Spheroplasts of the photosynthetic bacterium Rhodospirillum rubrum were prepared from cultures grown in either the presence or absence of light. Cells were converted into spheroplasts by using lysozyme and Versene and fixed in a sucrose-veronal-acetate buffer mixture containing osmium tetroxide. Some preparations were shadow-cast and examined whole; others were embedded in Epon 812 and sectioned. The action of lysozyme and Versene appears to result in removal of the cell wall in strips. The relationship of the chromatophores to the cytoplasmic membrane is readily visualized in sections of broken spheroplasts, and in areas the chromatophores are seen to be continuous with the membrane. In all preparations examined, no definite connections between individual chromatophores were observed. In some cells large spherical granules were evident which either possessed or lacked a clearly visible limiting membrane. On serial sectioning, all granules appeared bounded by a single membrane 40 A wide. The granule membrane was well defined only if the section came from the center of the granule. Sections at other levels showed either a diffuse membrane or no membrane at all. The reasons for this are discussed.

No abstract

Population-based and proportional odds ratios for various cancers, based on incidence data from 1974-1977 and mortality data from 1965-1975 for western Washington State, were calculated in relation to three measures of exposure to asbestos in community water supplies. Six odds ratios were calculated for each neoplasm that occurred in sufficient numbers in each sex. About half of the 332 odds ratios calculated were above unity and half were below unity, and no more of them differed significantly from unity at the 5% level than would be expected by chance. Odds ratios for tumors of the small intestine were consistently elevated in both sexes, as were those for neoplasms of the thyroid, eye, testis, and prostate in males; however, odds ratios for brain tumors and leukemia were consistently less than one in both sexes. Chance is the most likely explanation for these findings. Results of this study and prior studies of cancer in relation to waterborne asbestos are inconsistent, and provide little evidence that asbestos in community water supplies has altered the risk of any cancer. However, all investigations conducted to date are correlational studies which have an inherently higher probability of failing to detect actual increased risks associated with imbibed asbestos, and additional studies of individual exposures are warranted. Neoplasms of the pancreas and small intestine should be included in such studies.

The fine structure of the photosynthetic bacterium Rhodomicrobium vannielii was studied by the ultra thin scctioning technique. Cclls were fixed in buffered osmium tctroxide and embedded in Epoxy resin. The feature most common to nearly all cells was an array of intracellular membranes situated in a concentric manner at the periphery of the cell. The membranes were mostly paired and quite often five pairs were seen aligned together. Calculations from densitomctric tracings showed the average width of a "unit" membrane to be 65 A. Sections of material from disrupted cells after passage through a sucrose gradient revcaled vesicular forms composed of membranes similar in width to those in the intact cell. Absorption spectra of both intact cells and isolated membrancs were very similar in the bacteriochlorophyll regions. Septa and membranes were demonstrated in the filaments that join mature cells. No evidence for chromatophores was obtained although the methods used were adequate for their demonstration in Rhodospirillum rubrum.

The authors conducted a case-control, interview-based study of the risk of developing cancer from asbestos in drinking water. The Everett, Washington area was selected for the study because of the unusually high concentration of chrysotile asbestos in the drinking water it draws from the Sultan River (200 X 10(6) fibers/liter). Through a population-based tumor registry, the authors identified 382 individuals with cancer of the buccal cavity, pharynx, respiratory system, digestive system, bladder, or kidney, diagnosed between 1977 and 1980, and then interviewed them or their next-of-kin. The authors conducted similar interviews of a control group of 462 individuals. Finally, interviews were validated in several ways, including comparing the collected data with that from secondary sources. Estimates of exposure to asbestos in drinking water were based on residence and workplace history, and on individual water consumption. Four different measures of exposure were used. Cancer risk was estimated by logistic regression and other methods. The authors found no convincing evidence for cancer risk from imbibed asbestos. Exposure was similar between cases and controls. Confidence intervals for relative odds for almost all sites included unity. Out of 84 dependent estimates of risk by sex, site, and exposure measure, 63 indicated a protective effect and 21 indicated an increased risk. In instances where relative odds differed appreciably from unity for both males and females, the effect was protective. The relative odds of cancer for 20 years of exposure to Sultan River drinking water varied from 0.92 to 0.99 for females and 0.82 to 1.01 for males for all study sites grouped. For cancer of the digestive system, the corresponding range was 1.03 and 1.08 for females and 0.85 to 1.00 for males. There were six statistically significant associations (p less than 0.05). All involved male stomach (eight cases) and male pharynx (four cases), and indicate elevated risk. This number of significant associations is close to that expected (for the number of comparisons made). The female risks for these two sites indicate a protective effect, and it is concluded that the male results are probably due to chance.