The curious ability of polyethylene glycol fusion technologies to restore lost behaviors after nerve severance.

Traumatic injuries to PNS and CNS axons are not uncommon. Restoration of lost behaviors following severance of mammalian peripheral nerve axons (PNAs) relies on regeneration by slow outgrowths and is typically poor or nonexistent when after ablation or injuries close to the soma. Behavioral recovery after severing spinal tract axons (STAs) is poor because STAs do not naturally regenerate. Current techniques to enhance PNA and/or STA regeneration have had limited success and do not prevent the onset of Wallerian degeneration of severed distal segments. This Review describes the use of a recently developed polyethylene glycol (PEG) fusion technology combining concepts from biochemical engineering, cell biology, and clinical microsurgery. Within minutes after microsuturing carefully trimmed cut ends and applying a well-specified sequence of solutions, PEG-fused axons exhibit morphological continuity (assessed by intra-axonal dye diffusion) and electrophysiological continuity (assessed by conduction of action potentials) across the lesion site. Wallerian degeneration of PEG-fused PNAs is greatly reduced as measured by counts of sensory and/or motor axons and maintenance of axonal diameters and neuromuscular synapses. After PEG-fusion repair, cut-severed, crush-severed, or ablated PNAs or crush-severed STAs rapidly (within days to weeks), more completely, and permanently restore PNA- or STA-mediated behaviors compared with nontreated or conventionally treated animals. PEG-fusion success is enhanced or decreased by applying antioxidants or oxidants, trimming cut ends or stretching axons, and exposure to Ca(2+) -free or Ca(2+) -containing solutions, respectively. PEG-fusion technology employs surgical techniques and chemicals already used by clinicians and has the potential to produce a paradigm shift in the treatment of traumatic injuries to PNAs and STAs.

Polyethylene glycol-fused allografts produce rapid behavioral recovery after ablation of sciatic nerve segments.

Restoration of neuronal functions by outgrowths regenerating at ∼1 mm/day from the proximal stumps of severed peripheral nerves takes many weeks or months, if it occurs at all, especially after ablation of nerve segments. Distal segments of severed axons typically degenerate in 1-3 days. This study shows that Wallerian degeneration can be prevented or retarded, and lost behavioral function can be restored, following ablation of 0.5-1-cm segments of rat sciatic nerves in host animals. This is achieved by using 0.8-1.1-cm microsutured donor allografts treated with bioengineered solutions varying in ionic and polyethylene glycol (PEG) concentrations (modified PEG-fusion procedure), being careful not to stretch any portion of donor or host sciatic nerves. The data show that PEG fusion permanently restores axonal continuity within minutes, as initially assessed by action potential conduction and intracellular diffusion of dye. Behavioral functions mediated by the sciatic nerve are largely restored within 2-4 weeks, as measured by the sciatic functional index. Increased restoration of sciatic behavioral functions after ablating 0.5-1-cm segments is associated with greater numbers of viable myelinated axons within and distal to PEG-fused allografts. Many such viable myelinated axons are almost certainly spared from Wallerian degeneration by PEG fusion. PEG fusion of donor allografts may produce a paradigm shift in the treatment of peripheral nerve injuries.

Efficacy of wrist/palm warming as an EVA countermeasure to maintain finger comfort in cold conditions.

INTRODUCTION: This study explored the effectiveness of local wrist/palm warming as a potential countermeasure for providing finger comfort during extended duration EVA. METHODS: There were six subjects (five males and one female) who were evaluated in a liquid cooling/warming garment (LCWG) wearing modified liquid cooling/warming (LCW) gloves in three different experimental conditions: Condition 1: Stage 1--no LCWG, LCW glove inlet water temperature 33 degrees C; Stage 2--no LCWG, LCW glove inlet water temperature cooled to 8 degrees C; Stage 3--no LCWG, LCW glove inlet water temperature warmed to 45 degrees C; Condition 2: Stage 1--LCWG and LCW glove inlet water temperature 33 degrees C; Stage 2--LCWG inlet temperature cooled to 31 degrees C, LCW gloves, 8 degrees C; Stage 3--LCWG inlet water temperature remains at 31 degrees C, LCW glove inlet water temperature warmed to 45 degrees C; Condition 3: Stage 1--LCWG and LCW gloves 33 degrees C; Stage 2--LCWG inlet water temperature cooled to 28 degrees C, LCW gloves, 8 degrees C; Stage 3--LCWG remains at 28 degrees C, LCW glove water temperature warmed to 45 degrees C. RESULTS: Wrist/palm area warming showed a statistically significant increase in finger temperature (Tfing) in Stage 3 compared with Stage 2. Blood perfusion showed a trend toward a significantly greater value in Stage 3 compared with Stage 2. The LCW gloves were significantly more effective in increasing Stage 3 Tfing in Condition 1 (33 degrees C) compared with Condition 3 (28 degrees C). Across conditions, subjective perception of heat in the hands was significantly greater at Stage 3 than Stage 2; perception of overall body heat showed a trend for higher heat ratings in Stage 3 than Stage 2. CONCLUSIONS: Local wrist/palm warming was effective in increasing blood circulation to the distal upper extremities, suggesting the potential usefulness of this technique for enhancing astronaut comfort during EVA while decreasing power requirements.

Clinical evaluation of primary peripheral cysts of the iris.

BACKGROUND: Peripheral primary cyst of the iris is an uncommon benign condition that may masquerade as a tumor of the ciliary body. Careful examination utilizing the slit lamp and gonioscopy is necessary to successfully differentiate the two. CONCLUSIONS: Given their uncommon occurrence and the importance of ruling out melanoma or other malignancies, this review is a guide in the evaluation and diagnosis of patients with this condition.

True posterior ischemic optic neuropathy associated with herpes zoster ophthalmicus.

Although previous reports of ischemic optic neuropathy resulting from herpes zoster have appeared in the literature, these reports have not been convincing of a true optic neuropathy. The case presented is a true posterior ischemic optic neuropathy due to inflammation of the medial posterior ciliary artery, diagnosed on the basis of a deep, steep-sided altitudinal visual field defect. The herpes zoster infection also resulted in retinitis, damage to the iris sphincter, and corneal scarring. The effects of herpes zoster on the visual system are reviewed.

The Canadian Optometry Survey: report on the utilization of diagnostic pharmaceutical agents by Canadian optometrists.

This study represents the first national survey of optometrists in Canada. A mailed questionnaire was designed and implemented in order to discover how optometrists have reacted to the introduction of diagnostic pharmaceutical agent (DPA) legislation in Canada and to determine what variables are important predictors of DPA use. The data collected were also used to test the null hypothesis that DPA legislation does not affect the use of mydriatic/cycloplegic agents by optometrists. A stratified random sampling procedure was used to select 230 optometrists (roughly 10% of the practicing profession) for inclusion in the study. Over 90% of the subjects completed and returned the questionnaire. A statistically significant and important association was found between mydriatic/cycloplegic drug use and legislation (p less than 0.05 and odds ratio = 2.18). Legislation, type of practice, age, and optometry school attended were all found to be associated with DPA use.