Inhibition of uptake of transferrin-bound iron by human hepatoma cells by nontransferrin-bound iron

The liver acquires iron from transferrin by transferrin receptor-mediated (TR) and transferrin receptor-independent pathways (NTR) and from nontransferrin-bound iron (NTB-Fe). Iron uptake by the NTR processes involves an iron-carrier mediated step. Experiments, using human hepatoma cells (HuH7) transfected with TR antisense (sense for control) RNA expression vectors to suppress TR expression, were performed to examine the effect of unlabeled NTB-Fe as iron citrate on the uptake of 59Fe-125I-transferrin. This was to determine if the uptake of transferrin-bound iron (Tf-Fe) and NTB-Fe uptake is mediated by a common iron-carrier. Iron citrate inhibited the uptake of 59Fe-transferrin (2.5 micromol/L Fe) in a concentration-dependent manner with a maximum effect when the citrate-iron:Tf-Fe molar ratio was 10:1. Transferrin uptake was not affected. At a lower Tf-Fe concentration of (0.125 micromol/L) when uptake of iron is TR-mediated, a 10-fold molar excess of iron citrate had no effect on Tf-Fe uptake by HuH7 TR antisense and sense cells. However, at a higher Tf-Fe concentration (2.5 micromol/L), when uptake occurs mainly by the NTR-mediated process, there was a 40% reduction in the membrane-bound and intracellular uptake of iron. Iron citrate did not affect the maximum rate (Vmax) of Tf-Fe uptake but the Michaelis-Menten constant (Km) for Tf-Fe uptake by the NTR-mediated process was increased, indicating there was competitive inhibition of Tf-Fe uptake by iron citrate. These results suggest that the uptake of NTB-Fe and Tf-Fe by the NTR- mediated process occurs by the same cellular pathway, using a common iron-carrier.     

Inhibition of the intestinal absorption of iron by sodium alginate and guar gum in rats

Na-alginate as well as guar gum inhibit the absorption of a 59Fe-labelled iron dose (360 nmol) from tied-off jejunal segments of either normal or iron-deficient rats. In order to inhibit the absorption of the iron dose by half as compared with normal rats to which ionized iron was administered 1.2--8 mg of guar gum and 8-30 mg Na-alginate was necessary. In iron-deficient rats the highest dose dose of Na-alginate tested, 100 mg, inhibited the absorption of iron by about 20%; the highest dose of guar gum, 30 mg, inhibited the amount of iron absorbed by about 25%. An artificial diet containing 10% of either guar gum and Na-alginate fed for 3 days inhibited the absorption of iron in normal but not in iron-deficient rats. Also, in these experiments guar gum proved to be more effective than Na-alginate.     

Iron sufficiency in breast-fed infants and the availability of iron from human milk

Four infants were studied who had been exclusively breast-fed for periods varying from 8 to 18 months. All had grown sufficiently to have exhausted their prenatally acquired iron endowment with respect to meeting current needs for maintaining normal hemoglobin levels. All infants had normal hemoglobin values and normal serum iron values. Studies of iron absorption from breast milk and cow's milk were performed in ten normal adults. The absorption of iron from the human milk was significantly higher. These findings suggest that the iron present in human milk is sufficient to meet the iron requirements of the exclusively breast-fed infant until he approximately triples his birthweight.     

Copper, iron, and zinc contents of mature human milk

Daily, weekly, and within-day variations in copper, iron, and zinc contents of human milk were investigated in order to determine whether one sample from an individual is representative of these elements. Total solids, fat, and protein contents were also measured. Fifty women in their 6th to 12th week of lactation each provided seven milk samples consisting of five consecutive daily samples and two additional samples collected either within a single day or at weekly intervals. Fat varied the most of all constituents and total milk solids reflected this variability. Values ranged from 0.2 to 10.4 g/100 ml for fat and from 8.58 to 17.49 g/100 ml for total solids. Protein varied from 0.76 to 2.04 g/100 ml among individuals, with little variation within an individual. Copper content varied considerably among women and within the same woman. With a large proportion of low values, the range was 0.09 to 0.63 mug/ml. Iron content was also found to vary within women as well as among women. Values ranged from less than 0.1 to 1.6 mug/ml with a preponderance of low values. Zinc content was more evenly distributed over the range of 0.14 to 3.95 mug/ml,and within an individual it did not vary widely. A representative estimate of copper and iron contents would therefore require multiple samples, whereas only one sample may provide a representative estimate of zinc content. Comparison of morning, midday, and evening values showed that copper and zinc are higher in the morning and iron is lower at this time. Increased amounts of copper, iron, and zinc were found in multiparous women whether or not they had previously lactated. Milk from older women had lower iron and higher copper and zinc contents than that from younger women. No differences were found in milk of women receiving dietary mineral and vitamin supplements. Calculations indicated that fully breast fed infants under 3 months of age receive approximately 0.35 mg/kg per day of zinc and 0.05 mg/kg per day of both copper and iron.     

The kinetics of nitrogen absorption and desorption from a plasma arc by molten iron

A plasma torch and refractory-lined furnace with a 10 kg capacity were used to study the kinetics of nitrogen absorption and desorption in molten iron. In this study, melts containing both oxygen and sulfur were used. In accord with earlier studies, a limiting rate constant of 0.020 cm/s-pct was observed at high oxygen and/or sulfur contents. At lower oxygen and/or sulfur contents, the measured desorption rates are smaller than most of the reported values and appear to be limited by mixed melt, mass transfer chemical control. Absorption of nitrogen from the plasma arc is limited by mass transfer in the melt. The dominant form of convection in the vicinity of jet impingement is surface tension driven flow. The reaction N(g)=N(pct) appears to be responsible for the enhanced nitrogen content of the melt. The nitrogen content of a melt in equilibrium with the atomic nitrogen content of an Ar-5 pct N₂ plasma jet was determined to be 0.30 wt pct or thirty times the equilibrium value. T. B. KING, formerly Professor of Metallurgy at the Massachusetts Institute of Technology, Cambridge, MA, is deceased. This paper is based on a presentation made in the T.B. King Memorial Symposium on “Physical Chemistry in Metals Processing” presented at the Annual Meeting of The Metallurgical Society, Denver, CO, February, 1987, under the auspices of the Physical Chemistry Committee and the PTD/ISS.     

Inhibition of intestinal absorption of L-phenylalanine in vivo by l-Alanine

Neutrophilic leukocytes of patients with familial Mediterranean fever and of normal control subjects were studied in vitro. FMF neutrophils were found to be morphologically normal by light and electron microscopy and to have normal quantities of the lysosomal enzyme lysozyme. FMF cells demonstrated a slight decrease in their ability to migrate randomly in capillary tubes, this was primarily seen in Armenian patients and in those experiencing an acute attack. The leukocytes of these patients functioned normally in regard to their chemotactic and Candida-killing activity.     

Inhibition of cholesterol absorption by plant sterols for mass intervention

Mononuclear precursors of the human osteoclast have been identified in both bone marrow and the circulation in man, but osteoclast membership of the mononuclear phagocyte system (MPS) and its precise cellular ontogeny remain controversial. We isolated human hematopoietic marrow cells, blood monocytes, and peritoneal macrophages and incubated each of these cell populations with UMR106 osteoblast-like cells on glass coverslips and dentine slices in both the presence and absence of 1,25 dihydroxyvitamin D3 (1,25(OH)2D3), macrophage-colony stimulating factor (M-CSF), and dexamethasone. Cells isolated from peripheral blood and peritoneal dialysis fluid were positive only for monocyte/macrophage markers (CD11a, CD11b, CD14, and HLA-DR) and negative for osteoclast markers [tartrate-resistant acid phosphatase (TRAP), vitronectin reception (VNR), and calcitonin (CT) receptors and did not form resorption pits on dentine slices after 24 hours in culture. Similarly marrow cells did not form resorption pits on dentine slices after 24 hours in culture. However, after 14 days in co-culture with UMR106 cells, in the presence of 1,25(OH)2D3 and M-CSF, numerous TRAP, CT receptor, and VNR-positive multinucleated cells capable of extensive lacunar resorption were formed in co-cultures of all these preparations. The presence of 1,25 (OH)2D3, M-CSF, and UMR106 were absolute requirements for osteoclast differentiation. It is concluded that precursor cells capable of osteoclast differentiation are present in the marrow compartment, the monocyte fraction of peripheral blood, and in the macrophage compartment of extraskeletal tissues and that these cells are capable of differentiating into mature functional osteoclasts. These findings argue in favor of osteoclast membership of the human MPS.     

火焰原子吸收光谱法测定粗锌中铁

采用20mL盐酸(1+2)和2滴30%过氧化氢溶解粗锌样品,以体积分数为5%的盐酸为测定介质,使用空气-乙炔火焰,选定248.3nm为测定波长,建立了火焰原子吸收光谱法(FAAS)测定粗锌样品中铁的方法。在选定的仪器条件下,铁在0.20~3.00μg/mL范围内与其对应的吸光度呈良好的线性关系,相关系数为0.999 6,方法检出限为0.02μg/mL。干扰试验表明,锌基体和其他杂质元素均不干扰铁的测定。将实验方法应用于粗锌中质量分数在0.001%~0.50%之间铁的测定,结果的相对标准偏差(RSD,n=11)在1.0%~3.4%之间。采用实验方法对粗锌实际样品中铁进行测定,测得结果与国家标准GB/T 12689.5—2004中分光光度法的结果基本一致。     

离子液体双水相体系分离-火焰原子吸收光谱法测定铁尾矿中铁

利用［Bmim］BF₄离子液体-NaH₂PO₄双水相萃取分离体系对铁尾矿中铁进行萃取,采用火焰原子吸收光谱法测定了样品中铁的含量。考察了盐用量、温度、pH值等因素对萃取率的影响。结果表明,该离子液体双水相体系萃取铁离子的最佳条件如下：［Bmim］BF₄离子液体为1.5 mL,NaH₂PO₄·2H₂O为3.5 g,邻二氮菲溶液为2.0 mL,控制反应温度为70 ℃,pH值为6.0。方法的线性范围为0.002～60 μg/mL,校准曲线方程为A=0.104 5ρ+0.0165 2,相关系数为0.999 8,检出限为0.008 9 μg/mL,加标回收率在95%～98%之间。方法用于实际样品分析,测得结果与电感耦合等离子体原子发射光谱法一致,相对标准偏差（RSD,n=6）为4.2%~4.5%。使用后的离子液体经NaOH处理回收,其红外谱图与使用前基本一致,表明回收的离子液体可重复使用。     

Inhibition of beta-galactosidase biosynthesis in Escherichia coli by tetracycline residues in milk

Low levels of tetracyclines found as residues in milk inhibited the biosynthesis of beta-galactosidase in Escherichia coli. To produce the same effect, other antibacterials had to occur in concentrations that were more than 10-fold higher. This relative selectivity was exploited for the development of a screening test for tetracyclines in milk based on a chemiluminometric assay of beta-galactosidase. The method was validated with spiked samples of raw milk and applied to field samples contaminated with tetracyclines.     

高频燃烧-红外吸收法测定铁矿石中硫

目前测定铁矿石中硫主要有硫酸钡重量法和燃烧-碘酸钾滴定法两种。硫酸钡重量法虽然测试精度高,测量范围广,但操作繁琐,分析周期长,不适应生产控制分析;而燃烧-碘酸钾滴定法则存在管式炉升温速度慢,精度差,对于高含量样品,滴定时难于控制,容易造成分析结果偏低等问题,不能较好地满足生产实践的要求。     

原子吸收光谱法测定哈氏B合金中铁含量

研究并试验了用AAS法测定哈氏B合金中Fe,确定了试样前处理方法及仪器的工作条件,采用基体匹配法合成标准溶液绘制工作曲线,消除共存元素引起的基体效应,对样品直接测定.通过对样品进行分析和回收试验,结果满意.     

Hydrogen absorption of incoherent TiC particles in iron from environment at high temperatures

The effect of atmosphere in heat treatment on the hydrogen trapping of incoherent TiC particles in iron has been studied in order to clarify the origin of hydrogen trapped by incoherent TiC particles. The hydrogen trapped by incoherent TiC particles in iron after austenitizing and tempering treatments in air, in a nonprotective argon atmosphere, and in an ultrahigh vacuum (UHV) was identified and quantitatively measured by thermal-desorption spectrometry (TDS). Results showed that incoherent TiC particles in iron do not trap hydrogen at ambient temperature by a cathodic-charging method. It was justified that incoherent TiC particles trap hydrogen during high-temperature heat treatment in nonprotective atmospheres. The amount of hydrogen trapped by incoherent TiC particles decreases with increasing heat-treatment temperature, which is well explained by the equilibrium concentration of hydrogen trapped by incoherent TiC particles in iron under an atmosphere containing water vapor. The hydrogen is supplied through water-vapor oxidation of iron at high temperatures. According to this model, a binding energy between hydrogen and incoherent TiC of 53 kJ/mol was obtained. The energy barrier for hydrogen to jump into incoherent TiC was determined to range from 21 to 35 kJ/mol, which is too high for hydrogen to be trapped by incoherent TiC at low temperatures.     

The effects of food on methotrexate absorption

OBJECTIVE: To determine the effects of food on methotrexate (MTX) absorption in patients receiving MTX for the treatment of rheumatoid arthritis (RA). METHODS: Standard pharmacokinetic variables were determined in patients with RA after their usual maintenance dose of MTX, under fasting conditions and after they ate a standard breakfast. RESULTS: No significant differences in area under the serum concentration versus time curve, maximal MTX concentration after dosing (Cmax), time to Cmax), bioavailability, urinary MTX, renal clearance of MTX, or creatinine clearance were observed between the 2 dosing conditions. CONCLUSION: We observed no significant effect of food on MTX absorption or bioavailability. Patients may consume MTX without regard to meals.     

Immunologic protection of the premature newborn by human milk

During the past decade, considerable evidence has accrued regarding the immunologic uniqueness of human milk and of the important role that the immune system in human milk plays in protecting not only the mature, healthy newborn, but also the premature infant who is more prone to infections and the damage caused by inflammatory processes. However, there is a great deal more to learn about the prophylactic and therapeutic uses of human milk in low birth weight infants, including (1) the status of many of the host defense factors in preterm milk, (2) how to preserve the protective agents in human milk during processing and storage, (3) the dose and duration of treatment with human preterm or mature milk that will be needed to protect against a particular disorder, (4) whether non-maternal milk is as efficacious as maternal milk for these infants, and (5) in view of the concern of potential graft versus host reactions, whether it is desirable or contraindicated to maintain the leukocytes in human milk used to feed premature infants. These questions are not easily answered, but will be worthy considerations by neonatologists, clinical immunologists, epidemiologists, and others who are concerned with providing optimal nutritional/immunologic support for the premature infant.     

Killing of Chlamydia trachomatis by novel antimicrobial lipids adapted from compounds in human breast milk

The development of new methods for prevention of sexually transmitted Chlamydia trachomatis infection is a top public health priority. Topical self-administered vaginal microbicides represent one such approach in which the organism is eradicated at the time of initial exposure. To this end, we examined the activity of five synthetic lipids adapted from naturally occurring compounds found in human breast milk. C. trachomatis serovar D or F elementary bodies were added to serial dilutions of the lipids and incubated for various times. Aliquots were then cultured in monolayers of McCoy cells, and inclusions were counted. A 7.5 mM concentration of 2-O-octyl-sn-glycerol completely prevented growth of C. trachomatis after 120 min of contact with the organism. The remaining lipids, 1-O-octyl-, 1-O-heptyl-, 2-O-hexyl-, and 1-O-hexyl-sn-glycerol, showed less activity. On electron microscopic examination, the lipids were shown to have disrupted the chlamydial inner membrane, allowing leakage of the cytoplasmic contents from the cell. Lipid activity was unaffected by the presence of 10% human blood or alterations in pH from 4.0 to 8.0, conditions reflecting those sometimes found in the vagina. Our results suggest that these lipids, especially 2-O-octyl-sn-glycerol, may be effective as topical microbicides in preventing the transmission of C. trachomatis. Further efficacy and toxicity studies with these lipids and assessment of their activity against other sexually transmitted disease pathogens are in progress.