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Biomedical subjects

D A Lewis

Publications and source records attributed to D A Lewis.

At least 127 records · Page 7Linked to original sources
PubMed1998

Oral health behaviour and the prevalence of oral manifestations of HIV infection in a group of HIV positive adults.

The objectives of this study were to assess the prevalence of oral manifestations of HIV infection, the periodontal health status and the oral health behaviour of a group of 51 HIV infected adults. The design was a cross-sectional descriptive study which took place in a community dental clinic in south London dedicated to treatment of this group of patients. Data were collected through a self-administrated questionnaire, interview and clinical examination and results showed that 76.5 per cent had one or more oral manifestations of HIV infection. Intra-oral herpes, papilloma and non-Hodgkin's lymphoma were not identified. A very positive attitude towards oral hygiene was identified. Plaque levels were low. All individuals studied had some evidence of bleeding gums.

AIDS-Related Opportunistic Infections↗
PubMed1998

Torpor in lactating Siberian hamsters subjected to glucoprivation.

Daily torpor has never been reported for any rodent species during lactation. To test whether torpor and lactation are incompatible processes, we administered 2-deoxy-D-glucose (2-DG), a glucose analog that interferes with cellular glycolysis, to Siberian hamsters during the 2nd wk postpartum. 2-DG (2,500 mg/kg of body mass) induced torpor in lactating as well as nonlactating females. Although depth of torpor did not differ between groups, duration of torpor tended to be shorter in lactating animals. Evidence of new milk bands suggests that pups were able to obtain milk from torpid dams. By contrast, dams subjected either to a combination of brief food deprivation and subsequent food restriction or just food restriction failed to display torpor, but instead cannibalized one or more pups. We conclude that torpor is possible during lactation; whether lactating dams in nature become torpid in response to energy shortages or cannibalize or abandon one or more of their offspring remains unknown.

Animals↗
PubMed1998

Advances in the care of children with heart disease.

As we enter the next millennium, we are encouraged by the progress that has been made in the care of neonates, infants, and children with heart disease. Surgical repair can be offered at an earlier age with excellent results. Diseases that were uniformly fatal in the past have improved outcomes. Research continues in the area of interventional devices such that surgical repair might be eliminated or delayed. We continue to look forward to advances in the next several years that will allow for future improvement in outcome, better quality-of-life and better long-term results.

Child↗
PubMed1997

Management of clusters of meningococcal disease. PHIS Meningococcus Working Group and Public Health Medicine Environmental Group.

Guidance on the management of clustered cases of meningococcal disease has been revised following a review of the clusters that occurred in England and Wales between 1 April 1995 and 31 March 1996. Public health action is indicated for confirmed and probable cases but not in response to possible cases. The importance of microbiological confirmation is re-emphasised. Intervention is recommended for defined target groups when two or more confirmed or probable cases occur in a preschool group or school within a four week period. We present a framework to assist in the management of clusters of invasive serogroup C infections in larger and less defined communities.

Cluster Analysis↗
PubMed1997

Reduction of synaptophysin immunoreactivity in the prefrontal cortex of subjects with schizophrenia. Regional and diagnostic specificity.

BACKGROUND: Multiple lines of evidence indicate that the prefrontal cortex is a site of dysfunction in schizophrenia. However, the apparent absence of gross structural abnormalities in this area suggests that the pathophysiological characteristics of schizophrenia may involve more subtle disturbances in prefrontal cortical circuitry, such as alterations in synaptic connectivity and transmission. In this study, immunoreactivity for synaptophysin, an integral membrane protein of small synaptic vesicles, was used to assess the integrity of cortical synaptic circuitry in schizophrenia. METHODS: Using immunocytochemical techniques and adjusted optical density measurements, we examined synaptophysin immunoreactivity in prefrontal cortical areas 9 and 46 and in area 17 (the primary visual cortex) from 10 pairs of case subjects with schizophrenia and control subjects. matched on a pairwise basis for age, sex, race, and postmortem interval, and in 5 matched pairs of nonschizophrenic psychiatric case subjects and normal control subjects. RESULTS: Compared with levels found in matched control subjects, synaptophysin immunoreactivity in areas 46 and 9 was significantly decreased (P < .001 and P < .008, respectively) across all cortical layers in the case subjects with schizophrenia. In contrast, no differences were observed in area 17. In addition, levels of synaptophysin immunoreactivity in areas 46, 9, and 17 did not differ between 5 nonschizophrenic psychiatric case subjects and their matched controls, suggesting that decreased synaptophysin levels in the prefrontal cortex of patients with schizophrenia may be specific to that disorder. CONCLUSION: Additional studies are required to determine if the decrease in levels of synaptophysin immunoreactivity is caused by a decrease in the number or size of presynaptic terminals, a decrease in the number of synaptic vesicle per terminal, or a decrease in the expression of synaptophysin. However, all of these potential explanations are consistent with a disturbance in synaptic transmission in the prefrontal cortex of patients with schizophrenia.

Adult↗
PubMed1997

Reduction of synaptophysin immunoreactivity in the prefrontal cortex of subjects with schizophrenia. Regional and diagnostic specificity.

BACKGROUND: Multiple lines of evidence indicate that the prefrontal cortex is a site of dysfunction in schizophrenia. However, the apparent absence of gross structural abnormalities in this area suggests that the pathophysiological characteristics of schizophrenia may involve more subtle disturbances in prefrontal cortical circuitry, such as alterations in synaptic connectivity and transmission. In this study, immunoreactivity for synaptophysin, an integral membrane protein of small synaptic vesicles, was used to assess the integrity of cortical synaptic circuitry in schizophrenia. METHODS: Using immunocytochemical techniques and adjusted optical density measurements, we examined synaptophysin immunoreactivity in prefrontal cortical areas 9 and 46 and in area 17 (the primary visual cortex) from 10 pairs of case subjects with schizophrenia and control subjects matched on a pairwise basis for age, sex, race, and postmortem interval, and in 5 matched pairs of nonschizophrenic psychiatric case subjects and normal control subjects. RESULTS: Compared with levels found in matched control subjects, synaptophysin immunoreactivity in areas 46 and 9 was significantly decreased (P < .001 and P < .008, respectively) across all cortical layers in the case subjects with schizophrenia. In contrast, no differences were observed in area 17. In addition, levels of synaptophysin immunoreactivity in areas 46, 9, and 17 did not differ between 5 nonschizophrenic psychiatric case subjects and their matched controls, suggesting that decreased synaptophysin levels in the prefrontal cortex of patients with schizophrenia may be specific to that disorder. CONCLUSIONS: Additional studies are required to determine if the decrease in levels of synaptophysin immunoreactivity is caused by a decrease in the number or size of presynaptic terminals, a decrease in the number of synaptic vesicles per terminal, or a decrease in the expression of synaptophysin. However, all of these potential explanations are consistent with a disturbance in synaptic transmission in the prefrontal cortex of patients with schizophrenia.

Adult↗
PubMed1997

Axosomatic input to subpopulations of cortically projecting pyramidal neurons in primate prefrontal cortex.

Pyramidal cells, the major class of cortical excitatory neurons, can be divided into different subpopulations based upon the target region of their principal axon projection. The activity of pyramidal neurons is regulated in part through inhibitory synaptic inputs to the soma from local circuit neurons. However, little is known about how the density of these axosomatic inputs differs among subpopulations of pyramidal neurons in the prefrontal cortex of primates. In this study, retrograde transport of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) was used to identify pyramidal neurons in monkey prefrontal cortex (areas 9 and 46), which were labeled via either associational (ipsilateral hemisphere) or callosal (contralateral hemisphere) principal axon projections. Ultrastructural analysis revealed that the relative number of terminals apposed to the somatic membrane did not differ between associational and callosal neurons. However, neurons in the supragranular layers were apposed by a significantly greater number of axon terminals than were neurons in the infragranular layers. These findings suggest that the laminar environment of a neuron may play a more important role than principal axon projection in determining the amount of axosomatic inhibitory input it receives.

Analysis of Variance↗
PubMed1997

Prenatal ultrasonography frequently fails to diagnose congenital diaphragmatic hernia.

Despite increased use of prenatal ultrasonography and well-defined guidelines to aid in the detection of congenital diaphragmatic hernia (CDH), approximately half of neonates born with CDH undergo a prenatal scan that does not diagnose the defect. The purpose of this study was to (1) examine the use of prenatal ultrasonography in neonates with CDH, (2) determine possible reasons that contributed to the failure to detect the abnormality, and (3) evaluate the clinical impact of a diagnostic versus a nondiagnostic study. From 1985 to 1995, 136 consecutive neonates with CDH symptomatic within 24 hours of birth were treated at the University of Michigan Medical Center. Medical records and a University of Michigan CDH database were reviewed for prenatal ultrasound status, side of herniation, site of birth, survival, and extracorporeal life support (ECLS) use. Sonograms that did not diagnose CDH were collected and reviewed by a radiologist for possible-reasons why the diagnosis was missed. Over the 10-year period, use of ultrasonography increased from 33% to 100%, but the false-negative rate remained approximatedly 55%. In reviewing 40 nondiagnostic studies in 25 patients, 25% had technical difficulties, 57% failed to follow established guidelines (localization of the stomach and visulization of the heart with all four chambers), and 33% missed findings (intrathoracic stomach and mediastinal shift) consistent with CDH. There was no significant difference in survival or use of ECLS between neonates with a diagnostic versus nondiagnostic study (53% v 77% survival, P = 0.09; 64% v 42% ECLS, P = .29) Careful attention to following established guidelines and an increased appreciation for the abnormalities would be expected to increase the sensitivity of ultrasonography in detecting CDH. Increased prenatal diagnosis will allow for thorough evaluation for associated malformations, detection of chromosomal abnormalities, and early referra with intrauterine transport to a tertiary care center before delivery.

False Negative Reactions↗
PubMed1997

Peripubertal refinement of the intrinsic and associational circuitry in monkey prefrontal cortex.

The peripubertal elimination of axospinous synapses and dendritic spines in monkey prefrontal cortex suggests that this region undergoes substantial reorganization during late postnatal development. Understanding the functional impact of these maturational refinements requires knowledge of the specific presynaptic elements involved in these changes. Two potential sources of these presynaptic terminals are the intrinsic axon collaterals furnished by pyramidal cells within a region and the associational axons that arise from pyramidal neurons in other cortical regions in the same hemisphere. In the adult, both of these types of axon terminals form synapses predominantly with dendritic spines on other pyramidal neurons, and thus they may be preferentially involved in the peripubertal pruning of axospinous synapses and dendritic spines. In order to test this hypothesis, iontophoretic injections of the anterograde tracer biotinylated dextran amine were made into the superficial layers of areas 9 or 46 of the prefrontal cortex of four prepubertal juvenile (14.9-21.5 months old) and three young adult macaque monkeys. Tangential reconstructions revealed a stripe-like pattern of labeled terminals for intrinsic and associational projections in both juvenile and adult animals. During puberty, the intrinsic circuitry underwent extensive topographic refinement, as demonstrated by a 42.7% decrease in stripe area and a 28.0% increase in gap distance between stripes. Furthermore, the mediolateral tangential spread of labeled stripes around the injection site decreased by 27.0%. In contrast, topographic refinement was not evident in the associational circuitry. In both layers 1 and 3, the densities of varicosities and branch points on labeled axons decreased by about 50% in intrinsic stripes during puberty, but only by approximately 30% in associational stripes. These findings suggest that the spatial form and magnitude of peripubertal refinements in prefrontal cortical connectivity may be specific for certain neural elements.

Aging↗
PubMed1997

Specificity of head-up tilt testing in adolescents: effect of various degrees of tilt challenge in normal control subjects.

OBJECTIVES: This study sought to determine the specificity of commonly used tilt protocols in children. BACKGROUND: Tilt table testing is commonly utilized in the evaluation of children and adolescents with syncope despite a lack of uniformity in tilt protocols and a lack of studies of specificity in normal control subjects. METHODS: Sixty-nine normal control volunteers (12 to 18 years old, 38 male, 31 female) with no previous history of syncope, presyncope or arrhythmia underwent tilting to 80 degrees, 70 degrees or 60 degrees for a maximum of 30 min on a motorized table with a footboard support. Autonomic maneuvers, including deep breathing, carotid massage, Valsalva maneuver and diving reflex, were performed before tilt testing to determine whether the response to these maneuvers could identify subjects prone to fainting during tilt testing. RESULTS: Symptoms of presyncope and frank syncope were elicited in 24 of 69 subjects (13 male, 11 female): 6 (60%) of 10 were tilted at 80 degrees, 9 (29%) of 31 at 70 degrees and 9 (32%) of 28 at 60 degrees. Tilt testing at 80 degrees was terminated after the tenth subject by the institutional review board. The mean time to a positive test response was 10.5 min at 80 degrees, 14.2 min at 70 degrees and 13.2 min at 60 degrees. In the 80 degrees tilt, 4 of 10 subjects had a positive response within 10 minutes, whereas only 3 of 31 and 2 of 28 had a positive response within < 10 min at 70 degrees and 60 degrees tilt angles, respectively. Subjects with and without a positive response to tilt testing were similar with respect to age; gender; PR, QRS and QT intervals; and baseline heart rate and blood pressure. Likewise, responses to other autonomic function tests performed were similar in tilt-positive and tilt-negative patients. The power for detecting a significant difference between patients tilted at 80 degrees versus 60 degrees and 70 degrees was 0.45 and for detecting differences in autonomic tone between tilt-positive (n = 24) and tilt-negative (n = 45) subjects was 0.8. CONCLUSIONS: Children appear to be more susceptible to orthostatic stress than adults. Therefore, tilt protocols commonly used in adults lack specificity in teenage patients. A specificity > 85% may be obtained by performing the tilt test at 60 degrees or 70 degrees for no longer than 10 min.

Adolescent↗
PubMed1997

Production of endothelium-derived factors from sodded expanded polytetrafluoroethylene grafts.

PURPOSE: Experiments were designed to determine whether endothelium isolated from adipose tissue and sodded onto expanded polytetrafluoroethylene grafts release endothelium-derived vasoactive factors. METHODS: Thin-walled expanded polytetrafluoroethylene grafts (6 mm internal diameter, 6 cm length, 30 microm pore size), one sodded with autogenous endothelial cells, the other unsodded, were implanted bilaterally in carotid arteries of 30 male mongrel dogs. Dogs were treated with 325 mg aspirin daily. After 6 weeks grafts were excised and perfused in a bioassay system. Effluent from the grafts stimulated with either acetylcholine, thrombin, adenosine 5-diphosphate, or the calcium ionophore A23187 was superfused over rings of canine femoral arteries without endothelium contracted with phenylephrine. Effluent from the grafts was analyzed by radioimmunoassay for thromboxane B2, 6-keto-prostaglandin F1alpha, endothelin-1, and C-type natriuretic peptide. RESULTS: Ninety percent of the sodded grafts and 87% of the unsodded grafts were patent after 6 weeks. Bioassay rings superfused with effluent from sodded grafts stimulated with acetylcholine relaxed significantly more than rings superfused with effluent from similarly stimulated unsodded grafts. Biochemical analysis of the effluent showed an increase in 6-keto prostaglandin F1alpha and C-type natriuretic peptide and a decrease in endothelin-1 and thromboxane B2 release from the sodded compared with the unsodded grafts. Scanning electron microscopy showed a continuous layer of endothelial cells lining only the sodded grafts. Staining for alpha-actin and heavy-chain myosin showed a differentiated layer of smooth muscle below the endothelial layer on the sodded grafts. Finally, there was positive staining for C-type natriuretic peptide and endothelin-1 in the endothelium of the sodded grafts. CONCLUSIONS: These results indicate that endothelial cells of sodded expanded polytetrafluoroethylene grafts produce endothelium-derived vasoactive factors. In addition, receptor-coupled synthesis/release of these factors is retained in sodded endothelial cells.

6-Ketoprostaglandin F1 alpha↗
PubMed1997

Development of the prefrontal cortex during adolescence: insights into vulnerable neural circuits in schizophrenia.

Multiple lines of evidence suggest that the prefrontal cortex is a site of dysfunction in schizophrenia. In addition, one of the characteristics of this disorder is the tendency for clinical symptoms to appear first during late adolescence or early adulthood. Recent studies in nonhuman primates have shown that the connectivity of the prefrontal cortex is substantially refined during adolescence, suggesting that these developmental changes may be critical for the appearance of the clinical features of schizophrenia. This article reviews data demonstrating that these late developmental changes are selective for particular neural elements in the prefrontal cortex and that they are synaptically linked. It is suggested that these neural elements comprise a functional circuit that is likely to be especially vulnerable in schizophrenia, a hypothesis that can be directly tested in postmortem studies.

Adolescent↗
PubMed1997

Differential distribution of corticotropin-releasing hormone immunoreactive axons in monoaminergic nuclei of the human brainstem.

Corticotropin-releasing hormone (CRH) has been implicated in a variety of physiological and behavioral responses to stress, as well as in the pathophysiology of certain psychiatric disorders. Although studies in rodents support a neuromodulatory influence of CRH on monoamine neurotransmission in a number of brain regions, little information in available to support a similar role for CRH in the human brain. The present study used immunocytochemistry to characterize the anatomical organization of CRH-immunoreactive axons in the human brainstem. Substantial regional differences in the density and distribution of CRH-immunoreactive axons were found in the dopamine-, noradrenaline- and serotonin-containing cell body regions of the human brainstem. Dense networks of CRH-immunoreactive axons were found in the medial subnuclei of the ventral mesencephalon and in the dorsolateral region of the locus coeruleus. Moderate densities of CRH-positive fibers were located in the median and dorsal raphe, whereas lower numbers of CRH-labeled axons appeared in the substantia nigra pars compacta. In addition, differences in CRH innervation density were observed within each region. For example, the dorsal tier of the substantia nigra contained a greater density of CRH-labeled axons than the ventral tier. In all monoamine-containing nuclei, CRH-labeled axons exhibited numerous beaded varicosities and fine intervaricose segments. The differential distribution of CRH-containing axons across these human brainstem nuclei suggests that the influence of CRH on monoamine function may be neurotransmitter-specific.

Adult↗
PubMed1997

Schizophrenia and disordered neural circuitry.

The knowledge of how alterations in neural circuitry relate to the symptoms of schizophrenia may depend on our ability to disentangle a complex cascade of pathological events that affect multiple brain regions. Recent progress in Alzheimer's disease research may provide several useful guiding principles in this pursuit.

Alzheimer Disease↗
PubMed1997

Valve repair and replacement in children.

Therapy for valvular heart disease in children has undergone tremendous progress over the past two decades. Interventional catheterization techniques were pioneered with balloon valvuloplasty of pulmonic stenosis in infants. Therapeutic catheterization is the treatment of choice in critical pulmonic stenosis but remains somewhat controversial for neonatal aortic stenosis. The use of cryopreserved homografts has improved reconstruction of the right ventricular outflow tract. The pulmonary autograft (Ross) technique for aortic valve replacement has now been applied in neonates, infants, and small children. Medium-term results of this technique are now becoming available. Innovations have been few, however, in the therapy of tricuspid valve anomalies, especially Ebstein's malformation. Annuloplasty and repair techniques are used very effectively for mitral insufficiency, whereas congenital mitral stenosis remains extremely problematic in the younger child.

Bioprosthesis↗
PubMed1997

Gender and transcriptional regulation of NO synthase and ET-1 in porcine aortic endothelial cells.

Experiments were designed to determine whether normal fluctuations in sex steroid hormones alter gene transcription for endothelial nitric oxide synthase (NOS) and preproendothelin-1 (prepro-ET-1). Aortic endothelial cells were removed from adult, gonadally intact male and female or ovariectomized Yorkshire pigs. Endothelial cells were prepared for Northern blot analysis, Western blot analysis or enzyme activity. Nitric oxide products (NOx) and endothelin-1 (ET-1) in plasma were measured by chemiluminescence and radioimmunoassay, respectively. Northern blot analysis identified single bands corresponding to endothelial NOS and prepro-ET-1. Quantification of the blots showed an increase in expression of mRNA for both endothelial NOS and prepro-ET-1 in ovariectomized pigs compared with gonadally intact male and female pigs. There were no differences in amount of endothelial NOS protein identified by Western blot analysis among groups. On the contrary, plasma concentrations of NOx were significantly decreased in ovariectomized pigs, and there were no differences either in the concentrations of ET-1 in the plasma or extracts from the coronary arteries. These results suggest that expression of endothelial NOS and prepro-ET-1 may be regulated at transcriptional level by ovarian hormones. In addition, the ovarian hormones may regulate production of these endothelium-derived factors at the posttranscriptional level.

Animals↗
PubMed1997

Cytoarchitecture of the entorhinal cortex in schizophrenia.

OBJECTIVE: The purpose of this study was to determine whether schizophrenia is associated with abnormalities in neuronal migration in the entorhinal cortex. METHOD: Nissl-stained sections through three cytoarchitectonic subdivisions of the entorhinal cortex were examined in postmortem brain specimens from 10 schizophrenic subjects and 10 matched normal comparison subjects. RESULTS: No qualitative differences in cytoarchitecture were observed between the schizophrenic and comparison subjects. CONCLUSIONS: These findings do not replicate previous reports of cytoarchitectural disturbances in the entorhinal cortex of schizophrenic subjects and thus fail to support the hypothesis of abnormal neuronal migration in schizophrenia.

Entorhinal Cortex↗