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Biomedical subjects

D Washburn

Publications and source records attributed to D Washburn.

16 recordsLinked to original sources
PubMed2000

Topographic mapping of brain potentials in the newborn infant: the establishment of normal values and utility in assessing infants with neurological injury.

AIM: To demonstrate that quantitative EEG (qEEG) can be used as a non-invasive measure of brain injury by establishing normative data in term infants and contrasting it with other modalities of brain imaging. DESIGN: qEEG during quiet sleep was performed on 13 healthy full-term infants comprising a normal group and on 10 infants with neurological abnormalities identified on brain imaging studies (abnormal group) at 36-47 wk postconceptional age. Quantitative analysis was performed and topographic maps were produced for each patient. The EEG data from the normal group, after spectral analysis, yielded power data in the delta, theta, alpha, and beta frequency bands and coherence information, which then formed the normative database. qEEG from the infants in the abnormal group was then compared to this normative data. RESULTS: The normal group's mean absolute power in the delta, theta, alpha, and beta bands for all EEG leads combined were 278.48+/-83.83, 31.71+/-10.12, 29.20+/-2.04, and 35.76+/-11.35 uv2, respectively. The median frequency was 1.49+/-0.07, 5.45+/-3.46, 9.74+/-5.11, and 18.01+/-3.38 Hz, respectively. The qEEG was abnormal in all 10 study infants, while abnormalities were noted in the clinical EEG in 4 of 10, in the neuroultrasound in 5 of 10, in the CT in one of 6, and in the MRI in 2 of 2 tested. CONCLUSIONS: qEEG appears to be a useful non-invasive method for measuring brain injury as it correlates well with other modalities of brain imaging and, if corroborated by further study, may, in fact, be more sensitive in determining abnormalities in brain function.

Action Potentials↗
PubMed1999

Comparison of levels of human immunodeficiency virus type 1 RNA in plasma as measured by the NucliSens nucleic acid sequence-based amplification and Quantiplex branched-DNA assays.

This study compared levels of human immunodeficiency virus type 1 RNA in plasma as measured by the Quantiplex branched-DNA and NucliSens nucleic acid sequence-based amplification assays. RNA was detectable in 118 of 184 samples (64.13%) by the Quantiplex assay and in 171 of 184 samples (92.94%) by the NucliSens assay. Regression analysis indicated that a linear relationship existed between the two sets of values (P < 0.0001), although the Quantiplex and NucliSens values were significantly different (P < 0.001), with the NucliSens values being approximately 0.323 log higher. Spearman correlation analysis indicated that the overall changes in patient viral load patterns were highly correlative between the two assays: r = 0.912, P < 0.0001. The lower limits of sensitivity were determined to be approximately 100 copies/ml and 1,200 to 1,400 copies/ml for the NucliSens and Quantiplex assays, respectively.

DNA, Viral↗
PubMed1998

Educational outreach to mammography facility staff to assist with compliance with the Mammography Quality Standards Act in rural North Carolina.

RATIONALE AND OBJECTIVES: The purpose of this project was to develop and evaluate an educational program targeted at mammography facilities in rural areas of North Carolina that were having difficulty complying with the 1992 Mammography Quality Standards Act (MQSA). MATERIALS AND METHODS: Fourteen facilities deemed at risk for closure under MQSA were identified by state inspection personnel. Problems at the facilities were evaluated by a radiologist, a physicist-educator, and a radiation physicist through a written survey, review of phantom and clinical images, and a site visit. Individual advice and instruction were provided on-site by the physicist-educator, with written materials provided in follow-up. A repeat site visit was made 4-6 months after the initial visit. RESULTS: Of 51 problems identified at the 12 institutions that completed the program, 35 (69%) were corrected. All facilities that had failing phantom scores at the inspection prior to the intervention had passing scores at the inspection after the intervention. There was a statistically significant increase in the sum of the phantom scores for the facilities offered this intervention compared with those not offered it (P = .03). CONCLUSION: This educational program improved mammography quality at participating facilities.

Community-Institutional Relations↗
PubMed1997

Three-dimensional echocardiographic evaluation of aortic disorders with rotational multiplanar imaging: experimental and clinical studies.

Transesophageal echocardiography has become a highly valuable method to assess aortic disorders. With this method, however, aortic disease has been visualized only in two-dimensional views. Advances in computer technology have introduced three-dimensional (3D) echocardiography as a developing modality in cardiac imaging. Previous efforts to obtain 3D reconstructions of the aorta, by various techniques, had limited clinical applicability. In this study we attempted to explore the feasibility and potential of 3D reconstructions of the aorta employing a widely used multiplane transesophageal imaging technique in an experimental setting and in patients. In the in vitro study, we created 35 lesions in 28 pig aortic trees (15 aortic dissections, five saccular aneurysms, five coarctations, five atheromas, and five clots within dissections). Suspending these specimens in a water bath, sequential two-dimensional images were acquired over a 180-degree rotation with a commercially available multiplane transesophageal probe and ultrasound system with a 3D software package. Data processing (digital reformation, interpolation, and segmentation) and 3D display were accomplished on an off-line computer system. 3D reconstructions were achieved and displayed in wire-frame, surface-rendered, and volume-rendered images. These 3D reconstructions corresponded well with the actual anatomic specimens in delineating the various pathologic findings. In patient studies, we collected a total of 36 studies in both adults and children with a mean age of 44.5 years (range 1 month to 82 years). In addition to normal aortas (n = 13), the spectrum of abnormalities studied included six atheromatous lesions, four aortic dissections, 10 coarctations, one aneurysm with a thrombus, and one dilated aortic root. We were able to accomplish volume-rendered 3D images depicting the aortic lesions in their true form that could be viewed in many different perspectives in all patients. We conclude that 3D echocardiography is able to display the aorta and aortic disease in a realistic manner. Although this modality still has limitations, further improvements in computer and ultrasound technology would strengthen 3D echocardiography as a clinically viable diagnostic tool, in the evaluation of aortic disorders.

Adolescent↗
PubMed1997

Efficacy and feasibility of breast shielding during abdominal fluoroscopic examinations.

RATIONALE AND OBJECTIVES: The purpose was to measure radiation exposure to the breasts during abdominal fluoroscopic examinations and evaluate the efficacy of breast shielding with a leaded vest. MATERIALS AND METHODS: Sixty-six women underwent routine abdominal fluoroscopic examinations. During the examinations one breast was covered with a leaded shield. Radiation doses to both breasts were measured with a thermoluminescent dosimeter. The amount of radiation at the skin of the shielded breast was then compared with that at the skin of the nonshielded breast. RESULTS: Radiation exposure to the breasts varied substantially with the type of examination being performed and with the individual patient. The average radiation level at the skin of the unshielded breast was 119 mR (range, 0-6,320 mR), compared with 59.6 mR (range, 0-1,640 mR) at the shielded breast. The average reduction in radiation exposure was 50% with shielding. CONCLUSION: Although the average level of radiation exposure to the breast during abdominal fluoroscopic examinations is generally low, use of a leaded vest can further reduce radiation to the breast for different types of examinations.

Adolescent↗
PubMed1997

Diffraction enhanced x-ray imaging.

Diffraction enhanced imaging is a new x-ray radiographic imaging modality using monochromatic x-rays from a synchrotron which produces images of thick absorbing objects that are almost completely free of scatter. They show dramatically improved contrast over standard imaging applied to the same phantom. The contrast is based not only on attenuation but also the refraction and diffraction properties of the sample. This imaging method may improve image quality for medical applications, industrial radiography for non-destructive testing and x-ray computed tomography.

Biophysical Phenomena↗
PubMed1996

Mammographic phantom studies with synchrotron radiation.

PURPOSE: To explore the potential improvement in image contrast for breast imaging with use of monoenergetic photons. MATERIALS AND METHODS: The x-ray energy available from the National Synchrotron Light Source is from 5 to over 50 keV. A specific energy is selected with a tunable crystal monochromator. The object is scanned with a narrow beam of 80.0 x 0.5 mm. Mammography phantoms were imaged with plate and film as the imaging detectors. Phantom images were obtained at 16-24 keV and compared with images obtained with a conventional mammographic unit. RESULTS: Preliminary findings indicate improved image contrast of the monoenergetic images compared with that obtained from the conventional x-ray source, particularly at 18 keV and below. CONCLUSION: Pilot results are encouraging, and the authors presently continue to explore monoenergetic photon imaging with improved instrumentation, scatter rejection, and use of tissue samples.

Breast Neoplasms↗
PubMed1993

Human sepsis increases lymphocyte intracellular calcium.

OBJECTIVE: To determine whether free intracellular calcium is increased during human bacterial sepsis. DESIGN: Prospective controlled study of lymphocyte free intracellular calcium concentrations from patients with sepsis compared with critically ill nonseptic patients and healthy subjects. SETTING: A large multidisciplinary ICU of a university hospital. PATIENTS: Eleven patients with sepsis, six patients after cardiac surgery, six patients with head injury, and 22 healthy control subjects. INTERVENTIONS: Blood samples obtained for lymphocyte isolation and measurement of free intracellular calcium concentrations. MEASUREMENTS: Lymphocytes were isolated using Ficoll-paque centrifugation and free intracellular calcium concentrations were measured using the fluorescent dye fura-2. We also evaluated the effect of septic serum, endotoxin, tumor necrosis factor (TNF), and lysophosphatidylcholine on lymphocyte free intracellular calcium concentrations. MAIN RESULTS: Mean (+/- SEM) lymphocyte free intracellular calcium concentrations were significantly (p < .05) higher in the septic patients (176 +/- 12 nM) compared with cardiac surgical (112 +/- 9 nM), head-injured (110 +/- 11 nM), or healthy control patients (112 +/- 5 nM). Endotoxin (0.1 and 1.0 mg/mL) and TNF (10 and 100 ng/mL) did not alter lymphocyte free intracellular calcium values. Lysophosphatidylcholine (100 and 200 microM) significantly increased lymphocyte free intracellular calcium in a dose-dependent manner. Septic serum had no effect on resting lymphocyte free intracellular calcium concentrations but potentiated the free intracellular calcium response to lysophosphatidylcholine. CONCLUSIONS: Lymphocyte intracellular calcium homeostasis is altered during human sepsis. In addition, circulating factors present in septic serum are capable of altering cellular calcium handling.

Adolescent↗
PubMed1989

Circulating calcium modulates adrenaline induced cyclic adenosine monophosphate production.

Inotropic support of the failing myocardium may combine calcium with adrenaline in an attempt to augment the haemodynamic actions of each drug. We have previously shown, however, that calcium blunts adrenaline induced increases in blood pressure and cardiac output in animals and man. The mechanisms by which calcium may interfere with the haemodynamic actions of adrenaline are not well understood. Adrenaline is known to stimulate adenylate cyclase and increase levels of cellular cyclic adenosine monophosphate (cAMP), a crucial second messenger in cell regulation. We evaluated the effect of increased circulating calcium levels on adrenaline stimulated cAMP production in laboratory animals. Calcium infusion in rats nearly doubled the circulating ionised calcium concentration, from 1.27 (SEM 0.03) mM to 2.3(0.18) mM. Adrenaline infusion significantly increased plasma cAMP in saline infused control animals, from 26(6) pmol.ml-1 to 98(22) pmol.ml-1, whereas there was no increase in cAMP plasma levels in the calcium infused rats. The apparent inhibition of adenylate cyclase by calcium may participate in a negative feedback system which helps protect cells from harmful intracellular calcium overload.

Animals↗
PubMed1987

Teicoplanin and rifampicin singly and in combination in the treatment of experimental Staphylococcus epidermidis endocarditis in the rabbit model.

Teicoplanin and rifampicin were evaluated as single and combined agents in the treatment of endocarditis due to Staphylococcus epidermidis in the rabbit model. Rabbits were treated for ten days and the number of bacteria in vegetations determined. At the end of ten days the geometric mean number of bacteria in the vegetations were 5.53 X 10(8), 6.68 X 10(6). 1.10 X 10(4), 2.57 X 10(1) cfu/g of vegetation for control, teicoplanin, rifampicin, and teicoplanin plus rifampicin groups respectively. The MIC and MBC values of the S. epidermidis isolates were 0.78 mg/l for teicoplanin and less than or equal to 0.10 mg/l for rifampicin. In the rifampicin treated group three post-treatment isolates of S. epidermidis tested exhibited marked resistance to rifampicin with MIC and MBC values greater than or equal to 200 mg/l. Teicoplanin and rifampicin were both effective as single agents in the clearance of S. epidermidis from the bloodstream. Rifampicin was more effective than teicoplanin in the clearance of S. epidermidis from vegetations but teicoplanin in combination with rifampicin was more effective than either drug alone.

Animals↗
PubMed1983

The effect of acidosis and alkalosis on in vitro aldosterone production.

There are conflicting data concerning the effect of hydrogen ion concentration (H+) on aldosterone production in vivo. This study examines the effect of changes in H+ on in vitro aldosterone production in isolated adrenal capsular cells of rats. The pH was adjusted to 7.1 or 6.8 using lactic acid and to 7.7 using sodium hydroxide. Potassium and other ions in the incubation medium were maintained at nearly constant levels. There was a significant decrease in aldosterone production when the pH was lowered from 7.4 to 7.1 or to 6.8 and also when the pH was increased to 7.7. This decrease was highly significant when measured in absolute terms or relative to ACTH-stimulated control samples included in each assay. Acidosis and alkalosis both decrease rather than stimulate aldosterone production in vitro and indicate that the observed in vivo stimulation of aldosterone by acidosis most likely is mediated by other aldosterone stimuli. These data also confirm that a marked alkalosis decreases aldosterone production and supports further study of changes in a more physiologic range.

Adrenal Glands↗
PubMed1982

[Acquiring otoneurological results by computer. Evaluation after 2 years of experience].

Nearly all test performed in audiology and vestibulometry are based on quantitative paradigms and lead to results expressed in numerical form that are well suited for computer processing. Since 1980, the Oto-rhino-laryngology department of the Geneva University Hospital stores the complete patient record with all the results obtained in the otoneurological investigations (audiogram, impedance measurements, binaural tests, auditory-evoked potentials, electro-nystagmogram) on floppy disks using a PDP-11 micro-computer equipped with a low-speed printer and a Tektronix 4010 graphics terminal with an attached hard-copy unit. One of the main advantages of such a computer system is the gain in time for secretarial work such as patient record updating and archival. All test results are manually entered on a keyboard and the computer automatically produces reports with tables and graphs. The storage of patient files on floppy disks is fast, consumes little space and makes possible all types of statistical studies on the recorded clinical data. One should, however, be aware of the fact that the daily clinical use of even such a small computer system requires a solid technical infrastructure and lots of programming time. Nevertheless, the balance of our two years experience with this system is clearly positive and we foresee that the computer will become more and more an appreciated technical tool for several types of clinical work.

Electronystagmography↗
PubMed1979

Relapsing fever.

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Adult↗
PubMed1970

President's page.

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Education↗