M.Sc. / The senescence of climacteric flowers such as carnations is accompanied by an increase in ethylene synthesis during the later stages. This increase in ethylene synthesis is preceded by an increase in the sensitivity of the flowers to ethylene. The increase in ethylene sensitivity is accompanied by a concomitant increase in the levels of short-chain saturated fatty acids (SCSFAs). Treatment of carnation flowers with SCSFA results in an increase in ethylene sensitivity. It appears that these acids act by increasing membrane fluidity, causing slight conformational changes in membrane associated proteins and thereby increasing the ability of the tissue to bind ethylene to its membrane associated receptor molecules. The levels of SCSFAs in senescing carnation petals is controlled by the activity of the enzyme acetyl-coenzyme A carboxylase (ACCase). A decrease in the activity of this enzyme results in an increase in the levels of the SCSFAs and vice versa. During the senescence of carnation flowers, ACCase activity fluctuated from day to day. This fluctuation can be correlated to the fluctuations in the ethylene sensitivity of the flowers on a daily basis. In carnation petals, ACCase is located mainly in the plastids. ACCase activity could be controlled via feedback inhibition by long-chain fatty acids such as oleic acid. Treatment of carnation flowers with oleic acid resulted in a concomitant inhibition of ACCase activity, an increase in SCSFA-levels and an increase in ethylene sensitivity. Oleic acid is a competitive inhibitor of ACCase activity, and changes in the levels of oleic acid will affect the activity of the enzyme. An increase in oleic acid concentration resulted in a decrease in enzyme activity. However, in carnations it appears that ACCase activity is not controlled via feedback inhibition by long chain saturated fatty acids. The results of this study clearly show that ACCase activity is controlled directly by the expression of at least the biotinylated (BCCP) subunit of the enzyme. A decrease in the expression of the gene during the early stages of senescence coincided with a decrease in ACCase activity and was accompanied by a concomitant increase in ethylene sensitivity. These results indicate that the increase in ethylene sensitivity caused by an increase in SCSFA levels is directly controlled by the expression of the ACCase genes.

Detailed analyses of the lipid class and fatty acid composition were carried out for the marine microalgal species Nannoch/oropsis oculata (Droop) (CCAP strain no. 849/1) of the division Eustigmatophyceae (Hibberd). The alga was grown in batch and continuous culture using a novel culturing apparatus, the cage culture turbidostat, the construction of which is detailed in full. The total lipid extract yielded by the alga varied in a growth-phase dependent manner within the range 25 % to 80 % of the lyophilised cell mass. Of this between 40 % and 70 % was recovered as fatty acid methyl esters (FAME) upon transesterification. The total fatty acid composition of N. oculata consisted mainly of 16:0, 16:1 and 20:5(n-3), these three fatty acids often accounting for greater than 80 % of the total fatty acid mass. Between 9 % and 50 % of the mass of total FAME was accounted for by 20:5(n-3), the balance being accounted for by variations in the relative proportions of 16:0, 16:1, 18:1, 18:2 and 20:4. During periods of low cellular division rate, such as the lag- and stationary-phases, the proportion of polyunsaturated fatty acids (PUFA) (mainly 20:5(n-3» decreased. The total fatty acids became increasingly saturated as higher proportions of shorter chain length fatty acids accumulated, mainly in triacylglycerols (TAO). Increased cellular proportions of total lipid resulted from TAO accumulation which occurred on account of preferential partitioning of carbon into TAO biosynthesis whilst cellular division was suspended. The fatty acid composition of the TAO was more saturated at high synthesis rate and vice-versa at lower rates. The galactolipids, monogalactosyldiacylglycerol (MODO) and digalactosyldiacyl glycerol (DODO) were rich in 20:5(n-3) during exponential cell division containing up to 77 % and 53 % 20:5(n-3) respectively. Phosphatidylcholine (PC) was the only cl~s to contain significant proportions of CIS fatty acids during exponential growth, thus implicating its involvement in the acyl chain elongation reactions between the Cl6 and C20 fatty acids. Culture incubation temperature in the range 5 °C to 25°C did not influence the fatty acid composition of N. oculata. The effect of temperature upon culture dynamics at the lower culture incubation temperatures gave an apparent decrease in the PUFA content of the total fatty acid at a given point on the cultures growth curves. By expressing the data in tenns of culture doubling periods during the exponential-phases of growth it was found that temperature had no real effect upon fatty acid unsaturation or chain length. at either the total or the individual lipid class FAME level after the cells had passed through five doubling periods. Increasing the culture medium salinity from one quarter to one and a half times that of normal seawater decreased the un saturation and chain length of the fatty acids at both total and individual lipid class levels. The change resulted from the progressive accumulation of 18:1 and 18:2"at the expense of 20:5. Variation of salinity did not affect the dynamics of the cultures in the same respect as temperature in that a lag-phase was not observed on the cultures growth curves. However. such a phase was evident in the fatty acid profile of the cells in the period following inoculation. The 'effects of culture illumination intensity in the range 45 Jill m-2 sec-I to 170 Jill m 2 sec-! were examined under continuous culture conditions using the cage culture turbidostat Accumulation of saturated TAG by the cells at the higher illumination intensities gave an apparent decrease in the rate of PUFA biosynthesis. The polar lipid classes were found to be more highly unsaturated at higher illumination intensities. At lower illumination intensity TAG accumulation was reduced and the total fatty acid composition was accordingly more unsaturated. The fatty acid composition of the TAG component was more unsaturated but those of the polar lipid classes were less unsaturated than at higher illumination intensity. Increased illumination increased the degree of un saturation of the polar lipid cl~sses. Excess fixed carbon was partitioned into TAG biosynthesis. primarily as 16:0 and 16:1. The net accumulation of this lipid class even at high cell division rates resulted in a low overall unsaturation level. The effects of decreasing nitrate concentration in the range 1.0 mM N03 - to 0.001 mM N03 - had a similar basis to those of illumination in that the changes in the total fatty acid composition were largely governed by the rate of TAO accumulation. At high nitrate concentrations the cellular division rate was relatively high and the proportion of TAO in the total lipid extract was low. Consequently, both total and individual lipid classes contained high proportions of unsaturates, particularly 20:5(n-3). However, when the nitrate concentration was decreased, such that it began to limit the rate of cellular division, TAG accumulated Cursory analyses of the molecular species of the galactolipid classes, MODO and DODO, and phospholipid class PC are presented. The effects of environmental variables are discussed in tenns of the changes which may occur in the growth phase distribution of the cells in asynchronous culture, along with the concommitant changes in the lipid composition of the cells. The potential linkage of the elongation and desaturation reactions with both MODO and PC is also discussed briefly with reference to future research.

No description available.

Proton magnetic resonance has been measured in the temperature range -196° to 295°C for potassium caprylate, from -196° to 230°C for lithium stearate, and at -196° and 27°C for potassium caproate. Theoretical second moments for potassium caproate, caprylate and caprate at -196°C were computed using various molecular parameters and were compared with experimental values. Unfortunately the theoretical values were sufficiently alike for any one soap so that it could not be decided which of the parameters were applicable. The results do show, however, that the end methyl group rotates in potassium caproate at -196°C and probably does so in potassium caprylate and caprate. A sharp decrease in line width and second moment takes place in potassium caprylate between 50° and 55°C and between 283° and 286°C. The first transition corresponds to a known crystal phase change at 55°C. The second moment results suggest that some torsional oscillation about the longitudinal axes of the hydrocarbon chain portion of the potassium caprylate molecules takes place below 50° C. Above 55°C torsional oscillation of large amplitude or possibly even rotation of the hydrocarbon chain occurs. The transition between 283° and 286°C corresponds to onset of motion in the hydrocarbon chain restricted only by continued ordering of the polar end groups in the ionic layer of the soap. The proton magnetic resonance results in lithium stearate indicate transitions at 115°, 171+°, and 225°C. These pmr transitions correspond to known phase transitions. The second moment results suggest that the methyl group of the hydrocarbon chain in lithium stearate begins to rotate between-183° and -136°C. The second moment above 115°C is approximately equivalent to that estimated for rotation of the hydrocarbon chain about its long axis. Above 171°C very extensive motion of the chains occurs, although they are still held in position by the ionic layer. The ionic layer begins to break up in the region 215° to 218°C, with the compound becoming an isotropic liquid at about 225°C. / Science, Faculty of / Chemistry, Department of / Graduate

The management of acute myocardial infarction (AMI) has been improved by the realisation that the size of infarction can influence mortality (Sobel et al, 1972) and that the infarct size can be altered by subsequent therapy (Maroko et al, 1972). The identification of any factor which may have adverse effects on the ischaemic myocardium and which is amenable to treatment would therefore have important prognostic implications. Elevation of circulating free fatty acid (FFA) concentrations is a consistent feature (Kurien and Oliver, 1966; Oliver et al, 1968) of the profound, non-specific metabolic reaction associated with the onset of AMI (Opie, 1975). The FFA rise has been correlated with the development of arrhythmias (Oliver et al, 1968) after AMI, and with the severity of ischaemic damage (Oliver et al, 1968; Gupta et al, 1969; Russell & Oliver, 1978) on clinical grounds. The method of quantifying infarct size developed by Shell et al (1972) has provided a means of correlating the degree of metabolic disturbance with extent of myocardial damage, and of assessing the benefits of metabolic interventions. The purpose of the studies reported in this thesis was to examine in detail the FFA rise in the early phase of AMI and to correlate this rise with the development of arrhythmias and other complications of AMI and with enzymatically estimated infarct size, thus leading to a more rational approach to therapeutic interventions.

Fatty acid composition of five dwarf mistletoe species was analysed by Gas Liquid Chromatography. Because of the limitations of available equipment, only aerial shoots were analysed. Palmitic, oleic, linoleic and arachidic acids were the major components of total lipids. The sum of these acids accounted for 85-95 percent of total lipids present in the tissue. There was no apparent difference between species. The ratio of saturated acids to unsaturated acids in summer collections was higher than that of fall collections. Temperature may play an important role in controlling of these ratios. Lipid content varied from 3.25% to 8.5% on a dry weight basis depending on species.

This document only includes an excerpt of the corresponding thesis or dissertation. To request a digital scan of the full text, please contact the Ruth Lilly Medical Library's Interlibrary Loan Department (rlmlill@iu.edu).

This document only includes an excerpt of the corresponding thesis or dissertation. To request a digital scan of the full text, please contact the Ruth Lilly Medical Library's Interlibrary Loan Department (rlmlill@iu.edu).

The objectives of this study were to determine fatty acid composition and acrosome status from bull sperm with different freezabilities (n = 12). We hypothesized that lipid fractions had differentiated fatty acid compositions and such differences influence sperm freezability and the sperm acrosome. Fatty acids were extracted from fresh frozen sperm and fractionated by solid-phase extraction. Thirtyour fatty acids were quantified. Saturated fatty acids were predominant, accounting for 71 to 80% of fatty acids in both fractions. Differences in composition between fractions existed (P < 0.001). Branched chain fatty acid concentrations (15 to 18 µg) were almost twice that of polyunsaturated fatty acid concentrations found in the polar fractions (8 to 9 µg; P < 0.001). Sperm with differentiated freezabilities had few differences in 22:0, 18:1 cis 9, and 14:0 13-methyl fatty acids (P ≤ 0.011). Analyses of acrosome status of sperm revealed that acrosomes were affected differently among bulls.

No description available.