Stem cells and molecular strategies to restore hearing.

Hearing loss is a costly and growing problem for the elderly population worldwide with millions of people being affected. There are currently two prosthetic devices available to minimize problems associated with the two forms of hearing loss: hearing aids that amplify sound to overcome middle ear based conductive hearing loss and cochlear implants that restore some hearing after neurosensory hearing loss. The current presentation provides information on the treatment of neurosensory hearing loss. Although the cochlear implant solution for neurosensory hearing loss is technologically advanced; it still provides only moderate hearing capacity in neurosensory deaf individuals. Inducible stem cells and molecular therapies are appealing alternatives to the cochlear implant and may provide more than a new form of treatment as they hold the promise for a cure. To this end, current insights into inducible stem cells that may provide cells for seeding the cochlea with the hope of new hair cell formation are being reviewed. Alternatively, similar to induction of stem cells, cells of the flat epithelium that remains after hair cell loss could be induced to proliferate and differentiate into hair cells. In either of these strategies, hair cell specific genes known to be essential for hair cell differentiation or maintenance such as ATOH1, POU4F3, GFI1, and miRNA-183 will be utilized with the hope of completely restoring hearing to all patients with hearing loss.

Near-infrared laser illumination transforms the fluorescence absorbing X-Gal reaction product BCI into a transparent, yet brightly fluorescent substance.

The beta-galactosidase protein generated by the bacterial LacZ gene is widely used to map gene expression patterns. The ease of its use is only rivaled by green fluorescent protein, which can be used in combination with various other procedures such as immunocytochemistry, flow cytometry, or tract tracing. The beta-galactosidase enzymatic reaction potentially provides a more sensitive assay of gene expression than green fluorescent protein. However, the virtual impermeability and tendency to absorb light over a wide range limit the use of the most frequently used beta-galactosidase substrate, X-Gal, in combination with other fluorescent labeling procedures. Here, we provide details on a simple photoactivation procedure that transforms the light-absorbing X-Gal product, 5-bromo-4-chloro-3-indolyl (BCI) precipitate, into an intensely fluorescent product excited by 488 and 633 nm light. Photoactivation is achieved through exposure to 730 nm near-infrared light emitted from a femtosecond titanium-doped Sapphire laser. Photoactivation of BCI occurs in tissue sections suspended in buffered saline, glycerol, or even embedded in epoxy resin. A protocol for the use of BCI photoactivation is here provided. Importantly, the BCI photoactivated product is photoswitchable, displaying bistable photochromism. This permits the use of the fluorescent product in a variety of co-localization studies in conjunction with other imaging modalities. As with other bistable and photoswitchable products, the BCI reaction product shows concentration quenching at high density and can be degraded by continuous exposure to intense 730 nm illumination. Therefore, care must be taken in developing imaging strategies. Our findings have implications for the use of X-Gal in gene and protein detection and provide a novel substrate for high density digital information storage.

Smaller inner ear sensory epithelia in Neurog 1 null mice are related to earlier hair cell cycle exit.

We investigated whether co-expression of Neurog 1 and Atoh 1 in common neurosensory precursors could explain the loss of hair cells in Neurog 1 null mice. Analysis of terminal mitosis, using BrdU, supports previous findings regarding timing of exit from cell cycle. Specifically, we show that cell cycle exit occurs in spiral sensory neurons in a base-to-apex progression followed by cell cycle exit of hair cells in the organ of Corti in an apex-to-base progression, with some overlap of cell cycle exit in the apex for both hair cells and spiral sensory neurons. Hair cells in Neurog 1 null mice show cell cycle exit in an apex-to-base progression about 1-2 days earlier. Atoh 1 is expressed in an apex-to-base progression rather then a base-to-apex progression as in wildtype littermates. We tested the possible expression of Atoh1 in neurosensory precursors using two Atoh 1-Cre lines. We show Atoh 1-Cre mediated beta-galactosidase expression in delaminating sensory neuron precursors as well as undifferentiated epithelial cells at E11 and E12.5. PCR analysis shows expression of Atoh 1 in the otocyst as early as E10.5, prior to any histology-based detection techniques. Combined, these data suggest that low levels of Atoh 1 exist much earlier in precursors of hair cells and sensory neurons, possibly including neurosensory precursors. Analysis of Atoh 1-Cre expression in E18.5 embryos and P31 mice reveal beta-galactosidase stain in all hair cells but also in vestibular and cochlear sensory neurons and some supporting cells. A similar expression of Atoh 1-LacZ exists in postnatal and adult vestibular and cochlear sensory neurons, and Atoh 1 expression in vestibular sensory neurons is confirmed with RT-PCR. We propose that the absence of NEUROG 1 protein leads to loss of sensory neuron formation through a phenotypic switch of cycling neurosensory precursors from sensory neuron to hair cell fate. Neurog 1 null mice show a truncation of clonal expansion of hair cell precursors through temporally altered terminal mitosis, thereby resulting in smaller sensory epithelia.

Catheter-related colonization associated with percutaneous inserted central catheters.

The intravenous therapy team at Massachusetts General Hospital studied the potential infectious risks of maintaining percutaneous inserted central catheters (PICC) for prolonged periods. Cultures of 100 PICC sites and catheters were performed on removal of the catheters, which had remained in place for 2 to 43 days. The insertion sites and/or proximal or distal segments of the catheters were found to be colonized in 11% of the patients, with distal catheter tips significantly colonized in only four patients. Nine of the patients were colonized at the insertion site. Bacteremia did not occur as a result of the extended dwell time of the catheters.

New drug therapies: esmolol HCL, aztreonam and ganciclovir.

The I.V. nurse's monitoring specific drug therapy includes familiarity with a drug's action, with its performance in different clinical situations, with proper dosage and observations for adverse effects. This article presents three drugs in different classifications, indications for use and additional useful information.

Evaluation of a multiple-dose syringe pump system for intermittent i.v. drug delivery.

The feasibility of implementing a multiple-dose, multiple-flow-rate syringe pump system in a large teaching institution and a community hospital is described. The new syringe pump system was evaluated on medical and surgical wards in each hospital for a period of time sufficient to evaluate 40 courses of therapy in each hospital. At the time the new syringe pump system was implemented, the teaching hospital was using a gravity-dependent bottle and burette system and the community hospital was using a single-dose syringe pump system. At the end of the study period, the material costs of the existing i.v. infusion systems were compared with the material costs of the new syringe pump system, and the nurses involved in the study were questioned about their attitudes toward the new system. Use of the multiple-dose syringe pump system resulted in a savings of $934.81 in material costs compared with the bottle and burette system and $9.70 in material costs compared with the single-dose syringe pump system (based on 40 doses). When the cost of wasted drug was considered, the cost per day of the multiple-dose syringe pump system was substantially less (70%) than the cost per day of the bottle and burette system and approximately the same as the cost per day for the single-dose syringe pump system. The majority of nurses indicated that the new system was easier or no more difficult to use than the existing i.v. infusion system and were in favor of switching to the new system. Implementation of a multiple-dose, multiple-flow-rate syringe pump system may result in cost savings over a traditional bottle and burette system and could complement an existing single-dose syringe infusion system.

Pathophysiology of bends and decompression sickness. An overview with emphasis on treatment.

Current concepts in the pathophysiology of decompression sickness are reviewed. Mild, moderate, and severe forms of this syndrome resulting from gaseous and lipid emboli are described. Therapy is aimed at restoring or specifically treating each alteration. Plasma volume deficit is restored by colloidal re-expansion. Decompression sickness is partially treated when recompression alone is used. Blood lipid alterations are managed by use of antilipemic agents. Dextran is mentioned. Divers at depths of 61 m display changes in hematocrit, platelet, and blood lipid profiles. Cord paralysis may occur from bubbles in the vena cava. Retrograde migration blocks the venous circulation of the spinal cord. Ultrasonic devices can detect "silent" bubbles during decompression. Recompression, when available, is a lifesaving treatment for diving accidents involving saturation diving. Air embolism is discussed. Monitoring emboli by EEG and fundoscopy are reported.

Microembolization of the inner ear of the cat: a surgical technique.

A surgical technique for the microembolization of the inner ear of the cat is described, and photomicrographs of representative central neural areas and end organ structures are presented.