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Biomedical subjects

B E Lambert

Publications and source records attributed to B E Lambert.

At least 19 recordsLinked to original sources
PubMed2002

Uncertainties in dose coefficients for intakes of tritiated water and organically bound forms of tritium by members of the public.

The International Commission on Radiological Protection (ICRP) provides models for the calculation of doses from intakes of radionuclides, including intakes of tritium as tritiated water (HTO) or organically bound tritium (OBT). The ICRP models for HTO and OBT are explained and the assumptions made are examined. The reliability of dose estimates is assessed in terms of uncertainties in central estimates for population groups. The models consider intakes of HTO and OBT by ingestion and inhalation by adults and children and doses to the fetus following intakes by the mother. The analysis includes uncertainties in the absorption of OBT to blood, incorporation of tritium into OBT in body tissues, retention times in tissues, transfer to the fetus and the relative biological effectiveness (RBE) of tritium beta emissions compared with gamma rays. Heterogeneity of dose within tissues and cells is also considered. For intakes as HTO, dose is predominantly due to distribution and retention of HTO in body water and it was concluded that adult doses are reliable to within a factor of 2. For intakes of OBT, the extent of incorporation into OBT in body tissues results in greater uncertainties with estimates relying on animal data for selected compounds. The analysis indicated that adult doses from OBT can be considered to be known to within a factor of 3. Greater uncertainties in estimated doses for children and for in utero exposures were considered. Central values from the uncertainty analyses of doses for HTO and OBT were greater than the corresponding ICRP dose coefficients by about a factor of 2, mainly due to the inclusion of uncertainties in RBE for tritium. A detailed assessment of doses using appropriate parameters and considering uncertainties would be of particular importance in situations where the dose may approach dose limits or constraints. For exposures to known forms of OBT, specific dose assessments may be required.

Adult↗
PubMed1999

Chromosomal instability in haemopoietic cells of the foetus, mother and offspring after in utero irradiation of the CBA/Ca mouse.

PURPOSE: The present study was conducted to test the susceptibility of the mouse foetus to transmit chromosomal instability to the haemopoietic stem cells of offspring after in utero X-or plutonium-239-irradiation. MATERIALS AND METHODS: Pregnant CBA/Ca-mice were injected with 80 kBq/kg 239Pu or X-irradiated with 1 Gy X-rays on days 13 or 14 of gestation. CFU-A cultures were grown from haemopoietic stem cells sampled from foetal liver and the bone marrow from the offspring and from the mother. Non-clonal, unstable chromosomal aberrations were scored in metaphases from individual stem cell colonies. RESULTS: The relative excess (RE) of unstable chromosomal aberrations in foetal liver cells irradiated with 1 Gy X-rays increased from 1.6 at day 2 up to 2.7 at day 4 after irradiation. In the bone marrow cells from the mother, this value was 1.8 (average from cells sampled at days 3 and 14 after irradiation). After injection of the pregnant mice with 235Pu, the yield of unstable chromosomal aberrations per cell was 0.14+/-0.03 (RE approximately 10) in descendants of bone marrow cells from the mother, 0.11+/-0.02 (RE = 10) in descendants of foetal liver cells and 0.16+/-0.05 (RE = 10) in descendants of bone marrow cells from the offspring. CONCLUSIONS: From the numerical analysis of non-clonal, unstable aberrations in haemopoietic cells from the foetus, the mother and the offspring after in utero irradiation, it was concluded that in utero irradiation of the CBA/Ca mouse was not more efficient in inducing chromosomal instability in the offspring than in the foetus or the mother. All three cell populations exhibited a similar degree of unstable aberrations, both in terms of the absolute numbers of non-clonal aberrations and in terms of relative excess compared with unexposed controls.

Animals↗
PubMed1998

Standards for environmental, non-threshold, carcinogens: a comparison of the approaches used for radiation and for chemicals.

Environmental standards for ionising radiation and for chemical carcinogens have been developed independently of each other. Radiation standards have been derived by deciding upon what is an acceptable risk, and then finding the corresponding dose from the exposure/risk relationship-quantitative risk assessment (QRA). The extent and the quality of the exposure/risk data for radiation, and the authority of the recommendations of the International Commission on Radiological Protection (ICRP), have resulted in universally accepted guidance and standards. This is not the case for chemical, non-threshold carcinogens. Their carcinogenicity ranges from doubtful to well-established, the exposure/response data are generally of poor quality, and there is no authoritative international body analogous to the ICRP. For some of these carcinogens, some organisations have used QRA to derive environmental standards. Others consider the data inadequate for such an approach and have used more pragmatic methods. The problems associated with the various approaches used and the prospects of an integrated approach for both radiation and chemical carcinogens are discussed.

Carcinogens↗
PubMed1988

Single dose ciprofloxacin for the eradication of pharyngeal carriage of Neisseria meningitidis.

Single dose oral ciprofloxacin was given to all personnel in a naval training establishment as part of the management of an outbreak of meningococcal meningitis. Two thousand one hundred personnel received the drug and Neisseria meningitidis was eradicated from the pharynx of 97% of 570 who were swabbed two to four days later. In a cohort of 277 personnel who were followed for up to nine weeks, pharyngeal carriage was eliminated from 93% of 104 carriers. The overall prevalence of carriage fell from 19% to less than 1.5% as a result of the use of ciprofloxacin. Few side effects were encountered, compliance was good and meningococci resistant to the antibiotic were not found after therapy. A single oral dose of ciprofloxacin 500 mg eliminates pharyngeal carriage of N. meningitidis effectively and has few adverse reactions.

Carrier State↗
PubMed1986

Radiation effects in the lung.

This article outlines the principles of radiobiology that can explain the time of onset, duration, and severity of the complex reactions of the lung to ionizing radiation. These reactions have been assayed biochemically, cell kinetically, physiologically, and pathologically. Clinical and experimental data are used to describe the acute and late reactions of the lung to both external and internal radiation including pneumonitis, fibrosis and carcinogenesis. Acute radiation pneumonitis, which can be fatal, develops in both humans and animals within 6 months of exposure to doses greater than or equal to 8 Gy of low LET radiation. It is divisible into a latent period lasting up to 4 weeks; an exudative phase (3-8 weeks) and with an acute pneumonitic phase between 2 and 6 months. The latter is an inflammatory reaction with intra-alveolar and septal edema accompanied by epithelial and endothelial desquamation. The critical role of type II pneumonocytes is discussed. One favored hypothesis suggests that the primary response of the lung is an increase in microvascular permeability. The plasma proteins overwhelm the lymphatic and other drainage mechanisms and this elicits the secondary response of type II cell hyperplasia. This, in its turn, produces an excess of surfactant that ultimately causes the fall in compliance, abnormal gas exchange values, and even respiratory failure. The inflammatory early reaction may progress to chronic fibrosis. There is much evidence to suggest that pneumonitis is an epithelial reaction and some evidence to suggest that this early damage may not be predictive of late fibrosis. However, despite detailed work on collagen metabolism, the pathogenesis of radiation fibrosis remains unknown. The data on radiation-induced pulmonary cancer, both in man and experimental animals from both external and internal irradiation following the inhalation of both soluble and insoluble alpha and beta emitting radionuclides are reviewed. Emphasis is placed on the data showing that alpha emitters are at least an order of magnitude more hazardous than beta/gamma radiation and on recent data showing that the more homogeneous the irradiation of the lung, the greater is the carcinogenic hazard which contradicts the so-called "hot particle" theory.

Animals↗
PubMed1986

Translocation of 239Pu in mice following inhalation of sized 239PuO2.

This study showed that when SAS/4 mice were exposed to sized 239PuO2 only about 0.5% of the 239Pu was translocated from lung to other organs. The fraction of 239Pu translocated appeared to be independent of the particle size of the administered 239PuO2 within the range of AMADs investigated (0.8-2.2 microns). The distribution of translocated 239Pu was similar to that observed with other species in that most of the activity was associated with the lung-associated lymph nodes followed by bone and liver. The fraction of 239Pu translocated was comparable to that found in studies with rats (ICRP72) but less than that found in more extended studies with beagle dogs.

Aerosols↗
PubMed1986

Macrophage depletion of mouse lung following inhalation of 239PuO2.

Changes in the free-cell population of the lungs of two strains of mice (SAS/4 and CBA/H) were studied up to 4 months after inhalation exposure to a sized fraction of 239PuO2 particles (1.5 micron AMAD) to give initial alveolar depositions (IADs) ranging from 17 to 810 Bq. A sample of the free-cell population of the lung was recovered by bronchoalveolar lavage, and a radiometric method was used to estimate the total number of pulmonary alveolar macrophages (PAM) in the lung. The response of the lung to 239PuO2 was characterized by an initial, dose-dependent depression in the total number of PAM following an IAD as low as 50 Bq. At IADs greater than 150 Bq, the initial depression continued for longer, merging into a chronic phase in which the PAM were larger and were accompanied by a minor infiltration of leukocytes. These findings were confirmed by histology, which also revealed focal accumulations of Type II pneumocytes. The results indicate that inhaled alpha-emitting particles are effective at producing a depletion in the alveolar macrophage population at relatively low IADs and that chronic effects on the cells can be produced by higher concentrations.

Aerosols↗
PubMed1984

Retention of 239Pu in the mouse lung and estimation of consequent dose following inhalation of sized 239PuO2.

The retention of 239Pu in the lungs of SAS/4 mice following inhalation exposure to sized 239PuO2 particles is described. When the initial alveolar deposition (IAD) was less than 200 Bq, retention of 239Pu could be described by a two-component exponential expression, about 90% being cleared with a half-time of about 40 days and the remainder with a half-time of about 150 days. Similar amounts of 239Pu were retained up to 3 months with IADs greater than 800 Bq, but clearance was impaired thereafter, the half-time of the second component increasing to about 720 days. The retention of 239Pu was independent of the particle size of the administered 239PuO2. Studies of the retention of 239Pu by individual lobes indicated that there were intrinsic interlobar differences which were enhanced at higher IADs. Lung clearance was also studied by the measurement of 239Pu in feces excreted by groups of mice in the period immediately prior to sacrifice. The estimation of radiation dose to lung is discussed.

Aerosols↗
PubMed1983

Alveolar deposition of sized particles of 239PuO2 in the mouse.

Data on the alveolar deposition of 239PuO2 particles in the mouse are presented. It is shown that alveolar deposition falls with increasing activity median aerodynamic diameter (AMAD) over the range 0.6 to 2.4 microns. In the mouse, any peak in alveolar deposition must occur at an AMAD of less than 1 micron. Information is also provided on the relative lobar concentrations (RLCs) of 239PuO2. The RLC is greatest in the right apical lobe and increases quite sharply with AMAD. The RLCs of the other lobes of the right lung decline with AMAD. The RLC in the left lobe is relatively unaffected by AMAD.

Aerosols↗
PubMed1982

The effects of negative pions on spermatogonial survival in the mouse.

A study of the radiation effects of pi-mesons on the testes of the mouse has been carried out using the pion beam at the SRC Rutherford Laboratory. The cell killing effects on type B and intermediate spermatogonia have been assessed and compared with the effects of 20-0 kVp X rays, delivered at the same dose rate. It was found that not only did irradiation of the testes not disturb the kinetics of spermatogenesis, but also the RBE for pions measured in the Bragg peak and on the plateau was not significantly different from unity. The comparison of this result with those of others using other pion beams is discussed.

Animals↗
PubMed1981

A short term effect of homogeneous internal irradiation of the mouse lung with 170Tm2O3 particles.

The short term effects on the free macrophage population in the mouse lung, following inhalation of thulium-170 oxide, have been studied, with a view to using the system as a model with which to compare the short term effects of inhomogeneous alpha irradiation. The clearance and distribution of thulium-170 was followed up to 44 days post inhalation. The mice had an initial lung burden (+/- SE) of 6.7 +/- 0.5 microCi 170Tm/g of lung and the pattern of removal of this could be described by a single exponential of half time 31 +/- 4 days. This exposure resulted in a uniform dose of about 24 Gy to the lung. The macrophage population was studied by counting cells lavaged from the lungs at intervals over the period of the experiment. The lung burden of 170Tm2O3 was found to decrease the free macrophage numbers by about a factor of 2 in 14 days with some slight recovery at 6 weeks post inhalation. It was found that nearly 50% of the activity in the lung lobes was removed by the lavages and that this fraction remained constant throughout.

Aerosols↗
PubMed1979

A comparison of salbutamol and ritodrine when used to inhibit premature labour complicated by ante-partum haemorrhage.

A retrospective study was carried out in 26 patients in premature labour complicated by antepartum haemorrhage. Patients treated with the beta-adrenergic agonists, salbutamol or ritodrine, continued the pregnancy longer, had smaller subsequent blood losses, and delivered infants in better condition than patients no so treated. There was little difference between the effectiveness of either beta-adrenergic agonist.

Adult↗
PubMed1978

The effect of oral salbutamol on serum potassium and blood sugar.

Serum potassium and blood sugar concentrations were measured in six patients treated with oral salbutamol to inhibit premature labour. The fall in serum potassium and rise in blood sugar were variable and not present in every patient. The values returned to the normal range usually within 72 hours of continuous usage of the drug.

Albuterol↗
PubMed1978

Some effects of irradiation of mice in utero with tritiated compounds.

Mice have been exposed continuously, in utero, to tritiated water (via the maternal drinking water) or to tritiated thymidine (infused continuously into the mother). In both cases the patterns of labeling and subsequent loss of tritium over an extended period have been studied. The technique of infusion in unrestrained mice and its application in the production of fully tritium-labeled offspring is described in some detail. These fully labeled mice are being used to study a number of early and late effects, in particular, gonad cell effects and carcinogenesis, following this form of internal irradiation. Some preliminary results are presented. Similar results produced a homogeneous irradiation from tritiated water are also reported.

Animals↗