Study of ethane level in exhaled breath in patients with age-related macular degeneration: preliminary study.

PURPOSE: A variety of factors have been implicated in the pathogenesis of age-related macular degeneration (ARMD), and oxidative stress plays an important role in the onset and progression of the disease. Breath ethane is now considered a specific and non-invasive test for determining and monitoring the trend of lipid peroxidation and free radical-induced damage in vivo. This test provides an index of the patients' overall oxidative stress level. We evaluated the breath ethane concentration in exhaled air in patients with advanced ARMD. METHODS: In this study, we enrolled 13 patients with advanced ARMD and a control group, and a breath analysis was carried out by gas chromatography. RESULTS: The mean ethane level in the ARMD patients was 0.82 ± 0.93 nmol/l (range: 0.01-2.7 nmol/l) and the mean ethane value in the control group was 0.12 ± 0.02 nmol/l (range: 0.08-0.16 nmol/l). The difference between the values of the 2 groups was statistically significant (p < 0.005). Receiver operating characteristic analysis showed an elevated area under the curve (0.831; 95% CI: 0.634-0.948), with a significance level of p < 0.0014 (area = 0.5). CONCLUSIONS: These preliminary results seem to indicate that breath ethane levels are higher in most patients with ARMD. The breath ethane test could thus be a useful method for evaluating the level of oxidative stress in patients with ARMD. To our knowledge, there are no data on this type of analysis applied to ARMD.

Effect of two-hour daily hemodialysis and sham dialysis on breath isoprene exhalation.

BACKGROUND: Isoprene, a volatile hydrocarbon produced by the human organism, is currently being extensively investigated because the mechanisms underlying its endogenous origin are unknown and because experiments suggest it is toxic and cancerogenous. Previous reports of increases in breath isoprene concentrations during 4-hour, thrice-weekly hemodialysis, but not during continuous ambulatorial peritoneal dialysis, prompted us to assess the behavior of isoprene in another dialytic modality, i.e., short daily hemodialysis (short DHD). Furthermore, in order to determine whether removal of solutes and/or contact of blood with the dialytic membrane influenced the metabolism of isoprene, we performed a sham short hemodialysis session in a subgroup of 8 patients (sham short HD), i.e., with blood flowing through a dialyzer but without dialysate and ultrafiltration. METHODS: The present study evaluates the effects of a two-hour short DHD and a two-hour session of sham HD on isoprene breath levels, as determined by gas chromatography before, during and after sessions. Parallel analyses of ambient air and monitoring of blood pressure and heart rate were performed. RESULTS: Both short DHD and sham DHD induced an increase in breath isoprene exhalation in all patients without being associated with significant hemodynamic variations. CONCLUSION: These findings suggest that the increase in breath isoprene after a session of hemodialysis is neither a reaction to mevalonate depletion nor to metabolic variations induced by the depurative effect, because these changes do not occur during sham HD. It is not related to hemodynamic changes because none were observed in this experimental model. The isoprene increase seems to be of metabolic origin and appears to be connected in some way with the extracorporeal circuit. These interesting findings provide a further impulse to study the biosynthetic pathways involved and to investigate the medical and biological significance of isoprene in humans.

Organophosphate-resistant forms of acetylcholinesterases in two scallops--the Antarctic Adamussium colbecki and the Mediterranean Pecten jacobaeus.

We describe the acetylcholinesterase polymorphisms of two bivalve molluscs, Adamussium colbecki and Pecten jacobaeus. The research was aimed to point out differences in the expression of pesticide-resistant acetylcholinesterase forms in organisms living in different ecosystems such as the Ross Sea (Antarctica) and the Mediterranean Sea. In A. colbecki, distinct acetylcholinesterase molecular forms were purified and characterized from spontaneously soluble, low-salt-soluble and low-salt-Triton extracts from adductor muscle and gills. They consist of two non-amphiphilic acetylcholinesterases (G(2), G(4)) and an amphiphilic-phosphatidylinositol-membrane-anchored form (G(2)); a further amphiphilic-low-salt-soluble G(2) acetylcholinesterase was found only in adductor muscle. In the corresponding tissues of P. jacobaeus, we found a non-amphiphilic G(4) and an amphiphilic G(2) acetylcholinesterase; amphiphilic-low-salt-soluble acetylcholinesterases (G(2)) are completely lacking. Such results are related with differences in cell membrane lipid compositions. In both scallops, all non-amphiphilic AChEs are resistant to used pesticides. Differently, the adductor muscle amphiphilic forms are resistant to carbamate eserine and organophosphate diisopropylfluorophosphate, but sensitive to organophoshate azamethiphos. In the gills of P. jacobaeus, amphiphilic G(2) forms are sensitive to all three pesticides, while the corresponding forms of A. colbecki are sensitive to eserine and diisopropylfluorophosphate, but resistant to azamethiphos. Results indicate that organophosphate and/or carbamate resistant AChE forms are present in species living in far different and far away environments. The possibility that these AChE forms could have ensued from a common origin and have been spread globally by migration is discussed.

Fatty acid dietary intake and the risk of ischaemic stroke: a multicentre case-control study. UFA Study Group.

A low dietary intake of unsaturated fatty acids has been found in male patients with stroke as compared with controls in Italy, and a high consumption of meat has been associated with an increased risk of stroke in Australia. We present a case-control study, comparing the unsaturated and saturated fatty acids content of red cell membranes (which reflects the dietary intake of saturated and unsaturated fats) in 89 patients with ischaemic stroke and 89 controls matched for age and sex. In univariate analysis, besides hypertension, atrial fibrillation, ischaemic changes in ECG and hypercholesterolaemia, stroke patients showed a lower level of oleic acid (P = 0.000), but a higher level of eicosatrienoic acid (P = 0.009). Conditional logistic regression (dependent variable; being a case) showed that the best model included atrial fibrillation, hypertension, oleic acid and eicosatrienoic acids. These results confirm a possible protective role of unsaturated fatty acids against vascular diseases; however, we did not find any difference in the content of omega3 acids, which have been considered in the past to protect against coronary heart disease. We conclude that the preceding diet of patients with ischaemic stroke may be poor in unsaturated fatty acids (namely, oleic acid), and this defect is independent of other vascular risk factors. Only further studies will show whether changes in diet and/or supplement of unsaturated fatty acids might reduce the incidence of ischaemic stroke.

Biochemical studies on the nootropic drug, oxiracetam, in brain.

The aim of this work was to study the effects of the nootropic drug oxiracetam, on lipid metabolism in rat brain. Twenty-month-old rats and spontaneous hypertensive (SHR) rats with cerebrovascular lesions were used, which showed an impaired learning and memory rate if challenged with behavioral tests. Oxiracetam improves the in vitro and in vivo synthesis of phosphatidylcholine (PhC) and phosphatidylethanolamine (PhE) impaired by aging, when respectively added to the incubation medium or administered subacutely to animals. SHR rats drinking saline, and with cerebrovascular lesions, have a reduced choline incorporation into cerebral phospholipids and an increase of arachidonic acid release from the same lipids if compared to SHR rats (without cerebrovascular lesions) drinking water. They also show a decreased incorporation rate of arachidonic acid into PhC, PhE, and PhC plasmalogen and PhE plasmalogen. If oxiracetam is chronically administered (200 mg/kg/day for 14 weeks) a significant variation in the incorporation of both precursors takes place. In the first 2 h after the intracerebroventricular (i.c.v.) injection of choline and arachidonic acid the values are comparable to those observed in SHR rats with lesions; at longer time intervals, however, the rates of incorporation are similar and even better than those of SHR rats without lesions. Since the drug does not seem to influence the incorporation of the precursors in the first 2 h after their administration, we may assume that oxiracetam acts on the turnover of the phospholipids more than on their rate of synthesis from injected precursors.

Membrane-bound base-exchange reactions in animal tissues.

The calcium-stimulated incorporation of ethanolamine, L-serine and choline into rabbit synaptosomal phospholipids in vitro has been investigated. The synaptosomal membranes were prelabelled in vitro in their choline-, ethanolamine- or serine-phosphoglycerides by base-exchange and then chasing experiments were performed by displacing the lipid-bound base by ethanolamine, choline or L-serine labelled with a different isotope. The results indicate that membrane phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine are substrates for the exchange with all the three mentioned bases. A very small phospholipid pool (0.5-2% of the total available pool) is active in the calcium-dependent exchange between membrane phosphatidylcholine or phosphatidylethanolamine and free bases, whereas the pool of exchanging phosphatidylserine is sensibly larger (2-9%). In another series of experiments the effect of the base-exchange reaction upon the production of cyclic-AMP at the level of rat brain synaptic membranes has been examined. An exchange with ethanolamine produces a significant decrease of the NaF-stimulated production of the cyclic nucleotide, whereas it increases the noradrenaline-induced production. With some exceptions, the exchange with L-serine produces opposite effects. The possible physiological importance of phospholipid pool at the synaptosomal level is discussed.

Relationships between base-exchange reaction and synaptosomal phospholipid pool in the rabbit brain in vitro.

The calcium-stimulated incorporation of ethanolamine, L-serine and choline into rabbit synaptosomal phospholipids in vitro has been investigated. The synaptosomal membranes were prelabelled in vitro in their choline-, ethanolamine- or serine-phosphoglycerides by base-exchange and then chasing experiments were performed by displacing the lipid-bound base by ethanolamine, choline of L-serine labelled with a different isotope. The results indicate that membrane phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine are substrates for the exchange with all the three mentioned bases. A very small phospholipid pool (0.5-2% of the total available pool) is active in the calcium-dependent exchange between membrane phosphatidylcholine or phosphatidylethanolamine and free bases, whereas the pool of exchanging phosphatidylserine molecules is sensibly larger (2-9%). The possible physiological importance of these small phospholipid pools, involved in base-exchange reaction at brain membrane level, is discussed.

The activation of CTP: phosphocholine cytidylyltransferase from rat liver by polyunsaturated phospholipid.

Experimental evidence is reported that the addition in vitro of a polyunsaturated soybean phospholipid material (EPL) to a CTP:PC cytidylyltransferase preparation from rat liver (E.C. 2.7.7.15) produces noticeable stimulation of this enzymatic activity. Preincubation for different time intervals of EPL under air or oxygen further stimulates the activating effects. Little influence is exerted on the same enzyme by saturated lipids, such as dipalmitoyl-sn-glycero-3-phosphorylcholine and distearoyl-sn-glycero-3-phosphorylcholine. It is proposed that the lipid components of the EPL which exert the stimulatory action may be lyso-phospholipid moieties derived from EPL upon preincubation or directly present in the product. The biological significance of these activations in liver tissue is discussed.

Phospholipid base-exchange in brain microvessels.

The capillary endothelium of cerebral microvessels plays an important role in homeostasis within the central nervous system. The flux of fluids and solutes takes place through the lipid matrix of plasma membranes and the maintenance of their structural composition is necessary for cell membrane permeability and the cellular transport systems. Few studies have been carried out to clarify the relationships between brain microvessel lipid metabolism and the role of this metabolism. We have studied a particular aspect of the phospholipid metabolism, i.e. their hydrosoluble head group exchange with free choline, ethanolamine or serine, in capillaries from brains of both 4 month- old and 24 month-old rats. The results obtained indicate that microvessels possess the biochemical machinery of base-exchange reaction, whose activity rate appears unaffected by age.

Effect of age and strain on cerebral phospholipid metabolism.

It has been demonstrated that spontaneously hypertensive adult rats (SHR) develop severe hypertension and cerebrovascular lesions on drinking 1% NaCl from weaning. Phospholipid metabolism is actively altered in these severely lesioned animals (SHR-NaCl) as compared to SHRs which drink only water and showed only sporadic cerebrovascular lesions. We have tested the incorporation of water soluble phospholipid precursors into the corresponding phospholipid from different brain areas, by injecting either a mixture of labeled glycerol and choline or glycerol and ethanolamine into the lateral ventricle of the brain of adult (4 months old) and senescent (12 months old) SHR-NaCl. The results were compared to those obtained from 4 and 12 months old Wistar normotensive rats. When adult normotensive rats were compared with adult hypertensive rats (4-SHR-NaCl) incorporation was found to decrease in some areas according to the precursors injected. Similar results were obtained from 12 month old normotensive Wistar rats that, however, showed a decrease in phospholipid biosynthesis in all the area tested. Interestingly, no significant differences of incorporation rate were found between 12 month old normotensive and 12 month old hypertensive rats.