Diffusion Of Fluorescein Research Articles

Dispersal of motile bacteria from a plane layer

The dispersal of an initially well-defined concentration of the motile bacterium Escherichia coli was measured under nonchemotactic conditions. The distribution of bacteria along a glass observation cell was measured by recording the intensity of light scattered by the organisms. For comparison, the diffusion of fluorescein was also measured by determining the distribution of fluorescence throughout the observation cell. The dispersal of bacteria from a plane layer, under nonchemotactic conditions, can be adequately described by the Gaussian solution of the diffusion equation.

Experimental retinal detachment. VI. The permeability of the blood-retinal barrier.

Fluorophotometry was used to study the permeability of the blood-retinal barrier in six monkeys with stable rhegmatogenous retinal detachments. Fluorescein transport was inhibited by probenecid. The rate of fluorescein disappearance (KvVv) was determined following intravitreal injection. In a separate experiment the equilibrium vitreous-plasma concentration ratio (Cv/Cp) was determined following intraperitoneal administration. Expressed in equivalent volumes of vitreous, the rate of fluorescein diffusion across the blood-retinal barrier (K'vVvCv/Cp) was 0.29 microL/min in control eyes and 0.73 microL/min in detached eyes. The rate of fluid movement across the blood-retinal barrier (K'vVv) [1 - (Cv/Cp)] was 2.89 microL/min in control eyes and 6.38 microL/min in detached eyes. Posterior movement of fluid contributes to retinal apposition under normal conditions and accounts for the rapid resolution of retinal detachment following closure of the retinal hole.

Plasma pharmacokinetics and interstitial diffusion of macromolecules in a capillary bed.

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.

Fluorescence microscopy study of fluorescein in the posterior segment of the eye following local application of drugs

After local application of gentamicin, dexamethasone and tropicamide to rat eyes, no effect on the permeability or the caliber of retinal vessels was observed, nor any diffusion of fluorescein from the choriocapillaris to the outer retinal layers. The qualitative assessment of fluorescence microscopic preparations (and photographic reproductions of them) is relatively unreliable and has led to confusion in the literature. The results presented here, which to some extent contradict earlier findings published in 1971, are discussed. The authors expect to obtain more accurate results from the quantitative method which they are now using.

The diffusion of fluorescein in the stroma of rabbit cornea

The diffusion rate and the distribution ratio of fluorescein in the stroma was studied in rabbit cornea. A strip of corneal stroma was mounted in a chamber and fluorescein in a phosphate buffer solution was circulated across the end of the strip for 24hr. The change in fluorescence intensity was measured along the strip and the diffusion coefficient was calculated using Fick's diffusion equation. The mean coefficient of diffusion was 1·21±0·24 (± s.d.) × 10 −6 cm 2/sec at 19 °C. The ratio of fluorescence between the stroma and the solution was 1·34 to 1·33 for the concentrations ranging from 0·1 to 10 g/ml.

Interrelationships between the retinal pigment epithelium and the neurosensory retina.

The role of the retinal pigment epithelium in regulating transport between the choriocapillariss and sensory retina was studied by examining the diffusion fluorescent across the intact rabbit retinal pigment epithelium and the retinal pigment epithelium damaged by intravenous injection of sodium iodate. Destruction of the tight junctions of the retinal pigment epithelium allowed free diffusion of fluorescein from the choroid into the retina. The electrical characteristics of the cat retinal pigment epithelium which play an important role in governing transport of substances across the retinal pigment epithelium were studied. The apical membrane of the cat retinal pigment epithelium resembled that of the frog in having high sensitivity to apical K+, greater sensitivity to apical Na+, and less sensitivity to apical HCO3-. The apical membrane was sensitive to oubain which produced a rapid fall in the transepithelial potential. Previous studies of the electrical properties of the retinal epithelium in cold blooded preparations are summarized with emphasis on the important interactions between the retinal pigment epithelium and sensory retina and the implications that these studies have with regard to the regulation of photoreceptor function.

Histoenzymatic and Permeability Changes in Human Brain Adjacent to Meningioma

Cerebral specimens were removed from ten patients with meningioma. Vascular permeability was tested with sodium fluorescein and a correlative study of the oxidative and hydrolytic enzyme activity was performed. Vascular permeability change was observed in half of the specimens of cortex taken from the region of the tumor. Labeled tracer diffusion was found to be either perivascular or involved microscopic ischemic areas. Fluorescein diffusion of the edematous white matter was observed in only two specimens. Enzyme activity in walls of the blood vessels was modified in the fluorescent specimens. Alkaline phosphatase and oxidoreductase activities were decreased. Experimental results have shown a relationship between increased vascular permeability and metabolic disorder of both vascular walls and cerebral cortex. Our findings agree with Zülch's hypothesis regarding a "hemodynamic" mechanism in the formation of edema by extraneural compression.

Observation of injected fluorescein diffusion after laser treatment of cat fundi. An experimental study with angiography and microscopy.

Argon laser coagulations with a power of 100 mW and 300 mW, exposure time 0.02 and 0.02 sec, and constant spot size of 100 microns were applied on normal cat fundi. From 1 and 2 hrs to 7 days after the coagulation, the treated eyes were observed angiographically and by fluorescence microscopy after dye injection; freeze dried eyes were examined under a fluorescence microscope. Abnormal dye leakages originated from the chorid and from retinal vessels were detected in the specimens examined within 72 hrs after the coagulation.

Histologic Localization of Sodium Fluorescein in Human Ocular Tissues

We studied the distribution pattern of sodium fluorescein in human eyes microscopically. The ciliary body showed early and diffuse leakage, with staining of the basement membrane of the nonpigmented ciliary epithelium, indicating movement of fluorescein from the ciliary body into the aqueous humor. After five minutes the iris stroma stained with fluorescein, probably from the aqueous humor. The retinal vessels and retinal pigment epithelium were impermeable to fluorescein. Corresponding to the background fluorescence seen in fluorescein angiography, fluorescence was present in Bruch's membrane and in the stroma of the inner one third of the choroid. Drusen stained most intensely in areas of greatest PAS positively. Early fluorescence of the optic disk was the result of intravascular perfusion of the dye. Minimal diffusion of fluorescein from the fenestrated choroidal vessels across the border tissue of Elschnig into the peripheral optic nerve bundles was observed. Late fluorescene of the optic disk was due mainly to fluorescein staining of the lamina scleralis and glial columns.

Fluorescence angiography of chorioretinal burns.

The pathophysiological changes occurring in the area of a chorioretinal burn, as well as the effects of such a burn on the choroidal circulation, have been studied in the rabbit using the technique of fluorescence angiography. Several small burns or a large burn will interrupt the distal choroidal circulation. The extent of the interruption is related to the size of the damaged area. In the areas of minimal to moderate damage, there is rapid fluorescence which is interpreted to be the result of an increase in capillary permeability allowing the fluorescein to stain these areas. In the areas of extensive damage and presumed coagulation of protein, there is a late fluorescence which is interpreted as the result of slow diffusion of fluorescein into the area of occluded choriocapillaries.

The diffusion of fluorescein in the lens

The barriers to the diffusion of fluorescein in the lens have been observed and measured. In vitro the spread of small spots of dye placed on the bare cortex was noted. In vivo the exchange of the dye between the lens and the aqueous and vitreous humours was recorded with a fluorophotometer and subjected to numerical analysis. It was found that the dye diffused readily within the cytoplasm of the lens fibres but passed extremely slowly across the cell membrane from one fibre to its neighbours. The lens capsule introduced a negligible resistance to the exchange of dye between the lens and surrounding fluids. The epithelium represented a considerable barrier to its entry, equivalent to about 100 layers of cortical cells.