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Biomedical subjects

S Curtis

Publications and source records attributed to S Curtis.

At least 19 recordsLinked to original sources
PubMed1996

The effect of glycogen availability on power output and the metabolic response to repeated bouts of maximal, isokinetic exercise in man.

The relationship of glycogen availability to performance and blood metabolite accumulation during repeated bouts of maximal exercise was examined in 11 healthy males. Subjects performed four bouts of 30 s maximal, isokinetic cycling exercise at 100 rev.min-1, each bout being separated by 4 min of recovery. Four days later, all subjects cycled intermittently to exhaustion [mean (SEM) 106 (6) min] at 75% maximum oxygen uptake (VO2max). Subjects were then randomly assigned to an isoenergetic low-carbohydrate (CHO) diet [7.8 (0.6)% total energy intake, n = 6] or an isoenergetic high-CHO diet [81.5 (0.4)%, n = 5], for 3 days. On the following day, all subjects performed 30 min cycling at 75% VO2max and, after an interval of 2 h, repeated the four bouts of 30 s maximal exercise. No difference was seen when comparing total work production during each bout of exercise before and after a high-CHO diet. After a low-CHO diet, total work decreased from 449 (20) to 408 (31) J.kg-1 body mass in bout 1 (P < 0.05), from 372 (15) to 340 (18) J.kg-1 body mass in bout 2 (P < 0.05), and from 319 (12) to 306 (16) J.kg-1 body mass in bout 3 (P < 0.05), but was unchanged in bout 4. Blood lactate and plasma ammonia accumulation during maximal exercise was lower after a low-CHO diet (P < 0.001), but unchanged after a high-CHO diet. In conclusion, muscle glycogen depletion impaired performance during the initial three, but not a fourth bout of maximal, isokinetic cycling exercise. Irrespective of glycogen availability, prolonged submaximal exercise appeared to have no direct effect on subsequent maximal exercise performance.

Adult↗
PubMed1996

Predictors of persistence and remission of ADHD into adolescence: results from a four-year prospective follow-up study.

OBJECTIVE: To evaluate the predictors of persistence and the timing of remission of attention-deficit hyperactivity disorder (ADHD). METHOD: Subjects were 6- to 17-year old Caucasian, non-Hispanic boys with and without ADHD. DSM-III-R structured diagnostic interviews and blind raters were used to examine psychiatric diagnoses, cognitive achievement, social, school, and family functioning at a 4-year follow-up assessment. RESULTS: At the 4-year follow-up assessment, 85% of children with ADHD continued to have the disorder and 15% remitted. Of those who remitted, half did so in childhood and the other half in adolescence. Predictors of persistence were familiality of ADHD, psychosocial adversity, and comorbidity with conduct, mood, and anxiety disorders. CONCLUSIONS: The findings prospectively confirm that the majority of children with ADHD will continue to express the disorder 4 years later. For a minority of children, ADHD was a transient disorder that remits early in development. In addition, we have shown that persistence of ADHD is predictable. Familiality, adversity, and psychiatric comorbidity may be clinically useful predictors of which children with ADHD are at risk for a persistent disorder.

Achievement↗
PubMed1995

Health care reforms in Russia: the example of St Petersburg.

This paper describes the changes being introduced into the Russian health care system, particularly the introduction of a compulsory social health insurance system which is paralleled by encouragement of independent health insurance. An example of the implementation of these changes is provided by the early developments in St Petersburg. The effects of the likely changes on health care providers and users are discussed. It is argued that in the light of these reforms, as well as change in other countries, a revision is necessary in the perspectives adopted by geographers of health care to compare national health systems.

Ambulatory Care Facilities↗
PubMed1995

The application of disability data from epidemiological surveys to the development of indicators of service needs for dependent elderly people.

Increases in the prevalence of disability due to the ageing of the population have given rise to the need for simple indicators which may be used to estimate service needs and to assess whether resources have been fairly distributed. The present study involved the validation of an indicator based on confinement level by reference to epidemiological studies of disability, social support, and living conditions in three regions of France. Using factorial correspondence analysis and regression methods it was found that such an indicator could adequately summarize more complex empirical observations and thus provide a means of classifying elderly populations into four dependency groups. While comparisons of the percentage of persons classified at each level with national data suggest that the observations from the three studies may be reasonably representative of France as a whole, the application of this indicator to other European countries should be preceded by a preliminary validation involving regional or national health survey data for each country. The use of this indicator should also be complemented by individual need assessment procedures.

Activities of Daily Living↗
PubMed1995

Amphetamine paired with physical therapy accelerates motor recovery after stroke. Further evidence.

BACKGROUND AND PURPOSE: In animal models of brain injury, administration of numerous pharmaceuticals is reported to facilitate functional recovery. However, only drugs that increase the release of norepinephrine have been shown to promote recovery when administered late (days to weeks) after injury. To determine whether these findings were applicable to humans, we administered the norepinephrine stimulant dextroamphetamine, paired with physical therapy, to hemiplegic stroke patients. METHODS: Ten hemiplegic patients who suffered an acute ischemic infarction were entered between days 16 and 30 after onset and randomly assigned to receive either 10 mg of dextroamphetamine or a placebo orally every fourth day for 10 sessions paired with physical therapy. The Fugl-Meyer Motor Scale was used at baseline, within each session, and for 12 months after onset as the dependent measure. Confounding medications such as alpha-adrenergic antagonists or agonists were excluded in all subjects. RESULTS: Although there were no differences between the groups at baseline (P = .599), there was a significant (P = .047) difference between the groups when the drug had been discontinued for 1 week and at the 12-month follow-up visit (P = .047). CONCLUSIONS: Administration of dextroamphetamine paired with physical therapy increased the rate and extent of motor recovery in a small group of hemiplegic stroke patients. These data support and extend previous findings of the facilitatory aspects of certain types of drugs on recovery from brain injury. The use of neuromodulation may allow the nervous system to adapt previously unused or alternative pathways to relevant external input.

Administration, Oral↗
PubMed1995

Inability of clinical history to distinguish primary snoring from obstructive sleep apnea syndrome in children.

STUDY OBJECTIVE: To determine whether primary snoring (PS) could be distinguished from childhood obstructive sleep apnea syndrome (OSAS) by clinical history. DESIGN: Retrospective study of clinical history of 83 children with snoring and/or sleep disordered breathing who were referred for polysomnography. SETTING: Tertiary referral center; pediatric pulmonary sleep apnea clinic. MEASUREMENTS: We evaluated the ability of a clinical obstructive sleep apnea (OSA) score and other questions about sleep, breathing, and daytime symptoms to distinguish PS from OSAS in children. Parents were asked about the child's snoring, difficulty breathing, observed apnea, cyanosis, struggling to breathe, shaking the child to "make him or her breathe," watching the child sleep, afraid of apnea, the frequency and loudness of snoring, and daytime symptoms such as excessive daytime sleepiness (EDS). RESULTS: Based on polysomnography results, 48 patients were classified as PS and 35 as OSAS. Peak endtidal CO2 (49 +/- 3.2 vs 55 +/- 8.2 [SD] mm Hg); lowest arterial oxygen saturation measured by pulse oximetry (95 +/- 1.9 vs 82 +/- 14%); and apnea/hypopnea index (0.27 +/- .3 vs 8.4 +/- 6 events/h) indicated that the diagnostic criteria for PS versus OSA were reasonable. There were no differences between PS and OSA patients with respect to age, sex, race, failure to thrive, obesity, history of EDS, snoring history, history of cyanosis during sleep, or daytime symptoms except for mouth breathing. There were no significant differences in sleep variables between PS patients and those with any severity of OSAS. The OSA score misclassified about one of four patients. Comparing PS and OSA patients, significant findings were daytime mouth breathing (61 vs 85%; p = 0.024); observed apnea (46 vs 74%; p = 0.013); shaking the child (31 vs. 60%; p = 0.01); struggling to breathe (58 vs 89%; p = 0.003); and afraid of apnea (71 vs 91%; p = 0.028). However, none of these were sufficiently discriminatory to predict OSAS. CONCLUSION: We conclude that PS in children cannot be reliably distinguished from OSAS by clinical history alone.

Case-Control Studies↗
PubMed1994

Coronary heart disease: trends in spatial inequalities and implications for health care planning in England.

The idea of health gain has recently received particular emphasis in health policy in England. One of the areas where there is considerable scope for health gain is in the reduction of mortality due to Coronary Heart Disease. Some reduction in mortality rates due to this cause have already been achieved in England in the 1980s. However, the change in standardised mortality rates varies around the country. A review of studies of geographies of declining CHD mortality shows that such geographical variation is typical of other countries which have recently experienced a reduction in the CHD epidemic. The paper presents the results of an analysis of change in spatial inequality in coronary heart disease mortality among the population aged 35-74 for the 190 District Health Authorities in England over the period 1982-1989. Data were derived from counts of cause-specific deaths and population estimates published by the Office of Population Censuses and Surveys. Various approaches were used to assess the change in spatial disparity which has accompanied the average overall reduction in mortality rates over the study period. The results show that the trends vary between age and sex groups in the population and that, particularly for older people, overall health gain across the country is being achieved at the cost of greater inequality in health between areas. The implications for local health strategies with respect to coronary heart disease reduction are discussed.

Adult↗
PubMed1994

Polysomnographic characteristics of patients with Rett syndrome.

During wakefulness, patients with Rett syndrome have disordered breathing. To understand further this ventilatory control disorder, we performed polysomnography in 30 patients with Rett syndrome and 30 control subjects (female subjects with primary snoring). The median age was 7 years (range, 1 to 32 years) for Rett syndrome and 6 years (range, 1 to 17 years) for control subjects. During periods of wakefulness, 67% of patients with Rett syndrome had the characteristic pattern of disordered breathing (i.e., episodes of hyperventilation followed by central apnea and desaturation). No such events occurred during sleep. Sleep efficiency and sleep architecture were similar for both groups. During sleep, there was no difference in duration of periodic breathing, number of episodes of central apnea with desaturation, or number of episodes of obstructive apnea or end-tidal carbon dioxide tension between the two groups. Although arterial oxygen saturation during rapid eye movement (REM) sleep was slightly lower in patients with Rett syndrome (nadir, 94% +/- 2% vs 96% +/- 2%), it remained within the normal range. Parental history reflected the awake respiratory findings in most cases. We conclude that patients with Rett syndrome have normal breathing during non-rapid eye movement (NREM) sleep. We speculate that patients with Rett syndrome have normal brain-stem control of ventilation, and that the disordered breathing seen during wakefulness is due to an abnormality of the cortical influence on ventilation.

Adolescent↗
PubMed1993

Improving the accuracy of a new articulator.

The indications and features of the new Denar Combi articulator are reviewed. The Combi articulator was designed primarily as a set path instrument, but can also be used as a semiadjustable or fully adjustable stereographic articular. The articulator can be programmed for any of these modes, but the Combi model is limited when used as a stereographic instrument according to the manufacturer's instructions, with the instrument-precipitated geometric errors. These errors were identified mathematically, and an accurate technique for the instrument is described.

Dental Articulators↗
PubMed1993

Gap junctional connections between hair cells, supporting cells and nerves in a vestibular organ.

The pattern of gap-junctional connections between cells in the vestibular neuroepithelium of the posterior semicircular duct of the alligator lizard are described based upon the study of freeze fracture replicas and ultrathin sections with a transmission electron microscope. Both type I and type II hair cells are coupled to adjacent supporting cells by a series of small macular gap junctions located in a ring around the hair cell at the level of the apical circumferential belt of actin filaments. Adjacent supporting cells are extensively interconnected by gap junctions. A few cases of gap junctions between afferent dendrites and supporting cells, and between afferent dendrites and calyceal nerve endings were seen. These morphological observations together with data from other studies in the literature suggest a possible role for supporting cells in altering the micromechanical properties of the hair cell receptor organs during stimulation.

Actin Cytoskeleton↗
PubMed1992

Changes in cortical activity when subjects scan memory for tones.

The magnetoencephalogram (MEG) was used to detect regional changes in spontaneous cortical activity accompanying short-term memory search. This method was chosen because magnetic fields are detectable only within a few centimeters of the projections of their sources onto the scalp. The specific hypothesis that auditory cortex is involved in scanning memory for tones was tested by sensing the field of the magnetic counterpart to N100 (N100m) which is known to originate in auditory cortex. N100m was measured at many different positions and the spontaneous cortical rhythms in the alpha bandwidth (8-12 Hz) were measured at the same places. These rhythms were found to be suppressed while subjects scanned memory for musical tones in a Sternberg paradigm. For 3 subjects, both the MEG suppression time (ST) and reaction time (RT) increased linearly with memory set size. The correlation between ST measured over the left hemisphere and set size was significant for two subjects but not significant for the third, and the slopes of the regression lines relating ST to set size were too shallow to be related to the time required to scan memory. However, the correlation between ST of the right hemisphere and set size was highly significant for all subjects, and the slopes of the regression lines were comparable to those relating RT to set size. The electroencephalogram (EEG) recorded with midline electrodes failed to reveal a significant relationship between suppression time and set size for 2 of the subjects, thus ruling out global alpha blockage and generalized arousal as the basis for the task-related suppression duration. The electric N100, measured at Cz, decreased significantly in amplitude with set size for 2 subjects, but it increased significantly in amplitude for the third subject. In contrast, RT increased with set size for all subjects. N100m measured over the right hemisphere was similar to the behavior of N100, while N100m measured over the left hemisphere showed little change in amplitude with set size, thus establishing an asymmetry in N100 between the hemispheres. Since N100 amplitude is normally larger when attention is paid to auditory stimuli, differential attention alone cannot account for the relation between ST and set size. Furthermore, the processing negativity, which may be superimposed on N100 in selective attention tasks, was not discernible for any set size. It was also found that ST prior to the button press was not correlated with RT. Hence, the covariation of set size with ST is not attributable to preparation for a motor response.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1992

The role of diagnostic CT scanning of the brachial plexus and axilla in the follow-up of patients with breast cancer.

In order to assess the value of computed tomographic scanning of the axilla and brachial plexus in the management of patients with arm symptoms following treatment for breast cancer, the case notes and diagnostic films of 102 such patients who underwent scanning between 1985 and 1990 at this institution were analysed retrospectively. The clinical indications for requesting computed tomography (CT) of the brachial plexus and axilla included arm oedema (52 patients, 51%), brachial plexus neuropathy (73 patients, 72%), and/or the presence of a palpable axillary mass (18 patients, 18%). Of 102 CT scans, 80 showed either no abnormality (31 patients, 30%), or axillary fibrosis (49 patients, 48%), and 22 (21%) showed radiological evidence of recurrent tumour. Only 4 of 84 patients with no palpable mass had computed tomographic evidence of occult recurrent tumour; all of these had concurrent evidence of distant metastatic disease (lung, liver, bone). Patients have been followed up for from between 1 and 15 years from diagnosis (median 5.5 years). The extremely low yield of tumour recurrence on computed tomographic scanning in the absence of a palpable axillary mass (4/84 patients, 5%; 95% CI 1-12), cannot justify CT as a method of screening for clinically occult axillary relapse in patients with arm symptoms following axillary surgery and radiotherapy for breast cancer. Computed tomographic scanning in these patients should only be employed to confirm the clinical suspicion of tumour as a baseline prior to further treatment.

Axilla↗
PubMed1992

Promoting health through a developmental analysis of adolescent risk behavior.

Adolescents are the only U.S. population group not to improve morbidity and mortality since 1960. Social and behavioral etiologies of adolescent morbidity and mortality are best addressed in schools, since health care providers rarely are seen by teen-agers for other than organic health complaints. The relevance of physical, cognitive, and psychosocial development for adolescent risk-taking and their attendant health problems are discussed. Recognizing adolescent risk-taking as a means of achieving autonomy and identity, nurses and health educators can intervene to promote health-enhancing alternatives to achieve those ends. Social learning theory provides a basis for interventions to personalize the curricula, change behaviors, and shape the environment.

Adolescent↗
PubMed1991

Estrogen receptor stereochemistry: ligand binding and hormonal responsiveness.

Estrogen stimulation of the uterus produces a spectrum of biochemical responses that are customarily linked together. This report is an overview of a series of studies by our laboratory investigating the role of different ligand structures in eliciting hormonal responses. Diethylstilbestrol (DES) and certain structural analogs, indenestrol A (IA), indenestrol B (IB), and pseudo-DES, were used as probes to segregate various genomic responses previously considered interrelated, most notably the events of specific protein synthesis and DNA synthesis. These compounds have weak uterotrophic activity; however, they interact with high affinity specifically with mouse uterine estrogen receptors (ERs). All of them produce stoichiometrically similar amounts of ER complex in the nucleus. Indenestrol A and IB possess a single chiral carbon atom and exist as a mixture of enantiomers (ENTs). Competitive binding assays of pure ENTs and cytosolic ERs demonstrated a stereochemical chiral preference for the IA isomer but not IB. This preference was also evident from nuclear ER occupancy experiments. Biologic activity of the IA ENTs also demonstrated differences as seen by receptor binding. Ornithine decarboxylase (ODC) activity was stimulated 600% by DES and partially by IA (rac). All of the ODC activity produced by IA (rac) was due to the IA(C3)-S ENT. Uterine DNA synthesis was measured after treatment with the IA compounds. Indenestrol A (rac) increased DNA synthesis to 40% of the level seen with DES. The weak ENTs showed no activity and the active ENTs were weaker than the IA racemic. These compounds should be useful probes for studying the individual responses involved in estrogen-induced uterine growth.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Diethylstilbestrol metabolites and analogs: differential ligand effects on estrogen receptor interactions with nuclear matrix sites.

Estradiol (E), diethylstilbestrol (DES), and three structurally similar DES derivatives and analogs, consisting of racemic mixtures of indenestrol-A (IA; rac), indenestrol-B (IB; rac), and the Z-isomer of pseudo-DES (PD) were used as probes to determine the effect of ligand on receptor-nuclear acceptor site interactions. IA (rac), IB (rac), and Z-PD have been previously shown to interact with the mouse uterine estrogen receptor with high affinity (Kd, approximately 1.5-2.2 x 10(-10) M), occupy similar levels of receptor in the nucleus in vivo, and have nuclear retention times similar to those of E and DES. However, in spite of these similarities, they differentially stimulate estrogenic responses that were previously thought to be interrelated and obligatory for full estrogenic action. In an attempt to elucidate the mechanism of differential stimulation of estrogen-regulated responses, the temporal pattern of KCl-resistant receptor sites was examined after a single injection of E, DES, IA (rac), IB (rac), Z-PD, or saline. Z-PD displayed lower levels of KCl-resistant receptor than the other compounds, whereas IA (rac) and IB (rac) had patterns similar to those of E and DES. In cell-free binding assays, all of the different receptor-ligand complexes were equally effective at competitively inhibiting the binding of receptor-[3H]E complexes to mouse uterine nuclear matrix with a Ki of 1.1 x 10(-10) M. Direct binding analysis showed no difference in the number of nuclear binding sites (range, 40.4-63.9 fmol/100 micrograms DNA) or Kd (range, 1.3-1.8 x 10(-10) M) among the different receptor-ligand complexes. Dissociation studies performed at 4 C showed no differences among the different complexes. In contrast, Z-PD-receptor complexes dissociated much faster from matrix sites at 22 C than any of the other complexes. Significant differences were noted in the proportion of complexes that were resistant to extraction with 0.6 M KCl. Forty-three percent of receptor-E complexes and 44% of receptor-DES complexes were resistant to KCl extraction, while 61% of receptor-IA and 29% of receptor-PD complexes were resistant to extraction, paralleling their activity in eliciting some estrogenic responses. In contrast, no difference was seen by gel shift assays in the ability of the ligand-receptor complexes to bind to a specific PS2 estrogen-responsive DNA sequence. These results demonstrate that the ligand may significantly affect the interaction of the estrogen receptor with nuclear acceptor sites.

Animals↗
PubMed1991

Concentrations of serum constituents in cold-stressed calves from heifers fed inadequate protein and(or) energy.

A study with neonatal calves was conducted to determine the effects of maternal crude protein (CP) and(or) metabolizable energy (ME) malnutrition, cold stress (0 or 21 degrees C), and age on concentrations of selected serum constituents. For each of 2 yr, 60 artificially bred Angus heifers were assigned randomly to a 2 x 2 factorial nutritional plan 150 d before predicted parturition. The diets provided each heifer with either .32 or .96 kg/d of CP and 8.7 or 12.6 Mcal/d of ME. Blood samples were obtained from heifers at parturition and from their calves at birth and at 12, 24, 36, 48, and 72 h of age. Sera were analyzed for concentrations of blood urea nitrogen (BUN), creatinine (Creat), iron, total protein (TProt), alkaline phosphatase (AlkPhos), total bilirubin (TBil), and cholesterol (Chol). Mean correlations of these constituents in calf sera between 12-h adjacency intervals were high, but those between longer times (48 or 60 h) were low. Simple correlations of serum constituents between cows and calves at birth were low except for BUN (r = .578 and .295 for yr 1 and 2, respectively). There were significant main treatment effects for maternal CP consumption on BUN levels, for environmental temperature on BUN, Creat, and TBil levels, and for years on BUN, Creat, iron, and AlkPhos levels in calves. Significant polynomial relationships were found over hours of age for all variables. Blood urea N decreased in normal calves but remained relatively constant at a low level in deficient calves. Year x hour of age interactions occurred for iron, TProt, AlkPhos, TBil, and Chol. Protein x year x hour of age interactions were found for iron and Chol. These results suggest that random sampling times are not useful for decision making during the first 72 h after birth. Consideration must be given to multiple samples taken at specific calf ages, to environmental temperatures, and to maternal protein nutritional levels when interpreting calf blood sera data.

Alkaline Phosphatase↗