Red light initiates many important morphogenetic responses in plants through the mediation of the pigment, phytochrome. How phytochrome promotes photomorphogenesis is unknown. The evidence that photoactivated phytochrome initiates calcium fluxes in cells is reviewed and how these fluxes could regulate several known red-light induced effects in plants is discussed.
Achieving trainee diversity in science, technology, engineering, and mathematics is rapidly becoming a challenge faced by
many nations. Success in this area ensures the availability of a workforce capable of engaging in scientific practices that
will promote increased production capacity and creativity and will preserve global scientific competitiveness. The near-term
vision of achieving this goal is within reach and will capitalize on the growing numbers of underrepresented minority groups
in the population. Although many nations have had remarkable histories as leaders in science and technology, few have simultaneously
struggled with the challenge of meeting the educational and training needs of underrepresented groups. In this article, we
share strategies for building the agency of the scientific community to achieve greater diversity by highlighting four key
action areas: (1) aligning institutional culture and climate; (2) building interinstitutional partnerships; (3) building and
sustaining critical mass; and (4) ensuring, rewarding, and maximizing faculty involvement.
The impact of life on the atmosphere is examined through a discussion of the budgets of important atmospheric constituents and the processes that control their concentrations. Life profoundly influences oxygen and a number of minor atmospheric constituents, but many important gases, including those with the greatest effect on global climate, appear to be little altered by biological processes, at least in the steady state.
There is a particularly urgent need to analyze population policy debates because of the serious nature of the disagreements that exist and the serious consequences either of choosing the wrong policies or of choosing none. The significant sources of agreement and disagreement about population policy are described and include a description of 3 major groups whose population policy recommendations vie for acceptance: crisis environmentalists family planners and developmental distributivists. These 3 groups represent distinct policy orientations and priorities. The crisis environmentalists take the view that rapid population growth has already produced a serious crisis for the human species and the planet earth. They all agree that resources needed for the survival of the human species are finite and will be depleted unless population is held at a level that establishes a favorable balance between numbers of people and available resources. Family planners like crisis environmentalists also speak of overpopulation at times but their focus more often is upon unwanted fertility or rapid population growth. They favor complete voluntarism in the form of government investment in free-standing birth control clinics to offer all the available methods of birth control to those who would not otherwise be able to afford them. This is in contrast to the crisis environmentalists who recommend coercive government policies. The developmental distributivists believe that certain kinds of improvements in socioeconomic conditions lead to lower birthrates as observed in the demographic transition experienced in Western countries. This group regards unfavorable socioeconomic conditions as major causes of large families and rapid population growth. They argue that the key to lowering fertility lies in the extensiveness of the distribution of benefits.
Natural and synthetic estrogens are discussed with regard to their use as feed additives or as implanted pellets to increase the growth rate of ruminants. A system of evaluations is proposed to insure the safe use of estrogens as feed additives based on scientific principles and which will, after the necessary data are collected, provide a basis for making rational judgments. These principles should be applicable to other hormones which influence tumor formation. Relevant legislation controlling the use of feed additives are reviewed, as well as the results of earlier studies. The role of estrogens as carcinogens or cocarcinogens at high dosage levels is discussed and evidence that estrogens are not carcinogenic at all dosage levels is examined. Attention is also given to the available tests for determining the safety of hormonal residues, including suggested procedures for testing safe levels of the natural estrogens and alternative testing procedures for natural and synthetic estrogens.
It is possible that growing public concern reflects an increasing desire by individuals to control their own lives (and deaths) and increasing unwillingness to accept unquestionably the physician's judgment. If they are to exercise their rights in a meaningful fashion, patients and families alike will have to educate themselves in advance about the complexities of medical technology and the problems which it can create for medical care. By the time they are actually faced with such decisions, they should know what sorts of alternatives they prefer. Should this happen, physicians in the future may find it necessary to treat the chronically ill patient less as a dependent for whom decisions have to be made and more as an equal. The new demand for greater patient autonomy also means that it is imperative to resolve some of the differences which now separate the perspective of the physician on these matters from that of the layman and the lawyer.
Our minds are incarcerated by our words. The biological term symbiosis has been used in a way that obscures not only its literal meaning but also the phenomenon’s instrumental role in evolution. Biology textbooks define “symbiosis” anthropocentrically—as mutually helpful relationships or animal benefits, implying social contract or cost-benefit analysis by the partners. This definition is silly—symbiosis is a widespread biological phenomenon that preceded by eons the human world and the invention of money.
This paper addresses the traditional concept of the levels of biological organization and presents an alternative, organism-centered scheme, depicting four types of biological relationships. The scheme emphasizes essential differences between the nature of the relationships subsumed under the concepts of community and ecosystem.
In treatises on evolution and related topics, conflicting views on fundamental issues raise serious problems. Such diverse views are especially puzzling to the nonbiologist who wishes to attain a fundamental knowledge of these topics but is stymied as to whose doctrines are to be utilized. A plea for help is thus in order.
Natural selection has played an important role in establishing various phenotypes, but the molecular mechanisms of phenotypic adaptation are not well understood. The slow progress is a consequence of mutagenesis experiments in which present-day molecules were used and of the limited scope of statistical methods used to detect adaptive evolution. To fully appreciate phenotypic adaptation, the precise roles of adaptive mutations during phenotypic evolution must be elucidated through the engineering and manipulation of ancestral phenotypes. Experimental and quantum chemical analyses of dim-light vision reveal some surprising results and provide a foundation for a productive study of the adaptive evolution of various phenotypes.
An important aspect of environmental control in a life-support system is the monitoring and regulation of atmospheric gases (Sager et al. 1988) at concentrations required for the maintenance of all life forms. It will be necessary to know the rates of CO2 use, oxygen evolution, and water flux through evapotranspiration by a crop stand under various environmental conditions, so that appropriate designs and control systems for maintaining mass balances of those gases can be achieved for a full range of environmental regimes. Mass budgets of gases will also enable evaluation of crop health by monitoring directly the rates of gas exchange and indirectly the rate of accumulation of dry matter, based on rates of carbon dioxide use. This article focuses on the unique capabilities of the NASA biomass production chamber for monitoring and evaluating gas exchange rates, with special emphasis on results with wheat and soybean, two candidate species identified by NASA for CELSS.
This article represents an effort to examine the existing practices and the concepts which underlie them, and to indicate what can be done to help patients cope with dying without breaking the fundamental restrictions which our society justly places on the taking of lives.
The cellular slime mold system has many features that make it a unique model system for the study of cellular differentiation. In recent years, genetics has played an increasingly important role in the development of the system. This paper reviews that progress.
This paper summarizes the history and recent acceleration of progress in research on reproduction leading to improved means of contraception, in relation to worldwide funding. The authors list recommendations respecting the immediate need for a greatly expanded research effort to attain contraceptive means that are safe, effective, reversible, easily available, and widely acceptable for long-term use.
Cilia are highly conserved for their structure and also for their sensory functions. They serve as antennae for extracellular
information. Whether the cilia are motile or not, they respond to environmental mechanical and chemical stimuli and send signals
to the cell body. The information from extracellular stimuli is commonly converted to electrical signals through the repertoire
of ion-conducting channels in the ciliary membrane, which results in changes in concentrations of ions, especially calcium
ions, in the cilia. These changes, in turn, affect motility and the ability of the signaling pathways in the cilia and cell
body to carry on the signal transduction. We review here the activities of ion channels in cilia in animals from protists
Electric fish produce weak electric fields to image their world in darkness and to communicate with potential mates and rivals. Eavesdropping by electroreceptive predators exerts selective pressure on electric fish to shift their signals into less-detectable high-frequency spectral ranges. Hypopomid electric fish evolved a signal-cloaking strategy that reduces their detectability by predators in the lab (and thus presumably their risk of predation in the field). These fish produce broad-frequency electric fields close to the body, but the heterogeneous local fields merge over space to cancel the low-frequency spectrum at a distance. Mature males dynamically regulate this cloaking mechanism to enhance or suppress low-frequency energy. The mechanism underlying electric-field cloaking involves electrogenic cells that produce two independent action potentials. In a unique twist, these cells orient sodium and potassium currents in the same direction, potentially boosting their capabilities for current generation. Exploration of such evolutionary inventions could aid the design of biogenerators to power implantable medical devices, an ambition that would benefit from the complete genome sequence of a gymnotiform fish.
The case of Karen Ann Quinlan has focused nationwide attention on the legal bounds of a decision to withdraw life-preserving care from a lingering patient. This comment on the lower court decision in the Quinlan case suggests that the judge was overly restrictive of the family's prerogatives.
Artificial ecosystem selection is an experimental technique that treats microbial communities as though they were discrete
units by applying selection on community-level properties. Highly diverse microbial communities associated with humans and
other organisms can have significant impacts on the health of the host. It is difficult to find correlations between microbial
community composition and community-associated diseases, in part because it may be impossible to define a universal and robust
species concept for microbes. Microbial communities are composed of potentially thousands of unique populations that evolved
in intimate contact, so it is appropriate in many situations to view the community as the unit of analysis. This perspective
is supported by recent discoveries using metagenomics and pangenomics. Artificial ecosystem selection experiments can be costly,
but they bring the logical rigor of biological model systems to the emerging field of microbial community analysis.
Recently scientists have proposed that some, if not all, ancient glacial deposits are really impact deposits. The proposition that glaciation may not have occurred before the Cenozoic raises for reconsideration the surface temperature history of earth. The authors examine the information available and propose the following scenario. Just before the origin of life, the earth had a high carbon dioxide pressure-cooker atmosphere and soon after extreme thermophiles colonized the land, enhancing weathering rates, sequestering carbon dioxide into limestone deposits and cooling the Earth's surface. Subsequent cooling of the earth and enhancement of weathering was in part the result of microbial evolutionary developments and of the progressive biotic colonization of the land.
The inability to control successfully the world's rapidly increasing human population has led to further study of intrauterine devices. This article discusses the current knowledge of intrauterine contraception and its prospects for the future. It considers intrauterine contraception as an evolving method, and emphasizes the problems that accompany IUD use and the kinds of modifications that may improve their performance.
Direct energy coupling in mitochondria requires the participation of intrinsic ionophores. These protein-linked ionophores
are now demonstrable and isolatable. The central phenomena of energy coupling, such as how uncouplers act, how coupling in
cytochrome oxidase is mediated, and how ATP is synthesized, can be satisfactorily rationalized in terms of these intrinsic
For the past decade, the scientific and popular press have carried frequent articles about a catastrophic mass extinction that supposedly destroyed the majority of the earth's species, including the dinosaurs, approximately 65 million years ago. Since 1980, more than 2000 papers and books have dealt with some aspect of a mass extinction at the Cretaceous-Tertiary (K/T) boundary. One authoritative estimate of the severity of the extinctions is that 60-80% of all the living species became extinct at this boundary (Raup 1988). There appears to be a general acceptance of the fact that such a great catastrophe did occur. Most of the argument among scientists now is devoted to the determination of the cause. In this article, I argue that the species changes at the K/T boundary were neither sudden nor catastrophic. They were most likely caused by a regression of sea level that led to a decrease in primary production. NASA Edited
Plant scientists have sought to maximize the yield of food crops since the beginning of agriculture. There are numerous reports of record food and biomass yields (per unit area) in all major crop plants, but many of the record yield reports are in error because they exceed the maximal theoretical rates of the component processes. In this article, we review the component processes that govern yield limits and describe how each process can be individually measured. This procedure has helped us validate theoretical estimates and determine what factors limit yields in optimal environments.