Is a dietary n-3 fatty acid supplement able to influence the cardiac effect of the psychological stress?

Epidemiological studies suggest that n-3 polyunsaturated fatty acids (PUFA) are involved in the prevention of cardiovascular disease. Stress is known to increase the incidence of CVD and the present study was realised to evaluate some physiological and biochemical effects of dietary docosahexaenoic acid (DHA) in male Wistar rats subjected to a psycho social stress. Rats were fed for 8 weeks a semi-purified diet containing 10% of either sunflower seed oil or the same oil supplemented with DHA. This food supply represented 50% of their daily requirement. The remaining 50% were supplied as 45 mg food pellets designed to induce stress in rats by an intermittent-feeding schedule process. The control group (n = 12) was fed the equivalent food ration as a single daily feeding. The physiological cardiovascular parameters were recorded by telemetry through a transmitter introduced in the abdomen. At the end of the experimentation, the heart and adrenals were withdrawn and the fatty acid composition and the catecholamine store were determined. Dietary DHA induced a pronounced alteration of the fatty acid profile of cardiac phospholipids (PL). The level of all the n-6 PUFAs was reduced while 22:6 n-3 was increased. The stress induced a significant increase in heart rate which was not observed in DHA-fed group. The time evolution of the systolic blood pressure was not affected by the stress and was roughly similar in the stressed rats of either dietary group. Conversely, the systolic blood pressure decreased in the unstressed rats fed DHA. Similar data were obtained for the diastolic blood pressure. The beneficial effect of DHA was also observed on cardiac contractility, since the dP/dt_max increase was prevented in the DHA-fed rats. The stress-induced modifications were associated with an increase in cardiac noradrenaline level which was not observed in DHA-fed rats. The fatty acid composition of adrenals was significantly related to the fatty acid intake particularly the neutral lipid fraction (NL) which incorporated a large amount of DHA. Conversely, n-3 PUFAs were poorly incorporated in adrenal phospholipids. Moreover the NL/PL ratio was significantly increased in the DHA fed rats. The amount of adrenal catecholamines did not differ significantly between the groups. These results show that a supplementation of the diet with DHA induced cardiovascular alterations which could be detected in conscious animals within a few weeks. These alterations were elicited by a reduced heart rate and systolic and diastolic blood pressure.     

An alternate pathway to long-chain polyunsaturates: the FADS2 gene product ��8-desaturates 20:2n-6 and 20:3n-3

The mammalian Δ6-desaturase coded by fatty acid desaturase 2 (FADS2; HSA11q12-q13.1) catalyzes the first and rate-limiting step for the biosynthesis of long-chain polyunsaturated fatty acids. FADS2 is known to act on at least five substrates, and we hypothesized that the FADS2 gene product would have Δ8-desaturase activity. Saccharomyces cerevisiae transformed with a FADS2 construct from baboon neonate liver cDNA gained the function to desaturate 11,14-eicosadienoic acid (20:2n-6) and 11,14,17-eicosatrienoic acid (20:3n-3) to yield 20:3n-6 and 20:4n-3, respectively. Competition experiments indicate that Δ8-desaturation favors activity toward 20:3n-3 over 20:2n-6 by 3-fold. Similar experiments show that Δ6-desaturase activity is favored over Δ8-desaturase activity by 7-fold and 23-fold for n-6 (18:2n-6 vs 20:2n-6) and n-3 (18:3n-3 vs 20:3n-3), respectively. In mammals, 20:3n-6 is the immediate precursor of prostaglandin E1 and thromboxane B1. 20:3n-6 and 20:4n-3 are also immediate precursors of long-chain polyunsaturated fatty acids arachidonic acid and eicosapentaenoic acid, respectively. These findings provide unequivocal molecular evidence for a novel alternative biosynthetic route to long-chain polyunsaturated fatty acids in mammals from substrates previously considered to be dead-end products.     

How to use the paradigm of ischemic preconditioning to protect the heart?

Ischemic preconditioning affords the most powerful protection to a heart submitted to a prolonged ischemia-reperfusion. During the past decade, a huge amount of work allowed to better understand the features of this protective effect as well as the molecular mechanisms. Ischemic preconditioning reduces infarct size and improves functional recovery; its effects on arrhythmias remain debated. Triggering of the protection involves cell surface receptors that activate pro-survival pathways including protein kinase C, PI3-kinase, possibly Akt and ERK1/2, whose downstream targets remain to be determined. Much attention has been recently focused on the role of mitochondrial K(+)ATP channels and the permeability transition pore that seem to play a major role in the progression toward irreversible cellular injury. Based on these experimental studies attempts have been made to transfer preconditioning from bench to bedside. Human experimental models of ischemic preconditioning have been set up, including cardiac surgery, coronary angioplasty or treadmill exercise, to perform pathophysiological studies. Yet, protecting the heart of CAD (coronary artery disease) patients requires a pharmacological approach. The IONA trial has been an example of the clinical utility of preconditioning. It helped to demonstrate that chronic administration of nicorandil, a K(+)ATP opener that mimics ischemic preconditioning in experimental preparations, improves the cardiovascular prognosis in CAD patients. Recent experimental studies appear further encouraging. It appears that "postconditioning" the heart (i.e. performing brief episodes of ischemia-reperfusion at the time of reperfusion) is as protective as preconditioning. In other words, a therapeutic intervention performed as late as at the time of reflow can still significantly limit infarct size. Further work is needed to determine whether this may be transferred to the clinical practice.     

From Desirable Ornamental Plant to Pest to Accepted Addition to the Flora? – the Perception of an Alien Tree Species Through the Centuries

Prunus serotina, a forest tree of North American origin, was introduced to central Europe and planted for various purposes. In the course of the centuries it was regarded as a valuable timber tree by European foresters; subsequently, as a useful non-timber species in forestry, a forest pest, a controllable weed and, eventually, as a species we have to live with. All these perceived qualities served as motives for action by humans without seeking scientific evidence for them: millions of specimens of P. serotina were planted, later millions of euros were spent in attempts at control. The species, and its changing perception through time, may be an example of the need for science-based assessments as a basis for developing policies concerning non-native plants. This revised version was published online in July 2006 with corrections to the Cover Date.     

Does the response of the intestinal epithelium to keratinocyte growth factor vary according to the method of administration?

BACKGROUND: Keratinocyte growth factor (KGF) is a potent mitogen and may be of value for the treatment of conditions such as short bowel syndrome and chemotherapy-induced mucositis. However the most efficacious route and method of administration is unclear. METHODS: Rats maintained by total parenteral nutrition (TPN) were given KGF (1 mg/kg/rat/day, i.v.) infused continuously or as a once-daily injection. The same dose was also given s.c. to chow-fed rats. Changes in gut growth were assessed by measurement of wet weight, proliferation (vincristine induced metaphase arrest) and crypt branching index. Changes in gut hormone profile were also determined to examine if any trophic effects were mediated via this mechanism. RESULTS: KGF caused a 70-100% increase in wet weight of the stomach, small and large intestine of TPN-fed rats (P < 0.01) with no significant differences seen between the two methods of administration. The increase in metaphase counts was greatest in the stomach (about seven-fold P < 0.01), but was less pronounced in the distal small intestine and colon (about 50% increase). The trophic effect of KGF was much less prominent in orally-fed rats. Crypt branching index was significantly reduced by KGF in the proximal small intestine of TPN, but not orally-fed rats. Plasma gastrin, PYY, total glucagon, enteroglucagon and GLP-1 all increased by two-three-fold (all P < 0.01) in response to KGF whereas insulin levels fell by about 25% in the TPN group. CONCLUSIONS: The mitogenic action of KGF occurred predominantly in the stomach and proximal small intestine. Its efficacy was less pronounced in orally-fed animals, suggesting KGF may be of greatest benefit in conditions associated with lowered intestinal proliferation. Clinical trials of KGF can probably use single daily i.v. injections without reduction in efficacy.     

Stimulating the Need to Know…

Nations, James D. Tropical Rainforest: Endangered Environment . New York: Franklin Watts, 1988. 143 pp. $12.90 hardcover. Reviewed by Jorge Zamacona Evenes.

Sharp, D.W.A., ed. The Penguin Dictionary of Chemistry , 2d ed. New York: Penguin, 1990. 434 pp. $9.95 paperback. Reviewed by Wayne Hanley.

Hale, W.G., and J.P. Margham. The HarperCollins Dictionary of Biology. New York: Harper Collins, 1991. 569 pp. $12.95 paperback; $25.00 hardcover. Reviewed by Wayne Hanley.

Sparks, John, and Tony Soper. Penguins. New York: Fact On File, 1987. 246 pp. $1995 hardcover. Reviewed by Wayne Hanley.

Mountfort, Guy. Rare Birds of the World . A Collins/ICBP Handbook. New York: Penguin (The Stephen Greene Press), 1988. 256 pp. $2995 hardcover. Reviewed by John W. McLure.

Woodcock, Martin. Collins Handguide to the Birds of the Indian Subcontinent . New York: Penguin (The Stephen Greene Press), 1989. 176 pp. $11.95 paperback. Reviewed by James Scheib.

Harris, Michael. The Collins Field Guide to the Birds of Galapagos . New York: Penguin (The Stephen Greene Press), 1989. 160 pp. $1995 hardcover. Reviewed by Jim Fuller.

Brudenell-Bruce, P. G. C. The Collins Guide to the Birds of New Providence and the Babama Islands. New York: Penguin (The Stephen Greene Press), 1989. 142 pp. $14.95 paperback. Reviewed by Carol A. Thompson.     

How to Bring the “Unseen” Proteome to the Limelight via Electrophoretic Pre-Fractionation Techniques

The present review reports a panoply of electrophoretic methods as pre-fractionation tools in proteomic investigations in preparation for mass spectrometry or two-dimensional electrophoresis map analysis. Such electrophoretic pre-fractionation protocols include all those electrokinetic methodologies which are performed in free solution, most of them relying on isoelectric focusing steps (although some approaches based on gels and granulated media are also discussed). Devices associated with electrophoretic separations are multi-chamber apparatuses, such as the multi-compartment electrolyzers equipped with either isoelectric membranes or with isoelectric beads, Off-Gel electrophoresis in a multi-cup device and the Rotofor, an instrument also based on a multi-chamber system but exploiting the conventional technique of carrier-ampholyte-focusing. Other free-flow systems, as well as miniaturized chambers, are also described.     

n-6/n-3多不饱和脂肪酸比例对机体生理功能的调节

多不饱和脂肪酸(Polyunsaturated fatty acids,PUFA),尤其是n-6和n-3 PUFAs,不仅是人体必需营养素,在调节和预防人类疾病方面同时发挥着重要作用。n-6和n-3 PUFAs在哺乳动物细胞内不能相互转换,且是动植物细胞膜的重要组成成分,具有不同的生理功能。细胞膜多不饱和脂肪酸组成比例很大程度上由膳食决定,因此平衡膳食中n-6/n-3 PUFAs具有重要意义。本文总结了n-6和n-3 PUFAs的代谢途径和作用机制,结合临床试验,阐述了平衡n-6/n-3 PUFA的重要性。     

Is Mislocalization during Saccades Related to the Position of the Saccade Target within the Image or to the Gaze Position at the End of the Saccade?

A stimulus that is flashed around the time of a saccade tends to be mislocalized in the direction of the saccade target. Our question is whether the mislocalization is related to the position of the saccade target within the image or to the gaze position at the end of the saccade. We separated the two with a visual illusion that influences the perceived distance to the target of the saccade and thus saccade endpoint without affecting the perceived position of the saccade target within the image. We asked participants to make horizontal saccades from the left to the right end of the shaft of a Müller-Lyer figure. Around the time of the saccade, we flashed a bar at one of five possible positions and asked participants to indicate its location by touching the screen. As expected, participants made shorter saccades along the fins-in (<–>) configuration than along the fins-out (>–<) configuration of the figure. The illusion also influenced the mislocalization pattern during saccades, with flashes presented with the fins-out configuration being perceived beyond flashes presented with the fins-in configuration. The difference between the patterns of mislocalization for bars flashed during the saccade for the two configurations corresponded quantitatively with a prediction based on compression towards the saccade endpoint considering the magnitude of the effect of the illusion on saccade amplitude. We conclude that mislocalization is related to the eye position at the end of the saccade, rather than to the position of the saccade target within the image.     

α-Linolenic acid supplementation and conversion to n-3 long-chain polyunsaturated fatty acids in humans

Blood levels of polyunsaturated fatty acids (PUFA) are considered biomarkers of status. Alpha-linolenic acid, ALA, the plant omega-3, is the dietary precursor for the long-chain omega-3 PUFA eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA). Studies in normal healthy adults consuming western diets, which are rich in linoleic acid (LA), show that supplemental ALA raises EPA and DPA status in the blood and in breast milk. However, ALA or EPA dietary supplements have little effect on blood or breast milk DHA levels, whereas consumption of preformed DHA is effective in raising blood DHA levels. Addition of ALA to the diets of formula-fed infants does raise DHA, but no level of ALA tested raises DHA to levels achievable with preformed DHA at intakes similar to typical human milk DHA supply. The DHA status of infants and adults consuming preformed DHA in their diets is, on average, greater than that of people who do not consume DHA. With no other changes in diet, improvement of blood DHA status can be achieved with dietary supplements of preformed DHA, but not with supplementation of ALA, EPA, or other precursors.     

From the Zulu medicine to the European phytomedicine Umckaloabo®

Among the Zulus of South Africa a crude root drug of initially unknown botanical origin was used for the treatment of pulmonary diseases and tuberculosis (TB). An English TB patient called “Stevens” heard about it and travelled to South Africa where, according to his account, he was cured by taking an extract of the crude drug. It was extremely difficult to establish the imported crude herbal drug as a “new TB medicine”, as neither the plant from which the drug originated was identified nor were the constituents and pharmacological effects known at that time.It was only after a professional search and initial chemical and taxonomic investigations enabled the identity of the plant to be determined that the requirements were met for comprehensive chemical, pharmacological and clinical research into the crude drug.The following report traces the long and difficult path of this “mystery drug” from the Zululand of South Africa to the laboratories of Europe.     

Immunity to helminths: Ready to tip the biochemical balance?

Using data from recent laboratory and field studies, Peter Brophy and David Pritchard here summarize our current understanding of the approximate sequence of events leading to protective immune responses against some chronic parasitic helminth infections.     

How to determine the susceptibility of Meligethes aeneus to neonicotinoids?

Three different bioassays were used to determine the susceptibility to the neonicotinoid Biscaya^® of oilseed rape pollen beetles collected from fields in Bavaria. The one in which the test substance was applied to the inner wall of glass tubes is recommended for future studies on pollen beetles because it is not dependent on the availability of plant material and provides precise information on the amount of insecticide required per unit area.