Determining the lower limit of detection for personnel dosimetry systems.

A simple method for determining the lower limit of detection (LLD) for personnel dosimetry systems is described. The method relies on the definition of a critical level and a detection level. The critical level is the signal level above which a result has a small probability of being due to a fluctuation of the background. All results below the critical level should not be reported as an indication of a positive result. The detection level is the net signal level (i.e., dose received) above which there is a high confidence that a true reading will be detected and reported as a qualitatively positive result. The detection level may be identified as the LLD. A simple formula is derived to allow the calculation of the LLD under various conditions. This type of formula is being used by the Department of Energy Laboratory Accreditation Program (DOELAP) for personnel dosimetry. Participants in either the National Voluntary Laboratory Accreditation Program (NVLAP) for personnel dosimetry or DOELAP can use performance test results along with a measurement of background levels to estimate the LLDs for their dosimetry system. As long as they maintain their dosimetry system such that the LLDs are less than half the lower limit of the NVLAP or DOELAP test exposure ranges, dosimetry laboratories can avoid testing failures due to poor performance at very low exposures.

Telescopic video-otoscopy using a compact home video color camera.

Our method of telescopic video-otoscopy using a telescope (Hopkins) and a compact home video camera is presented. Telescopic video-otoscopy is a most effective method of demonstrating and documenting the anatomy and pathology of the tympanic membrane, ear canal, and mastoid cavity. It is of considerable value for teaching, patient counseling, and making a permanent record. It obtains instantaneously a video print-out either in black-and-white or in color of video images of telescopic otoscopy. A simple and economical method of telescopic pneumatic otoscopy (pneumatic teleotoscopy) is also described. Telescopic video otoscopy combined with the use of a video printer is a useful addition to the clinical practice of otology.

The extended pectoralis major flap in head and neck reconstruction.

Historically, major extirpative surgery for control of head and neck cancer developed well in advance of reconstructive procedures that could provide acceptable functional and cosmetic rehabilitation. Introduction of cutaneous axial and random flaps--followed more recently by the description of musculocutaneous flaps--represented major advances in reconstructive techniques.

Videophotolaryngography using a new low cost video printer. Instant electronic filmless photography.

We introduce a new concept of electronic videophotography of the larynx on the television screen using a new Mitsubishi video printer. With this method no standard film or chemical processing are used. Black and white prints of the television image can be electronically reproduced in less than 15 seconds by pressing a button on the video printer. This method is of great value for documentation of the progression of disease and comparison of the preoperative and postoperative appearances of the larynx. The printout of the black and white television image of the larynx can be attached to the patient's chart as a permanent pictorial record. Such prints can also be given to the patient or can be sent to the referring physician, the radiotherapist, and others involved in management of the patient. This method is also useful for demonstration of a pathological condition and for teaching at head and neck tumor conferences.

Facial paralysis in Lyme disease.

Lyme disease is a multisystemic illness caused by a tick-borne spirochete. Once considered unique to the Connecticut coastline, thousands of cases are now documented throughout the United States, northern Europe, and Australia. Unilateral and bilateral facial paralysis may occur in up to 11% of patients with Lyme disease. This paper reviews the clinical course, distinguishing features, and outcome of 124 such palsies in 101 patients seen between 1975 and 1984. The 99.2% spontaneous recovery rate demonstrates the unequivocally excellent prognosis of this palsy and confirms that operative intervention is not indicated. The otolaryngologist should consider this etiology in all otherwise idiopathic facial paralyses, especially when presenting in summer months in endemic areas, or when bilateral. Positive Lyme disease spirochete titers are helpful in the diagnosis. We believe antibiotics should be given to patients with this facial palsy in order to treat any other concurrent manifestations of the illness and to prevent subsequent complications.

Local intra-arterial streptokinase therapy for acute peripheral arterial occlusions. Should thrombolytic therapy replace embolectomy?

Locally administered low-dose streptokinase was used in 13 patients with acute arterial occlusions. Systemic fibrinolytic effects were noted in each of 11 patients in whom some effective thrombolysis was demonstrated. In the two patients with no angiographically demonstrable thrombolysis, a systemic lytic effect was absent. Bleeding complications were frequent (31%). Three patients required amputations and one patient died. The systemic lytic effects of streptokinase appear to be necessary for complete clot lysis. Locally administered streptokinase appears to have no significant benefit compared to high-dose systemic administration. Occlusions accessible to balloon embolectomy should probably be treated surgically, reserving fibrinolytic therapy for inaccessible lesions. More research is needed to clarify the specific indications, as well as to determine optimal methods of administration and dosage.

Neutron scattering studies of the H2a-H2b and (H3-H4)2 histone complexes.

Neutron scattering experiments have shown that both the (H3-H4)2 and H2a-H2b histone complexes are quite asymmetric in solution. The (H3-H4)2 tetramer is an oblate or flattened structure, with a radius of gyration almost as large as that of the core octamer. If the tetramer is primarily globular, it must have an axial ratio of about 1:5. It is more likely, however, that this asymmetry results in part from N-terminal arms that extend outward approximately within the major plane of the particle. If this is the case, less asymmetric models for the globular part of the tetramer, including a dislocated disk of the type proposed by Klug et al. (23), can be made consistent with the scattering data. The H2a-H2b dimer, on the other hand, is an elongated structure. The low resolution data are in good agreement with those calculated for a cylindrical model 64 X 27 A, but other elongated models fit those data almost as well, including one that approximates free N-terminal arms at each end. Free arms are not necessary, but they must extend from the ends if they exist. A contrast matching experiment done with 50% deuterated H2b and undeuterated H2a in the reconstituted dimer showed that these two histones must each be rather elongated within the complex and are not just confined to one end. The amount of scattering contrast between the undeuterated and 50% deuterated histones was sufficient to suggest further experiments using complexes reconstituted from mixtures of undeuterated and partially deuterated histones which will help elucidate their arrangement within the histone complexes and within the octamer core of the nucleosome core particle.

Small-angle neutron scattering study of Bence-Jones protein Mcg: comparison of structures in solution and in crystal.

Immunoglobulins fragments are composed of globular domains linked by extended polypeptide segments. The molecular flexibility inherent in this arrangement allows for significant potential differences between structures observed in the crystalline state and those attained in solution. Small-angle neutron scattering measurements in dilute solution were performed on the Mcg Bence-Jones protein dimer, for which performed on the Mcg Bence-Jones protein dimer, for which accurate atomic coordinates have been determined by crystallographic methods [Edmundson, A. B., Ely, K. R., Abola, E. E., Schiffer, M., & Panagiotopoulos, N. (1975) Biochemistry 14, 3953-3961; Schiffer, M. (1980) Biophys. J. 32, 230-232]. The measured radius of gyration (Rg) in H2O buffer is 24.0 +/- 0.4 A and in D2O buffer is 23.3 +/- 0.1 A; the calculated value of Rv (Rg in vacuo) is 24.0 A. The above values compare well with the calculated Rg value of 23.6 A when refined coordinates of the trigonal crystal form of the Mcg Bence-Jones protein are used. On the basis of a match point of 44.2% D2O concentration, the experimental partial specific volume is 0.74 cm3/g. The experimentally derived molecular weight of 47 000 is in very good agreement with that (45 500) calculated from the amino acid composition. For comparison with different Fab's (antigen binding fragments) exhibiting various "elbow bends" due to the flexibility of the switch peptide between variable and constant domains of the immunoglobulin chains, calculation of the Rg value of the Mcg dimer was performed as a function of the elbow bend. The Rg varied from 22.8 to 26.0 A as the elbow bend was opened from 100 degrees to 180 degrees; the maximum radius of gyration of the particle was 26.5 A with the switch peptide stretched by separating the variable and constant domains by an additional 1.5 A at an elbow bend of 180 degrees.

Neutron scattering data on reconstituted complexes of fd deoxyribonucleic acid and gene 5 protein show that the deoxyribonucleic acid is near the center.

We have performed low-angle neutron scattering studies on reconstituted complexes of fd DNA and the gene 5 protein that is produced during infection of Escherichia coli by filamentous fd phage. Essentially identical helical complexes have been made with normal protonated DNA or DNA in which at least 87% of the nonexchangeable protons are replaced by deuterium. From neutron scattering profiles of both complexes over a range of D2O/H2O solvent mixtures, the DNA deuteration is shown to have a dramatic influence on the measured cross-sectional radius of gyration. Most importantly, data for the complex containing deuterated DNA lead to a more negative slope in a plot of the square of the cross-sectional radius of gyration vs. the inverse of the solute-solvent contrast, compared with the slope of a plot of data for the complex containing protonated DNA. This means that, in a cross-sectional view of the complex, the DNA is near the center of the structure. By our analysis, the DNA has a cross-sectional radius of gyration of 17.6 +/- 3 A, while the protein has a cross-sectional radius of gyration of about 33.5 A. Therefore, the model for the structure of the helical complex that has been proposed from X-ray diffraction studies on gene 5 protein crystallized with oligodeoxynucleotides [McPherson, A., Jurnak, F., Wang, A., Kolpak, F., Rich, A., Molineux, I., & Fitzgerald, P. (1980) Biophys. J. 32, 155-170] is not valid for the complex in solution. From our neutron diffraction data we have also obtained values for the solvent-excluded volume and mass per unit length. The relation of our findings to the solution structure of the complex is discussed.

Ocular position in sentence-picture comparisons.

If oculomotor activity in verifying orally presented sentences about pictures is important, then there ought to be an increase in such activity in the area of a picture in which a critical feature in the analysis is missing. If the process is purely cognitive, there ought not be greater activity in that area. 32 sentences combining such attributes as positive/negative, true/false, subject of sentence shown/not shown, "before"/"after," resulting in sentences such as, "Star isn't before square," were orally presented to 10 college-age students along with tachistoscopically presented pictures with either an object on the right or left. True/false reaction times were recorded as well as horizontal eye fixations for the time interval via an electromyograph and chart recorder. Mean eye-location/time indices indicated that some sentence types seemed to be analyzed predominantly visually and others predominantly cognitively. Results suggested that there is a need for the development of a combined visual imagery and cognitive model.

Visual vs auditory encoding of linguistic material in comparison of sentences and pictures.

The present study was designed to determine if there is a facilitating effect of aural vs visual linguistic input in comprehension of a sentence which expresses a spatial relationship between objects in a picture, e.g., "Star is above square." The sample was composed of 10 male and 10 female undergraduate students in psychology. One group was presented with sentences aurally to compare with tachistoscopically presented pictures, while another was presented written sentences along with pictures. The main finding was that reaction times were significantly less in the auditory group than the visual group, while there was no statistically significant difference in errors. Several previous findings relating to the characteristics of sentence types were replicated. It was concluded that several alternative strategies are made possible when stimuli are presented aurally which are probably due to the compatibility of listening and looking tasks.

A simple method for the preparation of homogeneous phospholipid vesicles.

A new method is described for the preparation of homogeneously sized, single-lamellar phospholipid vesicles. This method, wich is based on differential high-speed ultracentrifugation, has the advantages of a higher vesicle yield without dilution and rapidity of preparation when compared to the molecular-sieve technique. The homogeneity of vesicle dispersions, prepared by this new method, is examined by several physical techniques and found to be comparable to the best samples prepared by molecular-sieve chromatography.

Chromatin nu bodies: isolation, subfractionation and physical characterization.

Monomer chromatin subunit particles (nu1) have been isolated in gram quantities by large-scale zonal centrifugation of micrococcal nuclease digests of chicken erythrocyte nuclei. nu1 can be stored, apparently indefinitely, frozen in 0.2 mM EDTA (pH 7.0) at less than or equal to 25 degrees C. Aliquots of the stored monomers have been subfractionated by dialysis against 0.1 M KCl buffers into a soluble fraction containing equimolar amounts of H4, H3, H2A, H2B associated with a DNA fragment of approximately 130-140 nucleotide pairs, and a precipitated fraction containing all of the histones including H5 and H1 associated with DNA fragments. The total nu1 and the KCl-soluble fraction of nu1 have been examined by sedimentation, diffusion, sedimentation equilibrium ultracentrifugation, low-angle X-ray diffraction, and electron microscopy. Physical parameters from all of these techniques are presented and correlated in this study.

Chromatin model calculations: Arrays of spherical nu bodies.

Chromatin fibers consists of globular nucleohistone particles (designated nu bodies) along the length of the chromatin DNA with approximately 6-to7-fold compaction of the DNA within the nu bodies. We have calculated theoretical small-angle x-ray scattering curves and have compared these with experimental data in the literature. Several models predict maxima at the correct angles. The first maximum (approximately 110 degrees A) results from interparticle interference, while both the spatial arrangement and the structure factor the nu bodies can contribute to the additional small-angle maxima. These calculations suggest models which can account for the electron microscopic observation that chromatin is seen as either approximately 100-or approximately 200-to 250 degrees A-diameter fibers, depending on the solvent conditions. They also account for the limited orientability of the x-ray pattern from pulled chromatin fibers.

Urea denaturation of chromatin periodic structure.

Isolated chicken erythrocyte nuclei dispersed in urea solutions (0-5.0 M) have been examined in terms of their low-angle X-ray diffraction and electron microscopic properties. At high urea concentrations, the characteristic low-angle X-ray reflections of chromatin are absent, and the spheroid chromatin particles (v bodies) are markedly perturbed. This lability of chromatin periodic structure to high concentrations of urea is consistent with previous hydrodynamic and spectroscopic studies.

Visualization of chromatin substructure: upsilon bodies.

Spread chromatin fibers, from isolated eucaryotic nuclei, reveal linear arrays of spherical particles (upsilon bodies), about 70 A in diameter, connected by thin filaments about 15 A wide. These particles have been observed in freshly isolated nuclei from rat thymus, rat liver, and chicken erythrocytes. In addition, upsilon bodies can be visualized in preparations of isolated sheared chromatin, and in chromatin reconstructed from dissociating solvent conditions (i.e., high urea-NaCl concentration). As a criterion for perturbation of native chromatin structure low-angle X-ray diffraction patterns were obtained from nuclear pellets at different stages in the preparation of nuclei fro electron microscopy. These results suggest that the particulate (upsilon body) structures observed by electron microscopy may be closely related to the native configuration of chromatin.