Modulation of gastric mucosal calcium channel activity by mucus glycoprotein

• 1.1. The effect of gastric mucus glycoprotein on the activity of calcium channel isolated from gastric epithelial cell membrane was investigated. The ⁴⁵Ca²⁺ uptake into the vesicle-reconstituted channels, while only moderately (14%) affected by the intact mucus glycoprotein, was found significantly inhibited (59%) by the acidic glycoprotein fraction. This effect was associated with the sialic acid and sulfate ester groups of the glycoprotein, as their removal caused a loss in the inhibition.
• 2.2. The channel complex in the presence of epidermal growth factor (EGF) and ATP responded by an increase in protein tyrosine phosphorylation of 55 and 170 kDa proteins, and the vesicles containing the phosphorylated channels showed a 50% increase in ⁴⁵Ca²⁺ uptake. The phosphorylation and the calcium uptake were susceptible to inhibition by a specific tyrosine kinase inhibitor, genistein.
• 3.3. The channel protein phosphorylation was inhibited by the acidic mucus glycoprotein, which also interfered with the binding of EGF to the channel protein. The inhibitory effect was dependent upon the presence of sulfate ester and sialic acid groups, as evidenced by the loss of the glycoprotein inhibitory capacity following their removal.
• 4.4. The results suggest that the acidic gastric mucus glycoproteins, by modulating the EGF-controlled calcium channel phosphorylation, play a major role in gastric mucosal calcium homeostasis.

     

Activation of gastric mucosal calcium channels by epidermal growth factor

• 1.1. Gastric mucosal calcium channel complex was isolated from the solubilized epithelial cell membranes by affinity chromatography on wheat germ agglutinin.
• 2.2. The complex following labeling with [³H]PN200-110 was reconstituted into phosphatidylcholine vesicles which exhibited active ⁴⁵Ca²⁺ uptake into intravesicular space as evidenced by La³⁺ displacement and osmolarity measurements. The ⁴⁵Ca²⁺ uptake was independent of sodium and potassium gradients indicating the electroneutral nature of the process.
• 3.3. The gastric mucosal channels on epidermal growth factor binding in the presence of ATP responded by an increase in protein tyrosine phosphorylation of 55 and 170 kDa subunits of calcium channel.
• 4.4. The phosphorylated channels following reconstitution into vesicles displayed at 48% greater ⁴⁵Ca²⁺ uptake, thus indicating the tyrosine kinase involvement in EGF dependent activation of calcium channel.
• 5.5. The results point towards the importance of epidermal growth factor in the maintenance of gastric mucosal calcium homeostasis.

     

Calcium uptake in the gorgonian Leptogorgia virgulata. The effects of atpase inhibitors

• 1.1. Longitudinally split or completely regenerated branch tips from Leplogorgia virgulata show no differences in calcium uptake between control and ouabain treatments. This indicates that there is no ouabain sensitive Na⁺, K⁺-ATPase involved in calcium uptake.
• 2.2. The tissue fractions of both regenerated and split branch tips show, at certain times, higher calcium uptake than control fractions. In the spicule fractions of these tips calcium uptake decreases in vandate treated specimens.
• 3.3. Pulse-chase experiments show an initial rapid release of calcium from the tips into surrounding seawater.
• 4.4. The results may suggest the presence of outwardly directed calcium pumps on the basal/lateral and apical plasma membranes of the epithelial cells. Outwardly directed calcium pumps may also be envisaged on the cell membranes of scleroblasts. In addition, pumps may move calcium into specific organelles of the scleroblasts en route to the spicule forming vacuoles.
• 5.5. These pumps are likely to be Ca²⁺-ATPase.

     

Epidermal growth factor alters the electrolyte profile of lactating ewes Ovis aries

• 1.1. Lactating ewes were treated with mouse epidermal growth factor (EGF) at a dose rate of 0.5 mg/day for 4 days and its effects on the electrolyte profile were observed.
• 2.2. There was no effect of EGF on plasma concentrations of sodium or potassium, although urinary and total (in urine and milk) losses of both were reduced.
• 3.3. EGF-induced hypocalcaemia was associated with reduced milk calcium secretion and increased urinary calcium excretion whereas EGF-induced hypermagnesaemia was associated with reduced urinary and total magnesium losses.
• 4.4. Glomerular filtration rate was reduced during EGF infusion.
• 5.5. Chronic intravenous EGF infusion affects the electrolyte profile by altering electrolyte secretion by the mammary gland and renal electrolyte excretion.

     

Effects of aluminium and pH on calcium fluxes,and effects of cadmium and manganese on calcium and sodium fluxes in brown trout (Salmo trutta L.)

• 1.1. Simultaneous measurement of calcium fluxes in brown trout, at low external [Ca] (20 μ mol 1⁻¹), provided evidence of active uptake of Ca from the medium.
• 2.2. At pH 4.5, calcium influx was inhibited and efflux was stimulated.
• 3.3. Cd and Mn, but not Al, at concentrations within the ranges found in acid waters experiencing fish population decline, inhibited calcium influx. Efflux was unaffected.
• 4.4. Cd and Mn stimulated sodium influx and efflux.

     

Feeding and a serotonergic interneuron activate an identified autoactive salivary neuron in Limax maximus

• 1.1. A single neuron is found in each buccal ganglion of the giant garden slug, Limax maximus, which is autoactive and has an axon in both the ipsilateral and contralateral salivary nerve.
• 2.2. This neuron, the bilateral salivary neuron (BSN), is a slow bursting neuron and is presynaptic to some of the secretory acinar cells of the salivary gland.
• 3.3. Increases in BSN action potential frequency and saliva flow during the generation of feeding motor program are shown, as is the relationship of BSN activity to that of other salivary neurons.
• 4.4. BSN is affected synaptically by the serotonergic metacerebral giant cell.

     

The effects of heavy metals and metabolic inhibitors on calcium uptake by gills and scales of Fundulus heteroclitus in vitro

• 1.1. Cadmium (Cd) and zinc (Zn) were inhibitory to calcium uptake by isolated gills of Fundulus heteroclitus in vitro. The metals appeared to act by displacing Ca²⁺ ions from protein carriers involved in facilitated diffusion.
• 2.2. In saltwater fish, transport of calcium across the serosal membrane of gill chloride cells is partly energy dependent and is likely mediated by Ca²⁺-ATPase. However, much of the calcium transport through the gill epithelium appears to occur by passive processes.
• 3.3. Cd (10⁻⁵M—10⁻³M) and Zn (10⁻⁷M—10⁻³ M) inhibited calcium uptake by isolated scale patches incubated in a physiological saline.
• 4.4. Cyanide, oubain, and quercetin treatment of scale patches produced results similar to those of the Cd and Zn treatments suggesting that metal-induced inhibition of ATPases may be responsible for reduced calcium transport by scale osteoblasts.

     

Differential expression of salivary mucin bacterial aggregating activity with caries status

• 1.1. The low and high mol. wt mucin forms were isolated from saliva of caries-resistant (CR) and caries-susceptible (CS) individuals, and assessed for their bacterial aggregating potential towards S. mutans and S. sanguis, the common cariogenic microorganisms encountered in the oral cavity.
• 2.2. The high mol. wt mucin from both groups of subjects exhibited similar protein and carbohydrate content, but the level ofcovalently bound fatty acids was significantly lower in the CR group. The mucin from CR group showed only a weak inhibitory potential, and no inhibitory activity was observed with the mucin of CS group.
• 3.3. The low mol. wt mucins from both groups, while displaying compositional similarities, showed a marked variation in the bacterial aggregating activity. With both bacteria, the activity of the mucin from CR group was at least 128-fold greater than that of CS group.
• 4.4. The conversion of the high mol. wt mucin to a low mol. wt form through the action of salivary protease produced in both groups enhancement in mucin's bacterial aggregating capacity. This enhancement was, however, considerably less pronounced in the case of mucin from CS group.
• 5.5. The results for the first time demonstrate that the bacterial aggregating epitope of salivary mucins is expressed to a greater extent in CR individuals, and that this epitope is apparently more accessible to bacteria in the low mol. wt mucin form.

     

Varying effects of calcium on the oxidation of palmitate and α-ketoglutarate in isolated rat liver mitochondria incubated in KCl-based and sucrose-based media

• 1.1. Isolated mitochondria from rat liver were incubated in the presence of [U-¹⁴C]palmitate, ATP, CoA, carnitine, EGTA (ethylene glycol bis (β-aminoethyl ether) N,N′-tetraacetic acid) and varying amounts of calcium.
• 2.2. When a KCl-based incubation medium was used, the oxidation of palmitate was inhibited when the concentration of free calcium was increased from about 0.1–10μM.
• 3.3. When a sucrose-based incubation medium was used, the basal rate of palmitate oxidation was about half of that observed with the KCl-medium and calcium had a stimulatory effect.
• 4.4. With the KCl-medium the rate of oxygen consumption was inhibited by calcium with α-ketoglutarate as well as palmitate as the respiratory substrate.
• 5.5. No inhibitory effect of calcium was observed with succinate or β-hydroxybutyrate.
• 6.6. With the KCl-medium and with α-ketoglutarate as the respiratory substrate, state 3 respiration but not state 4 respiration was inhibited by calcium.
• 7.7. When the sucrose-medium was used, state 3 respiration was first inhibited by calcium, but this inhibition was gradually relieved and the respiratory rate finally became higher than it was before calcium addition.

     

Taurine regulation of Ca2+ uptake and (Ca2+ + Mg2+)-ATPase in developing chick B-cells

• 1.1. The objective of the present study was to determine the effect of age and taurine on chick B cell calcium uptake and membrane (Ca²⁺ + Mg²⁺)-ATPase activity in 1–4-week-old chicks.
• 2.2. The calcium uptake rate decreased with age (P < 0.05) and was further decreased by taurine (P < 0.05).
• 3.3. (Ca²⁺ + Mg²⁺)-ATPase activity increased with age (P < 0.05) and was stimulated by taurine (P < 0.05).
• 4.4. The data demonstrate that the flux of calcium across the B-cell membrane changes during early post-hatch development, and that taurine regulates both the influx and efflux of calcium in chick B-cells.

     

Comparison of metabolic effects of EGF,TGF-α, and TGF-β1 in primary culture of fetal bovine myoblasts and rat L6 myoblasts

• 1.1. Comparative studies of EGF, TGF-α, and TGF-βl action on the synthesis of DNA and cellular proteins in rat L6 myogenic cells and fetal bovine myoblasts demonstrated considerable differences between particular growth factors, dependent on dose and target cells.
• 2.2. Among examined growth factors only EGF exerted mitostimulatory action, more pronounced at lower concentrations. EGF, progressively with dose, stimulated protein synthesis much more effectively in fetal bovine myoblasts than in L6 cells.
• 3.3. The dynamics of stimulation of protein synthesis by TGF-α was greater than by EGF in both examined types of cell cultures.
• 4.4. The maximal response of fetal bovine myoblasts to TGF-α in a concentration of 100 ng/ml reached 370%, whereas EGF in a 10 times higher concentration stimulated protein synthesis only to 123% of control.
• 5.5. In contrast to EGF, TGF-α significantly inhibits DNA synthesis. Inhibition of the mitogenic response with simultaneous stimulation of protein synthesis by TGF-α may indicate changes toward cell differentiation.
• 6.6. TGF-β 1 in smallest concentration inhibits both DNA and protein synthesis. The suppressive action of TGF-β 1 was more distinct in fetal bovine myoblasts than in the L6 cell line.
• 7.7. Increasing concentrations of TGF-β l diminished its inhibitory effect, even leading to stimulation of protein synthesis at higher doses in L6 myoblasts.

     

Characterization of subfractions of β2-glycoprotein I: Evidence for sialic acid microheterogeneity

• 1.1. β₂-Glycoprotein I is a sialic acid microheterogeneous protein and contains on the average 11 mol sialic acid/mol.
• 2.2. Linear correlation was found between sialic acid content and pI of isolated subfractions.
• 3.3. Asialo-β₂2-glycoprotein I consists of 2 isoforms. Each of which can originate from the same subfraction.
• 4.4. The isolated subfractions exhibited almost the same amino acid composition.

     

Crayfish retinular cells: Influence of extracellular sodium and calcium upon receptor potential

• 1.1. In crayfish, light stimulation of the retinular cells induces a depolarizing receptor potential.
• 2.2. Experiments were designed to determine the role of Na⁺ and Ca²⁺ on receptor potential during dark And light states.
• 3.3. Depolarization depends on Na⁺ and Ca²⁺ availability to the retinular cell.
• 4.4. Repolarization velocity and response duration depend on extracellular Ca²⁺ availability.
• 5.5. Light adaptation increases receptor potential dependence on calcium and sodium ions.
• 6.6. We analyse these results with respect to other invertebrate photoreceptors.

     

Responses of channel catfish (Ictalurus punctatus) swim-up fry to dietary calcium in soft and hard water

• 1.1. Responses of channel catfish (Ictalurus punctatus) swim-up fry to dietary calcium in soft (< 1 mg/1 as CaCO₃) and hard (> 100 mg/1 as CaCO₃) water were determined by feeding purified egg-white diets containing 0, 0.5, 1.0, or 2.0% calcium from CaCO₃ for 8 weeks.
• 2.2. Catfish fry fed the basal diet (0.03% Ca) in hard and soft water had lower whole-body ash and whole-body calcium concentrations but higher weight gain and survival than those fed calcium-supplemented diets.
• 3.3. Fry in soft water generally had lower whole-body ash, whole-body calcium, and survival, as well as a higher incidence of spinal deformities than fry in hard water.
• 4.4. Feeding higher levels of calcium to fry reared in soft water did not increase whole-body calcium levels or decrease spinal deformities to the levels observed for fry reared in hard water and fed supplemental calcium.
• 5.5. These data indicate that calcium derived solely from dietary or environmental sources was not sufficient for optimum health of channel catfish fry.

     

Modulation of the ATP induced [Ca2+]c increase in as-30D hepatoma cells

• 1.1. The regulation of the increase in the cytosolic calcium concentration ([Ca²⁺]c) induced by extracellular ATP in AS-30D hepatoma cells was studied.
• 2.2. Homologous desensitization involving the refilling of intracellular calcium pools and the participation of protein kinase C was found.
• 3.3. Isoproterenol, forskolin and dibutyril-cyclic AMP also induced an increase in [Ca²⁺]c.
• 4.4. Interestingly, synergism was found for isoproterenol or forskolin and ATP.
• 5.5. The results suggest that there are two pathways for mobilizing [Ca²⁺] in AS-30D hepatoma cells; one is activated by ATP receptors and the other by cyclic AMP.

     

Ependymins and their potential role in neuroplasticity and regeneration: Calcium-binding meningeal glycoproteins of the cerebrospinal fluid and extracellular matrix

• 1.1. Ependymins are unique, highly divergent secretory proteins of the fish endomeninx. Thus far, no homologous sequences have been characterized in mammals.
• 2.2. Soluble ependymins are the predominant constituents of the cerebrospinal fluid of many teleost fish. A bound form of these glycoproteins is associated with the extracellular matrix probably with collagen fibrils. The latter may be the functional form of ependymins.
• 3.3. Ependymins bind Ca²⁺ via N-linked sialic acid residues leading to a conformational transition.
• 4.4. The molecular function of ependymins seems to be related to cell contact phenomena involving the extracellular matrix. For example, adhesive or anti-adhesive interactions may possibly influence ingrowing axons.

     

The dynamics of the permeation of an analogue of insect juvenile hormone into nematodes

• 1.1. ¹⁴C-dichlorofarnesoate permeated rapidly into Haemonchus contortus (infective juveniles) and Panagrellus redivivus (mixed cultures) and was strongly bound by hydrophobic association (K_s > 10⁻⁴M).
• 2.2. Uptake rose linearly with increases in temperature (5–38°C) and external concentration (C₀; 0.07–2.15 × 10⁻⁴ M). Within 1 hr the internal concentration, C₁ was >C C₀.
• 3.3. The pH of the medium (6–8) did not affect uptake.
• 4.4. Efflux of dichlorofarnesoate was low: the half-time of release was > 18 hr.
• 5.5. The uptake curve approximated to the expression C₁/C₀ = a(1 − e^−bt) with a and b as constants and t in hr.
• 6.6. These results clarify previous work on the inhibitory action of juvenile hormone on the development of nematodes.

     

Age-related changes in total dna and rna and incorporation of uridine and thymidine in rat liver,kidney and spleen

• 1.1. Total content of DNA and RNA in liver, kidney and spleen were measured in young and aged rats. At the same time the incorporation of [¹⁴C]thymidine, a DNA precursor, and [³H]uridine, an RNA precursor, were also determined.
• 2.2. Changes in total organ DNA and RNA correlated with sexual maturation as did incorporation of precursors.
• 3.3. Young animals have more DNA per organ relative to RNA. with kidney and spleen DNA showing a decrease between maturity and senescence.
• 4.4. However, liver RNA increases with age. a change probably due to decreased catabolism of RNA since [³H]uridine uptake decreases.
• 5.5. Liver polyploid differentiation, and [¹⁴C]thymidine and [³H]uridine uptake, are correlated.
• 6.6. In kidney, incorporation of [³H]uridine is inversely related to [¹⁴C]thymidine incorporation.

     

Effect of bovine milk antigens and egg lysozyme on the binding of 59Fe-lactoferrin to platelet plasma membranes

• 1.1. Platelets bind specifically to lactoferrin. A significant similarity between human lactoferrin and some bovine milk proteins has been established.
• 2.2. Because of the structural homology of lactoferrin and cows milk proteins they are able to influence lactoferrins regulatory function on the level of its binding to membrane receptors on platelets.
• 3.3. An inhibitory effect of bovine α-lactalbumin and of β-lactoglobulin on lactoferrin-receptor interaction was shown.
• 4.4. Bovine α-lactalbumin competes with lactoferrin for the binding sites.
• 5.5. Scatchard plot analysis of data shows one binding site for lactoferrin in the presence of α-lactalbumin with an affinity constant, Ka = 0.46 × 10⁹ mol/1 and 335 receptors/cell.
• 6.6. The inhibitory effect of β-lactoglobulin reaches 62% and is different for the common fraction ⨿-lactoglobulin and the genetic variants β-lactoglobulin A and B.
• 7.7. β-lactoglobulin does not compete with lactoferrin for the membrane receptors.
• 8.8. Bovine casein and egg lysozyme stimulate ⁵⁹Fe-lactoferrin binding to the receptors. The mechanism of these effects is still unknown.
• 9.9. Tested alimentary antigens are able to interact with lactoferrin and also with some platelet membrane structures.
• 10.10. Established changes in lactoferrin binding to the platelet membrane might be in relation to lactoferrins regulatory function and (or) eliminating mechanisms of these alimentary antigens.

     

Identification of Salivary Biomarkers for Oral Cancer Detection with Untargeted and Targeted Quantitative Proteomics Approaches

1. Download : Download high-res image (173KB)
2. Download : Download full-size image

Highlights

• •iTRAQ-based analysis of saliva samples from oral cancer patients.
• •Proteome profiling of saliva samples from patients with oral premalignant lesions.
• •Verification of salivary biomarker candidates with MRM-MS and immunoassays.
• •Identification of salivary proteins as potential biomarkers of oral cancer.