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Biomedical subjects

N Salem

Publications and source records attributed to N Salem.

At least 145 records · Page 8Linked to original sources
PubMed1989

Analysis of aminophospholipid molecular species by high performance liquid chromatography.

A new method is described for the separation of individual molecular species of the aminophospholipids, phosphatidylethanolamine and phosphatidylserine. Trinitrobenzene-sulfonic acid was used to derivatize both aminophospholipids and the derivatives were purified by thin-layer chromatography. A reversed-phase high performance liquid chromatography technique was developed to separate and quantify individual molecular species based upon ultraviolet detection of the attached chromophore. The retention times of the molecular species on the C18 reversed-phase column were longer with increasing carbon chain length and decreasing degree of unsaturation of fatty acyl chain. The overall procedure allowed a quantitative recovery of the aminophospholipid species. The lower limit of detection was about 10 pmol and a linear response was observed in the range of 0.1-10 nmol of phospholipid. Using this method, we were able to separate and quantify trinitrophenyl-phosphatidylethanolamine molecular species of both subclasses (diacyl and alkenyl) from human red blood cells and rat brains. Separation of species was confirmed by gas-liquid chromatographic analysis of the fatty acid content of each peak and by thermospray liquid chromatography-mass spectrometry. This new method provides a convenient and sensitive technique for studies of aminophospholipid molecular species composition. Furthermore, it appears to be a useful tool for the analysis of asymmetric distribution of these species in biological membranes.

Adult↗
PubMed1988

GC/MS assay of prostaglandins in cerebrospinal fluid from humans and monkeys.

The objective of this project has been to develop a sensitive and specific assay for prostaglandins in human cerebrospinal fluid (CSF) from patients with alcoholism and appropriate controls using gas chromatography/mass spectrometry. This study was initiated because numerous literature reports strongly suggest that a relationship exists between ethanol's central nervous system effects and the central production of prostaglandins. In both human and animal studies, administration of prostaglandin synthesis inhibitors prior to administration of ethanol attenuated central nervous system effects of ethanol. Samples from alcoholics after a three week period of abstinence and normals contained none of the measured prostaglandins (PGE2, PGE1, PGF1a, PGF2a, 6-keto-PGF1a) at a concentration more than twice the limit of quantification (3 pg/mL CSF). Comparison of GC/MS and radioimmunoassay methods provided further validation for these results. Literature reports of much higher levels of prostaglandins in normal controls, i.e., tens to hundreds of pg/mL CSF, appear to be incorrect. Examination of monkey CSF provided a positive control, since several of the prostaglandins were easily quantifiable in these samples.

6-Ketoprostaglandin F1 alpha↗
PubMed1988

Polyunsaturated fatty acids and ethanol.

Ethanol exposure leads to a loss in membrane polyunsaturated fatty acids (PUFA). It is proposed that polyunsaturated species of phospholipids are not randomly distributed, but are concentrated in the cytosolic leaflets of the plasma membrane and are preferentially associated with membrane proteins. These lipids affect the physical state of environments surrounding membrane proteins and thereby serve to regulate many cellular functions. Disruption of these environments may occur even when a small percentage of total polyunsaturates is lost due to ethanol exposure. One possible mechanism of ethanol-induced polyunsaturate loss may be activation of a phospholipase A2 enzyme which is selective for these species of phospholipids. Fatty acids released would stimulate the production of prostaglandins and/or leukotrienes. Similarly, the released docosahexaenoate can be metabolized by rat brain to leukotriene-like compounds which are biologically active in smooth muscle systems. This metabolism is stimulated by ethanol in human platelets, in vitro.

Animals↗
PubMed1988

The effect of alcohol inhalation on the cardiovascular state of the rat.

Rats were exposed to alcohol vapors by an inhalation technique and blood pressure and its reactivity and platelet aggregation were measured. Acute exposure to alcohol levels which produced moderate blood alcohol concentration (BAC) was associated with increased vascular production of prostacyclin (PGI2) and plasma catecholamines, whereas platelet production of thromboxane (TXA2) decreased. Blood pressure is elevated in these animals, however, the platelet aggregating and pressor effects of noradrenaline (NE) were decreased. Chronic exposure to high BAC is associated with a dramatic reduction in vascular and platelet prostaglandin (PG) production and a marked increase in plasma catecholamine levels. Platelet aggregation decreased in these animals, however, the pressor effect of TXA2 and NE was significantly increased. The fatty acid precursors to PG were reduced by 50% in the lipid extracts of these preparations. These findings suggest that alterations in fatty acid metabolism may lead to a functional deficiency in PG production from dependent rats. Qualitative differences may exist between acute and chronic exposure with respect to the cardiovascular state. Locally produced PG and circulating catecholamines may mediate alcohol-induced alterations in vascular smooth muscle tone and platelet aggregation.

Animals↗
PubMed1988

Discovery of novel brain lipoxygenase products formed from docosahexaenoic acid (22:6w3).

It is known that alcohol exposure leads to a decline in brain docosahexaenoate (22:6w3). We hypothesized that alcohol could stimulate the metabolism of this polyunsaturated fatty acid to bioactive products. Several oxidized products of 22:6w3 were indeed observed when rat brain homogenate was incubated with 14C22:6w3 in vitro. A similar group of metabolites was formed in vivo from 14C-22:6w3 injected into the lateral ventricle. These metabolites were characterized by thermospray- and GC/MS as well as by the synthesis of standards using purified enzymes. Platelet lipoxygenase also proved useful in identifying one of the brain metabolites and served as a source of enzyme for preparative studies. Their physiological effects on smooth muscle tone and platelet aggregation will be presented.

Animals↗
PubMed1988

A new technique for lipid analysis using liquid chromatography/mass spectrometry.

It has been previously reported that ethanol alters the level of polyunsaturated fatty acids, and this may be related to alteration of membrane physical properties. Therefore, developing a technique to efficiently analyze lipid molecular species is of value for alcohol research. A new technique which can provide detailed structural information for most major lipid classes has been developed in our laboratory using thermospray liquid chromatography/mass spectrometry (LC/MS). In this technique, on-line LC separation is achieved with a conventional flow rate and the LC effluent is carried into the mass spectrometer via a heated capillary where it is vaporized and ionized. The results thus obtained for the major lipid classes including fast separation methods and quantitative aspects will be presented.

Animals↗
PubMed1988

Essential fatty acid deficiency and neutrophil function: studies of lipid-free total parenteral nutrition in monkeys.

Linoleic acid (18:2 omega 6), the obligate precursor of arachidonic acid (20:4 omega 6), is an essential nutrient for humans and other mammals. Because arachidonic acid release and metabolism are components of neutrophil activation by certain stimuli, we questioned whether neutrophils depleted of arachidonate as a result of essential fatty acid deficiency might be functionally impaired. We examined this possibility by producing essential fatty acid deficiency in monkeys with lipid-free total parenteral nutrition (TPN). Rhesus and African green monkeys were given calorically equal TPN for up to 23 days with and without a vegetable fat emulsion rich in linoleic acid. Fatty acids were analyzed in total lipid extracts of serum and isolated blood neutrophils by gas-liquid chromatography. Although fatty acids in the serum and neutrophils of monkeys given TPN with lipid did not change, linoleic acid levels decreased by at least 60% in serum and 50% in neutrophils from animals given TPN with no lipid. Moreover, arachidonate levels in neutrophil lipids decreased by at least 50% within 12 days of lipid-free TPN, and the abnormal fatty acid 20:3 omega 9 (characteristic of essential fatty acid deficiency) appeared and steadily increased with time. These biochemical signs of omega 6 fatty acid deficiency were associated with impaired neutrophil function in vitro. Both migration responses and superoxide generation stimulated by N-formyl-methionyl-leucyl-phenylalanine were significantly decreased by 12 days of lipid-free TPN, as was the capacity of activated cells to synthesize leukotriene B4. In contrast, functional responses of fatty acid-deficient neutrophils to leukotriene B4 and phorbol myristate acetate, which have little or no effect on arachidonate release or metabolism, were not significantly altered. These findings indicate that endogenous supplies of arachidonic acid and other essential omega 6 fatty acids influence the functional responsiveness of neutrophils. These studies also indicate that altered neutrophil function is a feature of essential fatty acid deficiency and that it may contribute to the increased risk of infection and decreased inflammatory responses observed in this condition.

Animals↗
PubMed1988

Smooth muscle effects of hydroxylated docosahexaenoates produced from human platelet.

Washed platelets (10(8)cells/ml) are capable of metabolizing docosahexaenoic acid (22:6w3, DHE) to 12-lipoxygenase derivatives. The two major metabolites of the DHE thus formed were collected and derivatized for analysis by GC/MS/EI. The structures assigned were 14(S) and 11(S) hydroxy-docosahexenoate (HDHE). 12-lipoxygenase inhibitors such as ETYA inhibited the production of HDHE. The metabolites formed are biologically active as they are capable of inducing a weak contraction in airway but not vascular smooth muscle preparations; a thromboxane-agonist (U46619) was 10 to 20-fold more efficacious than HDHE in the guinea pig lung parenchymal strip. HDHE may act in part through stimulation of leukotriene production as increased peptidyl-leukotriene levels were associated with the HDHE-induced contraction in this preparation and a lipoxygenase inhibitor (NDGA) was capable of a partial blockade of this response. In addition, HDHE antagonizes the contractile effects of the thromboxane-agonist, U46619, especially in vascular smooth muscle. Stimulation of the sulfidopeptido leukotrienes and thromboxane antagonism may therefore be important aspects of the biological function of HDHE.

Animals↗
PubMed1988

Specialization in membrane structure and metabolism with respect to polyunsaturated lipids.

The principal features of the hypotheses presented here are presented in a model (Figure 8). Polyunsaturated phospholipids are preferentially localized on the cytosolic leaflet of the plasma membrane and around proteins. They influence the physical state of these microenvironments and thereby help to regulate cellular functions. Losses of these species due to phospholipase attack, dietary deprivation or other pathological stimuli (such as alcohol), may lead to drastic alterations in some of these functions. The PUFA's released, including 22:6 omega 3, can be metabolised by a lipoxygenase enzyme in the brain and platelet and the products formed are biologically active.

Animals↗
PubMed1987

Determination of eicosanoids, phospholipids and related compounds by thermospray liquid chromatography-mass spectrometry.

Thermospray mass spectrometry has proven to be a useful technique for analyzing various biological compounds including eicosanoids and phospholipids. Molecular ions as well as fragment ions which reveal useful structural information are produced for underivatized eicosanoids and phospholipids using filament-off or filament-on thermospray mass spectrometry, respectively. In conjunction with on-line chromatographic separation, complex mixtures of biological samples can be rapidly analyzed with great reliability. Data will be presented concerning the analysis of prostaglandins, other eicosanoids and molecular species of phospholipids as well as the application of these methodologies to complex biological samples.

Animals↗
PubMed1987

Needle aspiration cytologic diagnosis of metastatic malignant melanoma of unknown primary origin: report of a case and review of the literature.

A rare case of metastatic malignant melanoma of unknown primary origin in a 49-year-old woman is reported. The swelling, localized in the right inguinal region, was partially immovable and associated with progressively increasing pain. Initial diagnosis was set by needle aspiration cytology and was confirmed postoperatively by histologic examination of a surgical specimen. Cytomorphologic features of metastatic malignant melanomas are described and the difficulties of identification discussed. A brief review of the literature is also made, and the rarity of the case and the value of cytologic diagnosis are emphasized.

Biopsy, Needle↗
PubMed1987

Plasma adenosine levels: measurement in humans and relationship to the anxiogenic effects of caffeine.

The effects of caffeine on plasma adenosine were examined in eight healthy normal volunteers. Subjects were randomly administered on 4 separate days, in a double-blind fashion, either placebo or three different doses of caffeine (240, 480, and 720 mg). Adenosine concentrations, measured by high performance liquid chromatography, were in the micromolar range when samples were drawn into tubes containing dipyridamole to prevent adenosine reuptake by red blood cells. Plasma adenosine levels did not change after caffeine administration. The effects of caffeine on anxiety were related to changes in plasma caffeine but not plasma adenosine levels. The potential interest of caffeine as a chemical model of anxiety is discussed.

Adenosine↗
PubMed1986

The effect of chronic alcohol inhalation on blood pressure and the pressor response to noradrenaline and the thromboxane-mimic U46619.

Rats were exposed to alcohol vapor for 6 days and the mean blood ethanol concentration (BEC) was obtained for each subject. Blood pressure and its reactivity to noradrenaline and a thromboxane-mimic U46619 were directly measured on day 6 via a catheter implanted in the tail artery of normal and ethanol-treated animals. The mean BEC for each subject correlated with mean arterial blood pressure (MAP); an increase in BEC was associated with a decrease in MAP (p less than 0.02). The mean MAP of subjects with BEC less than 168 mg% was 8% higher than normal (not significant), whereas, the mean MAP of subjects with BEC greater than 182 mg% decreased 27 +/- 4% (p less than 0.01). Conversely, the pressor response to U46619 was markedly enhanced (p less than 0.005) in rats with mean BEC greater than 182 mg% at all doses investigated (12.5-3200 ng per rat). Increases in the pressor response to noradrenaline in ethanol-treated rats were significant only when maximally stimulated by 400 and 800 ng doses (p less than 0.03). A 3-fold increase in sensitivity for U46619 was seen in subjects with high mean BEC, however, sensitivity for noradrenaline did not significantly change. Vasoreactivity was not effected in rats with mean BEC less than 168 mg%. These data demonstrate that a moderate mean BEC for 6 days induces a tendency towards a mild hypertension, whereas, high mean BEC induces marked hypotension which is associated with hyperreactivity. Long-term exposure to high blood ethanol concentrations may predispose the alcohol-dependent rats to hypertensive disease and vasospastic disorders, at least partially, as a result of enhanced sensitivity to prostaglandins such as thromboxane.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1986

Exfoliation of the beta-adrenergic receptor and the regulatory components of adenylate cyclase by cultured rat glioma C6 cells.

Cultured rat glioma C6 cells exfoliate membrane vesicles which have been termed 'exosomes' into the culture medium. The exosomes contained both stimulatory and inhibitory GTP-binding components of adenylate cyclase (the stimulatory, Gs, and the inhibitory, Gi, regulatory components) and beta-adrenergic receptors but were devoid of adenylate cyclase activity. It was therefore apparent that the catalytic component of adenylate cyclase was either not exfoliated or was inactivated during the exfoliation process. The presence of Gs or Gi in the exosomes was detected by ADP ribosylation using [alpha-32P]NAD in the presence of cholera or pertussis toxins, respectively. The exosomal concentration of each of the two components was estimated to be about one fifth of that of the cell membrane when expressed on a per mg protein basis. Exosomal Gs was almost as active as the membrane-derived Gs in its ability to reconstitute NaF- and guanine nucleotide-stimulated adenylate cyclase activity in membranes of S49 cyc- cells, which lack a functional Gs. The ability of exosomal Gs to reconstitute isoproterenol-stimulated activity, however, was much lower than that of membrane Gs. The density of beta-adrenergic receptors in the exosomes was much less than that found in the membranes. Although the exosomal receptors bound the antagonist iodocyanopindolol with the same affinity as receptors from the cell membrane, the affinity for the agonist isoproterenol was 13- to 18-fold lower in the exosomes. In addition, this affinity was not modulated by GTP in the exosomes. Thus, exfoliated beta-adrenergic receptors seem to be impaired in their ability to couple to and activate Gs. This was directly tested by coupling the receptors to a foreign adenylate cyclase using membrane fusion. The fusates were then assayed for agonist-stimulated activity. While significant stimulation of the acceptor adenylate cyclase was obtained using C6 membrane receptors, the exosomal receptors were completely inactive. Thus during exfoliation, there appear to be changes in the components of the beta-adrenergic-sensitive adenylate cyclase that results in a nonfunctional system in the exosomes.

Adenylate Cyclase Toxin↗
PubMed1986

Extraskeletal Ewing's sarcoma: first case report in Greece.

The first case of soft tissue Ewing's sarcoma in Greece is presented. The tumour was a circumscribed large mass at the right calf, was radically excised and histologically proved to be small cell malignant neoplasm, performing the characteristic structural and cytological pattern of Ewing's sarcoma. Systematic clinical and radiological examination was negative. Operation was followed by local radiotherapy and systematic chemotherapy and the patient remains disease-free and clinically in perfect health eight months after the operation. The case is presented with special reference to its histological appearance and its treatment.

Adult↗
PubMed1986

Synaptic effects of the synthetic pyrethroid resmethrin in rat brain in vitro.

Resmethrin (30 microM) induced release of transmitters was not affected by manipulation of the Na+ current with either choline or tetrodotoxin agents which readily reversed the effects of veratridine, deltamethrin and cypermethrin. Resmethrin (I50: 2.2 microM) inhibited the ATP dependent uptake of Ca2+ but deltamethrin and cypermethrin were much less effective. Resmethrin also displaced Ca2+ from crude synaptosomal membranes. The release promoting effects of resmethrin in rat brain in vitro are better explained by its effects on Ca2+ rather than through a specific effect on the Na+ channel. In contrast, the effects of deltamethrin and cypermethrin promote transmitter release by a Na+ dependent process.

Animals↗