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Biomedical subjects

M D Lee

Publications and source records attributed to M D Lee.

At least 73 records · Page 4Linked to original sources
PubMed1995

Evaluation of subcutaneous injection of local anesthetic agents as a method of tick removal.

The usefulness of subcutaneous injection of three local anesthetic agents to stimulate tick detachment in an animal model was evaluated. American dog ticks (Dermacentor variabilis) were placed on three New Zealand white rabbits and allowed to attach for 24 hours. Dead and unattached ticks were manually removed. Three local anesthetic agents were studied: 1% lidocaine (group A); 1% lidocaine with epinephrine 1:200,000 (group B); and 1% chloroprocaine (group C). For each group, a total of 0.25 mL of anesthetic agent was injected subcutaneously under the attached portion of each tick, resulting in formation of a 5- to 6-mm wheal. For all three anesthetic agents studied (group A, 34 ticks; group B, 28 ticks; group C, 31 ticks), none of the ticks spontaneously detached within 1 hour after injection. Subcutaneous injection of 1% lidocaine, 1% lidocaine with epinephrine, and 1% chloroprocaine are not effective methods for rapid tick removal in the animal model.

Anesthetics, Local↗
PubMed1995

Understanding performance and learning in consistent memory search: an age-related perspective.

This study was conducted to investigate learning in memory search tasks. Young and old participants were trained for 5,640 trials of consistent mapping (CM) and varied mapping (VM) memory search. After training, participants were transferred into New CM and CM Reversal conditions. During training, both young and old adults improved reaction time performance, with more rapid improvement for the young adults. In CM training, both age groups achieved zero comparison slopes, indicating automaticity in CM memory search. VM training maintained a large age-related difference in search times. Age did not moderate the transfer effects, suggesting similar learning mechanisms were responsible for the original CM training gains in both age groups; however, transfer effects were different for CM Reversal and New CM. The pattern of transfer data argues against several possible mechanisms for automaticity in memory search. The data are most compatible with a hypothesis of memory-set unitization as the locus of automaticity in memory search.

Adolescent↗
PubMed1995

Effect of spaceflight on oxidative and antioxidant enzyme activity in rat diaphragm and intercostal muscles.

There are limited data regarding changes in oxidative and antioxidant enzymes induced by simulated or actual weightlessness, and any additional information would provide insight into potential mechanisms involving other changes observed in muscles from animals previously flown in space. Thus, the NASA Biospecimen Sharing Program was an opportunity to collect valuable information. Oxidative and antioxidant enzyme levels, as well as lipid perioxidation, were measured in respiratory muscles from rats flown on board Space Shuttle mission STS-54. The results indicated that there was an increasing trend in citrate synthase activity in the flight diaphragm when compared to ground based controls, and there were no significant changes observed in the intercostal muscles for any of the parameters. However, lipid peroxidation was significantly (p<0.05) decreased in the flight diaphragm. These results indicate that 6 day exposure to microgravity may have a different effect on oxidative and antioxidant activity in rat respiratory muscles when compared to data from previous 14 day hindlimb suspension studies.

Animals↗
PubMed1994

Long-term retention of skilled visual search: do young adults retain more than old adults?

Young and old Ss received extensive consistent-mapping visual search practice (3,000 trials). The Ss returned to the laboratory following a 16-month retention interval. Retention of skilled visual search was assessed using the trained stimuli (assessment of retention of stimulus-specific learning) and using new stimuli (assessment of retention of task-specific learning). All Ss, regardless of age group, demonstrated impressive retention. However, age-related retention differences favoring the young were observed when retention of stimulus-specific learning was assessed. No age-related retention differences were observed when task-specific learning was assessed. The data suggest that age-related retention capabilities depend on the type of learning assessed.

Adult↗
PubMed1994

Glycothiohexide alpha, a novel antibiotic produced by "Sebekia" sp., LL-14E605. II. Isolation and physical-chemical characterization.

Glycothiohexide alpha was recovered from the fermentation broth of a "Sebekia" sp. by mixed solvent extraction, selective precipitation and adsorption chromatography on Diaion HP-20. The amount of glycothiohexide alpha present in the crude preparation was enriched by photolysis. Purification of glycothiohexide alpha was accomplished by repetitive countercurrent chromatography.

Actinomycetales↗
PubMed1994

A case of simultaneous multiple gastric cancers with p53 gene mutation.

Simultaneous multiple gastric cancers are rarely observed in clinical practice, and its association with p53 gene mutation has not been mentioned in any previous reports. We report a case of advanced gastric cancer with two primary lesions in the stomach who received total gastrectomy. Tumor and surrounding normal tissues from the surgical specimen were studied by using polymerase chain reaction-single strand conformation polymorphism analysis, restriction enzyme digestion method and direct sequencing. Point mutations of p53 gene at codon 248 (CGG-->TGG) were found in both primary tumor foci. The patient developed cancerous peritonitis eight months after the operation and expired six months later. This report suggests that p53 gene mutation can occur at an earlier stage in the tumorigenesis of gastric cancer than previously reported and it might be associated with an unusual clinical and pathological presentation.

Aged↗
PubMed1993

Disruption and maintenance of skilled visual search as a function of degree of consistency.

The present experiment was conducted to investigate the effects of varying degrees of task consistency on the performance and maintenance of skill in a semantic-category visual search task. Four groups of participants first received 6000 trials of consistent mapping (CM) training on two different categories. The participants then performed 4000 trials in which one of the previously trained categories remained 100% consistent, whereas the other previously trained category became either 100%, 67%, 50%, or 33% consistent. This second phase of the experiment allowed for the examination of disruption of the search skill as a function of degree of consistency. Subsequent to the degree of consistency manipulation, 100% consistency was restored and participants performed another 4200 CM trials. Results indicate that performance was disrupted by inconsistency and that disruption increased as consistency decreased. On the return of task consistency, performance improved rapidly to predisruption levels, though some performance disruption was evident. Theoretical and practical implications are discussed.

Adolescent↗
PubMed1992

Factors affecting endotoxin release from the cell surface of avian strains of Pasteurella multocida.

Two avian strains of Pasteurella multocida, a vaccine strain and a virulent field isolate, were investigated to determine their propensity to release endotoxin from the cell surface. Both organisms released comparable amounts of endotoxin when plasma complement proteins were present, however the virulent strain did so without the loss of viability that occurred in the vaccine strain. Blocking complement activity decreased the ability of plasma to elicit endotoxin release from the bacteria. When the cells were treated with divalent metal chelators such as trans-1, 2-diaminocyclohexane-N,N,N1,N1-tetraacetic acid (CDTA), more endotoxin was released from the vaccine strain than from the virulent isolate. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of purified lipopolysaccharide (LPS) from both strains revealed virtually identical patterns. Both had patterns considered typical of rough LPS. Challenge studies in 8 weeks old turkeys showed that the field strain induced endotoxemia of longer duration than the vaccine strain and produced greater mortality.

Animals↗
PubMed1992

Partial reversal of fluoxetine anorexia by the 5-HT antagonist metergoline.

Experiment 1 showed that the reduction of intake produced by 5 or 10 mg/kg fluoxetine in rats eating either a solid or a liquid meal was partially antagonised by 1 mg/kg of the 5HT1/5HT2 antagonist metergoline but not by 1 mg/kg of the 5HT2 antagonist ketanserin. Experiment 2 examined the meal patterning of rats given 5 mg/kg fluoxetine and 1 mg/kg metergoline. Fluoxetine alone increased the latency to feed, reduced meal size and shifted the inter-pellet interval (IPI) distribution to the right. Metergoline alone had little immediate effect on food intake or other feeding parameters but partially reversed the reduction of food intake produced by fluoxetine. There was a complete reversal of the increased latency to feed and a partial reversal of the depression of meal size. However, the rightward shift of the IPI distribution caused by fluoxetine, which indicated a depression of feeding rate, was more pronounced after combined treatment. We conclude that fluoxetine reduces food intake by enhancing satiety through a serotonergic dependent mechanism but reduces feeding rate through a separate mechanism, whose neurochemical basis remains to be established.

Animals↗
PubMed1992

Free-feeding and free-drinking patterns of male rats following treatment with opiate kappa agonists.

Three experiments investigated the effects of PD117302 and U50,488H on the patterns of food and water intake by male rats. Experiment 1 demonstrated early dose-related suppression of food and water intake after PD117302 (0, 1.25, 2.5, 5 mg/kg). The initial suppression of drinking was followed by a sustained increase 4-12 h after drug administration. Experiment 2 demonstrated that 2.5 mg/kg PD117302 failed to increase food intake whether given at the beginning of the night (high baseline food intake) or the beginning of the day (low baseline food intake). Experiment 3 showed that 0.5 mg/kg U50,488H significantly enhanced meal size but, at doses of 0.5, 1.0, and 2.0 mg/kg, had no effect on overall food intake. U50,488H also produced delayed, dose-related increases in water intake. The results suggest kappa receptors may have limited importance in modulating ad lib food intake and demonstrate the behavioural characteristics of increased drinking after excessive urine output.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1992

CT reconstruction algorithm for a dental panoramic x-ray unit.

A variable Jacobian and weighted backprojection algorithm, used for medical CT, was adapted to perform CT reconstructions on data obtained with a dental panoramic x-ray unit. A detector array, fitted to the unit for the purpose of acquiring digital panoramic radiographs, was used to collect the data. Compensations were made for the incomplete (230 degrees) rotation of the panoramic x-ray unit, the non-fixed centre of rotation, the irregular rotation of the x-ray target and detector, and the resulting variances in magnification. The algorithm was tested on mathematically simulated phantoms and on acquired data. Reconstruction of simulated data proved the success of the algorithm. Real data reconstructions showed some defects as a result of inaccuracies in quantifying the experimental panoramic device.

Algorithms↗
PubMed1991

The gene encoding rat nuclear pore glycoprotein p62 is intronless.

Glycoproteins of the nuclear pore complex are thought to play an important role in the transport of regulatory proteins and ribonucleoproteins across the nuclear envelope. However, the genetic elements and signals that control the expression of nuclear pore glycoproteins are poorly understood. To study the transcriptional regulation of mammalian nuclear pore glycoprotein biosynthesis, we have isolated the gene coding for the major rat nuclear pore glycoprotein p62. The p62 gene consists of a 2941-base pair region that is linear with the full length p62 cDNA with no intervening sequences. Quantitative Southern analysis revealed that the gene is present in single copy. The p62 gene encodes a 525-amino acid open reading frame that directs the synthesis of the 62-kDa pore glycoprotein in vitro and in transfected cultured cells. The 5'-flanking region contains two potential transcription start sites; primer extension analysis revealed that the furthest upstream site is preferentially used in vivo. When linked to a reporter gene, the 5'-flanking region of the p62 gene serves as an active promoter.

Animals↗
PubMed1991

A survey of potential virulence markers from avian strains of Pasteurella multocida.

Twenty-four isolates of Pasteurella multocida from clinical cases of fowl cholera and the Clemson University vaccine strain were surveyed for the presence of potential virulence markers. Membrane proteins, enzymatic activity of the membrane proteins, and carbohydrate fermentation patterns were also determined to demonstrate phenotypic relationships within the groups. Few differences were found in these phenotypic characteristics among the isolates. Almost all the organisms produced siderophore and were hemolytic on turkey red blood cells. No extracellular enzyme or bacteriocin activity was detected and little antibiotic resistance was found. However, many organisms contained plasmids and demonstrated some degree of resistance to complement. Both characteristics were correlative markers in Pasteurella multocida isolated from birds with fowl cholera.

Animals↗
PubMed1991

Recombination of automatic processing components: the effects of transfer, reversal, and conflict situations.

This research was conducted to evaluate the effects of compatible and incompatible automatic processes on performance. Subjects were trained for 8400 trials of consistent mapping practice in a semantic category visual search task and then transferred for 2352 trials to conditions that utilized the trained component processes in various ways. Results indicate that if the components were reused in a compatible fashion (target and distractor transfer), there was positive transfer. Target and distractor reversal resulted in equivalent and severe performance disruption that persisted for the entire retraining period. Target conflict produced disruption equivalent to the reversal conditions. Distractor conflict resulted in less initial disruption, which dissipated before the end of the retraining period. The results are discussed in terms of agreement with strength-theoretic views of visual search and in terms of practical training and retraining issues.

Adult↗
PubMed1991

Analysis of ras gene mutations in gastrointestinal cancers.

Point mutations of c-Ki-ras genes were analyzed in 33 samples of human gastrointestinal malignancy. DNA extracted from the frozen tissue was amplified by polymerase chain reaction (PCR) and analyzed by direct sequencing and slot-blot hybridization at codons 12, 13 and 61 of c-Ki-ras. In 7 cases out of 19 colorectal cancers, point mutations were found: 3 cases at codon 12, 1 at codon 13, 2 at codon 61 of c-Ki-ras and one case had double mutations at codon 12 and codon 13. In 11 cases of gastric cancer, 4 showed point mutations: 1 at codon 12 and 3 at codon 13 of c-Ki-ras. In 3 pancreatic carcinomas, 2 had point mutations: one at codon 12 and the other at codon 13 of c-Ki-ras. The results indicate that c-Ki-ras gene point mutations are involved in the tumorigenesis of the human gastrointestinal system.

Adult↗