Biomedical subjects

M Kates

Publications and source records attributed to M Kates.

At least 37 records · Page 2Linked to original sources

PubMed1990

Antibodies to liposomal phosphatidylcholine and phosphatidylsulfocholine.

Antibodies against dimyristoyl phosphatidylsulfocholine or dimyristoyl phosphatidylcholine were raised in rabbits after injection of liposomes containing phosphatidylsulfocholine or phosphatidylcholine, cholesterol, and lipid A. The antibody activities were assayed by complement-dependent immune damage to liposomes and by a solid-phase, enzyme-linked immunosorbent assay using purified dimyristoyl phosphatidylcholine or dimyristoyl phosphatidylsulfocholine as antigen. Each antiserum raised against phosphatidylsulfocholine reacted with liposomes containing phosphatidylcholine, and each antiserum raised against phosphatidylcholine reacted with liposomes containing phosphatidylsulfocholine. However, adsorption of dimyristoyl phosphatidylsulfocholine antiserum with liposomes containing dimyristoyl phosphatidylcholine removed all activity against dimyristoyl phosphatidylcholine, but did not eliminate antibody activity against dimyristoyl phosphatidylsulfocholine. These results indicate that the antiserum against phosphatidylsulfocholine contained mixed populations of antibodies. Polyclonal antisera that have been appropriately adsorbed can therefore be obtained with a high degree of specificity for phosphatidylsulfocholine and such antisera can distinguish between phosphatidylsulfocholine and phosphatidylcholine.

Animals↗

PubMed1990

Transfer of arachidonic acid from phosphatidylcholine to phosphatidylethanolamine during storage of human platelets for 5 days.

Human platelets are routinely stored for 5 days prior to transfusion, but they deteriorate during storage. Since very little information is available concerning the effect of storage on platelet phospholipid metabolism, the biosynthesis and remodelling of platelet phospholipids were studied. Platelets were incubated separately with [14C]glycerol, [14C]arachidonic acid, or a mixture of [14C]glycerol and [3H]arachidonic acid, and stored in a platelet storage medium at 22 degrees C. Maximum glycerol uptake (20%) was attained after 6 h. [14C]Glycerol was incorporated into phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol, and to a much lesser extent phosphatidylserine, under storage conditions for 5 days. The distribution of the initial arachidonic acid uptake was not as would be expected based on the molar composition of endogenous phospholipids. The arachidonic acid (75%) which was taken up within 10 min of incubation distributed 55% into the phosphatidylcholine and only 14% into the phosphatidylethanolamine; the molar composition is actually 18% phosphatidylcholine and 47% phosphatidylethanolamine. During storage, there was a continuous transfer of the radiolabelled arachidonic from phosphatidylcholine to phosphatidylethanolamine until, after 5 days, the distribution of arachidonic acid was identical to the endogenous distribution. In contrast, no change in the glycerol incorporation pattern was detected during storage. This suggested that the mechanism for arachidonic acid redistribution was not through exchange of polar head groups, but through acyl transfer of arachidonic acid from phosphatidylcholine to phosphatidylethanolamine.

Arachidonic Acid↗

PubMed1990

Levels of sulfogalactosylglycerolipid in capacitated motile and immotile mouse spermatozoa.

The purpose of this study was to determine whether sulfogalactosylglycerolipid (SGG) was desulfated during mouse sperm capacitation. Levels of [35S]SGG were determined in freshly retrieved caudal epididymal sperm, motile capacitated sperm, and immotile sperm, after feeding mature male mice with [35S]sulfate-laced chow for 32 days. Caudal epididymal sperm and coisolated epididymal cells were separated into pellet and interphase fractions by centrifugation through a two-step Percoll gradient (45 and 90%). Upon resuspension in Krebs-Ringer bicarbonate medium supplemented with 0.4% bovine serum albumin, the Percoll-gradient pellet fraction consisted mainly of motile capacitated sperm, whereas the interphase fraction comprised largely immotile sperm and fragmented epididymal epithelial cells. The level of [35S]SGG in the Percoll-gradient-pelleted sperm appeared to be much higher than that in the Percoll-gradient interphase sperm. Percoll-gradient-pelleted sperm were further incubated in the culture medium for 2 h. The level of [35S]SGG showed little or no change after 1 h, but was reduced appreciably after 2 h. At this time point, sperm motility was also decreased. Reduction of sperm SGG is correlated with sperm immotility and (or) senescence and may have no direct relation to the capacitation process.

Animals↗

PubMed1989

Correlation of enzyme activities with fluorescence anisotropy of dansyl-labeled cytochrome b5/NADH-cytochrome-b5 reductase systems in phosphatidylcholine vesicles.

The changes in steady-state fluorescence lifetimes and anisotropy decay parameters, as well as enzyme activities, of dansyl-labeled cytochrome b5 (DNS-cytochrome b5), on interaction with NADH-cytochrome-b5 reductase in DMPC vesicles, have been measured as a function of temperature. Steady-state fluorescence of DNS-cytochrome b5 in DMPC vesicles with and without cholesterol was increased on interaction with reductase at temperatures both above and below the DMPC phase transition. In all systems three fluorescence decay components of the dansyl label in DNS-cytochrome b5 were observed. In the reductase-containing system, the long (major) decay time component of DNS-cytochrome b5 and the fraction of the total fluorescence associated with this component increased over the temperature range 15-30 degrees C. In time-resolved anisotropy measurements, the order parameters of DNS-cytochrome b5 in DMPC vesicles increased on interaction with reductase at temperatures above the DMPC phase transition, and this increase was even more pronounced in cholesterol-containing vesicles, at temperatures from 15-30 degrees C. The enzyme activity of the DNS-cytochrome-b5 reductase system in DMPC vesicles was also greatly increased in the presence of cholesterol. These results show that interaction of vesicle-bound DNS-cytochrome b5 and NADH-cytochrome-b5 reductase leads to an increased degree of order of the dansyl-labeled cytochrome with little change in its rotational flexibility, and suggests that the increased order can be correlated with increased enzyme activity.

Animals↗

PubMed1989

Surface characteristics of phosphatidylglycerol phosphate from the extreme halophile Halobacterium cutirubrum compared with those of its deoxy analogue, at the air/water interface.

The relationship between area per molecule and surface pressure of monolayers of phosphatidylglycerol phosphate from extreme halophile Halobacterium cutrirubrum and its deoxy analogue, deoxyphosphatidylglycerol phosphate, spread at an air/water interface was examined. The effect of ionization of the primary and secondary acidic functions of the phosphate groups of the two lipids on surface characteristics of compression isotherms was determined by spreading monolayers on subphases with pH values ranging from below the apparent pKa of the primary ionization (pH 0) to greater than that of secondary ionization (pH 10.9). The limiting molecular area increases with decreasing pH below 2. Ionization of the primary phosphate functions of both phospholipids (with bulk pK1 values close to 4) is associated with a marked expansion of the films, as judged by values of limiting molecular area. Ionization of the secondary phosphate functions causes further expansion of the films, with the apparent pK2 of deoxyphosphatidylglycerol phosphate slightly less than that indicated for phosphatidylglycerol phosphate. Values of surface-compressibility modulus calculated from the surface characteristics of the phosphatidylglcerol phosphate monolayers showed that films spread on subphases with a pH of about the apparent pK1 of the primary phosphate functions were the least compressible. Increasing or decreasing subphase pH caused an increase in compressibility; this effect on compressibility was much less with monolayers of deoxyphosphatidylglycerol phosphate at high pH. The effect of inorganic counter-ions on monolayer characteristics of phosphatidylglycerol phosphate was examined by using subphases of NaCl concentrations varying from 0.01 to 1 M. The limiting molecular area was found to increase exponentially with respect to the subphase NaCl concentration.

Halobacterium↗

PubMed1989

Comparison of steady-state fluorescence polarization and urea permeability of phosphatidylcholine and phosphatidylsulfocholine liposomes as a function of sterol structure.

The well-known reduction in the permeability properties of liposomes of dimyristoylphosphatidylcholine (DMPC) by sterols has also been demonstrated for its sulfonium analog (DMPSC) in which the N+(CH3)3 group of choline is replaced by S+(CH3)2. We have now compared the effects of 25 mol% 24-methylenecholesterol and cholesterol on the initial rates of urea permeation into dipalmitoyl-PC (DPPC) and dipalmitoyl-PSC (DPPSC) liposomes above the gel-to-liquid-crystalline phase transition temperature and found a greater reduction with 24-methylenecholesterol/DPPSC than with cholesterol/DPPSC liposomes but little difference between the two sterols in DPPC liposomes. Fluorescence polarization studies, using diphenylhexatriene as a probe, show that polarization (P) values are considerably higher in DMPSC liposomes containing 20 and 30 mol% 24-methylenecholesterol than in DMPC liposomes containing 20 and 30 mol% cholesterol. Higher P values were also obtained in DMPSC liposomes containing other 24-alkyl-substituted sterols (beta-sitosterol, ergosterol and campesterol) than in DMPC liposomes containing the same sterols. Reduced permeability rates in PSC liposomes containing 24-alkyl-substituted sterols are correlated with higher polarization values, reflecting an increased degree of order and/or motion in these liposomes compared with liposomes from the corresponding PC. These results suggest that alkyl substitution at C-24 of the sterol molecule results in tighter interactions with the sulfonium analog of PC than with PC.

Cholesterol↗

PubMed1988

A simplified approach to the analysis of subclasses of phospholipids: application to human platelets.

A procedure for the determination of the proportions of diacyl, alkenylacyl and alkylacyl subclasses of glycerophospholipids was developed. The procedure involves: (1) acid methanolysis of the phospholipid followed by Bligh/Dyer extraction of fatty acid methyl esters (FAME) derived from acyl chain types, dimethylacetals (DMA) derived from alkenyl ether chain types, and lysoalkyl phosphatidic acids (lysoalkyl-PA) derived from alkyl ether chain types; and (2) subsequent acetolysis to convert the lysoalkyl-PA to monoalkyl glycerol diacetates (MAGD). GLC analysis and quantitation (using internal standard, 21:0 FAME) of FAME, DMA and MAGD allowed calculation of the proportions of the three molecular subclasses. The methanolysis/acetolysis procedure gave an overall mean phospholipid recovery of 95 +/- 3%. Analysis of the major phospholipids in four separate preparations of fresh resting human platelets by this procedure showed the following range of molecular subclasses: phosphatidylcholine (PC), 86-92 mol % diacyl, 6-10 mol % alkylacyl and 2-3 mol % alkenylacyl; and phosphatidylethanoline (PE), 39-60 mol % diacyl, 5-8 mol % alkylacyl and 34-55 mol % alkenylacyl. The results of these subclass analyses were in general agreement with those reported in the literature.

Acetates↗

PubMed1988

Synthesis and characterization of deoxy analogues of diphytanylglycerol phospholipids.

Novel analogues of diphytanyl phospholipids, 2,3-diphytanyl sn-1-glycerol-1-phosphoryl-1'-(1',3'-propanediol) (dPG), 2,3-diphytanyl-sn-glycerol-1-phosphoryl-1'-propanol (ddPG) and 2,3-diphytanyl-sn-glycerol-1-phosphoryl-1'-(1',3'-propanediol-3'-p hosphate) (dPGP), were synthesized according to modifications of previously published procedures. The samples were TLC and analytically pure and were characterized by 13C- and 1H-NMR and negative FAB/MS. The pK values of dPGP in aqueous dispersions or in methanol/water (1:1, v/v) were determined by potentiometric titration and compared with those of 2,3-diphytanyl-sn-glycerol-1-phosphoryl-3'-sn-glycerol-1'-phosphat e (PGP). The dissociation constant of the third ionizable POH group of dPGP was more than 2 pK units higher than that of PGP, indicating that the free glycerol hydroxyl group plays an important role in headgroup conformation and stabilization, perhaps through hydrogen bonding with the phosphate group(s).

Chemical Phenomena↗

PubMed1988

Structure, physical properties, and function of archaebacterial lipids.

The foregoing review of the structure, physical properties and function of membrane lipids in archaebacteria has revealed a remarkable variety of polar lipid classes, including phospholipids, glycolipids, phosphoglycolipids and sulfolipids, all derived from the one basic core structure, diphytanylglycerol (I). Even with the relatively limited knowledge that we have of the physical properties of these lipids, it is clear that they are well-adapted as membrane components to the particular environmental conditions of the three groups of archaebacteria, extreme halophiles, methanogens, and thermoacidophiles. However, much remains to be learned concerning the precise asymmetric arrangement of the lipids in the membrane bilayers or monolayers, the interaction of the lipids with the membrane proteins, and the function of this membrane lipid asymmetry with respect to ion transport, permeability to nutrients, proton transport and conductance, and energy transduction. Perhaps then these unusual lipids will not appear so strange and our knowledge of them will help us understand the function of the more familiar lipids in the eubacteria and eukaryotes.

Archaea↗

PubMed1984

Enteric receptors for 5-hydroxytryptamine.

[3H]5-hydroxytryptamine [( 3H]5-HT) was used as a radioligand to study enteric 5-HT receptors. Membranes were derived from preparations of longitudinal muscle with adherent myenteric plexus and of mucosa-submucosa dissected from guinea pig and rabbit small intestines. Filtration and radioautographic analyses were used. Specific [3H]5-HT binding was found in both preparations. Binding was saturable and dissociable with equilibrium dissociation constants (Kd) of 2.7 and 1.4 nM, respectively. A kinetic estimate of Kd (1.5 nM) was similar to that determined by saturation analysis and the Hill coefficient approximated unity. Ring-hydroxylation of indoles was found to be a requirement for antagonism of [3H]5-HT binding. On the other hand, substitutions could be made in the aliphatic side chain of tryptamines without destroying the affinity of analogues for the binding sites. The inability of antagonists to displace [3H]5-HT indicated that the binding sites were not muscarinic or nicotinic receptors, alpha- or beta-adrenoceptors, H1 or H2 histamine receptors, dopamine receptors or either the S1 or S2 types of 5-HT receptor that have been found in the brain. Frozen section dry-mount radioautography revealed the [3H]5-HT binding sites to be located in ganglia of the myenteric plexus and at the boundary between the mucosa and submucosa. The similarity between the structure-activity requirements for affinity at the [3H]5-HT binding sites and activation of neural or M receptors for 5-HT in the gut, as well as the characteristics and location of the binding sites suggests that they are enteric neural receptors for 5-HT.

Animals↗

PubMed1984

Occurrence of phosphatidylsulfocholine, the sulfonium analog of phosphatidylcholine in some diatoms and algae.

A survey of seven species of diatoms, one Euglena sp. and one dinoflagellate sp. for the presence of phosphatidylsulfocholine (PSC), the sulfonium analog of phosphatidylcholine (PC), was carried out using 1H-NMR spectroscopy and ammonia desorption chemical ionization mass spectrometry. PSC alone was found only in a non-photosynthetic diatom, Nitzschia alba. PSC, together with PC, was found in four of the diatoms (Nitzschia angularis, Cylindrotheca fusiformis, Phaeodactylum tricornutum and Navicula pelliculosa) in proportions of 6-24% of the total PC + PSC fraction, but little or no PSC (less than 2%) was detected in the remaining two (Cyclotella nana and Navicula incerta). Little or no PSC (less than 2%) was detected in a Euglena sp. by 1H-NMR but its presence was confirmed by 35S-labeling. The amount of PSC, if any, in the dinoflagellate (Amphidinium carterae) was below the level of detection by 1H-NMR.

Animals↗

PubMed1984

The dietary regulation of acyltransferase and desaturase activities in microsomal membranes of rat liver.

Dietary manipulation produces marked alterations in desaturase activities of rat liver microsomes with no concomitant changes in acyltransferase activities. Desaturation of stearoyl-CoA (delta 9-desaturase), linoleoyl-CoA (delta 6-desaturase), eicosatrienoyl-CoA (delta 5-desaturase) and eicosatrienoyl-phosphatidylcholine (delta 5-desaturase) was elevated in animals fed a corn oil diet and lowered in those fed a coconut oil diet compared to control animals. The delta 5-desaturase activities were also lowered in starved animals and elevated in starved animals refed a fat-free diet. However, no changes in acyl-CoA:1-acyl-sn-glycero-3-phosphocholine acyltransferase activity were observed in the membranes of animals maintained on any of the dietary regimens studied. These observations suggest that the desaturases of rat liver microsomes are regulated independently of the acyltransferases and that desaturation of eicosatrienoyl-phosphatidylcholine is regulated at the level of the desaturase itself and not by availability of the phospholipid substrate.

1-Acylglycerophosphocholine O-Acyltransferase↗

PubMed1984

Acyl-acyl carrier protein as substrate of the acyltransferase of rat liver microsomes.

Acyl-acyl carrier protein (acyl-ACP) can serve as well as acyl-CoA as substrate of the 1-acyl-sn-glycero-3-phosphocholine (1-acyl-GPC) acyltransferase of rat-liver microsomes. The product of the acylation with either thioester substrate is predominantly phosphatidylcholine (PC) (92-95%). The acyl-group transferred from either myristoyl-CoA or myristoyl-ACP is located at the C-2 position of the phospholipid (PL). The apparent Km values for the myristoyl-CoA and myristoyl-ACP were 46 microM and 63 microM, and the corresponding apparent Vmax values were 1.0 and 1.6 nmol/min/mg. The rate of acylation with the acyl-ACP was unaffected by the addition of free CoA-SH. These data suggest that acyl-CoA and acyl-ACP are transferred to 1-acyl-GPC by the same or similar enzyme systems.

Acyl Carrier Protein↗

PubMed1984

Adaptational changes in Staphylococcus aureus MF 31 grown above its maximum growth temperature when protected by sodium chloride: lipid studies.

Staphylococcus aureus MF31 was grown to stationary phase in a complex medium at 30, 37, and 43 degrees C in the absence of salt and at 37 and 46 degrees C in the same medium supplemented with 1 M NaCl. The principal phospholipids were cardiolipin, phosphatidylglycerol, aminoacylphosphatidyl glycerol, mono- and di-glycosyldiglyceride, and traces of phosphoglycolipid. The proportion of cardiolipin decreased with increasing growth temperature, but only slightly in the presence of 1 M NaCl, while that of aminoacylphosphatidyl glycerol was unaffected by growth temperature in absence of salt, but was about halved in the presence of 1 M NaCl. The net negative charge per mole phospholipid was greatly increased in the presence of 1 M NaCl. In the absence of salt, temperature had no effect on the total lipid content, but cells from the 46 degrees C culture in 1 M NaCl contained 25% less total lipid. The proportion of phospholipid in the total lipids, both in the absence and presence of salt, declined with increasing growth temperature. The proportion of glycolipids, however, increased with temperature both in the absence and presence of salt. It is suggested that the increase in glycolipid content and in negative charge/mole phospholipid is a part of the adaptation of S. aureus to the combination of high temperature and 1 M NaCl giving its membrane increased stability and possibly helping to exclude Cl- anion from the cell interior.

Chromatography, Thin Layer↗

PubMed1983

Influence of temperature and growth phase on desaturase activity of the mesophilic yeast Candida lipolytica.

Microsomal membranes prepared from Candida lipolytica cells grown at 10 degrees C had a higher lipid content and degree of unsaturation than membranes prepared from cells grown at 25 degrees C. The specific activities of stearoyl-CoA (18:0-CoA), oleoyl-CoA (18:1-CoA), and dioleoyl phosphatidylcholine (18:1-PC) desaturases in microsomes of cells grown at either 25 or 10 degrees C showed maximum values near midlog phase, coinciding with the respective maximum absolute content of linoleic (18:2) in the microsomal preparations. The 18:1-CoA desaturase activity in 10 degrees C cells was nearly double that in 25 degrees C cells, while the 18:0-CoA and 18:1-PC desaturases had considerably lower activities in 10 degrees C cells. An increase in aeration rate (shaking speed, 70 to 130 rpm) resulted in increased proportions of 18:2 (32 to 47%, respectively) in microsomes of cells grown at 25 degrees C and in increased 18:1-CoA desaturase specific activity (83 to 140 pmol X min-1 X mg-1); however, no significant changes occurred in 18:0-CoA or 18:1-PC desaturase activities.

Candida↗

PubMed1983

Pathways for desaturation of oleoyl chains in Candida lipolytica.

Incubation of microsomes from 25 degrees C- or 10 degrees C-grown cells of Candida lipolytica with [14C]oleoyl-CoA ( [14C]18:1-CoA) in the presence or absence of NADH resulted in rapid acyl transfer of [14C]18:1 to phospholipids (mainly phosphatidylcholine (PC) and phosphatidylethanolamine (PE) and to acylglycerols. Incorporation into PC was greatly enhanced when incubation was carried out in presence of lysophosphatidylcholine (lyso-PC). In all experiments, in the presence of NADH and O2, with and without added lyso-PC, the initial rate of formation of [14C]linoleoyl-PC was much greater than that of [14C]linoleoyl-CoA ( [14C]18:2-CoA). These results suggest that the actual substrate for the delta 12-desaturase is the oleoyl-PC, although some desaturation of 18:1-CoA cannot be eliminated. It is concluded that the main pathway for 18:2 formation proceeds from stearoyl-CoA (18:0-CoA) leads to 18:1-CoA leads to 18:1-phospholipid leads to 18:2-phospholipid; the pathway 18:0-CoA leads to 18:1-CoA leads to 18:2-CoA leads to 18:2-phospholipid is a minor pathway. Microsomes from cells grown at 10 degrees C had a higher content of 18:2 and a lower phospholipid desaturase activity at 25 degrees C than microsomes from cells grown at 25 degrees C, suggesting an inverse relationship between desaturase activity and membrane lipid fluidity.

Acyl Coenzyme A↗

PubMed1982

Phosphatidylsulfocholine bilayers. An infrared spectroscopic characterization of the polymorphic phase behavior.

The thermal response of aqueous dispersions of phosphatidylsulfocholines (dimyristoyl-, dipalmitoyl- and distearoyl-) was studied by Fourier transform infrared spectroscopy. Comparison with that of the corresponding phosphatidylcholines showed several close resemblances, including the observation in the gel phase of a "pretransition" and of a "subtransition". The similarity in the thermotropic phase behavior of these two lipid classes is consistent with the total replacement of phosphatidylcholine by phosphatidylsulfocholine in certain marine diatoms.

Lipid Bilayers↗

PubMed1982

Studies on fluorescence polarization of 1-acyl-2-cis- or trans-parinaroyl sn-3-glycerophosphorylcholines in model systems and microsomal membranes.

Fluorescent lecithin probes containing cis- or trans-parinaric acid (PnA) at the 2-position cis-parinaroylphosphatidylcholine (cis-PnPC) and trans-parinaroyl phosphatidylcholine (trans-PnPC)) showed similar behavior to that of the free cis- or trans-parinaric acids (cis-PnA or trans-PnA) in bilayer vesicles of synthetic saturated lecithins. Transition temperatures detected by cis-PnPC were about 1 degree C than those observed with trans-PnPC. In mixed lecithin vesicles, the trans-PnPC probe monitored a higher temperature melting component than did the cis-probe. Both probes were readily incorporated into microsomal membranes and into sonicated vesicles prepared from the microsomal phospholipids. With either cis- or trans-PnPC no change in polarization ratio was observed for microsomal membranes between 40 degrees C and 0 degrees C but this ratio increased with decreasing temperature between 0 degrees C and -5 degrees C. However, vesicles of extracted phospholipids showed a continuous increase in polarization ratio with decreasing temperature between 20 degrees C and -15 degrees C with trans-PnPC and between 5 degrees C and -15 degrees C with cis-PnPC. These results suggest that the two lecithin probes monitor different environments in the membranes and phospholipid vesicles prepared from them.

Animals↗