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Biomedical subjects

D L Miller

Publications and source records attributed to D L Miller.

At least 307 records · Page 17Linked to original sources
PubMed1989

Perforation complicating rifampin-associated pseudomembranous enteritis.

An 18-year-old man developed a perforated jejunum while receiving rifampin antituberculous chemotherapy. The perforations were located within longitudinal ulcers characteristic of pseudomembranous enterocolitis. Pseudomembranous inflammation was limited to the small intestine. The absence of colonic involvement delayed establishment of the diagnosis. Successful surgical intervention consisting of small-bowel resection with primary anastomosis was accomplished for this rare and potentially fatal complication of antituberculous chemotherapy.

Adolescent↗
PubMed1989

Addition of magnetic field capability to existing extremely-low-frequency electric field exposure systems.

Magnetic field systems were added to existing electric field exposure apparatuses for exposing cell suspensions in vitro and small animals in vivo. Two horizontally oriented, rectangular coils, stacked one directly above the other, have opposite electric currents. This configuration minimizes leakage fields and allows sham- and field-exposure systems to be placed in the same room or incubator. For the in vitro system, copper plates formed the loop-pair, with up to 900 A supplied by a 180:1 transformer. Electric fields were supplied via electrodes at the ends of cell-culture tubes, eight of which can be accommodated by each exposure system. Two complete systems are situated in an incubator to allow simultaneous sham and field exposure up to 1 mT. For the in vivo system, four pairs of 0.8 x 2.7-m coils made of copper bus bar are employed. This arrangement is energized from the power grid via a 30:1 transformer; horizontal magnetic flux densities up to 1 mT can be generated. Pairs of electrode plates spaced 30.5 cm apart provide electric field exposure of up to 130 kV/m. Four systems with a capacity of 48 rats each are located in one room. For both the in vitro and in vivo systems, magnetic exposure fields are uniform to within +/- 2.5%, and sham levels are at least 2,500-fold lower than exposure levels. Potential confounding factors, such as heating and vibration, were examined and found to be minimal.

Animals↗
PubMed1989

Radionuclide renography predicts functional changes in patients with renal artery involvement by Takayasu's arteritis.

Renovascular hypertension is a major complication of Takayasu's arteritis, which contributes to the high mortality associated with the disease. We studied 5 patients affected by different degrees of Takayasu's arteritis to assess the usefulness of radionuclide renography in evaluating renal perfusion and function, and to predict changes induced by the disease before and after therapeutic interventions. Computer-assisted dynamic renal imaging with Tc-99m diethylenetriaminepentaacetic acid (DPTA) and I-131 orthoiodohippurate (OIH), and renal arteriography were concurrently performed in all patients. Two patients with hemodynamically insignificant renal artery stenosis showed normal perfusion and function by renography. Three patients had significant renal artery stenosis and functional changes on renography. Subsequently, two of these patients had successful therapy (one had bilateral renal artery bypass grafts, and the other had renal artery angioplasty), and both showed functional improvement at renography. Our results demonstrate that radionuclide renography is valuable in the assessment of functional changes induced by Takayasu's arteritis as well as for determining the response to therapeutic interventions.

Adolescent↗
PubMed1989

Cytoplasmic free calcium concentration in dark-adapted retinal rod outer segments.

We measured the cytoplasmic free Ca concentration in the outer segment of intact, dark-adapted rods of the toad retina. The Ca indicator dye, Quin2, was loaded at concentrations of 0.273 +/- 0.06 mM into the rod cytoplasm by incubation of isolated retinas in the hydrophobic ester, Quin2AM. Quin2 did not alter the cytoplasmic Ca concentration in the dark, but it buffered light-dependent concentration transients and, hence, modified the rod photoresponse. In the presence of 1 mM external Ca, the cytoplasmic Ca concentration in the dark was 273 +/- 129 nM.

Aminoquinolines↗
PubMed1989

Single strand DNA breaks in human leukocytes induced by ultrasound in vitro.

Single strand breaks (SSBs) in the DNA of fresh human leukocytes were analyzed after in vitro exposure to ultrasound in an ice bath. The alkaline elution method was used to quantify the frequency of SSBs. Five different ultrasonic exposures were employed: (1) 53 mW/cm2 spatial-peak temporal-average intensity (SPTA), 0.37:100 microseconds pulsed 6.2 MHz ultrasound presumably without cavitation, (2) 470 mW/cm2 (SPTA) continuous 1.7 MHz ultrasound with gas-body activation, which is a form of cavitation lacking in chemical activity, (3) 10.8 W/cm2 (SPTA), 3.0:100 microseconds pulsed 1.48 MHz ultrasound, presumably without cavitation, (4) 161 W/cm2 (SPTA) continuous 1.45 MHz ultrasound with transient cavitation, and (5) 94 W/cm2 (SPTA) continuous 8 MHz ultrasound presumably without cavitation. All of these exposures produced negative results, except (4), which yielded a significantly increased frequency of SSBs relative to sham exposed cells. For this condition, the SSB effect was comparable in magnitude to that of 1 Gy of 60Co gamma-rays, and may have resulted from the chemical activity associated with transient cavitation. The SSBs were detected in cells which remained intact after exposure; however, it is uncertain if any of the ultrasonically-induced SSBs occurred in viable cells.

DNA Damage↗
PubMed1989

Investigation of cavitation in flowing media by lithotripter shock waves both in vitro and in vivo.

Cavitation produced by lithotripter shock waves was characterized in vitro in water and blood, and in vivo in aortic blood by means of a 1.6 MHz resonant bubble detector. This system was readily able to detect bubbles resulting from shock-wave induced cavitation in both water and blood flowing through plastic tubes in vitro, and even in blood pumped by the heart through a plastic arterio-venous shunt. However, this system was unable to detect evidence of shock-wave induced cavitational activity occurring within the intact vascular systems of dogs in vivo.

Animals↗
PubMed1989

Bubble cycling as the explanation of the promotion of ultrasonic cavitation in a rotating tube exposure system.

The cavitation-promotion effect of rotating a sample tube during ultrasound exposure is not yet fully understood. Cavitation-induced hemolysis was observed in 0.5% hematocrit suspensions of erythrocytes exposed for 5 min at 37 degrees C. For 1.61 MHz unfocused exposure an apparent threshold of 4 W/cm2 spatial-peak intensity was obtained for hemolysis in a 72 rpm rotating exposure chamber which was made of dialysis tubing. If the tube was not rotated, then no hemolysis was observed up to 16 W/cm2. Creation of standing waves in the sample by using a thick-walled culture tube, or by placing a styrofoam reflector behind the dialysis tube did not change the apparent threshold. Focused 1.45 MHz exposure gave the same apparent threshold in a rotating dialysis tube, but this increased to about 128 W/cm2 for the nonrotating case. When the focused ultrasound was turned on for half a rotation and off for half, results were similar to those for a nonrotating CW case, while on-off cycles synchronized to a quarter rotation gave results similar to the rotating CW case. A plausible explanation of the rotation effect, given these results, is that rotation brings bubbles on the rear wall, where the beam exits the tube, back around to the front again, where the bubbles may then re-nucleate the suspension, and thereby promote cavitation bioeffects in the rotating tube.

Animals↗
PubMed1989

The detection of renal carcinoma extension into the renal vein and inferior vena cava: a prospective comparison of venacavography and magnetic resonance imaging.

Accurate preoperative evaluation of the inferior vena cava and renal vein in patients with renal cell carcinoma is mandatory to plan a successful surgical approach. The presence of venous extension may alter transfusion and anesthetic requirements, as well as require the addition of a vascular surgeon to the operative team. Venacavography traditionally has been considered the most reliable method to identify tumor thrombus, although magnetic resonance imaging has been proposed as a possible noninvasive alternative. We compared prospectively the accuracy of these 2 methods in 44 consecutive patients with renal cell carcinoma who subsequently underwent nephrectomy. Of the 44 patients 11 (25%) had tumor extension into the inferior vena cava and 17 (39%) had involvement of the renal vein at operation. Venacavography and magnetic resonance imaging correctly identified 9 of the 11 patients (82%) with inferior vena caval thrombus. When the results of both tests were combined, all 11 cases of vena caval extension were identified. Venacavography was slightly more sensitive (71%) in identifying the presence of renal vein thrombus than magnetic resonance imaging (65%) but these differences were not statistically significant. Magnetic resonance imaging better localized the thrombus within the renal vein. We conclude that venacavography and magnetic resonance imaging offer equal diagnostic accuracy in the identification of venous extension of renal cell carcinoma. The combination of both tests results in higher diagnostic yield than either test alone. Neither test by itself is reliable in the presence of a large, bulky adenopathic lesion that compresses the inferior vena cava.

Adult↗
PubMed1989

The role of non-acoustic factors in the induction and proliferation of cavitational activity in vitro.

It is well known that a liquid exposed to relatively low intensities of MHz ultrasound may or may not cavitate depending upon a variety of non-acoustic factors. This paper shows that in some cases the material used as the acoustically transparent window and even the length of the sample chamber may also be important factors. Cling film, dialysis membrane and Parafilm are all equally acceptable as acoustically transparent windows for ultrasound, whereas glass cover slips or 'soft' surfaces (in which active bubbles may embed themselves) are not. All the results obtained confirm the validity of bubble recycling as being the dominant mechanism responsible for the enhancement of cavitational activity commonly observed when the sample chamber is rotated.

Acoustics↗
PubMed1989

A pilot study of sexual lifestyle in a random sample of the population of Great Britain.

Rates of sexual-partner change and patterns of high-risk behaviour are important determinants of the spread of HIV. We carried out a survey to assess the feasibility of studying sexual lifestyle in a random sample of the British population, aged 16-64 years, in November 1987. Two thousand and seventy-seven households were selected using a multi-stage probability sampling procedure. Seven hundred and eight-five adults participated in a structured interview. The schedule included demographic details, attitudes to AIDS, numbers of sexual partners in different time periods, history of homosexuality and contact with prostitutes. An interview was obtained in 61% of households where contact was made, but the overall response rate was low (48%). There was marked variability between individuals in numbers of sexual partners in given time intervals. Men and women in younger cohorts had experienced first sexual intercourse earlier and had higher numbers of sexual partners than people in older cohorts. Surprisingly few reported high-risk behaviour such as homosexuality and use of prostitution. The methodological problems in trying to obtain unbiased and valid data on sexual behaviour are discussed. Further work is necessary to improve the response rate and questionnaire design.

Adolescent↗
PubMed1989

Risk factors for HIV-1 infection in a British population: lessons from a London sexually transmitted diseases clinic.

Between September 1985 and June 1988, 6923 people (4550 men and 2373 women) were tested for HIV-1 antibodies at a sexually transmitted disease clinic, London, UK. Of the 6923 individuals tested, 558 (8%) were seropositive, of whom 523 (94%) were men and 35 (6%) women. Of the seropositives, 84% were homosexual or bisexual men, 5% were intravenous drug users, 4% were heterosexual contacts of HIV seropositives, 4% had multiple risk factors, 2% were heterosexual contacts of central African partners and 1% were heterosexuals with no other risk factors. This prevalence pattern conforms to that observed in other industrialized nations. For the women, heterosexual intercourse with an HIV-infected partner, intravenous drug use and heterosexual contact with a partner from central Africa were the main risk factors for infection. The important risk factors among the men were heterosexual contact with an HIV-seropositive partner, being homosexual or bisexual, intravenous drug use and heterosexual contact with a resident from central Africa. heterosexual and homosexual transmission were implicated as the main routes for viral spread in this British population.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Heparin in angiography: current patterns of use.

All members and fellows of the Society of Cardiovascular and Interventional Radiology were surveyed to determine current patterns of heparin use in angiography. Five hundred responses (68%) were received. In general, significant differences exist across the United States in the mean heparin dose for angiography, mean dose for angioplasty, heparin concentration in flush solutions, and, especially, frequency with which heparin is mixed with nonionic contrast media. Few respondents routinely use systemic (bolus) heparinization for angiography. Heparin concentration in flush solutions varies from 0 IU/L to 12,000 IU/L. Eleven percent of respondents mix heparin with nonionic contrast agents, at a median dose of 5 IU/mL. Results of this survey reveal patterns of practice but do not represent a standard of practice. Protocols for heparin use should be based on experimental evidence, and heparin dosage must be individualized for each procedure and each patient. Large-scale, prospective studies of the merits of systemic heparinization and of mixing heparin with nonionic contrast agents are needed.

Angiography↗
PubMed1989

Liver metastases: detection with MR imaging at 0.5 and 1.5 T.

Nineteen patients with known liver metastases were examined with two magnetic resonance (MR) pulse sequences at 0.5 T and three pulse sequences at 1.5 T. In addition, the patients were studied with computed tomography (CT) enhanced with ethiodized oil emulsion-13 (EOE-13). At 0.5 T a spin-echo (SE) 300/22 (repetition time/echo time, msec) sequence prospectively demonstrated 92.4% of the detectable liver metastases, while an SE 2,000/80 sequence showed 52.1% of the lesions. At 1.5 T, an SE 300/25 sequence depicted 68.3% and an SE 2,000/80 sequence 71.6%, while the more T1-weighted inversion recovery (IR) 2,000/600 (repetition time/inversion time, msec) sequence demonstrated 89.5% of the lesions. EOE-13 CT scans depicted 93.3%. These findings suggest that T1-weighted imaging is as successful at demonstrating liver metastases at 1.5 T with an IR 2,000/600 sequence as at 0.5 T with an SE 300/22 sequence. At both field strengths, MR imaging of the liver is comparable to state-of-the-art CT.

Humans↗
PubMed1989

Localization of parathyroid adenomas: superselective arterial DSA versus superselective conventional angiography.

A prospective comparison of superselective arterial digital subtraction angiography (DSA) and superselective conventional angiography (CA) was performed in a consecutive series of 26 patients with hyperparathyroidism, previous unsuccessful surgery, and single gland involvement. All patients had negative or inconclusive findings from noninvasive localization studies. Superselective studies included injection of both thyrocervical trunks, both internal mammary arteries, and both common carotid arteries in all patients in whom this was technically possible. DSA findings were true positive in 16 patients (62%); CA findings were true positive in ten patients (38%) and equivocal in four (15%) (P less than .046). There were no false-positive angiograms. DSA findings were positive in all patients in whom CA findings were positive or equivocal. Superselective DSA appears to be as sensitive as CA for preoperative parathyroid localization and may be more sensitive for the localization of mediastinal glands.

Adenoma↗
PubMed1989

Hepatic artery model for evaluating the distribution of intraarterial chemotherapy infusion: nonpulsed versus pulsed infusions.

The effect of a commercially available pulsatile slow-infusion system on the degree of infusate mixing and distribution was assessed in a life-size glass model of the hepatic arterial system. The authors determined, both visually and quantitatively, the mixing homogeneity of a low-flow infusion (1.4 mL/min) of red dye through a side-hole catheter (2.5 F outer diameter) into pulsatile flow (300 mL/min) of a fluid with the same viscosity as blood. When comparing nonpulsed versus pulsed infusion techniques, the authors found that the pulsatile infusion system did not significantly improve the inhomogeneity of dye distribution in the 16 hepatic arterial branches. The results of this in vitro study suggest that a pulsatile infusion system that uses low pulse velocities without regard for cardiac cycle is less than optimal and does not significantly improve drug mixing at the standard slow infusion rates. Moreover, as potential new intraarterial delivery systems are developed to improve drug mixing, in vitro models may be the most useful means of initially evaluating their efficacy.

Hepatic Artery↗
PubMed1989

Gastrinomas: comparison of MR imaging with CT, angiography, and US.

In this prospective study, magnetic resonance (MR) imaging was used to localize gastrinoma in 24 patients with Zollinger-Ellison syndrome. The results were confirmed by means of either surgery or percutaneous liver biopsy and compared with results of computed tomographic (CT) scanning, selective abdominal angiography, and abdominal ultrasound (US). For primary extrahepatic gastrinoma (intra-or extrapancreatic), MR imaging had a sensitivity of 20% and a specificity of 100%, with a positive predictive value of 100% and a negative predictive value of 11%. For metastatic gastrinoma in the liver, MR imaging had a sensitivity of 43% and a specificity of 100%, with a positive predictive value of 100% and a negative predictive value of 81%. The ability of MR imaging to depict extrahepatic gastrinomas was directly related to tumor size; no tumors smaller than 1 cm were detected, and 50% of tumors 3 cm or larger were detected. MR imaging was as effective as abdominal US but less effective than either CT scanning or selective abdominal angiography for the detection of extrahepatic gastrinoma. In seven patients with hepatic gastrinoma, three gastrinomas were detected with MR imaging and with abdominal US, while five were detected with CT scanning and with selective abdominal angiography. These results indicate that, at the present time, MR imaging is generally not useful in the initial attempt to localize gastrinomas.

Adult↗
PubMed1989

Ectopic adrenocorticotropic hormone syndrome: localization studies in 28 patients.

A variety of imaging procedures were performed in 28 patients with ectopic adrenocorticotropic hormone (ACTH) syndrome in an attempt to localize the ACTH-producing tumor. Diagnosis was made on the basis of removal of an ACTH-producing tumor or biopsy of metastases in the 19 patients with a proved source and the absence of ACTH gradients in bilateral samples of the inferior petrosal sinuses in the nine patients in whom an ACTH-secreting tumor had not been localized. Eleven bronchial carcinoids, two thymic carcinoids, three pheochromocytomas, and three islet-cell tumors constituted the proved sources. The condition has been cured in eight patients, six are alive with residual tumor, and five have died. Of the nine patients with undetected sites of ACTH production, one has died of pneumocystis pneumonia and eight are being treated medically or with bilateral adrenalectomy. Computed tomography (CT) of the chest and abdomen was the most helpful study in the detection of these tumors. Selective arteriography (bronchial and visceral), systemic and portal venous sampling, and iodine-131 meta-iodobenzylguanidine scintigraphy failed to demonstrate tumors when findings at CT were negative. Bronchial carcinoids constituted most of the ACTH-secreting tumors in this study (58%) and in a review of four large series (47%). To assure early detection of these potentially malignant tumors, pulmonary CT should be performed every 6 months, even after hypercortisolism has been medically or surgically controlled.

ACTH Syndrome, Ectopic↗