Changes In Calcium Content Research Articles

Calcium dynamics during the growth of Agaricus bisporus: implications for mushroom development and nutrition

BackgroundAgaricus bisporus (A. bisporus) is highly valued for its nutritional benefits and delicious taste, making it one of the most widely cultivated, highest yielding, and most consumed edible mushrooms worldwide. The yield and quality of A. bisporus were affected by its culture medium and environment. Among the culture base, the precise impact of calcium on A. bisporus cultivation and the dynamic changes in calcium concentration and chemical environment during the cultivation process remain unclear. This study aims to investigate the changes in calcium content and forms during the growth of A. bisporus and their implications for mushroom growth and nutrition.ResultsThrough the analysis of samples collected during the composting phase, mycelial development phase, and A. bisporus harvesting phase, the role of calcium in the growth process of button mushrooms is revealed. During the composting phase, the calcium content remains relatively stable, suggesting a consistent calcium source in the compost. The fermentation process shows a significant decrease in carbon content and an increase in oxygen content, indicating the degradation and oxidation of organic matter. In the mycelial development phase, both the cover soil and compost experience a decrease in calcium content, with a more pronounced reduction observed in the covering soil, indicating its primary role as an energy source for enzymatic activity and metabolic processes of the mycelium. During the A. bisporus harvesting phase, the changes in calcium, carbon, and oxygen content become less prominent, indicating a stable state of fruiting bodies growth that no longer requires a significant supply of organic matter.ConclusionsAnalysis of calcium forms reveals the presence of different calcium compounds, likely influenced by soil calcium sources, microbial activities, and mushroom metabolic byproducts. Calcium plays a crucial regulatory role in the growth and quality of A. bisporus. This study provides valuable insights into the significance of calcium in A. bisporus growth and offers theoretical guidance for optimizing mushroom production and quality improvement.Graphical

Changes in calcium content and expression of calcium sensor-related genes during sand pear (Pyrus prifolia) fruit cracking

Fruit cracking is a physiological disorder and results in significant economic losses. Calcium (Ca) plays important roles in the pear fruit cracking process, however, the underlying molecular mechanism of fruit cracking induced by Ca is poorly understood. In the present study, using cracking susceptible pear genotype ‘4–5–73′, we investigated the changes in Ca content and Ca sensors-related gene expression in the peel and flesh samples of cracked and non-cracked fruit. Cracking symptoms started to appear on the peel at 9 weeks after anthesis (WAA), and the total cracking rate gradually increased during fruit development until 15 WAA. During the early fruit cracking period (9 to 12 WAA), the Ca content in the peel and flesh of cracked fruit was lower than that of non-cracked fruit. Transcriptome sequencing indicated that 17 Ca sensors-related genes were differentially expressed in cracked and non-cracked fruit peel at 13 WAA. Among them, PpCML11 displayed higher expression in the peel and flesh of cracking fruit than that of non-cracked fruit. In addition, a positive correlation was observed between the PpCML11 expression level and the Ca content in the flesh of non-cracked fruit. Taken together, the present study suggests that PpCML11 might be involve in the sand pear flesh development process, and could play an important role in response to biotic stress after fruit cracking.

CML8 and GAD4 function in (Z)–3–hexenol–mediated defense by regulating γ–aminobutyric acid accumulation in Arabidopsis

(Z)–3–hexenol, a small gaseous molecule, is produced in plants under biotic stress and induces defense responses in neighboring plants. However, little is known about how (Z)–3–hexenol induces plant defense–related signaling. In this study, we uncovered how (Z)–3–hexenol treatment enhances plant resistance to insect attacks by increasing γ–aminobutyric acid (GABA) contents in Arabidopsis leaves. First, (Z)–3–hexenol increases the intracellular content of calcium as secondary messenger in Arabidopsis leaf mesophyll cells. Both intracellular and extracellular calcium stores regulate changes in calcium content. Then, CML8 and GAD4 transmit calcium signaling to affect (Z)–3–hexenol induced GABA content and plant resistance. Herein, CML8 interaction with GAD4 was examined via yeast two–hybrid assays, firefly luciferase complementation imaging, and GST pull–down assays. These results indicate that (Z)–3–hexenol treatment increased the GABA contents in Arabidopsis leaves based on CML8 and GAD4, thus increasing plant resistance to the insect Plutella xylostella. This study revealed the mechanism of activating plant insect defense induced by (Z)–3–hexenol, which guides the study of volatiles as biological pest control.

Bax inhibitor 1 inhibits vascular calcification in mice by activating optic atrophy 1 expression

To investigate the effects of Bax inhibitor 1 (BI- 1) and optic atrophy protein 1 (OPA1) on vascular calcification (VC). Mouse models of VC were established in ApoE-deficient (ApoE-/-) diabetic mice by high-fat diet feeding for 12 weeks followed by intraperitoneal injections with Nε-carboxymethyl-lysine for 16 weeks. ApoE-/- mice (control group), ApoE-/- diabetic mice (VC group), ApoE-/- diabetic mice with BI-1 overexpression (VC + BI-1TG group), and ApoE-/- diabetic mice with BI-1 overexpression and OPA1 knockout (VC+BI-1TG+OPA1-/- group) were obtained for examination of the degree of aortic calcification using von Kossa staining. The changes in calcium content in the aorta were analyzed using ELISA. The expressions of Runt-related transcription factor 2 (RUNX2) and bone morphogenetic protein 2 (BMP-2) were detected using immunohistochemistry, and the expression of cleaved caspase-3 was determined using Western blotting. Cultured mouse aortic smooth muscle cells were treated with 10 mmol/L β-glycerophosphate for 14 days to induce calcification, and the changes in BI-1 and OPA1 protein expressions were examined using Western blotting and cell apoptosis was detected using TUNEL staining. ApoE-/- mice with VC showed significantly decreased expressions of BI-1 and OPA1 proteins in the aorta (P=0.0044) with obviously increased calcium deposition and expressions of RUNX2, BMP-2 and cleaved caspase-3 (P= 0.0041). Overexpression of BI-1 significantly promoted OPA1 protein expression and reduced calcium deposition and expressions of RUNX2, BMP-2 and cleaved caspase-3 (P=0.0006). OPA1 knockdown significantly increased calcium deposition and expressions of RUNX2, BMP-2 and cleaved caspase-3 in the aorta (P=0.0007). BI-1 inhibits VC possibly by promoting the expression of OPA1, reducing calcium deposition and inhibiting osteogenic differentiation and apoptosis of the vascular smooth muscle cells.

Anti-echinococcal effect of verapamil involving the regulation of the calcium/calmodulin-dependent protein kinase II response in vitro and in a murine infection model

BackgroundEchinococcosis, which is caused by the larvae of cestodes of the genus Echinococcus, is a parasitic zoonosis that poses a serious threat to the health of humans and animals globally. Albendazole is the drug of choice for the treatment of echinococcosis, but it is difficult to meet clinical goals with this chemotherapy due to its low cure rate and associated side effects after its long-term use. Hence, novel anti-parasitic targets and effective treatment alternatives are urgently needed. A previous study showed that verapamil (Vepm) can suppress the growth of Echinococcus granulosus larvae; however, the mechanism of this effect remains unclear. The aim of the present study was to gain insight into the anti-echinococcal effect of Vepm on Echinococcus with a particular focus on the regulatory effect of Vepm on calcium/calmodulin-dependent protein kinase II (Ca2+/CaM-CaMKII) in infected mice.MethodsThe anti-echinococcal effects of Vepm on Echinococcus granulosus protoscoleces (PSC) in vitro and Echinococcus multilocularis metacestodes in infected mice were assessed. The morphological alterations in Echinococcus spp. induced by Vepm were observed by scanning electron microscopy (SEM), and the changes in calcium content in both the parasite and mouse serum and liver were measured by SEM-energy dispersive spectrometry, inductively coupled plasma mass spectrometry and alizarin red staining. Additionally, the changes in the protein and mRNA levels of CaM and CaMKII in infected mice, and in the mRNA levels of CaMKII in E. granulosus PSC, were evaluated after treatment with Vepm by immunohistochemistry and/or real-time quantitative polymerase chain reaction.ResultsIn vitro, E. granulosus PSC could be killed by Vepm at a concentration of 0.5 μg/ml or higher within 8 days. Under these conditions, the ultrastructure of PSC was damaged, and this damage was accompanied by obvious calcium loss and downregulation of CaMKII mRNA expression. In vivo, the weight and the calcium content of E. multilocularis metacestodes from mice were reduced after treatment with 40 mg/kg Vepm, and an elevation of the calcium content in the sera and livers of infected mice was observed. In addition, downregulation of CaM and CaMKII protein and mRNA expression in the livers of mice infected with E. multilocularis metacestodes was found after treatment with Vepm.ConclusionsVepm exerted a parasiticidal effect against Echinococcus both in vitro and in vivo through downregulating the expression of Ca2+/CaM-CaMKII, which was over-activated by parasitic infection. The results suggest that Ca2+/CaM-CaMKII may be a novel drug target, and that Vepm is a potential anti-echinococcal drug for the future control of echinococcosis.Graphical

Selective dopamine receptor 4 activation mediates the hippocampal neuronal calcium response via IP3 and ryanodine receptors

Intracellular calcium is a key factor in most cellular processes, including cell growth, differentiation, proliferation and neurotransmitter release. Dopamine (DA) mediates synaptic transmission by regulating the intracellular calcium content. It is not clear, however, which specific subunit of the DA receptor contributes to DA modulation of intracellular calcium content changes. Through the traditional technique of Fura-2 calcium imaging, this study demonstrated that the DA can induce transient calcium in cultured hippocampal neurons and that this response can be mimicked by a selective dopamine receptor 4 (DR4) agonist PD168077 (PD). PD-induced calcium transience can be blocked by a calcium chelator, such as BAPTA-AM, or by pre-treatment of neurons with thapsigargin, a IP3 receptor antagonist, or a micromolar concentration of ryanodine, a ryanodine receptor (RyR) antagonist. However PD-induced calcium transience cannot be blocked by pre-treatment of neurons with a free-calcium medium or a cocktail of NMDA receptor, L-type calcium channel and alpha7 nicotinic acetylcholine receptor blockers. These results indicate that the calcium response induced by DR4 activation is mainly through activation of IP3 receptor in internal stores, which is likely to contribute to the DA modulation of synaptic transmission and cognitive function.

Effects of various diets on the calcium and phosphorus composition of mealworms (Tenebrio molitor larvae) and superworms (Zophobas morio larvae).

OBJECTIVE To evaluate whether the nutritive quality of Tenebrio molitor larvae and Zophobas morio larvae, which are commonly cultured as live food sources, is influenced by 4 commercially available diets used as nutritional substrates; identify which diet best improved calcium content of larvae; and identify the feeding time interval that assured the highest calcium intake by larvae. ANIMALS 2,000 Zophobas morio larvae (ie, superworms) and 7,500 Tenebrio molitor larvae (ie, mealworms). PROCEDURES Larvae were placed in control and diet treatment groups for 2-, 7-, and 10-day intervals. Treatment diets were as follows: wheat millings, avian hand feeding formula, organic avian mash diet, and a high-calcium cricket feed. Control groups received water only. After treatment, larvae were flash-frozen live with liquid nitrogen in preparation for complete proximate and mineral analyses. Analyses for the 2-day treatment group were performed in triplicate. RESULTS The nutrient composition of the high-calcium cricket feed groups had significant changes in calcium content, phosphorus content, and metabolizable energy at the 2-day interval, compared with other treatment groups, for both mealworms and superworms. Calcium content and calcium-to-phosphorus ratios for larvae in the high-calcium cricket feed group were the highest among the diet treatments for all treatment intervals and for both larval species. CONCLUSIONS AND CLINICAL RELEVANCE A 2-day interval with the high-calcium cricket feed achieved a larval nutrient composition sufficient to meet National Research Council dietary calcium recommendations for nonlactating rats. Mealworm calcium composition reached 2,420 g/1,000 kcal at 48 hours, and superworm calcium composition reached 2,070g/1,000 kcal at 48 hours. These findings may enable pet owners, veterinarians, insect breeders, and zoo curators to optimize nutritive content of larvae fed to insectivorous animals.

Development of ready to drink calcium fortified shrimp soup in retortable pouches

The aim of the study was to develop ready to serve calcium fortified shrimp soup in retortable pouches. Shrimp soup was prepared from Indian white shrimp ( Fenneropenaeus indicus ) and thermal processed at 121, 115 and 110OC to an F0 value of 6. The calcium fortified soup was then compared with control samples. The effect of different process temperatures on quality was analysed. The samples processed at 110OC showed significantly higher (p≤0.05) cook value and 121.1 O C showed the least. All the pouches were found to be commercially sterile. The viscosity of soup was significantly higher (p≤0.05) in control packs compared to fortified soups. Significantly higher (p≤0.05) b* value was observed in fortified soup compared to control. Thermally processed calcium fortified shrimp soup was in acceptable condition during the storage period of 90 days at ambient temperature without any significant change in calcium content. Sensorily, the product processed at 121OC rated better compared to 115 and 110 O C.

In vitro toxicity of silver nanoparticles to kiwifruit pollen exhibits peculiar traits beyond the cause of silver ion release

The vast use of silver nanoparticles (AgNPs) mandates thorough investigation of their impact on biosystems at various levels. The cytotoxicity of PVP coated-AgNPs to pollen, the aploid male gametophyte of higher plants, has been assessed here for the first time. The negative effects of AgNPs include substantial decreases in pollen viability and performance, specific ultrastructural alterations, early changes in calcium content, and unbalance of redox status. Ag+ released from AgNPs damaged pollen membranes and inhibited germination to a greater extent than the AgNPs themselves. By contrast, the AgNPs were more potent at disrupting the tube elongation process. ROS deficiency and overproduction were registered in the Ag+- and AgNP-treatment, respectively. The peculiar features of AgNP toxicity reflected their specific modes of interaction with pollen surface and membranes, and the dynamic exchange between coating (PVP) and culture medium. In contrast, the effects of Ag+ were most likely induced through chemical/physicochemical interactions.

Content of macroelements in eggplant fruits depending on varied potassium fertilization

Eggplant fruits are abundant in potassium, the amount of which ranges from 200 to 600 mg K⋅100 g -1 FM, depending on a variety. They are also a rich source of phosphorus, magnesium, calcium, and iron. As there are no fertilization recommendations for eggplant cultivation under cover, this study been undertaken to evaluate the vegetable’s requirements. The aim was to test how the type and dose of potassium fertilizer influences nitrogen, phosphorus, calcium, and magnesium levels in eggplant fruits. The experiment on cv. Epic F1 eggplant was carried out in unheated polyethylene tunnel in 2004-2005. The eggplant was cultivated on peat subsoil in 10 dm3 capacity cylinders made of rigid plastic. The experiment was set up in a two-factor, completely randomized design. The influence of two factors was examined: I – type of potassium fertilizer (KCl, K 2 SO 4 , KNO 3 ), and II – potassium rate (8, 16, 24 g K⋅plant -1 ). Fruit samples for laboratory determinations were collected in mid-August, in the middle of fruiting stage. Fruits were harvested at the stage of technological maturity and the following were determined: N tot , P, K, Ca, Mg. The results were processed by variance analysis. Significantly higher total nitrogen and potassium concentrations in fruits of plants fertilized with potassium nitrate as compared to the other two fertilizer types were recorded. Increasing potassium doses, regardless the fertilizer type, considerably increased the element content in eggplant fruits and widened the K:Ca ratio value. The diversification of potassium fertilization did not have significant influence on phosphorus and magnesium concentrations in eggplant fruits. No significant changes in calcium content in fruits were observed when applying potassium sulfate or nitrate, while higher potassium chloride rates significantly decreased the concentration of this element in fruits.

Functional properties of milk protein concentrates: Emulsifying properties, adsorption and stability of emulsions

Aggregation of casein in milk protein concentrates (MPCs) is altered by changes in calcium content. Emulsifying properties of MPCs and stabilities of emulsions formed with MPCs were investigated by examining emulsions formation, adsorption behaviours of proteins and emulsion microstructures. Compared with emulsions formed with higher calcium MPCs at a given protein concentration, emulsions formed with low calcium MPCs were finer, the total surface protein concentration was lower and the protein composition on the surface of the emulsion droplets was altered. Thus, the aggregation state of casein dominates the emulsifying capability of MPC products and the adsorption behaviours of proteins in MPCs. In low-calcium-MPC-stabilized emulsions, the stability of the emulsions decreased with an increase in the emulsion size at low protein concentrations and decreased with increasing protein concentration beyond a maximum level, suggesting that the protein state in low calcium MPCs may cause depletion flocculation in the emulsions.

Low-Level Laser Therapy Stimulates Mineralization Via Increased Runx2 Expression and ERK Phosphorylation in Osteoblasts

This study examined the effects of low-level laser therapy (LLLT) on osteoblasts via insulin-like growth factor I (IGF-I) signal transduction. Because orthodontic treatment is usually accompanied by bone formation, if bone formation can be promoted, the treatment and retention periods will be shorter. Recently, we reported the stimulatory effects of LLLT on bone formation. It was dependent on increased IGF-I, which plays an essential role in the anabolic regulation of bone metabolism. However, the signal transduction of IGF-I stimulated by LLLT was not elucidated. Mouse osteoblastic MC3T3-E1 cells were cultured with or without LLLT (0.96-3.82 J/cm(2)), and the expression of IGF-I and Runt-related transcription factor 2 (Runx2) and the phosphorylation of extracellular-signal-regulated kinase (ERK) were determined by using real-time PCR and Western blot analysis. LLLT at 1.91 J/cm(2) significantly increased the expression of IGF-I and Runx2 and of ERK phosphorylation. Cyclolignan picropodophyllin (PPP; an IGF-I receptor inhibitor) partly inhibited the LLLT-induced expression of these factors. Moreover, when conditioned medium from the LLLT (1.91 J/cm(2)) cells was added to the MC3T3-E1 culture, the calcium content in the mineralized nodules increased significantly. PPP or noggin [a bone morphogenetic protein (BMP) antagonist] partly inhibited the LLLT-induced change in calcium content, and the addition of both PPP and noggin inhibited most of the LLLT-induced change in calcium content. These results suggest that LLLT stimulates in vitro mineralization through increased IGF-I and BMP production, through Runx2 expression and ERK phosphorylation in osteoblasts.

The Changes of Calcium Contents in Food During The Process of Cooking (Part I)

The Changes of Calcium Contents in Food During The Process of Cooking (Part I)

Structure and functions of plant calcium-dependent protein kinases.

Calcium ions as second messengers play an essential role in many important cellular processes. In plants, transient changes in calcium content in the cytosol (calcium signatures) have been observed during growth, development and under stress conditions. Such diverse functions require many different calcium sensors. One of the largest and most differentiated group of calcium sensors are protein kinases, among them calcium-dependent protein kinases (CDPKs) which were identified only in plants and protists. CDPKs have a regulatory domain which is able to bind calcium ions. For regulation of CDPKs activities not only calcium ions but also specific phospholipids and autophosphorylation are responsible. CDPKs have many different substrates, which reflects the diversity of their functions. Potential protein substrates of CDPK are involved in carbon and nitrogen metabolism, phospholipid synthesis, defense responses, ion and water transport, cytoskeleton organization, transcription and hormone responses. Presently, participation of CDPKs in stress signal transduction pathways (e.g., cold, drought, high salinity, wounding) is intensively studied in many laboratories. An intriguing, but still not fully clarified problem is the cross-talk via CDPKs among different signaling pathways that enables signal integration at different levels and ensure appropriate downstream responses.

Dynamic Changes in the Calcium Content of Several Apple Cultivars During the Growing Season

Dynamic changes in calcium content were investigated in eight apple cultivars. The results showed that the calcium concentration in leaves and shoots increased with fruit development. The cultivars displayed only a small difference in the calcium concentration during the early stage of development, the difference became very significant at the late stage of development, especially in shoots. In shoots, for example, calcium content was highest in Starkrimson (19 638.6 mg kg −1) and lowest in Fuji (8 751.3 mg kg −1). Calcium concentration was highest in young fruits and was found to decrease with the growth of fruit, and was characterized by a dramatic drop at the rapid expansion stage. There was a significant difference among cultivars. Young Starkrimson fruits contained the highest calcium concentration of 506.52 mg kg −1 among cultivars tested, followed by Pink Lady and Fuji. The calcium concentration in mature fruits from high to low is as follows: Starkrimson, Sansa, Pink Lady, Senshu, Gala, Fuji, Red General and New Century. In this study, it was found that eight cultivars continuously assimilated calcium during the whole growing season, especially at the young stage when fruit took up 35–46% of total calcium. The calcium content in fruitlets was low in all cultivars; in the expansion stage, there was rapid absorption of about 30% of total calcium, whereas in the ripening fruit, content of calcium was reduced. The calcium accumulation increased with fruit growth in stalk, similar to that in fruit.

Changes to the dispersive characteristics of soils along an evolutionary slope sequence in the Vera badlands, southeast Spain: implications for site stabilisation

In dispersive marls near Vera, badland gullies are eroding into a previously stable matorral-covered landscape. This relatively recent activity was probably triggered by minor climatic or land-use change. In this landscape, Calvo-Cases and Harvey [Earth Surface Processes and Landforms 21 (1996) 725] argued that new gully-head slopes with differing aspect represent a sequence of progressive erosion. Using this interpretation as a basis, slope surface materials were explored for evidence of material (chemical) stabilisation by sampling along profiles positioned centrally on those slopes. The extent to which the inferred geomorphic sequence is paralleled by progressive changes in site geochemistry is considered. Crusts and subsoils differ significantly in terms of pH and Sodium Adsorption Ratio (SAR), but not calcium content. The crust is thus distinctive but not calcic, rather the pH differences suggest a process involving an organic agent, probably algae. Slope position was an important discriminant; taking SAR alone, differences between crusts and subsoils were not significant at the slope base but increased in significance with distance up the profile. Considering differences between the three profiles, the ‘middle’ profile had significantly higher SAR values both in the crust and at depth, than the other profiles, whereas ‘late’ slope subsoils and crusts taken alone are not dispersive (SAR<10), nor are the soils at the base of the other two profiles. Whilst pH increases systematically with SAR up all the profiles, crust pH vs. SAR ‘signatures’ progressively bunch when compared to those of the subsoils. It is inferred that surfaces loose dispersive status first, with subsequent subsoil stabilisation occurring at the slope base. Although the poor statistical fit on some of the pH/SAR relationships rules out a conclusive proof that these three profiles represent a progressive or ‘ergodic’ geochemical stabilisation sequence, the progressive changes in calcium content of crust and subsurface from profile to profile is statistically significant. From this perspective, calcium may be involved over the longer term in the reduction of surface dispersivity. The potential ‘stabilisation’ of this type of badland soil and surface is finally considered. Whereas Harvey [Harvey, A.M., 1982. The role of piping in the development of badlands and gully systems in southeast Spain. In: Bryan, R., Yair, A. (Eds.), Badland Geomorphology and Piping. Geobooks, Norwich, pp. 317–335] argues that site morphology suggests that geomorphological instability increases through time, the soil sequence suggests decreases in material dispersivity and consequently, surface autostabilisation. It is concluded that the concept of badland ‘stabilisation’ needs further clarification.

Relation between echinocytosis and erythrocyte calcium content in hemodialyzed uremic patients.

A rise in intracellular calcium concentration in erythrocytes has multiple effects on these cells. The purpose of this study was to determine the changes of calcium content in red blood cells (RBCs) and of echinocyte percentages in uremic patients during hemodialysis sessions. In 30 uremic patients under hemodialysis, the calcium content of RBCs and echinocyte percentages were determined in 3 blood samples collected at 0 min hemodialysis (prehemodialysis), 45 min hemodialysis, and 240 min hemodialysis (end hemodialysis) for a 4 h hemodialysis session. Calcium content of RBCs and echinocytes were also determined in 22 normal subjects (controls). The findings of the present study were that the mean values (+/-SD) of calcium content of RBCs in patients at 0 min hemodialysis, 45 min hemodialysis, and 240 min hemodialysis were 2.00 +/- 1.0, 2.66 +/- 0.87, and 1.62 +/- 0.66 microg/ml respectively and 0.65 +/- 0.07 microg/ml in controls. These values show that the calcium content of RBCs in uremic patients at 0 min hemodialysis, 45 min hemodialysis, and 240 hemodialysis was significantly higher than in controls (p < 0.0001), and that RBC calcium content at 45 min hemodialysis was significantly higher in comparison to that at 0 min hemodialysis (p < 0.001) and to that at 240 min hemodialysis (p < 0.0001), while that at 240 min hemodialysis was significantly lower than at 0 min hemodialysis (p < 0.05). The mean values (+/-SD) of echinocyte percentages in patients at 0 min hemodialysis, 45 min hemodialysis, and 240 hemodialysis were 11.93 +/- 6.18, 17.23 +/- 4.1, and 7.96 +/- 5.67% respectively, and in controls ranged from 0 to 1%. The values in uremic patients show a transient increase of echinocyte percentages at 45 min hemodialysis, which is significant in comparison to that at 0 min hemodialysis (p < 0.001) and to that at 240 min hemodialysis (p < 0.0001). Echinocyte percentages at 240 min hemodialysis were significantly lower to those at 0 min hemodialysis (p < 0.001). Correlation between calcium content of erythrocytes and echinocyte percentages shows a significantly positive relationship at 45 min hemodialysis (r = 0.368, p < 0.05) but no significant relationship at 0 min hemodialysis and 240 min hemodialysis. In conclusion, uremic patients under hemodialysis present with high calcium content in erythrocytes and abnormal erythrocytes like echinocytes. A rapid and transient increase of erythrocyte calcium is also accompanied by transient elevation of echinocytes in the first hour of hemodialysis (45 min hemodialysis), which returns after hemodialysis to lower than prehemodialysis levels.

Age-related changes of elements in the human articular disk of the temporomandibular joint.

To elucidate compositional changes of the articular disk (AD) of the temporomandibular joint (TMJ) by aging, elements of the ADs resected from 18 cadavers were determined by inductively coupled plasma atomic-emission spectrometry. It was found that calcium contents of ADs in TMJs increased progressively with aging, whereas the sulfur contents of the ADs decreased slightly with aging. Regarding the content of phosphorus, the contents increased progressively with aging. The study revealed that age-related changes of calcium contents in the ADs of TMJs were similar to those in women's pubic symphyses, but not those in intervertebral disks and menisci.

Developmental changes in calcium content of ultrastructurally distinct subcellular compartments of preimplantation human embryos.

The ultrastructural localization of mobilizable Ca2+ in different subcellular compartments of human oocytes and preimplantation embryos was studied using the potassium-pyroantimonate technique and transmission electron microscopy; the specificity was confirmed by chelation experiments and X-ray microanalysis. In unfertilized oocytes, Ca2+ was detected in small vesicles beneath the plasma membrane as well as in other forms of smooth endoplasmic reticulum (SER) and in mitochondria but not in cortical granules. In pronuclear zygotes and blastomeres of cleaving embryos, Ca(2+)-rich vesicles were no longer present close to the plasma membrane, and the entire periphery was poor in Ca(2+)-containing organelles which, however, were abundant in the perinuclear region. The uneven Ca2+ loading of SER and mitochondria from the pronuclear stage onwards suggests that Ca2+ release from both these types of organelle contributes to the embryonic Ca2+ signals. During mitosis, less Ca2+ was detected with organelles, but the antimonate reaction product was more abundant in the cytosol. These data suggest that, in addition to different forms of SER, mitochondria also act as a source of mobilizable Ca2+ in preimplantation human embryos. The previously described developmental and cell cycle related changes in the characteristics of Ca2+ signals are associated with the redistribution and structural reorganization of these organelles.

Changes in calcium contents during melon ( Cucumis melo L.) fruit development

Melon ( Cucumis melo L. var. Maestro) plants were grown in soilless culture under plastic tunnels. A 17-day calcium deficiency was applied to plants bearing fruits of various ages (between 3 and 20 days after anthesis) and the fruits were harvested between 20 and 37 days after anthesis. The calcium concentrations in the fruits of the control plants decreased between 20 and 37 days after anthesis (ripe fruit): the decrease in calcium concentration was steady in the flesh whereas it occurred only in the last few days in the rind. Calcium accumulation within the fruit occurred quite early: 80% of calcium present in ripe fruit was already there 20 days after anthesis. Thus, a calcium deficiency applied to 20-day-old fruits had no significant effect on the calcium content at the time of harvest. In contrast, younger fruits were very susceptible to calcium deficiency and displayed a significant decrease in calcium content.