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Biomedical subjects

J M Miller

Publications and source records attributed to J M Miller.

At least 145 records · Page 8Linked to original sources
PubMed1998

Predictors of fluoroscopy time and estimated radiation exposure during radiofrequency catheter ablation procedures.

The objective of this study was to identify factors that predict fluoroscopy duration and radiation exposure during catheter ablation procedures. The patient population included 859 patients who participated in the Atakr Ablation System clinical trial at 1 of 9 centers (398 male and 461 female patients, aged 36 +/- 21 years). Each patient underwent catheter ablation of an accessory pathway, the atrioventricular junction, or atrioventricular nodal reentrant tachycardia using standard techniques. The duration of fluoroscopy was 53 +/- 50 minutes. Factors identified as independent predictors of fluoroscopy duration included patient age and sex, the success or failure of the ablation procedure, and the institution at which the ablation was performed. Catheter ablation in adults required longer fluoroscopy exposure than it did in children. Men required longer durations of fluoroscopy exposure than did women. The mean estimated "entrance" radiation dose was 1.3 +/- 1.3 Sv. The dose needed to cause radiation skin injury was exceeded during 22% of procedures. The overall mean effective absorbed dose from catheter ablation procedures was 0.025 Sv for female patients and 0.017 Sv for male patients. This degree of radiation exposure would result in an estimated 1,400 excess fatal malignancies in female patients and 2,600 excess fatal malignancies in male patients per 1 million patients.

Adolescent↗
PubMed1998

Role of glutathione in protection against noise-induced hearing loss.

A potential mechanism of hearing loss due to acoustic overstimulation is the generation of reactive oxygen species (ROS). ROS not removed by antioxidant defenses could be expected to cause significant damage to the sensory cells of the cochlea. We studied the influence of the antioxidant glutathione (GSH) on noise-induced hearing loss by using l-buthionine-[S,R]-sulfoximine (BSO), an inhibitor of GSH synthesis, and 2-oxothiazolidine-4-carboxylate (OTC), a cysteine prodrug, which promotes rapid restoration of GSH when GSH is acutely depleted. Pigmented female guinea pigs were exposed to broadband noise (102 dB SPL, 3 h/day, 5 days) while receiving daily injections of BSO, OTC, or saline. By weeks 2 and 3 after noise exposure, BSO-treated animals showed significantly greater threshold shifts above 12 kHz than saline-treated subjects, whereas OTC-treated animals showed significantly smaller threshold shifts at 12 kHz than controls. Histologically assessed noise-induced damage to the organ of Corti, predominantly basal turn row 1 outer hair cells, was most pronounced in BSO-treated animals. High performance liquid chromatographic analysis showed that OTC significantly increased cysteine levels, but not GSH levels, in the cochlea. These findings show that GSH inhibition increases the susceptibility of the cochlea to noise-induced damage and that replenishing GSH, presumably by enhancing availability of cysteine, attenuates noise-induced cochlear damage.

Animals↗
PubMed1998

Endolymphatic hydrops reduces retrograde labeling of trigeminal innervation to the cochlea.

This paper reports that endolymphatic hydrops causes a significant reduction of retrogradely labeled cell bodies of the ipsilateral trigeminal ganglion following application of horseradish peroxidase in the cochlea. We previously showed that the trigeminal ganglion is a source of primary sensory innervation to the cochlear blood vessels. The innervation of the cochlea from the trigeminal ganglion may provide the basis of an alternative mechanism for Ménière's syndrome (imbalance, hearing loss, tinnitus, and a sensation of fullness in the ear) for which a central neural basis has been speculated. Innervation patterns of sensory nerves from the trigeminal ganglion to the cochlear blood vessels were studied using retrograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). Healthy and hydropic guinea pigs were unilaterally implanted with an osmotic pump and a cannula for cochlear delivery of 2% WGA-HRP or vehicle alone. In other guinea pigs the cochlea was pretreated with 100 micromol capsaicin before administering 2% WGA-HRP. Histological sections of the ipsi- and contralateral trigeminal ganglia were obtained 48 h after WGA-HRP infusion. In the hydropic guinea pig, the number of labeled nerve cell bodies observed in the anteriomedial portion of the trigeminal ganglion at the origin of the ophthalmic nerve was reduced by 70% relative to normal animals. Capsaicin pretreatment nearly eliminated the labeled sensory fibers as expected. These data indicate that the trigeminal innervation to the cochlea could be involved in inner ear homeostatic disturbances, including the hydrops that is symptomatic of Ménière's disease.

Animals↗
PubMed1998

The vascular mechanism of action of betahistine in the inner ear of the guinea pig.

The aim of this study was to investigate the mechanism and site of action of betahistine dihydrochloride in the inner ear of the guinea pig. Betahistine-evoked increases in cochlear blood flow (CBF) have been presumed to be due to the drug effect on the later wall capillary bed or larger feeding vessels in the cochlea vascular system. As such, the mechanism of action could be due to inhibition of H3 receptors. Betahistine may also have a direct effect on postsynaptic H1/H2 receptors and/or an effect modulated by other autonomic receptors. Betahistine-evoked CBF responses were assessed by laser Doppler flowmetry in the presence of an H3 agonist (alpha N-methyl-histamine dihydrochloride), an H3 antagonist (thioperamide), an H2 antagonist (cimetidine) or an alpha 2 antagonist (idazoxan). The effects of betahistine on circulation in the anterior inferior cerebellar artery (AICA) and ipsilateral stria vascularis (SV) were assessed using intravital microscopy (IVM). Findings showed that betahistine increased CBF and reduced systemic blood pressure (BP). In contrast, alpha N-methylhistamine dihydrochloride had no effect on baseline CBF or BP and did not influence betahistine-induced increases in CBF. Thioperamide reversed the effects of betahistine on CBF, but had no effect on baseline CBF or BP. Cimetidine had no marked effect on baseline CBF or betahistine-induced increases in CBF Idazoxan had no consistent effects on baseline CBF, but abolished the effect of betahistine on CBF. The mean increase of red blood cell velocity in SV capillaries was 15% and occurred without a demonstrable change in capillary diameters. In contrast, the diameter of the AICA increased by 17-20%, indicating that betahistine-evoked increases in CBF resulted primarily from vasodilatation of the AICA. We suggest that this effect may be mediated via presynaptic H3 heteroreceptors and autonomic alpha 2 receptors.

Animals↗
PubMed1998

A comparative evaluation of collaborative prenatal care.

OBJECTIVE: To evaluate the effectiveness of an advanced-practice nurse-obstetrician collaborative prenatal practice. METHODS: A group of 194 consecutively enrolled medically low-risk obstetric patients was identified between January 1, 1994 and December 31, 1994 at Neighborhood Pregnancy Care, a collaborative-practice site. An equal number of medically low-risk patients attending the Louisiana State University obstetric clinic at the Medical Center of Louisiana at New Orleans was selected randomly from among those registering the same month. The two groups were compared on the primary outcome variable, low birth weight. Data were analyzed by chi2, Fisher exact test, t test, and regression models. RESULTS: We compared 179 collaborative-care and 181 university patients with retrievable information. By univariate analysis, collaborative-care patients more often were teenagers and black, and less likely to be married or employed. Collaborative-care patients had more prenatal visits and were more likely to participate in Medicaid, but less likely to deliver at the Medical Center of Louisiana at New Orleans. Birth weight and gestational age at delivery were greater. Both delivery before 37 weeks (7.3% versus 17.7%, P < .001) and birth weight less than 2500 g (8.9% versus 19.3%, P < .001) were less common. When differences identified at the initial obstetric visit were considered, multivariate weighted logistic regression confirmed the importance of prenatal care at the collaborative-practice program for low birth weight (odds ratio [OR] 0.37; 95% confidence interval [CI] 0.19, 0.71) and preterm delivery (OR 0.36; 95% CI 0.16, 0.78). When all differences were entered, low birth weight remained a significantly less likely occurrence at the collaborative-practice site (OR 0.46; 95% CI 0.23, 0.92). CONCLUSION: An advanced-practice nurse-obstetrician collaborative practice may be implemented successfully and lead to acceptable perinatal outcomes, as judged by low birth weight and prematurity.

Academic Medical Centers↗
PubMed1998

Effect of pelvic muscle exercise on transient incontinence during pregnancy and after birth.

OBJECTIVE: To test the effect of pelvic muscle exercise on postpartum symptoms of stress urinary incontinence and pelvic muscle strength in primigravidas during pregnancy and postpartum. METHODS: A prospective trial randomized women into treatment (standardized instruction in pelvic muscle exercise) or control (routine care with no systematic pelvic muscle exercise instruction). Urinary incontinence symptoms were measured by questionnaire. Pelvic muscle strength was quantified by an instrumented gynecologic speculum. Time points were 20 and 35 weeks' gestation and 6 weeks, 6 months, and 12 months postpartum. RESULTS: Outcomes are reported for 46 women with vaginal or cesarean birth and for a subsample of 37 women with vaginal birth. Longitudinal analyses are reported for cases with complete data across time points. Diminished urinary incontinence symptoms were seen in the treatment group, with significant treatment effects demonstrated at 35 weeks' gestation (F [1,43] = 4.36, P = .043), 6 weeks postpartum (F [1,43] = 4.94, P = .032), and 6 months postpartum (F [1,43] = 4.29, P = .044). A repeated measures analysis of variance showed a significant interaction between time and treatment for urinary incontinence (F [4, 41] = 2.83, P = .037). A significant effect of initial pelvic muscle strength was demonstrated; ie, pelvic muscle strength at 20 weeks' gestation predicted significantly 12-months postpartum strength (F [1, 13] = 8.12, P = .014). Group differences in pelvic muscle strength were observed (the treatment group had greater strength at 6 weeks and at 6 months postpartum than did controls), but these differences were not statistically significant. CONCLUSION: Practice of pelvic muscle exercise by primiparas results in fewer urinary incontinence symptoms during late pregnancy and postpartum.

Adult↗
PubMed1998

Quantification of cough-related urine loss using the paper towel test.

OBJECTIVE: To develop and test a simple and rapid method for quantifying the urine loss resulting from three deep coughs using an ordinary brown paper towel. METHODS: A brown paper towel is held lightly against the perineum during three single coughs performed in the upright stance. The resulting wetted area was calculated using simple geometry; if desired, leakage volume can be interpolated from a calibration curve, which demonstrates the relationship between wetted area (cm2) and volume (mL) of leakage. Four bench tests of the method were performed. In addition, the test-retest reliability of the method was evaluated in eight elderly women with mild stress urinary incontinence, a sample size adequate to detect a 1-mL difference with 80% power. RESULTS: The smallest measurable quantity of fluid resulted in a wetted area of 0.04 cm2 (equivalent to 0.2 microl). For leakage volumes up to 6 mL, the regression showed that each 1 mL of fluid volume resulted in an average 25.4 cm2 increase in wetted area (coefficient of determination: 0.97). In eight women with stress incontinence 95% of within- and across-visit comparisons of urine loss were within 1 mL. CONCLUSION: The paper towel test is a simple and reliable measure providing immediate visual and quantitative feedback of cough-related urine loss typical of mild-to-moderate stress urinary incontinence.

Aged↗
PubMed1998

Direct evidence of trigeminal innervation of the cochlear blood vessels.

This paper provides the first detailed description of the trigeminal innervation of the inner ear vasculature. This system provides a newly discovered neural substrate for rapid vasodilatatory responses of the inner ear to high levels of activity and sensory input. Moreover, this discovery may provide an alternative mechanism for a set of clinical disturbances (imbalance, hearing loss, tinnitus and headache) for which a central neural basis has been speculated. Iontophoretic injections of biocytin were made via a glass microelectrode into the trigeminal ganglion in guinea-pigs. Tissue for histological sections was obtained 24 h later. Labeled fibers from the injection site were observed as bundles around the ipsilateral spiral modiolar blood vessels, as individual labeled fibers in the interscala septae, and in the ipsilateral stria vascularis. The dark cell region of the cristae ampullaris in the vestibular labyrinth was also intensively labeled. No labeled fibers were observed in the neuroepithelium of the cristae ampullaris or the semicircular canals. These results confirm and localize an earlier indirect observation of the trigeminal ganglion projection to the cochlea. This innervation may play a role in normal vascular tone and in some inner ear disturbances, e.g., sudden hearing loss may reflect an abnormal activity of trigeminal ganglion projections to the cochlear blood vessels.

Animals↗
PubMed1998

Changes in cochlear blood flow due to intra-arterial infusions of angiotensin II (3-8) (angiotensin IV) in guinea pigs.

The effects of a newly discovered form of angiotensin, angiotensin IV (ANGIV), on cochlear blood flow (CBF) have been investigated utilizing the laser Doppler flowmetry (LDF) technique. Two specific questions were addressed: What are the effects of anterior inferior cerebellar artery infusions (AICA) of ANGIV on CBF and do angiotensin fragments other than ANGIV influence CBF in mature male and female guinea pigs. Infusions of ANGIV, and C-terminal shortened fragments were accomplished via micropipette into the AICA and changes in CBF were observed using LDF. The results demonstrated that 10 and 100 pmol/min doses of ANGIV increased CBF 22% and 75% (n = 6; P < 0.01) from baseline, respectively, with little change in mean arterial blood pressure (MAP). Pretreatment with the ANGIV antagonist divalanal-ANGIV (1 nmole/min) blocked increases in CBF due to infusions of 100 pmol/min of ANGIV. The infusion of the C-terminal shortened fragment ANGIV(1-5) and saline had no significant effect on either CBF or MAP. These results provide the evidence for a new subtype of the angiotensin receptor and indicate the likely role of circulating hormones in blood flow regulation in the inner ear.

Amino Acid Sequence↗
PubMed1998

Guinea pig auditory neurons are protected by glial cell line-derived growth factor from degeneration after noise trauma.

For patients with profound hearing loss, cochlear implants have become the treatment of choice. These devices provide auditory information through direct electrical stimulation of the auditory nerve. Prosthesis function depends on survival and electrical excitability of the cochlear neurons. Degeneration of the auditory nerve occurs after lesions of its peripheral target field (organ of Corti), specifically, including loss of inner hair cells (IHCs). There is now evidence that local treatment of the cochlea with neurotrophins may enhance survival of auditory neurons after aminoglycoside-induced deafness. Glial cell line-derived neurotrophic factor (GDNF) has recently been shown to be an important survival factor in other regions of the nervous system. By in situ hybridization, we now show that IHCs of the neonatal and mature rat cochlea synthesize GDNF and that GDNF-receptor alpha, but not c-Ret, is expressed in the rat spiral ganglion. We also show that GDNF is a potent survival-promoting factor for rat cochlear neurons in vitro. Finally, we examined GDNF efficacy to enhance cochlear-nerve survival after IHC lesions in vivo. We found that chronic intracochlear infusion of GDNF greatly enhances survival of guinea pig cochlear neurons after noise-induced IHC lesions. Our results demonstrate that GDNF is likely to be an endogeneous survival factor in the normal mammalian cochlea and it could have application as a pharmacological treatment to prevent secondary auditory nerve degeneration following organ of Corti damage.

Animals↗
PubMed1998

Heterotopic muscle pulleys or oblique muscle dysfunction?

INTRODUCTION: The description of connective tissue sleeves that function as pulleys for the rectus extraocular muscles (EOMs) suggests that abnormalities of EOM pulley position might provide a mechanical basis for some forms of incomitant strabismus. Pulleys determine the paths and thus the pulling directions of EOMs. METHODS: High-resolution magnetic resonance images spanning the orbits were obtained in primary position, upgaze, and downgaze for each subject. Paths of the EOMs were measured with reference to the orbital center and permitted inference of pulley locations. RESULTS: Data from 18 orbits of orthotropic subjects defined means and SDs of normal EOM pulley coordinates. Eight patients, aged 17 to 60 years, had heterotopic EOM pulleys, defined as displaced at least 2 SDs from normal. We found one to eight heterotopic pulleys (considering both orbits) in each of four patients who had been diagnosed with marked superior oblique (SO) overaction and mild to marked inferior oblique (IO) underaction. Each patient had superior mislocation of at least one lateral rectus pulley by 1.8 to 4.9 mm. Three patients diagnosed with mild to moderate IO overaction and mild to moderate SO underaction in only one orbit had one to three heterotopic EOM pulleys. Each of those patients had at least one lateral rectus pulley inferiorly dislocated by 1.9 to 4.9 mm. The final patient, who was diagnosed with mild IO underaction and normal SO function bilaterally, had bilateral superior mislocation of the medial rectus pulleys by greater than 2 mm. Computer simulations using the Orbit program (Eidactics, San Francisco) incorporating individually measured pulley positions reproduced the clinical patterns of incomitant strabismus in all cases without postulating abnormalities of oblique muscle innervation or contractility. CONCLUSION: Heterotopic EOM pulleys can cause patterns of incomitant strabismus that have been attributed to oblique muscle dysfunction. Even isolated mislocations of less than 2 mm, coupled with smaller mislocations of the other pulleys, can produce the clinical appearance of bilateral oblique dysfunction. Pulley heterotopy should be considered in the differential diagnosis of incomitant strabismus and oblique dysfunction.

Adolescent↗
PubMed1998

Recurrent chlamydial colonization during pregnancy.

To evaluate the prevalence of and associated factors for recurrent Chlamydia trachomatis infection in pregnant women, a retrospective cohort study was conducted in an urban prenatal clinic in an underserved area. Women with chlamydial carriage in pregnancy between 1992 and 1996 were identified by a direct DNA assay. Entrance criteria limited the population to those who were positive for chlamydia, were treated, had proof of cure and had at least one subsequent test for chlamydia, all in the same pregnancy. Of the 149 women who met entrance criteria, 25 (17%) had recurrent chlamydial carriage. The only identified risk factor was maternal age <20 years (21 of 98 vs. 4 of 51, odds ratio = 3.21). Infection with gonorrhea or other sexually transmitted diseases during the same pregnancy were not predictive of reinfection. Initial therapy with azithromycin, when compared to erythromycin, did not appear protective for recurrent infection. Pregnant adolescents are more likely to have recurrent chlamydial infection. Prenatal care programs should consider this when counseling and treating these patients.

Adolescent↗
PubMed1998

Risk of infection due to central venous catheters: effect of site of placement and catheter type.

OBJECTIVE: To determine the influence of catheter site and type (single- vs triple-lumen) on infection rates associated with central venous catheterization. DESIGN: Prospective observational study of all nontunneled central venous catheters over a 28-month period. Data collected included patient characteristics, insertion site, catheter type, and receipt of parenteral nutrition. End points were clinical infection (bacteremia or site infection) and catheter contamination (clinical infection or colonization with >15 colonies on semiquantitative culture). SETTING: Medical-surgical wards of Veterans' Affairs hospital. RESULTS: Three hundred catheters were inserted into 204 patients. Seventy percent were inserted into upper-body sites, and 30% were inserted into the femoral vein. Forty-five percent were triple-lumen catheters. Bacteremia occurred in 2.7% of catheter insertions; insertion-site infections developed in 1.3%, and catheter colonization developed in 12%. Catheter contamination was associated with emergent insertion (odds ratio [OR], 6.2; 95% confidence interval [CI95], 1.1-36.7; P=.04) by logistic regression and with femoral location (hazard, 4.2; CI95, 2.0-8.8; P=.0001) and history of transplantation (hazard, 2.8; CI95, 1.1-6.7; P=.024) by Cox regression. Clinical infection was not associated with any of the risk factors evaluated, although there was a trend for association with femoral location by Cox regression (hazard, 4.7; CI95, 0.82-26; P=.08). We did not identify an association between infection and use of triple-lumen catheters or parenteral nutrition. CONCLUSION: Our data support an association between intravenous catheter contamination and insertion at a femoral site.

Adult↗
PubMed1998

A pelvic muscle precontraction can reduce cough-related urine loss in selected women with mild SUI.

OBJECTIVES: To test the hypothesis that selected older women with mild-to-moderate stress urinary incontinence (SUI) can learn to demonstrate significantly reduced urine loss in 1 week by intentionally contracting the pelvic floor muscles before and during a cough (a skill we have termed "The Knack"). DESIGN: A prospective, randomized, single-blind interventional study. SETTING: The Older American Independence Center, a federally sponsored research program affiliated with the University of Michigan in Ann Arbor, Michigan. PARTICIPANTS: Twenty-seven women with a mean (SD) age of 68.0 (5.5) years, self-reported SUI, and demonstrable urine loss during a deep cough. INTERVENTION: Women were randomized to an immediate intervention group (Group I: n=13) who were taught the Knack after their first clinic visit, or a wait-listed control group (Group II: n=14) who were taught the Knack after 1 month. MEASUREMENTS: At 1 week after instruction, we tested the efficacy of the Knack in a standing stress test by (1) comparing the volumes of cough-related urine loss leaked by all subjects, with and without use of the Knack, and (2) comparing the volumes of cough-related urine loss leaked by Group I, using the Knack, with Group II, which had not yet been taught the Knack. RESULTS: Intra-individual results showed that at 1-week follow-up, the Knack was used to reduce urine loss resulting from a medium cough by an average of 98.2%, compared with that of a similar cough performed 1 minute before without the Knack (P=.009); likewise urine loss was reduced by an average of 73.3% (P=.003) in a deep cough. Reduction in urine loss was not significantly correlated with a digital measure of pelvic floor muscle strength. CONCLUSION: Within 1 week, selected older women with mild-to-moderate SUI can acquire the skill of using a properly-timed pelvic floor muscle contraction to significantly reduce urine leakage during a cough.

Aged↗
PubMed1998

First report of a human isolate of Erwinia persicinus.

Erwinia persicinus was first described in 1990 after being isolated from a variety of fruits and vegetables, including bananas, cucumbers, and tomatoes. In 1994, it was shown to be the causative agent of necrosis of bean pods. We now report the first human isolate of E. persicinus. The strain was isolated from the urine of an 88-year-old woman who presented with a urinary tract infection. By the hydroxyapatite method, DNA from this strain was shown to be 94.5% related at 60 degrees C and 86% related at 75 degrees C to the type strain of E. persicinus. The biochemical profile of E. persicinus is most similar to those of Erwinia rhapontici, Pantoea agglomerans, and Enterobacter species. It is negative in tests for lysine, arginine, ornithine, dulcitol, and urea. It is motile and positive in tests for D-sorbitol and sucrose. It is susceptible to the expanded-spectrum cephalosporins, aminoglycosides, and fluoroquinolones, but it is resistant to ampicillin, ticarcillin, and cefazolin.

Aged↗