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1.
Reyes RA Romanyukha A Trompier F Mitchell CA Clairand I De T Benevides LA Swartz HM 《Radiation and environmental biophysics》2008,47(4):515-526
The most significant problem of electron paramagnetic resonance (EPR) fingernail dosimetry is the presence of two signals
of non-radiation origin that overlap the radiation-induced signal (RIS), making it almost impossible to perform dose measurements
below 5 Gy. Historically, these two non-radiation components were named mechanically induced signal (MIS) and background signal
(BKS). In order to investigate them in detail, three different methods of MIS and BKS mutual isolation have been developed
and implemented. After applying these methods, it is shown here that fingernail tissue, after cut, can be modeled as a deformed
sponge, where the MIS and BKS are associated with the stress from elastic and plastic deformations, respectively. A sponge
has a unique mechanism of mechanical stress absorption, which is necessary for fingernails in order to perform its everyday
function of protecting the fingertips from hits and trauma. Like a sponge, fingernails are also known to be an effective water
absorber. When a sponge is saturated with water, it tends to restore to its original shape, and when it loses water, it becomes
deformed again. The same happens to fingernail tissue. It is proposed that the MIS and BKS signals of mechanical origin be
named MIS1 and MIS2 for MISs 1 and 2, respectively. Our suggested interpretation of the mechanical deformation in fingernails
gives also a way to distinguish between the MIS and RIS. The results obtained show that the MIS in irradiated fingernails
can be almost completely eliminated without a significant change to the RIS by soaking the sample for 10 min in water. The
proposed method to measure porosity (the fraction of void space in spongy material) of the fingernails gave values of 0.46–0.48
for three of the studied samples. Existing results of fingernail dosimetry have been obtained on mechanically stressed samples
and are not related to the “real” in vivo dosimetric properties of fingernails. A preliminary study of these properties of
pre-soaked (unstressed) fingernails has demonstrated their significant difference from fingernails stressed by cut. They show
a higher stability signal, a less intensive non-radiation component, and a nonlinear dose dependence. The findings in this
study set the stage for understanding fingernail EPR dosimetry and doing in vivo measurements in the future. 相似文献
2.
Alexander Romanyukha François Trompier Ricardo A. Reyes Doran M. Christensen Carol J. Iddins Stephen L. Sugarman 《Radiation and environmental biophysics》2014,53(4):755-762
In this paper, we report results of radiation dose measurements in fingernails of a worker who sustained a radiation injury to his right thumb while using 130 kVp X-ray for nondestructive testing. Clinically estimated absorbed dose was about 20–25 Gy. Electron paramagnetic resonance (EPR) dose assessment was independently carried out by two laboratories, the Naval Dosimetry Center (NDC) and French Institut de Radioprotection et de Sûreté Nucléaire (IRSN). The laboratories used different equipments and protocols to estimate doses in the same fingernail samples. NDC used an X-band transportable EPR spectrometer, e-scan produced by Bruker BioSpin, and a universal dose calibration curve. In contrast, IRSN used a more sensitive Q-band stationary spectrometer (EMXplus) with a new approach for the dose assessment (dose saturation method), derived by additional dose irradiation to known doses. The protocol used by NDC is significantly faster than that used by IRSN, nondestructive, and could be done in field conditions, but it is probably less accurate and requires more sample for the measurements. The IRSN protocol, on the other hand, potentially is more accurate and requires very small amount of sample but requires more time and labor. In both EPR laboratories, the intense radiation-induced signal was measured in the accidentally irradiated fingernails and the resulting dose assessments were different. The dose on the fingernails from the right thumb was estimated as 14 ± 3 Gy at NDC and as 19 ± 6 Gy at IRSN. Both EPR dose assessments are given in terms of tissue kerma. This paper discusses the experience gained by using EPR for dose assessment in fingernails with a stationary spectrometer versus a portable one, the reasons for the observed discrepancies in dose, and potential advantages and disadvantages of each approach for EPR measurements in fingernails. 相似文献
3.
Effect of low dose and moderate dose gamma irradiation on the mechanical properties of bone and soft tissue allografts 总被引:1,自引:0,他引:1
Balsly CR Cotter AT Williams LA Gaskins BD Moore MA Wolfinbarger L 《Cell and tissue banking》2008,9(4):289-298
The increased use of allograft tissue for musculoskeletal repair has brought more focus to the safety of allogenic tissue
and the efficacy of various sterilization techniques. Gamma irradiation is an effective method for providing terminal sterilization
to biological tissue, but it is also reported to have deleterious effects on tissue mechanics in a dose-dependent manner.
At irradiation ranges up to 25 kGy, a clear relationship between mechanical strength and dose has yet to be established. The
aim of this study was to investigate the mechanical properties of bone and soft tissue allografts, irradiated on dry ice at
a low absorbed dose (18.3–21.8 kGy) and a moderate absorbed dose (24.0–28.5 kGy), using conventional compressive and tensile
testing, respectively. Bone grafts consisted of Cloward dowels and iliac crest wedges, while soft tissue grafts consisted
of patellar tendons, anterior tibialis tendons, semitendinosus tendons, and fascia lata. There were no statistical differences
in mechanical strength or modulus of elasticity for any graft irradiated at a low absorbed dose, compared to control groups.
Also, bone allografts and two soft tissue allografts (anterior tibialis and semitendinosus tendon) that were irradiated at
a moderate dose demonstrated similar strength and modulus of elasticity values to control groups. The results of this study
support the use of low dose and moderate dose gamma irradiation of bone grafts. For soft tissue grafts, the results support
the use of low dose irradiation. 相似文献
4.
In the present study naturally loose deciduous molars were investigated. The feasibility of separating enamel from small size molars was analysed. EPR spectrum parameters of whole molars and separated enamel only were evaluated before and after laboratory irradiation. The Electron paramagnetic resonance (EPR) signal amplitudes of CO
2
−
and native signals were determined by spectrum deconvolution, as a function of radiation dose in the range 0.1–10 Gy. A detection threshold of absorbed dose from deciduous molars of 198 and 21 mGy is estimated for massive (that contained both enamel and dentine) and grainy samples (that contained enamel only), respectively. The elimination of the organic material from the massive deciduous samples reduced the mean bias dose for the native signal from 90±18 to 34±13 mGy. A decay of the background signal within 2 weeks after irradiation was found, while the dosimetric signal was stable before and after the irradiation process. The presented results suggest deciduous teeth to be suitable for retrospective dose assessment. To get reasonable dose estimates, however, any organic material must be eliminated, and the measurements should be performed 2 weeks after the chemical and mechanical preparation and the irradiation process are done.N. El-Faramawy: On leave from Department of Physics, Faculty of Science, Ain Shams University, 65511 Abbassia, Cario, Egypt. 相似文献
5.
6.
Lead and cadmium are toxic to humans at excessive levels, and monitoring the human body burden of these metals is important
in preventing adverse health effects. In this study, we assessed the exposure to lead and cadmium among an elderly population
60 years of age or older. Based on data from 115 participants, we found that the geometric mean lead concentrations in hair
and fingernails were 1.11 μg/g [95% confidence interval (CI) 0.78–1.58] and 1.11 μg/g (95% CI 0.81–1.51), respectively. The
lead concentrations in hair and fingernails were significantly related to cigarette smoking. The geometric mean cadmium concentrations
in hair and fingernails were 52.6 ng/g (95% CI 42.0–65.9) and 40.1 ng/g (95% CI 29.9–53.9), respectively. Cadmium concentrations
in hair were significantly related to body mass index and cigarette smoking, whereas higher fingernail cadmium concentrations
were related to alcohol drinking. Correlations between hair and fingernail concentrations of lead and of cadmium were slightly
positive. Our findings suggest that the body burden of lead and cadmium varies according to demographic factors, and hair
and fingernails could be used differentially as a biological medium for metal exposure. 相似文献
7.
Santhosh Acharya Ganesh Sanjeev N. N. Bhat K. Siddappa Y. Narayana 《Radiation and environmental biophysics》2009,48(2):197-203
The effect of electrons and gamma irradiation on the induction of micronuclei in cytokinesis-blocked human peripheral blood
lymphocytes was investigated to understand the relative biological effectiveness (RBE) of electrons compared with gamma rays.
Blood samples were irradiated with an 8 MeV pulsed electron beam, at a mean instantaneous dose rate of 2.6 × 105 Gy s−1. Gamma irradiation was carried out at a dose rate of 1.98 Gy min−1 using 60Co gamma source. A dose-dependent increase in micronuclei yield was observed. The dose–response relationships for induction
of micronuclei fitted well to a linear–quadratic relationship and the coefficients α and β of the dose–response curve were
estimated by fitting the data using error-weighted minimum χ
2 method. The RBE of 8 MeV electrons were found to be near unity as compared with gamma rays. 相似文献
8.
Zhi-Gang Ren Jian-Dong Zhao Ke Gu Jian Wang Guo-Liang Jiang 《Molecular biology reports》2012,39(4):3829-3836
The liver has powerful capability to proliferate in response to various injuries, but little is known as to liver proliferation
after irradiation (IR) injury. This study investigated whether liver proliferation could be stimulated in low-dose irradiated
liver by partial liver IR injury with high dose radiation. Sprague–Dawley rats were irradiated by 6-MV X-ray with single dose
of 25 Gy to the right-half liver, while the left-half liver was shielded (0.7 Gy) or irradiated with single doses of 3.2,
5.6, and 8.0 Gy, respectively. Hepatic proliferation in the shielded and low-dose irradiated left-half liver was evaluated
by serum hepatic growth factor (HGF), proliferating cell nuclei antigen (PCNA), liver proliferation index (PI), hepatocyte
mitosis index (MI). The observation time was 0 day (before IR), 30, 60, 90, and 120 days after IR. Our results showed that
serum HGF and hepatocyte HGF mRNA increased after IR with HGF mRNA peak on day 30 in the shielded and low-dose irradiated
left-half livers, and their values increased as the dose increased to the left-half liver. Liver PI and PCNA mRNA peaked on
day 60 with stronger expressions in higher doses-irradiated livers. MI increased after IR, with the peak noted on day 60 in
the shielded and on day 90 in the low-dose irradiated left-half livers. There was a 30 day delay between MI peaks in the shielded
and low-dose irradiated livers. In conclusion, 25 Gy partial liver IR injury could stimulate the shielded liver and low-dose
irradiated liver to proliferate. In the livers receiving a dose range of 3.2–8.0 Gy, the proliferation was stronger in higher
doses-irradiated liver than the low-dose irradiated. However, IR delayed hepatocyte mitosis. 相似文献
9.
Alexander Nevelsky Raquel Bar-Deroma Abraham Kuten 《Radiation and environmental biophysics》2009,48(4):385-389
Total body Irradiation (TBI) is often used for conditioning, prior to bone marrow transplantation. Doses of 8–14 Gy in 1–8
fractions over 1–4 days are administered using low dose rate external beam radiotherapy (EBRT). When necessary, consolidation
EBRT using conventional doses, fractionation and dose rate is given. The irradiated volume usually contains critical organs
such as spinal cord. The purpose of this study was to assess the biologic effect of TBI on the spinal cord in terms of EQD2 (equivalent dose given in fractions of 2 Gy). EQD2 values were calculated using the linear-quadratic generalized incomplete repair (IR) model that incorporates IR between fractions
and low dose rate irradiation corrections and accounts for mono and bi-exponential repair. Three fractionation schemes were
studied as function of dose rate: 8 Gy in 1 and 2 fractions and 12 Gy in 8 fractions. For the 12 Gy in 8 fractions scheme,
the influence of dose rate on EQD2 was limited because the effect of IR between fractions dominates. For the 8 Gy in 1 fraction scheme, significant sparing
of the spinal cord may be achieved for low dose rate (5–20 cGy/min). The extent of effects depends on the parameters used.
The IR model provides a useful mathematical framework for examination of the effects of fractionated treatments of varying
dose rate. Reliable experimental data are needed for accurate assessment of radiation damage to the spinal cord following
fractionated low dose rate TBI. 相似文献
10.
Cristina Correia Stéphane Besson Carlos D. Brondino Pablo J. González Guy Fauque Jorge Lampreia Isabel Moura José J. G. Moura 《Journal of biological inorganic chemistry》2008,13(8):1321-1333
Membrane-bound nitrate reductase from Marinobacter hydrocarbonoclasticus 617 can be solubilized in either of two ways that will ultimately determine the presence or absence of the small (Ι) subunit.
The enzyme complex (NarGHI) is composed of three subunits with molecular masses of 130, 65, and 20 kDa. This enzyme contains
approximately 14 Fe, 0.8 Mo, and 1.3 molybdopterin guanine dinucleotides per enzyme molecule. Curiously, one heme b and 0.4 heme c per enzyme molecule have been detected. These hemes were potentiometrically characterized by optical spectroscopy at pH 7.6
and two noninteracting species were identified with respective midpoint potentials at E
m = +197 mV (heme c) and −4.5 mV (heme b). Variable-temperature (4–120 K) X-band electron paramagnetic resonance (EPR) studies performed on both as-isolated and dithionite-reduced
nitrate reductase showed, respectively, an EPR signal characteristic of a [3Fe–4S]+ cluster and overlapping signals associated with at least three types of [4Fe–4S]+ centers. EPR of the as-isolated enzyme shows two distinct pH-dependent Mo(V) signals with hyperfine coupling to a solvent-exchangeable
proton. These signals, called “low-pH” and “high-pH,” changed to a pH-independent Mo(V) signal upon nitrate or nitrite addition.
Nitrate addition to dithionite-reduced samples at pH 6 and 7.6 yields some of the EPR signals described above and a new rhombic
signal that has no hyperfine structure. The relationship between the distinct EPR-active Mo(V) species and their plausible
structures is discussed on the basis of the structural information available to date for closely related membrane-bound nitrate
reductases.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
11.
Koek MM van der Kloet FM Kleemann R Kooistra T Verheij ER Hankemeier T 《Metabolomics : Official journal of the Metabolomic Society》2011,7(1):1-14
Due to the complexity of typical metabolomics samples and the many steps required to obtain quantitative data in GC × GC–MS
consisting of deconvolution, peak picking, peak merging, and integration, the unbiased non-target quantification of GC × GC–MS
data still poses a major challenge in metabolomics analysis. The feasibility of using commercially available software for
non-target processing of GC × GC–MS data was assessed. For this purpose a set of mouse liver samples (24 study samples and
five quality control (QC) samples prepared from the study samples) were measured with GC × GC–MS and GC–MS to study the development
and progression of insulin resistance, a primary characteristic of diabetes type 2. A total of 170 and 691 peaks were quantified
in, respectively, the GC–MS and GC × GC–MS data for all study and QC samples. The quantitative results for the QC samples
were compared to assess the quality of semi-automated GC × GC–MS processing compared to targeted GC–MS processing which involved
time-consuming manual correction of all wrongly integrated metabolites and was considered as golden standard. The relative
standard deviations (RSDs) obtained with GC × GC–MS were somewhat higher than with GC–MS, due to less accurate processing.
Still, the biological information in the study samples was preserved and the added value of GC × GC–MS was demonstrated; many
additional candidate biomarkers were found with GC × GC–MS compared to GC–MS. 相似文献
12.
Marcin Cyprowski Alina Buczyńska Anna Kozajda Ma?gorzata Sowiak Karolina Bródka Irena Szadkowska-Stańczyk 《Aerobiologia》2012,28(2):161-168
The aim of this study was to assess the exposure to organic dust and (1 → 3)-β-D-glucans in the buildings where an intensive
breeding of swine is going on and evaluation of the impact of the breeding technical conditions on the observed levels of
bioaerosols. The study was carried out in 30 swine farms differentiated by the size of the herd and technical conditions of
breeding. In 35 randomly selected buildings, air samples were collected by stationary measurements to determine the concentrations
of organic dust and (1 → 3)-β-D-glucans in inhalable and respirable fractions. Furthermore, each of the investigated buildings
was precisely characterized by means of a questionnaire for technical conditions and type of breeding. In each of the points,
the microclimate parameters were measured, i.e., temperature, relative humidity, CO2 concentration and air velocity. The analyzed levels of organic dust and (1 → 3)-β-D-glucans were characterized by a wide
range of concentrations. For inhalable fraction, they reached respectively: organic dust (0.43–11.8 mg/m3), (1 → 3)-β-D-glucans (14–3,594 ng/m3). For respirable fraction, the results were as follows: organic dust (0.01–4.69 mg/m3), (1 → 3)-β-D-glucans (1–703 ng/m3). The concentrations of (1 → 3)-β-D-glucans were positively correlated with organic dust (r = 0.68; p < 0.001). The most significant factor increasing the concentrations of organic dust and (1 → 3)-β-D-glucans was the use of
bedding in the form of cut straw. Additionally, the levels of (1 → 3)-β-D-glucans were affected by manual forage feeding,
mechanical manure disposal and the lack of the liquid manure container in breeding buildings. In view of the hazardous effects
of biological agents on the health of swine-breeding workers, the swine management systems without beddings should be used,
along with automated dosing techniques. 相似文献
13.
Production rates, abundance, chlorophyll a (Chl a) concentrations and pigment composition were measured for three size classes (<2 μm, 2–11 μm and >11 μm) of phytoplankton
from May to December 2000 in deep, mesotrophic, alpine lake Mondsee in Austria. The study focuses on differences among phytoplankton
size fractions characterised by their surface area to volume ratio ([mm2 l−1: mm3l−1]), pigment distribution patterns and photosynthetic rates. Particular attention was paid to autotrophic picophytoplankton
(APP, fraction <2 μm) since this size fraction differed significantly from the two larger size fractions. Among the three
fractions, APP showed the highest surface area to volume ratios and a high persistence in the pattern of lipophilic pigments
between temporarily and spatially successive samples (about 80% similarity of pigment composition between samples over seasons
and depths). The epilimnetic abundance of APP varied seasonally with an annual maximum of 180 × 103 cells ml−1 in June (at 4–9 m). The minimum (October at 12 m) was more than an order of magnitude lower (4.9 × 103 ml−1). APP peaked during autumn and contributed between 24% and 42% to the total area-integrated Chl a (10–23 mg m−2) and between 16% and 58% to total area-integrated production (5–64 mg m−2 h−1) throughout seasons. 相似文献
14.
The effect of heavy ion radiation exposure of the spinal cord on the properties of the motoneurons innervating the slow soleus
and fast plantaris muscles was investigated. A 15-, 20-, 40-, 50-, or 70-Gy dose of carbon ions (5 Gy/min) was applied to
the 2nd to the 6th lumbar segments of the spinal cord in rats. After a 1-month recovery period, the number and cell body size
of the irradiated motoneurons innervating the soleus and plantaris muscles did not differ from that of the non-irradiated
controls, irrespective of the dose received. However, the oxidative enzyme activity of these motoneurons was decreased by
heavy ion radiation at doses of 40, 50, and 70 Gy compared to that of the non-irradiated controls. This decrease in oxidative
enzyme activity levels in the motoneurons returned to that of the non-irradiated controls after a 6-month recovery period.
We conclude that heavy ion radiation at doses of 40–70 Gy reversibly decreases the oxidative enzyme activity of motoneurons
in the spinal cord of rats. 相似文献
15.
Francesco Cilurzo Francesca Selmin Paola Minghetti Luisa Montanari 《AAPS PharmSciTech》2008,9(4):1136-1142
This study aimed to design methyprednisolone (MP)-loaded poly(d,l lactide-co-glycolide) (PLGA) microspheres (MS) intended for intra-articular administration. MP was encapsulated in four different
types of PLGA by using an S/O/W technique. The effects of β-irradiation at the dose of 25 kGy were evaluated on the chemical
and physicochemical properties of MS and the drug release profiles. The S/O/W technique with hydroxypropylmethylcellulose
(HPMC) as surfactant allowed obtaining MS in the tolerability size (7–50 μm) for intra-articular administration. The MP encapsulation
efficiency ranged 56–60%. HPMC traces were evidenced in the loaded and placebo MS by attenuated total reflectance Fourier
transform infrared spectroscopy. MS made of the capped PLGA DL5050 2M (MS 2M) and uncapped PLGA DL5050 3A (MS 3A) prolonged
the release of MP over a 2- to 3-month period with a triphasic (burst release–dormant period–second release pulse) and biphasic
release pattern, respectively. The β-irradiation did not significantly alter the morphology, chemical, and physicochemical
properties of MS. The only variation was evidenced in the drug release for MS 2M in term of shorting of the dormant period.
The minimal variations in the properties of irradiated PLGA MS, which are in disagreement with literature data, may be attributed
to a radioprotecting effect exerted by HPMC. 相似文献
16.
Clemens Woda P. Jacob A. Ulanovsky I. Fiedler Y. Mokrov S. Rovny 《Radiation and environmental biophysics》2009,48(4):405-417
Recently discovered historical documents indicate that large releases of noble gases (mainly 41Ar and radioactive isotopes of Kr and Xe) from the Mayak Production Association (MPA) over the period from 1948 to 1956 may
have caused considerable external exposures of both, inhabitants of Ozyorsk and former inhabitants of villages at the upper
Techa River. To quantify this exposure, seven brick samples from three buildings in Ozyorsk, located 8–10 km north-northwest
from the radioactive gas release points, were taken. The absorbed dose in brick was measured in a depth interval of 3–13 mm
below the exposed surface of the bricks by means of the thermoluminescence (TL) and the optically stimulated luminescence
(OSL) method. Generally, luminescence properties using TL were more favorable for precise dose determination than using OSL,
but within their uncertainties the results from both methods agree well with each other. The absorbed dose due to natural
radiation was assessed and subtracted under the assumption of the bricks to be completely dry. The weighted average of the
anthropogenic dose for all samples measured by TL and OSL is 10 ± 9 and 1 ± 9 mGy, respectively. An upper limit for a possible
anthropogenic dose in brick that would not be detected due to the measurement uncertainties is estimated at 24 mGy. This corresponds
to an effective dose of about 21 mSv. A similar range of values is obtained in recently published dispersion calculations
that were based on reconstructed MPA releases. It is concluded that the release of radioactive noble gases from the radiochemical
and reactor plants at Mayak PA did not lead to a significant external exposure of the population of Ozyorsk. In addition,
the study demonstrates the detection limit for anthropogenic doses in ca. 60-year-old bricks to be about 24 mGy, if luminescence
methods are used. 相似文献
17.
Vávrová J Sinkorová Z Rezáčová M Tichý A Filip S Mokrý J Lukášová E 《Radiation and environmental biophysics》2012,51(2):205-213
In the work presented here, changes in haematopoiesis of mice (B6129SF2/J) were studied 1 year after their whole-body exposure
to a dose of 7 Gy (72% of mice survived). The irradiated mice were compared with non-irradiated younger (4 months of age)
and older (16 months of age) mice. There was a significant increase in the relative abundance of primitive stem cells with
long-term capability of the haematopoiesis recovery lin−/Sca-1+/CD117+/CD34− in the bone marrow of mice aged 16 months (irradiated and non-irradiated) compared with those aged 4 months. In terms of
the ability to respond to further whole-body irradiation at a dose of 1 Gy, the presence of γH2A.X foci was studied in lin− bone marrow cells. There was a considerable number of persisting foci in lin− stem cells isolated from the bone marrow of the older irradiated mice. In the blood count from the peripheral blood of the
older mice (both non-irradiated and irradiated at 7 Gy), there was a significant increase in granulocytes. In the group exposed
to 7 Gy, the numbers of thrombocytes significantly increased, and on the contrary, the numbers of erythrocytes, the amount
of haemoglobin, and haematocrit significantly decreased. 相似文献
18.
Ana?L.?Di Virgilio Josefina?Rivadeneira Cecilia?I.?Muglia Miguel?A.?Reigosa Nataliya?Butenko Isabel?Cavaco Susana?B.?Etcheverry
The complex of vanadyl(IV) cation with oxodiacetate, VO(oda) caused an inhibitory effect on the proliferation of the human
colon adenocarcinoma cell line Caco-2 in the range of 25–100 μM (P < 0.001). This inhibition was partially reversed by scavengers of free radicals. The difference in cell proliferation in
the presence and the absence of scavengers was statistically significant in the range of 50–100 μM (P < 0.05). VO(oda) altered lysosomal and mitochondria metabolisms (neutral red and MTT bioassays) in a dose–response manner
from 10 μM (P < 0.001). Morphological studies showed important transformations that correlated with the disassembly of actin filaments
and a decrease in the number of cells in a dose response manner. Moreover, VO(oda) caused statistically significant genotoxic
effects on Caco-2 cells in the low range of concentration (5–25 μM) (Comet assay). Increment in the oxidative stress and a
decrease in the GSH level are the main cytotoxic mechanisms of VO(oda). These effects were partially reversed by scavengers
of free radicals in the range of 50–100 μM (P < 0.05). Besides, VO(oda) interacted with plasmidic DNA causing single and double strand cleavage, probably through the action
of free radical species. Altogether, these results suggest that VO(oda) is a good candidate to be evaluated for alternative
therapeutics in cancer treatment. 相似文献
19.
Yoo L Gupta V Lee C Kavehpore P Demer JL 《Biomechanics and modeling in mechanobiology》2011,10(6):901-914
Reported mechanical properties of orbital connective tissue and fat have been too sparse to model strain–stress relationships
underlying biomechanical interactions in strabismus. We performed rheological tests to develop a multi-mode upper convected
Maxwell (UCM) model of these tissues under shear loading. From 20 fresh bovine orbits, 30 samples of connective tissue were
taken from rectus pulley regions and 30 samples of fatty tissues from the posterior orbit. Additional samples were defatted
to determine connective tissue weight proportion, which was verified histologically. Mechanical testing in shear employed
a triborheometer to perform: strain sweeps at 0.5–2.0 Hz; shear stress relaxation with 1% strain; viscometry at 0.01−0.5 s−1 strain rate; and shear oscillation at 1% strain. Average connective tissue weight proportion was 98% for predominantly connective
tissue and 76% for fatty tissue. Connective tissue specimens reached a long-term relaxation modulus of 668 Pa after 1,500 s,
while corresponding values for fatty tissue specimens were 290 Pa and 1,100 s. Shear stress magnitude for connective tissue
exceeded that of fatty tissue by five-fold. Based on these data, we developed a multi-mode UCM model with variable viscosities
and time constants, and a damped hyperelastic response that accurately described measured properties of both connective and
fatty tissues. Model parameters differed significantly between the two tissues. Viscoelastic properties of predominantly connective
orbital tissues under shear loading differ markedly from properties of orbital fat, but both are accurately reflected using
UCM models. These viscoelastic models will facilitate realistic global modeling of EOM behavior in binocular alignment and
strabismus. 相似文献
20.
Samantaray S Smith JA Das A Matzelle DD Varma AK Ray SK Banik NL 《Neurochemical research》2011,36(10):1809-1816
Spinal cord injury (SCI), depending on the severity of injury, leads to neurological dysfunction and paralysis. Methylprednisolone,
the only currently available therapy renders limited protection in SCI. Therefore, other therapeutic agents must be tested
to maximize neuroprotection and functional recovery. Previous data from our laboratory indicate that estrogen (17β-estradiol)
at a high dose may attenuate multiple damaging pathways involved in SCI and improve locomotor outcome. Since use of high dose
estrogen may have detrimental side effects and therefore may never be used in the clinic, the current study investigated the
efficacy of this steroid hormone at very low doses in SCI. In particular, we tested the impact of dosing (1–10 μg/kg), mode
of delivery (intravenous vs. osmotic pump), and delay in estrogen application (15 min–4 h post-SCI) on microgliosis and neuronal
death in acute SCI in rats. Treatment with 17β-estradiol (1–10 μg/kg) significantly reduced microglial activation and also
attenuated apoptosis of neurons compared to untreated SCI animals. The attenuation of cell death and inflammation by estrogen
was observed regardless of mode and time of delivery following injury. These findings suggest estrogen as a potential agent
for the treatment of individuals with SCI. 相似文献