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Concentration-time profiles of fluorescein isothiocyanate (FITC)-conjugated bovine serum albumin and a graded series of FITC-dextrans of 20,000-70,000 molecular weight were measured within the erythrocyte-free plasma layer in individual vessels and at various positions within the interstitial tissue space of mature granulation tissue grown in a rabbit ear chamber. Sodium fluorescein was used as a representative small molecule. The plasma pharmacokinetic data were found to follow a biexponential decay in time. A one-dimensional model of diffusion adequately described interstitial transport. Interstitial diffusion coefficients decreased progressively with Stokes-Einstein radius with values for albumin being significantly reduced from that for a dextran of equivalent hydrodynamic radius. Interstitial diffusion of sodium fluorescein and albumin agreed with a fiber-matrix model, whereas the interstitial diffusion of dextrans more closely corresponded to a pore model.

Plasma pharmacokinetics of sodium fluorescein, fluorescein isothiocyanate conjugated bovine serum albumin, and a graded series of dextrans of 19,400 to 71,800 MW were monitored continuously using a noninvasive photometric technique in individual blood vessels of tissue grown in a rabbit ear chamber. The data obtained were fitted with a two-compartment open model to obtain an effective permeability and an effective clearance. Both parameters decreased with increasing molecular radius for dextrans. Values for albumin were considerably less than expected on the basis of molecular radius, presumably due to the configuration, charge, and binding characteristics of albumin.

Extravascular transport of fluorescein isothiocyanate-conjugated bovine serum albumin and a graded series of fluorescein isothiocyanate-dextrans from Mr 19,400 to 71,800 were studied in both normal tissue (granulation) and tumor (VX2 carcinoma) grown in a rabbit ear chamber. Sodium fluorescein was used as a representative small molecule. A one-dimensional diffusion model adequately described extravascular transport in both normal and tumor tissue. Measured diffusion coefficients showed a relationship with molecular size which progressively deviates from that of free diffusion in water, with values for albumin being significantly reduced from that for a dextran of equivalent size. Macromolecular transport in tumor tissue was hindered to a lesser extent than in normal tissue, which is consistent with reports of reduced contents of glycosaminoglycans, and markedly large interstitial space in tumors. Diffusion coefficients for dextran were found to vary with molecular weight according to the expression, D = a(Mr)b, in both normal tissue (a = 10(6) and b = -2.96) and tumor (a = 2.51 X 10(-2) and b = 1.14).

The effects of satellite velocity aberration and atmospheric refraction on the direction of propagation of lagser radiation reflected from a satellite back to an observer on the earth are examined. A velocity aberration analysis for the two-dimensional case where the satellite passes directly overhead at velocity v is presented to first order in v/c in order to illustrate the method. The equations for the more general threedimensional case are then given to first order in v/c, and it is indicated that higher order treatments are normally unnecessary in typical experimental considerations. Following this, a simple approximate equation giving the atmospheric refraction to an accuracy of a few microradians is developed; it is indicated that greater accuracy is not important because of laser pointing limitations imposed by atmospheric scattering and turbulence. The atmospheric refraction equation depends only on the apparent zenith angle of the satellite reflector relative to the earth-based laser, on the satelli-te altitude, and on the index of refraction of the laser radiation in the atmosphere at the earth's surface. Both of these developments should be useful in the design and interpretation of satellite laser-communication experiments.