Bone resorption and Ca45 turnover in growing rats

1961 ◽  
Vol 200 (2) ◽  
pp. 335-340 ◽  
Author(s):  
Henry Jeffay ◽  
Harold R. Bayne
Keyword(s):  
Bone Resorption ◽  
Specific Activity ◽  
Total Calcium ◽  
Time Intervals ◽  
Growing Rats ◽  
Bone Calcium

A group of rats were maintained on a Ca45 diet for 21 days, then sacrificed at varying time intervals after substituting a nonradioactive diet. The total calcium and calcium specific activity of several bones, blood and urine were determined. After correcting for the dilution of radioactivity due to an increase in total bone calcium, it was found that there was little, if any, loss of Ca45 from rapidly growing bones. When the growth of the bone decreased, a small measurable loss was detected. It was assumed this slow loss of Ca45 represented bone resorption. Values for the rate of bone resorption (replacement rates) are presented and their significance in the growth of the bone discussed.

Studies on the effects of magnesium ion and propranolol on iris muscle phosphatidate phosphohydrolase

1984 ◽  
Vol 62 (2-3) ◽  
pp. 170-177 ◽  
Author(s):  
Ata A. Abdel-Latif ◽  
Jack P. Smith
Keyword(s):  
Smooth Muscle ◽  
Divalent Cation ◽  
Microsomal Fraction ◽  
Specific Activity ◽  
Divalent Cations ◽  
Dependent Manner ◽  
Soluble Enzyme ◽  
Microsomal Enzyme ◽  
Time Intervals ◽  
Phosphatidate Phosphohydrolase

The properties, subcellular distribution, and the effects of Mg2+ and propranolol on phosphatidate phosphohydrolase (EC 3.1.3.4) from rabbit iris smooth muscle have been investigated. The particulate and soluble (0–30% (NH4)2SO4 fraction) enzymes were assayed using aqueous phosphatidate dispersions and membrane-bound phosphatidate as substrates, respectively. When measured with aqueous substrate, activity was detected in both the particulate and soluble fractions, with the highest relative specific activity found in the microsomal fraction. Maximum dephosphorylation by the microsomal enzyme was about 1100 nmol of inorganic phosphate released/h per milligram protein and occurred at pH 7.0–7.5. In general Mg2+ inhibited the phosphohydrolase activity of the microsomal fraction and stimulated that of the soluble fraction, and the effects of the divalent cation on both of these activities were reversed by propranolol. The microsomal enzyme was slightly stimulated by deoxycholate and inhibited by the divalent cations Mg2+, Ca2+, and Mn2+ at concentrations > 0.25 mM. In contrast, the soluble enzyme was stimulated by Mg2+. Inhibition of the microsomal enzyme by Mg2+ (0.5 mM) was reversed by both EDTA, which also stimulated at higher concentrations (1 mM), and propranolol (0.1–0.2 mM). The inhibitory effect of Ca2+ on the enzyme was not reversed by propranolol. In the absence of Mg2+, the microsomal enzyme was inhibited by propranolol in a dose-dependent manner, and both in the absence and presence of the divalent cation the soluble enzyme was inhibited by the drug in a similar manner. These data suggest that the cationic moiety of propranolol may act by competing at the Mg2+-binding sites. Addition of propranolol (0.2 mM) to iris muscle prelabelled with [14C]arachidonic acid increased accumulation of [14C]phosphatidic acid at all time intervals (2.5–90 min) and brought about a corresponding initial decrease in the formation of [14C]diacylglycerol at short time intervals (2.5 min), thus implicating the phosphohydrolase as a possible site of action of the drug on glycerolipid metabolism in this tissue. In addition to reporting on the characteristics and distribution of phosphatidate phosphohydrolase in the iris smooth muscle, the data presented add further support to our hypothesis that propranolol redirects glycerolipid metabolism in the iris by exerting multiple effects on the enzymes involved in their biosynthesis.

EFFECTS OF INSULIN ON RATES OF GLUCOSE TRANSFER IN THE DEPANCREATIZED DOG

1955 ◽  
Vol 33 (6) ◽  
pp. 926-939 ◽  
Author(s):  
Margaret J. Henderson ◽  
Gerald A. Wrenshall ◽  
Paul Odense
Keyword(s):  
Plasma Glucose ◽  
Dynamic Equilibrium ◽  
Specific Activity ◽  
The State ◽  
Time Intervals ◽  
Lower Blood Glucose ◽  
In Vivo Experiments ◽  
Lower Blood ◽  
Before And After

An attempt to answer the question as to whether insulin acts to lower blood glucose by increasing utilization, or by decreasing production, or by both, has been made using a new experimental approach. A trace dose of radioactive glucose was injected into each of six postabsorptive depancreatized dogs which had been deprived of exogenous insulin for 66 hr. Blood samples were collected before and after the intravenous injection of insulin, and plasma glucose concentration and specific activity were measured. From these data the simultaneous rates of appearance and disappearance of plasma glucose were calculated for a sequence of time intervals, both before and after insulin, by a method which did not assume dynamic equilibrium. Previous in vivo experiments using radioactive tracers to measure rates of production and utilization of glucose have been made in animals which were in steady states, either with or without insulin, and the effects of insulin were ascertained by comparison of the state with insulin and the state without insulin. The method described in this paper has made it possible to follow the effects of insulin while it is acting in one and the same animal. Insulin was found to cause an abrupt and marked increase in the rate of disappearance of glucose, and this increased rate became less with time, reaching the preinsulin level in about 90 min. Insulin caused a slower and much smaller decrease in the rate of appearance, but the decrease became greater with time during the three hour period of observation. Thus, it appeared that insulin acted in vivo both to increase the utilization of glucose and to decrease its production, but the effects differed in magnitude and in speed of response.

Bone changes due to pregnancy and lactation: influence of vitamin D status

1986 ◽  
Vol 251 (4) ◽  
pp. E400-E406 ◽  
Author(s):  
P. J. Marie ◽  
L. Cancela ◽  
N. Le Boulch ◽  
L. Miravet
Keyword(s):  
Vitamin D ◽  
Bone Resorption ◽  
Bone Formation ◽  
Trabecular Bone ◽  
Formation Rate ◽  
Vitamin D Status ◽  
Bone Formation Rate ◽  
Bone Calcium ◽  
Pregnancy And Lactation ◽  
Stimulation Of

The effects of pregnancy and lactation on endosteal bone formation and resorption were evaluated in vitamin D-depleted (-D) and vitamin D-repleted (+D) rats. Pregnancy induced a marked stimulation of osteoclastic bone resorption and of static and dynamic parameters of bone formation and mineralization. Bone resorption increased independently of vitamin D status and did not correlate with plasma 1,25-dihydroxyvitamin D3 [1,25(OH)2D] levels, but it was associated with increased plasma immunoreactive parathyroid hormone (iPTH) concentrations. Stimulation of the endosteal bone formation rate was mainly impaired in D-depleted rats, resulting in trabecular bone loss, which, in -D mother rats, was associated with decreased bone ash and total bone calcium. Lactation further stimulated bone resorption and reduced the trabecular bone volume; ash weight and bone calcium content were also decreased independently of the vitamin D status and changes in plasma iPTH levels. In presence of vitamin D, the bone formation rate increased fourfold during lactation but was unchanged in -D lactating rats. During lactation, vitamin D-depleted rats lost twofold more calcified bone than +D rats because of impaired mineralization. Thus, the present study shows that both the endosteal bone resorption and formation are stimulated by pregnancy and lactation and that vitamin D is required for normal bone mineralization during the reproductive period.

PHOSPHORUS METABOLISM OF THE ADRENAL GLAND: THE MECHANISM OF THE CHANGE AFTER HYPOPHYSECTOMY

1954 ◽  
Vol 32 (3) ◽  
pp. 261-270 ◽  
Author(s):  
B. E. Riedel ◽  
R. J. Rossiter
Keyword(s):  
Adrenal Gland ◽  
Specific Activity ◽  
Extracellular Fluid ◽  
Phosphorus Metabolism ◽  
Time Intervals ◽  
Inorganic P ◽  
Fluid Compartment ◽  
Hypophysectomized Rats ◽  
Specific Activities ◽  
Isotope Equilibrium

The specific activity of the intracellular inorganic phosphate (P) of the adrenal gland relative to that of the inorganic P of the plasma is significantly decreased in hypophysectomized rats at time intervals as long as 16 hr. after the injection of inorganic P labelled with P32. The specific activity of the intracellular inorganic P was determined (1) by measuring the specific activity of the easily-hydrolyzable acid-soluble P, which rapidly comes into isotope equilibrium with the intracellular inorganic P, (2) by calculation, from the specific activity of the inorganic P of the whole adrenal, assuming values for the specific activity and the concentration of the inorganic P of the extracellular fluid and the volume of the extracellular fluid compartment, and (3) by measuring the specific activities of the inorganic P of both the adrenal gland and the plasma at a series of time intervals after the injection of the P32. It is concluded that the decrease in the relative specific activity of the intracellular inorganic P of the adrenal is the result of a slowing in the passage of inorganic P32 across the cell membrane, i.e. from the extracellular to the intracellular fluid.

Role of parathyroid hormone in regulation of main calcium fluxes in rats.

1977 ◽  
Vol 232 (6) ◽  
pp. E535
Author(s):  
B Haldimann ◽  
J P Bonjour ◽  
H Fleisch
Keyword(s):  
Parathyroid Hormone ◽  
Bone Resorption ◽  
Bone Formation ◽  
Bone Turnover ◽  
Linear Correlation ◽  
Constant Amount ◽  
Calcium Fluxes ◽  
Growing Rats

The effect of calcium deprivation on the various calcium fluxes was studied in growing rats either sham-operated (SHAM), thyroparathyroidectomized (TPTX), or thyroparathyroidectomized and supplemented with parathyroid hormone (PTH) (TPTX + PTH). In SHAM rats a decrease in the net absorption of calcium (Vna) has no influence on calcemia or on bone formation (Vo+), but leads to an increase in bone resorption (Vo-). In TPTX rats a decrease in Vna induces a decrease in calcemia and in Vo+ but still causes an increase in Vo-. The same is true in TPTX + PTH rats although all the variables measured are increased. In TPTX rats, both without and with PTH, a linear correlation exists between calcemia and Vo+ suggesting that calcemia influences bone formation. Furthermore, it appears that PTH is important in regulating bone turnover, but that the adaptation of Vo- to a change in Vna can occur in the absence or in the presence of a constant amount of this hormone. The mechanism of regulating this adaptation of bone resorption is still unknown.

Image intersification applied to biological problems

1972 ◽  
Vol 5 (3) ◽  
pp. 295-347 ◽  
Author(s):  
George T. Reynolds
Keyword(s):  
Specific Activity ◽  
Biological Research ◽  
Biological Processes ◽  
X Rays ◽  
Radioactive Tracers ◽  
X Ray Diffraction ◽  
Time Intervals ◽  
X Ray ◽  
Rapid Sequence ◽  
Short Time

In many important types of observations in biological research, the information provided by the specimens is in the form of photons-quanta of visible light, u.v., or X-rays. The process of observation becomes one of recording this information in useful form, with as high an efficiency as possible. The problem becomes particularly important when for some reason or other the total number or rate of quanta provided by the specimen is small. Examples of such limitations are included in the following: (i) Processes permitting only low-intensity illumination in order not to interfere with the biological processes under observation. (ii) Processes changing very rapidly and requiring rapid sequence recording. (iii) Processes providing only a limited number of photons per event, such as bioluminescence. (iv) Processes in which radioactive tracers are utilized, and observation of radioactivity is desirable at low specific activity or within short time intervals. (v) X-ray diffraction processes where the specimen is weakly diffracting or where the X-ray intensity must be kept low in order not to damage the specimen. (vi) Processes involving the observation of fluorescence, where the intensity is low because of limitations on the amount of tagging material.

Characterization studies on the membrane-bound adenosine triphosphatase (ATPase) of Azotobacter vinelandii

1975 ◽  
Vol 21 (11) ◽  
pp. 1807-1814 ◽  
Author(s):  
Peter Jurtshuk ◽  
John E. McEntire
Keyword(s):  
Electron Transport ◽  
Atpase Activity ◽  
Azotobacter Vinelandii ◽  
Specific Activity ◽  
Maximal Activity ◽  
Molar Ratio ◽  
Supernatant Fraction ◽  
Time Interval ◽  
Time Intervals ◽  
Membrane Bound

The adenosinetriphosphatase (ATPase) (EC 3.6.1.3) activity in Azotobacter vinelandii concentrates in the membranous R3 fraction that is directly associated with Azotobacter electron transport function. Sonically disrupted Azotobacter cells were examined for distribution of ATPase activity and the highest specific activity (and activity units) was consistently found in the particulate R3 membranous fraction which sediments on ultracentrifugation at 144 000 × g for 2 h. When the sonication time interval was increased, the membrane-bound ATPase activity could neither be solubilized nor released into the supernatant fraction. Optimal ATPase activity occurred at pH 8.0; Mg2+ ion when added to the assay was stimulatory. Maximal activity always occurred when the Mg2+:ATP stoichiometry was 1:1 on a molar ratio at the 5 mM concentration level. Sodium and potassium ions had no stimulatory effect. The reaction kinetics were linear for the time intervals studied (0–60 min). The membrane-bound ATPase in the R3 fraction was stimulated 12-fold by treatment with trypsin, and fractionation studies showed that trypsin treatment did not solubilize ATPase activity off the membranous R3 electron transport fraction. The ATPase was not cold labile and the temperature during the preparation of the R3 fraction had no effect on activity; overnight refrigeration at 4 °C, however, resulted in a 25% loss of activity as compared with a 14% loss when the R3 fraction was stored overnight at 25 °C. A marked inactivation (although variable, usually about 60%) did occur by overnight freezing (−20 °C), and subsequent sonication failed to restore ATPase activity. This indicates that membrane reaggregation (by freezing) was not responsible for ATPase inactivation. The addition of azide, ouabain, 2,4-dinitrophenol, or oligomycin to the assay system resulted in neither inhibition nor stimulation of the ATPase activity. The property of trypsin activation and that ATPase activity is highest in the R3 electron transport fraction suggests that its probable functional role is in coupling of electron transport to oxidative phosphorylation.

scholarly journals Glyphosate translocation in hairy fleabane (Conyza bonariensis) biotypes

2008 ◽  
Vol 26 (3) ◽  
pp. 637-643 ◽  
Author(s):  
E.A. Ferreira ◽  
L. Galon ◽  
I. Aspiazú ◽  
A.A. Silva ◽  
G. Concenço ◽  
...  
Keyword(s):  
Liquid Scintillation ◽  
Specific Activity ◽  
Resistance Mechanism ◽  
Time Intervals ◽  
Liquid Scintillation Spectrometer ◽  
Conyza Bonariensis ◽  
Translocation Efficiency ◽  
Plant Emergence ◽  
Treatment Application ◽  
Hairy Fleabane

The objective of this work was to evaluate the translocation of glyphosate in C. bonariensis plants resistant and susceptible to that herbicide. The 14C-glyphosate was mixed with commercial gyhphosate (800 g ha-1) and applied on the center of the adaxial face of a third node leaf, using a micro syringe, and adding 10 µL of a solution with specific activity of 1,400 Bq, 45 days after plant emergence. The concentration of the glyphosate translocated in the plant was evaluated at time intervals of 6, 12, 36 and 72 hours after being applied on the application leaf, stem, roots and leaves. Ten hours after treatment application, the distribution of the product in the application leaf, divided into base, center and apex, was also evaluated by measuring the radiation emitted by 14C-glyphosate in a liquid scintillation spectrometer. Greater glyphosate retention was observed in the resistant biotype leaf, approximately 90% of the total absorbed up to 72 hours. In the susceptible biotype, this value was close to 70% in the same period. Susceptible biotype leaves, stem and roots showed greater concentration of glyphosate, indicating greater translocation efficiency in this biotype. In the resistant biotype, the herbicide accumulated in greater quantity at the apex and center of the application leaf, while in the susceptible biotype greater accumulation was observed at the base and center leaf. Thus, it can be stated that the resistance mechanism is related to the differential translocation of this herbicide in the biotypes.

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