Estimation of neutron and other radiation exposure components in low earth orbit

The interaction of high-energy space radiation with spacecraft materials generates a host of secondary particles, some, such as neutrons, are more biologically damaging and penetrating than the original primary particles. Before committing astronauts to long term exposure in such high radiation environments, a quantitative understanding of the exposure and estimates of the associated risks are required. Energetic neutrons are traditionally difficult to measure due to their neutral charge. Measurement methods have been limited by mass and weight requirements in space to nuclear emulsion, activation foils, a limited number of Bonner spheres, and TEPCs. Such measurements have had limited success in quantifying the neutron component relative to the charged components. We will show that a combination of computational models and experimental measurements can be used as a quantitative tool to evaluate the radiation environment within the Shuttle, including neutrons. Comparisons with space measurements are made with special emphasis on neutron sensitive and insensitive devices.

Medium modified two-body scattering amplitude from proton-nucleus total cross-sections

Recently (R.K. Tripathi, J.W. Wilson, F.A. Cucinotta, Nucl. Instr. and Meth. B 145 (1998) 277; R.K. Tripathi, F.A. Cucinotta, J.W. Wilson, NASA-TP-1998-208438), we have extracted nucleon-nucleon (N-N) cross-sections in the medium directly from experiment. The in-medium N-N cross-sections form the basic ingredients of several heavy-ion scattering approaches including the coupled-channel approach developed at the NASA Langley Research Center. Here, we investigate the ratio of real to imaginary part of the two-body scattering amplitude in the medium. These ratios are used in combination with the in-medium N-N cross-sections to calculate total proton-nucleus cross-sections. The agreement is excellent with the available experimental data. These cross-sections are needed for the radiation risk assessment of space missions.

Persistent airway T-lymphocyte activation in chronic corticosteroid-treated symptomatic asthma

BACKGROUND

A small proportion of patients with asthma have persistent symptoms despite regular treatment with high-dose inhaled and/or oral corticosteroids. There is little information regarding immunopathology in such patients.

OBJECTIVE

To compare airway inflammatory changes in subjects with chronic corticosteroid-dependent symptomatic asthma (n = 5) and subjects with asthma that was clinically well controlled on inhaled corticosteroid therapy (n = 9). Subjects in the corticosteroid-dependent group were receiving long-term treatment with oral prednisolone and high-dose inhaled corticosteroids.

METHODS

Subjects underwent fiberoptic bronchoscopy with bronchoalveolar lavage (BAL) and bronchial biopsy. T-lymphocytes subsets and activation markers in BAL fluid and peripheral blood were determined by FACS analysis. Bronchial biopsies were stained immunohistochemically, and numbers of inflammatory cells quantitated. Inflammatory mediators in BAL fluid were measured by immunoassay.

RESULTS

There was significantly greater expression of CD25 (P = .02) and HLA-DR (P = .04) by BAL fluid T-lymphocytes in corticosteroid-treated symptomatic asthmatics. In bronchial biopsies there were no significant differences between the two groups in the numbers of AA1+ cells (mast cells), EG2+ cells (eosinophils) or MT1+ T-lymphocytes. Levels of albumin, histamine, tryptase, and eosinophil cationic protein in BAL fluid did not differ significantly between groups.

CONCLUSIONS

Chronic corticosteroid-treated symptomatic asthma is associated with persistent airway T-lymphocyte activation. This, however, is not necessarily accompanied by the recruitment and activation of inflammatory cells within the airways.

Overview of radiation environments and human exposures

Human exposures to ionizing radiation have been vastly altered by developing technology in the last century. This has been most obvious in the development of radiation generating devices and the utilization of nuclear energy. But even air travel has had its impact on human exposure. Human exposure increases with advancing aircraft technology as a result of the higher operating altitudes reducing the protective cover provided by Earth's atmosphere from extraterrestrial radiations. This increase in operating altitudes is taken to a limit by human operations in space. Less obvious is the changing character of the radiations at higher altitudes. The associated health risks are less understood with increasing altitude due to the increasing complexity and new field components found in high-altitude and space operations.

Radiation exposure for human Mars exploration

One major obstacle to human space exploration is the possible limitations imposed by the adverse effects of long-term exposure to the space environment. Even before human space flight began, the potentially brief exposure of astronauts to the very intense random solar energetic particle events was of great concern. A new challenge appears in deep-space exploration from exposure to the low-intensity heavy-ion flux of the galactic cosmic rays since the missions are of long duration, and accumulated exposures can be high. Because cancer induction rates increase behind low to moderate thicknesses of aluminum shielding, according to available biological data on mammalian exposures to galactic cosmic ray-like ions, aluminum shield requirements for a Mars mission may be prohibitively expensive in terms of mission launch costs. Alternative materials for vehicle construction are under investigation to provide lightweight habitat structures with enhanced shielding properties. In the present paper, updated estimates for astronaut exposures on a Mars mission are presented and shielding properties of alternative materials are compared with aluminum.

In vivo modulation of CYP enzymes by quinidine and rifampin

BACKGROUND

The metabolism of drugs and other xenobiotics is mediated by enzymes whose activities can be modulated by different compounds. The activities of these modulators have the potential to be used to optimize drug action, prevent toxicity, or identify the enzymes involved in a reaction. This approach requires that selective agents be used for specific enzymes. However, selectivity of action has been poorly characterized in vivo.

METHODS

This study investigated the effect of 3 and 28 days of treatment with quinidine (200 mg daily) and rifampin (INN, rifampicin) (600 mg daily) on the activities of four cytochrome P450 enzymes and N-acetyltransferase in 28 healthy young male volunteers divided into three groups with a cocktail of drug probes used, including caffeine, mephenytoin, debrisoquin (INN, debrisoquine), and dapsone.

RESULTS

Quinidine selectively and almost completely inhibited the activity of CYP2D6 from day 3 through day 28 without affecting any other enzymes. Rifampin showed evidence of time-dependent induction of the activities of all measured oxidative routes of metabolism but decreased the acetylation ratio in fast acetylators. The quinidine/rifampin combination resulted in selective CYP2D6 inhibition and induction of all other enzymes evaluated over this time period, suggesting that predictable complex interactions occur with the drug combination.

CONCLUSIONS

These observations illustrate the value of simultaneous assessment of the effect of modulators on the activities of multiple specific enzymes with the drug cocktail approach.

The effect of exogenous prostaglandin administration on tumor size and yield in Min/+ mice

This study set out to examine the effect of exogenous prostaglandin (PG) administration on tumor development in Min/+ mice. Mice were treated with the stable prostaglandin E2 analogue 16,16-dimethyl-PGE2 from 6-18 weeks of age. Mice were sacrificed, and tumor burden was assessed using morphometric techniques. Parameters measured were median tumor size, mean tumor size, the proportion of the area of the gastrointestinal mucosa covered with tumor, and the number of tumors per 1000 mm2 of gastrointestinal mucosa. In addition, proliferative and apoptotic indices were determined. These measurements were carried out for all regions of the small intestine (i.e., duodenum, jejunum, upper ileum, and lower ileum) and the large intestine (i.e., cecum and mid-colon/rectum). 16,16-Dimethyl-PGE2-treated animals showed a significant decrease in tumor burden (by approximately 50-70%), in comparison with those animals that were treated with vehicle alone (0.001% ethanol in 0.9% sterile saline), in all regions of the intestine (at P = 0.008 or better). This effect was contributed to by a reduction in the number of tumors (by approximately 20-50%) and a reduction in tumor size (by approximately 10-70%). An increase in tumor cell turnover was associated with this decrease in tumor burden, as determined by the changes in the levels of thymidine incorporation (significant at P = 0.003), apoptosis, and mitosis (nonsignificant).

A physician's primer to antiretroviral drug resistance testing

Evaluating the genetic composition of HIV has evolved from a traditional epidemiologic research tool into a widely used clinical asset in the management of HIV infection. Genotypic and phenotypic testing is designed to identify drugs less likely to be therapeutically effective. Genotypic assays identify specific "gene mutations" or nucleotide substitutions known to confer drug resistance, whereas phenotypic assays measure the amount of drug necessary to inhibit viral replication in vitro. Prospective studies of antiretroviral drug resistance testing have shown its value as an independent predictor of optimal virologic response to drug therapy. Current guidelines recommend use of these tests following treatment failure and during pregnancy; considerations for testing include primary infection and treatment-naive patients. The identification of drug resistance can help the clinician individualize treatment regimens to attain maximal viral suppression and patient longevity.

Comparative evaluation of three human immunodeficiency virus genotyping systems: the HIV-GenotypR method, the HIV PRT GeneChip assay, and the HIV-1 RT line probe assay

Evaluation of drug resistance by human immunodeficiency virus (HIV) genotyping has proven to be useful for the selection of drug combinations with maximum antiretroviral activity. We compared three genotyping methods for identification of mutations known to confer drug resistance in the reverse transcriptase (RT) and protease genes of HIV type 1 (HIV-1). The HIV-GenotypR method (GenotypR; Specialty Laboratories, Inc., Santa Monica, Calif.) with the ABI 377 DNA sequencer (Applied Biosystems Inc.), the HIV PRT GeneChip assay (GeneChip; Affymetrix, Santa Clara, Calif.), and the HIV-1 RT Line Probe Assay (LiPA; Innogenetics, Alpharetta, Ga.) were used to genotype plasma samples from HIV-infected patients attending the University of Wisconsin Hospitals and Clinics and the Mayo Clinic. At the time of analysis, patients were failing combination therapy (n = 18) or were treatment naive (n = 6). Forty codons of the RT and protease genes were analyzed by GenotypR and GeneChip for resistance-associated mutations. LiPA analyzed seven RT codons for mutations. Each sample was genotyped by all three assays, and each assay was subjected to pairwise comparisons. At least 92% of the codons tested (by the three assays) in paired comparisons were concordant. GenotypR and GeneChip demonstrated 96.6% concordance over the 40 codons tested. GenotypR identified slightly more mutations than GeneChip and LiPA; GeneChip identified all primary mutations that corresponded to failing treatment regimens. Each assay identified at least 84% of the mutations identified by the other assays. Mutations that were discordant between the assays mainly comprised secondary mutations and natural polymorphisms. The assays had better concordance for mutations that corresponded to current failing regimens, present in the more predominant viral quasispecies. In the treatment-naive patients, GenotypR, GeneChip, and LiPA mainly identified wild-type virus. Only the LiPA identified K70R, a possible transmitted zidovudine resistance mutation, in the RT gene of a treatment-naive patient. We conclude that although discrepancies in results exist between assays, each assay showed a similar capacity to identify potentially clinically relevant mutations related to patient treatment regimens.

Plasma granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor levels in critical illness including sepsis and septic shock: relation to disease severity, multiple organ dysfunction, and mortality

OBJECTIVE

To define the circulating levels of granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) during critical illness and to determine their relationship to the severity of illness as measured by the Acute Physiology and Chronic Health Evaluation (APACHE) II score, the development of multiple organ dysfunction, or mortality.

DESIGN

Prospective cohort study.

SETTING

University hospital intensive care unit.

PATIENTS

A total of 82 critically ill adult patients in four clinically defined groups, namely septic shock (n = 29), sepsis without shock (n = 17), shock without sepsis (n = 22), and nonseptic, nonshock controls (n = 14).

INTERVENTIONS

None.

MEASUREMENT AND MAIN RESULTS

During day 1 of septic shock, peak plasma levels of G-CSF, interleukin (IL)-6, and leukemia inhibitory factor (LIF), but not GM-CSF, were greater than in sepsis or shock alone (p < .001), and were correlated among themselves (rs = 0.44-0.77; p < .02) and with the APACHE II score (rs = 0.25-0.40; p = .03 to .18). G-CSF, IL-6, and UF, and sepsis, shock, septic shock, and APACHE II scores were strongly associated with organ dysfunction or 5-day mortality by univariate analysis. However, multiple logistic regression analysis showed that only septic shock remained significantly associated with organ dysfunction and only APACHE II scores and shock with 5-day mortality. Similarly, peak G-CSF, IL-6, and LIF were poorly predictive of 30-day mortality.

CONCLUSIONS

Plasma levels of G-CSF, IL-6, and LIF are greatly elevated in critical illness, including septic shock, and are correlated with one another and with the severity of illness. However, they are not independently predictive of mortality, or the development of multiple organ dysfunction. GM-CSF was rarely elevated, suggesting different roles for G-CSF and GM-CSF in human septic shock.

Natural transfer of viable microbes in space

The possibility and probability of natural transfer of viable microbes from Mars to Earth and Earth to Mars traveling in meteoroids during the first 0.5 Ga and the following 4 Ga are investigated, including: --radiation protection against the galactic cosmic ray nuclei and the solar rays, dose rates as a function of the meteorite's radial column mass (radius x density), combined with dose rates generated by natural radioactivity within the meteorite; and survival curves for some bacterial species using NASA's HZETRN transport code --other factors affecting microbe survival: vacuum; central meteorite temperatures at launch, orbiting, and arrival; pressure and acceleration at launch; spontaneous DNA decay; metal ion migration --mean sizes and numbers of unshocked meteorites ejected and percentage falling on Earth, using current semiempirical results --viable flight times for the microbe species Bacillus subtilis and Deinococcus radiodurans R1 --the approximate fraction of microbes (with properties like the two species studied) viably arriving on Earth out of those ejected from Mars during the period 4 Ga BP to the present time, and during the 700 Ma from 4.5 to 3.8 Ga. Similarly, from Earth to Mars. The conclusion is that if microbes existed or exist on Mars, viable transfer to Earth is not only possible but also highly probable, due to microbes' impressive resistance to the dangers of space transfer and to the dense traffic of billions of martian meteorites which have fallen on Earth since the dawn of our planetary system. Earth-to-Mars transfer is also possible but at a much lower frequency.

Analysis of MIR-18 results for physical and biological dosimetry: radiation shielding effectiveness in LEO

We compare models of radiation transport and biological response to physical and biological dosimetry results from astronauts on the Mir space station. Transport models are shown to be in good agreement with physical measurements and indicate that the ratio of equivalent dose from the Galactic Cosmic Rays (GCR) to protons is about 3/2:1 and that this ratio will increase for exposures to internal organs. Two biological response models are used to compare to the Mir biodosimetry for chromosome aberration in lymphocyte cells; a track-structure model and the linear-quadratic model with linear energy transfer (LET) dependent weighting coefficients. These models are fit to in vitro data for aberration formation in human lymphocytes by photons and charged particles. Both models are found to be in reasonable agreement with data for aberrations in lymphocytes of Mir crew members: however there are differences between the use of LET dependent weighting factors and track structure models for assigning radiation quality factors. The major difference in the models is the increased effectiveness predicted by the track model for low charge and energy ions with LET near 10 keV/micrometers. The results of our calculations indicate that aluminum shielding, although providing important mitigation of the effects of trapped radiation, provides no protective effect from the galactic cosmic rays (GCR) in low-earth orbit (LEO) using either equivalent dose or the number of chromosome aberrations as a measure until about 100 g/cm 2 of material is used.

A comparison of the multigroup and collocation methods for solving the low-energy neutron Boltzmann equation

A low-energy neutron transport algorithm for use in space-radiation protection is developed. The algorithm is based upon a multiple energy group analysis of the straight ahead Boltzmann equation utilizing a mean value theorem for integrals. The algorithm developed is then verified by using a collocation method solution on the same straight ahead Boltzmann equation. This algorithm was then coupled to the existing NASA Langley HZETRN (high charge and energy transport) code through the evaporation source term. Evaluation of the neutron fluence generated by the February 23, 1956 solar particle event for an aluminum-water shield-target configuration is then compared with the LAHET Monte Carlo calculation for the same shield-target configuration. The algorithm developed showed a great improvement in results over the unmodified HZETRN solution. A bidirectional modification of the evaporation source produced further improvement of the fluence.

Cosmic ray hits in the central nervous system at solar maximum

It has been suggested that a manned mission to Mars be launched at solar maximum rather than at solar minimum to minimize the radiation exposure to galactic cosmic rays. It is true that the number of hits from highly ionizing particles to critical regions in the brain will be less at solar maximum, and it is of interest to estimate how much less. We present here calculations for several sites within the brain from iron ions (z = 26) and from particles with charge, z, greater than or equal to 15. The same shielding configurations and sites in the brain used in an earlier paper for solar minimum are employed so that direct comparison of results between the two solar activity conditions can be made. A simple pressure-vessel wall and an equipment room onboard a spacecraft are chosen as shielding examples. In the equipment room, typical results for the thalamus are that the probability of any particles with 7 greater than or equal to 15 and from 2.3 percent to 1.3 percent for iron ions. The extra shielding provided in the equipment room makes little difference in these numbers. We conclude that this decrease in hit frequency (less than a factor of two) does not provide a compelling reason to avoid solar minimum for a manned mission to Mars. This conclusion could be revised, however, if a very small number of hits is found to cause critical malfunction within the brain.

Bcl-w expression in colorectal adenocarcinoma

We have found that the anti-apoptotic Bcl-2 family protein, Bcl-w, was frequently expressed in colorectal adenocarcinomas, with 69/75 showing positive staining with anti-Bcl-w IgG. Adenomas demonstrated a much lower frequency of Bcl-w expression (only 1 of 17), as did adenocarcinomas from other epithelial tissues such as breast (0/8), stomach (1112) and cervix (0/12). Bcl-w status could be related to the histopathological classification of the tumours, with TNM stage III tumours showing significantly higher levels of expression than tumours of better prognostic grade (at P = 0.009). Those patients with node involvement also had tumours with significantly elevated levels of Bcl-w (at P = 0.02), compared to those which were node-negative. The results suggest that Bcl-w could play a general role in the progression from adenoma to adenocarcinoma in the colorectal epithelium. Currently, more data are being collected to allow us to assess the importance of Bcl-w for disease progression and patient survival.

Effectiveness of antipsychotic therapy in a naturalistic setting: a comparison between risperidone, perphenazine, and haloperidol

BACKGROUND

Therapeutic ineffectiveness and noncompliance with antipsychotic agents are major contributors to rehospitalization in patients with psychotic disorders. It is unknown whether risperidone's favorable side effect profile compared with that of the conventional antipsychotics results in improved compliance and reduced hospitalizations in a naturalistic setting. The purpose of this study was to test the hypothesis that treatment with risperidone reduces readmission rates and associated costs when compared with treatment with perphenazine or haloperidol.

METHOD

Inpatients prescribed either risperidone, perphenazine, or haloperidol between January 1, 1995, and December 31, 1995, as a single oral antipsychotic at discharge were retrospectively identified. Data were collected for that index hospitalization and for a 1-year follow-up period. Primary outcome measures included re-admission rates, changes in antipsychotic therapy, anticholinergic drug use, and costs.

RESULTS

There were 202 evaluable patients (81 treated with risperidone, 78 with perphenazine, and 43 with haloperidol). Baseline demographics were similar between groups except that more patients in the risperidone group had a primary diagnosis of psychotic disorder or had been hospitalized in the year prior to study. The percentage of patients readmitted during the 1-year follow-up period was similar among drug groups (41% risperidone, 26% perphenazine, and 35% haloperidol) when controlled for baseline differences in diagnosis and hospitalization history (p = .32). Anticholinergic drug use was more common in the haloperidol group (p = .004). Mean yearly cost (drug + hospitalization) in the risperidone group was $20,317, nearly double that in the other treatment groups (p < .001).

CONCLUSION

The results from this naturalistic study indicate that the high cost of risperidone is not offset by a reduction in readmission rates when compared with conventional antipsychotics.

An antiinflammatory effect of salmeterol, a long-acting beta(2) agonist, assessed in airway biopsies and bronchoalveolar lavage in asthma

The addition of long-acting beta(2) agonists to inhaled corticosteroid (ICS) therapy in symptomatic patients with asthma improves clinical status more than increasing the dose of ICS. It has been suggested that these benefits could be at the cost of an increase in airway inflammation, but few histopathological studies have been performed in the relevant group. In a double-blind, parallel-group, placebo-controlled study, we randomly assigned 50 symptomatic patients with asthma who were receiving ICS (range, 100 -500 microgram/d) to 12 wk of supplementary treatment with salmeterol (50 microgram twice daily) or fluticasone (100 microgram twice daily) or placebo. Bronchial biopsies and BAL were obtained from 45 patients before and after treatment and analyzed. After treatment with salmeterol there was no deterioration of airway inflammation as assessed by mast cells, lymphocytes, or macrophages in BAL or biopsies, but rather a significant fall in EG1-positive eosinophils in the lamina propria (from a median 18.3 to 7.6 cells/mm, p = 0.01), which was not seen after treatment with fluticasone. The only cellular effect of added fluticasone was a decrease in BAL lymphocyte activation. There was a concurrent improvement in clinical status, more marked with salmeterol than with increased ICS. Thus, adding salmeterol to ICS is not associated with increased "allergic" airway inflammation, but conversely with a complementary antieosinophil effect.

The lure of unconventional therapy for rheumatic disease: how powerful is it?

Patients who suffer rheumatologic disease are known to try unconventional therapies in addition to, or instead of, medical therapy prescribed by their provider. Reasons for this include the chronic nature of their illness, the adverse effects of conventional medications, and widespread publicity about the purported efficacy of unconventional therapies. We undertook this study to assess the types of unconventional therapies used by patients in one rheumatology practice. A survey comprising nine questions and a cover letter was mailed to 300 patients in the practice, asking them to rank, in order of perceived effectiveness, unconventional therapies they had used and the treatments provided by the rheumatologist. We determined that the prevalence of unconventional therapy use was 44% (response rate, 45% [135 patients]). Patients' faith, attributes of the physician, and medications prescribed by the physician were ranked more highly effective in the healing process than all other unconventional therapies. We conclude that, although unconventional therapies were utilized by patients in this practice, they valued the physician's medical treatment plan and efforts most.

Beta2-adrenergic receptor agonists and cAMP arrest human cultured airway smooth muscle cells in the G(1) phase of the cell cycle: role of proteasome degradation of cyclin D1

Hyperplasia of airway smooth muscle (ASM) contributes to the airway hyperresponsiveness that characterizes asthma. We have investigated the relationship between cAMP-induced growth arrest of ASM cells and thrombin-stimulated, extracellular-regulated protein kinase (ERK) activity, cyclin D1, and the restriction protein retinoblastoma. The beta(2)-adrenergic receptor agonist albuterol (100 nM) inhibited DNA synthesis after incubation with ASM for periods as brief as 1 h when these coincided with the timing of the restriction point. Inhibition of thrombin-stimulated DNA synthesis by albuterol (1-100 nM), 8-bromo-cAMP (300 microM), or prostaglandin E(2) (1 microM) was accompanied by a reduction in cyclin D1 protein levels. The ERK kinase inhibitor PD98059 (3-30 microM) attenuated thrombin-stimulated ERK phosphorylation and activity and the increase in cyclin D1 protein levels, as did albuterol (1-100 nM) or 8-bromo-cAMP (300 microM). In contrast, neither albuterol (100 nM) nor PD98059 (30 microM) reduced cyclin D1 mRNA levels between 4 and 20 h after thrombin addition, which suggests that elevation of cAMP regulates cyclin D1 by a post transcriptional mechanism. The proteasome inhibitor MG132 (30 and 100 nM) and the calpain I inhibitor N-acetyl-Leu-Leu-leucinal (10 microM) attenuated the reduction in thrombin-stimulated cyclin D1 levels in ASM exposed to albuterol (100 nM), 8-bromo-cAMP (300 microM), or the phosphodiesterase inhibitor isobutylmethylxanthine (100 microM). Thus, the cAMP-induced arrest of ASM in the G(1) phase of the cell cycle is associated with a proteasomal degradation of cyclin D1 protein and a reduced protein retinoblastoma phosphorylation that prevents passage through the restriction point.

Accurate universal parameterization of absorption cross sections III--light systems

Our prior nuclear absorption cross sections model [R.K. Tripathi, F.A. Cucinotta, J.W. Wilson, Nucl. Instr. and Meth. B 117 (1996) 347; R.K. Tripathi, J.W. Wilson, F.A. Cucinotta, Nucl. Instr. and Meth. B 129 (1997) 11] is extended for light systems (A < or = 4) where either both projectile and target are light particles or one is light particle and the other is medium or heavy nucleus. The agreement with experiment is excellent for these cases as well. Present work in combination with our original model provides a comprehensive picture of absorption cross sections for light, medium and heavy systems. As a result the extended model can reliably be used in all studies where there is a need for absorption cross sections.

Glucocorticoids inhibit proliferation, cyclin D1 expression, and retinoblastoma protein phosphorylation, but not activity of the extracellular-regulated kinases in human cultured airway smooth muscle

We have previously shown that glucocorticoids inhibit mitogen-stimulated proliferation of human cultured airway smooth muscle (ASM) cells. The present study analyzed the effect of glucocorticoids on key regulatory pathways leading to passage of cells through the restriction point of the cell cycle, including those mediated by extracellular-regulated kinases (ERK) 1 and 2; the ERK upstream regulator MAPK kinase (MEK1); cyclin D1 levels; and levels and phosphorylation of retinoblastoma protein (pRb). Fluticasone propionate, a new inhaled glucocorticoid, was at least 10-fold more potent than dexamethasone in inhibiting thrombin-stimulated DNA synthesis and increases in cell number. Thrombin-stimulated increases in the levels and hyperphosphorylation of pRb were inhibited by glucocorticoids, which also reduced thrombin-stimulated cyclin D1 protein and messenger RNA (mRNA) levels. PD98059 (10 microM), an inhibitor of MEK1 activation, markedly attenuated thrombin stimulation of ERK activity and phosphorylation, DNA synthesis, and cyclin D1 levels. However, glucocorticoids had no effect on ERK activity or phosphorylation at 5 min, 2 h, or 12 h after addition of thrombin. In conclusion, glucocorticoid-induced reduction of cyclin D1 mRNA and protein levels, and of pRb phosphorylation, is sufficient to account for inhibition of ASM proliferation. Furthermore, these inhibitory effects of glucocorticoids on cyclin D1 and pRb occur on a component of the mitogen signaling cascade that is either downstream of or parallel to the ERK pathway.

Shielding from solar particle event exposures in deep space

The physical composition and intensities of solar particle event exposures of sensitive astronaut tissues are examined under conditions approximating an astronaut in deep space. Response functions for conversion of particle fluence into dose and dose equivalent averaged over organ tissues are used to establish significant fluence levels and the expected dose and dose rates of the most important events from past observations. The BRYNTRN transport code is used to evaluate the local environment experienced by sensitive tissues and used to evaluate bioresponse models developed for use in tactical nuclear warfare. The present results will help to clarify the biophysical aspects of such exposure in the assessment of RBE and dose rate effects and their impact on design of protection systems for the astronauts. The use of polymers as shielding material in place of an equal mass of aluminum would provide a large safety factor without increasing the vehicle mass. This safety factor is sufficient to provide adequate protection if a factor of two larger event than has ever been observed in fact occurs during the mission.

A Phase I trial of calcitriol (1,25-dihydroxycholecalciferol) in patients with advanced malignancy

Vitamin D is a steroid hormone best known for its activity in regulating calcium and bone metabolism. Epidemiological evidence suggests that vitamin D may play a role in inhibiting the development of colon and prostate cancer. Vitamin D receptors are expressed in many types of malignant cells; in vitro and in vivo vitamin D and vitamin D analogues are active in suppressing the development and inhibiting the growth of numerous human and animal tumors. The major toxicity of the active form of vitamin D, 1,25-dihydroxycholecalciferol (calcitriol), is the induction of hypercalcemia. There are no data indicating the maximum tolerated dose of calcitriol administered every other day (QOD) s.c. We hypothesized that this route and schedule would permit administration of higher doses of calcitriol, which might have anticancer activity. We conducted a Phase I trial of calcitriol given s.c. QOD in patients with advanced solid tumors. Thirty-six patients were entered at doses ranging from 2 to 10 microg QOD; dose-limiting toxicity (hypercalcemia) occurred in three of three patients entered at the 10-microg QOD dose. Hypercalciuria occurred at all dose levels examined. No other toxicity was seen. Assessment of serum calcitriol concentrations by a RIA revealed a decrease in concentration-time curves on day 7 compared to day 1 of therapy. A dose-dependent increase in peak serum level and estimated area under the concentration-time curve was seen. The maximum serum levels occurred at the 10-microg QOD dose: 288 +/- 74 and 321 +/- 36 pg/ml at days 1 and 7, respectively. The normal range of calcitriol serum concentration, determined using this assay, is 16-56 pg/ml. Serum calcitriol levels were maintained at near peak concentrations for at least 8 h following s.c. injection. This study indicates that substantial doses of calcitriol can be administered via this route with tolerable toxicity. Studies to explore approaches to ameliorate the hypercalcemia induced by calcitriol and to explore alternative schedules and interactions with other agents are warranted.

Medium modified nucleon-nucleon cross sections in a nucleus

A simple reliable formalism is presented for obtaining nucleon-nucleon cross sections within a nucleus in nuclear collisions for a given projectile and target nucleus combination at a given energy for use in transport, Monte Carlo and other calculations. The method relies on extraction of these values from experiments and has been tested for absorption experiments to give excellent results.