Biomedical subjects

M Kates

Publications and source records attributed to M Kates.

At least 37 records · Page 2Linked to original sources

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↗

PubMed1982

Polar lipids in phototrophic bacteria of the Rhodospirillaceae and Chromatiaceae families.

The polar lipids of photosynthetic purple bacteria of the genera Chromatium, Thiocapsa, Thiocystis, Ectothiorhodospira, Rhodopseudomonas, Rhodospirillum, and Rhodomicrobium were analyzed. Characteristic compositions of the polar lipids were found for most of the Rhodospirillaceae and Chromatiaceae species. Phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin were the major phospholipids in most species. Phosphatidylcholine was present as a major component in all species of the genus Ectothiorhodospira, but was not detected in the remaining Chromatiaceae. It was also present in most of the Rhodospirillaceae species. No glycolipids were found in any of the Ectothiorhodospira species. In the Rhodospirillaceae, the glycolipids mono- and digalactosyl diglycerides were generally absent. Sulfoquinovosyl diglyceride was present in significant amounts in at least three species of the Rhodospirillaceae and may have been present in most of them, but only in traces. All of the Chromatiaceae species contained several glycolipids, one of which was similar to monogalactosyl diglyceride. Ornithine lipids were found in large amounts in most Rhodospirillaceae, but were absent in Ectothiorhodospira and in the other Chromatiaceae. The species examined could be divided into three groups on the basis of their lipid composition: (i) the genus Ectothiorhodospira; (ii) the remaining Chromatiaceae; and (iii) the Rhodospirillaceae. The data presented are compared with those available in the literature, and differences from other phototrophic organisms are discussed.

Chromatiaceae↗

PubMed1981

[Can phosphatidyl sulfocholine, the sulfonium analog of lecithin, efficiently replace lecithin in natural membranes?].

Lecithin does not exist in the marine diatom, Nitzschia alba, being completely replaced by phosphatidylsulfocholine (PSC), the sulfonium analogue of phosphatidylcholine (PC). Thus, the question arises: how can PSC effectively replace lecithin in a natural membrane? We have compared the physical properties of a homologous series of synthetic PSC's (di - 14:0, di- 16:0, di- 18:0, di 18:1) in aqueous dispersion with those of a similar series of PC's. The PSC's formed liposomes having similar properties to those of the PC's. However, the saturated PSC homologues showed main transition temperatures 2-4 degrees C above those of the corresponding PC's as measured by differential scanning calorimetry, fluorescence polarization or electron paramagnetic resonance. Furthermore, there was no significant difference between the two types of membranes with respect to their permeability to urea or 6-carboxyfluorescein either in the presence or absence of cholesterol. We have also shown that yeast cells can grow and survive in spite of a complete replacement of PC by PSC in their membranes. The sulfonium analogue of lecithin would appear to be able to replace PC in natural membranes because of the similarity in their physical properties.

Choline↗

PubMed1979

Studies on the biosynthesis of sulfolipids in the Diatom Nitzschia alba.

Labeling of sulfolipids in Nitzschia alba was studied after growth of the cells in media containing L-[35S]cystine, L-[35S], L-[35S]cysteine, L-[35S]-methionine or a mixture of L-[Me-3H]methionine and L-[35S]methionine, [35S]Cysteine or [35S]cystine labeled the deoxyceramide sulfonate and the sulfonium analog, phosphatidylsulfocholine (and its lyso derivative) but not the sterol sulfate nor the sulfoquinovosyl diglyceride; [35S]methionine labeled only the phosphatidylsulfocholine and its lyso derivative. With the [35S]- and [Me-3H]methionine mixture (3H/35S ratio 1.0) the phosphatidylsulfocholine had a 3H/35 S ratio of 1.5 indicating that both sulfonium methyl groups were derived from methionine. Probable biosynthetic pathways for these novel sulfolipids are discussed.

Amino Acids, Sulfur↗

PubMed1979

Membrane-bound phospholipid desaturases.

This review covers studies on membrane-bound phospholipid desaturases in yeast and rat liver carried out in this laboratory. In yeast the desaturase system was shown to effect the direct desaturation of dioleoyl-lecithin to dilinoleoyl-lecithin. In rat liver the desaturase was capable of converting 2-eicosatrienoyl-lecithin to 2-arachidonoyl-lecithin. Both systems required reduced pyridine nucleotides, O2 and cytochrome b5. Eicosatrienoyl-lecithin desaturase along with eicosatrienoyl-CoA desaturase of rat liver microsomes was solubilized with detergents and purified 7-8-fold from the microsomal pellets. Both activities were reconstituted in the presence of deoxycholate on addition of the other components of the cytochrome b5-electron transport chain (cytochrome b5 and NADH-cytochrome b5 reductase) to the solubilized desaturase; addition of lecithin further stimulated the activities. The demonstration of desaturation of eicosatrienoyl-lecithin by a solubilized and partially purified desaturase provides strong evidence for the direct desaturation of the lecithin substrate without prior conversion to the acyl-CoA thiolester.

Acyl Coenzyme A↗

PubMed1979

Effect of glycerol on carotenogenesis in the extreme halophile, Halobacterium cutirubrum.

Growth of cells of Halobacterium cutirubrum in complex medium in the presence of 0.1 to 0.5% glycerol was slightly stimulated (about 10%), but the content of the major red pigment, bacterioruberin, was reduced fourfold and that of the minor red pigments, mono- and bisanhydrobacterioruberins, was also reduced but to a lesser extent. The content of the C40 carotenes, beta-carotene and lycopene, however, was greatly increased in 0.1 to 0.5% glycerol but was then reduced to negligible amounts at higher glycerol concentrations (1 to 5%). Similar effects of glycerol on carotenogenesis were observed when cells were grown in a chemically defined medium (BSMK), but growth of cells was considerably slower.

Carotenoids↗

PubMed1979

Studies of the biosynthesis of C50 carotenoids in Halobacterium cutirubrum.

Cells of Halobacterium cutirubrum were grown in the presence of [14C]mevalonate with and without 3 mM nicotine. Growth of cells was inhibited to a maximum extent of 25% but overall incorporation of 14C into total, neutral, or polar lipids was only inhibited about 16% during active growth and to a much lesser extent or not at all in stationary phase. Little effect of nicotine on labelling of squalenes, vitamin MK-8, geranylgeraniol, and phytoene was observed. However, labelling of bacterioruberin and monoanhydrobacterioruberin was extensively inhibited while that of lycopene and bisanhydrobacterioruberin was increased reciprocally by growth in the presence of 3 mM nicotine. Reincubation of the labelled nicotine-grown cells in fresh cold medium without nicotine restored the 14C-labelling of bacterioruberin and monoanhydrobacterioruberin at the expense of lycopene and bisanhydrobacterioruberin. These results confirm our previous findings suggesting that the C50 bacterioruberin is made by addition of a C5-isoprene unit to each end of the C40-lycopene chain, followed by introduction of four hydroxyl groups.

Carotenoids↗

PubMed1979

Chemical synthesis of sn-3-phosphatidyl sulfocholine, a sulfonium analog of lecithin.

A sulfonium analog of lecithin has been reported to replace the ubiquitous phosphatidyl choline in a non-photosynthetic diatom, Nitzschia alba. The structure of this sulfonium analog has now been established by chemical synthesis using the following methods: (i) condensation of sn-3-phosphatidic acid (dimyristoyl-, dipalmitoyl-, distearoyl-, distearoyl-, and dioleoyl-) with sulfocholine chloride in the presence of triisopropylbenzenesulfonylchloride in chloroform-pyridine (9:1); and (ii) phosphorylation of 1,2-dipalmitoyl-sn-glycerol with monophenylphosphoryl-dichloridate followed by a reaction with sulfocholine in the presence of pyridine and finally removal of the blocking phenyl group by catalytic hydrogenolysis. The desired synthetic products were obtained in overall yields of 50-70% and 11% for methods (i) and (ii), respectively, and were characterized by elemental analyses; infrared spectroscopy, nuclear magnetic resonance spectrometry, and mass spectrometry; optical rotation; and thin-layer chromatography mobilities. Comparison of the synthetic analogs with the natural sulfolecithin showed them to be identical, except for the nature of the fatty acid chains, thus establishing the natural product as sn-3-phosphatidyl sulfocholine.

Magnetic Resonance Spectroscopy↗

PubMed1978

The lipid composition of the non-photosynthetic diatom Nitzschia alba.

The lipid composition of the non-photosynthetic marine diatom, Nitzschia alba, has been quantitatively determined. Triglycerides accounted for 20% of the cell dry weight and 87% of the total lipids. Smaller amounts of 1,2- and 1,3-diglycerides, free sterol (24-methylene cholesterol), hydrocarbons and an unknown component were the remaining neutral lipids detected. Phosphatidylsulfocholine (phosphatidyl S,S-dimethylmercaptoethanol), present in amounts of 0.8% of cell dry weight (35% of total polar lipids), was the major polar lipid component. Other phospholipids were lysophosphatidylsulfocholine, phosphatidylglycerol, phosphatidylinositol and cardiolipin, but both phosphatidylcholine and phosphatidylethanolamine were completely absent. Another novel sulfolipid, deoxyceramide sulfonic acid, as well as the sulfate ester of the free sterol, were also present. Considerable amounts of the four lipids often associated with photosynthetic organisms, mono- and di-galactosyl diglycerides, sulfoquinovosyl diglyceride and phosphatidylglycerol, were identified in N. alba. However, the fatty acid components of the glycosyl diglycerides did not show the high amounts of polyunsaturated acids (18 : 2, 18 : 3) normally found in photosynthesizing organisms. All polar lipids were found to be associated with various cell membrane fractions in N. alba.

Cell Membrane↗

PubMed1978

Identification of the sulfolipids in the non-photosynthetic diatom Nitzschia alba.

The four major sulfolipids in the non-photosynthetic marine diatom, Nitzschia alba, were isolated in pure form and their structures were established spectrometrically and by identification of their hydrolysis products as (a) 24-methylene cholesterol sulfate, (b) 1-deoxyceramide-1-sulfonate, (c) phosphatidyl sulfocholine (a sulfonium analogue of phosphatidylcholine) and (d) sulfoquinovosyl diglyceride. The major characteristic fatty acids of the sulfolipids were: for the deoxyceramide sulfonate, 16 : 0 (26%) and 16 : 1-delta3-trans (64%); for the sulfonium analogue, 14 : 0 (30%), 18 : 1 (12%), 18 : 2 (8%), 20 : 5 (27%) and 22 : 6 (4%); and for the sulfoquinovosyl diglyceride (two species, respectively), 14 : 0 (9%, 22%), 16 : 0 (16%, 28%), 18 : 1 (8%, 22%), 20 : 5 (42%, 23%) and 22 : 6 (14%, 2%). Traces of lyso-derivatives of sulfoquinovosyl diglyceride and phosphatidyl sulfocholine were also detected. The deoxyceramide sulfonate and the phosphatidyl sulfocholine represent novel membrane lipid components not previously detected in other organisms. They may however have a widespread distribution in marine diatoms and perhaps in marine organisms generally.

Ceramides↗