunity in foxes vaccinated orally with ERA vaccine in a bait.

Red foxes (Vulpes vulpes) vaccinated orally with the ERA strain of rabies vaccine in a bait were challenged after 83 mo. Ten of 11 foxes that had seroconverted following vaccination resisted challenge with a virulent rabies virus which produced clinical signs of rabies in 6 of 6 unvaccinated foxes. Five of 11 vaccinated animals retained titers of rabies virus neutralizing antibody throughout the period. Although 6 of 11 had no detectable antibody at the time of challenge, 5 of these 6 resisted challenge and had an anamnestic response, as indicated by elevated titers of antibody when measured at day 77 postchallenge. These results show that foxes can be immunized successfully with a single oral dose of ERA vaccine, probably with protection against a lethal rabies challenge, for at least 7 y.     

The protective effect of two porcine enterovirus vaccines in swine.

The virus neutralizing substance in the gastrointestinal tract of swine vaccinated in different ways with porcine enterovirus strain T80 was characterized by tests for enhancement and absorption of virus neutralizing activity by class specific antiporcine Ig antisera. The gastrointestinal virus neutralizing activity of piglets which were vaccinated with live virus orally resided predominantly in the IgA class, although some activity was present also in the IgM and IgG classes. The serum virus neutralizing activity of this group was present in all three classes but primarily in the IgG class. The IgA in the serum of this group was presumably of gut origin. However, in piglets vaccinated with live virus intramuscularly, with formaldehyde-inactivated virus orally or intramuscularly or with ethylenimine-inactivated virus by both oral and subcutaneous routes, both serum and gastrointestinal virus neutralizing activity were attributable predominantly to antibodies of the IgG and IgM classes. None possessed serum IgA. There was evidence also for the presence of Ig fragments in some gastrointestinal extracts.     

A novel screening method for rice allelopathic potential: the inhibitory‐circle method

Screening crop accessions for allelopathic activity is of paramount importance for crop allelopathy research. Previous bioassays often did not use a mixed culture of donor and target plants, did not use soil and were not conducted under natural conditions. In this study, we designed an inhibitory‐circle method in which a rice accession (donor plant) and Echinochloa crus‐galli (target plant) were cultured together in paddy soil under natural conditions. First, we determined that the highest allelopathic activity of allelopathic rice accession PI312777 was at the 5‐leaf stage, and the suitable distance of rice seedlings and E. crus‐galli was 12 cm apart. This method was then validated by a field test. A further 40 rice accessions were evaluated for allelopathic activity to E. crus‐galli using this method. Two rice accessions, PI312777 and Taichung Native 1, had highly allelopathic activity to E. crus‐galli (inhibitory rate > 50%), while another accession, Lemont, had non‐allelopathic activity. These experimental results were in accordance with previous studies using direct field experiments. The inhibitory‐circle method integrated three necessary conditions, that is donor and target plants grown together, with soil as the medium and under natural conditions for reliable results. The ‘inhibitory‐circle method’, which combined donor and target plants, soil medium and field conditions, can give reliable results in one step, compared with laboratory screening methods. Also, the ‘inhibitory‐circle method’ gave results in 30‐35 days, thereby substantially reducing the requirements for time, labour and cost.     

Prevalence and epizootiology of equine salmonellosis.

Feces from 1,451 horses entering a veterinary hospital over a 13-month period were cultured for salmonella. A total of 46 horses (3.2%) yielded 1 or more salmonella-positive fecal cultures. Twenty horses were found to be excreting salmonella in the feces on admission, and 5 of these later had severe diarrhea associated with enteric salmonellosis. Abdominal surgery and other severe stresses were associated with all cases of severe enteric salmonellosis. Serotypes of salmonella isolated included Salmonella agona (15), S anatum (14), S typhimurium (7), S typhimurium var copenhagen (4), S infantis (2), S montevideo (1), S meleagridis (1), S drypool (1), and an unnamed Salmonella serotype (1). Seven deaths were attributed to 4 serotypes (S typhimurium, 3; S anatum, 2; S typhimurium var copenhagen, 1; and S montevideo, 1). A marked seasonal incidence is isolations was found with isolations highest in later summer to early fall and lowest in the spring. It was also found that horses can shed salmonella intermittently, and a minimal of 5 consecutive negative fecal cultures is recommended before considering a horse not to be infected with salmonella.