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Biomedical subjects

D L Butler

Publications and source records attributed to D L Butler.

At least 91 records · Page 5Linked to original sources
PubMed1983

Area of depictions versus insufficient transformations in volume judgments.

Two hypotheses about judgments of apparent volume of depicted objects were compared. One hypothesis was that the area of the depiction influences judgments. The alternative was that volume judgments are based on an incomplete transformation from the two-dimensional stimulus to the object "implied" by the drawing. 38 college undergraduates ranked 24 drawings of rectangular boxes according to apparent volume. Results strongly supported the incomplete transformation hypothesis.

Adult↗
PubMed1982

Predicting the perception of three-dimensional objects from the geometrical information in drawings.

Three experiments investigated the hypothesis that perceived dimensionality of drawings of an object increases with the complexity of the drawings. Experiment 1 examined drawings of transparent objects. The results strongly supported this hypothesis: Judgments of each object tested increased approximately as step functions of complexity. In addition, the complexity at which the step occurred increased with the complexity of the object. Similar results were obtained in Experiment 2, which investigated drawings of solid objects. These experiments also provided support for a measure of complexity that includes a measure of how much is in the drawing as well as how organized the drawing is. In Experiment 2, there were some judgments that did not fit the hypothesis. Experiment 3 investigated the possibility that the deviant judgments were produced by alternate three-dimensional interpretations of the drawings. Results indicated that 12% of the drawings had multiple three-dimensional interpretations, but this did not explain the deviant judgments. Several methods of expanding the complexity hypothesis to handle the multiple interpretations and the deviant judgments are discussed.

Adult↗
PubMed1982

Inability of niacin to protect from in vivo hyperoxia or in vitro microsomal lipid peroxidation.

The efficacy of niacin in protecting rats from normobaric hyperoxia was evaluated in vivo by exposing niacin treated animals and controls to greater than 95% O2 for 96 hours. The vitamin was also evaluated as a possible free radical scavenger in vitro using an Fe-ascorbate initiated microsomal lipid peroxidation system. No protective effects were observed in vivo either in mortality or in differences in lung wet and dry weights of the niacin treated rats when compared to controls. Niacin in varying concentrations also did not decrease lipid peroxidation in the microsomal systems. Although this vitamin has been reported to protect animals from paraquat toxicity when given intraperitoneally once daily, niacin administered in similar doses does not appear to protect rats from hyperoxia.

Animals↗
PubMed1981

Does brightness contrast really affect the Mueller-Lyer illusion.

Several writers have hypothesized that the Mueller-Lyer illusion is influenced by brightness contrast between figure and background. According to them, lateral inhibition in the retina causes displacement in Mueller-Lyer figures at the intersections of lines. They argue that the strength of the displacement varies with brightness contrast between the background and the figure, and they cite research by Pollack and others for support. The experiments reported here show that the Mueller-Lyer illusion is no more affected by changes in contrast than are judgment of single straight lines. These results are not consistent with the view that lateral inhibition in the retina has an effect on the illusion.

Adolescent↗
PubMed1980

Knee ligament tests: what do they really mean?

In summary, newer biomechanical concepts clarify human function, the clinical laxity tests, and functional stability of the joint. Biomechanical studies show that one or two ligaments provide the primary passive restraint for each plane of knee stability, with the remaining ligaments having a secondary, helping role. Correct interpretation of clinical laxity tests and surgical treatment of instability require understanding of this differentiation. Knowledge of the interaction between the primary and secondary restraints during the clinical laxity tests allows for more accurate interpretation of the extent of ligament injury. Weak secondary restraints may initially allow little laxity to be demonstrated in the clinical laxity tests. However, the secondary restraints will eventually stretch out and cause a greater laxity. In an acute knee injury, "a little laxity is a lot" and should be considered as serious. In knee injuries, an exact diagnosis of injury is required. This often requires examination under anesthesia and arthroscopy to define the extent of ligament damage. Functional stability of the knee is a primary treatment goal after ligament injury but the stability may be short term if it relies on muscle control alone without the finetuning action of the ligamentous system. Abnormal laxity on clinical examination means increased risk for joint wear, cartilage deterioration, and arthritis on a long-term basis. Close follow-up after ligament injuries, adequate rehabilitation, and correct advice on allowable activities are important treatment concepts after any serious ligament injury.

Biomechanical Phenomena↗
PubMed1980

Arthroscopy in acute traumatic hemarthrosis of the knee. Incidence of anterior cruciate tears and other injuries.

In a prospective study, all injured knees that had traumatic hemarthrosis and absent or negligible instability on clinical examination underwent arthroscopy and examination under anesthesia. Eighty-five knees (eighty-three patients) were examined over a 125-week period. Some degree of disruption of the anterior cruciate ligament was found in sixty-one (72 per cent) of the knees (a partial tear in 28 per cent and a complete tear in 44 per cent), frequently associated with an injury of varying severity to other joint structures. These included minor ligament sprains without laxity in 41 per cent, a major associated ligament injury in 21 per cent, meniscal tears in 62 per cent (partial in 30 per cent and complete in 70 per cent), and a femoral chondral fracture or surface defect in 20 per cent. A popping sensation at injury occurred in 33 per cent of knees with a normal anterior cruciate ligament and in 36 per cent of those with a disruption. One-third of the knees had no to slight pain at the time of injury. The anterior drawer test without anesthesia was positive in only 24 per cent of the knees with a torn anterior cruciate ligament. We concluded that: (1) a traumatic hemarthrosis indicates a significant knee injury; (2) examination under anesthesia plus arthroscopy allows a more accurate diagnosis of injury to joint structures; and (3) such data are required for a rational treatment program to be outlined.

Adolescent↗
PubMed1980

Effect of inline filtration on the potency of low-dose drugs.

Simulating actual conditions of intravenous infusion, a number of routinely used additive drugs were tested for potential binding to an inline i.v. filter containing a cellulose ester membrane. Two infusion solutions, 5% dextrose and 0.9% sodium chloride, were used to deliver the drugs. Drug samples were assayed before and after passage through the filter by the following methods: bleomycin sulfate, cyanocobalamin, ergonovine maleate, mithramycin, vinblastine sulfate, and vincristine sulfate by direct spectrophotometry; oxytocin by biological assay; levarterenol by fluorescence; and folic acid, heparin, insulin, and digitoxin by radiotracer methods. Measurable reduction in potency occurred in both infusion solutions with digitoxin, insulin, mithramycin, and vincristine sulfate. No reduction in potency was observed in either infusion solution with bleomycin sulfate, cyanocobalamin, ergonovine maleate, folic acid, heparin, leverterenol bitartrate, oxytocin, and vinblastine sulfate. The study results indicate that the potency of drugs administered intravenously in small doses could be significantly reduced during inline filtration through a filter containing a cellulose ester membrane.

Filtration↗
PubMedDate not supplied

Comparative in vitro activity of gemifloxacin, ciprofloxacin, levofloxacin and ofloxacin in a North American surveillance study.

The in vitro activity of gemifloxacin, a new fluoroquinolone, was compared to three marketed fluoroquinolones; ciprofloxacin, levofloxacin and ofloxacin against over 4,000 recent clinical isolates covering 29 species isolated in the United States and Canada between 1997-1999. Based on MIC(90)s, gemifloxacin was the most potent fluoroquinolone tested against a majority of Gram-positive isolates: Streptococcus pneumoniae, penicillin resistant S. pneumoniae, macrolide resistant S. pneumoniae, ciprofloxacin non-susceptible (MIC > or = 4 microg/mL) S. pneumoniae, S. pyogenes, S. agalactiae, viridans streptococci, Enterococcus faecalis, methicillin susceptible Staphylococcus aureus, methicillin resistant S. aureus, S. epidermidis, S. hemolyticus, and S. saprophyticus. Against Enterobacteriaceae and aerobic non-Enterobacteriaceae Gram-negatives, gemifloxacin was usually comparable to ciprofloxacin and levofloxacin and more potent than ofloxacin for the following species: Citrobacter freundii, Enterobacter aerogenes, E. cloacae, Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae, Morganella morganii, Proteus mirabilis, P. vulgaris, Providencia stuartii, Serratia marcescens, Acinetobacter lwoffii, A. baumannii, Burkholderia cepacia, Haemophilus influenzae, H. parainfluenzae, Moraxella catarrhalis, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia. Gemifloxacin was generally 16-64 fold more potent than the other fluoroquinolones tested against Gram-positive organisms and retains excellent activity comparable with ciprofloxacin and levofloxacin against a majority of Gram-negative pathogens.

Anti-Infective Agents↗
PubMedDate not supplied

In search of the architect of learning: a commentary on scaffolding as a metaphor for instructional interactions.

In this article, I accept Stone's invitation to reevaluate the metaphor of scaffolding, building on his helpful analysis. Specifically, I identify what has been appealing about the scaffolding metaphor by describing how, as an intervention researcher working with students with learning disabilities, I have used the metaphor to describe a specific instructional approach in my own research. Then, I revisit and critique scaffolding as an instructional metaphor. I also comment on Stone's assertion that a more explicit description of communicative interchanges is required to more clearly describe instructional scaffolding. Finally, I conclude that the scaffolding metaphor is fundamentally flawed and advance an alternative view that may more successfully promote correspondence between instructional activities and our emerging vision of the dynamics of teaching and learning.

Child↗
PubMedDate not supplied

Freeze dried anterior cruciate ligament allografts. Preliminary studies in a goat model.

One ACL in each of 11 mature goats was replaced with a freeze dried bone-ACL-bone allograft. One year following implantation the goats had their knees evaluated biomechanically and for microvascularity and histologic changes. The reconstructed knees had a significantly greater total AP laxity (3.8 +/- 0.6 mm) (mean and SEM) than the controls (1.0 +/- 0.1 mm). Differences in primary AP laxity were responsible for 81% of the difference in total laxity, with only a 0.4 mm difference in secondary laxity. Neutral stiffness in the reconstructive knee was 17% of control, while stiffness at 30 newtons (N) of anterior force was approximately 50% of controls. Ligament stiffness in the linear region for the ACL allograft was 35% of the control value of 686 N/mm. The maximum load of the allografts was 571 +/- 45 N, or 25% of the contralateral ACL control strength (2301 +/- 155 N). Five of the seven allografts failed at the femoral insertion. Both elongation (83%) and energy (21%) to maximum load were less for allografts than controls. Histologic evaluation of the allografts revealed the presence of a regular oriented dense connective tissue which resembled a normal ligament. Microangiography revealed a periligamentous and endoligamentous vascular pattern reminiscent of a normal ACL and complete revascularization of the bone plugs.

Animals↗
PubMedDate not supplied

Cruciate reconstruction using freeze dried anterior cruciate ligament allograft and a ligament augmentation device (LAD). An experimental study in a goat model.

One ACL in each of 11 mature goats was replaced with a freeze dried bone-ACL-bone allograft and a ligament augmentation device (LAD). The LAD was released from its tibial fixation at 3 months postoperation. Biomechanical, microvascular, and histological changes were evaluated 1 year following implantation. The reconstructed knees had a significantly greater total AP translation (3.1 +/- 0.5 mm) (mean and SEM) than the contralateral controls (1.0 +/- 0.1 mm). Differences in primary AP translation were responsible for 59% of the difference in total translation, with only a 0.6 mm difference in secondary translation. Neutral stiffness in the reconstructive knee was 22% of control, while stiffness at 30 N of anterior force was approximately 35% of controls. Ligament stiffness in the linear region for the ACL allograft/LAD was 53% of the control value of 691 N/mm. The maximum load of the allograft/LADs was 1,052 +/- 145 N, or 43% of the contralateral ACL control strength (2,448 +/- 144 N). Five of the six allografts failed at the femoral insertion. Energy (39%) to maximum load was less for allograft/LADs than controls but elongation to maximum load was the same as control. Histologic evaluation of the allograft/LADs revealed soft tissue cellular ingrowth into the LAD in the extraarticular portions. No bony growth into the LAD was observed. The collagen fibers of the graft appear to be arranged in a longitudinal orientation although some areas show chaotic collagen fibers. Microangiography revealed a periligamentous and endoligamentous vascular pattern reminiscent of a normal ACL and complete revascularization of the bone plugs.

Animals↗