2,174 results match your criteria CBE life sciences education[Journal]
Breast 2018 Nov 28;43:105-112. Epub 2018 Nov 28.
Prevention and Cancer Control, Cancer Care Ontario, Canada; Dalla Lana School of Public Health, University of Toronto, Canada.
Background: There is controversy about the value of clinical breast examination (CBE) in addition to mammography for breast screening. The study investigates the associations between risk factors such as mammographic density, hormone therapy use and family history and the effectiveness of screening mammography with or without CBE.
Methods: The cohort consists of women 50-69 years old screened at the Ontario Breast Screening Program. Read More
Neurobiol Dis 2018 Dec 4;124:289-296. Epub 2018 Dec 4.
Laboratory of Functional Neurochemistry, IRCCS Mondino Foundation, Pavia, Italy. Electronic address:
GBA1 gene encodes for the lysosomal membrane protein glucocerebrosidase (GCase). GBA1 heterozygous mutations profoundly impair GCase activity and are currently recognized as an important risk factor for the development of Parkinson's disease (PD). Deficits in lysosomal degradation pathways may contribute to pathological α-synuclein accumulation, thereby favoring dopaminergic neuron degeneration and associated microglial activation. Read More
CBE Life Sci Educ 2018 Dec;17(4):ar65
Department of Biological Sciences, Purdue University, West Lafayette, IN 47907.
As undergraduate biology curricula increasingly aim to provide students with access to courses and experiences that engage them in the practices of science, tools are needed for instruction, evaluation, and research around student learning. One of the important skills for undergraduate biology students to master is the selection and creation of appropriate graphs to summarize data they acquire through investigations in their course work and research experiences. Graphing is a complex skill, and there are few, discipline-informed tools available for instructors, students, and researchers to use. Read More
CBE Life Sci Educ 2018 Dec;17(4):ar64
Natural Reserve System, University of California San Diego, La Jolla, CA 92093.
The San Diego Biodiversity Project introduces undergraduate students at four different 2- and 4-year schools to a short-term research experience (SRE) that was implemented as a module in the last third of a traditional laboratory course. The study assesses the qualities of this SRE for students using three different methods. Twenty-one participants were interviewed about their experiences in the traditional and research components of their course. Read More
CBE Life Sci Educ 2018 Dec;17(4):mr1
Kewalo Marine Laboratory, Pacific Biosciences Research Center, University of Hawai'i at Mānoa, Honolulu, HI 96813.
Climate change is impacting the Pacific Islands first and most drastically, yet few native islanders are trained to recognize, analyze, or mitigate the impacts in these islands. To understand the reasons why low numbers of Native Hawaiians and Pacific Islanders enter colleges, enroll in science, technology, engineering, and mathematics (STEM) courses, or undertake life sciences/STEM careers, 25 representatives from colleges and schools in seven U.S. Read More
CBE Life Sci Educ 2018 Dec;17(4):ar63
Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721.
Providing opportunities for science, technology, engineering, and mathematics undergraduates to engage in authentic scientific practices is likely to influence their view of science and may impact their decision to persist through graduation. Laboratory courses provide a natural place to introduce students to scientific practices, but existing curricula often miss this opportunity by focusing on confirming science content rather than exploring authentic questions. Integrating authentic science within laboratory courses is particularly challenging at high-enrollment institutions and community colleges, where access to research-active faculty may be limiting. Read More
BMC Med Genomics 2018 Nov 27;11(1):108. Epub 2018 Nov 27.
Background: Molecular analyses such as whole-genome sequencing have become routine and are expected to be transformational for future healthcare and lifestyle decisions. Population-wide implementation of such analyses is, however, not without challenges, and multiple studies are ongoing to identify what these are and explore how they can be addressed.
Methods: Defined as a research project, the Personal Genome Project UK (PGP-UK) is part of the global PGP network and focuses on open data sharing and citizen science to advance and accelerate personalized genomics and medicine. Read More
J Interpers Violence 2018 Nov 26:886260518812797. Epub 2018 Nov 26.
2 University of Virginia, Charlottesville, USA.
Emerging research has shown that experiences of sexual violence are associated with cancer screening behaviors. However, to date, little attention has been given to the impact of sexual assault on cancer screening behaviors, particularly among men. To address this, we used data from the 2014 Kansas Behavioral Risk Factor Surveillance System. Read More
CBE Life Sci Educ 2018 Dec;17(4):ar61
Center for Integration of Science and Industry, Bentley University, Waltham, MA 02452.
The majority of students who enroll in undergraduate biology courses will eventually be employed in non-STEM (science, technology, engineering, and mathematics) business occupations. This work explores how representations of industry in undergraduate biology textbooks could impact STEM learning for these students and their ability to apply this learning in their chosen work. We used text analysis to identify passages with references to industry in 29 textbooks. Read More
CBE Life Sci Educ 2018 Dec;17(4):le2
Department of Chemistry, Wellesley College, Wellesley, MA 02481.
CBE Life Sci Educ 2018 Dec;17(4):ar60
Center for Evolution and Medicine, Arizona State University, Tempe, AZ 85281.
Group work is often a key component of student-centered pedagogies, but there is conflicting evidence about what types of groups provide the most benefit for undergraduate students. We investigated student learning outcomes and attitudes toward working in groups when students were assigned to groups using different methods in a large-enrollment, student-centered class. We were particularly interested in how students entering the class with different levels of competence in biology performed in homogeneous or heterogeneous groups, and what types of group compositions were formed using different methods of group formation. Read More
CBE Life Sci Educ 2018 Dec;17(4):ar62
Department of Anthropology, University of Wyoming, Laramie, WY 82071.
We argue that cultural capital plays an underexamined role in students' recognition as budding scientists by faculty. By triangulating interview data from undergraduates and faculty mentors in a multi-institutional biology research network, we identified a set of intersecting domains of capital that help render students recognizable to faculty. We argue that faculty recognition often reflects a (mis)alignment between the cultural capital that students possess and display and what faculty expect to see. Read More
Nat Commun 2018 11 15;9(1):4804. Epub 2018 Nov 15.
Laboratory of Genetics and Physiology, National Institute of Diabetes and Digestive and Kidney Diseases, US National Institutes of Health, Bethesda, MD, 20892, USA.
Base editing directly converts a target base pair into a different base pair in the genome of living cells without introducing double-stranded DNA breaks. While cytosine base editors (CBE) and adenine base editors (ABE) are used to install and correct point mutations in a wide range of organisms, the extent and distribution of off-target edits in mammalian embryos have not been studied in detail. We analyze on-target and proximal off-target editing at 13 loci by a variety of CBEs and ABE in more than 430 alleles generated from mouse zygotic injections using newly generated and published sequencing data. Read More
Perspect Med Educ 2018 Dec;7(6):362-372
Veterinary Clinical and Diagnostic Sciences, Faculty of Veterinary Medicine, University of Calgary, Calgary, Canada.
Introduction: Competency-based education (CBE) is now pervasive in health professions education. A foundational principle of CBE is to assess and identify the progression of competency development in students over time. It has been argued that a programmatic approach to assessment in CBE maximizes student learning. Read More
BMJ 2018 Nov 14;363:k4583. Epub 2018 Nov 14.
New Balance Foundation Obesity Prevention Center, Division of Endocrinology, Boston Children's Hospital, 300 Longwood Avenue, Boston, MA 02115, USA
Objective: To determine the effects of diets varying in carbohydrate to fat ratio on total energy expenditure.
Design: Randomized trial.
Setting: Multicenter collaboration at US two sites, August 2014 to May 2017. Read More
CBE Life Sci Educ 2018 Dec;17(4):ar58
Department of Chemistry, University of Massachusetts Boston, Boston, MA 02125.
The solving of problems in biochemistry often uses concepts from multiple disciplines such as chemistry and biology. Chemical identity (CI) is a foundational concept in the field of chemistry, and the knowledge, thinking, and practices associated with CI are used to answer the following questions: "What is this substance?" and "How is it different from other substances?" In this study, we examined the relevance of CI in biochemical contexts and first explored the ways in which practicing biochemists consider CI relevant in their work. These responses informed the development of creative exercises (CEs) given to second--semester biochemistry students. Read More
CBE Life Sci Educ 2018 Dec;17(4):ar57
Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Boulder, CO 80309.
Course-based undergraduate research experiences (CUREs) provide students opportunities to engage in research in a course. Aspects of CURE design, such as providing students opportunities to make discoveries, collaborate, engage in relevant work, and iterate to solve problems are thought to contribute to outcome achievement in CUREs. Yet how each of these elements contributes to specific outcomes is largely unexplored. Read More
CBE Life Sci Educ 2018 Dec;17(4):es16
Dean's Office, College of Science and Mathematics, North Dakota State University, Fargo, ND 58108.
For decades, formative assessment has been identified as a high-impact instructional practice that positively affects student learning. Education reform documents such as Vision and Change: A Call to Action expressly identify frequent, ongoing formative assessment and feedback as a key instructional practice in student-centered learning environments. Historically, effect sizes between 0. Read More
CBE Life Sci Educ 2018 Dec;17(4):ar59
Department of Biological Sciences, Bethel University, St. Paul, MN 55112.
Despite its value in higher education, academic rigor is a challenging construct to define for instructor and students alike. How do students perceive academic rigor in their biology course work? Using qualitative surveys, we asked students to identify "easy" or "hard" courses and define which aspects of these learning experiences contributed to their perceptions of academic rigor. The 100-level students defined hard courses primarily in affective terms, responding to stressors such as fast pacing, high workload, unclear relevance to their life or careers, and low faculty support. Read More
Mol Biol Cell 2018 Nov;29(22):2611-2613
Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602.
How did a moderately sized scientific society create what many consider to be the leading journal in biology education? As Editor-in-Chief of the education journal of the American Society for Cell Biology (ASCB), CBE-Life Sciences Education ( LSE) and recipient of the 2018 Bruce Alberts Award for Excellence in Science Education, I tell the story of the establishment, growth, and impact of ASCB's "other journal." Read More
Int J Hyperthermia 2018 Oct 25:1-11. Epub 2018 Oct 25.
c Department of Medical Imaging and Radiological Sciences , College of Medicine, Chang Gung University , Taoyuan , Taiwan.
Radiofrequency (RF) ablation (RFA) is the most commonly used minimally invasive procedure for thermal ablation of liver tumors. Ultrasound not only provides real-time feedback of the electrode location for RFA guidance but also enables visualization of the tissue temperature. Changes in backscattered energy (CBE) have been widely applied to ultrasound temperature imaging for assessing thermal ablation. Read More
Bundesgesundheitsblatt Gesundheitsforschung Gesundheitsschutz 2018 Dec;61(12):1505-1512
Screening Group, Early Detection and Prevention Section, International Agency for Research on Cancer (WHO), 150 cours Albert Thomas, 69372, Lyon Cedex 08, France.
Limited health system capacities and competing health priorities in low and middle income countries (LMICs) necessitate a pragmatic approach to population-based cancer screening. Thus, the challenges faced by LMICs to implement a 'western' model of screening for common cancers and the possible means to overcome these challenges are presented. Breast cancer is the number one cancer with a rising trend in the majority of LMICs. Read More
CBE Life Sci Educ 2018 Dec;17(4):ar53
Department of Biology, University of Kentucky, Lexington, KY 40506.
Based on positive student outcomes, providing research experiences from early undergraduate years is recommended for science, technology, engineering, and mathematics (STEM) majors. To this end, we designed a novel research experience called the "STEMCats Research Experience" (SRE) for a cohort of 119 second-semester freshmen with diverse college preparatory levels, demographics, and academic majors. The SRE targeted student outcomes of enhancing retention in STEM majors, STEM competency development, and STEM academic performance. Read More
CBE Life Sci Educ 2018 Dec;17(4):ar56
Department of Physics and Mallinson Institute for Science Education, Western Michigan University, Kalamazoo, MI 49008.
Academic departments are thought to be highly productive units of change in higher education. This paper investigates department-level instructional change via case studies analyzed with two change frameworks. One framework embodies prescribed change, emphasizing leader actions. Read More
CBE Life Sci Educ 2018 Dec;17(4):fe8
Department of Education, Tufts University, Medford, MA 02155.
CBE Life Sci Educ 2018 Dec;17(4):ar55
Department of Biological Sciences, Wright State University, Dayton, OH 45435.
Modern genetics is a relatively new domain, but it is increasingly important for students to have a firm grasp on the content, because genetic technologies are becoming more commonplace. In a previous study, we used the Learning Progression-based Assessment of Modern Genetics to assess high school students' knowledge of genetics concepts after an intensive inquiry-based genetics instructional period. Given that this type of intensive inquiry-based instruction is unique, we are now investigating how students' knowledge of genetics changes after instruction (i. Read More
CBE Life Sci Educ 2018 Dec;17(4):ar54
Department of Biology, University of Nebraska at Omaha, Omaha, NE 68182-0040.
The development of critical thinking skills in recent college graduates is keenly requested by employers year after year. Moreover, improving these skills can help students to better question and analyze data. Consequently, we aimed to implement a training program that would add to the critical thinking skills of undergraduate students: Nebraska Science, Technology, Engineering, and Math 4U (NE STEM 4U). Read More
Sci Rep 2018 Oct 15;8(1):15271. Epub 2018 Oct 15.
Department of Food Science, University of Guelph, Guelph, Ontario, Canada.
A cocoa butter equivalent (CBE) was synthesized enzymatically from readily available edible fats with fatty acid and triacylglycerol compositions that closely resemble the fat present in chocolate, cocoa butter. A commercially available immobilized fungal lipase, Lipozyme RM IM, was used as the reaction catalyst. Reaction parameters were a temperature of 65 °C, water activity of 0. Read More
Breast Cancer Res Treat 2018 Oct 12. Epub 2018 Oct 12.
Department of Surgery, Pontificia Universidad Javeriana, Bogota, Colombia.
Purpose: Clinical breast examination (CBE) is an important step in the assessment of patients with breast-related complaints. We developed a standardized simulation and multimedia-based (SSMBI) curriculum using current evidenced-based recommendations. This study aimed to determine if SSMBI training resulted in better performance (examination scores and detection of abnormal findings) than the traditional teaching method. Read More
Eur Urol Focus 2018 Oct 3. Epub 2018 Oct 3.
Robert D. Jeffs Division of Pediatric Urology, James Buchanan Brady Urological Institutions, Johns Hopkins Hospital, Johns Hopkins Medical Institutions, Charlotte Bloomberg Children's Hospital, Baltimore, MD, USA. Electronic address:
Background: A failed closure of classic bladder exstrophy (CBE) has a negative long-term impact on the patient and the health care system.
Objective: To investigate the outcomes of CBE patients with failed primary bladder closure.
Design, Setting, And Participants: A database of 1317 exstrophy-epispadias complex patients was retrospectively reviewed for CBE patients with failed primary bladder closure from 1965 to 2017 with subsequent repeat closure. Read More
Pathology 2018 10;50(6):698
Food Sci Biotechnol 2018 Feb 30;27(1):47-55. Epub 2017 Nov 30.
Department of Food Science and Technology, Chungnam National University, Daejeon, 34134 Republic of Korea.
This study examined the antibacterial activities of two different cinnamon essential oil emulsions against O157:H7 and Typhimurium on basil leaves. Cinnamon oil (0.25%) treatments containing CPC (0. Read More
Adv Immunol 2018 27;139:93-135. Epub 2018 Aug 27.
Program in Cellular and Molecular Medicine, Boston Children's Hospital, and Department of Genetics, Howard Hughes Medical Institute, Harvard Medical School, Boston, MA, United States.
An effective adaptive immune system depends on the ability of developing B and T cells to generate diverse immunoglobulin (Ig) and T cell receptor repertoires, respectively. Such diversity is achieved through a programmed somatic recombination process whereby germline V, D, and J segments of antigen receptor loci are assembled to form the variable region V(D)J exons of Ig and TCRs. Studies of this process, termed V(D)J recombination, have provided key insights into our understanding of a variety of general gene regulatory and DNA repair processes over the last several decades. Read More
J Glob Oncol 2018 Sep(4):1-8
Roziya Buribekova, Irina Shukurbekova, Surayo Ilnazarova, Nekruz Jamshevov, and Guldarbogh Sadonshoeva, Aga Khan Health Services, Dushanbe, Tajikistan; Saleem Sayani and Aliya Aminmuhammad, Aga Khan University; Farin Amersi, Sheemain Asaria, Mansoor Saleh, and Zohray Talib, Aga Khan Health Board, Karachi, Pakistan; Zohray Talib, George Washington University School of Medicine, Washington, DC; and Mansoor Saleh, University of Alabama at Birmingham Comprehensive Cancer Center, Birmingham, AL.
Purpose: To promote a systems-based approach for the early detection and downstaging of breast cancer at presentation in the remote mountainous region of Gorno Badakhshan Autonomous Oblast (GBAO), Tajikistan, by introducing breast cancer awareness into the community and training health care professionals in clinical breast evaluation (CBE).
Methods: Through a public-private partnership between the Ministry of Health, the Aga Khan Health Services, Tajikistan, and the Aga Khan Health Board, we organized breast cancer screening in the community and trained family medicine doctors (FMDs) and family medicine nurses (FMNs) in CBE. We identified and trained CBE master trainers, who, in turn, systematically trained FMNs to conduct CBEs in each of the remote regional clinics. Read More
J Glob Oncol 2018 Sep 8(4):1-8. Epub 2017 Sep 8.
Leeva F. Pinder, David Linyama, Jean-Baptiste Nzayisenga, Aaron Shibemba, Mulindi Mwanahamuntu, and Groesbeck P. Parham, University of Zambia School of Medicine; Kennedy Lishimpi, Cancer Diseases Hospital, Lusaka; Victor Kusweje, Kabwe General Hospital, Kabwe, Zambia; Leeya F. Pinder, Michael Hicks, and Groesbeck P. Parham, University of North Carolina at Chapel Hill, Chapel Hill, NC; Ronda Henry-Tillman, University of Arkansas for Medical Sciences, Little Rock, AR; and Vikrant Sahasrabuddhe, National Cancer Institute, Bethesda, MD.
Purpose: In 2005, the Cervical Cancer Prevention Program in Zambia (CCPPZ) was implemented and has since provided cervical cancer screen-and-treat services to more than 500,000 women. By leveraging the successes and experiences of the CCPPZ, we intended to build capacity for the early detection and surgical treatment of breast cancer.
Methods: Our initiative sought to build capacity for breast cancer care through the (1) formation of a breast cancer advocacy alliance to raise awareness, (2) creation of resource-appropriate breast cancer care training curricula for mid- and high-level providers, and (3) implementation of early detection and treatment capacity within two major health care facilities. Read More
J Bone Joint Surg Am 2018 Sep;100(18):e122
F. Edward Hebert School of Medicine, Bethesda, Maryland.
The observation of decreased resident autonomy, ultimately influencing the readiness of a new graduate to practice, has been supported with a number of recent surveys. This perceived lack of autonomy is felt to be due, in part, to many reasons, including duty-hour regulations, increased supervision requirements, patient safety measures, concern for complication rates, and other performance measures. Pressure on faculty members to have increased clinical productivity may not allow for more resident autonomy. Read More
BMC Womens Health 2018 Sep 19;18(1):152. Epub 2018 Sep 19.
Centre for Population and Reproductive Health, College of Medicine, Ibadan, Nigeria.
Background: Breast disorders cause great anxiety for women especially when they occur in pregnancy because breast cancer is the most common cause of cancer related deaths in women. Majority of the disorders are Benign Breast Diseases (BBD) with various degrees of associated breast cancer risks. With increasing breast cancer awareness in Nigeria, we sought to determine the prevalence and characteristics of breast disorders among a cohort of pregnant women. Read More
Br Dent J 2018 Sep;225(5):388
Blood 2018 Nov 13;132(19):2067-2077. Epub 2018 Sep 13.
INSERM Unité Mixte de Recherche (UMR) S 1176, Université Paris-Sud, Université Paris-Saclay, Le Kremlin Bicêtre, France.
The ephrin transmembrane receptor family of tyrosine kinases is involved in platelet function. We report the first variant affecting platelets in 2 siblings (P1 and P2) from a consanguineous family with recurrent bleeding and normal platelet counts. Whole-exome sequencing identified a c. Read More
J Womens Health (Larchmt) 2018 Sep 11. Epub 2018 Sep 11.
3 Division of Women's Health Internal Medicine, Mayo Clinic Arizona , Scottsdale, Arizona.
Background: In recently updated breast cancer screening guidelines, the American Cancer Society (ACS) and United States Preventive Services Task Force (USPSTF) recommended increasing mammography screening intervals for various age groups. In addition, ACS does not recommend clinical breast examination (CBE) for routine screening among average-risk women. Our study explores women's attitudes regarding screening mammography and CBE and evaluates the impact of the updated USPSTF and ACS guidelines on these attitudes. Read More
CBE Life Sci Educ 2018 09;17(3):es13
Department of Biology and Center for Outreach in Alzheimer's, Aging, and Community Health, North Carolina A&T State University, Greensboro, NC 27411.
CBE Life Sci Educ 2018 09;17(3):ar50
Psychology Department, West Virginia University, Morgantown, WV 26506-6212.
It is widely recognized that the United States needs to attract and retain more people in science, technology, engineering, and mathematics (STEM) careers. Intensive undergraduate research experiences (UREs) are one of the few strategies shown to improve longitudinal student interest and persistence in STEM-related career pathways; however, less is known about the underlying process linking activities to positive outcomes. The tripartite integration model of social influences (TIMSI) provides a framework for understanding the social influence processes by which students integrate into STEM careers and culture. Read More
CBE Life Sci Educ 2018 09;17(3):ar41
Department of Environmental and Life Sciences, Karlstad University, 65188 Karlstad, Sweden.
This study investigates how the domain-specific language of molecular life science is mediated by the comparative contexts of chemistry and biology education. We study upper secondary chemistry and biology textbook sections on protein synthesis to reveal the conceptual demography of concepts central to the communication of this subject. The term "conceptual demography" refers to the frequency, distribution, and internal relationships between technical terms mediating a potential conceptual meaning of a phenomenon. Read More
CBE Life Sci Educ 2018 09;17(3):es15
Office of Strategic Initiatives, Louisiana State University, Baton Rouge, LA 70803.
CBE Life Sci Educ 2018 09;17(3):ar47
Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06511.
Mounting evidence of the efficacy of active learning has prompted educators to consider adoption of these practices in college-level classrooms. One tenet of active learning is that most, if not all, students have the ability to learn. Instructors' perspectives on learning, however, may or may not be aligned with this. Read More
CBE Life Sci Educ 2018 09;17(3):ar49
Lyman Briggs College, Michigan State University, East Lansing, MI 48824.
Real-world processes are complex and require ideas from multiple disciplines to be explained. However, many science courses offer limited opportunities for students to synthesize scientific ideas into coherent explanations. In this study, we investigated how students constructed causal explanations of complex phenomena to better understand the ways they approach this practice. Read More
CBE Life Sci Educ 2018 09;17(3):ar42
Department of Plant Biology, University of Georgia, Athens, GA 30602.
Introducing group work in college science classrooms can lead to noticeable gains in student achievement, reasoning ability, and motivation. To realize these gains, students must all contribute. Strategies like assigning roles, group contracts, anonymous peer evaluations, and peer ratings all encourage student participation. Read More
Med J Islam Repub Iran 2018 21;32:51. Epub 2018 Jun 21.
Community Medicine Department, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran.
Studies have shown that participation of Iranian women with family history of breast cancer in screening service is low. This investigation has evaluated the effectiveness of health models according to peer group in improving clinical breast exam (CBE) among Iranian women with a family history of breast cancer. This was a randomized control trial conducted during June and August 2015 in Isfahan. Read More
CBE Life Sci Educ 2018 09;17(3):ar48
Institute for Clinical and Translational Research, University of Wisconsin-Madison, Madison, WI 53705.
An evidence-based research mentor training (RMT) curricular series has been shown to improve the knowledge and skills of research mentors across disciplines and career stages. A train-the-trainer model was used in the context of several targeted approaches aimed at sustainability to support national dissemination of RMT and expand the network of facilitators prepared to implement the curricula. These infrastructure elements included 1) an expansion initiative to increase the number of trained facilitators able to deliver train-the-trainer workshops nationwide; 2) adaptation of RMT curricula for multiple audiences and career stages to increase accessibility; 3) implementation resources to support facilitators and help them overcome implementation barriers; and 4) standardized evaluation of training. Read More
CBE Life Sci Educ 2018 09;17(3):ed1
Division of Training, Workforce Development, and Diversity, National Institute of General Medical Sciences, Bethesda, MD 20892.