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1.
Lead disrupts eicosanoid metabolism, macrophage function, and disease resistance in birds 总被引:1,自引:0,他引:1
Lead (Pb) affects elements of humoral and cell-mediated immunity, and diminishes host resistance to infectious disease. Evidence is presented supporting a hypothesis of Pb-induced immunosuppression stemming from altered fatty acid metabolism, and mediated by eicosanoids and macrophages (MØ). Chronic Pb exposure increases the proportion of arachidonate (ArA) among fatty acids in lipid from avian tissues, and this change provides precursors for eicosanoids, the oxygenated derivatives of ArA that mediate MØ acute inflammatory response. In the current study, we showed that the concentration of ArA in phospholipids of MØ elicited from turkey poults fed 100 ppm dietary Pb acetate was twice that of controls. In vitro production of eicosanoids by these MØ was substantially increased, and this effect was most pronounced following lipopolysaccharide stimulation: prostaglandin F2α was increased 11-fold, thromboxane B2 increased threefold, and prostaglandin E2 increased by 1.5 times. In vitro phagocytic potential of these MØ was suppressed, such that the percentage of MØ engulfing sheep red blood cell (RBC) targets was reduced to half that of control MØ. In vivo susceptibility of Pb-treated and control birds to Gram-negative bacteria challenge was also evaluated. The morbidity of chicks inoculated withSalmonella gallinarum and fed either control or 200 ppm Pb acetate-supplemented diets was similar, except early in the course of the disease when mortality among Pb-treated birds was marginally greater. In these studies, effects of Pb that could influence immunological homeostasis were demonstrated for MØ metabolism of ArA, for production of eicosanoids, and for phagocytosis. There was also the suggestion that these in vitro indices of immune function are related to in vivo disease resistance. 相似文献
2.
Activity of glutathione peroxidase, glutathione reductase, and lipid peroxidation in erythrocytes in workers exposed to lead 总被引:4,自引:0,他引:4
Kasperczyk S Kasperczyk A Ostalowska A Dziwisz M Birkner E 《Biological trace element research》2004,102(1-3):61-72
The aim of this study was to estimate the activity of glutathione peroxidase (GPx), glutathione reductase (GR), and malondialdehyde
(MDA) in erythrocytes in healthy male employees of zinc and lead steelworks who were occupationally exposed to lead over a
long period of time (about 15 yr). Workers were divided into two subgroups: the first included employees with low exposure
to lead (LL) (n=75) with blood lead level PbB=25–40 μg/dL and the second with high exposure to lead (HL) (n=62) with PbB over 40 μg/dL. Administration workers (n=35) with normal levels of PbB and zinc protoporphyrin in blood (ZPP) in blood were the control group. The activity of GPx
significantly increased in LL when compared to the control group (p<0.001) and decreased when compared to the HL group (p=0.036). There were no significant changes in activity of GR in the study population. MDA erythrocyte concentration significantly
increased in the HL group compared to the control (p=0.014) and to the LL group (p=0.024). For the people with low exposure to lead (PbB=25–40 μg/dL), the increase of activity of GPx by about 79% in erythrocytes
prevented lipid peroxidation and it appears to be the adaptive mechanism against the toxic effect of lead. People with high
exposure to lead (with PbB over 40 μg/dL) have shown an increase in MDA concentration in erythrocytes by about 91%, which
seems to have resulted from reduced activity of GPx and the lack of increase in activity of GR in blood red cells. 相似文献
3.
Previous work showed that dietary lead (Pb) increases the relative concentration of arachidonic acid (20∶4) as a percentage
of total fatty acids, and decreases the relative proportion of linoleic acid (18∶2) to arachidonic acid (18∶2/20∶4) in chick
liver, serum, and erythrocyte membranes. The present investigation was undertaken to examine the time-course and magnitude
of the fatty acid alterations with increasing dietary Pb levels. We also examined the effects of Pb on the fatty acid composition
and lipid peroxide content of hepatic subcellular organelles. In Exp. 1, chicks were fed diets containing 0, 62.5, 125, 250,
500, or 1000 ppm added Pb (as Pb acetate trihydrate) from 1 to 21 d of age. After 21 d, no growth effects were observed; however,
Pb lowered the 18∶2/20∶4 ratio and increased 20∶4 concentration in total liver and serum lipids, and in total hepatic phospholipids
in a dose-dependent manner. Hepatic mitochondrial membrane fatty acids were not altered, nor was there any increase in hepatic
lipid peroxidation. In Exp. 2, chicks were fed diets containing 0, 500, 1000, or 2000 ppm added Pb from 1 to 21 or 22 d of
age. Pb depressed growth in a dose-dependent manner. In addition, Pb lowered the 18∶2/20∶4 ratio and increased 20∶4 concentration
in total liver lipids and in hepatic mitochondrial and microsomal membranes in a dose-dependent manner. Total hepatic lipid
peroxidation was increased over control values by 1000 ppm Pb, and hepatic microsomal lipid peroxidation was increased by
dietary Pb levels of 1000 and 2000 ppm. In Exp. 3, body weight, hepatic microsomal lipid peroxidation, and fatty acid composition
were determined in 4-, 9-, 14-, 18-, and 23-d-old chicks fed 0 or 1500 ppm added Pb. Body weights of Pb-treated chicks were
significantly lower than those of control chicks by day 18. Microsomal 20∶4 concentration and peroxidation increased, and
the 18∶2/20∶4 ratio decreased with age in both groups, but the changes were of greater magnitude in the Pb-treated chicks.
The results suggest that some of the manifestations of Pb toxicity may be a reflection of increased concentration of 20∶4
in specific membranes. Further, since the Pb-induced alterations in fatty acid composition were noted in the absence of any
growth depression, we propose that fatty acid composition is more sensitive than growth rate to the presence of lead in the
diet. 相似文献
4.
Jasso-Pineda Y Díaz-Barriga F Calderón J Yáñez L Carrizales L Pérez-Maldonado IN 《Biological trace element research》2012,146(2):141-149
The aim of this study was to evaluate DNA damage and the capacity for DNA repair in children exposed to arsenic and lead.
During 2006, we studied a total of 85 healthy children (aged 4–11 years) who were residents of Villa de la Paz (community
A), Matehuala (community B), and Soledad de Graciano Sanchez (community C) in San Luis Potosi, Mexico. The quantification
of arsenic in urine (AsU) and lead in blood (PbB) was performed by atomic absorption spectrophotometry. The alkaline comet
assay was used to evaluate DNA damage and DNA repair. The highest levels of AsU and PbB in children were found in community
A (44.5 μg/g creatinine for arsenic and 11.4 μg/dL for lead), followed by community B (16.8 μg/g creatinine for arsenic and
7.3 μg/dL for lead) and finally by children living in community C (12.8 μg/g creatinine for arsenic and 5.3 μg/dL for lead).
When DNA damage was assessed, children living in community A had the highest DNA damage. Analysis of these same cells 1 h
after a challenge with H2O2 10 μM showed a dramatic increase in DNA damage in the cells of children living in community B and community C, but not in
the cells of children living in community A. Moreover, significantly higher levels of DNA damage were observed 3 h after the
challenge ended (repair period) in cells from individuals living in community A. Our results show that children exposed to
metals might be more susceptible to DNA alterations. 相似文献
5.
It is well established that lead (Pb) exposure in humans leads to learning and memory impairment. However, the biological
and molecular mechanisms are still not clearly understood. When over activated, serine/threonine protein phosphatases are
known to function as a constraint on learning and memory. Activation of these phosphatases can also result in cytoskeletal
changes that will adversely affect learning and memory. We investigated the effects of Pb exposure on these phosphatases in
primary cultures of human neurons. Neurons were exposed to physiologically relevant concentrations of Pb (5, 10, 20 and 40 μg/dL)
and total phosphatase and PP2A activities were determined in neuronal lysate using para-nitrophenyl phosphate (pNPP), and
a PP2A-specific phosphopeptide as substrates. Expression of various serine/threonine phosphatases, tau and its phosphorylation
state were determined by Western blot (WB) and immunocytochemistry (ICC). We found that the total phosphatase activity in
the neuronal lysate was increased by 30–50% by all the concentrations of Pb tested. PP2A activity was increased by 5 μg/dL
Pb only. PP1 expression was increased (ranging from 25–50%) by 10, 20 and 40 μg/dL of Pb. PP2B expression was increased substantially
(up to 2.5-fold) by 10 μg/dL Pb, whereas, higher concentrations did not show any effect. On the other hand, Pb (at all concentrations
used) decreased expression of PP2A and PP5. Pb exposure induced substantial hyperphosphorylation of tau at serine 199/202
by 5 and 10 μg/dL Pb, and Threonine 231 at higher doses. Expression of total tau was mostly unaffected by lead. Immunocytochemistry
data confirmed the WB results of expression of PP1, PP2A, tau protein and the phosphorylation of tau. These results support
our hypothesis that Pb exposure up regulates some of the serine/threonine phosphatases (PP1 and PP2B) that are known to impair
memory formation, and suggest a novel mechanism of Pb neurotoxicity. 相似文献
6.
James R. Petrie Qing Liu Anne M. Mackenzie Pushkar Shrestha Maged P. Mansour Stan S. Robert Dion F. Frampton Susan I. Blackburn Peter D. Nichols Surinder P. Singh 《Marine biotechnology (New York, N.Y.)》2010,12(4):430-438
The production of long-chain polyunsaturated fatty acids from precursor molecules linoleic acid (LA; 18:2ω6) and α-linolenic
acid (ALA; 18:3ω3) is catalysed by sequential desaturase and elongase reactions. We report the isolation of a front-end Δ6-desaturase
gene from the microalgae Ostreococcus lucimarinus and two elongase genes, a Δ6-elongase and a Δ5-elongase, from the microalga Pyramimonas cordata. These enzymes efficiently convert their respective substrates when transformed in yeast (39–75% conversion for ω3 substrate
fatty acids), and the Δ5-elongase in particular displays higher elongation efficiency (75% for conversion of eicosapentaenoic
acid (20:5ω3) to docosapentaenoic acid (22:5ω3)) than previously reported genes. In addition, the Δ6-desaturase is homologous
with acyl-CoA desaturases and shows a strong preference for the ω3 substrate ALA. 相似文献
7.
Both α-lipoic acid (LA) and ascorbic acid (vitamin C) have been shown to improve endothelial dysfunction, a precursor of atherosclerosis.
Since oxidant stress can cause endothelial dysfunction, we tested the interaction and efficacy of these antioxidants in preventing
oxidant damage to lipids due to both intra- and extracellular oxidant stresses in EA.hy926 endothelial cells. LA spared intracellular
ascorbate in culture and in response to an intracellular oxidant stress induced by the redox cycling agent menadione. Extracellular
oxidant stress generated by incubating cells for 2 h in with 0.2 mg/ml LDL and 5 μM Cu2+ caused a time-dependent increase of the lipid peroxidation product malondialdehyde in both cells and LDL, preceded by rapid
disappearance of` α-tocopherol in LDL. α-Lipoic acid at concentrations of 40–80 μM blunted these effects. Similarly, intracellular
ascorbate concentrations of 1–2 mM also prevented Cu2+-induced lipid peroxidation in LDL and cells. Cu2+-dependent oxidation of LDL in the presence of ascorbate-loaded cells decreased intracellular ascorbate by 20%, but this decrease
was not reversed by LA. Both LA and ascorbate protect endothelial cells and LDL from either intra- or extracellular oxidant
stress, but that LA does not spare ascorbate in oxidatively stressed cells. 相似文献
8.
α-Linolenic acid (ALA, C 18:3Δ9,12,15) has many important biological functions. ω-3 Fatty acid desaturase (FAD3), existing in cytosolic and plastidic compartments
of higher plants, catalyzes linoleic acid (LA) desaturation to produce ALA. GmFAD3A-2 and GmFAD3C genes encoding cytosolic FAD3 from Qihuang 29 soybean were cloned and inserted into p416 vector and expressed in K601 yeast
strain. Gas chromatography showed that the transformed yeast strains could produce ALA. The ALA accumulation levels for the
strains transformed with GmFAD3A-2 or GmFAD3C genes were 0.77 ± 0.1 and 4.13 ± 0.4% of total fatty acids, respectively, while, as compared with that of the control, the
contents of LA decreased from 14.34 ± 0.8 to 10.93 ± 0.0 and 7.85 ± 0.1%, respectively, implying that the GmFAD3C enzyme is
more vigorous or stable, than GmFAD3A-2.
Published in Russian in Fiziologiya Rastenii, 2009, Vol. 56, No. 4, pp. 629–634.
This text was submitted by the authors in English. 相似文献
9.
Postpartum scalp hair samples from 82 term-pregnancy mother/neonate pairs were analyzed for their concentration of zinc (Zn),
copper (Cu), cadmium (Cd), and lead (Pb), using inductively coupled plasma-mass spectrometry. Maternal and neonatal Zn concentrations
had geometric means (and 99% confidence intervals) of 122.5 μg/g (117.9–131.5 μg/g) and 146.9 μg (141.5–156.7 μg/g) respectively.
Corresponding Cu values were 18.4 μg/g (17.6–23.8 μg/g) and 6.7 μg/g (6.3–7.6 μg/g). Those of Cd were 0.49 μg/g (0.47–0.69
μg/g) in the mothers and 0.57 μg/g (0.55–0.86 μg/g) in the neonates. For Pb, they were 7.95 μg/g (7.60–9.32 μg/g) and 4.56
μg/g (4.39–5.56 μg/g). Cigaret smoking, despite its relatively low prevalence (19.5%), was associated with lower Zn and higher
Cd and Pb concentrations and in lower Zn/Cd and Zn/Pb molar concentration ratios. Smoking also altered interelemental relationships,
particularly those of Zn with Cd and Pb and those between Cd and Pb. Smoking frequency appeared to show negative dose-response
effects on maternal and neonatal Zn concentrations, Zn/Pb molar concentration ratios, and birth weight. Mothers with a history
of oral contraceptive (OC) usage had significantly higher Cu concentrations and lower Zn/Cu molar concentration ratios than
nonusers, with the highest Cu concentrations and lowest Zn/Cu values being associated with third-generation OCs. No similar
effects were elicited in the respective neonatal Cu concentrations. Neither alcohol consumption nor prenatal supplementation
with iron and/or folic acid had discernible effects on the maternal or neonatal elemental concentrations. The data from this
study suggest that in a given population of term-pregnancy mothers and neonates, significant interindividual variations in
hair trace element concentrations can occur, irrespective of commonality of general environment, and that lifestyle factors,
including cigaret smoking and OC usage history, can be significant contributory factors to such variations. The data are discussed
in relation to the effects of smoking-associated exposure to Cd and Pb exposure on Zn availability for placental transfer,
as well as on the quantitative maternal Zn supply levels to the fetus resulting from the known tendency of smokers to have
lower dietary intakes of Zn. The higher Cu concentrations in OC users are discussed in relation to altered Cu metabolism,
characterized by increased synthesis of the Cu-binding protein, ceruloplasmin, as an acute-phase antioxidant response to altered
lipid profile and increased lipid oxidation. 相似文献
10.
The concentrations of As, Be, Cd, Cr, Hg, Mn, Ni, Pb, Sn, Tl, and V were determined in hair of 96 school children and in blood
of 144 adults living in the vicinity of a hazardous waste incinerator (HWI) (Constantí, Tarragona County, Catalonia, NE Spain).
The results were compared with those obtained in previous (1998 and 2002) surveys performed in the same area. Data were analyzed
in terms of age, sex, and specific place of residence. Current mean concentrations in hair ranged between not detected (ND)
(As, Be, and Tl) and 1.31 μg/g for Cr. In blood, Be, Hg, Mn, Sn, and Tl levels were under the respective detection limits.
The mean blood concentrations of the remaining elements ranged from 0.34 μg/dL for Cd, to 2.40 μg/dL for Pb. Significant differences
in hair and blood in relation to gender were only noted for Pb in blood. In general terms, metal concentrations in hair and
blood from subjects living in Tarragona County are lower than most levels reported for other countries in recent years. 相似文献
11.
Ana Maria Ronco Yareni Gutierrez Nuri Gras Luis Muñoz Gabriela Salazar Miguel N. Llanos 《Biological trace element research》2010,136(3):269-278
The objective of this study was to evaluate whether lead (Pb) and arsenic (As) levels in biological fluids were associated
to the body composition in a group of reproductive-age women. Voluntary childbearing-age women (n = 107) were divided into three groups according to their body mass index (BMI: weight/height2 (kg/m2): low weight (BMI<18.5 kg/m2), normal $ \left( {{\text{BMI}} > 19\kern1.5pt<\kern1.5pt24.9\,{{\text{kg}} \mathord{\left/{\vphantom {{\text{kg}} {{{\text{m}}^{\text{2}}}}}} \right.} {{{\text{m}}^{\text{2}}}}}} \right) $ \left( {{\text{BMI}} > 19\kern1.5pt<\kern1.5pt24.9\,{{\text{kg}} \mathord{\left/{\vphantom {{\text{kg}} {{{\text{m}}^{\text{2}}}}}} \right.} {{{\text{m}}^{\text{2}}}}}} \right) , and overweight (BMI>25 kg/m2). Body composition and fat mass percentage were determined by the isotopic dilution method utilizing deuterated water. Blood
lead concentrations were determined by graphite furnace atomic absorption spectrometry and urinary arsenic (AsU) concentrations
by inductively coupled plasma mass spectrometry. The type and frequency of food consumption and lifestyle-related factors
were also registered. Most women had $ {\text{PbB}}\,{\text{levels}} > 2\kern1.5pt<\kern1.5pt10\,{\mu{{\text{ g}}} \mathord{\left/{\vphantom {\mu{{\text{ g}}} {\text{dL}}}} \right.} {\text{dL}}} $ {\text{PbB}}\,{\text{levels}} > 2\kern1.5pt<\kern1.5pt10\,{\mu{{\text{ g}}} \mathord{\left/{\vphantom {\mu{{\text{ g}}} {\text{dL}}}} \right.} {\text{dL}}} , and only 2.6% had AsU concentrations above 50 μg/L. The levels of these toxic elements were not found to be associated with
the fat mass percentage. 相似文献
12.
Raju M Lakshminarayana R Krishnakantha TP Baskaran V 《Molecular and cellular biochemistry》2006,288(1-2):7-15
Improving the bioavailability of β-carotene is vital to manage vitamin A deficiency. The influence of micellar oleic (OA), linoleic (LA) and eicosapentaenoic (EPA) acids on plasma β-carotene response and its conversion to retinol has been studied in rats employing single (9 h time course) and repeated (10 days) dose administrations. After a single dose, the levels (area under the curve) of plasma β-carotene and retinyl palmitate in OA and EPA groups were higher (p < 0.05) by 13, 7 and 11, 6 folds than LA group. The liver β-carotene level in OA and EPA groups were higher (p < 0.05) by 3 and 1.2 folds than LA group. After repeated dose, the plasma β-carotene and retinyl palmitate levels in OA (6.2%, 51.7%) and EPA (25.4%, 17.23%) groups were higher (p < 0.05) than LA group. The liver β-carotene level in OA (21.2%) and EPA (17.6%) groups were higher (p < 0.05) than LA group. In both the experiments, the activity of β-carotene 15,15′-dioxygenase in the intestinal mucosa and plasma triglyceride levels were also higher in OA and EPA groups than LA group. β-Carotene excreted through urine and feces of OA and EPA groups was lower than the LA group. These results demonstrate an improved absorption and metabolism of β-carotene when fed mixed micelles with OA or EPA compared with LA. Although the mechanism involved in selective absorption of fatty acids needs further studies, intestinal β-carotene uptake and its conversion to vitamin A can be modulated using specific fatty acids. 相似文献
13.
The use of hair and bone as media in evaluation of lead exposure was investigated in this study. For 12–16 wk rats were given
tap water containing lead acetate in the following concentrations: 41.7 mg Pb/L, 83.3 mg Pb/L, and 166.6 mg Pb/L. The animals
were sacrificed every 4 wk and their tibia bones and hair were collected for determination of lead content. In control animals,
the lead level amounted to 1.2 μg/g (range 0.8–1.3 μg/g) and 0.7 μg/g (range 0.4–2.0 μg/g) in bone and hair, respectively.
In the treated rats the accumulation of lead in bone and hair occurred in a dose-dependent manner. A positive corelation (r=0.876) was established between the lead levels in bone and hair of the rats. The regression equation was as follows: μg Pb/g
bone=0.842×μg Pb/g hair+1.868. After discontinuation of exposure, a significant decrease in the lead content in bone and hair
was noticed. About 9 wk after cessation of treatment, the lead content in hair declined to the pre-exposure level, but 64%
of the maximal lead concentration did remain in bone. The results of this study indicate that during a continuous exposure
the lead level in hair reflects its content in bone. Such phenomena did not occur during the postexposure period. 相似文献
14.
Lipids were extracted by a supercritical fluid extraction method from 10 species of filamentous red algae obtained from culture
collections and their fatty acid compositions were determined. The fatty acid profiles of the 10 species were similar. The
major fatty acids were 16:0, 20:4ω6 and 20:5ω3 (eicosapentaenoic acid, EPA), which amounted to over 70% of the total fatty
acids. The highest EPA content (29.8 mg/L), as a percentage of total fatty acids, was produced by Liagora boergesenii filaments, which has good potential for EPA mass production in pilot plants. 相似文献
15.
Hubert F. Loyke 《Biological trace element research》1992,33(1-3):129-133
With reports of either no change or reduction of blood pressure, the relationship between selenium and blood pressure has
not been clear. Normal Se values are not available for the Sprague Dawley (SD) rat or in the young and adult rat with various
models of experimental hypertension. This study measured serum Se levels in the young and adult normotensive (NT), Grollman
renal hypertensive (RH), and Okamoto-Aoki spontaneous hypertensive rats (SHR). The young animals have statistically significant
(P<0.001) lower Se values as measured by the fluorometric method than those found at adulthood. Selenium levels were found to
be altered in the adult SHR animals when compared with the RH and NT animals. The serum Se value for the normotensive SD rat
was found to be 65.0±3.5 μg/dL, and for the two experimental models, 63.7±4.6 μg/dL for the RH, whereas the SHR level was
elevated to 75.04±4.8 μg/dL (P<0.001). Elevated serum Se values in the adult SHR animals suggests an altered metabolism in SHR animals. 相似文献
16.
K. Hayakawa S. Tsujimura G. E. Napolitano S. Nakano M. Kumagai T. Nakajima C. Jiao 《Limnology》2002,3(1):29-35
The present study examined the fatty acid composition of Microcystis aeruginosa grown in a batch culture and that of Microcystis-dominated plankton collected in an experimental enclosure in a shallow, eutrophic embayment of Lake Biwa (Akanoi Bay). In
pure culture, we detected 16 : 0, 18 : 2ω6, 18 : 3ω3, 18 : 3ω6, and 18 : 4ω3 acids as major fatty acids of M. aeruginosa, with trace amounts of C20 polyunsaturated fatty acids. In both pure culture and the field enclosure, the ratio of total fatty acid weight to dry weight
decreased with decreasing availability of dissolved inorganic nitrogen. The ω3/ω6 ratios of C18 polyunsaturated fatty acids [(18 : 3ω3 + 18 : 4ω3)/(18 : 2ω6 + 18 : 3ω6)] varied greatly (range, 2–5) in response to the
changes in physical and chemical conditions for Microcystis growth. Most notably, the ω3/ω6 fatty acid ratios were significantly positively correlated with the growth rate of cells
in a batch culture. We suggest that the fatty acid composition is a useful indicator of the physiological state of Microcystis in freshwater lakes.
Received: March 2, 2001/ Accepted: December 19, 2001 相似文献
17.
18.
One hundred sixty-four adult male volunteers (29 controls [Group 1] and 135 combi drivers) enrolled in the study. The combi
drivers were divided into three groups as nonusers of either Maras powder or cigarette (Group 2), smokers (Group 3), and users of Maras powder (Group 4). Blood lead levels (BLLs) were analyzed by
atomic absorption spectrophotometer. BLL was detected as 2.8 ± 2.3 μg/dL in Group 1 (n = 29); however, it was 3.5 ± 1.6 μg/dL in Group 2 (n = 33), 3.8 ± 2.4 μg/dL in Group 3 (n = 62), and 3.9 ± 2.4 μg/dL in Group 4 (n = 40). BLL in Group 1 was found significantly lower than other groups (p < 0.05). The use of cigarette or Maras powder by the drivers did not give rise to a marked difference on the BLLs (p > 0.05). BLL of (combi) drivers was detected to be significantly higher than nondrivers; however, it was still under the
hazardous level of 10 μg/dL announced by WHO. Although there are publications reporting that usage of tobacco increases the
level of lead in blood, both smoking and use of Maras powder did not affect BLL markedly in our study.
Poster presented (the abstract section published in Congress Book) at the 7th Congress of Turkish Family Physicians, 23–26
May 2006, Cesme-IZMIR, Turkey. 相似文献
19.
Metabolism of polyunsaturated fatty acids and their toxicity to the microflora of the rumen 总被引:4,自引:0,他引:4
Ruminal microorganisms hydrogenate polyunsaturated fatty acids (PUFA) present in forages and thereby restrict the availability
of health-promoting PUFA in meat and milk. The aim of this study was to investigate PUFA metabolism and the influence of PUFA
on members of the ruminal microflora. Eleven of 26 predominant species of ruminal bacteria metabolised linoleic acid (LA;
cis-9,cis-12–18:2) substantially. The most common product was vaccenic acid (trans-11–18:1), produced by species related to Butyrivibrio fibrisolvens. α-Linolenic acid (LNA; cis-9,cis-12,cis-15–18:3) was metabolised mostly by the same species. The fish oil fatty acids, eicosapentaenoic acid (EPA; 20:5(n − 3)) and docosahexaenoic acid (DHA; 22:6(n − 3)) were not metabolised. Cellulolytic bacteria did not grow in the presence of any PUFA at 50 μg ml−1, nor did some butyrate-producing bacteria, including the stearate producer Clostridium proteoclasticum, Butyrivibrio hungatei and Eubacterium ruminantium. Toxicity to growth was ranked EPA > DHA > LNA > LA. Cell integrity, as measured using propidium iodide, was damaged by LA
in all 26 bacteria, but to different extents. Correlations between its effects on growth and apparent effects on cell integrity
in different bacteria were low. Combined effects of LA and sodium lactate in E. ruminantium and C. proteoclasticum indicated that LA toxicity is linked to metabolism in butyrate-producing bacteria. PUFA also inhibited the growth of the
cellulolytic ruminal fungi, with Neocallimastix frontalis producing small amounts of cis-9,trans-11–18:2 (CLA) from LA. Thus, while dietary PUFA might be useful in suppressing the numbers of biohydrogenating ruminal bacteria,
particularly C. proteoclasticum, care should be taken to avoid unwanted effects in suppressing cellulolysis. 相似文献
20.
Vasin B. L. Mal’kova S. V. Osipov M. V. Puzyrev V. N. Saakyan A. T. Starodub A. N. Fedotov S. I. Fronya A. A. Shutyak V. G. 《Plasma Physics Reports》2010,36(13):1255-1260
The optical scheme and design of a four-frequency polarizing microscope intended for simultaneous recording of plasma images
in the wavelength range 0.4–1.1 μm with the spatial resolution 12 μm in the entire spectral range are described. The effectiveness
of such a microscope in studies of plasmas produced on interaction of laser radiation with a target is demonstrated. The plasma
images are obtained at the frequencies ω0, (3/2)ω0, 2ω0, and (5/2)ω0, where ω0 corresponds to the frequency of heating radiation. The transformation coefficient that characterizes the efficiency of conversion
of heating radiation into the 2ω0, (3/2)ω0, and (5/2)ω0 harmonics generated in the plasma is determined. 相似文献