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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 3196-3198 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results of 1/f noise measurements in n-Si and p-Si between room temperature and liquid-nitrogen temperature are presented. The temperature dependence of the noise in the n-Si samples appears fairly complex, and it does not appear that one can find a simple model to explain it. Two different heat treatments of p-type samples were used. In those treated at 950 °C the noise declines with increasing reciprocal temperature in a manner similar to that found by other investigators. For p-type samples treated at 550 °C the noise at room temperature is two orders of magnitude smaller than for the high-temperature samples and the temperature dependence is much smaller.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 13 (1981), S. 0 
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The effect of neonatal thymectomy on the development of splenic and bone marrow natural cell-mediated cytotoxicity and on genetic resistance to bone marrow transplantation was examined in mice. Natural cytotoxicity was measured by a 51Cr release assay; the ability to engraft foreign bone marrow was assayed by the spleen colony method. The natural cytolytic response of spleen cells increased progressively from youth to early adulthood, whereas that of the bone marrow declined during the same age period. Neonatal thymectomy significantly elevated the natural killer cell response of young mice only (4 weeks, spleen; 6 weeks, bone marrow). In other experiments, neonatally thymectomized and sham-operated mice were lethally irradiated at 4 or 6 weeks of age and injected with 2.5, 5.0 or 10 million rat marrow cells. Six days later spleen colonies were markedly reduced in both 4- and 6-week-old neonatally thymectomized mice with all rat marrow cell doses tested. Neonatal thymectomy did not alter the percentage of erythroid versus other colonies at either 4 or 6 weeks. In both thymectomized and sham-operated mice the number of colonies increased with increases in marrow cell dose. The data are suggestive of a production and dissemination to the spleen of cells involved in the natural cytotoxic response from the bone marrow.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 27 (1988), S. 0 
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: To examine the possible relationship between the cells mediating resistance to tumour cells and those mediating rejection of foreign bone marrow transplants (BMT), the effect of tumour-bearing on BMT rejection has been measured by means of the spleen colony assay. Moderate doses (〈5.0 × 106) of bone marrow cells from DBA/2 strain mice, which normally produce few haemopoietic spleen colonies in γ-irradiated (950R) CBA/J strain mice, gave numerous (confluent) colonies when given soon after injection of Ehrlich ascites tumour (EAT) cells. Transfusion of [3H]UdR-labelled DBA/2 bone marrow cells demonstrated that the increased spleen colony formation in tumour-bearing mice was not due simply to changes in the total number of injected cells homing to the spleen. Injection of EAT ascites fluid alone, given to CBA/J mice before 950R+BMT, transiently reduced spleen colony development, the effect being more marked when fluid from older tumours was used. Supernatant fluid from EAT cells grown in vitro also depressed growth of BMT in vivo. The results reveal two processes in progress in mice bearing an ascites tumour: (1) an early reduction in the natural resistance to BMT allowing successful grafting and spleen colony formation, and (2) a progressive production by the tumour cells of short-acting soluble factors tending to suppress the proliferation of colony forming bone marrow cells in the transplant. The effect of the tumour-bearing state in weakening the natural resistance to foreign BMT strongly suggests that both tumour and foreign marrow graft resistance are mediated by the same or closely related effector cells.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of periodontal research 29 (1994), S. 0 
    ISSN: 1600-0765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Formation of cementum, alveolar bone and periodontal ligament was produced in 18 sites on buccal surfaces of mandibular premolars and molars of 11 adult dogs near to sites of local delivery of prostaglandin E1 (PGE) for three weeks. Mineralizing bone and cementum were labelled with fluorescent dyes and polarizing microscopy showed periodontal ligament fibers between these new mineralized tissues. These observations extend recent demonstrations that local application of PGE causes formation of new bone on the mandible and suggest the potential for predictable, site-directed periodontal regeneration.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0827
    Keywords: Vitamin D ; Vitamin D deficiency ; Cartilage ; Bone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary To test the importance of 24-hydroxylation of vitamin D3 on bone mineralization, rat pups born to vitamin D-deficient females were given either 25-hydroxyvitamin D3 or 24,24-difluoro-25-hydroxyvitamin D3 for 16 days beginning at the time of weaning. Following such treatment analysis of blood samples revealed no detectable 24R,25-(OH)2D3 and 1,25-(OH)2D3 in the rats given the difluoro compound while revealing the expected 24,24-difluoro-25-hydroxyvitamin D3 and 24,24-difluoro-1,25-dihydroxyvitamin D3. The rats given 25-hydroxyvitamin D3 had the expected levels of 25-hydroxyvitamin D3, 24,25-dihydroxyvitamin D3, and 1,25-dihydroxyvitamin D3. Following sacrifice at day 17, postweaning bone mineralization and modeling were studied in long bones using histological methods. Bones taken from vitamin D-deficient rats at the beginning and end of the experimental period had lesions typical of rickets. These included wide growth plates, excessive amounts of osteoid, and metaphyseal fibrosis. Following treatment with either 25-hydroxyvitamin D3 or 24,24-difluoro-25-hydroxyvitamin D3, bone mineralization returned to normal. Growth plate widths and the amount of osteoid on bone surfaces were both substantially reduced and to a similar degree in both treatment groups. Normal cartilage core formation and trabecularization of the metaphyseal primary spongiosa were also restored to a similar degree in both groups. In effect, no difference was observed in any bone parameter studied between the 25-hydroxyvitamin D3- and the 24,24-difluoro-25-hydroxyvitamin D3-treated animals. These results provide strong evidence that 24-hydroxylation of the vitamin D molecule plays little or no role in the modeling and mineralization of bone.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 64 (1999), S. 329-339 
    ISSN: 1432-0827
    Keywords: Key words: Carbonated apatites — Bone mineral — Solubility — Crystallinity — Calcium phosphates.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Previous studies have shown that carbonated apatites with a range of carbonate contents and crystallinities exhibit the phenomenon of metastable equilibrium solubility (MES) distributions. The purpose of the present study was to investigate the solubility behavior of bone mineral using the concepts of MES and MES distributions and, together with crystallinity and chemical composition data, examine the similarity of bone mineral to carbonated apatite (CAP). Bone samples were harvested from 1-, 5-, and 8-month-old rats. The organic components of the bone samples were removed by hydrazine deproteination. Carbonated apatite was synthesized by the hydrolysis of dicalcium phosphate dihydrate (DCPD) in a NaHCO3-containing media at 50°C. The MES distributions of bone mineral and CAP were determined by equilibrating predetermined amounts of CAP or bone mineral in a series of 0.1 M acetate buffers containing calculated levels of calcium and phosphate and maintained at essentially constant pHs of 5.0, 5.3, 5.7, and 6.5. From the compositions of the equilibrating buffer solutions, ion activity products based upon the stoichiometries of octacalcium phosphate, hydroxyapatite, and carbonated apatite were calculated in an attempt to determine the function governing the dissolution of CAP and bone mineral. The results of this study demonstrated that the MES distribution phenomenon appeared to hold for bone mineral and that the changes in crystallinity of bone mineral with age correlated well with changes in the MES values. A CAP sample was prepared that was found to be an excellent synthetic prototype closely mimicking the physicochemical behavior of bone mineral from an 8-month-old rat. Another finding of this study was that the ion activity product function based upon the hydroxyapatite stoichiometry well described the MES results obtained with both CAP and bone mineral. The interpretation that a surface complex with hydroxyapatite stoichiometry governs the solubility behavior of bone mineral is, therefore, consistent with the experimental data. Other calcium phosphate stoichiometries for the surface complex showed systematic variations in the MES profiles when the pH of the equilibrating solution was varied.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 48 (1992), S. 674-678 
    ISSN: 1420-9071
    Keywords: Indomethacin ; hemopoietic cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract During 21 days of indomethacin treatment, erythroid cells in the spleens of both young adult and older mice, and in the bone marrow of young adult mice, were increased significantly early, in treatment, relative to age-matched control organs, and remained high throughout treatment. During drug exposure, the numbers of myeloid cells in young adult bone marrow, but not spleen, were reduced, but in older mice these cells were elevated in both organs. Lymphoid cells in the young adult and older mouse spleens decreased and increased, respectively, during treatment, but were unchanged and decreased, respectively, in the bone marrow of young adult and older mice. Monocytemacrophage cells in the spleen were elevated but unchanged in the bone marrow of both age groups. During 14 days of indomethacin treatment of houng adult mice, the proportions of precursor cells in DNA synthesis of only the splenic erythroid lineage were increased. Thus, the major hemopoietic lineages in both the bone marrow and spleen are affected by exposure to indomethacin in a time-dependent and age-dependent manner. For all lineages studied, those of the bone marrow were least disturbed, and/or were first to recover, even during continued drug exposure.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-0827
    Keywords: Key words: Ovariectomy — Femoral neck — DEXA — Histomorphometry — SEM — Mechanical testing.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Eighty mature Sprague-Dawley rats were weight matched before ovariectomy (Ovx) or Sham surgery (Sham). Sham rats had free access to food and water throughout the experiment, whereas Ovx rats were kept on the pair-fed diet. Rats were euthanized at 4, 8, and 12 weeks after surgery, and had received fluorochrome bone markers at 9 and 2 days prior to euthanasia. In addition 10 rats were euthanized at the time of surgery serving as baseline controls. All rats were also scanned for body composition and bone mineral parameters by DEXA before surgery and euthanasia. Left proximal femurs (femoral necks) were used for bone histomorphometry, whereas right femurs were used for in vitro DEXA measurements and mechanical testing. Despite pair-feeding, ovariectomized rats had increased body weights and fat body mass, whereas the percent lean body mass steadily declined throughout the experiment. Mineral density of the whole femur and femoral neck was significantly higher in the Sham rats relative to Ovx animals. Ovariectomy reduced trabecular number and thickness, and increased trabecular separation and bone marrow space at the femoral midneck location. The structure of the remaining trabeculae was dramatically changed toward simpler struts as revealed by nodal analyses. Cortical thickness in Ovx rats was reduced because of the high endocortical resorption, which, in addition to cancellous bone resorption, resulted in fewer endocortico-trabecular connections. Femoral necks obtained from ovariectomized rats had reduced strength and were less stiff relative to controls. Because of the enormous clinical significance of the proximal femur for osteoporosis in humans, and the opportunity for studying bone BMD, mass, structure, and strength at the same skeletal location, the femoral neck appears superior to other skeletal sites routinely used for bone histomorphometry or mechanical testing in the Ovx rat model.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 34 (1978), S. 129-131 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In mice given3H-thymidine systemically during temporary circulatory occlusion of one hind limb, comparison of the labeling of rapidly-renewing small lymphocytes in the tibial marrows demonstrated that these cells were locally produced. Labeling by3H-thymidine infusion revealed that many marrow large lymphoid cells, presumptive small lymphocyte progenitors, had a marked proliferative activity and rapid turnover which varied according to cell size, was maximal in young mice and declined with increasing age.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 184 (1976), S. 325-333 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The effects of neonatal thymectomy on the development of the lymphoid, erythroid and granulocytic cell populations in mouse bone marrow have been assessed by quantitative techniques. The numbers per unit volume of bone marrow of 17 cell types were determined in neonatally thymectomized and sham thymectomized C3H mice at two, four and eight weeks of age, and compared with those of normal C3H mice. After neonatal thymectomy the numbers of small lymphocytes, large and medium-sized lymphoid cells, and erythroid cells reached normal levels at two weeks but fell progressively to 18%, 22% and 42% of normal, respectively, by eight weeks. In sham thymectomized mice these cell populations did not differ significantly from normal. Immature and mature granulocytes were elevated in numbers two weeks after either neonatal thymectomy or sham thymectomy, suggesting a transient non-specific stimulation of granulocytopoiesis. During continuous infusion of 3H-thymidine for ten days in neonatally thymectomized mice aged four weeks and eight weeks many bone marrow small lymphocytes remained unlabeled. The results demonstrate that early postnatal development of bone marrow lymphoid and erythroid cells proceeds normally in the absence of the thymus, in accord with the concept of the bone marrow as a primary site of lymphocyte production and differentiation. In addition, some slowly-renewing small lymphocytes in bone marrow appear to be thymus-independent cells.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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