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Biomedical subjects

E A Hansen

Publications and source records attributed to E A Hansen.

13 recordsLinked to original sources
PubMed2006

Relationship between efficiency and pedal rate in cycling: significance of internal power and muscle fiber type composition.

Cycling was performed to test the following two hypotheses: (1) muscular efficiency is unrelated to pedal rate (61, 88, and 115 r.p.m.) for a group of subjects with a wide range of slow twitch (ST) fibers in spite of decreasing whole-body efficiency and (2) muscular efficiency correlates positively with % ST muscle fibers, and this correlation is more pronounced at low pedal rates than at high pedal rates. Whole-body gross efficiency decreased from 20-22% at 61 r.p.m. to 15-18% at 115 r.p.m. Mean muscular efficiency for all subjects (n=16) was approximately 26%, with delta efficiency being constant and muscular efficiency (taking internal power into account) slightly increasing with pedal rate. Muscular efficiency correlated positively (R(2)=0.25) with % ST fibers (21-97% ST in m. vastus lateralis) at 115 r.p.m. while not at 61 and 88 r.p.m. In conclusion, the decrease in whole-body gross efficiency with increasing pedal rate was not explained by a decrease in muscular efficiency, and supported increase in internal power to account for the increase in metabolic power with increasing pedal rate. Furthermore, differences between individuals in muscle fiber type composition affected muscular efficiency, which correlated positively with % ST muscle fibers during fast pedalling.

Adult↗
PubMed2002

Muscle fibre type, efficiency, and mechanical optima affect freely chosen pedal rate during cycling.

UNLABELLED: This study investigated the variation in freely chosen pedal rate between subjects and its possible dependence on percentage myosin heavy chain I (%MHC I) in m. vastus lateralis, maximum leg strength and power, as well as efficiency. Additionally, the hypothesis was tested that a positive correlation exists between percentage MHC I and efficiency at pre-set pedal rates but not at freely chosen pedal rate. Twenty males performed cycling at low and high submaximal power output ( approximately 40 and 70% of the power output at which maximum oxygen uptake (VO(2max)) was attained at 80 r.p.m.) with freely chosen and pre-set pedal rates (61, 88, and 115 r.p.m.). Percentage MHC I as well as leg strength and power were determined. Freely chosen pedal rate varied considerably between subjects: 56-88 r.p.m. at low and 61-102 r.p.m. at high submaximal power output. This variation was only partly explained by percentage MHC I (21-97%) as well as by leg strength and power. Interestingly, %MHC I correlated significantly with the pedal rate at which maximum peak crank power occurred (r = -0.81). As hypothesized, %MHC I and efficiency were unrelated at freely chosen pedal rate, which was in contrast to a significant correlation found at pre-set pedal rates (r = 0.61 and r = 0.57 at low and high power output, respectively). CONCLUSIONS: Subjects with high percentage MHC I chose high pedal rates close to the pedal rates at which maximum peak crank power occurred, while subjects with low percentage MHC I tended to choose lower pedal rates, favouring high efficiency. Nevertheless, the considerable variation in freely chosen pedal rate between subjects was neither fully accounted for by percentage MHC I nor by leg strength and power. Previously recognized relationships between percentage Type I ( approximately %MHC I) and efficiency as well as between pedal rate and efficiency were confirmed for pre-set pedal rates, but for freely chosen pedal rate, these variables were unrelated.

Adolescent↗
PubMed2000

Linear free energy relationships implicate three modes of binding for fluoroaromatic inhibitors to a mutant of carbonic anhydrase II.

[figure: see text] Linear free energy relationships between binding affinity and hydrophobicity for a library of fluoroaromatic inhibitors of F131V carbonic anhydrase II (CA) implicate three modes of interaction. X-ray crystal structures suggest that F131 interacts with fluoroaromatic inhibitors, while P202, on the opposite side of the active site cleft, serves as the site of the hydrophobic contact in the case of the F131V mutant. 2-Fluorinated compounds bind more tightly, perhaps due to the field effect of the nearby fluorine on the acidity of the amide proton.

Carbonic Anhydrase Inhibitors↗
PubMed2000

Monocanalicular intubation for dacryostenosis in oculo-auriculo-vertebral dysplasia (hemifacial microsomia) with congenital corneal anesthesia.

PURPOSE: To present a case of oculo-auriculo-vertebral dysplasia associated with corneal anesthesia and ipsilateral dacryostenosis that was successfully treated with monocanalicular lacrimal intubation. METHODS: Case report. RESULTS: Previous neurotrophic corneal ulcers in a child with hemifacial microsomia had become secondarily infected from a stagnant tear lake, resulting in significant corneal scarring and visual loss. A single monocanalicular stent maintained nasolacrimal patency without causing further corneal trauma, despite constant medial gaze because of wide lateral tarsorrhaphy and contralateral occlusion therapy for amblyopia. CONCLUSIONS: Monocanalicular stents may aid the treatment of dacryostenosis in the face of compromised corneal sensation.

Abnormalities, Multiple↗
PubMed1990

Ocular anesthesia for cataract surgery: a direct sub-Tenon's approach.

We describe a new technique in which ocular anesthesia is obtained by dissection of the superior quadrants, as in strabismus or retinal surgery, followed by direct infusion of the retrobulbar space with local anesthetic agent, using a blunt 19-gauge cannula. In 112 cases of cataract surgery in which we used this direct sub-Tenon's approach, we found it to be a safe, simple, and effective method of achieving rapid ocular anesthesia.

Adult↗
PubMedDate not supplied

Escherichia coli chest-wall hemorrhagic cellulitis associated with central-line placement.

Cellulitis is a common clinical entity. Hemorrhagic cellulitis is distinctly unusual and is most frequent in compromised hosts. In normal or near normal hosts, hemorrhagic cellulitis may rarely complicate gram-negative sepsis. Usually, hemorrhagic cellulitis occurs below the waist. The differential diagnosis includes invasive streptococcal infection, mixed aerobic and anaerobic infection, gram-negative sepsis, and gross gangrene. We present the first-known case of Escherichia coli chest-wall hemorrhagic cellulitis associated with a central line in a patient with renal failure.

Aged↗
PubMedDate not supplied

Chorioretinitis sclopetaria from BB ex memoria.

Chorioretinitis sclopetaria presents a characteristic pattern of choroidal and retinal changes caused by a high velocity projectile passing into the orbit, in close proximity to the globe. While it is unlikely that a patient should completely forget the trauma causing such damage, preserved or compensated visual function may blur the patient's memory of these events over time. Characteristic physical findings help to clarify the antecedent history. Despite the lack of an acknowledged history of ocular trauma or surgery, in our case, the characteristic ocular findings discovered at presentation allowed for recognition of the underlying etiology. Because of good visual function, the patient had completely forgotten about the trauma that occurred 12 years earlier. Strabismus surgery was performed for treatment of the presenting symptomatic diplopia. The pathognomonic findings in chorioretinitis sclopetaria are invaluable in correctly diagnosing this condition, especially when a history of ocular trauma is unavailable.

Adult↗