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1.
Summary The experiments were carried out on 80 male Wistar rats, divided into four groups as follows: group 1, treated orally with ZnCl2 at a dose of 10 mg Zn2+/kg for 14 days; group 2, control; group 3, MgCl2-treated at a dose of 5 mg Mg2+/kg; group 4, treated with ZnCl2 plus MgCl2 in the same manner as groups 1 and 3. The influx of calcium into the rat duodenum slices was investigated in vitro by the method of Papworth and Patrick. Over a range of calcium concentrations (0–10 mM) the influx of this element was defined as a sum of a saturable term (active transport) and a linear term dependent on concentration (passive transport). In the zinc-treated rats only the saturable term was affected. The study of this term by Lineweaver-Burk plots showed a decrease of the half-saturation constant,K
t, while the maximal value,J
m, remained unchanged. Moreover, magnesium was shown to interact with zinc at gut level because simultaneous oral administration of Mg2+ and Zn2+ to rats protected them against the inhibition of calcium uptake observed when Zn2+ was given alone. 相似文献
2.
Three octahedral complexes built from N-alkylsubstituted imidazoles and magnesium as well as calcium chloride are reported. The obtained solid-state structures differ significantly from each other, depending on the size of the metal ion and the substituent on the imidazole. A chloro-bridged structure is found in the case of tert-butylimidazole, while for the iso-propylimidazole the calcium ion is coordinated by six imidazoles. For the smaller magnesium cation, we also found a sixfold coordination, but here only three of the iso-propylimidazoles coordinate to the magnesium, the three other positions are taken by water molecules. 相似文献
3.
Matrix vesicles (MVs) are involved in de novo mineral formation by nearly all vertebrate tissues. The driving force for MV mineralization is a nucleational core composed of three principal constituents: (i) amorphous calcium phosphate (ACP), complexed in part with phosphatidylserine (PS) to form (ii) calcium-phosphate-lipid complexes (CPLX), and (iii) annexin A5 (AnxA5), the principal lipid-dependent Ca(2+)-binding protein in MVs. We describe methods for reconstituting the nucleational core using a biomimetic approach and for analyzing the kinetics of its induction of mineral formation. The method is based on light scattering by the nascent crystallites at 340 nm and monitors mineral formation at regular intervals without disturbing the system using an automated plate reader. It yields precise replicate values that typically agree within less than 5%. As with MVs, mineral formation by the synthetic complex follows a sigmoidal pattern; following a quiescent induction period, rapid formation ensues for a limited time, followed by a distinct decline in rate that continues to slow, ultimately reaching a maximal asymptotic value. Key to quantization of mineral formation is the use of first-derivative analysis, which defines the induction time, the rate and the amount of initial mineral formation. Furthermore, using a five-parameter logistic curve-fitting algorithm, the maximal amount of mineral formation can be predicted accurately. Using these methods, we document the dramatic finding that AnxA5 synergistically activates PS-CPLX, transforming it from a very weak nucleator of mineral formation to a potent one. The methods presented should enable systematic study of the effects of numerous other factors thought to contribute to mineral formation. 相似文献
4.
Wadhwa DR Care AD 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(3):225-229
The net absorption rates of strontium ions from the ovine reticulo-rumen, isolated in situ in trained conscious animals,
were measured under controlled conditions. A linear positive response was obtained from the addition of Sr2+ ions to the artificial rumen fluid. This increase in the absorption of Sr was reflected in an increase in the plasma Sr concentration.
In contrast to the discrimination observed elsewhere in favour of the absorption of Ca relative to Sr, the absorption rate
of Sr from the reticulo-rumen was significantly greater than that of Ca, from solutions containing the same molar concentration.
A graded increase in the Sr concentration in the ruminal fluid from 1 mmol/l to 4 mmol/l led to a corresponding reduction
in the absorption rate of Ca but an increase in that of phosphate. The latter result is similar to that observed when the
intra-ruminal concentration of Ca2+ ions is increased. It is suggested that Ca and Sr share a common pathway for absorption from the reticulo-rumen and that
this may involve coupling with the absorption of phosphate ions.
Accepted: 18 January 2000 相似文献
5.
Salgueiro MJ Torti H Meseri E Weill R Orlandini J Urriza R Zubillaga M Janjetic M Barrado A Boccio J 《Biological trace element research》2006,110(1):73-77
The aim of the present study was to assess dietary zinc effects on femur weight and mineral content in growing rats. For this
purpose, 70 weanling Sprague-Dawley rats were divided into four groups. Each group was subject to a diet containing 2 (BZ),
5 (DZ), 10 (MZ), and 30 (CZ) ppm zinc. The calcium and magnesium content in all diets was 5 g/kg and 507 mg/kg, respectively.
The animals were kept on this regime for 28 d and then sacrificed and their femurs were removed for analysis using atomic
absorption spectrophotometry.
The weights of the BZ and DZ groups were significantly different from the MZ and CZ groups (38.5±10.5, 89.9±13.7, 118.6±13.6
and 134±19.9 g, p<0.01) respectively. There were no differences between the MZ and CZ groups. Femur weight also varied with dietary zinc, as
it was significantly different among all groups (BZ, 265±49 mg; DZ, 380±40 mg; MZ, 452±54 mg; CZ, 735±66 mg; p<0.01). The femur zinc content varied with diets, following a different pattern than the above parameters. Femur zinc from
the BZ group (51.5±5.4 ppm) was significantly different from the MZ and CZ groups (115.9±14.2 and 175.0±13.5 ppm, respectively),
whereas the DZ group (62.5±11.3 ppm) did not differ from the other three groups. The femur content of calcium (BZ, 83.2±9.8
mg/g; DZ, 88.0±9.2 mg/g; MZ, 90.2±13.6 mg/g; CZ, 83.1±14.7 mg/g) and magnesium (BZ, 1.82±0.13 mg/g; DZ, 1.98±0.09 mg/g; MZ,
1.93±14 mg/g; CZ, 1.83±0.19 mg/g) were not significantly different among the groups, nor was the calcium-magnesium ratio.
These results suggest that although dietary zinc deficiency retards growth and causes bone fragility, bone deposition of calcium
and magnesium and its ratio are not affected. 相似文献
6.
Ed T. Buurman José L. Boiardi M. Joost Teixeira de Mattos Oense M. Neijssel 《Archives of microbiology》1990,153(5):502-505
Magnesium-limited chemostat cultures of Klebsiella pneumoniae NCTC 418 with 20 M CaCl2 in the medium showed a low rate of gluconate plus 2-ketogluconate production relative to potassium- or phosphate-limited cultures. However, when the medium concentration of CaCl2 was increased to 1 mM, the glucose dehydrogenase (GDH) activities also increased and became similar to those observed in potassium- or phosphate limited cultures. It is concluded that this is due to Mg2+ and Ca2+ ions being involved in the binding of pyrroloquinoline quinone (PQQ) to the GDH apoenzyme. There seems to be an absolute requirement of divalent cations for proper enzyme functioning and in this respect Ca2+ ions could replace Mg2+ ions. The high GDH activity which has been found in cells grown under Mg2–-limited conditions in the presence of higher concentrations of Ca2+ ions, is compatible with the earlier proposal that GDH functions as an auxiliary energy generating system involved in the maintenance of high transmembrane ion gradients.Abbreviations PQQ
pyrroloquinoline quinone
- GDH
glucose dehydrogenase (EC 1.1.99.17)
- GaDH
gluconate dehydrogenase (EC 1.1.99.3)
- CAP
chloramphenicol
- WB
Wurster's Blue [1,4-bis-(dimethylamino)-benzene perchlorate] 相似文献
7.
Bautista-Gallego J Arroyo-López FN Chiesa A Durán-Quintana MC Garrido-Fernández A 《Journal of industrial microbiology & biotechnology》2008,35(8):889-900
The combined effect of NaCl, KCl, CaCl(2), and MgCl(2) on the water activity (a (w)) and the growth parameters of Saccharomyces cerevisiae was studied by means of a D-optimal mixture design with constrains (total salt concentrations < or = 9.0%, w/v). The a (w) was linearly related to the concentrations of the diverse salts; its decrease, by similar concentrations of salts, followed the order NaCl > CaCl(2) > KCl > MgCl(2), regardless of the reference concentrations used (total absence of salts or 5% NaCl). The equations that expressed the maximum specific growth (mu (max)), lag phase duration (lambda), and maximum population reached (N (max)) showed that the values of these parameters depended on linear effects and two-way interactions of the studied chloride salts. The mu (max) decreased as NaCl and CaCl(2) increased (regardless of the presence or not of previous NaCl); however, in the presence of a 5% NaCl, a further addition of KCl and MgCl(2) markedly increased mu (max). The lambda was mainly affected by MgCl(2) and the interactions NaCl x CaCl(2) and CaCl(2) x MgCl(2). The further addition of NaCl and CaCl(2) to a 5% NaCl medium increased the lag phase while KCl and MgCl(2) had negligible or slightly negative effect, respectively. N (max) was mainly affected by MgCl(2) and its interactions with NaCl, KCl, and CaCl(2); MgCl(2) stimulated N (max) in the presence of 5% NaCl while KCl, NaCl, and CaCl(2) had a progressive decreasing effect. These results can be of interest for the fermentation and preservation of vegetable products, and foods in general, in which this yeast could be present. 相似文献