Total Lipid Phosphorus Research Articles

Protein-Energy Malnutrition during Gestation and Lactation in Rats Affects Growth Rate, Brain Development and Essential Fatty Acid Metabolism

The influence of feeding a low protein diet to rat dams during gestation and lactation on lipid metabolism in pups was studied. Wistar rats were fed 5, 10, 15 and 25% dietary protein during gestation and lactation. Pup growth was monitored until weaning, and brain weight, protein concentration, proteolipid concentration and total lipid phosphorus concentration of brain were analyzed. The levels of fatty acids in dam milk as well as in pup liver phospholipids and brain prosphatidylcholine and phosphatidylethanolamine were determined. The progressive deprivation of maternal dietary protein produced a reduction in the total saturated fatty acid concentration of dam milk and an increment in the concentration of nonmetabolized linoleic acid. Pup body and brain weights as well as proteolipid, protein and total lipid phosphorus concentrations in brain were reduced in proportion to the degree of dietary protein deficiency. The products:precursor ratio of (n-6) fatty acids in liver phospholipids revealed an impairment in the elongation-desaturation pathway due to maternal protein deficiency. Both (n-6) and (n-3) polyunsaturated fatty acids within brain phosphatidylethanolamine were decreased by reduced maternal dietary protein intake, whereas only the linoleic acid-derived products were similarly affected in the corresponding phosphatidylcholine fraction. These results demonstrate the widespread and profound deleterious effects of low protein levels of maternal diet on the growth rate, brain development and fatty acid metabolism of rat pups.

Unique thermal behavior of sphingomyelin species with nonhydroxy and 2-hydroxy very-long-chain (C28-C32) PUFAs

In rat germ cells and spermatozoa, sphingomyelin (SM) contains molecular species with nonhydroxy (n) and 2-hydroxy (h) very-long-chain polyunsaturated fatty acids (V), the most abundant being SMs with (n- and h-) 28:4n-6, 30:5n-6, and 32:5n-6 as acyl chains. The aim of this study was to gain information about their thermotropic behavior and interactions with other lipids. After isolation from rat testis, multilamellar and giant unilamellar vesicles from these SMs were examined using fluorescent probes. Only n-32:5 SM and h-32:5 SM displayed a gel-liquid transition temperature (Tt ∼ 21-22°C), the rest remaining in the liquid state in the 5°C-45°C range. The degree of order was larger in bilayers of any of the h-V SMs than in those of their chain-matched n-V SMs. Both, but n-V SM relatively more than h-V SM, decreased the Tt of dimyristoylphosphatidylcholine as their proportion increased in binary phosphatidylcholine:SM liposomes. In contrast to the established ability of 16:0 SM to form lateral cholesterol/SM-rich ordered domains in ternary dioleoylphosphatidylcholine:cholesterol:SM bilayers, neither n-V SM nor h-V SM showed a tendency to do so. Thus, these SMs are in the fluid state and are not involved in this type of domains in spermatozoa at physiological temperatures. However, this state could be altered at the very low temperatures at which these gametes are usually preserved.

Effects ofdamand/orseqAMutations on the Fatty Acid and Phospholipid Membrane Composition ofSalmonella entericaSerovar Typhimurium

We examined the phospholipids (Phls) and the membrane fatty acid (FA) composition in Salmonella enterica serovar Typhimurium dam and/or seqA mutants. Phosphatidylglycerol, phosphatidylethanolamine (PE), and cardiolipin (CL) are the major Phls present in all the strains and accounted for greater than 95% of the total lipid phosphorus. Phosphatidic acid and phosphatidylserine are the minor ones. The seqA mutant showed a decrease in PE and an increase in CL and phosphatidylglycerol proportion compared with the wild-type strain. The same changes were observed with the seqA dam double mutant. However, the dam mutation caused an unusual accumulation of CL with a significant decrease in the PE content, compared with the isogenic wild-type strain. FA composition of the total lipids and the different fractions containing Phls have been determined. The major saturated FAs (SFAs) and unsaturated FAs (UFAs) found were C(14:0), C(16:0) and C(16:1w7), C(18:1w9), respectively. Cyclic FAs, cyc(17:0) and cyc(19:0), were also present in appreciable amounts. Moreover, dam and/or seqA mutations caused a decrease in UFA/SFA ratio and there was a progressive reduction in the content of C(16:1w7) and C(18:1w9), going through the order seqA, dam/seqA, and dam mutants. This decrease in UFA content was compensated for in all strains by an increase in the corresponding C(17-) and C(19-) cyclic FAs. So these UFAs were converted to their cyclopropane derivatives, which resulted in a low UFA/SFA ratio. SeqA and Dam proteins might regulate FA biosynthesis and Phls composition of Salmonella enterica serovar Typhimurium.

Alteration of the phospho- or neutral lipid content and fatty acid composition in Listeria monocytogenes due to acid adaptation mechanisms for hydrochloric, acetic and lactic acids at pH 5.5 or benzoic acid at neutral pH

This study provides a first approach to observe the effects on Listeria monocytogenes of cellular exposure to acid stress at low or neutral pH, notably how phospho- or neutral lipids are involved in this mechanism, besides the fatty acid profile alteration. A thorough investigation of the composition of polar and neutral lipids from L. monocytogenes grown at pH 5.5 in presence of hydrochloric, acetic and lactic acids, or at neutral pH 7.3 in presence of benzoic acid, is described relative to cells grown in acid-free medium. The results showed that only low pH values enhance the antimicrobial activity of an acid. We suggest that, irrespective of pH, the acid adaptation response will lead to a similar alteration in fatty acid composition [decreasing the ratio of branched chain/saturated straight fatty acids of total lipids], mainly originating from the neutral lipid class of adapted cultures. Acid adaptation in L. monocytogenes was correlated with a decrease in total lipid phosphorus and, with the exception of cells adapted to benzoic acid, this change in the amount of phosphorus reflected a higher content of the neutral lipid class. Upon acetic or benzoic acid stress the lipid phosphorus proportion was analysed in the main phospholipids present: cardiolipin, phosphatidylglycerol, phosphoaminolipid and phosphatidylinositol. Interestingly only benzoic acid had a dramatic effect on the relative quantities of these four phospholipids.

Increased phospholipid methylation and glycogen phosphorylase activation after a single dose of dexamethasone in mouse liver.

Two different effects on phospholipid methylation and glycogen phosphorylase a activation were accomplished by treating mice livers with dexamethasone. A biphasic effect on the glycogen phosphorylase a was determined in the homogenated liver of dexamethasone-treated animals: The enzymatic activity increased between 45 to 90 min and decreased about 3 h. Moreover, the increased activity of glycogen phosphorylase a was also found in adrenalectomized mice. Also, the incorporation of ethanolamine into PE1) and PC1) after 15 min of hormone-administration was 77% and 270%, respectively, over the control values. The increase in phospholipid methylation was maintained during the first hour. After 4 h the hormone-treated animals also showed significant differences compared to the controls. Finally, studies of total lipid phosphorus content in the liver fail to show any differences between control and hormone-treated mice.

Targeted Induction of Lung Endothelial Cell Apoptosis Causes Emphysema-like Changes in the Mouse

Pulmonary gas exchange relies on a rich capillary network, which, together with alveolar epithelial type I and II cells, form alveolar septa, the functional units in the lung. Alveolar capillary endothelial cells are critical in maintaining alveolar structure, because disruption of endothelial cell integrity underlies several lung diseases. Here we show that targeted ablation of lung capillary endothelial cells recapitulates the cellular events involved in cigarette smoke-induced emphysema, one of the most prevalent nonneoplastic lung diseases. Based on phage library screening on an immortalized lung endothelial cell line, we identified a lung endothelial cell-binding peptide, which preferentially homes to lung blood vessels. This peptide fused to a proapoptotic motif specifically induced programmed cell death of lung endothelial cells in vitro as well as targeted apoptosis of the lung microcirculation in vivo. As early as 4 days following peptide administration, mice developed air space enlargement associated with enhanced oxidative stress, influx of macrophages, and up-regulation of ceramide. Given that these are all critical elements of the corresponding human emphysema caused by cigarette smoke, these data provide evidence for a central role for the alveolar endothelial cells in the maintenance of lung structure and of endothelial cell apoptosis in the pathogenesis of emphysema-like changes. Thus, our data enable the generation of a convenient mouse model of human emphysema. Finally, combinatorial screenings on immortalized cells followed by in vivo targeting establishes an experimental framework for discovery and validation of additional ligand-directed pharmacodelivery systems.

Very Long-chain Polyunsaturated Fatty Acids Are the Major Acyl Groups of Sphingomyelins and Ceramides in the Head of Mammalian Spermatozoa

Very long-chain (C24 to C34) polyunsaturated fatty acids (VLCPUFA) are important constituents of sphingomyelin (SM) and ceramide (Cer) in testicular germ cells. In the present paper we focused on the SM and Cer and their fatty acids in spermatozoa and their main regions, heads and tails. In bull and ram spermatozoa, SM was the third most abundant phospholipid and VLCPUFA were the major acyl groups ( approximately 70%) of SM and Cer. In rat epididymal spermatozoa the SM/Cer ratio was low in the absence of and could be maintained high in the presence of the cation chelator EDTA, added to the medium used for sperm isolation. This fact points to the occurrence of an active divalent cation-dependent sphingomyelinase. Bull and rat sperm had an uneven head-tail distribution of phospholipid, with virtually all the VLCPUFA-rich SM located at the head, the lower SM content in the rat being determined by the lower sperm head/tail size ratio. Most of the SM from bull sperm heads was readily solubilized with 1% Triton X-100 at 4 degrees C. The detergent-soluble SM fraction was richer in VLCPUFA than the nonsoluble fraction and richer in saturated fatty acids. Cer was produced at the expense of SM, thus decreasing severalfold the SM/Cer ratio in rat spermatozoa incubated for 2 h in presence of the sperm-capacitating agents, calcium, bicarbonate, and albumin. The generation of Cer from SM in the sperm head surface may be an early step among the biochemical and biophysical changes known to take place in the spermatozoon in the physiological events preceding fertilization.

Evaluation of Bronchoalveolar Lavage Fluid Phospholipids and Cytokine Release by Alveolar Macrophages as Prognostic Markers in Sarcoidosis

Background: The clinical course of sarcoidosis is unpredictable and reliable laboratory prognostic parameters are lacking. Objectives: The aim of the present study was to estimate the prognostic value of bronchoalveolar lavage fluid (BALF) phospholipids and cytokine production by alveolar macrophages (AM) in pulmonary sarcoidosis. Methods: We investigated BALF parameters in 64 subjects (55 patients with sarcoidosis and 9 healthy volunteers as controls). After a period of 12 months, the total sarcoidosis study population was divided into three groups according to radiological, functional and laboratory dynamics: the group with a favorable (n = 15), the one with an unfavorable (n = 16) and the one with an intermediate clinical course of the disease (n = 24). Results: The group of patients with a poor clinical outcome was characterized by a lower percentage of lymphocytes in BALF [20% (4–56%)], rather small amounts of cytokines [TNF-α: 1.5 ng/ml/10⁶(0.08–8.6), IL-6: 5.75 ng/ml/10⁶ (1.7–22.5)] and a significant decrease in BALF phospholipids [total lipid phosphorus (TLP): 29.9 µmol/l (13.8–68.3) as compared to 67.5 µmol/l (33.2–127.2) in controls]. Patients with a favorable clinical outcome were shown to have higher lymphocytosis (40%, range 6–64, p < 0.05 versus poor outcome), intensive TNF-α and IL-6 release by AM, and close to normal phospholipid content in BALF. Conclusions: The level of TNF-α secretion by AM <3.9 ng/ml/10⁶ and total lipid phosphorus in BALF less than 30 µmol/l may serve as markers of poor prognosis in pulmonary sarcoidosis.

Distribution of lipid and protein in human semen fractions

Human semen is formed by the secretions of different glands. We fractionated semen by centrifugation and obtained four main fractions: (a) spermatozoa, (b) material precipitating at 10 000× g, (c) prostasomes (precipitate at 105 000× g), and (d) a soluble fraction. When required, fractions were purified further. We find that most semen protein (about 85%) is in the soluble fraction, 7% in spermatozoa and the remainder is scattered in the other fractions. We compared the electrophoretic pattern of soluble protein with the protein of prostasomes and found marked differences. On the other hand, prostasomes, that comprises only about 3% of total semen protein, contain about 45% of cholesterol and almost 15% of lipid phosphorus with a cholesterol to phospholipid molar ratio greater than 2. On the contrary, phospholipid is largely bound to the fraction containing spermatozoa (about 46% of total lipid phosphorus). This fraction is poor in cholesterol and has a cholesterol to phospholipid molar ratio of about 0.2. The distribution of lipid phosphorus among lipid classes shows some similarity in the soluble fraction and in prostasomes; in both fractions, sphingomyelin is the most abundant phospholipid (about 50%). On the other hand, phosphatidylcholine is the main phospholipid in spermatozoa-enriched fractions (about 35% of total lipid phosphorus). We conclude that the various fractions of seminal plasma obtained by centrifugation differ markedly from each other as to lipid and protein content.

Replenishment of docosahexaenoic acid in n-3 fatty acid-deficient fetal rats by intraamniotic ethyl-docosahexaenoate administration.

A procedure for intraamniotic ethyl-docosahexaenoate (Et-DHA) administration was used to restore the docosahexaenoic acid (DHA; 22:6 n-3) levels in n-3-deficient fetal rats. The state of deficiency, characterized by a 34% and 60% decrease in DHA content of fetal brain and liver, respectively, was attained by feeding the pregnant dams from day 8 and up to 20 days gestation, with an n-3 linolenic acid-deprived diet. After a single intraamniotic administration of Et-DHA on day 18 or 19, a rapid increase in both fetal brain and liver DHA was achieved. This increase was accompanied by a decrease in the docosapentaenoic acid (DPA; 22:5 n-6) level. After 48 hr following Et-DHA administration, the major phospholipids (PLs) phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylcholine (PC), together accounting for more than 90% of total lipid phosphorus in sunflower oil (SFO)-treated animals, regained the DHA content to levels similar to control animals in both fetal brain and liver tissues. Unlike brain, however, most of the DHA content in liver PLs was restored by 24 hr, suggesting that the fetal liver may have a higher metabolic turnover. The DHA/DPA ratio was used to assess the degree of DHA correction. Fetal brain PS, PC, and PE ratios following Et-DHA administration grew steadily over a period of 48 hr but reached only approximately 60% of the control levels. Liver PS regained a value similar to the control, while those of PC and PE were 33% and 46% lower than the controls, respectively. Alterations in the PL polar head-group composition were observed following the dietary manipulations and Et-DHA administration. Although the intraamniotic injection is an invasive approach, the ability to rapidly enhance DHA acylation during intrauterine life may hold potential clinical value whenever an indication for DHA deficiency exists.

Membrane lipids of Mycoplasma fermentans.

Membranes of Mycoplasma fermentans, incognitus strain, were isolated by a combination of osmotic lysis and sonication. Analysis of membrane lipids revealed, in addition to free and esterified cholesterol, six major polar lipids dominated by a de novo synthesized compound (compound X), which accounts for 64% of the total lipid phosphorus. Compound X was labeled by palmitate, but not by oleate. Mass spectrometry and gas liquid chromatography analyses of compound X revealed two molecular species with molecular masses of 1048 and 1076 representing, a dipalmitoyl- and a stearoyl-palmitoyl-glycerodiphosphatidylcholine. Compound X has the ability to stimulate human monocytes to secret TNF alpha and to enhance the fusion of small unilamellar vesicles with MOLT-3 lymphocytes.

Leupeptin and E-64, inhibitors of cysteine proteinases, prevent gentamicin-induced lysosomal phospholipidosis in cultured rat fibroblasts

Aminoglycoside antibiotics, such as gentamicin, cause an early lysosomal phospholipidosis in the renal cortex, which is considered as a key event in the onset of acute tubular necrosis induced by these drugs. In a model of primary cultures of embryonic rat fibroblasts which develop typical lysosomal phospholipidosis when incubated with gentamicin (decrease of sphingomyelinase activity; increase in total cells lipid phosphorus; appearance of so-called ‘myeloid bodies’ in lysosomes), we observed a protective effect exerted by inhibitors of cysteine proteinases (leupeptin, E-64) against this alteration on the basis of both biochemical and morphological criteria. Actually leupeptin and E-64 caused a marked stimulation of sphingomyelinase activity both in control and in gentamicin-treated cells, which we suggest to be the cause of protection.

Phenytoin increases specific triacylglycerol fatty esters in skeletal muscle from horses with hyperkalemic periodic paralysis

Previous studies have demonstrated that phenytoin decreases the levels of triacylglycerols in several tissues other than skeletal muscle. Since phenytoin is clinically effective in several skeletal muscle disorders, triacylglycerol metabolism in skeletal muscle from four normal Quarter horses and four Quarter horses with hyperkalemic periodic paralysis was examined. The horses with hyperkalemic periodic paralysis had low levels of 18:3 in the phospholipids, low levels of 16:0, 16:1 and 18:3 in the free fatty acids and low levels of 20:4 in triacylglycerols. Triacylglycerol levels were increased in skeletal muscle from seven (three controls, four hyperkalemic periodic paralysis) of the eight horses on treatment with oral phenytoin for one week. Instead of an increase in all fatty ester types only 16:0, 16:1, 18:1 and 18:2 were significantly increased. Total lipid phosphorus and the distributions of phospholipid fatty esters and free fatty acids were not significantly altered by phenytoin treatment in most cases. An alteration in triacylglycerol metabolism by phenytoin was also observed in primary cultures of normal equine skeletal muscle radiolabeled with 18:1, but not in those radiolabeled with 18:2. These findings suggest that phenytoin does not just increase the levels of triacylglycerol in skeletal muscle, but alters the utilization and incorporation of fatty esters. These findings suggest a potential involvement of triacylglycerol metabolism in the clinical efficacy of phenytoin in hyperkalemic periodic paralysis.

Comparative Studies on Fatty Acid Composition and Phospholipases A and C Activities in Rabbit and Bovine Iris-Ciliary Body

It is well established that production of prostaglandins by ocular tissues is dependent upon the species. The rabbit iris-ciliary body produces greater amounts of prostaglandins than that of the bovine. To throw more light on the biochemical basis underlying these differences we have compared the fatty acid composition and phospholipases A2 and C activities in rabbit and bovine irides. When the concentration of arachidonic acid is expressed as % of total fatty acids, phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol, separated from rabbit iris phospholipids, contained 56, 38 and 18% more arachidonic acid, respectively, than those of the bovine. The total lipid phosphorus in rabbit and bovine iris-ciliary body were found to be 13·74 and 9·34 μmol g-1 wet tissue, respectively. Subcellular fractions, prepared from rabbit iris, contained 30-230% more phospholipase C activity than those of the bovine, and about 5-41 times higher phospholipase A2 activity than those of the bovine. In the rabbit iris microsomal fraction, phospholipase C activity is 33 times higher than that of phospholipase A2. However, the data presented suggest that phospholipase A2, rather than phospholipase C, is the enzyme which is more involved in arachidonic acid release for eicosanoid biosynthesis. These findings suggest that the high contents of arachidonic acid and phospholipases A2 and C in the rabbit iris could contribute to its unique capacity to synthesize and release prostaglandins in the anterior segment as compared to that of other mammalian species.

Effect of Water Stress on the Lipid and Fatty Acid Composition of Sweet Pepper (Capsicum annuum L.)

Sweet pepper (Capsicum annuum L.) plants were grown under field irrigation and dryland conditions. Stress was imposed 12 d after planting by withholding water for 8 d, and seedlings were harvested for analysis 20 d after planting. In stressed plants, leaf water potential dropped from -0.65 to - 1.03 MPa and water saturation deficit increased by 40 %; plant height did not show a significant reduction. The fresh and dry weights of stressed seedlings and their ratio decreased. The total lipid and total phosphorus contents of stressed seedlings decreased by about 43 % and 71 %, respectively, in comparison to the contents of the watered seedlings. The diacylglycerol, free fatty acid and total polar lipid contents decreased significantly with stress, the last mentioned by more than 50 % in phospholipid levels. Glycolipid levels; were unchanged and the amount of triacylglycerol increase by about 30 % over the control. Despite the differences found in the fatty acid composition of various lipid classes and between treatments, the degree of unsaturation did not change significantly either in control or stressed seedlings. Under stress conditions, free sterol levels increased without showing any change in the ratio of ‘more planar’ to ‘less planar’ sterols. The increase in free sterols and the decrease in phospholipid levels under water deficit conditions raised the sterol/phospholipid molar ratio 3-fold. The different responses of the lipid classes to water deficits and their possible significance are discussed.

Phosphoinositides and inositol phosphates in Discopyge tschudii electrocyte membranes

1. 1. The metabolism of inositol (Ins)-containing phospholipids and inositol phosphates has been studied by following the incorporation and distribution of myo-[ 3 H]Ins in metabolically active electrocytes from the electric ray Discopyge tschudii. 2. 2. The apparent initial rate of myo-[ 3H]Ins incorporation into total phosphoinositides was ca 8.2 fmol/mg protein/hr. Phosphatidylinositol (Ptdlns) displayed the highest levels of labelling. Lithium inhibited this incorporation probably by limiting the recycling of myo-[ 3H]Ins from [ 3H]Ins-monophosphate. 3. 3. The formation of water-soluble products of phosphoinositides between 7 and 24 hr was 4.1 ± 0.2, 0.4 ± 0.2 and 3.0 ± 1.0 fmol/μmmol total lipid phosphorus for myo-[ 3H]InsP, -InsP 2 and Ins-P 3 respectively. 4. 4. Lithium ions are shown to modulate phosphoinositide synthesis and Ins-phosphate accumulation. Ins-mono-, bis- and tris-phosphate production was enhanced 5-, 3- and 2-fold by Li +. 5. 5. The above results suggest the participation of a C-type phospholipase and of Li-sensitive phosphatases in the modulation of phosphoinositide metabolism in the electrocyte.

Effect of linoleic acid-rich infant formula feeding on brain synaptosomal lipid accretion and enzyme thermotropic behavior in the piglet.

The effects of a vegetable oil-based infant formula, virtually devoid of n-6 and n-3 long chain polyenoid fatty acids (LCP) and high in 18:2(n-6) and 18:2(n-6)/18:3(n-3) ratio, on brain synaptosome lipid composition and enzyme thermotropic behavior were studied in neonatal piglets. Term gestation piglets were fed either sow milk (SMF) or formula (FF) from birth for 5, 10, 15, or 25 days. Synaptosomal cholesterol, total lipid phosphorus, and phospholipid class composition did not differ between SMF and FF piglets. Synaptosomal fatty acid composition, however, was influenced by diet. The proportion of n-3 LCP, especially 22:6(n-3), was decreased, while the n-6 LCP, especially 22:4(n-6) and 22:5(n-6), were increased in FF compared to SMF piglets. These diet-related changes were most pronounced in the ethanolamine glycerophospholipid fraction and increased with the duration of feeding. FF thus reversed an apparent developmental increase in the synaptosomal n-3/n-6 LCP ratio. The monoene content, especially 18:1, was also reduced in the synaptosomes of FF compared to SMF pigs. FF had no effect on the activity of synaptosomal acetylcholinesterase. However, higher transition temperatures for this enzyme, indicating decreased membrane fluidity, were found in the FF compared to SMF piglets. The data suggest that exclusive feeding of proprietary formulae, devoid of LCP and high in 18:2(n-6) and/or the 18:2 (n-6)/18:3(n-3) ratio, may compromise normal fatty acid accretion and physical properties of brain synaptosomal membranes.

Phospholipid Changes during Adaptation to Acidosis in Urinary Bladder of Bufo marinus

The purpose of this study was to determine whether phospholipids (PL) play a role in the adaptation to metabolic acidosis by toad urinary bladder epithelium. Toads were placed in an NH4Cl acidosis for 48 hr. Quarter bladders were removed and incubated with [32P]orthophosphate or [3H]arachidonic acid for 1 hr at 25 degrees C. PL were detected by thin layer chromatography, autoradiography, and quantitated by liquid scintillation counting or fractional amounts were determined from phosphate content and expressed as counts per minute per micromolar of total phosphate or as percentage of fraction of total PL. Incorporation of [3H]arachidonic acid into urinary bladder PL was measured in acidotic and normal toads. There was a higher rate of arachidonic acid incorporation into several PL in acidotic animals. Phosphatidic acid and phosphatidylserine fraction in acidosis was 37,705 +/- 6,821 and in normal bladders was 9,254 +/- 2,652 (P less than 0.005); phosphatidylcholine fraction in acidotic toads was 80,462 +/- 16,862 and in normal bladders was 26,892 +/- 5,198 (P less than 0.025); and the phosphatidylethanolamine (PE) fraction in acidotic was 48,665 +/- 10,998 and in normal animals was 17,441 +/- 3,905 (P less than 0.025). 32P labeling revealed a higher rate of incorporation in bladders from acidotic toads compared with normal toads. In the acidotic bladders, the phosphatidic acid and phosphatidylserine fraction was 19,754 +/- 3,597 and in normal bladders was 12,980 +/- 1,394 (P less than 0.05) and for PE acidotic bladders was 9,129 +/- 1,304 and in normal bladders was 3,285 +/- 416 (P less than 0.001). Fractional PL (reported as percentage of fraction of total PL based on total lipid phosphorus) analysis in normal toads revealed phosphatidylinositol = 8.1 +/- 0.6% and PE = 27 +/- 1.2%, whereas for acidotic toads phosphatidylinositol = 11 +/- 0.6% and PE = 32 +/- 1.0% (P less than 0.01 for both). Aldosterone, a known stimulator of acidification, had no effect on 32P incorporation into PL fractions of the bladder. The increase in PL turnover following induction of acidosis is consistent with increased membrane synthesis or turnover during metabolic acidosis and this may reflect an increased transport of vesicular H+-ATPase into the apical membrane or the result of a proliferation of acid-secreting mitochondria-rich cells or both.

Lipid Changes in Maize Seedlings in Response to Field Water Deficits

Maize seedlings (?ea mays Hybrid r i Montano; were grown under neid irrigation and dryland conditions, stress was imposed i ? d after planting by witholding water for 8 d, and seedlings were harvested for analysis 20 d after planting. In comparison to the control, leaf water potential drops from -0-65 to -103 MPa and water saturation deficit increases by 40%, but plant height does not show a significant reduction. The fresh and dry weights of stressed seedlings and their ratio decrease. The total lipid and total lipid phosphorus contents of seedlings exposed to dryland conditions decrease by about 43% and 71%, respectively, in comparison to the contents of the watered seedlings. The diacylglycerol, free fatty acid and total polar lipid contents decrease significantly with stress, but in the latter class the dryland conditions induce a decrease of more than 50% in phospholipid levels, whereas they do not cause any change in glycolipid levels; on the contrary, the triacylglycerol amount increases by about 30% over the control. Notwithstanding differences found in the fatty acid composition of the various lipid classes and between treatments, the degree of unsaturation never changes significantly either in the control or in the stressed seedlings. Under stress conditions, free sterol levels increase without showing any change in the ratio of 'more planar' to 'less planar' sterol. The increase in free sterols and the decrease in phospholipid levels under water deficit conditions raise the sterol/phospholipid molar ratio 3-fold. The different responses of the lipid classes to water deficits and their possible significance are discussed.

Polar lipids and fatty acids of Pseudomonas cepacia

The polar lipids and fatty acids produced by the reference strains for seven different O serogroups of Pseudomonas cepacia have been identified. Similar results were obtained for all strains. Contrary to a previous report, the only significant phospholipids in this species are phosphatidylethanolamine and bis(phosphatidyl)glycerol, which contributed 57–83% and 17–43%, respectively, of the total lipid phosphorus. The former lipid was found as two chromatographically distinct fractions. In the less polar fraction and in bis(phosphatidyl)glycerol, the major fatty acids were hexadecanoic acid, cis-9,10-methylenehexadecanoic acid, cis-octadec-11-enoic acid, and cis-11,12-methyleneoctadecanoic acid. In the more polar fraction of phosphatidylethanolamine, the fatty acid in one position is a 2-hydroxy acid, mainly 2-hydroxyhexadecenoic acid, 2-hydroxyhexadecanoic acid, 2-hydroxyoctadecenoic acid, or 2-hydroxymethyleneoctadecanoic acid. Compared with other phospholipids, this fraction of phosphatidylethanolamine was depleted in cis-9,10-methylenehexadecanoic acid. Each strain also produced two ornithine amide lipids. In the major lipid, 3-hydroxyhexadecanoic acid was amide-bound to the α-amino group and was itself probably esterified by a 2-hydroxy acid, mainly 2-hydroxyoctadecanoic acid or the derived cyclopropane acid. In the minor ornithine amide lipid, the ester-bound acids were mainly methyleneoctadecanoic acid and hexadecanoic acid. The unusual lipid profiles of P. cepacia are of chemotaxonomic interest.