Metabolism of lipids in rat testes: interconversions and incorporation of linoleic acid into lipid classes

Premature mortality related to United States cross-state air pollution

Outdoor air pollution adversely affects human health and is estimated to be responsible for five to ten per cent of the total annual premature mortality in the contiguous United States^1-3. Combustion emissions from a variety of sources, such as power generation or road traffic, make a large contribution to harmful air pollutants such as ozone and fine particulate matter (PM_2.5)⁴. Efforts to mitigate air pollution have focused mainly on the relationship between local emission sources and local air quality². Air quality can also be affected by distant emission sources, however, including emissions from neighbouring federal states^5,6. This cross-state exchange of pollution poses additional regulatory challenges. Here we quantify the exchange of air pollution among the contiguous United States, and assess its impact on premature mortality that is linked to increased human exposure to PM_2.5 and ozone from seven emission sectors for 2005 to 2018. On average, we find that 41 to 53 per cent of air-quality-related premature mortality resulting from a state's emissions occurs outside that state. We also find variations in the cross-state contributions of different emission sectors and chemical species to premature mortality, and changes in these variations over time. Emissions from electric power generation have the greatest cross-state impacts as a fraction of their total impacts, whereas commercial/residential emissions have the smallest. However, reductions in emissions from electric power generation since 2005 have meant that, by 2018, cross-state premature mortality associated with the commercial/residential sector was twice that associated with power generation. In terms of the chemical species emitted, nitrogen oxides and sulfur dioxide emissions caused the most cross-state premature deaths in 2005, but by 2018 primary PM_2.5 emissions led to cross-state premature deaths equal to three times those associated with sulfur dioxide emissions. These reported shifts in emission sectors and emission species that contribute to premature mortality may help to guide improvements to air quality in the contiguous United States.

Gamma-linolenic acid improves the constancy of contractions in uteri from sprayed rats and is metabolized to prostaglandin E1 but not to bisenoic prostanoids

The effects of gamma-linolenic acid (GLA) on the time-dependent constancy of spontaneous contractions (isometric developed tension = IDT and frequency of contractions = FC) in uterine strips isolated from spayed rats, were explored. Moreover, the influence of the unsaturated fatty acid on the basal generation and release of tissue prostaglandins (PGs) as well as the conversion of labelled GLA into prostanoids by the uterine tissue and the effects of p-bromo-phenacyl-bromide (BPB), were also studied. GLA (10(-7)M), attenuated significantly the spontaneous decrement of contractile constancy exhibited by control preparations during a period of 180 min of activity in isolation, whereas BPB (10(5) M) resulted in an augmented and faster decrement of inotropic constancy. Spontaneous changes in the constancy of uterine motility as time progressed involved similarly both IDT and FC. After 180 min of activity in isolation a basal generation and release of PGs E and F of the series 1 and 2, were detected. The challenge with 10(-7) M GLA (delivered immediately after isolation) enhanced significantly the output of PGE1 but did not influence the generation and release of PGE2 or PGF2 alpha. BPB (10(-5) M) had no significant effect on the basal output of PGE1, PGE2 or PGF2 but completely prevented the enhancing action of GLA on the synthesis and release of PGE1. Labelled GLA was mainly converted to PGE1 by rat uterine segments and negligible counts in the 2-series of prostanoids, were observed. In presence of BPB (10(-5) M) the conversion of 1-14C-GLA, to PGE1 was almost completely abolished. The foregoing evidences suggest that exogenous GLA is metabolized by the spayed rat uterus via an elongase, forming di-homogamma-linolenic acid (DHLA), which in turn is substrate for cyclo-oxygenase peroxidase reactions yielding finally PGE1. No evidence of a delta 5-desaturase activity, converting DHLA into arachidonate and further derivatives, was detected. Coincidently, exogenous GLA was able to support a better contractile constancy as a function of time than that evidenced in untreated uterine strips isolated from castrated rats.

Lipid metabolism of the yellow clam, Mesodesma mactroides: I. Composition of the lipids

The lipid composition of the yellow clam, Mesodesma mactroides, that lives in the northern beaches of the Buenos Aires province of Argentina was studied. The main nonpolar lipids are triglycerides and alkoxyglycerides. Phosphatidyl choline, phosphatidyl ethanolamine, and phosphatidyl serine are the main phospholipids. The predominant fatty acids are 16:0, 16:1omega7, 18:0, 18:1omega9, 20:5omega3, and 22:6omega3. They are mainly provided by the clam's food and stored in the hepatopancreas. The content of polyunsaturated acids increases in summer together with an increase in nonpolar lipids and is correlative with an increase in phytoplankton in the sea water. Sexual maturity modifies the lipid composition of gametes.

Fatty acid synthesis from 2-14C-acetate in rat testis mitochondrial and cytosol fractions in vitro

An in vitro system for acetate incorporation into fatty acids by the mitochondrial and the cytosol fractions of rat testis is described. The rate of incorporation of acetate into fatty acids was twice as fast with the mitochondrial as with the cytosol fraction; both systems were stimulated in the presence of adenosine triphosphate, reduced nicotinamide adenine dinucleotide phosphate, coenzyme A, and MgC1(2). The optimum pH was between 7.0-7.5 for the mitochondrial fraction and between 6.5-8.0 for the cytosol fraction. Radio gas chromatography showed that palmitic acid was the most highly labeled acid, followed by stearic acid, in the mitochondrial fraction in accord with the pathway of de novo fatty acid synthesis. Some of the labeled acetate was also incorporated into the 16:1 and 18:1 fatty acids of this fraction. Distribution of radioactivity among the mitochondrial lipid classes was highest in the phospholipids and monoglycerides, followed by diglycerides and cholesterol; little radioactivity was present in the triglyceride fraction. These observations are in accord with studies of the incorporation of labeled metabolites into testicular lipids following intratesticular injection and indicate the validity of the in vitro system for studies of specific reactions occurring in vivo.