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Biomedical subjects

R G Barr

Publications and source records attributed to R G Barr.

At least 19 recordsLinked to original sources
PubMed1998

Run-in periods in randomized trials: implications for the application of results in clinical practice.

Prerandomization run-in periods are being used to select or exclude patients in an increasing number of clinical trials, but the implications of run-in periods for interpreting the results of clinical trials and applying these results in clinical practice have not been systematically examined. We analyzed illustrative examples of reports of clinical trials in which run-in periods were used to exclude noncompliant subjects, placebo responders, or subjects who could not tolerate or did not respond to active drug. The Physicians' Health Study exemplifies the use of a prerandomization run-in period to exclude subjects who are nonadherent, while recent trials of tacrine for Alzheimer disease and carvedilol for congestive heart failure typify the use of run-in periods to exclude patients who do not tolerate or do not respond to the study drug. The reported results of these studies are valid. However, because the reported results apply to subgroups of patients who cannot be defined readily based on demographic or clinical characteristics, the applicability of the results in clinical practice is diluted. Compared with results that would have been observed without the run-in period, the reported results overestimate the benefits and underestimate the risks of treatment, underestimate the number needed to treat, and yield a smaller P value. The Cardiac Arrhythmia Suppression Trial exemplifies the use of an active-drug run-in period that enhances clinical applicability by selecting a group of study subjects who closely resembled patients undergoing active clinical management for this problem. Run-in periods can dilute or enhance the clinical applicability of the results of a clinical trial, depending on the patient group to whom the results will be applied. Reports of clinical trials using run-in periods should indicate how this aspect of their design affects the application of the results to clinical practice.

Clinical Protocols↗
PubMed1998

Crying in the first year of life: good news in the midst of distress.

Excessive crying and colic in the first 3 months of life remain as mysterious and unsolved clinical problems. The mystery is contributed to by the relative lack of long-term follow-up studies. The findings from four new follow-up studies of infants with prior colic are analyzed in an attempt to derive a clearer picture of what 'life after colic' might be like for parents, infants, and their interactions. The bad news is that, for a subgroup of infants and parents, especially those with substantial additional risk factors, early excessive crying may not resolve, but evolve into a more generalized 'persistent mother-infant distress' syndrome. For some mothers of infants with colic, the risk of depressive symptoms or decreased self-efficacy may be increased. However, there appears to be good news for a substantial majority of infants with colic and for their parents. This includes a significant reduction over time in the amount of crying, intact parental and infant capacities to be responsive in interactive contexts, no significant maternal stress, and normal attachment relationships.

Adult↗
PubMed1998

Colic and crying syndromes in infants.

Colic or excessive crying is one of the most frequent problems presented to pediatricians by new parents. Organic disease accounts for <5% of infants presenting with colic syndrome. Colic may be best viewed as a clinical manifestation of normal emotional development, in which an infant has diminished capacity to regulate crying duration.

Colic↗
PubMed1997

Nonadherence in tuberculosis treatment: predictors and consequences in New York City.

BACKGROUND: Poor adherence to antituberculosis treatment is the most important obstacle to tuberculosis control. PURPOSE: To identify and analyze predictors and consequences of nonadherence to antituberculosis treatment. PATIENTS AND METHODS: Retrospective study of a citywide cohort of 184 patients with tuberculosis in New York City, newly diagnosed by culture in April 1991-before the strengthening of its control program-and followed up through 1994. Follow-up information was collected through the New York City tuberculosis registry. Nonadherence was defined as treatment default for at least 2 months. RESULTS: Eighty-eight of the 184 (48%) patients were nonadherent. Greater nonadherence was noted among blacks (unadjusted relative risk [RR] 3.0, 95% confidence interval [CI] 1.1 to 8.6, compared with whites), injection drug users (RR 1.5, 95% CI 1.1 to 2.0), homeless (RR 1.4, 95% CI 1.0 to 1.8), alcoholics (RR 1.4, 95% CI 1.0 to 1.9), and HIV-infected patients (RR 1.4, 95% CI 1.1 to 1.9); also, census-derived estimates of household income were lower among nonadherent patients (P = 0.018). In multivariate analysis, only injection drug use and homelessness predicted nonadherence, yet 46 (39%) of 117 patients who were neither homeless nor drug users were nonadherent. Nonadherent patients took longer to convert to negative culture (254 versus 64 days, P < 0.001), were more likely to acquire drug resistance (RR 5.6, 95% CI 0.7 to 44.2), required longer treatment regimens (560 versus 324 days, P < 0.0001), and were less likely to complete treatment (RR 0.5, 95% CI 0.4 to 0.7). There was no association between treatment adherence and all-cause mortality. CONCLUSIONS: In the absence of public health intervention, half the patients defaulted treatment for 2 months or longer. Although common among the homeless and injection drug users, the problem occurred frequently and unpredictably in other patients. Nonadherence may contribute to the spread of tuberculosis and the emergence of drug resistance, and may increase the cost of treatment. These data lend support to directly observed therapy in tuberculosis.

AIDS-Related Opportunistic Infections↗
PubMed1997

Differential response to intraoral sucrose, quinine and corn oil in crying human newborns.

Intraoral sucrose induces rapid and sustained calm in crying newborns and transiently increases mouthing and hand-mouth contact. To determine whether these effects are specific to sucrose and to explore which properties of orogustatory stimuli might contribute to this effect, 60 crying newborns were randomized to receive 250 ul of 24% sucrose solution, 0.25% quinine hydrochloride solution, or corn oil as well as water in a mixed parallel crossover design. Relative to water, sucrose persistently reduced crying, and transiently increased mouthing and hand-mouth contact as previously demonstrated. While quinine produces a "disgust" face in calm infants, in crying infants it transiently decreased crying and increased mouthing, but did not affect hand-mouth contact. Corn oil had no specific effect on crying, mouthing or hand-mouth contact. The results imply that crying newborns respond differentially to orogustatory stimuli, that taste "salience" rather than positive hedonic valence may account for initial crying reduction and increased mouthing, and that these behavioral effects are not induced by at least one lipid nutrient.

Behavior↗
PubMed1997

Acalculous gallbladder disease: US evaluation after slow-infusion cholecystokinin stimulation in symptomatic and asymptomatic adults.

PURPOSE: To evaluate the measurement with ultrasonography (US) of the gallbladder ejection fraction after slow-infusion cholecystokinin stimulation in patients with biliary symptoms and in individuals without symptoms. MATERIALS AND METHODS: Gallbladder volumes were calculated in 60 healthy volunteers after a 30-minute infusion of sincalide. The time to maximum response, the gallbladder ejection fraction, and the rate of initial contraction were obtained at US. A total of 100 symptomatic patients were evaluated with this technique. Reference standards included surgical outcome or results of clinical follow-up of at least 1 year. RESULTS: The average ejection fraction +/- 2 standard deviations was 80% +/- 30. A fraction greater than 60% was considered to be a normal response to cholecystokinin stimulation. There was no statistically significant sex difference. Slow infusion did not produce any side effects. A sensitivity of 75% and a specificity of 100% for determination of gallbladder ejection fraction at US were obtained in patients with surgical and histopathologic proof of disease. CONCLUSION: The slow-infusion method is reliable, safe, and reproducible in evaluating gallbladder contraction. The cholecystokinin-stimulated gallbladder ejection fraction test may be useful in determining which patients could benefit from surgery.

Adult↗
PubMed1997

Acoustic characteristics of naturally occurring cries of infants with "colic".

Although infantile colic has long been defined by a perceived excessive amount of crying, acoustic attributes of the cry sound may also contribute to perceptions that this early social behavior is excessive or problematic. From an original sample of 76 infants (38 infants referred to physicians for problematic crying, or "colic," and 38 pair-matched comparison infants), 48 infants who produced naturally occurring cry bouts both before and after an evening feeding were studied: 11 infants with Wessel's colic, 15 infants with non-Wessel's colic, and 22 comparison infants. Standard and vociferous cry segments were selected from up to 2 min of tape-recorded crying for spectrum analysis. Vociferous cry segments had a longer duration, a higher fundamental frequency, and a greater percentage of dysphonation than did standard segments. No differences between infant groups were found in cries before feeding. After feeding, infants who were problematic criers, independent of Wessel's criteria, showed a greater percentage of dysphonation in the vociferous cry segment than did comparison infants. This finding resulted from a decrease in dysphonation in the cries of comparison infants after feeding and an increase in those of infants with non-Wessel's colic. The dominant frequency also increased after feeding in the vociferous cries of infants with Wessel's colic, resulting in these infants having higher-pitched cries after feeding than infants in the other 2 groups. Results indicate that infants who are perceived to have problematic crying have objectively different acoustic features in their cry sounds that are particularly aversive, and that complaints about excessive crying cannot be accounted for simply on the basis of reporting bias in overly concerned or emotionally labile parents.

Birth Weight↗
PubMed1996

Crying patterns in preterm infants.

Healthy infants born at term cry most in the first three months of life, with a peak and increased crying in the evening during the second month. To determine whether the crying of preterm infants manifests similar features, the pattern of crying from 40 weeks gestational age through 24 weeks corrected age was described for 35 relatively healthy preterm infants born between 28 and 34 weeks gestational age. Despite their additional extra-uterine experience, they still cried significantly more after 40 weeks gestational age, with a peak and evening clustering at 6 weeks corrected age. The age of peak crying was not related to gestational age at birth, weight for gestational age, or a variety of perinatal and neurological indices. The results support the argument that the early-peak pattern is a robust maturational feature of early development and may be universal to human infancy.

Age Distribution↗
PubMed1995

Ethidium bromide binding to unstructured and structured 2' GMP.

For disordered 2' GMP and 5' GMP the ethidium cation (Etd) was found to form 1:1 and 2:1 Eth:nucleotide complex. For alkali metal solution self-structured 2'GMP and 5'GMP Etd was found to form 1:1 and 2:1 Etd: order nucleotide complex. The best computer fit was obtained for a structured nucleotide stoichiometry of Na4(2'GMP)8. Binding constants for the Etd:disordered 2'GMP complexes were determined to be (1.6 +/- 0.1) x 10(4)M(-1) and 6.3 +/- 0.5 M(-1) at O degrees C and (1.1 +/- 0.2) x 10(4) M(-1) and 18 +/- 11M(-1) for 5'GMP at 5 degrees C for the 1:1 and 1:2 complex, respectively. For the 1:1 and 1:2 2'GMP:Etd species the enthalpies were determined to be -19.8 +/- 1.0 kcal/mole and 0.1 +/- 0.3 kcal/mole, respectively, and the entropies were -53.3 +/- 6.6 eu and 3.9 +/- 1.6 eu, respectively. Binding constants for the Etd: structured 2'GMP complex, assuming a complex with stoichoimetry (Na+)4 (2'GMP)8 for the structured unit, were determined to be (1.9 +/- 0.1) x 10(4)M(-1) and 5.8 +/- 0.6) x 10(2)M(-1), respectively at 0 degrees C.

Ethidium↗
PubMed1995

Do high doses of stimulants impair flexible thinking in attention-deficit hyperactivity disorder?

OBJECTIVE: To test the hypothesis that high doses of methylphenidate (MPH) impair cognitive flexibility in attention-deficit hyperactivity disorder (ADHD). METHOD: A double-blind crossover design was used in an acute dosage trial to assess effects of three dosages (0.3, 0.6, and 0.9 mg/kg) of MPH on the performance of 17 ADHD children on five tasks designed to assess divergent thinking, perseveration, and ability to shift mental set. The tasks also assessed convergent thinking, problem solving, and speed and accuracy of processing. RESULTS: There was minimal evidence of deleterious effects on flexible thinking or other cognitive processes, either in the ADHD group as a whole or in any subgroup. The most common pattern indicated linear improvement across dosages. CONCLUSIONS: Under the acute dosage conditions used in this study, MPH doses up to 0.9 mg/kg had an increasingly positive effect on measures of mental flexibility and other cognitive processes. Rather than eliciting perseveration, MPH appeared to improve persistence. The generalized nature of the cognitive and motivational changes observed suggests that MPH acts on central, self-regulatory processes. Because effects of two or more daily doses can accumulate when MPH is prescribed in the clinical situation, clinical doses of more than 0.6 mg/kg were not recommended.

Attention Deficit Disorder with Hyperactivity↗
PubMed1995

"Sucrose analgesia" and diphtheria-tetanus-pertussis immunizations at 2 and 4 months.

In human newborns, small amounts of sucrose reduce crying with procedural pain by about 50%. To determine whether "sucrose analgesia" could be extended to painful procedures beyond the newborn period, 57 infants were randomly assigned to receive three 250-microliters doses of 50% sucrose solution (g/100 mL) or water before their diphtheria-tetanus-pertussis immunizations at 2 and 4 months of age. Crying during and after injection was measured separately to determine whether sucrose modified crying during the noxious stimulus, recovery from the stimulus, or both. Sucrose was effective in reducing crying only from 83 to 69%, and the reduction was limited to the postinjection period. We conclude that, although sucrose continues to have some effect beyond the newborn period, the effect is limited to recovery from the noxious stimulus, is clinically modest, and is probably smaller than in the newborn period.

Crying↗
PubMed1995

Supplementary carrying compared with advice to increase responsive parenting as interventions to prevent persistent infant crying.

OBJECTIVE: To compare two interventions (supplementary carrying, increased parental responsiveness) introduced from birth for their effectiveness in reducing the amounts of crying in general community infants at 2, 6, and 12 weeks age. DESIGN AND PARTICIPANTS: Mothers and infants in newborn wards of maternity hospitals were assigned to carrying intervention, responsiveness intervention, or control groups. Follow-up measures were used to confirm that the interventions were implemented and to determine their effects on infant crying. SETTING AND MEASUREMENTS: Diary measurements completed in the home were employed to measure the aspects of parental behavior targeted by the interventions. Audio recordings, diaries, and questionnaires assessed the amounts the infants cried and the impact of the crying on their mothers and the health services. Sample sizes at 6 weeks of age were 59 (carrying intervention), 57 (responsiveness intervention), and 94 infants (control group). RESULTS: The carrying intervention successfully increased the amounts the infants were carried, particularly while settled, to the target levels. The responsiveness intervention led to more limited increases in carrying and to a modest increase in feeding frequency, but did not affect measures of parental interactiveness and play. No differences in amounts of crying and fussing were found between the three groups of infants on any of the measures. Subsidiary analyses confirmed that the dependent variable (infant fuss/crying) and main independent variable (carrying while settled) were not significantly correlated. CONCLUSION: It is not, at present, possible to recommend either supplementary carrying or increased parental responsiveness as primary, preventative interventions to reduce infant crying.

Crying↗
PubMed1994

The effect of war on tuberculosis. Results of a tuberculin survey among displaced persons in El Salvador and a review of the literature.

SETTING: During wartime, civilian populations usually experience a drop in caloric intake, disruption of housing, and a diminution in availability of medical services. These disturbances might be expected to result in increased reactivation of tuberculosis, which may result in increased transmission. Such privations occurred in El Salvador during its 1980-92 civil war, particularly among the 20% of the population, or over 1 million people, who were displaced. OBJECTIVE: (1) To estimate the rate of transmission of tuberculosis among displaced Salvadorians prior to and during the war, and (2) to compare this result with experience in the literature. DESIGN: (1) A tuberculin survey was conducted in El Salvador in July 1992 among all residents aged 1-30 years in 12 communities of formerly displaced persons. (2) The English language literature on tuberculosis during wartime was reviewed. RESULTS: (1) Overall, 21.2% of the non-BCG vaccinated had significant tuberculin reactions, equivalent to an annual risk of infection of 2.3%. The trend in the annual risk of infection was upward over the latter 6 years of the war, stable over the first 6 years, and was downward prior to the war years. The estimated incidence of smear positive pulmonary tuberculosis was 125 per 100,000 or 3 times the reported rate for El Salvador. (2) A review of the literature showed consistent evidence for increased morbidity and mortality from tuberculosis during wartime. Increased transmission was suggested by those studies showing a rise in both incidence of tuberculous meningitis during war years and excess morbidity and mortality many years after a war. Two major population-based studies found no evidence of increased transmission based on the calculated annual risk of infection; however other studies examining younger or more severely affected populations, or following more prolonged wars, detected an apparent increase in the transmission of tuberculosis. CONCLUSIONS: Conditions of war are associated with a rapid increase in morbidity and mortality from tuberculosis, which appears to result in increased transmission among populations most severely affected by war. This increased transmission will result in increased morbidity and mortality for many years, underscoring the need for improved tuberculosis control in the post-war period in countries such as El Salvador that have been devastated by war.

Adolescent↗
PubMed1994

Structure sensitivity of amino proton exchange in 2'- and 5' - guanosine monophosphate dianions.

Proton NMR line broadening methods were used to determine the rates of amino proton exchange for disordered 2'- and 5' - GMP dianions in aqueous solutions containing tetramethylammonium (TMA+) cations. Replacing TMA+ with Na+ does not substantially alter the exchange rates, provided that H-bonded, Na(+)-directed tetramer structures are absent. Activation enthalpies (kcal/mol) and entropies (eu) for 2'-GMP are: delta H not equal to = 18.5 +/- 1.3, delta S not equal to = 9.6 +/- 4.2 for TMA+ salt at pH 8.10, and delta H not equal to = 14.7 +/- 2.6, delta S not equal to = -3.7 +/- 8.0 for the Na+ salt at pH 8.11. Extrapolated values of pseudo first-order rate constants at 25 degrees C are in the range of k = 1-10 sec-1. At suitable concentrations and temperatures, the Na+ salts of both 2'- and 5' - GMP formed stacked and unstacked tetramer units. Relative to the exchange kinetics observed for the disordered nucleotide, the exchange process in the tetramer units was catalyzed in half the amino protons and inhibited in the other half. The catalytic process (k > 10(3) sec-1) has been attributed to amino protons not involved in interbase H-bonding, where as the inhibited process (k < 10(-1) sec-1) was assigned to those protons which do form such bonds. The structure-catalyzed process in both the stacked and unstacked tetramers was manifested by a loss of NMR amino proton intensity due to weighted time-averaging with the resonance for bulk water. A bridging water molecule between an amino proton and a phosphate on an adjacent nucleotide in the tetramer unit may provide a mechanistic pathway for the structure-catalyzed process.

Guanosine Monophosphate↗
PubMed1994

Effects of intra-oral sucrose on crying, mouthing and hand-mouth contact in newborn and six-week-old infants.

To determine whether a single intra-oral administration of sucrose would calm infants and elicit mouthing and hand-mouth contact, crying newborn and six-week-old infants were given sucrose solution before one feed and sterile water before another in a cross-over trial. Six-week-old infants were also given sucrose and water after feeding. For the newborn infants, the calming effect was rapid, substantial and lasted for at least four minutes. Mouthing and hand-mouth contact increased, but for shorter durations. For the six-week-old infants, sucrose calmed for one minute only before feeding, but had no effects on mouthing or hand-mouth contact. The results imply that intra-oral sucrose has acute age-related effects on crying and suckling-feeding behaviour mediated by a pre-absorptive mechanism. Sucrose may tap a functional system for reducing distress related to feeding and/or regulation of infant state.

Administration, Oral↗