5,321 research outputs found
Characterization of interstitial stem cells in hydra by cloning
A procedure has been developed for cloning interstitial stem cells from hydra. Clones are prepared by introducing small numbers of viable cells into aggregates of nitrogen mustard-inactivated host tissue. Clones derived from added stem cells are identified after 1–2 weeks of growth by staining with toluidine blue. The incidence of clones increases with increasing input of viable cells according to one-hit Poisson statistics, indicating that clones arise from single cells. After correction for cell losses in the procedure, about 1.2% of the input cells are found to form clones. This compares with estimates from in vivo experiments of about 4% stem cells in whole hydra [David, C. N., and Gierer, A. (1974). Cell cycle kinetics and development of Hydra attenuata. III. Nerve and nematocyte differentiation. J. Cell Sci. 16, 359–375.]
Differentiation of nematocytes and nerve cells in clones was analyzed by labeling precursors with [3H]thymidine and scoring labeled nerves and nematocytes 2 days later. Nine clones examined in this way contained both differentiated nerve cells and nematocytes, demonstrating that the interstitial stem cell is multipotent. This result suggests that the observed localization of nerve and nematocyte differentiation in whole hydra probably occurs at the level of stemcell determination. The observation that differentiated cells occur very early in clone development suggests that a stem cell's decision to proliferate or differentiate is regulated by shortrange feedback signals which are already saturated in young clones
A Water Distribution System for Cold Regions: The Single Main Recirculation Method: An Historical Review, Field Evaluation, and Suggested Design Procedures
Students and residents of the Arctic are familiar with the many
problems peculiar to the geographical area. This monograph will consider
an adequate, safe, and reliable water distribution system. Water supply,
together with housing, transportation, and waste disposal, are demanded
when a remote area becomes established as a permanent settlement.
As long as the population of the North was widely distributed in
small mining camps, villages, and individual cabins, water distribution
systems were not necessary, as shallow wells and nearby streams adequately
served most needs. With the rapidly increasing settlement of the vast
lands of the North, the population is being centered in communities rather
than distributed over large areas. The world population explosion will
undoubtedly contribute to increasing immigration into Arctic and sub-Arctic
areas. These changes have already created a need for modern water distribution
systems, a need which will become more critical with time.The research upon which this publication is based was performed in
accordance with Contract No. ph 86-67-18 with the U.S. Public Health Service,
Department of Health, Education, and Welfare. Lastly, the support of the Institute of Water Resources, University
of Alaska is acknowledged, through an Office of Water Resources Research
grant A-018-Alas
Aboriginal Maple Syrup Values Summary
This report examines the values associated with maple syrup practices in Aboriginal contexts. It is based on fifteen interviews conducted with Aboriginal people who have knowledge of maple syrup practices in Ontario. The interviewees included both First Nations and Metis people
A Program for the Collection, Storage, and Analysis of Baseline Environmental Data for Cook Inlet, Alaska
The scope of this report is to provide a general, yet comprehensive,
description of the Cook Inlet System which will serve as a
basis for understanding the interrelated natural and man-made factors
governing its future; to present a program of field research studies
for the estuarine environment that will describe the existing state of
the Inlet with respect to the water quality and biota; to provide a
framework whereby the program of studies can be evaluated and redirected
in light of the preliminary results; and, to provide a method of storing
and analyzing the data from the investigations so that it can be made
available to interested parties in the most efficient manner possible.This report was prepared by the Institute of Water Resources of the
University of Alaska for the Alaska Water Laboratory, Federal Water
Pollution Control Administration under Contract No. 14-12-449
BOOTSTRAPPING FORWARD SELECTION WITH BIC
This paper presents a method for bootstrapping the multiple linear regression model Y = β1 + β2x2 +···+ βpxp + e using forward selection with the BIC criterion
Approach to piano playing for class instruction: teacher's supplementary manual
Please see also: History of the piano class in the United States. Thesis (M.M.Ed.)--Boston University. http://hdl.handle.net/2144/527
HOMEWORK, AN EDUCATIONAL INSTRUCTIONAL TECHNIQUE USED IN THE MIDDLE SCHOOL SPECIAL EDUCATION CLASSROOM
The assignment patterns, frequency, and perceptions of homework as an educational instructional device was investigated in middle school special education classroom teachers. A general topic questionnaire was generated and administered to each of the middle school special education teachers who volunteered for this study. A population sample was used in the survey to represent, determine, and investigate the application of homework as an instructional technique. The survey also referenced specific questions on teachers\u27 attitudes and perspectives on whether homework should be employed as a device to improve learning, comprehension, and retention of materials being presented in the classroom. The results of the study indicated that homework, used as an educational instructional technique, was received in middle schools by special education students on a less than regular basis. Most middle school special education teachers believed that they had the time and resources to administer and complete homework assignments with their students in the classroom. Homework was considered by several respondents as an effective tool in checking comprehension of materials covered in class. However, homework was not believed to be an useful part of the classroom/educational experience; nor did they believe that homework increased a student\u27s learning ability or performance. Many special education teachers did use the students\u27 Individual Educational Plan as a reference for homework; however, an almost equal number stated that they did not. Results also showed that most middle school special education teachers felt that the students\u27 parents contributed very little in assisting their child with their homework assignments
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