Identification of a satellite RNA associated with turnip crinkle virus

Turnip plants infected with turnip crinkle virus (TCV) contain four major RNA species which are not found in uninfected plants (A = 1.3 x 10(6) MW, B = 0.28 x 10(6) MW, C = 0.17 x 10(6) MW, and D = 0.13 x 10(6) MW). At least two of these RNAs, RNA A and RNA C, are packaged in the mature virion, but only the large RNA A is required for infection. Plants infected with RNA A alone produce neither the small virion RNA C nor the small nonvirion RNAs B and D. The small virion RNA C is not infective by itself, but requires coinfection with RNA A to replicate in plants. RNA C increases the severity of symptoms in plants infected with RNA A and restores the production of the nonvirion RNAs B and D. T1 RNase oligonucleotide mapping and copy DNA hybridization analysis indicate that the virion RNAs A and C do not have extensive homology. These data suggest that the large virion RNA A contains the full TCV genome and that the smaller virion RNA C is a dispensible satellite, designated S-TCV.     

Synthesis of DNA in Toluene-Treated Chlamydomonas reinhardi

Toluene-treated Chlamydomonas reinhardi incorporate deoxynucleoside triphosphates (dNTPs) into DNA. Incorporation requires all four dNTPs, but requires neither ATP nor added DNA. The incorporation reaction is linear for nearly 20 min. The product of synthesis in treated cells is mainly chloroplast (beta-component) DNA. However, a small quantity of nuclear (alpha-component) DNA is also synthesized. Synchronously grown cells are most efficient in dNTP incorporation at a time in the cell cycle when chloroplast DNA is normally replicated. Toluene treatment disrupts the internal morphology of the cell, but leaves the outer membrane of the chloroplast intact.     

Variability in audiometric recording

Howell, R. W., and Hartley, B. P. R. (1972).Brit. J. industr. Med.,29, 432-435. Variability in audiometric recording. A study of initial and repeat audiograms by two operators on 143 young male new entrants to industry (free of previous occupational exposure) has shown that mean values (mean of both ears, readings at 3 and 4 kHz) differed significantly between operators, and that this difference was not attributable to transient medical conditions such as wax in the ears or temporary infection.

For nearly half the employees, the difference between the results obtained by the two operators amounted to 5 dB or more, with differences up to and including 21¼ dB. Of the two operators' lists of men in the lowest decile of hearing threshold levels, only half the names were common to both operators; there was clearly wide variation between the operators.

With such variability in audiometric recording, some of which may be attributable to variation in the patients' responses, it seems unlikely that small changes in recorded hearing levels will give confident early indication of deterioration in a susceptible ear.

It is suggested that further studies be carried out under industrial conditions to ascertain the advantages, if any, of two or more readings taken at one session (or within a short space of time) over single observations. Similar studies are needed using self-recording audiometry.

Consideration should be given to the basic training and potential of operators, to the need for monitoring their performance, and to periodic refresher training where appropriate.