Ocean acidification: synergistic inhibitory effects of protons and heavy metals on Ca uptake by lobster branchiostegite membrane vesicles.

Previous work with isolated outer membrane vesicles of lobster branchiostegite epithelial cells has shown that Ca uptake by these structures is significantly (p < 0.02) reduced by an incremental decrease in saline pH (increased proton concentration) and that this decrease is due to competitive inhibition between carrier-mediated transport of Ca and hydrogen ions. The present paper extends these previous findings and describes the combined effects of pH and cationic heavy metals on branchiostegite uptake of Ca.

Ocean acidification: effects of pH on Ca uptake by lobster branchiostegites.

Gill chambers of the Atlantic lobster, Homarus americanus, possess three structures that are involved with respiration and ion regulation: gill filaments, epipodites, and branchiostegites. This paper describes ion transport mechanisms present in the plasma membranes of branchiostegite epithelial cells and the effects of pH on the uptake of Ca by these processes. Partially purified membrane vesicles (PPMV) of branchiostegite cells were produced by a homogenization/centrifugation method that has previously been used to define ion transport processes in both crab and lobster gill tissues.

Functional characterization of a novel disaccharide transporter in lobster hepatopancreas.

In animals, the accepted model of carbohydrate digestion and absorption involves reduction of disaccharides into the monosaccharides glucose, fructose, and galactose followed by their individual transmembrane transport into cells. In 2011, a gene for a distinct disaccharide sucrose transporter (SCRT) was found in Drosophila melanogaster and characterized in a yeast expression system. The purpose of the present investigation was to functionally identify and characterize a putative disaccharide transporter analog in the hepatopancreas of the American lobster, Homarus americanus.

Molecular identification and functional characteristics of peptide transporters in the bonnethead shark (Sphyrna tiburo).

Elasmobranchs are considered to be top marine predators, and in general play important roles in the transfer of energy within marine ecosystems. Despite this, little is known regarding the physiological processes of digestion and nutrient absorption in these fishes. One topic that is particularly understudied is the process of nutrient uptake across the elasmobranch gastrointestinal tract.

Functional characterization of a putative disaccharide membrane transporter in crustacean intestine.

Transepithelial absorption of dietary sucrose in the American lobster, Homarus americanus, was investigated by mounting an intestine in a perfusion chamber to characterize mucosal to serosal (MS) (14)C-sucrose transport. These fluxes were measured by adding varying concentrations of (14)C-sucrose to the perfusate and monitoring their appearance in the bathing solution. Transepithelial (14)C-sucrose transport was the combination of a hyperbolic function of luminal concentration, following Michaelis-Menten kinetics, and apparent diffusion.

Analysis of glycylsarcosine transport by lobster intestine using gas chromatography.

Gas chromatography was used to measure transepithelial transport of glycylsarcosine (Gly-Sar) by perfused lobster (Homarus americanus) intestine. Unidirectional and net fluxes of dipeptide across the tissue and luminal factors affecting their magnitude and direction were characterized by perfusing the lumen with the dipeptide and measuring its appearance in saline on the serosal side of the organ. Transmural transport of 10 mM Gly-Sar resulted in serosal accumulation of only the dipeptide; no appearance of corresponding monomeric amino acids glycine or sarcosine was observed.

Comparative cation dependency of sugar transport by crustacean hepatopancreas and intestine.

Glucose is transported in crustacean hepatopancreas and intestine by Na(+)-dependent co-transport, while Na(+)-dependent D-fructose influx has only been described for the hepatopancreas. It is still unclear if the two sugars are independently transported by two distinct cation-dependent co-transporter carrier systems. In this study, lobster (Homarus americanus) hepatopancreas brush border membrane vesicles (BBMV) were used to characterize, in detail, the cation-dependency of both D-[(3)H]-glucose and D-[(3)H]-fructose influxes, while in vitro perfused intestines were employed to determine the nature of cation-dependent sugar transport across this organ.

Metabolic effects of sucralose on environmental bacteria.

Sucralose was developed as a low cost artificial sweetener that is nonmetabolizable in humans. Sucralose can withstand changes in pH and temperature and is not degraded by the wastewater treatment process. Since the molecule can withstand heat, acidification, and microbial degradation, it is accumulating in the environment and has been found in wastewater, estuaries, rivers, and the Gulf Stream.

Regulation of transmural transport of amino acid/metal conjugates by dietary calcium in crustacean digestive tract.

Effects of luminal Ca(2+) and Mn(2+) on transmural mucosal to serosal (MS) transport of (3) H-L-leucine were characterized in the isolated and perfused intestine of the American lobster, Homarus americanus. (3) H-L-leucine MS transport in the presence of 20 µM Mn(2+) was a sigmoidal function of luminal amino acid concentration, following the Hill equation for multisite cooperative, carrier-mediated, transport. Luminal Ca(2+) was a non-competitive inhibitor of Mn(2+) -stimulated (3) H-L-leucine MS flux.

L-leucine, L-methionine, and L-phenylalanine share a Na(+)/K (+)-dependent amino acid transporter in shrimp hepatopancreas.

Hepatopancreatic brush border membrane vesicles (BBMV), made from Atlantic White shrimp (Litopenaeus setiferus), were used to characterize the transport properties of (3)H-L-leucine influx by these membrane systems and how other essential amino acids and the cations, sodium and potassium, interact with this transport system. (3)H-L-leucine uptake by BBMV was pH-sensitive and occurred against transient transmembrane concentration gradients in both Na(+)- and K(+)-containing incubation media, suggesting that either cation was capable of providing a driving force for amino acid accumulation. (3)H-L-leucine uptake in NaCl or KCl media were each three times greater in acidic pH (pH 5.

K⁺-dependent ³H-D-glucose transport by hepatopancreatic brush border membrane vesicles of a marine shrimp.

The effects of sodium, potassium, sugar inhibitors, and membrane potential on ³H-D-glucose uptake by hepatopancreatic epithelial brush border membrane vesicles (BBMV) of the Atlantic marine shrimp, Litopenaeus setiferus, were investigated. Brush border membrane vesicles were prepared using a MgCl₂/EGTA precipitation method and uptake experiments were conducted using a high speed filtration technique. ³H-D-Glucose uptake was stimulated by both sodium and potassium and these transport rates were almost doubled in the presence of an inside-negative-induced membrane potential.

Cation-dependent nutrient transport in shrimp digestive tract.

Purified epithelial brush border membrane vesicles (BBMV) were produced from the hepatopancreas of the Atlantic White shrimp, Litopeneaus setiferus, using standard methods originally developed for mammalian tissues and previously applied to other crustacean and echinoderm epithelia. These vesicles were used to study the cation dependency of sugar and amino acid transport across luminal membranes of hepatopancreatic epithelial cells. (3)H-D: -glucose uptake by BBMV against transient sugar concentration gradients occurred when either transmembrane sodium or potassium gradients were the only driving forces for sugar accumulation, suggesting the presence of a possible coupled transport system capable of using either cation.

3H-L-leucine transport by the promiscuous crustacean dipeptide-like cotransporter.

The crustacean intestine and hepatopancreas display a variety of solute transport mechanisms for transmembrane transfer of dietary contents from lumen to epithelial cytosol. An in vitro intestinal perfusion apparatus was used to characterize mucosal to serosoal (MS) and serosal to mucosal (SM) Zn(2+) -dependent (3)H-L-leucine transport by the intestine of the American lobster, Homarus americanus. Transmural 20 µM MS (3)H-L-leucine fluxes across lobster intestine were a hyperbolic function of luminal zinc concentration (1-50 µM) following Michaelis-Menten kinetics (K(m) = 2.

Transepithelial D-glucose and D-fructose transport across the American lobster, Homarus americanus, intestine.

Transepithelial transport of dietary D-glucose and d-fructose was examined in the lobster Homarus americanus intestine using D-[(3)H]glucose and D-[(3)H]fructose. Lobster intestines were mounted in a perfusion chamber to determine transepithelial mucosal to serosal (MS) and serosal to mucosal (SM) transport mechanisms of glucose and fructose. Both MS glucose and fructose transport, as functions of luminal sugar concentration, increased in a hyperbolic manner, suggesting the presence of mucosal transport proteins.

Glucose and fructose uptake by Limulus polyphemus hepatopancreatic brush border and basolateral membrane vesicles: evidence for Na+-dependent sugar transport activity.

[(3)H]-fructose and [(3)H]-glucose transport activities were determined in brush border membrane vesicles (BBMV) and basolateral membrane vesicles (BLMV) from Limulus polyphemus (horseshoe crab) hepatopancreas. Glucose transport was equilibrative in the absence of sodium and sodium dependent in the presence of sodium in BBMV, suggesting GLUT-like and SGLT-like transport activity. Glucose transport by BLMV was equilibrative and sodium independent.

H(+) V-ATPase-energized transporters in brush border membrane vesicles from whole larvae of Aedes aegypti.

Brush border membrane vesicles (BBMVs) from Whole larvae of Aedes aegypti (AeBBMVWs) contain an H(+) V-ATPase (V), a Na(+)/H(+) antiporter, NHA1 (A) and a Na(+)-coupled, nutrient amino acid transporter, NAT8 (N), VAN for short. All V-ATPase subunits are present in the Ae. aegypti genome and in the vesicles.

Dual control of cytosolic metals by lysosomal transporters in lobster hepatopancreas.

This study describes the membrane transport mechanisms used by lobster (Homarus americanus) hepatopancreatic epithelial lysosomes to accumulate and sequester heavy metals from the cytosol, and thereby aid in the regulation of these ions entering the animal from dietary constituents. The present investigation extends previous work describing lysosomal metal uptake by cation exchange with protons and suggests that a second, parallel, lysosomal transport process involving metal-thiol conjugates may work in conjunction with the cation antiporter to control cytoplasmic metal concentrations. Transport of (65)Zn(2+) by lysosomal membrane vesicles (LMV) incubated in 1 mmol l(-1) glutathione (GSH) was not significantly different from metal transport in the absence of the tripeptide.

Identification of a novel sodium-dependent fructose transport activity in the hepatopancreas of the Atlantic lobster Homarus americanus.

[(3)H]Fructose and [(3)H]glucose transport were determined in brush-border membrane vesicles (BBMV), basolateral membrane vesicles (BLMV) and isolated cells (E, R, F, B) of H. americanus (Atlantic lobster) hepatopancreas. Glucose transport in BBMV was equilibrative in the absence of sodium and concentrative in the presence of sodium.

65Zn2+ transport by isolated gill epithelial cells of the American lobster, Homarus americanus.

Gills are the first site of impact by metal ions in contaminated waters. Work on whole gill cells and metal uptake has not been reported before in crustaceans. In this study, gill filaments of the American lobster, Homarus americanus, were dissociated in physiological saline and separated into several cell types on a 30, 40, 50, and 80% sucrose gradient.

Cloning of sarco-endoplasmic reticulum Ca2+ -ATPase (SERCA) from Caribbean spiny lobster Panulirus argus.

We have previously reported on calcium transport mechanisms in American lobster, Homarus americanus, using (45)Ca(2+) coupled with vesicle preparations of hepatopancreatic endoplasmic reticulum. The active transport of calcium across membranes bordering calcium-sequestering stores such as sarcoplasmic or endoplasmic reticulum is catalyzed by membrane-spanning proteins, the sarco-endoplasmic Ca(2+)-ATPases (SERCAs). In the study described here we used advanced bioinformatics and molecular techniques to clone SERCA from the economically important Caribbean spiny lobster, Panulirus argus.

S-nitrosohemoglobin deficiency: a mechanism for loss of physiological activity in banked blood.

RBCs distribute oxygen to tissues, but, paradoxically, blood transfusion does not always improve oxygen delivery and is associated with ischemic events. We hypothesized that storage of blood would result in loss of NO bioactivity, impairing RBC vasodilation and thus compromising blood flow, and that repleting NO bioactivity would restore RBC function. We report that S-nitrosohemoglobin (SNO-Hb) concentrations declined rapidly after storage of fresh venous blood and that hypoxic vasodilation by banked RBCs correlated strongly with the amounts of SNO-Hb (r(2) = 0.

Heavy metal detoxification in crustacean epithelial lysosomes: role of anions in the compartmentalization process.

Crustacean hepatopancreatic lysosomes are organelles of heavy metal sequestration and detoxification. Previous studies have shown that zinc uptake by lysosomal membrane vesicles (LMV) occurred by a vanadate- and thapsigargin-sensitive ATPase that was stimulated by a transmembrane proton gradient established by a co-localized V-ATPase associated with this organelle. In the present study, hepatopancreatic LMV from the American lobster Homarus americanus were prepared by standard centrifugation methods and 65Zn2+, 36Cl-, 35SO(4)2- and 14C-oxalate2- were used to characterize the interactions between the metal and anions during vesicular detoxification events.

Absorption of tetraethylammonium (TEA+) by perfused lobster intestine.

The organic cation, tetraethylammonium (TEA(+)), is actively secreted by mammalian nephrons and crustacean urinary bladders by similar processes in both animal groups. These mechanisms consist of a basolateral Organic Cation Transporter (OCT family) that employs the transmembrane electrical potential as a driving force for organic cation uptake from the blood and a brush border secondary active transport process that exchanges luminal protons for TEA(+). The present study examined the nature of (14)C-TEA(+) transport across the perfused intestinal epithelium of the American lobster, Homarus americanus, to ascertain whether the gut complemented the kidneys in the clearance of these organic metabolites from the blood.

Transepithelial transport of zinc and L-histidine across perfused intestine of American lobster, Homarus americanus.

The intestine of the American lobster, Homarus americanus, was isolated and perfused in vitro with a physiological saline, based on the ion composition of the blood, to characterize the mechanisms responsible for transmural transport of zinc and how the amino acid, L-histidine, affects the net movement of the metal across the tissue. Previous studies with this preparation, focusing on the characteristics of unidirectional mucosa to serosa (M to S) fluxes of (65)Zn(2+) and (3)H-L-histidine, indicated the presence of a brush border co-transport process responsible for simultaneously transferring the metal and amino acid across this tissue as an apparent bis-complex (Zn-[His](2)) using a PEPT-1-like dipeptide carrier mechanism. In addition, both zinc and L-histidine were also transferred toward the blood by separate transporters that were independent of the other substrate.

Calcium translocations during the moulting cycle of the semiterrestrial isopod Ligia hawaiiensis (Oniscidea, Crustacea).

Terrestrial isopods moult first the posterior and then the anterior half of the body. During the moulting cycle they retain a significant fraction of cuticular calcium partly by storing it in sternal CaCO(3) deposits. We analysed the calcium content in whole Ligia hawaiiensis and the calcium distribution between the posterior, the anterior ventral, and the anterior dorsal cuticle during four stages of the moulting cycle.