Decrease of internal exposure to chlororganic compounds and heavy metals in children in Baden-Württemberg between 1996/1997 and 2008/2009.

From 1996/1997 to 2008/2009, blood and urine were sampled from 9- to 11-year-old pupils in the state of Baden-Württemberg, South-West Germany. In blood samples the chlororganics DDE, HCB, PCB-138, PCB-153 and PCB-180 were analysed by gas chromatography and ECD detection. PCDD/PCDF were measured in pooled blood samples using GC/MS. Lead concentrations in blood were quantified by graphite furnace atomic absorption spectrometry (AAS), mercury in urine by using cold vapour AAS. For all chlororganics and heavy metals a distinct decrease of the internal concentration could be shown within the 12-year investigation period. For DDE, the median decreased from 0.32 µg/l to 0.11 µg/l. The median of HCB fell from 0.19 µg/l to 0.07 µg/l. The median of the sum of the three PCB-congeners PCB-138, PCB-153 and PCB-180 decreased from 0.47 µg/l to 0.18 µg/l. The burden of PCDD/PCDF in pooled blood samples resulted in approximately half the concentration after the 12-year period. The internal concentrations of the chlororganics were distinctly higher in breastfed children than in non-breastfed children. In 2008/2009, these differences were strongest for PCB and DDE (2-fold), moderate for PCDD/PCDF (1.6-fold), and slight for HCB (1.2-fold). The median of lead concentrations in blood dropped from 23.6 µg/l to 15.9 µg/l. The median of mercury concentrations in urine decreased from 0.25 µg/l to a value below the limit of quantification of 0.2 µg/l; the 95th percentile was reduced from 3.1 µg/l to less than 0.2 µg/l. The decline of amalgam fillings in children during the investigation period had a strong influence on internal concentrations of mercury. The internal concentration of the persistent xenobiotics investigated here decreased to a low level not likely to be of concern for human health.

Non-leaky vesiculation of large unilamellar vesicles (LUV) induced by plasma high density lipoproteins (HDL): detection by HPLC.

Interaction of large unilamellar phosphatidylcholine vesicles (LUV, 75nm) and plasma high density lipoproteins (HDL) resulted in a non-leaky vesiculation of LUV. This vesiculation was detected by a HPLC-system consisting of a combination of three TSK-gel columns (6000PW, 5000PW, 3000SW). With increasing incubation time liposomal [14C]PC, entrapped [3H]inulin, and apoprotein of HDL origin decreased. The decrease was accompanied by a formation of new particles, consisting of liposomal PC and apoprotein. These particles also enclosed [3H]inulin, reflecting a hydrophilic inner space. The formation of the particles reached a maximum after one day of incubation. Retention time was 21 minutes for LUV, 28 minutes for the new particles, and 36 minutes for HDL. In vesicles with membranes consisting of phosphatidylcholine and 30% cholesterol no interactions were observed.

Preparation of hemoglobin-containing liposomes using octyl glucoside and octyltetraoxyethylene.

Hemoglobin (Hb) was encapsulated in phosphatidylcholine vesicles by removal of the detergent n-octyl beta-D-glucoside (OG) or n-octyltetraoxyethylene (C8E4) out of mixed detergent-lipid micelles in Hb solution. Three types of apparatus were used for dialysis. Dialysis buffer flow rates, the surface area of the dialysis membranes, and detergent-lipid interactions determined the rate of dialysis, which influenced liposome size and lamellarity. Slow dialysis led to the formation of multilamellar liposomes, at increased dialysis rates Hb liposomes became smaller and unilamellar. Hb was enclosed at highest concentrations in larger liposomes, which included the negatively charged lipid phosphatidylserine or phosphatidic acid as a membrane component. Co-encapsulation of the allosteric factor inositol hexaphosphate led to oxygen dissociation curve values almost identical to those of whole blood. The oxygen-release capacity of Hb liposome suspensions in the physiological partial pressure range was comparable to whole blood. Storage of Hb liposomes for 2 months leaves oxygen-carrying characteristics virtually unchanged, with met-Hb levels increasing to only 11% of total Hb. Preparation of Hb liposomes by dialysis of octyl glucoside or C8E4 is a mild and efficient method for encapsulation of Hb. Since these Hb liposomes can be produced in scale-up batch sizes, they are a candidate for use as an oxygen-carrying blood surrogate.

Studies on the mechanism of bile salt-induced liposomal membrane damage.

The damage of phosphatidylcholine membranes by bile salts such as cholate, deoxycholate (DC), chenodeoxycholate (CDC), ursodeoxycholate (UDC), as well as their glyco- and tauroconjugates, and lithocholate (LC) were studied. The permeabilities of liposomes differing in size (700 and 1,700 A in diameter) were determined at increasing bile salt concentrations. The release of entrapped raffinose (3H) (MW: 594) or inulin (3H) (MW: 5,000) was measured by pelleting of the liposomes and subsequent determination of the radioactivities in the supernatant. The release of these uncharged volume markers of different size points to a formation of membrane leaks increasing in size with increasing bile salt concentration. Determination of the membrane damaging threshold concentrations of bile salts demonstrated a higher stability of the smaller liposomes. Incubation of the smaller liposomes with increasing DC concentrations results in a successive substitution of lecithin by DC. The predominantly DC-containing vesicles are of remarkable stability against higher DC concentrations. The damaging properties of bile salts increase with decreasing number of hydroxy groups, with the exception of UDC and its conjugates which are much less membrane toxic than the other dihydroxy bile salts. Conjugation with glycine or taurine slightly enhances the membrane toxicity of bile salts with the exception of UDC. Sulfation of the 3-alpha-hydroxy group of LC reduces the damaging effect to about 10%.