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Biomedical subjects

D L Miller

Publications and source records attributed to D L Miller.

At least 163 records · Page 9Linked to original sources
PubMed1996

Optimal evaluation of patients with nonobstructive esophageal dysphagia. Manometry, scintigraphy, or videoesophagography?

The aims of this study were to compare diagnostic accuracy, cost, and patient tolerance of videoesophagography and esophageal transit scintigraphy to esophageal manometry in the evaluation of nonobstructive esophageal dysphagia. Eighty-nine consecutive patients underwent videoesophagography, scintigraphy, and manometry. The sensitivities for diagnosing specific esophageal motility disorders, using esophageal manometry as the standard, were 75% and 68% for videoesophagography and scintigraphy, respectively, with positive predictive accuracies of 96% and 95% for achalasia, 100% and 67% for diffuse esophageal spasm, 100% and 75% for scleroderma, 50% and 67% for isolated LES dysfunction, 57% and 48% for nonspecific esophageal motility disorders, and 70% and 68% for normal esophageal motility. The cost for videoesophagography is less than that for either manometry or scintigraphy. Both videoesophagography and scintigraphy were better tolerated than manometry. It is concluded that videoesophagography and scintigraphy accurately diagnose primary esophageal motility disorders, achalasia, scleroderma, and diffuse esophageal spasm, but are less accurate in distinguishing nonspecific esophageal motility disorders from normal. When considering accuracy, cost, and patient acceptance, these findings suggest that videoesophagography is a useful initial diagnostic study for the evaluation of nonobstructive esophageal dysphagia.

Adult↗
PubMed1996

The role of cavitation in the induction of cellular DNA damage by ultrasound and lithotripter shock waves in vitro.

The induction of DNA strand breaks in Chinese hamster ovary cells was measured with the comet assay after continuous wave ultrasound or lithotripter shock wave exposure. Cell lysis and hydrogen peroxide production were measured to gauge the level of inertial cavitation activity. Significant DNA damage was found after 2.17-MHz ultrasound exposure at 37 degrees C to 0.82 MPa for 2 min or 4 min, and to 0.58 MPs for 4 min. A significant portion of the damage induced at the 0.82-MPa level was repaired by the cells when warmed. Neither exposure to 500 or 1000 shock waves at 37 degrees C in a thin-walled tube, nor exposure to 1000, 1500 or 2000 shock waves at 25 degrees C in a polyethylene pipette bulb produced a significant effect, when the flash of light from the spark-gap discharge was blocked. This finding was consistent with the generally lower lysis and hydrogen peroxide production by the shock wave exposure.

Animals↗
PubMed1996

A review of in vitro bioeffects of inertial ultrasonic cavitation from a mechanistic perspective.

This selective review of the biological effects of ultrasound presents a synopsis of our current understanding of how cells insonated in vitro are affected by inertial cavitation from the standpoint of physical and chemical mechanisms. The focus of this review is on the physical and chemical mechanisms of action of inertial cavitation which appear to be effective in causing biological effects. There are several fundamental conditions which must be satisfied before cavitation-related bioeffects may arise. First, bubbles must be created and then brought into proximity to cells. Exposure methods are critical in this regard, and simple procedures such as rotation of a vessel containing the cells during exposure can drastically alter the results. Second, once association is achieved between bubbles and cells, the former must interact with the latter to produce a bioeffect. It is not certain that the inertial event is the prime mechanism by which cells are lysed; there is evidence that the turbulence associated with bubble translation may cause lysis. Additionally, there appear to be chemical and other physical mechanisms by which inertial cavitation may affect cells; these include the generation of biologically effective sonochemicals and the apparent emission of ultraviolet (UV) and soft X-rays. The evidence for inertial cavitation occurring within cells is critically reviewed.

Animals↗
PubMed1996

Contrast-agent gas bodies enhance hemolysis induced by lithotripter shock waves and high-intensity focused ultrasound in whole blood.

Fresh canine whole blood was exposed in 1.3-mL disposable pipette bulbs with or without added Albunex contrast agent to lithotripter shock waves (rate: 2 Hz; mean pressure amplitude: 14.8 MPa) or 1.28-MHz high-intensity focused ultrasound up to a mean pressure amplitude of 17.8 MPa. Significant shock-wave-induced hemolysis up to about 10% was detected after 500 or more shock waves without added agent, after 200 with 1% added agent and after 100 with 10% added contrast agent. Hemolysis was increased somewhat with added contrast agent, but this enhancement was not statistically significant. For ultrasound exposure, significant hemolysis approaching 100% was detected for 100-ms continuous exposure at 17.8 MPa without added gas bodies. Addition of 1% contrast agent enhanced the hemolysis by reducing the apparent threshold to 10 MPa. Burst mode exposure with a 100-ms total on-time (20 microseconds, 100 microseconds and 1-ms bursts) also yielded hemolysis enhancement with added contrast agent, with results similar to the 100-ms continuous exposure. The added gas bodies appear to lower cavitation thresholds by serving as cavitation nuclei in the blood.

Albumins↗
PubMed1996

Managing fatigue in operational settings. 1: Physiological considerations and countermeasures.

The authors consider three aspects of managing fatigue in the workplace. They provide a brief overview of important scientific findings related to sleep and circadian physiology that establish the psychobiological foundation of fatigue. Their major focus is on the relevance of these findings to operational settings. In addition, they provide examples to describe practical fatigue countermeasures that can be used in operational settings.

Circadian Rhythm↗
PubMed1996

Managing fatigue in operational settings 2: An integrated approach.

The six domains that must be addressed in managing fatigue in operational settings are identified, and examples of how the aviation industry is dealing with the problems in each domain are given. Challenges facing healthcare providers in managing fatigue are also discussed.

Aviation↗
PubMed1996

Exposure to 60 Hz magnetic fields does not alter clinical progression of LGL leukemia in Fischer rats.

Associations between exposure to 60-Hz magnetic fields in residential and occupational environments and the incidence of leukemia and other cancers has been suggested by the results of a number of epidemiology studies. To address these potential associations, a study has been conducted to determine if 60-Hz magnetic fields can alter the clinical progression of leukemia. In the large granular lymphocytic (LGL) leukemia model, spleen cells from aged leukemic rats were transplanted into young, male Fischer 344 rats, producing leukemia in a relatively short period. A total of 72 animals were randomly assigned to four treatment groups (18/group) as follows: (1) 10 G; (2) sham exposed (null energized field) (approximately 20 mG); (3) ambient controls (<1 mG); and (4) positive controls (5 Gy whole body irradiation from Cobalt-60, 4 days before initiation of exposure). At the initiation of exposure or sham-exposure, all rats were injected (i.p.) with 2.2x10(7) fresh, viable, LGL leukemia cells. The magnetic fields were activated for 20 h per day, 7 days per week; all exposure conditions were superimposed over the natural ambient magnetic field. Eighteen rats from each treatment were bled at weeks 0, 2, 4, 5, 6, 7, 8 and 10 to monitor, in the same set of animals, the clinical progression of the LGL disease and survival of the animals. Peripheral blood hematological changes were monitored to evaluate the progression of the leukemia. In general, no significant or consistent differences were detected between the magnetic field exposed and the ambient field control groups, although some inconsistent and random differences were occasionally observed. These data indicate that the 10 G magnetic fields did not significantly alter the clinical progression of LGL leukemia in Fischer 344 rats.

Animals↗
PubMed1996

The use and cost of hospital services by London AIDS patients with different AIDS defining conditions.

BACKGROUND: Contracting for HIV service provision is now an established part of the National Health Service commissioning process. AIDS is a heterogeneous condition, comprising various opportunistic illnesses which require different services and which have different resource implications. This study describes the use of hospital services and associated costs for the management of different AIDS defining conditions. METHOD: A retrospective case-notes analysis was performed, of 335 AIDS patients treated at St Mary's Hospital, London, between 1 January 1983 and 30 September 1989, as well as a costing exercise of 37 clinical departments to calculate HIV-related costs. RESULTS: Mean age at time of AIDS diagnosis for these predominantly homosexual men was 38 years. Use of services varied, as did associated costs-from 8163 pounds per patient-year for patients with Constitutional Disease to 42,124 pounds for those with Cytomegalovirus Disease Most diagnostic categories showed a shift over the study period from an in-patient- to an out-patient-based service. Patients diagnosed after 1987 had overall lower costs per patient-year compared with those diagnosed before 1987: whereas out-patient costs for most groups had increased, in-patient expenditure decreased. For most categories, in-patient care costs and out-patient drugs prescribed provided the greatest proportion of total costs. Average costs per in-patient day ranged from 334 pounds to 433 pounds, and average costs per out-patient visit ranged from 99 pounds to 411 pounds for different AIDS defining conditions. CONCLUSIONS: Different opportunistic illnesses of symptomatic HIV disease have different treatment and resource implications. Casemix will need to be taken into consideration when contracting for HIV services, including extra-contractual referrals.

AIDS-Related Opportunistic Infections↗
PubMed1996

Behavioral intervention to improve calorie intake of children with cystic fibrosis: treatment versus wait list control.

Changes in calorie intake and weight gain were evaluated in five children with cystic fibrosis (CF) who received behavioral intervention and four children with CF who served as wait list controls. The behavioral intervention was a 6-week group treatment that provided nutritional education plus management strategies aimed at mealtime behaviors that parents find most problematic. The control group was identified prospectively and was evaluated on all dependent measures at the same points in time pre- and posttreatment as the intervention group. Difference scores on calorie intake and weight gain from pre- to posttreatment were compared between groups using t tests for independent samples. The behavioral intervention group increased their calorie intake by 1,032 calories per day, while the control group's intake increased only 244 calories per day from pre- to posttreatment [t(6) = 2.826, p = 0.03]. The intervention group also gained significantly more weight (1.7 kg) than the control group (0 kg) over the 6 weeks of treatment [t(7) = 2.588, p = 0.03] and demonstrated catchup growth for weight, as indicated by improved weight Z scores (-1.18 to -0.738). The control group showed a decline in weight Z scores over this same time period (-1.715 to -1.76). One month posttreatment, the intervention was replicated with two of the four children from the control group. Improved calorie intake and weight gain pre- to posttreatment were again found in these children. At 3- and 6-month follow-up study of children receiving intervention, maintenance of calorie intake and weight gain was confirmed. No changes were found on pulmonary functioning, resting energy expenditure, or activity level pre- to posttreatment. This form of early intervention appears to be promising in improving nutritional status and needs to be investigated over a longer period of time to evaluate the effects of treatment gains on the disease process.

Adipose Tissue↗
PubMed1996

First, do no harm.

Explore the source record for details and available documents.

Chemoembolization, Therapeutic↗
PubMed1996

Effects of dietary calcium and phosphorus on vitamin D metabolism and calcium absorption in hamster.

We studied the following responses to restriction of dietary calcium and phosphorus in the growing hamster: (i) serum concentrations of calcium, inorganic phosphorus, magnesium, and vitamin D metabolites; and (ii) calcium transport by ileum. Diets fed were normal calcium with normal or low phosphorus or low calcium with normal or low phosphorus. We found serum 1 alpha,25-dihydroxycalciferol (1,25-[OH]2D) concentration did not differ significantly among the diet groups. Calcium absorption, measured as serosal/mucosal calcium concentration ratio produced by everted ileal sac, was greater in the low calcium, normal phosphorous group than in all other groups. The other groups did not differ from one another in calcium absorption. Feeding the low calcium, normal phosphorus diet increased inorganic phosphorus and magnesium but decreased calcium concentration in serum in comparison with the three other diets. Both low phosphorus diets were without effect on serum calcium, but the low calcium, low phosphorus diet increased serum inorganic phosphorus and magnesium above that of the normal calcium, low phosphorus diet. Ileal calcium absorption in hamster (i) was independent of serum 1,25-(OH)2D concentration; (ii) increased in response to low dietary calcium if dietary phosphorus was normal; and (iii) was independent of dietary calcium, if dietary phosphorus was low. Despite increased calcium absorption, serum calcium was decreased in the low calcium-normal phosphorus group as compared with all other groups. Feeding low calcium diets increased serum inorganic phosphorus and magnesium as compared with feeding the corresponding normal calcium diets (i.e., independently of whether dietary phosphorus content was normal or low). These studies demonstrate that the interrelationships between calcium absorption and vitamin D and mineral metabolism in hamster differ from other mammals.

Absorption↗
PubMed1996

The role of ultraviolet light in the induction of cellular DNA damage by a spark-gap lithotripter in vitro.

PURPOSE: The purpose of this study was to investigate the mechanisms for DNA damage induced by a spark-gap lithotripter. MATERIALS AND METHODS: Cultured Chinese hamster ovary cells suspended in phosphate buffered saline were exposed in small chambers placed at the focus of a lithotripter in a 37C water bath. Viability was checked by trypan blue exclusion, and DNA strand breaks were evaluated with the comet assay after exposure. RESULTS: About 50% cell lysis and significant DNA damage in surviving cells were found after 500 discharges. The strand break effect, but not the lysis, could be eliminated by blocking the light emitted by the discharge. The exposure chamber material influenced the results, and use of nutrient medium with serum reduced the observed effects. The DNA damage was eliminated by added novobiocin and enhanced by added aphidicolin, as expected for strand breaks associated with repair of ultraviolet light damage. The DNA strand-break effect of 500 spark-gap discharges approximated that obtained from a positive control treatment with 38 J/m2. of 254 nm. ultraviolet light. CONCLUSIONS: Thus, the observed DNA damage appears to result from exposure of cells to the ultraviolet light emissions of the spark-gap discharge, rather than to the shockwaves or shockwave induced cavitation, which causes the cell lysis. Exposure of the skin to this ultraviolet light during lithotripsy might have some clinical implications for prolonged or repeated treatment.

Animals↗
PubMed1995

Localization of insulinomas to regions of the pancreas by intra-arterial stimulation with calcium.

OBJECTIVE: To determine the sensitivity of calcium injected into pancreatic arteries in localizing insulin-secreting tumors to regions of the pancreas. DESIGN AND PATIENTS: To stimulate the release of insulin, 25 patients with surgically proven insulinomas (average diameter, 15 mm) had calcium gluconate (0.025 mEq Ca++/kg body weight) injected before surgery into the arteries supplying the pancreatic head (gastroduodenal and superior mesenteric arteries) and the body and tail (splenic artery) of the pancreas. SETTING: Tertiary referral hospital. MEASUREMENTS: Insulin levels were measured in samples taken from the right and left hepatic veins before and 30, 60, and 120 seconds after calcium injection. A twofold increase in insulin level in the sample taken from the right hepatic vein 30 or 60 seconds after injection localized the insulinoma to the segment of the pancreas supplied by the selectively injected artery. Localization done using calcium stimulation was compared with localization done using transcutaneous ultrasonography (n = 22), computed tomography (n = 23), magnetic resonance imaging (n = 21), arteriography (n = 25), and portal venous sampling (n = 9). RESULTS: Calcium stimulation localized 22 of 25 insulinomas (sensitivity, 88% [95% CI, 68% to 97%]) to the correct region of the pancreas. The sensitivities of the other imaging methods were 9% for ultrasonography (CI, 1% to 23%), 17% for computed tomography (CI, 5% to 39%), 43% for magnetic resonance imaging (CI, 22% to 66%), 36% for arteriography (CI, 18% to 57%), and 67% for portal venous sampling (CI, 30% to 93%). Calcium stimulation added only a few minutes to the time needed for pancreatic arteriography and caused no morbid conditions. CONCLUSION: Intra-arterial calcium stimulation with right hepatic vein sampling for insulin gradients is the most sensitive preoperative test for localizing insulinomas.

Adult↗
PubMed1995

Esophageal resection for recurrent achalasia.

BACKGROUND: This study examined esophageal resection as treatment for recurrence or treatment complications of achalasia. METHODS: From 1976 through 1992, 37 patients (20 men and 17 women) underwent esophageal resection after initial surgical treatment for achalasia. The median age was 56 years (range, 19 to 84 years). Initial surgical treatment consisted of modified Heller myotomy in 28 patients, combined myotomy and antireflux procedure in 6, and antireflux procedure alone in 3. Twenty-six patients required an additional surgical procedure before esophageal resection (70.3%). Indication for esophageal resection was obstructive symptoms in 30 patients, cancer in 3, bleeding in 2, and perforation during dilation in 2. Reconstruction was established with the stomach in 26 patients, colon in 6, and small bowel in 5. Anastomosis was at the cervical level in 20 patients (54.1%) and intrathoracic in 17 (45.9%). RESULTS: There were two operative deaths (5.4%), both caused by intraoperative hemorrhage during transhiatal resection. Twelve patients (32.4%) had complications, which included cardiac dysrhythmia in 3, cervical anastomotic leak in 2, transient vocal cord paralysis in 2, pneumonia in 2, pulmonary embolus in 2, and reexploration for bleeding in 1. Follow-up was complete in all patients and ranged from 1.4 to 16 years (median, 6.3 years). Excellent or good long-term functional results were present in 32 patients (91.4%). CONCLUSIONS: Esophageal resection provides reasonable long-term functional results in patients with recurrence or treatment complications of achalasia. In our experience, transhiatal resection is associated with increased morbidity and mortality.

Adult↗
PubMed1995

Comet assay reveals DNA strand breaks induced by ultrasonic cavitation in vitro.

The induction of DNA strand breaks in cultured Chinese hamster ovary (CHO) cells was investigated in suspensions directly exposed to 2.17-MHz ultrasound. Production of hydrogen peroxide, a DNA-damaging sonochemical, by inertial cavitation was enhanced by the use of argon-and-oxygen-bubbled media and cell survival was improved by establishing standing waves and minimizing tube rotation. Viable cells were separated from the suspension after exposure and kept on ice for evaluation with the single-cell gel electrophoresis (comet) assay. With this assay, DNA damage from as little as 2-mumol/L hydrogen peroxide treatment for 30 min could be detected, and cell survival as low as 2-5% after ultrasound exposure was adequate for assay. An ultrasound dose-response trend was noted for increasing pressure amplitude up to 0.82 MPa (free field) and increasing exposure duration up to 4 min. The cells were able to repair some of the strand breaks when warmed to 28 degrees C for 30 min. The effect was not eliminated by addition of catalase, which indicates that the DNA damage was not due to the action of residual H2O2 alone. The results confirm the hypothesis of DNA damage in cells surviving inertial cavitation.

Animals↗
PubMed1995

Ultrasound contrast agents nucleate inertial cavitation in vitro.

Some ultrasound contrast agents contain stable bodies of gas, and this study was undertaken to determine if these agents could provide nuclei for inertial cavitation. Inertial cavitation was detected and assessed by the measurement of the sonochemical hydrogen peroxide after exposure to 2.17-, 2.95- or 3.8-MHz ultrasound. A noncavitating system was obtained by removing cavitation nuclei from the rotating tube exposure chambers by vacuum degassing, and from the phosphate-buffered saline medium by filtering. Albunex added at 10-2, 10-3 or 10-4 dilutions, or Levovist added at 2 mg mL-1, 0.2 mg mL-1 or 0.02 mg mL-1 all initiated significant H2O2 production for 2.17-MHz ultrasound at 0.41 MPa or higher spatial peak pressure amplitude for 5 min exposure gated at 0.25 s on and off with 60-rpm rotation. Not rotating the tube virtually eliminated H2O2 production. For 2.5-min continuous exposure, both agents initiated significant H2O2 production for 2.95-MHz exposure at 0.58 MPa or higher, but not for 3.8-MHz exposure up to 1.16 MPa. Bubble-based ultrasound contrast agents therefore appear to be able to provide nuclei for inertial cavitation in the rotating tube exposure system.

Albumins↗