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Biomedical subjects

J E Johnson

Publications and source records attributed to J E Johnson.

At least 109 records · Page 6Linked to original sources
PubMed1999

Hindfoot coronal alignment: a modified radiographic method.

Accurate clinical evaluation of the alignment of the calcaneus relative to the tibia in the coronal plane is essential in the evaluation and treatment of hindfoot pathologic condition. Previously described radiographic views of the foot and ankle do not demonstrate the true coronal alignment of the calcaneus relative to the tibia. Some of these views impose on the patient an unnatural posture that itself changes hindfoot alignment, whereas other methods distort the coronal alignment by the angle of the x-ray beam. Our purpose was to develop a modified radiographic view and measurement method for determining an angular measurement of hindfoot coronal alignment based on a cadaver study of the radiographic characteristics of the calcaneus and motion analysis of standing subjects. The view was obtained by having the subject stand on a piece of cardboard to create a foot template. The template was then positioned so that each foot was x-rayed perpendicular to the cassette while still maintaining the natural base of support. A method using multiple ellipses was developed to determine more accurately the coronal axis of the posterior calcaneus. A study using cadavers was performed in which radio-opaque markers were placed on multiple bony landmarks on the calcaneus. The tibia was held fixed in a vertical position, and the foot was x-rayed using the above techniques in different degrees of rotation without changing the relation of the calcaneus to the tibia. The radiographs of the modified Cobey and our view were examined to verify which markers were visible at different angles of rotation and how the hindfoot alignment measurements changed with foot rotation. To define further the differences between the views, an analysis of postural stability was conducted while the subjects were standing with the feet in the positions for imaging both the Buck modification of the Cobey view and our hindfoot alignment view. The combined results of the cadaver, radiographic measurement, and postural stability segments of the study reveal that this coronal hindfoot alignment view and measurement method is reproducible, more closely measures "true" coronal hindfoot alignment, and is more clinically applicable because the alignment is measured while the patient is standing with a normal angle and base of stance. The modified radiographic measurement method relies on posterior calcaneal anatomic landmarks, is less affected by rotation of the foot and ankle, and is reproducible between observers.

Adult↗
PubMed1999

Older rural women and the use of complementary therapies.

One hundred seventy-five rural women over the age of 70 participated in a study to assess their use of complementary therapies and practitioners. Data were collected via questionnaires and interviews. Findings suggest that these women used nontraditional health practices to treat a variety of symptoms, as well as to maintain their independence. However, very few of them informed their primary care providers that they used complementary therapies and practitioners. The majority were inadequately informed regarding the efficacy and safety of the therapies.

Aged↗
PubMed1999

Defects in thalamocortical axon pathfinding correlate with altered cell domains in Mash-1-deficient mice.

We have analyzed the pathfinding of thalamocortical axons (TCAs) from dorsal thalamus to neocortex in relation to specific cell domains in the forebrain of wild-type and Mash-1-deficient mice. In wild-type mice, we identified four cell domains that constitute the proximal part of the TCA pathway. These domains are distinguished by patterns of gene expression and by the presence of neurons retrogradely labeled from dorsal thalamus. Since the cells that form these domains are generated in forebrain proliferative zones that express high levels of Mash-1, we studied Mash-1 mutant mice to assess the potential roles of these domains in TCA pathfinding. In null mutants, each of the domains is altered: the two Pax-6 domains, one in ventral thalamus and one in hypothalamus, are expanded in size; a complementary RPTP(delta) domain in ventral thalamus is correspondingly reduced and the normally graded expression of RPTP(delta) in that domain is no longer apparent. In ventral telencephalon, a domain characterized in the wild type by Netrin-1 and Nkx-2.1 expression and by retrogradely labeled neurons is absent in the mutant. Defects in TCA pathfinding are localized to the borders of each of these altered domains. Many TCAs fail to enter the expanded, ventral thalamic Pax-6 domain that constitutes the most proximal part of the TCA pathway, and form a dense whorl at the border between dorsal and ventral thalamus. A proportion of TCAs do extend further distally into ventral thalamus, but many of these stall at an aberrant, abrupt border of high RPTP(delta) expression. A small proportion of TCAs extend around the RPTP(delta) domain and reach the ventral thalamic-hypothalamic border, but few of these axons turn at that border to extend into the ventral telencephalon. These findings demonstrate that Mash-1 is required for the normal development of cell domains that in turn are required for normal TCA pathfinding. In addition, these findings support the hypothesis that ventral telencephalic neurons and their axons guide TCAs through ventral thalamus and into ventral telencephalon.

Afferent Pathways↗
PubMed1999

Position-dependent processing of peptides presented on the surface of cowpea mosaic virus.

The plant virus cowpea mosaic virus (CPMV) has been developed as an epitope-presentation system. Numerous epitopes have been expressed in the betaB-betaC loop of the CPMV small coat protein, all of which undergo a cleavage reaction between their two carboxy-terminal residues. Although many peptides presented in this manner give an authentic immune response, this was not the case for the NIm-1A epitope from human rhinovirus-14. Crystallography revealed significant differences between the structure of NIm-1A on CPMV compared with its native configuration. The 3D structure of C PMV expressing NIm-1A was used to design alterations to the context of the NIm-1A graft.

Amino Acid Sequence↗
PubMed1999

Urban older adults and the forfeiture of a driver's license.

Frequently, it is assumed that urban older adults are not vulnerable to the consequences of forfeiting a driver's license because of the availability of public transportation. Although all of the study participants were involved in accidents prior to forfeiting their driver's licenses, 221 (78%) of them stated they had been safe drivers. The majority of participants indicated they had been given no choice by either their families or the bureaucracy in forfeiting their driver's licenses. Regret, loneliness, and immobility were the results of no longer being allowed to drive.

Adaptation, Psychological↗
PubMed1999

Use of computed tomography and plantar pressure measurement for management of neuropathic ulcers in patients with diabetes.

BACKGROUND AND PURPOSE: Total contact casting is effective at healing neuropathic ulcers, but patients have a high rate (30%-57%) of ulcer recurrence when they resume walking without the cast. The purposes of this case report are to describe how data from plantar pressure measurement and spiral x-ray computed tomography (SXCT) were used to help manage a patient with recurrent plantar ulcers and to discuss potential future benefits of this technology. CASE DESCRIPTION: The patient was a 62-year-old man with type 1 diabetes mellitus (DM) of 34 years' duration, peripheral neuropathy, and a recurrent plantar ulcer. Although total contact casting or relieving weight bearing with crutches apparently allowed the ulcer to heal, the ulcer recurred 3 times in an 18-month period. Spiral x-ray computed tomography and simultaneous pressure measurement were conducted to better understand the mechanism of his ulceration. OUTCOMES: The patient had a severe bony deformity that coincided with the location of highest plantar pressures (886 kPa). The results of the SXCT and pressure measurement convinced the patient to wear his prescribed footwear always, even when getting up in the middle of the night. The ulcer healed in 6 weeks, and the patient resumed his work, which required standing and walking for 8 to 10 hours a day. DISCUSSION: Following intervention, the patient's recurrent ulcer healed and remained healed for several months. Future benefits of these methods may include the ability to define how structural changes of the foot relate to increased plantar pressures and to help design and fabricate optimal orthoses.

Casts, Surgical↗
PubMed1999

An honest response.

Explore the source record for details and available documents.

Blue Cross Blue Shield Insurance Plans↗
PubMed1999

Bilevel multidisciplinary discharge planning and length of stay.

As health care funding gets more and more tenuous, leaders in all institutions are called upon to find innovative ways to reduce costs while maintaining quality. It is possible to realize undreamed-of savings by reengineering certain processes, but such an undertaking demands that wholesale changes in the corporate culture and substantial effort at all levels. This paper reports a long-term project at a large, urban, tertiary care institution, the redesign of discharge planning to improve patient care and reduce lengths of stay and related expenses.

Health Care Reform↗
PubMed1998

Imaging RNA and dynamic protein segments with low-resolution virus crystallography: experimental design, data processing and implications of electron density maps.

Single crystal diffraction data were collected from virus crystals in the resolution range of 270 to 14 A using a synchrotron X-ray source and a small-angle scattering instrument adapted for single crystal measurements. Reflections were measured from single crystals of the capsid of the double-stranded DNA bacteriophage HK97 and synthetic Flock House virus-like particles (sFHV). The quality of the low-resolution measurements was confirmed by excellent scaling statistics for both data sets. The sFHV amplitudes between 270 and 90 A resolution were closely similar to independently measured solution scattering data, and to data calculated from the Fourier transform of a uniform density sphere of 315 A diameter. A rotation function computed with the sFHV data between 70 and 20 A resolution was readily interpretable. A uniform density sphere model was used to compute phases for measured amplitudes between 270 and 68 A resolution. The calculated phases were refined and extended to 14 A resolution with real space averaging employing an external mask shape defined by the high-resolution structure. The resulting electron density map displayed regions interpretable as loosely ordered RNA that connected ordered RNA segments seen in a published 3.0 A resolution map. The published high-resolution electron density map lacked data inside 15 A resolution and the interior of the particle in that map appeared hollow. Difference electron density maps corresponding to bulk RNA were computed by subtracting the contribution of the protein shell, based on the available high-resolution atomic model, from either the cryo-electron microscopy density or the low-resolution X-ray density. Features of the RNA were closely similar in the cryo-electron microscopy and X-ray maps, demonstrating the consistency of the two imaging methods. Electron density maps computed at 14 and 6 A resolution with the X-ray amplitudes showed that RNA contributed little to the scattering beyond 14 A resolution.

Bacteriophages↗
PubMed1998

A plasma membrane localization signal in the HIV-1 envelope cytoplasmic domain prevents localization at sites of vesicular stomatitis virus budding and incorporation into VSV virions.

Previous studies showed that the HIV-1 envelope (Env) protein was not incorporated into vesicular stomatitis virus (VSV) virions unless its cytoplasmic tail was replaced with that of the VSV glycoprotein (G). To determine whether the G tail provided a positive incorporation signal for Env, or if sequences in the Env tail prevented incorporation, we generated mutants of Env with its 150-amino-acid tail shortened to 29, 10, or 3 amino acids (Envtr mutants). Cells infected with VSV recombinants expressing these proteins or an Env-G tail hybrid showed similar amounts of Env protein at the surface. The Env-G tail hybrid or the Envtr3 mutant were incorporated at the highest levels into budding VSV virions. In contrast, the Envtr29 or Envtr10 mutants were incorporated poorly. These results defined a signal preventing incorporation within the 10 membrane-proximal amino acids of the Env tail. Confocal microscopy revealed that this signal functioned by causing localization of human immunodeficiency virus type 1 Env to plasma membrane domains distinct from the VSV budding sites, where VSV proteins were concentrated.

Amino Acid Sequence↗
PubMed1998

Structure determination of Nudaurelia capensis omega virus.

The structure of Nudaurelia capensis omega virus (NomegaV), a single-stranded RNA virus, was determined to 2.8 A resolution. Triclinic crystals (a = 413.6, b = 410.2, c = 419.7 A, alpha = 59.13, beta = 58.9, gamma = 64.0 degrees ) diffracted X-rays beyond 2.7 A resolution. The unit cell contained one icosahedral virus particle, providing 60-fold non-crystallographic symmetry (n.c.s.) and structural redundancy. The particle orientation in the unit cell was determined by self-rotation function analyses. Initial phases to 18 A resolution were derived from a hollow spherical model of 192 A outer radius and 139 A inner radius, filled with uniform electron density. Radii of the model were determined by maximizing the correlation of the model-based calculated data with the low-resolution X-ray diffraction and solution-scattering data. Phases were refined by 60-fold non-crystallographic electron-density averaging and extended in small steps to a resolution of 5 A. The phases obtained represented a mixture of four different phase sets, each consistent with the icosahedral symmetry constraints. The resulting electron density was not interpretable. A difference Fourier map computed with the native and an isomorphous heavy-atom derivative data sets and phases refined by real-space averaging was interpretable only if data within the 10 A resolution shell were used. Maps calculated with data significantly higher than 10 A resolution failed to display a constellation of heavy-atom sites consistent with the T = 4 icosahedral symmetry. Attempts to extend the phases beyond 10 A resolution, starting with either phases based on a model or single isomorphous replacement, were unsuccessful. Successful phase extension was achieved by computing the phases for the higher resolution reflections from a partial atomic model (poly gly) built into the averaged 10 A electron-density map. Phases from this model served as the starting point for n.c.s. phase refinement and extension to slightly higher resolution. The atomic model was improved at each extension interval and these phases were used for the subsequent phase calculation and extension. The entire polypeptide backbone corresponding to the NomegaV structure was built into the map at 4 A. The same procedure for phase refinement was used to extend the phases to 2.8 A in small increments of resolution. The overall molecular averaging R factor and correlation coefficient at 2.8 A resolution were 18.4% and 0.87, respectively.

Capsid↗