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Biomedical subjects

D A Miller

Publications and source records attributed to D A Miller.

At least 19 recordsLinked to original sources
PubMed1999

Computing with self-excitatory cliques: A model and an application to hyperacuity-scale computation in visual cortex.

We present a model of visual computation based on tightly inter-connected cliques of pyramidal cells. It leads to a formal theory of cell assemblies, a specific relationship between correlated firing patterns and abstract functionality, and a direct calculation relating estimates of cortical cell counts to orientation hyperacuity. Our network architecture is unique in that (1) it supports a mode of computation that is both reliable and efficient; (2) the current-spike relations are modeled as an analog dynamical system in which the requisite computations can take place on the time scale required for an early stage of visual processing; and (3) the dynamics are triggered by the spatiotemporal response of cortical cells. This final point could explain why moving stimuli improve vernier sensitivity.

Models, Neurological↗
PubMed1999

Perinatal risks associated with borderline amniotic fluid index.

OBJECTIVE: Our purpose was to determine whether a borderline amniotic fluid index observed during antepartum testing confers a significant risk of adverse perinatal outcome. STUDY DESIGN: We conducted a retrospective review of all patients entering antepartum testing at Los Angeles County-University of Southern California Women's and Children's Hospital during a 4-month period beginning January 1, 1996. Women with singleton pregnancies who underwent antepartum testing within 1 week of delivery and who were delivered at our institution were identified for our study. An amniotic fluid index >5 and <10 cm was defined as "borderline" and an amniotic fluid index of 10 to 24 cm was considered normal. Markers of adverse perinatal outcome included intrapartum fetal distress, 5-minute Apgar score <7, meconium-stained amniotic fluid, and intrauterine growth restriction. RESULTS: There was a 2-fold increase in the incidence of adverse perinatal outcome among the women with borderline amniotic fluid index in comparison with control subjects with normal amniotic fluid volume. This difference reflected a 4-fold increase in the incidence of fetal growth restriction among women with a borderline amniotic fluid index. CONCLUSIONS: A borderline amniotic fluid index observed in antepartum testing is associated with an increased risk of intrauterine growth restriction and overall adverse perinatal outcome. These observations suggest that borderline amniotic fluid index merits twice-weekly antepartum testing.

Amniotic Fluid↗
PubMed1998

Brain activation during silent word generation evaluated with functional MRI.

This is a study of word generation during functional MRI (fMRI). Eleven normal healthy subjects were instructed to generate words covertly, (i.e., silently) that began with particular letters. Images were acquired on a conventional 1.5T scanner at three contiguous axial planes encompassing language-related areas of the temporal and frontal lobe. The data were analyzed at the level of a Talairach box, after individually fitting the proportional Talairach grid system to each slice. The main variable of interest was the number of activated pixels within a Talairach box. Boxes with a significant increase in the proportion of activated pixels were located in three regions of the left neocortex: (1) Brodmann areas 44 and 45 in the dorsolateral frontal cortex (Broca's area), (2) areas 21 and 37 in the temporal cortex, (3) and the striate/extrastriate cortex (areas 17 & 18). The results are discussed in terms of a cognitive model of word generation and are compared, in detail, with the results of prior relevant imaging studies.

Adolescent↗
PubMed1998

Stillbirth evaluation: what tests are needed?

OBJECTIVE: We sought to investigate what aspects of the stillbirth evaluation are considered to be essential and what tests can potentially be eliminated. STUDY DESIGN: A retrospective analysis of 745 stillbirths occurring from January 1990 to December 1994 was conducted. A stillbirth was defined by an estimated gestational age >20 weeks' gestational age or fetal weight >500 gm. We attempted to arrive at an apparent cause for each stillbirth after evaluation of genetic or chromosomal abnormalities, obstetric history, maternal medical illnesses, laboratory tests, autopsy findings, and placental pathologic conditions. RESULTS: We found that the most important aspects of stillbirth evaluation were placental pathologic conditions and autopsy. When the placenta was examined, a significant abnormality was detected in 30% (160 of 529) of the cases. When autopsy was performed, only 31% of fetal deaths (142 of 462) were unexplained; however, when no autopsy was performed, 44% (125 of 283) were unexplained (p = 0.0002). The following laboratory evaluations that were routinely performed were found to yield little definitive information: antinuclear antibody testing, Kleihauer-Betke test, and screening for congenital infections (toxoplasmosis, other viruses, rubella, cytomegalovirus, and herpes simplex virus). Overall, 36% (267 of 745) of stillbirths still remained unexplained despite a thorough evaluation in most cases. CONCLUSION: The causes of stillbirth are many and varied, with a large proportion having no obvious cause. As this study demonstrates, certain laboratory tests can be eliminated in the workup of fetal death. In the evaluation of stillbirth a complete systematic method that incorporates placental pathologic conditions, as well as autopsy findings, should prove to be beneficial.

Adolescent↗
PubMed1998

Spontaneous vaginal delivery: a risk factor for Erb's palsy?

OBJECTIVE: Our purpose was to determine whether Erb's palsies occurring in the absence of shoulder dystocia differ from those occurring after shoulder dystocia. STUDY DESIGN: We compared the time course of resolution and incidence of persistent injury at 1 year of age in 17 cases of Erb's palsy without shoulder dystocia and 23 cases associated with shoulder dystocia. RESULTS: The rate of persistence at 1 year was significantly higher in those Erb's cases without identified shoulder dystocia, 7 of 17 (41.2%) versus 2 of 23 (8.7%), p = 0.04. These cases of Erb's palsies also took longer to resolve (6.4 +/- 0.9 vs 2.6 +/- 0.7 months, p = 0.002), had a higher rate of associated clavicular fracture (12 of 17 vs 5 of 23, p = 0.006), and were more likely to occur in the posterior arm (10 of 15 vs 4 of 21, p = 0.009). CONCLUSIONS: Erb's palsy occurring without shoulder dystocia may be a qualitatively different injury than that occurring with shoulder dystocia.

Adult↗
PubMed1998

Are we selecting the right patients for treatment of localized prostate cancer? Results of an actuarial analysis.

OBJECTIVES: To determine our accuracy in selecting patients with at least a 10-year life expectancy for aggressive treatment of localized prostate cancer. METHODS: The medical records of 261 consecutive patients who underwent radical retropubic prostatectomy were submitted to the actuarial division of American General Life and Accident Insurance Company (AGLA) for estimation of life expectancy, excluding the diagnosis of prostate cancer. Survival curves were generated from predicted individual survivals. In patients with less than a 10-year life expectancy, AGLA provided us with the basis for assigning suboptimal survival rates. RESULTS: The mean life expectancy for the group was 15.2 years. Two hundred ten men (80%) were projected to have a life expectancy of more than 10 years, including 27 of 55 (49%) and 4 of 8 (50%) men who were older than or equal to 70 and 75 years of age, respectively. Coronary artery disease and diabetes mellitus were the most common coexisting medical conditions that adversely affected risk as single disease entities. CONCLUSIONS: Although clinicians do not estimate life expectancy with the scientific exactitude of an actuary, the ability to assess the patient in person and assimilate pertinent medical information in a less rigid format yields similar results. Selection of men for definitive treatment of localized prostate cancer should be based on the inherent aggressiveness of the disease and the health of the individual and should not be limited by specific age cutoffs. Populations of men undergoing radical prostatectomy are younger and healthier than those in reported series of watchful waiting for prostate cancer.

Actuarial Analysis↗
PubMed1998

Risk assessment of the toxicity of solvents of gutta-percha used in endodontic retreatment.

Three randomly assigned groups of single-canaled extracted teeth obturated with gutta-percha were retreated using controlled application of one of three organic solvents: chloroform, xylene, or halothane. Two additional groups of teeth served as positive and negative controls. Residual volume of solvent expressed through the apical foramen during retreatment was determined by the difference of pretreatment and posttreatment weights of hermetically sealed receptacles attached to the root surface of the teeth. Results indicate that the amount of solvent that has been determined to have leached out through the apical foramen is several orders of magnitude below the permissible toxic dose. Thus, it is proposed that the use of any of the aforementioned solvents used in the retreatment of root canals would pose negligible risk to the patient.

Chloroform↗
PubMed1998

Microleakage of endodontically treated teeth restored with posts.

A fluid filtration system using 15 psi of pressure on the penetrating fluid was used to quantify the amount of microleakage of a stainless-steel post and a carbon-fiber post system, each placed with various cements. Statistical analysis showed that there was a significant difference in microleakage between the cements (p < 0.001). Zinc phosphate cement showed the most microleakage, whereas C & B Metabond cement showed the least. There was no significant difference in microleakage between the stainless-steel and carbon-fiber posts. The results of this study showed that both posts, when cemented with dentin-bonding resin cements (C & B Metabond and Panavia-21), exhibited less microleakage than when cemented with non-dentin-bonding cements (glass ionomer and zinc phosphate).

Analysis of Variance↗
PubMed1998

Antepartum testing.

Among the methods of antepartum testing in use today, the nonprovocative tests (NST, BPP, MBPP) are safe and effective for use in ambulatory settings. Outpatient or office utilization of the CST is limited by the need for intravenous access (when oxytocin is used) and by the potential for uterine hyperstimulation and resultant acute FHR abnormalities. Regardless of the method of testing used, large studies have confirmed that the fetal death rate among patients undergoing antepartum testing is significantly lower than that in the general, untested population. This is a particularly encouraging observation in view of the fact that antepartum testing is used almost exclusively in complicated pregnancies at highest risk for poor outcome. In the future, protocols using adjunctive testing methods (fetal movement counting, fetal movement profile, Doppler velocimetry) in combination with standard methods (CST, NST, BPP, MBPP) may further reduce the incidence of fetal death in high-risk populations. At present, the beneficial effects of antepartum testing have created a situation in which the likelihood of fetal death in high-risk, tested populations is lower than that in low-risk, untested populations. This paradox will force us to consider the option of routine antepartum testing in all pregnancies.

Ambulatory Care↗
PubMed1998

Utility of the seven subtest WAIS-R short form in a female sample with brain damage.

We examined the accuracy of the WAIS-R seven subtest short form (Ward, 1990) for predicting IQs of 130 females with brain damage or dysfunction. Means for age, education, and FSIQ were 44.37 years (SD = 18.46), 12.74 years (SD = 2.42), and 87.64 (SD = 13.62). Results indicated that 93%, 84%, and 93% of short form estimated VIQs, PIQs, and FSIQs were within +/-5 points of their actual WAIS-R scores. In terms of Wechsler's (1981) seven category intelligence classification, levels of agreement were 83%, 72%, and 82% for the Verbal, Performance, and Full scales, respectively. These findings support the use of the seven subtest short form with brain-damaged women when time is at a premium and only a general estimate of intellectual functioning is required.

Adult↗
PubMed1998

The role of 99m-Tc HMPAO SPECT in the diagnosis of Creutzfeldt-Jacob disease.

A patient with acute dementia underwent imaging of the brain with technetium-99m hexamethylpropyleneamine oxime single-photon emission computed tomography. Regional perfusion abnormalities were identified in multiple locations, particularly in the left frontal lobe. This information was used to direct an open brain biopsy, which led to a diagnosis of Creutzfeldt-Jacob disease.

Biopsy↗
PubMed1997

Brachial plexus palsy associated with cesarean section: an in utero injury?

OBJECTIVE: Brachial plexus injury may be unrelated to manipulations performed at the time of delivery, occurring in the absence of shoulder dystocia and in the posterior arm of infants with anterior shoulder dystocia. To further support the hypothesis that some of these nerve injuries appear to be of intrauterine origin, we present a series of brachial plexus palsies associated with atraumatic cesarean delivery among fetuses presenting in the vertex position. STUDY DESIGN: We performed a computerized search of all deliveries from 1991 to 1995 for the discharge diagnoses of brachial plexus injury and cesarean section. Inclusion criteria included cephalic presentation at the time of delivery and the absence of traumatic delivery. RESULTS: We noted six cases of Erb's palsy, with four palsies in the anterior shoulder and two in the posterior arm. Among those five patients undergoing cesarean section because of labor abnormalities, two had uterine cavity abnormalities whereas one had a prolonged second stage of labor. One brachial plexus palsy occurred in the absence of active labor. All nerve injuries were persistent at age 1 year. CONCLUSIONS: Brachial plexus palsy can be associated with cesarean delivery. Such palsies appear to be of intrauterine origin and are more likely to persist.

Adult↗
PubMed1997

Clinical risk factors for placenta previa-placenta accreta.

OBJECTIVE: Our purpose was to define the clinical risk factors associated with placenta previa-placenta accreta. STUDY DESIGN: Hospital records were reviewed of all cases of placenta accreta confirmed histologically between January 1985 and December 1994. Additionally, we reviewed the records of all women with placenta previa and all those undergoing cesarean hysterectomy during the same period. Multiple logistic regression analysis was used to identify independent clinical risk factors for placenta accreta. RESULTS: Among 155,670 deliveries, 62 (1/2510) were complicated by histologically confirmed placenta accreta. Placenta accreta occurred in 55 of 590 (9.3%) women with placenta previa and in 7 of 155,080 (1/22,154) without placenta previa (relative risk 2065, 95% confidence interval 944 to 4516, p < 0.0001). Among women with placenta previa, advanced maternal age (> or = 35 years) and previous cesarean delivery were independent risk factors for placenta accreta. Placenta accreta was present in 36 of 124 (29%) cases in which the placenta was implanted over the uterine scar and in 4 of 62 (6.5%) cases in which it was not (relative risk 4.5, 95% confidence interval 1.68 to 12.07). Among women with placenta previa, the risk of placenta accreta ranged from 2% in women < 35 years old with no previous cesarean deliveries to almost 39% in women with two or more previous cesarean deliveries and an anterior or central placenta previa. CONCLUSION: Placenta accreta occurs in approximately 1 of 2500 deliveries. Among women with placenta previa, the incidence is nearly 10%. In this high-risk group advanced maternal age and previous cesarean section are independent risk factors.

Adult↗
PubMed1997

Intrapartum rupture of the unscarred uterus.

OBJECTIVE: To examine risk factors and maternal and neonatal outcomes in ten cases of intrapartum rupture of the unscarred uterus. METHODS: Uterine ruptures in women without previous cesarean deliveries were identified from an ongoing log for a 12-year period beginning January 1, 1983. Detailed information was obtained by review of hospital records. RESULTS: From January 1, 1983, through December 31, 1994, we identified 13 uterine ruptures in women without previous cesarean deliveries. Three resulted from motor vehicle accidents and were excluded from analysis. Ten occurred during labor and are the subjects of our report. The incidence of intrapartum rupture of an unscarred uterus was 1 in 16,849 deliveries. Associated factors included oxytocin use (four cases), prostaglandin use (three cases), use of vacuum or forceps (three cases), grand multiparity (two cases), and malpresentation (two cases). Intervention was prompted by fetal heart rate decelerations in seven cases and by severe hemorrhage in three. Uterine rupture was associated with acute abdominal pain in six cases, maternal tachycardia in five, and severe hypotension in two. Neonatal outcomes were normal in nine cases. There were no maternal or perinatal deaths. CONCLUSION: Intrapartum rupture of the unscarred uterus is a rare obstetric emergency. Maternal and perinatal outcomes are optimized by awareness of risk factors, recognition of clinical signs and symptoms, and prompt surgical intervention.

Adult↗
PubMed1997

All-trans retinoic acid for the treatment of acute promyelocytic leukemia in pregnancy.

BACKGROUND: Acute promyelocytic leukemia, a subset of acute myelogenous leukemia, is commonly associated with disseminated intravascular coagulation (DIC). All-trans retinoic acid is effective in the treatment of acute promyelocytic leukemia and may prevent an exacerbation of DIC. There is limited information, however, regarding the use of this agent in pregnancy. CASE: A 29-year-old woman with acute promyelocytic leukemia and DIC at 24 weeks' gestation was treated successfully with all-trans retinoic acid during the pregnancy, delivering a viable, normal infant at 33 weeks. CONCLUSION: This case illustrates the successful use of all-trans retinoic acid in pregnancy for the treatment of acute promyelocytic leukemia. With the combined, intensive efforts of the perinatal, neonatal, and hematology-oncology services, a favorable outcome was achieved.

Adult↗
PubMed1997

Histologic assessment of mineral trioxide aggregate as a root-end filling in monkeys.

Mineral Trioxide Aggregate (MTA) has been shown in a number of experiments to be a potential root-end filling material. The purpose of this study was to examine the periradicular tissue response of monkeys to MTA and amalgam as root-end fillings. The pulps were removed from all the maxillary incisors of three monkeys. The root canals were prepared and filled with laterally condensed guttapercha and sealer, and the access cavities were restored with amalgam. Buccal mucoperiosteal flaps were raised, and root-end resections were performed before root-end cavity preparation with burs. The root-end cavities in half of the teeth were filled with MTA, while amalgam was placed in the other cavities. After 5 months the periradicular tissue response was evaluated histologically. The results showed no periradicular inflammation adjacent to five of six root ends filled with MTA; also five of six root ends filled with MTA had a complete layer of cementum over the filling. In contrast, all root ends filled with amalgam showed periradicular inflammation, and cementum had not formed over the root-end filling material, although it was present over the cut root end. Based on these results and previous investigations, MTA is recommended as a root-end filling material in man.

Aluminum Compounds↗
PubMed1997

In vitro activities of ciprofloxacin and rifampin alone and in combination against growing and nongrowing strains of methicillin-susceptible and methicillin-resistant Staphylococcus aureus.

We characterized the effects of ciprofloxacin and rifampin alone and in combination on Staphylococcus aureus in vitro. The effects of drug combinations (e.g., indifferent, antagonistic, or additive interactions) on growth inhibition were compared by disk approximation studies and by determining the fractional inhibitory concentrations. Bactericidal effects in log-phase bacteria and in nongrowing isolates were characterized by time-kill methods. The effect of drug combinations was dependent upon whether or not cells were growing and whether killing or growth inhibition was the endpoint used to measure drug interaction. Despite bactericidal antagonism in time-kill experiments, our in vitro studies suggest several possible explanations for the observed benefits in patients treated with a combination of ciprofloxacin and rifampin for deep-seated staphylococcal infections. Notably, when growth inhibition rather than killing was used to characterize drug interaction, indifference rather than antagonism was observed. An additive bactericidal effect was observed in nongrowing bacteria suspended in phosphate-buffered saline. While rifampin antagonized the bactericidal effects of ciprofloxacin, ciprofloxacin did not antagonize the bactericidal effects of rifampin. Each antimicrobial prevented the emergence of subpopulations that were resistant to the other.

Anti-Infective Agents↗