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Space flight is normally associated with exposure to reduced acceleration (microgravity) and the medical consequences are well described. However, it inevitably also requires periods of increased acceleration during ascent and descent. These periods, although short in comparison to the length of the flight, are classified as long-duration by physiologists. The biological consequences for man [text incomplete]
Scanning electron microscopy (SEM) with immunogold labeling was employed to observe the undersurface of the human epidermis after it was split from dermal connective tissue, in an attempt to localize the molecules actually expressed on cell/tissue surfaces. We found that human leukocyte antigen-DR (HLA-DR) molecules were expressed on the surfaces of eccrine duct cells as well as those of epidermal Langerhans cells (LC) in normal skin. HLA-DR molecules, visualized by the deposition of gold particles, were distributed evenly on the LC surface but were present only along the interdigitating borders of the individual duct cells, thus producing a meshwork pattern on the duct surface. Transmission electron microscopy confirmed that the gold particles labeling cell surface HLA-DR molecules were seen only on the portions of duct cell membranes the interdigitated with neighboring duct cells. These findings suggest that the function of HLA-DR molecules may vary with their location and distribution. On the LC surface, the evenly distributed molecules seem to be well suited for promoting "accessory cell" functions. On duct cell surfaces, the HLA-DR molecules present along the intercellular spaces may be involved in trapping various peptide antigens that pass into the sweat gland filtrate and then are reabsorbed by the excretory duct, since these molecules have a highly permissive capacity for binding various peptides.
PURPOSE: To develop an isolated rat retina preparation suitable for the study of the reflectance of the mammalian retinal nerve fiber layer (RNFL). METHODS: A rat retina with a short piece of optic nerve attached was dissected free from the eye and stretched over a slit in a black membrane. The retina was placed in a black chamber perfused with warmed and oxygenated physiologic solution. Imaging microreflectometry was used to acquire images of the RNFL at wavelengths from 400 to 830 nm and over time. RESULTS: At all wavelengths the isolated retina provided high-contrast images of nerve fiber bundles against a uniform, dark background. The nerve fiber bundles had a speckled texture, especially at long wavelengths. Time-lapse movies showed that over a period of several minutes the speckle pattern slowly changed. Although the general appearance of the bundles was similar at two closely spaced wavelengths (660 and 680 nm), the detailed patterns were completely different. CONCLUSION: The isolated retina preparation is well suited to the study of the optical properties of the RNFL. The speckled texture of nerve fiber bundles probably results from optical interference in the scattered light. The slow change in pattern implies that the size and/or shape of the scattering structures must change with time.
Recently, we have reported that cell wall pectins are internalized into apical meristem root cells. In cells exposed to the fungal metabolite brefeldin A, all secretory pathways were inhibited, while endocytic pathways remained intact, resulting in accumulation of internalized cell wall pectins within brefeldin A-induced compartments. Here we report that, in addition to the already published cell wall epitopes, rhamnogalacturonan I and xyloglucans also undergo large-scale internalization into dividing root cells. Interestingly, multilamellar endosomes were identified as compartments internalizing arabinan cell wall pectins reactive to the 6D7 antibody, while large vacuole-like endosomes internalized homogalacturonans reactive to the 2F4 antibody. As all endosomes belong topographically to the exocellular space, cell wall pectins deposited in these "cell wall islands", enclosed by the plasma-membrane-derived membrane, are ideally suited to act as temporary stores for rapid formation of cell wall and generation of new plasma membrane. In accordance with this notion, we report that all cell wall pectins and xyloglucans that internalize into endosomes are highly enriched within cytokinetic cell plates and accumulate within brefeldin A compartments. On the other hand, only small amounts of the pectins reactive to the JIM7 antibody, which are produced in the Golgi apparatus, localize to cell plates and they do not accumulate within brefeldin A compartments. In conclusion, meristematic root cells have developed pathways for internalization and recycling of cell wall molecules which are relevant for plant-specific cytokinesis.
INTRODUCTION: This treatment-outcome assessment objectively compares Invisalign (Align Technology, Santa Clara, Calif) treatment with braces. METHODS: This study, a retrospective cohort analysis, was conducted in New York, NY, in 2004. Records from 2 groups of 48 patients (Invisalign and braces groups) were evaluated by using methods from the American Board of Orthodontics Phase III examination. The discrepancy index was used to analyze pretreatment records to control for initial severity of malocclusion. The objective grading system (OGS) was used to systematically grade posttreatment records. Statistical analyses evaluated treatment outcome, duration, and strengths and weaknesses of Invisalign compared with braces. RESULTS: The Invisalign group lost 13 OGS points more than the braces group on average, and the OGS passing rate for Invisalign was 27% lower than that for braces. Invisalign scores were consistently lower than braces scores for buccolingual inclination, occlusal contacts, occlusal relationships, and overjet. Invisalign's OGS scores were negatively correlated to initial overjet, occlusion, and buccal posterior crossibite. Invisalign patients finished 4 months sooner than those with fixed appliances on average. P < .05 was used to determine statistically significant differences. CONCLUSIONS: According to the OGS, Invisalign did not treat malocclusions as well as braces in this sample. Invisalign was especially deficient in its ability to correct large anteroposterior discrepancies and occlusal contacts. The strengths of Invisalign were its ability to close spaces and correct anterior rotations and marginal ridge heights. This study might help clinicians to determine which patients are best suited for Invisalign treatment.
A new kind of orientation representation called symmetric Euler orientation representation (SEOR) is presented. It is based on a combination of the conventional Euler orientation representations (Euler angles) and Hamilton's quaternions. The properties of the SEORs concerning orientational averaging are explored and compared to those of averaging schemes that are based on conventional Euler orientation representations. To that aim, the reflectance of a hypothetical polycrystalline material with orthorhombic crystal symmetry was calculated. The calculation was carried out according to the average refractive index theory (ARIT [T.G. Mayerhöfer, Appl. Spectrosc. 56 (2002) 1194]). It is shown that the use of averaging schemes based on conventional Euler orientation representations leads to a dependence of the result from the specific Euler orientation representation that was utilized and from the initial position of the crystal. The latter problem can be overcome partly by the introduction of a weighing factor, but only for two-axes-type Euler orientation representations. In case of a numerical evaluation of the average, a residual difference remains also if a two-axes type Euler orientation representation is used despite of the utilization of a weighing factor. In contrast, this problem does not occur if a symmetric Euler orientation representation is used as a matter of principle, while the result of the averaging for both types of orientation representations converges with increasing number of orientations considered in the numerical evaluation. Additionally, the use of a weighing factor and/or non-equally spaced steps in the numerical evaluation of the average is not necessary. The symmetrical Euler orientation representations are therefore ideally suited for the use in orientational averaging procedures.
The Late Proterozoic fossil record contains the remains of animals that may represent a grade of organization not found among living metazoans. These forms were segmented and large enough to require a hemocoel, yet evidently were not capable of forming penetrating burrows, which are essentially absent from contemporaneous sediments containing locally common but chiefly horizontal trace fossils. As has been noted, there is no evidence that Late Proterozoic invertebrates possessed a coelom suited for peristaltic burrowing. Therefore, the annelidan body plan had probably not appeared. It is not implausible, however, that coelomic spaces in the form of ducts or organ sacs were present in Late Proterozoic segmented forms. Uniramians, some of which employ the hemocoel hydrostatically in lobopodal locomotion, may be allied to segmented hemocoelic forms not unlike sprigginids. Coelomic spaces may have been exploited in some protoarthropod lineages to enhance pedal-wave locomotion, but probably there are no eucoelomic forms in arthropodan ancestry. Annelids may represent an early divergent branch of seriated worms, perhaps rather nemertine-like at first, that developed eucoelomic compartments only in Cambrian time. The extinct grade is most likely to have arisen from flatworm-like ancestors. Of all the proposed phylogenies examined, only that of Manton closely anticipates these interpretations of the early metazoan fossil record.
OBJECTIVES: To study the feasibility of continuously monitoring core temperatures of search and rescue divers, to compare core temperature gradients occurring during warm and cold diving events, and to identify conditions under which divers are subjected to extreme temperatures. METHODS: Between June 1994 and March 1995, emergency medical technicians (EMTs) from two midwestern dive teams volunteered to ingest an encapsulated temperature sensor developed for the National Aeronautics and Space Administration. The capsule monitored continuous core temperatures and transmitted the data to a recorder worn under the divers' dry suits. RESULTS: Twenty male EMTs, mean age 34 years and mean body weight 184 pounds, were monitored during training. Nine dives were ice dives, with ice thickness averaging 9 inches, and mean ambient temperatures of 33 degrees F. Eleven dives were warm-water dives; average water temperature was 70 degrees F and mean ambient temperature was 74 degrees F. The average time spent in the dry suit was 95 minutes, and the mean total bottom time was 15 minutes. The ice divers showed a mean increase in core temperature of 1.0 degrees C, while the warm-water divers showed a mean increase of 1.2 degrees C. Divers experiencing the most extreme fluctuations were those in the role of safety diver, regardless of the season. Divers reported more subjective discomfort during ice dives than during warm-water dives. CONCLUSIONS: Continuous monitoring of body temperature during the duration of dive operations is possible, but labor-intensive. Safety measures to protect divers from extreme core temperature fluctuations should focus on the safety diver as well as the active diver.
OBJECTIVES: Occupational therapists assess and adapt an environment to enhance clients' abilities to function. Therapists working in schools may assess several classroom environments in a week. Identifying relevant information in an efficient manner is essential yet presents a challenge for school therapists. METHOD: In this study, ethnographic research methodology was used to analyze the plethora of data gained from observations in eight classrooms. RESULTS: Three major categories were identified to structure observations: activities, people, and communication. These categories were used to compile a Classroom Observation Guide that gives therapists relevant questions to ask in each category. CONCLUSION: Using the Classroom Observation Guide, occupational therapists can recommend classroom activities that suit a particular teacher's style. For example, working with a teacher who prefers structural activities with clear time and space boundaries for one specific purpose, a therapist might suggest organized sensorimotor games with a distinct purpose to be carried out for a given time period.
Pelvic fractures, which are most often caused by blunt abdominal trauma in our motor vehicle-oriented society, continue to be associated with significant mortality and morbidity. Hemorrhage is the cause of death in nearly 60 per cent of those patients who die of pelvic fractures. With increasing awareness of the problem and improved methods of management, the mortality rate of acute hemorrhage secondary to pelvic fracture should decrease. Four cases of vascular injuries associated with severe pelvic fractures are discussed. One patient presented with bleeding from a false aneurysm of the superior gluteal artery 3 months after his pelvic fracture. This complication was successfully managed by selective arteriographic embolization. The other three patients required early angiography with embolization of hypogastric vessels to control acute hemorrhage after pelvic fracture. Pelvic arteriography with selective embolization of injured vessels is recommended in the management of hemorrhage secondary to severe pelvic fractures. Application of the Military Antishock Trousers (MAST) suit may also be a useful maneuver. These principles of management and a pertinent review of the literature are presented.
Health professionals are investigating an increasing number of possible disease clusters, and statistical tests play an important role in cluster description and analysis. Existing cluster statistics assume precise data, when in reality health events are often imprecise (for example, place of residence is known only to the census district or zip code) and uncertain (for example, 'I first became ill sometime in 1985'). This incompatibility--precise methods used to analyse imprecise data--is largely ignored, resulting in test statistics of unknown accuracy. Most cluster statistics can be written as the cross-product of two matrices where one matrix reflects nearest-neighbour, distance or adjacency relationships and the second matrix is health related (for example, case-control identities). This paper explores a general approach to clustering, which incorporates uncertainty regarding space-time locations into these nearest neighbour, distance or adjacency relationships. Because the approach is general it can be used with almost all existing cluster tests, and, because it accounts for imprecise location data, it is suited to the 'real-world' nature of disease cluster investigations.
This paper applies the outputs of a family of HIV/AIDS models to problems in disease control. The epidemic models comprising this suite include single and multiregion representations each adopting either a one or two risk population format. Here, risk is expressed in terms of activity rates and those at low risk are characterized by a reproduction rate of less than unity which defines a simulated epidemic that cannot start. These models are applied to the following problems in prevention and control: first, estimating the impact of national variations in population growth rates on the predicted size of the epidemic, second, constructing control charts to assess the impact of intended interventions, third, evaluating the consequences of targeting preventative action at those at high risk; and last, evaluating the implications for international control of differences between the serological and simulated pandemic pathways. The discussion sets these findings within the context of forming health policy.
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We present a method for condensing the photon energy and angular distributions obtained from Monte Carlo simulations of medical accelerators. This method represents the output as a series of correlated histograms and as such is well-suited for inclusion as the photon-source package for Monte Carlo codes used to determine the dose distributions in photon teletherapy. The method accounts for the isocenter-plane variations of the photon energy spectral distributions with increasing distance from the beam central axis for radiation produced in the bremsstrahlung target as well as for radiation scattered by the various treatment machine components within the accelerator head. Comparison of the isocenter energy fluence computed by this algorithm with that of the underlying full-physics Monte Carlo photon phase space indicates that energy fluence errors are less than 1% of the maximum energy fluence for a range of open-field sizes. Comparison of jaw-edge penumbrae shows that the angular distributions of the photons are accurately reproduced. The Monte Carlo sampling efficiency (the fraction of generated photons which clear the collimator jaws) of the algorithm is approximately 83% for an open 10x10 field, rising to approximately 96% for an open 40x40 field. Data file sizes for a typical medical accelerator, at a given energy, are approximately 150 kB, compared to the 1 GB size of the underlying full-physics phase space file.
The effects of data pretreatment, data scaling, and variable selection on three-dimensional quantitative structure-activity relationships derived by comparative molecular field analysis (CoMFA) using the GRID energy function were studied in detail for a set of inhibitors of the human synovial fluid phospholipase A2 (HSF-PLA2). The quality of the models was evaluated for predictive power and ability to map the receptor binding site by (a) comparison of predicted and experimental activities using cross-validation and external validation sets and (b) comparison of the regions selected in space in the CoMFA models with a crystal structure of a HSF-PLA2-inhibitor complex, with optimized comparative binding energy analysis (COMBINE) models (Ortiz et al., 1995) and with structure-activity relationships derived previously for different sets of compounds. It is found that (1) data scaling and dielectric modeling strongly influence CoMFA results. Unscaled data and a uniform dielectric constant of 4 are well suited to GRID-CoMFA studies for the present compound set. (2) The GOLPE and Q2-GRS variable selection methods select variables in roughly the same regions in Cartesian space, but they produce different models in chemometric space and differ in their sensitivity to data scaling and pretreatment and their tendency to overfitting. (3) CoMFA models are consistent with COMBINE models in that they identify approximately the same intermolecular interactions as relevant for activity. Our study provides support for the qualitative receptor-mapping properties of CoMFA models and for the validity of variable selection when applied with care and also provides guidelines for how to evaluate the quality of CoMFA models.
Significant differences in dose prediction for Space Station arise depending on whether or not the magnetic field model is extrapolated into the future. The basis for these calculations is examined in detail, and the importance of the residual atmospheric layer at altitudes below 1000 km, with respect to radiation attenuation is emphasized. Dosimetry results from Shuttle flights are presented and compared with the computed results. It is recommended that, at this stage, no extrapolation of the magnetic field into the future be included in the calculations. A model adjustment, to replace this arbitrary procedure is presented. Dose predictions indicate that, at altitudes below 500 km and at low inclination, and with nominal module wall thickness (0.125 in. aluminum), orbit stay times of 90 days in Space Station would result in quarterly radiation doses to the crew, which are well within present limits both for males and females. Countermeasures would be required for stay times of a year or more and the measure of increasing shielding is examined.