Lipid composition and temperature adaptation of the nervous system of the leech Hirudo medicinalis L

Development and validation of a stability-indicating method for determination of free sterols in the Asian medicinal leech Hirudo manillensis

A rapid, simple, sensitive, selective, precise and robust thin-layer chromatography densitometric method for the determination of free sterols in leech was developed and validated on silica gel layer using carbon tetrachloride-methanol-formic acid (9.5:1.5:0.55, v/v/v). Spectrodensitometric scanning was carried using a Camag TLC scanner III at 366 nm after spraying 2% methanolic sulphuric acid, which gave compact spots for cholesterol (R(F) = 0.35 ± 0.02). The regression analysis data for calibration plot implied a good linear relationship (r(2) = 0.99958) between response and concentration over the range 100-600 ng per spot with respect to peak area. The limits of detection and quantification were found to be 13.8 ± 0.51 and 45.01 ± 1.29 ng per spot, respectively. Validation was in accordance to the International Conference on Harmonization guidelines. Cholesterol was subjected to forced stress conditions of oxidation, hydrolysis and heat. Degradation products resulting from the forced stress did not interfere with detection because the degradant peaks were well separated from the cholesterol peak. The densitometric method can be regarded as stability-indicating and can be used for quality control assay of cholesterol in leech extract.

Cholesterol and its derivatives, are the principal steroids isolated from the leech species Hirudo medicinalis

Steroids were isolated from the blood-sucking leech species Hirudo medicinalis and their structure was studied with one- and two-dimensional NMR spectroscopy (DQF-COSY and HMQC), GC-MS and ESI-MS spectrometry. Fractionating leech lipid using silicic acid chromatography led to the isolation of cholesterol in an early chloroform-eluted peak. Only minor traces of cholest-4-en-3-one, 4 beta-methylcholesterol, and sitosterol were present. The subsequent acetone-eluted fraction contained steroidtriols that were further purified by preparative TLC; these included cholest-7-ene-3,5,6 triol, cholest-4,7-diene-3,6,15 triol and to a lesser amount, cholestane-3,5,6 triol. A developmental study on cholesterol content in the leech showed that it is also the principal steroid in embryonic and freshly hatched leeches prior to feeding. The abundance of cholesterol, comprising approximately 5% of the total leech lipid, suggests that H. medicinalis, a blood sucking leech, has adapted itself fully to its mammalian host in terms of its steroid content. It remains to be seen whether lipids are directly transferred from the host to the parasite or whether leeches have evolved mechanisms to synthesize their own steroids.

Morphological organization of neuropile glial cells in the central nervous system of the medicinal leech (Hirudo medicinalis)

Neuropile glial (NPG) cells in the central nervous system of the medicinal leech, Hirudo medicinalis, were studied by histological, histochemical and immunocytochemical techniques. The NPG cells are often surrounded by electron-dense microglial cells. The central cytoplasm of NPG cells shows a significant zonation. The zone around the nucleus contains mitochondria, glycogen and vesicles. The cytoplasm also contains many ribosomes, a few dictyosomes and distinct inclusions up to 2 microns in diameter. A second zone around the perinuclear region is marked by the occurrence of bundles of intermediate filaments that correspond in thickness to glial filaments of vertebrates. We found a positive reaction with polyclonal antibodies against human glial fibrillary acidic protein (GFAP), and the areas of intense fluorescence correspond to the regions where intermediate filaments were found to be abundant. The peripheral zone contains numerous membrane stacks that could not be contrasted by lanthane nitrate or tannic acid. Therefore, the membrane stacks could be part of an extensive smooth endoplasmic reticulum, which is characteristic of cells with active lipid metabolism.

Different contribution of phospholipid and triacylglycerol metabolism to esterification of free intracellular arachidonate: a study on SK-N-BE(2) human neuroblastoma cells

When SK-N-BE(2) human neuroblastoma cells were exposed for 1h to growth medium supplemented with [14C]arachidonic acid (AA) at final concentrations ranging from 1 microM to 100 microM, an amount of this fatty acid was uptaken ranging form a 2% to a 120% of that present in cells at steady state. As more [14C]AA was uptaken by cells, a larger fraction was progressively incorporated into triacylglycerols (TAG) in comparison to phospholipids (PL), with minor amounts remaining in a free form. By gas chromatographic analysis it was estimated that TAG from cells grown in ordinary medium contained about 2 nmoles AA per mg protein, but, after 1 h exposure to medium supplemented with 100 microM AA (label-free) this value rose to about 28 nmoles/mg protein; furthermore, as estimated on the basis of total fatty acid content, TAG mass was increased by a 16%. Cell exposure to medium enriched with 100 microM AA did not cause PL mass changes, whereas AA content was significantly increased only in phosphatidylcholine. Medium enrichment with 100 microM AA dramatically enhanced [3H]glycerol incorporation into TAG, as assessed after 1 h cell pulse, with minor but significant changes observed also for phosphatidylinositol and phosphatidylethanolamine, but not for phosphatidylcholine. In the light of these data, the contribution of PL and TAG to the removal of free intracellular AA is discussed.

Ca2(+)-dependence of arachidonic acid redistribution among phospholipids of cultured mouse keratinocytes

Mouse keratinocytes cultured in a medium containing less than 0.1 mM Ca2+ (low Ca2+) incorporated [1-14C]arachidonic acid (AA) into phospholipids by kinetics including; (i) a rapid labelling of phosphatidylinositol (PtdIns), phosphatidylserine (PtdSer) and both acid-stable and alkenylacyl forms of phosphatidylcholine (PtdCho); and (ii) a slow but long-lasting radiolabel incorporation into both acid-stable and alkenylacyl forms of phosphatidylethanolamine (PtdEtn), partly associated with a net radioactivity loss from acid stable-PtdCho. Under low Ca2+ conditions no radioactivity transfer apparently occurred between PtdIns and other phospholipid classes. When cells were prelabelled for 24 h with [1-14C]AA and reincubated in label-free medium containing 1.2 mM Ca2+ (normal Ca2+), an early and extensive loss of radioactivity from PtdIns was observed, reasonably in connection with Ca2+ stimulation of phosphoinositide turnover. Cell shift to normal Ca2+ did not result in an increased synthesis of labelled eicosanoids, but was consistent with an increase of radioactivity incorporation into diacylglycerol (DAG) and with a complex pattern of [1-14C]AA redistribution, eventually leading to a marked radioactivity incorporation into acid stable-PtdEtn (but not into alkenylacyl-PtdEtn) and to a labelling decrease of acid stable-PtdCho. The possible mechanisms driving AA recycling after cell shift to normal Ca2+ are discussed.

Arachidonic acid incorporation and redistribution in human neuroblastoma (SK-N-BE) cell phospholipids

The incorporation and redistribution of [1-14C]arachidonic acid in SK-N-BE human neuroblastoma cell phospholipids were investigated. By continuous labelling in serum-enriched medium, a rapid radioactivity incorporation into phosphatidylcholine (PtdCho), phosphatidylinositol, and phosphatidylserine was observed; initially, phosphatidylethanolamine (PtdEtn) was poorly labelled, but at later stages it displayed the highest level of arachidonic acid incorporation, in comparison with other phospholipid classes. Labelling of triacylglycerols was also observed. When cells were pulse-labelled with [1-14C]arachidonic acid and then reincubated in label-free medium, a decrease of the radioactivity in triacylglycerols was observed initially, paralleled by an increase of phospholipid labelling; thereafter, arachidonic acid redistribution was consistent with a net decrease of the radioactivity associated with PtdCho acid-stable forms (i.e., diacyl plus alkylacyl forms), concomitantly with a net labelling increase of both acid-stable PtdEtn and alkenylacyl-PtdEtn. Data indicate the following: (a) neuroblastoma cells incorporate arachidonic acid into phospholipids through complex kinetics involving transfer of the fatty acid from acid-stable PtdCho to both alkenylacyl-PtdEtn and acid-stable PtdEtn; and (b) triacylglycerols act as storage molecules for arachidonic acid which is subsequently incorporated into phospholipids. The possibility that arachidonic acid transfer to PtdEtn subclasses is driven by distinct mechanisms is discussed.