Bacteriophage φ6--structure investigated by fluorescence Stokes shift spectroscopy.

The Stokes shift of tryptophan (Trp) fluorescence from layers of the lipid-containing bacteriophage φ6 is compared to determine the relative effect of the layers on virus hydrophobicity. In the inner most layer, the empty procapsid (PC) which contains 80-90% of the virion Trp residues, λ(max) = 339.8 nm. The PC emission is substantially more redshifted than the other φ6 layers and nearer to that of the Pseudomonad host cell than the other φ6 layers. The Trp emission from the nucleocapsid (NC) with λ(max) = 337.4 nm, is blueshifted by 2.4 nm relative to the PC although the number of Trp in the NC is identical to the PC. This shift represents an increase in Trp hydrophobicity, likely a requirement for the maintenance of A-form doubled-stranded RNA. Fluorescence from the completely assembled virion indicates it is in a considerably more hydrophobic environment with λ(max) = 330.9 nm. Density measurements show that the water content in the NC does not change during envelope assembly, therefore the blueshifted φ6 emission suggests that the envelope changes the PC environment, probably via the P8 layer. This change in hydrophobicity likely arises from charge redistribution or envelope-induced structural changes in the PC proteins.

Management of heat in laser tissue welding using NIR cover window material.

BACKGROUND: Laser tissue welding (LTW) is a novel method of surgical wound closure by the use of laser radiation to induce fusion of the biological tissues. Molecular dynamics associated with LTW is a result of thermal and non-thermal mechanisms. OBJECTIVES: This research focuses exclusively on better heat management to reduce thermal damage of tissues in LTW using a near infrared laser radiation. METHODS: An infrared continuous-wave (CW) laser radiation at 1,450 nm wavelength corresponding to the absorption band from combination vibrational modes of water is used to weld together ex vivo porcine aorta. RESULTS: In these studies we measured the optimal laser power and scan speed, for better tensile strength of the weld and lesser tissue dehydration. Significant amount of water loss from the welded tissue results in cellular death and tissue buckling. Various thermally conductive optical cover windows were used as heat sinks to reduce thermal effects during LTW for the dissipation of the heat. The optimal use of the method prevents tissue buckling and minimizes the water loss. Diamond, sapphire, BK7, fused silica, and IR quartz transparent optical cover windows were tested. CONCLUSIONS: The data from this study suggests that IR-quartz as the material with optimal thermal conductivity is ideal for laser welding of the porcine aorta.

Characteristics and outcomes of malpractice claims after tonsillectomy.

OBJECTIVE: To characterize the background and outcomes of tonsillectomy malpractice claims. METHODS: Review of 69 New York State insurance claims (Part I) and 87 national court trials (Part II) alleging injury after tonsillectomy. RESULTS: Part I. New York State insurance cases were most commonly discontinued (44%) or settled (42%) before trial. Compensations with a settlement or verdict were made in 48 percent of cases. Part II. Death or major injury occurred in 52 percent of insurance cases, with a mean award of $403,656 being made to plaintiffs. Of cases reaching trial, 60 percent of plaintiffs were compensated. Awards against anesthesiologists were more frequent and higher than against surgeons ($5 million vs $839,650). Death or major injury occurred in 52 percent of court cases, resulting in mean indemnity of $3.8 million. Most cases of death or major injury were attributable to airway complications. CONCLUSIONS: Approximately half of both New York state claims and court cases involved death or devastating morbidity, mostly related to airway complications, resulting in large awards. Tonsillectomy is a source of uncommon but potentially high-dollar-value litigation exposure to the surgeon, often attributable to non-surgical complications.

The fluorescence of thyroid tissue.

OBJECTIVE: To investigate the fluorescent characteristics of different thyroid tissues. STUDY DESIGN: Fresh ex vivo thyroid tissue was surfaced scanned with a fluorescence spectrophotometer. Resultant spectra were evaluated via interpeak ratios. RESULTS: Interpeak ratios of all histologies were found to be significantly different from each other (P < 0.001). The diagnostic sensitivity and specificity of fluorescent spectroscopy was 86% and 91% for thyroid nodule capsule, 78% and 59% for papillary thyroid carcinoma, and 82% and 63% for normal thyroid, respectively. CONCLUSION: Fluorescent spectroscopy can been used to identify significant differences in the fluorescent characteristics of various thyroid histologies. SIGNIFICANCE: This study is the first investigation of the fluorescence of thyroid tissue. The diagnostic ability of fluorescent spectrometry may allow it to be used as a localization aid for fine needle aspiration, using optical fiber probes. Further investigations may enhance the sensitivity and specificity of fluorescent spectrometry allowing it to replace or compliment fine needle aspiration. EBM RATING: B-3.

NIR laser tissue welding of in vitro porcine cornea and sclera tissue.

BACKGROUND AND OBJECTIVE: The objective of this study was to test the hypothesis that an near infrared (NIR) laser system (1,455 nm) in combination with a motorized translational stage to control the position and speed of the laser beam and a shutter to control the laser exposure to the tissue being welded could be used to successfully weld ocular tissues. STUDY DESIGN/MATERIALS AND METHODS: Seventy-five porcine corneas and 23 porcine scleral tissues were welded in vitro in this study. The welded tissues were examined using histopathology and tensile strength analysis. Eight different welding conditions were analyzed for porcine cornea and one for sclera tissues. The tensile strength of the welded groups was compared to a sutured cornea control group. RESULTS: The NIR laser welding system provides strong, full thickness welds and does not require the use of extrinsic dyes, chromophores, or solders. Mean weld strengths of 0.15-0.45 kg/cm(2) were obtained for the cornea and 1.01 kg/cm(2) for sclera welds. The native H(2)O in the ocular tissue serves as an absorber of the 1,455 nm radiation and helps to induce the welds. CONCLUSIONS: We conclude that an NIR laser system using an optimal laser radiation wavelength of 1,455 nm can effectively weld cornea and sclera tissue and that this laser tissue welding (LTW) methodology typically causes minimal disruption of tissue, and thus, avoids opacities and irregularities in the tissue which may result in decreased visual acuity. The optimization of a laser welding system that leads to a strong full thickness tissue bond without tissue destruction, an instant seal that promotes wound healing, and the absence of a continued presence of a foreign substance like a suture, is of considerable importance to the ophthalmology medical community. This need is especially apparent with respect to corneal transplantation and fixing the position of corneal flaps in Laser-Assisted In Situ Keratomileusis (LASIK), a laser procedure used to permanently change the shape of the cornea.

Native fluorescence and excitation spectroscopic changes in Bacillus subtilis and Staphylococcus aureus bacteria subjected to conditions of starvation.

Fluorescence emission and excitation spectra were measured over a 7-day period for Bacillus subtilis (Bs), a spore-forming, and Staphylococcus aureus (Sa), a nonspore-forming bacteria subjected to conditions of starvation. Initially, the Bs fluorescence was predominantly due to the amino acid tryptophan. Later, a fluorescence band with an emission peak at 410 nm and excitation peak at 345 m, from dipicolinic acid, appeared. Dipicolinic acid is produced during spore formation and serves as a spectral signature for detection of spores. The intensity of the 410-nm band continued to increase over the next 3 days. The Sa fluorescence was predominantly from tryptophan and did not change over time. In 6 of the 17 Bs specimens studied, an additional band appeared with a weak emission peak at 460 cm and excitation peaks at 250, 270, and 400 nm. The addition of beta-hydroxybutyric acid to the Bs or the Sa cultures resulted in a two-order of magnitude increase in the 460-nm emission. The addition of Fe2+ quenched the 460 emission, indicating that a source of the 460-nm emission was a siderophore produced by the bacteria. We demonstrate that optical spectroscopy-based instrumentation can detect bacterial spores in real time.