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Biomedical subjects

S C Johnson

Publications and source records attributed to S C Johnson.

At least 73 records · Page 4Linked to original sources
PubMed1995

Nonspecific white matter degeneration following traumatic brain injury.

Morphometric analysis of magnetic resonance (MR) scans in 88 traumatic brain injury (TBI) patients demonstrated significantly larger ventricle-to-brain ratios (VBR) and temporal horn volumes, and significantly smaller fornix-to-brain ratios (FBR) and corpus callosum (CC) area measurements, compared to 73 controls. Additionally, TBI patients were grouped according to Glasgow Coma Scale (GCS) for a within-TBI sample comparison so that severity of injury on brain morphology could be examined. The severe TBI group (GCS = 3-6) differed from the mild and moderate injury groups on measures of the internal capsule, VBR, temporal horn volume, and CC. In a separate analysis wherein the TBI subjects were grouped by degree of fornix atrophy, the group with the smallest fornix size demonstrated the lowest memory performance. Furthermore, anatomic measures correlated with severity of injury, and tests of memory and motor function. Results demonstrate the diffuse nature of degeneration in TBI with more severe injury, and that quantified MR identified morphologic changes relate to neuropsychological outcome.

Adolescent↗
PubMed1995

Severe anoxia with and without concomitant brain atrophy and neuropsychological impairments.

Significant anoxia may cause a variety of neuropathologic changes as well as cognitive deficits. We have recently seen 3 patients who have suffered severe anoxic episodes all with initial Glasgow Coma Scores (GCS) of 3 with sustained coma for 10-14 d. All 3 patients had extended hospitalizations and rehabilitation therapy. A neuropsychological test battery was administered and volumetric analyses of MRI scans were carried out in each case at least 6 mo postinjury. Two of the patients display distinct residual cognitive and neuropathologic changes while 1 patient made a remarkable recovery without evidence of significant morphological abnormality. These three cases demonstrate, that even with similar admission GCS, the outcome is variable and the degree of neuropsychological impairment appears to match the degree of morphologic abnormalities demonstrated by quantitative MR image analysis. An important finding of this study is that even though subjects with an anoxic insult exhibit severe cognitive and memory impairments along with concomitant morphologic changes, their attention/concentration abilities appear to be preserved. MR morphometry provides an excellent means by which neural structural changes can be quantified and compared to neuropsychological and behavioral outcomes.

Adult↗
PubMed1995

Trauma-induced degenerative changes in brain injury: a morphometric analysis of three patients with preinjury and postinjury MR scans.

Three patients with pretraumatic and posttraumatic brain injury (TBI) MR imaging of the brain are presented. Two patients had moderate to severe injury, whereas the third patient sustained a mild injury. Using imaging software to conduct morphometric analyses, quantitative neuropathologic change was ascertained in each TBI patient. Each case was compared quantitatively to preinjury scans as well as to an age-matched control group. For the moderately to severely injured patients, extensive degenerative changes were found throughout the various cortical structures and the cerebellum, whereas most midbrain and brainstem measures did not demonstrate significant change. For these two patients, the most significant changes occurred within the ventricular system, where generalized ventricular dilation was observed post-TBI. In the mild case, no significant anatomic changes were evident. These case studies demonstrate the use of quantitative methods for examining the structural basis of TBI sequelae.

Adult↗
PubMed1995

District nebuliser compressor service: reliability and costs.

BACKGROUND: There is little information on the costs of maintaining a district nebuliser compressor service. This retrospective study examines the issue, reliability, and maintenance costs of electrical compressors to assist the prediction of future costs, taking into account recent safety legislation. METHODS: Records of issue, repair, and replacement for the period 1982-91 were reviewed. The current policy of repairing and replacing as necessary, and three other theoretical costings, were considered. RESULTS: The number of compressors being issued is increasing. Repaired compressors are less reliable and frequency of repair is a function of compressor age. The current policy is the most cost effective. CONCLUSIONS: To repair and replace nebuliser compressors as necessary is the most economical policy under the present terms offered by the manufacturers, but changes in safety legislation will affect the provision of such services.

Electric Power Supplies↗
PubMed1995

Quantitative volumetric analysis of brain MR: normative database spanning 5 decades of life.

PURPOSE: To present a normative volumetric database, spanning 5 decades of life, of cerebrospinal fluid, subarachnoid cerebrospinal fluid, total brain volume, total ventricular volume (component ventricular volumes of lateral, temporal horn, and third and fourth ventricles) and estimates of white and gray matter, based on a multispectral segmentation of brain MR. This database is presented as a reference for future studies comparing pathologic states. METHOD: One hundred ninety-four healthy subjects, ranging in age from 16 to 65 years, received standard axial intermediate- and T2-weighted spin-echo MR images. Multispectral segmentation and volume analysis were performed using ANALYZE. RESULTS: Normative volumetric estimates, both uncorrected and corrected for differences in total intracranial volume, were obtained for all subjects and presented by decade and sex. Age-related cerebrospinal fluid changes were evident for both male and female subjects. Most gender differences were eliminated by correction for differences in total intracranial volume. Standard and fast spin-echo acquisition methods gave comparable volume estimates. Total brain volume measurements from MR compare favorably with data from large autopsy series. CONCLUSION: Although there may be limitations to generalizations, these normative data tables can provide a comparison index for contrasting pathologic groups with a normative sample.

Adolescent↗
PubMed1995

Anterior cruciate ligament injury in elite Alpine competitors.

Balance in Alpine skiing is dynamic and tenuous. Loss of balance typically leads to the accumulation of forces that create severe bending moments at the knee. The modern ski binding, while effective at protecting the ankle and lower leg, is much less effective at protecting the knee. The result: knee injuries have increased nearly three-fold since 1972 with anterior cruciate ligament (ACL) injuries currently accounting for approximately 10% of all skiing injuries. The mechanism of ACL injury in elite competitors is distinct from recreational skiers and is typically associated with a characteristic, deeply flexed, seated body position, with the feet accelerating forward relative to the upper body. The risk of ACL injury in elite skiers is compounded by the functional characteristics of the modern ski binding and further exacerbated by the protocols used to set release tension for competition. It is apparent that the physical abilities of the elite competitor, combined with modern ski technique and equipment, expose the skier to forces that the human body cannot tolerate. Presently, the only solution to the problem would appear to be the development of "smarter" bindings and/or the adoption of standards that set limitations on performance for the sake of safety.

Anterior Cruciate Ligament↗
PubMed1994

The effects of aerobic exercise after lumbar microdiscectomy.

STUDY DESIGN: This study determined whether lumbar discectomy patients could endure an aerobic exercise program sufficient to achieve a training effect, and whether any functional advantages were derived. METHODS: Trained volunteers (n = 19) were compared with untrained control subjects (n = 18) after a 12-week aerobic and rehabilitation exercise program. Subjects completed a maximal graded exercise test, a hydrostatic weighing test, and a battery of self-report inventories. RESULTS: Using a discriminant analysis, as a post hoc test, maximal oxygen consumption was found to be the factor responsible for the difference between the groups (P < 0.006). CONCLUSION: Oxygen consumption was more than three times as important as any other single variable in differentiating between the groups.

Adult↗
PubMed1994

A synthetic route to 3-C-alkyl (or 3-C-phenyl-) 2,3-dideoxy-D-erythro-pentono-1,4-lactones: intermediates in the synthesis of 2(3H)-furanones.

A series of 3-C-alkyl- (and 3-C-phenyl-) 2,3-dideoxy-D-erythro-pentono-1,4-lactones, compounds which are important in the synthesis of modified nucleosides and antibiotic sugars, were synthesized from D-ribonolactone. By a route that proceeded via 5-O-protected D-ribonolactone, 5-O-protected 2,3-dideoxy-D-glycero-pent-2-enono-1,4-lactones were synthesized and reacted with R2CuLi or a complex PhSCu(RMgBr)n to give respectively the 3-C-alkyl or 3-C-phenyl compounds. Details of the preparation of the O-protected intermediates, as well as the selection of the organometallic reagents, are provided.

4-Butyrolactone↗
PubMed1994

Corpus callosum surface area across the human adult life span: effect of age and gender.

This magnetic resonance (MR) imaging study analyzed and provides normative data on the midsagittal surface area of the corpus callosum (CC) across the human adult life span in 200 normal volunteers. Using MR imaging scans, CC midsagittal surface area was quantified, along with midsagittal intracranial surface area and total intracranial volume (measures of cranial size). Results demonstrate that when head size is controlled, no major changes associated with normal aging are evident in the CC during the more active years of adult life span (up through 65). Overall, females had significantly larger CC relative to total intracranial volume. Results are discussed in terms of potential gender differences in CC size and the clinical application of this normative data.

Adolescent↗
PubMed1994

The effect of aerodynamic handlebars on oxygen consumption while cycling at a constant speed.

In this study, the oxygen consumption (VO2) of bicycling was measured at a fixed speed (40 km.h-1), on level terrain, with normal and aerodynamic handlebars using a Douglas bag collection system. Eleven elite (USCF category 1 or 2) men cyclists age 24 to 40 years (mean = 28.5, SD +/- 4.6) performed four consecutive (two with each bar in alternating order) steady state rides at 40 km.h-1 over a 4 km flat course (same direction each trial). Expired gases were collected in a 1501 Douglas bag attached to a following vehicle during the last 45 s (approx. 0.5 km) of each trial. A repeated measures analysis of variance revealed a significant (p < 0.02) handlebar effect. Specifically, VO2 was 2% lower under the aerodynamic handlebar treatment (mean = 4.26, SD +/- 0.36 l.min-1) when compared with that of the normal handlebar treatment (mean = 4.34, SD +/- 0.35 l.min-1). The results of this study demonstrate that the reported aerodynamic advantage of the aerodynamic handlebars produces a small but significant reduction in the VO2 of bicycling at 40 km.h-1.

Adult↗
PubMed1994

Double Z-plasty to enhance rhombic flap mobility.

BACKGROUND: Occasionally after a rhombic flap has been designed, cut, and undermined, it fails to transpose into the recipient wound as easily as had been anticipated. This problem may have occurred because of unexpected skin tension due to previous surgery near the operative site or improper orientation of the rhombic flap. OBJECTIVE: The purpose of this work is to show how unexpected restriction in rhombic flap movement can be overcome by using a double Z-plasty to increase tissue length. METHODS: A double Z-plasty was incorporated into the rhombic flap design in one patient. The biomechanics of the flap were analyzed, and the modified flap was used in three other patients. RESULTS: The addition of a double Z-plasty increased the movement of the rhombic flap in a predictable fashion in four patients. CONCLUSION: A double Z-plasty is useful to enhance rhombic flap mobility in certain uncommon situations.

Biomechanical Phenomena↗
PubMed1994

Isolation of Mycoplasma species from bronchoalveolar lavages of patients positive and negative for human immunodeficiency virus.

The rates of isolation of Mycoplasma species from bronchoalveolar lavages of human immunodeficiency virus (HIV)-infected patients and HIV-negative patients were compared. Mycoplasma species were more frequently isolated from HIV-positive patients. In most cases, a known pulmonary pathogen was also identified. All samples tested negative for Mycoplasma fermentans by PCR.

AIDS-Related Opportunistic Infections↗