Distribution of Lesions in Fetal Brains Following Experimental Infection of Pregnant Sheep With Toxoplasma gondii

Six ovine fetal brains were harvested 33 to 35 days postchallenge from 5 ewes, each of which was given 3000 Toxoplasma gondii oocysts on day 90 of pregnancy. Histopathologic examination of transverse sections taken at 13 levels in the fetal brains revealed the presence of toxoplasmosis-related lesions in all 6 brains. However, lesions were not randomly distributed ( P = .007); they were most numerous at the level of the optic tract, the rostral margin of the pons, and 4 mm caudal to the ansate sulcus and were absent in all sections at the level of the caudal cerebellum. Lesion distribution may be due to hemodynamic factors, differences in the expression of endothelial surface receptor molecules at the level of the blood-brain barrier, or the presence of localized permissive/inhibitory factors within the brain. The results have implications for the selection of areas of brain from aborted ovine fetuses to be examined histopathologically for laboratory diagnosis.

Relationships between clinical signs, pathological changes and tissue distribution of Mycobacterium avium subspecies paratuberculosis in 21 cows from herds affected by Johne's disease

Twenty-one cows from eight herds affected by Johne's disease were assigned to four groups: seven were not thriving and had persistent diarrhoea, six were not thriving and had intermittent diarrhoea, four were not thriving but did not have diarrhoea, and four were clinically normal. Postmortem, macroscopic lesions consistent with Johne's disease were identified in 17 of the cows and Mycobacterium avium subspecies paratuberculosis (MAP) was isolated from all of them. However, except for the fact that diarrhoea was correlated with the presence of lesions in the large intestine there was little correlation between the presence or absence of clinical signs and the lesions associated with Johne's disease. The tissue distribution of MAP was also poorly correlated with either the clinical signs or the lesions. The organism was widely distributed in 17 of the 21 cows, including three of the clinically normal animals, and was present in the mammary tissues of seven cows including two of the clinically normal animals. Three distinct histopathological patterns were observed in the affected intestines: infiltration of the lamina propria with giant cells, tuberculoid lesions, and lepromatous lesions; the lepromatous lesions were associated with extensive pathological changes.

The ovine placenta and placentitis-A review

An appreciation of the complexities of placental structure and function is essential to understanding the pathogenesis of infectious placentitis and abortion. This review aims to illustrate aspects of ovine pregnancy and placentation that will assist both the research worker and the diagnostic pathologist. Morphologically, the ovine placenta is classified as being chorioallantoic, villous, cotyledonary and synepitheliochorial. Apposition of foetal and maternal tissues in early pregnancy eventually leads to the formation of the definitive placenta. Physiological features of placentation that are essential to normal pregnancy and foetal development include modulation of immune responses at the placental interface, increasing placental bloodflow to allow for increasing foetal demand and the secretion of hormones for the recognition and maintenance of pregnancy. Descriptions of the morphology of the near-term placenta in a normal pregnancy and of the foetal membranes that are voided during normal parturition provide the proper context for understanding the morphological changes associated with placentitis and how these changes are likely to affect placental function.

Clinical and pathological features of experimental scrapie in Irish Blackface Mountain sheep

There have been no reports of natural scrapie in Irish Blackface Mountain (BM) sheep which account for approximately 16% of the Irish national sheep flock. The aim of this study was to determine if Irish BM sheep had unusual clinical and/or pathological features of scrapie which would account for failure to diagnose the disease in this breed. BM (n=7), Texel (n=3) and Suffolk sheep (n=1) of scrapie-susceptible PrP genotypes (ARQ/ARQ and VRQ/ARQ) were orally challenged with scrapie-infected brain inoculum. The incubation period, clinical signs, pathology and distribution of disease specific prion protein (PrP(d)) in scrapie-affected BM sheep were similar to scrapie in the Texel and Suffolk sheep. It was concluded that there was no evidence to suggest that scrapie in BM sheep differs clinicopathologically from scrapie in other breeds of sheep.

Immunohistochemical studies of scrapie archival material from Irish ARQ/ARQ sheep for evidence of bovine spongiform encephalopathy-derived disease

Since scrapie and bovine spongiform encephalopathy (BSE) in sheep are clinicopathologically indistinguishable, BSE in sheep may have been misdiagnosed as scrapie. Disease-specific prion protein (PrP(d)) patterns in archival tissues of 38 Irish ARQ/ARQ sheep diagnosed as scrapie-affected were compared to those in four Dutch BSE-challenged sheep. When medulla oblongata was immunolabelled with an antibody directed against amino acids 93-99 of ovine prion protein (ovPrP), intraneuronal PrP(d) was apparent in all 38 Irish sheep but was absent in BSE-challenged sheep. When lymphoid follicles were immunolabelled with antibodies directed against amino acids 93-106 of ovPrP, granule clusters of PrP(d) were seen in 34 of the 38 Irish sheep. Follicles of the remaining four archive sheep contained either no PrP(d) or single PrP(d) granules, similar to follicles from BSE-challenged sheep. Based on the medulla results, none of the archival cases had BSE-derived disease. The identification of some scrapie sheep with little or no intrafollicular PrP(d) suggests that this technique may be limited in discriminating between the two diseases.

Specific delayed-type hypersensitivity responses to ESAT-6 identify tuberculosis-infected cattle

Human and bovine tuberculosis have long been detected by skin testing with purified protein derivative (PPD), a complex mix of partly denatured mycobacterial antigens with suboptimal specificity. In the present study, skin tests based on ESAT-6, a recombinantly produced antigen highly specific for tuberculosis infection, were investigated. Although ESAT-6 was strongly recognized in vitro and induced high levels of gamma interferon, initial investigations demonstrated that higher doses of ESAT-6 than of PPD were needed to induce substantial delayed-type hypersensitivity reactions. Also, the kinetics of the skin test response differed for the two reagents; PPD showed maximal response at 72 h, but the response to ESAT-6 often peaked later at 96 h. Tests based on an optimized strategy (400 micro g of ESAT-6 measured between 72 and 96 h), in cattle infected with Mycobacterium bovis (n = 22) and animals sensitized by exposure to environmental mycobacteria showed ESAT-6 to have a promising diagnostic potential (sensitivity, 82%; specificity, 100%; optimal cutoff, 3 mm), compared with PPD (sensitivity, 86%; specificity, 90%; optimal cutoff, 4 mm). Larger investigations are required to refine cutoff points for any new diagnostic test, but the present results indicate great potential for skin tests based on specific antigens for accurate in vivo diagnosis of tuberculosis.

hMYH cell cycle-dependent expression, subcellular localization and association with replication foci: evidence suggesting replication-coupled repair of adenine:8-oxoguanine mispairs

The human MutY homolog, hMYH, is an adenine-specific DNA glycosylase that removes adenines or 2-hydroxyadenines mispaired with guanines or 8-oxoguanines. In order to prevent mutations, this activity must be directed to the newly synthesized strand and not the template strand during DNA synthesis. The subcellular localization and expression of hMYH has been studied in serum-stimulated, proliferating MRC5 cells. Using specific antibodies, we demonstrate that endogenous hMYH protein localized both to nuclei and mitochondria. hMYH in the nuclei is distinctly distributed and co-localized with BrdU at replication foci and with proliferating cell nuclear antigen (PCNA). The levels of hMYH in the nucleus increased 3- to 4-fold during progression of the cell cycle and reached maximum levels in S phase compared to early G(1). Similar results were obtained for PCNA, while there were no notable changes in expression of 8-oxoguanine glycosylase or the human MutT homolog, MTH1, throughout the cell cycle. The cell cycle-dependent expression and localization of hMYH at sites of DNA replication suggest a role for this glycosylase in immediate post-replication DNA base excision repair.

Hydrophobic forces dominate the thermodynamic characteristics of UvrA-DNA damage interactions

The Escherichia coli DNA repair proteins UvrA, UvrB and UvrC work together to recognize and incise DNA damage during the process of nucleotide excision repair (NER). To gain an understanding of the damage recognition properties of UvrA, we have used fluorescence spectroscopy to study the thermodynamics of its interaction with a defined DNA substrate containing a benzo[a]pyrene diol epoxide (BPDE) adduct. Oligonucleotides containing a single site-specifically modified N2-guanine (+)-trans-, (-)-trans-, (+)-cis-, or (-)-cis-BPDE adducts were ligated into 50-base-pair DNA fragments. All four stereoisomers of DNA-BPDE adducts show an excitation maximum at 350 nm and an emission maximum around 380 to 385 nm. Binding of UvrA to the BPDE-DNA adducts results in a five to sevenfold fluorescence enhancement. Titration of the BPDE-adducted DNA with UvrA was used to generate binding isotherms. The equilibrium dissociation constants for UvrA binding to (+)-trans-, (-)-trans-, (+)-cis-, and (-)-cis- BPDE adduct were: 7.4+/-1.9, 15. 8+/-5.4, 11.3+/-2.7 and 22.4+/-2.0 nM, respectively. There was a large negative change in heat capacity DeltaCpo,obs, (-3.3 kcal mol-1 K-1) accompanied by a relatively unchanged DeltaGoobs with temperature. Furthermore, varying the concentration of KCl showed that the number of ions released upon formation of UvrA-DNA complex is about 3.4, a relatively small value compared to the contact size of UvrA with the substrate. These data suggest that hydrophobic interactions are an important driving force for UvrA binding to BPDE-damaged DNA.

Formation of DNA repair intermediates and incision by the ATP-dependent UvrB-UvrC endonuclease

The Escherichia coli UvrB and UvrC proteins play key roles in DNA damage processing and incisions during nucleotide excision repair. To study the DNA structural requirements and protein-DNA intermediates formed during these processes, benzo[a]pyrene diol epoxide-damaged and structure-specific 50-base pair substrates were constructed. DNA fragments containing a preexisting 3' incision were rapidly and efficiently incised 5' to the adduct. Gel mobility shift assays indicated that this substrate supported UvrA dissociation from the UvrB-DNA complex, which led to efficient incision. Experiments with a DNA fragment containing an internal noncomplementary 11-base region surrounding the benzo[a]pyrene diol epoxide adduct indicated that UvrABC nuclease does not require fully duplexed DNA for binding and incision. In the absence of UvrA, UvrB (UvrC) bound to an 11-base noncomplementary region containing a 3' nick (Y substrate), forming a stable protein-DNA complex (Kd approximately 5-10 nM). Formation of this complex was absolutely dependent upon UvrC. Addition to this complex of ATP, but not adenosine 5'-(beta,gamma-iminotriphosphate) or adenosine 5'-(beta, gamma-methylene)triphosphate, caused incision three or four nucleotides 5' to the double strand-single strand junction. The ATPase activity of native UvrB is activated upon interaction with UvrC and enhanced further by the addition of Y substrate. Incision of this Y structure occurs even without DNA damage. Thus the UvrBC complex is a structure-specific, ATP-dependent endonuclease.

A congenital bovine epidermolysis resembling epidermolysis bullosa simplex of man

Twenty-five of 72 calves sired by a Simmental bull were affected with a congenital skin disease which appeared to be inherited as an autosomal dominant trait. The affected calves showed hypotrichosis, erythema and breaks in the integrity of the skin. The distribution of the lesions and the ease with which excoriations occurred suggested an abnormal vulnerability to trauma. Mortality was high but in affected survivors the clinical signs moderated with age. Histopathologically, dermoepidermal separation and cytolysis of the germinal cell layer of the epidermis were seen. The name bovine epidermolysis is proposed and a relationship with epidermolysis bullosa simplex of man is suggested.

Three months treatment with chemotherapy and radiotherapy for small cell lung cancer

Fifty-five patients with inoperable but limited stage small cell carcinoma of the bronchus and a further 15 patients with contra lateral neck nodes, pleural effusions and marrow involvement were entered into the study and treated. The 3 month treatment regimen comprised 3 courses of etoposide with cyclophosphamide at 2.5 gm-2 followed by methotrexate and radiotherapy, no maintenance treatment was given. The complete response rate in the total patient group was 54% and the partial response rate 21%. The median survival was 11 months for the 70 patients, 15 months for the complete responders, and those patients with a bronchoscopically confirmed complete response survived significantly longer. There was no significant difference between the patients with strictly limited stage disease and those in the broader category. Eight patients are tumour free and alive one year or more after the end of treatment. The median followup is 17 months. Twenty-four patients were delayed 1-2 weeks during treatment because of chemotherapy induced toxicity. Six patients died probably of infection associated with leucopaenia. The majority of the patients' Karnofsky performance improved with the treatment as did their breathlessness assessed on a respiratory score. The short intensive chemotherapy regimen of 3 months produced similar results to those following more prolonged treatment regimens.