Prion protein NMR structure and familial human spongiform encephalopathies

The refined NMR structure of the mouse prion protein domain mPrP(121-231) and the recently reported NMR structure of the complete 208-residue polypeptide chain of mPrP are used to investigate the structural basis of inherited human transmissible spongiform encephalopathies. In the cellular form of mPrP no spatial clustering of mutation sites is observed that would indicate the existence of disease-specific subdomains. A hydrogen bond between residues 128 and 178 provides a structural basis for the observed highly specific influence of a polymorphism in position 129 in human PrP on the disease phenotype that segregates with the mutation Asp-178-Asn. Overall, the NMR structure implies that only part of the disease-related amino acid replacements lead to reduced stability of the cellular form of PrP, indicating that subtle structural differences in the mutant proteins may affect intermolecular signaling in a variety of different ways.     

Bovine spongiform encephalopathy in Germany

Bovine spongiform encephalopathy (BSE) has been described as an epidemic central nervous disorder in cattle from the United Kingdom. The disease is thought to have emerged by an interspecies transmission of the scrapie agent of sheep to cattle, after feeding scrapie-contaminated meat and bone meal (MBM). The disease has caused substantial economic losses for the British cattle industry. Because of strict veterinary regulations for the import of adult British cattle by the European Union and for MBM by most of the member states the spread of BSE to continental Europe could be efficiently controlled, and only few cases have been described outside the UK. Here we report the first German case of BSE diagnosed in a Scottish Highland cow. The affected cow was imported into Germany before the import ban for cattle from the UK was implemented. BSE was confirmed by histopathology, immunohistochemistry, animal experiments, immunoblotting and by electron microscopic detection of scrapie-associated fibrils (SAFs).     

APOE in non-Alzheimer amyloidoses: transmissible spongiform encephalopathies

We have identified a member of the VEGF family by computer-based homology searching and have designated it VEGF-D. VEGF-D is most closely related to VEGF-C by virtue of the presence of N- and C-terminal extensions that are not found in other VEGF family members. In adult human tissues, VEGF-D mRNA is most abundant in heart, lung, skeletal muscle, colon, and small intestine. Analyses of VEGF-D receptor specificity revealed that VEGF-D is a ligand for both VEGF receptors (VEGFRs) VEGFR-2 (Flk1) and VEGFR-3 (Flt4) and can activate these receptors. However. VEGF-D does not bind to VEGFR-1. Expression of a truncated derivative of VEGF-D demonstrated that the receptor-binding capacities reside in the portion of the molecule that is most closely related in primary structure to other VEGF family members and that corresponds to the mature form of VEGF-C. In addition, VEGF-D is a mitogen for endothelial cells. The structural and functional similarities between VEGF-D and VEGF-C define a subfamily of the VEGFs.     

Making sense of bovine spongiform encephalopathy

The possibility of animals infected with bovine spongiform encephalopathy (BSE) causing Creutzfeldt-Jakob disease (CJD) in humans has caused public alarm resulting in the banning of the export of British beef. This paper explores the current understanding of BSE and its relationship to CJD. Although there are similarities between the diseases, there is no clear evidence of a causal link between the two.     

The use of transgenic mice in the investigation of transmissible spongiform encephalopathies

The prion, the transmissible agent that causes spongiform encephalopathies such as scrapie, bovine spongiform encephalopathy and Creutzfeldt-Jakob disease, is believed to be devoid of nucleic acid and to be identical to PrPSc (prion protein: scrapie form), a modified form of the normal host protein PrPC (prion protein: cellular form) which is encoded by the single copy gene Prnp. The 'protein only' hypothesis proposes that PrPSc, when introduced into a normal host, causes the conversion of PrPC into PrPSc; it therefore predicts that an animal devoid of PrPC should be resistant to prion diseases. The authors generated homozygous Prnp(o/o) ('PrP knockout') mice and showed that, after inoculation with prions, these mice remained free from scrapie for at least two years while wild-type controls all died within six months. There was no propagation of prions in the Prnp(o/o) animals. Surprisingly, heterozygous Prnp(o/+) mice, which express PrPC at about half the normal level, also showed enhanced resistance to scrapie despite high levels of infectious agent and PrPSc in the brain at an early stage. After introduction of murine PrP transgenes, Prnp(o/o) mice became highly susceptible to mouse--but not to hamster--prions, while the insertion of Syrian hamster PrP transgenes rendered the mice susceptible to hamster prions but much less susceptible to mouse prions. These complementation experiments enabled the application of reverse genetics. The authors prepared animals transgenic for genes encoding PrP with amino terminal deletions of various lengths and found that PrP that lacks 48 amino proximal amino acids (which comprise four of the five octa repeats of PrP) is still biologically active.     

The evolution of views on the nosological position of transmissible spongiform encephalopathies

We report here on the evolution of view on the nature of transmissible spongiform encephalopathies or prion disease. While the nosological position of these diseases is well understood, the nature of the agent is still a matter of dispute. There is no doubt, however, that the gene for PrP plays a major role in the whole group of neurodegenerations.     

Therapeutical approaches to transmissible spongiform encephalopathies (TSE): the case of amphotericin-B

Within 1987-1995 the authors observed 16 cases of tuberculosis in HIV-infected patients which accounted for 26.7% of AIDS patients treated by them. 14 cases were diagnosed intravitally, 2 postmortem. Infiltrative, generalized, cavernous, intrathoracic lymph node, intraabdominal lymph node tuberculosis and tuberculous pleurisy were identified in 5, 6, 2, 1, 1 and 1 patients, respectively. 6 patients from the above are still alive and are receiving treatment (5 of them with infiltrative tuberculosis), 10 died. Tuberculosis course and outcomes in HIV-infected subjects depended on the stage of their immunodeficiency. In moderate immunodeficiency (CD4-lymphocyte > 200/mm3) tuberculosis ran, as a rule, as local and infiltrative, sensitive to specific therapy. In severe damage to immune system (CD4 < 100/mm3) tuberculosis acquired a generalized course, sometimes fulminant, resistant to treatment. It is inferred that HIV-infected subjects with immunodeficiency need tuberculosis prophylaxis with isoniazide or rifampicin.     

Molecular analysis of bovine spongiform encephalopathy and scrapie strain variation

Five mouse scrapie strains, a mouse-passaged scrapie isolate derived from a field case in sheep in Germany, and 2 mouse-passaged bovine spongiform encephalopathy (BSE) isolates were analyzed by immunoblot in regards to banding patterns of proteinase K-digested pathologic prion proteins (PrPres). To obtain reliable results, the photo-imager technique was used for measurement of staining band intensities. Distinct and reproducible profiles were observed for the different strains or isolates. A British and a German BSE isolate were similar, suggesting the same source of infection. The German scrapie isolate resembled scrapie strain ME7, which has frequently been isolated from sheep scrapie in the past. In selected strains or isolates, no influence of the mouse lines used was observed on PrPres profiles, nor were brain region-specific differences apparent. This investigation suggests that PrPres glycotyping can be an invaluable tool for the in vitro differentiation of BSE and scrapie isolates.     

The incidence of bovine spongiform encephalopathy in the progeny of affected sires and dams

Case control study techniques were used to compare the incidence of bovine spongiform encephalopathy (BSE) in the progeny of two affected sires and 110 affected dams with the incidence of BSE in the progeny of animals known to be unaffected at the last record. All the progeny were born before the ban on ruminant-derived protein in feedstuffs issued in July 1988. The results provide little, if any, evidence of differences between the incidence in the progeny of the affected animals and the incidence in the progeny of the presumed unaffected animals. Data from five herds were used in a logistic regression analysis to study the effects of the disease status of the dam and the age of the dam at the birth of the calf on the incidence of BSE. The disease status of the dam did not significantly affect the disease status of its progeny, after allowance had been made for the effects of herd, year and the age at last record of the progeny. The difficulty of establishing maternal transmission if a high proportion of the dams are incubating the disease and transmission can occur early in the incubation period is discussed.     

Neuropathological findings in cattle with clinically suspect but histologically unconfirmed bovine spongiform encephalopathy (BSE)

Neuropathological observations were made in 200 clinically suspected cases of bovine spongiform encephalopathy (BSE) in which pathognomonic vacuolar changes were absent. Routine histological and immunocytochemical techniques were applied to formalin-fixed, paraffin-embedded sections of the central nervous system. Significant neuropathological findings were detected in 85 (42.5 per cent) cases. The most frequent lesion, detected in 46 (23 per cent) cases, was a focal white matter vacuolation principally affecting the substantia nigra, but its clinical significance was unclear. Listeriosis was diagnosed in 17 (8.5 per cent) cases. In three of seven cases of non-suppurative encephalitis, lesions suggested sporadic bovine encephalomyelitis, a disease not previously reported in the UK. Suppurative thromboembolic or granulomatous lesions accounted for other inflammatory changes. Neuroectodermal tumours were present in five cases (2.5 per cent); three were identical in form and considered to be atypical ependymoma. Cerebrocortical necrosis, oedema or both were detected in four cases. The remaining cases (4.5 per cent), comprised those in which the changes were minor and of doubtful significance. Incidental pathological findings included occasional degenerating or vacuolated neurones, which occurred in the red nucleus in 105 brains, in the habenular nucleus in 71 brains, and singly at other sites in 17 brains. In sections of 37 brains immunostained with antiserum to prion protein (PrP), no evidence of PrP accumulation was found, providing some evidence that the series did not contain bovine prion disease cases which, based on the histological diagnosis, had given a false negative result. It is suggested that, of 115 cases (57.5 per cent) which lacked significant histological lesions, some were suffering from metabolic disorders. The study identified diseases and lesions which feature in the differential diagnosis of BSE. Their more accurate diagnosis may become particularly important if, as predicted, the BSE epidemic declines.     

182 offspring of cows with bovine spongiform encephalopathy (BSE) in Switzerland. 1. Clinical findings

This study involved 182 calves, heifers and cows that were the first generation progeny of cows with bovine spongiform encephalopathy (BSE). All animals underwent clinical and neurological examinations. Blood, milk, urine, ruminal fluid and cerebrospinal fluid samples were examined. Each cow underwent a specific examination for BSE which included assessment of behaviour, sensitivity and locomotion. This examination was performed twice, and there was very good agreement between the results. The most common symptom was nervousness (14 animals). In the first examination, 68 animals were mildly to moderately sensitive to touching of the head, 44 animals were hypersensitive to a halogen light and 35 animals were hypersensitive to a camera flash. Twenty-four animals reacted by kicking when the hindlimbs were touched with a broom. None of the animals had disturbances in locomotion. Based on the interpretation of all findings and the comparison of the results of the first and second examinations, 173 animals were diagnosed as free of BSE. In 9 animals, the disease could not be ruled out; however, it could not be confirmed in any of them. Histological and immunohistochemical examinations of the brain of all animals were negative for BSE (see Part 2 of the study for details). The results of this study indicate that abnormal clinical findings may occur in clinically healthy cattle. However, none of the progeny of cows with BSE exhibited clinical signs typical of BSE, such as disturbances in behaviour; sensitivity and locomotion.     

Astroglial changes in the cerebral cortex of AIDS brains: a morphometric and immunohistochemical investigation

Sutureless phacoemulsification with implantation of a 7-mm PMMA intraocular lens was performed through a modified scleral tunnel in 100 consecutive patients. This was done to minimize postoperative astigmatism while retaining the advantages of implanting intraocular lenses with large optics. Visual and keratometric results and complications are reported after completion of a follow-up period of 6 months for the first 30 patients. Average uncorrected visual acuity improved from 0.13 preoperatively to 0.30 as early as 1 week postoperatively. Average best-corrected visual acuity improved from 0.23 before surgery to 0.51 as early as 1 week after surgery. No significant changes in visual acuity were recorded thereafter. The absolute value of keratometric astigmatism was not increased significantly at any postoperative examination time. The induced cylinder (Jaffe and Clayman) shifted from -1.27 D x 166 degrees at 1 week to 1.18 D x 91 degrees at 1 month postoperatively without further relevant changes thereafter. Endothelial cell loss did not differ from that reported by other authors after conventional cataract surgery. Corneal thickness was not increased significantly at any postoperative examination time. Implantation of intraocular lenses with large optics through a scleral tunnel allows quick visual rehabilitation as well as early stability of refraction.     

Bovine spongiform encephalopathy. Review of data collected since the statement of February 6, 1996

The observation in 1995 and 1996 of 10 cases of a new variant of Creutzfeldt-Jakob disease (V-CJD) in U.K. suggested a possible relation between this human cases and bovine spongiform encephalopathy (BSE). Recent papers about this topic are reviewed : hypothesis of a possible genetic link between man and cattle, hypothesis of a acquired resistance against the agent of BSE after a previous infection by a less virulent agent of ovine origin, importance of polymorphism at codon 129 according to the hypothesis of a virus-induced amyloidosis, diagnostic test with cerebrospinal fluid, epidemiology of BSE and prediction of future BSE spread.     

Preliminary observations on the pathogenesis of experimental bovine spongiform encephalopathy (BSE): an update

Further preliminary observations are reported of an experiment to examine the spread of infectivity and the occurrence of pathological changes in cattle exposed orally to infection with bovine spongiform encephalopathy. Calves were dosed at four months of age and clinically monitored groups were killed sequentially from two to 40 months after inoculation. Tissues were collected for bioassay, for histopathological examinations and for the detection of PrP. Previous reported observations have included the presence of infectivity in the distal ileum of cattle killed after six to 18 months, the earliest onset of clinical signs in an exposed animal after 35 months, and diagnostic histopathological changes in the brain, in association with clinical disease, after 36, 38 and 40 months. In spite of the relative inefficiency of the bioassay of scrapie-like agents across a species barrier the new observations confirm that the onset of clinical signs and pathological changes in the central nervous system (CNS) occur at approximately the same time. The earliest pathological change, the presence of abnormal PrP 32 months after inoculation, coincided with the earliest detected infectivity in the CNS and occurred shortly before there was evidence of typical spongiform changes in the brain 36 months after inoculation. Infectivity has now been demonstrated in the peripheral nervous system, in the cervical and thoracic dorsal root ganglia 32 to 40 months after inoculation and in the trigeminal ganglion 36 and 38 months after inoculation. At the time of writing evidence of infectivity in other tissues is confined to the distal ileum, not only after six to 18 months but also after 38 and 40 months, but these findings may be supplemented by the results of further mouse assays. Nevertheless, they are in general agreement with current knowledge of the pathogenesis of scrapie.