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Biomedical subjects

C J Martin

Publications and source records attributed to C J Martin.

At least 163 records · Page 9Linked to original sources
PubMed1974

Restricted diffusion in biophysical systems. Experiment.

The pulsed-gradient spin echo nuclear magnetic resonance (PGSENMR) technique was used to measure restricted diffusion of water in three types of animal tissue: human blood plasma and red cells; rat and rabbit heart; rat and rabbit liver. Characteristic lengths (L) for restriction of diffusion are estimated from dependence on the measuring time. Limitations on the range of observable restrictive lengths (1.5-15 mum) are discussed.The decrease in diffusivity due to 1 mum alumina powder (volume fraction = 0.18) in glycerin/water mixtures agrees with the Wang theory assuming spherical particles and no hydration. The characteristic length (L approximately 4 mum) is larger than the particle size (1 mum) or separation (1.8 mum). Comparison of the diffusivities in tissues at short diffusion times with the Wang theory indicates some bound or trapped water.For packed red blood cells, a restriction (L approximately 2.3 mum) was attributed tothe red cell membrane. A permeability p approximately 0.014 cm/s may be estimated from the decrease in diffusivity. Average values of diffusivity ratio in heart were: 0.36 +/- 0.02 for rat; and 0.26 +/- 0.03 for rabbit; and in liver: 0.25 +/- 0.01 for rat; 0.25 +/- .04 for 10-day old rabbit; and 0.195 +/- 0.03 for 2-yr old rabbit. A restriction (L approximately 2.7 mum) in rat liver probably results from the mitochondria.

Aluminum↗
PubMed1974

Lung volumes in diffuse obstructive pulmonary syndromes.

Lung volumes in irreversible diffuse obstructive pulmonary syndromes (DOPS(I)) have been studied by using an analog of the lung that simulates an 18-breath nitrogen washout. The functional residual capacity (FRC), the dead space volume (Vd), the distribution of ventilation, as well as the pattern of lung emptying have been measured in normal subjects and those with obstructive syndromes. The Vd increased progressively with severity of the obstructive syndrome, as did FRC. For all subjects, both normal and obstructed, the ratio of Vd/FRC remained relatively fixed with the regression line of Vd upon FRC showing a minimal value for Vd of 67 cm(3). Vd increased by an average value of 33 cm(3) per liter of lung volume above this value. The increase in FRC resulted from the increased volume of the poorly ventilated compartment for the most part. X-ray evidence of emphysema was poorly correlated with the changes in Vd or FRC. A significant increase in anatomical Vd in DOPS(I) makes up an appreciable portion of the total Vd (physiological).

Adult↗
PubMed1973

Simulation of tissue properties in irreversible diffuse obstructive pulmonary syndromes. Enzyme digestion.

The length-tension properties of alveolar wall from normal cats were studied before and after exposure to enzymes naturally found in mammals (elastase, trypsin, collagenase, hyaluronidase). Hyaluronidase effected little change while all the proteolytic enzymes altered the mechanical properties of lung tissue. Collagenase removed the "mechanical stop" and the alveolar walls fractured at low forces. The properties of wall exposed to trypsin resembled those of elastase-treated tissue. Elastase increased the extension necessary to reach a given force and increased the maximum length (L(max)) and resting length (L(o)). Maximum extensibility (lambda(max)), the ratio of L(max) to L(o), fell with both elastase and trypsin digestion. A reduction in lambda(max) simulates the changes in alveolar wall properties seen in the lungs of the aged and in those with an irreversible diffuse obstructive pulmonary syndrome (DOPS(I)). Unlike these states, however, the energy loss in stretching alveolar wall increased with elastolysis. Furthermore, the changes in L(o) necessary to effect a change in lambda(max) of alveolar wall comparable to that seen in DOPS(I) were excessive. The altered tissue properties that occur in man with obstructive pulmonary syndromes could not be produced with these proteolytic enzymes or with hyaluronidase.

Aging↗