High levels of extra-pair paternity in an isolated, low-density, island population of tree swallows (Tachycineta bicolor)

Molecular genetic studies have suggested that apparently nonbreeding males ('floaters') may account for a significant proportion of extra-pair paternity (EPP) in avian populations. Attempts to determine the influence of breeding density on EPP are therefore confounded by the presence of a subpopulation of floaters whose numbers are difficult to estimate. To study EPP in a tree swallow (Tachycineta bicolor) population with few floaters, we chose a nestbox grid on an island with an excess of available breeding sites and very few floaters. We obtained DNA samples from 13 complete families and performed DNA profiling on them using four microsatellite loci. For comparison, we also obtained a sample of 58 extra-pair young (EPY) from a mainland population typed at five microsatellite loci. Paternity assignments among resident males in both populations were made using the microsatellite profiles and a likelihood-based statistical method. Of the 67 island nestlings typed, we found 37 (55%) nestlings from 11 (85%) different nests that were EPY. The proportion of nestlings that were EPY and the proportion of broods containing EPY did not differ significantly between island and mainland populations studied previously. There was no significant difference between island and mainland populations in the proportion of extra-pair paternities assigned among neighbouring resident males. Male breeding density does not appear to affect the ability of female tree swallows to obtain extra-pair fertilizations, at least over the range of densities studied so far. The rate of EPP has remained remarkably consistent over many years, studies and populations implying an important role of active female choice in determining EPP.

Tedisamil in a chronic canine model of atrial flutter

Tedisamil inhibits several cardiac potassium channels including Ito, Ikr, and the adenosine triphosphate (ATP)-sensitive potassium channel (I(KATP)), which may be important in the initiation and maintenance of atrial arrhythmias. We herein report the efficacy of tedisamil in terminating and protecting against the reinduction of atrial flutter (AFL) in a conscious canine model. Sustained AFL (> 15 min) was induced in eight of 10 mongrel dogs by programmed atrial stimulation (PAS) 2-41 days after producing a surgical barrier to conduction in the right atrium. At the time of surgery, an epicardial electrode was attached to the right atrial appendage for pacing and recording. Normal saline, 1 ml/kg, was infused after 15 min of AFL as placebo. Tedisamil (1.0 mg/kg) was given intravenously after 30 min of sustained AFL while recording surface ECGs and atrial electrograms. Conversion to sinus rhythm was achieved in 10 of 10 trials (eight dogs) in a mean time of 20.5 s (SD, +/- 11.8 s). Tedisamil had a negative chronotropic effect lasting > or =2 h and was protective against the reinduction of AFL. In five dogs, PAS was able to induce AFL in only two of seven trials 2 h after drug infusion. The corrected QT interval (QTc) was lengthened for the first 15 min after tedisamil administration (mean, +/- 39.3 ms; p < 0.05), but thereafter returned to baseline. The QRS interval was not altered by tedisamil. Saline alone, given after 15 min of sustained AFL, converted AFL in one of 11 trials (eight dogs) but did not alter the RR interval, QTc, or QRS interval compared with values measured during AFL. No significant adverse effects of tedisamil were observed. The results indicate that tedisamil is effective in interrupting and/or preventing reinduction of canine AFL, possibly by prolonging atrial refractoriness through inhibition of one or more potassium ion repolarizing currents in atrial muscle. Further studies are required to address the exact mechanism by which tedisamil exerts its antiarrhythmic effect.

Effect of time on neonatal immune response to dietary selenium and fat

The effect of dietary selenium (0.03 mg/kg and 0.31 mg/kg), and fat (5% and 20% corn oil) on antibody formation in the neonatal rat was studied at two different time periods using four diets. The latter were fed to dams throughout pregnancy and lactation and to their pups starting at day 18. A week later, pups received intraperitoneal injections of the test antigen, fluorescein-bovine serum albumin in complete Freund's adjuvant (150 micrograms per 30 g body wt.). On days 7 or 9 post-injection, the pups were sacrificed. The antibody titer, as determined by the quenching of fluorescein by the test sera, and by ELISA, almost doubled from day 7 to day 9 (p < 0.05). There was no significant difference in antibody titers between dietary groups except at day 9 post-injection. Using ELISA, pairwise comparisons indicated that addition of 0.3 mg/kg Se to high fat diet was associated with low antibody titer (p < 0.05).

Solar ultraviolet spectroradiometry in New Zealand: instrumentation and sample results from 1990

In 1988 the New Zealand Department of Scientific and Industrial Research initiated a program to characterize the spectrum of solar ultraviolet radiation reaching the ground in New Zealand and to identify the extent and causes of its variability. Routine measurements began at Lauder (45 degrees S 170 degrees E) in December 1989. The instrumentation, measurement strategy, and calibration procedures are discussed and uncertainties in the measurements are analyzed. With the present system useful measurements at 1-nm resolution are limited to irradiances greater than 10(-3) microW cm(-2) nm(-1), which corresponds to a lower limit in wavelength in the region 290-295 nm (depending on the Sun angle and ozone amount). This is a useful lower limit for many applications of relevance to the biosphere. Results from the first year of operation are presented and discussed.

Effect of dietary alpha-linolenic acid on growth, metastasis, fatty acid profile and prostaglandin production of two murine mammary adenocarcinomas

The purpose of this study was to determine whether dietary (n-3) fatty acids would affect mammary tumor growth and metastasis. Weanling female BALB/c mice were fed diets that contained 10% corn oil (CO), linseed oil (LO) or a fish oil-corn oil mix (FO) for 3-8 wk prior to receiving subcutaneous injections of one of two syngeneic mammary tumor cell types (410 and 410.4). Tumor growth was assessed by monitoring mean tumor diameter and tumor weight upon removal. Feeding LO, but not FO, reduced the growth (p less than 0.05) of 410.4 mammary tumors compared with growth in those fed CO. Metastasis data paralleled the tumor growth rate. Feeding LO and FO enhanced (p less than 0.005) incorporation of (n-3) fatty acids into tumors. Tumor prostaglandin E (PGE) production was reduced (p less than 0.005) by LO and FO, compared with CO. FO feeding reduced 410.4 tumor PGE synthesis more (p less than 0.05) than LO feeding, yet tumor growth was only inhibited by LO. These data suggest an inhibitory effect of dietary linolenic acid [i.e., 18:3 (n-3)] on mammary tumor growth and metastasis. However, this effect did not directly correlate with diet-induced changes in PGE synthesis.

Modulation of eicosanoid production and cell-mediated cytotoxicity by dietary alpha-linolenic acid in BALB/c mice

The effects of dietary alpha-linolenic acid (18:3n-3) on fatty acid composition, eicosanoid production, and cell-mediated cytotoxic activity of immune cells before and after challenge with virus or poly I-C from BALB/c mice were studied. Weanling BALB/c mice were fed purified diets containing either 10%-by-weight corn oil or linseed oil providing a ratio of 18:3n-3 to 18:2n-6 of 1/32 or 2/1, respectively, for 6-10 weeks. Fatty acid analysis of splenocyte phospholipids showed an appreciable increase in the percentage of n-3, and a decrease in n-6, fatty acids in splenocytes from mice fed the linseed oil diet. Splenocyte prostaglandin E and peritoneal exudate cell leukotriene C production was significantly lower in the linseed oil-fed mice. In general, cell-mediated cytotoxic activity was similar for immune cells from linseed oil and corn oil-fed mice. However, 6 days after the viral challenge, splenocyte cell-mediated cytotoxic activity was significantly higher in linseed oil mice. This higher activity was associated with nonspecific cytotoxicity rather than that of viral-specific cytotoxic T-lymphocytes. Cell yields from the spleen and peritoneum were frequently significantly higher in linseed oil mice. Interactions between dietary 18:3n-3, eicosanoid production, and immune cell proliferation and/or migration are discussed. In summary, feeding mice a diet rich in 18:3n-3 elevates immune cell n-3 fatty acid content, reduces eicosanoid synthesis and, to a limited extent, enhances the cell-mediated cytotoxic response to a viral challenge.

Rapid autoxidation of fish oil in diets without added antioxidants

Feeding of purified diets containing fish oil without added antioxidant leads to rapid autoxidation of the oil and the possibility of artifactual results due to the feeding of autoxidation products. Purified diets containing menhaden oil without any added antioxidant deteriorate quickly. Peroxide value of the diet is elevated 5- to 6-fold within 24 h and 12-fold within 48 h when exposed to air at room temperature. Addition of 0.02% t-butylhydroquinone to the fish oil prevents this deterioration for at least 72 h. Determination of fatty acid composition is not a sensitive indicator of diet integrity. Supplementation of fish oil diets with vitamin E to help protect against in vivo peroxidation is discussed.

Lymphocyte activation, cell-mediated cytotoxicity and their relationship to dietary fat-enhanced mammary tumorigenesis in C3H/OUJ mice

The effects of dietary soybean oil (SBO) concentration (5 vs. 20% by weight) on mammary tumorigenesis, mitogen-induced blastogenesis, cell-mediated cytotoxicity and serum and lymphocyte fatty acid composition were studied in C3H/OUJ female mice. Weanling mice fed 20% SBO for 9 mo had a higher incidence (89 vs. 65%) and greater average size (2.9 vs. 1.9 g) of mammary tumor virus type S breast tumors than mice fed 5% SBO. The response of isolated splenocytes to the T-cell mitogens concanavalin A and phytohemagglutinin was 20-25% lower in mice fed 20% SBO than in mice fed 5% SBO for 20 wk. There was no effect of SBO concentration on the splenocyte response to lipopolysaccharide E55:B5, a B-cell mitogen, or to pokeweed mitogen, and B- and T-cell mitogen. Cell-mediated cytotoxicity to allogenic P815 tumor cells was 20% lower in mice fed 20% SBO than in mice fed 5% SBO for 12 wk. The lower cell-mediated immunity associated with 20% SBO was not due to changes in the fatty acid composition of the two major splenocyte membrane phospholipids, phosphatidylcholine and phosphatidylethanolamine. However, serum levels of linoleic acid were higher in mice fed 20% SBO. Raising dietary SBO from 5 to 20% by weight was associated with increased mammary tumorigenesis, reduced T-cell blastogenesis and lower cell-mediated cytotoxicity.

The influence of dietary essential fatty acids on rat immunocompetent cell prostaglandin synthesis and mitogen-induced blastogenesis

Sprague-Dawley rats were fed diets including 10% corn oil (CO), 10% hydrogenated coconut oil (HCO) or 10% linseed oil (LO), and immune cell populations isolated from peripheral blood and spleen were examined for alterations in prostaglandin E (PGE) synthesizing capacity and mitogen-induced blastogenesis. Culture conditions were optimized by incubating the cells in serum obtained from animals fed the same diet. The fatty acid profiles of these sera reflected the composition of the dietary fat ingested. Both the LO and HCO diet treatments resulted in significantly lower PG-synthesizing capacity by both unstimulated and phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear cells or splenocytes when compared to the CO group. Mitogen-induced [3H]thymidine uptake by splenocytes from rats fed the HCO diet was twofold higher than responses observed in cells from animals fed the LO or CO diets. The results suggest that mitogenesis is not influenced by the diet-induced change in immune cell PGE2 synthesizing capacity. Enhanced [3H]thymidine incorporation was associated with a greater degree of saturation of dietary fat.

Effect of culture in vitro with eicosatetraenoic (20:4(n-6) ) and eicosapentaenoic (20:5(n-3) ) acids on fatty acid composition, prostaglandin synthesis and chemiluminescence of rat peritoneal macrophages

Rat peritoneal macrophages were cultured in either eicosatetraenoic acid (20:4(n-6) ) or eicosapentaenoic acid (20:5(n-3) ) and the effects on phospholipid fatty acids, prostaglandin synthesizing capacity and the ability of the macrophages to show chemiluminescence were examined. Chemiluminescence is an activity resulting from the synthesis of reactive oxygen species. It has been reported that prostaglandins inhibit this activity. The fatty acid profile of the four major phospholipids reflected the fatty acid component of the medium. Macrophages cultured in 20:4(n-6) synthesized twice the prostaglandin produced by controls and those cultured in 20:5(n-3) synthesized 10% that of controls and 5% that of 20:4(n-6)-cultured cells. Macrophages cultured with 20:4(n-6) for 12 h showed half the chemiluminescence of those cultured with 20:5(n-3), while those cultured with 20:4(n-6) for 24 h showed 10% the chemiluminescence of 20:5(n-3)-cultured cells. Addition of the prostaglandin synthase inhibitor, indomethacin, had no effect on chemiluminescence.

Alterations in cerebral and microvascular prostaglandin synthesis by manipulation of dietary essential fatty acids

Sprague-Dawley rats were fed one of three purified diets--10% corn oil, 10% hydrogenated coconut oil, or 10% linseed oil--through two generations. At 60-80 days of age the animals were sacrificed. The fatty acyl composition of phosphatidylcholine, phosphatidylethanolamine, plasmalogen phosphatidylethanolamine, and combined phosphatidylinositol/phosphatidylserine from cerebral cortex and isolated cerebral microvessels was determined. Brain slice prostaglandin F2 alpha or microvascular prostacyclin synthesis was also measured. Major changes were noted in the fatty acid profiles, most dramatically in the phosphatidylethanolamine and ethanolamine plasmalogen fractions, with an active rise in docosahexaenoic acid resulting from linseed oil feeding. A depression in prostaglandin F2 alpha synthesis was seen in brain slices of hydrogenated coconut oil- and linseed oil-fed rats. Such a depression was also observed in microvascular prostaglandin synthesis at basal and stimulated levels but not in control incubations. The potential importance of these findings to cerebral microcirculation and hemostasis is discussed.

Humoral immunity in essential fatty acid-deficient rats and mice: effect of route of injection of antigen

Weanling male Lewis Mai F rats and A/J mice were fed semi-purified diets either adequate or deficient in essential fatty acids (EFA) for 50-60 days. After death livers were excised, the lipids were extracted, and the fatty acid profile was determined. Groups of rats and mice were immunized by injection with sheep red blood cells (sRBC) either i.v. or i.p. One group of rats received an injection of sRBC plus Bordetella pertussis organisms. The plaque-forming cell response (PFC) of all groups was determined. Samples of mouse spleens were analyzed for prostaglandin F2 alpha. EFA-deficient rat and mice liver fatty acid profiles showed elevated levels of omega 7 and omega 9 fatty acids and decreased omega 6 fatty acids. The fatty acid profiles of mice differed quantitatively from the rats. As determined by the ratios of 18:0 to 18:2 omega 6 and 18:2 omega 6 to 20:4 omega 6 mice showed a higher delta 9 and a lower delta 6 desaturase activity. When the antigen was injected i.v. the EFA-deficient animals of both species showed an increased PFC response compared to controls, but when it was injected i.p. there was no difference between dietary groups. The PFC response in rats receiving B. pertussis increased dramatically but the difference between dietary groups was abrogated. As had been previously shown in rats the increase in PFC response in the mice immunized by the i.v. route correlated with a decreased synthesis of PGF2 alpha by the spleen.

Dietary alpha-linolenic acid and prostaglandin synthesis: a time course study

A purified diet containing 10% linseed oil as the fat source was fed to rats over a 56-day period. After the 56th day the rats were fed the same basal diet but containing 10% corn oil in place of the linseed oil. Rats were killed and blood and liver samples were taken from four to six rats on 14 days of the feeding trial. Serum and liver fatty acid profiles were determined. The platelet prostaglandin E2 (PGE2) released in serum as a result of blood coagulation for 1 h at 37 degrees C was determined. Liver homogenates were incubated and PGF2 alpha synthesizing capacity was assayed. Both serum and liver fatty acid profiles reflected the high linolenic content of the linseed oil. There was a progressive increase in fatty acids of the omega 3 series and a decrease in the omega 6 series. Notably the PG-2 series precursor, arachidonic acid (20:4 omega 6) was decreased and the precursor of the PG-3 series timnodonic acid (20:5 omega 3) was increased. These changes were reversed when corn oil was fed. PGE2 content of serum and PGF2 alpha synthesis by liver homogenates progressively decreased as the 20:4 omega 6 levels fell and the 20:5 omega 3 levels increased. PG synthesis was quickly increased in both when corn oil diets were fed. This study has implications for dietary manipulation of PG synthesis by blood components and may provide a basis for manipulation of PG synthesis in systems in which they are regulatory.

The effect of dietary alpha-linolenic acid in the rat on fatty acid profiles of immunocompetent cell populations

Analysis of diet-induced fatty acid changes in the major phospholipids of various immune cell populations has not been previously documented, particularly modifications induced by dietary alpha-linolenic acid. Rats were fed purified diets containing either 10% corn oil (CO), 10% linseed oil (LO) or 10% soybean oil-linseed mixture (SL) for 8 weeks. The alpha-linolenic to linoleic acid ratios of the diets were 1:32, 1:1 and 3:1, respectively. Fatty acid analysis of cell populations isolated from he spleen, thymus, thoracic cavity and peripheral blood phospholipids showed increases in omega 3 fatty acids accompanied by decreases in the omega 6 fatty acids when diets high in alpha-linolenic to linoleic acid ratios were fed. The extent of change observed was dependent on the magnitude of the alpha-linolenic to linoleic acid ratio. Both magnitude of change and the specific fatty acids altered varied with the cell population examined.

Modulation of prostaglandin synthesis in rat peritoneal macrophages with omega-3 fatty acids

In view of the findings that omega 3 fatty acids inhibit the synthesis of prostaglandins (PG) from arachidonic acid (20:4 omega 6) and that among immunologically active cells, the macrophage is a major producer of PG, we undertook a study of the effect of dietary alpha-linolenic acid (18:3 omega 3) on PG synthesis in the macrophage. Rats were fed purified diets containing either 10% corn oil (CO) or linseed oil (LO), providing either a low (1/32) or high (3.5/1) ratio of 18:3 omega 3 to 18:2 omega 6, respectively, for 6 weeks. Fatty acid analysis of macrophage phospholipids showed that there was an appreciable increase in the percentage of omega 3 fatty acids and a decrease in the omega 6 fatty acids in macrophages from rats fed the LO diet. The changes in fatty acid composition were associated with a significant decrease in the synthesis of prostaglandin E (PGE) by macrophages from rats fed the LO diet. Macrophages from rats fed the 2 dietary oils did not differ in their ability to degrade PG, thus the difference in PG production appeared to be a consequence of decreased synthesis only. The dietarily induced changes in PGE synthesis were readily overcome in vitro by culturing macrophages with complexes of fat-free bovine serum albumin and either 20:4 omega 6 or 20:5 omega 3.

Sera fatty acid effects on cultured rat splenocytes

Rats were fed either a stock diet or purified diets containing either 10% by weight corn oil or linseed oil for 8 weeks. Splenocytes from rats on the stock ration were cultured for 48 hours in media containing either serum from the rats fed stock diet, corn oil or linseed oil, or fetal bovine serum (FBS). Populations were cultured without stimulation and with stimulation by leucogglutinin (PHA), and the production of prostaglandin F2 alpha by the cells was determined. The serum from the corn oil-fed rats differed markedly in composition from that of the linseed oil-fed rats notably in the higher level of arachidonic acid (20:4 omega 6) and lower level of timnodonic acid (20:5 omega 3). FBS also had a lower level of 20:4 omega 6. These changes were reflected in the fatty acid composition of the spleen choline glycerophosphatide. PGF2 alpha production was significantly depressed in the medium from linseed oil-fed rats compared to the corn oil group. This effect was due to the competition of 20:5 omega 3 for the cyclooxygenase. Viability of cells was better in rat serum than in FBS. The study shows that when studying functions in cultured cells obtained from rats fed different dietary fats the dietary effect will be abrogated or modified by use of FBS in the medium.

Essential fatty acid deficiency, prostaglandin synthesis and humoral immunity in Lewis rats

Essential fatty acid (EFA) deficiency is known to alter the immune response in several experimental systems. To further evaluate the effects of EFAs on immunity Lewis rats were fed diets either adequate or deficient in EFAs for 70-80 days. EFA-adequate rats responded to an i.v. injection of 5 X 10(8) sheep erythrocytes with a sharp, short-lived rise in splenic levels of PGE and PGF within 2 minutes after injection. EFA deficiency resulted in a diminution of this PG response. PG production in liver homogenates was also depressed in EFA-deficient liver. An i.v. injection of sheep erythrocytes resulted in a humoral response against this antigen, measured as hemolytic plaque-forming cells in the spleen. EFA deficiency, as well as pretreatment of EFA-adequate rats with indomethacin, an inhibitor of PG synthesis, resulted in a stimulation of the plaque-forming cell response over that observed in control, EFA-adequate rats. The alterations in immune response resulting from changes in PG synthetic capacity may be important in the etiology of certain immunodeficiency syndromes such as the lupus-erythematosus-like autoimmune disease in NZB/W mice.

Modulation of tissue prostaglandin synthesizing capacity by increased ratios of dietary alpha-linolenic acid to linoleic acid

Semipurified diets containing ratios of alpha-linolenic acid (18:3 omega 3) to linoleic acid (18:2 omega 6) of 1/32, 1/7, 1/1, and 3.5/1 in the form of corn oil, soybean oil, soybean/linseed oil mix and linseed oil were fed to rats for 2 months. The first 3 diets were fed to another group of rats for 4 months and to a group through the second generation. Fatty acid analysis of liver and spleen ethanolamine glycerophosphatide revealed that, as the level of 18:3 omega 3 in the diet increased, the elongated, desaturated metabolites of the omega 6 series decreased and the omega 3 series increased. Noteworthy was the depression in the amount of the precursor of the 2-series prostaglandins (PG) as the omega 3 levels increased. Synthesis of PG by liver of rats fed 2 or 4 months markedly decreased, but at 2 months in thymus and spleen, it showed a trend toward decreasing only. Brain slices showed no decrease in PGF2 alpha synthesis after 4 months, but did decrease significantly after feeding the diets to the second generation. Synthesis of PGE2 by spleen homogenate from the second generation also significantly decreased. The replacement of omega 6 series fatty acids by omega 3 series is explained by the effective competition of 18:3 omega 3 over 18:2 omega 6 for the delta 6 desaturase. Depressions in PG synthesis by high dietary 18:3 omega 3 is explained by the competitive inhibition of the PG synthetase complex by 20:5 omega 3 as well as by the decreased levels of 20:4 omega 6.

Incidence and severity of experimental allergic encephalomyelitis and cerebral prostaglandin synthesis in essential fatty acid deficient and aspirin-treated rats

Experimental allergic encephalomyelitis (EAE) was induced in rats of the Lewis strain fed diets adequate or deficient in essential fatty acids (EFA). After induction of the disease, the diets were supplemented with aspirin (3.75 g/kg diet), and the effects of the drug on the course of EAE and on the synthesis of prostaglandin F (PGF) by brain slices from diseased animals and their Freund controls were examined. Aspirin supplementation delayed the onset of EAE in both dietary groups. EFA-deficient rats experienced an incidence and severity of the disease similar to that of aspirin-free, EFA-deficiet rats, while the EFA-adequate group showed a greater severity but not an increased incidence, compared to aspirin-free controls. Aspirin treatment led to an increased PGF production by brain slices from rats on either diet and not subjected to an immunochallenge. When the diet was deficient in EFA, challenge with antigen plus adjuvant or adjuvant alone tended to decrease PGF synthesis by brain slices, and when the diet was adequate in EFA, immunochallenge caused a marked depression on PGF synthesis. It was concluded that the PG synthetase inhibitor aspirin can alter the course of EAE in the rat, providing further evidence that PGs or related metabolites may be involved in the immune response in this disease.

Cerebral prostaglandin synthesis during the dietary and pathological stresses of essential fatty acid deficiency and experimental allergic encephalomyelitis

Rats of the Lewis strain were fed diets adequate or deficient in essential fatty acids (EFA). At 70-80 days of age experimental allergic encephalomyelitis (EAE) was induced using adjuvants containing either Mycobacterium butyricum or Mycobacterium tuberculois H37Ra. When the former Mycobacterium was used, the incidence of EAE was greater in the EFA-deficient than in EFA-adequate controls; but when the rats challenged with M. tuberculosis, the incidence of the disease was the same in both dietary groups. Brain slices from EFA-deficient rats had a marginally depressed synthesis of prostaglandin F (PGF) compared to that of controls. Immunochallenge with adjuvant alone or adjuvant plus antigen tended to depress further PGF synthesis by brain slices from EFA-deficient rats and significantly depressed synthesis by slices from rats receiving adequate EFA. Whether or not rats were paralyzed had no effect on PGF synthesis when the diet was adequate in EFA, but a significant difference was seen in the EFA-deficient group. The results indicate a possible role for PGF synthesis in the degree of susceptibility of the rats to EAE under different dietary regimens.