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Biomedical subjects

J A Elliott

Publications and source records attributed to J A Elliott.

At least 19 recordsLinked to original sources
PubMed2005

Circadian phase in adults of contrasting ages.

There is evidence that aging may impair phase-shifting responses to light synchronizers, which could lead to disturbed or malsynchronized circadian rhythms. To explore this hypothesis, 62 elder participants (age, 58 to 84 years) and 25 young adults (age, 19 to 40 years) were studied, first with baseline 1-wk wrist actigraphy at home and then by 72 h in-laboratory study using an ultra-short sleep-wake cycle. Subjects were awake for 60 minutes in 50 lux followed by 30 minutes of darkness for sleep. Saliva samples were collected for melatonin, and urine samples were collected for aMT6s (a urinary metabolite of melatonin) and free cortisol every 90 minutes. Oral temperatures were also measured every 90 minutes. The timing of the circadian rhythms was not significantly more variable among the elders. The times of lights-out and wake-up at home and urinary free cortisol occurred earlier among elders, but the acrophases (cosinor analysis-derived peak time) of the circadian rhythm of salivary melatonin, urinary aMT6s, and oral temperature were not significantly phase-advanced among elders. The estimated duration of melatonin secretion was 9.9 h among elders and 8.4 h among young adults (p < 0.025), though the estimated half-life of blood melatonin was shorter among elders (p < 0.025), and young adults had higher saliva melatonin and urinary aMT6s levels. In summary, there was no evidence for circadian desynchronization associated with aging, but there was evidence of some rearrangement of the internal phase-angles among the studied circadian rhythms.

Adult↗
PubMed2004

Dim nocturnal illumination alters coupling of circadian pacemakers in Siberian hamsters, Phodopus sungorus.

The circadian pacemaker of mammals comprises multiple oscillators that may adopt different phase relationships to determine properties of the coupled system. The effect of nocturnal illumination comparable to dim moonlight was assessed in male Siberian hamsters exposed to two re-entrainment paradigms believed to require changes in the phase relationship of underlying component oscillators. In experiment 1, hamsters were exposed to a 24-h light-dark-light-dark cycle previously shown to split circadian rhythms into two components such that activity is divided between the two daily dark periods. Hamsters exposed to dim illumination (<0.020 lx) during each scotophase were more likely to exhibit split rhythms compared to hamsters exposed to completely dark scotophases. In experiment 2, hamsters were transferred to winter photoperiods (10 h light, 14 h dark) from two different longer daylengths (14 h or 18 h light daily) in the presence or absence of dim nighttime lighting. Dim nocturnal illumination markedly accelerated adoption of the winter phenotype as reflected in the expansion of activity duration, gonadal regression and weight loss. The two experiments demonstrate substantial efficacy of light intensities generally viewed as below the threshold of circadian systems. Light may act on oscillator coupling through rod-dependent mechanisms.

Analysis of Variance↗
PubMed2003

Photoperiod differentially modulates photic and nonphotic phase response curves of hamsters.

Circadian pacemakers respond to light pulses with phase adjustments that allow for daily synchronization to 24-h light-dark cycles. In Syrian hamsters, Mesocricetus auratus, light-induced phase shifts are larger after entrainment to short daylengths (e.g., 10 h light:14 h dark) vs. long daylengths (e.g., 14 h light:10 h dark). The present study assessed whether photoperiodic modulation of phase resetting magnitude extends to nonphotic perturbations of the circadian rhythm and, if so, whether the relationship parallels that of photic responses. Male Syrian hamsters, entrained for 31 days to either short or long daylengths, were transferred to novel wheel running cages for 2 h at times spanning the entire circadian cycle. Phase shifts induced by this stimulus varied with the circadian time of exposure, but the amplitude of the resulting phase response curve was not markedly influenced by photoperiod. Previously reported photoperiodic effects on photic phase resetting were verified under the current paradigm using 15-min light pulses. Photoperiodic modulation of phase resetting magnitude is input specific and may reflect alterations in the transmission of photic stimuli.

Animals↗
PubMed2001

Non-equilibrium thermodynamics of concentration polarization.

Ultrafiltration is a membrane separation process with many applications, including the treatment of industrial wastes and the processing of milk and juices. Academics are also interested in ultrafiltration as a possible tool for measuring empirical coefficients such as the diffusion coefficient and the permeability. One particular region of an ultrafiltration system that is not yet fully understood, and is related to a decline in the efficiency, is the concentration polarization layer, which develops as the macromolecules retained by the membrane form a highly concentrated layer that attempts to diffuse back toward the bulk of the solution. Using the postulates of classical non-equilibrium thermodynamics, a complete model, which accounts for the fact that a concentration polarization layer may have properties of both a porous medium and a region undergoing Brownian diffusion, has been derived and applied to several systems from the literature.

Animals↗
PubMed2001

Sleep estimation from wrist movement quantified by different actigraphic modalities.

Progress in transducer design and empirical characterization of wrist movement has led to diverse wrist activity monitors, each with its unique features and modality of operation. This study compared sleep--wake estimates from nocturnal wrist activity quantified by different motion-quantifying algorithms. Healthy young adults wore an Actillume and a Mini Motionlogger on the same wrist while nocturnal polysomnography data were recorded simultaneously in the laboratory. Activity data were analyzed with ACTION3 using scoring algorithms independently calibrated for each measurement modality. Overall, each modality yielded accurate and reliable sleep estimates relative to polysomnographic estimates (agreement rates: 91.4--96.5%, correlations for sleep duration: 0.79--0.94). Estimates derived from Actillume modalities were comparable to those of Mini Motionloggers, suggesting that the transducers of these two devices performed comparably for monitoring sleep and wakefulness. Wrist movement quantified by the Mini Motionlogger proportional-integrating mode yielded the best accuracy for detection of sleep--wake states.

Adult↗
PubMed2001

Intercellular ice propagation: experimental evidence for ice growth through membrane pores.

Propagation of intracellular ice between cells significantly increases the prevalence of intracellular ice in confluent monolayers and tissues. It has been proposed that gap junctions facilitate ice propagation between cells. This study develops an equation for capillary freezing-point depression to determine the effect of temperature on the equilibrium radius of an ice crystal sufficiently small to grow through gap junctions. Convection cryomicroscopy and video image analysis were used to examine the incidence and pattern of intracellular ice formation (IIF) in the confluent monolayers of cell lines that do (MDCK) and do not (V-79W) form gap junctions. The effect of gap junctions on intracellular ice propagation was strongly temperature-dependent. For cells with gap junctions, IIF occurred in a directed wave-like pattern in 100% of the cells below -3 degrees C. At temperatures above -3 degrees C, there was a marked drop in the incidence of IIF, with isolated individual cells initially freezing randomly throughout the sample. This random pattern of IIF was also observed in the V-79W monolayers and in MDCK monolayers treated to prevent gap junction formation. The significant change in the low temperature behavior of confluent MDCK monolayers at -3 degrees C is likely the result of the inhibition of gap junction-facilitated ice propagation, and supports the theory that gap junctions facilitate ice nucleation between cells.

Animals↗
PubMed2001

Circadian abnormalities in older adults.

This study examined the circadian phase adjustment of symptomatic elders ages 60-79 years in comparison with that of young, healthy adults ages 20-40 years. Seventy-two elders with complaints of insomnia or depression, and 30 young, healthy adults were assessed for 5-7 days at home. Sleep and illumination were recorded with Actillume wrist monitors and sleep diaries. Urine was collected over two 24-hr periods and assayed for 6-sulphatoxymelatonin (6-smt). The volunteers were then observed continuously for 5 nights and 4 days in the laboratory. In the laboratory, sleep periods were fixed at 8 hr with polysomnographic assessment of sleep, apnea-hypopnea, and nocturnal myoclonus. Circadian dispersion, defined as the mean variation of 6-smt acrophase from the median age-specific acrophase, was significantly greater in the older vs. young adults. Likewise, circadian malsynchronization, defined as the absolute number of hours (advance or delay) between the 6-smt acrophase and the middle of the sleep period, was significantly greater in the older vs. young volunteers. For the older volunteers, multiple regressions were calculated associating sleep with potential correlates of sleep disturbance. Nocturnal myoclonus and circadian malsynchronization were more strongly associated with sleep impairment than other factors (e.g., sleep apnea, depression). These observations suggest that circadian malsynchronization might be a common and significant cause of disturbed sleep among adults over age 60.

Adult↗
PubMed2000

Clonal groups of penicillin-nonsusceptible Streptococcus pneumoniae in Baltimore, Maryland: a population-based, molecular epidemiologic study.

Few data are available on the molecular subtypes of all penicillin-nonsusceptible Streptococcus pneumoniae (PNSP) from a defined population base. Pulsed-field gel electrophoresis (PFGE), serotyping, and antibiotic susceptibility testing were performed for all available invasive PNSP isolates for which the penicillin (MIC) was > or =0.1 microg/ml from Baltimore, Md., during 1995-1996 (n = 143). The dendrogram analysis of PFGE patterns included 32 distinct clonal groups. Six major clonal groups included two-thirds of the PNSP strains. Major clonal groups 2, 3, 4, and 6 strains were genetically related to four previously described international clones and were all multidrug resistant. Major clonal group 3 was genetically related to the Tennessee(23F)-4 clone and contained all four strains for which the penicillin MIC was 8 microg/ml. Most of the clonal group 1 and 5 strains had intermediate susceptibility to penicillin and were rarely multidrug resistant. The latter clonal groups represent two previously undescribed penicillin-intermediate pneumococcal clones. Clonal group homogeneity was greater for serotype 9V, 19A, and 23F strains than for serotype 6A, 6B, 14, and 19F strains. The classification of PNSP strains into clonal groups is essential for future population-based epidemiologic studies of PNSP.

Adolescent↗
PubMed2000

Perineal group A streptococcal disease in a pediatric practice.

OBJECTIVE: This study was designed to document the frequency and define the clinical, epidemiologic, and microbiologic characteristics of perineal disease caused by group A beta-hemolytic streptococci (GAS) in a pediatric practice in which increased numbers of cases had been observed. METHODS: Clinical, epidemiologic, and microbiologic data were collected on all culture-confirmed cases of perineal GAS disease during the calendar year 1997. GAS isolates from clinical cases and a comparison group of children with GAS pharyngitis were analyzed by T typing, emm gene analysis, and pulsed-field gel electrophoresis (PFGE). RESULTS: Twenty-three cases of GAS perineal disease were diagnosed during 4530 office visits in 1997. Thirteen cases had perianal disease, 8 had vulvovaginal infection, and 2 were infected at both sites. No cases of penile disease were identified. Infections peaked in late winter and early spring and affected children with an average age of 5 years with a range of perineal, gastrointestinal, and genitourinary symptoms. Analysis of T and emm types showed the majority (82%) of perineal isolates to be T 28 emm 28, showing 2 closely related PFGE patterns. In contrast, the pharyngeal isolates were distributed among 6 different T and emm types. CONCLUSION: Perineal infection caused by GAS may be a relatively common diagnosis in a pediatric or family practice setting. There may be specific GAS types that have a tropism for perineal tissues but the mechanism of infection is yet to be established.

Child↗
PubMed1999

Light mask 500 lux treatment for delayed sleep phase syndrome.

1. Bright light exposure has been demonstrated as an effective treatment for circadian rhythm sleep disorders. Recent studies suggest that more moderate intensities of light might affect endogenous rhythms. A light mask treatment, using light applied through eyelids during sleep, was tested for Delayed Sleep Phase Syndrome. 2. The active light group (n = 5) received 500 lux light for 3 hours prior to awakening for 12 days. The placebo light group (n = 5) received 0.1 lux light with the same timing. Circadian rhythm phase was assessed from core body temperature and urinary 6-sulfatoxymelatonin measurements. The SIGH-SAD-SR mood scale was administered to assess mood. 3. There were slight trends toward a phase advance of the body temperature rhythm and a phase delay of the melatonin rhythm, and both groups reported anti-depressant benefits. However, no statistically significant effects of 500 lux light mask treatment were demonstrated compared with the placebo-light treatment. 4. More extensive studies will be required to clarify the factors of dose-response and phase-response.

Adult↗
PubMed1999

Carriage of multidrug-resistant Streptococcus pneumoniae and impact of chemoprophylaxis during an outbreak of meningitis at a day care center.

Three cases of meningitis due to multidrug-resistant serotype 14 Streptococcus pneumoniae occurred at a day care center (DCC) over 5 days. Cultures of nasopharyngeal samples were done at the index DCC, 2 comparison DCCs, and a pediatrics practice. Isolates were serotyped and subtyped by pulsed-field gel electrophoresis (PFGE) with SmaI. Pneumococcal carriage rates ranged from 44%-65% at the 3 DCCs and 29% in the pediatrics practice. Carriage of multidrug-resistant serotype 14 S. pneumoniae was noted in 13%-19% of children at the 3 DCCs. An outbreak strain was identified by PFGE at the index DCC and 1 other DCC; a closely related strain was found in the third DCC. Carriage of the outbreak strain was associated with being age 0-24 months, antibiotic use, upper respiratory tract infections, and otitis media. DCC contacts of the ill children were offered chemoprophylaxis with rifampin and clindamycin, which produced a profound but transient decrease in carriage. No additional cases occurred.

Bacterial Vaccines↗
PubMed1999

Is sleep disturbed by vigorous late-night exercise?

PURPOSE: This experiment examined the influence of prolonged, vigorous late-night exercise on sleep. METHODS: Sixteen highly fit male cyclists completed each of two 60-h laboratory treatments involving a baseline night, an experimental treatment night, and a recovery night. In counterbalanced order, subjects 1) cycled for 3 h at 65-75% of heart rate reserve combined with bright light exposure (3000 lux) light, and 2) were exposed to a 3 h pulse of bright light (3000 lux) alone. RESULTS: On the baseline and recovery nights, subjects maintained their usual sleep-wake schedules. On the treatment night, exercise + bright light or bright light alone were centered at 6 h before their usual wake times, followed by bedtimes 30 min after the treatments. Illumination was 3000 lux during the experimental treatments, 0 lux during the sleep periods, and 50 lux at other times. Sleep was assessed with an Actillume (Ambulatory Monitoring, Inc., Ardsley, NY) wrist monitor to define sleep onset latency (SOL), wakefulness after sleep onset (WASO), and total sleep time. Subjective assessments of SOL, WASO, and insomnia were also gathered each morning. No significant differences in objective or subjective sleep variables were found between treatments. CONCLUSIONS: These data are inconsistent with the general opinion that vigorous exercise shortly before bedtime disturbs sleep.

Adult↗
PubMed1998

An outbreak of multidrug-resistant pneumococcal pneumonia and bacteremia among unvaccinated nursing home residents.

BACKGROUND: Outbreaks of pneumococcal disease are uncommon and have occurred mainly in institutional settings. Epidemic, invasive, drug-resistant pneumococcal disease has not been seen among adults in the United States. In February 1996, there was an outbreak of multidrug-resistant pneumococcal pneumonia among the residents of a nursing home in rural Oklahoma. METHODS: We obtained nasopharyngeal swabs for culture from residents and employees. Streptococcus pneumoniae isolates were serotyped and compared by pulsed-field gel electrophoresis. A retrospective cohort study was conducted to identify factors associated with colonization and disease. RESULTS: Pneumonia developed in 11 of 84 residents (13 percent), 3 of whom died. Multidrug-resistant S. pneumoniae, serotype 23F, was isolated from blood and sputum from 7 of the 11 residents with pneumonia (64 percent) and from nasopharygeal specimens from 17 of the 74 residents tested (23 percent) and 2 of the 69 employees tested (3 percent). All the serotype 23F isolates were identical according to pulsed-field gel electrophoresis. Recent use of antibiotics was associated with both colonization (relative risk, 2.3; 95 percent confidence interval, 1.3 to 4.2) and disease (relative risk, 3.6; 95 percent confidence interval, 1.2 to 10.8). Only three residents (4 percent) had undergone pneumococcal vaccination. After residents received pneumococcal vaccine and prophylactic antibiotics, there were no additional cases of pneumonia, and the rates of carriage decreased substantially. CONCLUSIONS: In this outbreak a single pneumococcal strain was disseminated among the residents and employees of a nursing home. The high prevalence of colonization with a virulent organism in an unvaccinated population contributed to the high attack rate. Clusters of pneumococcal disease may be underrecognized in nursing homes, and wider use of pneumococcal vaccine is important to prevent institutional outbreaks of drug-resistant S. pneumoniae infection.

Adult↗
PubMed1998

Invasive group A streptococcal disease in metropolitan Atlanta: a population-based assessment.

Active, population-based surveillance for invasive group A streptococcal (GAS) disease was conducted in laboratories in metropolitan Atlanta from 1 January 1994 through 30 June 1995. Clinical and laboratory records were reviewed and isolates characterized. One hundred and eighty-three cases of invasive GAS disease were identified (annual incidence, 5.2 cases/100,000). The incidence was highest among blacks (9.7/100,000 per year; relative risk (RR), 1.92; confidence interval (CI), 1.69-2.19; P < .0001) and the elderly, particularly nursing home residents (RR, 13.66; CI, 7.07-26.40; P < .0001). The mean age of patients was 41.3 years (range, 0-95 years). Skin and soft-tissue infections were most common. Mortality was 14.4%; risk of death was significantly higher for patients with streptococcal toxic shock syndrome (STSS) (RR, 9.73; CI, 3.34-29; P = .0008) and individuals infected with M-type 1 (RR, 7.40; CI, 1.5-16; P = .0084). Fourteen percent of invasive GAS infections were STSS and 3% were necrotizing fasciitis. Invasive GAS disease was associated with varicella infection in children (RR, 12.19; CI, 5.58-26.62; P < .0001). M (or emm) types included M1 (16%), M12 (12%), and M3 (11%). Continued study of GAS disease is essential to further define risk factors and risk of secondary cases and to develop effective prevention strategies.

Adolescent↗
PubMed1998

Serotype distribution of invasive group B streptococcal isolates in Maryland: implications for vaccine formulation. Maryland Emerging Infections Program.

Invasive group B streptococcal (GBS) infection is a major health problem among infants and adults. The formulation of GBS vaccines depends on knowledge of the GBS serotype distribution. Serotype V GBS infection appears to have recently emerged, suggesting that the serotype distribution changes over time. GBS isolates from 210 pediatric patients, 23 pregnant women, and 314 nonpregnant adults with invasive infection in Maryland were studied. The predominant serotypes from infants with early-onset disease were as follows: serotype III, 38% of isolates; serotype Ia, 36%; serotype V, 13%; and serotype II, 11%. Although the majority (60%) of isolates among infants with late-onset infection were serotype III, serotype Ia (23%) was also common. The predominant serotype among isolates from nonpregnant adult patients was serotype V, accounting for 29% of the isolates. The serotype distribution differs between pediatric patients and adults and is changing over time. The inclusion of a relatively small number of serotypes in a GBS vaccine could provide protection against the vast majority of isolates.

Adult↗
PubMed1998

Streptococcal emm types associated with T-agglutination types and the use of conserved emm gene restriction fragment patterns for subtyping group A streptococci.

The T-agglutination types were determined for a diverse collection of 1531 group A streptococci for which the 5' M protein gene (emm) sequences had been analysed. The majority of the T-agglutination types correlated with previously seen M/emm/T-type associations; however, several new associations were found. Analysis of a subset of this collection -- which included 1157 clinical isolates with multiply encountered emm types -- found that emm amplicon restriction profiles of isolates sharing identical T types and opacity factor phenotypes are useful for detecting groups of isolates with identical emm genes. Many emm genes of known 5' sequence display a highly conserved restriction pattern amongst clinical isolates widely separated both geographically and temporally.

Agglutination↗
PubMed1998

Melatonin excretion is not related to sleep in the elderly.

We examined the association between 6-sulphatoxymelatonin (6-SMT) excretion and sleep in 68 volunteers 60-79 years of age who complained of insomnia or depression. An Actillume wrist monitor was worn for 5-7 consecutive days and nights in home-living conditions. Activity was used to estimate total sleep time (TST) and wake after sleep onset (WASO). Throughout two 24 hr periods, urine was collected approximately every 2 hr during the day and after any voidings during the sleep period. During the next week, subjects spent 5 nights and 4 days in the laboratory. Sleep was measured and scored with standard polysomnographic techniques. Urine was collected, as for home recording, on days 1 and 4. Urinary concentrations of 6-SMT were assayed. Cosine-fitting of urine data across both days at home and both laboratory collections established the mesors and amplitudes of 24 hr 6-SMT excretion rhythms, but neither was significantly correlated with sleep. Mean and peak 6-SMT excretion during the sleep period was also determined. Significant correlations were found between mean 6-SMT during the laboratory sleep period and TST and WASO. However, these associations were not independent of circadian timing: sleep was better when sleep occurred near the circadian acrophase of 6-SMT excretion. These data indicate that low melatonin production may not be an important factor in insomnia among the elderly.

Aged↗