A recurrent nova super-remnant in the Andromeda galaxy.

The accretion of hydrogen onto a white dwarf star ignites a classical nova eruption1,2-a thermonuclear runaway in the accumulated envelope of gas, leading to luminosities up to a million times that of the Sun and a high-velocity mass ejection that produces a remnant shell (mainly consisting of insterstellar medium). Close to the upper mass limit of a white dwarf3 (1.4 solar masses), rapid accretion of hydrogen (about 10-7 solar masses per year) from a stellar companion leads to frequent eruptions on timescales of years4,5 to decades6. Such binary systems are known as recurrent novae. The ejecta of recurrent novae, initially moving at velocities of up to 10,000 kilometres per second7, must 'sweep up' the surrounding interstellar medium, creating cavities in space around the nova binary. No remnant larger than one parsec across from any single classical or recurrent nova eruption is known8-10, but thousands of successive recurrent nova eruptions should be capable of generating shells hundreds of parsecs across. Here we report that the most frequently recurring nova, M31N 2008-12a in the Andromeda galaxy (Messier 31 or NGC 224), which erupts annually11, is indeed surrounded by such a super-remnant with a projected size of at least 134 by 90 parsecs. Larger than almost all known remnants of even supernova explosions12, the existence of this shell demonstrates that the nova M31N 2008-12a has erupted with high frequency for millions of years.

Bacterial domestication: underlying assumptions.

On the basis of well-established principles of evolutionary biology and microbiology, I conclude that (i) the deliberate introduction of a novel bacterial strain to the environment is not substantially more dangerous than the accidental release of a smaller number of cells; (ii) distant organisms are less (rather than more) likely to yield dangerous hybrids than more closely related ones; and (iii) the complex attribute of pathogenicity is not likely to emerge from genetic alterations in nonpathogens. If these conclusions are correct, most engineered bacteria need not be regulated more strictly than the bacterial strains that have been tested in the field in the past. The only exceptions would be strains derived from cells, or appropriate genes, of microbes pathogenic for plants or animals. Microbiologists not only recognize the need to handle pathogens with caution: they have long accepted regulations, such as those governing transportation, that reinforce that recognition. It is remarkable that we can still be arguing, on the basis of analogies rather than firm scientific principles or evidence, about hypothetical disasters from kinds of organisms that are being produced in hundreds or thousands of laboratories without a trace of demonstrable harm. RAC required 6 years to adjust its initially conservative guidelines to the emerging understanding of the scientific realities, while maintaining public confidence. Since the level of public concern is not nearly as great today, EPA should be able to relax its excessive restrictions much more quickly. Even better would be a return to having RAC, or a single successor group, evaluate the problems of danger for all classes of engineered bacteria, since the applicable shared principles outweigh any specialized differences in the nature or use of the specific strains. But the regulations are unlikely to be unified in this way, or to be divested of unproductive restrictions, without broad encouragement from the scientific community-including, hopefully, many ecologists. The agenda has been set for too long by apocalyptic activists. To protect this promising field of research and technological application the scientific community must take initiative in helping the public and decision-makers to distinguish reasonable probabilities from remote fantasies.

Frontiers of the biological sciences.

The history of the molecular revolution in biology is described, emphasizing its dependence on the emergence of bacterial genetics, the fusion of genetics and biochemistry, and the development of greatly improved techniques for studying macromolecules. Central concepts have included molecular information transfer, both by nucleic acids and by allosteric proteins; the spontaneous conversion of one-dimensional information into three-dimensional structures; and the extraordinary unity in the molecular mechanisms underlying the rich diversity of biology. The merging of molecular and morphological studies, to yield the very broad field of cell biology, is described more briefly, as are also some present frontiers in several areas of biology that present challenges at other levels of organization.

Polysomes extracted from Escherichia coli by freeze-thaw-lysozyme lysis.

Polysomes can be extracted from Escherichia coli by freezing and thawing in the presence of lysozyme, followed by treatment with sodium deoxycholate. The method is simple and convenient; the yields consistently high.

The scientist's world.

This paper describes the features of the world of science, and it compares that world briefly with that of politics and the law. It also discusses some "postmodern" trends in philosophy and sociology that have been undermining confidence in the objectivity of science and thus have contributed indirectly to public mistrust. The paper includes broader implications of interactions of government and science.

The conceptual structure of the integrated exposure uptake biokinetic model for lead in children.

The integrated exposure uptake biokinetic model for lead in children was developed to provide plausible blood lead distributions corresponding to particular combinations of multimedia lead exposure. The model is based on a set of equations that convert lead exposure (expressed as micrograms per day) to blood lead concentration (expressed as micrograms per deciliter) by quantitatively mimicking the physiologic processes that determine blood lead concentration. The exposures from air, food, water, soil, and dust are modeled independently by several routes. Amounts of lead absorbed are modeled independently for air, food, water, and soil/dust, then combined as a single input to the blood plasma reservoir of the body. Lead in the blood plasma reservoir, which includes extracellular fluids, is mathematically allocated to all tissues of the body using age-specific biokinetic parameters. The model calculation provides the estimate for blood lead concentration for that age. This value is treated as the geometric mean of possible values for a single child, or the geometric mean of expected values for a population of children exposed to the same lead concentrations. The distribution of blood lead concentrations about this geometric mean is estimated using a geometric standard deviation, typically 1.6, derived from the analysis of well-conducted community blood studies.

Sequential thoracic metastasectomy prolongs survival by re-establishing local control within the chest.

OBJECTIVE: The value of sequential thoracic metastasectomies is unknown. We evaluate repeat metastasectomy for limited recurrences within the thorax. METHODS: From July 1988 to September 1998, 54 patients underwent 2 to 6 separate sequential procedures to excise metastases after recurrence isolated to the thorax. Kaplan-Meier survival and Cox modeling determined prognostic variables. RESULTS: Thirty-three men and 21 women, 22 to 76 years underwent 2 (100%, n = 54), 3 (50%), 4 (22%), or 5 to 6 (11%) metastasectomies. Fifty-four percent of patients had carcinoma, 35% sarcoma, 9% germ cell, and 2% melanoma. There were no operative deaths; all late deaths occurred from cancer. Median follow-up was 48 months. Cumulative 5-year survival from the second procedure was 57%. After the second, third, fourth, and fifth procedures, respectively, permanent control was achieved in 15 (27%) of 54 patients, 5 (19%) of 27, 1 (8%) of 12, and 0 of 7. Recurrence amenable to additional surgery occurred in 27 (50%) of 54, 12 (44%) of 27, 6 (50%) of 12, and 1 (17%) of 6. Mean hazard for the development of unresectable recurrence increased from 0.21 after the second procedure to 0.91 after the fifth procedure. The 5-year survival for the 27 patients undergoing only 2 metastasectomies was 60% (median not yet reached), 33% for the 15 patients undergoing only 3 metastasectomies (median 34.7 months), and 38% for the 12 patients undergoing 4 or more (median 45.6 months). From the time a recurrence was declared unresectable, patients had a 19% 2-year survival (median 8 months). CONCLUSIONS: Multiple attempts to re-establish intrathoracic control of metastatic disease is justified in carefully selected patients, but the magnitude of benefit decays with each subsequent attempt.

Psychological distress associated with waiting for results of diagnostic investigations for breast disease.

This paper presents the results of a multi-method research project investigating the psychological distress associated with waiting for results of diagnostic investigations in a delayed-results breast clinic. A cohort of 126 women completed standardized psychometric instruments to assess anxiety, mood and coping over 3 days. Semi-structured interviews were conducted with 20 respondents. The findings indicate that waiting sustained but did not exacerbate psychological distress. Peri-diagnostic anxiety, depression, uncertainty and confusion were associated with anxiety levels immediately following triple assessment. Women leaving the clinic with low anxiety retained this composure throughout the peri-diagnostic period. Those in the moderate and high anxiety groups recorded sustained anxiety, depression, uncertainty and confusion, with mean scores comparable to and exceeding those reported by psychiatric out-patients. Coping during the waiting period was typically accomplished by emotion-focused strategies. Qualitative data suggested the delayed-results clinic structure may facilitate psychological preparation for test results.

Transitioning the child fed by gastrostomy into school.

Young children dependent on gastrostomy feeding are examples of special-needs children now eligible for expanded nutrition services in schools through Public Law 99-457. With the implementation of this law, nutritionists have an opportunity to expand their roles as consultants to special education teachers. A team approach involving nutrition, nursing, and special education was used to prepare a gastrostomy-fed preschool child and his family for school. The family of the multihandicapped child had been isolated by the child's feeding problems and viewed the problems as barriers to his entering school. Components of a nutrition care plan for an interdisciplinary team included oral feeding readiness, nutritional adequacy and timing of meals, and mechanical aspects of gastrostomy feeding in the classroom. Nutrition interventions were adjusted for the classroom from those used in the home or clinical setting. The major activity in the transition program was behavioral management of the child's rumination, which affected nutritional status and feeding. The major outcome of the transition program was enrollment of the child in school, with gastrostomy feeding as a routine activity. A transition program for a gastrostomy-fed child is an appropriate mechanism for expanding the role of the nutritionist into the classroom.

Sun avoidance practices among non-Hispanic white Californians.

This study measures self-reported sun avoidance practices, use of protective clothing, and use of sunscreen among 4,749 non-Hispanic white adults living in households in California. Data are from the California Behavioral Risk Factor Survey, a population-based telephone survey of health behaviors and attitudes. The average respondent spent at least 15 minutes in the sun on 21.4 days out of the last 30 days. Regular use of protective clothing was reported by 30.7%, regular use of sunscreen by 22.2%, and regular sun avoidance by 17.1% of the respondents. Results varied by month, gender, skin tone, age, education, and presence of children in the household. Health strategies should target younger adults (especially men), households with children and adults with less than a high school education. Because of relatively low rates of sun avoidance behaviors overall, a general population campaign also is warranted.

A prospective trial of primary inguinal hernia repair by surgical trainees.

The main hypotheses were that the Lichtenstein inguinal hernia repair has a lower recurrence rate and similar incidence of chronic groin pain compared to sutured repairs when performed by surgical trainees. In a U.S. Veterans Administration Hospital, 150 primary hernia repairs were randomized to a Lichtenstein, McVay, or Shouldice repair. The Shouldice repair included a routine relaxing incision. First- and second-year residents, under the supervision of an experienced general surgeon, performed the procedure. Long-term follow-up was obtained in 81% of patients. Hernia recurrence rate was Lichtenstein 8%, McVay 10%, Shouldice 5% ( P>0.1) at 6-9 years follow-up. More patients had chronic groin pain following Lichtenstein repair (38%) than after Shouldice repair (7%) ( P<0.05). More information is needed on long-term groin pain following anterior mesh repair. The Shouldice inguinal hernia repair may have a role in open primary herniorrhaphy to decrease the risk of chronic groin pain.