Structural differences in unbleached and mildly-bleached synthetic tyrosine-derived melanins identified by scanning probe microscopies.

Using scanning tunneling microscopy (STM), we have imaged two types of mildly-bleached, synthetic tyrosine-derived melanins for comparison with the unbleached melanin from which they were prepared. These mildly-bleached melanins were generated by mild oxidation of the unbleached melanin, using either basic hydrogen peroxide or air/light. The unbleached melanin, and two mildly-bleached melanins, were independently deposited from very dilute tetrahydrofuran (THF) solutions onto highly oriented pyrolytic graphite (HOPG) substrate for STM imaging. Lateral dimensions (23 A, average of two directions) of structures from each of the three samples showed no differences. However, structures from both mildly-bleached melanins showed similar dramatic decreases (from approximately 15 A to approximately 5 A) in their STM-measured apparent heights, compared with structures from the unbleached melanin sample. These STM observations are compatible with structural models for unbleached and mildly-bleached melanins, incorporating a three-dimensional structure for unbleached melanin composed of multi-layered, pi-pi-stacked, carboxylic and amino variants of polyaromatic polymeric sheets. The STM-observed decrease in apparent heights after mild oxidation, which we associate with a change in stack height, has been confirmed by experiments using tapping mode atomic force microscopy (TM-AFM) for the unbleached and mildly-hydrogen-peroXide-bleached melanins (from approximately 14 A to approximately 6 A). In these TM-AFM experiments, the melanins were deposited directly onto magnesium cation-treated glass substrates in contact with methanolic solutions of each of the melanins. We interpret our mild-bleaching results as an oxidative conversion of the multi-layered, stacked sheets of mainly carboxylic and amino variants of polyquinhydrone-like moieties, to largely de-stacked, mildly-bleached melanin sheets. These oxidized and, hence, electron-deficient sheets should not readily form multi-layered, pi-pi interacting stacks, but instead appear to be either single-layer polyquinone sheets or, at most, double-layer polyquinhydrone sheets. The effects of such de-stacking on in vivo melanin photoprotection, and structural similarities between melanin derived from natural sources and the synthetic melanin samples used in this work are discussed.

Solution structure of copper ion-induced molecular aggregates of tyrosine melanin.

Melanin, the ubiquitous biological pigment, provides photoprotection by efficient filtration of light and also by its antioxidant behavior. In solutions of synthetic melanin, both optical and antioxidant behavior are affected by the aggregation states of melanin. We have utilized small-angle x-ray and neutron scattering to determine the molecular dimensions of synthetic tyrosine melanin in its unaggregated state in D(2)O and H(2)O to study the structure of melanin aggregates formed in the presence of copper ions at various copper-to-melanin molar ratios. In the absence of copper ions, or at low copper ion concentrations, tyrosine melanin is present in solution as a sheet-like particle with a mean thickness of 12.5 A and a lateral extent of approximately 54 A. At a copper-to-melanin molar ratio of 0.6, melanin aggregates to form long, rod-like structures with a radius of 32 A. At a higher copper ion concentration, with a copper-to-melanin ratio of 1.0, these rod-like structures further aggregate, forming sheet-like structures with a mean thickness of 51 A. A change in the charge of the ionizable groups induced by the addition of copper ions is proposed to account for part of the aggregation. The data also support a model for the copper-induced aggregation of melanin driven by pi stacking assisted by peripheral Cu(2+) complexation. The relationship between our results and a previous hypothesis for reduced cellular damage from bound-to-melanin redox metal ions is also discussed.

Office microlaparoscopy under local anesthesia in the diagnosis and treatment of chronic pelvic pain.

STUDY OBJECTIVE: To evaluate the safety of diagnostic and operative microlaparoscopy performed in the office under local anesthesia in the diagnosis and treatment of chronic pelvic pain. DESIGN: Prospective study (Canadian Task Force classification II-2). SETTING: Office-based, free-standing private obstetrics and gynecology practice. PATIENTS: Twenty women with chronic pelvic pain. INTERVENTION: Diagnostic and operative microlaparoscopy performed under local anesthesia with conscious sedation. MEASUREMENTS AND MAIN RESULTS: All 20 patients had diagnostic microlaparoscopy and 19 had conscious pain mapping. Nine of 14 patients with endometriosis underwent fulguration of lesions and 7 of 8 with pelvic adhesions had lysis of adhesions. Four women with uterosacral ligament involvement had laparoscopic uterosacral nerve ablation. All patients tolerated office diagnostic and operative procedures without difficulty and had no complications. CONCLUSION: In selected women, several laparoscopic procedures traditionally done in a hospital or ambulatory surgery center under general anesthesia can be performed safely in the office laparoscopy suite under local anesthesia with conscious sedation.

Appendectomy under local anaesthesia following conscious pain mapping with microlaparoscopy.

The appendix is an under-appreciated source of chronic pelvic pain. Laparoscopic evaluation of the appendix is limited without intra-operative patient feedback on the presence and absence of pain. New techniques using local anaesthesia with conscious sedation have enabled us to perform operative laparoscopic surgery while the patient is awake. We report the first two cases of microlaparoscopic appendectomies performed under local anaesthesia with conscious sedation following diagnosis obtained during conscious pain mapping.

Small trocar perforation of the small bowel: a case report.

Although laparoscopy is one of the most common surgical procedures done today, bowel perforations can and do occur during the initial insertion of the Veress needle and/or trocar. Recent advances in microlaparoscopy have reduced the morbidity of this complication when encountered. We report a case of small bowel perforation following insertion of a Veress needle with its 2 mm trocar and our minimally invasive intra-operative and postoperative management of the patient.

Conscious pain mapping.

STUDY OBJECTIVE: To present the technique and usefulness of conscious pain mapping. DESIGN: Prospective, observational study (Canadian Task Force classification II-2). SETTING: Gynecology departments of a university-affiliated hospital and a private community hospital. PATIENTS: Fifty consecutive women undergoing diagnostic microlaparoscopy. INTERVENTIONS: Conscious pain mapping was performed in all 50 women. MEASUREMENTS AND MAIN RESULTS: Conscious pain mapping helped to identify foci of chronic pelvic pain. The appendix and pelvic adhesions accounted for a significant amount of pelvic pain in these women. CONCLUSIONS: Conscious pain mapping helps to uncover sites of pelvic pain that might not be identified during traditional laparoscopy under general anesthesia.

A protocol for conscious sedation in microlaparoscopy.

To establish a protocol for conscious sedation in microlaparoscopy, we conducted a prospective, observational study of 74 women undergoing the procedure under local anesthesia with conscious sedation for the evaluation and treatment of chronic pelvic pain. Our protocol for conscious sedation allowed us to perform diagnostic microlaparoscopy under local anesthesia in all 74 women and operative microlaparoscopy in 52 (70.2%). This procedure is a safe and effective alternative to general anesthesia during microlaparoscopy in selected patients.

The fundamental unit of synthetic melanin: a verification by tunneling microscopy of X-ray scattering results.

A characteristic dimension of a melanin protomolecule synthesized from tyrosine has been investigated by scanning tunneling microscopy (STM). Identification of a melanin protomolecule of approximately approximately 20 A lateral extent and approximately 10 A height has been established. This size is in good agreement with models constructed to fit wide angle X-ray diffraction experiments on melanin. These protomolecules are believed to consist of Van der Waals interacting stacks of a basic random polymer of 5.6 indolequinone units. There is extensive pi-delocalization within the individual polymeric sheets. Structure minimization and molecular orbital techniques were employed to verify the X-ray and STM results.

The fluorescence quantum yield of vitamin A2.

The fluorescence quantum yield of all-trans 3,4-didehydroretinol (vitamin A2) was measured in hexane at room temperature, using quinine sulfate as a standard. Unlike all-trans retinol (vitamin A1) which possessed a relative quantum yield of 0.0298, 3,4-didehydroretinol was 37 times lower in fluorescence (i.e. 0.0008). In addition, a significant bathochromic shift (both excitation and emission maxima) and a general broadening of the fluorescence spectra were noted for 3,4-didehydroretinol. This information is important not only for the understanding of the basic structure of vitamin A but also the photochemistry of vision.