ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    A quantitative description of components of in vitro morphometric change in the rat osteoclast model: relationships with cellular function (1992)
    Springer
    European biophysics journal 21 (1992), S. 349-355 
    Details
    ISSN: 1432-1017
    Keywords: Cell shape ; Cell motility ; Osteoclasts ; Bone resorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract We describe the in vitro morphometric changes shown by rat osteoclasts that accompany their functional responses to the application of a range of regulatory agents of known physiological importance. We introduce a cellular motility parameter, µ, which was defined through a quantification of retraction-protrusion behaviour. This was used in conjunction with a net cell retraction, ϱ, which is derived from the change in total cell area following the application of an agent. These terms were used together for the description of cellular motility changes in response to specific cellular regulatory agents. The definition of retraction-protrusion was normalised against control cell area, to give a dimension-less variable independent of the net cell retraction. Thus, mutual terms present in either descriptor cancelled when the complementary parameter was held constant. Furthermore, the descriptor, µ remained time-invariant for extended intervals (around 20 min) even when ϱ was varying following cell introduction into culture. Interventions also with substances known to modify osteoclast function, were capable of altering each descriptor, to different extents. Thus elevation of the extracellular Ca2+ concentration ([Ca2+]e) at the osteoclast calcium “receptor” altered ϱ without changes in µ. In contrast, the polypeptide amylin (250 nM), within 20 minutes of application, elicited a marked change in µ, but only a relatively small change in ϱ. Finally, human calcitonin treatment (300 pM) influenced both descriptors. When combined together, these morphometric findings accordingly offer complementary descriptions of visible cellular changes in response to added agents of physiological relevance. Such an approach may be useful in the analysis of structure-function relationships in osteoclasts or other cell systems particularly in correlations between quantitative structure and functional responsiveness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00188348
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Elevated cytosolic calcium levels in human lymphocytes during surface virus infections (1994)
    Springer
    Molecular and cellular biochemistry 131 (1994), S. 61-66 
    Details
    ISSN: 1573-4919
    Keywords: lymphocyte ; calcium ; glucose transporter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary Generalised metabolic and electrolyte disturbances are known to accompany both plasma and surface virus infections. We have investigated whether these infections could impair the transport of Ca2+ from cells under conditions of controlled concentrations of the energy substrate glucose. Thus, cytosolic calcium levels ([Ca2+]i) were measured in single isolated lymphocytes obtained from healthy volunteers or those suffering from coryza. Before making measurements using a Ca2+-sensitive fluorescent dye indo 1, we incubated lymphocytes in buffers containing 0 mM-, 5.6 mM- or 11.2 mM-[glucose]. We found that [Ca2+]i of lymphocytes obtained from the sick were significantly higher than those from healthy controls both at 0 mM and 5.6 mM-[glucose], and that [Ca2+]i was inversely related to the media glucose concentration for both groups. These results suggest a diminished capacity of cation pumping in viral infections, such as coryza, in relationship to the available glucose as energy substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01075725
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    The effect of tetracyclines on quantitative measures of osteoclast morphology (1993)
    Springer
    Bioscience reports 13 (1993), S. 175-182 
    Details
    ISSN: 1573-4935
    Keywords: tetracyclines ; 4-dedimethylaminotetracycline ; osteoclastic resorption ; osteoclast Ca2+ receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We report the effects of the tetracycline analogues 4-dedimethylaminotetracycline (CMT-1) and minocycline on osteoclast spreading and motility. Both agents influenced the morphometric descriptor of cell spread area, ϱ, producting cellular retraction or an R effect (half-times: 30 and 44 minutes for CMT-1 and minocycline, respectively). At the concentrations employed, the tetracycline-induced R effects were significantly slower than, but were qualitatively similar to, those resulting from Ca2+ “receptor” activation through the application of 15 mM-[Ca2+] (slopes: −1.25, −0.18, and −4.40/minute for 10 mg/l-[CMT-1], 10 mg/l-[minocycline] and 15 mM-[Ca2+], respectively). In contrast, the same tetracycline concentrations did not influence osteoclast margin ruffling activity as described by μ, a motility descriptor known to be influenced by elevations of cellular cyclic AMP. Thus, the tetracyclines exert morphometric effects comparable to changes selectively activated by occupancy of the osteoclast Ca2+ “receptor” which may act through an increase in cytosolic [Ca2+].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01149962
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Tetracyclines modulate cytosolic Ca2+ responses in the osteoclast associated with “Ca2+ receptor” activation (1993)
    Springer
    Bioscience reports 13 (1993), S. 169-174 
    Details
    ISSN: 1573-4935
    Keywords: tetracycline ; osteoclasts ; cytosolic Ca2+
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We report the effects of tetracycline analogues on cytosolic Ca2+ transients resulting from application of ionic nickel (Ni2+), a potent surrogate agonist of the osteoclast Ca2+ “receptor”. Preincubation with minocycline (1 mg/l) or a chemically modified tetracycline, 4-dedimethyl-aminotetracycline (CMT-1) (1 or 10 mg/l), resulted in a significant attenuation of the magnitude of the cytosolic [Ca2+] response to an application of 5 mM-[Ni2+]. Preincubation with doxycycline (1 or 10 mg/l) failed to produce similar results. In addition, application of minocycline alone (0.1–100 mg/l) resulted in a 3.5-fold elevation of cytosolic [Ca2+]. The results suggest a novel action of tetracyclines on the osteoclast Ca2+ “receptor”.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01149961
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    A hypothesis for the local control of osteoclast function by Ca2+, nitric oxide and free radicals (1992)
    Springer
    Bioscience reports 12 (1992), S. 369-380 
    Details
    ISSN: 1573-4935
    Keywords: osteoclast ; Ca2+ receptor ; peroxide ; nitric oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Several important conclusions have recently emerged fromin vitro studies on the resorptive cell of bone, the osteoclast. First, it has been established that osteoclast function is modulated locally, by changes in the local concentration of Ca2+ caused by hydroxyapatite dissolution. It is thought that activation by Ca2+ of a surface membrane Ca2+ receptor mediates these effects, hence providing a feedback control. Second, a number of molecules produced locally by the endothelial cell, with which the osteoclast is in intimate contact, have been found to affect bone resorption profoundly. For instance, the autocoid nitric oxide strongly inhibits bone resorption. Finally, reactive oxygen species have been found to aid bone resorption and enhance osteoclastic activity directly. Here, we will attempt to integrate these control mechanisms into a unified hypothesis for the local control of bone resorption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01121500
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    The afterdepolarization in Rana temporaria muscle fibres following osmotic shock (1995)
    Springer
    Journal of muscle research and cell motility 16 (1995), S. 519-528 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Rana temporaria sartorius muscle fibres were exposed to varied sequences of solution and temperature changes that have been employed hitherto in procedures that sought to decouple the transverse tubules from the surface membrane. The incidence of such detubulation was assessed in large numbers of fibres through demonstrating a loss or otherwise of the after-depolarization that normally reflects successful tubular propagation of the surface action potential. This criterion yielded assessments of the existing detubulation techniques in agreement with earlier results. The experiments then developed an improved detubulation procedure that required only brief (15 min) exposures to glycerol, its replacement in a single step by a Ca2+/Mg2+-Ringer solution for 30 min, and rapid cooling from room temperature (19–21° C) to 6–10° C prior to final restoration of the normal Ringer solution. This sequence of steps yielded an optimal incidence (98%) of detubulation in viable surface fibres that were amenable to electrophysiological studies. Studies that systematically modified the detubulation procedure demonstrated that the omission of any one step in the protocol significantly reduced the incidence of detubulation with or without accompanying deteriorations in fibre resting potentials. Successful detubulation accordingly required an initial exposure to an optimal glycerol concentration that lasted for a minimal duration and for its abrupt withdrawal. Inclusion of a cooling step within 30 min after glycerol withdrawal was coincident with, and critical to, optimal tubular isolation. Thus, cooling steps that either preceded, or that followed the glycerol withdrawal step by more than 60 min, resulted in a sharp reduction in the incidence of detubulation. Similarly, a critical period of exposure to Ca2+/Mg2+ Ringer solution also promoted detubulation without compromising the recovery of stable and satisfactory resting potentials. The findings reported here remain consistent with a primarily osmotic mechanism for detubulation. However, they demonstrated additional and important influences of temperature and of divalent cation concentration on the extent of tubular detachment when such factors were modified during the time course of the expected volume changes that followed each adjustment in osmotic condition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00126436
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Loop diuretics inhibit detubulation and vacuolation in amphibian muscle fibres exposed to osmotic shock (2000)
    Springer
    Journal of muscle research and cell motility 21 (2000), S. 79-90 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The effect of loop diuretics at concentrations known to influence cellular water entry coupled to Na-K-Cl co-transport, upon the vacuolation and detubulation following osmotic shock, was investigated in amphibian skeletal muscles. These were exposed to a glycerol-Ringer solution (18 min), an isotonic Ca2+/Mg2+ Ringer solution and cooling. Adding bumetanide (1.0 and 2.0 μM) to these solutions sharply reduced the incidence of detubulation, assessed by abolition or otherwise of action potential after-depolarisations, from 93.9 ± 4.7% (n = 6) to 5.0 ± 1.1% (n = 4: mean ± SEM: 2.0 μM bumetanide). It dramatically reduced the number and fraction of muscle volume occupied by tubular vacuoles, measured using confocal microscopy, from 60.3 ± 4.3% (n = 10) to 9.0 ± 1.1% (n = 35). The incidence of large horseradish peroxidase-lined tubular vacuoles, viewed using electronmicroscopy, similarly was reduced with 2 μM bumetanide in the glycerol-Ringer solution. Bumetanide acted through cellular volume adjustments early in the detubulation protocol. Thus, it exerted its maximum effect when added to the glycerol-Ringer, rather than the Ca2+/Mg2+ Ringer solution. Furthermore, whereas fibre diameters measured using scanning electron microscopy returned to normal during glycerol treatment relative to those of control fibres left in isotonic Ringer, addition of 2.0 μM bumetanide in the glycerol Ringer left markedly smaller fibre diameters. Finally equipotent concentrations of the chemically distinct loop diuretics, furosemide and ethacrynic acid similarly influenced detubulation. These findings implicate Na-K-Cl co-transport in the water entry into muscle fibres that would be expected following introduction of extracellular glycerol. This might then enable the subsequent Na-K-ATPase dependent water extrusion that produces the tubular distension (vacuolation) and detachment (detubulation) following glycerol withdrawal, phenomena also observed in muscular dystrophy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005618720122
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Cardiac glycosides inhibit detubulation in amphibian skeletal muscle fibres exposed to osmotic shock (1999)
    Springer
    Journal of muscle research and cell motility 20 (1999), S. 45-53 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract It has recently been suggested that the ‘vacuolation’ of the transverse tubular system that follows the imposition of an osmotic shock is a component process in the eventual ‘detubulation’ of amphibian skeletal muscle. However, such a hypothesis requires net fluid transfers from the intracellular space into the lumina of the transverse tubules against the prevailing transmembrane osmotic gradients. The present experiments tested the effects of cardiac glycosides on the consequences of established osmotic protocols known reliably to achieve high levels of both detubulation and vacuolation in Rana temporaria sartorius muscle. Tubular isolation (detubulation) was assessed through electrophysiological observations of the abolition or otherwise of the after-depolarisation components of muscle action potentials. Vacuolation was assessed by stereological estimation of the volume fraction of muscle that was occupied by fluorescence-labelled vacuoles observed using confocal microscopy. Introduction of ouabain in the osmotic shock solutions sharply reduced such measures of vacuolation from 48.5±3.6% (mean±SEM; n=70) to 12.1±2.7% (n=190) of the total fibre volume. This was accompanied by sharp reductions in the incidence of detubulation (detubulation index reduced from 96.3±2.6% to 0.0±0.0%). The presence of ouabain was critical at the osmotic shock stage in the procedures at which the hypertonic glycerol- containing solutions were replaced by isotonic Ca2+–Mg2+-Ringer solutions. Finally, the alternative cardiac glycosides, strophanthidine and digoxin, exerted similar effects. These findings support a scheme in which the osmotic shock initiates a metabolically dependent fluid expulsion. This distends the transverse tubules into vacuoles that in turn lead to fibre detubulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005494114976
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Osmotic ’detubulation‘ in frog muscle arises from a reversible vacuolation process (1997)
    Springer
    Journal of muscle research and cell motility 18 (1997), S. 305-321 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Isolated Rana temporaria sartoriusmuscle fibres were subject to introduction and subsequentwithdrawal of 400 mm extracellular glycerol, exposures tohigh divalent ion concentrations and then cooling. Tubulardetachment was then assessed through changes in the actionpotential afterdepolarization. (1) The rapid (5--10 min) ratherthan slow cooling step (30 min) produced a gradual (30 min)development of detubulation arrested by the subsequentreplacement of glycerol and reversed by addition of 350 mmsucrose. Such osmotic agents influenced neither restingpotentials of intact or detubulated fibres nor action potentialsin intact fibres. (2) Full tubular detachment was achieved by 40min. Laser epifluorescence microscopy demonstrated anaccompanying tubular vacuolation through its trapping of aRhodamine dye. (3) Subsequent re-additions (at 10--80 min) ofglycerol restored the afterdepolarization in 30% of detubulatedfibres and correspondingly reduced vacuolation. Sustained (〉60 min) exposures to 350 mm sucrose, applied between 30--60min, both reversed tubular isolation in 70% of detubulated fibresand abolished tubular vacuolation. Finally, results fromtransient (10--30 min) sucrose exposures resembled theconsequences of sustained applications of glycerol, suggestingthat detubulation and its reversal result from an osmoticmechanism. (4) Nevertheless, irreversible changes developed after70--80 min in 70% of detubulated fibres, a process hastened byslow cooling steps in the initial osmotic stress. The presentstudy thus correlates morphological and electrophysiologicalconsequences of applying osmotic shock to skeletal muscle for thefirst time. It additionally differentiates reversible andirreversible components of detubulation. Finally, it suggeststhat detubulation results from the similarly reversiblevacuolation observed under comparable osmotic conditions, andthat such vacuolation can eventually lead to irreversibledetubulation
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018670025321
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Divalent cations mimic the inhibitory effect of extracellular ionised calcium on bone resorption by isolated rat osteoclasts: Further evidence for a “calcium receptor” (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 149 (1991), S. 422-427 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Osteoclast activity is thought to be regulated by calcitonin, as well as by the level of ionised calcium generated locally as a result of bone resorption. The exposure of isolated osteoclasts to elevated ambient calcium levels has been shown to lower resorptive activity and to reduce rates of enzyme release. We have attempted to determine whether these effects are mediated by a divalent cation-sensitive “calcium receptor,” as has been reported for the parathyroid chief cells. Thus, we compared the effect of alkaline earth metal cations on osteoclast function using a morphometric measure of bone resorption and a spectrophotometric method for measuring the activity of the released enzyme, acid phosphatase. The exposure of resorbing osteoclasts to between 5 and 20 mM extracellular ionised calcium ([Ca2+]e) inhibited bone resorption and enzyme release to an extent similar to that seen with 0.1 to 10 μM ionomycin. The effect of combining submaximal concentrations of [Ca2+]e (15 mM) and ionomycin (0.1 μM) resulted in additivity, suggesting that the influence of [Ca2+]e on bone resorption was mediated by elevated intracellular calcium levels ([Ca2+]e). The other cations studied (Mg2+, Ba2+) were effective and elicited similar effects, although some required higher concentrations. Thus, whilst Ca2+ and Mg2+ were effective at 10 to 15 mM levels, Ba2+ was effective only at high (20 mM) concentrations. These findings are consistent with an influence of [Ca2+]e on osteoclast activity through an action on a surface membrane “calcium receptor” that can also bind other divalent cations, rather than by passive changes of [Ca2+]i with [Ca2+]e elevation.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041490310
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...