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Biomedical subjects

J Thompson

Publications and source records attributed to J Thompson.

At least 181 records · Page 10Linked to original sources
PubMed1999

Fentanyl and morphine, but not remifentanil, inhibit acetylcholine release in pontine regions modulating arousal.

BACKGROUND: Opioids inhibit the rapid eye movement (REM) phase of sleep and decrease acetylcholine (ACh) release in medial pontine reticular formation (mPRF) regions contributing to REM sleep generation. It is not known whether opioids decrease ACh release by acting on cholinergic cell bodies or on cholinergic axon terminals. This study used in vivo microdialysis to test the hypothesis that opioids decrease ACh levels at cholinergic neurons in the laterodorsal tegmental nuclei (LDT) and LDT axon terminals in the mPRF. METHODS: Nine male cats were anesthetized with halothane, and ACh levels within the mPRF or LDT were assayed using microdialysis and high-pressure liquid chromatography (HPLC). ACh levels were analyzed in response to dialysis of the mPRF and LDT with Ringer's solution (control), followed by dialysis with Ringer's solution containing morphine sulfate (MSO4) or naloxone. ACh in the mPRF also was measured during either dialysis delivery or intravenous infusion of remifentanil and during dialysis delivery of fentanyl. RESULTS: Compared with dialysis of Ringer's solution, microdialysis with MSO4 decreased ACh by 23% in the mPRF and by 30% in the LDT. This significant decrease in ACh was antagonized by naloxone. MSO4 and fentanyl each caused a dose-dependent decrease in mPRF ACh when delivered by dialysis. Remifentanil delivered by continuous intravenous infusion or by dialysis into the mPRF did not alter mPRF ACh. CONCLUSIONS: Morphine inhibits ACh at the cholinergic cell body region (LDT) and the terminal field in the mPRF. ACh in the mPRF was not altered by remifentanil and was significantly decreased by fentanyl. Thus, MSO4 and fentanyl disrupt cholinergic neurotransmission in the LDT-mPRF network known to modulate REM sleep and cortical electroencephalographic activation. These data are consistent with the possibility that inhibition of pontine cholinergic neurotransmission contributes to arousal state disruption by opioids.

Acetylcholine↗
PubMed1999

Crystallization and preliminary X-ray analysis of the 6-phospho-alpha-glucosidase from Bacillus subtilis.

6-Phospho-alpha-glucosidase (GlvA) is the protein involved in the dissimilation of alpha-glycosides accumulated via a phosphoenolpyruvate-dependent maltose phosphotransferase system (PEP-PTS) in Bacillus subtilis. The purified enzyme has been crystallized in a form suitable for X-ray diffraction analysis. Thin rod-like crystals have been grown by the hanging-drop method in the presence of manganese and NAD. They diffract beyond 2.2 A using synchrotron radiation and belong to the space group I222 (or its enantiomorph) with unit-cell dimensions a = 83.26, b = 102.56, c = 145.31 A and contain a single molecule of GlvA in the asymmetric unit.

Bacillus subtilis↗
PubMed1999

N5-(L-1-carboxyethyl)-L-ornithine synthase: physical and spectral characterization of the enzyme and its unusual low pKa fluorescent tyrosine residues.

N5-(L-1-carboxyethyl)-L-ornithine synthase [E.C. 1.5.1.24] (CEOS) from Lactococcus lactis has been cloned, expressed, and purified from Escherichia coli in quantities sufficient for characterization by biophysical methods. The NADPH-dependent enzyme is a homotetramer (Mr approximately equal to 140,000) and in the native state is stabilized by noncovalent interactions between the monomers. The far-ultraviolet circular dichroism spectrum shows that the folding pattern of the enzyme is typical of the alpha,beta family of proteins. CEOS contains one tryptophan (Trp) and 19 tyrosines (Tyr) per monomer, and the fluorescence spectrum of the protein shows emission from both Trp and Tyr residues. Relative to N-acetyltyrosinamide, the Tyr quantum yield of the native enzyme is about 0.5. All 19 Tyr residues are titratable and, of these, two exhibit the uncommonly low pKa of approximately 8.5, 11 have pKa approximately 10.75, and the remaining six titrate with pKa approximately 11.3. The two residues with pKa approximately 8.5 contribute approximately 40% of the total tyrosine emission, implying a relative quantum yield >1, probably indicating Tyr-Tyr energy transfer. In the presence of NADPH, Tyr fluorescence is reduced by 40%, and Trp fluorescence is quenched completely. The latter result suggests that the single Trp residue is either at the active site, or in proximity to the sequence GSGNVA, that constitutes the beta alphabeta fold of the nucleotide-binding domain. Chymotrypsin specifically cleaves native CEOS after Phe255. Although inactivated by this single-site cleavage of the subunit, the enzyme retains the capacity to bind NADPH and tetramer stability is maintained. Possible roles in catalysis for the chymotrypsin sensitive loop and for the low pKa Tyr residues are discussed.

Amino Acid Oxidoreductases↗
PubMed1999

Clinico-neuropathological correlation of Alzheimer's disease in a community-based case series.

OBJECTIVES: Most clinico-neuropathological correlative studies of Alzheimer's Disease (AD) are based on research cohorts that are not necessarily generalizable to patients seen in the general medical community. In this study, we examine the accuracy of the criteria used in diagnosing AD in a community-based case series of patients with memory complaints. DESIGN AND PARTICIPANTS: Clinical and neuropathological diagnoses were obtained from 134 patients evaluated for dementia who subsequently underwent autopsy. SETTING: Subjects who exhibited new symptoms of dementia and were enrolled in the University of Washington/Group Health Cooperative Alzheimer's Disease Patient Registry were eligible for this study. MEASUREMENTS: Clinico-pathological correlation was performed using NINCDS-ADRDA (National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association) and CERAD (Consortium to Establish a Registry for Alzheimer's Disease) criteria. RESULTS: Ninety-five of the 134 cases studied met CERAD neuropathological criteria for AD. The sensitivity of NINCDS-ADRDA "probable AD" was 83% (diagnosing AD correctly) and overall clinical diagnostic accuracy was 75%. However, there was a high rate of additional neuropathological findings. Only 34 of the 94 cases had pure AD on neuropathology, whereas the remainder frequently had coexisting vascular or Parkinson's disease lesions. CONCLUSIONS: This study of a large series of community-based incident dementia cases provides a way of judging the adequacy of currently available clinical diagnostic criteria. It also shows that co-existing neuropathological findings are common in community-based AD.

Aged↗
PubMed1999

Signal recognition particle receptor (SRPR) is downregulated in a rat model of cyclosporin A-induced gingival overgrowth.

Differential display is a powerful technique which can be used to identify those genes whose expression is altered between two or more tissues under investigation. We have applied differential display to a rat model of cyclosporin A-induced gingival overgrowth (CIGO) to identify genes which are differentially expressed as a result of drug treatment. Ten weanling Wistar rats were fed with a pelleted diet containing cyclosporin A (CsA) at 120 mg/kg for 10 d and then 200 mg/kg for a further 30 d prior to culling. Experimental rats were compared with 10 age/sex-matched rats on a control diet. Significant evidence of overgrowth was observed in the interdental papilla between the mandibular first and second molar teeth in the CsA group. Differential display was performed on total cellular RNA extracted from the mandibular buccal gingiva. A cDNA product was isolated which was underexpressed in the overgrowth tissue and demonstrated a 95% sequence homology to the human signal recognition particle receptor (Human Docking Protein). Preliminary studies indicate that this gene is also underexpressed in human CIGO tissue. The method of approach and the potential implications of our findings are discussed.

Animals↗
PubMed1999

Bacterial species- and strain-dependent induction of tissue factor in human vascular endothelial cells.

A cardinal process in bacterial endocarditis (BE) is the activation of the clotting system and the formation of a fibrin clot on the inner surface of the heart, the so-called endocardial vegetation. The processes that lead to the activation of the clotting system on endothelial surfaces upon exposure to bacteria are largely unknown. In the present study, we investigated in an in vitro model whether infection of human endothelial cells (EC) with bacteria that are relevant to BE, such as Staphylococcus aureus, Streptococcus sanguis, and Staphylococcus epidermidis, leads to induction of tissue factor (TF)-dependent procoagulant activity (TFA) and whether this process is influenced by host factors, such as interleukin-1 (IL-1), that are produced in response to the bacteremia in vivo. The results show that S. aureus binds to and is internalized by EC, resulting in expression of TF mRNA and TF surface protein as well as generation of TFA within 4 to 8 h after infection. No TFA was found when EC were exposed to UV-irradiated S. aureus or bacterial cell wall fragments. S. sanguis and S. epidermidis, although also binding to EC, did not induce endothelial TFA. This indicates a species and strain dependency. EC also expressed TFA after exposure to IL-1. The enhanced TFA of EC after exposure to S. aureus was not prevented by IL-1 receptor antagonist, arguing against an auto- or paracrine contribution of endogenous IL-1. When IL-1 was applied together with bacteria, this had a synergistic effect on the induction of EC TFA. This was found in particular with S. aureus but also, although to a lesser degree, with S. sanguis and S. epidermidis. This influence of IL-1 on the species- and strain-dependent induction of EC TFA suggests that bacterial factors as well as host factors orchestrate the induction of coagulation in an early stage in the pathogenesis of endovascular disease, such as BE.

Cells, Cultured↗
PubMed1999

Cellobiose-6-phosphate hydrolase (CelF) of Escherichia coli: characterization and assignment to the unusual family 4 of glycosylhydrolases.

The gene celF of the cryptic cel operon of Escherichia coli has been cloned, and the encoded 6-phospho-beta-glucosidase (cellobiose-6-phosphate [6P] hydrolase; CelF [EC 3.2.1.86]) has been expressed and purified in a catalytically active state. Among phospho-beta-glycosidases, CelF exhibits unique requirements for a divalent metal ion and NAD(+) for activity and, by sequence alignment, is assigned to family 4 of the glycosylhydrolase superfamily. CelF hydrolyzed a variety of P-beta-glucosides, including cellobiose-6P, salicin-6P, arbutin-6P, gentiobiose-6P, methyl-beta-glucoside-6P, and the chromogenic analog, p-nitrophenyl-beta-D-glucopyranoside-6P. In the absence of a metal ion and NAD(+), purified CelF was rapidly and irreversibly inactivated. The functional roles of the cofactors have not been established, but NAD(+) appears not to be a reactant and there is no evidence for reduction of the nucleotide during substrate cleavage. In solution, native CelF exists as a homotetramer (M(w), approximately 200,000) composed of noncovalently linked subunits, and this oligomeric structure is maintained independently of the presence or absence of a metal ion. The molecular weight of the CelF monomer (M(r), approximately 50,000), estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, is in agreement with that calculated from the amino acid sequence of the polypeptide (450 residues; M(r) = 50,512). Comparative sequence alignments provide tentative identification of the NAD(+)-binding domain (residues 7 to 40) and catalytically important glutamyl residues (Glu(112) and Glu(356)) of CelF.

Amino Acid Sequence↗
PubMed1999

Molecular, serological and population studies of the alleles and products of HLA-B*41.

The HLA-B41 specificity was first identified over 25 years ago and, although both serological and biochemical studies have suggested its subdivision, it is only recently that two HLA-B*41 alleles (B*4101 and B*4102) have been identified and sequenced. We designed three oligonucleotide primers, combined in two mixtures to define these alleles by PCR using sequence-specific primers (PCR-SSP) in a random normal population of 9,464 HLA-A, B, DR, DQ typed Northern European Caucasoid donors from the Welsh Bone Marrow Donor Registry. The HLA-B41 phenotype frequency was 0.835%, and of the 79 HLA-B41 subjects 22 (27.85%) were B*4101 and 57 (72.15%) were B*4102. The phenotype frequencies of B*4101 and B*4102 were 0.232 and 0.602%, respectively, and the gene frequencies were 0.00116 and 0.00301, respectively. Formal two-locus linkage disequilibrium (LD) analysis demonstrated significant associations between B*4101 and A30 and DR11, and between B*4102 and A66 and DR13. LD analysis of three loci showed significant associations between B*4101, DR7, DQ2 and B*4101, DR11, DQ7 (DQB1*0301/0304) and between HLA-A3, B*4102, DR13; A66, B*4102, DR7; A66, B*4102, DR13; B*4102, DR13, DQ6 and B*4102, DR13, DQ7. Examination of the HLA phenotypes (including HLA-C) of the B*41 subjects, together with the LD analysis findings, suggested four different HLA haplotypes bearing B*4101 and five B*4102 haplotypes. The most frequent B*4101 haplotype was: HLA- A30 or other A allele, Cw*1701, B*4101, DRB1*1102, DQB1*0301 and the most freqent B*4102 haplotype was: A*6601 or A3 or other A allele, Cw*1701, B*4102, DRB1*1303, DQB1*0301. In addition, the well-known association of A66 with B41 was between A*6601 and B*4102, and although both B*41 alleles were commonly in association with Cw*1701, B*4101 was found with Cw*07. One-dimensional isoelectric focusing (1D-IEF) analysis of HLA-B proteins from 2 B*4101 and 2 B*4102 subjects clearly showed that the B41.1 and B41.2 1D-IEF variants, identified in the 10th International Histocompatibility Workshop, corresponded to B*4101 and B*4102 products, respectively. Serological titration studies, with 59 lymphocytotoxic pregnancy antisera, containing an HLA-B41 component and stimulated by up to five different HLA-B specificities, were unable to differentiate the two groups of B*41 subjects. This suggests that partition of the HLA-B41 specificity will not normally be achieved by classical serological methods. It is suggested that the previous alleged serological subdivision of HLA-B41 was founded on the unwitting use of antisera detecting the HLA-Cw*17 products.

Alleles↗
PubMed1999

Psychiatric aspects of sexual abuse involving persons with developmental disabilities.

OBJECTIVE: To consider psychiatric issues that relate to the prevention and management of sexual abuse involving persons with developmental disabilities as either abusers or victims. METHOD: Seven case descriptions illustrate the clinical challenges raised by allegations of sexual abuse. RESULTS: Mental disorders and communication problems often coexist with the cognitive impairment that is primary in developmental disabilities. Pedophilic behaviour prompts allegations of abuse, and posttraumatic stress disorder often follows abuse. Difficulties communicating with others may preclude the detection of abuse or normal legal proceedings once an allegation is made. CONCLUSIONS: Psychiatric expertise applied both directly and indirectly through others is relevant in the prevention of sexual abuse and the management of those with developmental disabilities who are abusers or abused.

Adult↗
PubMed1999

Effects of sleep and sleep deprivation on catecholamine and interleukin-2 levels in humans: clinical implications.

The objective of this study was to evaluate the effects of nocturnal sleep, partial night sleep deprivation, and sleep stages on catecholamine and interleukin-2 (IL-2) levels in humans. Circulating levels of catecholamines and IL-2 were sampled every 30 min during 2 nights: undisturbed, baseline sleep and partial sleep deprivation-late night (PSD-L; awake from 0300-0600 h) in 17 healthy male volunteers. Sleep was monitored somnopolygraphically. Sleep onset was associated with a significant (P < 0.05) decline of circulating concentrations of norepinephrine and epinephrine, with a nocturnal nadir that occurred 1 h after nocturnal sleep. On the PSD-L night, levels of norepinephrine and epinephrine significantly (P < 0.05) increased in association with nocturnal awakening. During stage 3-4 sleep, levels of norepinephrine, but not epinephrine, were significantly lower (P < 0.05) compared to average levels during the awake period, stages 1-2 sleep, and rapid eye movement sleep. Nocturnal levels of circulating IL-2 did not change with sleep onset or in relation to PSD-L or the various sleep stages. We conclude that sleep onset is associated with changes in levels of circulating catecholamines. Loss of sleep and disordered sleep with decreases in slow wave sleep may serve to elevate nocturnal catecholamine levels and contribute to cardiovascular disease.

Adult↗
PubMed1999

Radiation-induced DNA base damage detected in individual aerobic and hypoxic cells with endonuclease III and formamidopyrimidine-glycosylase.

X-ray-induced DNA base damage can be detected using endonuclease III and formamidopyrimidine-glycosylase, which create DNA strand breaks at enzyme-sensitive sites. Strand breaks can then be measured with excellent sensitivity using the alkaline comet assay, a single-cell gel electrophoresis method that detects DNA damage in individual cells. In using this approach to measure the oxygen enhancement ratio (OER) for radiation-induced base damage, we observed that the number of enzyme-sensitive sites increased with dose up to 4 Gy in air and 12 Gy in hypoxic WIL2NS cells. After rejoining of radiation-induced strand breaks, base damage was detected more easily after higher doses. The number of radiation-induced enzyme-sensitive sites was similar under both air and nitrogen. Base damage produced by hydrogen peroxide and 4-nitroquinoline-N-oxide (4NQO) was also measured. Results with hydrogen peroxide (20 min at 4 degrees C) were similar to those observed for X rays, indicating that enzyme-sensitive sites could be detected most efficiently when few direct strand breaks were present. Removing DNA-associated proteins before irradiation did not affect the ability to detect base damage. Base damage produced by 4NQO (30 min at 37 degrees C) was readily apparent after treatment with low concentrations of the drug when few 4NQO-induced strand breaks were present, but the detection sensitivity decreased rapidly as direct strand breaks increased after treatment with higher concentrations. We conclude that: (1) the OER for base damage is approximately 1.0, and (2) the presence of direct DNA strand breaks (>2000-4000 per cell) prevents accurate detection of base damage measured as enzyme-sensitive sites with the alkaline comet method.

4-Nitroquinoline-1-oxide↗
PubMed1999

The liver fatty acid binding protein--comparison of cavity properties of intracellular lipid-binding proteins.

The crystal and solution structures of all of the intracellular lipid binding proteins (iLBPs) reveal a common beta-barrel framework with only small local perturbations. All existing evidence points to the binding cavity and a poorly delimited 'portal' region as defining the function of each family member. The importance of local structure within the cavity appears to be its influence on binding affinity and specificity for the lipid. The portal region appears to be involved in the regulation of ligand exchange. Within the iLBP family, liver fatty acid binding protein or LFABP, has the unique property of binding two fatty acids within its internalized binding cavity rather than the commonly observed stoichiometry of one. Furthermore, LFABP will bind hydrophobic molecules larger than the ligands which will associate with other iLBPs. The crystal structure of LFABP contains two bound oleate molecules and provides the explanation for its unusual stoichiometry. One of the bound fatty acids is completely internalized and has its carboxylate interacting with an arginine and two serines. The second oleate represents an entirely new binding mode with the carboxylate on the surface of LFABP. The two oleates also interact with each other. Because of this interaction and its inner location, it appears the first oleate must be present before the second more external molecule is bound.

Amino Acid Sequence↗
PubMed1999

The hazards of vinyl glove ingestion in the mentally retarded patient with pica: new implications for surgical management.

OBJECTIVE: To report experience with the treatment of complications of vinyl glove ingestion in mentally retarded patients with pica. DESIGN: A retrospective case series. SETTING: Two university-affiliated hospitals. PATIENTS: Five mentally retarded patients, 4 with a history of pica, who were admitted for the management of complications resulting from the ingestion of vinyl gloves. MAIN OUTCOME MEASURES: Type of complication, treatment and operative outcome. FINDINGS: The patients ranged in age from 26 to 46 years. One patient died while awaiting surgical consultation of massive gastrointestinal bleeding from a large gastric ulcer caused by a vinyl glove bezoar (VGB). Four VGBs were removed surgically. Endoscopic removal was difficult or impossible because the gloves had become hardened and matted. CONCLUSIONS: VGB should be considered in institutionalized mentally retarded people with a history of pica when they present with gastrointestinal symptoms. VGBs should be removed directly by laparotomy, gastrotomy or enterotomy. Endoscopic removal is not recommended.

Adult↗
PubMed1999

Synergy of topotecan in combination with vincristine for treatment of pediatric solid tumor xenografts.

Topotecan and vincristine were evaluated alone or in combination against 13 independent xenografts and 1 vincristine-resistant derivative, representing childhood neuroblastoma (n = 6), rhabdomyosarcoma (n = 5), or brain tumors (n = 3). Topotecan was given by i.v. bolus on a schedule found previously to be optimal. Drug was administered daily for 5 days on 2 consecutive weeks with cycles repeated every 21 days over a period of 8 weeks. Doses of topotecan ranged from 0.16 to 1.5 mg/kg to simulate clinically achievable topotecan lactone plasma systemic exposures. Vincristine was administered i.v. every 7 days at a fixed dose of 1 mg/kg. Given as a single agent, vincristine induced complete responses (CRs) in all mice bearing two rhabdomyosarcomas (Rh28 and Rh30) and some CRs in Rh12-bearing mice (57%) but relatively few CRs (<29%) in other tumors. As a single agent, topotecan induced CR in a low proportion of tumor lines. A dose-response model with a logit link function was used to investigate whether the combination of topotecan and vincristine resulted in greater than expected responses compared with the activity of the agents when administered alone. Only CR was used to evaluate tumor responses. The combination resulted in significantly greater than expected CRs than individual agents in nine tumor lines (four neuroblastoma, three brain tumors, and two rhabdomyosarcomas). Similar event-free (failure) distributions were shown in SJ-GBM2 glioblastoma xenografts, whether vincristine was administered on day 1 or day 5 of each topotecan course. To determine whether the increased antitumor activity with the combination was attributable to a change in drug disposition, extensive pharmacokinetic studies were performed. However, little or no interaction between these two agents was determined. Toxicity of the combination was marked by prolonged thrombocytopenia and decreased hemoglobin. However, approximately 75 and 80% of the maximum tolerated dose of each single agent, topotecan (1.5 mg/kg) or vincristine (1 mg/kg), could be given in combination, resulting in a combination toxicity index of approximately 1.5. These results show that the therapeutic effect of combining topotecan with vincristine was greater than additive in most tumor models of childhood solid tumors, and toxicity data suggest that this can be administered to mice with only moderate reduction in the dose levels for each agent.

Animals↗
PubMed1999

Urinary catheters for intermittent use.

The long-term use of intermittent catheterisation is often suitable for patients with voiding problems who are able to perform self-care. Use of the technique may result in fewer urinary tract problems, the achievement of continence and improvements in quality of life.

Catheters, Indwelling↗