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Biomedical subjects

J R Hunter

Publications and source records attributed to J R Hunter.

At least 19 recordsLinked to original sources
PubMed2005

Temperature determination using Kalpha spectra from M -shell Ti ions.

The compact multipulse terawatt (COMET) laser facility at LLNL was used to irradiate Al-coated 2-50 microm Ti foils with approximately 10(19) W cm(-2) , 500 fs, 3-6 J laser pulses. Laser-plasma interactions on the front side of the target generate hot electrons with sufficient energy to excite inner-shell electrons in Ti, creating Kalpha emission which has been measured using a focusing spectrometer with spatial resolution aimed at the back surface of the targets. The spatial extent of the emission varies with target thickness. The high spectral resolution (lambda/Deltalambda approximately equal to 3800) is sufficient to measure broadening of the Kalpha emission feature due to the emergence of blueshifted satellites from ionized Ti in a heated region of the target. A self-consistent-field model is used to spectroscopically diagnose thermal electron temperatures up to 40 eV in the strongly coupled Ti plasmas.

Journal Article↗
PubMed2005

Plasma conditions for improved energy coupling into the gain region of the Ni-like Pd transient collisional x-ray laser.

We have directly probed the conditions in which the Ni-like Pd transient collisional x-ray laser is generated and propagates by measuring the near-field image and by utilizing picosecond resolution soft x-ray laser interferometry of the preformed Pd plasma gain medium. The electron density and gain region of the plasma have been determined experimentally and are found to be in good agreement with simulations. We observe a strong dependence of the laser pump-gain medium coupling on the laser pump parameters. The most efficient coupling occurs with the formation of lower density gradients in the preformed plasma and when the duration of the main heating pulse is comparable to the gain lifetime (approximately 10 ps for mid- Z Ni-like schemes). This increases the output intensity by more than an order of magnitude relative to the commonly utilized case where the same pumping energy is delivered within a shorter heating pulse duration (<3 ps) . In contrast, the higher intensity heating pulses are observed to be absorbed at higher electron densities and in regions where steep density gradients limit the effective length of the gain medium.

Journal Article↗
PubMed2005

Observation of a multiply ionized plasma with index of refraction greater than one.

We present clear experimental evidence showing that the contribution of bound electrons can dominate the index of refraction of laser-created plasmas at soft x-ray wavelengths. We report anomalous fringe shifts in soft x-ray laser interferograms of Al laser-created plasmas. The comparison of measured and simulated interferograms shows that this results from the dominant contribution of low charge ions to the index of refraction. This usually neglected bound electron contribution can affect the propagation of soft x-ray radiation in plasmas and the interferometric diagnostics of plasmas for many elements.

Journal Article↗
PubMed2002

Picosecond x-ray laser interferometry of dense plasmas.

We present the first results from picosecond interferometry of dense laser-produced plasmas using a soft x-ray laser. The picosecond duration and short wavelength of the 14.7 nm Ni-like Pd laser mitigates effects associated with motion blurring and refraction through millimeter-scale plasmas. This enables direct measurement of the electron-density profile to within 10 microm of the target surface. A series of high-quality two-dimensional (2D) density measurements provide unambiguous characterization of the time evolution in a fast-evolving plasma suitable for validation of existing 1D and 2D hydrodynamic codes.

Journal Article↗
PubMed1996

The novel protein kinase of the RR1 subunit of herpes simplex virus has autophosphorylation and transphosphorylation activity that differs in its ATP requirements for HSV-1 and HSV-2.

The large subunit of herpes simplex virus (HSV) ribonucleotide reductase (RR1) designated ICP6 and ICP10 for HSV-1 and HSV-2, respectively, has a novel protein kinase (PK) enzymatic activity. ICP10 is localized on the cell surface, a localization that depends on an intact transmembrane (TM) segment. We used immunocomplex PK assays to examine the PK activity of ICP10 in stably transfected eukaryotic cells. Activity was distinct from that of casein kinase II (CKII) in that it did not require monovalent ions and was not inhibited by zinc sulfate. PK activity was eliminated by deletion of the conserved PK catalytic motifs or of the TM segment and it was significantly impaired by mutation of the invariant Lys (Lys176). Loss of PK activity by Lys176 mutation resulted in the failure to bind ATP. A truncated ICP10 PK expressed in bacteria (pp29 1a1) retained auto- and transphosphorylating activity (for calmodulin) after purification to apparent homogeneity. PK activity was also absent in cells infected with a recombinant virus (ICP10 delta PK) deleted in the ICP10 PK catalytic motifs. In cells infected with HSV-1 or HSV-2, RR1 had auto- and transphosphorylating activity for the small subunit of HSV ribonucleotide reductase (RR2) and immunoglobulin G (IgG). Comparing the PK activity of ICP6 and ICP10 we found that ICP6 requires five-fold higher concentrations of [gamma-32P]ATP than ICP10 and both enzymes are Mn2+ dependent, which is also different from CKII that is primarily Mg2+-dependent. Similar results were obtained for various HSV strains and in different cell lines. The data are consistent with the conclusion that the RR1 PK activity is intrinsic.

Adenosine↗
PubMed1991

An observational study of isotretinoin recipients treated for acne in a health maintenance organization.

From September 1982 to June 1987, all members (N = 513) of the Group Health Cooperative of Puget Sound, Seattle, Wash, who were prescribed isotretinoin for acne were observed throughout the first 4- to 5-month course of therapy for effectiveness and adverse effects. The highest rates of use were among male subjects aged 15 to 24 years. Excluding 47 subjects whose prescriptions were stopped because of noncompliance or who left the care of Group Health Cooperative physicians, 39 (8.4%) of the remaining 466 discontinued taking the drug because of the following adverse effects: mucous/skin/musculoskeletal effects (17); elevated triglyceride levels (eight); headaches (five); increased liver enzyme levels (three); amenorrhea (two); and other (four). One subject, excluded from the 466 because of noncompliance, became pregnant while using medication from a previous prescription and had a therapeutic abortion; she was not under the care of a physician at the time of pregnancy. Most subjects (97%) developed a mucocutaneous symptom, and 42% developed musculoskeletal symptoms. Moderate elevations in liver enzyme levels developed in six (1.8%) of 341 subjects with normal baseline values. Of 389 subjects with normal baseline triglyceride values (less than 2.25 mmol/L), nine (2.3%) developed moderate elevations (4.5 to 9.0 mmol/L), and one (0.3%) developed a severe elevation (greater than or equal to 9.0 mmol/L). Of 24 subjects with elevated baseline triglyceride levels, three (12.5%) developed moderate elevations. Of an additional 53 subjects whose baseline serum triglyceride levels were not determined, two developed elevations during therapy, one up to 13.4 mmol/L. Subjects who were overweight or had elevated baseline serum triglyceride values had an increased risk of developing elevations in triglyceride levels during therapy (odds ratio, 6.0; 95% confidence interval, 1.6 to 22.0; and odds ratio, 4.35; 95% confidence interval, 0.9 to 20.2, respectively). Acne was improved for at least 94.0% of subjects.

Acne Vulgaris↗
PubMed1990

The relationship of oral contraceptive use to rheumatoid arthritis.

Current use of oral contraceptives among 71 women aged 17 to 45 diagnosed for the first time as having definite or probable rheumatoid arthritis at Group Health Cooperative of Puget Sound was compared with oral contraceptive use among matched controls. Twenty-three percent of cases and 13% of controls were current users of oral contraceptives at the index date (relative risk estimate = 2.0, 95% CI = 0.97-4.21). We conclude that current oral contraceptive use was not protective against the development of rheumatoid arthritis in this population.

Adolescent↗
PubMed1989

Follow-up study of tolmetin users.

A follow-up study of 8370 outpatients who filled over 24,000 prescriptions for tolmetin revealed no hospital admissions for acute allergic, blood, skin, or central nervous system illness within 90 days of filling a prescription or refill for the drug. There were two cases of liver disease and two cases of nephrotic syndrome in which an etiologic relationship to tolmetin seemed unlikely but could not be entirely ruled out. In addition, 11 patients were hospitalized for peptic ulcer disease and its complications. In all but two patients other risk factors were present that could readily explain the illness. The rate of hospitalization for peptic ulcer disease and its complications among tolmetin recipients appears to be of the same magnitude as that in patients who take other nonsteroidal antiinflammatory drugs in this population, and close to that of the population at large.

Adult↗
PubMed1989

Hospitalizations for pulmonary reactions following nitrofurantoin use.

Acute pulmonary illness compatible with previously described nitrofurantoin toxicity and requiring hospitalization occurred three times among 16,101 first courses of therapy with nitrofurantoin. One case of fatal pulmonary fibrosis was ascribed to long-term use of nitrofurantoin among 742 observed recipients of ten or more prescriptions.

Acute Disease↗
PubMed1988

An assessment of a premedical program in terms of its ability to serve black Americans.

If special programs to increase the number of blacks gaining entry into health professional schools can identify whom they best serve, changes in either the selection process or the curriculum can increase their effectiveness. As one part of an evaluation of the effectiveness of the various components of the prehealth professions program at Xavier University of Louisiana (XU), black freshmen entering the university from 1981 to 1983 in the university's premedical program were tracked to determine who gained entry into medical and related mainline health professional schools upon graduation.The analyses indicate that high-ability black freshmen entering Xavier are more than twice as likely to gain admission into medical school than are their black counterparts nationally, and that this difference is statistically significant beyond the 99 percent level. Fifty-seven percent of high-ability black freshmen (those with American College Testing [ACT] composite scores of 24 or above, the top 2 percent of blacks nationally) who entered XU's biology or chemistry programs during the period under study gained entry into medical school upon graduation, whereas a study by the Educational Testing Service indicates that only 24 percent of similar blacks nationally gain entry into any graduate or professional school.The present study suggests that XU's premedical program serves those blacks who are not in the high-ability group (those whose ACT scores are below 24) at least as well (relative to the national average) as it does the top students. It therefore seems reasonable to assume that XU's premedical program is successful because it increases the probability that students gain admission into health professional schools rather than because of any preselection of students. These results are similar to those obtained from a comparable analysis of XU's prepharmacy program, the other component of prehealth at Xavier.

Black or African American↗
PubMed1987

The direct lateral approach to the hip for arthroplasty. Advantages and complications.

The direct lateral approach to the hip as described by Hardinge in 1982 was used in the performance of 83 hip arthroplasties. This approach was found to give excellent visualization of the proximal femur and acetabulum and was found to have comparable operative time, blood loss, time to ambulation, and range of motion to other approaches. The postoperative dislocation rate was very low (2.5%) and redislocations have not occurred. The incidence of heterotopic ossification was high (61%) and this may limit the use of this approach in some cases.

Adult↗
PubMed1987

Predictors of MCAT scores for black Americans.

If minority students likely to score low on the Medical College Admissions Test (MCAT) can be identified in advance, they can be advised to take existing preparatory programs, or programs can be developed to meet their needs. Correlation coefficients for a number of available independent variables with MCAT scores were determined for a population of premedical students at Xavier University of Louisiana. American College Testing (ACT) and Scholastic Aptitude Test (SAT) scores were found to have similar ability to predict MCAT scores, with a correlation coefficient of 0.64 between ACT composite and MCAT total scores. Correlations of sophomore year grade point average (GPA) with MCAT scores were only slightly weaker. Use of subtest scores for the ACT and SAT, grades in science courses, and Nelson-Denny Reading Test scores did not improve prediction to any real extent, either when used alone or in multiple linear regression analysis. In contrast to some previous studies, predictions for black men were as good as those for black women. Use of only ACT composite and sophomore year GPA together gave correlations only slightly weaker than predictions using a full range of variables; data from ACT composite and sophomore year GPA can be used for calculating predictive equations on many available micro-computers. These procedures may not be applicable to minority students at majority institutions.

Black or African American↗
PubMed1986

Accumulation of nifedipine after multiple doses.

The single and multiple dose pharmacokinetics of oral nifedipine capsules, 10 mg, have been examined in five patients with peripheral vasospasm. After a single dose, nifedipine was rapidly absorbed in three and slowly absorbed in two patients. Mean bioavailability parameters included a tmax of 2.9 h, a Cmax of 33.3 ng ml-1 and a AUC0-8 h of 113.3 ng h ml-1. After multiple dosing with either 10 or 20 mg every 8 h for 10 days the mean tmax at steady state was 2.1 h while the mean dose-corrected (to 10 mg) Cmax and AUC0-8 h were 51.9 ng ml-1 and 146.9 ng h ml-1, respectively. The mean elimination rate constant was 0.173 h-1 after both single and multiple doses. The mean extent of accumulation of nifedipine, defined as the ratio of AUC0-8 h (steady state)/AUC0-8 h (single dose), was 1.3; we concluded that nifedipine accumulates in the body when it is administered every 8 h. This should be taken into account when predicting steady state serum concentrations and haemodynamic effects of nifedipine from single dose kinetic data.

Adult↗
PubMed1985

First-trimester drug use and congenital disorders.

The authors determined the prevalence of certain major congenital disorders among live-born infants of 6509 mothers in a prepaid health plan for the 30-month period of January 1, 1980 through June 30, 1982 who used a wide variety of drugs during the first trimester of pregnancy. The results were similar to those obtained in this population in a prior 30-month study. No strong associations between any of the commonly used drugs and the congenital disorders studied were present.

Abnormalities, Drug-Induced↗
PubMed1985

Oral contraceptives and nonfatal vascular disease.

A follow-up study of more than 65,000 healthy women aged 15 to 44 was conducted to assess the association between oral contraceptive use and thromboembolism, stroke, or nonfatal myocardial infarction from 1980 through 1982 at Group Health Cooperative of Puget Sound. A positive association existed between current oral contraceptive use and venous thromboembolism (rate ratio equals 2.8), but there was no positive association between current oral contraceptive use and stroke or myocardial infarction.

Adolescent↗