Biomedical subjects

R W Howard

Publications and source records attributed to R W Howard.

17 recordsLinked to original sources

PubMed1993

Analysis of lipids in the salivary glands of Amblyomma americanum (L.): detection of a high level of arachidonic acid.

Analysis of lipids in salivary glands of the lone star tick, Amblyomma americanum, demonstrated that arachidonic acid (20:4, n-6) comprises 8% of all fatty acids identified by gas chromatography. The occurrence of arachidonic acid and other C20 polyunsaturated fatty acids in tick salivary glands was confirmed by gas chromatography-mass spectrometry. Arachidonate is located entirely in the phospholipid fraction and is associated exclusively with phosphatidylcholine (PC) and phosphatidylethanolamine (PE). Salivary glands stored and frozen for several months had a similar lipid composition as freshly dissected salivary glands, with the exception of a small amount of free arachidonic acid and an increase in lysophosphatidylcholine. Incubation of salivary gland homogenates with snake venom phospholipase A2 showed that most saturated fatty acids are esterified in the sn-1 position of PC and PE, with the unsaturated fatty acids in the sn-2 position. Approximately 75% of arachidonic acid is in the sn-2 position of PC and PE, adding support to the hypothesis that arachidonic acid is released into the cytoplasm after activation of a phospholipase A2 for subsequent metabolism to prostaglandins and/or other eicosanoids.

Animals↗

PubMed1993

Arachidonic acid and prostaglandin E2 in Malpighian tubules of female yellow fever mosquitoes.

The fatty acid compositions of Malpighian tubules from adult females of the mosquito Aedes aegypti were determined for total lipids, phospholipids, triacylglycerols and three phospholipid fractions, namely phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol/phosphatidylserine (PI/PS). The prostaglandin precursor arachidonic acid (20:4n-6) occurred in total lipids and phospholipids, but not triacylglycerols. Within phospholipids, nearly all of the 20:4n-6 was detected in PC, with only traces in PE, and none was detected in PI/PS. Isolated Malpighian tubules incorporated exogenous radioactive 20:4n-6 into tissue phospholipids and diacylglycerols, with most of the radioactivity recovered in diacylglycerol. These data indicate selective incorporation of 20:4n-6 into tissue lipids. PGE2 was detected in Malpighian tubule whole mounts by immunohistochemical staining. These findings support the idea that prostaglandins are physiologically active in mosquito Malpighian tubules.

Aedes↗

PubMed1993

On what intelligence is.

Despite much controversy over the exact definition of intelligence, most researchers agree that it is a concept labelled by a word, or even several related concepts labelled by a word. The present study applies recent theorizing about the nature of concepts in general to clarify the notion (or notions) of intelligence. This theorizing defines a concept as a person's unique and individual information about a category and a category as a set of things in the world. An example of a concept/category pair is 'dog', with the category being the set of all dogs and an individual's concept of dog being his or her personal knowledge of dogs. This knowledge can be used to place things in or out of the category. Different individuals may have somewhat different knowledge about the same category and a single word may label several different concept/category pairs. A concept of intelligence thus consists of information about a general category labelled by the word 'intelligence'. This study analyses three major concept/category pairs of 'intelligence': (1) Spearman's g; (2) intelligence as a property of behaviour; and (3) intelligence as a set of abilities. Each concept contains different information, refers to a different category, and should be used in different ways. Several recurrent issues, such as whether the word 'intelligence' refers to a thing and what things are intelligent (e.g. animals, computers), can be resolved by considering each issue in relation to these concept/category pairs. For instance, the word 'intelligence' refers to a thing only if one uses the g concept. Similarly, only humans are intelligent according to the g concept but animals and computers may be considered intelligent if the other concepts are applied. Recent theorizing on the nature of concepts can be used to clarify other important psychological notions.

Aptitude↗

PubMed1991

Insect immune response to bacterial infection is mediated by eicosanoids.

Inhibition of eicosanoid formation in larvae of the tobacco hornworm Manduca sexta, using specific inhibitors of phospholipase A2, cyclooxygenase, and lipoxygenase, severely weakened the ability of larvae to clear the bacterium Serratia marscescens from their hemolymph. The reduced capability to remove bacteria is associated with increased mortality due to these bacteria. There is a dose-dependent relationship between the phospholipase A2 inhibitor dexamethasone and both the reduced bacterial clearance and increased larval mortality. The dexamethasone effects on larval survival were reversed by treatment with arachidonic acid. Maleic acid, a nonspecific antioxidant, did not interfere with the insects' ability to remove bacterial cells from hemolymph. The larvae were shown to contain all of the C20 polyunsaturated fatty acids necessary for eicosanoid biosynthesis and to be capable of converting radioactive arachidonic acid into several primary prostaglandins. These results strongly suggest that eicosanoids mediate transduction of bacterial infection signals into the complex of cellular and humoral responses that comprise invertebrate immunity.

Animals↗

PubMed1991

Cuticular hydrocarbon geographic variation among seven North American populations of Aedes albopictus (Diptera: Culicidae).

Cuticular hydrocarbons were used to differentiate among the following North American populations of Aedes albopictus: Chicago, Ill.; Milford, Del.; Jacksonville, Fla.; San Antonio, Tex.; New Orleans, La.; Houston, Tex.; and Lexington, Ky. Forty cuticular hydrocarbon peaks were identified from each population using gas chromatography electron impact-mass spectrometry: 16 n-alkanes, 21 monomethylalkanes, and 3 dimethylalkanes. Fourteen peaks occurred at equivalent chain lengths greater than 38.65 and consisted of complex mixtures of dimethyl- and trimethylalkanes. Quantitative analyses were performed on pooled samples of five females from each population using flame ionization gas chromatography. All populations contained the same cuticular hydrocarbons, but showed differences in percent composition. Five of seven populations were separable by discriminant analysis of hydrocarbon components.

Aedes↗

PubMed1989

In vitro inhibition of prostaglandin H synthase by compounds from the exocrine secretions of lace bugs.

1. Selected lace bug-derived and related compounds were shown to be in vitro inhibitors of mammalian and insect derived prostaglandin H synthase. 2. Two compounds, 2,6-dihydroxyacetophenone and 2,4,6-trihydroxyacetophenone, were significantly better inhibitors of prostaglandin synthesis than aspirin, whereas 2-nonyl-5,7-dihydroxychromone and 1-(2,6-dihydroxyphenyl) dodecan-1-one were equivalent to aspirin. 3. 2,4-Dihydroxyacetophenone was less effective in inhibiting the prostaglandin H synthase and 2-nonyl-5-hydroxychromanone showed no inhibition. 4. Three compounds, 2,6-dihydroxyacetophenone, 2,4,6-trihydroxyacetophenone and 1-(2,6-dihydroxyphenyl) dodecan-1-one were equal to aspirin in PSI inhibition with fat body preparations of the American cockroach Periplaneta americana L.

Animals↗

PubMed1979