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PubMed1983

Trial of low doses of aspirin as prophylaxis in sickle cell disease.

The effects of low doses of aspirin on the frequency and severity of painful vaso-occlusive crises were evaluated in children with sickle hemoglobinopathies. Aspirin was compared with placebo in 49 patients in a double-blind crossover study. Careful monitoring of patients revealed an average of 1.1 painful crises per patient year. During the 21 months of study, 70% of patients had a maximum of two painful crises, and 25% experienced four or more. The frequency and severity of crises were not affected by aspirin therapy. In view of aspirin's demonstrated effect on platelet function, we suggest that platelets do not contribute to the initiation or progression of the vaso-occlusive process.

Adolescent↗
PubMed2001

Case-crossover studies of occupational trauma: methodological caveats.

OBJECTIVES: The case-crossover study design was developed to examine triggers for the onset of myocardial infarction. This paper seeks to examine selected methodological issues when applying the case-crossover method to the study of traumatic injuries in the work environment. METHODS: Researchers known to be working on occupational case-crossover studies were invited to present at a workshop held at the National Occupational Injury Research Symposium in October 2000. Data from ongoing studies were used to illustrate various methodological issues involved in case-crossover studies of occupational injury. KEY FINDINGS AND ISSUES IDENTIFIED: To utilize the case-crossover design, investigators must clearly define the time during which a worker is at risk of injury, the period of time during which a particular transient exposure could cause an injury and carefully select control time periods that estimate the expected frequency of exposure. Other issues of concern are changing work tasks over time, correlated exposures over time and information bias. CONCLUSIONS AND FUTURE RESEARCH NEEDS: More case-crossover studies of occupational injury are needed to compare results from multiple studies. The validation of the timing of transient exposures relative to injury onset, whether done in a laboratory or field setting, should be conducted. Nested case-crossover designs in other epidemiological studies (case-control or cohort) can examine both transient and fixed risk factors for occupational injury, and should be attempted.

Accident Prevention↗
PubMed2003

Gastric electrical stimulation for medically refractory gastroparesis.

BACKGROUND & AIMS: This study investigated the efficacy of gastric electrical stimulation for the treatment of symptomatic gastroparesis unresponsive to standard medical therapy. METHODS: Thirty-three patients with chronic gastroparesis (17 diabetic and 16 idiopathic) received continuous high-frequency/low-energy gastric electrical stimulation via electrodes in the muscle wall of the antrum connected to a neurostimulator in an abdominal wall pocket. After implantation, patients were randomized in a double-blind crossover design to stimulation ON or OFF for 1-month periods. The blind was then broken, and all patients were programmed to stimulation ON and evaluated at 6 and 12 months. Outcome measures were vomiting frequency, preference for ON or OFF, upper gastrointestinal tract symptoms, quality of life, gastric emptying, and adverse events. RESULTS: In the double-blind portion of the study, self-reported vomiting frequency was significantly reduced in the ON vs. OFF period (P < 0.05) and this symptomatic improvement was consistent with the significant patient preference (P < 0.05) for the ON vs. OFF period determined before breaking the blind. In the unblinded portion of the study, vomiting frequency decreased significantly (P < 0.05) at 6 and 12 months. Scores for symptom severity and quality of life significantly improved (P < 0.05) at 6 and 12 months, whereas gastric emptying was only modestly accelerated. Five patients had their gastric electrical stimulation system explanted or revised because of infection or other complications. CONCLUSIONS: High-frequency/low-energy gastric electrical stimulation significantly decreased vomiting frequency and gastrointestinal symptoms and improved quality of life in patients with severe gastroparesis.

Adult↗
PubMed1994

Effect of subcutaneous nicotine injections of EEG alpha frequency in non-smokers: a placebo-controlled pilot study.

The effect of two subcutaneous injections of 0.6 mg nicotine, administered 40 min apart, was compared with placebo in four non-smoking subjects in a counter-balanced double-blind crossover design. The nicotine injections produced mean peak plasma nicotine concentrations of 5.3 ng/ml 10 min after the first injection and 8.5 ng/ml 10 min after the second injection. The nicotine injections produced an increase in mean dominant alpha frequency on the electroencephalogram (EEG) which was 2 Hz greater than the effect of placebo (P = 0.049) and also produced a heart-rate boost which was 8 beats per minute greater than that produced by placebo (P = 0.022). These effects on dominant alpha frequency and heart rate were most apparent in the 10 min following each nicotine injection. The increase in dominant alpha frequency found in non-smokers in this study was similar to that following nicotine inhalation in abstinent smokers in previous studies, and suggests that this is a primary effect of nicotine, rather than simply a reversal of withdrawal-induced EEG slowing.

Adult↗
PubMed1987

Double-blind study of vigabatrin in the treatment of drug-resistant epilepsy.

Thirty-one patients with severe drug-resistant epilepsy entered the study. Vigabatrin (2 to 3 g/d, stratified according to weight) and placebo were administered orally, as add-on therapy in random order under double-blind conditions, each for three months using a crossover design. Thirty patients completed both periods. Of these, ten patients (33%) showed a decrease in seizure frequency of 50% or more. In the 15 patients presenting with complex partial seizures, "temporal" electroencephalographic abnormalities, and relatively low seizure frequency, there was a significant reduction in seizure frequency during vigabatrin treatment. No significant treatment effect was found for the remaining 15 patients, who presented with mixed seizure types, multifocal electroencephalographic abnormalities, and high seizure frequencies. Tolerability to vigabatrin was good; the most frequently reported unwanted effect was drowsiness. Plasma concentrations of phenytoin showed a significant reduction during the vigabatrin period. The results demonstrate the efficacy and good tolerability of vigabatrin therapy in patients with severe complex partial epilepsy.

Adolescent↗
PubMed1984

Dihydroquinidine versus disopyramide: efficacy in patients with chronic stable ventricular ectopy.

Dihydroquinidine (DQ) is contained in substantial amounts in quinidine salts, but its direct antiarrhythmic action has not been studied. The efficacy of oral DQ (300 mg t. i. d.) compared to disopyramide (D) (200 mg t.i.d.) was thus investigated using a double-blind crossover placebo-controlled protocol in 12 patients, aged 13 to 67 years, with chronic stable high frequency premature ventricular beats (PVB), defined as greater than 100 PVB/h during 48-72-h control Holter monitoring. The protocol included three 72-h treatment periods: DQ, D, and placebo at random. On days 2 and 3 of each period a 24-h Holter recording was carried out; drug blood levels were determined at peak (days 2 and 3) and trough time (day 3). No significant difference in the mean PVB/h was found between control (735 +/- 400) and placebo periods (564 +/- 388), or between the two Holter recordings of each period. Compared to placebo both DQ (106 +/- 113, p less than 0.005) and D (240 +/- 263, p less than 0.05) reduced the mean PVB/h, but the decrease was significantly higher with DQ (78 versus 53%, p less than 0.02). Nine patients (75%) on DQ and 5 (42%) on D had a greater than 70% decrease in mean PVB/h; complex PVBs were abolished in 3 of 6 patients on both treatments. On day 3, DQ plasma levels were 1.31 +/- 0.44 (peak) and 0.92 +/- 0.45 (trough) mg/l; D plasma levels were 2.88 +/- 0.64 (peak) and 2.02 +/- 0.31 (trough) mg/l; no significant difference was found between day 2 and day 3 samples.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2004

The perception of two vocal qualities in a synthesized vocal utterance: ring and pressed voice.

Two vocal qualities, ring quality and pressed quality, were analyzed perceptually. Listeners were asked to rate (on a scale from 0 to 10) the "amount of ring" in one listening and the "amount of pressedness" in another listening. The stimulus was the synthesized utterance /ya-ya-ya-ya-ya/. In the continuum representation of ring, the skewing quotient and the cross section of the epilaryngeal tube area were systematically varied, independently and by a covariation rule. In the continuum representation of pressed, the flow amplitude and open quotient were similarly varied. Results indicated that the crossover point between ring and no ring occurred with an epilaryngeal area of around 1.0 cm2, and the crossover point between pressed and not pressed quality occurred at an open quotient of about 0.4. Fundamental frequency also had an effect on the perceptions, with a higher fundamental frequency receiving higher ratings of ring and pressed for otherwise the same parameters. Listeners demonstrated highly variable perceptions in both continua with poor intersubject, intrasubject, and intergroup reliability.

Adolescent↗
PubMed2002

Low heart rate variability is not caused by typical neuroleptics in schizophrenia patients.

Both elevated cardiovascular mortality and low cardio-vagal (parasympathetic) heart rate variability (HRV)--a risk factor for postmyocardial infarction--are reported in schizophrenia (SZ). Since a number of medications have strong effects of cardiac conductivity, we thought it important to examine if typical neuroleptic medications might also affect HRV. We examined cardiac vagal activity during both neuroleptic treatment and a drug-free condition in seven SZ patients who were participating in a pilot double-blind, crossover study of placebo and haloperidol treatment. Twenty-four-hour Holter electrocardiograms were analyzed for high frequency HRV, quantitated as the percent of successive normal interbeat intervals greater than 50 milliseconds (PNN50), which is a good index of parasympathetic cardiac modulation. The patients showed unchanged PNN50 (8.4+/-9.5 versus 8.3+/-10.5; t=.22, df=6, P=.5) between the haloperidol treatment and drug-free conditions. Despite the elapsed time, change in medication, and altered clinical state, the PNN50s were highly correlated (Spearman r=.98, P=.000). SAPS positive symptom scores declined with treatment from 12.8+/-6.5 to 8.5+/-3.5; paired t=3.26: df=6; P=.01. PNN50s were significantly associated with positive (r=-.86, df=6, P=.012) and negative symptom scores (r=-.87, df=6, P=.01). We found low cardiovagal modulation in medication-free SZ patients that was associated with core SZ symptoms and was unchanged by haloperidol and benztropine treatment. The reduced HRV in SZ patients at baseline may render them at greater cardiovascular risk than healthy subjects when treated with medications having strong cardiovascular effects.

Journal Article↗
PubMed1980

The effect of timolol vs placebo on angina pectoris.

The effect of timolol vs placebo on the frequency of anginal episodes, nitroglycerin consumption and exercise performance was investigated in a double-blind, randomized, crossover study in 23 patients with angina pectoris. The optimal dose of timolol (10-30 mg twice daily) for each patient was titrated by exercise studies. Compared with placebo, timolol decreased the weekly number of anginal attacks and the weekly number of nitroglycerin tablets consumed, reduced the resting heart rate, systolic and diastolic blood pressure, and product of systolic blood pressure times heart rate, decreased the heart rate, systolic and diastolic blood pressure, and product of systolic blood pressure times heart rate at the onset of angina pectoris or marked fatigue, prolonged exercise duration, and diminished electrocardiographic evidence of myocardial ischemia. Timolol is an excellent antianginal agent when prescribed twice daily, with the optimal dose titrated by exercise studies.

Angina Pectoris↗
PubMed1995

Modulation of cardiac autonomic control in humans by angiotensin II.

Angiotensin II (Ang II) exerts an inhibitory action on vagal activity in animals and may also facilitate sympathetic activity. The object of this study was to compare autonomic activity resulting from equivalent steady-state baroreflex activation during intravenous Ang II infusion with that resulting from a control infusion of phenylephrine. Eight healthy subjects aged 22 to 34 years were studied in a single-blind, randomized, prospective crossover study. Autonomic activity was determined by computer analysis of RR interval variability in the time and frequency domains. Despite equal experimental hypertension with Ang II and phenylephrine infusion, at peak infusion rates the mean RR interval was significantly shorter with Ang II (983 +/- 179 milliseconds; mean +/- SD) than with phenylephrine (1265 +/- 187 milliseconds, P < .01). The variability of RR intervals was not significantly different, but the variability (median interquartile difference) of RR interval successive differences was significantly lower with Ang II (66 milliseconds) than with phenylephrine (104 milliseconds, P < .02). Power spectral analysis revealed the power of the 0.25-Hz component in normalized units to be significantly smaller during Ang II infusion (20.5 +/- 12.7 U) than during phenylephrine (38.2 +/- 14.7 U, P < .05), whereas the power of the 0.1-Hz component was significantly greater during Ang II infusion (67.8 +/- 17.1 U) than phenylephrine (38.8 +/- 20.3 U, P < .05). Measures of vagal modulation of heart rate were significantly attenuated, and sympathetic modulation appeared to be increased during Ang II infusion compared with control phenylephrine infusions. These observations may underlie reports of increased vagal activity during angiotensin-converting enzyme inhibitor therapy.

Adult↗
PubMed1984

Verapamil in prophylactic therapy of migraine.

We conducted a double-blind, placebo-controlled crossover study of verapamil HCl in the prophylaxis of chronic migraine headaches. Verapamil significantly reduced both headache frequency and duration with few side effects. The drug may be useful for a segment of the migraine population refractory to other prophylactic agents or for those who cannot tolerate the side effects of other drugs.

Adult↗
PubMed2001

Randomized controlled trial of zonisamide for the treatment of refractory partial-onset seizures.

BACKGROUND: Zonisamide is a sulfonamide antiepilepsy drug with sodium and calcium channel-blocking actions. Experience in Japan and a previous European double-blind study have demonstrated its efficacy against partial-onset seizures. METHODS: A randomized, double-blind, placebo-controlled trial enrolling 203 patients was conducted at 20 United States sites to assess zonisamide efficacy and dose response as adjunctive therapy for refractory partial-onset seizures. Zonisamide dosages were elevated by 100 mg/d each week. The study design allowed parallel comparisons with placebo for three dosages and a final crossover to 400 mg/d of zonisamide for all patients. The primary efficacy comparison was change in seizure frequency from a 4-week placebo baseline to weeks 8 through 12 on blinded therapy. RESULTS: At 400 mg/d, zonisamide reduced the median frequency of all seizures by 40.5% from baseline, compared with a 9% reduction (p = 0.0009) with placebo treatment, and produced a > or =50% seizure reduction (responder rate) in 42% of patients. A dosage of 100 mg/d produced a 20.5% reduction in median seizure frequency (p = 0.038 compared with placebo) and a dosage of 200 mg/d produced a 24.7% reduction in median seizure frequency (p = 0.004 compared with placebo). Dropouts from adverse events (10%) did not differ from placebo (8.2%, NS). The only adverse event differing significantly from placebo was weight loss, though somnolence, anorexia, and ataxia were slightly more common with zonisamide treatment. Serum zonisamide concentrations rose with increasing dose. CONCLUSION: Zonisamide is effective and well tolerated as an adjunctive agent for refractory partial-onset seizures. The minimal effective dosage was 100 mg/d, but 400 mg/d was the most effective dosage.

Adolescent↗
PubMedDate not supplied

Comfortably engaging: which approach to alcohol screening should we use?

PURPOSE: We wanted to compare 2 screening instruments for problem drinking, the CAGE and a single question, assessing frequency of use, patient and clinician comfort, and patient engagement in change. METHODS: The study was a crossover, cluster-randomized clinical trial with 31 clinicians in Missouri and 13 in the American Academy of Family Physicians (AAFP) National Network for Family Practice and Primary Care Research; 2,800 patients provided data. The clinician was the unit of randomization. Clinicians decided whether to screen each patient; if they chose to screen, they used the screening approach assigned for that block of patients. The clinician and patient separately completed questionnaires immediately after the office visit to assess each one's comfort with screening (and any ensuing discussion) and the patient's engagement in change. RESULTS: Missouri clinicians screened more patients when assigned the single question (81%) than the CAGE (69%, P = .001 in weighted analysis). There was no difference among AAFP network clinicians (96% of patients screened with the CAGE, 97% with the single question). Eighty percent to 90% of clinicians and 70% of patients reported being comfortable with screening and the ensuing discussion, with no difference between approaches in either network. About one third of patients who were identified as problem drinkers reported thinking about or planning to change their drinking behavior, with no difference in engagement between screening approaches. CONCLUSIONS: Clinicians and patients reported similar comfort with the CAGE questions and the single-question screening tools for problem drinking, and the 2 instruments were equal in their ability to engage the patient. In Missouri, the single question was more likely to be used.

Adult↗
PubMed2003

Evaluation of betahistine for the prevention of seasickness: effect on vestibular function, psychomotor performance and efficacy at sea.

Betahistine was evaluated for the prevention of seasickness in a laboratory and sea study. The effect of 48 mg betahistine on the vestibulo-ocular reflex (VOR) and on psychomotor performance was evaluated in twelve young healthy subjects in a double-blind, placebo controlled, randomized, crossover design. The vestibulo-ocular reflex was evaluated by the Sinusoidal Harmonic Acceleration (SHA) test at frequencies of 0.01, 0.02, 0.04, 0.08 and 0.16 Hz. Psychomotor performance was assessed by both computerized and paper and pencil test batteries. No significant differences in VOR gain or phase were found between betahistine and placebo treatment for any of the frequencies tested. No significant differences were found between treatments for any of the psychomotor performance tests or other possible side effects. The effect of 48 mg betahistine on seasickness severity was evaluated in 83 subjects during a voyage in rough seas. Betahistine had a borderline non-statistically significant effect on the prevention of seasickness in comparison with placebo (p = 0.053), with no notable side effects. Although our results are insufficient to recommend betahistine as an anti-seasickness drug, further studies are required to determine its possible effectiveness in less provocative motion sickness situations.

Adult↗
PubMed1988

Variability and reproducibility in the measurement of tracheobronchial clearance in healthy subjects and patients with different obstructive lung diseases.

The purpose of this study was to establish the inter- and intra-subject/patient variability of tracheobronchial clearance, measured for 6 h, using a radioaerosol technique. Inter-subject variability was evaluated in five groups: 33 healthy non-smokers (NS); 19 asymptomatic smokers (S); 40 asthmatics (A); 27 chronic bronchitics (CB) and 12 bronchiectatics (B). Intra-subject variability was evaluated in 16 A and 27 CB who were studied twice. The inter-subject/patient coefficient of variation (CoV) of tracheobronchial clearance was 13% for NS and 28-39% for the remaining four groups. The intra-patient CoV was about half of the inter-patient CoV. Inter-subject CoV (for A and CB) appeared to be independent of initial tracheobronchial deposition of radioaerosol and frequency of cough. We were also able to estimate the approximate number of patients required for a crossover study in order to avoid statistical, type II errors when investigating the effect of a drug or of a therapeutic intervention on tracheobronchial clearance.

Adult↗
PubMed1973

Duplication-translocations of tryptophan operon genes in Escherichia coli.

Mutants of Escherichia coli were selected in which a single mutational event had both relieved the polar effect of an early trpE mutation on trpB and simultaneously released the expression of trpB from tryptophan repression. The frequency at which these mutations appeared was roughly equal to the frequency of point mutations. In each of these mutants, the mutation increased the function of trpB and also increased the activity of some, but not all, of the other four tryptophan operon genes. Genetic analysis showed that the mutations were not located within the trp operon since in each case the parental trp operon could be recovered from the mutants. Each mutant was shown to carry a duplication of a trp operon segment translocated to a new position near the trp operon. Polarity is relieved since the trpB duplication-translocation is not in the same operon as the trpE polar mutation. The duplicated and translocated segments are fused to operons not regulated by tryptophan, so trpB function is no longer subject to tryptophan repression. The properties of the mutants indicate that the length of the duplicated segment and the position to which it is translocated differ in each of the seven mutants studied. The duplications are unstable, but the segregation pattern observed is not consistent with a single crossover model for segregation. That such duplication-translocation events generate a variety of new genetic arrangements at a frequency comparable with point mutations suggests they may play an important role in evolution.

Chromosome Mapping↗
PubMed1997

Genetic stability of gene-targeted immunoglobulin loci. II. Influence of the cell line and the vector linearization site.

The site-specific integration of exogenous gene fragments by homologous recombination provides a convenient method for altering the immunoglobulin loci of B cells and specifically designing antibody molecules. To introduce a human isotype into the heavy chain locus of mouse hybridoma cells we compared the recombination frequencies of vectors that could be linearized either as integration or as replacement constructs in different cell lines. Integration as well as replacement recombination was observed, irrespective of the location of the site at which the vector was cleaved. Integration events involving the human IgG1 vectors were lost at high frequency due to secondary vector excision, so that all stable recombinations were found to be replacement events. Replacement recombination of an integration vector involves an illegitimate crossover at least at the 3' side and sometimes gives rise to deletion of the CH1 domain. However, a homologous event at the 3' side is more efficient than an illegitimate one, so that a homology that is distributed on both sides of the heterologous region promotes targeting at higher frequency than a contiguous sequence of the same total length. The position of the linearization site in the vector markedly influenced the targeting efficiency, but surprisingly, whether a double-strand break in the homology or in the heterology region more efficiently promoted integration was dependent on the cell line. In all cells, however, cleavage of the vector outside the homology region favoured stable replacements with a bias against CH1-truncated clones. We further show that the frequency of replacements induced by integration vectors is not correlated to the homology length and cannot be increased by irradiation of the cells. Our findings indicate that for targeting the IgH locus other mechanisms might be involved than at other loci.

Animals↗
PubMed1990

Side effects of methylphenidate in children with attention deficit hyperactivity disorder: a systemic, placebo-controlled evaluation.

The frequency and severity of 17 side effects presumably associated with stimulant medication were assessed during a rigorous, triple-blind, placebo-controlled, crossover evaluation of methylphenidate, 0.3 and 0.5 mg/kg twice a day, in 83 children with attention deficit hyperactivity disorder. Side effects were rated by parents and teachers at the end of each weekly drug condition. Three children (3.6%) had side effects that were sufficiently serious to warrant immediate discontinuation of medication. Parent ratings indicated that only the side effects of decreased appetite, insomnia, stomachaches, and headaches increased significantly in frequency and severity during the two active medication doses as compared with the placebo condition. Fewer than half of the children experienced these side effects and among those who did, ratings of mean severity remained in the mild range. Teacher ratings showed little change over drug conditions, except on ratings of staring, sadness, and anxiety, which declined with increasing dose of medication. Parent ratings indicated that only the side effects of decreased appetite, insomnia, stomachaches, and headaches increased significantly in frequency and severity during the two active medication doses as compared with the placebo condition. Fewer than half of the children experienced these side effects and among those who did, ratings of mean severity remained in the mild range. Teacher ratings showed little change over drug conditions, except on ratings of staring, sadness, and anxiety, which declined with increasing dose of medication. Surprisingly, a high frequency of these behavior side effects were reported during the placebo condition. Stimulant medication within this therapeutic range, therefore, results in few, generally mild side effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗