Hydrogel Ring for Topical Drug Delivery to the Ocular Posterior Segment.

PURPOSE: To investigate the efficacy of a topical hydrogel ring for drug delivery to the posterior segment of the rabbit eye. MATERIALS AND METHODS: Novel hydrogel corneal lenses (CL), scleral/corneal lenses (S/CL), and rings were prepared using poly(hydroxyethyl methacrylate). The devices were immersed in 0.3% ofloxacin ophthalmic solution (OOS) to homogeneously distribute the drug throughout the hydrogel. The medicated CL, S/CL, Ring 1 (standard ring), or Ring 2 (shape-optimized ring) was applied to the surface of the cornea, cornea/bulbar conjunctiva, or bulbar conjunctiva of albino rabbits, respectively. Medicated rings did not touch the corneal surface. In another group, one OOS drop was administered to the eye. After 0.25-8 hours, the hydrogel devices were removed and ocular tissues were harvested. High-performance liquid chromatography (HPLC) was used to measure the ofloxacin concentration in the devices and tissues. The drug concentrations in the posterior segment tissues were compared among ofloxacin delivery methods. RESULTS: One hour after placement, eyes treated with Ring 1 or S/CL had markedly higher ofloxacin levels in the posterior segment tissues (conjunctiva, sclera, and retina/choroid) than eyes treated with topical OOS or a CL. Lower levels of ofloxacin were found in anterior segment tissues (cornea and aqueous humor) in eyes treated with Ring 1 compared to those treated with S/CL. Ring 2 most effectively delivered ofloxacin to the retina/choroid. The tissue ofloxacin concentration in the fellow eye was markedly lower than the eye treated with Ring 2. CONCLUSIONS: Our results suggest that hydrogel rings are effective in delivering topical ophthalmic drugs to the posterior segment. The drugs are most likely delivered via the transconjunctival/scleral route by lateral diffusion across the bulbar conjunctiva and through the sclera. Systemic drug delivery to the posterior segment is minimal.

Synthesis of 5-thiodidehydropyranylcytosine derivatives as potential anti-HIV agents.

As a part of our ongoing efforts to identify new anti-HIV agents, a 5'-thiopyrano-nucleoside derivative 4, designed based on 4'-thioD4C 1 and cyclohexenylnucleoside 3, was synthesized. The dihydrothiopyran skeleton of 4 was constructed by the ring closing metathesis of 21 which was synthesized from but-2-yne-1,4-diol. After converting the protecting group from MOM to TBS followed by oxidation, a Pummerer-type thioglycosylation reaction of 24 with persilylated uracil gave the desired 5-thiodihydrothiopyranyluracils 25 and 26 as a mixture of anomers. The conversion of 25 to a cytosine derivative and subsequent deprotection gave a 5-thiodidehydropyranosylcytosine derivative 4 in good yield. The anti-HIV activity of 4 was also evaluated.

Hind-limb paraparesis in a rat model for neurolathyrism associated with apoptosis and an impaired vascular endothelial growth factor system in the spinal cord.

Neurolathyrism is a motor neuron disease characterized by lower limb paraparesis. It is associated with ingestion of a plant excitotoxin, beta-N-oxalyl-L-alphabeta-diaminopropionic acid (L-beta-ODAP), an agonist of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate-type glutamatergic receptors. Previously, a limited model of neurolathyrism was reported for the rat. To improve upon the model, we stressed rat pups by separation from their mothers, followed by the subcutaneous L-beta-ODAP treatment, resulting in a 4.6-fold higher incidence (14.0-15.6%) of the paraparesis compared with the prior study. The number and size of motor neurons in these rats were decreased only in the lumbar and sacral cord segments, at approximately 13-36 weeks after treatment. Only lumbar and sacral spinal cord tissue revealed pathological insults typical of physical and ischemic spinal cord injury in the surviving motor neurons. In addition, extensive but transient hemorrhage occurred in the ventral spinal cord parenchyma of the rat, and numerous TdT-mediated dUTP-biotin nick end-labeling (TUNEL)-positive cells were also observed. In parallel, vascular endothelial growth factor receptor (VEGFR)-2 (Flk-1) levels were significantly lowered in the lumbosacral spinal cord of the paraparetic rats compared with their controls, suggesting a failure of the VEGF system to protect neurons against L-beta-ODAP toxicity. We propose, based on these data, a novel pathological process of motor neuron death induced by peripheral L-beta-ODAP. For the first time, we present a model of the early molecular events that occur during chemically induced spinal cord injury, which can potentially be applied to other neurodegenerative disorders.

Expansion of the cell plate in plant cytokinesis requires a kinesin-like protein/MAPKKK complex.

The tobacco mitogen-activated protein kinase kinase kinase NPK1 regulates lateral expansion of the cell plate at cytokinesis. Here, we show that the kinesin-like proteins NACK1 and NACK2 act as activators of NPK1. Biochemical analysis suggests that direct binding of NACK1 to NPK1 stimulates kinase activity. NACK1 is accumulated specifically in M phase and colocalized with NPK1 at the phragmoplast equator. Overexpression of a truncated NACK1 protein that lacks the motor domain disrupts NPK1 concentration at the phragmoplast equator and cell plate formation. Incomplete cytokinesis is also observed when expression of NACK1 and NACK2 is repressed by virus-induced gene silencing and in embryonic cells from Arabidopsis mutants in which a NACK1 ortholog is disrupted. Thus, we conclude that expansion of the cell plate requires NACK1/2 to regulate the activity and localization of NPK1.