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31.
M McJury P D Tapper V P Cosgrove P S Murphy S Griffin M O Leach S Webb M Oldham 《Physics in medicine and biology》1999,44(10):2431-2444
It is well known that the experimental dosimetry of brachytherapy sources presents a challenge. Depending on the particular-dosimeter used, measurements can suffer from poor spatial resolution (ion chambers), lack of 3D information (film) or errors due to the presence of the dosimeter itself distorting the radiation flux. To avoid these problems, we have investigated the dosimetry of a clinical 192Ir source using a polyacrylamide gel (PAG) dosimeter. Experimental measurements of dose versus radial distance from the centre of the source (cross-line plots) were compared with calculations produced with a Nucletron NPS planning system. Good agreement was found between the planning system and gel measurements in planes selected for analysis. Gel dosimeter measurements in a coronal plane through the phantom showed a mean difference between measured absorbed dose and calculated dose of 0.17 Gy with SD = 0.13 Gy. Spatially, the errors at the reference point remain within one image pixel (1.0 mm). The use of polymer gel dosimetry shows promise for brachytherapy applications, offering complete, three-dimensional dose information, good spatial resolution and small measurement errors. Measurements close to the source, however, are difficult, due to some of the limiting properties of the polyacrylamide gel. 相似文献
32.
The neutrophil is a key player in immunity, and its activities are essential for the resolution of infections. Neutrophil-pathogen interactions usually trigger a large arsenal of antimicrobial measures that leads to the highly efficient killing of pathogens. In neutrophils, the phagocytic process, including the formation and maturation of the phagosome, is in many respects very different from that in other phagocytes. Although the complex mechanisms that coordinate the membrane traffic, oxidative burst, and release of granule contents required for the microbicidal activities of neutrophils are not completely understood, it is evident that they are unique and differ from those in macrophages. Neutrophils exhibit more rapid rates of phagocytosis and higher intensity of oxidative respiratory response than do macrophages. The phagosome maturation pathway in macrophages, which is linked to the endocytic pathway, is replaced in neutrophils by the rapid delivery of preformed granules to nonacidic phagosomes. This review describes the plasticity and dynamics of the phagocytic process with a special focus on neutrophil phagosome maturation. 相似文献
33.
P?Mallick J?Chakrabarti Mallick B?Guha AR?Khuda-BukhshEmail author 《BMC complementary and alternative medicine》2003,3(1):7
Background
Arsenic in groundwater and its accumulation in plants and animals have assumed a menacing proportion in a large part of West Bengal, India and adjoining areas of Bangladesh. Because of the tremendous magnitude of the problem, there seems to be no way to tackle the problem overnight. Efforts to provide arsenic free water to the millions of people living in these dreaded zones are being made, but are awfully inadequate. In our quest for finding out an easy, safe and affordable means to combat this problem, a homeopathic drug, Arsenicum Album-30, appears to yield promising results in mice. The relative efficacies of two micro doses of this drug, namely, Arsenicum Album-30 and Arsenicum Album-200, in combating arsenic toxicity have been determined in the present study on the basis of some accepted biochemical protocols. 相似文献34.
35.
目的数值模拟抗血管生成因子Angiostatin和Endostatin对肿瘤血管生成的影响。方法建立肿瘤内外血管生成的二维离散数学模型。模型耦合两种抗血管生成因子Angiostatin和Endostatin的抑制效应,数值模拟在促血管生成因子诱导下肿瘤微血管网生成,讨论血管生成抑制因子的影响。结果抗血管生成因子Angiostatin对肿瘤内外血管网络生成的速度和成熟度有抑制作用。抗血管生成因子Angiostatin和Endostatin耦合作用时,在肿瘤血管生成的早期有明显的抑制效应;在肿瘤血管生成的中后期,它们可以降低肿瘤血管化程度。结论本文模型能够较好的模拟抗血管生成因子Angiostatin和Endostatin对内皮细胞迁移和增殖的抑制作用。 相似文献
36.
Margaret E Loughnan Neville Nicholls Nigel J Tapper 《International journal of health geographics》2008,7(1):42
Background
Seasonal patterns in cardiac disease in the northern hemisphere are well described in the literature. More recently age and gender differences in cardiac mortality and to a lesser extent morbidity have been presented. To date spatial differences between the seasonal patterns of cardiac disease has not been presented. Literature relating to seasonal patterns in cardiac disease in the southern hemisphere and in Australia in particular is scarce. The aim of this paper is to describe the seasonal, age, gender, and spatial patterns of cardiac disease in Melbourne Australia by using acute myocardial infarction admissions to hospital as a marker of cardiac disease. 相似文献37.
Benzo[a]pyrene at an environmentally relevant dose is slowly absorbed by, and extensively metabolized in, tracheal epithelium 总被引:2,自引:0,他引:2
Gerde P; Muggenburg BA; Thornton-Manning JR; Lewis JL; Pyon KH; Dahl AR 《Carcinogenesis》1997,18(9):1825-1832
While tobacco smoke has been conclusively identified as a lung carcinogen,
there is much debate over which smoke constituent(s) are primarily
responsible for its carcinogenicity. Previous studies in our laboratory
suggested that highly lipophilic carcinogens are slowly absorbed in the
thicker epithelium of the conducting airways, potentially allowing for
substantial local metabolism. The bioactivation of polycyclic aromatic
hydrocarbons in airway epithelium may, hence, be important in tobacco
smoke-induced carcinogenesis. In the present study, the hypothesis of slow
absorption and substantial local metabolic activation of highly lipophilic
carcinogen in airway epithelium was tested in dogs. A single dose of
tritiated benzo[a]pyrene (BaP) dissolved in a saline/phospholipid
suspension was instilled in the trachea, just anterior to the carina. At
intervals of a few minutes up to 30 min over a 3-h period, blood samples
were drawn from the azygous vein, which drains the area around the point of
instillation, and from the systemic circulation. Tissue samples were taken
at the end of the experiment. The concentration of BaP with depth into the
tracheal mucosa was determined with autoradiography. BaP was slowly
absorbed into the trachea with a half-time of approximately 73 min, which
is consistent with diffusion-limited passage through the epithelium and
lead to local doses in the tracheal epithelium that were more than a
1000-fold those of other tissues. The long retention of BaP in the
epithelium provided the local metabolizing enzymes with high substrate
levels over a long period, resulting in extensive metabolism. At 3 h after
the exposure, 23% of the BaP-equivalent activity remained in the tracheal
mucosa. Of this fraction, 13% was parent compound, 28% was organic
extractable, 31% was water-soluble, and 28-7% of the instilled dose was
bound to tracheal tissues. These results explain the tendency of highly
lipophilic carcinogens, such as BaP, to induce tumors at the site of entry
and, furthermore, indicate that the highly lipophilic components of tobacco
smoke and polluted air may be the most important contributors to lung
tumors of the conducting airways.
相似文献
38.
MT Bardella N Molteni L Prampolini AM Giunta AR Baldassarri D Morganti PA Bianchi 《Archives of disease in childhood》1994,70(3):211-213
The use of follow up studies was evaluated in 128 patients with coeliac disease during their first visit to a department for adults. The original diagnosis had been made in childhood in all patients. Fifty eight (45%) of the subjects were following a gluten free diet, 23 (18%) were following a gluten free diet but with occasional gluten consumption, and 47 (37%) had adopted an unrestricted, gluten containing diet for a mean of 11.2 years. There was no correlation in individual subjects between the presence of symptoms, biochemical and immunological abnormalities, severity of histological findings, and the amount of dietary gluten, despite the greater frequency of symptoms in the group following an unrestricted diet than in the other two groups. Short stature and epilepsy with cerebral calcifications only occurred in patients following an unrestricted diet. As only diagnosis based on two or three biopsy samples and regular follow up correlated positively with dietary compliance, it is suggested that a histologically confirmed diagnosis of coeliac disease and regular lifelong follow up are essential in the management of these patients. 相似文献
39.
STOTT DJ; MCLELLAN AR; FINLAYSON J; CHU P; ALEXANDER WD 《QJM : monthly journal of the Association of Physicians》1991,78(1):77-84
The clinical and biochemical characteristics of 15 elderly patientswith low levels of thyrotrophin (TSH) (<0.1 mU/L) but normalfree tri-iodothyronine, (T3) and free thyroxine (T4) (groupS) were compared with 10 euthyroid subjects (group E) and 10hyperthyroid patients (group T). Free T3 and free T4 were significantlyhigher (p<0.05) in group S(6.3±0.5 and 18.6±1.0pmol/l, respectively) than in group E(4.6±0.3, 12.6+0.6).In common with elderly hyperthyroid patients (group T)patientsin group S had few signs or symptoms of thyrotoxocosis, butthe Wayne score (clinical index of hyperthyroidism) was higherin group S than in euthyroid subjects (p<0.05). Thyroid microsomal,thyrogolobulin or thyrotrophin receptor antibodies were commonin group T (n=9)but not in groups S(n=2) or E(n=1). This suggestsa low prevalence of Graves' disease in group S compared to groupT. Combined thyrotrophin releasing hormone (TRH; 200 µgi.v.) and gonadotrophin releasing hormone GnRH; 100 µgi.v.) tests were performed; no cases of low TSH due to hypopituitarismwere identified in group S. During a mean of 7.9 (412)months of observation TSH reverted to the normal range (>0.2mU/L)in 7 of 15 patients in group S; thyroid hormone concentrationsrose above the normal range in four, however, only two patientsrequired treatment for hyperthyroidism. It is unlikely thatthe suppressed TSH of patients in group S was due to mild thyroidhormone excess; although this is often a transitory phenomenon,these patients are at increased risk of developing overt hyperthyroidism. 相似文献
40.