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Biomedical subjects

S L Bailey

Publications and source records attributed to S L Bailey.

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

Arousal and cardiorespiratory responses to hypoxia in Prader-Willi syndrome.

Ventilatory responses to peripheral chemoreceptor stimuli are absent in patients with Prader-Willi syndrome (PWS) during wakefulness. Because arousal from sleep after rapidly developing hypoxia may require intact peripheral chemoreceptor function, we hypothesized that blunted hypoxic arousal responses during sleep Stage 3/4 would be present in PWS. Thirteen patients with PWS (mean age, 23.4 +/- 3.7 +/- SEM yr; 46% male; body mass index [BMI], 28.9 +/- 1.6 kg/m2) and 11 matched control subjects (mean age 28.0 +/- 5.4 yr; 54% male; BMI, 28.8 +/- 3.1 kg/m2) were studied. An abrupt decrease in inspired O2 tension to 80 mm Hg was introduced until arousal occurred or for a maximum of 3 min. One of the 13 patients with PWS and seven of the 11 control subjects were aroused by the hypoxic challenge (p < 0.02). During hypoxia, heart rate increased by 9 +/- 2% in the PWS group versus 22 +/- 4% in the control group (p < 0.005). Respiratory rate did not change in the PWS group (4 +/- 2%; p = NS), but it increased by 13 +/- 2% in the control group (p < 0.02). We conclude that abnormal arousal and cardiorespiratory responses to hypoxia are frequent in PWS. We postulate that intact peripheral chemoreceptor function is an important component underlying arousal mechanisms to rapidly developing hypoxia during sleep.

Adult↗
PubMed1995

Pesticide residues in urine of adults living in the United States: reference range concentrations.

We measured 12 analytes in urine of 1000 adults living in the United States to establish reference range concentrations for pesticide residues. We frequently found six of these analytes: 2,5-dichlorophenol (in 98% of adults); 2,4-dichlorophenol (in 64%); 1-naphthol (in 86%); 2-naphthol (in 81%); 3,5,6- trichloro-2-pyridinol (in 82%); and pentachlorophenol (in 64%). The 95th percentile concentration (95th PC) for 2,5-dichlorophenol (indicative of p-dichlorobenzene exposure) was 790 micrograms/liter; concentrations ranged up to 8700 micrograms/liter. 2,4-Dichlorophenol concentrations ranged up to 450 micrograms/ liter, and the 95thPC was 64 micrograms/liter. 1-Naphthol and 2-naphthol (indicative of naphthalene exposure) had 95thPCs of 43 and 30 micrograms/liter, respectively; concentrations of 1-naphthol ranged up to 2500 micrograms/liter. Chlorpyrifos exposure was indicated by 3,5,6-tricholoro-2-pyridinol concentrations of 13 (95thPC) and 77 micrograms/liter (maximum observed). Pentachlorophenol had a 95thPC of 8.2 micrograms/liter. Other analytes measured included 4-nitrophenol (in 41%); 2,4,5-trichlorophenol (in 20%); 2,4,6-trichlorophenol (in 9.5%); 2,4-dichlorophenoxyacetic acid (in 12%); 2-isopropoxyphenol (in 6.8%); and 7-carbofuranphenol (in 1.5%). The 95thPCs of these analytes were < 6 micrograms/liter. p-Dichlorobenzene exposure is ubiquitous; naphthalene and chlorpyrifos are also major sources of pesticide exposure. Exposure to chlorpyrifos appears to be increasing. Although pentachlorophenol exposure is frequent, exposure appears to be decreasing. These reference range concentrations provide information about pesticide exposure and serve as a basis against which to compare concentrations in subjects who may have been exposed to pesticides.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1995

Possible etiologic agents for toxic oil syndrome: fatty acid esters of 3-(N-phenylamino)-1,2-propanediol.

The etiologic agent(s) that was responsible for the 1981 toxic oil syndrome [TOS] epidemic in Spain has not been identified. Liquid chromatography combined with atmospheric pressure ionization tandem mass spectrometry was used for the analysis of oils associated with TOS. Analyses focused on measuring 3-(N-phenylamino)-1,2-propanediol [PAP], the 3-oleyl ester of PAP [MEPAP], and the 1,2-di-oleyl ester of PAP [DEPAP]. DEPAP and MEPAP were found more frequently and at higher concentrations in TOS case-associated oils than in control oils with odds ratios of 13.7 (95% CI 5.0-38) and 21.9 (95% 6.1-78), respectively. Other fatty acid esters of PAP are also likely to be present in the TOS case-associated oils. More significantly, DEPAP and MEPAP were found in aniline-denatured rapeseed oil refined at ITH, the oil refining company with the clearest link to TOS cases, yet these PAP esters were not detected in unrefined aniline-denatured samples of rapeseed oil delivered to ITH. These results show that the esters of PAP were products of the ITH refining process and were not formed spontaneously during storage. PAP esters were not detected in samples of other aniline-denatured rapeseed oils that were refined elsewhere, and which were not associated with illness. These findings provide strong support for the hypothesis that one or more of the fatty acid esters of PAP were the etiologic agents for TOS.

Aniline Compounds↗
PubMed1995

Cardiovascular recovery from laboratory stress: biopsychosocial concomitants in older adults.

Although cardiovascular recovery may be important to long term cardiovascular health, its biopsychosocial correlates have received much less attention than the correlates of cardiovascular reactivity. Of the few studies that have examined recovery, fewer still have examined men and women over 60 yr of age. This study examined relationships of psychosocial factors (e.g. state anxiety, anger, avoidance coping, Type A behavior, etc.) with recovery in 186 older married men (n = 63) and women (n = 123) (mean age = 69.7 +/- 6.1 yr). Regressions were performed to explain recovery variability in systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) in response to emotional and cognitive tasks. In each analysis, we controlled for the effects of gender, type of task, reactivity to the task, and other important covariates. Individuals with slower recovery had higher scores on anxiety (for SBP, p < 0.03 and DBP, p < 0.01), higher scores on avoidance coping (for DBP and HR, p < 0.01), and lower scores on anger held in (for DBP, p < 0.01). Psychosocial factors may be important in explaining recovery in older adults.

Adaptation, Psychological↗
PubMed1995

Determination of pesticide metabolites in human urine using an isotope dilution technique and tandem mass spectrometry.

A method that measures 12 analytes in urine and reflects possible exposure to pesticides was developed. The sample preparation involves enzyme hydrolysis and solvent extraction through the use of laboratory robotics, followed by phase-transfer catalysis derivatization and silica cleanup. Samples are analyzed by capillary gas chromatography and tandem mass spectrometry using an isotope dilution technique with 13C-labeled internal standards. The limit of detection is 1 microgram/L (1 part per billion) for most analytes, and most analytes have a linear response up to 100 micrograms/L. The precision of the method is reflected in the variation observed in quality control materials over 33 months; the variation averaged 17% for these analytes. On the basis of the detectable analyte levels of unspiked urine samples collected from unexposed volunteers, this method can be used to measure the low levels necessary for establishing reference range values of the selected pesticides or metabolites.

Calibration↗
PubMed1995

Hypercapnic arousal responses in Prader-Willi syndrome.

STUDY OBJECTIVE: Prader-Willi syndrome (PWS) is characterized by a number of abnormalities of hypothalamic function, such as hyperphagia, short stature, temperature instability, hypogonadotropic hypogonadism, and neurosecretory growth hormone deficiency. Patients with PWS are reported to have sleep-disordered breathing and have blunted hypercapnic ventilatory responses secondary to abnormal peripheral chemoreceptor function. Thus, we hypothesized that hypercapnic arousal responses would be abnormal in PWS. DESIGN: Hypercapnic arousal responses were tested in ten nonobese children and adults with PWS, aged 17.7 +/- 2.5 (SEM) years, 70% female, and nine control subjects, aged 14.2 +/- 2.6 years, 67% female. Hypercapnic challenges were performed during stage 3/4 non-rapid eye movement sleep. RESULTS: The PWS subjects had a significantly higher arousal threshold to hypercapnia compared with the controls (53 +/- 1.0 vs 46 +/- 1.7 mm Hg; p < 0.01). The PWS subjects had significantly higher baseline end-tidal CO2 levels (42 +/- 0.8 vs 38 +/- 1.1 mm Hg; p < 0.01) and more central apneas greater than 15 s/h of sleep (1.5 +/- 0.3 vs 0.1 +/- 0.1; p < 0.01). CONCLUSIONS: Elevated hypercapnic arousal thresholds during sleep are found in PWS subjects; these may be a manifestation of abnormal peripheral chemoreceptor function and may further contribute to sleep-disordered breathing in PWS patients.

Adolescent↗
PubMed1995

Strength of the quadriceps femoris muscle and functional recovery after reconstruction of the anterior cruciate ligament. A prospective, randomized clinical trial of electrical stimulation.

Immediately after reconstruction of the anterior cruciate ligament, 110 patients were randomly assigned to treatment with high-intensity neuromuscular electrical stimulation (thirty-one patients), high-level volitional exercise (thirty-four patients), low-intensity neuromuscular electrical stimulation (twenty-five patients), or combined high and low-intensity neuromuscular electrical stimulation (twenty patients). All treatment was performed isometrically with the knee in 65 degrees of flexion. All of the patients participated in an intensive program of closed-kinetic-chain exercise. After four weeks of treatment, the strength of the quadriceps femoris muscle and the kinematics of the knee during stance phase were measured. Quadriceps strength averaged 70 per cent or more of the strength on the uninvolved side in the two groups that were treated with high-intensity electrical stimulation (either alone or combined with low-intensity electrical stimulation), 57 per cent in the group that was treated with high-level volitional exercise, and 51 per cent in the group that was treated with low-intensity electrical stimulation. The kinematics of the knee joint were directly and significantly (p < 0.05) correlated with the strength of the quadriceps. There was a clinically and statistically significant (p < 0.05) difference in the recovery of the quadriceps and the gait parameters according to the type of operation that had been performed: the patients who had had reconstruction of the anterior cruciate ligament with use of an autologous patellar-ligament graft did poorly compared with the other patients.

Adult↗
PubMed1994

Use of electrical stimulation to enhance recovery of quadriceps femoris muscle force production in patients following anterior cruciate ligament reconstruction.

BACKGROUND AND PURPOSE: Electrical stimulation has been shown to be effective in aiding the recovery of quadriceps femoris muscle force production after anterior cruciate ligament reconstruction. The actual dosage of stimulation (training intensity) has not been well described. The purpose of this investigation was to establish a dose-response curve for electrical stimulation regimens designed to improve quadriceps femoris muscle recovery in patients after anterior cruciate ligament reconstruction. SUBJECTS AND METHODS: We analyzed data from a subsample (n = 52) of patients receiving electrical stimulation (N = 110) who were involved in a large, multicenter randomized clinical trial investigating treatment strategies designed to enhance quadriceps femoris muscle recovery. Fifty-two subjects (40 male, 12 female), with an age range of 15 to 43 years (mean = 25, SD = 7), participated in 4 weeks of quadriceps femoris muscle training using either portable, battery-powered home stimulators or console stimulators designed for clinical use. Training intensities were monitored by logging the electrically elicited knee extension torque and expressing this torque as a percentage of the uninvolved quadriceps femoris muscles' maximal voluntary contraction force. After the 4 weeks of training, isometric muscle torque was assessed and a dose-response curve was generated. The relationship between training intensity and quadriceps femoris muscle torque was assessed with Pearson Product-Moment Correlation Coefficients. RESULTS: A significant, linear correlation was found between training intensity and quadriceps femoris muscle torque. Subjects training with console, clinical generators trained at higher intensities than those training with portable, battery-operated generators; such training resulted in higher quadriceps femoris muscle torque. CONCLUSION AND DISCUSSION: These results support the use of high-intensity electrical stimulation and do not support the use of low-intensity or battery-powered stimulators when the goal is recovery of quadriceps femoris muscle force production in the early phases of rehabilitation after anterior cruciate ligament surgery. [Snyder-Mackler L, Delitto A, Stralka SW, Bailey SL. Use of electrical stimulation to enhance recovery of quadriceps femoris muscle force production in patients following anterior cruciate ligament reconstruction.

Adolescent↗
PubMed1993

Evolution of pulmonary function during an acute exacerbation in hospitalized patients with cystic fibrosis.

Few objective criteria have been validated for serial clinical monitoring in patients with cystic fibrosis (CF) during pulmonary exacerbations. While pulmonary function tests (PFT) are often used to monitor clinical improvement, it is not known which test correlates most closely with clinical improvement. To answer this, we measured routine PFT in 58 patients with CF before, during, and at discharge after 2-3 week hospital admission in 71 episodes of pulmonary exacerbation. Patients with CF were discharged based on clinical, radiological, and laboratory criteria. In general, all PFTs improved at midadmission and improved further by discharge, at which time forced expiratory volume in 1 second (FEV1), forced expiratory flow between 25% and 75% of forced vital capacity (FEF25-75), vital capacity (VC), maximal voluntary ventilation (MVV), and oxygen saturation by pulse oximetry (SPO2) increased. The residual volume to total capacity ratio (RV/TLC) and the slope of phase 3 in the single breath N2 washout curve (SP3 N2) decreased. The change in SP3 N2 was significantly greater than in any other PFT (P < 0.01 vs. VC and FEV1; P < 0.02 vs. RV and P < 0.001 vs. SPO2). A calculated optimal cut-off value for SP3 N2 improvement was significantly more sensitive in identifying patient improvement at discharge than any other pulmonary function test (P = 0.005). We speculate that clinical improvement in patients with CF is closely linked to improved distribution of ventilation.

Acute Disease↗
PubMed1993

Contaminants in L-tryptophan associated with eosinophilia myalgia syndrome.

In late 1989, an epidemic of eosinophilia-myalgia syndrome (EMS) that resulted in several thousand cases of the syndrome and 36 deaths was recognized in the United States. Physicians in New Mexico linked the epidemic to the ingestion of L-tryptophan (LT). Results of studies indicated that one or more trace contaminants in LT were likely causes of the EMS epidemic. Investigators traced the LT that was taken by most patients with EMS to a single manufacturer, Showa Denko K.K. of Japan. We now report results of high performance liquid chromatographic analysis of LT samples from this manufacturer. Three sets of blind-coded samples were analyzed: the priority case lot set, which included 54 case-associated LT lots and 50 noncase-associated LT lots that were taken by case and control subjects who used only one brand of LT; the single lot case set, which included 73 case-associated LT lots and 25 noncase associated LT lots taken by case and control subjects who used only a single lot of LT; and the South Carolina tablet set, which included LT tablets taken by case subjects (n = 26) and by control subjects (n = 52). We statistically compared the concentration of each contaminant in case-associated, noncase-associated, and control samples of each sample set. The analyses showed that there were more than 60 minor contaminants in the LT from Showa Denko K.K., and that six of these contaminants were associated with EMS. The structures of three contaminants are known, but the identities of the other three contaminants are currently unknown.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacillus↗
PubMed1993

Dimensions of adolescent problem drinking.

Issues involved in defining and measuring adolescent problem drinking have occupied the attention of alcohol researchers since the mid-1970s. However, appropriate definitions and measures of problem drinking remain important and unanswered conceptual and research questions. The research reported in this study was designed to address these issues by identifying multiple dimensions of adolescent problem drinking and examining correlates of these dimensions using multivariate regression models. A longitudinal sample of 2,771 students who had tried alcohol was used in these analyses. The sample was followed over three waves of data collection, between 1985 and 1990, in middle and high schools located in a southeastern U.S. county. Data from the third wave were used to characterize problem-drinking behavior. Results of exploratory factor analyses supported the conclusion made by others that adolescent problem drinking is a multidimensional phenomenon. Three dimensions measuring (1) level or frequency of alcohol use, (2) problems related to drinking and (3) symptoms of dependency were identified and were only moderately intercorrelated. The independent measures used to model the three problem-drinking measures were the same for each model, and the significant predictors and proportions of variance explained by the predictors differed widely across models. Results of the regression models confirmed the uniqueness of the three measures and suggested that the potency of specific risk factors varies for different types of problem drinking. Prevention implications and recommendations for this area of research are discussed.

Adolescent↗
PubMed1992

Normal polysomnographic values for children and adolescents.

Although polysomnography is routinely performed to evaluate children and adolescents with sleep-disordered breathing, normal polysomnographic values for the pediatric age group have not yet been established. We therefore performed overnight polysomnography in 50 normal children and adolescents (mean age 9.7 +/- 4.6 SD yr, range 1.1 to 17.4 yr). Of the children 56% were male. Chest wall motion, ECG, oronasal airflow, end-tidal PCO2 (PETCO2), arterial oxygen saturation (SaO2), and electrooculogram were monitored. Children had 0.1 +/- 0.5 (range 0 to 3.1) obstructive apneas per hour of total sleep time, with only 18% of children having any obstructive apneas. No child had obstructive apneas > 10 s in duration. Of the children 30% had central apneas > or = 10 s in duration, and one child had a central apnea associated with SaO2 < 90%. Peak PETCO2 was 46 +/- 4 mm Hg (range 38 to 53 mm Hg), and hypoventilation (PETCO2 > 45 mm Hg) occurred for 7 +/- 19% total sleep time (range 0 to 91%). The SaO2 nadir was 96 +/- 2% (range 89 to 98%), with only one child desaturating below 90% in association with a central apnea. We conclude that polysomnographic results in the pediatric age group differ from those in adults. Recommendations for normal polysomnographic criteria are given.

Adolescent↗
PubMed1992

The characterization of inconsistencies in self-reports of alcohol and marijuana use in a longitudinal study of adolescents.

The reliability of self-reported measures remains an important issue for research on adolescent alcohol and drug use. Many studies have concluded that adolescents' self-reports are valid and reliable, but few studies have excluded consistent nonusers from their reliability estimates, and no study has examined in detail the reliability of reported age at first use of substances. This study explores the consistency of self-reports of frequency of use and age of first use of alcohol and marijuana in a sample of 5,770 secondary school students in a southeastern U.S. county. Two waves of data were collected between 1985 and 1988 using state-of-the-art data collection procedures and self-administered instruments. Consistency of reports was examined by comparing reports at T1 and T2, approximately 1 year apart. Results showed that when consistent nonusers were dropped from the analysis, consistency rates of lifetime frequency of use dropped from 82.7% to 74.7% for alcohol and from 95.6% to 83.2% for marijuana. Reports were more consistent for lifetime marijuana use than for alcohol use, but these results must be interpreted with caution given differences in the measures for the two substances. Reliability of reported age of first use was very low for both substances. When consistent nonusers were dropped from the analysis, only 27.8% of respondents made consistent estimates of their age at first alcohol use and 34.4% for their age at first marijuana use. Implications and recommendations for this area of research are discussed.

Adolescent↗
PubMed1992

Adolescents' multisubstance use patterns: the role of heavy alcohol and cigarette use.

OBJECTIVES: Knowledge about the roles that heavy alcohol and cigarette use play in patterns of concurrent substance use among adolescents is lacking despite studies showing that adolescent substance users are typically multisubstance users and that alcohol and cigarettes are commonly used heavily by those who use illicit substances. METHODS: The roles of increasing use and heavy first-time use of alcohol and cigarettes in multisubstance use patterns were examined in a cohort of 4192 secondary students who were surveyed three times over a 4-year period. RESULTS: When subsequent use patterns were compared for students who increased their levels of alcohol or cigarette use and those who initiated use for the first time but at heavy frequencies, analyses indicated that the former group was more likely to initiate the subsequent use of other substances and to maintain and increase use already initiated. CONCLUSIONS: These results suggest that adolescents are likely to have been involved in a history of licit substance use characterized by increasing levels of use before progressing to and maintaining the use of other substances. Increasing frequencies of alcohol and cigarette use, therefore, may be markers for more serious patterns of substance use.

Adolescent↗
PubMed1992

Predicting continued use of marijuana among adolescents: the relative influence of drug-specific and social context factors.

Most research on the determinants of adolescent drug use has focused on predictors of either initiation or current use. Little attention has been given to the determinants of continued use of drugs after initiation, even though some researchers have found that the consequences of continued use are more serious than those associated with experimental or occasional use. In this study, a longitudinal sample of 456 secondary and high school students who had already tried marijuana was used to examine the determinants of continued use of marijuana. Nearly 38 percent of those who had tried marijuana continued using, according to the definition operationalized in this study. Potential predictor measures were grouped in a drug-specific domain and a social context domain, and their effects on continued use, controlling for background characteristics, were examined in logistic regression models. Results showed that only the drug-specific domain had a statistically significant effect on the likelihood of continued use. Students who felt that the adverse physical and psychological effects of marijuana were not very important reasons for discontinuing use and those who had gotten stoned during their experimental stage of use were the most likely to continue use after initiation. The results suggest that the perceived physical and psychological effects of the drug are more important determinants of continued use than are social factors or benefits related to use. Any relationships between social factors and continued use are mediated by the perceived effects and risks of the drug.

Adolescent↗
PubMed1990

Relationship of mood disorders to violence.

Past research on the relationship between mood disorders and violent behavior has been inconsistent, sometimes finding a relationship between the two and sometimes finding no relationship. Any relationship is arguably complex, and this area of research would benefit from attempts to clarify the relationship. This paper addresses the issue of complexity by examining the relationship between specific mood disorder categories and symptoms and six conceptually different indicators of violent behavior. Relationships are analyzed in logistic regression models where demographic and problem drinking variables are included to control variation that may be accounted for by these factors. The study uses a sample of 1140 recently incarcerated male felons. Psychiatric disorder diagnoses are based on the Diagnostic Interview Schedule. There is evidence of a direct relationship between a lifetime diagnosis of dysthymia and an arrest or incarceration history for robbery as well as with multiple incidents of fighting since age 18. Recurrent depression was significantly associated with a robbery incarceration history. Depression symptoms (regardless of whether a disorder diagnosis was made) were associated with multiple incidents of fighting since age 18. Manic symptoms were inconsistently associated with "expressive" violence and a number of mood disorder/violence models showed no significant relationship between the two.

Adult↗
PubMed1990

Developmental variation in the context of marijuana initiation among adolescents.

A longitudinal sample of 3,454 secondary school students is used to examine the variations in the contexts of marijuana initiation which may be attributable to developmental changes during adolescence. Concepts representing the context of initiation include attachments to parents and peers, exposures to drug-related attitudes of parents and peers and behaviors of peers, and the decision-making process, which involves the weighing of expected costs and benefits of use. Measures representing these concepts are included in logistic regression models predicting initiation. Regression parameters are compared for students in the sixth, seventh, and eighth grades. Results show that only parental attachment measures influence initiation for the youngest group; a mix of parental and peer attachment and peer exposure measures affects initiation for the middle group; and only measures of peer attachment and exposure and of the relative importance of the costs of use predict initiation for the oldest group. The results suggest that developmental factors do influence the context of marijuana initiation.

Adolescent↗