Mechanical stress and reactivity in organic solids.

Organic single crystals provide an ideal model for studying the factors that influence chemical processes in structured media. Reaction trajectories are well defined and reveal the influence of spontaneous mechanical stresses equivalent to tens of thousands of atmospheres. Analysis of molecular and crystal structures helps to explain both local mechanical properties, which influence reactions, and bulk properties such as melting point, compressibility, and surface energy.

[One-year results on the safety and efficacy of the InnFocus MicroShunt™ depending on placement and concentration of mitomycin C]. / Résultats à un an de l'efficacité et de l'innocuité du MicroShunt InnFocus selon l'emplacement et la concentration de MMC.

PURPOSE: To compare intraocular pressure (IOP) at one year with the InnFocus MicroShunt(®) with or without cataract surgery with according to placement and concentration of mitomycin C (MMC) DESIGN: A retrospective two-center, two-surgeon study (France and Dominican Republic). PATIENTS AND METHODS: Adults with POAG requiring filtering surgery. One MicroShunt(®) was placed in one eye of each patient. The effect of concentration and site of application of MMC was assessed by IOP and medication reduction at one year. RESULTS: Eighty-seven eyes were studied with one-year follow-up. Twenty-three eyes treated with 0.4 mg/mL MMC close to the limbus demonstrated a 55% reduction in IOP from 23.8 ± 5.3 at baseline to 10.7 ± 2.8 mmHg at one year. Topical glaucoma medication/patient was reduced 85% from 2.4 ± 0.9 to 0.3 ± 0.8. Thirty-one eyes treated with 0.2mg/mL MMC close to the limbus demonstrated a 52% reduction in IOP from 27.9 ± 6.7 at baseline to 13.3 ± 3.3 mmHg at one year. Topical glaucoma medication/patient was reduced 88% from 2.5 ± 1.4 to 0.5 ± 1.0. Thirty-three eyes treated with 0.4 mg/mL MMC deep in the pocket demonstrated a 38% reduction in IOP from 25.4 ± 7.9 at baseline to 15.7 ± 4.6 mmHg at one year. Topical glaucoma medication/patient was reduced 72% from 2.9 ± 1.0 to 0.8 ± 1.3. There were no sight-threatening long-term adverse events. CONCLUSION: The InnFocus MicroShunt(®) is a filtering surgery whose efficacy is related to the location of application and concentration of MMC used.

The arbZ gene from Lactobacillus delbrueckii subsp. lactis confers to Escherichia coli the ability to utilize the beta-glucoside arbutin.

From a genomic library of the industrially used strain Lactobacillus delbrueckii subsp. lactis DSM7290, a gene designated arbZ (869bp; encoding a 33.5kDa protein) was isolated by screening E. coli transformants for the ability to utilize the beta-glucoside arbutin. Out of 9000 transformants nine were able to ferment arbutin, whereas no utilization of the beta-glucosides salicin, esculin or cellobiose could be detected. Overexpression of arbZ using the T7-polymerase-T7-promoter-system resulted in the formation of insoluble, catalytically inactive protein aggregates (inclusion bodies). Accordingly, overexpression was not accompanied by an increase in ArbZ activity. Induction of arbZ controlled by the lac promoter under conditions that reduce protein aggregation resulted in a 12-fold increase in arbutin hydrolyzing activity of intact cells and a 13-fold increase in phospho-beta-glycosidase activity in cell-free extracts of the respective transformants. Nucleotide sequence analysis revealed a second gene upstream of arbZ that was designated arbX (830bp). ArbX (32.6kDa) shared similarity with several glycosyltransferases involved in the biosynthesis of lipopolysaccharides in Gram-negative bacteria. In Lb. delbrueckii subsp. lactis DSM7290 two transcripts, one covering arbX together with arbZ and one covering arbZ alone were detected by Northern blot analysis.

Colocalization of hyaluronan and water in rabbit corneas after photorefractive keratectomy by specific staining for hyaluronan and by quantitative microradiography.

PURPOSE: Endogenous hyaluronan (HA) has previously been shown to be a part of corneal wound healing after photorefractive keratectomy (PRK). HA is known to bind considerable amounts of water. This study aimed to show whether HA colocalized with water in the wound area after PRK. METHODS: Five New Zealand White rabbits were subjected to PRK in one eye each. After 4 weeks, the rabbits were killed and the corneas were freeze-sectioned. The freeze-dried sections were exposed to soft x-rays generated at 3 kV and the microradiographs were evaluated densitometrically. The same sections were then stained for the presence of HA using the HA-binding region of bovine nasal cartilage proteoglycans linked to biotin. RESULTS: The microradiographs showed, in a zone underlying the epithelium, that the water content was increased. In the corresponding zone, the cornea stained positive for HA. CONCLUSION: HA that is reactively formed in the corneal wound after PRK colocalized to the hydrated area of the corresponding location as revealed by quantitative microradiography. The findings suggest that HA causes local shifts in water content in the corneal wound and thereby also local shifts in transparency.

Short-term impact of corticosteroids on hyaluronan and epithelial hyperplasia in the rabbit cornea after photorefractive keratectomy.

PURPOSE: To investigate the impact of corticosteroids on subepithelial hyaluronan deposition and corneal epithelium thickness in the first 10 days after photorefractive keratectomy (PRK) and to analyze a possible contralateral effect of corticosteroids. METHODS: Thirty-two New Zealand white rabbits were assigned into two groups and had a transepithelial 5.0-mm diameter, 8.00-diopter myopic PRK performed on one eye. The corticosteroid treatment group (16 animals) received 0.1 mL of methylprednisolone 4% subconjunctivally on the operation table, followed by 0.1% dexamethasone eye drops six times a day during the postoperative period. The sodium chloride (NaCl) treatment group received topical isotonic NaCl eye drops six times a day. In each treatment group, eight animals were killed after 3 and 9 days, respectively. The harvested specimens were stained for hyaluronan and the epithelial thickness was measured. RESULTS: In contrast to the epithelial thickness, the subepithelial hyaluronan did not show a significant increase during the observation period. The corticosteroid treated group showed at both time-points significantly less subepithelial hyaluronan formation as well as a significantly thinner epithelium, when compared with the NaCl-treated group. At 9 days, the corticosteroid-treated group showed a mild epithelial hyperplasia in only one of eight eyes, whereas this was a common finding in the NaCl-treated group. We detected no hyaluronan deposits in any contralateral-untreated eye, and the epithelial thickness did not differ significantly between any of the four contralateral-untreated eye groups. CONCLUSIONS: Corticosteroid medication during the first 10 days after operation reduces the amount of subepithelial hyaluronan production and inhibits the epithelial proliferation, and epithelial hyperplasia is prevented. Neither a contralateral hyaluronan deposition nor a contralateral corticosteroid effect could be detected.

Application of an implantable bone conduction hearing device to patients with unilateral sensorineural hearing loss.

This investigation, comprised of five studies, was undertaken to determine if individuals with newly acquired profound unilateral hearing losses would benefit from an implantable bone-conduction hearing device. The bone conductor was implanted on the side of the deaf ear at the time of translabyrinthine acoustic tumor resection. Two areas greatly affected by unilateral hearing loss, speech recognition in noise and sound localization, were examined. No improvement in aided performance could be documented in either area.

Comparative studies of speech processing strategies for cochlear implants.

A wide variety of speech processing strategies for multichannel auditory prostheses were compared in studies of two patients implanted with the UCSF electrode array. Each strategy was evaluated using tests of vowel and consonant confusions, with and without lipreading. Included among the strategies were the compressed analog processor of the present UCSF/Storz prosthesis and a group of interleaved pulses processors in which the amplitudes of nonsimultaneous pulses code the spectral variations of speech. For these patients, each with indications of poor nerve survival, test scores were significantly higher with the interleaved pulses processors. We believe this superior performance was a result of 1. the substantial release from channel interactions provided by nonsimultaneous stimuli and 2. a fast enough rotation among the channels to support adequate temporal and spectral resolution of perceived speech sounds.

Auditory brainstem responses in children with early recurrent middle ear disease.

Auditory brainstem responses were recorded from an experimental group of 15 children with early histories of recurrent middle ear disease for the purpose of examining the effects of reduced auditory input on auditory brainstem function. The responses from these children were analyzed in terms of absolute latencies, interwave latencies and latency shifts across sensation level. Comparisons were made to a control group of children with no history of middle ear disease. Results indicated significant differences between the groups. The experimental group demonstrated greater absolute latencies for waves III and V as well as greater interwave latencies. These findings support the interpretation of an association between early recurrent middle ear disease and brainstem function.

A compliant Corethane/Dacron composite vascular prosthesis. Comparison with 4-mm ePTFE grafts in a canine model.

We have developed a composite vascular prosthesis with the inner blood interfacing layer made of a porous elastomeric membrane of spun Corethane fibers (10-15 microns in diameter, pore size 30-60 microns) impregnated with a gelatin-heparin complex and an outer soft tissue interfacing warp knitted Dacron sheath. Forty-eight Corethane/Dacron composite (CDC) vascular grafts, 4 mm in diameter and 5 cm in length, and 48 expanded polytetrafluoroethylene (ePTFE) vascular grafts of similar size were implanted bilaterally as end to end interposition grafts on opposite sides in the carotid and femoral arteries in dogs on low dose (162 mg/day) aspirin. Patency at 3 months was 37/48 (77%) for the ePTFE grafts and 44/48 (91.7%) for the CDC grafts. Fisher's exact test (two-tailed comparison) indicates the probability of superior CDC graft patency to be 95.5%. In the seven pairs of grafts in which one graft was occluded and the contralateral graft of another type was patent, the CDC graft was patent and the ePTFE graft was occluded in every instance. Explant histology and scanning electron microscopy showed greater collagenization, less residual platelet-fibrin and red blood cell deposits, and more frequent mid-graft endothelialization in the CDC grafts than in the ePTFE grafts.

A Corethane/polyester composite vascular prosthesis for vascular access. Comparison with expanded polytetrafluoroethylene grafts in a canine model.

An important need in hemodialysis is a self-sealing prosthesis for vascular access with at least equivalent patency and biostability to expanded polytetrafluoroethylene (ePTFE) alternatives. The authors have developed a Corethane/polyester composite (CPC) graft with an inner blood interfacing layer of spun Corethane fibers (10-15 microns diameter; pore size 30-60 microns) impregnated with a gelatin-heparin complex and an outer soft tissue interfacing warp-knitted polyester sheath. Twenty-six CPC grafts (6 mm internal diameter; 25-30 cm length) and eight Gore-Tex ePTFE grafts (same dimensions) were implanted as femoral artery-to-vein shunts in dogs on low dose (162 mg/day) aspirin, and subjected to weekly dialysis needle punctures for up to 52 weeks. Patency was 73% (19/26 with 15 at 52 weeks) for the CPC grafts and 63% (5/8 at 52 weeks) for the ePTFE controls, with more favorable healing (e.g., less extensive mural thrombi) of the CPC grafts. The hemostasis time per needle pair after removal (3.1 min mean for CPC versus 21.2 min mean for ePTFE) and the blood loss in achieving hemostasis (5.7 g mean for CPC versus 47.9 g for ePTFE) documented the significant (p < 0.0001) performance advantages of the CPC prosthesis.

Implantable bone-conduction hearing device: practical considerations.

An implantable bone conduction hearing device can be of significant benefit to carefully selected patients with noncorrectable conductive hearing losses. However, for some patients the device has significant limitations. This paper presents several practical issues that need to be considered before a decision is made regarding implant surgery. It is recommended that, whenever possible, air conduction hearing aids remain the first option considered when a patient's conductive hearing loss cannot be resolved through traditional medical management.

Application of maximum length sequence analysis to auditory brainstem response testing of premature newborns.

The feasibility of utilizing maximum length sequence analysis (MLSA) with newborns was examined on 40 premature infants residing in a neonatal intensive care unit (NICU). Auditory brainstem responses (ABRs) were initially obtained using a conventional stimulus rate of 33.3/sec. Using MLSA, responses were also recorded using much faster stimulus rates (227.3/sec, 454.5/sec, and 909.1/sec). As expected, faster stimulus rates resulted in longer ABR component wave latencies. Less expected was the clarity of the ABRs that were obtained through MLSA. Well-defined responses were obtained from premature infants at all stimulus rates. The findings suggest that MLSA may have clinical applications to newborn hearing screening.

Use of maximum length sequence analysis in newborn hearing testing.

The use of maximum length sequence analysis (MLSA) with rapid click rates may be of clinical value in newborn hearing screening because a greater number of individual responses can be signal averaged without adding to test time. To examine the potential clinical value of MLSA in newborn screening, auditory brainstem responses (ABRs) from 50 premature newborns were studied. ABRs were acquired with conventional signal averaging at four stimulus intensity levels (50 dB, 40 dB, 30 dB, and 20 dB nHL) using a click rate of 33.3/sec. These responses were directly compared with the ABRs acquired with MLSA using a rate of 227.3/sec. MLSA and conventional signal averaging yielded similar results with no statistically significant differences in the number of responses detected. Across babies, the overall quality of the tracings slightly favored MLSA, particularly when recording conditions were poor. Though the results of this investigation do not support the use of MLSA as the primary technique in newborn screening in the neonatal intensive care unit (NICU), they do support consideration of the use of MLSA as an alternative technique when the responses obtained with conventional signal averaging are poorly defined.

Auditory brain-stem response audiometry in children.

Auditory Brain-stem Response (ABR) Audiometry, also called Brain-stem Evoked Response Audiometry, is an effective procedure for assessing the hearing of children who cannot or will not perform satisfactorily on behavioral audiometric tests. Although ABR audiometry has limitations, it does permit an estimate of hearing status in nearly all children regardless of their age or developmental level.

Pitfalls in auditory brain stem response audiometry.

ABR audiometry is now a widely used clinical procedure. Although the technique provides valuable information about peripheral hearing status and assists in the detection of a retrocochlear lesion, it possesses a number of pitfalls which may not be readily apparent. This report discusses some of the limitations and problem areas in ABR audiometry.

Comparison of auditory brain stem response latency norms for premature infants.

Two investigations were conducted in an attempt to devise an improved set of auditory brain stem response (ABR) latency norms for premature infants. The first study utilized the responses of 130 infants to develop conventional ABR wave V latency norms for different conceptual ages. In addition, three sets of alternative norms were devised which utilized both waves III and V and used ABR interwave intervals as measures of brain stem maturation. A second study examined how well each of the four sets of latency norms predicted the ABR latencies of an additional group of 131 normal-hearing infants. The results of this second study demonstrated that norms utilizing wave III and the I-III interwave interval as an indicator of brain stem maturation were more sensitive than conventional norms, which provide expected wave V latencies for different conceptual ages.