Search PubMed⌕ Search

Biomedical subjects

D A Lewis

Publications and source records attributed to D A Lewis.

At least 163 records · Page 9Linked to original sources
PubMed1996

Twenty-year experience with repair of complete atrioventricular septal defects.

BACKGROUND: To determine factors predicting mortality and morbidity after repair of complete atrioventricular septal defect, we retrospectively analyzed preoperative, operative, and postrepair factors on the outcome of 115 consecutive complete atrioventricular septal defect repairs at The Children's Hospital of Wisconsin between January 1974 and December 1993. METHODS: For the entire experience the operative mortality was 13.9% (16 patients). During the most recent era, January 1988 to December 1993, operative mortality was 3.6% (2 of 55 patients). This was significantly improved from the two previous eras, January 1974 to December 1980, 28% (7 of 25) and January 1981 to December 1987, 20% (7 of 35 patients) (p = 0.02). There were seven late deaths; 10-year actuarial survival, including operative mortality was 81%. Age at complete repair decreased; before 1982 all patients were more than 12 months of age, whereas after 1982 64% (56 of 88 patients) were 12 months of age or less. RESULTS: Moderate or severe preoperative left atrioventricular valve regurgitation was not a risk factor for operative mortality. For operative survivors with moderate to severe preoperative left atrioventricular valve regurgitation (n = 17), late postoperative left atrioventricular valve regurgitation (follow-up data available on 15 patients) was significantly reduced (severe = 1, moderate = 5, mild = 9; p = 0.007). CONCLUSIONS: Early mortality was predicted by the era of surgical repair. Conversion to routine repair during infancy was achieved with a simultaneous decrease in operative mortality. For patients with moderate to severe preoperative left atrioventricular valve regurgitation, significant improvement in the degree of left atrioventricular valve regurgitation can be expected without an increase in operative or late mortality or morbidity.

Actuarial Analysis↗
PubMed1996

An education and training initiative on dental care for the HIV-positive patient.

Workshops were established on the theme of 'HIV and the General Dental Team' to meet the expressed needs of dentists working in one family health services authority (FHSA). The workshop's effect with regard to knowledge, attitudes and working practices was assessed. A questionnaire, completed at the beginning of the day by the 29 participants, explored areas of staff knowledge, attitudes, concerns and reported practices regarding treatment of people with HIV. A second questionnaire was completed at the end of the day to enable comparisons to be made before and after the course. After the workshop, there were general improvements in the levels of knowledge about clinical signs and symptoms, oral manifestations of HIV and AIDS and modes of the transmission of HIV. A change of attitude towards the provision of dental care for people with HIV was reported by 39%, 59% were more likely to provide this care and 72% of participants said they would change their working practices, principally with respect to infection control. A follow-up survey one year later reported long term behaviour changes and requests for further support in the form of a newsletter, video or telephone helpline and a confidentiality policy for use in general practice.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Axon terminals immunolabeled for dopamine or tyrosine hydroxylase synapse on GABA-immunoreactive dendrites in rat and monkey cortex.

Dopamine afferents to the cortex regulate the excitability of pyramidal neurons via a direct synaptic input. However, it has not been established whether dopamine also modulates pyramidal cell activity indirectly through synapses on gamma-aminobutyric acid (GABA) interneurons, and whether such inputs differ across cortical regions and species. We sought to address these issues by an immunocytochemical electron microscopic approach that combined peroxidase staining for dopamine or tyrosine hydroxylase (TH) with a pre-embedding gold-silver marker for GABA. In the deep layers of the rat prefrontal cortex and in the superficial layers of the monkey prefrontal and primary motor cortices, terminal varicosities immunoreactive for dopamine or TH formed primarily thin, symmetric synapses on distal dendrites. Both GABA-immunoreactive dendrites as well as unlabeled spines and dendrites were contacted by dopamine- or TH-immunoreactive terminals. Synaptic specializations were detected at some, but not all of these contacts. The relative frequency of these appositional and synaptic contacts did not appear to differ between the rat and monkey prefrontal cortex, or between the monkey prefrontal and motor cortices. Across regions and species, labeled and unlabeled targets of dopamine- or TH-positive terminals received additional synaptic input from unlabeled, and occasionally GABA-immunoreactive terminals. Close appositions between dopamine- or TH-immunoreactive and GABA-positive terminals were observed only rarely. These findings indicate that dopamine afferents provide direct synaptic inputs to GABA local circuit neurons in a consistent fashion across cortical regions and species. Thus, dopamine's cellular actions involve direct as well as modulatory effects on both GABA interneurons and pyramidal projection neurons.

Animals↗
PubMed1995

Local circuit neurons of the prefrontal cortex in schizophrenia: selective increase in the density of calbindin-immunoreactive neurons.

Schizophrenia has been reported to be associated with alterations in GABAergic local circuit neurons of the prefrontal cortex. In this study, immunocytochemical techniques and antibodies against the calcium-binding proteins calbindin (CB) and calretinin (CR) were used to determine the laminar distribution and relative density of separate subpopulations of local circuit neurons in prefrontal cortical areas 9 and 46 from five pairs of schizophrenic and control subjects, matched for age, sex, and post-mortem interval. The laminar distribution pattern of CB-immunoreactive local circuit neurons was similar in both schizophrenic and control subjects. In both prefrontal regions, however, the density of CB-labeled neurons was 50-70% greater in schizophrenic subjects compared with control subjects, with cortical layers III and V/VI being preferentially affected. In contrast, the density of CR-IR neurons did not differ significantly between schizophrenic and control subjects. These findings reveal a selective increase in the density of a subpopulation of GABAergic local circuit neurons in the prefrontal cortex. Although other explanations for these observations must be considered, they may be consistent with the hypothesis that gene expression in GABAergic neurons is altered in schizophrenia.

Adult↗
PubMed1995

Ultrastructural associations between dopamine terminals and local circuit neurons in the monkey prefrontal cortex: a study of calretinin-immunoreactive cells.

Dopamine terminals in the monkey prefrontal cortex (PFC) synaptically target the distal dendrites of both pyramidal cells and GABA interneurons. We sought to determine whether the latter input includes the innervation of interneurons that utilize calretinin (CalR) as a calcium-binding protein. Sections through prefrontal area 9 of cynomolgus monkeys were processed by immunoperoxidase for tyrosine hydroxylase (TH) to label dopamine varicosities and by pre-embedding immunogold for CalR. Electron microscopic examination of layers 1-3 revealed numerous TH-immunoreactive (TH-ir) terminals, but few were located in the vicinity of CalR-ir dendrites. Although close appositions were sometimes detected between these labeled processes, no synaptic inputs from TH-ir terminals to CalR-ir dendrites were observed. However, in adjacent sections from the same animals, TH-ir terminals were observed to synapse on GABA-ir dendrites. These findings suggest that dopamine afferents to the monkey PFC target the subclasses of GABA interneurons that do not contain CalR.

Animals↗
PubMed1995

Does an additional source of pulmonary blood flow alter outcome after a bidirectional cavopulmonary shunt?

BACKGROUND: The bidirectional cavopulmonary shunt has become an important intermediate step in the treatment of pediatric patients with single ventricle physiology who are ultimately destined for palliative surgery. We wanted to know whether there would be risks or benefits if an additional source of pulmonary blood flow was left after a bidirectional cavopulmonary shunt. METHODS AND RESULTS: We retrospectively reviewed the medical and surgical records of all patients who underwent a bidirectional cavopulmonary shunt at the Children's Hospital of Wisconsin between January 1991 and December 1993. A total of 43 patients were identified. Anatomic diagnoses included double inlet left ventricle (14 patients), tricuspid atresia (8 patients), pulmonary atresia with intact septum (6 patients), single right ventricle (5 patients), hypoplastic left heart (3 patients), unbalanced atrioventricular septal defect (3 patients), and other complex lesions (4 patients). We then divided the patients into two groups for purposes of analysis. Group 1 had only the cavopulmonary shunt as a source of pulmonary flow (22 patients); group 2 had an additional source of pulmonary flow (21 patients). Patient age at the time of cavopulmonary shunt ranged from 6 months to 12 years, with group 1 patients being younger (31 versus 45 months, P = .05). Group 2 patients had higher postoperative central venous pressures (17.8 versus 14.1 mm Hg, P < .001) and oxygen saturations (86% versus 81%, P < .001) than did group 1 patients. There was no statistical difference between groups in the number of chest tube days or hospital days. There was 1 early death in group 1 related to severe ventricular dysfunction and 1 late death in group 2 related to sepsis. Five patients in group 2 were readmitted to the hospital for drainage of a large chylothorax compared with none in group 1 (P < .02). CONCLUSIONS: We conclude that patients with an additional source of pulmonary blood flow after bidirectional cavopulmonary shunt have higher postoperative central venous pressures, have higher oxygen saturations, and are at risk for the late development of a chylothorax.

Child↗
PubMed1995

Flavinylation of monoamine oxidase B.

Monoamine oxidase B (MAO B) catalyzes the oxidative deamination of biogenic and xenobiotic amines. The oxidative step is coupled to the reduction of an obligatory cofactor, FAD, which is covalently linked to the enzyme at Cys397. In this study, we developed a novel riboflavin-depleted (Rib-) COS-7 cell line to study the flavinylation of MAO B. ApoMAO B can be obtained by expressing MAO B cDNA in these cells. We found that MAO B is expressed equally in the presence or absence of FAD and that apoMAO B can be inserted into the outer mitochondrial membrane. Flavinylation of MAO B was achieved by introducing MAO B cDNA and different flavin derivatives simultaneously into Rib- COS-7 cells via electroporation. Since the addition of riboflavin, FMN, or FAD resulted in equal levels of MAO B activity, we conclude that the flavin which initially binds to apoMAO B is FAD. In our previous work, we used site-directed mutagenesis to show that Glu34 in the dinucleotide-binding motif of MAO B is essential for MAO B activity, and we postulated that this residue is involved in FAD binding. In this study, we tested the role of residue 34 in flavin binding by expressing wild-type or mutant MAO B cDNA in Rib- COS-7 cells with the addition of [14C]FAD. We found that Glu34 is essential for both FAD binding and catalytic activity. Thus, FAD binds to MAO B in a dual manner at Glu34 noncovalently and Cys397 covalently. We conclude that Glu34 is critical for the initial non-covalent binding of FAD and is instrumental in delivering FAD to the covalent attachment site at Cys397.

Animals↗
PubMed1995

Postnatal maturation of the dopaminergic innervation of monkey prefrontal and motor cortices: a tyrosine hydroxylase immunohistochemical analysis.

The mature functional architecture of the primate prefrontal cortex arises during a protracted period of postnatal development. Although catecholaminergic afferents arrive in the primate cortex quite early during fetal development, several lines of evidence suggest that substantial changes in the dopaminergic innervation of prefrontal cortex may occur during postnatal development. In this study, we used immunocytochemical techniques and antibodies against tyrosine hydroxylase, the rate-limiting enzyme in catecholamine biosynthesis, to examine the precise time course from birth to adulthood of the maturational changes of tyrosine hydroxylase-labeled axons in prefrontal cortical areas 9 and 46 and primary motor cortex (area 4) of rhesus monkeys. In area 9, the densities of tyrosine hydroxylase-labeled axons and varicosities in the superficial and deep cortical layers remained relatively constant during postnatal development. In contrast, marked developmental changes in innervation density occurred in the middle cortical layers. For example, in deep layer III, the density of tyrosine hydroxylase-positive varicosities was relatively low and uniform in animals under 1 month of age but then increased by a factor of three in animals 2-3 months of age. The density of labeled varicosities continued to increase, reaching a peak (sixfold greater than in the youngest animals) in animals 2-3 years of age before declining to stable adult levels. Similar laminar-specific patterns of change also occurred in areas 46 and 4, although regional differences were present in the magnitude and precise time course of these developmental changes. These findings demonstrate that the innervation of monkey frontal cortex by tyrosine hydroxylase-immunoreactive axons undergoes a protracted, laminar-specific pattern of change during postnatal development that continues through adolescence and into early adulthood. These developmental refinements may interact with other modifications of cortical circuitry that underlie the functional maturation of these regions.

Animals↗
PubMed1995

Mutagenesis at a highly conserved tyrosine in monoamine oxidase B affects FAD incorporation and catalytic activity.

Monoamine oxidase B (MAO B), an integral protein of the outer mitochondrial membrane, catalyzes the oxidative deamination of various neuroactive and vasoactive amines. A covalently bound FAD cofactor at Cys-397 of human MAO B is required for the oxidation of the amine substrates. In addition to the covalent binding site, MAO B also contains a noncovalent FAD binding region (residues 6-34) known as the dinucleotide binding motif. Previously, we have shown that Glu-34 is required for catalytic activity, presumably by forming a hydrogen bond between the carboxylate group of glutamate and the 2'-hydroxyl group of ribose in the AMP moiety of FAD. In this work, we have identified a third FAD binding site in MAO B (residues 39-46) by sequence comparisons to other flavoenzymes. The conserved sequence contains a tyrosine residue (Tyr-44) which, based on the X-ray crystal structure of ferredoxin-NADP+ reductase, is postulated to participate in FAD binding through van der Waals contact with the isoalloxazine ring and a hydrogen bond to the 3'-hydroxy of the ribityl moiety. To test the postulated role of this tyrosine residue, site-directed mutants that encode substitutions at Tyr-44 were prepared and expressed in mammalian COS-7 cells. Variant MAO B enzymes were then characterized with respect to enzymatic activity and [14C]FAD incorporation. Substitution of tyrosine with phenylalanine had no effect on MAO B activity or the level of [14C]FAD incorporation compared to the wild-type enzyme, indicating that the hydroxyl group of the tyrosine residue was not essential at residue 44.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1995

An outbreak of Burkholderia (formerly Pseudomonas) cepacia respiratory tract colonization and infection associated with nebulized albuterol therapy.

OBJECTIVE: To investigate an outbreak of Burkholderia (formerly Pseudomonas) cepacia respiratory tract colonization and infection in mechanically ventilated patients. DESIGN: A retrospective case-control and bacteriologic study. SETTING: Veterans Affairs medical center. PATIENTS: 42 mechanically ventilated patients who developed respiratory tract colonization or infection with B. cepacia and 135 ventilator-dependent controls who were not colonized and did not develop infections. MEASUREMENTS: Clinical and demographic data; benzalkonium chloride concentrations and pH levels in albuterol sulfate solutions; repetitive-element polymerase chain reaction (PCR)-mediated molecular fingerprinting on eight patient isolates and three environmental B. cepacia isolates that were available for study. RESULTS: 42 patients had B. cepacia respiratory tract colonization or infection. Observation of intensive care unit and respiratory care personnel showed faulty infection control procedures (for example, the same multiple-dose bottle of albuterol was used for many mechanically ventilated patients). More case patients (39 [92.9%]) than controls (95 [70.4%]; P = 0.006) received nebulized albuterol, and case patients (67.5 treatments) received more treatments than controls (18 treatments; P < 0.001). In-use albuterol solutions had pH values that were unstable, and benzalkonium chloride concentrations declined over time to levels capable of supporting bacterial growth. Medication nebulizers and in-use bottles of albuterol harbored B. cepacia. Molecular fingerprints of patient isolates and environmental B. cepacia isolates were identical using repetitive-element PCR. No further isolates of B. cepacia were identified after institution of appropriate infection control procedures. CONCLUSIONS: Multiple-dose medications and reliance on benzalkonium chloride as a medication preservative provide a mechanism for nosocomial spread of microorganisms, particularly if infection control procedures are not carefully followed. Repetitive-element PCR is a useful fingerprinting technique for molecular epidemiologic studies of B. cepacia.

Aged↗
PubMed1995

Characterization of a dinucleotide-binding site in monoamine oxidase B by site-directed mutagenesis.

Monoamine oxidase B (MAO B), an integral protein of the outer mitochondrial membrane, catalyzes the oxidative deamination of neuroactive and vasoactive amines. The oxidation step is coupled to the reduction of an obligatory FAD cofactor. In this study, we have examined the role of one amino acid (Glu34) in human MAO B that is thought to play a crucial role in binding to the 2'-hydroxy group of ribose in the AMP moiety of FAD. Glu34 is located within a region of the MAO B molecule of high sequence identity to the dinucleotide-binding site in other flavoproteins. In MAO B, this region is postulated to consist of a beta 1-sheet-alpha-helix-beta 2-sheet motif which culminates with a Glu at the C-terminal end of the second beta-sheet. We used site-directed mutagenesis to convert Glu at position 34 to Asp, Gln, and Ala. The wild-type and mutant cDNAs were then transiently transfected into COS-7 cells and assayed for MAO B activity. All three variants exhibited a dramatic decrease in the enzymatic activity as compared to wild-type MAO B, and only the Asp variant retained any detectable activity. Our studies indicate that the Glu34 residue in human MAO B is essential for catalysis. Whether Glu34 is responsible only for alignment of the FAD for participation in the oxidation/reduction cycle or also for the initial binding of FAD to the apoenzyme remains to be determined.

Amino Acid Sequence↗
PubMed1995

Anatomical specialization of the anterior motor speech area: hemispheric differences in magnopyramidal neurons.

The lateralization of motor speech function to the left hemisphere is supported by multiple lines of evidence, but relatively little is known about the anatomical basis of that specialization. In a preliminary study, we recently reported that area 45 of the left hemisphere (Broca's area) contained a subpopulation of magnopyramidal neurons which were significantly larger than any seen in the homotopic region of the right hemisphere (Hayes & Lewis, 1993a). In the present study we examined a larger sample of cases in order to determine how consistently this difference is present in the population, if it is specific to Broca's area or is a general feature of cortical regions mediating lateralized functions, and whether the subpopulation of large magnopyramidal neurons in left area 45 can be distinguished by their chemical phenotype. In Nissl-stained sections from 19 human brains, the mean (+/- SD) cross-sectional area of the largest layer III pyramidal neurons in area 45 was significantly (p < .0001) greater in the left hemisphere (522.1 +/- 128.3 microns2) than in the right (454.1 +/- 121.5 microns2). This interhemispheric difference appeared to be a unique characteristic of the largest neurons, since the mean size of all layer III pyramids in this area was not significantly different in the left (206.2 +/- 93.5 microns2) and right (213.3 +/- 103.9 microns2) hemispheres. In contrast to area 45, there was no interhemispheric difference in the mean cross-sectional area of the largest layer III pyramids in another lateralized region, primary motor cortex. In addition, in area 46, a region of prefrontal association cortex not known to be functionally lateralized, the mean somal size of the largest layer III pyramidal neurons was significantly (p < .001) smaller in the left hemisphere (402.4 +/- 84.9 microns2) than in the right (437.8 +/- 88.3 microns2). Finally, although the large layer III pyramids in area 45 were immunoreactive for nonphosphorylated neurofilament protein in both hemispheres, the mean cross-sectional area of the largest labeled neurons was significantly larger (p < .002) in the left hemisphere (525.2 +/- 149.0 microns2) than in the right (490.3 +/- 154.1 microns2). These findings demonstrate that layer III of Broca's area contains a distinctive subpopulation of neurons that may play an important role in the specific functional architecture of this region.

Adult↗
PubMed1995

Synchronous development of pyramidal neuron dendritic spines and parvalbumin-immunoreactive chandelier neuron axon terminals in layer III of monkey prefrontal cortex.

Postnatal development of the primate cerebral cortex involves an initial proliferation and the subsequent attrition of cortical synapses. Although these maturational changes in synaptic density have been observed across the cortical mantle, little is known about the precise time course of developmental refinements in synaptic inputs to specific populations of cortical neurons. We examined the postnatal development of two markers of excitatory and inhibitory inputs to a subpopulation of layer III pyramidal neurons in area 9 and 46 of rhesus monkey prefrontal cortex. These neurons are of particular interest because they play a major role in the flow of information both within and between cortical regions. Quantitative reconstructions of Golgi-impregnated mid-layer III pyramidal neurons revealed substantial developmental changes in the relative density of dendritic spines, the major site of excitatory inputs to these neurons. Relative spine density on both the apical and basilar dendritic trees increased by 50% during the first two postnatal months, remained at a plateau through 1.5 years of age, and then decreased over the peripubertal age range until stable adult levels were achieved. As a measure of the postnatal changes in inhibitory input to the axon initial segment of these pyramidal neurons, we determined the density of parvalbumin-immunoreactive axon terminals belonging to the chandelier class of local circuit neurons. The density of these distinctive axon terminals (cartridges) exhibited a temporal pattern of change that exactly paralleled the changes in dendritic spine density. These results suggest that subpopulations of cortical neurons may be regulated by dynamic interactions between excitatory and inhibitory inputs during development and, in concert with other data, they emphasize the cellular specificity of postnatal refinements in cortical circuitry.

Aging↗
PubMed1995

The transfer of polystyrene microspheres from the gastrointestinal tract to the circulation after oral administration in the rat.

Factors relating to the transfer of latex microspheres of 0.87 micron mean diameter from the gastrointestinal tract (GIT) to the circulation have been investigated. The rapidity of appearance and the number of particles increased when the volume of water used as a suspending vehicle was increased. This was probably due to barrier cell integrity being compromised so that the movement of particles across the enterocytes would be enhanced. Particles were swept into these channels by the waterflow. The tonicity of the fluid was important as isotonic and hypertonic saline were not as effective as water in transferring particles. Particles were transferred from GIT segments adjacent to the stomach which may in part explain the rapid appearance of particles in the circulation. Particle uptake was blocked by cytochalasin B which suggests an active component may also be involved.

Administration, Oral↗
PubMed1995

Acute gonococcal arthritis: an unusual host and pathogen combination.

A 76 year old man was admitted for evaluation and treatment of acute oligoarticular arthritis having recently returned from India. He was diabetic on admission. Neisseria gonorrhoeae was isolated from pus collected by arthrocentesis of his right knee and was subsequently found to be chromosomally resistant to penicillin. The isolate required proline for growth and expressed the protein 1B-1 serovar. These characteristics of host and pathogen are atypical in that gonococcal arthritis usually occurs in young women and is usually caused by N gonorrhoeae isolates exhibiting hypersusceptibility to penicillin, the arginine, hypoxanthine and uracil requiring auxotype, and the protein 1A serotype. The patient responded well to therapy with oral ciprofloxacin and initial high dose penicillin.

Acute Disease↗