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At least 1,675 records · Page 93Linked to original sources
PubMed2001

Laser resurfacing of silicone-injected skin: the "silicone flash" revisited.

OBJECTIVE: To determine whether prior silicone injection increases the risks associated with carbon dioxide laser resurfacing. DESIGN: Laboratory determination of the effect of laser energy on liquid silicone; histologic evaluation of silicone-injected skin after lasing; and histologic demonstration of silicone deposits in all layers of dermis years after injection of silicone as filler fluid. SETTING: Tertiary care medical center. PATIENT-RELATED DATA: Histologic examination of freshly excised skin injected with microdroplets of liquid silicone and subjected to application of carbon dioxide laser energy; histologic examination of skin excised years after silicone injection. INTERVENTIONS: High-speed clinical photographic imaging of the effect of laser energy on silicone fluid; histologic examination of hematoxylin-eosin-stained sections of skin injected with liquid silicone and subsequently lased. MAIN OUTCOME MEASURES: Response of liquid silicone to application of laser energy; effect of this response on surrounding normal skin. RESULTS: Exposure of microdroplets of liquid silicone to carbon dioxide laser energy produced flaring with frank flame. Flaring of dermal silicone caused collateral skin damage. CONCLUSIONS: Prior injection with liquid silicone is a relative contraindication to cutaneous resurfacing with the carbon dioxide laser. Surgical excision of silicone-injected skin may be preferable for many patients. A strenuous needs assessment should be done, alternatives for skin rejuvenation considered, and comprehensive informed consent obtained from the patient before embarking on laser resurfacing of silicone-injected skin.

Carbon Dioxide↗
PubMed2002

Deprotonation and dimerization of maleimide in the triplet state: a laser flash photolysis study with optical and conductometric detection.

The photochemistry of maleimide in aqueous solution is governed by the coexistence of up to three different triplet states, the keto triplet (lambda(max)=250, 330 nm, lambda(min)=290 nm, pK(a)=4.4+/-0.1, tau=5 micros), the deprotonated or enolate triplet (lambda(max)=360, 260 nm, lambda(min)=320 nm, shoulder at 370-380 nm) and a dimer triplet. This biradical is formed by the addition of the keto triplet to the double bond of a ground state maleimide in competition with electron transfer, (k( (3)MI+MI)=2.6 x 10(9) dm(3) mol(-1) s(-1)). Its spectrum is identical to that of the maleimide H-adduct radical (lambda(max)=370-380 (broad), 255 nm (narrow), lambda(min)=290 nm) and its lifetime is 110 ns. While protolysis is confined to maleimide and aqueous solutions, the dimer triplet is also found in acetonitrile. Dimer triplet formation is also observed with N-ethylmaleimide. Time-resolved conductometry and buffer experiments were used to characterise excited state protolysis. Multi-wavelength "global analysis" of the time profiles allowed the separation of the transient spectra and study of the kinetics of the monomer and dimer triplets. The cyclobutane dimer yield (determined by GC) is independent of maleimide concentration. This indicates that the dimer triplet does not contribute significantly to the initiation of free-radical polymerisation. Time-dependent Hartree-Fock calculations agree with the experimental data and further confirm the proposed mechanisms.

Journal Article↗
PubMed2001

Interprotein Electron Transfer Reaction Regulated by an Artificial Interface We thank Prof. Dr. I. Morishima and his group for the arrangement of laser flash photolysis equipment. This work was supported by Nagase Science and Technology Foundation, and a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture, Japan. Y. H. was supported by Research Fellowships of the Japanese Society for the Promotion of Science for Young Scientists.

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Journal Article↗
PubMed2002

Lighting up gap junction channels in a flash.

Gap junction intercellular communication channels permit the exchange of small regulatory molecules and ions between neighbouring cells and coordinate cellular activity in diverse tissue and organ systems. These channels have short half-lives and complex assembly and degradation pathways. Much of the recent work elucidating gap junction biogenesis has featured the use of connexins (Cx), the constituent proteins of gap junctions, tagged with reporter proteins such as Green Fluorescent Protein (GFP) and has illuminated the dynamics of channel assembly in live cells by high-resolution time-lapse microscopy. With some studies, however, there are potential short-comings associated with the GFP chimeric protein technologies. A recent report by Gaietta et al., has highlighted the use of recombinant proteins with tetracysteine tags attached to the carboxyl terminus of Cx43, which differentially labels 'old' and 'new' connexins thus opening up new avenues for studying temporal and spatial localisation of proteins and in situ trafficking events.

Animals↗
PubMed1983

Oxygen activation by cytochrome oxidase: a new spectral intermediate observed by flow-flash.

The reaction of cytochrome-c-oxidase with O2 has been reinvestigated at 2 degrees C by a flow laser pulsed method. The experiments indicate that a new spectral intermediate, populated with a rate constant of approximately 5000/s, is observed in a wavelength range in which heme a is the only chromophore (445 and 430 nm). The results are interpreted with reference to previous data obtained in the near infrared region, and it is suggested that breakage of the (enzyme bound) dioxygen bond is associated to a spectral perturbation of the cytochrome a3-CuB binuclear center.

Animals↗
PubMed2005

Contrast-enhanced power Doppler sonography of malignant ovarian tumors using harmonic flash-echo imaging: preliminary experience.

To investigate the potential usefulness of contrast-enhanced intermittent harmonic sonography in the diagnosis of ovarian cancer, we evaluated 4 patients with complex adnexal masses suspected of malignancy using intermittent harmonic sonography after injection of a contrast agent. Tumor and/or mural nodule tissue enhancement was detected in all cases of ovarian malignancy. Contrast-enhanced, intermittent harmonic sonography provides a satisfactory visualization of blood flow in the solid portion of the tumor tissue and may support a diagnosis of ovarian malignancy. Depiction of blood vessels using low MI techniques may be possible with other vascular ultrasonographic contrast agents.

Contrast Media↗
PubMedDate not supplied

Black blood dual phase turbo FLASH MR imaging of the heart.

An MR imaging scheme for dark blood cardiac images acquired simultaneously in end diastolic and end systolic phases, in breath-hold times, is presented. The sequence consists of a magnetization preparation period followed by two segmented k-space acquisitions. Image quality was investigated with respect to different sequence parameters (optimal values are indicated in brackets): (a) echo time (TE)/repetition time (TR)/ flip angle (FA) (3/6.2 msec/20 degrees); (b) number of lines/ segments in the acquisition window (11 lines/segment); (c) location of acquisition windows and inversion time; and (d) thickness of slice "reinverted" during preparation (1.53 times the acquisition slice thickness). The image quality of the basal slices at end systole was critically dependent on the last parameter. High quality short axis views of the heart, with good blood signal suppression, were acquired with the optimized sequence on four volunteers from apex to base at two phases in 10 breath-holds.

Blood↗
PubMed2003

Effect of vascular crushing on FAIR perfusion kinetics, using a BIR-4 pulse in a magnetization prepared FLASH sequence.

Flow-sensitive alternating inversion recovery (FAIR) perfusion imaging suffers from high vascular signal, resulting in artifacts and overestimation of perfusion. With TurboFLASH acquisition, crushing of vascular signal by bipolar gradients after each excitation is difficult due to the requirement of an ultrashort repetition time. Therefore, insertion of a preparation phase in the FAIR sequence, after labeling and prior to TurboFLASH acquisition, is proposed. A segmented adiabatic BIR-4 pulse, interleaved with crusher gradients, was used for flow crushing. The effect of the crusher preparation is shown as a function of crusher strength for a flow phantom and in rat brain. Influence of crusher strength on the time-dependent FAIR signal from rat brain was also measured. Signal from flowing spins in a flow phantom and from arterial spins in rat brain was significantly suppressed. Image quality was improved and the overestimation of perfusion at short inflow times was eliminated.

Animals↗