Search PubMed⌕ Search

Biomedical subjects

D L Miller

Publications and source records attributed to D L Miller.

At least 271 records · Page 15Linked to original sources
PubMed1991

Insulinomas: localization with selective intraarterial injection of calcium.

To facilitate the noninvasive preoperative localization of islet cell tumors less than 15 mm in diameter, the authors examined the use of calcium as an insulin secretagogue in an arterial stimulation venous sampling (ASVS) technique. In four patients with episodic hypoglycemia, calcium gluconate (0.01-0.025 mEq Ca2+/kg) was injected directly into branches of the celiac plexus (gastroduodenal, splenic, and hepatic arteries) and the superior mesenteric artery. In all patients, serum levels of insulin rose abruptly in blood samples taken from the right hepatic vein 30 and 60 seconds after the infusion of calcium into the artery supplying the tumor; injection into an artery not supplying the tumor did not result in a similar rise. Accurate localization of the insulinomas was verified at surgery in three patients. In the fourth patient, who did not undergo surgery, arteriographic results were positive for insulinoma at the predicted site. On the basis of these results, the authors believe noninvasive ASVS may replace invasive portal venous sampling as the most effective method for the localization of occult insulinomas.

Angiography↗
PubMed1991

Zollinger-Ellison syndrome: prospective assessment of abdominal US in the localization of gastrinomas.

The ability of abdominal ultrasound (US) to help localize gastrinomas was prospectively studied in 79 patients with Zollinger-Ellison syndrome. The results were assessed by means of laparotomy, autopsy, or percutaneous liver biopsy. For hepatic gastrinoma, US had a sensitivity of 63% and a specificity of 100%, with a positive predictive value of 100% and a negative predictive value of 89%. US was slightly less sensitive for detecting gastrinoma in the liver than were computed tomography (CT) (66%) and selective angiography (78%). For detection of extrahepatic gastrinoma, US had a sensitivity of 30%, a specificity of 94%, a positive predictive value of 100%, and a negative predictive value of 25%. US enabled detection of tumor in eight cases not detected with CT and in four not detected with angiography. Specificity for extrahepatic gastrinoma was similar for all three modalities (89%-95%). CT and US were equally effective for the detection of extrahepatic gastrinoma, and angiography was significantly more effective than both US and CT (P less than .01). The authors conclude that US, although of low sensitivity, remains useful as the initial imaging modality in patients with Zollinger-Ellison syndrome.

Abdomen↗
PubMed1991

von Hippel-Lindau disease: inadequacy of angiography for identification of renal cancers.

Selective renal angiograms were retrospectively evaluated for the identification of renal cell cancers in patients with von Hippel-Lindau disease (VHL). Seven patients underwent angiography and surgery because of solid or complex renal masses identified at cross-sectional imaging. Nine kidneys underwent detailed examination by the surgeon and by a pathologist. There were 31 renal cancers. Angiography had enabled identification of only five cancers (16%), and six others (19%) had been suspected. Cancers detected angiographically were larger than those not detected (P less than .05). Solid tumors tended to appear less hypervascular than expected and occasionally had the angiographic appearance of atypical cysts. There were no false-positive angiograms. Angiography revealed only one cancer not previously suspected and changed the surgeon's approach for only one kidney (11%). The sensitivity and specificity of angiography were 35% and 100%, respectively. In these patients, selective renal angiography is not helpful for the detection or exclusion of cancer in a kidney. It does not have a limited role for vascular mapping prior to partial nephrectomy or tumor enucleation.

Adult↗
PubMed1991

Occlusive peripheral vascular disease: a multicenter trial of fluorescence-guided, pulsed dye laser-assisted balloon angioplasty.

Fluorescence-guided, laser-assisted balloon angioplasty was performed in 129 patients with iliac and femoropopliteal artery chronic occlusions (range, 0.5-50.0 cm; mean length, 9.9 cm) after failure of recanalization with standard guide-wire techniques. Laser recanalization and short-term angiographic success were achieved in 101 (72%) and 95 (68%) of 140 occlusions, respectively. Laser and balloon angioplasty failures were encountered in heavily calcified plaques or after perforations and dissections. Complications included perforations (19%), hematomas (5%), thromboses (4%), and distal embolizations (4%). Real-time fluorescence spectroscopy identified thrombus, white fibrous plaque, and media but could not avoid perforations in many cases because laser wire advancement outdistanced fluorescence sensing. Disruption of tissue by means of pressure transients and/or mechanical advancement occurred in at least 36% of lesions where the laser energy was insufficient (less than 0.4 J/cm) to ablate significant tissue. Integration of fluorescence guidance with pulsed dye laser ablation is feasible, but additional refinements are necessary to increase safety and efficacy.

Adult↗
PubMed1991

Results of a prospective strategy to diagnose, localize, and resect insulinomas.

Since 1982, 25 consecutive patients with benign sporadic (non-multiple endocrine neoplasia type I) insulinomas have been studied. Most were referred because either the tumor was not identified at the referring institution or the diagnosis was unclear. Each patient suffered severe neuroglycopenic symptoms for a median of 24 months before diagnosis of insulinoma, and 32% had hypoglycemic seizures. Eighteen patients (72%) had a confirmed weight gain. Each patient underwent a supervised fast until 72 hours or the onset of significant neuroglycopenic symptoms (median duration 16 hours), with serum levels of glucose (median 35 mg/dl; range 24 to 46 mg/dl), insulin (median 21 microU/ml; range 11 to 230 microU/ml), C-peptide (median 2.5 ng/ml; range 1.0 to 7.2 ng/ml), and proinsulin fraction (median 55%; range 14% to 86%) measured at the termination of the fast. Preoperative imaging with ultrasonography, computed tomography, magnetic resonance, and angiography visualized tumor in a minority of patients (26%, 17%, 25%, and 35%, respectively); in 48% of patients one or more imaging study results was positive. Selective portal venous sampling for insulin was the most informative localizing test (77% positive; no false-positive results). Tumor was resected for cure in 24 of 25 patients. Intraoperative ultrasonography identified nonpalpable tumor in seven patients and was crucial to the achievement of this high rate of surgical cure. We conclude that the diagnosis of insulinoma can be made by the results of a supervised fast, portal venous sampling is the most sensitive preoperative test for localizing insulinomas, and intraoperative ultrasonography is essential for intraoperative detection of insulinomas.

Adult↗
PubMed1991

Polishing the surface. A comparison of rubber cup polishing and airpolishing.

This study was designed to compare the clinical effectiveness of rubber cup polishing and airpolishing. Polishing time was controlled to approximate the time spent on plaque and stain removal in clinical dental hygiene practice. Effectiveness of polishing techniques was evaluated using indices to measure plaque, stain, and gingival trauma prior to and after the polishing treatment. Thirty adult subjects, with comparable numbers of teeth contralaterally, exhibiting observable plaque and stain, participated in the study. Patients with contra-indications for either polishing technique were excluded from the sample. Data were collected using a randomized split mouth design; one side of a subject's mouth was polished with a rubber cup and flour of pumice and the other side was polished with the Prophy-Jet airpolishing device. The time employed for both treatments was held constant at five minutes for each technique. Plaque, stain, and gingival trauma measurements were assessed prior to and following both polishing treatments. Analysis of variance was utilized to compute the data. Results indicate that, when comparing the effectiveness of polishing treatments, there is no statistically significant difference in plaque removal, stain removal, or gingival trauma within the established time interval. The authors conclude that other factors, in addition to effectiveness and time efficiency, should be considered when selecting rubbercup polishing with flour of pumice or an airpolishing device.

Adult↗
PubMed1990

Fluorescence characterization of the interaction of various transfer RNA species with elongation factor Tu.GTP: evidence for a new functional role for elongation factor Tu in protein biosynthesis.

The ubiquity of elongation factor Tu (EF-Tu)-dependent conformational changes in amino-acyl-tRNA (aa-tRNA) and the origin of the binding energy associated with aa-tRNA.EF-Tu.GTP ternary complex formation have been examined spectroscopically. Fluorescein was attached covalently to the 4-thiouridine base at position 8 (s4U-8) in each of four elongator tRNAs (Ala, Met-m, Phe, and Val). Although the probes were chemically identical, their emission intensities in the free aa-tRNAs differed by nearly 3-fold, indicating that the dyes were in different environments and hence that the aa-tRNAs had different tertiary structures near s4U-8. Upon association with EF-Tu.GTP, the emission intensities increased by 244%, 57%, or 15% for three aa-tRNAs due to a change in tRNA conformation; the fourth aa-tRNA exhibited no fluorescence change upon binding to EF-Tu.GTP. Despite the great differences in the emission intensities of the free aa-tRNAs and in the magnitudes of their EF-Tu-dependent intensity increases, the emission intensity per aa-tRNA molecule was nearly the same (within 9% of the average) for the four aa-tRNAs when bound to EF-Tu-GTP. Thus, the binding of EF-Tu.GTP induced or selected a tRNA conformation near s4U-8 that was very similar, and possibly the same, for each aa-tRNA species. It therefore appears that EF-Tu functions, at least in part, by minimizing the conformational diversity in aa-tRNAs prior to their beginning the recognition and binding process at the single decoding site on the ribosome. Since an EF-Tu-dependent fluorescence change was also observed with fluorescein-labeled tRNA(Phe), the protein-dependent structural change is effected by direct interactions between EF-Tu and the tRNA and does not require the aminoacyl group. The Kd of the tRNA(Phe).EF-Tu.GTP ternary complex was determined, at equilibrium, to be 2.6 microM by the ability of the unacylated tRNA to compete with fluorescent Phe-tRNA for binding to the protein. Comparison of this Kd with that of the Phe-tRNA ternary complex showed that in this case the aminoacyl moiety contributed 4.3 kcal/mol toward ternary complex formation at 6 degrees C but that the bulk of the binding energy in the ternary complex was derived from direct protein-tRNA interactions.(ABSTRACT TRUNCATED AT 400 WORDS)

Escherichia coli↗
PubMed1990

Effects of nucleotide- and aurodox-induced changes in elongation factor Tu conformation upon its interactions with aminoacyl transfer RNA. A fluorescence study.

The effects of GDP and of aurodox (N-methylkirromycin) on the affinity of elongation factor Tu (EF-Tu) for aminoacyl-tRNA (aa-tRNA) have been quantified spectroscopically by using Phe-tRNA(Phe)-Fl8, a functionally active analogue of Phe-tRNA(Phe) with a fluorescein dye convalently attached to the s4U-8 base. The association of EF-Tu.GDP with Phe-tRNA(Phe)-Fl8 resulted in an average increase of 33% in fluorescein emission intensity. This spectral change was used to monitor the extent of ternary complex formation as a function of EF-Tu.GDP concentration, and hence to obtain a dissociation constant, directly and at equilibrium, for the EF-Tu.GDP-containing ternary complex. The Kd for the Phe-tRNA(Phe)-Fl8.EF-Tu.GDP complex was found to average 28.5 microM, more than 33,000-fold greater than the Kd of the Phe-tRNA(Phe)-Fl8.EF-Tu.GTP complex under the same conditions. In terms of free energy, the delta G degree for ternary complex formation at 6 degrees C was -11.5 kcal/mol with GTP and -5.8 kcal/mol with GDP. Thus, the hydrolysis of the ternary complex GTP results in a dramatic decrease in the affinity of EF-Tu for aa-tRNA, thereby facilitating the release of EF-Tu.GDP from the aa-tRNA on the ribosome. Aurodox (200 microM) decreased the Kd of the GDP complex by nearly 20-fold, to 1.46 microM, and increased the Kd of the GTP complex by at least 6-fold. The binding of aurodox to EF-Tu therefore both considerably strengthens EF-Tu.GDP affinity for aa-tRNA and also weakens EF-Tu.GTP affinity for aa-tRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Bacterial Agents↗
PubMed1990

Exposure of mammalian cells to 60-Hz magnetic or electric fields: analysis of DNA repair of induced, single-strand breaks.

DNA damage was induced in isolated human peripheral lymphocytes by exposure at 5 Gy to 60Co radiation. Cells were permitted to repair the DNA damage while exposed to 60-Hz fields or while sham-exposed. Exposed cells were subjected to magnetic (B) or electric (E) fields, alone or in combination, throughout their allotted repair time. Repair was stopped at specific times, and the cells were immediately lysed and then analyzed for the presence of DNA single-strand breaks (SSB) by the alkaline-elution technique. Fifty to 75 percent of the induced SSB were repaired 20 min after exposure, and most of the remaining damage was repaired after 180 min. Cells were exposed to a 60-Hz ac B field of 1 mT; an E field of 1 or 20 V/m; or combined E and B fields of 0.2 V/m and 0.05 mT, 6 V/m and 0.6 mT, or 20 V/m and 1 mT. None of the exposures was observed to affect significantly the repair of DNA SSB.

Cobalt Radioisotopes↗
PubMed1990

Mitochondrial DNA of Physarum polycephalum: physical mapping, cloning and transcription mapping.

Mitochondrial DNA (mtDNA) has been isolated from four strains of Physarum polycephalum and a restriction site map has been determined using nine restriction enzymes. The restriction site maps of the four strains are similar but each strain is distinguished by insertions, deletions and restriction enzyme site polymorphisms. The sum of the restriction fragments gives mitochondrial genome sizes which vary from about 56 kb to 62 kb. In all four strains the composite map of the restriction enzyme sites for the mtDNA is circular. Knowledge of the restriction enzyme map has enabled cloning of mtDNA fragments representing the entire mtDNA of strain M3. The cloned fragments have been used to create a transcription map of the mtDNA.

Blotting, Northern↗
PubMed1990

Effects of resection on absorption and secretion of divalent cations by small intestine of rat.

Resection increases villus height and crypt depth of remaining intestine. We examined functional consequences of resection by measuring absorption of strontium and secretion of calcium and magnesium by proximal and distal segments remaining after resecting 70% of mid small intestine. Compared with the transected control group, resection decreased strontium absorption per unit weight of mucosa (specific absorption) in the proximal segment. The decreased specific absorption was compensated by increased mucosal growth in the resected group so that absorption per unit length of segment (per cm) was the same in both groups. Resection increased secretion of calcium and magnesium by 66% per unit weight of mucosa and by 145%/cm in the distal segment. Comparing proximal with distal segments in the resected group, secretion was greater in distal for calcium and in proximal for magnesium. Intestinal resection causes responses in absorption and secretion of divalent cations important in mineral homeostasis.

Animals↗
PubMed1990

Localization and surgical treatment of occult insulinomas.

Management of patients with biochemical evidence of insulinoma and negative preoperative imaging studies (occult) tumors is controversial, varying from primarily medical management to aggressive, blind nearly total pancreatectomy to extirpate the tumor. Since 1982, 12 consecutive patients with occult insulinoma underwent preoperative portal venous sampling (PVS) for insulin followed by surgical exploration with intraoperative ultrasound (IOUS). Eleven of twelve patients (92%) had insulinoma removed and were cured. Portal venous sampling correctly predicted the location of the insulinoma in 9 patients (75%) and that no tumor would be found in another patient. A fourfold insulin gradient in the pancreatic tail of one patient correctly predicted that a distal pancreatectomy would remove the insulinoma despite the fact that neither palpation nor IOUS identified any tumor. Intraoperative ultrasound was the single best method to identify occult tumors because it correctly identified 10 of 11 insulinomas that were found, including five pancreatic head tumors that were not palpable. Palpation identified five insulinomas. Of the 10 tumors that were identified during operation by palpation or ultrasound, IOUS identified significantly more (100% versus 50%, p = 0.03) and guided the successful enucleation of each. The results support the strategy of preoperative PVS and operation with IOUS to localize and remove insulinoma in patients with occult tumors. Most tumors (75%) will be correctly localized to a specific pancreatic region by preoperative PVS and identified by IOUS (83%), allowing simple enucleation and biochemical correction of hypoglycemia. Morbid blind pancreatic resections are no longer indicated and long-term medical management of hypoglycemia should be reserved for the occasional patient (8%) who fails preoperative PVS and operation guided by IOUS.

Adult↗
PubMed1990

Evidence for an effect of ELF electromagnetic fields on human pineal gland function.

A study was carried out to determine possible effects of 60-Hz electromagnetic-field exposure on pineal gland function in humans. Overnight excretion of urinary 6-hydroxymelatonin sulfate (6-OHMS), a stable urinary metabolite of the pineal hormone melatonin, was used to assess pineal gland function in 42 volunteers who used standard (conventional) or modified continuous polymer wire (CPW) electric blankets for approximately 8 weeks. Volunteers using conventional electric blankets showed no variations in 6-OHMS excretion as either a group or individuals during the study period. Serving as their own controls, 7 of 28 volunteers using the CPW blankets showed statistically significant changes in their mean nighttime 6-OHMS excretion. The CPW blankets switched on and off approximately twice as often when in service and produced magnetic fields that were 50% stronger than those from the conventional electric blankets. On the basis of these findings, we hypothesize that periodic exposure to pulsed DC or extremely low frequency electric or magnetic fields of sufficient intensity and duration can affect pineal gland function in certain individuals.

Adult↗