Mats Block

Helicobacter pylori entry into human gastric epithelial cells: A potential determinant of virulence, persistence, and treatment failures.

Background and Objectives. Intracellular location of Helicobacter pylori in human gastric epithelial cells has been observed in biopsies. Whether this reflects an ability to invade host cells and establish an intracellular niche remains to be determined.

Fast and high-yield synthesis of radioactive CH3203Hg(II)

A simple and fast synthesis of radioactive methylmercury is presented. It is based on the methylation of inorganic 203Hg(II) by methylcobalamin and isolation of resulting CH3203Hg(II) in a single extraction step. Time required is less than 4 hours and the final yield is ⩾90%.

Increased availability of cadmium to perfused rainbow trout (Salmo gairdneri, Rich.) gills in the presence of the complexing agents diethyl dithiocarbamate, ethyl xanthate and isopropyl xanthate

A study was made of the cadmium transfer through and retention of metal in perfused gill tissue from rainbow trout (Salmo gairdneri) in the presence of three cadmium complexing agents; DDC (diethyl dithiocarbamate), ethyl xanthate and isopropyl xanthate. The complexes formed are non-polar. The transfer of complexed cadmium was greater than the transfer of free cadmium ion. The retention of cadmium in gill tissue was increased about ten times in the presence of each of the two xanthates. However, the retention in gill tissue was not altered by DDC. It is concluded that cadmium uptake in fish gills in the presence of complexing agents is not simply a function of complexed versus free metal. It is also heavily dependent on the type of complexing agent present.

Excretion of cadmium during moulting and metamorphosis in Tenebrio molitor (Coleoptera; Tenebrionidae)

Abstract The effects of moulting between instars and metamorphosis on the contents of Cd were studied in T. molitor larvae both by following the radioactive tracer 108Cd ingested on one occasion and by analysing Cd concentration in larvae and newly hatched adults with a continuous intake of Cd. Larvae were given 109Cd in one meal. Contents of 109Cd were then determined periodically throughout the larval stage and in newly hatched adults. Moulting lowered the 109Cd contents, but to a smaller degree compared with metamorphosis. The rate of reduction during these processes decreased with time elapsed since ingestion of 109Cd and moulting or metamorphosis. At metamorphosis, the loss of 109Cd took place almost entirely at the pupation. With a continuous intake of Cd, concentrations in T. molitor were correlated to those in their food. Newly hatched adults had lower Cd concentrations than the corresponding larvae, when Cd concentrations in food were high.

Uptake of 109Cd by cultured gill epithelial cells from rainbow trout (Oncorhynchus mykiss)

Abstract Cadmium uptake was studied in respiratory epithelial gill cells from rainbow trout (itOncorhynchus mykiss). The cells were adherent and grown as a monolayer on the bottom of culture dishes. Experiments were made in chloride-free Cortland buffer, except when Cl was included as an experimental variable. Cadmium was mainly taken up in the cells as Cd 2− . but CdCl 2 uptake was also observed. Increase in the calcium concentration from 0.1 to 12.8 mM led to a small decrease in cadmium uptake. Zinc and lanthanum had no effect on the uptake of cadmium. In the presence of xanthate( 10 −6 − 10 −4 M) cadmium accumulation in the cells increased indicating that a hydrophobic xanthato complex was taken up across the phospholipid phase of the plasma membrane.

Effect of selenium on the uptake of methyl mercury across perfused gills of rainbow trout Oncorhynchus mykiss

Abstract The uptake of methyl mercury was measured across the perfused gills of rainbow trout Oncorhynchus mykiss. The effect of selenium, either in the blood (perfusion medium), or in the water was investigated. Methyl mercury was effectively taken up from the water across the gills into the perfusate. The uptake rate reached a stable level after 30 min perfusion. When the gills were placed in mercury free water after exposure to mercury in the water for 1 h, they continued to liberate significant amounts of accumulated mercury into the perfusate. Exposure to selenite (SeIV) or selenate (VI) (0.075–0.75 μM) in the external medium did not affect the uptake of methyl mercury across the gills or the liberation of the metal from the gills. Internal selenite or selenate (7.5 μM) augmented the uptake of methyl mercury across the gills and internal selenite also increased the amounts of liberated methyl mercury from the gills in the unload period. Internal selenium, increased the mercury accumulation in the gills, whereas, external selenium did not alter the mercury accumulation in the gills. Uptake of selenium from the water across the gills occurred very slowly.

Xanthate effects on cadmium intracellular distribution in rainbow trout (Oncorhynchus mykiss) gills

Abstract The uptake of 109 cadmium through perfused rainbow trout gills in the presence of xanthates was studied, and the subcellular distribution of cadmium in perfused gill tissue was determined. Pnenol absorption was also studied because xanthates form hydrophobic Cd complexes with a log P octanol/water similar to that of phenol. 1. Xanthate concentrations higher than 10 −5 M increased the rate of cadmium transfer through the gills and cadmium retention in gill tissue. Cadmium was present as a hydrophobic complex at this and higher xanthate concentrations. 2. A redistribution of cadmium from metallothionein to high molecular weight cadmium binding fractions occurred in the presence of 10 −4 M xanthate. 3. The rate of phenol transfer across the gill epithelium was much higher than the rate of cadmium transfer regardless of whether xanthate was present. The rate of phenol transfer stabilized much faster than the rate of cadmium transfer irrespective of whether xanthate was present, indicating that different uptake mechanisms were involved. We conclude that in the presence of xanthate concentrations higher than 10 −5 M cadmium is taken up as a hydrophobic Cd(xanthate) 2 complex by the epithelial cells. Within the cell the complex dissociates, and the metal ion is bound to intracellular cadmium-binding ligands. The metal is probably translocated through the basolateral membrane as a free ion.

Altered brain catecholamine levels in rainbow trout (Salmo gairdneri Richardson) exposed to diethyldithiocarbamate and amylxanthate

Abstract Rainbow trouts were exposed to 0.5 or 5.0 μM of diethyldithiocarbamate (DDC) or amylxanthate (AX) for 24 h. Both concentrations of DDC were found to decrease the brain-level of norepinephrine and increase the brain-level of dopamine. This suggests an inhibition of dopamine-β-hydroxylase, the enzyme synthesizing norepinephrine from dopamine. Also 5 μM AX was found to decrease the level of norepinephrine. Neither DDC nor AX had any significant effect on the brain-level of serotonin.

Influence of water quality on the accumulation of methyl 203mercury in gill tissue of minnow (Phoxinus phoxinus).

Effects of pH and concentrations of Cl and Ca on the uptake of methyl mercury (MeHg) in the gills of the minnow (Phoxinus phoxinus) were studied. Chloride concentration and pH in the water affect the speciation of MeHg. Ca was included because it affects the permeability of the gills and could therefore indirectly affect the amount of MeHg accumulated in the tissue. The species formed differ in hydrophobicity, as reflected in their octanol/water partition coefficients (Pow). Both a reduction in pH and an increase in Cl- concentration increased the Pow of MeHg. Ca had no effect on speciation. The accumulation of MeHg in the gill tissue increased with decreasing pH (from pH 7.0 to pH 3.9). Accumulation also increased as Cl- concentrations were increased from 10(-7) to 10(-1) M at pH 7.0. An increase in Ca concentration did not alter the accumulation of MeHg beyond a decrease in MeHg accumulation as Ca increased from 20 to 50 microM. We conclude that, of the water-quality factors studied, those affecting chemical speciation were most important in determining the MeHg uptake. The Ca concentration appears to be of minor importance.

Decreased norepinephrine and epinephrine contents in chromaffin tissue of rainbow trout (Oncorhynchus mykiss) exposed to diethyldithiocarbamate and amylxanthate

1. Rainbow trout (Oncorhynchus mykiss) were exposed to 0.5 or 5.0 microM of diethyldithiocarbamate (DDC) or amylxanthate (AX) for 24 hr. 2. Both DDC (0.5-5.0 microM) and AX (5.0 microM) significantly decreased norepinephrine and epinephrine levels in the head kidney as well as the quotients epinephrine/dopamine and/or norepinephrine/dopamine. 3. The results probably reflect an inhibition of dopamine-beta-hydroxylase, the enzyme responsible for the synthesis of norepinephrine and epinephrine from dopamine. 4. It is concluded that an exposure of fish to these complexing agents could disturb physiological processes controlled by catecholamines. 5. Diethyldithiocarbamate may prove to be a valuable pharmacological tool for the study of catecholamine function in fish.