共查询到20条相似文献,搜索用时 15 毫秒
1.
Ward Neil I. Abou-Shakra Fadi R. Durrant Steven F. 《Biological trace element research》1990,(1):177-187
The advantages and disadvantages of neutron activation analysis (NAA) and inductively coupled plasma-source mass spectrometry
(ICP-MS) for the analysis of biological materials is reviewed.
Comparison is made between NAA (instrumental) and ICP-MS (conventional pneumatic solution nebulization and laser ablation)
analysis of the biological reference material National Bureau of Standards (NBS) SRM 1577 Bovine Liver. Relatively good agreement
is achieved between the results for the 18 elements analyzed by both techniques and those either certified or reported in
the literature. Elemental concentrations for Li, Mg, Al, Ca, Cr, Mn, Fe, Cu, Zn, Br, Rb, and Cs are also reported for IAEA
Mixed Human Diet (H9), NBS SRM 909 Human Serum, and NBS SRM 1577a Bovine Liver, analyzed by solution nebulization ICP-MS. 相似文献
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3.
Oral administration of different concentrations of Strontium chloride to laboratory bred mice in vivo induced chromosomal aberrations in bone marrow cell metaphase preparations. The degree of clastogenicity was directly proportional to concentration used at 6, 12, and 24 h of treatment. Duration of treatment could only be related positively in the lower doses. The females showed greater susceptibility than the males at all concentrations used. 相似文献
4.
Feces, kidney, and small intestine were sampled from the mice bearing malignant ascites at different stages of tumor growth
to investigate the kinetics of elemental distribution in the body. The contents of 14 elements in samples were determined
by instrumental neutron activation analysis (INAA). The elements Br, Cl, Cu, Na, Se, and Zn increased, whereas Mn and Rb decreased
in kidney with the growth of the tumor. The elements Cl, Na, and Fe, however, appeared to have significantly different behavior
in the small intestine. 相似文献
5.
The accumulation of Cd in the kidneys is enhanced markedly if chelating agents that contain SH-groups like 2,3 dimercaptopropanol
(BAL) are injected immediately after the metal. This is not a transient effect but persists for more than 3 d. It is less
pronounced at higher chelate doses or when the pH of urine is increased. Our experiments indicate that chelating agents, which
form unstable complexes at acid pH and are able to pass through the cell membrane, will cause metal accumulation in the kidneys. 相似文献
6.
Balogun F. A. Akanle O. A. Spyrou N. M. Owa J. A. 《Biological trace element research》1994,(1):471-479
Instrumental neutron activation analysis (INAA) and protoninduced X-ray emission (PIXE) analysis have been employed to determine
the concentration of 13 elements in human breast milk, various infant formulas, and locally produced cereals from Nigeria,
as well as from various infant formulas and natural cow and goat milk available in the UK. The study shows that if the locally
produced cereal is to be used on a regular basis for babies in Nigeria, then their diet must be supplemented with essential
trace elements. Furthermore, parents should be discouraged from giving their infants cow and goat milk because of the high
concentration of major elements compared to human breast milk. 相似文献
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8.
F. N. Tarla P. R. Henry C. B. Ammerman P. V. Rao R. D. Miles 《Biological trace element research》1991,31(1):11-20
An experiment was conducted with 384 1-d-old male and female broiler-chicks. The basal corn-soybean meal diet (.07 ppm Se DM basis) was supplemented with 0, .1, .2, or .3 ppm added Se as either sodium selenite (Na2SeO3) or calcium selenite (CaSeO3), and fed for 1, 3, or 5 wk. There was no effect of Se source or level on feed intake or gain, but males consumed more (P less than .01) feed than females. There was no effect (P greater than .10) of sex or Se source on plasma, liver, or kidney Se concentration. The Se concentration of all tissues increased (P less than .01) with time and increasing dietary Se concentration. Based on multiple regression slope ratios of liver, kidney, and plasma Se concentrations, Se from CaSeO3 was as available (103%) as Se from Na2SeO3. 相似文献
9.
An experimental setup has been designed to allow fluorescence anisotropy measurements on labeled cell membranes under shear
stress. An important change is observed when increasing the shear stress and varying the experimental parameters indicates
that a decrease in membrane cohesion leads to a subsequent increase in the membrane alteration under shear stress. A model
has been developed that shows, in agreement with experiment, that the effect observed is mainly the result of the alteration
of the membrane, elongation, and orientation with respect to the fluid flow, which can be estimated. 相似文献
10.
Ralf Kemkemer Cornelia Neidlinger-Wilke Lutz Claes Hans Gruler 《Cell biochemistry and biophysics》1999,30(2):167-192
Cells like fibroblasts and osteoblasts are oriented by different extracellular guiding signals like an electric field, a bent surface, and a periodically stretched surface. An automatic controller is responsible for the cell alignment. The controller contains both a deterministic and a stochastic signal. The following machine properties were determined: (1) The angle dependence of the cellular signal transformer is cos 2(psi 0 - psi). (2) The set point of the automatic controller is psi 0 = +/- 90 degrees. The cells like to orient their long axis perpendicular to the direction of the applied guiding signal. (3) The signal transformer measures the extracellular signal in a quadratic fashion. The cells cannot register the sign of the guiding field. (4) The stochastic signal in the automatic controller can be quantified by a characteristic time (approximately 130 min for fibroblasts). (5) The extracellular signal is registered in cell-made standards (ratio of the deterministic and stochastic signal equals one): 0.3 +/- 0.05 V/mm for human fibroblasts (electric field) and 85 +/- 3 microns for human fibroblasts and osteoblasts (cyclindrically bent surface). (6) The lag-time in the signal transduction system of fibroblasts is approximately 4 min. 相似文献
11.
Yan G. Zorbas Youri F. Federenko Konstantin A. Naexu 《Biological trace element research》1994,41(3):253-267
The objective of this investigation was to determine the effect of daily intake of fluid and salt supplementation (FSS) on
increased urinary losses of microelements that developed during hypokinesia (decreased number of walking steps/d). The studies
were performed on 30 endurance-trained male volunteers aged 23–26 yr, with an averaged maximum oxygen uptake of 65 mL/kg/min
during 364 d of hypokinesia (HK). All volunteers were divided into three equal groups: Ten volunteers were placed continuously
under an average of 10,000 running steps/d (14.2 km/d) (control subjects), ten volunteers subjected continuously to HK without
the use of FSS (hypokinetic subjects), and ten volunteers were continuously submitted to HK and consumed daily FSS (hyperhydrated
subjects). For the simulation of the hypokinetic effect the hypokinetic and hyperhydrated volunteers were kept under an average
of 3,000 walking steps/d (2.7 km/d) for 364 d. Prior to their exposure to HK the volunteers were on an average of 10,000 running
steps/d (14.2 km/d). During the prehypokinetic period of 60 d and during the hypokinetic period of 364 d were determined renal
excretion of microelements responses of endurance-trained volunteers. In the hyperhydrated volunteers urinary excretion of
iron, zinc, copper, manganese, cobalt, nickel, lead, tin, chromium, aluminum, molybdenum, and vanadium decreased, whereas
in the hypokinetic volunteers it increased significantly. It was concluded that chronic hyperhydration may be used to attenuate
urinary excretion of microelements in endurance-trained volunteers during prolonged restriction of muscular activity. 相似文献
12.
Bode Peter de Bruin Marcel Oldenburg Siewart van der Wiel Albert Wolterbeek Bert 《Biological trace element research》1990,(1):111-118
A double label procedure with57Co and58Co has been developed for detailed in vivo studies of erythrocyte survival. A well-type Ge detector is used in the measurements.
The activities necessary for these experiments are very low, and the associated dose received by the test persons can be neglected. 相似文献
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14.
Most of the cancer cells arrested in the microcirculation during hematogenous metastasis are rapidly killed; one major mechanism is surface-membrane rupture, associated with the mechanical deformation of cancer cells in capillaries. The feasibility of increasing the susceptibility of cancer cells to lethal, deformation-associated trauma by doxorubicin, was tested in an in vitro mechanical model system, by filtering suspensions of L1210 leukemia cells through 8-μm pore-size Nuclepore® membranes, with or without prior incubation with 10-7M doxorubicin. The results showed that mechanically-induced loss of cancer cells immediately after filtration was increased from 18 to 55% in cells previously exposed to doxorubicin for 48 h. The results indicate the feasibility of chemotherapeutic enhancement of the mechanical killing-action of the microvasculature as a potential rate-regulator of hematogenous metastasis. 相似文献
15.
Nickel is a potent carcinogen and, at high concentrations, is toxic to mammalian cells. The effects associated with nickel
exposure are well-documented but its mechanism of action in the cell has not yet been fully described. In order to understand
the metabolic fate of nickel in mammalian cells, a variant cell population has been selected that continues to grow and divide
in the presence of nickel chloride concentrations that are toxic to the parental cell line (Balb/c-3T3 mouse fibroblasts).
Nickel resistance is not caused by altered uptake of nickel from the medium or increased clearance from the cells and is not
associated with changes in metallothionein expression. Compared to the normal cells, the nickel resistant cells have a decreased
number of chromosomes and numerous centromeric fusions. The expression of some proteins and the distribution of nickel bound
by various proteins are altered in the nickel resistant cells. Preliminary results indicate that the nickel resistant phenotype
may be transferred by genomic DNA-mediated transfection into a recipient NIH-3T3 cell line. Current investigations are directed
at identifying a gene responsible for nickel resistance. 相似文献
16.
This research compared the binding and release of recombinant human bone morphogenetic protein 2 (rhBMP-2) with a series of
hydrophobic and hydrophilic poly-lactide-co-glycolide (PLGA) copolymers. Porous microspheres were produced via a double emulsion
process. Binding and incorporation of protein were achieved by soaking microspheres in buffered protein solutions, filtering,
and comparing protein concentration remaining to nonmicrosphere-containing samples. Protein release was determined by soaking
bound microspheres in a physiological buffer and measuring protein concentration (by reversed-phase high-performance liquid
chromatography) in solution over time. Normalized for specific surface area and paired by polymer molecular weight. microspheres
made from hydrophilic 50∶50 or 75∶25 PLGA bound significantly more protein than microspheres made from the corresponding hydrophobic
PLGA. Increased binding capacity correlated with higher polymer acid values. With certain polymers, rhBMP-2 adsorption was
decreased or inhibited at high protein concentration, but protein loading could be enhanced by increasing the protein solution:PLGA
(volume:mass) ratio or by repetitive soaking. Microspheres of various PLGAs released unbound protein in 3 days, whereas the
subsequent bound protein release corresponded to mass loss. RhBMP-2 binding to PLGA was controlled by the acid value, protein
concentration, and adsorption technique. The protein released in 2 phases: the first occurred over 3 days regardless of PLGA
used and emanated from unbound, incorporated protein, while the second was controlled by mass loss and therefore was dependent
on the polymer molecular weight. Overall, control of rhBMP-2 delivery is achievable by selection of PLGA microsphere carriers.
Published: October, 7, 2001. 相似文献
17.
Global amplification of cDNA from limiting amounts of tissue. An improved method for gene cloning and analysis 总被引:2,自引:0,他引:2
In this study we present an improved polymerase chain reaction (PCR)-based methodology to generate large amounts of high-quality
complementary DNA (cDNA) from small amounts of initial total RNA. Global amplification of cDNA makes it possible to simultaneously
clone many cDNAs and to construct directional cDNA libraries from a sequence-abundance-normalized cDNA population, and also
permits rapid amplification of cDNA ends (RACE), from a limited amount of starting material. The priming of cDNAs with an
adapter oligo-deoxythymidine (oligo-dT) primer and the ligation of a modified oligonucleotide to the 3′ end of single-stranded
cDNAs, through the use of T4 RNA ligase, generates known sequences on either end of the cDNA population. This helps in the
global amplification of cDNAs and in the sequence-abundance normalization of the cDNA population through the use of PCR. Utilization
of a long-range PCR enzyme mix to amplify the cDNA population helps to reduce bias toward the preferential amplification of
shorter molecules. Incorporation of restriction sites in the PCR primers allows the amplified cDNAs to be directionally cloned
into appropriate cloning vectors to generate cDNA libraries. RACE-PCR done with biotinylated primers and streptavidin-coated
para-magnetic particles are used for the efficient isolation of either full-length coding or noncoding strands. 相似文献
18.
A rapid cyclic instrumental neutron activation analysis (CINAA) method has been used to determine the selenium content of
27 duplicate diet samples from each of the 27 districts surrounding Pinhel, Portugal. The accuracy and precision of the CINAA
method have been evaluated by analyzing certified reference materials and observed to be within ±5–10% for samples containing
at least 40 ppb of selenium. The detection limit has been found to vary between 26–42 ppb selenium depending on the sample
composition. The average daily dietary intake has been calculated as 37 μg of selenium per day. 相似文献
19.
M. G. Tozzi-Ciancarelli A. Di Giulio E. Troiani-Sevi A. D’Alfonso G. Amicosante A. Oratore 《Cell biochemistry and biophysics》1989,15(3):225-234
Specific fluorescent probes have been used to monitor changes in erythrocyte membranes in the first stages of the hemolytic
process induced by irradiation with visible light in the presence of protoporphyrin IX.
Although no change, or even a slight increase of fluorescence anisotropy, occurred with two probes having a preferential binding
to membrane proteins, such as fluorescamine and 3-pyrene maleimide, the fluorescence anisotropy of two lipophilic probes,
namely diphenyl-hexatriene and anilino-naphtalene sulfonate, underwent a substantial decrease upon irradiation. 相似文献
20.
Nickel ions produce selective damage in heterochromatic regions of chromosomes. Male Chinese hamster embryo cells, which have
heterochromatin along the entire long arm of the X-chromosome, exhibit an unusually high incidence of nickel-induced transformation
compared with female cells of the same species. However, 3-methylcholanthrene, a carcinogen that produces a random distribution
of chromosome damage, transforms female and male cells equally. Other species that do not have as much heterochromatin on
the X-chromosome exhibit similar incidences of nickel-induced tumors in males and females. Four out of five of the male nickel-transformed
Chinese hamster cell lines exhibit a deletion of the heterochromatic long arm of the X-chromosome as the only common karyotypic
aberration. This result indicates that a deletion of a heterochromatic chromosomal region may be an important feature of the
nickel-induced carcinogenic process. All of the male nickel transformed cells lines are able to form tumors in athymic nude
mice. 相似文献