Radiation transport modeling and assessment to better predict radiation exposure, dose, and toxicological effects to human organs on long duration space flights

NASA is very interested in improving its ability to monitor and forecast the radiation levels that pose a health risk to space-walking astronauts as they construct the International Space Station and astronauts that will participate in long-term and deep-space missions. Human exploratory missions to the moon and Mars within the next quarter century, will expose crews to transient radiation from solar particle events which include high-energy galactic cosmic rays and high-energy protons. Because the radiation levels in space are high and solar activity is presently unpredictable, adequate shielding is needed to minimize the deleterious health effects of exposure to radiation. Today, numerous models have been developed and used to predict radiation exposure. Such a model is the Space Environment Information Systems (SPENVIS) modeling program, developed by the Belgian Institute for Space Aeronautics. SPENVIS, which has been assessed to be an excellent tool in characterizing the radiation environment for microelectronics and investigating orbital debris, is being evaluated for its usefulness with determining the dose and dose-equivalent for human exposure. Thus far. the calculations for dose-depth relations under varying shielding conditions have been in agreement with calculations done using HZETRN and PDOSE, which are well-known and widely used models for characterizing the environments for human exploratory missions. There is disagreement when assessing the impact of secondary radiation particles since SPENVIS does a crude estimation of the secondary radiation particles when calculating LET versus Flux. SPENVIS was used to model dose-depth relations for the blood-forming organs. Radiation sickness and cancer are life-threatening consequences resulting from radiation exposure. In space. exposure to radiation generally includes all of the critical organs. Biological and toxicological impacts have been included for discussion along with alternative risk mitigation methods--shielding and anti-carcinogens.

Comorbidity of psychiatric and substance use disorders in late adolescence: a cluster analytic approach

Cluster analysis was used to identify subgroups of youths with past-year substance and/or psychiatric disorders (N = 110, mean age 19.0 years). Data for this study came from a community-based, prospective longitudinal investigation of speech/language (S/L) impaired children and matched controls who participated in extensive diagnostic and psychosocial assessments at entry into the study at 5 years of age and again at follow-up. Clustering variables were based on five DSM diagnostic categories assessed at age 19with the University of Michigan Composite International Diagnostic Interview. Using Ward's method, the five binary variables were entered into a hierarchical cluster analysis. An iterative clustering method (K-means) was then used to refine the Ward solution. Finally, a series of analyses of variance (ANOVAs) were run to analyze group differences between clusters on measures of Global Assessment of Functioning (GAF), criminal involvement, anxiety and depressive symptomatology, and frequency of drug use and heavy drinking. The analysis yielded eight replicable cluster groups, which were labeled as follows: (a) anxious (20.9%); (b) anxious drinkers (5.5%); (c) depressed (16.4%); (d) depressed drug abusers (10%); (e) antisocial (16.4%); (f) antisocial drinkers (10%); (g) drug abusers (8.2%); (h) problem drinkers (12.7%). These groups were differentiated by external criteria, thus supporting the validity of our cluster solution. Cluster membership was associated with a history of S/L impairment: A large proportion of the depressed drug abusers and the antisocial cluster group had S/L impairment that was identified at age 5. Clarification of the developmental progress of the youths in these cluster groups can inform our approach to early intervention and treatment.

Substance use disorders in young adults with and without LD: predictive and concurrent relationships

This article reports on young people with and without learning disabilities (LD) and substance use disorders (SUD). Participants were assessed for LD at ages 12 and 19 and for SUD and psychiatric disorders at age 19. Participants with LD at ages 12 and 19 were more likely to develop an SUD or a psychiatric disorder compared to participants without consistent LD. Participants with LD at age 19 were more likely to have a concurrent SUD or psychiatric disorder compared to those without LD at age 19, while participants with LD at age 12 showed only a trend toward increased rates of SUD at age 19 when compared to participants without LD at age 12. Participants with and without LD did not differ in substance use, consumption levels, or onset history. In a multivariate model, adolescent LD was associated with a three-fold increased risk for SUD after behavioral problems and family structure had entered the model. Although these results provide some support for the notion that adolescents with LD are at increased risk for SUD, LD also appears to confer a general risk for adverse outcomes.

The environment and vegetation of the flux measurement site near Skukuza, Kruger National Park

The SAFARI-2000 intensive study site is located 13 km WSW of Skukuza. Detailed measurements of the exchanges of energy, water, carbon dioxide and other substances between the savanna and the atmosphere have been made there since April 2000. This paper provides basic information regarding the climate, soils and vegetation at the site. The site is located near the top of a gentle rise in an undulating granitic landscape. Most of the data were collected within a 300 m square centred on the flux tower situated at 25@01.184' S, 31@29.813' E and oriented true north. The tower stands exactly on the ecotone between a ridgetop broad-leafed Combretum savanna on sandy soil and a midslope fme-leafed Acacia savanna on clayey soil. The ecotone is marked by a 10 m wide band of sedges. The tree basal area within the sample square was 6.8 mVha (@ 1.0 standard error), the tree density 128 @ 16 plants/ha and the tree crown cover 24 @ 4 . Shrubs, defined as woody plants greater than 0.5 m but less than 2.5 m tall, contributed a further 7.6 crown cover. The basal area weighted mean height of the trees was 9 m, and the maximum height 13m. Nineteen woody plant species were recorded within the square, with 70 of the woody plant basal area dominated by Combretum apiculatum, Sclerocarya birrea and Acacia nigrescens. The rooted basal area of grasses was 7.1 @ 0.6 and in June 2000 the grass standing crop was 400 g DM m2.

Comparison of the effects of two early intervention strategies on the health outcomes of malnourished hemodialysis patients

OBJECTIVE

To determine the efficacy and cost-effectiveness of providing oral supplementation early in the course of malnutrition for hemodialysis (HD) patients.

DESIGN

The study design consisted of 3 groups: an experimental group, a control group of patients with mild hypoalbuminemia (HA) (serum albumin [SA] = 3.5 to 3.7 g/dL), and a comparison group of patients with moderate to severe HA (SA = 2.5 to 3.4 g/dL).

SETTING

Ten outpatient hemodialysis centers in southeast lower Michigan.

PATIENTS

Treatment and control groups consisted of 32 HD patients with mild HA. Fourteen HD patients with moderate to severe HA comprised the comparison group.

INTERVENTION

The experimental group received diet counseling and oral supplementation, and the control group received diet counseling only. The comparison group received physician-prescribed oral supplements and dietary counseling to permit comparison of the experimental treatment with current supplementation practices.

MAIN OUTCOME MEASURES

Differences between groups in the number of patients reaching nutritional repletion, change in SA levels at the end of the study, and follow-up periods, were tested using chi-square analysis. Analysis of variance was used to compare group differences in treatment duration to repletion and number of hospitalization days.

RESULTS

During the study period, significantly more patients reached nutritional repletion in the experimental group and control group (50% and 57%, respectively) than in the comparison group (7%). Overall, repletion occurred more quickly in the experimental group (3.2 +/- 1.7 months) than in the control group (3.5 +/- 1.2 months), with a larger number of patients in the experimental group repleted by month 2 of the study phase. During follow-up, patients in the experimental group were far more likely to maintain nutritional repletion or continue to improve (61%) than patients in the control group (14%). Although too few patients were hospitalized to show statistical significance, there was a trend toward greater numbers of hospital days in more malnourished patients (208 days for the comparison group), followed by those with mild HA who did not receive oral supplements (107 days), and the experimental group (71 days).

CONCLUSION

Although the sample size for this study was too small for the results to be conclusive, it appears that use of nutritional supplements early in the course of malnutrition may provide benefits such as, attaining nutritional repletion more quickly, which results in less product usage. It is also more likely that good nutritional status will be maintained after supplementation is discontinued.

Antiphospholipid antibodies and hemodialysis vascular access thrombosis

Screening for the presence of APL for hemodialysis dependent individuals is yet another critical link where medical and nursing interventions will prolong vascular access survival and decrease morbidity. Because of the continuity they provide, hemodialysis nurses and advanced practice nurses are in excellent positions to identify individuals with persistent vascular thrombosis and make recommendations for further screening.

Neurons reduce glial responses to lipopolysaccharide (LPS) and prevent injury of microglial cells from over-activation by LPS

The microenvironment of the CNS has been considered to tonically inhibit glial activities. It has been shown that glia become activated where neuronal death occurs in the aging brain. We have previously demonstrated that neurons tonically inhibit glial activities including their responses to the bacterial endotoxin lipopolysaccharide (LPS). It is not clear whether activation of glia, especially microglia in the aging brain, is the consequence of disinhibition due to neuronal death. This study was designed to determine if glia regain their responsiveness to LPS once the neurons have died in aged cultures. When cultured alone, glia from postnatal day one rat mesencephalons stimulated with LPS (0.1-1000 ng/mL) produced both nitric oxide (NO) and tumor necrosis factor alpha (TNFalpha), yielding a sigmoid and a bell-shaped curve, respectively. When neuron-containing cultures were prepared from embryonic day 14/15 mesencephalons, the shape of the dose-response curve for NO was monotonic and the bell-shaped curve for TNFalpha production was shifted to the right. After 1 month of culture under conditions where neurons die, the production curves for NO and TNFalpha in LPS-stimulated glia shifted back to the left compared to mixed neuron-glia cultures. Immunostaining of rat microglia for the marker CR3 (the receptor for complement component C3) demonstrated that high concentrations of LPS (1 microg/mL) reduced the number of microglia in mixed-glial cultures. In contrast, reduction of CR3 immunostaining was not observed in LPS-stimulated mixed neuron-glia cultures. Taken together, the results demonstrate that disinhibition of the glial response to LPS occurs after neurons die in aged cultures. Once neurons have died, the responsiveness of glia to LPS is restored. Neurons prevented injury to microglia by reducing their responsiveness to LPS. This study broadens our understanding of the ways in which the CNS microenvironment affects cerebral inflammation.

Fourteen-year follow-up of speech/language-impaired and control children: psychiatric outcome

OBJECTIVE

To examine the association between early childhood speech and language disorders and young adult psychiatric disorders.

METHOD

In a longitudinal community study conducted in the Ottawa-Carleton region of Ontario, Canada, interviewers administered structured psychiatric interviews to age 19 participants who were originally identified as speech-impaired only, language-impaired, or nonimpaired at age 5. The first stage of the study took place in 1982 when participants were 5 years old, and the latest stage of the study took place between 1995 and 1997 when participants had a mean age of 19 years. This report examines the association between early childhood speech/language status and young adult psychiatric outcome.

RESULTS

Children with early language impairment had significantly higher rates of anxiety disorder in young adulthood compared with nonimpaired children. The majority of participants with anxiety disorders had a diagnosis of social phobia. Trends were found toward associations between language impairment and overall and antisocial personality disorder rates. Males from the language-impaired group had significantly higher rates of antisocial personality disorder compared with males from the control group. Age of onset and comorbidity did not differ by speech/language status. The majority of participants with a disorder had more than one.

CONCLUSIONS

Results support the association between early childhood speech and language functioning and young adult psychiatric disorder over a 14-year period. This association underscores the importance of effective and early interventions.

Cloning and expression of MP13 gene from rat hippocampus, a new factor related to guanosine triphosphate regulation

C-Fos and the Fos-related antigens (FRA) are induced by various stimuli. A novel 35-37 kDa FRA was induced much longer after the treatment using kainic acid (KA) and may be very important for neuronal survival after brain damage. To identify this long-term FRA, we have constructed a cDNA library derived from hippocampus after KA treatment and screened it with an antibody highly conserved M-peptide region of FRAs. One gene, MP13, was cloned with a 1662 bp open reading frame and coded for a 554-amino acid protein. MP13 has a leucine zipper region, a glutamine repeat region, and has high similarity to the activator of the small guanosine triphosphate (GTP)ase Rab5. Gel retardation analysis revealed that MP13 functions as a GTP regulation related factor.

Expression of angiogenic factor thymidine phosphorylase and angiogenesis in human atherosclerosis

In atherosclerosis, leukocyte migration into the plaque is thought to occur across the endothelium of the arterial lumen. However, intraplaque microvessels have been noted. While the significance of, and stimuli for these are uncertain, it seems possible that they may represent a second portal of entry for leukocytes into the plaque. This study performed a basic characterization of intraplaque microvessels and tested the hypothesis that the novel angiogenic factor thymidine phosphorylase (TP) is expressed in atherosclerosis. Immunocytochemistry was performed on aortic and coronary plaques and morphometry on coronary plaques. In plaques from both sites, macrophages, foam cells, and giant cells were immunoreactive for the angiogenic factors TP and vascular endothelial growth factor. Venule-like intraplaque microvessels expressed endothelial leukocyte adhesion molecules HLA-DR and ICAM-1, in contrast to the endothelium overlying the plaque. In coronary plaques, there was a correlation between severity of stenosis and plaque microvascular density. These results are consistent with a role for plaque macrophage/foam cell TP in stimulating plaque angiogenesis. While attention has focused on dysfunction of the endothelium overlying the plaque, microvascular endothelium may also represent a portal of entry for leukocytes into established plaques.

Factors involved in the initial mutation of the fragile X CGG repeat as determined by sperm small pool PCR

The fragile X syndrome is one of more than a dozen genetic diseases attributed to the amplification of a trinucleotide repeat. Despite the number of these disease loci, relatively little is known about the mechanism(s) that cause a stable allele to become unstable. Population and family studies of the fragile X CGG repeat have identified a number of factors that may play a role in repeat instability including the number of AGG interruptions, purity of the 3' and 5' end of the repeat and cis-acting factors as related to haplotype background. However, studies that assess whether these factors have an impact on the rate and magnitude of change of the repeat are lacking, mainly due to the lack of an appropriate model system. Therefore, in order to dissect the factors involved in the initial mutations of the CGG repeat, small pool (SP)-PCR was performed on DNA derived from sperm and blood from seven unaffected males whose repeat sizes range from 20 to 33. Using the SP-PCR-derived data, regression analyses suggested that components of the repeat structure such as the number of interruptions and purity of the 3' end of the repeat are important determinants of germline repeat instability. In contrast, elements other than repeat structure, such as haplotype background, seemed to have an impact on somatic repeat instability. The factors identified for either cell type, however, explained only a small portion of the variance, suggesting that other factors may be involved in this process.

The effect of selective ultrasound screening on late presenting DDH

We examined the impact of selective ultrasound screening on late presenting Developmental Dysplasia of the Hip (DDH) in the Salford area. In the years 1991-1995, babies with suspected clinical hip instability and a number of babies with known risk factors for DDH were referred to a designated Baby Hip clinic for sonographic hip examination. The decision for treatment was based solely on ultrasound findings. We found that nineteen babies reported as having a clinically normal hip by a Senior Registrar in Orthopaedics had sonographically abnormal hips and were treated successfully with an abduction splint. The incidence of late presenting DDH was not reduced when compared with two previous cohorts born at the same centre. None of the children that presented with a late DDH was referred for a sonographic examination after birth. A more widespread ultrasound screening programme including all babies with risk factors for DDH is advised in order to reduce late presentations.

Expression of angiogenic factor thymidine phosphorylase and angiogenesis in human atherosclerosis

In atherosclerosis, leukocyte migration into the plaque is thought to occur across the endothelium of the arterial lumen. However, intraplaque microvessels have been noted. While the significance of, and stimuli for these are uncertain, it seems possible that they may represent a second portal of entry for leukocytes into the plaque. This study performed a basic characterization of intraplaque microvessels and tested the hypothesis that the novel angiogenic factor thymidine phosphorylase (TP) is expressed in atherosclerosis. Immunocytochemistry was performed on aortic and coronary plaques and morphometry on coronary plaques. In plaques from both sites, macrophages, foam cells, and giant cells were immunoreactive for the angiogenic factors TP and vascular endothelial growth factor. Venule-like intraplaque microvessels expressed endothelial leukocyte adhesion molecules HLA-DR and ICAM-1, in contrast to the endothelium overlying the plaque. In coronary plaques, there was a correlation between severity of stenosis and plaque microvascular density. These results are consistent with a role for plaque macrophage/foam cell TP in stimulating plaque angiogenesis. While attention has focused on dysfunction of the endothelium overlying the plaque, microvascular endothelium may also represent a portal of entry for leukocytes into established plaques.

How five advanced practice nurses in nephrology spend their time

The purpose of this paper is to report the results of a descriptive study undertaken to examine the scope of practice of five Masters-prepared nephrology nurse practitioner/clinical nurse specialists (NP/CNS) in a mid-size university teaching hospital program. Four of the NP/CNSs practised in three acute care sites, and one in the regional dialysis program. Impetus for the study came from two sources. First, a sixth person practising in the role was retiring and was not to be replaced. Second, the current three-site model for acute care was being transformed into a two-site model, thus creating opportunities to reduce variability in practice among the NP/CNSs. The study examined the activities of the NP/CNS role through the completion of a time documentation tool (TDT) by five nurse practitioners on each of 10 consecutive days of practice. The TDT was adapted from Ackerman's Model of Advanced Practice (1996). The model outlines five domains of practice for advanced practice nurses (APN): direct comprehensive care, support of systems, research, education, and publication and professional leadership. The NP/CNSs spent an average of 9.21 hours at work daily with a range of 8.6 to 10.3 hours. The TDT captured an average of 8.6 hours of working time with a range of 7.3 to 9.9 hours. An average of 72% of time was spent in clinical practice (range 64-83%). An average of 16% (range 11-20%) of time was spent in support of systems. Research (average 4%, range 3-7%), education (average 6%, range 3-16%), and publication and professional leadership (average 2%, range 0-6%) figured less prominently. The major activities performed within the clinical practice domain and the support of systems domain showed less variability across sites than was anticipated. The results of the study have helped the NP/CNSs and their management colleagues analyze and adapt the role to changing clinical requirements and economic realities.

Immune modulatory effects of neural cell adhesion molecules on lipopolysaccharide-induced nitric oxide production by cultured glia

Activation of glial cells often occurs at sites of neuronal injury or death and where there is disruption of communication between glia and neurons. We have previously reported that neurons exert an inhibitory influence on LPS-stimulated nitric oxide (NO) production in glial cells. We hypothesized that neural cell adhesion molecules (NCAM) might mediate this inhibitory effect, and this study was designed to elucidate the role of NCAM on lipopolysaccharide (LPS)-induced NO production. We found that soluble NCAMs reduced LPS-stimulated NO production by cultured glia. A monoclonal antibody that recognizes the third immunoglobulin (Ig) domain and can mimic the functions of NCAMs reduced LPS-stimulated NO production, whereas another antibody that binds to other regions of the NCAM did not modulate NO production. Using a 10-amino acid peptide from the third Ig domain of the NCAM, a peptide fragment within the region recognized by the NCAM antibody, mimics the effect of the molecule in reducing NO production. This study demonstrated that NCAMs could modulate LPS-stimulated NO production, most likely via interaction between NCAMs. These results suggest that neuron-glia interactions via NCAMs play an important role in regulating the activities of glial cells in the brain.

Regional difference in susceptibility to lipopolysaccharide-induced neurotoxicity in the rat brain: role of microglia

Inflammation in the brain has been increasingly associated with the development of a number of neurological diseases. The hallmark of neuroinflammation is the activation of microglia, the resident brain immune cells. Injection of bacterial endotoxin lipopolysaccharide (LPS) into the hippocampus, cortex, or substantia nigra of adult rats produced neurodegeneration only in the substantia nigra. Although LPS appeared to impact upon mesencephalic neurons in general, an extensive loss of dopaminergic neurons was observed. Analysis of the abundance of microglia revealed that the substantia nigra had the highest density of microglia. When mixed neuron-glia cultures derived from the rat hippocampus, cortex, or mesencephalon were treated with LPS, mesencephalic cultures became sensitive to LPS at a concentration as low as 10 ng/ml and responded in a dose-dependent manner with the production of inflammatory factors and a loss of dopaminergic and other neurons. In contrast, hippocampal or cortical cultures remained insensitive to LPS treatment at concentrations as high as 10 microg/ml. Consistent with in vivo observations, mesencephalic cultures had fourfold to eightfold more microglia than cultures from other regions. The positive correlation between abundance of microglia and sensitivity to LPS-induced neurotoxicity was further supported by the observation that supplementation with enriched microglia derived from mesencephalon or cortex rendered LPS-insensitive cortical neuron-glia cultures sensitive to LPS-induced neurotoxicity. These data indicate that the region-specific differential susceptibility of neurons to LPS is attributable to differences in the number of microglia present within the system and may reflect levels of inflammation-related factors produced by these cells.

Cholinesterase inhibition by potato glycoalkaloids slows mivacurium metabolism

BACKGROUND

The duration of action for many pharmaceutical agents is dependent on their breakdown by endogenous hydrolytic enzymes. Dietary factors that interact with these enzyme systems may alter drug efficacy and time course. Cholinesterases such as acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) hydrolyze and inactivate several anesthetic drugs, including cocaine, heroin, esmolol, local ester anesthetics, and neuromuscular blocking drugs. Natural glycoalkaloid toxins produced by plants of the family Solanaceae, which includes potatoes and tomatoes, inhibit both AChE and BuChE. Here the authors assess the extent to which two solanaceous glycoalkaloids (SGAs), alpha-solanine and alpha-chaconine, can alter the effects of neuromuscular blocking drugs and cholinesterase inhibitors in vivo and in vitro.

METHODS

Inhibition of purified human AChE and BuChE by SGAs, neuromuscular blocking drugs, and cholinesterase inhibitors was assessed by an in vitro colorimetric cholinesterase assay. In vivo experiments were carried out using anesthetized rabbits to test whether SGAs affect recovery from mivacurium-induced paralysis.

RESULTS

SGAs inhibited human BuChE at concentrations similar to those found in serum of individuals who have eaten a standard serving of potatoes. Coapplication of SGAs (30-100 nm) with neuromuscular blocking drugs and cholinesterase inhibitors produced additive cholinesterase inhibition. SGA administration to anesthetized rabbits inhibited serum cholinesterase activity and mivacurium hydrolysis. In addition, SGA prolonged the time needed for recovery from mivacurium-induced paralysis (149 +/- 12% of control; n = 12).

CONCLUSIONS

These findings support the hypothesis that inhibition of endogenous enzyme systems by dietary factors can influence anesthetic drug metabolism and duration of action. Diet may contribute to the wide variation in recovery time from neuromuscular blockade seen in normal, healthy individuals.