Robert R. Lowry

Rapid colorimetric determination of free fatty acids.

In 1964, a method was described for the determination of free fatty acids (FFAs) in vegetable oil. This paper describes an expansion of that work, improving the sensitivity and reproducibility of the method, as well as examination of solubilities of the copper soaps as a function of chain length and unsaturation. Involvement of the micellar structure was reviewed. Finally, a procedure is described that permits very rapid determination of FFA at the 2.0–14.0 µmol (0.5–4.0 mg oleic acid) level, and the results with several oils are given. Particular attention was given to evaluation of solvent systems which would extract the copper complexes.

A simple, sensitive method for lipid phosphorus.

A method is described for quantitatively determining lipid phosphorus with a linear range from 0.7–10.0 μg. The method is simple and rapid, requiring one stable reagent and a single extraction with 1-butyl acetate after the phosphorus is converted to inorganic phosphate by means of a perchlorate digestion. The stable complex is read at 310 nm.

Lipid content, fatty acid composition, and the effect of diet on fats of aquatic insects

Abstract 1. 1. The majority of 58 genera of aquatic insects examined had total lipid contents of 10–20% of total dry wt. 2. 2. Arachidonic and eicosapentaenoic acids were found in all individuals in quantities up to 7.2 and 24.7%, respectively, of total fatty acids. The presence of large amounts of these acids, compared to terrestrial insects, appears to be an adaptation to the aquatic environment. Their physiological importance may be related to their presence in membranes or to their metabolic function as hormonal precursors. 3. 3. Relative compositions of other fatty acids were similar to those reported for related terrestrial species. 4. 4. Fatty acid composition differed predictably among orders and functional feeding groups.

THE BIOCHEMICAL ANALYSIS OF SOME ESTUARINE PHYTOPLANKTON SPECIES. I. FATTY ACID COMPOSITION12

The fatty acid composition of 10 species of estuarine phytoplankton was determined using gas‐liquid chromatography. Nine of the species were isolated from Yaquina Bay, Oregon. These species were common components of the phytoplankton of the bay. The tenth species, Isochrysis galbana, was obtained from the Culture Collection of Algae at Indiana University. The 10 organisms comprised 3 species of Chlorophyta, 1 species of Cryptophyta, and 6 species of Chrysophyta.

The Role of Lipids, Fungi, and Temperature in the Nutrition of a Shredder Caddisfly, Clistoronia magnifica

Diets of conditioned alder (Alnus rubra) leaves, alder plus fatty acid methyl esters, alder plus aquatic hyphomycete fungi, fungi alone, and alder plus wheat were fed to larvae of the shredder caddisfly, Clistoronia magnifica (Trichoptera: Limnephilidae), at two temperatures. Larvae did not complete development on the alder or alder plus fatty acids diets. Larvae fed diets of alder plus fungi and fungi alone completed development to adults but failed to reproduce. Alder plus wheat fed larvae completed development and reproduced. Large triglyceride stores synthesized from wheat starch allowed reproduction in alder plus wheat fed animals. Nitrogen did not appear to limit reproduction because protein content of animals did not differ between diets. Temperature did not affect survival or growth rate. However, at the higher, non-optimal temperature, triglyceride levels were reduced during the pupal stage of animals fed alder plus wheat. It is suggested that food quality should be defined in terms of reproductive capacity and that temperature-food quality interactions are mediated through lipid metabolism in this insect.

FATTY ACIDS IN LOTIC PERIPHYTON: ANOTHER MEASURE OF COMMUNITY STRUCTURE1

The fatty acid spectra of 6 periphyton communities developed in laboratory streams at different combinations of light intensity and current velocity were determined by gas‐liquid chromatography and silver nitrate thin‐layer chromatography. Differences in species composition of the communities apparently had no striking effect on proportions of palmitic and stearic acids, whereas concentrations of myristic, palmitoleic, oleic, linoleic, and linolenic acids and a C20:5 acid were more closely related to taxonomic differences. In general, communities dominated by blue‐green algae exhibited relatively high proportions of oleic, linolenic, and linolenic acids and low proportions of palmitoleic acid and a C20:5 acid, as compared to communities consisting primarily of diatoms. The data also indicated an inverse relationship between fatty acid redundancy and species diversity.

Effects of Herbivore Type and Density on Chemical Composition of Algal Assemblages in Laboratory Streams

The chemical composition of algal assemblages in laboratory streams was determined 3 and 27 d after adding snail (Juga silicula) and larval caddisfly (Dicosmoecus gilvipes) grazers. Three days after the herbivores were introduced (day 8 of algal growth), the fatty acid and amino acid profiles among algal assemblages were similar. Substantial differences were noted after 4 wk (day 32 of algal growth), however, especially with respect to the 16:0, 16:1, 16:3, 18:3, and 20:5 fatty acids. On day 32, algal assemblages subjected to zero or 125 snails/stream (66/m2) had higher levels of glycine, leucine, isoleucine, tyrosine, and the 16:3 and 18:3 fatty acids than assemblages exposed to 500 snails/stream (250/m2), 50 caddis/stream (25/m2), or 200 caddis/stream (100/m2). On the other hand, assemblages subjected to high grazing pressure (i.e., 500 snails/stream, 50 and 200 caddis/stream) had higher levels of alanine, glutamic acid/glutamine, and the 16:0, 16:1, and 20:5 fatty acids than algae exposed to zero or 125 snails/stream. These data provide detailed information on the food quality of lotic algae and may serve as a starting point for future research in this field.

Dietary effects on lipid and fatty acid composition of Clistoronia magnifica (Trichoptera: Limnephilidae)

Dietary influences on growth and biochemical composition of the caddisfly Clistoronia magnifica were examined with a variety of diets including wheat, microbially conditioned alder, and wheat plus alder. Larvae receiving wheat were able to override direct temperature effects, while those on alder could not. Based on larval growth rates, and pupal weights and lipid contents, we concluded that alder alone was a poor quality food for late instar C. magnifica. A diet of alder plus wheat allowed the most growth, and produced the largest pupae, however pupae from larvae given just wheat had the largest lipid stores. Among-treatment differences in protein and lipid content, and fatty acid composition verified the importance of fatty acids synthesized from dietary carbohydrate. It appears that a carbohydrate source for the metabolism of storage lipid is a major requirement for late instar C. magnifica.

Distribution and identification of the fatty acids from the coho salmon,Oncorhynchus kisutch (Walbaum)

To study the fatty acids of the coho salmon, entire fish were homogenized and the total lipids extracted with methanol-chloroform. The fish ranged in size from 75 to 85 mm total length and contained from 2.1%–6.9% lipid in the tissues. Methyl esters of the fatty acids were produced with anhydrous methanol and HCl. Qualitative identification of the fatty acid methyl esters was accomplished by gas-liquid chromatography.Thin layer silver nitrate-silicic acid plates were used to separate the component methyl esters according to the number of double bonds. Location of the ethylenic groups of the unsaturated fatty acid methyl esters was established by reductive ozonolysis and identification of the aldehydes and aldehyde-esters produced. The number of carbons in the unsaturated fatty acid methyl esters was determined by hydrogenation of each of the fractions.Fatty acids found in the highest concentrations were: 16∶0, 16∶1, 18∶0, 18∶1, 18∶4, and 22∶6. Fatty acids 16∶0, 18∶1, 18∶2, 20∶5, and 22∶6, differed markedly from concentrations found in tubificid worms, the exclusive diet of the fish during the experiment.

Utilization of fatty acids by the developing steelhead sac-fry, Salmo gairdneri.

Abstract 1. 1. The fatty acid content of both the yolk and the steelhead sac-fry, Salmo gairdneri , has been studied during development. 2. 2. Losses of individual fatty acids from the yolk were proportional to the mass of the particular fatty acid present and only 18:1 showed any tendency to be retained in this compartment. 3. 3. After hatching the fatty acid composition of the sac-fry was distinct from that of the yolk. 4. 4. Certain fatty acids, 16:0, 18:0 and 22:6, were preferentially retained in the sac-fry lipids. Other fatty acids, 16:1, 18:1, 20:1 and 22:5, were retained to a much smaller extent considering the quantities available. 5. 5. It is suggested that 22:6 plays a special role in the fatty acid metabolism of the fish.