PubMed Health⌕ Search

Biomedical subjects

J F Seely

Publications and source records attributed to J F Seely.

At least 19 recordsLinked to original sources
PubMed2006

Efficiency of a grazing-incidence off-plane grating in the soft-x-ray region.

Efficiency measurements of a grazing-incidence diffraction grating in the off-plane mount were performed using polarized synchrotron radiation. The grating had 5000 grooves/mm, an effective blaze angle of 14 degrees, and was gold coated. The efficiencies in the two polarization orientations (TM and TE) were measured in the 1.5-5.0 nm wavelength range and were compared with the efficiencies calculated using the PCGrate-SX code. The TM and TE efficiencies differ, offering the possibility of performing unique science studies of astrophysical, solar, and laboratory sources by exploiting the polarization sensitivity of the off-plane grating.

Journal Article↗
PubMed2005

Experimental benchmark for an improved simulation of absolute soft-x-ray emission from polystyrene targets irradiated with the Nike laser.

Absolutely calibrated, time-resolved spectral intensity measurements of soft-x-ray emission (hnu approximately 0.1-1.0 keV) from laser-irradiated polystyrene targets are compared to radiation-hydrodynamic simulations that include our new postprocessor, Virtual Spectro. This new capability allows a unified, detailed treatment of atomic physics and radiative transfer in nonlocal thermodynamic equilibrium conditions for simple spectra from low-Z materials as well as complex spectra from high-Z materials. The excellent agreement (within a factor of approximately 1.5) demonstrates the powerful predictive capability of the codes for the complex conditions in the ablating plasma. A comparison to data with high spectral resolution (E/deltaE approximately 1000) emphasizes the importance of including radiation coupling in the quantitative simulation of emission spectra.

Journal Article↗
PubMed2005

Flash x-ray observations of cavitation in cadaver thighs caused by high-velocity bullets.

BACKGROUND: The purpose of this study was to record flash x-ray images of cavitation in human cadaver thighs caused by the passage of high-velocity bullets. The images are an initial step for understanding the cavitation process in human tissue and for implementing a better definition of extensive tissue injury. METHODS: Bullets were fired through the mid-thighs of 13 cadaver legs. The bullets were of two calibers, 7.62-mm full metal jacket boat tail with strike velocities in the range of 794 m/s to 880 m/s (10 thighs) and 5.70 mm full metal jacket with velocities in the range of 973 m/s to 992 m/s (3 thighs). Short duration (35 ns) x-ray images were recorded at various selected times after the bullets passed near the femurs. This study was carried out at the Armed Forces Institute of Pathology under approved human subject protocols. RESULTS: The cavity sizes and shapes were observed for the two types of bullets and at a number of times during the expansion and collapse of the cavities. As the bullets passed through the thighs, narrow cavities behind the bullets were observed. At later times, large expanded cavities were observed that encompassed the entire mid-thigh region. The observed cavities are at variance with those which were reported previously in gelatin tissue simulants. CONCLUSION: Flash x-ray radiography is an effective technique for the observation of internal cavitation in cadaver thighs caused by high-velocity bullets. These observations suggest that gelatin is not a proven simulant for human cadaver tissue in the study of cavitation subsequent to high-velocity missile impact.

Cadaver↗
PubMed1998

Dual-energy bone densitometry using a single 100 ns x-ray pulse.

A pulsed, portable hard x-ray source has been developed for medical imaging and flash x-ray absorptiometry. The source is powered by a Marx generator that drives a field emission x-ray tube which produces a 30-300 keV x-ray pulse of 100 ns duration. The x-ray fluence has dual-energy properties. The x-ray energy is relatively high early in the pulse and lower later in the pulse. The feasibility of using a single x-ray pulse for precision bone densitometry was analyzed. A computer simulation model was developed for the x-ray source, the filtration that enhances the dual-energy distribution, the absorption of the energy distribution by bone mineral and soft tissue, and the dual-energy detection system. It is feasible to determine the bone mineral density (BMD) of axial sites such as the lumbar spine and proximal femur with 2% precision over an area that is 15-20 mm in size, depending on the bone mineral and soft tissue thicknesses. An algorithm for determining the absolute BMD, to an accuracy of 2%, using a Plexiglas/TiO2 calibration phantom is discussed. At a distance of 50 cm from the source, the patient exposure is 3.7 mR. The average absorbed bone and tissue doses are 0.6 and 4.3 mrem, respectively. Factors that facilitate diagnostic measurements in clinical settings are the short patient observation time and the portability of the x-ray source.

Absorptiometry, Photon↗
PubMed1997

The need for specialized training programs in palliative medicine.

Canada faces a significant and growing burden of terminal illness. There are major unresolved economic, ethical and social issues related to care at the end of life. Despite the international reputation for Canadian efforts in palliative care, the medical profession in Canada has largely failed to recognize the importance of the field, as evidenced by the lack of commitment on the part of most medical faculties at Canadian universities to developing academic strength in palliative medicine, the lack of content in the undergraduate curriculum and of postgraduate programs in palliative medicine, and the lack of support for research into end-of-life care. The authors propose a conjoint initiative by the Royal College of Physicians and Surgeons of Canada and the College of Family Physicians of Canada to develop specialized training programs in palliative medicine as a critical step in addressing this crisis.

Canada↗
PubMed1985

The spectrum of diseases associated with necrotizing glomerulonephritis and its prognosis.

Necrotizing glomerulonephritis (NGN) represents small-vessel vasculitis in the kidney. To assess the diseases associated with necrotizing glomerular changes and their prognosis we studied all 32 patients who had this histologic finding on kidney biopsy from 1969 to 1982 and compared them to those patients who had crescentic, diffuse, or focal and segmental glomerulonephritis without necrosis (n = 29). The diseases associated with NGN were systemic lupus erythematosus (n = 6/15), Henoch-Schönlein purpura (n = 3/4) Goodpasture's syndrome (n = 4/7), Wegener's granulomatosis (n = 6/6), polyarteritis (n = 4/5), infective endocarditis (n = 2/3), and idiopathic rapidly progressive glomerulonephritis (n = 7/21). Necrotizing glomerulonephritis occurred significantly more often in the vasculitides than in all the other disorders put together. The most difficult diagnosis problem occurred in patients with renal disease and pulmonary hemorrhage (n = 9), in three of whom diagnosis was uncertain even after autopsy (two autopsies done within one month and one within three months of presentation). A fourth patient had a linear staining for IgG along the glomerular basement membrane (GBM) on kidney biopsy but was subsequently diagnosed as having Wegener's granulomatosis. Comparison of patients with without NGN revealed no difference in outcome (death or dialysis) one year after biopsy (38% v 43%) or in serum creatinine levels one year later (4.6 v 4.8 mg/dL). The prognostic effect of NGN was not obscured by unequal distribution of other adverse prognostic factors in the two groups. The most important prognostic characteristics we identified for outcome were serum creatinine at biopsy (chi 2 = 24.0, P less than .0004) and the sum of activity and chronicity indexes on biopsy (chi 2 = 12.7, P = .0004). These variables were similarly distributed in patients with and without necrosis, mean serum creatinine levels at biopsy being 4.3 v 4.2 mg/dL and sum of indexes 7.8 v 8.0. Other factors such as clinical diagnosis and therapy were not important prognostically and therefore could not explain our results. We conclude that NGN in patients with active proliferative glomerulonephritis has multiple causes. Diagnostic difficulties occurred in those with anti-GBM-negative pulmonary hemorrhage. The appearances of small-vessel vasculitis in the kidney did not appear to have prognostic significance.

Adolescent↗
PubMed1985

Effects of vitamin D on renal handling of calcium, magnesium and phosphate in the hamster.

The effects of 1,25(OH)2D3 on the renal handling of calcium (Ca), magnesium (Mg), and phosphate (Pi) in the thyroparathyroidectomized (TPTX) hamster were studied in the presence of exogenous PTH. Clearance experiments were performed in the following groups: acutely TPTX animals (group 1), acute TPTX plus continuous infusion of PTH in low or high doses sufficient to (1) reduce or (2) abolish the hypocalcemic effect of TPTX (groups 2 and 3, respectively), and acute TPTX plus Ca (group 4) or Pi (group 5) infusion. Each group was subdivided into control and experimental subgroups. In all animals an initial control phase was followed by a second phase in which experimental animals received an infusion of 1,25(OH)2D3 (1 U prime + 0.5 U/hr) while control animals received only the ethanol vehicle. GFR and urine flow rate, were not altered significantly in any of the groups. PCa and PMg increased significantly in group 3 only. Group 2 showed an increase in FECa (5.2 +/- 1.4 to 13.2 +/ 2.2%, P less than 0.001) and FEMg (7.3 +/- 1.3 to 17.3 +/- 2.2%, P less than 0.001) in response to 1,25(OH)2D3. Group 3 showed a significant increase in FEMg only (2.2 +/- 0.4 to 5.5 +/- 1.0%, P less than 0.01). The changes in the control groups were not significant. The administration of 1,25(OH)2D3 reduced phosphate excretion only in the presence of PTH. The FEPi decreased from 11.9 +/- 2.1 to 3.6 +/- 0.9% (P less than 0.001) in group 2 and 29.2 +/- 4.0 to 16.5 +/- 2.5% (P less than 0.02) in group 3.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

The impact of renal transplantation on the course of hepatitis B liver disease.

To establish the impact of transplantation on the course of chronic hepatitis B liver disease we performed a prospective study of the clinical and pathological sequelae of hepatitis B disease in all 22 patients who had renal allografts that functioned for more than 1 year and who were hepatitis B surface antigen (HBsAg)-positive following transplantation. No patient converted to HBsAg-negative. During a mean follow-up of 83 months serial liver biopsies were performed in 20 patients and 1 liver biopsy was available in the remaining 2 patients. Eleven patients died of liver disease, 5 of whom died of hepatic failure, 3 with hepatoma, 2 of gastrointestinal hemorrhage, and 1 of ascites with pleuroperitoneal fistula. Aggressive liver disease was observed in the vast majority of patients: 12 ultimately developed cirrhosis, (mean follow-up 81 months), 6 chronic active hepatitis (mean follow-up 93 months), 3 chronic persistent hepatitis (mean follow-up 89 months), and in 1 patient the presence of HB virus in hepatocytes was the sole morphologic alteration (follow-up 42 months). There was a marked tendency to progression in that 82% of patients with virus only, reactive hepatitis, or chronic persistent hepatitis on initial biopsy subsequently developed chronic active hepatitis or cirrhosis. For comparison, 10 HBsAg-positive patients whose renal failure had been treated by hemodialysis were also studied over a comparable period. Four patients converted to the negative state. Biochemical evidence of persistent liver dysfunction occurred in only 1 patient and no patient has died from complications of liver disease. We conclude that in the immunosuppressed renal transplant patient HB infection often results in the development of cirrhosis, leading to death from hepatoma and hepatic failure. This course is worse than that in dialysis patients. Renal transplantation of HBsAg-positive patients with end-stage renal failure may be inadvisable.

Aspartate Aminotransferases↗
PubMed1985

Renal function following infusion of radiologic contrast material. A prospective controlled study.

In a prospective, controlled study undertaken to assess renal function following infusion of radiologic contrast material, serum creatinine level was determined before scan and for three days after scan in 193 patients undergoing computed tomographic (CT) brain scan with contrast enhancement (contrast medium volume, 60 to 350 mL) and in 233 controls undergoing CT scan without infusion. Renal failure developed in four patients who had infusion of contrast material and in three patients who had no infusion (greater than or equal to 50% increase in serum creatinine level and above normal). In the high-risk group (serum creatinine level greater than or equal to 1.5 mg/dL or diabetes mellitus), renal failure developed in none of the 19 patients infused and in two of 46 in the noninfused group. It was concluded that previous uncontrolled studies may have overestimated the risk of renal failure induced by contrast material.

Acute Kidney Injury↗
PubMed1984

Late development of purpura in a patient with glomerulonephritis.

A 20-year-old man with a 10-year history of glomerulonephritis presented with a purpuric rash on his legs. A renal biopsy specimen obtained when he was 11 years old had shown mesangial glomerulonephritis; staining 9 years later for IgA had negative results. A second renal biopsy, performed when the rash was present, revealed mesangial glomerulonephritis and mesangial deposits of IgA; biopsies of the involved skin showed leukocytoclastic vasculitis. In this case isolated glomerulonephritis appeared to change to a multisystem illness, with a different immunologic character, through one of several possible pathogenetic mechanisms.

Adult↗
PubMed1982

Subspecialty consultations in a teaching hospital.

A chart review of 60 consultations by the nephrology service of a teaching hospital was carried out to determine their diagnostic and therapeutic utility. General medicine residents on elective rotations in nephrology performed 72% of the consultations, only 26% being written by residents in the subspecialty. Consultants made an average of 2.2 diagnoses per patient, of which 57% confirmed the working diagnosis already in the medical record. They made an average of 3.0 recommendations for further investigation per patient, but referring physicians implemented only 58% of these. An average of 1.6 recommendations for therapy were made per patient, of which 64% were implemented. The apparent neglect of the consultant's advice for investigation and therapy suggests that the written consultation to some extent fails to convey information useful for the referring physician and the patient. Further study is needed to determine if this failure reflects inadequate training of house officers as consultants.

Hospitals, Teaching↗
PubMed1981

Effect of glucose on renal excretion of electrolytes in the rat.

Glucose ingestion or infusion increases calcium and magnesium excretion in the human. To assess the role of renal tubular glucose reabsorption and of the parathyroid glands in this phenomenon, we performed standard two-phase clearance experiments in fed, volume-expanded male Sprague-Dawley rats. When compared with a group of animals receiving only 0.9% NaCl (group I), animals infused with glucose (group II) excreted significantly more calcium at any given level of sodium excretion (delta FECa, 1.95 +/- 0.24 vs. 0.69 +/- 0.18, P < 0.001). Normoglycemic hyperinsulinemia (group III) did not reproduce this increase in calcium excretion. In the group given phloridzin during sustained hyperglycemia (group IV), calcium excretion was well below that of control animals at any given level of sodium excretion. The glycosuric-hyperglycemia group (group V) used to assess the effect of glycosuria seen in group IV responded with a striking calciuria (delta FECa, 3.31 +/- 0.43, P < 0.001, compared with group IV). TPTX animals responded to glucose in the same way as intact animals (delta FECa, 4.8 +/- 0.5 vs. 2.18 +/- 0.3 in TPTX saline controls, P < 0.001). Magnesium excretion in all groups followed the same pattern as calcium. We conclude that renal tubular glucose reabsorption is essential for glucose to augment calcium and magnesium excretion. The presence of the parathyroid glands was not required for this phenomenon to occur.

Animals↗