DTs-ll is a highly diphtheria toxin (DT)-sensitive cell line previously isolated by transfection of wildtype DT-resistant mouse L-M(TK-) cells with the cDNA encoding a monkey Vero cell DT receptor. DTs-II (Mr 37,195). The cytotoxic action ofDT occurs by the following steps: (i) binding to specific cell-surface receptors, (ii) internalization of the (toxin-receptor) complexes into vesicles, and (iii) translocation of the A fragment from acidified vesicles into the cytosol, where it inhibits protein synthesis by ADP-ribosylation of elongation factor 2 (1-3).Our laboratory has recently used expression cloning to identify a receptor for DT (4). The gene encoding the receptor was cloned by transfecting wild-type toxin-resistant mouse L-M(TK-) cells with a cDNA library prepared from highly toxin-sensitive monkey Vero cells; the transfectants were screened for DT sensitivity employing a replica plate system that allowed for the detection of those mouse cells whose protein synthesis is inhibited upon exposure to DT and that, at the same time, preserved a "replica" ofthose cells (4,5

We report on modeling and bench test results targeted at better understanding of valved glaucoma drainage devices (GDDs), a common current surgical treatment for glaucoma. A simple equivalent circuit is described to model fluid mechanical behavior of the aqueous humor in an eye with glaucoma, both before and after implantation of a valved GDD. Finite element method simulations (FEM), based on the lubrication-von Kármán model, are then performed to analyze the valve's mechanical and fluidic performance. Using nanoporous membranes to mimic the in vivo fibrous capsule, we have developed a microfluidic bench test to simulate the aqueous humor flow and the post-implantation fibrous tissue encapsulation around the GDD back plate. Our numerical and bench test results show that, contrary to the prevailing belief, the valve significantly contributes to the total pressure drop even after fibrous capsule formation. Furthermore, we show that bypassing the valve through a simple polyimide tube insertion will dramatically lower the intraocular pressure (IOP) after fibrous capsule formation. This may offer a new treatment option in some patients with advanced glaucoma.

No abstract

Glaucoma, one of the leading causes of irreversible blindness, is a progressive neurodegenerative disease. Chronic elevated intraocular pressure (IOP), a prime risk factor for glaucoma, can be treated by aqueous shunts, implantable devices, which reduce IOP in glaucoma patients by providing alternative aqueous outflow pathways. Although initially effective at delaying glaucoma progression, contemporary aqueous shunts often lead to numerous complications and only 50% of implanted devices remain functional after 5 years. In this work, we introduce a novel micro-device which provides an innovative platform for IOP reduction in glaucoma patients. The device design features an array of parallel micro-channels to provide precision aqueous outflow resistance control. Additionally, the device's microfluidic channels are composed of a unique combination of polyethylene glycol materials in order to provide enhanced biocompatibility and resistance to problematic channel clogging from biofouling of aqueous proteins. The microfabrication process employed to produce the devices results in additional advantages such as enhanced device uniformity and increased manufacturing throughput. Surface characterization experimental results show the device's surfaces exhibit significantly less non-specific protein adsorption compared to traditional implant materials. Results of in vitro flow experiments verify the device's ability to provide aqueous resistance control, continuous long-term stability through 10-day protein flow testing, and safety from risk of infection due to bacterial ingression.

Glaucoma is the leading cause of irreversible blindness. The loss of sight in glaucoma is due to the permanent optic nerve damage which is the result of a chronic elevated intraocular pressure. In this paper, we report a completely new concept to treat glaucoma using a nano-drainage device fabricated through MEMS and nanofabrication technologies. This involves replacing the functionality of diseased drainage pathway for aqueous humor outflow (i.e., trabecular meshwork). By enhancing aqueous humor outflow, the artificial drainage implant will lead to a decrease in the intraocular pressure and a halt in the progression of glaucoma.

The Ahmed glaucoma valve (AGV) is a popular glaucoma drainage device, allowing maintenance of normal intraocular pressure in patients with reduced trabecular outflow facility. The uniquely attractive feature of the AGV, in contrast to other available drainage devices, is its variable resistance in response to changes in flow rate. As a result of this variable resistance, the AGV maintains a pressure drop between 7 and 12 mm Hg for a wide range of aqueous humor flow rates. In this paper, we demonstrate that the nonlinear behavior of the AGV is a direct result of the flexibility of the valve material. Due to the thin geometry of the system, the leaflets of the AGV were modeled using the von Kármán plate theory coupled to a Reynolds lubrication theory model of the aqueous humor flow through the valve. The resulting two-dimensional coupled steady-state partial differential equation system was solved by the finite element method. The Poisson's ratio of the valve was set to 0.45, and the modulus was regressed to experimental data, giving a best-fit value 4.2 MPa. Simulation results compared favorably with previous experimental studies and our own pressure-drop/flow-rate data. For an in vitro flow of 1.6 microL/min, we calculated a pressure drop of 5.8 mm Hg and measured a pressure drop of 5.2 +/- 0.4 mm Hg. As flow rate was increased, pressure drop rose in a strongly sublinear fashion, with a flow rate of 20 microL/min giving a predicted pressure drop of only 10.9 mm Hg and a measured pressure drop of 10.5 +/- 1.1 mm Hg. The AGV model was then applied to simulate in vivo conditions. For an aqueous humor flow rate of 1.5-3.0 microL/min, the calculated pressure drops were 5.3 and 6.3 mm Hg.

Glaucoma is the leading cause of irreversible blindness. The loss of sight in glaucoma is due to the permanent optic nerve damage which is the result of a chronic elevated intraocular pressure. In this paper, we report a completely new concept to treat glaucoma using a nano-drainage device fabricated through MEMS and nanofabrication technologies. This involves replacing the functionality of diseased drainage pathway for aqueous humor outflow (i.e., trabecular meshwork). By enhancing aqueous humor outflow, the artificial drainage implant will lead to a decrease in the intraocular pressure and a halt in the progression of glaucoma.

Quantitative assay methods for CAMP factor activity of group B streptococci and for neutralization of this activity by animal sera are described. The course of the CAMP reaction is influenced by preincubation of red cells with staphylococcal beta-hemolysin and the rate of the reaction by the concentration of CAMP factor. The production of CAMP factor is enhanced by substitution of maltose for glucose in culture broth. Rising inhibitory titers to CAMP activity in sera of rabbits injected with sterile culture supernates of group B streptococci suggest that CAMP factor is an antigen in the rabbit. Cows with experimentally induced group B streptococcal mastitis also demonstrated significant rises in neutralizing titers for CAMP activity.