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  • 1
    ISSN: 0736-0266
    Keywords: Arthrosis ; Osteoarthritis ; Mechanical changes in joints ; Animal models ; Experimental arthrosis ; Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We studied changes in subchondral bone and articular cartilage in an animal model of osteoarthrosis. In this model we applied repetitive impulsive loads to rabbits' knees. Their legs were held in short leg splints so the rabbits were unable to dampen the peak applied load with ankle flexion. After sacrifice, at 1 day to 6 weeks, we studied proximal tibial load-bearing cartilage histologically, biochemically, and with radioactive sulfate uptake. We also studied the subchondral bone under that cartilage histologically, histomorphometrically, with bone scan (99mTc pyrophosphate), and by tetracycline labeling. An increase in 99mTc labeling of the subchondral bone was the first reliable change observed. This was followed by an increase in tetracycline labeling, bone formation, and a decrease in porosity, which has been associated with relative stiffening of bone. Horizontal splitting and deep fibrillation of the overlying articular cartilage followed the early bone changes. All of these changes preceded changes in content and characterization of cartilage proteoglycans or increased chondrocyte activity as manifested by incorporation of radioactive sulfate. In this model the early bone changes preceded changes in the articular cartilage. The deep splitting of articular cartilage occurred prior to metabolic alteration of that tissue.
    Additional Material: 10 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 161 (1981), S. 85-100 
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The relationship between hair-follicle development and adipocyte formation in the rat hypodermis was studied. Skin samples from rats of various body weights were prepared for histological, histochemical, and electron microscopic analysis. Adipocyte formation in the rat hypodermis was linked spatially and temporally with hair-follicle growth and development. Cells trapped along the invading edge of hair follicles developed into adipocytes after the descent of the follicles through the dermis. Histochemical characteristics of the outermost cells of hair follicles indicated hypoxic conditions. These conditions may have directed a vascularization process that resulted in a network of adipocytes and capillaries around these follicles. Thus, under normal conditions, adipocyte formation is an integral phase of hair-follicle development in the rat.
    Additional Material: 20 Ill.
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  • 3
    ISSN: 0730-2312
    Keywords: mRNA levels ; regulation of biosynthesis ; light-harvesting chlorophyll a/b complex ; chloroplast ; ribulose bisphosphate carboxylase ; oxygenase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The photoregulation of chloroplast development in pea leaves has been studied by reference to three polypeptides and their mRNAs. The polypeptides were the large subunit (LSU) and the small subunit (SSU) of ribulose 1,5-bisphosphate carbox-ylase/oxygenase (RUBISCO), and the light-harvesting chlorophyll a/b protein (LHCP). The polypeptides were assayed by a sensitive radioimmune assay, and the mRNAs were assayed by hybridization to cloned DNA probes. LSU, LSU mRNA, and LHCP mRNA were detectable in etiolated seedlings but LHCP, SSU, and SSU mRNA were at or below the limit of detection. During the first 48 hr of de-etiolation under continuous white light, the mRNAs for LSU, SSU, and LHCP increased in concentration per apical bud by about 40-fold, at least 200-fold, and about 25-fold, respectively, while the total RNA content per apical bud increased only 3.5-fold. In the same period, the LSU, SSU, and LHCP contents per bud increased at least 60-, 100-, and 200-fold, respectively. The LHCP increased steadily in concentration during de-etiolation, whereas the accumulation LSU, SSU, and SSU mRNA showed a 24-hr lag. The accumulation of SSU, SSU mRNA, and LHCP mRNA showed classical red/far-red reversibility, indicating the involvement of phytochrome in the regulatory mechanism. LSU and LSU mRNA were induced equally well by red and far-red light. The LHCP failed to accumulate except under continuous illumination. These results indicate that the accumulation of SSU is controlled largely through the steady-state level of its mRNA, which is in turn almost totally dependent on light as an inducer and on phytochrome as one of the photoreceptors. The accumulation of LSU is largely but not totally determined by the level of its mRNA, which appears to be under strong photoregulation, which has yet to be shown to involve phytochrome. Phytochrome is involved in the regulation of LHCP mRNA levels but substantial levels of the mRNA also occur in the dark. LHCP accumulation is not primarily governed by the levels of LHCP mRNA but by posttranslational stabilization in which chlorophyll synthesis plays a necessary but not sufficient role.
    Additional Material: 1 Ill.
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  • 4
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: One method used to examine the relationship between behavioral strategies and anatomical adaptation is to study the results of mechanical stress associated with a given behavior and compare this with skeletal adaptations to other behaviors. This comparative approach is appropriate for highlighting combinations of features that are specializations to specific types of behavior. The purpose of this paper is to compare femoral mechanics in Galago senegalensis with previously collected data for macaques and humans as a basis for discussing structural adaptations in the primate hindlimb to leaping. The stiffness and load carrying capabilities of the femoral diaphyses of 27 G. senegalensis were analyzed using the SCADS computer program. The data suggest that the galago femur is well adapted to sustain large sagittal plane compressive loads rather than large bending loads. The straightness of the femoral shaft and large midshaft area moments of inertia prevent buckling from these large compressive loads. Calculations indicate that the ratio of critical buckling load to body weight in galago is 31 times that in macaques and 55 times that in humans. The femur of this saltatory primate is morphologically adapted to resist buckling when subjected to large compressive loads, while those of macaques and humans are better adapted to resist bending moments caused by ground reaction forces acting on the extended limb. The differences between galago on the one hand and macaques and humans on the other suggest that relatively smaller moments about the hip and relatively larger moments about the knee accompany more quadrupedal and bipedal walking, while habitual leaping is associated with relatively larger moments about the hip. These data reinforce the apparent similarity of the mechanical effects of quadrupedal and bipedal locomotion on the femur and dissimilarity with femoral mechanics in habitually saltatory primates.
    Additional Material: 6 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 186 (1989), S. 186-216 
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Recent evidence suggests that skeletal adaptation is organized by a functional unit that includes cells of diverse origin working in coordination. Genetic and metabolic factors control and regulate the processes of modeling and remodeling, only rarely acting on the isolated individual functions of specific cell lines. Errors in the genetic or metabolic regulation of the functional unit affect the entire process of skeletal adaptation rather than specific elements of it. Viewed in this way, some metabolic bone diseases can be understood as relatively simple errors in factors that control the coordinated activities of the entire functional unit. This paper reviews the modeling and remodeling processes and demonstrates how abnormal morphological characteristics of bone tissue can be viewed as products of specific errors in the adaptive process.
    Additional Material: 23 Ill.
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  • 6
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Additional Material: 23 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ [u.a.] : Wiley-Blackwell
    Journal of Orthopaedic Research 5 (1987), S. 445-452 
    ISSN: 0736-0266
    Keywords: Osteonal remodeling ; Screw implantation ; Canine femora ; Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We examined the patterns of osteonal remodeling associated with the implantation of a screw in the femoral diaphysis of four mongrel dogs. The dogs were killed at intervals ranging from 11 to 93 days after implantation, and resorption spaces and tetracycline-labeled osteons were counted as functions of postimplant time and distance from the screw. The contralateral femur was used as a control. We found that implantation of the screw initiated a sequence of remodeling activity at the screw site; numerous resorption spaces were observed after 3 weeks, followed by numerous refilling osteons at 7 weeks. When sequential sections along the shaft adjacent to the screw were examined, it appeared that the increased resorption and refilling activity subsequently migrated away from the screw site, both proximally and distally. Also, both the implanted and control femurs exhibited occasional zones along the shaft within which the numbers of labeled osteons were sharply reduced. These “extinction zones” were found to be asscoiated with local maxima in resorption space density. We further noted that the ratio of singly to doubly labeled osteons in the experimental control femurs was high as compared with that in humans, but similar to that previously observed in the canine iliac crest.
    Additional Material: 5 Ill.
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  • 8
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have found that PHA produces an alteration in the lymphocyte membrane which allows 86Rb+ or 42K+ in prelabeled lymphocytes to exchange for cations present in washing solutions. These observations suggested that PHA might induce an increase in the exodus of intracellular potassium during incubation in physiologic media. We, therefore, examined 86Rb+ and 42K+ efflux from rat and human lymphocytes during incubation in tissue culture medium. The rate constant for efflux, Ke, was significantly increased by PHA.86Rb+ efflux was increased by 27% in rat thymic lymphocytes and by 78% in human blood lymphocytes following PHA treatment.
    Additional Material: 3 Ill.
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  • 9
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The K+ content of human lymphocytes has been examined during the initial 24 hours after exposure of cells to phytohemagglutinin (PHA). We have reconfirmed that lymphocyte K+ exchanges rapidly for extracellular counterions during preparative washing if cells are exposed to PHA. By using a technique to measure cation content which does not require removal of cells from their culture medium, we have shown that K+ does not change for 24 hours following PHA treatment. Previous reports have demonstrated that an enhanced uptake of K+ occurs in lymphocytes treated with PHA. This increased uptake may be a compensatory change for an increased exodus, explaining the failure of K+ to change following lectin treatment.
    Additional Material: 1 Ill.
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  • 10
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The exposure of rat and human lymphoid cells to mitogenic concentrations of phytohemagglutinin resulted in an apparent decrease in cellular K+ without a significant change in cellular Na+ when the cells were washed with isotonic Hepes buffered choline chloride prior to cation determination. The apparent reduction in total cellular Na+ plus K+ concentration, however, was not accompanied by a change in cell volume. We inferred that the constant cell volume could occur only if the lost intracellular K+ was exchanged for an external cation during the washing procedure used to prepare cells for Na+ and K+ measurement. This inference was supported by the quantitative recovery of lost cellular K+ in the choline chloride washing solution and the demonstration that a comparable proportion of 86Rb+ (K+ analogue) 42K+ was lost from prelabelled cells during choline chloride washing. Use of medium 199 with Hanks salts, 150 mM NaCl, or 100 mM MgCl2 as the washing solution did not prevent K+ exchange although exchange was less in the presence of MgCl2. These findings indicate that phytohemagglutinin produces a rapid alteration in lymphocyte plasma membranes so as to allow abnormal K+ exchange. This observation is of importance because investigators who measure intracellular solutes in phytohemagglutinin-treated lymphocytes must consider the possibility of loss during preparative washes. Also, changes in membrane permeability following phytohemagglutinin treatment may modulate mitogenesis and/or permit the transmission of chemical messages between cells.
    Additional Material: 6 Ill.
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