Hiroyuki Okada

A pathological study of bovine alimentary mycosis

A 10-year study showed that 45 of 692 cattle aged > 6 months had systemic mycosis and, of these, 38 had alimentary mycosis. The percentages of these 38 cattle with lesions in various sites were: rumen (73.7), omasum (71.1), abomasum (34.2), reticulum (21.1), intestine (15.8), omasoabomasal orifice (7.9) and tongue (2.6). Infections in both the forestomachs and abomasum occurred in 31.6 per cent; mucormycosis was found in 94.7 per cent and aspergillosis in 31.6 per cent; 26.3 per cent (10 cattle) had complicated infections with both Mucorales and Aspergillus and eight of these animals had mixed lesions of both mucormycosis and aspergillosis. Macroscopically, focal haemorrhagic necrosis was seen in all 38 cattle. Histologically, thrombosis, coagulative necrosis and hyphae typical of the order Mucorales or of Aspergillus spp. were found. Many of the cattle were also affected by ruminal acidosis-inducing factors (ruminal atony 81.6 per cent, mastitis 63.2 per cent, downer cow syndrome 57.9 per cent and parturition 50.0 per cent), which may have predisposed to alimentary mycosis.

Suppression of immunological responses in rabbits experimentally infected with bovine leukemia virus

Ten 2- to 4-month-old rabbits were inoculated subcutaneously with bovine leukemia virus (BLV)-infected bovine or sheep cells. By 6 weeks after inoculation all ten rabbits had converted to BLV antibody-positive, and BLV or BLV antigen was detected in lymphocytes from most of the rabbits tested, although there were few antigen-producing cells. Three rabbits showed continuous respiratory symptoms after infection and one died with pneumonia. Humoral immune responses against mouse serum were significantly suppressed in BLV-infected rabbits compared with non-infected control rabbits. The lymphocyte blastogenesis response was also suppressed in BLV-infected rabbits. At the time of necropsy, six rabbits showed pulmonary lesions; however, none of the BLV-infected rabbits had tumors during an observation period of over 1 year.

Brainstem auditory evoked potentials in experimentally-induced bovine spongiform encephalopathy

This study was carried out to evaluate the features of neurological dysfunction in experimentally-induced bovine spongiform encephalopathy (BSE)-infected cattle using brainstem auditory evoked potentials (BAEP). The progressive prolongation of peak latency of waves III and V was observed right-and-left bilaterally at the onset of neurological symptoms. The peak latency of wave V and the I-V interpeak latency (IPL) in BSE cattle 22 and 24 months after intracerebral inoculation were significantly (P<0.05) prolonged compared with the control cattle. In addition, the amplitude of the BAEP waves of the BSE cattle were low compared with the control cattle. Hearing loss occurred in the BSE cattle that showed advanced neurological symptoms such as tremor. It is thought that this BAEP data reflects a functional disorder in the central auditory nerve pathways characteristic of experimentally-induced BSE.

High induction of phenol UDP-glucuronosyltransferase in the kidney medulla of β-naphthoflavone-treated rats

Phenol UDP-glucuronosyltransferase activity was highly induced in the microsomes of the kidney medulla of rats by beta-naphthoflavone treatment. In the medulla, phenol UDP-glucuronosyltransferase and its mRNA were greatly increased in both immunoblotting and Northern blot analyses following beta-naphthoflavone treatment of the rats. In untreated rat kidneys, phenol UDP-glucuronosyltransferase was detected by immunohistochemical analysis only in proximal convolution tubular cells located in the cortex. After beta-naphthoflavone treatment of the rats, UDP-glucuronosyltransferase appeared in the epithelial cells in the straight portion of the distal tubules located in the medulla. In conclusion, the medullary distal tubular cells have high latent glucuronidation activity and are thought to play an important role in drug excretion.

The Screening of Cattle with Potential for Developing Leukemia by Using Monoclonal Antibody against Bovine Leukemia Cells

Tumor cells from cattle with enzootic bovine lymphosarcoma (EBL) have a tumor‐associated antigen (TAA) which is distinct from bovine leukemia virus (BLV)‐induced antigens. We were able to sacrifice 8 TAA‐positive cattle with no clinical signs of EBL and to examine whether or not they had gross or histological tumors. At necropsy, 4 animals had tumors macroscopically. Three animals had no tumors histologically but had initial lesions showing follicular hyperplasia and had the TAA on affected lymph nodes. The remaining one showed medullary hyperplasia in the spleen but there were no findings of tumors. These results suggest that most BLV‐infected cattle which are TAA‐positive but have no clinical signs of EBL, do have tumors and have a higher potential for developing EBL in the future when compared to BLV‐infected but TAA‐negative cattle.

Neuropathological Changes in Auditory Brainstem Nuclei in Cattle with Experimentally Induced Bovine Spongiform Encephalopathy

Bovine spongiform encephalopathy (BSE) is characterized by the appearance of spongy lesions in the brain, particularly in the brainstem nuclei. This study evaluated the degenerative changes observed in the central auditory brainstem of BSE-challenged cattle. The neuropathological changes in the auditory brainstem nuclei were assessed by determining the severity of vacuolation and the presence of disease-associated prion protein (PrP(Sc)). Sixteen female Holstein-Friesian calves, 2-4 months of age, were inoculated intracerebrally with BSE agent. BSE-challenged animals developed the characteristic clinical signs of BSE approximately 18 months post inoculation (mpi) and advanced neurological signs after 22 mpi. Before the appearance of clinical signs (i.e. at 3, 10, 12 and 16 mpi), vacuolar change was absent or mild and PrP(Sc) deposition was minimal in the auditory brainstem nuclei. The two cattle sacrificed at 18 and 19 mpi had no clinical signs and showed mild vacuolar degeneration and moderate amounts of PrP(Sc) accumulation in the auditory brainstem pathway. In the animals challenged with BSE agent that developed clinical sings (i.e. after 20 mpi), spongy changes were more prominent in the nucleus of the inferior colliculus compared with the other nuclei of the auditory brainstem and the medial geniculate body. Neuropathological changes characterized by spongy lesions accompanied by PrP(Sc) accumulation in the auditory brainstem nuclei of BSE-infected cattle may be associated with hyperacusia.

Peripartum heart disease in cows

Thirteen Holstein dairy cows aged 5.1-10.6 years died or were killed as a result of severe illness during the peripartum period, associated with lateral recumbency, moaning, tachycardia and dyspnoea. They were all high milk producers (> 9000 kg/year) and had experienced at least three pregnancies. The average duration of the clinical course was 2.5 +/- 1.7 days. Electro-cardiography revealed marked tachycardia associated with atrial fibrillation or atrioventricular dissociation. Serum clinical chemistry showed severe hypocalcaemia (3.6 +/- 1.3 mg/dl) and at necropsy multifocal myocardial necrosis was invariably found. Myocardial necrosis was accompanied by neutrophilic and mononuclear cellular infiltrates with interstitial fibrosis. The cause of this lesion was not established.

Histochemistry of glandular metaplasia at the trigone of the urinary bladder in cows

The epithelium at the trigone of the urinary bladder showed intestinal metaplasia of a colonic type in three Holstein-Friesian cows affected with chronic polypoid cystitis. Except for Ricinus communis (RCA-I), almost all goblet cells in the whole crypt were positive to periodic acid-Schiff (PAS), alcian blue (AB) pH 2.5, AB pH 1.0, periodate borohydride-potassium hydroxide-PAS (PB-KOH-PAS), Ulex europaeus (UEA-I), Triticum vulgare (WGA) and Arachis hypogaea (PNA) after neuraminidase digestion. This result indicated that most goblet cells contained acidic and neutral glycoconjugates as O-acetylated sialomucin, L-fucose, N-acetyl-glucosamine, neuraminic acid residues and sialic acid-galactose dimers and were devoid of beta-D-galactose. The goblet cells at the surface in the upper half of the crypt contained both sulpho- and sialo-mucins with N-acetyl-galactosamine residues by AB (pH 2.5)-PAS, high iron diamine (HID)-AB (pH 2.5), Dolichos biflorus (DBA) and Glycine maximus (SBA) reactions. On the other hand, the lower goblet cells were found to contain predominantly sulphated mucins with D-mannose and D-glucose residues by AB-PAS, HID-AB and Concanavalia ensiformis (Con A) reactivities. This suggested that mucin secreted from these cells was similar to that secreted from the goblet cells of the large intestine in cattle.

Effects of gallium nitrate in nude mice bearing a canine adenocarcinoma model of humoral hypercalcemia of malignancy: Biochemical, histomorphometric, and ultrastructural investigations

Hypercalcemic nude mice bearing a canine adenocarcinoma (CAC-8) model of humoral hypercalcemia of malignancy (HHM) were treated daily with gallium nitrate (60 mg/kg elemental gallium subcutaneously on day 0 followed by 20 mg/kg day for four days. Concentrations of gallium in bone were undetectable (<0.00005 µg/g bone) in vehicle-treated mice but markedly elevated in gallium-treated mice (>235 ± 6 µg/g bone). Gallium nitrate significantly decreased serum calcium and urinary calcium excretion in tumor-bearing mice compared with vehicle-treated controls. Histomorphometric evaluation of lumbar vertebrae revealed a significant decrease in the number of osteoclasts/mm trabecular bone in gallium-treated tumor-bearing mice compared with controls. Osteoclasts from tumor-bearing mice treated with gallium nitrate were significantly decreased in size, had reduced tartrate-resistant acid phosphatase staining intensity and ultrastructurally had fewer intracytoplasmic vesicles compared with vehicle-treated controls. Osteoclasts in gallium-treated mice were small and flattened with poorly developed cytoplasmic organelles. The findings of this investigation indicated that gallium nitrate reduced serum calcium in an animal model of HHM by inhibiting osteoclastic bone resorption.