Search PubMed⌕ Search

Biomedical subjects

L Marshall

Publications and source records attributed to L Marshall.

At least 19 recordsLinked to original sources
PubMed2007

A matched case-control study: investigating the relationship between youth assets and sexual intercourse among 13- to 14-year-olds.

BACKGROUND: The number of teenagers engaging in sexual intercourse has consistently changed over the past several years. This can become a major challenge when trying to determine why teens continue to have sex. The purpose of this paper was to investigate the relationship between youth assets and sexual intercourse among 13- to 14-year-olds. METHODS: Cross-sectional data were collected using in-person at-home interviews from a random sample of inner-city neighbourhood 13- to 14-year-old teenagers (n = 64 matched pairs; 36% 13-year-olds, 53% female, 45% white, 28% African-American, 16% Hispanic and 11% Native American). Nine individual youth assets were analysed using conditional logistic regression (matching for several demographic variables) to assess the association between assets and abstinence in younger teens. RESULTS: Conditional logistic regression analyses showed that two assets, positive Peer Role Models [odds ratios (OR) = 4.67, 95% confidence intervals (CI) = 1.93, 11.27] and Use of Time (Religion) (OR = 2.20, 95% CI = 1.04, 4.65), were significantly related (P < 0.05) to younger teens never having engaged in sexual activity. CONCLUSION: These findings suggest, when considering abstinence behaviour, involvement in religious activities and having positive peer role models appear to be protective factors related to delaying sexual intercourse among teens aged 13-14 years.

Adolescent↗
PubMed2005

Gain-of-function mutation in Nav1.7 in familial erythromelalgia induces bursting of sensory neurons.

Erythromelalgia is an autosomal dominant disorder characterized by burning pain in response to warm stimuli or moderate exercise. We describe a novel mutation in a family with erythromelalgia in SCN9A, the gene that encodes the Na(v)1.7 sodium channel. Na(v)1.7 produces threshold currents and is selectively expressed within sensory neurons including nociceptors. We demonstrate that this mutation, which produces a hyperpolarizing shift in activation and a depolarizing shift in steady-state inactivation, lowers thresholds for single action potentials and high frequency firing in dorsal root ganglion neurons. Erythromelalgia is the first inherited pain disorder in which it is possible to link a mutation with an abnormality in ion channel function and with altered firing of pain signalling neurons.

Action Potentials↗
PubMed2003

Spindle and slow wave rhythms at slow wave sleep transitions are linked to strong shifts in the cortical direct current potential.

Electroencephalographic activity at the transition from wakefulness to sleep is characterized by the appearance of spindles (12-15 Hz) and slow wave rhythms including delta activity (1-4 Hz) and slow oscillations (0.2-1 Hz). While these rhythms originate within neocortico-thalamic circuitry, their emergence during the passage into slow wave sleep (SWS) critically depends on the activity of neuromodulatory systems. Here, we examined the temporal relationships between these electroencephalogram rhythms and the direct current (DC) potential recorded from the scalp in healthy men (n=10) using cross-correlation analyses. Analyses focused on transitions from wakefulness to SWS in the beginning of the sleep period, and from SWS to lighter sleep and rapid eye movement (REM) sleep at the end of the first sleep cycle. For spindle, delta and slow oscillatory activity strong negative correlations with the DC potential were found at the transition into SWS with peak correlation coefficients (at zero time lag) averaging r=-0.81, -0.88 and -0.88, respectively (P<0.001). Though slightly lower, distinct negative correlations between these measures were also found at the transition from SWS to REM sleep (-0.78, -0.77 and -0.77, respectively, P<0.001). Fast oscillatory activity in the beta frequency band (15-25 Hz) was correlated positively with the DC potential (r=+0.75, P<0.05, at the passage to SWS). Data indicate close links between increasing spindle, delta and slow oscillatory activity and the occurrence of a steep surface negative cortical DC potential shift during the transition from wake to SWS. Likewise, a DC potential shift toward surface positivity accompanies the disappearance of these oscillatory phenomena at the end of the non-REM sleep period. The DC potential shifts may reflect gradual changes in extracellular ionic (Ca2+) concentration resulting from the generation of spindle and slow wave rhythms, or influences of neuromodulating systems on cortical excitability thereby controlling the emergence of cortical spindle and slow wave rhythms at SWS transitions.

Adult↗
PubMed2002

Women with HIV infection: a model of university-based care, training and research.

The growth of human immunodeficiency virus type-1 (HIV) infection among women in the USA has been coincident with an international momentum to better address the specific health care needs of women. This paper provides an overview of a demonstration model for comprehensive HIV care of adolescent and adult women in an academic setting. The paper contains a descriptive summary of a university-based demonstration model of comprehensive care for women with HIV infection. During 1997-1998, there were 279 urban and rural Midwest adolescent and adult women with HIV infection in care at this model programme. Medical care encompassed subspecialty HIV care, obstetrical and gynaecological care, primary care of non-HIV comorbidities, mental health assessments and family planning in a safe, university-based environment. For 279 women during the two-year period, health services included the detection and treatment of sexually transmitted diseases (56%) and cervical dysplasia (35%), perinatal care (12%) and screening and referral for substance abuse treatment (30%). There was no mother-to-child HIV transmission among 33 pregnant women enrolled in the Center prior to delivery, and transmission by three of nine women enrolled after delivery. Only 167 (60%) women were compliant with biannual medical visits during 1997-1998. Integral to the health services delivery was the provision of ancillary support services intended to enhance optimal medical care for this cohort of women. This university-based model of care also incorporated HIV provider training and formative HIV research. Structured medical and public health experiential learning opportunities occurred for medical and social work students, medicine residents, infectious diseases fellows, nurses and other professional health care workers. Clinical investigations of adolescent and adult women have complemented care and training, with funded research in HIV medication adherence and health services research. In follow-up, 71% of these women remained active in care in 1999. Retention of vulnerable populations in care may be a big challenge over the next decade, despite the availability of potent antiretroviral therapies.

Adolescent↗
PubMed2001

A high-throughput assay for mitochondrial membrane potential in permeabilized yeast cells.

A fluorometric assay for mitochondrial membrane potential in permeabilized yeast cells has been developed. This method involves permeabilizing the plasma membrane and measuring the distribution of a mitochondrial membrane potential sensitive probe 3,3'-dipropylthiadicarbocyanine iodide (DiSC(3)(5); DiSC(3)). In permeabilized cells, DiSC(3) fluorescence decreased when introduced into energized mitochondria and increased three- to sixfold when the mitochondrial membrane potential was dissipated by the chemical uncoupler carbonylcyanide m-chlorophenyl hydrazone. Plasma membrane potential was abolished by permeabilization, as shown by a lack of polarization of the plasma membrane induced by K(+) and glucose. Uncoupling protein 1 (UCP1), a mitochondrial H(+) transporter, was used as a model for method validation. The fluorescence intensity responded vigorously to specific modulators in UCP1-expressing cells. This method has been adapted as a high-throughput assay to screen for modulators of mitochondrial membrane potential.

Benzothiazoles↗
PubMed2001

Scalp recorded direct current (DC) potential shifts associated with food intake in hungry humans.

In humans, eating is assumed to be regulated within a neuronal circuitry integrating hypothalamic "feeding centers" with neocortical regions. Here, DC potentials were recorded in food deprived men to demonstrate a graded tuning of neocortical excitability in conjunction with meal ingestion. In the beginning of food ingestion a pronounced negative DC potential shift developed (P<0.01) which was replaced by a gradual positive potential shift reaching a maximum within 5 min after cessation of food intake (P<0.05). Both negative and positive shifts showed a widespread cortical distribution. The initial negative DC potential presumably reflecting increased depolarisation of apical cortical dendrites, may serve to facilitate eating behavior. The succeeding positivity points to a growing inhibitory influence on cortical processing with increasing satiety that may support termination of meal intake.

Adult↗
PubMed2001

Changes in immune cell counts and interleukin (IL)-1beta production in humans after a somnogenically active growth hormone-releasing hormone (GHRH) administration.

Growth hormone-releasing hormone (GHRH) has been shown to enhance slow-wave sleep (SWS) and non-rapid eye movement sleep in animals and humans. In animals the somnogenic effect of interleukin (IL)-1beta appears to be mediated by GHRH. Neuroimmunological interactions in sleep are most frequently studied in humans by sleep deprivation or by cytokine administration. The present study, in contrast, investigates in humans the effect of enhanced sleep through GHRH administration on selected immune parameters. Results reveal that a single intravenous bolus of 50 microg GHRH which enhanced SWS stage 4 in the first half of the night suppressed circulating suppressor T cell (CD3+/CD8+) numbers, with a similar tendency for B cells (CD19+) and suppressed mitogen-stimulated IL-1beta production. When the same amount of GHRH was administered distributed across five repetitive boluses of 10 microg GHRH within 1 h, neither corresponding sleep nor immune parameters were changed significantly compared to placebo. These data suggest that GHRH can modulate immune functions through brain mechanisms which are also involved in the regulation of sleep.

Adult↗
PubMed2001

Insecticidal proteins from Bacillus thuringiensis protect corn from corn rootworms.

Field tests of corn co-expressing two new delta-endotoxins from Bacillus thuringiensis (Bt) have demonstrated protection from root damage by western corn rootworm (Diabrotica virgifera virgifera LeConte). The level of protection exceeds that provided by chemical insecticides. In the bacterium, these proteins form crystals during the sporulation phase of the growth cycle, are encoded by a single operon, and have molecular masses of 14 kDa and 44 kDa. Corn rootworm larvae fed on corn roots expressing the proteins showed histopathological symptoms in the midgut epithelium.

Animals↗
PubMed2000

Dimensional complexity and power spectral measures of the EEG during functional versus predicative problem solving.

Electroencephalograms were recorded in 22 men while solving tasks of visual-pattern completion and during mental relaxation. They were primed (by foregoing trials) to solve these tasks either in a predicative or functional mode of thinking. Predicative thinking required that in order to complete the pattern the subject had to get involved with the logic of the static structure of the pattern and therefore had to recognize the recurrence of certain features of the elements (e.g., shape, color, and size). Functional thinking required involvement in a dynamic reading of the logic of the pattern and therefore to search for operations and actions to be performed on the pattern elements (e.g., pushing, mirroring, and rotating). The EEG complexity during predicative thinking decreased in comparison to functional thinking and mental relaxation, with this reduction being most pronounced over the right parietal cortex. A reduction in dimensional complexity during functional thinking as compared to mental relaxation, which was concentrated over the left central cortex, although significant, was less clear. The reduced EEG complexity during predicative thought, dominant over the right hemisphere, could reflect increased competitive inhibition among respective cortical neuron assemblies in association with the visual analysis of static element features, converging upon those predicates relevant for the solution.

Adult↗
PubMed2000

Slow cortical DC-potential responses to sweet and bitter tastes in humans.

Processing of hedonic stimulus quality is assumed to be accompanied by a tuning of cortical arousal and excitability. In this pilot study in 11 healthy humans scalp-recorded DC potentials were assessed during application of a sweet (sucrose) and bitter (quinine hydrochloride) taste, i.e., primary reinforcers of positive and negative quality. Muscular, ocular, and skin potential activity were controlled. Application of sucrose induced a widespread positive DC-potential shift with an amplitude of 40-50 microV and persisting for more than 120-s post-stimulus onset. Following administration of quinine hydrochloride, this positive shift was reduced, most distinctly between 48- and 88-s post-stimulus onset. The reduction appeared to be most consistent at anterior midline recording sites (Fz, Cz). It is assumed that the higher DC-potential positivity during sweetness than during bitterness points to a differential tuning of cortical excitability by a widespread decrease in depolarization of apical dendrites.

Adult↗
PubMed2000

Identification of best practices in the delivery of patient food services through public/private sector partnerships.

This article describes the evolution of public/private sector partnership in patient food service delivery and identifies skills required by executives to manage partnerships effectively, features that may be generalized to other areas; and the importance of labour relations. Site visits conducted across Canada demonstrate that when partners understand each other's objectives, commit to providing strong leadership, and create meaningful labour relations and communications strategies, partnerships can be successful.

Benchmarking↗
PubMed2000

Changes in direct current (DC) potentials and infra-slow EEG oscillations at the onset of the luteinizing hormone (LH) pulse.

An essential function of the neuroendocrine system lies in the coordination of hypothalamo-pituitary secretory activity with neocortical neuronal activity. Cortical direct current (DC) potential shifts and EEG were monitored in conjunction with the circulating concentration of luteinizing hormone (LH) in humans while asleep to assess a hypothalamic-neocortical interaction. The onset of an LH pulse was accompanied (i) at frontocortical locations by a transient positive DC potential shift of approximately 3 min duration and peak amplitude 50 microV; (ii) at frontal and central locations by an increase in power of infra-slow EEG oscillations for periodicities between 64 and 320 s. Results uniquely demonstrate a coupling of hypothalamo-pituitary activity with regulation of neocortical excitability.

Activity Cycles↗
PubMed2000

Evaluation of real-time imaging using a laparoscopic ultrasound probe during operative endoscopic procedures.

OBJECTIVES: To evaluate rigid and flexible ultrasound transducers introduced through a laparoscopic port to image pelvic anatomy during operative endoscopy as a means of mapping the pelvic anatomy, detecting pathology, and for real-time tracking of intra-uterine procedures. DESIGN: Prospective, descriptive, non-comparative. MATERIALS AND METHODS: Laparoscopy, hysteroscopy and real-time, gray-scale ultrasonography were performed simultaneously in 36 patients. Laparoscopic ultrasound was performed using 10 mm diameter, 7.5 MHz gray-scale rigid and steerable transducers for imaging of the ovaries and uterus during operative endoscopy (Aloka, Wallingford, CT, USA). All patients underwent intra-operative evaluation using this probe to assess uterine and ovarian structures and to track instruments intra-operatively during complex intra-uterine hysteroscopic procedures and for intra-operative sonohysterography. RESULTS: Laparoscopic ultrasound provided visualization of structures and delineation of ovarian anatomy needle placement for tracking microscissors and intra-operative sonohysterography. The ultrasonography provided information useful for determining the configuration of normal anatomic structures, the localization of and more precise incision placement for anatomic abnormalities and for intra-operative guidance during hysteroscopic resection of intra-uterine adhesions. The imaging also provided details of intra-uterine anatomy through sonohysterography performed during chromotubation. However, no additional information regarding ovarian or uterine abnormalities was noted beyond that detected on pre-operative transvaginal ultrasonography. No technical problems were encountered. No additional operative time was required. CONCLUSIONS: Real-time laparoscopic ultrasound imaging is useful in monitoring complex intra-uterine operative procedures and in detailing intra-uterine anatomy during intra-operative sonohysterography. However, it did not provide more enhanced imaging of ovarian anatomy beyond images obtained with pre-operative transvaginal imaging. This imaging technique may have broad application for a variety of endoscopic operative procedures with the potential to impact on operative decision-making and requires further evaluation.

Endosonography↗
PubMed2000

Prolonged hypernatremia controls elevated intracranial pressure in head-injured pediatric patients.

OBJECTIVE: To determine the effects continuous infusions of hypertonic saline (3% NaCl) on intracranial pressure (ICP) control and describe the physiologic effects of hypertonic saline administered to closed head injury children. DESIGN: Retrospective chart review. SETTINGS: Pediatric intensive care unit of a children's hospital. PATIENTS: Sixty-eight children with closed head injury. INTERVENTIONS: Intravenous infusion of 3% hypertonic saline to increase serum sodium to levels necessary to reduce ICP < or =20 mm Hg. MEASUREMENTS AND MAIN RESULTS: The patients enrolled had similar Injury Severity Scores. Treatment effectively lowered ICP in these patients and ICP was under good control a majority of the time. Only three patients (4%) died of uncontrolled elevation of ICP. No adverse effects of supraphysiologic hyperosmolarity such as renal failure, pulmonary edema, or central pontine demyelination, were noted. CONCLUSIONS: Hypertonic saline administration to children with closed head injury appears to be a promising therapy for control of cerebral edema. Further controlled trials are required to determine the optimal duration of treatment before widespread use is advocated.

Child↗
PubMed2000

Traumatic brain injury: patterns of failure of nonoperative management.

OBJECTIVE: The circumstances of failure for nonoperative management of blunt traumatic brain injury have been poorly defined. In this study, all trauma patients identified over a 12-year period with progression of neurologic injury requiring craniotomy were retrospectively reviewed. METHODS: Data collected included demographic information, mechanism of injury, field and admission vital signs, and Glasgow Coma Scale score, medications, associated injuries, and coagulopathy. Head computed tomographic scans were reviewed, and anatomic findings were correlated with clinical changes (change in mental status or elevation of intracranial pressure) that led to subsequent CT scan and craniotomy. RESULTS: Of 20,100 patients, there were 852 who had computed tomographic scans with acute intracranial injuries on admission; 462 patients were managed nonoperatively. Fifty-seven patients had progression of neurologic injury (34 < 24 hours = early; 23 > 24 hours = late) that required surgery. CONCLUSION: Of the variables investigated, only anatomic location of injury was found to be predictive of early failure of nonoperative management. Frontal intraparenchymal hematomas are particularly prone to early failure. Clinical examination and intracranial pressure monitoring are equally important in detecting failure and should be an integral part of nonoperative management.

Adult↗
PubMed2000

Assessment of hearing in persons with learning disabilities: the Phoenix NHS Trust, January 1997 to September 1998.

People with learning disabilities are at increased risk of impaired hearing. The aims of this study were to assess the prevalence of hearing impairment and ear disease in people attending the specialist Otolaryngology/Hearing Therapy clinic at the Phoenix NHS Trust, Bristol. The present and future process of such a service was explored. Data were obtained from the referral form and notes made by the consultant otolaryngologist. In 20 months, there were 226 consultations, 188 of which were new referrals. The majority of patients had verbal communication to some extent. Suspected infection/inflammation and unobtainable/abnormal tympanograms, each accounted for 43 per cent of reasons for referral. Twenty per cent of patients were normal otologically. Eighteen per cent were provided with hearing aids and nine per cent required surgery. Ten patients underwent brainstem evoked response testing, half of whom had aidable hearing. Our results are comparable to published data of similar units. It is recommended that combined otolaryngology/specialist hearing therapy services are continued and further developed.

Adult↗
PubMed2000

Scalp recorded direct current potential shifts associated with quenching thirst in humans.

As an indicator of cortical excitability, direct current (DC) potentials were recorded from thirsted subjects before, during and after drinking 400 ml of water. Self-rated thirst was distinctly reduced after drinking. Compared with control conditions in which the subjects remained thirsty, during drinking a widespread negative potential shift occurred averaging over -70 microV at Cz. At the transition from the consumatory phase to the postconsumption phase, a slow positive potential shift commenced that was most pronounced over the anterior cortex (averaging over +40 microV at Fz) and persisted for more than 3 min after drinking. Control conditions excluded muscle activity, ocular movements, and changes in body fluid and serum osmolality as possible non-neuronal sources of the DC-potential changes. The sequence of negative and positive potential shifts associated with drinking indicates a coordinate regulation of cortical excitability that may facilitate consumatory behavior and its context-dependent encoding into memory.

Adult↗