Acquisition of haemoglobin-bound iron by Histophilus somni

Histophilus somni is an important pathogen of cattle and sheep. H. somni requires iron and can use ruminant transferrins as iron sources for growth. Here, we investigated the abilities of bovine (strains 649 and 2,336) and ovine (strains 9L and 3384Y) isolates of H. somni to acquire iron from haemoglobins. Using growth assays, the bovine isolates were shown to acquire iron from bovine haemoglobin, but not from ovine, porcine or human haemoglobins; the ovine isolates, however, failed to use any of these haemoglobins as iron sources for growth. In solid phase binding assays, the bovine isolates, grown under iron-restricted conditions in the presence of bovine haemoglobin, bound not only bovine but also ovine and human haemoglobins. Competition binding assays indicated that all three haemoglobins were bound by the same receptor(s) and SDS-PAGE of membrane fractions revealed that expression of haemoglobin-binding activity was associated with the production of an approximately 120-kDa outer membrane protein. PCR approaches allowed the amplification and sequencing of hgbA, and also hugX and hugZ homologues from strains 649, 9L and 3384Y. While hgbA of strain 649 was predicted to encode an HgbA precursor that is processed to yield a mature, 123.9-kDa haemoglobin-binding protein, the hgbA genes of strains 9L and 3384Y were predicted to give rise to truncated products. RT-PCR experiments revealed that in strain 649, hugX, hugZ and hgbA are co-transcribed and iron-regulated and additional sequencing suggested that in strain 2336, expression of HgbA is subject to phase variation involving a poly C tract within hgbA.     

原子吸收分光光度法测定右旋糖酐铁注射液的含量

建立了原子吸收分光光度法测定右旋糖酐铁注射液含量的方法,以盐酸溶液(1→100)为溶剂,检测波长248.3 nm,在5～20 μg/mL范围内吸收度与浓度呈良好的线性关系,r=0.999 5,回收率98.8%,RSD为1.5%(n=5),稳定性好.本方法与碘量法相比,操作简便、快速,结果准确.     

Protection by iron salts against sporidesmin intoxication in sheep

A number of iron compounds have been shown to protect sheep against the harmful effects of the facial eczema toxin, sporidesmin. Various salts were found to be effective; the oxidation state of the metal was not important although water-solubility did appear to be a prerequisite for prophylactic activity. The effect of iron salts was additive with that of zinc, and it is suggested that the protective action of these compounds results from their ability to inhibit the absorption of copper, consistent with the previously-proposed freeradical mechanism for sporidesmin toxicity.     

Protection by iron salts against sporidesmin intoxication in sheep

A number of iron compounds have been shown to protect sheep against the harmful effects of the facial eczema toxin, sporidesmin. Various salts were found to be effective; the oxidation state of the metal was not important although water-solubility did appear to be a prerequisite for prophylactic activity. The effect of iron salts was additive with that of zinc, and it is suggested that the protective action of these compounds results from their ability to inhibit the absorption of copper, consistent with the previously-proposed free-radical mechanism for sporidesmin toxicity.     

Evaluation of iron status in lemurs by analysis of serum iron and ferritin concentrations, total iron-binding capacity, and transferrin saturation

OBJECTIVE: To assess serum iron and ferritin concentrations, total iron-binding capacity, and transferrin saturation as indicators of iron metabolic status in 3 genera of lemurs and determine whether these variables are useful for screening for iron overload. DESIGN: Cross-sectional study. ANIMALS: 11 ring-tailed lemurs (Lemur catta), 11 black lemurs (Eulemur macaco macaco), and 11 red-ruffed lemurs (Varecia rubra). PROCEDURES: Blood samples were collected weekly for 3 weeks and assayed for serum iron and ferritin concentrations and total iron-binding capacity. Liver biopsy specimens were evaluated histologically and assayed for total iron, nonheme iron, and trace mineral concentrations. Deposition of iron was scored on Prussian blue-stained slides. RESULTS: Hepatic iron content ranged from 497 to 12,800 Pg/g dry weight (median, 2,165 Pg/g). Differences were seen in mean hepatic iron content across genera, with ruffed lemurs having the highest concentrations and ring-tailed lemurs having the lowest. Iron accumulation in the liver was mild, and cellular pathologic changes associated with iron storage disease were not detected in any lemur. Ferritin concentration was the only variable that correlated significantly with hepatic iron content in all 3 genera of lemurs; however, both transferrin saturation and serum iron concentration were correlated with hepatic iron concentration in ring-tailed and ruffed lemurs. CONCLUSIONS AND CLINICAL RELEVANCE: Serum ferritin concentration was the only variable that was consistently correlated with hepatic iron content in all 3 genera. Mean hepatic iron content varied across genera, suggesting that the propensity for lemurs to develop iron overload in captivity may vary across taxa.     

Zinc, copper and iron utilisation by chicks fed various concentrations of zinc

1. Zinc, iron and copper interactions were examined in chicks (New Hampshire X Single Comb White Leghorn) grown individually in stainless steel cages and fed on purified diets with three concentrations of zinc: control (37 mg Zn/kg), moderate (100 mg Zn/kg) and excess (2000 mg Zn/kg) in three studies. 2. Chicks given either moderate or excess zinc excreted more than twice as much 65Zn from a test diet as those fed on the control diet. Thus chicks given the moderate amount of zinc had concentrations of zinc in tissues similar to those of controls but chicks given excess zinc accumulated zinc in their tissues. 3. The specific activity of 65Zn in the tissues, especially in the bursa of Fabricius, of chicks given excess zinc was not reduced as much as would be predicted. Thus, ingestion of excess zinc appeared to reduce tissue turnover of 65Zn, especially in the bursa. However, humoral immune responses, as measured by antibody titres to sheep red blood cells, were not affected. 4. Chicks given excess zinc or pair-fed on the control diet retained less 59Fe from a test diet than chicks given control or moderate concentrations of zinc ad libitum. The iron concentrations in tibiae of chicks given excess zinc were depressed.     

母猪补小肽铁对乳猪缺铁状况的影响

采食开食料前的哺乳仔猪铁的需要来源于胎儿期的储备和母乳,如能通过给妊娠和泌乳母猪补铁满足乳猪铁的需要,将避免直接给乳猪补铁产生的许多问题。Hansand指出,母畜将矿物质转移至胎儿的能力,受母畜和被转移物质的大小、重量和电荷的影响。一般补铁剂（无机铁、有机酸铁、右旋糖苷铁）中的铁在体内需通过运铁蛋白才能到达机体各功能部位,由于运铁蛋白的分子量较大,不能自由通过具有屏障作用的组织,因此母猪补铁并不能有效地增加胎儿的铁储和母乳中铁的含量。小肽铁具有特有的代谢方式,能够以完整的形式到达需铁部位。 本试验目的旨在研究母猪补小肽铁对乳猪铁     

Acquisition of haemoglobin-bound iron by strains of the Actinobacillus minor/"porcitonsillarum" complex

Members of the Actinobacillus minor/"porcitonsillarum" complex are common inhabitants of the swine respiratory tract. Although avirulent or of low virulence for pigs, these organisms, like pathogens, do grow in vivo and must, therefore, be able to acquire iron within the host. Here, we investigated the abilities of six members of the A. minor/"porcitonsillarum" complex to acquire iron from transferrin and various haemoglobins. Using growth assays, all six strains were shown to acquire iron from porcine, bovine and human haemoglobins but not from porcine transferrin. Analyses of whole genome sequences revealed that A. minor strains NM305(T) and 202, unlike the swine-pathogenic actinobacilli, A. pleuropneumoniae and A. suis, lack not only the transferrin-binding protein genes, tbpA and tbpB, but also the haemoglobin-binding protein gene, hgbA. Strains NM305(T) and 202, however, were found to possess other putative haemin/haemoglobin-binding protein genes that were predicted to encode mature proteins of ～ 72 and ～ 75 kDa, respectively. An affinity procedure based on haemin-agarose allowed the isolation of ～ 65 and ～ 67 kDa iron-repressible outer membrane polypeptides from membranes derived from strains NM305(T) and 202, respectively, and mass spectrometry revealed that these polypeptides were the products of the putative haemin/haemoglobin-binding protein genes. PCR approaches allowed the amplification and sequencing of homologues of both haemin/haemoglobin-binding protein genes from each of the other four strains, strains 33PN and 7ATS of the A. minor/"porcitonsillarum" complex and "A. porcitonsillarum" strains 9953L55 and 0347, suggesting that such proteins are involved in the utilization of haemoglobin-bound iron, presumably as surface receptors, by all six strains investigated.     

Role of uteroferrin in placental iron transport: effect of maternal iron treatment on fetal iron and uteroferrin content and neonatal hemoglobin

Uteroferrin, an Fe-containing, progesterone-induced glycoprotein is involved in maternal to fetal Fe transport in swine. These studies examined the effect of im Fe injection of dam on conceptus and piglet Fe stores. In Exp. I, eight gilts were bred and assigned to either treatment I (no Fe injections) or treatment II (total of 22 mg iron-dextran/kg body weight on d 40, 45, 50, 55 and 60 of gestation) and hysterectomized on d 90 to determine whether Fe injections increased Fe stores in the conceptus. Total Fe in allantoic fluid (P less than .10) as well as uteroferrin concentration (P less than .05) and total uteroferrin (P less than .05) in placentae were greater for gilts in treatment II. In Exp. II, 19 cross-bred sows were bred and assigned to treatments I and II (d 40, 50 and 60 of gestation), as in Exp. I, and treatment III (total of 22 mg iron-dextran/kg body weight on d 90, 100 and 110 of gestation) to determine effects of treatment on hemoglobin (Hb) values of the piglets at 8 +/- 1 h and d 4 postpartum. Piglets from treatment II had higher (P less than .01) Hb at 8 +/- 1 h, but not on d 4 postpartum. Experiment III was a replication of Exp. II except that Hb values were determined at 8 +/- 1 h, d 4 and d 7 postpartum. On d 7, piglets from treatment II had higher (P less than .05) Hb, but differences at 8 +/- 1 h and d 4 were not significant (P greater than .10).(ABSTRACT TRUNCATED AT 250 WORDS)     

Efficiency of inorganic and organic iron sources under iron depleted conditions in broilers

1. A total of 240?d-old male Ross chicks (average BW 37·15?±?0·49?g) were fed on an iron (Fe)-deficient semi-synthetic diet (45?mg Fe/kg) from d 1-7 post hatching.

2. At d 7, all 240 chicks (average BW 140·15?±?1·4?g) with depleted Fe-stores were randomly assigned to three treatments on the basis of BW to study the efficiency of dietary inorganic and organic iron (Fe) utilisation. Each treatment had 4 replicates with 20 birds in each.

3. Dietary treatments were: maize-soyabean meal-based basal diet, containing 103 to 106?mg Fe/kg (control); and basal diets supplemented with an additional 80?mg/kg Fe either from an inorganic (FeSO₄?·?H₂O, 28% Fe) or organic (ferrous methionine chelate, 10% Fe) source. The starter and finisher diets were fed from d 7 to 21 and d 21 to 35, respectively.

4. Improved body weight gain and FCR during finisher phase and overall study period; and greater DM and CP retention, and excreta Fe excretion, at d 20 to 21 and d 34 to 35; were observed in birds fed on Fe supplemented diets when compared with birds fed on control diet. At d 35, the RBC, Hb, haematocrit, and Fe concentration in plasma, tibia and liver were higher in birds fed on Fe supplemented diets than birds fed on the control diet.

5. Supplementation of Fe in organic form resulted in greater Fe concentration in the tibia and liver and less Fe excretion at d 34 to 35, when compared with birds receiving inorganic Fe.

6. These results indicate the necessity to supplement Fe in the commercial diets of broilers; however, organic and inorganic sources of Fe supplementation at 80?mg/kg were equally effective in improving performance, nutrient retention and haematological indices. In addition, Fe supplementation through an organic source seems to be more efficient in depositing Fe in the haemopoietic organs (liver and tibia) of birds under Fe depleted conditions.     

The Ins and Outs of siderophore mediated iron uptake by extra-intestinal pathogenic Escherichia coli

Extraintestinal pathogenic E. coli (ExPEC) are responsible for many infectious diseases in livestock, such as airsacculitis in poultry, acute mastitis in dairy animals and neonatal septicaemia and urinary tract infections (UTI) in pigs and cattle. In their animal hosts, ExPEC have to cope with low iron availability. By using different strategies, ExPEC strains are able to retrieve iron sequestered by host proteins. One of these strategies is the use of siderophores, which are small secreted molecules with high affinity for iron. ExPEC are known to synthesize up to four different types of siderophores: enterobactin, salmochelins, yersiniabactin and aerobactin. Steps required for iron acquisition by siderophores include (1) siderophore synthesis in the cytoplasm, (2) siderophore secretion, (3) ferri-siderophore reception, (4) ferri-siderophore internalization and (5) iron release in the cytoplasm. Each siderophore has specific properties and may be differentially regulated to provide different advantages, potentially allowing ExPEC to adapt to different environmental conditions or to overcome host innate immunity. Iron acquisition by siderophores plays a significant role in ExPEC virulence and, as it requires outer membrane receptors, it constitutes an interesting target for the development of vaccines that could be used to limit the number of infectious diseases due to ExPEC in livestock.     

Effect of dietary iron content on hematologic and other measures of iron adequacy in dogs

Eighteen 9- to 10-week old Beagles were fed casein-based diets (4,710 kcal of metabolizable energy/kg of body weight) containing either 12, 80, or 160 mg of iron/kg of diet. Growth and feed consumption were monitored throughout the 47-day study. Hematocrit (Hct), hemoglobin (Hb) concentration, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), RBC numbers, erythrocyte protoporphyrin (EP) concentration, serum iron concentration, serum total iron-binding capacity (TIBC), and serum ferritin concentration were determined weekly. Growth rate and feed efficiency were not significantly influenced by dietary iron content. At 14 days, Hb concentration, Hct, MCV, MCH, RBC numbers, and serum iron concentration were significantly (P less than 0.05) lower in dogs fed the 12 mg/kg diet, and remained significantly low for the remainder of the study. Erythrocyte protoporphyrin concentration increased significantly (P less than 0.05) by 14 days in dogs fed the basal diet, and remained significantly high relative to that in dogs of the other dietary groups for the remainder of the study. Serum ferritin concentration decreased in dogs of the group fed the basal diet, with a significant (P less than 0.05) difference beyond day 42. Differences in Hct, MCH, MCV, or hemoglobin, serum iron, serum ferritin, or EP concentration were not found between groups fed 80 and 160 mg of iron/kg of diet. Liver nonheme iron content was significantly (P less than 0.05) affected by dietary iron content.     

铁代谢的研究进展

本文综述了机体对铁的吸收、转运、储藏及其对铁代谢的调节。     

Influence of low dietary iron and iron overload on urethan-induced lung tumors in mice.

Weanling male CD-1 mice were fed low iron (7 ppm), control (120 ppm) and iron loaded diets (3000 or 5000 ppm) for 19 weeks. After seven weeks, the mice received 1.5 mg urethan/g ip, and tumor development was evaluated 12 weeks later. The low iron diet increased the incidence of lung adenomas by 86%. The iron loaded diets did not influence adenoma development. Tumor size was unaffected by iron status (p = 0.297). These results indicate that low iron body status promotes tumor development and are inconsistent with the hypothesis that excess iron promotes cancer growth and that low iron protects against tumor growth.