Influence of intraocular pressure on aqueous outflow facility in enucleated eyes of different mammals.

Freshly enucleated monkey, calf, and human eyes were quantitatively perfused with mock aqueous humor through the anterior chamber by a constant pressure technique. After baseline perfusion at 15 mm Hg, intraocular pressure was raised to 45 mm Hg and later reduced back to 15 mm Hg. Calf and human (both adult and infant) eyes had lower outflow facilities at 45 than at 15 mm Hg. However, four types of monkey eyes did not show decreased facility of outflow at elevated perfusion pressure, and after return of pressure to 15 mm Hg, facility of outflow actually increased compared to baseline, unlike both calf and human eyes. The results indicate that there are significant differences in the response of enucleated mammalian eyes to an elevation in perfusion pressure. Factors other than, or in addition to, collapse of Schlemm's canal may be important in the pathogenesis of the pressure-induced decrease in outflow facility found in human eyes.

Effect of iodoacetamide perfusion on outflow facility and metabolism of the trabecular meshwork.

Freshly enucleated eyes were quantitatively perfused via the anterior chamber with varying dosages of iodoacetamide at constant pressure. Iodoacetamide caused a significant increase in facility of outflow in a dose-response manner in calf and monkey eyes. Almost complete inhibition of glycolysis in the calf trabecular meshwork was produced by a dosage of iodoacetamide that was too low to appreciably alter the facility. A similar response was produced by a higher dosage, which did significantly increase the facility. Our results, taken together with what is known of the properties of iodoacetamide, suggest that cellular sulfhydryl groups may be involved in a mechanism for aqueous flow through the trabecular meshwork and that iodoacetamide probably acts directly on cellular permeability rather than by inhibition of glycolysis or interference with the production of energy in the trabecular meshwork.

Serum obstruction of aqueous outflow in enucleated eyes.

We perfused enucleated human eyes via the anterior chamber by the constant pressure technique. Infusion of human serum into the anterior chamber of enucleated human eyes for 30 minutes at 23 mm Hg pressure induced a 42% decrease in facility of outflow, which was not relieved by irrigation of the anterior chamber with balanced salt solution or alpha-chymotrypsin. Diluted serum also reduced the facility of outflow. Measured in a glass viscometer, diluted serum had less viscosity than undiluted, but interfered with outflow from the eye more than anticipated on the basis of viscosity alone. When we used lens depression to induce tension on the iridocorneal angle to simulate the effects of contraction of the ciliary muscle, outflow facility increased in control eyes that had not been exposed to serum and in serum-perfused eyes. However, the partial obstruction to outflow that had been induced by serum persisted. Normal serum components may become adsorbed or entrapped in the aqueous outflow system so as to obstruct outflow, and this may result in secondary glaucoma in eyes with chronic uveitis.

Experimental perfusions through the anterior and vitreous chambers with possible relationships to malignant glaucoma.

Enucleated eyes were perfused alternately via the anterior and vitreous chambers. At low intraocular pressure (IOP), vitreous humor presented considerable resistance to forward flow of perfusion fluid in calf eyes, but not in human eyes. In human eyes when the perfusion pressure was increased to 60 mm Hg, the resistance to flow forward from the vitreous body increased, but became practically nil again when the IOP was decreased. At high pressure the volume of the vitreous body apparently increases and the anterior hyaloid membrane probably presses against the ciliary body, reducing the area of hyaloid membrane through which fluid can flow. Whether increased perfusion pressure can in some other manner change the permeability of human vitreous to resemble that of the calf remains unanswered. Our results suggest that factors other than, or in addition to, simple diversion of aqeous humor must be important in malignant glaucoma.

Twin-screw extrusion of cassava starch and isolated soybean protein blends.

The effects of the extrusion parameters on isolated soybean protein (ISP) and cassava starch (CS) blends were studied. Extruded samples were prepared by using a ZSK-30 Werner and Pfleiderer twin-screw extruder. The study was carried out using Response Surface Methodology. The ISP followed by the moisture content were the most important linear variables significantly affecting axial expansion, specific volume, water solubility index and colour difference. The radial and axial expansion ranged from 2.30 to 3.77 and from 1.02 to 2.62, respectively. The highest ISP concentrations in the blends resulted in the highest specific volumes of the extrudates. Simultaneous increases of the barrel temperature and ISP level increased the water absorption index and lowered the water solubility index of the extrudates. Extruded products were softer at higher barrel temperature. The greatest difference in colour values was for the blends with the highest ISP concentration.