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Biomedical subjects

D C Walker

Publications and source records attributed to D C Walker.

61 records · Page 4Linked to original sources
PubMed1981

The site of leukocyte migration through the tracheal mucosa in the guinea pig.

The tracheal mucosa of the guinea pig was examined using light microscopy, thin section, and freeze-fracture replicas with transmission electron microscopy and scanning electron microscopy. These studies demonstrated that inflammatory cells en route to the mucosal surface migrate through the epithelium in file through solitary openings rather than randomly between epithelial cells. The fact that leukocytes migrate through these openings rather than randomly between epithelial cells has important implications. First, it provides a pathway for circulating cells to gain access to the surface of the airway where they can function as the first line of defense against inhaled material. Second, the movement of leukocytes through specified pathways rather than randomly between cells minimizes the number of openings required for cell transit so that fluid and solute movement can be more tightly controlled. Third, the prevention of random migration may also be important in minimizing the contact between the migratory cells and the epithelial sensory nerve net.

Animals↗
PubMed1976

Polarized bremsstrahlung not the source of optical activity.

An evaluation is made of the previously proposed scheme (polarized beta-particles leads to circularly polarized bremsstrahlung leads to optically active molecules) by which dissymmetry at the elementary particle level may be transmitted to the molecular level. The calculations suggest that much too small a fraction of the total energy of the electron appears as light, capable of causing photochemical resolution, to explain results obtained in the laboratory on the preferential radiation-induced decomposition one enantiomer of chiral amino acids.

Amino Acids↗
PubMed1975

Vasodilator therapy in acute myocardial infarction. A comparison of sodium nitroprusside and nitroglycerin.

Twenty-six patients with complicated acute myocardial infarction were studied in order to compare the hemodynamic effects of sodium nitroprusside (NP) and nitroglycerin (GTN). All patients received NP and 18 of the 26 also received GTN to evaluate both drugs in the same individuals. Both agents produced significant declines in mean arterial pressure, total peripheral resistance (TPR), and heart rate systolic blood pressure product. However, in the 18 patients who received both drugs GTN produced a greater fall (P less than 0.05) in pulmonary capillary wedge pressure (PCW) (25 to 15 mm Hg) than did NP (24 to 17 mm Hg) and a greater increment (P less than 0.01) in (see article) (0.98 to 1.43) than NP (0.98 to 1.16). These data confirm the potent vasodilatory effects of NP and GTN and suggest that NP has a relatively balanced effect on the arterial and venous circulation, and GTN seems to produce more potent venodilatation than arterial dilatation. These observations provide a basis for a more rational choice of vasodilator agents based on initial hemodynamic measurements in complicated acute myocardial infarction.

Acute Disease↗
PubMedDate not supplied

The epitheliome: agent-based modelling of the social behaviour of cells.

We have developed a new computational modelling paradigm for predicting the emergent behaviour resulting from the interaction of cells in epithelial tissue. As proof-of-concept, an agent-based model, in which there is a one-to-one correspondence between biological cells and software agents, has been coupled to a simple physical model. Behaviour of the computational model is compared with the growth characteristics of epithelial cells in monolayer culture, using growth media with low and physiological calcium concentrations. Results show a qualitative fit between the growth characteristics produced by the simulation and the in vitro cell models.

Algorithms↗
PubMedDate not supplied

Cultured human nasal epithelial multicellular spheroids: polar cyst-like model tissues.

We report here a new readily cultured nonadherent hollow spheroidal epithelial tissue model: human nasal epithelial multicellular spheroids, prepared from brushings of human nasal epithelium in vivo. Although cultured cyst-like epithelial models developed from embryonic, transformed, or polypoid tissues have been reported previously, human nasal epithelial multicellular spheroids are derived from normal mature nontransformed human airway epithelial cells. In our studies, spheroids ranged in size from 50 to 700 microns diameter (averaging approximately 250 microns). Cells of the spheroid displayed morphological polarity and formed junctional complexes. Transcellular electrolyte transport may underlie the increase in spheroid size which occurred in culture. The ease and simplicity of the brushing and culture procedures reported here render normal and diseased human cell populations more readily accessible to investigation. We believe human nasal epithelial multicellular spheroids may have important applications in the study of electrolyte and fluid transport processes, ciliary motility, epithelial polarity, cellular metabolism, and drug cytotoxicity in normal and pathophysiological states of the human respiratory tract (e.g., cystic fibrosis).

Biological Transport, Active↗