The increased breast cancer risk in female night shift workers has been postulated to result from the suppression of pineal melatonin production by exposure to light at night. Exposure of rats bearing rat hepatomas or human breast cancer xenografts to increasing intensities of white fluorescent light during each 12-hour dark phase (0-345 MW/cm 2 ) resulted in a dose-dependent suppression of nocturnal melatonin blood levels and a stimulation of tumor growth and linoleic acid uptake/metabolism to the mitogenic molecule 13-hydroxyoctadecadienoic acid. Venous blood samples were collected from healthy, premenopausal female volunteers during either the daytime, nighttime, or nighttime following 90 minutes of ocular bright, white fluorescent light exposure at 580 MW/cm 2 (i.e., 2,800 lx). Compared with tumors perfused with daytimecollected melatonin-deficient blood, human breast cancer xenografts and rat hepatomas perfused in situ, with nocturnal, physiologically melatonin-rich blood collected during the night, exhibited markedly suppressed proliferative activity and linoleic acid uptake/metabolism. Tumors perfused with melatonin-deficient blood collected following ocular exposure to light at night exhibited the daytime pattern of high tumor proliferative activity. These results are the first to show that the tumor growth response to exposure to light during darkness is intensity dependent and that the human nocturnal, circadian melatonin signal not only inhibits human breast cancer growth but that this effect is extinguished by short-term ocular exposure to bright, white light at night. These mechanistic studies are the first to provide a rational biological explanation for the increased breast cancer risk in female night shift workers. (Cancer Res 2005; 65(23): 11174-84)

-The theory of plate tectonics provides a basic framework for evaluating the potential for future great earthquakes to occur along major plate boundaries. Along most of the transform and convergent plate boundaries considered in this paper, the majority of seismic slip occurs during large earthquakes, i.e., those of magnitude 7 or greater. The concepts that rupture zones, as delineated by aftershocks, tend to abut rather than overlap, and large events occur in regions with histories of both long-and short-term seismic quiescence are used in this paper to delineate major seismic gaps.In detail, however, the distribution of large shallow earthquakes along convergent plate margins is not always consistent with a simple model derived from plate tectonics. Certain plate boundaries, for example, appear in the long term to be nearly aseismic with respect to large earthquakes. The identification of specific tectonic regimes, as defined by dip of the inclined seismic zone, the presence or absence of aseismic ridges and seamounts on the downgoing lithospheric plate, the age contrast between the overthrust and underthrust plates, and the presence or absence of back-arc spreading, have led to a refinement in the application of plate tectonic theory to the evaluation of seismic potential.The term seismic gap is taken to refer to any region along an active plate boundary that has not experienced a large thrust or strike-slip earthquake for more than 30 years. A region of high seismic potential is a seismic gap that, for historic or tectonic reasons, is considered likely to produce a large shock during the next few decades. The seismic gap technique provides estimates of the location, size of future events and origin time to within a few tens of years at best.The accompanying map summarizes six categories of seismic potential for major plate boundaries in and around the margins of the Pacific Ocean and the Caribbean, South Sandwich and Sunda (Indonesia) regions for the next few decades. These categories range from what we consider high to low potential for being the site of large earthquakes during that period of time. Categories 1, 2 and 6 define a time-dependent potential based on the amount of time elapsed since the last large earthquake. The remaining categories, 3, 4, and 5, are used for areas that have ambiguous histories for large earthquakes; their seismic potential is inferred from various tectonic criteria. These six categories are meant to be interpreted as forecasts of the location and size of future large shocks and should not be considered to be predictions in which a precise estimate of the time of occurrence is specified.Several of the segments of major plate boundaries that are assigned the highest potential, i.e., category I, are located along continental margins, adjacent to centers of population. Some of them are hundreds of kilometers long. High priority should be given to instrumenting and studying several of these major seismic gaps since many are now poorly instrumented. The categories of potent...

SUMMARY This study determined the incidence and concentration of methane-producing bacteria in tap water enema samples of 130 individuals taken before sigmoidoscopy. The number of subjects classified in five major colonic groups were as follows: normal colon 36, diverticulosis 57, inflammatory bowel disease 11, colon polyps 34, and colon cancer 11. Some patients were placed in more than one category. Ninety four of the subjects or 72% had methanogenic bacteria ranging in concentration from 6 to about 3 x 1010/g dry weight of faeces.The predominant methanogen in all groups was Methanobrevibacter smithii. Chi-square analysis showed that the incidence of methanogens in concentrations of 107/g dry weight of faeces or greater in patients with diverticulosis (58%) was significantly greater than in normal patients (25%). High methanogen concentrations are associated with excretion of methane in the breath.Studies by Bond et all showed that methane in man is produced by bacteria in the colon and indicated that most methane production occurs in the left colon. Methane is not metabolised further in man. It was estimated' that 20% of that produced is excreted through the lungs and that the remainder is passed as flatus. Miller and Wolin2 3 showed that the predominant methane producing organism in humans is Methanobrevibacter smithii. It produces methane by using hydrogen to reduce carbon dioxide. This organism remains at about the same concentration in the faeces of individuals studied over a period of 10-13 months.4 Thirty to 61% of adults excrete methane in the breath. -9 Breath methane is established in individuals between the ages of two and 10.1 Unlike breath hydrogen, breath methane does not usually increase when methane producers are given a non-absorbed carbohydrate.' 1(0 Breath methane does, however, increase in producers with high endogenous methane production after they are given a large dose of a non-absorbed carbohydrate.6 r-1 12

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