Increment In Ca Research Articles

Advancing RCCI engine performance via optimal acetylene premix ratios and advanced diesel injection timing: An experimental investigation

AbstractReactivity controlled compression ignition (RCCI) stands out as an innovative combustion strategy, effectively reconciling stringent emission regulations with precise combustion management and optimal engine performance. In this research, the influence of injection timing of diesel, acting as highly reactive fuel (HRF), alongside variable premix ratios of acetylene, a low reactive fuel (LRF), operating within the RCCI framework has been investigated. In a first‐of‐its‐kind attempt, with a thorough experimental design, the present investigation encompasses a progressive advancement of HRF injection timing, extending up to 110° CA bTDC with 20° CA increments, coupled with LRF integration at premix ratios of up to 70%. Optimal operational conditions materialize at an HRF injection timing advancement of 90° CA bTDC, complemented by a 40% LRF contribution. This configuration yields substantial gains, including a 28.2% upsurge in the cylinder pressure and an 18.6% elevation in the cylinder temperature compared to conventional diesel (CDC) operations. Additionally, the combustion process exhibits an advanced start of combustion (SoC) relative to the CDC baseline, with an 8.53% decline in heat release rate, at 40% LRF enrichment. Under optimal circumstances, moderate hydrocarbon (HC) emissions are noted, while smoke emissions experience a noteworthy reduction of 55.9%, all the while upholding overall output performance. A remarkable 69.8% peak increase in brake thermal efficiency is attained, underscoring the merits of judiciously advancing HRF injection timing and extending LRF utilization within the RCCI paradigm. Thus, the study underscores the synergistic potential between augmented HRF injection timing and controlled LRF integration, offering a promising avenue for elevating the RCCI approach.

Basic oxygen furnace and ground granulated blast furnace slag based alkali-activated pastes: Characterization and optimization

The steel production shows tremendous increase all over the world and the enormous production of steel has subsequently led to huge amount of basic oxygen furnace (BOF) slag generation which causes several environmental issues. Previous studies generally considered the use of BOF slag as aggregate, cement replacement material, and binder in combination with metakaolin, fly ash, gold mine tailings, and ferronickel slag in alkali-activated systems. Apart from these, the present study proposes alkali-activation of BOF slag in replacement with ground granulated blast furnace slag (GGBFS) using sodium hydroxide (NaOH) as the activator. The fresh-state, mechanical, and microstructural properties of the alkali-activated paste samples were analyzed on 24 mixes. Test results showed that BOF slag ratio and the NaOH concentration modified the workability and the setting time, and their effect was remarkable for 6 M of NaOH and BOF content beyond 20%. The alkali-activated pastes containing 20 and 40% of BOF slag had comparable strength, however the strength reduced significantly upon further BOF slag inclusion. The increment of Ca(OH)2 with increased BOF slag ratio revealed by thermogravimetric analysis denotes its less consumption in the formation of C–S–H and support the decreasing compressive strength at 28 days. The X-Ray diffraction analysis revealed phases such as C–S–H and hydrotalcite due to hydration reactions. The scanning electron microscopy analysis showed that the microstructure was altered with BOF slag incorporation, and the micro-cracks were lowered compared to the reference. The optimization study showed that 25.5% of BOF slag and 6 M of NaOH provided higher compressive strength within the analyzed range, which was experimentally verified. Alkali-activation of BOF slag blended with GGBFS can be an efficient way of utilizing BOF slag to reduce its environmental impacts.

Characterization of Anthocyanin Associated Purple Sweet Potato Starch and Peel-Based pH Indicator Films.

In food packaging, smart indicator films based on natural resources have greatly attracted researchers to minimize the environmental issues as well as to satisfy consumer preferences for food safety. In this research, pH-sensitive films were prepared using purple-fleshed sweet potato starch (SPS) and sweet potato peel (SPP). Two categories of the film (i) SPS and (ii) SPS/SPP, were fabricated via solvent casting technique, incorporating different concentrations of commercial purple sweet potato anthocyanin (CA) at 0%, 1%, 1.5%, and 2% (w/v) and the physicochemical, mechanical, thermal, and morphological properties of the films were investigated. The thickness, water solubility, and swelling degree of the films increased with the increment of CA, whereas there were no significant changes in the water content (WC) of the films. Water vapor permeability (WVP) was decreased for SPS films while statistically similar for SPS/SPP films. The addition of CA reduced the tensile strength (TS) and tensile modulus (TM) yet increased the elongation at break (EaB) of the films as compared to films without CA. The FTIR results confirmed the immobilization of anthocyanin into the film. In SEM images, roughness in the surfaces of the CA-associated films was observed. A reduction of thermal stability was found for the films with anthocyanin except for the SPS/SPP CA 2% film. Furthermore, the CA-associated films showed a remarkable color response when subjected to pH buffers (pH 1 to 12) and successfully monitored chicken freshness. The fastest color migration was observed in acidic conditions when the films were immersed into aqueous, acidic, low fat, and fatty food simulants. The findings of this work demonstrated that the developed pH indicator films have the potential to be implemented as smart packaging to monitor food freshness and quality for safe consumption.

Influence of interactions between alumina crucible and Si-Ca-Fe melt on B and P removal from silicon

The effect of alumina crucible on different aspects of the solvent refining of silicon by the Si-Ca-Fe system was investigated in this paper. Ca and Fe were added to Si in a wide range of concentrations (0–20 wt%), and the melt composition change resulting from melt-alumina interactions was studied thermodynamically and experimentally. The ratio of Ca concentration in the final melt to its value in the initial mixture was in the range of 0.17–0.23. On the other hand, a considerable amount of Al was identified in the melt together with CaAl4O7, Ca2Al2SiO7, and CaAl2O4 phases as oxide interaction products. A conceptual mechanism was proposed for the evolution of these products. Then, the segregation behavior of impurities during solidification was studied based on Fe or Ca increment in the system, and B and P removal rates were calculated in particular. The higher the Ca or Fe content were, the higher removal rates were achieved. They were also enhanced by cooling the samples in the furnace rather than quenching from 1493 K (1220 °C). The directional solidification method was also examined, and it showed the best overall removal rate with 94.9% for P and 63% for B, while its impact on B reduction was more than P.

Effects of photodynamic therapy for dental caries prevention on trace elements in tooth enamel

Objective To study the application of photodynamic therapy (PDT) for dental caries prevention using whole body luminescence fiber, and to investigate the effects of PDT on the content of Ca and P in rat molar enamel. Method The rat dental caries model was established by inoculating with S.mutans. Eighty male rats were randomly divided into five groups, including three experimental groups: 17 mW (8 mW/cm2) PDT (group A), 34 mW (15 mW/cm2) PDT (group B), 68 mW (30 mW/cm2) PDT (group C), a positive control group: 20 g/L NaF solution (group D), and a negative control group: 0.9% physiological saline (group E). The experimental groups were treated by 40 μg/mL hematoporphyrin monomethyl ether (HMME) and 650 nm diode laser irradiation. The experiments were conducted for 4 weeks. The contents of Ca and P in the molars of each group were measured by inductively coupled plasma emission spectrometry. Results The contents of Ca and P in group B, C and D after PDT were significantly higher than those in group A and E (all P<0.05). The contents of Ca and P in group A showed no significant difference before and after PDT, while those in groups B and C showed significant increase after PDT (all P<0.05). The increment of Ca in group A after PDT was lower than that in group D (P<0.05), while those in group B and C were significantly higher than those in group D (all P<0.05). There was no significant difference in the increment of Ca and P between group B and C after PDT. Conclusions In the range of the experimental parameters, the PDT promoted effect of tooth remineralization is better than 20 g/L NaF. The levels of Ca and P in the tooth enamel can be promoted by PDT treatment, and the contents of Ca and P are related to the pewer of PDT. The effect of low power PDT on the remineralization of enamel is not obvious. The contents of Ca and P in the tooth enamel are increased with laser power of PDT. When the laser power increased to a certain value, the change in contents of the two elements is not obvious. PDT can maintain the tooth remineralization microenvironment. Key words: Photodynamic therapy; Trace elements; Inductively coupled plasma optical emission spectrometer; Remineralization

Effect of Blending Doum (&amp;lt;i&amp;gt;Hyphaene thebaica&amp;lt;/i&amp;gt;) Powder with Wheat Flour on the Nutritional Value and Quality of Cake

Pastry is an essential part of food stuff people like, especially preferring those made of wheat flour: cakes, biscuits, pancakes, etc. The nutritive value of the products mentioned above is not high. Therefore, there is a need to increase it by adding something like doum fruit (Hyphaene thebaica L.), which is a widespread in Upper Egypt. Doum fruit is a rich source of fibers and antioxidants, also other valuable substances such as carbohydrates and minerals especially potassium (K for people suffering from blood pressure problems). This investigation was carried out to study the possibility of utilization doum fruit powder in cake production. Five levels of wheat flour substitution were used 0%, 5%, 10%, 15% and 20% to produce cake. Also, the effects of blends on farinograph parameters were studied. Results indicated that substitution of doum powder (D.P) led to increase the water absorption (%) and dough weakening (B.U), whereas dough stability (min) was decreased. The water holding capacity of blends increased with increasing the level of substitution. The chemical, physical and sensory characteristics of the prepared cakes were studied. Results showed that increasing the levels of substitution increased the total fat, crude fiber and ash contents in produced cake compared with control. Minerals of the produced cake showed an increment in K and Mg, while slightly increment in Ca, Fe and Zn with increasing the level of substitution. Total phenol and antioxidant activity (AO) increased in substituted cake. Physical attributes of the produced cakes were evaluated and results showed that volume of substituted cakes decreased with increasing the level of replacement except for 10% level it increased. Results of textural analysis showed that D.P fiber decreased all the parameters. Concerning cake color, as the percentage of D.P increased, the color of the cake became darker and had high a and b values. The sensory evaluation results showed an insignificantly decrease in the acceptability by increasing the doum powder substitution comparing with control.

Effect of calcium on the microstructure and mechanical properties of brazed joint using Ag–Cu–Zn brazing filler metal

The induction brazing of 316LN stainless steel using Ag–Cu–Zn filler metal containing various content of Ca was carried out to investigate the influence of impurity element Ca on the microstructure and mechanical properties of the brazed joint. The results showed that Ca additions caused the coarser of the grains and their irregular distribution. Increase of the Ca content resulted in the formations of brittle intermetallic compounds (IMCs) CaCu which perhaps lead to the formations of voids. All of the calcium-containing brazed joints performed better in microhardness than calcium-free ones and brazed joints containing 0.003wt.% Ca showed the highest microhardness of 203HV. While the tensile strength decreased with the increment of Ca, from 460MPa to 400MPa. The combination effects of coarser grains, brittle IMCs and voids conduced to the reduction of tensile strength and microhardness of the brazed joints.

Phytophthora erythroseptica (Pink Rot) Development in Russet Norkotah Potato Grown in Buffered Hydroponic Solutions I. Calcium Nutrition Effects

Phytophthora erythroseptica Pethyb. causes a disease known as pink rot in potatoes, which is responsible for substantial pre and post harvest tuber loss. Disease outbreaks are associated with excessive soil moisture, moderate temperature, late season development, and a lack of potato cultivar resistance. Because disease resistance is becoming less effective, understanding other potential solutions is critical. Mineral nutrition of plants is known to be associated with disease development and severity of many diseases, but is not generally considered in relation to outbreaks of pink rot. Calcium (Ca) is essential and considered one of the most important nutrients associated with plant defense, but it has not been studied or consequently linked to the severity of pink rot in potato. A hydroponic growth system was established to study the effects of calcium on P. erythroseptica infection and colonization in Russet Norkotah potato roots. Russet Norkotah potatoes were grown with 3, 86, 172, and 343 mg L−1 Ca in association with the pathogen. The degree of disease severity was assessed by means of quantitative real time polymerase chain reaction (RT PCR). The suppression of infection and disease severity by increased available Ca was statistically significant, decreasing with each increment of Ca between 3 and 343 mg L−1. These data provide strong evidence that Ca nutrition is important in disease suppression and that the amount of available soil Ca can affect plant health and the ability of P. erythroseptica to infect the host.

Interactive effects of organic fertilizer, CaSO4 and amino acid Ca on Fuji apple in Burozem soil in China

A two-year trial was conducted to test the interactive effects of special-for-apple organic fertilizer, CaSO4, and amino acid Ca on Fuji/Balenghaitang (Malus robusta Rehd.) rootstock in Burozem soil in China. Total Ca, exchangeable Ca, and fruit Ca were significantly improved by the soil application of CaSO4 with the highest exchangeable Ca and fruit Ca observed in Fuji apple trees treated at the rate of 3.5 kg CaSO4 per tree. 3.5 kg CaSO4 was divided into two applications, with first application in the first month after full bloom, and the second in the second month after full bloom in summer, progressively to improve fruit Ca concentration. Dividing CaSO4 into two applications in combination with organic fertilizer or amino acid Ca spray, proved to be more effective on improving the fruit Ca concentration, with the highest level of 179.17 mg/kg FW in Fuji apple trees treated with 2 kg CaSO4 applied and amino acid Ca sprayed in the first month after full bloom, 1.5 kg CaSO4 applied in summer, organic fertilizer applied in winter. Organic fertilizer applied in winter alone remarkably improved the fruit Ca concentration, as well as storage Ca in roots and stems, and the best effect was observed in Fuji apple trees which were supplemented organic fertilizer (10 kg) in winter and CaSO4 (1 kg) in the first month after full bloom per tree. The effect on Ca increment became less pronounced when the amount of organic fertilizer reached 15 kg or CaSO4 was more than 3.5 kg per tree. There was a positive correlation between the Ca/Mg ratio in soil and fruit, exchangeable Ca, and fruit Ca concentration, while a negative correlation was observed between the N/Ca ratio in fruit, available P, available K in soil, and fruit Ca concentration. Both N/Ca ratio and Ca/Mg ratio in fruit were affected by different fertilization regime, and bitter pit incidence at the end of storage kept acceptable only if N/Ca < 17 and Ca/Mg ≥ 7 at harvest. The commercial fertilization regime turned out to be organic fertilizer in combination with CaSO4 applied in soil in winter, amino acid Ca sprayed in the first month after full bloom, and CaSO4 applied in soil in summer.

Cytotoxicity induced in myotubes by a Lys49 phospholipase A 2 homologue from the venom of the snake Bothrops asper: Evidence of rapid plasma membrane damage and a dual role for extracellular calcium

Acute muscle tissue damage, myonecrosis, is a typical consequence of envenomations by snakes of the family Viperidae. Catalytically-inactive Lys49 phospholipase A 2 homologues are abundant myotoxic components in viperid venoms, causing plasma membrane damage by a mechanism independent of phospholipid hydrolysis. However, the precise mode of action of these myotoxins remains unsolved. In this work, a cell culture model of C2C12 myotubes was used to assess the action of Bothrops asper myotoxin II (Mt-II), a Lys49 phospholipase A 2 homologue. Mt-II induced a dose- and time-dependent cytotoxic effect associated with plasma membrane disruption, evidenced by the release of the cytosolic enzyme lactate dehydrogenase and the penetration of propidium iodide. A rapid increment in cytosolic Ca 2+ occurred after addition of Mt-II. Such elevation was associated with hypercontraction of myotubes and blebbing of plasma membrane. An increment in the Ca 2+ signal was observed in myotube nuclei. Elimination of extracellular Ca 2+ resulted in increased cytotoxicity upon incubation with Mt-II, suggesting a membrane-protective role for extracellular Ca 2+. Chelation of cytosolic Ca 2+ with BAPTA-AM did not modify the cytotoxic effect, probably due to the large increment induced by Mt-II in cytosolic Ca 2+ which overrides the chelating capacity of BAPTA-AM. It is concluded that Mt-II induces rapid and drastic plasma membrane lesion and a prominent Ca 2+ influx in myotubes. Extracellular Ca 2+ plays a dual role in this model: it protects the membrane from the cytolytic action of the toxin; at the same time, the Ca 2+ influx that occurs after membrane disruption is likely to play a key role in the intracellular degenerative events associated with Mt-II-induced myotube damage.

The cAMP response to isoprenaline in mononuclear cells is markedly increased in the presence of platelets

We have previously shown that the addition of platelets to mononuclear cells (MNC) increases cAMP in MNC. This response may be of interest because the physical interaction between platelets and MNC plays an important role in the inflammatory process. We have now demonstrated that the addition of both isoprenaline and platelets to MNC resulted in a marked amplification of the cAMP response. Prostaglandins, ATP and adenosine and the P-selectin ligand PSGL-1 could not account for the response. No substance was found in the supernatant that could increase cAMP in MNC. W7, a Ca 2+-calmodulin inhibitor and the addition of EDTA reduced the response to both platelets and isoprenaline. Furthermore, we have demonstrated that mRNA for type I adenylyl cyclase, which is sensitive to Ca 2+, is present in MNC. No increase in Ca 2+ in the cytoplasma in MNC was recorded, however, by quantitative fluorescence microscopy after addition of platelets to MNC. It is possible that there are small increments in Ca 2+ at the binding sites, which we were unable to detect by our technique. Alternatively the binding of platelets to MNC may induce intermolecular interactions in the cell membrane which may facilitate the synthesis of cAMP.

A Phase II study of gemcitabine and cisplatin in advanced biliary tract cancer

The authors performed a Phase II study of combination chemotherapy with gemcitabine and cisplatin in patients with inoperable biliary tract cancer to evaluate efficacy and toxicity of this combination. In addition, the correlation between the CA 19-9 response and clinical outcome was analyzed. The eligibility criteria for this study were 1) histologically or cytologically confirmed inoperable biliary tract cancer in patients with metastatic or recurrent disease; 2) age between 18 and 70 years; 3) at least 1 measurable lesion according to Response Evaluation Criteria in Solid Tumors (RECIST) criteria; 4) an Eastern Cooperative Oncology Group (ECOG) performance status < or = 2; 5) a life expectancy of at least 3 mos; and 6) adequate bone marrow, hepatic, and renal function. The patients received gemcitabine (1250 mg/m(2), Days 1 and 8) and cisplatin (60 mg/m(2), Day 1) every 3 weeks. Tumor response was assessed by RECIST criteria every 2 cycles of chemotherapy. Treatment was continued until progression of disease was documented. Twenty-nine patients were enrolled. The median age of these patients was 52 years (range, 37 to 69 yrs), and the median ECOG performance status was 1. No complete response was observed, and 10 of 29 patients had partial responses. The overall response rate was 34.5% (95% confidence interval [CI], 17.9-54.3) for the intent-to-treat analysis. Stable disease was observed in 4 (13.8%) patients and progressive disease in 13 (44.8%) patients. The median follow-up time was 10.0 months (95% CI, 7.2-12.8). The median time to progression (TTP) was 3.0 months (95% CI, 2.12-3.88), and the median overall survival was 11 months (95% CI, 5.49-16.5). Although these results showed a better response rate (57.1 % vs. 27.3%) and survival (12 vs. 10 mos) in patients with a decline in CA 19-9 of at least 25%, these data were statistically not significant. In addition, there was a significant positive correlation between the increment in CA 19-9 values and tumor progression as determined with RECIST criteria (r = 0.96, P < 0.01). However, there was no definite correlation between the CA 19-9 response and the response according to RECIST criteria (P = 0.087). National Cancer Institute (NCI) common toxicity criteria (CTC) Grade 3 or 4 hematologic toxicities included neutropenia in 4 (14%) patients and anemia in 1 (3%) patient. Two of 4 patients with Grade 3 or 4 neutropenia had febrile episodes (7%) and required hospital admissions. NCI-CTC Grade 3 or 4 nonhematologic toxicity included nausea in 1 (3%) patient. There were no treatment-related deaths. The combination chemotherapy with gemcitabine and cisplatin in inoperable biliary tract cancer was tolerable for most patients and showed modest response rates. The role of CA 19-9 monitoring as a surrogate biomarker in patients with BTC treated with gemcitabine chemotherapy should be further investigated.

Direct coupling between arachidonic acid-induced Ca 2+ release and Ca 2+ entry in HEK293 cells

Arachidonic acid (AA) modulates intracellular Ca 2+ signaling via Ca 2+ release or/and Ca 2+ entry. However, the mechanism underlies either process is unknown; nor is it clear as to whether the two processes are mechanistically linked. By using Fura2/AM, we found that AA induced mobilization of internal Ca 2+ store and an increment in Ca 2+, Mn 2+ and Ba 2+ influx in HEK293 cells. The AA-mediated Ca 2+ signaling was not due to AA metabolites, and insensitive to capacitative Ca 2+ entry inhibitors. Interestingly, isotetrandrine and Gd 3+ inhibited both AA-induced Ca 2+ release and Ca 2+ entry in a concentration-dependent manner without affecting Ca 2+ discharge caused by carbachol, caffeine, or thapsigargin. Additionally, similar pattern of inhibition was observed with tetracaine treatment. More importantly, the three compounds exhibited almost equal potent inhibition of AA-initiated Ca 2+ release as well as Ca 2+ influx. Therefore, this study, for the first time, provides evidence for a direct coupling between AA-mediated Ca 2+ release and Ca 2+ entry.

Irreversible water–rock mass transfer accompanying the generation of the neutral, Mg–HCO 3 and high-pH, Ca–OH spring waters of the Genova province, Italy

In a recent survey of the spring waters of the Genova province, many neutral Mg–HCO 3 waters and some high-pH, Ca–OH waters were found in association with serpentinites. All the springs are of meteoric origin as indicated by the stable isotopes of water and dissolved N 2 and Ar. Interaction of these meteoric waters with serpentinites determines a progressive evolution in the chemistry of the aqueous phase from an immature Mg-rich, SO 4–Cl facies of low salinity to an intermediate Mg–HCO 3 facies (pH 7.0–8.5, P CO 2 10 −3.5–10 −2.5 bar, Eh 150–250 mV), and to a mature Ca–OH facies (pH 10–12, P CO 2 10 −9.4−10 −10.6 bar, Eh-390 to-516 mV). The irreversible water–rock mass transfer leading to these chemical changes in the aqueous phase was simulated through reaction path modeling, assuming bulk dissolution of a local serpentinite, and the precipitation of gibbsite, goethite, calcite, hydromagnesite, kaolinite, a montmorillonite solid mixture, a saponite solid mixture, sepiolite, and serpentine. The simulation was carried out in two steps, under open-system and closed-system conditions with respect to CO 2, respectively. The calculated concentrations agree with analytical data, indicating that the computed water-rock mass transfer is a realistic simulation of the natural process. Moreover, the simulation elucidates the role of calcite precipitation during closed-system serpentinite dissolution in depleting the aqueous solution of C species, allowing the concurrent increment in Ca and the acquisition of a Ca–OH composition. Calcium–OH waters, due to their high pH, tend to absorb CO 2, precipitating calcite. Therefore, these waters might be used to sequester anthropogenic CO 2, locally preventing environmental impact to the atmosphere.

Ultramicrohardness cross-profiling of CVD diamond/steel brazed junctions

Abstract Thick microwave plasma chemical vapour deposition (MPCVD) diamond films (240, 480, 1000 μm) were grown, laser cut and vacuum brazed to steel bars with an Ag/Cu/Ti (100 μm) reactive filler metal. Displacement sensing indentation experiments using a dynamic ultramicrohardness tester on the brazing layer were performed on different samples. A calibration curve for the residual depth values was made by linear regression to diagonal measurements on Vickers impressions. Corrected depth values were then used to evaluate the hardness. The thicker the films were, the higher the hardness was found to be. Hardness changes from 1.35 to 1.72 GPa, respectively, for the thinnest and the thicker film joints, getting an increment of ca 35%. These data indicate a hardening effect during the cooling stage caused by thermal expansion coefficients mismatch. An increment of ca 25% on the flexural stresses imposed by the film/substrate curvature was theoretically evaluated. The same trend variation with film thickness was found for both the hardness values and the brazing strength from previous work. Brazing layer hardness evaluation can be regarded as a non-destructive indirect way to assess the mechanical resistance of the diamond/steel joints.

Use of a soluble tetrazolium compound to assay metabolic activation of intact β cells

Although assessments of metabolic activation are central to studies of β-cell function, available techniques are tedious, insensitive, and/or require cell disruption. We have investigated the use of a new water-soluble tetrazolium salt, MTS (3-[4,5,dimethylthiazol-2-yl]-5-[3-carboxymethoxy-phenyl]-2-[4-sulfophenyl]-2H -tetrazolium, inner salt), in the presence of phenazine methosulfate (PMS), an intermediate electron acceptor that amplifies its signal (fluorescence at 490 nm). During static incubations of glucose-responsive (HIT-T15 or INS-1) dispersed β cells with increasing glucose concentrations, there was a progressive increase in MTS reduction, with a maximum signal-to-noise ( S N ) ratio of 24 with HIT-T15 cells and 10 with INS-1 cells. This was associated with, but not attributable to, parallel increases in insulin secretion. Pure mitochondrial fuels (α-ketoisocaproate [KIC], methyl pyruvate [MP], or l-glutamine [GLN] + l-leucine [LEU]) also increased the reduction of MTS in INS-1 cells (6.5-, 4.8-, and 14.4-fold, respectively), but generally less than glucose, suggesting a major role of glycolysis in the signal induced by glucose. Inhibitors of glucose metabolism (mannoheptulose [MH], Iodoacetate [IA], or 2-deoxyglucose [2-DG]) markedly reduced the glucose-stimulated MTS signal. In comparison to another tetrazolium compound, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), MTS assay provided a better S N ratio with glucose or other nutrient secretagogues. Extant theory holds that activation of mitochondrial dehydrogenases by increments in Ca 2+ influx couples glycolysis to mitochondrial oxidation of glucose-derived fuels. However, reduction of fuel-induced calcium influx (by Ca 2+-free medium or diazoxide [DZX]) or direct stimulation of calcium influx (by 40 mmol/L K +) failed to significantly modulate the signal, arguing against this theory. We conclude that the MTS assay is a facile test that reflects the global metabolic function of insulin-secreting β cells. Furthermore, since this assay does not require disruption of cells to solubilize the formazan product, and therefore also allows concomitant measurement of insulin secretion, it offers considerable advantages over earlier methods.

Isotopic substitution effects on the volumetric and viscosimetric properties of water-dimethylsulfoxide mixtures at 25°C

Densities and viscosities of binary mixtures (H2O or D2O) (1) + (DMSO or DMSO-D6)(2) have been measured over the entire mole fraction range; and the excess volumes, excess viscosities, and excess partial molar volumes Vf of the components have been obtained. All systems show negative excess volume Ve at all compositions, values for mixtures containing D2O being more negative than those with H2O byca. 0.03 cm3-mol-1 at x1, = 0.6, where a minimum is observed. The difference between DMSO and DMSO-D6 containing mixtures is negligible. The excess viscosity ηe is always positive and shows a maximum at x1 = 0.65; at this composition, the substitution of H2O with D2O causes an excess viscosity increment ofca. 0.35 mPa-s, while deuteration of DMSO brings about a smaller increase,ca. 0.1 mPa-s. The trend of V2E with concentration shows the characteristic features of moderately hydrophobic solutes in water (negative values and a minimum in the water-rich region), features that are slightly but significantly more marked in D2O than in H2O. The V2E values in the water-diluted region and at x1, =0 are more negative for D2O than for H2O.

Effects of neuraminidase on cellular calcium and contraction in cultured cardiac myocytes

Mammalian plasma membranes, including the myocardial sarcolemma, are abundantly glycosylated. Sialic acid is a ubiquitous anionic sugar found at the periphery of sarcolemmal glycoconjugates. The physiological role of this sugar is not clear, but neuraminidase, which specifically hydrolyzes sialic acid from the sarcolemma, has been found to increase calcium exchange, cause electrophysiological abnormalities, and enhance the transient (T) calcium current in cardiac myocytes. The purpose of this study was to better characterize the effect of neuraminidase on cellular calcium (Ca) and contractile function. Neuraminidase removed up to 57% of total sialic acid from the cells. 45Ca exchange was measured and neuraminidase was found to increase cell calcium proportional to the amount of sialic acid removed (18·6 ± 0·8 mmol/kg dry w, maximally). Over 80% of the increment in calcium remained rapidly exchangeable ( t 1 2 < 15 s ) under non-perfusion limited conditions and was inhibited by cations (La > Cd > Mn > Mg) and nifedipine. Using a video-monitoring system, neuraminidase was observed to transiently increase cell shortening during contraction (30 ± 9%), with progression to arrhythmias followed by cessation of contraction. These results indicate that neuraminidase, probably by removing sarcolemmal sialic acid residues, greatly augments cellular calcium in cultured cardiac myocytes. Most of the increment in Ca induced by neuraminidase was very rapidly exchangeable and most likely mediated by a Ca specific mechanism. Additionally, neuraminidase treatment altered contractile function in a manner consistent with elevated cellular Ca. Despite the many-fold increase in cellular Ca induced by sialic acid removal, cells recovered and demonstrated rhythmic contractions upon return to control incubation conditions.

Comparison of ATP-dependent calcium transport and calcium-activated ATPase activities of cardiac sarcoplasmic reticulum and sarcolemma from rats of various ages

Age-associated decline in the Ca 2+ pump function of cardiac sarcoplasmic reticulum (SR), and increase in the Ca 2+ pump activity of sarcolemma (SL) were suggested by my previous study which compared the ATP-energized in vitro Ca 2+ transport activities of these membranes from young (3–4-month-old) and aged (24–25-month-old) rat myocardium ( Biochim. Biophys. Acta, 678 (1981) 442–459). In the present study, ATP-dependent Ca 2+ transport and Ca 2 sensitive ATPase activities of SR and SL derived from the myocardium of rats aged 3 (young), 6 (young adult), 12 (adult), 18 (aging) and 24 (aged) months were determined so as to further characterize age-related changes in the Ca 2+ transport function of these membranes. The rates of ATP-dependent Ca 2+ accumulation by SR from 3- and 6-month-old rats were virtually similar whereas the rates of Ca 2+ accumulation by this membrane from 12-, 18- and 24-month-old rats were significantly lower when compared to 3- or 6-month-old rats; the magnitude of this age-related decline amounted to approx. 18, 45 and 50%, respectively, for SR from 12-, 18- and 24-month-old animals. In contrast to the above findings with SR, SL from 18- and 24-month-old rats displayed substantially higher rates (approx. 45 and 80% increase, respectively, at 18 and 24 months of age) of ATP-dependent Ca 2+ accumulation than SL preparations from 3-, 6- and 12-month-old rats; no significant age-related difference was evident between the latter three age groups. The divergent age-related changes in the Ca 2+ accumulating activities of SR and SL were seen at varying Ca 2+ concentrations (0.54–25.2 μM). With either membrane, kinetic analysis showed that the velocity of Ca 2+ transport, but not the apparent affinity of the transport system for Ca 2+, underwent age-related changes. The Ca 2+-stimulated ATPase activities of SR and SL were not altered significantly with increasing age from 3 to 24 months. Comparison of the ‘combined Ca 2+ transport activity’ of SR and SL from rats of various ages showed a significant overall age-related decline in the rates of Ca 2+ transport via the ATP-driven membrane Ca 2+ pumps; this decrement in membrane function was moderate at 12 months of age (approx. 16%) and became pronounced with advancing age thereafter (approx. 35 and 38%, respectively, at 18 and 24 months of age). Similar progressive age-related decline was observed in the ATP-dependent Ca 2+ sequestering activity of cardiac homogenates. No significant age-related difference was evident in the ATP- and respiration-supported Ca 2+ uptake activity of mitochondria isolated from 6- and 24-month-old rats. The above findings suggest that, barring compensatory age-related increment in Ca 2+ efflux via Na +-Ca + exchange across the SL, the overall ability of the myocardial cell to sequester Ca 2+ from the sarcoplasm declines with aging, mainly due to deterioration in the Ca 2+ pump activity of SR. This impairment in SR function is likely the major factor underlying the prolongation of cardiac relaxation seen with aging. The age-associated decline in the Ca 2+ transport activity of SR may involve uncoupling of the energy transduction and ion translocation functions of this membrane Ca 2+ pump.

Regional distribution of brain blood flow during maximal exertion in splenectomized ponies

It has been reported in exercising ponies that O 2 supply to all regions of the brain increased primarily due to a large increment in Ca O 2 and it was implied that this may reflect a generalized increase in brain metabolism during strenous exercise. Splenectomy ameliorates the rise in Ca O 2 observed with exercise in ponies. Thus, the objective of the present study was to examine changes in regional brain blood flow and O 2 supply of splenectomized ponies with sub-maximal and maximal exercise and to compare these data with previous observations in normal ponies. It was reasoned that in the absence of a marked rise in Ca O 2 , the brain blood flow of splenectomized ponies would have to increase markedly if brain metabolism also increased with severe exercise. Regional brain blood flow was studied using 15 μm diameter radionuclide labeled microspheres injected into the left atrium during rest (control) and sub-maximal as well as maximal exertion on a treadmill. It was observed that despite marked arterial hypocapnia and acute systemic hypertension which developed during exercise, blood flow as well as O 2 supply in the cerebral cortex, caudate nuclei, cerebral white matter, cerebellar white matter, thalamus-hypothalamus, mid-brain, pons and medulla were not different from control values. In the cerebellar cortex, however, blood flow and O 2 supply increased with both work intensities. Thus, it was concluded that in exercising ponies, metabolic O 2 requirement increased in the cerebellar cortex but was most likely not different from control (rest) in other regions of the brain.