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Making Manual Plasmid Mini-Preps a Thing of the Past igh Purity Sufficient for automated, fluorescent and manual t- sequencing ^.Direct leading of Harvey Mudd: Top Ranked In her News .irtiele "Some small schools are big on manufacturing scientists" (In novations on Campus, 4 Nov., p. 850), Anne Simon Moffat recognizes what we at Harvey Mudd College have known all along: small student-faculty ratios com bined with a demanding curriculum that stresses hands-on laboratory experience provide undergraduates in the sciences with the education and tools to succeed at the graduate level. However, Moffat's article may leave the impression that only the schools she lists produce high percentages of graduates who go on to earn Ph.D.'s. This is not the case. In a study prepared by the National Research Council and the U.S. Depart ment of Education that reviewed the num ber and percentage of alumni from 1413 colleges and universities who graduated with bachelor's degrees between 1971 and 1980 and earned Ph.D.'s between 1979 and 1988, Harvey Mudd College ranked first in the nation in the percentage of graduates who went on to earn Ph.D.'s in chemistry and mathematics and second in physics and astronomy. The Higher Edu cation Data Sharing Consortium study she cites does not include the Carne gie Classification--specialty engineering schools--to which Harvey Mudd College belongs; most schools in this category have outstanding science departments, as is the case at Harvey Mudd College. Henry E. Riggs President, Harvey Mudd College, 301 East Twelfth Street, Claremont, CA 91711-5990, USA Chrysolite, Tremolite, and Mesothelioma Five years ago (Letters, 24 Aug. 1990, p. 844), we discussed the possibility that the deaths of Quebec chrysotile miners and millers by mesothelioma might have been caused by contamination with amphibole fibers in the tremolite series. Clear evi dence is now available to address this question. We recently reported that in our cohort of almost 11,000 men bom be tween 1891 and 1920 (followed continu ously since 1966), there had been 33 cases of mesothelioma among some 7300 deaths from all causes by the end of 1988 (I). Analysis at that stage suggested that the risk of mesothelioma was appreciably higher among miners and millers in Thetford Mines than at Asbestos, and higher still among workers in a small asbestos products factory in Asbestos. It was known that the level of fibrous rremolire contanjj ination was several-fold higher m Thet- tord than in Asbestos and that crocidolitc had been used in the factory. Since then the follow-up has contin ued. and bv the end of 1^92, 37 mesothe lioma deaths had been identified among 8000 deaths from all causes. Twenty-four of the 37 were from Therford Mines and 13 from Asbestos, including five from the factory. The 24 mesothelioma cases in Thetford have now been the subject of detailed study. First, 10 controls were sought tor each subject from men in the cohort with the same year of birth who survived. In one case, only six controls could be found and, in another, only one; these two subjects and their controls were excluded from fur ther study. From detailed employment records, the number of years worked by subjects and controls in each of 15 mines in the Thetford region were calculated. Periods of service within 20 years of death of a subject were excluded, as in the eti ology of mesothelioma such exposure would probably be unimportant. It was immediately obvious that man-years of employment of the cases was concentrated in a localized area of five mines (Area A), where the ratio of man-years for controls to cases was 5.3 (1881/354), compared with 21.6 (1275/59) in the 10 mines lo cated peripherally (Area B)--a fourfold difference. Data for the two excluded cases and their available controls had the same pattern. The possibility that this distribution might be related to the concentration of fibrous tremolite in the two areas was then tested with data on asbestos fiber concen trations in lung tissue from 83 cohort mem bers from Thetford Mines who had died from causes other than mesothelioma and had been examined by electron microscopy in 1988 (2). The number of lungs examined was 58 from Area A and 25 from Area B; the groups were similar in duration of em ployment (36 and 37 years) and time from termination to death (8 years in both), but estimated accumulative dust exposure was about 30% higher in group B. The geomet ric mean concentrations of fibers equal to or greater than 5 micrometers in length per microgtam of dried lung were as follows; chrysotile, Area A, 7; Area B, 13 (not significant); tremolite. Area A, 32; Area B, 7 (P = 0.0002). The more than fourfold observed differ ence in tremolite concentration between the two areas suggests that the relatively rare cases of mesothelioma mainly or per haps wholly resulted from amphibole fiber contamination. These findings have impor tant implications, but it should be emph sized that they represent the result of lo ,l(. 7 Sit me 7IS- 771 LMU) AC-16? HWBUI0007961 -v- LETTERS ny.ivv expe'.ircs 20-to 70 years ago. The ..ologicil distribution of tremoiite within JSHucbcc chry.sotile ore body may well VPfi time and place and, at present levels ,t environmental control, any mesothelio ma risk from exposure in either area A or B would he tar below the limits of epidemio logical detection. J. Corbett McDonald Alison D. McDonald National Heart and Lung Institute, London University, Royal Brampton Hospital, London $W3 6LY, United Kingdom References j. C. McDonald, F. D. K. Liddell, A. Duiresne. A. D. McDonald, Br. J. Ind. Meet. 50. 1073 (1993). 2. P S. Sebastien. J. C. McDonald, A. D. McDonald, B. Case, R. Harley, ibid. 46. 180 (1989). Corrections and Clarifications In the report "GDNF: A potent survival factor tor motoneurons present in peripheral nerve and muscle" by C. E. Henderson el al. (11 Nov., p. 1062), the seventh author's name should have been "Laura Simmons." The af filiation for authors H. S. Phillips. M. Armanini, and Amon Rosenthal should have been "Department of Neuroscience, Genentech, South San Francisco, CA 94080-4960, USA.'' The affiliation tor B. Motfet and R. A. Vandlen should have been "Pcpartnwnt of Protean Chemistry. Cenentech." and that tor Laura Simmons should have been "LX'partment ot Cell Genetics. Genenreeh." Akin M. Davies is at the L niversirv of St. Andrews. St. Andrcws, Fite, Scotland KYlO 9AJ, United Kingdom, and Vassilis E. Koliatsos is in the Departments of Pathology, Neurology, and Neuroscience and the Neuropathology Labo ratory. Johns Hopkins University School of Medicine, Baltimore. MD 21208, USA. Be ginning on line 19 ot the first column on page 1064, the text should have read. "The average volume of the surviving motoneurons in the facial nuclei that received GDNF was 5186 -- 308 close to that in the control nuclei (6081 105 |a!) (n = 3). In contrast, al though BDNF and NT-4/5 both enhanced motoneuron survival to a similar degree as did GDNF (2, 3), neither of them prevented the axotomy-induced shrinkage of facial motoneu rons. In BDNF and NT-4/5-treated nuclei, the volume of the surviving motoneurons was only 65.5 r 4% and 63.3 2.6% of the control nuclei, respectively (n = 3) (14)." Throughout the Research Article "Autoprote olysis in hedgehog protein biogenesis " by John J. Lee et al. (2 Dec., p. 1528) the word "disc" was incorrectly spelled "disk." In figure 4C (p. 1531), lane 9 should have been labeled "flu227," not ``flu408." We'll Help You Build A New Lab Let the free Science product in formation service put you in touch with the vendors whose products you will need. Simply write us a letter stating the specifics about your proposed lab and the instruments and supplies you need. We will do the rest. Write to: SCIENCE Magazine New Lab Service Department 1333 H Street, N.W., Rm 830 Washington, DC 20005 SdENCE V * iA, *ii *>ir*irii1liinfiif nf- iiinfliiiiiifiiQi1||||ij|ii|y Circle No. 14 on Readers' Service Card HWBUI0007962