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R B Dyer

Publications and source records attributed to R B Dyer.

At least 19 recordsLinked to original sources
PubMed1992

Resonance Raman studies of Rieske-type proteins.

Resonance Raman (RR) spectra are reported for the [2Fe-2S] Rieske protein from Thermus thermophilus (TRP) and phthalate dioxygenase from Pseudomonas cepacia (PDO) as a function of pH and excitation wavelength. Depolarization ratio measurements are presented for the RR spectra of spinach ferredoxin (SFD), TRP, and PDO at 74 K. By comparison with previously published RR spectra of SFD, we suggest reasonable assignments for the spectra of TRP and PDO. The spectra of PDO exhibit virtually no pH dependence, while significant changes are observed in TRP spectra upon raising the pH from 7.3 to 10.1. One band near 270 cm-1, which consists of components at 266 cm-1 and 274 cm-1, is attributed to Fe(III)-N(His) stretching motions. We suggest that these two components arise from conformers having a protonated-hydrogen-bonded imidazole (266 cm-1) and deprotonated-hydrogen-bonded imidazolate (274 cm-1) coordinated to the Fe/S cluster and that the relative populations of the two species are pH-dependent; a simple structural model is proposed to account for this behavior in the respiratory-type Rieske proteins. In addition, we have identified RR peaks associated with the bridging and terminal sulfur atoms of the Fe-S-N cluster. The RR excitation profiles of peaks associated with these atoms are indistinguishable from each other in TRP (pH 7.3) and PDO and differ greatly from those of [2Fe-2S] ferrodoxins. The profiles are bimodal with maxima near 490 nm and > approx. 550 nm. By contrast, bands associated with the Fe-N stretch show a somewhat different enhancement profile. Upon reduction, RR peaks assigned to Fe-N vibrations are no longer observed, with the resulting spectrum being remarkably similar to that reported for reduced adrenodoxin. This indicates that only modes associated with Fe-S bonds are observed and supports the idea that the reducing electron resides on the iron atom coordinated to the two histidine residues. Taken as a whole, the data are consistent with an St2FeSb2Fe[N(His)]t2 structure for the Rieske-type cluster.

Burkholderia cepacia↗
PubMed1992

Ultrafast infrared spectroscopy.

Recent advances in ultrafast infrared spectroscopy are described, including experimental details and fundamental limitations. The utility of this technique is illustrated with two recent examples.

Animals↗
PubMed1992

Reaction of cyanide with cytochrome ba3 from Thermus thermophilus: spectroscopic characterization of the Fe(II)a3-CN.Cu(II)B-CN complex suggests four 14N atoms are coordinated to CuB.

Cytochrome ba3 from Thermus thermophilus reacts slowly with excess HCN at pH 7.4 to create a form of the enzyme in which CuA, cytochrome b, and CuB remain oxidized, while cytochrome a3 is reduced by one electron, presumably with the formation of cyanogen. We have examined this form of the enzyme by UV-visible, resonance Raman, EPR, and electron nuclear double resonance spectroscopies in conjunction with permutations of 13C- and 15N-labeled cyanide. The results support a model in which one CN- binds through the carbon atom to ferrous a3, supporting a low-spin (S = 0) configuration on the Fe; bridging by this cyanide to the CuB is weak or absent. Four 14N atoms, presumably donated by histidine residues of the protein, provide a strong equatorial ligand field about CuB; a second CN- is coordinated through the carbon atom to CuB in an axial position.

Binding Sites↗
PubMed1992

Workmens' compensation and byssinosis in South Africa: a review of 32 cases.

Byssinosis has been compensable in the Republic of South Africa (RSA) since 1973. The legal and administrative provisions for byssinosis compensation are reviewed. A series of 32 cases of presumed byssinosis was submitted to the compensation authorities by the authors. Identical reports were submitted to an independent medical panel. The findings and outcomes in these cases are presented and compared. Seventeen of the 32 claims initially received compensation and four were subsequently accepted following appeals. Analysis of the medical basis of decision making indicated that seven claims were refused and at least four had their awards reduced as a consequence of inconsistent decisions. Arguable decisions resulted in five claims being refused and one award being reduced. Our experience illustrates problems inherent in the compensation system in South Africa. Initiation of a claim is expensive relative to wages in the industry, and awards are low since they are linked to wages (mean $60.47 per week). Processing of a claim took a mean of 13.8 months, while appeals for refusal to compensate took a further 29.8 months. It is argued that consensus medical definitions of compensable occupational disease should be used routinely and that provision must be made to facilitate entry of claimants into the compensation system.

Adult↗
PubMed1992

Transurethral laser prostatectomy in the canine model.

A technique for performing transurethral prostatectomy was devised using a Neodymium:Yttrium Aluminum Garnet laser in a canine model. Six dogs underwent transurethral laser prostatectomy following establishment of a perineal urethrostomy. The efficacy of the prostatectomies was judged by retrograde urethrography, transrectal prostate ultrasonography, cystoscopy, and histologic examination. The method of applying laser energy while holding the tip of the fiberoptic light guide 2-3 mm away from the prostate was ineffective; with power ranging from 40 to 70 watts, this technique resulted mainly in coagulation necrosis and removal of only a small amount of tissue. However, placing the tip of the light guide in direct contact with the prostate and using power from 70 to 100 watts produced impressively large prostatectomy defects by tissue vaporization. We conclude that this newly devised technique for transurethral prostatectomy in the canine model can be performed safely and effectively using a Neodymium:Yttrium Aluminum Garnet laser (Neodymium:YAG).

Aluminum Silicates↗
PubMed1992

Intraluminal renal metastasis from colon cancer simulating a fungus ball.

Reports of renal metastasis from colon cancer are unusual, and none have described intraluminal renal metastasis. We describe a patient with a radiolucent filling defect in the renal pelvis that was discovered by percutaneous nephrostomy during prophylactic nephrostomy tube change. Imaging and laboratory results indicated a fungus ball, but pathologic diagnosis of the percutaneously extracted mass was metastatic colonic adenocarcinoma.

Adenocarcinoma↗
PubMed1991

Nature and functional implications of the cytochrome a3 transients after photodissociation of CO-cytochrome oxidase.

Time-resolved electronic absorption, infrared, resonance Raman, and magnetic circular dichroism spectroscopies are applied to characterization of the intermediate that is formed within 20 ps after photodissociation of CO from cytochrome a3 in reduced cytochrome oxidase. This intermediate decays with the same half-life (approximately 1 microseconds) as the post-photodissociation CU+B-CO species previously observed by time-resolved infrared. The transient UV/visible spectra, kinetics, infrared, and Raman evidence suggest that an endogenous ligand is transferred from CuB to Fea3 when CO binds to CuB, forming a cytochrome a3 species with axial ligation that differs from the reduced unliganded enzyme. The time-resolved magnetic circular dichroism results suggest that this transient is high-spin and, therefore, five-coordinate. Thus we infer that the ligand from CuB binds on the distal side of cytochrome a3 and displaces the proximal histidine imidazole. This remarkable mechanistic feature is an additional aspect of the previously proposed "ligand-shuttle" activity of the CuB/Fea3 pair. We speculate as to the identity of the ligand that is transferred between CuB and Fea3 and suggest that the ligand shuttle may play a functional role in redox-linked proton translocation by the enzyme.

Binding Sites↗
PubMed1991

Spontaneous perinephric hemorrhage: imaging and management.

We report on 10 patients with spontaneous perinephric hemorrhage associated with underlying disease, including renal cell carcinoma (5), angiomyolipoma (2), malignant melanoma (1), periarteritis nodosa (1) and severe portal hypertension (1). The etiology could not be identified with computerized tomography (CT) in 5 cases (50%), including 2 renal cell carcinomas, 1 angiomyolipoma, 1 periarteritis nodosa and 1 portal hypertension. Arteriography demonstrated underlying lesions in 4 of these 5 cases (80%) including the case of vasculitis. CT combined with magnetic resonance imaging is accurate for the diagnosis of spontaneous perinephric hemorrhage but the underlying pathological condition is often undetectable in the acute phase due to the perinephric blood. CT should be the first study performed if this diagnosis is suspected. Arteriography is recommended if a renal mass is not detected. If a mass is not identified with these 2 imaging studies and the patient is clinically stable, followup thin slice CT should be performed.

Adult↗
PubMed1991

A comparison of anatrophic nephrolithotomy and percutaneous nephrolithotomy with and without extracorporeal shock wave lithotripsy for management of patients with staghorn calculi.

A retrospective study was conducted comparing anatrophic nephrolithotomy (10 cases), percutaneous nephrolithotomy alone (4 cases) or percutaneous nephrolithotomy combined with extracorporeal shock wave lithotripsy (23 cases) for the treatment of large staghorn calculi. A comparison based on collecting system anatomy demonstrated that anatrophic nephrolithotomy resulted in a greater stone-free rate, shorter hospitalization and lower costs while complication rates were similar. Anatrophic nephrolithotomy should still be considered a viable treatment option, especially for patients with large branched calculi in complex collecting systems.

Adult↗
PubMed1991

Percutaneous management of localized emphysematous pyelonephritis.

The authors report a case of emphysematous pyelonephritis that was successfully treated with radiologically guided percutaneous drainage. This case illustrates that in certain patients with focal abnormalities, functioning renal tissue can be salvaged and emphysematous pyelonephritis can be eradicated with a combination of antibiotics and radiologically guided percutaneous drainage.

Aged↗
PubMed1990

CT features of renal cell carcinoma with emphasis on relation to tumor size.

Computed tomography (CT) is the current standard for diagnosing and staging renal cell carcinoma (RCC). Although general diagnostic guidelines exist, no large studies to date have delineated the CT features of RCC. We reviewed the CT appearances of 78 pathologically proven RCCs. Of the 61 RCCs larger than 50 mm (78%) there was imaging evidence of extrarenal spread (87%), intratumoral necrosis (61%) and differential growth rates within the tumor (64%). Tumors 50 mm or smaller often had a "benign" appearance with sharp, rounded margins (88%), homogeneous density (65%), and distinct interface with the kidney (82%). The significance of these lesions should not be underestimated. Although RCCs often showed transient marked enhancement after bolus contrast material injection (41%), during the infusion phase 97% were hypodense compared with the kidney regardless of tumor size. Calcifications were visible in 31% of RCCs. Although 22% of RCCs were predominantly cystic, none fulfilled all CT criteria of simple renal cysts.

Adult↗
PubMed1990

Vicarious contrast material excretion in patients with acute unilateral ureteral obstruction.

Radiographs of 45 patients with evidence of acute unilateral ureteral obstruction at intravenous urography, obtained at least 24 hours after injection of contrast material, were retrospectively studied. Vicarious contrast material excretion (VCME) as evidence by gallbladder opacification on delayed radiographs was seen in 19 patients (42%), 10 of whom also showed extravasation of contrast material. A total of 15 of the 45 patients developed spontaneous extravasation; 10 (67%) showed VCME, while only nine of the 30 patients (30%) who did not have spontaneous extravasation of contrast material showed VCME. The creatinine level was elevated (greater than 1.5 mg/dL [133 mumol/L]) in four patients with VCME and in six patients without. This series indicates that VCME is more common than previously appreciated in patients with acute unilateral ureteral obstruction and occurs with greater frequency when obstruction is associated with contrast material extravasation.

Diatrizoate Meglumine↗
PubMed1990

Radiology in the diagnosis and staging of renal cell carcinoma.

Renal cell carcinoma (RCC), a potentially curable lesion, is the most common primary renal malignancy. Due to the importance of early diagnosis and the lack of specific clinical features of RCC, imaging plays a vital role in the diagnosis and management of RCC. Newer imaging modalities have superseded plain-film radiography in the diagnosis of RCC by offering greater sensitivity and specificity in both diagnosis and staging. RCC can be diagnosed with computed tomography (CT) with greater than 95% accuracy. Once an RCC is detected, tumor staging becomes paramount for treatment planning. Greater than 90% staging accuracy can be accomplished with CT alone using techniques described in this article. Magnetic resonance imaging (MRI) can be used to achieve staging accuracy similar to CT. MRI and ultrasonography (US) should be used to aid the diagnosis and staging of RCC in equivocal CT cases. The appropriate use of additional staging adjuncts including arteriography, phlebography, skeletal and thoracic imaging is described in this article.

Carcinoma, Renal Cell↗
PubMed1989

Percutaneous dislodgement of an impacted cystic duct stone.

An obstructing cystic duct stone was dislodged with an angiographic catheter and guidewire via a percutaneous cholecystostomy tract in a mildly sedated patient. After brief stenting of the cystic duct, the patient remained asymptomatic with internal bile drainage. When endoscopic negotiation of the cystic duct is difficult, an impacted cystic duct stone can sometimes be dislodged with standard angiographic techniques.

Aged↗
PubMed1989

Angiomyolipoma arising in the renal sinus: a difficult radiologic diagnosis.

We report a case of angiomyolipoma (AML) occurring in the renal sinus evaluated by intravenous urography (IVU), renal ultrasound (US), angiography, and computed tomography (CT). Imaging features of this lesion are identical to AMLs elsewhere, but preoperative diagnosis was complicated by the unusual occurrence of the tumor in this location in a patient with abdominal pain. Accurate preoperative diagnosis will allow tumorectomy or conservative management.

Female↗