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Biomedical subjects

G W Patterson

Publications and source records attributed to G W Patterson.

At least 19 recordsLinked to original sources
PubMed1999

Dopaminergic synapses mediate neuronal changes in an analogue of operant conditioning.

Feeding behavior in Aplysia can be modified by operant conditioning in which contingent reinforcement is conveyed by the esophageal nerve (E n.). A neuronal analogue of this conditioning in the isolated buccal ganglia was developed by using stimulation of E n. as an analogue of contingent reinforcement. Previous studies indicated that E n. may release dopamine. We used a dopamine antagonist (methylergonovine) to investigate whether dopamine mediated the enhancement of motor patterns in the analogue of operant conditioning. Methylergonovine blocked synaptic connections from the reinforcement pathway and the contingent-dependent enhancement of the reinforced pattern. These results suggest that dopamine mediates at least part of the neuronal modifications induced by contingent reinforcement.

Animals↗
PubMed1997

Use of an improved internal-standard method in the quantitative sterol analyses of phytoplankton and oysters.

Most work reporting the sterol composition of living organisms has not been done quantitatively, although good quantitative data are available for fatty acids and many other cellular components using an internal-standard method that compensates for errors during gas chromatographic analysis. In this paper, we report on the use of 7-stigmastenyl acetate as an internal standard for sterol analysis in two species of phytoplankton and oysters produced with two different diets. This internal-standard method provides an internal standard for this entire process of analysis, not just the gas chromatographic analysis. When analyzing 50-microgram samples of cholesterol acetate after hydrolysis and acetylation, about 30% of the sample was lost, resulting in a 30% error using the older external-standard method. Using the internal-standard method, the analysis error was less than 2%. Losses of sterol during analysis apparently are greater with plant and animal samples than with pure sterol standards. This internal-standard method was shown to be extremely useful, especially for samples with less than 500 micrograms of sterol. Finally, the standard error in sterol analysis is much lower when the internal-standard method is used, allowing statistical distinctions that are not possible otherwise. Use of 7-stigmastenyl acetate as an internal standard offers several advantages over the use of cholestane.

Animals↗
PubMed1994

Sterols of eustigmatophytes.

The oyster cannot synthesize sterols from smaller molecules but must obtain them from its diet, which consists of detritus and small organisms, i.e., mostly single-celled algae. Algae differ widely in their effectiveness as oyster food. Small (< 5 microns) algae which are abundant in sterols and polyunsaturated fatty acids appear to be most effective. Recent studies have shown the occurrence of cholesterol in strains of the unicellular algae Tetraselmis, Chaetoceros and Skeletonema, sometimes in large quantities. In the study reported here, six isolates of a recently constructed algal class, the Eustigmatophyceae, have been examined for sterols and fatty acids by gas chromatography and gas chromatography/mass spectrometry. All strains were shown to contain cholesterol as the principal sterol. Two isolates contained large amounts of total sterol (400-1000 fg/cell), and one (Sticho 0-18) also contained large amounts of eicosapentaenoic acid (20:5n-3). These biochemical characteristics are desirable in a potential food source for oysters.

Animal Feed↗
PubMed1990

A chilling sensitive mutant of Arabidopsis with altered steryl-ester metabolism.

A chilling-sensitive mutant of Arabidopsis thaliana was isolated and subjected to genetic, physiological, and biochemical analysis. The chilling-sensitive nature of the mutant line is due to a single recessive nuclear mutation at a locus designated chs1. In contrast to wild-type plants, which are not adversely affected by low temperatures, the chs1 mutant is killed by several days of exposure to temperatures below 18 degrees C. Following exposure to chilling temperatures, the mutant displays two common symptoms of chilling injury-leaf chlorosis and electrolyte leakage. In these respects, the physiological response of the mutant to low temperatures mimics the response observed in some naturally occurring chilling sensitive species. The biochemical basis of chilling sensitivity was explored by examining the pattern of incorporation of (14)CO(2) into soluble metabolites and lipids in wild-type and mutant plants. The only difference observed between the mutant and wild type was that following low temperature treatment, the mutant accumulated 10-fold more radioactivity in a specific class of neutral lipids which were identified by a variety of criteria to be steryl-esters. The accumulation of radioactivity in the steryl-ester fraction occurs 24 hours before there is any visible evidence of chilling injury. These results suggest one of two possible explanations: either the mutation directly affects sterol metabolism, which in turn leads to chilling sensitivity, or the mutation affects another unidentified function and the accumulation of radioactivity in steryl-esters is a secondary consequence of chilling injury.

Journal Article↗
PubMed1988

Effects of cyclopropenoid fatty acids on fungal growth and lipid composition.

Cyclopropenoid fatty acids (CPE) isolated from Sterculia foetida oil by urea clathration and reverse phase high performance liquid chromatography (HPLC) were introduced into fungal cultures. Stearate levels in phospholipids and triacylglycerols from Ustilago maydis sporidia rose considerably in response to 30 microM CPE. In addition, CPE themselves were incorporated into glycerolipid fractions. Sterol composition was unaffected. Changes in lipid composition were accompanied by inhibition of dry weight accumulation and sporidial number. Treated sporidia showed irregular wall deposition and a branched morphology. Oleate alleviated CPE effects on growth and morphology. Hyphal extension by Rhizoctonia solani was inhibited somewhat by 30 microM sterculate, while Fusarium oxysporum showed no appreciable response. Although CPE appeared to inhibit fatty acid desaturation by F. oxysporum, gross increases in the proportion of stearate were limited to the triacylglycerol fraction during 30 microM treatments. The possibility that the CPE synthesized by plants serve as antifungal agents is discussed.

Fatty Acids, Unsaturated↗
PubMed1988

A Rapid and Simple Procedure for Purification of Indole-3-Acetic Acid Prior to GC-SIM-MS Analysis.

A simple and rapid procedure for the purification of indole-3-acetic acid prior to gas chromatography-selected ion monitoring-mass spectrographic analysis was developed using an amino anion exchange minicolumn and a short high resolution C18 column. Since multiple samples can be prepared at one time, the procedure is more rapid and the sample preparation time is reduced to one-third that normally required. In addition, the final recovery was improved by 40 to 50% over that of a solvent partitioning procedure.

Journal Article↗
PubMed1984

Comparative effects of growth inhibitors on sterol metabolism in the nematode Caenorhabditis elegans.

An analogous series of dimethylalkyl compounds, consisting of four amines, an amide, and a phosphonate ester, inhibited motility and reproduction of the nematode Caenorhabditis elegans. Dimethylamines with straight-chain lengths of 12, 14, or 16 carbon atoms were equally active nematicides, causing greater than 80% population growth inhibition at a concentration of 25 ppm. The C12 straight-chain amine and its corresponding amide produced similar inhibition and were much more potent than either the corresponding C12 phosphonate or a C12 branched-chain amine. Inhibition of the delta 24-sterol reductase system was exhibited by all four amines, but not by the amide or phosphonate, in the following order of activity: C12 branched-chain amine greater than C12 straight-chain amine greater than C14 amine greater than C16 amine. The C12 branched amine also blocked the C-24(28)-dehydrogenase system in the conversion of sitosterol to fucosterol, the initial step in sitosterol dealkylation.

Amides↗
PubMed1980

Effect of Steric and Nuclear Changes in Steroids and Triterpenoids on Sexual Reproduction in Phytophthora cactorum.

The comparative biological activity of 21 naturally occurring or synthetically derived steroids, 7 tetracyclic and pentacylic triterpenoids, and antheridiol incubated with cultures of Phytophthora cactorum has been examined. There was greater dependence on precise steric features of the sterol side chain than on the extent of nuclear unsaturation in inducing oospore formation. There was no significant effect on oospore formation by changing nuclear unsaturation in ring B from Delta(5) to Delta(7) or to Delta(5,7). Converting the unsaturated sterol to its corresponding stanol resulted in a significant reduction in the number of oospores produced. The effectiveness of sterols bearing different side chains in inducing oospores was found to be in the following relative order: 24alpha-ethyl = trans-Delta(22)-24alpha-ethyl > trans-Delta(22)-24beta-ethyl = 24alpha-E-ethylidene = 24alpha-methyl > 24beta-methyl = trans-Delta(22)-24beta-methyl = 26-methyl = saturated C(7) side chain and C-20 R (17-alphaH, 20-alphaH, right-handed conformer) = cis-Delta(22)-C(7) side chain and C-20 R > saturated C(7) side chain and C-20 S (17-alphaH, 20-betaH, right-handed conformer) > no sterol = 29-hydroxyporiferasterol = 20alpha-hydroxycholesterol = 24xi-hydroxy-24-vinylcholesterol. Of the sterols examined the most significant stereochemical criterion for the induction of oospore formation was absence of bulk on the front face of C-20. This follows from the observation that 20-isocholesterol and 20alpha-hydroxycholesterol, in which a methyl and hydroxy group, respectively, project to the front in the right handed conformation, were inactive in stimulating production of oospores. None of the triterpenoids studied induced oospore formation to any significant degree. Oospore formation was not induced by antheridiol nor 29-hydroxyporiferasterol in combination or added separately to growing cultures of P. cactorum in the concentration range 0.01 - 10.0 milligrams per liter.

Journal Article↗
PubMed1976

Metabolism of 2,4-3H-14alpha-methyl-5alpha-ergost-8-enol and 2,4-3H-5alpha-ergosta-8,14-dienol in Ochromonas malhamensis.

Tritium-labeled 14alpha-methyl-5alpha-ergost-8-enol and 5alpha-ergosta-8,14-dienol were converted to brassicasterol and poriferasterol in Ochromonas malhamensis. This indicates that the organism can rearrange these sterol structures so that they contain the naturally occurring 5(6) double bond, and suggests that O. malhamensis is able to introduce a 24(28) double bond into a nine-carbon saturated side chain which is alkylated to produce a C-29 sterol.

Animals↗
PubMed1975

Sterols of scallop. I. Application of hydrophobic sephadex derivatives to the resolution of a complex mixture of marine sterols.

Column chromatography on a hydroxyalkoxypropyl derivative of Sephadex LH-20 and on Anasil B has been applied to the resolution of complex marine sterol mixture in combination with argentation thin-layer chromatography and gas chromatography. This approach permits isolation in quantity of individual sterols from a complex mixture and separation of sterol mixtures that were not resolved without the modified Sephadex step. Seventeen sterols were detected in the scallop Placopecten magellanicus. 24-Methyl-cholesterol, 24-ethyl-cholesterol, 24-methyl-22-dehydrocholesterol and 24-ethyl-22-dehydrocholesterol, i.e. sterols whose configuration at C-24 had not been definitively established, were isolated in sufficient quantities for further study by nuclear magnetic resonance spectroscopy.

Animals↗
PubMed1974

Inhibition of Sterol Biosynthesis in Chlorella sorokiniana by Triparanol.

When Chlorella sorokiniana was cultured in the presence of 1 mg/1 triparanol succinate, there was a 42% reduction in total sterol concentration. Algal biomass was reduced by approximately the same amount. In addition to the cycloartenol, cyclolaudenol, 24-methyl-pollinastanol, ergosta-5, 7-dien-3beta-ol, and ergosterol that occur in control culture, pollinastanol, 14alpha-methyl-5alpha-ergost-8-en-3beta-ol, 5alpha-ergosta-8, 14, 22-trien-3beta-ol, 5alpha-ergosta-8(14), 22-dien-3beta-ol, 5alpha-ergosta-8(9), 22-dien-3beta-ol, 5alpha-ergosta-8, 14-dien-3beta-ol, 5alpha-ergost-8(9)-3n-3beta-ol, 5alpha-ergost-8(14)-en-3beta-ol, 5alpha-ergosta-7, 22-dien-3beta-ol, and 5alpha-ergost-7-en-3beta-ol were isolated and identified from triparanol succinate-treated cells. A biosynthetic pathway for sterol biosynthesis in this organism is postulated based on all the sterols that were isolated and identified in triparanol-treated cultures of C. sorokiniana. Cyclolaudenol appears to be the product of the first alkylation at C-24 in this organism rather than the more common 24-methylene cycloartanol. Since 24-methylene sterols are needed for the second alkylation reaction, this would explain the absence of C-29 sterols in C. sorokiniana. Four of the sterols identified in C. sorokiniana are reported for the first time in a living organism. They are: 24-methyl pollinastanol, 5alpha-ergosta-8, 14, 22-trien-3beta-ol, 5alpha-ergosta-8(14), 22-dien-3beta-ol and 5alpha-ergost-8(14)-en-3beta-ol.

Journal Article↗
PubMed1974

Effects of cation levels of the nutrient medium on the biochemistry of chlorella: I. Concentration series.

The effects of variations in nutrient cation levels on the growth and biochemistry of Chlorella were investigated. This study involved concentration-series experiments in which the levels of Mg(2+), K(+), and Ca(2+) varied from deficiency to toxicity levels for growth. The nutrient sufficiency concentrations of Mg(2+) and K(+) were 0.08 and 0.10 meq/1, respectively. Deficiencies of Mg(2+) or K(+) reduced the growth rate, as well as cellular total nitrogen and unsaturated fatty acid levels. K(+) deficiency increased total lipid levels, while total fatty acids were unaffected. Increasing Mg(2+) or K(+) concentrations in the nutrient media were accompanied by corresponding increases in growth rate and certain biochemical fractions. Calcium was without effect except at a toxicity level. Cellular sufficiency concentrations for Mg(2+) and K(+) were 0.3 and 1.2% of the dry weight, respectively.

Journal Article↗
PubMed1974

Effects of Cation Levels of the Nutrient Medium on the Biochemistry of Chlorella: II. Factorial Experiment.

A factorial experiment was designed to study the effects of Mg(2+), K(+), and Na(+) on the growth and biochemistry of Chlorella sorokiniana. Raising Mg(2+) or K(+) concentration in the nutrient medium increased growth rates as well as total N levels and Mg(2+) and K(+) accumulation by the cells. The total N effect was Mg(2+)-dependent-if Mg(2+) was below a certain level in the medium-increasing the K(+) concentration did not raise the total N level of cells. Low nutrient levels of K(+) decreased the levels of unsaturated fatty acids (especially 18:1 and 18:3), while increasing the levels of palmitic acid (16:0), total fatty acids, and total lipid. Increasing nutrient K(+) concentrations were accompanied by increases in levels of some unsaturated fatty acids, with a concomitant reduction in 16:0, total fatty acids and total lipid. Low Mg(2+) levels in the nutrient medium reduced the cellular levels of palmitic acid, total fatty acids, total lipid, and certain unsaturated fatty acids (though this last effect also depended on the nutrient level of K(+)). These relationships indicate that Mg(2+) may be important in the initial steps of fatty acid synthesis, whereas K(+) may be necessary for the formation of certain unsaturated fatty acids. Variations in Na(+) concentration did not have any significant effect on the growth and biochemistry of C. sorokiniana.

Journal Article↗