Biomedical subjects

M E Howard

Publications and source records attributed to M E Howard.

15 recordsLinked to original sources

PubMed2005

Quadrupole deformation of the self-conjugate nucleus 72Kr.

We report on the first determination of the absolute B(E2;0+(1)-->2+(1)) excitation strength in the N=Z nucleus 72Kr. 72Kr is the heaviest N=Z nucleus for which this quantity has been measured and provides a benchmark in a region of the nuclear chart dominated by rapidly changing deformations and shapes mediated by the interplay of strongly oblate and prolate-driving orbitals. The deduced quadrupole deformation strength is in agreement with a variety of self-consistent models that predict an oblate shape for the ground state of 72Kr. Large-scale shell-model Monte Carlo calculations reproduce the experimental B(E2) value and link the result to the occupation of the deformation-driving g9/2 orbit.

Journal Article↗

PubMed2001

An in situ study of metal complexation by an immobilized synthetic biopolymer using tapping mode liquid cell atomic force microscopy.

Near-field scanning optical microscopy and tapping mode, liquid cell atomic force microscopy were used to study the conformational changes in simple short-chain silica-immobilized biopolymer, poly(L-cysteine) (PLCys), as the polymer was exposed to reducing, metal-rich, and acidic environments, respectively, to simulate on-line metal preconcentration. In a reducing environment (0.01 M dithiothreitol in pH 7.0 ammonium acetate buffer), the PLCys features resembled islands on the surface of the glass, 36 +/- 7 nm in height and 251 +/- 60 nm in diameter. Upon exposure to metal (Cd2+ buffered at pH 7.0), the PLCys islands broke up into smaller metal binding clusters whose features were lower in height, 22 +/- 5 nm, and diameter, 213 +/- 53 nm. Exposure to 0.01 M HCl used for metal stripping resulted in protonation of the polymer chains and further reduction in the polymer height to 12 +/- 5 nm. These changes in molecular structure have given new insight into the mechanisms involved to achieve strong binding as well as rapid, quantitative release of bound metals to flexible short-chain synthetic biopolymers.

Biopolymers↗

PubMed2001

Pulmonary presentations of amyloidosis.

Respiratory tract involvement with amyloid is rare. We report eight cases of lower respiratory tract amyloidosis including a case of isolated pulmonary interstitial amyloidosis treated with chemotherapy, two cases of recurrent endobronchial amyloid with airway obstruction successfully treated with laser therapy and three cases of localized nodular pulmonary amyloidosis. The subjects with endobronchial and nodular amyloid demonstrated good long-term survival, while those with systemic or interstitial pulmonary amyloid had progressive disease and poor survival. Circulating monoclonal immunoglobulins were identified in five of the eight cases as the likely cause of the amyloid.

Adult↗

PubMed1998

Effect of lower extremity muscular fatigue on motor control performance.

PURPOSE: The purpose of this study was to determine whether lower extremity fatigue affects the ability of an individual to balance on an unstable platform. METHODS: Twenty healthy subjects (average age, 29 yr, range, 20 to 39 yr) were tested on an instrumented balance assessment system. Static tests were done on the limbs unilaterally and then bilaterally, and finally a dynamic test was performed in which the subject moved the platform in a circular manner to chase a moving object on a computer screen. After testing, subjects were fatigued using an isokinetic dynamometer, which imposes closed kinetic chain antagonistic exercise on the ankle, knee, and hip, similar to a stair stepper. No rest was allowed, and subjects were fatigued to less than 50% of their initial tested force. Subjects were then immediately retested on the unstable platform using the same testing protocol. All subjects completed the testing. RESULTS: Analysis of pre- and post-fatigue balance results demonstrated significant decreases in motor control performance on the three static tests following exercise to fatigue in all subjects (P < 0.001). CONCLUSIONS: Our findings support anecdotal evidence that fatigued individuals are at increased risk of injury because of loss of balance. Avoidance of fatigue and preconditioning may prevent injury.

Accidental Falls↗

PubMed1996

Bone-patellar tendon-bone grafts for anterior cruciate ligament reconstruction: the effects of graft pretensioning.

Viscoelastic creep is a well-known phenomenon associated with collagenous soft tissues under sustained tensile load. Despite our understanding of this phenomenon and the potential for "loosening" of the graft over time, pretensioning of bone-patellar tendon-bon (B-PT-B) grafts for reconstruction of the anterior cruciate ligament (ACL) to eliminate this elastic deformation is not commonly practiced. This investigation quantified viscoelastic creep in B-PT-B grafts using both an in vivo and an in vitro model. In vivo, 10-mm B-PT-B grafts were procured and prepared in a standard manner for arthroscopically assisted ACL reconstruction. A total of 153 grafts were evaluated. During preparation, each graft was tensioned using a commercially available graft preparation board (Smith & Nephew DonJoy). An initial tensile load of 2.25 N (0.5 lb) was applied to the graft and a measurement was taken between bone-tendon junctions at either end. A sustained load of 89 N (20 lb) was then applied for a minimum of 4 minutes and the measurement repeated. In the in vitro model, grafts were harvested in a standard manner, then placed in a servohydraulic for tensile loading. A differential variable reluctance transducer was implanted in each graft to quantify net displacement during 15 minutes of sustained tensile loading at 89 N (20 lb). A total of 13 specimens were evaluated. In the in vivo model, mean pretension bone-tendon junction length was 43.6 mm (range, 29 to 64 mm; SD, +/- 6.7). Mean post-tension bone-tendon length was 49.6 mm (range, 33 to 71 mm; SD, +/- 7.1), representing a mean increase in length of 6.0 mm (range, 2 to 12; SD, +/- 2.1) or 14.0% (range, 3.8 to 28.6; SD, +/- 5.2). In the in vitro model, the mean pretension tendon length was 42.81 m (range, 35.20 to 51.48; SD, 4.54). The mean post-tension length was 47.11 mm (range, 38.05 to 56.23; SD, +/- 5.04) representing a mean increase of 4.30 mm or 10.12%. These data would seem to support the hypothesis that without pretensioning, significant postimplantation graft creep will occur.

Adolescent↗

PubMed1995

Early motion after repair of Achilles tendon ruptures.

The purpose of this study was to evaluate the clinical outcome of patients treated with limited immobilization and early motion after repair of acute Achilles tendon ruptures. Thirteen consecutive patients with complete ruptures of the Achilles tendon were identified, repaired, and rehabilitated with early motion starting an average of 10 days after surgery. Active range of motion was begun at an average of 23 days and weightbearing in a walking boot was started at an average of 3.5 weeks after surgery. The average length of follow-up was 27 months. Twelve of 13 patients returned to running activities in an average of 3 months. All 12 patients who participated in lateral motion activities before their injury returned to similar activities in an average of 7 months. The patients rated their overall status at an average of 93% of their preinjury level. Follow-up Cybex testing demonstrated plantarflexion strength averaging 92%, plantarflexion power averaging 88%, and plantarflexion endurance averaging 88% of the nonindexed extremity. Early range of motion after Achilles repair is safe and there is no increased risk of rerupture in compliant patients. The patients achieved good return of plantarflexion strength, power, and endurance.

Achilles Tendon↗

PubMed1993

Rehabilitation of anterior cruciate ligament injuries.

Rehabilitation of the anterior cruciate ligament absent or reconstructed knee is becoming a true artform. Accelerated, but controlled rehabilitation, is becoming more commonplace. Scientific-based data along with clinical experiences are the basis of the rehabilitation guidelines brought forth in this article. Anterior cruciate ligament strain and implications for exercise, continuous passive motion, proprioceptive exercise, and the role of knee bracing are all discussed in relation to the overall rehabilitation program.

Anterior Cruciate Ligament Injuries↗

PubMed1985

Ion transport in goby intestine: cellular mechanism of urotensin II stimulation.

The Na- and Cl-absorbing goby posterior intestinal epithelium is composed predominantly of mitochondria-rich, tall columnar cells. Glass intracellular microelectrode recording technique was applied to absorptive cells of this relatively leaky epithelium to measure apical cell membrane potential difference (psi mc) and apical membrane fractional resistance. As determined by ion-substitution studies, absorptive cells are characterized by a large, Ba2+-inhibitable apical K conductance, which is a major factor determining psi mc and smaller Cl and Na conductances. Inhibition of the apical Na-Cl-coupled influx directly by furosemide or indirectly by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine produced hyperpolarization of psi mc, consistent with the greater apical membrane conductance to Cl than Na. The urophysial neurosecretory peptide urotensin II, which stimulates Na-Cl-coupled absorption, markedly depolarized psi mc in posterior intestinal tissues from 5% seawater-adapted gobies. This response is consistent with a stimulatory effect of urotensin II at the apical membrane carrier rather than at the basolateral Na-K-ATPase. Urotensin II is without effect on psi mc in tissues from seawater-adapted fish and somatostatin, a natural analogue of urotensin II, is without effect on tissues from fish adapted to either salinity. This specificity parallels that determined using radiotracer fluxes.

Animals↗

PubMed1985