Biomedical subjects

M E DeMont

Publications and source records attributed to M E DeMont.

5 recordsLinked to original sources

PubMed2000

The mechanics of locomotion in the squid Loligo pealei: locomotory function and unsteady hydrodynamics of the jet and intramantle pressure.

High-speed, high-resolution digital video recordings of swimming squid (Loligo pealei) were acquired. These recordings were used to determine very accurate swimming kinematics, body deformations and mantle cavity volume. The time-varying squid profile was digitized automatically from the acquired swimming sequences. Mantle cavity volume flow rates were determined under the assumption of axisymmetry and the condition of incompressibility. The data were then used to calculate jet velocity, jet thrust and intramantle pressure, including unsteady effects. Because of the accurate measurements of volume flow rate, the standard use of estimated discharge coefficients was avoided. Equations for jet and whole-cycle propulsive efficiency were developed, including a general equation incorporating unsteady effects. Squid were observed to eject up to 94 % of their intramantle working fluid at relatively high swimming speeds. As a result, the standard use of the so-called large-reservoir approximation in the determination of intramantle pressure by the Bernoulli equation leads to significant errors in calculating intramantle pressure from jet velocity and vice versa. The failure of this approximation in squid locomotion also implies that pressure variation throughout the mantle cannot be ignored. In addition, the unsteady terms of the Bernoulli equation and the momentum equation proved to be significant to the determination of intramantle pressure and jet thrust. Equations of propulsive efficiency derived for squid did not resemble Froude efficiency. Instead, they resembled the equation of rocket motor propulsive efficiency. The Froude equation was found to underestimate the propulsive efficiency of the jet period of the squid locomotory cycle and to overestimate whole-cycle propulsive efficiency when compared with efficiencies calculated from equations derived with the squid locomotory apparatus in mind. The equations for squid propulsive efficiency reveal that the refill period of squid plays a greater role, and the jet period a lesser role, in the low whole-cycle efficiencies predicted in squid and similar jet-propelled organisms. These findings offer new perspectives on locomotory hydrodynamics, intramantle pressure measurements and functional morphology with regard to squid and other jet-propelled organisms.

Animals↗

PubMed1997

Microfibrils provide non-linear elastic behaviour in the abdominal artery of the lobster Homarus americanus.

1. Microfibrils are becoming increasingly recognized as an important component of the extra-cellular matrix. However, almost nothing is known about their mechanical role in the diversity of tissues in which they are found. 2. Microfibrils form the principal structural component in the wall of the abdominal artery of the lobster Homarus americanus. We have used previous estimates of the mechanical properties of these microfibrils, estimates of the fraction of the aorta wall volume occupied by the microfibrils, and their angular distribution as a function of strain in a numerical model that predicts the macroscopic mechanical properties of the whole tissue. 3. Microfibrils alone, when their reorientation and deformation are accounted for, characterize the stress-strain behaviour of the vessel. Evidence of the evolutionary conservation of fibrillin between medusans, echinoderms and vertebrates implies that the mechanical properties of lobster microfibrils may apply to microfibrillar function in other taxa. This will have profound implications on the perceived roles of microfibrils in development, physiology and disease.

Animals↗

PubMed1996

The modulus of elasticity of lobster aorta microfibrils.

The presence of elastic fibres in the extracellular matrix (ECM) provides physiologically important elastic properties for many tissues. Until recently, microfibrils, one component of the ECM, were thought primarily to serve as a scaffolding on which elastin is deposited during development to form elaunin fibres [1]. The most prominent protein that forms mammalian microfibrils is fibrillin. It is known that mutations in the fibrillin gene cause a heterogenous connective tissue disease called Marfan syndrome [2], so information on mechanical properties of microfibrils or their role in tissue function would be useful. Microfibrils are also found in the ECM of some invertebrate tissues, and there is growing evidence that the protein forming the structure is homologous to mammalian fibrillin [3,4]. It has been shown that the microfibril-based arterial wall of the lobster has viscoelastic properties [5], and we have now utilized this primitive artery to measure the modulus of elasticity of microfibrils. It is similar to that of the rubber-like protein elastin.

Animals↗

PubMed1995

The structure and physical properties of invertebrate and primitive vertebrate arteries.

Light and electron microscopy and in vitro inflation experiments were conducted on the aortae of three different invertebrate species: the lobster Homarus americanus, the horseshoe crab Limulus polyphemus and the whelk Busycon contrarium. Inflation experiments were also performed on the aortae of two species of primitive vertebrates, the sea lamprey Petromyzon marinus and the Atlantic hagfish Myxine glutinosa. The inflation experiments demonstrated similar overall biomechanical properties in each case, despite the existence of differences in tissue structure. The vessels were compliant at low strains, but demonstrated nonlinear elasticity, increasing in stiffness as strains increased; this property could act as protection against artery wall rupture. The vessels of the lamprey, hagfish and lobster are capable of acting as fairly efficient elastic reservoirs and of smoothing blood flow during circulation as they had low hysteresis values (13-18%). The aortae of the horseshoe crab and whelk, if performing this function, have much higher energy losses, up to more than 30% per cycle. The microscopy studies of the aortae of the lobster, horseshoe crab and whelk revealed tissue structures which differ widely from each other as well as from the structures of the lamprey and hagfish. None of these arteries contained elastin, but all contained fibrillar material which differed in appearance, size and arrangement between species. These materials were conjectured to contribute to the elastic properties of the tissue.

Animals↗

PubMed1987

Interpersonal skills education in entry-level physical therapy programs.

The purpose of this study was to determine the current status of interpersonal skills (IPS) education in entry-level physical therapy programs with respect to content, course work requirements, and evaluation strategies. The disciplines of faculty members who teach IPS and their materials and methods also were explored. Using a 32-item questionnaire, we surveyed in 1984 all accredited baccalaureate (BS), certificate (CERT), and entry-level master's degree (MS) programs (N = 107) in physical therapy. Seventy-two responses (67.2%) were received, reflecting returns from 57 BS (64.7%), 5 CERT (83.3%), and 10 MS (76.9%) program respondents. Nearly all (97.2%, n = 70) of the respondents explicitly taught IPS in the classroom, but fewer of them evaluated learning (74.3%, n = 52). Overall, respondents teaching in MS programs consistently reported including a greater concentration of IPS content than the other two types of programs. All of the MS programs required specific IPS course work, compared with 50 (87.7%) of the BS programs and 3 (60%) of the CERT programs. Predominantly, faculty members who teach IPS are academically based physical therapists who use an extensive variety of methods and materials.

Curriculum↗