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Biomedical subjects

J V Johnson

Publications and source records attributed to J V Johnson.

At least 37 records · Page 2Linked to original sources
PubMed1995

The psychosocial work environment of physicians. The impact of demands and resources on job dissatisfaction and psychiatric distress in a longitudinal study of Johns Hopkins Medical School graduates.

This study examines the relationship between the psychosocial work environment and cross-sectional job dissatisfaction and prospective psychiatric distress in a cohort of Hopkins Medical School graduates in midcareer. An instrument was constructed consisting of five scales: psychological job demands, patient demands, work control, physician resources, and coworker support. The results of scale reliability and factor analysis are presented. Higher job demands were found to be associated with increases in job dissatisfaction and psychiatric distress and greater resources were associated with decreased levels of dissatisfaction and distress. In multiple-regression analysis, only work control and social support were found to be independently associated with dissatisfaction and distress. These results suggest that the presence of control and social support at work protects physicians from developing job dissatisfaction and psychiatric distress.

Adult↗
PubMed1994

Gas-phase ion-molecule reactions: a model for the determination of biologically reactive electrophilic contaminants in the environment.

A promising instrumental technique has been investigated to rapidly screen complex environmental samples for chemical contaminants having the propensity to covalently bond to biomacromolecules such as DNA. Radical molecular ions of pyridine, a model compound for nucleophilic bases of DNA, were mass-selected and allowed to react with electrophilic environmental contaminants in the collision cell of a triple quadrupole mass spectrometer. Analytes were introduced into the collision cell via a gas chromatographic column. Reactive chemicals are then characterized by scanning Q3 to identify associative reaction products. A good qualitative correlation was observed for the gas-phase reactivity of a series of electrophilic reagents with both their alkylating reactivity in solution (4-(4-nitrobenzyl)pyridine) and AMES test mutagenicity which had been previously published. Femtomole limits of detection for specific associative reaction products were demonstrated. Gas-phase reactions of ions of environmental contaminants (introduced into the source) with neutral pyridine (in the collision cell) were also investigated. Reactions of the radical molecular ion of the allyl reagents with neutral pyridine were similar to results from the mass-selected reaction of the pyridine radical molecular ion with neutral allylic reagents.

Alkylation↗
PubMed1994

Short-column gas chromatography/tandem mass spectrometry for the detection of underivatized anabolic steroids in urine.

Short-column (3.5 m) gas chromatography (GC)/tandem mass spectrometry (MS/MS) has been investigated for the detection of structurally related, underivatized anabolic steroids in urine. The approach described here demonstrates the ability to rapidly and qualitatively detect underivatized anabolic steroids in spiked urine matrices. In this approach, underivatized steroids are determined using a short-column GC separation, ionized by positive ion chemical ionization, and detected by selected reaction monitoring MS/MS. This approach permits positive identification of underivatized anabolic steroids based on retention time and the production of characteristic product ions. Preliminary detection limits studies in spiked urine samples showed quantitative results between 2 and 40 ng steroid per milliliter of uterine. The potential advantages of this approach compared to present screening methods based on conventional (30 m) GC/MS are its rapidity and selectivity. Reliable qualitative identification can be performed with a short-column GC/MS/MS analysis of less than 6 min with a reduction in sample preparation time due to the elimination of the derivatization step.

Anabolic Agents↗
PubMed1994

Efficacy and safety of single-dose systemic methotrexate in the treatment of ectopic pregnancy.

OBJECTIVE: To evaluate the safety and efficacy of single-dose systemic methotrexate (MTX) in the treatment of ectopic pregnancy (EP). DESIGN: A database was started and continued prospectively for 35 patients meeting criteria for MTX therapy from June 1991 to October 1993. Follow-up was performed retrospectively on all patients with EPs (n = 82) by evaluating hospital and clinic records and by contacting affiliated physicians and individual patients. SETTING: The University of Vermont Reproductive Endocrinology Service. INTERVENTIONS: Methotrexate 50 mg/m2 was administered IM; blood samples were collected on days 0, 4, and 7 of MTX therapy and weekly thereafter until hCG titers became < 4 mIU/mL. RESULTS: Thirty-five of 82 (42.7%) patients diagnosed with EP were treated with MTX. The mean hCG concentration on day of treatment was 1388.1 +/- 463.5 (+/- SE) mIU/mL, and mean time to complete resolution of hCG was 23.1 +/- 2.9 days. Thirty of 35 (85.7%) were successfully treated with a single dose of MTX. Five of 35 (14.3%) failed therapy and required laparoscopic surgery. Twelve of 35 (34.3%) experienced mild side effects that resolved spontaneously. Ten of 13 (76.9%) demonstrated tubal patency at follow-up hysterosalpingogram. Of the 15 patients seeking pregnancy, 3 of 15 (20.0%) conceived, resulting in 3 term deliveries and 2 spontaneous abortions. CONCLUSIONS: Our results support the use of single-dose systemic MTX for the treatment of unruptured EP in carefully selected patients.

Adolescent↗
PubMed1993

Benzoquinazoline inhibitors of thymidylate synthase: enzyme inhibitory activity and cytotoxicity of some sulfonamidobenzoylglutamate and related derivatives.

Several folate-like thymidylate synthase inhibitors are described in which the pteridine nucleus of the folic acid molecule is replaced by a benzoquinazoline moiety, which in turn is attached to the benzoylglutamate side chain by a sulfonamide link. The most potent compounds had Ki values as low as 2.5 nM against the human enzyme, were good substrates for the cellular reduced folate transport system and for folylpolyglutamate synthetase, and had IC50 values for growth inhibition of tumor cell lines as low as 70 nM.

Glutamates↗
PubMed1993

Benzoquinazoline inhibitors of thymidylate synthase: enzyme inhibitory activity and cytotoxicity of some 3-amino- and 3-methylbenzo[f]quinazolin-1(2H)-ones.

The synthesis and thymidylate synthase (TS) inhibitory activity of a series of simple benzo[f]-quinazolin-1(2H)-ones are described. Fully aromatic 3-amino compounds with compact lipophilic substituents in the 9-position were found to have I50 values as low as 20 nM on the isolated enzyme, and represent the first examples of potent, folate-based TS inhibitors that completely lack any structural feature corresponding to the (p-aminobenzoyl)glutamate moiety of the cofactor. A number of the compounds also showed moderate growth inhibitory activity against a human colon adenocarcinoma cell line (SW480), with IC50 values as low as 2 microM.

Adenocarcinoma↗
PubMed1993

Work activities and the onset of first-time low back pain among New York City fire fighters.

In a prospective study of first-time low back pain among New York City fire fighters, a total of 115 cases and 109 randomly selected controls were interviewed by telephone between December 1988 and July 1989 to examine the role of recent work activities in the onset of first-time low back pain. After adjusting for known risk factors and off-duty activities, statistically significant high-risk work activities included operating a charged hose inside a building (odds ratio (OR) = 3.26), climbing ladders (OR = 3.18), breaking windows (OR = 4.45), cutting structures (OR = 6.47), looking for hidden fires (OR = 4.32), and lifting objects > or = 18 kg (OR = 3.07). Low-risk activities included connecting hydrants to pumpers (OR = 0.36), pulling booster hose (OR = 0.19), and participating in drills (OR = 0.09) or physical training (OR = 0.16). When further adjusted for exposure to smoke (OR = 13.59), a surrogate for severity of alarms, the ORs associated with high-risk activities were no longer significant. This, however, does not diminish the role of activities in the onset of low back pain. Instead, it suggests an inseparable role for activities and environmental hazards. To examine this, the risk of low back pain was measured within five work zones sequential in time relative to location and distance from a structural fire. The risk gradually increased as the fire fighter moved away from the firehouse (OR = 0.10) and closer to the site of fire (OR = 3.91).

Case-Control Studies↗
PubMed1993

Management of maxillofacial infections: a review of 50 cases.

Maxillofacial infections often place the oral and maxillofacial surgeon in situations where timely decisions have to be made. These decisions can be life-saving. This study reviews 50 infections treated over a 3-year period. The results reveal rapid resolution of the infections by adhering to fundamental principles in their management: recognition of airway compromise, surgical intervention, and the administration of the appropriate antibiotic. A protocol for the management of maxillofacial infections is described.

Adolescent↗
PubMed1993

Rigid fixation of comminuted mandibular fractures.

Treatment of comminuted mandibular fractures has traditionally involved closed reduction with external fixation in an effort to avoid stripping periosteum from the bony segments. The purpose of this study was to evaluate retrospectively the success rate of rigid fixation used to treat 16 consecutive comminuted fractures of the mandible in 15 patients. The comminuted fractures were as follows: symphysis and body, 10; angle, 3; and ramus, 3. In 13 cases, AO stainless steel reconstruction plates were applied, with a minimum of three 2.7-mm tapped bone screws in each of the two stable segments. In most cases additional screws were placed into the comminuted fragments to stabilize them. In two patients, the mandibular ramus was comminuted (one case bilaterally), which made it impossible to place a large plate. These fractures were stabilized with multiple titanium miniplates (2.0 mm, tapped). All patients' fractures healed to a bony union without bone grafting. The mean maximum incisal opening at longest follow-up was 40 mm (range, 20 to 50 mm). All patients had a satisfactory facial form and none required further surgery for facial recontouring or malocclusion. Complications were observed in three patients. Two patients (13%) developed infections. Both infections were caused by loose hardware and responded to removal of the hardware and did not require any other treatment. One mandible refractured during manipulation after coronoidectomy to treat mandibular hypomobility, a sequellae of a gunshot wound that traversed both mandibular rami. This fracture healed after plate removal and a course of maxillomandibular fixation without bone grafting. This study suggests that rigid fixation of comminuted mandibular fractures is a viable treatment that satisfies the necessity for reestablishment of form and function with minimal morbidity.

Adult↗
PubMed1993

Plasma cyclic guanosine monophosphate in chronic heart failure: hemodynamic and neurohormonal correlations and response to nitrate therapy.

This study evaluated the relation between plasma cyclic guanosine monophosphate (cGMP) and hemodynamic and neurohormonal parameters in patients with chronic congestive heart failure and assessed the effect of organic nitrate on plasma cGMP levels. Plasma cGMP was fourfold higher in 18 patients with congestive heart failure compared with 15 control subjects (16.7 +/- 9.7 versus 4.0 +/- 1.0 pmol/ml; p < 0.0001) but did not correlate with plasma levels of catecholamines, renin, atrial natriuretic peptide, or with baseline hemodynamic values. The administration of a hemodynamically effective dose of oral isosorbide dinitrate (40 mg) resulted in a transient reduction in plasma cGMP from 16.7 +/- 9.7 pmol/ml at baseline to 13.0 +/- 6.6 pmol/ml at 1 hour (p < 0.05). This change was associated with small and statistically insignificant changes in neurohormonal values and had no relation to any of the hemodynamic changes. We concluded that (1) elevated plasma cGMP in congestive heart failure does not correlate with other neurohormonal or hemodynamic parameters and may be an independent parameter of heart failure, (2) in contrast to previously documented nitrate-mediated increases in intracellular cGMP, nitrate therapy results in a reduction in plasma cGMP, and (3) changes in plasma cGMP cannot serve as a surrogate measurement of changes in intracellular cGMP.

Administration, Oral↗
PubMed1993

Measuring work organization exposure over the life course with a job-exposure matrix.

In most epidemiologic studies of occupational stress, work exposure is measured at only one point in time. This article presents a methodology for measuring the intensity and duration of work organization exposure over a lifetime. A job-exposure matrix for work organization was developed from data on a random sample (N = 12,084) of the Swedish labor force. The matrix consisted of mean exposure estimates for work control, social support, psychological and physical job demands, and job hazards for 261 occupations. Several validations of the matrix were undertaken. The matrix scores were found to be significantly correlated with individual self-report scores, and a similar increase in chronic disease prevalence with decreasing work control was found for both the matrix and the individual scores. The matrix was applied to occupational history data to construct lifetime exposure profiles. Potential problems in using attribution systems for exposure assessment are discussed.

Adolescent↗
PubMed1992

Persistent hemodynamic improvement with short-term nitrate therapy in patients with chronic congestive heart failure already treated with captopril.

To evaluate the therapeutic potential of organic nitrates in patients with chronic congestive heart (CHF) failure already treated with angiotensin-converting enzyme (ACE) inhibitors, the temporal hemodynamic effects of oral isosorbide dinitrate, 40 to 120 mg administered every 6 hours to 11 nitrate responders who had been treated with captopril 89 +/- 32 mg/day, were studied. The administration of isosorbide dinitrate resulted in a significant decline in mean right atrial pressure, from 13 +/- 6 mm Hg at baseline (mean value of measurements performed every 2 hours for 24 hours with captopril therapy) to 9 +/- 4 mm Hg at 1 hour with persistent effect for most of the study period. Mean pulmonary artery pressure decreased from 38 +/- 7 mm Hg at baseline to 29 +/- 9 mm Hg at 1 hour, with effect persisting for 24 hours. Mean pulmonary artery wedge pressure also decreased from 24 +/- 6 to 15 +/- 7 mm Hg at 1 hour and remained significantly reduced for 20 hours. Systemic blood pressure demonstrated a transient decrease lasting 2 hours after initiation of therapy which was asymptomatic in all patients. The results of this study demonstrate a preserved vasodilatory effect of organic nitrates in patients already treated with ACE inhibitors. Nitrates mediated improvement in right and left ventricular filling pressures, and reduction of pulmonary hypertension demonstrates a rationale for the use of these therapeutic methods in combination and suggest the need for long-term evaluation of the effect of nitrate therapy in patients with chronic CHF already treated with ACE inhibitors.

Adult↗
PubMed1992

Optimization of short-column gas chromatography/electron ionization mass spectrometry conditions for the determination of underivatized anabolic steroids.

A gas chromatographic/mass spectrometric method based on the use of short capillary gas chromatograph columns (3-5 m) and electron ionization mass spectrometry has been optimized and evaluated for the determination of underivatized anabolic steroids. The short-column gas chromatographic/mass spectrometric method was shown to result in short analysis times and to require minimal sample preparation, but suffered from some loss in sensitivity and chromatographic resolution compared with conventional gas chromatographic/mass spectrometric techniques for derivatized steroids. Therefore, short-column gas chromatographic conditions were optimized to maximize the sample transfer efficiency (sensitivity) from the gas chromatograph into the ion source of the mass spectrometer, while maintaining chromatographic integrity and minimizing thermal decomposition. Mass spectrometric conditions were optimized to maximize ionization efficiency with respect to the intensity of the molecular ion and degree of fragmentation such that positive identification of each steroid could be made based on the resulting mass spectra. Under optimized conditions, we have shown that underivatized anabolic steroids spiked into urine samples can be determined at low-nanogram levels using short-column chromatography/full-scan electron ionization mass spectrometry.

Anabolic Agents↗
PubMed1992

A prospective, randomized trial comparing two different intrauterine insemination regimens in controlled ovarian hyperstimulation cycles.

OBJECTIVE: To compare a single periovulatory intrauterine insemination (IUI) with a regimen employing two IUIs, one before ovulation and one after ovulation, in patients undergoing controlled ovarian hyperstimulation with human menopausal gonadotropins (hMG) combined with human chorionic gonadotropin (hCG). DESIGN: A randomized, prospective trial. PARTICIPANTS: Thirty-one consecutive patients undergoing 49 cycles of controlled ovarian hyperstimulation/IUI were studied in a tertiary care setting. MAIN OUTCOME MEASURES: Ovulation was determined sonographically. The establishment of a clinical pregnancy was defined by either ultrasonographic verification of cardiac activity within an intrauterine fetus, or histologic confirmation of trophoblast in a surgical specimen. RESULTS: Clinical pregnancies developed in 2 of 23 cycles in the single insemination group, compared with 12 of the 23 cycles in the double insemination group. Cycle fecundity was significantly higher for group II (0.522) than for group I (0.087) patients (P = 0.003). CONCLUSION: In hMG/hCG cycles, two IUIs timed as described above are superior to one periovulatory insemination.

Cryopreservation↗
PubMed1992

Ethiodol oil contrast medium inhibits macrophage phagocytosis and adherence by altering membrane electronegativity and microviscosity.

OBJECTIVE: To examine the effect of Ethiodol oil-soluble contrast medium and Sinografin aqueous-soluble contrast medium on macrophage function. After the observation that Ethiodol alters macrophage phagocytosis and adherence, we sought to determine the mechanism of action by which oil-soluble contrast medium alters the macrophage membrane. DESIGN: The P388D1 cell line was used as a consistent source of macrophages for all experiments. The uptake of 3H-labeled candida albicans was determined in macrophages exposed to 1:100, 1:400, or 1:800 dilutions of Ethiodol, Sinografin (S.R. Squibb, Princeton, NJ) or untreated media. To evaluate the macrophage adherence, 51Cr-labeled macrophages were exposed to the same dilutions of the contrast media. Specific membrane properties, Fc receptor levels, electronegativity, and microviscosity were assessed by flow cytometry after exposure to 1:100 dilutions of Ethiodol or Sinografin. RESULTS: Macrophage phagocytosis was decreased upon exposure to 1:100 and 1:400 dilutions of Ethiodol contrast medium, whereas adherence was reduced at the 1:100 dilution of Ethiodol. There was no effect of any dilution of Sinografin. There was a reduction in membrane electronegativity and microviscosity, but not Fc receptor levels, after exposure to a 1:100 dilution of Ethiodol. CONCLUSIONS: This study establishes a decrease in macrophage phagocytosis and adherence after exposure to Ethiodol oil-soluble contrast medium. We established that this alteration in membrane function is caused by a reduction of membrane negative surface charge and microviscosity. This may suggest a mechanism of action for the therapeutic effect of oil-contrast hysterosalpingograms in women with unexplained infertility.

Animals↗