Relationship between clinical signs and postmortem test status in cattle experimentally infected with the bovine spongiform encephalopathy agent

Background  

Various clinical protocols have been developed to aid in the clinical diagnosis of classical bovine spongiform encephalopathy (BSE), which is confirmed by postmortem examinations based on vacuolation and accumulation of disease-associated prion protein (PrP^d) in the brain. The present study investigated the occurrence and progression of sixty selected clinical signs and behaviour combinations in 513 experimentally exposed cattle subsequently categorised postmortem as confirmed or unconfirmed BSE cases. Appropriate undosed or saline inoculated controls were examined similarly and the data analysed to explore the possible occurrence of BSE-specific clinical expression in animals unconfirmed by postmortem examinations.     

Severing of F-actin by yeast cofilin is pH-independent

Cofilin plays an important role in actin turnover in cells by severing actin filaments and accelerating their depolymerization. The role of pH in the severing by cofilin was examined using fluorescence microscopy. To facilitate the imaging of actin filaments and to avoid the use of rhodamine phalloidin, which competes with cofilin, alpha-actin was labeled with tetramethylrhodamine cadaverine (TRC) at Gln41. The TRC-labeling inhibited actin treadmilling strongly, as measured by epsilonATP release. Cofilin binding, detected via an increase in light scattering, and the subsequent conformational change in filament structure, as detected by TRC fluorescence decay, occurred 2-3 times faster at pH 6.8 than at pH 8.0. In contrast, actin filaments severing by cofilin was pH-independent. The pH-independent severing by cofilin was confirmed using actin labeled at Cys374 with Oregon Green 488 maleimide. The depolymerization of actin by cofilin was faster at high pH.     

Transgenic mouse brains for the evaluation and quality control of BSE tests

Rapid BSE tests are widely used diagnostics in veterinary medicine and more than 11 million tests are applied worldwide. The evaluation of new rapid BSE tests and the quality assurance of approved BSE tests pose a challenge owing to the natural scarcity of BSE-infected bovine brainstems and regional variations in prion titer. Transgenic mice expressing bovine prion protein (Tg4092) offer an alternative approach to these problems. To determine whether BSE-infected Tg4092 mouse brains could serve as a general standard for rapid BSE tests, we inoculated Tg4092 mice intracerebrally with BSE prions, harvested brains at defined time points post-infection and analyzed cerebral hemispheres with several approved rapid BSE tests. The results show that de novo formation of the disease-causing prion protein isoform, PrP(Sc), can be monitored during the course of infection. We demonstrate that BSE-infected Tg4092 mouse brains provide a renewable and controllable source of reference samples and suggest that such samples can generally be used for the evaluation and quality control of rapid BSE tests.     

The Mitosis and Neurodevelopment Proteins NDE1 and NDEL1 Form Dimers, Tetramers, and Polymers with a Folded Back Structure in Solution

Paralogs NDE1 (nuclear distribution element 1) and NDEL1 (NDE-like 1) are essential for mitosis and neurodevelopment. Both proteins are predicted to have similar structures, based upon high sequence similarity, and they co-complex in mammalian cells. X-ray diffraction studies and homology modeling suggest that their N-terminal regions (residues 8–167) adopt continuous, extended α-helical coiled-coil structures, but no experimentally derived information on the structure of their C-terminal regions or the architecture of the full-length proteins is available. In the case of NDE1, no biophysical data exists. Here we characterize the structural architecture of both full-length proteins utilizing negative stain electron microscopy along with our established paradigm of chemical cross-linking followed by tryptic digestion, mass spectrometry, and database searching, which we enhance using isotope labeling for mixed NDE1-NDEL1. We determined that full-length NDE1 forms needle-like dimers and tetramers in solution, similar to crystal structures of NDEL1, as well as chain-like end-to-end polymers. The C-terminal domain of each protein, required for interaction with key protein partners dynein and DISC1 (disrupted-in-schizophrenia 1), includes a predicted disordered region that allows a bent back structure. This facilitates interaction of the C-terminal region with the N-terminal coiled-coil domain and is in agreement with previous results showing N- and C-terminal regions of NDEL1 and NDE1 cooperating in dynein interaction. It sheds light on recently identified mutations in the NDE1 gene that cause truncation of the encoded protein. Additionally, analysis of mixed NDE1-NDEL1 complexes demonstrates that NDE1 and NDEL1 can interact directly.     

Tropomyosin regulates elongation by formin at the fast-growing end of the actin filament

The balance between dynamic and stable actin filaments is essential for the regulation of cellular functions including the determination of cell shape and polarity, cell migration, and cytokinesis. Proteins that regulate polymerization at the filament ends and filament stability confer specificity to actin filament structure and cellular function. The dynamics of the barbed, fast-growing end of the filament are controlled in space and time by both positive and negative regulators of actin polymerization. Capping proteins inhibit the addition and loss of subunits, whereas other proteins, including formins, bind at the barbed end and allow filament growth. In this work, we show that tropomyosin regulates dynamics at the barbed end. Tropomyosin binds to constructs of FRL1 and mDia2 that contain the FH2 domain and modulates formin-dependent capping of the barbed end by relieving inhibition of elongation by FRL1-FH1FH2, mDia1-FH2, and mDia2-FH2 in an isoform-dependent fashion. In this role, tropomyosin functions as an activator of formin. Tropomyosin also inhibits the binding of FRL1-FH1FH2 to the sides of actin filaments independent of the isoform. In contrast, tropomyosin does not affect the ability of capping protein to block the barbed end. We suggest that tropomyosin and formin act together to ensure the formation of unbranched actin filaments, protected from severing, that could be capped in stable cellular structures. This role, in addition to its cooperative control of myosin function, establishes tropomyosin as a universal regulator of the multifaceted actin cytoskeleton.     

Chimeric RNase H-competent oligonucleotides directed to the HIV-1 Rev response element

Chimeric oligo-2'-O-methylribonucleotides containing centrally located patches of contiguous 2'-deoxyribonucleotides and terminating in a nuclease resistant 3'-methylphosphonate internucleotide linkage were prepared. The oligonucleotides were targeted to the 3'-side of HIV Rev response element (RRE) stem-loop IIB RNA, which is adjacent to the high affinity Rev protein binding site and is critical to virus function. Thermal denaturation experiments showed that chimeric oligonucleotides form very stable duplexes with a complementary single-stranded RNA, and gel electrophoretic mobility shift assays (EMSA) showed that they bind with high affinity and specificity to RRE stem-loop II RNA (K(D) approximately 200 nM). The chimeric oligonucleotides promote RNase H-mediated hydrolysis of RRE stem-loop II RNA and have half-lives exceeding 24h when incubated in cell culture medium containing 10% fetal calf serum. One of the chimeric oligonucleotides inhibited RRE mediated expression of chloramphenicol acetyl transferase (CAT) approximately 60% at a concentration of 300 nM in HEK 293T cells co-transfected with p-RRE/CAT and p-Rev mammalian expression vectors.     

Medicine and place: an inquiry

This essay explores the various places inhabited by doctors and patients, in order to lead doctors to a more complex understanding of their patients' experiences of illness. Using Adam Haslett's "The Good Doctor" (2002), we examine what happens when doctors enter the worlds of their patients, both the literal landscapes of their patients' homes and the hidden landscapes of their minds. We illustrate the impact place has on doctors' understanding of their patients and on the patients' attitudes toward their illness. In addition, we examine how place informs readers' perceptions of both the coherence and the divide between the worlds of doctor and patient.     

Proteins with Intrinsically Disordered Domains Are Preferentially Recruited to Polyglutamine Aggregates

Intracellular protein aggregation is the hallmark of several neurodegenerative diseases. Aggregates formed by polyglutamine (polyQ)-expanded proteins, such as Huntingtin, adopt amyloid-like structures that are resistant to denaturation. We used a novel purification strategy to isolate aggregates formed by human Huntingtin N-terminal fragments with expanded polyQ tracts from both yeast and mammalian (PC-12) cells. Using mass spectrometry we identified the protein species that are trapped within these polyQ aggregates. We found that proteins with very long intrinsically-disordered (ID) domains (≥100 amino acids) and RNA-binding proteins were disproportionately recruited into aggregates. The removal of the ID domains from selected proteins was sufficient to eliminate their recruitment into polyQ aggregates. We also observed that several neurodegenerative disease-linked proteins were reproducibly trapped within the polyQ aggregates purified from mammalian cells. Many of these proteins have large ID domains and are found in neuronal inclusions in their respective diseases. Our study indicates that neurodegenerative disease-associated proteins are particularly vulnerable to recruitment into polyQ aggregates via their ID domains. Also, the high frequency of ID domains in RNA-binding proteins may explain why RNA-binding proteins are frequently found in pathological inclusions in various neurodegenerative diseases.     

Production and characterization of chimeric monoclonal antibodies against Burkholderia pseudomallei and B. mallei using the DHFR expression system

Burkholderia pseudomallei (BP) and B. mallei (BM) are closely related gram-negative, facultative anaerobic bacteria which cause life-threatening melioidosis in human and glanders in horse, respectively. Our laboratory has previously generated and characterized more than 100 mouse monoclonal antibodies (MAbs) against BP and BM, according to in vitro and in vivo assay. In this study, 3 MAbs (BP7 10B11, BP7 2C6, and BP1 7F7) were selected to develop into chimeric mouse-human monoclonal antibodies (cMAbs) against BP and/or BM. For the stable production of cMAbs, we constructed 4 major different vector systems with a dihydrofolate reductase (DHFR) amplification marker, and optimized transfection/selection conditions in mammalian host cells with the single-gene and/or double-gene expression system. These 3 cMAbs were stably produced by the DHFR double mutant Chinese hamster ovarian (CHO)-DG44 cells. By ELISA and Western blot analysis using whole bacterial antigens treated by heat (65°C/90 min), sodium periodate, and proteinase K, the cMAb BP7 10B11 (cMAb CK1) reacted with glycoproteins (34, 38, 48 kDa in BP; 28, 38, 48 kDa in BM). The cMAb BP7 2C6 (cMAb CK2) recognized surface-capsule antigens with molecular sizes of 38 to 52 kDa, and 200 kDa in BM. The cMAb CK2 was weakly reactive to 14～28, 200 kDa antigens in BP. The cMAb BP1 7F7 (cMAb CK3) reacted with lipopolysaccharides (38～52 kDa in BP; 38～60 kDa in B. thailandensis). Western blot results with the outer surface antigens of the 3 Burkholderia species were consistent with results with the whole Burkholderia cell antigens, suggesting that these immunodominant antigens reacting with the 3 cMAbs were primarily present on the outer surface of the Burkholderia species. These 3 cMAbs would be useful for analyzing the role of the major outer surface antigens in Burkholderia infection.