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Biomedical subjects

J Hogan

Publications and source records attributed to J Hogan.

At least 73 records · Page 4Linked to original sources
PubMed1991

Kinetics of the barotropic ripple (P beta')/lamellar liquid crystal (L alpha) phase transition in fully hydrated dimyristoylphosphatidylcholine (DMPC) monitored by time-resolved x-ray diffraction.

We present here the first study of the use of a pressure-jump to induce the ripple (P beta')/lamellar liquid crystal (L alpha) phase transition in fully hydrated 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). The transition was monitored by using time-resolved x-ray diffraction (TRXRD). Applying a pressure-jump from atmospheric to 11.3 MPa (1640 psig, 111.6 atm) in 2.5 s induces the L alpha to P beta' phase transition which takes place in two stages. The lamellar repeat spacing initially increases from a value of 66.0 +/- 0.1 A (n = 4) to a maximum value of 70.3 +/- 0.8 A (n = 4) after 10 s and after a further 100-150 s decreases slightly to 68.5 +/- 0.3 A (n = 4). The reverse transition takes place following a pressure jump in 5.5 s from 11.3 MPa to atmospheric pressure. Again, the transition occurs in two stages with the repeat spacing steadily decreasing from an initial value of 68.5 +/- 0.3 A (n = 3) to a minimum value of 66.6 +/- 0.3 A (n = 3) after 50 s and then increasing by approximately 0.5 A over a period of 100 s. The transition temperature increases linearly with pressure up to 14.1 MPa in accordance with the Clapeyron relation, giving a dT/dP value of 0.285 degrees C/MPa (28.5 degrees C/kbar) and an associated volume change of 40 microliters/g. A dynamic compressibility of 0.13 +/- 0.01 A/MPa has been determined for the L alpha phase. This value is compared with the equilibrium compressibilities of bilayer and nonbilayer phases reported in the literature. The results suggest testable mechanisms for the pressure-induced transition involving changes in periodicity, phase hydration, chain order, and orientation. A more complete understanding of the transition mechanism will require improvement in detector spatial resolution and sensitivity, and data on the pressure sensitivity of phase hydration.

Biophysical Phenomena↗
PubMed1991

A database of lipid phase transition temperatures and enthalpy changes.

The systematic study of the mesomorphic phase properties of synthetic and biologically derived lipids began some 30 years ago. In the past decade, interest in this area has grown enormously. As a result, there exists a wealth of information on lipid phase behavior, but unfortunately, these data have, until now, been scattered throughout the literature in a variety of books, proceedings, and journals. The data have recently been compiled in a centralized database with a view to providing ready access to the same and to the appropriate literature. The compilation facilitates review of what has thus far been accomplished and highlights what remains to be done in this active research area. As such, it represents a convenient summary of the existing data which, when evaluated, will enable us to identify where deficits exist in the data, to reveal the fundamental physicochemical principles upon which lipid phase behavior is based, and to understand more completely lipid phase relations in biological, reconstituted, and formulated systems. The compilation consists of a tabulation of all known mesomorphic and polymorphic phase transition temperatures and enthalpy changes for synthetic and biologically derived lipids in the dry and in the partially and fully hydrated states. Also included is the effect on these thermodynamic values of pH, and of salt and metal ion concentration and other additives such as proteins, drugs, etc. The methods used in making the measurements and the experimental conditions are reported. Bibliographic information includes complete literature referencing and list of authors. As of this writing, the database is current through June 1990 and contains 9500 records. Each record contains 28 fields. Here, we describe how the database originated, its scope and contents, data abstraction procedures, and issues relating to mesophase and lipid nomenclature, data analysis, and evaluation, and database maintenance and distribution.

Databases, Factual↗
PubMed1991

Structure of physical performance in occupational tasks.

Two lines of research concerning the dimensionality of physical performance in occupational tasks are described. In the first, the physical requirements of tasks are analyzed as reflected in job analyses. In the second, the structure of physical abilities tests used to predict performance in physically demanding jobs is evaluated. Principal components analyses of both job analysis and test performance data suggest that the structure of physical abilities has three major components--strength, endurance, and movement quality. This structure appears to be independent of job type or level of incumbents' performance.

Adult↗
PubMed1990

Down syndrome and autoimmune chronic active hepatitis: satisfactory outcome with therapy.

A case of autoimmune chronic active hepatitis (C.A.H.) in a 12-year old Down Syndrome child is described. This represents the second only documented case of autoimmune C.A.H. occurring in Down Syndrome; the first well-described case died from the disease. The patient described below had a satisfactory response to steroid therapy with restoration of normal liver histological appearances and function despite severe disease at presentation. Chronic hepatitis in Down Syndrome, although more usually of hepatitis B viral aetiology, may also be autoimmune in nature and resolve satisfactorily with appropriate therapy.

Autoimmune Diseases↗
PubMed1990

Pulmonary vascular occlusive disease presenting as sudden death.

We report a case of pulmonary vascular occlusive disease (also termed pulmonary veno occlusive disease) which caused the sudden death of an eleven-year-old girl. The post-mortem findings are described and the current theories of aetiology and pathogenesis of this unusual condition are reviewed. The clinical picture is characterized by pulmonary hypertension with marked increase of pulmonary arterial pressure but often normal or only slightly elevated wedge pressure. The pulmonary vasculature, especially the veins, show progressive fibrotic occlusion. The aetiology is unknown but an infective cause is considered most likely. Definitive diagnosis usually depends on an open lung biopsy or, more commonly, autopsy examination.

Child↗
PubMed1989

Personality correlates of physical fitness.

In this article, I examine the relation between personality and physical fitness. One group (N = 97) of male adults completed the Hogan Personality Inventory and five nationally recognized physical fitness batteries. A second group (N = 35) completed the Minnesota Multiphasic Personality Inventory and a set of medical and physical performance assessments. Results indicate that physical fitness must be defined in multidimensional terms and that fitness is related to self-confidence and self-discipline. Measures of psychopathology were unrelated to measures of health and fitness. These data suggest that the personal qualities associated with fitness are also those that promote and extend health.

Adolescent↗
PubMed1986

The thickness of the alveolar capillary wall in the human lung at high and low altitude.

An ultrastructural study of lung biopsy specimens from an adult mestizo highlander from La Paz (3800 m) and three lowlanders from London showed no significant difference in the thickness of the alveolar capillary wall, the thickness in the highlander being 0.65 micron and the range in the lowlanders being 0.57-0.69 micron. The thickness of the blood-air barrier in a mestizo girl of 4 years born and living in La Paz was 0.47 micron. These findings suggest that the alveolar capillary wall in the acclimatized highlander does not differ in thickness from the lowlander. This contrasts with our previous findings in native high altitude guinea pigs which indicate that the alveolar capillary wall is thinner in such indigenous mountain species which are adapted genetically rather than acclimatized to hypobaric hypoxia.

Adult↗
PubMed1986

The thickness of the alveolar capillary wall in guinea-pigs at high and low altitude.

The thickness of the alveolar-capillary wall was measured in the lungs of seven guinea-pigs born and living at La Raya, in the Peruvian Andes, at an altitude of 4200 m and in seven sea-level representatives of the same species. This was achieved by carrying out morphometric studies on electron micrographs to obtain the so-called arithmetic and harmonic mean thicknesses. The arithmetic mean thickness was always the larger, this being due to the greater emphasis which the technique employed places on the copious amounts of connective tissue in the interstitial space of the alveolar capillary wall in this species. These thicker portions of the alveolar wall are not concerned with gaseous diffusion. The harmonic mean thickness probably gives a more physiologically realistic estimate of the magnitude of the diffusion barrier to oxygen. This proved to be smaller in the animals from high altitude and may facilitate diffusion of oxygen from alveolar spaces to blood, thus making less steep the "oxygen cascade" from inspired air to mitochondria.

Altitude↗
PubMed1983

Severe neutropenia consequent to sustained-release procainamide.

A patient with reversible severe neutropenia and relative eosinophilia caused by sustained-release procainamide is described. Significant early and very late complications of therapy with procainamide preparations have been rarely described so far. The important pharmacokinetic aspects of sustained release procainamide are discussed, and the postulated mechanisms of induction of blood dyscrasias are reviewed.

Journal Article↗