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Biomedical subjects

M L Allen

Publications and source records attributed to M L Allen.

At least 19 recordsLinked to original sources
PubMed2001

The comparison of midazolam and topical lidocaine spray versus the combination of midazolam, meperidine, and topical lidocaine spray to sedate patients for upper endoscopy.

BACKGROUND: Whether an opiate-benzodiazepine combination is superior to benzodiazepine alone for sedation in upper endoscopy is controversial. The purpose of this study was to compare the effectiveness of intravenous midazolam alone versus the combination of intravenous midazolam and intravenous meperidine for the sedation of patients undergoing upper endoscopy. METHODS: One hundred seven patients scheduled for outpatient diagnostic esophagogastroduodenoscopy were randomly assigned to receive 50 mg intravenous meperidine (53 of 107) or placebo (54 of 107). All patients received topical lidocaine spray and as much midazolam as the endoscopist thought the patient needed. Patients and endoscopists were blinded as to assignment. Data collected included intubation time (seconds), procedure time (minutes), pulse, blood pressure, complications, and the need for reversal agents. The endoscopist evaluated the quality of sedation immediately after the procedure (1 = excellent, 2 = good, 3 = fair, and 4 = poor). The patient evaluated the procedure the next day by phone (1 = no discomfort or did not remember, 2 = slightly uncomfortable, 3 = extremely uncomfortable, and 4 = unacceptable). Patients were also asked whether they would agree to another esophagogastroduodenoscopy if their doctor thought it was medically necessary. RESULTS: The intubation time, procedure time and blood pressure were not significantly different between the 2 groups. In comparing the meperidine group versus placebo group, the highest pulse (82.3 vs. 93.7, p = 0.0010), lowest pulse (67.2 vs. 72.3, p = 0.0194) and amount of midazolam used (4.0 vs. 4.8 mg, p = 0.0185 or 0.53 vs. 0.67 mg/kg, p = 0.0083) were significantly different by using a t test analysis. Patient evaluations comparing meperidine versus placebo showed responses of 1 (52 vs. 49), 2 (1 vs. 3), 3 (0 vs. 2) and 4 (0 vs. 0), which were not significantly different. The endoscopists'evaluation comparing meperidine versus placebo gave responses of excellent (44 vs. 27), good (6 vs. 22), fair (3 vs. 5) and poor (0 vs. 0), which were highly significantly different (p < 0.001) by using chi-square statistical techniques. CONCLUSION: The addition of meperidine to midazolam in sedating patients undergoing upper endoscopy adds no benefit from the patient viewpoint, whereas endoscopists favored the use of both medications.

Administration, Topical↗
PubMed2001

Stable, germ-line transformation of Culex quinquefasciatus (Diptera: Culicidae).

A Hermes-based transposable element transformation system incorporating an enhanced green fluorescent protein (EGFP) marker was used to produce two transgenic lines of Culex quinquefasciatus (Say). The transformation frequency was approximately 12% and transformation of Culex was shown to be dependent on the presence of Hermes transposase. Injected Culex embryos were treated with four different heat shock regimes, two of which produced transformed individuals. These individuals were mated with wild-type mosquitoes and produced offspring which expressed the dominant EGFP gene in Mendelian ratios predicted for the stable integration of a gene at a single locus. The two transformed lines displayed distinct patterns of phenotypic expression, the expression of which has remained stable after fifteen generations. In these transgenic lines both the Hermes element and flanking plasmid DNA integrated into the Culex genome, as has been previously seen in Hermes-mediated transgenic strains of Aedes aegypti (L.). The high frequency of Culex transformation together with the dependence on the presence of Hermes transposase suggests that, as for Ae. aegypti, this mode of transposition into the germ-line genome occurs by an alternate mechanisms to the cut and paste type of transposition seen for this element in other insect species and in the somatic nuclei of mosquitoes. This is the first report of the genetic transformation of a species in the genus Culex and demonstrates that this medically important mosquito species can now, along with several other Culicine and Anopheline mosquito species, be genetically manipulated.

Aedes↗
PubMed2000

End expiration is more accurate than mid respiration in measuring lower esophageal sphincter pressure.

BACKGROUND/AIMS: Two ways popularly used to measure lower esophageal sphincter pressure are the mid-respiratory and end-expiratory methods. The aim of this study was to compare the suitability of these methods in the manometric assessment of patients with endoscopically documented esophagitis. METHODS: Manometry was performed on 22 consecutive patients to determine whether medical therapy or surgery was the more appropriate treatment strategy. Lower esophageal sphincter pressure was measured during a slow station pull-through. End-expiratory lower esophageal sphincter pressure was assessed by measuring the highest trough which coincided with end expiration. Mid-respiratory lower esophageal sphincter pressure was assessed by bracketing the highest pressure over >/=3 respiratory cycles and measuring the mid point. RESULTS: Mid-respiratory lower esophageal sphincter pressure (25.6 mm Hg) was higher (p < 0.0001) than end-expiratory lower esophageal sphincter pressure (15.7 mm Hg). Nine (41%) end-expiratory lower esophageal sphincter pressures were abnormally low (i.e., <10 mm Hg), whereas three (14%) mid-respiratory lower esophageal sphincter pressures were abnormally low (i.e., <14 mm Hg; p = 0.042). CONCLUSIONS Mid-respiratory lower esophageal sphincter pressure measurement includes respiratory artifact and does not accurately measure lower esophageal sphincter pressure. End-expiratory sphincter pressure better identifies potential surgical candidates.

Adult↗
PubMed1999

Serologic hepatitis B immunity in vaccinated health care workers.

BACKGROUND: Hepatitis B vaccination is recommended for health care workers but has a nonresponse rate of 5% to 32% and an unknown duration of immunity. There is no standardized postvaccination protocol to confirm, monitor, and maintain immunity. OBJECTIVE: To assess the hepatitis B serologic immune status in health care workers who were previously vaccinated. METHODS: A convenience survey and an objective laboratory study, which included testing for hepatitis B surface antigen, core antibody, and qualitative and quantitative surface antibody (anti-HBs), were performed. The data collected included vaccination date, number of doses of vaccine, whether and when titers had previously been checked, titer results, sex of patient, job description, and age at the time of our study and at vaccination. RESULTS: Group A (n = 109, 71%) had detectable anti-HBs titers, and group B (n = 45, 29%) had no detectable anti-HBs titers. Group A was vaccinated 4.80 +/- 0.30 (mean +/- SEM) years prior to our testing, received 2.91 +/- 0.04 (mean +/- SEM) vaccinations, and had a mean +/- SEM titer of 112.91 +/- 5.18 mIU/mL. There was no statistical significance in time since vaccination, number of doses of vaccine, sex, job description, age at the time of our serologic testing, or age at the time of vaccination between groups A and B. Six of 6 subjects given booster doses of vaccine in group B developed anti-HBs. Only 62 subjects (40%) in the entire study population had anti-HBs status previously determined, with 48 (77%) reporting immunity to hepatitis B virus. CONCLUSIONS: Twenty-nine percent of the health care workers who were vaccinated against hepatitis B showed no serologic evidence of hepatitis B immunity. It is unclear whether these subjects are nonresponders, lost immunity, or retained anamnestic potential. Booster vaccination response in 6 of 6 subjects suggests immunity. We recommend (1) postvaccination testing within 1 to 2 months to document immunity, (2) periodic anti-HBs monitoring, and (3) booster vaccination to maintain protective titer levels.

Adult↗
PubMed1998

Cyclic AMP regulates potassium channel expression in C6 glioma by destabilizing Kv1.1 mRNA.

The tissue distributions and physiological properties of a variety of cloned voltage-gated potassium channel genes have been characterized extensively, yet relatively little is known about the mechanisms controlling expression of these genes. Here, we report studies on the regulation of Kv1.1 expressed endogenously in the C6 glioma cell line. We demonstrate that elevation of intracellular cAMP leads to the accelerated degradation of Kv1.1 RNA. The cAMP-induced decrease in Kv1.1 RNA is followed by a decrease in Kv1. 1 protein and a decrease in the whole cell sustained K+ current amplitude. Dendrotoxin-I, a relatively specific blocker of Kv1.1, blocks 96% of the sustained K+ current in glioma cells, causing a shift in the resting membrane potential from -40 mV to -7 mV. These data suggest that expression of Kv1.1 contributes to setting the resting membrane potential in undifferentiated glioma cells. We therefore suggest that receptor-mediated elevation of cAMP reduces outward K+ current density by acting at the translational level to destabilize Kv1.1 RNA, an additional mechanism for regulating potassium channel gene expression.

1-Methyl-3-isobutylxanthine↗
PubMed1998

Disposition of butadiene epoxides in Sprague-Dawley rats following exposures to 8000 ppm 1,3-butadiene: comparisons with tissue epoxide concentrations following low-level exposures.

1,3-Butadiene (BD), a compound used extensively in the rubber industry, is weakly carcinogenic in Sprague-Dawley rats after chronic exposures to concentrations of 1000 and 8000 ppm. Conversely, in B6C3F1 mice, tumors occur after chronic exposures to concentrations as low as 6.25 ppm. Previously, we have shown that tissue concentrations of the mutagenic BD metabolites, butadiene monoepoxide (BDO) and butadiene diepoxide (BDO2), are present in greater concentrations in mice than in rats following acute exposures to low levels (100 ppm or less). This disparity was particularly significant for the diepoxide. We hypothesized that if these epoxides are involved in the carcinogenic response of BD, then they will also be present in rat tissues at relatively high concentrations following exposures to 8000 ppm BD. In the present study, concentrations of the BD epoxides, BDO and BDO2, were determined in blood of female Sprague-Dawley rats following a single 6-h exposure and 10 repeated exposures to a target concentration of 8000 ppm BD. Concentrations of these epoxides were also determined in a number of other tissues, including the primary rat target organ-mammary gland-following 10 repeated exposures. Blood concentrations of BDO were 4030 pmol/g +/- 191 following a 6-h exposure and were 18% lower following the 10-day exposure. Blood concentrations of BDO2, following the 8000 ppm exposures, were very similar to those previously observed after exposures to 62.5 ppm BD (11 +/- 1 and 17 +/- 1 pmol/g following exposures of 6h and 6h/day for 10 days, respectively.) Concentrations of BDO ranged from 740 +/- 110 (femur) to 8990 +/- 1150 (fat) pmol/g tissue. Concentrations of BDO2 were similar among eight tissues analyzed, ranging from 5 +/- 1 (femur) to 17 +/- 3 (heart) pmol/g tissue. Tissue concentrations of butadiene monoepoxide were increased by 17- to 50-fold in tissues from rats exposed by inhalation to 8000 ppm BD as compared to tissues from rats exposed to 62.5 ppm BD. Based on earlier studies at our institute the internal dose of BD increases approximately 14-fold in the 8000 ppm-exposed rats compared to rats exposed to 62.5 ppm BD. Concentrations of butadiene diepoxide in rat tissues following an exposure to 8000 ppm BD were similar to those observed in rat tissues following exposures to 62.5 ppm BD. This study shows that pathways responsible for the accumulation of BDO2 in rats are saturated following low-level BD exposures. This suggests that the primary determinant of BD tumorigenicity in rats is not butadiene diepoxide. The high levels of BDO observed in rat mammary tissue suggest that this metabolite may be a more important determinant of BD carcinogenesis in the rat.

Animals↗
PubMed1998

Manometric measurement of anal canal resting tone: comparison of a rectosphincteric balloon probe with a water-perfused catheter assembly.

The purpose of this study was to compare the manometric measurements of a rectosphincteric balloon probe with a water-perfused catheter assembly on anal canal resting tone. Ten normal subjects (9 males, 1 female; mean age: 32 years; range 27-46 years) underwent station pull-through (0.5 cm/3 sec) beginning in the rectum with a water-perfused catheter assembly and a rectosphincteric balloon probe. Both the probe and the catheter were 5 mm in diameter. Three catheter side ports were perfused at 1 ml/min, and the rectal balloon was inflated with 5 ml of air. Measurements were taken on the same day in a counterbalanced manner. Data were analyzed on a computerized system. Mean (+/-SEM) values with the balloon were 82.3 (+/-8.9) mm Hg and 97.1 (+/-9.3) mm Hg with the catheter. These values were not significantly different (P=0.22). A significant order effect (P=0.04) was found where the first measure (101.3+/-10.2 mm Hg) was higher than the second measure (78.1+/-6.6 mm Hg), which was controlled for in the experimental design. A rectosphincteric balloon probe can accurately measure the resting tone of the anal canal compared to a water-perfused catheter assembly. Caution should be used when measuring anal canal resting tone early in an anorectal manometry assessment.

Adult↗
PubMed1998

Ultrasound screening for deep venous thrombosis after total knee arthroplasty. 2-year reassessment.

The efficacy of ultrasound compared with ascending venography for the detection of deep venous thrombosis immediately after total knee arthroplasty was assessed after a 2-year interval. One hundred thirty-seven patients were eligible for the study; however, 31 patients received only one of the screening methods and a color Doppler examination was inconclusive in six patients. Therefore, 100 patients had a Doppler examination and a venogram. Overall, the sensitivity of ultrasound was 85%, the specificity 97%, the positive predictive value 85%, the negative predictive value 97%, and the accuracy 95%. The sensitivity in the calf was 83%, in the popliteal vein 86%, and in the femoral vein 100%. Two years ago, the initial assessment of ultrasound for the detection of deep venous thrombosis after surgery in patients who had total joint arthroplasty revealed a 75% sensitivity, 99% specificity, 91% positive predictive value, 97% negative predictive value, and 97% accuracy. The sensitivity in the calf was 83%; the sensitivity in the popliteal vein was 40%; and the sensitivity in the femoral vein was 50%. After 2 years of using this screening test with one technician and one radiologist, an improvement with this noninvasive technique was shown. However, it was found that Doppler imaging is not as sensitive as venography for detecting calf thrombi. Any imaging technique should be validated by each institution to determine the validity of the instrument and the learning curve of the technician administering the examination.

Adult↗
PubMed1997

Cloning and characterization of actin depolymerizing factor from Toxoplasma gondii.

We determined the predicted amino acid sequence of actin depolymerizing factor (ADF) from Toxoplasma gondii by sequencing the full-length cDNA. T. gondii ADF consists of 118 amino acids (calculated molecular weight 13,400) and shares a high degree of sequence similarity to other low molecular weight actin monomer sequestering proteins, especially Acanthamoeba actophorin, plant ADFs and yeast and vertebrate cofilin. ADF from T. gondii is smaller and does not contain a nuclear localization sequence like the related vertebrate proteins. Southern blot analysis indicates that T. gondii ADF is a single-copy gene. Homogeneous recombinant T. gondii ADF purified from E. coli is active in binding actin monomers and depolymerizing F-actin. Localization of ADF by immunofluorescence and immunoelectron microscopy indicates ADF is scattered throughout the cytoplasm and prominently localized beneath the plasma membrane in T. gondii.

Actin Depolymerizing Factors↗
PubMed1997

The effect of gravity on oesophageal peristalsis in humans.

Many mammalian species including non-human primates consume water in a body position not aided by gravity and it has been conjectured that oesophageal peristalsis overcomes gravity in humans. The purpose of this study was to determine the effects of gravity on oesophageal peristalsis in humans in response to water swallows. Six females (30-43 years old) and six males (27-46 years old) without oesophageal symptoms underwent oesophageal motility testing with intraluminal microtransducers placed 5, 7.5, 10 and 15 cm above the lower oesophageal sphincter. Subjects received ten 5 mL water swallows every 30 sec in the supine, standing, and head down (30 degrees) prone positions which were counterbalanced. Oesophageal contractile pressure (115, 98, 126 mmHg), duration (3.5, 3.0, 3.7 sec), onset velocity (4.7, 4.9, 4.7 cm sec-1), peak velocity (5.1, 4.8, 4.1 cm sec-1), average upstroke (dP/dT) (78, 75, 84 mmHg sec-1), or maximum upstroke (132, 120, 141 mmHg sec-1) were not significantly different among the head down prone, upright and supine positions, respectively. The frequency of abnormal contractile activity was statistically different among the positions. More abnormal contractions (i.e. simultaneous, retrograde, non-transmitted) occurred in the upright position (26%) when compared to either the supine (12%, P = 0.005) or head down prone (13%, P = 0.013) positions. The oesophagus tends to function normally to water swallows when unassisted by gravity. Oesophageal peristaltic dysfunction to water swallows may be more pronounced when assisted by the force of gravity.

Adult↗
PubMed1996

Manometric diagnosis of diffuse esophageal spasm.

There are no requirements concerning the amplitude of simultaneous contractions among the present criteria for the manometric diagnosis of diffuse esophageal spasm. The purpose of this investigation was to determine whether the current criteria effectively identify an appropriately homogenous patient population. Sixty consecutive motility tracings that met the criteria for diffuse esophageal spasm were evaluated. A bimodal distribution of the highest simultaneous esophageal contraction for each patient was observed. One group's (N = 29) highest simultaneous esophageal contractile amplitude was < or = 74 mm Hg, the other's (N = 31) highest simultaneous esophageal contractile amplitude was > or = 100 mm Hg. Group 1 had significantly decreased lower esophageal sphincter pressure, lower peristaltic amplitude, more aperistalsis, fewer simultaneous contractions, and fewer complaints of chest pain. These comparisons suggest that consideration be given to the amplitude of simultaneous esophageal contractions in the manometric diagnosis of diffuse esophageal spasm.

Adult↗
PubMed1996

Mechanisms of gastroesophageal acid reflux and esophageal acid clearance in heartburn patients.

OBJECTIVES: Gastroesophageal reflux can occur because of low resting pressure, transient relaxation, or normal relaxation of the lower esophageal sphincter. Mechanisms for delayed esophageal clearance include impaired peristalsis, infrequent swallowing, and impaired sphincter relaxation. The purpose of this study was to examine esophageal function in patients with gastroesophageal reflux and to determine esophageal acid clearance. METHODS: Esophageal contractile pressure, duration, velocity, pH, sphincter pressure, and deglutition were monitored in 12 heartburn patients 1 h before and 3 h postprandially twice. RESULTS: Eighty-seven episodes of gastroesophageal reflux occurred during normal sphincter relaxation, and 72 episodes occurred during transient sphincter relaxation; however, the frequency with normal sphincter relaxations was quite low (1%) compared with transient sphincter relaxations (33%). Mean and median esophageal acid exposure was not different during normal sphincter relaxation (71 and 80 s) compared with during transient sphincter relaxation (71 and 81 s). There were 284 instances of primary peristalsis, with 157 resulting in esophageal acid clearance, compared with simultaneous contractions (6 of 66), secondary peristalsis (1 of 7), and tertiary contractions (0 of 45). Contractile pressures were higher and durations were longer with acid clearance, but velocities were not different. CONCLUSIONS: Frequency of gastroesophageal reflux is the same during normal and transient sphincter relaxation in heartburn patients. Primary peristalsis is necessary to accomplish acid clearance. Secondary peristalsis is rare and ineffective.

Adult↗
PubMed1995

Hypomyelination alters K+ channel expression in mouse mutants shiverer and Trembler.

Voltage-gated K+ channels are localized to juxtaparanodal regions of myelinated axons. To begin to understand the role of normal compact myelin in this localization, we examined mKv1.1 and mKv1.2 expression in the dysmyelinating mouse mutants shiverer and Trembler. In neonatal wild-type and shiverer mice, the focal localization of both proteins in axon fiber tracts is similar, suggesting that cues other than mature myelin can direct initial K+ channel localization in shiverer mutants. In contrast, K+ channel localization is altered in hypomyelinated axonal fiber tracts of adult mutants, suggesting that abnormal myelination leads to channel redistribution. In shiverer adult, K+ channel expression is up-regulated in both axons and glia, as revealed by immunocytochemistry, RNase protection, and in situ hybridization studies. This up-regulation of K+ channels in hypomyelinated axon tracts may reflect a compensatory reorganization of ionic currents, allowing impulse conduction to occur in these dysmyelinating mouse mutants.

Aging↗
PubMed1995

Gastrointestinal blood loss with low dose (325 mg) plain and enteric-coated aspirin administration.

OBJECTIVES: The purpose of this study was to assess gastrointestinal blood loss with low dose (325 mg) plain and enteric-coated aspirin. METHODS: A total of 47 healthy volunteers participated in randomized, controlled acute and chronic trials. Seventeen participated in a repeated measures acute trial, and 30 participated in an independent sample chronic trial. Gastrointestinal blood loss was determined by obtaining 72-hour stool collections and quantitating Chromium-51 labeled erythrocytes. RESULTS: Acute phase trials: gastrointestinal blood loss during base line was 0.47 (+/- 0.11) mL/day, 0.96 (+/- 0.12) mL/day with enteric-coated aspirin (p < 0.0006), and 1.82 (+/- 0.35) mL/day with plain aspirin (p < 0.0001 vs. base line, p = 0.0476 vs. enteric-coated aspirin). Chronic phase trials: gastrointestinal blood loss was 1.12 (+/- 0.31) mL/day with enteric-coated aspirin (p = 0.0024 vs. control) and 2.60 (+/- 0.68) with plain aspirin (p < 0.0001 vs. control, p = 0.0364 vs. enteric-coated aspirin). CONCLUSIONS: During acute and chronic ingestion, plain aspirin at a dose of 325 mg/day significantly increased gastrointestinal blood loss when compared to control or enteric-coated aspirin values, although enteric-coated aspirin values were also significantly increased compared to control. Gastric adaptation does not decrease blood loss with low dose aspirin consumption.

Adaptation, Physiological↗
PubMed1994

Properties of voltage-gated K+ currents expressed in Xenopus oocytes by mKv1.1, mKv1.2 and their heteromultimers as revealed by mutagenesis of the dendrotoxin-binding site in mKv1.1.

Two similar mouse Shaker-like K+ channel genes, mKv1.1 and mKv1.2, have been shown to form heteromultimers in vivo. The predicted amino acid sequence of each channel is nearly identical in mice, rats and humans, suggesting that each has been highly conserved evolutionarily. Here we report the biophysical and pharmacological properties of each channel when expressed alone or when coexpressed in Xenopus oocytes. The voltage sensitivities of activation were similar for both, but the voltages at which the K+ conductances were half-maximal (V1/2) were -37 mV and -27 mV for mKv1.1 and mKv1.2 respectively. Both displayed voltage-dependent, but incomplete, inactivation following a prepulse with mKv1.2 showing the greater degree of inactivation. For mKv1.1, the onset and recovery from inactivation could be described by single, slow time constants (2-4 s), whereas for mKv1.2 the onset and recovery from inactivation displayed a second, faster time constant (< 400 ms). Using a mutant mKv1.1 that is 100-fold less sensitive to dendrotoxin-I than mKv1.1, we demonstrate that this mutant mKv1.1 and wild-type mKv1.2 subunits can form heteromultimeric channels. With some exceptions, of unknown significance, the biophysical properties of the heteromultimeric channels formed by wild-type mKv1.1 and mKv1.2 subunits were intermediate between those of mKv1.1 and mKv1.2 homomultimers, but quantitatively more similar to the more abundant subunit.

Animals↗
PubMed1994

Fecal Clostridium difficile carriage among medical housestaff.

Housestaff, physician assistants, and hospitalized patients at a teaching hospital were tested for fecal carriage of Clostridium difficile. The test results showed that fecal carriage of C. difficile may not be important in the epidemiology of hospital-acquired diarrhea.

Carrier State↗