Action of Disinfectants on Experimental Mouse Scrapie

Abstract

intermediates in a process leading to the formation of 4S RNA, which, by virtue of a looser secondary structure, are less effectively retained by columns of 'Sephadex 0-100'. To evaluate this, a "chase" type of experiment was carried out. The tumour cells were labelled for 5 min, treated with actinomycin D (50 fJ-g/ml.) for 15 min to inhibit synthesis of 5S and 4S RNA, washed twice and finally suspended in fresh medium containing large amounts of non-radioactive uridine (0•1 mmolar), Lmethionine (0•1 mmolar), cytidine (1 mmolar) and sodium formate (20 mmolar) and incubated for a further 1 h. This "actinomycin-pulse" before the "chase" procedure is required with these tumour cells to obtain maximal blocking of RNA synthesis, because it is difficult to dilute the radioactivity in the nucleotide precursor pools sufficiently quickly. The result of this type of experiment is shown in Fig. 1d, and demonstrates that the level of tritium radioactivity eluting in the region corresponding to 4S RNA after the "chase" correlates well with a redistribution of the radioactivity which originally appeared, for example, in the C and D regions after 5 min of incubation (Fig. la). If the additional components (peaks C and D) represent intermediate steps of a process leading to the "maturation" of 4S RNA, the question arises as to whether or not a puromycin-sensitive step is involved, as seems to be the case in the process leading to the synthesis of ribosomal RNA from precursor RNA (refs. 6 and 7). When the incubation of the tumour cells was carried out in the presence of puromycin the "maturation" process appeared to be unaffected (Fig. la), although the radioactivity in the excluded ribosomal peak was reduced. It seemed also of interest to determine to what extent the process depended on methylation of RNA. Previous treatment of the tumour cells with DL-ethionine was sufficient to depress, by about 75 per cent, the subsequent incorporation of labelled methyl groups from labelled (methyl)-L-methionine into RNA. Presumably this was because enough S-adenosylethionine 8 • 9 was formed within the cells to impair either the formation, or functioning, of 8-adenosyl-L-methionine, the donor of methyl groups to RNA. The pattern of incorporation of label from tritiated uridine added after the preincubation period with DL-ethionine indicates that the "maturation" process was only slightly impaired, which suggests that, a lthough possibly a number of steps are involved in the biogenesis of 4S RNA in Krebs II ascites tumour cells, insertion of methyl groups appears to be a refinement rather than an obligatory step, although there is some evidence from bacterial systems that "methyl-deficient" transfer RNA has altered physical properties 10 • One of us (B. M. L.) is a Colombo Plan Fellow. 'Ve thank Professor J. N. Davidson for his interest and for providing the facilities with the aid of a grant from the British Empire Cancer Campaign for Research. We also thank Miss E. A. Jess for technical assistance.

Guideline for Disinfection and Sterilization of Prion-Contaminated Medical Instruments

“…16,77 On the basis of the disinfection studies, many, but not all, disinfection processes fail to inactivate clinically important numbers of prions (Table 3). 16,[27][28][29][30][31][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52] There are several chemicals that reduce the prion titer by 13 log 10 in 1 hour, but few of them have been used as disinfectants in healthcare facilities (Table 3). Of these chemical compounds, chlorine and NaOH have provided the most consistent prion inactivation results.…”

“…Until recently, low-temperature sterilization technologies (eg, use of ethylene oxide) have not demonstrated their 16 with information from other studies. [27][28][29][30][32][33][34][35][37][38][39]42,[44][45][46][47][48][49]60,61,64,66,[78][79][80][81][82][83][84][85][86][87][88] effectiveness at inactivating prions (Table 2) and have not been used to sterilize prion-contaminated medical instruments. Several peer-reviewed studies have revealed that newer low-temperature sterilization technologies (ie, hydrogen peroxide gas plasma used in the Sterrad NX [ASP] and vaporized hydrogen peroxide) can eliminate the infectivity of prions on stainless steel wires and may be useful for reducing (or preventing) risk associated with prion-contaminated devices.…”

Inactivation of Template-Directed Misfolding of Infectious Prion Protein by Ozone

“…Water and wastewater may act as transport agents for prions from liquid wastes from slaughtering houses, rendering plants, agricultural digesters, and some septic systems (27). PrP Sc appears to be resistant to conventional municipal water and wastewater treatment regimens, such as chlorination (usually ϳ1 mg/liter available Cl 2 in water) (38), UV irradiation (11), and mesophilic anaerobic sludge digestion (12). The high resistivity of PrP Sc to conventional inactivation in water and wastewater intensifies concerns about prion contamination of the environment; thus, effective approaches for prion decontamination in aqueous environment are desirable.…”

Absence of Spiroplasma or Other Bacterial 16S rRNA Genes in Brain Tissue of Hamsters with Scrapie

“…Early experiments showing that TSE infectivity passed through bacterial filters (54) and was resistant to disinfection by common bacteriocides (27,10,41,42,9) seemingly eliminated bacteria as the agent. However, the discovery in the 1970s of spiroplasmas, very small, thermostable, wall-less, helical-fibrillar bacteria that pass through 0.2-m bacterial filters and show remarkable resistance to many common biocides including heat (47), provided a possible bacterial candidate for the infectious agent of TSEs.…”