Kenneth L. Campbell

Bio: Kenneth L. Campbell is an academic researcher from University of Massachusetts Boston. The author has contributed to research in topics: Population & Crash. The author has an hindex of 24, co-authored 78 publications receiving 2449 citations. Previous affiliations of Kenneth L. Campbell include Aberdeen Royal Infirmary & University of North Carolina at Chapel Hill.

Freeze-fracture analysis of gap junction disruption in rat ovarian granulosa cells

Abstract: The effects of chemical dissociation on rat ovarian granulosa cell gap junctions has been studied using freeze-fracture electron microscopy. Sequential exposure of granulosa cells within follicles to solutions containing 6·8 mM EGTA [ethylene-bis-(β-aminoethyl ether)-N,N′-tetra acetic acid] and 0·5 M sucrose results in extensive cellular dissociation of the follicular epithelium. Freeze-fracture replicas made from fixed, control or EGTA-treated ovarian follicles exhibit extensive gap junctions between granulosa cells that are characterized by a range of packing order of constituent P-face particles or E-face pits. In contrast, exposure to 0·5 M sucrose containing 1·8 mM EGTA for as little as 1 min results in a consistently close packing of particles or pits which is accompanied by splitting of gap junctions between granulosa cells. The process of junction splitting was studied in detail in replicas prepared from follicles treated sequentially for various periods of time with EGTA and sucrose solutions. Initially, large gap junctions lose their regular shape and fragment into numerous tightly packed aggregates of P-face particles or E-face pits which are separated by unspecialized areas of plasma membrane. Subsequent to junction fragmentation, individual junction plaques separate at sites of cell contact and generate hemijunctions that border the intercellular space, Hemijunctions undergo particle dispersion of the P fracture face which results in an increased density of large intramembrane particles; no corresponding change in E-face pits is discernible at this stage. Morphometric analysis of replicas of tissue undergoing junction splitting indicates that junctional surface area decreases to 10–20% of control levels during this same treatment and so further supports the qualitative observations on junction fragmentation. Viabilities of granulosa cells obtained by these techniques also agree with the sequence observed in the morphometric analysis of the replicas. Finally, within 15 min after placing ovaries in isotonic, Ca 2+ -containing salt solutions, gap junction reformation occurs by aggregation of particles at sites of intercellular contact. These sites are distinguished by the appearance of short surface protrusions or indentations on their respective P and E fracture faces. The data suggest a mechanism for EGTA-sucrose mediated cellular dissociation in the follicular epithelium in which gap junctional particles are free to move in the plane of the plasma membrane and may be re-utilized to form gap junctions in the presence of extracellular calcium.

Rapid changes in the synthesis of specific ovarian granulosa cell proteins induced by human choriogonadotropin

Abstract: Total ovarian granulosa cell proteins were labeled in vitro with [35S]methionine and analyzed by two-dimensional polyacrylamide gel electrophoresis. Of the 100-150 distinct proteins resolved by this method, 1-2% demonstrated an observable change in their synthesis during the early phases of luteinization after hormone administration. Two specific proteins first appeared as early as 30 min after treatment with human choriogonadotropin, while four additional new proteins became apparent at 3 hr. These changes in the synthesis of specific proteins occurred far in advance of the morphological changes associated with luteinization, which occur 24-72 hr later, and thus may play an important role in this process of hormonally induced cell differentiation in the rat ovary.

Center of gravity height: a round-robin measurement program

Abstract: A round-robin center of gravity height measurement study was conducted to assess current practice in the measurement of the vertical position of the center of gravity (c.g.) of light truck-type vehicles. The study was performed by UMTRI for the Mototr Vehicle Manufacturers' Association. Chrysler, Ford, General Motors and the National Highway Traffic Safety Administration perticipated. The primary objectives were (i) to determine to what extent the differing experimental procedures currently used by the participating laboratories result in significant differences in the measured vertical position of the center of mass of light truck-type vehicles, and (ii) to gain insight into the physical causes of such differences. The results of the program shoved (i) that there were significant differences between the c.g. height measurement results obtained by different laboratories, (ii) repeatability of results within the individual laboratories was generally good, and (iii) close examination of the individual procedures tended to explain the differences in results between laboratories, this providing the expecctation that variability in this regard could be significantly reduced.

Differential truck accident rates for michigan

Abstract: Major changes in the trucking industry have resulted from federal legislation that relaxed the regulation of trucks in interstate commerce, allowed the use of double-trailer combinations nationwide on Interstate highways, and required states to regulate trailer length instead of overall length. Because Michigan has long had extremely liberal truck size and weight regulations, its experience with truck safety is of significant interest. A project by the University of Michigan and Michigan State University was undertaken to develop statistical information on accidents, travel, and the risk of accident involvement for Michigan-registered trucks in Michigan. The study objective was to calculate disaggregate truck accident rates by road class, day or night, and urban or rural operating conditions for tractors without trailers (bobtails) and in single- and double-trailer configurations. Major findings included the following: bobtails consistently have the highest accident rates; all-accident and casualty rates for single and double configurations are similar to one another; the most significant and consistent factor associated with truck accident rates was the roadway class (highest rates on the "local" road system, lowest on limited-access highways); urban accident rates were lower than rural rates; night rates were higher than day rates for casualty accidents but lower for all accidents; and tractor drivers aged 19-20 have an accident rate five times the average. The findings indicate that differences in truck safety by roadway class are more important than those between singles and doubles. Discussion and recommendations concerning improvements in truck accident and exposure data as well as further work on the relationship between truck accidents and geometry are included.

The Theory of Island Biogeography

Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

Human MotivationThe Mind in Action: A Study of Motives and Values. A. Campbell Garnett

Abstract: In his Preface the author' says that he started out to review all the more important theories upon the topics ordinarily discussed under human motivation but soon found himself more and more limited to the presentation of his own point of view. This very well characterizes the book. It is a very personal product. It is an outline with some defense of the author's own thinking about instincts and appetites and sentiments and how they function in human behavior. And as the author draws so heavily upon James and McDougall, especially the latter, the book may well be looked upon as a sort of sequel to their efforts. There is a thought-provoking distinction presented between instinct and appetite. An instinct is said to be aroused always by something in the external situation; and, correspondingly, an appetite is said to be aroused by sensations from within the body itself. This places, of course, a heavy emphasis upon the cognitive factor in all instinctive behaviors; and the author prefers to use the cognitive factor, especially the knowledge of that end-experience which will satisfy, as a means of differentiating one instinct from another. In this there is a recognized difference from McDougall who placed more emphasis for differentiation upon the emotional accompaniment. The list of instincts arrived at by this procedure is much like that of McDougall, although the author is forced by his criteria to present the possibility of food-seeking and sex and sleep operating both in the manner of an appetite and also as an instinct. The Shand-McDougall concept of sentiment is taken over and used in the explanation of moral motivation. There is the development within each personality of a sentiment for some moral principle. But this sentiment is not a very powerful motivating factor. It is reinforced by social pressures and by religion, which is treated as an effort of finite man to live in harmony with the infinite reality. Those whose psychological thinking is largely in terms of McDougall will doubtless find this volume a very satisfying expansion; but those who are at all inclined to support their psychological thinking by reference to experimental studies will not be so well pleased. The James-Lange theory, for example, is discussed without mention of the many experimental studies which it has provoked. Theoretical sources appear in general to be preferred to experimental investigations.

Growth at Adolescence.

Abstract: argument is often, if not acrimonious, at least heated. It gives an impression of the fluidity of opinion on many fundamental ideas under discussion and of the urgency with which cardiac cyanosis in the newborn is regarded. When Dr. William Muscott says that the earliest he has operated for pulmonary stenosis is on an infant 3 days old, and Sir Russell Brock agrees that the earlier in the first month that operation is undertaken the better, and when Dr. Varco asks Dr. Senning 'so far as I know they have never yet catheterized any child intrauterine in Sweden, but they have done it through the delivery canal sometimes-would you tell us the indications of the Scandinavian group for catheterization in the immediate newborn period?', one is indeed being kept up with the times. But that was two years ago and already some of the questions then debated have since been answered. This beautifully printed and well-illustrated stiff paperbacked volume is, and will for a few years yet remain, an invaluable companion to a full-scale textbook on congenital heart disease.

Timing of Pubertal Maturation in Girls: An Integrated Life History Approach.

Abstract: Life history theory provides a metatheoretical framework for the study of pubertal timing from an evolutionary-developmental perspective. The current article reviews 5 middle-level theories--energetics theory stress-suppression theory psychosocial acceleration theory paternal investment theory and child development theory--each of which applies the basic assumptions of life history theory to the question of environmental influences on timing of puberty in girls. These theories converge in their conceptualization of pubertal timing as responsive to ecological conditions but diverge in their conceptualization of: a. the nature extent and direction of environmental influences and; b. the effects of pubertal timing on other reproductive variables. Comparing hypotheses derived from the 5 perspectives are evaluated. An extension of W.T. Boyce and B.J. Elliss (in press) theory of stress reactivity is proposed to account for both inhibiting and accelerating effects of psychosocial stress on timing of pubertal development. This review highlights the multiplicity of (often unrecognized) perspectives guiding research raises challenges to virtually all of these and presents an alternative framework in an effort to move research forward in this arena of multidisciplinary inquiry. (authors)