Bioassay studies support the potential for latrogenic transmission of variant Creutzfeldt Jakob disease through dental procedures

Background: Evidence is required to quantify the potential risks of transmission of variant Creutzfeldt Jakob (vCJD) through dental procedures. Studies, using animal models relevant to vCJD, were performed to address two questions. Firstly, whether oral tissues could become infectious following dietary exposure to BSE? Secondly, would a vCJD-contaminated dental instrument be able to transmit disease to another patient? Methods: BSE-301V was used as a clinically relevant model for vCJD. VM-mice were challenged by injection of infected brain homogenate into the small intestine (Q1) or by five minute contact between a deliberately-contaminated dental file and the gingival margin (Q2). Ten tissues were collected from groups of challenged mice at three or four weekly intervals, respectively. Each tissue was pooled, homogenised and bioassayed in indicator mice. Findings: Challenge via the small intestine gave a transmission rate of 100% (mean incubation 157±17 days). Infectivity was found in both dental pulp and the gingival margin within 3 weeks of challenge and was observed in all tissues tested within the oral cavity before the appearance of clinical symptoms. Following exposure to deliberately contaminated dental files, 97% of mice developed clinical disease (mean incubation 234±33 days). Interpretation: Infectivity was higher than expected, in a wider range of oral tissues, than was allowed for in previous risk assessments. Disease was transmitted following transient exposure of the gingiva to a contaminated dental file. These observations provide evidence that dental procedures could be a route of cross-infection for vCJD and support the enforcement of single-use for certain dental instruments

The effect of open-air fumigation with SO2 and O3 on carbohydrate metabolism in Scots pine (Pinus sylvestris) and Norway spruce (Picea abies).

The carbohydrate metabolism of the needles of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) has been examined in trees that were exposed to SO2, and O3, in an open-air fumigation experiment located in the Liphook forest in southern England. Two-year-old seedlings were planted in 1985 in seven experimental plots. Five plots received fumigation treatments of SO2, O3 or a combination of these gases to give a 2 × 3 factorial design with one additional ambient plot Fumigation with SO2, occurred from May 1987 to December 1990 and O3, fumigation occurred from March to December 1988, May to December 1989 and February to December 1990. Five samples of needles for investigation of carbohydrate metabolism were taken between February and July 1989. The concentrations of soluble carbohydrates (including sucrose and hexoses) were greatly reduced in the needles taken from Scots pine growing in the treated plots, and were also reduced, but to a lesser extent, in the needles taken from Norway spruce. Little variation in the concentration of starch in the needles of either species was detected. The activities of the two final enzymes of sucrose synthesis, sucrose phosphate synthase and sucrose 6-phos-phate phosphatase, were greatly reduced in the needles of Scots pine and were also reduced, but to a lesser extent, in the needles of Norway spruce in the fumigated plots. These reductions could be correlated with decreases in rates of photosynthetic CO2 assimilation determined by independent groups of researchers working on the Liphook site

Comparison of the cull dates for the mice challenged via the gingival margin.

<p>Panel A; Frequency distribution plots show the presence of a normally distributed population with a mean incubation period of around 250 days plus a small number of animals with significantly shorter incubations ranging from 140–188 days. Panel B; when these two groups are compared they show distinct means and distribution and are considered as distinct populations (p<0.001).</p