Lactobacillus rhamnosus GG versus Placebo for Acute Gastroenteritis in Children.

BACKGROUND: Acute gastroenteritis develops in millions of children in the United States every year, and treatment with probiotics is common. However, data to support the use of probiotics in this population are limited. METHODS: We conducted a prospective, randomized, double-blind trial involving children 3 months to 4 years of age with acute gastroenteritis who presented to one of 10 U.S. pediatric emergency departments. Participants received a 5-day course of Lactobacillus rhamnosus GG at a dose of 1×1010 colony-forming units twice daily or matching placebo. Follow-up surveys were conducted daily for 5 days and again 14 days after enrollment and 1 month after enrollment. The primary outcome was moderate-to-severe gastroenteritis, which was defined as an illness episode with a total score on the modified Vesikari scale of 9 or higher (scores range from 0 to 20, with higher scores indicating more severe disease), within 14 days after enrollment. Secondary outcomes included the duration and frequency of diarrhea and vomiting, the duration of day-care absenteeism, and the rate of household transmission (defined as the development of symptoms of gastroenteritis in previously asymptomatic household contacts). RESULTS: Among the 971 participants, 943 (97.1%) completed the trial. The median age was 1.4 years (interquartile range, 0.9 to 2.3), and 513 participants (52.9%) were male. The modified Vesikari scale score for the 14-day period after enrollment was 9 or higher in 55 of 468 participants (11.8%) in the L. rhamnosus GG group and in 60 of 475 participants (12.6%) in the placebo group (relative risk, 0.96; 95% confidence interval, 0.68 to 1.35; P=0.83). There were no significant differences between the L. rhamnosus GG group and the placebo group in the duration of diarrhea (median, 49.7 hours in the L. rhamnosus GG group and 50.9 hours in the placebo group; P=0.26), duration of vomiting (median, 0 hours in both groups; P=0.17), or day-care absenteeism (median, 2 days in both groups; P=0.67) or in the rate of household transmission (10.6% and 14.1% in the two groups, respectively; P=0.16). CONCLUSIONS: Among preschool children with acute gastroenteritis, those who received a 5-day course of L. rhamnosus GG did not have better outcomes than those who received placebo. (Funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development and others; ClinicalTrials.gov number, NCT01773967 .).

Glucosylceramide synthase protects glioblastoma cells against autophagic and apoptotic death induced by temozolomide and Paclitaxel.

Glioblastoma is a deadly cancer with intrinsic chemoresistance. Understanding this property will aid in therapy. Glucosylceramide synthase (GCS) is associated with resistance and poor outcome; little is known about glioblastomas. In glioblastoma cells, temozolomide and paclitaxel induce ceramide increase, which in turn promotes cytotoxicity. In drug-resistant cells, both drugs are unable to accumulate ceramide, increased expression and activity of GCS is present, and its inhibitors hinder resistance. Resistant cells exhibit cross-resistance, despite differing in marker expression, and cytotoxic mechanism. These findings suggest that GCS protects glioblastoma cells against autophagic and apoptotic death, and contributes to cell survival under chemotherapy.

Pyrene derivatives as markers of transbilayer effect of lipid peroxidation on neuronal membranes.

Two different pyrene derivatives, namely 12-(1-pyrene)dodecanoic acid (P12-FA) and N-(12-(1-pyrene)dodecanoyl)-galactosylsphingosine I3-sulfate (P12-CS) have been used to follow lipid peroxidation both in model and natural membranes. The malondialdehyde (MDA) production in small unilamellar vesicles of dipalmitoylphosphatidylcholine/arachidonic acid (80:20, molar ratio), symmetrically labelled with both probes determined a progressive decrease of pyrene fluorescence due to an involvement of pyrene in the peroxidative reaction. Nervous membranes are particularly sensitive to lipid oxidation which differentially acts on the two layers of the membrane determining a greater rigidity of the exofacial one. Thus, we consider the possibility to asymmetrically introduce the pyrene ring, as P12-FA or P12-CS, in synaptosomes for monitoring lipid peroxidation in each layer of the membrane. The amount of the two probes incorporated in the membrane was 20 +/- 3 and 10 +/- 2 nmol/mg of protein for P12-FA and P12-CS, respectively. P12-FA was symmetrically distributed in the two layers, whereas 95% of P12-CS was incorporated in the exofacial layer of the membrane as determined by TNBS measurements. The decrease in fluorescence of synaptosome associated pyrene was, in the early stages of lipid peroxidation, greater for P12-CS than for P12-FA labelled membranes, indicating a greater susceptibility of the exofacial layer to iron-induced peroxidation.

Correlation of the dispersion state of pyrene cerebroside sulfate and its uptake and degradation by cultured cells.

This study aimed at increasing the efficiency and shortening the time required for administering cerebroside sulfate to cultured cells. For this purpose several modes of dispersion of a fluorescent derivative of cerebroside sulfate (sulfatide), in which the natural fatty acid has been replaced by pyrenedodecanoic acid (P12), were incubated with the cells. This fluorescent derivative of cerebroside sulfate (P12-CS) was introduced into the growth medium of the cells using the three following modes of dispersion: (1) P12-CS was dissolved in dimethylsulfoxide and added to the medium, (2) it was precomplexed with serum albumin or (3) incorporated into small, unilamellar vesicles (SUV) of phosphatidylcholine. With each of these respective modes of dispersion, the P12-CS was incubated for periods up to 48 h with cultured lymphoblasts or fibroblasts. Uptake by the cells could be determined by recording directly the cell-associated fluorescence, using a suspension of washed intact cells. The cell lipids were subsequently extracted with mixtures of chloroform/methanol and their fluorescence recorded. When related to the incubation time, uptake of P12-CS by the cells increased continuously using each of the above dispersions. The appearance of fluorescence at 475 nm ('excimer') and the ratio of this to the monomolecular fluorescence at 378 nm ('E/M') could be used as a measure for the presence of the internalized P12-CS in aggregated or fully dispersed states. These values (i.e., E/M), recorded on the suspensions of intact cells were rather high using the aqueous dispersions, intermediate values were observed using the SUV and rather low E/M values (0.5 or less) were observed using the preformed albumin-(P12-CS) complexes. Increasing the mole ratio of albumin to P12-CS (i.e., from 1:2 to 2:1 m/m), decreased the quantity of sulfatide which was taken up by the cells but also further decreased the E/M ratio, suggesting a fully dispersed state of the pyrene lipid within the cell. This indicated that, using an optimal albumin to P12-CS ratio of 1-2 (or its equivalent values in fetal calf serum) permitted an influx of single molecules of P12-CS into the cells. After 48 h, about 50% of the fluorescence of skin fibroblasts was found in metabolic degradation products of P12-CS. The parallel value for fibroblasts derived from a patient with metachromatic leukodystrophy was only about 5%. Appearance of the excimeric emission of a dispersion of P12-CS in water permitted estimation of its critical micellar concentration as being 7.5 x 10(-7) M.

Calcitonin-induced changes in the organization of sulfatide-containing membranes.

The interactions of salmon calcitonin with glycosphingolipid sulfatide are studied by right angle light scattering from the lipid suspension, by the excimer to monomer ratio (E/M) of the fluorescence intensity of pyrene phosphatidylcholine and pyrene sulfatide and by the leakage of carboxyfluorescein. It was found that calcitonin strongly modified the structure of the sulfatide aggregate, as indicated by the light scattering determinations. At a lipid peptide ratio 100:1 (molar ratio) light scattering from the suspension was negligible, indicating the formation of peptide-sulfatide complexes with a structure different from that of the lipid aggregate. The interactions of calcitonin with sulfatide when the latter is a component of a bilayer were also evaluated. A specific calcitonin-membrane sulfatide interaction was demonstrated by determining the temperature-dependent E/M of pyrene phosphatidylcholine and pyrene sulfatide in dipalmitoyl phosphatidylcholine/sulfatide (80:20, molar ratio) liposomes. The E/M curves were modified by calcitonin only when the liposomes were labelled with fluorescent sulfatide which probes the sulfatide behavior in the membrane. Furthermore, the addition of calcitonin to the incubation medium of liposomes containing sulfatide promoted the release of vesicle entrapped carboxyfluorescein without disrupting the bilayer structure, the release being correlated with the amount of sulfatide in the bilayer and the calcitonin concentration in the medium.

Synthesis of pyrene derivatives of cerebroside sulfate and their use for determining arylsulfatase A activity.

Two fluorescent derivatives of cerebroside sulfate ('sulfatide') have been synthesized and used as substrates for determining arylsulfatase A activity. These were 12-(1-pyrene)dodecanoyl cerebroside sulfate (P12-sulfatide) and 12(1-pyrenesulfonylamido)dodecanoyl cerebroside sulfate (PSA12-sulfatide). When incubated at pH 5.0 in the presence of 5 mM MnCl2 and 5.5 mM of taurodeoxycholate, either substrate was hydrolyzed by arylsulfatase A of human leukocytes. The rate of hydrolysis was proportional to the incubation time and concentration of enzyme; Michaelis-Menten type kinetics were observed with increasing concentrations of substrate. For determining the rate of hydrolysis, each of the two products (i.e., P12- and PSA12-cerebrosides) were separated from the bulk of respective unreacted sulfatide on small columns of DEAE-Sephadex A-25 and their fluorescence intensities read at 343-378 and 350-380 nm for the excitation and emission wavelengths for P12- and PSA12-cerebrosides, respectively. When extracts of skin fibroblasts derived from normal individuals and patients with Maroteaux-Lamy (lacking arylsulfatase B) or metachromatic leukodystrophy (lacking arylsulfatase A) were used as source of enzyme, P12-sulfatide was hydrolyzed by the former two but not by the latter cell extract. Several derivatives of cerebroside sulfate were also synthesized and found to inhibit the hydrolysis of pyrenesulfatide by leukocyte arylsulfatase A. The results demonstrate that these two pyrene containing sulfatides can be effectively used as specific substrates for the determination of arylsulfatase A activity in extract of cells and most probably also of tissues.

Plasma dependent pH sensitivity of liposomes containing sulfatide.

In this study we investigated the possibility to define relatively plasma-stable liposomal preparations in which the sensitivity to moderate drops of pH (i.e., from 7.4 to 6.8) would be induced by the presence of plasma itself. The liposome stability was monitored by determining the release of entrapped 5,6-carboxyfluorescein (CF). Using small unilamellar vesicles composed of egg phosphatidylcholine (EPC) and bovine brain sulfatide (CS) (4:1, molar ratio), the amount of CF released at pH 6.8 in the presence of 50% plasma was 3-fold that at pH 7.4, whereas no significant differences in the amount of CF released were observed when the same liposomes were incubated in buffer at pH 7.4 and 6.8, respectively. The increase in plasma induced leakage as a consequence of a drop in the pH medium, seems to specifically depend on the presence of sulfatide molecule in the bilayer since neither the acidic cholesterol 3-sulfate nor galactocerebroside, are able to induce pH sensitivity in EPC liposomes. Of all the plasma components considered (VLDL, LDL, HDL, protein fraction), VLDL seemed preferentially involved in the pH sensitivity induced by CS since they promoted an almost complete release of CF from EPC/CS small unilamellar vesicles. Thus, these liposomes are potentially a useful tool for a specific drug delivery to those pathological tissues such as tumors, inflammation sites and ischemic areas in which it is known that a lowering of the pH can occur.

pH sensitivity and plasma stability of liposomes containing N-stearoylcysteamine.

In this study, we investigated the pH sensitivity of different liposomal formulations containing 10 mol% N-stearoylcysteamine, as pH sensitive molecule. Liposome stability was monitored by determining the release of different entrapped water soluble molecules, 5,6-carboxyfluorescein (CF) being the marker of leakage mainly used. Small unilamellar vesicles composed of egg phosphatidylcholine (EPC) and N-stearoylcysteamine (9:1 molar ratio) incubated at 20 degrees C in citrate phosphate buffer released, at pH 6.8, 2.5 fold the amount of CF released at pH 7.4. The addition of plasma to the incubation medium and an increase of temperature to 37 degrees C led to significantly increased the CF release from EPC/N-stearoylcysteamine SUV, both at pH 7.4 and 6.8. The addition of cholesterol had a stabilizing effect on liposomal vesicles with respect to both temperature and plasma, without affecting pH sensitivity. In fact, at 37 degrees C and in 25% plasma the ternary mixture showed the highest CF release, as a consequence of the moderate acidification of the medium from 7.4 to 6.8. Thus, these liposome formulations are potentially a useful tool for specific drug delivery to pathological tissues such as tumours, inflammation sites and ischemic areas where it is known that a lowering of the pH can occur.

Pyrene lipids as markers of peroxidative processes in different regions of low and high density lipoproteins.

Three different pyrene derivatives, pyrene decanoyl phosphatidylcholine (P10PC), pyrene dodecanoyl sulfatide (P12CS) and cholesteryl pyrenyl hexanoate (P6Chol), were used to follow lipid peroxidation in low and high density lipoproteins. Probe-labelled lipoproteins were subjected to Cu2+ catalyzed peroxidation. In all cases the fluorescence of the probes progressively decreased due to the involvement of pyrene in the peroxidative reaction. Thus, we used the fluorescence decrease of P6Chol to monitor the lipid peroxidation in the hydrophobic core of LDL and HDL, and that of the amphipatic probes, P10PC and P12CS, to follow lipid peroxidation in the envelope of both lipoproteins. The possibility of following lipid peroxidation in individual lipoprotein regions could lead to more detailed information on the oxidative modifications that play an important role in the altered cholesterol homeostasis involved in the formation of atherosclerotic lesions. No differences were observed in the peroxidation kinetics of the hydrophobic core of HDL and LDL monitored with P6Chol. On the contrary kinetics obtained with P10PC and P12 CS demonstrated the HDL envelope to be more susceptible to Cu2+ -dependent lipid peroxidation than that of the LDL. This could be due to a greater radical generating capacity of the HDL envelope and can be explained on the basis of low vitamin E levels and large amounts of polyunsaturated fatty acids esterified on phospholipids determined in HDL, and on literature evidence that indicates HDL as the principal vehicle of circulating plasma lipids peroxides.

Nosocomial infections in the rehabilitation department.

AIM: The patients of a Rehabilitation Department are at high risk of nosocomial infections because they generally have a long term hospitalisation and more and more frequently immune-compromised subjects, like old patients or with chronic illness, are admitted to rehabilitation programs. However, to evaluate the real infectious risk of a Rehabilitation Unit, it is important to consider also that a high number of patients are transferred from other hospitals after a specific therapy of the acute phase of their medical or surgical pathology and so many nosocomial microrganisms previously acquired may spread to a Rehabilitation Unit. METHODS: From January to December 2003 we have performed a screening of the bacteruria among the patients at admittance to the Rehabilitation Unit of S. Orsola Fatebenefratelli Hospital of Brescia (Italy). RESULTS: A significant bacteruria (>100000 cfu/mL) in 28.9% of 114 patients coming from home and in 41.9% of 179 patients transferred from other hospitals without antibacterial treatment has been documented. CONCLUSIONS: These findings confirm the presence of an high number of patients colonized or infected by nosocomial bacteria previously acquired in hospital and underline the need, in addition to specific skill, of wide infectious knowledge among the medical staff of a Rehabilitation Unit. A specific approach to the infectious problem in the Rehabilitation Department in order to reduce the risk of nosocomial infections may be suggested.

GM3 ganglioside inhibits endothelin-1-mediated signal transduction in C6 glioma cells.

We found that sparse and confluent C6 glioma cells differ both in GM3 content, which increases with cell density, and in endothelin-1 (ET-1)-induced phosphoinositide hydrolysis, which was markedly higher in the sparse cells than in the confluent. Also after manipulation of the cellular GM3 content through treatment with exogenous GM3 or with drugs known to affect GM3 metabolism, the ET-1 effect was inversely related to GM3 cellular levels. Cell treatment with an anti-GM3 mAb resulted in the enhancement of ET-1-induced phospholipase C activation and restored the capacity of GM3-treated cells to respond to ET-1. These findings suggest that the GM3 ganglioside represents a physiological modulator of ET-1 signaling in glial cells.

Behaviour of nitric oxide synthase in rat cerebellar granule cells differentiating in culture.

The possible relation between nitric oxide synthase (NOS) activity and neural differentiation was investigated using primary cultures of rat cerebellar granule cells differentiating in culture. NOS activity was measured in the cytosolic and particulate fractions obtained from cell homogenate. In the experimental conditions used the optimal pH for NOS activity was about 6.4, the activity being about 3-fold higher than at pH 7.4. Cerebellar granule cell differentiation was associated with marked increases in NOS activity. In undifferentiated cells the enzyme was almost evenly distributed between the cytosolic and particulate fractions, during differentiation there was a 12-fold increase in activity in the cytosolic enzyme and a 3-fold increase in the particulate one. This indicates a marked preferential enrichment of the cytosolic enzyme during differentiation. Cerebellar granule cells produced and released NO in the culture medium; NO formation being markedly higher in differentiated cells (7-12 DIC) than in undifferentiated (2-3 DIC) ones. These data demonstrate a relationship between NOS expression and NO production and the differentiation of cerebellar granule cells, supporting the notion that NO may play a role in this process.

Sphingosine inhibits nitric oxide synthase from cerebellar granule cells differentiated in vitro.

The effects of different bioactive sphingoid molecules on NOS activity of differentiated cerebellar granule cells were investigated by measuring the conversion of [3H]arginine to [3H]citrulline. Cytosolic Ca2+-dependent NOS activity was strongly inhibited in a dose-dependent manner by sphingosine in concentrations of 1-40 microM. This inhibition seems to be peculiar to sphingosine in that ceramide, N-acetylsphingosine, sphingosine-1P, sphinganine and tetradecylamine have no effect on the cytosolic enzyme at the considered concentrations, suggesting that it is the bulk of the sphingosine hydrophilic portion that is critical for cytosolic NOS inhibition. This inhibition of cytosolic NOS is not reversed by increasing the arginine concentration, so a competitive mechanism can be excluded. Instead, increasing the concentrations of calmodulin led to loss of sphingosine inhibition, suggesting that sphingosine interferes with the calmodulin-dependent activation of the enzyme by a competitive mechanism. Sphingosine and related compounds had no effect on the particulate Ca2+-independent NOS activity. The data obtained suggest that sphingosine could be involved in the regulation of NO production in neurons.

Nitric oxide production in living neurons is modulated by sphingosine: a fluorescence microscopy study.

An investigation was carried out into the possible effect of sphingosine (Sph) on nitric oxide (NO) production in living neurons. Differentiated granule cells were used in a dynamic videoimaging analysis of single cells labeled, simultaneously, with FURA-2 and the NO indicator 4,5-diaminofluorescein. The results demonstrate that Sph exerts a potent inhibitory effect on the Ca2+-dependent production of NO, without modifying the [Ca2+]i. The effect appears to be specific as neither ceramide nor Sph-1-phosphate had any effect on the NO and [Ca2+]i levels. The data demonstrate that Ca2+-dependent NO production is a specific Sph target in living granule cells, suggesting that this bioactive sphingoid plays a relevant role in neuronal NO signaling.

Salvage pathways in glycosphingolipid metabolism.

In this review, the focus is on the role of salvage pathways in glycosphingolipid, particularly, ganglioside metabolism. Ganglioside de novo biosynthesis, that begins with the formation of ceramide and continues with the sequential glycosylation steps producing the oligosaccharide moieties, is briefly outlined in its enzymological and cell-topological aspects. Neo-synthesized gangliosides are delivered to the plasma membrane, where their oligosaccharide chains protrude toward the cell exterior. The metabolic fate of gangliosides after internalization via endocytosis is then described, illustrating: (a) the direct recycling of gangliosides to the plasma membrane through vesicles gemmated from sorting endosomes; (b) the sorting through endosomal vesicles to the Golgi apparatus where additional glycosylations may take place; and (c) the channelling to the endosomal/lysosomal system, where complete degradation occurs with formation of the individual sugar (glucose, galactose, hexosamine, sialic acid) and lipid (ceramide, sphingosine, fatty acid) components of gangliosides. The in vivo and in vitro evidence concerning the metabolic recycling of these components is examined in detail. The notion arises that these salvage pathways, leading to the formation of gangliosides and other glycosphingolipids, sphingomyelin, glycoproteins and glycosaminoglycans, represent an important saving of energy in the cell economy and constitute a relevant event in overall ganglioside (or glycosphingolipid, in general) turnover, covering from 50% to 90% of it, depending on the cell line and stage of cell life. Sialic acid is the moiety most actively recycled for metabolic purposes, followed by sphingosine, hexosamine, galactose and fatty acid. Finally, the importance of salvage processes in controlling the active concentrations of ceramide and sphingosine, known to carry peculiar bioregulatory/signalling properties, is discussed.

The effects of exogenous sphingosine on Neuro2a cells are strictly related to the overall capacity of cells to metabolize sphingosine.

Neuro2a cells were exposed to different doses (1-40 nmol/10(6) cells) of [C3-3H]sphingosine and the relationship between metabolism and biological effects of sphingosine was investigated. Sphingosine appeared to be rapidly taken up and metabolized. The incorporation of sphingosine was not merely dependent on its concentration but primarily on the dose per cell of administered sphingosine. At low doses, [3H]sphingosine represented a minor portion of the cellular radioactivity, and N-acylated metabolites, particularly ceramide, largely prevailed over degradation products. Concomitantly with ceramide increase, Neuro2a differentiation took place. With increasing exogenous sphingosine/doses, the acylation process reached saturation. From this point on, [3H]sphingosine started accumulating and eventually cell toxicity occurred. In conclusion, the biological effects exerted by exogenous sphingosine on Neuro2a cells are not merely dependent on the long-chain base concentration in the culture medium, but are strictly related to the cellular dose of exogenous sphingosine and to the capacity of cells to metabolize sphingosine.

Metabolic fate of exogenous sphingosine in neuroblastoma neuro2A cells. Dose-dependence and biological effects.

The possible relationship between metabolism and biological effects of sphingosine was investigated in Neuro2a cells. [C3-3H]-sphingosine, administered at different doses (80 pmol-80 nmol/mg cell protein). Amounts up to hundredfold were rapidly taken up and metabolized, the intracellular content of sphingosine being processed within 2 h. At low doses, [3H]-sphingosine represented a minor portion of the cellular radiolabel, and N-acylated metabolites, particularly ceramide, prevailed over degradation products. Neuro2a cell differentiation took place in conjunction with ceramide increase. At increasing exogenous sphingosine/cell ratio, the acylation process became saturated while sphingosine degradation increased proportionally. From this point on [3H]-sphingosine accumulated and cell toxicity occurred. In conclusion, in Neuro2a cells the biological effects exerted by exogenous sphingosine are strictly connected to the exogenous sphingosine/cell ratio and to the capacity of the cell to metabolize sphingosine.

A fluorescence method for the determination of plasma susceptibility to lipid peroxidation.

OBJECTIVE: We propose a fluorescence kinetics method for monitoring plasma susceptibility to peroxidation. DESIGN AND METHOD: Plasmatic peroxidation was induced by CuSO4 (500 microM), and fluorescence was measured every 30 min. Kinetics were represented by a sigmoidal curve from which it was possible to calculate the latency time (lag-time) and the propagation velocity (slope) of plasma peroxidation. RESULTS: The lag-time monitored by the fluorescence kinetics method corresponded to the formation of thiobarbituric acid reactive substances, and to progressive depletion of polyunsaturated fatty acids and alpha-tocopherol. The mechanism of reaction appeared to be dependent upon plasmatic hydroperoxides, and independent of oxygen radicals. Plasma storage is possible for at least two months at -80 degrees C, and reproducibility of the method is very good. CONCLUSIONS: Fluorescence kinetics provide a highly comprehensive picture of plasma susceptibility to peroxidation in comparison with the conventional measurements of anti- and pro-oxidant ratios.

Studies on peroxidation processes of model membranes: role of pyrophosphate.

Phosphate-containing compounds of both a lipophilic (dipalmitoylphosphatidic acid, lysophosphatidic acid and dicetylphosphate) and hydrophilic nature (orthophosphate, 3-phosphoglyceric acid, 2,3-diphosphoglyceric acid and pyrophosphate in particular) have been found to inhibit to varying degrees the lipoperoxidation of liposomal arachidonic acid. Lipophilic compounds seem to act exclusively at the lipid component level of the membrane, giving rise to polyanionic complexes with free arachidonic acid or its radical derivatives that could bind the Fe2+ strongly (thereby inhibiting the iron pro-oxidation activity) or to minimize the lateral mobility of the lipid radicals (thereby reducing the propagation of lipid peroxidation). The high antiperoxidative power of hydrophilic compounds, and in particular of pyrophosphate, must, on the contrary, be primarily attributed to their ability to form very stable complexes with the Fe present in the solution surrounding the liposomal membranes. The possible contribution of these physiological compounds to the in vivo defense mechanism against radical-induced damage is discussed.

Fluorospectroscopic studies of mixtures of distearoylphosphatidylcholine and sulfatides with defined fatty acid compositions.

Simple study models characteristic for lamellar organization of distearoylphosphatidylcholine and sulfatide have been prepared for fluorospectroscopic investigations on the influence of these glycolipids on the chemico-physical properties of lecithin bilayers. The motion of 1,6-diphenyl-1,3,5-hexatriene in mixed lecithin-sulfatide bilayers changed with temperature, with the compositional ratio of the two lipids, with the presence of divalent cations such as Ca2+ and with the fatty acid composition of sulfatide moiety. Steady-state fluorescence measurements of the average motion of the fluorophore permit evaluation of the gel to liquid-crystalline phase transition in all these membrane models containing different sulfatides.