X-ray diffraction study of the ultrathin Al2O3 layer on NiAl110.

Ultrathin Al2O3 layers on alloys are used as templates for model catalysts, tunneling barriers in electronic devices, or corrosion-resistant layers. The complex atomic structure of well-ordered alumina overlayers on NiAl110 was solved by surface x-ray diffraction. The oxide layer is composed of a double layer of strongly distorted hexagonal oxygen ions that hosts aluminum ions on both octahedral and tetrahedral sites with equal probability. The alumina overlayer exhibits a domain structure that can be related to characteristic growth defects and is generated during the growth of a hexagonally ordered overlayer (Al2O3) on a body-centered cubic (110) substrate (NiAl).

Control of hypobiotic and benzimidazole-resistant nematodes of sheep.

In studies comprising a total of 117 naturally infected crossbred lambs, it was found that lambs turned out to spring pasture were exposed to immediate infection with overwintered Ostertagia, Nematodirus, and Trichostrongylus spp, but did not acquire Haemonchus contortus infection until July. With all species, there appeared to be only one major disease-producing generation of worms per year; it was responsible for serious worm burdens and clinical disease from July onward. High frequencies of hypobiosis (arrested development) were demonstrated in H contortus (98% to 100%), Ostertagia circumcincta (89% to 96%), and Nematodirus filicollis (77% to 90%) by late November; Trichostrongylus spp comprised most of the adult (egg-laying) worm population at that time. The onset of hypobiosis appeared to be induced by seasonal stimuli rather than by host-immune responses. The results of these studies showed benzimidazole resistance to be a major problem. In the first year, fenbendazole (5 mg/kg) reduced worm burdens by 46% and 20% in September and December, respectively. In December of the second year, levamisole (8 mg/kg) reduced worm burdens by 99%, thiabendazole (44 mg/kg) by 55%, fenbendazole (5 mg/kg) by 47%, and fenbendazole (15 mg/kg) by 11%. Levamisole was highly efficient (99%) against adult worms, hypobiotic worms, and benzimidazole-resistant worms. Ostertagia circumcincta was strongly resistant to the benzimidazole drugs at all dosages tested, while H contortus and Trichostronglylus spp were partially resistant. There was no evidence of reversion of resistant worms to susceptibility on this farm, even though benzimidazole drugs had not been used for 9 years.

Sarcocystis fayeri sp. n. from the horse.

Hearts, diaphragms, esophagi, and spinal cords from 266 horses were obtained at slaughter in Creston, Ohio. Tissues were examined microscopically for Sarcocystis in sections, digested in trypsin to obtain bradyzoites, and fed to 10 dogs and 10 cats. Intramuscular cysts were found in selections of two hearts from 57 horses and four esophagi from 107 horses. The cysts were up to 900 micron long and up to 70 micron wide. The cyst wall was 1 to 2 micron thick and cross-striated. The enclosed bradyzoites were banana-shaped, 15 to 20 by 20 to 3 micron, and contained several PAS-positive granules. Bradyzoites were found in trypsin digests of seven of 57 (13%) equine tissues (heart, diaphragm, esophagus but not spinal cord) in one experiment and 10 of 47 (21%) esophagi, eight of 47 (17%) diaphragms but none of 47 hearts and spinal cords in another experiment. All of 10 dogs shed sporulated sporocysts or oocysts in feces 12 to 15 days (12 in one, 13 in eight, and 15 days in one) after digesting tissues from 169 horses. The sporocysts were 11 to 13 (12.0 +/- 0.5) by 7 to 8.5 (7.9 +/- 0.5) micron. In histologic sections of canine small intestine the sporocysts were located in the lamina propria near the tips of the villi. The 10 cats fed tissues from 266 horses did not shed Sarcocystis. A new name, S. fayeri, is proposed for this organism. Sarcocystis fayeri sporocysts (12 by 8 micron) are shorter than those of S. betrami (15 by 10 micron), the other species of Sarcocystis from the horse. The prepatent period is 12 to 15 days for S. fayeri and 8 days for S. bertrami (synonym S. equicanis Rommel and Geisel 1975).

Prevalence of Dirofilaria immitis infection in dogs from a humane shelter in Ohio.

Hearts of 500 dogs more than 1 year old from a humane shelter in Columbus, Oh, were examined for Dirofilaria immitis infection. Peripheral blood from dogs with worms in the heart was examined for microfilariae. Dirofilaria immitis adults were found in 24 (4.8%) hearts. The number of worms in infected hearts were: 19 (1 dog), 6 (2 dogs), 5 (1 dog), 4 (2 dogs), 3 (1 dog), 2 (9 dogs), and 1 (8 dogs). Of the 24 infected dogs, 4 had only male worms, 8 had only female worms, and 12 had worms of both sexes. Microfilariae were found in 12 dogs--11 dogs having D immitis microfilariae, and 1 having only Dipetalonema reconditum microfilariae. The dog with D reconditum microfilariae had only 1 male D immitis adult in its heart.

Prevalence of Toxoplasma infection in cattle slaughtered at an Ohio abattoir.

Specimens of heart, diaphragm and, in 159 instances, esophagus were taken from 352 cattle slaughtered in an Ohio abattoir. The total weight of the material was 32 kg, and this was fed to 12 specific-pathogen-free cats to test for Toxoplasma infectivity. None of the 12 cats acquired Toxoplasma infection, as evidenced by their failure to excrete oocysts or to develop antibodies, and by failure to isolate Toxoplasma from their tissues by inoculation into mice. In further tests, a 650-g sample of beef from 77 of the 352 cattle was digested in 1% trypsin, then inoculated intraperitoneally into 40 mice. Toxoplasma was not isolated from the mice. Serums from 186 of the 352 cattle were inactivated at 60 C for 1 hour, then examined by the Sabin-Feldman (dye) test for antibodies to Toxoplasma. None had titers of more than 1:8. Of the 186 serums, 77 were also examined for antibodies in the indirect hemagglutination test. One had a titer of 1:64, which was considered nonspecific. Thus, evidence for Toxoplasma infection was not found in 352 cattle.

Prevalence of Sarcocystis infection and other intestinal parasitisms in dogs from a humane shelter in Ohio.

Fecal specimens from 500 stray dogs in Columbus, Oh, were examined for evidence of intestinal parasitisms. Prevalences (%) of coccidia were: Sarcocystis sp, 1.8; Isospora canis, 1.8; and Isospora ohioensis, 3.6. Prevalences (%) of helminths were: Toxocara canis, 19.2; Toxascaris leonina, 10.2; Trichuris sp, 42.2; Capillaria sp; 1.0; Ancylostoma sp, 60.8; Uncinaria sp, 2.4; and Taenia sp, 7.4.