Evaluation of the utility of air-dried whole mounts for quantitative electron microprobe studies of platelet dense bodies.

A variety of electronmicroscope techniques have been used to examine how the air-drying process may affect the dense bodies in whole mounts of platelets. (a) Selected-area-diffraction and electron microprobe studies suggest that the air-drying process can result in the formation of crystalline precipitates of sodium chloride on grid films and platelets. However, no crystals were detected in the calcium-and-phosphorus-containing matrix of dense bodies. (b) Tilting studies show that dense bodies in human platelets are spherical or ellipsoidal in shape. Dense bodies in rabbit platelets, in contrast, appear flattened in a horizontal plane. (c) Human-platelet dense bodies probed with a small (20 nm diameter) spot vary widely in their peak/background ratios for calcium and phosphorus-a finding that suggests that the two elements may not be evenly distributed throughout the dense-body matrix. Nevertheless, when dense bodies are probed with a larger (200 nm diameter) spot, they do not appear to differ appreciably among themselves in their calcium or phosphorus content. The data suggest that with human platelets, air drying may be a preparative procedure which permits comparison by microprobe techniques of dense-body matrix content in platelet populations.     

Phosphorus requirements and optimum calcium/phosphorus ratio in the diet of mrigal Cirrhinus mrigala (Ham.) fingerlings

An experiment was conducted to investigate phosphorus requirements and the optimal calcium/phosphorus (Ca/P) ratio on growth and carcass tissue composition of mrigal Cirrhinus mrigala (c. 6 g). Five purified diets were formulated to contain Ca/P ratios of 1 : 0 (0.35 : 0), 1 : 1 (0.35 : 0.35), 1 : 2 (0.31 : 0.63), 1 : 3 (0.24 : 0.71), and 1 : 4 (0.19 : 0.75), respectively. Growth performance and feed conversion ratio of mrigal responded significantly (P < 0.01) to the Ca =0.19 : P = 0.75 diet. Carcass protein, lipid, and P percentage also increased significantly with the higher P level. Based on this study, it may be concluded under the given conditions that the optimum Ca : P ratio in mrigal feed is 0.19 : 0.75.     

Cytosolic free Ca2+ concentration and intracellular calcium distribution of Ca2+-tolerant isolated heart cells

The cytosolic free Ca2+ concentration of calcium-tolerant rat myocytes has been measured by the null point titration technique using arsenazo III as a Ca2+ indicator and digitonin to permeabilize the plasma membrane. The mean value obtained for 8 separate preparations was 270 +/- 35 nM. The distribution of releasable calcium between the mitochondrial and sarcoplasmic reticular compartments was measured by the successive additions of uncoupler and A23187 to cells pretreated with ruthenium red. The relative distribution of calcium in each pool was independent of the cell calcium content up to the maximum value of releasable calcium investigated (4.5 nmol/mg of cell dry weight) and was distributed in the approximate ratio of 2:1 in favor of the sarcoplasmic reticulum. The cells contained 1 nmol of calcium/mg of cell dry weight in a form nonreleasable by A23187, which was independent of the total cell calcium content as measured by atomic absorption spectroscopy. It is calculated that the calcium content of mitochondria in heart under physiological conditions is about 5 nmol/mg of mitochondrial protein. At this level, the mitochondria are likely to provide effective buffering of the cytosolic free Ca2+ concentration of quiescent heart cells. The corresponding intramitochondrial free Ca2+ is in a range above values needed to regulate the activity of Ca2+-dependent enzymes of the citric acid cycle in heart. The physiological calcium content of the sarcoplasmic reticulum in heart cells is estimated to be about 2.5 nmol/mg of cell dry weight, which is at least 5-fold greater than the amount of calcium release calculated to cause maximum tension development of cardiac muscle.     

无鱼粉低磷饲料中添加中性蛋白酶和植酸酶对建鲤生长及营养物质利用的影响

在无鱼粉低磷饲料中添加中性蛋白酶、中性植酸酶, 考察对建鲤(Cyprinus carpio var. Jian)生长、营养物质消化率和沉积率、血浆生化指标及肠道组织学的影响。配制含鱼粉5%和磷酸二氢钙1.5%的正对照饲料、无鱼粉饲料、无鱼粉低磷饲料(磷酸二氢钙1.0%)和在无鱼粉饲料中添加175 mg/kg蛋白酶, 在无鱼粉低磷饲料中添加175 mg/kg蛋白酶+300 mg/kg植酸酶的5组等蛋白饲料, 饲喂初始体重为(52.5±2.0) g的建鲤10周。结果表明: 对照组具有最高增重率和最低饲料系数(P<0.05), 无鱼粉饲料和无鱼粉低磷饲料组的增重率、蛋白质和磷沉积率、蛋白质和钙消化率均显著下降(P<0.05); 在无鱼粉饲料中添加蛋白酶后, 提高了建鲤增重率13.1%(P<0.05), 达到和对照组基本一致的水平; 显著提高了蛋白质、钙消化率和肠绒毛高度, 降低了饲料系数(P<0.05); 在无鱼粉低磷饲料中添加蛋白酶和植酸酶后, 显著提高了脂肪、蛋白质、磷沉积率和蛋白质、钙、磷消化率(P<0.05), 增加了前肠绒毛长度和隐窝深度(P<0.05), 提高了血浆磷浓度(P<0.05)。以上结果表明, 在全植物性蛋白饲料中添加蛋白酶, 在全植物蛋白的低磷饲料中同时添加蛋白酶和植酸酶可以促进建鲤生长, 提高对营养物质的消化率和沉积率, 促进肠道生长发育。     

Energy dispersive X-ray microanalysis of neurosecretory granules of mouse pituitary on fresh air-dried tissue spreads

Electron microscopy of fresh air dried spreads of unstained posterior lobe tissue from mouse pituitary disclosed neurosecretory granules. Each granule showed a seemingly homogeneous dense core surrounded by a halo and a bounding membrane. The area between granules in the cytoplasm was relatively well preserved. The energy dispersive X-ray microanalysis revealed peaks for sulfur, chlorine and potassium in two granules. The third granule displayed peaks for phosphorus and chlorine. These elements probably contribute to the high electron density of the granules. There was no peak for calcium, in contrast to the dense bodies of human blood platelets.     

Relationships among element contents in the internal jugular vein similar to the arteries

To elucidate compositional changes of the veins with aging, the authors investigated the relationships among element contents in the internal jugular veins, in which a higher accumulation of calcium and phosphorus occurred with aging. The subjects consisted of 15 men and 10 women, ranging in age from 40 to 98 yr. The element contents of the internal jugular veins were determined by inductively coupled plasma-atomic emission spectrometry. It was found that there were extremely significant direct correlations among the contents of calcium, phosphorus, magnesium, and sodium in the internal jugular vein. In addition, very significant direct correlations were also found both between zinc and either iron or silicon contents and between sulfur and iron contents in the vein. As calcium and phosphorus increased in the internal jugular vein, the mass ratios of Mg/Ca and Mg/P decreased gradually in the vein, whereas the mass ratio of Ca/P hardly decreased. These results indicated that with regard to both the relationships among the contents of calcium, phosphorus, and magnesium and the changes of the mass ratios of Mg/Ca and Mg/P, the internal jugular vein was very similar to the arteries.     

Physiologic and environmental factors influencing the calcium-to-tissue ratio in populations of three species of freshwater pulmonate snails

Summary A study of three species of freshwater pulmonate snails, Physa gyrina (11 populations), Physa integra (17 populations), and Helisoma anceps (18 populations) was carried out from 1973 to 1976, primarily in Michigan.The ratio of whole animal calcium content to tissue dry weight (Ca: tissue ratio) changes with age, but these changes are largely restricted to early growth and do not significantly affect individuals over 40 mg total dry weight, regardless of species.Parasitization by larval trematodes was found to have no significant effect on the Ca: tissue ratio in the populations examined regardless of species.Ca: tissue ratio of P. gyrina did not vary greatly between populations and showed a narrow range over a wide range of environmental calcium concentrations. Shell mass in P. gyrina is therefore either physiologically regulated in all populations (at a species specific constant level) or interpopulation variation is minimized by moderately high levels of gene flow between populations.There was no relationship between Ca: tissue ratio and environmental calcium for either P. integra or H. anceps over a wide range of snail and environmental calcium values. In both of the foregoing species, shell calcium content varied greatly between populations. This variation did not conform to any apparent geographic cline.In 7 of the population sites studied, P. integra and H. anceps coexist, and when these sites are listed from highest to lowest Ca: tissue ratios, the rank orders for the two species are nearly identical. This suggests that there is some environmental factor (possibly trophic conditions) at these localities that influences shell mass.In 8 other species of pulmonates briefly examined, differences in Ca: tissue ratio between populations of the same species were often as great as or greater than differences between species.While the patterns of shell mass and environmental calcium for these species are not unlike those previously reported, the proposed causal factors for these patterns are clearly distinct from those suggested for other freshwater pulmonates.     

Impact of season and sex on calcium and phosphorus content in the meat of roach (Rutilus rutilus L.) from the Brda River (Poland, Bydgoszcz)

The aim of this work was to compare the concentrations of calcium and phosphorus and Ca/P ratio in the meat of females and males of the roach (Rutilus rutilus L.) caught from the Brda River. The study involved 40 roach individuals caught in fall and spring (10 females and 10 males from each season). The muscle samples for analyses were taken from the large side muscle of the fish body above the lateral line. Ca concentrations were determined by atomic absorption spectrophotometry; P content was analyzed by the colorimetric method. Calcium concentration in the meat of analysed roach was higher in samples collected from fish caught in spring and equaled 1.82 g kg(-1) in females and 1.93 g kg(-1) in males. Values for individuals from autumn amounted to 0.83 and 1.10 g kg(-1), respectively. Statistically significant differences in calcium content were detected between individuals caught in different seasons, but samples taken from females and males caught within one season did not differ substantially. The mean value of P in the meat of analysed roach caught in spring was higher than in fish from autumn, and it was respectively 2.24 g kg(-1) in females and 2.30 g kg(-1) in males from spring, and 1.89 g kg(-1) in the tissue of females and 2.01 g kg(-1) in males in fish from autumn. The ratio of calcium to phosphorus in the meat of analysed wild roach ranged from 0.43:1 to 0.82:1. A negative and statistically significant correlation between Ca and P concentrations was found in the meat and the body length of analysed roach from the Brda River.     

Calcium,phosphorus, calcium-phosphorus ratio in rib bone of healthy humans

Calcium and phosphorus concentrations as well as the Ca/P ratio were estimated in intact rib bone samples from healthy humans, 37 women and 45 men, aged 15–55 yr. For Ca and P concentration measurements, instrumental neutron activation analysis was used. The mean values (mean±SD) for the investigated parameters were 19.3±4.5% of dry bone weight, 8.42±2.14% of dry bone weight, and a ratio of 2.33±0.34, respectively. Statistically significant differences for the above parameters were not observed to be related either to age or sex. The mean values for Ca, P, and the Ca/P ratio were within a very wide range of published data and close to their medians. The individual variation for the Ca/P ratio in rib bone from healthy humans was lower than those for Ca and P taken separately. An indication is that the specificity of the Ca/P ratio improves upon that for Ca and P concentrations and may be more reliable in the diagnosis of bone disorders.     

Possible regulation of phospholipase C activity in human platelets by phosphatidylinositol 4',5'-bisphosphate

Phospholipase C from human platelets was found to catalyze the Ca2+-dependent degradation of phosphatidylinositol (PI), phosphatidylinositol 4'-phosphate (DPI), and phosphatidylinositol 4',5'-bisphosphate (TPI) at Ca2+ concentrations from 150 microM to 5 mM. Both DPI and TPI inhibited the hydrolysis of [2-3H]inositol-labeled PI (250 microM) in a concentration-dependent manner. The use of DPI and TPI from beef brain, both of which have fatty acid compositions different from that of soybean PI, permitted an assessment of the inhibitory effect of polyphosphoinositides on the hydrolysis of PI by phospholipase C. Fatty acid analysis of the diacylglycerols formed demonstrated that DPI and TPI, when incubated in mixture with PI, were competitive substrates for PI hydrolysis. Increasing the DPI/PI ratio from 0 to 0.3 caused a shift in the degradation of PI to DPI without greatly affecting the formation of 1,2-diacylglycerol. TPI alone, or in mixture with PI, was a poor substrate for phospholipase C. Increasing the TPI/PI ratio from 0 to 0.21, on the other hand, inhibited both PI degradation (greater than or equal to 95%) and overall formation of 1,2-diacylglycerol (greater than or equal to 82%). Kinetic analysis revealed that TPI acts as a mixed-type inhibitor with a Ki of about 10 microM. The Ka for Ca2+ in PI hydrolysis was profoundly increased from 5 to 180 microM when TPI (36 microM) was included with PI (250 microM). Optimum PI degradation under these conditions was only attained when the calcium concentration approached 4 mM. Analysis of phospholipids from unstimulated human platelets from five different donors revealed DPI/PI and TPI/PI ratios of 0.42 and 0.16, respectively. These findings, combined with the observed inhibition of PI hydrolysis by TPI at a TPI/PI ratio of 0.16, would suggest that in unstimulated platelets phospholipase C activity may be inhibited by greater than or equal to 75%. Changes in 33P-prelabeled phospholipids of intact platelets upon stimulation with thrombin indicated a transient decline in 33P label of both TPI and DPI (15 s) followed by an increase in [33P]phosphatidic acid but no change in [33P]PI. The finding that DPI is selectively degraded by phospholipase C in mixture with PI at DPI/PI ratios determined to be present in unstimulated platelets indicates that DPI may be more important than PI in the formation of 1,2-diacylglycerol which is believed to serve as precursor of arachidonic acid for thromboxane biosynthesis. Furthermore, the results suggest that in human platelets TPI may serve as modulator for the formation of 1,2-diacylglycerol from inositol phospholipids.     

饲料钙磷含量和钙磷比对生长期大鼠体重增长与骨骼发育的影响

目的研究饲料中不同的钙磷含量和钙磷比对生长期实验大鼠体重及骨骼发育的影响。方法采用完全随机化设计方案,取1月龄（100±10）g清洁级Wistar雄性大鼠70只,随机分成7组,每组10只,饲喂7种不同钙磷含量的饲料。自由采食,饮用去离子水,试验期42 d。各组于实验开始和结束时称重。试验结束后,处死动物并分离一侧胫骨和股骨用于实验指标的检测。结果当保持饲料中钙或者磷中的一种含量不变的情况下,调整另一种的含量即改变钙磷比例时,1.2∶1的正常钙磷比例组生长期实验大鼠增重及骨骼发育要明显好于0.4∶1的低钙磷比例组和4∶1的高钙磷比例组（P〈0.05）,并且当保持饲料中钙磷比例不变时,即使在低钙低磷和高钙高磷进食水平下,正常钙磷比例组大鼠增重及骨骼发育都较好,但低钙磷比例组和高钙磷比例组大鼠增重及骨骼发育则由于饲料中钙磷含量的变化波动较大（P〈0.05）。结论饲料中钙和磷需按比例添加,如果两者绝对含量相差过大就会影响到动物的增重及骨骼发育,本实验证明饲料钙磷比为1.2∶1时生长期实验大鼠增重及骨骼发育较好。     

Influence of low dietary calcium during pregnancy and lactation on zinc levels in maternal blood and bone in rats.

The effect of low dietary calcium on maternal zinc nutritional status was studied. Two groups of 6 adult female Wistar rats were fed during pregnancy and lactation with experimental diets containing either 0.2 g (LCa) or 0.6 g (NCa) of calcium/100 g. Both diets contained/100 g: 20.0 g protein (potassium caseinate), 3.5 mg Zn, 0.6 g P. A third group (n = 6) was fed a "stock diet" (SG), containing/100 g: 24.8 g protein, 1.5 g Ca, 0.6 g P, 11.6 mg Zn. Maternal blood samples were drawn from the tail before mating (To), at delivery (D) and at weaning (W); dams were sacrificed at weaning and the right femur was excised. Determinations (atomic absorption spectrometry) were: Zinc in red blood cells (RBC), Zn and Ca in ashed femur. The results (mean +/- SD) were: RBCZn (microg/mL) at To: 8.65 +/- 1.80, which did not change in the SG or in the NCa groups, but increased significantly in the LCa group (p < 0.001) (D: 18.20 +/- 4.63; W: 26.70 +/- 6.02), regarding To. Femur Zn (microg/100 mg) showed an increase (p < 0.001) in the LCa group (30.2 +/- 2.1) regarding both SG (25.3 +/- 0.7) and NCa groups (24.1 +/- 0.7). Femur Ca (mg/100 mg) decreased (p < 0.05) in the LCa group (19.2 +/- 0.9) regarding both SG (24.0 +/- 0.5) and NCa groups (21.4 +/- 0.7) and leading to a significant increase in Zn/Ca ratio (p < 0.001) in the LCa group. Therefore, dietary calcium deficiency during pregnancy and lactation would produce an increase of Zn utilization, reflected in the increase of maternal blood Zn levels and in femur Zn content.     

Human platelet dense granules contain polyphosphate and are similar to acidocalcisomes of bacteria and unicellular eukaryotes

Inorganic polyphosphate (polyP) has been identified and measured in human platelets. Millimolar levels (in terms of Pi residues) of short chain polyP were found. The presence of polyP of approximately 70-75 phosphate units was identified by 31P NMR and by urea-polyacrylamide gel electrophoresis of platelet extracts. An analysis of human platelet dense granules, purified using metrizamide gradient centrifugation, indicated that polyP was preferentially located in these organelles. This was confirmed by visualization of polyP in the dense granules using 4',6-diamidino-2-phenylindole and by its release together with pyrophosphate and serotonin upon thrombin stimulation of intact platelets. Dense granules were also shown to contain large amounts of calcium and potassium and both bafilomycin A1-sensitive ATPase and pyrophosphatase activities. In agreement with these results, when human platelets were loaded with the fluorescent calcium indicator Fura-2 acetoxymethyl ester to measure their intracellular Ca2+ concentration ([Ca2+]i), they were shown to possess a significant amount of Ca2+ stored in an acidic compartment. This was indicated by the following: 1) the increase in [Ca2+]i induced by nigericin, monensin, or the weak base, NH4Cl, in the nominal absence of extracellular Ca2 and 2) the effect of ionomycin, which could not take Ca2+ out of acidic organelles and was more effective after alkalinization of this compartment by the previous addition of nigericin, monensin, or NH4Cl. All of these characteristics of the platelet dense granules, together with their known acidity and high density (both by weight and by electron microscopy), are similar to those of acidocalcisomes (volutin granules, polyP bodies) of bacteria and unicellular eukaryotes. The results suggest that acidocalcisomes have been conserved during evolution from bacteria to humans.     

Extended X-ray absorption fine structure (EXAFS) studies on calcium in crystalline and amorphous solids of biological interest

Using synchroton radiation, the calcium K-edge extended x-ray absorption fine structure (EXAFS) for a number of calcium-containing solids of biological interest was measured. These included synthetic analogues of platelet dense bodies, rat tibia mineral, and synthetic bone-like calcium phosphates. The mean CaO distances in all of the solids examined were essentially the same. However, in contrast to the crystalline calcium solids studied, the dense body analogues showed sufficient structural disorder that CaP and CaCa atom pair contributions to the EXAFS spectra could not be observed. The absence of these second-shell contributions suggest that these analogues are truly amorphous rather than microcrystalline in structure. The EXAFS spectrum of the bone mineral was more similar to carbonate-apatite than to any of the other synthetic apatites studied.     

Impaired platelet activation in familial high density lipoprotein deficiency (Tangier disease)

ATP binding cassette transporter A1 (ABCA1) is involved in regulation of intracellular lipid trafficking and export of cholesterol from cells to high density lipoproteins. ABCA1 defects cause Tangier disease, a disorder characterized by absence of high density lipoprotein and thrombocytopenia. In the present study we have demonstrated that ABCA1 is expressed in human platelets and that fibrinogen binding and CD62 surface expression in response to collagen and low concentrations of thrombin, but not to ADP, are defective in platelets from Tangier patients and ABCA1-deficient animals. The expression of platelet membrane receptors such as GPVI, alpha2beta1 integrin, and GPIIb/IIIa, the collagen-induced changes in phosphatidylserine and cholesterol distribution, and the collagen-induced signal transduction examined by phosphorylation of LAT and p72syk and by intracellular Ca2+ mobilization were unaltered in Tangier platelets. The electron microscopy of Tangier platelets revealed reduced numbers of dense bodies and the presence of giant granules typically encountered in platelets from Chediak-Higashi syndrome. Further studies demonstrated impaired release of dense body content in platelets from Tangier patients and ABCA1-deficient animals. In addition, Tangier platelets were characterized by defective surface exposure of dense body and lysosomal markers (CD63, LAMP-1, LAMP-2, CD68) during collagen- and thrombin-induced stimulation and by abnormally high lysosomal pH. We conclude that intact ABCA1 function is necessary for proper maturation of dense bodies in platelets. The impaired release of the content of dense bodies may explain the defective activation of Tangier platelets by collagen and low concentrations of thrombin, but not by ADP.     

Elemental composition of <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis> under conditions of lake nutrient depletion

Electron probe X-ray microanalysis (XRMA) was used to determine the elemental composition of the blue-green alga, Microcystis aeruginosa, in a stratified freshwater lake during the late summer. Colonies of this alga were initially observed in mid-July, at a time when phosphorus concentration in the lake water had decreased to minimal levels (total P 0.04 mg l⁻¹). The P quota of these cells was high (mean concentration 132 mmol kg⁻¹ dry weight) with a cell P to lake water P concentration ratio of 10⁵. The elemental concentrations of Microcystis remained relatively stable throughout the sampling period (July–September), with mean cell concentrations of Mg, P, S and Ca showing no significant changes. Mean elemental ratios and the ratio of monovalent/divalent cations were also relatively constant (SE <10% mean). The pattern of cell elemental associations, determined by Factor and Pearson correlation analysis, was consistent throughout – with Mg, P, K and S forming a core tetrad of inter-correlated elements. The relative constancy of cell composition seen in Microcystis would be expected of an alga with a K-selection strategy. The continued high P quota over a period of nutrient depletion in lake water is consistent with the ability of this alga to sink to nutrient-rich lower regions of the water column.     

Heterogeneity of calcium compartmentation: Electron probe analysis of renal tubules

Summary The objective of this study has been to determine the intracellular localization of calcium in cryofixed, cryosectioned suspensions of kidney proximal tubules using quantitative electron probe X-ray microanalysis. Two populations of cells have been identified: 1) Viable cells, representing the majority of cells probed, are defined by their relatively normal K/Na concentration ratio of 41. Their measured Ca content is 4.1±1.4 (sem) mmol/kg dry wt in the cytoplasm and 3.1 ± 1.1 mmol/kg dry wt in the mitochondria, or an average cell calcium content of 3.8 mmol/kg dry wt. 2) Nonviable cells, defined by the presence of dense inclusions in their mitochondria and a K/Na concentration ratio of 1. The Ca content is 15±2 mmol/kg dry wt in the cytoplasm and 685±139 mmol/kg dry wt in the mitochondria of such cells. Assuming 25 to 30% of the cell volume is mitochondrial, the overall calcium content of such nonviable cells is 210 mmol/kg dry wt. The presence of these inclusions in 4 to 5% of the cells would account for the average total Ca content measured in perchloric acid extracts of isolated proximal tubule suspensions ( 18 nmol/mg protein or 12.6 mmol/kg dry wt). Whole kidney tissues display a large variability in toal Ca content (4.5 to 18 nmol/mg protein, or 3.4 to 13.5 mmol/kg dry wt), which could be accounted for by inclusion in 0 to 4% of the cells. The electron probe X-ray microanalysis (EPXMA) data conclusively demonstrate that thein situ mitochondrial Ca content of viable cells from the kidney, proximal tubule is low and support the idea that mitochondrial Ca may regulate dehydrogenase activity but probably does not normally control cytosolic free Ca.     

Calcium stores in differentiated Dictyostelium discoideum: prespore cells sequester calcium more efficiently than prestalk cells

Dictyostelium discoideum pseudoplasmodia exhibit a gradient of the cytosolic free Ca2+-concentration ([Ca2+]i) along their anterior-posterior axis involved in cell-type specific differentiation. [Ca2+]i is high in prestalk and low in prespore cells. We determined the content and localization of calcium and other elements in cryosectioned cells of pseudoplasmodia and fruiting bodies by X-ray microanalysis. Granular stores rich in Ca, Mg and P were identified. Average Ca was higher in prespore than prestalk granules (225vs 111 mmol/kg dry weight). Total Ca stored in granules was also higher in prespore than prestalk cells. The amount of P and S in granules differed between the two cell types indicating different store composition. In spores mean granular Ca was 120 mmol/kg dry weight. Stalk cells had smaller granules with 360 mmol Ca/kg dry weight. Complementary to microanalysis, vesicular Ca2+-fluxes were studied in fractionated cell homogenates. The rate of Ca2+-uptake was higher in pellet fractions of prespore than prestalk amoebae (4.7 vs 3.4 nmol/min x mg). Ca2+-release was greater in supernatant fractions from prestalk than prespore cells (16.5vs 7.7 nmol/10(8)cells). In summary, prestalk and prespore cells possess qualitatively different, high-capacity stores containing distinct amounts of Ca and probably being involved in regulation of the anterior-posterior [Ca2+]i-gradient.     

Effect of lipid composition on the calcium/adenosine 5'-triphosphate coupling ratio of the Ca2+-ATPase of sarcoplasmic reticulum

The Ca2+-ATPase of sarcoplasmic reticulum was purified and depleted of proteolipids by solubilization in Triton X-100 and by fractionation on a DE-52 column. The protein reconstituted by deoxycholate-cholate dialysis at low lipid to protein ratios (2-5 mg of lipid/mg of protein), with either dioleoylphosphatidylethanolamine or monogalactosyldiglyceride, exhibited high initial rates of ATP-dependent Ca2+ uptake [300-900 nmol min-1 (mg of protein)-1] and coupling ratios (Ca2+ transported/ATP hydrolyzed) up to 1.2. Ca2+-ATPase reconstituted with lipids of increasing degrees of methylation (dioleoylphosphatidylethanolamine, dioleoylmonomethylphosphatidylethanolamine, dioleoyldimethylphosphatidylethanolamine and dioleoylphosphatidylcholine) or increasing degrees of glycosylation (monogalactosyldiglyceride and digalactosyldiglyceride) revealed a progressive decrease in both ATP-dependent Ca2+-uptake and coupling ratios. The rate and extent of Ca2+ uptake decreased as the dioleoylphosphatidylethanolamine/dioleoylphosphatidylcholine or monogalactosyldiglyceride/dioleoylphosphatidylcholine molar ratios in the reconstituted vesicles were reduced. Vesicles reconstituted with high molar ratios of dioleoylphosphatidylethanolamine/dioleoylphosphatidylcholine or monogalactosyldiglyceride/dioleoylphosphatidylcholine and at a high lipid to protein ratio became leaky and released the Ca2+ accumulated inside the vesicles when the temperature of the incubation mixture was increased (e.g., from 20 to 37 degrees C).(ABSTRACT TRUNCATED AT 250 WORDS)     

The Effect of Age on 12 Chemical Element Contents in the Intact Prostate of Adult Men Investigated by Inductively Coupled Plasma Atomic Emission Spectrometry

The effect of age on 12 chemical element contents in intact prostate of 64 apparently healthy, 13-60-year-old men (mean age 36.5 years) was investigated by inductively coupled plasma atomic emission spectrometry. Mean values (M ± SΕΜ) for mass fraction (milligrams/kilogram, on dry weight basis) of Ba, Ca, Cu, Fe, K, Mg, Na, P, S, Sr, and Zn were: Ba 1.18 ± 0.12, Ca 2,178 ± 160, Cu 10.7 ± 0.9, Fe 122 ± 5, K 12,530 ± 360, Mg 1,100 ± 70, Na 10,470 ± 320, P 7,580 ± 300, S 8,720 ± 180, Sr 1.85 ± 0.28, and Zn 782 ± 97, respectively. The upper limit of mean content of V was ≤0.22 mg/kg. A tendency of age-related increase in Ca, Fe, Na, and Zn mass fraction as well an increase in Zn/Ba, Zn/Ca, Zn/Cu, Zn/Fe, Zn/K, Zn/Mg, Zn/Na, Zn/P, Zn/S, and Zn/Sr ratios in prostate was observed. A significant positive correlation was seen between the prostatic zinc and Ca, Cu, Fe, Mg, Na, and P contents.