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Biomedical subjects

C Wilcox

Publications and source records attributed to C Wilcox.

At least 19 recordsLinked to original sources
PubMed1995

Diagnosis of renal artery stenosis: feasibility of combining MR angiography, MR renography, and gadopentetate-based measurements of glomerular filtration rate.

OBJECTIVE: Our aim was to evaluate the feasibility of combining in a single test (1) structural evaluation of renal arteries with MR angiography, (2) functional evaluation of global glomerular filtration rates calculated on the basis of plasma disappearance of gadopentetate dimeglumine, and (3) renographic analysis of individual kidneys based on the dynamic changes in signal intensity that occur after administration of gadopentetate dimeglumine. SUBJECTS AND METHODS: We used unenhanced MR angiography to measure patency of the renal arteries in 10 healthy volunteers and in 10 patients with renal artery stenosis. Calculations of global glomerular filtration rate were based on measurements of plasma disappearance of gadopentetate dimeglumine as shown by MR relaxometry. For renography with gadopentetate dimeglumine, we generated curves that showed changes in signal intensity in both kidneys over time; intrarenal kinetics were studied by measuring the time of arrival of gadopentetate dimeglumine in the cortex and outer medulla of the kidney. Conventional angiograms, measurements of global glomerular filtration rate based on plasma disappearance of 99mTc-DTPA, and 99mTc-DTPA renograms were used as reference standards. We compared the two different methods of determining global glomerular filtration rates by computing the correlation coefficient of the linear regression of rates derived from studies with gadopentetate dimeglumine versus rates derived from studies with 99mTc-DTPA. RESULTS: In all volunteers, renal arteries were well visualized, and global glomerular filtration rates based on plasma clearance of gadopentetate dimeglumine were normal. In nine of 10 patients, correlation was good between findings on MR angiograms and findings on conventional arteriograms. Finding were discordant in one patient because the patient moved during the MR angiography. For all six patients studied, correlation was good between measurements of global glomerular filtration rates based on plasma clearance of gadopentetate dimeglumine and those based on clearance of 99mTc-DTPA (r = 98%). CONCLUSION: Our results suggest the potential of magnetic resonance for a comprehensive approach for detection of renal artery stenosis. This novel approach provides structural evaluation of renal arteries with unenhanced MR angiography. MR renography is done and global glomerular filtration rates are determined by using MR relaxometry after injection of contrast material. Corticomedullary transit times can be determined on the basis of the dynamic changes in signal intensity that occur after administration of gadopentetate dimeglumine.

Adult↗
PubMed1994

Gas-phase infrared spectroscopy for determination of double bond configuration of monounsaturated compounds.

Gas-phase Fourier-transform infrared spectra allow unambiguous determination of the configuration of the double bonds of long-chain unsaturated compounds bearing RCH=CHR' type bonds. Although the infrared absorption at 970-967 cm-1 has been used previously for the identification of trans bonds, the absorption at 3028-3011 cm-1 is conventionally considered to be incapable of distinguishing cis and trans isomers. In this paper, we present a large number of gas-phase spectra of monounsaturated long-chain acetates which demonstrate that an absorption, highly characteristic for the cis configuration, occurs at 3013-3011 cm-1, while trans compounds fail to show any bands in this region. However, if a double bond is present at the C-2 or C-3 carbon atoms, this cis=CH stretch absorption shows a hypsochromic shift to 3029-3028 and 3018-3017 cm-1, respectively. Similarly, if a cis double bond is present at the penultimate carbon atom, this band appears at 3022-3021 cm-1. All the spectra of trans alkenyl acetates showed the expected C-H wag absorption at 968-964 cm-1. In addition, the spectra of (E)-2-alkenyl acetates show a unique three-peak "finger-print" pattern which allows the identification of the position and configuration of this bond. Furthermore, by synthesizing and obtaining spectra of appropriate deuteriated compounds, we have proved that the 3013-3011 cm-1 band is representative of the C-H stretching vibration of cis compounds of RCH=CHR' type.

Alkenes↗
PubMed1994

A mock disaster.

Explore the source record for details and available documents.

Disaster Planning↗
PubMed1990

A study of radiologists viewing multiple computed tomography examinations using an eyetracking device.

Understanding the scan patterns radiologists use to view medical images is critical to the design of image viewing devices. In this study, an eyetracker, a device for recording eye and head movement, was used to determine the scan patterns during the interpretation of single and multiple computed tomographic (CT) examinations presented on a four-over-four viewbox. CT examinations were used because they represent complex viewing situations. In two separate studies, radiologists viewed patient folders containing single or multiple CT chest examinations and dictated a report. Eye movement was recorded with an eyetracker and video camera. After mounting the films in order, radiologists generally started with a sequential scan through the entire examination, followed by careful viewing of two to four clusters of three to six images, followed by dictation. These results indicate that a well designed radiology workstation should provide an image index, sufficient display area to simultaneously view 10 or more images, random and sequential movement through the examination, image comparison, and image marking.

Ergonomics↗
PubMed1987

Preparation and characterization of monoclonal antibodies against the fifth component of rabbit complement (C5).

By immunizing mice genetically deficient in C5 we were able to obtain a group of monoclonal antibodies to rabbit C5 that cross-react with C5 from a wide variety of mammalian sera, including mouse. The specificity of the monoclonal antibodies was against native C5 and C5b but not C5a. The antibodies strongly inhibit the expression of C5 hemolytic activity. We suggest that these monoclonal antibodies will be useful for studying C5 as well as providing a way to selectively deplete C5 from plasma in vitro or in vivo.

Animals↗
PubMed1987

Acylation of proteins with myristic acid occurs cotranslationally.

Several proteins of viral and cellular origin are acylated with myristic acid early during their biogenesis. To investigate the possibility that myristylation occurred cotranslationally, the BC3H1 muscle cell line, which contains a broad array of myristylated proteins, was pulse-labeled with [3H]myristic acid. Nascent polypeptide chains covalently associated with transfer RNA were isolated subsequently by ion-exchange chromatography. [3H]Myristate was attached to nascent chains through an amide linkage and was identified by thin-layer chromatography after its release from nascent chains by acid methanolysis. Inhibition of cellular protein synthesis with puromycin resulted in cessation of [3H]myristate-labeling of nascent chains, in agreement with the dependence of this modification on protein synthesis in vivo. These data represent a direct demonstration that myristylation of proteins is a cotranslational modification.

Acylation↗
PubMed1986

Regulation of myogenic differentiation by type beta transforming growth factor.

Type beta transforming growth factor (TGF beta) has been shown to be both a positive and negative regulator of cellular proliferation and differentiation. The effects of TGF beta also are cell-type specific and appear to be modulated by other growth factors. In the present study, we examined the potential of TGF beta for control of myogenic differentiation. In mouse C-2 myoblasts, TGF beta inhibited fusion and prevented expression of the muscle-specific gene products, creatine kinase and acetylcholine receptor. Differentiation of the nonfusing muscle cell line, BC2Hl, was also inhibited by TGF beta in a dose-dependent manner (ID50 approximately 0.5 ng/ml). TGF beta was not mitogenic for either muscle cell line, indicating that its inhibitory effects do not require cell proliferation. Inhibition of differentiation required the continual presence of TGF beta in the culture media. Removal of TGF beta led to rapid appearance of muscle proteins, which indicates that intracellular signals generated by TGF beta are highly transient and require continuous occupancy of the TGF beta receptor. Northern blot hybridization analysis using a muscle creatine kinase cDNA probe indicated that TGF beta inhibited differentiation at the level of muscle-specific mRNA accumulation. These results provide the first demonstration that TGF beta is a potent regulator of myogenic differentiation and suggest that TGF beta may play an important role in the control of tissue-specific gene expression during development.

Animals↗
PubMed1985

A comparison of fluoxetine, imipramine, and placebo in patients with major depressive disorder.

The efficacy and safety of fluoxetine were compared with those of imipramine and of placebo in a 6-week randomized double-blind parallel study of patients with major depressive illness. Mean values for all efficacy measurements were improved over baseline with fluoxetine and imipramine treatment (p less than .001). More fluoxetine patients completed the study than did imipramine or placebo patients. Predominant adverse experiences reported by imipramine patients were dry mouth and dizziness/lightheadedness. Predominant adverse experiences reported by fluoxetine patients were drowsiness/sedation and excessive sweating. In a subsequent 48-week open-label study, the predominant adverse experience in the fluoxetine group was excessive sweating and in the imipramine group was still dry mouth. In this study, fluoxetine relieved the symptoms of major depressive illness effectively and significantly better than placebo and was better tolerated than imipramine.

Adult↗
PubMed1979

The pressor actions of noradrenaline, angiotensin II and saralasin in chronic autonomic failure treated with fludrocortisone.

1 Treatment of postural hypotension due to chronic autonomic failure with fludrocortisone increased the pressor sensitivity to intravenous noradrenaline. Fludrocortisone increased the blood pressure in the standing but not the lying position. These effects of fludrocortisone may be the result of increased sensitivity of vascular receptors to noradrenaline. 2 The pressor action of angiotensin II, to which patients were supersensitive, may have involved the stimulation of alpha-adrenoceptors since it was partially antagonised by phentolamine. 3 Saralasin had a marked, paradoxical, pressor effect. This may have been mediated by vascular alpha-adrenoceptors because log dose-response curves of saralasin-induced increases in systolic pressure were shifted to the right in a parallel fashion after phentolamine. 4 Fludrocortisone treatment increased the pressor sensitivity to intravenous saralasin but not to angiotensin-II.

Aged↗
PubMed1976

Susceptibility of "enterobacteria" to aminoglycoside antibiotics: comparisons with tetracyclines, polymyxins, chloramphenicol, and spectinomycin.

Strains of enterobacteria, including common, aerobic, pathogenic gram-negative bacilli, and enterococci were tested for susceptibility to 11 aminoglycoside antibiotics by a twofold agar-dilution method with an inocula replicator. For comparison, similar tests were done with seven tetracycline analogues, two polymyxins, chloramphenicol, and spectinomycin. Tobramycin compared favorably with the more active aminoglycosides, with some exceptions related to individual strains of species. The tetracyclines and chloramphenicol were generally less active than the more active aminoglycosides. The polymyxins were as active or more active against most species of gram-negative rods but were essentially inactive against Proteus, Providencia, and many strains of Enterobacter.

Acinetobacter↗
PubMed1976

Susceptibility of "enterobacteria" to penicillins, cephalosporins, lincomycins, erythromycin, and rifampin.

Agar dilution tests for susceptibility of gram-negative rods and enterococci were done with a number of penicillins, cephalosporins, lincomycin analogues, erythromycin, and rifampin. Many in the first three categories were investigational drugs. All were generally less active than aminoglycoside and tetracycline antibiotics against gram-negative rods and more active against enterococci. Cephalosporins as a group were more active than penicillins against Klebsiella pneumoniae and Escherichia coli and less active enterococci. Both groups were equally active against Enterobacter, Proteus, and Providencia but inactive against most strains of Serratia and all strains of Pseudomonas; however, ticarcillin, carbenicillin, and BL-1654 were active against most strains of Pseudomonas. Penicillins and cephalosporins were more active against Proteus mirabilis than against indole-positive Proteus. Lincomycins had little or no activity against gram-negative rods but were moderately active against enterococci. Erythromycin was more active than the lincomycins, but rifampin was much more active than either of these types of drug. Of the penicillins, ticarcillin, carbenicillin, and BL-P1654 were the most active against gram-negative rods, whereas BL-P1654, amoxicillin, and ampicillin were the most active against enterococci. The penicillinase-resistant penicillins, cyclacillin, and penicillin V were essentially inactive against gram-negative rods. Of the cephalosporins tested, cephanone and cefamandole were the most active against most gram-negative rods, whereas cephaloridine and cephacetrile were the most active against enterococci. The least active of the cephalosporins against most species were cephradine, cephalexin, and cephapirin, but cefoxitin was the least active against enterococci.

Acinetobacter↗