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Biomedical subjects

D W Becker

Publications and source records attributed to D W Becker.

At least 19 recordsLinked to original sources
PubMed2001

PET imaging of somatostatin receptors using [68GA]DOTA-D-Phe1-Tyr3-octreotide: first results in patients with meningiomas.

UNLABELLED: Imaging of somatostatin receptors (SSTRs) using [111In]diethylenetriaminepentaacetic-acid-octreotide (DTPAOC) has proven to be helpful in the differentiation of meningiomas, neurinomas or neurofibromas, and metastases as well as in the follow-up of meningiomas. A drawback of the SPECT method is its limited sensitivity in detecting small meningiomas. Because of PET's increased spatial resolution and its ability to absolutely quantify biodistribution, a PET tracer for SSTR imaging would be desirable. METHODS: 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic-acid-D-Phe1-Tyr3-octreotide (DOTATOC) was labeled using the positron-emitting generator nuclide 68Ga. We acquired dynamic PET images over 120 min after intravenous injection of 175 MBq [68Ga]DOTATOC in 3 patients suffering from 8 meningiomas (WHO I degrees; 7- to 25-mm diameter). Patients' heads had been fixed using individually shaped fiber masks equipped with an external stereotactic localizer system to match PET, CT, and MRI datasets. RESULTS: [68Ga]DOTATOC was rapidly cleared from the blood (half-life alpha, 3.5 min; half-life beta, 63 min). Standardized uptake values (SUVs) of meningiomas increased immediately after injection and reached a plateau 60-120 min after injection (mean SUV, 10.6). No tracer could be found in the surrounding healthy brain tissue. All meningiomas (even the 3 smallest [7- to 8-mm diameter]) showed high tracer uptake and could be visualized clearly. Tracer boundaries showed a good correspondence with the matched CT and MRI images. PET provided valuable additional information regarding the extent of meningiomas located beneath osseous structures, especially at the base of the skull. CONCLUSION: According to our initial experiences, [68Ga]DOTATOC seems to be a very promising new PET tracer for imaging SSTRs even in small meningiomas, offering excellent imaging properties and a very high tumor-to-background ratio.

Gallium Radioisotopes↗
PubMed2000

A water-cooled spherical niobium target for the production of [18F]fluoride.

A new automated target system for the routine production of [18F]fluoride from (18)O-enriched water has been constructed. It consists of a small spherical niobium target chamber mounted into a special holder, which provides rapid cooling by water flow around the sphere. The target is irradiated with 21 MeV protons; the incident energy in the target chamber is 13 MeV. The system is operated without external over-pressure and has been tested for beam currents up to 50 microA. 95% of the theoretical yield of [18F]fluoride has been extracted and used for the synthesis of [18F]2-fluoro-2-deoxy-D-glucose.

Fluorides↗
PubMed1993

An aid to nasotracheal intubation in orthognathic surgery.

An atraumatic and reliable technique of nasal intubation in patients with previous pharyngoplasty or pharyngeal flap is presented. Using the tight and smooth fit of the fluted end of a red rubber catheter over the end of a nasotracheal tube is the technique described.

Catheterization↗
PubMed1991

Use of the carbon dioxide laser in treating multiple cutaneous neurofibromas.

The CO2 laser is presented as a useful tool for the removal of large numbers of neurofibromas, the major source of cosmetic disfigurement in the patient with peripheral neurofibromatosis. Its advantages include high patient satisfaction with the rapid, staged removal of thousands of neurofibromas, with minimal morbidity and an enhanced appearance. The operative technique for each of the forms of neurofibroma, that is, pedunculated, sessile, and subcutaneous, is described. As with all procedures involving a change in appearance, it is essential that the patient be fully aware of the limitations of the procedure and the expected final result. This is easily accomplished in this procedure by the use of a "test treatment."

Adult↗
PubMed1988

Laser silicone flash.

Use of the CO2 laser to remove breast siliconosis is described. The flash accompanying this use of the laser is described, and a photograph is submitted to document this previously undescribed phenomenon.

Adult↗
PubMed1987

Total arm flap.

The development of an unusual and rarely indicated total arm flap is described in the context of widely indicated and automatically used principles passed down by the recognized father of plastic surgery, Sir Harold G. Gillies.

Arm↗
PubMed1987

Laser deepithelialization: an adjunct to reduction mammaplasty.

A new use is described for the CO2 laser--that of deepithelialization. Deepithelialization is a technique used in a myriad of plastic surgical procedures. This paper introduces the use of the laser for deepithelialization and illustrates its advantages in 44 consecutive patients undergoing reduction mammaplasty. Advantages are the precise removal of the upper dermis and epidermis--a true deepithelialization--with preservation of the lower dermis and pilosebaceous units. Associated decreased blood loss and more rapid operating time without an increase in complications makes this an attractive adjunctive technique with a wide variety of applications. No adverse effects or contraindications to the use of the CO2 laser for deepithelializing have been found.

Adolescent↗
PubMed1986

Studies on the Photoactivation of the Water-Oxidizing Enzyme: II. Characterization of Weak Light Photoinhibition of PSII and Its Light-Induced Recovery.

Inactivation of the water splitting enzyme complex in leaves or isolated chloroplasts results in increased susceptibility of photosystem II (PSII) to damage by light. Photoinhibition under this condition occurs in very weak light. The site of damage is exclusive of the water splitting complex yet still on the oxidizing side of PSII, as the Q(B) locus is unaffected while photoreduction of silicomolybdate is inhibited. The kinetics of loss in PSII activity are more complex than apparent first-order, and the quantum efficiency is low. We observe no evidence of deletion from thylakoid membranes of any PSII polypeptide as a consequence of photoinhibition, although recovery from the photoinhibition is dependent upon both light and 70S protein synthesis. Enhanced synthesis of two proteins occurs during recovery, only one of which (D2) appears to be causally related to the recovery. We present a model which describes the relationship of weak light photoinhibition and its recovery to photoactivation of the S-state water oxidizing complex.

Journal Article↗
PubMed1985

Anacystis nidulans Demonstrates a Photosystem II Cation Requirement Satisfied Only by Ca or Na.

Anacystis nidulans exhibits a total loss of photosystem II (PSII) activity upon incubation in a nutrient medium deficient in Ca(2+) and Na(+) and containing a divalent cation chelator. This loss of activity is light-dependent, which corresponds to an energy requirement. Likewise, Ca(2+) efflux takes place only in cells incubated in light. The loss of PSII activity is reversible by addition of submillimolar amounts of either Ca(2+) or Na(+) to the external medium but not by the addition of any other cation. Restoration of lost PSII activity also requires light. Light saturation curves for partially depleted cells demonstrate both lower maximum O(2) evolution rates and decreased relative quantum yields when compared to control cells. Partial electron transport reactions isolate the site of the Ca(2+)/Na(+) effect to the reaction center itself or immediately on its oxidizing side and exclude the water-splitting complex. O(2) flash yields decline during cation depletion, indicating a decrease in the number of functional PSII reaction centers, but the maximum turnover rate for still functional reaction centers does not decline. Thus, PSII of A. nidulans exhibits an all-or-none cation requirement, satisfied only by Ca(2+) or Na(+).

Journal Article↗
PubMed1984

Evidence for direct roles of calcium in photosynthesis.

Calcium may function directly in several aspects of photosynthesis. It appears to modulate activity of the phosphatase enzymes in the carbon reduction cycle and also to regulate chloroplast NAD+ kinase activity through a calmodulin-like protein. Some evidence supports a calcium function in the water-splitting complex, and other evidence indicates a reaction center function in photosystem II. Calcium in reaction center II may be tightly bound in chloroplasts and weakly bound in blue-green algal thylakoids. Free calcium concentration in stroma is probably less than 10(-6) M, although the absolute concentration is not yet known. Intrathylakoid calcium content is likely very high. Stromal calcium may regulate several enzyme activities, while intrathylakoid calcium may promote photosystem II constitutively. Results to date demonstrate the need for more attention to cation composition in studies of both light and dark reactions of photosynthesis, and the need to identify free calcium levels in chloroplasts.

Calcium↗
PubMed1980

Metastatic minimal-deviation melanoma.

A case of metastatic minimal-deviation melanoma that appeared twelve months after radical surgery is presented. It is suggested that newly described varieties of melanoma be treated as standard varieties (on the basis of depth of invasion) until statistically significant numbers of such lesions are reported.

Adult↗