Additional Calcium Source Research Articles

Optimization of gluten-free cake formulation by replacement of rice flour and baking powder with different levels of eggshell powder using response surface methodology

AbstractThe shell and membrane of the egg constitute approximately 11% of the whole egg and is an important food industry waste. Eggshells can be used as an additional source of calcium to the diet because of their low cost and high bioavailability. This study aimed to design and produce the optimum formulation for the gluten-free cake using eggshell powder as rice flour and baking powder replacer by Face-Centered Composite Design. According to the results, it was determined that the optimized formulation should contain 9.85% eggshell powder as a rice flour replacer and 32.78% eggshell powder as a baking powder replacer to obtain a gluten-free cake with a desirable profile in terms of hardness, specific volume, color ($${\text{L}}_{{{\text{crust}}}}^{*}$$ L crust ∗ and $${\text{L}}_{{{\text{crumb}}}}^{*}$$ L crumb ∗ values), ash content, calcium content, and overall acceptability. The gluten-free cake with eggshell powder obtained was characterized as a product rich in calcium, high in ash content, high in specific volume, with a brighter colour and good sensory acceptability. Also, the proximate properties of the gluten-free cake produced with the optimum formulation were also reported. These findings show for the first time that eggshell powder can be used as a rice flour and a baking powder replacer for the formulation of gluten-free cake.

Poly(Aspartic Acid) Promotes Odontoblast-like Cell Differentiation in Rat Molars with Exposed Pulp.

Mechanical pulp exposure was performed in the upper molars of 56 Wistar rats, randomly divided as follows (n = 14): control (no treatment); MTA group-pulp capping with mineral trioxide aggregate (MTA Angelus); pAsp group-application of 20 μL of pAsp solution (25 mg·mL-1); MTA+pAsp group-application of MTA mixed with pAsp (5:1 by mass). Animals were euthanized after 7 or 21 days. Histological sections were submitted to hematoxylin-eosin and Brown and Brenn staining and immunohistochemical analysis for osteopontin (OPN) and dentin matrix protein 1 (DMP 1). At 7 days, an acute inflammatory infiltrate and the presence of disorganized mineralized tissue were observed in all groups. At 21 days, the quality and thickness of the reparative dentin in treated groups were superior to the control, and bacterial contamination was observed in two MTA-pAsp specimens. While all treated groups showed intense immunostaining for OPN at 21 days, only the pAsp group expressed DMP 1, indicating the presence of fully differentiated odontoblast-like cells. Poly(aspartic) acid promoted dentin regeneration in rat molars in the absence of an additional calcium source and may be an alternative to MTA as a pulp-capping agent.

Enamel remineralisation and efficacy of remineralising agents: A Review

To review current information and technology for tooth remineralisation. Searches in the "Scopus" and "Web ofKnowledge" databases, which date back to 1970s. English was the only language allowed. The study incorporatedboth original research and previously published reviews. Tooth remineralisation agents, products, and treatmentshave progressively increased in recent years due to the growing awareness of the significance of good dentalhealth among patients and general community. Both in vitro and in vivo tooth remineralisation anddemineralization research have been published regularly. Theobromine has been proposed as an effectiveremineralising agent and a viable alternative to fluorides in recent years. According to research, fluoride treatmentscan prevent dental enamel demineralization and remineralisation. An increasing number of products containingcalcium salts or calcium-based compounds have been added to oral care products to boost the delivery andretentiveness of fluoride into teeth. Calcium salts or materials, which provide an additional source of calcium,may aid in accelerating enamel remineralisation or hinder demineralization processes. These effects are possiblebecause calcium is a mineral. A new area of research inspired by bioactive materials for bone repair andregeneration, bioglass, in particular calcium silicates, shows promise for improving enamel health and is one typeof bioglass that contains calcium silicate.

EFFECT OF CALCIUM ADDITION ON THE PROPERTIES AND MICROSTRUCTURE OF FLY ASH-BASED GEOPOLYMERS FOR APPLICATIONS IN SUSTAINABLE CONSTRUCTIONE

The article describes a study of the physical and mechanical properties and microstructure of geopolymer materials for construction based on low-calcium fly ash from CHP-22, depending on the type of activator, temperature and humidity conditions of curing and the introduction of an additional source of calcium (CaO) in the amount of 10, 15 and 20 wt. %. It was found that for the fly ash under study, the most promising type of activator is a sodium silicate solution with a silicate modulus SiO2 / Na2O = 1; the preferred curing mode is steam treatment at 90 °C. With the introduction of 15 % CaO into the geopolymer mixture, it was possible to increase the compressive strength by more than 2.5 times (to 38 МПа), the open porosity decreased from 24 to 7 %, and the water absorption from 15 to 3 %. However, a further increase in the CaO content leads to degradation of properties due to a significant reduction in the setting time of the raw mixture.

Curd paste for calcium metabolism correction

Calcium is one of critical elements influencing metabolic processes in the body. It is an essential ingredient of bone tissue. Once its amount in the blood is insufficient, bone calcium resorption occurs that leads to osteoporosis development. The goal of this publication is to demonstrate feasibility of introducing curd paste supplemented with additional source of calcium in the diet of population for improving antioxidant defense and strengthening bone tissue. This publication summarizes our previous research on developing calcium-enriched dairy products for osteoporosis prevention. It is supplemented with new data on significance of separate ingredients of curd paste, including whey protein antioxidant properties; ability of calcium and potassium salts as counterparts of strontium and cesium to reduce radionuclides absorption from gastrointestinal tract and others. Based on natural ingredients and targeted the mass consumer, Vitacalcin paste can provide a solid competition to domestic and foreign products. Formulations and technological process for curd paste Vitacalcin enriched with calcium from either eggshell powder or calcium alginate, and functional additives, such as nettle or garlic, has been developed. Products have been tested in animals and patients of Central Institute of Traumatology with primary form of osteoporosis. Bioavailability of calcium is more pronounced when consuming pastes with ESP and sulfur-containing additive. In animal model, bone mass increase has been observed after 28 days of curd paste consumption. Patients with pronounced osteoporosis consuming 200 g of curd paste daily for 30 days have demonstrated increased serum calcium level. It has been shown that the new product has a positive impact on bone tissue formation, and possesses antioxidant properties. As a result of the research, technical documentation for Vitacalcin curd paste is developed. The Institute of Nutrition recommends this product for osteoporosis prevention and correction of calcium balance.

Low cost and sustainable repair material made from alkali-activated high-calcium fly ash with calcium carbide residue

In this work, a study on a low cost and sustainable repair material made from alkali-activated high-calcium fly ash (FA) incorporated with calcium carbide residue (CCR) is reported. The FA was partially replaced with CCR (additional calcium source) at the dosages of 0%, 10%, 20%, and 30% by weight of binder. The alkaline activators were sodium silicate (SS) and sodium hydroxide (SH) solutions with SS-to-SH ratios of 1.0, 1.5, 2.0 and 2.5 by weight. The alkali activator liquid/solid binder (FA + CCR) ratio of 0.60 and curing at 25 °C (ambient temperature) were used for all mixes. Experimental results showed that the setting time of mortar decreased with increases of CCR replacement level and SS-to-SH ratio, whereas the strength development increased. XRD and SEM results demonstrated that an optimum level of CCR replacement and SS-to-SH ratio resulted in the additional formation of C-S-H (calcium silicate hydrate) that coexisted with N-A-S-H (sodium aluminosilicate hydrate). The bond strength of the alkali-activated mortar with concrete substrate was also improved. The setting time and strengths complied with the requirement of the ASTM standards for repair materials and thus indicated its suitable as an alternative repair material in terms of environmentally friendly and low cost.

Influence of supplementary cementitious materials on hydration and microstructure development of concrete

Several supplementary cementitious materials (SCM) were blended with Portland cement clinker in order to produce more sustainable binders. The use of such materials, where no additional clinkering process is involved, leads to a significant reduction in CO2 emissions per ton of cementitious materials (grinding, mixing and transport of concrete and use very little energy compared to the clinkering process) and is a means to (re)utilize by-products of industrial manufacturing processes. Fly ash, for example, is the most commonly used supplementary cementitious material. The blending of Portland cement with fly ash results in the reduction of the total amount of portlandite in the hydrated mixture [1-4], somewhat less pronounced than for silica fume as: the reactivity of fly ash is very limited and as the CaO in the fly ash is an additional source of calcium [5]. Since fly ash particles are more spherical in shape than cement particles, workability and pumpability can be improved, by adding fly ash, also, fly ashes can cause low early strengthening. In this paper, the effects of Fly-ash as SCM’s on microstructure and hydration kinetics are studied.

Development of fish soups technology with using food supplements from fish remaining feedstock

This article describes the technology for the whiting cream puree production using food supplement from fish remaining feedstock. The sociological survey results and analysis of consumer preferences of Murmansk population regarding enriched food are presented, the degree of public awareness of the food effect quality to the general health state, interest in a balanced diet to maintain health is studied, and the population attitude to the enrichment of traditional products with natural nutrients such as like calcium and phosphorus. A basic recipe for puree soup has been developed and has been optimized by computer simulation. To search for a near-optimal mineral composition and consistency of soup, has been used the planning and experiment method with processing non-linear regression of the results by the Datafit 9.0 computer program. The chemical composition experimental results of the puree soup and its caloric content are presented, and the content of calcium and phosphorus in one portion is determined with analysis of the results. It is ascertained that the course belongs to high-protein, medium-calorie and is a source of calcium and phosphorus. Optimal for the absorption and assimilation of the ratio of phosphorus to calcium in the diet according to various sources ranges from 1: 1 to 1: 1.5. The ratio of phosphorus to calcium in haddock bones flour is 1: 1.3, in the prepared soup-puree 1: 1, and, therefore, can be considered optimal. The prepared course has excellent organoleptic characteristics, high nutritional value and can be used as an additional source of calcium and phosphorus.

Calcium Microdomain Formation at the Perisynaptic Cradle Due to NCX Reversal: A Computational Study.

It has recently been proposed using a multi-compartmental mathematical model that negatively fixed charged membrane-associated sites constrain the flow of cations in perisynaptic astroglial processes. This restricted movement of ions between the perisynaptic cradle (PsC), principal astroglial processes and the astrocyte soma gives rise to potassium (K+) and sodium (Na+) microdomains at the PsC. The present paper extends the above model to demonstrate that the formation of an Na+ microdomain can reverse the Na+/Ca2+ exchanger (NCX) thus providing an additional source of calcium (Ca2+) at the PsC. Results presented clearly show that reversal of the Na+/Ca2+ exchanger is instigated by a glutamate transporter coupled increase in concentration of cytoplasmic [Na+]i at the PsC, which and instigates Ca2+ influx through the NCX. As the flow of Ca2+ along the astrocyte process and away from the PsC is also constrained by Ca2+ binding proteins, then a Ca2+ microdomain forms at the PsC. The paper also serves to demonstrate that the EAAT, NKA, and NCX represent the minimal requirement necessary and sufficient for the development of a Ca2+ microdomain and that these mechanisms directly link neuronal activity and glutamate release to the formation of localized Na+ and Ca2+ microdomains signals at the PsC. This local source of Ca2+ can provide a previously underexplored form of astroglial Ca2+ signaling.

Effect of calcium lactate on compressive strength and self-healing of cracks in microbial concrete

This paper presents the effect on compressive strength and self-healing capability of bacterial concrete with the addition of calcium lactate. Compared to normal concrete, bacterial concrete possesses higher durability and engineering concrete properties. The production of calcium carbonate in bacterial concrete is limited to the calcium content in cement. Hence calcium lactate is externally added to be an additional source of calcium in the concrete. The influence of this addition on compressive strength, self-healing capability of cracks is highlighted in this study. The bacterium used in the study is bacillus subtilis and was added to both spore powder form and culture form to the concrete. Bacillus subtilis spore powder of 2 million cfu/g concentration with 0.5% cement was mixed to concrete. Calcium lactates with concentrations of 0.5%, 1.0%, 1.5%, 2.0%, and 2.5% of cement, was added to the concrete mixes to test the effect on properties of concrete. In other samples, cultured bacillus subtilis with a concentration of 1×105 cells/mL was mixed with concrete, to study the effect of bacteria in the cultured form on the properties of concrete. Cubes of 100 mm×100 mm×100 mm were used for the study. These cubes were tested after a curing period of 7, 14 and 28 d. A maximum of 12% increase in compressive strength was observed with the addition of 0.5% of calcium lactate in concrete. Scanning electron microscope and energy dispersive X-ray spectroscopy examination showed the formation of ettringite in pores; calcium silicate hydrates and calcite which made the concrete denser. A statistical technique was applied to analyze the experimental data of the compressive strengths of cementations materials. Response surface methodology was adopted for optimizing the experimental data. The regression equation was yielded by the application of response surface methodology relating response variables to input parameters. This method aids in predicting the experimental results accurately with an acceptable range of error. Findings of this investigation indicated the influence of added calcium lactate in bio-concrete which is quite impressive for improving the compressive strength and self-healing properties of concrete.

Sulfuric acid resistance of fly ash based geopolymer concrete

The sulfuric acid resistance of fly ash based geopolymer concrete blended with an additional calcium source is presented in this paper. Ordinary Portland cement (OPC) was added as additional calcium in the geopolymer system as fly ash replacement (0, 10, 20 & 30%). The specimens were exposed to 2% sulfuric acid solution up to the age of 365days, and the deterioration was identified in terms of mass loss and compressive strength retained. Microstructural analysis; SEM, XRD, and EDS was also carried out.The results indicate that the inclusion of OPC (as fly ash replacement) improves the compressive strength of fly ash based geopolymer concrete specimens significantly whereas it did not have a similar effect on its resistance to sulfuric acid. The increase in compressive strength for the unexposed geopolymer concrete specimens was due to the additional calcium hydrated products which co-existed with alumina-silicate polymer structures. On the other hand, for the specimens exposed to sulfuric acid for 365days, the inclusion of OPC at 10% showed the maximum retained compressive strength of around 52% of the strength value achieved for unexposed specimens at the same age. However, OPC inclusion beyond 10% decreases the ability of geopolymer concrete specimens to retain compressive strength. Maximum deterioration was observed when fly ash was replaced by OPC at 30%. This was due to the formation of additional calcium sulfate which increased with the increase in calcium products in the mixture. Microstructural changes were also observed for the exposed specimens at 365days and confirmed the presence of sulfur compounds as a major cause for the deterioration.

Mechanical Properties of Concrete with Enterococcus Faecalis and Calcium Lactate

Concrete is an important material used globally, diverse as it can be applied in all construction type or modify to be apply in specialize construction fields. Adding bacteria in concrete can improve the concrete properties and increase durability due deposited calcite by bacteria. However, calcite deposition by bacteria is limited by calcium available in cement. The objective of this research is to determine the effect of adding calcium lactate as an additional calcium source and bacteria on the concrete properties. The bacteria used is locally isolated and enriched to suite concrete environment. The type of the bacteria used is identified as Enterococcus faecalis. The calcium lactate is added into concrete mix with concentrations of 0.001mol/l, 0.005mol/l and 0.01mol/l. Whereas, the bacteria is added as 3% Enterococcus Faecalis. Mechanical properties test such as compressive strength, flexural strength and tensile strength was conducted. Cubes of size 150mm × 150mm × 150mm were prepared for compressive strength test while of Dia 150mm by 300mm cylinder were prepared for tensile strength test. Flexural strength test was performed on prism of size 100mm × 100mm × 500mm. The result of compressive strength shows that adding Enterococcus faecalis with 0.005mol/l of calcium lactate gave the highest strength of 42.8MPa compared to control of 36MPa. The tensile strength and flexural strength has a similar trend as compressive strength results.Where, both results were optimum with 0.005mol/l concentration of calcium lactate. The result of tensile strength shows that Enterococcus faecaliswith 0.005mol/l obtained 3.18MPa compared to control of 2.54MPa. Flexural strength test result was 6.67MPa for Enterococcus faecalis with 0.005mol/l compared to control of 4.78MPa. The overall results of bacteria with added calcium lactate showed promising result and further study on self healing capability is encouraging.

Effect of calcium, phosphorus premix with synergistic herbs supplementation in improving overall performance, carcass quality and tibial mineralization in broiler chickens

Objective: Efficacy of AV/CSP/29 premix (Ca, P supplement with Vit. A & D3 along with synergistic herbs) (M/S Ayurvet Ltd.) was evaluated in commercial broiler chicks. Materials and methods: A total of 144 day-old chicks were randomly divided into three groups. Group T0 (n=48) control group, supplemented with basal diet without any additional source of calcium (Ca) and phosphorus (P). Group T1 (n=48) was administered with AV/CSP/29 premix at 500 gm/ton of feed and Group T2 birds (n=48) were supplemented with Brand A at 500 gm/ton of feed for 0 to 42 days. Parameters viz., growth, performance, serum biochemical and carcass quality traits were evaluated. Results: More gain in body weight was observed in the AV/CSP/29 premix supplemented group (T1) birds as compared to other groups. Similarly, FCR was improved in the AV/CSP/29 premix supplemented group (T1) birds. Blood Ca and P concentrations were comparatively improved in AV/CSP/29 premix supplemented birds. Parameters viz., carcass yield, dressing percentage, tibial mineralization, water holding capacity and extract release volume were also found to be better in AV/CSP/29 premix supplemented group (T1) birds. Conclusion: The results from the current study suggest that feeding of AV/CSP/29 premix to broiler chickens may have a beneficial effect on bone quality and in improving overall performance.

Calcium Lactate addition in Bioconcrete: Effect on Compressive strength and Water penetration

This paper presents compressive strength and water penetration of bioconcrete with addition of calcium lactate. Bioconcrete has higher engineering concrete properties and durability compared to normal concrete but the natural production of calcium carbonate is limited to the calcium content in cement. Therefore, additional calcium is added as an additional calcium source to study the influence towards compressive strength and water penetration. The bacteria used in this research are Enterococcus faecalis and Bacillus sp . Calcium lactate was added into concrete mix in concentrations of 0.001mol/l, 0.005mol/l and 0.01mol/l of liquid used. The concentration of bacteria added into the mix is by partial replacement of water used in casting, which are 3% for Enterococcus faecalis and 5% for Bacillus sp . Both compressive strength and water penetration test used cubes of 150mm × 150mm × 150mm. The cubes were tested after 28 days. The result of compressive strength for control is 36 MPa while partial replacement of bacteria yields 38.2 MPa for 3% Enterococcus faecalis and 37.0 MPa for 5% Bacillus sp . Calcium lactate with 0.005 mol/L has the best performance with 42.8 MPa for Enterococcus faecalis and 39.6 MPa for Bacillus sp . Whereas for water penetration, the best concentration of calcium lactate which yielded the lowest water penetration is 0.01 mol/l for both Enterococcus faecalis and Bacillus sp which are 8.7 cm and 8 cm respectively. The addition of calcium lactate into bioconcrete is quite promising for improvement of concrete properties and durability.

Activity dependent modulation of synaptic transmission by presynaptic calcium stores: A dichotomy of short-term depression and facilitation

Ongoing electrical activity can initiate a positive feedback loop via Inositol Triphosphate Receptors (IP3Rs) and Ryanodine Receptors (RyRs) on the Endoplasmic Receptors (ER) that can lead to release of calcium from the ER. We investigated how the presence of this additional source of calcium in the presynaptic terminals in addition to the Voltage Dependent Calcium Channels (VDCCs) can regulate synaptic transmission. We carried out 3D Monte Carlo simulations of all the molecular interactions that govern transmitter release in a 1) Canonical CA3-CA1 synapse 2) A synapse reconstructed from serial section Transmission Electron Microscope images. The relatively simple geometry of CA3-CA1 synapses allows activity-dependent local calcium at the active zone and the related transmitter release profiles to be quantitatively analyzed. In paired-pulse stimulation, the presence of the molecular pathways that regulate the calcium stores increased the calcium buffering capacity of the synapse, which decreased release probability and enhanced paired-pulse facilitation. In contrast, a high-frequency stimulus could trigger the activation of presynaptic RyRs and Metabotropic Glutamate Receptors (mGluRs) leading to IP3 production and ultimately to release of calcium from the SER. IP3Rs and RyRs operated at a much slower time scale, on the order of seconds compared to the millisecond timescale of the VDCCs. This led to an increase in the basal level of intracellular calcium and enhanced transmitter release rates. In reconstructions of hippocampal neuropil, the ER appears in a majority of the presynaptic terminals in varying degrees of abundance. We further explored the functional implications of the range of ER geometries and therefore the calcium carrying capacity, observed in the synaptic ultrastructure and the effect of different arrangements between IP3Rs and VDCCs on synaptic plasticity. The synaptic ultrastructure precisely orchestrated the degree of facilitation and depression at the synapse and the existence of presynaptic calcium stores provided the synapse with an additional intrinsic time scale that could be regulated by activity.

Effects of Presynaptic Calcium Stores on Short-Term Synaptic Plasticity

In reconstructions of hippocampal neuropil, Smooth Endoplasmic Reticulum (SER) appears in a majority of the presynaptic terminals. In the presence of ongoing electrical activity, Inositol Triphosphate Receptors (IP3Rs) on the SER initiate a positive feedback loop that can lead to release of calcium from the SER via an IP3-mediated pathway. We investigated how the presence of this additional source of calcium in addition to the Voltage Dependent Calcium Channels (VDCCs) can regulate synaptic transmission. We carried out 3D Monte Carlo simulations of the molecular interactions that govern transmitter release in a 1) Canonical CA3-CA1 synapse 2) Synapse reconstructed from serial section Transmission Electron Microscope images. The relatively simple geometry of CA3-CA1 synapses allows activity-dependent local calcium at the active zone and the related transmitter release profiles to be quantitatively analyzed. In paired-pulse stimulation, the presence of molecular pathways that regulate the calcium stores increased the calcium buffering capacity of the synapse, which decreased the initial release probability and enhanced paired-pulse facilitation. In contrast, a high-frequency stimulus could trigger the activation of presynaptic Metabotropic Glutamate Receptors (mGluRs) leading to IP3 production and ultimately to release of calcium from the SER. IP3Rs operated at a much slower time scale, on the order of seconds compared to the millisecond timescale of the VDCCs. This led to an increase in the basal level of intracellular calcium and enhanced transmitter release rates. We further explored the functional implications of the range of SER geometries observed in the synaptic ultrastructure and the effect of different arrangements between IP3Rs and VDCCs on synaptic plasticity. The synaptic ultrastructure precisely orchestrated the degree of facilitation and depression and the existence of presynaptic calcium stores provided the synapse with an additional intrinsic time scale that could be regulated by activity.

CHEMICAL COMPOSITION, PHYSICAL PROPERTIES AND MICROSTRUCTURE OF PIDAN WHITE AS AFFECTED BY DIFFERENT DIVALENT AND MONOVALENT CATIONS

ABSTRACT Changes in chemical composition, physical property and microstructure of pidan white were monitored during pickling in the presence of different divalent (CaCl2, MgCl2) and monovalent (KCl) cations at different levels (0.2 and 0.5%) up to 3 weeks, followed by aging for another 3 weeks. Pidan prepared following the commercial process, in which 0.2% PbO2 or 0.2% ZnCl2 was incorporated, was also tested. Hardness, cohesiveness and adhesiveness of pidan white gradually increased during pickling, but these parameters decreased during aging time (P < 0.05), regardless of cations used. Nevertheless, pidan white treated with 0.2% PbO2 retained hardness and cohesiveness but had a slight decrease in adhesiveness, when pickling/aging time increased up to week 6 (P < 0.05). Transmission electron microscopic studies indicated that the aggregation of egg proteins took place in pidan white gels treated with 0.2% PbO2, 0.2% ZnCl2 or 0.2% CaCl2 during pickling. However, the degree of aggregation varied with cations used. PRACTICAL APPLICATIONS Pidan has been of safety concern for the consumers due to the presence of lead, commonly used to stabilize egg white gel and render the dark brown color. The use of cations, especially divalent such as CaCl2 at an appropriate level, could be an alternative process to make the pidan without toxicity from heavy metal. Furthermore, it can serve as the additional source of calcium for pidan.

The combined effect of lead exposure and high or low dietary calcium on health and immunocompetence in the zebra finch ( Taeniopygia guttata)

The widespread contamination by lead and the acidification of the environment ask for a better understanding of the effects of the interaction between lead and calcium on various aspects of health, including disease defense, in wildlife. Here, we investigated the effects of chronic exposure to sublethal levels of lead, combined with high or low dietary calcium, on health and several components of immunity in male and female zebra finches ( Taeniopygia guttata). Thirty individuals of each sex were randomly assigned to three groups: a control group, a group exposed to lead with an additional calcium source (i.e. grit) and a group exposed to lead without access to an extra calcium source. Lead was administered as lead acetate via the drinking water (20 ppm) for 38 consecutive days. Exposure to lead increased significantly the concentrations of lead in kidney and bone in individuals of the experimental groups. Furthermore, the lack of a calcium supplement significantly enhanced the uptake of lead. Lead did not affect health indices such as hematocrit, spleen mass and body mass, nor the adrenal stress response. Cell-mediated immune responsiveness, assessed by a delayed-type hypersensitivity response to phytohaemagglutinin, was also not affected by lead exposure. On the other hand, lead exposure did significantly suppress the secondary humoral immune response towards sheep red blood cells in females, but only when the additional calcium source was not available. This effect was not found in males, suggesting sexual differences in susceptibility of humoral immunity to lead treatment in zebra finches.

Eggshell strength

Eggshell quality was studied in two groups of Shaver hens (300 hens per group) 30 weeks of age. All hens received a basic diet of the same composition with pulverized limestone as a source of calcium. The experimental group received 2 g of granular limestone (particle size 1.1-1.4 mm) per hen per day during one week, adding on the concentrate in the afternoon. Significantly lower deformation (19 m), higher breaking force (4,1 kg) and shell thickness (39, 3 x 0.01 mm) were registered for eggs of experimental group of hens than for eggs of control group (24 m; 3.3 kg 36.5 x 0.01 mm, respectively). The results obtained in our investigation showed possibilities of eggshell strength improvement using 2 g of larger particle size of limestone as additional source of calcium.

THE BIOAVAILABILITY OF OXALATE FROM OCA (OXALIS TUBEROSA)

It is believed that soluble oxalate has higher bioavailability than insoluble oxalate. Oca (Oxalis tuberosa) is moderately high in oxalate and contains oxalate in soluble form only. We estimated the bioavailability of oxalate in oca based on the urinary excretion of oxalate after oxalate loading with oca to estimate the bioavailability of oxalate in oca. We also clarified whether bioavailability differs in various oxalate loads from the same food source and studied the effect of an additional calcium source on the bioavailability of oxalate from oca. Four men and 4 women ingested 50, 100 and 150 gm. oca as well as 100 gm. oca with 100 gm. sour cream. Oxalate was measured in a 6-hour urine sample from each volunteer. The mean bioavailability of oxalate from oca plus or minus standard deviation was 1.44% +/- 1.31% during the 6-hour period after intake. There was no significant difference in oxalate bioavailability among oxalate intake levels in this study, although oca consumption with sour cream significantly decreased the uptake of oxalate (p <0.01). The variation in bioavailability among individuals was high in our study. The bioavailability of oxalate in oca appears to be similar to that in spinach. However, bioavailability varies among individuals and depends on other constituents of a combined meal.