The Effect of Sodium Alginate on the Absorption of Strontium and Calcium in Human Subjects

The effect of sodium alginate on the gastrointestinal absorption of the tracers strontium-85 and calcium-47 was investigated in 19 human subjects. The tracers were administered orally with 100 mg. of a calcium carrier—calcium chloride. At the same time, sodium alginate was given in a commercial jelly. The sevenday per cent retentions of tracers were measured with a whole-body counter. After one month, the experiments were repeated without alginate so that each subject acted as his own control. Fifteen volunteers were given 1.5 g. of alginate, two were given 3.0 g. and two 0.3 g. 1.5 g. of alginate reduced the absorption of strontium by a factor of two with no significant effect on calcium absorption. The smaller dose of alginate (0.3 g.) appeared to have no effect on strontium or calcium absorption and the larger dose (3.0 g.) had no greater effect than the 1.5 g. dose.     

Macropinocytosis is the Major Mechanism for Endocytosis of Calcium Oxalate Crystals into Renal Tubular Cells

During an initial phase of kidney stone formation, the internalization of calcium oxalate (CaOx) crystals by renal tubular cells has been thought to occur via endocytosis. However, the precise mechanism of CaOx crystal endocytosis remained unclear. In the present study, MDCK renal tubular cells were pretreated with inhibitors specific to individual endocytic pathways, including nystatin (lipid raft/caveolae-mediated), cytochalasin D (actin-dependent or macropinocytosis), and chlorpromazine (CPZ; clathrin-mediated) before exposure to plain (non-labeled), or fluorescence-labeled CaOx monohydrate (COM) crystals. Quantitative analysis by flow cytometry revealed that pretreatment with nystatin and CPZ slightly decreased the crystal internalization, whereas the cytochalasin D pretreatment caused a marked decrease in crystal uptake. Immunofluorescence study and laser-scanning confocal microscopic examination confirmed that the cytochalasin D-pretreated cells had dramatic decrease of the internalized crystals, whereas the total number of crystals interacted with the cells was unchanged (crystals could adhere but were not internalized). These data have demonstrated for the first time that renal tubular cells endocytose COM crystals mainly via macropinocytosis. These novel findings will be useful for further tracking the endocytosed crystals inside the cells during the course of kidney stone formation.     

The Role of Overweight and Obesity in Calcium Oxalate Stone Formation

Objective: The aim of the study was to assess the influence of overweight and obesity on the risk of calcium oxalate stone formation. Research Methods and Procedures: BMI, 24‐hour urine, and serum parameters were evaluated in idiopathic calcium oxalate stone formers (363 men and 164 women) without medical or dietetic pretreatment. Results: Overweight and obesity were present in 59.2% of the men and in 43.9% of the women in the study population. Multiple linear regression analysis revealed a significant positive relationship between BMI and urinary uric acid, sodium, ammonium, and phosphate excretion and an inverse correlation between BMI and urinary pH in both men and women, whereas BMI was associated with urinary oxalate excretion only among women and with urinary calcium excretion only among men. Serum uric acid and creatinine concentrations were correlated with BMI in both genders. Because no association was established between BMI and urinary volume, magnesium, and citrate excretion, inhibitors of calcium oxalate stone formation, the risk of stone formation increased significantly with increasing BMI among both men and women with urolithiasis (p = 0.015). The risk of calcium oxalate stone formation, median number of stone episodes, and frequency of diet‐related diseases were highest in overweight and obese men. Discussion: Overweight and obesity are strongly associated with an elevated risk of stone formation in both genders due to an increased urinary excretion of promoters but not inhibitors of calcium oxalate stone formation. Overweight and obese men are more prone to stone formation than overweight women.     

纳米珍珠粉对大鼠钙吸收利用的影响

目的研究纳米珍珠粉对大鼠钙吸收利用的影响,并比较纳米和微米珍珠粉对大鼠生长发育和骨钙水平作用的差异。方法出生21d断乳SD大鼠100只,喂养低钙饲料2周。随机分为5组,雌雄各半,Ⅰ～Ⅱ组分别为微米珍珠粉低、高剂量组,喂饲饲料为低钙饲料混合不同剂量的微米珍珠粉;Ⅲ～Ⅳ分别为纳米珍珠粉低、高剂量组,喂饲饲料为低钙饲料混合不同剂量的纳米珍珠粉;Ⅴ组为低钙对照组,喂饲低钙饲料;另取10只SD大鼠为实验本底组(即Ⅵ组),Ⅵ组于实验开始前处死。实验期为4周。结果2个不同剂量的纳米珍珠粉组的大鼠体重、股骨干重及长度、钙吸收率、钙存留率均高于2个相应剂量的微米珍珠粉组,且差异有显著性(P<0.05)。结论纳米珍珠粉能够被大鼠很好地吸收利用,具有增加骨钙含量的功能,在钙吸收利用作用方面明显优于微米珍珠粉。     

Some Observations on the Demonstration of Calcium Oxalate in Tissue Sections

Crystal deposits in human kidney and thyroid, identified as calcium oxalate by microincineration and Solubility tents, were used to assess the staining of oxahtes by selected methods for calcium. No method that stained the crystals was considered specific for calcium oxalate, but, after removal of possible phosphate and carbonate with 2 M acetic acid, the silver nitrate-rubeanic acid sequence was found to give the best visualisation of the crystals, and could be considered reasonably selective. Deposits in kidneys included a pronounced colloidal matrix composed chiefly of acid mucopolysaccharides. This matrix often showed a lamellar pattern and was well-demonstrated by alcian blue at pH 25 and by dialysed iron after removal of the crystals with 1 N hydrochloric acid. Such a matrix Could only be detected in trace amount in the thyroid deposits.     

Effect of L-Pipecolic Acid on Flowering in Lemna paucicostata and Lemna gibba

L-Pipecolic acid was found to be effective in inducing floweringof Lemna paucicostata 151, 381, 441 and 6746, and of Lemna gibbaG3. When the plants were grown on half-strength Hutner's medium,L-pipecolic acid caused profuse flowering of L. paucicostata151 maintained under 9 and 10 h of light daily. In L. paucicostata441 and 6746, L-pipecolic acid had a strong flower-promotingeffect under a near critical photoperiod. In L. paucicostata381, by contrast, L-pipecolic acid had only a very small effecton flowering. In L. gibba G3 substantial promotion of floweringwas observed under continuous light. When one-twentieth-strengthHutner's medium was used as the basic medium, L-pipecolic acidstimulated flowering in all strains of Lemna examined, evenunder continuous light. When L. paucicostata 151 was grown on one-tenth-strength M mediumor one-twentieth-strength Hutner's medium, the flower-inducingactivity of L-pipecolic acid was greatly enhanced by cytokininunder continuous light. However, when this strain was grownwith 9 h of illumination daily, this synergistic effect of cytokininwas only slight. A short-term (even 1-h) treatment with L-pipecolicacid resulted in flowering, suggesting that L-pipecolic acidis involved in the induction of flowering, rather than its evocation.D-Pipecolic acid also had flower-inducing activity, but itsactivity was 50 times lower than that of the L-isomer. (Received January 23, 1992; Accepted March 9, 1992)     

The Effect of Light on the Structure and Organization of Lemna Peroxisomes

The effect of light on a number of Lemna minor enzyme activitieswas investigated. The levels of activity of glycolate oxidase,catalase and RuBPCase increased with increasing irradiance,paralleling the increase in Lemna growth rate. In contrast withresults obtained for other species, no glycolate oxidase activitycould be detected in etiolated Lemna fronds or when these weretreated with light or glycolate, in vivo or in vitro, for upto 24 h. The number of peroxisome profiles per cell section was determinedin Lemna grown under different light conditions. When frondswere grown under dim light, the number of peroxisome profilesper cell section appeared to increase with increasing irradiance,although no further increase in the peroxisome number was apparentwhen the fronds were grown under higher irradiances. The levelof glycolate oxidase activity per peroxisome was shown to increasewith increasing irradiance, whereas that of catalase remainedrelatively constant, indicating that differential addition ofenzymes to pre-existing peroxisomes is possible. Peroxisomes from Lemna grown under high irradiance were subjectedto serial sectioning and examined under the electron microscope.Some peroxisomes were found to have a three dimensional structuresuggesting either fission and/or fusion or branching of theseorganelles, supporting the hypothesis of a peroxisomal reticulum.The dynamic relationship between the various shapes is discussed. Key words: Peroxisomes, glycolate oxidase, catalase     

The Effect of Salicylic Acid on the Growth of Lemna gibba

Salicylic acid added as the iron chelate causes extension ofthe pedicels and distortion in the growth of daughter frondsof Lemna gibba, when included in a nutrient salt medium whichcontains the ammonium ion. The effect is abolished if iron orcopper is omitted from the nutrient solution or if the mediumcontains only nitrate nitrogen. The effect is specific for salicylicacid or acetyl salicylic acid; substituted or analogous compoundsare without effect.     

Absorption of Copper by Lemna as Influenced by Some Factors Which Nullify the Copper Effect on Flowering and Growth

The effect of copper on flowering and growth of Lemna paucicostata6746 and Lemna gibba G3 in a copper-containing medium is nullifiedby the addition of EDTA, ammonium ions or salicylic acid tothe medium or a decrease in its nitrate concentration. Thesefactors were examined for their effects on the absorption ofcopper by the plants. The addition of EDTA to the medium completelyinhibited the absorption of copper in both species, thus eliminatingthe copper effect. Ammonium ions also inhibited copper absorption,their effectiveness rising with their concentration. Loweringthe nitrate concentration in the medium nullified the coppereffect on flowering in L. paucicostata 6746, and the additionof salicylic acid to the medium also nullified the copper effectin L. gibba G3, both without affecting the absorption of copper. (Received June 7, 1982; Accepted August 27, 1982)     

The Role of Druse and Raphide Calcium Oxalate Crystals in Tissue Calcium Regulation in Pistia stratiotes Leaves

Abstract: Ca oxalate crystal formation was examined in Pistia stratiotes L. leaves during excess Ca and Ca-deficient conditions. Pistia produces druse crystal idioblasts in the adaxial mesophyll and raphide idioblasts in the abaxial aerenchyma. Raphide crystals were previously found to grow bidirectionally, and here we show that Ca is incorporated along the entire surfaces of developing druse crystals, which are coated with membrane-bound microprojections. Leaves formed on plants grown on 0 Ca medium have fewer and smaller druse crystals than leaves formed under 5 mM Ca ("control") conditions, while raphide crystal formation is completely inhibited. When plants were moved from 0 to 15 mM ("high") Ca, the size and number of crystals in new leaves returned to (druse) or exceeded (raphide) control levels. High Ca also induced formation of druse, but not raphide, crystals in differentiating chlorenchyma cells. When plants were transferred from 15 mM Ca to 0 Ca, young druse crystals were preferentially partially dissolved. Oxalate oxidase, an enzyme that degrades oxalate, increased during Ca deficiency and was localized to the crystal surfaces. The more dynamic nature of druse crystals is not due to hydration form as both crystal types are shown to be monohydrate. Part of the difference may be because raphide idioblasts have developmental constraints that interfere with a more flexible response to changing Ca. These studies demonstrate that excess Ca can be stored as Ca oxalate, the Ca can be remobilized under certain conditions, and different forms of Ca oxalate have different roles in bulk Ca regulation.     

植物草酸钙晶体的形成和功能

草酸钙晶体在植物中普遍存在,其形成是一种基本的生理过程。总结了目前对草酸钙晶体的生化、结构、形成、调控以及在植物生长发育过程中所起作用等方面的研究进展。     

Mucilage Cells, Calcium Oxalate Crystals and Soluble Calcium in Opuntia ficus-indica

The subcellular location of soluble calcium in parenchymatousand mucilage cells of Opuntia ficus-indica was determined histochemically.Soluble calcium was observed in crystal chambers containingcalcium oxalate on the membrane of the vesicles. Calcium wasalso present in the plasmalemma, in plasmodesmata, in cell walls,in mitochondria and in the vacuoles. Especially marked was thepresence of soluble calcium in vesicles free or fused with theplasmalemma. Little free calcium was observed in other cellcompartments. In the calcium economy of tissues the location of soluble calciumand the transport of calcium to and from mucilage cells to parenchymatouscells and calcium oxalate idioblasts will play a role. Chelationof calcium by mucilage or oxalate, which depends on pH, ionicstrength, etc., will be important in this respect. Opuntia ficus-indica, calcium oxalate, mucilage cells, transport of calcium     

The Effect of Drugs on the Growth of Lemna minor C.

Lemna minor fronds were grown for periods of between 90 and190 days in nutrient solutions to which non-lethal doses ofone of the following drugs were added: sodium nitrite, sodiumazide, brilliant green, proflavine, propamidine isethionate,and dinitrobutyl phenol. Over these periods there was no signof any increase in the growth-rate with time, such as mightbe expected if Lemna showed adaptation to drugs similar to thatfound in micro-organisms. ‘Changeover’ experimentsshowed that the growth-rate of fronds in a drug solution wasgenerally less if they had been previously exposed to that drugthan if they had not. The sensitivity of the fronds, inducedby growth in solutions containing sodium nitrite, persistedover five to six generations of growth in nitrite-free solutions.     

Calcium Oxalate Crystals in Developing Seeds of Soybean

Young developing soybean seeds contain relatively large amountsof calcium oxalate (CaOx) monohydrate crystals. A test for Caand CaOx indicated that Ca deposits and crystals initially occurredin the funiculus, where a single vascular bundle enters theseed. Crystals formed in the integuments until the embryo enlargedenough to crush the inner portion of the inner integument. Crystalsthen appeared in the developing cotyledon tissues and embryoaxis. All crystals formed in cell vacuoles. Dense bodies andmembrane complexes were evident in the funiculus. In the innerintegument, cell vacuoles assumed the shape of the future crystals.This presumed predetermined crystal mould is reported here forthe first time for soybean seeds. As crystals in each tissuenear maturity, a wall forms around each crystal. This intracellularcrystal wall becomes contiguous with the cell wall. Integumentcrystals remain visible until the enlarging embryo crushes theinteguments; the crystals then disappear. A related study revealedthat the highest percent of oxalate by dry mass was reachedin the developing +16 d (post-fertilization) seeds, and thendecreased during late seed maturation. At +60 d, CaOx formationand disappearance are an integral part of developing soybeanseeds. Our results suggest that Ca deposits and crystals functionallyserve as Ca storage for the rapidly enlarging embryos. The oxalate,derived from one or more possible metabolic pathways, couldbe involved in seed storage protein synthesis. Copyright 2001Annals of Botany Company Calcium, crystals, development, Glycine max, ovule, oxalate, seed, soybean     

Influence of Calcium and Magnesium on Manganese Absorption

Mutual effects between Mn, Ca, and Mg were studied during steady-state absorption experiments with excised barley roots. Calcium appeared to enhance the rate of Mn absorption; whereas, Mg had a highly depressive effect. The combination of both Ca and Mg was even more inhibitory to Mn absorption than Mg alone. Manganese had no effect on the usual negligible Ca absorption by this tissue, but effectively inhibited the absorption of Mg. Although divalent cation absorption from the Ca-Mg-Mn system was essentially nil, K absorption was greatly stimulated in the presence of these cations.These mutual effects and others reported in the literature are explained by the hypothesis that selectivity in ion absorption results from cation-induced conformational changes in the structure of the carrier molecule.