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Biomedical subjects

N J Johnson

Publications and source records attributed to N J Johnson.

At least 37 records · Page 2Linked to original sources
PubMed1996

The shape of the relationship between income and mortality in the United States. Evidence from the National Longitudinal Mortality Study.

A follow-up study based on a large national sample was used to examine differences in the well-established inverse gradient between income and mortality at different income levels. The study showed the income-mortality gradient to be much smaller at high income levels than at low to moderate income levels in the working age (25 to 64 years) and elderly (over 65 years) populations for men and women both before and after adjustment for other socioeconomic variables. In addition, a much larger gradient existed for working age women at extreme poverty levels than for those women at low to moderate income levels. The income-mortality gradient was much smaller in the elderly than in the working age population. The study also examined the ability of several different mathematic functions of income to delineate the relationship between income and mortality. The study suggested that the health benefits associated with increased income diminish as income increases.

Adult↗
PubMed1996

Economic evaluation of new treatments: haematopoietic growth factors.

The clinical benefits of new healthcare interventions usually receive considerable attention, but their impact on the economic aspects of care provision are not so well considered. Among the issues that different audiences will want to see addressed are: how clinical benefits translate into resource use savings in practice; the extent to which clinical trial outcomes can be said to be representative or normal practice and the value of the economic impact to purchasers and providers. In this review we consider these elements using the haematopoietic growth factors as an example.

Clinical Trials as Topic↗
PubMed1996

Validity of education information on the death certificate.

We compared education as recorded on the death certificate with education ascertained before death from a household survey of 10,423 persons age 25 years or more who died in 1989. There was a tendency for the decedent's education to be reported at a higher level on the death certificate than at baseline. Of those who were reported as high school graduates on the death certificate, 38% reported that they had less than a high school education at baseline. The bias was more pronounced in older than younger decedents.

Adult↗
PubMed1996

Salvage of infected ICDs: management without removal.

During the 7-year period from August 1986 to December 1993, 242 patients with malignant ventricular arrhythmias underwent 242 ICD implantations and 50 subcutaneous generator changes. Wound infections developed in 5 patients (1.7%): in 3 cases, after primary implantation (3/242 [1.2%]); and in 2 following a generator change (2/50 [4.0%]). This difference was not statistically significant. Infection developed at the generator pocket and became clinically manifest between 6 weeks and 40 months, postoperatively. Our treatment approach with the first patient consisted of simple debridement of the pocket and reimplantation of the existing generator. This led to recurrence, and the generator was safely explanted. In the remaining four patients, our approach has been that of local treatment, with wide debridement of the pocket, and placement of a closed irrigation system with continuous irrigation with a bacitracin, polymyxin, neomycin solution, and culture-specific antibiotic therapy. We have successfully controlled the infection and salvaged the generator with this approach in all four patients, who are all alive and well at a mean follow-up of 25.0 +/- 17.3 months with no recurrence. The good results obtained in these patients suggest that the concept of total explanation of the infected ICD should be reassessed.

Aged↗
PubMed1995

Factor analysis of spatiotemporal and ethological measures in the murine elevated plus-maze test of anxiety.

Recent research employing the elevated plus-maze to assess anxiety in rodents has incorporated a variety of behavioral elements in addition to the standard parameters of entries onto and time spent in the aversive open arms. In the present study, we have used a large database comprising the behavioral profiles of 90 undrugged mice to examine the relationship between the standard spatiotemporal measures and a range of specific behaviors related to the defensive repertoire of the mouse. A factor analysis applied to the standard measures revealed two factors related to anxiety and locomotor activity. The simple addition of center time (an infrequently recorded measure) to the analysis yielded a third factor, most probably related to decision making. A large-scale factor analysis applied to all measures further confirmed the existence of factors related to anxiety, locomotor activity, and decision making, and revealed three further factors thought to represent risk assessment, vertical activity, and exploratory behavior. Thus, the inclusion of ethological measures not only confirmed prior knowledge based on a very limited range of measures, but also demonstrated the existence of additional behavioral dimensions. The potential applications of this knowledge are discussed.

Animals↗
PubMed1995

Combined internal cardioverter-defibrillator implantation and myocardial revascularization for ischemic ventricular arrhythmias: optimal cost-effective strategy.

During the 7-year period from August 1986 to July 1993, 203 patients with malignant ventricular arrhythmias underwent 203 implantable cardioverter-defibrillator (ICD system) implantations at the University Hospitals of Cleveland. Sixty-four patients had significant coronary artery stenoses amenable to myocardial revascularization and thus, at the time of the operation for ICD placement, also underwent coronary artery bypass graft. A retrospective analysis of the course of these 64 patients was carried out to determine the effect of two different treatment strategies on the outcome and cost of therapy. Thirty-six patients (group 1) underwent concomitant implantation of the ICD leads, patches and generator at the time of myocardial revascularization; 28 patients (group 2) underwent a two-stage strategy of initial placement of the ICD leads and patches at the time of myocardial revascularization followed by postoperative electrophysiologic testing to determine the persistent need for generator implantation. Of this latter group, 16 patients still had inducible sustained ventricular tachycardia during postoperative electrophysiologic testing and underwent generator implantation; 12 patients did not receive an ICD generator. The overall 30-day mortality rate was 4.7%. Two patients died in group 1 for a mortality rate of 5.5% and one died in group 2 for a mortality rate of 3.6%. The mean(s.d.) length of stay was 22.8(9.6) days at a mean(s.d.) cost of $93,000(33,000) for group 1 and 24.5(9.6) days at a mean cost of $82,900(30,000) for group 2 (P = n.s.). The mean(s.d.) postoperative length of stay was 13.7(7.8) days for group 1 and 15.4(6.5) days for group 2 (P = n.s.). Other complications occurred in 23% of surviving patients in group 1 and 29% of surviving patients in group 2 (P = n.s.). Mean follow-up was 33 months for group 1 and 23 months for group 2. At the end of 2 years, 78% of patients in group 1 and 86% in group 2 were alive (P = n.s.).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Inconsistent response to rapid atrial rhythms in a DDD pacemaker with the fallback feature.

Dual chamber pacing may be problematic in patients with paroxysmal atrial arrhythmias. The fallback feature has been incorporated into some devices to avoid tracking of rapid atrial rhythms. A case is reported in which the initiation of fallback was inconsistent during paroxysms of atrial flutter. Evaluation of the ventricular output of an isolated device in response to various applied atrial rates revealed that fallback occurred consistently only when 2xTARP (ms) < or = URL (ms).

Aged↗
PubMed1995

Regular wide QRS complex tachycardia during atrial fibrillation in a patient with preexcitation syndrome: a case report.

We report an unusual case of a relatively regular wide QRS complex tachycardia alternating with periods of an irregular narrow QRS complex tachycardia during atrial fibrillation in a patient with Wolff-Parkinson-White syndrome. Both tachycardias resulted from atrial fibrillation, the wide QRS complex tachycardia being due to 2:1 AV conduction of a type I atrial fibrillation across a posteroseptal accessory AV connection.

Aged↗
PubMed1995

Cholecystokinin and anxiety: promises and pitfalls.

In the past 5 years, considerable interest has been expressed in the possible involvement of cholecystokinin (CCK) receptor mechanisms in anxiety disorders. Stemming from early clinical observations in the 1960s and electrophysiological findings some twenty years later, this interest now encompasses research on the behavioral effects of CCK receptor agonists and antagonists at both clinical and preclinical levels. The results to date have been encouraging enough to prompt a number of pharmaceutical companies to "fast track" the development of CCK receptor antagonists as antipanic agents. The present review critically assesses research findings in this area and concludes that the field is rife with inconsistency, the date are subject to a variety of methodological and interpretative pitfalls, and, unfortunately, the promise of therapeutic advance through CCK receptor antagonists may be illusory.

Animals↗
PubMed1994

Mortality in the uninsured compared with that in persons with public and private health insurance.

OBJECTIVE: To compare mortality in persons with employer-provided health insurance, Medicare, Medicaid, military health benefits, other private health insurance, and no health insurance, before and after adjustment for income and employment status. DESIGN: Cohort study using national survey data containing information on social, economic, and demographic factors and health insurance, with deaths identified through matching to the National Death Index resulting in a mortality follow-up period of 5 years. SETTING: Noninstitutionalized population of the United States. PARTICIPANTS: Approximately 150,000 respondents to national surveys conducted by the US Bureau of the Census (Current Population Surveys), aged 25 to 64 years. RESULTS: After adjustment for age and income, persons with Medicare and Medicaid had the highest mortality in comparison with those with employer-provided insurance, with relative risks generally greater than 2. With adjustment for age and income, persons without insurance had higher mortality than those with employer-provided insurance, with relative risks of 1.2 for white men and 1.5 for white women. These relationships held after adjustment for employment status, with the working uninsured showing mortality between 1.2 and 1.3 times higher than that of the working insured. Mortality was higher in those with lower incomes after adjustment for insurance status. Those with annual income of $10,000 or less per year had mortality about two times that of persons with incomes greater than $25,000 per year. CONCLUSION: Mortality was lowest in employed persons with employer-provided health insurance. The higher mortality in those with public insurance or with no insurance reflects an indeterminate mix of selection on existing health status and access to medical care.

Adult↗
PubMed1994

Mapping the conversion of atrial flutter to atrial fibrillation and atrial fibrillation to atrial flutter. Insights into mechanisms.

It is not generally believed that there is a relation between atrial flutter, thought to be due to a single reentrant circuit, and atrial fibrillation, thought to be due to simultaneously circulating multiple-reentrant wave fronts. However, there are many reasons to suggest that these rhythms are more closely related than previously thought. To test the hypothesis that the length of an area of functional block in the right atrial free wall is critical to the conversion of atrial flutter to atrial fibrillation and of atrial fibrillation to atrial flutter, we studied spontaneous and ATP-induced conversion of stable atrial flutter to sustained atrial fibrillation and spontaneous conversion of sustained atrial fibrillation to stable atrial flutter. We studied 13 episodes of the conversion of stable atrial flutter to sustained atrial fibrillation and sustained atrial fibrillation to stable atrial flutter in seven dogs with sterile pericarditis. Six episodes were spontaneous and seven were ATP related. All episodes were studied by using a multisite mapping system to record 190 unipolar electrograms (converted in the software to 95 bipolar electrograms) from the right atrial free wall along with ECG lead II. Atrial flutter induction was attempted by atrial stimulation (S1S2 or S1S2S3) or by rapid atrial pacing for > or = 20 beats from selected sites at selected rates. For both the spontaneous and the ATP-related episodes, stable atrial flutter was defined as any episode of > or = 5 minutes, and sustained atrial fibrillation was any episode of > or = 1 minute. During all the episodes of stable atrial flutter, a line of functional block with a mean length of 24 +/- 4 mm was localized on the right atrial free wall. When the previously stable line of functional block decreased to a mean of 16 +/- 3 mm (P < .05), either spontaneously or after ATP administration (40 mg i.v.), the new line of functional block was not long enough to maintain stable atrial flutter, and conversion to atrial fibrillation resulted. This shortened line of functional block continued to change and migrate over the right atrial free wall throughout sustained atrial fibrillation. These observations were similar for both spontaneous and ATP-induced conversions. When sustained atrial fibrillation evolved to stable atrial flutter, there was reformation of a long line of functional block, long enough (> or = prior length) to create a stable reentrant circuit, which then captured the right atrial free wall and subsequently both atria.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Triphosphate↗
PubMed1993

Mortality by Hispanic status in the United States.

OBJECTIVE: To compare all-cause and cause-specific mortality rates between Hispanic and non-Hispanic groups and estimate the effect of family income, place of birth, and place of residence on these rates. DESIGN: Cohort study using national survey data matched to the National Death Index, with a mortality follow-up period of 9 years. SETTING: The noninstitutionalized population of the United States. PARTICIPANTS: Approximately 700,000 respondents (aged 25 years or older), including 40,000 Hispanics, to national surveys conducted by the US Bureau of the Census (Current Population Surveys). OUTCOME MEASURES: All causes and underlying cause of death, coded from the death certificate, occurring between 1979 and 1987. RESULTS: Adjusting for age, Hispanics were shown to have lower mortality from all causes compared with non-Hispanics (standardized rate ratio [SRR], 0.74 for men, 0.82 for women), lower mortality from cancer (SRR, 0.69 for men, 0.61 for women), lower mortality from cardiovascular disease (SRR, 0.65 for men, 0.80 for women), higher mortality from diabetes (SRR, 1.86 for men, 2.38 for women), and higher mortality from homicide (SRR, 3.60 for men). After adjusting for differences in annual family income, the relative mortality ratios were even lower for Hispanics than non-Hispanics. CONCLUSIONS: These data describe, in a large national cohort study, a lower mortality in Hispanics than in non-Hispanics. This mortality is particularly low after adjustment for differences in family income.

Adult↗
PubMed1992

Black-white mortality differences by family income.

Death rates among US black men and women under 75 years of age are higher than for their white counterparts. The explanation for this excess risk, though attributed to socioeconomic factors, remains unclear. We calculated mortality rates by family income for blacks and whites in a representative sample of the US population (National Longitudinal Mortality Study). For persons aged less than 65 years of age, mortality rates are lower in those with higher family income for both blacks and whites, and both men and women. However, at each level of income, blacks have higher mortality than whites. Higher levels of family income are also associated with lower death rates from cardiovascular disease, cancer, and deaths from causes other than cardiovascular disease or cancer. After adjustment for income, blacks have higher death rates from each of these three general causes. For subjects below 65 years, the mortality gradient by income is larger than the gradient by race. The differences in mortality rates by race not accounted for by income may be due to other differences such as access to health care, type or quality of medical care, or behavioral risk factors that disadvantage black populations.

Adult↗
PubMed1992

Strategies in the surgical treatment of malignant ventricular arrhythmias. An 8-year experience.

Introduction of the automatic implantable cardioverter defibrillator (AICD) has dramatically affected the surgical treatment of malignant ventricular tachyarrhythmias. The authors continue to perform electrophysiologically directed subendocardial resection (SER) of left ventricular (LV) scars in selected patients, and we revascularize (CABG) those patients undergoing AICD implantation who have significant myocardial ischemia. In an attempt to define the optimal role of each procedure, this report analyzes our 8-year experience with 348 consecutive patients treated surgically for these arrhythmias (SER since 1983 and AICD since 1986). All patients undergoing SER had organized ventricular tachycardia (VT) as a result of myocardial infarction, and most had LV aneurysms; of those undergoing AICD or AICD/CABG, 60% had VT, 15% had ventricular fibrillation, and 25% had both or were noninducible. The thirty-day mortality rate was 1.5% (3/197) for AICD, 5.4% (5/93) for AICD/CABG, and 8.6% (5/58) for SER; these mortality figures are not significant different. Late deaths in all groups were predominantly due to congestive heart failure, and actuarial survival as well as freedom from sudden death was similar between the groups at 4 years. Recurrent VT occurred in 167 of 282 (59%) of long-term survivors of AICD or AICD/CABG during follow-up and in nine of 53 (17%) of those with SER. Forty-eight per cent of survivors of AICD or AICD/CABG required antiarrhythmic medications, whereas only 11% of those with SER required antiarrhythmics. Long-term survival in each group is much higher than that reported for comparable patients with severe LV dysfunction treated medically. In those patients with organized VT and LV aneurysm who are judged able to survive the procedure, SER offers a high likelihood of cure rather than simple prevention of sudden death.

Actuarial Analysis↗
PubMed1992

Validity of demographic characteristics on the death certificate.

In a sample of the United States population from the Census Bureau's current Population Surveys, we compared demographic characteristics with those recorded on the death certificate for the 43,000 decedents in the samples followed from 1979 to 1985. Overall percentage agreements were: Sex 99.5, Race 99.4, Place of birth 99.4, Hispanic origin 98.7, and Veteran status 95.2. Relatively fewer American Indians and Asian/Pacific Islanders had death certificates that agreed with the baseline race (73.6% and 82.4%, respectively). The direction of disagreement suggests that current estimates of mortality rates for American Indians and Asian/Pacific Islanders are underestimated.

Bias↗
PubMed1992

The effect of combined therapy with ranitidine and pirenzepine in the treatment of reflux oesophagitis.

The combination of a histamine H2-receptor antagonist and a muscarinic receptor antagonist has been reported to result in greater suppression of intragastric acidity than either agent alone. The present randomized, double-blind, multicentre trial compared the effects of the oral combination of 150 mg ranitidine b.d. plus 50 mg pirenzepine b.d. with 150 mg ranitidine b.d. plus placebo pirenzepine b.d. in the treatment of patients with reflux oesophagitis. All 157 patients had symptoms of gastro-oesophageal reflux with endoscopically confirmed oesophageal erosions (Savary and Miller grades I-III). After four weeks of treatment, healing rates were 32/75 (43%) in the combined treatment group and 34/76 (45%) in the group receiving ranitidine alone. After eight weeks, the cumulative healing rates had increased to 48/72 (67%) and 51/75 (68%), respectively. More patients receiving ranitidine plus pirenzepine had complete relief of day- and night-time heartburn after four weeks compared with those receiving ranitidine alone (day: 59% vs. 38%, P = 0.02; night: 69% vs. 52%, P = 0.04). After eight weeks, symptom relief was comparable in both groups. Clinical adverse effects were reported by nine patients receiving ranitidine and by 19 patients receiving the combination. It is concluded that combining ranitidine with pirenzepine does not aid the healing of reflux oesophagitis but does improve symptom relief at four weeks.

Administration, Oral↗
PubMed1991

Biochemical modulation of 5-bromo-2'-deoxyuridine and 5-iodo-2'-deoxyuridine incorporation into DNA in VX2 tumor-bearing rabbits.

The thymidine analogues 5-bromo-2'-deoxyuridine (Brd-Urd) and 5-iodo-2'-deoxyuridine (IdUrd) compete with thymidine for incorporation into the DNA of replicating cells. This incorporation results in radiosensitizing effects which are directly related to the degree of analogue substitution. In vitro and in vivo evidence suggests that preadministration or coadministration of the thymidylate synthetase inhibitors fluorouracil and 5-fluoro-2'-deoxyuridine (FdUrd) can modulate analogue incorporation into DNA. We have evaluated in the rabbit VX2 tumor model the effects of thymidylate synthetase inhibitor (fluorouracil or FdUrd) coadministration (as 24-hour, intravenous infusions) on the incorporation of BrdUrd or IdUrd into the DNA of relevant normal tissues (bone marrow, gut mucosa) and intrahepatic VX2 tumor. Tissues were harvested and processed for gas chromatography-mass spectrometry analysis of the thymine, 5-bromouracil, and 5-iodouracil contents in hydrolyzed DNA. Coadministration of FdUrd resulted in statistically significant (P less than .01) enhancement of IdUrd incorporation into the DNA of intrahepatic VX2 tumor and normal (bone marrow and duodenal mucosa) rabbit tissues. Coadministered fluorouracil, on the other hand, significantly enhanced IdUrd incorporation only into DNA of intrahepatic VX2 tumor. Statistically significant enhancement of BrdUrd incorporation was achieved only with FdUrd coadministration and then only into the DNA of intrahepatic VX2 tumor. The percent of thymine replaced by analogue (I) is related to the steady-state arterial plasma drug concentration (C) by the Michaelis-Menten equation: I = I(MAX.) C/(C50 + C). The primary effect of FdUrd coadministration on BrdUrd incorporation into VX2 tumor DNA was a reduction of the C50 parameter (plasma BrdUrd concentration eliciting I = I(MAX)/2) from 8.17 microM to 1.78 microM. On the other hand, the I(MAX) parameter (I as C approaches infinity) was only slightly affected (29.7% to 25.2%). Thus, the degree to which the modulator enhanced analogue incorporation varied inversely with the analogue's steady-state plasma concentration. These results, which describe potential tissue specificity of modulator efficacy and characterize the effects of thymidylate synthetase inhibitor modulation on thymidine analogue incorporation pharmacodynamics, should provide guidance as to dose scheduling of BrdUrd and IdUrd in clinical trials for improved tumor specificity of uptake.

Animals↗