Local administration of DFO-loaded lipid particles improves recovery after end-to-end reconstruction of rat median nerve

PURPOSE

The improvement of regeneration and functional recovery after peripheral nerve injury is a major challenge in neurosurgery. Although microsurgical techniques for nerve reconstruction have seen great advancements over the last years, the clinical outcome with patients is often unsatisfactory. The aim of the present study was to investigate if administration of the iron chelator Deferroxamine (DFO), can improve postoperative outcome in the rat median nerve reconstruction model.

METHODS

After complete transection, the right median nerve was repaired by end-to-end neurorrhaphy. The suture site was wrapped by a 1-cm-long external jugular vein segment, either empty or filled with DFO-loaded lipid particles (Perineurin or with a vehicle (unloaded lipid particles) alone. Functional testing was carried out weekly by means of the grasping test. At the time of withdrawal, 12 weeks post-operatively, muscle tropism recovery was assessed by weighing flexor digitorum sublimis muscle that is innervated by the median nerve only. Before harvesting of the nerve specimens electrophysiological analyses were performed with measuring the latency, the threshold and the conduction velocity. Finally, the repaired nerves were withdrawn for immunocytochemistry with a neurofilament antibody and axon quantitative morphology.

RESULTS

The comparison between the groups showed that intraoperative application of the DFO-loaded lipid particles at the neurorrhaphy site led to a significant increase in the density of regenerating axons as well as to an accelerated recovery of both muscle tropism and motor function. The electrophysiological results demonstrated a decrease of the threshold, a lower latency, and a higher conduction velocity in the Perineurin-treated animals.

CONCLUSIONS

The results of the present study suggest that local administration of Perineurin might have a therapeutic potential for improving the postoperative outcome after microsurgical nerve reconstruction in patients.

Measurement of pressure-gradient-driven currents in tokamak edge plasmas

Localized currents driven by pressure gradients play a pivotal role in the magnetohydrodynamic stability of toroidal plasma confinement devices. We have measured the currents generated in the edge of L- (low) and H- (high confinement) mode discharges on the DIII-D tokamak, utilizing the Zeeman effect in an injected lithium beam to obtain high resolution profiles of the poloidal magnetic field. We find current densities in excess of 1 MA/m2 in a 1 to 2 cm region near the peak of the edge pressure gradient. These values are sufficient to challenge edge stability theories based on specific current formation models.

Identification of an amplified gene cluster in glioma including two novel amplified genes isolated by exon trapping

Gene amplification, which occurs in more than 50% of malignant gliomas, is considered to play a pivotal role in tumorigenesis. There are, however, few studies aimed toward the isolation of novel genes from amplified sequences. Previously, we reported amplification of the protooncogene MET (hepatocyte growth factor receptor; 7q31) in more than 20% of glioblastomas. For an approximate size estimation of the amplification unit we analyzed three glioblastomas all of which carried an amplified MET gene, by Southern blot analysis and/or competitive polymerase chain reaction using eight DNA markers. Although the extent of the amplified domain varied, the close vicinity of the MET gene was the only region consistently amplified in these glioblastomas. A yeast artificial chromosome (YAC) contig of 900 kb was refined spanning the amplified region flanking the MET gene. The YAC inserts were subcloned into 59 cosmids, which were used for exon trapping. Eight sequences were identical to parts of the genes MET and CAPZA2 (human actin capping protein alpha-subunit). Two newly identified exons and the CAPZA2 exons were amplified in tumor TX3095, which retains an amplified MET gene. The new exons were localized close to MET and CAPZA2. Characterization of the clones, which were termed glioma-amplified sequence (GAS)7-1 and GAS7-2, showed an open reading frame and a different expression pattern in multiple human tissues. This study reports the identification of a cluster of amplified genes including two novel genes in a region amplified in more than 20% of glioblastomas.

Quality control in the determination of cortisol in plasma/serum by using, on every sample, two different three-step separation methods including ultrafiltration, restricted-access high-performance liquid chromatography and reversed-phase high-performance liquid chromatography, and contrasting results to immunoassays

Tests of HPLC columns with restricted access, polymer covered alumina, polymer, and different ODS phases showed that base-acid compatible ODS columns gave the best peak shapes of cortisol, internal standard, as well as of plasma/serum (P/S) matrix components. Further trials with cortisol in P/S showed that three separation steps were essential in order to obtain chromatographic data which were superior to immunoassay data. Also, sufficient confidence in results required determination of each sample with two newly developed separation methods: (a) pre-separation with a restricted access column, concentration of the desired cut with a 20 mm base-acid compatible ODS column, and analysis with a 250 mm column filled with the same ODS; (b) pre-separation with an ultrafilter followed by the last two steps in (a). For detection UV was preferred over fluorescence. This twin multistep chromatography showed that immunoassays were very treacherous in that they produced a spectrum of results ranging from good to untenable without any warning whatever about functionality. The measurement of official controls, with reference values derived via gas chromatography-isotope dilution mass spectrometry, also demonstrated the superiority of the double HPLC method.

Measurement of platelet-activating factor in a canine model of coronary thrombosis and in endarterectomy samples from patients with advanced coronary artery disease

Platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is a potent phospholipid mediator of numerous inflammatory and thrombotic responses. The purpose of this study was to determine if PAF synthesis is elevated in damaged coronary arteries after a sustained period of cyclic flow variation (CFV), a phenomenon caused by alternating periods of thrombosis and reperfusion at sites of endothelial injury. Cyclic flow was established and maintained in the left anterior descending coronary arteries (LADs) of 10 dogs. After 8 hours of CFV, the section of damaged LAD containing the thrombus and control sections of the circumflex artery, carotid artery, and saphenous vein was excised, and the total lipids were extracted. The PAF was then purified by silica column chromatography and high-performance liquid chromatography and assayed by both a rabbit platelet bioassay and a PAF radioimmunoassay. With the platelet bioassay, PAF levels of 8.9 +/- 4.0 (range, 4.8 to 15.5) pg/mg wet wt were found in the damaged LADs from the 10 dogs. This PAF bioactivity was completely inhibited by a PAF receptor antagonist. When the radioimmunoassay was used, slightly higher PAF levels of 16.3 +/- 12.9 (range, 4.5 to 41.8) pg/mg wet wt were observed in the LADs. Overall, these PAF levels were 3- to 64-fold higher than in the control vessels when either assay method was used. Although increases in PAF were observed in the damaged LADs, measurements of PAF in blood samples taken from the LAD and the aorta (control) failed to demonstrate any site-specific increase of PAF in the blood. In related experiments, PAF was also measured in 23 endarterectomy samples taken from the coronary arteries of 16 patients with severe atherosclerosis. The PAF levels in these samples were highly variable (2.9 +/- 2.2 [range, 0.3 to 8.5] pg/mg wet wt) and showed no correlation with tissue mass, suggesting that PAF is affected by factors other than the simple presence of atherosclerotic tissue in the vessel. These findings provide direct evidence that PAF is synthesized locally at the site of endothelial injury during thrombosis and that PAF accumulates in the atherosclerotic plaque of some patients with advanced coronary artery disease.

Strategy for chromosomal assignment of expressed sequences derived from heteronuclear RNA

The chromosomal localization of transcribed sequences/genes is one of the objectives of the human genome project. Here, we describe a novel strategy for fast and dependable chromosomal assignment of expressed sequences that contain Alu sequences. Alu-PCR was performed on cDNA that was derived from heteronuclear (hn) RNA. hn-cDNA libraries are utilized for the identification of genes from extended human chromosomal regions or entire chromosomes. For chromosomal assignment, Alu-PCR products larger than 500 bp were hybridized against genomic DNA of somatic cell hybrids that was also amplified by Alu-PCR. Hybridization signals obtained within 2-3 h of exposure allow localization of cDNA-derived Alu-PCR products to single chromosomes. This technique is particularly useful for the analysis of cDNA libraries derived from hn-RNA. Using hn-cDNA clones from different chromosomes, we demonstrate the accuracy and reliability of the mapping strategy.

The endogenous ouabain-like sodium pump inhibitor in cold injury-induced brain edema

An endogenous ouabain-like factor (EOLF) was measured in brain tissue of cats 12 and 24 hrs after cold injury-induced edema. EOLF was assayed via its inhibition of 86Rb+ uptake in human red blood cells in a fraction which was obtained from brain tissue by methanol extraction, chloroform treatment and purification of the water phase by C-18 HPLC. As compared to the contralateral hemispheres with an EOLF concentration of 605 +/- 71 pmol ouabain equivalents per g wet weight, the edematous hemisphere had significantly higher concentrations: 12 hours after cold injury it was 2600 +/- 1762 pmol (p < 0.03) and fell to 857 +/- 160 pmol ouabain equivalents/g wet weight after 24 hrs. Similar kinetics were evident for the EOLF concentrations in cerebrospinal fluid. It is suggested that the increase of EOLF in the edematous brain hemisphere may participate as a mediator in the development of vasogenic brain edema in the disturbance of the sodium metabolism.

Characterization of phospholipase A2 secretion from human platelets

Human platelets secreted phospholipase A2 in a dose- and time-dependent manner when challenged with thrombin, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), or collagen. Enzyme release was maximal at concentrations of 0.1 units/ml of thrombin, 100 nM TPA, or 2 micrograms/ml of collagen; and complete by 2 min in platelets treated with thrombin or TPA. Cells challenged with collagen required up to 5 min for maximal secretion. Besides dose and time functions, phospholipase A2 secretion was also dependent on platelet concentration and the levels of bovine serum albumin in the incubation medium. The secreted enzyme was soluble and exhibited substrate and Ca2+ requirements similar to a detergent-solubilized, partially purified phospholipase A2 from whole platelets [Kramer et al., Biochim. Biophys. Acta (1988) 959, 269-279]. The pH optimum of the secreted enzyme, however, was 1-2 units lower than the pH optimum of the phospholipase A2 from whole cells. Secreted phospholipase A2 hydrolyzed phosphatidylethanolamine at 5-12 times the rate of phosphatidylcholine when the substrates were present in pure form. These apparent differences in activity were greatly diminished, though, when 1:1 molar mixtures of the two substrates were employed. Because phospholipase A2 catalyzes a key reaction during the formation of bioactive arachidonate metabolites, the secretion of this enzyme from platelets may be important in the regulation of thrombosis.

Results of continuous long-term intravenous application of octreotide via an implantable pump system in acromegaly resistant to operative and X-ray therapy

Long term results after surgery for growth hormone (GH)-secreting adenomas indicate only a limited cure rate, particularly in patients with tumours invading the dural boundaries of the sella with suprasellar extension. Since octreotide had become a treatment option, it was used i.v. via an implantable pump system in five patients (age range 24-46 yr) showing symptoms of uncontrolled acromegaly, in spite of previous surgery and X-ray therapy. The octreotide doses used permanently for a cumulative treatment period of 8.8 yr ranged between 300 and 1000 micrograms/24 h. Serial evaluations of clinical findings, 24-h GH and insulin profiles, insulin growth factor-1 (IGF-1), oral glucose tolerance test and pituitary function revealed sustained GH suppression, without interim escape, below 2 ng/ml in two and below 5 ng/ml in three patients, IGF-1 decrease in all with normalization in two patients and no clinically relevant disturbances of carbohydrate tolerance or thyroid-stimulating hormone secretion. In one case of previous unresponsiveness to dopamine agonists i.v. octreotide application for 29 months facilitated later disease control by bromocriptine only. In two patients octreotide was terminated after 15 and 30 months of i.v. administration, respectively, because the effects of irradiation had occurred. For a subgroup of patients with resistant acromegaly continuous i.v. octreotide can be considered as a safe and effective alternative, which increases patients' independency from the inconvenience of daily repeated s.c. injections.

Synthesis of 1-acyl-2-[3H]acetyl-SN-glycero-3-phosphocholine, a structural analog of platelet activating factor, by vascular endothelial cells

Human umbilical vein endothelial cells (HUVECS) were challenged with thrombin in the presence of [3H]acetate to stimulate the production of radiolabeled platelet activating factor (PAF, 1-O-alkyl-2-[3H]acetyl-sn-glycero-3-phosphocholine, 1-O-alkyl-2-[3H]acetyl-GPC). The 3H-product was isolated by thin-layer chromatography, and 1-radyl-2[3H],3- diacetylglycerols were prepared by phospholipase C digestion and subsequent acetylation at the sn-3 position. When the 1-radyl-2[3H],3-diacetylglycerols were analyzed by zonal thin-layer chromatography, 96-97% of the radiolabeled derivative migrated with 1-acyl-2,3-diacetylglycerol standard. Only minor amounts (3-4%) of 1-alkyl-2[3H],3-diacetylglycerol were observed, demonstrating that the predominant acetylated product synthesized by thrombin-stimulated HUVECS was 1-acyl-2-[3H]acetyl-GPC. This relative abundance of 1-acyl-2-[3H]-acetyl-GPC was not significantly affected by thrombin dose, incubation time, or cell passage, and was also observed in HUVECS challenged with ionophore A23187. In addition, the acetylated product from ionophore A23187- or bradykinin-stimulated bovine aortic endothelial cells contained 90% 1-acyl-2-[3H]acetyl-GPC, suggesting that the synthesis of the 1-acyl PAF analog is not unique to HUVECS. These findings demonstrate that PAF is a minor synthetic component of HUVECS and bovine aortic endothelial cells. In light of the integral role which the vascular endothelial cell plays in the regulation of thrombosis, these findings also suggest that the production of 1-acyl-2-acetyl-GPC may be biologically important.

C20 polyunsaturated fatty acids and phorbol myristate acetate enhance agonist-stimulated synthesis of 1-radyl-2-acetyl-sn-glycero-3-phosphocholine in vascular endothelial cells

This study has investigated the effect of supplementation of vascular endothelial cells with arachidonate and other polyunsaturated fatty acids on the agonist-stimulated synthesis of platelet activating factor (PAF; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine; 1-alkyl-2-acetyl-GPC). Incubation of calf pulmonary artery endothelial cells for 48 h in medium containing 40 microM arachidonate resulted in a 2-3-fold enhancement of [3H]acetate incorporation into 1-radyl-2[3H]acetyl-GPC in response to either bradykinin or calcium ionophore A23187. The effects of arachidonate supplementation were both dose- and time-dependent, requiring a minimum exogenous arachidonate concentration of 2.5 microM and an incubation time of 4-6 h. Eicosapentaenoate and docosahexaenoate also enhanced the synthesis of 1-radyl-2-[3H]acetyl-GPC, but were less potent than arachidonate; alpha-linolenate, linoleate and oleate were without effect. Although not effective as an agonist, phorbol myristate acetate potentiated A23187- and bradykinin-stimulated synthesis of 1-radyl-2-[3H]acetyl-GPC. The effects of arachidonate supplementation were synergistic with potentiation by phorbol myristate acetate. Sphingosine inhibited agonist-stimulated incorporation of [3H]acetate into 1-radyl-2-[3H]acetyl-GPC both in the presence and absence of PMA. Characterization of the radiolabeled material indicated that the primary product was the acyl analogue of PAF (1-acyl-2-acetyl-GPC) rather than PAF. The results from this study suggest that agonist-stimulated synthesis of 1-radyl-2-acetyl-GPC in vascular endothelial cells is modulated both by cellular fatty acyl composition and activation of protein kinase C. Enrichment of vascular endothelial cells with fatty acids, which are mobilized by agonist-stimulated phospholipase A2, may enhance subsequent deacylation of choline phospholipids and, thus, increase synthesis of both 1-acyl-2-acetyl-GPC and PAF.

Different types of postoperative diabetes insipidus and the relation to basal and stimulated serum prolactin levels in patients with hypothalamo-hypophyseal tumorous lesions

To evaluate the interrelationships between anterior pituitary function and the antidiuretic system in patients harbouring hypothalamo-hypophyseal tumorous lesions, combined anterior pituitary stimulation tests were performed in the pre (n = 192 patients) and postoperative (n = 151 patients) state. Basal and stimulated plasma antidiuretic hormone, serum as well as urinary osmolality and diuresis were analyzed to determine the residual functional capacity of the antidiuretic system. In 106 patients with non-prolactin (PRL) secreting tumours basal and stimulated PRL secretion of the residual anterior pituitary was studied pre- and postoperatively. It was found that in the preoperative state latent (n = 12 patients) or manifest (n = 10 patients) types of diabetes insipidus (DI) were related to a significant decrease of maximal stimulated levels of thyroid stimulating hormone as well as basal and maximal stimulated levels of follicle stimulating hormone relative to patients without DI. In the postoperative state DI lasting longer than 10 days (n = 51 patients) was associated with decreased basal and maximal stimulated concentrations of cortisol, luteinizing and follicle stimulating hormone, whereas basal and maximal stimulated levels of PRL were significantly increased compared to those patients without DI (n = 61 patients). Decompression (n = 65 procedures) via the transnasal route was related with a lower frequency of the more severe types of DI (n = 7 patients) and a significant decrease of basal and maximal PRL levels in patients with non-PRL secreting tumours. The transcranial approach (n = 86 procedures) caused a higher rate of severe DI types (n = 33 patients) and an increase of PRL secretion from the residual anterior pituitary lobe. Patients without DI or DI of mild severity (n = 50), as a group, had a significant decrease of basal and maximal PRL levels compared with preoperative values (preoperative: basal = 14.3 +/- 1.5 ng/ml, max = 31.4 +/- 1.5 ng/ml, postoperative: basal = 9.6 +/- 1.1 ng/ml, max = 24.9 +/- 2.9 ng/ml). In patients with severer degrees of DI (n = 40) PRL levels were significantly increased, respectively (preoperative: basal = 15.3 +/- 3.1 ng/ml, max = 23.9 +/- 7.6 ng/ml, postoperative: basal = 19.7 +/- 3.4 ng/ml, max = 38.6 +/- 7.9 ng/ml). It was concluded that in the surgical treatment of non-PRL secreting hypothalamo-hypophyseal lesions the results of early postoperative assessment of basal and stimulated PRL levels may predict the type of postoperative DI.(ABSTRACT TRUNCATED AT 400 WORDS)

Relationship between plasma antidiuretic hormone and atrial natriuretic peptide during the triphasic diuresis response to experimentally induced acute intracranial hypertension

Plasma antidiuretic hormone (pADH) and atrial natruiretic peptide (pANP) were determined during the triphasic diuresis response to acute cerebral compression in cats. The first, the polyuric phase, was accompanied by the cardiovascular response, characterized by a simultaneous increase of pADH and pANP. During the second, the oliguric phase and the third phase of diabetes insipidus pADH and pANP concentrations decreased to initial values. These changes were accompanied by symptoms of central vegetative dysregulation namely hypotension, respiratory arrest and EEG cessation. Thus, the results exhibited the same pattern of vasopressinergic and atriopeptinergic activities after induction of an acute intracranial hypertension and suggest that the mutual interaction of both systems may modify the type of diuresis response.

Dissociation between activation of the hypothalamo-hypophyseal antidiuretic system and the type of diuresis during acute intracranial hypertension. Experimental observation

Acute cerebral compression by a supra- and infratentorial balloon produced a triphasic pattern of diuresis. The 1st phase was characterized by polyuria associated with five fold increase of plasma (p) antidiuretic hormone (ADH) concentration, decreased urine osmolality in spite of natriuresis and blood pressure elevation. The 2nd phase was characterized by oliguria, a decrease of pADH and reduced urine Na+ concentration, whereas urine osmolality transiently increased. At this stage there was respiratory arrest and fall of blood pressure. The final stage was diabetes insipidus (DI), when EEG activity had disappeared. An increase of serum osmolality mainly occurred during the last DI phase. Serum Na+ concentration fluctuated slightly during the whole period of diuresis. These results present evidence, that the diuresis pattern reflects the hypothalamo-hypophyseal antidiuretic system (HHAS) reaction to acute intracranial pressure (ICP) increase with the vegetative symptoms of cerebral shock.

The significance of electron spin resonance of the ascorbic acid radical in freeze dried human brain tumours and oedematous or normal periphery

The ESR spectrum, attributed to the ascorbic acid (ascorbyl) radical and obtained by exposing freeze dried material to air, can not be used as proof for the occurrence of in vivo free radical reactions. Depending on the method of freeze drying, the content of blood or hemolyzed blood is the dominant factor in creating higher than normal ESR signals in brain or related tissue. These findings explain why the signal, though larger in many human brain tumours than in their surroundings, is not indicative of malignancy. No differences are seen between oedematous and normal tissue. The ascorbyl radical is definitely not stable in aqueous solution, which indicates that fresh tissue sections can also not be used to study in vivo radicals by ESR.

The molecular species distribution of platelet-activating factor synthesized by rabbit and human neutrophils

In this study, the molecular species distribution of 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (platelet-activating factor) synthesized by rabbit peritoneal and human peripheral neutrophils was examined. Radiolabeled platelet-activating factor synthesized from [3H]acetate by neutrophils stimulated with ionophore A23187, opsonized zymosan, or N-formyl-methionyl-leucyl-phenylalanine was separated into the individual molecular species on the basis of length and degree of unsaturation of the 1-O-alkyl chain using reverse-phase high-performance liquid chromatography. The predominant alkyl chains in the labeled platelet-activating factor synthesized by ionophore- or zymosan-stimulated rabbit cells were 15:0 (4%), 16:0 (43%), 18:0 (11%), and 18:1 (26%). This is in contrast to the alkyl chain distribution of the widely accepted precursor of platelet-activating factor, 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine, present in the cell. The major alkyl chains contained in the labeled platelet-activating factor synthesized by ionophore-, zymosan-, or N-formyl-methionyl-leucyl-phenylalanine-stimulated human neutrophils were 16:0 (40%), 17:0 (8 and 5%; two isomers), 18:0 (16%), and 18:1 (18%). As found with the rabbit cells, this distribution differs from the alkyl chain content of 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine in human neutrophils, which contains less than 1% of each 17:0 isomer. We demonstrate here that the platelet-activating factor synthesized by rabbit peritoneal and human peripheral polymorphonuclear neutrophils is heterogeneous and that some selectivity exists in the choice of the 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine precursor for platelet-activating factor synthesis in these cells. It also appears that the molecular species distribution of platelet-activating factor is independent of the stimulus used to elicit its synthesis.

1-O-alkyl-linked glycerophospholipids of human neutrophils: distribution of arachidonate and other acyl residues in the ether-linked and diacyl species

This study was done to determine whether human neutrophils contain sufficient 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine to support the synthesis of platelet activating factor by a deacylation-reacylation mechanism, and to examine the relative distribution of arachidonate among the 1,2-diacyl, 1-O-alkyl-2-acyl, and the 1-O-alk-1'-enyl-2-acyl classes of choline- and ethanolamine-containing phospholipids. The predominant phospholipid species of human neutrophils were choline-containing glycerophospholipids (41%), ethanolamine-containing glycerophospholipids (39%), and sphingomyelin (14%), with smaller quantities of phosphatidylserine (4%) and phosphatidylinositol (1%). The choline-linked fraction contained high amounts of 1-O-alkyl-2-acyl-X (44%) and 1,2-diacyl-sn-glycero-3-phosphocholine (47%), and a lesser amount of 1-O-alk-1'-enyl-2-acyl-sn-glycero-3-phosphocholine (9%). In contrast, the ethanolamine-linked fraction contained a large amount of 1-O-alk-1'-enyl-2-acyl-sn-glycero-3-phosphoethanolamine (66%), and lower levels of the 1,2-diacyl (24%) and 1-O-alkyl-2-acyl (10%) species. The major 1-O-alkyl and 1-O-alk-1'-enyl ether chains found in the choline and ethanolamine phospholipid pools were 16:0, 18:0, 18:1, and 20:0. The predominant fatty acyl residues found in the 1,2-diacyl and the sn-2 position of the 1-O-alkyl-2-acyl and 1-O-alk-1'-enyl-2-acyl choline and ethanolamine glycerophospholipids were 16:0, 18:0, 18:1, 18:2, and 20:4.(ABSTRACT TRUNCATED AT 250 WORDS)

1-O-alkyl-linked phosphoglycerides of human platelets: distribution of arachidonate and other acyl residues in the ether-linked and diacyl species

In this study, the 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine content of human platelets was determined. The distribution of arachidonate among the 1,2-diacyl, 1-O-alkyl-2-acyl, and 1-O-alk-l'-enyl-2-acyl classes of choline- and ethanolamine-containing phosphoglycerides was also assessed. The major platelet phospholipids were choline-containing phosphoglycerides (38%), ethanolamine-containing phosphoglycerides (25%) and sphingomyelin (18%), with smaller amounts of phosphatidylserine (11%) and phosphatidylinositol (4%). In addition to the diacyl class, the choline-linked fraction was found to contain both 1-O-alkyl-2-acyl (10%) and 1-O-alk-l'-enyl-2-acyl (9%) species. The ethanolamine-linked fraction, on the other hand, had an elevated level of the 1-O-alk-1'-enyl-2-acyl (60%) species and a small amount of the 1-O-alkyl-2-acyl component (4%). The major fatty acyl residues found in all classes of the choline and ethanolamine phospholipids were 16:0, 18:0, 18:1 (delta 9), 18:2(n-6) and 20:4(n-6). The 1-O-alkyl and 1-O-alk-1'-enyl fraction of the ethanolamine-linked phospholipids also contained substantial amounts of 22:5(n-3) and 22:6(n-3) acyl chains. Arachidonate comprised 44% of the acyl residues in the sn-2 position of 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine. Corresponding values for the diacyl and 1-O-alk-1'-enyl-2-acyl species were 23% and 25%, respectively, based on all 20:4(n-6) being linked to the sn-2 position of all classes.(ABSTRACT TRUNCATED AT 250 WORDS)

Biosynthesis of platelet activating factor in rabbit polymorphonuclear neutrophils

The synthesis of platelet activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) was studied in rabbit peritoneal polymorphonuclear neutrophils. Upon stimulation with ionophore A23187 and Ca2+, these cells are able to incorporate [3H]acetate or 1-O-[3H]alkyl-2-lyso-sn-glycero-3-phosphocholine into platelet activating factor. Under the same incubation conditions, however, the cells do not synthesize platelet activating factor from [14C]hexadecanol, which is an immediate precursor of O-alkyl chains in the de novo pathway. In the absence of ionophore, [14C] hexadecanol is incorporated into 1-O-alkyl-2-acyl-sn-glycerol-3-phosphate and subsequently into the 1-O-alkyl-linked choline and ethanolamine phosphoglyceride pools. However, in the presence of ionophore, [14C] hexadecanol incorporation is limited to phosphatidic acid, perhaps due to the inhibition of choline phosphotransferase. These findings provide strong evidence that platelet activating factor is synthesized by a deacylation-reacylation mechanism. Upon stimulation, these cells can utilize both plausible substrates of this pathway to make the final product, while under the same conditions it appears that a key step of the de novo pathway is inhibited.

Glass capillary gas chromatography of the serum fatty acid fraction via automatic injection of lipid extracts

The combination of a consecutive double capillary column gas chromatographic system (Deans type) with a fully automatic injection device was developed to determine quantitatively the fatty acid fraction of serum extracts, without prior removal of the other lipids. A major difficulty arose through ghosting (memory), via reaction of methylating reagents with lipid deposits, mainly in the injection port. Use of diazomethane circumvented this, as the reagent was easily removed prior to analysis. The combination methyl iodide--potassium carbonate, convenient handling of which requires coinjection of methyl iodide, proved to be less than completely dependable. Dimethylformamide dimethylacetal is completely out of the question as a coinjectant. Lipid deposits in the injection port produced peak area drifts which could, however, be counteracted. The apparatus is capable of analyzing samples completely unattended for at least 20 hours (80 samples). It has been operated non-stop, day and night, for between 4 and 7 days with occasional reloading and servicing.

Ether lipid content and fatty acid distribution in rabbit polymorphonuclear neutrophil phospholipids

This study was undertaken to determine if rabbit neutrophils contain sufficient ether-linked precursor for the synthesis of 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (platelet activating factor) by a deacylation-reacylation pathway. The phospholipids from rabbit peritoneal polymorphonuclear neutrophils were purified and quantitated, and the choline-containing and ethanolamine-containing phosphoglycerides were analyzed for ether lipid content. Choline-containing phosphoglycerides (37%), ethanolamine-containing phosphoglycerides (30%), and sphingomyelin (28%) were the predominant phospholipid classes, with smaller amounts of phosphatidylserine (5%) and phosphatidylinositol (less than 1%). The choline-linked fraction contained high amounts of 1-O-alkyl-2-acyl-(46%) and 1,2-diacyl-sn-glycero-3-phosphocholine (54%), with a trace of the 1-O-alk-1'-enyl-2-acyl species. The ethanolamine-linked fraction contained high amounts of 1-O-alk-1'-enyl-2-acyl-(63%) and 1,2-diacyl-sn-glycero-3-phosphoethanolamine (34%), and a low quantity of the 1-O-alkyl-2-acyl species (3%). The predominant 1-O-alkyl ether chains found in the sn-1 position of the choline-linked fraction were 16:0 (35%), 18:0 (14%), 18:1 (26%), 20:0 (16%), and 22:0 (9%). The major 1-O-alk-1'-enyl ether chains found in the sn-1 position of the ethanolamine-linked fraction were 14:0 (13%), 16:0 (44%), 18:0 (27%), 18:1 (12%) and 18:2 (3%). The major acyl groups in the sn-1 position of 1,2-diacyl-sn-glycero-3-phosphocholine and 1,2-diacyl-sn-glycero-3-phosphoethanolamine were 16:0, 18:0 and 18:1. The most abundant acyl group in the sn-2 position of all classes of choline- and ethanolamine-linked phosphoglycerides was 18:2. Although this work does not define the biosynthetic pathway for platelet activating factor, it does show that there is ample precursor present to support its synthesis by a deacylation-reacylation pathway.

Purification and properties of human placental acid lipase

Two peaks of lysosomal acid lipase activity were purified from normal human placenta. Acid lipase I, with an estimated molecular weight of 102 500, was purified 1016-fold while acid lipase II, with an estimated molecular weight of 30 600, was purified 3031-fold. The final yields of enzyme activity for acid lipase I and II were 0.9% and 2.2% respectively. The purity of the final preparations was documented by demonstration of a single protein band on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Both preparations of the purified enzyme demonstrated activity towards triolein, cholesteryl oleate and the artificial substrate 4-methylumbelliferyl oleate. Examination of Km values, thermal stability, pH optima, and electrophoretic mobility revealed similar properties for the two enzyme peaks. The response of the two enzyme preparations to inhibitors was similar with both being significantly inhibited by 0.2 M NaCl, 0.2 M KCl, 5 mM HgCl2 and 5 mM p-chloromercuribenzoate. The activity of the two preparations as assayed with either triolein or cholesterol oleate was not significantly affected by the addition of bovine serum albumin. In contrast, the 4-methylumbelliferyl oleate activity of both preparations was significantly inhibitred by albumin. These findings support the hypothesis that the same enzyme or enzymes are responsible for the intralysosomal hydrolysis of triacylglycerols and cholesterol esters in human tissues.